The characteristically intense neutron source generated in deuterium-tritium (DT) fusion power presents notable challenges for materials comprising the structure of the device which are exposed to them. These include radiation damage effects leading to degradation of structural properties with impact on maintenance and replacement frequency, but also induced radioactivity, albeit generated with comparatively lower radiotoxicity compared with those generated in, for example, fission fuel during operations. Fusion generated waste arisings and other nuclear quantities of interest may be predicted using 3D neutronics and activation codes with underpinning nuclear data. Experimental activities at JET as part of the EUROfusion JET3 project will expose ITER construction material samples to fusion neutrons in the forthcoming DT experimental campaign, and then quantify nuclides that are present in samples for comparison against equivalent computational predictions.
We report activation measurements and calculational predictions for the JET fusion environment for a range of supply chain ITER materials that were recently exposed to neutrons during deuterium fusion plasma operations. The ITER materials include: poloidal field (PF) coil jacket and toroidal field coil radial closure plate steels, EUROFER 97-2 steel, W and CuCrZr materials from the divertor, Inconel 718, CuCrZr, 316L stainless steel for blanket modules and vacuum vessel forging samples.
The measurement of nuclides present in these samples using high resolution gamma spectrometry techniques is discussed, to date principally measurements for activation products of importance to remote handling in operations and early decommissioning phases are identified. Preliminary findings reveal some variations in observed nuclides that are present in steels from different suppliers. We also present calculation predictions for ITER materials on longer, waste disposal timescales and discuss the radiometric challenges in future experimental plans to identify long-lived nuclides that could be present in irradiated samples.
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/T012250/1]. The views and opinions expressed herein do not necessarily reflect those of the European Commission.