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Title: Laboratory-scale evaluations of alternative plutonium precipitation methods

Abstract

Plutonium(III), (IV), and (VI) carbonate; plutonium(III) fluoride; plutonium(III) and (IV) oxalate; and plutonium(IV) and (VI) hydroxide precipitation methods were evaluated for conversion of plutonium nitrate anion-exchange eluate to a solid, and compared with the current plutonium peroxide precipitation method used at Rocky Flats. Plutonium(III) and (IV) oxalate, plutonium(III) fluoride, and plutonium(IV) hydroxide precipitations were the most effective of the alternative conversion methods tested because of the larger particle-size formation, faster filtration rates, and the low plutonium loss to the filtrate. These were found to be as efficient as, and in some cases more efficient than, the peroxide method. 18 references, 14 figures, 3 tables.

Authors:
; ;
Publication Date:
Research Org.:
Rockwell International Corp., Golden, CO (USA). Rocky Flats Plant
OSTI Identifier:
5318991
Report Number(s):
RFP-3589
ON: DE84007334
DOE Contract Number:
AC04-76DP03533
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; PLUTONIUM; PRECIPITATION; BENCH-SCALE EXPERIMENTS; CRYSTAL STRUCTURE; OXALATES; PARTICLE SIZE; PLUTONIUM CARBONATES; PLUTONIUM FLUORIDES; PLUTONIUM HYDROXIDES; PLUTONIUM PEROXIDES; ACTINIDE COMPOUNDS; ACTINIDES; CARBON COMPOUNDS; CARBONATES; CARBOXYLIC ACID SALTS; ELEMENTS; FLUORIDES; FLUORINE COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; HYDROGEN COMPOUNDS; HYDROXIDES; METALS; OXYGEN COMPOUNDS; PEROXIDES; PLUTONIUM COMPOUNDS; SEPARATION PROCESSES; SIZE; TRANSURANIUM COMPOUNDS; TRANSURANIUM ELEMENTS; 052001* - Nuclear Fuels- Waste Processing; 400105 - Separation Procedures; 050800 - Nuclear Fuels- Spent Fuels Reprocessing

Citation Formats

Martella, L.L., Saba, M.T., and Campbell, G.K.. Laboratory-scale evaluations of alternative plutonium precipitation methods. United States: N. p., 1984. Web. doi:10.2172/5318991.
Martella, L.L., Saba, M.T., & Campbell, G.K.. Laboratory-scale evaluations of alternative plutonium precipitation methods. United States. doi:10.2172/5318991.
Martella, L.L., Saba, M.T., and Campbell, G.K.. Wed . "Laboratory-scale evaluations of alternative plutonium precipitation methods". United States. doi:10.2172/5318991. https://www.osti.gov/servlets/purl/5318991.
@article{osti_5318991,
title = {Laboratory-scale evaluations of alternative plutonium precipitation methods},
author = {Martella, L.L. and Saba, M.T. and Campbell, G.K.},
abstractNote = {Plutonium(III), (IV), and (VI) carbonate; plutonium(III) fluoride; plutonium(III) and (IV) oxalate; and plutonium(IV) and (VI) hydroxide precipitation methods were evaluated for conversion of plutonium nitrate anion-exchange eluate to a solid, and compared with the current plutonium peroxide precipitation method used at Rocky Flats. Plutonium(III) and (IV) oxalate, plutonium(III) fluoride, and plutonium(IV) hydroxide precipitations were the most effective of the alternative conversion methods tested because of the larger particle-size formation, faster filtration rates, and the low plutonium loss to the filtrate. These were found to be as efficient as, and in some cases more efficient than, the peroxide method. 18 references, 14 figures, 3 tables.},
doi = {10.2172/5318991},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 08 00:00:00 EST 1984},
month = {Wed Feb 08 00:00:00 EST 1984}
}

Technical Report:

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  • H-Canyon and HB-Line are tasked with the production of PuO{sub 2} from a feed of plutonium metal. The PuO{sub 2} will provide feed material for the MOX Fuel Fabrication Facility. After dissolution of the Pu metal in H-Canyon, the solution will be transferred to HB-Line for purification by anion exchange. Subsequent unit operations include Pu(IV) oxalate precipitation, filtration and calcination to form PuO{sub 2}. This report details the results from SRNL anion exchange, precipitation, filtration, calcination, and characterization tests, as requested by HB-Line1 and described in the task plan. This study involved an 80-g batch of Pu and employed testmore » conditions prototypical of HB-Line conditions, wherever feasible. In addition, this study integrated lessons learned from earlier anion exchange and precipitation and calcination studies. H-Area Engineering selected direct strike Pu(IV) oxalate precipitation to produce a more dense PuO{sub 2} product than expected from Pu(III) oxalate precipitation. One benefit of the Pu(IV) approach is that it eliminates the need for reduction by ascorbic acid. The proposed HB-Line precipitation process involves a digestion time of 5 minutes after the time (44 min) required for oxalic acid addition. These were the conditions during HB-line production of neptunium oxide (NpO{sub 2}). In addition, a series of small Pu(IV) oxalate precipitation tests with different digestion times were conducted to better understand the effect of digestion time on particle size, filtration efficiency and other factors. To test the recommended process conditions, researchers performed two nearly-identical larger-scale precipitation and calcination tests. The calcined batches of PuO{sub 2} were characterized for density, specific surface area (SSA), particle size, moisture content, and impurities. Because the 3013 Standard requires that the calcination (or stabilization) process eliminate organics, characterization of PuO{sub 2} batches monitored the presence of oxalate by thermogravimetric analysis-mass spectrometry (TGA-MS). To use the TGA-MS for carbon or oxalate content, some method development will be required. However, the TGA-MS is already used for moisture measurements. Therefore, SRNL initiated method development for the TGA-MS to allow quantification of oxalate or total carbon. That work continues at this time and is not yet ready for use in this study. However, the collected test data can be reviewed later as those analysis tools are available.« less
  • Treatability studies were performed to evaluate the treatment of Manufactured Gas Plant (MGP) site groundwaters using the following treatment processes: gravity separation, coagulation/flocculation, sand filtration, air stripping, carbon adsorption, and chemical oxidation. Treatment results for conventional parameters, inorganic compounds, metals, volatile aromatics, phenolics, and polynuclear aromatic hydrocarbons are presented and compared to regulatory limits associated with discharge to a Publicly Owned Treatment Works (POTW), discharge to a surface water body, or subsurface injection. Equipment costs as well as operating and maintenance costs are presented for several treatment strategies designed to achieve compliance with alternative discharge requirements.
  • The H-Canyon facility will be used to dissolve Pu metal for subsequent purification and conversion to plutonium dioxide (PuO{sub 2}) using Phase II of HB-Line. To support the new mission, SRNL conducted a series of experiments to produce calcined plutonium (Pu) oxide and measure the physical properties and water adsorption of that material. This data will help define the process operating conditions and material handling steps for HB-Line. An anion exchange column experiment produced 1.4 L of a purified 52.6 g/L Pu solution. Over the next nine weeks, seven Pu(IV) oxalate precipitations were performed using the same stock Pu solution,more » with precipitator feed acidities ranging from 0.77 M to 3.0 M nitric acid and digestion times ranging from 5 to 30 minutes. Analysis of precipitator filtrate solutions showed Pu losses below 1% for all precipitations. The four larger precipitation batches matched the target oxalic acid addition time of 44 minutes within 4 minutes. The three smaller precipitation batches focused on evaluation of digestion time and the oxalic acid addition step ranged from 25-34 minutes because of pump limitations in the low flow range. Following the precipitations, 22 calcinations were performed in the range of 610-690 C, with the largest number of samples calcined at either 650 or 635 C. Characterization of the resulting PuO{sub 2} batches showed specific surface areas in the range of 5-14 m{sup 2}/g, with 16 of the 22 samples in the range of 5-10 m2/g. For samples analyzed with typical handling (exposed to ambient air for 15-45 minutes with relative humidities of 20-55%), the moisture content as measured by Mass Spectrometry ranged from 0.15 to 0.45 wt % and the total mass loss at 1000 C, as measured by TGA, ranged from 0.21 to 0.58 wt %. For the samples calcined between 635 and 650 C, the moisture content without extended exposure ranged from 0.20 to 0.38 wt %, and the TGA mass loss ranged from 0.26 to 0.46 wt %. Of these latter samples, the samples calcined at 650 C generally had lower specific surface areas and lower moisture contents than the samples calcined at 635 C, which matches expectations from the literature. Taken together, the TGA-MS results for samples handled at nominally 20-50% RH, without extended exposure, indicate that the Pu(IV) oxalate precipitation process followed by calcination at 635-650 C appears capable of producing PuO{sub 2} with moisture content < 0.5 wt% as required by the 3013 Standard. Exposures of PuO{sub 2} samples to ambient air for 3 or more hours generally showed modest mass gains that were primarily gains in moisture content. These results point to the need for a better understanding of the moisture absorption of PuO{sub 2} and serve as a warning that extended exposure times, particularly above the 50% RH level observed in this study will make the production of PuO{sub 2} with less than 0.5 wt % moisture more challenging. Samples analyzed in this study generally contained approximately 2 monolayer equivalents of moisture. In this study, the bulk of the moisture released from samples below 300 C, as did a significant portion of the CO{sub 2}. Samples in this study consistently released a minor amount of NO in the 40-300 C range, but no samples released CO or SO{sub 2}. TGA-MS results also showed that MS moisture content accounted for 80 {+-} 8% of the total mass loss at 1000 C measured by the TGA. The PuO{sub 2} samples produced had particles sizes that typically ranged from 0.2-88 {micro}m, with the mean particle size ranging from 6.4-9.3 {micro}m. The carbon content of ten different calcination batches ranged from 190-480 {micro}g C/g Pu, with an average value of 290 {micro}g C/g Pu. A statistical review of the calcination conditions and resulting SSA values showed that in both cases tested, calcination temperature had a significant effect on SSA, as expected from literature data. The statistical review also showed that batch size had a significant effect on SSA, but the narrow range of batch sizes tested is a compelling reason to set aside that result until tests with larger batch sizes are completed. When feed acidity was not included as a variable, calcination time had a significant effect on SSA. However, including feed acidity as a variable showed that neither feed acidity nor calcination time had a significant effect on SSA in this study. Also, for both cases the statistical review also indicated that digestion time did not have a significant effect on SSA.« less
  • This report describes a design for a laboratory-scale capability to produce plutonium oxide (PuO 2) for use in identifying and validating nuclear forensics signatures associated with plutonium production, as well as for use as exercise and reference materials. This capability will be located in the Radiochemical Processing Laboratory at the Pacific Northwest National Laboratory. The key unit operations are described, including PuO 2 dissolution, purification of the Pu by ion exchange, precipitation, and re-conversion to PuO 2 by calcination.