Mapping and evaluation of natural radioactivity levels at the proposed nuclear research centre site in Chongwe.
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Date
2022
Authors
Muwowo, Sampa
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
In Chongwe at the site proposed for the Centre for Nuclear Science and Technology (CNST) soil, plant and water samples from the dam nearby had the activity concentrations of natural radionuclides measured. The natural radionuclides whose activity concentrations were measured are Uranium-238 (238U), Thorium-232 (232Th) and Potassium-40 (40K), using a hyper pure germanium (HPGe) detector. The absorbed dose rates (ADR), annual effective dose rates (AED), external hazard indexes (Hex) and radium equivalent indexes (Raeq) were determined from the measured activity concentrations. The average value of activity concentration in soil samples of 40K was 120.39±5.37 Becquerel/kilogram (Bq/kg), for 238U was 4.75±0.23 Bq/kg and for 232Th was 9.63±0.35 Bq/kg. The average values in soil samples of ADR, AED, Hex , Raeq were 13.00±1.32 non Grays (nGy/h), 0.02±0.001 millisieverts/year (mSv/y), 0.07±0.01 and 27.33±3.09 Bq/kg, respectively. The average values of activity concentration in plant samples of 40K, 238U, 232Th were 172±5.34 Bq/kg, 9.91±0.89 Bq/kg and 9.81±1.76 Bq/kg respectively. The average value in plant samples of ADR was 16.44±6.71 nGy/h. In plant samples, the average value of AED was 0.019±0.01 mSv/y while average Hex was 0.092±0.04 and Raeq was 34.89±13.41 Bq/kg. The average values of activity concentrations in water samples of 40K, 238U,and 232Th were 44.82±0.053 Bq/l, 7.83±0.32 Bq/l and 3.03±0.22 Bq/l respectively. The average value in water samples of ADR was 5.90±2.52 nGy/h while AED was 0.01±0.00 mSv/y and Hex was 0.03±0.01. The average value of Raeq in water samples was 14.56±3.70 Bq/kg. The results of average values of activity concentration of 40K,238U and 232Th for all the samples were observed to be lower than the world average values of 420 Bq/kg,33 Bq/kg and 45 Bq/kg, respectively as reported in the United Nations Committee on the Effects of Atomic Radiation (UNSCEAR) report of 2000. The average values of ADR for all samples were lower than world average value of 59 nGy/h. The average values of AED dose rates for all samples were below both the world average of 2.40 mSv/y and the annual exposure limit of 1 mSv/y as recommended by International Commission on Radiological Protection (ICRP). The average values of Hex for all samples were below unity, the safety limit index set by ICRP which showed that radioactivity at the site was negligible. The average values of Raeq for all the samples were below both the world average value of 58 Bq/kg and the recommended maximum activity value of 370 Bq/kg ,set by ICRP for radiation to be considered not to be hazardous at an area. The data acquired showed that natural ionising radiation at the proposed site for the Centre is below general public exposure limit of 1 mSv/y at the moment.
Description
Master Of Science In Physics
Keywords
Nuclear science and technology. , Natural radionuclides.