Structural materials for fusion reactors

Fusion Reactors will require specially engineered structural materials, which will simultaneously satisfy the harsh conditions such as high thermo mechanical stresses, high heat loads and severe radiation damage without compromising on safety considerations. The fundamental differences between fusion and other nuclear reactors arise due to the 14MeV neutronics of structural materials. There exists considerable uncertainty in the nuclear data at such energies because there aren't any strong enough sources for such neutrons except fusion reactors themselves! We thus encounter a problem of iterative nature in which we must try several experiments with the available materials in the near term. The development of such structural materials is thus going to require the experimental data of the kind that may be generated on reactors like ITER, high-performance modeling and a penetrating metallurgical insight to overcome technological challenges in terms of achieving required properties such as low activation by controlling the impurities, good thermo-mechanical properties by microstructure engineering, good chemical compatibility and high radiation resistance. These materials need to withstand a neutron wall load of the order of 2-3 MW/m(2), which can lead up to 30 dpa of radiation damage and 300 appm helium production per full power year in DEMO like reactors. Such conditions lead to unprecedented events related to the failure of materials due to irradiation creep, Ductile-Brittle Transition Temperature (DBTT) shift and helium embrittlement. The development of fusion materials program is oriented towards fulfilling the requirements of Test Blanket Modules, various prototype activities of SST-2 and DEMO reactor. The materials identified for first wall and blanket modules for Indian DEMO are LAFMS and ODS steels. The development program plan for these materials include (i) Manufacturing of LAFMS steel through VIM/VAR methods by controlling the impurities such as S, P and Si. (ii) ODS steel development with nano-size Y(2)O(3) dispersoids in ferritic martensitic matrix by powder metallurgy route. The advanced structural materials like SiC(f) /SiC composites and SiC(f) /n-SiC are planned under National Fusion Program projects for indigenous development. An overview of the planned program in this direction will be presented.