<Original Papers>Removal of Cesium and Strontium from High-Activity-Level Water by Zeolites

The selective removal of Cs and Sr from high-activity-level water (HALW) has been studied by the use of various zeolites. The rate of adsorption of Cs and Sr increased with a decrease in size of zeolite particles, and the adsorption reached almost 100% after 5 h and 10 h of shaking for Cs and Sr, respectively. High distribution coefficients of Cs (K_=10^4～10^5) were obtained in the solution/zeolite ratio (V/m) region of about 300 to 1000. The presence of sodium ion fairly affected the distribution of Cs^+ and Sr^, and K_d values decreased with increasing concentration of Na^+. While the presence of boron almost had no effect on the distribution of Cs ; high K_ values (K_≧10^5) were obtained below 5000 ppm of boron. Distribution coefficients of Cs and Sr were also independent of the equilibrium pH in neutral and alkaline regions at the ionic strength of 0.1. The removal of Cs and Sr from simulated HALW was effectively achieved by the use of mixed zeolites, and the K_d value was 7.0×10^3ml/g at the mixing ratio of 48/52 of X/chabazite