During the reporting period from 1 July 2020 - 30 September 2020 there were two incidents at nuclear licensed sites within Great Britain that met the Ministerial Reporting Criteria (MRC) as defined within the Nuclear Installations (Dangerous Occurrences) Regulations 1965 and ONR guidance in relation to notifying and reporting incidents and events.
A routine inspection of an organic peroxide stored in a cupboard on the ground floor of Sellafield Ltd’s Magnox Reprocessing Facility was undertaken on 11 August 2020. As part of the inspection, the sealed container holding the chemical was lifted out of the cupboard when it was noted that the chemical had separated out into two distinct layers. Advice from subject matter experts within Sellafield Ltd and externally was that this change in composition meant the chemical should be treated as potentially explosive.
The chemical was stored within a designated chemical storage vault and segregated from nuclear material by a brick wall, spatial separation and a further reinforced concrete wall. ONR judges that there were no potential nuclear safety consequences should there have been an inadvertent detonation, given the amount of chemical present coupled with the protection afforded by the structure.
The Sellafield local Incident Control Centre and Sellafield Emergency Control Centre were established, and the conservative decision was made to bring in the Army Explosive Ordnance Disposal (EOD) team to assist in the safe disposal of the chemical. This was completed in a safe, controlled manner by EOD within one day of the separated chemical being identified.
ONR is satisfied that Sellafield Ltd followed its arrangements in its initial response to this incident and implemented appropriate actions to safely dispose of the chemical in a controlled manner.
Sellafield Ltd is currently implementing improvements to its arrangements for managing waste chemicals across the site, including implementing a plan for disposal of problematic wastes. This chemical was listed by Sellafield Ltd for disposal, but no date had been set. ONR will monitor Sellafield Ltd’s progress with its improvement plan and chemical disposals through a Regulatory Issue, routine inspections and regular engagement with senior personnel across the site.
The licensee’s own internal investigation to establish the root cause of the incident is ongoing. As part of our routine regulatory oversight, we will continue to follow this up with Sellafield Ltd, to ensure appropriate learning is identified and that associated improvements are implemented effectively across the site.
There were no radiation dose consequences to the workforce or the public as a result of this incident. The incident was rated as Level 0 (Below Scale / No Safety Significance) on the International Nuclear and Radiological Event Scale (INES).
On 10th September 2020, Sellafield Ltd reported that a small leak of Uranyl Nitrate (UN) had occurred from a pipe on the Sellafield Nuclear Licensed Site. The affected pipe is routed on an overhead pipe bridge running between two buildings and evidence of UN was found both on the pipe bridge structure as well as the area below.
Upon identification of the leak, the transfer of UN was immediately halted to prevent any further leakage. Sellafield Ltd cordoned off the area and confirmed that the spill was contained within the immediate area of the leak site. Further surveys confirmed that there had been no loss of the UN into the surface water drains.
Sellafield Ltd reported the incident as a release or spillage of radioactive substance, which is likely to exceed the quantity specified in the Ionising Radiations Regulations 2017 (IRR17) Schedule 7, and correctly notified ONR in accordance with the regulations.
Whilst the leak breached the IRR17 reportable levels for notification to ONR, ONR is satisfied that it was a small quantity that was released, and the material was contained within the immediate area of the leak site. We are content that the incident was of low radiological consequence.
Sellafield Ltd subsequently inspected the pipework and a small section close to the leak site showed evidence of internal corrosion. There was no evidence of external corrosion. The affected pipe will be sent off for metallurgical examination to understand the cause of the internal corrosion. Once complete, ONR will consider the results of the metallurgical examination and the need for any follow up action by Sellafield Ltd. The affected section of pipe has been replaced, pressure tested, and the system returned to service.
Sellafield Ltd is undertaking work to assess the area of the spill with a view to remediating the land at the leak site.
The licensee’s own internal investigation to establish the root cause of the incident is ongoing. As part of our routine regulatory oversight, we will continue to follow this up with Sellafield Ltd to ensure appropriate learning is identified and that associated improvements are implemented effectively across the site.
There were no radiation dose consequences to the workforce or the public as a result of this incident. The incident has been classified as Level 1 (Anomaly) on the International Nuclear and Radiological Event Scale (INES).