The diffusion coefficients of D2 in Nb—1 wt% Zr were determined in the range from 923 to 1148 K. A hollow-cylinder model, used as the frame of reference, adequately described the transport of D2 through the alloy containing oxygen impurities. The diffusion coefficient is temperature dependent and is best described byD (m2/s) =8.5 ± 7 × 10−8 exp (−48.2 ± 6.7 × 103/RT) .