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THERMODYNAMICS OF NEPTUNIUM(V) FLOURIDE AND SULFATE AT ELEVATED TEMPERATURES

Description: Complexation of neptunium(V) with fluoride and sulfate at elevated, temperatures was studied by microcalorimetry. Thermodynamic parameters, including the equilibrium constants and enthalpy of protonation of fluoride and sulfate, and the enthalpy of complexation between Np(V) and fluoride and sulfate at 25-70 C were determined. Results show that the complexation of Np(V) with fluoride and sulfate is endothermic and that the complexation is enhanced by the increase in temperature--a threefold inc… more
Date: March 6, 2006
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Variation of stability constants of thorium citrate complexes and of thorium hydrolysis constants with ionic strength

Description: Citrate is among the organic anions that are expected to be present in the wastes planned for deposition in the Waste Isolation Pilot Plant repository. In this study, a solvent extraction method has been used to measure the stability constants of Thorium(IV)[Th(IV)] with citrate anions in aqueous solutions with (a) NaClO{sub 4} and (b) NaCl as the background electrolytes. The ionic strengths were varied up to 5 m (NaCl) and 14 m (NaClO{sub 4}). The data from the NaClO{sub 4} solutions at varyin… more
Date: September 1, 1995
Creator: Choppin, Gregory R.; Erten, Hasan N. & Xia, Yuan-Xian
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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STABILITY CONSTANTS OF NP(V) COMPLEXES WITH FLOURIDE AND SULFATE AT VARIABLE TEMPERATURES

Description: A solvent extraction method was used to determine the stability constants of Np(V) complexes with fluoride and sulfate in 1.0 M NaClO{sub 4} from 25 C to 60 C. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of fluoride and sulfate were increased. Stability constants of the 1:1 Np(V)-fluoride complexes and the 1:1 Np(V)-sulfate and 1:2 Np(V)-sulfate complexes, dominant in the aqueous phase under the experimental conditions, were… more
Date: July 11, 2005
Creator: Xia, Yuanxian; Friese, Judah I.; Moore, Dean A. & Rao, Linfeng
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Actinide Thermodynamics at Elevated Temperatures

Description: The postclosure chemical environment in the proposed Yucca Mountain repository is expected to experience elevated temperatures. Predicting migration of actinides is possible if sufficient, reliable thermodynamic data on hydrolysis and complexation are available for these temperatures. Data are scarce and scattered for 25 degrees C, and nonexistent for elevated temperatures. This collaborative project between LBNL and PNNL collects thermodynamic data at elevated temperatures on actinide complexe… more
Date: November 16, 2007
Creator: Friese, Judah I.; Rao, Linfeng; Xia, Yuanxian; Bachelor, Paula P. & Tian, Guoxin
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Spectrophotometric and Calorimetric Studies of Np(V) Complexation with Sulfate at 10-70oC

Description: Sulfate, one of the inorganic constituents in the groundwater of nuclear waste repository, could affect the migration of radioactive materials by forming complexes. Spectrophotometric and microcalorimetric titrations were performed to identify the Np(V)/sulfate complex and determine the equilibrium constants and enthalpy of complexation at 10-70 C. Results show that the complexation of Np(V) with sulfate is weak but slightly enhanced by the increase in temperature. The complexation is endotherm… more
Date: June 16, 2008
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Complexation of Neptunium(V) with Fluoride at Elevated Temperatures

Description: Complexation of neptunium(V) with fluoride at elevated temperatures was studied by spectrophotometry and microcalorimetry. Two successive complexes, NpO{sub 2}F(aq) and NpO{sub 2}F{sub 2}{sup -}, were identified by spectrophotometry in the temperature range of 10-70 C. Thermodynamic parameters, including the equilibrium constants and enthalpy of complexation between Np(V) and fluoride at 10-70 C were determined. Results show that the complexation of Np(V) with fluoride is endothermic and that t… more
Date: June 16, 2008
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Thermodynamics of neptunium(V) fluoride and sulfate at elevatedtemperatures

Description: Complexation of neptunium(V) with fluoride and sulfate at elevated temperatures was studied by microcalorimetry. Thermodynamic parameters, including the equilibrium constants and enthalpy of protonation of fluoride and sulfate, and the enthalpy of complexation between Np(V) and fluoride and sulfate at 25 - 70 C were determined. Results show that the complexation of Np(V) with fluoride and sulfate is endothermic and that the complexation is enhanced by the increase in temperature - a three-fold … more
Date: October 31, 2006
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Complexation of Plutonium (IV) with Fluoride at Variable Tempeartures

Description: Complexation of Pu(IV) with fluoride was studied by solvent extraction at 25, 40 and 55 C in 2.2 mol {center_dot} kg{sup -1} HClO{sub 4}. The distribution ratio of Pu(IV) between the organic and aqueous phases decreased as the concentration of fluoride was increased due to the formation of Pu(IV)-F complexes in the aqueous phase. Two complexes, PuF{sup 3+} and PuF{sub 2}{sup 2+}, were identified under the conditions in this work and their stability constants at 25, 40 and 55 C and I = 2.2 mol {… more
Date: June 10, 2009
Creator: Xia, Yuanxian; Rao, Linfeng; Friese, Judah I.; Moore, Dean A. & Bachelor, P. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bridging the Gap in the Chemical Thermodynamic Database for Nuclear Waste Repository: Studies of the Effect of Temperature on Actinide Complexation

Description: Recent results of thermodynamic studies on the complexation of actinides (UO{sub 2}{sup 2+}, NpO{sub 2}{sup +} and Pu{sup 4+}) with F{sup -}, SO{sub 4}{sup 2-} and H{sub 2}PO{sub 4}{sup -}/HPO{sub 4}{sup 2-} at elevated temperatures are reviewed. The data indicate that, for all systems except the 1:1 complexation of Np(V) with HPO{sub 4}{sup 2-}, the complexation of actinides is enhanced by the increase in temperature. The enhancement is primarily due to the increase in the entropy term (T{Delt… more
Date: December 21, 2009
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian; Friese, Judah I.; Zanonato, PierLuigi & Di Bernardo, Plinio
Item Type: Refine your search to only Book
Partner: UNT Libraries Government Documents Department
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Technetium Chemistry in HLW: Role of Organic Complexants

Description: Tc contamination is found within the DOE complex at those sites whose mission involved extraction of plutonium from irradiated uranium fuel or isotopic enrichment of uranium. At the Hanford Site, chemical separations and extraction processes generated large amounts of high level and transuranic wastes that are currently stored in underground tanks. Technetium is thought to have followed U in bismuth phosphate, REDOX and PUREX extraction campaigns and the Cs and Sr isotope recovery efforts. The … more
Date: June 1, 2004
Creator: Hess, Nancy J.; Blanchard, David L., Jr.; Cho, Herman M.; Xia, Yuanxian; Campbell, James A.; Rai, Dhanpat et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Technetium Chemistry in HLW: Role of Organic Complexants

Description: Technetium complexation with organic compounds in tank waste plays a significant role in the redox chemistry of Tc and the partitioning of Tc between the supernatant and sludge components in waste tanks. These processes need to be understood so that strategies to effectively remove Tc from high-level nuclear waste prior to waste immobilization can be developed and so that longterm consequences of Tc remaining in residual waste after sludge removal can be evaluated. Only limited data on the stab… more
Date: June 1, 2002
Creator: Hess, Nancy J.; Blanchard, David L. Jr.; Campbell, James A.; Cho, Herman M.; Rai, Dhanpat, Rai; Xia, Yuanxian et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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