PNNL

Abstract

Samples taken from tungsten rods irradiated by 800 MeV protons in the Los Alamos Neutron Science Center beam line have been used in experiments to study the effects of radiation damage and subsequent annealing on the retention of hydrogen isotopes. The tungsten samples had been originally irradiated to proton doses of approximately 0.3 and 8 dpa. These samples were first annealed and then exposed to energetic deuterium ions using a DC glow discharge. Following exposure, the samples were subjected to a linear temperature ramp from ~300 K to ~1500 K, and the offgas analyzed by mass spectrometry. The results indicate that annealing to a temperature of only 1273 K for 6 hours effectively removed all irradiation-produced traps, and also indicated that hydrogen trapping at voids is not as prevalent as had been assumed. Modeling the deuterium release suggests that most of the trapping occurred in a combination of near-surface 1.4 eV traps, a low concentration of uniform 1.4 eV traps, and 0.95 eV traps likely resulting from oxygen diffusion from the original water-cooled irradiation environment.