KSTAR 극저온헬륨시스템 운전결과

Korea Superconducting Tokamak Advanced Research (KSTAR) was constructed for Korean fusion research and has been operated successfully since 2008. Different from other tokamak devices, KSTAR is fully superconducting (SC) magnet tokamak which consists of 30 magnets and is made of Nb₃Sn and NbTi superconductor. To reach appropriate operating condition of the KSTAR SC magnets, the magnets temperature should be cooled down to liquid helium temperature. A Helium Refrigeration System(HRS) with an exegetic equivalent cooling power of 9㎾ at 4.5K is dedicated to cool down and keep the KSTAR SC magnets in cryogenic temperature. Since the commissioning period and the first campaign of KSTAR, the HRS has showed sufficient performance for the KSTAR SC magnets operation. The estimated time of cool-down for KSTAR cold components was 30 days, but the KSTAR SC magnets were reached to cryogenic temperature in 23 days at the first cool-down operation. Due to the long period of the KSTAR campaign, the reliable operation of the HRS is as important as its performance. During the past 4 years of campaign, the abnormal events were occurred several times and they were influenced to the reliability of the KSTAR HRS and the system availability was decreased. This paper will present the operation result of the KSTAR HRS since the first campaign and the record of the abnormal events and reliability will be discussed.