- Site: Dungeness B
- IR number: 21-070
- Date: August 2021
- LC numbers: 17, 23, 24. 28
Executive summary
Purpose of Intervention
This intervention was a planned intervention at EDF Energy Nuclear Generation Limited’s (NGL’s) Dungeness B power station. The intervention consisted of reactive preliminary enquiries for two reported incidents, routine intelligence gathering and ONR information exchange meetings. This intervention was supported by the Site Recovery Inspector.
Interventions Carried Out by ONR
The following intervention areas are outlined below:
- Undertook preliminary enquiries into the loss of water chemistry control to reactor 22 boilers.
- Undertook preliminary enquiries into the loss of boiler 27 superheater penetrations carbon dioxide in air monitoring equipment.
- Undertook a plant visit to the radiological controlled area (RCA).
- Undertook an information exchange meeting with station representatives.
During this inspection I held a monthly meeting with the station’s safety representatives, the station’s internal safety regulator and observed a site excellence tour of turbine hall 22.
Explanation of Judgement if Safety System Not Judged to be Adequate
No system-based inspection was undertaken during this visit.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
This intervention centred on preliminary enquiries regarding two reported incidents.
For the loss of water chemistry control to reactor 22 boilers event, I undertook interviews with several members of the station’s senior leadership team and technical staff who were responsible in ensuring the water chemistry to reactor 22 boilers was controlled. This intervention also included a visited to the station’s water chemistry control plant areas. From my preliminary enquiries, I identified that there have been significant shortfalls in meeting the expected standards as defined within ONR’s technical inspection guides:
- NS-INSP-GD-017 - LC17 Management Systems
- NS-INSP-GD-023 - LC23 Operating Rules
- NS-INSP-GD-024 - LC24 Operating Instructions
- NS-INSP-GD-028 - LC 28 Examination, inspection, maintenance and testing
In light of my findings and observations, I have rated the above license conditions as REDand will apply ONR’s Enforcement Management Model (EMM) to determine the most appropriate enforcement action in order to bring the station back into compliance.
For the loss of boiler 27 superheater penetrations carbon dioxide in air monitoring equipment, I held discussions with the central control room staff, the reactor engineering group head and the station’s technical safety and support manager. I also undertook a plant visit into the RCA to visually inspect the equipment that was left disconnected.
The station is undertaking an investigation into the events surrounding this incident, I am content that there were other diverse systems available which would provide early indications of a boiler tube leak. I therefore do not intend to follow this event any further.
Conclusion of Intervention
For the loss of water chemistry control to reactor 22 boilers event I have rated licence conditions 17, 23, 24 and 28 at RED. I will apply ONR’s Enforcement Management Model (EMM) to determine the most appropriate enforcement action. Further follow-up of this event will be undertaken in order to bring the station back into compliance.
For the loss of boiler 27 superheater penetrations carbon dioxide in air monitoring equipment, the station is undertaking an investigation into the events surrounding this incident. I am content that there were other diverse systems available which would provide early indications of a boiler tube leak. I therefore do not intend to follow this event any further.