Office for Nuclear Regulation

Quarterly Statement of Civil Incidents reported to ONR

1 October 2018 to 31 December 2018

A statement of incidents at nuclear installations in Great Britain and during the transport of radioactive material, which meet Ministerial Reporting Criteria (MRC), is provided to the Secretary of State for Business, Energy and Industrial Strategy and the Secretary of State for Scotland and Wales, and is published each quarter by the Office for Nuclear Regulation.

For the period 1 October 2018 to 31 December 2018, there was one incident which met the MRC. In addition, one incident occurred during transport of radioactive materials which was rated Level 2 (an incident) on the International Nuclear and Radiological Event Scale (INES).

EDF Dungeness B - Corrosion of pipework and storage vessels - 12 December 2018.

Ministerial Reporting Criterion - Examination, inspection, maintenance, test or operation of any part of the plant revealing that the safe operation or condition of the plant may be significantly affected.

INES Rating 2

In September 2018, as part of ONR’s regulatory intervention on external corrosion management, the Office for Nuclear Regulation (ONR) issued a Direction under Licence Condition 15(4) for Dungeness B nuclear power station to carry out a review and reassessment of safety, addressing the corrosion of concealed systems that fulfil a safety function.  The licensee commenced the inspections during the planned shutdown period for both reactors in August 2018.

Inspections carried out by the licensee in response to the Direction identified that seismic restraints, pipework and storage vessels associated with multiple systems that provide a safety function were found to be corroded to an unacceptable level. This condition would have been present whilst the reactor was at power, although, the affected systems were not called upon to perform a safety function.

Rectification of much of the degradation has been undertaken by the licensee during the shutdown period, which has resulted in the replacement of more than 300m of pipework associated with reactor cooling systems.  The renewal of numerous seismic pipework supports has also been undertaken, together with remediation of carbon dioxide storage vessels, other tanks, pipework, electrical cabling supports and civil structures associated with trenches.

Both reactors at Dungeness B remain shutdown as part of an extension to the licensee’s planned shutdown period to deal with this issue and other emergent work following outage inspections and allow the recovery program to address the corrosion issues to continue. ONR is monitoring the licensee’s recovery activities and will not issue our Consent to allow the reactors to return to service until we are satisfied that the necessary work has been completed to ensure their safe operation.

The licensee’s own internal investigation into the incident is on-going to establish the root causes and to communicate any lessons learnt to the wider EDF fleet.

There were no safety consequences to people or the environment as a result of this event. 

The event has been rated as INES 2 as a result of the erosion of the expected levels of defence in depth required to operate a nuclear power station in the UK.

Colnbrook - Transfer of Radioactive Materials - 24 September 20182

INES Rating 2 - Incident

Two packages, each containing a high activity sealed radioactive source, were being transited via Heathrow airport. The sources involved are a type commonly used in industrial applications throughout the world, including oil well logging, oil refining and construction.

The two sources safely arrived at a storage and distribution hub close to the airport, before being consigned to a nearby storage depot.  They were transported by two logistics companies that did not have the required safety procedures in place, therefore breaching UK legal requirements. When the sources were delivered to the storage depot, the nature of the packages was identified and arrangements made for their safe transfer to an appropriate facility.

There were no safety consequences to people or the environment as a result of this incident, but the Office for Nuclear Regulation (ONR) requires evidence that lessons have been learnt and the required procedural improvements have been made.

We have taken enforcement action, issuing a number of Improvement Notices to the two companies concerned in order to secure improvements against the shortfalls and legal non-compliances highlighted by the incident, and prevent a reoccurrence. Details of this enforcement action have been published on the ONR website.

The event has been rated as INES 2 as a result of the degradation of the defence in depth, specifically a significant failure in the safety provisions but with no actual consequences.

INES Level 2 - "Incident" - denotes more serious degradations of the safety systems or with some, though not severe, consequences for people or the environment.