Precipitation of Plutonium(iii) Oxalate and Calcination to Plutonium Dioxide.

Porter, John A.; Symonds, A.E.

doi:10.2172/4649172

Cited by 7 publications

(9 citation statements)

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“…This reference 35 discusses the precipitation of plutonium(III) oxalate from nitric acid, hydrochloric acid, and sulfamic acid solutions then its calcination. This reference indicates that Pu(III) oxalate decomposes between 300 and 400 °C.…”

Section: Reference 35: Precipitation Of Plutonium(iii) Oxalate and Camentioning

confidence: 99%

Literature Review of Puo2 Calcination Time and Temperature Data for Specific Surface Area

Daniel¹

2012

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Section: Reference 35: Precipitation Of Plutonium(iii) Oxalate and Camentioning

confidence: 99%

Literature Review of Puo2 Calcination Time and Temperature Data for Specific Surface Area

Daniel¹

2012

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“…Plutonium(III) oxalate has the formula Pu 2 (C 2 O 4 ) 3 •10H 2 O. The precipitation process may follow the chemical conditions given in an existing RPL procedure (a) based on SRS experience, [18] but other conditions may be used as outlined in a review of Pu(III) oxalate precipitation chemistry. [19] The optimum batch conditions for more concentrated Pu feed solutions involve slowly adding 1 M H 2 C 2 O 4 (oxalic acid) solution (in direct-strike fashion) to the Pu(III) [19] The precipitation system is designed to accommodate Pu concentrations in the range 30 to 100 g Pu/L in a single batch.…”

Section: Precipitationmentioning

confidence: 99%

“…In air, the thermal decomposition of both Pu(IV) and Pu(III) oxalate to PuO 2 is mostly complete at 450°C, [20] although higher temperatures, approximately 800°C, [18,21] are often used to drive off residual carbon by air oxidation. The highest published temperature range used was 1,200-1,250°C for complete conversion to PuO 2 .…”

Section: Calcinationmentioning

confidence: 99%

“…[20] The prescribed standard method for conversion of Pu 2 (C 2 O 4 ) 3 •10H 2 O by Porter and Symonds recommends heating Pu 2 (C 2 O 4 ) 3 •10H 2 O in a stream of air from room temperature to 125°C at a rate of about 1.5°C/min (over approximately 1 h), and holding for 1 h at 125°C to convert to the anhydrous form Pu 2 (C 2 O 4 ) 3 . [18] After the 1 h holding period, the temperature is increased at a rate of 3-5°C/min until the final calcination temperature is reached (most often between 450°C and 750°C), which is maintained for 1 to 2 h. The resulting PuO 2 is then cooled to room temperature under the air stream. Samples can be taken and analyzed both before and after calcination to verify complete conversion to the oxide.…”

Section: Calcinationmentioning

confidence: 99%

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Design of the Laboratory-Scale Plutonium Oxide Processing Unit in the Radiochemical Processing Laboratory

Lumetta

Meier

Tingey

et al. 2015

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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 reconversion to PuO 2 by calcination. v Summary The National Technical Nuclear Forensics Center (NTNFC) within the Domestic Nuclear Detection Office (DNDO) of the Department of Homeland Security (DHS) has funded Pacific Northwest National Laboratory (PNNL) to establish a laboratory-scale (up to 200 g Pu per batch) 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 is being installed in Room 604 in the Radiochemical Processing Laboratory (RPL). The key unit operations for producing PuO 2 are as follows. The feed plutonium material is received in the RPL in oxide form. The as-received oxide is dissolved in nitric acid media (with fluoride added as needed). The resulting solution is subjected to ion exchange to remove impurities from the plutonium stream, and then the plutonium is precipitated in the form of a salt (e.g., oxalate, peroxide, or hydroxide). Finally, this Pu salt is converted back to PuO 2 by heating (calcining). In order to make this capability a useful tool for identifying and validating nuclear forensics signatures, the system is designed to be flexible, allowing variations in the different process parameters (e.g., temperature, manner of reagent addition, or type of precipitating agent). This report describes the laboratory-scale PuO 2 production capability being established at PNNL. The key features include:  Plutonium oxide is received at the RPL and 200 g aliquots are transferred to a glovebox in RPL Room 604 for processing.  The PuO 2 is dissolved in nitric acid media. If necessary, fluoride (in the form of calcium fluoride or hydrofluoric acid) is added to aid in dissolving the PuO 2.  The plutonium solution is clarified by filtration and then purified by anion exchange using Reillex HPQ ® anion-exchange resin, or another suitable anion-exchange resin.  Although the design allows for a variety of plutonium precipitation steps, the design is based primarily on Pu(III) oxalate [Pu 2 (C 2 O 4) 3 •10H 2 O] precipitation. The purified Pu solution is adjusted to the +3 oxidation state with ascorbic acid, then is treated with oxalic acid to precipitate Pu 2 (C 2 O 4) 3 •10H 2 O.  The Pu 2 (C 2 O 4) 3 •10H 2 O is calcined in a muffle furnace to convert it to PuO 2.  The PuO 2 product is packaged and distributed as directed by the NTNFC. Functional descriptions are provided for each unit operation, and the various requirements f...

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“…Combining the granular, +140 mesh Na 2 O 2 with the high-fired PuO 2 , which typically has a maximum particle size of about 45 µm (325 mesh), (8) does not result in efficient mixing of the materials prior to fusion. For this reason, a series of experiments was performed in which the Na 2 O 2 was ground using a mortar and pestle to a particle size less than 200 mesh (74 µm) to measure the impact on plutonium recovery.…”

Section: Reagent Particle Sizementioning

confidence: 99%

Recovery of Plutonium from Refractory Residues Using a Sodium Peroxide Pretreatment Process

Rudisill

2005

Separation Science and Technology

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The recycle of plutonium from refractory residues is a necessary activity for the nuclear weapon production complex. Traditionally, high-fired plutonium oxide (PuO 2 ) was leached from the residue matrix using a nitric acid/fluoride dissolving flowsheet. The recovery operations were time consuming and often required multiple contacts with fresh dissolving solution to reduce the plutonium concentration to levels where residual solids could be discarded. Due to these drawbacks, the development of an efficient process for the recovery of plutonium from refractory materials is desirable. To address this need, a pretreatment process was developed which utilizes a sodium peroxide (Na 2 O 2 ) fusion to oxidize plutonium from the 4+ to the 6+ valence forming an acid-soluble ternary oxide. The development program utilized a series of small-scale experiments to optimize processing conditions for the fusion process and demonstrate the plutonium recovery efficiency using ceramic materials developed as potential long-term storage forms for PuO 2 and an incinerator ash from the Rocky Flats Environmental Technology Site (Rocky Flats) as test materials.Process optimization studies using high-fired PuO 2 demonstrated that the efficiency of plutonium recovery increased with the Na 2 O 2 fusion temperature (up to 700°C), increasing Na 2 O 2 to PuO 2 ratio, and a decrease in the Na 2 O 2 particle size. Complete recovery of high-fired PuO 2 was obtained by dissolving the fused product in 8M nitric acid following fusion at 700°C for 2 h with 100% excess in the amount of Na 2 O 2 required for complete conversion to the ternary oxide. The amount of Na 2 O 2 required to maximize plutonium recovery is also dependent upon other materials associated with the PuO 2 which readily oxidize. Carbon or organic materials should be removed by calcination prior to fusion and nominally 100% excess Na 2 O 2 should be added for impurities which react to form ternary oxides.The recovery of plutonium following pretreatment by Na 2 O 2 fusion was demonstrated using two residues containing high-fired PuO 2 . Initially, ceramic materials developed as potential longterm storage forms for PuO 2 were fused and dissolved in 8M nitric acid. Plutonium recovery efficiencies ranging from approximately 95% to essentially complete recovery were obtained following fusion at 700°C for 2 h using 100% excess Na 2 O 2 .The second demonstration of the fusion process was performed using incinerator ash from Rocky Flats. In experiments with ash containing 17-18 wt% plutonium (based on accountability data), 90-95% recovery was obtained following dissolution of the fused product in 8M nitric acid. The fusions were performed at 700°C for 2 h using 75-100% excess Na 2 O 2 based on the estimated plutonium concentration and assuming the ash contained 50 wt% silicon oxide (SiO 2 ). The WSRC-MS-2003-00280 reduction in excess Na 2 O 2 had no effect on the plutonium recovery efficiency; however, it is likely the excess Na 2 O 2 was more than sufficient for complete oxidati...

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Precipitation of Plutonium(iii) Oxalate and Calcination to Plutonium Dioxide.

Abstract: Nuclear Technology-Chemistry and Chemical E n g i n e e r i n g (M-3679, 43rd Ed.

Cited by 7 publications

References 0 publications

Literature Review of Puo2 Calcination Time and Temperature Data for Specific Surface Area

Literature Review of Puo2 Calcination Time and Temperature Data for Specific Surface Area

Design of the Laboratory-Scale Plutonium Oxide Processing Unit in the Radiochemical Processing Laboratory

Recovery of Plutonium from Refractory Residues Using a Sodium Peroxide Pretreatment Process

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