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Level 11 : Journeyman Taco
Posted 02/20/13 2:36:30 pm
The story ofÂ Chernobyl
Â Â Â Â Â Â Â Â Â Â Â Engineers on the evening shift atÂ Chernobyl'sÂ number four reactor began an experiment to see whether the cooling ump system could still function using power generated from theÂ reactorÂ under low power should theÂ auxiliaryÂ electricityÂ supply fail.
Â Â Â Â Â Â Â Â Â Â Â At 2300 control rods, which regulate the fission process in the nuclear reactor by absorbing neutrons and slowing the chain reaction, were lowered to reduce the output to about 20% of normal output required for the test. However, too many rods were lowered andÂ outputÂ dropped too quickly, resulting in an almost complete shutdown.
Â Â Â Â Â Â Â Â Â Â Â Concerned by possible instability, the engineers began to raise the rods increase output. At 0030 the decision was taken to carry on. By 0100 power was still only at about 7%, so more rods were raised. The automatic shutdown system was disabled to allow the reactor to continue working under low power conditions. The engineers continued to raise rods. By 0123, the power had reached 12% and the test began, but seconds later, the power levels suddenly surged into dangerous levels.
Â Â Â Â Â Â Â Â Â Â Â The reactor began to overheat and its water coolant started to turn to steam. At this point it is thought that all six control rods had been removed from the reactor core - the minimum safe operating number was considered to be 30. TheÂ emergencyÂ shutdown button was pressed. Control rods started to enter the core, but their reinsertion from the top displaced coolant andÂ concentratedÂ re-activityÂ in the lower core.
Â Â Â Â Â Â Â Â Â Â Â With power roughly at 100 times normal, the fuel pellets in the core began to explode, rupturing the fuel channels. At about 0124, two explosionsÂ occurred, causing the reactors dome-shaped roof to be blown off the contents to erupt outwards. As air was sucked in to the shattered reactor, it ignited flammable carbon monoxide gas causing a reactor fire that burned for nine days. Because the reactor was notÂ housedÂ in reinforced concrete shell, as isÂ standardÂ practiceÂ in most countries, the building sustained severe damage and large amounts of radioactive debris escaped into theÂ atmosphere.Â
Â Â Â Â Â Â Â Â Â Â Â Due to this horrific accident, over 534,000 were killed from the explosion, 3.5 million from radiation over the course of 15 years, and years later roughly 7.6 million were reported due to radiation poisoning caused by the disaster.
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