Thermodynamic Properties of Actinide-Zirconium Dioxide Solid-Solutions Relevant for Advanced Nuclear Fuels

Conference · Tue Jul 01 00:00:00 EDT 2008

OSTI ID:21326163

Shuller, L C; Ewing, R C ^[1]; Pavenayotin, N; Ewing, R C ^[2]; Skomurski, F N ^[3]; Ewing, R C; Becker, U ^[4]

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1. Materials Science and Engineering Department, University of Michigan (United States)
2. University of Michigan, Nuclear Engineering (United States)
3. Geological Sciences Department, University of Michigan (United States)
4. EMSL, Pacific Northwest National Laboratory (United States)

Currently, spent nuclear fuel (SNF) from commercial reactors is composed of 95-99% UO{sub 2} and 1-5% fission products and transuranium elements. Thus, the primary waste form is the UO{sub 2} matrix, which over time will corrode to a variety of U(VI)-secondary phases. Alternative nuclear fuels, such as inert-matrix fuels and mixed-oxide fuels, have been studied for their in-reactor performance; however little research has been conducted to understand the behavior of these fuels as a wasteform. We use density functional theory and Monte-Carlo methods to understand the solid solution behavior of (Ac, Zr)O{sub 2} (Ac = Th, U, Np, Pu) phases. The end members of interest include ZrO{sub 2}, ThO{sub 2}, UO{sub 2}, NpO{sub 2}, and PuO{sub 2}, and all share the cubic-fluorite structure. The excess enthalpy of mixing ({delta}H{sub excess}), excess Gibbs free energy of mixing ({delta}G{sub excess}), and excess configurational entropy ({delta}S{sub excess}) are calculated for the above solid solution series, and from {delta}G{sub excess}, miscibility gaps are identified. In conclusion: Density functional theory and Monte Carlo simulations were used in this study to determine the thermodynamic properties of binary oxide solid solutions that are useful for advanced nuclear fuel applications. The DFT results for each solid solution series is of the single cubic unit cell; therefore, only one interaction parameter was calculated. Based on the Monte-Carlo results, on the order of 25% Zr can be incorporated into the AcO{sub 2} structures (Ac = Th, U, Np, or Pu). However, only trace amounts of the actinides can be incorporated into ZrO{sub 2}. Considering larger systems in the DFT calculations will improve results, because more cation-cation interaction parameters can be calculated. Configurational ordering can also be considered with larger systems. Molecular dynamic simulations will be used to determine the temperature dependence of the different solid solutions that is more specific to their respective lattice dynamics. (authors)

• Research Organization: WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
• OSTI ID: 21326163
• Report Number(s): INIS-US-10-WM-08438; TRN: US10V0617067528
• Resource Relation: Conference: WM'08: Waste Management Symposium 2008 - HLW, TRU, LLW/ILW, Mixed, Hazardous Wastes and Environmental Management - Phoenix Rising: Moving Forward in Waste Management, Phoenix, AZ (United States), 24-28 Feb 2008; Other Information: Country of input: France; 10 refs
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
36 MATERIALS SCIENCE
ACTINIDES
COMPUTERIZED SIMULATION
DENSITY FUNCTIONAL METHOD
ENTROPY
FISSION PRODUCTS
FREE ENTHALPY
MIXED OXIDE FUELS
MIXING HEAT
MONTE CARLO METHOD
NEPTUNIUM OXIDES
PERFORMANCE
PLUTONIUM OXIDES
SOLID SOLUTIONS
SPENT FUELS
TEMPERATURE DEPENDENCE
THORIUM OXIDES
TRANSURANIUM ELEMENTS
URANIUM DIOXIDE
WASTE FORMS
ZIRCONIUM OXIDES