R&D on nitride fuel cycle for MA transmutation to enhance safety and economy, 14; Dimensional recovery of He-accumulated nitride pellet containing Cm by annealing

Takano, Masahide ; Takaki, Seiya  

To clarify the influence of high temperature He gas release on the MA transmutation fuel behavior, annealing experiments on a Cm-bearing nitride pellet were carried out after two years of storage at room temperature, and the results were compared with those on the Cm-bearing dioxide. Just before the annealing, the nitride pellet showed the large expansion value of 1.1%, which suggests that vacancies in grains formed voids at room temperature. During the annealing experiments, the gas swelling of the nitride pellet due to He release above 800C was relatively slight. From the microstructure images, smaller grains and higher open-porosity of the nitride pellet resulted in the slight gas swelling. After the annealing at 1300C, the nitride pellet still had expansion value of 0.6%, that should be taken into account when designing the pellet-cladding gap.