稀土矿放射性污染快速监测与评价方法研究

Taking Bayan Obo, rare earth mine in Inner Mongolia, and Baotou tailings dam as the research object, the research on the problems will be launched. These problems are: radioactivity concentration of uranium-238 and thorium-232 was equal to zero and some Th/U ratio value were far greater than the world average value, based on the quantitative calculation data of airborne gamma-ray spectrometry (not due to flying height correction). .We focus on: to study on the methods for fast identification of radioactive sources and determination of the activity concentration of the sources, especially extraction and decomposition of full spectrum data, and dose rate estimation model, atmospheric radon correction method, and to decrease interference due to thorium, when there are higher thorium contents on the tailings or in the area of contaminated soil. The research results will improve and expand the geophysical methods in the application of radioactive pollution monitoring and evaluation of the uranium / rare earth minerals, and provide a method for the rapid evaluation of potential radioactive contamination in associated minerals mining, nuclear facilities decommissioning; also provide improved, effectively methods for decreasing thorium interference and atmospheric radon correction during airborne gamma-ray spectrum data processing..This study will provide important basic data support for the development of relevant standards and technical specifications, and provide an important basis for the prevention and control of tailings dam.

以内蒙古白云鄂博稀土矿和包头尾矿坝为研究对象，针对该地区航空伽马能谱定量计算的部分铀/钍含量等于零，及钍/铀比值远大于世界平均值的问题（非高度修正引起）展开研究，重点研究快速识别放射源种类及测定源活度浓度的方法，尤其是当尾矿渣或污染土壤中存在高钍含量条件下的伽马能谱全谱数据特征及剂量率估算模型；采用全谱分解和时间序列分析方法，研究压制钍干扰的解谱及大气氡校正方法;研究露天开采和尾矿渣因干燥而导致钍-232再悬浮可能造成工人或公众吸入钍射气及其子体辐射剂量增高的问题；研究并建立稀土矿放射性污染风险评估方法。该成果将改进、拓展地球物理方法在放射性污染监测与评价的应用、为铀矿/稀土矿和伴生矿开采、核设施退役等潜在放射性污染监测应用领域提供快速评价方法，为航空伽马能谱数据处理提供改进的、有效的压制钍干扰的解谱方法和大气氡校正方法，为相关标准和技术规范研制、尾矿坝污染防治提供重要的基础数据支撑。

针对内蒙古包头市白云鄂博含稀土铁矿露天开采及尾矿坝潜在放射性污染问题，重点开展了快速识别放射污染源种类及测定源活度浓度的方法研究。研究了稀土矿区航空伽马能谱全谱数据特征并探索了钍元素干扰修正方法。采用NaI(Tl)闪烁伽马能谱仪实施了现场伽马能谱测量，以及现场剂量吸收剂量率测量；采用脉冲电离室（AlphaGAUD）和氡及其子体测量仪（RAD7和ERS-RDM-2S）测定了室内外氡/钍射气及其子体的浓度。研究结果表明：白云鄂博矿区潜在的放射性污染源是钍-232及其衰变子体。相对伽马吸收剂量率评价方法，伽马能谱方法，无论是航空还是现场测量，不仅能快速识别放射性污染源的种类，还能测定活度浓度；采用合适的测量网度和采样时间，可以快速圈定污染范围。白云鄂博矿区居室内氡和钍射气平均浓度分别为62.6±44.6Bq/m3和108.3±94.5Bq/m3，室外空气中氡和钍射气的平均浓度分别为12.9±6.3Bq/m3和55.8±18.5Bq/m3。随距离矿区和尾矿坝越近，室内钍射气浓度呈上升趋势，这表明矿山露天开采和尾矿坝表面因干燥而导致大气尘土中钍-232系列子体浓度较高，将可能引起工人或当地居民吸入钍射气及其子体引起辐射剂量的增高。该研究成果将进一步拓展地球物理方法在放射性污染监测与评价的应用、为铀矿/稀土矿和伴生矿开采、核设施退役等潜在放射性污染监测应用领域提供快速评价方法，为相关标准和技术规范研制、尾矿坝污染防治提供重要的基础数据支撑。