A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nuclear fission is passed to a working fluid,which in turn runs through steam turbines. These either drive a ship's propellers or turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use,or for production of weapons-grade plutonium. As of 2022,the International Atomic Energy Agency reports there are 422 nuclear power reactors and 223 nuclear research reactors in operation around the world.
Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission,nuclear decay and nuclear fusion reactions. Presently,the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium in nuclear power plants. Nuclear decay processes are used in niche applications such as radioisotope thermoelectric generators in some space probes such as Voyager 2. Generating electricity from fusion power remains the focus of international research.
Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities,including nuclear medicine,nuclear research,nuclear power generation,nuclear decommissioning,rare-earth mining,and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment.
Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes:uranium-238,uranium-235,and uranium-234. 235U is the only nuclide existing in nature that is fissile with thermal neutrons.
The nuclear fuel cycle,also called nuclear fuel chain,is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end,which are the preparation of the fuel,steps in the service period in which the fuel is used during reactor operation,and steps in the back end,which are necessary to safely manage,contain,and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed,the fuel cycle is referred to as an open fuel cycle;if the spent fuel is reprocessed,it is referred to as a closed fuel cycle.
Nuclear reprocessing is the chemical separation of fission products and actinides from spent nuclear fuel. Originally,reprocessing was used solely to extract plutonium for producing nuclear weapons. With commercialization of nuclear power,the reprocessed plutonium was recycled back into MOX nuclear fuel for thermal reactors. The reprocessed uranium,also known as the spent fuel material,can in principle also be re-used as fuel,but that is only economical when uranium supply is low and prices are high. Nuclear reprocessing may extend beyond fuel and include the reprocessing of other nuclear reactor material,such as Zircaloy cladding.
A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. These reactors can be fueled with more-commonly available isotopes of uranium and thorium,such as uranium-238 and thorium-232,as opposed to the rare uranium-235 which is used in conventional reactors. These materials are called fertile materials since they can be bred into fuel by these breeder reactors.
The integral fast reactor is a design for a nuclear reactor using fast neutrons and no neutron moderator. IFR would breed more fuel and is distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.
The Megatons to Megawatts Program,also called the United States-Russia Highly Enriched Uranium Purchase Agreement,was an agreement between Russia and the United States whereby Russia converted 500 metric tons of "excess" weapons-grade uranium into 15,000 metric tons of low enriched uranium,which was purchased by the US for use in its commercial nuclear power plants. The official name of the program is the "Agreement between the Government of the Russian Federation and the Government of the United States of America Concerning the Disposition of Highly-Enriched Uranium Extracted from Nuclear Weapons",dated February 18,1993. Under this Agreement,Russia agreed to supply the United States with low-enriched uranium (LEU) obtained from high-enriched uranium (HEU) found to be in excess of Russian defense purposes. The United States agreed to purchase the low-enriched uranium fuel.
The International Framework for Nuclear Energy Cooperation (IFNEC) is a forum of states and organizations that share a common vision of a safe and secure development of nuclear energy for worldwide purposes. Formerly the Global Nuclear Energy Partnership (GNEP),IFNEC began as a U.S. proposal,announced by United States Secretary of Energy Samuel Bodman on February 6,2006,to form an international partnership to promote the use of nuclear power and close the nuclear fuel cycle in a way that reduces nuclear waste and the risk of nuclear proliferation. This proposal would divide the world into "fuel supplier nations," which supply enriched uranium fuel and take back spent fuel,and "user nations," which operate nuclear power plants.
In the United States,nuclear power is provided by 92 commercial reactors with a net capacity of 94.7 gigawatts (GW),with 61 pressurized water reactors and 31 boiling water reactors. In 2019,they produced a total of 809.41 terawatt-hours of electricity,which accounted for 20% of the nation's total electric energy generation. In 2018,nuclear comprised nearly 50 percent of US emission-free energy generation.
Reactor-grade plutonium (RGPu) is the isotopic grade of plutonium that is found in spent nuclear fuel after the uranium-235 primary fuel that a nuclear power reactor uses has burnt up. The uranium-238 from which most of the plutonium isotopes derive by neutron capture is found along with the U-235 in the low enriched uranium fuel of civilian reactors.
Portsmouth Gaseous Diffusion Plant is a facility located in Scioto Township,Pike County,Ohio,just south of Piketon,Ohio,that previously produced enriched uranium,including highly enriched weapons-grade uranium,for the United States Atomic Energy Commission (AEC),the U.S. nuclear weapons program and Navy nuclear propulsion;in later years,it produced low-enriched uranium for fuel for commercial nuclear power reactors. The site never hosted an operating nuclear reactor.
Nuclear power has various environmental impacts,both positive and negative,including the construction and operation of the plant,the nuclear fuel cycle,and the effects of nuclear accidents. Nuclear power plants do not burn fossil fuels and so do not directly emit carbon dioxide. The carbon dioxide emitted during mining,enrichment,fabrication and transport of fuel is small when compared with the carbon dioxide emitted by fossil fuels of similar energy yield,however,these plants still produce other environmentally damaging wastes. Nuclear energy and renewable energy have reduced environmental costs by decreasing CO2 emissions resulting from energy consumption.
The liquid fluoride thorium reactor is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based molten (liquid) salt for fuel. In a typical design,the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.
The National Nuclear Security Administration (NNSA) is a United States federal agency responsible for safeguarding national security through the military application of nuclear science. NNSA maintains and enhances the safety,security,and effectiveness of the U.S. nuclear weapons stockpile;works to reduce the global danger from weapons of mass destruction;provides the United States Navy with safe and effective nuclear propulsion;and responds to nuclear and radiological emergencies in the United States and abroad.
The Energy Multiplier Module is a nuclear fission power reactor under development by General Atomics. It is a fast-neutron version of the Gas Turbine Modular Helium Reactor (GT-MHR) and is capable of converting spent nuclear fuel into electricity and industrial process heat.
Centrus Energy Corp. is an American company that supplies nuclear fuel for use in nuclear power plants and works to develop and deploy advanced centrifuge technology to produce enriched uranium for commercial and government uses,including for national security.
Thorium-based nuclear power generation is fueled primarily by the nuclear fission of the isotope uranium-233 produced from the fertile element thorium. A thorium fuel cycle can offer several potential advantages over a uranium fuel cycle—including the much greater abundance of thorium found on Earth,superior physical and nuclear fuel properties,and reduced nuclear waste production. One advantage of thorium fuel is its low weaponization potential. It is difficult to weaponize the uranium-233 that is bred in the reactor. Plutonium-239 is produced at much lower levels and can be consumed in thorium reactors.
A nuclear microreactor is a plug-and-play type of nuclear reactor which can be easily assembled and transported by road,rail or air. Microreactors are 100 to 1,000 times smaller than conventional nuclear reactors,and when compared with small modular reactors (SMRs),their capacity is between 1 and 20 megawatts whereas SMRs comes in the range from 20 to 300 megawatts. Due to their size,they can be deployed to locations such as isolated military bases or communities affected by natural disasters. It can operate as part of the grid,independent of the grid,or as part of a small grid for electricity generation and heat treatment. They are designed to provide resilient,non-carbon emitting,and independent power in challenging environments. The nuclear fuel source for the majority of the designs is "High-Assay Low-Enriched Uranium",or HALEU.
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