부산대학교 도서관

The upgrade to JT-60SA tokamak (R = 3 m, a = 1.2 m) was conducted within a Europe-Japan collaboration agreement featuring the implementation of superconducting magnets. In 2021, the magnet system commissioning was initiated, undergoing cool-down and energization of the 18 Nb-Ti Toroidal Field (TF) coils (400 tonnes) up to full nominal current. TF energization was smoothly processed but it was observed during current load a higher outlet temperature increase of TF02 coil versus others, indicating a higher resistance in this coil circuit and therefore a possible risk in future operation. The present paper analyses the different risk factors that can impact the TF operation safety margins and their quantitative contribution. To this end on the one hand ad-hoc thermal & thermo-hydraulic models were developed by CEA and F4E to represent the TF02 whole circuit including feeder zone where high resistance is suspected to be located. The outcomes of those models on chosen TF and PF current scenarios including transient loads and their impact on temperature margin in risky zones such as terminal joint (TJ) are presented. On the another hand a 3D electrical circuit of TJ was modelled using TF cables tomography, giving a realistic quantitative insight into local current distribution, therefore on current sharing temperature. The analyses outcomes synthesis is depicted under strategic considerations and tentatively contributes to establishing guidelines for future operation scenarios in which magnets will undergo demanding conditions.