Dounreay nuclear plant is facing New Year strikes after trade unions officially served notice of a ballot on industrial action over pay.
Hundreds of staff could be affected if members vote in favour of action next month.
The notice was served on nuclear decommissioning site operator DSRL, after workers rejected the latest pay offer.
Dounreay Site Restoration Limited (DSRL) management has offered a 1.75% increase on the basic rate of pay.
However unions – the GMB, Unite and Prospect – have described the offer, which is 2% below inflation, as “derisory”.
GMB Scotland organiser Liz Gordon said: “This pay offer makes a mockery of DSRL’s claim that they want to be recognised as a European reference site and global leader for nuclear decommissioning.
“Dounreay is the focal point of the Caithness economy and this is a highly localised workforce, so it is absolutely imperative that pay matches the cost of living to help deliver prosperity not just for our members but also our local communities.
“We are in the business of defending the interests of our members who deliver the decommissioning of this safety intensive site and we will settle for nothing less than the proper recognition and reward for this workforce.
“Our members have helped generate healthy profits for DSRL and its executives but this below-inflation pay offer is derisory.
“DSRL need to think again if they want to avoid industrial action in the New Year.”
The unions claim DSRL, a wholly owned subsidiary of its parent body organisation Cavendish Dounreay Partnership, increased its profits in 2016 for the second consecutive year to over £9million.
The industrial action ballot will run from next Friday, December 1, until Thursday, December 21.
A Dounreay spokeswoman said: “We are disappointed that the trade unions are proceeding to ballot their members as we are still actively negotiating and have made an offer that we believe to be comparable, if not better, than other publicly-funded organisations in the nuclear decommissioning industry.”