He jishu (Apr 2024)
Calculation of decay tank capacity and minimum storage time for the wastewater of nuclear medicine department based on the total emission control
Abstract
BackgroundIn the process of accelerated development of nuclear medicine department in recent years, the construction of decay tanks and the storage time of radioactive wastewater containing 131I have become issues of great concern for environmental regulatory agencies and hospitals. Regulations and standards, such as "Basic Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources" (GB 18871-2002), "Radiation Protection and Safety Requirements for Nuclear Medicine" (HJ 1188-2021), and "Reply to Consultation on Several Clauses of the Nuclear Medicine Standard", have stipulated the compliant discharge methods for radioactive wastewater containing 131I from hospitals.PurposeThis study aims to demonstrate the methods for calculating the optimal volume of the decay tank and the minimum storage time so as to minimize the unnecessary construction costs and land use while ensuring compliance with regulations.MethodsFirstly, according to theoretical induction, a formula for the upper bound of total activity of 131I was presented for a full decay tank in a hospital. Then, the RJ (Radioactivity Judgement) equation group was put forward to address the calculation of minimum decay time and volume of the decay tank. Finally, the actual monitoring data from four hospitals were applied to verification the recommendation of this study.ResultsVerification results demonstrate that when the temporary storage period for radioactive wastewater containing 131I reaches the minimum time calculated by the RJ equations, the total discharge activity of 131I complies with the national environmental protection standards. Among the three compliant discharge methods for radioactive wastewater containing 131I in the decay tank, the method specified in GB 18871-2002 is advantageous for the operation of the nuclear medicine department in the hospital.ConclusionsWith the methodologies detailed in this paper, it is possible to significantly reduce the required volume of the decay tank and the minimum storage time. These findings provide clear and specific guidance for the construction of decay tanks in nuclear medicine departments and for the supervision and inspection conducted by regulatory authorities.
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