is still an order of magnitude higher than typical costs for geological disposal. In particular due to the risks of explosion during takeoff, any protection system would have to be extremely robust – which would increase costs considerably. This is unthinkable for the thousands of tonnes of spent fuel produced each year and hence presumes an efficient (and expensive) reprocessing programme to concentrate the most ‘‘problematic’’ isotopes and immobilise them for disposal. In addition, a space programme to dispose of all problematic waste from the global nuclear power industry would certainly also have significant environmental detriments from the effects of the launches themselves.

Paper studies of future space transportation systems have considered more exotic alternatives to rockets, such as rail-gun launchers and space elevators (e.g., Cosman, 1985). Apart from requirements for major advances in materials technology, such novel concepts must inevitably be associated with high costs and risks of catastrophic failure. In theory, at least, a space elevator combined with an electro-magnetic rail-gun could provide an option for firing waste packages beyond earth’s orbit. Further speculation involves so many assumptions about ‘‘possible’’ future developments that it falls into the realms of science fiction rather than technical analysis. As such, space disposal is no longer a serious option for any national programme (see also comments in Dutton et al., 2004).

3.4.3.3. Icesheets and permafrost

This is another option which has a certain amount of popular appeal due to the images of remote ‘‘frozen deserts’’ – including icecaps, glaciers and permafrost (Fig. 3.8). These have been studied for a long time (e.g., Philberth, 1959; Schneider and Platt, 1974) and, indeed, permafrost disposal has been implemented for some waste types and can, if deep enough, be considered a variant of geological disposal (section 3.3.2). Due to the high transport and handling costs, study of this option generally focuses on higher activity wastes. Such heat-emitting wastes would be ‘‘self-sinking’’ in ice, eventually ending up on the bedrock under the icecap if not actually anchored from the surface (Fig. 3.9).

As noted in section 3.4.2, this option is excluded by the Antarctic Treaty, leaving only sites in Greenland and certain Canadian and Russian islands as alternative options. As the basis of such disposal is the permanence of the icesheet over timescales of interest, these are now seen as less credible due to concerns raised by global warming. Massive retreat of ‘‘permanent’’ continental icesheets and melting of permafrost over the last decades make predictions of future behaviour completely impossible on the basis of existing climatic models – which have such ranges of uncertainty that even complete melting of the Antarctic icesheet over coming centuries cannot be precluded. It seems unlikely that any technological development within the near future will reduce such uncertainties to the point that a credible safety case could be produced. They are thus not presently considered to be credible for implementation in any national programme, despite a recent patent for such a concept (Valfells, 2002).

3.4.4. Non-options; long-term surface storage

There is often a grey area between storage and disposal – as even disposal sites may be actively controlled and monitored (often termed ‘‘institutional control’’) for a time period long enough for activity to decay to some ‘‘negligible’’ level (typically several hundred

Fig. 3.9. Placing waste below icecaps. The heat from the waste package should melt the ice, allowing the packages to ‘‘self-sink’’ to the bedrock below if not anchored from the surface.

years). Storage here is taken to mean holding waste in a facility that is not only controlled and monitored but is also fully inspectable and the waste is easily retrievable at any time. For both disposal with institutional control and storage, a particular concern is the longevity of the institutions charged with this work. Such institutional stability is, however, much more critical for storage as, in effect, there are no other safety barriers of the type included in a disposal facility. Also, after institutional control, a disposal site can, in principle, be abandoned. After storage, the waste still needs to be disposed of and, though its radiological hazard should then be negligible, it still may need to be treated as chemotoxic waste.

In either case, the IAEA (IAEA, 1992, 2002, 2003) feels that true institutional control is only realistic for wastes dominated by short-lived isotopes and, given the volatility of human history over the last century, achieving confidence in the longevity of institutions (and funding) for such periods is particularly difficult for most countries (see also the discussion in Nagra, 1997, on societal stability versus geological stability). Nevertheless, storage variants over ‘‘indefinite’’ time periods have also been seriously proposed for long-lived waste. Strange as it seems, this is not without precedent – e.g., the chemotoxic waste depot at Teuftal (Canton Berne) is specified to require supervision for ‘‘as long as Switzerland remains a populated country’’ (Nagra, 1997). Similarly, contaminated sites in the USA may simply be set aside for restricted access ‘‘indefinitely.’’