Kinetic properties during absorption in aged palladium–tritium system

Abstract

The time-dependence of tritium absorption on aged (3 years) palladium powder in α and α&β areas has been experimentally measured for initial tritium pressures in the range 40–200 kPa and tritide temperatures in the range 22–65 °C. The results show that the absorption rate increases with initial tritium pressure (at constant temperature) in both α and α&β areas, and decreases with increasing temperature at constant pressure in the α&β area. The overall tritium absorption process of aged palladium is determined by two steps: (1) the chemisorption reaction on the surface of palladium tritide at the start of the absorption, when only the temperature of the palladium tritide influences the chemisorption reaction rate; (2) diffusion of tritium atoms through tritide during tritium absorption, when both the tritide temperature and the initial pressure of tritium molecules affect the reaction rate. The diffusion activation energy and chemisorption activation energy are 13.66 and 19.38 kJ/mol, respectively at 22–65 °C, the sum of which agrees with absorption and desorption transition enthalpies of the same unaged and aged palladium tritide at 35–75 °C.