Effect of Gamma-ray Irradiation on Corrosion and Cobalt Accumulation of Type 304 Stainless Steel in High-temperature Water in the Presence of Zinc Ion

Abstract

The effect of γ irradiation on the corrosion and the cobalt accumulation of type 304 stainless steel exposed to water at 561 K has been investigated. The exposure tests were carried out with and without the presence of 1.2×10³ Gy/h γ irradiation and 50 ppb zinc addition. The structure and elemental depth distributions of the corrosion surface were analyzed by EPMA, XRD and GDS. In the case of no zinc addition, the amount of corrosion did not appear to change with the γ irradiation. However, the amount of crud release, the amount of corrosion film and the cobalt accumulation in the outer layer increased with the γ irradiation. In the case of zinc addition, the amount of corrosion and the corrosion film significantly increased and also the amount of cobalt accumulation increased with the γ irradiation. It is considered that these differences are related to the reaction of metal ions and radiolysis products of water. On the other hand, the zinc addition suppressed the corrosion and the cobalt accumulation even with γ irradiation. These suppression effects were reduced compared with the no γ irradiation condition.