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Title: STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION

Abstract

UO/sub 2/, when heated in air, will transform to U/sub 3/O/sub 8/. The U/sub 3/O/sub 8/ which is formed exhibits appreciable vapor pressure at temperatures in excess of l200 deg C. The need for a stable high-temperature nuclear fuel requires prevention of the U/sub 3/O/sub 8/ transformation as well as a lowering of the vapor pressure. A method by which this may be accomplished involves compensation of the valence change of U, as it undergoes oxidation. This is accomplished by massive addition of other metal oxides. Solid-state studies of the U-La-O system were conducted in the investigation to elicit more detailed understanding of the processes involved The oxidation and vaporization characteristics of UO/sub 2/ were compared directly to solid solutions of U0/sub 2/ containing from 30 to 60 wt. % of La/sub 2/O/sub 3/. These solid solutions. which have the fluorite structure, were formed by reacting U0/sub 2/ and La/sub2/ O/sub3/ in vacuo. When these materials were oxidized the fluorite structure was retained with, however, reduced lattice parameters. These were shown to be equivalent to reacting U/sub 3/O/sub 8/ with La/sub 2/O/sub 3/. The volatility of the resultin g solid solutions was found to vary with the amount of additive.more » The composition exhibiting the lowest vapor pressure was further related to a stoichiometry between the cation and anion content. The usual approach in alloying to improve oxidation resistance is to retard the rate of oxidation. The present approach differs in that the alloying material is added to stabilize the structure and results in rapid oxidation. However. since no phase change is involved marked improvement in stabilization is obtained. An attempt a generalize the concepts developed for apolication to ether aide systems is made. (auth)« less

Authors:
Publication Date:
Research Org.:
Battelle Memorial Inst., Columbus, Phio
OSTI Identifier:
4234349
Report Number(s):
BMI-1318
NSA Number:
NSA-13-016198
DOE Contract Number:  
W-7405-ENG-92
Resource Type:
Technical Report
Resource Relation:
Other Information: Orig. Receipt Date: 31-DEC-59
Country of Publication:
United States
Language:
English
Subject:
METALLURGY AND CERAMICS; AIR; ANIONS; CALCIUM FLUORIDES; CATIONS; CHEMICAL REACTIONS; FLUORITE; FUELS; HEATING; HIGH TEMPERATURE; LANTHANUM OXIDES; LATTICES; MINERALS; OXIDATION; PHASE DIAGRAMS; PRESSURE; QUANTITY RATIO; REACTION KINETICS; SOLID SOLUTIONS; STABILITY; U3O8; URANIUM; URANIUM DIOXIDE; VACUUM; VAPORS; VOLATILITY

Citation Formats

Wilson, W.B. STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION. United States: N. p., 1959. Web. doi:10.2172/4234349.
Wilson, W.B. STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION. United States. doi:10.2172/4234349.
Wilson, W.B. Sun . "STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION". United States. doi:10.2172/4234349. https://www.osti.gov/servlets/purl/4234349.
@article{osti_4234349,
title = {STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION},
author = {Wilson, W.B.},
abstractNote = {UO/sub 2/, when heated in air, will transform to U/sub 3/O/sub 8/. The U/sub 3/O/sub 8/ which is formed exhibits appreciable vapor pressure at temperatures in excess of l200 deg C. The need for a stable high-temperature nuclear fuel requires prevention of the U/sub 3/O/sub 8/ transformation as well as a lowering of the vapor pressure. A method by which this may be accomplished involves compensation of the valence change of U, as it undergoes oxidation. This is accomplished by massive addition of other metal oxides. Solid-state studies of the U-La-O system were conducted in the investigation to elicit more detailed understanding of the processes involved The oxidation and vaporization characteristics of UO/sub 2/ were compared directly to solid solutions of U0/sub 2/ containing from 30 to 60 wt. % of La/sub 2/O/sub 3/. These solid solutions. which have the fluorite structure, were formed by reacting U0/sub 2/ and La/sub2/ O/sub3/ in vacuo. When these materials were oxidized the fluorite structure was retained with, however, reduced lattice parameters. These were shown to be equivalent to reacting U/sub 3/O/sub 8/ with La/sub 2/O/sub 3/. The volatility of the resultin g solid solutions was found to vary with the amount of additive. The composition exhibiting the lowest vapor pressure was further related to a stoichiometry between the cation and anion content. The usual approach in alloying to improve oxidation resistance is to retard the rate of oxidation. The present approach differs in that the alloying material is added to stabilize the structure and results in rapid oxidation. However. since no phase change is involved marked improvement in stabilization is obtained. An attempt a generalize the concepts developed for apolication to ether aide systems is made. (auth)},
doi = {10.2172/4234349},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1959},
month = {2}
}