MST-Department of Physics

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Browsing MST-Department of Physics by Subject "Assessment"

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    Assessment of Radioactivity Concentration and Radiation Hazards Index for Building Materials Used in Babadogo Estate, Nairobi City County, Kenya
    (Kenyatta University, 2022) Oborah, Amukah Kenneth; Nadir O. Hashim; Charles M. Migwi
    Natural radioactive materials in certain conditions can get to hazardous radiological level. Some of these hazards are not prone to control as well as, they are usually referred to as the background radiation. The aim of my research work is to evaluate natural radioactivity concentration and radiological impacts on representative sampled building materials collected from different locations in Babadogo estate within Nairobi City County. The selected samples were crushed, sieved dried and store for four weeks after which, analysis done using gamma ray spectrometer was put into action for spectral data acquisition then analysis. The activity concentration levels of 238U, 232Th and 40K for the selected samples of building materials was measured by the use of gamma- ray spectrometry method. Radiological parameters were evaluated based on the prerequisite activity concentration obtained. The analyzed data compared with the standard acceptable values. The activity concentration in 40K varied from 55±3 to 2647±132 Bq/kg giving average value of 831 ±42 Bq/kg, 238U varied from 39±2 to 3602±180Bq/kg giving average figures of 378±19Bqkg¯1and 232Th ranged from 5.000±0.300 to 4213±211Bqkg¯1 giving mean figure of 290±15Bq/kg . Calculated mean figures for activity concentration surpassed the world mean figures of 420Bq/kg, 33Bq/kg, 45Bq/kg in 40K, 238U and 232Th respectively. Absorbed dose rate calculated ranges between 73±4 and 4777±239nGyh¯1 having average value of 540±27nGyh¯1 .The mean number for the absorbed dose rate was above the world acceptable mean value of 54nGyh¯1. The calculated annual effective dose rate varied from 0.040±0.002mSvy¯1 to 2.340±0.117mSvy¯1 having average figure of 0.260±0.013mSvy¯1 ,which was above the world average of 0.070mSvy¯1but below the maximum dose constraint of 1mSvy¯1.These results show that building materials in Babadogo estate are safe and can be used for construction of buildings and thus can be continued using as further research is done on other building materials not covered in my research work.
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    Radiometric Assessment of Natural Radioactivity Levels and Radiation Hazard Indices for Soil Samples in Kericho County, Kenya
    (Kenyatta University, 2020-10) Kiprono, Vincent
    Throughout their lives, human beings are continually exposed to radiation from terrestrial radionuclides particularly 40K, 238U, 232Th and their decay products. The radiation, usually in the form of gamma rays and alpha particles, is largely attributed to building materials for instance rock and concrete mainly used in developed countries and cities around the world, or soil which is principally used in most parts of rural Africa. Radiation exposure from terrestrial sources may be more of a concern in indoor settings under certain conditions. As an example, houses constructed using building materials high in 238U and 232Th content often contain elevated concentrations of radon which, according to the World Health Organization, is the leading cause of lung cancer among non-smokers. Owing to the potential risk, many countries especially in the developed world have quantified 40K, 238U and 232Th in their environments and mapped the radiation risk-prone areas. In Kenya however as in most parts of Africa, data on the terrestrial radionuclides is largely absent. The reported study involved measurement of specific activities of 40K, 238U and 232Th in surface soil of Bureti Sub-County, Kericho County, Kenya, for purposes of evaluating the risk indices that included radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), outdoor gamma dose rate and outdoor annual effective dose rate. Bureti Sub-County has a rural setting and as such, soil forms the main building material for house construction. The region is also a relatively rich agricultural zone with tea and maize being the main crops grown. Soil samples were randomly collected from twenty one sampling stations within tea and maize plantations and after requisite preparation analyzed for 40K, 238U and 232Th activity concentrations using calibrated NaI (Tl) gamma ray spectrometer and the associated electronics. The specific activities of 40K varied from 39 ± 2 to 2129 ± 106 BqKg-1 with an average of 1086 ± 49 BqKg-1 , 238U ranged from 34 ± 2 to 265 ± 13 BqKg-1 with a mean of 143 ± 7 BqKg-1 whereas 232Th ranged from 3 ± 1 to 150 ± 9 BqKg-1 with a mean of 95 ±4 BqKg-1 . The average values of 40K, 238U and 232Th exceeded the world averages by factors of 2.6, 4.3 and 2.1 respectively. Raeq varied from 130 ±7 to 590 ± 30 BqKg-1 with a mean of 362±18 BqKg-1 which is within the recommended range while Hex and Hin varied from 0.35± 0.02 to 1.60± 0.08 with a mean of 0.98±0.05 and 0.44±0.02 to 2.16±0.11 with a mean of 1.36±0.07 respectively. While Hex average value is within the reference level of 1, that of Hin exceeds the value by 36%. The estimated outdoor absorbed gamma dose rate ranged from 59 ±3 to 273±14 nGyh-1 with a mean of 169 ±8 nGyh-1, about 3 times the world average. The outdoor annual effective gamma dose rate averaged 0.41 ± 0.02 mSvy-1 which though significantly higher than the world average of 0.07 mSvy-1 is less than half the maximum dose constraint of 1 mSvy-1 recommended by ICRP for the general public. Thus, radiation exposure in Bureti Sub-County is within the acceptable safety limit. Nonetheless, soil when used as a building material may to some degree contribute to indoor radon concentration hence the need to quantify radon concentration in earthen dwellings in the region.