Most of reactor vessel internals (RVIs) have been constructed by austenitic stainless steels (ASSs) to support and protect core from high temperature coolant and radiation particles. However, if they are operated in the harsh environment for a long time, ASS materials may undergo significant changes in micro-structural features, macroscopic deformation and strengths due to age-related degradation mechanisms (ARDMs). In this study, user subroutines were developed based on material constitutive models of recently revised technical reports to reflect irradiation embrittlement, irradiation enhanced creep and void swelling behaviors. Benchmark analyses for a simple rod and detailed numerical analyses for a RVI sub-components assembly with welds were conducted via coupling the subroutines. With regard to the latter analyses, not only typical normal operating sequences but also three fuel cycles associated with specific core loading patterns were taken into account with a constant initial weld residual stress distribution. Adequacy of the subroutines was verified through analytical solutions generated from temperature and radiation damage dependent equations. Complex neutron dose, temperature and pressure profiles of the assembly were successfully determined from thermal and mechanical finite element analyses. Structural integrity assessment in terms of the ductility, embrittlement and irradiation assisted stress corrosion cracking susceptibility ratio after 40-years of operation led to acceptable in spite of the ARDMs. Contributions of factors and interaction effects were further quantified and discussed via design of experiment approach.

反应堆容器的大部分内部零件（RVI）由奥氏体不锈钢（ASS）制成，以支撑和保护堆芯免受高温冷却剂和辐射颗粒的侵害。但是，如果它们在恶劣的环境中长时间运行，由于与年龄相关的降解机制（ARDM），ASS材料可能会发生微观结构特征，宏观变形和强度的重大变化。在这项研究中，基于最近修订的技术报告的材料本构模型开发了用户子例程，以反映辐照脆化，辐照增强的蠕变和空隙膨胀行为。通过耦合子程序进行了简单杆的基准分析，以及带有焊接的RVI子组件装配的详细数值分析。关于后面的分析，在恒定的初始焊接残余应力分布的情况下，不仅考虑了典型的正常操作顺序，而且考虑了与特定堆芯负载模式相关的三个燃料循环。通过从温度和辐射损伤相关方程生成的解析解验证了子例程的充分性。通过热和机械有限元分析成功确定了组件的复杂中子剂量，温度和压力曲线。尽管使用了ARDM，但在运行40年后，根据延性，脆性和辐照辅助应力腐蚀裂纹敏感性的结构完整性评估仍然可以接受。通过实验方法的设计进一步量化和讨论了因素的贡献和相互作用的影响。