Members of the GMB union at the Dounreay nuclear power complex are continuing to plan for strike action after rejecting a new pay offer.
Workers who are members of Prospect and Unite had also planned to take industrial action in January.
Prospect said its members had voted to accept an improved offer made to them and the union has withdrawn its notice of strike action.
Unite's position on the new offer could not be confirmed.
Earlier this month, members of the three unions voted to go on strike after rejecting a 1.75% increase in pay.
Prospect said that its members had since been made an improved offer.
It said the offer to its members was a three-year pay deal worth between 6.7% and 7.7% depending on inflation, with an opportunity to reopen negotiations in the third year if inflation remains above 3%.