Natural radioactivity and radiological hazards assessment of bone-coal from a vanadium mine in central China

A comprehensive utilization project of bone-coal in a vanadium mine was proposing in recent years in central China. Based on the analysis of 31 representative bone-coal samples from 9 boreholes at various depth drilled in planning initial minery, the average activity concentrations of U-238, Ra-226, Th-232 and K-40 were determined in the range of 196.4-653.3 Bq/kg, 200.2-564.4 Bq/kg, 9.4-64.6 Bq/kg and 71.5-345.4 Bq/kg, respectively. The major natural radionuclides were identified as U-series nuclides with the activity concentrations obviously higher than common coal. The estimated absorbed dose rates in the air varied between 107.1 and 310.5 nGy/h. The averaged external annual effective dose due to the radioactivity in the bone-coal was predicted as 0.37 mSv/a, and the main contribution is 87.5% for U-series. The radium equivalent activity, the external and internal indices of most of the samples were shown with high values of an unacceptable level, which indicated the bone-coal would carry a considerable radiation hazard to the workers and the local individuals. The hazard of radon inhalation should be focused during mining and following processes. Further radiological assessment should be carried out as the natural radioactivity in the bone-coal would be technically enriched during the combustion process of the bone-coal and utilization of the byproducts. (C) 2014 Elsevier Ltd. All rights reserved.