MOISTURE AND SURFACE AREA MEASUREMENTS OF PLUTONIUM-BEARING OXIDES Page: 3 of 9
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WSRC-STI-2008-00119, Rev. 1
halide-containing materials, and also reduces the potential for radiolytic hydrogen generation and
subsequent pressurization of sealed vessels. Stored plutonium-bearing oxides have a wide range of
plutonium contents and contain various impurities, including uranium oxides and chloride salts. Some
chloride (Cl-) phases, such as MgCl2, are known to be quite hygroscopic. Past investigation has shown that
the specific surface area of pure and impure Pu-bearing oxides is reduced as the calcination temperature is
increased [4,5]. Calcination at 950 C effectively reduces the specific surface area (SSA), which limits the
amount of moisture that is re-adsorbed by the surface. Because of the expected low surface area and low
moisture of these materials, this study did not investigate the presence of PuO2,+, which has been reported
in high surface area plutonium oxides in the presence of water . The results presented demonstrate the
effectiveness of the plutonium stabilization process through the characterization of materials that have been
stored in sealed containers for more than four years, after being packaged at the Department of Energy's
Rocky Flats site.
Sealed containers of plutonium-bearing oxide were opened and sampled immediately. These
samples were analyzed by Thermogravimetric Analysis-Mass Spectroscopy (TGA-MS) using a Netzsch
STA 409 Luxx model TGA connected to a Pfeiffer ThermoStar MS. The permanent gases pass from the
TGA portion of the instrument through a heated transfer tube maintained at > 150 C to the MS. During
analyses, samples were heated from ambient to 1000 C (at 15 C/min) under a flowing argon gas stream
which was analyzed by the MS. Gypsum standards were used to develop an MS moisture calibration
curve, as described elsewhere [7,8]. Additional samples from the same parent container were analyzed for
surface area with a Micromeritics Gemini 2360 analyzer using the Brunauer-Emmett-Teller (BET) method
with nitrogen adsorbate. All analyses were performed in duplicate unless otherwise indicated. Soluble
chloride salt content was determined by leaching 0.5-g samples in water at 90 C for one hour. After
cooling, aliquots were analyzed to determine selected anions (by ion chromatography) and selected cations
(by inductively coupled plasma-emission spectroscopy). In addition to the oxide sample characterization,
gas samples from the headspace of the cans (collected during storage vessel opening) were analyzed by gas
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Crowder, M.; Duffey, J.; Livingston, R.; Scogin, J.; Kessinger, G. & Almond, P. MOISTURE AND SURFACE AREA MEASUREMENTS OF PLUTONIUM-BEARING OXIDES, article, September 28, 2009; South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc927297/m1/3/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.