Annealing behavior of (Pu,Cm)O lattice and bulk expansion from self-irradiation damage

Takano, Masahide ; Akabori, Mitsuo; Arai, Yasuo

In order to investigate the effect of self-irradiation damage and accumulation of He on the oxide fuel pellet containing minor actinides, the expansion and annealing behavior of (PuCm)O lattice and bulk were examined comparatively. Since the lattice and bulk expansion at room temperature showed the similar dependence on the storage duration, the main factor of bulk swelling was found to be the lattice expansion due to the generation of point defects. The lattice parameter recovered to the undamaged value by annealing at 1429 K for 2 h, whereas the bulk expanded again by annealing at 1433 K and did not recover to the undamaged value at all. On the micrographs of fracture surface of the annealed pellet, formation of gas bubbles along grain boundaries was confirmed. The accumulated He atoms migrated to the grain boundaries and formed gas bubbles, which caused the He gas swelling of the pellet.