The lead-cooled fast reactor is a

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 ...

design that uses molten

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 ...

or lead-bismuth eutectic as its

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 ...

. These materials can be used as the primary coolant because they have low neutron absorption and relatively low

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 ...

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 are slowed less by interaction with these heavy nuclei (thus not being

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 ...

s) so these reactors operate with

fast 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 with ...

s. The concept is generally similar to

sodium-cooled 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 ...

s, and most liquid-metal fast reactors have used sodium instead of lead. Few lead-cooled reactors have been constructed, except for the Soviet submarine K-27 and the seven 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 (though these were

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

-moderated intermediate energy reactors rather than fast reactors). Some proposed new nuclear reactor designs are lead-cooled. Fuel designs being explored for this reactor scheme include fertile uranium as a metal, metal

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

or metal

nitride In chemistry, a nitride is a chemical compound of nitrogen. Nitrides can be inorganic or organic, ionic or covalent. The nitride anion, N3−, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitr ...

. The lead-cooled reactor design has been proposed as a

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 ...

. Plans for future implementation of this type of reactor include modular arrangements rated at 300 to 400 MWe, and a large monolithic plant rated at 1,200 MWe.

Operation

Lead-cooled fast reactors operate with

s and molten

or lead-bismuth eutectic

. Molten lead or lead-bismuth eutectic can be used as the primary coolant because especially lead, and to a lesser degree bismuth, have low neutron absorption and relatively low

s are slowed less by interaction with these heavy nuclei (thus not being

s), and therefore help make this type of reactor a

fast-neutron reactor A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV, on average), as opposed to slow t ...

. If a neutron hits a particle with a similar mass (such as hydrogen in a

pressurized water reactor A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan, India and Canada). In a PWR, water is used both as ...

(PWR), it tends to lose

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

. If it hits a much heavier atom such as lead, the neutron will "bounce off" without losing this energy. The coolant serves as a

neutron reflector A neutron reflector is any material that reflects neutrons. This refers to elastic scattering rather than to a specular reflection. The material may be graphite, beryllium, steel, tungsten carbide, gold, or other materials. A neutron reflect ...

, returning some escaping neutrons to the core. Smaller capacity lead-cooled fast reactors (such as SSTAR) can be cooled by natural

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

, while larger designs (such as ELSY) use forced circulation in normal power operation, but will employ natural circulation emergency cooling. No operator intervention is required, nor pumping of any kind to cool the residual heat of the reactor after shutdown. The reactor outlet coolant temperature is typically in the range of 500 to 600 °C, possibly ranging over 800 °C with advanced materials for later designs. Temperatures higher than 800 °C are theoretically high enough to support thermochemical

production of hydrogen 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 the sulfur-iodine cycle, although this has not been demonstrated. The concept is generally very similar to

s, and most liquid-metal fast reactors have used sodium instead of lead. Few lead-cooled reactors have been constructed, except for some Soviet

nuclear submarine A nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed. Nuclear submarines have considerable performance advantages over "conventional" (typically diesel-electric) submarines. Nuclear propulsion ...

reactors in the 1970s, but some proposed new nuclear reactor designs are lead-cooled, with one under construction.

Fuel

Fuel designs being explored for this reactor scheme include fertile uranium as a metal, metal

or metal

Small modular reactors

Reactors that use lead or lead-bismuth eutectic can be designed in a large range of power ratings. The Soviet Union was able to operate the

s with a lead-bismuth cooled intermediate-spectrum reactor moderated with

from the 1960s to 1998, which had approximately 30 MW of mechanical output for 155 MW thermal power (see below). Other options include units featuring long-life, pre-manufactured cores, that do not require refueling for many years. The lead-cooled fast reactor battery is a small turnkey-type power plant using cassette cores running on a closed fuel cycle with 15 to 20 years' refuelling interval, or entirely replaceable reactor modules. It is designed for generation of electricity on small grids (and other resources, including

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

production and desalinisation process for the production of

potable water Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...

Advantages of lead in fast reactors

The use of lead as a coolant has several advantages when compared to other methods for reactor cooling: * Molten lead does not significantly

moderate Moderate is an ideological category which entails centrist views on a liberal-conservative spectrum. It may also designate a rejection of radical or extreme views, especially in regard to politics and religion. Political position Canad ...

neutrons. Moderation occurs when neutrons are slowed down by repeated collisions with a medium. When the neutron collides with atoms that are much heavier than itself, almost no energy is lost in the process. Thus, the neutrons are not slowed down by lead, which ensures that the neutrons keep their high energy. This is similar to other fast reactor concepts, including the molten liquid sodium designs. * Molten lead acts as a reflector for neutrons. Neutrons escaping the core of the reactor are to some extent directed back into the core, which allows a better neutron economy. This in turn enables more spacing between the fuel elements in the reactor, allowing better heat removal by the lead coolant. * Lead undergoes almost no activation by neutrons. Thus, virtually no radioactive elements are created by absorption of neutrons by the lead. This is in contrast to the lead-bismuth eutectic which was used in other fast designs, including in Russian submarines. The

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 ...

in this mixture (which has a lower

, 123.5 °C, than that of pure lead) is activated to form ²¹⁰Po,

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– ...

, which is a dangerous alpha emitter. * Although lead absorbs few neutrons, because of its high

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

(10.66 g/cm³, for liquid at its

), lead is very effective at absorbing

gamma rays 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 ...

and other less penetrating

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

(

alpha Alpha (uppercase , lowercase ) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter ''aleph'' , whose name comes from the West Semitic word for ' ...

and

beta particle A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus, known as beta decay. There are two forms of beta decay, β− decay and � ...

s). This ensures that radiation outside the reactor is kept at a low level. * In contrast to molten

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 ...

metal, another metallic coolant used in fast reactors, lead does not have issues with flammability, and will solidify from a leak. * The very wide temperature range at which lead remains liquid (up to 1400 K or 1126 °C) implies that any thermal excursions are absorbed without any pressure increase. In practice, the operational temperature will be kept at around – , mainly because of the limitations of metallic alloys used in reactor structural components, such as their sensitivity to

corrosion 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 ...

by a liquid metal ( liquid metal embrittlement) and amalgam-driven metal dissolution (continuous Cr and Ni extraction from the

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

). * As with all fast reactor designs, because of the high temperature and high thermal inertia,

passive cooling Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat fro ...

is possible in emergency situations. Thus, no electrical pumping assistance should be required, natural convection being sufficient to remove residual heat after shutdown. To achieve this, reactor designs include dedicated passive heat removal systems that require no electrical power and no operator action. * All fast reactor designs operate at substantial higher temperatures in the core than water cooled (and moderated) reactors. This allows a significantly higher

thermodynamic 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 a he ...

in the

steam generators A steam generator is a form of low water-content boiler (steam generator), boiler, similar to a flash steam boiler. The usual construction is as a spiral coil of water-tube boiler, water-tube, arranged as a single, or monotube boiler, monotube, c ...

. Thus, a larger portion of the

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactiv ...

energy can be converted into electricity. More than 40 % efficiency is achievable in real conditions, compared to around 30 % in water-cooled reactors. * Similarly, as with all fast spectrum reactors, the coolant is not pressurized. This means that no

pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...

is required, and the piping and ducts can be constructed with less pressure-resistant steel and alloys. Any leak in the primary coolant circuit will not be ejected at very high pressure. * Lead has a high

thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

(35 W/m・K) compared to that of water (0.58 W/m・K), which means that heat transport from the fuel elements to the coolant is efficient. * Instead of regular refueling, the whole core can be replaced after many years of operation. Such a reactor is suitable for countries that do not plan to build their own nuclear infrastructure.

Disadvantages

* Lead and lead-bismuth are very

dense Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be use ...

, increasing the weight of the system and therefore requiring more structural support and

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

protection, which increases building cost. * While lead is cheap and abundant,

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 ...

is expensive and quite rare. Depending on its size, a grid-connected lead-bismuth reactor requires hundreds or thousands of tonnes of lead-bismuth. * Solidification of lead-bismuth solution blocks the coolant circulation and immobilizes parts of the reactor control systems, rendering the reactor inoperable. However, lead-bismuth eutectic (LBE) has a comparatively lower melting temperature of , making melting a less difficult task. Lead has a higher melting point of 327.5 °С, but is often used as a pool type reactor where the large bulk of lead does not quickly freeze. * By leaking and solidifying, the coolant may damage equipment (see Soviet submarine K-64) if no measures are taken to contain such leaks. * Lead-bismuth produces

from

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emi ...

. This radioactive nuclide will dissolve in the lead-bismuth and is an alpha emitter with a

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: ...

of 138.38 days. This can seriously complicate maintenance and pose a severe plant alpha-contamination risk. The

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

emitted by has a high energy (~ 5.4 MeV). It is, therefore, highly radiotoxic in case of internal contamination of the body (

inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

and

ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, inge ...

risks) because of its high ionization density severely damaging the cells affected in the contaminated tissues. * The most challenging problems of liquid lead and LBE are the possible damage caused by

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and

to the fuel elements and reactor internals. Surface erosion is aggravated by the high

and associated

of the liquid metal circulating at elevated speed in the reactor, especially if it would become contaminated by

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

solid particles (oxides detached from metallic surfaces) or metallic debris. Corrosion is fuelled by the dissolution of metals present in

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 ...

s (e.g., Ni, Cr, released from

) in the liquid metal coolant (formation of liquid amalgam with precipitation of the dissolved metals at cold points) and the liquid metal embrittlement (LME) of the fuel claddings and structural materials of the reactor internals. To mitigate the corrosion problem, it is necessary to form a very thin and as dense as possible oxide film passivating the metallic surface. This could be achieved by accurately controlling the dissolved

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

/metallic oxides in the metallic coolant. Insufficient oxygen level would expose the bare metallic surface to severe corrosion problems. At the same time, an excess would generate thick

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

oxide films prone to be detached from the metal surface and aggravating erosion and blocking problems. The corrosion rate also increases with temperature. Newly developed alloys, such as

alumina Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...

forming austenitic steels (containing Al added as passivating agent), which maintain a protective oxide layer onto the surface of the metallic reactor components, are also being studied as candidate materials to attempt to mitigate corrosion problems. * The high density of lead and LBE means that the fuel elements, control rods and mobile reactor components are all floating in the metallic coolant, complicating the engineering systems needed to handle them and avoid floating debris. * Metallic coolants (Pb, LBE, Na) are opaque to visible light, seriously complicating the refueling and maintenance operations of the reactor, therefore requiring special systems to handle the fuel elements and the control rods safely. However, the design and operational experience already existing for sodium-cooled fast breeders could also be applied to lead-cooled fast reactors. * Lead has a positive

void coefficient In nuclear engineering, the void coefficient (more properly called void coefficient of reactivity) is a number that can be used to estimate how much the reactivity of a nuclear reactor changes as voids (typically steam bubbles) form in the reactor ...

, or void reactivity, meaning that as voids occur in the circulating coolant an increase in fertile fission and a decrease in the capture rate of all heavy nuclides results in reactivity increases as the void content inside the reactor increases, potentially leading to a positive feedback loop unless controlled by automatic mechanisms.

Implementation

Russia/USSR

Two types of lead-cooled reactor were used in

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

s of the 1970s. The OK-550 and BM-40A designs were both capable of producing 155MWt. They were significantly lighter than typical water-cooled reactors and had an advantage of being capable to quickly switch between maximum power and minimum noise operation modes.. These included a beryllium moderator and were therefore not fast-neutron reactors, but rather intermediate-neutron reactors. A joint venture called AKME Engineering was announced in 2010 to develop a commercial lead-bismuth reactor. The SVBR-100 ('Svintsovo-Vismutovyi Bystryi Reaktor' - lead-bismuth fast reactor) is based on the Alfa designs and will produce 100MWe electricity from gross thermal power of 280MWt, about twice that of the submarine reactors. They can also be used in groups of up to 16 if more power is required. The coolant increases from to as it goes through the core. Uranium oxide enriched to 16.5% U-235 could be used as fuel, and refuelling would be required every 7–8 years. A prototype was planned for 2017. Another two lead-cooled fast reactors are developed by Russians: BREST-300 and BREST-1200. The BREST-300 design was completed in September 2014. WNA mentions Russia role on boosting other countries interest in this field:

Proposals and in-development

Belgium

The

MYRRHA Myrrha (; ), also known as Smyrna (), is the mother of Adonis in Greek mythology. She was transformed into a myrrh tree after having intercourse with her father, and gave birth to Adonis in tree form. Although the tale of Adonis has Semitic r ...

project (for Multi-purpose hYbrid Research Reactor for High-tech Applications) is aimed to contribute to design a future nuclear reactor coupled to a proton accelerator (so-called Accelerator-driven system, ADS). This could be a 'lead-bismuth-cooled, or a lead-cooled, fast reactor' with two possible configurations: sub-critical or critical. It could be a pool-, or a loop-type, reactor. The project is managed by SCK CEN, the Belgian research center for nuclear energy. It is based on a first small prototype research demonstrator, the Guinevere system, derived from the zero-power reactor Venus existing at SCK CEN since the beginning of the 1960s and modified to host a bath of molten lead-bismuth eutectic (LBE) coupled to a small proton accelerator. In December 2010, MYRRHA was listed by the

European Commission The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...

as one of 50 projects for maintaining European leadership in nuclear research in the next 20 years. In 2013, the project entered a further development phase when a contract for the front-end engineering design was awarded to a consortium led by

Areva Areva S.A. was a French multinational group specializing in nuclear power, active between 2001 and 2018. It was headquartered in Courbevoie, France. Before its 2016 corporate restructuring, Areva was majority-owned by the French state through t ...

. Aiming at a compact core with high power density (''i.e.'' with a high

neutron flux The neutron flux is a scalar quantity used in nuclear physics and nuclear reactor physics. It is the total distance travelled by all free neutrons per unit time and volume. Equivalently, it can be defined as the number of neutrons travelling ...

) to be able to operate as a

materials testing reactor A materials testing reactor (MTR) is a high-flux research nuclear reactor aimed at studying materials exposed to a high neutron flux. Examples Materials testing reactors include: * SCK_CEN#BR2, BR2, the Belgian Reactor 2, moderated with a parabo ...

, the fuel to be used in the ADS MYRRHA must be highly enriched in a fissile isotope. A highly enriched

MOx Mox or MOX may refer to: People * Jon Moxley (born 1985), American professional wrestler * Mox McQuery (1861–1900), American baseball player Technology * Mac OS X, a computer operating system * Microsoft Open XML, a file format * Mixed ox ...

fuel with of was first selected to obtain the desired neutronic performances. However, according to Abderrahim ''et al.'' (2005) "this choice should still be checked against the non-proliferation requirements imposed to new test reactors by the RERTR (Reduced Enrichment of fuel for Research Testing Reactors) program launched by US DOE in 1996". So, the fuel to be selected for MYRRHA also needs to respect the criteria of non-proliferation while keeping its neutronic performance. Moreover, such a highly enriched MOx fuel has never been industrially produced and poses severe technical and safety challenges in order to prevent any

criticality accident A criticality accident is an accidental uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, divergent chain reaction, or simply critical. Any such event involves the uninten ...

during handling in the factory. In 2009, under the auspices of the

Nuclear Energy Agency The Nuclear Energy Agency (NEA) is an intergovernmental agency that is organized under the Organisation for Economic Co-operation and Development (OECD). Originally formed on 1 February 1958 with the name European Nuclear Energy Agency (ENEA)—t ...

(NEA,

OECD The Organisation for Economic Co-operation and Development (OECD; , OCDE) is an international organization, intergovernmental organization with 38 member countries, founded in 1961 to stimulate economic progress and international trade, wor ...

), an international team of experts (MYRRHA International Review Team, MIRT) examined the MYRRHA project and delivered prudent recommendations to the

Belgian government The Federal Government of Belgium ( ; ; ) exercises executive power in the Kingdom of Belgium. It consists of ministers and secretaries of state ("junior", or deputy-ministers who do not sit in the Council of Ministers) drawn from the polit ...

. Beside the technical challenges identified, they were also financial and economical risks related to the construction and exploitation costs expected to strongly increase when the project should enter a more detailed design stage. Long construction delays related to design complications, underestimated technical difficulties and insufficient budget are not uncommon for such a project. The limited participation of the Belgian State (40% of all the costs) and the uncertain benefits for the external project owners were also pointed out. Because of recurrent financial shortcomings and also important uncertainties still subsisting in the reactor design ( pool-, or loop-type, reactor?) and the choice still to be made for the liquid metal coolant (in LBE, is neutron activated producing the highly radiotoxic ⍺-emitting ) the front-end engineering design (FEED) activities had to be suspended and have not progressed beyond the preliminary stage. Quite surprisingly, the preliminary results of the FEED activities were published in a journal absolutely not related to the field of ADS or fast neutron reactor: the ''

International Journal of Hydrogen Energy The ''International Journal of Hydrogen Energy'' is a peer-reviewed scientific journal covering all aspects of hydrogen energy, including hydrogen generation and storage. It is published by Elsevier and is an official journal of the Internation ...

(IJHE)'' while there was never any question of producing

with MYRRHA. The choice of this journal to present the preliminary results of the FEED activities is disconcerting. The journal where the FEED activities were announced, ''Physics Procedia'', is also discontinued. Beside continuously increasing costs and financial uncertainties, the project still has to address many technical challenges: severe corrosion issues ( liquid metal embrittlement, amalgam-driven dissolution in the molten metal of Cr and Ni from the

used for the fuel claddings and reactor structure materials), operating temperature (metal solidification risks versus increased corrosion rate), nuclear criticality safety issues... The mass inventory of the lead-bismuth eutectic (LBE) for the proposed pool-type design of MYRRHA considered in the preliminary FEED analyses of 2013-2015 represents 4500 tons metallic Pb-Bi. This would lead to the production of more than 4 kg of during the reactor operations. After the first operating cycle, 350 g of would already be formed in the LBE exposed to a high

of the order of 10 neutrons・cm・s, typical for a

(MTR). This would correspond to an activity of 5.5 × 10

becquerel The becquerel (; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as an activity of one per second, on average, for aperiodic activity events referred to a radionuclide. For applicatio ...

s, or 1.49 × 10 curies of , just for the first operation cycle. The presence of such a large ponderable quantity of highly radiotoxic represents a considerable radiological safety challenge for the maintenance operations and the storage of the MYRRHA nuclear fuel. Because of the high volatility of , the plenum space above the reactor could also become alpha-contaminated. As pointed out by Fiorito ''et al.'' (2018): "Some polonium will migrate to the cover gas in the reactor plenum and will diffuse outside the primary system when the reactor is opened for refueling or maintenance". All operations in contaminated areas will require appropriate radiological protection measures much more severe than for the handling, or to be completely performed by remotely-operated robots. An envisaged mitigation strategy could consist into a continuous removal of polonium from LBE, but the considerable heat generated by represents a major obstacle. In 2023, based on interviews with key SCK CEN players and documents publicly available, Hein Brookhuis explored the interactions between the MYRRHA promoters and the Belgian media and political spheres to show how MYRRHA was developed in a narrative that made the project seems essential to the future of SCK CEN, the Belgian nuclear research center.

France/Italy

Paris based company newcleo is developing 30 MWe and 200 MWe lead-cooled

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 ...

s for naval and land use. The first operational reactor is planned to be deployed in 2031 in France. By 2026 a electrical simulator of a liquid-lead cooled reactor named PRECURSOR is to be built by ENEA and newcleo at the ENEA Research Center in Brasimone (Bologna, Italy).

Germany

The '' dual fluid reactor'' (DFR) project was initially developed by a German research institute, the Institute for Solid-State Nuclear Physics, in Berlin. In February 2021, the project was transferred to a newly founded Canadian company, Dual Fluid Energy Inc., to industrialize the concept. The DFR project attempts to combine the advantages of 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 mixture of molten salt with a fissile material. Two research MSRs operated in the United States in the mid-20th ...

with these of the

liquid metal cooled reactor A liquid metal cooled nuclear reactor (LMR) is a type of nuclear reactor where the primary coolant is a liquid metal. Liquid metal cooled reactors were first adapted for breeder reactor power generation. They have also been used to power nuclear ...

. As a fast breeder reactor, the proposed DFR reactor is designed to burn both natural

uranium Uranium is a chemical element; it has chemical symbol, 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. Ura ...

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

, as well as transmutating and fissioning minor

actinide The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...

s. Due to the high

of the molten metal, the residual decay heat of a DFR reactor could be passively removed.

Italy/Romania

ALFRED Alfred may refer to: Arts and entertainment *''Alfred J. Kwak'', Dutch-German-Japanese anime television series * ''Alfred'' (Arne opera), a 1740 masque by Thomas Arne * ''Alfred'' (Dvořák), an 1870 opera by Antonín Dvořák *"Alfred (Interlu ...

(Advanced Lead Fast Reactor European Demonstrator) is a lead cooled fast reactor demonstrator designed by

Ansaldo Energia Ansaldo Energia S.p.A. is an Italian power engineering company based in Genoa, Italy. The original parent company, Gio. Ansaldo & C., was founded in 1853, and merged with Finmeccanica in 1993 (now Leonardo S.p.A.). In 2024, the company's sha ...

from Italy, planned to be built in Mioveni, Romania. ATHENA, a molten lead pool used for research purposes, is going to be built in the same site as well.

Russia

The BREST reactor is currently under construction. This reactor will employ pure lead as coolant, a plutonium/uranium nitride fuel, generate 300 MWe (electric) from 750 MWth, and is a pool type reactor. The foundation has been completed in November 2021. The reactor sits as the Siberian Chemical Combine's (SCC's) Seversk site.

Sweden

The company Blykalla is in collaboration with

KTH Royal Institute of Technology KTH Royal Institute of Technology (), abbreviated KTH, is a Public university, public research university in Stockholm, Sweden. KTH conducts research and education in Institute of technology, engineering and technology and is Sweden's largest te ...

and

Uniper Uniper SE is a German multinational energy company based in Düsseldorf, Germany, which has been a state-owned enterprise since late 2022. It is one of the biggest energy companies by revenue in Europe. The name of the company is a portmanteau o ...

developing the SEALER-55 (Swedish Advanced Lead Reactor) reactor, a 55 MW lead-cooled mass-produced reactor using uranium nitride as fuel. The

Government of Sweden The Government of the Kingdom of Sweden () is the Cabinet (government), national cabinet of Sweden, and the country's Executive (government), executive authority. The Government consists of the Prime Minister of Sweden, Prime Minister and their ...

committed 720 million

Swedish krona The krona (; plural: ''kronor''; sign: kr; code: SEK) is the currency of Sweden. Both the ISO code "SEK" and currency sign "kr" are in common use for the krona; the former precedes or follows the value, the latter usually follows it but, espec ...

and started building a test facility in early 2025 for a lead-cooled prototype reactor. The reactor, called SEALER-E, is planned to be built by 2026 in collaboration with

ABB ABB Group is a Swedish-Swiss multinational electrical engineering corporation. Incorporated in Switzerland as ABB Ltd., and headquartered in Zurich, it is dual-listed on the Nasdaq Nordic exchange in Stockholm, Sweden, and the SIX Swiss Excha ...

. The first commercial nuclear reactor (SEALER-One) is planned to be built in Oskarshamn in with the hope of reaching criticality in 2029. Serial production of the SEALER-55 is planned to start in the early 2030's.

United States

The initial design of the Hyperion Power Module was to be of this type, using uranium nitride fuel encased in HT-9 tubes, using a quartz reflector, and lead-bismuth eutectic as coolant. The firm went out of business in 2018. The

Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...

developed SSTAR was a lead-cooled design.

References

External links

* * ttps://web.archive.org/web/20100814214140/http://www.inl.gov/research/lead-cooled-fast-reactor/ Idaho National Laboratory: Lead-cooled Fast Reactor – Fact sheet
Heavy-metal aerosol transport in a lead-bismuth cooled fast reactor with in-vessel direct-contact steam generation.
(from web.archive.org)
RBEC-M lead-bismuth cooled fast reactor benchmarking calculations
* * {{Nuclear fission reactors Liquid metal fast reactors Lead