A partial meltdown occurred at the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, on March 28, 1979, when a cooling system malfunction caused the reactor core to overheat. Confusing instrument readings led operators to make decisions that worsened the situation. Though the containment held and radiation release was minimal, the incident terrified the public and effectively halted new nuclear power plant construction in the United States for three decades. The cleanup took 14 years and cost nearly $1 billion.