Assessment of X-ray tomography for irradiated IFMIF/HFTM RIG

An inspection procedure to assess the mechanical integrity of IFMIF capsules and rigs during the irradiation campaign is necessary. In a number of experiments, we previously proved that X-ray tomography is a reliable solution for official inspections of the structural integrity of IFMIF complete assemblies before and after various tests (tensile, creep-fatigue, fracture toughness, crack growth, microstructure swelling). The next main challenge is to qualify the transmission microtomography inspection as a tool for non-destructive inspection during maintenance (beam-off) periods and after irradiation campaigns. The influence of the sample gamma radioactivity (produced by neutron activation during irradiation campaigns) on the tomographic reconstruction quality is investigated in this paper. The evaluation is performed for the specific configuration of newly manufactured IFMIF irradiation capsules. Experimental X-ray radiographic data together with simulated gamma radiographic images were considered. Latest activation data were incorporated. For the numerical simulations, a working environment able to provide a realistic numerical simulation was constructed on the basis of two well established Monte Carlo computer codes: SIMIND and ITS. The optimal parameters of the collimation system, essential for the investigation of the irradiated samples, were determined. It is proved that transmission tomography is practicable, providing good quality reconstruction which allows accurate geometrical measurements. The procedure developed for tomography of irradiated HFTM can be applied for the inspection of other irradiated structures for which X-ray tomography represents a non-destructive inspection technique (NDT).