Study on the residence time of deep groundwater for high-level radioactive waste geological disposal

Residence time of deep groundwater is one of the most important parameters in safety and performance assessment for high-level radioactive waste geological disposal. In this study, we collected the deep groundwater samples of Jijicao in Gansu Beishan pre-selected region. The deep groundwater residence time at two depths estimated by Helium-4 accumulation method were 3.8 ka and 5.0 ka respectively upon measurement and calculation, which indicates that the deep groundwater is not derived from the deep crust circulation process. Hence, deep groundwater is featured with long residence time as well as slow circulation and update rate, and such features are conductive to the safe disposal of high-level radioactive waste.     

高放废物深地质处置地下水数值模拟应用综述

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。     

我国高放废物深地质处置战略规划探讨

本文探讨我国高放废物地质处置的战略规划，提出我国高放废物处置库的开发可参考采用“三步曲”式的技术路线，即处置库选址和场址评价一特定场址地下实验室研究一处置库建设。处置库的选址和场址评价工作可与地下实验室研究的相关工作结合。以2040年前后建成处置库为目标，把工作划分为4个阶段，即选址和场址评价阶段、场址确认和地下实验室建设阶段、现场实验和示范处置阶段及处置库建设阶段，规划出各阶段的工作目标和工作内容。论证各项工作内容之间的逻辑关系，指出选址和场址评价是基础、基础研究和地下实验室研究是支撑、性能评价是“指挥棒”、设计并建造出符合标准的处置库是目标。将选址工作划分为预选地段对比、预选场址对比和场址确认3个阶段。按此规划设想，我国将在2015年以前确定处置库和地下实验室的场址，并开始建造地下实验室。2025年左右建成地下实验室，2040年建成处置库。     

高放废物深地质处置地下水流数值模拟方法研究进展

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。     

Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste

The interaction of groundwater with cement in a geological disposal facility (GDF) for intermediate level radioactive waste will produce a high pH leachate plume. Such a plume may alter the physical and chemical properties of the GDF host rock. However, the geochemical and mineralogical processes which may occur in such systems over timescales relevant for geological disposal remain unclear. This study has extended the timescale for laboratory experiments and shown that, after 15 years two distinct phases of reaction may occur during alteration of a dolomite-rich rock at high pH. In these experiments the dissolution of primary silicate minerals and the formation of secondary calcium silicate hydrate (C–S–H) phases containing varying amounts of aluminium and potassium (C–(A)–(K)–S–H) during the early stages of reaction (up to 15 months) have been superseded as the systems have evolved. After 15 years significant dedolomitisation (MgCa(CO₃)₂ + 2OH⁻ → Mg(OH)₂ + CaCO₃ + CO₃²⁻_(aq)) has led to the formation of magnesium silicates, such as saponite and talc, containing variable amounts of aluminium and potassium (Mg–(Al)–(K)–silicates), and calcite at the expense of the early-formed C–(A)–(K)–S–H phases. This occured in high pH solutions representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a KOH and NaOH or a Ca(OH)₂ dominated solution but a greater extent of alteration in the higher pH KOH/NaOH leachate. The high pH alteration of the rock over 15 years also increased the rock’s sorption capacity for U(VI). The results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite-rich rock in the geosphere. These processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geological disposal.     

Minimal alteration of montmorillonite following long-term interaction with natural alkaline groundwater: Implications for geological disposal of radioactive waste

Bentonite is one of the more safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. Bentonite is utilised because of its favourable properties which include plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides and stability in geological environments of relevance to waste disposal. However, bentonite is unstable under the highly alkaline conditions induced by Ordinary Portland Cement (OPC: initial porewater pH > 13) and this has driven interest in using low alkali cements (initial porewater pH9-11) as an alternative to OPC. To build a robust safety case for a repository for radioactive wastes, it is important to have supporting natural analogue data to confirm understanding of the likely long-term performance of bentonite in these lower alkali conditions. In Cyprus, the presence of natural bentonite in association with natural alkaline groundwater permits the zones of potential bentonite/alkaline water reaction to be studied as an analogy of the potential reaction between low alkali cement leachates and the bentonite buffer in the repository. Here, the results indicate that a cation diffusion front has moved some metres into the bentonite whereas the bentonite reaction front is restricted to a few millimetres into the clay. This reaction front shows minimal reaction of the bentonite (volumetrically, less than 1% of the bentonite), with production of a palygorskite secondary phase following reaction of the primary smectites over time periods of 10⁵–10⁶ years.     

Hydrogeology of a fractured shale (Opalinus Clay): Implications for deep geological disposal of radioactive wastes

As part of the Swiss programme for high-level radioactive-waste disposal, a Jurassic shale (Opalinus Clay) is being investigated as a potential host rock. Observations in clay pits and the results of a German research programme focusing on hazardous waste disposal have demonstrated that, at depths of 10–30 m, the permeability of the Opalinus Clay decreases by several orders of magnitude. Hydraulic tests in deeper boreholes (test intervals below 300 m) yielded hydraulic conductivities <10^–12 m/s, even though joints and faults were included in some of the test intervals. These measurements are consistent with hydrogeological data from Opalinus Clay sections in ten tunnels in the Folded Jura of northern Switzerland. Despite extensive faulting, only a few indications of minor water inflow were encountered in more than 6,600 m of tunnel. All inflows were in tunnel sections where the overburden is less than 200 m. The hydraulic data are consistent with clay pore-water hydrochemical and isotopic data. The extensive hydrogeological data base – part of which derives from particularly unfavourable geological environments – provides arguments that advective transport through faults and joints is not a critical issue for the suitability of Opalinus Clay as a host rock for deep geological waste disposal. Electronic Publication     

深部地质钻探钻孔结构设计与施工分析

根据长期深部钻探施工经验,分析了深部地质钻探钻孔结构设计的主要依据和原则,通过典型深孔钻孔结构设计与实施的案例,总结了几种钻孔结构实施程序：（1）在地质预测与实际相差不大的熟悉工区,根据经验有针对性地选择钻孔结构进行施工的按设计施工法;（2）在不能预测下部地层复杂情况的条件下,采用探索、扩孔并根据实际调整钻孔结构的探索施工法;（3）利用大口径尽可能向下钻进的充分施工法等。通过实际案例分析,为深孔、超深孔钻探钻孔结构设计与施工提供一定的经验参考。     

Approaches to stress monitoring in deep boreholes for future CCS projects

There is no monitoring technology available to observe possible changes of stress in the rock mass of a CO₂ reservoir or its cap rock formations. Any development of a stress-monitoring technique must be related to the natural regional stress conditions and must be adjusted to the possibly changing in situ stress conditions due to CCS activity. As a step towards an in situ stress-monitoring probe, a lab scale device was developed and used for investigations on the practicability of a hard-inclusion tool for stress monitoring. In situ stress conditions, as deduced from the Altmark Gas Field, were applied to evaluate the efficiency and the limits of this stress-monitoring technique. At lab-scale the applied stresses resp. stress differences with moderate amounts of 9?C15?% of the vertical stress component Sv coincide sufficiently with the resulting strain answers of the hard inclusion tool (i.e., a steel tube corresponding to the liner in the borehole). Therefore, it was possible to re-calculate the stresses and to compare them with the applied ones. The resulting coincidence, however, can be disturbed at high pressure levels due to rock failure around the borehole with extended deformations. In addition, the results are influenced by the mechanical behaviour of the surrounding rock mass type. Nevertheless, a further development of a hard inclusion probe for monitoring of stress changes in deep boreholes can be successful and may be the only possible way to detect stress changes without fracturing damages in deep boreholes.     

有关深部地质填图和立体地质填图的几个问题

大多数20世纪下半叶建立的矿山,资源已近枯竭或出现了资源危机,都需要寻找接续资源。为此提出在成矿远景好的地区有计划地开展“深部地质填图”和“立体地质填图”的设想。“深部地质填图”是找寻隐伏矿和半隐伏矿的深部地质研究的战略性工作,“立体地质填图”则是其战术性工作。两者既有联系又有区别。前者是为了寻找隐伏矿、半隐伏矿的“靶区”,或为“靶区”提供背景地质资料;后者是为了找到“新矿体”、“新矿层”,扩大矿床规模和矿山远景。“深部地质填图”要采用地质、物探、化探及少量钻探等综合手段,提交比例尺不小于1∶5万的地表地质图和深部地质图;“立体地质填图”主要是按一定间距(100～200m)进行钻探,结合物探剖面,发现新矿体,提交立体地质图。当前应全面开展资源危机矿山外围的“深部地质填图”,积极慎重地进行“立体地质填图”试点,并将此项工作作为一项独立的地质工作纳入地质调查之中。     

赣东北景德镇四村矿化蚀变带成矿地质条件及找矿潜力

四村矿化蚀变带是在塔前—赋春矿集区新发现的1处铜多金属矿化蚀变带, 通过与朱溪钨铜多金属矿床进行地质、矿化蚀变、地球物理-地球化学-遥感异常等对比, 认为二者的成矿地质条件相似.根据四村地区浅表闪长玢岩、煌斑岩和辉长辉绿岩脉地质特征, 推测其深部可能存在花岗质岩体.结合晚古生代碳酸盐岩、断裂破碎带和层间破碎带地质特征, 推测花岗质岩浆上侵并与碳酸盐岩接触交代, 可形成矽卡岩型矿床或热液脉型矿床, 具有较好的找矿潜力.下一步找矿重点为侵入岩与碳酸盐岩接触带、断裂带和层间破碎带.     

废物处置场地地质屏障的环境安全评价

当前由于科技进步,经济快速发展,也需要对环境质量提出更高的要求,要求各种环境处理、处置工程能达到永久安全,一劳永逸的保护环境的效果。这种效果的实现唯一的要靠地质屏障发挥的效应,因此笔者就地质屏障的基本作用,对地质屏障的安全评价,如何利用地质屏障解决环境问题等,利用大量的实验数据和实践经验进行详细论证。提出中国具有各种各样有利的地质条件和许多可利用的优良地质屏障,依靠地质科学的基本理论来解决环境问题,促使环境状态和生态环境逐渐向良好方向发展。     

基于数字地球平台的地质钻孔三维模拟与可视化

研究了地质钻孔信息的管理和可视化技术,提出了一种在数字地球平台中进行城市钻孔信息模拟和可视化的方法。该方法基于一个统一的钻孔数据库标准,首先将钻探点位信息和地层分层信息组织成具有不同细节层次的钻探点位模型、钻孔分层散点模型和钻孔管段模型,然后构建基于细节层次模型的海量钻孔信息多尺度表达机制,最后将这些模型加载到数字地球平台中进行可视化及查询、分析。在上海市的应用实例显示,该方法实现过程简单、自动性高,生成的模型易于在国际互联网上进行分发、集成与共享。该方法的应用将有助于地质工作者向其他科技人员以及社会公众展示、分发自己拥有的钻孔信息,为以钻孔数据为代表的城市地质信息的社会化服务奠定基础。     

有关深部地质填图和立体地质填图的几个问题

大多数20世纪下半叶建立的矿山,资源已近枯竭或出现了资源危机,都需要寻找接续资源。为此提出在成矿远景好的地区有计划地开展“深部地质填图”和“立体地质填图”的设想。“深部地质填图”是找寻隐伏矿和半隐伏矿的深部地质研究的战略性工作,“立体地质填图”则是其战术性工作。两者既有联系又有区别。前者是为了寻找隐伏矿、半隐伏矿的“靶区”,或为“靶区”提供背景地质资料;后者是为了找到“新矿体”、“新矿层”,扩大矿床规模和矿山远景。“深部地质填图”要采用地质、物探、化探及少量钻探等综合手段,提交比例尺不小于1：5万的地表地质图和深部地质图;“立体地质填图”主要是按一定间距(100～200m)进行钻探,结合物探剖面,发现新矿体,提交立体地质图。当前应全面开展资源危机矿山外围的“深部地质填图”,积极慎重地进行“立体地质填图”试点,并将此项工作作为一项独立的地质工作纳入地质调查之中。     

高放废物地质处置元数据设计与编辑模块开发

在对元数据的含义、作用、组成及对高放领域研究的数据内容和特点分析的基础上,对元数据编辑模块的设计进行了详细描述,并在VS2005平台下应用C#语言进行了模块的实际开发,最终实现了便于进行数据共享的XML格式存储功能。元数据编辑模块的应用将促进我国高放废物地质处置信息化工作的进一步深入。     

煤田地质勘探钻孔瓦斯突出危险性评价

基于灰色关联分析法和模糊综合评判理论,综合考虑煤体结构、瓦斯压力和含量、地质构造、煤层埋深以及煤厚等因素,利用勘探钻孔所测瓦斯资料,建立了勘探钻孔煤层瓦斯突出危险性评价模型,并以重庆松藻矿区为例,对矿区勘探钻孔附近煤层瓦斯突出危险性进行了评价。结果表明：模型评判结果与矿井实际生产揭露情况一致,评判结果可靠。该模型避免了以往勘探阶段仅利用单项指标或简单综合指标进行突出危险评价的不足,使评价指标更全面,评判结果更可靠。     

世界各国高放废物地质处置最新进展

核废物的安全处理处置问题一直是困扰核工业全面发展的关键因素，而其中高放废物的处置尤为突出。对于高放废物的处置问题，目前国际上主要倾向采用深地质埋藏的方法，本文根据最新资料（截止２０００年１０月）介绍世界上各主要有核国家在此方面的研究进展。目前已经有３个候选高放废物处置库：芬兰的Ｏｌｋｉｌｕｔｏ、美国的ＹｕｃｃａＭｏｕｎｔａｉｎ与德国的Ｇｏｒｌｅｂｅｎ，但德国的Ｇｏｒｌｅｂｅｎ由于政治方面的原因从而存在问题［１］。俄罗斯：俄罗斯正在进行高放废物深地质处置库的选址工作，目前正在进行大规模的场址调查工…     

The hydrogeology of granitic rocks in deep boreholes used for compressed air storage

The compressed air energy storage(CAES) is a much-awaited new system for load leveling power supply. An economical system must be developed, preventing leakage of stored air (with pressures of more than 20 atm) using groundwater pressure surrounding an unlined cavern in hard rock. The air tightness of the rock around the cavern must be confirmed. In this study, the hydrogeology of the test site was examined prior to field air tightness tests in the borehole. The results indicate that, when evaluating the hydrogeology of the test site related to the air tightness of rocks, it is necessary to understand the geological structure and fracture characteristics of the site. This is done by means of a field survey, investigations and tests in and between the boreholes, and the examination of the distribution of permeability and pore water pressures.