Calculation of dose conversion coefficients for radiation workers in various postures

Abstract

The present study investigates the impact of various body postures on dose assessment. Existing radiation protection systems that assume a standing posture are generally valid in most situations; however, they may not be effective in assessing the dose received by individuals in specific conditions such as radiation accidents. To address this, we used the Geant4 simulation code and mesh-type reference computational phantoms (MRCPs) to model and calculate the dose conversion coefficients (DCCs) for 19 representative working postures. These representative postures were developed by referencing existing industrial posture categories, combining movements of arms, torso, and legs. The exposure geometries considered in the present study include generalized parallel beams such as anterior-posterior (AP), posterior-anterior (PA), left-lateral (LLAT), and right-lateral (RLAT), and isotropic exposures from all sides (rotational (ROT) and isotropic (ISO)), along with semi-isotropic forms of ground and ceiling contamination ranging from 30 cm to 50 m in radius. The results demonstrate that the dose ratios between a personal dosimeter and whole-body (i.e. DCCs) are significantly influenced by the body posture and the exposure geometry. Particularly, exposures involving significant body shielding, such as ground and ceiling contamination and PA direction exposures, were mainly affected by the degree of torso bending. For instance, a DCC of 2.3 was recorded for a posture with approximately 45 degrees of torso bending under PA exposure. Additionally, in a ground contamination scenario having a 1 m radius beam, DCCs ranged from 0.8 to 2.5 depending on the degree of torso bending, and in a 2 m radius ceiling contamination scenario, DCCs of 1.2–1.7 were observed in postures with 90 degrees of torso bending. These findings emphasize the importance of posture-specific dose assessments in various contamination scenarios.