Towards the Development of a Damage Tolerance Assessment Methodology for Graphite Core Components Designed Per ASME Section III Division 5

Abstract The concept of damage tolerance applied to graphite core assemblies (GCAs) refers to their ability to sustain cracking while maintaining safety and design functions. While ASME BPVC Section III Division 5 (ASME III.5) HHA-3100 mandates the evaluation of the reactor’s core damage tolerance, it provides limited guidance on quantitative assessment and acceptability criteria. The authors propose considerations for developing a damage tolerance assessment methodology (DTAM) under ASME III.5 design rules, including the review of past strategies, failure criteria definition, whole-core modeling, code validation, and inspection requirements. The methodology consists of five steps: reviewing design and safety functions, defining acceptance criteria, identifying cracking configurations of relevance, developing numerical models, and linking assessments to inspection and monitoring. Concepts are illustrated using the Kairos Power Fluoride salt-cooled, High-Temperature Demonstration Reactor (KP-FHR), Hermes. This work aims to provide a framework for assessing and ensuring the damage tolerance of GCAs in diverse reactor technologies.