Survey of N isotopic enrichment plant and its cost for nitride fuel fabrication (Contract research)

Takano, Masahide 

Nitride is one of the potential fuel forms for minor actinide transmutation by the accelerator driven system. However, to avoid the C production from N by (n, p) reaction in the fuel, the special N gas highly enriched with N is needed for the fuel fabrication. To realize the availability of such gas has been an important issue. In this report, the degree of N enrichment and gas amount required for the fuel fabrication are shown first, and then among the existing isotopic enrichment methods, N cryogenic distillation is found to be a promising method from the viewpoint of constructing a huge scale plant because of its non-hazardous feature. Some commercial plants for O enrichment based on the similar method have already been operated in Japan. Its technology and components can be applied to the N enrichment plant. Assuming the supply of N gas from a cryogenic distillation plant, a series of enrichment simulation is performed to evaluate the plant size as functions of targeted degree of enrichment and annual production. By using the simulation results, the basic specifications for plant components and equipment are designed. As a result, a huge plant for annual production of 1000 kg N gas with 99% enrichment is found to be technically feasible. The N gas production cost is also evaluated to be approximately 1/30 of the current distribution price. This survey shows the availability of N gas required for the nitride fuel fabrication in both technical and economic aspects.