Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Horace Heffner's message of Tue, 14 Mar 2006 04:05:24 -0900: Hi Horace, [snip] >A LiBr in D2O solution might also work as a neutron moderator plus >energy extractor. With a molecular weight of 86.85 and solubility of >2540 g/l, that's about .2 g/cm^3 of lithium. What was wrong with your original suggestion of LiOD? Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
A LiCl in D2O solution might also work as a neutron moderator plus energy extractor. With a molecular weight of 42.39 and solubility of 1300 g/l, that's about .21 g/cm^3 of lithium. The problem with LiCl is the 3x10^5 half life of 36Cl. LiBr looks better. LiI also has high solubility but some unfortunate byproducts. Horace Heffner
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
A LiBr in D2O solution might also work as a neutron moderator plus energy extractor. With a molecular weight of 86.85 and solubility of 2540 g/l, that's about .2 g/cm^3 of lithium.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
Steven Krivit wrote: Who has ever seen a major science journal expose the flaws of hot fusion in such a straightforward and raw manner? Is this as new as it appears to me? If you are interested, I'll send you the article. Steve Send it to me. I've got an interest in that question.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Jones Beene's message of Sun, 12 Mar 2006 18:42:48 -0800: Hi Jones, [snip] >Hi Robin, > >You said: According to >http://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=H-2&n=2 >the (n,2n) cross section for 14 MeV neutrons on D is 177 mb > >That sounds about right - but this is very low - and if memory >serves this is actually about the same as the capture >cross-section of oxygen for thermals - and you know how rare that >is - plus since you get many more collisions at thermal energy - >you will actually loose neutrons to the oxygen of heavy water >faster than you can make extra neutrons via (n,2n) The thermal neutrons are not really the problem, because they get grabbed by the Li long before anything else gets them. However what I did neglect to take into account are the competing reactions with Oxygen for the high energy neutrons. I.e. (n,p) Cross Section * at 14 MeV = 43.70 mb * Fission spectrum avg. = 20.26 micro barn (n,d) Cross Section * at 14 MeV = 15.40 mb * Fission spectrum avg. = 3.888 micro barn (n,alpha) Cross Section * at 14 MeV = 109.0 mb There is also (n,na) Cross Section * at 14 MeV = 36.61 mb These add up to 204.7. mb. Still there are 2 deuterons for every oxygen. The elastic scattering cross section for O16 @ 14 MeV is ~ 900 mb. So there's about a 19% chance that a fast neutron will be destroyed by oxygen during a collision with oxygen. That cuts into our supply of fast neutrons. > >> IOW we should get about 1.5 thermal neutrons out for every fast > >> neutron going in, and nearly all of the thermal neutrons are >> going >> to produce T. This should still be a breeder. > >Taking the ratio of the two - as you did is just a ballpark calc - >and not the correct way to figure it - Indeed, I miscalculated this anyway. Even using the same assumptions, it should only have been about 39%, not 47%. But that wasn't taking the oxygen reactions into account. The margin keeps getting slimmer. >but I will have to get the >experimental data out of some hard copy files tomorrow - suffice >it to say that the best TBR you can get with current technology >using beryllium and highly enriched 6Li is about 1.3 in real >tests - That sounds about right. >and the actual neutron (n,2n) ratio for any reasonable >amount of heavy water is slightly underunity - for the reasons >mentioned above. This sounds like it might be a figure for pure heavy water, not a Li6 solution. IOW in pure heavy water, at least some of the thermal neutrons will eventually be absorbed uselessly. > >Millibarn cross sections allow for much unpredictability, in >general, and it is tough to build a breeder on that kind of >rarity - you could actually get a full neutron decay before a >(n,2n) multiplication in "just" heavy water - with no lithium. While technically true of course, I don't think this would make a significant impact on statistics. Even at only thermal energies, on average a neutron would undergo hundreds of trillions of collisions before decaying (7E14). The chances of being swallowed whole by anything at some point during those trillions of collisions is so close to certainty, as to trivialize the importance of decay. With Li6 in the water, it is even more trivial. > >BTW - almost forgot - you CANNOT use dissolved lithium hydroxide >in the blanket at all - as the T will preferentially displace a D >in D2O and you will loose all of your precious tritium to >tritiated heavy water - and it becomes such a small percentage >that it is "effectively" lost. This may be possible anyway, depending on the actual amount of heavy water present. A very rough calculation yields a concentration of about 1/1000 after a year of operation. It should be possible to extract this, much as D is currently extracted from normal water. However I have no idea what percentage would be lost in the process. Besides, about 5-10% of the T would also decay in that year. (No one cares how much D is lost when producing heavy water). Bottom line, I still think this may be marginally possible, but it would require more detailed analysis to be sure, and of course real experimental evidence already gained doesn't hurt. ;) [snip] Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
Hi Robin, You said: According to http://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=H-2&n=2 the (n,2n) cross section for 14 MeV neutrons on D is 177 mb That sounds about right - but this is very low - and if memory serves this is actually about the same as the capture cross-section of oxygen for thermals - and you know how rare that is - plus since you get many more collisions at thermal energy - you will actually loose neutrons to the oxygen of heavy water faster than you can make extra neutrons via (n,2n) IOW we should get about 1.5 thermal neutrons out for every fast neutron going in, and nearly all of the thermal neutrons are going to produce T. This should still be a breeder. Taking the ratio of the two - as you did is just a ballpark calc - and not the correct way to figure it - but I will have to get the experimental data out of some hard copy files tomorrow - suffice it to say that the best TBR you can get with current technology using beryllium and highly enriched 6Li is about 1.3 in real tests - and the actual neutron (n,2n) ratio for any reasonable amount of heavy water is slightly underunity - for the reasons mentioned above. Millibarn cross sections allow for much unpredictability, in general, and it is tough to build a breeder on that kind of rarity - you could actually get a full neutron decay before a (n,2n) multiplication in "just" heavy water - with no lithium. BTW - almost forgot - you CANNOT use dissolved lithium hydroxide in the blanket at all - as the T will preferentially displace a D in D2O and you will loose all of your precious tritium to tritiated heavy water - and it becomes such a small percentage that it is "effectively" lost. You must capture the bred T as a gas - from a porous metal, preferably and cannot let it even get close to water of any kind - as it immediately displaces a lighter hydrogen and is effectively lost. Jones
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Jones Beene's message of Sun, 12 Mar 2006 16:17:22 -0800: Hi Jones, [snip] >Robin, > >> Using only Li6 (in heavy water as Horace suggested), and running >> a >> few numbers I get a neutron breeding ratio of about 2.7 (from >> the >> deuterium), i.e. for every incident fast neutron about 1.7 extra >> slow neutrons. > >Actually it is close to unity. The (n,2n) reaction is extremely >rare with most light elements - 7Li and Be - being the ONLY >exceptions. Fast neutrons simply do not breed many neutrons with >either heavy water or 6Li. [snip] According to http://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=H-2&n=2 the (n,2n) cross section for 14 MeV neutrons on D is 177 mb, while the elastic scattering cross section for 14 MeV neutrons is only 624 mb. IOW at 14 MeV there is a 28% chance that a collision will produce an extra neutron. What I did, as previously mentioned is assume that this ratio (i.e. 28%) holds constant while the energy remains above 2.2 MeV. That is not so. Actually the 177 mb drops off while at the same time the elastic scattering cross section increases. IOW the ratio drops back. A more accurate calculation results in about 0.47 extra neutrons for every initial fast neutron, not including secondaries. (It takes about 4-5 worst case collisions for the fast neutron to lose so much energy that it is no longer capable of fissioning a D). IOW we should get about 1.5 thermal neutrons out for every fast neutron going in, and nearly all of the thermal neutrons are going to produce T. This should still be a breeder. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
Robin, Using only Li6 (in heavy water as Horace suggested), and running a few numbers I get a neutron breeding ratio of about 2.7 (from the deuterium), i.e. for every incident fast neutron about 1.7 extra slow neutrons. Actually it is close to unity. The (n,2n) reaction is extremely rare with most light elements - 7Li and Be - being the ONLY exceptions. Fast neutrons simply do not breed many neutrons with either heavy water or 6Li. This is probably a bit off because it assumes that the ratio of the fission and elastic scattering cross sections is constant for any incident neutron energy above 2.2 MeV. Yes It is way off. Fast neutrons are very funny - and you simply cannot base the situation on what thermal neturons do. Fast neutrons only react certain nuclei. This has all been worked out by careful experiment, and has been known for decades. Nevertheless it takes no account of extra neutrons flowing from secondary collisions, of energetic deuterium nuclei, which in turn result from elastic collisions with energetic neutrons. So it may not be too far off. There are always too few without a true multiplier - which is the (n,2n) reaction. It just doesn't happen with light lithium or heavy water. Sorry. You need to get hold of old issues of "Fusion Technology" for the confirmation of this, but I am pretty certain of the details Since nearly all of these neutrons are going to react with Li6 to create T, this would appear to actually be a T breeder. This is based on an incorrect assumtpion. Fast neutrons do not multiply with light lithium or heavy water, so there is always less than one thermal for every incident 14 MeV high energy one (since some few will go though a meter of heavy water without interacting - even the scattering cross section for fast neturons is low). (The reaction cross section for the reaction n + Li6 -> He4 + T + 4.78 MeV is about 940 b for thermal neutrons, which totally swamps the cross section for any other potential reaction). Yes. Most thermal neutrons will react with the 6Li - the problem is that fewer are multiplied than the ones which escape, so the result is too little tritium to sustain. Taking into account the fact that there are going to be about 2.7 of these reactions for every fusion reaction, That is not a fact. In fact it is a considerably large error, because you are assuming (n,2n) multiplication in a situation where there is none. Jones
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Jones Beene's message of Sun, 12 Mar 2006 08:26:54 -0800: Hi, [snip] >To restate the facts, no tritium occurs in nature since it has a >10 year half-life. The most promising source of in-situ tritium is >the breeding of tritium from lithium-6 by neutron bombardment of >thermal neutrons - except that Li-6 is only 7.5% of natural, and >the losses drop you way below what is needed to self-sustain. You [snip] Looking at the long term, I'm not really sure that this makes any difference, for two reasons. 1) There's a huge reservoir of Li salts in the ocean, even though these are extremely dilute. 2) Even the restricted quantity available on land is likely to last long enough for us to develop reactors that no longer use the D-T reaction, hence no longer rely on Li6 availability. The huge cross section of the Li6 + n -> He4 + T reaction gives me hope that the cross section of the Hy + Li7 -> 2 x He4 reaction would be even greater. This despite the fact that the cross section for p-Li7 is quite low. IOW I suspect that the long confinement times and high densities made possible by hydrinos will drastically alter the reaction cross section. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Jones Beene's message of Sun, 12 Mar 2006 08:26:54 -0800: Hi, [snip] >CUT TO THE CHASE: > >The BEST (by far) method of getting the needed tritium is to breed >most of it from a cheaper reactor thermal blanket, as Robin/Horace >suggest using heavy water and natural lithium hydroxide - this >gives you about 75% of the tritium you need to self-sustain. This >was what we were planning on doing in the 1960s, until it was >discovered that it came up short. [snip] Using only Li6 (in heavy water as Horace suggested), and running a few numbers I get a neutron breeding ratio of about 2.7 (from the deuterium), i.e. for every incident fast neutron about 1.7 extra slow neutrons. This is probably a bit off because it assumes that the ratio of the fission and elastic scattering cross sections is constant for any incident neutron energy above 2.2 MeV. Nevertheless it takes no account of extra neutrons flowing from secondary collisions, of energetic deuterium nuclei, which in turn result from elastic collisions with energetic neutrons. So it may not be too far off. Since nearly all of these neutrons are going to react with Li6 to create T, this would appear to actually be a T breeder. (The reaction cross section for the reaction n + Li6 -> He4 + T + 4.78 MeV is about 940 b for thermal neutrons, which totally swamps the cross section for any other potential reaction). Taking into account the fact that there are going to be about 2.7 of these reactions for every fusion reaction, the net energy from this reaction increases to 12.9 MeV / fusion reaction, which is about 73% of the fusion energy. IOW the breeding step nearly doubles the overall energy output. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
Jones Beene asks: > > It there something going on, in the wider-population on > **Sundays** and in the methodology of a prevalent meme - which > tends to draw out the maximum "rant-potential" in even normally > introspective observers...? > Typical response to the Lunar Cycle, Jones. Check the vortex archives date index against this moon phase calculator. :-) Something to do with the potassium level in the Pineal Gland and the 29 day Spike of TeraHz Radiation from the moon. Something to do with Seratonin-Melatonin & "Hor Moans". Johnny Carson read my note to him to the world on this back in May of 1981 it replayed on "Best of Carson" a couple of years later. My phone didn't stop ringing for days after. :-) http://tycho.usno.navy.mil/vphase.html For Your "third eye" :-) http://tycho.usno.navy.mil/cgi-bin/vphase-post.sh
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
-Original Message- From: Jones Beene The blankets are neutron multipliers using tin/beryllium or lead to multiply neutrons. Paul Brown's battery used beryllium/copper wires but a Sr90 beta source. But that was a different thread. It there something going on, in the wider-population on **Sundays** and in the methodology of a prevalent meme - which tends to draw out the maximum "rant-potential" in even normally introspective observers...? A 95% full, waxing gibbous moon, IMO. -hohlrauml6d ___ Try the New Netscape Mail Today! Virtually Spam-Free | More Storage | Import Your Contact List http://mail.netscape.com
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
A good idea below from Robin. Might also be possible to use LiOH solution with Li at 0.175 g/cm^3 in hot solution. Maybe the O18 generated would also find a use. 8^) Horace Heffner On Mar 11, 2006, at 6:32 PM, Robin van Spaandonk wrote: ... expensive blanket/shielding can be replaced by a cheap 4 layer shield/blanket. 1) Inner layer - thin vacuum wall. 2) Thick layer of (cheap;heavy?) water, acts as neutron moderator, and removes heat. 3) Thin metal layer that chemically separates water layer from the Lithium layer. 4) Thin (and hence cheaper) Lithium layer that absorbs neutrons, slowed by the water layer, and produces Tritium. This layer can now afford to be much thinner , because the neutrons have already been slowed in the moderator (water) layer.
Re: Science exposes Hot Fusion weaknesses: March 11, 2006
In reply to Steven Krivit's message of Sat, 11 Mar 2006 16:18:52 -0800: Hi, [snip] I quote:- "This is a volume of 3400 m3, which, at an average density of about 3 g/cm3,would weigh 10,000 metric tons. A conservative cost would be ~$180/kg, for a total blanket-shield cost of $1.8 billion. This amounts to $1800/kWe of rated capacitymore than nuclear fission reactor plants cost today (8)." What is wrong with this is that the fusion reaction in question produces mono-energetic neutrons. This means that the expensive blanket/shielding can be replaced by a cheap 4 layer shield/blanket. 1) Inner layer - thin vacuum wall. 2) Thick layer of (cheap;heavy?) water, acts as neutron moderator, and removes heat. 3) Thin metal layer that chemically separates water layer from the Lithium layer. 4) Thin (and hence cheaper) Lithium layer that absorbs neutrons, slowed by the water layer, and produces Tritium. This layer can now afford to be much thinner , because the neutrons have already been slowed in the moderator (water) layer. This sort of arrangement should work, because the neutrons are mono-energetic, and hence the thickness of the water layer can be pre-determined such that it removes most of the energy from the neutrons, but allows e.g. 95% them to pass, leaving them free to enter the Li layer and react at thermal energies, where the reaction cross section is much higher, and hence the layer can be much thinner. Furthermore, this design has built in heat removal in the form of the water layer, which means that the heat removal per square meter of surface area can be much higher, and therefore the overall size much smaller, resulting in a far cheaper design. Furthermore, the heat created in the Li layer is also easily conducted back to the water layer as well, such that the water layer easily cools the entire reactor. Some of the hydrogen in the water will absorb a neutron and eventually convert to Tritium which can then be removed and used in the reactor. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
Science exposes Hot Fusion weaknesses: March 11, 2006
Who has ever seen a major science journal expose the flaws of hot fusion in such a straightforward and raw manner? Is this as new as it appears to me? If you are interested, I'll send you the article. Steve
