| Abstract: | In order to examine influences of coexistent hydrogen isotopes on diffusion behavior of tritium in niobium, tracer diffusion coefficients Dt of tritium in alpha phase of hydrogenated and deuterized niobium (α-NbHxTy and α-NbDxTy (x<0,8,y<Dt show typical hydrogen concentration dependence: Dt of tritium for both α-NbHxTy, and α-NbDxTy, decreases with hydrogen concentration under all experimental conditions. The obtained concentration dependence of Dt of tritium differs from that of Dt of protium in α-NbHx or of deuterium in α-NbHxTy. On the other hand, no appreciable differences in the concentration dependence of Dt of tritium between α-NbHxTy, and α-NbDxTy, are observed: there are no definite isotope effects due to the coexisting hydrogen isotopes. This result suggests that Dt of tritium for a tritiated niobium (α-NbTx) is not very different from that for α-NbHxTy and α-NbDxTy. The chemical diffusion coefficient D* of tritium is also evaluated on the basis of the obtained Dt of tritium and of a literature value of a thermodynamic factor F for Nb-H and Nb-D systems. |
