First-Principles Study of Surface Properties of U{sub 3}Si{sub 2} for Accident Tolerant Fuel

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Transactions of the American Nuclear Society

OSTI ID:22992135

Mei, Zhi-Gang; Yacout, Abdellatif M.; Miao, Yinbin ^[1]; Andersson, David ^[2]

---

1. Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439(United States)
2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

Due to the high thermal conductivity and uranium density compared to UO{sub 2} fuel used in current Light Water Reactors (LWRs), U-Si fuels, such as the U{sub 3}Si{sub 2} and U{sub 3}Si{sub 5} compounds, are currently under investigation for the development of accident tolerant fuels (ATF) in response to the Fukushima Daiichi accident in Japan. In order to perform meaningful mesoscale and macroscale fuel performance simulations, fundamental material properties of nuclear fuels should be known. One example is the simulations of fission gas bubble evolution and gas bubble-induced swelling in nuclear fuels using mesoscale methods, such as phase field and rate theory. To properly describe the gas bubble behavior in the fuel, it is crucial to know the surface energies of the fuel. Unfortunately, there is no study of the surface properties of U{sub 3}Si{sub 2} from both experiment and theory. To this end, we systematically investigate the surface properties of U{sub 3}Si{sub 2} using density functional theory (DFT) based first-principles calculations. Of several low index facets, we studied the (001) and (100) surfaces of tetragonal U{sub 3}Si{sub 2} with all the possible terminations. Since all the studied surfaces are not stoichiometric, we also investigated the effect of elemental chemical potentials on the formation of surface. We systematically investigate the surface properties of U{sub 3}Si{sub 2} using density functional theory calculations. Of several low-index facets, the (001) and (100) surfaces show similar averaged surface energies calculated using even number of layers. At the high Si chemical potential, the Si-terminated U{sub 3}Si{sub 2}(100) and U{sub 3}Si{sub 2}(001) surfaces show lower energies than those of the U-terminated surfaces, with U,Si-terminated U{sub 3}Si{sub 2}(001) as the most stable surface. The surface energies of all non-stoichiometric U{sub 3}Si{sub 2} are linearly dependent on the Si chemical potential. The surface energies of U-terminated surfaces decrease as Si potential decreases. The U{sub 2}-terminated U{sub 3}Si{sub 2}(100) surface becomes that the most stable surface at U-rich side. Based on the current results, an averaged surface energy of U{sub 3}Si{sub 2}, i.e., 1.45 J/m{sup 2}, is recommended for the description of the rounded facets of gas bubbles in U{sub 3}Si{sub 2} by mesoscale simulations. (authors)

• OSTI ID: 22992135
• Journal Information: Transactions of the American Nuclear Society, Vol. 114, Issue 1; Conference: Annual Meeting of the American Nuclear Society. Embedded topical meeting 'Nuclear fuels and structural material for the next generation nuclear reactors', New Orleans, LA (United States), 12-16 Jun 2016; Other Information: Country of input: France; 7 refs.; Available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 United States; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
97 MATHEMATICAL METHODS AND COMPUTING
ACCIDENT-TOLERANT NUCLEAR FUELS
DENSITY FUNCTIONAL METHOD
FISSION PRODUCTS
FUKUSHIMA DAIICHI NUCLEAR POWER STATION
REACTOR ACCIDENTS
SIMULATION
SURFACE ENERGY
SURFACES
THERMAL CONDUCTIVITY
URANIUM
URANIUM DIOXIDE
URANIUM SILICIDES
WATER COOLED REACTORS
WATER MODERATED REACTORS