Fabrication of (U,Pu)N fuel pellets

Uranium-plutonium mixed nitride, (U,Pu)N, was fabricated by the carbothermic reduction in a N2-8% H2 mixed gas stream from UO2 and PuO2. The influence of the sintering conditions, such as milling time, compacting pressure, sintering temperature, sintering atmosphere and pore former content, on the characteristics of (U,Pn)N pellets was systematically investigated. High density (≅ 95% TD) pellets were obtained by sintering at 2023 K in an Ar-8% H2 or Ar stream without loss of plutonium using the highly activated powder. On the other hand, low density (≅ 85% TD) pellets with excellent thermal stability were fabricated by sintering with pore former particles. The difference in the microsctructure or composition was discussed in connection with the sintering conditions. Certain increase in the lattice parameter of (U,Pu)N was observed during sintering stage. (orig.)