The effect of hydrodynamic dispersion parameters on process optimization of S-109 partial waste retrieval
- Florida International Univ., Miami (United States)
- CH2MHILL (United States)
The removal of cesium by draining the supernate and interstitial salt solution from the salt-cake while fresh water is continuously being added at the top of the tank requires modeling of the transport in variably saturated porous media, and possibly includes a diffusion component. The uncertainties in this method are based on the highly inhomogeneous properties of the salt-cake and limited knowledge of the drainage and transport parameters, more specifically, its hydraulic constraints and hydrodynamic dispersion properties. The hydraulic parameters of the salt-cake (hydraulic conductivity and van Genuchten parameters) have significance with respect to tank drainage and re-saturation and 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. One of the most important parameters for determining the transport properties of the porous media is the hydrodynamic dispersion tensor. The hydrodynamic dispersion can be applied to describe the spreading of cesium mass spatially and temporally. It combines effects from local variations in pore fluid velocity dispersion and molecular diffusion. In this study, the hydrodynamic dispersion parameters, the Peclet number for molecular diffusion, and the resulting uncertainties have been estimated from pilot scale column experiments using S-109 salt-cake simulant. A 2-D axisymmetric finite element model has been developed to couple the flow in variably saturated regime with transport of non-reacting cesium. The model used unsaturated hydraulic properties as determined from previous experimental work. The study performed sensitivity analysis of the hydrodynamic dispersion factor and provided information about its significance with respect to cesium temporal and spatial distribution. The model was used to compare relevant operating parameters during the replacement of cesium rich supernatant with fresh water. The effects of hydrodynamic dispersion variations were analyzed to predict the uncertainty of the volumes that must be added and pumped for the concentration of cesium to drop below the limits required by the Demonstration Bulk Vitrification System (DBVS) facility. These parameters were used to determine the most optimal drainage scenarios, which are driven by minimization of the Double Shell Tank (DST) space needed. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 21294690
- Report Number(s):
- INIS-US--09-WM-07307
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DIFFUSION
DRAINAGE
FINITE ELEMENT METHOD
FRESH WATER
HYDRAULIC CONDUCTIVITY
HYDRODYNAMICS
KINETICS
POROUS MATERIALS
RADIOACTIVE WASTE MANAGEMENT
RADIOACTIVE WASTES
SENSITIVITY ANALYSIS
TANKS
VITRIFICATION
WASTE RETRIEVAL