Office for Nuclear Regulation

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SBI 17 - Gas Circulator Systems

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake a system based inspection of the Gas Circulators at EDF Nuclear Generation Limited’s (NGL’s) Heysham 1 power station in line with the planned inspection programme contained in the Heysham 1 Integrated Intervention Strategy (IIS) for 2015/16.

Interventions Carried Out by ONR

The ONR Nominated Site Inspector and an ONR Electrical Engineering Specialist Inspector performed a System Based Inspection (SBI) of the Gas Circulators to judge the system performance against its safety function.  Through examination of this system and associated sub-systems we performed compliance inspections against Licence Conditions LC10 (Training), LC23 (Operating rules), LC24 (Operating instructions), LC27 (Safety mechanisms, devices and circuits) and LC28 (Examination, inspection, maintenance and testing). The inspections were based on sampling the implementation of the arrangements in place at the station against each licence condition.

The standard consideration of licence conditions during system based inspections includes LCs 10, 23, 24, 27, 28 and 34, with conditions added or excluded depending on their applicability. In this case, LC 34 that relates to leakage and escape of radioactive material and waste is not applicable to the electrical aspects of the gas circulators and therefore deemed not applicable to the inspection.

Explanation of Judgement if Safety System Not Judged to be Adequate

From the inspection, we judge that overall the Gas Circulators meet the requirements of the safety case and is adequate.

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

During the course of the system based inspection it was found that Heysham 1 has made arrangements to ensure that the Gas Circulators are maintained and operated in accordance with its safety case and the arrangements are deemed to be implemented in an adequate manner, based on the areas sampled by the inspection.  The inspection identified a number of areas for potential improvement relating to the standard of records, and although none gave rise to significant concern the station has agreed to take action to address them.  The site inspector will pursue this through the existing ONR issue 4150.

In summary, the outcome from the safety inspection of the Gas Circulators is that the arrangements and their implementation are deemed to be adequate and therefore we have given IIS ratings of 3 (adequate) in relation to LCs 10, 23, 24, 27 and 28.  

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

Conclusion of Intervention

After considering all the evidence examined during the sample inspections undertaken against LCs 10, 23, 24, 27, and 28 we considered that the Gas Circulators met the requirements of the safety case.

There are no findings from this inspection that could significantly undermine nuclear safety.  At present, no additional regulatory action is needed over and above the planned interventions of Heysham 1 power station as set out in the Integrated Intervention Strategy, which will continue as planned.