Experimental study on water desorption behavior of Li₄SiO₄ ceramic pebbles

Water desorption behavior of Li4SiO4 ceramic pebbles was studied using temperature programmed desorption (TPD/TDS) method. The experiment results showed that water desorption was mainly followed by four peaks. The peak around 100 ℃ can be attributed to physisorbed water, the peak around 150 ℃ to water chemisorbed on surface oxygen ions through hydrogen bonds, and the peaks around 250 ℃ and 400 ℃ to chemisorbed water in hydroxylated form such as Li－OH and Si－OH. According to the fact that the processes of tritium release and water desorption proceeded almost simultaneously and the release form of tritium was mainly tritiated water (HTO), three mechanisms of tritium release as HTO form were proposed: (1) －OT+H2O－OH+HTO; (2) －OH+－OHH2O, －OT+H2O－OH+HTO; (3) －OT+－OHHTO.