Indoor Gamma Ray Measurements, Activity Concentrations And Radiation Hazard Assessment Of Residential Mud Buildings In Miango, North Central Nigeria.

Abstract

Natural radioactivity levels and radiation risks from mud buildings in Miango, North Central Nigeria have been assessed. The town is located within Naraguta Sheet 168 NW. The area is underlain mainly by porphyritic Pan-African granites, Mesozoic anarogenic Younger Granite consisting of biotite granite and granite porphyry, and newer basalt. Weathering and decomposition of these rocks have produced thick layers of clayey soils (mud) which are used for building residential houses. Concentrations of ²³⁸U, ²³²Th and ⁴⁰K in the mud houses were determined using RS-230 Gamma Spectrometer integrated with a BGO (Bismuth Germanate Oxide) detector for improved accuracy. The content of ²³⁸U, ²³²Th and ⁴⁰K in the mud houses varies from 3.77-10.77ppm, 27.08-73.77ppm, and 1.47–6.27% respectively. Activity concentrations of these radioelements vary from 46.52-132.97 Bq/Kg for ²³⁸U, 109.76-299.49 Bq/Kg for ²³²Th, and 459.07-1961.47 Bq/Kg for ⁴⁰K. On the basis of these activity concentrations, radiation exposure parameters such as absorbed dose rate in air, annual effective dose equivalent, radium equivalent activity, excess lifetime cancer risk, and internal hazard index were calculated for the buildings. Results obtained vary from 146.79-291.69 nGy/h, 0.68-1.34 mSv/yr, 322.49-642.26 Bk/kg, 2.36 x10^-3- 4.70 x10^-3, and 1.00-2.08 respectively. These values are generally high for safety, thus suggesting that there is a good chance that using the clayey soils from this area for building houses may have negative health implications on the inhabitants in the long term.

Keywords: Uranium. Thorium. Potassium.  Activity concentration.  Absorbed dose rate in air. Annual effective dose equivalent. Radium equivalent activity. Excess lifetime cancer risk. Internal hazard index. Miango.