Georeactor

[daleboyce@charter.net]

Jaro,



Thanks for the reply.  I accept that the directional/delayed coincidence

method would work.  Pretty neat trick.  However, I'm having problems

accepting the premise of a georeactor in the core for the following reasons:



Uranium is not expected to concentrate in the core like the platinum metals

such as iridium.  It's chemical properties cause it to fractionate into the

crust.  The earth's crust contains about 1.4 ppm of uranium on average while

meteorites contain about 0.008 ppm. Meteorites are thought to better

represent the mantle/core. See for example:



http://www.uic.com.au/nip78.htm



I also see a problem with the physics.  The U238 decay chain releases about

52 MeV per decay(8 alphas and several betas).  A U235 fission releases about

200 MeV.  So for the U235 fission to reach the energy output of the U238

decay chain the fission rate would have to be 25% of the U238 decay rate.

Since U235 is about 0.7% of uranium present day, the partial half-life due

to fission would have to be about 1.6E8 years to reach the energy output of

the U238 decay chain. This is more than 4 times shorter than the physical

half-life of U235. Without breeding all of the U235 would have been burned

up in fission by now.



Given today's natural abundances, the ratios of fission cross section in

U235 vs. the capture cross section in U238 are such that the fission and

capture rates are similar depending on the neutron spectrum. So in earlier

times the fission rate would have exceeded the capture rate until the U235

abundance reached a balance with the breeding rate.  Without doing a lot

more calculating I can't say this would save the possibility.  I would say

that it would be very fortuitous if it did, and one would expect that

U235/U238 ratios would be different from the crustal material we observe

today.



I found a reference online (which I failed to bookmark) that estimated the

average heat loss from the earth to be 70 to 80 milliwatts per square meter.

This is a difficult number to measure BTW since noon insolation reaches 1 kW

per square meter, temperature gradients are hard to characterize. The earth

is about 5E14 m^2 so we need about 4E13 watts 40 (TW) to match this heat

loss, less power is needed since it is thought that the earth is cooling.



If I plug in the concentrations from uranium given above to various parts of

the earth's structure I come up with way too much heat from the U238 chain

using crustal concentration, and too little power using meteoritic

concentration. The lower mantle makes up almost half the earth's mass, and

should have an intermediate concentration of uranium. Oh and I forgot to add

in thorium and potassium which contribute as well, and fractionate in a

similar way to uranium.



Dale







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