[meteorite-list] Earths core

[stan .]

>    Is it possible that a reactor in the core would simply be large enough
>to self-moderate?  Any nuclear engineers out there care to have a shot
>at this?

it would have to be.. dont forget that the core is liquid (discounting the 
solid inner core, as presumably it wouldnt differentiate very much) and 
subject to immense confining pressure. if a region achieved criticality it 
would create a local hotspot, and presumably disrupt it's self - if it didnt 
energy output would increase exponentially till the point that very bad 
things would happen, provided there was enough fissile material locally

AFIK the natural reactors that have been seen in dense areas of uranium ore 
were moderated by ground water. the reactor was critical when groundwater 
seeped into the ore, then shut it's self off as the building energy forced 
out superheated water.

on a related note - there have been several prompt critical reactors built. 
basically little more than 2 hunks of fissile material that start a nuclear 
chain reaction when brought close enough together. Such reactors produce 
energy at an exponentially increasing manner untill they are either shut 
off, or destroy themselves via overheating - melting or actually fragmenting 
from shock due to rapid heating (there arent too many ways to heat a 110 lbs 
block of uranium from room temp to 3000 degrees in 2 seconds, but an 
uncontrolled chain reaction is certainly one of them! :) )

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