Read the IAEA report on the Chernobyl disaster.
It reads like bad comedy; operators trying to follow a test program while the reactor was in a completely unstable state.
The REAL kicker: The SCRAM command to shut down the reactor made it go "Prompt Critical" and explode.
"As can be seen from the foregoing, the event which initiated the accident was the pressing of the EPS-5 button (SCRAM Button) when the RBMK-1000 reactor was operating at low power with a greater than permissible number of manual control rods withdrawn from the reactor. " pp67
Scariest thing I've read this decade.