IMPACT ASSESSMENT OF EXISTING VADOSE ZONE CONTAMINATION AT THE HANFORD SITE SX TANK FARM

Journal Article · Thu Nov 01 04:00:00 EDT 2007 · VADOSE ZONE JOURNAL - Published On-Line 11/2007

DOI:https://doi.org/10.2136/vzj2006.0176· OSTI ID:922131

R, KHALEEL

The USDOE has initiated an impact assessment of existing vadose zone contamination at the Hanford Site SX tank farm in southeastern Washington State. The assessment followed the Resource Conservation and Recovery Act (RCRA) Corrective Action process to address the impacts of past tank waste releases to the vadose zone at the single-shell tank farm. Numerical models were developed that consider the extent of contamination presently within the vadose zone and predict contaminant movement through the vadose zone to groundwater. The transport of representative mobile (technetium-99) and immobile (cesium-137) constituents was evaluated in modeling. The model considered the accelerated movement of moisture around and beneath single-shell tanks that is attributed to bare, gravel surfaces resulting from the construction of the underground storage tanks. Infiltration, possibly nearing 100 mm yr{sup -1}, is further amplified in the tank farm because of the umbrella effect created by percolating moisture being diverted by the impermeable, sloping surface of the large, 24-m-diameter, buried tank domes. For both the base case (no-action alternative) simulation and a simulation that considered placement of an interim surface barrier to minimize infiltration, predicted, groundwater concentrations for technetium-99 at the SX tank farm boundary were exceedingly high, on the order of 10{sup 6} pCi L{sup -1}. The predicted concentrations are, however, somewhat conservative because of our use of two-dimensional modeling for a three-dimensional problem. A series of simulations were performed, using recharge rates of 50, 30, and 10 mm yr{sup -1}, and compared to the basecase(100 mm yr{sup -1}) results. As expected, lowering meteoric recharge delayed peak arrival times and reduced peak concentrations at the tank farm boundary.

• Research Organization: Hanford Site (HNF), Richland, WA
• Sponsoring Organization: USDOE - Office of Environmental Management (EM)
• DOE Contract Number: AC27-99RL14047
• OSTI ID: 922131
• Report Number(s): RPP-35977 Rev 0
• Journal Information: VADOSE ZONE JOURNAL - Published On-Line 11/2007, Journal Name: VADOSE ZONE JOURNAL - Published On-Line 11/2007 Journal Issue: 4 Vol. 6
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CESIUM 137
CONTAMINATION
FLOW MODELS
GROUND WATER
HANFORD RESERVATION
RADIOACTIVE WASTE FACILITIES
RADIOECOLOGICAL CONCENTRATION
RADIONUCLIDE MIGRATION
SOILS
STORAGE FACILITIES
TECHNETIUM 99
WATER INFLUX