NNB GenCo - Specification, control and oversight of on-site welding operations on components
- Site: Hinkley Point C
- IR number: 18-022
- Date: January 2019
- LC numbers: 19
Purpose of Intervention
Systems and components at Hinkley Point C (HPC) are assigned Design Quality Requirements commensurate with their nuclear safety role. Design Quality Requirements are identified as being Q1, Q2, Q3 or unclassified. Components having Design Quality Requirements of Q3 are currently being welded during site construction at HPC. To have confidence that the required quality and weld integrity has been achieved, the licensee, NNB Generation Company (HPC) Ltd (NNB GenCo), is required to demonstrate appropriate Intelligent Customer capability to adequately specify, control and oversee the welding operations.
It was deemed proportionate to conduct a planned intervention, on the implementation of licensee arrangements linked to Licence Condition (LC) 19 for welding of components having Design Quality Requirements of Q2 or Q3.
Interventions Carried Out by ONR
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”.
ONR carried out the following LC19; Construction or installation of new plant inspection:
A two day inspection at HPC covering the following topics relating to welding:
- roles, responsibilities and competency
- operational experience
- specification of welding requirements
- control of Q2 and Q3 welding operations at HPC
- welder training
- consumable storage and issue
- oversight of Q2 and Q3 welding operations at HPC
- observation of a Q3 welding operation
- lifetime records
The aims of the intervention were:
- To demonstrate the adequacy of NNB GenCo’s ability to specify, control and oversee key Q2 / Q3 welding operations on site.
- To determine how the experience gained by the construction of previous EPR projects has been used to inform the design and surveillance processes for the HPC project.
- To determine the adequacy of the supply chain management arrangements for the completion of the welding operations on Q2 / Q3 components in terms of ONR expectations set out in relevant Safety Assessment Principles and Technical Assessment Guides.
- To determine compliance with LC19.
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
- NNB GenCo demonstrated that it has an adequate understanding of Design Quality Requirements and how to determine the quality requirements assigned to the component.
- NNB GenCo has adequate arrangements in place to specify welding requirements for Q2 components, and the welding requirements that have been specified for Q3 components are appropriate.
- Welding Procedures for Q2 and Q3 components are produced, reviewed and approved by personnel with knowledge and experience in welding. However, it was noted that these personnel are not qualified welding engineers. There is an action on NNB GenCo to justify this.
- The Q3 welding procedures relevant to the observation have been produced in a way which does not control the risk of corrosion during service. There is an action on NNB GenCo to justify this.
- The Boccard welder, who performed the welding that was observed, had limited command of the English language and relied on their supervisor to translate the Weld Procedure Specifications. This will be taken forward by the ONR HPC Organisational Capability team.
- When a welding procedure has been translated, the welder follows the instructions and recommendations stated on the procedure.
- The level of surveillance that Bylor is providing is proportionate at this stage of the project. However, this may need to be increased as the amount of welding increases on site.
- NNB GenCo and Bylor surveillance personnel are deemed to be competent to fulfil their role.
- NNB GenCo is providing an appropriate level of surveillance on-site for components having design quality requirements of Q2 and Q3.
- The Inspection and Test Plan in place provides hold points to ensure non-destructive testing is accepted prior to commencing subsequent operations.
Conclusion of Intervention
NNB GenCo has adequate arrangements in place to specify welding requirements for Q2 components. The specified welding requirements which have been sampled for Q3 components are appropriate. However, the findings which have been identified throughout this intervention require justification and resolution. Actions have been placed on NNB GenCo to justify and resolve the findings in a timely manner. A Level 4 Regulatory Issue has been raised to capture the actions.
NNB GenCo has suggested that the findings can be justified and resolved in appropriate timescales. In addition, NNB GenCo is providing an appropriate level of surveillance on-site for components having design quality requirements of Q2 and Q3. Therefore, an inspection rating of GREEN (no formal action at this stage) is appropriate for LC19 (Construction or installation of new plant).