Magnox Ltd - Wylfa Power Station - Planned Intervention
- Site: Wylfa
- IR number: 15-085
- Date: September 2015
- LC numbers: 10, 23, 24, 27, 28
Purpose of intervention
This was a planned inspection of Magnox Ltd’s Wylfa power station, undertaken as part of the planned intervention strategy for the Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).
The work was carried out in line with the planned inspection programme contained in the Wylfa Integrated Intervention Strategy (IIS).
Interventions Carried Out by ONR
This inspection bounded planned compliance inspections against the following Licence Conditions (LCs):
- LC10 – Training
- LC23 – Operating Rules
- LC24 – Operating Instructions
- LC27 – Safety Mechanisms
- LC28 – Examination, inspection, maintenance and testing
Licence Conditions 10, 23, 24, 27 & 28 were covered as the safety system inspection of the Wylfa power station arrangements for the High Voltage (HV) systems.
In addition to the inspections identified above a number of liaison meetings were attended to monitor progress with current activities and maintain awareness of any matters of regulatory interest. These included the following topic:
- Review of recent issues and actions from regulatory inspections
- Alteration of Operating Rules on Dry Store Cell 4 (DSC4)
- Review of DSC4 Fuel Corrosion Debris Recovery
- Environmental Impact Assessment for Decommissioning Regulations (EIADR)
- Intermediate Level Waste Storage in Reactor Voids
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable – the system was judged to be adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From the system based inspection on the HV Systems we concluded that:
- LC 10 (Training) – We examined the training and SQEP records for a sample of the personnel involved in the maintenance of the HV Systems. The records identified the essential training requirements for each role profile and we found that all essential training was in date. The manner in which training and SQEP was managed in the Electrical Maintenance department was found to be exemplary. We therefore assigned an IIS rating of 2 (good) to this inspection.
- LC 23 (Operating Rules) – We found no licensee approved Operating Rules that were applicable to the HV Systems; however, high reliability of these systems is important to prevent spurious reactor tripping. Hence we examined how the HV System configuration is controlled, and found that the operating procedure was comprehensive, key interlocks were in good order, and all Protection relay setting values are securely documented. We therefore assigned an IIS rating of 3 (adequate) to this inspection.
- LC 24 (Operating Instructions) – We asked the licensee for operating procedures for normal & emergency operation of the HV Systems. We also looked at the Maintenance Schedule, the maintenance procedure for the 11 kV Air Circuit Breakers, and calibration documentation for a sample Protection relay. We also questioned how the control of the HV Systems was shared between the Power Station and the National Grid. The supplied documentation was of a good quality and followed the standard formatting and layout. The Station personnel demonstrated a sound understanding of the equipment and the maintenance requirements. We assigned an IIS rating of 3 (adequate) to this inspection.
- LC 27 (Safety Mechanisms, Devices and Circuits) – We judged that the HV Systems were properly connected and in good working order. We considered that the presented documentation accurately reflected the as-built plant and that the plant was being regularly monitored, inspected and maintained. We noted that the HV Systems system performance statistics indicated a reliable system and following discussions with plant personnel it was clear that obsolescence was being adequately managed. We therefore assigned an IIS rating of 3 (adequate) to this inspection.
- LC 28 (Examination, Inspection, Maintenance and Testing) – We reviewed the periodic inspection & testing of oil filled transformers, and the periodic maintenance of Protection relays. We noted the Information Technology systems that had been developed to plan LC28 work and track the task execution. Given the quality of the LC28 process management and the extensive experience and expertise of the Magnox staff responsible for the maintenance of the HV Systems, we assigned an IIS rating of 2 (good) to this inspection.
- LC 34 (Leakage and Escape of Radioactive Material and Radioactive Waste) – We established that LC34 was not applicable to the HV Systems, and therefore no assessment was made against this LC.
Overall, we concluded that the arrangements and their implementation on the HV Systems met the requirements of the safety case and were deemed to be adequate.
The various liaison meetings undertaken provided useful updates on matters of regulatory interest and confirmed adequate progress is being made by Magnox Ltd in delivering against the topics discussed.
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 were no findings from this inspection that could significantly undermine nuclear safety. At present, no additional regulatory action is needed over and above the planned interventions of Wylfa power station as set out in the Integrated Intervention Strategy, which will continue as planned.