Office for Nuclear Regulation

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Structural Integrity Compliance Inspection of Licence Condition 28 during Reactor 7 2015 Periodic Shutdown

Executive summary

Purpose of intervention

This report records the findings of an intervention visit to the Heysham 2 Nuclear Power Station during the 2015 Reactor 7 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 7 in complying with the requirements of Licence Condition 28. I concentrated my intervention on items I judged important to nuclear safety related. 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 half way through the periodic shutdown. The status of the inspections highlighted good progress on the reactor external inspection programme, with 298 out of the 468 programmed inspections completed, and most of the reactor internal inspections were complete.

No potentially significant issues had been found from this inspection programme at the time of my visit, although it had been recognised that the boilers had suffered an unexpected thermal transient during the reactor shutdown which was in the process of being justified. The transient is considered less severe than a boiler overfeed transient that had previously occurred, and is justified, but I will confirm that a suitable justification is put in place prior to the reactor returning to service in my structural integrity assessment report on the return to service of Reactor 7.     

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 working of 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 and found evidence of the panel taking a conservative approach on the findings.       

I undertook a plant walk down during my visit, escorted by the OAP chair. The OAP chair was 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 observed a good level of housekeeping in the areas we visited as well as what appeared to be good management of activities in the areas where work was being performed.

I reviewed progress with the gas circulator impeller inspection programme. This was in line with the periodic shutdown programme. I also sampled the inspection records for the gas circulator impeller attached to circulator 7AX1 and found due process was followed satisfactorily.

I discussed progress on inspection and replacement activities associated with the seawater systems.  The visual inspection programmes were complete and had identified some areas where local degradation of the lining had occurred and lining repairs were taking place.   The replacement programme involved replacing the remaining accessible sections of pipework on Reactor 7 with high density polyethylene pipework. The work was said to be progressing well, and this was consistent with what I found during the plant walk down, where it was possible to witness some of the installation work.  A report on the seawater systems will be presented to the OAP.

I discussed progress on the inspection of the metallic reactor internal components using remote visual in-vessel inspection techniques. I sampled video footage from the inspections. The footage was clear and in focus providing the assessor with adequate footage to make an assessment. No significant results had been found to date, and importantly the video footage from the around the GH02 peripheral in-service inspection standpipe extension sleeve showed that the clamping arrangement installed in 2011 remained in good condition thus supporting the Licensee’s case for a further period of operation without manned vessel entry.   

I discussed progress on examinations inspections undertaken by the Pressure Systems Safety Regulations (PSSR) competent person during the periodic shutdown. The work was progressing to programme and no significant issues had been found to date. There was evidence to show that licensee’s inspection work was being taken into account by the PSSR competent person.

I discussed progress on steam pipework hanger survey and restraint load check programme. The pre-outage hot hanger survey was complete, and the cold survey was in progress. The restraint load check programme was also in progress. Minor rectification work was in progress, but there were no significant findings to date. Final results will be reported through the OAP.  In addition, it was found that the bolting material used to clamp a small sub-set of seismic Snubbers to the pipework had become loose due to the use of non-creep resistant material. These clamping bolts will be replaced with suitably specified material during the periodic shutdown.

Most of the inspections for flow assisted corrosion (FAC) were either complete or in progress, and the results are reported through the OAP. I also witnessed some of the inspection preparation work during my plant walk down.  Only minor FAC degradation had been reported to date.

Conclusion of Intervention

I judge that Heysham 2 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 is adequately managing the 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 7 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 Heysham 2 Reactor 7 following its 2015 periodic shutdown.

Based on my intervention, I conclude that the licensee has performed the work to a good standard. I propose that an IIS rating of 2 (good) is appropriate.