TRUEX Solvent Research Articles

A COUNTER CURRENT EXPERIMENT FOR THE SEPARATION OF TRIVALENT ACTINIDES AND LANTHANIDES BY THE SETFICS PROCESS

ABSTRACT The SETFICS process, a variation of TRUEX process, was developed for the recovery of Am and Cm from acidic waste solution and the separation of actinides (III) and light lanthanides. The process uses the general TRUEX solvent as the extracting reagent and a DTPA-sodium nitrate solution for selective stripping of actinides(III). The basic flow sheet is composed of four steps: extraction-scrubbing; acid stripping; actinide(III) stripping; and lanthanide stripping. To demonstrate the usefulness of the SETFICS process, a counter current experiment was conducted using a real TRUEX product solution. Americium and curium were successfully recovered with a solution of 0.05 M DTPA-4 M NaNO3 (pH 2.0). Although the actinide(III) product solution contained Sm and Eu, the decontamination factor of 144Ce/241Am was 72, and most of the light lanthanides, specifically La, Ce, Pr, Nd, were removed. At least 80 % of the lanthanides were separated from the Am and Cm end products. In order to minimize the acidity in the actinide(III) stripping step, the nitric acid which extracted with the trivalent metals was previously removed with a solution of 0.5 M NaNO3 (pH 2.0) in the “acid stripping” step.

Substituted malonamides as extractants for partitioning of actinides from nuclear waste solutions

Pentaalkyl malonamides are suggested as alternatives to organophosphorous reagents for the extraction of actinides from high level liquid waste generated during the reprocessing of irradiated fuels. With a view to study the extraction behaviour of these actinides from nitric acid medium, four diamides namely (1) N,N,N′,N′-tetrabutyl undecyl malonamide (TBUDMA), (2) N,N,N′,N′-tetrabutyl tetradecyl malonamide (TBTDMA), (3) N,N′-dimethyl- N,N′-dibutyl undecyl malonamide (DMDBUDMA) and (4) N,N′-dimethyl- N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) were prepared by substitution on the basic skeletons of N,N,N′,N′-tetraalkyl-2-alkyl malonamides. The substituted diamides showed good extractability towards Am, Pu, Np and U into n-dodecane from nitric acid solutions of concentrations ranging from 3 to 8 M except for DMDBUDMA which showed third phase formation beyond 2 M HNO 3. Extraction maxima for Am with TBUDMA and TBTDMA were seen at 6–7 M whereas DMDBTDMA showed maximum extraction at 5 M nitric acid. Am(III) and Pu(IV) extracted as trisolvates whereas U(VI) was extracted as disolvate. Distribution behaviour of fission products using DMDBTDMA was also investigated. DMDBTDMA was found to be a promising alternative to the TRUEX solvent for the actinide partitioning from simulated High Level Waste (HLW).

Application of Single-Ion Activity Coefficients to Determine the Solvent Extraction Mechanism for Components of High-Level Nuclear Waste

The TRUEX solvent extraction process is being developed to remove and concentrate transuranic (TRU) elements from high-level and TRU radioactive wastes that are currently stored at U.S. Department of Energy sites. Phosphoric acid is one of the chemical species of concern in the application of solvent extraction processes for removal of actinides, for instance at the Hanford site, where bismuth phosphate was used to recover plutonium. The mechanism of phosphoric acid extraction with TRUEX-NPH solvent at 25°C was determined from phosphoric acid distribution ratios, which were measured by using a phosphoric acid radiotracer and a variety of aqueous phases containing different concentrations of nitric acid and nitrate. A model was developed for predicting phosphoric acid distribution ratios as a function of the thermodynamic activities of nitrate ion, and hydrogen ion. The Generic TRUEX Model (GTM) was used to calculate these activities based on the Bromley method. The derived model supports extraction by CMIO and TBP in TRUEX-NPH solvent of a phosphoric acid-nitric acid complex and a CMPO-phosphoric acid complex.

Thermodynamic Modeling of the Extraction of Cadmium Nitrate by the TRUEX-NPH Solvent

Abstract The TRUEX solvent extraction process is being developed to remove low concentrations of transuranic (TRU) elements from high-level and TRU wastes currently stored at US Department of Energy sites. Cadmium is an important constituent of some of these wastes, especially at the Idaho Chemical Processing Plant. Cadmium distribution ratios were measured by using a radioactive Cd tracer under a variety of aqueous-phase compositions to elucidate the mechanism of cadmium extraction by TRUEX-NPH solvent at 25°C. A model for predicting cadmium distribution ratios was developed as a function of the thermodynamic activities of water and nitrate ion. The Generic TRUEX Model (GTM) was used to calculate these activities. The GTMs calculation of activity coefficients is based on a Bromley method.

MERCURY EXTRACTION BY THE TRUEX PROCESS SOLVENT. II. SELECTIVE PARTITIONING OF MERCURY FROMCO-EXTRACTED ACTINIDES IN A SIMULATED ACIDIC ICPP WASTE STREAM1

ABSTRACT The TRUEX process is being evaluated at the Idaho Chemical Processing Plant (ICPP) as a means to partition the actinides from acidic sodium-bearing waste (SBW). The mercury content of this waste averages 1 g/1. Because the chemistry of mercury has not been extensively evaluated in the TRUEX process, mercury was singled out as an element of interest. Radioactive mercury, 203Hg, was spiked into a simulated solution of SBW containing 1 g/1 mercury. Successive extraction batch contacts with the mercury spiked waste and successive scrubbing and stripping batch contacts of the mercury loaded TRUEX solvent (0.2 M CMPO-1.4 M TBP in dodecane) show that mercury will extract into and strip from the solvent. The extraction distribution coefficient for mercury, as HgCl2, from SBW having a nitric acid concentration of 1.4 M and a chloride concentration of 0.035 M was found to be 3. The stripping distribution coefficient was found to be 0.5 with 5 M HN03M and 0.077 with 0.25 M Na2C03. Because experiments described here show that mercury can be extracted from SBW and stripped from the solvent, a process has been developed to partition mercury from the actinides in SBW.

PRELIMINARY EVALUATION OF CHROMATOGRAPHIC TECHNIQUES FOR THE SEPARATION OF RADIONUCLIDES FROM HIGH-LEVEL RADIOACTIVE WASTE

ABSTRACT Three commercially available chromatographic materials were tested in a column mode for use in separating Am, Pu, and ™Sr from actual neutralized cladding removal waste (NCRW) taken from a Hanford waste tank. For these experiments, the NCRW was dissolved in HNO3/HF solutions. TRU-Spec™ was evaluated for the separation of transuranic elements. TRU-Spec™ removed Am and Pu from a dissolved NCRW solution, but not as effectively as the TRUEX solvent extraction process. Sr. Spec™ and SuperLig™ 601 were evaluated for the separation of Sr, Sr- Spec™ performed very well in the separation of SK from dissolved NCRW solution; Sr was not detectable in the column effluent after six bed volumes of solution had been passed through the column. SuperLig™ 601 was less effective than Sr- Spec™ at separating Sr from dissolved NCRW solution under the conditions used in this experiment. The poor performance of SuperLig Spec™ 601 has been attributed to slow kinetics of absorption of Sr.

Evaluation of 1-Hydroxyethane-1,1-diphosphonic Acid and Sodium Carbonate as Stripping Agents for the Removal of Am(III) and Pu(IV) from TRUEX Process Solvent

Abstract The TRUEX solvent extraction process is being developed for the removal of the transuranic (TRU) elements from some of the wastes stored in tanks at the U.S. Department of Energy's Hanford Site. Initial flowsheets for this process call for the stripping (back extraction) of TRUs with 0.2 M 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) followed by washing of the process solvent with 0.25 M sodium carbonate. The stripped TRU stream is to be neutralized with caustic for interim storage in carbon steel tanks prior to vitrification. Such a scenario would result in a considerable amount of phosphorus and sodium in the TRU stream, which could preclude this material from being efficiently vitrified in the proposed Hanford Waste Vitrification Plant (HWVP). An examination of alternative stripping processes suggests that the amount of phosphorus and sodium in the feed to HWVP can be reduced by 1) using a less concentrated solution of HEDPA in the strip step, or 2) using sodium carbonate as the stripping age...

PARTITIONING OF ACTINIDES AND FISSION PRODUCTS IN HIGHLY-ACTIVE RAFFIN ATE FROM PUREX PROCESS BY MIXER-SETTLERS

ABSTRACT Batch, and counter-current flowsheet tests using mixer-settlers have been carried out in the chemical processing facility (CPF), Tokai-works, PNC. Counter-current experiments aim to provide the data for prediction of the Truex process applicability in actinides partitioning in high level liquid waste (HLLW) from die Purex process. Real highly-active (HA) raffinate from FBR spent fuel reprocessing experiments were used in these runs without adjusting the acidity. A mixed solvent composed of 0.2M CMPO in the purex solvent was employed as a Truex solvent. Although very reasonable extraction behaviors for actinides and rare earth elements were observed based on the results of batchwise distribution studies, some noteworthy behaviors for ruthenium were recognized; The rare earths and some fraction of ruthenium were coextracted to the actinides stream. Although they were stripped out by dilute nitric acid as expected, plutonium and some of ruthenium also remained in the organic phase during the strippi...

Analysis of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide and TRUEX process solvent by gas and liquid chromatography

Complementary analytical procedures using capillary gas chromatography (GC) and high-performance liquid chromatography (HPLC) have been developed for the analysis of the TRUEX process solvents (CMPO-TBP-tetrachloroethylene or normal paraffinic hydrocarbons) and the extractant CMPO. GC analyses are accomplished in 20 min using a 15 m × 0.25 μm I.D. DB-5 capillary column with flame ionization detection. The analysis requires derivatization with diazomethane. HPLC analyses are performed in 10 min using a C 18 reversed-phase column and a mobile phase consisting of acetonitrile-water-triethylamine (79:29.5:0.5) with refractive index and ultraviolet detection. The methods provide information regarding the presence of acidic and neutral impurities in stock extractant, fresh process solvent, and recovered TRUEX solvent.

Thermodynamic Modeling of Chemical Equilibria in Metal Extraction

Abstract Models of equilibrium extraction data are being developed for use in computer simulations of metal extraction processes. The correlations are based on chemical mass action principles in which the effects of metal complexation and aqueous phase activity coefficients are considered. Activity coefficients in mixed electrolyte solutions at high ionic strengths are calculated using methods available in the literature. This modeling approach is demonstrated for HNO3 extraction with both the PUREX and TRUEX solvents and for Am3+ extraction by octylphenyl-N, N-diisobutylcarbamoylmethylphosphine oxide, which is the primary extractant in the TRUEX solvent.

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THE SOLVENT EXTRACTION OF SELECTED ORGANIC COMPLEXANTS BY TRUEX PROCESS SOLVENT∗

ABSTRACT The extraction by TRUEX solvent of 14C-labelled acetic, glycolic, and citric acids, and 14C-labelled glycine, EDTA, and ethylenediamine has been studied from aqueous solutions having different nitric acid concentrations. Only acetic and citric acids are extracted to a significant extent. Their behavior can be compared to that of oxalic acid. If the aqueous phase contains a high concentration of aluminum and iron(III) species, as in some nuclear waste solution, the extraction of aqueous complexants into the organic phase is strongly suppressed. By measuring distribution ratios of irradiated 14C-labelled acetic acid, citric acid and EDTA, it has been demonstrated that the radiolytic degradation of these compounds leads, at least in part, to oxalic acid. A scrub procedure, utilizing basic aluminum nitrate, has been successfully tested in order to remove any co-extracted oxalic acid from the TRUEX solvent.