Study of stress corrosion cracking susceptibility of irradiated ferrite-martensitic stainless steel 07Kh12NMFB in supercritical water. Part 2. Development of corrosion crack identification technique and analysis of autoclave test results

The studies of stress corrosion cracking have been carried out for the stainless ferritic-martensitic steel with chromium content of 12% irradiated to a damage neutron dose of ~12 dpa. This steel was chosen as a candidate material for the internals of supercritical water-cooled reactors (SWCR).The first part of the paper was devoted to autoclave testing of specially designed disk specimens under constant load in a supercritical water environment (at 450°C and 250 atm pressure). In this part of the article the developed technique for corrosion cracks identification is presented and analysis of autoclave tests results is performed.As a result of the experiments performed, the threshold stress values below which stress corrosion cracking initiation doesn’t occur. The values of threshold stresses are determined for the studied steel irradiated at temperatures of 390 and 550°C. Possible mechanisms of stress corrosion cracking of the studied steel are analyzed and directions for further research are proposed.