COVER STORY | DEFUELING AGRS
Right: EDFE had some spare flasks that had never been used, which it had held for 30 years. The company spent three or four years refurbishing these.
bring them up to standard and it is now using them to cope with the defueling peak. There were 31 flasks in the fleet during the generation
phase. The company fully refurbished 12 of the 15 spares and of these, six have been deployed into active service to provide additional capacity. Once deployed the casks are contaminated, so the other six are stored in a controlled environment until they are needed. A change in skip marking increased capacity by 7%.
Original skip capacity was 15 compartments but only 14 were used, with the 15th compartment closed off for historic reasons. EDFE now it marks the skips in a different way, which allows it to remove the temporary ID and open the 15th compartment up. Exton says, “It wasn’t an issue during generation, because it wasn’t on the critical path, but that 7% increase in capacity has saved thousands of flask journeys” and means fewer rail journeys are required. The change is expected to save £160m (US$215m) across the AGR defueling programme. Flask transporters (ie heavy goods vehicles) are used to
transport the fuel to the rail head for the journey to Sellafield and in this case new transporters were procured that meet modern emissions standards. Although the distances to the rail head are small (for example 12 miles (20 km) at Hinkley and just 2 miles (3 km) at Dungeness) it is a logistically complicated process. They transporters have to do some longer journeys as well, as EDFE found it was necessary if the new HGVs were to operate optimally. EDFE procured four each for Hinkley Point B and Hunterston B, and they will be used in turn at future defueling sites.
A new critical process
With the clock running and an objective to reduce time and cost, defueling became the plant’s critical path activity. It had to become a ‘production line’ that would keep running on a 24-hour, seven-day basis. That is a change of mindset that “you can’t expect someone to turn on overnight,” says Exton. “The whole station organisation needs to get tuned into that new critical path activity.” Refuelling demand during generation had resulted in
an average dispatch rate of less than a flask a week. The defueling schedule required an average of three a week to
24 | January 2026 |
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meet the 3.5 year target, which often meant four or five per week to allow for a ‘ramp up’ as staff got used to the new process and for inspection and maintenance outages (a few weeks every six months). The ‘production line’ has had breakdowns and failures, but
Exton says some of his team have worked in manufacturing and the team is learning from process industries about maximising up-time. The biggest interruption so far was at Hunterston. A tie-bar end fitting has to be removed from the end of each fuel stringer to allow the fuel to be dismantled into its into elements. For some, removing the bolt required disproportionate force. During the operation phase engineers would typically want to know exactly what caused the issue, but in the process phase the important thing was to find a safe solution. “We had to stop while we figured out a way to work around it, so we engineered a solution then we wrote a safety case to justify it, we made some modifications to the irradiated fuel disposal facilities where the operation is done and it was successful,” said Exton. The solution was passed on to Hinkley Point and to other plants, where Exton says, “we have now built in preparatory work at all those plants to look at that specific design and think about what the solution should be at that plant”. The process mindset makes the time taken to diagnose a
fault, fix it and get the process up and running again much more important. Exton explains that is all about analysis of the downtime, which requires that every delay and event is logged in and recorded so the data can be analysed and trended. EDFE makes sure that there are always engineers on shift that can diagnosis these faults, fix it and get going again within a shift, rather than waiting until the next morning. The overall numbers on each shift have not changed, but the mix of skill sets has. The company had always planned for that shift to ‘process’, but it is ‘learning by doing’ at Hunterston and Hinkley. Other sites are now preparing to take on that process mindset. Defueling preparation teams have been on-site from all the plants that will follow, even those with a few years until shutdown. The next sites are already better set up for the change and will be able to draw on several years of experience from Hunterston, Hinkley and Dungeness. There may be more gains to be made in speeding up defueling. ■
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