Chernobyl

Human Failure

Operators were conducting an experiment on the RBMK-1000 graphite-moderated uranium reactor to determine how much energy would continue to be expended by the turbine rotor if the reactor should fail. The experiment was started in the afternoon of April 25, 1986, as scheduled. However, at the request of a load dispatcher in Kiev, the removal of the unit from the grid was delayed. Since that day operators had already begun reducing output as needed for the experiment, unit 4 was kept operating with the core cooling system switched off, clearly breaching safety rules.

The operators conducting the test in the early morning of April 26 also violated multiple nuclear safety rules. The operators shut off the automatic controls, blocked the protection systems, and reduced the operational reactivity reserve below the permissible level, rendering the emergency power reduction system useless. To quickly increase power, the graphite control rods were removed by hand, causing the reactor to become more sensitive to fluctuations. When the cooling water overheated and turned to steam, the control rods could not be lowered fast enough. Because the heat was so intense, the tips of the graphite rods that were inserted caused a reaction that only increased the temperature further. The resulting explosions blasted the thousand-ton “safety” cover off the top of the reactor and shot burning graphite and radio-nuclides high into the air.

Very few operators in the entire plant were actually trained in nuclear technology. Most operators were electrical engineers with experience in coal and gasification plants. While an explosion at such a thermal power station will no doubt cause destruction, the devastation will not continue to be found in cancer-causing radioactive particles for literally hundreds of years after the explosion, as is the case with nuclear power plants. Peter Gould, in his analysis of the democratic consequences of Chernobyl, explained that little shared knowledge exists between electrical engineers and atomic engineers. Grigori Medvedev, a nuclear physicist who once worked at Chernobyl, documented that operators were hired and promoted based not on their knowledge and ability to work with nuclear technology but on their standing in the Communist Party and on past experience with the station director at thermal plants. The safety programs should not have been ignored during the test, but the operators had little knowledge as to the devastation such lax protocols could inflict. Six operators, including the chief engineer and station director, were eventually prosecuted for “violations of discipline.”

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