Thermal Behavior and Quench of the ITER TF System During a Fast Discharge and Possibility of a Secondary Quench Detection

Abstract

During a fast discharge of the TF system, eddy currents and high associated heat production in the winding plates can induce a quench by heat transfer. A quasi 2D model based on the coupled GANDALF and FLOWER codes [1] allows the calculation of the radial heat transfer from the plates to the CICC through the conductor insulation as well as hydraulic transients with an external cryogenic circuit. This model is used in three particular cases: 1) Plasma Disruption (PD) with associated heat deposition followed by a Fast Discharge (FD) (with self Joule heating of conductor) with 2 s delay; 2) Quench initiation with Minimum Quench Energy (MQE), followed by a 2 s heat deposition associated with a plasma disruption and then FD; 3) Case where the quench has not been detected earlier by the primary detector (“undetected quench” [2]). The signals regarding temperature, pressure and mass low rate reach significantly high values especially in the conductor, at the inlet and outlet of the helium channel in the feeder at the Cold Termination Box (CTB), where the sensors are located, and at the exhaust cryolines. A feasibility of a secondary detection, provided by thermohydraulics signals is studied.