Cliff Conner

DEVELOPMENT OF A SOLVENT EXTRACTION PROCESS FOR CESIUM REMOVAL FROM SRS TANK WASTE

An alkaline-side solvent extraction process was developed for cesium removal from Savannah River Site (SRS) tank waste. The process was invented at Oak Ridge National Laboratory and developed and tested at Argonne National Laboratory using singlestage and multistage tests in a laboratory-scale centrifugal contactor. The dispersion number, hydraulic performance, stage efficiency, and general operability of the process flowsheet were determined. Based on these tests, further solvent development work was done. The final solvent formulation appears to be an excellent candidate for removing cesium from SRS tank waste.

Centrifugal Contactors for Laboratory-Scale Solvent Extraction Tests

Abstract A 2-cm contactor (minicontactor) was developed and used at Argonne National Laboratory for laboratory-scale testing of solvent extraction flowsheets. This new contactor requires only 1 L of simulated waste feed, which is significantly less than the 10 L required for the 4-cm unit that had previously been used. In addition, the volume requirements for the other aqueous and organic feeds are reduced correspondingly. This paper (1) discusses the design of the minicontactor, (2) describes results from having applied the minicontactor to testing various solvent extraction flowsheets, and (3) compares the minicontactor with the 4-cm contactor as a device for testing solvent extraction flowsheets on a laboratory scale. The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. W-31-109-ENG-38. Accordingly, the U. S. Government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, ...

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.

Optimization of Magnetite Carrier Precipitation Process for Plutonium Waste Reduction

Abstract Transuranic (TRU) waste that is being generated at Argonne National Laboratory has a TRU activity ranging from 102 to 107 nCi/g with a wide variety of chemical compositions. Currently, the waste is stored in highly acidic solutions that must be neutralized for intermediate storage. A magnetite carrier precipitation process has been adapted to concentrate TRU isotopes in a noncorrosive solid phase. In this paper, we report the results of a series of laboratory tests done to optimize the process. The parameters we optimized included (1) magnetite concentration used to precipitate plutonium from solution, (2) formation of magnetite (in situ or ex situ), (3) processing pH, and (4) temperature and mixing time of the carrier precipitation. We also studied the effects of anions, cations, and complexing agents in the waste solutions on the carrier precipitation and the effect of magnetite solids loading on the filtration equipment. An overview is given of the planned full-scale process, which will be ope...

TRUEX Processing of Plutonium Analytical Solutions at Argonne National Laboratory

Abstract The TRUEX (TRansUranic EXtraction) solvent extraction process was developed at Argonne National Laboratory (ANL) for the Department of Energy. A TRUEX demonstration completed at ANL involved the processing of analytical and experimental waste generated there and at the New Brunswick Laboratory. A 20-stage centrifugal contactor was used to recover plutonium, americium, and uranium from the waste. Approximately 84 g of plutonium, 18 g of uranium, and 0.2 g of americium were recovered from about 118 L of solution during four process runs. Alpha decontamination factors as high as 65,000 were attained, which was especially important because it allowed the disposal of the process raffinate as a lowlevel waste. The recovered plutonium and uranium were converted to oxide; the recovered americium solution was concentrated by evaporation to approximately 100 mL. The flowsheet and operational procedures were modified to overcome process difficulties. These difficulties included the presence of complexants i...

Proof-of-concept flowsheet tests for caustic-side solvent extraction of cesium from tank waste.

A caustic-side solvent extraction (CSSX) process to remove cesium from Savannah River Site (SRS) high-level waste was tested in a minicontactor (2-cm centrifugal contactor). In the first phase of this effort, the minicontactor stage efficiency was improved from 60% to greater than 80% to meet the SRS process requirements using a 32-stage CSSX flowsheet. Then, the CSSX flowsheet was demonstrated in a 32-stage unit, first without solvent recycle, then with it. In both cases, the key process goals were achieved: (1) the cesium was removed from the waste with decontamination factors greater than 40,000 and (2) the recovered cesium was concentrated by a factor of 15 in dilute nitric acid. Oak Ridge National Laboratory (ORNL) analysis of the recycled solvent showed no evidence of impurity buildup.

Preliminary Plan for Treating Mixed Waste

A preliminary waste treatment plan was developed for disposing of radioactive inorganic liquid wastes that contain hazardous metals and/or hazardous acid concentrations at Argonne National Laboratory. This plan, which involves neutralization and sulfide precipitation followed by filtration, reduces the concentration of hazardous metals and the acidity so that the filtrate liquid is simply a low-level radioactive waste that can be fed to a low-level waste evaporator.