Effect of dissolved oxygen in intergranular stress corrosion cracking of sensitized SUS304 in high temperature water under γ-ray irradiation

Intergranular stress corrosion cracking (IGSCC) of sensitized SUS304 has been investigated at 288degC water under γ-ray irradiation with a high dose rate of 2.6 x 103 C/kgh using a developed slow strain rate tensile test equipment. The IGSCC susceptibility was increased by γ-ray irradiation in water with 8 ppm dissolved oxygen (DO), and the corrosion potential was also increased by γ-ray irradiation. The IGSCC susceptibility was decreased with decreasing DO in water from 32 ppm to 0.2 ppm. No IGSCC susceptibility was observed in the hydrogen injected water under γ-ray irradiation. Radical concentrations decomposed by γ-ray irradiation into water were calculated using a computer code. The result suggested that, the radiolytic products were mainly H2O2. An increase in IGSCC susceptibility by γ-ray irradiation seems to be related to an increase in corrosion potential due to the formation of H2O2 by γ-ray irradiation. H2O2 concentration is remarkably decreased due to hydrogen injection into water under γ-ray irradiation. (author)