RESUSPENSION FACTORS

[Gary_F_Boothe@rl.gov]

     Reply to danny_l_rice@rl.gov:
     
     The problem with resuspension of radioactive materials is that it can 
     vary tremendously, depending on conditions, primarily the physical 
     characteristics of the contamination. By resuspension, I mean the 
     mechanical process by which solid materials go airborne.  That is, 
     solid materials and fine powders "evaporate" to some extent, by 
     molecular vibration, bombardment and entrainment in air.  As you say, 
     if you look in the literature values from 1.0E-4 to 1.0E-8 and even 
     less are given.  
     
     I have found that the best technical basis for resuspension factors is 
     to simply use the most likely dust loading in air.  That is, the dust 
     loading in air for extremely dusty conditions is about 1.0E-8 g/cc.  
     So, if the contamination can be expressed in terms of Ci/cc, it is 
     pretty simple to determine airborne concentrations under extrememly 
     dusty conditions.  If the contamination is truly on the surface and 
     can be expressed only in terms of Ci/cm2, I have found that an 
     effective depth of 30 microns and the 1.0E-8 g/cc number can be used 
     to calculate airborne concentrations for extremely dusty conditions.  
     These calculated numbers seem to agree well with the resuspension of 
     fine, thinly spread powders in a glovebox.  
     
     If conditions are not extremely dusty, then the 1.0E-8 g/cc number can 
     be lowered accordingly, in any magic way you want or by actual dust 
     loading measurements.  I have found that resuspension under damp 
     conditions (extremely low dust loading in air) seems to lower this 
     number by at least three orders of magnitude.
     
     I don't know if this will help, but it summarizes my experience in 
     designing airborne controls for contaminated powders.