Salt-free technique for solvent washing process in NEXT process

NEXTプロセスにおけるソルトフリー技術開発

佐野 雄一   ; 鍛治 直也; 柴田 淳広  ; 竹内 正行 ; 鷲谷 忠博 

Sano, Yuichi; Kaji, Naoya; Shibata, Atsuhiro; Takeuchi, Masayuki; Washiya, Tadahiro

As a part of the development of the advanced aqueous reprocessing process which aims at eliminating low radioactive waste containing sodium salt, we studied some salt-free techniques for solvent washing process which is one of the main sources of sodium salt waste in the conventional PUREX process. The batch-wise and counter-current solvent washing experiments were carried out with salt-free reagents, hydrazine carbonate and hydrazine oxalate, and genuine spent solvent. The phase separation behavior and solvent washing efficiency, i.e. DF of Pu, some FP and DBP, were investigated in these experiments, and it was confirmed that the salt-free reagents showed the almost same performance as sodium salt, NaCO, under the appropriate solvent washing condition. In addition to these solvent washing experiments, decomposition methods of spent reagents containing impurities, such as DBP, were also investigated. Several beaker-scale experiments for electrooxidative or thermal decomposition were carried out with the salt-free reagents containing the simulated impurities. These experimental results clarified the degradation behavior of hydrazine and oxalic ions in the salt-free reagents, and indicated that the generation of explosive degradation products, i.e. hydrogen azide and ammonium, could be kept low enough to avoid an explosive hazard.