Around 200 jobs at the Dounreay nuclear site are expected to go in the next year as decommissioning progresses.
Dounreay Site Restoration Limited (DSRL), the company delivering the closure programme at the Caithness site, said jobs will reduce as some projects come to an end.
Up to 150 DSRL employees are expected to leave under voluntary redundancy arrangements.
The rest will be from the agency and contract workforce largely associated with projects which are due to end.
The Unite union said it is “disappointed” over the plans as it believes there is enough work to support all the existing jobs.
DSRL said it will work with trade unions and other stakeholders to ensure everyone is treated fairly and with respect throughout the process.
In a letter to members of the Dounreay Stakeholder Group, Dounreay managing director Phil Craig said: “The site, its workforce and the community have long planned for such reductions and we have seen numbers reduce in the past.
“More than £10 million has been invested by Dounreay and the Nuclear Decommissioning Authority in socio-economic projects in the last decade, which has helped leverage more than £35 million of additional funding.
“This is helping to create new and sustainable jobs in Caithness and north Sutherland and we will soon share our updated socio-economic plan for the next three years, including ongoing support for the regeneration partnership.”
The reactor at Dounreay stopped operating in 1994 and is more than halfway through decommissioning.
Unite regional officer Ian Ewing said: “We are very disappointed and concerned that the company have announced redundancies when we believe there is enough work to sustain the resources presently employed.
“We will work with the company to minimise the numbers at risk and we will not entertain any compulsory redundancies.”