“Unit Two shut down on Wednesday evening, reasons unknown,” said Dumitru Dina, who heads the NPP operator Nuclearelectrica National Nuclear Power Corp.

Dina added that the shutdown was “nothing serious” and posed no threat.

The news came about a month after Unit One of the NPP briefly shut down when a storm in the area caused disruptions in electricity transmission lines in December 2012.

Cernavoda, the country’s only nuclear power plant, is located about 100 miles east of the capital Bucharest and accounts for about 18 percent of the country’s total electricity output. It was designed in the 1980s by Atomic Energy of Canada Limited and has two units with Canadian-made CANDU (CANada Deuterium Uranium) pressurized heavy water reactors.