Measurement of unsaturated hydraulic properties of salt cake simulant relevant to hanford and SRS high-level waste tanks using a pilot-scale setup
- Florida International Univ., Miami (United States)
Closure of the remaining tanks and final disposition of the radioactive waste is a high priority task at both Savannah River Site (SRS) and Hanford. The radioactive waste in the tanks are generally found in layers: supernate (on top) containing soluble fission products, and salt-cake and sludge (on the bottom of the tank) containing insoluble actinides. One strategy for minimizing the waste volume is to segregate the low curie salt waste from the high curie salt supernate by draining the supernate and interstitial salt solution from the salt-cake. The retrieval of the interstitial fluid will require knowledge of relevant properties of salt-cake waste including drainage parameters, more specifically, its hydraulic properties. The hydraulic parameters of the salt-cake have significance with respect to: 1) Kinetics of the retrieval process; and 2) Equilibrium conditions of the drainage. While the saturated hydraulic properties of the salt waste (hydraulic conductivity in the vertical and horizontal direction) can be used to determine the kinetics of the flow through the salt waste, the unsaturated properties are needed in order to assess not only the time frame of tank drainage but also the equilibrium conditions. How much and how fast fluid can be drained at given initial and boundary conditions (atmospheric pressure and temperature) can be analyzed. A series of dissolution and drainage experiments was conducted using S-112, S-109 and Tank 41 simulants in a pilot-scale column (1' diameter, 10' high). The major goal of these experiments was to determine the hydraulic parameters of flow through the column and the dissolution patterns upon addition of fresh water. The hydraulic experiments were conducted using interstitial fluid as well as fresh water. A series of one-step outflow experiments were used to evaluate the drainage patterns for salt-bed heights ranging from 1' to 8'. Measured data include bulk densities and saturated hydraulic conductivities as a function of temperature, and water retention characteristics for ambient temperature. Experiments in the range of 22-43 deg. C confirmed that the hydraulic conductivity in the vertical direction is strongly dependent on the temperature with variations most likely caused by physical-chemical changes in the salt-cake structure and the viscosity of the interstitial fluid. Evidence for the changes in salt-cake structure include: increased effluent specific gravity to 1.47, appearance of voids in the column, and a 10% reduction of the column height. A two-orders-of-magnitude difference in viscosity was observed when the temperature increased from 22 deg. C to 43 deg. C. The liquid retention parameters were determined using static retention points (derived from the multi-step outflow time series). Inverse analyses of the outflow data yielded additional unsaturated hydraulic conductivity parameters. The inverse analysis was performed by fixing saturated and residual water contents and the pore connectivity factor. Numerical simulations showed that the amount of drained fluid is directly related to van Genuchten's shape parameters n and {alpha} . On the other hand, the rate of drainage was directly related to saturated hydraulic conductivity. The recommended values for {alpha} and n with uncertainties in the parenthesis are respectively: 3.2(0.32) 1/m and 2.6(0.4). The recommended value for saturated hydraulic conductivity of salt-cake is 6.0E-06(3E-06). This work provides critical data about unsaturated hydraulic properties which can be used in numerical models to better predict removal of interstitial liquid from tanks that directly impact tank and site cleanup schedule and costs. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 21290874
- Report Number(s):
- INIS-US-09-WM-07288; TRN: US10V0200038285
- Resource Relation:
- Conference: WM'07: 2007 Waste Management Symposium - Global Accomplishments in Environmental and Radioactive Waste Management: Education and Opportunity for the Next Generation of Waste Management Professionals, Tucson, AZ (United States), 25 Feb - 1 Mar 2007; Other Information: Country of input: France; 15 refs
- Country of Publication:
- United States
- Language:
- English
Similar Records
Modeling of Pilot-Scale Salt-cake Dissolution
Method development for determining the hydraulic conductivity of fractured porous media
Related Subjects
ACTINIDES
BOUNDARY CONDITIONS
COMPUTERIZED SIMULATION
DRAINAGE
FISSION PRODUCTS
FRESH WATER
HANFORD RESERVATION
HIGH-LEVEL RADIOACTIVE WASTES
HYDRAULIC CONDUCTIVITY
KINETICS
LIQUIDS
RADIOACTIVE WASTE DISPOSAL
SALTS
SAVANNAH RIVER PLANT
SLUDGES
TANKS