Office for Nuclear Regulation

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Intervention to inspect the structural integrity aspects of the Reactor 1 graphite core inspection programme

Executive summary

Purpose of intervention

Under Licence Condition 30 (3) the licensee, EdF Energy Nuclear generation Limited (NGL) require Consent from the Office for Nuclear Regulation (ONR) to start up Hartlepool Reactor 1 after a Periodic Shutdown. I have undertaken this intervention to inspect the structural integrity aspects of the Reactor 1 graphite core inspection programme. The findings of this intervention record and my subsequent assessment report will be used to decide whether to issue Consent for start-up the reactor on completion of its 2014 shutdown.

Interventions Carried Out by ONR

My intervention consisted of the following activities:

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable to this intervention

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

The graphite core inspection programme, included in the licensee's outage intentions document, had targets for remote visual inspection and dimensional measurement of twenty fuel channels, prototype eddy current inspection of six fuel channels, trepanning thirty six graphite samples and remote visual inspection of one control rod channel.

At the time of my site inspection on 1 and 2 September, the licensee had completed all of the planned inspections apart from the remote visual inspection of the control rod channel, which is planned for 17 September. I undertook a sample inspection of the training records licensee's contract staff that maintain and operate the graphite core inspection equipment and judged the records were adequate.

I viewed sample inspections of the fuel channel remote visual inspections and discussed them with the Licensee's independent assessor. We discussed how he assessed the inspections. I was content with the explanations given.

I observed the Graphite Assessment Panel (GAP) meeting where the panel members discussed and sentenced the findings of the remote visual inspections and dimensional measurements of the twenty fuel channels. The trepanned samples require off site processing, which takes many months to complete. The panel confirmed that thirty six samples had been taken.

The GAP sentenced all the remote visual inspections and dimensional measurements. The panel compared the findings to statistical model predictions and judged the number of single and double full height axial cracks were respectively at the high end of expectations and in line with expectations. The fuel channel bore dimensional measurements were also considered to be within expectations. The panel attributed all the cracking observed as having initiated at the brick bore. At the end of the meeting I provided feedback that I considered the use of the GAP brick cracking guide sheet, which has been recently introduced by the licensee, would enhance the consistency and rigour of the panel's work.

I received assurance from the licensee that the findings from the graphite core inspection programme for Reactor 1 periodic shutdown do not challenge the safety case limits. I gave the licensee two actions, one confirming the inspection results do not challenge the core safety case now and at the beginning of the next periodic shutdown and the other a request for documentation. I will consider the licensee's response to these actions in my assessment of the return to service report.

Conclusion of Intervention

The licensee has provided sufficient evidence to indicate they have undertaken all the graphite core inspections listed in the Reactor 1 outage intentions document and that the inspection findings have been sentenced in accordance with their company process. The licensee has concluded that the inspection findings are in line with expectations and do not challenge the graphite core safety case. I will consider the licensee's inspection programme and findings in my assessment of the return to service report.

From what I observed during my inspection, I consider the licensee performed adequately against the requirements of Licence Condition 28, examination, inspection, maintenance and testing, and so have given an integrated intervention strategy (IIS) rating of 3, adequate.