Return to Genesis of Eden?

 

Asking for trouble The Tokaimura nuclear plant was an accident waiting to happen NS 9 oct 1999

IT'S the cardinal rule for any nuclear worker: never, ever bring a critical mass of highly enriched uranium together, or you'll unleash a nuclear chain reaction. In breaking that rule last week, workers at japan's Tokaimura plant triggered the world's worst nuclear accident since Chernobyl Nuclear experts are flabbergasted that the unit did not have built-in safeguards that would have made such errors impossible. They also say that the plant was using a method for processing highly enriched uranium that is inherently risky. New Scientist's inquiries indicate that, apart from japan, only Kazakhstan has in recent years used a similar procedure. The Tokaimura plant lies some 150 kilometres northeast of Tokyo. The accident happened in a building, run by a company called JCO, used for one step in the process of making reactor fuel rods. This involves adding an oxide of uranium, U308, to nitric acid. The solution is then mixed in a sedimentation tank with a solution of ammonium salt to form a precipitate of ammonium diuranate. This is later processed to form uranium dioxide fuel. The UO, and nitric acid were supposed to be mixed in an elongated container-a shape designed to prevent a critical mass of uranium coming together-before being fed into the sedimentation tank in carefully controlled quantities. Automated checks should have ensured that a critical mass couldn't be added in one go. Many details of what happened on 30 September are unclear. But workers appear to have mixed U30, and nitric acid and then poured the solution into the tank using buckets. "The way they did this was incredible," says Jinzaburo Takagi, who until 1998 headed the Citizens' Nuclear Information Centre in Tokyo. After the seventh bucket, the sedimentation tank contained 16 kilograms of uranium, enriched so that 18.8 per cent was the fissile isotope uranium-235. At 10.35 am, it formed a critical mass and started a chain reaction. Workers nearest to the tank would have seen a flash of blue light as the air was ionised by a blast of radiation.

The first chain reaction forced the uranium apart, so it soon fizzled out. But the critical mass later reassembled, starting another chain reaction and releasing more neutrons and gamma radiation. This cycle repeated several times over many hours. The process was facilitated by water, both in the sedimentation tank and in the .16 cooling jacket surrounding it. Water acts as e a "moderator", slowing down neutrons released by decaying uranium-235 nuclei so that they are more likely to trigger another nucleus to decay. The water jacket also reflected neutrons back into the tank. JCO and the Japanese govemment have been widely criticised for their sluggish response (see Diagram). Indeed, it wasn't until 2.30 am on I October that JCO staff initiated a plan to bring the sedimentation tank under control. If they could drain away the water in the cooling jacket, they realised, the reactions should cease. But this proved difficult. In the end, workers rushing into the irradiated building for just minutes at a time had to dismantle the pipes leading from the jacket to drain it.

The accident may have happened because workers weren't used to handling highly enriched uranium. According to JCO, they only began processing the material to make fuel for a fast breeder reactor on 22 September, after a three-year break. But even if the uranium had been less highly enriched, workers shouldn't have been pouring it into the sedimentation tank by hand, and the plant should have been engineered to prevent them doing so. 'What totally baffles me is why the technology allowed these workers to do what they did," says Malcolm Grimston, a nuclear analyst at the Royal Institute of International Affairs in London. Coming after previous lapses (see 'Cat- alogue of errors"), there are widespread fears that japan's nuclear industry lacks a "Safety first" culture. This may extend to its choice of procedure for processing highly enriched uranium. Because of the extra hazards posed by the moderating effects of water, manufacturers such as British Nuclear Fuels now use a "dry" process to prepare highly enriched uranium. It appears that Japan and Kazakhstan are the only countries to persist in processing the material in an aqueous solution. As New Scientist went to press, the two most severely irradiated workers looked certain to lose their lives. The extent of con- tamination inside and around the plant remained unclear. -You cannot eliminate the possibility of more deaths," wams Murdoch Baxter, editor of the Journal of Environmental Radioactivity. But even if nobody else dies, the name Tokaimura will cast a long and frightening shadow for years to come. Peter Hadfield, Tokyo, Rob Edwards, Justin Mullins

Getting critical NS Oct 30 1999

FOCUS Last month's disaster in Japan was the latest in a long chain of nuclear accidents stretching back to the 1940s. Why are we finding it so difficult to stop history repeating itself?

AT 10.50 am on Tuesday, 17 June 1997, Aleksander Zakharov made a fatal mistake. Alone, behind concrete walls three metres thick in an underground bunker at the secretive Arzamas-16 nuclear research centre in Russia, he placed a thin shell of copper on a sphere of highly enriched uranium. Suddenly, a huge burst of radiation turned the air blue as the uranium went critical. Zakharov, an internationally respected expert on nuclear criticality, would have realised immediately what had happened. He left the bunker, closed its hatch, notified a manager and lost consciousness. Three days later, aged 42, he died in a Moscow hospital, his nervous system destroyed by the radiation. Before the accident at the uranium processing plant at Tokaimura in Japan on 30 September this year, Zakharov was the most recent person to die in what the nuclear industry euphemistically calls an "excursion"-an uncontrolled chain reaction that happens when uranium-235 or plutonium-239 atoms split. Scientists know how to use fission to drive nuclear reactors with fuel pellets enclosed in zirconium alloy sheaths. But in fuel-processing plants uch as Tokaimura, where people are handling the materials, the opportunity for disaster is much greater. Two new international studies show that mistakes made in the past three years in Russia and Japan mirror those made decades ago during the Cold War, suggesting that nuclear engineers have learnt nothing over the years. "That is the tragedy," says Enrico Sartori, a criticality analyst from the OECD's Nuclear Energy ;Agency (NEA) near Paris, which @co-ordinates international nuclear policy. "The technology is difficult and each generation has to relearn it."

Chain reaction

The day the Tokaimura accident ended, the French nuclear safety agency, IPSN, coincidentally published an authoritative analysis of the world's accidental criticalities. Including Tokaimura, 17 people have been killed and 104 more irradiated by 60 accidents since 1945. Of these accidents, 33 happened in the US, 19 in Russia, two in Canada and one each in Britain, France, Belgium, Yugoslavia, Argentina and Japan.

Because the history of Soviet criticalities was a secret until now, the IPSN report comes as a big surprise. Accidents happened regularly in the 1950s and 1960s, but although the frequency of incidents decreased as expertise increased, they still kept on happening. There were five in the 1970s, including three in the former Soviet Union-one in the 1980s, two in 1997 (both in Russia) and now one in Japan in 1999. "We didn't expect that," observes Sartori. "We almost expected them to stop." A forthcoming study for the US Department of Energy points out that Zakharov's accident bore remarkable similarities to two events in the US more than half a century earlier. While constructing the experimental critical assembly, Zakharov seems to have miscalculated the critical mass of uranium in the configuration he was using. Copper played the crucial role of reflecting neutrons from splitting uranium-235 atoms back into the uranium sphere to trigger the chain reaction. In a paper to be published in the November issue of Health Physics (vol 77, p 505), George Vargo from the Pacific Northwest National Laboratory in Richland, Washington, compares this accident to two atLos Alamos National Laboratory, New Mexico, during the Manhattan Project to build the atomic bomb. In one accident in 1945, Harry Daghlian was killed after he caused a criticality in a sphere of plutonium by dropping a block of tungsten on top of it. The following year, Louis Slotin suffered the same fate when a screwdriver he was using to stop a beryllium shell from covering a sphere of plutonium slipped. Like the copper at Arzamas-16, the tungsten and the beryllium reflected neutrons back into the plutonium spheres and started the chain reaction. But it is not only neutron reflectors that nuclear engineers have to be wary of. In an analysis of 13 other previously unreported criticality accidents at nuclear plants in Russia, Vargo concludes that nine of them could have been prevented by using containers whose shape made it impossible for fissile uranium or plutonium to form critical masses. Cylinders and pipes, he says, should be long and thin rather than short and fat. Unfortunately, determining critical masses is not that simple. It depends not only on the availability of neutron reflectors and the shape of the fissile material but also on the ratio of its isotopes. According to the NEA, the critical mass of uranium enriched so that 3 per cent of it contains the uranium-235 isotope is 101 kilograms in an aqueous solution. The critical mass of 20 percent enriched uranium in the same solution, however, is just 5-39 kg. The presence of moderators, which slow down escaping neutrons and make them more likely to cause further fissions, is also important. Vargo points out that water was a moderator in 11 of the Russian accidents, and its role as both a moderator and a reflector was key in the Tokaimura accident (New Scientist, 9 October 1999, p 4).

"Any use of water in the processing of fissile material has to be carefully engineered and controlled," he argues. But Vargo's account shows how difficult it is to plan for every eventuality. In one of the seven criticalities at the Mayak nuclear complex in the Urals in 1957, he describes how three workers died after a tank of highly enriched uranium solution they were trying to empty went critical. The reaction started because the workers themselves became "human neutron reflectors". The IPSN study also points out that 20 of the 21 criticalities that have occurred worldwide in nuclear facilities other than reactors involved plutonium or uranium in solution. "You have to be more careful when dealing with solutions because they can change their shape," warns Cassiano De Oliveira, a physicist investigating criticality at Imperial College in London. Many of the accidents were caused, as at Tokaimura, by excessive amounts of solutions being mixed together.

The effects of last month's accident on public health is also a matter for concem. For nearly 11 hours after the criticality, 4.5 millisieverts per hour of radiation washed over the nearest house 100 metres from the fabrication plant. People exposed to this would have received 10 times as much in one day as nuclear power workers might ordinarily expect to receive in one year. Exactly what happened at Tokaimura a month ago is still uncertain.

'Privately, foreign experts are scathing about management standards at the plant'

But Westem experts investigating the accident are now coming to the conclusion that poor management and organisation were as much to blame as occasional safety breaches. London-based independent nuclear consultant John Large is scomful of suggestions that the Tokaimura accident resulted from inexperienced workers slopping buckets around. "The plant is under International Atomic Energy Agency supervision; there were even thought to be IAEA inspectors on site at the time of the accident." He adds: 'Whenever the nuclear industry has an accident or needs to pass the buck they say the people involved were inexperienced. But even if that is the case, surely it's their responsibility to ensure sufficiently experienced staff are doing the job in the first place." Publicly, nuclear operators outside Japan make politely critical remarks about the lack of training and the need for better safety procedures. Privately, however, they are scathing. "Management broke all the rules," says one. "It was criminal." The police are investigating whether such assertions are justified. Regardless of their investigation, it seems inevitable that nuclear safety agencies will have to take on board the lessons from Tokaimura. After the Japanese accident, the Nuclear Inspectorate quizzed the operators of all the British sites that handle fissile material, including Sellafield, the Aldermaston nuclear weapons establishment in Berkshire and the Dounreay nuclear plant in Scotland, to make sure they were safe. Elsewhere around the world, nuclear regulators are making similar checks, all hoping the next nuclear excursion will not be in their back yards. Ag if to underline the problem, Aldermaston this week admitted that "deficiencies in the system" meant that rules to minimise the risk of accidental criticalities had been breached eight times since February. Rob Edwards

Recurring nightmare

Hiroshima's victims are showing the full truth about radiation

A HEAVY dose of radiation may lead to strokes, heart attacks or liver disease. A survey of Japan's atomic bomb survivors suggests that radiation has caused almost as many deaths from these diseases as it has from cancer. Doctors are familiar with acute radiation sickness, and it's clear that radiation can cause cancer by damaging DNA. But most researchers have been sceptical of a link between radiation and other diseases, partly because no one had a convincing explanafion of how radiation could cause them. That scepticism is being challenged by American and Japanese scientists at the Radiation Effects Research Foundation in Hiroshima, who have studied 86 572 survivors of the atomic bombs dropped on Japan in 1945. They conclude that those exposed to a dose of 1 sievert-a thousand rimes the international annual safety limit for the general public-suffered 10 per cent more deaths from cardiovascular and digestive diseases than people who were not exposed to radiation. The researchers investigated whether this apparent link could be explained by diseases being wrongly classified or by differences in smoking habits or diet. "It is very unlikely that any of these could explain the effect," says Donald Pierce, a member of the team.

The study, published in Radiation Research (vol 152, p 374), suggests that radiation from the bombs could have been responsible for between 140 and 280 deaths from strokes, heart disease, chronic liver disease and other noncancerous conditions, compared to over 300 deaths from cancer. There was no significant association between diseases other than cancer and exposure to less than 0-5 sieverts of radiation, however. The most plausible biological mechanism for this is radiation damage to the immune system, Pierce believes. He points out that 1 sievert is enough to kill more than half the stem cells in the bone marrow. This would have a permanent effect on the immune system, leaving people more vulnerable to infections that trigger heart and liver disease. But Alison Gurney of the University of Strathclyde in Glasgow, has another explanation. Radiation damages muscle cells that help keep blood vessels dilated, she says. This could raise blood pressure, triggering strokes and heart attacks. Such damage has been found in animals exposed to radiation after the 1986 Chernobyl disaster. Gu.rney is now looking for these effects in people affected by the accident. 'Chernobyl didn't only cause a rise in the cancer rate, but also a significant increase in the number of cardiovascular diseases," she says. Rob Edwards

Under a cloud NS 6 Nov 99

FOCUS When it comes to arms control, logic can't compete with party politics and paranoia

THE latest attempt to halt the spread of nuclear weapons, the Comprehensive Test Ban Treaty, lies dead on the floor of the US Senate. The CTBT, created back in 1996 to stop nuclear weapons proliferating throughout the world, still needed to be signed by another 18 countries-including the US-before it came into force. The US rejection effectively kills the agreement. Republicans who dominate the Senate claimed the CTBT was dangerous: not only was it impossible to detect rogue states' clandestine tests, it threatened the reliability and safety of America's nuclear arsenal. Dismayed Democrats and international observers dismissed the Senate's move as reckless party politics. Thirty-two American Nobel prizewinning scientists attacked the logic of the decision, claiming that technology no longer required the US to explode weapons in order to test the reliability of its nuclear arsenal. The first nuclear weapon, the "Little Boy" that obliterated Hiroshima, was merely a modified anti-aircraft gun that smashed two chunks of the heavy metal uranium into each other. When the lumps of metal reached a critical mass, the atoms began splitting at an ever-increasing rate: a fission chain reaction. But more sophisticated and powerful bombs require nuclear fusion, the process whereby the nuclei of lighter atoms, such as hydrogen, stick together. It's much harder to achieve than fission, because there's no chain reaction to do all the work. Nevertheless, the US managed it in 1952, when it detonated the first hydrogen bomb. This redirected the radiation from an atomic bomb "primary" onto a flask full of deuterium (heavy hydrogen) to achieve fusion. At about 10 megatons, d-ds was some 750 times more powerful than Little Boy. This hydrogen bomb and its ever more sophisticated descendants have required extensive testing as part of their development. Thus, the CTBT would theoretically have prevented nations like India and Pakistan from developing more powerful and more reliable weapons, and prevented rogue states from starting modern nuclear programmes. However, opponents of the CTBT say that if you want to test a weapon for safety (shooting a bullet into it and ensuring that it doesn't blow up) or reliability (letting it sit in a hangar for 30 years and making sure it will still explode on command), nuclear tests are obviously a boon. But the 32 Nobel laureates noted that there were viable alternatives. Among them is the US Department of Energy's Stockpile Stewardship Program, dedicated to keeping nuclear weapons safe and reliable without the use of nuclear tests. It has two major tools. The first is hydrodynamic testing, in which engineers check the plutonium part of the warhead. In the second, confinement fusion testing, engineers check the hydrogen component of the weapon. The Stockpile Stewardship Program can't test a bomb from the explosion of its first stage to the ignition of its second stage. But it can verify that a bomb with a wellunderstood design is working because all its individual components are in good order. "We understand the weapons very well," says engineer Frank Von Hippel, of Princeton University's Program on Nuclear Policy Alternatives. This is why he says that non-nuclear testing is sufficient to ensure that a weapon will perform as advertised. "I think that the Stockpile Stewardship Program is even more than we need for reliability." Jon Wolfsthal, of the Carnegie Endowment for International Peace in Washington DC, agrees. "The hawkish view is that our weapons will not remain reliable and safe, but they misunderstand that stockpile stewardship is actually working today." International observers are also unconvinced by the argument for testing. Philip Towle, director of the Centre of International Studies at Cambridge University, says: "They've had a very long time to test the reliability of trigger systems, and there are some states like Israel that are at much greater risk from nuclear attack who have not needed to carry on testing."

Another objection by the opponents of the CTBT is the plan's supposed inability to identify violators. "Well, this is kind of a distortion of the evidence," says Jeffrey Parlc, a geophysicist at Yale University. "We do monitor, currently, known test sites at fairly low magnitudes-2-5 or 2 on the Richter scale-and a 1-kiloton nuclear blast is roughly equivalent to a magnitude 4 earthquake. We've got a good capability now." The CTBT would have provided for an improved network of seismic sensors to plug holes in existing coverage. "The idea is not to give a potential tester any wiggle room," says Park. It is possible that by hollowing out a large cavity, a state trying to evade the treaty might be able to set off a small nuclear blast-less than one kiloton-without being detected. But anyone testing a hydrogen bomb or a boosted weapon would need a yield much greater than that to collect the required data. "We thought you'd be able to detect tests down to about 1 kiloton," says Von Hippel. "Below that, there isn't much interesting you can do." So if the stockpile is safe and geophysicists can detect significant tests, why was the CTBT kicked out by the Senate? Most believe the explanation is largely political, not scientific. The President is a Democrat and the Senate majority is Republican. "Half of the Republicans, really, are very sceptical of arms control," says Von Hippel. "All of them hate Clinton." US commentators note that, during the debate on CTBT ratification, Jesse Helms, the far-right chairman of the Senate's Foreign Relations Committee, thought it relevant to include references to the Monica Lewinsky affair. But what effect will the death of the CTBT have on intemational security? According to Towle: "The Senate vote certainly makes it easier for the Indians to resume testing if they want. But whether it would tip the balance with a state that is considering the nuclear arena, such as Iran, is less likely." The coup last month in Pakistan-India's bitter regional enemy and itself an emerging nuclear power-has fuelled concem over the CrBT's demise. The new regime in Islamabad, already under intemational pressure for introducing martial rule, is unlikely to start rattling nuclear sabres-at the moment. Others are more philosophical. L. K. Sharma, London correspondent of The Times of India and an authority on Indian defence and foreign policy, says: "Developing nations do not need encouragement by the US to develop nuclear weapons. If they have the means and desire they'll do it anyway." But according to Maleeha Lodhi, Pakistan's ambassador to the US from 1994 to 1997: "It's conceivable that before the year was out India and Pakistan would have been signed up."

India has declared a moratorium on nuclear tests. But some Western observers believe that India cannot credibly deliver even small nuclear weapons at the moment. And Pakistan is behind India. Ifs distinctly possible that both states (with India taking the lead) may seek to refine their weapons. If Lodhi's hunch is right, the Senate's action represents a lost opportunity. But looking beyond domestic politics and the paranoia over warhead reliability, some observers detect more calculated thinking on the floor of the US Senate. There are commercial interests in weapons investment. And John Simpson, director of the Mountbatten Centre for International Studies in Southampton, notes that the ascendant "unilateralist movement" in US politics is talking up the issue of missile defence systems again. The Anti-Ballistic Missile Treaty looks vulnerable. He suspects some right-wingers are looking forward ten years to a time when the US may be in the position to test new devices powered by nuclear explosion. Indeed, senator John Warner, who chairs the Armed Services Committee, says: "Many of the nuclear systems that we developed to deter the Soviet Union are simply not suited to the subtle, and perhaps more difficult, task of deterring rogue states from nuclear, chemical or biological weapons ... Such weapons do not exist today in the US arsenal." Helms's success in having the Arms Control and Disamiament Agency (effectively a watchdog to stop the Pentagon jeopardising intemational arms control agreements) abolished last year fuels such speculation. If we're about to witness a new push on the part of the world's only superpower to subvert science for dubious political ends, it won't be the first time. In the meantime, according to observers like William Walker of St Andrew's University: "It looks like arms control is falling apart." Charles Seife, Washington DC, and Michael Day

UN Criticizes Nuclear Stonewalling Feb 20 2000
NEW YORK - A dangerous new arms race is looming and the- nuclear powers are to blame, particularly the United States, says UN Secretary-General Kofi Annan. As the United Nations prepares for a conference in three months reviewing the 1968 nuclear non-proliferation treaty, Annan said: 'It is hard to approach it with much optimism, given the discouraging list of nuclear disarmament measures in suspense, negotiations not initiated and opportunities not taken. 'A dangerous new arms race looms on the horizon," he told the Advisory Board on Disarmament Matters, a UN think tank of 20 weapons experts. Annan said the 1993 Start 2 treaty between the United States and Russia had not taken effect and Start 3 talks had not begun. "The Comprehensive Test Ban Treaty [CTBT] has been rejected by the Senate of the United States, which had been its leading champion," he said, adding that nuclear weapons were still on high alert in several countries. The Senate - against the wishes of President Bill Clinton - last year refused to ratify the CTBT, a global pact that bans nuclear tests but has not received the required back- ing to take effect. Again alluding to the US, Annan said: "Deployment of ballistic missile defences seems increasingly likely, posing a serious threat to the Anti-Ballistic Missile [ABM] Treaty and the strategic stability it embodies." The United States is proposing modifications to the 1972 ABM Treaty, which sharply limits anti-missile defences, so that it can build a system capable of countering missiles launched by "rogue states" - though not a mass attack by a big nuclear power. Russia and China strongly oppose any modification of the ABM neaty, signed by the US and the former Soviet Union. The treaty is based on the theory that an anti-missile shield would only tempt the other side to build more missiles in hopes of being able to pen6trate the defences. Moscow and Bejing say any tampering with the ABM neaty would undermine the global strategic balance. REUTERS

Pie in the sky A ballistic missile defence system is still just a dream

NS 10 Apr 99

JUST before dawn on 29 March, the world's most advanced missile flared into life, illuminating the New Mexican desert. It streaked towards its target at thousands of kilometres an hour ... and missed, exploding 10 seconds later. This is the sixth time in a row that the US military's Theater High-Altitude Area Defense (THAAD) system has failed to intercept a ballistic missile-the job it was designed for. And the timing could hardly be more embarrassing: Congress is pressing for a major increase in spending on anti-ballistic missile technology. So far THAAD has run up a bill of $4 billion. Its backers are putting a brave face on the latest flop. "While we're not where we want to be, I am encouraged," Lieutenant General Paul Kern of the US Army's Acquisition Corps told reporters at a Pentagon briefing last week. He points out that the missile came within 10 to 30 metres of its target. But other observers are less sanguine. "Oh my God, these guys can't hit the broad side of a barn," says Joseph Cirincione, director of the Carnegie Non-Proliferation Project in Washington DC. "They're serving up clay pigeons to this thing to pop out of the sky, and it still can't hit." Indeed, THAAD's target in the latest test was virtually a sitting duck. The missile it was meant to hit had been designed to mimic incoming Scuds, which are large and relatively slow. THAAD is supposed to destroy small, fast warheads., Congressional backers of anti-ballistic missile technology are blaming the company that built the system, Lockheed Martin of Bethesda, Maryland. "Most of the failures, if you look at them, are due to contractor quality control," says Pete Peterson, a spokesman for Congressman Curt Weldon of Pennsylvania. But Jeffery Adams, a spokesman for Lockheed Martin, disputes this claim. "We entirely disagree with that," he says. "Quality takes precedence over anything else, including cost and schedule." If, as some experts suggest, shooting down ballistic missiles is really beyond the capacity of even the best available technology, the US government may be poised to throw good money after bad. Congress has just passed a bill that requires the US to deploy a national ballistic missile defence system (This Week, 27 March, p 27). The $6.6 billion project would use a "kill vehicle" based on the same broad principles as THAAD. There are also other projects in the pipeline, such as an airborne laser and a sea-based defence system. While a less ambitious project-a modified Patriot missile-did score a direct hit on a Scud-like target last week, sceptics believe that building an effective national missile defence system is still way beyond reach. "At the rate we've been going in the past fifteen years, it seems that it will not be technologically feasible in the lifetime of anyone now living," says John Pike of the Federation of American Scientists in Washington DC. Charles Seife, Washington DC

Lethal legacy The nuclear-dad-is-bad theory may have been right after all

NS 29 May 99

A NEW British study suggests the children of men exposed to radiation while working at nuclear plants are twice as likely to develop leukaemia. Researchers from the University of Leeds and the London School of Hygiene and Tropical Medicine looked at the health of 39 557 children born to 18 131 male workers at 15 nuclear sites, including Sellafield in Cumbria, Dounreay in Caithness and Aldermaston in Berkshire. Funded by the British government's Department of Health and the Health and Safety Executive, the study is the most comprehensive survey of nuclear workers and their families ever undertaken. The study is an attempt to confirm or reject the work of the late Martin Gardner, an epidemiologist from the University of Southampton. In 1990, he suggested that the high rate of leukaemias suffered by children around Sellafield was linked with the radiation to which their fathers had been exposed at the plant. Gardner's theory was rejected, however, by the authors of the last major study carried out by the National Radiological Protection Board and others (This Week, 15 November 1997, p 5). Now researchers led by Eve Roman, an epidemiologist with the Leukaemia Research Fund at the University of Leeds, have concluded that Gardner's theory "could not be disproved" on the basis of their findings. In this week's British Medical journal, the team reports that the risk of leukaemia among the children of fathers exposed to radiafion before conception was twice that of children whose fathers were not exposed to radiation. The leukaemia rate in children whose fathers accumulated the highest doses of radiation before conception (more than 100 millisieverts) was nearly six times greater. The researchers point out, however, that the total number of leukaemia cases is still very low. They also confirm that the overall rate of all types of cancer amongst the children is not significantly different from that of the general population. The team presented their results to workers at Sellafield last week, but the findings have clearly riled British Nuclear Fuels (BNFL), the government-owned company that runs the site. "We find the study scientifically to be deeply and probably irretrievably flawed," says Andy Slovak, BNFL's chief medical officer. He suggests that future analyses of the survey results, which will look at infertility, miscarriages and other aspects of child health, could also be thrown into doubt. The researchers strongly reject BNFus accusations, however, arguing that the company has failed to understand what they were doing. "It is one of the biggest and most definitive studies," says Martin Bobrow, a medical geneticist at Cambridge University and part of the study's steering group. "And it is well designed." Janine Allis-Smith, from Sellafield's local anti-nuclear group, Cumbrians Opposed to a Radioactive Environment, welcomes the findings. "I am pleased for all of us who have always believed that Martin Gardner was right," she says. Rob Edwards

Israel's Nuclear Capability Revealed Feb 2000

JERUSALEM The first public parliamentary debate of Israel's topsecret nuclear weapons arsenal degenerated into an ugly confrontation when an Arab legislator said Israel had up to 300 nuclear warheads, prompting Jewish lawmakers to call him a spokesman for terrorists. Military censorship has always forbidden reports in the local media about the nuclear arsenal. But Mahoul's speech, broadcast live yesterday on television, gave Israelis their first opportunity to hear details from one of their own. Most of the Jewish lawmakers marched out of the Knesset (parliament) in protest. A visibly uncomfortable cabinet minister, Haim Ramon, responded by repeating Israel's well-known, yet vague nuclear policy statement and denying Mahoul's premise that the public has the right to know. Ramon said Israel would not be the first to introduce nuclear weapons into the Middle East, a decades-old policy known hqre as "ambiguity," implying that Israel has nuclear arms capability but not bombs. Two diplomats from the Egyptian Embassy in Tel Aviv watched the debate from the gallery. Egypt has been pressing for Israel to sign the nuclear non-proliferation treaty And get rid of the weapons it has never admitted having. Jewish members interrupted Mahoul's speech with catcalls as he declared: "All the world knows that Israel is a vast warehouse of atomic, biological and chemical weapons that serves as the anchor for the Middle East arms race." Some lawmakers called him a spokesman for Arab terrorists. "You are committing a crime against Israeli Arabs today," shouted Ofer Pines-Paz, an Arab and chairman of Prime Minister Ehud Barak's coalition in parliament. Undeterred, Mahoul went on to claim that Israel's three new German-built submarines "will be fitted with nuclear weapons" to provide the capacity to retaliate if Israel was hit with a nuclear attack. Mahoul said the policy undermined Government claims that its nuclear threat was a deterrent to attack. He warned that the nuclear stockpile was a hazard, turning "this little piece of territory into a nuclear garbage bin, poisoned and poisoning, that could send us all up in a mushroom cloud." Mahoul said Israel's vague policy statement had lost all credibility, pointing to disclosures by Mordechai Vanunu, who worked at a desert nuclear reactor before revealing weapons secrets to the Sunday Times in 1986. He was sentenced to 18 years prison for treason. A dozen Israeli anti-nuclear weapons activists, invited Mahoul's Hadash party, sat in gallery. One of them, Gideon Spiro said the Government's ambiguity policy was wearing thin. The debate was raucous bitter even by the standards Israel's unruly parliament created a rare public split on ethnic lines, with Jews from all political backgrounds opposing the Arab members, though party often sides with the members and counts on them political support. Arab lawmaker Ahmed said the Jews considered themselves Israeli patriots, but they see us traitors." Arabs make up about 16 per of Israel's citizens.