Behaviour of helium and hydrogen in vanadium alloys – innovative fusion reactor first wall materials: a review. Part 1. V – Ti and V – Fe alloys

Abstract

This paper is the first part of a three-part review that looks at the effect of doping elements on the behaviour of helium, the development of gas porosity, as well as at the amount of retained hydrogen introduced into vanadium alloys with Ti, Cr, W and Ta (using different techniques) with a rapid decay of induced radioactivity. The same regularities have been identified regarding how the chemical composition of the alloys impacts the hydrogen entrapment and retention regardless of the way it is introduced: either through pressure saturation without defect formation or through ion implantation with radiation-induced defects entailed. It was established that when vanadium is doped with a chemically active element (V – Ti alloys), the concentration of the latter has a nonmonotonic effect on the helium porosity and the mass fraction of retained hydrogen. It can be attributed to the way titanium interacts with oxygen and nitrogen in vanadium, which dictates how much titanium hydride will form. The paper demonstrates that pre-irradiation of the alloy with helium ions results in a higher amount of retained hydrogen when it is introduced further, regardless of the temperature.