Electrochemical Properties of Oxide Films Formed on Cold Worked Alloy600 and Alloy690 in Simulated PWR Primary Water Environments

加圧水型原子炉の一次系冷却水を模擬した高温高圧水中にて，冷間加工を加えたAlloy600，Alloy690に生成する不働態皮膜を光電気化学応答によって評価した．一部の試料について放射光をX線源とする光電子分光法による表面分析を実施した．Alloy600とAlloy690に生成する不働態皮膜は，バンドギャップ3.5 eVのp型半導体としての性質を示す酸化物層と2.3 eVのn型半導体的性質を示す水酸化物層から構成されていることが分かった．しかし，酸化物層中には，一般にp型半導体としての性質を示すNi酸化物はほとんど含まれていなかった．一方，皮膜生成時の溶存水素とこれら合金に対する冷間加工の影響はAlloy600で顕著に現れたがAlloy690ではほとんど見られなかった．すなわち，Alloy600に生成する不働態皮膜は溶存水素により薄くなる．また，冷間加工によってやや厚くなり，保護性が低下することが明らかとなった．Passive films formed on Alloy 600 and Alloy 690 in the simulated primary water of pressurized water reactor were characterized by photo electrochemical current response focusing on the influence of the dissolved hydrogen and cold working. Some specimens were also analyzed by X-ray photoelectron spectroscopy using the hard X-ray generated by SPring-8. Passive films on both alloys consisted of the oxide layer of p-type semiconductor properties with band gap energy (Eb) of 3.5 eV and the hydroxide layer of n-type semiconductor with Eb of 2.3 eV. However, the content of Ni in the oxide layer which may induce p-type semiconductor property is negligible small. The passive films on Alloy 600 become thinner by dissolved hydrogen, and less protective by cold working. Whereas passive films on Alloy 690, which were more protective than that on Alloy 600, were rarely influenced by cold working and dissolved hydrogen