A meaning: it means that a nuclear power plant reactor is going to explode
WARNING CORE OVERHEATING NUCLEAR MELTDOWN IMMINENT
by WordMeanings July 17, 2019
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Getting so intoxicated that you become unable to form rational thoughts thus completely embarassing yourself in front of friends and/or strangers.
Chris drank a fifth of Jack by himself and had a nuclear meltdown, falling down in the street and cutting his hands open then stealing a package of string beans from a deli and throwing them at random strangers.
by Johnny Riviera January 9, 2005
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An situation when the temperature inside reactor core reaches such high levels that the fuel rods (made from Uranium) begin to melt their way down and destroy the reactor.

It usually happens when fuel rods cannot be cooled by a cold substance (for example heavy water) and they start vaporising every single molecule of water nearby, thus accelerating the process of building heat. The only thing operators can do now to stop it is to drop control rods, but it can be impossible because of built up pressure (that's how Chernobyl happened). When the control rods are down, the nuclear power plant crew still needs to resume water delivery to the reactor because of nuclear decay

TL:DR Nuclear fuel gets hot and burn it's way down the reactor.
Guy from Fukushima: The tsunami shut down our water pumps and now now the heat level is over the critical point. We have to evacuate whole wing of power plant and get fireman over here. Tell them there's high risk of Nuclear meltdown.
by Tomsow(12) January 28, 2020
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