Water-cooled lead and ceramic breeder (WLCB) breeding blanket (BB) for the EU DEMO: Neutronic campaigns for T breeding optimization

• Water-cooled Lead and Ceramic Breeder Advanced BB explored for DEMO. • Neutronic simulation campaigns conducted to optimize performance. • Key design parameters varied to achieve the best Tritium Breeding Ratio. • Varied layouts, cooling, 6 Li, packing factors, multiplier and breeder materials. • Final design delivered with good potential for further multi-physics iterations. A novel Breeding Blanket (BB) concept, the Water-cooled Lead and Ceramic Breeder (WLCB) BB, has been developed under the EUROfusion Programme to address key challenges identified during the Pre-Conceptwual Design (PCD) phase for the driver BB concepts: Water-Cooled Lithium Lead (WCLL) and Helium-Cooled Pebble Bed (HCPB). The WLCB design represents an alternative hybrid approach, combining advantageous features of both WCLL and HCPB to mitigate their respective limitations: (1) shielding inefficiencies, challenging neutron multiplier technology, and integration concerns in HCPB; (2) challenges with tritium extraction from PbLi in WCLL variants; and (3) the reliance on anti-permeation barriers. In lieu of beryllium, alternative neutron multipliers—particularly lead—have been explored. This work focuses on the neutronic optimization of the WLCB concept, with an emphasis on tritium breeding performance. Extensive neutronic simulation campaigns were conducted to optimize key design parameters, including toroidal and radial blanket layouts, cooling plate dimensions and water content, neutron multiplier zoning and materials (Pb, Be 12 Ti, Zr 5 Pb 3 , C, ZrH 2 ), 6 Li enrichment, ceramic breeder material, ceramic packing factor, and First Wall (FW) design to achieve the best results in terms of Tritium Breeding Ratio (TBR). The resulting preliminary design − based on the best balance between neutronic performances and viability considerations, among others − achieves the EU DEMO TBR target of 1.15, representing a promising candidate for further development and integration into future design iterations.