- Site: Hinkley Point C
- IR number: 21-028
- Date: September 2021
- LC numbers: 19
Executive summary
Purpose of Intervention
Licence Condition (LC) compliance interventions are an essential element of the Office for Nuclear Regulation’s (ONR’s) overall intervention strategy and consist of a series of interventions which are each intended to establish whether NNB Generation Company (HPC) Ltd (hereafter known as ‘the licensee’) has adequate arrangements in place for compliance with a specific LC.
Welding requires high levels of control to ensure quality requirements are met and hence ONR seeks to ensure the licensee has developed appropriate arrangements to ensure welded items are manufactured to the appropriate quality. Therefore, it was deemed proportionate to conduct a planned intervention (coded WN4) to gain confidence that the licensee’s arrangements comply with LC19, in relation to specification, control and oversight of site welding and non-destructive testing (NDT) of the Hinkley Point C (HPC) In-containment Refuelling Water Storage Tank (IRWST).
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”.
The purpose of the intervention is to gain confidence that the licensee has adequate arrangements in place for compliance with LC19, in relation to welding and NDT of the HPC IRWST.
The objectives of the intervention are to:
- Form a judgement on the adequacy of the licensee’s specified requirements for welding and NDT of the HPC IRWST.
- Form a judgement on the adequacy of the licensee’s control and oversight of welding and NDT for the HPC IRWST.
- Form a judgement on compliance with LC19.
Interventions Carried Out by ONR
An intervention scope for WN4 was provided to the licensee prior to the intervention (CM9: 2020/303642), and a kick-off meeting was held on 18 January 2021 (CM9: 2021/8204).
The WN4 intervention was split up into the following four parts:
Part 1A (Remote) – Completed on 11 May 2021 (CM9: 2021/38691):
- Welding quality requirements
Part 1B (Remote) – Completed on 30 June 2021 (CM9: 2021/53604):
- OPEX (Process, Distortion, NDT access)
- Welding procedure compliance and demonstration of adequate mechanical properties (including corrosion resistance)
- NNB review and acceptance of welding procedures
- Control of welding operations, authorisation and hold points (ITP)
- Surveillance frequencies (NNB and contractors)
- NDT requirements and frequencies (percentages)
- Welding lifetime quality records
Part 2A (Remote): – Completed on 22 July 2021 (CM9: 2021/56806):
- Welding Centre of Excellence (Welder Training and Qualification) arrangements
- Competency
- IRWST defect rates
Part 2B (Site visit): – Completed on 30 September 2021 (CM9: 2021/56806):
- NNB arrangements in place for storage, control and issue of welding consumables (including consumable store visit)
- COSHH and RPE face fitting
- ONR observation of IRWST welding, including welder application of the procedure during welding and the adequacy of contractor surveillance
- IRWST NDT access demonstration (radiography of leak-tight welds)
- Nuclear safety culture
Explanation of Judgement if Safety System Not Judged to be Adequate
N/A as this was not a safety systems inspection.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
The findings presented here are a synthesis of the separate parts of the intervention described above.
The licensee’s welding technical assessment is broadly based on BS EN ISO 3834 (Quality requirements for welding) and BS EN ISO 14731 (Welding coordination tasks and responsibilities) which I consider to be adequate from a structural integrity perspective.
The licensee’s specified technical requirements cover the broad aspects identified in ISO 3834-2 (comprehensive quality requirements) however a limited number of areas have been identified where ISO 3834-2 details more explicit requirements than captured in the licensee’s specified requirements. The licensee plans to address this by issuing a guidance document to the supply chain, engage with Supply Chain Audit and Quality Management teams, and raise a learning report to capture the areas for improvement which have been identified. The licensee stated that this will be progressed under the licensee’s Welding Quality Working Group which I consider to be adequate from a structural integrity perspective.
Based on the welding procedures sampled, I am content that they are adequate. I am also content that the NDT requirements and frequencies are adequate.
I am content that the Welding Centre of Excellence (Welder Training and Qualification) arrangements are adequate.
I observed compliance with the welding procedure during welding and based on the demonstration given during the site visit, I am content that there is sufficient access to carry out radiography of the IRWST leak-tight welds.
I am content that the licensee’s arrangements in place for specification and control of site welding and non-destructive testing of the IRWST are adequate. With regards to oversight, the contractor’s surveillance frequencies do not appear to reflect relevant good practice. An action has been placed on the licensee to resolve this. This will be monitored via level 4 regulatory issue 8867.
Conclusion of Intervention
On balance, I judge that an inspection rating of GREEN is appropriate at this stage for LC19 (construction or installation of new plant).
An action has been placed on the licensee to resolve the finding raised during this intervention. Level 4 regulatory issue 8867 has been raised to capture the action.