Influence of coexisting hydrogen isotopes on diffusion of tritium in niobium

The tracer diffusion coefficient of tritium in Nb has been measured at 523 K under the condition that tritium coexists with protium or deuterium. Thes e data suggest the trend that the tracer diffusion coefficient of tritium i n NbHxTy is somewhat larger than that in NbDxTy, though a definite conclusi on has been reserved because their difference is small and comparable to th e scattering of the experimental data. The concentration dependence of trac er diffusion coefficient of tritium in NbHxTy and NbDxTy can be practically considered to be equal to that of NbTx. On the basis of these experimental data and the data reported by Fukai et al., it has been suggested that the tracer diffusion coefficient of lighter hydrogen isotopes is appreciably i nfluenced by coexisting heavier hydrogen isotopes but that of heavier hydro gen isotopes is scarcely influenced by coexisting lighter hydrogen isotopes . (C) 1998 Elsevier Science B.V. All rights reserved.