Executive summary
Date(s) of inspection:
- November 2025
Aim of inspection
Part 1 of the inspection will consider the adequacy of the arrangements relating to requirements traceability to address the actions under RI-12090 raised at the requirements traceability to commissioning inspection in May 2024 (IIS-51661).
Subject(s) of inspection
- LC 21 - Commissioning - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
This was a planned compliance inspection delivering intervention H25-17 part 1, KCM requirements traceability to commissioning. The KCM (Level 1 I&C – conventional island & electrical distribution HF- & HM-) cabinets are the first I&C cabinets to be installed and commissioned on site, and are required to support the auxiliary transformer energisation (TAE) milestone and for demonstrating the commissioning arrangements at HPC.
Traceability of design and safety requirements to commissioning test procedures is important to demonstrating that the commissioning test scope is sufficient. Inspection IIS-51661 in May 2024 identified significant shortfalls relating to a lack of clear traceability from safety functional requirements (SFR) to commissioning procedures, and deviation from the established processes described in the safety case. The Level 3 regulatory issue RI-12090 was therefore raised to track the required improvements. This inspection, IR-52692, is a follow up with the aim of gaining confidence that NNB Gen Co (NNB) have now adequately implemented the four improvement actions identified in RI-12090.
This inspection sampled NNB’s records in order to support a judgement on the traceability of requirements from design to commissioning, considering the adequacy of the process arrangements and implementation. Overall, the evidence sampled provided confidence that NNB have implemented adequate arrangements to provide robust requirements traceability to commissioning documentation. I assigned a GREEN rating for licence condition (LC) 21, commissioning. Throughout the inspection I observed a good level of knowledge from all staff involved, and a well co-ordinated approach from a cross-organisational team.
I consider the inspection provided evidence that NNB have made improvements to address the shortfalls previously identified in IIS-51661. Following the inspection I have therefore closed the associated RI-12090. I have also provided five items of advice for consideration by NNB GenCo and EDF Nuclear Services.
Conclusion
Throughout the inspection I observed a good level of knowledge from all participants, who consistently demonstrated positive behaviours during the engagement and were open and transparent about the matters discussed. I observed the team approach was well co-ordinated despite the involvement of separate organisations including HPC CommOps, EDF Nuclear Services and EPR-E. I consider participants were receptive to ONR advice offered in improving the documentation produced to support requirements traceability to commissioning, and it was clear improvements have been made since the previous inspection.
LC 21
I judge that an inspection rating of GREEN (no formal action) is appropriate for LC 21: commissioning.
The focus of the inspection was the processes in place and evidence to allow for adequate traceability of functional requirements from the design to commissioning to address RI-12090 actions raised at the previous inspection on requirements traceability to commissioning in May 2024.
To achieve this, for functional requirements I have sampled the process established by traceability paths leg 1 and 2, depending on whether the requirements are safety feature criterion or I&C functional requirements respectively. The safety justification report (SJR) for SPPA-T2000 systems has been revised to provide an adequate description of the traceability arrangements discussed and sampled during this inspection.
Based on my sampling, I consider the process and evidence produced is a significant improvement from that previously presented at IIS-51661. The sufficiency analysis note (SAN) provides traceability for safety criterion to commissioning activities via leg 1. The requirements traceability matrix (RTM) provides traceability (for TAE scope) via leg 2 for I&C functional requirements to commissioning tests, including capturing the extent to which the functional requirements (FR) have previously been tested as part of factory acceptance testing (FAT), and therefore informing the scope of the required commissioning test.
Although not the focus of this inspection, I am broadly content with the traceability arrangements presented for non functional requirements in leg 3 and 4.
I therefore judge that an overall rating of GREEN is appropriate for LC 21.
RI-12090
I intend to close the actions of RI-12090 on the basis of the evidence sampled during this inspection:
Action 1 sought adequate evidence that all the commissioning activities required to justify SFRs for the C&I systems supporting TA energisation have been identified and are traceable to requirements. I consider this action can be closed based on the documented process in the SJR and sampling of the implementation evidence produced at the inspection.
Action 2 sought details on how and when the safety case will be updated to reflect the process being used; specifically the use of a RTM replacing the SAN. I consider this action can be closed based on confirmation of the reinstatement of the SAN and use of the RTM as detailed in the revised SJR for SPPA-T2000 systems which is referenced from the ‘level 1 and 2 computer-based I&C systems (KC. and KIC)’ system substantiation summary document (S3D).
Action 3 required a process map (or equivalent) to clarify how the use of the RTM will be defined in the relevant processes. I consider this action can be closed based on the description of the process provided in the revised SJR for SPPA-T2000 systems which is referenced from the KC. and KIC S3D, noting the process map diagram in Figure 1 of Appendix 3 of the SJR.
Action 4 sought clarity on the scope of the systems that will use the RTM based approach for commissioning requirements traceability. NNB subsequently clarified the RTM based process where the SAN is wholly replaced by RTM is limited to the centralised I&C scope provided under the Framatome UK4101 contract. For the SPPA-T2000 based systems provided under the Siemens UK4601 contract, the SAN is supplemented by RTM as presented at this inspection for KCM. I consider this action closed based on the confirmation the scope.
I also intend to close the RI on the basis that all associated actions are closed.