Re: Absence of radionuclides

[The Turners <dwturners@earthlink.net>]

Hi Claude,
For nuclear power plants many of the licensee's use the minimum detectable
concentration values in their Offsite Dose Calculation Manual to
demonstrate a specific isotope is "not present".  This allows establishing
a counting time for the specified percent uncertainty.  Procedures or
Technical specifications at older reactors sometimes designate a specific
gross activity such as less than 100 ccpm with a thin window GM or
equivalent as "no detectable activity".

Doug Turner <dwturners@earthlink.net>

At 11:36 AM 6/30/98 -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   
>
>