In this report, the interaction of monoamide/diamide and monoamide/diglycolamide mixtures with $${\text{UO}}_{2}^{2 + }$$ are investigated in pH = 1 methanolic nitric acid media. These monoamides include N,N-dimethylacetamide (DMAA), N,N-diethylacetamide (DEAA), N,N-dibutylacetamide (DBAA) and N,N-dibutylbutanamide (DBBA). N,N,N′N′-tetraethylmalonamide (TEMA) and N,N,N′,N′-tetraethyldiglycolamide (TEDGA), which were chosen as model diamides and diglycolamides, respectively. Complex stability constants for each ligand were modelled using the Stability Quotients Using Absorbance Data program using UV–visible data. Complex stoichiometry of ligand mixtures was determined using Job plots and UV–Vis spectrometry. Monoamides were confirmed to produce only disolvate complexes with $${\text{UO}}_{2}^{2 + }$$ in solution. The log10(K) values for monoamides were found to be independent of amine-side chain length, but were slightly dependent on the carbonyl-side chain length. TEDGA was found to produce multiple uranyl complexes in solution. Job plot data indicated that the uranyl cation strongly prefers to bond either only with the monoamide or diamide in ternary monoamide–diamide–UO2 systems. Monoamide–diglycolamide–UO2 systems were more complicated, with Job plot data indicating the potential for multiple ternary species being present is dependent on the monoamide structure.

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Macroreticular anion exchange resin cleanup of tbp solvents.

Spectrophotometric analysis of ternary uranyl systems to replace tri-N-butyl phosphate (TBP) in used fuel reprocessing

/pdf/macroreticular-anion-exchange-resin-cleanup-of-tbp-solvents-2synuizsrs.pdf

Strong base macroretibuZar anion exchange resins (e.g., AmberZyst A-26) remove fission products, dibutyZ phosphopic acid, and diZuent degradation products from used TBP extractants. AppZication of these resins in routine cteanup of such•soZvents : is potentiaZZy attractive to eZiminate or, at Zeast, minimize the Zarge voZumes of radioactive waste generated by presentZy used soZvent wash procedures. Both unwashed Hanford Purex pZant 30% TBP-NPH and PZutonium RecZamation Fae€Zity 20% TBP-CCZ•4 sotvents demonstrate the high capacity of A-26 res€n for sorbing soZvent impurities.

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Typical applications include purification of aqueous uranium feedstocks in uranium refineries, recovery of [1] uranium and/or plutonium from metallurgical scrap [2, 3] and, most importantly, the Purex process for reprocessing all kinds of .irradiated nuclear reactor fuels. [4].

Chemical and radiolytic degradation of TBP extractants and solvent treatment procedures have been reviewed by several authors. [5-8].

Progress and findings of these latest resin solvent treatment studies are highlighted'in this paper.

DISCLAIMER

From used Purex solvent by A-26 resin were significantly.

Kinetics of fission product and HDBP uptake by A-26 resin also increased with decreasing resin particle size.

HF solutions were best for eluting fission products and HDBP from A-26 resin.

High capacity of A-26 resin for sorbing extractant impurities was indicated in very preliminary column runs.

Physical and chemical properties of the effluent solvent in these runs were equal to or superior to those of Hanford Purex plant carbonate-washed material.

Kinetics of sorption of fission products and HDBP

As-received Cl-form A-26 resin was converted to the OH-form by treatment with excess 4M NaOH, washed with water, and dried in air.

Prior to use with 1CW solution, all resin beds were classified by upflow of water.

Both upflow and downflow conditiohs were used with NaOH eluents.

MATERIALS

Table II summarizes conditions and results of column runs made to study effects of flow rate and solution residence time on A-26 resin cleanup of Purex process solvent.

With one exception, these runs were made at a bed height:diameter ratio of 4.

Such solvent was produced only after breakthrough of fission product activity.

In plant-scale operation, eluates resulting from regeneration of A-26 resin beds would become, after evaporation, part of the Purex process high-level liquid waste stream.

Calculations to establish economically permissible frequency and volume have not been made, however.

PUREX PROCESS SOLVENTS Flow Rate Tests

The authors have emphasized application of OH-form Amberlyst A-26 resin for cleaning up used Purex process solvent.

But other macroreticular strong base anion exchange resins (e.g., Amberlyst A-29, J. T. Baker Company A-641, etc.) can also be used for this purpose.

In the as-received Cl-form A-26 resin does not efficiently sorb fission products from Purex 1CW solvent (Table VI ).

The yellow color bodies are thought to be nitration products of the NPH diluent, but they have not been positively identified as such.

Sorption of these yellow colored compounds by A-26 resin is in line with manufacturer's claims for this resin. [10].

Miscellaneous Observations and Tests

Straight chain paraffin mixtures (e.g., NPH) suitable for use as a diluent for TBP have been commercially available only since about 1966.

Before then, commonly used diluents (e.g., Soltrol 170, Shell E-2342, etc.) contained various amounts of branched paraffins, olefins, and napthenes.

Abundant experimental evidence exists [5- to account for the removal of the zirconium and niobium.

Conversely, the authors find in both batch and column tests that Distribution ratios for sorption of I2 from 1CW and laboratoryprepared 30% TBP-NPH solvents were only 2.8 and 12.2, respectively.

Much of the iodine which may be present in TBP extractants used with highexposure fuels could be there as organic iodides.

Limited test data shown in

Depending on economic factors and operating philosophies, there may be as many ways to use A-26 resin in cleaning up degraded Purex process solvents as there are Purex plants.

One solvent wash step and its attendant high-level aqueous waste are thus eliminated.

Scheme 2 features resin treatment of both first and second cycle solvents.

Counterbalancing this advantage, however, is the likely need for frequent resin regeneration and/or replacement of the resin used to treat first cycle solvent.

Detailed economic calculations (which have not been made) are required to decide the merit, if any, of Scheme 2.

Resin Application Schemes

Of carbonate-washed first cycle solvent is, potentially, the most efficient way to take advantage of their favorable properties.

Such washing will remove the bulk of the fission product activity, essentially all .the HDBP and any entrained HN03, and provide an effective buffer zone to negate effects of periodic coextraction cycle upsets.

The overall effect should be to ensure a very long useful life for the A-26 resin bed before its replacement becomes necessary.

Operability of the "one solvent" system, particularly the use of resin-treated .first cycle solvent in the second uranium cycle, has not been demonstrated.

Loaded resin can be incinerated (see p. 33) or destroyed by reaction with HN03-H2S04 solutions according to the process being developed by Westinghouse Hanford Company workers. [21].

Application of macroreticular resins in tailend cleanup

A solvent extraction process involving extensive product reflux is used in Hanford's PRF to recover and purify plutonium from various types of metallurgical scrap.

Sufficient resin capacity would be provided in both cases to treat used 8 solvent for one week before resin replacement.

Spent resin would be incinerated at about 760 °C in the present PRF in- [22] cinerator, and plutonium would be recovered from the ash by standard HN03-HF dissolution techniques.

Also, carbonate washing provides a buffer zone to ensure removal of HN03 and U02(N03)2, both of which A-26 resin also sorbs considerable yellow color from both CUW and CXW streams.

Exotherms occur at about 325 and 500 °C in the differential thermal analysis curve for OHform A-26 resin ; at about 550 °C the resin burns completely to leave a small amount of white ash.

Macroreticular anion exchange resin cleanup of tbp solvents.

Citations

Spectrophotometric analysis of ternary uranyl systems to replace tri-N-butyl phosphate (TBP) in used fuel reprocessing

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