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U.S. Department of Energy
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Caustic-Side Solvent Extraction Full-Scale Test

Conference ·
OSTI ID:21319795
;  [1];  [2];  [3]
  1. General Atomics, San Diego, CA (United States)
  2. Parsons, Aiken, SC (United States)
  3. Energy Solutions, Aiken, SC (United States)
A Full-Scale Test (FST) program was performed by Parsons and its team members General Atomics and Energy Solutions to assess the performance of full-scale centrifugal contactors specified for the Department of Energy Salt Waste Processing Facility (SWPF). The SWPF, to be located at the Savannah River Site (SRS) in Aiken, South Carolina, will remove highly radioactive waste constituents, principally actinides, strontium (Sr), and cesium (Cs) radionuclides, from salt waste solutions currently stored in SRS high-level waste tanks. Caustic-side Solvent Extraction (CSSX) removes Cs from waste feed that has been treated upstream to remove actinides and Sr. CSSX uses a custom solvent to extract Cs from the salt solution in a series of single stage centrifugal contactors. The test system comprised (a) eleven 25.4 cm (10'') full-scale contactors (versus 36 in SWPF) for the extraction, scrub, strip, and wash stages; (b) two solvent recovery coalescers; and (c) the associated hardware and control system, packaged in four skid mounted modules. This paper describes the results of tests performed to define both hydraulic performance parameters (maximum hydraulic capacity and phase carryover) and solvent extraction performance parameters (Cs mass transfer efficiencies) using simulated SWPF waste and actual CSSX solvent. The test results confirmed key design features of the CSSX process and, as a consequence, the use of CSSX in the SWPF. In conclusion: Total throughput was initially limited to 85% of maximum flow during FST. Minor system modifications performed prior to mass transfer testing series resulted in the realization of 100% throughput. The 100% flow equates to slightly more than 35.6 x 10{sup 6} L/yr (9.4 Mgal/yr) of waste processed in SWPF which is anticipated to be the peak plant throughput. To achieve the best hydraulic performance in extraction, it is recommended that the extraction contactors be operated at the highest reasonable speed possible (>2100 rpm). Vibration, hardware limitations, bearing life, and other factors should be considered prior to final selection of extraction contactor speeds in SWPF. In strip (also scrub and wash) aqueous carryover decreased and organic carryover increased as the rotor speeds increased. It is recommended that the strip, scrub, and wash contactors be operated at intermediate speeds (between 1500 and 2100 rpm) to achieve a performance compromise between aqueous and organic carryover. Curved-vane bottom plates showed a significant hydraulic performance (aqueous and organic carryover) advantage over straight-vane bottom plates in extraction. There was no significant mass transfer performance advantage for either plate type in extraction. Thus, curved-vane bottom plates in extraction may be the better option for use in SWPF. There was no significant hydraulic performance difference between the plate types in strip. Straight-vanes provided significantly better mass transfer performance in strip compared to curved-vanes. Based solely on mass transfer performance, straight-vane bottom plates in the strip, scrub, and wash contactors are recommended for use in SWPF. Utilizing straight-vanes in the stripping section, the overall SWPF CSSX performance is expected to meet or exceed the target DF of 40,000 with minimum extraction D{sub Cs} of 10. (authors)
Research Organization:
WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
OSTI ID:
21319795
Report Number(s):
INIS-US--10-WM-08431
Country of Publication:
United States
Language:
English