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Present strategies for the long-term disposal of high-level nuclear wastes are based on the construction of repositories hundreds of meters below the earth surface. Although the surrounding host-rocks are relatively isolated from the light at the earth surface they are by no means lifeless. Microorganisms rule the deep part of the biosphere and it is well established that their activity can alter chemical and physical properties of these environments. Microbial processes can directly and indirectly affect radionuclide migration in multiple ways. Within 6th FP IP FUNMIG the interplay between microbial biofilms and radionuclides and the effect of microbially induced redox transformations of Fe on radionuclide mobility have been investigated. For the first time, formation of U(V) as a consequence of microbial U(VI) reduction in a multi-species biofilm was detected in vivo by combining laser fluorescence spectroscopy and confocal laser scanning microscopy. Furthermore, it was demonstrated that addition of U(VI) can lead to increased respiratory activity in a biofilm. Increased respiration in a biofilm can create microenvironments with lower redox potential, and hence induce reduction of radionuclides. Transient mobilization of U was observed in experiments with Fe oxides containing adsorbed U(VI) in which the activity of SO4-reducing organisms was mimicked by sulfide addition. Faster reaction of sulfide with Fe oxides compared to U(VI) reduction, and decreasing U(VI) adsorption due to the transformation of Fe oxides into FeS can explain the observed intermittent U mobilization. The presented research on microbe-radionuclide interactions performed within FUNMIG addresses only a few aspects of the potential role of microorganisms in the performance assessment of nuclear waste repositories. For this reason, additionally, this article provides a cursory overview of microbial processes which were not studied within the FUNMIG project but are relevant in the context of performance assessment. The following aspects are presented: (a) the occurrence and metabolic activity of microorganisms of several proposed types of host-rocks, (b) the potential importance of microorganisms in the near-field of nuclear waste repositories, (c) indirect effects of microbial processes on radionuclide mobility in the repository far-field, (d) binding of radionuclides to microbial biomass, (e) microbial redox transformations of radionuclides, and (f) the implementation of microbial processes in reactive transport models for radionuclide migration. 相似文献
3.
DECOVALEX Project: from 1992 to 2007 总被引：3，自引：0，他引：3
The DECOVALEX project is a unique international research collaboration, initiated in 1992, for advancing the understanding
and mathematical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) processes
in geological systems—subjects of importance for performance assessment of radioactive waste repositories in geological formations.
From 1992 up to 2007, the project has made important progress and played a key role in the development of numerical modelling
of coupled processes in fractured rocks and buffer/backfill materials. The project has been conducted by research teams supported
by a large number of radioactive-waste-management organizations and regulatory authorities, including those of Canada, China,
Finland, France, Japan, Germany, Spain, Sweden, UK, and the USA. Through this project, in-depth knowledge has been gained
of coupled THM and THMC processes associated with nuclear waste repositories, as well as numerical simulation models for their
quantitative analysis. The knowledge accumulated from this project, in the form of a large number of research reports and
international journal and conference papers in the open literature, has been applied effectively in the implementation and
review of national radioactive-waste-management programmes in the participating countries. This paper presents an overview
of the project. 相似文献
4.
David Hodgkinson Hakim Benabderrahmane Mark Elert Aimo Hautojärvi Jan-Olof Selroos Yasuharu Tanaka Masahiro Uchida 《Hydrogeology Journal》2009,17(5):1035-1049
An overview is presented of a 4-year study by the Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes, whose primary aim was to build a bridge between the approaches used for site characterisation (SC) and performance assessment (PA) associated with nuclear waste repositories. Eleven modelling teams representing six national radioactive waste organisations participated in eight modelling exercises whose objectives were: to assess simplifications used in PA models; to determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models; to support the design of SC programmes to assure that the results have optimal value for PA calculations; and to improve the understanding of site-specific flow and transport behaviour at different scales using SC models. The modelling tasks were concerned with flow and transport through single and multiple near-planar features on SC and PA timescales, including the diffusion of solutes into multiple immobile zones adjacent to fracture surfaces. In general, tracer tests provide only limited quantitative constraints on retention parameter values relevant to PA but nevertheless provide insight about the flow and transport processes, which is a key element of the bridge between SC and PA. 相似文献
5.
Li Yu Eef Weetjens Xavier Sillen Tim Vietor Xiangling Li Pierre Delage Vincent Labiouse Robert Charlier 《Rock Mechanics and Rock Engineering》2014,47(1):3-19
A proper evaluation of the perturbations of the host rock induced by the excavation and the emplacement of exothermic wastes is essential for the assessment of the long-term safety of high-level radioactive waste disposals in clay formations. The impact of the thermal transient on the evolution of the damaged zone (DZ) has been explored in the European Commission project TIMODAZ (thermal impact on the damaged zone around a radioactive waste disposal in clay host rocks, 2006–2010). This paper integrates the scientific results of the TIMODAZ project from a performance assessment (PA) point of view, showing how these results support and justify key PA assumptions and the values of PA model parameters. This paper also contextualises the significance of the thermal impact on the DZ from a safety case perspective, highlighting how the project outcomes result into an improved understanding of the thermo–hydro–mechanical behaviour of the clay host rocks. The results obtained in the TIMODAZ project strengthen the assessment basis of the safety evaluation of the current repository designs. There was no evidence throughout the TIMODAZ experimental observations of a temperature-induced additional opening of fractures nor of a significant permeability increase of the DZ. Instead, thermally induced plasticity, swelling and creep seem to be beneficial to the sealing of fractures and to the recovery of a very low permeability in the DZ, close to that of an undisturbed clay host rock. Results from the TIMODAZ project indicate that the favourable properties of the clay host rock, which guarantee the effectiveness of the safety functions of the repository system, are expected to be maintained after the heating–cooling cycle. Hence, the basic assumptions usually made in PA calculations so far are expected to remain valid, and the performance of the system should not be affected in a negative way by the thermal evolution of the DZ around a radioactive waste repository in clay host rock. 相似文献
6.
Nick D. Bryan Liam Abrahamsen Nick Evans Peter Warwick Gunnar Buckau Liping Weng Willem H. Van Riemsdijk 《Applied Geochemistry》2012
Some recent developments made during the European Union 6th Framework Integrated Project FUNMIG in the understanding and prediction of behaviour in ternary systems of radionuclides, humic substances and mineral surfaces are described. These developments are placed in the context of the existing literature. The aim is to describe the current understanding of humic substance mediated radionuclide transport as it may be applied to calculations in support of Radiological Performance Assessment. Some improvements in experimental techniques that provide the raw data to calibrate metal ion binding models are explained. The various metal ion binding models that are available are described and contrasted, before the recent development of ternary system models, in particular the Ligand Charge Distribution model that can predict metal ion and humic substance behaviour in ternary systems. The kinetic effects in ternary systems are described along with the models that are used to describe them. Finally, the remaining challenges in making predictions of radionuclide transport for the Radiological Performance Assessment of radioactive waste repositories are discussed. 相似文献
7.
缓冲层热—湿—力耦合作用研究简介 总被引：2，自引：0，他引：2
介绍了高放射性废物深地质处置库热－湿－力耦合作用，着重给出了国际高压实缓冲层热－湿－力耦合作用的研究进展，指出与高放射性废物处置库有关的热－湿－力耦合过程研究是核废物地质处置提出的新课题，涉及多学科，需广大有识之士共同合作研究。 相似文献
8.
基于“多重屏障原理”的深地质处置是国内外公认的处置高放射性核废物的合适方法。本文从处置库建造与运行对环境的影响及环境对处置库反作用两方面探讨高放废物深地质处置中涉及的有关环境问题,并指出为确保处置库的长期安全性,必须特别注重选址及多因素耦合作用研究。 相似文献
9.
高放废物处置库中乏燃料持续释放的热量对围岩的应力场和渗流场及其长期稳定性具有重要影响。围岩的热学参数依赖于岩石矿物组成、孔隙率和孔隙流体等因素,准确取值是进行高放废物地质处置库多场耦合分析的前提。通过细观力学分析,建立了围岩等效热学参数（热容、热传导系数、热膨胀系数）取值方法,并基于Biot孔隙介质理论,建立应力?温度?渗流三场耦合模型,进而提出了高放废物处置库围岩应力?渗流?温度耦合数值模拟方法。最后通过COMSOL Multiphysics多场耦合软件,利用瑞士Mont Terri高放废物地下试验室围岩温度?渗流?应力多场耦合现场试验数据对数值模拟方法进行验证,并探讨了温度?渗流?应力耦合过程的演化规律。研究表明,模拟结果和试验值吻合良好。研究结果可为我国高放废物处置库的安全评估和选址提供科学依据。 相似文献
10.
Prussian Blue, FeIII
4[FeII(CN)6]3, and structurally related transition metal compounds are used as cesium ion exchangers in decontamination procedures of liquid radioactive waste. The used ion exchangers are conditioned as a cementitious waste form for interim storage and finally will become part of the radioactive waste in geological repositories. The problem discussed here is the long-term behaviour of the ion exchangers FeIII
4[FeII(CN)6]3 and Ni2[Fe(CN)6] in planned geological repositories. The worst-case scenario is the instantaneous and complete dissolution and decomposition of the ion exchangers in the cementitious environment and the release of free cyanide. All radionuclides belonging to the class of hard acceptors, e. g. Cs, Sr, Ra, U, Np, Pu, Am and Cm, are not affected by cyanide complexation under these conditions. Radionuclides belonging to the class of soft acceptors and borderline metals, e.g. Co, Ni, Tc, Cd, Pb, Pd and Ag, are affected to various degrees by cyanide complexation. Strong complexation and extensive cyanide leaching is found for Ni, Co, Pd, Ag. 相似文献
11.
N. P. Laverov B. I. Omel’yanenko S. V. Yudintsev S. V. Stefanovsky B. S. Nikonov 《Geology of Ore Deposits》2013,55(2):71-95
Reprocessing of spent nuclear fuel (SNF) for recovery of fissionable elements is a precondition of long-term development of nuclear energetics. Solution of this problem is hindered by the production of a great amount of liquid waste; 99% of its volume is low- and intermediate-level radioactive waste (LILW). The volume of high-level radioactive waste (HLW), which is characterized by high heat release, does not exceed a fraction of a percent. Solubility of glasses at an elevated temperature makes them unfit for immobilization of HLW, the insulation of which is ensured only by mineral-like matrices. At the same time, glasses are a perfect matrix for LILW, which are distinguished by low heat release. The solubility of borosilicate glass at a low temperature is so low that even a glass with relatively low resistance enables them to retain safety of under-ground LILW depositories without additional engineering barriers. The optimal technology of liquid confinement is their concentration and immobilization in borosilicate glasses, which are disposed in shallow-seated geological repositories. The vitrification of 1 m3 liquid LILW with a salt concentration of ～300 kg/m3 leaves behind only 0.2 m3 waste, that is, 4–6 times less than by bitumen impregnation and 10 times less than by cementation. Environmental and economic advantages of LILW vitrification result from (1) low solubility of the vitrified LILW in natural water; (2) significant reduction of LILW volume; (3) possibility to dispose the vitrified waste without additional engineering barriers under shallow conditions and in diverse geological media; (4) the strength of glass makes its transportation and storage possible; and finally (5) reliable longterm safety of repositories. When the composition of the glass matrix for LILW is being chosen, attention should be paid to the factors that ensure high technological and economic efficiency of vitrification. The study of vitrified LILW from the Kursk nuclear power plant with high-power channel reactors (HPCR; equivalent Russian acronym, RBMK) and the Kalinin nuclear power plant with pressurized water reactors (PWR; equivalent Russian acronym VVER) after their 14-yr storage in the shallow-seated repository at the MosNPO Radon testing ground has confirmed the safety of repositories ensured by confinement properties of borosilicate matrix. The most efficient vitrification technology is based on cold crucible induction melting. If the content of a chemical element in waste exceeds its solubility in glass, a crystalline phase is formed in the course of vitrification, so that the glass ceramics become a matrix for such waste. Vitrified waste with high Fe; Na and Al; Na, Fe, and Al; Na and B is characterized. The composition of frit and its proportion to waste depends on waste composition. This procedure requires careful laboratory testing. 相似文献
12.
地质系统热-水-力耦合作用的随机建模初步研究 总被引：2，自引：0，他引：2
热-水-力(THM)耦合作用是岩石力学与环境地质中的重要基础理论问题,核废料地质处置库周围的缓冲材料和围岩中的热-水-力耦合现象将影响其力学稳定性、热传导性和渗透性,进而影响放射性核素在裂隙岩体中的迁移规律。核废料或放射性废料的地下深埋处置是国际上正在研究的永久性隔离的有效方法之一。因此,对核废料地质处置法安全性评估的一个重要内容就是对裂隙岩体中力学稳定性与构造应力、地下水渗流及热载荷等的耦合作用之数值模拟和评估。这已成为当前刻不容缓的重要的环境影响评价课题。笔者研究了温度场-渗流场-应力场中热传导系数和渗透率以及岩体力学参数的空间变异性,用实验方法研究三场耦合效应及裂隙岩体的场性能等效处理,试图建立热-水-力耦合作用的随机性数学模型及可视化数值模拟方法,为核废料地质处置安全性评估提供直观的新方法。 相似文献
13.
The Fundamentals of Radionuclide Migration (FUNMIG) project was organised in some Research and Technological Development Components (RTDCs) integrated by a number of Work Packages (WP’s) attempting to cover the key migration processes at different scales (laboratory to repository) and in different geological media, mainly clay and granite, but also some salt rock related work was performed. The main RTDCs of interest for this review paper are numbers 1 and 2, which concerned laboratory studies of well-established and less-established migration processes. Some additional interesting outcomes arise also from RTDCs 3, 4 and 5 devoted to the upscaling and applicability of migration processes to clay, granite and salt rock environments, respectively. This review discusses the contribution of the various parts of the FUNMIG project in the process oriented context of understanding the mechanistic approximation to what can be seen as the final and thermodynamically stable stage of the long chain of processes which are covered under the general term of sorption and that culminate in the formation of solid solutions. 相似文献
14.
Javier Cuadros 《Geology Today》2008,24(3):99-103
Nuclear waste from thermal plants poses a lasting risk to the biosphere because of its long radioactive life. The planned definitive storage place for it is in deeply buried repositories. Such repositories would need to be both impermeable to water, and plastic during deformation, in order to avoid the formation of cracks that may allow water in. One of the clay minerals, smectite, has these two properties and is an ideal candidate as a sealing material or even host rock for nuclear waste repositories. The chemical stability of smectite in the repository environment is sufficient to maintain good sealing properties during the active life of the relevant radionuclides. 相似文献
15.
Many geoscientific fields use reactive transport codes to set up and interpret experiments as well as to understand natural processes. Reactive transport codes are also useful to give insights in the long term evolution of systems such as radioactive waste repositories or CO2 storage sites, for which experiments cannot reach the targeted time scale nor the dimension of those systems. The consideration of kinetic reaction rates is often required to reproduce correctly the geochemical and transport processes of interest. However, kinetic data are scattered in the literature, making data and selection a tedious task. Kinetic parameters on a single system are also highly variable depending on data choice, interpretation and chosen kinetic modelling approaches, thus making inter-comparison of modelling studies difficult. The present work aims at proposing a compilation of kinetic parameters to overcome part of above cited problems. The proposed selection was done (i) to ensure consistency of data selection criteria and data treatment and (ii) to ease the use of common kinetic parameters that are independent of the chosen geochemical modelling code. For those two reasons, the kinetic formalism of the transition state theory (TST) was chosen. The selection of minerals is currently limited to those present in clay rich rocks and cements, reflecting the effort made at predicting the evolution of radioactive waste underground storage systems. Still, the proposed compilation should also be useful for other applications such as CO2 sequestration. 相似文献
16.
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
17.
Can we use tracer tests to obtain data for performance assessment of repositories for nuclear waste?
With regard to the long-term safety of repositories for spent nuclear fuel, tracer tests have commonly been used in site characterisation (SC) for finding information that can be later used for performance assessment (PA). The question arises as to whether data obtained in tracer tests performed over a time scale of weeks or months are relevant for PA calculations. As part of a study overseen by the Äspö Task Force, the mechanisms that determine the radionuclide residence time under SC and PA conditions are addressed, given that they influence the validity of data transference from SC to PA. The results show that radionuclide transport in SC and PA, although governed by the same retardation mechanisms, are dominated by different sub-processes. In a practical sense this means that the parameter values (typically fracture apertures and “in situ” apparent retention data) determined in tracer tests, performed as a part of the SC program, should not be used directly for making PA predictions. The emphasis in SC should focus more on the determination of other parameters of relevance at PA timescales. The PA-specific flow rate, flow connectivity, and flow-wetted surface to flow ratio are given here as examples. 相似文献
18.
H.N. Khoury E. Salameh I.D. Clark P. Fritz W. Bajjali A.E. Milodowski M.R. Cave W.R. Alexander 《Journal of Geochemical Exploration》1992,46(1)
The highly alkaline springs of the Maqarin area of northern Jordan are currently under examination as part of an international project testing the models used to analyse the safety of repositories for low and intermediate level radioactive waste (L/ILW). The Maqarin area contains a rock-groundwater system which is an ideal natural analogue of a concrete-filled L/ILW repository emplaced in a sedimentary host rock. The high pH (12.5) groundwaters at this site are the product of interaction with naturally occurring cement minerals and not of the alteration of ultramafic minerals. Stable isotope data for the hyperalkaline groundwaters lie below both the local meteoric water line and the eastern Mediterranean water line. At least part of the shift appears to be the result of groundwater interaction with the cement minerals. This paper introduces the site of the natural analogue study and, in presenting novel data on the chemistry and stable isotopic signature of the groundwater, provides background information which is used in a companion paper (Alexander et al., 1992) on testing the predictive capabilities of geochemical thermodynamic codes (and their associated databases) which will be utilised as part of the safety assessment of a L/ILW repository. 相似文献
19.
It is essential that computer-based models used in the safety assessment of radioactive waste repositories accurately represent the processes occurring in real field systems. Confidence in long-term predictions of radionuclide migration will then depend upon the completeness of data available, particularly those obtained from the disposal site, and correct implementation of the model. The study of natural geochemical systems provides information on the adequacy of the underlying “generic” database and enhances our understanding of the transport mechanisms which form the basis of performance assessment. This paper concentrates on speciation-solubility modelling and describes four natural occurrences of uranium, each of which displays a different facet of uranium migration behaviour. The attributes of each site and the means by which uranium is immobilised are described. Retardation is highly species specific and this is illustrated through the use of site data in equilibrium speciation and coupled chemical transport calculations. Oxidation of U(IV) to U(VI) species promotes leaching of uranium ore at all the locations studied, emphasising the need to ensure that reducing conditions persist in a repository dominated by its actinide inventory. 相似文献
20.
膨润土缓冲材料热传导特性的研究,对于高放废物深地质处置系统的安全评价至关重要。基于串、并联原理,通过将土体孔隙划分为与固相基质并联和串联两部分,提出了考虑矿物成分、颗粒亲水性、孔隙率及饱和度等因素的非饱和膨润土有效热传导系数的4种预测形式,建立了基于4种形式线性组合的有效热传导特性预测模型。详细讨论了模型参数的确定方法,并讨论了孔隙率、饱和度和孔隙结构、颗粒亲水性等因素对土体有效热传导特性的影响。基于MX-80膨润土和高庙子膨润土热传导特性试验成果,对模型的预测性能进行了验证。结果表明,由于膨润土颗粒尺寸较小且具有亲水特性,孔隙内的空气与水宜采用并联描述。研究成果对于非饱和膨润土的导热性能以及工程屏障系统的THM耦合数值模拟研究具有一定的参考价值。 相似文献