Design progress of EU DEMO divertor cassette

• Revision of Divertor cassette design working at PWR conditions for EU-DEMO is discussed. • A preliminary comparative assessment between two design solutions is shown. • Preliminary structural assessment are presented for both solutions, to provide a general feedback on the structural response. • Manufacturing processes are discussed as relevant figure of merit for the comparative assessment. In the context of EUROfusion activities for the development of the DEMO reactor design, the divertor configuration is a major challenge. The current conceptual divertor design is based on the use of EUROFER97 for the divertor cassette body, while tungsten monoblocks bonded to CuCrZr pipes are used for plasma-facing targets. The evaluations developed to identify the best water coolant thermal–hydraulic conditions avoiding material embrittlement (for EUROFER 97) and softening/hardening (for copper alloy pipes) led to the identification of a new divertor baseline solution, based on the new cooling water operating conditions, named Divertor Single Null High-Temperature (SNHT). Such conditions require water at relatively high temperature (295°C) and pressure (15.5 MPa), posing new challenging issues related to the general layout of the divertor cassette, its structural robustness and the manufacturing technologies. This work presents a comparative assessment between two different solutions proposed for the design and manufacturing of the divertor cassette body. A preliminary structural assessment and technological parameters are considered, as well as shielding and thermo-hydraulic performances.