Fission-product tellurium and cesium telluride chemistry revisited

摘要

The chemistry of fission-product tellurium is discussed with a focus on conditions in an operating CANDU reactor and in an accident scenario, i.e., a loss of coolant accident (LOCA). Cesium telluride, Cs(sub 2)Te, is likely to be one of the most abundant tellurium species released to containment. Available thermodynamic data on gas phase Cs(sub 2)Te is not complete; hence the volatility of cesium telluride was studied by Knudsen-cell mass spectrometry. Cesium telluride was found to vapourize incongruently, becoming more tellurium- rich in the condensed phase as vapourization progressed. Vapour-phase species that were observed were elemental cesium and tellurium, CsTe, Cs(sub 2)Te, Cs(sub 2)Te(sub 2) and Cs(sub 2)Te(sub 3). Second-law enthalpies and entropies were obtained for many of these species, and a third-law value, (Delta)H(sub 298)(sup o), of 186 (+-) 2 kJ(center-dot)mol(sup -1) was obtained for Cs(sub 2) Te. (author) 101 refs., 9 tabs., 14 figs.