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Atomistic and Continuum Simulations of Phase Stability of Alloys - Advanced Models and Simulations of Nuclear Fuel Mate

Atomistic and Continuum Simulations of Phase Stability of Alloys - Advanced Models and Simulations of Nuclear Fuel Materials. Characterization of Advanced Materials under Extreme Environments for the Next Generation Energy Systems Workshop Brookhaven National Laboratory, Sept. 25-26, 2009.

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Atomistic and Continuum Simulations of Phase Stability of Alloys - Advanced Models and Simulations of Nuclear Fuel Mate

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  1. Atomistic and Continuum Simulations of Phase Stability of Alloys - Advanced Models and Simulations of Nuclear Fuel Materials Characterization of Advanced Materials under Extreme Environments for the Next Generation Energy Systems Workshop Brookhaven National Laboratory, Sept. 25-26, 2009 Marius Stan Computational Physics Group Los Alamos National Laboratory UNCLASSIFIED

  2. Outline • Multi-scale methods and simulations can qualitatively predict phase stability of alloys… • …and nuclear fuel performance • In the future, experiment, theory and computation will work hand in hand to create materials with spectacular properties.

  3. Multi-scale theoretical and computational methods1 1M. Stan, J. Nucl. Eng. Techn., 41 (2009) 39-52. 2M. Stan, et al., J. Alloys Comp., 444–445 (2007) 415–423

  4. Phase Stability of Pu-Ga Alloys Will -Pu decompose into -Pu and Pu3Ga, at room temperature and 1 atm.? No, δ-phase will not decompose at room temp. Yes, δ-phase will (eventually) decompose at room temp. N. T. Chebotarev, E. S. Smotriskaya, M. A. Adrianov, and O. E. Kostyuk, in Plutonium 1975 and Other Actinides, Proc. of the Fifth International Conference on Plutonium and Other Actinides, Baden Baden, Germany, September 10-13, 1975, Edited by North-Holland Publishing Company, New York, 1976, p.37-45. F. H. Ellinger, C. C. Land, and V. O. Strebing, The Plutonium-Gallium System, J. Nucl. Mat., 12 (1964) p. 226.

  5. Melting of gallium at 1 atm. • Molecular Dynamics simulations1 • MEAM potential2 • Ga atoms Liquid Solid (A11) Liquid 1Courtesy of S. M. Valone 2M.I. Baskes et al., Phys. Rev. B, 66 (2002), p. 104–107.

  6. Radiation damage in plutonium at 1 atm. • Molecular Dynamics simulations1 • Distorted -Pu structure at 300 K • MEAM potential2 (010) view direction • Distorted- Pu • Interstitial Pu • Initial atom 1S. M. Valone et al., J. Nucl. Mater., 324 (2004) 41-51 2M. I. Baskes, Phys. Rev. B 62, 15532 (2000).

  7. Multi-scale method for alloys1 PredictedPu-Ga diagram.2 Electronic Structure Atomistic Free energy of all phases Chemical potentials Experimental Pu-Ga diagram.3 Thermodynamic equilibrium Phase diagram 1M. I. Baskes and M. Stan, Metall. Mater. Trans. 34A (2003) 435-39. 2M. I. Baskes, et al. JOM, 55 (2003) 41-50. 3N. T. Chebotarev, et al. Proc. Fifth International Conf. on Plutonium and Other Actinides, Baden Baden, Germany, Sept. 10-13, 1975, North-Holland Publishing, NY, 1976, p.37-45.

  8. Irradiation Effects on Fission Reactor Materials • Issues: • Fission products accumulation, gas bubbles formation • Formation of dislocations, cracks. • Localized melting, phase transformations • Fuel-cladding chemical Interactions • Consequences: • Fuel and clad swelling, deformation • Loss of mechanical integrity • Decrease in heat release, overheating. • Fuel element replacement. Fuel restructuring, changes in chemistry1 1From Donald R. Olander, "Fundamental Aspects of Nuclear Reactor Fuel Elements," TID-26711-P1, Technical Information Service, U.S. Department of Commerce, Springfield, Virginia.

  9. Understand and control atomic-scale phenomena: defect formation and fission products migration • Fission products (FP) migrate in the grain and at the grain boundary (GB). • At high doses (burnup) point defects interact and form clusters1-2 • Point defect and clusters are nucleation centers for FP gas bubbles and cracks. • Defect formation time = ps • Recombination time = 1-10 ps • Defects (clusters) size 1-10 nm. grain boundary (GB) From ES To meso-scale - Defect formation energy- Diffusion energy barriers • - GB structure, orientation, and energy • FPs mobility at GBsand in the bulk • Nucleation sites • Free energy model Xe From experiment To experiment - Grain size, orientation - FPs diffusivity (bulk) - Chemical potentials - Nucleation sites Schematic representation of grain boundary defect formation from MD3. 1M. Stan, et al., J. Alloys Comp., 444–445 (2007) 415–423. 2P. Cristea et al., J. Optoelectr. Adv. Mater, 9 (2007) 1750-1756. 3Courtesy of John Wills

  10. Understand and control meso-scale phenomena: microstructure evolution • Fission products migrate in the nuclear fuel and form gas bubbles. • The gas bubbles can lead to formation of “tunnels” (channels) that release the gas into the gap (fuel-clad) region. • Radiation induced changes in microstructure decrease the effective thermal conductivity1. Phase Field simulation using empirical free energy model2 Experiment: Irradiated UO2in PWR3 • Nucleation times = ps • Coalescence times = µs • Size distributions of gas bubbles 1nm-10µm. From atomistic To continuum 10mm • - GB structure, orientation, and energy • FPs mobility at GBsand in the bulk • Nucleation sites • Free energy model 10mm • Thermal cond. model • Thermal exp. model • Crack nucleation andevolution model To experiment From experiment - Pore distribution - FPs distribution - Grain size, orientation - FPs diffusivity (bulk) 1M. Stan, J. Nucl. Eng. Technology, 41 (2009) 39-52. 2S.Y. Hu et al., J. Nucl. Mater. 392 (2009) 292–300. 3I. Zacharieet. al.,  J. Nucl. Mater. 255 (1998), 92-104.

  11. Understand and control continuum phenomena : heat and chemical transport • Finite Element Method (FEM) simulations of coupled heat transport, oxygen diffusion and thermal expansion in a UO2 fuel element with steel cladare show that including the dependence of thermal conductivity on defects and local oxygen content can lead to changes in the predicted centerline temperature and displacements of 5% or more1,2. • Following a power excursion of 1 ms: • Thermal time to steady state = seconds • Displacement time to steady state = seconds • Composition time to steady state = weeks! To reactor level From meso-scale • Centerline temp. • Fuel pin deformation • Thermal cond. model • Thermal exp. model • Crack nucleation andevolution model To experiment From experiment - Temp. distribution - Chemical speciesdistribution (O, FPs). • Crack distribution • Burnup effects 1J. C. Ramirez et al, J. Nucl. Mater, 359 (2006) 174-184. 2B. Mihailaet al., J. Nucl. Mater (2009) in press. Radial profile of properties2

  12. The institutes will integrate experiment, theory, and computation. The scientists will be trained in all areas and experts in one of them1,2. State of the art laboratories for small-scale experiments A computational materials science hub for model development and small-scale simulations Meeting rooms equipped with visualization capabilities for discussions Offices for staff, guest scientists and students Meeting/Visualizationrooms IMDD Computational Materials Science Hub Laboratories Offices The Future: Institutes for Materials Discovery and Design (IMDD) International knowledge base for fuels and materials • Experimental and computational data • Models (mathematical) • Simulations (pictures, movies) • Fully searchable 1M. Stan and S. Yip, white paper DOE workshop on Advanced Modeling and Simulation for Nuclear Fission Energy Systems, Washington DC, May 11-2, 2009: https://www.cels.anl.gov/events/workshops/extremecomputing/nuclearenergy/agenda.php. 1M. Stan, Materials Today , Nov. (2009) accepted.

  13. Meetings of potential interest • Materials Models and Simulations for Nuclear Fuels Workshop, Albuquerque, NM, Oct. 19-21, 2009. See: http://inside.mines.edu/~tsemi/MMSNF8.html • From Basic Concepts to Real Materials Conference, Santa Barbara, CA, Nov. 2-6, 2009. See: http://www.kitp.ucsb.edu/activities/auto/?id=982. • The Nuclear Materials Congress, Karlsruhe, Germany, 4-8 October 2010,Contact: Marius Stan, mastan@lanl.gov.

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