Sellafield nuclear power station staff will vote on Monday whether to strike over pay.
Talks aimed at solving the pay dispute broke down on Thursday with trade unions claiming that Sellafield Ltd had not made a significant improvement on its previous offer.
Employees rejected by 85% to 15% an earlier pay offer worth 2% plus an increases in bonuses.
Trade unions led by the GMB are representing more than 10,000 Sellafield Ltd employees at both the Sellafield site in Cumbria and at Capenhurst nuclear plant in Cheshire.
Strike ballots will now commence on Monday 11 August, with a result due on 2 September.
GMB regional officer Steve Gibbons said: “We are confident of an overwhelming vote for industrial action when the result is tabled.”
Sellafield Ltd insisted it had made an improved offer this week.
A statement from the employer said: “The overall value of what was discussed would have offered the opportunity of earnings up to 4.5%, with the lower paid having the opportunity to achieve 5%. Employees would also be able to achieve consolidation of up to 3.75% on basic pay. The company view the revised position as comparable with other settlements currently being reached.”