The Chernobyl disaster occurred at 01:23 a.m. on April 26, 1986 at the Chernobyl nuclear power plant in Pripyat, Ukraine. It is regarded as the worst accident in the history of nuclear power. Because there was no containment building, a plume of radioactive fallout drifted over parts of the western Soviet Union, Eastern and Western Europe, Scandinavia, the British Isles, and eastern North America. Large areas of Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of over 336,000 people. About 60% of the radioactive fallout landed in Belarus, according to official post-Soviet data . According to the 2006 TORCH report, half of the radioactive fallout landed outside the three Soviet republics  . The disaster released as much as 300 times more radioactive fallout than the atomic bomb of Hiroshima.
The accident raised concerns about the safety of the Soviet nuclear power industry, slowing its expansion for a number of years, while forcing the Soviet government to become less secretive. The now-independent countries of Russia, Ukraine, and Belarus have been burdened with continuing and substantial decontamination and health care costs of the Chernobyl accident. It is difficult to tally accurately the number of deaths caused by the events at Chernobyl, as Soviet-era cover-up made it difficult to track down victims. Lists were incomplete, and Soviet authorities later forbade doctors to cite "radiation" on death certificates. Most of the expected long-term fatalities, especially those from cancer, have not yet actually occurred, and will be difficult to attribute specifically to the accident. Estimates and figures vary widely. A 2005 report prepared by the Chernobyl Forum, led by the International Atomic Energy Agency (IAEA) and World Health Organization (WHO), attributed 56 direct deaths (47 accident workers, and nine children with thyroid cancer), and estimated that as many as 9000 people, among the approximately 6.6 million most highly exposed, may die from some form of cancer (one of the induced diseases).  For its part, Greenpeace estimates a total death toll of 93,000 but cites in their report The most recently published figures indicate that in Belarus, Russia and the Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004.. .
Immediate crisis management after the Chernobyl disaster
The scale of the tragedy was exacerbated by both the unpreparedness of local administrators and the lack of proper equipment. All but two dosimeters present in the reactor 4 building had limits of 1 millirrntgen per second. The remaining two had limits of 1000 RRs-1; access to one of them was blocked by the explosion, and the other one broke when turned on. Thus the reactor crew could ascertain only that the radiation levels in much of the reactor building were above 4 RRh-1 (true levels were up to 20,000 RRh-1 in some areas; lethal dose is around 500 R over 5 hours).
This allowed the chief of reactor crew, Alexander Akimov, to assume that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 4:30 a.m. were dismissed under the assumption that the new dosimeter must have been defective. Akimov stayed with his crew in the reactor building until morning, trying to pump water into the reactor. None of them wore any protective gear. Most of them, including Akimov himself, died from radiation exposure in the three weeks following the accident.
Shortly after the accident, firefighters arrived to try to extinguish the fires. The first one to the scene was a Chernobyl Power Station firefighter brigade under the command of Lieutenant Vladimir Pravik, who died on May 9, 1986. They were not told how dangerously radioactive the smoke and the debris were. The fire was extinguished by 5 a.m., but many firefighters received high doses of radiation.
The explosion and fire threw into the air not just the particles of the nuclear fuel but also far more dangerous radioactive elements like caesium-137, iodine-135, strontium-90 and other radionuclides. The residents of the surrounding area observed the radioactive cloud on the night of the explosion. The cloud was noticeably glowing.
The government committee, led by Valeri Legasov, formed to investigate the accident arrived at Chernobyl in the evening of April 26. By that time two people were dead and 52 were hospitalized. During the night of April 26>April 27>more than 24 hours after the explosionnthe committee, faced with ample evidence of extremely high levels of radiation and a number of cases of radiation exposure, had to acknowledge the destruction of the reactor and order the evacuation of the nearby city of Pripyat. In order to reduce baggage, the residents were told that the evacuation would be temporary, lasting approximately three days. As a result, Pripyat still contains personal belongings that can never be moved due to radiation. From eyewitness accounts of the firefighters involved before they died (as reported on the BBC television series Witness), one described his experience of the radiation as "tasting like metal", and feeling a sensation similar to that of pins and needles all over his face.
The water that had hurriedly been pumped into the reactor building in a futile attempt to extinguish the fire had run down underneath the reactor floor to the space underneath. The problem presented by this was that the smouldering fuel and other material on the reactor floor was starting to burn its way through this floor, and was being made worse by materials being dropped from helicopters, which simply acted as a furnace to increase the temperatures further. If this material came into contact with the water, it would have generated a thermal explosion which would have arguably been worse than the initial reactor explosion itself, and would have, by many estimates, rendered land in a radius of hundreds of miles from the plant uninhabitable for at least 100 years.
In order to prevent this, soldiers and workers (called "liquidators") were sent in as cleanup staff by the Soviet government. Two of these were sent in wet suits to open the sluice gates to vent the radioactive water, and thus prevent a thermal explosion. These men, just like the other liquidators and firefighters that helped with the cleanup, were not told of the danger they faced.
The worst of the radioactive debris was collected inside what was left of the reactor. The reactor itself was covered with bags with sand, lead and boric acid thrown off helicopters (some 5,000 tons during the week following the accident). By December 1986 a large concrete sarcophagus had been erected, to seal off the reactor and its contents.. Many of the vehicles used by the "liquidators" remain scattered around the Chernobyl area to this day.. The "liquidators" received high doses of radiation. According to Soviet estimates, between 300,000 and 600,000 liquidators were involved in the cleanup of the 30-km evacuation zone around the reactor, but many of them entered the zone two years after the accident.
Right after the accident, the main health concern involved radioactive iodine, with a half-life of eight days. Today, there is concern about contamination of the soil with strontium-90 and caesium-137, which have half-lives of about 30 years. The highest levels of caesium-137 are found in the surface layers of the soil where they are absorbed by plants, insects and mushrooms, entering the local food supply.
Some persons in the contaminated areas were exposed to large thyroid doses of up to 50 grays (Gy) because of an intake of radioactive iodine-131, a relatively short-lived isotope with a half-life of eight days, from contaminated milk produced locally. Several studies have found that the incidence of thyroid cancer in Belarus, Ukraine and Russia has risen sharply. So far, no increase in leukemia in the general population is discernible. Some scientists fear that radioactivity will affect the local population for the next several generations.
Soviet authorities started evacuating people from the area around the Chernobyl reactor 36 hours after the accident.  By May 1986, about a month later, all those living within a 30-kilometre (18 mile) radius of the planttabout 116,000 peopleehad been relocated. This region is often referred to as the Zone of alienation. However, radiation affected the area in a much wider scale than this 30 km radius.
The issue of long-term effects of Chernobyl disaster on civilians is controversial. Over 300,000 people were resettled because of the accident; millions lived and continue to live in the contaminated area. On the other hand, most of those affected received relatively low doses of radiation; there is little evidence of increased mortality, cancers or birth defects among them; and when such evidence is present, existence of a causal link to radioactive contamination is uncertain.
Aside from obstacles posed by Soviet policies during and after the catastrophe, scientific studies may still be limited by a lack of democratic transparency. In Belarus, Yuri Bandazhevsky, a scientist who questioned the official estimates of Chernobyl's consequences and the relevance of the official maximum limit of 1000 Bq/kg, has allegedly been a victim of political repression. He was imprisoned from 2001 to 2005 on a bribery conviction, after his 1999 publication of reports critical of the official research being conducted into the Chernobyl incident.
n April 1986 several European countries, excluding France, had enforced food restrictions, most notably on mushrooms and milk. Twenty years after the catastrophe, restriction orders remain in place in the production, transportation and consumption of food contaminated by Chernobyl fallout, in particular caesium-137, in order to prevent them from entering the human food chain. In parts of Sweden and Finland, restrictions are in place on stock animals, including reindeer, in natural and near-natural environments. "In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland, wild game, including boar and deer, wild mushrooms, berries and carnivore fish from lakes reach levels of several thousand Bq per kg of caesium-137", while "in Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The average level is 6800 Bq/kg, more than ten times the EU limit of 600 Bq/kg", according to the TORCH 2006 report. The European Commission has stated that "The restrictions on certain foodstuffs from certain Member States must therefore continue to be maintained for many years to come". 
In the United Kingdom, under powers in the 1985 Food and Environment Protection Act (FEPA), Emergency Orders have been used since 1986 to impose restrictions on the movement and sale of sheep exceeding the limit of 1000 Bq/kg. This safety limit was introduced in the UK in 1986 based on advice from the European Commission's Article 31 group of experts. However, the area covered by these restrictions has decreased by 95% since 1986: while it covered at first almost 9000 farms and over 4 million sheep, as of 2006 it covers 374 farms covering 750 km 2 and 200 000 sheep. Only limited areas of Cumbria, South Western Scotland and Northern Wales are still covered by restrictions. . In Norway, the Sami people were affected by contaminated food. Their reindeer had been contaminated by eating lichens, which extract radioactive particles from the atmsophere along with their nutrients.
After the disaster, four square kilometres of pine forest in the immediate vicinity of the reactor went ginger brown and died, earning the name of the Red Forest, according to the BBC. Some animals in the worst-hit areas also died or stopped reproducing. Mice embryos simply dissolved, while horses left on an island 6 km from the power plant died when their thyroid glands disintegrated. Cattle on the same island were stunted due to thyroid damage, but the next generation were found to be surprisingly normal. In the years since the disaster, the exclusion zone abandoned by humans has become a haven for wildlife, with nature reserves declared (Belarus) or proposed (Ukraine) for the area. 
According to an April 2006 report by the German affiliate of the International Physicians for Prevention of Nuclear Warfare (IPPNW), entitled "Health Effects of Chernobyl", more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected. The report projected tens of thousands dead among the liquidators. In Europe, it alleges that 10,000 deformities have been observed in newborns because of Chernobyl's radioactive discharge, with 5000 deaths among newborn children. They also claimed that several hundreds of thousands of the people who worked on the site after the accident are now sick because of radiation, and tens of thousands are dead  .
Since March 2001 400 lawsuits have been filed in France against "X" by the French Association of Thyroid-affected People, including 200 in April 2006. These persons are affected by thyroid cancer or goitres, and have filed lawsuits alleging that the French government, at the time led by Prime Minister Jacques Chirac, had not adequately informed the population of the risks linked to the Chernobyl radioactive fallout. The complaint contrasts the health protection measures put in place in nearby countries (warning against consumption of green vegetables or milk by children and pregnant women) with the relatively high contamination suffered by the east of France and Corsica. Although the 2006 study by the French Institute of Radioprotection and Nuclear Safety said that no clear link could be found between Chernobyl and the increase of thyroid cancers in France, it also stated that papillary thyroid cancer had tripled in the following years .
map of chernobyl contaminated areas
Paths of radiation exposure.
An authoritative multi-agency study published in 2005 quantified the effects. Overall some 56 people were killed or have subsequently died, including the 9 children from thyroid cancer - which could have been avoided. Among some 200,000 workers exposed in the first year, 2200 radiation-related deaths can be expected. On the basis of statistical dose-effect models, a total of the order of 4000 eventual deaths from the accident are possible, though most scientists involved were reported to oppose publication of such a specific estimate.
The 600-page report says that people in the area have suffered a paralysing fatalism due to myths and misperceptions about the threat of radiation, which has contributed to a culture of chronic dependency. Some "took on the role of invalids." Mental health coupled with smoking and alcohol abuse is a very much greater problem than radiation, but worst of all at the time was the underlying level of health and nutrition. Apart from the initial 116,000, relocations of people were very traumatic and did little to reduce radiation exposure, which was low anyway. Psycho-social effects among those affected by the accident are similar to those arising from other major disasters such as earthquakes, floods and fires.
The 2005 Chernobyl Forum study involved over 100 scientists from eight specialist UN agencies and the governments of Ukraine, Belarus and Russia. Its conclusions are in line with earlier expert studies, notably the UNSCEAR* 2000 Report which said that "apart from this [thyroid cancer] increase, 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." As yet there is little evidence of any increase in leukaemia, even among clean-up workers where it might be most expected. However, these workers remain at increased risk of cancer in the long term. the United Nations Scientific Commission on the Effects of Atomic Radiation, which is the UN body with a mandate from the General Assembly to assess and report levels and health effects of exposure to ionizing radiation.
Some exaggerated figures have been published regarding the death toll attributable to the Chernobyl disaster. A publication by the UN Office for the Coordination of Humanitarian Affairs (OCHA) entitled Chernobyl - a continuing catastrophe lent support to these. However, the Chairman of UNSCEAR made it clear that "this report is full of unsubstantiated statements that have no support in scientific assessments," and the 2005 report also repudiates them.
The 50-page version of the 2005 Chernobyl Forum report is available on the web. Copies of the Conclusions from the UNSCEAR 2000 report on the health effects of Chernobyl are appended. A May 2004 paper by Z. Jaworowski on Lessons of Chernobyl, including evaluation of health effects, is also appended. (this is PDF: 0.5 MB, html version is on WNA web site)
Geographical location and extent of radioactive contamination. Swiss Agency for Development and Cooperation. (quoting the "Committee on the Problems of the Consequences of the Catastrophe at the Chernobyl NPP: 15 Years after Chernobyl Disaster", Minsk, 2001, p. 5/6 ff., and the "Chernobyl Interinform Agency, Kiev und", and "Chernobyl Committee: MailTable of official data on the reactor accident")