What Lies Beneath

“Onkalo,” which means cavity, or cavern, in Finnish, is an apt name for Finland’s repository for radioactive waste. Touted as a “100,000-year tomb,” the Onkalo facility on Olkiluoto—a small island in western Finland—is currently being built at a depth of 450 metres, inside bedrock. It will be the world’s first permanent disposal site for spent nuclear fuel.

Other countries, including the United States, the United Kingdom, Sweden, France, Germany, Canada and Japan have attempted, for years, to set up nuclear-waste disposal sites, but their plans have stalled because of political, environmental and social roadblocks. Finnish leaders, on the other hand, have managed to drum up popular support for the repository by convincing locals that it will be a financial asset to their community. The Finnish government granted Posiva—a nuclear-waste management company—the construction licence for Onkalo in 2015 and the firm expects to begin depositing waste in the facility in the early 2020s. Tunnels will first be drilled into granite bedrock. Copper canisters, 5.2 metres long, will be filled with spent nuclear fuel, and buried in tunnels whose openings will be sealed with bentonite clay, a material that expands when it comes into contact with water. On its website, Posiva states that copper is known to last hundreds of thousands of years without corroding, and that bentonite clay will prevent groundwater from reaching the canisters. Over the next century, if all goes as planned, Onkalo will be home to roughly 70 kilometres of tunnels, which will store 3,250 copper canisters containing about 6,500 tonnes of spent nuclear fuel. This makes it an especially immense project for a small country.

Spent nuclear fuel, which contains uranium and plutonium, is highly radioactive, and its disposal is regulated by international safeguards. At the moment, countries with nuclear-power plants store their waste in interim storage facilities located above the ground or near the surface. Although such “high-level waste” comprises only 3 percent of the total volume of waste produced by nuclear generation, it produces 95 percent of the radioactivity arising from nuclear power, making it the industry’s most lethal by-product. There is a growing consensus among several countries for the geological disposal of this fuel—a solution that seeks to isolate it, blocking its interaction with the biosphere for centuries, until the radioactivity falls to safe levels.

A project of this nature needs suitable technology, the right site and support from local communities. Considering the progress at Onkalo, Finland appears to have ticked all these boxes. However, some experts are circumspect. Posiva’s final disposal plans are based on the KBS-3 method developed in the 1970s by the Swedish Nuclear Fuel and Waste Management Company, or SKB. It involves storing spent fuel in tunnels behind protective barriers—the copper canisters, bentonite seals on the tunnels—to ensure that the failure of a single barrier does not compromise isolation. Though this is an elaborate system, scientists and geologists have argued that it may fall short in practice. Betting on copper canisters is risky because any cracks in them caused by corrosion, rock movements or earthquakes could lead to leaks of radioactive waste.

Johan Swahn, the director of MKG—a Swedish environmental NGO working on nuclear-waste disposal—argued that the strategy deployed in Germany, where naturally occurring salt domes are used as barriers, is safer. “The primary concern is that the KBS-3 method relies on artificial barriers to isolate spent fuel over long time scales—up to a million years. There is a long-term problem here,” he said. In 2016, the Swedish government deferred the plans for its own repository project, Forsmark, after a government advisory body on nuclear waste challenged the predictions for the corrosion levels of SKB’s copper canisters. Since Finland and Sweden are geologically similar, concerns raised in Sweden are valid in the Finnish context too, and many believe that Onkalo is a cause for anxiety.

“Copper corrosion is much faster than they”—Posiva and SKB—“claim,” Peter Szakálos, a corrosion researcher at the Royal Institute of Technology in Sweden, told me over Skype this June. “SKB has stated in its document that less than one copper canister will fail in one million years. But if you look at the corrosion rate that happens in groundwater, we say the first canister will fail in 100 years and the majority will fail in 1,000 years.” The reports from Posiva and SKB’s laboratories are alarming, Szakálos added. “Their tests didn’t match their theoretical predictions.”

Posiva insisted that the mismatch was a minor glitch. “It’s not a corrosion issue, it is a test set-up issue,” Tiina Jalonen, the senior vice president of development at Posiva, told me. “Most of the concerns have been solved by us. We investigated a lot and conducted many experiments and modeling. A few scientific groups repeated the tests that raised the concerns regarding copper corrosion and they found some issues that have been resolved now.” However, Finland’s Radiation and Nuclear Safety Authority, or STUK, which validated Posiva’s analysis, is closely watching the proceedings at Onkalo. “Before the operation licence is issued and any waste goes underground, we need to be really sure about the corrosion issue,” said Jussi Heinonen, the director of the Nuclear Waste and Material Regulation department at STUK.

But corrosion is not the only factor that STUK wants Posiva to study further. It has also demanded information about the behaviour of bentonite clay during dry periods or phases of increased water flow, as well as geological risk factors such as earthquakes and hydrological problems. The Finnish geologist Matti Saarnisto raised similar concerns about the risk of highly active radioactive waste being stored in granitic bedrock that, he pointed out, is broken in many places. The cracks, he argued, would allow groundwater to enter the storage area and hasten the corrosion process. Saarnisto explained that over the next hundred thousand years, there is a strong chance that permafrost could penetrate Onkalo. If it does, that could result in hydrostatic pressure—pressure exerted by a liquid in a confined space—leading to canister failure and radiation leaking into the biosphere, which would be disastrous for future generations.

Opinion remains divided on whether there is a viable way to ensure that the canisters do not leak. Some experts have suggested using superior corrosion-resistant metals, such as titanium or bronze, which are considered to be more corrosion-resistant than copper. Others, including the academic Matti Kojo—a social scientist at Finland’s Tampere University—have worried that the issue is not being discussed enough. According to him, the voices of academics, scientists, nuclear experts and NGOs have not been given the prominence they deserve in the Finnish media, which has downplayed the corrosion issue.

The Finnish government’s early start on nuclear-waste disposal might have been central to its success. The country’s Nuclear Energy Act, enforced in 1994, banned the export of spent nuclear fuel and forced companies creating the waste, such as TVO, to take responsibility for its disposal. It could also be that Posiva managed to acquire public backing. In a research paper published in 2017, Kojo noted that Posiva shifted focus from searching for the “geologically best site” to “the most suitable site from a socio-technical perspective”—as Kojo explained, in the Finnish system the local council has the last word on the placement of sites and the government cannot overpower it, making local support crucial.

The municipality of Eurajoki—where Onkalo is being built—was the first choice, because it had already hosted two nuclear reactors and so, as Jalonen of Posiva recalled, the residents were already familiar with nuclear-fuel-related projects. A majority of the 9,300-resident population of Eurajoki worked at Posiva or TVO, and also stood to gain benefits such as lower taxes, good public services and a home for the elderly if they accepted Onkalo’s presence in the area. Johanna Huhtala, the business development coordinator of Eurajoki, however, put the decision to build Onkalo in Eurajoki down to trust. “Transparency between companies and municipalities is something that may not be common worldwide, but we have it in Finland,” she said. Kojo, too, suggested that part of the reason the public has not demanded more information about the repository could be that local politicians and people trust STUK’s assessment, which, Heinonen insisted, is because of the regulator’s “openness and transparency.”

The near absence of resistance to Finland’s nuclear-waste repository is a sharp contrast to the situation in other countries. In the United States, for instance, a planned nuclear-waste facility in Nevada’s Yucca Mountain continues to draw fierce opposition from large factions of the state’s residents and elected officials. In Germany, a proposed repository in Gorleben, Lower Saxony, has become the focus of constant protests by environmentalists and locals. The United Kingdom, too, is struggling to find an appropriate disposal site for its nuclear waste.

This May, the Indian government approved a plan to add ten nuclear reactors to the country’s existing 22 plants. They are expected to have a combined output of 7,000 megawatts, roughly doubling India’s current nuclear capacity. For now, spent fuel is processed at facilities in Trombay, a Mumbai suburb; at Tarapur, in Maharashtra; andat Kalpakkam, near Chennai. India’s apparently ambitious growth in nuclear power does mean, however, that the country will soon need a waste disposal site.

It is not clear whether the Finnish model for the disposal of radioactive waste is one that other countries would want to replicate. For the next hundred years or so, at the very least, there is no way of knowing whether this model will be successful.