A Unified Formulation for Uncertainty Calculations in Personal Dosimetry

Periodic monitoring of radiation exposure of radiation workers (individual dosimetry) is an unavoidable safety requirement and standard in centers using ionizing radiation. Laboratories performing this monitoring are required to report measurement results with correct uncertainty estimates, in accordance with the requirements of ISO/IEC 17025. However, a precise and unified formulation for calculating this uncertainty in the field of individual dosimetry has not been widely presented. This paper aims to fill this gap by providing a systematic formulation for calculating measurement uncertainty in individual exposure measurements, mainly by the thermoluminescence (TLD) method. In this regard, the most important sources of uncertainty (such as non-uniformity of dosimeter response, background radiation effect, response nonlinearity, angular and energy dependence, calibration error and fading) have been identified and categorized based on the IAEA-GSG-7 Guide. For each source, the corresponding statistical distribution (normal for type A and rectangular for type B uncertainties) has been determined and the governing mathematical relationships have been extracted. The result of this study is the presentation of a final unified formula for calculating the total uncertainty. This formulation can be used as a comprehensive and reliable guide for dosimetry laboratories to assist them in estimating uncertainty in accordance with international standards and reporting the results reliably.