Radiation Levels in Buildings on the Main Campus of Haramaya University and at the Towns of Harar and Dire Dawa, Eastern Ethiopia

Abstract

Indoor radiation is a concern for people living in buildings constructed from materials with high emission of radionuclides. In this study, radiation rate measurements of 39 rooms in nine buildings of three different age groups at three locations were made using Electronic Personal Dosimeter (EPD). The measurements included both interiors and exteriors of the rooms. Interior measurements were made in two perpendicular directions from two adjacent walls at distance interval of 0.5 m. The EPD measurement revealed a decrease in the magnitude of the radiation as the days of measurement progressed, and that necessitated the need of correction factors, which were evaluated using background radiation rates of each location separately. All measured radiation rates were then corrected using the respective correction factors. The results obtained are summarized as follows. Background radiation doses at HU campus and Harar and Dire Dawa towns, averaged over the measurement days is, 4.1, 2.8 and 2.4 mSv/y, respectively. These values reflect effective external doses of 0.82, 0.55 and 0.47 mSv/y, respectively, for the three locations. Dire Dawa old building differed from all the other buildings of the three locations and it exhibited the highest interior radiation of average dose of 0.027±0.011 mSv/y above the background radiation. There were no significant differences between the new and the intermediate buildings of the three locations. When averaged out, irrespective of building ages of each location, HU buildings showed average dose of 0.004±0.004 mSv/y, Harar, -0.008±0.006 mSv/y and Dire Dawa, 0.009±0.008 mSv/y. No difference in radiation rates were observed between the two directions but radiation rates slightly increased from walls to the centers of rooms up to a certain point. Radiation rates of the interior and exterior of each room did not show a significant difference. Though differences were observed among buildings of the three different ages, the differences were not uniform at the three locations. The doses from all the rooms were within the limit set by IAEA for indoor radiation.

Keywords: Background radiation variability; Indoor radiation; Electronic Personal Dosimeter; Radiation rate; Building age