Corium (nuclear reactor) from the pre-meltdown reactor or be due to spontaneous fission of reactor-created actinides. In the absence of adequate cooling, the materials inside of the reactor vessel overheat and deform as they undergo thermal expansion, and the reactor structure fails once the temperature reaches the melting point of its structural materials. The corium melt then accumulates at the bottom of the reactor vessel. In the case of adequate cooling of the corium melt, the melt can solidify and the spread of damage is limited to the reactor itself. However, corium may melt through the reactor vessel and flow out or be
Nuclear reactor accidents in the United States damage costs include destruction of property, emergency response, environmental remediation, evacuation, lost product, fines, and court claims. Because nuclear reactors are large and complex, accidents onsite tend to be relatively expensive. In the U.S., at least 56 nuclear reactor accidents have occurred. The most serious of these U.S. accidents was the Three Mile Island accident in 1979. According to the Nuclear Regulatory Commission, the Davis–Besse Nuclear Power Station has been the source of two of the top five most dangerous nuclear incidents in the United States since 1979. The United States Government Accountability Office reported more than 150 incidents from