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Thermodynamic modeling of neptunium(V) solubility in concentrated Na-CO{sub 3}-HCO{sub 3}-Cl-ClO{sub 4}-H-OH-H{sub 2}O systems

Description: Safety assessments of nuclear waste repositories often require estimation of actinide solubilities as a function of groundwater composition. Although considerable amount of research has been done on the solubility and speciation of actinides, relatively little has been done to unify these data into a model applicable to concentrate brines. Numerous authors report data on the aqueous chemical properties of Np(V) in NaClO{sub 4}, Na{sub 2}CO{sub 3}, and NaCl media, but a consistent thermodynamic … more
Date: October 1, 1994
Creator: Novak, C. F. & Roberts, K. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The experimental determination of the solubility product for NpO{sub 2}OH in NaCl solutions

Description: The solubility of Np(V) was measured in NaCl solutions ranging from 0.30 to 5.6 molal at room temperature ({approximately}21 {plus_minus} 2{degrees}C). Experiments were conducted from undersaturation and allowed to equilibrate in a CO{sub 2}-free environment for 37 days. The apparent solubility products varied with NaCl concentration and were between 10{sup -9} and 10{sup -8} mol{sup 2}{sm_bullet}L{sup -2}. Using the specific ion interaction theory (SIT), the log of the solubility product of Np… more
Date: September 1, 1995
Creator: Roberts, K.E.; Torretto, P.C. & Prussin, T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Precipitation of neptunium dioxide from aqueous solution

Description: Tens of thousands of metric tons of highly radioactive, nuclear waste have been generated in the US. Currently, there is no treatment or disposal facility for these wastes. Of the radioactive elements in high-level nuclear waste, neptunium (Np) is of particular concern because it has a long half-life and may potentially be very mobile in groundwaters associated with a proposed underground disposal site at Yucca Mountain, Nevada. Aqueous Np concentrations observed in previous, short-term solubil… more
Date: December 1, 1999
Creator: Roberts, K E
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neptunium_Oxide_Precipitation_Kinetics_AJohnsen

Description: We evaluate the proposed NpO{sub 2}{sup +}(aq)-NpO{sub 2}(cr) reduction-precipitation system at elevated temperatures to obtain primary information on the effects of temperature, ionic strength, O{sub 2} and CO{sub 2}. Experiments conducted on unfiltered solutions at 10{sup -4} M NpO{sub 2}{sup +}(aq), neutral pH, and 200 C indicated that solution colloids strongly affect precipitation kinetics. Subsequent experiments on filtered solutions at 200, 212, and 225 C showed consistent and distinctiv… more
Date: June 8, 2012
Creator: Johnsen, A. M.; Roberts, K. E. & Prussin, S. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The Need for a Neutron Source at the Rare Isotope Accelerator

Description: An intense neutron source facility with radiochemical processing capability is necessary at the Rare Isotope Accelerator to fully realize its potential benefit to stockpile stewardship and astrophysics. While many of the important physics missions of RIA can be addressed with radioactive ion beams, direct neutron cross-section measurements of interest to stockpile stewardship and astrophysics cannot because one cannot make a neutron target. Thus, one must collect a sufficient amount of the appr… more
Date: May 13, 2005
Creator: Ahle, L. E.; Rusnak, B.; Roberts, K. E.; Roeben, M. D.; Hausmann, M.; Reifarth, R. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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