Studies on the permeation of Hydrogen and Tritium through heat resistant alloys

At temperatures of 750 to 950°C the permeation of hydrogen through bare, heat resistant alloys was studied from 1 to 40 bar, the diffusion and permeation of tritium in the partial pressure range of 10 −4 bar. Among the alloys studied were Incoloy 800, 800 H, 802, Inconel 617, 625, the Ni-based alloy Nimonic PE 13, and several non-commercial steels. At a given temperature, the permeation rate through samples with clean surfaces — substantially free of oxide films — was found to be proportional to the square root of the hydrogen pressure. The C and the Cr contents of the steels investigated proved to exert a strong influence on the activation energies of diffusion and permeation. In some alloys a reduction of the permeation rate was observed that can be attributed to the precipitation of intermetallic phases. In one case a decrease of the permeation rate occurred during the measurements due to a phase transformation.