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Safe licensing and operation of future fusion reactions requires demonstrating material performance after extreme irradiation conditions. This needs to be demonstrated through material irradiation in a suitable neutron source facility under fusion-relevant conditions
IFMIF-DONES is an accelerator-based neutron irradiation facility, providing the necessary irradiation data for the qualification of materials for the DEMO fusion power plant. This is achieved by the interaction of a 125 mA, 40 MeV deuteron beam with a liquid lithium courting, producing up to 6.75x1016 n/s. Additional secondary radiation sources arise from interactions between the deuterons and interceptive components such as scrapers and collimators used for beam shaping, as well as beam dumps and the beam duct. These interactions generate activation induced by both deuterons and secondary neutrons. The activation will give rise to delayed radiation fields during the shutdown periods, when the maintenance activities are carried out. These radiation fields need to be characterized to minimize the risk of exposure during both the operation and shutdown of the machine.
In this work, we first investigate the differences in the neutron source in IFMIF-DONES due to Li(d,xn) reactions when using different nuclear data libraries and simulation approaches. We also compared the results of simulations using different nuclear data libraries and simulation approaches with available experimental information, in order to obtain a better understanding of the application to IFMIF-DONES. In general, a good agreement between methodologies was found.
Finally, we also investigated the activation process and the applicability of the Direct-One-Step (D1S) method to IFMIF-DONES. The D1S methodology allows obtaining responses associated with decay photons in a single simulation thanks to the coupling of transport and activation calculations. But this approach relies on the assumption that radioisotopes are produced by one-step reactions, as well as negligible radioisotope burnup (Single Neutron Interaction and Low Burnup criteria). We identified the most relevant activation chains due to the neutron and deuteron irradiation, considering all the possible exposed materials, as well as typical spectrums, irradiation and decay times. Only two reaction chains with more than one step were found, verifying the D1S applicability.
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