MEASUREMENTS OF NATURAL RADIOACTIVITY AND RADON EXHALATION RATES FROM DIFFERENT BRANDS OF CEMENT USED IN PAKISTAN

摘要

The measurement of activity due to the naturally occurring radionuclide has been carried out in different brands of cement available in Pakistan. The gamma spectra of the collected samples were obtained using high-purity germanium detector and analysed for the presence of ~(232)Th, ~(238)U and ~(40)K. The assessment of radiological hazards due to these radionuclides has also been made. The studies concerning the determination of radon-exhalation rates from these samples of cement were also carried out using CR-39 based NRPB radon dosimeters. The range of activity concentrations were found for ~(226)Ra (from 25.10 ± 1.55 to 52.60 ± 3.20 Bq kg~(-1)), ~(232)Th (from 10.30 ± 0.65 to 30.40 ± 1.70 Bq kg~(-1)) and ~(40)K (from 17.25 ± 1.55 to 292.95 ± 23.05 Bq kg~(-1)). The estimated value of radium equivalent concentration was from 11.16 ± 2.60 to 114.98 ± 7.11 Bq kg~(-1). The calculated absorbed dose rate in air and the annual effective dose were in the range from 18.54 ± 1.17 to 52.90 ± 3.31 nGy h~(-1) and 0.09 ± 0.01 to 0.26 ± 0.02 mSv, respectively. The external and internal hazard indices were in the range from 0.11 ± 0.01 to 0.31 ± 0.02 and 0.18 ± 0.01 to 0.45 ± 0.03, respectively. The radon exhalation rates from different brands of cement were found in the range from 3.3 ± 0.7 to 8.1 ± 1.7 mBq kg~(-1) h~(-1).