Abstract A floating nuclear power plant (FNPP) is a kind of nuclear power plant on a barge moored specifically in an area of the sea. This study focuses on a severe accident induced by cold leg small break loss of coolant accident (SBLOCA) occurring in a small modular reactor (SMR) in a FNPP of 100 MWt 2-loop pressurized water reactor (PWR) type. The severe accident was modeled using MELCOR computer code. A MELCOR model was developed for the primary and secondary systems, the engineered safety features, and the containment of the SMR. Three severe accident mitigation measures were analyzed using the model, namely the pressurizer (PZR) relief extension, the external vessel reactor cooling (EVRC), and the passive autocatalytic recombiners (PARs). The progression of the severe accident and the effects of three mitigation measures against the severe accident were analyzed. The simulation results indicated that the reactor core was exposed and heat up due to the coolant leakage and finally melted down due to high-pressure and lower-pressure injection failure. However, with the mitigation measures against the severe accident, the reactor pressure vessel (RPV) and containment integrity were maintained, thus preventing the large release of radioactive products into other cabins and the environment. Comparative analysis results also showed that all the three measures performed their scheduled functions and were significant in mitigating the accident. The study is useful in gaining insights into the processes of the severe accident induced by cold leg SBLOCA and can be used to identify appropriate mitigation strategies and countermeasures to deal with the severe accident in the FNPP.

中文翻译：

---

MELCOR 模拟浮式核电站中 SMR SBLOCA 引发的严重事故

摘要 浮动核电站（FNPP）是一种专门停泊在某海域的驳船上的核电站。本研究的重点是在 100 MWt 2 回路压水堆 (PWR) 型 FNPP 中的小型模块化反应堆 (SMR) 中发生冷段小断流冷却剂事故 (SBLOCA) 引发的严重事故。严重事故是使用 MELCOR 计算机代码模拟的。MELCOR 模型是为初级和次级系统、设计的安全功能以及 SMR 的安全壳开发的。使用该模型分析了三种严重事故缓解措施，即增压器 (PZR) 减压扩展、外部容器反应堆冷却 (EVRC) 和被动自催化复合器 (PAR)。分析了严重事故的发展过程以及三种缓解措施对严重事故的影响。模拟结果表明，反应堆堆芯因冷却剂泄漏而暴露并升温，最终因高压和低压注入失败而熔化。然而，通过针对严重事故的缓解措施，反应堆压力容器（RPV）和安全壳的完整性得以保持，从而防止了放射性产物大量释放到其他舱室和环境中。对比分析结果还表明，三项措施均发挥了预定功能，对缓解事故具有重要意义。