Executive summary
Date(s) of inspection:
June 2025
Aim of inspection
This inspection was based in the HPC simulators:
- to confirm that suitable and sufficient user interfaces are provided within the HPC main control room (MCR) to provide effective monitoring and control of the facility in normal operations, fault operations and accident conditions
- to build confidence that the current maturity of UK HMI designs are also suitable and sufficiently representative to support training, operability trials and other substantiation activities ahead of future integrated system validation (ISV) trials.
The inspection examined how NNB Generation Company (HPC) Limited (NNB GenCo) has implemented its compliance arrangements associated with the following licence conditions:
- LC14 (Safety Documentation) – This was specifically considered in relation to the HMI design evidence for this stage of the project, noting that validation activities are ongoing.
- LC 17 (Management systems) – processes for design change management and configuration control to ensure both equipment and software associated with HMIs maintain accuracy and currency with the evolving HPC safety case.
- LC 19 (Construction of New Plant) – provision of adequate documentation to control the construction and installation of HMIs within the Unit 1 MCR in order to support safety case assumptions and claims.
Subject(s) of inspection
- LC14 - Safety documentation - Rating: Green
- LC17 - Management systems - Rating: Green
- LC19 - Construction or installation of new plant - Rating: Green
Key findings, inspector's opinions and reasons for judgement made
The following high level aspects were considered:
- Modifications and updates to I&C system functionality - how these requirements have been managed and implemented on the HMIs.
- Visual representation of key equipment and systems on the HMIs.
- Display format and graphics.
- User navigation and user-system interaction.
- Presentation of safety-related information to users.
- Provision of visual and auditory channels to convey information to the operators.
- Identification of HMI failure or degraded conditions.
- Embedded electronic procedures.
- User assistance and advisory functions.
NNB GenCo provided a suite of supporting documentation both pre and post inspection. This was used in conjunction with inspector observations gained via the HMI walk-throughs, system interactions and scenario simulations (by Pre Ops representatives).
We sampled a scenario that would initiate a reactor trip function implemented in the protection system (PS) and NNB GenCo demonstrated that the reactor trip actuated as expected with an output displayed on the process information control system (PICS) in accordance with the system functional diagrams (SFD) for the function. In addition, NNB GenCo adequately explained the basis for establishing the requirements for providing confirmation of the output of a PS function to various HMI panels.
We were broadly satisfied with the configuration management processes outlined for both the simulator and the I&C designs.
We found that HF design substantiation evidence had continued to progress and kept pace with the evolving maturity of the panel designs. NNB GenCo have provided a suite of new documents associated with overall MCR design, specific HMI panel designs, HF verification and validation approaches, output from the OPEX reviews conducted in France and findings from the UK operability testing conducted to-date. Where shortfalls against HF RGP and evidence gaps have been identified, a suitable forward plan is outlined to support ongoing safety case development. The audible alarms provided a distinct alert which could also be heard when multiple sounds co-occurred.
Conclusion
Noting the evolving of maturity of both the HMI designs and the HPC safety case, it was evident that since the latest safety case submission (SSCD#2) considerable effort has been made to further document the HF design substantiation evidence and recent operability trials. Although the verification and validation work is ongoing, this demonstrates a positive direction of travel. This inspection highlighted no significant issues although some areas for ongoing improvement/ de-snagging of the MCR human-machine interfaces were identified.
On that basis LC14, LC17 and LC19 were all rated green. Minor observations have been raised for future consideration HPC. I therefore judge that the HMIs within the HPC simulator facilities are adequate to support ongoing operability trials and support operator training programmes.