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Title: Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO 2

The diffusivity of the solid fission products (FP) Zr (Zr 4+), Ru (Ru 4+, Ru 3+), Ce (Ce 4+), Y (Y 3+), La (La 3+), Sr (Sr 2+) and Ba (Ba 2+) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. Furthermore, for all solid FPs except Y 3+, the migration of the FP has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. But, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru 3+ and Ru 4+ diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO 2, and the tendency to form metallic and oxidemore » second phase inclusions.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
OSTI Identifier:
1402584
Report Number(s):
LA-UR-14-28421
Journal ID: ISSN 0022-3115; TRN: US1703113
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 459; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS