Radon exhalation rate and uranium estimation in rock samples from Bihar uranium and copper mines using the SSNTD technique

Widespread uranium mineralization is associated with copper, nickel and other sulphides in the Singhbhum shear zone developed at the northern margin of the Singhbhum craton in the state of Bihar of India. The south-eastern part of the shear zone between Surda-Mosabani-Badia is rich in copper mineralization while the central part between Jaduguda-Bhatin-Nimdih and Narwapahar-Garadih-Turamdih is enriched in uranium. In the present study, trace uranium concentration in geological samples from the Mosabani copper mine and the Narwapahar and Jaduguda uranium mine areas have been determined using fission track registration technique. For the measurement of the radon exhalation rate, the 'can technique' using alpha sensitive LR-115 type II plastic track detectors were used, Uranium concentrations were found to vary from 1.5 to 2097.9 ppm whereas the radon exhalation rate varied from 0.2 to 19.2 Bq m(-2) h(-1). The values of radon exhalation rate from crushed rock and soil samples are found to correspond with the measured values of uranium in the corresponding samples. A positive correlation has been found between radon exhalation rate and uranium concentration in the samples. The linear coefficients are found to be 0.40, 0.98 and 0.95 in the Mosabani, Narwapahar and Jaduguda mine areas respectively. High values of radon exhalation in subsurface mines like Jaduguda (depth similar to 800 m) and Mosabani (depth > 1000 m) seem to emphasize the need for adequate ventilation for the removal of radon and its progenies from the mines. (C) 1999 Elsevier Science Ltd. All rights reserved.