The European Union country currently relies on Russian nuclear fuel for both units at the 2,000 megawatt Kozloduy plant, but is seeking to boost energy security following Russia's invasion of Ukraine.

The plant produces about 35% of the country's electricity and currently uses nuclear fuel supplied by Russian firm Rosatom.

Kozloduy is also aiming to sign a deal with France's Framatome, a unit of EDF, for its other reactor, Unit 6.

"We have finally made a step towards diversifying the nuclear fuel for our plant. This way we are ensuring our energy security," said Kozloduy CEO Georgi Kirkov.

Bulgarian Energy Minister Rossen Hristov said that at present nuclear fuel shipments from Russia were unclear, so the new 10-year contract with Westinghouse helped secure the plant's operation.

The new fuel will be used from mid-2024, he said, while current fuel stores can be used until then.

Last month, parliament urged Bulgaria's caretaker government to secure alternative nuclear fuel supplies for the plant by April 2024 to and mitigate risks for the country's energy security.

Bulgaria's Nuclear Regulatory Agency must still license Westinghouse's fuel for use in the country.

(Reporting by Tsvetelia Tsolova; editing by Jason Neely; Editing by Jason Hovet)