Failure behavior of BWR lower head due to reaction with molten metallic materials

溶融金属との反応によるBWR原子炉圧力容器下部ヘッド破損挙動

佐藤 拓未 ; 山下 拓哉  ; 下村 健太 ; 永江 勇二 

Sato, Takumi; Yamashita, Takuya; Shimomura, Kenta; Nagae, Yuji

The reaction between the molten metallic debris pool and the structural materials of reactor pressure vessels (RPV) is important in understanding the RPV failure behavior. In this study, the ELSA (Experiment on Late In-vessel Severe Accident Phenomena)-1 test, which focuses on the damage caused by the eutectic melting of the liquid metal pool and control rod drive (CRD) structures, was conducted. A test sample simulating the CRD structure at the lower head was fabricated and loaded with Fe-Zr alloy as the simulated metal debris. The sample was gradually heated to about 1400 C using the LIESAN test facility, and in-situ observation was performed using a video camera. The test results showed that the CRD structural material reacted with the metal debris and melted at about 1050-1250 C, which was lower than the melting point of the CRD itself. It was also observed that the molten material flowed into the CRD, suggesting that the CRD structure was preferentially damaged during the severe accident.