Executive summary
Date(s) of inspection:
March 2026
Aim of inspection
The purpose of this inspection was to gain assurance that boiler feed diversity risk is being managed effectively at Heysham 1 and to support permission of the Consolidated Boiler Feed Safety Case. To achieve this the inspection targeted the implementation of modifications and arrangements to deliver the safety functions as claimed in the safety case.
Subject(s) of inspection
- Overall inspection rating - Rating: Green
Key findings, inspector's opinions and reasons for judgement made
This inspection focused on gaining assurance that EDF has effectively implemented Heysham 1 engineering change document “Consolidated Post-Trip Boiler Feed Safety Case Taking Account of the Removal of Townswater Claim”. This plant modification implements additional demineralised water sources to support post-trip boiler feed systems now that towns water is no longer claimed. The inspection included sampling relevant documentation, speaking to appropriate system and operations staff and undertaking a plant walkdown focused on the implementation of plant modifications.
This inspection was a permissioning inspection and hence no ratings are provided against the licence conditions and comprised of a plant walkdown, sampling of various documentation and conversations with site personnel. Key findings from this inspection will support ONR’s future permissioning assessment of the Consolidated Post-Trip Boiler Feed Safety Case at Heysham 1 and Hartlepool.
We sampled relevant Technical Specifications and associated operating instructions that were amended as part of the consolidated boiler feed safety case. We judged from these documents, alongside conversations with operators, that the requirements of the consolidated boiler feed safety case have been implemented, or where they were not at the time of the inspection, are subject to appropriate arrangements that provide sufficient confidence of timely delivery .
The plant walkdown focused on the implementation of plant modifications in support of the consolidated post-trip boiler safety case, including consideration of hazards and human factors aspects. This included Trimpell Tank 9 (TT9), demineralised water trailers, fire hydrant system, Reserve Feedwater Tanks (RFTs), Outage Cooling Water (OCW) Pumphouse, Deployable Back-Up Equipment High Pressure Pump, and pipework associated with these systems.
Through sampling of training needs analysis, records and plans associated with boiler feed diversity, EDF demonstrated that operator training has been updated to include recent modifications to the post-trip boiler feed safety case and requirements are being appropriately tracked and delivered. We judged that adequate training and SQEP arrangements associated with the modification are in place at Heysham 1.
We sampled maintenance arrangements for plant systems credited in the consolidated boiler feed safety case, focusing on TT9 and the fire hydrant system. The evidence demonstrated that inspection, testing and maintenance activities have been undertaken in line with requirements set out in EDF’s maintenance schedules and that issues identified through testing were appropriately addressed. TT9 was found to be maintained by Heysham B and records of this were available on request. We judged that adequate evidence was provided that maintenance has been carried out in line with the requirements of the safety case.
Conclusion
Based on our sample, we judged that Heysham 1 has adequately demonstrated its implementation arrangements for use of demineralised water sources to support post-trip boiler feed systems, as set out in the consolidated post-trip boiler feed safety case (EC 376249).
This inspection was a permissioning inspection and hence no ratings are provided against the licence conditions.
This inspection will support ONR’s future permissioning assessment of the Consolidated Post-Trip Boiler Feed Safety Case at Heysham 1 and Hartlepool.