Darchem Engineering are the preferred bidder for a new contract at Hinkley Point. They will provide reactor tank liners for the nuclear project in an agreement worth £100m.
Bosses say the deal will create a number of local jobs and allow the company to strengthen its apprenticeship programme.
The firm, based at Stillington near Darlington, has spent years planning for a boost in the nuclear engineering sector. Darchem previously invested £8m on expanding its facilities, which has equipped them for the surge in demand.
The company also recently won a £50m contract to deliver over 1,000 stainless steel storage tanks to the Sellafield plant in Cumbria.