A Proposed Regulatory Framework for Ageing Management of Nuclear Research Reactors: Evidence from the Brazilian IPR-R1 TRIGA® Case

Abstract

Nuclear Research Reactors (NRRs) are essential infrastructures for radioisotope production, materials research, education, training and technological development related to low-carbon energy systems. A large share of the global NRR fleet has operated for several decades, which increases the regulatory relevance of physical degradation, technological obsolescence and preservation of organizational knowledge. This paper proposes a graded regulatory framework for ageing management of Brazilian research reactors, using the IPR-R1 TRIGA^® reactor as an applied regulatory case. The method combines documentary and normative analysis, comparative assessment of international guidance and a regulatory-technical case study. The evidence base included IAEA safety standards and reports, U.S. NRC non-power reactor guidance, Brazilian licensing instruments, the IPR-R1 ageing management documentation and the institutional transition from Brazilian Nuclear Energy Commission (CNEN) to Brazilian Nuclear Safety Authority (ANSN). The results show that ageing management for research reactors should not be treated as a direct equivalent of long-term operation or license renewal for power reactors. Instead, it should be structured as a continuous, risk-informed and auditable regulatory process. The proposed framework is organized around five elements: mandatory ageing management programmes; screening and classification of structures, systems and components important to safety; TLAA-equivalent or residual-life assessments when original time-limited design data are unavailable; periodic safety review as an integrated regulatory anchor; and clear allocation of responsibilities between the operator and the regulatory body. The Brazilian IPR-R1 case demonstrates the feasibility of using existing operational, maintenance and licensing evidence to support continued safe operation, provided that the evidence is consolidated into a traceable regulatory model. The study concludes that a specific regulation or preparatory technical note for research reactors would improve regulatory predictability, institutional coherence and alignment with international best practices.