Evaluation of occupational radiation dose estimates due to inhalation of Iodine-123 during metaiodobenzylguanidine and ultra pure sodium iodide production at Nuclear Engineering Institute, Brazil

The production process for obtaining metaiodobenzylguanidine (MIBG) and ultrapure sodium iodide (NaI), both labeled with iodine-123, is performed in Radiopharmaceuticals Division (Dira) of the Institute of Nuclear Engineering (IEN). Such processes are carried out in armored cells, which are maintained under negative pressure surrounded by a positive pressure zone ensuring that appropriate air quality requirements are met. However, there may be leaks or iodine leakage from the cells to the laboratory environment. Due to high volatility of iodine, under environmental conditions, from the synthesis laboratory, there is an inhalation exposure risk in individuals occupationally exposed (IOE). Thus, the control and inhalation dose estimation are necessary to meet the requirements set out by the CNEN regulatory standards and to ensure the radiological safety and the health of workers in radiation facilities. The control is performed by air sampling in the synthesis laboratory. We used a vacuum pump with activated carbon filter for the retention of iodine-123 and through gamma-ray spectrometry with NaI (Tl), which the gamma-ray spectra were analyzed by using a data acquisition software, the air pollutant concentration was determined. According to the pollutant concentration, the inhalation radiation doses were estimated by analytical calculation method, considering the exposure factors and mean inhalation rate values. The results have shown that the inhalation occupational dose estimates of iodine-123 are well below the recommended limits by national and international standards. The study concluded that, regarding the radiopharmaceuticals production, the associated risks are not considered significant, from the radiation protection point of view. (author)