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Hello, this is probably a pretty simple question but, when performing gamma spectroscopy on natural uranium ore specimens, why do we look for the decay daughters of uranium vs the uranium itself. All of the sample spectra that I have seen look at different daughters and not the specific isotopes of uranium itself. Are the energies too low to detect or what?

Gamma spectroscopy of ore has no real gamma signature for uranium beyond some low end, under 100kev, electron shell stuff mostly due to electron shell stuff (XRF) from all the daughter gammas kicking them up from the Uranium. Ore in a gamma spectro is all about the radium daughters. Modern ores can have their uranium percentage content readily determined by counting the radium daughters against a known, graded sample of ore.

Please note that the above information is for a common NaI:Tl crystal gamma spec. of the type the advanced amateur is most likely to be able to have and successfully operate.

Typically, the calibrated sample is in a kit of samples of various percentages in the form of a fine powder. In the kit, is an empty container of the exact size and volume as those of the calibrated samples. The unknown ore is pulverized to a similar powder size, loaded into the empty container. A gamma spectrograph is made of the unknown and printed out. One of the calibrated samples is selected and again a spectrograph is done on it. The gamma pulse heights (counts for significant gamma peaks) are compared and a little simple math can give a rough estimate of the Uranium content percentage in the unknown. If their is a sample in the kit close to what the math says, it is run through the spectro and the unknown ore should be very close as a double check on the math.

I have done this with some calibrated samples I have on some of the Utah ore I have collected.

In the old days, an electroscope was used to determine and ore's percentage of uranium.....Again, this still used the daughter's radiation which is always much more than the uranium radiation. All samples are in powdered form in a controlled volume, both then and now.

Richard Hull

Thank you very much for the detailed answer. For some reason, there isn't much info on this online. Not sure why, but hey, it is what it is. Again, thanks.

Ben,

Just adding to Richards answer, you can find the common U238 x-rays etc and other isotopes of Uranium here.

http://nucleardata.nuclear.lu.se/toi/nu ... iZA=920238

http://nucleardata.nuclear.lu.se/toi/

A couple of low intensity gamma rays , which are mostly drowned out by other gamma and x-rays from uranium daughters.

Steven