Requirements and ideas for the neutron instrumentation of the IFMIF test facilities

IFMIF will be an accelerator-based neutron source, currently under engineering design phase, with the purpose of testing and fully qualify fusion candidate materials. Fission chambers were identified as good candidates to control on-line the irradiation level and mapping of the flux reaching the irradiated specimens. However, their use within the harsh environment of IFMIF (neutron fluxes up to 10¹¹–10¹⁵ neutrons/cm²/s, fluence up to 2x10²² neutrons/cm², gamma doses of about 10⁴ Gy/h, high temperatures, etc) is still under a validation process. It is necessary then, the assessment of another kind of diagnostics, in order to get complete and redundant information concerning the radiation field. In this line, the present work proposes diagnostics based on optical measurements and particle interactions. They consist of a radiation monitor for the IFMIF - High Flux Test Module (the module receiving higher neutron doses) based on the radioluminescence of specific materials; and a radiation monitor which measures the fluorescence of the Test Cell atmosphere. The experimental system will have to be capable of measuring the high neutron fluxes expected for IFMIF, substituting or complementing the information of the fission chambers.