Comparison of Radon (۲۲۲Rn) and Thoron (۲۲۰Rn) Gamma Dosimetry in the Environment Using the ORNL Mathematical Phantom

Background: The potential hazards of exposure to radiation from radon have been of great concern worldwide, as it is associated with an increased risk of lung cancer. Radon (۲۲۲Rn) and its progeny are the main sources of radioactivity in the environment. The half-life of ۲۲۲Rn (۳.۸۲ days) is long enough for it to diffuse into and build up in homes. ۲۲۰Rn or thoron from the ۲۳۲Th series, and ۲۱۹Rn—a decay product of ۲۳۵U—have very short half-lives (۵۵.۶ and ۳.۹۶ sec, respectively) and are of minor significance compared to ۲۲۲Rn in the ۲۳۸U series. However, these sources, like thoron, are important in uranium mines. Radon and thoron progeny decay by emitting β particles accompanied by γ radiation. Although γ rays are comparatively less damaging to the respiratory system than α and β particles, it is the principal deposited energy in other organs.Methods: Comparison of radon and thoron γ radiation dosimetry was performed using a modified Oak Ridge national laboratory (ORNL) adult mathematical phantom and the Monte Carlo N-particle transport code (MCNP).Results: The results showed that the highest amount of the absorbed dose was in the lung followed by the thymus and heart, according to the ICRP۱۰۳ publication.Conclusions: The absorbed dose from thoron was quite large in comparison to radon because thoron has more high-energy particles than radon.