Office for Nuclear Regulation

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Civil Engineering Meeting

Executive summary

Purpose of intervention

The purpose of my intervention was to discuss with the licensee, NNB Generation Company Ltd (NNB GenCo), and the Responsible Designer, the development of the civil engineering design being undertaken for Hinkley Point C power station. My focus was on those structures identified for early construction and also the on-going design studies for the nuclear island buildings.

My intention was to examine how NNB GenCo's design authority maintains control and direction of the design activities. The evidence collected will be used to assist in forming a view on the adequacy of the design and will support the Office for Nuclear Regulation's (ONR's) permissioning decision for first nuclear safety-related construction.

Interventions Carried Out by ONR

I attended this level 4 telephone conference with NNB GenCo and the Responsible Designer.

Civil engineering is topic stream B6 in ONR's Hinkley Point C construction intervention strategy. This intervention was one of the regular level 4 meetings and telephone conferences between ONR and NNB GenCo, as outlined in ONR's Intervention Project Records (IPR).

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable as this intervention was not related to a safety system inspection.

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

This intervention provided a useful forum to discuss the progress of the civil engineering design and for ONR to identify the optimum timing for topic specific interventions. I was also able to discuss ONR's expectations for planned cross-cutting interventions in the areas of design change and resolution of assessment findings resulting from ONR's generic design assessment (GDA) work.

The meeting provided the first opportunity to discuss ONR's response to NNB GenCo's draft Ground Water Safety Strategy. This strategy was prepared in response to ONR's concerns, first raised in 2012, relating to the reliability of the proposed drainage gallery to adequately reduce and maintain the site ground water levels within acceptable limits. The draft strategy is a significant step forward in developing an adequate safety case for the control of ground water on the site. It identifies a list of further studies to be completed in 2014, and these are focussed on delivering appropriate evidence in support of the claims made on the system. Despite this progress, I remain concerned that it is still proposed that the instruments used to monitor the ground water pressure (known as piezometers), and their associated monitoring system, will not be safety classified. I have advised NNB GenCo that in this situation the piezometers should be ignored when making safety claims on the drainage gallery system.

Conclusion of Intervention

The intervention provided useful evidence of progress in the various current work areas relating to civil engineering, and confirmed that detailed design work has started for the earthworks and technical galleries and is imminent for the pump house and forebay.

I noted that progress continues to be made with the production of resolution plans for the GDA assessment findings and that civil engineering plans are almost complete. I informed NNB GenCo that ONR intends to examine a range of the resolution plans as part of a cross-cutting intervention and that this would be arranged when an adequate sample of resolution plans is available.

No attendee from NNB GenCo's independent technical assessment (ITA) team was present. I highlighted that there is an ONR level 4 issue (No. 1999) requiring NNB GenCo to provide their strategy and plans for the independent assessment of civil engineering designs. This issue was raised due to a lack of suitably qualified and experienced civil engineers within the ITA team, which is a particular concern now that detailed design work has commenced. I was advised that this issue has been noted by NNB GenCo's Assurance Department and that there are recruitment plans in place.

I again highlighted ONR's concerns that no formal hold point associated with the start of construction of the pre-stressing gallery is proposed. NNB GenCo agreed to discuss this matter further with their safety case team.

The red, amber, green (RAG) rating provides a broad indication of the current level of risk, in relation to a suitable project convergence point, which in this case is on progress towards the commencement of first nuclear safety-related construction. I conclude that the RAG rating is AMBER for permissioning, which is a reflection of the further work required to address the current regulatory issues.

An integrated intervention strategy (IIS) rating of 4 (below standard) has been assigned to the civil engineering topic stream. This is a result of the areas of uncertainty that require regulatory follow-up; in particular the 6 level 3 regulatory issues, and is consistent with the AMBER status.