40 years after meltdown, Three Mile Island plant may shut down The 1979 meltdown at Three Mile Island remains the worst nuclear accident in US history. Forty years later, the owner of the Pennsylvania plant has announced plans to shut down the money-losing facility. Its closure would be a relief for local residents who lived through the accident, but workers whose jobs are at risk say they will fight for the plant to stay open. IMAGES AND SOUNDBITES