- Site: Hunterston B
- IR number: 22-001
- Date: May 2022
- LC numbers: 22
Executive summary
Purpose of Intervention
ONR undertook two planned inspections covering the electrical engineering aspects of activities associated with the isolation of Hunterston B reactor three control rods and primary vessel cooling water system (hereinafter referred to as “reactor systems”) in preparation for the commencement of this reactor’s defueling operations post end of generation. The intervention also provided an opportunity to undertake an electrical engineering inspection of Hunterston B’s implementation of Licence Condition (LC) 22 (modification or experiment on existing plant) compliance and electrical safe working practices.
These inspections were carried out in accordance with the ONR Hunterston B defueling strategy and were used to judge the adequacy of the electrical engineering activities carried out by the licensee that allows defueling operations of reactor three to commence.
Interventions Carried Out by ONR
I undertook an on-site inspection supplemented by a further remote inspection of the implementation of electrical engineering changes to the reactor systems in preparation for defueling of Hunterston B reactor three. The assurance obtained during the on-site inspection provided me with sufficient confidence that the second inspection could be completed remotely.
The inspection sample targeted the electrical engineering aspects of activities planned as part of the Hunterston B preparations for the commencement of reactor three defueling operations. The inspections focussed on the reactor systems that required isolation prior to the commencement of defueling operations.
The intervention was performed in line with ONR's guidance requirements (as described in our
technical inspection guides) in the areas inspected.
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
Based on the discussions, explanations and the samples reviewed at each inspection I was satisfied that there were no significant shortfalls identified in the implementation of electrical engineering aspects of the changes to the reactor systems or compliance with LC22 arrangements. The targeted inspections confirmed that the electrical engineering aspects of the activities associated with the isolation of Hunterston B reactor three reactor systems was appropriate and that changes to the systems were carried out in accordance with established LC22 arrangements.
During the inspections I sampled a number of electrical isolation activities and was advised that no significant issues had arisen during their implementation. Testing of the changed reactor systems confirmed that inadvertent operation of the systems could not occur. Through explanations, discussions and a live demonstration using the station’s asset management system I was satisfied that there were clear, auditable links between the changes required to the reactor systems and the instructions developed to make them.
A plant walk-down was conducted and for the areas sampled I observed acceptable standards of general housekeeping. The electrical plant and equipment inspected was in an acceptable condition and there were no visible signs of corrosion or flaking paintwork. The station staff spoken to and those accompanying us on the walk-down, all presented a knowledgeable and professional approach, and provided open and honest responses to our questions.
I considered that the implementation of electrical engineering aspects of the changes to the reactor systems to allow the defueling operations of reactor three to commence, and the implementation of LC 22 arrangements related to these changes was judged to be adequate. Therefore, a green inspection rating, no formal action, was awarded.
Conclusion of Intervention
From the sample inspected, it is judged that for the electrical engineering aspects of the activities associated with the changes to the reactor systems to allow the defueling operations of reactor three to commence on reactor three at Hunterston B were being carried out effectively and in compliance with LC22 requirements. Therefore a ‘Green’ rating, no formal action, was given.
Based on the targeted interventions there were no issues identified from the electrical engineering aspects of the activities which would prevent Hunterston B commencing the defueling operations on reactor three.
From the evidence gathered during this intervention, there were no matters identified that have the potential to impact significantly on nuclear safety.