Abstract Cesium (137Cs) is a major component of intermediate level radioactive wastes. In this study, the possibility of immobilization of cesium after adsorption with analcime zeolite modified with nickel hexacyanoferrate was evaluated by heat-treating at temperatures of 300, 600, 900, 1100 oC and leaching tests. The results showed that the immobilization ability of the cesium ion into modified with nickel hexacyanoferrate analcime zeolite increased significantly with increasing temperature, and analcime zeolite was changed to pollucite and cristobalite at 1100 oC. Also the inhibition of the cesium ions adsorbed in the heat treated Cs-analcime zeolite was determined to 100 % at 1100 oC.
