Design and experimental investigation of the ability of large superconducting magnets to operate under nuclear heating

Abstract

Abstract Development testing in the Large Coil Task (LCT) has included investigation of superconducting coils' tolerance for various forms of healing, such as may be encountered in the magnets of a fusion reactor. The nuclear heating in coils is strongly influenced by the reactor design. The LCT coils are the first large superconducting magnets to provide experimental perspectives on nuclear heating. The Japanese LCT coil is one of three pool-boiling cooled coils in a six-coil toroidal array at Oak Ridge National Laboratory. The coil size is about one half that of fusion reactor coils. Simulated nuclear heating tests were performed on the Japanese coil. The coil was designed to be fully cryostable at the magnetic field of 8 T, and experimental results indicated that a local nuclear heating power density of 55 mW/cm3 has negligible influence on the stability of the coil. It corresponds to an equivalent nuclear heating power density of 5 mW/cm3 in the innermost turn of the winding. Excessive heating power resulted in a coil quench due to vapor accumulation. While the boundary of the tolerance was not surveyed, the value of 5 mW/cm3 is considered to be the limit for nuclear heating in a pool-boiling cooled coil. As for a forced-flow cooled coil, its tolerance seems to be smaller.