ABSTRACT Hitachi has developed the chemical decontamination method to remove radioactive oxides on structural materials by alternately using a mixed solution of oxalic acid and hydrazine for a reductive process and potassium permanganate or permanganic acid solution for an oxidative process. In the decontamination of carbon steel (CS) by applying oxalic acid, a film of iron(II) oxalate dihydrate that has low solubility is formed on the CS surface. During the formation of iron(II) oxalate dihydrate, Co-60 in the reductive decontamination solution may be incorporated into the formed film. This phenomenon may cause a decrease in the decontamination efficiency of the CS. A corrosion test of CS in a reductive decontamination solution containing Co-60 as tracer was carried out in order to evaluate this recontamination. It was confirmed that Co-60 was incorporated into the iron(II) oxalate dihydrate film, and the amount of Co-60 increased with increasing formation of this film. About 50% of the Co-60 added to the reductive decontamination solution was incorporated into iron(II) oxalate dihydrate formed on the CS and the Co-60 incorporation ratio was proportional to the iron(II) oxalate dihydrate formation. This result means that the recontamination during chemical decontamination of CS can be predicted.

中文翻译：

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Co-60 掺入化学去污过程中形成的二水草酸铁 (II) 中的碳钢再污染

摘要 日立开发了一种化学净化方法，通过交替使用草酸和肼的混合溶液进行还原过程和高锰酸钾或高锰酸溶液进行氧化过程来去除结构材料上的放射性氧化物。在应用草酸对碳钢 (CS) 进行净化时，在 CS 表面形成了溶解度低的二水草酸铁 (II) 薄膜。在二水合草酸铁 (II) 的形成过程中，还原性去污溶液中的 Co-60 可能会结合到形成的薄膜中。这种现象可能会导致 CS 的去污效率降低。在含有 Co-60 作为示踪剂的还原性去污溶液中进行了 CS 的腐蚀试验，以评估这种再污染。已证实 Co-60 被掺入到二水草酸铁 (II) 薄膜中，并且 Co-60 的量随着该薄膜形成的增加而增加。添加到还原性去污溶液中的约 50% 的 Co-60 被掺入在 CS 上形成的二水草酸铁 (II) 中，并且 Co-60 掺入率与草酸铁 (II) 二水合物的形成成正比。该结果意味着可以预测 CS 化学净化过程中的再污染。