Office for Nuclear Regulation

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System Based Inspection

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a system inspection of the carbon dioxide (CO2) storage and distribution system at EDF Energy Nuclear Generation Ltd's (NGL's) Heysham 1 power station.

The work was carried out in line with the planned intervention programme contained in the Heysham 1 integrated intervention strategy (IIS)

Interventions Carried Out by ONR

The ONR nominated site inspector, a leadership and management for safety specialist inspector and I, a specialist structural integrity assessor, carried out an inspection of the CO2 storage and distribution system (reactor primary coolant system) at Heysham 1 power station. The inspection was based upon sampling of compliance arrangements that were in place relating to safety case requirements, operational limits and conditions, maintenance, and training records. A plant inspection was undertaken to further inform the inspection. The inspection considered Licence Condition (LC) 10, (training), LC23 (operating rules), LC24 (operating instructions), LC27 (safety mechanisms, devices and circuits), LC28 (examination, inspection, maintenance and testing). We judged that LC34 (leakage and escape of radioactive material and radioactive waste) was not applicable to this part of the CO2 system as it contained clean (not radioactive) liquid and gas.

Explanation of Judgement if Safety System Not Judged to be Adequate

We judged that from the sample inspections undertaken the CO2 storage and distribution system is adequate.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

From an LC10 perspective, from the evidence sampled during this inspection, we considerer the training of the staff are adequate, warranting an IIS rating of 3 (adequate).

From an LC23 perspective, from the evidence sampled during this inspection, the safety case and operating rules, for the systems selected necessary for compliance, are considered adequate, warranting an IIS rating of 3 (adequate).

From an LC24 perspective, from the evidence sampled during this inspection we consider the operating instructions for this system are adequate in terms of content and implementation, warranting an IIS rating of 3 (adequate).

From an LC27 perspective, from the evidence sampled during this inspection we established that the licensee does not specifically define safety mechanisms. We judge that the systems are being appropriately maintained under LC28. As far as the safety case is concerned, we considered that the LC27 requirements have been adequately addressed by appropriate implementation of LC28, warranting an IIS rating of 3 (adequate).

From an LC28 perspective, from the evidence sampled during the inspection, we considered that the system is being appropriately maintained in compliance with the licensee's arrangements, apart from the storage plant pipework and pipework supports, which were not included in the maintenance schedule. This did not meet our expectations and so an Issue was raised on the ONR Issues Database for the licensee to address this matter. The licensee provided evidence they had undertaken inspection and remediation work on the storage system pipework to establish its condition. We consider the action taken is sufficient to address the shortfall at this stage. We consider an IIS rating of 4, below standard, is appropriate.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Conclusion of Intervention

After considering all the evidence witnessed during the sampling inspections undertaken against LCs 10, 23, 24, 27 and 28 we consider that the CO2 storage and distribution system meets the requirements of the safety case and its' implementation is deemed adequate. There are no findings from this inspection that could significantly undermine nuclear safety.

The planned interventions set out in the integrated intervention strategy for Heysham 1 remain valid and will be followed for future inspections.