Chloride-induced stress corrosion cracking (CISCC) in the weldments of austenitic stainless steel canisters is one of the primary safety concerns during the dry storage of used nuclear fuel at Independent Spent Fuel Storage Installations in coastal areas. In order to evaluate the CISCC behavior in the canister, a 3D sequentially coupled thermo-mechanical finite element model was built to simulate the residual stresses induced by two intersecting longitudinal and circumferential multi-pass welds in austenitic stainless steel mockup canister. Weld-induced residual stresses from simulation were in good agreement with the experimental measurement results by deep-hole drilling and contour methods. Through-wall high tensile axial and hoop stresses were observed in both the fusion zone and heat affected zone (HAZ) in the longitudinal and circumferential weld, respectively. On the other hand, the microstructure within the weldments of 304 stainless steel mockup was characterized using optical microscopy, scanning electron microscopy, electron back-scattered diffraction and energy dispersive X-ray spectroscopy methods. A few amount of MnS inclusions in both the base metal and HAZ, and a lot of (Mn,Si)_xO_y inclusions in the fusion zone were found. Meanwhile, there is some α′-martensite in the base metal, while the martensite was reversed in the HAZ. In the fusion zone, there is a lot of δ-ferrite. The martensite reversion phenomenon was also verified by the combination of Feritscope test and thermal simulation, which could predict a martensite reversion temperature as 400C°. The welding residual stresses and microstructure analysis results could offer the instructive information for the prediction of CISCC behavior of the spent nuclear fuel canisters.

奥氏体不锈钢罐焊接件中的氯化物引起的应力腐蚀开裂（CISCC）是沿海地区独立乏燃料存储设施中干核废燃料干燥过程中的主要安全问题之一。为了评估罐中的CISCC行为，建立了3D顺序耦合热机械有限元模型，以模拟奥氏体不锈钢样机罐中两个相交的纵向和周向多道次焊缝引起的残余应力。模拟产生的焊接引起的残余应力与深孔钻削和轮廓法的实验测量结果非常吻合。在纵向焊缝和周向焊缝的熔合区和热影响区（HAZ）中，均观察到贯穿壁的高拉伸轴向应力和环向应力。另一方面，使用光学显微镜，扫描电子显微镜，电子背散射衍射和能量色散X射线光谱法对304不锈钢样件焊件内的显微组织进行了表征。贱金属和热影响区中都有少量的MnS夹杂物，以及大量的（Mn，Si）在融合区发现了_x O _y夹杂物。同时，贱金属中存在一些α'马氏体，而热影响区中的马氏体则相反。在熔合区，有许多δ铁素体。马氏体回火现象也通过Feritscope试验和热模拟相结合得到了验证，可以预测马氏体回火温度为400℃。焊接残余应力和显微组织分析结果可为预测乏核燃料罐的CISCC行为提供指导性信息。