Characterization of Solids in Residual Wastes from Underground Storage Tanks at the Hanford Site, Washington, U.S.A.
Solid phase physical and chemical characterization methods have been used in an ongoing study of residual wastes from several single-shell underground waste tanks at the U.S. Department of Energy’s Hanford Site in southeastern Washington State. Because these wastes are highly-radioactive dispersible powders and are chemically-complex assemblages of crystalline and amorphous solids that contain contaminants as discrete phases and/or co-precipitated within oxide phases, their detailed characterization offers an extraordinary technical challenge. X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS) are the two principal methods used to characterize solid phases and their contaminant associations in these wastes. Depending on the specific tank, numerous solids (such as čejkaite; Na2U2O7; clarkeite; gibbsite; boehmite; dawsonite; cancrinite; Fe oxides such as hematite, goethite, and maghemite; rhodochrosite; lindbergite; whewellite; nitratine; and several amorphous phases) have been identified in residual wastes studied to date. Because many contaminants of concern are heavy elements, SEM analysis using the backscattered electron (BSE) signal has proved invaluable in distinguishing phases containing elements, such as U and Hg, within the complex assemblage of particles that make up each waste. XRD, SEM/EDS, and synchrotron-based methods provide different, but complimentary characterization data about the morphologies, crystallinity, particle sizes, surface coatings, and compositions of phases in the wastes. The impact of these techniques is magnified when each is used in an iterative fashion to help interpret the results from the other analysis methods and identify additional, more focused analyses.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 921426
- Report Number(s):
- PNNL-SA-52789; 830403000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CLARKEITE
DAWSONITE
ELECTRONS
EXAFS
GIBBSITE
GOETHITE
HEMATITE
Hanford
OXIDES
PARTICLE SIZE
RADIOACTIVE WASTES
SEM
SURFACE COATING
TANKS
UNDERGROUND STORAGE
WASTES
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
XANES
XRD
boehmite
cancrinite
clarkeite
dawsonite
gibbsite
goethite
hematite
lindbergite
maghemite
nitratine
rhodochrosite
sodium uranate
tank waste
whewellite
čejkaite