THE HANDSTAND

JULY 2006

Documents reveal hidden fears over Britain's nuclear plants

Unexplained cracks in reactor cores increase likelihood of accident, say government inspectors

John Vidal and Ian Sample
Wednesday July 5, 2006
The Guardian


Revelations of safety concerns at Britain's AGR power stations come at a crucial time for the nuclear industry, with results of the government's energy review due in the next fortnight. Photograph: Martin Argles
 


Government nuclear inspectors have raised serious questions over the safety of Britain's ageing atomic power stations, some of which have developed major cracks in their reactor cores, documents reveal today.

The safety assessments, obtained under Freedom of Information legislation, show the Nuclear Safety Directorate (NSD) has issued warnings over the deterioration of reactor cores at Hinkley Point B in Somerset and other British nuclear plants. The directorate also criticises British Energy, which operates 13 advanced gas-cooled nuclear reactors including Hinkley.

According to the papers, the company does not know the extent of the damage to the reactor cores, cannot monitor their deterioration and does not fully understand why cracking has occurred. They reveal that in June last year, the NSD said it was faced with "significant regulatory issues ... for all operating AGR reactors".

The NSD's most recent safety assessment of Hinkley, completed in April, warns that its continued operation is likely to increase the risk of an accident. While the NSD says it does not believe that there is any immediate radiation danger to the public, it says there is a possibility of serious faults developing that would force the long term or permanent closure of other nuclear plants of the same design.

"While I do not believe that a large release [of radiation] is a likely scenario, some lesser event ... is, I believe, inevitable at some stage if a vigilant precautionary approach is not adopted. There is an an increased likelihood of increased risk should we agree to continued operation," says the inspector.

The documents show the NSD wants more frequent and more probing inspections of the reactor cores at all Britain's AGR plants. These inspections require the reactors to be shut down for weeks. The premature closing of any nuclear power plant could throw Britain's electricity supplies into chaos. Closure of Hinkley Point would be likely to lead to closure of at least three other nuclear stations built at the same time, which are also known to be suffering from cracks in their cores.

Cracks in the graphite brick cores of ageing reactors have been observed for some time but until now there has been little public knowledge of the extent of the problem. British Energy warned in 2004 that its Hinkley Point B, Hunterston B, Heysham 2 and Torness plants might not be able to be extend their 30-year lives because of cracked bricks, but it gave few details of the extent of the problem.

British Energy is keen to extend the life of its AGR reactors but the papers, obtained by Greenpeace via Stop Hinkley, a local nuclear watchdog group, suggest that unless British Energy improves safety checks, the plants might have to be closed.

The revelations come at a critical point, with the government's energy review expected to be published in the next two weeks and both Tony Blair and Gordon Brown having indicated that a new generation of nuclear power is needed. Yesterday the prime minister told the Commons liaison committee that he had altered his position in favour of nuclear power since the last white paper on energy policy in 2003. "I'll be totally honest with you, I've changed my mind," he said.

However, John Large, an independent nuclear engineer who has advised the government and who reviewed the FoI papers for Greenpeace yesterday said it was "gambling with public safety" to allow Hinkley Point to continue operating. Calling for other AGR stations to be closed, he said: "The reactors should be immediately shut down and remain so until a robust nuclear safety case free of uncertainties has been established".

He accused the NSD of being reluctant to call for the closure of Hinkley Point because of the Mr Blair's stated intention to review nuclear power. "What nuclear installations inspector is going to close a plant down at such a politically critical time?", he asked.

In the papers from June 2005, an inspector concludes of Britain's AGR power stations: "I judge that there is significant uncertainty in the likelihood and consequences for the core safety functionality posed by ... core damage. The assessor needs to assume worst case consequences of ... core damage unless the licensee is able to provide robust arguments."

In a 2004 assessment, the inspector complains about the "lack of clarity" by British Energy, "continued uncertainty" in the prediction of behaviour in reactor cores, and the "lack of progress" made by British Energy in addressing issues in all AGR reactors.

British Energy said yesterday it had provided new evidence to the NSD. "If the health and safety executive [the government body that oversees the NSD] were not confident in the safety of the reactor cores we would not allow the reactors to operate. The assessment report was part of the ongoing regulatory process ... The Nuclear Safety Directorate is monitoring closely British Energy's work on graphite and, where necessary, is influencing the scope and extent of the reactor core inspections that the company carries out.

"British Energy has also been working on methods to monitor the cores whilst the reactors are in service. This will provide added re-assurance on the condition of the cores."

Stephen Tindale , executive director of Greenpeace said: "These documents show the incompetence of the government and British Energy who have known about these cracks yet have refused to do anything about it."

Problem sites

Hinkley Point B, Somerset (switched on 1976)
Known to have core damage

Hartlepool, Cleveland (1983)
Known to have core damage

Hunterston B, Ayrshire (1976)
Known to have core damage

Heysham 1, Lancashire (1983)
Known to have core damage

Dungeness, Kent (1983)
Documents hint that core damage found

Torness, East Lothian (1988)
Documents hint that core damage found


Why cracks at the cores of ageing AGRs worried safety inspector

· Report raises fears over four nuclear power plants
· Independent expert says dangers downplayed


Ian Sample, science correspondent
Wednesday July 5, 2006
The Guardian

No one knows when the cracks first started to appear, but as long ago as 2004, British Energy voiced concerns about fractures in the cores of its 14 reactors.

The cracks were spotted in graphite bricks in the cores of all the company's advanced gas-cooled reactors, or AGRs. Collectively, they provide the country with nearly one fifth of its electricity. But the extent of the potential damage, and the consequences that might flow from it, were uncertain.

However, the latest report by the government's Nuclear Safety Directorate (NSD), obtained via the Freedom of Information Act, makes clear that nuclear inspectors have raised repeated concerns about the dangers of continuing to operate Hinkley Point B nuclear power station in Somerset and other nuclear plants weakened by cracks. British Energy, they say, knows too little about the cracks to be confident they can operate without incident.

According to the NSD report, British Energy does not fully understand why the bricks are cracking; how many are damaged; and the number of cracks that would make the reactor unsafe.

Graphite bricks are used to build the heart of a reactor core. They work by slowing down fast-moving neutrons in the nuclear reaction, making them more likely to split uranium atoms when they slam into the reactor's fuel rods. From the top, a reactor core resembles a giant pepper pot. Thousands of graphite bricks are stacked up to make a cylinder 12 metres high and nearly as wide, with holes running down through it. Hundreds of the holes - fuel channels - are designed to receive fuel rods, which are lowered in when the plant is running. A further 60 or so holes are used to trim the station's power - or in emergencies, shut it down completely - by lowering in control rods that mop up neutrons and halt the nuclear reaction immediately.

The NSD report raises fears that cracks in bricks at Hinkley Point and other nuclear plants at Hunterston B in Ayrshire, Heysham 1 in Lancashire, and Hartlepool in Co Durham could send the precision holes in the reactor out of alignment. That possibility, it says, increases the risks of an accident significantly: fuel rods could become jammed in the reactor, and misalignment could make it hard, if not impossible, to lower in control rods to close the power plant down.

The report, compiled by a nuclear installations inspector for the NSD, states: "Whilst I do not believe that a large release due to failure to shut down on demand is a likely scenario, some lesser event (such as impairment of control rod insertion or fuel movement) is I believe inevitable at some stage if a vigilant precautionary approach is not adopted."

Jammed fuel or control rods could stop cooling gas circulating around the core properly, potentially causing fuel rods to overheat, cladding to melt and a release of radiation into the immediate enclosure surrounding the reactor core. The leak would be contained, but would still lead to the shutdown of the plant.

John Large, an independent nuclear consultant who has reviewed the documents, believes the NSD is downplaying the potential dangers. British Energy has no way of knowing how strong the reactor core at Hinkley Point is, and an otherwise minor accident at the plant might trigger a dangerous and widespread release of radioactivity, he said.

"If the bricks are weakened, and they are, you run the risk of having an accident giving you a reactor that you can't close down, which has a big hole in the side, and that is when you get a major release of radioactivity," said Dr Large. "The NSD is saying they are going to have a gamble here by allowing these to operate, that they're not going to have an accident in the remaining life of these reactors, and you cannot say that."

Dr Large believes the NSD has held off calling for the ageing nuclear plants to be shut down because of Tony Blair's renewed interest in nuclear power in the forthcoming energy review.

"If the NSD called for the closure of Hinkley, they would also have to close Hunterston, Hartlepool and Heysham I, which have cracks and are of a similar age. But what nuclear installations inspector is going to close down a plant at such an incredibly critical time?" he said.

Footnotes

Graphite bricks
Graphite bricks slow down fast-moving neutrons that drive nuclear reactions, boosting efficiency. Radiation ages bricks, but because levels of radiation vary, predicting which bricks are most damaged is difficult.

Advanced gas-cooled reactors
Second generation of British nuclear reactors built in 1970s. Fuelled by enriched uranium oxide pellets and cooled by carbon dioxide, pumped at pressure around reactor core

Nuclear Safety Directorate
Arm of government's Health and Safety Executive. Regulates industry in attempt to prevent major accidents.

Fuel rods
Fuel is added to reactor by lowering fuel "stringers" into holes in core. Fuel is enriched to 2.5% to 3.5% uranium 235.

Control rods
Lowered into holes in reactor to slow nuclear reaction, but can be dropped in rapidly to shut it down. Made of boron alloy, which absorbs neutrons needed to sustain chain reaction.


Bad news at crucial time for nuclear industry

Terry Macalister
Wednesday July 5, 2006
The Guardian

Safety scares at British nuclear sites could not come at a worse time for an industry which believes that the government is poised to give the green light to a new generation of atomic plants.

The energy review - to be published as early as next week - will endorse a new era for an energy sector that was written off by critics as environmentally dirty, obsessively secretive, and financially suspect. But the twin fears of global warming and foreign energy dependency have convinced policymakers that the public is willing to give another chance to an atomic industry that has only just escaped its military heritage. What Tony Blair does not need at this moment are revelations that suggest conflict at the heart of the nuclear industry about the safety of the country's ageing fleet of reactors.

British Nuclear Group looks unlikely to hear this Friday what fine it will pay for failing to run the Thorp reprocessing plant at Sellafield in Cumbria safely. Carlisle court business is said to be so congested that the penalty - and surrounding negative publicity - will not materialise until well into the summer holidays. Nuclear operators will dismiss the latest graphite scare as an old issue that is being well monitored and can ultimately be taken care of easily enough, and will want to talk of the future.

Already, big American and other foreign nuclear contractors such as Bechtel, Fluor and Washington Group International have beefed up their presence in London and started lobbying for work - some through big public relations firms. They are partly here to clean up some of the the waste and mess from the current generation of atomic plants but they are also mindful that there could be rich pickings from a new building programme.

They know, as Mr Blair does, that public opinion remains volatile and, at best, split down the middle over nuclear power. Many of those in favour do not want to hear bad news at this juncture - especially as it comes three months after the publicity given to the anniversary of the Chernobyl disaster and reminders that sheep on Welsh mountainsides are still contaminated 20 years on from that accident.


BNG to be prosecuted over leak at Sellafield

· Nuclear inspectorate to act as spill keeps Thorp closed
· Negligence charges puts plans for sale in question


Paul Brown and Terry Macalister
Thursday April 20, 2006
The Guardian

The British Nuclear Group (BNG) is to be prosecuted for breaches of health and safety regulations at Sellafield in a move that could hit government sell-off plans.

The negligence charges follow an accident that closed the Thermal Oxide Reprocessing Plant (Thorp) a year ago and which is causing huge stockpiles of spent fuel to mount up at the Cumbrian site.

The Health and Safety Executive (HSE) would not comment on BNG, which runs Thorp and the wider Sellafield complex, but well-placed sources said a formal announcement would come within days.

BNG said last night that it was aware that the HSE legal department was considering the situation but the company would not make any predictions. "We understand that no decision has been made to prosecute and that a case will only be brought if the HSE lawyer is satisfied that there is sufficient evidence to provide a realistic prospect of conviction and it passes the public interest test," it said.

BNG also stated its confidence that it would shortly be allowed to bring the plant back into action. "We are planning on restarting the plant in the summer, subject to regulatory consent and NDA [Nuclear Decommissioning Authority] approval," it added.

Despite this optimism, there is still no date for its start-up and a string of 49 demands have apparently been made by the HSE's Nuclear Installations Inspectorate before the facility is allowed to reopen.

Thorp has contracts to reprocess spent fuel from a number of foreign plants plus all reactors run by British Energy. With fuel still arriving from BE power stations and the facility shut, Sellafield has been running out of space to store the fuel. The leak at Thorp, which triggered the prosecution, was formally detected on April 20 last year although the problem had apparently been going on for nine months.

The HSE is understood to have felt compelled to prosecute because the plant's sophisticated gauges and measuring devices had shown for a long time that thousands of litres of dissolved fuel, the most dangerous liquid known, were unaccounted for. This liquid, which contains 20 tonnes of uranium and 160kg of plutonium, has now been recovered from the floor of a giant sealed room of the plant. It is stored in a tank within the plant to await reprocessing when Thorp reopens.

Fractured pipes, through which 80 cubic metres of nuclear fuel dissolved in nitric acid leaked into the interior of the plant, have still not been repaired because they are too highly radioactive and are inaccessible to humans. The NDA estimated the cost of the Thorp shutdown at £50m but has declined requests for documents under the Freedom of Information Act, probably due to the looming prosecution.

Immediate permanent closure of the plant has been ruled out by the NDA and the Department of Trade and Industry because there are still several contracts to reprocess spent fuel from foreign companies, mostly Swiss, German and Swedish.

About 700 tonnes of irradiated fuel belonging to foreign companies lies in cooling ponds at Sellafield and should have been reprocessed many years ago. Opponents of Thorp believe that reopening the plant would be hazardous because, they argue, there can be no guarantee that a similar accident would not happen again.

The company disagrees and has produced a "safety case" that it says justifies a start-up. Martin Forwood, of Cumbrians Opposed to Radioactive Environment, said: "We have taken advice from experienced nuclear engineers and come to the conclusion that there is no way to tell whether the second set of pipes won't also spring a leak. Both lots of pipes have been carrying similar quantities of highly corrosive liquid ... If one lot failed, why should the second lot not do so? Restarting the plant is a gamble with safety."