Office for Nuclear Regulation

Return to Service Readiness Inspection (Human Factors)

Executive summary

Purpose of Intervention

EDF Energy Nuclear Generation Ltd’s (NGL’s) Dungeness B (DNB) nuclear power station’s two reactors have been in extended outage as a result of the station’s event recoveries, including corrosion, steam main cracking and delivery of an adequate boiler tube safety case.  During this period there has been a significant turnover of staff and a number of significant events that has resulted in the station receiving Enhanced Regulatory Attention.

The purpose of this intervention was to assess DNB’s readiness to return to service (RTS).

Interventions Carried Out by ONR

The inspection was a follow up to a previous ONR RTS inspection at DNB in February 2020.  The previous inspection covered training, operating rules and instructions, and event investigations.

This intervention was carried out remotely by ONR’s Human Factors (HF) Inspector and the DNB Recovery Site Inspector over the period 2nd to 11th December 2020.  Additional information was provided via walkdowns performed by NGL’s Independent Nuclear Assurance (INA) HF Specialist. 

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, no system-based inspection was undertaken.

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

Licence Condition 10 – Training – GREEN (No Formal Action)

Licence Condition 24 – Operating Instructions - AMBER (Seek Improvement)

Licence Condition 28 – Examination, Inspection, Maintenance and Testing - GREEN (No Formal Action)

In addition, I considered that the focus of INA’s HF aspects of the joint inspection were appropriate and well considered.  I reviewed INA’s conclusions and findings and considered that they were comprehensive and provided evidence of a rigorous approach.

Conclusion of Intervention

Interventions ratings of Green, against LCs 10 and 28, with one Regulatory Issue being raised.  Recommendations for consideration were also raised regarding maintenance records and the Procedures Improvement Working Group.

An intervention rating of Amber was assigned against LC 24.  Procedural Quality at DNB is subject to an existing Level 3 Regulatory Issue (#8258) and an enforcement letter and as such this Amber rating will be pursued via the existing Regulatory Issue and no additional regulatory action is considered necessary.