共查询到19条相似文献，搜索用时 171 毫秒
1.
放射性核素在地下介质中迁移机理与模型研究 总被引：5，自引：0，他引：5
介绍了铀尾矿库的物理、化学概念模型和其中重金属、放射性核素迁移的一般过程 ;论述了沉淀作用、络合作用和胶体作用对放射性核素迁移的影响 ;重点讨论了描述吸附作用的离子交换模型和表面络合模型的建模机理 ;对定量模拟放射性核素迁移行为的 Kd模型、表面络合模型及“反应 -运移模型”的应用进行了评述。 相似文献
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放射性核素地在下介质中迁移机理与模型研究 总被引：2，自引：0，他引：2
介绍了铀尾矿库的物理、化学概念模型和其中重金属、放射性核素迁移的一般过程;论述了沉淀作用、络合作用和胶体作用对放射性核素迁移的影响;重点讨论了描述吸附作用的离交换模型和表面络合模型的建模机理;对定量模拟放射性核素迁移行为的Ｋｄ模型、表面络合模型及“反应－运移模型”的应用进行了评述。 相似文献
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铀水冶尾矿库地下水流特征与模拟分析：以某矿为例 总被引：4，自引：1，他引：3
张金辉 《水文地质工程地质》1998,25(2):38-41
铀水冶尾矿库中地下水流动特征控制了核素向周围环境扩散与迁移。本文以某矿山谷型尾矿库为例,运用二维有限元模拟了库内地下水分布及流动,结合水文地质条件进行了分析与讨论。 相似文献
4.
《矿物岩石地球化学通报》2020,(2)
缓冲材料作为高放废物处置库中多重屏障体系的最后一道人工屏障,其对放射性核素的阻滞性能将直接影响放射性核素随地下水进入天然地质屏障后重返生物圈的能力,进而影响到处置库的长期稳定性和安全性。用具有低渗透性和良好膨胀自愈性的膨润土作为集成缓冲材料的基材,以凹凸棒石为辅料,用黄铁矿为添加剂,三者按质量比为63∶27∶10均匀混合构成集成缓冲材料B_7AP,采用恒定源扩散实验分析了铀在干密度为1.70 g/cm~3试样中的扩散特性。结果表明,B_7AP缓冲材料对铀具有良好的阻滞性能,其表观扩散系数为4.07×10~(-12) m~2/s。同时,根据多孔介质污染物迁移理论,建立了铀在B_7AP中迁移的对流-弥散-吸附简化方程,并用Matlab软件模拟分析了不同时间尺度、渗流速度、表观扩散系数和阻滞因子条件下,铀在B_7AP中的迁移距离,为提高放废物处置库料缓冲材料阻滞性能、筛选及优化缓冲材料配方设计提供了科学依据。 相似文献
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放射性核素在不同介质中的迁移研究进展 总被引：1，自引：4，他引：1
从受关注的放射性核素、不同介质及实验模拟等方面,对当前放射性核素在不同介质中的迁移研究进展进行了较为全面的分析总结。提出了今后放射性核素迁移的重点研究方向:①核素在多介质之间的迁移研究;②核素在三维空间的迁移模式研究;③核素在非均匀介质中的迁移规律研究,特别是对其滞留机制的研究。 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
8.
在对我国南方某大型尾矿库库区水文地质条件概化的基础上 ,运用国际最新版本的三维地下水流动与污染物运移的模拟软件VisualMODFLOW建立了研究区U(Ⅵ )在浅层地下水系统中迁移的反应 -输运耦合模型 ,讨论了不同条件下U(Ⅵ )在地下水中的迁移情况 .模拟结果指示 ,在不治理的条件下 ,U(Ⅵ )对库区地下水污染严重 ;而在尾矿库治理条件下 ,由于地下水系统的自净作用 ,对于尾矿库在运营期间下渗的U(Ⅵ ) ,地下水系统完全可以“消化” . 相似文献
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根据高放废物地质处置库概念设计,以北山花岗岩为参考岩性,内蒙古高庙子膨润土为参考缓冲材料,使用数值模拟软件tough2对放射性核素135Cs在处置单元及其围岩中的迁移行为进行了数值模拟研究,考虑放射性核素衰变释热对核素迁移的影响。研究表明:膨润土对核素具有较强的滞留作用,模拟200000年后核素在花岗岩中迁移了1 m左右,且峰值为10-6个数量级;前10 a模型的温度变化最剧烈且温差最大,10 a后模型整体温度开始降低,2 000 a后整体温度接近于初始温度;温度的变化会引起核素迁移速率的改变,但总体温度对核素迁移的影响不大。 相似文献
11.
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
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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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双重介质中核素迁移模型的解析解及其应用 总被引：2，自引：0，他引：2
给出了具有单裂隙的双重介质中，裂隙一端有分时注入源情形下的迁移模型的解析解及一些简化条件下的解析解，并利用解析解研究了核素在双重介质中的迁移问题。 相似文献
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《Applied Geochemistry》1991,6(5):565-574
Natural colloids (1–450 nm) and suspended particles (>450 nm) were characterized in groundwaters of the Whiteshell Research Area of southern Manitoba to evaluate their potential role in radionuclide transport through fractured granite. Data on particle concentrations, size distributions, compositions and natural radionuclide content were collected to predict radionuclide formation and to provide a database for future colloid migration studies. The concentrations of colloids between 10 and 450 nm ranged between 0.04 and 1 mg/l. The concentrations of suspended particles, which require higher groundwater velocities for transport, varied from 0.04 to 14 mg/l. Colloid (10–450 nm) concentrations as low as these observed in Whiteshell Research Area groundwater would have a minimal effect on radionuclide transport, assuming that radionuclide sorption on colloids is reversible. If radiocolloid formation is not reversible, and radionuclide-containing colloids cannot sorb onto fracture walls, the importance of natural colloids in radionuclide transport will depend upon particle migration properties. 相似文献
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《Applied Geochemistry》1993,8(6):605-616
The Cigar Lake U deposit is located in northern Saskatchewan in the eastern part of the Athabasca Sandstone Basin, and consists of a high-grade ore body (up to 55% U) located at a depth of ∼430 m. As part of a study to evaluate the analog features of this deposit with respect to a disposal vault for waste nuclear fuel, colloids (1–450 nm) and suspended particles (450nm) in groundwater have been investigated to evaluate their effect on element transport through the U deposit. Tangential-flow ultrafiltration was used to concentrate particles from 501 groundwater samples in order to characterize the size distribution, concentration, composition and natural radionuclide content of particles in representative parts of the U deposit. Although Cigar Lake groundwaters contain particles in all sizes ranging from 10 nm to slightly larger than 20 μm, most samples contained a relatively high concentration of colloids in the 100–400 nm size range. Particle compositions are similar to the composition of minerals in the sandstones and ore body, suggesting that particles in groundwater are generated by the erosion of fracture-lining minerals. As a result, particle concentrations in groundwater are affected by the integrity of the host rock. In some piezometers the high initial concentrations of suspended particles, which may have been drilling artifacts, decreased during the collection of the first 350 1. Although colloid concentrations fluctuated during sampling, there are no indications that these concentrations will be permanently reduced by continued groundwater pumping. The observed colloid and suspended particle concentrations in the deep groundwaters are too low to have a significant impact on radionuclide migration, provided that radionuclide sorption is reversible. If radionuclides are irreversibly sorbed to particles they cannot sorb to the host rock and their migration can only be evaluated with an understanding of particle mobility. The data for dissolved and particulate U, Th and Ra were used to calculate field-derived distribution ratios (Rd) between particles and groundwater. The wide range of observed Rd values indicates that these radionuclides in particulate form are not in equilibrium with groundwater. U-series isotope data indicated that most of the U and Ra on particles was derived from groundwater. Some particles could have retained their U for as long as 8000 a. The U and Ra contents of particles in the ore and surrounding clay zones are significantly higher than in particles from sandstone, suggesting that the clay has been an effective barrier to particle migration. 相似文献
17.
V. I. Malkovsky V. I. Velichkin Yu. E. Gorlinsky E. I. Vladimirova 《Geology of Ore Deposits》2009,51(4):275-289
The convective transfer of 137Cs and 90Sr by groundwater on the territory of the Russian Research Centre Kurchatov Institute (RRCKI) was modeled. Geological data
on the RRCKI site and possible sources of radionuclides show that the uppermost aquifer, composed of Quaternary sediments,
is the most probable region of spreading of radioactive contamination. Since the lateral migration of radionuclides is predominant,
a 2D horizontal model was used for the forecasting of spreading of radioactive contaminants in the subsurface medium. Transient
or long-term repositories of radioactive materials at the RRCKI site (concentrated sources) and aquifer rocks contaminated
in the course of removal of radionuclides from these repositories (distributed source) are responsible for groundwater pollution.
The initial 137Cs and 90Sr distributions used in the forecasting of radionuclide migration were determined from their contents in core samples taken
from wells drilled in contaminated areas of the RRCKI site. The zone of radionuclide migration is limited by poorly permeable
moraine loam from below and by the water table from above. To determine the upper and lower boundaries, these surfaces were
mapped in plan view. The data of meteorological observations over a long period were used to map the intensity of precipitation
in the studied territory. The density of rocks in the uppermost aquifer and partition coefficients of radionuclides between
rocks and groundwater were estimated from the data of laboratory examination of the core samples. The available data on the
permeability of rock samples and the results of test pumping out of some wells were involved in the consideration. The results
obtained and the data on the water table allowed us to define a gauge problem for determining the distribution of the filtration
coefficient in the uppermost aquifer. This problem was solved taking the intensity of precipitation into account. The properties
of the uppermost aquifer and the initial radionuclide distribution therein were used as initial data for modeling 137Cs and 90Sr migration on the territory of the RRCKI over 50 years. 相似文献
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S. R. Joshi 《Environmental Geology》1989,14(3):203-207
Four possible sources of analytical error in the measurement of unsupported210Pb and/or nuclear fallout radionuclide (such as137Cs) profiles in sediment cores are pointed out. Each of these errors, if present, can significantly alter the true profile of the radionuclide under consideration. It is shown that simple procedural modifications can substantially improve the quality of analytical data that are subsequently used to develop intricate mathematical models to aid the interpretation of observed radionuclide profiles. 相似文献