A behavior of O/M ratio and its effect for material accounting in high plutonium concentration MOX fabrication process

An evaluation test to investigate the behavior of the Oxygen to Metal ratio (hereinafter refer to O/M ratio) drift and its effect to material accounting in high plutonium concentration MOX fuel fabrication process was carried out in operational MOX fuel fabrication process of FBR line, Plutonium Fuel Production Facility (hereinafter refer to PFPF), Power Reactor and Nuclear Fuel Development Corporation (PNC). Because of the oxidation of uranium by the decay heat from plutonium in MOX, the O/M ratio may drift in powder treatment processes, and this may affect plutonium concentration of MOX, which is fundamental parameter of material control in MOX fabrication facility. To understand the behavior of O/M ratio, therefore, is important for material accounting in MOX facility. Also, if a non-uniform distribution of O/M ratio exists within a container accommodating feed powder or interim product of in-process, sample taking procedure should be established in such a way to obtain representative sample. Based on those consideration, the test was carried out in 1995 with PFPF. Gained experience with the improvement for material accounting system is discussed in this paper. (author)