On Fri, Mar 25, 2016 at 10:16 PM, Bob Cook <frobertc...@hotmail.com> wrote:
If you believe slide 13 of the AP report, there was very little Zn in the > fuel to start with and even less after reaction. Ni amounted to 60 weight > % to start and Zn was reported to be .0135 %. There was not much Zn-64 in > any case. > I've found the calculation a little hard to work through, lacking knowledge of and information about how the percentages in the Parkhomov slides are derived, but consider that the slides allege that 4.4 percent of the starting nickel was 64Ni. I assume these percentages are derived from the ratio of counts at the m=64 mass peak to counts at all mass peaks for naturally occurring isotopes of nickel (m=58,59,60,61,62,64). That is to say, I think we're dealing atomic percentage rather than percentage by weight. Rather than try to disentangle the original counts for different mass peaks from this information, I'll note that the natural abundance of 64Ni is 0.9%, in contrast to Parkhomov's starting NA of 4.4%, and just take a shortcut and assume for the sake of argument that ~ 0.9/4.4% = 20% of the counts at m=64 were actually 64Ni and the remaining 80% of the alleged 64Ni were actually 64Zn, giving ~ 0.8 * 4.4% = 3.5% 64Zn as a fraction of the nickel present. Since the percentage of nickel by atom was 36.4% (from slide 13), that gives 0.035 * 36.4% = 1.2% 64Zn in terms of 100% of atoms. Because the natural abundance of 64Zn is 48%, that implies that there should have been 1.2%/0.48 = 2.5% zinc atoms per 100% of atoms. The reported value was 0.7%, which is off by a factor of 4, but not 40 or 400. So unless I've made a big error, we're in the right ballpark. If there was a lot experimental uncertainty in the reported amounts, e.g., because the fuel was heterogeneous or the procedure was not very accurate, then being off by a factor of 4 is not difficult to imagine. Eric
