Dounreay inspectors raise further red flag about sodium storage
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The Office for Nuclear Regulation (ONR) has issued an enforcement letter to Magnox Ltd after recording a breach of its nuclear site licence.
Sodium was used to cool the prototype fast reactor (PFR) whose closure in 1994 sounded the death knell for the experimental power plant.
Since its removal from the redundant plant, some of the highly volatile liquid metal has been stored in drums.
ONR’s latest concern follows an inspection at the end of April.
The agency has concluded that the storage arrangements do not comply with good practice.
Its latest report states: “The dutyholder has failed to safely protect the drums against degradation via air and moisture ingress; large stocks of the inventory are not available for inspection due to the way in which it has been stored; and a number of the storage vessels of the material are not identified on the site maintenance system.”
ONR found that Magnox – a wholly owned subsidiary of the Nuclear Decommissioning Authority – had breached the Control of Substances Hazardous to Health Regulations 2002 and its nuclear site licence.
It followed up its enforcement letter with a ‘holding-to-account’ meeting on site in June with Magnox directors.
According to ONS, this was arranged to ‘further secure a commitment to return to compliance.”
In June, the Scottish Environment Protection Agency (Sepa) had fired off a warning letter about a minute leak of radioactive tritium from a sodium drum stored at the PFR in November last year.
The leak was well below the public dose limit and the watchdog rated the risk to the public or the environment as extremely low.
Speaking after the letter was received, Dounreay’s security and resilience director Mac MacGill said it was working with Sepa to address the issue.
He said: “We recognise that this is not just a single drum. We have other things to deal with.”
Of the latest matter raised by the ONR a Magnox spokeswoman said: “The sodium referenced in the enforcement notice is held in a number of containers, each with multiple layers of protection.
“We have an asset management and inspection regime in place and corrective actions are taken when problems are identified.
“Significant remedial works have been carried out on the related building structures with more planned this year to restore full weather-tight integrity.
“This forms part of our ongoing care of the site assets.”
The spokeswoman added: “We are also examining the options for the treatment of the various forms of sodium and developing a strategy that brings together the treatment and storage with the long-term management of the assets.”
“This will be discussed with regulators and we have written to ONR with our response to the enforcement letter and continue to engage with both ONR and Sepa.”
Magnox has meanwhile acted to address concern on another safety front at Dounreay.
ONR had issued an enforcement letter earlier this year about some of the site’s elderly electrical equipment.
It focused on the condition of a number of transformers and other plant dating back to the 1950s and 1960s.
Magnox has withdrawn the equipment from use and been implementing an improvement programme.
An ONR spokesperson said: “ONR has received responding letters and communications from site confirming the actions they have taken.
“ONR considers that Dounreay have taken reasonable responses and once sufficient detail of the implementation of these actions is received ONR considers it will be in a position to close out this enforcement action.
A leak at PFR’s sodium tank farm had triggered an overnight emergency in April last year.
A subsequent Sepa probe found that the plant operators had breached its authorisation and earlier this year issued a final warning letter.
Magnox has meanwhile acted to address concern on another safety front at Dounreay.
ONR had issued an enforcement letter earlier this year about some of the site’s elderly electrical equipment.
It focused on the condition of a number of transformers and other plant dating back to the 1950s and 1960s.
Magnox has withdrawn the equipment from use and been implementing an improvement programme.
An ONR spokesperson said: “ONR has received responding letters and communications from site confirming the actions they have taken.
“ONR considers that Dounreay have taken reasonable responses and once sufficient detail of the implementation of these actions is received ONR considers it will be in a position to close out this enforcement action.”
