Office for Nuclear Regulation

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Systems Based Inspection - SBI22 - CO2 Systems

Executive summary

Purpose of Intervention

This was a planned inspection of EDF Energy Nuclear Generation Ltd.’s (NGL’s) Hunterston B Power Station, undertaken as part of the planned intervention strategy for the Operating Facilities Division (OFD) of the Office for Nuclear Regulation (ONR).

The work was carried out in accord with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy (IIS) for 2018/19.

Interventions Carried Out by ONR

As ONR Specialist Inspector, Structural Integrity I carried out an inspection of the CO2 storage and distribution system (reactor primary coolant system) at Hunterston B power station (HNB).  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 aspects of :

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable, system judged adequate.

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

From an LC10 perspective, from the evidence sampled during this inspection, I consider the training of the staff are adequate.  I, therefore, assigned a rating of Green (no formal action) for LC10.

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.  I, therefore, assigned a rating of Green (no formal action) for LC23.

From an LC24 perspective, from the evidence sampled during this inspection the operating instructions are not relevant to the plant as installed and commissioned at HNB.  I, therefore, assigned a rating of Amber (seek improvement) for LC24.

From an LC27 perspective, from the evidence sampled during this inspection I established that the licensee does not specifically define safety mechanisms.  I 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.  I, therefore, assigned a rating of Green (no formal action) for LC27.

From an LC28 perspective, from the evidence sampled during the inspection, I consider that the system is being appropriately maintained in compliance with the licensee’s arrangements I, therefore, assigned a rating of Green (no formal action) for LC10.

Conclusion of Intervention

There was a single finding from this inspection that I consider to be significant to nuclear Safety, which is the failure of the site to properly update the Plant Item Operating Instructions (PIOIs).  These are key documents instructing the plant operators in the work that should be done in maintaining the plant and so their being out of date presents a risk that the incorrect work might be done.  I note that the reason that certain PIOIs are out of date was because the site has installed and commissioned a new CO2 plant and not yet updated the appropriate documentation.  I judge that installation of the new plant has led to a significant reduction in overall plant risk, but consider that improvement should be sought in updating the associated documentation.  I, therefore, assigned a rating of Amber (seek improvement) for LC24 and for the intervention as a whole, and have recorded this on the ONR regulatory issues database to ensure appropriate follow-up