LOW-ACTIVATION AUSTENITIC MN-STEEL FOR IN-VESSEL FUSION MATERIALS

Several compositions of austenitic manganese steels (Mn-steels) were i nvestigated for in-vessel component materials in D-T fueled fusion rea ctor with respect to radiation exposure and waste disposal management. The 24.5Mn-13.5Cr steel was developed in which undesired impurities, such as Ni, Mo, Nb and Co, were controlled and C (similar to 0.025wt%) and N (similar to 0.22wt%) contents were well adjusted for corrosion resistance and weldability. Experimental observation has shown that th is steel has a single gamma-phase structure and good properties for va cuum vessel almost the same grade as Type 316 stainless steel (316SS), such as low permeability, good weldability, good mechanical propertie s of strength and toughness and good corrosion resistance. Activation calculations were performed adopting this material for the JT-60 Super Upgrade (JT-60SU) vacuum vessel and the effectiveness of low activati on was confirmed. (C) 1998 Elsevier Science B.V. All rights reserved.