Maintenance plan of the ITER Radial Neutron Camera: Verification and validation by virtual reality simulation

The Radial Neutron Camera (RNC) is an ITER diagnostic designed to measure the un-collided 14 MeV and 2.5 MeV neutrons from deuterium-tritium (DT) and deuterium-deuterium (DD) fusion reactions, through an array of detectors covering a poloidal plasma section along collimated Lines Of Sight (LOS). The Ex-Port RNC is located in the Port Cell (PC) Interspace zone, the first area outside the Vacuum Vessel, and includes several detector units, mounted inside detector boxes. On the base of reliability considerations, the Radial Neutron Camera Maintenance Plan (RNC-MP) has foreseen a hands-on maintenance task to replace detectors unit equipment in case of failure. Despite not precluding workers access, the radiation field at shutdown in the PC Interspace zone requires optimization of hands-on operations to enable the minimization of occupational radiation exposure under the ALARA (As Low As Reasonably Achievable) principle. The relevant complexity and dimensions of the Ex-Port RNC requires a maintenance evaluation method different from a physical mock-up. The Virtual Reality technology may help to create a digital mock-up for evaluating the detectors replacement operations. The paper aims to demonstrate the potentialities of such technologies, in a field where safety and worker ergonomics are primary priorities. Thanks to the virtual scenario built, the RNC-MP updated steps are evaluated, improved and finally validated. The VR simulation is as well validated via a simple physical mock-up of the detector box.