Physics Commons^™

The Electrochemical Separation Of Curium And Americium: Quaterly Report August-December 2004, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium. The following pages outline the progress on our project to date. We have been actively performing research on this project for three months and are currently on schedule in terms of the proposed timelines.

The initial focus of the project involved setting up the laboratories for the studies outlined in the grant proposal. The instrumentation needed included an electrochemical work station that will perform the bulk of the electrochemical studies. This instrument will complement the electrochemical instrumentation in Dr. Hatchett’s laboratory and …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Quarterly Report, October 2004 To December 2004, Earl Wolfram, Thomas Hartmann, Kenneth Czerwinski

Fuels Campaign (TRP)

This project will examine inert matrix fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of ²³⁹Pu. Ceramics will be synthesized and characterized based on the reactor physics results. The solubility the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, will be investigated in a manner to provide …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Fridman, A. Galperin, E. Shwageraus

Fuels Campaign (TRP)

Second task of the BGU part of “Dissolution, Reactor, and Environmental Behavior of ZrO₂-MgO Inert Fuel Matrix” project aims at evaluation of the fertile free fuel matrix composition effect on the fuel reactivity and corresponding reactivity limited burnup. Fertile free fuel with different MgO to ZrO₂ ratio in the matrix will require different PuO₂ loading in order to assure certain fuel cycle length. This is due to the fact that absorption cross section of Zr is slightly higher than that of Mg, although absorption in both of these elements is small compared to Pu. Therefore, the …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Quarterly Report, July 2004 To September 2004, Kenneth Czerwinski, Earl Wolfram

Fuels Campaign (TRP)

This project will examine inert fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10 % of ²³⁹Pu. Ceramics will be synthesized and characterized based on the reactor physics results. The solubility the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, will be investigated in a manner to provide …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Fridman, A. Galperin, E. Shwageraus

Fuels Campaign (TRP)

This progress report presents results of analysis performed within the framework of “Dissolution, Reactor, and Environmental Behavior of ZrO₂-MgO Inert Fuel Matrix” project managed by University of Nevada at Las Vegas, Harry Reid Center for Environmental Studies.

The BGU working program includes the following four tasks:

1. Benchmark of computational tools

2. Determination of fissile Pu loading

3. Evaluation of burnable poison designs

4. Evaluation of reactivity feedback coefficients

This progress report presents the results of Task 1. The main objective of this task is to confirm the validity of the ELCOS ¹ code system for inert matrix …

Nondipole Effects In The Photoionization Of Xe 4d5/2 And 4d3/2: Evidence For Quadrupole Satellites, Oliver Hemmers, Renaud Guillemin, D. Rolles, A. Wolska, Dennis W. Lindle, K. T. Cheng, W. R. Johnson, H. L. Zhou, S. T. Manson

Environmental Studies Faculty Publications

Measurements of nondipole parameters in spin-orbit-resolved Xe 4d photoionization demonstrate dynamical differences arising from relativistic effects. The experimental data do not agree with relativistic random-phase approximation calculations of single ionization dipole and quadrupole channels. It is suggested that the discrepancy is due to the omission of multiple-excitation quadrupole channels, i.e., quadrupole satellite transitions.

Afci Quarterly Input – Unlv July Through September, 2004, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Probing Cation Antisite Disorder In Gd2ti2o7 Pyrochlore By Site-Specific Nexafs And Xps, Ponnusamy Nachimuthu, S. Thevuthasan, Mark H. Engelhard, W. J. Weber, D. K. Shuh, N. M. Hamdan, B. S. Mun, E. M. Adams, D. E. Mccready, V. Shutthanandan, Dennis W. Lindle, G. Balakrishnan, R. C. Ewing

Chemistry and Biochemistry Faculty Research

Disorder in Gd₂Ti₂O₇ is investigated by near-edge x-ray-absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti⁴⁺ ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O 1s XPS spectra obtained with a charge neutralization system from Gd₂Ti₂O₇(100) and the Gd₂Ti₂O₇ pyrochlore used by Chen et al. [Phys. Rev. Lett. 88, 105901 (2002)], both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for …

Spectroscopic And Microscopic Investigation Of The Corrosion Of 316/316l Stainless Steel By Lead-Bismuth Eutectic (Lbe) At Elevated Temperatures: Importance Of Surface Preparation, Allen L. Johnson, Denise Parsons, Julia Manzerova, Dale L. Perry, Daniel Koury, Brian D. Hosterman, John Farley

Transmutation Sciences Materials (TRP)

The corrosion of steel by lead–bismuth eutectic (LBE) is an important issue in proposed nuclear transmutation schemes. Russian scientists at the IPPE exposed steel samples to oxygen-controlled LBE at temperatures up to 823 K and exposure times up to 3000 h. We have characterized these post-exposure steel samples and unexposed controls, using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS). Previous researchers have investigated the corrosion by LBE of steel of varying composition. In the present work, we compared two samples having the same composition (standard nuclear grade 316/316L) but different surface preparation: a cold-rolled …

Nearest-Neighbor-Atom Core-Hole Transfer In Isolated Molecules, Renaud Guillemin, Oliver Hemmers, D. Rolles, S. W. Yu, A. Wolska, I. Tran, A. C. Hudson, J. Baker, Dennis W. Lindle

Environmental Studies Faculty Publications

A new phenomenon sensitive only to next-door-neighbor atoms in isolated molecules is demonstrated using angle-resolved photoemission of site-selective core electrons. Evidence for this interatomic core-to-core electron interaction is observable only by measuring nondipolar angular distributions of photoelectrons. In essence, the phenomenon acts as a very fine atomic-scale sensor of nearest-neighbor elemental identity.

Thickness Dependence Of Magneto-Transport In Cu-Co Granular Thin Films, Jian Qing Wang, Ngocnga Dao, Ham H. Kim, Scott L. Whittenburg

Chemistry and Biochemistry Faculty Publications

This work explores the thickness dependence of magneto-transport properties in granular thin films with different thickness. These results are compared with silver-based film series studied earlier. It was observed that the thickness dependence of the GMReffect was sensitive to the surface chemistry of the films. The extraordinary Hall effect (EHE) in these films was measured and found to be different from the Ag-based system. In the Cu-based system, the EHE is a weak function of film thickness over the range studied. When the variation of the spontaneous magnetization is taken into account the effective EHE has a universal thickness dependence

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to develop a method for the separation of Am from Cm based on electrochemical techniques. Electrochemical systems that allow the thermodynamics of actinide and lanthanide complexes to be systematically evaluated and tuned will be examined. The influence of complex formation on the ability to selectively isolate a given species electrochemically will be evaluated. Metal-ligand complex formation provides a useful derivation technique to increase solubility in solution environments that favor precipitation. In addition, the thermodynamic properties of a complex relative to the isolated species may be shifted to more suitably measurable electrochemical separation regimes. Electrochemical …

Preparation Studies For Secondary Electron Emission Experiments On Superconducting Niobium, Anoop George, Robert A. Schill Jr.

Transmutation Sciences Materials (TRP)

Accelerator driven transmutation of waste is one complementary approach to deal with spent nuclear fuel as compared to permanent storage. High-energy protons generated by a particle accelerator collide with a heavy metal target producing neutrons. Long-lived radioactive isotopes interacting with the neutrons transmute into shorter-lived isotopes. To generate the high-energy protons efficiently, linear accelerators use multi-cell superconducting radio frequency (RF) cavities made of niobium. Superconducting niobium cavities have several advantages, including small power dissipation. The high electromagnetic fields present in these cavities may result in undesired field emission from surface imperfections with the probability of generating an avalanche of secondary …

The Electrochemical Separation Of Curium And Americium: Quaterly Report January - March 2004, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Data collection and analysis of the Ce³⁺/Ce⁴⁺ redox couple in various supporting electrolytes has continued. All electrolyte systems were investigated at Pt, Au, and Glassy Carbon working electrodes. Analysis of these data was accomplished by performing appropriate background subtractions to reveal net peaks due to Ce redox behavior. Successful identification of the Ce redox couple was achieved with all electrolyte/electrode systems, although a decline in peak resolution was observed with increasing acid concentration. Optimal conditions in this experiment were …

Afci Quarterly Input – Unlv January Through March, 2004, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process based on the traditional …

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

There is an active international interest in lead-bismuth eutectic and similar liquid lead systems because of the relevance to the transmutation of nuclear waste, fast reactors, and spallation neutron sources. A successful program in nuclear waste processing that includes transmutation in accelerator-driven systems and fast reactors, would significantly decrease the space requirements for geological repositories.

Materials in these systems must be able to tolerate high neutron fluxes, high temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge because the corrosive behaviors of materials in LBE are not well understood. Most of the available information …

Investigation Of Optical Spectroscopy Techniques For On-Line Materials Accountability In The Solvent Extraction Process, Gary Cerefice, Kenneth Czerwinski

Safeguards Campaign (TRP)

The goal of this project is to examine the potential for using optical spectroscopy techniques, such as UV-Visible Spectroscopy and Laser Fluorescence Spectroscopy, for special nuclear materials accountability applications for the UREX+ and other solvent extraction processes. To increase the inherent proliferation resistance of the solvent extraction process, it is necessary to develop on-line techniques to directly measure the concentrations of special nuclear materials in-process. By providing on-line materials accountability for the processes, the potential for covert diversion of the materials streams becomes much more difficult to implement. On-line monitoring of material streams will also allow for improved plant operation, …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski

Fuels Campaign (TRP)

This project will examine inert fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10 % of ²³⁹Pu. Ceramics will be synthesized and characterized based on the reactor physics results. The solubility the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, will be investigated in a manner to provide …

University Of Nevada, Las Vegas Transmutation Research Program Annual Report Academic Year 2003-2004, Anthony Hechanova, Elizabeth Johnson, Gary Cerefice

Transmutation Research Program Reports (TRP)

It is my pleasure to present the UNLV Transmutation Research Program’s third annual report that highlights the academic year 2003 – 2004. Supporting this document are the many technical reports and scientific papers that have been generated over the past three years.

In the third year of our program, we experienced infrastructure growth despite a decreasing budget. This past year we continued into the final phases of the initial 16 independent student research tasks started in 2001 and 2002, supporting 45 graduate students and 11 undergraduates in 6 academic departments across the UNLV scientific and engineering communities during the academic …

Excimer Emission From Cathode Boundary Layer Discharges, Mohamed Moselhy, Karl H. Schoenbach

Bioelectrics Publications

The excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm, was studied in xenon and argon in a pressure range from 75 to 760 Torr. The thickness of the “cathode boundary layer” plasma, in the 100 μm range, and a discharge sustaining voltage of approximately 200 V, indicates that the discharge is restricted to the cathode fall and the negative glow. The radiant excimer emittance at 172 nm increases with pressure and reaches a value of 4 W/cm² for …

Performance Characteristics Of Beamline 6.3.1 From 200 Ev To 2000 Ev At The Advanced Light Source, Ponnusamy Nachimuthu, J. H. Underwood, C. D. Kemp, Eric M. Gullikson, Dennis W. Lindle, David K. Shuh, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

Bend magnet beamline 6.3.1 at the Advanced Light Source operates from 200 eV to 2000 eV, primarily used for x-ray absorption fine structure investigations. The beamline optics consist of a compact, entrance-slitless, Hettrick-Underwood type variable-line-spacing plane-grating monochromator and refocusing mirrors to provide a 25 μm × 500 μm spot at the focal point in the reflectometer end station. Wavelength is scanned by the simple rotation of the grating and illuminates a fixed exit slit. The LabView based beamline control and data acquisition computer code has been implemented to provide a convenient interface to the user. The dedicated end station is …

Study Of Structural And Magnetic Properties Of Iron-Rich Mixed Rare-Earth Nddyfe (17-Y-X)Coxsiy Compounds, Kishore Kamaraju, Jinbo Yang, William B. Yelon, Oran Allan Pringle, M. S. Kim, Qingsheng Cai, William Joseph James

Physics Faculty Research & Creative Works

A series of NdDyFe(17-y-x)CoxSiy solid solutions with = 2 and 3 and = 0.5 1.0 and 1.5 were prepared by induction melting stoichiometric amounts of high-purity elements. The postannealed samples consist of two phases belonging to the space groups R3 m and P63 mmc . The lattice parameters and the unit cell volumes were calculated from the refinements of the magnetic and structural unit cells using the FULLPROF version of the Rietveld program. For a fixed content of Co, the maximum Curie temperatures (305 C to 405 C) were observed in samples with = 1 and having two phases, a …

Large Dielectric Constant And Maxwell-Wagner Relaxation In Bi2/3cu3ti4o12, Jianjun Liu, Chun-Gang Duan, Wei-Guo Yin, Wai-Ning Mei, Robert W. Smith, John R. Hardy

Physics Faculty Publications

We studied frequency and temperature dependences of impedance, electric modulus, and dielectric permittivity of Bi2/3Cu3Ti4O12 in the ranges of 10−1–106 Hz and −150–200 °C, respectively. We first observed two electrical responses in the impedance and modulus formalisms. Then we detected a Debye-like relaxation in the permittivity formalism. Most interestingly, we found that the large dielectric constant of Bi2/3Cu3Ti4O12 is independent of the temperature and frequency below 150°C. The results are interpreted in terms of a two-layer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance …

Electronic Properties Of Nacdf3: A First-Principles Prediction, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, Wei-Guo Yin, John R. Hardy, Robert W. Smith, M. J. Mehl, L. L. Boyer

Physics Faculty Publications

Based on first-principles total energy calculations, we predict that NaCdF3 could be formed in a ferroelectric crystal structure. Using a symmetry guided search with structure optimization, we found two ferroelectric structures, nearly degenerate in energy, competing for the ground state: a rhombohedral structure with space group R3c and an orthorhombic structure with space group Pna21. The energies of both structures are '60 meV lower than the sum of those of the constituents, NaF and CdF2, implying chemical stability.

Superionicity In Na3Po4: A Molecular Dynamics Simulation, Wei-Guo Yin, Jianjun Liu, Chun-Gang Duan, Wai-Ning Mei, Robert W. Smith, John R. Hardy

Physics Faculty Publications

Fast ionic conduction in solid Na₃PO₄ is studied by use of molecular dynamics simulation based on the modified Lu-Hardy approach. We obtain reasonable agreement with experiment for the structural transition and diffusion of the sodium ions. All the sodium ions are found to contribute comparably to the high ionic conductivity. The results of the simulation are discussed in terms of the relative magnitude of the two proposed transport mechanisms: percolation and paddle-wheel. It appears to us that the percolation mechanism dominates the sodium diffusion.

Laser Writing Of Semiconductor Nanoparticles And Quantum Dots, Massimo F. Bertino, Raghuveer Reddy Gadipalli, J. Greg Story, C. G. Williams, Guo-Hui Zhang, Chariklia Sotiriou-Leventis, Akira Tokuhiro, Suchi Guha, Nicholas Leventis

Physics Faculty Research & Creative Works

Silica aerogels were patterned with CdS using a photolithographic technique based on local heating with infrared (IR) light. The solvent of silica hydrogels was exchanged with an aqueous solution of the precursors CdNO₃ and NH₄ OH, all precooled to a temperature of 5°C. Half of the bathing solution was then replaced by a thiourea solution. After thiourea diffused into the hydrogels, the samples were exposed to a focused IR beam from a continuous wave, Nd-YAG laser. The precursors reacted in the spots heated by the IR beam to form CdS nanoparticles. We lithographed features with a diameter of …