More than 700kg of explosives have been used in the first stage demolition of four concrete plinths that bore the weight of two turbo generator units weighing 605 tonnes each at the UK’s Sizewell A NPP.
Sizewell A’s two 210 MWe Magnox gas-cooled reactors operated from 1966 until 2006. Defuelling began in 2009 and the fuel was placed in the site’s used fuel storage ponds before being packaged in transport containers for shipment to the Sellafield site in Cumbria for reprocessing. The last flask of fuel was shipped to Sellafield in August 2014 and the plant was declared completely fuel free in February 2015. This marked the removal of 99% of the radioactive hazard from the plant site.
Planning consent was given to demolish the turbine hall and electrical annexe in August, since when more than 35 miles of cabling and 8,000 scaffolding boards, clips and pipes have been taken out. More than 1,200 holes were drilled into the plinth structures. The charges were then set and the plinths wrapped ready for detonation. This method reduced the need for heavy machinery – saving time, cost, reducing noise and dust levels.
Nuclear Restoration Services, which is part of the Nuclear Decommissioning Authority (NDA), said this established a new record for the largest use of explosives on a nuclear site for conventional demolition purposes in decades. Large machinery has now removed the weakened material, taking this significant demolition project a huge step forward.
To date, more than 7,100 tonnes of metal have been removed from the site. This is being recycled and sold on the metals market to generate income. Over 17,000 tonnes of demolition rubble will also be re-used and recycled. The overall turbine hall structure is expected to be demolished in Spring 2025 creating a footprint the size of a large football pitch. This land will eventually be restored and released for re-use. It follows the sale of 1.2 hectares of land on the site transferred to EDF Nuclear Generation Limited (ENGL) earlier this year.
NRS said this delivered on a multitude of NDA and NRS strategic objectives – marking tangible progress in the completion of the decommissioning mission and delivering benefit to the local community and the wider economy.
Alan Walker, Sizewell A Site Director, commented: “It’s fantastic to see Nuclear Restoration Services (NRS), our contract partners and the Office for Nuclear Regulation (ONR), pushing the boundaries of innovation in de-plant and conventional demolition together.”
He added that the detailed planning and stakeholder engagement for this were exemplary. “Everyone involved has done an outstanding job and this success demonstrates our commitment to achieving safe, efficient decommissioning processes. The ONR strictly governed the use of explosives. Their presence and oversight gave confidence that every aspect of the set up and execution had been thoroughly checked to ensure maximum safety.”
Andrew Bull, ONR’s Nominated Site Inspector at Sizewell A, said this was a great example of joint working between regulator and duty holder “and everybody being open to considering and actioning novel and forward-thinking technological solutions to bring about efficiencies”. He added: “ONR’s stance as a consistently enabling regulator means that we will always support proactive and innovative methods of working provided these are conducted safely and securely.”
NDA Group Chief Assurance and Performance Officer, Alan Cumming, during a visit to the site, said: “This is what mission delivery is all about. Decommissioning, knocking stuff down and dispatching the waste. It’s an incredible achievement and testament to the expertise, capability and innovative mindset each partner brought to the project.”
He continued: “It showcases the power of collaboration and our capability as a sector to deliver groundbreaking progress, while still maintaining the most rigorous safety standards, paving the way for future advancements. This is a substantial step towards completion of the safe, secure and sustainable decommissioning of Sizewell A, leaving a positive legacy for the community and future generations.”
The success of the project means that NRS will be able to employ the same technique at some of the other 12 sites currently being decommissioned.
