The facility, set to begin operation in 2024, isn't based on a foolproof concept
Finland, a nuclear energy champion, claimed it has figured out how to tackle one of the bigger issues with nuclear energy: Safely managing radioactive waste.
The country plans to store its nuclear waste in an underground facility called Onkalo. The structure, named after the Finnish word for “pit”, is a 500-meter-deep underground disposal facility designed to store used nuclear fuel permanently.
The deep geological repository is usually built in places containing a stable rock.
Finland can become the first to commission a plant to permanently store spent nuclear fuel. The idea is to encase the waste in corrosion-resistant copper canisters. These will be further encapsulated in a layer of water-absorbing clay. The setup will be buried in an underground tunnel.
The facility is now equipped with 500 sensors to monitor the functioning of the entire system, according to VTT Technical Research Centre of Finland Ltd, a state-owned company and one of the contributors to the project.
“Monitoring brings evidence that the repository will be keeping the outside world safe from the nuclear fuel waste,” Arto Laikari, senior scientist from VTT, said. The state-owned company’s collaborator Posiva, a Finnish nuclear waste management organisation, has submitted the operating license for the facility and is awaiting approval.
In 2023, Posiva will do a final trial run of the disposal mechanism but without radioactive material, Erika Holt, project manager from VTT, told Down To Earth. It is expected to begin operations in 2024.
Problem of disposing nuclear waste
For years, the nuclear industry has been trying to find solutions to the waste problem. They are generated at various steps during the nuclear life cycle: Mining uranium ore, producing uranium fuel and generating power in the reactor.
The waste can remain radioactive for a few hours, several months or even hundreds of thousands of years. Depending on the extent of radioactivity, nuclear wastes are categorised as low-, intermediate- and high-level waste.
About 97 per cent of the waste is either low- or intermediate-level. The remaining is high-level waste, such as used or spent uranium fuel.
A 1,000-megawatt plant creates about 30 tonnes of high-level nuclear waste every year, according to the International Atomic Energy Agency.
“Even at low levels, exposure to this waste will be harmful to people and other living organisms as long as it remains radioactive,” Ramana explained.
Some nations are storing waste on-site. But it carries the risk of radioactive leakage. In the United States, for instance, spent fuel is stored in a concrete-and-steel container called a dry cask, according to the US Energy Information Administration.
India and a handful of other nations reprocess about 97-98 per cent of the spent nuclear fuel to recover plutonium and uranium, according to data from the Bhabha Atomic Research Centre.
India also recovers other materials like caesium, strontium and ruthenium, which finds application as blood irradiators to screen transfusions, cancer treatment and eye cancer therapeutics, respectively, according to the research institute.
The remaining 1-3 per cent end up in a storage facility. India also immobilises the wastes by mixing them with glass, which is kept under surveillance in storage facilities.
But there are problems with this approach as well. Except for the plutonium and uranium, all the radioactive material present in the spent fuel is redistributed among different waste streams, Ramana said. “These enter the environment sooner or later.”
The plutonium and uranium intended for reuse in other nuclear reactors will also turn into radioactive waste, he added.
Nations like Finland, Canada, France and Sweden are also looking at deep geological repositories to tackle spent nuclear fuel wastes.
In January 2022, the Swedish government greenlit an underground repository for nuclear waste. Construction in Sweden will take at least 10 more years, Johan Swahn, director of MKG Swedish NGO Office for Nuclear Waste Review, a non-governmental environmental organisation, said.
Finland can share its experience with colleagues and partners worldwide, Holt said. “But each country and programme must have their own solutions. Worldwide, we work together to show nuclear energy (and the holistic views for responsible waste management) are viable for meeting CO2 targets,” she added.
Is the approach safe?
Experts associated with the project said that 40-years of theoretical and lab-based studies suggest that the geological repository is safe.
The bedrock provides a natural barrier to protect from radioactive release to the environment, such as water bodies and air, Holt explained.
The use of clay and copper provides a protective layer to ensure no release due to extreme conditions like earthquakes.
But Ramana argues that theoretical safety studies are not foolproof. There are significant uncertainties stemming from various long-term natural processes. These include climate change and the unpredictability of human behaviour over these long periods of time, he added.
Besides, design failure could undermine claims about safety, the expert noted. For instance, a few scientists fear that copper canisters can become corrosive and crack.
Finland’s team chose copper because it corrodes slowly. But Peter Szakálos, a chemist at the KTH Royal Institute of Technology in Stockholm, is not quite sure.
In a 2007 study, Szakálos and his team observed that copper could corrode in pure, oxygen-free water. “It’s just a matter of time — anything from decades to centuries — before unalloyed copper canisters start to crack at Onkalo,” he told Science journal.
On February 14, 2014, radioactive materials such as americium and plutonium leaked out of the Waste Isolation Pilot Plant, a deep geological long-lived radioactive waste repository, following an accident. The facility dealt solely with a special class of wastes from nuclear weapons production.
“If a failure like this happened within two decades of opening the repository, what are the odds that such failures won’t happen over the millennia that these repositories [Finland’s Onkalo] are supposed to operate safely?”
Both the Finnish project and the Swedish decision are very important for the international nuclear industry because the latter can point to these facilities to prove the nuclear waste problem is solved, Swahn said. “But it is very uncertain whether copper as a container material is a good idea.”
The projects may still fail as the understanding of how copper behaves in a repository environment is still developing, the expert added.
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