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Radiochemical Processing Laboratory

Analytical Transmission Electron Microscope

The Intermediate Voltage Transmission Electron Microscope for Actinide Materials

Staff using AEM
Staff using AEM

The new Tecnai 30S-Twin 300 keV analytical transmission electron microscope (AEM) operated by the Radiochemical Processing Laboratory allows investigators to see through thicker specimens, permitting more microstructural analysis and improved image resolution. The AEM will be used to characterize a wide variety of radioactive materials including tank wastes sludges, actinide-containing biogeochemical samples, technetium- and actinide-containing soils and sediments, spent nuclear fuels, corroded metals, and oxidized transuranic solids. The AEM not only images microstructures directly, but it can also identify any phases present in a sample. The following AEM characterization techniques are available on the PNNL actinide-capable system.

Characterization of Microstructure, Corrosion Behavior, and Colloidal Phases

  • Bright- and Dark-Field Imaging: the AEM enables images of the internal microstructure of materials, corrosion rinds, heavy metal precipitates on microbial membranes, and structures such as dislocations and metallic epsilon particles in nuclear fuels. The AEM can also be used to observe precipitates, colloids, and phase separation in glasses.
  • High-Resolution Imaging: crystal lattice spacings can be made visible with multi-beam imaging on the AEM.
  • Electron Diffraction (Selected Area Diffraction) and Microdiffraction: both techniques help investigators identify crystal structures. Electron diffraction patterns from areas as small as 0.5 micrometer can be obtained. In the case of isolated nanometer-sized particles, electron diffraction can provide structural information. Furthermore, the presence of amorphous structures can be confirmed with electron diffraction.

Other techniques, such as weak beam microscopy for examining dislocation structures and oblique textured electron diffraction, which is useful for examining clays, can also be performed on the AEM.

Characterization of Chemical Composition

  • Energy-Dispersive X-ray Spectroscopy: The light element detector allows qualitative analysis of all elements above carbon and quantitative analysis of most elements above sodium with the appropriate standards.

With Future Upgrades (Image Filter and Scanning AEM unit)

  • Electron Energy-Loss Spectroscopy and Imaging: Valence state determination and elemental mapping may be obtained with the aid of an image filter or scanning transmission electron microscopy (STEM) unit. Analysis of Li, B, and C samples and low-level detection of actinides in complex matrices is also readily achievable with an energy-loss spectrometer.

Point of Contact:
Edgar Buck, Nuclear Chemistry & Engineering
Phone: (509) 375-5611

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