Operational Results of a Thermal-Hydraulic Quench Detection System for the KSTAR TF Superconducting Coils

The Korea Superconducting Tokamak Advanced Research (KSTAR) device is equipped with a prototype of the safety quench detection system (SQD), making use of the variation of the pressure and flow rate in supercritical helium (SHe) in the event of a quench, for the toroidal field (TF) superconducting coils. The SQD prototype measures absolute and differential pressures on orifice flow meters at SHe supply manifolds by using radio-resistant pressure transducers, then variation of the measurements is discriminated by using analog signal interfaces and hard-wired logic solvers of a two-out-of-three (2oo3) voting configuration for validation. The SQD prototype is being operated to obtain technical expertise in KSTAR. TF coil charging and PF coil pulsed operation had a different impact on the temperature variations due to eddy current of the TF coils and structure. Accordingly, the inlet pressure of the TF coils increased by small amount in comparison to the quench detection criterion of the SQD prototype. The plasma current seemed to increase impulse voltage, but only, by ∼10 mV in quench detection signals of normal-voltage detection method, and such a noise did not disturbed quench detectors. On the other hand application of the PF currents and plasma current increased outlet temperatures of the TF coils and structure by approximately 0.1 K. The inlet pressure variation due to the temperature variation was too small to achieve the quench detection criterion