Engineering Challenges in the Geological Disposal of Radioactive Waste and Carbon Dioxide

In Japan, site selection for geological disposal of radioactive waste (RW) and carbon dioxide (CO2) is very important because of the large regional differences in tectonic activity. Assessment of the long-term stability of geological environments is key to geological RW disposal in Japan. A comprehensive system of long-term prediction of crustal movement and the groundwater regime around the virtual RW disposal sites has been developed in Japan. CO2 is naturally abundant, but geological disposal of the gigantic volumes of CO2 may have big impacts on the environment. One of the adverse effects of underground fluid injection is that it may induce earthquakes. Underground carbon microbubble injection accelerates advanced geological disposal mechanisms. The autogenously sealed ‘CO2 capsules’ can be formed in large basaltic sheets, ophiolite complex and oceanic crust. Sub-seabed aquifers under the deep sea floor can provide very safe and virtually limitless CO2 disposal. Different disposal strategies for CO2 and RW are needed because of the extreme difference in their toxicity and volume. The dispersion and dilution principle is possible for the CO2 disposal, while RW is strictly contained by the multiple barrier system. The stability of the geological environment is important for both CO2 and RW disposal.

This paper compares the policy, regulatory and institutional (PRI) settings of Radioactive Waste (RW) and Carbon Dioxide (CO2) disposal for selected countries. This comparison is premised on the following arguments: (a) the policy/political acceptance of nuclear power and coal power with Carbon Capture and Storage (CCS) technology to redress the climate change challenge will be essentially determined by the efficacy of the PRI settings; and (b) the existing discussion on these technologies is largely neglectful of the significance of these settings. The comparison suggests that: (a) while the overall PRI settings for RW and CO2 disposal are generally fuzzy, discordant and fragmented, they are relatively well defined for RW disposal than for CO2 disposal; and (b) PRI settings for RW and CO2 disposal cannot be analysed in isolation from broader settings for nuclear and coal-CCS power, and – more importantly – in isolation from macro-level energy, economic, environmental and socio-political policy settings.

Many governments are at various stages of planning to dispose of ­radioactive waste (RW) in geological formations. Many governments expressly expect to use geological formations to dispose of the carbon dioxide (CO2) ­produced in fossil fuel combustion. This chapter compares, in the light of climate change, the ethical issues involved in disposing of RW and CO2 in geological formations, given their potential to cause harm and given the risks involved in the deployment of these disposal technologies. It highlights the ethical issues triggered by the need for a high level of scientific certainty regarding the ability of potential disposal sites to counteract the migration of substances of concern away from disposal areas. However, the ethical issues entailed in geological disposal of RW and CO2 may need to be re-evaluated in light of the fact that disposal contributes to climate change mitigation. It is concluded, however, that as long as alternative methods for mitigating climate change are available that do not involve geological disposal of CO2 and as long as scientific uncertainty remains about the efficacy of disposal sites to contain RW and CO2, such alternative methods are ethically preferable. The chapter identifies another ethical issue, namely that the development and deployment of alternative technologies to reduce greenhouse gas emissions could be delayed by reliance on geological disposal of CO2.

Public acceptability of risky technologies is not only related to the objective risks involved, but to a number of subjective factors as well. Therefore, various studies examined psychological factors related to acceptability judgements. In this chapter we demonstrate the relevance of psychological factors that contribute to the explanation of the acceptability of radioactive waste disposal and carbon dioxide (CO2) disposal technologies. The acceptability of CO2 disposal has received far less attention in psychological studies than the acceptability of radioactive waste disposal, and therefore we have made an assessment of possible psychological determinants based on research on the acceptability of the latter. We conclude that the acceptability of CO2 disposal may be explained by similar factors to those influencing the acceptability of radioactive waste disposal, i.e. risk characteristics (dread and the unknown), affect, values and worldviews, fairness and trust. We argue that these psychological factors are directly related to the acceptability of CO2 disposal as well as indirectly, via the perceived risks and benefits of CO2 disposal. Furthermore, we discuss group differences (i.e. lay versus experts, and cross-cultural differences) in acceptability of radioactive waste disposal and, again, translate these results for possible consequences in psychological research in the area of the acceptability of geological disposal of CO2. Finally, we integrate the psychological factors into a conceptual model and discuss the limitations of current research, future research directions and policy implications for the acceptability of both types of technologies.

Preface H.-H. Rogner Introductory chapter Comparing the Geological Disposal of Carbon Dioxide and Radioactive Waste: Introduction and Overview Section A Thematic Assessments Geological Media and Factors for the Long-term Emplacement and Isolation of Carbon Dioxide and Radioactive Waste Environmental Issues in the Geological Disposal of Carbon Dioxide and Radioactive Waste Risk Assessment, Risk Management and Remediation for the Geological Disposal of Radioactive Waste and Storage of Carbon Dioxide Monitoring Methods Used to Identify the Migration of Carbon Dioxide and Radionuclides in the Geosphere Transport of Carbon Dioxide and Radioactive Waste Engineering Challenges in the Geological Disposal of Radioactive Waste and Carbon Dioxide The Costs of the Geological Disposal of Carbon Dioxide and Radioactive Waste Managing Liability: Comparing Radioactive Waste Disposal and Carbon Dioxide Storage Public Acceptance of Geological Disposal of Carbon Dioxide and Radioactive Waste: Similarities and Differences Comparative Ethical Issues Entailed in the Geological Disposal of Radioactive Waste and Carbon Dioxide in the Light of Climate Change Psychological Perspectives on the Geological Disposal of Radioactive Waste and Carbon Dioxide Section B Regional Assessments Comparative Assessment of Status and Opportunities for Carbon Dioxide Capture and Storage and Radioactive Waste Disposal in North America Comparing the Geological Disposal of Carbon Dioxide and Radioactive Waste in Western Europe Carbon Dioxide and Radioactive Waste in Central and Eastern Europe: A Regional Overview of Geological Storage and Disposal Potential Comparison of the Geological Disposal of Carbon Dioxide and Radioactive Waste in European Russia Comparison between Geological Disposal of Carbon Dioxide and Radioactive Waste in China Geological Disposal of Carbon Dioxide and Radioactive Waste in the Geotectonically Active Country of Japan The Geological Storage of Carbon Dioxide and Disposal of Nuclear Waste in South Africa Assessment of the Geological Disposal of Carbon Dioxide and Radioactive Waste in Brazil, and Some Comparative Aspects of their Disposal in Argentina Index

A comparative assessment of the post environmental issues for the geological disposal of carbon dioxide (CO2) and radioactive waste (RW) is made in this chapter. Several criteria are used: the characteristics of RW and CO2; their potential environmental impacts; an assessment of the hazards arising from RW and CO2; and monitoring of their environmental impacts. There are several differences in the way that the long-term safety of the disposal of RW and CO2 is regulated and evaluated. While the regulatory procedures relating to the development of a facility for the disposal of RW in many countries with nuclear power programmes are well defined having evolved over several decades, those relating to CO2 disposal are less well developed. The results of this assessment show that, despite key differences, many of the approaches addressing environmental issues are similar. Additionally, much can be learned from the RW disposal experience which will be particularly relevant to the assessments of site performance for CO2 within a regulatory framework, particularly in the methods and approaches to long-term site performance assessment.KeywordsCarbon dioxide storageEnvironmental impactsRadioactive waste disposalTechnology comparison

The public perception of ultimate disposal facilities for Radioactive Waste (RW) and carbon dioxide (CO2) is crucial for the selection, construction and operation of such sites. This paper presents a cross-national comparison of the public perceptions of ultimate disposal facilities for RW and CO2 in the Czech Republic, Germany and Lithuania. The results of the comparison revealed similarities and differences in public perceptions in the three countries, as well as similarities and differences in the public perception of the two issues of RW and CO2 disposal. Key lessons learnt from the comparisons are that (a) public knowledge about RW and CO2 disposal is still low, (b) misconceptions about RW and CO2 disposal are widespread, (c) risk perceptions of CO2 disposal sites among the public might be influenced by risk perceptions of RW disposal sites and (d) the social context of public perceptions should be taken into account.

The deep subsurface biosphere has been regarded as an emerging topic in geo-bioscience and industry for the past few decades, and has been approached by terrestrial and seafloor drillings. Terrestrial sites have better proximity and greater relevance to the anthroposphere and technosphere, i.e., human habitats and societies, than do seafloor sites. Therefore, understanding the subterranean biosphere has more direct importance to issues related to a sustainable civilization, and issues such as formation/maturation of hydrocarbon reservoirs and ore deposits, disposal of radioactive wastes and carbon dioxide, and postulated association between seismogenic and microbial activities. Microbiological studies in the terrestrial deep subsurface have been prompted to respond to such human-related issues, and microbial life in sedimentary and crystalline rocks as well as pore-filling fluids has been studied to evaluate rock stability and (im) mobilization of redox-sensitive elements/nuclides, for instance. This is in contrast to subseafloor microbiology, which focuses more on microbial interactions with hydrothermal circulation, relevant biogeochemical processes including gas hydrate formation, associated diversity of life, and modern analogs of origin-of-life. Avoiding man-induced contamination of cored samples and pumped fluids has been a microbiological issue. Technical (both instrumental and operational) measures to minimize contamination were first developed in subterranean microbiology, because of easier accesses to test sites for repetition, evaluation, improvement, etc. of attempted measures on land. Then, anti-contamination expertise was introduced into subseafloor practices, and anti-contamination protocols and facilities are now better developed by the Integrated Ocean Drilling Program (IODP) than the International Continental Scientific Drilling Program (ICDP). Newly developed techniques are also applied to measure/monitor geological and geochemical parameters that are used to characterize microbial habitats and processes occurring there. Lessons from subterranean microbiology are directly applicable to subglacial microbiology that may retrieve microbial life from sub-million-year-old ice cores, although additional measures are needed for glacier drilling. Because land and icy surfaces are common in Earth-like planets or potentially life-bearing satellites, lessons (experiences and expertise) from subterranean microbiology should be applicable to astrobiological searches for extraterrestrial life.

The principal aim in geological disposal of solid radioactive wastes is to provide long term isolation of the wastes from the accessible environment, so that most of their radionuclide content can decay to stable products. However, on very long timescales, small quantities of some long lived radionuclides can be transported back to the biosphere, typically by migration in groundwaters. In these circumstances, there is a need to determine whether the releases that are assessed to occur give rise to radiological impacts that are judged to be acceptable. There is, therefore, a need to have tools in place to calculate the distribution and transport of radionuclides in the range of biosphere systems that may exist in the future, and to evaluate the radiological impacts of those radionuclides on hypothetical future individuals and population groups. Furthermore, criteria have to be developed by which the acceptability of these radiological impacts can be judged. In this paper, an account is given of the radiological protection criteria that have been developed for geological disposal of radioactive wastes. This outlines international and national regulations and guidance, with a particular emphasis on material relevant to the UK. The regulations and guidance emphasise the need to undertake assessments applicable to very long timescales, sometimes of the order of a million years, and to ensure that individuals or small population groups do not incur annual radiation exposures or risks in excess of specific limits, targets, or constraints. Such assessments require innovative approaches to characterising the range of potential environments that may occur at any specific site and to modelling radionuclide transport through those environments. In order to develop and justify such innovative approaches, it is appropriate to complement assessment studies with a substantial programme of research and site characterisation activities. Therefore, having set out the criteria relevant to geological disposal of radioactive wastes in the UK, an account is given of the approach adopted by UK Nirex Ltd for demonstrating compliance with those criteria, emphasising the role of biosphere modelling in that approach and the close links with both a long term, generic research programme and the site characterisation studies undertaken at Sellafield (Cumbria, UK). Finally, some reflections are provided on issues arising from the work undertaken to date. In particular, attention is given to the role of the biosphere component of an assessment in determining the acceptability of a proposed facility. Specifically, emphasis is placed on the need to complement acceptance criteria with a methodology for demonstrating compliance that is consistent with the principles upon which the acceptance criteria were based.

The principal aim in geological disposal of solid radioactive wastes is to provide long term isolation of the wastes from the accessible environment, so that most of their radionuclide content can decay to stable products. However, on very long timescales, small quantities of some long lived radionuclides can be transported back to the biosphere, typically by migration in groundwaters. In these circumstances, there is a need to determine whether the releases that are assessed to occur give rise to radiological impacts that are judged to be acceptable. There is, therefore, a need to have tools in place to calculate the distribution and transport of radionuclides in the range of biosphere systems that may exist in the future, and to evaluate the radiological impacts of those radionuclides on hypothetical future individuals and population groups. Furthermore, criteria have to be developed by which the acceptability of these radiological impacts can be judged. In this paper, an account is given of the radiological protection criteria that have been developed for geological disposal of radioactive wastes. This outlines international and national regulations and guidance, with a particular emphasis on material relevant to the UK. The regulations and guidance emphasise the need to undertake assessments applicable to very long timescales, sometimes of the order of a million years, and to ensure that individuals or small population groups do not incur annual radiation exposures or risks in excess of specific limits, targets, or constraints. Such assessments require innovative approaches to characterising the range of potential environments that may occur at any specific site and to modelling radionuclide transport through those environments. In order to develop and justify such innovative approaches, it is appropriate to complement assessment studies with a substantial programme of research and site characterisation activities. Therefore, having set out the criteria relevant to geological disposal of radioactive wastes in the UK, an account is given of the approach adopted by UK Nirex Ltd for demonstrating compliance with those criteria, emphasising the role of biosphere modelling in that approach and the close links with both a long term, generic research programme and the site characterisation studies undertaken at Sellafield (Cumbria, UK). Finally, some reflections are provided on issues arising from the work undertaken to date. In particular, attention is given to the role of the biosphere component of an assessment in determining the acceptability of a proposed facility. Specifically, emphasis is placed on the need to complement acceptance criteria with a methodology for demonstrating compliance that is consistent with the principles upon which the acceptance criteria were based.

Based on the diagenesis, classification and its physical, mechanical, and hydromechanical properties of fractured rock, this paper describes the current status of the fractured rock seepage models and their characteristics. Especially from the point of the safety assessment of the geological disposal of the high level radioactive waste, the discrete fracture network model, the equilibrium continuous medium model and the double media continuous model have been elaborated, and has been analyzed and compared with each other. Furthermore, the double fracture systems for rock flow have been introduced as the much better suitable seepage model for the geological disposal of the high level radioactive waste. In the double fracture systems seepage model, the seepage flow is described and reflected by the main fracture system, and the water store property is given by the subordinate fracture system. The appropriate seepage model for the geological disposal of the high level radioactive waste can be achieved through the double fracture systems, combined with the hydrological testing data in site and other geological information.

<p>Clay minerals are the main promising materials for engineering safety barriers in the disposal of radioactive waste in geological formations. Clays have high chemical stability, good sorption properties, and low diffusion coefficients. Bentonite clays combine the most optimal properties - high swelling pressure, low diffusion coefficients. At the moment, there is no unified international concept of the clay barrier density and its composition. Also, the parameters of the influence of biogenic processes on the properties of clay materials have not been correctly determined. It is planned to use of bentonite barrier between the metal container and the external environment in the design of the supercontainer for the new disposal of radioactive waste in the Nizhnekanskiy gneiss massif.</p><p>Within the studies of microbiological processes in the Yeniseisky disposal site, big attention will be paid to clay barriers as sources of biogenic elements in the system and microflora and organic and inorganic carbon.</p><p>Special attention will be paid to thermophilic microorganisms characterized by high growth rates and high levels of metabolic processes, which, along with the extreme impact of radioactive waste (temperature, gas release) on a site in the mountain range, can lead to the destruction of safety barriers.</p><p>Based on the data of phylogenetic analysis of the 16S rRNA gene sequences in clay materials, which are planned to be used as a barrier material, bacteria of the fermentative type of metabolism, capable of forming biogenic gases and organic acids, sulfate-reducing microflora, and a wide variety of microorganisms of the iron cycle were found. We investigating the processes under conditions corresponding to both the internal and external conditions of the clay barrier. As a result of our studies, in model experiments, the effect of microflora activation by radiolysis products, carbon steel corrosion products, hydrogen, and carbon dioxide was found. A thermophilic microbiota was found in samples with bentonite clays of the Khakass and Dinosaur deposits cultivated at temperatures of 50, 70, 90° C. High content of aluminum and silicon amorphous oxide phases was found in the liquid phase after cultivation, and an increase in bioleaching was observed with increasing temperature. Screening of biocidal additives was performed to suppress microbial activity, primarily sulfate reduction. The most effective, thermally stable biocide with prolonged action was polyhexamethylguanidine at a concentration of 0.5 wt. %.</p>

In a deep geological repository (DGR) for the long-term disposal of radioactive waste, gases (e.g., hydrogen (H2), carbon dioxide (CO2) and methane (CH4)) can be generated through a number of processes, such as corrosion of various metals and alloys and degradation of organic materials. If gas induced pressure exceeds the containment capacity of the engineered barrier systems (EBS) or the host rock, the gases could migrate through these barriers and potentially expose people and the environment to radiation. Therefore, a good understanding on the long-term performance of these barriers against gas migration is an important component in DGR design and safety assessment. In the present work, a numerical model has been developed to simulate the diffusion of CO2 (one of the gas species) in the near field of a DGR with the generation from related chemical reactions. The generation of CO2 was investigated to determine if it is a critical factor to impact the DGR safety under Canadian geological formations. A commercial computational fluid dynamics (CFD) code, ANSYS Fluent was used for the calculations. The model considered pH and temperature effects on CO2 migration under Canadian DGR geochemistry conditions.

Performance assessments for the geological storage of carbon dioxide: Learning from the radioactive waste disposal experience

In the 1980s, HADES (High-Activity Disposal Experimental Site) was the first underground research laboratory (URL) dedicated to the study of the geological disposal of radioactive waste in a deep clay formation, the Boom Clay. It was not until the early 2000s, after a siting process, that ANDRA implemented the Meuse/Haute-Marne URL, in the Callovo-Oxfordian formation at a depth of about 500 m in order to develop the Cigéo project (French industrial centre for geological disposal). ANDRA therefore relied heavily on the work carried out in HADES, through numerous co-operation projects (participation in in situ experiments) both between ANDRA and ONDRAF/NIRAS and SCK CEN (EURIDICE) and/or with Mont Terri consortium, and within European projects (CLIPEX, RESEAL, etc.). This was driven by a dual objective: (1) to prepare its own experimental programmes in the Meuse/Haute-Marne underground laboratory (methodology, experimental devices and protocols, etc.); and (2) to acquire general knowledge on the behaviour of argillaceous rocks, in particular in terms of similarity and differences between the various argillaceous rocks. This paper illustrates the contribution of HADES to the ANDRA programme. This concerns the characterization of the claystone behaviour, host rock and swelling clay-based seals (hydromechanical, thermo-hydromechanical, excavation damaged zone, etc.), and the design and the behaviour of underground structures and seals in deep clay formation (constructability, lining/support, etc.).