PROGRESS IN VANADIUM ALLOY DEVELOPMENT FOR FUSION APPLICATIONS

Vanadium alloys have been identified as a leading candidate low-activa tion structural material for fusion first-wall blanket applications. C andidate vanadium alloys exhibit favorable safety and environmental ch aracteristics, good fabricability, high temperature and heat load capa bility, good compatibility with liquid metals and resistance to irradi ation damage. The focus of the vanadium alloy development program has been on the vanadium-chromium-titanium (0-15%Cr, 1-20%Ti) alloy system . Investigations include effects of minor alloy elements such as Si, A l and Y and substitution of iron for chromium in the ternary alloy. A V-4Cr-4Ti alloy is currently regarded as the reference alloy. Signific ant progress has been made in the development of vanadium alloys for f usion applications. Two production-scale heats (500 and 1200 kg) of th e V-4Cr-4Ti alloys have been produced with controlled levels of impuri ties. The baseline properties of the 500 kg heat are similar to those of the previous laboratory-scale heats. Additional data have been obta ined on baseline tensile and fracture properties. Results obtained on several heats with minor variations in composition indicate high unifo rm and total elongation of these alloys at temperature from RT to 700 degrees C. Results obtained to date indicate that the V-Cr-Ti alloys a re resistant to swelling and embrittlement after exposure to relativel y high neutron fluences at temperatures of 400-600 degrees C. The prop erties are not significantly different when modest amounts of helium a re generated during neutron irradiation by the dynamic helium charging experiment method. However, recent results have indicated that these alloys are susceptible to irradiation embrittlement at lower temperatu res. Additional irradiation experiments are in progress to investigate these effects at temperatures of 200-400 degrees C. This paper presen ts an update on the experimental results on candidate low activation v anadium alloys. (C) 1998 Published by Elsevier Science S.A. All rights reserved.