Plant Life Extensions

On 4th December 2012 EDF Energy announced that it will extend the operating life of two of its nuclear power stations by seven years. The announcement made no mention of the Periodic Safety Review which regulators will carry out in 2015. Even then, regulatory approval is no guarantee of safety. The oldest reactor at Fukushima in Japan received a ten year life-extension from regulators just one month before the earthquake and tsunami.

Hinkley Point B and Hunterston B power stations are now expected to remain operational until at least 2023, according to EDF Energy. The decision follows the five year extensions to Heysham 1 and Hartlepool announced in 2010 and “comes after extensive reviews of the plants’ safety cases and continuing work with the independent nuclear regulator”.

EDF Energy expects an average of seven-year life extensions across all its Advanced Gas-cooled Reactor (AGR) stations and a 20-year extension for Sizewell B, the only Pressurised Water Reactor (PWR) in the UK.

Hinkley Point B and Hunterston B opened in 1976 which makes them older, or the same age as, all but one of the eight reactors which Germany has already shut down. A major study of reactor hazards by two leading scientists and an international energy specialist, published by Greenpeace in April 2005, concluded that risks from ageing reactors are higher because age-related degradation mechanisms are not well understood and are difficult to predict. AGRs do not have a secondary containment, so there is a high potential for large radioactive releases.1

Despite being opposed to the construction of new reactors in Scotland, Scottish ministers have repeatedly said they will not oppose plans by EDF Energy to apply to UK regulators to keep Hunterston B going until 2023. So the Nuclear Free Local Authorities, Friends of the Earth Scotland and WWF Scotland wrote to Scottish Energy Minister Fergus Ewing in June 2011 asking him to commission an independent study on the risks of continuing to operate 35-year old graphite moderated reactors, and extending the life of such reactors beyond 2016. They highlighted a report by Large Associates – an independent nuclear engineering consultancy – on problems at Hinkley Point B which analysed a bundle of documents received under the Freedom of Information Act, and concluded that there are:

“…significant uncertainties over the structural integrity and residual strength of the moderator cores in …AGR plants in view of the increased risk presented by continued operation of these nuclear plants, the reactors should be immediately shut down and remain so until a robust nuclear safety case free of such uncertainties has been established.2

John Large of Large Associates said it was “gambling with public safety” to allow Hinkley Point and Hunterston to continue operating.3

The documents, written by the former Nuclear Installations Inspectorate, reveal that AGRs are structurally defective and their continued operation is increasing the risk of a radioactive accident. The bricks which make up the reactor cores of the AGRs are cracked. These bricks, made of graphite, help control the nuclear reaction by influencing the speed of neutrons. Channels also run through the bricks which enable key safety mechanisms, such as the entry of rods designed to shut-down the reactor in an emergency. However, the cracked graphite bricks could cause safety mechanisms to fail in a severe event and the nuclear fuel to overheat, potentially resulting in a radiological release.4

Periodic Safety Review

The UK Office for Nuclear Regulation (ONR) does not have a formal decision-making process on life extensions. Instead it is considered when each reactor undergoes its periodic safety review every 10 years. ONR will tell the nuclear operator what modifications it needs to make to keep the station running then the operator decides whether implementing the required changes is economic.5 ONR says it is working with EDF Energy to extend the life of its nuclear power stations and that it is “content for the plants to continue to operate“, as long as they pass regular safety tests.6

Hunterston B and Hinkley B are both due to undergo a periodic safety review (PSR) in 2015 according to ONR. But ONR doesn’t expect to make a decision on whether to grant EDF Energy a renewed license until 2016. A PSR is carried out for each operating nuclear power station in the UK every ten years. The review requires an operator to prove that its nuclear power plant is safe and complies with site license conditions. EDF Energy has previously said it expects to achieve life extensions of an average of seven years for each reactor across its AGR fleet. The 4th December decision to extend the life of the two AGRs is a purely commercial one.7 According to The Telegraph, EDF Energy needed to tell the Nuclear Decommissioning Authority by 2013 if it was planning to close Hunterston and Hinkley in 2016.8

Even after the Periodic Safety Review process has been carried out by the regulators there will be no guarantee of safety. Just a month before a powerful earthquake and tsunami crippled the Fukushima Daiichi plant, government regulators approved a 10-year extension for the oldest of the six reactors at the power station despite warnings about its safety.9

Hunterston B and Hinkley B were originally expected to close in 2011 after 35 years of operation.  If the last pair of AGRs to be built at Torness and Heysham 2 receive a similar life extension they could be operating until 2035-6.10

Electricity Market Reforms will give EDF Energy a windfall for its existing reactor of at least £1bn through the carbon floor price. Extending the life of the AGRs is like a licence to print money – an Atomic ATM.11

An ageing reactor fleet

The Union of Concerned Scientists (UCS) describes the profile of risk over the lifetime of a reactor as a ‘bathtub’ curve. New reactors start out as a high-risk as they are ‘broken-in’. In the middle of their life, reactors should be in peak health where the risks are at their lowest. Then as reactors get older they enter a ‘wear-out’ phase with a high risk that components will wear out and fail.12

At the start of 2005 there were 441 nuclear power reactors, operating in 31 countries. Of these, over 300 were more than 20 years old. Clearly, as with any other sort of equipment, as reactors get older there is an increased risk of age-related failures. All the more worrying then that across the globe there is a general trend towards extending the life of reactors.

At the time of their construction it was usually assumed that reactors would not operate more than forty years. However, now, in order to retain the nuclear share of the market and maximize profits – with, in theory, the large construction and decommissioning costs paid for – life-extension offers an attractive proposition for nuclear operators. In the US between 2000 and 2005 32 reactors, received 20-year extensions to their 40-year life, and applications for 16 more reactors were in the pipeline.

Ageing processes are not always easy to recognize and can increase plant risk considerably. They are difficult to detect because they usually occur on the microscopic level of the inner structure of materials. They frequently become apparent only after a component failure – for example, break of a pipe -has occurred. For a nuclear power plant, whatever the reactor type, the ageing phase will begin after about twenty years of operation. This, however, is a rule-of-thumb number only and ageing phenomena can begin earlier.

See also Nuclear Reactor Safety, N2NP Briefing January 2007

1. Nuclear Reactor Hazards by Helmut Hersch, Oda Becker, Mycle Scheneider, Anthony Froggatt, Greenpeace International, April 2005.

2. Brief Review of the Documentation Relating to the Graphite Moderator Cores at Hinkley Point B and Other Advanced Gas-Cooled Reactors. Large and Associates, June 2006.
3. See Guardian 5th July 2006  and Stop Hinkley Press Release 20th February 2012 and New Scientist 26th Marc h 2005
4. Greenpeace Press Release 5th July 2006
5. i-Nuclear 16th February 2012
6. Guardian 22nd May 2012
7. Nucleonics Week 13th September 2012
8. Telegraph 9th September 2012
9. New York Times 21st March 2011
10. Herald 13th August 2012
11. Edie 7th June 2011
12. Lochbaum, D, US Nuclear Plants in the 21st Century: The Risk of a Lifetime, UCS, May 2004


Published: 4 December 2012
Last updated: 8 December 2012