Development of treatment method for analytical waste solutions in STRAD project; Role of trace chloride ion in ammonium ion oxidation with the presence of Co(II) ion

STRADプロジェクトにおける分析廃液処理方法の開発; Co(II)存在下でのアンモニウムイオン酸化反応に与える微量塩化物イオンの影響

粟飯原 はるか   ; 渡部 創  ; 北脇 慎一 ; 神谷 裕一*

Aihara, Haruka; Watanabe, So; Kitawaki, Shinichi; Kamiya, Yuichi*

Many kinds of radioactive liquid wastes have been generated and accumulated in nuclear research facilities, and disposal or treatment procedures have not been established for those wastes due to their complicated compositions. Japan Atomic Energy Agency (JAEA) is developing technologies for the treatment of radioactive liquid waste containing various chemical species through joint research project with several organizations named as STRAD (Systematic Treatment of RAdioactive liquid wastes for Decommissioning). Chemical processing facility (CPF) in JAEA was selected as a model case, and fundamental studies have been conducted for treatments of the liquid wastes accumulated in the CPF. Decomposition of the ammonium ions (NH) in advance with formation of explosive ammonium nitrate is one of promising treatments of the analytical liquid wastes. We have been focusing on catalytic ozonation of NH as a suitable method for the decomposition under mild conditions with small secondary waste. Detail reaction mechanism has not been revealed yet. In this study, concentration of each component was parametrically changed and the reaction mechanism was investigated. Test solutions containing NH, Co and Cl with various concentrations were prepared, and the ozone oxidation experiments were conducted at 333 K. The oxidation reaction of NH proceeds even under low Cl concentration, it is suggested that once chloramine are formed, thus the chlorine was released by decomposition. The above catalytic ozonation was applied to the genuine radioactive liquid waste stored at CPF, and concentration of NH in the waste solutions was successfully reduced. This experience would contribute to treatment of radioactive liquid wastes in other facilities.