Hydrogen Solubility in Zr-Nb Alloys

Abstract

We present a fast and accurate method for predicting the thermodynamics of hydrogen solubility and trapping in alloys, which is two orders of magnitude faster than conventional ab-initio approaches. The model hinges on the finding that the solubility of H is dominated by its nearest neighbour environment. We apply the method to the problem of hydrogen redistribution in Nb-containing Zr nuclear fuel cladding, and validated it against brute-force ab-initio approaches. We find that, in un-irradiated alloys, hydrogen preferentially dissolves into β-Zr over α-Zr, but not into β-Nb. After irradiation, the opposite is true: the change in composition of primary β-Nb particles increases their hydrogen-trapping strength, and the nano-platelets reported to form under irradiation are potentially even stronger hydrogen sinks, especially if induced by proton irradiation rather than neutrons; while in alloys containing metastable β-Zr, H is likely to redistribute out into the α phase following the decomposition of β-Zr.