The pressure relief valves are equipped in the primary circuit loop to release steam to prevent high temperature core melting in severe accident. When severe accident occurs, whether the valve can be opened smoothly and worked reliably are crucial for ensuring the safety of the reactor. In this study, the analysis and evaluation of operability and integrity of the pressure relief valve are performed. The 3D thermo-mechanical coupling simulation is conducted for closed gate valve to predict its operability by taking account of the contact nonlinearities, temperature load and mechanical load. Besides, the structural integrity analysis of the fully-open gate valve under transient thermal shock is investigated by transient fluid flow and heat transfer simulation, instantaneous stress analysis and creep analysis. The instantaneous mechanical performances at critical locations and the creep characteristics of the valve during the pressure releasing process are analyzed and then evaluated according to the RCC-MR criterion. The results show that the valve can be opened smoothly, and the integrity with negligible creep and significant creep can be ensured in the studied severe accident case. The systematic evaluation method of the structural operability and integrity in severe nuclear accident is achieved in this work.

一回路回路中装有泄压阀，用于释放蒸汽，以防止严重事故中的高温堆芯熔化。当发生严重事故时，阀门能否顺利开启和可靠工作，对保证反应堆安全至关重要。在这项研究中，对泄压阀的可操作性和完整性进行了分析和评估。通过考虑接触非线性、温度载荷和机械载荷，对封闭式闸阀进行3D热机耦合模拟，以预测其可操作性。此外，通过瞬态流体流动和传热模拟、瞬时应力分析和蠕变分析，研究了瞬态热冲击下全开闸阀的结构完整性分析。根据RCC-MR准则对阀门关键部位的瞬时力学性能和泄压过程中的蠕变特性进行了分析和评价。结果表明，在所研究的严重事故案例中，阀门能够顺利打开，并保证了蠕变可忽略不计和蠕变显着的完整性。本工作实现了严重核事故中结构可操作性和完整性的系统评价方法。