Analysis Method of 131 I Activity in Carbon Cartridge and Internal Dose Assessment for Nuclear Medicine Workers

Inhalation of 131 I is the main route for internal doses to nuclear medicine workers. This study aimed to establish a simple analysis method for determining 131 I activity in carbon cartridges, explore the activity concentration of 131 I in nuclear medicine departments, and evaluate the internal dose of workers. A total of 21 nuclear medicine departments in the hospital conducted air sampling using a high-volume air sampler equipped with carbon cartridges and glass fiber filters to collect gaseous 131 I and aerosol 131 I, respectively. Furthermore, a mathematical model was developed to analyze the 131 I activity with inhomogeneous distribution in cartridges. Based on the 131 I activity measured by the HPGe γ spectrometer, the personal annual inhalation effective dose was estimated. The results showed that there is a significant difference in the activity of gaseous 131 I and aerosol 131 I, with the activity ranging from 1.5±0.08 Bq m -1 to 3,944.23±197.21 Bq m -3 and ND (not detectable) to 842.11±42.11 Bq m -3 , respectively. The activity of aerosol 131 I is about 1% to 7% of that of gaseous 131 I. The annual committed effective dose caused by inhalation of 131 I for workers is 3.6 μSv to 8.23 mSv, which is lower than the dose limit of 20 mSv y -1 . In general, the 131 I contamination in the nuclear medicine department cannot be ignored, and the concentration of 131 I should be regularly monitored to prevent and control the internal radiation to which workers may be exposed.