TTT Try Pat et TT q —— OSITE A AT SECURITY FENCE ~--OSITE AB BETWEEN A AND B SSITE & AT CATILE FENCE . o AER SAMPLING HEIGHT, m on J & n oed po IMPACTOR 50% CUT-OFF DIAMETER, um oa ¥ # a ~ = 4 a: Ql | 1 <—O—-*MOUNTAIN SITE pe tall a tal pe tal 10 10° 4 AIRBORNE no"Py CONCENTRATION, aCi!m ww {ALL WINDS. SITE AB) FIGURE 3. FIGURE 2. Airborne °9pu Concentration at Site AB I 4 ati j eal pe yl 10 0 arsorne 2%Py CONCENTRATION, acim? ‘ALL WINDS) w 239 Airborne Pu Concentrations from Impactor 2.0 um Stage Collections as a Function of Impactor Collection Site The general trend of the complete airborne plutonium-239 concentration data 1s a decrease in concentration with increasing distance eastward from site A {Sehmel and Lloyd, 7976a). As might be expected, this decrease in concen- trations corresponded to increasing distance from the original oi! storage area, which was the principal source of ground contamination. However, significant deviations did occur in the concentration profiles of airborne plutonium-239 with both distance and height. These deviatfons might be attributed to sampling "hot" soil particles which contain relatively more Plutonium than average. These increases in average airborne plutonium-239 concentrations were present at both sites AB and B, As indicated in Figure 3 for site AB, “hot" particles may have been present in the 2.0-um size range. In this case, the concentration at the 1-m height of site AB is 1 to 2 orders of magnitude greater than at other heights for this site. More important to the "hot" particle concept is the concentration at the 10-m height of B. This concentration of 230 aCi/m? was the Jargest plutonium-239 concentration for 2-um particles measured at any location. This relatively high concentration was unexpected since this sampling location was the most remote from both the ground and the original oi) storage area. This Suggests that other relatively "hot" particles could also be escaping from the plant boundaries; however, due caution is indicated in interpreting this "hot" particle cgncept. The total of 6 dis/min collected on the 2-ym stage or 230 aCi/m? is much less than the maximum per- missible air concentration of 2 x 106 aCi/m3 (occupational). It is con- ceivable that the majority of this "hot" plutonium might have been attached to one soil particle. 188 Even with the limited plutonium data collected in this experiment, it was evident that airborne plutonium-239 concentrations increased with an increase in wind speed. In Figure 4, total airborne concentrations are shown for air sampled at al? wind Speeds (average wind speed of 0.9 m/sec), at wind speeds from 4.1 to 6.3 m/sec, and at wind speeds from 6.3 to 9.8 m/sec. Airborne plutonium-239 concentrations at wind speeds from 4.1 to 6.3 m/sec are definitely larger than average airborne concentrations for continuous air sampling. However, the 2c radiochemical counting statistics error limits are too targe to determine the wind speed dependency. Nevertheless, an attempt to approximate airborne plutonium-239 concentrations and consequently the resuspension rate dependency upon wind speed was made for the 7-um-diameter particles. This was for the 0.3-m height at sampling site AB. For the three data points taken at the 0.3-m height, plutonium-239 concentrations tended to increase as the 5.9th power of wind speed. This July 1973 plutonium resuspension experiment at Rocky Flats showed resuspension of both plutonium-238 and plutonium-239. However, all airborne plutonium concentrations were significantly below maximum permissible concentrations in air. Since plutonium-239 was collected on each particle cascade impactor stage, the suggestion is that most plutonium was attached to soil particles when the plutonium was resuspended,