- Site: Hinkley Point C
- IR number: 21-022
- Date: September 2021
- LC numbers: 14, 17
Executive summary
Purpose of Intervention
The purpose of this intervention was to gain confidence in the output from the Responsible Designer’s implementation of its methodology for the nuclear safety classification of system components and that the results align with the components’ contributions to meeting the system’s safety functional requirements.
The intervention also sought to review the implementation of NNB Generation Company (HPC) Ltd’s (NNB GenCo) arrangements for control and oversight of the System Component Classification Lists produced by the Responsible Designer.
Interventions Carried Out by ONR
ONR undertakes a variety of inspections to ensure nuclear safety is duly prioritised in the design, manufacturing, commissioning, operation and decommissioning of UK nuclear assets. The inspections are intended to establish whether the licensee has adequate arrangements and is adequately implementing the arrangements.
The intervention was carried out over a period of time where an extensive desktop review was carried out to assess various System Component Classification Lists. Follow up meetings with NNB GenCo were held to raise queries and to explore NNB GenCo capability for reviewing the Responsible Designer’s System Component Classification Lists.
The intervention focussed on two systems covered by different teams in NNB GenCo. These were the Fire Fighting Water Supply System and the Chemical and Volume Control System.
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
I have reviewed the System Component Classification Lists and associated documentation for the Fire Fighting Water Supply System and the Chemical and Volume Control System, and I am assured that the System Component Classification Lists identify the major components required for the sampled safety features and that they have been appropriately classified.
I am satisfied for the components sampled that the project’s classification methodology is being applied as intended. Furthermore, I am satisfied that the classification of sampled components meets the expectations of Safety Assessment Principle ECS.2 – safety classification of structures, systems, and components.
The Fire Fighting Water Supply System and the Chemical and Volume Control System are comprised of multiple components which are claimed across multiply safety features. In accordance with the project’s classification methodology, if components are common across safety features then the highest claimed safety feature dictates the final classification of the component. The System Component Classification Lists for these systems lay out a series of piping and instrumentation diagrams which denote the final overall classification of components for the entirety of the system. I have reviewed a selection of the components and am satisfied that where components are claimed by multiple safety features, the safety feature with the highest classification dictates the final classification of the component.
Finally, I have reviewed NNB GenCo’s review and acceptance of the Responsible Designer’s System Component Classification Lists and am satisfied that the process has been implemented adequately with evidence of amendments to the System Component Classification Lists to address comments as appropriate. I consider the sampling approach that NNB GenCo has taken to be appropriate.
Conclusion of Intervention
Based on my assessment and the discussions and evidence from NNB GenCo gathered during my assessment, I consider the project’s implementation of its arrangements for the classification of components, in line with Licence Condition 14, to be GREEN (no formal action required). I also consider NNB GenCo’s Licence Condition 17 arrangements for control and oversight of the System Component Classification Lists to be GREEN (no formal action required).