An investigation into a fire at the Dounreay nuclear plant in Scotland that resulted in a radioactivity leak has found that safety procedures were not being followed properly.
The incident on 7 October took place in the prototype fast reactor sodium tank building of the experimental plant in the north of Scotland, which is currently being decommissioned, and affected a storage place where residues of sodium used in the past to cool down the reactor are being kept.
The investigation, launched by the site operator Dounreay Site Restoration Limited (DSRL) at the request of the Nuclear Decommissioning Authority, found shortcomings in staff behaviours and practices and substantial non-compliances with safety procedures.
"The investigation thoroughly checked each aspect of the work and identified procedural non-compliances and behavioural practices that were factors in the incident, and fell short of the values and standards expected of our people,” DSRL said in a statement.
"It also confirmed the release of radioactivity via an unauthorised route."
In light of the investigation results, the Office for Nuclear Regulation (ONR) issued an improvement notice to DSRL on 11 November, requesting adjustments to be made to the site’s safety procedures and practices.
"We have accepted the improvement notice and will co-operate fully with the regulators,” said the site’s managing director Mark Rouse.
"We are determined to improve our behaviours and compliance to ensure that we always meet the high standards expected on a nuclear site."
The company said a safety improvement plan was in place and work would not restart at the tank building until ONR is satisfied with the changes.
The Dounreay nuclear power facility was established in 1955 with the aim to develop new types of nuclear reactor. Overall three reactors were constructed at the site over the following 20 years, with the Prototype Fast Reactor affected by the recent fire being the latest and final one.
Launched in 1977, the Prototype Fast Reactor stopped operating in 1994 and is currently half-way through the decommissioning process.
A 75-tonne robot, dubbed the Reactorsaurus, is expected to be used to dismantle the plant in the coming years, as the task would be too dangerous for human workers due to high levels of radioactivity.
The remotely operated robot with a 32-metre arm span will be remotely controlled by operators from a control room using binocular cameras to control each arm.