Borehole disposal

In the summer 2022 issue, Mike Bowman and colleagues state that the safe and secure disposal of radioactive waste is a pressing global issue and discuss the role for geoscience in this endeavour, while Max Dobson and Dennis O’Leary reflect on the history of the US programme at Yucca Mountain and emphasise that public opinion is a significant barrier to a long-term solution for spent fuel. The focus on a solution for disposal is more acute than ever, especially in the UK with a recent government policy announcement to build eight new nuclear power stations. While a Geological Disposal Facility (GDF), a mined repository at 200 to 1,000 m below ground, is the preferred option of Nuclear Waste Services (NWS), we argue that Deep Borehole Disposal (DBD) could prove more socially acceptable and thus may represent a more rapid solution. 

For a GDF, the identification of potential sites, detailed investigations, selection process and eventual construction will take many years. Given that a GDF would almost certainly be expected to take new spent fuel that requires 50 years plus for pre-disposal cooling, the placement of waste, sealing and abandonment will probably take another 150 years or so. Additionally, such a major national infrastructure project could be prone to huge delays, technical problems, overruns and cost escalation. In contrast, as discussed by Matthew Cotton (Cotton, 2021), DBD could be more socially acceptable and, because of the smaller footprint of a DBD facility, would facilitate local decision making, thereby offering societal stability during the relatively short timescale of disposal and sealing. 

DBD is becoming increasingly accepted as an alternative to a GDF for the geological disposal of high-level waste (including spent fuel) because it has the potential to outperform a GDF in terms of safety, cost, environmental impact, speed of implementation and land take. For example, DBD of the existing vitrified waste at Sellafield is estimated to cost only 10% of that for disposal in a GDF, and could be disposed of and sealed in just ten years, with the right investment (Gibb and Beswick, 2022). DBD provides the required isolation and relies predominantly on geological rather than engineered barriers.

DBD could be more socially acceptable and, because of the smaller footprint of a DBD facility, would facilitate local decision making, thereby offering societal stability during the relatively short timescale of disposal and sealing

The concept of DBD was first considered in 1957 by the US National Academy of Sciences, but was rejected because, at the time, the technology for drilling sufficiently large holes to depths of a few kilometres did not exist. Since then, there have been major advances in drilling technology. First pioneered in the underground nuclear bomb tests from the 1960s to 1990s, the blind shaft drilling method now has the capability to drill very deep, large-diameter boreholes and is widely used in the mining industry for mine access and ventilation shafts. Coupled with the major advances in very deep drilling for geoscience research, oil, gas and geothermal projects worldwide (including in basement rocks), these technologies mean that DBD now offers a serious alternative to a GDF, and several countries are already considering the DBD option for their waste inventories.

Development of the concept of DBD has progressed substantially over the last 35 years, based mainly on studies in Sweden, the US and the UK. In the US, following the Blue Ribbon Commission Report (2012), the DBD concept was re-investigated by Sandia National Laboratories on behalf of the US Department of Energy. Sandia had reached the stage of drilling a deep, large-diameter demonstration borehole when the project was abandoned for purely political reasons. The safety case for DBD was also investigated by Sandia and showed that DBD could comfortably meet the necessary international ‘standards’ in terms of received dosage at the surface (Freeze et al., 2019). In the UK, recent papers have discussed the challenges and the solution for the high-level vitrified waste stored at Sellafield (Beswick et al., 2014; Gibb and Beswick, 2022).

Dobson and O’Leary reiterate that safe disposal of hazardous wastes is not just a matter of engineering and geoscience, but public acceptability. Considering the long-term ambitions in the UK to develop a GDF, it is relevant to reflect also on the political influences, both locally and nationally, as these may affect the implementation of such a project at any time in the future. The other key matter to consider is whether or not a sufficiently sound safety case can be made for a GDF in the UK where the geology is complex. Investigations at Sellafield and Dounreay during the 1990s illustrated the difficulty of reaching a consensus about the soundness of the case for geological isolation (e.g. McDonald et al., 1996; Smyth, 2011). This means the focus must be on the engineered barriers, which are complex in a GDF facility (and the associated access infrastructure). It could even be argued that in such a case the geology in terms of isolation is only cosmetic.

To develop the concept of DBD requires a research-and-development programme involving a 5-km-deep slim hole for testing the host rock at a suitable location, as well as a full-scale, large-diameter borehole to 4 or 5 km depth to demonstrate the engineering. The programme would also include placement of non-active waste packages and sealing of the borehole. Additionally, preliminary investigations of the deep geology at the current UK nuclear sites would allow evaluation of their potential suitability for DBD of both legacy and new waste. On the scale of a comprehensive geological investigation of the onshore and inshore areas currently being considered by NWS for a GDF, the extra cost of this combined programme would be modest.

Given the debate and concern about the safe disposal of high-level radioactive waste, it is both important and responsible to consider all options, including DBD. This solution to the disposal of high-level waste could be more socially acceptable than a mined repository on the grounds of cost, implementation within a generation (rather than at some time in the distant future), the short period before sealing of each borehole and a more local solution, particularity if most of the waste can be disposed of at or near the source. Moreover, as we argue here, DBD offers an inherently better safety argument and a greater likelihood of more geologically suitable sites being available. 

John Beswick
Director, Marriott Drilling Group, has researched the concept of deep borehole disposal for 35 years, including studies for SKB, Sweden, the UK Nuclear Decommissioning Agency and the US Department of Energy.

Fergus Gibb
Emeritus Professor of Petrology & Geochemistry at the University of Sheffield, has researched radioactive waste disposal for over 30 years, pioneered the renaissance of deep borehole disposal, and was a member of the UK Committee on Radioactive Waste Management (2007 – 2012). 

Further reading

• Bowman, M. et al. (2022) Safe disposal. Geoscientist 32(2), 42-44
• Dobson, M. & O’Leary, D. (2022) Nuclear challenges. Geoscientist 32(2), 20-21
• Cotton, M. (2022) Deep borehole disposal of nuclear waste: trust, cost and social acceptability. Journal of Risk Research 25(5), 632-647; https://doi.org/10.1080/13669877.2021.1957988
• Beswick, A.J. et al. (2014). Deep borehole disposal of nuclear waste: engineering challenges. Proceedings of the Institution of Civil, Engineers: Energy 167(2), 47-66; https://doi.org/10.16809/ener.13.00016
• Gibb, F.G.F. & Beswick, A.J. (2022). A deep borehole disposal solution for the UK’s high-level radioactive waste. Proceedings of the Institution of Civil, Engineers: Energy 175(1), 11-29; https://doi.org/10.1680/jener.21.00015

Beswick, J. & Gibb, F. Borehole disposal. Geoscientist 32 (3), 10-11, 2022; https://doi.org/10.1144/geosci2022-022

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