Office for Nuclear Regulation

Dungeness B - External Hazards compliance inspection

Executive summary

Purpose of Intervention

This was a planned inspection of EDF Energy Nuclear Generation Ltd.’s Dungeness B Nuclear Power Station. This inspection forms part of the planned intervention strategy for the Operating Facilities Division of the Office for Nuclear Regulation (ONR)

The work was carried out in accordance with the planned inspection programme contained in the Dungeness B 2018/19 Integrated Intervention Strategy (IIS) which was undertaken by two ONR external hazards specialist inspectors.

During the inspection, the nominated site inspector undertook routine engagement and intelligence gathering activities with the station representatives. This involved observing various meetings discussions with senior management team members, a plant visit and the follow-up of reported events to ONR.

Interventions Carried Out by ONR

On 12 – 13 March 2019, I (the specialist external hazards inspector) undertook an on-site licence condition (LC) compliance inspection in relation to seismic hazards and drought. The inspection addressed the following LCs:

The purpose of the inspection was to:

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 – this was not a system-based inspection.

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

LC23 (Operating rules) – I sampled technical specifications (tech specs) for nuclear safety significant systems claimed by the Licensee as protecting against seismic and drought hazards. No issues were identified from this sample, and I judge that the Licensee has met ONR’s expectations for compliance with LC23 and I assign a Green (no formal action) rating. 

LC24 (Operating instructions) – I inspected a sample of operating instructions relevant to the seismic hazard and drought, including: Site Operating Instructions (SOIs), Plant Item Operating Instructions (PIOIs) and a Symptom Based Emergency Response Guideline (SBERG). No issues were identified from this sampling and I consider that the Licensee has adequate documentation available relating to the seismic and drought hazards. I therefore judge that the Licensee has met ONR’s expectations for compliance with LC24 and I assign a Green (no formal action) rating.

LC27 (Safety mechanisms, devices and circuits) – I compared the safety cases for seismic and drought hazards with the Licensee’s diverse and redundant SMDCs. There is clear evidence of a thread through the Licensee’s documentation from the safety case, through the tech specs, SOIs, PIOIs to the maintenance of the plant. I also judged there is adequate defence-in-depth measures to ensure that the simultaneous loss of SMDCs is as low as reasonably practicable (ALARP). I therefore assigned a rating of Green (no formal action) for LC27.

LC28 (Examination, inspection, maintenance and testing) – I sampled a selection of the LC28 Nuclear Safety Maintenance Schedule, instructions and evidence relating to the examination, inspection, maintenance and testing of safety systems claimed against the seismic and drought hazards. Whilst I am aware of on-going work by the Licensee to address concerns over corrosion and degradation of plant covered by ONR Regulatory Issue 661, based on my sample, I am content that Dungeness B has adequate arrangements in place for compliance with LC28. I therefore assign a Green (no formal action) rating for LC28.

During the intervention I identified a potential shortfall in the evidence required for characterisation of the seismic hazard at Dungeness B and I raised an ONR Issue for the licensee to rectify this.

The nominated site inspector followed-up a recent Incident Notification Form (INF) relating to the modification of seismically qualified plant.  He identified some minor shortfalls during his discussions with the station; an ONR Issue was raised in order to track the station’s progress in addressing the minor shortfalls.

Conclusion of Intervention

After considering the evidence sampled during the inspection for LCs 23, 24, 27 and 28, I judge that the Licensee is compliant with its legal duties relating to seismic and drought hazards.  

I judge that there are no external hazards findings from this inspection that could significantly undermine nuclear safety at Dungeness B. Two regulatory issues have been raised; the first relating to characterisation of the seismic hazard at Dungeness B; the second was raised by the ONR nominated site inspector to track the station’s progress on the modification of seismically qualified plant with some identified minor issues.  No additional regulatory action is needed over and above the planned interventions at Dungeness B Power Station as set out in the Integrated Intervention Strategy 2018-19.