Solubility and Diffusion of Hydrogen in Pure Metals and Alloys

Tritium Formation and Mitigation in High Temperature Reactors

“…The permeability of diatomic hydrogen has been of interest for many years 26 because of its roles in chemicals manufacturing, petroleum refining, and nuclear engineering. Classical diffusion theory predicts that diffusivity (and hence, permeability) for two particles with different masses could be corrected according to Equation 14, known as the "isotope effect":…”

“…One possible reason for the comparatively large number of studies on tritium permeability is the theoretical similarity of diatomic hydrogen gas to HT and the interest in hydrogen permeability through a variety of alloys in many industries. 26 In general, hydrogen diffuses in pure metals by occupying interstitial spaces. Permeation rate is dependent on partial pressure of hydrogen (tritium) and system temperature.…”

“…Permeation rate is dependent on partial pressure of hydrogen (tritium) and system temperature. 26 At the temperatures of interest for a high-temperature MSRs, permeation occurs relatively easily in pure metals. Since metal oxides are partially resistant to hydrogen permeation, 1 it has been suggested that oxidizing system piping prior to run-time may help reduce the rate of hydrogen loss into the atmosphere.…”

Rational design of Nb-based alloys for hydrogen separation: A first principles study

“…On the other hand, membranes based on group-V elements (e.g., V, Nb, and Ta) have also been studied due to their lower cost and higher hydrogen permeability than Pd-based ones. [4][5][6] With a BCC structure, the group-V metals can dissolve larger amount of hydrogen and allow faster hydrogen diffusion (and hence higher permeability) than Pd and Pd-based alloys of an FCC structure. However, the high solubility of hydrogen often results in H embrittlement fracture under service conditions.…”

“…3,6 When the H concentration (H/M) is greater than 0.7, the structure of the metal-hydrogen solid solution system changes from α to β (or γ ) phase, which is susceptible to brittle fracture. This mechanical failure has severely hindered commercial application of these membranes.…”