OPERATIONAL ASPECTS OF DISPOSAL OF RADIOACTIVE WASTES IN HORIZONTAL BOREHOLES

Deep Isolation developed a safe, secure, and permanent deep geological disposal method for high-level waste, including spent nuclear fuel and other highly radioactive materials. The disposal method uses horizontal drilling techniques and emplaces the disposal canisters in a horizontal orientation deep underground.

A 2020 study was published by the Electric Power Research Institute (EPRI) examining the feasibility of co-locating borehole disposal technology with an advanced reactor for onsite waste management. The study invokes Deep Isolation’s horizontal drilling and emplacement method as the reference borehole technology. This approach could potentially allow the siting and development of the disposal system in parallel with reactor development. Such an approach presents the opportunity for greater system efficiencies throughout the project life-cycle as well as more productive engagement with stakeholders.

The reference scenario defined for the study assumed that each emplacement borehole consists of a 1,000 m vertical access hole that gradually transitions to a 1,500 m horizontal section where the waste canisters are emplaced. The deep borehole disposal facility modeled in the report (10 boreholes spaced 100 m apart with a capacity of 1,000 metric tons of waste) would occupy approximately 2.6 km² (640 acres) of land. The disposal canister will be nominally 34 cm in diameter, 5.5 m in length and made from corrosion-resistant material such as Alloy 625.

Emplacement is accomplished by lowering the canister down the vertical shaft then using a wireline tractor to push the canister along the horizontal section. Once the canister has reached its intended location, the canister is locked into place and the emplacement tool separates and returns to the surface. This emplacement process is repeated until the horizontal borehole reaches its design capacity. The disposal operations would take less than three years. Following final canister emplacement and confirmation testing, the borehole is closed with ongoing system performance tracked via remote monitoring systems.

Using an on-site, horizontal borehole approach, the entire waste inventory for a single advanced reactor can be disposed of at a savings of over 60% or more when compared to the cost of a mined repository.