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 300000 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 ...