PING: Steve Willner
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From: Androcles on 23 Apr 2010 16:10 "John Park" <af250(a)FreeNet.Carleton.CA> wrote in message news:hqst1r$ris$1(a)theodyn.ncf.ca... > Yousuf Khan (bbbl67(a)spammenot.yahoo.com) writes: >> Steve Willner wrote: >>> 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. >> >> What I was saying is that fission is a form of radioactive decay. >> >>>> 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. >> >> Okay, back to the original question, then. What form of radioactive >> decay are you talking about if it isn't a form of fission? >> > Fission, as I understand it, refers to a nucleus spltting into *roughly* > equal parts; it does not include alpha, beta, gamma or neutron emission, > electron capture... Oh, but it does. Your understanding is way off. http://www.atomicarchive.com/Fission/FissionMov1.shtml Fission reactions are controlled by absorbing the neutrons, the fuel rods are lowered into a core alongside graphite control rods. Once the fuel rods are in place the control rods are partly raised, allowing the neutrons to hit nearby fuel rods and triggering more fission. To shut down, the control rods are dropped and block the paths the neutrons can take. In a fission bomb no control rods exist, the fuel pieces are kept apart until a chemical explosion slams the chunks together and the fission runs away.
From: Yousuf Khan on 23 Apr 2010 17:04 John Park wrote: > Yousuf Khan (bbbl67(a)spammenot.yahoo.com) writes: >> Okay, back to the original question, then. What form of radioactive >> decay are you talking about if it isn't a form of fission? >> > Fission, as I understand it, refers to a nucleus spltting into *roughly* > equal parts; it does not include alpha, beta, gamma or neutron emission, > electron capture... > > --John Park No, fission involves one of the usual radioactive decay mechanisms, regulated by the Weak force. They have not yet found a decay mechanism in which a nucleus is cleaved immediately into two nearly equal pieces. You might theoretically find a process which ends up with the final nucleus having half the size of the original nucleus, but it would be achieved through a series of standard radioactive decay steps, such as beta decay. Also at the end you won't have two nearly equal-but-half sized nuclei, you'll only have one half-sized nucleus and a whole bunch of small nuclei no bigger than helium. Yousuf Khan
From: Yousuf Khan on 23 Apr 2010 12:24 Steve Willner wrote: > 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. What I was saying is that fission is a form of radioactive decay. >> 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. Okay, back to the original question, then. What form of radioactive decay are you talking about if it isn't a form of fission? >> 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. I had, though I had forgotten about it. The main objection to this theory is that it's not necessary to explain the processes inside the Earth, as other theories work too. It's not to say that it was wrong, just not necessary. However, this finding about geo-neutrinos would probably mean that this theory is wrong, if confirmed. >> 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. We're only able to detect electron neutrinos in our neutrino detectors right? Yousuf Khan
From: John Park on 23 Apr 2010 15:39 Yousuf Khan (bbbl67(a)spammenot.yahoo.com) writes: > Steve Willner wrote: >> 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. > > What I was saying is that fission is a form of radioactive decay. > >>> 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. > > Okay, back to the original question, then. What form of radioactive > decay are you talking about if it isn't a form of fission? > Fission, as I understand it, refers to a nucleus spltting into *roughly* equal parts; it does not include alpha, beta, gamma or neutron emission, electron capture... --John Park
From: Steve Willner on 23 Apr 2010 19:00
In article <4bd1c9da(a)news.bnb-lp.com>, Yousuf Khan <bbbl67(a)spammenot.yahoo.com> writes: > What I was saying is that fission is a form of radioactive decay. I was using "radioactive decay" to refer specifically to alpha and beta emission. That's the way I've heard it used in the past, but it could also be used more generally to include spontaneous fission. In regards to some other postings, there are a few nuclides that decay by spontaneous fission, but usually the half life for spontaneous fission is much longer than the half life for some other decay process. There seems to be good information at http://en.wikipedia.org/wiki/Spontaneous_fission but I haven't checked it in detail. Only beta emission and fission give neutrinos, so they're the processes relevant to the original topic. > Okay, back to the original question, then. What form of radioactive > decay are you talking about if it isn't a form of fission? Beta decay. Alpha decay also contributes to the Earth's internal heat production, but it doesn't produce neutrinos. Gamma emission also contributes to Earth's internal heat, but it only occurs as a result of one of the other decay processes. > We're only able to detect electron neutrinos in our neutrino detectors > right? It depends on the detector. The original article of this thread is based on electron anti-neutrinos, but other flavors can be detected by different experiments. Maybe someone on sci.physics will know whether all six neutrinos (including anti-particles) have been detected or not. Or a web search might turn something up. -- 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 |