TRANSURANIC AND TRACER SIMULANT RESUSPENSION 263 



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 1972 1973 1974 1975 



DATE 



Fig. 18 Range of airborne ^'"Am concentrations (above radiochemical detection 

 limits) at on-site Hanford resuspension sites compared with fallout levels. 



included. If all airborne plutonium is assumed respirable and soluble, a maximum 

 calculated ^^^Pu concentration is (5 X 10"'V0.038) 1.3 X lO"*"^ iuCi/cm^ which is 

 still significantly less than the MPC of 6 X 10 * ^ ^iCi/cm^ for occupational exposure. 



Americium Resuspension at Hanford 



At Hanford airborne ^"^ Am concentrations measured (Sehmel, 1977c) at U-Pond, Z-19, 

 S-16, and HMS tower Areas ranged from about 10"'^ to 10~^^ jLtCi/cm^ . However, 

 other filter samples indicated that the total ■^'*'Am collected was below radiochemical 

 detection limits. In Fig. 18 airborne ^"^^ Am concentrations are compared with the 300 

 Area fallout levels (Thomas, 1976). However, the comparisons are incomplete since data 

 for •^^^ Am fallout level were not reported for all time periods. In addition, many data 

 for fallout level were below radiochemical detection limits; these are indicated by short 

 horizontal dotted lines. Obviously, actual fallout levels for these time periods could have 

 been significantly less. 



Airborne ^"^^ Am concentrations at the U-Pond were of the same order of magnitude 

 as reported fallout levels. In contrast, airborne concentrations at the Z-19 and S-16 Areas 

 were significantly above fallout levels during February to May 1975. Comparisons of 

 upwind and downwind tower air sample results at the S-16 Area showed that increased 

 ^'^ ^ Am airborne concentrations were from ^'* ' Am resuspension from the dry S-16 Area. 

 (This area has since been covered.) Maximum ^^^Am concentrations measured in 



