ON feasibility of using nitride and metallic fuel in the MBIR reactor core

Abstract MBIR is a multipurpose fast sodium cooled research reactor with a thermal power of 150 MW designed for a broad range of applications in the field of experimental research, including endurance tests and optimization of operating modes for advanced types of fuel, fuel elements, absorber elements and fuel assemblies, radiation tests of advanced structural materials, production of isotopes for a variety of applications and so on [1,2] . Therefore, one of the major requirements to this reactor is a high flux of neutrons (not lower than 5⋅10 15 n/cm 2 s) depending, in turn, on the type of the fuel used. Vibrocompacted MOX fuel with a plutonium weight content of ∼38% has been adopted currently as the standard MBIR fuel. The capabilities offered by the use of alternative highly dense fuel types in this reactor appear to be promising for the future large-scale nuclear power. The most attractive fuel types for advanced fast reactors are mixed nitride uranium–plutonium fuel and mixed metallic fuel (a three-component uranium-plutonium-zirconium alloy). Studies on the MBIR reactor, involving advanced dense fuel types, have shown that nitride fuel does not make it possible to achieve the required neutron flux value, while metallic fuel provides for the required neutron flux (practically the same as MOX fuel) and a high dpa rate but requires modified temperature conditions of irradiation. The specific neutronic properties of these fuel types, as compared to the standard MOX fuel, have also been identified.