Nuclear meltdown of fission product radioactivity, by simple convection. The second test, deliberate shut-off of the secondary coolant loop that supplies the generators, caused the primary circuit to undergo the same safe shutdown. This test simulated the case of a water-cooled reactor losing its steam turbine circuit, perhaps by a leak. This is a list of the major reactor failures in which meltdown played a role: The China syndrome (loss-of-coolant accident) is a hypothetical nuclear reactor operations accident characterized by the severe meltdown of the core components of the reactor, which then burn through the containment vessel and the housing building, then
Fukushima Daiichi nuclear disaster (Unit 2 Reactor) severely. In the hours and days that followed, Reactors 1, 2 and 3 experienced full meltdown. In an attempt to halt a meltdown, the government ordered that seawater be used to cool the reactors, as no alternative was available at the time. Because of the delay in this process, meltdown progressed, depositing most of the melted fuel at the bottom of the reactor vessel. The heat and pressure of the melting reactors, caused a reaction between the nuclear fuel metal cladding and the remaining water producing explosive hydrogen gas. As workers struggled to cool and shut down the reactors, several