Kozloduy Unit 5 in Bulgaria has resumed electricity generation after completing its scheduled annual maintenance outage. The 1,000 MW reactor was reconnected to the national grid on Monday, 15 June. Return to service followed authorization from the Nuclear Regulatory Agency, after it reviewed the maintenance results and approved the unit’s restart.
Maintenance outage timeline and scope
The maintenance outage began on 9 May. During the shutdown, engineers carried out inspection, repair, and modernization activities focused on maintaining safe and efficient operation of the unit. In addition to routine maintenance work, upgrades were implemented to support long-term operational sustainability of the reactor.
Westinghouse reload and RWFA fuel use
A key part of the shutdown process involved loading fresh nuclear fuel supplied by Westinghouse. The restart follows a cycle in which RWFA fuel assemblies were used for the third consecutive operating period. Bulgaria continues efforts to diversify fuel sources for its VVER-1000 reactors as part of that approach.
Fuel diversification program and EU context
Bulgaria’s fuel diversification program was initiated in 2024. Plant officials said the country has become the first European Union member state to introduce an alternative fuel source for this reactor type. They added that the initiative has drawn attention from the broader European nuclear industry amid growing concerns over fuel security and supply chain resilience in recent years.
