Three Mile Island: Fifty-Two Percent of a Meltdown

The cooling towers visible from this stretch of the Susquehanna are ten miles south of Harrisburg's state capitol dome. They belong to Three Mile Island, and on the morning of March twenty-eighth, nineteen seventy-nine, this view became one of the most watched and most feared sights in the United States.

At four in the morning, an automatically operated valve in the Unit Two reactor closed unexpectedly, cutting off the main water supply to the cooling system. A series of operator errors and equipment failures followed. The core began to overheat. Cooling water contaminated with radiation drained into adjoining buildings. By the time engineers brought the situation under control, fifty-two percent of the reactor core had melted. The containment structure held, preventing a full atmospheric release, but in the first hours no one outside the plant fully understood what was happening inside it.

Governor Dick Thornburgh had been in office seventy-one days when the phone rang at that hour. He later described knowing almost nothing about nuclear power, radiation, or how to manage a mass evacuation. On March thirtieth, on the advice of the Nuclear Regulatory Commission, he recommended that pregnant women and pre-school-age children within five miles of the plant evacuate. The recommendation, because of how it was worded, hit the public like an alarm. Within days, one hundred forty thousand people had left the surrounding area. Schools closed. Dairies stopped selling milk.

No radiation-related deaths have been confirmed from the accident. Studies conducted in the years after found no measurable increase in cancer rates in the surrounding population, though the question of long-term health effects has been genuinely contested in the scientific literature, and to be transparent here, the research is not fully settled. What is not contested is the accident's political effect. No new nuclear reactors were ordered by American utility companies from nineteen seventy-nine until around two thousand twelve. A single malfunctioning valve, ten miles downriver from the capital, reshaped the energy history of the country.