Office for Nuclear Regulation

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IIS Site 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 planned interventions: listed in the Integrated Intervention Strategy (IIS) plan for the station; to cover any emergent work; and, to follow-up any matters raised during previous visits, as deemed necessary.

Interventions carried out by ONR

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

Licence Conditions 12, 23, 24, 27, 28 & 34 were covered as part of a safety system inspection of the pre-stressed concrete reactor pressure vessel.

The reactor 1 start-up meeting was attended during the intervention.

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.

From the inspection, I judged that overall the pre-stressed concrete pressure vessel safety system provisions meet the requirements of the safety case and are adequate.

Key findings, inspector's opinions and reasons for judgements made

A safety system inspection of the pre-stressed concrete pressure vessel system was carried out as part of the programme of safety system inspections included on the Wylfa site intervention plan for 2013/14, to identify the adequacy of the station arrangements made to ensure the system will perform its safety function. In deciding if suitable and sufficient measures have been put in place for the safety system, these inspections consider compliance with a number of licence conditions to test the adequacy of the arrangements implemented. The standard consideration of licence conditions during safety system inspections includes LCs 12, 23, 24, 27, 28 & 34, with conditions added or excluded depending on their applicability.

During the course of the system inspection, it was found that station has made arrangements to ensure that the pre-stressed concrete pressure vessel system is maintained and operated in accordance with its safety case, and that the arrangements are deemed to be implemented in an adequate manner, on the basis of the areas sampled by the inspection. The inspection identified an area where the station documentation could be made clearer and they have agreed to address this finding.

In summary, the outcome from the safety inspection of the pre-stressed concrete pressure vessel system is that the arrangements and their implementation are deemed to be adequate, therefore I have given an inspection rating 3 (adequate) in respect of LCs inspected, and judged that overall the safety system meets the requirements of the safety case and is adequate.

ONR inspectors attended the Wylfa reactor 1 start-up meeting on 21 March 2014. The meeting provided an opportunity for Station/Company to inform ONR of the outcome from planned and emergent work undertaken during the 2014 periodic shutdown of reactor 1, for ONR to review progress against the intended work programme, and to identify actions to be completed prior to the start-up of the reactor and operation for a further period. Station currently intends to apply for ONR consent to return reactor 1 to service during April 2014, following completion of the required actions. At this stage no matters of safety concern have been identified, with the potential to affect return to service of the reactor. This element of my inspection was carried out as part of information gathering in relation to work undertaken during the periodic shutdown, and has not been given an inspection rating.

The Wylfa Emergency Planning Consultative Committee (EPCC) was attended by the ONR site inspector for Wylfa power station. The meeting allowed ONR to observe the matters discussed by the EPCC members, who include representatives from the local authorities, emergency services, and duty-holders, and to respond to questions related to safety on the site. This activity has not been given an inspection rating.

During the intervention visit, opportunity was taken to inspect station's response to emergent work. I consider that the sample inspections conducted confirmed that station has responded adequately to incidents on the site, including those notified to ONR, and has taken appropriate action in the interest of safety to address instances of emergent adverse plant conditions. On the basis of the sample inspections, I deem 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 responses to be adequate.

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

Conclusion of the intervention

From the information gathered and evidence obtained during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety on the station at this time. Therefore, I consider that no additional regulatory action arising from this visit is necessary currently, and the interventions for Wylfa power station, set out in the Integrated Intervention Strategy, should continue to be implemented as planned. I deem the corrective action taken by station in response to emergent adverse conditions to be appropriate in the prevailing circumstances. The outcome from the inspections has been captured within the station event and action tracking arrangements as necessary, in the actions recorded in this intervention report, and in the ONR issues database as appropriate.


I recommend that actions resulting from this intervention and listed in this report should be monitored during future routine inspections, with their resolution recorded in subsequent intervention reports for Wylfa power station.