Application of the RCC-MRx entrance key to the structural design of HCCP TBM-set components

The Test Blanket Module (TBM) installed in the ITER device must satisfy fusion-specific thermo-mechanical requirements as well as European and French nuclear regulatory constraints, since it operates within a French nuclear installation under high-temperature and high-radiation conditions. A clear and consistent application of design codes and regulations at an early design stage is therefore essential to ensure regulatory compliance and design consistency. This study applies the RCC-MRx Entrance Key methodology to the structural design of the Helium-Cooled Ceramic Pebble (HCCP) TBM-set, focusing on the TBM-box and the TBM-shield as functionally distinct components. Their functional roles, structural characteristics, and system boundary definitions are examined, and component-specific Entrance Keys are defined by integrating RCC-MRx criteria with regulatory applicability under the Pressure Equipment Directive (PED) and the French regulation for nuclear pressure equipment (ESPN). Based on the defined Entrance Keys, the applicable RCC-MRx design subsections are identified, and the implications for structural design, fabrication, inspection, and qualification are discussed. The results demonstrate that the Entrance Key provides a practical framework for aligning design code application with regulatory requirements for fusion blanket components.