Over 2,100 tonnes of solid radioactive waste – the equivalent weight of 153 Big Ben bells – have been retrieved and safely stored at Hunterston A nuclear decommissioning Site, completing a major NRS milestone.

Hunterston A holds the largest inventory of solid ILW across all the NRS sites. This waste consists of contaminated metallic components, debris removed from spent fuel elements and 30,000 fuel element graphite sleeves from when the site was generating low carbon electricity 1964 – 1999.

Mark Blackley, Hunterston A Site Director, said: “This is a fantastic achievement which has safely and compliantly reduced one of the most significant hazards on site. Over 85% of the intermediate level waste (ILW) inventory has now been retrieved. This is a tremendous testament to everyone who has been involved in or who has supported this project.”

“The remaining 15% of ILW inventory are residual sludges from the spent fuel storage ponds and acids. These are in the process of being recovered and treated.

Gareth Taylor, Group Performance Improvement Director, Nuclear Decommissioning Authority, said: “This is a significant milestone in our mission to safely and securely decommission our legacy nuclear sites. It is fantastic to see the culmination of many years of hard work and planning.

“It’s a collective achievement that the whole team are rightfully proud of, and we will be looking to take forward the lessons learned and apply them across our other sites.”

The waste was transported via underground tunnels and stored in one of five above-ground concrete bunkers that were constructed on site between the 1960s and 1980s.

The Solid Active Waste Bunker Retrieval (SAWBR) project was established to remove the waste and empty the five bunkers in sequence by breaking through the walls one by one.

The initial breakthrough at bunker five was conducted manually in 2014 using core drills and wire saws to remove an 800mm deep concrete slab. Then a remotely operated vehicle broke through the remaining 400mm depth to create the first full opening.

Remotely operated vehicles were used to recover the waste to a purpose-built facility built on the side elevation of bunker five. The waste was then loaded in to three metre cube size stainless steel boxes. The filled boxes were then transported to the site’s ILW store pending future encapsulation at the solid intermediate level waste encapsulation (SILWE) facility before being returned to the ILW store for long term storage in line with the Scottish Government’s higher activity waste policy.

ILW becomes a site’s highest radiological hazard when all the spent fuel has been removed and is often located in hard-to-reach areas. This means that the task of retrieving the waste is a complicated business requiring, in some cases, many years of engineering work before it can begin in earnest.

Stuart Blair, Waste Operations Manager at Hunterston A, commented: “The process to empty the bunkers has not been without its challenges. The team has overcome many technical challenges throughout, employing operational experience and innovation to progress the waste recoveries safely and efficiently.”

“This represents a major milestone for the entire site with all colleagues across functions and departments playing a key role in supporting this achievement. Most of the team that has completed this work has been involved since day one of retrievals which makes the achievement especially satisfying. With safe and sustainable decommissioning, the process takes decades to complete, so I am also mindful of former colleagues who have contributed significantly over the course of the 20 years since the recovery concept was born.”

NRS are a leading organisation in the UK responsible for the active decommissioning and restoring of Government nuclear sites, to ensure all our futures are more safe, secure and sustainable.