1

Introduction

Linda E. McKinleya, W. Russell Alexanderb

aVilligen, Switzerland

bBedrock Geosciences, Auenstein, Switzerland

1.1. Background and objectives

The disposal of radioactive waste (radwaste) is a hot topic. It involves attempting to solve what has been claimed to be one of the greatest challenges facing mankind – or indeed an insoluble problem. The waste itself is certainly unpleasant, the highest activity material being so radioactive that heat generation is one of the issues which has to be carefully considered during handling, storage and disposal. It is also being increasingly debated as concern about global warming refocuses attention on the lesser environmental impact of nuclear power. It is surprising, therefore, that few books exist which give a comprehensive overview of this field.

It is certainly not that there is a shortage of published material. Technical papers on various aspects of radwaste management appear in thousands of journals and there are many publications and series of conferences dedicated entirely to radwaste management and disposal. The national and international organisations working in this field also publish at a range of technical levels and, increasingly, much of such information is available on the internet. The problem may actually be too much information – in too diverse a range of topical areas – which makes achieving an overview an extremely difficult task.

There are fundamental problems with presenting an overview, associated with both the great diversity of technical fields involved and the very high performance standards now expected. Repositories should ensure that releases of radiation to the environment are orders of magnitude below natural background. Such a requirement is unique – release guidelines for other industries and wastes are specified in terms of orders of magnitude above natural levels. Not only are performance levels high, but these have to be assured for periods of time beyond normal human comprehension – hundreds of thousands or millions of years, or even for all time! The claim to meet such performance levels is often met with complete disbelief, which is hard to counter with simple supporting arguments.

Of course, the communication barriers are also associated with the recent highly publicised failures of the nuclear power generation community and the past lax standards associated with radwaste disposal – especially within military projects. Drastic failures in the safety culture and a trend to cover up failures have built a general feeling of

distrust. To gain acceptance, it is increasingly required to clearly explain the arguments supporting repository projects to all those with an interest – ranging from technical expert groups who are not specialists in this area to the general public.

The aim of the book is thus to present a critical review of the state-of-the-art in designing, siting, constructing and demonstrating the safety and environmental impact of deep repositories for radwaste. It is intended to provide a broad perspective of this multi-faceted, multi-disciplinary topic, with an appropriate level of detail to allow a nonspecialist to understand the fundamental principles involved and with extensive references to sources of more detailed information.

The emphasis is on ‘‘deep’’ geological disposal – at least several hundred metres to several kilometres below the land surface. Additionally, only radwaste is considered directly – even though such wastes often also contain significant chemotoxic or otherwise hazardous components. Many of the principles involved are generally applicable to other disposal options (e.g., near-surface or on-surface disposal) and, indeed, to other types of hazardous waste but this will be discussed only briefly.

Although the focus is on technical issues, emphasis will also be placed on how such issues can be communicated to all stakeholders – in particular the general public. If there is one major lesson which has been learned by the organisations responsible for radwaste management over the last couple of decades, it is that repository projects cannot be implemented without the acceptance of local communities. Indeed, such acceptance may be the biggest constraint on repository realisation in many countries.

The general principles discussed will be illustrated by examples from national programmes, but there will be no attempt to rigorously document the status of all such programmes (as such work exists elsewhere). Indeed, given the extreme vulnerability of repository projects to political whims, such a status report would be out of date within weeks of being written. Nevertheless, example sources of information on national programmes and some other useful international resources available on the internet are listed in Table 1.1.

Table 1.1

An example of sources of information available on the internet

The aim is to identify and discuss the key issues involved at a sufficient level to clearly distinguish the areas of general consensus from open questions or areas where controversy exists. This necessarily involves including socio-economic and public communication issues which, unfortunately, were rather neglected in the earlier stages of many national programmes. This undoubtedly contributed to many of the problems and delays that were subsequently experienced. This book hopefully marks the further emergence of a wider-based and more open approach to the entire field of radwaste management which, we hope, will remove this issue from the much more critical debate on how future demands for safe, environmentally friendly power can be met given the strains caused by rapidly expanding populations in a time of rapidly depleting resources. Regardless of any decisions taken today on the future (or otherwise) of nuclear power, radwaste exists and needs to be dealt with – and not ignored until it becomes a burden for future generations.

1.2. Content, format and presentation

The book consists of nine chapters written by acknowledged experts in particular technical areas. As their remit, the authors were provided with a rough breakdown of chapter content and were encouraged to adopt a standardised structure to ease readability and use as a source of reference. Chapters are, however, strongly co-ordinated and edited to standardise terminology, ensure consistency, maximise coverage and minimise overlaps or duplication.

The chapters have a common structure presenting, in turn:

The fundamental principles involved

State-of-the-art examples and case studies from relevant national programmes

Problem areas, open questions and communication of conclusions to key audiences

Sources of more detailed information (conventional literature and internet)

In Chapter 2, it is shown that, before the various options for managing the waste can be considered, it is necessary to invest significant resources in properly characterising the materials in question. To date, this fundamental tenet has not yet been appreciated by all national waste programmes1 and production of a fully characterised waste inventory should be a priority for all countries generating waste. Of note is that this should also cover research, industry and medical wastes from, e.g., high-energy particle accelerators or pharmaceutical research centres; these are likely to be much more ‘‘exotic’’ and hence potentially problematic for repository implementers than the relatively well characterised reactor wastes. A comprehensive inventory of all present waste production, complemented by estimates of historical wastes (which may be less well characterised) and potential future arisings (possibly for a range of different scenarios), forms the basis for development of an optimised programme for their safe management.

1 Indeed, it is probably more accurate to say that those programmes with a well characterised inventory are in a significant minority, including the UK, Sweden and Switzerland. Numerous other programmes have partially completed inventories, including Finland, Japan, the USA and Italy, but these do not include a full characterisation of all waste types.

In the early days of ‘‘atomic power’’, there was great optimism that a repository could be quickly constructed by a group of engineers with some ‘‘. . . suitably trained geologists’’ (NRC, 1957). Now, alas, we know that this was a little naive and that a radioactive waste disposal programme requires not only engineers and geologists but also physicists, biologists, chemists, metallurgists, transport specialists, communications and media experts, statisticians, lawyers – the list goes on and on. Chapter 3 discusses the range of disposal options which have been attempted and gives an overview of the experience gained – both positive and negative. To put this in context, the alternatives to geological disposal are considered and their limitations explained, thus providing the technical background for the general consensus that deep geological disposal is the only practical option for safe management of more toxic, longer-lived radioactive wastes within the constraints set by present international conventions. For completeness, a range of alternatives to the standard designs of radioactive waste repository are considered. These place a much higher weighting on acceptability to stakeholders, and in particular local populations, in recognition that this will probably be an essential requirement for success in all twenty-first century programmes.

A key feature of geological disposal is the power of the geological barrier. It is thus important to ensure that the site and host formation are suitable for assuring this role – both now and for required periods of hundreds of thousands of years or more into the future. In Chapter 4, the range of site selection strategies is examined, including relatively new approaches such as specifically (as compared to incidentally) seeking out volunteer communities, as has been initiated (in different forms) most recently in Japan and the Republic of Korea. What is clear from this chapter is that such volunteer approaches can significantly change the options considered for a repository host rock. Indeed, volunteering can lead to a wider range of host rocks being considered, including some options which might have otherwise been considered marginal due, e.g., to the complexity of the site. In developing trade-offs of the pros and cons of options, acceptability may be much more highly weighted than ease of making a very long-term safety case. This is quite a change from the more technocratic approach to siting that was the previous norm.

The sites selected and, indeed, the entire siting approach chosen can have a knock-on effect on the repository design process. In Chapter 5, the approach of tailoring the repository design to the specific environment available makes it clear that the ‘‘original’’ concepts explored in Chapter 3 are merely the starting-point for developing a wider range of potential designs. Despite this flexibility, this chapter also stresses that only a subset of possible design options has been explored to date and that optimisation of designs is an area where significant benefits can be gained in the future. The focus to date has been very much on post-closure safety. In the future, construction and operational safety and practicality will play a bigger role, with subsequent design modifications being needed.

Despite the other factors which are important in the siting and repository design process, the bottom line is that safety still has to be assured for extremely long periods of time. In Chapter 6, the ‘‘black box’’ of repository safety assessment (SA) is examined by highlighting the relatively simple processes which constitute the core of these performance evaluations. As noted above, assuring safe radioactive waste disposal is very complex and, arguably, the raison d’eˆtre of SA is to simplify the confusing web of relevant features, events and processes into a meaningful whole which can then be

quantified and compared against regulatory goals and guidelines. It should, however, be emphasised that, although the job of a SA modeller is to assess the behaviour of the repository over the duration of the assessment period, they do not claim to predict the future regarding actual doses or risks arising from any radionuclides released. The difference between bounding estimates which constrain the limits of potential releases and detailed future predictions is subtle and often misunderstood, even by technical staff working in radwaste management who are not directly involved in SA. The recent development of ‘‘safety case’’ terminology places more emphasis on complementing quantitative assessments with more qualitative arguments for safety which should, in the future, make the process of demonstrating compliance with regulatory goals more understandable to all interested parties.

By now, the recurring theme of the need for acceptance can be seen as a kind of leitmotif for this book. Chapter 7 provides an overview of the various socio-political constraints on a repository project. Although there are significant differences internationally, the various stages are generally similar enough to allow direct inter-comparison. One point is clear: in the twenty-first century, repository implementation can only be successfully undertaken if an appropriate legal and organisational framework has been established and a disposal strategy has been agreed by the responsible stakeholders. Another feature of repository projects is the (by normal socio-political standards) long timescale to implementation which, together with the novel nature of the task, means that not only must the activities themselves be carried out in stages, but the socio-political framework must change to reflect this multi-generational approach. The chapter concludes with an overview of the estimated cost of deep repositories and how the substantial financial requirements can be met – an issue of considerable importance with the recent focus on total system costs in the comparison of power generation options.

Although representing only a minute fraction of the costs associated with nuclear power and other uses of radioactive material, the R&D programmes to support geological disposal are large in absolute terms, corresponding to many hundreds of millions of Euros every year. Chapter 8 outlines the national and international R&D infrastructure required to support repository implementation programmes. The point is made that, while conventional R&D infrastructures can be utilised, there is much in the radioactive waste field which requires specific, specialised support to look into the processes and mechanisms which are unique to this segment. These obviously include studies of the waste itself, the associated engineered barriers and the processes influencing any released radionuclides, which require special research facilities. More significant investment is also needed for underground research laboratories (URLs) in which the processes of relevance to a deep geological repository can be studied directly. Investigations in URLs include both basic science (e.g., associated with the transport of radionuclides in deep groundwater systems) and development of the special engineering technology needed to meet the specific requirements associated with safely handling large, heavy, radioactive waste containers in small-diameter tunnels using robust, tele-operated systems – which must be fully tested and quality assured well before waste begins to be introduced into a deep repository.

Given the need to build public acceptance of radioactive waste disposal projects, the question arises of how this can actually be done in practice. The essential starting-point, as emphasised in Chapter 9, is establishing trust and building effective communication and, hopefully, dialogue. The waste community must shrug off its habits of secrecy