MapGIS在东天山高放废物地质处置库选址中的应用

根据高放废物选址的要求,利用MapGIS对东天山地区不同时代岩体的空间位置、分布形态、出露面积,以及岩体与断裂构造、地震和矿床点等的空间关系进行了研究,对海量资料信息进行分析处理,可起到事倍功半的效果。利用MapGIS分析结果,初步筛选出阿奇山1号岩体、雅满苏北岩体作为高放废物地质处置库选址的有利岩体。     

我国高放废物地质处置库场址筛选总体技术思路探讨

综合对比瑞典、加拿大、芬兰和美国等国高放废物地质处置库场址筛选技术思路,分析国外高放废物地质处置库场址筛选过程中取得的经验、教训,总结了我国处置库选址工作取得的成果和存在的问题。在综合研究基础上,分析提出我国高放废物地质处置库场址筛选总体技术思路,包括应遵循的原则、工作范围、目标和总体技术步骤等,以利于今后处置库选址工作更系统、规范和统一。     

热液体系溶解度实验和热力学计算方法在成矿过程模拟中的应用

热液流体对金属元素的迁移、富集及沉淀成矿起着关键作用,定量刻画金属元素在热液成矿过程中的运移是矿床学研究的重点和难点。以热力学理论为基础,通过开展溶解度实验,揭示金属元素在热液流体中的地球化学行为,是研究金属元素迁移、富集沉淀机制行之有效的重要手段。其中,基于钛合金反应釜开展不同物理化学条件下金属元素在热液流体中的溶解度实验,结合相关的热力学模拟,能够精确测定金属元素在热液流体中的溶解度、络合物配位数、气液两相中的分配系数及相关热力学参数,为定量模拟热液成矿过程提供重要的实验依据。文章归纳了近年来针对热液体系的实验矿床学方法,分析了各类实验方法与分析手段的优点与不足。重点介绍钛合金反应釜溶解度实验和热力学模拟计算方法,并结合该方法模拟钪矿床成矿的水岩反应过程,说明该方法在成矿过程模拟中的应用,最后阐述了其存在的问题,并对该领域未来的研究趋势提出了展望,以期推动该方法在战略性关键金属超常富集机制研究中的应用。     

The influence of an excavation damaged zone on the thermal-mechanical and hydro-mechanical behaviors of an underground excavation

In Korea, a reference disposal system, KRS, was proposed in 2006 after 10 years of research and development. In the KRS, the high-level radioactive waste repository is considered to be located in a crystalline rock likes granite. For a validation of the feasibility, safety, and stability of the KRS, an underground research tunnel, KURT was constructed in Nov. 2006. During the construction of KURT by a controlled blasting, the size and characteristics of an excavation damaged zone(EDZ) were investigated by in situ as well as laboratory tests. The possible influences of an EDZ around a tunnel on the thermal, hydraulic and mechanical behaviors of the near field were investigated by using hydro-mechanical and thermo-mechanical coupling analyses. From this study, it was found that the existence of an EDZ can influence the thermal, hydraulic, and mechanical behaviors of the near field and it was recommended that an EDZ should be considered as an important parameter during the design of underground repositories.     

新疆地区选建高放射性核废物处置库的可能性

高放废物选址是一项万年大计工程,需要多个预选场地的综合比较,决策废物处置库的具体选建场地。论述了高放废物处置库选址过程中需要考虑的主要问题,然后针对新疆的自然环境,水资源、花岗岩体和缓冲/回填材料的分布,以及区域地壳稳定性等因素,讨论了在新疆选建高放废物地质处置库的可能性,并提出了选址方法。     

新疆地区选建高放射性核废物处置库的可能性

高放废物选址是一项万年大计工程,需要多个预选场地的综合比较,决策废物处置库的具体选建场地。论述了高放废物处置库选址过程中需要考虑的主要问题,然后针对新疆的自然环境,水资源、花岗岩体和缓冲/回填材料的分布,以及区域地壳稳定性等因素,讨论了在新疆选建高放废物地质处置库的可能性,并提出了选址方法。     

Reactive transport modelling of the long-term interactions of corrosion products and compacted bentonite in a HLW repository in granite: Uncertainties and relevance for performance assessment

Here we present a long-term nonisothermal reactive transport model for the interactions of the corrosion products of a carbon-steel canister and the compacted bentonite of the engineered barrier of a high-level radioactive waste repository in granite. Canister corrosion causes an increase in the pH and the concentration of dissolved Fe²⁺ of the bentonite porewater. Iron precipitates as magnetite and siderite and sorbs via cation exchange and surface complexation on weak sites. Magnetite precipitation reduces significantly the porosity of the bentonite near the canister. The thickness of the zone of reduced porosity is 7 cm at t = 1 Ma. This thickness increases significantly when the dependence of the corrosion rate on the chemical conditions is considered and decreases 3 cm when smectite dissolution and analcime precipitation are taken into account. Model results are not significantly sensitive to the thermal transient and the effect of temperature on the corrosion rate. The conclusions of our simulations are consistent for the most part with those reported by others for engineered barrier systems at similar chemical conditions.     

Simulation of groundwater and nuclide transport in the near-field of the high-level radioactive waste repository with TOUGHREACT

In order to know the mechanism of groundwater transport and the variation of ion concentrations in the near-field of the high-level radioactive waste repository, the whole process was simulated by EOS3 module of TOUGHREACT. Generally, the pH and cation concentrations vary obviously in the near-field saturated zone due to interaction between groundwater and bentonite. Moreover, the simulated results showed that calcite precipitation could not cause obvious variations in the porosity of media in the near-filed if the chemical components and their concentrations of groundwater and bentonite pore water are similar to those used in this study.     

高放废物地质处置新场岩体三维地质模型构建与应用

我国高放废物地质处置经过30多年研究,已初步确定新场为地下实验室推荐场址。开展新场岩体三维地质建模研究,一方面能够充分利用已有资料准确地表达各种地质现象,直观再现地质单元的空间展布及其相互关系;另一方面可以挖掘隐含的地质信息,方便地质分析和工程决策,这在地下实验室研究阶段非常重要。在对新场已有资料综合分析和解译的基础上,建立了岩体的三维地质模型,直观地再现了新场岩体地质环境特征;并基于地质建模结果,开展了钻孔设计等工程应用,取得了较好的效果。本研究可为我国高放废物地质处置后续工作中地质分析与工程设计提供有益参考和技术支持。     

我国固体废物处理处置现状及对策

在分析我国固体废物产生及处理处置现状的基础上,阐述了固体废物处理处置的基本原则,提出了适合我国国情的综合治理措施。     

核废物地质处置中热-水-应力耦合对迁移影响的三维有限元模拟

将所建立的热-水-应力-迁移耦合模型及开发的有限元程序,由二维分析拓展到三维分析,并从方法论研究的角度,以一个简单的核废物地质处置模型为算例,进行热-水-应力-迁移耦合过程的三维数值模拟,考察了近场的温度、饱和度、核素浓度、孔隙水压力、位移、正应力、流速等的分布与变化,认为计算结果符合规律,得出了若干结论：为了精确地模拟放射性核素迁移,就必须将温度场、渗流场、应力场和核素浓度场进行耦合分析;核废物埋存若干年后将在处置孔壁附近产生较高的压应力;缓冲层内各点的核素浓度达到相对稳定的时间要比温度和饱和度达到相对稳定的时间长得多。     

Analysis of the hydration of a bentonite seal in a deep radioactive waste repository

A deep geological repository for nuclear waste requires the backfilling and sealing of shafts and galleries to block any preferential path for radioactive contaminants. The paper presents the coupled hydromechanical analyses of an in situ test carried out in the HADES underground laboratory in Mol, Belgium. The test examines the effectiveness of an expansive clay seal in a horizontal borehole specifically drilled for this purpose. The analysis covers the phase of seal hydration up to saturation and subsequent pore pressure equilibration. Hydraulic and mechanical constitutive laws suited to expansive clay materials have been chosen for the analyses with all the parameters determined independently of the in situ test. A quite good agreement has been found between test observations and computed results suggesting that the numerical formulation employed is able to reproduce the main features of a real sealing system.     

西北某放射性废物处置预选区地下水水化学特征及地球化学模拟

在放射性废物处置库的选址过程中,地下水水化学特征是最重要的因素之一。为了查明西北某放射性废物处置预选区地下水水化学特征及其演化机制,对该区地下水水样进行了水质测试,综合运用Piper三线图法、相关性分析、饱和指数模拟和质量平衡反应模拟,全面分析了该预选区地下水水化学类型的空间分布和地下水水演化的主要水文化学过程。结果表明:研究区地下水在北部山区接受补给,并向南运移,地下水类型随径流由SO4.Cl—Na型转变为Cl.SO4—Na型。地下水在径流过程中主要经历了溶滤作用、蒸发浓缩作用和阳离子交换作用等水文化学过程,它们是控制该区地下水水化学组分演化的关键。     

高放处置罐铁释放诱发膨润土矿物相变研究进展

作为高放废物处置罐候选金属材料,低碳钢在处置库服役期间,其腐蚀产物侵入缓冲屏障,导致缓冲材料矿物相变与性能变异,威胁多重屏障体系的长期安全稳定。本文详细综述了国内外处置库深部还原环境所处的弱碱性化学场与中低温度场的变化趋势,认为处置库深部化学-温度还原条件可导致处置罐Fe腐蚀释放Fe~(2+)。在处置库长期运行过程中,蒙脱石与Fe~(2+)接触发生矿物相变,一方面Fe~(2+)置换蒙脱石八面体晶格中的Al~(3+)和Mg~(2+),还原Fe~(3+)或直接占据空位,生成次生矿物;另一方面Fe~(2+)交换蒙脱石层间的Na~+、K~+和Ca~(2+),转化为铁基蒙脱石。矿物相变可诱发缓冲屏障性能变异甚至退化。基于"抗矿物转化"理念,提出了下一阶段缓冲材料矿物相变研究方向,为地下实验室碳素钢选型、缓冲屏障验证试验设计以及屏障体系安全评价提供科学依据。     

孔隙气压对核废物地质处置热-流-固耦合影响的有限元分析

为考察孔隙气体压力对高放废物地质处置中的热-流-固耦合过程的影响,借用Leiws等建立的可变形孔隙介质中非等温空气流和水流模型,在其水连续性方程中加入了温度梯度引起的水分扩散项,研制出相应的热-水-气-应力耦合弹塑性二维有限元程序。针对一个假定的高放废物地质处置库模型,在相同的初始温度、孔隙水压力和岩体应力条件下,取3种缓冲层中的初始孔隙气体压力,通过数值模拟考察了处置库近场的主应力、饱和度、气和水的流速、温度和孔隙压力的分布与变化。结果显示,当缓冲层中的初始孔隙气压力较高时,其对围岩中应力影响较大。     

Retardation capacity of altered granitic rock distributed along fractured and faulted zones in the orogenic belt of Japan

There are wide areas of granitic rocks in the Japanese orogenic belt. These granitic bodies inevitably contain fracture and fault systems associated with alteration zones. However, relatively little attention has been given to the possible influence of such widely distributed alteration zones on the migration of radionuclides from any radioactive waste repository that might in future be sited within granitic rock. In particular, the influences of alteration products and micro-fractures, due to chemical sorption and/or physical retardation require further consideration. In order to understand the retardation capacity of the altered deep granitic rocks, detailed geometrical characterization of pores, geochemical analysis, and batch sorption and flow-through experiments have been carried out. Those results show that the altered granite has a large volume of accessible pores, particularly in potassium-feldspar grains, which would influence nuclide retardation more than the accessible porosity in other minerals present, such as biotite. The distribution coefficients, Kd estimated from batch sorption tests and flow-through experiments suggest that altered granite has a high capability to retard the migration of nuclides. The retardation would probably be due to sorption on altered minerals such as sericite and iron hydroxides formed along grain boundaries and in pores created by dissolution, in addition to sorption on primary sorptive minerals. These results provide confidence that even altered and fractured parts of any granitic rock that might be encountered in a site for the disposal of high level radioactive waste may still retard radionuclide migration and thereby help the geosphere to function as a barrier.     

Stochastic analysis of the effect of heterogeneity and fractures on radionuclide transport in a low-permeability clay layer

Deep low-permeability clay layers are considered as safe environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is a candidate host rock for deep geological disposal. In this study, we analyze the effects of fractures and spatially variable hydraulic conductivity on radionuclide migration through the clay. Fracture geometry and properties are simulated with Monte Carlo simulation. The heterogeneity of hydraulic conductivity is simulated by direct sequential co-simulation using measurements of hydraulic conductivity and four types of secondary variables. The hydraulic conductivity and fracture simulations are used as input for a transport model. Radionuclide fluxes computed with this heterogeneous model are compared with fluxes obtained with a homogeneous model. The output fluxes of the heterogeneous model differ at most 8% from the homogeneous model. The main safety function of the Boom Clay is thus not affected by the fractures and the spatial variability of hydraulic conductivity.     

Stochastic analysis of the effect of spatial variability of diffusion parameters on radionuclide transport in a low permeability clay layer

Most studies that incorporate subsurface heterogeneity in groundwater flow and transport models only analyze and simulate the spatial variability of hydraulic conductivity. Heterogeneity of the other flow and transport parameters are usually neglected. This approach is often justified, but there are, however, cases in which disregarding the heterogeneity of the other flow and transport parameters can be questionable. In low permeability media, for instance, diffusion is often the dominant transport mechanism. It therefore seems logical to incorporate the spatial variability of the diffusion parameters in the transport model. This study therefore analyses and simulates the spatial variability of the effective diffusion coefficient and the diffusion accessible porosity with geostatistical techniques and incorporates their heterogeneity in the transport model of a low permeability formation. The formation studied was Boom clay (Belgium), a candidate host rock for the deep geological disposal of high-level radioactive waste. The calculated output radionuclide fluxes of this model are compared with the fluxes calculated with a homogeneous model and a model with a heterogeneous hydraulic conductivity distribution. This analysis shows that the heterogeneity of the diffusion parameters has a much larger effect on the calculated output radionuclide fluxes than the heterogeneity of hydraulic conductivity in the low permeability medium under study.     

Arsenic content and groundwater geochemistry of the San Antonio-El Triunfo, Carrizal and Los Planes aquifers in southernmost Baja California, Mexico

 The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California, has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin) aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As). Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the Carrizal and Los Planes aquifers. Received: 4 May 1999 · Accepted: 22 February 2000