Certified reference materials in nuclear forensics: Foundations, applications, and future directions.

Certified Reference Materials (CRMs) are the cornerstone of traceable nuclear measurements, yet their role in nuclear forensic science has not been comprehensively reviewed. This work presents a critical analysis of existing uranium-, plutonium-, and mixed-actinide-based CRMs, highlighting their metrological design, analytical applications, and forensic relevance. Drawing on data from the IAEA, JRC-Geel, NIST, and national metrology institutes, the review delineates the evolution of CRMs from bulk isotopic standards to gravimetrically certified, radiochronometric, and micro-particulate materials relevant to nuclear forensic investigations. The study identifies persistent gaps in CRM availability for advanced fuel cycles, minor actinides, and nanoparticulate systems, which limit analytical comparability and forensic traceability. Case studies illustrate the integration of CRMs into isotope-dilution mass spectrometry and age-dating using the 241Pu-241Am chronometer, demonstrating their indispensable role in establishing data reliability and legal defensibility in nuclear forensic contexts. Beyond technical evaluation, the paper introduces a conceptual framework positioning CRMs as tools supporting both measurement accuracy and nuclear forensic interpretation. Collectively, the review outlines priorities for the next generation of nuclear forensic CRMs, linking analytical precision to nuclear security applications.