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The Chernobyl disaster was an accident at the Chernobyl Nuclear Power Plant on April 26th, 1986 at 01:23 a.m., consisting of an explosion at the plant and subsequent radioactive contamination of the surrounding geographic area. It is regarded as the worst Nuclear accident ever in the history of Nuclear power. A plume of radioactive fallout drifted over parts of the western Soviet Union, Eastern and Western Europe, Scandinavia, the UK, Ireland and eastern sections of 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.

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 the 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 or even impossible to attribute specifically to the accident. :: from Wikipedia :: [read more]

Causes and who is Responsible?

The causes of the 1986 Chernobyl disaster have been variously attributed to the operating personnel, the plant management, the design of the reactor and the lack of adequate safety information in the Soviet nuclear industry.Six persons, representing only the plant management, were convicted, in view of the human losses, on the grounds of having violated safety regulations for potentially explosive facilities. The chairman presiding over the court said some words to the effect of proceeding with the investigations as regards “those who failed to take measures to improve the plant design”. He also mentioned the responsibility of department officials, local authorities and medical services. But, in fact, it was clear that the case was closed. Nobody else was held responsible for the greatest disaster in the history of nuclear technology.

Immediate Impact

It is estimated that all of the xenon gas, about half of the iodine and caesium, and at least 5% of the remaining radioactive material in 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. The main casualties were among the firefighters, including those who attended the initial small fires on the roof of the turbine building. All these were put out in a few hours, but radiation doses on the first day were estimated to range up to 20,000 millisieverts (mSv), causing 28 deaths in the next four months and 19 subsequently. The next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. 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, average around 100 millisieverts. Some 20,000 of them received about 250 mSv and a few received 500 mSv. Later, the number of liquidators swelled to over 600,000 but most of these received only low radiation doses. About 1000 emergency workers and on-site personnel received the highest doses during the first day of the accident. Img. copyright J.Smith and N.A. Beresford, “Chernobyl: Catastrophe and Consequences” (Praxis, Chichester, 2005).

Initial radiation exposure in contaminated areas was due to short-lived iodine-131; later caesium-137 was the main hazard. (Both are fission products dispersed from the reactor core, with half-lives of 8 days and 30 years respectively. 1.8 Ebq of I-131 & 0.085 Ebq of Cs-137 were released.) About five million people lived in areas contaminated (above 37 kBq/m2 Cs-137) and about 400,000 lived in more contaminated areas of strict control by authorities (above 555 kBq/m2 Cs-137).

On 2-3 May, some 45,000 residents were evacuated from within a 10 km radius of the plant, notably from the plant operators’ town of Pripyat. On 4 May, all those living within a 30 kilometer radius - a further 116 000 people from the more contaminated area - were evacuated and later relocated. About 1,000 of these have since returned unofficially to live within the contaminated zone. Most of those evacuated received radiation doses of less than 50 mSv, although a few received 100 mSv or more. Reliable information about the accident and resulting contamination was not available to affected people for about two years following the accident. This led to distrust and confusion about health effects. In the years following the accident a further 210 000 people were resettled into less contaminated areas, and the initial 30 km radius exclusion zone (2800 km2) was modified and extended to cover 4300 square kilometers. This resettlement was due to application of a criterion of 350 mSv projected lifetime radiation dose, though in fact radiation in most of the affected area (apart from half a square kilometre) fell rapidly so that average doses were less than 50% above normal background of 2.5 mSv/yr.

Chernobyl 20 years later: Radioactivity in the damaged reactor would need to be contained for 100,000 years to ensure safety. That is a challenge not only for today, but also for many generations to come.

After the accident, Soviet authorities resettled more than 350,000 people outside the worst areas, including all 50,000 people from nearby Pripyat, but millions of people continue to live in contaminated areas.In November 2000, the Ukrainian president shut down Reactor No. 3 in an official ceremony that finally closed the Chernobyl facility. Reactor No. 4, which was damaged in the 1986 explosion and fire, is still full of radioactive material encased inside a concrete barrier, called a sarcophagus, that is aging badly and needs to be replaced. Water leaking into the reactor carries radioactive material throughout the facility and threatens to seep into the groundwater. The sarcophagus was designed to last about 30 years, and current designs would create a new shelter with a lifetime of 100 years.

The Exclusion Zone (30-kilometer (19 –mile) radius area around the Chernobyl nuclear plant) and radioactive waste – there are more than 800 temporary storage paces for radioactive wastes

The radiological monitoring the Dneiper river water basin. Which provides water for 32 million people and for the irrigation of 1,8 million hectares of land.

Belarus, Ukraine and Russia were heavily contaminated, but more than half of Chernobyl’s fallout was deposited outside these countries.

Other ongoing effects of the disaster.

  • Birth Defects
  • Genetic Mutations
  • Leukemia
  • Thyroid cancer
  • Mental Disorders
  • Heart Diseases

“It’s incredible that we could create something that toxic that future generations will be cursing us for, generation after generation.”
-Daniel Hirsch, President “Committee to Bridge the Gap”.

Glossary of Terms Used

  • Caesium-137 - is a radioactive isotope, which is formed mainly by nuclear fission. It has a half-life of 30.23 years.
  • Exclusion Zone - the 30-km (19-mile) exclusion zone around the site of the Chernobyl nuclear reactor disaster.
  • Half-life - is the time required for the quantity to decay to half of its initial value.
  • Iodine-131 – is a radioactive chemical that has a half-life of 8 days and it is absorbed by the body and may cause damage to the thyroid.
  • Millisievert (mSv) - the millisievert (mSv) is commonly used to measure the effective dose in diagnostic medical procedures (e.g. X- (e.g. X-rays, nuclear medicine, positron emission tomography and computed tomography). The natural background effective dose varies considerably from place to place, but typically is around 2.4 mSv/year.
  • Liquidator - a person who took part in elimination of consequences of the Chernobyl disaster on the event site.