Thermal expansion of corium prepared from UO and zircalloy-2

Hirooka, Shun ; Akashi, Masatoshi ; Uchida, Teppei; Morimoto, Kyoichi ; Kato, Masato   

As a part of severe accident research in LWRs, physical and chemical properties of corium formed by meltdown of the reactor core have been studied. The corium consists of two kinds of phases, Zr-rich phase and U-rich phase. The U-rich phase has fluorite structure and Zr-rich phase has monoclinic structure which transforms to tetragonal and fluorite structure with temperature. These phase transformations with temperature change cause volume change and cracks. In this study, the corium was prepared from Zry-2 and UO, and thermal expansion was measured. Then, volume change with phase transformation was analyzed from the results.