Measurement of radon concentration for assessment of the radiological hazard in the Chakwal coalmines of the Salt Range, Pakistan.

Radon and its progeny are prevalent everywhere on the lithosphere especially in the mining environment. Coal exists in the Salt Range that passes through Pakistan. The aim of the present study was to measure radon concentration and assess the associated radiological hazard in the coalmines developed in that portion of the Salt Range which passes through the district of Chakwal in Pakistan. Among the various coalmines in the coalfield, five were selected for radon survey. A passive integrated technique consisting of SSNTDs (solid state nuclear track detectors) was employed for the measurement of radon concentration in these coalmines. Box type dosimeters containing CN-85 detectors were placed for three months at six locations in every selected coalmine. After removing the dosimeters, the CN-85 detectors were etched in alkaline solution to enlarge the alpha tracks in the detectors and counted under an optical microscope. The track densities were converted to radon concentration. The average concentration of radon in the coalmines varied in the range 50-114  Bq m(-3). Radon exhalation rates from the samples of coal and shale collected from the coalmines were determined to be respectively 934 (830-1010) and 1302 (1020-1580)  mBq m(-2) h(-1). The radiation dose and corresponding health risk for the mine workers were also estimated.