Estimation of the core-material-relocation behaviors to the pedestals in Fukushima-Daiichi Units 2 and 3

Sato, Ikken*; Yamaji, Akifumi*; Li, X. ; Yamashita, Takuya  ; Mizokami, Shinya*

The current presentation used published MAAP and ANSYS analyses to evaluate core-material relocation from the Reactor Pressure Vessels (RPVs) to the pedestals in Fukushima Daiichi Units 2 and 3. Although uncertainties remain regarding the effectiveness of alternative water injection for cooling, these evaluations provide a basis for estimating RPV boundary degradation and core-material relocation. In Unit 2, the ELSA-1 experiment indicates that CRD penetration melting occurring at 1523K to 1573 K led to significant molten metal relocation in the afternoon of March 15, accompanied by predicted RPV side-wall creep failure. In Unit 3, early-morning CRD penetration melting (ca. 3:00 to 5:00) resulted in both molten metals and oxidic debris relocating to the pedestal. A two-step increase in PCV pressure further supports a multi-stage relocation process.