Office for Nuclear Regulation

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Dungeness B Site Visit Covering Fire Improvements Projects and Turbine Hall Fire Event from July 2012

Executive summary

Purpose of intervention

There has been a long standing ONR intervention at Dungeness B power station (DNB) relating to fire improvements arising from a reappraisal of safety at this site following an oil fire within one of the boiler houses in 2009. This led to EDF NG Ltd developing projects aimed at improving the robustness of the fire safety case at DNB. Some of the projects are extensive in scope and have necessarily taken several years to come to maturity.

During the 2014 statutory outage of reactor 21 (R21) at DNB, several significant fire improvement projects were carried out. Part of the rationale for the meeting was to monitor and review the overall fire improvement project. The previous ONR monitoring meeting on the fire improvements project was January 2014, so a project update meeting was timely.

On 1st July 2014, DNB turbine 21 experienced a fire event during its return to service after the overhaul during the statutory outage. The fire was of limited extent, and terminated with only minor damage to lagging. There appeared to be common features with other recent turbine fires across the fleet, and the Site Inspector asked the specialist inspector for internal hazards to look at whether the DNB fire should have been avoided if the station had learned lessons from the recent events. As a result the opportunity was taken to combine the project meeting on the fire improvements project with a series of meetings related to the investigation of the 1st July fire, and other aspects of fire improvements at DNB. This included an inspection of the area of the turbine hall at which the event took place.

Interventions Carried Out by ONR

The inspection had several elements - a project update meeting (level4) on the DNB fire improvements projects, a meeting with the manager who had investigated the 1st July turbine fire, a meeting with the owner for the station "Fire Safety Excellence" plan, and a meeting with the INA site inspector (INA being the licensees "internal regulator").

ONR was represented by the specialist inspector for internal hazards (which includes fire), supported for part of the day with the nominated site inspector.

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

The project update meeting was a useful exchange of information. Key achievements since the January 2014 update had been installation of equipment associated with two significant fire risk reduction projects onto R21, and completion of an "interim fire safety case" which was submitted as an update to the licensee's nuclear safety committee. ONR gave good feedback on the clarity of the elements sampled of the safety case, and also thought an initiative from INA to improve the visibility of the plan to complete the remaining commitments was also a useful improvement. ONR also welcomed the sharing of lessons learned from the experience of the installation of two major modifications on R21, and thought that these should lead to achievement of satisfactory installation of the equivalent projects on R22 in the 2015 statutory outage.

The investigation of the 1st July turbine fire was viewed as an honest appreciation by the licensee that they had not learned as much as they could have from the April Hartlepool turbine fire event. As against that, visiting the site of the event allowed ONR to appreciate that there were some key differences between the two events, so it was not just a repeat event. ONR viewed the overall approach that EDF NG Ltd has taken to the investigation as very constructive. A negative from the visit was that in some areas of the turbine visited, there was more visible evidence of standing oil leaks than would be desirable. The station plans include reducing the number of oil leaks and improvements to the material conditions in the turbine hall basement.

There has been some progress on elements of the "Fire Safety Excellence" (FSE) plan since the last update. In particular DNB has commenced its programme of additional "fire awareness training", which involves all site staff (and permanent contractors). DNB is behind much of the fleet, because of the timing of the DNB R21 Outage. Additionally, station is aware that one effect of outage work priorities at DNB has been a slowing up of some other elements of the FSE plan. ONR welcomed that this has been recognised and that station is re-invigorating this plan.

The meeting with the INA site inspector covered progress on addressing issues from the Fire Referential carried out in 2013 by INA, and also on some corporate level initiatives from INA. ONR viewed the meeting as useful in showing good alignment between INA and ONR on fire improvement issues.

Conclusion of Intervention

The DNB fire improvement projects are a live issue on the ONR risks and issues database. The ONR specialist inspector for internal hazards said that he would intend to close this issue once the two major fire improvement projects have been installed and satisfactorily commissioned, and put into service on both reactors - which is due to be in mid 2015. At that stage the only remaining aspect of the fire improvement project will be the "long term safety case", which will be a category 1 submission to the NSC so will be addressed by ONR via the normal processes for category 1 submissions.