CSPACE (Core meltdown, Safety and Performance Analysis CodE for nuclear power plants) for a simulation of severe accident progression in a Pressurized Water Reactor (PWR) is developed by coupling of verified system thermal hydraulic code of SPACE (Safety and Performance Analysis CodE for nuclear power plants) and core damage progression code of COMPASS (Core Meltdown Progression Accident Simulation Software). SPACE is responsible for the description of fluid state in nuclear system nodes, while COMPASS is responsible for the prediction of thermal and mechanical responses of core fuels and reactor vessel heat structures. New heat transfer models to each phase of the fluid, flow blockage, corium behavior in the lower head are added to COMPASS. Then, an interface module for the data transfer between two codes was developed to enable coupling. An implicit coupling scheme of wall heat transfer was applied to prevent fluid temperature oscillation. To validate the performance of newly developed code CSPACE, we analyzed typical severe accident scenarios for OPR1000 (Optimized Power Reactor 1000), which were initiated from large break loss of coolant accident, small break loss of coolant accident, and station black out accident. The results including thermal hydraulic behavior of RCS, core damage progression, hydrogen generation, corium behavior in the lower head, reactor vessel failure were reasonable and consistent. We demonstrate that CSPACE provides a good platform for the prediction of severe accident progression by detailed review of analysis results and a qualitative comparison with the results of previous MELCOR analysis.

CSPACE（核电厂堆芯熔化、安全和性能分析代码）用于模拟压水反应堆（PWR）中的严重事故进程，它是通过耦合已验证的 SPACE（核安全和性能分析代码）系统热工水力代码而开发的。发电厂）和 COMPASS（堆芯熔化进展事故模拟软件）的堆芯损坏进展代码。SPACE 负责描述核系统节点中的流体状态，而 COMPASS 负责预测堆芯燃料和反应堆容器热结构的热和机械响应。COMPASS 中添加了针对流体每一相、流动阻塞、下封头的真皮行为的新传热模型。然后，开发了用于两个代码之间数据传输的接口模块以实现耦合。应用壁面传热的隐式耦合方案来防止流体温度振荡。为了验证新开发代码CSPACE的性能，我们分析了OPR1000（Optimized Power Reactor 1000）典型的严重事故场景，这些事故包括大破水事故、小破水事故和电站停电事故。包括 RCS 的热水力行为、堆芯损坏进展、氢气生成、下封头的真皮行为、反应堆容器故障等结果是合理和一致的。我们通过详细审查分析结果以及与先前 MELCOR 分析的结果进行定性比较，证明 CSPACE 为预测严重事故进展提供了一个良好的平台。