Office for Nuclear Regulation

System Based Inspection SBI-012, Fuelling Machine and Decay Store

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a system based inspection (SBI) of the fuelling machine and decay store at EDF Energy Nuclear Generation Limited’s (NGL’s) Dungeness B power station in line with the planned inspection programme contained in the Dungeness B Integrated Intervention Strategy (IIS) for 2018/19.

Interventions carried out by ONR

An ONR C&I Specialist Inspector and a Mechanical Engineering Specialist Inspector undertook a System Based Inspection of the fuelling machine and decay store, to judge the system performance against its safety function. However, as the decay store had been the focus of another recent inspection, this inspection focused on the fuelling machine. Through sampling of documentation, plant walk down and discussions with staff, we examined NGL’s compliance with the following nuclear site licence conditions (LCs), which are applicable provisions of the Energy Act 2013:

We judged that LC34 - Leakage and escape of radioactive materials was not applicable to the system under consideration for the purpose of this inspection.

The inspection was based on sampling the implementation of the licensee’s arrangements at Dungeness B against the LCs. The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements.

During the intervention the Mechanical Engineering Specialist Inspector also took the opportunity to discuss NGL’s progress in addressing Regulatory Issue 3317 (Findings from system based intervention on ponds and flasks) with the Fuel Route Group Head.

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

From the system based inspection, we judge that the implementation of the arrangements for the fuelling machine did meet the requirements of the safety case.

Key findings, inspectors’ opinions and reasons for judgements made

Based on the areas sampled during this system based inspection, we judged that the licensee has implemented adequate arrangements to ensure that the fuelling machine is maintained and operated in accordance with the safety case. This was supported by observations made by ONR Inspectors during the plant walk down and discussions with the licensee’s staff.

The inspection identified a number of areas of good practice such as the System Engineer’s knowledge of the system and both the Central Control Room and Fuelling Machine Operators’ knowledge of operating instructions and the associated safety case claims. Maintenance records had been signed off by the technician and system engineer, in addition, there was good evidence of challenge to work instruction record sheets and document modifications being implemented.

Improvements in addressing ageing and obsolescence were evident and recent surveys in accordance with NGL’s processes had been undertaken. We have requested copies of two of these reports when completed.

During a review of the maintenance activities it was noted that one of these activities was undertaken at twice the required frequency. NGL provided a sound justification for this; however, we requested further information to ensure there was no detriment to the system from more frequent testing. We also identified that a specific hoist test did not have adequate tolerances identified and there was some potential ambiguity in the instruction. NGL agreed to review this. A regulatory Issue has been raised to track progress against the actions raised with the licensee.

Overall we judged that the arrangements in respect of the fuelling machine generally met relevant good practice and therefore we have given an intervention rating of Green in relation to compliance with LCs 10, 23, 24, 27 and 28. 

Conclusion of Intervention

From the targeted sampling of documentation, consideration of the evidence examined, discussions with the licensee staff and the plant walk down during this SBI; we consider that the fuelling machine met the requirements of the safety case.

There are 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 at Dungeness B Power Station.