[3K01-09] 1F Accident 2

[3K07] Estimation of RPV damage and fuel debris relocation behavior in the PCV at Fukushima Daiichi Nuclear Power Station

(7)Clarification of boundary conditions for evaluation of the core material relocation behavior

*Ikken Sato¹, Akifumi Yamaji¹, Xin Li², Takuya Yamashita yamashita² (1. Waseda University, 2. Japan Atomic Energy Agency)

Keywords:Fukushima Daiichi Nuclear Power Station (1F), Unit 2 accident progression behavior, Estimation of 1F plant internal condition, debrisEye

Concerning core material relocation behavior to the pedestal, certain progress has been made in clarification of boundary conditions for Unit 3 through plant data analysis and analytical evaluations. On the other hand, there was large uncertainty regarding Unit 2 due to missing periods of plant data. However, there has been significant progress in recent researches addressing this, such as those in this series (Series (2)(4)(5)) and a comprehensive review of radioactive material release to environment. Based on these latest research results, boundary conditions related to evaluation (such as Series (2) (8)) of core material relocation behavior in Unit 2 were derived. As a result, it was understood that the relocation of Unit 2 core materials to the pedestal mainly occurred in the afternoon of March 15^th, and that the relocation consisted mainly of molten metals, possibly through leakage at the CRD (Control Rod Drive mechanism) housing penetrations on the RPV (Reactor Pressure Vessel) wall, in addition to the RPV side wall failure discussed in Series (5).