Office for Nuclear Regulation

Hunterston B Planned Intervention

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake Licence Condition [LC] compliance inspections at EDF Energy Nuclear Generation Ltd’s [NGL’s] Hunterston B power station, in line with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy [IIS] for 2015/16.

Interventions carried out by ONR

This intervention included planned compliance inspections against the following Licence Conditions:

A technical specialist provided assistance in performing this element of my inspection.

In addition I undertook the following interactions with the licensee:

Explanation of judgement if safety system not judged to be adequate

During this intervention no system based inspection was undertaken.

Key findings, inspector's opinions and reasons for judgements made

During the LC28 compliance inspection:

We were satisfied that the station compliance arrangements adequately provide for systematic examination, inspection, maintenance and testing of plant and systems. We advised NGL that the visibility with which the arrangements provide for governance and control of the plant maintenance schedule could be improved.  We advised them to consider consolidating the licence compliance arrangements to better reflect the incorporation of LC28 reviews into the equipment reliability review process.

We sampled two maintenance routines and were satisfied they had been adequately planned and executed in accordance with the plant maintenance schedule. We observed good standards of pre-job briefing, demonstrable use of human performance tools and adequate work instructions with appropriate hold-points to control the activities.

We observed a well embedded defect management strategy that has demonstrably and effectively reduced total and elective defects.

We sampled arrangements for and implementation of maintenance interval extensions. We were satisfied from the sample undertaken that the modifications were implemented in accordance with the station’s LC22 arrangements.

The outage intentions meeting for the Reactor 3 statutory outage provided sufficient information against which to plan ONR specialist inspection resources. There are no significant deviations from the 2012 periodic shutdown in scope and range of planned maintenance, statutory examinations and plant modifications. ONR inspectors and the station agreed the importance of ensuring mutual understanding of regulatory expectations in respect to the possible detection of keyway root cracking in the graphite core, thus to ensure efficient decision making during the statutory outage.

I discussed the relevance of a recent outage-related LC 7 reportable event at Hinkley Point B to Hunterston B. The event relates to a near miss event occurred on the Hinkley Point B pile cap when an outage closure plug was ejected from a buffer storage tube. There were no nuclear safety implications or damage to the plant, no fuel was involved and nobody was injured.  The station is currently reviewing the comparable plant to prevent a similar incident, and have committed to undertake a comprehensive review of the Hinkley Point B investigation report when complete. I was satisfied that the station has made adequate progress in responding the event at Hinkley Point B.

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

I am satisfied that station is demonstrably compliant with arrangements made under Licence Condition 28; the station demonstrated good practice in a number of areas of the maintenance organisation. We therefore allocated an IIS rating of 2 – ‘Good Standard’ to this element of the inspection.

There are no findings from this inspection that could significantly undermine nuclear safety.