Integration of the Neutral Beam Injector System Into the DCLL Breeding Blanket for the EU DEMO

The integration of plant systems involving penetrations into the in-vessel components, such as heating and current drive, fuel cycle, and diagnostics, is a complex task constrained by top-level requirements of remote maintainability and high reliability. Within the EUROfusion Power Plant Physics and Technology Program, some activities are ongoing to assess the integration of different systems into the breeding blanket (BB), specifically neutral beam injector (NBI), electron cyclotron resonance heating launchers, diagnostics sightlines, fueling lines, and specific protections for the first wall (like startup limiters). This paper describes the integration of the NBI system into the Dual-Coolant Lithium-Lead (DCLL) BB for the EU DEMO. After identifying the major issues impacting the mechanical, thermal-hydraulic and neutronic behavior of the blanket, the integration efforts have been focused on minimizing the invasiveness of the NBI system and exploring different NBI options for the best compromise between plasma heating and BB performance. This paper describes the adaptation of the DCLL BB design to allocate the neutral beam duct. A particular attention is devoted to the redistribution of breeding and shielding functions, the new path of fluid circuits, and the additional cooling needs. The consequences of design modifications on key neutronic aspects like tritium breeding ratio and shielding capability are addressed. Besides, the thermal loads transferred to the BB walls from the neutral beam and the plasma are discussed, and a preliminary thermal assessment of the proposed solution is presented.