Japan was first hit by a massive earth quake, then a ruthless tsunami washed away thousands of homes and now they fear the worst – meltdown of nuclear power stations in the quake hit year.

Nuclear meltdowns are horrifying – remember the Chernobyl incident in Russia? The Chernobyl reactor meltdown released 400 times more radio active material than the atomic bombing of Hiroshima. The effects of nuclear meltdowns are beyond imagination of a common man, thousands of people loose their lives and many more lakhs of people suffer with radiation related diseases for many years. Nuclear Meltdowns are dangerous, but how do they happen? What causes a nuclear meltdown?

In simple terms – Nuclear meltdown is an accident that happens due to severe overheating of a nuclear reactor and results in release of nuclear radiation into the environment. 

How A Nuclear Meltdown Happens?

According to Wikipedia

A meltdown occurs when a severe failure of a nuclear power plant system prevents proper cooling of the reactor core, to the extent that the nuclear fuel assemblies overheat and melt. A meltdown is considered very serious because of the potential that radioactive materials could be released into the environment.

The fuel assemblies in a reactor core can melt if heat is not removed. A nuclear reactor does not have to remain critical for a core damage incident to occur, because decay heat continues to heat the reactor fuel assemblies after the reactor has shut down, though this heat decreases with time.

A core damage accident is caused by the loss of sufficient cooling for the nuclear fuel within the reactor core. The reason may be one of several factors, including a loss of pressure control accident, a loss of coolant accident (LOCA), an uncontrolled power excursion or, in some types, a fire within the reactor core. Failures in control systems may cause a series of events resulting in loss of cooling. Contemporary safety principles of defense in depth, ensure that multiple layers of safety systems are always present to make such accidents unlikely.

Video – What Causes Nuclear Meltdown

AlJazeera news has a good analysis on feared nuclear meltdown of Japan’s nuclear plants and also an animation on what causes Nuclear Meltdown.

cc image credit: flickr/jtjdt

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