Development of a method to lower recontamination after chemical decontamination by depositing Pt nano particles: (II) consideration of the Pt effect on oxide composition

The Pt coating (Pt-C) process has been developed to lower the recontamination by ⁶⁰Co which was incorporated in oxides on piping surface after chemical decontamination. In order to determine the suppression mechanism of ⁶⁰Co deposition by Pt-C, it is important to investigate the formation of oxide film ⁶⁰Co deposition behavior on oxide with Pt-C specimens. In this paper, we observed the composition change of oxide after a ⁶⁰Co deposition test under the hydrogen water chemistry condition, and considered the ⁶⁰Co deposition behavior on oxide for Pt-C specimens. The Ni and Co metal concentrations in oxide were dramatically changed by Pt-C process. The Ni metal concentrations in oxide for specimens with and without the Pt-C process were 11.2% and 18.0%, respectively. On the other hand, the Co metal concentrations in oxide for specimens with and without the Pt-C process were 1.2% and 0.2%, respectively. This composition change of the oxides indicated that ⁶⁰Co incorporation for the Pt-C specimens was suppressed by replacing ⁶⁰Co with Ni. We concluded that the Ni²⁺ ions were incorporated into the 8a site of the oxide spinel structure instead of Co²⁺ ions due to the effect of the conversion deposition energy.     

提高氧化物介质膜层损伤阈值的研究

采用新清洗工艺对K9玻璃基片进行了清洗,镀制了多种氧化物介质膜,镀膜后的膜层损伤阈值比一般清洗要高出一倍多。用等离子体光法和相衬显微镜观察法相结合来判断损伤,分别用1-on-1测试法和R-on-1测试法确定了膜层的激光损伤阈值。     

Development of a suppression method for deposition of radioactive cobalt after chemical decontamination: (III) the suppression mechanism with preoxidized ferrite film for deposition of radioactive cobalt

The Hitachi ferrite coating film process (Hi-F) has been developed to lower recontamination after chemical decontamination. In this process, the chemical decontamination process is carried out, and a fine Fe₃O₄ coating film is formed on the surface of stainless steel piping in an aqueous solution. In order to improve the suppression of ⁶⁰Co deposition further, we combined the original Hi-F with a preoxidation step. We found the deposited amount of ⁶⁰Co with preoxidized Hi-F coating film (OHi-FC) was 1/10 of that for non-coated specimens. In this study, we investigated the suppression mechanism of ⁶⁰Co for the OHi-FC. The composition of OHi-FC was changed from Fe₃O₄ to Fe₂O₃ and then the crystals in the OHi-FC grew three times larger than those of the original Hi-F coating film. Consequently the corrosion amount of the stainless steel base metal was reduced by getting larger grains in the coating film. Because ⁶⁰Co was incorporated into the corrosion oxide, the suppression effect of ⁶⁰Co deposition by preoxidation was attributed to the suppression of the formation of the corrosion oxide by the OHi-FC.