The Chernobyl accident

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Introduction
01 Cancer
02 Ozone
03 Urban air
04 Air pollutants
05 Blue-green algae
06 Water mutagens
07 Contamination
08 Chernobyl
09 Radon
10 Medical geology
11 Renal hazards
12 Organohalogens
13 Estrogens
14 Food hazards
15 Mycotoxins
16 Poisoning
17 Genetics
18 Risk

Ordering

(Excerpt from Chapter 8)

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The accident

Early in the morning on 26 April 1986 at 1.24 local time, a very severe accident occurred at the fourth unit of the Chernobyl nuclear power plant in the former Soviet Union. The operators made some serious errors which resulted in a drastic increase of the effect and ended up in two explosions. The buildings were severely damaged and fuel fragments and burning graphite blocks were found outside them. Material from the reactor core, including large amounts of radioactive material and smoke from the fire, were ejected vertically several kilometers into the air. The reactor core was open to the air and in the following days sealing materials were dumped into the core. However, this resulted in increased core temperature and increased release of radioactive material. It was not until May 5 that they managed to cool the reactor with liquid nitrogen and the release of radioactive material could be stopped or at least reduced to a low amount. The unit 4 core contained an inventory of 4x10¹⁹ Bq and it has been estimated that at least 1x10¹⁸ to 2x10¹⁸ Bq was released. During these 10 days, a large part of the inventory of radionuclides of the reactor was spread out not only over a part of the Soviet Union but also over most of the countries in Europe and detectable amounts over nearly all parts of the northern hemisphere. One of the biggest accidents in the world had occurred.

The early phase near the reactor

After the two explosions, large amounts of burning material were spread out around the buildings and fires occurred on several sites. Shortly after the accident, three fire-fighting teams arrived and augmented the teams at the site. The main challenges were to prevent the fire from spreading to unit 3 since the roof of the machine hall shared by units 3 and 4 was burning. The fire-fighters did not have appropriate protective clothing and they received quite high radiation doses, both whole-body irradiation due to the high external dose rate and also high beta contamination that caused severe beta skin burns. Many of them suffered from acute radiation sickness, with vomiting and nausea already during the fire-fighting. Of the on-site personnel, about 300 were hospitalized due to acute radiation syndromes and burns. Of these, 28 died due to acute radiation injuries.

On April 27, the 45,000 inhabitants in Pripiat, the nearest town, were evacuated, followed some days later by all 135,000 people living within a radius of 30 km. Probably none of them will return and live within the 30 km zone. In addition to the people, some tens of thousands of cattle were also evacuated from the 30 km zone.

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Karl J. Johanson has been professor of radioecology at the Agricultural University of Sweden since 1983. As of December 1997 he is retired. Before the accident at Chernobyl, the main scientific direction was radiation biology, mainly studies on damage to the DNA and its repair. Since the Chernobyl accident the principal direction of science has been the radioecology of the forests.