在核反应堆发生的材料破损事故中,出现较多的是回路冷却水循环系统不锈钢管焊接接头热影响区的晶间应力腐蚀开裂。本文叙述了这类事故的发生状况及支配因素、裂纹产生及扩展的实际观察情况,并以此为基础阐述了防止措施的原理和实际应用情况。随着碳化物形成而出现贫铬区是产生应力腐蚀开裂的直接原因,这一点早已为人所知。同时,焊接中产生的残余应力,以及沸水反应堆特有的高温水的水化学条件的共同作用,加速了应力腐蚀开裂。作为防止措施,目前已掌握了减少材料的敏化倾向、减少残余应力和水中溶解氧含量技术。今后的课题是预测长期的 In the material damage accident occurred in the nuclear reactor, there is more of the loop cooling water circulation system stainless steel pipe welded joints heat affected zone intergranular stress corrosion cracking. This paper describes the occurrence and dominance of such accidents, the actual observation of the occurrence and propagation of cracks, and explains the principle and practical application of preventive measures. It has long been known that the occurrence of chromium-depleted zones with the formation of carbides is the direct cause of stress corrosion cracking. At the same time, the residual stress generated during welding and the combined effect of the hydrochemical conditions of the hot water, which is characteristic of boiling water reactors, accelerate the stress corrosion cracking. As a precautionary measure, technologies to reduce sensitization of materials and to reduce residual stress and dissolved oxygen in water have been mastered at present. Future topics are to predict long-term