There has been an unplanned shutdown of one of the reactors at Torness nuclear power station in East Lothian. Operators EDF energy have not indicated when Reactor 2 will return to service after the unit "tripped" on Monday. This refers to the reactor being rapidly shut down by the insertion of its control rods. The company said the cause of the incident is under investigation. Torness station, 33 miles east of Edinburgh, generates enough electricity to power more than two million homes. Statutory outages occur every three years to allow the units to undergo inspection and maintenance work. WWF Scotland director Lang Banks said: "With this unplanned shutdown at Torness coming so soon after news of cracking in the bricks surrounding the reactor at Hunterston, nuclear power is once again revealing itself to be a creaking and increasingly unreliable source of energy. "It underlines why Scotland is right to be choosing to harness more power from renewable energy sources."