A HOLISTIC APPROACH | COVER STORY HIGHER ACTIVITY WASTE ONLY Op Safety
In-hole / Cu In-tunnel / steel Heat-managed cavern Deep boreholes Existing deep mine
EI Flexibility EI MIXED WASTES Op Safety
Left and below, figure 3: Strengths and weaknesses of different radwaste disposal options
Flexibility
Economics
Robustness Economics
Robustness
Resilience
Resilience
low-level contaminated material that is usually declared as waste. Nuclear steel could, however, be recycled to construct waste containers or MPCs – especially if all operations are remote handled and small levels of radiation from the steel are of no significance. A range of other decommissioning wastes could also be used as backfill for underground openings, rather than the specialist clays and concretes with an especially large CO2
footprint that are
currently considered. Even plugs, which can play a role in isolating emplacement zones, could be replaced by nuclear- steel bulkheads – potentially with even better functionality and options for failsafe in the event of a perturbation. Indeed, there are many other non-nuclear wastes that
could greatly benefit from deep disposal as opposed to near-surface dumping, as often occurs. Even if it is too complex to incorporate such wastes into the disposal panels, repository designs commonly include a huge number of access tunnels, shafts and ramps which are simply backfilled after waste is emplaced. For example, in the reference Japanese HLW repository this could be ≈1-2 million m3
here would be those that are unlikely to significantly perturb geological barrier roles such as materials like asbestos and heavy metals. Finally, the entire need to construct a special disposal
facility can potentially be reconsidered. Disposal in disused mines has been an option considered in the past for radwaste, for example at Morsleben in Germany and is already the basis of an international industry for disposal of chemotoxic wastes. From the viewpoint of the global fuel cycle, the particular benefits of some uranium mines being used as disposal facilities should be noted. These are not only likely to be particularly suitable from a geological point of view, having contained uranium ore for millions of years, but using existing excavations could greatly reduce the carbon footprint compared to a repository built from scratch. Again, as many uranium producing nations are not doing so well with meeting carbon reduction targets, any contribution to reducing global climate perturbations may be an argument that facilitates public acceptance. It should be emphasised that there is no “best” disposal option that can be applied to all applications and, to move
Economics Robustness
Operational safety
Environmental impact
Flexibility
Very favourable Acceptable
Very unfavourable (“killer”)
Resilience
. Potential wastes that could be readily included
forward, the pros and cons of different variants should be assessed for specific programme boundary conditions (see Figure 3). In addition to the concepts outlined above, further variants are possible such as disposal in deep boreholes rather than a conventional repository. However, this approach is likely to be applicable only for special conditions – such as small waste inventories and favourable boundary conditions. The very wide spectrum of options available also provides considerable flexibility for optimisation in terms of the detailed design of the disposal facility and the way in which it will be implemented.
Future perspective of waste Fundamentally, the risks from a radwaste disposal facility are trivial compared to those from global warming – which should put discussions about nuclear expansion into context. Nevertheless, there is a moral obligation to ensure that all wastes are managed in as responsible a manner as possible. Consideration of waste management in a holistic manner highlights the huge benefits that are available if we can break from existing paradigms. This will, however, require changes in the institutional culture of implementing and regulating organisations. It also requires education of decision makers so that they can consider the associated technical and socio-political issues in an unbiased manner, free from past pre-conceptions. ■
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