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Geologic Disposal of Spent Nuclear Fuel: An Earth Science Perspective
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... 원자력 발전소를 운영 중인 대부분의 국가에서 HLW 지질처분장 건설을 계획하고 있다. 지질처분장의 다중 방 벽 시스템(multi-barrier system)은 기술적으로 유사한 형 태를 따르지만 (Birkholzer et al., 2012) (Kong et al., 2017;Hall et al., 2021 (Grauer, 1994;Wersin, 2003;Wersin et al., 2007;Zhang et al., 2012 (Bredehoeft and Maini, 1981;Alley and Parker, 2014;Grambow, 2016;Swift and Bonano, 2016;von Berlepsch and Haverkamp, 2016), 이 중 화강암(결정질 암석)과 셰일(점토 기반 암석)이 전 세 740 최재훈 · 유순영 · 박선주 · 박정훈 · 윤성택 계적으로 가장 광범위하게 조사되고 있다 (Alley and Parker, 2014). 처분장의 다양한 기반암별 지질 조건에 따른 장점 과 단점, 공학적 방벽의 중요성과 적용 사례에 대하여 (Bredehoeft and Maini, 1981;Smellie et al., 1985;Vira, 2017 (Nordstrom et al., 1985;Fairhurst et al., 1993;Witherspoon, 2000 Table 3. Hydrochemical parameters for site investigation of deep groundwaters and reasons for requiring data (modified after Andrews et al., 1988;Bath, 2002) (1) To be included in reconnaissance and detailed/monitoring programs (Yang et al., 1998;Ahlers et al., 1999;Doughty, 1999a;Haukwa et al., 1999;Pruess et al., 1999;Ritcey and Wu, 1999;Wu et al., 1999 (Sonnenthal and Bodvarsson, 1999). ...
... 원자력 발전소를 운영 중인 대부분의 국가에서 HLW 지질처분장 건설을 계획하고 있다. 지질처분장의 다중 방 벽 시스템(multi-barrier system)은 기술적으로 유사한 형 태를 따르지만 (Birkholzer et al., 2012) (Kong et al., 2017;Hall et al., 2021 (Grauer, 1994;Wersin, 2003;Wersin et al., 2007;Zhang et al., 2012 (Bredehoeft and Maini, 1981;Alley and Parker, 2014;Grambow, 2016;Swift and Bonano, 2016;von Berlepsch and Haverkamp, 2016), 이 중 화강암(결정질 암석)과 셰일(점토 기반 암석)이 전 세 740 최재훈 · 유순영 · 박선주 · 박정훈 · 윤성택 계적으로 가장 광범위하게 조사되고 있다 (Alley and Parker, 2014). 처분장의 다양한 기반암별 지질 조건에 따른 장점 과 단점, 공학적 방벽의 중요성과 적용 사례에 대하여 (Bredehoeft and Maini, 1981;Smellie et al., 1985;Vira, 2017 (Nordstrom et al., 1985;Fairhurst et al., 1993;Witherspoon, 2000 Table 3. Hydrochemical parameters for site investigation of deep groundwaters and reasons for requiring data (modified after Andrews et al., 1988;Bath, 2002) (1) To be included in reconnaissance and detailed/monitoring programs (Yang et al., 1998;Ahlers et al., 1999;Doughty, 1999a;Haukwa et al., 1999;Pruess et al., 1999;Ritcey and Wu, 1999;Wu et al., 1999 (Sonnenthal and Bodvarsson, 1999). ...
... Table 1. Summary of geologic options for radioactive waste repositories (modified afterAlley and Parker, 2014) ...
... REPOSITORY According to [6], unresolved issues with final disposal of radioactive wastes limit the use of nuclear fuels for power generation. In practise, low permeability rocks and soils are used to store canisters of spent fuels in open cavity of rocks or at predetermined depths in soils. ...
... Thus, to guarantee safe disposal, deep repository operations technically consider physical and chemical interactions between the host soil and reposed radio active waste. In this regard, [6] strongly suggested that the natural ability of the host soil to resist the movement radionuclides should also be a fundamental requirement for siting repository. However, radionuclide retention of the host soil depends on the relative stability of physical and chemical interactions between the radionuclide and soil. ...
... However, radionuclide retention of the host soil depends on the relative stability of physical and chemical interactions between the radionuclide and soil. Perharps, due to the recommendations of [6], modern geotechnical disposal practices now consider multiple barrier layers around buried canisters. Despite this precaution, the possibility of leakage cannot be completely excluded. ...
This work determines the relative capabilities of some geological formations in Nigeria as radioactive wastes repository. Reaction term of the advection-diffusion-reaction transport in porous media was reworked to address nonlinear radioactive decay and sorption. Lyapunov's indirect method identified three critical points. A stable attractor at the origin, flanked by two symetric saddles. Phase Potraits show that Caesium and Strontium are well stabilized in sandstone, consolidated clay and limestone. In shale, the focus at the origin indicates weak stability for the two radionuclides. However, for Plutonium, the origin is consisitently a weak node. Hence, its dynamics/disappearance rate is very slow. At half-lifes, breakthrough curves in 200cm radius of host soils show that Strontium and Caesium are best contained in sandstone and consolidated clay. However, they deeply infilterate limestone. Similarly, a fifth of Plutonium's reposed concentration completely infiltrated the simulation aperture. Hence, Plutonium should not be reposed in natural formations.
... Many countries are considering different rock types for hosting rock types based on their availability and rock properties (Delay et al. 2010;Chapman and Hooper 2012;Cherry et al. 2014). In the USA, salt formations are the primary focus, given their low permeability and ductility (Cherry et al. 2014). ...
... Many countries are considering different rock types for hosting rock types based on their availability and rock properties (Delay et al. 2010;Chapman and Hooper 2012;Cherry et al. 2014). In the USA, salt formations are the primary focus, given their low permeability and ductility (Cherry et al. 2014). Shale and argillite formations are currently being considered in France and Switzerland given their impermeability and plasticity, while granites and other crystalline rocks are under consideration in Russia, China, Finland, and Sweden because of their strength and thermal properties Siren et al. 2015;Laverov et al. 2016). ...
The Ghareb Formation is a shallowly buried porous chalk in southern Israel that is being considered as a host rock for a geologic nuclear waste repository. Setup and operation of a repository will induce significant mechanical, hydrological and chemical perturbations in the Ghareb. Developing a secure repository requires careful characterization of the rock behavior to different loads. To characterize hydromechanical behavior of the Ghareb, several short- and long-term deformation experiments were conducted. Hydrostatic loading tests were conducted both dry and water-saturated, using different setups to measure elastic properties, time-dependent behavior, and permeability. A set of triaxial tests were conducted to measure the elastic properties and rock strength under differential loading at dry and water-saturated conditions. The hydrostatic tests showed the Ghareb began to deform inelastically around 12–15 MPa, a relatively low effective pressure. Long-term permeability measurements demonstrated that permeability declined with increasing effective pressure and was permanently reduced by ~ 1 order of magnitude after unloading pressure. Triaxial tests showed that water saturation significantly degrades the rock properties of the Ghareb, indicating water-weakening is a significant risk during repository operation. Time-dependent deformation is observed during hold periods of both the hydrostatic and triaxial tests, with deformation being primarily visco-plastic. The rate of deformation and permeability loss is strongly controlled by the effective pressure as well. Additionally, during holds of both hydrostatic and triaxial tests, it is observed that when water-saturated, radial strain surpassed axial strain when above effective pressures of 13–20 MPa. Thus, deformation anisotropy may occur in situ during operations even if the stress conditions are hydrostatic when above this pressure range.
... Constraining the dynamic interface between circulating meteoric waters and deeper more stagnant saline fluids is important for groundwater supplies (Ferguson, McIntosh, Perrone, & Jasechko, 2018;Kang & Jackson, 2016), mineral resources (Garven, 1995;Sanford, 1994), energy extraction and storage (Garven, 1989;Spangler et al., 1996;Zheng et al., 2012), isolation of anthropogenic waste products (Cherry et al., 2014;Ferguson, McIntosh, Perrone, & Jasechko, 2018;Sturchio et al., 2014), and subsurface microbial life (Lollar et al., 2021;Warr et al., 2018). Circulating meteoric waters, present in the upper few kilometers of the Earth's crust , transport an appreciable mass of fluids and solutes on timescales of tens of years to ka to Ma (Aggarwal et al., 2015;Castro, Goblet, et al., 1998;Castro, Jambon, et al., 1998;Gerber et al., 2017;Jasechko et al., 2017;Lehmann et al., 2003;Schlegel et al., 2011;Zhou et al., 2005). ...
Krypton‐81 dating provides new insights into the timing, mechanisms, and extent of meteoric flushing versus retention of saline fluids in the subsurface in response to changes in geologic and/or climatic forcings over 50 ka to 1.2 Ma year timescales. Remnant Paleozoic seawater‐derived brines associated with evaporites in the Paradox Basin, Colorado Plateau, are beyond the ⁸¹Kr dating range (>1.2 Ma) and have likely been preserved due to negative fluid buoyancy and low permeability. ⁸¹Kr dating of formation waters above the evaporites indicates topographically‐driven meteoric recharge and salt dissolution since the Late Pleistocene (0.03–0.8 Ma). Formation waters below the evaporites (up to 3 km depth), in basal aquifers, contain relatively young meteoric water components (0.4–1.1 Ma based on ⁸¹Kr) that partially flushed remnant brines and dissolved evaporites. We demonstrate that recent, rapid denudation of the Colorado Plateau (<4–10 Ma) activated deep, basinal‐scale flow systems as recorded in ⁸¹Kr groundwater age distributions.
... Considerations of such long time periods may also provide important insights into how the legacy of the Anthropocene might be preserved over deep time in the subsurface. These efforts are also urgently needed in the short term in the race for porosity between both conventional and emerging energy projects in the subsurface (Ferguson, 2013;McIntosh & Ferguson, 2019;Vengosh et al., 2014), waste isolation (Benson & Cole, 2008;Cherry et al., 2014), CO 2 sequestration (Benson & Cole, 2008), and protection of strategic water resources (Ferguson, McIntosh, Perrone, & Jasechko, 2018;Perrone & Jasechko, 2019). ...
Global groundwater volumes in the upper 2 km of the Earth's continental crust—critical for water security—are well estimated. Beyond these depths, a vast body of largely saline and non‐potable groundwater exists down to at least 10 km—a volume that has not yet been quantified reliably at the global scale. Here, we estimate the amount of groundwater present in the upper 10 km of the Earth's continental crust by examining the distribution of sedimentary and crystalline rocks with depth and applying porosity‐depth relationships. We demonstrate that groundwater in the 2–10 km zone (what we call “deep groundwater”) has a volume comparable to that of groundwater in the upper 2 km of the Earth's crust. These new estimates make groundwater the largest continental reservoir of water, ahead of ice sheets, provide a basis to quantify geochemical cycles, and constrain the potential for large‐scale isolation of waste fluids.
... Considerations of such long time periods may also provide important insights into how the legacy of the Anthropocene might be preserved over deep time in the subsurface. These efforts are also urgently needed in the short term in the race for porosity between both conventional and emerging energy projects in the subsurface (Ferguson, 2013;McIntosh & Ferguson, 2019;Vengosh et al., 2014), waste isolation (Benson & Cole, 2008;Cherry et al., 2014), CO 2 sequestration (Benson & Cole, 2008), and protection of strategic water resources (Ferguson, McIntosh, Perrone, & Jasechko, 2018;Perrone & Jasechko, 2019). ...
... The extent and controls on deep groundwater circulation are poorly understood, creating challenges for groundwater resource assessment (Gleeson et al., 2016;Richey et al., 2015), waste isolation (Cherry et al., 2014;Ferguson, McIntosh, Perrone, et al., 2018), integration of groundwater into catchment hydrology (Condon et al., 2020;Frisbee et al., 2017) and Critical Zone science (Küsel et al., 2016), and the distribution and evolution of life in the subsurface (Lollar et al., 2019;Warr et al., 2018). Permeability exerts an important control on the rate of groundwater circulation (and groundwater age) and there have been a number of attempts to assess the variations in permeability with depth (Achtziger-Zupančič et al., 2017;Ingebritsen & Manning, 1999;Stober & Bucher, 2007). ...
Plain Language Summary
Deep circulation of waters, coming from precipitation, connects the Earth's surface with deeper subsurface environments, transferring water, energy, and life critical for key processes, such as deep mineral weathering and release of nutrients, and geothermal energy systems. Deeper, more saline groundwater is typically, only weakly, connected to the rest of the hydrologic cycle. The penetration depth of precipitation‐derived waters and the bottom of the more active hydrologic cycle is relatively unknown. This study shows the depth of meteoric water circulation varies considerably across North America as a function of topography and fluid density, in addition to permeability. Study results help constrain locations of deeper meteoric water penetration and potential hydrologic connections to the Earth's surface, which has important implications for the extent of water resources and transport and long‐term storage of anthropogenic contaminants in the subsurface.
... The requirement for long-term geological sequestration of CO 2 [1,2] and nuclear waste management [3][4][5] has prompted increased interest in low-permeability, clay-rich sedimentary rocks [6][7][8][9][10][11][12]. These rocks are characterized by Figure 1: Pore-scale conceptual model for clay-rich sedimentary rock. ...
Characterization of porewater chemistry in low-permeability, clay-rich rocks provides insights into solute transport mechanisms and the origin and residence time of porewater. Extraction of porewater for chemical quantification is challenging, and several methods have been applied including squeezing, advective displacement, crush and leach, and a relatively new technique that extracts porewater by absorption into a cellulosic paper by capillary action. Here we compare porewater Cl ⁻ and Br ⁻ mass ratios from samples using the paper-absorption and crush-and-leach techniques. Samples were obtained from Upper Ordovician shales in the Michigan Basin in Ontario, the Opalinus Clay at the Mont Terri Rock Laboratory in Switzerland, and the Upper Ordovician Lorraine Group shale in southern Quebec. The data display consistent and reproducible differences among methods for Cl ⁻ and Br ⁻ mass ratios, with the paper-absorption method producing systematically lower Cl ⁻ : Br ⁻ ratios. The observed differences in Cl ⁻ : Br ⁻ ratios are attributed primarily to anion exclusion effects which are stronger for Br ⁻ than for Cl ⁻ , resulting in higher Br ⁻ concentrations in the largest pores that are preferentially sampled by the paper-absorption technique. In addition, calculations suggest that Cl ⁻ is more effective than Br ⁻ in forming ion pairs and clusters with neutral or positive charge which can enter the diffuse double layer. This causes a further decrease in the Cl ⁻ : Br ⁻ ratios for the mobile water. One important message from this work is that different extraction methods should not be expected to converge on a unique porewater Cl ⁻ : Br ⁻ ratio because each method reflects different proportions of the interlayer, diffuse double layer, and mobile fractions of porewater.
Nuclear energy production leaves behind waste that endangers human health for over 100,000 years. Governments and nuclear power producers around the world are scrambling to safely and sustainably dispose of these byproducts. To manage nuclear waste, Finland began constructing the Onkalo spent nuclear fuel repository, which is the first structure in the world engineered to last over one hundred millennia. The purpose of this article is to examine competing imaginaries in the deep-time policymaking process. This paper analyzes the history of the repository and the decision-making process authorizing its creation, arguing that deep time policy decisions are mediated by the expected technological progress of future generations. I present two different imaginaries: the progressive and the precautionary. The progressive imaginary believes that the technology of future generations will outpace natural challenges, so contemporary decisionmakers should prioritize future flexibility. In contrast, the precautionary imaginary is skeptical that technology will consistently advance and favors immediate action to mitigate long-term risks. I suggest that Onkalo’s development and adoption rested upon a prevailing precautionary imagination, which is explained in part by Finnish society’s general deference to established expertise. I argue the progressive-precautionary framework can help explain both cross-national variations in deep time policymaking and single case studies of long-term policy decisions. I conclude by considering the generalizability of my analysis and areas for future research.
Dissolution of actinide dioxides, including neptunium dioxide (NpO2(s)), is paramount for prediction of environmental fate of nuclear materials. Quantifying dissolution rates, as well as understanding qualitative dissolution mechanisms, informs performance assessment for geologic disposal of spent nuclear fuel and management of legacy radioactive waste. The aim of this research was to measure the dissolution rate of nanocrystalline NpO2(s), produced through legacy nuclear waste processing, under oxidizing conditions, as well as to characterize surface alteration to the material. The solid phase was characterized using electron microscopy techniques (SEM/STEM) and x-ray photoelectron spectroscopy (XPS), indicating preferential dissolution of Np-hydroxide contained in the grain boundaries of NpO2(s) and fragmentation of grains from the matrix. The oxidative dissolution was monitored over 40 weeks, yielding a two-step kinetic dissolution model involving hydration of NpO2(s) and subsequent oxidation and dissolution of the hydroxide phase. The proposed dissolution models for nanocrystalline NpO2(s) suggest that microstructural features such as grain boundaries are key factors affecting dissolution, including release of colloidal particles, and ultimately, environmental fate and transport of nuclear materials.
The author proposes seven rules that together add up to a checklist for the responsible development and use of models used at the science/policy interface. The checklist covers the entire modeling process, and it draws on methods and strategies from two formal processes for assessing uncertainty, one called global sensitivity analysis and the other commonly known by the acronym NUSAP. NUSAP collectively integrates five qualifiers represented in its name. These are numeral, unit, spread, assessment, and pedigree. Assessment and pedigree in particular reveal how the information was produced and document the contentiousness of any claims. Simpler models enable scientists and stakeholders alike to understand how assumptions and outputs are linked. One rule prescribes that questions must be raised about who benefits from the model and what motivations and incentives animate model developers. Another rule is to check that uncertainty has not been over- or underestimated to yield a result that advances the model proponents' preferences.
Consideration of the geosphere for isolation of nuclear waste has generated substantial interest in the origin, age, and movement of fluids and gases in low-permeability rock formations. Here, we present profiles of isotopes, solutes, and helium in porewaters recovered from 860 m of Cambrian to Devonian strata on the eastern flank of the Michigan Basin. Of particular interest is a 240-m-thick, halite-mineralized, Ordovician shale and carbonate aquiclude, which hosts Br--enriched, post-dolomitic brine (5.8 molal Cl) originating as evaporated Silurian seawater. Authigenic helium that has been accumulating in the aquiclude for more than 260 m.y. is found to be isolated from underlying allochthonous, He-3-enriched helium that originated from the rifted base of the Michigan Basin and the Canadian Shield. The Paleozoic age and immobility of the pore fluids in this Ordovician aquiclude considerably strengthen the safety case for deep geological repositories, but also provide new insights into the origin of deep crustal brines and opportunities for research on other components of a preserved Paleozoic porewater system.
Even as cleanup efforts after Japan's Fukushima disaster offer a stark reminder of the spent nuclear fuel (SNF) stored at nuclear plants worldwide, the decision in 2009 to scrap Yucca Mountain as a permanent disposal site has dimmed hope for a repository for SNF and other high-level nuclear waste (HLW) in the United States anytime soon. About 70,000 metric tons of SNF are now in pool or dry cask storage at 75 sites across the United States [Government Accountability Office, 2012], and uncertainty about its fate is hobbling future development of nuclear power, increasing costs for utilities, and creating a liability for American taxpayers [Blue Ribbon Commission on America's Nuclear Future, 2012].
By 2050, almost all U.S. nuclear reactors will have reached their 60-year maximum expected life. Many will shut down sooner. With no assurance that the current approach for finding a geologic repository or interim storage sites will succeed, used nuclear fuel could be stranded indefinitely at more than 70 sites in 35 states. Societal discussions about the future of nuclear waste should be framed in terms of the relative risks of all alternatives. We review and compare onsite storage, interim storage, and a geologic repository, as well as how these alternatives are presented to the public.
Key Words unsaturated flow in fractures, nuclear waste transport, spent fuel chemistry, fracture flow and transport, Nuclear Waste Policy Act s Abstract The nation has over 40,000 metric tonnes (MT) of nuclear waste des-tined for disposal in a geologic repository at Yucca Mountain. In this review, we highlight some of the important geoscience issues associated with the project and place them in the context of the process by which a final decision on Yucca Mountain will be made. The issues include understanding how water could infiltrate the reposi-tory, corrode the canisters, dissolve the waste, and transport it to the biosphere during a 10,000-year compliance period in a region, the Basin and Range province, that is known for seismic and volcanic activity. Although the site is considered to be "dry," a considerable amount of water is present as pore waters and as structural water in zeolites. The geochemical environment is oxidizing, and the present repository design will maintain temperatures at greater than 100 • C for thousands of years. Geoscientists in this project are challenged to make unprecedented predictions about coupled ther-mal, hydrologic, mechanical, and geochemical processes governing the future behavior of the repository and to conduct research in a regulatory and legal environment that requires a quantitative analysis of repository performance.
An examination of the Palaeozoic sedimentary sequence of S Ontario as a radioactive waste disposal medium. A major asset in siting a repository in such a sequence is the ability to locate zones with favourable geotechnical properties in suitable hydrogeologic environments by application of a large data base to the relatively simple stratigraphic model.-from Authors
The differing roles of the geosphere in safety cases considering crystalline-basement and sedimentary-rock (clays, shales, marls) host formations for deep disposal of radioactive waste are discussed. These roles are then illustrated using the Swiss and Finnish programmes as examples. The analysis of relevant FEPs (features, events and processes) and scenarios provides the basis for the quantification of radionuclide transport. The key geosphere-related FEPs for Opalinus Clay in Switzerland and for crystalline rocks at Olkiluoto in Finland are compared and their effects on calculated radionuclide fluxes are evaluated. Finally, recent developments in host-rock characterisation are discussed, including in situ characterisation of matrix porosity and of the microstructure of the pore space and chemical characterisation of pore fluids.
Today, the issue of waste management is as prominent as reactor safety in the controversies surrounding nuclear power and is particularly topical in the US since the 2010 closure of the Yucca Mountain repository project. William and Rosemarie Alley provide an engaging and authoritative account of the controversies and possibilities surrounding disposal of nuclear waste in the US, with reference also to other countries around the world. The book tells the full history from the beginnings after World War II up to today, bringing to life the pioneering science, the political wrangling and media drama, and the not-in-my-backyard communities fighting to put waste elsewhere. Written in down-to-earth language, by an expert with key involvement in the Yucca Mountain project, this is a timely book for public interest groups, affected communities, policymakers, environmentalists and research scientists working in related fields and anyone interested in finding out more about this important issue.
In the aftermath of the March 2011 accident at Japan's Fukushima Daiichi nuclear power plant, the future contribution of nuclear power to the global energy supply has become somewhat uncertain. Because nuclear power is an abundant, low-carbon source of base-load power, on balance it could make a large contribution to mitigation of global climate change and air pollution. Using historical production data, we calculate that global nuclear power has prevented about 1.84 million air pollution-related deaths and 64 gigatonnes (Gt) CO2-equivalent greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning. Based on global projection data that take into account the effects of Fukushima, we find that by mid-century, nuclear power could prevent an additional 420,000 to 7.04 million deaths and 80 to 240 GtCO2-eq emissions due to fossil fuels, depending on which fuel it replaces. By contrast, we assess that large-scale expansion of natural gas use would not mitigate the climate problem and would cause far more deaths than expansion of nuclear power.
The permanent disposal of high-level radioactive waste is one of the major technical hurdles that must be addressed if electrical power production by nuclear energy is to remain viable. The main challenge is that the waste must be effectively isolated from interactions with the biosphere for hundreds of thousands of years. A number of permanent disposal options have been proposed and reviewed by various countries and scientific organizations during the past few decades, and there appears to be a consensus today that mined geologic disposal is the most practical and effective method. Several variations on mined geologic disposal are being intensively studied by waste-producing countries. These investigations address a wide range of scientific questions, such as the behavior of geological and engineered barriers over time and the use of quantitative modeling and/or qualitative observational evidence to demonstrate the safety of disposal. The present review provides an overview of current approaches, scientific issues, and safety assessments related to mined geologic repositories for high-level radioactive waste.