Office for Nuclear Regulation

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Hunterston B - R4 2017 Outage - Mechanical Engineering Inspection

Executive summary

Purpose of Intervention

The purpose of this intervention was to carry out licence compliance inspections at EDF Energy Nuclear Generation Limited's Hunterston B power station in line with the planned inspection programme contained in the Hunterston B Integrated intervention Strategy for 2017/18.

Interventions Carried Out by ONR

ONR inspectors carried out inspections against the requirements of Licence Condition 28: examination, inspection, maintenance and testing, to inform the ONR decision relating to the issue of a licence instrument for consent for return to service of Hunterston B Reactor 4 following its periodic shutdown. The activities examined were selected due to their nuclear safety significance.

The intervention included:

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

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

Based on my sampling, I am satisfied from a mechanical engineering perspective that during the Hunterston B Reactor 4 2017 periodic shutdown:

Examination, inspection, maintenance and testing associated with gas circulators and reactor gas safety relief valves is being adequately controlled, in line with the requirements of the safety case.

Control rod drop times are within safety case limits.

Sufficient records are being kept and monitored to identify problems both reactively and proactively.

I have raised a level 4 issue for updating gas circulator work order cards and procedures acceptance criteria for bearing Insulation resistance (ONR Issue 5771).

Conclusion of Intervention

Based on my sampling undertaken as part of this intervention, I am satisfied that the Licence Condition 28 arrangements in place are adequate and have been adequately implemented with no significant shortfalls. I have therefore given this inspection an Integrated Intervention Strategy rating of Green.

I would therefore support a request under Licence Condition 30 to return Hunterston B Reactor 4 to operation following its 2017 periodic shutdown.