Status of India-specific Reduced Activation Ferritic-Martensitic steel and fabrication technologies development for LLCB TBM

Abstract

India is developing the Lead Lithium Ceramic Breeder Test Blanket Module (LLCB TBM) for in-situ experiments in ITER. India-specific Reduced Activation Ferritic-Martensitic (IN-RAFM) steel is the chosen structural material for the fabrication of LLCB TBM. IN-RAFM steel plates with different thickness are being produced from commercial heats. Presently, characterization for mechanical and physical properties is in progress in order to generate material properties database from these commercial heats.In order to avoid welds on plasma facing surface of TBM First Wall (FW), scaled down mock-ups of FW are being fabricated using Hot Isostatic Pressing (HIP). Electron Beam (EB) welding, Laser/laser-hybrid welding and Narrow Gap-Tungsten Inert Gas (NG-TIG) welding, are being developed for fabrication of other TBM components. These welding processes have distinct advantage over conventional welding processes because of their high depth to width ratio, minimal HAZ, lower weld volume, reduced distortion and lower residual stresses in the weld joints. Mock-ups of LLCB TBM components are being fabricated using Grade 91/IN-RAFM steel to investigate the accessibility for the envisaged welding processes and to identify and develop the non-destructive evaluation (NDE) techniques. In addition, this would also help to establish the assembly sequence of LLCB TBM. Ultrasonic based methodologies are under development to assure integrity of these joints in the fabricated components.Details of these developments in IN-RAFM steel as structural material, fabrication technologies and mock-ups fabrication towards realization of the LLCB TBM are discussed in this paper.