Three Mile Island Nuclear Accident

The accident at the Three Mile Island Unit 2 (TMI-2) nuclear power plant near Middletown, Pennsylvania, on March 28, 1979, was the most serious in a commercial nuclear power plant in the United States, even though it led to no deaths or injuries to plant workers or members of adjacent communities. It had major implications for the nuclear industry because it resulted in major changes in the regulatory requirements involving emergency response planning, reactor operator training, radiation monitoring, human factors engineering, radiation protection, and other areas of nuclear plant operations. It also caused the U.S. Nuclear Regulatory Commission (NRC) to tighten and heighten its regulatory oversight.

The accident at TMI-2 was initiated at 4 a.m. by a minor malfunction, or “transient,” in the nonnuclear part of ...