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The most interesting thing about the elephant's foot was that it disproved the "China Syndrome" hypothesis. That hypothesis of course was that an uncontrolled meltdown would simply melt down through to China (not that it could really go past the core :-) However, what the elephant's foot showed was that the melted core would diffuse into the material as it was melting, eventually it loses enough mass that it goes subcritical, re-freezes and that's that.

That is why pretty much every western reactor has a reservoir of sand under the containment vehicle, if the worst of the worst happens, it melts into the sand which becomes glass.




> the "China Syndrome" hypothesis

Having seen the movie, suspect that a lot of people saw what they wanted to see, and not what the movie actually said. I'm fairly certain the comment about the core melting "all the way to China" was a joke/hyperbole.


IIRC from the movie, it wasn't that it would burrow through to China, but that it would burrow to groundwater and then become a rocket propelled by steam.


Nuclear fusion (the next gen of energy - as opposed to the current, radioactive fission) requires temperatures of 1m degrees. In case of meltdown, would the sand be enough, or would we have something closer to a China Syndrome?


No. If a fusion reactor fails, the fusion plasma would dissipate in less than a microsecond. There are no secondary outputs so the plant would simple "turn off". Unlike a fission reaction which can occur spontaneously on its own[1] the amount of energy to keep a fusion reaction going is tremendous, without that energy it stops.

[1] http://www.scientificamerican.com/article/ancient-nuclear-re...


Fission and fusion are fundamentally different in the way they work. If a fission reaction goes out of control, it can continue releasing enormous amounts of energy for days or even weeks, because it's based around releasing radioactive energy stored in the nuclear fuel.

Fusion OTOH is fusing together atoms of fuel that are relatively benign on their own - fusion is only possible at the high temperatures inside the reactor. I'm no expert on the physics, but AFAIK as soon as a fusion reactor is breached the conditions needed to sustain the reaction will quickly disappear and the reaction will almost immediately stop.


I doubt you will melt very far. For the same reason it is difficult to sustain super-liquidus magmas on earth-you just melt more material until your composition and temperature converge.

Even a fusion reactor has small thermal mass relative to the rest of the earth.




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