Progress in vanadium alloy development for fusion applications

Abstract

Vanadium alloys have been identified as a leading candidate low-activation structural material for fusion first-wall blanket applications. Candidate vanadium alloys exhibit favorable safety and environmental characteristics, good fabricability, high temperature and heat load capability, good compatibility with liquid metals and resistance to irradiation 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, Al and Y and substitution of iron for chromium in the ternary alloy. A V-4Cr-4Ti alloy is currently regarded as the reference alloy. Significant progress has been made in the development of vanadium alloys for fusion applications. Two production-scale heats (500 and 1200 kg) of the V-4Cr-4Ti alloys have been produced with controlled levels of impurities. The baseline properties of the 500 kg heat are similar to those of the previous laboratory-scale heats. Additional data have been obtained on baseline tensile and fracture properties. Results obtained on several heats with minor variations in composition indicate high uniform and total elongation of these alloys at temperature from RT to 700°C. Results obtained to date indicate that the V-Cr-Ti alloys are resistant to swelling and embrittlement after exposure to relatively high neutron fluences at temperatures of 400–600°C. The properties are not significantly different when modest amounts of helium are 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 temperatures. Additional irradiation experiments are in progress to investigate these effects at temperatures of 200–400°C. This paper presents an update on the experimental results on candidate low activation vanadium alloys.