1968 San Onofre U.S.

At the San Onofre nuclear plant in southern California a turbine blade breaks, causing alarmed operators to turn off the reactor too quickly. This activates a back up cooling system which should have been turned off. As a plant spokesman later says: "Someone forgot". This causes a drop in pressure thus causing the emergency core cooling system to turn on; however, there is no place for the emergency cooling water to go. This causes both the plant and its emergency core cooling system to be damaged by the resulting vibrations, and the plant is shut down for months.