Emmanuel Perez

Profile Information
Dr. Emmanuel Perez
Savannah River National Laboratory
Materials Scientist/Engineer

Emmanuel Perez holds a position as a Materials Engineer specializing in microstructural development and chemical interactions between fresh fuels and their respective cladding materials. He is the Instrument Scientist for CAES and currently is the technical lead scientist for two university projects. He received a bachelor’s of engineering degree in Chemical Engineering from Columbia University, a Master of Science and Doctorate degrees in Materials Science and Engineering from the University of Central Florida. Prior to obtaining his MS degree, he held a position for seven years as a Thermal and Mechanical Engineer at a Diversified Heat Transfer, Inc., where he was tasked with the design and manufacture of industrial heat transfer equipment. Emmanuel has 13 years of experience operating scanning electron microscopes (SEM), 8 years of operational experience with Electron Probe Microanalysis (EPMA), 11 years of operational experience with sample preparation via Focused Ion Beam (FIB), and 11 years operational experience in characterization via Transmission Electron Microscopy (TEM).

Bachelor’s of engineering degree in Chemical Engineering
Master of Science and Doctorate degrees in Materials Science and Engineering

Fuel Cladding Chemical Interaction (FCCI), Material Characterization, Mechanical Properties, Thermodynamics, U-Mo Fuel, U-Zr Fuels
"Characterization of Interaction Layer in U-Mo-X (X = Nb, Zr) and U-Nb-Zr vs. Al Diffusion Couples Annealed at 600 degrees C for 10 Hours" Emmanuel Perez, Ashley Paz y Puente, Dennis Keiser, Yongho Sohn, Defects and Diffusion Forum Vol. 312-315 2011 1055-1062 Link
U-Mo has thus far proven to be one of the most feasible metallic fuel alloys for use in research and test reactors due to its high density and stability during irradiation. However, an adverse diffusional interaction can occur between the fuel alloy and the Al based matrix. This forms an interaction layer (IL) that has undesirable thermal properties and irradiation behavior leading to accelerated swelling and reduced fuel efficiency. This study focused on the effects of ternary alloying additions on the formation of IL between U based alloys and Al. Diffusion couples of U-8Mo-3Nb, U-7Mo-6Zr, and U-10Nb-4Zr (wt.%) vs. pure Al were assembled and annealed at 600 Degrees C for 10 hours. Both thickness and phase constituent analyses were performed via electron microscopy. The major phase constituent of the IL was determined to be the UAl3 intermetallic compound. The Nb and Zr alloying additions did not reduce growth rate of IL (1.3-1.4 m/sec1/2) as compared to couples made between binary U-Mo and Al (0.9-1.8 m/sec1/2).
"Laser weld-induced formation of amorphous Mn-Si precipitate in 304 stainless steel" Janelle Wharry, Keyou Mao, Yaqiao Wu, Cheng Sun, Emmanuel Perez, Materialia Vol. 3 2018 174-177 Link
"Measurement of grain boundary strength of Inconel X-750 superalloy using in-situ micro-tensile testing techniques in FIB/SEM system" Yachun Wang, Xiang Liu, Daniel Murray, Fei Teng, Wen Jiang, Mukesh Bachhav, Laura Hawkins, Emmanuel Perez, Cheng Sun, Xianming Bai, Jie Lian, Colin Judge, John Jackson, Robert Carter, Lingfeng He, Materials Science & Engineering Vol. 849 2022 Link
"Microstructural Analysis of As-Processed U-10wt.%Mo Monolithic Fuel Plate in AA6061 Matrix with Zr Diffusion Barrier" Emmanuel Perez, B. Yao, Dennis Keiser, Yongho Sohn, Journal of Nuclear Materials Vol. 402 2010 8-14 Link
For higher U-loading in low-enriched U–10 wt.%Mo fuels, monolithic fuel plate clad in AA6061 is being developed as a part of Reduced Enrichment for Research and Test Reactor (RERTR) program. This paper reports the first characterization results from a monolithic U–10 wt.%Mo fuel plate with a Zr diffusion barrier that was fabricated as part of a plate fabrication campaign for irradiation testing in the Advanced Test Reactor (ATR). Both scanning and transmission electron microscopy (SEM and TEM) were employed for analysis. At the interface between the Zr barrier and U–10 wt.%Mo, going from Zr to U(Mo), UZr2, γ-UZr, Zr solid-solution and Mo2Zr phases were observed. The interface between AA6061 cladding and Zr barrier plate consisted of four layers, going from Al to Zr, (Al, Si)2Zr, (Al, Si)Zr3 (Al, Si)3Zr, and AlSi4Zr5. Irradiation behavior of these intermetallic phases is discussed based on their constituents. Characterization of as-fabricated phase constituents and microstructure would help understand the irradiation behavior of these fuel plates, interpret post-irradiation examination, and optimize the processing parameters of monolithic fuel system.
"Microstructural Characterization of U-7Mo/Al-Si Alloy Matrix Dispersion Fuel Plates Fabricated at 500 C" Emmanuel Perez, Dennis Keiser, Jan-Fong Jue, Bo Yao, Yongho Sohn, Curtis Clark, Journal of Nuclear Materials Vol. 412 2011 90-99 Link
The starting microstructure of a dispersion fuel plate will impact the overall performance of the plate during irradiation. To improve the understanding of the as-fabricated microstructures of U–Mo dispersion fuel plates, particularly the interaction layers that can form between the fuel particles and the matrix, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed on samples from depleted U–7Mo (U–7Mo) dispersion fuel plates with either Al–2 wt.% Si(Al–2Si) or AA4043 alloy matrix. It was observed that in the thick interaction layers, U(Al, Si)3 and U6Mo4Al43 were present, and in the thin interaction layers, (U, Mo) (Al, Si)3, U(Al, Si)4, U3Si3Al2, U3Si5, and possibly USi-type phases were observed. The U3Si3Al2 phase contained some Mo. Based on the results of this investigation, the time that a dispersion fuel plate is exposed to a relatively high temperature during fabrication will impact the nature of the interaction layers around the fuel particles. Uniformly thin, Si-rich layers will develop around the U–7Mo particles for shorter exposure times, and thicker, Si-depleted layers will develop for the longer exposure times.
"Microstructural Characterization of U-Nb-Zr, U-Mo-Nb, and U-Mo-Ti Alloys via Electron Microscopy" Emmanuel Perez, Ashley Ewh, Dennis Keiser, Yongho Sohn, Journal of Phase Equilibria and Diffusion Vol. 31 2010 216-222 Link
Ternary uranium molybdenum alloys are being examined for use as dispersion and monolithic nuclear fuels in research and test reactors. In this study, three such ternary alloys, with compositions U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti in wt.%, were examined using scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM). These alloys were homogenized at 950 °C for 96 h and were expected to be single-phase bcc-γ-U. However, upon examination, it was determined that despite homogenization, each of the alloys contained a small volume fraction precipitate phase. Through SEM and XRD, it was confirmed that the matrix retained the bcc-γ-U phase. TEM specimens were prepared using site-specific focused ion beam (FIB) in situ lift out (INLO) technique to include at least one precipitate from each alloy. By electron diffraction, the precipitate phases for the U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti alloys were identified as bcc-(Nb,Zr), bcc-(Mo,Nb), and bcc-(Mo,Ti) solid solutions, respectively. The composition and phase information collected in this study was then used to construct ternary isotherms for each of these alloys at 950 °C.
"Microstructural development from interdiffusion and reaction between U-Mo and AA6061 alloys annealed at 600° and 550 °C" Dennis Keiser, Emmanuel Perez, Yongho Sohn, Journal of Nuclear Materials Vol. 477 2016 178-192 Link
The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the UMo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, U7 wt%Mo, U10 wt%Mo, and U12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanning electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples UMo vs. high purity Al and binary AlSi alloys. The diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.
"Microstructure characterization of as-fabricated and 475ºC annealed U-7wt.%Mo dispersion fuel in Al-Si alloy matrix" Emmanuel Perez, Bo Yao, Dennis Keiser, Jan-Fong Jue, Curtis Clark, Nicolas Woolstenhulme, Yongho Sohn, Journal of Alloys and Compounds Vol. 509 2011 9487-9496 Link
High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U–Mo fuel alloy dispersed in Al–Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 °C for 4 h) U–Mo dispersion fuels in Al–Si matrix with a Si concentration of 2 and 5 wt.%, named as “As2Si”, “As5Si”, “An2Si”, “An5Si” accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al–5 wt.% Si matrix consistently yielded thicker interaction layers developed between U–Mo particles and Al–Si matrix, than those with Al–2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., “As2Si”, “As5Si”), and this layer mainly consisted of U3Si3Al2 phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U–Mo side, and an Al-rich layer near the Al–Si matrix side. The U3Si5 appeared as the main phase in the Si-rich layer in “An2Si” sample, while both U3Si5 and U3Si3Al2 were identified in sample “An5Si”. The Al-rich layer in sample “An2Si” was amorphous, whereas that in sample “An5Si” mostly consisted of crystalline U(Al,Si)3, along with a small fraction of U(Al,Si)4 and U6Mo4Al43 phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance.
"Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 °C)" Emmanuel Perez, Dennis Keiser, Yongho Sohn, Metallurgical and Materials Transactions A Vol. 42 2011 3071-3083 Link
U-Mo dispersion and monolithic fuels are being developed to fulfill the requirements for research reactors, under the Reduced Enrichment for Research and Test Reactors program. In dispersion fuels, particles of U-Mo alloys are embedded in the Al-alloy matrix, while in monolithic fuels, U-Mo monoliths are roll bonded to the Al-alloy matrix. In this study, interdiffusion and microstructural development in the solid-to-solid diffusion couples, namely, U-15.7 at. pct Mo (7 wt pct Mo) vs pure Al, U-21.6 at. pct Mo (10 wt pct Mo) vs pure Al, and U-25.3 at. pct Mo (12 wt pct Mo) vs pure Al, annealed at 873 K (600 °C) for 24 hours, were examined in detail. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase interaction layer with an approximately constant average composition of 80 at. pct Al. Extensive TEM was carried out to identify the constituent phases across the interaction layer based on selected area electron diffraction and convergent beam electron diffraction (CBED). The cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43, and cubic-UMo2Al20 phases were identified within the interaction layer that included two- and three-phase layers. Residual stress from large differences in molar volume, evidenced by vertical cracks within the interaction layer, high Al mobility, Mo supersaturation, and partitioning toward equilibrium in the interdiffusion zone were employed to describe the complex microstructure and phase constituents observed. A mechanism by compositional modification of the Al alloy is explored to mitigate the development of the U6Mo4Al43 phase, which exhibits poor irradiation behavior that includes void formation and swelling.
"Phase constituents of Al-rich U–Mo–Al alloys examined by transmission electron microscopy" Emmanuel Perez, Ashley Ewh, Jinwei Liu, Dennis Keiser, Yongho Sohn, Journal of Nuclear Materials Vol. 394 2009 160-165 Link
To supplement the understanding of diffusional interactions involving Al-rich region of the U–Mo–Al system, alloys with composition 85.7Al–11.44U–2.86Mo and 87.5Al–10U–2.5Mo in at.%, were examined to determine the equilibrium phase constituents at 500 °C. These alloys were triple arc-melted, homogenized at 500 °C for 200 h, and water-quenched to preserve the high temperature microstructure. X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (XEDS), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM) were employed for the characterization. Alloy specimens for TEM/STEM were prepared using site-specific focused ion beam (FIB) in situ lift-out (INLO) technique. Despite the homogenization time and temperature, five different phases, namely fcc-Al solid solution, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20, were observed. Based on U–Al, U–Mo and Al–Mo binary phase diagrams, previously proposed U–Mo–Al isotherms, and the solidification microstructure of these alloys, the Al-rich region of the equilibrium ternary isotherm at 500 °C was constructed. The fcc-Al solid solution, orthorhombic-UAl4, and diamond cubic-UMo2Al20 which were determined to be the equilibrium phases in 85.7Al–11.44U–2.86Mo and 87.5Al–10U–2.5Mo alloys.
"Phase development in a U–7 wt.% Mo vs. Al–7 wt.% Ge diffusion couple" Emmanuel Perez, Dennis Keiser, Yongho Sohn, Journal of Nuclear Materials Vol. 441 2013 159-167 Link
Fuel development for the Reduced Enrichment for Research and Test Reactors (RERTR) program has demonstrated that U–Mo alloys in contact with Al develop interaction regions with phases that have poor irradiation behavior. The addition of Si to the Al has been considered with positive results. In this study, compositional modification is considered by replacing Si with Ge to determine the effect on the phase development in the system. The microstructural and phase development of a diffusion couple of U–7 wt.% Mo in contact with Al–7 wt.% Ge was examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The interdiffusion zone developed a microstructure that included the cubic-UGe3 phase and amorphous phases. The UGe3 phase was observed with and without Mo and Al solid solution developing a (U,Mo)(Al,Ge)3 phase.
"Role of Si on Diffusional Interaction between U-Mo and Al-Si Alloys at 823K (550 C)" Emmanuel Perez, Dennis Keiser, Yongho Sohn, Metallurgical and Materials Transactions A Vol. 44 2012 584-595 Link
U-Mo dispersions in Al-alloy matrix and monolithic fuels encased in Al-alloy are under development to fulfill the requirements for research and test reactors to use low-enriched molybdenum stabilized uranium alloys fuels. Significant interaction takes place between the U-Mo fuel and Al during manufacturing and in-reactor irradiation. The interactions products are Al-rich phases with physical and thermal characteristics that adversely affect fuel performance and lead to premature failure. Detailed analysis of the interdiffusion and microstructural development of this system was carried through diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo in contact with pure Al, Al-2wt.%Si, and Al-5wt.%Si, annealed at 823K for 1, 5 and 20 hours. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for the analysis. Diffusion couples consisting of U-Mo vs. pure Al contained UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases. The addition of Si to the Al significantly reduced the thickness of the interdiffusion zone. The interdiffusion zones developed Al and Si enriched regions, whose locations and size depended on the Si and Mo concentrations in the terminal alloys. In the couples, the (U,Mo)(Al,Si)3 phase was observed throughout interdiffusion zone, and the U6Mo4Al43 and UMo2Al20 phases were observed only where the Si concentrations were low. (PDF) Role of Si on the Diffusional Interactions Between U-Mo and Al-Si Alloys at 823 K (550 °C). Available from: https://www.researchgate.net/publication/255813658/download [accessed Sep 06 2018].
"Selected Observations in Phase Constituents, Growth Kinetics and Microstructural Development of Aluminides in U-Mo vs. Al and 6061 Diffusion Couples Annealed at 600°C" Emmanuel Perez, Dennis Keiser, Yongho Sohn, Defects and Diffusion Forum Vol. 289-292 2009 41-49 Link
This paper presents selected experimental observations of phase constituents, growth kinetics, and microstructural development of aluminide phases that develop in solid-to-solid diffusion couples assembled with U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. Al and 6061 alloy after a diffusion anneal at 600°C for 24 hours. Scanning electron microscopy coupled with energy dispersive spectroscopy, electron microprobe analysis, and transmission electron microscopy via focused ion beam in-situ lift-out were employed to characterize the interaction layer that develops by interdiffusion. While concentration profiles exhibited no significant gradients, microstructural analysis revealed the presence of extremely complex and nano-scale phase constituents with presence of orthorhombic--U, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20 phases. Presence of multi-phase layers with microstructure, which suggest a significant role of grain boundary diffusion, was observed.
"STEM-EDS/EELS and APT characterization of ZrN coatings on UMo fuel kernels" Lingfeng He, Mukesh Bachhav, Dennis Keiser, Emmanuel Perez, Brandon Miller, Jian Gan, Ann Leenaers, Sven Van den Berghe, Journal of Nuclear Materials Vol. 511 2018 174-182 Link
NSUF Articles:
DOE Awards 33 Rapid Turnaround Experiment Research Proposals - Projects total approximately $1.2 million These projects will continue to advance the understanding of irradiation effects in nuclear fuels and materials in support of the mission of the DOE Office of Nuclear Energy. Monday, June 18, 2018 - Calls and Awards