II. The human side: Training and tools to help the operator

A clogged demineralizer line that caused a turbine to trip, a leaky pressurizer that disguised a loss of coolant accident, and a valve that stuck open - these were the equipment problems that triggered the accident at Three Mile Island. Since that accident, however, study after study has observed that if the automatic safety systems had been untouched by human hands, these hardware failures might not have led to the calamity at TMI. The real damage at TMI was caused by unprepared operators, confused by both inadequate training and poor control room diagnostic aids, who inadvertently, but systematically, checkmated every automatic safety system until the core began inciting. What the accident at TMI showed was that ill-prepared operators could make things worse.