反应堆严重事故卸压管线瞬态传热特性与高温蠕变效应研究

The transient heat transfer and Larson-Miller creep failure analysis of severe accident relief pipeline

严重事故预防和缓解措施能够保障反应堆安全稳定运行,在核动力厂设计中具有重要意义.本研究构建了反应堆严重事故卸压管线瞬态响应模型,实现了适用于卸压管线的传热特性及蠕变特性仿真.基于某三代压水堆典型假想严重事故的瞬态特性及严重事故卸压管线的功能性要求,采用RELAP/SCDAPSIM和CFX程序开展了传热特性研究,明确了严重事故工况下的管道壁面的压力和温度特点,进一步采用Larson-Miller模型实现了管道蠕变特性研究.研究表明,在典型严重事故工况下严重事故卸压管线温度远低于反应堆堆芯熔融温度1200°C,但为防止高温蠕变失效,在瞬态设计时应尽量避免来流介质压力和温度同时偏高的情况;此外,严重事故卸压管线采用奥氏体不锈钢时钢材中的铬(Cr)含量对管道高温蠕变失效有较大的敏感性影响,铬含量原则上应高于12%.本研究为严重事故卸压管线的瞬态工况确定、管线高温蠕变失效评定和设计优化提供了理论支撑,对核电厂严重事故预防和缓解措施的设计有着重要意义.

During postulated severe reactor accidents, severe accident relief valves are activated, and products, including water vapor and hydrogen gas, are released to prevent high-pressure core melting. The severe accident relief pipeline is specified with functional requirements based on typical severe accident scenarios, creating the risk of high-temperature creep failure. A numerical simulation of the transient heat transfer characteristics using RELAP/SCDAPSIM and CFX was performed, and the Larson-Miller model was applied. The results indicate that the relief pipeline temperature is much lower than the core melting point 1200℃, and to avoid hightemperature creep failure, the design pressure and temperature of the entering fluid products should not be high values simultaneously.Moreover, the Cr content of the pipe’s austenitic stainless steel is critical, and content with no less than 12% Cr is advised. The investigation thus elucidates the inherent characteristics of the severe accident relief pipeline during postulated severe reactor accidents.