UK nuclear regulator approves restart of three EDF reactors

* Heysham 1-2, Hartlepool 2 set to restart on Saturday

* Hartlepool 1 set to come back on Nov. 26 (Adds more detail)

By Nina Chestney

LONDON, Nov 21 (Reuters) - Britain's Office for Nuclear Regulation (ONR) gave the go-ahead on Friday for EDF Energy to restart three nuclear reactors over the next week which have been off line since August for inspections necessitated by a fault on a similar unit.

UK power traders have been monitoring the dates the reactors will return to service because Britain faces tight electricity supplies this winter due to the unexpected closure of some power plants. There are currently nearly 5 gigawatts of nuclear capacity offline due to planned and unplanned outages.

"ONR has today granted permission for three reactors at Hartlepool and Heysham 1 to return to service," it said in a statement.

EDF Energy, whose parent is French utility EDF (Paris: FR0010242511 - news) , had to show it was safe to bring the three reactors back online before approval would be granted.

"ONR has completed an independent assessment ... and is satisfied that EDF has demonstrated the continued safe operation for these reactors," the ONR said.

Two of the reactors, Heysham 1-2 and Hartlepool 2, are scheduled to reconnect to the grid on Saturday, while Hartlepool 1 is set to come back online on Nov. 26.

In August, EDF Energy had to take these three reactors off the grid for inspection after a crack was discovered on a boiler spine on Heysham 1-1 reactor.

That reactor had already been offline since June for refuelling and is not expected to return to service until the end of December.

The ONR said EDF Energy will present a separate safety justification for Heysham 1-1 which will be subject to independent assessment and will again require the regulator's formal permission from ONR before it can restart. (Editing by Jason Neely and David Holmes)