Monitoring intervals for the measurement of the radionuclides ¹²⁵I and ¹²⁹I in the thyroid gland

This paper shows the monitoring intervals that can be implemented in the Internal Contamination Laboratory of the Center for Radiation Protection and Hygiene for direct measurement of the radionuclides ¹²⁵I and ¹²⁹I in the Thyroid gland. Two measuring systems were used, one of them uses a scintillation detector and the other one uses a Phoswich detector. Both detectors were situated inside of one shielding chamber of 2.5 x 2.5 x 2.5 m of dimension, cover with 15 cm of steel, 3 mm of lead, 1.8 mm of tin, and 1.5 mm of copper. For each system was calculated the minimum detectable activity and in function of it were determined the monitoring intervals. The results obtained showed that for the radionuclide ¹²⁵I all the evaluated intervals (120, 90, 60, 30, 14 and 7 days).can be implemented with both systems. For the case of the radionuclide ¹²⁹I it can only be implemented the intervals (120, 90, and 60 days) using the scintillation detector and all of them with the Phoswich detector. (author)