Doses of external exposure in Jordan house due to gamma-emitting natural radionuclides in building materials.

The use of building materials containing naturally occurring radionuclides as K-40, Th-232, and U-238 and their progeny results in external exposures of the residents of such buildings. In the present study, indoor dose rates for a typical Jordan concrete room are calculated using Monte Carlo method. Uniform chemical composition of the walls, floor and ceiling as well as uniform mass concentrations of the radionuclides in walls, floor and ceiling are assumed. Using activity concentrations of natural radionuclides typical for the Jordan houses and assuming them to be in secular equilibrium with their progeny, the maximum annual effective doses are estimated to be 0.16, 0.12 and 0.22 mSv a(-1) for K-40, Th-232- and U-238-series, respectively. In a total, the maximum annual effective indoor dose due to external gamma-radiation is 0.50 mSv a(-1). Additionally, organ dose coefficients are calculated for all organs considered in ICRP Publication 74. Breast, skin and eye lenses have the maximum equivalent dose rate values due to indoor exposures caused by the natural radionuclides, while equivalent dose rates for uterus, colon (LLI) and small intestine are found to be the smallest. More specifically, organ dose rates (nSv a(-1) per Bq kg(-1)) vary from 0.044 to 0.060 for K-40, from 0.44 to 0.60 for radionuclides from U-238-series and from 0.60 to 0.81 for radionuclides from Th-232-series. The obtained organ and effective dose conversion coefficients can be conveniently used in practical dose assessment tasks for the rooms of similar geometry and varying activity concentrations and local-specific occupancy factors