Integrated Methodology for Design and Analysis of First Wall in the STEP Project: A Case Study in the SPR-45 Conceptual Design

The Spherical Tokamak for Energy Production (STEP) program aims to achieve net electricity production from fusion through the STEP prototype power plant (SPP) by 2040. A major challenge in attaining fusion power is plasma exhaust, which the STEP program addresses through a double-null (DN) divertor configuration, showing promise in reducing radiation requirements. This article presents a case study applying an integrated methodology for the initial design of the STEP first wall in the SPR-45 conceptual design. The methodology involves managing charged particles and radiation heat loads and has been detailed in a separate paper. The models and procedures for predicting wall heat loads, designing the 2-D poloidal contour, and evaluating radiation loading have been seamlessly integrated into BLUEMIRA, a versatile reactor design framework, that supports rapid iterations and sensitivity studies. The integrated methodology enables rapid iterations and sensitivity studies, resulting in an optimized first wall geometry profile. Its flexibility facilitates cross-functional collaboration, allowing the sharing of first wall profiles for additional studies and geometry enhancements by other teams, such as vertical displacement or limiter profiles. These modified profiles can then be reinserted into the methodology for updated assessments of charged particle heat flux and radiation heat loads. This case study demonstrates the integrated methodology's effectiveness in addressing plasma exhaust complexities and heat management challenges. The seamless collaboration among cross-functional teams exemplifies the methodology's versatility, making it a valuable tool in the development of fusion power plant designs.