At the earliest, construction of the facility, with a price tag of at least 10 billion pounds, or about $17 billion, would begin in 2020, with the goal of having the first reactor online in 2024.
"It is a step forward for the nuclear industry, but a lot of questions and hurdles need to be overcome in the next five or six years," said Antony Froggatt, an analyst at Chatham House, a London-based research organization.
The British government is concerned about not having enough sources of power in the coming decades. In addition, energy costs are a major issue in Britain with consumers' complaining about what they say are high prices. The government hopes that having more than one supplier of nuclear power will help bring down the soaring cost of building new plants.
The government's incentives, which include guaranteed electricity prices, are attracting the interest of international nuclear power players like Toshiba, General Electric and Hitachi, which are prospecting for new markets for their equipment and services.
EDF, another French utility, is the leading player in the British nuclear industry, having bought most of the country's existing plants through its acquisition of British Energy in 2008. EDF has spent hundreds of millions of pounds on preliminary work for a new nuclear plant at Hinkley Point in southwest England.
In the latest project, the reactor design for Moorside needs to be approved through a lengthy process, and possible objections on environmental grounds would need to be addressed. And, most important, whatever government is in place would need to decide how much taxpayers and consumers will spend to subsidize what is likely to be a costly undertaking.
The announcement strengthens the role of an important supplier of nuclear technology — Toshiba and its Westinghouse unit — as the crucial player in the project. In a reorganization completed recently, Toshiba will be taking a 60 percent stake in the joint venture that would build the plants, buying the 50 percent share held by Iberdrola, a Spanish utility, and a 10 percent slice from GDF Suez, for a total of about 100 million pounds. GDF Suez will retain 40 percent.
The joint venture, called NuGen, announced that new management was taking over under the leadership of the chief executive Sandy Rupprecht, an American who formerly headed development of the Westinghouse AP1000 reactor.
NuGen plans to build its plants just north of Sellafield on a site with a long history in the nuclear industry, including a fire in 1957 that caused radioactive contamination of the surrounding region.
Sellafield, where weapons-grade plutonium was once made, now houses facilities for reprocessing and storing spent fuel as well as for cleaning up old equipment. Martin Forwood, a local environmental campaigner, said NuGen would face many challenges, including limited water supplies to use as coolant for the reactors.
Forwood, who is a leader of a group called Cumbrians Opposed to a Radioactive Environment, said that by the time the developers had overcome all the obstacles, nuclear energy might seem obsolete.
"More and more renewable energy is being built" in the area, he said. "If the nuclear industry does not get its act together, it will wind up being redundant."
The station would be powered by Westinghouse AP1000 reactors, eight of which are now being built in North America and China.
If the new project does move ahead, Britain might have two large nuclear stations under construction after not building any since the 1990s. Only one British plant, called Sizewell B and completed in 1995, is considered modern, and with British companies lacking recent experience in building commercial nuclear plants, the government is relying on international providers.
The government welcomed the Moorside project, which it said might create as many as 21,000 jobs. "This announcement," the British energy minister, Michael Fallon, said in a statement, "shows how attractive the U.K. is for investors."