Hanford Tank 241-C-106: Impact of Cement Reactions on Release of Contaminants from Residual Waste Page: 27 of 177
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Krupka et al. (2004) prepared and analyzed by XRD a sample consisting of only a dry film of the
collodion solution so that its contribution relative to the background signals of the XRD patterns for the
sludge samples could be quantified. The resulting XRD pattern for the collodion solution film is shown
in Figure 3.5. The most obvious feature of this diffraction pattern is the broad peak positioned between
100 and 30020. The symmetry of this peak is characteristic of those resulting from the XRD of
amorphous (noncrystalline) material. Although subtracting the collodion background from sludge XRD
patterns allows for better phase matching, this process may eliminate minor reflections and inconspicuous
features of a pattern. Therefore, each as-measured XRD pattern was examined before and after back-
ground subtraction to ensure that the integrity of the pattern was maintained. For background subtraction,
the JADE software provides the user with control over the selection of background-subtraction points.
This process allows a better fit to 20 regions under broad reflections, such as those resulting from
amorphous materials. On average, 30 to 40 background points were selected from each XRD pattern, and
a cubic-spline curve was then fit through each set of points. Adjustments to this curve were made by
selecting additional background points in regions of a pattern that were difficult to fit. Once a well-
matched curve was fitted to a pattern, the background was subtracted from each as-measured XRD
pattern, resulting in a smooth tracing.
2500
Collodion Film
2000
& 1500
1000
500
0
5 10 15 20 25 30 35 40 45 50 55 60 65
26 (degrees)
Figure 3.5. XRD Pattern for Collodion Film Measured in the Absence of any Sludge Material (from
Krupka et al. 2004)
Identification of the mineral phases in the background-subtracted patterns was based on a comparison
of the XRD patterns measured for the sludge samples with the mineral powder diffraction files (PDFTM)
published by the Joint Committee on Powder Diffraction Standards (JCPDS) International Center for
Diffraction Data (ICDD). As a rule of thumb, a crystalline phase must be present at greater than 5 wt% of
the total sample mass (greater than 1 wt% under optimum conditions) to be readily detected by XRD. In
general, the measured peak intensities depend on several factors, including the combined mass of each
crystalline phase in the sample. Due to the physical characteristics of these tank sludge samples such as
high radioactivity, high dispersibility, and variable moisture content, the mass of tank sludge combined
with the collodion solution for each XRD mount could not be controlled or easily determined. Dissimi-
larities in mineral segregation (settling) resulting from the different densities of minerals mixed with the3.8
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Deutsch, William J.; Krupka, Kenneth M.; Lindberg, Michael J.; Cantrell, Kirk J.; Brown, Christopher F. & Schaef, Herbert T. Hanford Tank 241-C-106: Impact of Cement Reactions on Release of Contaminants from Residual Waste, report, September 1, 2006; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc887933/m1/27/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.