Station director Paul Winkle said: “Whilst carrying out routine maintenance in the conventional turbine part of the plant there was an issue with a valve and our operations team took prompt action and manually shut down the reactor, putting safety first.
“Cooling to the reactor was maintained at all times and there were no safety, health or environmental impacts. The reactor will be returned to power as soon as maintenance is satisfactorily completed.”
A spokeswoman for EDF Energy said the unplanned shutdown of reactor 2 is expected to be short-lived and reactor 1 is still generating power.
WWF Scotland director Lang Bank said: “This might be the first unplanned shutdown at Torness this year, but given similar incidents in the past few years it’s clear that nuclear power is showing itself to be an increasingly unreliable source of energy.
“It underlines why Scotland is right to be choosing to harness more power from renewable energy sources.”