Simulation of the radioactive concentrations of radon and its daughters in the dwellings

Abstract

A compartmental model has been established for simulation of the transport processes of the natural radionuclides as the noble gas 222Rn and its daughters in the dwelling. The model has been described by an ordinary differential equation system. According to the simulation results, the differences in the time course of the radiation Energy Rate (ER) and the Radon concentration (Rn) influence both the local and the time-integral values of the ratio. Namely, a very short but intensive ventilation modifies the ratio of EN/Rn by 40–50%. Therefore, the measured radon concentration, in the room does not precisely reflect either the radiation energy or the dose rates due to the inhalation. The relatively high radon exhalation from the building material could provide in equilibrium nearly 1000 Bq/m 3 indoor radon concentration and the ratio of ER/Rn contributed to the inhalation dose in a closed room increases to nearly 1.5pW per Bq/m 3. The parameter uncertainty analysis provided by the Monte Carlo simulations show that the main parameters contribute to the variation of the ratio EN/Rn are the normal ventilation rate, the deposition of the aerosols to the room surfaces and their resuspension back into the air. The radon exhalation rate from the building material has a large influence on the radiation energy rate and on the indoor radon concentration but not on their ratio.