Deep in Europe’s largest mine. Ancient rocks teach Czechs what to do with nuclear waste

In the north of Sweden, beyond the Arctic Circle, deep beneath the town of Grüna lies a maze more complex than anywhere else in the world. It has a huge underground iron ore mine. The ancient rocks here have been interacting with each other for hundreds of millions of years. They can reveal more about themselves to scientists than any laboratory experiment. For example, how to safely store radioactive waste in the Czech Republic.

From our special correspondent – It seems incredible how easily geologist Ulf Andersen navigates the winding corridors of the Kiruna mine. An elderly Swede drives a white van through a convoluted underground complex where iron ore has been mined for 123 years.

Minus 300, 500, 700 meters, the markings on the gradual walls tell us how deep we are below the surface. There seems to be a second city under Kiruna with a population of 20,000. The mine employs thousands of people and exports 80 percent of all iron ore in the European Union. It corresponds to traffic in local narrow corridors. We pass staff cars, but also trucks or buses carrying miners.

“By elevator? Why? They transport iron ore here. We only drive cars,” Andersen replies in surprise when asked when we’ll board the elevator that takes us deeper into the mine. Like any other place there are rules of the road. We see signs indicating priority or speed limits, and the radar flashes from time to time.

According to Swedish tradition, workers like to sit down for an afternoon coffee break, or a complete dining room with an underground café completes the look of the city.

Because of that, a group of Czech scientists from the management of radioactive waste repositories was not here. We need to go deeper. We are already almost a kilometer and a half underground, and the fluorescent lights, signs and other cars are gradually diminishing. Geologist Ulf Andersen is increasingly excited.

Photo: Tomáš Klézl

We stop at a seemingly random spot in the middle of one of the corridors. Only the starting van and headlamp on Anderson’s helmet are lit here. We are performing. Know the depth. When it’s below zero and there’s snow on the surface, you can be cozy here in a t-shirt and sweatshirt.

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Ulf shines a light on one of the walls. It has not yet been mined here, and there are still pits carved into the walls. “This is one of the places where the models you use come in,” Andersen points out to the Czech scientists.

On one side of the depression, pieces of silvery stone with a brown color can be identified – magnetite, an almost pure iron ore. On the other hand, the gray rock, though clayey, binds the local corridors together. For billions of years they have been interwoven like this in the depths beneath the Krishna. Yet according to some estimates, clay may have formed as early as a billion years ago. “If this is true, it would be the oldest clay in the world,” says Andersen, a geologist.

There is no other place in the world where one can better observe how one rock affects another. It is absolutely necessary for Czech scientists. “Local magnetite is made of iron, similar to the steel container chosen for storing nuclear waste. And hundreds of millions of years interact with the clay here. The same will happen with our planned nuclear repository,” the repository management materials explain. Expert Michaela Matulová, Why did scientists go to the mines?

Natural analog

Exploring the interactions between clay and iron is one of the many pieces of the puzzle that is the deep radioactive waste repository project. The Czech Republic plans to permanently store spent fuel from Demilin and Dukovan in an underground system. It contains dangerous radionuclides for hundreds of thousands of years, and keeping them deep underground is the safest way to deal with the waste, scientists suggest.

Five hundred meters below the surface, people and nature will be protected from the release of radionuclides, in which sex storage places will be dug, but by steel containers surrounded by layers of bentonite – a rock with a high clay content. For example, people may recognize it as a cat litter refill, a similar substance that is part of the Smecta diarrhea product.

“It is a material that seals the surroundings of the container and provides long-term stable conditions. It is completely natural, it cannot be changed in any way. The Czech Republic is also rich in deposits, so we have an advantage over other countries,” explains Lucie Hausmannová, research and development coordinator of the repository.

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But it is important to check whether bentonite, a mixture of clay and steel, is actually safe to use as its main component, iron. So, for example, how quickly steel begins to corrode after prolonged contact with bentonite and does it damage the container.

This is what the mine at Kiruna will best demonstrate, paying for what scientists call a natural analogue in this regard. “For the mathematical models, we use data from our experiments, which are only a few decades old at most. If we want to check what happens between two rocks over a long period of time, we can look at nature,” Hausmannova says.

Similarly, in the past, scientists have already studied a place in Gabon, Africa, which acts as a kind of natural nuclear reactor. Using his example, they observed how far radionuclides can travel in what time. “We are inspired by what nature has already created. We see that it has worked here for billions of years. This is important to demonstrate the preservation of the repository,” says the research coordinator.

Although countries developing deep storage actively cooperate, the Czechs must verify the safety of the steel container themselves. Domestic scientists have determined that the use of steel containers is more suitable for Czech conditions, although it is the Swedes or Finns who use copper.

“They are suitable because they are close to the sea. This is not the case here. Steel is very affordable and we can predict its behavior for a million years and check its function,” says Marketa. Dohnalkova, head of the Czech Repository Project.

Photo: Tomáš Klézl

Scientists are drawing promising conclusions from observations made on Kiruna. “Based on our latest studies, we can say that the clay here has practically not been changed, it has not changed in any way. This indicates that the long-term preservation of the underground repository can be guaranteed,” he says. Michaela Matulová, subject matter expert in warehouse management.

Time is running out

Scientists from storage management have been collaborating with Swedish experts for a long time. While the Czech Republic is still looking for a place to store the waste, it has been known since 2009 that the Swedes will dig near the village of Forsmark in the south of the country. They will be built from 2030 onwards. And after five years, they should become the second country, after Finland, to start storing waste.

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In the Czech Republic, the process is slower. The search for the best location has been going on since the 1990s. It is now clear that it will be in one of these four places: Janoch near Demilin, Horka in Trebišk, Hradec in Zihlavsk or Bresov Podok in Kladovsk. 2028 should be clear.

“We are looking for a suitable rock massif that is large enough and durable enough to meet all conservation requirements,” explains Dohnalkova. The repository will be operational from 2050, a deadline requested by the European Commission from countries with active nuclear power plants.

Among other things, the Czechs face a problem that the Swedes need to solve. Scientists face opposition from residents of villages near the selected sites. They fear the impact of construction on the environment or the influx of residents moving here to work at the storage facility.

Even in Sweden, there were protests against the repository in some places, but the victorious Forsmark, on the other hand, actively applied for its location. “They knew it would bring growth to the municipalities. More employment, better schools and roads,” Peter Wikberg, former head of research at the Swedish Nuclear Waste Management Agency, told Aktuálně.cz last year.

And same is the case with Kiruna Mine. It is already the largest source of iron ore in the EU today, and it is still abundant underground. And so the mine continues to expand. Even to places where the city stands today of 20,000. A part of its residents will have to move, but there are no significant objections – most of them understand this.

The story about the city of Kiruna and its inhabitants was brought to Aktuálně.cz in a report.

Czech scientists are also interested in mining the Swedish krona. | Video: Tomáš Klézl

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