Thus, virtually no radioactive elements are created by absorption of neutrons by the lead. Lead undergoes almost no activation by neutrons.This in turn enables more spacing between the fuel elements in the reactor, allowing better heat removal by the lead coolant. ![]() Neutrons escaping the core of the reactor are to some extent directed back into the core, which allows a better neutron economy. Molten lead acts as a reflector for neutrons.This is similar to other fast reactor concepts, including the molten liquid sodium designs. Thus, the neutrons are not slowed down by lead, which ensures that the neutrons keep their high energy. When the neutron collides with atoms that are much heavier than itself, almost no energy is lost in the process. Moderation occurs when neutrons are slowed down by repeated collisions with a medium. Molten lead does not significantly moderate neutrons.The use of lead as a coolant has several advantages if compared to other methods for reactor cooling. It is designed for generation of electricity on small grids (and other resources, including hydrogen and potable water).Īdvantages of lead in fast reactors 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. Other options include units featuring long-life, pre-manufactured cores, that do not require refueling for many years. ![]() The Soviet union successfully operated the Alfa class submarines with a lead-bismuth cooled fast reactor in the sixties and seventies, which had approximately 30 MW of mechanical output for 155 MW thermal power (see below). Reactors that use lead or lead-bismuth eutectic can be designed in a large range of power ratings. ![]() 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. The lead-cooled reactor design has been proposed as a generation IV reactor. The concept is generally very similar to sodium-cooled fast reactor, and most liquid-metal fast reactors have used sodium instead of lead.įew lead-cooled reactors have been constructed, except for some Soviet nuclear submarine reactors in the 1970s, but a number of proposed and one in construction new nuclear reactor designs are lead-cooled. Temperatures higher than 800 ☌ are theoretically high enough to support thermochemical production of hydrogen through the sulfur-iodine cycle, although this has not been demonstrated. The reactor outlet coolant temperature is typically in the range of 500 to 600 ☌, possibly ranging over 800 ☌ with advanced materials for later designs. No operator interference is required, nor pumping of any kind to cool the residual heat of the reactor after shutdown. Smaller capacity lead-cooled fast reactors (such as SSTAR) can be cooled by natural convection, while larger designs (such as ELSY ) use forced circulation in normal power operation, but will employ natural circulation emergency cooling. The coolant does, however, serve as a neutron reflector, returning some escaping neutrons to the core.įuel designs being explored for this reactor scheme include fertile uranium as a metal, metal oxide or metal nitride. In contrast, if it hits a much heavier atom such as lead, the neutron will "bounce off" without losing this energy. In simple terms, if a neutron hits a particle with a similar mass (such as hydrogen in a Pressurized Water Reactor PWR), it tends to lose kinetic energy. Neutrons are slowed less by interaction with these heavy nuclei (thus not being neutron moderators) and therefore, help make this type of reactor a fast-neutron reactor. 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 melting points. ![]() The lead-cooled fast reactor is a nuclear reactor design that features a fast neutron spectrum and molten lead or lead-bismuth eutectic coolant. Type of nuclear reactor cooled by molten lead
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