Design Approach and Analysis Results for Structure Feeders of ITER Magnets

The superconducting magnet system of ITER has ~5,000 tons of cold mass as steel structures to support the gravity and electromagnetic forces. These steel structures need to be maintained at ~4.4 K during magnet operations. The magnet system has three STR (structure) feeders for distribution, monitoring and control of helium to remove heat loads from these large steel structures during cool down and normal operation. One SHe (supercritical helium) circulation pump for flow rate of ~2.7 kg/s, in a closed loop is used only for cooling of structures, and these 3 STR feeders are part of this loop. Each STR feeder has 3 main components: SCVB (structure cooling valve box), CFT (cryostat feed through) and ICF (in-cryostat feeder). Unlike the coil feeders, STR feeders do not have bus bars, current leads & SBB (“S”-bend box), and present some difference in the design approach. The SCVB is placed outside the enclosure of the nuclear radiation shield and hence contains elements needing maintenance like valves and instruments required for diagnosis and operation of the cooling paths. Each SCVB has to accommodate about 20 valves within a limited available space. Some SHe lines will have running length of about 50 m from SCVB to coil structures, but the layout is such that the use of expansion joints can be avoided. The details of the design approach and analysis results will be presented in this paper.