Office for Nuclear Regulation

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System based inspection at Hunterston B

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake a system based inspection at EDF Energy Nuclear Generation Limited’s (NGL’s) Hunterston B power station in line with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy (IIS) for 2016/17.

The inspection was undertaken by the nominated site inspector, a specialist C&I inspector and two specialist Fault Studies inspectors.

Interventions Carried Out by ONR

During this intervention, a system based inspection of the Reactor Safety Systems – trip parameters (SBI 27) was undertaken. During this inspection, we examined compliance against the following Licence Conditions (LC):

During this intervention, we considered that the requirements of LC 34 – ‘Leakage and Escape of Radioactive Material and Radioactive Waste’ did not specifically relate to Reactor Safety Systems, and so was not rated.

Also during this intervention, I met with the Independent Nuclear Assurance (INA) evaluator and undertook a general plant inspection.

Explanation of Judgement if Safety System Not Judged to be Adequate

Based on the sample made during this inspection we judged that the Reactor Safety Systems – trip parameters adequately meets the requirement of the safety case.

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

Based on the areas sampled during this system inspection, it was found that Hunterston B has adequate arrangements to ensure that the reactor safety system (trip parameters) is maintained and operated in accordance with the safety case and the station’s arrangements.

In relation to LC 10, we sampled general and relevant system-specific training records in for the system engineer, technical advice engineer and two maintenance technicians. We also examined, where relevant, authorisations of staff with responsibility for signing of EIM&T as complete. Based on the personnel records sampled, we were satisfied that the records adequately reflect SQEP (suitably qualified and experienced personnel) status of staff undertaking system specific tasks, with the exception of certain instances where the station consider that training records are lagging with respect to local SQEP records maintained by team leaders. We did not collect any evidence to the contrary but this will be subject to a self-assessment to be supported by INA.

In relation to LC 23, we were satisfied that the safety case conditions and limits have been identified and, where necessary, have been incorporated into technical specifications. With one exception, justifications for the limiting values for these parameters were described within the safety documentation as referenced from the Commentary to Technical Specification 4.2.1. However there was a need for modifications to the Commentary to Technical Specification 4.2.1 and Hunterston B raised an Action Request (AR) to record the need for the changes and ensure they are made.

In relation to LC 24, we were satisfied that adequate operating instructions were in place to support plant operations.

In relation to LC 27, we were satisfied that suitable and sufficient safety mechanisms, devices and circuits (LC 27) are connected and in working order to meet the requirements of the safety case and identified operating limits and conditions. We were further satisfied that the system health is generally maintained to a good standard.

In relation to LC 28, we sampled the EIMT documentation associated with a range of plant items listed on the maintenance inspection and test schedule (MITS). In all but one instance, we observed that the MIT task had been undertaken to the expected standard and recorded appropriately. In one instance, there was no indication on the check sheet that there had been a failure against expected tolerance. In addition, the failure was not identified during the supervisor verification of the check sheet and there was no record of a failure recorded on AMS. We were subsequently assured that the affected equipment was in good working order. The station further committed to review the quality of associated maintenance job instructions.

During a routine plant walkdown, I observed below standard accumulation of waste in a waste sorting room that contained significant quantities of combustible material. I also observed four obstructed nuclear fire doors that may otherwise hinder prompt evacuation. The station undertook immediate action to rectify these matters. Level 3 issues have been raised through which to monitor longer term solutions to prevent reoccurrence.

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

From the evidence gathered during this intervention we considered that the requirements of the safety case have been adequately implemented at Hunterston B. In relation to the requirements of LC 10, 23, 24, 27 and 28, ratings of ‘Green’ were allocated in each instance.

There are no findings from this inspection that could significantly undermine nuclear safety.