Preliminary Study on Use of Zeolite for Isolation and Removal of Long-Lived Cesium in Liquid Waste from Nuclear Power Stations

Abstract

Environmental contamination with long-lived radiocesium (137Cs) should cause difficulties in proceeding with deep sea disposal of radioactive waste solidified in cement. The problem would be solved, if 137Cs could be isolated from the radioactive waste for separate disposal. For this purpose, a preliminary study was carried out on the isolation and removal of 137Cs with zeolite, an inorganic exchanger. Zeolites from Futatsui in Akita Prefecture and from Itaya in Yamagata Prefecture showed a strong selective affinity for Cs in preference to various other co-present ions. The best performance in practical isolation and removal was obtained with the zeolite (clinoptilolite) from Itaya sized to 40~100 mesh, and with the liquid passed at a specific space velocity of 25. In practical application, a selective zeolite column could be installed upstream of the conventional demineralizer equipping the liquid waste treatment system of nuclear power stations, in order to adsorb and eliminate 137Cs and prevent its reaching the conventional demineralizer. This should solve one of problems encountered in deep sea disposal of radioactive waste.