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Radioactive waste

Radioactive waste is used or spent radioactive material produced by the medical, industrial, defense, research, processing and power sectors, or non-radioactive material which has been contaminated through exposure to radioactive sources. As it decays, radioactive waste emits radiation which can have negative health and environmental effects if encountered at critical doses. Radioactive waste is created in nuclear medicine, nuclear research, nuclear power generation, and nuclear weapons reprocessing.[1] The classification of material as radioactive waste, its storage and disposal is defined and regulated by government agencies and courts in order to protect human health and the environment.

Thailand Institute of Nuclear Technology (TINT) low-level radioactive waste barrels.

Radioactive waste is broadly classified into low-level waste (LLW), intermediate-level waste (ILW) high-level waste (HLW), and other special catagories such as transuranic and spent nuclear fuel.

In nuclear reprocessing plants about 96% of spent nuclear fuel is recycled back into uranium-based and mixed-oxide (MOX) fuels. The residual 4% is minor actinides and fission products the latter of which are a mixture of stable and quickly decaying (most likely already having decayed in the spent fuel pool) elements, medium lived fission products such as strontium-90 and caesium-137 and finally seven long-lived fission products with half lives in the hundreds of thousands to millions of years. The minor actinides meanwhile are heavy elements other than uranium and plutonium which are created by neutron capture. Their half lives range from years to millions of years and as alpha emitters they are particularly radiotoxic. While there are proposed - and to a much lesser extent current - uses of all those elements, commercial scale reprocessing using the PUREX-process disposes of them as waste together with the fission products. The waste is subsequently converted into a glass-like ceramic for storage in a deep geological repository.

The time radioactive waste must be stored for depends on the type of waste and radioactive isotopes it contains. Short-term approaches to radioactive waste storage have been segregation and storage on the surface or near-surface. Burial in a deep geological repository is a favored solution for long-term storage of high-level waste, while re-use and transmutation are favored solutions for reducing the HLW inventory. Boundaries to recycling of spent nuclear fuel are regulatory and economic as well as the issue of radioactive contamination if chemical separation processes cannot achieve a very high purity. Furthermore, elements may be present in both useful and troublesome isotopes, which would require costly and energy intensive isotope separation for their use - a currently uneconomic prospect.

A summary of the amounts of radioactive waste and management approaches for most developed countries are presented and reviewed periodically as part of the International Atomic Energy Agency (IAEA)'s Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management.[2]

Nature and significance

A quantity of radioactive waste typically consists of a number of radionuclides, which are unstable isotopes of elements that undergo decay and thereby emit ionizing radiation, which is harmful to humans and the environment. Different isotopes emit different types and levels of radiation, which last for different periods of time.

Physics

Medium-lived
fission products[further explanation needed]
t½
(year)
Yield
(%)
Q
(keV)
βγ
155Eu 4.76 0.0803 252 βγ
85Kr 10.76 0.2180 687 βγ
113mCd 14.1 0.0008 316 β
90Sr 28.9 4.505   2826 β
137Cs 30.23 6.337   1176 βγ
121mSn 43.9 0.00005 390 βγ
151Sm 88.8 0.5314 77 β
Nuclide t12 Yield Q[a 1] βγ
(Ma) (%)[a 2] (keV)
99Tc 0.211 6.1385 294 β
126Sn 0.230 0.1084 4050[a 3] βγ
79Se 0.327 0.0447 151 β
93Zr 1.53 5.4575 91 βγ
135Cs 2.3   6.9110[a 4] 269 β
107Pd 6.5   1.2499 33 β
129I 15.7   0.8410 194 βγ
  1. ^ Decay energy is split among β, neutrino, and γ if any.
  2. ^ Per 65 thermal neutron fissions of 235U and 35 of 239Pu.
  3. ^ Has decay energy 380 keV, but its decay product 126Sb has decay energy 3.67 MeV.
  4. ^ Lower in thermal reactors because 135Xe, its predecessor, readily absorbs neutrons.

The radioactivity of all radioactive waste weakens with time. All radionuclides contained in the waste have a half-life — the time it takes for half of the atoms to decay into another nuclide. Eventually, all radioactive waste decays into non-radioactive elements (i.e., stable nuclides). Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131.[3] 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 uranium-235.

The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans.[4] 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.[5] This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state.

Pharmacokinetics

Exposure to radioactive waste may cause health impacts due to ionizing radiation exposure. In humans, a dose of 1 sievert carries a 5.5% risk of developing cancer,[6] and regulatory agencies assume the risk is linearly proportional to dose even for low doses. Ionizing radiation can cause deletions in chromosomes.[7] If a developing organism such as a fetus 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 small, as in most mammals, because of natural cellular-repair mechanisms, many just now coming to light. These mechanisms range from DNA, mRNA and protein repair, to internal lysosomic digestion of defective proteins, and even induced cell suicide—apoptosis[8]

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 through 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 relative biological effectiveness, making it far more damaging to tissues per amount of energy deposited. Because of such differences, the rules determining biological injury differ widely according to the radioisotope, time of exposure, and sometimes also the nature of the chemical compound which contains the radioisotope.

Sources

Actinides[9] by decay chain Half-life
range (a)
Fission products of 235U by yield[10]
4n 4n + 1 4n + 2 4n + 3 4.5–7% 0.04–1.25% <0.001%
228Ra 4–6 a 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 a 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 a 137Cs 151Smþ 121mSn
248Bk[11] 249Cfƒ 242mAmƒ 141–351 a

No fission products have a half-life in the range of 100 a–210 ka ...

241Amƒ 251Cfƒ[12] 430–900 a
226Ra 247Bk 1.3–1.6 ka
240Pu 229Th 246Cmƒ 243Amƒ 4.7–7.4 ka
245Cmƒ 250Cm 8.3–8.5 ka
239Puƒ 24.1 ka
230Th 231Pa 32–76 ka
236Npƒ 233Uƒ 234U 150–250 ka 99Tc 126Sn
248Cm 242Pu 327–375 ka 79Se
1.53 Ma 93Zr
237Npƒ 2.1–6.5 Ma 135Cs 107Pd
236U 247Cmƒ 15–24 Ma 129I
244Pu 80 Ma

... nor beyond 15.7 Ma[13]

232Th 238U 235Uƒ№ 0.7–14.1 Ga

Radioactive waste comes from a number of sources. In countries with nuclear power plants, nuclear armament, or nuclear fuel treatment plants, the majority of waste originates from the nuclear fuel cycle and nuclear weapons reprocessing. 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

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 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.[14]

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 anti-tank shells, and on at least one occasion even a sailboat keel.[15] 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 (half-life 245 thousand years), neptunium-237 (2.144 million years), plutonium-238 (87.7 years) and americium-241 (432 years), and even sometimes some neutron emitters such as californium (half-life of 898 years for californium-251). 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 (see high-level waste below). 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 usually "stored", while in other 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.[16] The fission products removed from the fuel are a concentrated form of high-level waste as are the chemicals used in the process. While most countries reprocess the fuel carrying out single plutonium cycles, India is planning multiple plutonium recycling schemes [17] and Russia pursues closed cycle.[18]

Fuel composition and long term radioactivity

 
Activity of U-233 for three fuel types. In the case of MOX, the U-233 increases for the first 650 thousand years as it is produced by the decay of Np-237 which was created in the reactor by absorption of neutrons by U-235.
 
Total activity for three fuel types. In region 1, there is radiation from short-lived nuclides, in region 2, from Sr-90 and Cs-137, and on the far right, the decay of Np-237 and U-233.

The use of different fuels in nuclear reactors results in different spent nuclear fuel (SNF) composition, with varying activity curves. The most abundant material being U-238 with other uranium isotopes, other actinides, fission products and activation products.[19]

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. Its radioactive decay will strongly influence the long-term activity curve of the SNF around a 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, no thorium). For RGPu and WGPu, the initial amount of U-233 and its decay around a million years can be seen. This has an effect on the total activity curve of the three fuel types. The initial 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. Nuclear reprocessing can remove the actinides from the spent fuel so they can be used or destroyed (see Long-lived fission product § Actinides).

Proliferation concerns

Since uranium and plutonium are nuclear weapons materials, there have been proliferation 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 extremely difficult to separate, and more cost-effective ways of obtaining fissile material exist (e.g., uranium enrichment or dedicated plutonium production reactors).[20]

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 have pointed out the difficulty of recovering useful material from sealed deep storage areas makes other methods preferable. Specifically, high radioactivity and heat (80 °C in surrounding rock) greatly increase the difficulty of mining a storage area, and the enrichment methods required have high capital costs.[21]

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. 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 alpha-emitting 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. Naturally occurring uranium is not fissile because it contains 99.3% of U-238 and only 0.7% of U-235.

Legacy waste

Due to historic activities typically related to the radium industry, uranium mining, and military programs, numerous sites 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."[22] Despite copious quantities of waste, the DOE has stated a goal of cleaning all presently contaminated sites successfully by 2025.[22] 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."[22] The United States has at least 108 sites designated as areas that are contaminated and unusable, sometimes many thousands of acres.[22][23] DOE wishes to clean or mitigate many or all by 2025, using the recently developed method of geomelting,[citation needed] 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.[22] 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.[22]

Medicine

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:

Industry

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.[24]

Naturally occurring radioactive material

 
Annual release of uranium and thorium radioisotopes from coal combustion, predicted by ORNL to cumulatively amount to 2.9 Mt over the 1937–2040 period, from the combustion of an estimated 637 Gt of coal worldwide.[25]

Substances containing natural radioactivity are known as NORM (naturally occurring radioactive material). After human processing that exposes or concentrates this natural radioactivity (such as mining bringing coal to the surface or burning it to produce concentrated ash), it becomes technologically enhanced naturally occurring radioactive material (TENORM).[26] 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), typically 17 milligrams in the body at a time and 0.4 milligrams/day intake.[27] Most rocks, especially granite, have a low level of radioactivity due to the potassium-40, thorium and uranium contained.

Usually ranging from 1 millisievert (mSv) to 13 mSv annually depending on location, average radiation exposure from natural radioisotopes is 2.0 mSv per person a year worldwide.[28] This makes up the majority of typical total dosage (with mean annual exposure from other sources amounting to 0.6 mSv from medical tests averaged over the whole populace, 0.4 mSv from cosmic rays, 0.005 mSv from the legacy of past atmospheric nuclear testing, 0.005 mSv occupational exposure, 0.002 mSv from the Chernobyl disaster, and 0.0002 mSv from the nuclear fuel cycle).[28]

TENORM is not regulated as restrictively as nuclear reactor waste, though there are no significant differences in the radiological risks of these materials.[29]

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.[25][30] The more active ash minerals become concentrated in the fly ash precisely because they do not burn well.[25] 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.[31] According to U.S. National Council on Radiation Protection and Measurements (NCRP) reports, population exposure from 1000-MWe power plants amounts to 490 person-rem/year for coal power plants, 100 times as great as nuclear power plants (4.8 person-rem/year). The exposure from the complete nuclear fuel cycle from mining to waste disposal is 136 person-rem/year; the corresponding value for coal use from mining to waste disposal is "probably unknown".[25]

Oil and gas

Residues from the oil and gas industry often contain radium and its decay products. 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.[32]

Radioactive elements are an industrial problem in some oil wells where workers operating in direct contact with the crude oil and brine can be actually exposed to doses having negative health effects. Due to the relatively high concentration of these elements in the brine, its disposal is also a technological challenge. In the United States, the brine is however exempt from the dangerous waste regulations and can be disposed of regardless of radioactive or toxic substances content since the 1980s.[33]

Rare-earth mining

Due to natural occurrence of radioactive elements such as thorium and radium in rare-earth ore, mining operations also result in production of waste and mineral deposits that are slightly radioactive.[34]

Classification

Classification of radioactive waste varies by country. The IAEA, which publishes the Radioactive Waste Safety Standards (RADWASS), also plays a significant role.[35] The proportion of various types of waste generated in the UK:[36]

  • 94% – low-level waste (LLW)
  • ~6% – intermediate-level waste (ILW)
  • <1% – high-level waste (HLW)

Mill tailings

 
Removal of very low-level waste

Uranium tailings are waste by-product materials left over from the rough processing of uranium-bearing ore. They are not significantly radioactive. Mill tailings are sometimes referred to as 11(e)2 wastes, from the section of the Atomic Energy Act of 1946 that defines them. Uranium mill tailings typically also contain chemically hazardous heavy metal 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.

Although mill tailings are not very radioactive, they have long half-lives. Mill tailings often contain radium, thorium and trace amounts of uranium.[37]

Low-level waste

Low-level waste (LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. Low-level wastes include paper, rags, tools, clothing, filters, and other materials which contain small amounts of mostly short-lived radioactivity. Materials that originate from any region of an Active Area are commonly designated as LLW as a precautionary measure even if there is 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. Example LLW includes wiping rags, mops, medical tubes, laboratory animal carcasses, and more.[38] LLW waste makes 94% of all radioactive waste volume in the UK.[1]

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, class B, class C, and Greater Than Class C (GTCC).

Intermediate-level waste

 
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 t

Intermediate-level waste (ILW) contains higher amounts of radioactivity compared to low-level waste. It generally requires shielding, but not cooling.[39] Intermediate-level wastes includes resins, chemical sludge and metal nuclear fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen or mixed with silica sand and vitrified for disposal. As a general rule, short-lived waste (mainly non-fuel materials from reactors) is buried in shallow repositories, while long-lived waste (from fuel and fuel reprocessing) is deposited in geological repository. Regulations in the United States do not define this category of waste; the term is used in Europe and elsewhere. ILW makes 6% of all radioactive waste volume in the UK.[1]

High-level waste

High-level waste (HLW) is produced by nuclear reactors and the reprocessing of nuclear fuel.[40] The exact definition of HLW differs internationally. After a nuclear fuel rod serves one fuel cycle and is removed from the core, it is considered HLW.[41] Spent fuel rods contain mostly uranium with fission products and transuranic elements generated in the reactor core. Spent fuel is highly radioactive and often hot. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear electricity generation but it contributes to less than 1% of volume of all radioactive waste produced in the UK. Overall, the 60-year-long nuclear program in the UK up until 2019 produced 2150 m3 of HLW.[1]

The radioactive waste from spent fuel rods consists primarily of cesium-137 and strontium-90, but it may also include plutonium, which can be considered transuranic waste.[37] The half-lives of these radioactive elements can differ quite extremely. Some elements, such as cesium-137 and strontium-90 have half-lives of approximately 30 years. Meanwhile, plutonium has a half-life that can stretch to as long as 24,000 years.[37]

The amount of HLW worldwide is currently increasing by about 12,000 tonnes every year.[42] A 1000-megawatt nuclear power plant produces about 27 t of spent nuclear fuel (unreprocessed) every year.[43] For comparison, the amount of ash produced by coal power plants in the United States alone is estimated at 130,000,000 t per year[44] and fly ash is estimated to release 100 times more radiation than an equivalent nuclear power plant.[45]

 
The current locations across the United States where nuclear waste is stored

In 2010, it was estimated that about 250,000 t of nuclear HLW were stored globally.[46] This does not include amounts that have escaped into the environment from accidents or tests. Japan is estimated to hold 17,000 t of HLW in storage in 2015.[47] As of 2019, the United States has over 90,000 t of HLW.[48] HLW have been shipped to other countries to be stored or reprocessed and, in some cases, shipped back as active fuel.

The ongoing controversy over high-level radioactive waste disposal is a major constraint on the nuclear power's global expansion.[49] Most scientists agree that the main proposed long-term solution is deep geological burial, either in a mine or a deep borehole.[50][51] As of 2019 no dedicated civilian high-level nuclear waste is operational[49] as small amounts of HLW did not justify the investment before. Finland is in the advanced stage of the construction of the Onkalo spent nuclear fuel repository, which is planned to open in 2025 at 400–450 m depth. France is in the planning phase for a 500 m deep Cigeo facility in Bure. Sweden is planning a site in Forsmark. Canada plans a 680 m deep facility near Lake Huron in Ontario. The Republic of Korea plans to open a site around 2028.[1] The site in Sweden enjoys 80% support from local residents as of 2020.[52]

The Morris Operation in Grundy County, Illinois, is currently the only de facto high-level radioactive waste storage site in the United States.

Transuranic waste

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 of more cautiously than either low- or intermediate-level waste. In the United States, it arises mainly from nuclear weapons production, and consists of clothing, tools, rags, residues, debris, and other items contaminated with small amounts of radioactive elements (mainly plutonium).

Under U.S. law, transuranic waste is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of the radiation dose rate 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/h (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 1,000,000 mrem/h (10,000 mSv/h). The United States currently disposes of TRUW generated from military facilities at the Waste Isolation Pilot Plant (WIPP) in a deep salt formation in New Mexico.[53]

Prevention

A future way to reduce waste accumulation is to phase out current reactors in favor of Generation IV reactors, which output less waste per power generated. Fast reactors such as BN-800 in Russia are also able to consume MOX fuel that is manufactured from recycled spent fuel from traditional reactors.[54]

The UK's Nuclear Decommissioning Authority published a position paper in 2014 on the progress on approaches to the management of separated plutonium, which summarises the conclusions of the work that NDA shared with UK government.[55]

Management

 
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 15.7 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).[56] 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.[57] 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.[58]

 
The Onkalo is a planned deep geological repository for the final disposal of spent nuclear fuel[59][60] near the Olkiluoto Nuclear Power Plant in Eurajoki, on the west coast of Finland. Picture of a pilot cave at final depth in Onkalo.

In the second half of the 20th century, several methods of disposal of radioactive waste were investigated by nuclear nations,[61] which are :

  • "Long-term above-ground storage", not implemented.
  • "Disposal in outer space" (for instance, inside the Sun), not implemented—as it would be currently too expensive.
  • "Deep borehole disposal", not implemented.
  • "Rock melting", not implemented.
  • "Disposal at subduction zones", not implemented.
  • Ocean disposal, by the USSR, the United Kingdom,[62] Switzerland, the United States, Belgium, France, the Netherlands, Japan, Sweden, Russia, Germany, Italy and South Korea (1954–93). This is no longer permitted by international agreements.
  • "Sub-seabed disposal", not implemented, not permitted by international agreements.
  • "Disposal in ice sheets", rejected in Antarctic Treaty
  • "Deep well injection", by USSR and USA.
  • Nuclear transmutation, using lasers to cause beta decay to convert the unstable atoms to those with shorter half-lives.

In the United States, waste management policy completely broke down with the ending of work on the incomplete Yucca Mountain Repository.[63] At present there are 70 nuclear power plant sites where spent fuel is stored. A Blue Ribbon Commission was appointed by President Obama to look into future options for this and future waste. A deep geological repository seems to be favored.[63] 2018 Nobel Prize for Physics-winner Gérard Mourou has proposed using Chirped pulse amplification to generate high-energy and low-duration laser pulses to transmute highly radioactive material (contained in a target) to significantly reduce its half-life, from thousands of years to only a few minutes.[64][65]

Initial treatment

Vitrification

 
The Waste Vitrification Plant at Sellafield

Long-term storage of radioactive waste requires the stabilization of the waste into a form that will neither react nor degrade for extended periods. It is theorized that one way to do this might be through vitrification.[66] 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.[67]

The 'calcine' generated is fed continuously into an induction heated furnace with fragmented glass.[68] The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies. As a melt, this product is poured into stainless steel cylindrical containers ("cylinders") in a batch process. When cooled, the fluid solidifies ("vitrifies") into the glass. After being formed, the glass is highly resistant to water.[69]

After filling a cylinder, a seal is welded onto the cylinder head. 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 thousands of years.[70]

The glass inside a cylinder is usually a black glossy substance. All this work (in the United Kingdom) is done using hot cell systems. Sugar is added to control the ruthenium chemistry and to stop the formation of the volatile RuO4 containing radioactive ruthenium isotopes. In the West, the glass is normally a borosilicate glass (similar to Pyrex), while in the former Soviet Union it is normal to use a phosphate glass.[71] 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.[72] 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.[67][73]

Phosphate Ceramics

Vitrification is not the only way to stabilize the waste into a form that will not react or degrade for extended periods. Immobilization via direct incorporation into a phosphate-based crystalline ceramic host is also used.[74] The diverse chemistry of phosphate ceramics under various conditions demonstrates a versatile material that can withstand chemical, thermal, and radioactive degradation over time. The properties of phosphates, particularly ceramic phosphates, of stability over a wide pH range, low porosity, and minimization of secondary waste introduces possibilities for new waste immobilization techniques.

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.[75] 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.[76] 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 U.S. military wastes). Synroc was invented by Prof Ted Ringwood (a geochemist) at the Australian National University.[77] 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. A Synroc waste treatment facility began construction in 2018 at ANSTO.[78]

Long-term management

The time frame in question when dealing with radioactive waste ranges from 10,000 to 1,000,000 years,[79] according to studies based on the effect of estimated radiation doses.[80] Researchers suggest that forecasts of health detriment for such periods should be examined critically.[81][82] Practical studies only consider up to 100 years as far as effective planning[83] and cost evaluations[84] are concerned. Long term behavior of radioactive wastes remains a subject for ongoing research projects in geoforecasting.[85]

Remediation

Algae has shown selectivity for strontium in studies, where most plants used in bioremediation have not shown selectivity between calcium and strontium, often becoming saturated with calcium, which is present in greater quantities in nuclear waste. Strontium-90 with a half life around 30 years, is classified as high-level waste.[86]

Researchers have looked at the bioaccumulation of strontium by Scenedesmus spinosus (algae) in simulated wastewater. The study claims a highly selective biosorption capacity for strontium of S. spinosus, suggesting that it may be appropriate for use of nuclear wastewater.[87] A study of the pond alga Closterium moniliferum using non-radioactive strontium found that varying the ratio of barium to strontium in water improved strontium selectivity.[86]

Above-ground disposal

Dry cask storage typically involves taking waste from a spent fuel pool and sealing it (along with an inert gas) in a steel cylinder, which is placed in a concrete cylinder which acts as a radiation shield. It is a relatively inexpensive method which can be done at a central facility or adjacent to the source reactor. The waste can be easily retrieved for reprocessing.[88]

Geologic disposal

 
Diagram of an underground low-level radioactive waste disposal site
 
On Feb. 14, 2014, radioactive materials at the Waste Isolation Pilot Plant leaked from a damaged storage drum due to the use of incorrect packing material. Analysis showed the lack of a "safety culture" at the plant since its successful operation for 15 years had bred complacency.[89]

The process of selecting appropriate deep final repositories for high-level waste and spent fuel is now underway in several countries with the first expected to be commissioned sometime after 2010.[citation needed] 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 metres (1,600 ft) to 1,000 metres (3,300 ft) 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.[citation needed]

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.[90] 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."[91]

Ocean floor disposal of radioactive waste has been suggested by the finding that deep waters in the North Atlantic Ocean do not present an exchange with shallow waters for about 140 years based on oxygen content data recorded over a period of 25 years.[92] They include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the Earth's mantle,[93][94] 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.[95]

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,[96] and as the state-of-the-art as of 2001 in nuclear waste disposal technology.[97] Another approach termed Remix & Return[98] 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 of highly toxic radioactive elements such as plutonium within it.

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 5 kilometres (3.1 mi) 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. The Earth's crust contains 120 trillion tons of thorium and 40 trillion tons of uranium (primarily at relatively trace concentrations of parts per million each adding up over the crust's 3 × 1019 ton mass), among other natural radioisotopes.[99][100][101] Since the fraction of nuclides decaying per unit of time is inversely proportional to an isotope's half-life, the relative radioactivity of the lesser amount of human-produced radioisotopes (thousands of tons instead of trillions of tons) would diminish once the isotopes with far shorter half-lives than the bulk of natural radioisotopes decayed.

In January 2013, Cumbria county council rejected UK central government proposals to start work on an underground storage dump for nuclear waste near to the Lake District National Park. "For any host community, there will be a substantial community benefits package and worth hundreds of millions of pounds" said Ed Davey, Energy Secretary, but nonetheless, the local elected body voted 7–3 against research continuing, after hearing evidence from independent geologists that "the fractured strata of the county was impossible to entrust with such dangerous material and a hazard lasting millennia."[102][103]

Horizontal drillhole disposal describes proposals to drill over one km vertically, and two km horizontally in the earth’s crust, for the purpose of disposing of high-level waste forms such as spent nuclear fuel, Caesium-137, or Strontium-90. After the emplacement and the retrievability period,[clarification needed] drillholes would be backfilled and sealed. A series of tests of the technology were carried out in November 2018 and then again publicly in January 2019 by a U.S. based private company.[104] The test demonstrated the emplacement of a test-canister in a horizontal drillhole and retrieval of the same canister. There was no actual high-level waste used in this test.[105][106]

European Commission Joint Research Centre report of 2021 (see above) concluded:[107]

Management of radioactive waste and its safe and secure disposal is a necessary step in the lifecycle of all applications of nuclear science and technology (nuclear energy, research, industry, education, medical, and others). Radioactive waste is therefore generated in practically every country, the largest contribution coming from the nuclear energy lifecycle in countries operating nuclear power plants. Presently, there is broad scientific and technical consensus that disposal of high-level, long-lived radioactive waste in deep geologic formations is, at the state of today’s knowledge, considered as an appropriate and safe means of isolating it from the biosphere for very long time scales.

Transmutation

There have been proposals for reactors that consume nuclear waste and transmute it to other, less-harmful or shorter-lived, 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 eventually canceled by the U.S. 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 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 United States in April 1977 by President Carter due to the danger of plutonium proliferation,[108] but President Reagan rescinded the ban in 1981.[109] Due to economic losses and risks, the 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 United States is actively promoting research on transmutation technologies needed to markedly reduce the problem of nuclear waste treatment.[110]

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.[111]

Re-use

Spent nuclear fuel contains abundant fertile uranium and traces of fissile materials.[19] Methods such as the PUREX process can be used to remove useful actinides for the production of active nuclear fuel.

Another option is to find applications for the isotopes in nuclear waste so as to re-use them.[112] 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 can reduce the quantity of waste produced.

The Nuclear Assisted Hydrocarbon Production Method,[113] 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 fractures the formation and 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 is 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.

Breeder reactors can run on U-238 and transuranic elements, which comprise the majority of spent fuel radioactivity in the 1,000–100,000-year time span.

Space disposal

Space disposal is attractive because it removes nuclear waste from the planet. It has significant disadvantages, such as the potential for catastrophic failure of a launch vehicle, which could spread radioactive material into the atmosphere and around the world. A high number of launches would be required because no individual rocket would be able to carry very much of the material relative to the total amount that needs to be disposed of. This makes the proposal impractical economically and increases the risk of one or more launch failures.[114] To further complicate matters, international agreements on the regulation of such a program would need to be established.[115] Costs and inadequate reliability of modern rocket launch systems for space disposal has been one of the motives for interest in non-rocket spacelaunch systems such as mass drivers, space elevators, and other proposals.[116]

National management plans

 
Anti-nuclear protest near nuclear waste disposal centre at Gorleben in northern Germany

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."[117]

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.[118]

The U.S. EPA's proposed standard for greater than 10,000 years is 250 times more permissive than the European limit.[118] The U.S. EPA proposed a legal limit of a maximum of 3.5 millisieverts (350 millirem) each annually to local individuals after 10,000 years, which would be up to several percent of[vague] the exposure currently received by some populations in the highest natural background regions on Earth, though the U.S. United States Department of Energy (DOE) predicted that received dose would be much below that limit.[119] Over a timeframe of thousands of years, after the most active short half-life radioisotopes decayed, burying U.S. nuclear waste would increase the radioactivity in the top 2000 feet of rock and soil in the United States (10 million km2) by approximately 1 part in 10 million over the cumulative amount of natural radioisotopes in such a volume, but the vicinity of the site would have a far higher concentration of artificial radioisotopes underground than such an average.[120]

Mongolia

After serious opposition about plans and negotiations between Mongolia with Japan and the United States of America to build nuclear-waste facilities in Mongolia, Mongolia stopped all negotiations in September 2011. These negotiations had started after U.S. Deputy Secretary of Energy Daniel Poneman visited Mongolia in September 2010. Talks took place in Washington, D.C. between officials of Japan, the United States, and Mongolia in February 2011. After this the United Arab Emirates (UAE), which wanted to buy nuclear fuel from Mongolia, joined in the negotiations. The talks were kept secret and, although the Mainichi Daily News reported on them in May, Mongolia officially denied the existence of these negotiations. However, alarmed by this news, Mongolian citizens protested against the plans and demanded the government withdraw the plans and disclose information. The Mongolian President Tsakhiagiin Elbegdorj issued a presidential order on September 13 banning all negotiations with foreign governments or international organizations on nuclear-waste storage plans in Mongolia.[121] The Mongolian government has accused the newspaper of distributing false claims around the world. After the presidential order, the Mongolian president fired the individual who was supposedly involved in these conversations.

Illegal dumping

Authorities in Italy are investigating a 'Ndrangheta mafia clan accused of trafficking and illegally dumping nuclear waste. According to a whistleblower, 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 United States, 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, sending them to the sea bed off the Calabrian coast.[122] 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.[123]

Accidents

A few 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.[124] 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.[125] 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.[citation needed] In Italy, several radioactive waste deposits let material flow into river water, thus contaminating water for domestic use.[126] In France in the summer of 2008, numerous incidents happened:[127] 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;[128] in another case, over 100 staff were contaminated with low doses of radiation.[129] There are ongoing concerns around the deterioration of the nuclear waste site on the Enewetak Atoll of the Marshall Islands and a potential radioactive spill.[130]

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.[131] 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.[131]

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.[132]

On 15 December 2011, top government spokesman Osamu Fujimura of the Japanese government admitted that nuclear substances were found in the waste of Japanese nuclear facilities. Although Japan did commit itself in 1977 to these inspections in the safeguard agreement with the IAEA, the reports were kept secret for the inspectors of the International Atomic Energy Agency.[citation needed] Japan did start discussions with the IAEA about the large quantities of enriched uranium and plutonium that were discovered in nuclear waste cleared away by Japanese nuclear operators.[citation needed] At the press conference Fujimura said: "Based on investigations so far, most nuclear substances have been properly managed as waste, and from that perspective, there is no problem in safety management," But according to him, the matter was at that moment still being investigated.[133]

Associated hazard warning signs

See also

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Cited sources

  • Vandenbosch, Robert & Vandenbosch, Susanne E. (2007). Nuclear waste stalemate. Salt Lake City: University of Utah Press. ISBN 978-0874809039.

External links

  • (annotated bibliography)
  • Euridice European Interest Group in charge of Hades URL operation (link)
  • (link)
  • Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security (PDF)
  • Environmental Protection Agency – Yucca Mountain (documents)
  • Grist.org – How to tell future generations about nuclear waste (article)
  • (links)
  • (documents)
  • Nuclear Regulatory Commission – Radioactive Waste (documents)
  • Nuclear Regulatory Commission – Spent Fuel Heat Generation Calculation (guide)
  • Radwaste Solutions (magazine)
  • UNEP Earthwatch – Radioactive Waste 2008-12-23 at the Wayback Machine (documents and links)
  • World Nuclear Association – Radioactive Waste 2010-06-11 at the Wayback Machine (briefing papers)
  • Worries can't be buried as nuclear waste piles up, Los Angeles Times, January 21, 2008

radioactive, waste, used, spent, radioactive, material, produced, medical, industrial, defense, research, processing, power, sectors, radioactive, material, which, been, contaminated, through, exposure, radioactive, sources, decays, radioactive, waste, emits, . Radioactive waste is used or spent radioactive material produced by the medical industrial defense research processing and power sectors or non radioactive material which has been contaminated through exposure to radioactive sources As it decays radioactive waste emits radiation which can have negative health and environmental effects if encountered at critical doses Radioactive waste is created in nuclear medicine nuclear research nuclear power generation and nuclear weapons reprocessing 1 The classification of material as radioactive waste its storage and disposal is defined and regulated by government agencies and courts in order to protect human health and the environment Thailand Institute of Nuclear Technology TINT low level radioactive waste barrels Radioactive waste is broadly classified into low level waste LLW intermediate level waste ILW high level waste HLW and other special catagories such as transuranic and spent nuclear fuel In nuclear reprocessing plants about 96 of spent nuclear fuel is recycled back into uranium based and mixed oxide MOX fuels The residual 4 is minor actinides and fission products the latter of which are a mixture of stable and quickly decaying most likely already having decayed in the spent fuel pool elements medium lived fission products such as strontium 90 and caesium 137 and finally seven long lived fission products with half lives in the hundreds of thousands to millions of years The minor actinides meanwhile are heavy elements other than uranium and plutonium which are created by neutron capture Their half lives range from years to millions of years and as alpha emitters they are particularly radiotoxic While there are proposed and to a much lesser extent current uses of all those elements commercial scale reprocessing using the PUREX process disposes of them as waste together with the fission products The waste is subsequently converted into a glass like ceramic for storage in a deep geological repository The time radioactive waste must be stored for depends on the type of waste and radioactive isotopes it contains Short term approaches to radioactive waste storage have been segregation and storage on the surface or near surface Burial in a deep geological repository is a favored solution for long term storage of high level waste while re use and transmutation are favored solutions for reducing the HLW inventory Boundaries to recycling of spent nuclear fuel are regulatory and economic as well as the issue of radioactive contamination if chemical separation processes cannot achieve a very high purity Furthermore elements may be present in both useful and troublesome isotopes which would require costly and energy intensive isotope separation for their use a currently uneconomic prospect A summary of the amounts of radioactive waste and management approaches for most developed countries are presented and reviewed periodically as part of the International Atomic Energy Agency IAEA s Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management 2 Contents 1 Nature and significance 1 1 Physics 1 2 Pharmacokinetics 2 Sources 2 1 Nuclear fuel cycle 2 1 1 Front end 2 1 2 Back end 2 1 3 Fuel composition and long term radioactivity 2 1 4 Proliferation concerns 2 2 Nuclear weapons decommissioning 2 3 Legacy waste 2 4 Medicine 2 5 Industry 2 6 Naturally occurring radioactive material 2 6 1 Coal 2 6 2 Oil and gas 2 6 3 Rare earth mining 3 Classification 3 1 Mill tailings 3 2 Low level waste 3 3 Intermediate level waste 3 4 High level waste 3 5 Transuranic waste 4 Prevention 5 Management 5 1 Initial treatment 5 1 1 Vitrification 5 1 2 Phosphate Ceramics 5 1 3 Ion exchange 5 1 4 Synroc 5 2 Long term management 5 2 1 Remediation 5 2 2 Above ground disposal 5 2 3 Geologic disposal 5 2 4 Transmutation 5 2 5 Re use 5 2 6 Space disposal 5 3 National management plans 5 3 1 Mongolia 5 4 Illegal dumping 6 Accidents 7 Associated hazard warning signs 8 See also 9 References 10 Cited sources 11 External linksNature and significance EditA quantity of radioactive waste typically consists of a number of radionuclides which are unstable isotopes of elements that undergo decay and thereby emit ionizing radiation which is harmful to humans and the environment Different isotopes emit different types and levels of radiation which last for different periods of time Physics Edit Main article Fission product yield See also Radioactive decay Medium lived fission products further explanation needed t year Yield Q keV bg155Eu 4 76 0 0803 252 bg85Kr 10 76 0 2180 687 bg113mCd 14 1 0 0008 316 b90Sr 28 9 4 505 2826 b137Cs 30 23 6 337 1176 bg121mSn 43 9 0 00005 390 bg151Sm 88 8 0 5314 77 bLong lived fission productsvte Nuclide t1 2 Yield Q a 1 bg Ma a 2 keV 99Tc 0 211 6 1385 294 b126Sn 0 230 0 1084 4050 a 3 bg79Se 0 327 0 0447 151 b93Zr 1 53 5 4575 91 bg135Cs 2 3 6 9110 a 4 269 b107Pd 6 5 1 2499 33 b129I 15 7 0 8410 194 bg Decay energy is split among b neutrino and g if any Per 65 thermal neutron fissions of 235U and 35 of 239Pu Has decay energy 380 keV but its decay product 126Sb has decay energy 3 67 MeV Lower in thermal reactors because 135Xe its predecessor readily absorbs neutrons The radioactivity of all radioactive waste weakens with time All radionuclides contained in the waste have a half life the time it takes for half of the atoms to decay into another nuclide Eventually all radioactive waste decays into non radioactive elements i e stable nuclides Since radioactive decay follows the half life rule the rate of decay is inversely proportional to the duration of decay In other words the radiation from a long lived isotope like iodine 129 will be much less intense than that of a short lived isotope like iodine 131 3 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 uranium 235 The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans 4 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 5 This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state Pharmacokinetics Edit Exposure to radioactive waste may cause health impacts due to ionizing radiation exposure In humans a dose of 1 sievert carries a 5 5 risk of developing cancer 6 and regulatory agencies assume the risk is linearly proportional to dose even for low doses Ionizing radiation can cause deletions in chromosomes 7 If a developing organism such as a fetus 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 small as in most mammals because of natural cellular repair mechanisms many just now coming to light These mechanisms range from DNA mRNA and protein repair to internal lysosomic digestion of defective proteins and even induced cell suicide apoptosis 8 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 through 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 relative biological effectiveness making it far more damaging to tissues per amount of energy deposited Because of such differences the rules determining biological injury differ widely according to the radioisotope time of exposure and sometimes also the nature of the chemical compound which contains the radioisotope Sources EditActinides and fission products by half life vteActinides 9 by decay chain Half life range a Fission products of 235U by yield 10 4n 4n 1 4n 2 4n 3 4 5 7 0 04 1 25 lt 0 001 228Ra 4 6 a 155Euth244Cmƒ 241Puƒ 250Cf 227Ac 10 29 a 90Sr 85Kr 113mCdth232Uƒ 238Puƒ 243Cmƒ 29 97 a 137Cs 151Smth 121mSn248Bk 11 249Cfƒ 242mAmƒ 141 351 a No fission products have a half life in the range of 100 a 210 ka 241Amƒ 251Cfƒ 12 430 900 a226Ra 247Bk 1 3 1 6 ka240Pu 229Th 246Cmƒ 243Amƒ 4 7 7 4 ka245Cmƒ 250Cm 8 3 8 5 ka239Puƒ 24 1 ka230Th 231Pa 32 76 ka236Npƒ 233Uƒ 234U 150 250 ka 99Tc 126Sn248Cm 242Pu 327 375 ka 79Se 1 53 Ma 93Zr237Npƒ 2 1 6 5 Ma 135Cs 107Pd236U 247Cmƒ 15 24 Ma 129I 244Pu 80 Ma nor beyond 15 7 Ma 13 232Th 238U 235Uƒ 0 7 14 1 Ga has thermal neutron capture cross section in the range of 8 50 barnsƒ fissile primarily a naturally occurring radioactive material NORM th neutron poison thermal neutron capture cross section greater than 3k barns Radioactive waste comes from a number of sources In countries with nuclear power plants nuclear armament or nuclear fuel treatment plants the majority of waste originates from the nuclear fuel cycle and nuclear weapons reprocessing 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 Edit Main articles Nuclear fuel cycle and Spent nuclear fuel See also Nuclear power Front end Edit 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 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 14 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 anti tank shells and on at least one occasion even a sailboat keel 15 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 Edit See also Nuclear reprocessing 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 half life 245 thousand years neptunium 237 2 144 million years plutonium 238 87 7 years and americium 241 432 years and even sometimes some neutron emitters such as californium half life of 898 years for californium 251 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 see high level waste below 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 usually stored while in other 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 16 The fission products removed from the fuel are a concentrated form of high level waste as are the chemicals used in the process While most countries reprocess the fuel carrying out single plutonium cycles India is planning multiple plutonium recycling schemes 17 and Russia pursues closed cycle 18 Fuel composition and long term radioactivity Edit Activity of U 233 for three fuel types In the case of MOX the U 233 increases for the first 650 thousand years as it is produced by the decay of Np 237 which was created in the reactor by absorption of neutrons by U 235 See also Spent nuclear fuel and High level waste Main article Long lived fission product Total activity for three fuel types In region 1 there is radiation from short lived nuclides in region 2 from Sr 90 and Cs 137 and on the far right the decay of Np 237 and U 233 The use of different fuels in nuclear reactors results in different spent nuclear fuel SNF composition with varying activity curves The most abundant material being U 238 with other uranium isotopes other actinides fission products and activation products 19 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 Its radioactive decay will strongly influence the long term activity curve of the SNF around a 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 no thorium For RGPu and WGPu the initial amount of U 233 and its decay around a million years can be seen This has an effect on the total activity curve of the three fuel types The initial 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 Nuclear reprocessing can remove the actinides from the spent fuel so they can be used or destroyed see Long lived fission product Actinides Proliferation concerns Edit See also Nuclear proliferation and Reactor grade plutonium Since uranium and plutonium are nuclear weapons materials there have been proliferation 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 extremely difficult to separate and more cost effective ways of obtaining fissile material exist e g uranium enrichment or dedicated plutonium production reactors 20 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 have pointed out the difficulty of recovering useful material from sealed deep storage areas makes other methods preferable Specifically high radioactivity and heat 80 C in surrounding rock greatly increase the difficulty of mining a storage area and the enrichment methods required have high capital costs 21 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 In pyrometallurgical fast reactors the separated plutonium and uranium are contaminated by actinides and cannot be used for nuclear weapons Nuclear weapons decommissioning Edit 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 alpha emitting 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 Naturally occurring uranium is not fissile because it contains 99 3 of U 238 and only 0 7 of U 235 Legacy waste Edit Due to historic activities typically related to the radium industry uranium mining and military programs numerous sites 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 22 Despite copious quantities of waste the DOE has stated a goal of cleaning all presently contaminated sites successfully by 2025 22 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 22 The United States has at least 108 sites designated as areas that are contaminated and unusable sometimes many thousands of acres 22 23 DOE wishes to clean or mitigate many or all by 2025 using the recently developed method of geomelting citation needed 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 22 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 22 Medicine Edit 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 and external radiotherapy 30 years Tc 99 product of the decay of Technetium 99m 221 000 years Industry Edit 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 24 Naturally occurring radioactive material Edit Annual release of uranium and thorium radioisotopes from coal combustion predicted by ORNL to cumulatively amount to 2 9 Mt over the 1937 2040 period from the combustion of an estimated 637 Gt of coal worldwide 25 Substances containing natural radioactivity are known as NORM naturally occurring radioactive material After human processing that exposes or concentrates this natural radioactivity such as mining bringing coal to the surface or burning it to produce concentrated ash it becomes technologically enhanced naturally occurring radioactive material TENORM 26 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 typically 17 milligrams in the body at a time and 0 4 milligrams day intake 27 Most rocks especially granite have a low level of radioactivity due to the potassium 40 thorium and uranium contained Usually ranging from 1 millisievert mSv to 13 mSv annually depending on location average radiation exposure from natural radioisotopes is 2 0 mSv per person a year worldwide 28 This makes up the majority of typical total dosage with mean annual exposure from other sources amounting to 0 6 mSv from medical tests averaged over the whole populace 0 4 mSv from cosmic rays 0 005 mSv from the legacy of past atmospheric nuclear testing 0 005 mSv occupational exposure 0 002 mSv from the Chernobyl disaster and 0 0002 mSv from the nuclear fuel cycle 28 TENORM is not regulated as restrictively as nuclear reactor waste though there are no significant differences in the radiological risks of these materials 29 Coal Edit 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 25 30 The more active ash minerals become concentrated in the fly ash precisely because they do not burn well 25 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 31 According to U S National Council on Radiation Protection and Measurements NCRP reports population exposure from 1000 MWe power plants amounts to 490 person rem year for coal power plants 100 times as great as nuclear power plants 4 8 person rem year The exposure from the complete nuclear fuel cycle from mining to waste disposal is 136 person rem year the corresponding value for coal use from mining to waste disposal is probably unknown 25 Oil and gas Edit Residues from the oil and gas industry often contain radium and its decay products 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 32 Radioactive elements are an industrial problem in some oil wells where workers operating in direct contact with the crude oil and brine can be actually exposed to doses having negative health effects Due to the relatively high concentration of these elements in the brine its disposal is also a technological challenge In the United States the brine is however exempt from the dangerous waste regulations and can be disposed of regardless of radioactive or toxic substances content since the 1980s 33 Rare earth mining Edit Due to natural occurrence of radioactive elements such as thorium and radium in rare earth ore mining operations also result in production of waste and mineral deposits that are slightly radioactive 34 See also Rare earth element Environmental considerationsClassification EditClassification of radioactive waste varies by country The IAEA which publishes the Radioactive Waste Safety Standards RADWASS also plays a significant role 35 The proportion of various types of waste generated in the UK 36 94 low level waste LLW 6 intermediate level waste ILW lt 1 high level waste HLW Mill tailings Edit Main article Uranium tailings See also Uranium Mill Tailings Remedial Action Removal of very low level waste Uranium tailings are waste by product materials left over from the rough processing of uranium bearing ore They are not significantly radioactive Mill tailings are sometimes referred to as 11 e 2 wastes from the section of the Atomic Energy Act of 1946 that defines them Uranium mill tailings typically also contain chemically hazardous heavy metal 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 Although mill tailings are not very radioactive they have long half lives Mill tailings often contain radium thorium and trace amounts of uranium 37 Low level waste Edit Main article Low level waste Low level waste LLW is generated from hospitals and industry as well as the nuclear fuel cycle Low level wastes include paper rags tools clothing filters and other materials which contain small amounts of mostly short lived radioactivity Materials that originate from any region of an Active Area are commonly designated as LLW as a precautionary measure even if there is 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 Example LLW includes wiping rags mops medical tubes laboratory animal carcasses and more 38 LLW waste makes 94 of all radioactive waste volume in the UK 1 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 class B class C and Greater Than Class C GTCC Intermediate level waste Edit 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 t Intermediate level waste ILW contains higher amounts of radioactivity compared to low level waste It generally requires shielding but not cooling 39 Intermediate level wastes includes resins chemical sludge and metal nuclear fuel cladding as well as contaminated materials from reactor decommissioning It may be solidified in concrete or bitumen or mixed with silica sand and vitrified for disposal As a general rule short lived waste mainly non fuel materials from reactors is buried in shallow repositories while long lived waste from fuel and fuel reprocessing is deposited in geological repository Regulations in the United States do not define this category of waste the term is used in Europe and elsewhere ILW makes 6 of all radioactive waste volume in the UK 1 High level waste Edit Main article High level waste High level waste HLW is produced by nuclear reactors and the reprocessing of nuclear fuel 40 The exact definition of HLW differs internationally After a nuclear fuel rod serves one fuel cycle and is removed from the core it is considered HLW 41 Spent fuel rods contain mostly uranium with fission products and transuranic elements generated in the reactor core Spent fuel is highly radioactive and often hot HLW accounts for over 95 of the total radioactivity produced in the process of nuclear electricity generation but it contributes to less than 1 of volume of all radioactive waste produced in the UK Overall the 60 year long nuclear program in the UK up until 2019 produced 2150 m3 of HLW 1 The radioactive waste from spent fuel rods consists primarily of cesium 137 and strontium 90 but it may also include plutonium which can be considered transuranic waste 37 The half lives of these radioactive elements can differ quite extremely Some elements such as cesium 137 and strontium 90 have half lives of approximately 30 years Meanwhile plutonium has a half life that can stretch to as long as 24 000 years 37 The amount of HLW worldwide is currently increasing by about 12 000 tonnes every year 42 A 1000 megawatt nuclear power plant produces about 27 t of spent nuclear fuel unreprocessed every year 43 For comparison the amount of ash produced by coal power plants in the United States alone is estimated at 130 000 000 t per year 44 and fly ash is estimated to release 100 times more radiation than an equivalent nuclear power plant 45 The current locations across the United States where nuclear waste is stored In 2010 it was estimated that about 250 000 t of nuclear HLW were stored globally 46 This does not include amounts that have escaped into the environment from accidents or tests Japan is estimated to hold 17 000 t of HLW in storage in 2015 47 As of 2019 the United States has over 90 000 t of HLW 48 HLW have been shipped to other countries to be stored or reprocessed and in some cases shipped back as active fuel The ongoing controversy over high level radioactive waste disposal is a major constraint on the nuclear power s global expansion 49 Most scientists agree that the main proposed long term solution is deep geological burial either in a mine or a deep borehole 50 51 As of 2019 no dedicated civilian high level nuclear waste is operational 49 as small amounts of HLW did not justify the investment before Finland is in the advanced stage of the construction of the Onkalo spent nuclear fuel repository which is planned to open in 2025 at 400 450 m depth France is in the planning phase for a 500 m deep Cigeo facility in Bure Sweden is planning a site in Forsmark Canada plans a 680 m deep facility near Lake Huron in Ontario The Republic of Korea plans to open a site around 2028 1 The site in Sweden enjoys 80 support from local residents as of 2020 52 The Morris Operation in Grundy County Illinois is currently the only de facto high level radioactive waste storage site in the United States Transuranic waste Edit Main article Transuranic waste The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject You may improve this article discuss the issue on the talk page or create a new article as appropriate November 2013 Learn how and when to remove this template message 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 of more cautiously than either low or intermediate level waste In the United States it arises mainly from nuclear weapons production and consists of clothing tools rags residues debris and other items contaminated with small amounts of radioactive elements mainly plutonium Under U S law transuranic waste is further categorized into contact handled CH and remote handled RH on the basis of the radiation dose rate 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 h 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 1 000 000 mrem h 10 000 mSv h The United States currently disposes of TRUW generated from military facilities at the Waste Isolation Pilot Plant WIPP in a deep salt formation in New Mexico 53 Prevention EditA future way to reduce waste accumulation is to phase out current reactors in favor of Generation IV reactors which output less waste per power generated Fast reactors such as BN 800 in Russia are also able to consume MOX fuel that is manufactured from recycled spent fuel from traditional reactors 54 Main article BN 800 reactor The UK s Nuclear Decommissioning Authority published a position paper in 2014 on the progress on approaches to the management of separated plutonium which summarises the conclusions of the work that NDA shared with UK government 55 Management Edit Modern medium to high level transport container for nuclear waste See also High level radioactive waste management List of nuclear waste treatment technologies and Environmental effects of nuclear power 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 15 7 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 56 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 57 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 58 The Onkalo is a planned deep geological repository for the final disposal of spent nuclear fuel 59 60 near the Olkiluoto Nuclear Power Plant in Eurajoki on the west coast of Finland Picture of a pilot cave at final depth in Onkalo In the second half of the 20th century several methods of disposal of radioactive waste were investigated by nuclear nations 61 which are Long term above ground storage not implemented Disposal in outer space for instance inside the Sun not implemented as it would be currently too expensive Deep borehole disposal not implemented Rock melting not implemented Disposal at subduction zones not implemented Ocean disposal by the USSR the United Kingdom 62 Switzerland the United States Belgium France the Netherlands Japan Sweden Russia Germany Italy and South Korea 1954 93 This is no longer permitted by international agreements Sub seabed disposal not implemented not permitted by international agreements Disposal in ice sheets rejected in Antarctic Treaty Deep well injection by USSR and USA Nuclear transmutation using lasers to cause beta decay to convert the unstable atoms to those with shorter half lives In the United States waste management policy completely broke down with the ending of work on the incomplete Yucca Mountain Repository 63 At present there are 70 nuclear power plant sites where spent fuel is stored A Blue Ribbon Commission was appointed by President Obama to look into future options for this and future waste A deep geological repository seems to be favored 63 2018 Nobel Prize for Physics winner Gerard Mourou has proposed using Chirped pulse amplification to generate high energy and low duration laser pulses to transmute highly radioactive material contained in a target to significantly reduce its half life from thousands of years to only a few minutes 64 65 Initial treatment Edit Vitrification Edit The Waste Vitrification Plant at Sellafield Long term storage of radioactive waste requires the stabilization of the waste into a form that will neither react nor degrade for extended periods It is theorized that one way to do this might be through vitrification 66 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 67 The calcine generated is fed continuously into an induction heated furnace with fragmented glass 68 The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies As a melt this product is poured into stainless steel cylindrical containers cylinders in a batch process When cooled the fluid solidifies vitrifies into the glass After being formed the glass is highly resistant to water 69 After filling a cylinder a seal is welded onto the cylinder head 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 thousands of years 70 The glass inside a cylinder is usually a black glossy substance All this work in the United Kingdom is done using hot cell systems Sugar is added to control the ruthenium chemistry and to stop the formation of the volatile RuO4 containing radioactive ruthenium isotopes In the West the glass is normally a borosilicate glass similar to Pyrex while in the former Soviet Union it is normal to use a phosphate glass 71 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 72 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 67 73 Phosphate Ceramics Edit Vitrification is not the only way to stabilize the waste into a form that will not react or degrade for extended periods Immobilization via direct incorporation into a phosphate based crystalline ceramic host is also used 74 The diverse chemistry of phosphate ceramics under various conditions demonstrates a versatile material that can withstand chemical thermal and radioactive degradation over time The properties of phosphates particularly ceramic phosphates of stability over a wide pH range low porosity and minimization of secondary waste introduces possibilities for new waste immobilization techniques Ion exchange Edit 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 75 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 76 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 Edit 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 U S military wastes Synroc was invented by Prof Ted Ringwood a geochemist at the Australian National University 77 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 A Synroc waste treatment facility began construction in 2018 at ANSTO 78 Long term management Edit See also Economics of nuclear power plants Waste disposal costs The time frame in question when dealing with radioactive waste ranges from 10 000 to 1 000 000 years 79 according to studies based on the effect of estimated radiation doses 80 Researchers suggest that forecasts of health detriment for such periods should be examined critically 81 82 Practical studies only consider up to 100 years as far as effective planning 83 and cost evaluations 84 are concerned Long term behavior of radioactive wastes remains a subject for ongoing research projects in geoforecasting 85 Remediation Edit Algae has shown selectivity for strontium in studies where most plants used in bioremediation have not shown selectivity between calcium and strontium often becoming saturated with calcium which is present in greater quantities in nuclear waste Strontium 90 with a half life around 30 years is classified as high level waste 86 Researchers have looked at the bioaccumulation of strontium by Scenedesmus spinosus algae in simulated wastewater The study claims a highly selective biosorption capacity for strontium of S spinosus suggesting that it may be appropriate for use of nuclear wastewater 87 A study of the pond alga Closterium moniliferum using non radioactive strontium found that varying the ratio of barium to strontium in water improved strontium selectivity 86 Above ground disposal Edit Dry cask storage typically involves taking waste from a spent fuel pool and sealing it along with an inert gas in a steel cylinder which is placed in a concrete cylinder which acts as a radiation shield It is a relatively inexpensive method which can be done at a central facility or adjacent to the source reactor The waste can be easily retrieved for reprocessing 88 Geologic disposal Edit Diagram of an underground low level radioactive waste disposal site On Feb 14 2014 radioactive materials at the Waste Isolation Pilot Plant leaked from a damaged storage drum due to the use of incorrect packing material Analysis showed the lack of a safety culture at the plant since its successful operation for 15 years had bred complacency 89 The process of selecting appropriate deep final repositories for high level waste and spent fuel is now underway in several countries with the first expected to be commissioned sometime after 2010 citation needed 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 metres 1 600 ft to 1 000 metres 3 300 ft 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 citation needed 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 90 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 91 Ocean floor disposal of radioactive waste has been suggested by the finding that deep waters in the North Atlantic Ocean do not present an exchange with shallow waters for about 140 years based on oxygen content data recorded over a period of 25 years 92 They include burial beneath a stable abyssal plain burial in a subduction zone that would slowly carry the waste downward into the Earth s mantle 93 94 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 95 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 96 and as the state of the art as of 2001 in nuclear waste disposal technology 97 Another approach termed Remix amp Return 98 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 of highly toxic radioactive elements such as plutonium within it 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 5 kilometres 3 1 mi 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 The Earth s crust contains 120 trillion tons of thorium and 40 trillion tons of uranium primarily at relatively trace concentrations of parts per million each adding up over the crust s 3 1019 ton mass among other natural radioisotopes 99 100 101 Since the fraction of nuclides decaying per unit of time is inversely proportional to an isotope s half life the relative radioactivity of the lesser amount of human produced radioisotopes thousands of tons instead of trillions of tons would diminish once the isotopes with far shorter half lives than the bulk of natural radioisotopes decayed In January 2013 Cumbria county council rejected UK central government proposals to start work on an underground storage dump for nuclear waste near to the Lake District National Park For any host community there will be a substantial community benefits package and worth hundreds of millions of pounds said Ed Davey Energy Secretary but nonetheless the local elected body voted 7 3 against research continuing after hearing evidence from independent geologists that the fractured strata of the county was impossible to entrust with such dangerous material and a hazard lasting millennia 102 103 Horizontal drillhole disposal describes proposals to drill over one km vertically and two km horizontally in the earth s crust for the purpose of disposing of high level waste forms such as spent nuclear fuel Caesium 137 or Strontium 90 After the emplacement and the retrievability period clarification needed drillholes would be backfilled and sealed A series of tests of the technology were carried out in November 2018 and then again publicly in January 2019 by a U S based private company 104 The test demonstrated the emplacement of a test canister in a horizontal drillhole and retrieval of the same canister There was no actual high level waste used in this test 105 106 European Commission Joint Research Centre report of 2021 see above concluded 107 Management of radioactive waste and its safe and secure disposal is a necessary step in the lifecycle of all applications of nuclear science and technology nuclear energy research industry education medical and others Radioactive waste is therefore generated in practically every country the largest contribution coming from the nuclear energy lifecycle in countries operating nuclear power plants Presently there is broad scientific and technical consensus that disposal of high level long lived radioactive waste in deep geologic formations is at the state of today s knowledge considered as an appropriate and safe means of isolating it from the biosphere for very long time scales Transmutation Edit Main article Nuclear transmutation There have been proposals for reactors that consume nuclear waste and transmute it to other less harmful or shorter lived 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 eventually canceled by the U S 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 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 United States in April 1977 by President Carter due to the danger of plutonium proliferation 108 but President Reagan rescinded the ban in 1981 109 Due to economic losses and risks the 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 United States is actively promoting research on transmutation technologies needed to markedly reduce the problem of nuclear waste treatment 110 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 111 Re use Edit Main article Nuclear reprocessing Spent nuclear fuel contains abundant fertile uranium and traces of fissile materials 19 Methods such as the PUREX process can be used to remove useful actinides for the production of active nuclear fuel Another option is to find applications for the isotopes in nuclear waste so as to re use them 112 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 can reduce the quantity of waste produced The Nuclear Assisted Hydrocarbon Production Method 113 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 fractures the formation and 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 is 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 Breeder reactors can run on U 238 and transuranic elements which comprise the majority of spent fuel radioactivity in the 1 000 100 000 year time span Space disposal Edit Space disposal is attractive because it removes nuclear waste from the planet It has significant disadvantages such as the potential for catastrophic failure of a launch vehicle which could spread radioactive material into the atmosphere and around the world A high number of launches would be required because no individual rocket would be able to carry very much of the material relative to the total amount that needs to be disposed of This makes the proposal impractical economically and increases the risk of one or more launch failures 114 To further complicate matters international agreements on the regulation of such a program would need to be established 115 Costs and inadequate reliability of modern rocket launch systems for space disposal has been one of the motives for interest in non rocket spacelaunch systems such as mass drivers space elevators and other proposals 116 National management plans Edit See also High level radioactive waste management Anti nuclear protest near nuclear waste disposal centre at Gorleben in northern Germany 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 117 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 118 The U S EPA s proposed standard for greater than 10 000 years is 250 times more permissive than the European limit 118 The U S EPA proposed a legal limit of a maximum of 3 5 millisieverts 350 millirem each annually to local individuals after 10 000 years which would be up to several percent of vague the exposure currently received by some populations in the highest natural background regions on Earth though the U S United States Department of Energy DOE predicted that received dose would be much below that limit 119 Over a timeframe of thousands of years after the most active short half life radioisotopes decayed burying U S nuclear waste would increase the radioactivity in the top 2000 feet of rock and soil in the United States 10 million km2 by approximately 1 part in 10 million over the cumulative amount of natural radioisotopes in such a volume but the vicinity of the site would have a far higher concentration of artificial radioisotopes underground than such an average 120 Mongolia Edit After serious opposition about plans and negotiations between Mongolia with Japan and the United States of America to build nuclear waste facilities in Mongolia Mongolia stopped all negotiations in September 2011 These negotiations had started after U S Deputy Secretary of Energy Daniel Poneman visited Mongolia in September 2010 Talks took place in Washington D C between officials of Japan the United States and Mongolia in February 2011 After this the United Arab Emirates UAE which wanted to buy nuclear fuel from Mongolia joined in the negotiations The talks were kept secret and although the Mainichi Daily News reported on them in May Mongolia officially denied the existence of these negotiations However alarmed by this news Mongolian citizens protested against the plans and demanded the government withdraw the plans and disclose information The Mongolian President Tsakhiagiin Elbegdorj issued a presidential order on September 13 banning all negotiations with foreign governments or international organizations on nuclear waste storage plans in Mongolia 121 The Mongolian government has accused the newspaper of distributing false claims around the world After the presidential order the Mongolian president fired the individual who was supposedly involved in these conversations Illegal dumping Edit Main article Toxic waste dumping by the Ndrangheta Authorities in Italy are investigating a Ndrangheta mafia clan accused of trafficking and illegally dumping nuclear waste According to a whistleblower 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 United States 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 sending them to the sea bed off the Calabrian coast 122 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 123 Accidents EditMain article Nuclear and radiation accidents and incidents A few 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 124 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 125 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 citation needed In Italy several radioactive waste deposits let material flow into river water thus contaminating water for domestic use 126 In France in the summer of 2008 numerous incidents happened 127 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 128 in another case over 100 staff were contaminated with low doses of radiation 129 There are ongoing concerns around the deterioration of the nuclear waste site on the Enewetak Atoll of the Marshall Islands and a potential radioactive spill 130 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 131 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 Goiania accident 131 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 132 On 15 December 2011 top government spokesman Osamu Fujimura of the Japanese government admitted that nuclear substances were found in the waste of Japanese nuclear facilities Although Japan did commit itself in 1977 to these inspections in the safeguard agreement with the IAEA the reports were kept secret for the inspectors of the International Atomic Energy Agency citation needed Japan did start discussions with the IAEA about the large quantities of enriched uranium and plutonium that were discovered in nuclear waste cleared away by Japanese nuclear operators citation needed At the press conference Fujimura said Based on investigations so far most nuclear substances have been properly managed as waste and from that perspective there is no problem in safety management But according to him the matter was at that moment still being investigated 133 Associated hazard warning signs Edit The trefoil symbol used to indicate ionizing radiation 2007 ISO radioactivity danger symbol intended for IAEA Category 1 2 and 3 sources defined as dangerous sources capable of death or serious injury 134 The dangerous goods transport classification sign for radioactive materialsSee also EditDucrete Environmental remediation Human Interference Task Force Lists of nuclear disasters and radioactive incidents Material unaccounted for Mixed waste radioactive hazardous Microbial corrosion Nuclear 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