Tritium and helium release from irradiated beryllium

Tritium and helium release behavior has been measured for Be specimens irradiated at 75 degree C in the Advanced Test Reactor (ATR) to a fast neutron fluence of 5x1022 n/cm2. Stepped-isothermal anneal experiments were conducted from room temperature to above the melting point of Be, with the temperature steps varied from one experiment to the other. In-line ion chambers and quadrupole mass spectrometers were used to measure the gases released to an Ar process gas stream flowing across a heated specimen. Gases released from the specimens included H2, 3He, 4He, and tritium as HT and T2. Release of the hydrogenic and tritium gases were observed to be concurrent with the release of helium, providing direct evidence of these gases in microscopic helium bubbles in the irradiated Be. Tritium and helium release kinetics were dependent on the magnitude of the temperature steps between 600 degree C and 800 degree C. 17 refs., 6 figs