Simulation of Thermal-Hydraulic Transients in the KSTAR PF1 Coil Using the 4C Code

KSTAR is a fully superconducting tokamak in operation since 2008 at the National Fusion Research Institute in Korea. All coils are wound using cable-in-conduit conductors and cooled with forced-flow supercritical helium at 4.5 K and 5.5 bar. We consider here the central pair, PF1U/L, of the central solenoid coils; during operation, these coils are subjected to sharp current transients, which induce ac losses in the coil. The thermal hydraulic transient following a trapezoidal current pulse, with a ramp-up to 10 kA at a rate of 1 kA/s and a ramp-down to 0 kA at a rate of 10 kA/s, is simulated here using the 4C code, and the results are compared with the measurements.