Chernobyl

The accident

On April 26, 1986, Soviet's Union Chernobyl nuclear plant exploded letting out a massive amount of radiation that all Russian citizens would debate for years to come. At exactly 1:21 am. on April 26th 1986 in Chernobyl, a city near the Pripiat River the No. 4 reactor exploded and released thirty to forty times the radiation of the Nagasaki and Hiroshima bombing. The exact causes of the explosion

are not known, however scientists and researchers, under thorough investigation, have uncovered possible causes to the explosion.

The reason

The main reason why the explosion might have occurred was that the operators of the plant were attempting to conduct an experiment with the emergency cooling system turned off, they made six fatal errors which sealed everyone's fate. Soviet officials clamed that, if the technicians would have avoided at least one of those mistakes, then the plant could have been saved. The technicians began the test one day before the explosion. They started reducing the reactor's power level so they could run the turbine experiment, however in order for the plant to run at lower power they had to turn off the automatic control system, which powered all emergency limitations that the plant should make in case it goes out of control. Turning of the cooling system was an unnecessary action and though it did not cause the explosion, it made the consequences more fatal. Just then, the operator's receive a call from the local grid controller in Kiev who needed the power and asked the technicians to stop lowering it. Once that was done the reactor was running with out the cooling system, which was a very serious mistake. At 11:10 p.m. the grid controller said he no longer needed the power, and the operators returned to reducing the power. At twenty minutes past midnight the operators forgot to set the regulator properly, it was the second fatal error. At that point the operators would have abandoned the experiment, but they attempted to rescue it, for the next time they would be able to conduct would be in one year only.

The senior authorities that had ordered the test would have been furious and would have found out the regulator problem, so the operators decided to pull out the stops to restore the reactor's power. Their third fatal mistake was the pulling out of control rods. The plant's rule was to have thirty in at all times however they left all but six. By 1:00 Am the power was still to low for the experiment, however the operators continued. In a few minutes they made their fourth fatal error, by turning on two extra pumps to join the six that were already cooling the core. This procedure under such low power caused a massive steam disorder.

Fifth was the turning off of the automatic shut off, which would turn off the reactor. At 1:23 a.m. on Saturday April 26, the workers began the actual experiment. Then they turned off the last safety system. It took the shift manager thirty-seconds to realize what was happening and shouted at other operators to press button AZ-5 which would driven all the control rods back into the core, but because the rods were melted from serious heat they didn't fit properly into the core. As the manager looked down at the control panel several loud banging noises were heard. Immediately the one thousand ton roof of the reactor blew off sky high, and brought down the giant two hundred tone refueling crane onto the core, destroying more cooling systems. Thirty fires spread around the plant. Finally the over-heating and steam build up caused a second explosion, which destroyed the reactor and part of the building.

The graphite began to burn ferociously once exposed to air, as core reached temperatures as high as 2,800* F a massive amount of radioactive dust was let out into the air, which was picked by winds and carried thousands of miles into every direction. Previous to the testing, the technicians drew up plans, but did not discuss them with physicists or nuclear safety staff at the plant. Though they sent experiment plans to the designers of the plant, the designers never got a chance to take a look and never issued any authority or made any confirmation. All soviet officials were certain that the explosion

occurred not because of the plant, but because of human negligence. "The engineer who designed the plant and its safety systems did not include such a scenario in his project," said Valeri Legasov, first deputy director of the Kurchatov Atomic Institute. During an interview with Legasov, he stated that many discussions about the test had been going on and not everyone agreed to the test ever being conducted. However, not everyone was satisfied with the technician's theory and researchers proposed an additional theory.

Unlike Chernobyl, the power plants in the rest of the world have a contaminant structure which is a huge reinforced concrete dome designed to prevent radioactive materials from escaping during an

accident. When the reactor exploded and the core began to burn, Soviet officials tried as hard as they could to put the fire out. It took them twelve long days to finally put out the devastating fire. Unlike in any other explosion where the radioactive materials would remain buried in the ground the Chernobyl graphite fire sucked in oxygen and spewed radioactive isotopes in the air.

The evacuation

Immediately without any explanation, residents from the Chernobyl area were quickly evacuated. Kiev buses transported over 50,000 people. Only by Monday morning did people start getting suspicious. Monitoring stations in other parts of the country reported radiation levels up to one hundred times the norm. By that afternoon Swedish scientists found isotopes like krypton, xenon, iodine, cesium and cobalt in the fallout, a radioactive mix that could only have come from an accident of a reactor. The Swedes concluded that a meltdown occurred somewhere. Later on, they determined when the cloud arrived and what rout it took, so they began backtracking. They were able to draw a line going through Latvia over Moscow and into Minsk. However further testing proved that Chernobyl was the site of the meltdown.