By John R. Hallam
At 1.46 on the morning of April 26, 1986, the shift supervisor of the Chernobyl-4 reactor — part of the massive reactor complex close to Kiev, capital of the Ukraine — pressed a button in a routine end to what was supposed to be a routine test of the plant's safety functions.
The button was supposed to shut down the plant safely. Instead, it sent the reactor into an uncontrolled power excursion that exploded it, blowing the 2500-tonne steel and concrete lid off and sending at least one quarter of the reactor's contents 1000 metres into the air and setting off radiation alarms in Sweden, Finland, Germany, the UK and even Japan.
To this day, reindeer meat in Sweden and Finland is too radioactive to eat, as is lamb from parts of Wales and Cumbria.
The Chernobyl disaster killed 31 people more or less immediately, killed 200 clean-up personnel more slowly, and has claimed the lives of at least a further 10,000 soldiers and emergency personnel.
It is now having a catastrophic effect on the health of millions of Ukrainians, Byelorussians and Russians.
According to the Ukrainian Central Information Service, nearly 2 million people still live on contaminated land. Five million hectares of Ukrainian farmland and 1.8 million ha of forest are contaminated. Most of these areas will be unsuitable for habitation or cultivation for the next 100 years, while the more seriously contaminated areas will be unsafe for 1000 years.
Ukrainian doctors and the Ukrainian Green Party report that about 160,000 Ukrainian children under seven years old have received radiation doses high enough to cause thyroid cancer. Since 1986, there has been a 92% increase in all children's cancers, while congenital birth defects, blood and nervous system disorders and thyroid cancers have doubled.
Children in the more heavily contaminated areas suffer from thyroid problems, baldness, anaemia, nosebleeding, headaches and weak eyesight. Birth rates in the Ukraine have fallen by 13%, while the overall death rate has risen by 6.8%.
An October 1991 appeal by the Diocese of Bryansk and Orel of the Moscow Patriarchate reads in part: "The elementary analysis of blood tests is horrifying ... Only 3-5% of our children were found to be healthy. We have no means to cure the remainder or to
nurse them back to health."
Further danger
The "sarcophagus" built to contain the ruins of the reactor is showing signs of imminent collapse. According to a report in Nuclear Engineering International, "Chernobyl's Sarcophagus ... was intended to last a maximum of 30 years. But, a sixth of the way through its designed life, Soviet scientists doubt whether it can hold out much longer. A major release of dust is likely within 5 to 7 years if nothing is done."
The 2500-tonne lid of the reactor, up-ended by the explosion and now supported shakily on its side by ceramic pillars, may fall down, breaking the sarcophagus and releasing hundreds of tonnes of radioactive dust.
The sarcophagus itself is exceedingly leaky, with cracks and fissures covering an area of almost 16,000 square feet. Birds, mice and rats go in and out, and the reactor interior is abuzz with mosquitoes, "which are definitely larger than normal". Rain and snow fall through the roof, and streams of water run through the corridors, carrying disintegrated fuel.
In the lower parts of the reactor, much of the original 180 tonnes of fuel has melted and reset to form a unique "lava".
A French construction company has been hired to build a second sarcophagus. This is supposed to last 100 years. However, there are fears that the weight of a second sarcophagus will force contaminated water out from under the reactor.
While engineers contemplate structures that will have to last at least as long as the pyramids, decontamination work on the Chernobyl site has come to a halt because the Swiss firms doing the work have not been paid.
The Ukrainian government says that it hasn't the resources to tackle the problems at Chernobyl alone, and certainly not to build a new sarcophagus. According to Georgy Gotovchits, Ukraine's minister for civil protection, International Atomic Energy Agency estimates of radiation damage to human health in the Ukraine are gross underestimates, as are estimates of soil contamination. The technical problems of decontamination are "seriously underfunded", and the Ukraine is requesting "concrete and rapid assistance".
Common problems
Chernobyl has focussed a harsh light on the safety problems of
Soviet reactors. There is an increasing consensus that the RBMK reactor has fundamental design problems with its emergency shutdown system, which seems to be able to cause the reactor to explode under conditions of low power.
Concern has focussed to an even greater extent on the Soviet-
style pressurised water reactor known as a VVER. VVER reactors in what was East Germany have been shut down permanently as unable to meet western safety standards. VVER plants in Czechoslovakia are under question. Four VVER plants in Bulgaria are considered by the World Association of Nuclear Plant Operators (WANO) to be a disaster waiting to happen; WANO wants them shut down immediately.
However, Hungary and Finland both have VVER plants, and have notched up the best performances in the world with them, while VVER (and RBMK) safety problems have equivalents in western plants.
A frequent criticism of RBMK (Chernobyl-type) plants is that they do not have a containment structure. But neither do any the UK's ageing Magnox plants and not-so-old AGR plants. The RBMK does have an elaborate system of pressure suppression and confinement cells, which the UK AGRs and Magnox plants do not.
Similarly, early model VVER plants do not have a conventional containment, but do have a "confinement system" reminiscent of that employed by General Electric's BWR plants. Questions raised about the RBMK and VVER containment systems thus apply equally to all UK reactors and one-third of US reactors.
The possibility that the reactor pressure vessel may become brittle and crack during an emergency shutdown has been an issue at German, Bulgarian and Russian VVER plants. But it is equally an issue at many of the older plants in France and the US.
Problems with reactivity control, cited as a major issue with RBMK plants, and exacerbated by the diabolical emergency shutdown system, have also been pointed out in safety studies of Canadian CANDU reactors.
Prior to the Chernobyl disaster, Soviet nuclear proponents used to boast that the 1979 Three Mile Island incident in the US "couldn't happen here". Both the RBMK and the VVER designs were considered by IAEA and western analysts to have unique safety advantages!
The Chernobyl disaster is thus a warning to all nuclear nations of the inherent risks of nuclear technology, whether North
American, French, Japanese, British or Soviet.