Office for Nuclear Regulation

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Civil Engineering Interim Arrangements for Design Change

Executive summary

Purpose of intervention

This was an Office for Nuclear Regulation (ONR) cross cutting intervention into NNB GenCo's interim arrangements for accepting design modifications into Hinkley Point C Reference Configuration 1. The focus of this intervention was on design changes relating to the civil engineering topic. The intervention will support an overall cross cutting assessment report that will consider the adequacy of the licensee's interim arrangements and will inform ONR's judgement of the licensee's controls and capability for entering into full Licence Condition 20 arrangements after Reference Configuration 1.

This intervention comprised a detailed examination by ONR civil engineering inspectors of NNB GenCo's application of the interim arrangements to a sample of modifications considered for inclusion into Reference Configuration 1.

Interventions Carried Out by ONR

Two ONR inspectors attended a level 4 meeting with the licensee that included attendees from both the safety case and civil engineering branches of NNB GenCo's Design Authority.

Civil engineering is topic stream B6 in ONR's Hinkley Point C construction intervention strategy. This intervention was a planned level 4 meeting between ONR and NNB GenCo, as outlined in ONR's Intervention Project Record (IPR) number NNB-HPC2-IPR-070.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

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

Based on sampling of a range of modifications identified as being related to civil engineering, I found that a robust procedure has been applied to categorisation and technical review. I did not find any evidence that NNB GenCo's procedures were not being followed.

Based on a review of a sample of screening records I consider that modifications are being categorised appropriately by NNB GenCo.

I identified that the licensee's 'Master List' of modifications contains a number of potential error traps, including the use of a range of formats; both French and English descriptions are used; basic modification titles are too brief to appreciate the nature of the modification; and the identity of relevant disciplines that require involvement in technical review is unclear.

It was apparent that some of the forms that notify changes to NNB GenCo have not been completed sufficiently clearly to enable the modification to be appropriately screened and that this has resulted in queries being issued back to the Responsible Designer. I am satisfied that where this has occurred the screening committee or technical review lead has made the appropriate enquiries to ensure that the modification is clearly understood before completion of sentencing.

I noted a number of discrepancies between the categorisation of modifications by the Responsible Designer and by NNB GenCo. Upon investigation I am satisfied that NNB GenCo are taking an appropriately conservative approach to categorisation, and where doubt occurs about the significance of a modification, are either seeking further information or carrying out a technical review irrespective of the modification category.

I was content that where a modification affects several disciplines that the lead technical reviewer was consulting with an appropriate range of other specialists prior to finalising their review.

Although I noted that the screening lead for some modifications did not seem to come from the most appropriate technical specialism, I was satisfied that in such cases the appropriate specialists were consulted prior to finalising the category of the modification.

Conclusion of Intervention

The intervention enabled a good understanding to be gained of NNB GenCo's interim arrangements for design change and provided evidence to inform ONR's cross cutting assessment report for those arrangements.

Based on the selected samples within the civil engineering topic I consider that NNB GenCo's procedures to enable them to act as intelligent customer for changes initiated by the Responsible Designer are sufficiently robust and are being adequately followed. I did identify a number of areas in which improvements could be made, particularly to the 'Master List' used to record and track the progress of the modifications. I am content that the need for such changes is recognised by NNB GenCo and that they intend to improve the clarity of this document.

There was no attendee at the meeting from NNB GenCo's internal assurance function however none of the modifications selected had yet reached the stage of requiring independent technical assessment.

An integrated intervention strategy (IIS) rating of 3 (adequate) has been assigned to this intervention. This rating reflects my observations that there are some improvements that can be made to the modification process and that these have been recognised by NNB GenCo and are being implemented.