Molten Fuel Fast Reactor: Concept of Core, Fuel Efficiency, and Safety

This paper examines two options for a fast reactor core with the molten metal fuel. It is proposed to use fuel elements in the form of the sealed tungsten capsules filled with a mixture of waste metal uranium powders (80%) and concentration of the
²³⁵
U isotope of about 0.2% and metallic plutonium (20%) extracted from the spent nuclear fuel from a VVER (water-water energy reactor), which was previously purified from the
²³⁸
Pu isotope. Molten fuel natural convection in the fuel rods would make it possible to separate fission products during the reactor operation. They would be concentrated in the upper layer of the liquid fuel rods, i.e. above the core. During reactor operation, the fuel burns out, and the core height would gradually decrease. This helps in reducing the reactivity void effect. Criticality is compensated by the secondary fuel production, i.e. the breeding factor in the core is about 1.06. The reactor is able to operate on the lowenriched fuel: the fissile material concentration does not exceed 6…7%. Calculations show that such a reactor is safe. It is able to operate in the high-temperature and ultra-high-temperature reactor modes.