Radiological Impact Assessment in Underground Goldmine; Measurements, Statistical Analysis And Radiation Protection Viewpoint

Abstract

Measurements of indoor radon concentrations, environmental factors, soil and rock samples were collected monthly over a period of one year in 10 different levels in an underground goldmine to determine the radiological impact on workers. The detectors were installed in batches within four quarters. The measurements were carried out using LR115 solid state nuclear track detectors. Statistical models were applied in the prediction and analysis of the radon concentration at various depths. The results show that the activity concentration of radon in the underground mine ranges from a minimum of 2 Bqm-3 to a maximum of 284 Bqm-3 with a mean value of 58.51 Bqm-3.The highest radon concentration was observed in the second quarter when the season was warm and the lowest radon concentration was observed in the first quarter when the season was colder. The exposure rate, annual effective dose and excess lung cancer risk were below the acceptable limit. A positive relationship was observed between dry bulb temperature, relative humidity and radon concentration while a negative relationship was observed between barometric pressure, air quantity, wet bulb temperature, wet kata temperature and radon concentration. Statistical analysis of the results indicate that all the relationships were insignificant. Principal component analysis deduced three main factors that influences the indoor radon concentration of which wet bulb temperature was statistically significant. The hazard indices, exposure rate, excess lung cancer risk and annual effective dose from the rock and soil samples possess no radiological hazard if used for building materials. Even though radon concentration increases with increased depth, the assumption of the time series model confirmed a reduced radon concentration with adequate ventilation.