Centrica raises more questions than answers over UK's nuclear future But the decision is none the less embarrassing because it highlights a mounting list of doubts over new nuclear. Who will build the reactors? What will they cost? And what will be done with the radioactive waste they produce? Centrica's withdrawal does not mean new nuclear plants won't be built but it does mean it is highly unlikely that any UK companies will be involved. Centrica's decision was based on a fundamental mismatch between the proposal and the kind of investments its shareholders wanted - ones with faster and less risky returns. "Investment in new nuclear presents a unique risk profile which may be suitable for some companies and not for others," George Borovas, nuclear expert at law firm Pillsbury said. New investors will quickly move to take Centrica's position. China's Guangdong Nuclear Power Group is understood to be waiting in the wings to take on at least the 20pc stake in the venture that Centrica opted against, and quite possibly up to 49pc. That may salvage one project but questions remain over who will build reactors at the other three sites. Japan's Hitachi bought the Horizon nuclear venture last year, after German giants RWE and E.ON pulled out, but it will need to attract financial backers before it builds reactors at its sites on Anglesey and in Gloucestershire. While Iberdrola has repeatedly denied it is pulling out of the NuGen consortium to build reactors in Cumbria, it is hard to see the numbers stacking up for the Spanish utility any more than they have for Centrica. Ministers have long touted public support for new nuclear but the prospect of Chinese state corporations having access to assets that are so critical to national security and the economy is likely to unnerve some. Then there is the question of cost. Back in 2008 EDF told London investors its reactors cost about €4bn each (£3.4bn) and their production cost in the UK would be £45/MWh. The first new reactor was due to be running by the end of 2017. Neither EDF nor Centrica would disclose figures yesterday but senior sources suggest reactor costs are now nearer £7bn and the first reactor is unlikely before 2021. A combination of the Fukushima disaster, which prompted modifications to reactor designs, and EDF's experience of cost overruns at its Flamanville site in France have contributed to these revisions. The reactors are thought likely to require close to £100/MWh to run. This matters because EDF will be given a contract guaranteeing that price, with all UK energy consumers facing a levy on bills to top up the market price to that level. EDF is negotiating with the Government and expects a deal "soon." EDF Energy chief executive Vincent de Rivaz insisted his company had given the Government final construction costs that were "well understood and stable" and it was confident it could deliver on them. But Centrica insisted costs remained uncertain. "Just because your estimate has been stable for a while, it doesn't mean there is no uncertainty in it," Mr Luff said. As has been seen at Flamanville, even after you start building you can't necessarily be certain of the costs. Even if the players and the costs fall into place, there is still the question of what to do with the radioactive waste any new nuclear plants will create. Just yesterday MPs released a scathing report that said successive Governments had failed to tackle problems of Britain's nuclear waste. Estimated costs of decommissioning waste at Sellafield have now hit £67.5bn with "no indication of when that cost will stop rising." Unlike the operators of Britain's existing nuclear reactors, which were built without taking into account decommissioning costs, EDF will pay into a fund to cover the costs of its clean-up. But the question of what to do with it remains unresolved. Ministers want to bury it underground in a giant store where it can remain forever. Last week Cumbria, the only area considering taking the waste, voted against a burial site in the county. The Department of Energy and Climate Change says it is determined that nuclear "will play a key role in our future energy mix." That may be so but, after yesterday's news, the questions still outnumber the answers.