The government’s energy policy is under renewed pressure after the prolonged closure of one of Britain’s oldest nuclear reactors due to cracks in its graphite core raised questions over the future of six other plants built in the 1970s and 1980s.
The temporary shutdown of reactor three at Hunterston B in Scotland is also expected to burn an estimated £120m hole in the revenues of its owner, EDF Energy.
EDF said this week it was taking the reactor offline for six months, after inspections found more cracks than expected in the graphite bricks at the reactor’s core.
However, while safety fears have been quashed, the potential impact on wider energy strategy has alarmed experts who warn the reactor may never restart.
Peter Atherton, an analyst at the consultancy Cornwall Insight, said: Let’s say worst-case scenario they found a big graphite core problem and Hunterston never comes back on.
That would be a big hole in the plan [for electricity supplies]. The gas-fired power stations, we’ve probably got enough of them, but it would be pretty tight. It would also be a knock-back to carbon targets. You could build more windfarms, but that would take time.
The Hunterston plant is one of seven using advanced gas-cooled reactors (AGRS), which were switched on during the 1970s and 80s. Several of the reactors have had their lifetimes extended, but all are due to close by the end of the next decade.
The Hunterston outage is the longest yet over the graphite issue, which EDF calls a “unique challenge” projected to cost £100m, with 150 people working on restoring the reactor.
The graphite core is used to moderate the neutrons in a nuclear reaction, but over time that neutron irradiation degrades the graphite, ultimately leading to cracks. The cracks cause a series of knock-on effects that can impair the ability to control the nuclear reaction.
The UK nuclear regulator points out the total number of cracks is well below specified safety limits. It has also welcomed more frequent inspections like the ones that led EDF to take the Hunterston reactor offline.
Experts estimate the 40% cut in the power station’s output it normally supplies enough electricity for 1.8m homes – will cost the French state-owned firm £100m 120m in lost revenue.
That is small compared with the impact of temporary safety closures at EDF’s French plants, which led profits to fall 16% last year. But it is still a blow the company could do without as it ramps up construction of the £20bn Hinkley Point C nuclear power station in Somerset.
EDF will not be the only energy company affected by the outage.
Deepa Venkateswaran, an analyst at Bernstein bank, said she thought it would also hurt the price that British Gas’s parent company, Centrica, will fetch for its stake in the plants. Centrica recently said it hoped to sell its 20% share by 2020.
Brian Cowell, EDF’s generation managing director, told the Guardian he was very confident the Hunterston reactor would come back online in mid-November.
So far, significant cracks have only been found at reactors three and four at Hunterston B.
But Hinkley Point B, which came online in the same year as Hunterston, is offline to carry out checks for cracks. Those inspections will finish in three to four weeks.
The one that will be worrying them is Hinkley [Point B], said John Large, a nuclear consultant who has advised the UK government.
Hinkley Point has not only become a showcase for the industry of why new nuclear should be built in the UK, but the old power station is providing electricity for the 3,500-strong workforce constructing the new plant.
EDF maintains that the prospect of more old reactors having a sustained outage is highly unlikely, but experts said it would pose a significant challenge to power supplies if they did.
While nuclear provides about a fifth of UK electricity today, experts said this week that it would slump to 10% by 2027, as the old plants are retired.
BMI Research said it did not expect Hinkley Point C to come online by 2025 as planned, given recent warnings of further delays to EDF’s Flamanville plant in France, which uses the same reactor design.