ITER In-Cryostat inspection and repair feasibility studies

The ITER In-Cryostat maintenance study is an important precondition to guarantee the operation over the ITER lifetime. The ITER operation is subdivided mainly into two phases: 1. Hydrogen phase (non-nuclear operation phase). 2. Deuterium/Tritium phase (nuclear DT phase). The commissioning phase includes the initial phase of assembly. Within the first phase the ITER components will be tested; afterwards they will go into operation. The In-Cryostat maintenance shall facilitate all operations that could be required by In-Cryostat systems and the Cryostat itself. In cases of failures or unlikely events (e.g. earthquakes) it is necessary to provide man and tool access to In-Cryostat components. Overall functions which have to be implemented are: • Inspection of components including leak localization (helium, water, air). • Repair and replacement of component (instrumentation, parts or complete components). • Regulatory inspections. It is presumed that most of component failure would occur at the beginning of the operational phase. This failure rate is expected to be very unlikely when ITER is being operating during the nuclear phase. For maintenance activities it is assumed that: • The intervention frequency on each component is limited during its lifetime (e.g. inspections/repair during global shutdown). • Most of these interventions will be required during the inactive phase. According to ALARA (As Low as Reasonable Achievable) rules maintenance activities will be planned in order to minimize the required human interventions during the active phase. Different tools have to be designed to perform the maintenance actions. As there are quiet all heavy components to be handled and removed, humans cannot perform the work without semi hands-on tools. The required permanent fixtures and tools are considered and pre-designed.