Desorption of H 2O and H 2 from steel and LiAlO 2 by temperature programmed desorption

Abstract

Temperature programmed desorption (TPD) measurements with a steel sample tube and helium sweep gas are in progress to provide data describing the kinetics of desorption of H 2O(g) and H 2(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H 2O being consumed and H 2 being evolved. There is also evidence of some dissolution of H 2 in the steel. However, it is possible to stabilize the steel in the absence of added H 2 so that useful desorption measurements with H 2O(g) can be made. Initial work was on the LiAlO 2-H 2O(g) system. Fresh samples of LiAlO 2 bear large amounts of adsorbed H 2O. TPD spectra were measured for LiAlO 2 that had been equilibrated in a helium stream with 200 ppm H 2O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied, questions of possible peak overlap still remain to be resolved. An activation energy for desorption of H 2O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. This result agrees with the value reported in the literature for decomposition of LiOH, and suggests that some sites on LiAlO 2 might resemble sites on Li 2O in their adsorptive properties. For a 773 K equilibration, the activation energy of desorption appears considerably higher.