It is very important to clariy the stress corrosion cracking behavior of low alloy steals for the pressure boundary component materials of LWR primary coolant systems. The slow sttran rate tensile test (SSRT) was carried out on three typee of heavy-thick low alloy steels in high temperature water containing various levels of dissolved oxygen(DO) to investigate the effects of DO and material factors on the SCC behavior. The results obtained are as follows; 1) Susceptibility to SCC of each steel increased with DO concentration. 2) The rolled steel with higher impurity concentration had higher susceptibility to SCC at low DO concentration (100 ppb) condition. 3) The forged steel with Iow impurity level had superior SCC resistence even at high DO concentration (8ppm) condition.
Keywords: reactor pressure vessel, low alloy steel, SCC, high temperature water, SSRT, dissolved oxygen, MnS, sulfurcontent, rolling, forging