Browsing by Author "Phefo, Lebogang"

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    Determining the Radon Emanation Coefficient for Soil Samples
    (University of Zululand, 2020) Phefo, Lebogang
    Exposure to high concentrations of radon and radon decay products are known to increase lung cancer in humans. This study is in preparation for a national indoor radon survey to be conducted in South Africa. The aim of this study is to determine the radon emanation coefficient for soil samples collected in various areas in South Africa. The radon emanation coefficient is important for identifying areas with high radium concentrations which emanate radon which could lead to high levels of radon in houses. The areas of interest for this study include Paarl and Saldanha (having granite outcrops), Kloof and Boksburg mine dumps, Centurion, West Coast and Richards Bay Minerals where high radon levels are expected. The soil samples were collected and analysed in the laboratory. Both alpha and gamma spectrometry were used for determining the radium activity concentration of the soil samples and the radon released by the soil from which the radon emanation coefficient can be found. The samples were sealed for a period of 21 days to achieve secular equilibrium between radium and radon and then counted using a NaI(Tl) detector to measure the radium activity using a 214Bi full-energy peak. The radon concentration was determined using an active radon monitor, the RAD7 which measures the alpha particles emitted from the radon progenies, 218Po and 214Po. The values obtained for the radium activity concentration varied in the range of 9.206 × 103, 94 - 1146, 339 - 368, 64 147, 72, 18 - 34 and 11 Bq.kg−1 for West Coast, Boksburg, Kloof, Paarl, Richards Bay Minerals, Saldanha and Centurion samples, respectively. The radon concentration values built up in the accumulation chamber (of 10 litres) to values of 233, 175 - 596, 225 - 352, 218 - 223, 358, 61 - 99, 58 Bq.m−3 in West Coast, Boksburg, Kloof, Paarl, Richards Bay Minerals, Saldanha, and Centurion for soil samples having the mass of about 0.256 kg, respectively. Finally, the emanation coefficient was determined as the fraction of the radon atoms created that is exhaled into the air and the radium activity. The values of the emanation coefficient obtained in this study for sample mass of 0.256 kg ranges from, 0.073 - 0.146, 0.063 - 0.313, 0.214 - 0.541, 0.276 - 0.847, 0.812, 0.765 and 0.004, in Kloof, Boksburg, Paarl, Saldanha, Centurion, Richards Bay Minerals and West Coast, respectively. The radon emanation coefficient for sample mass of 0.512 kg are in the ranges from 0.092 - 0.108, 0.139 - 0.326, 0.171 - 0.572, 0.169 - 0.774, 0.188, 0.003, in Kloof, Boksburg, Paarl, Saldanha, Centurion, Richards Bay Minerals and West Coast, respectively. The radon emanation for the final sample mass to be investigated ranges from 0.089 - 0.113, 0.139 - 0.275, 0.245 - 0.373, 0.296 - 0.738, 0.686, 0.157, 0.003, Kloof, Boksburg, Paarl, Saldanha, Centurion, Richards Bay Minerals and West Coast, respectively. These values of the emanation coefficient are in line with wide ranging values of 0.01 - 0.8 reported in the UNSCEAR 2000 report. These values will help to choose the distribution of houses that should be measured in the planned survey of radon in houses.