RESUMO
Objective:To explore whether or not radioactive wastewater leakage or overflow exists in the nuclear medicine decay pool after the 7·20 extraordinary rainstorm disaster and to analyze its causes, so as to provide scientific basis for the design, construction and maintenance of the nuclear medicine decay pool and the radiation protection management of nuclear medicine in the future.Methods:Three hospitals A, B and C where 131I therapy are being performed were selected in Zhengzhou city, Henan province. Sampling points were set based on the monitoring result of the environmental radiation level around the nuclear medical decay pool in line with the relevent standard method. Soil samples were collected at different depths. The 131I radioactivity level in the soil was measured using HPGe gamma spectrometer, with the measured result being processed and analyzed. Results:Except for Hospital B where no 131I was detected, different 131I activity concentrations were detected in the soil samples collected around the nuclear medicine decay pool at Hospitals A and C. The 131I activity concentrations ranged from 16.4 to 98 111.8 Bq/kg at Hospital A and from 10.6 to 7 176.6 Bq/kg at Hospital C. After a time period of decay, the repeated detection has shown that the 131I activity concentrations ranged from 1.3 to 17.0 Bq/kg at Hospital A and from 3.9 to 7.1 Bq/kg at Hospital C. The 131I activity concentration in the soil at the depth of 0-5 cm was higher than that at the depth of 5-10 cm soil at the same sampling point. The ratios of activity concentration of 131I between different depths ranged from 1.3 to 13.1, with the median value of 5.9. Conclusions:After the 7·20 extraordinary rainstorm disaster, the surrounding environment of nuclear medicine decay pools at a few hospitals was contamminated by 131I to some extent. To prevent the risk of leakage of radioactive wastewater, the safety evaluation and management of radiation protection should be made better with increased awareness during the design, evaluation, construction and use of nuclear medicine decay pools.
RESUMO
Objective:To provide the calculation method for evaluating and designing the volume of nuclear medicine intermittent decay pool, so as to provide technical reference for medical institutions, environmental impact assessment institutions and management departments, etc.Methods:By constructing a mathematical model and deriving the calculation formula, the relationship between the volume of intermittent decay pool and the radioactivity level of wastewater was established.Results:There were differences in the number of diagnosis and treatment of patients, the amount of nuclide used and the amount of waste water produced in the nuclear medicine department at different medical institutions, so the evaluation and design of the intermittent decay pool were also different as a result . But the result should meet the relevant requirements of the standards GB 18871-2002 and HJ 1188-2021: the total activity discharged every month ≤10 ALImin, and the activity discharged once≤1 ALImin; gross alpha activity ≤1 Bq/L, gross β activity ≤10 Bq/L, 131I activity concentration ≤10 Bq/L; the temporary storage time after filled with radioactive wastewater ≥10 times longest half-life, and the temporary storage time of 131I in patient waste water ≥180 d. Conclusions:The calculation method provided in this paper can be used to evaluate and design the volume of intermittent decay pool in nuclear medicine departments.