Hunterston B defuelling operations begin

19 May 2022

EDF Energy has started removing the used fuel from the core of Hunterston B's Reactor 3, an advanced gas-cooled reactor (AGR) that shut down in November 2021. Defuelling is the first stage of the nuclear decommissioning process.

Hunterston B (Image: EDF Energy)

The Hunterston B plant in Scotland comprises two 490 MWe AGR reactors - Reactors 3 and 4. Reactor 3 came online for the first time in February 1976, was initially expected to run for 25 years but had its generating lifespan increased to more than 45 years. The station's other unit, Reactor 4, started up in March 1977 and was taken offline in January this year. Preparations for defuelling the plant have been under way for some time.

Defuelling the plant will involve removing more than 300 channels of fuel from each of the reactors. The fuel channels will be stripped and processed then taken to the on-site fuel storage pond to cool before being packaged into used fuel flasks and transported via rail to Sellafield, England.

The first empty fuel plug unit has now been returned to Reactor 3 (R3).

"Following the successful completion of its R3 pre-defueling outage, the station has now officially started defueling," EDF Energy Managing Director of Generation Matt Sykes told employees. "This is an historic moment for our company, as the first of our AGR sites enters the next stage in the nuclear lifecycle."

The entire defuelling process is expected to take three years to complete, with the site then due to be handed over by EDF to the UK's Nuclear Decommissioning Authority for its subsidiary Magnox to continue with the decommissioning.

"To achieve this three-year target, an average of three flasks will need to be processed a week (compared to an average of one per week today)," Sykes said.

He added: "The team at Hunterston has taken a deliberate and systematic approach in its preparations to start defuelling. Much is being learned as we progress this new activity and reaching this milestone is a huge credit to everyone at the station, as well as to all those across Generation and our partners who have supported them."

EDF had originally been responsible for total lifetime decommissioning of the seven AGR stations, which comprise Torness and Hunterston B in Scotland, Dungeness B in Kent, Hartlepool in Teesside, Heysham 1 and 2 in Lancashire and Hinkley Point B in Somerset. All these plants are scheduled to reach the end of their operational lives this decade.

However, in June 2021, the UK government and EDF agreed improved arrangements to safely and efficiently decommission the AGRs. Under the agreement, EDF will aim to shorten the time it takes to safely remove the fuel from the power stations as they come offline, before working closely with the NDA to transfer ownership of the stations to the NDA.

EDF said it aims to take up to five years to complete defuelling at each site, but Dungeness B will take longer to defuel than the other six AGRs "due to its unique design and requirement for extra preparation time".

Researched and written by World Nuclear News