TFTR TF coil thermal analysis and test

A water-cooling-passage leak which developed in a TFTR (Tokamak Fusion Test Reactor) toroidal-field (TF) coil has precipitated interest in developing alternative cooling options for this coil system. A test on a spare coil was performed to establish a low-power heating schedule (in preparation for an elevated temperature dry-out cycle on the leaking coil) and to determine the efficacy of gas cooling the TF coils. A computer analysis was performed using the test results to benchmark the code. The investigation of gas cooling was initiated as a contingency in the event of future irreparable leaks developing in the TF-coil cooling passages. It is believed that gas leakage into the electrical insulation would have a relatively benign effect on its dielectric strength, whereas recent experience on the TFTR indicated a substantial degradation of dielectric strength when in contact with water (the use of high-dielectric silicone oil as an alternative coolant is discussed elsewhere in these proceedings). Two- and three-dimensional thermal models are described, and a cooling analysis of the TF coil that compares air cooling, helium cooling and sulfurhexafluoride cooling is presented. >