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.

摘要

福岛第一核电站 1-3 号机组的反应堆压力容器 (RPV) 故障时间是通过考虑下腔室中的金属相互作用来估计的。重新熔化的核心材料可能会侵蚀并穿透焊缝，因此，材料科学方面有望提供有助于估计 RPV 故障的见解。首先，为了检查在重新定位和坍塌过程中熔融燃料和不锈钢之间的化学相互作用，根据 U-Zr-O-Fe-Cr 的解析关系计算了作为反应产物输送到不锈钢的铀的质量相互作用。其次，当每个单元被认为已经变干时，使用衰变热计算不锈钢轴承铀液化和侵蚀不锈钢焊缝所需的时间。最后，获得 RPV 故障时间，并与从热-水力方面估计的时间进行比较。计算结果与最新的失效时间在 0.5 h 范围内吻合良好，金属相互作用场景可以成功地提供解释。可能会提高估计的准确性，以将局部成分和孔隙率与金属部件系统的特性相关联。