- Site: Heysham 2
- IR number: 21-077
- Date: September 2021
- LC numbers: 10, 23, 24, 27, 28
Executive summary
Purpose of Intervention
The main purpose of this intervention was to conduct a system-based inspection (SBI) of EDF Energy Nuclear Generation Ltd.’s (NGL) Heysham B (HYB) Power Station in relation to the fuel route. The fuel route at HYB is large, so the scope of the inspection was limited to the Fuelling Machine, which I considered an appropriate sample.
The Fuelling Machine has a number of functions, including the transfer of new and irradiated fuel elements into and out of the reactor. Whilst connected to the reactor, the Fuelling Machine forms part of the primary circuit pressure boundary. Currently only Off-load Depressurised Refuelling (ODR) is permitted by the HYB safety case, therefore ODR was the focus of this inspection.
This inspection was undertaken as part of a series of planned interventions that are listed in the HYB Integrated Intervention Strategy 2021/2022. The inspections were undertaken by the ONR nominated site inspector and two ONR nuclear specialist inspectors for mechanical engineering and probabilistic safety analysis (PSA), which for the purpose of this intervention report shall be referred to as “I”.
Interventions Carried Out by ONR
I performed a safety case informed SBI of the Fuelling Machine, covering the following license conditions (LCs):
- LC10 (Training)
- LC23 (Operating Rules)
- LC24 (Operating Instructions)
- LC27 (Safety Mechanisms and Devices)
- LC28 (Examination, Inspection, Maintenance and Testing)
The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements.
The interventions were performed in line with the requirements of ONR’s guidance (as set out in ONR’s technical inspection guides.
Explanation of Judgement if Safety System Not Judged to be Adequate
From the evidence obtained during the inspection, I judge that overall the Fuelling Machine meets the requirements of the safety case.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
LC10: I was satisfied, on the basis of my sample of relevant staff, that Heysham B has adequately implemented its arrangements for training staff with responsibilities for the Fuelling Machine. Based on the evidence sampled, I was satisfied that the licensee provided an adequate level of assurance and evidence to demonstrate compliance with LC10 and consider the licensee merits a ‘Green’ inspection rating.
LC23: I sampled the operating rules for ODR, with a focus on ensuring that ODR was undertaken in conditions compliant with the safety case. I was satisfied that the safety case requirements were identified within the Technical Specifications. I identified a shortfall in the quality plan to ensure that the limits within Technical Specification were confirmed prior to ODR activities if failed fuel was present in the reactor. NGL recognised this shortfall and have raised a condition report to record and address it. I confirmed that no recent operations had been impacted by the shortfall as there is no identified failed fuel within the reactors at HYB.
I identified a difference in the arrangements for control of availability of alarms and indications between the reactor and the fuel route. Availability of nuclear safety significant alarms and indications on the reactor is controlled by a Technical Specification. There is no equivalent Technical Specification for the fuel route. I identified no evidence of occasions where this difference has affected nuclear safety or plant operations. I recommend that NGL review this position.
Based on the evidence sampled, I was satisfied that the licensee provided an adequate level of assurance and evidence to demonstrate compliance with LC23 and consider the licensee merits a ‘Green’ inspection rating.
LC24: I sampled the instructions available to operators to respond to a fault during ODR. I was satisfied that operating instructions were in place to support plant operations, however I recommended that NGL consider what actions can be taken without advice from system engineers and the provision for providing advice out of regular office hours.
To perform ODR various set points on the Fuelling Machine need to be changed. This is controlled through a system of interlock keys. I reviewed the interlock logic and found it to be robust.
Based on the evidence sampled, I was satisfied that the licensee provided an adequate level of assurance and evidence to demonstrate compliance with LC24 and consider the licensee merits a ‘Green’ inspection rating.
LC27: I examined several Fuelling Machine interlock management quality plans. All steps within the quality plans examined were completed and signed, so I was content that this activity was appropriately being managed. However, I identified that the final sign off page of the quality plans examined were routinely not completed. As all individual steps were confirmed to be signed in all quality plans examined, I judge this to be a minor administrative shortfall.
I also performed a plant walkdown as part of the inspection. I considered that the plant observed was generally in good working order and met my expectations. In addition, I considered the standard of housekeeping was acceptable.
Based on the evidence sampled, I was satisfied that the licensee provided an adequate level of assurance and evidence to demonstrate compliance with LC27 and consider the licensee merits a ‘Green’ inspection rating.
LC28: I examined several work order cards together with LOLER and PSSR thorough examination returns.
I examined the Fuelling Machine hoist chain visual examination maintenance procedure and found it to also cover chain exchange and lubrication. The procedure does not prompt any record of the chain exchanged, I noted this as a minor shortfall. Additional chain stretch tests are being considered to check for chain strength and chain length measuring are being undertaken to counter chain kinking and manage spurious interlock activation.
The last LOLER thorough examination resulted in 4 minor observations which were all being appropriately managed. No observations were recorded during the PSSR examination.
I identified that the Fuelling Machine hoist manual override did not have a dedicated maintenance procedure. However, I determined that the hand wind was regularly exercised as part of other maintenance procedures. NGL confirmed that they would consider introducing an additional maintenance procedure.
Based on the evidence sampled, I was satisfied that the licensee provided an adequate level of assurance and evidence to demonstrate compliance with LC28 and consider the licensee merits a ‘Green’ inspection rating.
Conclusion of Intervention
After considering all the evidence examined during the inspections undertaken against LCs 10, 23, 24, 27 and 28, I judged that the requirements of the safety case have been adequately implemented at HYB, with a rating of green assigned against licence conditions 10, 23, 24, 27 and 28.
I have raised a single level 4 regulatory issue to capture and track resolution of areas where I made recommendations to NGL or identified any potential improvements.