Immobilization of cesium-137 in cement-waste composites by addition of mineral zeolites.

Abstract-The reduction of cesium leachability by addition of mineral zeolites to enhance the safety of solidification of wastes with cement has been examined. Leaching tests were carried out by the method recommended by IAEA. The naturally occurring mineral zeolites containing mordenite and clinoptilolite (Zeolite I), which have high atom ratios of silicon and aluminum, possess an extremely high effectiveness for immobilizing 137Cs in a cement matrix. By addition of zeolite I, the leachability is reduced by a factor of about 100. However, since increasing the amount of zeolites decreases the leachability and workability concurrently, the content of zeolites should be less than 0.25 for good workability. On the basis of the results obtained, estimates were made on the amount of ‘37Cs leached from a cement composite (200 1. drum size), with or without Zeolite I, that is exposed to a water environment for extended periods.