Root causes of the Three Mile Island accident

The accident at Unit 2 of the Three Mile Island nuclear power plant, at that time operated and partly owned by Metropolitan Edison Company, occurred 40 years ago, on March 28, 1979. Following the accident, two major investigations were conducted, one by the President's Commission on the Accident at Three Mile Island [1], appointed by President Carter, and the other by the Nuclear Regulatory Commission's Special Inquiry Group. [2] The investigations documented the timeline of the accident and the availability and failure of equipment, and addressed operator actions during the accident, the training of operators, and NRC procedures that applied to the event. The design process for the plant and the designer's responsibilities, including the plant's safety analysis, were not addressed. Many additional studies and papers have been published over the past 40 years, none of which have addressed the design process or the safety analysis of the plant. The only effort specifically addressing the design of the plant and responsibility for the accident was Metropolitan Edison's lawsuit against Babcock & Wilcox (B&W), the designer of the plant. A trial began but was terminated, and the case was settled out of court. The court records are sealed; information is not available.