Evaluation of Fluorapatite as a Waste-Form Material: Fourth Quarter Report, June 1 - September 30, 2004

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. Highlights of Accomplishments: 1. Fluorapatite containing Sr and Zn surrogates (replacing the Ca) have been synthesized, annealed and analyzed using various techniques such as SEM, IR, XPS, Raman, DSC, TGA, EDS, XRD and XANES. 2. Non-annealed samples of the same surrogate samples have been analyzed with the same techniques. 3. The phosphate in fluorapatite and hydroxyapatite is not replaced by the nitrate ions of the surrogates during synthesis

Evaluation of Fluorapatite as a Waste-Form Material

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal is for renewal of the UNLV portion of a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. At UNLV, characterization of the material will be accomplished by probing molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performances of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. The work in the third year of the project will continue to progress along two parallel paths: Fabrication and Natural-Analog Characterization. The Fabrication path, led by the KRI team, will evaluate various techniques for the fabrication of synthetic fluorapatite, will synthesize fluorapatite, and will begin the examination of waste loading and fabrication process factors on the synthetic fluorapatite. The Characterization path, led by the UNLV team, has been performing baseline spectroscopic studies of natural and pristine (no artificially added impurities) apatite materials and is beginning to apply the same techniques to more-complex fluorapatite-based waste forms made by the KRI Fabrication team. The ultimate goal is to use these techniques to achieve a molecular-level understanding of natural fluorapatite and other fluorine-bearing phases as natural analogs for waste-form materials. These techniques will also be used to examine changes in surface chemistry caused by environmental degradation

Evaluation of Fluorapatite as a Waste-Form Material: First Quarter Report (2004-05), October 1 - December 31, 2004

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. Highlights of Accomplishments: 1) Multiple samples of hydroxyapatite prepared some with surrogates (varying Ca/Zn weight ratios) and some pure samples which have then been analyzed with IR, TGA/DSC and XRD techniques. 2) Fluorapatite samples synthesized using the reflux method and analyzed with SEM, XPS, XRD and single point IR. 3) Experiments conducted with natural fluorapatite and hydroxyl apatite using the precipitation method to determine if procedure to synthesize fluorapatite differs based on samples used. XRD was used to analyze the synthesized samples. 4) Synthesized yttrium and cesium containing FAP samples using the same method that was used for Strontium (explained in last report) and obtained XRD, SEM and DSC data for samples

Photoelectron Spectroscopy and the Dipole Approximation

Over the past three decades, the dipole approximation has facilitated a basic understanding of the photoionization process in atoms and molecules. Advances in gas-phase photoemission experiments using synchrotron radiation have recently highlighted nondipole effects at relatively low photon energies while probing the limits of the dipole approximation. Breakdowns in this approximation are manifested primarily as deviations from dipolar angular distributions of photoelectrons. Detailed new results demonstrate nondipolar angular-distribution effects are easily observable in atomic gases at energies well below 1 keV, and, in molecules, a previously unexpected phenomenon greatly enhances the breakdown of the dipole approximation just above the core-level ionization threshold

Evaluation of Fluorapatite as a Waste-Form Material: First Quarter Report, January 1 - March 31, 2005

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. Highlights of Accomplishments: 1) Obtained SEM/EDS, FTIR and XRD for Zn-containing samples prepared using 75, 50 and 25% Ca/Zn molar ratios and the sintered sample of Ca/Zn molar ratio 75%. Additionally, XPS data were obtained for these samples together with a fluorapatite and a 100% Zn sample. 2) Prepared 4 different amounts of Zr-containing apatites using precipitation method and sintered these 4 samples at 1200 degrees of centigrade for one hour. SEM, XRD, FTIR and high temperature TGA/DSC data were obtained for these samples. A detailed analysis is in progress. 3) Determined the dependability of the Ca/P and (Ca +Sr)/P ratios in FAP based on the amount of Sr surrogate used in synthesis. 4) Preparation of Cu and Ni containing fluorapatite samples and powder diffraction spectra were obtained for the Cu-FAP sample

Evaluation of Fluorapatite as a Waste-Form Material

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline

Evaluation of Fluorapatite as a Waste-Form Material: Third Quarter Report, March 1 - May 31 2003

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. Highlights of Accomplishments: 1. Baseline spectroscopic measurements have been obtained for commercial hydroxyapatite and natural fluorapatite using a wide variety of techniques (e.g., Raman, XPS, FT-IR) useful for probing the chemical and physical properties of materials. 2. Detailed SEM images of natural fluorapatite crystals indicate the presence of naturally included minerals (e.g., Ni), offering the possibility of studying natural analogs to waste-loaded apatite materials

Evaluation of Fluorapatite as a Waste-Form Material

Argonne National Laboratory has proposed a new extraction procedure to handle TRISO-coated fuels, the Fluoride Extraction Process, or FLEX. The FLEX process is designed to separate the uranium in the fuel from the actinides and most fission products by taking advantage of the unique properties of uranium hexafluoride (UF6). In the FLEX process, the used TRISO fuel is reacted with zirconium fluoride salt, forming UF6 and the fluoride salts of the actinides and fission products. At process temperatures, the UF6 volatizes into a gas, and is released from the molten salt mixture. This leaves behind the actinides and most fission products in a fluoride salt, which is subsequently processed using pyrochemical techniques to recover the actinides and other long lived fission products for transmutation. The UF6 is then cooled, causing it to sublime into solid form, which is then further processed for disposal or reuse. Originally, the research effort had been divided along two parallel paths: the Fabrication Path, led by collaborators at the Khlopin Radium Institute (KRI) in St. Petersburg, Russia; and the Characterization Path, led by researchers from UNLV. The Fabrication Path is focused on examining and evaluating various techniques for fabricating synthetic fluorapatite; synthesizing synthetic fluorapatite; and examining the impacts of waste loading and other fabrication process factors on the performance of the synthetic fluorapatite as a potential waste form. The Characterization Path is focused on adapting and refining the X-ray spectroscopy techniques currently used to characterize borosilicate glass for use in examining the fluorapatite system. This path also encompassed the examination of the ceramic and synthetic mineral waste forms created at KRI, with subsequent examination of these techniques to develop a molecular-level understanding of natural fluorapatite and other fluorine-bearing natural phases as natural analogs for the waste form. These techniques will also be used to examine the changes in surface chemistry caused by environmental degradation of these materials

High-brightness Beamline for X-ray Spectroscopy at the Advanced Light Source

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1-6 keV photon-energy range, designed to achieve the goals of high energy resolution, high flux, and high brightness at the sample. When completed later this year, it will be the first ALS monochromatic hard-x-ray beamline, and its brightness will be an order-of-magnitude higher than presently available in this energy range. In addition, it will provide flux and resolution comparable to any other beamline now in operation. To achieve these goals, two technical improvements, relative to existing x-ray beamlines, were incorporated. First, a somewhat novel optical design for x rays, in which matched toroidal mirrors are positioned before and after the double-crystal monochromator, was adopted. This configuration allows for high resolution by passing a collimated beam through the monochromator, and for high brightness by focusing the ALS source on the sample with unit magnification. Second, a new “Cowan type” double-crystal monochromator based on the design used at NSLS beamline X-24A was developed. The measured mechanical precision of this new monochromator shows significant improvement over existing designs, without using positional feedback available with piezoelectric devices. Such precision is essential because of the high brightness of the radiation and the long distance (12 m) from the source (sample) to the collimating (focusing) mirror. This combination of features will provide a bright, high resolution, and stable x-ray beam for use in the x-ray spectroscopy program at the ALS

Evaluation of Fluorapatite as a Waste-Form Material: Third Quarter Report, March 1- May 31, 2004

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline. Highlights of Accomplishments: 1. Synthezised Sr containing hydroxyapatite using the reflux method and acquired SEM, EDS and XPS data for these samples. 2. More samples of Sr containing hydroxyapatite synthezised using various lengths of refluxing time and stirring to check the thermodynamic effects on the crystalline character/shape of the samples. 3. First samples of fluorapatite and Sr-containing fluorapatite synthesized and analyzed with IR spectroscopy. 4. Synthesized Zn containing hydroxyapatite using the reflux method and obtained IR data