Office for Nuclear Regulation

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Hunterston B - Planned Intervention for SBI28

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 Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).

The work was carried out in line with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy (IIS).

Interventions Carried Out by ONR

We carried out a System Based Inspection (SBI) on enhanced shutdown and diverse hold down systems, supported by an ONR Principal Mechanical Engineering Inspector.

In addition to the SBI, the nominated Site Inspector also:

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

From this inspection, we judge that the enhanced shutdown and diverse shutdown systems met the requirements of the safety case and are adequate.

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

From the system based inspection on enhanced shutdown and diverse hold down systems, we concluded that:

During the LC 34 compliance inspection, I undertook a review against elements of the company licence compliance arrangements; a review of progress against the 5-yearly LC 34 assessments required under recent changes to arrangements; a sample of routine maintenance associated with structures systems and components claimed within the safety case and a review of station progress towards specific flagging of radioactive leaks when sentencing leaks within work request prioritisation.

During this compliance inspection the station demonstrated that the specific ‘radioactive leak’ category has been added to the asset management system (AMS), and presented an audit trail of emails to demonstrate that Duly Authorised persons have been duly briefed of this option when sentencing leaks. Although this has yet to be fully embedded, it fulfils the regulatory commitment raised under ONR issue 3824, which will now be recorded as complete.

Overall, I am satisfied that the station has adequately implemented the recently revised compliance arrangements and therefore I consider compliance with LC34 to be adequate with an IIS rating of 3.  Notwithstanding this, I have proposed a Level 4 regulatory issue which will seek from the station specific evidence as to the adequacy of engineering substantiation for ‘run-to-failure’ strategy applied to active effluent treatment plant differential pressure transmitters.

During the Licence Condition 36 compliance inspection, I undertook  a review against elements of the company licence compliance arrangements; a review of a recent Independent Nuclear Assurance (INA) surveillance of the station’s organisational capability and progress towards opportunities for improvement identified therein; an examination of the most recently completed management of change and associated risk assessment and a discussion on potential challenges to the nuclear safety baseline towards approach to end of generating life.

In my opinion, INA’s surveillance this was a thorough audit of the station’s compliance arrangements against a company referential. The surveillance identified no areas of non-compliance but one minor opportunity for improvement. The most recent management of change completed by the station was implemented in line with the company arrangements and appropriately categorised. Accordingly I consider that the station compliance with LC36 is adequate with an IIS rating of 3.

I also attended the biannual emergency preparedness consultation committee (EPCC) held on 22nd March 2016 at Liberator House, Prestwick Airport.  This meeting discussed updates to the Hunterston B site emergency arrangements and offsite emergency arrangements, lessons learnt from recent emergency exercises and looked forward to the level 2 exercise due to be held in September 2016.

Conclusion of Intervention

After considering the evidence presented, we considered that the arrangements and their implementation associated with the enhanced shutdown and diverse hold down systems met the requirements of the safety case with compliance against LCs 10, 23, 24, 27, 28 and 34 adequate with IIS ratings of 3.

On the basis of the areas sampled it was judged that the station compliance with LC34 and LC36 were adequate with IIS ratings of 3.

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