Lou, I wish it was great work. Unfortunately, there was an important flaw once again. From Robin's Web site I obtained the total cross sections, and from your Web site I obtained the neutron capture cross sections. It is the total cross section, only one component of which is the neutron capture cross section, that should be used in the attenuation calculation. As a result, I was to a certain extent comparing apples to oranges. The primary outcome is that the data that were presented are harder to interpret than they should have been, but I think they still give a useful order-of-magnitude estimate.
This same error also appears to have been behind my conclusion, below, that your and Robin's Web sites give different maximum values for the cross sections. What seems to be going on is that there are resonances that cause the total cross section to go way up in the KeV range, but the absorption cross section, from both your site and Robin's, remains smaller in that energy region than in the low energy region of around 1E-3 to 1E-5 eV. So once one avoids confusing a graph of the total cross section with that of the absorption cross section, the two sites appear to agree fairly closely. Eric On Sun, Mar 24, 2013 at 10:40 AM, <[email protected]> wrote: > Eric, > > Great work. Thanks. > > I was not aware that official data was imprecise. Nice to know that. > > If the thermal neutron generation is actually occurring, it seems there > should be a small amount of radioactive ash (maybe short-lived) after the > reaction is stopped. I believe some of the sonofusion experiments report > this. I do not know if these reports are reliable. > > As far as build up of Ni59 - > Perhaps its cross section guarantees that it lasts only for a short time > in the reaction chain before converting to copper. > > Also, in most experiments, the liquid of the Ni-nanoparticle emulsion may > have a significant impact. > > Cheers, > Lou Pagnucco > > Eric Walker wrote: > > On Sat, Mar 23, 2013 at 5:11 PM, <[email protected]> wrote: > > > > Then you should be able to follow the same procedure, but include all the > >> natural isotopes, no? > >> > > > > I've gone back and corrected the calculation to take into account the > > missing isotopes. This time I obtained upper and lower bounds for the > > total cross section, from both Robin's Web site [1] and Lou's site [2], > > and > > I did the calculation using Robin's method along with a modified version > > of > > that method. > > > > Here are the estimated upper and lower bounds for the total neutron cross > > sections for nickel as it is found in its natural isotopic abundances. > > The > > combined cross sections are the weighted values of the cross sections for > > individual isotopes of nickel. > > > > UB Kaeri: 206 barns > > LB Kaeri: 45 barns > > UB NDS: 94 barns > > LB NDS: 29 barns > > > > On the basis of these cross sections, I calculated the upper and lower > > bounds for the transmitted fraction of an incident beam of neutrons at > 1mm > > and 10mm, using Robin's approach as well as a modified version of Robin's > > approach relying upon the mean free path described in Wikipedia's article > > on the neutron capture cross section [3]. The two sets of calculations > > agreed to within two degrees of precision, which was nice to see. Since > > they agreed, I'll just give the transmitted percentages using Robin's > > approach: > > > > UB, 1mm: 76.6 percent > > LB, 1mm: 15.2 percent > > UB, 10mm: 7 percent > > LB, 10mm: small > > > > For 1W of power being generated by way of neutron capture, assuming > around > > 10 MeV per capture, there would be about 624 billion neutrons generated > > per > > second. The number of neutrons per second that would be transmitted > > through 1mm and 10mm of inactive nickel shielding would be: > > > > UB, 1mm: 478 billion > > LB, 1mm: 94 billion > > UB, 10mm: 43 billion > > LB, 10mm: 4000 > > > > This assumes that there are no neutrons being generated in the nickel > > shielding surrounding the active core, an assumption that runs counter to > > conjecture that LENR (in Pd/D) is a surface effect. > > > > An interesting thing that I discovered as I was looking into this was > that > > Robin's Web site and Lou's Web site disagree significantly on what > happens > > to the total cross sections when the energies are small. In general, > > Robin's Web site gave values that were well below the maximums, at around > > 10E-4 MeV, while Lou's site gave values that were highest at the very > > lowest energies, around 10E-10 MeV. I'm not sure what was going on > there. > > Just to be safe, the above calculations make use of both the cross > > sections at the lowest energies as well as the maximum values for the > > cross > > sections. > > > > It interesting to note that the combined cross section can be expected to > > go way up as 58Ni transmutes to 59Ni, which normally exists in trace > > amounts but would build up over time, as 59Ni has an extremely large > > neutron capture cross section. Note that nickel would become dangerously > > radioactive over time as it was activated under this kind of neutron > flux. > > > > Eric > > > > > > [1] http://atom.kaeri.re.kr/ > > [2] http://www-nds.iaea.org/ngatlas2/ > > [3] http://en.wikipedia.org/wiki/Neutron_cross_section > > > > >
