甘肃北山新场深部地下水中铀的赋存形态及其影响因素的地球化学模拟研究  

Geochemical Simulation on U Species and Their Influence Factors in Deep Groundwater from Xinchang of Beishan,Gansu

作　　者：吴鹏 王驹[3,4] 凌辉 周志超[3,4] 段佳欣 李南[2] 段先哲 WU Peng;WANG Ju;LING Hui;ZHOU Zhichao;DUAN Jiaxin;LI Nan;DUAN Xianzhe(School of Resource Environment and Safety Engineering,University of South China,Hengyang 421001,China;Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes,Hengyang 421001,China;Beijing Research Institute of Uranium Geology,Beijing 100029,China;CAEA Innovation Center for Geological Disposal of High-level Radioactive Waste,Beijing 100029,China)

机构地区：[1]南华大学资源环境与安全工程学院,湖南衡阳421001 [2]稀有金属矿产开发与废物地质处置技术湖南省重点实验室,湖南衡阳421001 [3]核工业北京地质研究院,北京100029 [4]国家原子能机构高放废物地质处置创新中心,北京100029

出　　处：《原子能科学技术》2024年第5期1007-1016,共10页Atomic Energy Science and Technology

基　　金：国家原子能机构高放废物地质创新中心基金(CXJJ21102211);湖南省自然科学基金(2023JJ30505);湖南省教育厅科研项目重点基金(23A0327);南华大学科研项目(CX20230966;20224130214)。

摘　　要：核能的快速发展产生了大量的高水平放射性废物(简称高放废物),对生态环境和人类健康构成了巨大的威胁,其安全处置已成为国际放射性废物管理的重难点问题。深部地质处置被普遍认为是高放废物最安全可靠、技术上非常可行的处置方法。目前,我国已启动了甘肃北山新场高放废物地质处置地下实验室的建设,放射性元素铀在深部地下水中的形态分布及其影响因素从微观层面能为北山深地质处置性能评价提供基础数据,但尚不明晰,亟需开展相关地球化学模拟研究。基于PHREEQC中的llnl.dat数据库,添加NEA-TDB和ThermoChimie数据库中U(Ⅵ)的热力学数据,使用地球化学模拟软件PHREEQC.v3和PhreePlot.v11对铀在我国甘肃北山新场高放废物地质处置地下实验室场址BS28孔深部地下水中的赋存形态及分布进行了模拟计算,旨在厘清铀在北山深部地下水中的赋存形态,探讨pH、pE以及Ca^(2+)与HCO_(3)^(-)浓度比对铀在北山深部地下水中形态分布的影响。模拟结果表明,在该深部地下水环境下,铀主要以六价的形式存在,Ca_(2)UO_(2)(CO_(3))_(3)(aq)和CaUO_(2)(CO_(3))_(3)^(2-)是主要的赋存形态,其占比分别为84.14%和15.16%。受氧化还原氛围的影响,铀的价态在pE<1时逐渐由U(Ⅵ)转变为U(Ⅳ),且在pE=-1~1时,UO_(2)(s)和可溶性碳酸铀酰络合物可同时存在。Ca^(2+)与HCO_(3)^(-)的浓度比低倾向于形成CaUO_(2)(CO_(3))_(3)^(2-),浓度比高易于形成Ca_(2)UO_(2)(CO_(3))_(3)(aq)。Ca^(2+)-UO_(2)^(2+)-CO_(3)^(2)三元体系很大程度上会影响铀在北山深部地下水的溶解度和迁移能力。本研究结果将有助于查明铀在北山花岗岩裂隙中的迁移和吸附机理。The rapid development of nuclear power reduced the consumption of fossil fuels,effectively reduced the environmental pollution of liquid waste,solid waste,and harmful gases,playing a crucial role in reducing carbon dioxide emissions.However,it also generated a large amount of high-level radioactive wastes(HLWs).HLWs contain a quantity of elements,high toxicity,high-level radioactivity,long half-life period,and large heat release,posing a huge threat to the ecological environment and human health.Its safe disposal has become a key and difficult issue in international radioactive waste management.Deep geological disposal is widely regarded as the safest,most reliable,and technically feasible method for disposing HLWs.Deep geological disposal refers to the establishment of a geological disposal repository of HLWs in rocks at a depth of 500-1000 meters underground,a site buring the processed HLWs,and isolating HLWs from the biosphere through a multiple barrier system to achieve long-term and effective safe disposal.At present,the construction of an underground research laboratory(URL)has been initiated for the geological disposal of HLWs in Xinchang of Beishan,Gansu.The distribution of U species in deep groundwater and its influence factors can provide basic data for the performance assessment of a deep geological disposal system at the micro level,but they remain unclear,urgently needed relevant geochemical simulation.Based on the database(llnl.dat)in PHEEQC,with an addition of thermodynamic data of U(Ⅵ)from NEA-TDB and ThermoChimie databases,the U species and their distribution in the deep groundwater of BS28 borehole of the URL were simulated using PHEEQC.v3 and PhreePlot.v11,to clarify the U species in the deep groundwater from Xinchang of Beishan and elucidate the influence of pH,pE,and concentration ratio of Ca^(2+)and HCO_(3)^(-)(c(Ca^(2+))/c(HCO_(3)^(-)))on the distribution of U species.The simulation results indicate that U occurs as U(Ⅵ)in this deep groundwater environment,with the main species of Ca_(2

关 键 词：高放废物 铀赋存形态 深部地下水 地球化学模拟 甘肃北山新场 

分 类 号：TL942.1[核科学技术—辐射防护及环境保护] X591[环境科学与工程—环境工程]