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
Nuclear meltdown was replaced by better-based newer studies, and now the Nuclear Regulatory Commission has disavowed them all and is preparing the overarching State-of-the-Art Reactor Consequence Analyses <nowiki>[SOARCA]</nowiki> study - see the Disclaimer in NUREG-1150.) It has not been determined to what extent a molten mass can melt through a structure (although that was tested in the Loss-of-Fluid-Test Reactor described in Test Area North's fact sheet). The Three Mile Island accident provided some real-life experience, with an actual molten core within an actual structure; the molten corium failed to melt through the Reactor Pressure Vessel after over six hours of exposure, due