Structure of image crystal in uranium dioxide arised from precipitated helium

Serizawa, Hiroyuki  ; Kaji, Yoshiyuki  ; Oishi, Yuji*; Yamanaka, Shinsuke*; Matsunaga, Junji*

We found that porous UO grain was formed by the precipitation of helium injected by HIP. Scanning electron microscopy analysis showed that polyhedral negative crystals were formed in the sample. The shape of the negative crystal changes dramatically with the conditions of helium precipitation. A truncated octahedron-type, an octa-triacontahedron-type, and a pentacontahedron-type negative crystal were observed. Our study implies that the shape of the negative crystal should change depending on the helium inner pressure enclosed in the negative crystal.