Purification and recovery of hydrogen isotopes using palladium based dense metallic membranes is of utmost importance in fusion fuel clean-up systems. Permeation behavior of hydrogen isotopes in the dense metallic membrane is the deciding factor for their applicability. Here, we report the hydrogen and deuterium permeation behavior of 100 mu m thick Pd0.72Ag0.23 and Pd0.77Ag0.10Cu0.13 alloy membranes using a closed recirculatory feed gas loop at low transmembrane pressures of 50, 100 and 150 kPa in the temperature range 523-673 K. These membranes were found to have infinite hydrogen selectivity. This study revealed the higher permeability of hydrogen and deuterium in Pd0.77Ag0.10Cu0.13 than Pd0.72Ag0.23 at all experimental temperatures and transmembrane pressures. Further, the deuterium permeability was found to be lower than that of hydrogen in both the membranes. Diffusion of hydrogen/deuterium in the bulk of the membrane was found to be the rate liming step. We also report here the pertinence of Pd0.77Ag0.10Cu0.13 membrane in purification of He-3 contaminated with tritium to obtain high purity He-3 for use in neutron detector. (C) 2016 Elsevier B.V. All rights reserved.