Criteria and practices for identifying anomalies in the marine radiological environment

With the increasing utilization of nuclear energy, potential risks of nuclear accidents, and discharges of radioactive waste, marine radiological monitoring and anomaly identification have become crucial tasks for nuclear safety assurance and ecological environmental protection. This paper systematically reviews the criteria, technical methodologies, and practical cases for identifying anomalies in the marine radiological environment. It focuses on threshold setting, data analysis techniques, and assessment procedures under relevant international and domestic standards. In the context of insufficiently established standards and criteria for anomaly identification, the Background Range Method, Spatio-Temporal Trend Analysis, and Isotopic Fingerprint/Ratio Method have emerged as the primary technical guidelines for current anomaly detection. Applications are illustrated through monitoring and evaluation practices in the waters near Fukushima and Daya Bay, highlighting the differences in anomaly characteristics, identification techniques, and management responses under both nuclear accident conditions and normal operation of nuclear facilities. Furthermore, the paper proposes recommendations for advancing marine radiological monitoring and anomaly identification, aiming to provide a theoretical foundation for the formulation and revision of national standards and industrial guidelines, to provide a scientific basis for safeguarding marine nuclear safety and managing radiological risks in the marine environment.