The Czech Republic launched a tender on Thursday to build a new reactor at the Dukovany nuclear plant as the country aims to increase nuclear power generation.

Three companies — U.S. Westinghouse, France’s EDF and Korea’s KHNP — have passed a Czech government security appraisal and are expected to bid for the lucrative project.

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The project’s estimated cost of around 6 billion euros ($6.6 billion) is the biggest single investment in the Czech Republic, Industry and Trade Minister Jozef Sikela said.

Russian and Chinese companies, including Russia’s energy giant Rosatom and China’s CNG, have been excluded from the tender on security grounds.

Prime Minister Petr Fiala said Russian participation in the key project for the country’s energy security was "unimaginable" following the Kremlin’s invasion of Ukraine.

FILE - Four of the cooling towers of the Dukovany nuclear power plant rise high above the natural surroundings of Dukovany, Czech Republic, Sept. 27, 2011. The Czech Republic launched a tender on Thursday, March 17, 2022 to build a new nuclear unit at the Dukovany plant as the country is aiming to increase its reliance on nuclear power. Three companies that have passed a security assessment by the Czech government are expected to bid for the lucrative multi billion dollars project. It’s U.S. Westinghouse, France’s EDF and Korea’s KHNP. (AP Photo/Petr David Josek)

FILE - Four of the cooling towers of the Dukovany nuclear power plant rise high above the natural surroundings of Dukovany, Czech Republic, Sept. 27, 2011. The Czech Republic launched a tender on Thursday, March 17, 2022 to build a new nuclear unit at the Dukovany plant as the country is aiming to increase its reliance on nuclear power. Three companies that have passed a security assessment by the Czech government are expected to bid for the lucrative multi billion dollars project. It’s U.S. Westinghouse, France’s EDF and Korea’s KHNP. (AP Photo/Petr David Josek) (AP)

The new reactor will complement Dukovany’s four 510-megawatt units that were completed in the late 1980s. It should become operational by 2036, Fiala said.

"We want to make another step for the Czech Republic to become energy self-sufficient," Fiala said. He said more such projects will follow but didn’t disclose details.

The winning bidder is expected to be selected by 2024 with a construction permit to be issued by 2029, Fiala said.

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The Czech Republic already relies on six nuclear reactors to generate more than a third of its total electricity. Besides the four in Dukovany, state-controlled power company CEZ operates another two 1,000-megawatt reactors at the Temelin plant. CEZ will be in charge of the tender.

CEZ chief executive Daniel Benes said participants will have to submit preliminary bids by the end of November and then will have another 20 months to complete the final bids. A deal with the winner will be signed in 2024.

Unlike its western neighbors Austria and Germany, the Czech Republic is doubling down on nuclear power and renewable energy sources after deciding to phase out coal as a fuel for energy generation by 2033 in order to reduce carbon emissions.

Another two European Union countries in Central Europe, Slovakia and Hungary, have also been working to expand nuclear power production.

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The Transparency International watchdog published an open letter to the Czech industry and trade minister, criticizing a lack of information about the project, specifically details about how it will be financed and the final price.