Re: NUREG-1400 Release Fractions -Reply

["Dr. Marvin Goldman" <mgoldman@ucdavis.edu>]

>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
>>
>>
>>

Reply:
For an up-to-date coverage of resuspension factors, note there is no single
magic number, (It's particle size ,AMAD, dependent). Contact
LAnspaugh@aol.com direct for the latest on environmental resuspension.
mgoldman@ucdavis.edu