Chernobyl Catastrophe
The Reactor
The Chernobyl reactors were some of the best reactors the USSR had made, providing power to the cities around it. Yet while building, constructors missed design flaws, which eventually led to the reactor's explosion killing 31 people right away.
The Test
The biggest reason was the safety test that would find if there was a problem in the safety grid right after a shutdown, the reactors could make enough energy to restart the generators. The test involves seeing if the reactors are able to handle a shutdown of the coolers.
Chernobyl Control Room 3, forgottenchernobyl.net, date unknown
Chernobyl Control Room 4, gizmodo.com date unknown
The Explosion
This test is the worst thing that the Chernobyl engineers could do, and they didn’t get safety authorization to do it, though they did it anyway. The engineers did the test the morning of April 26th, 1986 causing Chernobyl Reactor 4's core to melt and explode on 1:23 A.M, April 26th, 1986. [1]
Radiation quickly spread from the location and it was required to wear safety equipment 19 miles from the reactor. Quickly, cities like Chernobyl and Pripyat were quickly evacuated. People were taken from their house, leaving all their stuff behind, because the Soviets told them they would come back, though they never would.
“For the first time, we confront the real force of nuclear energy, out of control." -Mikhail Gorbachev
[1] Chernobyl Ruins, CBS news, date unkown.