The Three Mile Island Nuclear Power Plant, near Middleton, Pennsylvania, was the site of the worst U.S. nuclear accident in 1979.

Photograph by Chris Hamilton, National Geographic
  • On March 28, 1979, the Three Mile Island nuclear power plant near Middleton, Pennsylvania, had a partial meltdown. The meltdown was linked to both human error and technical failures. The accident released minute amounts of radioactive materials into the environment, and threatened the health and safety of people living near the plant. Ultimately, state and federal officials evacuated the most at-risk populations from the area and the accident did not cause any injuries or deaths.

    The incident at Three Mile Island caused many people to question the safety of nuclear energy

  • Term Part of Speech Definition Encyclopedic Entry
    environment Noun

    conditions that surround and influence an organism or community.

    evacuate Verb

    to leave or remove from a dangerous place.

    incident Noun

    event or happening.

    minute Adjective

    very small amount.

    nuclear energy Noun

    energy released by reactions among the nuclei of atoms.

    Encyclopedic Entry: nuclear energy
    population Noun

    total number of people or organisms in a particular area.

    radioactive Adjective

    having unstable atomic nuclei and emitting subatomic particles and radiation.