Required, achievable and target TBR for the European DEMO

This work presents an up-to-date assessment of the TBR (Tritium Breeding Ratio) requirements for the European DEMO which is under development in the EUROfusion PPPT (Power Plant Physics and Technology) programme. Previous requirements were updated in accordance with the recent advances in the fuel cycle concept, the progress achieved with the DEMO design, and the additional requirement to generate the start-up tritium inventory for a follow-up fusion power reactor. The assessment results in a requirement of TBR >= 1.05 which is needed to provide the amount of tritium to the fuel cycle required to attain self-sufficiency. The TBR design target, which includes margins for calculation uncertainties and incomplete models, was set to TBR >= 1.15. The attainability of this design target is to be demonstrated with a neutronics calculation using an appropriate simulation model, without considering auxiliary systems, limiters, extra ports, etc. With the latest blanket design versions, this requirement can be fulfilled by the driver blanket candidates considered for DEMO, the HCPB (Helium Cooled Pebble Bed) and the WCLL (Water Cooled Lithium Lead) breeding blankets.