Untersuchungen zur Diffusion von Tritium in Übergangsmetallen

Abstract

Investigations of the diffusion of tritium in transition metals have been carried out by using "time-lag" methods. The β-radiation, originating from tritium decay within a thin layer near the external surface of the metal, was taken as the signal to follow the change of tritium concentration with time in this layer. No passage of tritium atoms through the phase boundary is necessary for this method; the influence of energy barriers, which might retard this passage, can therefore not interfere. Measurements with palladium at temperatures between 16.5 °C and 50 °C and vanishing hydrogen content in the Pd yielded: D0 T = (10.5 ± 3.0) • 10-3 • exp{- (6350 ± 300)/RT} cm2 s-1, (R T in cal/mole). The observed isotope effects in the diffusion of H, D and T in palladium are discussed. At 25 °C diffusion coefficients of tritium in Pd/Ag-alloys of different compositions (0 - 70 atom-% Ag) were determined. They first decrease slowly with rising silver content up to 30% and then drop sharply to very low values at higher Ag-contents. Measurements with tantalum at 25 °C yielded: DT = (0.50 ±0.25) • 10-6 cm2 s-1