However, the Fukushima disaster has also clearly demonstrated that scenarios which are assumed to be impossible and are therefore excluded from contingency planning can nonetheless occur in reality.Īfter the Fukushima disaster, Japan began a temporary shutdown of all its nuclear power plants to 2012. Instead, the operator – by his own admission – had sought to keep costs low and avoid any discussion of facility safety. They had ignored recent warnings about potential risks to the facility and had failed to implement international recommendations to improve safety. Both the regulatory authorities and the plant operator lacked safety awareness and had failed to take appropriate safety measures at the site. The earthquake was the direct cause of the loss of the external power supply, while the tsunami disabled all the cooling systems and much of the plant’s own power supply.Īpplicable reactor safety principles – such as storage of emergency diesel and batteries for the back-up power supply at physically separate locations – had not been properly implemented at the plant.
As a result, no proper measures were in place to protect it from this type of earthquake-tsunami disaster. At the same time, the fuel rods became so hot that major damage to the reactor cores, including meltdown, occurred in the first, second and third reactor.ĭetailed information can be found in an article by Dr Christian Pistner from the Oeko-Institut: Fukushima – Unfallablauf und wesentliche Ursachen, in the journal sicher ist sicher, 2013.įukushima Daiichi nuclear plant was not designed and had not been retrofitted to withstand an earthquake of this magnitude and its safety systems were not equipped to deal with such a massive tsunami or such high waves. These explosions caused various degrees of destruction in the reactors.
FUKUSHIMA REACTOR MELTDOWN IN JAPAN SERIES
When there was an attempt to release pressure from the reactor vessels, high pressure pushed this hydrogen into the reactor buildings, where it came into contact with oxygen, causing a series of explosions. The metal fuel rod claddings and the steam reacted chemically and produced large quantities of hydrogen. As a consequence, the temperature of the fuel assemblies rose dramatically. Without sufficient cooling, the water in the reactors steadily heated up and the volumes of water remaining in reactors 1-3 at the Fukushima Daiichi plant evaporated until finally the fuel rods were no longer covered with water. A replacement power supply could not be procured and activated in time. It also disabled the emergency electricity supply, which had been started automatically, to five out of six reactors a station blackout occurred.Īs a result, the electric pumps, which are imperative for long-term residual heat removal, failed. The tsunami caused the cooling water systems at all six Fukushima Daiichi reactors to malfunction. With the earthquake causing widespread disruption to the national electricity grid, the plant was cut off from its external power supply. The reactors that were operating when the earthquake struck were automatically shut down immediately. The power plant site was inundated and large parts of the installations were destroyed. Fukushima Daiichi sustained the worst damage, sparking a chain of events which led to core meltdown, major hydrogen explosions and massive releases of radiation. The 2011 earthquake and tsunami also struck several nuclear power plants. The masses of water caused large-scale flooding and destroyed roads, the power supply and other infrastructure along Japan’s eastern seaboard. The quake triggered a tsunami, with waves as high as 38 metres. Ten years ago, in the afternoon of 11 March 2011, a major earthquake measuring 9 on the Richter scale hit the east coast of Japan.
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