A dose-reconstruction study of the 1997 Sarov criticality accident using animated dosimetry techniques

Most computational human phantoms are static, representing a standing individual. There are, however, cases when these phantoms fail to represent accurately the detailed effects on dose that result from considering varying human posture and even whole sequences of motion. In this study, the feasibility of a dynamic and deformable phantom is demonstrated with the development of the Computational Human for Animated Dosimetry (CHAD) phantom. Based on modifications to the limb structure of the previously developed RPI Adult Male, CHAD's posture is adjustable using an optical motion capture system that records real-life human movement. To demonstrate its ability to produce dose results that reflect the changes brought about by posture-deformation, CHAD is employed to perform a dose-reconstruction analysis of the 1997 Sarov criticality accident, and a simulated total body dose of 13.3 Gy is observed, with the total body dose rate dropping from 1.4 Gy s to 0.25 Gy s over the first 4 s of retreat time. Additionally, dose measurements are calculated for individual organs and body regions, including a 36.8-Gy dose to the breast tissue, a 3.8-Gy dose to the bladder, and a 31.1-Gy dose to the thyroid, as well as the changes in dose rates for the individual organs over the course of the accident sequence. Comparison of results obtained using CHAD in an animated dosimetry simulation with reported information on dose and the medical outcome of the case shows that the consideration of posture and movement in dosimetry simulation allows for more detailed and precise analysis of dosimetry information, consideration of the evolution of the dose profile over time in the course of a given scenario, and a better understanding of the physiological impacts of radiation exposure for a given set of circumstances.