Three of the toroidal field (TF) coils of the JET tokamak have developed interturn faults. These faults have not been catastrophic and it has been possible to continue operation and replace the faulty coils with spares at the next pre-planned shutdown. The faults were found to be due to water leaks. The coil coolant was changed from water to an insulating fluid. All known faulty coils have been changed and latest measurements do not detect any faults on the installed coils.
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