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Generation IV reactors (Gen IV) are six
nuclear reactor 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 fr ...
designs recognized by the Generation IV International Forum. The designs target improved safety, sustainability, efficiency, and cost. The most developed Gen IV reactor design is the
sodium fast reactor A sodium-cooled fast reactor is a fast neutron reactor cooled by liquid sodium. The initials SFR in particular refer to two Generation IV reactor proposals, one based on existing liquid metal cooled reactor (LMFR) technology using mixed oxide fue ...
. It has received the greatest share of funding that supports demonstration facilities, as well as two commercial reactors in Russia. One of these has been in commercial operation since 1981. Its principal Gen IV features relates its sustainable closed fuel cycle. Moir and Teller consider the
molten-salt reactor 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 molten salt mixture. Only two MSRs have ever operated, both research reactors in the United States. The 1950's ...
, a less developed technology, as potentially having the greatest inherent safety of the six models. The very-high-temperature reactor designs operate at much higher temperatures than prior generations. This allows for high temperature electrolysis or for sulfur–iodine cycle for the efficient production of hydrogen and the synthesis of
carbon-neutral fuel Carbon-neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In practice, this usually means fuels that are made using carbon dioxide (CO2) as a feedstock. Proposed carbon-neutral fuels can broadly be grouped in ...
s. The first commercial plants are not expected before 2040–2050, although the
World Nuclear Association World Nuclear Association is the international organization that promotes nuclear power and supports the companies that comprise the global nuclear industry. Its members come from all parts of the nuclear fuel cycle, including uranium mining, u ...
in 2015 suggested that some might enter commercial operation before 2030. The majority of reactors in operation around the world are second generation reactor systems, as the majority of the first generation systems have been retired. Only a few
Generation III reactor Generation III reactors, or Gen III reactors, are a class of nuclear reactors designed to succeed Generation II reactors, incorporating evolutionary improvements in design. These include improved fuel technology, higher thermal efficiency, sign ...
s were in operation as of December 2022.
Generation V reactor 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 n ...
s are purely theoretical and are not yet considered feasible.


Generation IV International Forum

The Generation IV International Forum (GIF) was initiated in January 2000 by the
Office of Nuclear Energy The Office of Nuclear Energy (NE) is an agency of the United States Department of Energy which promotes nuclear power as a resource capable of meeting the energy, environmental, and national security needs of the United States by resolving technic ...
of the U.S. Department of Energy’s (DOE)''Origins of the GIF.''
GEN IV International Forum Nov 2021)
"as a co-operative international endeavour seeking to develop the research necessary to test the feasibility and performance of fourth generation nuclear systems, and to make them available for industrial deployment by 2030." It was established in 2001. As of 2021, active members include:
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
, the European Atomic Energy Community (Euratom),
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
,
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
,
South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...
,
Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
, the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...
and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
. The non-active members are
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
and
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
. The 36th GIF meeting in
Brussels Brussels (french: Bruxelles or ; nl, Brussel ), officially the Brussels-Capital Region (All text and all but one graphic show the English name as Brussels-Capital Region.) (french: link=no, Région de Bruxelles-Capitale; nl, link=no, Bruss ...
was held in November 2013. A brief overview of the reactor designs and activities by each forum member has been made available. An update of the technology roadmap which details R&D objectives for the next decade was published in January 2014.


Timelines

The GIF Forum introduced timelines for each of the six systems. Research and development divide into three phases: * Viability: test basic concepts under relevant conditions; identify and resolve all "potential technical show-stoppers"; * Performance: verify and optimise "engineering-scale processes, phenomena and materials capabilities" under prototypical conditions; * Demonstration: complete and license the detailed design and carry out construction and operation of prototype or demonstration systems. In 2000, GIF stated, "After the performance phase is complete for each system, at least six years and several US$ billion will be required for detailed design and construction of a demonstration system."''A Technology Roadmap for Generation IV Nuclear Energy Systems''
p. 79-82 (4.5 MB). U.S. DOE Nuclear Energy Research Advisory Committee and the GIF, Dec 2002
In the Roadmap update of 2013, the performance and demonstration phases were considerably shifted to later dates, while no targets for the commercialisation phases are set. According to the GIF, "It will take at least two or three decades before the deployment of commercial Gen IV systems."''FAQ 2: When will Gen IV reactors be built?''
GEN IV International Forum (accessed Nov. 2021)


Reactor types

Many reactor types were considered initially; the list was then refined to focus on the most promising technologies. Three systems are nominally
thermal reactor A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...
s and four are fast reactors. The Very High Temperature Reactor (VHTR) potentially can provide high quality process heat. Fast reactors offer the possibility of burning actinides to further reduce waste and can breed more fuel than they consume. These systems offer significant advances in sustainability, safety and reliability, economics, proliferation resistance (depending on perspective) and physical protection.


Thermal reactors

A
thermal reactor A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...
is a
nuclear reactor 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 fr ...
that uses slow or
thermal neutrons The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium wi ...
. A
neutron moderator In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely m ...
is used to slow the
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the atomic nucleus, nuclei of atoms. Since protons and ...
s emitted by fission to make them more likely to be captured by the fuel.


High-temperature gas-cooled reactor (HTGR)

A
high temperature gas-cooled reactor A high-temperature gas-cooled reactor (HTGR), is a nuclear reactor that uses a graphite moderator with a once-through uranium fuel cycle. The HTGR is a type of high-temperature reactor (HTR) that can conceptually have an outlet temperature of ...
(HTGR) typically operates at temperatures two or three times those of conventional reactors. It is graphite-moderated and typically uses helium cooling. It offers lower power density. The concept originated in the 1940s and has only begun to mature. HTGR runs on TRi-structural ISOtropic ( TRISO) particle fuel. It is made of individual particles Instead of rods. TRISO consists of uranium, carbon, and oxygen sealed in three layers of carbon or ceramics materials to stabilize the eventual waste products. These particles are formed into stable cylindrical pellets or billiard-ball-sized spheres called "pebbles." It is more resistant to neutrons, corrosion, oxidation, and high temperatures than conventional fuels. These pebbles do not melt in the reactor, which can run at higher temperatures. The fuel gradually proceeds through the reactor,. Spent pebbles exit the bottom of the reactor while fresh pebbles replace them at the top. The Chinese government began construction of a demonstration
HTR-PM The HTR-PM (球床模块式高温气冷堆核电站) is a small modular nuclear reactor in China. It is the world’s first prototype of a high-temperature gas-cooled (HTGR) pebble-bed generation IV reactor. The reactor unit has a thermal capac ...
200-MW high temperature pebble bed reactor in 2012 as a successor to its
HTR-10 HTR-10 is a 10 MWt prototype pebble bed reactor at Tsinghua University in China. Construction began in 1995, achieving its first criticality in December 2000, and was operated in full power condition in January 2003. Two HTR-PM reactors, scaled ...
.


Very-high-temperature reactor (VHTR)

The very-high-temperature reactor (VHTR) uses a graphite-moderated core with a once-through uranium fuel cycle, using helium or molten salt. This reactor design envisions an outlet temperature of 1,000°C. The reactor core can be either a prismatic-block or a pebble bed reactor design. The high temperatures enable applications such as process heat or hydrogen production via the thermochemical sulfur-iodine cycle process. In 2012, as part of its
next generation nuclear plant A Next Generation Nuclear Plant (NGNP) is a specific proposed generation IV very-high-temperature reactor (VHTR) that could be coupled to a neighboring hydrogen production facility. It could also produce electricity and supply process heat. Up to ...
competition,
Idaho National Laboratory Idaho National Laboratory (INL) is one of the national laboratories of the United States Department of Energy and is managed by the Battelle Energy Alliance. While the laboratory does other research, historically it has been involved with nu ...
approved a design similar to
Areva Areva S.A. is a French multinational group specializing in nuclear power headquartered in Courbevoie, France. Before its 2016 corporate restructuring, Areva was majority-owned by the French state through the French Alternative Energies and Atom ...
's prismatic block Antares reactor to be deployed as a prototype by 2021. In January 2016,
X-energy X-energy is an American private nuclear reactor and fuel design engineering company. It is developing a Generation IV high-temperature gas-cooled pebble-bed nuclear reactor design. Since its founding in 2009, it has received various government ...
was awarded a five-year $53 million partnership by the
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 manages the research and development of nuclear power and nuclear weapons in the United States ...
to advance their reactor development. The Xe-100 is a
PBMR The Pebble Bed Modular Reactor (PBMR) is a particular design of pebble bed reactor developed by South African company PBMR (Pty) Ltd from 1994 until 2009. PBMR facilities include gas turbine and heat transfer labs at the Potchefstroom Campus of ...
that will generate 200-
MWt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
and approximately 76- MWe. The standard Xe-100 four-pack plant generates approximately 300-MWe and will sit on as few as 13 acres.


Molten-salt reactor (MSR)

A molten salt reactor (MSR) is a type of reactor where the primary coolant or the fuel itself is a molten salt mixture. It operates at high temperature and low pressure. Molten salt can be used for thermal, epithermal and fast reactors. Since 2005 the focus has been on fast spectrum MSRs (MSFR). Other designs include integral molten salt reactors (e.g. IMSR) and molten chloride salt fast reactors (MCSFR). Early thermal spectrum concepts and many current ones rely on uranium tetrafluoride (UF4) or
thorium tetrafluoride Thorium(IV) fluoride ( Th F4) is an inorganic chemical compound. It is a white hygroscopic powder which can be produced by reacting thorium with fluorine gas. At temperatures above 500 °C, it reacts with atmospheric moisture to produce ThO ...
(ThF4), dissolved in molten
fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...
salt. The fluid reaches criticality by flowing into a core with a
graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
moderator. The fuel may be dispersed in a graphite matrix. These designs are more accurately termed an epithermal reactor than a thermal reactor due to the higher average speed of the neutrons that cause the fission events. MCSFR does away with the graphite moderator. They achieve criticality using a sufficient volume of salt and fissile material. They can consume much more of the fuel and leave only short-lived waste. Most MSR designs are derived from the 1960s Molten-Salt Reactor Experiment (MSRE). Variants include the conceptual ''
Dual fluid reactor The Dual Fluid Reactor is a reactor concept of the Canadian company Dual Fluid Energy Inc. combining the advantages of the molten salt reactor with those of the liquid metal cooled reactor, it is supposed to reach the criteria for reactors of the ...
'' that uses lead as a cooling medium with molten salt fuel, commonly a metal chloride, e.g.
plutonium(III) chloride Plutonium(III) chloride is a chemical compound with the formula PuCl3. This ionic plutonium salt can be prepared by reacting the metal with hydrochloric acid. Structure Plutonium atoms in crystalline PuCl3 are 9 coordinate, and the structure is ...
, to aid in greater closed-fuel cycle capabilities. Other notable approaches include the
Stable Salt Reactor The Stable Salt Reactor (SSR) is a nuclear reactor design under development by Moltex Energy Canada Inc. and its subsidiary Moltex Energy USA LLC, based in Canada, the United States, and the United Kingdom, as well as MoltexFLEX Ltd., based in ...
(SSR) concept, which encases the molten salt in the well-established fuel rods of conventional reactors. This latter design was found to be the most competitive by consultancy firm Energy Process Development in 2015. Another design under development is TerraPower's Molten Chloride Fast Reactor. This concept mixes the liquid natural uranium and molten chloride coolant in the reactor core, reaching very high temperatures at atmospheric pressure. Another notable feature of the MSR is the possibility of a thermal spectrum nuclear waste-burner. Conventionally only fast spectrum reactors have been considered viable for utilization or reduction of the spent nuclear fuel. Thermal waste-burning was achieved by replacing a fraction of the
uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
in the spent nuclear fuel with
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...
. The net production rate of transuranic elements (e.g.
plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exh ...
and
americium Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was n ...
) is below the consumption rate, thus reducing the nuclear storage problem, without the
nuclear proliferation Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as " Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Wea ...
concerns and other technical issues associated with a fast reactor.


Supercritical-water-cooled reactor (SCWR)

The supercritical water reactor (SCWR) is a reduced moderation water reactor concept. Because the average speed of the fission-causing neutrons within the fuel is faster than
thermal neutron The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium wi ...
s, it is more accurately termed an epithermal reactor than a thermal reactor. It uses
supercritical water Supercritical water oxidation (SCWO) is a process that occurs in water at temperatures and pressures above a mixture's thermodynamic critical point. Under these conditions water becomes a fluid with unique properties that can be used to advantag ...
as the working fluid. SCWRs are basically
light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...
s (LWR) operating at higher pressure and temperatures with a direct, once-through heat exchange cycle. As commonly envisioned, it would operate on a direct cycle, much like a boiling water reactor (
BWR A boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. It is a design different from a Soviet graphite-moderated RBMK. It is the second most common type of electricity-generating nuc ...
). Since it uses
supercritical water Supercritical water oxidation (SCWO) is a process that occurs in water at temperatures and pressures above a mixture's thermodynamic critical point. Under these conditions water becomes a fluid with unique properties that can be used to advantag ...
(not to be confused with
critical mass In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fi ...
) as the working fluid, it would have only one water phase. This makes the heat exchange method more similar to a pressurized water reactor ( PWR). It could operate at much higher temperatures than both current PWRs and BWRs. Supercritical water-cooled reactors (SCWRs) offer high thermal efficiency (i.e., about 45% vs. about 33% efficiency for current LWRs) and considerable simplification. The mission of the SCWR is generation of low-cost
electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describe ...
. It is built upon two proven technologies, LWRs, the most commonly deployed power generating reactors, and superheated
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ma ...
fired
boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central ...
s, also in wide use. 32 organizations in 13 countries are investigating the concept. SCWRs share the steam explosion and radioactive steam release hazards of BWRs and LWRs as well as the need for extremely expensive heavy duty pressure vessels, pipes, valves, and pumps. These shared problems are inherently more severe for SCWRs due to their higher temperatures. One SCWR design under development is the
VVER The water-water energetic reactor (WWER), or VVER (from russian: водо-водяной энергетический реактор; transliterates as ; ''water-water power reactor'') is a series of pressurized water reactor designs originally de ...
-1700/393 (VVER-SCWR or VVER-SKD) – a Russian SCWR with double-inlet-core and a breeding ratio of 0.95.


Fast reactors

A fast reactor directly uses fission neutrons without moderation. Fast reactors can be configured to "burn", or fission, all actinides, and given enough time, therefore drastically reduce the actinides fraction in spent nuclear fuel produced by the present world fleet of thermal neutron
light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...
s, thus closing the fuel cycle. Alternatively, if configured differently, they can
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...
more actinide fuel than they consume.


Gas-cooled fast reactor (GFR)

The gas-cooled fast reactor (GFR) features a fast-neutron spectrum and closed fuel cycle. The reactor is
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
-cooled. Its outlet temperature is 850 °C. It moves the very-high-temperature reactor (VHTR) to a more sustainable fuel cycle. It uses a direct Brayton cycle gas turbine for high thermal efficiency. Several fuel forms are under consideration: composite
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, ...
fuel, advanced fuel particles, or ceramic-clad actinide compounds. Core configurations involve pin- or plate-based fuel assemblies or prismatic blocks. The European Sustainable Nuclear Industrial Initiative provided funding for three Generation IV reactor systems: * Allegro: a 100 MWt gas-cooled fast reactor, planned for central or eastern Europe. The central European Visegrád Group are pursuing the technology. * GoFastR'':'' In 2013 German, British, and French institutes finished a 3-year collaboration study on the follow-on industrial scale design. They were funded by the EU's 7th FWP framework programme, with the goal of making a sustainable VHTR.


Sodium-cooled fast reactor (SFR)

Sodium-cooled fast reactors (SCFRs) have been operated in multiple countries since the 1980s. The two largest experimental sodium cooled fast reactors are in Russia, the BN-600 and the BN-800 (880 MWe gross). These NPPs are being used to provide operating experience and technological solutions that will be applied to the construction of the BN-1200 ( OKBM Afrikantov first Gen IV reactor). The largest ever operated was the French Superphenix reactor at over 1200 MWe, successfully operating before decommissioning in 1996. In India, the Fast Breeder Test Reactor (FBTR) reached criticality in October 1985. In September 2002, fuel burn up efficiency in the FBTR for the first time reached the 100,000 megawatt-days per metric ton uranium (MWd/MTU) mark. This is considered an important milestone in Indian breeder reactor technology. Using that experience, the
Prototype Fast Breeder Reactor The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe fast breeder nuclear reactor presently being constructed at the Madras Atomic Power Station (MAPS) in Kalpakkam, India. The Indira Gandhi Centre for Atomic Research (IGCAR) is responsible f ...
, a 500 MWe Sodium cooled fast reactor is being built at a cost of INR 5,677 crores (~US$900 million). After numerous delays, the government reported in March 2020 that the reactor might be operational in December 2021. The PFBR was to be followed by six more Commercial Fast Breeder Reactors (CFBRs) of 600 MWe each. The Gen IV SFR is a project that builds on the oxide fueled fast breeder reactor and the metal fueled
integral fast reactor The integral fast reactor (IFR, originally advanced liquid-metal reactor) is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFR would breed more fuel and is distinguished by a nuclear fuel cycle ...
. Its goals are to increase the efficiency of uranium usage by
breeding Breeding is sexual reproduction that produces offspring, usually animals or plants. It can only occur between a male and a female animal or plant. Breeding may refer to: * Animal husbandry, through selected specimens such as dogs, horses, and r ...
plutonium and eliminating transuranic isotopes. The reactor design uses an unmoderated core running on fast neutrons, designed to allow any transuranic isotope to be consumed (and in some cases used as fuel). SFR fuel expands when the reactor overheats, automatically slowing down the chain reaction, making it passively safe. One SFR reactor concept is cooled by liquid
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
and fueled by a metallic alloy of uranium and
plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exh ...
or spent nuclear fuel, the "nuclear waste" of
light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...
s. The SFR fuel is contained in steel cladding. Liquid sodium fills the space between the clad elements that make up the fuel assembly. One of the design challenges is the risks of handling sodium, which reacts explosively if it comes into contact with water. The use of liquid metal instead of water as coolant allows the system to work at atmospheric pressure, reducing the risk of leakage. The European Sustainable Nuclear Industrial Initiative funded three Generation IV reactor systems. Advanced Sodium Technical Reactor for Industrial Demonstration ( ASTRID) was a sodium-cooled fast reactor, that was cancelled in August 2019. Numerous progenitors of the Gen IV SFR exist, such as the 400 MWe Fast Flux Test Facility operated for ten years at Hanford. The 20 MWe EBR II operated for over thirty years at Idaho National Laboratory, and was shut down in 1994. GE Hitachi's PRISM reactor is a modernized and commercial implementation of the Integral Fast Reactor (IFR), developed by
Argonne National Laboratory Argonne National Laboratory is a science and engineering research national laboratory operated by UChicago Argonne LLC for the United States Department of Energy. The facility is located in Lemont, Illinois, outside of Chicago, and is the l ...
between 1984 and 1994. The primary purpose of PRISM is burning up spent nuclear fuel from other reactors, rather than
breeding Breeding is sexual reproduction that produces offspring, usually animals or plants. It can only occur between a male and a female animal or plant. Breeding may refer to: * Animal husbandry, through selected specimens such as dogs, horses, and r ...
new fuel. The design reduces the half lives of the fissionable elements present in spent nuclear fuel while generating electricity largely as a byproduct.


Lead-cooled fast reactor

The lead-cooled fast reactor (LFR) features a fast-neutron-spectrum
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
or
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
/
bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
eutectic ( LBE) coolant with a closed fuel cycle. Proposals include a small 50 to 150 MWe that features a long refueling interval, a modular system rated at 300 to 400 MWe, and a large monolithic plant at 1,200 MWe. The fuel is metal or nitride-based containing fertile uranium and transuranics. The reactor is cooled by natural
convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
with a reactor outlet coolant temperature of 550-800 °C. The higher temperature enables the production of hydrogen by thermochemical processes. The European Sustainable Nuclear Industrial Initiative is funding a 100 MWt LFR, an accelerator-driven sub-critical reactor called MYRRHA. It is to be built in Belgium with construction expected by 2036. A reduced-power model called Guinevere was started up at Mol, Belgium, Mol in March 2009 and became operational in 2012. Two other lead-cooled fast reactors under development are the SVBR-100, a modular 100 MWe lead-bismuth cooled fast neutron reactor concept designed by OKB Gidropress in Russia and the BREST (Reactor), BREST-OD-300 (Lead-cooled fast reactor) 300 MWe, to be developed after the SVBR-100, it will dispense with the Uranium-238, fertile blanket around the core and will supersede the sodium cooled BN-600 reactor design, to purportedly give enhanced proliferation resistance. Preparatory construction work commenced in May 2020.


Assessment

The GEN IV Forum reframes the reactor safety paradigm from accepting that nuclear accidents can occur and should be mastered to eliminating the possibility of an accident. Active and passive nuclear safety, passive safety systems would be at least as effective as those of Generation III systems and render the most severe accidents physically impossible.''What is the risk of a severe accident resembling Chernobyl or Fukushima in a Gen IV design?''
GEN IV International Forum (accessed Nov. 2021).
"The aim of Generation IV systems is to maintain the high level of safety achieved by today's reactors, while shifting from the current principle of "mastering accidents" (i.e. accepting that accidents can occur, but taking care that the population is not affected) to the principle of "excluding accidents"."
Relative to Gen II-III, Gen IV reactors include: * Nuclear waste that remains radioactive for a few centuries instead of millennia * 100–300x energy yield from the same amount of nuclear fuel * Broader range of fuels, including unencapsulated raw fuels (non-pebble Molten Salt Reactor, MSR, Liquid fluoride thorium reactor, LFTR). * Potential to burn existing nuclear waste and produce electricity: a closed nuclear fuel cycle, fuel cycle. * Improved safety via features such as ambient pressure operation, automatic passive reactor shutdown, and alternate coolants. Nuclear reactors do not emit CO2 during operation, although mining and construction typically produce CO2 emissions. A 2012 review analyzed life cycle assessment, life cycle (LCA) emissions from nuclear power stated that "the collective LCA literature indicates that life cycle Greenhouse gas, GHG [greenhouse gas] emissions from nuclear power are only a fraction of traditional fossil sources and comparable to renewable technologies." Although the paper primarily dealt with data from Generation II reactors, and did not analyze
Generation III reactor Generation III reactors, or Gen III reactors, are a class of nuclear reactors designed to succeed Generation II reactors, incorporating evolutionary improvements in design. These include improved fuel technology, higher thermal efficiency, sign ...
s, it stated about Fast Breeder Reactors (FBRs): "The limited literature that evaluates this potential future technology reports median life cycle GHG emissions... similar to or lower than LWRs [Gen II
light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...
s] and purports to consume little or no uranium market, uranium ore." A specific risk of the SFR is related to using metallic sodium as a coolant. In case of a breach, sodium explosively reacts with water. Argon is used to prevent sodium oxidation. Argon can displace oxygen in the air and can pose hypoxia (environmental), hypoxia concerns for workers. This was a factor at the LMFBR, loop type Monju Nuclear Power Plant, Prototype Fast Breeder Reactor Monju at Tsuruga, Japan. Using lead or molten salt coolants mitigates this problem as they are less reactive and have a high freezing temperature and ambient pressure. Lead has much higher viscosity, much higher density, lower heat capacity, and more radioactive neutron activation products than sodium. Multiple proof of concept Gen IV designs have been built. For example, the reactors at Fort St. Vrain Generating Station and
HTR-10 HTR-10 is a 10 MWt prototype pebble bed reactor at Tsinghua University in China. Construction began in 1995, achieving its first criticality in December 2000, and was operated in full power condition in January 2003. Two HTR-PM reactors, scaled ...
are similar to the proposed Gen IV VHTR designs, and the LMFBR, pool type EBR-II, Phénix, BN-600 and BN-800 reactor are similar to the proposed pool type Gen IV SFR designs. Nuclear engineer David Lochbaum cautions, "the problem with new reactors and accidents is twofold: scenarios arise that are impossible to plan for in simulations; and humans make mistakes". As one director of a U.S. research laboratory put it, "fabrication, construction, operation, and maintenance of new reactors will face a steep learning curve: advanced technologies will have a heightened risk of accidents and mistakes. The technology may be proven, but people are not".


Design projects


See also

* List of small modular reactor designs * Nuclear reactor * Nuclear material * Nuclear physics * List of reactor types * Generation II reactor *
Generation III reactor Generation III reactors, or Gen III reactors, are a class of nuclear reactors designed to succeed Generation II reactors, incorporating evolutionary improvements in design. These include improved fuel technology, higher thermal efficiency, sign ...
* Integral Fast Reactor * Liquid fluoride thorium reactor * Breeder reactor * Small modular reactor * List of nuclear reactors


References


External links


Article from Idaho National Laboratory detailing some current efforts at developing Gen. IV reactors.

Generation IV International Forum (GIF)


* [https://web.archive.org/web/20060512033030/http://www.engr.utk.edu/nuclear/colloquia/slides/Gen%20IV%20U-Tenn%20Presentation.pdf Gen IV presentation]
Science or Fiction - Is there a Future for Nuclear?
(Nov. 2007) - A publication from the Austrian Ecology Institute (Austria), Ecology Institute about 'Generation IV' and Fusion reactors. * "In the wake of a severe plant accident, advanced reactor designs are getting renewed attention."
International Thorium Energy Organisation - www.IThEO.org

International Thorium Energy Committee - iThEC
{{Nuclear fission reactors Nuclear power reactor types Idaho National Laboratory