Radioprotection 2025, 60( 1), 91 – 98 © G. Yunwen, Published by EDP Sciences, 2025 https:// doi. org / 10.1051 / radiopro / 2024042 Available online at: www. radioprotection. org
ARTICLE
Determination of decay tank capacity and minimum storage time for liquid radioactive effluent based on environmental requirements
G. Yunwen *
Department of Medical Physics and Biomedical Engineering, University College London, London, UK. Received: 3 July 2024 / Accepted: 28 August 2024
Abstract – According to China’ s environmental protection requirements, liquid radioactive effluent containing excreta from patients undergoing radionuclide treatments, such as iodine-131 and lutetium-177, must be temporarily stored in decay tanks until it meets discharge standards. The specific and total activity of the discharged liquid effluent is strictly regulated by China’ s environmental standards and regulatory documents. Before constructing a nuclear medicine department, hospitals must conduct an environmental impact assessment( EIA) and obtain approval from regulatory authorities. In the EIA, hospitals must demonstrate that the intended capacity of the decay tanks and the storage time for liquid effluent during the operation of the nuclear medicine department will ensure compliance with regulatory discharge requirements. This paper introduces the regulatory requirements for the discharge of radioactive effluent. This paper presents a formula for calculating the activity of iodine-131 and lutetium-177 in decay tanks. Based on the constraining environment requirements in practice, this paper provides a method for determining the necessary decay tank capacity and minimum storage time for liquid radioactive effluent to ensure compliant discharge. The findings offer guidance for the construction of decay tanks, the management of liquid effluent discharge in nuclear medicine departments, and inspection by regulatory authorities.
Keywords: hospital / decay tank / liquid radioactive effluent / iodine-131 / lutecium-177
1 Introduction
Currently, in China, 131 I radionuclide is primarily used for thyroid cancer treatment in nuclear medicine departments, while the usage of 177 Lu and the number of patients treated with it are also increasing. According to the Medium and Longterm Development Plan for Medical Isotopes( 2021 – 2035)( CAEA et al., 2021), the usage of 131 I in China was 3.7 10 14 Bq in 2019, with an expected annual growth rate of 15 %. 177 Lu is highly effective in treating neuroendocrine tumors and prostate cancer. The usage of 177 Lu was 1.85 10 12 Bq, with domestic demand projected to grow at an annual rate of 30 %. According to the data from the National Radiation Safety Management System for Nuclear Utilization, as of the end of December 2023, about 100 hospitals had obtained radiation safety licenses for using 177 Lu, and many more hospitals were planning to apply for such licenses.
* Corresponding Author: huaxie _ geyunwen @ 163. com
The Medium and Long-term Development Plan for Medical Isotopes( 2021 – 2035) aims to establish at least one nuclear medicine department in each county across China by 2035. Following the release of this plan, the construction of nuclear medicine departments in China has significantly accelerated, with many new departments planning to set up treatment wards for radionuclide therapy using 131 Ior 177 Lu. The management of patients undergoing radionuclide therapy varies across countries( Barquero et al., 2008). For instance, since the late 20th century, the United States has not required patients treated with 131 I to be hospitalized, allowing their excreta to enter municipal sewage systems directly( US NRC, 1997). In contrast, China and most European countries, following recommendations from the International Atomic Energy Agency and other organizations, require patients to be hospitalized until the 131 I level in the patient’ s body meets certain standards( ICRP, 1991; IAEA, 2002). During hospitalization, the excreta of patients containing 131 I is stored in decay tanks until it meets discharge requirements. Regarding 177 Lu therapy, currently, it is not explicitly required in China for patients receiving 177 Lu treatment to be
This is an Open Access article distributed under the terms of the Creative Commons Attribution License( https:// creativecommons. org / licenses / by / 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.