ESTIMATION OF RADIOACTIVITY LEVEL AND ASSOCIATED RADIOLOGICAL HAZARDS OF LIMESTONE AND GYPSUM USED AS RAW BUILDING MATERIALS IN RAWALPINDI/ISLAMABAD REGION OF PAKISTAN

摘要

This study was undertaken to asses the radioactivity level of limestone and gypsum and its associated radiological hazard due to the presence of naturally occurring radioactive materials. Representative samples of limestone and gypsum were collected from cement factories located in the Rawalpindi/Islamabad region of Pakistan and were analysed by using an N-type high-purity germanium detector of 80 % relative efficiency. The average activity concentration of ~(40)K, ~(226)Ra and ~(232)Th were 60.22 ± 3.47, 29.25 ± 5.23 and 4.07 + 3.31 Bq kg~(-1), respectively, in limestone and 70.86 ± 4.1, 5.01 ± 2.10 and 4.49 ± 3.1 Bq kg~(-1), respectively, in gypsum. The radiological hazard parameters radium equivalent activities, absorbed dose rate in air, external hazard index, internal hazard index, annual effective dose equivalent, gamma index and alpha index were computed. The results of the average activity concentrations of ~(40)K, ~(226)Ra and ~(232)Th and radiological hazard parameters were within the range of the reported average worldwide/United Nations Scientific Committee on the Effect of Atomic Radiation values. It is concluded that limestone and gypsum used in the Rawalpindi/Islamabad region does not pose any excessive radiological health hazard as a building raw materials and in industrial uses.