|1.||(in a nuclear reactor) the melting of the fuel rods as a result of a defect in the cooling system, with the possible escape of radiation into the environment|
|2.||informal a sudden disastrous failure with potential for widespread harm, as a stock-exchange crash|
|3.||informal the process or state of irreversible breakdown or decline: the community is slowly going into meltdown|
|meltdown (mělt'doun') Pronunciation Key
Severe overheating of a nuclear reactor core, resulting in melting of the core and escape of radiation.
The most serious accident that can occur at a nuclear reactor. In a meltdown, the radioactive material in the reactor becomes very hot, melting some or all of the fuel in the reactor. A meltdown may or may not be followed by the release of radioactive material to the environment. A partial meltdown, with very little external radiation, occurred at Three Mile Island in 1979; a complete meltdown happened at Chernobyl in 1986.