塩廃棄物の処理に関する基礎試験(2)

The basis examination for the processing of the salt waste (2)

照沼 仁*; 新井 修*

Terunuma, Hitoshi*; Arai, Osamu*

乾式再処理プロセスより発生する塩廃棄物を、ガラス固化処理に適応することを目的に、高温で水蒸気と反応させ、塩素を塩化水素の形態で分離する酸化転換処理について検討した。前年度試験より、塩化物の酸化転換処理には、酸化ホウ素添加が有効であることが確認された。一方高温処理のため、塩化物が揮発し処理系外へ移行する現象が確認された。実機への適用は、放射性核種の処理系外流出が問題となった。本試験では、核分裂生成元素であるセシウムに重点をおき、塩化物の高効率酸化転換処理と塩化物揮発の低減を目的に試験を実施した。試験の結果、塩化物揮発は、装荷容器の変更、ジャマ板の付加等の装置改造を行うことで減少できることが確認された。塩化セシウム試料、および塩化ナトリウム、塩化セシウム混合試料に酸化促進剤である酸化ホウ素を添加し処理することで、100%に近いオーダーで酸化転換処理できることが確認された。またセシウム、ナトリウムは処理容器に多く残存し揮発が抑制されていることも確認した。ハイドロソーダライトは、塩化水素を処理試料内に安定固定化する目的で用いたが、その効果は不明であり、熱分解により再び塩化物を生成することが問題となった。

Oxidation exchange treatment, chlorine is separated from salt wastes generated from dry reprocessing as a from of hydrogen chlolide by a reaction between salt waste and vapor at high temperature, was investigated for the purpose of adaptation of salt waste to the glassification. According to the last experiments, it has been clarified that the addition of boron oxide was effective to the oxidation exchange treatment of chloride. On the other hand, a phenomenon which chlolide is evaporated by high temperature and effused from the treatment was occurred. Therefore, this phenomenon has been a problem for the practical adaptation. In this study, experiments attach importance to the oxidation exchange of cesium chlolide, the fission products, were performed for the purposes of effective oxidation exchange treatment of chlolide and evaporation reduction of chloride. As a result of this experiment, the evaporation reduction of chlolide was confirmed by reconstructions of equipment such as a vessel for samples and a buffle plate. It has been clarified that nearly 100% of chloride could be separated from the salt waste by oxidation exchange treatment by addition of boron oxide, the oxidation stimulator, to a specimen of cesium chlolide and a mixed specimen of sodium chloride and cesium chloride. Furthermore, some amount of cesium and sodium were remained in the vessel for the treatment and the evaporation of chloride was depressed. Hydrosodalite was applied in order to adsorb and remove hydrogen chloride from the treated specimen, however, the effects of its was unknown and there was a problem that chloride is regenerated by the thermal separation.