Chernobyl was a nuclear power plant in Ukraine. Within a 30 km radius of the plant the total population was between 115,000 and 135,000 prior to the accident. On April 25, 1986, during a system test, reactor 4 exploded due to an extreme power increase and inexperienced workers. Intense steam generation then spread throughout the whole core causing an explosion and releasing fission products to the atmosphere. Fission is a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy. This explosion resulted in the death of two workers. The graphite and fuel from the explosion became incandescent, thus sparking various fires leading to the majority of radioactivity released into the environment.
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Between the second to tenth day after the accident, 5000 numerous substances such as boron, dolomite, sand, clay and lead were dropped onto the burning core via helicopter in hopes to put out the fire and limit the release of radioactive particles.
Immediate EffectsDEVASTATION This explosion caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation. Large quantities of radioactive substances were released into the air for about 10 days. The Chernobyl 4 reactor core was released in the accident. Most of the released material was deposited close by as dust and debris, but the lighter material was carried by wind over the Ukraine, Belarus, Russia and to some extent over Scandinavia and Europe. Along with the two workers that died, 28 other people died as a result of acute radiation poisoning.CLEAN UPThe next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted. About 200,000 people ('liquidators') from all over the Soviet Union were involved in the recovery and clean-up during 1986 and 1987. They received high doses of radiation, averaging around 100 millisieverts. Environmental and Health Effects
A study done by UNSCEAR 2000 states that "there is no evidence of a major public health impact attributable to radiation exposure 14 years after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality or in non-malignant disorders that could be related to radiation exposure." Although one would expect it, there is little evidence of any increase in leukaemia, among the clean-up crew. They became at a increased risk of cancer for a long period of time. There have been approximately 500-600 excess cases of thyroid cancer, mostly in children, in the areas most affected by the radioactive fallout. 116,000 people were relocated initially.



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