Countries that rely on nuclear power, including Canada and the US, will have to reckon with their nuclear waste. Used fuel stays radioactive for a million years or longer, and experts say the safest place for it is deep underground, where it can ideally sit undisturbed.
But our world, in a million years, will look much different than it does today. Ice ages will once again come and go, as they did in ancient history, meaning the crushing weight of glaciers will press down upon the Earth and potentially impact any nuclear vault buried deep underground. Even if no humans are around in tens of thousands of years to see the next Ice Age—or maybe no humans as we'd recognize them—scientists still have to take this into account when they plan deep geological repositories to house radioactive waste.
Right now, all of Canada's high-level nuclear waste is sitting at the reactors where it was produced. The Nuclear Waste Management Organization (NWMO) is responsible for figuring out what to do with this radioactive garbage. They want to bury it underground, and they're considering seven possible host communities for the planned vault, all in Ontario.
While that process chugs slowly ahead—they're hoping to have a site selected by 2023, and it could begin accepting used fuel about 20 years later—scientists are modelling the future.
As part of this, the NWMO partnered with similar agencies that deal with radioactive waste in Sweden and Finland, two other nuclear-powered countries, on the Greenland Analogue Project. It uses the Greenland ice sheet as a stand-in for the next Ice Age, to inform their planning for a long-lasting nuclear dump. According to the NWMO, the Greenland ice sheet is comparable to the kinds of ice sheets that could cover both Canada and Scandinavia again in the far future.
"What we're trying to understand is, in the future, when there's two or three kilometers of ice over where we're sitting now, what the impact will be," explained Monique Hobbs, a geoscientist with NWMO, in a phone interview. "We're looking for a place to store used nuclear fuel passively for over one million years, at depths of about 500 meters."
Using hot, pressurized water, scientists drilled 23 boreholes down through the Greenland ice sheet to the rock below, Hobbs told me. Some were up to 700 meters deep. Three more were drilled into the bedrock next to the ice sheet—one with a depth of 649 meters below ground surface. It was drilled on an incline, extending right under the ice sheet.
Scientists studied factors like movement of the ice sheet, meltwater runoff, and how water transfers from the ice sheet to areas below the surface to understand how a future repository could be affected. With that knowledge, Hobbs told me, "we can do simulations to understand how that might impact the water at the depth where our repository will be."
Canada, which is looking at building a second repository for its low- and intermediate-level nuclear waste, published a final report on this project in September 2016. Sweden and Finland are still monitoring the boreholes as they move ahead with their own nuclear dumps, Hobbs told me. Those two countries are further along than Canada with their plans: Sweden has already selected a site to accept its radioactive garbage, as has Finland.
Studying Greenland to get an idea about how Ontario might look, in tens of thousands of years, drives home just how long this waste will be in the ground. "The timeframes are mindboggling," Hobbs agreed. "The idea is that even if human beings are no longer around in a million years, [the repository] can contain and isolate used fuel to protect the environment and whatever creatures are around on the Earth's surface."