Heysham 1 Power Station has shut down both of its nuclear reactors after an electrical fault in a gas turbine generator.
Firefighters were called to the plant at around 10.30pm on last night (Thursday) after a sprinkler system was set off.
A Lancashire Fire and Rescue Service spokesman said there was “an activation of a fire protection system”, which site operatives identified was caused by an electrical fault.
Four fire engines attended the scene and officers spent around two hours on the site.
He said: “In accordance with procedures for a nuclear plant we were called along to check on the work they were doing.
“The crews established there was no fire. As a precautionary measure the two nuclear reactors were shut down.”
The station has four gas turbines, which provide back-up electricity if there is a loss of power from the National Grid.
Ian Stewart, station director, said: “We took the decision last night to shut down both reactors as part of our standard process, when our back up systems are not available.
“This is something we always seek to do proactively in this type of situation.
“Thank you to Lancashire Fire and Rescue Service who attended the site as part of our normal, well-practiced emergency arrangements and checked our procedures and gave advice.”