Could Deep Boreholes Solve Our Nuclear Waste Problem?

upstart writes:

Small bore holes could provide an alternative to centralized waste repositories:

There's one thing every planned permanent repository for spent nuclear fuel has in common: They're all underground mines.

Like any mine, a mined repository for nuclear waste is a complex feat of engineering. It must be excavated by blasting or a boring machine, it must keep the tunnels stable using rock supports, and it must have ventilation, seals, and pumps to handle groundwater and make it safe for people and machinery. Unlike a mine, however, a repository must also transport and entomb canisters of radioactive waste, and it must be engineered to exacting standards that ensure the tunnels will keep the canisters safe for many millennia.

There is an alternative idea that dispenses with most of those downsides: disposal in deep boreholes. But can they be both feasible and safe?

[...] The US Department of Energy was planning to drill a vertical borehole 4 to 5 kilometers (2.5 to 3 miles) to gain experience with the process, but the project was canceled in 2017. This borehole would have been about 10 times deeper than a mined repository, but such depths are not unusual for oil and gas boreholes.

Governments aren't the only ones interested in the approach. Deep Isolation, a company founded in 2016 and headquartered in California, aims to offer nuclear waste disposal in deep boreholes as a commercial service anywhere in the world. "Depending on your geology, we can design a borehole for it," said John Midgley, a geologist with Deep Isolation. The company's designs could be anything from deep vertical boreholes to shallower J-shaped holes with horizontal disposal sections. Again, the oil and gas industry has gotten there first, drilling around 160,000 boreholes with horizontal sections in the USA alone.

"There are lots of oil and gas wells that deep, so the problem is going to be how hard the rocks are and how often your drill bits wear out, things like that, but in general... I don't think [depth] presents any additional problems," said Sherilyn Williams-Stroud of the University of Illinois, an expert on geological disposal of nuclear waste and CO2.

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