Irradiation and testing of off-the-shelf seal materials for water hydraulic applications in ITER remote handling equipment

Remote handling (RH) is one of the most challenging aspects of the ITER project, and the European home team is building a major prototype of the divertor region (the Divertor Test Platform 2) to confirm practically the RH concepts proposed in this area. To handle the 9 Tonne divertor cassette, water hydraulics has been selected because it offers high forces and precise control in a compact envelope, with minimal long-term contamination should a leak develop. Water hydraulic components use mainly stainless steel – unaffected by gamma radiation – but the integral seals and O-rings are known to be sensitive. For radiation testing of these components, a modular approach was adopted, enabling up to 11 seal carriers assemblies to be irradiated simultaneously in the limited space available, with individual carriers being removed at varying total doses up to 10 MGy. Each carrier was then installed in a real hydraulic rig for testing, revealing not only at what total dose the components became unusable, but also how they fail, enabling condition monitoring to assess the state of the seals long before their failure might render the RH equipment irrecoverable.