The Modular Accident Analysis Program version 5(MAAP5) is a computer code that can simulate the response of light water reactor power plants during severe accident sequences. The present work aims to simulate the severe accident of AP1000 with the Modular Accident Analysis Program version 5(MAAP5). The pressurizer (PZR) safety valve stuck-open is essentially a small break loss-of-coolant accident which becomes one of the major concerns on severe accident initiating event of pressurized water reactor (PWR). For such improbable accidents, four cases of PZR safety valve stuck-open accidents are simulated for comparison. This analysis is performed at 100% core power with different assumptions. For all cases, the primary system pressure can long term be maintained at a low level, and the ERVC system has enough capability to remove the heat from the molten pool. The total mass of hydrogen production in the core of the cases without auto depressurization system (ADS) is more significant than those cases with ADS. The results are meaningful and significant for comprehending the detail process of AP1000 severe accident, which is the basic standard for establishing the severe accident management guidelines.

模块化事故分析程序版本5（MAAP5）是一种计算机代码，可以模拟轻水反应堆电厂在严重事故序列期间的响应。本工作旨在使用模块化事故分析程序版本5（MAAP5）模拟AP1000的严重事故。增压器（PZR）安全阀完全打开是一种很小的冷却剂中断损失事故，这成为压水堆（PWR）发生严重事故的主要关注点之一。对于此类不太可能发生的事故，模拟了4种PZR安全阀卡死事故，以进行比较。该分析是在不同假设下以100％核心功率执行的。在所有情况下，主系统压力都可以长期保持在较低水平，ERVC系统具有足够的能力从熔池中去除热量。在没有自动降压系统（ADS）的情况下，核心产品中氢气的总生产量比有ADS的情况下更为重要。研究结果对于理解AP1000严重事故的详细过程具有重要意义，是制定严重事故管理指南的基本标准。