Episode
Three Mile Island Meltdown
- Podcast
- Disturbing History
- Published
- Aug 30, 2026
- Duration seconds
- 5581
- Processing state
not_requested
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Summary
On March 28, 1979, at 4:00 a.m., a relief valve at Three Mile Island opened as designed—and then failed to close. For more than two hours, operators believed it had shut because the control-room indicator showed the electrical command, not the valve’s actual position. By the time the mistake was understood, roughly half the fuel in Unit Two had melted.The men in the control room did not know how bad it was. Neither did the Nuclear Regulatory Commission. The full extent of the damage would not be confirmed until engineers lowered a camera into the reactor vessel three years later and found a five-foot void where the top of the core had once been. In this episode of Disturbing History, Brian goes beyond the familiar story of America’s worst commercial nuclear accident and into the warnings, failures and unanswered questions that came before and after it.Eighteen months before the meltdown, another Babcock & Wilcox reactor at Davis-Besse experienced a nearly identical stuck-open relief valve. Engineers warned that operators could misread the signs of a loss-of-coolant accident and shut down emergency cooling at exactly the wrong moment. One NRC inspector was concerned enough to travel to Washington on his own time just six days before Three Mile Island to warn commissioners that something was badly wrong. The Kemeny Commission later concluded that the correct operating guidance was never passed along to the utilities.The episode reconstructs the accident minute by minute: the closed emergency feedwater valves, the overwhelming alarm system, the printer that fell so far behind that critical records were lost, temperature readings above 2,000 degrees Fahrenheit that operators dismissed as impossible, and a hydrogen burn inside containment that was initially written off…