Office for Nuclear Regulation

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Framatome St Marcel, observation of welding operation and review of documentation

Executive summary

Purpose of Intervention

The manufacture of the main Nuclear Steam Supply System (NSSS) components for the Hinkley Point C (HPC) project is moving into the next phase. Until now the Office for Nuclear Regulation’s (ONR) regulatory focus has been on specification, control and oversight of the key forgings which will make up the pressure boundary.

In the next phase of manufacture the forgings will be welded together to form the pressure boundary. These welds have been identified as High Integrity Components (HIC) hence the highest reliability is required.

In line with ONR Safety Assessment Principle (SAP) EMC.1 there is an expectation that those components where the highest reliability is required are as defect free as possible. To have confidence that the required quality has been achieved and that the welds are as defect free as possible, the HPC licensee will need to demonstrate appropriate Intelligent Customer capability to adequately specify, control and oversee the welding process.

Interventions Carried Out by ONR

As Framatome is a key supplier for HPC, and given the problems encountered manufacturing the reactor pressure vessel domes at the Framatome Creusot Forge facility, it was deemed proportionate to conduct a planned intervention, on the implementation of licensee arrangements linked to Licence Condition (LC) 19 in relation to welding of the steam generator 429 high shell to conical shell.

The specific objectives for this part of the intervention were:

This intervention was to gather evidence first hand, to form a judgement on the HPC licensee’s organisation and the effectiveness of its arrangements.

The intervention activities took place at the Framatome St Marcel Facility in France. The interventions included:

This intervention activity was part of a wider intervention, which also includes consideration of the Intelligent Customer capability of the HPC licensee’s organisation.

Key Findings

Conclusion of Intervention

Through a sample observation of the welding activity, and speaking to the relevant HPC licensee, Framatome and surveillance personnel, I am content that Framatome is capable of complying with the Weld Procedure Specification, and that when surveillance is carried out on a welding operation, it is performed adequately. Therefore, I judge that an inspection rating of GREEN (no formal action at this stage) is appropriate for LC19 (Construction or installation of new plant).

There are some findings which require further discussion. These will be followed-up during the regular regulatory engagement with the HPC licensee, NNB Generation Company (HPC) Ltd.