Norman C. Schroeder

Preconcentration of low levels of americium and plutonium from waste waters by synthetic water-soluble metal-binding polymers with ultrafiltration

A preconcentration approach to assist in the measurement of low levels of americium and plutonium in waste waters has been developed based on the concept of using water-soluble metal-binding polymers in combination with ultrafiltration. The method has been optimized to give over 90% recovery and accountability from actual waste water.

Evaluation of synthetic water-soluble metal-binding polymers with ultrafiltration for selective concentration of americium and plutonium

Water-soluble metal-binding polymers in combination with ultrafiltration are shown to be an effective method for selectively removing dilute actimide ions from acidic solutions of high ionic strength. The actinide-binding properties of commercially available water-soluble polymers and several polymers which have been reported in the literature were evaluated. The functional groups incorporated in the polymers were pyrrolidone, amine, oxime, and carboxylic, phosphonic, or sulfonic acid. The polymer containing phosphonic acid groups gave the best results with high distribution coefficients and concentration factors for241Am(III) and238Pu(III)/(IV) at pH 4 to 6 and ionic strengths of 0.1 to 4.

SORPTION BEHAVIOR OF PERTECHNETATE ION ON REILLEXTM-HPQ ANION EXCHANGE RESIN FROM HANFORD AND MELTON VALLEY TANK WASTE SIMULANTS AND SODIUM HYDROXIDE/SODIUM NITRATE SOLUTIONS

ABSTRACT The batch distribution coefficients (Kd, mL solution /g dry resin) for pertechnetate (TcO4) between ReillexTMHPQ anion exchange resin and various caustic solutions have been determined. The average Kd value in 1.5 M NaNO3/l.0 M NaOH solution is (262.2 ± 12.6) mL7sol;g for TcO4 − ranging from 1.0 × 10TM M to 5.0 × 10−4 M. Pertechnetate Kd values were measured in a series of NaOH7sol;NaNO3 solutions. The series are: 1.00 M NaOH with 0.010 to 5.00 M NaNO3; 0.100 M NaOH with 0,010 to 5.00 M NaNO3; 0.100 MNaNO3 with 0.10 to 5.00M NaOH; 1.00MNaNO3 with 0.10 to 5.00 M NaOH; 1.50 M NaNO3 with 0.10 to 5.00 M NaOH; 3.50 M NaNO3 With 0.10 to 5.00 M NaOH. The Kd values are described by the following equation. This equation was used to predict the Kd values for a series of tank waste simulants. The predicted Kd values are different from the measured values with an average absolute difference of (29 ± 10)%. Pertechnetate kdvalues for 101-SY, 103-SY, DSS, DSSF-2.33, DSSF-5, DSSF7, 101-AW, and Melton Valley simu...

Feed Adjustment Chemistry for Hanford 101-SY and 103-SY Tank Waste: Attempts to Oxidize the Non-Pertechnetate Species

More than 50% of the technetium in Hanford 101-SY and 103-SY tank waste is not pertechnetate (TcO4−). These non-pertechnetate species (TcN) are stable, soluble, reduced complexes of technetium. In order to remediate these waste, it will be necessary to oxidize these species to TcO4−. For radioanalytical purposes, oxidation requires digestion in Ce(IV)/16M HNO3. Many oxidants are ineffective. Sodium peroxydisulfate, sodium peroxydisulfate/silver(I), and ozone oxidize all of the technetium species to pertechnetate.

SELECTIVE EXTRACTION OF TRIVALENT ACTINIDES FROM LANTHANIDES WITH DITHIOPHOSPHINIC ACIDS AND TRIBUTYLPHOSPHATE

A variety of chemical systems have been developed to separate trivalent actinides from lanthanides based on the slightly stronger complexation of the trivalent actinides with ligands that contain soft donor atoms. The greater stability of the actinide complexes in these systems has often been attributed to a slightly greater covalent bonding component for the actinide ions relative to the lanthanide ions. We have investigated several synergistic extraction systems that use ligands with a combination of oxygen and sulfur donor atoms to achieve a good group separation of the trivalent actinides and lanthanides. For example, the combination of dicyclohexyldithiophosphinic acid and tributylphosphate has shown separation factors of up to 800 for americium over europium in a single extraction stage. Such systems could find application in advanced partitioning schemes for spent nuclear fuel and nuclear waste.

Breakthrough volumes of TcO 4 − on Reillex™-HPQ anion exchange resin in a Hanford Double Shell Tank simulant

The breakthrough volumes on Reillex™-HPQ anion exchange resin columns for TcO4− solutions have been determined. The feed solutions were a Handford Double Shell Tank Slurry (DSS) simulant of ionic strength (μ) of 6.22 M and a TcO4− of 5.00×10−5 M and a 1∶3 dilution of the DSS simulant, μ =2.07 M, with a TcO4− of 1.67×10−5 M. The DSS flow rates {mL simulant/(cross section area of column.min)} through the column varied from 0.19 to 20.5 cm/min. The 1% breakthrough volumes varied from 50.0 to 1.3 bed volumes (BV), respectively. The 1∶3 DSS flow rate varied from 0.95 to 11.0 cm/min and had 1% breakthrough volumes ranging from 94 to 20 BV, respectively. At a flow rate of 1.0 cm/min, the breakthrough bed volumes are 10.2 and 95.8 BV for the DSS and 1∶3 DSS solutions, respectively. Obviously, there is an advantage in processing the 1∶3 dilution of the feed stream.

REILLEX™-HPQ ANION EXCHANGE COLUMN CHROMATOGRAPHY: REMOVAL OF PERTECHNETATE FROM DSSF-5 SIMULANT AT VARIOUS FLOW RATES

The 1% breakthrough volumes (BTV) for TcO{sub 4}{sup {minus}} on Reillex-HPQ anion exchange resin columns have been measured as a function of flow rate. The 1% BTV is defined as that point in the column loading when an aliquot of eluent contains 1% of the activity of an equivalent aliquot of column feed solution. The 2.54 x 50 cm resin columns were loaded with a DSSF-5 [Hanford Waste] simulant containing 5.0 x 10{sup {minus}5} M {sup 99}TcO{sub 4}{sup {minus}} and {sup 95m}TcO{sub 4}{sup {minus}} tracer. Seven flow rate experiments were performed with flow rates varying from 15 to 65 mL/min. The columns were up-flow eluted with a 1.0 M NaOH/1.0 M ethylenediamine/0.0050 M SnCl{sub 2} solution. For six flow experiments, the average technetium eluted was (97.1 {+-} 6.0) percent and the average technetium accountability for loading and eluting was (97.8 {+-} 5.9) percent. Loading experiments to 90% breakthrough were performed at a flow rate of 60 mL/min for Reillex-HPQ and AG{reg_sign}MP-1 columns. The Reillex-HPQ displayed better column loading performance as indicated by smaller percent breakthrough volumes. However, in this experiment, the AG MP-1 gave 100% elution, whereas the Reillex-HPQ gave only 70% elution.

The Removal of Pu(IV) from Aqueous Solution Using 2,3‐Dihydroxyterephthalamide‐Functionalized PEI with Polymer Filtration

Abstract Polymer filtration (PF) uses a size‐exclusion ultrafiltration membrane to retain higher molecular weight species while allowing the passage of smaller species through the membrane. Metal‐ion separations from aqueous streams are accomplished with PF by using water‐soluble chelating‐polymers (WSCP), which are appropriately sized polymers that have covalently attached metal‐binding ligands. In this study, a new WSCP was prepared by modifying polyethylenimine (PEI) through an amide linkage to attach 2,3‐dihydroxyterephthalamide (TAM) groups that have high binding constants for high valent metal cations. The TAM ligand contains a dimethylethylenediamine side chain that was found to maintain polymer solubility throughout the working pH and ionic strength ranges studied. The new WSCP (designated PDT) showed selectivity for Pu(IV) over Am(III). For example, at pH 4.5, the distribution coefficient (D) was 1.6 × 103 for Am(III) (14% bound) and 1.3 × 106 for Pu(IV) (99.3% bound). The Pu(IV) D increased as a function of pH, and the highest D was 4.8 × 106 at pH 11.4, corresponding to 99.8% bound. Varying the PDT concentration from 0.1% to 0.001% had little effect on Pu(IV) D values. The high formation constant of the Pu(IV)‐PDT complex appears to promote the oxidation of Pu(III) to Pu(IV), even in the presence of a high concentration of reductant, 0.25‐M hydroxylamine nitrate (HAN). The same high formation constant allows the TAM‐containing polymer to compete with plutonium polymer formation, as plutonium absorbed on the walls of a glass vessel dissolved after contacting it with PDT for 2 days.

Identification of Non-Pertechnetate Species In Hanford Tank Waste, Their Synthesis, Characterization, And Fundamental Chemistry

Technetium, as pertechnetate (TcO4 -), is a mobile species in the environment. This characteristic, along with its long half-life, (99Tc, t1/2 = 213,000 a) makes technetium a major contributor to the long-term hazard associated with low level waste (LLW) disposal. Technetium partitioning from the nuclear waste at DOE sites may be required so that the LLW forms meet DOE performance assessment criteria. Technetium separations assume that technetium exists as TcO4 - in the waste. However, years of thermal, chemical, and radiolytic digestion in the presence of organic material, has transformed much of the TcO4 - into unidentified, stable, reduced, technetium complexes. To successfully partition technetium from tank wastes, it will be necessary to either remove these technetium species with a new process, or reoxidize them to TcO4 - so that conventional pertechnetate separation schemes will be successful.

Fundamental chemistry, Characterization, and Separation of Technetium Complexes in Hanford Waste

The ultimate goal of this project is to separate technetium from Hanford tank waste. Our prior work with Hanford Site tank waste indicates that the presence of complexants has produced unidentified, reduced technetium species not amenable to current separation technologies, or readily oxidized to pertechnetate. Consequently, we are synthesizing and characterizing some of the major classes of technetium complexes that may be formed under tank waste conditions. These complexes will be used as standards to characterize the nonpertechnetate species in actual wastes and to develop efficient oxidation or separation methods.