Dounraey Fire Caused Unauthorised Radioactive Release
A fire at Dounreay caused what's described as an 'unauthorised release' of radioactivity.
Last month's blaze was in part of the prototype fast reactor where sodium is stored.
Emergency crews put out the flames within half an hour, and no one was hurt.
Site operators blamed "procedural non-compliances and behavioural practices" as a facotr in the incident.
Work has stopped in the area for improvements to be put in place.
Managing Director of DSRL, Mark Rouse, said: “We have accepted the Improvement Notice and will co-operate fully with the regulators.
"Our investigation identified unacceptable behaviours and practices that fell well short of our values and standards. It is important to take the time to ensure as many lessons are learned from this incident as possible.
“We are determined to improve our behaviours and compliance to ensure that we always meet the high standards expected on a nuclear site.”