Cs immobilization using the formation of the glassy phase by the heat-treatment of natural mordenite

Abstract The Cs ion was partially adsorbed (4.0% in all of the alkali cation sites) on natural mordenite as a simulated decontamination, then heat-treated to immobilize the Cs in the decomposed zeolite. Although the mordenite phase was maintained for the samples even heated at 800 °C, a glassy amorphous phase formed due to the decomposition of the mordenite at 900 °C. In the case of the non-treated sample, 3.6% Cs ion from all of the adsorbed Cs was eluted by a dissolution test in deionized water for 14 days. The elution ratio of the Cs ion decreased by the heat treatment. The Cs ion did not elute when the sample was heated at 1000 °C and higher temperature due to the Cs containment in the glassy phase. Na2CO3 powder was mixed with the mordenite for lowing the glass-forming temperature. The mordenite mixed with Na2CO3 had a lower melting point and immobilized the Cs at 900 °C. The Cs evaporation during the heating was also depressed by the Na2CO3 addition.