site.btaKozloduy Unit 5 Switch to Westinghouse Fuel "Proceeding Smoothly"

The transition from using Russian fuel at Unit 5 of the Kozloduy Nuclear Power Plant to fuel supplied by Westinghouse is currently proceeding smoothly and in line with the documentation on the basis of which the Nuclear Regulatory Agency (NRA) issued its permit, NRA Chair Tsanko Bachiyski said on Tuesday. He was speaking at the Agency's annual press conference, held at its training centre in Sofia.

Bachiyski said two reload batches have been loaded into the core of Unit 5 – that is, 42 and 43 fuel assemblies of Westinghouse Electric Company fuel. "Everything currently indicates that the fuel is behaving as justified in the submitted documentation on the basis of which we issued the permit," he commented.

Unit 5 is scheduled to be shut down on May 9 for maintenance and refuelling, during which another batch of Westinghouse fuel will be loaded. The expected outage period is 40 days. Monitoring of the fuel's behaviour will continue, and in 2027, the entire core is expected to be loaded with the new fuel. "Then it will become completely clear whether there are any problems or not," Bachiyski added, reiterating that none have been identified so far.

The transition to a full replacement with Westinghouse fuel is expected to be completed in the spring of 2027, and in 2028 it will be finally determined whether its use will continue or whether other measures will be required.

The successful diversification of nuclear fuel for Unit 5 at the Kozloduy NPP is one of the two areas of good performance highlighted for Bulgaria following the completed tenth review of national reports by the parties to the Convention on Nuclear Safety, which is held every three years and of which Bulgaria has been a member since 1995. The NRA noted that this recognition is particularly significant in a European context, as Bulgaria is the first EU country to successfully implement a nuclear fuel diversification programme for a VVER-1000 reactor.

During the press conference, Bachiyski also said that the Kozloduy NPP submitted an application to the NRA requesting permission to place six test assemblies of the new fuel in the core of Unit 6. However, the documentation was returned to the plant because the application did not meet the criteria for a formal review, the regulator's chair clarified. The Agency has given the plant two months to provide the missing documents so that the substantive review can proceed.

"We are ready to carry out a safety assessment, we have sufficient experience," Bachiyski said. He was adamant that the Kozloduy NPP will receive the permit once the regulator is satisfied that the replacement is safe. The transition and operation of the six assemblies lasts four years, so the NRA is not expected to take a decision and issue a permit for the use of another type of fuel before that period, Bachiyski added.