Framatome St Marcel, observation of welding operation and review of documentation
- Site: Hinkley Point C
- IR number: 18-015
- Date: September 2018
- LC numbers: 19
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.
- LC19 requires that the licensee “shall make and implement adequate arrangements to control the construction or installation”.
The specific objectives for this part of the intervention were:
- to provide confidence that the specified technical requirements of the design had been achieved;
- to gather evidence that supports a judgement that the licensee has achieved and retained the required level of Intelligent Customer capability to deliver the necessary safety assurance and enable continued construction of HPC; and
- to gather evidence that will inform a judgment on whether the licensee has deployed adequate oversight and surveillance.
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:
- observation of steam generator 429 high shell to conical shell weld;
- observation of the Framatome St Marcel facility and consumable storage arrangements;
- observation of the HPC licensee’s oversight arrangements at the Framatome St Marcel facility; and
- review of key manufacturing documentation held at the Framatome St Marcel facility.
This intervention activity was part of a wider intervention, which also includes consideration of the Intelligent Customer capability of the HPC licensee’s organisation.
- From my discussions with the relevant surveillance bodies, I am content that multiple layers of surveillance are active at the Framatome St Marcel facility.
- As a result of the activity witnessing and speaking to Framatome personnel on the shop floor, I am content that Framatome personnel were capable of complying with the parameters specified within the Weld Procedure Specification.
- I observed the quality documentation at the work stations. It was clear that the document contained the relevant steps of the operations and had been completed adequately. This documentation is transcribed to final manufacturing documentation by the quality department and reviewed internally. I observed evidence of transcription and verification.
- I noted that the RCC-M code states that the practice of recycling fluxes in not recommended but is allowed in defined proportions. It was not clear why this practice was acceptable for a High Integrity Component.
- I noted that the ranges of parameters (Volts, Amperage, travel speed and heat input) presented in the Weld Procedure Specification were wider than that used within the Weld Procedure Qualification Record. I asked the HPC licensee to justify why it considers applying a range to voltage, amperage, travel speed and heat input is a suitable approach for a HIC.
- The HPC licensee was not able to demonstrate that the Weld Procedure Qualification Record carbon equivalent value was representative of the steam generator production carbon equivalent value. I asked the licensee to provide a demonstration of representative and adequate carbon equivalents used during the Weld Procedure Qualification Record.
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.