When we survey the history of the nuclear industry in any part of the world, we see a catalogue of accidents, disasters and near-misses. We see an inherently unsafe technology which, from its inception in the 1940s has been plagued by accidents small and large; some which came to light, others which were covered up. We see that it is by luck rather than judgement that Western world has not suffered the equivalent of Chernobyl or worse.

Secret History

The problem suffered by the nuclear industry surfaced almost as soon as the first reactor became operational and they have continued to plague us. The first ever experimental fast reactor, EBR-1, sited at the US government base at Idaho, began operating in December 1951. Just four years later, it very nearly blew its top because of a runaway chain reaction caused by the fuel creeping and distorting inside the core. The reactor was no more than half a second away from exploding, when a scientist bystander had the presence of mind to press the button that allowed the reactor core to drop away, so bringing the chain reaction to an end. Few people know about this; had another half a second elapsed, the whole world would have done. But it is not an exception; it is typical of nuclear power's safety record right from its earliest years.

The Fermi fast reactor, less than 20 miles outside Detroit, began life in 1963. It suffered innumerable teething problems, including creeping of fuel elements under intense neutron bombardment, sodium corrosion of metallic structures in the core and subsequent problems with the steam-generating plant.

[Image: The Mitensy graveyard, Chernobyl, where victims of the 1986 accident are buried]

Three years later, as the operators were taking the reactor up to full power, a loose metal flange, jammed across some fuel elements and prevented the flow of liquid sodium coolant. The heating caused some fuel elements to bow in towards each other and the power took off. Luckily the accident was limited to just one part of the core, and luckily too the operators managed to prevent a major explosion. If not, Detroit would have been lost.

The notorious fire at Windscale [Now: Sellafield] No. 1 plutonium pile in October 1958, was, at the time, the worst accident to hit the nuclear industry in the West. It resulted from the building-up of pent-up energy, because of the constant bombardment by neutrons. This energy was routinely released by raising the power of the reactor so as to heat up the graphite moderator and then letting the core cool down. But it went wrong, and the graphite overheated to the point where it caught fire, even though bathed with hot carbon dioxide gas. The intense heat caused uranium fuel to catch fire and the two started burning furiously together. Fortunately (though almost as an afterthought) the designer had added a filter to the reactor chimney; without this, the release of volatile fission products such as iodine, caesium and strontium as well as small particles of plutonium would have been far worse. As it was, as much as 20,000 curies of iodine-131 escaped into the atmosphere, which with the remaining radionuclides may have resulted in up to 1,000 premature deaths, according yo the UK National Radiological Protection Board.

Nuclear accidents do not only occur within the reactors themselves. A year before the Windscale accident, the Soviet Union had experienced an explosion in a nuclear waste repository at Kyshtym, which devastated more than 13,000 square kilometres and - like Chernobyl would later do - led to villages being evacuated. It is not known how many deaths resulted from this. Just before the Windscale Inquiry in 1977, scientist Zhores Medvedev, who had carried out radioecological studies on flora and fauna in the Kyshtym area before defecting to the UK, pointed to Kyshtym as exemplifying some of the risks associated with nuclear waste management. The then-head of the UK Atomic Energy Authority, Sir John Hill, publicly derided Medvedev announcing that the Kyshtym disaster was "rubbish - a figment of the imagination... pure science fiction." But radio-isotope analysis later carried out at the US government's Oak Ridge Laboratory, showed that the accident had probably resulted from the failure of a cooling system in a nuclear waste repository.

In addition to reactor explosions and problems with waste dumps, accidental radioactive releases into the atmosphere have been a regular feature of the nuclear age. Indeed, British Nuclear Fuels, through their reprocessing and nuclear waste activities, have released sufficient radioactive waste into the environment to be on a par with all but the worst accidents. Over a 15-year period, from 1961 to 1977, discharges of caesium-137 went up more than 100-fold, to 120,000 curies a year. According to its own admission at the 1977 Windscale Inquiry, between 1950 and 1977 Windscale had suffered 194 reportable incidents, 11 of which involved fires or explosions and 45 of which involved releases of plutonium into the environment. A German study of reactor safety in 1980 showed that during 1976 and 1977 commercial power plants had suffered accidents on average once every three days. In 1976, out of 139 accidents in all, 24 involved the release of "more than permissible amounts of radioactivity".

The Myth of Safety

At Chernobyl, in 1986, the most notorious nuclear accident the world has yet known, the operators were carrying out a test in which they hoped to show that sufficient power could be obtained from the turbines during a sudden shut-down to ensure that essential safety systems would run before back-up diesels kicked in. In other words, it was a safety test that caused the accident. In essence, the explosion at Chernobyl was caused because the operators tried simultaneously to keep the power down and the temperature up, which they did by disengaging the automatic "scram" (safety) system, and by trying to regulate water pressure in the reactor. They got it wrong, and within a few seconds the power soared uncontrollably and they had a slow, but fatal, atomic bomb on their hands.

Ever since Chernobyl, the public in the West has repeatedly been assured that "it couldn't happen here." The nuclear industry has tried hard to distance itself from the Soviet RBMK reactor design (of which the Chernobyl reactor was an example), as if it were flawed in ways that would never be tolerated in the West. In fact, though - and crucially - this is not the case. The RBMK reactor is not very different in concept and design from reactors currently operating across Europe and the USA.

In the UK we have six AGR (advanced gas reactor) stations, each with twin reactors. Like Chernobyl, the AGR uses a graphite moderator, but carbon dioxide instead of water as coolant. The fuel is encased in stainless steel tubes. John Large, adviser to both the government and Greenpeace on nuclear safety matters, baldly stated after Chernobyl that AGR were essentially "benign" reactors, and supposedly immune from a Chernobyl-like explosion.

Yet, as Philip Cade and I demonstrated in a 1987 report for Greenpeace, entitled "Chernobyl UK", AGRs have the potential for accidents just as catastrophic as that of Chernobyl. For example, a sequence of events in which the AGR's gas circulatory system failed, followed by a failure of the reactor to shut down could lead within minutes to a massive explosion, far in excess of that which destroyed Chernobyl. The key to that event would be the melting of the steel cladding from the fuel at a faster rate than the fuel would collapse. Steel is a potent absorber of neutrons to push up the chain reaction to the critical point.

Having created a mathematical model of the AGR, in which he could follow the course of a potential accident, nuclear engineer Richard Webb gave a critical review of our Greenpeace thesis. Whereas the UK Atomic Energy Authority and the Electricity Board had denied that an accident involving gas circulatory failure and failure to shut-down would lead to an explosion, on the grounds that the fuel would first melt into a non-critical state (a nonetheless major admission). Webb showed that the accident could be far worse than envisaged, because vaporising fuel would increase substantially the rate of neutron production and lead to an escalation in the runaway chain reaction. In effect, the reactor's power would increase thousand of times above the maximum operating power in a matter of seconds.

As our Greenpeace report pointed out, one of the criticisms of the Russian-built RBMK reactor was its poor containment by Western standards. Yet, in one of those paradoxical twists, that "failing" allowed the reactor to explode early on and therefore with less impact than were the containment to have held longer. Just imagine if the explosion had been big enough to destroy the other two working reactors then in operation at Chernobyl - the result would have been a virtual holocaust.

AGRs are certainly designed to contain any accidents more effectively than are Soviet reactors. They have a massive 7-metre thick reinforced concrete pressure vessel which, in order for it to be blown apart, a combination of events, in which both the coolant circulators and the scramming of control rods fail simultaneously, would be necessary. While this is highly improbable, the gas circulators in AGRs have failed on several occasions - one being during the storm that caused power to fail at Hinkley Point in Somerset in the winter of 1990.

Just after the Chernobyl accident, when the nuclear industry was congratulating itself that such a disaster would be most unlikely in the West, the US Nuclear Regulatory Commissioner, James Asselstine remarked with regard to commercial reactors in the US:
"The bottom line is that, given the present level of safety being achieved by the operating nuclear power plants in this country, we can expect to see a core meltdown accident within the next 20 years [italics mine]; and it is possible that such an accident could result in off-site releases of radiation which are as large as, or larger than, the releases estimated to have occurred in Chernobyl."

The real bottom line is that nuclear power, wherever it is in the world, whatever safety standards imposed and whatever reassurances its advocates give, is an inherently unsafe technology. Its history so far amply demonstrates this simple fact. The only truly safe option is to shut it down permanently.