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Development of geological disposal concepts

Ian G. McKinleya, W. Russell Alexanderb, Petra C. Blaserc

aDepartment of Environmental Engineering and Architecture, Graduate School of Environmental Sciences, Nagoya University, Japan bBedrock Geosciences, Auenstein, Switzerland

cPetraconsult, Uetikon a.S., Switzerland

3.1. Introduction

In this chapter, the development of geological disposal concepts is examined in some detail, beginning with an introduction to the historical evolution of disposal of radioactive wastes (section 3.2), and a consideration of the range of options available. As indicated in Fig. 3.1, many different possibilities exist for the relatively small volumes involved, but this book focuses on those classed as geological disposal. The general international consensus of this being the best approach is explained in terms of the fundamental properties of the geological environments currently under consideration to host repositories (section 3.3), which includes illustrations of repository design evolution using examples from Sweden and Switzerland.

To put this in perspective, however, a short overview is given on the alternatives to geological disposal (section 3.4), which are classed as politically blocked options such as sub-seabed disposal (section 3.4.1), technically impractical options such as partitioning and transmutation (P&T) (section 3.4.2) and ‘‘non-options’’ such as long-term storage (section 3.4.3). Section 3.5 looks into alternatives to ‘‘conventional’’ mined repositories which are the current focus of most national programmes. Although quite novel, such options are receiving increasing attention as more national programmes move towards repository implementation and begin to realise the potential shortcomings in many of the conventional designs. Finally, the chapter concludes with section 3.6, which considers the prospects for future developments in this area.

3.2. Historical evolution of geological disposal concepts

All materials are naturally radioactive to some extent and so are all wastes. Wastes with enhanced levels of naturally occurring radionuclides have been produced by mining and industrial activities since prehistoric times, but significant quantities of wastes with

Fig. 3.1. Radioactive waste management options.

radiologically meaningful activities of radionuclides began to arise only at the end of the nineteenth century. Despite the widespread interest in radioactivity following its discovery, there was no particular concern about wastes and, indeed, many applications of radionuclides in the early part of the twentieth century focussed on their assumed benefits to health. Identification of ‘‘radioactive waste’’ as a special category is related to the dramatic increase in the production of such material associated with the early nuclear weapons programmes and the subsequent growth of nuclear power. Nevertheless, ‘‘legacy wastes’’ requiring special handling are continually discovered from abandoned facilities which predate this period (e.g., factories which produced or used luminous ‘‘radium’’ paint).

The development of waste management options in the early days is best documented for the US, although the situation in the other nuclear powers of the time (the UK, USSR and France) was certainly similar. In the early days, atomic energy (as it was then called) was part of the military programme of the US and the first plants were, for security reasons, established in isolated places with few inhabitants so little heed was taken of waste problems (Fig. 3.2). As A.E.Gorman noted ‘‘. . . as problems of waste disposal arose they were not too difficult to take care of because of this isolation’’ (Gorman, 1955).

Most waste disposal was, in any case, rather basic. A 1952 USAEC-sponsored survey of radwaste producers found that ‘‘. . . about 41% of the users disposed of radioactive wastes by dilution and discharge into sewers. Although this may not be a hazardous procedure at present (owing to the limited quantities of isotopes currently in use), the procedure is not a wise one and should be discouraged’’ (Miller et al., 1954).

Fig. 3.2. Until 1970, solid low-level and transuranic waste at the Atomic Energy Commission’s nuclear weapons facilities (shown here is Hanford Reservation, circa 1950s) ‘‘was frequently disposed of in cardboard boxes. Once filled, this unlined trench would have been covered with dirt, leaving the cardboard to deteriorate . . .’’ (US Dept. of Energy, http://www.ocrwm.doe.gov/).

As the nuclear power industry began to develop after the second world war, it was accepted that such an approach could not continue and, in 1955, the USAEC signed a contract with the NRC to set up the Committee on Disposal of Radioactive Waste on Land, specifically to look into the problem with the aim of ‘‘Evaluating all suggestions and research to date on disposal methods that involve land surface or underground sites . . .’’ (NRC, 1957). A very early focus was on disposal in salt bodies (see section 3.3) and other deep rock formations and this approach has continued to the present day.

Nevertheless, it was also recognised at an early stage that there were a range of variants of this option and, indeed, possible alternatives to geological disposal on land (e.g., USAEC, 1974; Schneider and Platt, 1974). The latter studies were carried out in a fairly comprehensive manner and often form the basis for reviews of alternatives to national geological disposal concepts which seem to re-appear in the literature on a 5–10 year repeat cycle (recent examples being SKB, 2000; Nirex, 2002; Dutton et al., 2004; CoRWM, 2005). It is often forgotten, however, that socio-political and technical boundary conditions were very different three decades ago and hence the pros and cons of different options are now weighted in a very different manner.

A good illustration of this is provided by D&D (dilute and disperse) options which were extensively studied – and implemented – in particular association with nuclear weapons programmes (e.g., Fig. 3.3). It may seem incredible today that direct disposal (dumping) of MegaCuries (PBq-EBq) of radioactive waste into aquifers, rivers, lakes and seas was considered acceptable practice. This occurred, however, at a time when