Gas retention in irradiated beryllium

Helium (an inert gas) with low solubility in beryllium is trapped in irradiated beryllium at low temperatures ( 1 MeV). In these samples the calculated helium generated was {approximately} 14,000 appm. They are described in terms of swelling, annealing, microstructure, and helium bubble behavior (size, density and mobility). A second sample was irradiated to {approximately}5 {times} 10{sup 22} n/cm{sup 2} (E > 1 MeV). In that one the calculated helium and tritium generated were {approximately}24,000 appm He and {approximately}3720 appm, and tritium content was examined in a dissolution experiment. Most of the tritium was released as gas to the glovebox indicating the generated tritium was retained in the helium bubbles. In a third set of experiments a specimen was examined by annealing at a succession of temperatures to more than 600{degree}C for tritium release. In the temperature range of 300--500{degree}C little release (0.01--0.4%) occurred, but there was a massive release at just over 600{degree}C. Theories of swelling appear to adequately describe bubble behavior with breakaway release occurring at high helium contents and at large bubble diameters. 8 refs., 6 figs