Office for Nuclear Regulation

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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 compliance inspections against the following Licence Conditions:

I also attended a monthly information exchange meeting to review matters relating to the graphite safety case and progress against commitments made by the licensee before Reactor 3 was returned to service in December 2015. Inspectors at Bootle attended by telecon.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable as no system inspection was undertaken during this intervention.

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

I undertook a compliance inspection of Licence Condition 7, during which I sampled for station compliance with its arrangements in the following areas:

I was satisfied that the process for apportioning initial Condition Report categorisations is suitably robust with appropriate evidence that the guidance within the company arrangements is being used by the station.

Discussions with the station independent nuclear assurance (INA) evaluators and examination of ONR’s own statistics for INF1 notifications to ONR indicate that Hunterston B reports the fewest of all stations in the NGL fleet, a statistic that has been sustained in recent years. INA has recently investigated this trend and has encouraged more conservatism in cases where incidents are borderline with respect to INF1 criteria.

I am satisfied that the station is demonstrably compliant with company arrangements for incident reporting, notification and investigation; the station appears to be categorising incidents in an appropriately conservative manner with appropriate oversight and challenge from the corrective action review board, where appropriate. I have observed no discernible reason for concern with Hunterston B reporting the fewest INF1s across the fleet. There appears to be appropriate challenge and oversight from INA and internally within the corrective action programme.

I undertook a compliance inspection of Licence Condition 27, during which I sampled the following areas:

I focussed the compliance element of this standalone inspection through examining compliance with arrangements for controlling plant status, the ‘properly connected’ element of the licence condition. In particular:

I observed some inconsistent rigour with which individual keys are logged as ‘returned’ and also inconsistency in the frequency and visibility with which anomalies are reconciled by the duly authorised person. The station committed to follow-up and manage this matter through its corrective action programme.

I examined the Tech Spec compliance status log and verified appropriate monitoring of parameters that demonstrate availability of safety mechanism devices and circuits required by the Tech Specs, specifically for safety circuits and boilers.

I observed from the control room records that in recent years, urgent modifications are generally closed-out within a calendar month. I observed a small number of modifications that have remained open for a prolonged period.  No regulatory issue was raised in light of the generally well-managed arrangements for controlling urgent modifications.

Based on the samples taken, I am satisfied that the station works to appropriate arrangements for monitoring and controlling plant status and is thus demonstrably compliant with the requirements of its arrangements made under LC 27 for ensuring safety mechanisms devices and circuits are properly connected.      

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

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