Executive summary
Date(s) of inspection:
September 2025
Aim of inspection
The aim of this inspection was to confirm that the Turbine Overspeed Protection System (TOPS) is able to meet the safety functional requirements defined in the Safety Case, and to confirm that the licensee's arrangements in relation to the following Licence Conditions (LCs) are being adequately implemented:
- LC10 - Training.
- LC27 - Safety mechanisms, devices and circuits (SMDC).
- LC28 - Examination, inspection, testing and maintenance (EIMT).
Subject(s) of inspection
- LC10 - Training - Rating: GREEN
- LC23 - Operating rules - Rating: GREEN
- LC24 - Operating instructions - Rating: GREEN
- LC27 - Safety mechanisms, devices and circuits - Rating: GREEN
- LC28 - Examination, inspection, maintenance and testing - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
The key findings of ONR's system based inspection (SBI) of the Heysham 2 (HY2) turbine overspeed protection system (TOPS) are:
- LC10 – Training: We examined how personnel were deemed to be suitably qualified and experienced personnel (SQEP) to undertake TOPS equipment management and examination, inspection, maintenance and testing (EIMT) activities and considered that the associated arrangements were adequate. However, we provided regulatory advice regarding the production of a system handover document and mentor guide. We, therefore, assigned an intervention rating of Green (no formal action) for LC10.
- LC27 – Safety mechanisms, devices, and circuits (SMDCs): We reviewed several engineering and maintenance documents, undertook a plant walkdown and spoke to key stakeholders. As a result, we judged that the configuration of TOPS related equipment was being adequately controlled, and that it was correctly connected and in good working order. We also considered that sustainment support for the equipment and the number of available spares was adequate. We, therefore, assigned an inspection rating of Green (no formal action) for LC27.
- LC28 – EIMT: We examined several TOPS related plant item maintenance instructions (PIMIs) and the associated work order cards (WOCs) and checksheets. On the whole, we considered that the associated tasks had been adequately defined; however, we did highlight areas where enhancements could be made. We also considered that, overall, the tasks appeared to have been carried out as specified. We, therefore, judged that the TOPS was being adequately examined, inspected, maintained, and tested. We, therefore, assigned an inspection rating of Green (no formal action) for LC28.
Conclusion
From the evidence sampled during this SBI against LC 10, 27 and 28, we judged that the TOPS was able to fulfil its safety duties (safety functional requirements) in line with the safety case.
There are no findings from this intervention that could significantly undermine nuclear safety at HY2. At present, no additional regulatory action is needed over and above the planned interventions at HY2, which will continue as planned.
We, therefore, judged the overall rating for the SBI to be Green (no formal action).