Office for Nuclear Regulation

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Dungeness B - LC22 Intervention

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a licence condition (LC) compliance inspection at EDF Energy Nuclear Generation Limited (NGL) Dungeness B Power Station, in line with the inspection programme contained in the Dungeness B integrated intervention strategy (IIS) for 2016/17. Specifically, this was part of a fleet-wide, corporate LC22 inspection.

Interventions Carried Out by ONR

As part of this intervention, we inspected NGL’s LC22 arrangements for Modification or Experiment on Existing Plant, in accordance with ONR guide NS-INSP-GD-022 Revision 3. We focused on configuration control of plant in the process of being modified. The intervention was based upon a review of associated procedures and interrogation of various lists including open Category 1, 2 and 3 lists of modifications, safety case anomalies, defeat of interlocks and long term out of service plant, interviews with station staff and a plant tour.

Explanation of Judgement if Safety System Not Judged to be Adequate

No safety system inspection was undertaken, hence this is not applicable.

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

From our inspection of the arrangements for the control of a modification, focusing on configuration control of plant being modified, we noted sufficient checks and balances within the procedures, electronic modification form and Asset Management System (AMS) to allow for adequate configuration control.

We sampled how all the open modifications on the station are controlled. This showed that a number of key performance indicators are monitored, and review meetings are conducted. However, we found that it was not easy to interrogate the AMS database. We did note a number of long standing modifications which appeared to be master or replicant modifications, which were essentially repeat modifications. These made identifying the real longer term active modifications more difficult. We also noted the need for procedures to be established for effective Responsible Engineer accountability, as well as support, in progressing modifications. However, the overall trend of open modifications has reduced in recent years and management are clear regarding areas for improvement.

The list of long term out of service plant showed that there was no long term out of service plant, which indicated that isolations were under control.

The station management of safety case anomalies looked to be in good order.

There were a high number of interlock defeats in use, with some in force for many years. The management are aware and have focussed efforts this year to resolve, resulting in a large downward trend, however a Level 4 Regulatory Issue has been raised.

Based on our inspection, we judged that overall, the implementation of the arrangements for LC22 reflect relevant good practice and have rated this intervention as Green.

Conclusion of Intervention

Overall, we consider that the arrangements and their associated implementation for LC22 for the sample undertaken met with legal requirements, however a Level 4 Regulatory Issue has been raised relating to the management of interlock defeats. We have therefore rated this inspection as Green.

There are no findings from this inspection that could significantly undermine nuclear safety nor require a change to the planned interventions and inspections of Dungeness B.