higher melting point of 327.5 °С, but is often used as a pool type reactor where the large bulk of lead does not easily freeze. By leaking and solidifying, the coolant may damage equipment (see Soviet submarine K-64), if measures to contain such leaks are not taken. Lead-bismuth produces a considerable amount of polonium from neutron activation of bismuth. This radioactive element will dissolve in the lead-bismuth, and is an alpha emitter with a half-life of 138 days. This can complicate maintenance and pose a plant contamination problem. The alpha particle emitted has a high energy, and is therefore hazardous. Pure lead produces orders of magnitudes less polonium, and so has an advantage over lead-bismuth in this regard. The most challenging problem of lead is the potential for erosion and corrosion of the reactor internals. New specialized materials such as alumina forming austenitic steels, which maintain a protective oxide layer on the reactor components, are candidates under investigation. 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