Melting temperatures of the ZrO-MOX system

ZrO-MOX系の融点

内田 哲平; 廣岡 瞬 ; 菅田 博正*; 柴田 和哉*; 佐藤 大介*; 加藤 正人   ; 森本 恭一 

Uchida, Teppei; Hirooka, Shun; Sugata, Hiromasa*; Shibata, Katsuya*; Sato, Daisuke*; Kato, Masato; Morimoto, Kyoichi

Severe accidents occurred at the Fukushima Daiichi Nuclear Power Plant of Unit 1-3 on March 11, 2011, where the MOX fuels were loaded in the Unit 3. For thermal analysis of the severe accident, melting temperature and phase state of MOX corium were investigated. The simulated coria were prepared from 4%Pu-containing MOX, 8%Pu-containing MOX and ZrO. Then X-ray diffraction, density and melting temperature measurements were carried out as a function of zirconium and plutonium contents. The cubic phase was observed in the 25%Zr-containing corium and the tetragonal phase was observed in the 50% and 75%Zr-containing coria. The lattice parameter and density monotonically changed with Pu content. Melting temperature increased with increasing Pu content; melting temperature were estimated to be 2932K for 4%Pu MOX corium and 3012K for 8%Pu MOX corium in the 25%ZrO-MOX system. The lowest melting temperature was observed for 50%Zr-containing corium.