X-ray diffraction study of the lattice deformation due toHe3bubble formation in a tantalum tritide

A previous x-ray-diffraction study of the lattice deformation developing in a tantalum tritide during the first 75 d after tritium charging is extended over about three years. The lattice spacing first increases slightly with increasing helium concentration built up upon tritium decay, reverses this tendency around 1 at. % ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and eventually decreases at a rate somewhat larger than the one corresponding to the decrease in the tritium concentration. Peak broadening increases almost linearly with the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ concentration but speeds up significantly around 1 at. % ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. Peak shifting and broadening combined with recent dilatometric measurements yield a consistent picture of the damage evolution. The main result is that in the range studied most of the tantalum self-interstitials produced on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ bubble formation are incorporated into an evolving dislocation network.