Hanford low-level tank waste interim performance assessment

Vadose zone infiltration rate at Hanford, Washington, inferred from Sr isotope measurements

“…[58] One advantage of the Sr isotope measurements over the lysimeter studies is that they do not cause any distur-bance prior to measurement, hence preferential paths in the soil structure are captured in the Sr isotopic method. Tracer studies such as 137 Cs, 3 H, and Cl are limited by both the textural nature of the soils and the degree of prior chemical and physical disturbance at the site and thus are often not amenable to coarse-textured or engineered sites [Mann et al, 1997;Tindall and Kunkel, 1999].…”

“…In the 200 West Area, the heterogeneous Hanford Formation is divided into several sub-facies: a medium-grained sand (HFSD1), a pebble gravel (HFGD), and another fine to coarse-grained sand and interbedded silt unit (HFSD2) [U.S. DOE, 2002]. The cataclysmic Pleistocene flooding that deposited the Hanford Formation ended approximately 13,000 years ago [Mann et al, 1997]. Underneath the Hanford Formation is the Pliocene Cold Creek Unit (CCUf(lam-mas), a facies composed of intercalated layers of fine sand and silt and some weakly developed paleosols [U.S. DOE, 2002].…”

“…The model was also relatively insensitive to changes in the ratio of C d to C f for the range measured in the initial data, so the average value for each parameter was used in the model. The value of the dispersivity (l) was set to 7 m based on previous studies of vadose zone transport at the Hanford Site [Mann et al, 1997]. The range of values for K ret (3 to 118) was chosen based on the previous discussion of the retardation factor for the 299-W22-48 borehole and other independent estimates of K d for uncontaminated waters at a site proximal to the 200 West area.…”

Two‐region flow and rate‐limited sorption of uranium (VI) during transport in an unsaturated silt loam

“…The PA includes analyses that predict the transport of radionuclides and/or contaminants from a source to a receptor. Previous analyses for proposed disposal actions on the Hanford Site show that the groundwater transport pathway presents the greatest threat for long-term dose uptake by humans [Mann et al, 1998]. For vertical travel of the contaminant plume through a 80-m unsaturated zone, followed by horizontal travel through a 100-m saturated zone, it was shown that >99% of the water travel time was in the unsaturated zone.…”

“…Thus accurate representation of the unsaturated transport processes is especially critical to these calculations. Uranium is among the key risk drivers at the proposed Hanford disposal site [Mann et al, 1998] and is among the top three most frequently occurring radionuclides in groundwater at Department of Energy facilities [Riley and Zachara, 1992].…”