TRANSPORTING THE HUNTERSTON A LEGACY WASTE | DECOMMISSIONING
concrete wall slab. Then a remotely operated vehicle (ROV) broke through the remaining 400mm depth to create the first opening between the bunkers. Waste retrievals then commenced under active commissioning arrangements until the facility could demonstrate repeatability in the process to allow normal operations status to be achieved.
Waste retrieval process Retrievals were carried out using ROVs – one to recover the waste, load it into metal containers and then transport the filled containers onto an automated conveyor for gamma radiation monitoring. A second ROV was on standby within the PEF to act a safe point of recovery should the ‘duty’ ROV encounter an issue in operation. Gamma radiation monitoring was required to ensure the
waste was within permitted levels for export and into storage. The waste container then progressed along the conveyor into an elevated position to enable the contents to be tipped down a chute to fill an industry standard 3m3-high integrity stainless steel box. Further pre-programmed robotic checks ensured the
box lid and sealing system was clear of dust and debris to fit correctly. It was then sealed and transported via a 10 tonne overhead crane through a shielded door to the box preparation area. Within the box preparation area another robot was utilised to replace the lid bolts and perform final radiation monitoring checks to ensure the box was clear of any contamination and was ready for export to the site’s intermediate level waste store via a purpose-built shielded transporter. Highly skilled operators viewed closed-circuit television
of all the retrieval and process operations via the ROVs on-board cameras and overview cameras strategically placed in order to follow the entire process.
Operational excellence and innovation Graeme Busby, Hunterston A project engineer, has been involved with the project since its inception. He sums up the active commissioning experience: “The team analysed and challenged everything to overcome the technical difficulties and optimise the opportunities this phase presented. These measures reduced box processing cycle time from nine hours to just under four hours from the import, filling, swabbing and export of a package of HAW waste”. Among the measures introduced to accelerate the
process, the control system was reprogrammed to make the plant operate in parallel rather than sequential. This was the biggest gain in terms of time and followed a detailed analysis of every individual step involved in the overall process. Improved packing efficiencies also resulted in a 10% overall reduction in the number of boxes required. In addition, the number of swabs needed to release a
package were reduced from 64 to 21 and eventually to three at less than four minutes per swab. The revised swabbing regime still provided robust assurance with respect to ensuring there was no contamination to the externals of the package, thus meeting the required export criteria. Furthermore, the automated control system was
reprogrammed to import a box with eight lid-holding bolts instead of 28. Whilst the box was in another area of the facility the other 20 bolts could be manually placed into the bolt tray to support export preparation without being time critical. A further 18 minutes were saved on the box cycle time with this change.
The project progressed to breakthrough each bunker in a 4, 3, 2 sequence culminating in bunker 1 which contained 188 tonnes of HAW – the highest of the 10-year project. The final waste package was completed in April 2024 bringing a safe conclusion to retrieving and storing over 2,300 tonnes of solid HAW from the five bunkers and significantly reducing hazardous waste. Stuart Blair, Hunterston A Waste Manager, commented:
“It’s a real pleasure to work with such committed and talented colleagues within waste operations. No matter the challenges faced they always find solutions. “This fantastic achievement has safely and compliantly
reduced one of the most significant hazards on site. Over 85% of the HAW inventory has now been retrieved. This is a tremendous testament to everyone who has been involved in or who has supported this project.”
Next steps The 1,216 packages of recovered waste will be encapsulated in cementitious grout and stored on site until such time that the Scottish Government’s HAW policy identifies final storage and disposal options for this level of radioactive waste. Post operational clean out of the SAWBR facility is underway to prepare the building and bunkers for eventual demolition as part of the ongoing decommissioning programme on site. The Hunterston A site is immediately adjacent to the Hunterston B plant, an advanced gas-cooled reactor, owned and operated by EDF. This will be joining the NRS family in spring 2026 for its decommissioning and subsequent site restoration. ■
www.neimagazine.com | July 2025 | 25
Above top: The SAWBR project timeline
Above bottom: An ROV was used to remove bunker waste and place it in stainless steel boxes for transport. This image shows bunker 2
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