Re: Absence of radionuclides

[Schoenhofer <schoenho@via.at>]

At 11:35 30.06.1998 -0500, you wrote:
>The old 10CFR20 had a method in Appendix B to determine the absence of any
>radionuclides in a mixture.  If each 'absent' radionuclide was less than
10% of
>it's MPC and the sum ratio of 'absent' radionuclides to their respective MPCs
>were less than 25%, than those radionuclides were absent from the mixture.
 The
>new Part 20 requires that the absence of the radionuclides be demonstrated. 
>These appears to be another case of "if it's detectable, it's there."
Have any
>NRC licensees had to 'demonstrate' the absence of radionuclides in a
mixture? 
>If so, how?
>
>Claude Flory
>Northeast Utilities
>floryca@gwsmtp.nu.com   
>
>---------------------------------------------------------

My laboratory is in charge of controlling waste water from two nuclear
research installations in Austria. At one of these installations compliance
with the regulations valid for the installation is expressed in a formula
which regulates the maximum permissible concentrations of various
radionuclides (like tritium, C-14, Ra-226, Sr-90.....) and groups of
radionuclides (alpha-emitters, beta-emitters). We check by performing an
LSC-analysis with a gel-forming cocktail and analysing the pulse-height
spectra. It is easy to distinguish alpha-emitters because of their
relatively sharp peaks. If no such peaks can be seen, then Ra-226 and other
alpha-emitters can be excluded. For Sr-90: If in the high energy range no
counts above background or only slightly elevated are registered, then no
Sr-90 (and Y-90) is present. The energy range of C-14 can be checked and if
it is below the MPC then also C-14 is below the MPC. Tritium shows a
characteristic peak in the lowest-energy range and after excluding
chemoluminescence, which is possible with our Quantulus ultra low-level
counters, we can estimate easily the tritium concentration - if necessary
we use an internal tritium standard to calculate the efficiency. 

This all is done with just one single measurement (except when an internal
standard measurement is necessary).

With this method you could state "If it is detectable, it is there" - which
is obviously true, but moreover you can confirm that MPC's are not exceeded.

This method might be applicable to your problem. Further inquiries to my
e-mail address welcome. Good luck!

Franz

 
Franz Schoenhofer
Habicherg. 31/7
A-1160 Vienna
Austria
Tel.: +43-1-495 53 08
Fax.: same number
mobile phone: +43-664-338 0 333
e-mail: schoenho@via.at

Office:
Federal Institute for Food Control and Research
Department of Radiochemistry
Kinderspitalg. 15
A-1095 Vienna
Austria
Tel.: +43-1-40 491 520
Fax.: +43-1-40 491 540
e-mail: schoenhofer@baluf.via.at