A hardened onsite emergency response centre was unable to be used in grappling with the situation, due to radioactive contamination. Some of the Tepco staff had lost homes, and even families, in the tsunami, and were initially living in temporary accommodation under great difficulty and privation, with some personal risk. This was undertaken by hundreds of Tepco employees as well as some contractors, supported by firefighting and military personnel. Thereafter, many weeks of focused work centred on restoring heat removal from the reactors and coping with overheated spent fuel ponds.
The three units lost the ability to maintain proper reactor cooling and water circulation functions. This disabled 12 of 13 backup generators onsite and also the heat exchangers for dumping reactor waste heat and decay heat to the sea. The other three, at Fukushima Daiichi, lost power at 3.42 pm, almost an hour after the earthquake, when the entire site was flooded by the 15-metre tsunami. Power, from grid or backup generators, was available to run the residual heat removal (RHR) system cooling pumps at eight of the eleven units, and despite some problems they achieved 'cold shutdown' within about four days. The reactors proved robust seismically, but vulnerable to the tsunami. The main problem initially centred on Fukushima Daiichi 1-3. Fukushima Daiichi units 4, 5&6 were not operating at the time, but were affected. The operating units which shut down were Tokyo Electric Power Company's (Tepco's) Fukushima Daiichi 1, 2, 3, and Fukushima Daini 1, 2, 3, 4, Tohoku's Onagawa 1, 2, 3, and Japco's Tokai, total 9377 MWe net. Subsequent inspection showed no significant damage to any from the earthquake. The tsunami inundated about 560 km 2 and resulted in a human death toll of about 19,500 and much damage to coastal ports and towns, with over a million buildings destroyed or partly collapsed.Įleven reactors at four nuclear power plants in the region were operating at the time and all shut down automatically when the earthquake hit. Japan moved a few metres east and the local coastline subsided half a metre. An area of the seafloor extending 650 km north-south moved typically 10-20 metres horizontally. The earthquake was centred 130 km offshore the city of Sendai in Miyagi prefecture on the eastern coast of Honshu Island (the main part of Japan), and was a rare and complex double quake giving a severe duration of about 3 minutes. The Great East Japan Earthquake of magnitude 9.0 at 2.46 pm on Friday 11 March 2011 did considerable damage in the region, and the large tsunami it created caused very much more. Disaster-related deaths are in addition to the about 19,500 that were killed by the earthquake or tsunami.
Government nervousness has delayed the return of many. There have been no deaths or cases of radiation sickness from the nuclear accident, but over 100,000 people were evacuated from their homes as a preventative measure.This task became newsworthy in August 2013. Apart from cooling, the basic ongoing task was to prevent release of radioactive materials, particularly in contaminated water leaked from the three units.Official 'cold shutdown condition' was announced in mid-December. After two weeks, the three reactors (units 1-3) were stable with water addition and by July they were being cooled with recycled water from the new treatment plant.All four Fukushima Daiichi reactors were written off due to damage in the accident – 2719 MWe net.The accident was rated level 7 on the International Nuclear and Radiological Event Scale, due to high radioactive releases over days 4 to 6, eventually a total of some 940 PBq (I-131 eq).All three cores largely melted in the first three days. Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident beginning on 11 March 2011.
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