Office for Nuclear Regulation

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Hunterston B Reactor 4 2014 periodic shutdown- inspection of the structural integrity aspects of the steels inspection programme

Executive summary

Purpose of intervention

Under Licence Condition 30 (3), EdF Energy Nuclear generation (NGL) the licensee responsible for safety at Hunterston B Nuclear Power station require Consent from the Office for Nuclear Regulation (ONR) to start up Reactor 4 after its 2014 triennial Periodic Shutdown. I have undertaken this intervention to gather the evidence necessary to assess the adequacy of the inspections, maintenance and testing, conducted under Licence Condition 28.

The findings of this intervention record and my subsequent assessment report will be used as part of the decision as to whether to issue Consent to start-up the reactor on completion of its 2014 periodic shutdown.

Interventions Carried Out by ONR

I discussed the progress and results of the inspections of welds (external to the reactor), essential cooling water systems and reactor internals (steel components) during the periodic shutdown with station personnel. The intended scope of the Licensees inspections are detailed in a number of documents in order to comply with the requirements of the nuclear safety cases. My intervention consisted of the following activities:

in order to confirm that the inspections have the potential to fulfil the outage scope.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable to this intervention

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

At the time of the visit, 437 welded components, external to the reactor, of the 497 scheduled within the outage programme had been inspected. There have been no significant findings to date which could challenge return to service or operation during the next period.

A number of Category C weld inspection findings had been reported which required further assessment work by the Structural Analysis Group at Barnwood; most had been cleared by the Outage Assessment Panel (OAP) at the time of the visit and none challenged the return to service of Reactor 4. A number of deletions had been made from the outage programme and either alternative welds had been substituted for inspection or the deletions had been adequately justified.

Maintenance has been conducted on the steam pipe supports and the essential cooling system in compliance with the Licensees guidance.

Inspections of the main reactor boilers had been completed utilising manned vessel entry. Three repairs have been conducted on components which had the potential to be outside the requirements of the boiler tube failure safety case during the next operating period. No isolations of boiler tubes were required and I judge the boilers are fit to re-enter service for a period of three years.

Conclusion of Intervention

The licensee has provided sufficient evidence to indicate that they are conducting the inspections in accordance with the scope of their outage intentions documents. Inspection findings have been sentenced in accordance with their company process. No issues were identified that might affect decisions on return to service.

From what I observed during my inspection, I consider the licensee performed adequately against the requirements of Licence Condition 28, examination, inspection, maintenance and testing, and so have given an integrated intervention strategy (IIS) rating of 3, adequate.