Low alloy steels have been used as the pressure boundary component materials of LWR primary coolant systems. So it is very important to clarify the stress corrosion cracking behavior of the alloys. The slow strain rate tensile test(SSRT) was carried out on three heats of heavy-thick low alloy steels in high temperature water containing various levels of dissolved oxygen(DO0) at various temperature to investigate the stress corrosion cracking (SCC) behavior. The results obtained are as follows; 1) Rolled steels with high sulfur content have SCC susceptibility in the wide region of temperature -DO concentration combination, even below DO < 0.005 ppm at 473 K. 2)A forged steel with extremely low sulfur content is almost immune to SCC. 3) SCC maps showing SCC region were made for each steel.
Keywords: reactor pressure vessel, low alloy steel, SCC, high temperature water, SSRT, dissolved oxygen, temperature, sulfur content, SCC map