[en] Comparisons between standard aperture optics and a custom designed monolithic capillary x-ray optic for the Kevex Omicron are presented. The results demonstrate the feasibility of retrofitting an Omicron with a monolithic capillary. Increased flux is observed especially at lower energies which results in an increase in sensitivity and potentially an increase in spatial resolution. Alignment is a critical factor in achieving optimal performance of the monolithic capillary. Further improvements in flux output, spot size and overall sensitivity are expected with better alignment

[en] X-ray fluorescence is usually regarded as a bulk analytical method with limited sensitivity and requiring several grams of sample for analysis. This typically restricts application of XRF from small mass samples and to concentrations well above the parts-per-million level. The advent of lab based x-ray microfluorescence instrumentation is providing a new tool to address some of these limitations of macro XRF excitation instruments. Dried spot methodology was demonstrated by Meltzer in 1991 that sub-ppm detection limits could be achieved on macro instrumentation. The advantage of using the dried spot technique is that the specimen is within the thin film regime which minimizes matrix effects, thereby allowing almost a universal calibration. It also couples preconcentration with minimized background to increase sensitivity. EDXRF has experienced limited application to radioactive samples due to the background caused by the activity of the sample. This paper will demonstrate the use of x-ray microfluorescence for trace analysis using the dried spot methodology of Meltzer and application to analysis of radioactive samples. The radioactive background is minimized by physically reducing the specimen size and permitting direct analysis of hot samples

[en] Mixed oxide (MOX) fuel feed material surrogates composed of Ga₂O₃ in CeO₂ were characterized by X-ray fluorescence (XRF) and micro-X-ray fluorescence (MXRF). This work is significant because MOX fuel contains trace levels of Ga₂O₃ that could potentially damage the fuel cladding. Because a majority of Ga₂O₃ is extracted during MOX fuel feed processing via reduction to volatile and mobile Ga₂O, XRF spatially resolved spot analyses, line scans, and elemental maps were acquired to determine the gallium distribution in surrogate pellets. These modes of analyses, when combined, provided a comprehensive picture of the sample gallium dispersal. The surrogate pellets were reduced at temperatures ranging from 600 to 1200 C with 6% hydrogen in argon, and the internal gallium was found to migrate toward the outer surface and top of the pellets. This process was more kinetically favorable with increasing reduction temperature. Different quantities of surrogate powders were also reduced from 600 to 1200 C, and XRF quantitative analysis demonstrated that more gallium was eliminated from the smaller sample lots (as well as at higher temperatures) due to the hydrogen diffusing more effectively into the smaller mass powder samples

[en] This document details the research and development (R and D) activities that will be conducted in Fiscal Year 1998 (FY98) by the Thermally Induced Gallium Removal System (TIGRS) team for the Department of Energy Office of Fissile Materials Disposition. This work is a continuation and extension of experimental activities that have been conducted in support of using weapons-derived plutonium in the fabrication of mixed-oxide (MOX) nuclear fuel for reactor-based plutonium disposition. The ultimate purpose of this work is to demonstrate adequate Thermally Induced Gallium Removal with a prototypic system. This Test Plan presents more than the FY98 R and D efforts in order to frame the Task in its entirety. To achieve the TIGRS Program objectives, R and D activities during the next two years will be focused on (1) process development leading to a prototypic TIGRS design, and (2) prototypic TIGRS design and testing leading to and including a prototypic demonstration of TIGRS operation. Both the process development and system testing efforts will consist of a series of surrogate-based cold tests and plutonium-based hot tests. Some of this testing has already occurred and will continue into FY99

[en] A point charge model based upon charge induction theory has been developed to describe the proposed detection mechanisms of laser-enhanced ionization (LEI). The model predictions are in good agreement with experimentally observed LEI electron and ion signal pulses. The predicted effects of alkali metal matrix concentration and laser beam position are also confirmed by experimental results. The development of this model provides a basis for establishing experimental methodology that is necessary for the development of LEI as a technique for trace metal analysis. 23 references, 8 figures, 2 tables

[en] Laboratory-based confocal micro X ray fluorescence offers novel characterization capabilities not found in conventional analytical techniques. CMXRF has been used to characterize a range of uranium oxide from 100 to 10 micrometers in diameter, an inertial confinement fusion target composed of a Be doped sphere and compared with radiographic images obtained with micro X ray computed tomography. These two imaging platforms were integrated in the characterization of a surface mount resistor, demonstrating the increased information content of combining the structural information of the MXCT and the elemental information of the CMXRF. Density measurements using the CMXRF have been demonstrated on aerogel samples, identifying a high density skin on cast and machined aerogels. A prototype thermal inkjet picofluidic system has been used to deposit picoliter volumes from 300 to 1 pL of aqueous solutions to create custom reference materials for calibration of MXRF instrumentation. (author)

[en] Highlights: • Alpha-prototype benchtop instrument based on monochromatic WDXRF. • Calibration and testing in an operational nuclear material processing environment. • Direct determination of Pu and U in 7 μL of solution using sample microcell. • Rapid, nondestructive, reduced waste methodology with Pu LOD of 3 × 10⁻⁵ g/L. • 10% expanded uncertainty for Pu determination up to 20 g/L total Pu and U content. An alpha-prototype benchtop instrument was developed and tested for measuring Pu and U in spent fuel dissolver tanks in a nuclear fuel reprocessing plant. The high resolution X-ray (hiRX) instrument was designed with the aim of providing a new capability to measure samples with high radiation background with selectivity, accuracy, and precision using ultra-low volumes (7 μL) of liquid. The instrument was tested with specimens from the operational reprocessing facility at Savannah River National Laboratory. The results showed that bias was < 6% for Pu nitrate process solution and < 18% for Pu in U/HNO₃ matrix. Instrumental precision was < 1% RSD while between microcell repeatability was < 6% RSD. The limit of detection for Pu in HNO₃ matrix was 3 × 10⁻⁵ g/L (100 s, 35 W). This study demonstrates that hiRX technology has the potential to provide rapid and simultaneous quantification of Pu and U without sample preparation, making it suitable for process monitoring and materials control and accountability applications.

[en] Micro Xray fluorescence (MXRF) imaging is a relatively new method to map the constituent elements of a surface to a depth of tens to hundreds of microns, and at high spatial resolution, i.e., 40 to 50 microns. The feasibility of MXRF imaging is investigated as a potential NDE method to detect and characterize spalling failure of chromium disilicide diffusion coatings on Space Shuttle Reaction Control System (RCS) thruster chambers