Chernobyl 25 years ago; radioactive Cesium 137 cloud over Russia and Europe

25 years ago, on 26 April 1986, a nuclear power plant catastrophe took place in Chernobyl, near Kiev, in the Ukraine. It was the worst nuclear power plant accident in history. The accident was the result of a flawed reactor design that was operated with inadequately trained personnel. Ironically, the disaster occurred during a systems safety test performed to test whether the reactor had the capability to ride through the first 60--70 seconds of a total loss of electric power during an emercengy shutdown. A sudden high power output surge took place, and when an attempt was made for emergency shutdown, a more extreme spike in power output, about 10 times the rated maximum output, occurred leading to reactor core explosion. This threw large quantities of radioactive core materials into the atmosphere and exposed the graphite moderator components of the reactor to air so they started to burn. The resulting fire sent a cloud of radioactive fallout into the atmosphere and over an extensive geographical area, including the nearby town Pripyat. The cloud drifted over large parts of the western Soviet Union, and Europe. Large areas in Ukraine, Belarus, and Russia had to be evacuated, with over 300,000 people resettled.
Two Chernobyl plant workers died on the night of the accident, and a further 28 people died within a few weeks as a result of acute radiation poisoning. Radiation doses on the first day were estimated to range up to 20000 millisieverts (mSv).
The next task was cleaning up the radioactivity at the site. 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. Some 20,000 of them received about 250 mSv and a few received 500 mSv. The highest doses were received by about 1000 emergency workers and on-site personnel during the first day of the accident.
Initial radiation exposure in contaminated areas was due to short-lived iodine-131; later cesium-137 was the main hazard. About five million people lived in areas contaminated (above 37000 Bq/m2 Cs-137) and about 400000 lived in more contaminated areas of strict control by authorities (above 555000 Bq/m2 Cs-137).
Among the residents of Belarus, the Russian Federation and Ukraine there had been, up to 2002, about 4000 cases of thyroid cancer reported in children and adolescents who were exposed at the time of the accident, and more cases are to be expected during the next decades. Many of those cancers were most likely caused by radiation exposures shortly after the accident.
Videos about radiation detection:

Radioactive Americium 241 containing smoke detector dismantled:
http://www.youtube.com/watch?v=LaU3zMzO5Xk

Deflection of Americium 241 alpha particles by a Neodymium magnet:
http://www.youtube.com/watch?v=AkO4PZn2_Vs

High alpha's cpm count should not be interpreted as high µSv/hr (gamma) reading:
http://www.youtube.com/watch?v=toHatTVryZM

Video about Radium-226 radiation from Jefferson Mystery clock:
http://www.youtube.com/watch?v=nAJJTZVo2SY

Video about radioactive granite kitchen sink:
http://www.youtube.com/watch?v=lns0jqzNkew

Video about the Cesium-137 cloud from Chernobyl which I, ironically, uploaded one month before "Fukushima" :
http://www.youtube.com/watch?v=2ApKvCtHGDc

Видео Chernobyl 25 years ago; radioactive Cesium 137 cloud over Russia and Europe канала Alfred Appel