PRODUCTION OF HIGH-PURITY VANADIUM, CHROMIUM AND TITANIUM FOR USE IN LOW ACTIVATION MATERIALS

The presence of radiologically potent tramp elements must be strictly controlled if the intrinsic low activation properties of alloys based on vanadium and chromium are to be fully realised. In this study the incidence of critical impurity elements in commercial sources of vanadium, chromium and titanium metals and precursor compounds is investigated using techniques for trace element analysis. MaxiMUM permitted concentrations corresponding to the attainment of the "hands-on" dose rate limit of 25 muSvh-1 after 100 yr cooling of first wall material were adopted as target values. Chromium and titanium from commercial sources are able to satisfy the purity target. Commercially available vanadium may contain unacceptable levels of Mo, Ag, Nb or Co and additional purification steps designed to remove these impurities are described.