Re: 2X Background Reference

[Erick Lindstrom <avrel@gemini.oscs.montana.edu>]

Here's a blurb from a portion of NRC's Draft decommissioning criteria (that
relates somewhat to the thread).  The draft reg guides and supporting
documentation can be found at the NRC's homepage under "What's New at NRC."
They're soliciting comments on this....

Thanks to all who responded privately to my Gold Mine post.  I'm sure a
number of us will be commiserating in the future!

-Erick Lindstrom

 Indistinguishable from Background

The term "indistinguishable from background" has been used to describe a
level of residual radioactivity which
cannot be distinguished from the background radiation present at a facility,
using existing survey methods.
Amounts of material that are indistinguishable from background are, by the
provisions of 10 CFR 20.1404,
acceptable for meeting the reduced documentation requirements for
demonstrating ALARA.

To apply the "indistinguishable from background" criteria, the concentration
of individual radionuclides comprising the residual radioactivity at a site
are compared to the concentration of those same radionuclides present in
local background areas that have been matched to the site in terms of
geological, chemical, and biological attributes, but which have not been
affected by site operations. This comparison establishes a site-specific
criterion for individual radionuclides that is dependent on the local
variability of background. The distribution of residual radioactivity that
is measured in affected areas on site is compared to the distribution of
background radionuclides measured in unaffected areas (reference areas),
with compliance dependant on the distributions being statistically
indistinguishable. The implementation of this criteria will vary depending
on the background level for all radionuclides at the site, the temporal and
spatial variations in background at the site, and the radionuclides under
investigation.


 Erick Lindstrom
 Radiation Safety Officer
 309 Montana Hall
 Montana State University
 Bozeman, MT  59717-0244
 Phone: (406) 994-2108
 Fax:	(406) 994-4792
 avrel@gemini.oscs.montana.edu