Progress on the helium cooled Molten Lead Ceramic Breeder concept, as a near-term alternative blanket for EU DEMO

Abstract Within the EUROfusion framework, a Molten Lead Ceramic Breeder (MLCB) breeding blanket is being developed at KIT as an alternative, cost-effective and low technology-risk solid breeder blanket for EU DEMO. The use of molten lead as neutron multiplier has been identified very promising, solving key potential issues coupled with the use of Be in solid breeder blankets. This MLCB concept has been derived from the enhanced Helium Cooled Pebble Bed, which is based on fission-like “fuel-breeder pin” configuration. Compared to former cooling-plate configuration, this concept greatly reduce the pressure drop, enabling the use of existing helium-circulator. After initial design studies with this concept for the previous EU DEMO baseline (BL2015), the status of the design activities on MLCB for the latest EU DEMO baseline (BL2017) is presented in this paper. First, neutronics analyses have been performed to assess and optimize the tritium breeding performance. Then, structural integrity under in-box LOCA has been assessed and the design has been iterated to fulfill the design criteria. Thereafter, thermo-hydraulic analyses have been conducted to evaluate the temperatures and pressure drops. After several design iterations to satisfy the temperature and pressure drop requirements, a structural assessment under normal condition has been conducted respecting the RCC-MRx rules. The results show that the current MLCB design fulfills the basic nuclear and thermo-mechanic-hydraulic requirements, setting the path for a consolidated design of this concept. Due to the absence of water-reactive elements in MLCB concept, water can be also used as coolant, which is under investigation.