Copper Alloys Used for Support Units of ITER Blanket Modules Compression and Tension Properties

Four flexible support units are used for each first wall module bracing to the vacuum vessel of ITER. The support unit consists of fastening bolt, flexible cartridge and collar for compensation of thermal expansion. The collar made of copper alloy operates under considerable compression load. The performed structural analysis shows that stresses in the collar exceed the design allowable value specified in ITER Structural Design Criteria for In-Vessel components (SDC-IG) for CuCrZr-IG alloy. The ITER SDC-IC design allowables for CuCrZr-IG alloy were based on tensile data for solution annealed and age material. There is a potential to keep structural integrity if material with higher strength will be used. It is also reasonable to use real compression data for specification of allowable stresses. This paper deals with the compression and tension tests of CuCrZr and CuNiCrSi alloys proposed for collar of flexible support of ITER first wall modules. Tensile tests and comparative analysis of stress-strain curves under tension and compression were performed at RT and 300 degrees C. Conclusion made on the bases of experimental data: - CuCrNiSi alloy exhibits higher strength in comparison with CuCrZr alloy both under tension and compression; - CuCrZr alloy in solution annealed, cold worked and aged condition is preferred for the collar (due to higher yield strength) in comparison with solution annealed and aged material; - yield stress at 0.2% offset under compression were about 4-10% higher (depending on material and temperature) than that one under tension; Utilization of material with higher strength (i.e. CuCrNiSi) or CuCrZr alloy in solution annealed, cold worked and aged condition allows to satisfy design stress limits specified for ITER (in SDC-IC) and to keep the structural integrity of flexible support unit.