Molten salt reactor
Encyclopedia
A molten salt reactor is a type of nuclear fission reactor in which the primary coolant
, or even the fuel itself is a molten salt
mixture. MSRs run at higher temperatures than water-cooled reactors for higher thermodynamic efficiency, while staying at low vapor pressure
.
The ability to operate at near atmospheric pressures reduces the mechanical stress endured by the system, thus simplifying aspects of reactor design and improving safety. The nuclear fuel may be solid fuel rods or dissolved in the coolant itself.
In many designs the nuclear fuel
is dissolved in the molten fluoride
salt coolant as uranium tetrafluoride
(UF4). The fluid becomes critical in a graphite
core which serves as the moderator
. Fluid fuel reactors have significantly different safety
issues compared to solid fuel designs; the potential for major reactor accidents is reduced, while the potential for processing
accidents is increased.
More recent research has focused on the practical advantages of the high-temperature low-pressure primary cooling loop. Many modern designs rely on ceramic fuel dispersed in a graphite matrix, with the molten salt providing low pressure, high temperature cooling. The salts are much more efficient at removing heat from the core, reducing the need for pumping, piping, and reducing the size of the core as these components are reduced in size.
The early Aircraft Reactor Experiment (1954) was primarily motivated by the small size that the design could provide, while the Molten-Salt Reactor Experiment
(1965–1969) was a prototype for a thorium fuel cycle
breeder reactor
nuclear power plant
. One of the Generation IV reactor
designs is a molten salt-cooled, solid-fuel reactor; the initial reference design is 1000 MWe
with a deployment target date of 2025.
Another advantage of a small core is that it has fewer materials to absorb neutrons. In a reactor employing thorium fuel, the improved neutron economy
makes more neutrons available to breed thorium-232 into uranium-233. Thus, the compact core makes the molten salt design particularly suitable for the thorium fuel cycle
.
Extensive research into molten salt reactors started with the U.S. Aircraft Reactor Experiment (ARE) in support of the U.S. Aircraft Nuclear Propulsion
program. The ARE was a 2.5 MWth nuclear reactor experiment designed to attain a high power density for use as an engine in a nuclear powered bomber. The project included several reactor experiments including high temperature reactor and engine tests collectively called 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. The ARE used molten fluoride salt NaF-ZrF4-UF4 (53-41-6 mol%) as fuel, was moderated by beryllium oxide
(BeO), used liquid sodium as a secondary coolant, and had a peak temperature of 860 °C. It operated for 100 MW-hours over nine days in 1954. This experiment used Inconel
600 alloy for the metal structure and piping.
(ORNL) took the lead in researching the MSR through 1960s, and much of their work culminated with the Molten-Salt Reactor Experiment
(MSRE). The MSRE was a 7.4 MWth test reactor simulating the neutronic "kernel" of a type of inherently safe epithermal thorium molten salt breeder reactor called the Liquid fluoride thorium reactor
. It tested molten salt fuels of uranium and plutonium. The tested 233UF4 fluid fuel has a unique decay path
that minimizes waste. The 650 °C temperature of the reactor could power high-efficiency heat engines such as gas turbines. The large, expensive breeding blanket of thorium salt was omitted in favor of neutron measurements.
The MSRE was located at ORNL. Its piping, core vat and structural components were made from Hastelloy
-N and its moderator was pyrolytic graphite. It went critical in 1965 and ran for four years. The fuel for the MSRE was LiF-BeF2-ZrF4-UF4 (65-30-5-0.1), the graphite core moderated it, and its secondary coolant was FLiBe
(2LiF-BeF2). It reached temperatures as high as 650 °C and operated for the equivalent of about 1.5 years of full power operation.
of 705 °C.
The molten salt reactor offers many potential advantages:
(VHTR) have been selected as potential designs to be studied under the Generation Four Initiative (GEN-IV). A version of the VHTR currently being studied is the Liquid Salt Very High Temperature Reactor (LS-VHTR), also commonly called the Advanced High Temperature Reactor (AHTR). It is essentially a standard VHTR design that 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 would be in 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 has many attractive features, including: the ability to work at very high temperatures (the boiling point of most molten salts being considered are >1400 °C), low pressure cooling that can be used to more easily match hydrogen
production facility conditions (most thermo chemical cycles require temperatures in excess of 750 °C), better electric conversion efficiency than a helium cooled VHTR operating at similar conditions, passive safety systems, and better retention of fission products in the event of an accident. This concept is now referred to as Fluoride Salt Cooled High Temperature Reactor (FHR).
LFTR, using technology similar to the Oak Ridge National Laboratory Reactor. It is being developed by a consortium including members from Japan, the U.S. and Russia. It would likely take 20 years to develop a full size reactor but the project seems to lack funding.
(CAS) annual conference in January 2011. Its ultimate target is to investigate and develop a thorium based molten salt nuclear system in about 20 years.
and particularly liquid fluoride thorium reactor
s. In 2011, Sorensen founded Flibe Energy
, a company aimed at developing 20-50 MW LFTR reactor designs to power military bases. (it is easier to approve novel military designs than civilian power station designs in today's US nuclear regulatory environment).
to be fabricated and validated, delaying deployment by up to twenty years from project inception. However, since it uses fabricated fuel, reactor manufacturers can still profit by selling fuel assemblies.
The MSCR retains the safety and cost advantages of a low-pressure, high-temperature coolant, also shared by liquid metal cooled reactor
s. Notably, there is no steam in the core to cause an explosion, and no large, expensive steel pressure vessel. Since it can operate at high temperatures, the conversion of the heat to electricity can also use an efficient, lightweight Brayton cycle
gas turbine.
Much of the current research on MSCRs is focused on small compact heat exchanger
s. By using smaller heat exchangers, less molten salt needs to be used and therefore significant cost savings could be achieved.
Molten salts can be highly corrosive, more so as temperatures rise. For the primary cooling loop of the MSR, a material is needed that can withstand corrosion
at high temperatures and intense radiation
. Experiments show that Hastelloy
-N and similar alloys are quite suited to the tasks at operating temperatures up to about 700 °C. However, long-term experience with a production scale reactor has yet to be gained. Higher operating temperatures would be desirable, but at 850 °C thermo chemical production of hydrogen
becomes possible, which creates serious engineering difficulties. Materials for this temperature range have not been validated, though carbon
composites, molybdenum
alloys (e.g. TZM), carbide
s, and refractory metal based or ODS alloys
might be feasible.
(as chlorine does). It does not easily become radioactive under neutron bombardment. It 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 also must be very hot before they break down into their simpler components, such molten salts are "chemically stable" when maintained well below their boiling points.
Reactor salts are also eutectic mixtures to reduce their melting point. This makes a heat engine
more efficient, because more heat can be removed from the salt before reheating it in the reactor.
Some salts are so useful that isotope separation
is worthwhile. Chloride
s permit fast breeder reactors to be constructed using molten salts. Not nearly as much work has been done on reactor designs using them. Chlorine must be purified
to chlorine-37 to reduce production of sulfur tetrafluoride
when the radioactive chlorine decays to sulfur. Also, any lithium
in a salt mixture must be purified
lithium-7 to reduce tritium
production (the tritium forms hydrogen fluoride
).
Due to the high "redox
window" of fused fluoride salts, the chemical potential
of the fused salt system can be changed. Fluorine-Lithium-Beryllium ("FLiBe
") can be used with beryllium
additions to lower the electrochemical potential and almost eliminate corrosion. However, since beryllium is extremely toxic, special precautions must be engineered into 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 the neutron economy. This process occurs when the Beryllium nucleus re-emits two neutrons after absorbing a single neutron. For the fuel carrying salts, generally 1% or 2% (by mole
) of UF4 is added. thorium
and plutonium
fluorides have also been used. The MSFR is the only system that has run a single reactor, the MSRE, from all three known nuclear fuels.
(HF) which is extremely corrosive. Other impurities can cause non-beneficial chemical reactions and would most likely have to be cleansed from the system. In conventional power plants where water is used as a coolant, great pains are taken to purify and deionize the water to reduce its corrosive properties.
The possibility of online reprocessing can be an advantage of the MSR design. Continuous reprocessing would reduce 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
. In some thorium breeding scenarios, the intermediate product protactinium
-233 would be removed from the reactor and allowed to decay into highly pure uranium-233
, an attractive bomb-making material. If left in the fuel, protactinium would absorb too many neutrons to make breeding with a graphite moderator and thermal spectrum possible. More modern design propose to use a larger quantity of thorium. 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 is not absorbed but instead knocks a neutron out of the nucleus), generate uranium-232. Because U-232 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 processing a larger quantity of blanket salt. Other designs propose to use heavy water as a super efficient moderator to improve neutron economy allowing more loss to protactinium absorption. However these designs would operate at lower temperatures and thus lower thermal efficiency. The necessary fuel salt reprocessing technology has been demonstrated, but only at laboratory scale. A prerequisite to full-scale commercial reactor design is the R&D to engineer an economically competitive fuel salt cleaning system.
UK, France, Japan, Russia and India currently operate some form of fuel reprocessing.
Some U.S. Administration departments have feared that fuel reprocessing in any form could pave the way to the plutonium economy with its associated proliferation dangers.
A similar argument led to the shutdown of the Integral Fast Reactor
project in 1994.
The proliferation risk for a thorium fuel cycle stems from the potential separation of uranium-233, which might be used in nuclear weapons, though only with considerable difficulty.
Some types of molten salt reactors are very inexpensive. Since the core and primary coolant loop are low pressure, it can be constructed of thin, relatively inexpensive weldments. So, it can be far less expensive than the massive pressure vessel required by the core of a light water reactor.
Also, some form of fluid-fueled thorium breeder could use less fissile
material per megawatt than any other reactor. Molten salt reactors can run at extremely high temperatures, yielding high efficiencies to produce electricity. The temperatures of some proposed designs are high enough to produce process heat for hydrogen production or other chemical reactions. Because of this, they have been included in the GEN-IV roadmap for further study.
The MSR also has far better neutron economy and, depending on the design, a harder neutron spectrum than conventional light water reactors. So, it can operate with less reactive fuels. Some designs (such as the MSRE
) can operate a single design from all three common nuclear fuels. For example, it can breed from uranium-238, thorium or even burn the transuranic spent nuclear fuel
from light water reactor
s. In contrast, a water-cooled reactor cannot completely consume the plutonium it produces, because the increasing impurities from the fission wastes capture too many neutrons, "poisoning" the reaction.
MSRs scale over a wide range of powers. Reactors as small as several megawatts have been constructed and operated. Theoretical designs up to several gigawatts have been proposed.
Because of their lightweight structures and compact cores, MSRs weigh less per watt (that is, they have a greater "specific power") than other proven reactor designs. So, in small sizes, with long refueling intervals, they are an excellent choice to power vehicles, including ships, aircraft and spacecraft. This was proved by their initial prototype, the aircraft reactor experiment.
Coolant
A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
, or even the fuel itself is a molten salt
Molten salt
Molten salt refers to a salt that is in the liquid phase that is normally a solid at standard temperature and pressure . A salt which is normally liquid at STP is usually called a room temperature ionic liquid, although technically molten salts are a class of ionic liquids.-Uses:Molten salts have...
mixture. MSRs run at higher temperatures than water-cooled reactors for higher thermodynamic efficiency, while staying at low vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
.
The ability to operate at near atmospheric pressures reduces the mechanical stress endured by the system, thus simplifying aspects of reactor design and improving safety. The nuclear fuel may be solid fuel rods or dissolved in the coolant itself.
In many designs the nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
is dissolved in the molten fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
salt coolant as uranium tetrafluoride
Uranium tetrafluoride
Uranium tetrafluoride is a green crystalline solid compound of uranium with an insignificant vapor pressure and very slight solubility in water. Uranium in its tetravalent state is very important in different technological processes...
(UF4). The fluid becomes critical in a graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
core which serves as the moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
. Fluid fuel reactors have significantly different safety
Nuclear safety
Nuclear safety covers the actions taken to prevent nuclear and radiation accidents or to limit their consequences. This covers nuclear power plants as well as all other nuclear facilities, the transportation of nuclear materials, and the use and storage of nuclear materials for medical, power,...
issues compared to solid fuel designs; the potential for major reactor accidents is reduced, while the potential for processing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
accidents is increased.
More recent research has focused on the practical advantages of the high-temperature low-pressure primary cooling loop. Many modern designs rely on ceramic fuel dispersed in a graphite matrix, with the molten salt providing low pressure, high temperature cooling. The salts are much more efficient at removing heat from the core, reducing the need for pumping, piping, and reducing the size of the core as these components are reduced in size.
The early Aircraft Reactor Experiment (1954) was primarily motivated by the small size that the design could provide, while the Molten-Salt Reactor Experiment
Molten-Salt Reactor Experiment
The Molten-Salt Reactor Experiment was an experimental molten-salt reactor at the Oak Ridge National Laboratory researching this technology through the 1960s; constructed by 1964, it went critical in 1965 and was operated until 1969....
(1965–1969) was a prototype for a thorium fuel cycle
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
breeder reactor
Breeder reactor
A breeder reactor is a nuclear reactor capable of generating more fissile material than it consumes because its neutron economy is high enough to breed fissile from fertile material like uranium-238 or thorium-232. Breeders were at first considered superior because of their superior fuel economy...
nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
. One of the Generation IV reactor
Generation IV reactor
Generation IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030...
designs is a molten salt-cooled, solid-fuel reactor; the initial reference design is 1000 MWe
MWE
MWE may refer to:*Manufacturer's Weight Empty*McDermott Will & Emery*Midwest Express, an airline*Merowe Airport - IATA code*Multiword expressionMWe may refer to:*Megawatt electrical...
with a deployment target date of 2025.
Another advantage of a small core is that it has fewer materials to absorb neutrons. In a reactor employing thorium fuel, the improved neutron economy
Neutron economy
Neutron economy is defined as the ratio of an adjoint weighted average of the excess neutron production divided by an adjoint weighted average of the fission production....
makes more neutrons available to breed thorium-232 into uranium-233. Thus, the compact core makes the molten salt design particularly suitable for the thorium fuel cycle
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
.
The Aircraft Reactor Experiment
Aircraft Nuclear Propulsion
The Aircraft Nuclear Propulsion program and the preceding Nuclear Energy for the Propulsion of Aircraft project worked to develop a nuclear propulsion system for aircraft. The United States Army Air Force initiated Project NEPA on May 28, 1946...
program. The ARE was a 2.5 MWth nuclear reactor experiment designed to attain a high power density for use as an engine in a nuclear powered bomber. The project included several reactor experiments including high temperature reactor and engine tests collectively called the Heat Transfer Reactor Experiments: HTRE-1, HTRE-2, and HTRE-3 at the National Reactor Test Station (now Idaho National Laboratory
Idaho National Laboratory
Idaho National Laboratory is an complex located in the high desert of eastern Idaho, between the town of Arco to the west and the cities of Idaho Falls and Blackfoot to the east. It lies within Butte, Bingham, Bonneville and Jefferson counties...
) as well as an experimental high-temperature molten salt reactor at Oak Ridge National Laboratory - the ARE. The ARE used molten fluoride salt NaF-ZrF4-UF4 (53-41-6 mol%) as fuel, was moderated by beryllium oxide
Beryllium oxide
Beryllium oxide , also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and actually exceeds that of some metals. As an amorphous solid, beryllium...
(BeO), used liquid sodium as a secondary coolant, and had a peak temperature of 860 °C. It operated for 100 MW-hours over nine days in 1954. This experiment used Inconel
Inconel
Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys. Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco"...
600 alloy for the metal structure and piping.
The Molten-Salt Reactor Experiment
Oak Ridge National LaboratoryOak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...
(ORNL) took the lead in researching the MSR through 1960s, and much of their work culminated with the Molten-Salt Reactor Experiment
Molten-Salt Reactor Experiment
The Molten-Salt Reactor Experiment was an experimental molten-salt reactor at the Oak Ridge National Laboratory researching this technology through the 1960s; constructed by 1964, it went critical in 1965 and was operated until 1969....
(MSRE). The MSRE was a 7.4 MWth test reactor simulating the neutronic "kernel" of a type of inherently safe epithermal thorium molten salt breeder reactor called the Liquid fluoride thorium reactor
Liquid fluoride thorium reactor
The liquid fluoride thorium reactor is a thermal breeder reactor which uses the thorium fuel cycle in a fluoride-based molten salt fuel to achieve high operating temperatures at atmospheric pressure....
. It tested molten salt fuels of uranium and plutonium. The tested 233UF4 fluid fuel has a unique decay path
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
that minimizes waste. The 650 °C temperature of the reactor could power high-efficiency heat engines such as gas turbines. The large, expensive breeding blanket of thorium salt was omitted in favor of neutron measurements.
The MSRE was located at ORNL. Its piping, core vat and structural components were made from Hastelloy
Hastelloy
Hastelloy is the registered trademark name of Haynes International, Inc. The trademark is applied as the prefix name of a range of twenty two different highly corrosion-resistant metal alloys loosely grouped by the metallurgical industry under the material term “superalloys” or “high-performance...
-N and its moderator was pyrolytic graphite. It went critical in 1965 and ran for four years. The fuel for the MSRE was LiF-BeF2-ZrF4-UF4 (65-30-5-0.1), the graphite core moderated it, and its secondary coolant was FLiBe
FLiBe
FLiBe is a mixture of lithium fluoride and beryllium fluoride . As a molten salt it is proposed as a nuclear reactor coolant, and two different mixtures were used in the Molten-Salt Reactor Experiment....
(2LiF-BeF2). It reached temperatures as high as 650 °C and operated for the equivalent of about 1.5 years of full power operation.
Oak Ridge National Laboratory Molten Salt Breeder Reactor
The culmination of the Oak Ridge National Laboratory research during the 1970–76 timeframe resulted in an Molten Salt Breeder Reactor (MSBR) design which would use LiF-BeF2-ThF4-UF4 (72-16-12-0.4) as fuel, was to be moderated by graphite with a 4 year replacement schedule, use NaF-NaBF4 as the secondary coolant, and have a peak operating temperatureOperating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
of 705 °C.
The molten salt reactor offers many potential advantages:
- inherently safe design (safety by passive components and the strong negative temperature coefficient of reactivity)
- using an abundant supply of thoriumThoriumThorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
to breed uranium-233 fuel. - much cleaner: as a full recycle system, the discharge wastes from the reactor are predominately fission products, most of which have relatively short half lives compared to longer-lived actinide wastes. This can result in a significant reduction in the containment period in a geologic repository (300 years vs. tens of thousands of years)
- can "burn" some problematic radioactive waste (with transuranic elements from traditional solid-fuel nuclear reactors)
- possible even in small, even 2–8 MW(thermal) or 1–3 MW(electric). Submarine or aircraft size is possible
- can react to load changes in less than 60 seconds (unlike "traditional" solid-fuel nuclear power plants)
Liquid salt very high temperature reactor
Research is currently picking up again for reactors that utilize molten salts for coolant. Both the traditional molten salt reactor and the Very High Temperature ReactorVery high temperature reactor
The Very High Temperature Reactor , or High Temperature Gas-cooled Reactor , is a Generation IV reactor concept that uses a graphite-moderated nuclear reactor with a once-through uranium fuel cycle. The VHTR is a type of High Temperature Reactor that can conceptually have an outlet temperature of...
(VHTR) have been selected as potential designs to be studied under the Generation Four Initiative (GEN-IV). A version of the VHTR currently being studied is the Liquid Salt Very High Temperature Reactor (LS-VHTR), also commonly called the Advanced High Temperature Reactor (AHTR). It is essentially a standard VHTR design that 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 would be in 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 has many attractive features, including: the ability to work at very high temperatures (the boiling point of most molten salts being considered are >1400 °C), low pressure cooling that can be used to more easily match hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
production facility conditions (most thermo chemical cycles require temperatures in excess of 750 °C), better electric conversion efficiency than a helium cooled VHTR operating at similar conditions, passive safety systems, and better retention of fission products in the event of an accident. This concept is now referred to as Fluoride Salt Cooled High Temperature Reactor (FHR).
Liquid fluoride thorium reactor
The research and development of molten thorium salt fueled MSR variant called LFTR is also picking up. Private companies from Japan, Russia, USA and well as Chinese government expressed interest in developing the technology.The Fuji MSR
The FUJI MSR is a 100 to 200 MWeMWE
MWE may refer to:*Manufacturer's Weight Empty*McDermott Will & Emery*Midwest Express, an airline*Merowe Airport - IATA code*Multiword expressionMWe may refer to:*Megawatt electrical...
LFTR, using technology similar to the Oak Ridge National Laboratory Reactor. It is being developed by a consortium including members from Japan, the U.S. and Russia. It would likely take 20 years to develop a full size reactor but the project seems to lack funding.
Chinese Thorium MSR project
The People’s Republic of China has initiated a research and development project in thorium molten-salt reactor technology. It was formally announced at the Chinese Academy of SciencesChinese Academy of Sciences
The Chinese Academy of Sciences , formerly known as Academia Sinica, is the national academy for the natural sciences of the People's Republic of China. It is an institution of the State Council of China. It is headquartered in Beijing, with institutes all over the People's Republic of China...
(CAS) annual conference in January 2011. Its ultimate target is to investigate and develop a thorium based molten salt nuclear system in about 20 years.
Flibe Energy
Kirk Sorensen, former NASA scientist and Chief Nuclear Technologist at Teledyne Brown Engineering, has been a long time promoter of thorium fuel cycleThorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
and particularly liquid fluoride thorium reactor
Liquid fluoride thorium reactor
The liquid fluoride thorium reactor is a thermal breeder reactor which uses the thorium fuel cycle in a fluoride-based molten salt fuel to achieve high operating temperatures at atmospheric pressure....
s. In 2011, Sorensen founded Flibe Energy
Flibe Energy
Flibe Energy is a company that intends to design, construct and operate small modular reactors based on liquid fluoride thorium reactor technology.-Corporation:...
, a company aimed at developing 20-50 MW LFTR reactor designs to power military bases. (it is easier to approve novel military designs than civilian power station designs in today's US nuclear regulatory environment).
The Weinberg Foundation
The Weinberg Foundation is a British non-profit organisation founded in 2011 dedicated to promotion and development of a liquid fluoride thorium reactor.Molten-salt fueling options
- The thorium-fueled variant called Liquid fluoride thorium reactorLiquid fluoride thorium reactorThe liquid fluoride thorium reactor is a thermal breeder reactor which uses the thorium fuel cycle in a fluoride-based molten salt fuel to achieve high operating temperatures at atmospheric pressure....
, has been very exciting to many nuclear engineers. Its most prominent champion was Alvin Weinberg, who patented the light-water reactor and was a director of the U.S.'s Oak Ridge National Laboratory, a prominent nuclear research center. It has recently been the subject of a renewed interest.
- MSRMSRMSR has several meanings:*MSR Studios, a New York recording studio*Machine state register, is a feature in Intel X86 and X86-64 processors*Magnetic Stripe Reader, to read Magnetic stripe cards, for example Credit Cards...
can be fueled using enriched Uranium-235Uranium-235- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
.
- MSRMSRMSR has several meanings:*MSR Studios, a New York recording studio*Machine state register, is a feature in Intel X86 and X86-64 processors*Magnetic Stripe Reader, to read Magnetic stripe cards, for example Credit Cards...
can be fueled using fissile material from dismantled nuclear weapons.
Molten-salt cooled reactors
Molten-salt-fueled reactors are quite different from molten-salt-cooled solid-fuel reactors, called simply "Molten Salt Reactor System" in the Generation IV proposal, also called MSCR, which is also the acronym for the Molten Salt Converter Reactor design. It cannot reprocess fuel easily and has fuel rods that needto be fabricated and validated, delaying deployment by up to twenty years from project inception. However, since it uses fabricated fuel, reactor manufacturers can still profit by selling fuel assemblies.
The MSCR retains the safety and cost advantages of a low-pressure, high-temperature coolant, also shared by liquid metal cooled reactor
Liquid metal cooled reactor
A liquid metal cooled nuclear reactor, liquid metal fast reactor or LMFR is an advanced type of nuclear reactor where the primary coolant is a liquid metal. Liquid metal cooled reactors were first adapted for nuclear submarine use but have also been extensively studied for power generation...
s. Notably, there is no steam in the core to cause an explosion, and no large, expensive steel pressure vessel. Since it can operate at high temperatures, the conversion of the heat to electricity can also use an efficient, lightweight Brayton cycle
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the airbreathing jet engine and others. It is named after George Brayton , the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber...
gas turbine.
Much of the current research on MSCRs is focused on small compact heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s. By using smaller heat exchangers, less molten salt needs to be used and therefore significant cost savings could be achieved.
Molten salts can be highly corrosive, more so as temperatures rise. For the primary cooling loop of the MSR, a material is needed that can withstand corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
at high temperatures and intense radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
. Experiments show that Hastelloy
Hastelloy
Hastelloy is the registered trademark name of Haynes International, Inc. The trademark is applied as the prefix name of a range of twenty two different highly corrosion-resistant metal alloys loosely grouped by the metallurgical industry under the material term “superalloys” or “high-performance...
-N and similar alloys are quite suited to the tasks at operating temperatures up to about 700 °C. However, long-term experience with a production scale reactor has yet to be gained. Higher operating temperatures would be desirable, but at 850 °C thermo chemical production of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
becomes possible, which creates serious engineering difficulties. Materials for this temperature range have not been validated, though carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
composites, molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
alloys (e.g. TZM), carbide
Carbide
In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides...
s, and refractory metal based or ODS alloys
ODS alloys
Oxide dispersion strengthened alloys are used for high temperature turbine blades and heat exchanger tubing. Alloys of nickel are the most common but work is being done on iron aluminum alloys. ODS steels are used in nuclear applications....
might be feasible.
Fused salt selection
The salt mixtures are chosen to make the reactor safer and more practical. Fluorides are favored because fluorine does not need expensive isotope separationIsotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
(as chlorine does). It does not easily become radioactive under neutron bombardment. It also absorbs fewer neutrons and slows ("moderates
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
") neutrons better. Low-valence
Valence (chemistry)
In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...
fluorides boil at high temperatures, though many pentafluorides and hexafluorides boil at low temperatures. They also must be very hot before they break down into their simpler components, such molten salts are "chemically stable" when maintained well below their boiling points.
Reactor salts are also eutectic mixtures to reduce their melting point. This makes a heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
more efficient, because more heat can be removed from the salt before reheating it in the reactor.
Some salts are so useful that isotope separation
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
is worthwhile. Chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
s permit fast breeder reactors to be constructed using molten salts. Not nearly as much work has been done on reactor designs using them. Chlorine must be purified
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
to chlorine-37 to reduce production of sulfur tetrafluoride
Sulfur tetrafluoride
Sulfur tetrafluoride is the chemical compound with the formula SF4. This species exists as a gas at standard conditions. It is a corrosive species that releases dangerous HF upon exposure to water or moisture...
when the radioactive chlorine decays to sulfur. Also, any lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
in a salt mixture must be purified
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
lithium-7 to reduce tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
production (the tritium forms hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
).
Due to the high "redox
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
window" of fused fluoride salts, the chemical potential
Chemical potential
Chemical potential, symbolized by μ, is a measure first described by the American engineer, chemist and mathematical physicist Josiah Willard Gibbs. It is the potential that a substance has to produce in order to alter a system...
of the fused salt system can be changed. Fluorine-Lithium-Beryllium ("FLiBe
FLiBe
FLiBe is a mixture of lithium fluoride and beryllium fluoride . As a molten salt it is proposed as a nuclear reactor coolant, and two different mixtures were used in the Molten-Salt Reactor Experiment....
") can be used with beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
additions to lower the electrochemical potential and almost eliminate corrosion. However, since beryllium is extremely toxic, special precautions must be engineered into 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
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
.
To date, most research has focused on FLiBe
FLiBe
FLiBe is a mixture of lithium fluoride and beryllium fluoride . As a molten salt it is proposed as a nuclear reactor coolant, and two different mixtures were used in the Molten-Salt Reactor Experiment....
, 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 the neutron economy. This process occurs when the Beryllium nucleus re-emits two neutrons after absorbing a single neutron. For the fuel carrying salts, generally 1% or 2% (by mole
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
) of UF4 is added. thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
and plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
fluorides have also been used. The MSFR is the only system that has run a single reactor, the MSRE, from all three known nuclear fuels.
| Material | Total neutron capture relative to graphite (per unit volume) | Moderating ratio (Avg. 0.1 to 10 eV) |
|---|---|---|
| Heavy water | 0.2 | 11449 |
| Light water | 75 | 246 |
| Graphite | 1 | 863 |
| Sodium | 47 | 2 |
| UCO | 285 | 2 |
| UO2 | 3583 | 0.1 |
| 2LiF–BeF2 | 8 | 60 |
| LiF–BeF2–ZrF4 (64.5–30.5–5) | 8 | 54 |
| NaF–BeF2 (57–43) | 28 | 15 |
| LiF–NaF–BeF2 (31–31–38) | 20 | 22 |
| LiF–ZrF4 (51–49) | 9 | 29 |
| NaF–ZrF4 (59.5–40.5) | 24 | 10 |
| LiF-NaF–ZrF4 (26–37–37) | 20 | 13 |
| KF–ZrF4 (58–42) | 67 | 3 |
| RbF–ZrF4 (58–42) | 14 | 13 |
| LiF–KF (50–50) | 97 | 2 |
| LiF–RbF (44–56) | 19 | 9 |
| LiF–NaF–KF (46.5–11.5–42) | 90 | 2 |
| LiF–NaF–RbF (42–6–52) | 20 | 8 |
Fused salt purification and reprocessing
Salts must be extremely pure initially, and would most likely be continuously cleaned in a large-scale molten salt reactor. Any water vapor in the salt will form hydrofluoric acidHydrofluoric acid
Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
(HF) which is extremely corrosive. Other impurities can cause non-beneficial chemical reactions and would most likely have to be cleansed from the system. In conventional power plants where water is used as a coolant, great pains are taken to purify and deionize the water to reduce its corrosive properties.
The possibility of online reprocessing can be an advantage of the MSR design. Continuous reprocessing would reduce 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
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
. In some thorium breeding scenarios, the intermediate product protactinium
Protactinium
Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume...
-233 would be removed from the reactor and allowed to decay into highly pure uranium-233
Uranium-233
Uranium-233 is a fissile isotope of uranium, bred from Thorium as part of the thorium fuel cycle. It has been used in a few nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years....
, an attractive bomb-making material. If left in the fuel, protactinium would absorb too many neutrons to make breeding with a graphite moderator and thermal spectrum possible. More modern design propose to use a larger quantity of thorium. 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 is not absorbed but instead knocks a neutron out of the nucleus), generate uranium-232. Because U-232 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 processing a larger quantity of blanket salt. Other designs propose to use heavy water as a super efficient moderator to improve neutron economy allowing more loss to protactinium absorption. However these designs would operate at lower temperatures and thus lower thermal efficiency. The necessary fuel salt reprocessing technology has been demonstrated, but only at laboratory scale. A prerequisite to full-scale commercial reactor design is the R&D to engineer an economically competitive fuel salt cleaning system.
Political issues
To exploit the molten salt reactor's breeding potential to the fullest, the reactor must be co-located with a reprocessing facility. Nuclear reprocessing does not occur in the U.S. because no commercial provider is willing to undertake it. The regulatory risk and associated costs are very great because the regulatory regime has varied dramatically in different administrations.UK, France, Japan, Russia and India currently operate some form of fuel reprocessing.
Some U.S. Administration departments have feared that fuel reprocessing in any form could pave the way to the plutonium economy with its associated proliferation dangers.
A similar argument led to the shutdown of the Integral Fast Reactor
Integral Fast Reactor
The Integral Fast Reactor is a design for a nuclear reactor using fast neutrons and no neutron moderator . IFR is distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.The U.S...
project in 1994.
The proliferation risk for a thorium fuel cycle stems from the potential separation of uranium-233, which might be used in nuclear weapons, though only with considerable difficulty.
Comparison to ordinary light water reactors
MSRs can be safer than ordinary light water reactors. Molten salts trap fission products chemically, and react slowly or not at all in air. Also, the fuel salt does not burn in air or water. The core and primary cooling loop is operated at near atmospheric pressure, and has no steam, so a pressure explosion is impossible. Even in the case of an accident, most radioactive fission products would stay in the salt instead of dispersing into the atmosphere. A molten core is meltdown-proof, so the worst possible accident would be a leak. In this case, the fuel salt can be drained into passively cooled storage, managing the accident. Neutron-producing accelerators have even been proposed for some super-safe subcritical experimental designs, and the initiation of thorium transmutation to 233U can be directly accomplished with what is essentially a medical proton-beam source.Some types of molten salt reactors are very inexpensive. Since the core and primary coolant loop are low pressure, it can be constructed of thin, relatively inexpensive weldments. So, it can be far less expensive than the massive pressure vessel required by the core of a light water reactor.
Also, some form of fluid-fueled thorium breeder could use less fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
material per megawatt than any other reactor. Molten salt reactors can run at extremely high temperatures, yielding high efficiencies to produce electricity. The temperatures of some proposed designs are high enough to produce process heat for hydrogen production or other chemical reactions. Because of this, they have been included in the GEN-IV roadmap for further study.
The MSR also has far better neutron economy and, depending on the design, a harder neutron spectrum than conventional light water reactors. So, it can operate with less reactive fuels. Some designs (such as the MSRE
Molten-Salt Reactor Experiment
The Molten-Salt Reactor Experiment was an experimental molten-salt reactor at the Oak Ridge National Laboratory researching this technology through the 1960s; constructed by 1964, it went critical in 1965 and was operated until 1969....
) can operate a single design from all three common nuclear fuels. For example, it can breed from uranium-238, thorium or even burn the transuranic spent nuclear fuel
Spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...
from light water reactor
Light water reactor
The light water reactor is a type of thermal reactor that uses normal water as its coolant and neutron moderator. Thermal reactors are the most common type of nuclear reactor, and light water reactors are the most common type of thermal reactor...
s. In contrast, a water-cooled reactor cannot completely consume the plutonium it produces, because the increasing impurities from the fission wastes capture too many neutrons, "poisoning" the reaction.
MSRs scale over a wide range of powers. Reactors as small as several megawatts have been constructed and operated. Theoretical designs up to several gigawatts have been proposed.
Because of their lightweight structures and compact cores, MSRs weigh less per watt (that is, they have a greater "specific power") than other proven reactor designs. So, in small sizes, with long refueling intervals, they are an excellent choice to power vehicles, including ships, aircraft and spacecraft. This was proved by their initial prototype, the aircraft reactor experiment.
See also
- Atomic physicsAtomic physicsAtomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and...
- Generation IV reactorGeneration IV reactorGeneration IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030...
- Integral Fast ReactorIntegral Fast ReactorThe Integral Fast Reactor is a design for a nuclear reactor using fast neutrons and no neutron moderator . IFR is distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.The U.S...
- Liquid metal cooled reactorLiquid metal cooled reactorA liquid metal cooled nuclear reactor, liquid metal fast reactor or LMFR is an advanced type of nuclear reactor where the primary coolant is a liquid metal. Liquid metal cooled reactors were first adapted for nuclear submarine use but have also been extensively studied for power generation...
- Nuclear aircraftNuclear aircraftA nuclear aircraft is an aircraft powered by nuclear energy. Research into them was pursued during the Cold War by the United States and the Soviet Union as they would presumably allow a country to keep nuclear bombers in the air for extremely long periods of time, a useful tactic for nuclear...
- Nuclear powerNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
- Nuclear reactorNuclear reactorA nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
- Nuclear fuelNuclear fuelNuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
- Nuclear materialNuclear materialNuclear material refers to the metals uranium, plutonium, and thorium, in any form, according to the IAEA. This is differentiated further into "source material", consisting of natural and depleted uranium, and "special fissionable material", consisting of enriched uranium , uranium-233, and...
- Thorium fuel cycleThorium fuel cycleThe thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
- Liquid fluoride thorium reactorLiquid fluoride thorium reactorThe liquid fluoride thorium reactor is a thermal breeder reactor which uses the thorium fuel cycle in a fluoride-based molten salt fuel to achieve high operating temperatures at atmospheric pressure....
- Flibe EnergyFlibe EnergyFlibe Energy is a company that intends to design, construct and operate small modular reactors based on liquid fluoride thorium reactor technology.-Corporation:...
Further reading
- Energy from Thorium's Document Repository Contains scanned versions of many of the U.S. government engineering reports, over ten thousand pages of construction and operation experience. This repository is the main reference for the aircraft reactor experiment and molten-salt fueled reactor's technical discussion.
- The First Nuclear Era : The Life and Times of a Technological Fixer by Alvin Martin Weinberg
- Bruce Hoglund's Eclectic Interests Home Page Nuclear Power, Thorium, Molten Salt reactors, etc.
- Generation IV International Forum MSR website
- INL MSR workshop summary
- Molten Salt Chemistry Plays a Prominant (sic) Role in Accelerator-Driven Transmutation Systems
- Materials Consideration for Molten Salt Accelerator-Based Plutonium Conversion Systems
- Material Considerations for Molten Salt Accelerator-based Plutonium Conversion Systems J.H. Devan et al.
External links
- Idaho National Laboratory Molten Salt Reactor Fact Sheet
- Energy from Thorium Blog / Website
- Google TechTalks – Liquid Fluoride Thorium Reactor: What Fusion Wanted To Be by Dr. Joe Bonometti NASA / Naval Post Graduate School YouTube
- Wikibooks
- Pebble Bed Advanced High Temperature Reactor
- Thorium Remix LFTR in 5 Minutes and other LFTR Documentaries.