PING: Steve Willner
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From: Yousuf Khan on 11 Apr 2010 11:16 Steve Willner wrote: > In article <4bbd0360$1(a)news.bnb-lp.com>, > Yousuf Khan <bbbl67(a)yahoo.com> writes: >> So what you're saying is that of the 30 TW of radioactive decay >> happening naturally inside the Earth, only 3 TW comes out of the core? > > No, not at all. The distinction is between radioactive decay, which > has to occur for every radionuclide, and a reactor, i.e., nuclear > fission. Standard models of Earth's interior include radioactive > decay but no fission. I gather there has been speculation that > fission might be occurring, but according to the paper, fission can't > be more than 10% of the radioactive heat. So you're distinguishing radioactive decay from fission by what criterion? Radioactive decay is different from fission because there is no sustained chain reaction? I think that this research is an answer to a theory proposed by Marvin Herndon, about a possible nuclear reactor inside the Earth's core. The following is a good summary (albeit skeptical) of Herndon's hypothesis. *** The Nuclear Core "Herndon is captivated by a real example�the actual natural reactor that once existed at Oklo, in the African nation of Gabon, some 1800 million years ago. I don't blame him; it's a geologic wonder. The Oklo example proves that a natural fission reactor can exist, under certain unusual conditions near the Earth's surface. But it is not evidence for anything in the Earth's core. " http://geology.about.com/od/wildgeotheories/a/nuclearcore.htm *** > There's more at > http://en.wikipedia.org/wiki/Geothermal_gradient > but I'm not enough of an expert to verify much of the article. I > didn't spot anything that looks obviously wrong, though. This link acknowledges that as much as 10-25% of the heat could be from nuclear fission, and not just radioactive decay. However, it also says that radioactive decay could account for 45-90%. >> I'm always puzzled by how they can even tell whether a neutrino is >> coming from inside the Earth, from a nuclear power plant, from the Sun, >> or from a supernova somewhere. > > That's in the paper. Separation of decay neutrinos and reactor > neutrinos is by energy, which is measured in the experiment. Solar > and supernova neutrinos aren't mentioned; I'd assume they are > negligible in this experiment. The geo-reactor measurement isn't > discussed in detail -- the authors seem to consider it a minor result > -- but it comes from subtracting the expected power reactor neutrinos > from the observed reactor neutrinos. What sort of energy differences would there be between neutrinos produced in man-made reactors vs. geo-reactors? Aren't they using the same fissile materials? Actually F/32's original link in this thread showed that they had to redo the Japanese experiment in an area not as close to Japan's nuclear reactors. The Japanese nuclear reactors were affecting the background noise of neutrinos. The new Italian data allowed them to subtract out which part was from geo-neutrinos and which were man-made neutrinos. >> Didn't they also say at one time >> that the Sun was producing less neutrinos than they expected? > > That was a problem for, what, 30 years or so? The answer is neutrino > oscillations. Neutrinos measured on Earth are only 1/3 of the ones > emitted by the Sun because the "flavors" have mixed by the time the > neutrinos reach Earth. > > More at > http://en.wikipedia.org/wiki/Solar_neutrino_problem So who's to say that there isn't neutrino oscillation going on within geo-neutrinos, too? Yousuf Khan
From: Yousuf Khan on 11 Apr 2010 11:23 F/32 Eurydice wrote: > On Apr 7, 1:50 pm, will...(a)cfa.harvard.edu (Steve Willner) wrote: >> In article <aefb0bf2-deab-4c3d-8ffa-d57438031...(a)l25g2000yqd.googlegroups.com>, >> "F/32 Eurydice" <f32euryd...(a)sbcglobal.net> writes: > >> the paper puts a 95% confidence limit on its output of 3 TW. > > Is 3 TW enough to account for the heat balance of the earth? Probably depends on how good the insulation layer of the Earth is, i.e. the crust. One link that Steve W. gave says that the total output of the Earth is 45 TW, so 3 TW's of it from a natural geo-reactor would be less than 10%, i.e. 6.67% actually. I think if the heat output from the inside of the Earth were reduced somewhat, then the heat escaping from the Earth would be reduced by the fact that there would be less volcanism and tectonic plate activity. Yousuf Khan
From: Odysseus on 11 Apr 2010 16:45 In article <4bc1e7e8(a)news.bnb-lp.com>, Yousuf Khan <bbbl67(a)spammenot.yahoo.com> wrote: <snip> > The following is a good summary (albeit skeptical) of Herndon's hypothesis. > > *** > The Nuclear Core > "Herndon is captivated by a real example�the actual natural reactor that > once existed at Oklo, in the African nation of Gabon, some 1800 million > years ago. I don't blame him; it's a geologic wonder. The Oklo example > proves that a natural fission reactor can exist, under certain unusual > conditions near the Earth's surface. But it is not evidence for anything > in the Earth's core. " > http://geology.about.com/od/wildgeotheories/a/nuclearcore.htm There was a story about natural reactors on _Quirks & Quarks_ a few months ago: <http://www.cbc.ca/quirks/archives/09-10/qq-2009-11-14.html> (scroll down to "Natural Nukes"). IIRC in the interview Jay Cullen said that the concentration of radionuclides like U-235 would only have been high enough to support fission for the first couple of billion years of the Earth's history; most of the 'hottest' isotopes have decayed since then. -- Odysseus
From: YKhan on 12 Apr 2010 15:29 On Apr 11, 4:45 pm, Odysseus <odysseus1479...(a)yahoo-dot.ca> wrote: > In article <4bc1e...(a)news.bnb-lp.com>, > Yousuf Khan <bbb...(a)spammenot.yahoo.com> wrote: > > <snip> > > > The following is a good summary (albeit skeptical) of Herndon's hypothesis. > > > *** > > The Nuclear Core > > "Herndon is captivated by a real example the actual natural reactor that > > once existed at Oklo, in the African nation of Gabon, some 1800 million > > years ago. I don't blame him; it's a geologic wonder. The Oklo example > > proves that a natural fission reactor can exist, under certain unusual > > conditions near the Earth's surface. But it is not evidence for anything > > in the Earth's core. " > >http://geology.about.com/od/wildgeotheories/a/nuclearcore.htm > > There was a story about natural reactors on _Quirks & Quarks_ a few > months ago: > > <http://www.cbc.ca/quirks/archives/09-10/qq-2009-11-14.html> > > (scroll down to "Natural Nukes"). > > IIRC in the interview Jay Cullen said that the concentration of > radionuclides like U-235 would only have been high enough to support > fission for the first couple of billion years of the Earth's history; > most of the 'hottest' isotopes have decayed since then. That's true of natural reactors on the surface of the Earth, but as far as I remember about Herndon's theory is that there would be a much bigger reactor at the core of the Earth that could be sustained over the billions of years in a repeating stop-start fashion. Namely, the reactor would run for thousands or millions of years at a time, then it would get poisoned by its own waste ash and shutdown. Eventually new Uranium would filter down to the center and the ash would wash out of the center, and the cycle would repeat itself. That was his theory for why the magnetic fields would reverse them repeatedly too. Yousuf Khan
From: Steve Willner on 16 Apr 2010 16:27
In article <4bc1e7e8(a)news.bnb-lp.com>, Yousuf Khan <bbbl67(a)spammenot.yahoo.com> writes: >So you're distinguishing radioactive decay from fission by what >criterion? They are completely different physical processes. I'm sure there must be good explanations on the web somewhere. > Radioactive decay is different from fission because there is >no sustained chain reaction? Fission doesn't require a chain reaction, though it's pretty rare without one. "Reactor" (or "bomb") would imply a chain reaction, of course. >http://geology.about.com/od/wildgeotheories/a/nuclearcore.htm A good guess at the origin of the hypothesis. I hadn't seen the idea before. >What sort of energy differences would there be between neutrinos >produced in man-made reactors vs. geo-reactors? None, or at least not significant. As I wrote, the article doesn't discuss the geo-reactor upper limit in detail, but the idea is to subtract the known man-made reactor neutrinos from the detected reactor neutrinos, giving an upper limit on a geo-reactor. >So who's to say that there isn't neutrino oscillation going on within >geo-neutrinos, too? All neutrinos are expected to oscillate in flavor. That has to be taken into account in all calculations, including the ones for man- made reactors. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 swillner(a)cfa.harvard.edu Cambridge, MA 02138 USA |