Worst-case scenario sheer quantity of radioactivity that might be released

B215 is just one of the many unprepossessing structures that make up the vast nuclear reprocessing complex at Sellafield in Cumbria. Inside, however, are 21 concrete and steel tanks containing more than 1500 cubic metres of high-level radioactive liquid waste.

Reprocessing involves dissolving old fuel rods in acid and extracting the plutonium. The leftover liquid, which contains a mixture of wastes including caesium-137, is stored in the tanks in B215. It is so radioactive that the tanks have to be constantly cooled to prevent their contents from boiling and leaking out.

No one can be sure what would happen if a hijacked airliner plunged into B215. But the impact would almost certainly break open some of the tanks. The accompanying explosion would fling a plume of radioactivity into the atmosphere, according to Gordon Thompson, executive director of the Institute for Resource and Security Studies in Cambridge, Massachusetts.

Afterwards, the burning fuel would continue to pump radioactivity into the air. Putting this fire out wouldn't be easy. Fire crews struggled to dampen down the fire after the Pentagon crash on 11 September—and they didn't have deadly radiation to contend with.

One problem was that they didn't have the foam needed to quash jet fuel fires. Does Sellafield? British Nuclear Fuels (BNFL), the state-owned company that operates the reprocessing plant, won't say.  The explosion and the fire would just be the beginning. A crash of such magnitude would probably destroy the cooling systems too. Tanks that survived the initial impact would heat up and start to spew out more radioactivity within hours.

After the Chernobyl disaster in Ukraine in 1986, an exclusion zone of 4800 square kilometres had to be set up around the plant, more than a quarter of a million people were resettled and radiation spread so far that sheep in Wales still have to be tested to check they're safe to eat. So far 11,000 cases of thyroid cancer have been reported in the Ukraine and Belarus.

According to Thompson, who has been investigating the high-level waste tanks for local authorities in Britain for the past five years, as much as half of the 2400 kilograms of caesium-137 in the tanks at B215 could escape into the air. That would be 44 times more caesium-137 than was released by the Chernobyl disaster. Four million terabecquerels of radioactivity would contaminate large parts of Britain and, depending on which way the wind was blowing, Ireland, continental Europe and beyond. Some places could become uninhabitable.

Britain, of course, is much more densely populated than the Ukraine. Immediately after the attack there would be widespread chaos as authorities tried to organise mass evacuations. In years to come, the death toll might be terrible. Thompson calculates that the radiation released by such a disaster could cause more than 2 million cancers in the following 50 years—assuming that the pattern of public exposure was similar to that after Chernobyl.

Neither BNFL, nor the Nuclear Installations Inspectorate (NII) that regulates it, nor the Office for Civil Nuclear Security, the little-known government agency meant to protect nuclear facilities, would directly answer any of New Scientist's questions about what was being done to address this threat. Instead, BNFL released a statement intended to reassure:

"Major nuclear facilities, including for example reactors and highly active waste stores, are constructed to extremely robust engineering standards and incorporate large quantities of reinforced concrete as an integral part of the construction," says the company. "These facilities are resistant to many terrorist threats including aircraft impact. Safety cases and contingency plans take these events into account."

But the 21 high-level waste tanks in B215 have certainly not been constructed to withstand crashing planes. "There has been no specific design provision to protect against crashing aircraft," states a safety report on Sellafield published in February 2000 by the NII. Both Sellafield Ltd. and NII thought that the risk of a plane hitting the tanks was too remote to be worth considering.

It is also highly unlikely that other ageing buildings containing large amounts of radioactivity at Sellafield are strong enough to resist a falling airliner. John Large, an independent nuclear engineer, has identified seven potential terrorist targets at Sellafield, including the high-level waste tanks and a store containing over 70 tonnes of plutonium. All their radioactive inventories are published, and detailed aerial photographs showing their precise locations are easy to get hold of.

"It would be very easy for a terrorist group," he claims. Aviation sources point out that every year thousands of large passenger jets fly along the English coast near Sellafield, on their way from European airports to the West Coast of the US. Lockerbie, where Pan Am Flight 103 crashed in 1988, is only about 75 kilometres away.

One of the disturbing things about Sellafield is that it's not even supposed to be storing so much high-level waste in such a dangerous form.  Sellafield Ltd. is meant to solidify the liquid waste into blocks of glass to make it safer, but technical problems are holding up the process.

Anxious about the build-up of "highly active liquors" in B215, the NII demanded that Sellafield Ltd. reduce the volume in the tanks or shut down reprocessing at the plant.  An attack on Sellafield is perhaps the worst-case scenario because of the sheer quantity of radioactivity that might be released. But it's not the only target. There are similar storage facilities in several countries, including the US and Russia. A recent study by the World Information Service on Energy (WISE) in Paris highlighted the vulnerability of the French reprocessing plant at La Hague on the Normandy coast.

The site includes a 55-tonne plutonium store, 7484 tonnes of nuclear fuels in five cooling ponds and more than 11,650 cubic metres of radioactive sludge. The WISE study suggests that a large airliner crashing on one of the La Hague cooling ponds could release 60 times as much caesium-137 as Chernobyl—although this isn't directly comparable to the Sellafield estimate because it's based on the assumption that all, rather than half, the caesium would be released.

Nor are storage facilities the only vulnerable sites. Since the attacks on 11 September, British officials will say only that security at nuclear installations is now under review. But other countries have admitted that few nuclear reactors could cope with large aircraft crashes.

It's true that the containment vessels of some plants built since the 1970s were designed to withstand impacts from small planes like Cessnas, which weigh up to 6 tonnes. But none was meant to resist hits from modern airliners. The WISE study points out that the kinetic energy of a crashing 560-tonne Airbus 380 is 2557 times greater than that of a Cessna 210.

The US, France, Germany, Belgium, the Netherlands, Sweden, Switzerland and Australia have all admitted that hundreds of nuclear facilities are vulnerable. And their statements have been backed up by officials from the International Atomic Energy Agency, the United Nations body in Vienna responsible for nuclear power. Large offers one crumb of comfort by suggesting that advanced gas-cooled reactors (AGRs) might survive an aircraft crash because of the strength of their 1-metre-thick reinforced concrete containment vessels. British Energy, a company based in East Kilbride that operates Britain's seven AGR stations, agrees. It points out that in a joint US and Japanese crash test in 1989, the engines of an F4 Phantom jet flying at 800 kilometres an hour only penetrated six centimetres into a concrete wall 3.7 metres thick.

An F4 Phantom, however, weighs only 28 tonnes. Researchers at the Nuclear Control Institute, a lobby group based in Washington DC, estimate that the engines of a 179-tonne Boeing 767 travelling at 850 kilometres an hour could penetrate at least a metre of reinforced concrete.

Perhaps the clearest statement came on 21 September from the US Nuclear Regulatory Commission, which is responsible for 103 reactors. "The NRC did not specifically contemplate attacks by aircraft such as Boeing 757s or 767s, and nuclear power plants were not designed to withstand such crashes," it said. What should be done in the face of such a threat? Measures are already being taken to prevent planes being hijacked (New Scientist, 22 September, p 10), and to ensure that any planes that do get hijacked are shot down before they reach their targets.

Officials at the International Atomic Energy Agency have even suggested that anti-aircraft batteries should be installed around sensitive sites, ready to shoot down planes before they crash. But this has obvious drawbacks. Siting guns near nuclear plants would create new safety hazards. What if they shot down an innocent aircraft? And experts doubt that they would have much chance of hitting a jet dropping from the sky. "It would be like trying to shoot down a bomb," says Frank Barnaby of the Oxford Research Group, an independent group of scientists studying nuclear issues.

The terrible consequences of failing to prevent an attack put a new question mark over the future of the nuclear industry. Before 11 September, President Bush was talking of building more nuclear reactors. And it's thought that Britain's energy review will also recommend building more plants.
If these countries go ahead, they should perhaps follow the example of the former Soviet Union. Some of its earliest plutonium production reactors at Zheleznogorsk (formerly Krasnoyarsk 26) in Siberia were built more than 250 metres underground. "They may now be the safest reactors in the world as far as aircraft attacks are concerned," says Shaun Burnie from Greenpeace International.
Anti-nuclear groups, of course, argue that the best way to protect people against the risk of nuclear terrorism is to dismantle nuclear facilities and convert radioactive wastes into more stable, safer forms. Yet even if the political will were there, decommissioning the 438 nuclear power reactors generating electricity worldwide would take decades.

Kommentarer

Populære innlegg fra denne bloggen

Møter miljøvernministeren