Abstract Reactor pressure vessel (RPV) failure analysis is a thermo-fluid-structure coupled problem involving the melt pool heat transfer and RPV structural failure. It is of great importance to the qualification of severe accident mitigation strategies as well as the general assessment of severe accident risk in light water reactors. Two coupling approaches, i.e. volume loads mapping (VLM) and surface loads mapping (SLM), are widely employed to resolve this problem. The present study was intended to compare the performance of the two coupling approaches by simulating vessel failure problems of the FOREVER-EC2 experiment and a reference boiling water reactor (BWR) during a postulated severe accident. Simulations of the experiment using the two different approaches showed good agreements with experimental data in terms of total deformation in vertical direction of bottom point and wall thickness changes. The spatial distributions of creep strain and total deformation were also similar between the two approaches. For the reference BWR case, good agreements were achieved between the two approaches in predicting the maximum creep strain and the total deformation in vertical direction of bottom point. The deformation rate of the vessel wall was slow at the beginning, and then increased with time, and finally accelerated to a drastic deformation prior to vessel failure. Similar spatial distributions of creep strain and total deformation were also predicted by the two approaches. Although the SLM approach predicted the deformation acceleration began slightly earlier than the VLM, the difference between the predicted failure times was negligible if considering the very long vessel failure time (~ 10 4 s) and various uncertainties. Generally speaking, the VLM approach was computationally more efficient than the SLM, while both approaches had similar performances in terms of their predictability of experiment and applicability to reactor case.

中文翻译：

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两种热-流-固耦合方法反应堆压力容器失效对比分析

摘要 反应堆压力容器（RPV）失效分析是一个涉及熔池传热和RPV结构失效的热-流体-结构耦合问题。它对减轻严重事故战略的资格以及对轻水反应堆严重事故风险的一般评估具有重要意义。两种耦合方法，即体积载荷映射（VLM）和表面载荷映射（SLM），被广泛用于解决这个问题。本研究旨在通过模拟 FOREVER-EC2 实验和参考沸水反应堆 (BWR) 在假定严重事故期间的容器故障问题来比较两种耦合方法的性能。使用两种不同方法的实验模拟表明，在底部点垂直方向的总变形和壁厚变化方面与实验数据具有良好的一致性。两种方法的蠕变应变和总变形的空间分布也相似。对于参考 BWR 情况，两种方法在预测最大蠕变应变和底部点垂直方向的总变形方面取得了良好的一致性。血管壁的变形速度开始缓慢，然后随着时间的推移而增加，最终加速到容器破坏前的剧烈变形。两种方法还预测了蠕变应变和总变形的相似空间分布。尽管 SLM 方法预测变形加速开始的时间略早于 VLM，但如果考虑到非常长的容器失效时间（~ 10 4 s）和各种不确定性，预测失效时间之间的差异可以忽略不计。一般来说，VLM 方法在计算上比 SLM 更有效，而两种方法在实验的可预测性和反应堆案例的适用性方面具有相似的性能。