Re: Fe-60, can it occur in NPReactors?

[daleboyce@charter.net]

Forgive me I'm doing this on the fly so I don't know the result I'll get.  I'll be doing a lot of handwaving (guesstimating) since I don't have all of the necessary data.There are two mechanisms that I see for producing it.  Multiple neutron capture on Fe58 and fission. 



It is certainly produced at some level, albeit tiny. It comes from neutron capture in radioactive Fe59 which is from neutron capture on Fe58. I don't have a good reference handy that lists saturation activity for Fe59 in a reactor. If you can find the Fe59 activity you can calculated the number of atoms of target material you have(not very many. About 2e17 atoms/Ci of Fe59 or 20ug/Ci)) and compare that to the number target atoms of Fe58 you have (a whole bunch comparatively about 3e22 atoms of Fe58/Ci of Fe59 assuming a flux of 1e12n/cm^2/sec). Higher fluxes improves the ratio.  Estimate a capture cross section (for the heck of it let's assume the Fe59 cross section is the same as that for Fe58).



This assumed, the saturation activity would be the ratio of target atoms Fe59/Fe58 or about 6 uCi Fe60/Ci of Fe59.  Now pick a number of years for the ingrowth in you component.  This isn't fuel so it is probably more than three years.  Let's say 10 years for a saturation factor of 7e-5 giving a ratio of Fe60/Fe59 of 4.4E-10.



Somewhere out around 150 years or so you might start to see a tail in the Co60 decay depending on the Fe58/Co59 ratio in your stainless.



You might have a better chance of seeing it directly from fission though I doubt it. At A = 72 the fission yield is 0.000027% and is dropping about a factor of 3 per unit mass.  3^12 is about 500,000 so maybe 2E-13 atoms/fission.  A kilogram of U235 fission is a GW day so 3 years of running is about a metric ton of fissions =1e6/235*6e23 = 2.6e27 fissions.  2.6e27 * 2e-13/fission = 5e14 atoms of Fe60 or about 100 Bq or so.



If you're seeing any there is some exotic mechanism that I'm missing.



Hope this helps



Dale



daleboyce@charter.net



  ----- Original Message ----- 

  From: Szakács Sándor 

  To: radsafe_Lista 

  Sent: Wednesday, April 07, 2004 4:34 AM

  Subject: Fe-60, can it occur in NPReactors?





  Dear Radsafers,



  pls help if you can re this exotic nuclide: Fe-60. Does it occur in Nuclear Power Reactor waste, or core (fuel rod deposition)? How can it appear? In the sixth edition (1967) of Lederer-Hollander-Perlman's Table of Isotopes there is hardly any information. Because of its 59 keV (Co-60m) gamma decay could be easily identified as Am-241 by the gamma spectrometer software, causing discrepancy with the alpha counts of the same smear sample population.



  I've seen some documents (DOE? NRC?) re the permitted activity levels of Fe-60 but couldn't find anything else on Internet. Search or literature tips welcome.



  Thanks and best regards,



  Sandor Szakacs

  lazsadis@okk.antsz.hu

  National Research Inst. for Radiobiology and Radiohygiene, 

  Budapest, Hungary