The Microbiology of Nuclear Waste Disposal

The Microbiology of Nuclear Waste Disposal is a state-of-the-art reference featuring contributions focusing on the impact of microbes on the safe long-term disposal of nuclear waste. This book is the first to cover this important emerging topic, and is written for a wide audience encompassing regulators, implementers, academics, and other stakeholders. The book is also of interest to those working on the wider exploitation of the subsurface, such as bioremediation, carbon capture and storage, geothermal energy, and water quality.

Planning for suitable facilities in the U.S., Europe, and Asia has been based mainly on knowledge from the geological and physical sciences. However, recent studies have shown that microbial life can proliferate in the inhospitable environments associated with radioactive waste disposal, and can control the long-term fate of nuclear materials. This can have beneficial and damaging impacts, which need to be quantified.

• Encompasses expertise from both the bio and geo disciplines, aiming to foster important collaborations across this disciplinary divide
• Includes reviews and research papers from leading groups in the field
• Provides helpful guidance in light of plans progressing worldwide for geological disposal facilities
• Includes timely research for planning and safety case development

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 22, 2020
• ISBN: 9780128186961

Book preview

Republic

Introduction

Jonathan R. Lloyda; Andrea Cherkoukb, a Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester, United Kingdom, b Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

The nuclear fuel cycle has generated large quantities of higher-level radioactive waste, and the preferred long-term management solution for this legacy is storage or disposal into a deep geological repository. This is considered a grand challenge for our society. There are many concepts for disposal, dictated by factors including the wasteforms and host geology, but a common theme is the use of a multibarrier system including the container where the waste is emplaced, a geotechnical barrier (e.g., bentonite, cement, or salt breeze), and the final geological barrier (e.g., crystalline, salt, or clay rock is favored). Robust safety cases are prepared for repository operation, and these have been largely built on abiotic interactions within the barrier system. However, there is increasing evidence that microorganisms may colonize areas within the disposal facility, adapting to the extreme conditions present. Propelled by recent advances in genomics, our understanding of extremophile microbiology, including surveys of an extensive deep biosphere, it is becoming clear that microbial processes could play a significant role in controlling the long-term performance of a deep geological repository. For example, microorganisms, which are present in the geotechnical and geological barrier materials as well those introduced during the construction of the repository, may impact on wasteform evolution in situ, multibarrier integrity, and ultimately radionuclide migration from the repository into the surrounding geosphere. An important concern is, therefore, the quantification of specific measurable impacts of microbial activity on safety cases under repository-relevant conditions, leading to refinements of current or developing safety case models currently being implemented to evaluate the long-term evolution of radioactive waste repositories. This is a rapidly developing area of frontier science, and this book links pioneering microbiological work on a range of analogue sites, to newer laboratory and underground research facility studies, that aim to assess and quantify the potential long-term impact of microbes on the safe long-term disposal of nuclear waste. Much of this underpinning work was generated through the recently completed EU program MIND (www.mind15.eu), which was a substantial cross-European study, comprising 15 research groups with guiding input from waste management organizations from the European Union, United States, and Asia.

Microbial metabolism is linked to the availability of nutrients and energy sources, and it is, therefore, important to understand the potential substrates that may support life in a geological disposal facility. Chapter 1 of this book offers an overview of the organic materials present in the large volumes of intermediate level (ILW) or long-lived low-level waste (LLW) destined for disposal. Key organic materials are discussed in detail, and these include bitumen, organic ion exchange resins, halogenated and nonhalogenated polymers, and cellulose materials and these are discussed in this chapter in the context of national inventories. Although focusing on EU inventories, the materials described will be present in wastes in countries outside Europe. Once disposed, organic materials will provide a major source of organic carbon that has the potential, following degradation, to fuel a range of anaerobic microbial processes that are relevant to the safety of LLW/ILW repositories. Understanding the biodegradation of these materials is also important as microbial processes may play a role in controlling the fate of organic complexants, which could facilitate the transport of radionuclides from the repository. This important topic is picked up in other contributions to this volume including Chapter 10, which offers an overview of chemical, radiolytical, and microbial degradation processes of cellulose, PVC, ion exchange resins and bitumen, and also Chapter 8, which develops the concept of a biobarrier that could develop to limit radionuclide transport, fueled by some of these organic substrates.

Early in this book, there is a recognition that much of our emerging understanding of the microbiology of nuclear waste disposal has been based on the study of sites that are natural analogues for geological disposal facilities. For this reason, Chapter 2 gives a review of the extensive literature on this topic, including sites that are analogues for facilities containing clay and cement barriers, and archeological studies that offer information of the long-term fate of materials mimicking metallic containers.

The following chapters then focus on the microbiology of specific disposal concepts that encompass crystalline, salt, and clay systems. Chapter 3 gives an overview of key aspects of the Fennoscandian Shield deep crystalline bedrock biosphere identified to date, with examples of putative biogeochemical cycles that prevail in these settings, and may impact on radwaste disposal in this environment. The microbiology of clay-rich environments, including bentonite buffer materials, has also attracted much recent attention, but clay substrates can prove challenging systems for microbiologists to study. Chapter 4, therefore, provides a state-of-the-art review of microbial characterization methods available for work in this area. The efficiency of different DNA extraction methods from clay materials is compared, alongside the performance of various sequencing and bioinformatic pipelines used for 16S rRNA gene profiling of microbial communities. Moreover, non-DNA-based techniques used to assess microbial activity and viability in clay samples are addressed. Chapter 5 summarizes the potential for microbial colonization of salt-based nuclear waste repositories, including a discussion of the types of microorganisms that could be expected, and the impacts that they could have on repository performance.

Chapter 6 focuses on microbially influenced corrosion (MIC), the control of which is crucial to maintain the integrity of metallic cannisters used in multibarrier systems in deep geological radioactive waste repositories. This chapter describes the principles of biofilm development on metal surfaces, reviews the microorganisms involved in MIC (with a strong focus on sulfate-reducing bacteria) and considers their potential for colonization in situ. To illustrate these points, the results of a long-term study on carbon steel corrosion in deep natural groundwater containing sulfate-reducing bacteria is included, focusing on the impact of temperature on biofilm formation and corrosion behavior.

Bentonite barriers can be used to control microbial activity (including MIC) and therefore Chapter 7 reviews the latest findings on the structure and composition of microbial communities in bentonites, with an emphasis on repository relevant conditions (high temperature, high pressure, presence of electron donors/acceptors, etc.), and including both, laboratory and large-scale experiment results. In addition, the impact of microbial processes on the mobility of radionuclides at the bentonite/microbe/radionuclide interface are reviewed. In contrast, Chapter 8 looks at the largely beneficial impact of microbial colonization of the alkaline disturbed zone of cementitious intermediate-level waste repositories, introducing the concept of a microbial biobarrier which may attenuate the long-term transport of radionuclides from the repository into the geosphere. A range of processes is considered including chelate biodegradation, radionuclide biomineralization, and gas (e.g., hydrogen) metabolism. Further information on the microbial processes that can result in radionuclide immobilization is covered in Chapter 11. The priority elements of focus include uranium, plutonium, neptunium, technetium, selenium, and iodine.

Chapter 9 discusses microbial impacts on gas production in ILW and LLW, which is important to the safety of near-surface and deep geological nuclear waste repositories. Microbial processes are of principal importance in the generation of methane from cellulose containing wastes, but also have other effects on gas production, such as by consuming hydrogen generated by corrosion and radiolysis. In this chapter, the complex role that microbes play in the production and attenuation of gases from cellulose-containing LLW/ILW is discussed, based on understanding gained from a long-term study of gas generation from the disposal of LLW at Okiluoto, Finland.

A key challenge in understanding the long-term impact of microorganisms on the performance of deep subsurface repositories is extrapolating from relatively short-term experiments to long-term (many thousands of years) predictions. Analogue studies can help build conceptual models of the processes (as discussed earlier), while forward modeling can help further support safety case development. Chapter 12 gives an overview of how models of microbial processes can be used to underpin and provide rate data and other quantitative inputs for safety assessment models of radiological impacts. An approach to modeling microbial kinetic processes is described, based on the Generalized Repository Model (GRM). In biogeochemical reactive-transport models such as GRM, microbial processes can be coupled to corrosion, chemical and transport processes, which affect gas generation and radionuclide migration.

Finally, with the increasing acceptance that microbial processes should be considered when developing safety cases for deep geological repositories, it is becoming more important for microbiologists to play a role in communicating their science with a wide range of stakeholders. In Chapter 13, communication guidelines are provided to help facilitate these discussions. Different theories of risk perception and risk communication are described, and results of an online survey presented, which explores how different communication stimuli affect the perception of the role of microbes in radioactive waste management RWM (RWM) among different target groups.

Radwaste disposal is a multidisciplinary grand challenge, and this book is aimed at a wide audience encompassing scientists from many areas, including educators and students, regulators, implementers, and other stakeholders. We would like to thank all authors for their contributions.

Chapter 1: Organic-containing nuclear wastes and national inventories across Europe

Liam Abrahamsen-Millsa; Joe S. Smalla,b    a National Nuclear Laboratory, Chadwick House, Warrington, United Kingdom

b Dalton Nuclear Institute, University of Manchester, Manchester, United Kingdom

Abstract

A wide range of organic-containing wastes exists throughout Europe, the majority of which can be classed as intermediate-level or long-lived low-level waste. In some countries, organic-containing wastes have already been disposed within near-surface or geological disposal facilities, whilst in others, the wastes are stored pending the availability of a suitable disposal facility. The organic materials can be summarized as follows: bitumen, organic ion-exchange resins, halogenated and nonhalogenated polymers, cellulose materials, and other polymers such as rubber, polyurethane, polyamides, etc. The amounts and proportions of these organic materials vary by country and this reflects their different nuclear industry and power generation activities. In many countries, ion-exchange resins dominate the inventory of organic ILW, where it results from nuclear power generation using light-water reactors. Higher inventories of halogenated plastics and other related plastic and cellulose wastes result from countries that undertake fuel reprocessing and have a larger inventory from nuclear research. In addition to inorganic cement encapsulants, bitumen has been commonly used to condition a range of wastes. Once disposed of, these organic materials will provide a major source of organic carbon that has the potential, following degradation, to fuel anaerobic microbial processes.

Keywords

Waste; Inventory; Organic; Bitumen; Ion exchange; Resins; Plastic; Polymer; Cellulose

1: Introduction

This chapter collates and reviews information from published sources concerning anthropogenic organic wastes present in intermediate-level waste (ILW) and some low-level waste (LLW) considered for geological disposal throughout Europe. For most countries, geological disposal is the preferred option for the disposal of higher activity radioactive wastes. The nature and quantities of wastes requiring disposal vary between nations, depending on factors including their history of power generation, fuel reprocessing, industry and research activities. In some countries, spent fuel reprocessing leads to the generation of a complex mixture of waste types, whilst in countries with an open fuel cycle, spent fuel will be disposed of directly. LLW and ILW resulting from reprocessing and the operation of nuclear power plants are compositionally diverse, heterogeneous, and are more likely to be directly affected by microbial activity than spent fuel and vitrified high-level waste (HLW), which may lack vital elements such as C and N for biomass growth. In addition, the physical nature, high radiation dose, and elevated temperature of spent fuel and HLW may limit the viability of microbial processes in these wastes. The effects of microbial activity on the engineered barrier system (waste canisters and bentonite backfill) for HLW and spent fuel is of primary significance to repository safety (Chapters 6 and 7).

The presence of organic materials in LLW and ILW is particularly relevant to microbiology in nuclear waste disposal as it provides a source of organic carbon for heterotrophic microbial growth and provides an energy source (electron donor) for terminal electron-accepting processes such as sulfate reduction, fermentation processes, and methane gas generation (Chapter 9). The presence of organics in LLW and ILW can directly affect repository safety, through the effects of soluble organic complexants, which can enhance the solubility and reduce the sorption of some radionuclides. Typically, such organic complexants are formed by hydrolysis of cellulose and other polymers, but their effects may be mitigated by microbial activity which enables complete degradation and oxidation to CO2 (Chapters 8 and 10). When assessing how the microbial activity will influence the evolution of organic-containing wastes in a repository, it is important to consider the different waste types and inventories that will be disposed.

Whilst there is some consistency in approaches, countries often classify and categorize wastes differently; some have different definitions and thresholds for LLW, ILW, HLW, etc. Some place importance on the origin of the material, how long-lived the activity is, and heat generation, for example. LLW that requires geological disposal normally includes wastes with alpha-emitting radionuclides such as plutonium- contaminated materials. In this chapter, the abbreviations ILW and LLW are used where appropriate. Other abbreviations are also in use, which categorize the wastes by half-life, for example, the term ‘long-lived low- and intermediate-level radioactive wastes’ (LILW-LL) is used in Belgium. In this chapter, these country-specific abbreviations are defined and used when describing specific wastes.

The information presented in this chapter includes inventories of existing near-surface repositories: SFR repository (Sweden), VLJ repository (Finland), and repositories in the Czech Republic, as well inventories of countries at various stages of planning for deep geological disposal of ILW: Belgium, France, Spain, Switzerland, the Netherlands, and the United Kingdom. A fuller description can be found in the MIND Project Deliverable D1.1 A Review of Anthropogenic Organic Wastes and Their Degradation Behaviour (Abrahamsen et al., 2015).

A wide range of organic materials is present in ILW and LLW requiring geological disposal, including:

1.1: Bitumen

Organic materials such as bitumen and some specific polymers [e.g., vinyl ester styrene (VES) and epoxy resins] are used to encapsulate ILW. These materials are typically used to encapsulate water-soluble residues from reprocessing and effluent treatment, such as sludges and concentrated salt solutions. They have also been used to encapsulate ion-exchange resins, ashes, and miscellaneous plastic, and other solid wastes.

1.2: Organic ion-exchange resins

Organic ion-exchange resins (IERs) are used in nuclear facilities to remove radioactivity from process liquids and wastes streams. Significant amounts of IERs are used to reduce the radioactivity of the primary circuit of pressurized and boiling water reactors (PWR/BWR). Organic IERs may also be used to reduce levels of radioactivity in fuel storage ponds and to treat effluents from reprocessing plants. IERs for use in the nuclear industry have been designed to be radiation resistant. Such resins typically comprise a styrene-divinylbenzene copolymer with amine or sulfonate functional groups for anion and cation exchange, respectively.

1.3: Halogenated and nonhalogenated polymers

Halogenated polymers mainly comprise polyvinylchloride (PVC), which is used in a range of processes within the nuclear fuel cycle and research activities. Plastic sheeting is used to wrap miscellaneous waste, is used in glove box posting bags, protective suits, barriers, and other packaging. As well as PVC, these materials include other chlorinated and fluorinated polymers. Nonhalogenated polymers include polyethylene and polypropylene and are used for many of the same applications as their halogenated counterparts. Organic polymers often contain a variety of other organic compounds such as plasticizers to provide flexibility, and fire retardants.

1.4: Cellulose materials

Cellulose is a natural polymer and is often a significant contributor by mass and volume to LLW and some ILW inventories due to its use in the form of cotton, clothing, paper, tissue, etc. within the nuclear, medical, and research industries. It may be present in wastes destined for geological disposal if contaminated with plutonium or other long-lived radionuclides. Cellulose is of particular significance due to the formation of the strong radionuclide complexant isosaccharinic acid (ISA) formed by alkaline hydrolysis under the hyperalkaline (pH >  12) conditions of the cementitious engineered barrier system of LLW/ILW repositories (e.g., Glaus and Van Loon, 2008).

1.5: Other organic materials

Other organic materials present in ILW include rubber, polyurethane, polyamides, nylon, and epoxy resins. Cement encapsulants may contain organic additives, known as superplasticizers, used to decrease the viscosity and reduce the water content of cement slurry and to optimize the encapsulation and curing process. Older additives were based on vinyl copolymers, but more recently developed reagents are based on polycarboxylate ethers (PCE) and are used at a lower concentration. Other organic complexants such as amino carboxylic acids (EDTA, DTPA, and NTA) may also be present in trace amounts in some ILW streams.

2: Overview of the nature of anthropogenic organic polymers and materials

Organic polymers can be classified in terms of their mode of polymerization, which reflects the chemical structure and stability of the polymer:

Addition polymers C double bond. Important addition polymers include PE and PVC which are formed by polymerization of ethene (CH2CH2) and vinyl chloride (chloroethene; CH2CHCl), respectively. Addition polymers are formed of chains of carbon atoms with strong C-H bonds and are resistant to biodegradation.

Condensation polymers are formed by the elimination of water or other small molecules from two or more reactant monomers. Common condensation polymers include polyamides and polyesters; here the polymer structure contains polar amide or ester groups, which are susceptible to biodegradation. Cellulose is a natural condensation polymer comprising glucose monomers.

Polymers comprising chains of monomers formed by addition or condensation reactions may form cross-linked structures, which are induced by heat, pressure, and radiation, or by chemical effects, e.g., pH. Vulcanization of rubber is a common example of cross-linking in response to temperature, which can be accelerated by the addition of sulfur or specific sulfur catalysts. Thermoplastic polymers such as PE may become brittle under UV radiation due to cross-linking. Copolymers formed by two monomers can be used to form highly cross-linked structures. Styrene and divinylbenzene (DVB) react together to form the copolymer styrene-divinylbenzene, which is a commonly used ion-exchange resin. Under irradiation, some polymer structures tend to cross-link and are stable, whilst others will degrade. This allows the allocation of polymers into two broad groups, as shown in Table 1.

Table 1

Bitumen is a highly viscous form of petroleum, which in its refined form is used in the nuclear industry as a thermoplastic encapsulant. Bitumen is not a polymer material, but a mixture of saturated hydrocarbons, aromatics, polar aromatics, and heterocyclic compounds. The viscosity is related to the content and molecular weight of saturated hydrocarbons present in which other more complex organics are dissolved. Although it occurs in natural deposits, bitumen used in industry is a by-product of crude oil refining. For radioactive waste encapsulation, two forms have generally been manufactured: soft bitumen, which is obtained from the residue of crude oil distillation; and hard bitumen, formed by blowing air through certain petroleum fractions.

3: National inventories

In this section, inventory information concerning the nature and quantities of organic-containing ILW and LLW is presented. Inventory information is presented in alphabetical order for countries with stocks of organic wastes that may be considered for geological disposal. Additional information is also provided for operating underground disposal facilities for ILW and LLW disposal in the Czech Republic, Finland, and Sweden.

Due to differences in the classification of waste types between countries, it is not always possible to make direct comparisons of the quantities of certain waste types held. However, the inventory data are useful in identifying the key organic waste types destined for geological disposal across Europe.

In the figures shown, the waste types include bitumen used as an encapsulant, but do not specifically include cemented wasteforms, since these are not considered to be an organic wasteform, even though they may contain low levels of organic species, such as superplasticizer additives.

3.1: Belgium

The Belgian Agency for Radioactive Waste and Fissile Materials (Organisme National des Déchets Radioactifs et des Matières Fissiles/Nationale Instelling voor Radioactief Afval en Splijtstoffen or ONDRAF/NIRAS) is responsible for all aspects of the management of radioactive waste generated in Belgium. There are three main sources of radioactive waste in the country: nuclear power generation from seven reactors, spent fuel reprocessing, and research performed at the Belgian Nuclear Research Center (SCK  ∙  CEN), the Institute for Reference Materials (IRMM) and some universities. Wastes are categorized as one of the three main internationally defined categories (LLW, ILW, HLW). Distinctions are made based on the radiological activities of the waste and possible heat generation. Wastes that have similar packaging, storage, and potential disposal methods are assigned to 20 classes (ONDRAF/NIRAS, 2001) that are finally allocated to about 60 families (ONDRAF/NIRAS, 2013).

In Belgium, long-lived low and intermediate-level waste (LILW-LL) is encapsulated in either bitumen or cement following various treatment or processing steps. Consequently, bitumen is the most important organic fraction of the waste by volume. Both soft and hard forms of bitumen have been used, the latter being the Eurobitum type and comprising around 80% of bituminized wastes in Belgium.

A summary of the relative amounts of organics comprised in the Belgian LILW-LL waste is presented in Fig. 1. Around 90% of the organics present in the LILW-LL comprises bitumen, 4% are halogenated polymers which are mostly PVC (including phthalate plasticizers), 2.5% comprises cellulose (wood, paper, cotton, etc.), 2% are nonhalogenated polymers, including resins (mostly polystyrene-based) and polyethylene. Among others, the following contaminants are also likely to be present in the waste at very low concentrations: EDTA, citrate, tributylphosphate, oxalic acid, and tartaric acid (Abrahamsen et al., 2015).

Fig. 1 Distribution of organic materials (% volume) in the LILW-LL waste in Belgium. Data from Abrahamsen, L., Arnold, T., Brinkmann, H., Leys, N., Merroun, M., Mijnendonckx, K., Moll, H., Polvika, P., Ševců, A., Small, J., Vikman, M., Wouters, K., 2015. A Review of Anthropogenic Organic Wastes and Their Degradation Behaviour. MIND Project Deliverable D1.1, EC Grant Agreement 661880.

3.2: Czech Republic

The Radioactive Waste Repository Authority (SÚRAO) has statutory responsibility for the safe disposal of all radioactive waste produced in the Czech Republic. Radioactive waste is categorized as follows: nuclear fuel cycle waste, institutional waste, decommissioning liabilities, used sealed sources, and mining and milling waste (SÚJB, 2017). Wastes are categorized as gaseous, liquid, and solid, and are further categorized based on storage requirements due to radioactivity levels, presence of long-lived isotopes, and heat generation.

Three low- and intermediate-level waste repositories are currently in operation in the Czech Republic: the Bratrství repository, near Jáchymov, the Richard repository, near Litoměřice, and the Dukovany repository sited at one of the country’s nuclear power plants. Wastes deemed not acceptable for surface or near-surface disposal are stored prior to placement within a future geological disposal facility (SÚRAO, 2014).

The majority (around 80% volume) of radioactive waste produced in the Czech Republic arises from nuclear power plant operations at the Dukovany and Temelín plants. Liquid wastes, such as concentrates, are bituminized and stored in 200 L galvanized drums (SÚJB, 2017). Since 2010, an aluminosilicate geopolymer matrix has been used for encapsulating sludge and spent polystyrene ion exchangers. In 2014, 1189 barrels (200 L) of bitumen and 1053 barrels of aluminosilicate conditioned waste were stored (SÚRAO, 2014). The number of bitumen barrels each year remains constant, but there has been an increase in the numbers of barrels using the aluminosilicate matrix since 2010.

The total volumes of liquid wastes currently stored and awaiting encapsulation are 1018 m³ active water concentrates and 44 m³ used sorbents (spent ion-exchange resins) from the Dukovany NPP, and 310 m³ active water concentrates and 67.3 m³ used sorbents (spent ion-exchange resins) from the Temelín NPP, as of December, 2016 (SÚJB, 2017). It is expected that these materials will be disposed of to near-surface repositories once conditioned.

Institutional radioactive waste generated in hospitals, agriculture, industry, and research accounts for roughly 20% of the total volume of radioactive waste. Annually, around 450 tons of LLW and ILW originates from medicine, research, and other nuclear technologies (SÚJB, 2015). There are several hundreds of producers of institutional radioactive waste, the most important being ÚJV Řež a.s., which produces about 90% of this kind of waste. Institutional radioactive waste comprises a wide range of material types (Fig. 2) and is more variable than that of nuclear power plants. Around half of the institutional waste comprises organic materials, with wood and biological materials (that will be susceptible to biodegradation) comprising 27% of the waste volume and plastic (i.e., halogenated and nonhalogenated polymers) comprising 15% (Fig. 2).

Fig. 2 Distribution of materials (% volume) within the institutional waste in the Czech Republic. Data from Bromová, E. Vargončík, D., Sovadina, M. Simopt, 2013. Nuclear Energy and Energetics (Jaderná energie a energetika) ČEZ, in Czech.

3.3: Finland

In Finland, nuclear waste is primarily generated in the nuclear power plants at Loviisa and Olkiluoto. Radioactive waste is categorized according to the activity level into high-level waste (activity more than 10 GBq kg−  1; spent fuel), intermediate-level waste (1 MBq kg−  1–10 GBq kg−  1) and low-level waste (not more than 1 MBq kg−  1) (STUK, 2015).

The Finnish nuclear power companies Fortum Power and Heat Oy (Fortum, Loviisa, Finland) and Teollisuuden Voima Oyj (TVO, Olkiluoto, Finland) process and dispose of the LLW and ILW arising from the power plants at facilities on the existing sites. The Olkiluoto repository for operational waste (VLJ repository) consists of two rock silos, a hall connecting the two and auxiliary facilities constructed at a depth of 60–100 m inside the bedrock (see Chapter 9). Low-level waste is deposited in the rock silo inside a concrete box. Intermediate-level waste is deposited in the rock silo comprising steel-reinforced concrete (Posiva, 2012). The organic components of ILW at Olkiluoto comprise ion-exchange resins (powders and granules), while the organic components of LLW are maintenance wastes comprising cellulose and other polymers (Fig. 3). At Olkiluoto, ILW ion-exchange resins are encapsulated in bitumen in 200 L steel drums.

Fig. 3 Distribution (% volume) of organic LLW and ILW (resins) disposed at Olkiluoto as of 2014. Note: excludes bitumen used to encapsulate ion-exchange resins. Data from Posiva, 2015. Nuclear Waste Management of the Olkiluoto and Loviisa Nuclear Power Plants Summary of Operations in 2014. In Finnish.

The inventory of the wastes generated by Fortum comprises similar materials, with ion-exchange resins representing the majority (90%) of the radioactivity, but a low fraction of the volume (~  16%). Currently, ion-exchange wastes are stored in liquid prior to solidification in cement. LLW and ILW generated during operation of the Loviisa power plant is disposed of in the bedrock-excavated final repository (VLJ cave) owned and used by Fortum. The repository consists of a 1170-m-long access tunnel and hall facilities situated at a depth of about 110 m.

3.4: France

The French National Inventory (Andra, 2018) includes sources of radioactive waste from five economic sectors: nuclear power, defense, research, industry, and medical. Radioactive waste is classified into four main categories; high level, intermediate level, low level, and very low level. Waste is also classified according to its half-life, where long-lived waste contains a large quantity of radionuclides with half-lives longer than 31 years. High-level waste and long-lived intermediate-level waste (LL-ILW) is currently being stored until a geological disposal site is available.

LL-ILW comprises several waste package types with designation B1 to B9, and of these, the B2 wastes are notable in that they contain bituminized waste, while the B3 waste packages contain a variety of organic materials encapsulated in a cement matrix. Fig. 4 shows the distribution of organic materials present in some example B wastes. B3.1.2 includes wastes from the La Hague reprocessing site. Here the organic wastes comprise mainly chlorinated and non-chlorinated plastics encapsulated in a cement matrix. The chlorinated plastics include PVC, Hypalon and neoprene. The non-chlorinated plastics comprise polyethylene and polypropylene (Andra, 2009). A lower proportion of chlorinated organics is present in the more recent CBF-C'2 B3.1.2 wastes (Fig. 4). B3.1.3 wastes also comprise a large proportion of chlorinated plastics, including PVC or polyethylene sheeting, clothing, overshoes, cotton and fabrics, laboratory glassware, and various metal items (Andra, 2009). B3.3.7 comprises metallic and organic waste from maintenance and operation at the Marcoule site, which includes higher proportions of cellulose.

Fig. 4 Distribution (by mass) of organic materials in some French LL-ILW wastes. (A) B3.1.2 waste, CBF-C2’2 container; (B) B3.1.2 waste, CAC container; (C) B3.1.3 waste; (D) B3.3.7 waste. Data from Andra, 2009. JALON 2009 HA-MAVL—Référentiel de connaissances et modèle d’inventaire des colis de déchets à haute activité et à moyenne activité à vie longue—Tome 2. In French.

In addition to the organic wastes that arise from reprocessing and laboratory operations, a significant inventory of organic ion-exchange resins arises from nuclear power reactors in France operated by EDF. The EU Framework 7 CAST project (Rizzato et al., 2015) has studied the use of organic exchange materials used to decontaminate cooling water in pressurized water reactors in France. Cationic exchange resins are sulfonated polystyrene divinylbenzene copolymers, in hydrogen or lithium form depending on the application. Anion-exchange resins are of the strong base quaternary trimethylamine type, in hydroxide form. Spent resins are stored underwater for several months for short-lived radioactivity to decay before being processed using the Mercure process that encapsulates the materials in an epoxy resin within concrete containers for surface disposal.

Fig. 5 illustrates the distribution of organic wastes considered for geological disposal in the Dossier Argile (Andra, 2005). This projected inventory represents the waste arising from a scenario (S1a) which assumes that all the spent fuel unloaded by EDF power plants in France currently operating will be reprocessed. The total mass of organic waste is estimated to be 2.6  ×  10⁶ kg. This inventory of organic waste does not include the bitumen present in the B2 wastes (Andra, 2005) which have a mass of approximately 1.37  ×  10⁷ kg.

Fig. 5 Distribution of the forward inventory of organic LL-ILW materials by mass. Data from Andra, 2005. Evaluation of the Feasibility of a Geological Repository in an Argillaceous Formation. Dossier 2005 Argile.

3.5: Spain

The classification of radioactive waste in Spain defines two main categories (Enresa, 2006):

•Waste with low and medium level and short half-life (LILW) contains mainly beta-gamma emitting radionuclides with half-lives less than 30 years and which contain very low levels of long-lived radionuclides. LILW is disposed at the El Cabril nuclear facility.

•HLW contains long-lived alpha-emitting radionuclides in appreciable concentrations above 0.37 GBq/t, with a half-life of more than 30 years. This mainly includes spent fuel and vitrified waste but also includes medium high-level waste (MHLW), which is not suitable for disposal at the El Cabril facility.

In the category of LILW, 93% of the waste volume arises from nuclear power plants, with an estimated 36,300 m³ generated by 2028 (Enresa, 2006).

Fig. 6 illustrates the distribution of all the materials present in Spanish LILW that has been conditioned, excluding materials present at the nuclear power plants at that time. Of the total, 25% of the conditioned LILW inventory comprises resins used to clean cooling water of the light-water reactor power plants operating in Spain. A further 25% of the conditioned LILW comprises evaporator concentrates and smaller quantities of sludge and filters resulting from the treatment of cooling water and other liquid wastes produced at nuclear power plants. The resin, concentrate, sludge, and filter materials are conditioned in a cement matrix within 220 L drums.

Fig. 6 Distribution (% volume) of conditioned LILW in Spain in 2004. Data from Enresa, 2006. Inventory of Radioactive Waste and Spent Fuel Edition 2004.

The remaining solid waste comprising cloth, debris, metal components, personal protective equipment, paper, wood, etc. is divided into compactable and non-compactable LILW. Ion-exchange resins thus comprise the main organic material present in Spanish LILW, with compactable waste likely including cellulose and polymer materials. The amount and proportion of compactable and non-compactable solid wastes are anticipated to increase as nuclear sites are decommissioned (Enresa,