Plans for two new nuclear power stations have taken a "major leap forward" after a reactor design was approved by regulators.
The Office for Nuclear Regulation (ONR) gave the green light for an advanced boiling water reactor (ABWR) designed by Hitachi planned for Horizon Nuclear Power's plants at Wylfa on Anglesey and in Oldbury-on-Severn in South Gloucestershire.
Horizon chief executive Duncan Hawthorne said: "This is a huge milestone for Horizon and a major leap forward for us in bringing much-needed new nuclear power to the UK.
"Nuclear can deliver high volumes of stable low-carbon energy, which makes it a vital part of the country's electricity mix and, once up and running, both Wylfa Newydd and our Oldbury site will supply clean, reliable power to the UK for decades to come.
"It's testament to the strength of the combined team, and the proven nature of the technology, that the GDA process has been completed and delivered on time."
Tadashi Kume, president of Hitachi-GE, said: "Meeting the famously high standards of the UK regulators and completing generic design assessment (GDA) within our five-year target further demonstrates the strength of this project, and capability of the team delivering it.
"GDA is a thorough and rigorous assessment, and receiving approval on schedule is a credit to the outstanding design of the UK ABWR.
"Since 2012, we have been the subject of extensive assessment and scrutiny by the regulators. Throughout this process, their expertise and professionalism has been second to none. We now look forward to supporting Horizon's ramp-up of site-specific licensing for Wylfa Newydd."
ONR chief nuclear inspector Mark Foy said: "The completion of the generic design assessment of the UK ABWR is a significant step in our regulation of the overall process to construct this type of reactor in the UK, ensuring that the generic design meets the highest standards of safety that we expect in this country.
"We're already working on our assessment of Horizon's site licence application and on the development of the site specific safety case to progress, in due course, the construction and operation of these reactors at Wylfa Newydd."
Tom Greatrex, chief executive of the Nuclear Industry Association, said: "The design approval of the UK ABWR is good news for the UK's new nuclear programme and signals the conclusion of a thorough, rigorous and detailed process by the UK's independent regulators, widely acknowledged as world-class.
"With two-thirds of UK power stations closing between 2010 and 2030, this is an important step in providing secure, reliable and low-carbon nuclear power for the future, to homes, businesses and public services."