Diffusion of hydrogen in metals

The present status of our understanding of the diffusion of hydrogen in metals, both experimental and theoretical, is reviewed. Discussions are focused on the mechanism of diffusion of hydrogen isotopes H, D and T in f.c.c. and b.c.c. metals; the positive muon (μ +) is referred to where appropriate. An up-to-date compilation of diffusion data as a function of temperature and isotope mass has been made, and a clear distinction in general diffusion behaviour in f.c.c. and b.c.c. metals is noted. Subsequently, the results obtained from the Gorsky effect, nuclear magnetic resonance and quasi-elastic neutron scattering that provide information on elementary jump processes are discussed. A conceptual framework of the quantum diffusion of light interstitials in metals is given, including the recent Kondo theory that emphasizes the crucial importance of particle-conduction electron interactions in the diffusion process, especially at low temperatures. It is shown with the help of recent estimates of the ...

Non-Pd BCC alloy membranes for industrial hydrogen separation

Tritium is a radioactive form of hydrogen. Because it is radioactive, its release to the environment must be minimized. Most of the materials used in fusion reactors are metals that have a relatively high permeability for tritium. The fusion community has been working on barrier materials to minimize tritium release by permeation through structural materials. Unfortunately, most barrier materials work very well during laboratory experiments, but fail to meet requirements when placed in radiation environments.

This chapter presents tritium permeation characteristics of various materials used in fusion reactors, including plasma-facing, structural, and barrier materials. The parameters necessary for tritium release calculations for various regions of a fusion reactor are given.

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4.16 – Tritium Barriers and Tritium Diffusion in Fusion Reactors

Gorsky-effect measurements of the diffusion coefficient of tritium (T) in V, Nb and Ta are reported. The measurements were performed at small T concentrations (less than about 1.4 at.%), and in the temperature range from -140 degrees C to 100 degrees C. Comparison with results obtained for H and D shows an increase of the activation energy with increasing isotopic mass. For Nb and Ta, the pre-exponential factors are identical for all the isotopes, whereas for V this factor is appreciably larger for T and for H and D. The reduction of the relaxation strength in the presence of precipitation allows a rough determination of the solubility limit, which is found to be isotope independent for Nb and Ta. In V, the solubility limit for T is shifted slightly to lower temperatures. The H, D or T induced lattice expansion calculated from the relaxation strength shows no dependence on isotopic mass.

https://iopscience.iop.org/article/10.1088/0305-4608/13/10/015/pdf

G. Alefeld

Papers

Influence of nitrogen on the diffusion coefficient of hydrogen in niobium

Influence of impurities on the diffusion coefficient of hydrogen and deuterium in vanadium

X-ray investigation of the niobium hydrogen phase diagram

Comments on “a possible problem in measuring hydrogen diffusivity at low temperatures by the Gorsky effect”

Comments on “on Gorsky effect measurements of hydrogen diffusion in niobium” by Matusiewicz, Booker, Keiser and Birnbaum