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The water-cooled lithium-lead breeding blanket is in the pre-conceptual design phase. It is a candidate option for European DEMO nuclear fusion reactor. This breeding blanket concept relies on the liquid lithium-lead as breeder-multiplier, pressurized water as coolant and EUROFER as structural material. Current design is based on DEMO 2017 specifications. Two separate water systems are in charge of cooling the first wall and the breeding zone: thermo-dynamic cycle is 295-328°C at 15.5 MPa. The breeder enters and exits from the breeding zone at 330°C. Cornerstones of the design are the single module segment approach and the water manifold between the breeding blanket box and the back supporting structure. This plate with a thickness of 100mm supports the breeding blanket and is attached to the vacuum vessel. It is in charge to withstand the loads due to normal operation and selected postulated initiating events. Rationale and progresses of the design are presented and substantiated by engineering evaluations and analyses. Water and lithium lead manifolds are designed and integrated with the two consistent primary heat transport systems, based on a reliable pressurized water reactor operating experience, and six lithium lead systems. Open issues, areas of research and development needs are finally pointed out.

The water-cooled lithium–lead breeding blanket is a candidate option for the European Demonstration Power Plant(DEMO) nuclear fusion reactor. This breeding blanket concept relies on the liquid lithium– lead as breeder–multiplier,pressurized water as coolant, and EUROFER as structural material. The current design is based on DEMO 2015specifications and represents the follow-up of the design developed in 2015. The single-module-segment approach isemployed. This is constituted by a basic geometry repeated along the poloidal direction. The power is removed by meansof radial–toroidal (i.e., horizontal) water cooling tubes in the breeding zone. The lithium–lead flows in a radial–poloidaldirection. On the back of the segment, a 100-mm-thick plate is in charge of withstanding the loads due to normal operationand selected postulated initiating events. Water and lithium–lead manifolds are designed and integrated with a consistentprimary heat transport system, based on a reliable pressurized water reactor operating experience, and the lithium–leadsystem. Rationale and features of the single-module-segment water-cooled lithium–lead breeding blanket design arediscussed and supported by thermo-mechanic, thermo-hydraulic, and neutronic analyses. Preliminary integration withthe primary heat transfer system, the energy storage system, and the balance of plant is briefly discussed. Open issues, areasof research, and development needs are finally pointed out

Plasma exhaust has been identified as a major challenge towards the realisation of magnetic confinement fusion. To mitigate the risk that the single null divertor (SND) with a high radiation fraction in the scrape-of-layer (SOL) adopted for ITER will not extrapolate to a DEMO reactor, the EUROfusion consortium is assessing potential benefits and engineering challenges of alternative divertor configurations. Alternative configurations that could be readily adopted in a DEMO design include the X divertor (XD), the Super-X divertor (SXD), the Snowflake divertor (SFD) and the double null divertor (DND). The flux flaring towards the divertor target of the XD is limited by the minimum grazing angle at the target set by gaps and misalignments. The characteristic increase of the target radius in the SXD is a trade-off with the increased TF coil volume, but, ultimately, also limited by forces onto coils. Engineering constraints also limit XD and SXD characteristics to the outer divertor leg with a solution for the inner leg requiring up-down symmetric configurations. Capital cost increases with respect to a SND configuration are largest for SXD and SFD, which require both significantly more poloidal field coil conductors and in the case of the SXD also more toroidal field coil conductors. Boundary models with increasing degrees of complexity have been used to predict the beneficial effect of the alternative configurations on exhaust performance. While all alternative configurations should decrease the power that must be radiated in the outer divertor, only the DND and possibly the SFD also ease the radiation requirements in the inner divertor.

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