The synthesis and air oxidation behavior of U-Si-Al and U-Si-B compositions

Conference · Fri Jul 01 00:00:00 EDT 2016

OSTI ID:22765215

Sooby Wood, E.; White, J. T.; Byler, D. D.; Nelson, A. T. ^[1]

---

1. Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States)

Uranium silicide intermetallic compounds are currently under investigation by the DOE-NE Advanced Fuels Campaign as candidate accident tolerant nuclear fuel concepts for light water reactors. While many U-Si compounds offer benefits compared to reference UO{sub 2} in terms of heavy metal density and thermal conductivity, they have been shown to display poor resistance to oxidizing atmospheres above 400 Celsius degrees. The general oxidation behavior of all U-Si compounds is oxidation of uranium; formation of UO{sub 2} followed by U{sub 3}O{sub 8} leads to rapid pulverization of the material. It is hypothesized that introducing an additional compositional degree of freedom by exploring U-Si-X (X=Al or B) ternary systems may provide the means to design a candidate nuclear fuel which optimizes the benefits of each binary. Phase analysis and preliminary oxidation testing were performed on four compositions containing alloying additions to U{sub 3}Si{sub 2} and U{sub 3}Si{sub 5}. Aluminum additions to U{sub 3}Si{sub 2} were observed to increase the oxidation resistance by delaying the onset of oxidation during synthetic air ramp testing. U{sub 3}Al{sub 2}Si{sub 3} delayed the onset of oxidation to T>650 C. degrees. During a 10 hour isothermal hold at 400 C. degrees in air the compound gained very little mass, indicating that it could be stable at reactor operating temperatures. Further analysis of this material is necessary to determine its oxidation behavior in steam and determine the specific mechanism that is providing the delayed oxidation. Boron additions to U{sub 3}Si{sub 5} do not appear to provide any additional oxidation resistance to the compound as tested in this work. The 1.67 at.% addition of B produced primarily single-phase composition. Melting and sintering studies followed by further compositional and thermal analyses are required to advance this composition as a candidate composite fuel additive. Lastly, the nominally U{sub 3}BSi{sub 4} composition produced a multi-phase system which provided no additional oxidation resistance following either a synthetic air ramp oxidation test or a pre-passivation isothermal hold at 800 C. degrees.

• Research Organization: American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 22765215
• Resource Relation: Conference: TOP FUEL 2016: LWR fuels fuels with enhanced safety and performance, Boise, ID (United States), 11-15 Sep 2016; Other Information: Country of input: France; 9 refs.; Related Information: In: TOP FUEL 2016 Proceedings| 1670 p.
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
36 MATERIALS SCIENCE
ACCIDENT-TOLERANT NUCLEAR FUELS
AIR
ALUMINIUM ADDITIONS
BORON ADDITIONS
COMPARATIVE EVALUATIONS
FUEL ADDITIVES
HEAVY METALS
INTERMETALLIC COMPOUNDS
MELTING
OXIDATION
SINTERING
TEMPERATURE RANGE 0400-1000 K
THERMAL ANALYSIS
THERMAL CONDUCTIVITY
URANIUM
URANIUM DIOXIDE
URANIUM OXIDES U3O8
URANIUM SILICIDES
WATER COOLED REACTORS
WATER MODERATED REACTORS