Monica C. Regalbuto

A SPREADSHEET ALGORITHM FOR STAGEWISE SOLVENT EXTRACTION

ABSTRACT The material balance and equilibrium equations for solvent extraction processes have been combined with computer spreadsheets in a new way so that models for very complex multicomponent multistage operations can be setup and used easily. A part of the novelty is the way in which the problem is organized in the spreadsheet. In addition, to facilitate spreadsheet setup, a new calculational procedure has been developed. The resulting Spreadsheet Algorithm for Stagewise Solvent Extraction (SASSE) can be used with either IBM or Macintosh personal computers as a simple yet powerful tool for analyzing solvent extraction flowsheets.

Extraction behaviour of actinides and lanthanides in TALSPEAK, TRUEX and NPEX processes of UREX+

Abstract Bench-scale studies to determine the extraction behavior of Pu, Np, Am and lanthanides with the organophosphorus extractants TBP, CMPO and HDEHP have been carried out. Based on the results obtained using actual spent nuclear fuel solutions, enhancements to the NPEX, TRUEX and TALSPEAK processes have been successful. In NPEX, >99.94% of both Np and Pu were separated from the fission products. In TRUEX, essentially complete recovery of the actinides (An) and the lanthanides (Ln) was achieved. In TALSPEAK, the complete separation of Pu, Np and Am from the lanthanides was demonstrated several times under various process conditions. The recovery of transuranics (TRU), including Am and Cm, is nearly 100% (below detection limit in the Ln stream), while the total recovery of Ln in the product stream exceeded 99.97%.

Experimental Verification of Caustic‐Side Solvent Extraction for Removal of Cesium from Tank Waste

Abstract A caustic‐side solvent extraction (CSSX) process was developed to remove Cs from Savannah River Site (SRS) high‐level waste. The CSSX process was verified in a series of flowsheet tests at Argonne National Laboratory (ANL) in a minicontactor (2‐cm centrifugal contactor) using simulant. The CSSX solvent, which was developed at Oak Ridge National Laboratory (ORNL), consists of a calixarene‐crown ether as the extractant, an alkyl aryl polyether as the modifier, trioctylamine as the suppressant, and Isopar®L as the diluent. For Cs removal from the SRS tank waste, the key process goals are that: (1) Cs is removed from the waste with a decontamination factor greater than 40,000 and (2) the recovered Cs is concentrated by a factor of 15 in dilute nitric acid. In the flowsheet verification tests, the objectives were to: (1) prove that these process goals could be met; (2) demonstrate that they could be maintained over a period of several days as the CSSX solvent is recycled; and (3) verify that the process goals could still be met after the solvent composition was adjusted. The change in composition eliminated the possibility that the calixarene‐crown ether could precipitate from the solvent. The process goals were met for each of the verification tests. The results of these tests, which are summarized here, show that the CSSX process is a very effective way to remove Cs from caustic‐side waste. #The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W‐31‐109‐ENG‐38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid‐up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

C3-symmetric tripodal thio/diglycolamide-based ligands for trivalent f-element separations

Abstract Three new C 3‐symmetric ligands bearing diglycolamide and thiodiglycolamide units on a triphenoxymethane platform have been synthesized and evaluated as trivalent f‐element extractants from nitric acid media. Liquid‐liquid extraction studies of eleven different lanthanides from 1 M nitric acid into dichloromethane revealed a strong influence of the amidic substituents on the extraction efficiency. A comparison of the 1H NMR spectrum of the Lu(III) complex formed with the tris‐DGA ligand and the organic solution after the extraction experiment confirms that all three arms bind the metal during the extraction experiment and form a C 3‐symmetric complex. The newly synthesized lipophilic di‐n‐butyl tris‐diglycolamide was found to be a significantly weaker extractant in comparison to the di‐isopropyl analogs. The distance separating the metal binding groups from the triphenoxymethane platform had little influence on the selectivity or binding efficiency of the ligands. Experiments with the tris‐thiodiglycolamide derivative highlighted the importance of the etheric oxygens for metal binding.

Highly efficient binding of trivalent f-elements from acidic media with a C3-symmetric tripodal ligand containing diglycolamide arms

Tripodal chelates bearing three diglycolamide units precisely arranged on a triphenoxymethane platform were synthesized to mimic the preferred tricapped trigonal prismatic geometry favored by lanthanides with oxygen donor ligands, and the ligand binds heavier lanthanides very efficiently in acidic media.

A new model for solvent extraction in columns

Abstract A new model is proposed for analyzing solvent extraction processes carried out in any type of column. Each column is treated as a series of well-defined equilibrium stages where the backmixing (other-phase carryover) between stages can be large. It is assumed that mass transfer effects can be modeled by a proper choice for stage height and backmixing. With this model, the same number of stages can be used for all extracted chemical components no matter what their distribution coefficients. Thus, this model greatly simplifies the calculations required when evaluating multicomponent solvent extraction processes and so, is more appropriate than either the Height of an Equivalent Theoretical Stage (HETS) or the Height of a Transfer Unit (HTU). Initial evaluation shows that the new model works as well as the HTU method and better than the HETS method when correlating actual pulse column data.

RESULTS OF EXTERNAL TECHNICAL REVIEWS OF SITE MODELING EFFORTS THAT SUPPORT SYSTEM PLANS

An External Technical Review (ETR) team evaluated the system-level modeling and simulation tools in support of Savannah River Site and Office of River Protection liquid waste processing and disposal systems. The reviews focused on the following primary areas: software and modeling tools, capability to model needed facilities and operations, rate at which predictions are performed, and need for additional tools. The Liquid Waste Disposition Systems at these sites are highly integrated operations that involve safely storing liquid waste in underground storage tanks; removing, treating, and disposing low-activity fraction on-site; vitrifying high-level waste; and storing the vitrified waste until permanent disposition at a Federal Repository. The purpose of the ETR team was to evaluate the current process simulation tools that support the planning basis for life cycle liquid waste disposition system plans. These plans establish a base for processing the constituents of liquid waste systems to the end of the program mission. Observations and recommendations were made for each of the review areas. In general, tools appear to provide reasonable estimates for their intended purposes; however, additional functionality and new tools are needed, as well as greater flexibility and improved performance in producing estimates for planning purposes.