Interdiffusion and reactions between U–Mo and Zr at 650°C as a function of time

Journal Article · Wed Dec 31 23:00:00 EST 2014 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2014.09.040· OSTI ID:1177653

Park, Y. ^[1]; Keiser, Jr., D. D. ^[2]; Sohn, Y. H. ^[1]

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1. Univ. of Central Florida, Orlando, FL (United States). Advanced Materials Processing and Analysis Center
2. Idaho National Lab. (INL), Idaho Falls, ID (United States). Nuclear Fuels and Materials Div.

Development of monolithic U-Mo alloy fuel (typically U-10wt.%Mo) for the Reduced Enrichment for Research and Test Reactors (RERTR) program requires a use of Zr diffusion barrier to eliminate the diffusional interaction between the fuel alloy and Al-alloy cladding. The application of Zr barrier to the U-Mo fuel requires co-rolling process that utilizes a soaking temperature of 650°C, which represents the highest temperature the fuel system is exposed to during both fuel manufacturing and reactor application. Therefore, in this study, development of phase constituents, microstructure and diffusion kinetics of U-10wt.%Mo and Zr was examined using solid-to-solid diffusion couples annealed at 650°C for 240, 480 and 720 hours. Diffusional interactions were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Within the diffusion zone, a single-phase layer of ß-Zr was observed along with a discontinuous layer of Mo₂Zr at the interface between the terminal γ-U(Mo) alloy and ß-Zr. In the vicinity of Mo₂Zr phase, islands of ß-U and a-Zr phases were also found. In addition, accicular a-Zr phases were observed within the γ-U(Mo). Growth rate of this diffuaional interaction layer was determined to be 8.76 x 10^-15 m²/sec, however with an assumption of certain incubation period. Consistency in these observation along with concentration profiles and diffusion paths are presented and discussed with respect to the diffusion couple that was furnace-cooled, annealed at 700°C in our previous study, and isothermal ternary phase diagram at 700°C.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1177653
• Report Number(s): INL/JOU--13-30286
• Journal Information: Journal of Nuclear Materials, Journal Name: Journal of Nuclear Materials Journal Issue: C Vol. 456; ISSN 0022-3115
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ANNEALING
BINARY ALLOY SYSTEMS
DIFFUSION
INTERFACES
KINETICS
LAYERS
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NUCLEAR FUELS
PHASE DIAGRAMS
RESEARCH AND TEST REACTORS
ROLLING
SCANNING ELECTRON MICROSCOPY
TEMPERATURE RANGE 0400-1000 K
TIME DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
URANIUM BASE ALLOYS
ZIRCONIUM
diffusion
nuclear fuel
uranium molybdenum alloy