Organic cooling fluids for the JET toroidal and divertor field coils

When the inter-turn electrical fault was found on the JET toroidal field coil 3.1 a series of studies were carried out to find an alternative cooling fluid to demineralised water with a high intrinsic electrical resistivity. The initial selection examined the physical characteristics of the fluids and ruled out all but three organic compounds. This paper describes the further tests and studies which were carried out to assess the performance and suitability of these organic cooling fluids. The plant implications including storage vessels, vent pipework, pump mechanical seals vapour detection scheme and leak detection are examined together with the waste management and the environmental aspects of using organic cooling fluids.