Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO2

Technical Report · Wed May 30 00:00:00 EDT 2012

DOI:https://doi.org/10.2172/1049666· OSTI ID:1049666

Li, Yulan; Hu, Shenyang Y; Montgomery, Robert O; Gao, Fei; Sun, Xin

Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at grain boundaries for given grain boundary properties. More validation of the model capability in polycrystalline is underway.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1049666
• Report Number(s): PNNL-21417; NT0108060; TRN: US1204567
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ABSORPTION
ANNEALING
ATOMS
BENCHMARKS
BUBBLE GROWTH
BUBBLES
DEFECTS
DIFFUSION
FISSION
GRAIN BOUNDARIES
IRRADIATION
KINETICS
MICROSTRUCTURE
MONOCRYSTALS
MORPHOLOGY
NUCLEAR FUELS
RESOLUTION
SEGREGATION
SWELLING
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
TRAPPING
VALIDATION
Phase-field approach
Atomistic simulation
Grain boundary
Fission gas bubbles
Uranium dioxide
Post-irradiation thermal annealing.