Office for Nuclear Regulation

HM Nuclear Installations Inspectorate,
Quarterly statement of nuclear incidents at nuclear installations

A statement on incidents at nuclear installations in Britain which meet Ministerial reporting criteria is reported to the Secretary of State for the Department of Energy and Climate Change and the Secretary of State for Scotland and is published every quarter by the Health and Safety Executive.

For the period 1 January 2010 to 31 March 2010 there was one incident at the Dungeness B nuclear licensed installation that met the reporting criteria.

For the period 1 October 2009 to 31 December 2009 we said there was one incident that could meet the reporting criteria. The incident, that occurred at the Urenco - Capenhurst site, is considered to meet ministerial reporting criteria and an update is provided below.

British Energy Generation Limited - Dungeness B

On 23 November 2009 a fire occurred in the boiler annexe area of Dungeness B Reactor 22. The fire forced the shutdown of the affected reactor. The unaffected reactor on the site was on its periodic shutdown during the event. The licensee, British Energy Generation Limited, supported by Kent Fire & Rescue Service responded well to the incident. The event gave rise to no injuries and no release of radioactive material.

The incident was not reported in the fourth quarter 2009 statement, but is reported in the statement for the current period for three reasons. First, HSE's preliminary investigation of the event has now been completed. Second, in the current quarter the licensee increased the significance of this incident under their arrangements. Finally, on 13 January 2010 during significant safety assessment and safety improvement work undertaken by the licensee in relation to the event, the licensee identified cables in the boiler annexes of both reactors that were insufficiently protected against hot gas release, and challenges safety case requirements. Therefore this outcome is considered to meet the reporting criteria.

In respect of the fire, the Dungeness B Station Director has provided a written undertaking to consult with HSE prior to the return to service of Reactor 22. Since the other reactor was on periodic shutdown at the time, reactor operation at Dungeness B could not re-start until HSE is satisfied.

To assist in deciding on a regulatory response an enforcement action plan was developed, this involved application of the HSE Enforcement Management Model. The enforcement action plan required letters to be sent to the licensee defining HSE requirements, both for return to service and for longer-term improvements.

In response to both the fire and the unprotected cable aspects of the event, the licensee responded positively throughout and HSE's requirements were met prior to the return to service of Reactor 22 in February 2010. These included the licensee completing significant safety assessment work and associated plant improvements prior to return to service. The licensee also provided a commitment to consult with HSE with respect to longer-term improvements to reduce fire risk in the boiler annexes. HSE's requirements relating to fire and the unprotected cables aspects for Reactor 21 will be met prior to return to service of the reactor.

HSE is continuing to investigate the unprotected cables aspects, to decide if further enforcement action is warranted to secure improvements to nuclear safety.

Urenco UK Limited - Capenhurst

Urenco UK Limited - Capenhurst reported on 17th December 2009 that during a periodic review of the Plant Maintenance schedule, the licensee identified that some safety related equipment items had not been placed on to the Plant Maintenance Schedule; some since 2005.  This potential shortfall related to extensions to the latest enrichment facility, which was actively commissioned over the period 2005 to 2009.  Consequently, affected safety related equipment items may not have been maintained in accordance with the plant safety case.  Urgent checks were made of the safety related equipment items, three were found to be out of operation but of low safety significance, and were promptly repaired.  No evidence was found of operation of the plant outside the envelope for safe operation specified by the safety case.  The licensee conducted a timely Board of Inquiry, and the implementation of the recommendations arising from the inquiry are being monitored by HSE.  The licensee has also acted promptly on HSE advice to improve labelling of structures, systems and components across the site.  HSE will continue to monitor the licensee's implementation of the further improvements to decide if enforcement action is warranted.

Single copies of statements are available free from the Health and Safety Executive, Nuclear Directorate, Division 4, Building 4.N2, Redgrave Court, Merton Road, Bootle, L20 7HS,