External detection and measurement of inhaled radionuclides using thermoluminescent dosimeters

Many radiation detection programs use bio-assays, whole-body counters, or air sampling to estimate internal doses. This study examines the possibility of using a common external thermoluminescent dosimeter (TLD) badge as a device for detecting inhaled radionuclides through radiation those radionuclides emit which escape the body. The three common radionuclides chosen for modeling due to their varying decay modes and use or production in the nuclear industry were Cs-137, U-238, and Sr-90. These three radionuclides were modeled for biological and radiological removal in the dynamic systems modeling program of STELLA II and modeled for TLD dose per organ in the geometry and radiation simulation program of MCNP. The results show that none of the nuclides in the study can be detected at air concentrations below regulatory limits for acute inhalation exposures. To achieve a detectable dose from an 8-hour work exposure, with a 90-day wait until the TLD is read, the airborne concentrations for the inhalation classes that produced the most dose per Bq would be 37.9 kBq/m3, 146 MBq/m3, and 1.67 MBq/m3 for Cs-137, U-238, and Sr-90, respectively.