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125-502: A molten-salt reactor ( MSR ) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a mixture of molten salt with a fissile material. Two research MSRs operated in the United States in the mid-20th century. The 1950s Aircraft Reactor Experiment (ARE) was primarily motivated by the technology's compact size, while the 1960s Molten-Salt Reactor Experiment (MSRE) aimed to demonstrate

250-403: A nuclear power plant using a thorium fuel cycle in a breeder reactor . Increased research into Generation IV reactor designs renewed interest in the 21st century with multiple nations starting projects. As of June 2023, China has been operating its TMSR-LF1 thorium unit. MSRs eliminate the nuclear meltdown scenario present in water-cooled reactors because the fuel mixture is kept in

375-475: A nuclear proliferation risk as they can be configured to produce plutonium , as well as tritium gas used in boosted fission weapons . Reactor spent fuel can be reprocessed to yield up to 25% more nuclear fuel, which can be used in reactors again. Reprocessing can also significantly reduce the volume of nuclear waste, and has been practiced in Europe, Russia, India and Japan. Due to concerns of proliferation risks,

500-553: A " neutron howitzer ") produced a barium residue, which they reasoned was created by fission of the uranium nuclei. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening the possibility of a nuclear chain reaction . Subsequent studies in early 1939 (one of them by Szilárd and Fermi), revealed that several neutrons were indeed released during fission, making available

625-403: A closed fuel cycle—as opposed to the once-through fuel currently used in conventional nuclear power generators. MSRs exploit a negative temperature coefficient of reactivity and a large allowable temperature rise to prevent criticality accidents . For designs with the fuel in the salt, the salt thermally expands immediately with power excursions. In conventional reactors the negative reactivity

750-441: A crucial role in generating large amounts of electricity with low carbon emissions, contributing significantly to the global energy mix. Just as conventional thermal power stations generate electricity by harnessing the thermal energy released from burning fossil fuels , nuclear reactors convert the energy released by controlled nuclear fission into thermal energy for further conversion to mechanical or electrical forms. When

875-445: A gas or a liquid metal (like liquid sodium or lead) or molten salt – is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. Most reactor systems employ a cooling system that is physically separated from the water that will be boiled to produce pressurized steam for the turbines , like the pressurized water reactor . However, in some reactors

1000-686: A helium-cooled VHTR operating in similar conditions; passive safety systems and better retention of fission products in the event of an accident. Reactors containing molten thorium salt, called liquid fluoride thorium reactors (LFTR), would tap the thorium fuel cycle . Private companies from Japan, Russia, Australia and the United States, and the Chinese government, have expressed interest in developing this technology. Advocates estimate that five hundred metric tons of thorium could supply U.S. energy needs for one year. The U.S. Geological Survey estimates that

1125-442: A large fissile atomic nucleus such as uranium-235 , uranium-233 , or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, (the fission products ), releasing kinetic energy , gamma radiation , and free neutrons . A portion of these neutrons may be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, and so on. This

1250-407: A large variety of fuel compositions due to its on-line fuel control and flexible fuel processing. The standard MSFR would be a 3000 MWth reactor that has a total fuel salt volume of 18 m with a mean fuel temperature of 750 °C. The core's shape is a compact cylinder with a height to diameter ratio of 1 where liquid fluoride fuel salt flows from the bottom to the top. The return circulation of

1375-424: A less effective moderator. In other reactors, the coolant acts as a poison by absorbing neutrons in the same way that the control rods do. In these reactors, power output can be increased by heating the coolant, which makes it a less dense poison. Nuclear reactors generally have automatic and manual systems to scram the reactor in an emergency shut down. These systems insert large amounts of poison (often boron in

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1500-472: A moderator (usually graphite) to slow the neutrons down and moderate temperature. They can accept a variety of fuels (low-enriched uranium, thorium, depleted uranium , waste products) and coolants (fluoride, chloride, lithium, beryllium, mixed). Fuel cycle can be either closed or once-through. They can be monolithic or modular, large or small. The reactor can adopt a loop, modular or integral configuration. Variations include: The molten-salt fast reactor (MSFR)

1625-476: A molten state. The fuel mixture is designed to drain without pumping from the core to a containment vessel in emergency scenarios, where the fuel solidifies, quenching the reaction. In addition, hydrogen evolution does not occur. This eliminates the risk of hydrogen explosions (as in the Fukushima nuclear disaster ). They operate at or close to atmospheric pressure , rather than the 75–150 times atmospheric pressure of

1750-470: A neutron to become Cl , then degrades by beta decay to S . Lithium must be in the form of purified Li , because Li effectively captures neutrons and produces tritium . Even if pure Li is used, salts containing lithium cause significant tritium production, comparable with heavy water reactors. Reactor salts are usually close to eutectic mixtures to reduce their melting point. A low melting point simplifies melting

1875-570: A number of ways: A kilogram of uranium-235 (U-235) converted via nuclear processes releases approximately three million times more energy than a kilogram of coal burned conventionally (7.2 × 10 joules per kilogram of uranium-235 versus 2.4 × 10 joules per kilogram of coal). The fission of one kilogram of uranium-235 releases about 19 billion kilocalories , so the energy released by 1 kg of uranium-235 corresponds to that released by burning 2.7 million kg of coal. A nuclear reactor coolant – usually water but sometimes

2000-461: A patent on reactors on 19 December 1944. Its issuance was delayed for 10 years because of wartime secrecy. "World's first nuclear power plant" is the claim made by signs at the site of the EBR-I , which is now a museum near Arco, Idaho . Originally called "Chicago Pile-4", it was carried out under the direction of Walter Zinn for Argonne National Laboratory . This experimental LMFBR operated by

2125-635: A peak temperature of 860 °C. It produced 100 MWh over nine days in 1954. This experiment used Inconel 600 alloy for the metal structure and piping. An MSR was operated at the Critical Experiments Facility of the Oak Ridge National Laboratory in 1957. It was part of the circulating-fuel reactor program of the Pratt & Whitney Aircraft Company (PWAC). This was called Pratt and Whitney Aircraft Reactor-1 (PWAR-1). The experiment

2250-737: A pile (hence the name) of graphite blocks, embedded in which was natural uranium oxide 'pseudospheres' or 'briquettes'. Soon after the Chicago Pile, the Metallurgical Laboratory developed a number of nuclear reactors for the Manhattan Project starting in 1943. The primary purpose for the largest reactors (located at the Hanford Site in Washington ), was the mass production of plutonium for nuclear weapons. Fermi and Szilard applied for

2375-407: A planned typical lifetime of 30–40 years, though many of those have received renovations and life extensions of 15–20 years. Some believe nuclear power plants can operate for as long as 80 years or longer with proper maintenance and management. While most components of a nuclear power plant, such as steam generators, are replaced when they reach the end of their useful lifetime, the overall lifetime of

2500-471: A reactor. One such process is delayed neutron emission by a number of neutron-rich fission isotopes. These delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder (termed " prompt neutrons ") released immediately upon fission. The fission products which produce delayed neutrons have half-lives for their decay by neutron emission that range from milliseconds to as long as several minutes, and so considerable time

2625-518: A set of theoretical nuclear reactor designs. These are generally not expected to be available for commercial use before 2040–2050, although the World Nuclear Association suggested that some might enter commercial operation before 2030. Current reactors in operation around the world are generally considered second- or third-generation systems, with the first-generation systems having been retired some time ago. Research into these reactor types

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2750-413: A slow-decaying isotope between them which facilitates neutron absorption by Cl . Chlorides permit fast breeder reactors to be constructed. Much less research has been done on reactor designs using chloride salts. Chlorine, unlike fluorine, must be purified to isolate the heavier stable isotope, Cl , thus reducing production of sulfur tetrachloride that occurs when Cl absorbs

2875-534: A typical light-water reactor (LWR). This reduces the need and cost for reactor pressure vessels . The gaseous fission products ( Xe and Kr ) have little solubility in the fuel salt, and can be safely captured as they bubble out of the fuel, rather than increasing the pressure inside the fuel tubes , as happens in conventional reactors. MSRs can be refueled while operating (essentially online- nuclear reprocessing ) while conventional reactors shut down for refueling (notable exceptions include pressure tube reactors like

3000-606: Is a proposed design with the fuel dissolved in a fluoride salt coolant. The MSFR is one of the two variants of MSRs selected by the Generation IV International Forum (GIF) for further development, the other being the FHR or AHTR. The MSFR is based on a fast neutron spectrum and is believed to be a long-term substitute to solid-fueled fast reactors. They have been studied for almost a decade, mainly by calculations and determination of basic physical and chemical properties in

3125-575: Is also a proposed Generation IV molten-salt reactor variant regarded promising for the long-term future. The FHR/AHTR reactor uses a solid-fuel system along with a molten fluoride salt as coolant. One version of the Very-high-temperature reactor (VHTR) under study was the liquid-salt very-high-temperature reactor (LS-VHTR). It uses liquid salt as a coolant in the primary loop, rather than a single helium loop. It relies on " TRISO " fuel dispersed in graphite. Early AHTR research focused on graphite in

3250-667: Is delayed since the heat from the fuel must be transferred to the moderator. An additional method is to place a separate, passively cooled container below the reactor. Fuel drains into the container during malfunctions or maintenance, which stops the reaction. The temperatures of some designs are high enough to produce process heat, which led them to be included on the GEN-IV roadmap. MSRs offer many potential advantages over light water reactors: MSRs can be cooled in various ways, including using molten salts. Molten-salt-cooled solid-fuel reactors are variously called "molten-salt reactor system" in

3375-504: Is focused on a particular energy challenge. Two of the eight hubs are included in the EERE budget and will focus on integrating smart materials, designs, and systems into buildings to better conserve energy and on designing and discovering new concepts and materials needed to convert solar energy into electricity. Another two hubs, included in the DOE Office of Science budget, were created to tackle

3500-413: Is inserted deeper into the reactor, it absorbs more neutrons than the material it displaces – often the moderator. This action results in fewer neutrons available to cause fission and reduces the reactor's power output. Conversely, extracting the control rod will result in an increase in the rate of fission events and an increase in power. The physics of radioactive decay also affects neutron populations in

3625-428: Is known as a nuclear chain reaction . To control such a nuclear chain reaction, control rods containing neutron poisons and neutron moderators are able to change the portion of neutrons that will go on to cause more fission. Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if monitoring or instrumentation detects unsafe conditions. The reactor core generates heat in

3750-405: Is mined, processed, enriched, used, possibly reprocessed and disposed of is known as the nuclear fuel cycle . Under 1% of the uranium found in nature is the easily fissionable U-235 isotope and as a result most reactor designs require enriched fuel. Enrichment involves increasing the percentage of U-235 and is usually done by means of gaseous diffusion or gas centrifuge . The enriched result

3875-452: Is no longer a problem. This results in a breeder reactor with a fast neutron spectrum that operates in the Thorium fuel cycle. MSFRs contain relatively small initial inventories of U . MSFRs run on liquid fuel with no solid matter inside the core. This leads to the possibility of reaching specific power that is much higher than reactors using solid fuel. The heat produced goes directly into

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4000-543: Is not absorbed but instead knocks a neutron out of the nucleus), generate U . Because U has a short half-life and its decay chain contains hard gamma emitters, it makes the isotopic mix of uranium less attractive for bomb-making. This benefit would come with the added expense of a larger fissile inventory or a 2-fluid design with a large quantity of blanket salt. The necessary fuel salt reprocessing technology has been demonstrated, but only at laboratory scale. A prerequisite to full-scale commercial reactor design

4125-540: Is not created in the core (as is present in boiling water reactors ), and no large, expensive steel pressure vessel (as required for pressurized water reactors ). Since it can operate at high temperatures, the conversion of the heat to electricity can use an efficient, lightweight Brayton cycle gas turbine. Much of the current research on FHRs is focused on small, compact heat exchangers that reduce molten salt volumes and associated costs. Molten salts can be highly corrosive and corrosivity increases with temperature. For

4250-401: Is produced. Fission also produces iodine-135 , which in turn decays (with a half-life of 6.57 hours) to new xenon-135. When the reactor is shut down, iodine-135 continues to decay to xenon-135, making restarting the reactor more difficult for a day or two, as the xenon-135 decays into cesium-135, which is not nearly as poisonous as xenon-135, with a half-life of 9.2 hours. This temporary state is

4375-448: Is reaching or crossing their design lifetimes of 30 or 40 years. In 2014, Greenpeace warned that the lifetime extension of ageing nuclear power plants amounts to entering a new era of risk. It estimated the current European nuclear liability coverage in average to be too low by a factor of between 100 and 1,000 to cover the likely costs, while at the same time, the likelihood of a serious accident happening in Europe continues to increase as

4500-416: Is required to determine exactly when a reactor reaches the critical point. Keeping the reactor in the zone of chain reactivity where delayed neutrons are necessary to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; otherwise the time between achievement of criticality and nuclear meltdown as a result of an exponential power surge from

4625-453: Is the R&;D to engineer an economically competitive fuel salt cleaning system. Reprocessing refers to the chemical separation of fissionable uranium and plutonium from spent fuel. Such recovery could increase the risk of nuclear proliferation . In the United States the regulatory regime has varied dramatically across administrations. A systematic literature review from 2020 concludes that there

4750-418: Is the lead-cooled, salt-fueled reactor. MSR research started with the U.S. Aircraft Reactor Experiment (ARE) in support of the U.S. Aircraft Nuclear Propulsion program. ARE was a 2.5 MW th nuclear reactor experiment designed to attain a high energy density for use as an engine in a nuclear-powered bomber. The project included experiments, including high temperature and engine tests collectively called

4875-461: Is then converted into uranium dioxide powder, which is pressed and fired into pellet form. These pellets are stacked into tubes which are then sealed and called fuel rods . Many of these fuel rods are used in each nuclear reactor. United States Department of Energy The United States Department of Energy ( DOE ) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production ,

5000-434: Is triggered and achieved by redundant and reliable devices such as detection and opening technology. During operation, the fuel salt circulation speed can be adjusted by controlling the power of the pumps in each sector. The intermediate fluid circulation speed can be adjusted by controlling the power of the intermediate circuit pumps. The temperature of the intermediate fluid in the intermediate exchangers can be managed through

5125-445: Is very limited information on economics and finance of MSRs, with low quality of the information and that cost estimations are uncertain. In the specific case of the stable salt reactor (SSR) where the radioactive fuel is contained as a molten salt within fuel pins and the primary circuit is not radioactive, operating costs are likely to be lower. While many design variants have been proposed, there are three main categories regarding

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5250-561: The Code of Federal Regulations , in Title 10: Energy : The official seal of the Department of Energy "includes a green shield bisected by a gold-colored lightning bolt, on which is emblazoned a gold-colored symbolic sun , atom , oil derrick , windmill , and dynamo . It is crested by the white head of an eagle , atop a white rope. Both appear on a blue field surrounded by concentric circles in which

5375-669: The Department of Energy Organization Act , which established the Department of Energy. The new agency, which began operations on October 1, 1977, consolidated the Federal Energy Administration , the Energy Research and Development Administration , the Federal Power Commission , and programs of various other agencies. Former Secretary of Defense James Schlesinger , who served under Presidents Nixon and Ford during

5500-726: The Human Genome Project originating from a DOE initiative. The department is headed by the secretary of energy , who reports directly to the president of the United States and is a member of the Cabinet . The current secretary of energy is Jennifer Granholm , who has served in the position since February 2021. The department's headquarters are in southwestern Washington, D.C. , in the James V. Forrestal Building , with additional offices in Germantown, Maryland . In 1942, during World War II ,

5625-484: The Manhattan Project . Eventually, the first artificial nuclear reactor, Chicago Pile-1 , was constructed at the University of Chicago , by a team led by Italian physicist Enrico Fermi, in late 1942. By this time, the program had been pressured for a year by U.S. entry into the war. The Chicago Pile achieved criticality on 2 December 1942 at 3:25 PM. The reactor support structure was made of wood, which supported

5750-514: The PWR , BWR and PHWR designs above, and some are more radical departures. The former include the advanced boiling water reactor (ABWR), two of which are now operating with others under construction, and the planned passively safe Economic Simplified Boiling Water Reactor (ESBWR) and AP1000 units (see Nuclear Power 2010 Program ). Rolls-Royce aims to sell nuclear reactors for the production of synfuel for aircraft. Generation IV reactors are

5875-515: The U.S. Atomic Energy Commission produced 0.8 kW in a test on 20 December 1951 and 100 kW (electrical) the following day, having a design output of 200 kW (electrical). Besides the military uses of nuclear reactors, there were political reasons to pursue civilian use of atomic energy. U.S. President Dwight Eisenhower made his famous Atoms for Peace speech to the UN General Assembly on 8 December 1953. This diplomacy led to

6000-477: The Vietnam War , was appointed as the first secretary. President Carter proposed the Department of Energy with the goal of promoting energy conservation and energy independence, and developing alternative sources of energy to reduce the use of fossil fuels . With international energy's future uncertain for America, Carter acted quickly to have the department come into action the first year of his presidency. This

6125-477: The coolant also acts as a neutron moderator . A moderator increases the power of the reactor by causing the fast neutrons that are released from fission to lose energy and become thermal neutrons. Thermal neutrons are more likely than fast neutrons to cause fission. If the coolant is a moderator, then temperature changes can affect the density of the coolant/moderator and therefore change power output. A higher temperature coolant would be less dense, and therefore

6250-408: The corrosivity of hot salts and the changing chemical composition of the salt as it is transmuted by the neutron flux . MSRs, especially those with fuel in the molten salt, offer lower operating pressures, and higher temperatures. In this respect an MSR is more similar to a liquid metal cooled reactor than to a conventional light water cooled reactor. MSR designs are often breeding reactors with

6375-568: The earth itself, and gold represents the creation of energy in the release of natural forces. By invoking this symbolism , the color scheme represents the Nation's commitment to meet its energy needs in a manner consistent with the preservation of the natural environment ." The Department of Energy operates a system of national laboratories and technical facilities for research and development, as follows: Other major DOE facilities include: Airstrip: The DOE/ NNSA has federal responsibility for

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6500-402: The "iodine pit." If the reactor has sufficient extra reactivity capacity, it can be restarted. As the extra xenon-135 is transmuted to xenon-136, which is much less a neutron poison, within a few hours the reactor experiences a "xenon burnoff (power) transient". Control rods must be further inserted to replace the neutron absorption of the lost xenon-135. Failure to properly follow such a procedure

6625-566: The 1986 Chernobyl disaster and 2011 Fukushima disaster . As of 2022 , the International Atomic Energy Agency reported there are 422 nuclear power reactors and 223 nuclear research reactors in operation around the world. The US Department of Energy classes reactors into generations, with the majority of the global fleet being Generation II reactors constructed from the 1960s to 1990s, and Generation IV reactors currently in development. Reactors can also be grouped by

6750-472: The DOE to issue loan guarantees to eligible projects that "avoid, reduce, or sequester air pollutants or anthropogenic emissions of greenhouse gases " and "employ new or significantly improved technologies as compared to technologies in service in the United States at the time the guarantee is issued". In loan guarantees, a conditional commitment requires to meet an equity commitment, as well as other conditions, before

6875-404: The Department of Energy's handling of his case. Republican senators thought that an independent agency should be in charge of nuclear weapons and security issues, rather than the DOE. All but one of the 59 charges against Lee were eventually dropped because the investigation proved the plans the Chinese obtained could not have come from Lee. Lee filed suit and won a $ 1.6 million settlement against

7000-495: The European Union and Russian Federation. A MSFR is regarded sustainable because there are no fuel shortages. Operation of a MSFR does in theory not generate or require large amounts of transuranic (TRU) elements . When steady state is achieved in a MSFR, there is no longer a need for uranium enrichment facilities. MSFRs may be breeder reactors . They operate without a moderator in the core such as graphite, so graphite life-span

7125-540: The Generation IV proposal, molten-salt converter reactors (MSCR), advanced high-temperature reactors (AHTRs), or fluoride high-temperature reactors (FHR, preferred DOE designation). FHRs cannot reprocess fuel easily and have fuel rods that need to be fabricated and validated, requiring up to twenty years from project inception. FHR retains the safety and cost advantages of a low-pressure, high-temperature coolant, also shared by liquid metal cooled reactors . Notably, steam

7250-631: The Heat Transfer Reactor Experiments: HTRE-1, HTRE-2 and HTRE-3 at the National Reactor Test Station (now Idaho National Laboratory ) as well as an experimental high-temperature molten-salt reactor at Oak Ridge National Laboratory – the ARE. ARE used molten fluoride salt NaF/ZrF 4 /UF 4 (53-41-6  mol% ) as fuel, moderated by beryllium oxide (BeO). Liquid sodium was a secondary coolant. The experiment had

7375-475: The Molten-Salt Reactor Experiment (MSRE). MSRE was a 7.4 MW th test reactor simulating the neutronic "kernel" of a type of epithermal thorium molten salt breeder reactor called the liquid fluoride thorium reactor (LFTR). The large (expensive) breeding blanket of thorium salt was omitted in favor of neutron measurements. Nuclear fission reactor Nuclear reactors have their origins in

7500-458: The Office of Energy Efficiency and Renewable Energy would be lowered to $ 696 million under the plan, down from $ 1.3 billion in fiscal year 2017. Overall, the department's energy and related programs would be cut by $ 1.9 billion. Energy Savings Performance Contracts (ESPCs) are contracts under which a contractor designs, constructs, and obtains the necessary financing for an energy savings project, and

7625-708: The U.S. military sought other uses for nuclear reactor technology. Research by the Army led to the power stations for Camp Century, Greenland and McMurdo Station, Antarctica Army Nuclear Power Program . The Air Force Nuclear Bomber project resulted in the Molten-Salt Reactor Experiment . The U.S. Navy succeeded when they steamed the USS Nautilus (SSN-571) on nuclear power 17 January 1955. The first commercial nuclear power station, Calder Hall in Sellafield , England

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7750-472: The United States does not engage in or encourage reprocessing. Reactors are also used in nuclear propulsion of vehicles. Nuclear marine propulsion of ships and submarines is largely restricted to naval use. Reactors have also been tested for nuclear aircraft propulsion and spacecraft propulsion . Reactor safety is maintained through various systems that control the rate of fission. The insertion of control rods, which absorb neutrons, can rapidly decrease

7875-708: The United States started the Manhattan Project to develop the atomic bomb under the U.S. Army Corps of Engineers . After the war, in 1946, the Atomic Energy Commission (AEC) was created to control the future of the project. The Atomic Energy Act of 1946 also created the framework for the first National Laboratories . Among other nuclear projects, the AEC produced fabricated uranium fuel cores at locations such as Fernald Feed Materials Production Center in Cincinnati, Ohio . The Energy Reorganization Act of 1974 split

8000-546: The World War II Allied Manhattan Project . The world's first artificial nuclear reactor, Chicago Pile-1, achieved criticality on 2 December 1942. Early reactor designs sought to produce weapons-grade plutonium for fission bombs , later incorporating grid electricity production in addition. In 1957, Shippingport Atomic Power Station became the first reactor dedicated to peaceful use; in Russia, in 1954,

8125-565: The area was contaminated, like Fukushima, Three Mile Island, Sellafield, and Chernobyl. The British branch of the French concern EDF Energy , for example, extended the operating lives of its Advanced Gas-cooled Reactors (AGR) with only between 3 and 10 years. All seven AGR plants were expected to be shut down in 2022 and in decommissioning by 2028. Hinkley Point B was extended from 40 to 46 years, and closed. The same happened with Hunterston B , also after 46 years. An increasing number of reactors

8250-770: The beginning of his quest to produce the Einstein-Szilárd letter to alert the U.S. government. Shortly after, Nazi Germany invaded Poland in 1939, starting World War II in Europe. The U.S. was not yet officially at war, but in October, when the Einstein-Szilárd letter was delivered to him, Roosevelt commented that the purpose of doing the research was to make sure "the Nazis don't blow us up." The U.S. nuclear project followed, although with some delay as there remained skepticism (some of it from Enrico Fermi ) and also little action from

8375-548: The challenges of devising advanced methods of energy storage and creating fuels directly from sunlight without the use of plants or microbes. Yet another hub was made to develop "smart" materials to allow the electrical grid to adapt and respond to changing conditions. In 2012, the DOE awarded $ 120 million to the Ames Laboratory to start a new EIH, the Critical Materials Institute, which will focus on improving

8500-458: The choices of coolant and moderator. Almost 90% of global nuclear energy comes from pressurized water reactors and boiling water reactors , which use water as a coolant and moderator. Other designs include heavy water reactors , gas-cooled reactors , and fast breeder reactors , variously optimizing efficiency, safety, and fuel type , enrichment , and burnup . Small modular reactors are also an area of current development. These reactors play

8625-467: The complexities of handling actinides , but significant scientific and technical obstacles remain. Despite research having started in the 1950s, no commercial fusion reactor is expected before 2050. The ITER project is currently leading the effort to harness fusion power. Thermal reactors generally depend on refined and enriched uranium . Some nuclear reactors can operate with a mixture of plutonium and uranium (see MOX ). The process by which uranium ore

8750-526: The department. In December 1999, the FBI was investigating how China obtained plans for a specific nuclear device. Wen Ho Lee was accused of stealing nuclear secrets from Los Alamos National Laboratory for the People's Republic of China . Federal officials, including then-Energy Secretary Bill Richardson , publicly named Lee as a suspect before he was charged with a crime. The U.S. Congress held hearings to investigate

8875-401: The deposition of solid particles in reactor operation. Sulfur must be removed because of its corrosive attack on nickel-based alloys at operational temperature. Structural metals such as chromium, nickel, and iron must be removed for corrosion control. A water content reduction purification stage using HF and helium sweep gas was specified to run at 400 °C. Oxide and sulfur contamination in

9000-437: The design to prevent its release into the environment. Many other salts can cause plumbing corrosion, especially if the reactor is hot enough to make highly reactive hydrogen. To date, most research has focused on FLiBe, because lithium and beryllium are reasonably effective moderators and form a eutectic salt mixture with a lower melting point than each of the constituent salts. Beryllium also performs neutron doubling, improving

9125-470: The design, testing and production of all nuclear weapons. NNSA in turn uses contractors to carry out its responsibilities at the following government owned sites: On May 7, 2009 President Barack Obama unveiled a $ 26.4 billion budget request for DOE for fiscal year (FY) 2010, including $ 2.3 billion for the DOE Office of Energy Efficiency and Renewable Energy (EERE). That budget aimed to substantially expand

9250-429: The development of the technologies and their link to our future capabilities. The lightning bolt represents the power of the natural forces from which energy is derived and the Nation's challenge in harnessing the forces." "The color scheme is derived from nature, symbolizing both the source of energy and the support of man's existence. The blue field represents air and water , green represents mineral resources and

9375-660: The dissemination of reactor technology to U.S. institutions and worldwide. The first nuclear power plant built for civil purposes was the AM-1 Obninsk Nuclear Power Plant , launched on 27 June 1954 in the Soviet Union . It produced around 5 MW (electrical). It was built after the F-1 (nuclear reactor) which was the first reactor to go critical in Europe, and was also built by the Soviet Union. After World War II,

9500-485: The energy of the neutrons that sustain the fission chain reaction : In principle, fusion power could be produced by nuclear fusion of elements such as the deuterium isotope of hydrogen . While an ongoing rich research topic since at least the 1940s, no self-sustaining fusion reactor for any purpose has ever been built. Used by thermal reactors: In 2003, the French Commissariat à l'Énergie Atomique (CEA)

9625-433: The federal agency makes payments over time to the contractor from the savings in the agency's utility bills. The contractor guarantees the energy improvements will generate savings, and after the contract ends, all continuing cost savings accrue to the federal agency. Energy Innovation Hubs are multi-disciplinary , meant to advance highly promising areas of energy science and technology from their early stages of research to

9750-572: The federal government and news agencies. The episode eventually led to the creation of the National Nuclear Security Administration , a semi-autonomous agency within the department. In 2001, American Solar Challenge was sponsored by the DOE and the National Renewable Energy Laboratory . After the 2005 race, the DOE discontinued its sponsorship. Title XVII of Energy Policy Act of 2005 authorizes

9875-524: The first small nuclear power reactor APS-1 OBNINSK reached criticality. Other countries followed suit. Heat from nuclear fission is passed to a working fluid coolant (water or gas), which in turn runs through turbines . In commercial reactors, turbines drive electrical generator shafts. The heat can also be used for district heating , and industrial applications including desalination and hydrogen production . Some reactors are used to produce isotopes for medical and industrial use. Reactors pose

10000-407: The fission process generates heat, some of which can be converted into usable energy. A common method of harnessing this thermal energy is to use it to boil water to produce pressurized steam which will then drive a steam turbine that turns an alternator and generates electricity. Modern nuclear power plants are typically designed for a lifetime of 60 years, while older reactors were built with

10125-529: The form of boric acid ) into the reactor to shut the fission reaction down if unsafe conditions are detected or anticipated. Most types of reactors are sensitive to a process variously known as xenon poisoning, or the iodine pit . The common fission product Xenon-135 produced in the fission process acts as a neutron poison that absorbs neutrons and therefore tends to shut the reactor down. Xenon-135 accumulation can be controlled by keeping power levels high enough to destroy it by neutron absorption as fast as it

10250-475: The form of graphite rods that would be inserted in hexagonal moderating graphite blocks, but current studies focus primarily on pebble-type fuel. The LS-VHTR can work at very high temperatures (the boiling point of most molten salt candidates is >1400 °C); low-pressure cooling that can be used to match hydrogen production facility conditions (most thermochemical cycles require temperatures in excess of 750 °C); better electric conversion efficiency than

10375-424: The fuel rods. This allows the reactor to be constructed with an excess of fissionable material, which is nevertheless made relatively safe early in the reactor's fuel burn cycle by the presence of the neutron-absorbing material which is later replaced by normally produced long-lived neutron poisons (far longer-lived than xenon-135) which gradually accumulate over the fuel load's operating life. The energy released in

10500-440: The fuel salt. Usually the fuel salt temperature can be brought down by 100 °C using a 3% proportion of bubbles. MSFRs have two draining modes, controlled routine draining and emergency draining. During controlled routine draining, fuel salt is transferred to actively cooled storage tanks. The fuel temperature can be lowered before draining, this may slow down the process. This type of draining could be done every 1 to 5 years when

10625-472: The heat transfer fluid. In the MSFR, a small amount of molten salt is set aside to be processed for fission product removal and then returned to the reactor. This gives MSFRs the capability of reprocessing the fuel without stopping the reactor. This is very different compared to solid-fueled reactors because they have separate facilities to produce the solid fuel and process spent nuclear fuel. The MSFR can operate using

10750-490: The heavy water CANDU or the Atucha-class PHWRs, light water cooled graphite moderated RBMK , and British-built gas-cooled reactors such as Magnox , AGR ). MSR operating temperatures are around 700 °C (1,292 °F), significantly higher than traditional LWRs at around 300 °C (572 °F). This increases electricity-generation efficiency and process-heat opportunities. Relevant design challenges include

10875-447: The idea of nuclear fission as a neutron source, since that process was not yet discovered. Szilárd's ideas for nuclear reactors using neutron-mediated nuclear chain reactions in light elements proved unworkable. Inspiration for a new type of reactor using uranium came from the discovery by Otto Hahn , Lise Meitner , and Fritz Strassmann in 1938 that bombardment of uranium with neutrons (provided by an alpha-on-beryllium fusion reaction,

11000-428: The intermediate product protactinium Pa would be removed from the reactor and allowed to decay into highly pure U , an attractive bomb-making material. More modern designs propose to use a lower specific power or a separate thorium breeding blanket. This dilutes the protactinium to such an extent that few protactinium atoms absorb a second neutron or, via a (n, 2n) reaction (in which an incident neutron

11125-458: The inventory of fission products, control corrosion and improve neutron economy by removing fission products with high neutron absorption cross-section, especially xenon . This makes the MSR particularly suited to the neutron-poor thorium fuel cycle . Online fuel processing can introduce risks of fuel processing accidents, which can trigger release of radio isotopes . In some thorium breeding scenarios,

11250-522: The largest-known U.S. thorium deposit, the Lemhi Pass district on the Montana - Idaho border, contains thorium reserves of 64,000 metric tons. Traditionally, these reactors were known as molten salt breeder reactors (MSBRs) or thorium molten-salt reactors (TMSRs), but the name LFTR was promoted as a rebrand in the early 2000s by Kirk Sorensen. The stable salt reactor is a relatively recent concept which holds

11375-586: The loan guarantee is completed. In September 2008, the DOE, the Nuclear Threat Initiative (NTI), the Institute of Nuclear Materials Management (INMM), and the International Atomic Energy Agency (IAEA) partnered to develop and launch the World Institute for Nuclear Security (WINS), an international non-governmental organization designed to provide a forum to share best practices in strengthening

11500-409: The molten salt fuel statically in traditional LWR fuel pins. Pumping of the fuel salt, and all the corrosion/deposition/maintenance/containment issues arising from circulating a highly radioactive, hot and chemically complex fluid, are no longer required. The fuel pins are immersed in a separate, non-fissionable fluoride salt which acts as primary coolant. A prototypical example of a dual fluid reactor

11625-406: The name of the agency, in gold, appears on a green background." "The eagle represents the care in planning and the purposefulness of efforts required to respond to the Nation's increasing demands for energy . The sun , atom , oil derrick , windmill , and dynamo serve as representative technologies whose enhanced development can help meet these demands. The rope represents the cohesiveness in

11750-450: The neutron economy. This process occurs when the beryllium nucleus emits two neutrons after absorbing a single neutron. For the fuel carrying salts, generally 1% or 2% (by mole ) of UF 4 is added. Thorium and plutonium fluorides have also been used. Techniques for preparing and handling molten salt were first developed at ORNL. The purpose of salt purification is to eliminate oxides, sulfur and metal impurities. Oxides could result in

11875-449: The normal nuclear chain reaction, would be too short to allow for intervention. This last stage, where delayed neutrons are no longer required to maintain criticality, is known as the prompt critical point. There is a scale for describing criticality in numerical form, in which bare criticality is known as zero dollars and the prompt critical point is one dollar , and other points in the process interpolated in cents. In some reactors,

12000-581: The opportunity for the nuclear chain reaction that Szilárd had envisioned six years previously. On 2 August 1939, Albert Einstein signed a letter to President Franklin D. Roosevelt (written by Szilárd) suggesting that the discovery of uranium's fission could lead to the development of "extremely powerful bombs of a new type", giving impetus to the study of reactors and fission. Szilárd and Einstein knew each other well and had worked together years previously, but Einstein had never thought about this possibility for nuclear energy until Szilard reported it to him, at

12125-406: The physics of radioactive decay and are simply accounted for during the reactor's operation, while others are mechanisms engineered into the reactor design for a distinct purpose. The fastest method for adjusting levels of fission-inducing neutrons in a reactor is via movement of the control rods . Control rods are made of so-called neutron poisons and therefore absorb neutrons. When a control rod

12250-493: The point that the risk level will be low enough for industry to commercialize the technologies. The Consortium for Advanced Simulation of Light Water Reactors (CASL) was the first DOE Energy Innovation Hub established in July 2010, for the purpose of providing advanced modeling and simulation (M&S) solutions for commercial nuclear reactors. The 2009 DOE budget includes $ 280 million to fund eight Energy Innovation Hubs, each of which

12375-460: The power plant is limited by the life of components that cannot be replaced when aged by wear and neutron embrittlement , such as the reactor pressure vessel. At the end of their planned life span, plants may get an extension of the operating license for some 20 years and in the US even a "subsequent license renewal" (SLR) for an additional 20 years. Even when a license is extended, it does not guarantee

12500-474: The president, who assumes the duties of the secretary in the secretary's absence. The department also has three under secretaries, each appointed by the president, who oversee the major areas of the department's work. The president also appoints seven officials with the rank of Assistant Secretary of Energy who have line management responsibility for major organizational elements of the department. The Energy Secretary assigns their functions and duties. Excerpt from

12625-671: The primary cooling loop, a material is needed that can withstand corrosion at high temperatures and intense radiation . Experiments show that Hastelloy-N and similar alloys are suited to these tasks at operating temperatures up to about 700 °C. However, operating experience is limited. Still higher operating temperatures are desirable—at 850 °C (1,560 °F) thermochemical production of hydrogen becomes possible. Materials for this temperature range have not been validated, though carbon composites, molybdenum alloys (e.g. TZM), carbides , and refractory metal based or ODS alloys might be feasible. The salt mixtures are chosen to make

12750-563: The reactor fleet grows older. The neutron was discovered in 1932 by British physicist James Chadwick . The concept of a nuclear chain reaction brought about by nuclear reactions mediated by neutrons was first realized shortly thereafter, by Hungarian scientist Leó Szilárd , in 1933. He filed a patent for his idea of a simple reactor the following year while working at the Admiralty in London, England. However, Szilárd's idea did not incorporate

12875-720: The reactor safer and more practical. Fluorine has only one stable isotope ( F ), and does not easily become radioactive under neutron bombardment. Compared to chlorine and other halides, fluorine also absorbs fewer neutrons and slows (" moderates ") neutrons better. Low- valence fluorides boil at high temperatures, though many pentafluorides and hexafluorides boil at low temperatures. They must be very hot before they break down into their constituent elements. Such molten salts are "chemically stable" when maintained well below their boiling points. Fluoride salts dissolve poorly in water, and do not form burnable hydrogen. Chlorine has two stable isotopes ( Cl and Cl ), as well as

13000-416: The reactor will continue to operate, particularly in the face of safety concerns or incident. Many reactors are closed long before their license or design life expired and are decommissioned . The costs for replacements or improvements required for continued safe operation may be so high that they are not cost-effective. Or they may be shut down due to technical failure. Other ones have been shut down because

13125-437: The reactor's output, while other systems automatically shut down the reactor in the event of unsafe conditions. The buildup of neutron-absorbing fission products like xenon-135 can influence reactor behavior, requiring careful management to prevent issues such as the iodine pit , which can complicate reactor restarts. There have been two reactor accidents classed as an International Nuclear Event Scale Level 7 "major accident":

13250-547: The research and development of nuclear power , the military's nuclear weapons program , nuclear reactor production for the United States Navy , energy-related research, and energy conservation . The DOE was created in 1977 in the aftermath of the 1973 oil crisis . It sponsors more physical science research than any other U.S. federal agency, the majority of which is conducted through its system of National Laboratories . The DOE also directs research in genomics , with

13375-431: The responsibilities of the AEC into the new Nuclear Regulatory Commission , which was charged with regulating the nuclear power industry, and the Energy Research and Development Administration , which was assigned to manage the nuclear weapon, naval reactor, and energy development programs. The 1973 oil crisis called attention to the need to consolidate energy policy. In 1977, President Jimmy Carter signed into law

13500-536: The role of molten salt: The use of molten salt as fuel and as coolant are independent design choices – the original circulating-fuel-salt MSRE and the more recent static-fuel-salt SSR use salt as fuel and salt as coolant; the DFR uses salt as fuel but metal as coolant; and the FHR has solid fuel but salt as coolant. MSRs can be burners or breeders. They can be fast or thermal or epithermal . Thermal reactors typically employ

13625-451: The salt at startup and reduces the risk of the salt freezing as it is cooled in the heat exchanger. Due to the high " redox window" of fused fluoride salts, the redox potential of the fused salt system can be changed. Fluorine-lithium-beryllium (" FLiBe ") can be used with beryllium additions to lower the redox potential and nearly eliminate corrosion. However, since beryllium is extremely toxic, special precautions must be engineered into

13750-413: The salt mixtures were removed using gas sparging of HF / H 2 mixture, with the salt heated to 600 °C. Structural metal contamination in the salt mixtures were removed using hydrogen gas sparging, at 700 °C. Solid ammonium hydrofluoride was proposed as a safer alternative for oxide removal. The possibility of online processing can be an MSR advantage. Continuous processing would reduce

13875-463: The salt, from top to bottom, is broken up into 16 groups of pumps and heat exchangers located around the core. The fuel salt takes approximately 3 to 4 seconds to complete a full cycle. At any given time during operation, half of the total fuel salt volume is in the core and the rest is in the external fuel circuit (salt collectors, salt-bubble separators, fuel heat exchangers, pumps, salt injectors and pipes). MSFRs contain an emergency draining system that

14000-420: The sectors are replaced. Emergency draining is done when an irregularity occurs during operation. The fuel salt can be drained directly into the emergency draining tank either by active devices or by passive means. The draining must be fast to limit the fuel salt heating in a loss of heat removal event. The fluoride salt-cooled high-temperature reactor (FHR), also called advanced high temperature reactor (AHTR),

14125-508: The security and safety of nuclear and radioactive materials and facilities. The department announced a reorganization with new names of under secretaries in 2022. The department is under the control and supervision of a United States Secretary of Energy , a political appointee of the President of the United States . The Energy Secretary is assisted in managing the department by a United States Deputy Secretary of Energy , also appointed by

14250-637: The small number of officials in the government who were initially charged with moving the project forward. The following year, the U.S. Government received the Frisch–Peierls memorandum from the UK, which stated that the amount of uranium needed for a chain reaction was far lower than had previously been thought. The memorandum was a product of the MAUD Committee , which was working on the UK atomic bomb project, known as Tube Alloys , later to be subsumed within

14375-513: The stimulus spending was in the form of grants and contracts. For fiscal year 2013, each of the operating units of the Department of Energy operated with the following budgets: In March 2018, Energy Secretary Rick Perry testified to a Senate panel about the Trump administration's DOE budget request for fiscal year 2019. The budget request prioritized nuclear security while making large cuts to energy efficiency and renewable energy programs. The proposal

14500-557: The use of renewable energy sources while improving energy transmission infrastructure. It also proposed significant investments in hybrids and plug-in hybrids , smart grid technologies, and scientific research and innovation. As part of the $ 789 billion economic stimulus package in the American Recovery and Reinvestment Act of 2009, Congress provided Energy with an additional $ 38.3 billion for fiscal years 2009 and 2010, adding about 75 percent to Energy's annual budgets. Most of

14625-420: The use of a double bypass. This allows the temperature of the intermediate fluid at the conversion exchanger inlet to be held constant while its temperature is increased in a controlled way at the inlet of the intermediate exchangers. The temperature of the core can be adjusted by varying the proportion of bubbles injected in the core since it reduces the salt density. As a result, it reduces the mean temperature of

14750-424: The water for the steam turbines is boiled directly by the reactor core ; for example the boiling water reactor . The rate of fission reactions within a reactor core can be adjusted by controlling the quantity of neutrons that are able to induce further fission events. Nuclear reactors typically employ several methods of neutron control to adjust the reactor's power output. Some of these methods arise naturally from

14875-494: Was a $ 500 million increase in funds over fiscal year 2017. It "promotes innovations like a new Office of Cybersecurity, Energy Security, and Emergency Response (CESER) and gains for the Office of Fossil Energy. Investments would be made to strengthen the National Nuclear Security Administration and modernize the nuclear force, as well as in weapons activities and advanced computing." However, the budget for

15000-476: Was a key step in the Chernobyl disaster . Reactors used in nuclear marine propulsion (especially nuclear submarines ) often cannot be run at continuous power around the clock in the same way that land-based power reactors are normally run, and in addition often need to have a very long core life without refueling . For this reason many designs use highly enriched uranium but incorporate burnable neutron poison in

15125-530: Was an extremely important issue of the time as the oil crisis was causing shortages and inflation . With the Three Mile Island accident , Carter was able to intervene with the help of the department. Through the DOE, Carter was able to make changes within the Nuclear Regulatory Commission , including improving management and procedures, since nuclear energy and weapons are responsibilities of

15250-781: Was officially started by the Generation ;IV International Forum (GIF) based on eight technology goals. The primary goals being to improve nuclear safety, improve proliferation resistance, minimize waste and natural resource utilization, and to decrease the cost to build and run such plants. Generation V reactors are designs which are theoretically possible, but which are not being actively considered or researched at present. Though some generation V reactors could potentially be built with current or near term technology, they trigger little interest for reasons of economics, practicality, or safety. Controlled nuclear fusion could in principle be used in fusion power plants to produce power without

15375-463: Was opened in 1956 with an initial capacity of 50 MW (later 200 MW). The first portable nuclear reactor "Alco PM-2A" was used to generate electrical power (2 MW) for Camp Century from 1960 to 1963. All commercial power reactors are based on nuclear fission . They generally use uranium and its product plutonium as nuclear fuel , though a thorium fuel cycle is also possible. Fission reactors can be divided roughly into two classes, depending on

15500-426: Was run for a few weeks and at essentially zero power, although it reached criticality. The operating temperature was held constant at approximately 675 °C (1,250 °F). The PWAR-1 used NaF/ZrF 4 /UF 4 as the primary fuel and coolant. It was one of three critical MSRs ever built. Oak Ridge National Laboratory (ORNL) took the lead in researching MSRs through the 1960s. Much of their work culminated with

15625-544: Was the first to refer to "Gen II" types in Nucleonics Week . The first mention of "Gen III" was in 2000, in conjunction with the launch of the Generation IV International Forum (GIF) plans. "Gen IV" was named in 2000, by the United States Department of Energy (DOE), for developing new plant types. More than a dozen advanced reactor designs are in various stages of development. Some are evolutionary from

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