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NERI PROJECT REVIEW
NERI 08-041Performance of Actinide-Containing
Fuel Matrices Under Extreme Radiation and Temperature Environments
University of IllinoisBrent J. Heuser
Panel No. 1 Session 7
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Project Objectives
Establish UO2 thin film growth capability with controlled microstructure, stoichiometry, and actinide surrogate concentrations.
Determine transport properties of actinide surrogates and implanted volatile fission gases under conditions that mimic the fission process in nuclear reactors.
Investigate affect of microstructure, stoichiometry, and impurity concentration of transport properties.
Develop and apply predictive computational models of transport mechanisms at an atomistic level.
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Project Work Scope Task 1—construction of dedicated UO2
thin film growth facility; grow CeO2 surrogate films in the interim.
Task 2—perform transport studies of actinide surrogate and fission gases.
Task 3—develop computational tools for predictive modeling.
Task 4—apply computational models to actinide/fission gas transport.
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Project Participants Lead Organization: University of Illinois
PI: Brent J. Heuser CoPIs: J. Stubbins, R. Averback. P. Bellon, J.
Eckstein
Collaborating Organizations: Georgia Institute of Technology/CoPIs: C. Deo,
M. Li University of Michigan/CoPI: L. Wang South Carolina State University/CoPI: M. Danjaji
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Organizational Roles University of Illinois
Provide thin film samples; study transport phenomena; develop computational tools for predictive transport studies based on MC, MD, kMC.
Georgia Institute of Technology Perform first-principles and kMC computations of
transport phenomena; develop digital microstructure. University of Michigan
Perform in situ studies of actinide/fission gas transport. South Carolina State University
Participate in experimental studies performed at Illinois via student/faculty exchange.
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Task 1 (Film Growth) Progress
Design and construction of dedicated thin film growth facility at Illinois complete.
Commissioning of facility underway.
MBE capability for CeO2 surrogate thin films with actinide surrogates established.
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Crystal Structure
Fluorite Structure—anions red, cations white
CeO2Tm=2673 Ka=5.4114 A
UO2Tm=3138 Ka=5.466 A
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Molecular Beam EpitaxyR-plane sapphire + CeO2 or UO2Lattice mismatch: CeO2 <2% UO2 <1%
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XRD Analysis of MBE CeO2 film
CM2 TP2
TP1
Forelinepump
FV1 FV2
GV1
GV2Sample Trans. Arm
PrimaryChamber
Load-lock
S1 S2 S3
CG1
IG1
CM1
ThicknessMonitor
O2AirAr1 Ar2
CG2 IG2
VV1
VV2
MassSpec.
SV5
SV2 SV3SV1
MFC2
SV6SV4
MFC1
TCG
TP—turbo pumpGV—gate valveFV—foreline valveVV—vent valveSV—solenoid valveRV—relief valve
CG—convectron gaugeIG—ion gaugeTCG—thermocouple gaugePG—Pirani gaugeCM—capacitance manometerMFC—mass flow controllerS—sputter gun
SPUTTER DEPOSITION FACILITY SCHEMATIC
CM3
RV
PG
APC
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Magnetron Sputtering System at Illinois
Targets: depleted U; Ce; NdPower Supply: 2 DC; 1 RFGas Supply: O2: 0 to 10 sccm Ar: 1 to 100 sccmMax. Ts=850 C
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MBE—2302 RGS—3
MBE vs. Reactive Gas Sputtering (RGS)Comparison of SIMS Positive Ion Collection
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Berg Model for Reactive Gas SputteringThin Solid Films, 476 (2005) 215
metal mode
poison mode
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Poison vs. Metal Modes in Reactive Gas Sputtering
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Poison vs. Metal Sputtering Modes
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XRD Analysis of Sputtered CeO2 film
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Control of RGS Film Microstructure
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Task 1 Planned Activities
Thin film growth facility finished—currently growing CeO2 films for benchmarking, commissioning.
UO2 films in the next few months. UO2 films with controlled microstructure, actinide
surrogate concentration, stoichiometry. CeO2 films via MBE with actinide surrogates to
continue. Additional implantation of UO2 and CeO2 films
w/Xe.
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Task 1 Issues or Concerns Shutter design of source flange somewhat
problematic and may require periodic (~quarterly) adjustment.
Debris build up will require the system to be opened occasionally (~quarterly).
Do not control MBE system—can expect 1 to 4 samples per month.
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Task 2 (Experimental Transport Studies) Progress
Performed RED measurements of cation sublattice in CeO2 with a La marker layer.
Performed low-energy Xe implantations in CeO2 at two concentrations for fission gas bubble dissolution experiments.
Irradiated Xe-implanted CeO2 samples with Kr. Developed TEM specimen preparation techniques. Performed ex situ TEM analysis of irradiated CeO2 and
Xe-implanted CeO2. Performed in situ TEM analysis of Xe-implanted CeO2. Performed EXAFS measurements of Xe implanted
(unirradiated) CeO2.
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Experimental Facilities at Illinois
Microanalytical: AES, SIMS, RBS, XRD/XRR, TEM, SEM, AFM.
Implantation: tandem van de Graaff (0.5-2.3 MeV; H, He, Xe, Kr, Ne; ~100 nA)
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SIMS of Irradiated Single Crystal CeO2360 A thickness w/1 ML La at centerline
1.8 MeV Kr; 1 ion/A2 at RT
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La Depth ProfilesRT Irradiation 1.8 MeV Kr
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Mixing Parameter Analysis in CeO2 at RT
1.8 MeV Kr
=6 A5/eV
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Radiation-Enhanced Diffusion in CeO21.8 MeV Kr at dose of 1 ion/Å2
Dth=2.64x10-16 exp(-0.154 eV/kT) [cm2/sec]DRED=5.25x10-16 exp(-0.091 eV/kT) [cm2/sec]
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Task 2 Planned Activities
RED investigation of anion sublattice with O-18 in CeO2 and UO2.
Further RED investigations on cation sublattice in UO2 and CeO2.
Implementation of model based on kinetic rate equations for RED.
EXAFS, SAXS, SIMS studies of precipitation of actinide surrogates and Xe.
Further in situ and ex situ TEM analysis of actinide surrogate precipitation and Xe bubble formation/dissolution.
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Task 2 Issues or Concerns
Availability of ANL in situ TEM facility—Saclay facility available for use via P. Bellon.
Supply of samples to L. Wang (U. Mich) delayed—Xe implanted samples, other samples within next month.
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Task 3/4 (Development/Application of Computational Tools for Predictive
Modeling) Progress
Development of combined MC-MD approach to model UO2 at Illinois complete.
Study of Xe bubble homogeneous re-solution in UO2 via MC-MD complete.
Study of Xe bubble heterogeneous re-solution in UO2 via MD complete.
Development of DFT-kMC capability for UO2 at Georgia Institute of Technology complete.
Initial studies of oxygen transport in UO2 using DFT-kMC complete.
Development of geometric computational methods for polycrystalline media based on constrained Voronoi tessellation (digital microstructure) complete.
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Interatomic Interaction Potential
Molecular Dynamics
Develop w/DFT Existing
DFT
short time scales [ps]displacement cascades kMC
Em
long time scalesdiffusive motion
rate catalog
Computational Method
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MC-MD Study of Homogeneous Xe Bubble Re-solution in UO2
Xe recoil spectrum from MC.
Homogeneous re-solution: Interaction of fission fragment with fission gas atoms in bubble via energetic collisions (ballistic ejection).
Heterogeneous re-solutions: Interaction of displacement cascade with entire bubble.
Schwen et al., J. Nuclear Materials, 392 (2009) 35.
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MC-MD Study of Homogeneous Xe Bubble Re-solution in UO2
Computational Details
MC: BCM, ZBL potential, based TRIM algorithm to treat arbitrary geometries and irradiation conditions (not fixed layer geo.).
MD: LAMMPS code Long range Coulomb U-O treated PPPM method. Rigid-ion potential;
U-UU-OO-O all Morelon potential in UO2
plusU-O Born-Mayer-Huggins covalent bondingO-O Born-Mayer + polynomial + 1/r6
U-U pure Coulombic
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MC-MD Study of Homogeneous Xe Bubble Re-solution in UO2
Histogram of displacement lengthsof Xe atoms from bubble center.
Probability of Xe atoms leaving Bubble vs. Xe PKA energy.
Re-solution parameter: 3x10-6 s-1 Xe knock-outs per Xe gas atomsThis result is factor of 50 lower than analytical work of Nelson.
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Channeling
Xe atom displacement histograms
MC+MD
MC
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MD Simulations of HeterogeneousXe Bubble Re-solution in UO2
Huang et al., to be submitted 9/2009
Two temperature model couplingelectronic and phonon (atom) contributions based on sputteringyield benchmarks.
dE/dx=55.4 keV/nm
dE/dx=47.0 keV/nm
dE/dx=32.8 keV/nm
Conclusions
No Xe re-solution dE/dx<34 keV/nm (ff: 18-22 keV/nm)
ff cross section for interaction w/bubble ~5 nm2
1-5 ff-bubble interactions per ffcomplete bubble destruction never observed
13 11
6 2
079 Xe atoms
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DFT-kMC Simulations of Oxygen Diffusion in UO2+x
Buckingham Potential for UO2 DFT LDA+U for UO2
di-interstitial mechanism
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Task 3 Planned Activities Further MC-MD studies of Xe bubble behavior;
coupling of computational studies to experimental investigations (EXAFS, SAXS, in situ TEM) of bubble behavior in UO2.
Further DFT and kMC studies of transport phenomena in UO2; coupling of computational studies to experimental investigations (RED) of transport behavior in UO2.
Application of geometric methods of microstructure to polycrystalline UO2 in MC and MD; coupling of MC polycrystalline models to RED in polycrystalline UO2.
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Task 3 Issues or Concerns None.
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Project Milestones Schedule
Milestone Description Planned Start Date
Planned Completion Date
Status1
Constr. of thin film growth facility;Commissioning of facility
1/20081/2009
1/20094/2009
CB
Establish MBE capability for CeO2 films
4/2008 9/2008 C
Experimental studies of transport phenomena in CeO2
9/2008 1/2010 O
Experimental studies of transport phenomena in UO2
4/2009 1/2011(2) B
Development of computational tools—MC, MD, kMC, DFT
1/2008 9/2008 C
Computational studies of transport phenomena
10/2008 1/2011(2) O
Note 1: Enter ‘C’ if milestone has been completed; ‘O’ if milestone is on schedule for completion; or, ‘B’ if milestone is behind schedule for completion.
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Year 1 Planned Vs. Actual Costs
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Year 2 Planned Vs. Actual Costs
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Year 3 Planned Vs. Anticipated Costs
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Project Accomplishments—To Date
Dedicated thin film growth facility completed. Commissioning nearly completed. Control of microstructure (via Ts), stoichiometry (via O2
pressure) and actinide concentration (via gun power level) demonstrated.
RED on cation sublattice in CeO2 measured up to 1208 K. Initial in situ TEM analysis of Xe bubble resolution in CeO2
performed. Initial EXAFS measurements of Xe bubble resolution in
CeO2 performed. Computational tools in place; initial set of studies (Xe
bubble resolution, oxygen diffusion, microstructure modeling via inverse MC) complete.
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Project Accomplishments—Anticipated
Demonstrate of UO2 thin film growth with controlled stoichiometry, microstructure, actinide surrogate concentration.
RED measurements on cation and anion sublattices in UO2 under different bombardment conditions (T, dose, E).
Measurements of Xe and actinide surrogate precipitation behavior in UO2 under different bombardment conditions.
Determination of synergistic effect of UO2 microstructure, bombardment conditions, impurity concentrations.
Further kMC and MD simulations of transport behavior.
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R&D Programs Benefits Project addresses the nuclear fuel cycle by
investigating materials aspects of actinide incorporation into UO2 matrices.
Project will provide: Measurements of actinide and fission gas transport
properties in UO2. Computational tools for predictive modeling of transport
properties. Successful completion of this project will facilitate
an improved understanding of fuel behavior within a closed fuel cycle.
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Programmatic Contributions
Contribution to NERI Program objectives:
Project helps close the fuel cycle by providing data and predictive modeling capabilities that promote better understanding of UO2 containing actinides.
Project will advance the state of nuclear technology in the U.S. by 1) aiding in the reduction of waste disposition time scales and 2) increasing fuel efficiency via recovery of major actinide energy content.
Project addresses nuclear science and engineering infrastructure through the training of young researches:
Illinois: 4 UG, 8 Grad, 2 post-doct.Georgia: 5 GradMichigan: 1 Grad, 1 post-doct.
And the development of capabilities at Illinois and Georgia Tech.
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Commercialization Potential
Potential exists through Hitachi GE Nuclear.
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Potential Future R&D Efforts
A dedicated UO2 thin film growth facility at Illinois represents a unique capability; we anticipate studies beyond the current NERI grant within the AFCI.
Development of computational tools at Illinois and Georgia Institute of Technology offers potential for further synergistic efforts of collaboration between the two institutions within the AFCI.