Energy giant EDF is set to make its long-awaited final investment decision on the planned nuclear power station at Hinkley Point, ending doubts over the massive £18 billion project.
The French firm's board is meeting in Paris on Thursday and is expected to give the go-ahead for the first nuclear power station to be built in the UK for a generation.
UK unions will warmly welcome the much-delayed decision, saying workers were "raring to go" - with 25,000 jobs set to be created.
But environmental groups such as Greenpeace will criticise the go-ahead, calling for investment in home grown renewable energy like offshore wind.
Fresh criticism is also expected on the Government's promise to pay EDF £92.50 for each megawatt hour of energy it generates.
Hinkley Point C (HPC) will provide 7% of the UK's electricity over its estimated lifetime of 60 years and is scheduled to begin generating power in 2025, several years later than planned.
The main reason for the delay has been worries over the financing of the project by EDF, which is 85% owned by the French government, with French trade unions warning it could ruin the company's finances.
China General Nuclear Power Corporation (CGN) is set to be confirmed as taking a 33.5% stake in the project.
Ahead of the decision, EDF said: "HPC is a unique asset for French industry as it would benefit the whole of the nuclear industry and support employment in major companies and smaller enterprises in the sector.
"This project has been the subject since 2013 of a significant sharing of information with employees and their representatives, illustrating the commitment of the company to quality social dialogue."
Unite national officer for energy Kevin Coyne said: "We urge the EDF board to give the financial go-ahead on a project which will generate thousands of decent skilled jobs and help meet the energy needs of the UK for generations to come.
"The cost of not doing so could result in the lights going out in Britain and the West Country missing out on the much needed economic boost which this major infrastructure project would bring."