Around 400 Sellafield workers went on strike on Wedensday and four more walkouts are planned over the coming weeks.
Workers from 15 construction firms based at the nuclear site took part in the two-and-a-half-hour action.
They staged pickets lines at Sellafield’s three main gates.
The latest action is part of an ongoing dispute between workers and their contracting firms.
Further strikes are planned on September 2, 9 and 16 from 5.30am to 9am, followed by a full-day action on September 23, in addition to an overtime ban and work-to-rule policy that is due to start next week.
The dispute, involving members of the Unite union from firms including Shepley Engineers, PPS Electrical, Hertel and Balfour Beatty, centres on contractors’ health and safety concerns.
They are asking for a full-time union convenor on site and a health and safety committee for the contractors.
But the NAECI contractor group at Sellafield says its current system is successful and has no plans to alter it.
The matter has escalated, says the union, after members offered to end a previous overtime ban and work-to-rule “as a gesture of goodwill”, however, four contracting firms responded by imposing their own overtime ban on its staff.
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