Lead-cooled fast reactor

The lead-cooled fast reactor is a nuclear reactor design that features a fast neutron spectrum and molten lead or lead-bismuth eutectic coolant. 
Molten lead or lead-bismuth eutectic can be used as the primary coolant because lead and bismuth have low neutron absorption and relatively low melting points. 
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. 
The coolant does, however, serve as a neutron reflector, returning some escaping neutrons to the core.
Fuel designs being explored for this reactor scheme include fertile uranium as a metal, metal oxide or metal nitride.
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 with natural circulation emergency cooling. 
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 high enough to support thermochemical production of hydrogen through the sulfur-iodine cycle.
The concept is generally very similar to sodium-cooled fast reactor, and most liquid-metal reactors have used sodium instead of lead. 
Few lead-cooled reactors have been constructed, except for some Soviet nuclear submarine reactors in the 1970s, but a number of proposed new nuclear reactor designs are lead-cooled.
The lead-cooled reactor design has been proposed as a generation IV reactor.
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.
Modular nuclear reactors.
Options include a range of plant ratings, including a number of 50 to 150 MWe (megawatts electric) units featuring long-life, pre-manufactured cores.
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 and potable water).
Implementation.
Russia/USSR.
Two types of lead-cooled fast reactor were used in Soviet Alfa class submarines 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.
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 is planned for 2017.
Another two lead cooled 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 project (for Multi-purpose hYbrid Research Reactor for High-tech Applications) is a first-of-a-kind design of a nuclear reactor coupled to a proton accelerator (so-called Accelerator-driven system (ADS)). This will be a 'Lead-bismuth-cooled fast reactor' with two possible configurations: sub-critical or critical.
The project is managed by SCK•CEN, the Belgian center for nuclear energy. It will be built based on a first successful demonstrator: GUINEVERE. The project entered a new phase of development in 2013 when a contract for the front-end engineering design was awarded to a consortium led by Areva.
MYRRHA enjoys international recognition and was listed in December 2010 by the European Commission as one of 50 projects for maintaining European leadership in high-tech research in the next 20 years.
United States.
According to Nuclear Engineering International, 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 Lawrence Livermore National Laboratory developed SSTAR is a lead-cooled design.
Germany.
The "dual fluid reactor" (DFR) is a German project combining the advantages of the molten salt reactor with the ones of the liquid metal cooled reactor. As a breeder reactor the DFR can burn both natural uranium and thorium, as well as recycle nuclear waste. Due to the high thermal conductivity of the molten metal, the DFR is an inherently safe reactor (the decay heat can be removed passively).