How It Happened
Reactor 4 at the Chernobyl Nuclear Power Plant was scheduled for a shutdown to perform routine maintenance on April 25th, the day before the disaster. This shutdown was to take place, in part, so an experiment could be undertaken. The engineers at the plant intended to test the turbines running the generators in the reactor to see if they would continue to run even if there was an external power outage. This would be an important safety component, as the reactor type used at Chernobyl requires a constant spray of water in order to remain cool. Of course, the turbines could not turn forever under their own momentum (or else there would be no need for a nuclear power plant). There was a forty second delay between the shutdown of the electricity and the initiation of the backup generators. The engineers needed to test if the turbines could continue to turn for a minimum of forty seconds, thus producing a seamless transition in the event of a power outage.
In a twist of fate, the grid controller in the area requested that the reactor stay online, however, rather than decreasing power output….