Conclusions to a recently published paper suggest that high-level radioactive waste from advanced reactor fuel recycling can be safely stored deep underground in 18in wide horizontal boreholes.
Initial results from an Oklo Energy-led project confirmed that nuclear waste streams are compatible with deep borehole disposal, "demonstrating a safe and practical pathway for permanent isolation".
Deep Isolation said it completed work under the U.S Department of Energy's ARPA-E ONWARDS project in paper titled Enabling the Near Term Commercialization of an Electrorefining Facility to Close the Metal Fuel Cycle.
Modelling showed that high-level waste when disposed of in Deep Isolation's deep borehole canister system within generic shale and granitic host rocks s surpassed long-term safety levels and current radiation exposure standards.
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Deep Isolation, a technology company founded and headquartered in Berkeley, California, which took part in the research, says the findings "provide confidence that borehole disposal could serve as a viable option for high-level radioactive waste".
However, U.S. regulators would need to change existing laws to allow the use of borehole depositories for nuclear waste.
Deep Isolation's Executive Vice President of Engineering Jesse Sloane said: "By pairing innovation in fuel recycling with advanced deep geologic disposal technology, we are helping to build the technical foundation for a fully integrated, sustainable nuclear future."
Rather than excavating large tunnels in a mine, Deep Isolation uses directional drilling technology to place waste hundreds of metres underground within stable geological formations.
According to the company, borehole repositories can provide substantial isolation for many types of high-level waste in a wide range of locations, but far below drinking water aquifers.
A Deep Isolation horizontal repository begins with a vertical access hole extending thousands of feet deep before gently turning horizontally, Canisters (pictured) containing nuclear waste are then stored in the horizontal section.
The company says one borehole 1.5km long can store ten years of waste from a Pressurized Water Reactor (PWR).
