Impact of the Synthesis Process on Structure Properties for AFCI Fuel Candidates

The research objectives are: • To explore a low-temperature fluoride route to synthesize actinide nitrides. • To characterize actinide nitrides structurally and thermally. • To use high resolution TEM techniques to explore the microstructure of the radioactive samples

Dissolution, Reactor, and Environmental Behavior of ZrO2-MgO Inert Fuel Matrix

This project examines 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 are 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 are synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, are investigated in a manner to provide thermodynamic data necessary for modeling. The research objectives of this project are as follows: To examine the neutronic behavior of MgO-ZrO2 inert fuels. Analysis of Gd, Er, and Hf for reactivity control ranging from 5-10% lanthanides. Analysis of reactor grade Pu as fissile component ranging from 5-10% Pu. Results will be used as parameters for fuel composition. To synthesize and characterize of MgO-ZrO2 ceramics containing burnable poison and fissile composition. Synthesis is based on a precipitation method. Characterization of ceramics will include density, X-ray diffraction, surface area analysis, X-ray absorption fine structure spectroscopy, and chemical composition. Results will be applied to behavior in high temperature water, acid, and environmental conditions. To describe the chemical behavior of synthesized ceramics. Chemical thermodynamic and kinetic analysis will use equilibrium data, kinetic data, and surface area normalized dissolution. Different conditions will include reactor conditions (high temperature and high pressure water) and reprocessing conditions (nitric acid and elevated temperature). Environmental conditions will be near neutral solution conditions. To utilize project data in kinetic and thermodynamic modeling codes to evaluate the speciation of the elements in the ceramics under reactor, reprocessing, and repository conditions

Fundamental Chemistry of U and Pu in the TBP-Dodecane-Nitric Acid System

The research objective is to experimentally evaluate the fundamental speciation of Pu and U in the TBP-dodecane-nitric acid- AHA system and the effect of pertechnetate, specifically: To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration, actinide ion concentration, temperature, and time. To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and Pu are evaluated as a function of AHA concentration, metal ion concentration, metal ion redox state, pH, and temperature. To determine the interaction of AHA with pertechnetate, and the effect on the interaction of AHA and pertechnetate with U and Pu. To incorporate thermodynamic and kinetic data into existing modeling codes. All of the initial experiments were performed with uranyl, UO22+. The results obtained from U are the basis for further experiments with Pu. In extraction experiments, the aqueous and organic phases are contacted in equal volumes from 0.3 to 5.0 mL

Separation of Technetium from Uranium and Waste Form Synthesis

In this project, systematic investigations on the Tc-Zr binary metal system will be evaluated for the first time. The synthesis of metallic Tc as well as its alloys with Zr will be evaluated. In order to provide valuable data to AFC R&D, the thermodynamic equilibrium phases, as well as their performance under repository conditions, will be examined. The research objectives of this project are as follows: • Evaluate anion exchange methods for achieving the separation of Tc from U. • Synthesize metallic Tc from the separated product. • Synthesize and characterize Tc alloys. • Investigate Tc-corrosion and Tc-leaching of binary Tc-Zr phases under a range of conditions. The following experimental techniques are used in the evaluation of the solutions and solids from the experiments: ultravioletvisible spectroscopy, time-resolved laser fluorescence spectroscopy, X-ray Absorption Fine-Structure Spectroscopy (XAFS), and microscopy

Evaluation of fundamental radionuclide extraction data for UREX

The speciation of technetium and actinides in advanced solvent extraction systems is the basis for their manipulation in separations. The ability to understand and predict radionuclide speciation is paramount to successful modeling of proposed separation systems. This project will examine the speciation of radionuclides in different stages of the UREX separation scheme, providing data useful to modeling. The areas to be examined include the speciation of U and Pu with tributylphosphate and the kinetics and thermodynamics of lanthanides and actinides in the TALSPEAK system. The complexation constants of U and Pu with tributylphosphate will be evaluated. In the TALSPEAK system, studies will elucidate the difference in complexation kinetics for the lanthanides and actinides. Computational studies based on density functional theory will be performed for both systems

Fundamental Chemistry of U and Pu in the TBP-Dodecane-Nitric Acid System

The research objectives of this project are as follows: To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration (by the addition of NaNO3), actinide ion concentration, temperature, and time. To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and Pu are evaluated as a function of AHA concentration, metal ion concentration, metal ion redox state, pH, and temperature. Experiments will initially examine the aqueous phase then examine the two phase system. To incorporate thermodynamic and kinetic data into existing modeling codes

Investigation of Optical Spectroscopy Techniques for On-Line Materials Accountability in the Solvent Extraction Process

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, as well as serving as an additional safety measure for plant operations. Laser fluorescence and UV-Visible spectroscopy have been demonstrated for use in determining the concentration of the actinides at the laboratory scale. These processes are adaptable to flow-thru applications, and should be highly radiation-tolerant, which suggests that they should be applicable to the spent fuel treatment environment

Impact of the Synthesis Process on Structure Properties for AFCI Fuel Candidates

Transmutation work at Los Alamos National Laboratory is currently focused on mono-nitride ceramic fuel forms, and consists of closely coordinated “hot” actinide and “cold” inert and surrogate fuels work. Matrix and surrogate materials work involves three major components: (1) fuel matrix synthesis and fabrication, (2) fuel performance, and (3) fuel materials modeling. The synthesis and fabrication component supports basic material studies, as well as actinide fuel fabrication work through fuel fabrication process development. Fuel performance studies are examining the tolerance of nitride-type fuel to heavy irradiation damage. The fuel materials simulation work involves both atomistic and continuum scale modeling employing first principals, molecular dynamics, and thermo-chemical calculations. This modeling work is closely integrated with fuel design and experimental work where it provides prediction of phase transformation and stability, reaction kinetics, radiation damage mechanism and tolerance, and fission product retention. Results for fuel fabrication and radiation tolerance studies based on the proposed ZrN fuel matrix material will be reviewed as well as experimental surrogate studies for volatilization and phase stability. The actinide fuel effort at LANL emphasizes in synthesis and fabrication of actinide-bearing nitride fuel pellets. These pellets are designed for being inserted into the Advanced Test Reactor and contain varying amounts of Pu, Am, Cm, and Np. For now, fuel materials simulation work which involves atomistic and continuum scale modeling, molecular dynamics, and thermo-chemical calculations is purely based on a theoretical understanding of crystal structure and microstructure of inert matrix fuels. We intent to support the AFCI program by delivering real structural data on surrogate and radioactive fuels. We will determine crystal structure and nano structures of the individual fuel type, oxides and nitrides, as considered for GEN IV fuels. Furthermore we will mainly apply two different ways to synthesis fuels: (1) wet chemical route (precipitation from solution, calcinations, grinding, pelletization, sintering with binder and PEG, grinding, pelletization, and sintering with carbon-thermal reduction (later for nitride fuels only), and (2) dry chemical route (grinding of oxides, pelletization, sintering with binder and PEG, grinding, pelletization, and sintering with carbon-thermal reduction (later for nitride fuels only). The chemical behavior of the ceramics under repository, reprocessing, and reactor conditions will also be examined. This data will provide the basis for a full analysis of the fuel in an advanced fuel cycle. We will analyze the impact of fuel processing parameters on the crystal structure and nano structure of the inert matrix fuel desired for GEN IV reactors. Therefore we will - beside other analytical techniques - mainly apply (1) X-ray powder diffraction (XRD) in combination with Rietveld structure refinement to refine or to determine actinide occupancies within the crystal lattices of the fuels, and (2) high resolution electron microscopy (transmission electron microscopy) in combination with, nano probe X-ray spectrometry (EDS), parallel energy loss spectroscopy (PEELS), energy-filter electron microscopy, and scanning transmission electron microscopy. We will use stateof- the-art analytical instrumentation on X-ray diffraction (PANalytical X-Pert Pro with X’Celarator solid state detector and Bruker AXS Topas2 Rietveld structure refinement software), and high resolution electron microscopy (Tecnai F 30 STEM with a FEG field emission gun, scanning option, PEELS, EDS, Energy-Filter, 300 kV acceleration, and a point resolution of 2.2 Å). We can take advantage of two fully equipped sample preparation laboratories, one for the preparation of surrogate fuel, one for the preparation of radioactive fuel specimens. The analytical work scope as proposed will promote the Harry Reid Center for Environmental Studies of UNLV as the top academic institution in the U.S. for analyzing radioactive fuel samples on nano-scale

Investigation of Optical Spectroscopy Techniques for On-Line Materials Accountability in the Solvent Extraction Process

The goal of this project is to evaluate the application of these analytical techniques to the on-line, real-time measurement of the actinide elements in the process streams of a solvent extraction process, with particular attention to the UREX+ and PUREX processes. Based on the experience gained through this effort, engineers will have the information necessary to decide if these technologies should be advanced to the prototype stage and tested at the pilot plant level. Through the experimental work planned as part of this effort, researchers will also develop a better understanding of the chemical interactions of the actinide elements, providing additional data for the development of first-principles based models of the solvent extraction process. The information gathered through these experiments will also add to the database on the UREX+ solvent extraction process, particularly in the off-normal operating regimes

Dissolution, Reactor, and Environmental Behavior of ZrO2-MgO Inert Fuel Matrix: Quarterly Report, July 2004 to September 2004

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 thermodynamic data necessary for modeling. In this quarter work was performed on synthesis of ceramics and reactor physics calculation