Sandia National Laboratories
All of the planned permanent storage facilities for spent nuclear fuel have one thing in common. They are all underground mines.
Like any mine, a mined repository for nuclear waste is a complex feat of engineering. It must be excavated with a blasting or boring machine, use bedrock to stabilize the tunnel, and have ventilation, seals, and pumps to treat groundwater and ensure the safety of people and machinery. However, unlike mines, repositories must transport and bury canisters of radioactive waste, and tunnels must be designed to exacting standards to ensure the canisters remain safe for thousands of years.
I have another idea that omits most of these shortcomings. It is dumping into a deep borehole. But can they be viable and safe?
deep underground
At first glance, disposal of deep boreholes seems perfectly viable.
The U.S. Department of Energy had planned to drill a 4 to 5 kilometer (2.5 to 3 mile) vertical borehole to gain experience with the process, but the project was canceled in 2017. , but such depths are not uncommon in oil and gas boreholes.
Governments aren’t the only ones interested in this approach. Founded in 2016 and headquartered in California, Deep Isolation aims to provide deep borehole nuclear waste disposal as a commercial service anywhere in the world. Deep Isolation geologist John Midgley said: The company’s designs range from deep vertical boreholes to shallow J-shaped holes with horizontal disposal sections. Again, the oil and gas industry got there first, drilling about 160,000 horizontal section boreholes in the United States alone.
Illustration of a J-shaped deep horizontal borehole repository for nuclear waste (not to scale).
deep separation
“There are a lot of oil and gas wells that deep, so the question is how hard is the rock, how often does the drill bit wear out, etc. But in general… I don’t think so.” I do not think so. [depth] Sherilyn Williams-Stroud of the University of Illinois, an expert on geological disposal of nuclear waste and CO2, said:2.
Multiple disposal pits can be drilled and spread underground from a single point on the surface, minimizing costs and environmental impact, and removing and dumping far less rock than mining. . So, in theory, every nuclear power plant could have its own disposal borehole, eliminating the need to ship spent fuel across the country.
Deep boreholes should be able to take in hotter waste than mined repositories, as the canisters are placed end-to-end and cooled by the surrounding rock. This means that you no longer need to consume spent fuel in the pool. Proponents also argue that deep boreholes take up less space, are much deeper, and are unoccupied, making surveying the geology of the site much less and easier, saving even more time and money. .
Also, the borehole should be able to accept waste more quickly. Deep Isolation Chief Operating Officer Rod Baltzer said: This is in stark contrast to his 10 or 20 years required to develop a mined repository. Baltzer also told me that Deep Isolation’s initial calculations suggest the company could dispose of nuclear waste at “less than half the cost of mined repositories.”
As a bonus, this method is particularly attractive for disposing of some nuclear weapons waste. Placing weapons-grade plutonium at the bottom of a 4-kilometer borehole is inherently safer than placing it in an accessible mined repository, and is highly radioactive and heat-generating, containing cesium-137 and strontium-90. “Hanford Capsule”, all in one oil industry standard borehole for disposal.
However, the same attributes that make deep boreholes attractive limit their utility.
