Tritium diffusion in V-4Cr-4Ti alloy

Characteristics of the tritium diffusion coefficient D-T in V-4Cr-4Ti alloy, including a bending in the Arrhenius plot of D-T, are examined. Based on a trap model, the possible trap sources and their binding energies for tritium in the alloy are evaluated using the experimental data of D-T in pure V which are measured with a tritium tracer method and the literature data of protium diffusion in V-Ti and V-Cr alloys. The result of the evaluation suggests the presence of two trap sources in the alloy. The first would be attributed to a trap at each substitutional alloying atom which is likely to be Ti. The binding energy E-B of 0.08 eV gives the best fit to the observed value of D-T above 300 K The bending in the Arrhenius plot below 300 K is caused by a second trap site with a higher E-B, and a lower concentration than those of each alloying atom. The trap is probably formed by the alloying atoms presence to neighboring Ti atoms. The contribution of Cr atom to the trap effect seems to be rather small in this alloy.