Nuclear regulators have found “clear breaches” of safety rules while investigating a chemical leak at the Dounreay plant in the Highlands.
The site operators have been ordered to carry out improvements to prevent a repeat of the incident in April.
Emergency crews were called to the prototype fast reactor at the former nuclear facility in Caithness following the leak at the sodium storage tanks in the building.T
Dounreay Site Restoration Ltd (DSRL), which is in charge of the decommissioning of the complex, said at the time that a planned reaction of material inside a tank resulted in an “excursion” which caused the release of a “small amount of caustic liquor”.
No one was injured and the environmental impact was estimated to be “low”.
However, the Office for Nuclear Regulation (ONR) has since probed the incident and found “clear breaches in meeting legislative requirements”.
Safety ‘shortfalls’
The regulator told DSRL it must “address shortfalls” with its procedures before restarting work at that section of the site.
The incident has been judged to meet the criteria for a “level one” event on the International Nuclear Event Scale, meaning it was considered an “anomaly”.
A spokesman for the nuclear regulator said: “We have conducted enquiries into the incident, including a site visit to Dounreay Site Restoration Limited.
“ONR inspectors identified that DSRL had contravened one or more relevant statutory provisions and have issued an enforcement letter to the dutyholder, seeking the necessary improvements in its arrangements to prevent a reoccurrence and return DSRL to compliance.
“The regulator has instructed DSRL to implement improved arrangements before restarting its activities at the prototype fast reactor sodium tank farm.
“We continue to monitor the progress of DSRL’s response.”
Worker needed treatment
Just six days after the April 20 incident, regulators said a separate incident led to a Dounreay worker requiring treatment at Caithness General Hospital.
During lifting operations, the employee failed to adhere to safety requirements by placing his hand on the load as it was lifting, resulting in his fingers getting trapped.
The nuclear power site was opened in 1955 and three reactors were built over the next 20 years – the Dounreay fast reactor, prototype fast reactor and the Dounreay materials test reactor.
The prototype fast reactor was the last of the three to shut down in 1994 and they are all being decommissioned as part of a hugely-complex clean-up operation at the site.
A further two reactors were built at Dounreay for the Ministry of Defence’s Vulcan nuclear submarine testing centre.
Fire in 2014
In 2014, a fire at the prototype fast reactor facility sodium tank farm led to an “unauthorised release” of a radioactive isotope.
At the time, the ONR said it had been concerned by poor compliance and “unacceptable behaviours of personnel” at the site.
Following a probe into the latest incident at the site in April, a DSRL spokeswoman said yesterday: “The DSRL investigation into the sodium tank farm has now concluded and information provided to the regulators.
“ONR have carried out a preliminary enquiry into this incident and SEPA investigation, under the powers of the Environment Act 1995, is ongoing.
“ONR have concluded that there are a number of issues relating to the project and have issued an enforcement letter placing regulator hold points on restarting the operation.”