Molecular properties at air-liquid and liquid-liquid interface hold the key to many processes involving molecular transport across phase boundaries from aerosol formation to carbon cycling and material separation using solvent extraction techniques. Using dibutyl phosphate (DBP) as a representative for partially aqueous soluble surfactants, the specific ion effect (SIE) of the Hofmeister series cations Cs+, Na+, Li+, and Mg2+ on the partition and interaction between surfactant molecules and water molecules in the air-aqueous interface are investigated using vibrational sum frequency generation spectroscopy and surface tension measurements. In the presence of 1 mM and 1M bulk aqueous phase ionic strength salt concentrations, fundamental qualitative relationships are observed for the salting out of DBP relative to bulk aqueous phase nitrate salt concentrations and the specific cations species. At 1 mM ionic strength, the interfacial charge and hence the interfacial potential modulates the electrostatic interactions; in particular, the counter cations partially screen the negatively charged interface induced by the DBP in a direct Hofmeister order. At 1M ionic strength, the electric field at the interface or interfacial potential is effectively neutralized, and the counter cations promote the partitioning of DBP to the interface depending on their specific interaction with the DBP head group and metal ion hydration properties. The present results lay a foundation to study SIEs of heavier metals on hydrophobic-aqueous DBP interfaces.

Liquid-liquid extraction is a separation technique implemented in a wide variety of areas, achieving particular success in both the nuclear and biomedical fields. In this work, vibrational sum frequency generation spectroscopy (vSFG) and surface tension measurements were used to investigate the adsorption of dibutyl phosphate (DBP) at air-aqueous interfaces to simulate liquid-liquid systems relevant to the Plutonium Uranium Redox Extraction (PUREX) Process. The objective of this work is to establish qualitative relationships between changes in the bulk aqueous phase concentrations of DBP and its concentration and structure at the air-liquid interface as probed with vSFG. Nitric acid concentration and solution ionic strength were varied to examine their effect on the interfacial DBP. Introduction of DBP into neat water resulted in reduction of the vSFG spectral intensity in the dangling O-H region (3680 - 3800 cm(-1)) but a large increase in the H-bonded O-H stretch frequency region (3000 - 3500 cm(-1)) and the appearance of the CH3 symmetric stretch and CH3 Fermi resonance peaks at similar to 2880 and 2945 cm(-1), respectively, indicating DBP at the air-water interface. The intensity of the C-H strecth peaks increased as DBP concentration increased from 0.24 to 32 mM, accompanied by decreasing surface tension values. At fixed DBP concentration, the addition of either or both HNO3 and NaNO3 to an ionic strength of 1 M or 3 M led to significant reduction of the O-H vSFG peaks and enhancement of the C-H peaks. The origins of these experimental observations are attributed to both an increase of HDBP molecules partitioning and adsorbing to the interface and the protonation of the interfacial DBP- molecules.

NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract Session 2577 The Western Nuclear Science Alliance Authors: Stephen E. Binney, Wade J. Richards, Walter D. Loveland, Steven R. Reese, Kathryn A. Higley, James T. Elliston, Sue B. Clark, Edward C. Morse, John Bennion Oregon State University/University of California Davis/Oregon State University/ Oregon State University/Oregon State University/Washington State University/Washington State University/University of California Berkeley/Idaho State University Introduction The Western Nuclear Science Alliance (WNSA) came into existence in September 2002 when Oregon State University (OSU) as the lead institution teamed with University of California Davis (UCD) and other organizations to receive one of the four five-year awards under DOE’s Innovations in Nuclear Infrastructure and Education (INIE) program. The objective of these INIE awards was "to strengthen U.S. university nuclear engineering education programs through innovative use of the university research and training reactors and encouraging strategic partnerships between the universities, the DOE national laboratories, and U.S. industry." The method whereby WNSA addresses this objective is discussed below. Structure of WNSA WNSA is initially composed of five western universities (OSU, UCD, Washington State University (WSU), University of California Berkeley (UCB), and Idaho State University (ISU)). Together these universities operate four research reactors and have three nuclear engineering programs and two radiochemistry programs. In addition, six western national Department of Energy and NASA laboratories (Argonne National Laboratory-West, Idaho National Engineering and Environmental Laboratory, Jet Propulsion Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Pacific Northwest National Laboratory), and several nuclear industrial organizations from around the country (Adelphi Technology, Energy Northwest, Entergy, Nova Scientific, and SAIC) are initial members of WNSA (see Figure 1). WNSA program progress is monitored by a Management Council. The Management Council is responsible for providing management and decision-making capabilities for WNSA, coordinating all activities of WNSA, including the preparation of annual reports and renewal proposals, and providing vision for expansion of programs under WNSA. The Management Council is composed of six members, including the Chair, with an equal number from OSU and UCD. The Management Council is initially chaired by an OSU member with the Chair alternating between OSU and UCD each September. A Vice-Chair of the Management Council is selected from the other university. Replacement of Management Council members is at the discretion of the Management Council membership. Members may serve

The Basic Energy Science Advisory Committee (BESAC) was charged with forming a subcommittee to assess the scientific justification for a U.S. domestic high-performance reactor-based research facility in order to continue providing the U.S scientific community with leading neutron capabilities in support of DOE's missions in science, energy, environment, and national security. The assessment included consideration of current international plans and existing domestic facility infrastructure. The subcommittee held a series of meetings from August 19, 2019 to April 24, 2020 that included DOE senior officials, leaders of national and international neutron facilities (SNS, HFIR, NIST, ILL, FRM-II), chairs of the NAS and POPA HEU-LEU committees, and outside experts on important areas of science, technology, and industry where high flux nuclear reactor facilities make important contributions. Also included were tours of neutron facilities (SNS, HFIR, NIST, BR2 reactor, and the planned Jules Horowitz Reactor). This July 2020 (revised 10-28-2020) report describes scientific use cases, brief summaries of existing and planned neutron facilities in the US and Europe, a comprehensive review of HFIR, a comprehensive discussion of the current state of progress on HEU-LEU conversion, user information from NIST and ORNL, and three recommendations to DOE for moving forward.

The rapid preconcentration of lanthanides in aqueous solution is of interest to enable follow-on analysis of nuclear fallout samples. The large negative overpotential of La reduction along with its instability in aqueous solutions has limited electrode-assisted preconcentration efforts to Hg amalgam and carbon paste electrodes. Previous work has shown that lanthanum films can be deposited on the electrochemical quartz crystal microbalance (eQCM). The frequency response of the eQCM tracked the formation of a La film during the cathodic sweep of cyclic voltammograms that resulted in the hydrogen reduction reaction. Recent findings determined that the lanthanum film associated with potentials beyond the cathodic stability limit of water are directly related to the increase in surface pH due to water hydrolysis. Additionally, x-ray photoelectron spectrometry and auger nanoprobe spectrometry results confirm that the films produced in this manner are La(OH)3. The formation of lanthanum film is likely to follow an electroprecipitation mechanism due to the basic environment on the electrode surface during the hydrogen reduction reaction. Surprisingly, the addition of the ligand α-hydroxyisobutyric acid resulted in films of the form La2O3 rather than La(OH)3. The mechanism of ligand-assisted La2O3 formation is being investigated. These findings will aid in miniaturizing the electrochemical preconcentration of lanthanides on microelectrodes.

Electrospray ionization-mass spectrometry (ESI-MS) was tested for its use in monitoring spent nuclear fuel (SNF) constituents including U, Pu, dibutyl phosphate (DBP), and tributyl phosphate (TBP). Both positive and negative ion modes were used to evaluate the speciation of U and Pu with TBP and DBP. Furthermore, apparent stability constants were determined for U complexed to TBP and DBP. In positive ion mode, TBP produced a strong signal with and without complexation to U or Pu, but, in negative ion mode, no TBP, U-TBP, or Pu-TBP complexes were observed. Apparent stability constants were determined for [UO2(NO3)2(TBP)2], [UO2(NO3)2(H2O)(TBP)2], and [UO2(NO3)2(TBP)3]. In contrast DBP, U-DBP, and Pu-DBP complexes were observed in both positive and negative ion modes. Apparent stability constants were determined for the species [UO2(DBP)], [UO2(DBP)3], and [UO2(DBP)4]. Analyzing mixtures of U or Pu with TBP and DBP yielded the formation of ternary complexes whose stoichiometry was directly related to the ratio of TBP to DBP. The ESI-MS protocols used in this study will further demonstrate the utility of ESI-MS and its applicability to process control monitoring in SNF reprocessing facilities.

Plutonium (Pu), americium (Am), and curium (Cm) activities were measured in sediments from a former radioactive waste disposal basin located on the Savannah River Site, South Carolina, and in subsurface aquifer sediments collected downgradient from the basin. In situ Kd values (Pu concentration ratio of sediment/groundwater) derived from this field data and previously reported groundwater concentration data compared well to laboratory Kd values reported in the literature. Pu isotopic signatures confirmed multiple sources of Pu contamination. The ratio of (240)Pu/(239)Pu was appreciably lower for sediment samples compared to the associated groundwater. This isotopic ratio difference may be explained by the following: (1) (240)Pu produced by decay of (244)Cm may exist predominantly in high oxidation states (Pu(V)O2(+) and Pu(VI)O2(2+)) compared to Pu derived from the disposed waste effluents, and (2) oxidized forms of Pu sorb less to sediments than reduced forms of Pu. Isotope-specific Kd values calculated from measured Pu activities in the sediments and groundwater indicated that (240)Pu, which is derived primarily from the decay of (244)Cm, had a value of 10 ± 2 mL g(-1), whereas (239)Pu originating from the waste effluents discharged at the site had a value of 101 ± 8 mL g(-1). One possible explanation for the isotope-specific sorption behavior is that (240)Pu likely existed in the weaker sorbing oxidation states, +5 or +6, than (239)Pu, which likely existed in the +3 or +4 oxidation states. Consequently, remediation strategies for radioactively contaminated systems must consider not only the discharged contaminants but also their decay products. In this case, mitigation of Cm as well as Pu will be required to completely address Pu migration from the source term.

XANES (X-ray Absorption Near Edge Spectroscopy) has been employed to evaluate the efficacy of a process designed to encapsulate and reduce TcO 4 - in cement matrices, thereby immobilizing Tc. The oxidation state of Se following bioremediation of Se by bacteria has also been determined by XANES. The XANES measurements were performed at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS) at the respective K edges of Tc (21.0 keV) and Se (12.7 keV). Comparison of the XANES spectra of Tc in untreated cement to Tc in slag treated cement and to the chemical shifts of reference materials, shows that the oxidation state of Tc is the same in both cements. Thus, the addition of a reducing agent to the cement formulation does not significantly reduce the TcO 4 - . The common soil bacterium, Bacillus subtilis , is known to incorporate Se on or within the cell wall when exposed to a Se(IV) solution. The Se XANES spectra of B. subtilis , as well as bacillus isolated from selenium rich soil, show that the organisms reduce selenite to the red allotrope of elemental Se.

Abstract Current work indicates that trivalent lanthanides will consistently sorb to a rotating disk mercury film electrode in bulk aqueous solution thus allowing the user to pre-concentrate trivalent lanthanides for further separation. However, the mechanism of sorption to the mercury film is largely unknown, making it difficult if not impossible to predict a priori the conditions under which pre-concentration is optimized. In the present study, we explore some of the electrochemical factors affecting this pre-concentration process to optimize the technique for use in a wide variety of aqueous media. Trivalent neodymium (Nd(III)) is used as a model for the trivalent f-element cations. The factors investigated include pH of solution, rotation rate of the electrode, concentration of mercury, potential application waveforms, order of deposition, and time dependency.

EDTA, a common chelating agent, is becoming a major organic pollutant in the form of metal-EDTA complexes in surface waters, partly due to its recalcitrance to biodegradation. Even an EDTA-degrading bacterium, BNC1, does not degrade stable metal-EDTA complexes. In the present study, an ABC-type transporter was identified for possible uptake of EDTA because the transporter genes and the EDTA monooxygenase gene were expressed from a single operon in BNC1. The ABC-type transporter had a periplasmic-binding protein (EppA) that should confer the substrate specificity for the transporter; therefore, EppA was produced in Escherichia coli, purified, and characterized. EppA was shown to bind free EDTA with a dissociation constant as low as 25 nM by using isothermal titration calorimetry. When unstable metal-EDTA complexes, e.g., (Mg-EDTA)(2-), were added to the EppA solution, binding was also observed. However, experimental data and theoretical analysis supported EppA binding only of free EDTA. When stable metal-EDTA complexes, e.g., (Cu-EDTA)(2-), were titrated into the EppA solution, no binding was observed. Since EDTA monooxygenase in the cytoplasm uses some of the stable metal-EDTA complexes as substrates, we suggest that the lack of EppA binding and EDTA uptake are responsible for the failure of BNC1 cells to degrade the stable complexes.

The combined effects of increasing industrialization around the world, the threat of global climate change, and decreasing availability of "clean" fossil fuels will make the development of alternative energy sources more important in the coming decades. For fission-based nuclear power to contribute significantly to future energy supplies, it will be essential to maintain the improvements that have been made in plant operational efficiency, to license geological repositories for waste disposal, and to consider again the issue of recycling of spent nuclear fuels to recover its fuel value and to reduce the long-term radiotoxicity of the wastes. In this chapter, we present an overview of the nuclear fuel cycle from spent fuel recycling through the repository performance in the context of its importance to energy production in the 21(st) Century. (c) 2006 American Chemical Society

A fission track analysis and alpha track analysis were developed to detect fissile particles such as uranium and plutonium isotopes as well as to identify particle-bound plutonium in contaminated soil or sediment. To record a reference point, a locator SEM grid electroplated with boron was used to obtain a recorded grid image on the Lexan or CR-39 detector. With the fission track technique, the track images of the grid coated with boron and the fissile nuclides on the CR-39 detector were clearly recorded so that the location of the fissile particles could be easily identified in the radio-contaminated soil matrix. With the alpha track technique, many of the hot particles in the BOMARC soil turned out to be contaminated with plutonium isotopes rather than uranium isotopes.

Chromium is of great concern in the vitrification of high-level nuclear waste sludges because it forms separate crystallites in the molten glass. Inadequate removal of chromium from sludges could result in the production of an unacceptably large volume of HLW glass. Alkaline oxidative leaching is considered one of the pretreatment strategies to remove chromium before the vitrification. In this study, Cr(III) hydroxide solids were prepared under different conditions and characterized by EXAFS and IR. The rate of oxidation of the solids by hydrogen peroxide in alkaline solutions was studied by UV absorption spectroscopy. EXAFS and IR experiments indicate that the degree of oligomerization in the Cr(III) hydroxide solids increases with the increase in the concentration of NaOH in solution, the aging temperature and the aging time. The rate of oxidation of the solids follows the same order previously observed for Cr(III) oligomers in solution, i.e., species with higher degree of oligomerization are oxidized more slowly.