STABILIZATION OF UO$sub 2$ BY VALENCE COMPENSATION

Technical Report · Sun Feb 01 00:00:00 EST 1959

DOI:https://doi.org/10.2172/4234349· OSTI ID:4234349

Wilson, W. B.

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)

• Research Organization: Battelle Memorial Inst., Columbus, Phio
• DOE Contract Number: W-7405-ENG-92
• NSA Number: NSA-13-016198
• OSTI ID: 4234349
• Report Number(s): BMI-1318
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-59
• Country of Publication: United States
• Language: English

Related Subjects

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