共查询到19条相似文献，搜索用时 140 毫秒
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高放废物的特点为放射性水平高,发热量大,并含有对生物极有害的α放射性的长寿命核素.深地质处置目前被国际公认为处置高放废物的有效方法. 相似文献
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随着世界各国大力发展核电，放射性废料的安全处置已成为当今研究热点和前沿学科。高放废物深地质处置的安全性主要取决于处置库内放射性核素向生物圈的迁移程度。在侵入岩中，放射性核素主要是通过地下水沿岩石孔隙从处置库向生物圈迁移的。为了理解放射性核素在花岗岩体接触带的迁移行为，本文根据两花岗岩体接触带中样品的铀系核素放射性活度比值（^234U/^238U,^230Th/^234U,^226Ra/^230Th,^230Th/^238U)，利用 α-反冲（弹射）作用引起的放射性不平衡理论，计算了铀系核素子体^234U,^230Th,^226Ra在后期地下水的作用下在花岗岩体接触带及其裂隙内的迁出率、迁入率、并进行了质量平衡的计算。结果表明，经α-反冲作用进入流体的核素的迁出率要远大于因核素自然衰变的消亡率；裂隙充填物及裂隙能阻滞大量核素的迁移，其沉淀核素来自接触带花岗岩；花岗岩能强烈阻滞核素的迁移，可作为阻止放射性核素从核废料地下处置库向外迁移的有利天然屏障。 相似文献
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高放废物地质处置过程中涉及的核素在围岩裂隙地下水中的迁移问题已引起广泛关注,数值模拟是研究核素粒子运移的重要方法。目前裂隙介质中渗流模型主要是等效连续介质模型、双重介质模型和离散裂隙网络模型。对于岩体尺度裂隙地下水的流动,离散裂隙网络模型能充分表现裂隙介质的各向异性、不连续性等特征。因此,针对裂隙介质准确概化及核素迁移模拟等难点,文章结合Monte Carlo随机生成裂隙方法、裂隙渗流有限元算法和高放射性核素衰变方程等方法,依据花岗岩深钻孔裂隙统计数据,采用离散裂隙网络模型对内蒙古阿拉善高放废物地质处置预选区展开了核素粒子迁移数值模拟研究,并讨论了实例预测分析结果。结果显示:针对设定的地质模型,核素粒子从中心运移到边界的迁移路径长度平均为1293.35 m,粒子运移到边界耗费的时间平均为1.70E+11 d。 相似文献
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高放废物地质处置系统核素迁移模型研究 总被引：2，自引：0，他引：2
高放废物地质处置系统核素迁移研究是高放废物安全处理和处置的重要内容。从整个系统的角度出发,把高放废物地质处置系统核素迁移过程分为三种模式:工程屏障中的释放—扩散模型;地质屏障中的对流—弥散模型和在生物圈中的分区传递模型。在分区传递模型中利用转移系数描述核素在各分区之间的迁移。通过对每种模型核素迁移机理的分析得出概化模型,并给出了相应的数学描述。 相似文献
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对一近地表铀矿体中某些铀系长寿命核素的放射性平衡状态和１４种微量元素迁移特征研究得出，自该铀矿床６３Ｍａ前生成至今，仅近１Ｍａ来，当上覆花岗岩遭剥蚀使矿体近地表时，矿石中天然放射性核和微量元素才因水－岩反应沿围岩破碎带，裂隙发生迁移；裂隙两侧岩石受水－岩反应影响的范围较小，裂隙面的化学组分以溶失为主，裂隙两侧粘土化花岗岩中则以核素、元素的扩散和吸附为主，最后阐述了本研究结果对高放废物处置库安全评价 相似文献
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高放废物深地质处置及国内研究进展 总被引：3，自引：2，他引：1
核能在产生电力造福社会的同时 ,也留下了放射性废物。我们有责任对这些废物实施安全和正确的管理。本文阐述了高放废物深地质处置的一般概念及处置库选址研究中的若干问题 ,同时介绍了国内高放废物深地质处置研究的进展. 相似文献
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Shuping Yi Haiyi Ma Chunmiao Zheng Guocheng Ren Xueling Hu 《Environmental Earth Sciences》2014,72(11):4427-4439
A regional strategy for safety disposal of low- and intermediate-level radioactive wastes (LILW) has been implemented in China to protect humans and the environment. A joint onsite and laboratory investigation was conducted for a field site in southern China to assess the probability for safe disposal of LILW, which requires the understanding of long-term radionuclide transport behaviors under field conditions. This study presents the field-scale modeling of radionuclide transport through weathered granites for a conservative, a weakly sorbing and a strongly sorbing tracer by incorporating laboratory and field data. The field-scale radionuclide transport model was developed on the basis of a validated long-term groundwater flow model and field-measured dispersion coefficient, as well as laboratory-characterized strontium and cesium distribution coefficients in the weathered granites. The model was then used to perform the long-term transport prediction and risk assessment of radionuclide pollution for both the natural site setting and the graded site setting. Model simulation reveals that the numerical sensitivities of calculated concentrations are tracer dependent and changing with time. The conservative radionuclide is most sensitive to changes in hydraulic conductivity (K) while slightly sensitive to changes in effective porosity (φ), specific yield (μ) and longitudinal dispersion coefficient (D L), indicating advection is the main transport process of conservative radionuclide. The weakly and strongly sorbing tracers, on the other hand, are most sensitive to changes in the distribution coefficient (K d) and less sensitive to changes in the rest of model parameters, revealing that sorption is the main process for controlling the transport of sorbing tracers. A conservative radionuclide plume moves at an average velocity of about 54 m/a, which is too fast to be considered as safe disposal under the natural site setting. However, the plume of the conservative radionuclide could be slowed down to a velocity around 5.3 m/a due to the reduction of the hydraulic gradient under the graded site setting. Therefore, the conservative radioactive wastes could be disposed at the mid-eastern part of the site under the graded site setting because the transport path has been prolonged and thus no conservative radionuclides could migrate out of the site in a reasonable timeframe. For the sorbing tracers, however, results of the computed transport distance are 40 and 2 m at 500 years, respectively. Therefore, they can be disposed safely at the site under both natural and graded site settings. This study provides an insight to the field-scale long-term behaviors of radionuclide transport. The integrated modeling method presented in this study is most useful for the environmental impact assessment of the site conditions relevant to the safe disposal of hazardous wastes. 相似文献
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开展地下水数值模拟研究是高放废物处置场地安全评价的重要组成部分,然而深地质处置介质类型的复杂性、基岩深部资料的相对匮乏性导致模拟结果存在不确定性,如何刻画深部地下水动力场并评估可能引起的风险已成为高放废物处置安全评价中重点关注的问题。在大量文献调研的基础上,综述了世界典型国家高放废物深地质处置场地的地下水数值模拟与不确定性分析应用,并归纳总结该领域研究经验,得到以下认识:（1）深地质处置场深部构造、裂隙的发育与展布决定了地下水循环条件,探究适用于基岩裂隙地区新的水文地质试验方法是提高地下水数值模型仿真性的基础;（2）不同尺度模型融合是解决深地质处置地下水模拟的有效技术方法,区域尺度多采用等效连续介质法,场地尺度使用等效连续多孔介质和离散裂隙网络耦合模型,处置库尺度使用离散裂隙网络方法,其次需重点关注未来大时间尺度下放射性核素在地质体中的迁移转化规律,模拟预测场址区域地下水环境长期循环演变对核素迁移的潜在影响;（3）考虑到不同的处置层主岩岩性以及在多介质中发生的THMC（温度场—渗流场—应力场—化学场）过程,目前国内外常用的地下水模拟软件有:Porflow、Modflow、GMS及MT3DMS等用于模拟孔隙或等效连续介质,Connectflow、Feflow及FracMan等用于模拟地下水和核素在结晶岩、花岗岩等裂隙中的迁移,TOUGH系列软件主要应用于双重介质的水流、溶质及热运移模拟;（4）指导开展有针对性的模型和参数的不确定性分析工作,减少投入工作量,提高模型精度,并可针对处置库长期演变、废物罐失效、极端降雨等多情景预测模拟,为处置库安全评价及设计提供基础数据支撑;（5）针对我国深地质处置地下水数值模拟研究现状,下一步应加强区域地质、水文地质、裂隙测量以及现场试验等相关的调查及监测工作,多介质耦合、多场耦合模拟及不确定性分析研究将会是未来的研究重点。 相似文献
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K. Geetha Manjari G. L. Sivakumar Babu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(1):60-73
As per the regulatory requirements controlling the disposal of radioactive waste, the performance of waste disposal facilities needs to be assessed quantitatively using predictive models. This estimates the potential impact of disposal on the environment and public health. Near Surface Disposal Facilities (NSDFs), constructed to contain the low level radioactive waste are considered to model the radionuclide migration from the system to the geo-sphere. The radiation dose experienced by an individual through drinking water pathway is the endpoint of assessment of the model. A three dimensional groundwater contaminant transport model with a decaying source is modelled numerically to determine the radiation dose for short-lived and long-lived radionuclides. The consideration of uncertainties constitutes an intrinsic part of modelling. The uncertain input parameters include porosity, longitudinal dispersivity, transverse dispersivity, diffusion coefficient and distribution coefficient. The uncertainty propagation and quantification is carried out using collocation based stochastic response surface method (CSRSM). To run the simulations for the huge set of input, a code is developed using built-in python interface in the numerical model. The results are processed further to obtain the sensitive parameters affecting the output concentrations. Further, the probability of radiation dose exceeding permissible value is estimated by subset simulation. 相似文献
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地下水流数值模型不仅是认识深部水动力场形成演化机制的有效工具,也是建立核素迁移数值模型的基础,因而是高放废物处置场选址和安全评价中重要的技术手段。高放废物深地质处置地下水流数值模拟方法较多,如何选择适当的方法也是值得关注的问题。针对高放废物深地质处置地下水流数值模拟技术展开研究,通过阅读大量国内外文献,文章系统阐述了目前常用的4 类地下水流数值模拟方法的研究进展、适用条件和实例应用;综述了深地质处置中常用的模型不确定性分析方法及研究成果,列表给出了适用于放射性废物地质处置的地下水流数值模拟软件及其在废物处置选择和安全评价中的应用。研究结果表明:等效连续介质模型适用于大区域、长序列、裂隙发育程度较高或较均匀的地区,该类模型方法成熟、所需的数据和参数易于获得,但是不能精确刻画裂隙介质中地下水的流动特征。离散裂隙网络模型适合解决处置场地、储罐尺度等需要精细刻画的地下水流问题,但由于需要大量裂隙及其连通性数据、相关参数等,该方法存在着工作量大、耗时多的缺点。双重介质模型主要用于解决区域尺度裂隙水流问题,但并不能表现出裂隙介质的各向异性、不连续性等特征,因而适用范围存在一定的限制。等效-离散耦合模型可以通过区域分解法对裂隙密度大的区域采用等效连续介质模型,对于裂隙密度较小的地区采用离散裂隙网络模型,从而更符合一般地质条件下裂隙渗流的特征,但也存在交换量难以确定、模型耦合技术问题。通过灵敏度分析,将不同敏感因子对模型敏感指标的影响程度进行排序,提高模型精度、减少参数不确定性分析的工作量。蒙特卡罗法是目前常用的一种模型不确定性方法,原理简单、易于实现。文章展望了数值模型在仿真性、不确定性分析、预测和多介质耦合等方面的研究前景。 相似文献
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The degradation of organic wastes and the corrosion of metallic wastes and steel containers in low and intermediate level radioactive waste (LLW/ILW) repositories are important processes that affect repository geochemistry and the speciation and transport of radionuclides. Gas is generated in association with these degradation processes and this has the potential to overpressure the repository, which can promote transport of groundwater and gas, and consequently radionuclide transport. Microbial activity plays an important role in organic degradation, corrosion and gas generation through the mediation of reduction–oxidation reactions. 相似文献
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Predicting the long-term safety and performance of a repository for intermediate- to high-level radioactive wastes requires the evaluation of various scenarios which may influence the integrity of the repository system. One such scenario, radionuclide transport, is described, and some of the geochemical processes which serve to enhance or retard transport are illustrated with examples selected from natural analogue or natural system studies. These studies, as distinct from laboratory simulations, help considerably in understanding how near- and far-field radionuclide transport mechanisms work over geological timescales (thousands to hundreds of thousands of years), more in line with the anticipated lifespan of a repository.
Processes addressed include: stability of the spent fuel UO2 matrix; bentonite backfill as a barrier to radionuclide diffusion; retention of radionuclides by absorption on fracture minerals; transport and diffusion of radionuclides controlled by interconnected bedrock porosity; geochemical influence and behaviour of repository construction materials on radionuclide transport. 相似文献
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The limitations and feasibility of the land disposal of solid wastes containing organic solvents and refrigerants (chlorinated fluorocarbons) were investigated by evaluating the attenuation capacity of a hypothetical waste-disposal site by numerical modeling. The basic theorem of this approach was that the land disposal of wastes would be environmentally acceptable if subsurface attenuation reduced groundwater concentrations of organic compounds to concentrations that were less than health-based, water-quality criteria. Computer simulations indicated that the predicted concentrations of 13 of 33 organic compounds in groundwater would be less than their health-based criteria. Hence, solid wastes containing these compounds could be safely disposed at the site. The attenuation capacity of the site was insufficient to reduce concentrations of four compounds to safe levels without limiting the amount of mass available to leach into groundwater. Threshold masses based on time-dependent migration simulations were estimated for these compounds. The remaining 16 compounds, which consisted mainly of chlorinated hydrocarbons and fluorocarbons could not be safely landfilled without severe restrictions on the amounts disposed. These organic compounds were candidates to ban from land disposal. 相似文献
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Chen Jiajun Xu Zhaoyi Tian Kaiming
China University of Geostiences Beijing Tian Jiping
Guangzhou University Guangzhou 《中国地质大学学报(英文版)》1991,(1)
Unsaturated radionuclide migration experiments were conducted in a pit inside thetesting hall.Several types of radionuclides were used in the experiments.Tritium wasused as a tracer for water movement in unsaturated loess.Other kinds of radionuclideswere also used in order to obtain fundamental parameters for radionuclide migration sothat further environmental assessment of low—level radioactive waste disposal can be car-ried out.Mechanisms governing unsaturated flow in loess,that is,principles ofone—way lateral flow,are presented qualitatively in this paper.And a continuumone—dimensional model for radionuclide migration testing is developed based on the ex-periments conducted under the particular conditions at the test site.The data measuredfrom the tests were compared with solutions of this one—dimensional model.Resultsshow that this model is feasible for modeling radionuclide migration in unsaturatedloess. 相似文献