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Within the EUROfusion framework, two reactor architectures are being developed as possible candidates for the EU DEMO. One is based on the Water Cooled Lithium Lead (WCLL) Breeding Blanket (BB) concept and the other on the Helium Cooled Pebble Bed (HCPB) BB concept. The two DEMO variants result in completely different reactor and ancillary system designs due to the use of different coolants (i.e water or helium) as well as different neutron multipliers, tritium breeders, and carriers (i.e. PbLi for the WCLL and solid ceramic and beryllide with helium as a purge gas for the HCPB). As a consequence, the definition of the tritium management systems for the extraction and the control of inventories and environmental releases also needs to be tuned for each variant. Furthermore, dedicated technologies for tritium extraction and removal must be developed and specific working points for the two architectures must be defined. It is, therefore, necessary to rely on holistic approaches for the analysis of tritium management issues of the BB, its ancillary systems and fueling systems. In this work, an overview of the tritium permeation issues and the applied mitigation measures (e.g. permeation barriers) are described. Furthermore, design limits given by tritium extraction technologies as well as experimental campaigns (e.g. determination of the Sieverts' constant of tritium in PbLi at DEMO relevant temperatures) to substantiate the modelling approach are also reported. Finally, the impact on the fueling system due to the tritium inventories sequestered in the BB and other systems is described, providing information on the doubling time and initial tritium inventories for a given tritium breeding ratio. [ABSTRACT FROM AUTHOR]

• 18 cm blocks of hydrates like ZrH1.6 or TiH2 can potentially lead to less dpa accumulation in the VV compared to the WCLL blanket. • 16 N and 17 N produced by coolant activation: cumulated doses after 7 fpy in the UPC due to the γ 16 N decay have been calculated referring to the current end of life dose of 2 MGy of valves used in PHTS. • Two dedicated experimental rigs at TLK aim at quantifying co-permeation of Q2 species in He/He or He/water set-ups. • R&D efforts aim at characterizing the two anti-permeation coatings, PLD and ALD, in terms of fabrication and performances under relevant operational conditions. • A combination of anti-permeation coatings and CPS would allow to rely on existing technology for the water detritiation. In the frame of the EUROfusion consortium activities the Helium Cooled Pebble Bed (HCPB) and the Water Cooled Lithium Lead (WCLL) concepts are being developed as possible candidates to become driver Breeding Blanket (BB) for the EU DEMO, which aims at the tritium self-sufficiency and net electricity production. The two BB design options encompass water or helium as coolants and solid ceramic with beryllium/beryllides or PbLi as tritium breeder and neutron multipliers. The BB segments have evolved towards a more stable conceptual design taking into account multiple feasibility aspects and requirements imposed by interfacing systems. Possible solutions to improve shielding capabilities of Helium cooled BB are investigated and the impact of water coolant activation is assessed by studying the spatial distribution of 16N and 17N isotopes dose rates, in particular in proximity of isolation valves. The reference and back-up technologies for the Tritium Extraction and Removal (TER) from the helium purge gas and the PbLi are developed addressing key feasibility aspects and implications on the tokamak layout and with considerable R&D efforts. As the BB internals offer an ideal environment (high temperatures, thin structural material) to promote the tritium permeation, studies are devoted to establish a tritium balance in the different systems during operation, with special care to the permeation rate and inventory in the coolant. Those are the key parameters for the feasibility assessment and technology selection for the Coolant Purification Systems (CPS). [ABSTRACT FROM AUTHOR]