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Site selection and characterisation

Tim McEwen

McEwen Consulting, Melton Mowbray, England, UK

4.1. Introduction

Radioactive waste can remain a hazard for a considerable time and repositories need to be found where such waste can be disposed of safely. To ensure that radioactive waste is managed in an appropriate manner, a suitable process needs to be followed to select any radioactive waste disposal site. Such a process needs to be both transparent and defensible, so that the community where a site is eventually located has confidence that it was selected properly.

The selection of sites for the disposal of long-lived radioactive waste is often the most contentious part of a disposal programme and the selection process can be very timeconsuming. There are several examples throughout the world where site selection programmes have had to be abandoned and only a few examples where the process of selection of deep disposal sites has proceeded in a relatively smooth manner and where a site has been selected for repository construction. The best example of a success story is

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that of the situation in Finland (McEwen and Aikas, 2000).

There is a variety of strategies that can be applied in selecting disposal sites. A previous review of such options is provided in Savage (1995), which is itself partly a summary of work presented in an earlier report to SKB by McEwen and Balch (1993). There have been further developments in site selection strategies since these reviews, to take account of the more inclusive approach that is now generally followed in making decisions regarding sensitive siting issues, with the result that there is now a greater emphasis on volunteerism in site selection and more interaction with the public and other stakeholders during the siting process (see also the discussions in Chapters 7 and 9).

Generally, the process of site selection can be defined in terms of two key factors: first, the extent to which an overtly rational, rather than a pragmatic, approach is adopted and, second, the extent to which satisfactory technical solutions are imposed rather than advocated and accepted by recipient communities. Another broad distinction can be made between geologically led and advocacy led approaches. In this context, geologically led means that the primary determinants in defining areas of search are related to geological and hydrogeological characteristics of the sites. In contrast, an

The strategy followed in any particular country may lie anywhere between these broad categories of strategies, which represent end-members of a continuous spectrum of possibilities. Examples are provided in Table 4.1 to illustrate the range of approaches that have been, or are currently being, followed and the extent to which they have been successful.

4.1.1. Prescriptive/geologically led

The USA possesses a well developed legislative framework for the assessment of potential repository sites. The open, decentralised style of government is also coupled with easy access to judicial review of the decision-making process. This environment encouraged the development during the 1980s of a sophisticated, if rather mechanistic and prescriptive, site selection methodology for a HLW disposal site, the aim of which was to meet objections head on in a rational and demonstrably equitable manner. The later stages of the site selection programme used Multi-attribute Utility Analysis (MUA; see also MAA or MADA), described by Merkhoffer and Keeney (1987), Keeney (1987) and Keeney and von Winterfeldt (1994), that led to the stepwise identification of three possible sites. MUA (Keeney and Raiffa, 1976) is a technique recommended by the ICRP for use in optimisation problems (ICRP, 1989).

The approach followed in the USA was, in fact, geologically led in that assumptions were made initially as to the most appropriate geological formations. The next stage was to define rigorous repository performance measures in terms of a range of health and safety, environmental, socio-economic and economic impacts and then to compare relative aggregate performance. In particular, the process was designed to make explicit assumptions, judgements, preferences and trade-offs in a systematic manner. The design of the selection process and the legislation that accompanied it made the selection programme complex and legalistic, in marked contrast to the situation in Sweden and Finland.

Having selected three potential sites (Hanford, Deaf Smith County and Yucca Mountain), site characterisation programmes were started at these sites. The final choice of Yucca Mountain was, however, political and this site was selected mainly because the State of Nevada had less political power in Congress than did the states of Texas and Washington (and perhaps, because of the proximity of the site to the Nevada Test Site, little opposition was expected). The original plan was also to develop a second repository for HLW in the eastern part of the USA but, due to political pressure, this programme was shelved before it had reached the stage of selecting a shortlist of potential sites (see also comments in Chapter 10).

4.1.2. Sophisticated/advocacy led

This approach has become more common over the last decade or two as problems with the use of other approaches to site selection have become apparent. The essential element of this approach that distinguishes it from others is substantial public participation in the selection process, which may include the use of volunteer sites – depending on the specific structure of the site selection programme, areas or sites are able to volunteer either during the early stages of the programme or later as the programme proceeds. A key characteristic is an emphasis on providing mechanisms for community

involvement and an exchange of information on risks and benefits at the earliest stage of the selection process. Another feature is that the costs to the local community are often explicitly recognised, either in being able to carry out their own independent analysis of the investigations or the proposed development of a repository (as has been the case in Sweden), or in making provision for compensation if a repository is developed (as is the situation in Switzerland and France). Examples of this volunteer approach are provided by the site selection programmes in Sweden (Milnes, 2002), Finland (McEwen and

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Aikas, 2000) and Japan (NUMO, 2002), with a somewhat different approach being followed in France, where a site has been selected not for a repository, but for a URL (e.g., Bataille, 1993), as part of a research programme on the management of radioactive waste (see also details on a variety of approaches in Chapter 9). Generally, it is agreed with the local community that no radioactive wastes can be disposed of in such a URL although, if the geological environment proves suitable for radioactive waste disposal, there is the possibility of selecting a nearby location, or a similar geological environment

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elsewhere, as a potential repository site (cf. the situation in SKB’s URL in Aspo in Sweden). A recent recommendation from AkEnd (AkEnd, 2002) regarding a future site selection programme in Germany also comes to the same conclusions regarding the desirability, or actually the necessity, of public participation at all stages. AkEnd introduced the concept of ‘‘willingness to participate’’, rather than volunteerism, to refer to the process of public involvement in selecting sites for investigation and possibility later for underground exploration.

Nagra in Switzerland began an extended process around three decades ago. For L/ILW, a set of 100 sites was originally selected based on predominantly geological considerations. MAA, using both geological and socio-economic criteria, was used to narrow this down to 20 and then three sites (note that the entire process was documented in openly available Nagra technical reports). A fourth site was added following a government recommendation (a late volunteer site that was, in fact, one of the original 100). Following detailed site characterisation at all four sites, Wellenberg was selected based on an extensive MAA, including a full SA and detailed logistical analyses. The selection procedure was widely publicised (e.g., Nagra, 1983a,b) and selection of the site was accepted by the government and regulatory authorities, only to be finally excluded in a local referendum. For HLW, siting focused on geological stability criteria due to a regulatory requirement to show safety ‘‘for all time’’ (HSK, 1993). Exclusion criteria eliminated much of the country, leaving only a band of possible host rocks, including both sediments and crystalline basement, in the north of the country. Stepwise, regional characterisation was initiated – first sequentially, then with sediment and crystalline host rock options running in parallel. As the aim was only to show the ‘‘feasibility of finding a site’’ (rather than actually defining a site, as in the L/ILW case), a decision was taken to focus on the sedimentary option (in particular, the Opalinus Clay) due to reasons of explorability.

SKB in Sweden started its site selection programme in the early 1990s, following research over the previous fifteen years at six ‘‘study sites’’, at other drilling sites and in two URLs (Milnes, 2002). This research allowed for the development of a country-wide feasibility study (SKB, 1995), covering geological and other aspects relevant to the disposal of spent fuel. However, this study drew considerable information from another study which had been carried out on the geology of Sweden for more general purposes (Fre´den, 1994). This was followed by feasibility studies in eight municipalities over a