Office for Nuclear Regulation

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Reactor 4 (R4) Control and Instrumentation (C&I) Statutory Outage Inspection

Executive summary

Purpose of intervention

This intervention report covers my control and instrumentation (C&I) inspection performed as a part of an ONR civil nuclear reactor programme (CNRP) intervention applicable to EDF Nuclear Generation Ltd (EDFNGL) during the outage of Reactor 4 (R4) at Hunterston B (HNB) Power Station. The main focus of my inspection was to verify that relevant work activities have been carried out in relation to C&I equipment and systems important to safety in order to confirm that this remains fit for its intended purpose at HNB.

Interventions Carried Out by ONR

My inspection was made in support of ONR's 2014/15 Statutory Outage inspection programme. The outcome of my inspection, which included a review of progress made in various work items and projects associated with C&I equipment and systems important to safety at HNB, covered EDFNGL's arrangements under Licence Conditions 28 (Examination, inspection, maintenance and testing). This is intended to provide a contribution towards ONR's regulatory decision as to whether a Consent in accordance with LC30 (Periodic shutdown) should be issued to allow R4 at HNB to return to normal operating service.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable

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

I raised four actions relating to emergent work. These actions are described in section 3 of this report. Three of the actions do not require resolution prior to return to service of R4 and will be monitored during future C&I specialist intervention inspections at HNB. The second action relates to the neutron flux detectors (NFDs) used at HNB in the measurement of reactor power. I have stipulated that where any NFD does not meet its specification upon on or off-load testing that EDFNGL provide a formal justification of why those detectors are considered fit for use as part of a reactor safety system. I have received assurance from the station that the formal justification will be provided. This issue will require resolution prior to return to service and will be examined in my associated assessment report.

Based on these findings I have assigned an integrated intervention strategy (IIS) rating of 3 (adequate) to LC 28.

Conclusion of Intervention

On the basis of my inspection of the C&I aspects of the HNB R4 outage, I recommend that support be given for a Consent to allow R4 at HNB to return to normal operating service pending the satisfactory resolution of the action number 2.