Diffusion and trapping of tritium in vanadium alloys

Tritium diffusion in a vanadium alloy (V-4Cr-4Ti) has been investigated at temperatures ranging from 230 K to 573 K. Tritium was loaded into the surface layers of the alloy specimen with an ac-glow discharge. Before and after diffusion annealing of the specimen, tritium diffusion profiles were measured by means of an imaging plate (IP) technique. Tritium diffusion coefficients (D_T), which were evaluated by fitting a numerical solution of the diffusion geometry employed here to the obtained diffusion profiles, were a little smaller than those for pure V with the activation energy of 0.13 ± 0.01 eV. Below 320 K, in addition, the Arrhenius plot of D_T bent downwards showing a larger activation energy of 0.19 ± 0.01 eV, probably owing to the trapping effect of both of Cr and Ti. The effect of alloying elements on tritium diffusion and the influence of tritium release from the surface were discussed.