On April 26, 1986, the worst nuclear power plant accident in the world occurred at the Chernobyl nuclear power plant in the Soviet Union. Thirty-two people died and dozens more suffered radiation burns in the early days of the crisis, but it was only after Swedish authorities reported the fallout that the Soviet authorities admitted to reluctantly that an accident had occurred.
The Chernobyl station was located in the Pripyat settlement, approximately 65 miles north of Kiev in Ukraine. Built in the late 1970s on the banks of the Pripyat River, Chernobyl had four reactors, each capable of producing 1,000 megawatts of electricity. On the evening of April 25, 1986, a group of engineers began an electrical engineering experiment on reactor number 4. The engineers, who had little knowledge of reactor physics, wanted to see if the reactor turbine could operate water pumps inertial power backup.
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As part of their ill-conceived experiment, the engineers disconnected the emergency safety systems from the reactor and its power regulation system. Then, they aggravated this recklessness with a series of errors: they operated the reactor at a power level so low that the reaction became unstable, then removed too many control rods from the reactor in an attempt to relight it. The power of the reactor reached more than 200 megawatts but proved increasingly difficult to control. However, at 1:23 a.m. on April 26, the engineers continued their experiment and stopped the turbomachine to see if its inertial rotation would power the reactor water pumps. In fact, it did not supply the water pumps properly and without cooling water, the power level in the reactor increased.
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To avoid the merger, the operators reinserted all of the approximately 200 control rods into the reactor at once. The control bars were supposed to reduce the reaction but had a design flaw: the graphite tips. Thus, before the five meters of absorbent material from the control rod could penetrate the heart, 200 graphite points were entered simultaneously, thus facilitating the reaction and causing an explosion which caused the heavy steel and concrete cover to explode. of the reactor. It was not a nuclear explosion, as nuclear power plants are unable to produce such a reaction, but it was chemical, caused by the ignition of the gases and steam generated by the runaway reaction. In the explosion and fire that followed, more than 50 tonnes of radioactive material was released into the atmosphere, where it was transported by air currents.
On April 27, the Soviet authorities began the evacuation of the 30,000 residents of Pripyat. Concealment was attempted, but on April 28, Swedish radiation monitoring stations, located more than 800 miles northwest of Chernobyl, reported radiation levels 40% higher than normal. Later that day, the Soviet news agency admitted that a major nuclear accident had occurred in Chernobyl.
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In the first days of the crisis, 32 people died in Chernobyl and dozens more were burned with radiation. The radiation that escaped into the atmosphere, which was several times that produced by the atomic bombs dropped on Hiroshima and Nagasaki, was propagated by the wind over the north and east of Europe, contaminating millions of acres of forest and agricultural land. It is estimated that 5,000 Soviet citizens eventually died from cancer and other radiation-induced diseases caused by their exposure to Chernobyl radiation, and millions more had health problems. In 2000, the last reactors in service at Chernobyl were closed and the plant was officially closed.