Operational experience with a variety of plasma facing tile assemblies at JET

During the June 1999 JET shutdown, 3000 plasma facing Tile Assemblies were found to be loose and had to be re-torqued remotely using the Mascot force reflecting manipulator. Whilst the integrity of these Tile Assemblies has been monitored during previous man access shutdowns, with the introduction of tritium to the machine in May 1996, the majority had not been checked since March 1996. This paper reviews typical plasma facing Tile Assembly designs within the JET torus and summarises the experience gained for use in future machine applications. This includes loosening processes/mechanisms and their prevention, applications of surface coatings to avoid seizing of un-lubricated assemblies, and the use of vibration resistant thread profiles. The design of attachments to minimise combined mechanical and thermal stresses in the tiles, material selection and other engineering aspects are also discussed.