Implications on dose estimation and dispersion patterns of thoron in a typical indoor environment.

A model that describes the pollutant sources/sinks and inlet-outlet can help to assess the indoor exposure. Short half-life of radioactive thoron (220Rn) makes it vital and an interesting element to study its dispersion behavior. This work presents an extensive depiction of the influence of indoor environment thoron dispersion under fixed boundary conditions within the volume domain of 90 m3 using computational fluid dynamics (CFD) software. For the desirable air flow, inlet and outlet are considered in the room and the k-ɛ model is used. The thoron distribution is studied at different locations and different heights to cover the whole room. Obtained dispersion patterns vary at different locations and indicate non-uniformity of thoron level with elevated values in the room corners. Mean concentration was found to be 11 Bq/m3 with the exhalation rate of 0.102 Bqm-2 s-1. Some stagnant zones were found especially at the corners where the concentration is almost 5 times the average concentration. Such varying thoron level results in the overestimation and underestimation of the dose. The inhomogeneous behavior of thoron may cause variation in equilibrium factor. A simulated model is beneficial in understanding the radioactive gas behavior and has its importance in planning to find the correct dose estimation and, therefore, the best mitigation techniques.