Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 67(9): 435-446 (2018)

技術報告Technical Report

Natural Radioactivity Measurements in Soil, External Dose and Radiological Hazard Assessment in the Uranium and Thorium Bearing Region of Lolodorf, Cameroon

1Nuclear Technology Section, Institute of Geological and Mining Research ◇ P.O. Box 4110 Yaoundé, Cameroon

2Department of Physics, Faculty of Science, University of Yaoundé I ◇ P.O. Box 812 Yaoundé, Cameroon

受付日:2018年2月12日Received: February 12, 2018
受理日:2018年5月17日Accepted: May 17, 2018
発行日:2018年9月15日Published: September 15, 2018

The level of natural radioactivity has been evaluated for soil samples collected from the uranium and thorium bearing region of Lolodorf in the southwestern Cameroon. Specific activities of 226Ra, 232Th and 40K in these soil samples were determined using γ-ray spectrometry with sodium iodide (NaI(Tl)) detector. The specific activities for the whole study areas where consist of five inhabited localities were compared with the world average and permissible recommended limits. Specific activities of 226Ra, 232Th and 40K ranged from 5–120, 2–170 and 50–253 Bq kg−1, with average values of 22±2, 37±6 and 98±7 Bq kg−1, respectively. The average values of absorbed dose rate in air (Da), external effective dose (Eext), radium equivalent activity (Raeq), external hazard index (Hext) and representative level index (Iγ) were 36.7±5.0 nGy h−1, 0.29±0.04 mSv y−1, 83±14 Bq kg−1, 0.22±0.03 and 0.58±0.10 respectively, which, were lower than their recommended values. Although this study shows that radioactivity level is normal in the study areas, except some areas where the uranium and potassium anomalies had been found by previous investigations, the possibility of developing cancer cases among individuals must not be neglected. The soil from the sampling areas in this study can be used safely as building materials apart from some points within Ngombas and Kribi.

Key words: uranium; thorium; soil; NaI detector; specific activity; air absorbed dose; radiological hazard

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