The Sellafield nuclear site in England will be operated at "reduced manning levels" today following "the detection of elevated levels of radioactivity", the company said.
Sellafield says the radiation levels are well below that which would call for any actions to be taken by the workforce.
The elevated levels are at one of the on-site radiation monitors at the north end of the site, and the UK nuclear site is still operating normally.
Sellafield lies about 180km from Ireland's coastline.
In a statement, Sellafield said the site was operating at reduced manning levels.
It said as “a result of a conservative and prudent decision, the Sellafield site is operating normally but with reduced manning levels today.
“This follows the detection of elevated levels of radioactivity at one of the on-site radiation monitors at the north end of the site.
“Essential workers only are being asked to report for work.
It continued: “Levels of radioactivity detected are above naturally occurring radiation but well below that which would call for any actions to be taken by the workforce on or off the site.
“The site is at normal status and employees and operational plants are continuing to operate as investigations continue.
“All our facilities have positively confirmed there are no abnormal conditions and are operating normally.”