Three Mile Island nuclear power plant incident

There were several root causes for the Three Mile Island Nuclear Power Plant incident that occurred in March 1979.Inadequate follow-up to... 

The infamous Three Mile Island nuclear power plant incident occurred partly because the operators became confused between the actual position of a relief valve on the containment building and the indicated position of the relief valve on their control panel. 

On March 28, 1979, a loss of containment incident occurred at the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania. An overheated reactor released radioactive steam and water to the atmosphere resulting in a mass evacuation of the surrounding community. Although no direct injuries were attributed to the incident, environmental effects were later observed and public outcry resulted in a slowdown in the growth of the nuclear power industry. 

During the major loss of coolant incident at the Three Mile Island nuclear power plant, 500 or more audio and visual warnings went off during the first minute of the incident sequence. Over 800 warnings occurred by the end of the second minute. Operators had sensory overload. They had trouble deciding which warning to act on first. The confusion contributed to the overall severity of the incident. 

Nuclear power has achieved an excellent safety record. Exceptions are the accidents at Three Mile Island in 1979 and at Chernobyl in 1986. In the United States, safety can be attributed in part to the strict regulation provided by the Nuclear Regulatory Commission, which reviews proposed reactor designs, processes appHcations forUcenses to constmct and operate plants, and provides surveillance of all safety-related activities of a utiUty. The utiUties seek continued improvement in capabiUty, use procedures extensively, and analy2e any plant incidents for their root causes. Similar programs intended to ensure reactor safety are in place in other countries. 

Even if terrorists succeeded in detonating an explosive at a reactor site, the health consequences would be limited. The reactor accident at the Three Mile Island, Pennsylvania nuclear power plant caused a small release of radiation, insufficient to cause any radiation injuries. Bypassing several safety systems caused the Chernobyl reactor incident, involving two explosions, fires and reactor core meltdown. This accident caused the following early phase health effects (1) ... 

The worst nuclear power accident in the U.S. occurred at the Three Mile Island plant in Pennsylvania. In this accident no one was killed and no one was directly injured. The event at Three Mile Island occurred from faulty instrumentation that gave erroneous readings for the reactor vessel environment. A series of equipment failures and human errors along with inadequate instrumentation allowed the reactor core to be compromised and go into a partial melt. The radioactive water that was released from the core was confined within the containment building and very little radiation was released. In the Three Mile Island incident, the safety devices worked as planned and prevented any serious injury. This accident resulted in improved procedures, instrumentation, and safety systems being implemented. 

The total number of immediate deaths attributable directly to these incidents over 35 or more years of nuclear reactor operation is less than 35—three at a military prototype reactor in 1981 in the USA and 31 at Chernobyl. However, three subsequent deaths have been reported at Chernobyl (see Appendix 7). Of the fuel meltdown incidents (excluding Chernobyl-4), eight relatively serious incidents have been selected and subjected to some analysis in the following subsection. It is noted that, of these fuel meltdown incidents, only one (Three Mile Island-2) was at an operating, fully developed power plant. All of the other incidents involved research reactors or developmental or prototype plant. Three relatively minor incidents are also reviewed where single channel fuel overheating occurred in graphite-moderated plant. 

The Rolls-Royce prefabricated nuclear plant is a 300 MW power station mounted on two barges. The nuclear Island is contained on one barge and the conventional plant on the other. Essentially the nuclear Island consists of a compact 4-loop PWR using standard components and designed to meet UK safety criteria with appropriate equipment redundancy and diversity (Fig. 1). The reactor has been designed to take full advantage of PWR safety Improvements since the Three Mile Island incident in 1979. Basic data are given in Table 1. 

In recognition of the importance which reactor safety has assumed, both within the nuclear industry and with the public at large, the remainder of the book is devoted to a study of the safety and environmental aspects of nuclear reactors. After a discussion of the biological effects of radiation, the potential hazards from both routine operation and accidents at nuclear power plants are evaluated in the light of the most recent studies. These are illustrated by reference to incidents such as that at the Three Mile Island reactor. Other... 

The Three Mile Island incident—usually referred to by its initials of TMI—occurred at a nuclear power plant located near Harrisburg, Pennsylvania, in the year 1979. The island on which the facility is located gets its name from the fact that it is 3 miles long. 

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