MODELLING THE INDOOR RADIATION DOSES: A REVIEW AND PERSPECTIVE.

Abstract

Theoretical models to calculate the indoor gamma and radon doses are reviewed, refined and applied. The model for gamma doses is built based on the relative effects of the different room elements that control the amount of radiation. The relative doses are calculated by the MCNP5 simulation software. The gamma sources are due to the natural radiation from the 238U series, 232Th series and the radionuclide 40K. An application of the model that involves all the considered elements is demonstrated. The elements are the thickness of the walls, the density of the building material, the dimensions of the room, the existence of other rooms surrounding the room under study, the split of some walls into two portions, the existence of internal thin partial walls inside the room, the existence of windows and doors, and the incompleteness of the secular equilibrium in the 238U decay series due to radon release from the building materials. The model for radon doses is built based on Fick's laws. The radon surface exhalation rate from a wall and that from a building material sample are calculated from a one-dimension and three-dimension diffusion description by Fick's second law, respectively. The two rates are compared, and the radon indoor concentration and inhalation doses are formulated.