Conclusions
A steady-state, planetary-scale reactor, continuously operating throughout geologic time, was maintained in the numerical simu- lation through the instantaneous removal of fission products. In a reactor deep inside the Earth, one would expect fission products, having an average density about 60% that of actinides, to diffuse radially outward as the fuel reconcentrates radially inward because of gravity. Variable andor intermittent reactor operation would be the natural and expected consequence. Nuclear fission reactor variability, we suggest, is evidenced by the observed reversals of direction and changes in intensity of the geomagnetic field (2). Preliminary results suggest that, during the first 1.5 billion years after the formation of the Earth, geomagnetic reversals might have been less prevalent than in recent times. Clearly, further investiga- tions, both nuclear and paleomagnetic, are necessary for a more precise characterization.
Nuclear fission, as shown in the present paper, provides a viable mechanism for the deep-Earth production of 3He, rather than the assumed origin from a yet non-degassed part of the Earth. The helium observed in such geological samples, the authors suggest, may be evidence of deep-Earth nuclear fission. The absence of cross-section data for neon, the next lightest noble gas, precluded calculating fission and decay yields for this element. Comparison of calculated and measured results for neon may provide further evidence. Detection of 10Be in rock originating from deep-mantle magma would provide strong evidence of deep-Earth nuclear fission because of its relatively short half-life and the fact that the only other significant mechanism for 10Be production takes place in the upper atmosphere.
In terms of energy production, a nuclear fission geo-reactor is clearly an acceptable alternative to previously postulated energy sources for the geomagnetic field, mainly, the latent heat of fusion presumably released during the assumed growth of the inner core (31). But unlike release of the latent heat of fusion from inner core growth, nuclear fission geo-reactor output can be variable andor intermittent, a fact that is quite consistent with the observed variability of the geomagnetic field.
A nuclear reactor actinide subcore, surrounded by a subshell, possibly fluid or slurry, composed of fission products and lead from radioactive decay is expected to exist at the center of the inner core of the Earth (6). Moving charges create magnetic fields. A nuclear fission geo-reactor will produce a plethora of charged particles and copious amounts of ionizing radiation. One might wonder whether the geomagnetic field might origi- nate, in some yet unspecified manner, from this assemblage rather than from fluid motions in the main core of the Earth.
This research was performed at the Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC, for the U.S. Department of Energy under contract No. DE-AC05– 00OR22725.
Hollenbach and Herndon