Lessons learned from the Three Mile Island accident

The Three Mile Island accident occurred in the Unit 2 reactor near Harrisburg, Pa., on March 28, 1979. The accident was real world proof that the U.S. design for a nuclear power plant would protect the public and the environment in the worst kind of accident, a meltdown of the reactor’s core.

In the United States, a massive, reinforced concrete containment building houses the reactor. At TMI, water from the reactor’s cooling system passed into the reactor building, but within the containment building. The heat build-up melted the fuel in the reactor’s core. But the containment building prevented the release of radiation at harmful levels.

Although a small amount of radiation was released, no injuries, deaths or discernible direct health effects were caused, according to over a dozen studies conducted between 1981 and 1991. See especially the University of Pittsburgh Graduate School of Public Health study, updated in November 2002, covering the years 1979-1992 and involving 32,135 individuals.

To make sure that this kind of accident does not happen again, the nuclear energy industry established the Institute of Nuclear Power Operations in Oct. 1979. INPO sets performance objectives, criteria, and guidelines industry-wide for overall nuclear plant operations, and conducts regular evaluations of nuclear plants as well as events analysis. In addition, INPO formed the National Academy for Nuclear Training in 1985 to accredit nuclear utilities' training programs for plant operators and supervisors of operations.

Since TMI, the nuclear energy industry has compiled an outstanding safety record. For more information see, the Web section, Three Mile Island and the Institute of Nuclear Power Operations, the fact sheet, The TMI 2 Accident: Its Impact, Its Lessons, and the fact sheet, Three Mile Island: Myths and Facts.

Nuclear Energy Institute—Washington, DC
August 2000