There is a certain irony in the shorthand that experts commonly use when discussing this country’s closest brush with nuclear cataclysm: TMI. Today, those letters are widely understood to mean “too much information.” But well before the advent of social media, TMI referred principally to the Three Mile Island Nuclear Generating Station, a power plant on the Susquehanna River in central Pennsylvania. Disaster struck there in 1979, and when it did, too much information — solid, unassailable information — was not part of the mix. Months later, a presidential commission cited a “lack of communication at all levels” as cause for grave concern. Americans were frightened, and not just those in Pennsylvania. Fear was intensified because, as the commission said, their right to know what was going on had been sorely compromised.

Then again, so many things went wrong on the Susquehanna back in 1979. Disaster struck at 4 a.m. on March 28 when water-coolant pumps failed at the plant’s new second reactor, known as TMI-2. That led to the reactor’s overheating, with the temperature rising steadily after a stuck valve misled the operators into halting the flow of emergency cooling water. Half the core was later found to have melted.

Details of the accident are recounted in the latest offering from Retro Report, a weekly series of video documentaries examining major news stories from the past and their lessons for today. In a nutshell, TMI-2 lurched through a series of crises for nearly a week. The presidential panel later found plenty of blame to go around. The plant’s designer, Babcock & Wilcox; the federal Nuclear Regulatory Commission; the local utility, Metropolitan Edison; TMI-2 managers and workers; and the news media collectively — none were spared in a report carrying the subtitle “Need to Change.”

The worst of it fell on March 30, when radiation was purposefully released into the air to relieve pressure within the system. That action fed apprehension beyond the plant’s concrete walls that the situation had spun out of control. Rumors flew. So did thoughts of a possible mass evacuation. Pennsylvania’s governor, Richard L. Thornburgh, was loath to go that far, but he did advise pregnant women and small children near the island to find more distant shelter. Contributing to the pervasive dread was a film that had just come out, “The China Syndrome,” a thriller about a safety crisis at a nuclear power plant in California. (“China syndrome” in the nuclear industry’s argot describes a meltdown so severe that the material might burrow clear to the other side of the world, to China.) During the crisis, some moviegoers emerged from theaters to see scary newspaper headlines about an unsettling scenario in Pennsylvania evocative of the on-screen terror they had just witnessed.