HELSINKI (AP) — Sweden on Monday shut down one of four nuclear reactors at its largest power station after over 40 years of operation, with operators citing a lack of profitability and rising maintenance costs.

Swedish news agency TT said the Ringhals 2 reactor in southwestern Sweden was permanently shut down in accordance with a 2015 decision by its owners — Swedish state-owned energy group Vattenfall and German utility Uniper.

The Ringhals power station, located some 65 kilometers (40 miles) south of Sweden’s second largest city of Goteborg, is one of Sweden’s three nuclear power plants and has so far generated 15%-20% of the Nordic country’s total electricity consumption.

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Vattenfall says on its webpage that Ringhals is the biggest power station in the entire Nordic region.

“It’s clear that there’s a bit of a sad feeling at the moment,” Lars Bjornkvist, project manager for the Ringhals 2 closure, told TT. The pressurized water reactor was provided by Westinghouse Electric Corp. in 1970 and started commercial operation in 1975.

Sweden has seen a long-running debate on the pros and cons of nuclear power among politicians and citizens in the past years.

In 2010, Swedish lawmakers made a decision to allow replacement of the country’s existing nuclear reactors with new ones, and opinion polls have shown majority support among Swedes for that initiative over the years.

Power plant operators, however, have for a long time complained that Sweden’s unique nuclear capacity tax and required heavy investments on safety have made nuclear power an unreasonably costly energy generating method in the country. Swedish lawmakers agreed in 2016 to phase out the nuclear capacity tax completely by the end of this year.

Vattenfall and Uniper have decided to also shut down the Ringhals 1 reactor at the end of 2020, while Ringhals 3 and Ringhals 4 are due to keep running until the 2040s.

Work to manage radioactive waste at Ringhals 1 is due to get under way immediately, and Ringhals 1 and 2 reactors will be torn down by the end of 2022. The entire decommissioning process is to take at least eight years, TT reported.

Following the closure of Ringhals 1, Sweden has a total of seven reactors at three nuclear plants across the country: three reactors at the Forsmark plant north of Stockholm, one reactor at the Oskarshamn plant in southeastern Sweden and three at Ringhals.

They generate about 40 percent of electricity in Sweden, a nation of 10 million people.