After 12% drop in generation, experts say existing nuclear plants are likely to close early

Britain’s nuclear power stations recorded a 12% decline in their contributions to the country’s energy system over the past month, as outages raised concerns over how long the ageing plants will be able to keep operating.

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A temporary closure of two of the country’s eight nuclear plants resulted in a double-digit drop in nuclear generation in January, compared to the same period last year.

Prospects for new nuclear projects have commanded headlines and government attention in recent weeks, with Hitachi and Toshiba scrapping their plans for major new plants.

But the fate of the existing plants, which usually provide about a fifth of the UK’s electricity supplies, has been pulled into focus by outages due to safety checks and engineering works running over schedule. Nuclear outages also push up carbon emissions because any capacity shortfall will typically be replaced by fossil fuel power stations.

Seven of the nuclear power stations use an advanced gas reactor (AGR) design, the oldest of which is 43 years old and the youngest 30 years.

Most were built with a lifetime of about 35 years in mind. All are due to be closed in the 2020s after owner EDF Energy extended their lives, but there are now fears that ageing infrastructure may reduce their output or even lead them to shut early.

Iain Staffell, lecturer in sustainable energy at Imperial College, which compiled the nuclear output data, said: “Just as Toshiba and Hitachi have pulled out of building new reactors, we have one third of the existing nuclear capacity unavailable either for maintenance or because their maximum power has been reduced as they get older.

“Many of our reactors were built in the late 70s, and like your typical 40-year-old they aren’t in peak physical condition any more.”

Hunterston B on the west coast of Scotland is temporarily offline after inspections revealed more cracks than expected in the reactor’s graphite cores. The graphite bricks slow down the neutrons in a nuclear reaction, but over years the process changes the graphite’s structure.

Reactor 3 at Hunterston has been offline for nearly a year since it powered down in March last year. EDF Energy told The Guardian last May it was “very confident” the reactor would come back online by last November, but the latest estimate is 30 April. The power station’s other reactor is due back on 31 March.

However, the company will only be able to restart the plant if the nuclear regulator gives the green light for the safety case presented by EDF.

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The company also announced this week that it was pushing back the reopening of its Dungeness plant in Kent, due to maintenance related to pipes carrying steam from its boiler. Rather than restarting in late February, Dungeness should now come back in April.

Martin Freer, head of nuclear physics at the University of Birmingham and director of the Birmingham Energy Institute, said: “It is clear they are showing their age. When they were originally built they weren’t built to operate as long as they will.”

The issue is not one of safety because of tight regulation of the plants, he said, but it showed the UK’s need to get on and build new nuclear power stations.

By the time Dungeness is hoped to return, another old plant, Hinkley B in Somerset, will have been taken offline for graphite inspections. Any unexpected rate of cracking found there could lead to a longer outage.

Francis Livens, director at the University of Manchester’s Dalton Institute, said the struggle to green-light new nuclear projects had made the need to keep the old ones on more acute.

Freer said he hoped the plants would make it to their planned closure dates rather than retiring early – Hunterston is officially meant to last until 2023 – but feared some would not. “It may just be a run of unfortunate incidents, or it might be a trend of reducing reliability,” he said. “My suspicion is not all of them will make it through to the end.”

EDF said its investments meant the old plants were performing well and it had spent more than £100m over the past six years on the issue of graphite cracking. The company’s figures show generation from the company’s eight plants, including the newer one at Sizewell, growing after it bought them in 2008 before peaking in 2016 and declining since.

Brian Cowell, managing director of generation, said: “EDF Energy’s seven advanced gas-cooled and one pressurised water nuclear power stations [Sizewell B] are delivering at ever better levels thanks to sustained investment and the expertise accumulated over more than 40 years of operation.”

Several of the old plants are also undergoing safety reviews by the Office for Nuclear Regulation. Heysham 1 and Hartlepool both had a periodic safety review in January, with Heysham 2 and Torness to follow next January.