TRANSURANIC AND TRACER SIMULANT RESUSPENSION 267 



Airborne nonrespirable ^^^Pu fluxes also were calculated for these Prosser barricade 

 samples. Horizontal flux calculations were made for both the total time wind was 

 between 3 and 1 1 m/sec and 190 to 260° and for the total time cowl air samplers were in 

 the field. Fluxes are shown in the last two columns of Table 8. When ihe shorter time 

 period (3 to 11 m/sec winds) is used for calculating the horizontal plutonium flux, fluxes 

 range from 3.9 x 10"^ to 1.4 X 10~^ /aCi m~^ day"^ . This Prosser barricade flux range 

 is within the range measured near site A at Rocky Flats (shown in Fig. 8). However, if 

 the total time cowl air samplers were in the field is used for calculation, Prosser barricade 

 airborne nonrespirable off-site plutonium fluxes were lower and comparable to those 

 measured at Rocky Flats sites AB and B (see Fig. 8). 



These cross-comparison data show that there is a comparable plutonium flux on 

 nonrespirable particles off site at Hanford, on site at Hanford U-Pond, and on site at 

 Rocky Flats for the fime periods invesfigated. Comparable fluxes may be caused by more 

 soil being transported from off site at the Prosser barricade site. As shown by the range of 

 ^^^Pu concentrations on airborne soil from 1.3 x 10~^ up to 2.1 x 10~^ iJ-Ci/g, this 

 range is greater than fallout levels in soil-surface samples. As shown in Table 3, reported 

 ■^■^^Pu concentrations in surface samples 19 to 34 km from Hanford had a range from 

 3.6 X 10"^ to 7.6 X 10~^ AfCi/g. These last values are similar to a fallout level of 

 3.8 X 10"^ juCi/g measured (Hardy, 1974) at North Eastham, Mass. 



Most plutonium collected appears not to have originated from fallout. Rather, most 

 plutonium collected on these airborne nonrespirable particles near the Prosser barricade 

 resembles weapons-grade plutonium (Krey, 1976; Krey et al., 1976a). Plutonium isotopic 

 ratios (^^°Pu/'^^^''^^°Pu) (in atom percent) for these nonrespirable samples were 

 6.10 ± 0.02 at 0.3-m heiglit, 6.31 ± 0.02 at 2-m height, and 6.28 ± 0.03 at 5.8-m height. 

 In comparison, the isotopic ratio determined from a sample of forest-fire smoke plume 

 near Mt. St. Helens, Wash., was 13.82 ±0.05. Isotopic ratios for respirable particles 

 sampled near the Prosser barricade were not determined. Although plutonium was 

 blowing from off site near the Prosser barricade, airbome respirable plutonium 

 concentrations were below MPC's, as is shown in Fig. 20. 



Relative Amounts ef Radionuclide "Clusters " on Particles Resuspended 



Data from these studies indicate that occasionally some more-radioactive-than-normal 

 particles or clusters of radioactive particles were resuspended and collected on sampling 

 filters. In the October 1973 plutonium data for Hanford shown in Figs. 7 and 14, one 

 filter at 6.1-m heiglit coUected 6.5 x 10"^ ^iCi/g of airborne sohd (1.2 x 10"^^ )i;Ci/cm^ 

 of filtered air). The plutonium measurement was 36 times as great as the maximum value 

 of 1.8 X 10"^ fiCilg of airborne soHd (4.0 x 10"^^iuCi/cm^ of filtered air) collected on 

 other filters simultaneously sampling at heiglits of 6.1 and 0.3 m. We hypothesize that 

 this relatively high plutonium collection on this filter was due to collecfion of one or 

 more larger (more radioactive than normal usually resuspended and sampled) particles or 

 clusters of particles. 



The size of the larger particle(s) cannot be measured since the filter samples were 

 dissolved for plutonium analysis. Nevertheless, tlie relative size can be estimated from the 

 ratio of radioactivities collected for "normal" and "larger" particle sizes. Assuming that 

 the radioactivity of a particle is proportional to its volume, then flie filter with a 

 plutonium activity 36 times as great as the next highest measured activity may have 

 collected larger particles of plutonium activity 36 times as great as the activity of normal 



