Re: NUREG-1400 Release Fractions -Reply

[rkathren@tricity.wsu.edu (Ron L. Kathren)]

There seems to be a bit of misunderstanding and/or misinformation with
respect to the Brodsky 'magic number'.  The so-called Brodsky 'magic number'
is a value for the RESUSPENSION FACTOR -- ie the ratio of airborne activity
concentration to surface contamination level -- and therefore has dimensions
of reciprocal length.  Resuspension factors have been extensively studied,
and as reported in the literature range over at least 12 orders of magnitude
(that's right, 12 orders of magnitude).  Brodsky concluded that 10E-6 would
generally be a suitable 'rule of thumb' value to use for the resuspension
factor for facility design purposes, and planning for operational health
physics.  This is the ONLY application of the resuspension factor.

He then extended his observations and noted an apparent numerical
coincidence been the value of !0E-6 per meter for the resuspension factor,
and other radioactivity release/intake scenarios -- eg potential fractional
intake of 10E-6 for airborne materials -- hence the 'magic number' concept.
He further noted that the use of this numerical value in seven specific
cases, one of which was resuspension factor, and another the intake fraction
from a serious transportation accident or fire, might be appropriate for
health physics planning purposes.

Most significantly, Brodsky concluded his rather provacative article Health
Phys. 39:992-100, 1980) with the following:

"Is 10E-6 a magic number?  To find out, the author pleads for much better
documentation of these factors by practicing health physicists involved in
future incidents."

Ron Kathren

..

 03:36 PM 1/23/98 -0600, Stephen McGuire wrote:
>It has been almost 3 weeks since the questions was posted, but perhaps an
answer is
>better late than never.
>
>The question concerned the release fractions and intake fractions in NUREG-1140
>and NUREG-1400 and how they relate to Brodsky's magic number of 10-6.
>
>First note that NUREG-1140 considers dose outside a building having an
accident and
>NUREG-1400 deals with worker doses inside abuilding.
>
>Brodsky's 10-6 for outside a building is based on meteorological
considerations.  He
>proposed that no one outside of a building would be likely to have an
intake exceeding
>10-6 of the material released.  NUREG-1140 evaluated that, found it to be a
valid
>assumption, build further upon it, and then added a release fraction to
determine how
>much might become airborne.  Sorensen referenced the DRAFT NUREG-1140.  The
>final NUREG-1140 (January 1988) explained the release fractions in much greater
>detail than the draft.
>
>For worker dose inside buildings, Brodsky also found 10-6 to be a valid
fraction. 
>However, the measurements supporting the conclusion were based on iodine,
which is
>very volatile.  He provided no data on non-volative materials.  NUREG-1400
expanded
>the Brodsky proposal to non-volatiles.  Considering that there are
similarities in the
>mechanisms of how materials are suspended and become airborne in both accidents
>and in workplace activities, it is reasonable that the airborne fractions
should not be
>totally dissimilar.  This was supported by some other data including a
thesis by Scott
>Pennington at Georgetown Univeristy, who looked at uranium processing and found
>that a fraction of 10-9 provided a good fit with the data (10-6 x 0.001). 
>
>I hope this is useful.
>
>Stephen McGuire, sam2@nrc.gov
>
> "Sorensen, Scott" <ssorensen@doeal.gov> 01/06/98 12:06pm >>>
>Greetings!
>
>NUREG-1400, Air Sampling in the Workplace (Sept. 1993), adopts the use
>of Allen Brodsky's "Magic Number" of 1e-6 in its methodology for
>evaluating potential annual intake from airborne hazards.  However, the
>"Magic Number" is then modified by release fractions from NUREG-1140, A
>Regulatory Analysis on Emergency Preparedness for Fuel Cycle and Other
>Radioactive Material Licensees (June 1985).  These release fractions are
>based on "severe facility fire" scenarios.  NUREG-1400  states that
>their use is "generally suitable for releases to air in the workplace."
>
>Does anyone know what is the basis behind this statement?  It appears to
>me that the NUREG-1140 release fractions were intended to be used in
>accident analyses without modification by the Magic Number.  As such,
>why is it appropriate to modify the Magic Number by these values when
>used to guestimate the need for air sampling at facilities operating
>under normal conditions?  Please note that NUREG-1400's use of release
>fractions result in a less conservative guestimate.
>
>Appreciate your thoughts...
>
>Scott A. Sorensen
>ssorensen@doeal.gov
>
>
>