PWR一次冷却水環境の照射下での水素注入効果の評価,7; ステンレス鋼とNi基合金のECPの比較

The Effects of hydrogen addition on the corrosive conditions of PWR primary coolant under irradiation, 7; Comparison of ECPs of stainless steel and Ni base alloy

内田 俊介; 端 邦樹 ; 塙 悟史 ; 知見 康弘

Uchida, Shunsuke; Hata, Kuniki; Hanawa, Satoshi; Chimi, Yasuhiro

鉄系の合金であるステンレス鋼とNi基合金では、高温水中でのアノード分極特性が異なり、同じ水化学環境でも異なる腐食電位(ECP)を示す。FeとNiの溶解度に及ぼす温度とpHの影響を解析し、放射線分解生成種、HO, OおよびHがECPに及ぼす影響の差異を検討した。この結果、PWRの1次冷却系では、Ni基合金はステンレス鋼より若干低い値を取り、pH依存性も若干異なることを示した。シリーズ(6)で求めたラジオリシス評価結果に基づいて、PWR炉心部、その周辺部および蒸気発生器(SG)部でのECPを解析し、1次冷却系主要箇所での水素注入のECPへの影響を評価した。

Stainless steel (Fe base alloy) and Ni base alloy are different in anodic polarization curves in high temperature water, which results in different ECP under the same water chemistry conditions. Based on analysis of the effects of temperature and pH on solubilities of Fe and Ni, the effects of radiolytic species, HO, O and H, on ECP are analyzed. As a result of the analysis, Ni base alloy showed a little lower ECP than that of stainless steel, and its pH dependence was different from that of stainless steel. The ECPs in the core, its peripherals and SG were analyzed based on radiolytic species concentrations shown in the previous presentation, which were applied to evaluation of the hydrogen injection effects on the major component in the primary cooling system.