Office for Nuclear Regulation

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Dungeness B Power Station - Reactor 22 Statutory Outage 2015 - LC28 Compliance Inspection in support of Structural Integrity

Executive summary

Purpose of intervention

This report records the findings of an intervention visit to the Dungeness B Nuclear Power Station during the 2015 Reactor 22 periodic shutdown. The intervention was undertaken to confirm the adequacy of the work conducted by the licensee, EDF Energy Nuclear Generation Limited (NGL), to comply with the requirements of Licence Condition 28, examination, inspection, maintenance and testing.

Interventions Carried Out by ONR

I undertook on-site meetings and plant inspections with relevant staff from NGL and their contractors to determine the adequacy of the work being undertaken on Reactor 22 in complying with the requirements of Licence Condition 28. I concentrated my intervention on items I judged important to nuclear safety, focussed on structural integrity. I sampled aspects of the inspection programme undertaken during the periodic shutdown on the steam and feed systems and other safety related systems external to the reactor pressure vessel. I also sampled aspects of the inspection programme undertaken on the metallic components internal to the reactor pressure vessel. 

Key Findings, Inspector's Opinions and Reasons for Judgements Made

I visited site approximately one third through the periodic shutdown. The status of the inspections highlighted good progress on the reactor external inspection programme, with 259 out of the 525 inspections completed at the time of this inspection, and most of the reactor internal inspections were complete.

I sampled the inspection work that had been undertaken as part of the reactor external inspection programme, looking at both the inspection work itself and the categorising of the results, and was satisfied with what I found. 

I observed the licensee’s outage assessment panel (OAP) during my visit. The OAP meets to review the inspection work undertaken during the periodic shutdown and sentences the inspection findings. I was satisfied that the OAP was following due process.

I undertook a plant walk down during my visit, escorted by the Auxiliary and Dump Steam System Engineer and the Site Materials Lead. Both NGL staff were able to provide detailed explanations of both the operation of the systems and the inspection/maintenance of the systems planned or already performed during the periodic shutdown.

I reviewed the reactor internal inspection programme, satisfactory progress was reported with no major issues. I sampled video footage showing the roof cover plate distortion and viewed stills from monitored reheat cracking; I judged that due process was being followed satisfactorily. No significant issues that could affect the In Vessel Inspection (IVI) planned work were reported. Sentencing of non-conformances followed due process and was presented to the OAP during my visit.

I discussed progress on inspection, maintenance and testing activities associated with the seawater systems. The work programme was said to be progressing well, with efforts made to replace some plant with modern equivalents.

I discussed progress on examinations and inspections undertaken by the Pressure Systems Safety Regulations (PSSR) Competent Person during the periodic shutdown. The work was progressing to plan and no significant issues had been found to date.

I discussed progress on steam pipework hanger survey. The pre-outage hot hanger survey was complete, and the cold survey was complete and in the reporting stage. Final results will be reported through the OAP. Following the Return to Service (RTS), a post-outage hot survey will be performed.

Conclusion of Intervention

I judge that, at the time of my visit Dungeness B nuclear power station personnel were conducting their inspections in line with the pre-periodic shutdown intentions documentation and associated inspection specifications.  The inspections conducted so far have not raised any nuclear safety significant issues of concern and the licensee appears to be adequately managing any defects or anomalies identified.

At the time of my visit, and from my sample inspections, I found nothing that in my opinion would prevent Reactor 22 returning to service following completion of the 2015 periodic shutdown.  I will use the minutes from the remaining OAPs to monitor for any emerging issues from the inspections that have yet to be completed and report on this in my structural integrity assessment report on the return to service of Dungeness B Reactor 22 following its 2015 periodic shutdown.

It should also be noted that a further visit will be required at a later date during the outage to discuss progress made with FAC inspections and assessment of pipework supports in the North Wall plant rooms

Based on my intervention to date, I conclude that the licensee has performed the work to an adequate standard. I propose that an IIS rating of 3 (adequate) is appropriate.