The nuclear power plant was set up to be the safest nuclear power plant ever built. On April 25th, there factor was schedule to shut down for maintenance. While preparing for the shutdown, the operator wanted to perform a test to see how long the turbines could run the emergency cooling system if power is interrupted by accident. With the reactor slowing down in preparation of shutdown, the power in reactor number 4 drops to 1600 mega watts. At this point, only 6 of the minimum of 30 control rods were down making the power to crash down to 30 mega watts only, making the reactor hard to control. The power then were raised by the operator to 200 mega watts. The the operator make a simple but fatal error by setting the regulator improperly. There were one last safety system that will shut down the reactor but it was disabled. The operator blocked the automatic shutdown because the fear of the shutdown would abort the test and they will have to repeat the test. The operator begin the test, cutting of the steam supply of the remaining turbines. As coolant water began to decrease, the power level began to rise.
Thirty-six seconds after the test has begun,the shift supervisor attempts to drop all control rods back into the reactor realizing the power was rising beyond its limit. In four and a half seconds, the power level inside the reactor rises 120 times the reactor's capacity. The first explosion broke the pressure tubes, releasing steam which blew the contamination lid off the reactor. The second explosion was the reactor fuel and graphite inside the core exploding, sending chunks f graphite and others radioactive elements flying. It destroyed the building and caused more than 30 roof fire.
