Estimation of reactor vessel failure by metallic interaction in Fukushima Daiichi Nuclear Power Plant accident

ABSTRACT

The reactor pressure vessel (RPV) failure timing in Unit 1–3 of the Fukushima Daiichi Nuclear Power Plant was estimated by considering the metallic interactions in the lower plenum. The re-molten core materials could attack and penetrate the weld and, hence, the materials science aspect is expected to provide insights that can assist in the estimation of RPV failure. First, to examine the chemical interaction between the molten fuel and the stainless steel during relocation and slumping, the mass of uranium transported to the stainless steel as reaction products was computed based on the analytical relations for the U-Zr-O-Fe-Cr interaction. Second, the time required for the stainless-steel bearing uranium to liquefy and attack the stainless-steel welds was calculated using decay heat when each unit was considered to have dried out. Finally, the RPV failure timings were obtained and compared with those estimated from the thermal–hydraulic aspects. The calculated results show good agreement with the latest failure timing within the range of 0.5 h, and the metallic interaction scenario could successfully provide the interpretation. It may become possible to improve the accuracy of the estimation to account for the local composition and porosity in the relation with the properties of the metallic component systems.

KEYWORDS:

• Fukushima Daiichi Nuclear Power Plant
• RPV failure
• metallic interaction
• U-Zr-O/stainless-steel interaction
• severe accident
• BWR
• core melt progression

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Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).