Re: Georeactor

[daleboyce@charter.net]

RE: GeoreactorThanks Jaro,



The second link you provided was especially helpful. I haven't fully digested it, but I follow most of it. One thing I am stuck on is I come up with 4.6 TW in the decay energy of the combined U235 and U238 chains using the masses given in Table 1. as opposed to the 1.3TW cited in the paper.



The density of uranium silicide is less than that of iron metal (ANL website). The following indicates that enstatite chondrite would come from the surface of a body, and is talking explicitly about Abee cited in your second link.



http://www.meteorlab.com/METEORLAB2001dev/abeetxt.htm



I've long heard about the He3 anomaly. My lab in grad school was on a floor that was spilt between nuclear chemists and meteorite folk, and there was a lot of overlap in the groups.  The georeactor concept is interesting because it explains the He3 problem, but I still have some doubts. I'm trying to keep an open mind, and will continue to dig into it.  



Dale









----- Original Message ----- 

  From: Franta, Jaroslav 

  To: radsafe@list.Vanderbilt.Edu 

  Sent: Friday, April 16, 2004 10:50 AM

  Subject: RE: Georeactor





  Dale, 



  The questions you raise below have been addressed numerous times in various publications, including the Dutch paper I referenced in my initial post of this thread (ie. http://www.nuclearplanet.com/0404046.pdf ).



  I quote: 

  "Calculations at Oak Ridge National Laboratory (Hollenbach and Herndon, 2001) show that a 

  planetary-scale nuclear reactor can operate over the lifetime of the Earth as a breeder reactor" 

  The paper is also available through a link at the nuclearplanet.com web site, at http://www.pnas.org/cgi/reprint/98/20/11085.pdf



  Regarding the uranium question, 

  " The possibility of a nuclear georeactor is linked to the state of oxidation in the deep interior of the Earth. Herndon has convincing arguments for a state of oxidation like an enstatite chondrite, different from the more oxidised, ordinary chondrites considered by Birch. 



  As a consequence of the highly reduced state some so-called lithophile elements including some Si, Mg, Ca, U and possibly Th occur in part of the core. These elements, tending to be incompatible in an iron alloy, are expected to precipitate at relative high temperatures. Due to their density MgS and CaS will float to the core-mantle boundary, whereas uranium sulphide (US) and nickel silicide will sink to the Earth's centre.



  At pressures that prevail in the core, U and Th, being high-temperature precipitates and the densest substances would tend to concentrate in the Earth core by the action of gravity. In that process it will ultimately form a fissionable, critical mass. Fission produces less (half) dense fission products that tend to separate from the more dense actinides. In this way a critical reactor condition can maintain. "



  This is again from the Dutch paper. 



  Several of Herndon's papers on this subject are available in pdf format on the nuclearplanet.com web site. 



  Also, according to a recent paper in Nature (vol.427, 505 - 509, 5 February 2004); 

  Mixing, volatile loss and compositional change during impact-driven accretion of the Earth 

  ALEX N. HALLIDAY 

  <snip> "....impacting core material did not always mix efficiently with the silicate portions of the Earth before being added to the Earth's core. "<snip>



  Thanks for your interest. 



  Jaro 



  http://www.cns-snc.ca/branches/quebec/quebec.html 



  ^^^^^^^^^^^^^^^^^^^^^^^^^ 









  -----Original Message----- 

  From: daleboyce@charter.net [mailto:daleboyce@charter.net] 

  Sent: Friday April 16, 2004 11:00 AM 

  To: radsafe@list.vanderbilt.edu 

  Subject: Georeactor 







  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