The determination of equilibrium factor of radon and thoron using LR-115 type II detector in a selected area from Basra Governorate, Iraq

Abstract

Abstract The inhalations of radon 222Rn progeny are the most important source of irradiation of the human respiratory. Studies of underground miners of uranium and other minerals have provided reasonably firm estimates of the risk of lung cancer associated with exposure to radon progeny. It is well established that the absorbed radon dose in the lung is mainly due to radon progeny, but not the radon gas itself. Therefore, long-term measurements of the concentrations of radon progeny or the equilibrium factor F, together with a measurement or an estimation of the aerosol size distribution, are needed to accurately assess the health hazards contribution from radon progeny. Radon, thoron and their progeny are present in the indoor atmosphere as free and bound fractions. The ventilation level in the house played an important effect on the equilibrium between them. This paper presents the results of the measurement of the equilibrium factor F between radon, thoron and their progenies in dwellings and estimates an experimental relationship for the F-factor based on track density instead of typical value of UNISCEAR (about 0.4), which varies significantly with time and place. In this paper, we described a method of theoretical calculation of F and experimentally determined the F-factor using LR-115 type-2 plastic track detectors in closed and bare mod. The exposures were made with a cup and bare dosimeters distributed in 34 houses distributed in different locations of Basra Governorate. The measured F-factor between radon and progeny varied from 0.01 to 0.98 with an average value of 0.38 while the same factor for thoron and progeny was found to vary from 0.0004 to 0.3794 with an average value of 0.0877. These values were in a good agreement with the global F-factor estimated by ICRP. In present investigation about the F-factor, theoretical calculations using graphical solutions supported by experimental technique have been carried out. It is found that the globally assumed F-factor from UNSCEAR and our experimentally obtained value are in good agreement. For a more accurate estimation of the effective dose, one should measure the F-factor at each site considering all the effective parameters like the ventilation factors. The equilibrium factor was found to be small in some houses due to the very intensive ventilation system in the house.