From Storage to Discharge: Analysis of Iodine-131 Decay Tank Operations in Korean Medical Facilities Based on Safety Reports

This study aimed to analyze the operational status and management patterns of iodine-131 (I-131) radioactive waste decay tanks in Korean medical institutions using the data documented in radiation safety reports.This study systematically analyzed the data from Korean medical institutions operating nuclear medicine departments using accessible radiation safety reports.The key parameters included the presence of decay tanks, drainage methods, therapy ward capacity, licensed I-131 limits, annual average inflow activity, tank capacity, retention times, and discharge concentrations.To assess the operational margin, the "conservative storage ratio (%)" was defined and calculated based on the actual storage duration relative to the time required to reach full capacity.Of the 102 surveyed institutions, 80 possessed decay tanks, and their presence was correlated with the availability of therapy wards.The discharge pathways in institutions with decay tanks were classified into three types: "decay tank→septic tank→water reclamation center," "decay tank→water reclamation center," and "decay tank→multistage septic tank→water reclamation center."The institutions without decay tanks generally lacked therapy wards and discharged their liquid waste via septic tanks or directly to water reclamation centers.Overall, institutions with decay tanks tended to possess large capacities, with storage periods significantly exceeding the time required to reach full capacity.In all 11 institutions analyzed, the measured discharge concentrations were below the regulatory limit of 30 Bq/L.Most Korean medical institutions have managed decay and discharge procedures with sufficient storage capacity and retention periods, while adhering to legal standards.While this approach contributes to radiation safety, it also suggests the potential for operational redundancy.These findings can be integrated into policy discussions to establish fieldoriented evaluation systems and improve regulatory efficiency.However, since this study is based on limited cases, follow-up research on actual administered activities is recommended.