1. University of Illinois
NERI PROJECT REVIEW
NERI
Performance of Actinide-Containing Fuel Matrices Under Extreme Radiation and Temperature Environments
University of Illinois
Brent J. Heuser
Panel No. 1 Session 7

2. 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.
4/24/2017
NERI PROJECT NO

3. 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.
4/24/2017
NERI PROJECT NO

4. 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
4/24/2017
NERI PROJECT NO

5. 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.
4/24/2017
NERI PROJECT NO

6. 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.
4/24/2017
NERI PROJECT NO

7. Crystal Structure Fluorite Structure—anions red, cations white CeO2
Tm=2673 K
a= A
UO2
Tm=3138 K
a=5.466 A
4/24/2017
NERI PROJECT NO

8. Molecular Beam Epitaxy
R-plane sapphire + CeO2 or UO2
Lattice mismatch: CeO2 <2%
UO2 <1%
4/24/2017
NERI PROJECT NO

9. XRD Analysis of MBE CeO2 film
4/24/2017
NERI PROJECT NO

10. Sputter Deposition Facility Schematic
CM2
TP2
TP1
Foreline
pump
FV1
FV2
GV1
GV2
Sample
Trans.
Arm
Primary
Chamber
Load-
lock S1 S2 S3
CG1
IG1
CM1
Thickness
Monitor O2
Air
Ar1
Ar2
CG2
IG2
VV1
VV2
Mass
Spec.
SV5
SV2
SV3
SV1
MFC2
SV6
SV4
MFC1
TCG
TP—turbo pump
GV—gate valve
FV—foreline valve
VV—vent valve
SV—solenoid valve
RV—relief valve
CG—convectron gauge
IG—ion gauge
TCG—thermocouple gauge
PG—Pirani gauge
CM—capacitance manometer
MFC—mass flow controller
S—sputter gun
Sputter Deposition Facility Schematic
CM3 RV PG
APC

11. Magnetron Sputtering System at Illinois
Targets: depleted U; Ce; Nd
Power Supply: 2 DC; 1 RF
Gas Supply: O2: 0 to 10 sccm
Ar: 1 to 100 sccm
Max. Ts=850 C
4/24/2017
NERI PROJECT NO

12. MBE vs. Reactive Gas Sputtering (RGS) Comparison of SIMS Positive Ion Collection
4/24/2017
NERI PROJECT NO

13. Berg Model for Reactive Gas Sputtering
Thin Solid Films, 476 (2005) 215
metal mode
poison mode
4/24/2017
NERI PROJECT NO

14. Poison vs. Metal Modes in Reactive Gas Sputtering
4/24/2017
NERI PROJECT NO

15. Poison vs. Metal Sputtering Modes
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NERI PROJECT NO

16. XRD Analysis of Sputtered CeO2 film
4/24/2017
NERI PROJECT NO

17. Control of RGS Film Microstructure
4/24/2017
NERI PROJECT NO

18. 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.
4/24/2017
NERI PROJECT NO

19. 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.
4/24/2017
NERI PROJECT NO

20. 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.
4/24/2017
NERI PROJECT NO

21. Experimental Facilities at Illinois
Microanalytical: AES, SIMS, RBS, XRD/XRR, TEM, SEM, AFM.
Implantation: tandem van de Graaff ( MeV; H, He, Xe, Kr, Ne; ~100 nA)
4/24/2017
NERI PROJECT NO

22. SIMS of Irradiated Single Crystal CeO2
360 A thickness w/1 ML La at centerline
1.8 MeV Kr; 1 ion/A2 at RT
4/24/2017
NERI PROJECT NO

23. La Depth Profiles RT Irradiation 1.8 MeV Kr
4/24/2017
NERI PROJECT NO

24. Mixing Parameter Analysis in CeO2 at RT 1.8 MeV Kr
x=6 A5/eV
4/24/2017
NERI PROJECT NO

25. Radiation-Enhanced Diffusion in CeO2 1.8 MeV Kr at dose of 1 ion/Å2
Dth=2.64x10-16 exp( eV/kT) [cm2/sec]
DRED=5.25x10-16 exp( eV/kT) [cm2/sec]
4/24/2017
NERI PROJECT NO

26. 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.
4/24/2017
NERI PROJECT NO

27. 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.
4/24/2017
NERI PROJECT NO

28. 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.
4/24/2017
NERI PROJECT NO

29. Computational Method Interatomic Interaction Potential
Molecular Dynamics
Develop w/DFT
Existing
DFT
short time scales [ps]
displacement cascades
kMC Em
long time scales
diffusive motion
rate catalog
4/24/2017
NERI PROJECT NO

30. 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.
4/24/2017
NERI PROJECT NO

31. 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-U
U-O
O-O all Morelon potential in UO2
plus
U-O Born-Mayer-Huggins covalent bonding
O-O Born-Mayer + polynomial + 1/r6
U-U pure Coulombic
4/24/2017
NERI PROJECT NO

32. MC-MD Study of Homogeneous Xe Bubble Re-solution in UO2
Histogram of displacement lengths
of 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 atoms
This result is factor of 50 lower than analytical work of Nelson.
4/24/2017
NERI PROJECT NO

33. Xe atom displacement histograms
Channeling
Xe atom displacement histograms
MC+MD MC
4/24/2017
NERI PROJECT NO

34. MD Simulations of Heterogeneous Xe Bubble Re-solution in UO213 11
Two temperature model coupling
electronic and phonon (atom)
contributions based on sputtering
yield benchmarks.
dE/dx=55.4 keV/nm 6 2
Conclusions
No Xe re-solution dE/dx<34 keV/nm
(ff: keV/nm)
ff cross section for interaction w/bubble ~5 nm2
1-5 ff-bubble interactions per ff
complete bubble destruction never observed
dE/dx=47.0 keV/nm
dE/dx=32.8 keV/nm
79 Xe atoms
Huang et al., to be submitted 9/2009
4/24/2017
NERI PROJECT NO

35. DFT-kMC Simulations of Oxygen Diffusion in UO2+x
Buckingham Potential for UO2
DFT LDA+U for UO2
di-interstitial mechanism
4/24/2017
NERI PROJECT NO

36. 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.
4/24/2017
NERI PROJECT NO

37. Task 3 Issues or Concerns
None.
4/24/2017
NERI PROJECT NO

38. Project Milestones Schedule
Milestone Description
Planned Start Date
Planned Completion Date
Status1
Constr. of thin film growth facility;
Commissioning of facility
1/2008
1/2009
4/2009 C B
Establish MBE capability for CeO2 films
4/2008
9/2008
Experimental studies of transport phenomena in CeO2
1/2010 O
Experimental studies of transport phenomena in UO2
1/2011(2)
Development of computational tools—MC, MD, kMC, DFT
Computational studies of transport phenomena
10/2008
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.
4/24/2017
NERI PROJECT NO

39. Year 1 Planned Vs. Actual Costs
4/24/2017
NERI PROJECT NO

40. Year 2 Planned Vs. Actual Costs
4/24/2017
NERI PROJECT NO

41. Year 3 Planned Vs. Anticipated Costs
4/24/2017
NERI PROJECT NO

42. 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.
4/24/2017
NERI PROJECT NO

43. 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.
4/24/2017
NERI PROJECT NO

44. 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.
4/24/2017
NERI PROJECT NO

45. 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 Grad
Michigan: 1 Grad, 1 post-doct.
And the development of capabilities at Illinois and Georgia Tech.
4/24/2017
NERI PROJECT NO

46. Commercialization Potential
Potential exists through Hitachi GE Nuclear.
4/24/2017
NERI PROJECT NO

47. 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.
4/24/2017
NERI PROJECT NO