In the early minutes of the accident, workers didn’t realize that the valves on the emergency coolant pipes had mistakenly been shut—one of the indicator lights on the control panel was hidden by a repair tag. Perrow soon learned that similar mistakes had occurred during the operation of other nuclear power plants. At a reactor in Virginia, a worker cleaning the floor got his shirt caught on the handle of a circuit breaker on the wall. He pulled the shirt off it, tripped the circuit breaker, and shut down the reactor for four days.
