【摘 要】
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Mankind has always been living with the radioactive materials and ionizing radiations since the dawn of life on the earth.There has been an increased interest in the human exposures to the naturally o
【机 构】
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Department of Physics,Cotton College,Guwahati 781001,Assam,India
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Mankind has always been living with the radioactive materials and ionizing radiations since the dawn of life on the earth.There has been an increased interest in the human exposures to the naturally occurring alpha-emitting radionuclides in mines,dwellings,caves,building materials,industrial wastes,coal fuel cycles,water supplies,soils,etc.The risk to human health posed by ionizing radiation is an established fact.The naturally occurring radioactive radon (222Rn) gas is the greatest contributor to the ionizing radiation dose received by the general population1.Radon is a chemically inert radioactive gas and is found as the immediate decay product of radium (226Ra) of uranium (238U) decay series,and as such it is ubiquitous in soils and rocks2.Upon inhalation,alpha particles emitted by radon and its short-lived progenies can damage cellular DNA and radon has been established as a human lung carcinogen2,3.The radon exhalation from ground is vital in assessing the indoor radon concentrations.The Tiru valley coal field of Mon district,Nagaland,India bears significant geological characteristics.Keeping in view of health risks,in this work a study has been made on the radon exhalations and its effective doses from the coal bearing Tikak Parbat horizon of the Barail Group of the Tiru valley coal field,Mon district,Nagaland.The radon activity,mass exhalation,surface exhalation,radium content and effective dose were found to be in the range of 520.2 - 1112.3 Bq.m-3,6.5 - 14.0 mBq.kg-1.h-1,217.4 - 464.8 mBq.m-2.h-1,6.7 - 14.3 Bq.kg-1 and 15.8 - 33.8 μSv.y-1 for coal samples,559.8 - 912.3 Bq.m-3,7.0 - 11.4 mBq.kg-1.h-1,234.0 - 381.1 mBq.m-2.h-1,7.2 - 11.8 Bq.kg-1 and 17.0- 27.7 μSv.y-1 for shale samples and 815.8 - 1602.4 Bq.m-3,10.2- 20.1 mBq.kg-1.h-1,340.9- 669.8 8 mBq.m-2.h-1,10.5- 20.6 Bq.kg-1 and 24.8- 48.6 μSv.y-1 for sandstone samples respectively.A good correlation coefficient has been obtained between the radon exhalation and radium contents in the samples.
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