Thermal-hydraulic scaling of the prototypical mock-up for European DEMO HCPB breeding blanket

• Thermal-hydraulic scaling methodology for the first Wall- Prototype Mock-up in regards to EU DEMO HCPB first wall. • Power-to-Volume scaling within the hierarchical two-tiered scaling methodology (H2TS) is adopted for prototypical Mock-up first wall channels. • Methodology of scaling the component dimensions is adopted for the hydraulic scaling of manifold section. The Helium-Cooled Pebble Bed (HCPB) blanket concept is a leading candidate for the driver blanket in the European Fusion Demonstration Power Plant (DEMO), developed within the EUROfusion framework's Work Package Breeding Blanket (WPBB). A crucial component of the HCPB blanket is the First Wall (FW), which must withstand high heat fluxes from the plasma while maintaining a uniform temperature distribution as much as possible. This uniformity is achieved through an alternating coolant flow design. The present study focuses on the thermal-hydraulic scaling methodology for the First Wall-Prototype Mock-Up (FW-PMU) to replicate the HCPB blanket's thermal and hydraulic performance. The FW-PMU is designed to emulate the flow distribution and thermal behavior of the HCPB Breeding Blanket (BB) First Wall, including flow patterns from the Breeder Zone Manifold to the fuel-breeder pins. In the present work, a power-to-volume scaling approach is employed to maintain the characteristic time ratio by analyzing non-dimensional parameters, while scaling of component dimensions in the breeder zone manifold ensures a consistent velocity field. The FW-PMU is set for testing in HELOKA, a high-pressure, high-temperature helium facility at the Karlsruhe Institute of Technology to validate the HCPB First Wall design under realistic operating conditions, advancing its potential deployment in fusion energy systems.