RE: Comments on NRC Soil Limits

["Frame, Paul" <FrameP@orau.gov>]

In response to the complaints (forgive me if I am so bold as to use the term
"whines") that the NRC generic soil limits can be impossible to distinguish
from background:

In 10 CFR 20.1402 the NRC states: "A site will be considered acceptable for
unrestricted use if the residual radioactivity that is distinguishable from
background radiation results in a TEDE...that does not exceed 25 mrem"
 
The point is that the NRC regulations are saying that the residual
contamination "is distinguishable from background"

MARSSIM refers to, but does not describe, the use of Scenario B in which the
licensee releases the property if the residual contamination cannot be shown
to be distinguishable from background.  The methodology for implementing
Scenario B is described in detail in NUREG 1505. The latter states
"Demonstrating indistinguishability from background using scenario B will be
a useful option when the residual radioactivity consists of radionuclides
that appear in background and the variability of the background is
relatively high. Background variability may be considered high when
differences in estimated mean concentration measured in potential reference
areas are comparable to screening level DCGLs."  The NRC even provides some
guidance wrt Scenario B in Draft Reg Guide 4006.

With regard to the comment that the field instruments must be capable of
detecting the contamination at the DCGL so that the sampling locations can
be identified, this is simply not true. The sampling points used to
determine compliance are located randomly or in a grid like pattern. 

MARSSIM does put requirements of a sort on the scan sensitivity of a survey
instrument but it also recognizes that some nuclides cannot be easily
detected.  In such cases, MARSSIM directs the licensee to work out a
reasonable approach in consultation with the regulator. 

The key is for the licensee and the regulator to work together and make
reasonable accommodations to the other party's need. If we go into this
process assuming that the relationship is going to be adversarial, it
probably will be.

Paul Frame
Professional Training Programs
ORAU
framep@orau.gov
http://www.orau.gov/ptp/ptp.htm
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