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89-471: The energy sector emits more greenhouse gas worldwide than any other sector. Therefore, energy policies are closely related to climate policies . These decisions affect how high the greenhouse gas emissions by that country are. Access to energy is critical for basic social needs, such as lighting, heating, cooking, and healthcare. Given the importance of energy, the price of energy has a direct effect on jobs, economic productivity, business competitiveness, and

178-462: A free neutron , and the isotope is therefore said to be a " fissile " isotope. The nucleus of a U-238 atom on the other hand, rather than undergoing fission when struck by a free neutron, will nearly always absorb the neutron and yield an atom of the isotope U-239. This isotope then undergoes natural radioactive decay to yield Pu-239, which, like U-235, is a fissile isotope. The atoms of U-238 are said to be fertile, because, through neutron irradiation in

267-465: A chain reaction. They are also capable of breeding fissile isotopes from fertile materials; a breeder reactor is one that generates more fissile material in this way than it consumes. During the nuclear reaction inside a reactor, the fissile isotopes in nuclear fuel are consumed, producing more and more fission products , most of which are considered radioactive waste . The buildup of fission products and consumption of fissile isotopes eventually stop

356-471: A considerable number of new reactors being built in China, South Korea, India, and Russia. As of June 2011, countries such as Australia , Austria , Denmark , Greece , Ireland , Latvia, Lichtenstein, Luxembourg , Malta , Portugal , Israel , Malaysia , and Norway have no nuclear power stations and remain opposed to nuclear power. Public policy has a role to play in renewable energy commercialization because

445-440: A good policy record of encouraging public transport links with cities, despite encountering problems with high speed trains, which have the potential to reduce dramatically domestic and short-haul European flights. The policy does not, however, significantly encourage hybrid vehicle use or ethanol fuel use, options which represent viable short term means to moderate rising transport fuel consumption. Regarding renewable energy ,

534-491: A higher concentration of the fissionable isotope before being used as nuclear fuel in such reactors. The level of enrichment for a particular nuclear fuel order is specified by the customer according to the application they will use it for: light-water reactor fuel normally is enriched to 3.5% U-235, but uranium enriched to lower concentrations is also required. Enrichment is accomplished using any of several methods of isotope separation . Gaseous diffusion and gas centrifuge are

623-412: A metal to the surfaces of soil particles does not completely fix the metal. According to Jiří Hála's text book , the distribution coefficient K d is the ratio of the soil's radioactivity (Bq g ) to that of the soil water (Bq ml ). If the radioisotope is tightly bound to the minerals in the soil, then less radioactivity can be absorbed by crops and grass growing on the soil. In dairy farming, one of

712-448: A rate of up to 8 channels per day out of roughly 400 in CANDU reactors. On-load refueling allows for the optimal fuel reloading problem to be dealt with continuously, leading to more efficient use of fuel. This increase in efficiency is partially offset by the added complexity of having hundreds of pressure tubes and the fueling machines to service them. After its operating cycle, the reactor

801-405: A rim temperature of 200 °C. The uranium dioxide (because of its poor thermal conductivity) will overheat at the centre of the pellet, while the other more thermally conductive forms of uranium remain below their melting points. The nuclear chemistry associated with the nuclear fuel cycle can be divided into two main areas; one area is concerned with operation under the intended conditions while

890-417: A slurry, spray drying it before heating in hydrogen/argon to 1700 °C. In SIMFUEL, 4.1% of the volume of the solid was in the form of metal nanoparticles which are made of molybdenum , ruthenium , rhodium and palladium . Most of these metal particles are of the ε phase ( hexagonal ) of Mo-Ru-Rh-Pd alloy, while smaller amounts of the α ( cubic ) and σ ( tetragonal ) phases of these metals were found in

979-625: A while, eventually resulting in stranded assets , such as Nord Stream 2 . Energy policy is closely related to climate change policy because totalled worldwide the energy sector emits more greenhouse gas than other sectors. Energy policy decisions are sometimes not taken democratically. In 2019, some companies “have committed to set climate targets across their operations and value chains aligned with limiting global temperature rise to 1.5°C above pre-industrial levels and reaching net-zero emissions by no later than 2050”. Corporate power purchase agreements can kickstart renewable energy projects, but

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1068-414: Is policy about climate change . It is often decided by national governments - for example the climate policy of China . It may include policy on reducing greenhouse gas emissions to limit climate change , and also adapting to climate change . Or not. National climate policy sometimes conflicts with sub-national or bloc policy, for example the climate change policy of Washington (state) diverges from

1157-467: Is a basic practice, with reprocessed uranium being recycled and plutonium used in MOX, at present only for fast reactors. Mixed oxide, or MOX fuel , is a blend of reprocessed uranium and plutonium and depleted uranium which behaves similarly, although not identically, to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to low-enriched uranium (LEU) fuel used in

1246-451: Is a special grade. Attempts to use the pigment grade used in paints have not been successful. Note that a source of data on the subject of caesium in Chernobyl fallout exists at [1] ( Ukrainian Research Institute for Agricultural Radiology ). The IAEA assume that under normal operation the coolant of a water-cooled reactor will contain some radioactivity but during a reactor accident

1335-409: Is an ambitious goal to reduce carbon dioxide emissions in future years, but it is unclear whether the programmes in place are sufficient to achieve this objective. Regarding energy self-sufficiency, UK policy does not address this issue, other than to concede historic energy security is currently ceasing to exist (due to the decline of North Sea oil production). The United Kingdom historically has

1424-487: Is an ongoing issue in reactor operations as no definitive solution to this problem has been found. Operators use a combination of computational and empirical techniques to manage this problem. Used nuclear fuel is studied in Post irradiation examination , where used fuel is examined to know more about the processes that occur in fuel during use, and how these might alter the outcome of an accident. For example, during normal use,

1513-509: Is at a historic low and now below 10% down from a maximum of 17.5% in 1996. Following the March 2011 Fukushima I nuclear accidents , China, Germany, Switzerland, Israel, Malaysia, Thailand, United Kingdom, and the Philippines are reviewing their nuclear power programs. Indonesia and Vietnam still plan to build nuclear power plants. Thirty-one countries operate nuclear power stations , and there are

1602-469: Is dominated by other government policies. For example energy policy may dominate, supplying free coal to poor families and schools thus supporting social policy , but thus causing air pollution and so impeding heath policy and environmental policy . On the other hand energy policy may be dominated by defense policy , for example some counties started building expensive nuclear power plants to supply material for bombs. Or defense policy may be dominated for

1691-585: Is equal to 46.13% of total primary energy consumption. India is largely dependent on fossil fuel imports to meet its energy demands – by 2030, India's dependence on energy imports is expected to exceed 53% of the country's total energy consumption. The energy policy of the United Kingdom refers to the United Kingdom's efforts towards reducing energy intensity , reducing energy poverty , and maintaining energy supply reliability. The United Kingdom has had success in this, though energy intensity remains high. There

1780-573: Is likely that the modern releases of all these isotopes from the Windscale event is smaller. Some reactor designs, such as RBMKs or CANDU reactors , can be refueled without being shut down. This is achieved through the use of many small pressure tubes to contain the fuel and coolant, as opposed to one large pressure vessel as in pressurized water reactor (PWR) or boiling water reactor (BWR) designs. Each tube can be individually isolated and refueled by an operator-controlled fueling machine, typically at

1869-486: Is more detailed than energy policy. Some governments state an explicit energy policy. Others do not but in any case, each government practices some type of energy policy. A national energy policy comprises a set of measures involving that country's laws, treaties and agency directives. There are a number of elements that are contained in a national energy policy. Some important elements intrinsic to an energy policy include: Energy policy sometimes dominates and sometimes

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1958-422: Is not reprocessed, the fuel cycle is referred to as an open fuel cycle (or a once-through fuel cycle ); if the spent fuel is reprocessed, it is referred to as a closed fuel cycle . Nuclear power relies on fissionable material that can sustain a chain reaction with neutrons . Examples of such materials include uranium and plutonium . Most nuclear reactors use a moderator to lower the kinetic energy of

2047-404: Is shut down for refueling. The fuel discharged at that time (spent fuel) is stored either at the reactor site (commonly in a spent fuel pool ) or potentially in a common facility away from reactor sites. If on-site pool storage capacity is exceeded, it may be desirable to store the now cooled aged fuel in modular dry storage facilities known as Independent Spent Fuel Storage Installations (ISFSI) at

2136-422: Is so tightly bonded to the iron that it is safe for a human to eat several grams of Prussian blue per day. The Prussian blue reduces the biological half-life (different from the nuclear half-life ) of the caesium. The physical or nuclear half-life of Cs is about 30 years. This is a constant which can not be changed but the biological half-life is not a constant. It will change according to the nature and habits of

2225-587: Is stored as uranium hexafluoride (UF 6 ). For use as nuclear fuel, enriched uranium hexafluoride is converted into uranium dioxide (UO 2 ) powder that is then processed into pellet form. The pellets are then fired in a high temperature sintering furnace to create hard, ceramic pellets of enriched uranium . The cylindrical pellets then undergo a grinding process to achieve a uniform pellet size. The pellets are stacked, according to each nuclear reactor core 's design specifications, into tubes of corrosion-resistant metal alloy . The tubes are sealed to contain

2314-561: Is the third biggest with 6% global share after China and USA. The total primary energy consumption from coal (452.2 Mtoe; 45.88%), crude oil (239.1 Mtoe ; 29.55%), natural gas (49.9 Mtoe; 6.17%), nuclear energy (8.8 Mtoe; 1.09%), hydroelectricity (31.6 Mtoe; 3.91%) and renewable power (27.5 Mtoe; 3.40%) is 809.2 Mtoe (excluding traditional biomass use) in the calendar year 2018. In 2018, India's net imports are nearly 205.3 million tons of crude oil and its products, 26.3 Mtoe of LNG and 141.7 Mtoe coal totaling to 373.3 Mtoe of primary energy which

2403-403: Is then mixed with pure hydrogen resulting in uranium dioxide and dihydrogen monoxide or water. After that the uranium dioxide is mixed with four parts hydrogen fluoride resulting in more water and uranium tetrafluoride. Finally the end product of uranium hexafluoride is created by simply adding more fluoride to the mixture. For use in reactors such as CANDU which do not require enriched fuel,

2492-421: Is then processed into either of two substances depending on the intended use. For use in most reactors, U 3 O 8 is usually converted to uranium hexafluoride (UF 6 ), the input stock for most commercial uranium enrichment facilities. A solid at room temperature, uranium hexafluoride becomes gaseous at 57 °C (134 °F). At this stage of the cycle, the uranium hexafluoride conversion product still has

2581-505: Is usually a good policy. Nuclear fuel cycle The nuclear fuel cycle , also called nuclear fuel chain , is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end , which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end , which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel . If spent fuel

2670-577: Is why the fuel had to be removed. These fissile and fertile materials can be chemically separated and recovered from the spent fuel. The recovered uranium and plutonium can, if economic and institutional conditions permit, be recycled for use as nuclear fuel. This is currently not done for civilian spent nuclear fuel in the United States , however it is done in Russia. Russia aims to maximise recycling of fissile materials from used fuel. Hence reprocessing used fuel

2759-803: The Department for Science, Innovation and Technology in 2023. Energy markets are regulated by the Office of Gas and Electricity Markets (Ofgem). The energy policy of the United States is determined by federal, state, and local entities. It addresses issues of energy production, distribution, consumption, and modes of use, such as building codes, mileage standards, and commuting policies. Energy policy may be addressed via legislation , regulation, court decisions, public participation, and other techniques. Energy policies vary by country, see tables below. Climate policies Climate policy or climate change policy

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2848-690: The climate change policy of the United States , and EU climate policy can conflict with other national policies. Climate policies may have very big co-benefits for health policy such as by: reducing air pollution , increasing walking and cycling , and eating less beef; they may also help energy policy by reducing oil imports. Public support for policies depends on: how effective people think they are in reducing emissions, their impact on poor people, their effect on respondents’ households, and how well they understand them. Climate-economy modelling may help when deciding policy. Policy, such as target dates for net-zero emissions , may be put into law. Tax

2937-406: The fission process that consumes the fuels, the old fuel rods must be replaced periodically with fresh ones (this is called a (replacement) cycle). During a given replacement cycle only some of the assemblies (typically one-third) are replaced since fuel depletion occurs at different rates at different places within the reactor core. Furthermore, for efficiency reasons, it is not a good policy to put

3026-415: The minor actinides ), the effect of adding an alpha emitter ( Pu) to uranium dioxide on the leaching rate of the oxide has been investigated. For the crushed oxide, adding Pu tended to increase the rate of leaching, but the difference in the leaching rate between 0.1 and 10% Pu was very small. The concentration of carbonate in the water which is in contact with the used fuel has a considerable effect on

3115-627: The social sciences to gain insights into energy consumer behavior can help policymakers to make better decisions about broad-based climate and energy options. This could facilitate more efficient energy use , renewable-energy commercialization , and carbon-emission reductions. The attributes of energy policy may include legislation , international treaties, incentives to investment, guidelines for energy conservation , taxation and other public policy techniques. Economic and energy modelling can be used by governmental or inter-governmental bodies as an advisory and analysis tool. Energy planning

3204-620: The SIMFUEL. Also present within the SIMFUEL was a cubic perovskite phase which is a barium strontium zirconate (Ba x Sr 1−x ZrO 3 ). Uranium dioxide is minimally soluable in water, but after oxidation it can be converted to uranium trioxide or another uranium(VI) compound which is much more soluble. Uranium dioxide (UO 2 ) can be oxidised to an oxygen rich hyperstoichiometric oxide (UO 2+x ) which can be further oxidised to U 4 O 9 , U 3 O 7 , U 3 O 8 and UO 3 .2H 2 O. Because used fuel contains alpha emitters (plutonium and

3293-514: The U 3 O 8 may instead be converted to uranium dioxide (UO 2 ) which can be included in ceramic fuel elements. In the current nuclear industry, the volume of material converted directly to UO 2 is typically quite small compared to that converted to UF 6 . The natural concentration (0.71%) of the fissile isotope U-235 is less than that required to sustain a nuclear chain reaction in light water reactor cores. Accordingly, UF 6 produced from natural uranium sources must be enriched to

3382-579: The U.S. form an international partnership to see spent nuclear fuel reprocessed in a way that renders the plutonium in it usable for nuclear fuel but not for nuclear weapons . As an alternative to the disposal of the PUREX raffinate in glass or Synroc matrix, the most radiotoxic elements could be removed through advanced reprocessing. After separation, the minor actinides and some long-lived fission products could be converted to short-lived or stable isotopes by either neutron or photon irradiation. This

3471-479: The United Kingdom has goals for wind and tidal energy . The 2007 White Paper on Energy set a target that 20% of the UK's energy must come from renewable sources by 2020. The current energy policy of the United Kingdom is the responsibility of the Department for Energy Security and Net Zero (DESNZ), after the Department for Business, Energy and Industrial Strategy was split into the Department for Business and Trade and

3560-596: The activity of the fuel of a 1 GWe reactor is as the IAEA predicts, then the coolant activity after an accident such as the Three Mile Island accident (where a core is uncovered and then recovered with water) can be predicted. It is normal to allow used fuel to stand after the irradiation to allow the short-lived and radiotoxic iodine isotopes to decay away. In one experiment in the US, fresh fuel which had not been allowed to decay

3649-487: The amounts of ore that are estimated to be recoverable at stated costs. Naturally occurring uranium consists primarily of two isotopes U-238 and U-235, with 99.28% of the metal being U-238 while 0.71% is U-235, and the remaining 0.01% is mostly U-234. The number in such names refers to the isotope 's atomic mass number , which is the number of protons plus the number of neutrons in the atomic nucleus . The atomic nucleus of U-235 will nearly always fission when struck by

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3738-459: The best countermeasures against Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the Cs out of reach of the shallow roots of the grass, hence the level of radioactivity in the grass will be lowered. Also after a nuclear war or serious accident, the removal of top few cm of soil and its burial in a shallow trench will reduce the long-term gamma dose to humans due to Cs, as

3827-425: The casks' shell will have at least one layer of radiation-resistant material, such as lead. The inside of the tube will also vary depending on what is being transported. For example casks that are transporting depleted or unused fuel rods will have sleeves that keep the rods separate, while casks that transport uranium hexafluoride typically have no internal organization. Depending on the purpose and radioactivity of

3916-453: The commonly used uranium enrichment methods, but new enrichment technologies are currently being developed. The bulk (96%) of the byproduct from enrichment is depleted uranium (DU), which can be used for armor , kinetic energy penetrators , radiation shielding and ballast . As of 2008 there are vast quantities of depleted uranium in storage. The United States Department of Energy alone has 470,000 tonnes . About 95% of depleted uranium

4005-577: The conventional energy resources continue even today to bias markets by burying many of the real societal costs of their use". The energy policy of India is to increase the locally produced energy in India and reduce energy poverty , with more focus on developing alternative sources of energy , particularly nuclear , solar and wind energy. Net energy import dependency was 40.9% in 2021-22. The primary energy consumption in India grew by 13.3% in FY2022-23 and

4094-402: The coolant radioactivity level may rise. The IAEA states that under a series of different conditions different amounts of the core inventory can be released from the fuel, the four conditions the IAEA consider are normal operation , a spike in coolant activity due to a sudden shutdown/loss of pressure (core remains covered with water), a cladding failure resulting in the release of the activity in

4183-416: The core, some eventually yield atoms of fissile Pu-239. Uranium ore can be extracted through conventional mining in open pit and underground methods similar to those used for mining other metals. In-situ leach mining methods also are used to mine uranium in the United States . In this technology, uranium is leached from the in-place ore through an array of regularly spaced wells and is then recovered from

4272-474: The cost of goods and services. Frequently the dominant issue of energy policy is the risk of supply-demand mismatch (see: energy crisis ). Current energy policies also address environmental issues (see: climate change ), particularly challenging because of the need to reconcile global objectives and international rules with domestic needs and laws. The "human dimensions" of energy use are of increasing interest to business , utilities, and policymakers. Using

4361-519: The course of over forty years of operation by the nuclear industry, a number of specialized facilities have been developed in various locations around the world to provide fuel cycle services and there is a need to transport nuclear materials to and from these facilities. Most transports of nuclear fuel material occur between different stages of the cycle, but occasionally a material may be transported between similar facilities. With some exceptions, nuclear fuel cycle materials are transported in solid form,

4450-477: The energy policies of some countries do not allow or discourage them. Nuclear energy policy is a national and international policy concerning some or all aspects of nuclear energy and the nuclear fuel cycle , such as uranium mining , ore concentration, conversion, enrichment for nuclear fuel , generating electricity by nuclear power , storing and reprocessing spent nuclear fuel , and disposal of radioactive waste . Nuclear energy policies often include

4539-441: The exception being uranium hexafluoride (UF 6 ) which is considered a gas. Most of the material used in nuclear fuel is transported several times during the cycle. Transports are frequently international, and are often over large distances. Nuclear materials are generally transported by specialized transport companies. Since nuclear materials are radioactive , it is important to ensure that radiation exposure of those involved in

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4628-545: The fissile isotope U-233 . Both plutonium and U-233 are produced from the absorption of neutrons by irradiating fertile materials in a reactor, in particular the common uranium isotope U-238 and thorium , respectively, and can be separated from spent uranium and thorium fuels in reprocessing plants . Some reactors do not use moderators to slow the neutrons. Like nuclear weapons, which also use unmoderated or "fast" neutrons, these fast-neutron reactors require much higher concentrations of fissile isotopes in order to sustain

4717-540: The form that occurs in nature, and requires fuel enriched to higher concentrations of fissile isotopes. Typically, LWRs use uranium enriched to 3–5% U-235 , the only fissile isotope that is found in significant quantity in nature. One alternative to this low-enriched uranium (LEU) fuel is mixed oxide (MOX) fuel produced by blending plutonium with natural or depleted uranium, and these fuels provide an avenue to utilize surplus weapons-grade plutonium. Another type of MOX fuel involves mixing LEU with thorium , which generates

4806-486: The free market system has some fundamental limitations. As the Stern Review points out: "In a liberalised energy market, investors, operators and consumers should face the full cost of their decisions. But this is not the case in many economies or energy sectors. Many policies distort the market in favour of existing fossil fuel technologies." The International Solar Energy Society has stated that "historical incentives for

4895-427: The fuel and the cladding. After diffusing into these voids, it decays to caesium isotopes. Because of the thermal gradient which exists in the fuel during use, the volatile fission products tend to be driven from the centre of the pellet to the rim area. Below is a graph of the temperature of uranium metal, uranium nitride and uranium dioxide as a function of distance from the centre of a 20 mm diameter pellet with

4984-423: The fuel expands due to thermal expansion, which can cause cracking. Most nuclear fuel is uranium dioxide, which is a cubic solid with a structure similar to that of calcium fluoride . In used fuel the solid state structure of most of the solid remains the same as that of pure cubic uranium dioxide. SIMFUEL is the name given to the simulated spent fuel which is made by mixing finely ground metal oxides, grinding as

5073-533: The fuel in a furnace under oxidizing conditions) the majority of the tritium can be recovered from the fuel. [4] A paper was written on the radioactivity in oysters found in the Irish Sea . These were found by gamma spectroscopy to contain Ce, Ce, Ru, Ru, Cs, Zr and Nb. Additionally, a zinc activation product ( Zn) was found, which is thought to be due to the corrosion of magnox fuel cladding in spent fuel pools . It

5162-452: The fuel pellets: these tubes are called fuel rods. The finished fuel rods are grouped in special fuel assemblies that are then used to build up the nuclear fuel core of a power reactor. The alloy used for the tubes depends on the design of the reactor. Stainless steel was used in the past, but most reactors now use a zirconium alloy . For the most common types of reactors, boiling water reactors (BWR) and pressurized water reactors (PWR),

5251-427: The fuel/cladding gap (this could be due to the fuel being uncovered by the loss of water for 15–30 minutes where the cladding reached a temperature of 650–1250 °C) or a melting of the core (the fuel will have to be uncovered for at least 30 minutes, and the cladding would reach a temperature in excess of 1650 °C). Based upon the assumption that a Pressurized water reactor contains 300 tons of water , and that

5340-404: The gamma photons will be attenuated by their passage through the soil. Even after the radioactive element arrives at the roots of the plant, the metal may be rejected by the biochemistry of the plant. The details of the uptake of Sr and Cs into sunflowers grown under hydroponic conditions has been reported. The caesium was found in the leaf veins, in the stem and in the apical leaves. It

5429-426: The high energy density of nuclear fuel. Safe management of these byproducts of nuclear power, including their storage and disposal, is a difficult problem for any country using nuclear power . A deposit of uranium, such as uraninite , discovered by geophysical techniques, is evaluated and sampled to determine the amounts of uranium materials that are extractable at specified costs from the deposit. Uranium reserves are

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5518-437: The import and export of nuclear technology , electricity , nuclear waste , and uranium . Since about 2001 the term nuclear renaissance has been used to refer to a possible nuclear power industry revival, but nuclear electricity generation in 2012 was at its lowest level since 1999. Since then it had increased back to 2,653 TWh in 2021, a level last seen in 2006. The share of nuclear power in electricity production however

5607-510: The isotope signature of a hypothetical accident may be very different from that of a planned normal operational discharge of radioactivity to the environment. Just because a radioisotope is released it does not mean it will enter a human and then cause harm. For instance, the migration of radioactivity can be altered by the binding of the radioisotope to the surfaces of soil particles. For example, caesium (Cs) binds tightly to clay minerals such as illite and montmorillonite , hence it remains in

5696-489: The leach solution at a surface plant. Uranium ores in the United States typically range from about 0.05 to 0.3% uranium oxide (U 3 O 8 ). Some uranium deposits developed in other countries are of higher grade and are also larger than deposits mined in the United States. Uranium is also present in very low-grade amounts (50 to 200 parts per million) in some domestic phosphate -bearing deposits of marine origin. Because very large quantities of phosphate-bearing rock are mined for

5785-449: The light water reactors which predominate nuclear power generation. Currently, plants in Europe are reprocessing spent fuel from utilities in Europe and Japan. Reprocessing of spent commercial-reactor nuclear fuel is currently not permitted in the United States due to the perceived danger of nuclear proliferation . The Bush Administration's Global Nuclear Energy Partnership proposed that

5874-426: The likely leaching behaviour of uranium dioxide. The study of the nuclear fuel cycle includes the study of the behaviour of nuclear materials both under normal conditions and under accident conditions. For example, there has been much work on how uranium dioxide based fuel interacts with the zirconium alloy tubing used to cover it. During use, the fuel swells due to thermal expansion and then starts to react with

5963-484: The material is panned out and washed off. The solution will repeat this process of filtration to pull as much usable uranium out as possible. The filtered uranium is then dried out into U 3 O 8 uranium. The milling process commonly yields dry powder-form material consisting of natural uranium, " yellowcake ", which is sold on the uranium market as U 3 O 8 . Note that the material is not always yellow. Usually milled uranium oxide, U 3 O 8 ( triuranium octoxide )

6052-403: The material that the ore is made of is particularly resistant to acids then an alkali is used instead. After being treated chemically the uranium particles are dissolved into the solution used to treat them. This solution is then filtered until what solids remain are separated from the liquids that contain the uranium. The undesirable solids are disposed of as tailings . Once the solution has had

6141-413: The materials some casks have systems of ventilation, thermal protection, impact protection, and other features more specific to the route and cargo. A nuclear reactor core is composed of a few hundred "assemblies", arranged in a regular array of cells, each cell being formed by a fuel or control rod surrounded, in most designs, by a moderator and coolant , which is water in most reactors. Because of

6230-410: The natural isotopic mix (99.28% of U-238 plus 0.71% of U-235). There are two ways to convert uranium oxide into its usable forms uranium dioxide and uranium hexafluoride; the wet option and the dry option. In the wet option the yellowcake is dissolved in nitric acid then extracted using tributyl phosphate. The resulting mixture is then dried and washed resulting in uranium trioxide. The uranium trioxide

6319-479: The neutrons and increase the probability that fission will occur. This allows reactors to use material with far lower concentration of fissile isotopes than are needed for nuclear weapons . Graphite and heavy water are the most effective moderators, because they slow the neutrons through collisions without absorbing them. Reactors using heavy water or graphite as the moderator can operate using natural uranium . A light water reactor (LWR) uses water in

6408-451: The new assemblies exactly at the location of the removed ones. Even bundles of the same age will have different burn-up levels due to their previous positions in the core. Thus the available bundles must be arranged in such a way that the yield is maximized, while safety limitations and operational constraints are satisfied. Consequently, reactor operators are faced with the so-called optimal fuel reloading problem , which consists of optimizing

6497-406: The nuclear reaction, causing the fuel to become a spent nuclear fuel . When 3% enriched LEU fuel is used, the spent fuel typically consists of roughly 1% U-235, 95% U-238, 1% plutonium and 3% fission products. Spent fuel and other high-level radioactive waste is extremely hazardous, although nuclear reactors produce orders of magnitude smaller volumes of waste compared to other power plants because of

6586-461: The organism for which it is expressed. Caesium in humans normally has a biological half-life of between one and four months. An added advantage of the Prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of Prussian blue required for the treatment of humans or animals

6675-474: The other area is concerned with maloperation conditions where some alteration from the normal operating conditions has occurred or ( more rarely ) an accident is occurring. The releases of radioactivity from normal operations are the small planned releases from uranium ore processing, enrichment, power reactors, reprocessing plants and waste stores. These can be in different chemical/physical form from releases which could occur under accident conditions. In addition

6764-416: The production of wet-process phosphoric acid used in high analysis fertilizers and other phosphate chemicals, at some phosphate processing plants the uranium, although present in very low concentrations, can be economically recovered from the process stream. When Uranium is mined out of the ground it does not contain enough pure uranium per pound to be used. The process of milling is how the cycle extracts

6853-657: The rate of corrosion, because uranium (VI) forms soluble anionic carbonate complexes such as [UO 2 (CO 3 ) 2 ] and [UO 2 (CO 3 ) 3 ] . When carbonate ions are absent, and the water is not strongly acidic, the hexavalent uranium compounds which form on oxidation of uranium dioxide often form insoluble hydrated uranium trioxide phases. Thin films of uranium dioxide can be deposited upon gold surfaces by ‘ sputtering ’ using uranium metal and an argon / oxygen gas mixture. These gold surfaces modified with uranium dioxide have been used for both cyclic voltammetry and AC impedance experiments, and these offer an insight into

6942-587: The reactor site or at a facility away from the site. The spent fuel rods are usually stored in water or boric acid, which provides both cooling (the spent fuel continues to generate decay heat as a result of residual radioactive decay) and shielding to protect the environment from residual ionizing radiation , although after at least a year of cooling they may be moved to dry cask storage . Spent fuel discharged from reactors contains appreciable quantities of fissile (U-235 and Pu-239), fertile (U-238), and other radioactive materials, including reaction poisons , which

7031-527: The rearrangement of all the assemblies, the old and fresh ones, while still maximizing the reactivity of the reactor core so as to maximise fuel burn-up and minimise fuel-cycle costs. This is a discrete optimization problem, and computationally infeasible by current combinatorial methods, due to the huge number of permutations and the complexity of each computation. Many numerical methods have been proposed for solving it and many commercial software packages have been written to support fuel management. This

7120-407: The regulation of energy use and standards relating to the nuclear fuel cycle . Other measures include efficiency standards, safety regulations, emission standards , fiscal policies , and legislation on energy trading, transport of nuclear waste and contaminated materials, and their storage. Governments might subsidize nuclear energy and arrange international treaties and trade agreements about

7209-434: The risk in transporting highly radioactive materials, containers known as spent nuclear fuel shipping casks are used which are designed to maintain integrity under normal transportation conditions and during hypothetical accident conditions. While transport casks vary in design, material, size, and purpose, they are typically long tubes made of stainless steel or concrete with the ends sealed shut to prevent leaks. Frequently

7298-407: The surface of the zirconium alloy, forming a new layer which contains both fuel and zirconium (from the cladding). Then, on the fuel side of this mixed layer, there is a layer of fuel which has a higher caesium to uranium ratio than most of the fuel. This is because xenon isotopes are formed as fission products that diffuse out of the lattice of the fuel into voids such as the narrow gap between

7387-435: The tailings removed the uranium is extracted from the rest of the liquid solution, in one of two ways, solvent exchange or ion exchange . In the first of these a solvent is mixed into the solution. The dissolved uranium binds to the solvent and floats to the top while the other dissolved materials remain in the mixture. During ion exchange a different material is mixed into the solution and the uranium binds to it. Once filtered

7476-462: The transport of such materials and of the general public along transport routes is limited. Packaging for nuclear materials includes, where appropriate, shielding to reduce potential radiation exposures. In the case of some materials, such as fresh uranium fuel assemblies, the radiation levels are negligible and no shielding is required. Other materials, such as spent fuel and high-level waste, are highly radioactive and require special handling. To limit

7565-413: The tubes are assembled into bundles with the tubes spaced precise distances apart. These bundles are then given a unique identification number, which enables them to be tracked from manufacture through use and into disposal. Transport is an integral part of the nuclear fuel cycle. There are nuclear power reactors in operation in several countries but uranium mining is viable in only a few areas. Also, in

7654-399: The upper layers of soil where it can be accessed by plants with shallow roots (such as grass). Hence grass and mushrooms can carry a considerable amount of Cs which can be transferred to humans through the food chain. But Cs is not able to migrate quickly through most soils and thus is unlikely to contaminate well water. Colloids of soil minerals can migrate through soil so simple binding of

7743-487: The usable uranium from the rest of the materials, also known as tailings. To begin the milling process the ore is either ground into fine dust with water or crushed into dust without water. Once the Materials have been physically treated, they then begin the process of being chemically treated by being doused in acids. Acids used include hydrochloric and nitrous acids but the most common acids are sulfuric acids. Alternatively if

7832-407: Was found that 12% of the caesium entered the plant, and 20% of the strontium. This paper also reports details of the effect of potassium , ammonium and calcium ions on the uptake of the radioisotopes. In livestock farming, an important countermeasure against Cs is to feed animals a small amount of Prussian blue . This iron potassium cyanide compound acts as an ion-exchanger . The cyanide

7921-472: Was reprocessed (the Green run [2] [3] ) to investigate the effects of a large iodine release from the reprocessing of short cooled fuel. It is normal in reprocessing plants to scrub the off gases from the dissolver to prevent the emission of iodine. In addition to the emission of iodine the noble gases and tritium are released from the fuel when it is dissolved. It has been proposed that by voloxidation (heating

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