After a decade of dealmaking and political brinkmanship, Electricite de France SA finally won the green light to build what will be the most expensive nuclear power station ever built, an 18 billion-pound ($24 billion) behemoth at Hinkley Point on England’s west coast.  It will cost more than the tunnel that connects England to France, use enough steel for a railway track between London and Rome and require enough concrete to build 75 sports stadiums. Now, the French utility just needs to prove that its EPR technology—the most powerful, complex and expensive in the world—works. And that it can build the two 1,650-megawatt reactors on time and on budget. It hasn’t yet. “We know that the hardest lies in front of us,” EDF Chief Executive Officer Jean-Bernard Levy said Thursday after the U.K. government approved the project. “My top concern is to show that we can rise to this industrial challenge.” The EPR was designed more than a decade ago to offer unrivaled safety —including a concrete shell thick and resilient enough to withstand a commercial plane cash—- and reduce atomic waste. French nuclear group Areva SA broke ground on the first project using the technology in Finland in 2005, and EDF followed at Flamanville in France in 2007. Then things started to go wrong. What Makes Hinkley Point So Expensive? In Finland, Areva has lost 5.5 billion euros ($6.2 billion) and the plant is almost 10 years late. At Flamanville, EDF’s costs have more than tripled to 10.5 billion euros, the project is six years behind schedule and the French authorities are investigating flaws in the reactor vessel manufactured by Areva. Both plants are due to be completed in 2018. “Given the project history of the EPR technology, market confidence in Hinkley Point C being built on time or on budget, and therefore create shareholder value, is understandably low,” Ahmed Farman, an analyst at Jefferies Ltd. in London, said in a note Thursday. Those concerns drove out EDF’s chief financial officer earlier this year. Thomas Piquemal quit his post in March saying that the Hinkley Point project put the whole company at risk. Chinese Investment To help shoulder the construction costs, EDF convinced China General Nuclear Power Corp. to take 33.5 percent of the U.K. project. The Chinese utility said in May it’s hoping to start operating the two EPRs it’s building with EDF in Taishan as soon as next year. CGNPC is also due also help fund two more EPRs in the U.K. at a later stage. In exchange, EDF will help CGNPC get a license to build a Chinese-designed reactor at Bradwell in the U.K. For EDF, which needs to prepare for the progressive replacement of part of its 58 reactors in France and of its 15 aging reactors in the U.K.— which hasn’t built a nuclear plant in more than 20 years—the challenge is also financial. EDF “will have to shoulder the financial implications of a very long construction phase during which the investment will not generate any cash flow,” Paul Marty, a vice president at Moody’s Investors Service, said Thursday in an e-mail. To shore up its balance sheet, EDF plans to sell 4 billion euros of new shares by early next year and 10 billion euros of assets by 2020. It will also have to buy a majority stake in Areva’s reactor-manufacturing business, one of the main suppliers for Hinkley Point, as part of a French government-led rescue plan for the struggling nuclear group. To attract the French and Chinese interest, the U.K. guaranteed that they can sell power generated by the plant at 92.50 pounds per megawatt-hour, more than double current market prices, for as long as 35 years. That price is cheaper than power at recent offshore wind farm auctions, and the U.K. needs both nuclear and wind power, EDF Energy CEO Vincent de Rivaz said at a conference in London Friday. He reaffirmed that Hinkley Point will be on time and on budget. The Hinkley Point investment will benefit from the lessons of the projects in France, China and Finland, and will generate an annual rate of return of 9 percent, Levy said. It may also encourage other European countries to build the low-carbon technology, he added. “We have to roll up our sleeves,” Levy said. “It gives us a great responsibility.”