Bulgaria’s Kozloduy fuel switch to Westinghouse on track, BNRA says

Bulgaria’s push to diversify nuclear fuel supplies at the Kozloduy power plant is moving forward on schedule, according to the Bulgarian Nuclear Regulatory Agency (BNRA). The regulator said the ongoing replacement of Russian fuel with assemblies supplied by Westinghouse Electric Company at Unit 5 is proceeding without disruptions—an outcome investors and grid planners will watch closely because it reduces the operational risk that can accompany major fuel changes.

Unit 5 transition: batches installed, monitoring continues

BNRA Chairman Tsanko Bachiyski confirmed that the change is being carried out in line with approved technical documentation. He said two batches of new fuel assemblies have already been inserted into the reactor core, and early monitoring is indicating stable and expected performance levels.

The next step is tied to a planned shutdown scheduled for May 9. During a maintenance outage expected to last around 40 days, another set of fuel assemblies will be introduced. BNRA said continuous monitoring will remain in place throughout the process.

Timeline through 2027 and final assessment in 2028

The regulator set a longer horizon for completion and verification. It targets full fuel transition completion in 2027, while a final assessment of long-term performance is expected in 2028. That sequencing matters because it reflects how regulators typically validate not just immediate reactor behavior but also longer-run safety and reliability characteristics after a significant supply shift.

EU milestone for VVER-1000 diversification

BNRA described the diversification effort as a notable milestone within the European Union. Bulgaria is set to become the first EU member state to successfully implement such a transition for a VVER-1000 reactor, and the achievement was recognized during the latest review under the Convention on Nuclear Safety.

Unit 6 request returned over documentation gaps

While Unit 5 work advances, Kozloduy’s operator has also submitted a request to introduce test assemblies of the new fuel into Unit 6. BNRA said that application was returned for revision because of incomplete documentation. The plant has been given two months to address the issues before the review process can continue.

Regulatory approval hinges on safety compliance and data availability

Bachiyski emphasized that any regulatory approval will depend entirely on compliance with strict safety standards. He added that evaluating performance of test assemblies in Unit 6 will require several years of operational data, meaning any final decision on broader fuel replacement would only come after sufficient evidence has been collected.