Office for Nuclear Regulation

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Wylfa IIS Inspection

Executive summary

Purpose of intervention

This report covers the nuclear safety related inspection of Wylfa power station undertaken as part of a series of interventions including those listed in the Integrated Intervention Strategy (IIS) plan, inspections deemed necessary to cover emergent work, and follow-up of matters carried forward from previous visits.

Interventions Carried Out by ONR

This intervention included planned and reactive compliance inspections against the following Licence Conditions (LCs):

  1. LC7 - Incidents on the site.
  2. LC15 - Periodic safety review.
  3. LC28 - Examination, inspection, maintenance and testing.
  4. LC36 - Organisational capability.

Progress by the station to address actions recorded in intervention records and issues recorded on the ONR issues database were reviewed.

An event notified to ONR under the arrangements made for reporting incidents on the site was followed-up during the visit.

Other matters of a routine nature that are deemed unlikely to have a significant effect on nuclear safety, and which are being addressed routinely under the licensee's arrangements, were also covered during the inspections.

Explanation of Judgement if Safety System Not Judged to be Adequate

No safety system inspections were carried out during the visit.

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

An inspection was conducted into the arrangements to comply with LC 7 relating to making and implementing arrangements for responding to incidents on the licensed site. The inspection confirmed that the arrangements are based on generic guidance produced by the company for all its licensed sites, and on the basis of the inspection sample they are judged to provide the means to meet the overall requirements of the condition. However, the inspection identified that the local compliance documents could include additional information about how particular requirements of the licence condition are addressed, and station has agreed to review the documents referenced in station Management Control Procedure 1 (MCP1) to improve this aspect of the arrangements. In view of the fact that the station has made and implemented arrangements to address LC7, has introduced improvements since the previous inspection, and has agreed to include additional information in the compliance documents, we have given this work an inspection rating 3 (adequate).

An inspection was carried out of the arrangements to comply with LC 28 concerning the making and implementing of arrangements to ensure that plant which may affect safety at Wylfa power station receives regular and systematic examination, inspection, maintenance and test. The inspection found that station has arrangements to address LC28 which meet the overall requirements of the condition, and that on the basis of the inspection sample the implementation of the arrangements is satisfactory. However, they agreed that they would review MCP1 to ensure that the site licence compliance arrangements were described in greater detail, and they would also make the arrangements for controlling repeat extensions to maintenance schedule intervals more robust. In view of the fact that overall the arrangements for LC28 are deemed to be satisfactory and they have agreed to make improvements as necessary, we have given this work an inspection rating 3 (adequate).

An inspection was conducted into the arrangements to comply with LC 15 relating to making and implementing arrangements for the periodic and systematic review and reassessment of safety cases (PSR). The licensee submitted the Wylfa power station periodic safety review to ONR for assessment in September 2013, to allow ONR to make a decision by September 2014 on the adequacy of the case made to operate the plant for a further period. The inspection identified that they are making progress to complete the work they have identified as necessary, and to address the findings identified by ONR. During the inspection, the timescale was agreed for submission of information to ONR for assessment in advance of completing the decision making process. The inspection provided a useful opportunity to agree the actions necessary to complete our assessment of the Wylfa PSR submission. On the basis that at this stage we have not identified any issues of significant safety concern, and they have agreed in principle to undertake a programme of work to address findings that are ongoing, we have given this work an inspection rating 3 (adequate).

An inspection was carried-out of the station arrangements for controlling organisational change at Wylfa power station in accordance with LC36. During the inspection, we confirmed that commitments identified from previous inspections of this licence condition are being progressed. They provided copies of draft LC36 documentation that has been revised and supplemented to describe the improved site licence compliance arrangements that have been developed. The documents included an amended version of the station management of change document currently approved by ONR, which when finalised will be submitted to their safety committee prior to requesting approval by ONR. In view of the fact that overall arrangements are in place to provide a means to control organisational changes on the Wylfa site and they are addressing improvement opportunities, we have given this work an inspection rating 3 (adequate).

Station notified ONR of an event under the arrangements for reporting incidents on the site, where they exceeded the limit on the positional spread of control rods in the core during an operation to weigh a single control rod with the reactor at power. Examination of the station operating rules confirmed that a safety case is in place to permit a control rod to exceed the limit on spread provided it is unavailable for duty and all other limits and conditions are met. Following discussion it was agreed that station would consider introducing an instruction to operators to declare a control rod unavailable during a weighing operation to prevent uncertainty about the availability of the rod for tripping during its weighing operation. While the definition of terms used in the station operating rules permits a control rod to exceed the limit on spread by being unavailable, the operators should be aware of control rod position at all times, which was not the case on this occasion. They are continuing to investigate this matter to help prevent a re-occurrence, and will keep ONR informed through the routine arrangements for following-up events. While the licensee's response to the incident was appropriate under the incident reporting arrangements, the event involved the operator not being aware of the actual position of a control rod during a weighing operation. Therefore, I have given an inspection rating 4 (below standard) in respect of LC23, from this component of my inspection.

During the intervention visit, opportunity was taken to inspect station's response to incidents on the site, including those notified to ONR, and I consider that the inspections carried-out confirm that they have responded adequately to emergent plant conditions. On the basis of the sample inspections, I judge that they have complied with licence condition arrangements in relation to emergent work, which has arisen since the previous inspection visit and is not covered separately in this report; hence I consider their response to this aspect of my inspection is adequate.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Conclusion of Intervention

From the information gathered and evidence obtained during this intervention, no matters have been identified that are likely to have an adverse impact on nuclear safety on the station that are not being addressed. Therefore, I consider that no additional regulatory action arising from this visit is necessary currently, and the interventions for Wylfa power station should continue to be implemented as set out in the Integrated Intervention Strategy. I judge the corrective action taken by station in response to emergent matters to be appropriate in the prevailing circumstances. The outcome from the inspections has been captured within the station event and action tracking arrangements, in the actions recorded in this intervention report, and in the ONR issues database, as appropriate.