A final depository

The method, proposed by the Swedish Nuclear Fuel and Waste Management Company (SKB), relies on the stability of the granitic bed-rock and two engineered barriers: a copper-cast iron canister enclosed by highly compacted bentonite clay.

Critics argue that sufficient testing is lacking

"The government supports the assessment by the Swedish Radiation Protection Authority, expert authorities and researchers that the method is safe for storing the waste," Strandhäll said.

While there are over 400 nuclear power plants in operation across 38 countries, Sweden is first in the world to approve the use of a so-called "final depository."

Will the capsules hold up?

Still, controversy remains over whether the storage technique will hold up under pressure. Nuclear waste must be stored safely for at least 100,000 years to allow the radiation to go down to the same levels of natural uranium ore. In an interview with Dagens Nyheter, Jessica Palmqvist, head of the research and development at SKB, claimed that the copper capsules will essentially last forever.

But critics argue that sufficient testing is lacking. For example, the capsules haven’t yet been exposed to live radiation while in the storage environment. "No one knows exactly how long the copper capsules will last," said Christofer Leygraf, professor emeritus in corrosion theory at the Royal Institute of Technology. "But it is more about them lasting 100 years than 100,000 years."

Of course, estimating the resilience of any material meant to last for 4,000 generations involves a lot of variables. For example, the final repository needs to withstand earthquakes, climate change and the weight of the 3.5-km thick ice which could cover the area during the next ice age in 50,000 years or so. That is also the reason why many other countries, such as Spain, have made the decision to rely on intermediary storage space while more testing is carried out.

Nuclear power is increasingly emerging as part of the answer

But Sweden was hard-pressed to reach a decision. The Scandinavian country announced last year that it's running out of intermediary space to store the waste produced by its six reactors that supply roughly one third of the nation’s power — risking a national power crisis should plants need to be halted as the storage site reaches full capacity by 2024.

In August, the government announced an expansion of the intermediate storage — where radioactive waste is put in water basins 30 meters into the bedrock — from 8,000 to 11,000 tons. But as constructing the permanent depository will take ten years, and the actual waste disposal another 50-60 years, the final sealing of the repository won’t take place until the turn of the next century. Should the decision drag out, the temporary storage risks filling up before it can be moved to the new facility.

Finland and China follow suit

Despite the controversy, more countries are likely to follow Sweden’s lead. In Finland, a final depository for nuclear waste is already under construction using the same techniques as in Sweden. Although a decision is yet to be made regarding the actual disposal, the facility will be ready in 2024. In China, where another 22 reactors will soon be added to the country’s existing 32, construction started last year of an underground laboratory in the Gobi Desert to decide whether it would be a suitable location for a nuclear waste dump. In Canada, a four-year drilling program to assess the geographical conditions for a depository in northwestern Ontario was wrapped up last month and is now entering a water-testing phase.

Meanwhile, the European Union has drawn up a landmark proposal to classify some nuclear power as green investments. If approved, it could set off a landslide of nuclear energy projects on the continent.

In the U.S., the White House's Bipartisan Infrastructure Deal signed in November last year allocated $6 billion to prevent premature retirement of existing zero-carbon nuclear plants. More broadly, an Associated Press survey of the energy policies across all U.S. states found that about two thirds say nuclear — in one form or another — will help take the place of fossil fuels.

Indeed, as the world has so far failed in significantly bending the global emission curve, and the energy sector remains the largest emitter of greenhouse gasses, nuclear power is increasingly emerging as part of the answer. As such, we can only hope that today’s climate decisions don’t end up harming future generations once again.