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 oth er sulphides in the Singhbhum shear zone developed at the northern margin o f the Singhbhum craton in the state of Bihar of India. The south-eastern pa rt of the shear zone between Surda-Mosabani-Badia is rich in copper mineral ization while the central part between Jaduguda-Bhatin-Nimdih and Narwapaha r-Garadih-Turamdih is enriched in uranium. In the present study, trace uran ium concentration in geological samples from the Mosabani copper mine and t he Narwapahar and Jaduguda uranium mine areas have been determined using fi ssion track registration technique. For the measurement of the radon exhala tion 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 r adon exhalation rate and uranium concentration in the samples. The linear c oefficients 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 s ubsurface mines like Jaduguda (depth similar to 800 m) and Mosabani (depth > 1000 m) seem to emphasize the need for adequate ventilation for the remov al of radon and its progenies from the mines. (C) 1999 Elsevier Science Ltd . All rights reserved.