On March 28, 1979, a release valve on a reactor at the Three Mile Island plant outside Harrisburg, Pa., became stuck. No one realized what the computer monitor was telling them -- that the coolant had leaked, and there was a dangerous buildup of heat in the nuclear fuel rods. This melted the protective coating on the rods, so that when coolant was reintroduced, it became contaminated and overheated. When the steam was released, the radioactive contaminant was released into the surrounding area. However, the amount released was not enough to harm local food supplies, animals or people.
The Three Mile Island plant was mothballed, and cost $975 million to decontaminate to low levels of radiation, and to safely dispose of the radioactive fuel. Another plant on the Three Mile Island site continued to safely operate.
The economic cost of the Three Mile Island disaster is nowhere near the cost of other nuclear power plant disasters. Japan's nuclear meltdown could cost $200 billion. The Chernobyl nuclear disaster cost in the hundreds of billions of dollars.
Hurricane Katrina was the most expensive U.S. disaster, costing between $125 billion to $250 billion. It knocked GDP growth to 1.3% in the 4th quarter 2005. It affected 19% of U.S. oil production and briefly spiked gas prices to $5 a gallon.