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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A method for dissolving plutonium dioxide comprises adding silver ions to a nitric acid-hydrofluoric acid solution to significantly speed up dissolution of difficultly soluble plutonium dioxide.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A method for dissolving plutonium dioxide comprises adding silver ions to a nitric acid-hydrofluoric acid solution to significantly speed up dissolution of difficultly soluble plutonium dioxide.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
PuO.sub. 2 -containing solids, particularly residues from incomplete HNO.sub. 3 dissolution of irradiated nuclear fuels, are dissolved in aqueous HI. The resulting solution is evaporated to dryness and the solids are dissolved in HNO.sub. 3 for further chemical reprocessing. Alternatively, the HI solution containing dissolved Pu values, can be contacted with a cation exchange resin causing the Pu values to load the resin. The Pu values are selectively eluted from the resin with more concentrated HI.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The H-Canyon facility will be used to dissolve Pu metal for subsequent purification and conversion to plutonium dioxide (PuO2) using Phase II of HB-Line. To support the new mission, the development of a Pu metal dissolution flowsheet which utilizes concentrated (8-10 M) nitric acid (HNO3) solutions containing potassium fluoride (KF) is required. Dissolution of Pu metal in concentrated HNO3 is desired to eliminate the need to adjust the solution acidity prior to purification by anion exchange. The preferred flowsheet would use 8-10 M HNO3, 0.015-0.07 M KF, and 0.5-1.0 g/L Gd to dissolve the Pu up to 6.75 g/L. An alternate flowsheet would use 8-10 M HNO3, 0.1-0.2 M KF, and 1-2 g/L B to dissolve the Pu. The targeted average Pu metal dissolution rate is 20 mg/min-cm2, which is sufficient to dissolve a 'standard' 2250-g Pu metal button in 24 h. Plutonium metal dissolution rate measurements showed that if Gd is used as the nuclear poison, the optimum dissolution conditions occur in 10 M HNO3, 0.04-0.05 M KF, and 0.5-1.0 g/L Gd at 112 to 116 C (boiling). These conditions will result in an estimated Pu metal dissolution rate of ≈11-15 mg/min-cm2 and will result in dissolution times of 36-48 h for standard buttons. The recommended minimum and maximum KF concentrations are 0.03 M and 0.07 M, respectively. The maximum KF concentration is dictated by a potential room-temperature Pu-Gd-F precipitation issue at low Pu concentrations. The purpose of the experimental work described in this report was two-fold. Initially a series of screening experiments was performed to measure the dissolution rate of Pu metal as functions of the HNO3, KF, and Gd or B concentrations. The objective of the screening tests was to propose optimized conditions for subsequent flowsheet demonstration tests. Based on the rate measurements, this study found that optimal dissolution conditions in solutions containing 0.5-1.0 g/L Gd occurred in 8-10 M HNO3 with 0.04-0.05 M KF at 112 to 116 C (boiling). The testing also showed that solutions containing 8-10 M HNO3, 0.1-0.2 M KF, and 1-2 g/L B achieved acceptable dissolution rates in the same temperature range. To confirm that conditions identified by the dissolution rate measurements for solutions containing Gd or B can be used to dissolve Pu metal up to 6.75 g/L in the presence of Fe, demonstration experiments were performed using concentrations in the optimal ranges. In two of the demonstration experiments using Gd and in one experiment using B, the offgas generation during the dissolution was measured and samples were analyzed for H2. The experimental methods used to perform the dissolution rate measurements and flowsheet demonstrations and a discussion of the results are presented.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The deinventory and deactivation of the Savannah River Site's (SRS's) FB-Line facility required the disposition of approximately 2000 items from the facility's vaults. Plutonium (Pu) scraps and residues which do not meet criteria for conversion to a mixed oxide fuel will be dissolved and the solution stored for subsequent disposition. Some of the items scheduled for dissolution are composite materials containing Pu and tantalum (Ta) metals. The preferred approach for handling this material is to dissolve the Pu metal, rinse the Ta metal with water to remove residual acid, and burn the Ta metal. The use of a 4 M nitric acid (HNO3) solution containing 0.2 M potassium fluoride (KF) was initially recommended for the dissolution of approximately 500 g of Pu metal. However, prior to the use of the flowsheet in the SRS facility, a new processing plan was proposed in which the feed to the dissolver could contain up to 1250 g of Pu metal. To evaluate the use of a larger batch size and subsequent issues associated with the precipitation of plutonium-containing solids from the dissolving solution, scaled experiments were performed using Pu metal and samples of the composite material. In the initial experiment, incomplete dissolution of a Pu metal sample demonstrated that a 1250 g batch size was not feasible in the HB-Line dissolver. Approximately 45% of the Pu was solubilized in 4 h. The remaining Pu metal was converted to plutonium oxide (PuO2). Based on this work, the dissolution of 500 g of Pu metal using a 4-6 h cycle time was recommended for the HB-Line facility. Three dissolution experiments were subsequently performed using samples of the Pu/Ta composite material to demonstrate conditions which reduced the risk of precipitating a double fluoride salt containing Pu and K from the dissolving solution. In these experiments, the KF concentration was reduced from 0.2 M to either 0.15 or 0.175 M. With the use of 4 M HNO3 and a reduction in the KF concentration to 0.175 M, the dissolution of 300 g of Pu metal is expected to be essentially complete in 6 h. The dissolution of larger batch sizes would result in the formation of PuO2 solids. Incomplete dissolution of the PuO2 formed from the metal is not a solubility limitation, but can be attributed to a combination of reduced acidity and complexation of fluoride which slows the dissolution kinetics and effectively limits the mass of Pu dissolved.
Author: William J. Jenkins Publisher: ISBN: Category : Plutonium Languages : en Pages : 12
Book Description
Plutonium metal was found to dissolve readily in sulfamic acid and in mixtures of sulfamic and nitric acid. This method of dissolution is convenient in a plant process for the recovery of off-standard metal.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A two-step process for dissolving plutonium metal, which two steps can be carried out sequentially or simultaneously. Plutonium metal is exposed to a first mixture containing approximately 1.0M-1.67M sulfamic acid and 0.0025M-0.1M fluoride, the mixture having been heated to a temperature between 45.degree. C. and 70.degree. C. The mixture will dissolve a first portion of the plutonium metal but leave a portion of the plutonium in an oxide residue. Then, a mineral acid and additional fluoride are added to dissolve the residue. Alteratively, nitric acid in a concentration between approximately 0.05M and 0.067M is added to the first mixture to dissolve the residue as it is produced. Hydrogen released during the dissolution process is diluted with nitrogen.
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Author: R. G. Gutmacher
Author: F. E. Butler
Author: W. S. Gilman
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Author: William J. Jenkins
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Author: E. L. Whittaker