Irradiation tests on water hydraulic polymer components

Remote handling operations in ITER will require the use of hydraulic systems for lifting and moving activities, such as those envisaged for the cassette multifunctional mover (CMM) and the cassette toroidal mover (CTM). In these situations polymer materials employed as seals, glide rings, O-rings, and wipers on the pistons and cylinders will be subjected to gamma radiation in the presence of water or high humidity. To examine their reliability several standard polymer materials have been gamma irradiated to 1.0, 3.3, and 10.0 MGy at 30 C, in dry nitrogen and deionised water. The polyethylene, polyurethane, and rubber type materials proposed for seals, O-rings, and wiper rings showed no notable degradation up to 10 MGy. However, by this dose the hard fabric composite material for the glide ring was severely degraded, with the fibre dissolving out of the matrix, and production of residues, in particular fluorides in the water.