This research paper discusses the Three Mile Island Incident to include what started it, the results afterward, and how it could have been prevented. The Three Mile Island Unit 2 (TMI-2) reactor, near Middletown, Pennsylvania, partially melted down on March 28, 1979. This was the most serious accident in the operational history of a U.S. commercial nuclear power plant, although its small radioactive releases had not taken place. detectable health effects on plant workers or the public. Its consequences brought radical changes involving emergency response planning, reactor operator training, human factors engineering, radiation protection, and many other areas of nuclear power plant operations. It also prompted the Nuclear Regulatory Commission (NRC) to strengthen and intensify its regulatory oversight. All of these changes have significantly improved the safety of U.S. reactors. A combination of equipment malfunctions, design issues and worker errors led to the partial meltdown of TMI-2 and very small releases of radioactivity off-site. What happened to Three Mile Island? There are three main reasons that were directly responsible for what happened to Three Mile Island. Equipment design, mechanical malfunctions, and human error were major factors contributing to the Three Mile Island Unit 2 reactor meltdown. The accident began around 4 a.m. on Wednesday, March 28, 1979. A mechanical or electrical problem prevented the water pumps from cooling the reactor core. This caused the reactor to overheat to the point of breaking the long tubes that contain the nuclear fuel pellets. Immediately, the pressure in the primary system (the part of the nuclear plant) began to rise. As a means of managing that pressure, the pilot-operated safety valve (the upper pressure valve... center of paper...) related to what actually happened at Three Mile Island. These organizations reported what they knew to be true to the best of their accounting of the accident. With new safety standards in place, power plant operators may not see another accident like the one at Three Mile's Unit 2 reactor Island due to proper training and regulated policies that keep them compliant with standards. .Works CitedND (2014, April 25). General Information on the Three Mile Island Incident Retrieved from USNRC: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.htmND. (2010, August). Retrieved from Nuclear Energy Institute: http://www.nei.org/Master-Document-Folder/Backgrounders/Fact-Sheets/The-Tmi-2-Accident-Its-Impact-Its. -LecturesKeebler, J.R. (2013, March 4). Retrieved from kmuw: http://kmuw.org/post/human-factor-how-three-mile-island-could-have-been-prevented.