Nuclear disaster of March 2011 Fukushima Daiichi Nuclear Power Plant

three of reactors @ fukushima daiichi overheated, causing meltdowns led explosions, released large amounts of radioactive material air.

on march 11, 2011, earthquake categorized 9.0 mw on moment magnitude scale occurred @ 14:46 japan standard time (jst) off northeast coast of japan, 1 of powerful earthquakes in history. units 4, 5 , 6 had been shut down prior earthquake planned maintenance. remaining reactors shut down/scramed automatically after earthquake, , remaining decay heat of fuel being cooled power emergency generators. subsequent destructive tsunami waves of 14 meters over-topped station, had seawalls, disabled emergency generators required cool reactors , spent fuel pools in units 1-5. on following 3 weeks there evidence of partial nuclear meltdowns in units 1, 2 , 3: visible explosions, suspected caused hydrogen gas, in units 1 , 3; suspected explosion in unit 2, may have damaged primary containment vessel; , possible uncovering of spent fuel pools in units 1, 3 , 4. units 5 & 6 reported on march 19, station-wide alert log updates of iaea, have gradually rising spent fuel pool temperatures had likewise lost offsite power, onsite power provided unit 6 s 2 diesel generators had not been flooded, configured double-duty , cool both unit 5 , 6 s spent fuel pools , cores . precautionary measure, vents in roofs of these 2 units made prevent possibility of hydrogen gas pressurization , ignition.

radiation releases units 1-4 caused large evacuations, concern food , water supplies, , treatment of nuclear workers. radiation releases contaminated 2011 harvest.

the events @ units 1, 2 , 3 have been rated @ level 5 each on international nuclear event scale, , @ unit 4 level 3 (serious incident) events, overall plant rating @ level 7 (major release of radioactive material widespread health , environmental effects requiring implementation of planned , extended countermeasures).