Executive summary
Date(s) of inspection: October 2024
Aim of inspection
Licence Condition (LC) compliance inspections are an essential element of ONR's intervention strategy on any nuclear site and consist of a series of inspections, each of which is intended to establish whether NNB Generation Company (HPC) Ltd and it’s supporting services (hereafter referred to as the licensee), have adequate arrangements in place, and are adequately implementing these arrangements, for compliance with a specific LC.
The aim of this inspection was to establish whether the licensee has adequate arrangements in place, and are adequately implementing these arrangements, for compliance with LC19 with regards to the primary circuit in the reactor building. LC19 requires that: 'Where the licensee proposes to construct or install any new plant which may affect safety the licensee shall make and implement adequate arrangements to control the construction or installation.'
This inspection targeted the arrangements in place, and the implementation of these arrangements on a pre-production welding test piece, prior to their application to the first primary circuit welding onsite (associated with the licensee's hold point 2.2.16).
The release of the hold point will initiate the site welding of the unit 1 primary circuit which entails connecting the main coolant line (MCL) pipework to the primary circuit vessels (reactor pressure vessel, steam generators, pumps). The licensee has classed most of the primary circuit as high integrity which requires a high level of demonstration of structural reliability and a commensurate attention to quality. This includes beyond code measures such as qualified non-destructive testing (NDT).
Subject(s) of inspection
- LC 19 - Construction or installation of new plant - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
This inspection was undertaken as part of a series of planned interventions in accordance with the Hinkley Point C (HPC) Intervention Strategy for 2024/2025. The inspection was carried out over one day at HPC site and targeted the arrangements for the first primary circuit welding onsite (associated with hold point 2.2.16). The inspection tested the implementation of the arrangements through their application to a pre-production welding test piece. I sampled the licensee’s arrangements for welding readiness review meetings, personnel availability, surveillance plans, arrangements for non-conformances in relation to high integrity components (HIC) welds onsite, the inspection and test plan / follow-up document, relevant contingency measures, and end of manufacturing non-destructive testing (NDT) qualification and procedure. I visited the welding consumable area and was satisfied that appropriate controls were in place for managing consumables. I also saw the pre-production welding taking place and was satisfied that Framatome had considered the site conditions. I identified a minor shortfall in the arrangements for capture and governance of metallurgical arguments to support the maintenance of mechanical properties in the event of repairs and I have raised a Level 4 regulatory issue to resolve this shortfall. From the information I have sampled, I am content that the licensee's and Framatome's arrangements will provide an adequate level of control over the production of the primary circuit HIC welds performed at site.
Conclusion
At the time of my intervention, and from the information I have sampled, I am content that the licensee has adequate LC19 arrangements in place for HIC welding and NDT of the MCL at HPC site. Overall, I consider that, in accordance with ONR guidance on the application of inspection ratings, a GREEN rating is appropriate for this inspection.