ABSTRACT

The vapor formation within the reactor pressure vessel (RPV) is regarded to represent heat removal from core materials to the coolant, while the hydrogen generation within the RPV is regarded to represent heat generation by metal oxidation. Based on this understanding, the history of the vapor/hydrogen generation in the in-vessel phase of Fukushima Daiichi Nuclear Power Station Unit 3 was evaluated based on the comparison of the observed pressure data and the GOTHIC code analysis results. The resultant vapor/hydrogen generation histories were then converted to heat removal by coolant and heat generation by oxidation. The effects of the decay power and the heat transfer to the structures on the core material energy were also evaluated. The core materials are suggested to be significantly cooled by water within the RPV, especially when the core materials are relocated to the lower plenum. The results of this study combined with the existing severe accident (SA) code analyses suggested that the debris relocated to the lower plenum was effectively cooled down near the liquid water temperature within a few hours after the relocation.

摘要

在反应堆压力容器（RPV）中形成的蒸气被认为代表了从堆芯材料到冷却剂的热量去除，而在RPV中产生的氢被认为代表了由金属氧化产生的热量。基于该认识，基于观察到的压力数据和GOTHIC代码分析结果的比较，评估了福岛第一核电站3号机组船内相中蒸汽/氢气产生的历史。然后将所得的蒸气/氢气产生历史转换成通过冷却剂除热和通过氧化产生热量。还评估了衰减功率和热传递到结构对核心材料能量的影响。建议核心材料被RPV中的水显着冷却，尤其是在将核心材料移至下充气室时。这项研究的结果与现有的严重事故（SA）规范分析相结合，表明搬迁到下气室的碎片在搬迁后数小时内在液态水温度附近得到了有效冷却。