The ongoing replacement of Russian nuclear fuel with supplies from Westinghouse Electric Company at Unit 5 of the Bulgarian nuclear power plant Kozloduy is progressing without disruptions, according to the national nuclear regulator Bulgarian Nuclear Regulatory Agency (BNRA).
BNRA Chairman Tsanko Bachiyski confirmed that the transition is proceeding in line with approved technical documentation. Two batches of new fuel assemblies have already been inserted into the reactor core, and early monitoring indicates stable and expected performance levels.
The unit is scheduled for a planned shutdown on May 9, when another set of fuel assemblies will be introduced during a maintenance outage expected to last around 40 days. Continuous monitoring will remain in place, with the full fuel transition targeted for completion in 2027, while a final assessment of long-term performance is expected in 2028.
The regulator highlighted that the fuel diversification effort represents a notable milestone within the European Union, as Bulgaria becomes the first EU member state to successfully implement such a transition for a VVER-1000 reactor. This achievement was also recognized during the latest review under the Convention on Nuclear Safety.
At the same time, the operator of the Kozloduy plant has submitted a request to introduce test assemblies of the new fuel into Unit 6. However, the application has been returned for revision due to incomplete documentation, with the plant given two months to correct the issues before the review process continues.
Bachiyski emphasized that regulatory approval will depend entirely on compliance with strict safety standards. He also noted that evaluating the performance of test assemblies in Unit 6 will require several years of operational data, meaning any final decision on broader fuel replacement will only be made after sufficient evidence is collected.
