Deep borehole disposal cannot replace the UK's need for a geological disposal facility (GDF) but may nevertheless have a helpful role to play in the disposal of some of the country's nuclear waste inventory, according to a study conducted by Deep Isolation on behalf of the UK's Nuclear Decommissioning Authority (NDA).
Deep Isolation's concept for the disposal of nuclear fuel and high-level waste (Image: Deep Isolation)
The purpose of the study is to provide NDA with information that enables it to assess the potential suitability of
Deep Isolation's directional borehole disposal solution for elements of the UK's radioactive waste inventory.
Deep Isolation's solution for the management of used nuclear fuel and high-level radioactive waste involves emplacing it in corrosion-resistant canisters placed in deep horizontal drillholes. The technology uses existing directional drilling technology. The waste can be retrieved during a determined time frame or permanently secured. In 2019, Deep Isolation publicly demonstrated its concept when it successfully placed and then retrieved a prototype nuclear waste canister hundreds of metres underground via a borehole.
The study found that 63% by volume of the UK's Inventory for Geological Disposal (IGD) is intrinsically not compatible with borehole disposal. A further 26% can in principle be transferred to Deep Isolation disposal canisters for borehole disposal, but the existing plans for disposal in a mined repository are likely to be more cost-effective. This leaves 11% of the IGD that, based on this preliminary study, is operationally and commercially suitable for disposal in a deep borehole repository. This comprises all the UK's high heat generating waste (HHGW) - accounting for 96% of NDA's forecast for radioactivity levels of the IGD in 2200.
Deep Isolation developed 15 scenarios, which show its estimated, unvalidated cost of disposing all the UK's
HHGW and also selected sub-sets. These describe how costs vary across geological environments, and between single site and multi-site approaches. The scenarios for disposing 100% of HHGW show estimated costs between GBP2.98 billion and GBP4.45 billion (USD3.64 billion and USD5.44 billion). More narrowly focused scenarios show that all the UK's legacy used fuel can be disposed of for GBP1.0-1.4 billion and all high-level waste for GBP256-288 million.
"Further work is needed to evaluate the impact of such an approach on the overall costs, benefits and risks of the UK's integrated waste management strategy," the study concludes.
Deep Isolation's recommendations to NDA include: undertaking more detailed business case work to assess the possible role for the technology as part of the NDA's integrated waste management strategy; and engagement in international collaboration on demonstration of deep borehole technology.
Nuclear Waste Services (NWS), which is responsible for the delivery of the UK's GDF, said it "recognises the insight afforded by Deep Isolation's study and will continue to engage with such developments, while recognising that a GDF will still be required for the majority of the UK higher activity waste inventory, even when Deep Isolation's directional borehole technology is developed to sufficient maturity for potential implementation".
It added: "In line with government policy, NDA and NWS continue to review new and emerging technologies which could have the potential to improve the long-term management of some of the UK's higher activity radioactive wastes."
"We are excited to have delivered this project for the UK's Nuclear Decommissioning Authority," said Deep Isolation CEO Elizabeth Muller. "NDA is a global leader, and I welcome their commitment to exploring the benefit of new and innovative options for nuclear waste disposal."
