Volatile Impurities in the Plutonium Immobilization Ceramic Wasteform Page: 3 of 10
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The feedstock for the plutonium designated for immobilization is from a variety of sources. Some of these
sources contain a significant quantity of impurities8. Impurities in a ceramic wasteform can negatively affect
the ability of the wasteform to retain actinides, reducing the durability of the ceramic. The reduction in
durability is a result of the formation of significant quantities of undesirable (low durability) phases driven
by the presence of impurities.
The compositions and the amounts of impurities to be examined were set based on the history of the
plutonium feedstock8. Table II lists the three compositions that were used in the impurity study. A0 is the
baseline formulation and targets the preferred composition. The "Ce" designation indicates a ceria
substitution for plutonium oxide on a molar basis. B3-7 is a compositional extreme that targets a 50%/50%
pyrochlore/zirconolite phase assemblage and uses ceria as a surrogate for plutonium oxide on a molar basis.
B3-8 is a compositional extreme that targets a 50%/50% pyrochlore/brannerite phase assemblage and, like
B3-7, uses ceria as a surrogate for plutonium. These compositions were the base compositions to which the
impurities will be added. It is expected that the range of occurrence of any of the impurity materials will
range from 0 - 0.6 moles of impurity per mole of plutonium.
Table II. Base Compositions for the Volatile Impurity Study.
Raw Material Composition in Mol Percent
AO/Ce B3-7 B3-8
Projected Mineralogy Pyrochlore Zirconolite/ Pyrochlore Brannerite/ Pyrochlore
[ CaO 21.37 19.96 13.29
TiO2 54.05 51.35 59.13
HfO2 6.09 13.94 6.02
Gd203 2.64 2.21 2.23
[ UO2 10.56 I 6.91 13.22
CeO2 (PuG2) 5.28 4.28 6.11
Al2O3 0.00 1.35 0.00
Total 99.99 100.00 100.00
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Cozzi, A.D. Volatile Impurities in the Plutonium Immobilization Ceramic Wasteform, article, October 15, 1999; South Carolina. (digital.library.unt.edu/ark:/67531/metadc622583/m1/3/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.