Preparation of Ceramic Solid Forms Immobilizing Cesium and/or Strontium and Evaluation of their Physical and Chemical Properties

Ceramic solid forms immobilizing Cs and/or Sr were produced by the calcination of Cs-mordenite and Sr-zeolite A at 1,200°C for 1 h. Cesium and strontium were fixed in the mineral phases of pollucite (CsAlSi ₂O₆) and Sr-feldspar (SrAl₂Si₂O ₈), respectively, and they were uniformly dispersed in the solid forms. The contents of Cs, Sr and Na in the solid forms produced from (Cs,Sr)A zeolite were determined to be 12.5, 17.4 and 1.2 wt%. The solid forms showed no thermal change up to 900°C. The compressive strength of solid forms increased with decreasing particle size of starting zeolites, yielding the value above 1.2 GPa for the Cs products, reachability of Cs was in the order, 0.1 M HNO₃ > 0.1 M NaOH > 0.1 M NaCl > deionized water (DW). The Sr products had lower leach rate compared with Cs products, and no Sr was detected in DW up to 90°C. No appreciable alteration was observed on the outermost surface of the solid forms exposed to DW at 90°C for 30 days. The ceramic solid forms immobilizing Cs and Sr are thus promising for the effective utilization of these nuclides.