Deuterium and helium desorption/retention properties of low-activation vanadium alloys possible for reuse in a short time in fusion reactors

Low-activation vanadium (V) alloys are alternative to the reduced-activation ferritic/martensitic steels due to their high-temperature strength, superior irradiation properties and non-magnetic characteristics. To make the reusage of the alloys possible in a short time in fusion reactors, new design concepts of V alloy have been suggested in National Institute for Fusion Science. In the present study, the deuterium and helium retention/desorption behaviors of the new designed V alloys were investigated. A major desorption peak of D 2 appeared at 600 -750 K for the irradiation at room temperature. This peak would be originated from D atom in a binding state in the alloy. In the case of the irradiation at 773 K, a new peak appeared around 820 K only for the alloy with low purity and high Ti content. Discussion with results of EELS analysis suggests that the desorption around 820 K were originated form D trapped by the precipitates. Other V alloy samples used in the present study showed low D retention for the case of the 773 K irradiation. The helium desorption which was originated from the blisters appeared at the high temperature region. The amounts of these desorption for the alloy with high Ti content was large, compared with the case of low Ti content.