Effect of Recrystallization on Gas Bubble Swelling in UMo Fuels

Journal Article · Sat Jul 01 04:00:00 EDT 2017 · Transactions of the American Nuclear Society

OSTI ID:23047465

Hu, Shenyang; Lavender, Curt A.; Joshi, Vineet ^[1]

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1. Pacific Northwest National Laboratory, P. O. Box 999, Richland, WA 99352 (United States)

The development of low-enriched uranium (LEU) fuels such as UMo dispersion fuels and monolithic UMo fuels is part of a global effort on nuclear nonproliferation. Although UMo fuels have the advantage of high density, excellent irradiation performance and good thermal conductivity, the volumetric swelling in irradiated metallic fuels is known to be an important design parameter because it affects not only the thermal conductivity of the fuels but also the mechanical integrity of fuel structures. Experiments also show that recrystallization dramatically affects the gas bubble swelling kinetics. A series of materials processes such as casting, mechanical rolling and thermal treatment are used in fuel fabrication. Resulting microstructure, such as grain size, porosity, and second phase, strongly depends on the material processes and process parameters. Therefore, a fundamental understanding how fabricated microstructures and irradiation conditions affect the nucleation of gas bubbles, recrystallization and gas bubble swelling kinetics is essential for optimizing material processes to obtain desired microstructure and fuel performance. Great effort has been made in the development of modeling capability for predicting gas bubble swelling kinetics and fission gas release kinetics in nuclear fuels. However, these models are based on the assumptions that the inter- and intra-granular gas bubble sizes are independent of position and only depend on time or fission density. Therefore, they are applicable to a material with uniform microstructure such as equiaxed grains with homogeneous defect distributions, homogeneous thermodynamic and kinetic properties of defects, and uniform radiation conditions. Very recently, we developed a three dimension (3D) microstructure dependent gas bubble swelling model for investigating the effect of heterogeneous microstructures and inhomogeneous thermodynamic properties of defects on gas bubble swelling in polycrystalline UMo fuels. However, the model doesn't take into account the effect of recrystallization on swelling kinetics. In this work, the spatially dependent rate theory is used to describe the evolution of interstitials and interstitial loop density. Recrystallization is described by a phase-field model with a concept of 'phase transition' when the local interstitial loop density is larger than a critical value. The intra- and inter- granular gas bubble evolution is described by the spatially dependent Booth model. A model integrating all the microstructure evolution enables one to study the effect of heterogeneous microstructures, recrystallization, and the metallic fuel thermodynamic and kinetic properties on gas bubble swelling kinetics.

• OSTI ID: 23047465
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 116; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
36 MATERIALS SCIENCE
CASTING
CASTINGS
ENRICHED URANIUM
FISSION
FISSION PRODUCT RELEASE
GRAIN SIZE
HEAT TREATMENTS
INTERSTITIALS
IRRADIATION
KINETICS
NUCLEAR FUELS
NUCLEATION
PERFORMANCE
PHASE TRANSFORMATIONS
POLYCRYSTALS
RECRYSTALLIZATION
ROLLING
SWELLING
THERMAL CONDUCTIVITY
THERMODYNAMICS