More than 100 safety staff who work in the nuclear part of a Plymouth dockyard are planning to strike next week.
Some staff would continue working during the strike to ensure safety
The planned walkout by workers at Devonport Dockyard follows a dispute about their grading.
DML, which runs the yard, said it was "an ongoing matter" and that "discussions were continuing".
The industrial action is due to take place on Tuesday, 9 November, but the GMB union said a skeleton staff would stay on duty to ensure safety.
The GMB said the industrial action would involve 108 members who are Health Physics Monitors, who are responsible for all aspects of safety for people working in the nuclear site.
The staff have been negotiating for three years over their grading. They want more money and more recognition of the responsibility involved in their job.
The GMB said almost all of the yard's Health Physics Monitors were union members and that, in a ballot, 100% voted for some form of action and 90% favoured a strike.
Devonport is currently the UK's only refitting and defuelling site for nuclear submarines.
DML said it was committed to ensuring that the risks to the public, its workforce, contractors and nearby navy personnel arising from its nuclear-related activities were "reduced to as low as is reasonably practicable".