The fall in operating profit was due to a planned 45-day shutdown of the power plant's first reactor, which implied higher costs compared to the previous year and a decrease in production, Nuclearelectrica told SeeNews in an emailed statement.
Last year, the planned shutdown of the second reactor at the country's nuclear power plant in Cernavoda lasted only 20 days.
The first reactor, shut down on May 5, 2012 for maintenance, was reconnected to the grid on June 13.
The company's turnover rose to 1.19 billion lei through September from 1.16 billion lei a year ago, Nuclearelectrica added.
Last month, Romania picked a consortium of local companies SSIF Swiss Capital and BT Securities to manage the initial public offering on the Bucharest bourse of a state-owned 10% stake in Nuclearelectrica.
Romania owns 90.27% of Nuclearelectrica and property restitution fund Proprietatea owns a 9.73% stake in the company.
The plant in Cernavoda operates two 700 megawatt reactors which cover around one fifth of Romania's electricity needs.
(1 euro = 4.5269 Romanian lei)