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Title: ACCURATE QUANTIFICATION OF DRIED RESIDUE THIN FILMS USING X-RAY FLUORESCENCE

Abstract

An XRF specimen preparation method was developed to quantify the concentration of gallium in plutonium metal while minimizing the risk of contaminating the instrument with radioactive material. To ensure that homogeneous specimens are examined, plutonium is dissolved in dilute HCl and HNO{sub 3} prior to analysis. In the preliminary work here, non-radioactive aqueous gallium standards were prepared, and zinc was added as an internal standard to improve the accuracy and precision. Aliquots from these solutions were cast on Mylar XRF films and air dried prior to analysis. Two methods of casting the solutions were evaluated: (1) casting as a thin layer using a surfactant to wet the support film and (2) casting multiple small spots on the support film. Aqueous gallium standards were prepared and cast as dried residue specimens using each method. These specimens were then analyzed, and calibration curves were prepared. Highly linear calibrations were obtained for each preparation method when zinc was used as the internal standard (RMS values {le}1% of the standards concentration range in both cases). Based on this preliminary work, this dried residue process appears very promising for the accurate quantification of gallium in plutonium.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
768772
Report Number(s):
LA-UR-00-4155
TRN: AH200123%%392
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Sep 2000
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALIBRATION; CASTING; FLUORESCENCE; GALLIUM; MYLAR; PLUTONIUM; RADIOACTIVE MATERIALS; RESIDUES; SURFACTANTS; THIN FILMS; ZINC

Citation Formats

C. WORLEY, and G. HAVRILLA. ACCURATE QUANTIFICATION OF DRIED RESIDUE THIN FILMS USING X-RAY FLUORESCENCE. United States: N. p., 2000. Web.
C. WORLEY, & G. HAVRILLA. ACCURATE QUANTIFICATION OF DRIED RESIDUE THIN FILMS USING X-RAY FLUORESCENCE. United States.
C. WORLEY, and G. HAVRILLA. Fri . "ACCURATE QUANTIFICATION OF DRIED RESIDUE THIN FILMS USING X-RAY FLUORESCENCE". United States. doi:. https://www.osti.gov/servlets/purl/768772.
@article{osti_768772,
title = {ACCURATE QUANTIFICATION OF DRIED RESIDUE THIN FILMS USING X-RAY FLUORESCENCE},
author = {C. WORLEY and G. HAVRILLA},
abstractNote = {An XRF specimen preparation method was developed to quantify the concentration of gallium in plutonium metal while minimizing the risk of contaminating the instrument with radioactive material. To ensure that homogeneous specimens are examined, plutonium is dissolved in dilute HCl and HNO{sub 3} prior to analysis. In the preliminary work here, non-radioactive aqueous gallium standards were prepared, and zinc was added as an internal standard to improve the accuracy and precision. Aliquots from these solutions were cast on Mylar XRF films and air dried prior to analysis. Two methods of casting the solutions were evaluated: (1) casting as a thin layer using a surfactant to wet the support film and (2) casting multiple small spots on the support film. Aqueous gallium standards were prepared and cast as dried residue specimens using each method. These specimens were then analyzed, and calibration curves were prepared. Highly linear calibrations were obtained for each preparation method when zinc was used as the internal standard (RMS values {le}1% of the standards concentration range in both cases). Based on this preliminary work, this dried residue process appears very promising for the accurate quantification of gallium in plutonium.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2000},
month = {Fri Sep 01 00:00:00 EDT 2000}
}

Conference:
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  • Determining the concentration of gallium in plutonium metal is imperative in manufacturing nuclear weapons. X-ray fluorescence (XRF) is an effective method used to quantify the gallium content in plutonium; however, the sample and specimen preparation methods currently employed could be improved from a time and safety standpoint. Recently, a dried residue specimen preparation method was developed as an alternative to the established aqueous approach. The method currently certified to prepare plutonium for gallium analysis by XRF involves dissolving the sample and removing the plutonium with ion exchange chromatography. The gallium remaining in solution is then analyzed. This method has beenmore » thoroughly developed, and relative accuracy and precision values less than 1% can be achieved. However, this process is time consuming, and the specimen solution is radioactive due to the presence of residual plutonium and trace americium. Thus, an alternate process was developed to avoid these issues in which the plutonium solution is cast in {mu}L spots on Mylar XRF film, dried, and sealed inside a sample cell for analysis. This specimen preparation method is considerably faster and also safer than the solution process. Previous studies have demonstrated that a very linear calibration can be obtained from dried residue standards. In the present work, accuracy and precision results will be compared from using the aqueous and dried residue specimen preparation methods. The strengths and limitations of each method will also be discussed. In summary, this work will illustrate both the challenges faced with analyzing radioactive materials by XRF and the high accuracy and precision achievable with proper sample and specimen preparation.« less
  • Two XRF specimen preparation methods were investigated for quantifying gallium in plutonium metal. Gallium in plutonium was chosen here as an example for demonstrating the efficacy of wavelength dispersive XRF for quantifying radioactive materials. The steps necessary to handle such materials safely will also be discussed. Quantification of plutonium samples by a well-established aqueous specimen preparation method resulted in relative precision and accuracy values of well less than 1%. As an alternative to the aqueous approach, a dried residue method was studied. Quantification of gallium in samples using this method resulted in relative precision and accuracy values an order ofmore » magnitude worse, but the method is faster, safer, and generates less waste than the aqueous process. The specimen preparation details and analysis results using each method will be presented here.« less
  • The accumulation of trace metals by planktonic protists influences the growth of primary producers, metal biogeochemical cycling, and metal bioaccumulation in aquatic food chains. Despite their importance, unequivocal measurements of trace element concentrations in individual plankton cells have not been possible to date. We have used the 2-ID-E side-branch hard x-ray microprobe at the Advanced Photon Source to measure trace elements in individual marine plankton cells. This microprobe employs zoneplate optics to produce the sub-micron spatial resolution and low background fluorescence required to produce trace element maps of planktonic protist cells ranging in size from 3 to >50 {micro}m. Wemore » have developed preservation, rinsing, and mounting protocols that remove most of the salt from our marine samples, thus simplifying the identification of unknown cells and reducing high Cl-related background fluorescence. We have also developed spectral modeling techniques that account for the frequent overlap of adjacent fluorescence peaks and non-uniform detector response. Finally, we have used parallel soft x-ray transmission and epifluorescence microscopy images to estimate C normalized trace element concentrations, identify functional cell types (e.g., photosynthetic vs. non-photosynthetic), and correlate cell structures with spatial patterns in trace element fluorescence.« less
  • No abstract prepared.
  • The purpose is: (1) To develop a synchrotron X-ray diffraction (SXRD) method to monitor phase transitions during the entire freeze-drying cycle. Aqueous sodium phosphate buffered glycine solutions with initial glycine to buffer molar ratios of 1:3 (17:50 mM), 1:1 (50 mM) and 3:1 were utilized as model systems. (2) To investigate the effect of initial solute concentration on the crystallization of glycine and phosphate buffer salt during lyophilization. Phosphate buffered glycine solutions were placed in a custom-designed sample cell for freeze-drying. The sample cell, covered with a stainless steel dome with a beryllium window, was placed on a stage capablemore » of controlled cooling and vacuum drying. The samples were cooled to -50 C and annealed at -20 C. They underwent primary drying at -25 C under vacuum until ice sublimation was complete and secondary drying from 0 to 25 C. At different stages of the freeze-drying cycle, the samples were periodically exposed to synchrotron X-ray radiation. An image plate detector was used to obtain time-resolved two-dimensional SXRD patterns. The ice, {beta}-glycine and DHPD phases were identified based on their unique X-ray peaks. When the solutions were cooled and annealed, ice formation was followed by crystallization of disodium hydrogen phosphate dodecahydrate (DHPD). In the primary drying stage, a significant increase in DHPD crystallization followed by incomplete dehydration to amorphous disodium hydrogen phosphate was evident. Complete dehydration of DHPD occurred during secondary drying. Glycine crystallization was inhibited throughout freeze-drying when the initial buffer concentration (1:3 glycine to buffer) was higher than that of glycine. A high-intensity X-ray diffraction method was developed to monitor the phase transitions during the entire freeze-drying cycle. The high sensitivity of SXRD allowed us to monitor all the crystalline phases simultaneously. While DHPD crystallizes in frozen solution, it dehydrates incompletely during primary drying and completely during secondary drying. The impact of initial solute concentration on the phase composition during the entire freeze-drying cycle was quantified.« less