The Chernobyl nuclear accident occurred in the city of Chernobyl. At the time of the accident, Chernobyl was a city in the Soviet Union. Today it is located in Ukraine, north of Kiev.
It was the night of 25th -26th, April 1986 when the Chernobyl accident occurred. The reactor of Unit 4 of the Chernobyl Nuclear Power Plant was being prepared for shutdown. This was a routine procedure, enabling maintenance and repairs to be carried while a series of tests on the unit's turbines were performed. Anatoli Dyatlov, deputy chief of Unit 4, Gennady Matlenko from the equipment manufacturers and several Chernobyl engineers had gathered in the control room, hoping to learn from the experiment. At the main control board, shift foreman, Alexander Akimov and 26-year-old engineer Leonid Toptunov scanned the complicated dials and gauges.
The tests were performed without automatic emergency system on as the emergency system could affect the results.
The tests were performed to try to learn what would happen if all the power were lost to the reactor core and also to see how long the turbines would continue to operated during a power failure. The turbine would continue to spin just as a bicycle wheel keeps spinning for a while after you stop pedaling.
The Soviet Union was short of electricity. For this reason, Chernobyl was built with a lot of speed, and the new town of Pripyat had sprung up to house its workers. Unit 4 began operating in March 1984. It was crucial to the electric power grid at Kiev, Soviet Union's 3rd largest city. On that Friday, when the accident occurred, there was an order to postpone shut down as Unit 4's output was urgently needed. Late at night, permission to continue the operation of shut down was finally given.