INTERDIFFUSION BETWEEN URANIUM-BEARING REACTOR FUELS AND REFRACTORY-METAL THERMIONIC EMITTERS

Technical Report · Tue May 01 04:00:00 EDT 1962

OSTI ID:4774952

Weinberg, A; Yang, L

Material compataibility as related to the ''marriage '' of reactor fuels to refractory-metal thermionic emitters is under investigation. Fuel materials such as UC, UC/sub 2/, UZrC and UO/sub 2/ are being studied in combdnation with W, Mo, Ta, and Nb at 1200 to 2000 deg C. A tehnique was dedeloped for simultaneously studying the interdiffusion between a specified U- bearing material and each of the refractory metals. UC in contact with Nb and Ta at 1875 deg plus or minus 20 deg C and 1925 deg plus or minus 30 deg C, respectively, reacted to form a liquid phase identified as almost pure U metal. Mo also reacted with UC at 1800 deg plus or minus 20 deg C, while at the same temperature W appeared relatively unaffected. However, after being in contact with UC at 2000 deg plus or minus 20 deg C for 30 hr, W exhibited a mild reaction. The reaction mechanism for all of these metals appears to be UC + M = MC + U. Formation of this liquid phase was suppressed at 1800 deg C when UC-UC2 mixtures were substituted for the UC. The kinetics of uniform metal-carbide- layer formation were studied for UCUC/sub 2/ mixtures in contact with the refractory metals at 1800 deg C. In addition to the uniform carbide layers formed, severe carbide penetration of the grain boundaries was observed in Nb, Ta, and Mo. Investigation of the interaction between UZrC (6.0 mole% U--45.8 mole% Zr--48.2 mole % C) and the same four refractory metals at 1800 deg C for 50 hr showed that the stabilization of the carbide phase by the addition of Zr improves the diffusion characteristics. Electron-microprobe analyses of these diffusion couples were made, the results of which are discussed. Preliminary investigations of UO/sub 2/-refractory metal compatibility were completed at 1200, 1800, and 2000 deg C. Indications of transport of one or more of the fuel components through grain boundaries were observed. (auth)

• Research Organization: General Atomic Div. General Dynamics Corp., San Diego, Calif.
• NSA Number: NSA-16-033468
• OSTI ID: 4774952
• Report Number(s): GA-3124
• Country of Publication: United States
• Language: English

Related Subjects

CARBIDES
CHEMICAL REACTIONS
DIFFUSION
ELECTRON MICROSCOPY
EMISSION
FUELS
GRAIN BOUNDARIES
HIGH TEMPERATURE
LAYERS
METALS, CERAMICS, AND OTHER MATERIALS
MIXING
MOLYBDENUM
NIOBIUM
PHASE DIAGRAMS
REACTION KINETICS
REACTORS
REFRACTORIES
STABILITY
TANTALUM
TESTING
THERMIONICS
TUNGSTEN
URANIUM CARBIDES
URANIUM DIOXIDE
ZIRCONIUM CARBIDES