I’ve been putting this off for a long time, but I think it’s finally time to eviscerate the “georeactor” hypothesis, which was floating around some pro-nuclear websites a while back. The idea goes that the Earth’s core is a huge fast-breeder reactor, constantly extracting waste by settling it out and generating more fuel by converting uranium-238 into plutonium using a critical assembly (’seed’) of ~30% U-235 surrounded by a ‘blanket’ of U-238. It is utterly, totally, and completely wrong.
1. There is no way to make natural uranium (at any time in the past) go critical in the fast spectrum, which is required for breeding in the uranium-plutonium fuel cycle. Presumably, there is no huge supply of heavy water in the Earth’s core, or external neutron source; furthermore, settling-based arguments for isotope separation would form a perfectly inverted assembly (i.e., the U-238 would form a ball, with the U-235 as a small shell around it, which does not a seed-and-blanket configuration make). That settling does not actually happen; neither would the required settling out of fission products, and certainly not at the rate required. If correctly assembled, this reactor would work; however, no mechanism is proposed that would in fact assemble such a configuration.
2. Uranium would not settle to the center of the Earth, as it is not pure uranium in nature. Yellowcake is actually less dense than the iron and nickel in the inner and outer core. The minuscule amount of uranium found in metallic form in some meteorites cannot account for all the uranium on Earth, or why that uranium is not in this chemical form elsewhere.
3. The amount of uranium necessary to form a georeactor would make the Earth significantly heavier than it actually is, which would alter the planet’s orbit. Nowhere is it shown where this material actually comes from, nor is the lack of stable fission product daughters in the mantle explained.
4. The neutrinos from this huge hypothetical reactor have never been detected.
5. There is enough heat output from decay heat to explain the Earth’s internal heat content. The georeactor hypothesis does not explain where this heat goes, or where the extra heat from the decay of highly-radioactive fission products goes.
6. The rotation of the iron core relative to the rest of the planet fully explains the Earth’s magnetic field. Without even invoking Occam’s Razor, the georeactor hypothesis must explain why this effect does not work. This explanation is not provided.
7. A variation on the georeactor hypothesis states that Jupiter is a fission-fusion hybrid reactor, similar to the crackpot idea circulating around the internet a few years ago that said that the Galileo probe’s plutonium would cause a thermonuclear explosion inside that planet upon reentry. This is so laughably wrong it needs no more explanation. Even stranger versions of this concept suggest that protostars are started by fission reactors, which does not even begin to explain where the first stars came from, as uranium is formed exclusively by supernovae. If a purely thermonuclear mechanism is present for the first stars, why should it not work for later ones?
8. Producing the amount of helium inside the Earth does not require any more alpha radiation than comes from the uranium decay chain. The georeactor hypothesis does not explain the absence of this extra helium.
Dear friends, this does not make us look good. It makes us look bad in the scientific community and gives the anti-nuclear activists ammunition. Do we “need” an example of a natural fission reactor to make nuclear power environmentally friendly? Absolutely not. Do we have one? Actually, yes: Oklo–which is an actual reactor whose existence is accepted by the scientific community. The last thing we need is for anti-nuclear activists to be able to lump Oklo together with the georeactor, which is what could happen if we don’t let this clown Herndon wither off in the hole in the wall from whence he came and in which he belongs.
Filed under Crackpots, Physics, Strange
Posted on March 31, 2007 by Stewart Peterson | 4 Comments »




