Temperature-programmed desorption of tritium loaded into beryllium

Abstract

The influence of grain size and amount of beryllium oxide BeO on the tritium release characteristics of the S-65H and I-220H beryllium grades was investigated. The beryllium samples were loaded with hydrogen at a temperature of 1123 K for 6 h at a pressure of 4 bar in a gas mixture of molecular protium with 45 wppm tritium. The tritium release measurements were performed using a stepped heating ramp with steps of 50 K in the temperature range of 473–1373 K with a duration of each step of 1 h. Five major release peaks were observed. Interpretations of the nature of the peaks are suggested. In particular, we ascribe the low-temperature peaks (300–723 K) to desorption from the surface and connect the shift of the peak at elevated temperature (900–1000 K) with the enhanced diffusion of hydrogen along grain boundaries. The high temperature peak (1123–1373 K) is attributed to dissociation of beryllium hydroxide Be(OH)2, which is formed on the surface and grain boundaries of a sample in a reaction of hydrogen isotopes with beryllium oxide.