Re[2]: Kr-85

[Field@amrf-po.pmeh.uiowa.edu]

        Bob,

          I did not see any concern from cloud submersion during the
          venting of Three Mile Island when many curies of Kr85 and
          Xenon-133 were released.  Bill Kirk at the Health
          Department in Pennsylvania wrote his Ph.D. Thesis on Kr-85
          and oversaw the venting at TMI as the onsight EPA official.
          I am sure he would have some invaluable insights concerning
          Kr85.

          Bill Field
          University of Iowa
          bill-field@uiowa.edu





>Dr. Franz-
>
>A look at your books (I appreciate your caveate of being at home) will show
>you that Kr-85 is not a pure beta emitter, albeit an infrequent gamma
>emitter, its signature can be observed in nuclear power reactor spectra at
>514 keV with a low abundance of 0.43%, with an averge beta energy of 250
>keV, thus resulting in a significant external skin dose factor from cloud
>submersion. (The average energy for C-14 is about 49 keV.)
>
>I have the good fortune of working at home and thus have the convenience of
>many of my references at hand to confirm my recollections.
>
>Bob Hearn
>Unafilliated
>rah@america.net
_____________________________________________________________

Bob,

Thanks for your comment. I work in environmental monitoring and therefore
the low abundance of 0.43% of the gamma rays is of no help in determination
by high resolution gamma spectrometry - not to talk about the problem to get
the Kr-85 from air into a usable and reproducable geometry (activated
charcoal for instance) and how to calibrate it .... So I did not take it
into consideration. We can determine Kr-85 by using our (liquid)
scintillation spectrometers, using a plastic scintillator. The spectra of
the betas emitted and recorded due to the transfer from the plastic
scintillator show up at the pulse height range of C-14 when using a liquid
scintillation cocktail - forgive my misleading mentioning of "energy". I
usually criticize the uncorrect mixture of "energy" and "pulse height" in
liquid scintillation spectrometry, but now I have done it myselve.... Sorry.

But I still think that the activity concentration of Kr-85 in air and even
in isolated Kr is so low, that nobody has to be afraid of it and that no
significant exposure can be recorded from Kr in the high pressure steel
tanks. The situation is of course different when you are immersed in a Kr-85
cloud from nuclear fuel!

Franz
Schoenhofer
Habichergasse 31/7
A-1160 WIEN
AUSTRIA/EUROPE
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e-mail:         schoenho@via.at