Influence of Alloying Elements and Effect of Stress on Anisotropic Hydrogen Diffusion in Zr-Based Alloys Predicted by Accelerated Kinetic Monte Carlo Simulations

Conference · Mon May 01 04:00:00 EDT 2017

DOI:https://doi.org/10.1007/978-3-319-68454-3_46· OSTI ID:1409685

Yu, Jianguo; Jiang, Chao; Zhang, Yongfeng

The formation of hydrides degrades the toughness of Zr-based claddings, and thus is one of the primary concerns regarding cladding integrity during fuel operation and used fuel storage. However, the formation mechanism of hydrides, particularly the nucleation mechanism, is yet to be fully understood. To explore the nucleation process, atomic scale studies including density functional theory, molecular dynamics and kinetic Monte Carlo have been used to investigate H diffusion, segregation, and the possible nucleation paths of hydrides. Here, density functional theory calculations are used to parameterize a kinetic Monte Carlo model, which can accurately predict the effective H diffusivity in various Zr-based claddings including Zircaloy, Zirlo and Zr-2.5Nb. Assisted by density functional theory calculations, a recently developed charge-optimized-many-body potential is further improved and used to investigate the possible nucleation paths of hydrides. It’s shown that the formation of face-centered hydrides starts with coherent zeta-phase, shearing of which in the basal plane changes the hcp stacking into fcc and leads to the formation of gamma-hydride nuclei. The shearing involves a negligible barrier and negligible strain accumulation in the matrix by adopting three equivalent shear partials. The results obtained at the atomic scale are consistent with previous theory and experiments, and improves the current understanding on how and how fast hydride forms in Zr based cladding.

• Research Organization: Idaho National Laboratory, Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1409685
• Report Number(s): INL/CON-16-40548
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
Hydrogen diffusion
Zr cladding
hydride formation