Lead-bismuth eutectic or LBE is a eutectic

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

(44.5 at%) and

bismuth Bismuth is a chemical element; it has 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 nat ...

(55.5 at%) used as a

coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corr ...

in some

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

s, and is a proposed coolant for the

lead-cooled fast reactor The lead-cooled fast reactor is a nuclear reactor design that uses molten lead or lead-bismuth eutectic as its coolant. These materials can be used as the primary coolant because they have low neutron absorption and relatively low melting poi ...

, part of the

Generation IV reactor Generation IV (Gen IV) reactors are nuclear reactor design technologies that are envisioned as successors of generation III reactors. The Generation IV International Forum (GIF) – an international organization that coordinates the development of ...

initiative. It has a

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

of 123.5 °C/254.3 °F (pure lead melts at 327 °C/621 °F, pure bismuth at 271 °C/520 °F) and a

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

of 1,670 °C/3,038 °F. Lead-bismuth alloys with between 30% and 75% bismuth all have melting points below 200 °C/392 °F. Alloys with between 48% and 63% bismuth have melting points below 150 °C/302 °F. While lead expands slightly on melting and bismuth contracts slightly on melting, LBE has negligible change in volume on melting.

History

The Soviet

Alfa-class submarine The Alfa class, Soviet designation Project 705 Lira (, meaning "Lyre", NATO reporting name Alfa), was a class of nuclear-powered attack submarines in service with the Soviet Navy from 1971 into the early 1990s, with one serving in the Russian Na ...

s used LBE as a coolant for their nuclear reactors throughout the

Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...

OKB Gidropress OKB Gidropress () is a Russian state construction office which works on the design, analysis, development, and production of nuclear power plant reactors, most notably the VVER range. OKB stands for experimental design bureau (опытно-кон ...

(the Russian developers of the

VVER The water-water energetic reactor (WWER), or VVER (from ) is a series of pressurized water reactor designs originally developed in the Soviet Union, and now Russia, by OKB Gidropress. The idea of such a reactor was proposed at the Kurchatov Instit ...

-type

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 reacto ...

s) has expertise in LBE reactors. The SVBR-75/100, a modern design of this type, is one example of the extensive Russian experience with this technology. Gen4 Energy (formerly Hyperion Power Generation), a United States firm connected with

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...

, announced plans in 2008 to design and deploy a uranium nitride fueled

small modular reactor The small modular reactor (SMR) is a class of small nuclear fission reactor, designed to be built in a factory, shipped to operational sites for installation, and then used to power buildings or other commercial operations. The term SMR refers t ...

cooled by lead-bismuth eutectic for commercial power generation,

district heating District heating (also known as heat networks) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heater, space heating and w ...

, and desalinization. The proposed reactor, called the Gen4 Module, was planned as a 70 MW_th reactor of the sealed modular type, factory assembled and transported to site for installation, and transported back to the factory for refuelling. Gen4 Energy ceased operations in 2018.

Advantages

As compared to sodium-based liquid metal coolants such as liquid

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

or NaK, lead-based coolants have significantly higher

s, meaning a reactor can be operated without risk of coolant boiling at much higher temperatures. This improves

thermal efficiency In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc. For ...

and could potentially allow

hydrogen production Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Article in press. Most hydrogen is ''gray hydrogen'' made through steam methane reforming. In this process, ...

through thermochemical processes. Lead and LBE also do not react readily with water or air, in contrast to sodium and NaK which ignite spontaneously in air and react explosively with water. This means that lead- or LBE-cooled reactors, unlike sodium-cooled designs, would not need an intermediate coolant loop, which reduces the

capital investment Investment is traditionally defined as the "commitment of resources into something expected to gain value over time". If an investment involves money, then it can be defined as a "commitment of money to receive more money later". From a broade ...

required for a plant. Both lead and bismuth are also an excellent radiation shield, absorbing

gamma radiation A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

while simultaneously being virtually transparent to

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s. In contrast, sodium forms the potent gamma emitter

sodium-24 There are 20 isotopes of sodium (11Na), ranging from to (except for the still-unknown 36Na and 38Na), and five isomers (two for , and one each for , , and ). is the only stable (and the only primordial) isotope. It is considered a monoisotopi ...

(

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

15 hours) following intense

neutron radiation Neutron radiation is a form of ionizing radiation that presents as free neutrons. Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides— ...

, requiring a large radiation shield for the primary cooling loop. As heavy nuclei, lead and bismuth can be used as

spallation Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...

targets for non-fission neutron production, as in accelerator transmutation of waste (see energy amplifier). Both lead-based and sodium-based coolants have the advantage of relatively high boiling points as compared to water, meaning it is not necessary to pressurise the reactor even at high temperatures. This improves safety as it reduces the probability of a loss of coolant accident (LOCA), and allows for

passively safe Passive nuclear safety is a design approach for safety features, implemented in a nuclear reactor, that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a saf ...

designs. The

thermodynamic cycle A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve heat transfer, transfer of heat and work (physics), work into and out of the system, while varying pressure, temperature, and other state variables within t ...

(

Carnot cycle A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Nicolas Léonard Sadi Carnot, Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem (thermodynamics), Carnot's theorem, it provides ...

) is also more efficient with a larger difference of temperature. A disadvantage of higher temperatures is also the higher corrosion rate of metallic structural components in LBE due to their increased

solubility In chemistry, solubility is the ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...

in liquid LBE with temperature (formation of amalgam) and to liquid metal embrittlement.

Limitations

Lead and LBE coolant are more

corrosive Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

than sodium, and this puts an upper limit on the velocity of coolant flow through the reactor due to safety considerations. Furthermore, the higher melting points of lead and LBE (327 °C and 123.5 °C respectively) may mean that solidification of the coolant may be a greater problem when the reactor is operated at lower temperatures. Finally, upon

bismuth-209 Bismuth-209 (Bi) is an isotope of bismuth, with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and a magic number of 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass unit ...

, the main isotope of bismuth present in LBE coolant, undergoes

neutron capture Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, wh ...

and subsequent

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

, forming

polonium-210 Polonium-210 (210Po, Po-210, historically radium F) is an isotope of polonium. It undergoes alpha decay to stable 206Pb with a half-life of 138.376 days (about months), the longest half-life of all naturally occurring polonium isotopes (210– ...

, a potent alpha emitter. The presence of radioactive

polonium Polonium is a chemical element; it has symbol Po and atomic number 84. A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tel ...

in the coolant would require special precautions to control alpha contamination during refueling of the reactor and handling components in contact with LBE.

References

External links

NEA 2015 LBE Handbook
{{DEFAULTSORT:Lead-Bismuth Eutectic Fusible alloys Nuclear reactor coolants Nuclear materials Bismuth Lead alloys

History

Advantages

Limitations

See also

References

External links