Three Mile Island Meltdown
Published: August 30, 2026
Duration: 1:33:01
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 thre...
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 thre...