Office for Nuclear Regulation

LC19 management arrangements for the HPC main steam line (NSSS7)

Executive summary

The nuclear steam supply system (NSSS) includes items of the highest nuclear safety significance for Hinkley Point C (HPC) and those items include components for the main steam line (MSL).

This intervention is informed by regulatory intelligence from the Flamanville-3 (FA3) EPR where issues relating to material properties and weld quality of the MSL were encountered. Contractual responsibility for the MSL has moved to NNB Generation Company (HPC) Limited (NNB) and the supply of the MSL is part of a larger scope of supply, most of which is for non-high integrity component (HIC) items. The Office for Nuclear Regulation (ONR) seeks confidence that the requirements for the specific HIC activities are not lost amongst the wider scope and that the FA3 operational experience (OPEX) has been considered adequately.

Purpose of Intervention

The purpose of the intervention was to review the adequacy of the management arrangements NNB has in place for the MSL components.  The intervention comprised a meeting at Bridgewater House to discuss those arrangements.

Interventions Carried Out by ONR

The intervention assessed NNB’s arrangements for compliance with LC19: Construction or installation of new plant.

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.

During the intervention, NNB presented an overview of its arrangements during which I questioned the NNB staff on particular matters and discussed specific areas of regulatory interest.

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

In my opinion NNB’s arrangements relating to the production of the MSL are adequate for the current stage of the project. NNB has taken appropriate measures to ensure that the technical scope of the work has been correctly specified and that the particular requirements for the HIC have been captured.

The procedures that were required for commencement of the pouring of the base material were approved (code A).

The FA-3 OPEX has been considered and addressed where appropriate and technical changes have been made to reduce some of the risks associated with the mechanical properties.

Additional project management and governance arrangements, including senior management oversight, have been put in place to support the normal arrangements for management through a staged release of activities.

I was not convinced that the surveillance arrangements for the early stages of the manufacture of the MSL adequately reflected the HIC classification and a level 4 regulatory issue has been identified to address this matter.

Conclusion of Intervention

Based upon the evidence gathered during the intervention, I have rated NNB’s arrangements as GREEN for the current stage of the manufacture of the HPC MSL as no significant shortfalls were identified. A level 4 regulatory issue has been identified related to the manufacturing surveillance arrangements.

Since the MSL project is at a relatively early stage of manufacture, further interventions will be considered to review and examine implementation of NNB’s arrangements as the activities become more advanced.