Combination of liquid lithium with Reduced Activation Feritic/Martensitic Steel (RAFM) is one of the options for Test Blanket Module (TBM) in early ITER period and early DEMO blanket, as well as an intermediate step toward Li/V DEMO blanket. In this paper, characterization of a Li/RAFM blanket was carried out and compared with a Li/V blanket from neutronics and compatibility viewpoints.

Although the local Tritium Breeding Ratio (TBR) will be reduced by ∼0.1 by the change from Li/V to Li/RAFM, Li/RAFM seems to be still feasible, with enhanced neutron shield, from the tritium self-sufficiency viewpoint. A similar tritium production rate for the Li/V and the Li/RAFM TBMs suggests that the Li/RAFM TBM simulates well the tritium production of Li/V TBM and thus will be suitable for Li/V DEMO blanket design as well as Li/RAFM blanket.

Based on the available data, V-alloys are thought to be highly compatible with Li when the impurity level in the Li is low. New compatibility experiments of RAFM with Li showed transformation of martensitic to ferritic phase in addition to corrosion loss. However, the compatibility issue is estimated to be small for ITER-TBM conditions.

The present study showed the significance of starting with a Li/RAFM TBM during the early phase of ITER operation for development of both Li/RAFM and Li/V DEMO blankets.