There is no doubt about the interest of achieving as fast as possible the capability to build and operate high performance reactors that finally allow fusion competing in the electricity market. An advanced breeding blanket based on the Dual Coolant Lithium Lead concept with single module segment architecture, designed for the European DEMO, is certainly aligned with such objective. This work describes some recent outcomes of the efforts carried out in the framework of the Prospective R&D Work Package in EUROfusion to develop this line. The evolution of the design has been guided by strategies aimed to achieve an equilibrium between tritium breeding & shielding requirements and mechanical integrity. To enhance the thermodynamic cycle efficiency and reduce the recirculation power by minimizing pressure losses in both the breeding zone and the first wall have been complementary guidelines. Specific models have been created to characterize phenomena like heat transfer and tritium permeation in the breeder channels. The experimental activities, which in general have produced promising results, have consisted in the characterization of different ceramic materials (carbides and oxides) in terms of functional properties at high temperature (as-received and irradiated/implanted samples) and compatibility with PbLi.

IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source) is a facility whose purpose is to obtain data on materials by irradiating them under conditions equivalent to those of the DEMO (DEMOstration) fusion reactor. Tungsten and CuCrZr alloy are two candidate materials to be used in DEMO, tungsten for the first wall and divertor (DIV) and CuCrZr alloy for the DIV. So, studying the behavior of these materials in IFMIF-DONES facility and comparing the results with the DEMO environment is crucial. In the high flux test module in IFMIF-DONES has been considered a realistic distribution of specimens. The IFMIF-EVEDA beam have been used with a footprint size of 20 × 5 cm², the nominal energy is 40 MeV with a current of 125 mA, for the calculation other energies have been considered 25, 30 and 35 MeV. The results of IFMIF-DONES have been compared with different DEMO concepts, Dual Coolant Lithium Lead, Water Cooled Lithium Lead and Helium Cooled Pebble Bed. In general, the primary displacement damage rate meets between IFMIF-DONES and DEMO, while the gas production is at the limit for W and fulfilled for the CuCrZr alloy.

The Stellarator Power Plant Studies Prospective R&D Work Package in the Eurofusion Programme was settled to bring the stellarator engineering to maturity, so that stellarators and particularly the HELIAS (HELical-axis Advanced Stellarator) configuration could be a possible alternative to tokamaks. However, its complex geometry makes designing a Breeding Blanket (BB) that fully satisfies the requirements for such a HELIAS configuration, which is a difficult task. Taking advantage of the acquired experience in BB design for DEMO tokamak, CIEMAT is leading the development of a Dual Coolant Lithium Lead (DCLL) BB for a HELIAS configuration. To answer the specific HELIAS challenges, new and advanced solutions have been proposed, such as the use of fully detached First Wall (FW) based on liquid metal Capillary Porous Systems (CPS). The proposed solutions have been studied in a simplified 1D model that can help to estimate the relative variations in Tritium Breeding Ratio (TBR) and displacement per atom (dpa) to verify their effectiveness in simplifying the BB integration and improving the machine availability while keeping the main BB nuclear functions (i.e., tritium breeding, heat extraction and shielding). This preliminary study demonstrates that the use of FW CPS would drastically reduce the radiation damage received by the blanket by 29% in some of the selected configurations along with a small decrease of 4.9% in TBR. This could even be improved to just a 3.8% TBR reduction by using a graphite reflector. Such an impact on the TBR is considered affordable, and the results presented, although preliminary in essence, have shown the existence of margins for further development of the FW CPS concept for HELIAS, as they have been not found, at least to date, to be significant showstoppers for the use of this technological solution.