Thirty years ago, in March 1979, a group of badly trained operators in the control room at Three Mile Island's unit 2 confronted a minor malfunction. The problem, a simple pump shutdown, was quickly made worse by an instrument panel that failed to inform the operators about a stuck valve and by an alarm system that overloaded after the first malfunction. The operators botched an attempt to solve the rapidly escalating problem, allowing a small leak to drain most of the cooling water out of the $700 million reactor. In about two hours, they converted America's newest nuclear plant, which had begun commercial operation just three months earlier, into a $1 billion liability.

The event at the reactor, near Harrisburg, PA, provoked near-panic, and although government reports said the maximum possible radiation exposure was too small to have much effect on human health, one major casualty was the outlook for the nuclear industry itself. The meltdown did not end the first round of nuclear construction in this country; 50 reactors already under construction were completed after the accident, and orders for new plants had effectively ceased anyway. (The last order for a nuclear plant that was actually built came in 1973.) But for years to come, it remained unthinkable to plan new reactors as part of the nation's energy portfolio.