what happened in the nuclear disaster in chernobyl
Chernobyl disaster The event occurred during a late-night safety test which simulated a station blackout power-failure and in which safety systems were deliberately turned off. A combination of inherent reactor design flaws and the reactor operators arranging the core in a manner contrary to the checklist for the test, eventually resulted in uncontrolled reaction conditions. Water flashed into steam generating a destructive steam explosion and a subsequent open-air graphite fire.[note 1] This fire produced considerable updrafts for about nine days. These lofted plumes of fission products into the atmosphere. The estimated radioactive inventory that was released during this very hot fire phase approximately equalled in magnitude the airborne fission products released in the initial destructive explosion.[1] Practically all of this radioactive material would then go on to fall-out/precipitate onto much of the surface of the western USSR and Europe.
Nuclear power in Japan Though all of Japan's nuclear reactors successfully withstood shaking from the 2011 Tohoku earthquake, flooding from the ensuing tsunami caused the failure of cooling systems at the Fukushima I Nuclear Power Plant on March 11. Japan's first-ever nuclear emergency was declared, and 140,000 residents within 20 km (12 mi) of the plant were evacuated. A comprehensive assessment by international experts on the health risks associated with the Fukushima I nuclear power plant disaster concluded in 2013 that, for the general population inside and outside Japan, the predicted risks were low and no observable increases in cancer rates above baseline rates were anticipated.[7] All Japan's nuclear plants were closed, or their operations suspended for safety inspections. The last of Japan's fifty reactors (Tomari-3) went offline for maintenance on May 5, 2012,[8] leaving Japan completely without nuclear-produced electrical power for the first time since 1970.