RailsConf 2018: Who Destroyed Three Mile Island? by Nickolas Means On March 28, 1979 at exactly 4:00am, control rods flew into the reactor core of Three Mile Island Unit #2. A fault in the cooling system had tripped the reactor. At 4:02, the emergency cooling system automatically kicked in as reactor temperature continued to climb. At 4:04, one of the operators switched the emergency cooling system off, dooming the reactor to partial meltdown. Why? Let’s let the incredibly complex failure at Three Mile Island teach us how to dig into our own incidents. We'll learn how the ideas behind just culture can help us learn from our mistakes and build stronger teams.