[2E10-13] Accident Progression

5:15 PM - 5:30 PM JST(8:15 AM - 8:30 AM UTC)

[2E12] FP migration analysis in the D/W of Fukushima Daiichi NPP Unit-2 before and after the core damage using GOTHIC code

*Kenichiro Nozaki¹, Penghui Chai¹, Shoichi Suehiro¹, Masato Mizokami², Mutsumi Hirai², Akitoshi Hotta², Shinya Mizokami² (1. TEPSYS, 2. TEPCO HD)

Keywords:

Fukushima Daiichi Nuclear Power Plant Unit-2,FP migration,D/W CAMS readings,GOTHIC code

To estimate the time and amount of Cs that caused the high dose rate at the shield plug of Fukushima Daiichi NPP Unit-2, the behavior of FP migration inside the Unit 2 D/W during the period of core damage progression was estimated using GOTHIC v8.4(QA). CsI aerosols, which would be the main source of radiation at the time, were introduced in a way that was consistent with the D/W CAMS readings. A temporary gas leakage from the D/W top head flange were tentatively assumed. As a result, it was estimated that the amount of CsI leaked from D/W during this period was small and the leakage that caused the high contamination at the shield plug occurred at a later stage.