<Original Papers>Effects of Fluoride Ion on Denitration of High-Level Radioactive Liquid Waste and Separation of Cesium and Strontium

The effects of HF have been studied on the denitration process of high-level radioactive liquid waste and on the separation of Cs and Sr with zeolite from the denitrated waste solutions. In the denitration process, the addition of HF up to 0.1M gave no effect on the residual nitrate concentration, pH and the residual fluoride concentration, while further addition of HF more than 0.1M resulted in the decrease of the residual nitrate concentration and pH. Zeolite A was stable in HF solution less than 0.1M, but it was completely destroyed with the formation of chiolite (Na_5Al_3F_) in the case more than 1M HF. Synthetic mordenite was stable up to 1M HF, but mordenite structure was completely destroyed in the HF (>3M) solution. The distribution coefficient (K_d) of Cs for mordenite and zeolite A markedly decreased with increase in HF concentration more than 10^M. The K_d value of Sr for zeolite A and mordenite showed the lowest value at 10^M HF and increased by further addition of HF owing to the formation of SrF_2 precipitate