Office for Nuclear Regulation

NNB GenCo - Specification, control and oversight of on-site welding operations on components

Executive summary

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:

The aims of the intervention were:

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

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).