PLANT OPERATION MANAGEMENT(4)

Mitigation of Stress Corrosion Cracking Specimens sensitized to SCC (made by heat treatment) are elongated slowly and fractured forcibly in the autoclave filled with reactor water (SSRT: Slow Strain Rate Test). Fractured surfaces of specimens tested without hydrogen injection show uneven broken-out section caused by SCC, while those of specimens tested with hydrogen injection do not show such a section. These tests prove the effectiveness of hydrogen addition on the occurrence of SCC.

Reduction of O2 Concentration Dissolved oxygen concentration in reactor coolant is decreased with increasing the hydrogen injection rate.

Effect of Mitigating IGSCC Susceptibility The SCC fractured surface rations, i.e. the fractured surface area with SCC to the original cross section area of test specimens, were plotted as a function of dissolved oxygen. This chart could suggest the optimum injection rate as well as demonstrating the effectiveness of hydrogen injection.