# Presentation: 534414

## Thermodynamic and Basic Science Issues Associated with Fuels

**Workshop on****Basic Research Needs for Advanced Nuclear Energy Systems**Washington DC, July 31–August 2, 2006

- UNCLASSIFIED, LA-UR-06-3845

- Marius Stan
- Los Alamos National Laboratory, Los Alamos, NM 87544, U. S. A.
- mastan@lanl.gov

## GNEP-BES Basic Research

***Workshop Charge***
*To identify basic research needs and opportunities in advanced nuclear energy systems and related areas, with a focus on new, emerging and scientifically challenging areas that have the potential to have significant impact in science and technologies. Highlighted areas will include improved and new materials and relevant chemical processes to overcome short-term showstoppers and long-term grand challenges for the effective utilization of nuclear energy.*

**Proposed SCIENCE AND TECHNOLOGY OBJECTIVES**
-  Develop predictive models of  irradiation effects on the properties of nuclear fuel element materials, using multi-scale experiments, theory, and computation.
-  Provide the fundamental understanding, capabilities, and a roadmap to reduce the time and costs of reactor materials design and development.

- Study real nuclear materials: fuel rod and cladding. No “surrogates”.
- Reasons:
-  Extensive existing literature and databases.
-  Most difficult but most rewarding.
-  Best chances to get accepted by the Nuclear Regulatory Commission (NRC) and similar.

## Multi-Scale Methods

- Simulations of heat transfer and diffusion in nuclear fuels

- Phase Field simulations of void formation and evolution

- Thermo-chemical models of oxygen diffusivity

- Molecular dynamics calculations of point defect energy

**Nucleation sites**

- Electronic Structure Calculations (DFT)

**Inter-atomic potential ****parameters**

**Porosity**

***D*****(T,x,p)**

***k*****(T,x,p)**

**thermal conductivity** **(LFC)**

**Irradiation**

- Experiments and atomistic models provide input for continuum simulations.
- Continuum simulations validate provide feedback to experiments and validate atomistic models.

## The Advanced Fuel Performance Code (AFPC)Design Template and Modules

**Output (XML)**

**Input (GUI)**

- Main Driver

**Users (people or other codes)**

**Simulations**

**External****Databases**

**Models**-Continuum-Atomistic-Electronic  Structure

- InternalDatabase

- Heat Transfer

- Thermo- Mechanics

- Fluid Flow

- Neutronics

- Mass Transport

- Solvers

**Users**

**Other Codes**

**AFPC**

- Users only see the **red** boxes

## Proposed tasks(ordered by scale, not necessary importance or urgency)

-  Perform electronic structure calculations of actinide compounds (oxides, nitrides,...etc).
-  Add charge transfer to inter-atomic potentials of actinide ceramics.
-  Develop models and simulate microstructure evolution in irradiated materials.
-  Develop experimental methods and determine defect types and concentrations to validate atomistic models.
-  Replace empirical correlations with theory-based models.Example: Thermal conductivity of MOX as function of temperature and stoichiometry.
-  **Calculate phase diagrams of multi-component systems such as U-Pu-Am-Cm-X and include uncertainty analysis.**
-  Review existing fuel performance codes and document capabilities, incorporated models, and databases.
-  Include 3-D distributions of macroscopic defects in the heat transfer and species diffusion simulations.
-  Couple neutron diffusion with heat and mass transport simulations.
-  Implement theory-based models in existing codes and perform sensitivity analysis to determine required accuracy in the input.
-  Develop complex meshes of the reactor core and perform 3-D simulations of accident scenarios.
-  Develop short-term and long-term plans and evaluate the necessary resources (people, computers, validation experiments, and funding).

## Pu-Ga phase diagram for theEnhanced Surveillance Campaign(M. Stan, M. Baskes, et al)

- 1M. I. Baskes, K. Muralidharan, M. Stan, S. M. Valone, and F. J. Cherne, JOM, **55** (2003) 41-50.
- 2 N. T. Chebotarev, E. S. Smotriskaya, M. A. Adrianov, and O. E. Kostyuk, in Plutonium 1975 and Other Actinides, Proceedings 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.

- New phase diagram

- Free energy of all phases

- Chemical potentials

- Thermodynamic equilibrium

- Electronic Structure

- Atomistic

- Minimal input from the binary1

## The Grand Challenge for ESC: Pu-Ga-Fe

* *Pu has *f* electrons.
-  Difficult electronic structure calculations for the elements.
-  Binaries poorly modeled.
-  Ternary is very complex.

## The Grand Challenges for GNEP: U-Pu-Zr-X    (X = fission  products)

-  Difficult electronic structure calculations for the elements.
-  Binaries poorly modeled.
-  No ternary!

## The Grand Challenge for GNEP: U-Pu-O-X    (X = fission  products)

-  Difficult electronic structure calculations for the elements.
-  Binaries poorly modeled.
-  Some ternary sections known.

## The Uncertainty of the UO2-PuO2 Phase Diagram(M. Stan and B. Reardon)*

- Collect available data

- Bayesian Statistics

- Calculate diagram anderror bars

- Evaluate uncertainty

- * M. Stan and B. J. Reardon, *CALPHAD*, **27** (2003) 319-323.
- [1]  M. G. Adamson, E. A. Aitken, and R. W. Caputi, J. Nucl. Mater.,** 130** (1985) 349-365.
- [2] T. D. Chikalla, J. Am. Ceram. Soc., **47** (1964) 309-309.

- Note: The diagram was assessed: the free energies of phases have been calculated to fit the experimental points.

## The Grand Challenge for GNEP: U-Pu-N-X    (X = fission  products)

-  Difficult electronic structure calculations for the elements.
-  Binaries poorly modeled.
-  No ternary!

-  **Example: U-Pu-N**

## Long-Term Objectives

- To predict thermodynamic properties of multi-component systems based on the known properties of their subsystems. To produce a set of criteria for stability of phases (compounds and solutions) based on the electronic structure of the elements.

**Long-Term Objectives**

- Predict the ternary phase diagram solely based on the binary diagrams and the properties of the elements, with NO previous knowledge of the properties of the ternary.

- Predict the Excess Gibbs free energy of a ternary phase using values of the Gibbs free energy of the binary subsystems and the properties of the elements.

## A Multi-Scale and Multi-Physics Method1

**U&V **= Uncertainty evaluation & model validation

**Electronic Structure Calculations**

- (RSPT)

**Inter**

**-**

**Atomic Potential**

- (MEAM)

**Thermodynamic Properties**

**Electronic Structure Calculations**

**Inter**

**-**

**Atomic Potential**

**Thermodynamic Properties**

- (MathCad)

**Phase Stability, Phase Transformations**

- (PANDAT, ThermoCalc)

**Experiment**

- (X-Ray, Calorimetry, etc)

**Simulations**

- (TRUCHAS)

**U&V**

**U&V**

- (DYN)

**Molecular Dynamics**

- 1 M. Stan, Trans. Amer. Nucl. Soc, **91** (2004) 131-133.

**!**

## Thermodynamic Properties of Multi-Component Fuel Element Materials

**THEORY**

**Computation**

**People**

- Thermodynamic Properties of Multi-Component Fuel Element Materials

- CALPHADMolecular DynamicsDensity Functional TheorySolid State PhysicsThermodynamicsTransport Theory

- PANDATFACTSAGETHERMOCALCFEMLABCASTEPVASPRSPT

- M. Stan (LANL)
- T. M. Bessmann (ORNL)Z. K. Liu (PennState)A. Chang (U. Wisconsin)

- Continuum

- Atomistic

- Electr. Str.

- Technology

- Charact./Valid.

- Calorimetry DilatometryMicroscopyX-Ray DiffractionCrystal Growth

- Task: Integrate Theory, Experiment, and Computation.

- P. Turchi  (LLNL)
- J. Wills (LANL)

- R. Kennedy (INL)
- K. McClellan (LANL)
- P. Fink (ANL) R. Konings (ITU)
- C. Gueneau (CEA)

- R. Grimes (Imp. College)
- S. Phillpot (UFL)A. Caro (LLNL)

- J. Tulenko (UFL)
- K. Pasamehmetoglu(INL)

## Materials Models and Simulations for Nuclear FuelsMMSNF-5

** **Organized by Martin Kissane (IRSN), Paul Van Uffelen (ITU), Robin Grimes (Imperial College), James Tulenko (Univ. of Florida), and Marius Stan (LANL).
- 	Sponsored by IRSN and LANL (DOE-AFC).
-  The MMSNF Workshop series aims at stimulating research and discussions on models and simulations of nuclear fuels and coupling the results with the fuel performance codes.
- SESSIONS:
-  Fundamental modelling of fuel properties.
-  Integral fuel performance codes and their validation.
-  Collaborations and integration of activities.
**MMSNF-6 in  Japan   or   Canada**
- Contact:  Marius Stan, _mastan@lanl.gov_
**International Nuclear Energy Research Initiative (I-NERI) meeting, ****Washington DC, July 10-13, 2006.**
**New projects:**
- M. Stan (LANL)-Paul Van Uffellen (ITU): **Thermal conductivity of nitride fuels**. Participants: LANL, INL ---ITU (Germany), CEA( France), JAERI (Japan):
- M. Stan (LANL)-Christine Gueneau (CEA): **Phase Stability of Multi-Component Nuclear Fuel Materials**. Participants: LANL, LLNL, ORNL , INL---CEA (France), ITU (Germany), KTH (Sweden):

- Materials Models and Simulations for Nuclear FuelsMMSNF-5

## Proposed tasks(ordered by scale, not necessary importance or urgency)

-  Perform electronic structure calculations of actinide compounds (oxides, nitrides,...etc).
-  Add charge transfer to inter-atomic potentials of actinide ceramics.
-  Develop models and simulate microstructure evolution in irradiated materials.
-  Develop experimental methods and determine defect types and concentrations to validate atomistic models.
-  Replace empirical correlations with theory-based models.Example: Thermal conductivity of MOX as function of temperature and stoichiometry.
-  **Calculate phase diagrams of multi-component systems such as U-Pu-Am-Cm-X and include uncertainty analysis.**
-  Review existing fuel performance codes and document capabilities, incorporated models, and databases.
-  Include 3-D distributions of macroscopic defects in the heat transfer and species diffusion simulations.
-  Couple neutron diffusion with heat and mass transport simulations.
-  Implement theory-based models in existing codes and perform sensitivity analysis to determine required accuracy in the input.
-  Develop complex meshes of the reactor core and perform 3-D simulations of accident scenarios.
-  Develop short-term and long-term plans and evaluate the necessary resources (people, computers, validation experiments, and funding).