Office for Nuclear Regulation

Planned intervention at Magnox Ltd’s Wylfa licensed site, undertaken as part of a series of planned interventions outlined in the ONR Integrated Intervention Strategy (IIS) Plan Wylfa Power Station 2015/2016

Executive summary

Purpose of intervention

Planned intervention at Magnox Ltd’s Wylfa licensed site, undertaken as part of a series of planned interventions outlined in the ONR Integrated Intervention Strategy (IIS) Plan Wylfa Power Station 2015/2016.Interventions Carried Out by ONR

Explanation of Judgement if Safety System Not Judged to be Adequate

No safety system based inspections were undertaken during this intervention.

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

Inspection of Licence Condition 6 and 25 found that whilst adequate arrangements exist for compliance, the implementation is not entirely consistent with the documented procedures. This is in part due to the Approval of a records retention schedule by ONR that has not been maintained by Magnox Ltd to be consistent with the documented procedures. It is concluded that the fundamental requirements of these licence conditions is met but some specific examples of failure to follow the procedures exist and consequently an IIS rating of 4 is assigned to LCs 6 and 25 and an ONR issue raised requiring these examples to be addressed by Magnox Ltd. It is understood that Magnox Ltd is currently seeking withdrawal of the ONR approval of the records retention schedule to allow the schedules to be updated to accurately reflect regulatory expectations and those of Magnox Ltd.

Inspection of Licence Condition 27 found that adequate arrangements exist for demonstrating compliance. ONR is discussing some additional improvements to arrangements to ensure better clarity and consistency of definition of Safety Mechanisms Devices and Circuits. Inspection of Licence Condition 28 arrangements and subsequent implementation found that arrangements meet guidance and are adequately implemented. Areas for improvement are known to the site and the licensee is progressing to meet a satisfactory outcome when considered against current operational demands. Based on this inspection an IIS rating of 3 is assigned to licence conditions 27 and 28.

Liaison meetings covered the following topics

For each of the topics covered suitable responses by either Magnox Ltd or ONR were identified to progress matters towards adequate conclusions.

A further inspection into Magnox Ltd’s response to a reported incident associated with the Reactor 1 Gas Circulator Diffuser Support Pad cooling was undertaken. Following the original reporting of this incident to ONR as an INES 0 event, the licensee subsequently revised its rating to INES 1 (International Nuclear and Radiological Nuclear Event Scale (INES) is a tool for promptly communicating to the public in consistent terms the safety significance of reported nuclear and radiological incidents and accidents. On this scale, INES 0 has no nuclear safety significance and INES 1 is considered as an anomaly.). It was judged that ONR should undertake an inspection into Magnox Ltd’s investigation and subsequent response from a human factors perspective to confirm that risks of reoccurrence of similar incidents are minimised. Constructive discussions were held with Magnox Ltd site representatives regarding the potential causes of the event, the potential consequences of similar events and work currently underway to prevent re-occurrence / minimise future risks. Overall, ONR is satisfied that the Licensee had acknowledged the significance of the Human Factors related issues that had contributed to this incident and is implementing appropriate remedial action to ensure the risk of recurrence is minimised. Therefore, ONR does not require the Licensee to undertake additional actions, above and beyond those they have already identified. The ONR Site Inspector will continue to monitor progress in terms of the completion of actions and consider their effectiveness at managing risks as the station transitions to reactor shutdown.

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 and no change to the planned interventions and inspections of Wylfa power station.