TRANSURANIC AND TRACER SIMULANT RESUSPENSION 237 



Resuspension occurs when particles on a surface are disturbed and carried up into the air 

 by air currents. Wind-caused resuspension is the process by which wind blows particles 

 from a surface into the air and transports them downwind. For radionuclide- 

 contaminated surfaces, wind might cause radionuclide particles to be resuspended and 

 transported to other sites. Resuspension occurs at radionuclide-contaminated sites on the 

 Hanford reservation in Washington (Sehmel, 1977c; Pacific Northwest Laboratory, 

 September 1973-October 1974), at Rocky Flats in Colorado (Johnson, Tiball, and 

 Severson, 1976; Krey et al., 1976b; 1976c; Sehmel, 1976a; Sehmel and Lloyd, 1976b; 

 Volchok, Knuth, and Klemman, 1972), at the Nevada Test Site (Anspaugh et al., 1969; 

 Wilson, Thomas, and Stannard, 1961), at the Savannah River Laboratory reservation in 

 South Carolina (Milham et al., 1976), and at other sites (Mishima, 1964; Stewart, 1967). 

 However, with our present knowledge (Horst, 1976; Oksza-Chocimowski, 1976), amounts 

 of wind-caused resuspension and its effects cannot be adequately predicted. 



Radioactive particles deposited on natural or man-made surfaces are resuspended by 

 both wind and mechanical activity. Wind resuspension can occur over a wide area as well 

 as over a local area. In contrast, mechanical-activity resuspension is usually more localized 

 and can present an immediate inhalation problem to the worker in a contaminated zone. 

 Although mechanical activity is frequently at a point, integration of mechanical activity 

 over time could result in an area source. For example, an area source could be generated 

 during the plowing of a field. In both wide-area and local resuspension of radionuclide 

 particles, particles transported downwind could become a potential radiological concern 

 to man. Sources for resuspended particles include radioactive fallout as well as releases 

 from nuclear faciHties. At present the significance of fallout resuspension is unknown. 

 Data are needed to define the relative inhalation hazard of fallout-particle resuspension 

 vs. the direct delivery of stratospheric debris. 



Radioactive-particle resuspension is probably more important at nuclear faciHties 

 where the surrounding environment has been contaminated with radioactive particles. 

 These particles can be resuspended by both wind stresses and mechanical disturbances. 

 However, resuspension mechanisms are poorly understood, and consequently resus- 

 pension rates and . potential airborne inhalation hazards cannot now be adequately 

 predicted. 



The need for such predictions is not new: for many years resuspension has been 

 known to be occurring at nuclear sites. Some of the earliest data were obtained 

 (Anspaugh et al., 1969; Wilson, Thomas, and Stannard, 1961) at the Nevada Test Site. 

 Ground radioactivity contours were determined as a function of time after a test 

 detonation. Initially, ground-surface concentrations were caused by plume deposition. 

 Subsequent ground radioactivity contours showed (Anspaugh et al, 1969) a migration of 

 radionucUdes from the Test Site which indicated that resuspension had occurred. 

 Similarly, aerial surveys at Hanford (Bruns, 1976) have shown transport of ^"^^ Am by 

 wind resuspension. 



Resuspension is of considerable interest at the Rocky Flats nuclear plant in Colorado 

 where ground surfaces were contaminated with plutonium from leaking storage barrels 

 containing plutonium-contaminated cutting oil (Johnson, Tiball, and Severson, 1976; 

 Krey et al., 1976b; 1976c; Sehmel, 1976a; Sehmel and Lloyd, 1976b; Volchok, Knuth, 

 and Klemman, 1972). After the leakage was discovered, the barrels were removed and 

 corrective actions were taken, but plutonium resuspension from residually contaminated 

 soil surfaces is still occurring. 



