Radionuclide content of sand used for construction in Kakamega county and associated indoor radon diffusion doses

Abstract

The greatest portion of radiation received by world‟s population comes from natural radioactive sources. Everyone on earth receives natural radiation; some get much more than others depending on where they live. Primordial radionuclide in building sand and gravels from quarries are some of the sources of radiation hazards common in dwellings and working places. In this study, activity concentrations of naturally occurring radionuclide in mineral sand used for construction collected in old gold mining belt of Kakamega County were measured using gamma ray spectrometry technique, [NaI(Tl)]. The results of the concentrations of naturally occurring radionuclide were as follows: 226Ra ranged from 36.79±8.89 to185.21±5.89 Bqkg-1, 232Th ranged from 51.12±2.56 to 158.92±7.95 Bqkg-1 and 40K ranged from 322.38±16.12 to 960.53±48.03 Bqkg-1. The calculated radium equivalent activity (Raeq), the absorbed dose rate (D), and the external hazard index (Hex) were within the international recommended values. Hence construction sands from the study region do not pose any risk to the inhabitants in terms of the acceptable limits. The movement of radon by diffusion from the walls of classrooms constructed from such sand into indoor air was modeled based on radiological parameters. The posed model predicted an ambient indoor radon concentration of 9 Bqm-3, 15.6 Bqm-3 and 28.7 Bqm-3 in three monitoring stations (classrooms) in the region. The modeled radon concentrations were lower than measured; the model reproduced the general trends associated with diffused indoor radon fluxes. Thus it can be helpful in estimating radon concentrations for other similar processes such as estimating radon concentration in caves and mines.