The SMART is a system-integrated modular reactor in which a nuclear steam supply system with a thermal power of 365 MW is contained inside of the reactor vessel. Although the probability is very low, the reactor core can be damaged during a small break loss-of-coolant accident when both the passive safety injection system and the passive residual heat removal system are completely unavailable. In this work, a total of five cases were analyzed considering the reactor vessel condition and the availability of the radioactivity removal tanks and the ancillary containment spray system as containment condition variables using MELCOR code. It was estimated that there is no containment failure based on pressure, hydrogen mole fraction, and ablation depth, so that the release fractions of the 12 classes of fission products in MELCOR were evaluated considering design leak only for all cases. The overall source term of the case in which the integrity of the reactor vessel is maintained by the early initiation of the cavity flooding system was similar to that of the reactor vessel failure case. While the release fraction of cesium to the environment was analyzed to increase when there is no water in the radioactivity removal tanks, the fraction is small enough at which the radioactivity of the released cesium-137 remains well below 100 TBq, a regulatory limit. Moreover, it was found that the source term can be cut in half if the ancillary containment spray system is available. The results of this study verify the safety performance of the SMART under the small break loss-of-coolant severe accident condition with respect to the source term of interest.

中文翻译：

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SMART中SBLOCA引发的严重事故情况下的源术语估计

SMART是系统集成的模块化反应堆，其中反应堆容器内部装有热功率为365 MW的核蒸汽供应系统。尽管概率很小，但是当被动安全注入系统和被动余热排除系统都完全不可用时，在很小的冷却剂中断损失事故中，反应堆堆芯可能会损坏。在这项工作中，使用MELCOR代码将反应堆容器的状况以及放射性去除罐和辅助安全壳喷雾系统的可用性作为安全壳条件变量进行了总共五种情况的分析。根据压力，氢摩尔分数和烧蚀深度，估计没有安全壳失效，因此，仅考虑所有情况下的设计泄漏，即可评估MELCOR中12类裂变产物的释放分数。通过型腔溢流系统的早期启动来维持反应堆容器完整性的情况的总的源术语类似于反应堆容器故障情况的情况。当在放射性去除罐中没有水时，分析了铯向环境的释放分数增加，但该分数足够小，在此分数下，释放出的铯137的放射性仍远低于规定的极限100 TBq。此外，还发现如果可以使用辅助安全壳喷淋系统，则可以将源术语减少一半。