“The storm damaged the power supply lines, causing an automatic safety shutdown at Unit 1 in Cernavoda,” state-run power company Nuclearelectrica said in a statement.
It said the situation was being assessed and the reactor should be up and running Thursday morning.
There were no reports of safety issues due to the shutdown.
Nuclearelectrica operates two 700-megawatt reactors in Cernavoda, covering around 20% of Romania’s energy consumption.