- Inspection date(s): 27/09/2022
Purpose of inspection
The purpose of the inspection was to gain confidence that the licensee, NNB Generation Company (HPC) Limited (NNB GenCo), has sufficient oversight of its contractor, AEG Power Solutions (AEG), for the manufacture of the control and instrumentation (C&I) power supplies, through adequate implementation of its Licence Conditions (LC) 12, 14 and 17 compliance arrangements. This included gaining confidence in the application of the C&I power supplies diversity basis of safety case (BoSC), in particular how the arrangements claimed in the safety case to ensure adequate diversity between the AC/DC and DC/DC power convertors have been applied in practice by AEG.
LC12 (Duly authorised persons and other suitably qualified and experienced persons) requires a licensee to ensure that anyone carrying out work that may affect nuclear safety on the site is a suitably qualified and experienced person (SQEP). This includes all of the supply chain of the site and, where appropriate, off-site work by contractors and vendors, wherever in the world they happen to be.
LC14 (Safety documentation) requires that the licensee shall make and implement adequate arrangements for the production and assessment of safety cases consisting of documentation to justify safety during the design, construction, manufacture, commissioning, operation and decommissioning phases of the installation.
LC17 (Management systems) requires a licensee’s quality management arrangements to robustly encompass all work carried out for the site, including by contractors – whether as an on-site contractor or as a vendor of products and services.
I reviewed each stage of manufacture, from goods inwards to completed converter cabinets and testing. At each stage, I sought evidence that demonstrated whether the claims made within the safety case are being adequately implemented with a focus on equipment and human diversity claims, to make a judgement on whether the diversity arrangements for C&I power supplies reduces risk as low as reasonably practicable (ALARP).
Subject(s) of inspection
The following actives were the subject of this inspection:
- LC12 – Duly authorised and other suitably qualified and experienced persons – Rating – Green
- LC14 – Safety documentation – Rating – Green
- LC17 – Management systems – Rating – Green
Based on the evidence presented, areas of good practice were identified relating to:
- the overall demonstration of how diversity of the C&I power supplies is achieved;
- the understanding demonstrated by AEG and NNB GenCo of these diversity requirements; and
- the internal AEG quality management system (QMS).
The following minor shortfalls were identified:
- unmarked portable test equipment was found that could potentially be used on each diverse production line -this was addressed during the intervention;
- there was a lack of a formal failure mode and effects analysis (FMEA) performed for individual supplies as these were designed and developed prior to being used in a class 1 application – I consider this adequate for Hinkley Point C (HPC) but any future changes or re-design of the supplies for use at HPC and/or SZC should be subject to a formal FMEA, which will be followed up through normal regulatory business; and
- inconsistent and ambiguous use of the project quality control plan (PQCP) matrix, introducing error traps and traceability issues for users of the document – I have raised a regulatory issue to track this.
I judge that an intervention rating of GREEN is appropriate for LCs 12, 14 and 17 because I found NNB GenCo to be compliant with its legal duties with only minor areas for further improvement.
LC12 – I found adequate arrangements in place which had been implemented to ensure only SQEPs perform duties that may impact nuclear safety. Where shortfalls were identified in a previous quality management system audit, I am content that these actions had been appropriately addressed.
LC14 – I consider the arrangements in place to identify diversity requirements and maintain equipment (component) diversity and human diversity for all stages of manufacturing and testing for each converter type adequate. From witnessing the arrangements and subsequent explanation and clarification provided by AEG and NNB GenCo, I am content the claims made in the BoSC are being realised during the manufacturing and testing process.
LC17 – I consider that the evidence provided by AEG and NNB GenCo relating to management systems demonstrated areas of good practice in the documentation, such as the use of follow up documents (FUDs) and the non-conformance report (NCR) process and its implementation.I found areas for improvement related to the use of the PQCP and have raised a regulatory issue. However, I do not consider this shortfall to be significant and I am content that the management systems in place are well understood and, where shortfalls exist, NNB GenCo is committed to remedying these issues.