Regulators are expected to announce that they have approved the design for nuclear reactors put forward by EDF and Areva as suitable to be built in the UK.
The move will mark the end of a five-year, £35 million "generic design assessment" process by the Office for Nuclear Regulation (ONR) and the Environment Agency to assess the companies' UK EPR reactor for use in the UK.
The regulators have secured 82 design changes to improve safety and security, including a number brought in following the Fukushima disaster in Japan, when nuclear reactors went into meltdown after a massive earthquake and tsunami.
These include additional flooding protection for electricity supplies and provision of mobile pumps and generators and places to plug them in.
It will not mean construction can begin on EDF's planned plant at Hinkley Point, Somerset, which, if it goes ahead, will be the first new nuclear power station built in the UK for a quarter of a century.
Site-specific construction consents and environmental permits are still needed, along with a planning decision by Energy Secretary Ed Davey, which is expected by March next year.
The project is also subject to EDF's final investment decision on whether to go ahead with building two new reactors at Hinkley Point.
But regulators believe approving the generic design for the type of reactor would be a "significant step" in constructing a new nuclear plant.
Completing the assessment while the designs are still on paper will prevent changes having to be implemented during construction when it would have been more costly, difficult or time-consuming, officials said.
The UK EPR design is just one of four designs that started the process in 2007, with the other three pulling out or putting their projects on hold.
Hitachi, which bought the Horizon project to build two nuclear power plants at Wylfa in Anglesey and Oldbury, Gloucestershire, has yet to formally begin the process.