The maintenance of the plant’s Unit 6 reactor is scheduled to be completed in early November, it said in a statement.
Reactors at Kozloduy are refuelled every 12 months.
Kozloduy’s other reactor, Unit 5, currently operates at full capacity, the plant added.
Nuclear power accounts for a third of the country’s domestic production. The Kozloduy plant, on the Danube, generated 35.2% of Bulgaria’s total electricity output last year.