Calibration of HPGe detector and identification of Gamma Emitting Radionuclides in some Lancaster Samples
North-West University, South Africa
The aim of this research project was to calibrate the HPGe detector in Centre for Applied Radiation Science and Technology and to determine gamma emitting radionuclides in Lancaster soil samples. The soil samples were collected from different locations near the Lancaster Dam from Gauteng province, Krugersdorp, and were analysed using gamma-ray spectroscopy. The activity concentrations of gamma emitting radionuclides of 238U, 232Th, and 40K were determined using HPGe detector. The range of activity concentration of 238U, 232Th, and 40K was 54.51±0.48-386.69±1.39Bq.kg-1 with mean average value of 225.56±0.97Bq.kg-1 for 238U, 232Th, range of 10.84±0.18-52.61±0.38 Bg.kg-1 with average value of 30.59±0.30Bq.kg-1, and 40K range was 33.92±2.60-132.80±6.16Bq.kg-1 with an average value of 86.15±4.49Bq.kg-1. The activity concentrations were compared to the values of the worldwide average concentrations which are 35Bq.kg-1 for 238U, 30Bq.kg-1 for 232Th, and 400Bq.kg-1 for 40K by the international UNSCEAR, 2000. The mean average activity concentration of 238U and is higher than the worldwide average activity concentration of 35Bq.kg-1 and activity concentration of 232Th is within the world value of 30Bq.kg-1, however, the mean average activity concentration of 40K is lower than the worldwide average activity concentration of 400Bq.kg-1. Since the activity concentration of Uranium is higher than the worldwide average value, people living near the Lancaster Dam may be exposed to high level of radiation. The absorbed dose rate calculated form the activity concentrations of 238U, 232Th, and 40K ranges from 27.77 to 120.64nGy.h-1 with mean average value of 75.57nGy.h-1which is slightly higher than 57 nGy.h-1.The Radium equivalence (Raeq) for the soil samples in Lancaster Dam is between 72.62 to 472.15Bq.kg-1 with an average mean value of 275.9515Bq.kg-1. The mean value of radium equivalence is lower than 370Bq.kg-1. The external hazard index values are from 0.19 to 1.27 with the average mean value of 0.48. the mean value of 0.48 falls within 1mSv.y-1. The external hazard values of L37 and L42 which are 0.98 and 1.27 are above the expected limit of 1mSv.y-1, however, the mean value of all sample which is 0.74 falls within limit of unity of 1mSv.y-1. Therefore, further studies must be done to evaluate the potential radiological risk to the people in the vicinity, especially from inhalation of dust and ingestion of water, however, since the external hazard value of 0.74 falls within the expected limit of 1mSv.y-1, the external hazard is unlikely to cause radiological health effects to the people living near the Lancaster Dam.