Experimental refutation of the deuterium permeability in vanadium, niobium and tantalum

Deuterium permeability through Nb, V, and Ta was measured in the temperature range between similar to 300-500 degrees C and 100-1000 mbar. For the three materials, the permeation rate at 500 degrees C was between two and torders of magnitude below expected values which were obtained by combining diffusivity and solubility data and which have been traditionally accepted due to the insufficient experimental available data. Comparison with existing literature suggests a complex dependence of permeability with temperature, which helps explain this discrepancy. Given the important role of the surface condition on the permeability, additional deuterium permeation tests were carried out in vanadium for more realistic sample preparation. Results indicate that native oxides formed at room temperature introduce a permeation reduction of several orders of magnitude, and must be considered for practical applications.