The Nuclear Decommissioning Authority

 

It's now all systems go for defuelling both reactors at Dungeness A, following successful roof repairs to one of the reactor buildings. 

The roof of reactor two was severely damaged during a violent storm in 2008, leaving the route for fuel removal out of action, although the safety of the core was intact. Reactor one was unaffected. 

After the completion of major roof work, the reactor two fuel route has been returned to service. With both fuel routes now operating, potentially twice as many flasks could transport spent fuel to Sellafield for reprocessing, bringing Dungeness A closer to being completely fuel free. 

Due to the damage, reactor two is 9% defuelled, while the other is more than 30% defuelled. Mark England, site director, said:

"This was an extensive and challenging job for us. The team worked at heights of about 60 metres and I am extremely pleased that we were able to put the temporary water-tight seal in place, remove the pile cap protection and replace more than 2,000 m2 of roofing safely. 

"Our team, made up principally of shift operations, infrastructure, fuel route support staff and others, also carried out a programme of inspection, maintenance, testing and re-commissioning of the fuel route equipment. This allowed defuelling to restart as soon as the roof repair was completed." 

The severity of the 2008 storm and subsequent reactor roof damage could not have been predicted. Routine inspections had previously shown the roof to be sound. Inspecting the damage was a massive challenge due to uncertainty over whether the roof was safe to walk on, so a special gantry was created which was supported by the roof structure beams rather than the roof itself. 

A lot of rainwater had made its way into the building, adversely affecting the reactor two fuel route but not compromising the safety of the core. Shift staff worked continually to protect sensitive plant and equipment. 

During the project, 24 gas safety exhaust stacks and 10 existing roof vent fans were removed, bringing decommissioning forward.   

Reactor one was unaffected during the repair work with defuelling and flask despatch continuing as usual. Dungeness is now tackling the roof replacement on reactor one and using recent experience to ensure the fuel route remains open. Good progress is being made and, weather permitting, it should be completed by the end of year. 

New cladding for reactors

 

Both reactors at Dungeness A have now been completely re-clad in one of the biggest decommissioning projects the site has tackled since generation stopped at the end of 2006. 

The re-cladding on reactor two is now finished, following a project that took a total of 14 months to complete and which saw the removal and replacement of more than 11,000 sq metres of cladding. 

The re-cladding will leave the reactor buildings in a safe and weatherproof envelope for at least 15 years as the site moves into the next phase of decommissioning. A survey in June 2007 found that the original cladding had severely degraded and that some sections were in an unstable condition. 

The site project team managed a team of specialists from the contractor Rainham Industrial Services (RIS). The success of the project was down to the flexibility of the workforce which was moved, if necessary, to areas protected from driving wind and rain as the work progressed. Now the final work to take down the remaining scaffolding is on target to be finished by the end of September.