贵州省部分矿山放射性水平的评价

Evaluation of radiation level in selected mines in Guizhou

目的调查和评价贵州省铝、锰、锑、磷、汞等部分矿山放射性水平。方法对矿区氡气、钍气浓度进行累积1年的现场检测；采集矿石、矿山周围土壤进行放射性核素分析；对矿区β辐射水平进行测量；对矿山渗透水进行总α、总β测量。结果某铝矿山春、夏两季井下氡浓度水平为626．0～3866Bq／m^3，秋、冬两季为38．9～655．0Bq／m^3，全年平均值为1374Bq／m^3；春、夏两季井下钍浓度水平为626．0～4834Bq／m^3，秋、冬两季为40．9～344．0Bq／m^3，全年平均值为1221Bq／m^3。其余矿山均低于此水平。矿石放射性核素^226Ra为6．9～511．9Bq／kg、^232Th为1．4～536．7Bq／kg、^40K为〈17．5～433．7Bq／kg。γ外照射最高的为铝矿，平均值（87．0±8．1）×10^-8 Gy／h，最低的为锑矿，平均值（6．0±1．9）×10^-8 Gy／h。矿山井下水总α为小于探测下限～17．5（×10^-2 Bq／L），总β为小于探测下限～37．4（×10^-2 Bq／L）。结论此次调查的部分矿山，大多采用机械和自然相结合的通风方式，通风情况较好。但铝矿井下的氡、钍浓度水平明显高于井外，全年平均值分别是井外的78倍和15倍；铝矿的γ外照射平均值（87．0±8．1）×10^-8 Gy／h，也明显高于贵州省γ天然辐射平均值（13．3×10^-8 Gy/h）。这将对该矿的矿工增加一定的附加剂量。

Objective To investigate and assess the radiation level in selected mines including mines of aluminum, manganese, antimony, phosphate and mercury in Guizhou province. Methods Radon and thoron concentrations were measured for 2×6 months using integrating method. Radionuclides in ore and soil, levels of γ-rays in mine lanes, and total α- and β-radioactivity in mine water were determined. Result Higher levels of radon and thoron were found in an aluminum mine. Radon concentration ranged between 626.0 and 3 866.0 Bq/m^3 in the first half year, and between 38.9 and 655.0 Bq/m^3 in the second half of the year; average was estimated to be 373.7 Bq/m^3 . For thoron, the corresponding values were 626.0-4 834.0 Bq/m^3 , 40.9-344.0 Bq/m^3 , and 1 221.4 Bq/m^3 , respectively. Radon and thoron were found in all other mines but with lower levels. Radionuelide concentration in the ore was normal, 6.9-511.9 （Bq/kg） for ^226 Ra, 1.4-536.7 （ Bq/ kg） for ^232Th, and 〈 17.5-433.7 （Bq/kg） for 40K. Highest γ-radiation level was found in the aluminum mine with average of （87.0±8.1 ） ×10^-8Gy/h, and lowest values in an antimony mine with average of （6.0 ± 1.9） ×10^-8Gy/h. Total α-radioactivity in ore ranged from 〈 LLD to 17.5 × 10^-2Bq/L, and β-radioactivity from 〈 LLD to 37.4 ×10^-2Bq/L. Conclusions High concentrations of radon and thoron were found in the mine lanes in the selected aluminum mine, about 78 and 15 times higher than those in the nearby open-air environment, though the mine were relatively good in term of mechanical ventilation and natural ventilation. γ-radiation level was elevated too, about 6.5 times higher than the provincial average of environmental γ-radiation level. Workers working in the aluminum mines received extra dose from their occupation exposures to natural radiation.