UPDATE 1-Centrica to become nuclear power player

* To take 20 percent stake in British Energy

* To form joint venture with British Energy owner EDF

LONDON, Nov 13 (Reuters) - British utility Centrica's (CNA.L) planned move into atomic energy by buying a 20 percent stake in British Energy is to go ahead, placing it at the forefront of Britain's nuclear new-build plan, it said on Friday.

Centrica's plan hinged on selling its 51 percent stake in Belgian utility SPE to British Energy's owner, French utility EDF (EDF.PA), a deal that was cleared by European Union regulators on Thursday. [ID:nLC576323]

Centrica has no experience in nuclear power generation but hopes teaming up with EDF, the world's biggest nuclear player, will give it a piece of a sector set to grow because of concerns over carbon emissions from coal and gas fired power plants.

EDF is to form an 80/20 joint venture with Centrica to build four European pressurised reactors (EPRs) in Britain, with the first expected to be built by 2017 as part of a government plan to replace the country's ageing atomic energy facilities.

"Nuclear energy is an essential component in ensuring clean, secure energy for the UK and we are proud to be part of the nuclear renaissance in the UK," Centrica chief executive Sam Laidlaw said on Friday.

On Monday, Britain set out plans to speed up the planning process for new nuclear power plants and big wind farms, naming 10 sites where reactors could be built, mostly alongside existing facilities. [ID:nL9055107]

About 20 percent of Britain's electricity was generated from existing nuclear power reactors in the second quarter of 2009, but all except one of them is due to shut by 2025.

Previous attempts to build new nuclear plants have been delayed by the exhaustive planning process. It took six years and cost 30 millions pounds ($50 million) to secure planning consent to build the last reactor, Sizewell B in southern England.

"The price secured for the sale of SPE will help preserve our balance sheet firepower as we focus on other investment opportunities that will further underpin UK energy supply security," Centrica, the owner of British Gas, Britain's biggest household energy supplier, said.

Former British gas monopoly Centrica has a growing portolio of gas-fired power plants and wind farms.

The EDF deal will also see Centrica take a fifth of British Energy's output that has not yet been sold.

Under the terms of the agreement, the British Energy and SPE transactions were expected to be sealed simultaneously on Nov. 26. (Reporting by Daniel Fineren; Editing by Dan Lalor) ($1 = 0.6017 pound)