Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPD.4 Known and Suspected ReleasesD.4.1Cesium ProngPotentially Affected Media:Potentially Affected WMAs:surface soil, subsurface soil, sediments1, 2, 3, 4, 5, 6, 10, 12 (northern portion)In 1968, a ventilation system filter in the Process Building (in WMA 1) failed, releasingcontaminated particulate up the Process Building stack. A mixture of radionuclides was released,with Cs-137 predominant. Approximately 0.33 Ci particulate gross beta radioactivity wasreleased. The contaminated particulate was deposited on surface soils, resulting in a large area ofcontamination around the Process Building and to the north-northwest. Detectable depositsextend several miles, including beyond the WVDP premises. WMAs 1, 2, 3, 4, 5, 6, 10, and 12North likely are affected. Because Cs-137 is predominant, this area of contamination is known as“the cesium prong” (DOE 2009 Table 2-17, DOE 2010 Section 3.11.5).As originally deposited, surface soil activity concentrations should have decreased towards thenorth, away from WMA 1. However, the surface features of many areas within the WVDPpremises have been reworked significantly since the release; as a result, the current spatial anddepth distribution of soil contamination may be significantly different than the original footprint.In addition, the surface soil contamination likely has been naturally spread by erosion and runoffinto surface drainage features; this phenomenon may have enlarged the area impacted bydeposition, although detailed data regarding this effect are not available (DOE 2010Section 3.11.5).Finally, other releases from the Process Building stack may have produced minor impacts. Theseother releases include the 1968 failure of a dissolver off-gas system filter, resulting in 0.28 Ci ofparticulate activity, and the 1968 failure of a vessel off-gas system filter, resulting in the March1968 releases to exceed the monthly allowance by 15 percent (DOE 2010 Section 3.11.5).Rev. 1 D-3