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Title: Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results

Abstract

The saturation of impurity-rich accessory phases in a Ce-analog baseline ceramic formulation for the immobilization of excess plutonium has been tested by synthesizing an impurity-rich baseline compositions at 1300 C, 1350 C, and 1400 C in air. Impurity oxides are added at the 10 wt% level. The resulting phases assemblages are typically rich in pyrochlore, Hf-zirconolite (hafnolite), brannerite and rutile, but in many instances also contain an accessory mineral enriched in the impurity oxide. The concentration of that oxide in coexisting pyrochlore sets the saturation limit for solid solution of the component in question. In most cases, the accessory phase does not contain significant amounts of Ce, Gd or U. Exceptions are the stabilization of a Ca-lanthanide phosphate and a phosphate glass when P{sub 2}O{sub 5} is added to the formulation. P{sub 2}O{sub 5} addition is also very effective in reducing the modal amount of pyrochlore in the form relative to brannerite. Addition of the sodium-aluminosilicate, NaAlSiO{sub 4}, also results in the formation of a grain boundary melt at run conditions, but the fate of this phase on cooling is not well determined. At temperatures above 1300 C, addition of 10 wt% Fe{sub 2}O{sub 3} also leads to melting. Substitutionmore » of cations of different valences can also be associated with model-dependent changes in the oxidation state of uranium via charge transfer reactions. A set of simple components is suggested for the description of pyrochlores in both impurity-free and impurity-rich formulations.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15005706
Report Number(s):
UCRL-ID-139093-PT-1
TRN: US0305609
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 25 May 2000
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BRANNERITE; CERAMICS; MELTING; OXIDES; PHOSPHATE GLASS; PHOSPHATES; PLUTONIUM; PYROCHLORE; SATURATION; SOLID SOLUTIONS; TITANATES; TRANSFER REACTIONS; URANIUM; VALENCE

Citation Formats

Ryerson, F J, Ebbinghaus, B, Kirkorian, O, and VanKonynenburg, R. Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results. United States: N. p., 2000. Web. doi:10.2172/15005706.
Ryerson, F J, Ebbinghaus, B, Kirkorian, O, & VanKonynenburg, R. Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results. United States. doi:10.2172/15005706.
Ryerson, F J, Ebbinghaus, B, Kirkorian, O, and VanKonynenburg, R. Thu . "Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results". United States. doi:10.2172/15005706. https://www.osti.gov/servlets/purl/15005706.
@article{osti_15005706,
title = {Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results},
author = {Ryerson, F J and Ebbinghaus, B and Kirkorian, O and VanKonynenburg, R},
abstractNote = {The saturation of impurity-rich accessory phases in a Ce-analog baseline ceramic formulation for the immobilization of excess plutonium has been tested by synthesizing an impurity-rich baseline compositions at 1300 C, 1350 C, and 1400 C in air. Impurity oxides are added at the 10 wt% level. The resulting phases assemblages are typically rich in pyrochlore, Hf-zirconolite (hafnolite), brannerite and rutile, but in many instances also contain an accessory mineral enriched in the impurity oxide. The concentration of that oxide in coexisting pyrochlore sets the saturation limit for solid solution of the component in question. In most cases, the accessory phase does not contain significant amounts of Ce, Gd or U. Exceptions are the stabilization of a Ca-lanthanide phosphate and a phosphate glass when P{sub 2}O{sub 5} is added to the formulation. P{sub 2}O{sub 5} addition is also very effective in reducing the modal amount of pyrochlore in the form relative to brannerite. Addition of the sodium-aluminosilicate, NaAlSiO{sub 4}, also results in the formation of a grain boundary melt at run conditions, but the fate of this phase on cooling is not well determined. At temperatures above 1300 C, addition of 10 wt% Fe{sub 2}O{sub 3} also leads to melting. Substitution of cations of different valences can also be associated with model-dependent changes in the oxidation state of uranium via charge transfer reactions. A set of simple components is suggested for the description of pyrochlores in both impurity-free and impurity-rich formulations.},
doi = {10.2172/15005706},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {5}
}

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