Clearance level study of liquids released with medical radioisotopes ^99mTc, ¹³¹I, ⁹⁰Y, ²²³Ra in wastewater

BackgroundIn most cases, the radionuclides present in wastewater generated by medical utilization have relatively short half-lives, and their discharge periods are also relatively short. Radiation doses of the released wastewater with radionuclides to the public and the environment could be relatively low. From the perspective of radiation protection optimization and environmental release requirements enforcement, it is possible to rationalize the release of these radionuclides through an appropriate approach of regulatory control to the environment.PurposeThis study aims to introduce an approach to derive clearance levels for liquids release with medical radioisotopes to ensure public health and environmental safety by optimizing the management limits for the discharge of medical radioisotopes 99mTc, 131I, 90Y, and 223Ra in wastewater.MethodsFirstly, based on the environmental impact assessment model proposed by the International Atomic Energy Agency (IAEA), a process to derive clearance levels of liquids release of four radionuclides which are 99mTc, 131I, 90Y, and 223Ra. The derived process focused on the potential impact on the public under two scenarios: the sludge scene, assuming that all radionuclides remain in the sludge, and the river scene assuming that all radionuclides remain in the water body then being discharged into the river. Then, the derived clearance levels were determined based on the criterion that the annual effective dose to the public from annual radioisotopes releases should not exceed 10 μSv.ResultsThe clearance levels of the four radioisotopes for liquid released in wastwater are 3.14×108 Bq∙a-1 for 99mTc, 2.38×107 Bq∙a-1 for 131I, 4.30×107 Bq∙a-1 for 90Y, and 1.45×107 Bq∙a-1 for 223Ra. Depending on the volume of radioactive wastewater generated annually from nuclear medicine of medical institutions, the clearance levels annually can be transformed into the release activity concentration.ConclusionsThis study provide a theoretical foundation and practical demonstration for deriving clearance level for the wastewater with medical radionuclides. With further research and continuous advancements in monitoring technologies, it is perspective that the findings of this study, combined with practical applications, will further improve relevant standards and regulations, thereby better supporting the application and new developments of medical radionuclides in China.