EDF will extend the lifetimes of two UK nuclear power plants—Heysham 1 in Lancashire and Hartlepool in Teesside—by an additional 12 months to March 2028 in a bid to secure the country’s energy security as it faces a looming nuclear capacity cliff and heightened reliance on imported gas.
The French-owned utility confirmed that 1.2-GW Heysham 1 in Lancashire and 1.2-GW Hartlepool in Teesside will continue generating beyond their previously scheduled March 2027 shutdown dates. The decision, which was finalized following EDF executive board meetings on Sept. 1, was based on “positive results” from nine months of graphite core inspections at both facilities.
A Boost for UK’s Legacy AGRs
The two reactors are part of the UK’s legacy advanced gas-cooled reactor (AGR) fleet, a British technology that has been the backbone of the country’s nuclear generation since the 1980s. The country currently operates nine nuclear reactors at four locations—eight AGRs and one pressurized water reactor (PWR) at Sizewell B—with a combined capacity of approximately 5.9 GW. The AGR fleet originally comprised 14 reactors at seven sites built between 1976 and 1988, but three stations (Dungeness B, Hunterston B, and Hinkley Point B) have already been shut down and entered defueling. Of the UK’s nine operational reactors at five sites, however, eight are scheduled for closure by 2030.
For now, the UK is pursuing an ambitious nuclear expansion aimed at quadrupling the country’s nuclear power capacity by 2050 set out a series of goals and actions that could enable the delivery of 3 GW to 7 GW every five years from 2030 to 2044. The country wants to add at least four EPR reactors across two sites. The 3.2-GW Hinkley Point C, which EDF is currently building, is slated to come online in 2029-2031. A twin plant, the 3.2-GW Sizewell C, received final investment approval in July 2025. The government confirmed it will take an initial 44.9% stake in that project, becoming the single largest equity shareholder.
Plans for additional EPR reactors include a proposed 3.2-GW Moorside clean energy hub in Cumbria, where EDF announced plans in 2020 to construct an EPR as a near replica of Hinkley Point C and Sizewell C. In June 2025, however, the UK government said it would free up land at the Cumbria site for clean energy development, including potential small modular reactors (SMRs).
Last Energy, a U.S.-based microreactor developer, is meanwhile advancing plans to build four 20-MW PWR-20 reactors at the former Llynfi Coal Power Station site in South Wales, potentially becoming the first new commercial nuclear site to enter UK licensing since Torness in 1978. In June, regulators completed a preliminary design review, and the company is now targeting a site license decision by December 2027.
As notably, in June, the UK government selected Rolls-Royce SMR as the preferred bidder to develop the country’s first SMR fleet in partnership with Great British Nuclear, a government agency tasked with delivering the UK’s nuclear program by 2050. Great British Nuclear has said it will work to allocate a site for the Rolls-Royce SMRs later this year and connect projects to the grid in the mid-2030s.
Graphite Core Safety Under Scrutiny
Heysham 1 and Hartlepool, which have a combined capacity of 2.3 GW, began commercial operations in 1983 with an original 25-year design life. Both have operated for over four decades through successive life extensions. EDF notes that since acquiring the UK nuclear fleet in 2009, it has invested approximately £8 billion in lifetime extensions and reliability improvements.
While EDF’s December 2024 review of the two projects initially extended their lifetimes to 2027, the extension was conditional on critical safety inspections scheduled for 2025. Separately—not part of the latest review—in December 2024, Heysham 2 and Torness, the UK’s other two operating AGR stations, received two-year extensions to March 2030.
Centrica, which owns the four stations, said the total life extensions announced since December 2024 are projected to add approximately 12 TWh to the Company’s electricity generation volumes between 2026 and 2030. The company suggested significant implications for UK energy security amid ongoing geopolitical tensions.
The extensions hinge on the aging graphite moderator cores within AGR reactors. The UK, notably, is the only country that operates graphite-moderated, carbon dioxide-cooled commercial reactors. “The UK has a long history of using graphite as a moderator from the early Magnox reactors to the Advanced Gas-cooled Reactors (AGRs),” the UK Office of Nuclear Regulation (ONR) explains. “The moderator slows down the speed of neutrons produced during nuclear fission and helps to sustain the chain reaction so that the heat can be used for electricity production. In both of these designs, the core is constructed from thousands of interlocking graphite bricks, which also form a large number of important channels. These channels contain the nuclear fuel, the reactor control rods, and allow the passage of carbon dioxide coolant gas to remove heat from the reactor fuel and core.”
A crucial issue associated with graphite bricks, however, is graphite core aging. Graphite core aging occurs as the graphite moderator bricks in AGR reactors gradually deteriorate over decades of operation through weight-loss from oxidation by carbon dioxide coolant and cracking in four distinct patterns, ONR notes. Keyway root cracking, the most serious phenomenon, will typically determine when most AGRs must shut down permanently since it can progressively affect many bricks across the core and compromise essential safety functions like control rod movement and fuel handling, it says.
ONR, which maintains stringent oversight of the aging cores, requires EDF to demonstrate through comprehensive safety cases that operations remain safe. Recent inspections examined graphite weight loss across all four generating AGRs, keyway root cracking at Heysham 1 and Hartlepool, and seal ring groove wall cracking at Heysham 2 and Torness. “The results of inspections of the graphite cores during 2025 have supported EDF’s decision to extend station lifetimes,” EDF said.
EDF stressed that the decisions on end-of-generation dates for EDF’s nuclear power stations in the UK “are independent of the regulator or government and are taken by EDF’s licensee board following recommendations from EDF Nuclear Generation Limited’s Executive.” It adds that the dates are forecasts. “Precise dates will be determined by the results of regular graphite inspections and how those results are interpreted within EDF and by the independent regulator, the Office for Nuclear Regulation.” It has also however said that “EDF’s ambition is to continue making zero-carbon electricity at its four generating Advanced Gas-cooled Reactor (AGR) stations for as long as it is safe and commercially viable to do so and will keep station lifetimes under review.”
“A further year of operation for these two stations has the potential to power more than four million homes and reduce the need for imported gas,” said Dr. Mark Hartley, managing director of EDF’s Nuclear Operations business.
A life extension for Sizewell B may also be on the horizon. “Sizewell B is a different type of nuclear power station, and its lifetime was not reviewed as part of this process,” the company said. “There is also a good opportunity to extend the lifetime of the Sizewell B station for a further 20 years, out to 2055. This will require securing a sustainable commercial model before an investment decision is taken.”
—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).
