Development of the Helium Inlet and Outlet for the CFETR Central Solenoid Model Coil

Abstract

China fusion engineering test reactor (CFETR) central solenoid model coil (CSMC) made with cable in conduit conductor superconductor had been developed in the Institute of Plasma Physics, Chinese Academy of Sciences. The highest magnetic field of CSMC is 12 T when the running current is 47.65 kA at 4.5 K, and the largest magnetic field change rate is 1.5 T/s. CSMC mainly consists of one Nb 3 Sn inner coil, one Nb 3 Sn outer coil, and three NbTi coils cooled by supercritical He flow. There are totally ten helium inlets and outlets distributed in CSMC. Due to the geometrical discontinuity within the helium inlet and outlet, the helium inlet area is one of the regions, where high stresses can be expected in the CFETR CSMC. This paper describes the structure design, stress analyses, welding R&D of helium inlet and outlet. A local finite element model based on structure design is created to calculate the stress on the helium inlet under electromagnetic load. The welding R&D activities, including welding trials, destructive test, and NDE have been carried out to develop welding technology.