Radioactive waste is a waste containing radioactive material. Radioactive waste is usually a by-product of nuclear power plants and other applications of nuclear fission or nuclear technology, such as research and medicine. Radioactive waste is harmful to all life and environmental forms, and is governed by government agencies to protect human health and the environment.
Radioactivity will naturally decay over time, so radioactive waste must be isolated and confined at the proper disposal facility for an extended period of time until it is no longer a threat. Radioactive waste time should be stored because it depends on the type of waste and radioactive isotope. Current approaches to managing radioactive waste are segregation and storage for short-lived waste, near surface disposal for middle and low waste, and deep burial or partition/transmutation for high-level waste.
A summary of the amount of radioactive waste and management approaches for most developed countries is presented and reviewed periodically as part of the International Atomic Energy Agency (IAEA) Joint Convention on Security of Fuel Management and on the Security of Radioactive Waste Management.
Video Radioactive waste
Nature and significance
Radioactive waste usually consists of a number of radionuclides: the configuration of a rotting unstable element, emitting ionizing radiation that can be harmful to humans and the environment. This isotope emits different types and levels of radiation, which persist for different periods of time.
Physics
Radioactivity from all radioactive waste weakens over time. All the radionuclides contained in the waste have a half-time time required for half the atoms to decompose into other nuclides - and finally, all radioactive waste decays into non-radioactive elements (ie, stable nuclides). Certain radioactive elements (such as plutonium-239) will remain harmful to humans and other creatures for hundreds of thousands of years. Other radionuclides remain dangerous for millions of years. Thus, this waste must be protected for centuries and isolated from the environment for thousands of years. Because radioactive decay follows the half-life rule, the rate of decay is inversely related to the duration of decay. In other words, radiation from long-lived isotopes such as iodine-129 will be much stronger than short-lived isotopes such as iodine-131. Both tables show some of the major radioisotopes, their half-lives, and their radiation results as a proportion of uranium-235 fission results.
The energy and type of ionizing radiation emitted by radioactive substances is also an important factor in determining the threat to humans. The chemical properties of the radioactive element will determine how cellular the substance is and how much it spreads to the environment and contaminates humans. This is further complicated by the fact that many radioisotopes do not immediately decay to a stable state but rather to radioactive decay products in the decay chain before finally reaching a stable state.
Pharmacokinetics
Exposure to radioactive waste may cause serious harm or death. In humans, a dose of 1 sievert carries a 5.5% risk of cancer, and regulatory bodies consider the risk to be linearly comparable to doses even for low doses. Ionizing radiation causes chromosome removal. If a developing organism such as a fetus is irradiated, it may be possible to induce birth defects, but it is unlikely that this defect will be in a gamete or gamete-forming cell. The incidence of radiation-induced mutations in small humans, as in most mammals, due to natural cellular repair mechanisms, many have just been revealed. These mechanisms range from DNA, mRNA and protein repair, to the digestion of damaged internal lysosomes of proteins, and even cell suicide induced - apoptosis
Depending on the decay mode and pharmacokinetics of an element (how the body processes it and how quickly), the threat posed by exposure to certain radioisotope activities will be different. For example iodine-131 is a short-lived beta and gamma emitter, but because it concentrates on the thyroid gland, it is more capable of causing injury than cesium-137 which, due to water soluble, is rapidly excreted through urine. In the same way, actinides emitting alpha and radium are considered very dangerous because they tend to have a long biological half-life and their radiation has a relatively high biological effectiveness, thus far more damaging to tissue per amount of stored energy. Because of these differences, the rules that determine biological injury differ widely in accordance with radioisotopes, exposure times and sometimes also the nature of chemical compounds containing radioisotopes.
Maps Radioactive waste
Source
Radioactive waste comes from a number of sources. In countries with nuclear power plants, nuclear weapons, or nuclear fuel processing plants, most of the waste comes from the nuclear fuel cycle and nuclear weapons reprocessing. Other sources include medical and industrial waste, as well as natural radioactive materials (NORM) that can be concentrated as a result of processing or consumption of coal, oil and gas, and some minerals, as discussed below.
Cycle of nuclear fuel
Front end
Waste from the front end of the nuclear fuel cycle typically emits alpha waste from uranium extraction. It often contains radium and decay products.
The concentration of uranium dioxide (UO 2 ) from mining is a thousand times more radioactive like granite used in buildings. This is purified from yellowcake (U 3 O 8 ), then converted to uranium hexafluoride gas (UF 6 ). As a gas, it undergoes enrichment to increase U-235 content from 0.7% to about 4.4% (LEU). This then turns into a hard ceramic oxide (UO 2 ) for assembly as a fuel element of the reactor.
The main byproduct of enrichment is uranium (DU), especially the U-238 isotope, with a content of U-235 ~ 0.3%. This is stored, either as UF 6 or as U 3 O 8 . Some are used in applications where very high density makes it valuable as anti-tank shells, and at least once even sailing ships. It is also used with plutonium to make mixed oxide fuel (MOX) and to dilute, or downblend, highly enriched uranium from the stock of weapons that are now diverted to reactor fuel.
The back
The back 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 (part-time 245-thousand years), neptunium-237 (2,144 million year), plutonium-238 (87.7 years) and americium-241 (432 years), and sometimes even some neutron emitters such as californium (half 898 years for Cf-251). This isotope is formed in nuclear reactors.
It is important to distinguish uranium processing to make fuel from reprocessing spent fuel. Used fuel contains radioactive fission products (see high levels of waste below). Many of these are neutron dampers, called toxic neutrons in this context. This eventually builds to a level where they absorb so many neutrons that the chain reaction stops, even with the control rod completely removed. At that point the fuel must be replaced in a reactor with fresh fuel, although there is still a large amount of uranium-235 and present plutonium. In the United States, this spent fuel is usually "stored", while in other countries such as Russia, Britain, France, Japan and India, the fuel is recycled to remove fission products, and the fuel can then return. former. Fission products released from fuel are concentrated forms of high-level waste such as chemicals used in the process. While these countries reprocess the fuel that runs a single plutonium cycle, India is the only country known to plan some plutonium recycling schemes.
Fuel compositions and long-term radioactivity
The use of different fuels in nuclear reactors produces a different composition of nuclear fuel (SNF), with various activity curves.
Long-lived radioactive waste from the back end of the fuel cycle is particularly relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, actinides in the SNF have a significant influence because of their long half-life. Depending on what the nuclear reactor produces, the actinide composition in the SNF will be different.
An example of this effect is the use of nuclear fuel with thorium. Th-232 is a fertile material that can undergo neutron fishing reactions and two beta decay is reduced, resulting in the production of a fissile U-233. SNF of the cycle with thorium will contain U-233. Radioactive decay will greatly affect the long-term SNF activity curve of about a million years. Comparison of activities associated with U-233 for three different types of SNF can be seen in the image at the top right. Burning fuel is thorium with reactor level plutonium (RGPu), thorium with weapon grade plutonium (WGPu) and Mixed Oxide fuel (MOX, no thorium). For RGPu and WGPu, the initial number of U-233 and its decay of about a million years can be seen. It has an effect in the total activity curve of all three types of fuel. The early absence of U-233 and its derivative products in MOX fuel resulted in lower activity in region 3 of the lower right image, while for RGPu and WGPu, the curves were maintained higher due to the presence of the U-233 which has not yet completely decomposed. Nuclear reprocessing can remove actinides from spent fuel so they can be used or destroyed (see long-lived fission products # Actinide).
Proliferation worries
Since uranium and plutonium are nuclear weapons, there are concerns of proliferation. Usually (in spent fuel), plutonium is a reactor level plutonium. In addition to plutonium-239, which is very suitable for building nuclear weapons, it contains a large number of undesirable contaminants: plutonium-240, plutonium-241, and plutonium-238. This isotope is very difficult to separate, and a more cost-effective way of obtaining fissile material exists (eg uranium enrichment or special plutonium production reactors).
High-level waste is full of high-radioactive fission products, most of which are short-lived. This is of concern because if the waste is stored, it may be in deep geological storage, for years decaying decomposition products, reducing waste radioactivity and making plutonium more accessible. Unwanted contaminants Pu-240 decays faster than Pu-239, and thus the quality of bomb material increases over time (though its quantity decreases during that time). Thus, some argue, over time, this deep storage area has the potential to become a "plutonium mine," from which materials for nuclear weapons can be obtained with relatively little difficulty. Criticism of the latter notion suggests the difficulty of recovering useful material from a sealed storage, making other methods more favorable. In particular, high radioactivity and heat (80 ° C in surrounding rocks) greatly increase the difficulty of storage area mining, and the necessary enrichment methods have high capital costs.
Pu-239 decays into a U-235 suitable for weapons and has a very long half-life (approximately 10 9 year). Thus plutonium can decay and leave uranium-235. However, modern reactors are only enriched sufficiently with U-235 relative to U-238, so U-238 continues to function as a denaturation agent for every U-235 produced by decay of plutonium.
One solution to this problem is to recycle plutonium and use it as fuel for example. in a fast reactor. In fast pyrometallurgical reactors, the separated plutonium and uranium are contaminated by actinides and can not be used for nuclear weapons.
Decommissioning nuclear weapons
Waste from decommissioning nuclear weapons is unlikely to contain much beta or gamma activity other than tritium and americium. It is more likely to contain an alpha-emitting actinide such as Pu-239 which is a fissile material used in bombs, plus some materials with higher specific activities, such as Pu-238 or Po.
In the past, neutron triggers for atomic bombs tend to beryllium and high activity alpha emitters such as polonium; the alternative to polonium is Pu-238. For national security reasons, modern bomb design details are not usually released to open literature.
Some designs may contain radioisotope thermoelectric generators using Pu-238 to provide long-lasting electrical resources for electronics in devices.
It is likely that the fissile material of the old bomb to be refitted will contain decay products of the plutonium isotope used in it, this may include U-236 of Pu-240 impurities, plus some U-235 of Pu-239 decay; because of the relatively long half-life of the Pu isotope, the waste from radioactive decay of the core material of this bomb will be very small, and in any case, far less harmful (even in the case of simple radioactivity) than Pu-239 itself.
Pu-241 beta decay forms Am-241; the growth of americium tends to be a greater problem than the decay of Pu-239 and Pu-240 because the americium is a gamma emitter (increasing external exposure to workers) and is an alpha transmitter that can cause heat formation. Plutonium can be separated from americium by several different processes; this will include a pyrochemical process and an aqueous/organic solvent extraction. The extracted PUREX type extraction process will be one of the possible methods for separation. Naturally occurring uranium is not fissile because it contains 99.3% of U-238 and only 0.7% of U-235.
Legacy waste
Because historic activities are typically associated with the radium industry, uranium mining, and military programs, many 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 fuel and nuclear fuel" as well as "huge amounts of contaminated soil and water." Despite considerable waste, the DOE has stated the goal of cleaning up all contaminated sites is now successful by 2025. The Fernald, Ohio site for example has "31 million pounds of uranium product", "2.5 billion pounds of waste", "2.75 million cubic yard of contaminated soil and debris, "and" the 223 acre section of the underlying Great Miami Aquifer has a level of uranium above drinking standards. "The United States has at least 108 sites designated as contaminated and unusable territories, sometimes thousands hectare. DOE wants to clean or reduce much or all by 2025, using recently developed geomelting methods, but the task can be difficult and recognize that some may never be completely fixed. In just one of these 108 larger titles, the Oak Ridge National Laboratory, for example there is a "167 known release of contaminants" in one of three 37,000 acre subdivisions (150 km 2 ) sites. Some US sites are smaller in nature, however, cleaning issues are easier to handle, and DOE has successfully completed cleaning, or at least closing, from some sites.
Medicine
Radioactive medical waste tends to contain beta particles and gamma-ray generators. 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. Much of this can be disposed of by letting it rot for a short time before being disposed of as regular waste. Other isotopes used in medicine, with half-lives in parentheses, include:
- Y-90, used to treat lymphoma (2.7 days)
- I-131, used for thyroid function tests and for treating thyroid cancer (8.0 days)
- Sr-89, used to treat bone cancer, intravenous injection (52 days)
- Ir-192, used for brachytherapy (74 days)
- Co-60, used for brachytherapy and external radiotherapy (5.3 years)
- Cs-137, used for brachytherapy, external radiotherapy (30 years)
Industry
Industrial waste may contain alpha, beta, neutron or gamma producers. Gamma emulsification is used in radiography while neutron transmitter sources are used in many applications, such as oil well logging.
Natural radioactive material
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 carrying coal to the surface or burning it to produce concentrated ash), it becomes a natural, technologically enhanced (TENORM) radioactive material. Much of this waste is the alpha particle emitting matter from the uranium and thorium decay chains. The main source of radiation in the human body is potassium-40 ( 40 K), usually 17 milligrams in the body at a time and 0.4 milligrams/day intake. Most rocks, because of their components, have a low level of radioactivity. Usually ranging from 1 millisievert (mSv) to 13 mSv each year depending on location, the average radiation exposure of natural radioisotopes is 2.0 mSv per person per year worldwide. This represents the majority of total doses (with average annual exposure of other sources of 0.6 mSV from medical tests averaged across the population, 0.4 mSv from cosmic rays, 0.005 mSv from the legacy of atmospheric atmospheric testing in the past, 0.005 mSv occupational exposure, 0.002 mSv from Chernobyl disaster, and 0.0002 mSv from nuclear fuel cycle).
TENORM is not limited to nuclear reactor waste, although there is no significant difference in the radiological risk of these substances.
Coal
Coal contains a small amount of radioactive uranium, barium, thorium, and potassium, but, in the case of pure coal, this is much less than the average concentration of these 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 'dirty' coal ash content. The more active ash miner is concentrated in fly ash precisely because they are not burning properly. The radioactivity of fly ash is almost the same as black flakes and is less than phosphate rock, but more of a concern because a small amount of fly ash ends in the atmosphere where it can be inhaled. According to the US NCRP report, population exposure from 1000-MWe power plants amounts to 490 people-brakes/year for coal-fired power plants, 100 times larger than nuclear power plants (4.8 people-brakes/year). (Exposure of the complete nuclear fuel cycle from mining to waste disposal is 136 people-brakes/year, the appropriate value for use of coal from mining to waste disposal "may not be known".)
Oil and gas
Residues from the oil and gas industries often contain radium and decay products. The sulfate scale of the oil wells can be very rich in radium, while water, oil and gas from wells often contain radon. Radon decays form a solid radioisotope that forms a layer on the inside of the pipe. In an oil processing plant, the factory area where processed propane is often one of the more contaminated plant areas because radon has the same boiling point as propane.
Classification
The classification of radioactive waste varies by country. The IAEA, which publishes Radioactive Waste Security Standards (RADWASS), also plays an important role.
Mill tailings
Tailings of uranium are the remaining byproducts left over from the rough uranium-bearing ore processing. They are not radioactive significantly. Tailings Mill is sometimes referred to as 11 (e) 2 waste , from the section on the Atomic Energy Act of 1946 that defines it. Tailings uranium factories usually also contain heavy metals that are chemically dangerous such as lead and arsenic. Large mounds of uranium factory tailings are left on many old mining sites, especially in Colorado, New Mexico, and Utah.
Although the factory tailings are not very radioactive, they have a long half-life. Tailings Mill often contains radium, thorium and trace amounts of uranium.
Low-level trash
Low-level waste ( LLW ) is generated from hospitals and industry, as well as nuclear fuel cycles. Low-level waste includes paper, duster, equipment, clothing, filters, and other materials containing a small amount of short-lived radioactivity. Material originating from each region of the Active Area is usually designated as LLW as a precaution even if there is only the remote possibility of being contaminated with radioactive material. Such LLW usually indicates no higher than expected radioactivity of the same material is discharged in a non-active area, such as a normal office block.
Some high activity LLWs require shielding during handling and transportation but most LLW is suitable for shallow ground burials. To reduce the volume, often compacted or burned before disposal. Low level waste is divided into four classes: class A , class B , class C , and Larger From Class C ( GTCC ).
Middle garbage
Medium waste ( ILW ) contains higher amounts of radioactivity and generally requires a shield, but does not cool. Medium waste includes resins, chemical sludges and metal nuclear fuel cladding, as well as materials contaminated from reactor decommissioning. It can be solidified in concrete or asphalt to be discarded. As a general rule, short-lived waste (especially non-fuel materials from reactors) is buried in shallow repositories, while long-lived waste (from fuel and refueling) is stored in a geological repository. The US regulation does not define this waste category; this term is used in Europe and elsewhere.
High-level trash
High-level garbage ( HLW ) is produced by nuclear reactors. The exact definition of HLW differs internationally. Once the nuclear fuel rod serves one cycle of fuel and is removed from the core, it is considered HLW. The fuel rods contain the fission products and transurane elements produced in the reactor core. The fuel used is highly radioactive and often hot. HLW accounts for more than 95 percent of the total radioactivity generated in the nuclear power generation process. The number of HLWs worldwide is currently increasing by about 12,000 metric tons annually, which is equivalent to about 100 double-decker buses or two-story structures with basketball court sizes. The 1,000 MW nuclear power plant produces about 27 tons of spent (unprocessed) nuclear fuel annually. In 2010, an estimated 250,000 tonnes of nuclear power plants, excluding the number that passes into the environment from accidents or tests. Japan is estimated to hold 17,000 tonnes of HLW in storage by 2015. HLW has been shipped to other countries for storage or reprocessing, and in some cases, shipped back as active fuel.
Radioactive waste from spent fuel rods mainly consists of cesium-137 and strontium-90, but may also include plutonium, which can be considered as transuranic waste. The beak of these radioactive elements can be very different. Some elements, such as cesium-137 and strontium-90 have a half-life of about 30 years. Meanwhile, plutonium has a half-life that can stretch up to 24,000 years.
The ongoing controversy over high-level radioactive waste disposal is a major obstacle to the global expansion of nuclear power. Most scientists agree that the proposed major long-term solution is deep geological cemeteries, either in mines or deep boreholes. However, almost six decades after commercial nuclear energy began, no government has managed to open such repositories for high-level civilian nuclear waste, although Finland is in the advanced stages of construction of the facility, Onkalo consume nuclear fuel storage. Reprocessing or recycling of available nuclear fuel options or in active development still generates waste and therefore is not a total solution, but it can reduce the amount of waste, and there are many such active programs around the world. Deep geological burial remains the only responsible way to deal with high levels of nuclear waste. Morris's current operation is the only high-level de facto radioactive waste store in the United States.
Transuranic waste
Transuranic waste ( TRUW ) as defined by US regulations, irrespective of form or origin, waste contaminated with alpha transuranic radionuclides with beaks greater than 20 years and more concentrations large from 100 Â ° nCi/g (3.7 MBq/kg), excluding high-level waste. Elements that have an atomic number greater than uranium are called transuranic ("outside uranium"). Due to the long half life, TRUW is removed more carefully than low or medium-level waste. In the US, it mainly arises from the production of weapons, and consists of clothing, equipment, fabrics, residues, debris and other items contaminated with small amounts of radioactive elements (especially plutonium).
Under U.S. law, transuranic waste is further categorized into "contact-handled" (CH) and "remotely treated" (RH) based on radiation dose levels measured on the surface of the waste container. CH TRUW has a surface dose level of not more than 200 mrem per hour (2 mSv/hr), while RH TRUW has a surface dose level of 200 mrem/h (2 mSv/h) or greater. CH TRUW does not have very high radioactivity from high-level waste, or high heat generation, but RH TRUW can be highly radioactive, with a surface dose level of up to 1,000,000 mrem/hour (10,000 mSv/hr). The US is currently dumping TRUW generated from military facilities at Wastewater Insulation Pilot Plant (WIPP) in deep salt formation in New Mexico.
Prevention
The theoretical way to reduce waste accumulation is to stop the current reactor to support the Generation IV Reactor, which produces less waste per power generated. Rapid reactors can theoretically consume some of the waste. The British Nuclear Discharge Authority publishes position papers in 2014 on progress on a separate plutonium management approach, which summarizes the conclusions of the work NDA shares with the British government.
Management
Particular attention in the management of nuclear waste is two long-lived fission products, Tc-99 (half-life of 220,000 years) and I-129 (half-life of 15.7 million years), which dominate the use of radioactive fuel after several thousand years. The most troublesome transuranic elements in spent fuel are Np-237 (two million years of half-life) and Pu-239 (half life 24,000 years). Nuclear waste requires sophisticated care and management to successfully isolate it from interacting with the biosphere. This usually requires care, followed by a long-term management strategy that involves storing, disposing or transforming waste into non-toxic forms. Governments around the world are considering various waste management and disposal options, although there has been limited progress towards long-term waste management solutions.
In the second half of the 20th century, several methods of radioactive waste disposal were investigated by nuclear states:
- "Long-term storage above ground", not implemented.
- "Exhaust in space" (for example, in the Sun), is not applied - because it would be too expensive at the moment.
- "Drill hole deep", not implemented.
- "Rock-melting", not implemented.
- "Disposal in subduction zone", not implemented.
- " Ocean disposal ", carried out by the Soviet Union, the United Kingdom, 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 treaties.
- "Subsea disposal", not implemented, not authorized by international agreement.
- "Disposal in ice sheet", rejected in Antarctic Agreement
- " Direct injection ", performed by USSR and US.
In the United States, waste management policies are completely damaged by the completion of work at the incomplete Yucca Mountain Repository. There are currently 70 nuclear power plant locations where spent fuel is stored. The Blue Ribbon Commission was appointed by President Obama to see future options for this and future waste. A deep geological repository seems to be preferred.
Initial treatment
Vitrification
Long-term radioactive waste storage requires the stabilization of waste into a form that will not react or degrade for long. It is theorized that one way to do this might be through vitrification. Currently in Sellafield, high-level waste (PUREX raffinate first cycle) is mixed with sugar and then calcined. Calcination involves passing the waste through a heated spinning tube. The purpose of calcination is to evaporate water from waste, and de-nitrate the fission products to assist the stability of the resulting glass.
The resulting 'calcine' is fed continuously into an induction heating furnace with a fragmented glass. The resulting glass is a new substance in which the waste product is bonded into a glass matrix when solidified. As melted, this product is poured into a stainless steel ("cylinder") container in a batch process. When cooled, the liquid solids ("vitrifies") into the glass. Once formed, the glass is very resistant to water.
After filling the cylinder, the seal is welded to the cylinder head. The cylinder is then washed. Once checked for external contamination, steel cylinders are stored, usually in an underground repository. In this form, waste products are expected to be immobilized for thousands of years.
Glass inside the cylinder is usually a glossy black substance. All this work (in the UK) is done using a hot cell system. Sugar is added to control the chemistry of ruthenium and to stop the formation of a turbulent RuO 4 containing radioactive ruthenium isotope. In the West, glass is usually a borosilicate glass (similar to Pyrex), while in the former Soviet bloc it is normal to use phosphate glasses. The amount of fission products in a glass should be limited because some (palladium, other Pt group metal, and tellurium) tend to form metallic phases separate from glass. Mass vitrification uses electrodes to dilute soil and waste, which are then buried underground. In Germany, the vitrification plant is in use; this treats waste from a small demonstration processing factory that has since closed.
Ion exchange
It is common for the medium active waste in the nuclear industry to be treated with ion exchange or other means of centralizing radioactivity into small volumes. Most of the radioactive (after treatment) is often subsequently discarded. For example, it is possible to use an iron hydroxide floc to remove radioactive metal from the aqueous mixture. After the radioisotope is absorbed into the iron hydroxide, the resulting sludge can be placed in the metal drum before it is mixed with cement to form solid waste form. To obtain better long-term performance (mechanical stability) of such shapes, they can be made from a mix of fly ash, or blast furnace slag, and Portland cement instead of normal concrete (made with Portland cement, gravel and sand). ).
Synroc
Synroc (synthetic stones) Australia is a more sophisticated way to paralyze such waste, and this process can eventually be used commercially for civil waste (currently being developed for US military waste). Synroc was invented by Prof. Ted Ringwood (a geochemist) at the Australian National University. Synroc contains minerals of pyrochlore and cryptomelane. The original form of Synroc (Synroc C) is designed for high-grade liquid waste (PUREX raffinate) from light water reactors. The main mineral in Synroc is the hollandite (BaAl 2 Ti 6 O 16 ), zirconolite (CaZrTi 2 O < sub> 7 ) and perovskite (CaTiO 3 ). Zirconolite and perovskite are hosts for actinides. Strontium and barium will be repaired in perovskite. Cesium will be fixed in hollandite.
Long-term management
The time frame in question when dealing with radioactive waste ranges from 10,000 to 1,000,000 years, according to a study based on the estimated effect of radiation doses. The researchers suggest that the estimated health loss for the period should be critically examined. Practical studies only consider up to 100 years as far as effective planning and cost evaluation are concerned. The long-term behavior of radioactive waste remains a subject for ongoing research projects in geoforecasting.
Above ground
Dry-dry storage usually 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 that acts as a radiation shield. This is a relatively inexpensive method that can be done at a central facility or adjacent to a reactor source. Trash can easily be retrieved for reprocessing.
Geological disposal
The process of selecting the right in-line repository for high-grade waste and spent fuel is now underway in some countries with the first expected to be commissioned sometime after 2010. The basic concept is to find large, stable geological formations and use mining technology. to dig tunnels, or large dusty drilling machines (similar to those used to drill the Channel Tunnel from England to France) to drill a shaft of 500 meters (1,600 feet) to 1,000 meters (3,300 feet) below the surface where the room or safes can be dug for high-level radioactive waste disposal. The goal is to permanently isolate nuclear waste from the human environment. Many people remain uncomfortable with the immediate cessation of management of this exhaust system, suggesting sustainable management and monitoring will be wiser.
Because some radioactive species have a half-life of over a million years, even very low container leaks and radionuclide migration rates must be taken into account. In addition, it may take more than a half-time until some nuclear material loses enough radioactivity to stop being deadly living things. A 1983 review of the Swedish radioactive waste disposal program by the National Academy of Sciences found that the country's forecasts of several hundred thousand years - perhaps up to a million years - are required for the isolation of "fully justified" waste.
Oceanic waste water floor dumping has been suggested by findings that deep waters in the North Atlantic Ocean do not present a shallow-water exchange for about 140 years based on 25 years of recorded oxygen content data. They include burial under stable abyssal plains, burials in subduction zones that will slowly bring waste down into Earth's mantle, and burial beneath natural or remote man-made islands. While these approaches all have benefits and will facilitate an international solution to the problem of radioactive waste disposal, they will require an amendment to the Law of the Sea.
Article 1 (Definition) 7. of the 1996 Protocol on the Convention on the Prevention of Pollution by Waste Disposal and Other Materials, (London Dumping Convention) states:
- "" Sea "means all marine waters other than the internal waters of the State, as well as the seabed and subsoil, not including sub-marine sub-basin repositories accessible only from land."
The proposed land-based waste disposal method disposes nuclear waste in the subduction zone accessed from the ground and is therefore not prohibited by international treaties. This method has been described as the most feasible way to dispose of radioactive waste, and as a state-of-the-art in 2001 in nuclear waste disposal technology. Another approach called Remix & amp; Returns will combine high levels of waste with uranium mines and factory tailings down to the original radioactivity level of uranium ore, then replace them in inactive uranium mines. This approach has the advantage of providing employment for miners to be doubled as disposal staff, and facilitating the cradle-to-grave cycle for radioactive material, but would be inappropriate for reactor fuel that is exhausted without reprocessing, due to the presence of highly radioactive elements toxic as plutonium in it.
Disposal of deep boreholes is the concept of dumping high levels of radioactive waste from nuclear reactors in very deep boreholes. The drill hole discharges in the attempt to place waste as far as 5 kilometers (3.1 mi) below the surface of the Earth and rely primarily on the enormous natural geological barrier to limit waste safely and permanently so as to never pose a threat to the environment. The Earth's crust contains 120 trillion tons of thorium and 40 trillion tons of uranium (especially at the relative concentrations of parts per million each of the additions above the crust of 3 * 10 19 tons), among other natural radioisotopes.. Since the decaying nucoid fraction per unit time is inversely proportional to the half-life of the isotope, the relative radioactivity of the fewer human-produced radioisotopes (thousands of tons rather than trillions of tonnes) will decrease as soon as the isotope is much shorter than half the life of most radioisotopes of decomposing nature.
In January 2013, the Cumbria county council rejected a proposal by the British central government to begin work on underground storage for nuclear waste close to the Lake District National Park. "For each host community, there will be a massive, multi-million-pound community benefit package," said Ed Davey, Secretary of Energy. However, local elections voted 7-3 to continuing research, after hearing evidence from geologists independent. that "the fractured strata in the area could not have been entrusted with such dangerous substances and the dangers that lasted for thousands of years."
Transmutation
There are proposals for reactors that consume nuclear waste and convert them into other nuclear waste, less harmful or shorter. In particular, the Integral Rapid Reactor is a proposed nuclear reactor with a nuclear fuel cycle that produces no transuranic waste and, in fact, can consume transuranic waste. This continued as far as large-scale tests, but was later canceled by the US Government. Another approach, considered more secure but requires more development, is to dedicate subcritical reactors to the transmutation of the remaining transuranic elements.
An isotope found in nuclear waste and which represents attention in terms of proliferation is Pu-239. The large stock of plutonium is the result of its production in uranium-fueled reactors and the re-processing of weapons-grade plutonium during the weapons program. The option to get rid of this plutonium is to use it as fuel in a traditional Lightweight Water Reactor (LWR). Several types of fuels with different plutonium destruction efficiencies are being investigated.
Transmutation was banned in the US in April 1977 by President Carter because of the dangers of plutonium proliferation, but President Reagan overturned the ban in 1981. Due to economic losses and risks, the construction of processing plants returned during this time was not continued. Due to high energy demand, work on methods continues in the EU. This results in a practical nuclear research reactor called Myrrha where transmutation is possible. In addition, a new research program called ACTINET has begun in the EU to enable transmutation on a large industrial scale. According to the 2007 Global Nuclear Energy Partnership (GNEP) Partnership, the United States is now actively promoting research on transmutation technologies needed to reduce the problem of handling nuclear waste.
There is also a theoretical study involving the use of a fusion reactor such as the so-called "actinide burner" in which plasma fusion reactors such as in tokamak, can be "doped" with a small number of "minor" transuranic atoms to be transmuted. (meaning maligned in case of actinide) for lighter elements in successive bombardment by very high energy neutrons produced by deuterium and tritium fusion in the reactor. A study at MIT found that only 2 or 3 fusion reactors with parameters similar to the International Referential Terroruclear Reactor (ITER) can transmit all of the annual minor actinic production of all light water reactors currently operating in the US fleet at the same time. generating about 1 gigawatt of power from each reactor.
Reuse
Another option is to find applications for isotopes in nuclear waste so they can reuse them. Already, cesium-137, strontium-90 and several other isotopes are extracted for specific industrial applications such as food irradiation and radioisotope thermoelectric generators. While reuse does not eliminate the need to manage radioisotopes, it can reduce the amount of waste generated.
Methods of Production of Nuclear Helper Substances, Canada Patent Application 2,659,302, is a method for temporary or permanent storage of nuclear waste materials comprising placing waste materials into one or more repositories or boreholes constructed into unconventional oil formations. The thermal flux of the waste material breaks formations and changes the chemical and/or physical properties of hydrocarbon materials in underground formations to allow removal of altered materials. A mixture of hydrocarbons, hydrogen, and/or other formation liquids is produced from the formation. High-level radioactive radioactivity wastes provide proliferative resistance to plutonium placed on the periphery of the repository or the deepest part of the borehole.
The breeding reactor can run on U-238 and transuranic elements, comprising most of the spent fuel radioactivity in the time span of 1,000-100,000 years.
Space dump
Space disposal is interesting because it removes the planet's nuclear waste. It has significant losses, such as potential catastrophic launch vehicle failures, which can spread radioactive material to the atmosphere and around the world. A large number of launches will be necessary because there are no individual rockets that can carry very much material relative to the total amount to be discarded. This makes the proposal economically impractical and increases the risk of at least one or more launch failures. To further complicate matters, international agreements on such program arrangements need to be established. Inadequate cost and reliability of the modern rocket launch system for space disposal has been one of the motives for interest in non-rocket launch systems such as mass drivers, space elevators, and other proposals.
National management plan
Most countries are far ahead of the United States in developing a high-level radioactive waste disposal plan. Sweden and Finland are the most distant in committing to certain disposal technologies, while many others are reprocessing spent fuel or contracting with France or Great Britain to do so, recovering the resulting plutonium and high levels of waste. "The increase in plutonium backlog from reprocessing is evolving in many countries... It is very doubtful that the recycling process makes economic sense in the present environment of cheap uranium."
In many European countries (eg, England, Finland, the Netherlands, Sweden and Switzerland) the risk or dose limits for radiation exposed public members of future high-level nuclear waste facilities are much stricter than those suggested by the International Commission on Radiation Protection or proposed in the United States. The European limit is often tighter than the standard suggested in 1990 by the International Commission on Radiation Protection by a factor of 20, and more stringent by a factor of ten than the standard proposed by the US Environmental Protection Agency (EPA) for Yucca's nuclear waste repository for the first 10,000 years after closing.
The US EPA's proposed standard for more than 10,000 years is 250 times more permissive than the European border. The US EPA proposes a maximum legal limit of 3.5 millisieverts (350 millirem) annually to local individuals after 10,000 years, which will reach some percent of the exposure currently accepted by some populations in the highest natural terrain on Earth, although the US DOE estimates that the dose received will be well below that limit. Over a period of thousands of years, after the most active short-lived radioactive decay, burying US nuclear waste will increase radioactivity above 2,000 feet of rock and soil in the United States (10 million km 2 ) by? 1 part in 10 million more than the cumulative number of natural radioisotopes in such volumes, but the area around the site will have an underground radioisotope concentration much higher than such an average.
Mongolia
After serious opposition emerged about plans and negotiations between Mongolia and Japan and the United States to build a nuclear waste facility in Mongolia, Mongolia halted all negotiations in September 2011. The negotiations began after US Deputy Secretary of Energy Daniel B. Poneman visited Mongolia in September, 2010 The talks took place in Washington DC between Japanese, US and Mongolian officials in February 2011. After this the United Arab Emirates (UAE), which wants to buy nuclear fuel from Mongolia, joins the negotiations. The talks were kept secret, and although The Mainichi Daily News reported in May, Mongolia officially rejected this negotiation. However, worried by the news, Mongolians protested against the plan, and demanded the government withdraw plans and disclose information. Mongolian President Tsakhiagiin Elbegdorj issued a presidential order on Sept. 13 banning all negotiations with foreign governments or international organizations on a nuclear waste storage plan in Mongolia. The Mongolian government has accused newspapers of spreading false claims across the globe. After the president's order, the Mongolian president dismissed the person who should have been involved in this conversation.
Illegal logging
Authorities in Italy are investigating the Ndrangheta mafia clan allegedly trading and disposing of nuclear waste illegally. According to a disclosure of facts, a manager of the Italian state energy research agency, Enea pays clans to get rid of 600 toxic and radioactive waste drums from Italy, Switzerland, France, Germany and the US, with Somalia as the destination, where garbage is buried after buying local politicians. Former Enea employees allegedly paid criminals to waste their hands in the 1980s and 1990s. Deliveries to Somalia continued into the 1990s, while the Ndrangheta clan also detonated shiploads, including radioactive hospital waste, sending them to the seabed off the coast of Calabria. According to environmental group Legambiente, former members of 'Ndrangheta have said that they are paid to sink a ship with radioactive material for the last 20 years.
Accident
Several incidents have occurred when the radioactive material is disposed of incorrectly, protecting during transport is damaged, or when it is simply abandoned or even stolen from the waste store. In the Soviet Union, the waste stored in Lake Karachay was blown over the area during a dust storm after the lake was partially dry. At Maxey Flat, a low-level radioactive waste facility located in Kentucky, the trenches were covered with soil instead of steel or cement, collapsing under heavy rainfall into the trenches and filled with water. The water that invaded the moat became radioactive and had to be disposed of in the Maxey Flat facility itself. In other cases the accident of radioactive waste, lakes or ponds with radioactive waste accidentally overflowed into the river during a remarkable storm. In Italy, some piles of radioactive waste let materials flow into river water, thus polluting water for domestic purposes. In France, in the summer of 2008 many incidents occurred; in one, at the Areva plant in Tricastin, it was reported that during the drying operation, unrefined uranium-containing fluids overflowed out of the damaged tank and about 75 kg of radioactive material seeped into the soil and, from there, to two nearby rivers. ; in other cases, more than 100 staff were contaminated with low-dose radiation.
The abandonment of abandoned radioactive material has been the cause of some other cases of radiation exposure, especially in developing countries, which may have slight regulation of hazardous substances (and sometimes less general education on radioactivity and hazards) and markets for scrap and scrap metal. The scavengers and those who buy the material almost always do not realize that the material is radioactive and is chosen because of its aesthetic or scrap value. No responsibility for the part of owners of radioactive material, usually hospitals, universities or the military, and the absence of radioactive waste regulations, or the lack of enforcement of these regulations, have been a significant factor in radiation exposure. For examples of accidents involving radioactive cuts coming from hospitals, see GoiÃÆ' nà ± nia accident.
Transport accidents involving spent nuclear fuel from power plants may not have serious consequences due to the power of the used nuclear fuel shipping barrels.
On December 15, 2011, top government spokesman Osamu Fujimura from the Japanese government acknowledged that nuclear substances were found in Japanese nuclear waste facilities. Although Japan had committed in 1977 to this inspection in a protection agreement with the IAEA, the report was kept confidential to the inspectors of the International Atomic Energy Agency. Japan initiated discussions with the IAEA about the large amount of enriched uranium and plutonium found in nuclear waste cleared by Japanese nuclear operators. At a press conference Fujimura said: "Based on the investigation so far, most nuclear substances have been well managed as waste, and from that perspective, there is no problem in safety management," but he said the problem was still under investigation at the time.
Related warning signs
See also
References
Source cited
- Vandenbosch, Robert & amp; Vandenbosch, Susanne E. (2007). Nuclear waste deadlock . Salt Lake City: University of Utah Press. ISBN: 0874809037.
External links
- Alsos Digital Library - Radioactive Waste (annotated bibliography)
- Euridice European Interest Group responsible for Hades URL (link) operation
- Ondraf/Niras, waste management authority in Belgium (link)
- The Critical Clock: Three Mile Island, The Nuclear Legacy, And National Security (PDF)
- Environmental Protection Agency - Yucca Mountain (document)
- Grist.org - How to let future generations know about nuclear waste (articles)
- International Atomic Energy Agency - Internet Directory of Nuclear Resources (links)
- Nuclear Files.org - Yucca Mountain (document)
- Nuclear Regulatory Commission - Radioactive Waste (document)
- Nuclear Regulatory Commission - Spend Heat Filling Calculation (guidance)
- Radwaste Solutions (magazine)
- UNEP Earthwatch - Radioactive Waste (documents and links)
- World Nuclear Association - Radioactive Waste (briefing paper)
- Concerns can not be buried due to nuclear waste accumulate, Los Angeles Times, January 21, 2008
- RadWaste.org
- Radioactivity.eu.com
Source of the article : Wikipedia
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