INTERNATIONAL JOURNAL OF ENGINEERING, SCIENCE AND - Volume 4, Issue 1 , March 2015

Pages: 45-59

Date of Publication: 01-Mar-2015

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DETERMINATION OF NATURAL RADIOACTIVITY LEVELS OF 238U, 232TH AND 40K IN ROCKS AROUND GONDAR CITY, NORTHWEST ETHIOPIA

Author: W. Tsegaye Birhanu* A.K Chaueby* T. Tessema Teklemariam* Y.A. Ahmed** Bappah Ibrahim**

Category: Engineering, Science and Mathematics

Abstract:

The aim of the present work was to assess the terrestrial radionuclides distribution and their radiological health related risks in rocks around Gondar city using NaI (Tl) detector gamma-ray spectrometry. The samples were dried, pulverized, homogenized and then on average 300g from each rocks were packed in polyethylene containers. The polyethylene containers were tightly sealed for 4 weeks until the parent radionuclides 238U, 232Th and their daughter products in the rock samples attained in secular equilibrium. Based on the characteristic spectral peaks produced by daughter nuclides of 208Tl (in 238U series) at 2614.4kev, 214Bi (in 232Th) at 1764.4kev and the singly decaying 40K at 1460.8kev, the activity concentrations were determined for 226Ra (238U) from 18.06 ± 5.59 BqKg-1 to 27.05 ± 4.60 BqKg-1 with an average value of 21.36 BqKg-1; for 232Th from 54.57 ± 1.42 BqKg-1 to 106.32 ± 1.65 BqKg-1 with mean activity 59.60 ± 2.34 BqKg-1 and for 40K from 152.68 ± 14.10 BqKg-1 to 873.01 ± 13.08 BqKg-1. The calculated absorbed dose rate and the annual effective dose rates were varied from 49.98±1.99 to102.26±2.84 and from 0.061to 0.126 μSvy -1 respectively.

Keywords: Natural radionuclides; gamma-ray spectrometer, activity concentration; radiation hazard indices