First Edition, 2011
ISBN 978-93-81157-55-8
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Published by: The English Press 4735/22 Prakashdeep Bldg, Ansari Road, Darya Ganj, Delhi - 110002 Email:
[email protected] Table of Contents
Chapter 1- Environmental Effects of Nuclear Power Chapter 2 - Waste Streams Chapter 3 - Radioactive Waste Chapter 4 - Nuclear Fallout Chapter 5 - Nuclear Winter Chapter 6 - Chernobyl Disaster Effects Chapter 7 - High-Level Radioactive Waste Management
Chapter- 1
Environmental Effects of Nuclear Power
Nuclear power activities involving the environment; mining, enrichment, generation and geological disposal. Nuclear power has an effect on the environment through the nuclear fuel cycle, through operation, and from the lingering effects of the Chernobyl disaster.
Waste streams
Nuclear power have at least four waste streams that contaminate and degrade land: • • • •
(1) they create spent nuclear fuel at the reactor site (including plutonium waste) (2) they produce tailings at uranium mines and mills (3) during operation they routinely release small amounts of radioactive isotopes (4) during accidents they can release large quantities of pollution
Radioactive waste High level waste Around 20-30 tons of high-level waste are produced per month per nuclear reactor. Currently most spent nuclear fuel outside the U.S. is reprocessed for the useful components, leaving only a much smaller volume of short half-life waste to be stored. In the U.S. reprocessing is currently prohibited by executive order, and the spent nuclear fuel is therefore stored in dry cask storage facilities (this has the disadvantage of keeping the long-lived isotopes with the other waste, thus greatly extending the half-life of the waste). Several methods have been suggested for final disposal of high-level waste, including deep burial in stable geological structures, transmutation, and removal to space. So far, none of these methods have been implemented. Recognising that long-term management options may require significant time to be achieved, interim storage is currently used. Since the spent nuclear fuel has nowhere to go, some experimental nuclear reactors, such as the Integral Fast Reactor, have been proposed that use a different nuclear fuel cycle that avoids producing waste containing long-lived radioactive isotopes or actually "burns" those isotopes from other plants, via transmutation into elements with lower radioactivity. According to anti-nuclear organizations and current public opinion in the US, rendering nuclear waste harmless is not being done satisfactorily and it remains a hazard for anywhere between a few years to many thousands of years, depending on the particular isotopes. The same organizations lobby against processing the waste to reduce its radioactivity and longevity, claming that the method has proliferation concerns and is uneconomic. The length of time waste has to be stored is controversial because there is a question of whether one should use the original ore or surrounding rock as a reference for safe levels. Anti-nuclear organizations tend to favor using normal soil as a reference, in contrast to pro-nuclear organizations who tend to argue that geologically disposed waste can be considered safe once it is no more radioactive than the uranium ore it was produced from.
Other waste
Moderate amounts of low-level waste are produced through chemical and volume control system (CVCS). This includes gas, liquid, and solid waste produced through the process of purifying the water through evaporation. Liquid waste is reprocessed continuously, and gas waste is filtered, compressed, stored to allow decay, diluted, and then discharged. The rate at which this is allowed is regulated and studies must prove that such discharge does not violate dose limits to a member of the public. Solid waste can be disposed of simply by placing it where it will not be disturbed for a few years. There are three low-level waste disposal sites in the United States in South Carolina, Utah, and Washington. Solid waste from the CVCS is combined with solid radwaste that comes from handling materials before it is buried off-site.
Power plant emissions Radioactive gases and effluents
The Grafenrheinfeld Nuclear Power Plant. The tall chimney releases effluent gases. Most commercial nuclear power plants release gaseous and liquid radiological effluents into the environment as a byproduct of the Chemical Volume Control System, which are monitored in the US by the EPA and the NRC. Civilians living within 50 miles (80 km)
of a nuclear power plant typically receive about 0.01 milli-rem per year. For comparison, the average person living at or above sea level receives at least 26 milli-rem from cosmic radiation. The total amount of radioactivity released through this method depends on the power plant, the regulatory requirements, and the plant's performance. Atmospheric dispersion models combined with pathway models are employed to accurately approximate the dose to a member of the public from the effluents emitted. Effluent monitoring is conducted continuously at the plant. Limits for the Canadian plants are shown below: Regulatory limits on Radioactive Effluents from Canadian Nuclear Power Plants Noble IodineCarbonEffluent Tritium Particulates 131 Gases 14 (TBq(TBqb × (TBq × Units (TBq) (TBq) MeVc × 104) 103) 104) Point Lepreau Nuclear 43.0 9.9 7.3 5.2 3.3 Generating Station Bruce Nuclear 38.0 1.2 25.0 2.7 2.8 Generating Station A Bruce B 47.0 1.3 61.0 4.8 3.0 Darlington 21.0 0.6 21.0 4.4 1.4 Pickering Nuclear 34.0 2.4 8.3 5.0 8.8 Generating Station A Pickering B 34.0 2.4 8.3 5.0 8.8 Gentilly-2 44.0 1.3 17.0 1.9 0.91 Effluent emissions for Nuclear power in the United States are regulated by 10 CFR 50.36(a)(2). Boron letdown Towards the end of each cycle of operation (typically 18 months to two years in length), each pressurized water reactor reduces the amount of boron in its primary coolant system (the water that flows past and cools the nuclear reactor core). As a consequence, some of this irradiated boron is discharged from the plant and into whatever body of water the plant's cooling water is drawn from. The maximum amount of radioactivity permitted in each volume of discharge is tightly regulated (see above). Tritium Effluent Limits Country Limit (Bq/L)
Australia
76,103
Finland
30,000
WHO
10,000
Switzerland
10,000
Russia
7,700
Ontario, Canada
7,000
United States
740
European Union
1001
California Public Health Goal 14.8 Tritium A leak of radioactive water at Vermont Yankee in 2010, along with similar incidents at more than 20 other US nuclear plants in recent years, has kindled doubts about the reliability, durability, and maintenance of aging nuclear installations in the United States. Tritium is a radioactive isotope of Hydrogen that emits a low-energy beta particle and is usually measured in Becquerels per Liter (Bq/L). Tritium becomes dissolved in ordinary water when released from a nuclear plant. The primary concern for Tritium release is the presence in drinking water, in addition to biological magnification leading to Tritium in crops and animals consumed for food. Legal concentration limits have differed greatly to place to place (see table right). For example, in June 2009 the Ontario Drinking Water Advisory Council recommended lowering the limit from 7,000 Bq/L to 20 Bq/L. According to the NRC, Tritium is the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quick. The amount released by any given plant also varies greatly; the total release for plants in the United States in 2003 was at least counted to be 0 and at most 2,080 Curries. Uranium mining Uranium mining can use large amounts of water - for example, the Roxby Downs mine in South Australia uses 35 million litres of water each day and plans to increase this to 150 million litres per day.
Risk of cancer There have been several epidemiological studies that claim to demonstrate increased risk of various diseases, especially cancers, among people who live near nuclear facilities. Among recent studies, a widely cited 2007 meta-analysis of 17 research papers was published in the European Journal of Cancer Care. It offered evidence of elevated leukemia rates among children living near 136 nuclear facilities in the United Kingdom,
Canada, France, United States, Germany, Japan, and Spain. Elevated leukemia rates among children were also found in a 2008 German study that examined residents living near 16 major nuclear power plants in Germany. These recent results are not consistent with many earlier studies that have tended not to show such associations. But no credible alternate explanations for the recent findings have so far emerged.
Comparison to coal-fired generation In terms of net radioactive release, the National Council on Radiation Protection and Measurements (NCRP) estimated the average radioactivity per short ton of coal is 17,100 millicuries/4,000,000 tons. With 154 coal plants in the United States, this amounts to emissions of 0.6319 TBq per year for a single plant. In terms of dose to a human living nearby, it is sometimes cited that coal plants release 100 times the radioactivity of nuclear plants. This comes from NCRP Reports No. 92 and No. 95 which estimated the dose to the population from 1000 MWe coal and nuclear plants at 490 person-rem/year and 4.8 person-rem/year respectively (a typical Chest x-ray gives a dose of about 6 milli-rem for comparison). The Environmental Protection Agency estimates an added dose of 0.03 milli-rem per year for living within 50 miles (80 km) of a coal plant and 0.009 milli-ren for a nuclear plant for yearly radiation dose estimation. In short, nuclear power plants have more radioactivity than coal-fired power plants, but since they use shielding, coal power plants emit more. Unlike coal-fired or oil-fired generation, nuclear power generation does not directly produce any sulfur dioxide, nitrogen oxides, or mercury (pollution from fossil fuels is blamed for 24,000 early deaths each year in the U.S. alone). However, as with all energy sources, there is some pollution associated with support activities such as manufacturing and transportation.
Contrast of radioactive accident emissions with industrial emissions Proponents argue that the problems of nuclear waste "do not come anywhere close" to approaching the problems of fossil fuel waste. A 2004 article from the BBC states: "The World Health Organization (WHO) says 3 million people are killed worldwide by outdoor air pollution annually from vehicles and industrial emissions, and 1.6 million indoors through using solid fuel." In the U.S. alone, fossil fuel waste kills 20,000 people each year. A coal power plant releases 100 times as much radiation as a nuclear power plant of the same wattage. It is estimated that during 1982, US coal burning released 155 times as much radioactivity into the atmosphere as the Three Mile Island accident. The World Nuclear Association provides a comparison of deaths due to accidents among different forms of energy production. In their comparison, deaths per TW-yr of electricity produced from 1970 to 1992 are quoted as 885 for hydropower, 342 for coal, 85 for natural gas, and 8 for nuclear.
Environmental effects of accidents
The worst accidents at nuclear power plants have resulted in severe environmental contamination.
Chernobyl disaster
The major plume of radiation released by the Chernobyl Nuclear Accident was carried directly over what is now called the Red Forest. Radioactive particles settled on trees, killing areas of pine forest. The 1986 Chernobyl disaster in the Ukraine was the world's worst nuclear power plant accident, resulting in an estimated 4,056 deaths. Large amounts of radioactive contamination were spread across Europe, and cesium and strontium contaminated many agricultural products, livestock and soil. The accident necessitated the evacuation of 300,000 people from Kiev, rendering an area of land unusable to humans for an indeterminate period. The habitability of the area for animals, however, has been less clear - some researchers have claimed to have detected depressed numbers of insects and spiders, while others have claimed that wildlife has flourished due to the absence of humans.
Windscale fire On October 8, 1957, the Windscale fire in the U.K. ignited the plutonium "piles", resulting in the contamination of surrounding dairy farms. The main sources of radioactivity were cesium-137 and iodine-131. Overall, the accident resulted in 33 cancer
deaths and US$78 million in property damage. The primary cause of the accident had been the second nuclear heating, applied too soon and too rapidly. It was triggered to release Wigner energy.
Water usage Waste heat
The North Anna plant uses direct exchange cooling into an artificial lake. As with some thermal power stations, nuclear plants exchange 60 to 70% of their thermal energy by cycling with a body of water or by evaporating water through a cooling tower. This thermal efficiency is somewhat lower than that of coal fired power plants, thus creating more waste heat. The cooling options are typically once-through cooling with river or sea water, pond cooling, or cooling towers. Many plants have an artificial lake like the Shearon Harris Nuclear Power Plant or the South Texas Nuclear Generating Station. Shearon Harris uses a cooling tower but South Texas does not and discharges back into the lake. The North Anna Nuclear Generating Station uses a cooling pond or artificial lake, which at the plant discharge canal is often about 30°F warmer than in the other parts of the lake or in
normal lakes (this is cited as an attraction of the area by some residents). The environmental effects on the artificial lakes are often weighted in arguments against construction of new plants, and during droughts have drawn media attention. The Turkey Point Nuclear Generating Station is credited with helping the conservation status of the American Crocodile, largely an effect of the waste heat produced. The Indian Point nuclear power plant in New York is in a hearing process to determine if a cooling system other than river water will be necessary (conditional upon the plants extending their operating licenses). It is possible to use waste heat in cogeneration applications such as district heating. The principles of cogeneration and district heating with nuclear power are the same as any other form of thermal power production. One use of nuclear heat generation was with the Ågesta Nuclear Power Plant in Sweden. In Switzerland, the Beznau Nuclear Power Plant provides heat to about 20,000 people.. However, district heating with nuclear power plants is less common than with other modes of waste heat generation: because of either siting regulations and/or the NIMBY effect, nuclear stations are generally not built in densely populated areas. Waste heat is more commonly used in industrial applications. During Europe's 2003 and 2006 heat waves, French, Spanish and German utilities had to secure exemptions from regulations in order to discharge overheated water into the environment. Some nuclear reactors shut down.
Uranium mining Uranium mining can use large amounts of water - for example, the Roxby Downs mine in South Australia uses 35 million litres of water each day and plans to increase this to 150 million litres per day.
Greenhouse gas emissions Nuclear power plant operation emits no or negligible amounts of carbon dioxide. However, all other stages of the nuclear fuel chain – mining, milling, transport, fuel fabrication, enrichment, reactor construction, decommissioning and waste management – use fossil fuels and hence emit carbon dioxide. There has been a debate on the quantity of greenhouse gas emissions from the complete nuclear fuel chain. Many commentators have argued that an expansion of nuclear power would help combat climate change. Others have pointed out that it is one way to reduce emissions, but it comes with its own problems, such as risks related to severe nuclear accidents the challenges of more radioactive waste disposal. Other commentators have argued that there are better ways of dealing with climate change than investing in nuclear power, including the improved energy efficiency and greater reliance on decentralized and renewable energy sources.
Various life cycle analysis (LCA) studies have led to a large range of estimates. Some comparisons of carbon dioxide emissions show nuclear power as comparable to renewable energy sources. On another hand, a 2008 meta analysis of 103 studies, published by Benjamin K. Sovacool, determined that renewable electricity technologies are "two to seven times more effective than nuclear power plants on a per kWh basis at fighting climate change".
Decommissioning Both nuclear reactors and uranium enrichment facilities must be carefully decommissioned using processes that are occupationally dangerous, and hazardous to the natural environment, expensive, and time-intensive.
Chapter- 2
Waste Streams
Spent nuclear fuel
Spent fuel pool at a nuclear power plant. Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant) to the point where it is no longer useful in sustaining a nuclear reaction.
Nature of spent fuel Nanomaterial properties
Spent low enriched uranium nuclear fuel is an example of a nanomaterial that existed before the term nano became fashionable. In the oxide fuel, intense temperature gradients exist which cause fission products to migrate. The zirconium tends to move to the centre of the fuel pellet where the temperature is highest, while the lower-boiling fission products move to the edge of the pellet. The pellet is likely to contain lots of small bubble-like pores which form during use; the fission xenon migrates to these voids. Some of this xenon will then decay to form caesium, hence many of these bubbles contain a large concentration of 137Cs.
A used MOX which has 63 GW days(thermal) of burnup and has been examined with a scanning electron microscope using electron microprobe attachment. The lighter the pixel on the right hand side, the higher the plutonium content of the material at that spot
A used MOX which has 63 GW days(thermal) of burnup and has been examined with a scanning electron microscope using electron microprobe attachment. The lighter the pixel, the higher the neodymium (left) or xenon (right) content of the material at that spot In the case of the MOX the xenon tended to diffuse out of the plutonium-rich areas of the fuel, and it was then trapped in the surrounding uranium dioxide. The neodymium tended to not be mobile. Also metallic particles of an alloy of Mo-Tc-Ru-Pd tend to form in the fuel. Other solids form at the boundary between the uranium dioxide grains, but the majority of the fission
products remain in the uranium dioxide as solid solutions. A paper describing a method of making a non-radioactive "uranium active" simulation of spent oxide fuel exists.
Fission products 3% of the mass consists of fission products of 235U and 239Pu (also indirect products in the decay chain); these are considered radioactive waste or may be separated further for various industrial and medical uses. The fission products include every element from zinc through to the lanthanides; much of the fission yield is concentrated in two peaks, one in the second transition row (Zr, Mo, Tc, Ru, Rh, Pd, Ag) and the other later in the periodic table (I, Xe, Cs, Ba, La, Ce, Nd). Many of the fission products are either non-radioactive or only short-lived radioisotopes. But a considerable number are medium to long-lived radioisotopes such as 90Sr, 137Cs, 99Tc and 129I. Research has been conducted by several different countries into segregating the rare isotopes in fission waste including the "fission platinoids" (Ru, Rh, Pd) and silver (Ag) as a way of offsetting the cost of reprocessing; however, this is not currently being done commercially. The fission products can modify the thermal properties of the uranium dioxide; the lanthanide oxides tend to lower the thermal conductivity of the fuel, while the metallic nanoparticles slightly increase the thermal conductivity of the fuel. Table of chemical data The chemical forms of fission products in uranium dioxide Element Gas Metal Oxide Solid solution Yes Br Kr Yes Yes Rb Yes Yes Sr Yes Y Yes Yes Zr Yes Nb Yes Yes Mo Yes Tc Ru Rh Pd Ag Cd In Sb Yes Yes Yes Yes Te Yes I Xe Yes Yes Cs Yes Yes Ba Yes La Ce Pr Nd Pm Sm Eu -
Plutonium
Spent nuclear fuel stored underwater and uncapped at the Hanford site in Washington, USA. About 1% of the mass is 239Pu and 240Pu resulting from conversion of 238U, which may be considered either as a useful byproduct, or as dangerous and inconvenient waste. One of the main concerns regarding nuclear proliferation is to prevent this plutonium from being used by states, other than those already established as nuclear weapons states, to produce nuclear weapons. If the reactor has been used normally, the plutonium is reactor-grade, not weapons-grade: it contains much 240Pu and less than 80% 239Pu, which makes it less suitable, but not impossible, to use in a weapon. If the irradiation period has been short then the plutonium is weapons-grade (more than 80%, up to 93%).
Uranium 96% of the mass is the remaining uranium: most of the original 238U and a little 235U. Usually 235U would be less than 0.83% of the mass along with 0.4% 236U. Reprocessed uranium will contain 236U, which is not found in nature; this is one isotope which can be used as a fingerprint for spent reactor fuel. If using a thorium fuel to produce fissile U-233, the SNF will have U-233, with a half-life of 159,200 years. This will have an impact on the long-term radioactive decay of the spent fuel. If compared with MOX fuel, the activity around one million years in the cycles with thorium will be higher due to the presence of the not fully decayed U-233.
Minor actinides
Traces of the minor actinides are present in spent reactor fuel. These are actinides other than uranium and plutonium and include neptunium, americium and curium. The amount formed depends greatly upon the nature of the fuel used and the conditions under which it was used. For instance, the use of MOX fuel (239Pu in a 238U matrix) is likely to lead to the production of more 241Am and heavier nuclides than a uranium/thorium based fuel (233U in a 232Th matrix). For natural uranium fuel: Fissile component starts at 0.71% 235U concentration in natural uranium. At discharge, total fissile component is still 0.50% (0.23% 235U, 0.27% fissile 239 Pu, 241Pu) Fuel is discharged not because fissile material is fully used-up, but because the neutron-absorbing fission products have built up and the fuel becomes significantly less able to sustain a nuclear reaction. Some natural uranium fuels use chemically active cladding, such as Magnox, and need to be reprocessed because long-term storage and disposal is difficult. For highly-enriched fuels used in marine reactors and research reactors, the isotope inventory will vary based on in-core fuel management and reactor operating conditions.
Fuel composition and long term radioactivity
Activity of U-233 for three fuel types
Total activity for three fuel types Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different. An example of this effect is the use of nuclear fuels with thorium. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting in the production of fissile U-233. The SNF of a cycle with thorium will contain U-233, an isotope with a half-life of 160,000 years. Its radioactive decay will strongly influence the long-term activity curve of the SNF around 1,000,000 years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right. The burnt fuels are Thorium with Reactor-Grade Plutonium (RGPu), Thorium with Weapons-Grade Plutonium (WGPu) and Mixed Oxide fuel (MOX). For RGPu and WGPu, the initial amount of U-233 and its decay around 10E5 years can be seen. This has an effect in the total activity curve of the three fuel types. The absence of U-233 and its daughter products in the MOX fuel results in a lower activity in region 3 of the figure on the bottom right, whereas for RGPu and WGPu the curve is maintained higher due to the presence of U-233 that has not fully decayed. The use of different fuels in nuclear reactors results in different SNF composition, with varying activity curves.
Spent fuel corrosion Noble metal nanoparticles and hydrogen
According to the work of the corrosion electrochemist Shoesmith the nanoparticles of Mo-Tc-Ru-Pd have a strong effect on the corrosion of uranium dioxide fuel. For instance his work suggests that when hydrogen (H2) concentration is high (due to the anaerobic corrosion of the steel waste can), the oxidation of hydrogen at the nanoparticles will exert a protective effect on the uranium dioxide. This effect can be thought of as an example of protection by a sacrificial anode, where instead of a metal anode reacting and dissolving it is the hydrogen gas which is consumed.
Disposal of Nuclear reprocessing can separate spent fuel into various combinations of reprocessed uranium, plutonium, minor actinides, fission products, remnants of zirconium or steel cladding, activation products, and the reagents or solidifiers introduced in the reprocessing itself. In this case the volume that needs to be disposed of is greatly reduced. Alternatively, the intact Spent Nuclear Fuel (SNF) can be disposed of as radioactive waste. The United States has planned disposal in deep geological formations, such as the Yucca Mountain nuclear waste repository, where it has to be shielded and packaged to prevent its migration to mankind's immediate environment for thousands of years. However, on March 5, 2009, Energy Secretary Steven Chu told a Senate hearing that "the Yucca Mountain site no longer was viewed as an option for storing reactor waste."
Radionuclide A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits a gamma ray(s) and/or subatomic particles. These particles constitute ionizing radiation. Radionuclides may occur naturally, but can also be artificially produced. The number of radionuclides is uncertain because the number of very short-lived radionuclides that have yet to be characterized is extremely large and potentially unquantifiable. Even the number of long-lived radionuclides is uncertain (to a smaller degree), because many "stable" nuclides are calculated to have half lives so long that their decay has not been experimentally measured. The nuclide list contain 90 nuclides that are theoretically stable, and 255 total stable nuclides that have not been observed to decay. In addition, there exist about 650 radionuclides that have been experimentally observed to decay, with half lives longer than 60 minutes. Of these, about 339 are known from nature (they have been observed on Earth, and not as a consequence of man-made activities). Including artificially produced nuclides, more than 3300 nuclides are known (including ~3000 radionuclides), including many more (> ~2400) that have decay half lives shorter
than 60 minutes. This list expands as new radionuclides with very short half lives are characterized. Radionuclides are often referred to by chemists and physicists, as radioactive isotopes or radioisotopes. Radioisotopes with suitable half lives play an important part in a number of constructive technologies (for example, nuclear medicine). However, radionuclides can also present both real and perceived dangers to health.
Origin Naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides and cosmogenic radionuclides. Primordial radionuclides originate mainly from the interiors of stars and, like uranium and thorium, are still present because their half-lives are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Artificially produced radionuclides can be produced by nuclear reactors, particle accelerators or by radionuclide generators: •
•
•
•
Radioisotopes produced with nuclear reactors exploit the high flux of neutrons present. The neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is thallium-201 and iridium-192. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high neutron cross-section. Particle accelerators such as cyclotrons accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron emitting radioisotopes e.g. fluorine-18. Radionuclide generators contain a parent isotope that decays to produce a radioisotope. The parent is usually produced in a nuclear reactor. A typical example is the technetium-99m generator used in nuclear medicine. The parent produced in the reactor is molybdenum-99. Radionuclides are produced as an unavoidable side effect of nuclear and thermonuclear explosions.
Trace radionuclides are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives that are significantly shorter than the age of the Earth. Synthetic isotopes are inherently not naturally occurring on Earth, but can be created by nuclear reactions.
Uses
Radionuclides are used in two major ways: for their chemical properties and as sources of radiation. Radionuclides of familiar elements such as carbon can serve as tracers because they are chemically very similar to the non-radioactive nuclides, so most chemical, biological, and ecological processes treat them in a near identical way. One can then examine the result with a radiation detector, such as a geiger counter, to determine where the provided atoms ended up. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive. In nuclear medicine, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about a person's internal anatomy and the functioning of specific organs. This is used in some forms of tomography: single photon emission computed tomography and positron emission tomography scanning. Radioisotopes are also a promising method of treatment in hemopoietic forms of tumors, while the success for treatment of solid tumors has been limited so far. More powerful gamma sources sterilise syringes and other medical equipment. About one in two people in Western countries are likely to experience the benefits of nuclear medicine in their lifetime. In biochemistry and genetics, radionuclides label molecules and allow tracing chemical and physiological processes occurring in living organisms, such as DNA replication or amino acid transport. In food preservation, radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. In agriculture and animal husbandry, radionuclides also play an important role. They produce high intake of crops, disease and weather resistant varieties of crops, to study how fertilisers and insecticides work, and to improve the production and health of domestic animals. Industrially, and in mining, radionuclides examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels. Most household smoke detectors contain the radionuclide americium formed in nuclear reactors. Radionuclides are also used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers. Natural radionuclides are used in geology, archaeology, and paleontology to measure ages of rocks, minerals, and fossil materials.
Dangers
If radionuclides are released into the environment, through accident, poor disposal, or other means, they can potentially cause harmful effects of radioactive contamination. They can also cause damage if they are excessively used during treatment or in other ways applied to living beings. This is called radiation poisoning. Radionuclides can also cause malfunction of some electrical devices.
Summary table for classes of nuclides, "stable" and radioactive Following is a summary table for the total list of nuclides with half lives greater than one hour. Only 90 of these 905 nuclides are theoretically stable, except to proton-decay (which has never been observed). About 255 nuclides have never been observed to decay, and are classically considered stable. The remaining 650 radionuclides with half lifes longer than 1 hour, have half-lives that are well characterized. They include 27 nuclides with measured half-lives longer than the estimated age of the universe (13.7 billion years), and another 6 nuclides with half-lives long enough (> 80 million years) that they are radioactive primordial nuclides, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the solar system, about 4.6 billion years before the present. Another ~51 short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides, are known solely from artificial nuclear transmutation. Note that numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half lives. This is a summary table for the 905 nuclides with half lives longer than one hour (including those that are stable), given in list of nuclides. Note that numbers are not exact, and may change slightly in the future, as "stable" nuclides are observed to be radioactive with very long half lives.
Stability class
Theoretically stable to all but proton decay
Energetically unstable to one or more known decay modes, but no decay yet seen. Spontaneous fission possible for "stable" nuclides > niobium-93; other mechanisms possible for heavier nuclides. All considered
Number Running of total nuclides
90
165
90
255
Notes on running total Includes first 40 elements. Proton decay yet to be observed. Total of classically stable nuclides.
"stable" until decay detected.
Radioactive primordial nuclides.
33
Radioactive non-primordial, but naturally occurring on Earth.
~ 51
Radioactive synthetic (half life > 1 hour). Includes most useful radiotracers.
556
Radioactive synthetic (half life < 1 hour).
>2400
Total primordial elements include bismuth, 288 uranium, thorium, plutonium, plus all stable nuclides. Carbon-14 (and other isotopes generated by cosmic rays); ~ 339 daughters of radioactive primordials, such as francium, etc. These 905 nuclides are 905 listed in the article List of nuclides. Includes all well>3300 characterized synthetic nuclides.
List of commercially available radionuclides Gamma only Isotope
Activity Half Life
Energies (KeV)
Barium 133
1uCi
10.7 years 81.0, 356.0
Cadmium 109
1uCi
453 days
88.0
Cobalt 57
1uCi
270 days
122.1
Cobalt 60
1uCi
5.27 years 1173.2, 1332.5
Europium 152
1uCi
13.5 years 121.8, 344.3, 1408.0
Manganese 54
1uCi
312 days
Sodium-22
1uCi
2.6 years 511.0, 1274.5
Zinc 65
1uCi
244 days
Technetium 99m 1uCi
834.8 511.0, 1115.5
6.01 hours 140
Beta only Isotope
Activity Half Life Energies (KeV)
Strontium 90 0.1uCi
28.5 years 546.0
Thallium 204 1uCi
3.78 years 763.4
Carbon 14
5730 years 49.5 (average)
10uCi
Alpha only Isotope
Activity Half Life Energies (KeV)
Polonium 210 0.1uCi
138 days 5304.5
Multiple radiation emitters Isotope
Activity
Half Life Radiation Types
Caesium 137 1, 5, 10 uCi 30.1 years Gamma & Beta
Energies (KeV) G: 32, 661.6 B: 511.6, 1173.2
High level waste High level waste (HLW) is a type of nuclear waste created by the reprocessing of spent nuclear fuel. It exists in two main forms: •
First and second cycle raffinate and other waste streams created by nuclear reprocessing.
•
Waste formed by vitrification of liquid high level waste.
Liquid high level waste is typically held temporarily in underground tanks pending vitrification. Most of the high level waste created by the Manhattan project and the
weapons programs of the cold war exists in this form because funding for further processing was typically not part of the original weapons programs. Both spent nuclear fuel and vitrified waste are considered as suitable forms for long term disposal, after a period of temporary storage in the case of spent nuclear fuel. HLW contains many of the fission products and transuranic elements, generated in the reactor core and is the highest activity type of nuclear waste. HLW accounts for over 95% of the total radioactivity produced in the nuclear power process. In other words, while most nuclear waste is low-level and intermediate-level waste such as protective clothing and equipment that have been contaminated with radiation, the majority of the radioactivity produced from the nuclear power generation process becomes high-level waste. In the US, HLW from reprocessing of spent fuel from electrical power stations amounts to less than 1% of the total volume of US HLW; the rest is defence related. Some other countries, particularly France, reprocess commercial spent fuel. High level waste is very radioactive and, therefore, requires special shielding during handling and transport. It also needs cooling, because it generates a great deal of heat. Most of the heat, for the first several hundred years, is from the medium-lived fission products cesium-137 and strontium-90. A typical large nuclear reactor produces 25–30 tons of spent fuel per year. If the fuel were reprocessed and vitrified, the waste volume would be only about three cubic meters per year, but the decay heat would be almost the same. It is generally accepted that the final waste will be disposed of in a deep geological repository, and many countries have developed plans for such a site, including France, Japan, and the United States.
Definitions High-level waste is the highly radioactive waste material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations; and other highly radioactive material that is determined, consistent with existing law, to require permanent isolation. Spent (used) reactor fuel. •
Spent nuclear fuel is used fuel from a reactor that is no longer efficient in creating electricity, because its fission process has slowed due to a build-up of reaction poisons. However, it is still thermally hot, highly radioactive, and potentially harmful.
Waste materials from reprocessing.
•
Materials for nuclear weapons are acquired by reprocessing spent nuclear fuel from breeder reactors. Reprocessing is a method of chemically treating spent fuel to separate out uranium and plutonium. The byproduct of reprocessing is a highly radioactive sludge residue.
Disposing of high-level wastes High-level radioactive waste is stored temporarily in spent fuel pools and in dry cask storage facilities. In 1997, in the 20 countries which account for most of the world's nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilised. With annual additions of about 12,000 tonnes, issues for final disposal are not urgent. The status of disposal plans in various countries is described in the article High-level radioactive waste management.
Chapter- 3
Radioactive Waste
Radioactive waste is a waste product containing radioactive material. It is usually the product of a nuclear process such as nuclear fission, though industries not directly connected to the nuclear power industry may also produce radioactive waste. Radioactivity diminishes over time, so in principle the waste needs to be isolated for a period of time until it no longer poses a hazard. This can mean hours to years for some common medical or industrial radioactive wastes, or thousands of years for high-level wastes from nuclear power plants and nuclear weapons reprocessing. The majority of radioactive waste is "low-level waste", meaning it has low levels of radioactivity per mass or volume. The main approaches to managing radioactive waste to date have been segregation and storage for short-lived wastes, near-surface disposal for low and some intermediate level wastes, and deep burial or transmutation for the long-lived, high-level wastes. A summary of the amounts of radioactive wastes and management approaches for most developed countries are presented and reviewed periodically as part of the IAEA Joint Convention on Safety of Spent Fuel Management and the Safety of Radioactive Waste Management.
The nature and significance of radioactive waste Radioactive waste typically comprises a number of radioisotopes: unstable configurations of elements that decay, emitting ionizing radiation which can be harmful to humans and the environment. Those isotopes emit different types and levels of radiation, which last for different periods of time.
Physics
The radioactivity of all nuclear waste diminishes with time. All radioisotopes contained in the waste have a half-life—the time it takes for any radionuclide to lose half of its radioactivity—and eventually all radioactive waste decays into non-radioactive elements. Certain radioactive elements (such as plutonium-239) in “spent” fuel will remain hazardous to humans and other creatures for hundreds of thousands of years. Other radioisotopes remain hazardous for millions of years. Thus, these wastes must be shielded for centuries and isolated from the living environment for millennia. Some elements, such as iodine-131, have a short half-life (around 8 days in this case) and thus they will cease to be a problem much more quickly than other, longer-lived, decay products, but their activity is much greater initially. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium235. The faster a radioisotope decays, the more radioactive it will be. The energy and the type of the ionizing radiation emitted by a pure radioactive substance are important factors in deciding how dangerous it is. The chemical properties of the radioactive element will determine how mobile the substance is and how likely it is to spread into the environment and contaminate humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to a radioactive decay product leading to decay chains.
Pharmacokinetics
244
Cm
232
U
241
Actinides Pu f 250Cf
f
238
Cf
249
4n 240
Pu
f
Half-life Cm 10–30 y
Pu
f is for 69–90 y 242 Am fissile 141–351
Am
241
251
Cf
Th
Cm
243
Cmf 250Cm
239
229
233
U
246
f
230
Th
U 242 Pu 234
248
Cm
4n+1
Np 4n+2 U 244 Pu 4n+1 232 238 Th U 237
236
137
Fission products Cs 90Sr 85Kr Sm nc➔
151
f
245
4n
f
243
f
Am
431–898 5–7 ky
Pu f 8–24 ky
231
Pa
No fission product has half-life 102 to 2×105 years
32–160
126 Sn 79Se 211–290 99Tc 4n+3 340–373 Long-lived fission products 1–2 my 93Zr 135Cs nc➔
Cmf
247
235
U
f
107 Pd 129I 6–23 80 my >7% >5% >1% >.1% 0.7–12by fission product yield
Exposure to high levels of radioactive waste may cause serious harm or death. Treatment of an adult animal with radiation or some other mutation-causing effect, such as a cytotoxic anti-cancer drug, may cause cancer in the animal. In humans it has been calculated that a 5 sievert dose is usually fatal, and the lifetime risk of dying from radiation induced cancer from a single dose of 0.1 sieverts is 0.8%, increasing by the
same amount for each additional 0.1 sievert increment of dosage. Ionizing radiation causes deletions in chromosomes. If a developing organism such as an unborn child is irradiated, it is possible a birth defect may be induced, but it is unlikely this defect will be in a gamete or a gamete forming cell. The incidence of radiation-induced mutations in humans is undetermined, due to flaws in studies done to date. Depending on the decay mode and the pharmacokinetics of an element (how the body processes it and how quickly), the threat due to exposure to a given activity of a radioisotope will differ. For instance iodine-131 is a short-lived beta and gamma emitter, but because it concentrates in the thyroid gland, it is more able to cause injury than caesium-137 which, being water soluble, is rapidly excreted in urine. In a similar way, the alpha emitting actinides and radium are considered very harmful as they tend to have long biological half-lives and their radiation has a high linear energy transfer value. Because of such differences, the rules determining biological injury differ widely according to the radioisotope, and sometimes also the nature of the chemical compound which contains the radioisotope.
Sources of waste Radioactive waste comes from a number of sources. The majority of waste originates from the nuclear fuel cycle and nuclear weapons reprocessing. However, other sources include medical and industrial wastes, as well as naturally occurring radioactive materials (NORM) that can be concentrated as a result of the processing or consumption of coal, oil and gas, and some minerals, as discussed below.
Nuclear fuel cycle The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end, which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed, the fuel cycle is referred to as an open fuel cycle (or a once-through fuel cycle); if the spent fuel is reprocessed, it is referred to as a closed fuel cycle.
Fuel cycles Once-through nuclear fuel cycle
A once through (or open) fuel cycle Not a cycle per se, fuel is used once and then sent to storage without further processing save additional packaging to provide for better isolation from the biosphere. This method is favored by six countries: the United States, Canada, Sweden, Finland, Spain and South Africa. Some countries, notably Sweden and Canada, have designed repositories to permit future recovery of the material should the need arise, while others plan for permanent sequestration in a geological repository like the Yucca Mountain nuclear waste repository in the United States.
Plutonium cycle
A fuel cycle in which plutonium is used for fuel Several countries, including Japan, Switzerland, and previously Spain and Germany, are using or have used the reprocessing services offered by BNFL and COGEMA. Here, the fission products, minor actinides, activation products, and reprocessed uranium are separated from the reactor-grade plutonium, which can then be fabricated into MOX fuel. Because the proportion of the non-fissile even-mass isotopes of plutonium rises with each pass through the cycle, there are currently no plans to reuse plutonium from used MOX fuel for a third pass in a thermal reactor. However, if fast reactors become available, they may be able to burn these, or almost any other actinide isotopes.
Minor actinides recycling It has been proposed that in addition to the use of plutonium, the minor actinides could be used in a critical power reactor. Tests are already being conducted in which americium is being used as a fuel. A number of reactor designs, like the Integral Fast Reactor, have been designed for this rather different fuel cycle. In principle, it should be possible to derive energy from the fission of any actinide nucleus. With a careful reactor design, all the actinides in the fuel can be consumed, leaving only lighter elements with short half-lives. Whereas this has been done in prototype plants, no such reactor has ever been operated on a large scale, and the first plants with full actinide recovery are expected to be ready for commercial deployment in 2015 at the earliest. However, such schemes would most likely require advanced remote reprocessing methods due to the neutron emitting compounds formed. For instance if curium is irradiated with neutrons it will form the very heavy actinides californium and fermium which undergo spontaneous fission. As a result, the neutron emission from a used fuel element which had included curium will be much higher, potentially posing a risk to workers at the back end of the cycle unless all reprocessing is done remotely. This could be seen as a disadvantage, but on the other hand it also makes the nuclear material difficult to steal or divert, making it more resistant to nuclear proliferation It so happens that the neutron cross-section of many actinides decreases with increasing neutron energy, but the ratio of fission to simple activation (neutron capture) changes in favour of fission as the neutron energy increases. Thus with a sufficiently high neutron energy, it should be possible to destroy even curium without the generation of the transcurium metals. This could be very desirable as it would make it significantly easier to reprocess and handle the actinide fuel. One promising alternative from this perspective is an accelerator driven subcritical reactor. Here a beam of either protons (United States and European designs) or electrons (Japanese design) is directed into a target. In the case of protons, very fast neutrons will spall off the target, while in the case of the electrons, very high energy photons will be generated. These high-energy neutrons and photons will then be able to cause the fission of the heavy actinides. Such reactors compare very well to other neutron sources in terms of neutron energy: • • • • • • •
Thermal 0 to 100 eV Epithermal 100 eV to 100 KeV Fast (from nuclear fission) 100 KeV to 3 MeV DD fusion 2.5 MeV DT fusion 14 MeV Accelerator driven core 200 MeV (lead driven by 1.6 GeV protons) Muon-catalyzed fusion 7 GeV.
As an alternative, the curium-244, with a half life of 18 years, could be left to decay into plutonium-240 before being used in fuel in a fast reactor.
A pair of fuel cycles in which uranium and plutonium are kept separate from the minor actinides. The minor actinide cycle is kept within the green box. Fuel or targets for this actinide transmutation To date the nature of the fuel (targets) for actinide transformation has not been chosen. If actinides are transmuted in a Subcritical reactor it is likely that the fuel will have to be able to tolerate more thermal cycles than conventional fuel. An accelerator driven sub critical reactor is unlikely to be able to maintain a constant operation period for equally long times as a critical reactor, and each time the accelerator stops then the fuel will cool down. On the other hand, if actinides are destroyed using a fast reactor, such as an Integral Fast Reactor, then the fuel will most likely not be exposed to many more thermal cycles than in a normal power station. Depending on the matrix the process can generate more transuranics from the matrix. This could either be viewed as good (generate more fuel) or can be viewed as bad (generation of more radiotoxic transuranic elements). A series of different matrices exist which can control this production of heavy actinides. Fissile nuclei, like Uranium-235, Plutonium-239 and Uranium-233 respond well to delayed neutrons and are thus important to keep a critical reactor stable, and this limits the amount of minor actinides that can be destroyed in a critical reactor. As a consequence it is important that the chosen matrix allows the reactor to keep the ratio of
fissile to non-fissile nuclei high, as this enables it to destroy the long lived actinides safely. In contrast, the power output of a sub-critical reactor is limited by the intensity of the driving particle accelerator, and thus it need not contain any uranium or plutonium at all. In such a system it may be preferable to have an inert matrix that doesn't produce additional long-lived isotopes.
Actinides in an inert matrix The actinides will be mixed with a metal which will not form more actinides, for instance an alloy of actinides in a solid such as zirconia could be used.
Actinides in a thorium matrix Thorium will on neutron bombardment form uranium-233. U-233 is fissile, and has a larger fission cross section than both U-235 and U-238, and thus it is likely to produce very little additional actinides through neutron capture.
Actinides in a uranium matrix If the actinides are incorporated into a uranium-metal or uranium-oxide matrix, then the neutron capture of U-238 is likely to generate new plutonium-239. An advantage of mixing the actinides with uranium and plutonium is that the large fission cross sections of U-235 and Pu-239 for the less energetic delayed-neutrons could make the reaction stable enough to be carried out in a critical fast reactor, which is likely to be both cheaper and simpler than an accelerator driven system.
Mixed matrix It is also possible to create a matrix made from a mix of the above mentioned materials. This is most commonly done in fast reactors where one may wish to keep the breeding ratio of new fuel high enough to keep powering the reactor, but still low enough that the generated actinides can be safely destroyed without transporting them to another site. One way to do this is to use fuel where actinides and uranium is mixed with inert zirconium, producing fuel elements with the desired properties.
Thorium cycle In the thorium fuel cycle thorium-232 absorbs a neutron in either a fast or thermal reactor. The thorium-233 beta decays to protactinium-233 and then to uranium-233, which in turn is used as fuel. Hence, like uranium-238, thorium-232 is a fertile material. After starting the reactor with existing U-233 or some other fissile material such as U-235 or Pu-239, a breeding cycle similar to but more efficient than that with U-238 and plutonium can be created. The Th-232 absorbs a neutron to become Th-233 which quickly decays to protactinium-233. Protactinium-233 in turn decays with a half-life of 27 days to U-233. In some molten salt reactor designs, the Pa-233 is extracted and
protected from neutrons (which could transform it to Pa-234 and then to U-234), until it has decayed to U-233. This is done in order to improve the breeding ratio which is low compared to fast reactors. Thorium is at least 4-5 times more abundant in nature than all of uranium isotopes combined; thorium is fairly evenly spread around Earth with a lot of countries having huge supplies of it; preparation of thorium fuel does not require difficult and expensive enrichment processes; the thorium fuel cycle creates mainly Uranium-233 contaminated with Uranium-232 which makes it harder to use in a nuclear weapon; elimination of at least the transuranic portion of the nuclear waste problem is possible in MSR and other breeder reactor designs. One of the earliest efforts to use a thorium fuel cycle took place at Oak Ridge National Laboratory in the 1960s. An experimental reactor was built based on molten salt reactor technology to study the feasibility of such an approach, using thorium fluoride salt kept hot enough to be liquid, thus eliminating the need for fabricating fuel elements. This effort culminated in the Molten-Salt Reactor Experiment that used 232Th as the fertile material and 233U as the fissile fuel. Due to a lack of funding, the MSR program was discontinued in 1976.
Current industrial activity Currently the only isotopes used as nuclear fuel are uranium-235 (U-235), uranium-238 (U-238) and plutonium-239, although the proposed thorium fuel cycle has advantages. Some modern reactors, with minor modifications, can use thorium. Thorium is approximately three times more abundant in the Earth's crust than uranium (and 550 times more abundant than uranium-235). However, there has been little exploration for thorium resources, and thus the proved resource is small. Thorium is more plentiful than uranium in some countries, notably India. Heavy water reactors and graphite-moderated reactors can use natural uranium, but the vast majority of the world's reactors require enriched uranium, in which the ratio of U235 to U-238 is increased. In civilian reactors the enrichment is increased to as much as 5% U-235 and 95% U-238, but in naval reactors there is as much as 93% U-235. The term nuclear fuel is not normally used in respect to fusion power, which fuses isotopes of hydrogen into helium to release energy. Front end Waste from the front end of the nuclear fuel cycle is usually alpha emitting waste from the extraction of uranium. It often contains radium and its decay products. Uranium dioxide (UO2) concentrate from mining is not very radioactive - only a thousand or so times as radioactive as the granite used in buildings. It is refined from yellowcake (U3O8), then converted to uranium hexafluoride gas (UF6). As a gas, it undergoes
enrichment to increase the U-235 content from 0.7% to about 4.4% (LEU). It is then turned into a hard ceramic oxide (UO2) for assembly as reactor fuel elements. The main by-product of enrichment is depleted uranium (DU), principally the U-238 isotope, with a U-235 content of ~0.3%. It is stored, either as UF6 or as U3O8. Some is used in applications where its extremely high density makes it valuable, such as the keels of yachts, and anti-tank shells. It is also used with plutonium for making mixed oxide fuel (MOX) and to dilute, or downblend, highly enriched uranium from weapons stockpiles which is now being redirected to become reactor fuel. Back end The back end of the nuclear fuel cycle, mostly spent fuel rods, contains fission products that emit beta and gamma radiation, and actinides that emit alpha particles, such as uranium-234, neptunium-237, plutonium-238 and americium-241, and even sometimes some neutron emitters such as californium (Cf). These isotopes are formed in nuclear reactors. It is important to distinguish the processing of uranium to make fuel from the reprocessing of used fuel. Used fuel contains the highly radioactive products of fission. Many of these are neutron absorbers, called neutron poisons in this context. These eventually build up to a level where they absorb so many neutrons that the chain reaction stops, even with the control rods completely removed. At that point the fuel has to be replaced in the reactor with fresh fuel, even though there is still a substantial quantity of uranium-235 and plutonium present. In the United States, this used fuel is stored, while in countries such as Russia, the United Kingdom, France, Japan and India, the fuel is reprocessed to remove the fission products, and the fuel can then be re-used. This reprocessing involves handling highly radioactive materials, and the fission products removed from the fuel are a concentrated form of high-level waste as are the chemicals used in the process. While these countries reprocess the fuel carrying out single plutonium cycles, India is the only country known to be planning multiple plutonium recycling schemes. Fuel composition and long term radioactivity
Activity of U-233 for three fuel types
Total activity for three fuel types Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for spent nuclear fuel (SNF). When looking at long term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different. An example of this effect is the use of nuclear fuels with thorium. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting
in the production of fissile U-233. The SNF of a cycle with thorium will contain U-233, an isotope with a half-life of maximum 20 years. Its radioactive decay will strongly influence the long-term activity curve of the SNF around 1 million years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right. The burnt fuels are thorium with reactor-grade plutonium (RGPu), thorium with weapons-grade plutonium (WGPu) and Mixed Oxide fuel (MOX). For RGPu and WGPu, the initial amount of U-233 and its decay around 1 million years can be seen. This has an effect in the total activity curve of the three fuel types. The absence of U-233 and its daughter products in the MOX fuel results in a lower activity in region 3 of the figure on the bottom right, whereas for RGPu and WGPu the curve is maintained higher due to the presence of U-233 that has not fully decayed. The use of different fuels in nuclear reactors results in different SNF composition, with varying activity curves. Proliferation concerns Since uranium and plutonium are nuclear weapons materials, there have been proliferations concerns. Ordinarily (in spent nuclear fuel), plutonium is reactor-grade plutonium. In addition to plutonium-239, which is highly suitable for building nuclear weapons, it contains large amounts of undesirable contaminants: plutonium-240, plutonium-241, and plutonium-238. These isotopes are difficult to separate, and more cost-effective ways of obtaining fissile material exist (e.g. uranium enrichment or dedicated plutonium production reactors). High-level waste is full of highly radioactive fission products, most of which are relatively short-lived. This is a concern since if the waste is stored, perhaps in deep geological storage, over many years the fission products decay, decreasing the radioactivity of the waste and making the plutonium easier to access. The undesirable contaminant Pu-240 decays faster than the Pu-239, and thus the quality of the bomb material increases with time (although its quantity decreases during that time as well). Thus, some have argued, as time passes, these deep storage areas have the potential to become "plutonium mines", from which material for nuclear weapons can be acquired with relatively little difficulty. Critics of the latter idea point out that the half-life of Pu240 is 6,560 years and Pu-239 is 24,110 years, and thus the relative enrichment of one isotope to the other with time occurs with a half-life of 9,000 years (that is, it takes 9000 years for the fraction of Pu-240 in a sample of mixed plutonium isotopes, to spontaneously decrease by half—a typical enrichment needed to turn reactor-grade into weapons-grade Pu). Thus "weapons grade plutonium mines" would be a problem for the very far future (>9,000 years from now), so that there remains a great deal of time for technology to advance to solve it. Pu-239 decays to U-235 which is suitable for weapons and which has a very long half life (roughly 109 years). Thus plutonium may decay and leave uranium-235. However,
modern reactors are only moderately enriched with U-235 relative to U-238, so the U-238 continues to serve as a denaturation agent for any U-235 produced by plutonium decay. One solution to this problem is to recycle the plutonium and use it as a fuel e.g. in fast reactors. But in the minds of some, the very existence of the nuclear fuel reprocessing plant needed to separate the plutonium from the other elements represents a proliferation concern. In pyrometallurgical fast reactors, the separated plutonium and uranium are contaminated by actinides and cannot be used for nuclear weapons.
Nuclear weapons decommissioning Waste from nuclear weapons decommissioning is unlikely to contain much beta or gamma activity other than tritium and americium. It is more likely to contain alphaemitting actinides such as Pu-239 which is a fissile material used in bombs, plus some material with much higher specific activities, such as Pu-238 or Po. In the past the neutron trigger for an atomic bomb tended to be beryllium and a high activity alpha emitter such as polonium; an alternative to polonium is Pu-238. For reasons of national security, details of the design of modern bombs are normally not released to the open literature. Some designs might contain a radioisotope thermoelectric generator using Pu-238 to provide a long lasting source of electrical power for the electronics in the device. It is likely that the fissile material of an old bomb which is due for refitting will contain decay products of the plutonium isotopes used in it, these are likely to include U-236 from Pu-240 impurities, plus some U-235 from decay of the Pu-239; due to the relatively long half-life of these Pu isotopes, these wastes from radioactive decay of bomb core material would be very small, and in any case, far less dangerous (even in terms of simple radioactivity) than the Pu-239 itself. The beta decay of Pu-241 forms Am-241; the in-growth of americium is likely to be a greater problem than the decay of Pu-239 and Pu-240 as the americium is a gamma emitter (increasing external-exposure to workers) and is an alpha emitter which can cause the generation of heat. The plutonium could be separated from the americium by several different processes; these would include pyrochemical processes and aqueous/organic solvent extraction. A truncated PUREX type extraction process would be one possible method of making the separation.
Legacy waste Due to historic activities typically related to radium industry, uranium mining, and military programs, there are numerous sites that contain or are contaminated with radioactivity. In the United States alone, the Department of Energy states there are "millions of gallons of radioactive waste" as well as "thousands of tons of spent nuclear fuel and material" and also "huge quantities of contaminated soil and water." Despite
copious quantities of waste, the DOE has stated a goal of cleaning all presently contaminated sites successfully by 2025. The Fernald, Ohio site for example had "31 million pounds of uranium product", "2.5 billion pounds of waste", "2.75 million cubic yards of contaminated soil and debris", and a "223 acre portion of the underlying Great Miami Aquifer had uranium levels above drinking standards." The United States has at least 108 sites designated as areas that are contaminated and unusable, sometimes many thousands of acres. DOE wishes to clean or mitigate many or all by 2025, however the task can be difficult and it acknowledges that some may never be completely remediated. In just one of these 108 larger designations, Oak Ridge National Laboratory, there were for example at least "167 known contaminant release sites" in one of the three subdivisions of the 37,000-acre (150 km2) site. Some of the U.S. sites were smaller in nature, however, cleanup issues were simpler to address, and DOE has successfully completed cleanup, or at least closure, of several sites. It is a common misconception that nuclear waste has to be stored in a cave after its 20year decommissioning process.
Medical Radioactive medical waste tends to contain beta particle and gamma ray emitters. It can be divided into two main classes. In diagnostic nuclear medicine a number of short-lived gamma emitters such as technetium-99m are used. Many of these can be disposed of by leaving it to decay for a short time before disposal as normal waste. Other isotopes used in medicine, with half-lives in parentheses, include: • • • • • •
Y-90, used for treating lymphoma (2.7 days) I-131, used for thyroid function tests and for treating thyroid cancer (8.0 days) Sr-89, used for treating bone cancer, intravenous injection (52 days) Ir-192, used for brachytherapy (74 days) Co-60, used for brachytherapy and external radiotherapy (5.3 years) Cs-137, used for brachytherapy, external radiotherapy (30 years)
Nuclear waste is perfectly safe and ready to reuse within 20 years.
Industrial Industrial source waste can contain alpha, beta, neutron or gamma emitters. Gamma emitters are used in radiography while neutron emitting sources are used in a range of applications, such as oil well logging.
Naturally occurring radioactive material (NORM) Processing of substances containing "natural" radioactivity is often known as NORM. A lot of this waste is alpha particle-emitting matter from the decay chains of uranium and thorium. The main source of radiation in the human body is potassium-40 (40K). Most rocks, due to their components, have a certain, but low level, of radioactivity.
Coal Coal contains a small amount of radioactive uranium, barium, thorium and potassium, but, in the case of pure coal, this is significantly less than the average concentration of those elements in the Earth's crust. The surrounding strata, if shale or mudstone, often contain slightly more than average and this may also be reflected in the ash content of 'dirty' coals. The more active ash minerals become concentrated in the fly ash precisely because they do not burn well. The radioactivity of fly ash is about the same as black shale and is less than phosphate rocks, but is more of a concern because a small amount of the fly ash ends up in the atmosphere where it can be inhaled. Oil and gas Residues from the oil and gas industry often contain radium and its daughters. The sulfate scale from an oil well can be very radium rich, while the water, oil and gas from a well often contain radon. The radon decays to form solid radioisotopes which form coatings on the inside of pipework. In an oil processing plant the area of the plant where propane is processed is often one of the more contaminated areas of the plant as radon has a similar boiling point to propane.
Types of radioactive waste
Removal of very low-level waste Although not significantly radioactive, uranium mill tailings are waste. They are byproduct material from the rough processing of uranium-bearing ore. They are sometimes referred to as 11(e)2 wastes, from the section of the U.S. Atomic Energy Act that defines them. Uranium mill tailings typically also contain chemically hazardous heavy metals such as lead and arsenic. Vast mounds of uranium mill tailings are left at many old mining sites, especially in Colorado, New Mexico, and Utah. Low level waste (LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters, etc., which contain small amounts of mostly short-lived radioactivity. Commonly, LLW is designated as such as a precautionary measure if it originated from any region of an 'Active Area', which frequently includes offices with only a remote possibility of being contaminated with radioactive materials. Such LLW typically exhibits no higher radioactivity than one would expect from the same material disposed of in a non-active area, such as a normal office block. Some high activity LLW requires shielding during handling and transport but most LLW is suitable for shallow land burial. To reduce its volume, it is often compacted or incinerated before disposal. Low level waste is divided into four classes, class A, B, C and GTCC, which means "Greater Than Class C". Intermediate level waste (ILW) contains higher amounts of radioactivity and in some cases requires shielding. ILW includes resins, chemical sludge and metal reactor fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. As a general rule, short-lived waste (mainly non-fuel materials from reactors) is buried in shallow repositories, while longlived waste (from fuel and fuel-reprocessing) is deposited in deep underground facilities. U.S. regulations do not define this category of waste; the term is used in Europe and elsewhere.
Spent Fuel Flasks are transported by railway in the United Kingdom. Each flask is constructed of 14 in (360 mm) thick solid steel and weighs in excess of 50 tons High level waste (HLW) is produced by nuclear reactors. It contains fission products and transuranic elements generated in the reactor core. It is highly radioactive and often thermally hot. HLW accounts for over 95% of the total radioactivity produced in the
process of nuclear electricity generation. The amount of HLW worldwide is currently increasing by about 12,000 metric tons every year, which is the equivalent to about 100 double-decker buses or a two-story structure with a footprint the size of a basketball court. A 1000-MWe nuclear power plant produces about 27 tonnes of spent nuclear fuel (unreprocessed) every year. Transuranic waste (TRUW) as defined by U.S. regulations is, without regard to form or origin, waste that is contaminated with alpha-emitting transuranic radionuclides with half-lives greater than 20 years, and concentrations greater than 100 nCi/g (3.7 MBq/kg), excluding High Level Waste. Elements that have an atomic number greater than uranium are called transuranic ("beyond uranium"). Because of their long half-lives, TRUW is disposed more cautiously than either low level or intermediate level waste. In the US it arises mainly from weapons production, and consists of clothing, tools, rags, residues, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium). Under US law, transuranic waste is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of radiation dose measured at the surface of the waste container. CH TRUW has a surface dose rate not greater than 200 mrem per hour (2 mSv/h), whereas RH TRUW has a surface dose rate of 200 mrem per hour (2 mSv/h) or greater. CH TRUW does not have the very high radioactivity of high level waste, nor its high heat generation, but RH TRUW can be highly radioactive, with surface dose rates up to 1000000 mrem per hour (10000 mSv/h). The US currently permanently disposes of TRUW generated from nuclear power plants and military facilities at the Waste Isolation Pilot Plant.
Management of waste
Modern medium to high level transport container for nuclear waste. Of particular concern in nuclear waste management are two long-lived fission products, Tc-99 (half-life 220,000 years) and I-129 (half-life 17 million years), which dominate spent fuel radioactivity after a few thousand years. The most troublesome transuranic elements in spent fuel are Np-237 (half-life two million years) and Pu-239 (half life 24,000 years). Nuclear waste requires sophisticated treatment and management to successfully isolate it from interacting with the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving storage, disposal or transformation of the waste into a non-toxic form. Governments around the world are considering a range of waste management and disposal options, though there has been limited progress toward long-term waste management solutions.
Initial treatment of waste Vitrification
A vitrification experiment for the study of nuclear waste disposal Long-term storage of radioactive waste requires the stabilization of the waste into a form which will neither react nor degrade for extended periods of time. One way to do this is through vitrification. Currently at Sellafield the high-level waste (PUREX first cycle raffinate) is mixed with sugar and then calcined. Calcination involves passing the waste through a heated, rotating tube. The purposes of calcination are to evaporate the water from the waste, and de-nitrate the fission products to assist the stability of the glass produced. The 'calcine' generated is fed continuously into an induction heated furnace with fragmented glass. The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies. This product, as a melt, is poured into
stainless steel cylindrical containers ("cylinders") in a batch process. When cooled, the fluid solidifies ("vitrifies") into the glass. Such glass, after being formed, is highly resistant to water. After filling a cylinder, a seal is welded onto the cylinder. The cylinder is then washed. After being inspected for external contamination, the steel cylinder is stored, usually in an underground repository. In this form, the waste products are expected to be immobilized for a long period of time (many thousands of years). The glass inside a cylinder is usually a black glossy substance. All this work (in the United Kingdom) is done using hot cell systems. The sugar is added to control the ruthenium chemistry and to stop the formation of the volatile RuO4 containing radio ruthenium. In the west, the glass is normally a borosilicate glass (similar to Pyrex), while in the former Soviet bloc it is normal to use a phosphate glass. The amount of fission products in the glass must be limited because some (palladium, the other Pt group metals, and tellurium) tend to form metallic phases which separate from the glass. Bulk vitrification uses electrodes to melt soil and wastes, which are then buried underground. In Germany a vitrification plant is in use; this is treating the waste from a small demonstration reprocessing plant which has since been closed down. Ion exchange It is common for medium active wastes in the nuclear industry to be treated with ion exchange or other means to concentrate the radioactivity into a small volume. The much less radioactive bulk (after treatment) is often then discharged. For instance, it is possible to use a ferric hydroxide floc to remove radioactive metals from aqueous mixtures. After the radioisotopes are absorbed onto the ferric hydroxide, the resulting sludge can be placed in a metal drum before being mixed with cement to form a solid waste form. In order to get better long-term performance (mechanical stability) from such forms, they may be made from a mixture of fly ash, or blast furnace slag, and Portland cement, instead of normal concrete (made with Portland cement, gravel and sand). Synroc The Australian Synroc (synthetic rock) is a more sophisticated way to immobilize such waste, and this process may eventually come into commercial use for civil wastes (it is currently being developed for US military wastes). Synroc was invented by the late Prof Ted Ringwood (a geochemist) at the Australian National University. The Synroc contains pyrochlore and cryptomelane type minerals. The original form of Synroc (Synroc C) was designed for the liquid high level waste (PUREX raffinate) from a light water reactor. The main minerals in this Synroc are hollandite (BaAl2Ti6O16), zirconolite (CaZrTi2O7) and perovskite (CaTiO3). The zirconolite and perovskite are hosts for the actinides. The strontium and barium will be fixed in the perovskite. The caesium will be fixed in the hollandite.
Long term management of waste
The time frame in question when dealing with radioactive waste ranges from 10,000 to 1,000,000 years, according to studies based on the effect of estimated radiation doses. Researchers suggest that forecasts of health detriment for such periods should be examined critically. Practical studies only consider up to 100 years as far as effective planning and cost evaluations are concerned. Long term behavior of radioactive wastes remains a subject for ongoing research projects. Geologic disposal The process of selecting appropriate deep final repositories for high level waste and spent fuel is now under way in several countries (Schacht Asse II and the Waste Isolation Pilot Plant) with the first expected to be commissioned some time after 2010. The basic concept is to locate a large, stable geologic formation and use mining technology to excavate a tunnel, or large-bore tunnel boring machines (similar to those used to drill the Channel Tunnel from England to France) to drill a shaft 500–1,000 meters below the surface where rooms or vaults can be excavated for disposal of high-level radioactive waste. The goal is to permanently isolate nuclear waste from the human environment. Many people remain uncomfortable with the immediate stewardship cessation of this disposal system, suggesting perpetual management and monitoring would be more prudent. Because some radioactive species have half-lives longer than one million years, even very low container leakage and radionuclide migration rates must be taken into account. Moreover, it may require more than one half-life until some nuclear materials lose enough radioactivity to cease being lethal to living things. A 1983 review of the Swedish radioactive waste disposal program by the National Academy of Sciences found that country’s estimate of several hundred thousand years—perhaps up to one million years— being necessary for waste isolation “fully justified.” Storing high level nuclear waste above ground for a century or so is considered appropriate by many scientists. This allows the material to be more easily observed and any problems detected and managed, while decay of radionuclides over this time period significantly reduces the level of radioactivity and associated harmful effects to the container material. It is also considered likely that over the next century newer materials will be developed which will not break down as quickly when exposed to a high neutron flux, thus increasing the longevity of the container once it is permanently buried. Sea-based options for disposal of radioactive waste include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the Earth's mantle, and burial beneath a remote natural or human-made island. While these approaches all have merit and would facilitate an international solution to the problem of disposal of radioactive waste, they would require an amendment of the Law of the Sea.
Article 1 (Definitions), 7., of the 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, (the London Dumping Convention) states: “Sea” means all marine waters other than the internal waters of States, as well as the seabed and the subsoil thereof; it does not include sub-seabed repositories accessed only from land.” The proposed land-based subductive waste disposal method disposes of nuclear waste in a subduction zone accessed from land, and therefore is not prohibited by international agreement. This method has been described as the most viable means of disposing of radioactive waste, and as the state-of-the-art in nuclear waste disposal technology. Another approach termed Remix & Return would blend high-level waste with uranium mine and mill tailings down to the level of the original radioactivity of the uranium ore, then replace it in inactive uranium mines. This approach has the merits of providing jobs for miners who would double as disposal staff, and of facilitating a cradle-to-grave cycle for radioactive materials, but would be inappropriate for spent reactor fuel in the absence of reprocessing, due to the presence in it of highly toxic radioactive elements such as plutonium. Deep borehole disposal is the concept of disposing of high-level radioactive waste from nuclear reactors in extremely deep boreholes. Deep borehole disposal seeks to place the waste as much as five kilometers beneath the surface of the Earth and relies primarily on the immense natural geological barrier to confine the waste safely and permanently so that it should never pose a threat to the environment. Transmutation There have been proposals for reactors that consume nuclear waste and transmute it to other, less-harmful nuclear waste. In particular, the Integral Fast Reactor was a proposed nuclear reactor with a nuclear fuel cycle that produced no transuranic waste and in fact, could consume transuranic waste. It proceeded as far as large-scale tests, but was then canceled by the US Government. Another approach, considered safer but requiring more development, is to dedicate subcritical reactors to the transmutation of the left-over transuranic elements. An isotope that is found in nuclear waste and that represents a concern in terms of proliferation is Pu-239. The estimated world total of plutonium in the year 2000 was of 1,645 MT, of which 210 MT had been separated by reprocessing. The large stock of plutonium is a result of its production inside uranium-fueled reactors and of the reprocessing of weapons-grade plutonium during the weapons program. An option for getting rid of this plutonium is to use it as a fuel in a traditional Light Water Reactor (LWR). Several fuel types with differing plutonium destruction efficiencies are under study.
Transmutation was banned in the US in April 1977 by President Carter due to the danger of plutonium proliferation, but President Reagan rescinded the ban in 1981. Due to the economic losses and risks, construction of reprocessing plants during this time did not resume. Due to high energy demand, work on the method has continued in the EU. This has resulted in a practical nuclear research reactor called Myrrha in which transmutation is possible. Additionally, a new research program called ACTINET has been started in the EU to make transmutation possible on a large, industrial scale. According to President Bush's Global Nuclear Energy Partnership (GNEP) of 2007, the US is now actively promoting research on transmutation technologies needed to markedly reduce the problem of nuclear waste treatment. There have also been theoretical studies involving the use of fusion reactors as so called "actinide burners" where a fusion reactor plasma such as in a tokamak, could be "doped" with a small amount of the "minor" transuranic atoms which would be transmuted (meaning fissioned in the actinide case) to lighter elements upon their successive bombardment by the very high energy neutrons produced by the fusion of deuterium and tritium in the reactor. A study at MIT found that only 2 or 3 fusion reactors with parameters similar to that of the International Thermonuclear Experimental Reactor (ITER) could transmute the entire annual minor actinide production from all of the light water reactors presently operating in the United States fleet while simultaneously generating approximately 1 gigawatt of power from each reactor. Re-use of waste Another option is to find applications for the isotopes in nuclear waste so as to re-use them. Already, caesium-137, strontium-90 and a few other isotopes are extracted for certain industrial applications such as food irradiation and radioisotope thermoelectric generators. While re-use does not eliminate the need to manage radioisotopes, it reduces the quantity of waste produced. The Nuclear Assisted Hydrocarbon Production Method, Canadian patent application 2,659,302, is a method for the temporary or permanent storage of nuclear waste materials comprising the placing of waste materials into one or more repositories or boreholes constructed into an unconventional oil formation. The thermal flux of the waste materials fracture the formation, alters the chemical and/or physical properties of hydrocarbon material within the subterranean formation to allow removal of the altered material. A mixture of hydrocarbons, hydrogen, and/or other formation fluids are produced from the formation. The radioactivity of high-level radioactive waste affords proliferation resistance to plutonium placed in the periphery of the repository or the deepest portion of a borehole. A 1990 proposed type of breeder reactor called a traveling wave reactor is claimed, if it were to be built, to be able to be fueled by depleted uranium, which is currently considered nuclear waste. Space disposal
Space disposal is an attractive notion because it permanently removes nuclear waste from the environment. It has significant disadvantages, not least of which is the potential for catastrophic failure of a launch vehicle which would spread radioactive material into the atmosphere and around the world. The high number of launches that would be required — because no individual rocket would be able to carry very much of the material relative to the material needed to be disposed of—makes the proposal impractical (for both economic and risk-based reasons). To further complicate matters, international agreements on the regulation of such a program would need to be established. In the future, alternative, non-rocket spacelaunch technologies may provide a solution. It has been suggested that through the use of a stationary launch system many of the risks of catastrophic launch failure could be avoided. A promising concept is the use of high power lasers to launch "indestructible" containers from the ground into space. Such a system would require no rocket propellant, with the launch vehicle's payload making up a near entirety of the vehicle's mass. Without the use of rocket fuel on board there would be little chance of the vehicle exploding.
National management plans Most countries are considerably ahead of the United States in developing plans for highlevel radioactive waste disposal. Sweden and Finland are furthest along in committing to a particular disposal technology, while many others reprocess spent fuel or contract with France or Great Britain to do it, taking back the resulting plutonium and high-level waste. “An increasing backlog of plutonium from reprocessing is developing in many countries... It is doubtful that reprocessing makes economic sense in the present environment of cheap uranium.” In many European countries (e.g., Britain, Finland, the Netherlands, Sweden and Switzerland) the risk or dose limit for a member of the public exposed to radiation from a future high-level nuclear waste facility is considerably more stringent than that suggested by the International Commission on Radiation Protection or proposed in the United States. European limits are often more stringent than the standard suggested in 1990 by the International Commission on Radiation Protection by a factor of 20, and more stringent by a factor of ten than the standard proposed by the US Environmental Protection Agency (EPA) for Yucca Mountain nuclear waste repository for the first 10,000 years after closure. Moreover, the U.S. EPA’s proposed standard for greater than 10,000 years is 250 times more permissive than the European limit.
Illegal dumping Authorities in Italy are investigating a 'Ndrangheta mafia clan accused of trafficking and illegally dumping nuclear waste. According to a turncoat, a manager of the Italy’s state energy research agency Enea paid the clan to get rid of 600 drums of toxic and radioactive waste from Italy, Switzerland, France, Germany, and the US, with Somalia as the destination, where the waste was buried after buying off local politicians. Former employees of Enea are suspected of paying the criminals to take waste off their hands in
the 1980s and 1990s. Shipments to Somalia continued into the 1990s, while the 'Ndrangheta clan also blew up shiploads of waste, including radioactive hospital waste, and sending them to the sea bed off the Calabrian coast. According to the environmental group Legambiente, former members of the 'Ndrangheta have said that they were paid to sink ships with radioactive material for the last 20 years.
Accidents involving radioactive waste A number of incidents have occurred when radioactive material was disposed of improperly, shielding during transport was defective, or when it was simply abandoned or even stolen from a waste store. In the Soviet Union, waste stored in Lake Karachay was blown over the area during a dust storm after the lake had partly dried out. At Maxey Flat, a low-level radioactive waste facility located in Kentucky, containment trenches covered with dirt, instead of steel or cement, collapsed under heavy rainfall into the trenches and filled with water. The water that invaded the trenches became radioactive and had to be disposed of at the Maxey Flat facility itself. In other cases of radioactive waste accidents, lakes or ponds with radioactive waste accidentally overflowed into the rivers during exceptional storms. In Italy, several radioactive waste deposits let material flow into river water, thus contaminating water for domestic use. In France, in the summer of 2008 numerous incidents happened; in one, at the Areva plant in Tricastin, it was reported that during a draining operation, liquid containing untreated uranium overflowed out of a faulty tank and about 75 kg of the radioactive material seeped into the ground and, from there, into two rivers nearby; in another case, over 100 staff were contaminated with low doses of radiation. Scavenging of abandoned radioactive material has been the cause of several other cases of radiation exposure, mostly in developing nations, which may have less regulation of dangerous substances (and sometimes less general education about radioactivity and its hazards) and a market for scavenged goods and scrap metal. The scavengers and those who buy the material are almost always unaware that the material is radioactive and it is selected for its aesthetics or scrap value. Irresponsibility on the part of the radioactive material's owners, usually a hospital, university or military, and the absence of regulation concerning radioactive waste, or a lack of enforcement of such regulations, have been significant factors in radiation exposures. For an example of an accident involving radioactive scrap originating from a hospital see the Goiânia accident. Transportation accidents involving spent nuclear fuel from power plants are unlikely to have serious consequences due to the strength of the spent nuclear fuel shipping casks.
Chapter- 4
Nuclear Fallout
Fallout is the residual radiation hazard from a nuclear explosion, so called because it "falls out" of the atmosphere after the explosion. It commonly refers to the radioactive dust created when a nuclear weapon explodes. This radioactive dust, consisting of hot particles, is a kind of radioactive contamination. It can lead to the contamination of ground and the animal food chain.
Types There are many types of fallout, ranging from the global type to the more area-restricted types of fallout.
Worldwide After an air burst, fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a fine suspension of small particles 10 nm to 20 µm in diameter. These particles may be quickly drawn up into the stratosphere, particularly if the explosive yield exceeds 10 kt.
Atmospheric nuclear weapon tests almost doubled the concentration of radioactive 14C in the Northern Hemisphere, before levels slowly declined following the Partial Test Ban Treaty. Initially little was known about the dispersion of nuclear fallout on a global scale. The AEC assumed that fallout would be dispersed evenly across the globe by atmospheric winds and gradually settle to the Earth's surface after weeks, months, and even years as worldwide fallout. Nuclear products were deposited in the Northern Hemisphere becoming "far more dangerous than they had originally been estimated." The radio-biological hazard of worldwide fallout is essentially a long-term one because of the potential accumulation of long-lived radioisotopes (such as strontium-90 and caesium-137) in the body as a result of ingestion of foods containing the radioactive materials. This hazard is less serious than local fallout, which is of much greater immediate operational concern.
Local In a land or water surface burst, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it condenses with fission products and other radiocontaminants that have become neutronactivated. Most of the isotopes in the table below mostly decay into the isotopes that
many people are more familiar with. Some radiation would taint large amounts of land and drinking water causing formal mutations throughout animal and human life.
The roughly 280 mile long fallout plume from 15 Mt shot Castle Bravo, ca. 1954 Table (according to T. Imanaka et al.) of the relative abilities of isotopes to form solids Isotope
Refractory index
91
Sr
0.2
92
Sr
1.0
Zr
1.0
Mo
1.0
95 99
106
Ru
0.0
131
Sb
0.1
132
Te
0.0
134
Te
0.0
137
Cs
0.0
140
Ba
0.3
141
La
0.7
144
Ce
1.0
Per capita thyroid doses in the continental United States resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site from 19511962. A surface burst generates large amounts of particulate matter, composed of particles from less than 100 nm to several millimeters in diameter—in addition to very fine particles that contribute to worldwide fallout. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, so fallout begins to arrive near ground zero within an hour. More than half the total bomb debris lands on the ground within about 24 hours as local fallout. Chemical properties of the elements in the fallout control the rate at which they are deposited on the ground. Less volatile elements deposit first. Severe local fallout contamination can extend far beyond the blast and thermal effects, particularly in the case of high yield surface detonations. The ground track of fallout from an explosion depends on the weather situation from the time of detonation onwards. In stronger winds, fallout travels faster but takes the same time to descend, so although it covers a larger path, it is more spread out or diluted. So the width of the fallout pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any given time is the same irrespective of the wind pattern, so overall casualty figures from fallout are generally independent of winds. But thunderstorms can bring down activity as rain more rapidly than dry fallout, particularly if the mushroom cloud is low enough to be below ("washout"), or mixed with ("rainout"), the thunderstorm.
Whenever individuals remain in a radiologically contaminated area, such contamination leads to an immediate external radiation exposure as well as a possible later internal hazard from inhalation and ingestion of radiocontaminants, such as the rather short-lived iodine-131, which is accumulated in the thyroid.
Factors affecting fallout Location There are two main considerations for the location of an explosion: height and surface composition. A nuclear weapon detonated in the air, called an air burst, produces less fallout than a comparable explosion near the ground. In case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water; these can have a cloud seeding effect causing local rainout and areas of high local fallout. Fallout from a seawater burst is difficult to remove once it has soaked into porous surfaces because the fission products are present as metallic ions that chemically bond to many surfaces. Water and detergent washing effectively removes less than 50% of this chemically bonded activity from concrete or steel. Complete decontamination requires aggressive treatment like sandblasting, or acidic treatment. After the Crossroads underwater test, it was found that wet fallout must be immediately removed from ships by continuous water washdown (such as from the fire sprinkler system on the decks). Parts of the sea bottom may become fallout. After the Castle Bravo test, white dust contaminated calcium oxide particles originating from pulverized and calcined corals fell for several hours, causing beta burns and radiation exposition to the inhabitants of the nearby atolls and the crew of the Daigo Fukuryu Maru fishing boat. The scientists called the fallout Bikini snow. For subsurface bursts, there is an additional phenomenon present called "base surge". The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is caused by an excessive density of dust or water droplets in the air. For underwater bursts, the visible surge is, in effect, a cloud of liquid (usually water) droplets with the property of flowing almost as if it were a homogeneous fluid. After the water evaporates, an invisible base surge of small radioactive particles may persist. For subsurface land bursts, the surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.
Meteorological
Comparison of fallout gamma dose and dose rate contours for a 1 Mt fission land surface burst, based on DELFIC calculations. Because of radioactive decay, the dose rate contours contract after fallout has arrived, but dose contours continue to grow Meteorological conditions greatly influence fallout, particularly local fallout. Atmospheric winds are able to bring fallout over large areas. For example, as a result of a Castle Bravo surface burst of a 15 Mt thermonuclear device at Bikini Atoll on March 1, 1954, a roughly cigar-shaped area of the Pacific extending over 500 km downwind and varying in width to a maximum of 100 km was severely contaminated. There are three very different versions of the fallout pattern from this test, because the fallout was only measured on a small number of widely spaced Pacific Atolls. The two alternative versions both ascribe the high radiation levels at north Rongelap to a downwind hotspot caused by the large amount of radioactivity carried on fallout particles of about 50-100 micrometres size . After Bravo, it was discovered that fallout landing on the ocean disperses in the top water layer (above the thermocline at 100 m depth), and the land equivalent dose rate can be calculated by multiplying the ocean dose rate at two days after burst by a factor of about 530. In other 1954 tests, including Yankee and Nectar, hotspots were mapped out by ships with submersible probes, and similar hotspots occurred in 1956 tests such as Zuni and Tewa However, the major U.S. 'DELFIC' (Defence Land Fallout Interpretive Code) computer calculations use the natural size distributions of particles in soil instead of the
afterwind sweep-up spectrum, and this results in more straightforward fallout patterns lacking the downwind hotspot. Snow and rain, especially if they come from considerable heights, accelerate local fallout. Under special meteorological conditions, such as a local rain shower that originates above the radio-active cloud, limited areas of heavy contamination just downwind of a nuclear blast may be formed.
Effects A wide range of biological changes may follow the irradiation of animals. These vary from rapid death following high doses of penetrating whole-body radiation, to essentially normal lives for a variable period of time until the development of delayed radiation effects, in a portion of the exposed population, following low dose exposures. The unit of actual exposure is the Röntgen, defined in ionisations per unit volume of air. All ionisation based instruments (including geiger counters and ionisation chambers) measure exposure. However, effects depend on the energy per unit mass, not the exposure measured in air. A deposit of 1 joule per kilogram has the unit of 1 gray (Gy). For 1 MeV energy gamma rays, an exposure of 1 röntgen in air produces a dose of about 0.01 gray (1 centigray, cGy) in water or surface tissue. Because of shielding by the tissue surrounding the bones, the bone marrow only receives about 0.67 cGy when the air exposure is 1 röntgen and the surface skin dose is 1 cGy. Some lower values reported for the amount of radiation that would kill 50% of personnel (the LD50) refer to bone marrow dose, which is only 67% of the air dose.
Short term
Fallout shelter sign on a building in New York City. The dose that would be lethal to 50% of a population is a common parameter used to compare the effects of various fallout types or circumstances. Usually, the term is defined for a specific time, and limited to studies of acute lethality. The common time periods used are 30 days or less for most small laboratory animals and to 60 days for large animals and humans. The LD50 figure assumes that the individuals did not receive other injuries or medical treatment. In the 1950s, the LD50 for gamma rays was set at 3.5 Gy, while under more dire conditions of war (a bad diet, little medical care, poor nursing) the LD50 was 2.5 Gy (250 rad). There have been few documented cases of survival beyond 6 Gy. One person at Chernobyl survived a dose of more than 10 Gy, but many of the persons exposed there were not uniformly exposed over their entire body. If a person is exposed in a nonhomogeneous manner then a given dose (averaged over the entire body) is less likely to be of a lethal dose. For instance, if a person gets a hand/low arm dose of 100 Gy, which gives them an overall dose of 4 Gy, they are more likely to survive than a person who gets a 4 Gy dose over their entire body. A hand dose of 10 Gy or more would likely result in loss of the hand. A British industrial radiographer who got a lifetime hand dose of 100 Gy lost his hand because of radiation dermatitis. Most people become ill after an exposure to 1 Gy or more. The fetuses of pregnant women are often more vulnerable to radiation and may miscarry, especially in the first trimester.
One hour after a surface burst, the radiation from fallout in the crater region is 30 grays per hour (Gy/h). Civilian dose rates in peacetime range from 30 to 100 µGy per year. Fallout radiation decays exponentially relatively quickly with time. Most areas become fairly safe for travel and decontamination after three to five weeks. For yields of up to 10 kt, prompt radiation is the dominant producer of casualties on the battlefield. Humans receiving an acute incapacitating dose (30 Gy) have their performance degraded almost immediately and become ineffective within several hours. However, they do not die until five to six days after exposure, assuming they do not receive any other injuries. Individuals receiving less than a total of 1.5 Gy are not incapacitated. People receiving doses greater than 1.5 Gy become disabled, and some eventually die. A dose of 5.3 Gy to 8.3 Gy is considered lethal but not immediately incapacitating. Personnel exposed to this amount of radiation have their performance degraded in two to three hours, depending on how physically demanding the tasks they must perform are, and remain in this disabled state at least two days. However, at that point they experience a recovery period and can perform non-demanding tasks for about six days, after which they relapse for about four weeks. At this time they begin exhibiting symptoms of radiation poisoning of sufficient severity to render them totally ineffective. Death follows at approximately six weeks after exposure, although outcomes may vary.
Long term Late or delayed effects of radiation occur following a wide range of doses and dose rates. Delayed effects may appear months to years after irradiation and include a wide variety of effects involving almost all tissues or organs. Some of the possible delayed consequences of radiation injury are life shortening, carcinogenesis, cataract formation, chronic radiodermatitis, decreased fertility, and genetic mutations.
Tactical military considerations
Comparison of predicted fallout "hotline" with test results in the 3.53 Mt 15% fission Zuni test at Bikini in 1956. The predictions were made under simulated tactical nuclear war conditions aboard ship by Edward A. Schuert. In many cases, Blast injuries and thermal burns from nuclear weapons will far outnumber radiation injuries. However, radiation effects are considerably more complex and varied than are blast or thermal effects and are subject to considerable misunderstanding. The closer to ground an atomic bomb is detonated, the more dust and debris is thrown into the air, resulting in greater amounts of local fallout. From a tactical standpoint, this has the disadvantage of hindering any occupation/invading efforts until the fallout clears, but more directly, the impact with the ground severely limits the destructive force of the bomb. For these reasons, ground bursts are not usually considered tactically advantageous, with the exception of hardened underground targets such as missile silos or command centers, however "salting" enemy territory with a fallout-heavy atomic burst or a salted bomb can be used to deny ill-equipped civilians/military personnel access to a contaminated area.
Fallout protection During the Cold War, the governments of the U.S., the USSR, Great Britain, and China attempted to educate their citizens about surviving a nuclear attack by providing procedures on minimizing short-term exposure to fallout. In the U.S. and China, this effort became known as Civil Defense.
Nuclear reactor accident Fallout can also refer to nuclear accidents, although a nuclear reactor does not explode like a nuclear weapon. The isotopic signature of bomb fallout is very different from the fallout from a serious power reactor accident (such as Chernobyl). The key differences are in volatility and half-life.
Volatility The boiling point of an element (or its compounds) is able to control the percentage of that element a power reactor accident releases. In addition, the ability of an element to form a solid controls the rate it is deposited on the ground after having been injected into the atmosphere by a nuclear detonation or accident.
Half-life A large amount of short-lived isotopes such as 97Zr are present in bomb fallout. This isotope and other short-lived isotopes are constantly generated in a power reactor, but because the criticality occurs over a long length of time, the majority of these short lived isotopes decay before they can be released. Below is shown a comparison of the calculated gamma dose rates in open air from the fallout of a fission bomb and of the Chernobyl release. It is clear that average half-life of the Chernobyl release is longer than that for the bomb fallout.
A comparison of the gamma dose rates from Chernobyl and bomb fallout, to 10,000 days. These have been normalised to the same Cs-137 level.
Gamma dose rates from Chernobyl and bomb fallout, to 1,000 days.
Gamma dose rates from Chernobyl and bomb fallout, to 100 days.
Chapter- 5
Nuclear Winter
Nuclear winter is a predicted climatic effect of nuclear war. It has been theorized that severely cold weather and reduced sunlight for a period of months or years could be caused by detonating large numbers of nuclear weapons, especially over flammable targets such as cities, where large amounts of smoke and soot would be ejected into the Earth's stratosphere. Similar climatic effects can be caused by a comet or asteroid impact, also sometimes termed an impact winter, or of a supervolcano eruption, known as a volcanic winter.
Mechanism The nuclear winter scenario predicts that the huge fires caused by nuclear explosions (particularly from burning urban areas) would loft massive amounts of dark smoke and aerosol particles from the fires into the upper troposphere / stratosphere. At 10-15 kilometers (6–9 miles) above the Earth's surface, the absorption of sunlight would further heat the smoke, lifting it into the stratosphere where the smoke would persist for years, with no rain to wash it out. This would block out much of the sun's light from reaching the surface, causing surface temperatures to drop drastically.
Consequences Climatic effects A study presented at the annual meeting of the American Geophysical Union in December 2006 found that even a small-scale, regional nuclear war could disrupt the global climate for a decade or more. In a regional nuclear conflict scenario where two opposing nations in the subtropics would each use 50 Hiroshima-sized nuclear weapons (about 15 kiloton each) on major populated centers, the researchers estimated as much as five million tons of soot would be released, which would produce a cooling of several degrees over large areas of North America and Eurasia, including most of the grain-
growing regions. The cooling would last for years and could be "catastrophic" according to the researchers. Ozone depletion A 2008 study published in the Proceedings of the National Academy of Science found that a nuclear weapons exchange between Pakistan and India using their current arsenals could create a near- global ozone hole, triggering human health problems and wreaking environmental havoc for at least a decade. The computer-modeling study looked at a nuclear war between the two countries involving 50 Hiroshima-sized nuclear devices on each side, producing massive urban fires and lofting as much as five million metric tons of soot about 50 miles (80 km) into the stratosphere. The soot would absorb enough solar radiation to heat surrounding gases, setting in motion a series of chemical reactions that would break down the stratospheric ozone layer protecting Earth from harmful ultraviolet radiation. Column ozone losses could exceed 20% globally, 25–45% at mid-latitudes, and 50–70% at northern high latitudes persisting for 5 years, with substantial losses continuing for 5 additional years. Column ozone amounts would remain near or below 220 Dobson units at all latitudes even after three years, constituting an extra-tropical “ozone hole”. Human health ailments like cataracts and skin cancer, as well as damage to plants, animals and ecosystems at mid-latitudes would likely rise sharply as ozone levels decreased and allowed more harmful UV light to reach Earth, according to the PNAS study. This study demonstrates that a small-scale, regional nuclear conflict is capable of triggering ozone losses even larger than losses that were predicted in the 1980s following a full-scale nuclear war. The missing piece back then was that the models at the time could not account for the rise of the smoke plume and consequent heating of the stratosphere.
Recent modeling Based on new work published in 2007 and 2008 by some of the authors of the original studies, several new theories have been put forth. A minor nuclear war with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas could produce climate change unprecedented in recorded human history. A nuclear war between the United States and Russia today could produce nuclear winter, with temperatures plunging below freezing in the summer in major agricultural regions, threatening the food supply for most of the planet. The climatic effects of the smoke from burning cities and industrial areas would last for several years, much longer than previously thought. New climate model simulations, which are said to have the capability of including the entire atmosphere and oceans, show that the smoke would be lofted by solar heating to the upper stratosphere, where it would remain for years. Compared to climate change for the past millennium, even the smallest exchange modeled would plunge the planet into temperatures colder than the Little Ice Age (the period of history between approximately 1600 A.D. and 1850 A.D.). This would take
effect instantly, and agriculture would be severely threatened. Larger amounts of smoke would produce larger climate changes, and for the 150 Tg case produce a true nuclear winter, making agriculture impossible for years. In both cases, new climate model simulations show that the effects would last for more than a decade.
2007 study on global nuclear war A study published in the Journal of Geophysical Research in July 2007, Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences, used current climate models to look at the consequences of a global nuclear war involving most or all of the world's current nuclear arsenals (which the authors described as being only about a third the size of the world's arsenals twenty years earlier). The authors used a global circulation model, ModelE from the NASA Goddard Institute for Space Studies, which they noted "has been tested extensively in global warming experiments and to examine the effects of volcanic eruptions on climate." The model was used to investigate the effects of a war involving the entire current global nuclear arsenal, projected to release about 150 Tg of smoke into the atmosphere (1 Tg is equal to 1012 grams), as well as a war involving about one third of the current nuclear arsenal, projected to release about 50 Tg of smoke. In the 150 Tg case they found that: A global average surface cooling of –7°C to –8°C persists for years, and after a decade the cooling is still –4°C (Fig. 2). Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about –5°C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land ... Cooling of more than –20°C occurs over large areas of North America and of more than –30°C over much of Eurasia, including all agricultural regions. In addition, they found that this cooling caused a weakening of the global hydrological cycle, reducing global precipitation by about 45%. As for the 50 Tg case involving one third of current nuclear arsenals, they said that the simulation "produced climate responses very similar to those for the 150 Tg case, but with about half the amplitude," but that "the time scale of response is about the same." They did not discuss the implications for agriculture in depth, but noted that a 1986 study which assumed no food production for a year projected that "most of the people on the planet would run out of food and starve to death by then" and commented that their own results show that "this period of no food production needs to be extended by many years, making the impacts of nuclear winter even worse than previously thought."
Kuwait wells in the first Gulf War Following Iraq's invasion of Kuwait, Carl Sagan and other scientists predicted that burning oil wells could cause environmental damage comparable to nuclear winter. Nearly 700 oil wells were set ablaze by the retreating Iraqi army and the fires were not fully extinguished until November 6, 1991, eight months after the end of the war. The fires consumed an estimated six million barrels of oil daily.
According to a 1992 study from Peter Hobbs and Lawrence Radke daily emissions of sulfur dioxide were 57% of that from electric utilities in the United States, emissions of carbon dioxide were 2% of global emissions and emissions of soot were 3,400 metric tons per day. However, pre-war claims of wide scale, long-lasting, and significant global environmental impacts were not borne out and found to be significantly exaggerated by the media and speculators, with climate models at the time of the fires predicting only more localized effects such as a daytime temperature drop of ~10 °C within ~200 km of the source. At the peak of the fires, the smoke absorbed 75% to 80% of the sun’s radiation. The particles were never observed to rise above 6 km and when combined with scavenging by clouds gave the smoke a short residency time in the atmosphere and localized its effects; Professor Carl Sagan of the Turco, Toon, Ackerman, Pollack, Sagan (TTAPS) study hypothesized in January 1991 that enough smoke from the fires "might get so high as to disrupt agriculture in much of South Asia...." Sagan later conceded in his book The Demon-Haunted World that this prediction did not turn out to be correct: "it was pitch black at noon and temperatures dropped 4°–6°C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared." The 2007 study discussed above noted that modern computer models have been applied to the Kuwait oil fires, finding that individual smoke plumes are not able to loft smoke into the stratosphere, but that smoke from fires covering a large area, like some forest fires or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere: Stenchikov et al. [2006b] conducted detailed, high-resolution smoke plume simulations with the RAMS regional climate model [e.g., Miguez-Macho et al., 2005] and showed that individual plumes, such as those from the Kuwait oil fires in 1991, would not be expected to loft into the upper atmosphere or stratosphere, because they become diluted. However, much larger plumes, such as would be generated by city fires, produce large, undiluted mass motion that results in smoke lofting. New large eddy simulation model results at much higher resolution also give similar lofting to our results, and no small scale response that would inhibit the lofting [Jensen, 2006].
History Early work In 1974, John Hampson suggested that a full-scale nuclear exchange could result in depletion of the ozone shield, possibly subjecting the earth to ultraviolet radiation for a year or more. In 1975, the United States National Research Council (NRC) reported on ozone depletion following nuclear war, judging that the effect of dust would probably be slight climatic cooling.
1982
In 1981, William J. Moran began discussions and research in the NRC on the dust effects of a large exchange of nuclear warheads. An NRC study panel on the topic met in December 1981 and April 1982. As part of a study launched in 1980 by Ambio, a journal of the Royal Swedish Academy of Sciences, Paul Crutzen and John Birks circulated a draft paper in early 1982 with the first quantitative evidence of alterations in short-term climate after a nuclear war. In 1982, a special issue of Ambio devoted to the possible environmental consequences of nuclear war included a paper by Crutzen and Birks anticipating the nuclear winter scenario. The paper discussed particulates from large fires, nitrogen oxide, ozone depletion and the effect of nuclear twilight on agriculture. Crutzen and Birks showed that smoke injected into the atmosphere by fires in cities, forests and petroleum reserves could prevent up to 99% of sunlight from reaching the Earth's surface, with major climatic consequences: "The normal dynamic and temperature structure of the atmosphere would therefore change considerably over a large fraction of the Northern Hemisphere, which will probably lead to important changes in land surface temperatures and wind systems." An important implication of their work was that a "first strike" nuclear attack would have severe consequences for the perpetrator.
1983 In 1982, the so-called TTAPS team (R.P. Turco, O.B. Toon, T.P. Ackerman, J.B. Pollack and C.E. Sagan) undertook a computational modeling study of the atmospheric consequences of nuclear war, publishing their results in Science in December 1983. The phrase "nuclear winter" was coined by Turco just prior to publication. In this early work, TTAPS carried out the first estimates of the total smoke and dust emissions that would result from a major nuclear exchange, and determined quantitatively the subsequent effects on the atmospheric radiation balance and temperature structure. To compute dust and smoke impacts, they employed a one-dimensional microphysics/radiative-transfer model of the Earth's lower atmosphere (to the mesopause), which defined only the vertical characteristics of the global climate perturbation. Around this time, interest in nuclear war environmental effects also arose in the USSR. After becoming aware of the work of the Swedish Academy and, in particular, papers by N.P.Bochkov and E.I.Chazov, Russian atmospheric scientist Georgy Golitsyn applied his research on dust-storms to the situation following a nuclear catastrophe. His suggestion that the atmosphere would be heated and that the surface of the planet would cool appeared in The Herald of the Academy of Sciences in September 1983. Upon learning of the TTAPS scenarios, Vladimir Alexandrov and G. I. Stenchikov soon published a report on the climatic consequences of nuclear war based on simulations with a two-level global circulation model, which produced results consistent with the TTAPS findings.
1986 In 1984 the WMO commissioned Georgy Golitsyn and N. A. Phillips to review the state of the science. They found that studies generally assumed a scenario that half of the
world's nuclear weapons would be used, ~5000 Mt, destroying approximately 1,000 cities, and creating large quantities of carbonaceous smoke - 1–2 × 1014 grams being mostly likely, with a range of 0.2 – 6.4 × 1014 grams (NAS; TTAPS assumed 2.25 × 1014). The smoke resulting would be largely opaque to solar radiation but transparent to infra-red, thus cooling by blocking sunlight but not causing warming from enhancing the greenhouse effect. The optical depth of the smoke can be much greater than unity. Forest fires resulting from non-urban targets could increase aerosol production further. Dust from near-surface explosions against hardened targets also contributes; each Mt-equivalent of explosion could release up to 5 million tons of dust, but most would quickly fall out; high altitude dust is estimated at 0.1-1 million tons per Mt-equivalent of explosion. Burning of crude oil could also contribute substantially. The 1-D radiative-convective models used in these studies produced a range of results, with coolings up to 15-42 °C between 14 and 35 days after the war, with a "baseline" of about 20 °C. Somewhat more sophisticated calculations using 3-D GCMs (Alexandrov and Stenchikov (1983); Covey, Schneider and Thompson (1984); which would be considered primitive by modern standards) produced similar results: temperature drops of between 20 and 40 °C, though with regional variations. All calculations show large heating (up to 80 °C) at the top of the smoke layer at about 10 km; this implies a substantial modification of the circulation there and the possibility of advection of the cloud into low latitudes and the southern hemisphere. The report made no attempt to compare the likely human impacts of the post-war cooling to the direct deaths from explosions.
1990 In 1990, in a paper entitled "Climate and Smoke: An Appraisal of Nuclear Winter," TTAPS give a more detailed description of the short- and long-term atmospheric effects of a nuclear war using a three-dimensional model: First 1 to 3 months: •
10 to 25% of soot injected is immediately removed by precipitation, while the rest is transported over the globe in 1 to 2 weeks
•
SCOPE figures for July smoke injection: o 22 °C drop in mid-latitudes o 10 °C drop in humid climates o 75% decrease in rainfall in mid-latitudes o Light level reduction of 0% in low latitudes to 90% in high smoke injection areas
•
SCOPE figures for winter smoke injection: o Temperature drops between 3° and 4 °C
Following 1 to 3 years: •
25 to 40% of injected smoke is stabilised in atmosphere (NCAR). Smoke stabilised for approximately 1 year.
•
Land temperatures of several degrees below normal
•
Ocean surface temperature between 2 and 6 °C
•
Ozone depletion of 50% leading to 200% increase in UV radiation incident on surface.
Criticism and debate The TTAPS study was widely reported and criticized in the media. Later model runs in some cases predicted less severe effects, but continued to support the overall conclusion of significant global cooling. Recent studies (2006) substantiate that smoke from urban firestorms in a regional war would lead to long lasting global cooling but in a less dramatic manner than the nuclear winter scenario, while a 2007 study of the effects of global nuclear war supported the conclusion that it would lead to full-scale nuclear winter. The original work by Sagan and others was criticized as a "myth" and "discredited theory" in the 1987 book Nuclear War Survival Skills, a civil defense manual by Cresson Kearny for the Oak Ridge National Laboratory. Kearny said the maximum estimated temperature drop would be only about by 20 degrees Fahrenheit (11 degrees Celsius), and that this amount of cooling would last only a few days. He also suggested that a global nuclear war would indeed result in millions of deaths from hunger, but primarily due to cessation of international food supplies, rather than due to climate changes. Kearny, who was not a climate scientist himself, based his conclusions almost entirely on the 1986 paper "Nuclear Winter Reappraised" by Starley Thompson and Stephen Schneider. However, a 1988 article by Brian Martin in Science and Public Policy states that although their paper concluded the effects would be less severe then originally thought, with the authors describing these effects as a "nuclear autumn", other statements by Thompson and Schneider show that they "resisted the interpretation that this means a rejection of the basic points made about nuclear winter". In addition, the authors of the 2007 study above state that "because of the use of the term 'nuclear autumn' by Thompson and Schneider [1986], even though the authors made clear that the climatic consequences would be large, in policy circles the theory of nuclear winter is considered by some to have been exaggerated and disproved [e.g., Martin, 1988]." And in 2007 Schneider emphasized the danger of serious climate changes from a limited nuclear war of the kind analyzed in the 2006 study above, saying "The sun is much stronger in the tropics than it is in mid-latitudes. Therefore, a much more limited war [there] could have a much larger effect, because you are putting the smoke in the worst possible place."
Policy implications In an interview in 2000, Mikhail Gorbachev, in response to the comment "In the 1980s, you warned about the unprecedented dangers of nuclear weapons and took very daring steps to reverse the arms race," said "Models made by Russian and American scientists showed that a nuclear war would result in a nuclear winter that would be extremely destructive to all life on Earth; the knowledge of that was a great stimulus to us, to people of honor and morality, to act in that situation."
Chapter- 6
Chernobyl Disaster Effects
The Chernobyl disaster triggered the release of substantial amounts of radiation into the atmosphere in the form of both particle and gaseous radioisotopes, and is the most significant unintentional release of radiation into the environment to date. It has been suggested that the Chernobyl disaster released as much as 400 times the radioactive contamination of the Atomic bombings of Hiroshima and Nagasaki. However, the work of SCOPE suggests that the two events can not be simply compared with a number suggesting that one was x times larger than the other; the isotopes released at Chernobyl tended to be longer-lived than those released by a bomb detonation, producing radioactivity curves that vary in shape as well as size.
Dose to the general public within 30 km of the plant The inhalation dose (internal dose) for the public (during the time between the accident occurring and their evacuation from the area) in what is now the 30 km evacuation zone around the plant has been estimated (based ground deposition of caesium-137) to be between 3 and 150 mSv {between a 1 in 6666.67 and a 1 in 133.33 chance of a fatal cancer, assuming the ICRP risk factor of a 5% of a fatal cancer per Sv of exposure} for adults (depending on the distance from the reactor and the day of evacuation) and for one year old children a dose estimate of between 10 and 700 mSv {between a 1 in 2000 and a 1 in 28.57 chance of fatal cancer} has been made. Thyroid doses for adults were between 20 and 1000 mSv, while for the one year old infants these were higher at 20 to 6000 mSv. For those who left at an early stage in the accident the internal dose due to inhalation was 8 to 13 times higher than the external dose due to gamma/beta emitters. For those who remained until later (day 10 or later) the inhalation dose was 50 to 70% higher than the dose due to external exposure. The majority of the dose was due to Iodine-131 (circa 40%), tellurium and rubidium isotopes (circa 20 to 30% for Rb and Te). The ingestion doses in this same group of people have also been estimated using the caesium activity per unit of area, isotope ratios, average day of evacuation, intake rate of milk and green vegetables and what is known about the transfer of radioactivity via plants/animals to humans. For adults the dose has been estimated to be between 3 and
180 mSv while for the one year old infants a dose of between 20 and 1300 mSv has been estimated. Again the majority of the dose was due to Iodine-131 and the external dose was much smaller than the internal dose due to the radioactivity in the diet.
Short-term health effects and immediate results The explosion at the power station and subsequent fires inside the remains of the reactor provoked a radioactive cloud which drifted not only over Russia, Belarus and Ukraine, but also over the European part of Turkey, Greece, Moldova, Romania, Bulgaria, Lithuania, Finland, Denmark, Norway, Sweden, Austria, Hungary, Czechoslovakia, Slovenia, Croatia, Poland, Estonia, Switzerland, Germany, Italy, Ireland, France (including Corsica), Canada and the United Kingdom (UK). In fact, the initial evidence in other countries that a major exhaust of radioactive material had occurred came not from Soviet sources, but from Sweden, where on April 27 workers at the Forsmark Nuclear Power Plant (approximately 1100 km from the Chernobyl site) were found to have radioactive particles on their clothes. It was Sweden's search for the source of radioactivity, after they had determined there was no leak at the Swedish plant, that led to the first hint of a serious nuclear problem in the Western Soviet Union. In France, the government then claimed that the radioactive cloud had stopped at the Italian border. Therefore, while some kinds of food (mushrooms in particular) were prohibited in Italy because of radioactivity, the French authorities took no such measures, in an attempt to appease the population's fears (see below). Contamination from the Chernobyl disaster was not evenly spread across the surrounding countryside, but scattered irregularly depending on weather conditions. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. A large area in Russia south of Bryansk was also contaminated, as were parts of northwestern Ukraine. 203 people were hospitalized immediately, of whom 31 died (28 of them died from acute radiation exposure). Most of these were fire and rescue workers trying to bring the disaster under control, who were not fully aware of how dangerous the radiation exposure (from the smoke) was (for a discussion of the more important isotopes in fallout see fission products). 135,000 people were evacuated from the area, including 50,000 from the nearby town of Pripyat, Ukraine. Health officials have predicted that over the next 70 years there will be a 2% increase in cancer rates in much of the population which was exposed to the 5–12 EBq (depending on source) of radioactive contamination released from the reactor. An additional 10 individuals have already died of cancer as a result of the disaster. Soviet scientists reported that the Chernobyl Unit 4 reactor contained about 180–190 metric tons of uranium dioxide fuel and fission products. Estimates of the amount of this material that escaped range from 5 to 30 percent, but some liquidators, who have actually been inside the sarcophagus and the reactor shell itself — e.g. Mr. Usatenko and Dr. Karpan — state that not more than 5–10% of the fuel remains inside; indeed, photographs of the reactor shell show that it is completely empty. Because of the intense heat of the
fire, much of the ejected fuel was lofted high into the atmosphere (with no containment building to stop it), where it spread.
Workers and liquidators
Soviet badge awarded to 600,000+ liquidators. The workers involved in the recovery and cleanup after the disaster, called "liquidators", received high doses of radiation. In most cases, these workers were not equipped with individual dosimeters to measure the amount of radiation received, so experts can only estimate their doses. Even where dosimeters were used, dosimetric procedures varied. Some workers are thought to have been given more accurate estimated doses than others. According to Soviet estimates, between 300,000 and 600,000 people were involved in the
cleanup of the 30 km evacuation zone around the reactor, but many of them entered the zone two years after the disaster. Estimates of the number of "liquidators" vary; the World Health Organization, for example, puts the figure at about 800,000; Russia lists as liquidators some people who did not work in contaminated areas. In the first year after the disaster, the number of cleanup workers in the zone was estimated to be 211,000, and these workers received an estimated average dose of 165 millisieverts (16.5 rem). The plume of radioactive debris has been said to be equal to the contamination of 400 Hiroshima bombs. This is correct, but misleading. The main effect of the bomb was the direct radiation from the gamma blast. Compared to that, the contamination was only a minor addition. Furthermore the comparison to bomb fallout is very misleading, as an atomic bomb has a very different isotope signature to a power reactor. In bomb fallout plenty of the very short-lived isotopes are present while the activity in used power reactor fuel tends have a medium to long half-life. The time required for the dose rate to decline by a factor of 10 in an area covered with fallout from an atomic bomb which has detonated an hour ago is much shorter than the time required for the same reduction in dose rate due to Chernobyl fallout (one hour after the reactor suffered the steam explosion). A sevenfold increase in DNA mutations has been identified in liquidators' children conceived after the accident, when compared to their siblings conceived before. However, the effect diminishes sharply with time.
Evacuation
Map showing Caesium-137 contamination in the Chernobyl area as of 1996 Soviet authorities started evacuating people from the area around Chernobyl only on the second day after the disaster (after 36 hours). By May 1986, about a month later, all those living within a 30 km (18 mile) radius of the plant — about 116,000 people — had been relocated. This area is often referred to as the zone of alienation. However, radiation affected the area in a much wider scale than this 30 km radius. According to reports from Soviet scientists, 28,000 km² (10,800 mi²) were contaminated by caesium-137 to levels greater than 185 kBq/m². Roughly 830,000 people lived in this area. About 10,500 km ² (4,000 mi²) were contaminated by caesium-137 to levels greater than 555 kBq/m². Of this total, roughly 7,000 km² (2,700 mi²) lie in Belarus, 2,000 km² (800 mi²) in the Russian Federation and 1,500 km² (580 mi²) in Ukraine. About 250,000
people lived in this area. These reported data were corroborated by the International Chernobyl Project.
Civilians Some children in the contaminated areas were exposed to high radiation doses of up to 50 grays (Gy) because of an intake of radioactive iodine-131, a relatively short-lived isotope with a half-life of 8 days, from contaminated milk produced locally. Several studies have found that the incidence of thyroid cancer among children in Belarus, Ukraine and Russia has risen sharply. The IAEA notes "1800 documented cases of thyroid cancer in children who were between 0 and 14 years of age when the disaster occurred, which is as far higher than normal", but fails to note the expected rate. The childhood thyroid cancers that have appeared are of a large and aggressive type but, if detected early, can be treated. Treatment entails surgery followed by iodine-131 therapy for any metastases. To date, such treatment appears to have been successful in the vast majority of cases. Late in 1995, the World Health Organisation (WHO) linked nearly 700 cases of thyroid cancer among children and adolescents to the Chernobyl disaster, and among these some 10 deaths are attributed to radiation. However, the rapid increase in thyroid cancers detected suggests that some of it at least is an artifact of the screening process. Typical latency time of radiation-induced thyroid cancer is about 10 years, but the increase in childhood thyroid cancers in some regions was observed as early as 1987. Presumably either the increase is unrelated to the disaster or the mechanisms behind it are not well understood. So far, no increase in leukemia is discernible, but this is expected to be evident in the next few years along with a greater, though not statistically discernible, incidence of other cancers. There has been no substantiated increase attributable to Chernobyl in congenital abnormalities, adverse pregnancy outcomes or any other radiation-induced disease in the general population, either in the contaminated areas or further afield. This is contradicted by documentary "The Battle of Chernobyl", which relates how much information has either not been gathered, or covered up. Congenital deformities and increased risk of cancer was documented, but difficult to affirm due to the lack of proper research.
Plant and animal health A large swath of pine forest killed by acute radiation was named the Red Forest. The dead pines were bulldozed and buried. Livestock were removed during the human evacuations. Elsewhere in Europe, levels of radiation were examined in various natural foodstocks. In both Sweden and Finland, fish in deep freshwater lakes were banned for resale and landowners were advised not to consume certain types. Information regarding physical deformities in the plant and animal populations in the areas affected by radioactive fallout require capture and DNA testing of individuals to determine if abnormalities are the result of natural mutation, radiation poisoning, or exposure to other
contaminants in the environment such as pesticides, industrial waste, or agricultural runoff.
Suggested long-range effects •
•
•
Down syndrome (trisomy 21). In West Berlin, Germany, prevalence of Down syndrome (trisomy 21) peaked 9 months following the main fallout.[ 11, 12] Between 1980 and 1986, the birth prevalence of Down syndrome was quite stable (i.e., 1.35–1.59 per 1,000 live births [27–31 cases]). In 1987, 46 cases were diagnosed (prevalence = 2.11 per 1,000 live births). Most of the excess resulted from a cluster of 12 cases among children born in January 1987. The prevalence of Down syndrome in 1988 was 1.77, and in 1989, it reached pre-Chernobyl values. The authors noted that the isolated geographical position of West Berlin prior to reunification, the free genetic counseling, and complete coverage of the population through one central cytogenetic laboratory support completeness of case ascertainment; in addition, constant culture preparation and analysis protocols ensure a high quality of data. Chromosomal aberrations. Reports of structural chromosome aberrations in people exposed to fallout in Belarus and other parts of the former Soviet Union, Austria, and Germany argue against a simple dose-response relationship between degree of exposure and incidence of aberrations. These findings are relevant because a close relationship exists between chromosome changes and congenital malformations. Inasmuch as some types of aberrations are almost specific for ionizing radiation, researchers use aberrations to assess exposure dose. On the basis of current coefficients, however, one cannot assume that calculation of individual exposure doses resulting from fallout would not induce measurable rates of chromosome aberrations. Neural tube defects (NTDs) in Turkey. During the embryonic phase of fetal development, the neural tube differentiates into the brain and spinal cord (i.e., collectively forming the central nervous system). Chemical or physical interactions with this process can cause NTDs. Common features of this class of malformations are more or less extended fissures, often accompanied by consecutive dislocation of central nervous system (CNS) tissue. NTDs include spina bifida occulta and aperta, encephalocele, and—in the extreme case— anencephaly. The first evidence in support of a possible association between CNS malformations and fallout from Chernobyl was published by Akar et al.. in 1988. The Mustafakemalpasa State Hospital, Bursa region, covers a population of approximately 90,000. Investigators have documented the prevalence of malformations since 1983. The prevalence of NTDs was 1.7 to 9.2 per 1,000 births, but during the first 6 months of 1987 increased to 20 per 1,000 (12 cases). The excess was most pronounced for the subgroup of anencephalics, in which prevalence increased 5-fold (i.e., 10 per 1,000 [6 cases]). In the consecutive months that followed (i.e., July–December 1987), the prevalence decreased again (1.3 per 1,000 for all NTDs, 0.6 per 1,000 for anencephaly), and it reached preChernobyl levels during the first half of 1988 (all NTDs: 0.6 per 1,000;
anencephaly: 0.2 per 1,000). This initial report was supported by several similar findings in observational studies from different regions of Turkey.
Long-term health effects Science and politics: the problem of epidemiological studies
An abandoned village near Prypiat, close to Chernobyl The issue of long-term effects of the Chernobyl disaster on civilians is very controversial. The number of people whose lives were affected by the disaster is enormous. Over 300,000 people were resettled because of the disaster; millions lived and continue to live in the contaminated area. On the other hand, most of those affected received relatively low doses of radiation; there is little evidence of increased mortality, cancers or birth defects among them; and when such evidence is present, existence of a causal link to radioactive contamination is uncertain. An increased incidence of thyroid cancer among children in areas of Belarus, Ukraine and Russia affected by the Chernobyl disaster has been firmly established as a result of screening programs and, in the case of Belarus, an established cancer registry. The findings of most epidemiological studies must be considered interim, say experts, as analysis of the health effects of the disaster is an ongoing process.
Epidemiological studies have been hampered in the former Soviet Union by a lack of funds, an infrastructure with little or no experience in chronic disease epidemiology, poor communication facilities and an immediate public health problem with many dimensions. Emphasis has been placed on screening rather than on well-designed epidemiological studies. International efforts to organize epidemiological studies have been slowed by some of the same factors, especially the lack of a suitable scientific infrastructure. Furthermore, the political nature of nuclear energy may have affected scientific studies. In Belarus, Yury Bandazhevsky, a scientist who questioned the official estimates of Chernobyl's consequences and the relevancy of the official maximum limit of 1,000 Bq/kg, was imprisoned from 2001 to 2005. Bandazhevsky and some human rights groups allege his imprisonment was a reprisal for his publication of reports critical of the official research being conducted into the Chernobyl incident. The activities undertaken by Belarus and Ukraine in response to the disaster — remediation of the environment, evacuation and resettlement, development of uncontaminated food sources and food distribution channels, and public health measures — have overburdened the governments of those countries. International agencies and foreign governments have provided extensive logistic and humanitarian assistance. In addition, the work of the European Commission and World Health Organization in strengthening the epidemiological research infrastructure in Russia, Ukraine and Belarus is laying the basis for major advances in these countries' ability to carry out epidemiological studies of all kinds.
Caesium radioisotopes Immediately after the disaster, the main health concern involved radioactive iodine, with a half-life of eight days. Today, there is concern about contamination of the soil with strontium-90 and caesium-137, which have half-lives of about 30 years. The highest levels of caesium-137 are found in the surface layers of the soil where they are absorbed by plants, insects and mushrooms, entering the local food supply. Some scientists fear that radioactivity will affect the local population for the next several generations. Note that caesium is not mobile in most soils because it binds to the clay minerals. Recent tests (ca. 1997) have shown that caesium-137 levels in trees of the area are continuing to rise. There is some evidence that contamination is migrating into underground aquifers and closed bodies of water such as lakes and ponds (2001, Germenchuk). The main source of elimination is predicted to be natural decay of caesium-137 to stable barium-137, since runoff by rain and groundwater has been demonstrated to be negligible.
24 years later after the catastrophe Twenty four years after the catastrophe, restriction orders remain in place in the production, transportation and consumption of food contaminated by Chernobyl fallout. In the UK, they remain in place on 369 farms covering 750 km² and 200,000 sheep. In parts of Sweden and Finland, restrictions are in place on stock animals, including reindeer, in natural and near-natural environments. "In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland, wild game (including boar and
deer), wild mushrooms, berries and carnivorous fish from lakes reach levels of several thousand Bq per kg of caesium-137", while "in Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The average level is 6,800 Bq/kg, more than ten times the EU limit of 600 Bq/kg", according to the TORCH 2006 report. The European Commission has stated that "The restrictions on certain foodstuffs from certain Member States must therefore continue to be maintained for many years to come". As of 2009, sheep farmed in some areas of the UK are still subject to inspection which may lead to them being prohibited from entering the human food chain because of contamination arising from the accident: "Some of this radioactivity, predominantly radiocaesium-137, was deposited on certain upland areas of the UK, where sheep-farming is the primary land-use. Due to the particular chemical and physical properties of the peaty soil types present in these upland areas, the radiocaesium is still able to pass easily from soil to grass and hence accumulate in sheep. A maximum limit of 1,000 becquerels per kilogramme (Bq/kg) of radiocaesium is applied to sheep meat affected by the accident to protect consumers. This limit was introduced in the UK in 1986, based on advice from the European Commission's Article 31 group of experts. Under power provided under the Food and Environment Protection Act 1985 (FEPA), Emergency Orders have been used since 1986 to impose restrictions on the movement and sale of sheep exceeding the limit in certain parts of Cumbria, North Wales, Scotland and Northern Ireland... When the Emergency Orders were introduced in 1986, the Restricted Areas were large, covering almost 9,000 farms, and over 4 million sheep. Since 1986, the areas covered by restrictions have dramatically decreased and now cover 369 farms, or part farms, and around 200,000 sheep. This represents a reduction of over 95% since 1986, with only limited areas of Cumbria, South Western Scotland and North Wales, covered by restrictions. 369 farms and 190,000 sheep are still affected, a reduction of 95% since 1986. In Norway, the Sami people were affected by contaminated food (the reindeer had been contaminated by eating lichen, which are very sensitive to radioactivity).
Effect on the natural world
The major plume of radiation released by the Chernobyl Nuclear Accident was carried directly over what is now called the Red Forest. Radioactive particles settled on trees, killing areas of pine forest.
Earth Observing-1 image of the reactor and surrounding area in April of 2009. According to reports from Soviet scientists at the First International Conference on the Biological and Radiological Aspects of the Chernobyl Accident (September 1990), fallout levels in the 10 km zone around the plant were as high as 4.81 GBq/m². The socalled "Red Forest" of pine trees, previously known as Worm Wood Forest and located immediately behind the reactor complex, lay within the 10 km zone and was killed off by heavy radioactive fallout. The forest is so named because in the days following the disaster the trees appeared to have a deep red hue as they died because of extremely heavy radioactive fallout. In the post-disaster cleanup operations, a majority of the 4 km² forest was bulldozed and buried. The site of the Red Forest remains one of the most contaminated areas in the world. In recent years there have been many reports of Nels Peterson suggesting the zone may be a fertile habitat for wildlife. For example in the 1996 BBC Horizon documentary 'Inside Chernobyl's Sarcophagus', birds are seen flying in and out of large holes in the structure itself. Other casual observations suggest biodiversity around the massive radiation spill has increased due to the removal of human influence. Storks, wolves, beavers, and eagles have been reported in the area. Barn swallows sampled between 1991 and 2006 both in the Chernobyl exclusion zone had more physical abnormalities than control sparrows sampled elsewhere in Europe. Abnormal barn swallows mated with lower frequency, causing the percentage of abnormal swallows to decrease over time. This demonstrated the selective pressure against the abnormalities was faster than the effects of radiation that created the
abnormalities. "This was a big surprise to us," Dr. Mousseau said. "We had no idea of the impact." It is unknown whether fallout contamination will have any long-term adverse effect on the flora and fauna of the region, as plants and animals have significantly different and varying radiologic tolerance compared with humans. Some birds are reported with stunted tail feathers (which interferes with breeding). There are reports of mutations in some plants in the area, leading to unsubstantiated tales of a "forest of wonders" containing many strangely mutated plants. Specifically, some trees have weirdly twisted branches that do not reach for the sky. The Chernobyl area has not received very much biological study, although studies that have been done suggest that apparently healthy populations may be sink instead of source populations; in other words, that the apparently healthy populations are not contributing to the survival of species. Using robots, researchers have actually retrieved samples of highly melanized black fungus from the walls of the reactor core itself. It has been shown that certain species of fungus, such as Cryptococcus neoformans and Cladosporium, can actually thrive in a radioactive environment, growing better than non-melanized variants, implying that they use melanin to harness the energy of ionizing radiation from the reactor.
The Chernobyl Forum report and criticisms In September 2005, a comprehensive report was published by the Chernobyl Forum, comprising a number of agencies including the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), United Nations bodies and the Governments of Belarus, the Russian Federation and Ukraine. This report titled: "Chernobyl's legacy: Health, Environmental and Socio-Economic Impacts", authored by about 100 recognized experts from many countries, put the total predicted number of deaths due to the disaster around 4,000 (of which 2,200 deaths are expected to be in the ranks of 200,000 liquidators). This predicted death toll includes the 47 workers who died of acute radiation syndrome as a direct result of radiation from the disaster, nine children who died from thyroid cancer and an estimated 4000 people who could die from cancer as a result of exposure to radiation. The report also stated that, apart from a 30 kilometre area around the site and a few restricted lakes and forests, radiation levels had returned to acceptable levels. The methodology of the Chernobyl Forum report has been disputed by some advocacy organizations opposed to nuclear energy, such as Greenpeace and the International Physicians for Prevention of Nuclear Warfare (IPPNW), as well as some individuals such as Elisabeth Cardis of the International Agency for Research on Cancer, Dr. Michel Fernex, retired medical doctor from the WHO and campaigner Dr. Christopher Busby (Green Audit, LLRC). The main criticism has been with regard to the restriction of the Forum's study to Belarus, Ukraine and Russia. Furthermore, it only studied the case of 200,000 people involved in the cleanup, and the 400,000 most directly affected by the released radiation. German Green Party Member of the European Parliament Rebecca
Harms, commissioned a report on Chernobyl in 2006 (TORCH, The Other Report on Chernobyl). The 2006 TORCH report claimed that: "In terms of their surface areas, Belarus (22% of its land area) and Austria (13%) were most affected by higher levels of contamination. Other countries were seriously affected; for example, more than 5% of Ukraine, Finland and Sweden were contaminated to high levels (> 40,000 Bq/m² caesium-137). More than 80% of Moldova, the European part of Turkey, Slovenia, Switzerland, Austria and the Slovak Republic were contaminated to lower levels (> 4,000 Bq/m² caesium-137). And 44% of Germany and 34% of the UK were similarly affected." While the IAEA/WHO and UNSCEAR considered areas with exposure greater than 40,000 Bq/m², the TORCH report also included areas contaminated with more than 4,000 Bq/m² of Cs-137. The TORCH 2006 report "estimated that more than half the iodine-131 from Chernobyl [which increases the risk of thyroid cancer] was deposited outside the former Soviet Union. Possible increases in thyroid cancer have been reported in the Czech Republic and the UK, but more research is needed to evaluate thyroid cancer incidences in Western Europe". It predicted about 30,000 to 60,000 excess cancer deaths, 7 to 15 Times greater than the figure of 4,000 in the IAEA press release; warned that predictions of excess cancer deaths strongly depend on the risk factor used; and predicted excess cases of thyroid cancer range between 18,000 and 66,000 in Belarus alone depending on the risk projection model. Another study claims possible heightened mortality in Sweden. Greenpeace quoted a 1998 WHO study, which counted 212 dead from only 72,000 liquidators. The environmental NGO estimated a total death toll of 93,000 but cite in their report that “The most recently published figures indicate that in Belarus, Russia and the Ukraine alone the disaster could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004.” In its report, Greenpeace suggested there will be 270,000 cases of cancer alone attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal compare with the IAEA 2005 report which claimed that "99% of thyroid cancers wouldn't be lethal". Blake Lee-Harwood, campaigns director at Greenpeace, declared that cancer was likely to be the cause of less than half of the final fatalities; "intestinal problems, heart and circulation problems, respiratory problems, endocrine problems, and particularly effects on the immune system," are also concerns. Lee-Harwood alleged that the nuclear industry had a "vested interest in playing down Chernobyl because it's an embarrassment to them". Responding to these criticisms, the WHO spokesman Gregory Hartl explained that "the Greenpeace report is looking at all of Europe, whereas our report looks at only the most affected areas of the three most affected countries,". Though it should be noted that Greenpeace is decidedly anti-nuclear power in its stance.
According to the Union Chernobyl, the main organization of liquidators, 10% of the 600,000 liquidators are now dead, and 165,000 disabled. According to a April 2006 report by the International Physicians for Prevention of Nuclear Warfare (IPPNW), entitled "Chernobyl's consequences on health", more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected. In Europe, the IPPNW claims that 10,000 deformities have been observed in newborns because of Chernobyl's radioactive discharge, with 5,000 deaths among newborn children. They also claim that several hundreds of thousands of the people who worked on the site after the disaster are now sick because of radiation, and tens of thousands are dead.
Controversy over human health effects The majority of premature deaths caused by Chernobyl are expected to be the result of cancers and other diseases induced by radiation in the decades after the event. This will be the result of a large population (some studies have considered the entire population of Europe) exposed to relatively low doses of radiation increasing the risk of cancer across that population. It will be impossible to attribute specific deaths to Chernobyl, and many estimates indicate that the rate of excess deaths will be so small as to be statistically undetectable, even if the ultimate number of extra premature deaths is large. Furthermore, interpretations of the current health state of exposed populations vary. Therefore, estimates of the ultimate human impact of the disaster have relied on numerical models of the effects of radiation on health. Furthermore, the effects of low-level radiation on human health are not well understood, and so the models used, notably the linear no threshold model, are open to question. Given these factors, several different studies of Chernobyl's health effects have come up with substantially different conclusions and are the subject of considerable scientific and political controversy. The following section presents some of the major studies on this topic.
The Chernobyl Forum report In September 2005, a draft summary report by the Chernobyl Forum, comprising a number of UN agencies including the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), the United Nations Development Programme (UNDP), other UN bodies and the Governments of Belarus, the Russian Federation and Ukraine, put the total predicted number of deaths due to the accident at 4000. This death toll predicted by the WHO included the 47 workers who died of acute radiation syndrome as a direct result of radiation from the disaster and nine children who died from thyroid cancer, in the estimated 4000 excess cancer deaths expected among the 600,000 with the highest levels of exposure. The full version of the WHO health effects report adopted by the UN, published in April 2006, included the prediction of 5000 additional fatalities from significantly contaminated areas in Belarus, Russia and Ukraine and predicted that, in total, 9000 will die from cancer among the 6.9 million most-exposed Soviet citizens.
This report is not free of controversy, and has been accused of trying to minimize the consequences of the accident.
The TORCH report In 2006 German Green Party Member of the European Parliament Rebecca Harms commissioned two UK scientists for an alternate report (TORCH, The Other Report on CHernobyl) in response to the UN report. The report included areas not covered by the Chernobyl forum report, and also lower radiation doses. It predicted about 30,000 to 60,000 excess cancer deaths and warned that predictions of excess cancer deaths strongly depend on the risk factor used, and urged more research stating that large uncertainties made it difficult to properly assess the full scale of the disaster.
Greenpeace
Demonstration on Chernobyl day near WHO in Geneva Greenpeace claimed contradictions in the Chernobyl Forum reports, quoting a 1998 WHO study referenced in the 2005 report, which projected 212 dead from 72,000 liquidators. In its report, Greenpeace suggested there will be 270,000 cases of cancer
attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal, but state in their report that "The most recently published figures indicate that in Belarus, Russia and Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004." Blake Lee-Harwood, campaigns director at Greenpeace, believes that cancer was likely to be the cause of less than half of the final fatalities and that "intestinal problems, heart and circulation problems, respiratory problems, endocrine problems, and particularly effects on the immune system," will also cause fatalities. However, concern has been expressed about the methods used in compiling the Greenpeace report.
The April 2006 IPPNW report According to an April 2006 report by the German affiliate of the International Physicians for Prevention of Nuclear Warfare (IPPNW), entitled "Health Effects of Chernobyl", more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected. The report projected tens of thousands dead among the liquidators. In Europe, it alleges that 10,000 deformities have been observed in newborns because of Chernobyl's radioactive discharge, with 5000 deaths among newborn children. They also claimed that several hundreds of thousands of the people who worked on the site after the accident are now sick because of radiation, and tens of thousands are dead.
Other studies and claims •
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The Ukrainian Health Minister claimed in 2006 that more than 2.4 million Ukrainians, including 428,000 children, suffer from health problems related to the catastrophe. Psychological after-effects, as the 2006 UN report pointed out, have also had adverse effects on internally displaced persons. In a recently published study scientists from Forschungszentrum Jülich, Germany, published the “Korma-Report” with data of radiological long-term measurements that were performed between 1998 and 2007 in a region in Belarus that was affected by the Chernobyl accident. The internal radiation exposure of the inhabitants in a village in Korma County/Belarus caused by the existing radioactive contamination has experienced a significant decrease from a very high level. The external exposure, however, reveals a different picture. Although an overall decrease was observed, the organic constituents of the soil show an increase in contamination. This increase was not observed in soils from cultivated land or gardens. According to the Korma Report the internal dose will decrease to less than 0.2 mSv/a in 2011 and to below 0.1 mSv/a in 2020. Despite this, the cumulative dose will remain significantly higher than “normal” values due to external exposure. Resettlement may even be possible in former prohibited areas provided that people comply with appropriate dietary rules. Another study alleged heightened mortality in Sweden. According to the Union Chernobyl, the main organization of liquidators, 10% of the 600,000 liquidators are now dead, and 165,000 disabled. One study reports increased levels of birth defects in Germany and Finland in the wake of the accident.
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A change in the human sex ratio at birth in several European countries has been linked to Chernobyl fallout.
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In the Czech Republic, thyroid cancer has increased significantly after Chernobyl.
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A report from the European Committee on Radiation Risk (a body sponsored by the European Green Party) claims that the World Health Organization, together with most other international and national health bodies, has marginalized or ignored, perhaps purposely, the terrible consequences of the Chernobyl fallout to protect the vested interests of the nuclear industry. The Abstract of the April 2006 International Agency for Research on Cancer report Estimates of the cancer burden in Europe from radioactive fallout from the Chernobyl accident stated "It is unlikely that the cancer burden from the largest radiological accident to date could be detected by monitoring national cancer statistics. Indeed, results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates – other than of thyroid cancer in the most contaminated regions – that can be clearly attributed to radiation from the Chernobyl accident." However, while undetectable, they estimate, based on the linear no threshold model of cancer effects, that 16,000 excess cancer deaths could be expected from the effects of the Chernobyl accident up to 2065. Their estimates have very wide 95% confidence intervals from 6,700 deaths to 38,000.
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The application of the linear no threshold model to predict deaths from low levels of exposure to radiation was disputed in a BBC (British Broadcasting Corporation) Horizon documentary, broadcast on July 13, 2006. It offered statistical evidence to suggest that there is an exposure threshold of about 200 millisieverts, below which there is no increase in radiation-induced disease. Indeed it went further, reporting research from Professor Ron Chesser of Texas Tech University, which suggests that low exposures to radiation can have a protective effect. The program interviewed scientists who believe that the increase in thyroid cancer in the immediate area of the explosion had been over-recorded, and predicted that the estimates for widespread deaths in the long term would be proved wrong. It noted the view of the World Health Organization scientist Dr Mike Rapacholi that, while most cancers can take decades to manifest, leukemia manifests within a decade or so: none of the previously expected peak of leukemia deaths has been found, and none is now expected. Identifying the need to balance the "fear response" in the public's reaction to radiation, the program quoted Dr Peter Boyle, director of the IARC: "Tobacco smoking will cause several thousand times more cancers in the [European] population." Professor Wade Allison of Oxford University (a lecturer in medical physics and particle physics) gave a talk on ionising radiation Nov 24, 2006 in which he gave an approximate figure of 81 cancer deaths from Chernobyl (excluding 28 cases from acute radiation exposure and the thyroid cancer deaths which he regards as "avoidable"). In a closely reasoned argument using statistics from therapeutic radiation, exposure to elevated natural radiation (the presence of radon gas in
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homes) and the diseases of Hiroshima and Nagasaki survivors he demonstrated that the linear no-threshold model should not be applied to low-level exposure in humans, as it ignores the well-known natural repair mechanisms of the body. A photographic essay by photojournalist Paul Fusco documents the legacy of the meltdown on local children
French legal action Since March 2001 400 lawsuits have been filed in France against "X" (the French equivalent of John Doe, an unknown person or company) by the French Association of Thyroid-affected People, including 200 in April 2006. These persons are affected by thyroid cancer or goitres, and have filed lawsuits alleging that the French government, at the time led by Prime Minister Jacques Chirac, had not adequately informed the population of the risks linked to the Chernobyl radioactive fallout. The complaint contrasts the health protection measures put in place in nearby countries (warning against consumption of green vegetables or milk by children and pregnant women) with the relatively high contamination suffered by the east of France and Corsica. Although the 2006 study by the French Institute of Radioprotection and Nuclear Safety said that no clear link could be found between Chernobyl and the increase of thyroid cancers in France, it also stated that papillary thyroid cancer had tripled in the following years.
Comparisons to other radioactivity releases Here we, compares the radioactivity release and decay from the Chernobyl disaster with various other events which involved a release of uncontrolled radioactivity.
Chernobyl compared to background radiation Natural sources of radiation are very prevalent in the environment, and come from cosmic rays, food sources (bananas in particular are a high source), radon gas, granite and other dense rocks, and others. The collective radiation background dose for natural sources in Europe is about 500,000 man sieverts per year. The total dose from Chernobyl is estimated at 80,000 man sieverts, or roughly 1/6 as much. However, some individuals, particular in areas adjacent the reactor, received significantly higher doses. Chernobyl's radiation was detectable across Western Europe. Average doses received ranged from 0.02 mrem (Portugal) to 38 mrem (portions of Germany). For comparison sake, the dose received from eating one banana per day for one year is roughly 3.3 mrem.
Chernobyl compared with an atomic bomb Far fewer people died as an immediate result of the Chernobyl event than died of radiation at Hiroshima, and the eventual total is also significantly less when including those predicted by the WHO to die in the future. Due to the differences in half-life the different radioactive fission products undergo exponential decay at different rates. Hence
the isotopic signature of an event where more than one radioisotope is involved will change with time. Some comments have been made in which the radioactive release of the Chernobyl event is claimed to be 300 or 400 times that of the bomb dropped on Hiroshima. The work of SCOPE suggests that the two events can not be simply compared with a number suggesting that one was XX times larger than the other. The radioactivity released at Chernobyl tended to be more long lived than that released by a bomb detonation hence it is not possible to draw a simple comparison between the two events. Also, a dose of radiation spread over many years (as is the case with Chernobyl) is much less harmful than the same dose received over a short period. The relative size of the Chernobyl release when compared with the release due to a hypothetical ground burst of a bomb similar to the Fat Man device dropped on Nagasaki. A ground burst creates considerably more fallout than the air bursts used at Hiroshima or Nagasaki. Ratio between the release due to the bomb and the Chernobyl Isotope accident 90
Sr
137
Cs
131 133
I
1:87 1:890 1:25
1:31 Xe A comparison of the gamma dose rates due to the Chernobyl accident and the hypothetical nuclear weapon.
Normalized to the same Cs-137 level. (logarithmic scale).
Normalized to the same dose rate for day one.
Normalized to the same Cs-137 level (dose rate on day 10000). The graph of dose rate as a function of time for the bomb fallout was done using a method similar to that of T. Imanaka, S. Fukutani, M. Yamamoto, A. Sakaguchi and M. Hoshi, J. Radiation Research, 2006, 47, Suppl A121-A127. Our graph exhibits the same shape as that obtained in the paper. The bomb fallout graph is for a ground burst of an implosion-based plutonium bomb which has a depleted uranium tamper. The fission was assumed to have been caused by 1 MeV neutrons and 20% occurred in the 238U tamper of the bomb. It is assumed that no separation of the isotopes occurred between the detonation and the deposit of radioactivity. The following gamma-emitting isotopes are modeled 131I, 133I, 132Te, 133I, 135I, 140Ba, 95Zr, 97Zr, 99Mo, 99mTc, 103Ru, 105Ru, 106Ru, 142 La, 143Ce, 137Cs, 91Y, 91Sr, 92Sr, 128Sb and 129Sb. The graph ignores the effects of beta emission and shielding. The data for the isotopes was obtained from the Korean table of the isotopes. The graphs for the Chernobyl accident were computed by an analogous method.
Chernobyl compared with Tomsk-7 The release of radioactivity which occurred at Tomsk-7 (an industrial nuclear complex located in Seversk rather than the city of Tomsk) is another comparison with the Chernobyl release. During reprocessing activities, some of the feed for the second cycle (medium active part) of the PUREX process escaped in an accident involving red oil. According to the IAEA it was estimated that the following isotopes were released from the reaction vessel: •
106
Ru 7.9 TBq
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103
Ru 340 GBq Nb 11.2 TBq 95 Zr 5.1 TBq 137 Cs 505 GBq (estimated from the IAEA data) 141 Ce 370 GBq 144 Ce 240 GBq 125 Sb 100 GBq 239 Pu 5.2 GBq 95
It is important to note that the very short lived isotopes such as 140Ba and 131I were absent from this mixture, and the long lived 137Cs was only at a small concentration. This is because it is not able to enter the tributyl phosphate/hydrocarbon organic phase used in the first liquid-liquid extraction cycle of the PUREX process. The second cycle is normally to clean up the uranium and plutonium product. In the PUREX process some zirconium, technetium and other elements are extracted by the tributyl phosphate. Due to the radiation induced degradation of tributyl phosphate the first cycle organic phase is always contaminated with ruthenium (later extracted by dibutyl hydrogen phosphate). Because the very short lived radioisotopes and the relatively long lived caesium isotopes are either absent or in low concentrations the shape of the dose rate vs. time graph is different from Chernobyl both for short times and long times after the accident. The size of the radioactive release at Tomsk-7 was much smaller, and while it caused moderate environmental contamination it did not cause any early deaths.
Normalized to the same first day dose rate. (logarithmic scale).
Chernobyl compared with the Goiânia accident While both events released 137Cs, the isotopic signature for the Goiânia accident was much simpler. It was a single isotope which has a half-life of about 30 years. To show how the activity vs. time graph for a single isotope differs from the dose rate due to Chernobyl (in the open air) the following chart is shown with calculated data for a hypothetical release of 106Ru.
Normalized to the same first day dose rate. (logarithmic scale).
Chernobyl compared with the Three Mile Island accident Three Mile Island-2 was an accident of a completely different type than Chernobyl. Chernobyl was a human-caused power excursion causing a steam explosion resulting in a graphite fire, uncontained, which lofted radioactive smoke high into the atmosphere; TMI was a slow, undetected leak that lowered the water level around the nuclear fuel, resulting in over a third of it melting. Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material. Containment at TMI did not fail. A small quantity of radioactive gases from the leak were vented into the atmosphere through specially designed filters under operator control. A government report concluded that the accident caused no increase in cancer rates for local residents.
Chernobyl compared with criticality accidents During the time between the start of the Manhattan project and the present day, a series of accidents have occurred in which nuclear criticality has played a central role. The criticality accidents may be divided into two classes.
Process accidents In the first class (process accidents) during the processing of fissile material, accidents have occurred when a critical mass has been created by accident. For instance at Charlestown, Rhode Island, United States on July 24, 1964 one death occurred and at Tokaimura nuclear fuel reprocessing plant, on September 30, 1999 two deaths and one non fatal overexposure occurred as result of accidents where too much fissile matter was placed in a vessel. These accidents tend to lead to very high doses due to direct irradiation of the workers within the site, but due to the inverse square law the dose suffered by members of the general public tends to be very small. Also very little environmental contamination normally occurs as a result of these accidents. A release of radioactivity occurred as a result of the Tokaimura event. The building in which the accident occurred was not designed as a containment building, yet it was able to retard the spread of radioactivity. Because the temperature rise in the nuclear reaction vessel was small, the majority of the fission products remained in the vessel.
Reactor accidents In this type of accident a reactor or other critical assembly releases far more fission power than was expected, or it becomes critical at the wrong moment in time. The series of examples of such events include one in an experimental facility in Buenos Aires, Argentina, on September 23, 1983 (one death) and during the Manhattan Project several people were irradiated (two, Harry K. Daghlian and Louis Slotin, fatally) during "tickling the dragon's tail" experiments. These accidents tend to lead to very high doses due to direct irradiation of the workers within the site, but due to the inverse square law the dose suffered by members of the general public tends to be very small. Also very little environmental contamination normally occurs as a result of these accidents. For instance at Sarov according to the IAEA report (2001) the radioactivity remained confined to within the actinide metal objects which were part of the experimental system. Even the SL-1 accident failed to release much radioactivity outside the building in which it occurred.
Chapter- 7
High-Level Radioactive Waste Management
High-level radioactive waste management concerns management and disposal of highly radioactive materials created during production of nuclear power and nuclear warheads. The technical issues in accomplishing this are daunting, due to the extremely long periods radioactive wastes remain deadly to living organisms. Of particular concern are two long-lived fission products, Technetium-99 (half-life 220,000 years) and Iodine129 (half-life 15.7 million years), which dominate spent nuclear fuel radioactivity after a few thousand years. The most troublesome transuranic elements in spent fuel are Neptunium-237 (half-life two million years) and Plutonium-239 (half-life 24,000 years). Consequently, high-level radioactive waste requires sophisticated treatment and management to successfully isolate it from the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving permanent storage, disposal or transformation of the waste into a non-toxic form. Governments around the world are considering a range of waste management and disposal options, usually involving deep-geologic placement, although there has been limited progress toward implementing long-term waste management solutions. This is partly because the timeframes in question when dealing with radioactive waste range from 10,000 to millions of years, according to studies based on the effect of estimated radiation doses.
Challenges with radioactive waste management Hannes Alfvén, Nobel laureate in physics, described the as yet unsolved dilemma of high-level radioactive waste management: "The problem is how to keep radioactive waste in storage until it decays after hundreds of thousands of years. The geologic deposit must be absolutely reliable as the quantities of poison are tremendous. It is very difficult to satisfy these requirements for the simple reason that we have had no practical experience with such a long term project. Moreover permanently guarded storage requires a society with unprecedented stability."
Thus, Alfvén identified two fundamental prerequisites for effective management of highlevel radioactive waste: (1) stable geological formations, and (2) stable human institutions over hundreds of thousands of years. As Alfvén suggests, no known human civilization has ever endured for so long, and no geologic formation of adequate size for a permanent radioactive waste repository has yet been discovered that has been stable for so long a period. Nevertheless, avoiding confronting the risks associated with managing radioactive wastes may create countervailing risks of greater magnitude. Radioactive waste management is an example of policy analysis that requires special attention to ethical concerns, examined in the light of uncertainty and futurity: consideration of 'the impacts of practices and technologies on future generations'. There is a debate over what should constitute an acceptable scientific and engineering foundation for proceeding with radioactive waste disposal strategies. There are those who have argued, on the basis of complex geochemical simulation models, that relinquishing control over radioactive materials to geohydrologic processes at repository closure is an acceptable risk. They maintain that so-called “natural analogues” inhibit subterranean movement of radionuclides, making disposal of radioactive wastes in stable geologic formations unnecessary. However, existing models of these processes are empirically underdetermined: due to the subterranean nature of such processes in solid geologic formations, the accuracy of computer simulation models has not been verified by empirical observation, certainly not over periods of time equivalent to the lethal half-lives of high-level radioactive waste. On the other hand, some insist deep geologic repositories in stable geologic formations are necessary. National management plans of various countries display a variety of approaches to resolving this debate. Researchers suggest that forecasts of health detriment for such long periods should be examined critically. Practical studies only consider up to 100 years as far as effective planning and cost evaluations are concerned. Long term behaviour of radioactive wastes remains a subject for ongoing research. Management strategies and implementation plans of several representative national governments are described below.
Geologic disposal The process of selecting appropriate permanent repositories for high level waste and spent fuel is now under way in several countries with the first expected to be commissioned some time after 2017. The basic concept is to locate a large, stable geologic formation and use mining technology to excavate a tunnel, or large-bore tunnel boring machines (similar to those used to drill the Chunnel from England to France) to drill a shaft 500–1,000 meters below the surface where rooms or vaults can be excavated for disposal of high-level radioactive waste. The goal is to permanently isolate nuclear waste from the human environment. However, many people remain uncomfortable with the immediate stewardship cessation of this disposal system, suggesting perpetual management and monitoring would be more prudent. Because some radioactive species have half-lives longer than one million years, even very low container leakage and radionuclide migration rates must be taken into account.
Moreover, it may require more than one half-life until some nuclear materials lose enough radioactivity to no longer be lethal to living organisms. A 1983 review of the Swedish radioactive waste disposal program by the National Academy of Sciences found that country’s estimate of several hundred thousand years—perhaps up to one million years—being necessary for waste isolation “fully justified.” Storing high level nuclear waste above ground for a century or so is considered appropriate by many scientists. This allows the material to be more easily observed and any problems detected and managed, while decay of radionuclides over this time period significantly reduces the level of radioactivity and associated harmful effects to the container material. It is also considered likely that over the next century newer materials will be developed which will not break down as quickly, thus increasing the longevity of the container once it is permanently buried. Sea-based options for disposal of radioactive waste include burial beneath a stable abyssal plain and burial in a subduction zone that would slowly carry waste downward into the Earth's mantle. These approaches are currently not being seriously considered because of technical considerations, legal barriers in the Law of the Sea, and because in North America and Europe sea-based burial has become taboo from fear that such a repository could leak and cause widespread contamination. The proposed land-based subductive waste disposal method would dispose of nuclear waste in a subduction zone accessed from land, and therefore is not prohibited by international agreement. This method has been described as a viable means of disposing of radioactive waste, and as a state-of-the-art nuclear waste disposal technology. In nature, sixteen repositories were discovered at the Oklo mine in Gabon where natural nuclear fission reactions took place 1.7 billion years ago. The fission products in these natural formations were found to have moved less than 10 ft (3 m) over this period, though the lack of movement may be due more to retention in the uraninite structure than to insolubility and sorption from moving ground water; uraninite crystals are better preserved here than those in spent fuel rods because of a less complete nuclear reaction, so that reaction products would be less accessible to groundwater attack.
Materials for geological disposal In order to store the high level radioactive waste in long-term geological depositories, specific waste forms need to be used which will allow the radioactivity to decay away while the materials retain their integrity for thousands of years.. The materials currently being used can be broken down into a few classes: glass waste forms, ceramic waste forms, and nanostructured materials. The glass forms include borosilicate glasses and phosphate glasses. Borosilicate nuclear waste glasses are currently used on an industrial scale to immobilize high level radioactive waste in many countries which are currently producers of nuclear energy or have nuclear weaponry. The glass waste form have the advantage of being able to
accommodate a wide variety of waste-stream compositions, they are easy to scale up to industrial processing, and they are stable against thermal, radiative, and chemical perturbations. These glasses function by binding radioactive elements to nonradioactive glass-forming elements Phosphate glasses while not being used industrially have much lower dissolution rates than borosilicate glasses, which make them a more favorable option. However, no single phosphate material has the ability to accommodate all of the radioactive products so phosphate storage requires more reprocessing to separate the waste into distinct fractions. Both glasses have to be processed at elevated temperatures making them unusable for some of the more volatile radiotoxic elements. The ceramic waste forms offer higher waste loadings than the glass options because ceramics have crystalline structure. Also, mineral analogues of the ceramic waste forms provide evidence for long term durability. Due to this fact and the fact that they can be processed at lower temperatures, ceramics are often considered the next generation in high level radioactive waste forms. Ceramic waste forms offer great potential, but a lot of research remains to be done. Nanostructured materials seem to be the frontier beyond ceramic waste forms. These vary the pore size to integrate radionuclides instead of specific atomic sites. This allows for greater chemical flexibility. Also, nanostructured materials have lower temperature processing and can be later altered to make more durable waste forms.
National management plans Finland, the United States and Sweden are the most advanced in developing a deep repository for high-level radioactive waste disposal. Countries vary in their plans on disposing used fuel directly or after reprocessing, with France and Japan having an extensive commitment to reprocessing. The country-specific status of high-level waste management plans are described below. In many European countries (e.g., Britain, Finland, the Netherlands, Sweden and Switzerland) the risk or dose limit for a member of the public exposed to radiation from a future high-level nuclear waste facility is considerably more stringent than that suggested by the International Commission on Radiation Protection or proposed in the United States. European limits are often more stringent than the standard suggested in 1990 by the International Commission on Radiation Protection by a factor of 20, and more stringent by a factor of ten than the standard proposed by the U.S. Environmental Protection Agency (EPA) for Yucca Mountain nuclear waste repository for the first 10,000 years after closure. Moreover, the U.S. EPA’s proposed standard for greater than 10,000 years is 250 times more permissive than the European limit. The countries that have made the most progress towards a repository for high-level radioactive waste have typically started with public consultations and made voluntary siting a necessary condition. This consensus seeking approach is believed to have a greater chance of success than top-down modes of decision making, but the process is
necessarily slow, and there is "inadequate experience around the world to know if it will succeed in all existing and aspiring nuclear nations".
Asia China In the Peoples Republic of China, ten reactors provide about 2% of electricity and five more are under construction. China made a commitment to reprocessing in the 1980s; a pilot plant is under construction at Lanzhou, where a temporary spent fuel storage facility has been constructed. Geological disposal has been studied since 1985, and a permanent deep geological repository was required by law in 2003. Sites in Gansu Province near the Gobi desert in northwestern China are under investigation, with a final site expected to be selected by 2020, and actual disposal by about 2050. India Sixteen nuclear reactors produce about 3% of India’s electricity, and seven more are under construction. Spent fuel is processed at facilities in Trombay near Mumbai, at Tarapur on the west coast north of Mumbai, and at Kalpakkam on the southeast coast of India. Plutonium will be used in a fast breeder reactor (under construction) to produce more fuel, and other waste vitrified at Tarapur and Trombay. Interim storage for 30 years is expected, with eventual disposal in a deep geological repository in crystalline rock near Kalpakkam. Japan With 55 nuclear reactors producing about 29% of its electricity, the Japanese policy is to reprocess its nuclear waste. Originally spent fuel was reprocessed under contract in England and France, but after public outcry a major reprocessing plant was built in Rokkasho, with operations expected to commence in 2007. The policy to use recovered plutonium as mixed oxide (MOX) reactor fuel was questioned on economic grounds because there are few reactors capable of using it, and in 2004 it was revealed the Ministry of Economy, Trade and Industry had covered up a 1994 report indicating reprocessing spent fuel would cost four times as much as burying it. In 2000, a Specified Radioactive Waste Final Disposal Act called for creation of a new organization to manage high level radioactive waste, and later that year the Nuclear Waste Management Organization of Japan (NUMO) was established under the jurisdiction of the Ministry of Economy, Trade and Industry. NUMO is responsible for selecting a permanent deep geologic repository site, construction, operation and closure of the facility for waste emplacement by 2040. Site selection was begun in 2002 and application information was sent to 3,239 municipalities, but by spring 2006, no local government had volunteered to host the facility. Final selection of a repository location is expected between 2023 and 2027.
Europe Belgium The deep disposal of high-level radioactive waste (HLW) has been studied in Belgium for more than 30 years. Boom Clay is presently studied as a reference host formation for HLW disposal. The Hades underground research laboratory (URL) is located at −223 m in the Boom Formation at the Mol site. The Belgian URL is operated by the Euridice European Interest Group, a joint organisation between SCK•CEN, the Belgian Nuclear Research Centre which initiated the research on waste disposal in Belgium in the 1970s and 1980s and Ondraf/Niras, the waste management authorities. In Belgium, the regulatory body in charge of guidance and licensing approval is the Federal Agency of Nuclear Control, created in 2001. Finland In 1983, the government decided to select a site for permanent repository by 2010. With four nuclear reactors providing 29% of its electricity, Finland in 1987 enacted a Nuclear Energy Act making the producers of radioactive waste responsible for its disposal, subject to requirements of its Radiation and Nuclear Safety Authority and an absolute veto given to local governments in which a proposed repository would be located. Producers of nuclear waste organized Posiva Oy with responsibility for site selection, construction and operation of a permanent repository. A 1994 amendment to the Act required final disposal of spent fuel in Finland, prohibiting the import or export of radioactive waste. Environmental assessment of four sites occurred in 1997–98, Posiva Oy chose the Olkiluoto site near two existing reactors, and the local government approved it in 2000. The Finnish Parliament approved a deep geologic repository there in igneous bedrock at a depth of about 500 meters in 2001. The repository concept is similar to the Swedish model, with containers to be clad in copper and buried below the water table beginning in 2020. An underground characterization facility is under construction at the site (2009). France With 59 nuclear reactors contributing about 75% of its electricity, the highest percentage of any country, France has been reprocessing its spent reactor fuel since the introduction of nuclear power there. Some reprocessed plutonium is used to make fuel, but more is being produced than is being recycled as reactor fuel. France also reprocesses spent fuel for other countries, but the nuclear waste is returned to the country of origin. Radioactive waste from reprocessing French spent fuel is expected to be disposed of in a geological repository, pursuant to legislation enacted in 1991 that established a 15 year period for conducting radioactive waste management research. Under this legislation, partition and transmutation of long-lived elements, immobilization and conditioning processes, and long-term near surface storage are being investigated by a Commissariat a l’Energy Atomique (CEA). Disposal in deep geological formations is being studied by the French
agency for radioactive waste management, Agence Nationale pour la gestion des Dechets Radioactifs, in underground research labs. Three sites were identified for possible deep geologic disposal in clay near the border of Meuse and Haute-Marne, near Gard, and at Vienne. In 1998 the government approved the Meuse/Haute Marne Underground Research Laboratory, a site near Meuse/Haute-Marne and dropped the others from further consideration. Legislation was proposed in 2006 to license a repository by 2015, with operations expected in 2025. Germany Nuclear waste policy in Germany is in flux. With 17 reactors in operation, accounting for about 30% of its electricity, German planning for a permanent geologic repository began in 1974, focused on salt dome Gorleben, a salt mine near Gorleben about 100 kilometers northeast of Braunschweig. The site was announced in 1977 with plans for a reprocessing plant, spent fuel management, and permanent disposal facilities at a single site. Plans for the reprocessing plant were dropped in 1979. In 2000, the federal government and utilities agreed to suspend underground investigations for three to ten years, and the government committed to ending its use of nuclear power, closing one reactor in 2003. In 2005 Angela Merkel was elected Chancellor with a promise to change the policy moving away from nuclear power, but was unsuccessful in doing so through November 2006. Meanwhile, electric utilities have been transporting spent fuel to interim storage facilities at Gorleben, Lubmin and Ahaus until temporary storage facilities can be built near reactor sites. Previously, spent fuel was sent to France or England for reprocessing, but this practice was ended in July 2005. Russia In Russia, the Ministry of Atomic Energy (Minatom) is responsible for 31 nuclear reactors which generate about 16% of its electricity. Minatom is also responsible for reprocessing and radioactive waste disposal, including over 25,000 tons of spent nuclear fuel in temporary storage in 2001. Russia has a long history of reprocessing spent fuel for military purposes, and previously planned to reprocess imported spent fuel, possibly including some of the 33,000 metric tons of spent fuel accumulated at sites in other countries who received fuel from the U.S., which the U.S. originally pledged to take back, such as Brazil, the Czech Republic, India, Japan, Mexico, Slovenia, South Korea, Switzerland, Taiwan, and the European Union. An Environmental Protection Act in 1991 prohibited importing radioactive material for long-term storage or burial in Russia, but controversial legislation to allow imports for permanent storage was passed by the Russian Parliament and signed by President Putin in 2001. In the long term, the Russian plan is for deep geologic disposal. Most attention has been paid to locations where waste has accumulated in temporary storage at Mayak, near Chelyabinsk in the Ural Mountains, and in granite at Krasnoyarsk in Siberia.
Sweden In Sweden there are ten operating nuclear reactors that produce about 45% of its electricity. Two other reactors in Barsebäck were shut down in 1999 and 2005. When these reactors were built, it was expected their nuclear fuel would be reprocessed in a foreign country, and the reprocessing waste would not be returned to Sweden. Later, construction of a domestic reprocessing plant was contemplated, but has not been built. Passage of the Stipulation Act of 1977 transferred responsibility for nuclear waste management from the government to the nuclear industry, requiring reactor operators to present an acceptable plan for waste management with “absolute safety” in order to obtain an operating license. In early 1980, after the Three Mile Island meltdown in the United States, a referendum was held on the future use of nuclear power in Sweden. In late 1980, after a three-question referendum produced mixed results, the Swedish Parliament decided to phase out existing reactors by 2010. The Swedish Nuclear Fuel and Waste Management Co. (Svensk Kärnbränslehantering AB, known as SKB), was created in 1980 and is responsible for final disposal of nuclear waste there. This includes operation of a monitored retrievable storage facility, the Central Interim Storage Facility for Spent Nuclear Fuel at Oskarshamn, about 150 miles south of Stockholm on the Baltic coast; transportation of spent fuel; and construction of a permanent repository. Swedish utilities store spent fuel at the reactor site for one year before transporting it to the facility at Oskarshamn, where it will be stored in excavated caverns filled with water for about 30 years before removal to a permanent repository. Conceptual design of a permanent repository was determined by 1983, calling for placement of copper-clad iron canisters in granite bedrock about 1,650 feet underground, below the water table in what is known as the KBS-3 method. Space around the canisters will be filled with bentonite clay. After examining six possible locations for a permanent repository, three were nominated for further investigation at Osthammar, Oskarshamn, and Tierp. The first two are still under consideration, with a final selection expected in 2009. On 3 June 2009 Swedish government choose location for deep level waste site at Östhammar, near Forsmark Nuclear Powerplant. Switzerland Switzerland has four nuclear reactors that provide about 43% of its electricity.. Some Swiss spent nuclear fuel has been sent for reprocessing in France and the United Kingdom; most fuel is currently being stored without reprocessing. An industry-owned organization, ZWILAG, built and operates a central interim storage facility for spent nuclear fuel and high-level radioactive waste, and for conditioning low-level radioactive waste and for incinerating wastes. Other interim storage facilities predating ZWILAG continue to operate in Switzerland. The Swiss program is currently considering options for the siting of a deep repository for high-level radioactive waste disposal, and for low & intermediate level wastes. Construction of a repository is not foreseen until well into this century. Research on
sedimentary rock (especially Opalinus Clay) is presently carried out at the Swiss Mont Terri rock laboratory; the Grimsel Test Site, an older facility in crystalline rock is also still active. United Kingdom Great Britain has 19 operating reactors, producing about 20% of its electricity. It processes much of its spent fuel at Sellafield on the northwest coast across from Ireland, where nuclear waste is vitrified and sealed in stainless steel canisters for dry storage above ground for at least 50 years before eventual deep geologic disposal. Sellafield has a history of environmental and safety problems, including a fire in a nuclear plant in Windscale, and a significant incident in 2005 at the main reprocessing plant (THORP). In 1982 the Nuclear Industry Radioactive Waste Management Executive (NIREX) was established with responsibility for disposing of long-lived nuclear waste and in 2006 a Committee on Radioactive Waste Management (CoRWM) of the Department of Environment, Food and Rural Affairs recommended geologic disposal 200–1,000 meters underground. NIREX developed a generic repository concept based on the Swedish model but has not yet selected a site. A Nuclear Decommissioning Authority is responsible for packaging waste from reprocessing and will eventually relieve British Nuclear Fuels Ltd. of responsibility for power reactors and the Sellafield reprocessing plant.
North America Canada The 18 operating nuclear power plants in Canada generated about 16% of its electricity in 2006. A national Nuclear Fuel Waste Act was enacted by the Canadian Parliament in 2002, requiring nuclear energy corporations to create a waste management organization to propose to the Government of Canada approaches for management of nuclear waste, and implementation of an approach subsequently selected by the government. The Act defined management as “long term management by means of storage or disposal, including handling, treatment, conditioning or transport for the purpose of storage or disposal.” The resulting Nuclear Waste Management Organization(NWMO) conducted an extensive 3-year study and consultation with Canadians. In 2005, they recommended Adaptive Phased Management, an approach that emphasized both technical and management methods. The technical method included centralized isolation and containment of spent nuclear fuel in a deep geologic repository in a suitable rock formation, such as the granite of the Canadian Shield or Ordovician sedimentary rocks. Also recommended was a phased decision making process supported by a program of continuous learning, research and development.
In 2007, the Canadian government accepted this recommendation, and NWMO was tasked with implementing the recommendation. No specific timeframe was defined for the process. Currently (2009) the NWMO is designing the process for site selection; siting is expected to take 10 years or more. United States The Nuclear Waste Policy Act of 1982 established a timetable and procedure for constructing a permanent, underground repository for high-level radioactive waste by the mid-1990s, and provided for some temporary storage of waste, including spent fuel from 104 civilian nuclear reactors that produce about 19.4% of electricity there. The United States in April 2008 had about 56,000 metric tons of spent fuel and 20,000 canisters of solid defense-related waste, and this is expected to increase to 119,000 metric tons by 2035. The U.S. opted for Yucca Mountain nuclear waste repository, a final repository at Yucca Mountain in Nevada, but this project was widely opposed, with some of the main concerns being long distance transportation of waste from across the United States to this site, the possibility of accidents, and the uncertainty of success in isolating nuclear waste from the human environment in perpetuity. Yucca Mountain, with capacity for 70,000 metric tons of radioactive waste, was expected to open in 2017. However, the Obama Administration rejected use of the site in the 2009 United States Federal Budget proposal, which eliminated all funding except that needed to answer inquiries from the Nuclear Regulatory Commission, "while the Administration devises a new strategy toward nuclear waste disposal." On March 5, 2009, Energy Secretary Steven Chu told a Senate hearing "the Yucca Mountain site no longer was viewed as an option for storing reactor waste." The Waste Isolation Pilot Plant in the United States is the world's first underground repository for transuranic waste.
International repository Although Australia does not have any nuclear power reactors, Pangea Resources considered siting an international repository in the outback of South Australia or Western Australia in 1998, but this stimulated legislative opposition in both states and the Australian national Senate during the following year. Thereafter, Pangea ceased operations in Australia but reemerged as Pangea International Association, and in 2002 evolved into the Association for Regional and International Underground Storage with support from Belgium, Bulgaria, Hungary, Japan and Switzerland. A general concept for an international repository has been advanced by one of the principals in all three ventures. Russia has expressed interest in serving as a repository for other countries, but does not envision sponsorship or control by an international body or group of other countries. South Africa, Argentina and western China have also been mentioned as possible locations. In the EU, COVRA is negotiating a European-wide waste disposal system with single disposal sites that can be used by several EU-countries. This EU-wide storage possibility is being researched under the SAPIERR-2 program.
