A major concern in fusion reactor design is possible hydrogen-isotope-induced embrittlement of structural alloys in the neutron environment expected in these reactors. Hydrogen fractionation occurs between lithium and various refractory metals according to a temperature-dependent distribution coefficient, KH, that is defined as the ratio of the hydrogen concentration in the metallic specimen to that in the liquid lithium. In the present work, KHwas determined for pure vanadium and several binary (V-10Cr, V-15Cr, V-5Ti, V-15Ti, V-20Ti, V-30Ti) and ternary alloys (V-10Cr-5Ti, V-15Cr-1Ti, V-15Cr-5Ti, V-3Ti-0.5Si), and the commercial Vanstar 7 (V-10Cr-3Fe-1Zr). Hydrogen distribution studies were performed in an austenitic steel forced-circulation lithium loop. Equilibrium concentrations of hydrogen in vanadium-base alloys exposed to flowing lithium at temperatures of 350 to 550°C were measured by inert gas fusion techniques and residual gas analysis. Thermodynamic calculations are consistent with the effect of chromium and titanium in the alloys on the resultant hydrogen fractionation. Experimental and calculated results indicate that KHvalues are very low; i.e., the hydrogen concentrations in the lithium-equilibrated vanadium-base alloy specimens are about two orders of magnitude lower than those in the lithium. Because of this low distribution coefficient, embrittlement of vanadium alloys by hydrogen in lithium would not be expected. © 1991.
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