Solid State Nuclear Track Detectors Applied to Assess Workers Exposure to Radon in Small Scale Tanzanite Mines in Tanzania

The Solid State Nuclear Track Detectors (SSNTD) type CR-39 were used to measure levels of radon gas in the Small Scale Tanzanite Mining blocks B, C and D at Mirerani area, Northern Tanzania. Workers Exposure to Radon was assessed using the concepts of Working Level, Working Level Month and dose conversion factors recommended by the International Commission on Radiological Protection (ICRP). Results revealed that radon levels ranged from below action level of 300 Bqm-3 recommended by the ICRP to 5.3 times higher. The corresponding mean annual effective doses ranged from 0.8 to 11.8 mSvy-1, 1.4 to 4.4 mSvy-1 and 1.9 to 2.3 mSvy-1 for block B, D and C, respectively. These results indicate that the estimated doses are below the regulatory limit of 20mSvy-1. However, measures to keep the exposures as low as reasonably achievable are recommended as mining advance to deeper layers where the available means of ventilation may not be sufficient to lower radon levels.