PWR条件の照射下での水素注入効果の評価,4; 一次冷却系中のステンレス鋼のECPに及ぼす水素の直接及び間接効果

The Effects of hydrogen addition on the corrosive conditions of PWR primary coolant under irradiation, 4; Direct and indirect effects of pH on ECP of stainless steel in the primary cooling water

内田 俊介; 端 邦樹 ; 塙 悟史 ; 知見 康弘

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

前回の発表(副題2)では、PWR一次冷却系では、水素の酸化電流が水素注入によるECP低減に大きな影響を与えることを示した。PWRでは、BWRに比べ、水素濃度のほかに、pH, 照射線量率などECPに影響を及ぼす因子に大きな違いがある。本発表では、特にpHに注目し、ラジオリシス,表面性状,金属イオン溶解度などpHがECPに及ぼす直接及び間接影響について議論した。この結果、PWR1次系とBWRを含む広いpH範囲の腐食環境を同一のラジオリシスおよびECP解析コードを用いて、pH依存性を考慮した定数を適用するだけで一元的に評価できることを示した。

The direct effects of hydrogen concentrations on the ECP were discussed in the previous presentation (the series #2). The parameters to determine ECP, e.g., pH and dose rate as well as hydrogen concentration, were different between in PWRs and BWRs. In the presentation, the direct and indirect effects of pH on ECP due to water radiolysis, surface properties and metallic ion solubilities are discussed. It was concluded that the corrosive conditions in the wide pH range which covered both PWR primary cooling water and BWR cooling water could be evaluated with a set of analysis codes for water radiolysis and ECP with applying the pH-dependent reaction constants.