Conceptual design study for CFETR divertor target using CLAM steel as structural material

Abstract Monoblock technology with CuCrZr as the structural material is the standard divertor target design for the initial phase of the China Fusion Engineering Test Reactor (CFETR). The design concept with China Low Activation Martensitic (CLAM) steel as the structural material provides another candidate solution for the CFETR divertor target. This paper presents a design study of an optimized monoblock to meet the requirements for CFETR operating conditions, which establishes a good basis for engineering design of CFETR. The monoblock uses tungsten as armour and CLAM steel as the structural material, with a copper interlayer. The operating temperature window of CLAM steel was determined by irradiation embrittlement, softening, and other aging effects. Initial design rules for the W/CLAM monoblock were checked; thermal results by finite element analysis (FEA) show that the design concept is able to withstand a heat flux of 10 MW/m2 after examining the temperature for each material and the margin to the wall critical heat flux (WCHF) on the tube. Mechanical results indicate that the CLAM steel meets the ITER SDC-IC elastic rules under potential irradiation level of CFETR, irrespective of residual stress. Also the fatigue criteria were checked for unirradiated conditions with a reasonable life time of 16,000 cycles.