Education

Research Description

Dr. Eapen's research interests are in science-based modeling and simulation of nuclear fuel for advanced reactors, nano-structured materials, plasma-material interactions, energy transport at nano-scales and interfaces, modeling of diffusion and viscosity in glass matrices for radioactive waste management.

Publications

Ion hopping and constrained Li diffusion pathways in the superionic state of antifluorite Li2O

Annamareddy, A., & Eapen, J. (2017), Entropy, 19(5).

Entropic crossovers in superionic fluorites from specific heat

Eapen, J., & Annamareddy, A. (2017), Ionics, 23(4), 1043-1047.

Low dimensional string-like relaxation underpins superionic conduction in fluorites and related structures

Annamareddy, A., & Eapen, J. (2017), Scientific Reports, 7.

Disordering and dynamic self-organization in stoichiometric UO2 at high temperatures

Annamareddy, A., & Eapen, J. (2017), Journal of Nuclear Materials, 483, 132-141.

Modeling irradiation creep of graphite using rate theory

Sarkar, A., Eapen, J., Raj, A., Murty, K. L., & Burchell, T. D. (2016), Journal of Nuclear Materials, 473, 197-205.

Mobility propagation and dynamic facilitation in superionic conductors

Annamareddy, A., & Eapen, J. (2015), Journal of Chemical Physics, 143(19).

Creep behavior of hydrogenated zirconium alloys

Sarkar, A., Boopathy, K., Eapen, J., & Murty, K. L. (2014), Journal of Materials Engineering and Performance, 23(10), 3649-3656.

Waxing and waning of dynamical heterogeneity in the superionic state

Annamareddy, V. A., Nandi, P. K., Mei, X. J., & Eapen, J. (2014), Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics, 89(1).

Absolute thermodynamic properties of molten salts using the two-phase thermodynamic (2PT) superpositioning method

Wang, J., Chakraborty, B., & Eapen, J. (2014), Physical Chemistry Chemical Physics, 16(7), 3062-3069.

Multicomponent diffusion in molten LiCl-KCl: Dynamical correlations and divergent Maxwell-Stefan diffusivities

Chakraborty, B., Wang, J., & Eapen, J. (2013), Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics, 87(5).

View all publications via NC State Libraries

Grants

Turbulent MHD flow modeling in annular linear induction pumps with validation experiments

US Dept. of Energy (DOE)(10/01/16 - 9/30/19)

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Turbulent MHD flow modeling in annular linear induction pumps with validation experiments

Sponsor: US Dept. of Energy (DOE)

Start Date: 10/01/16

End Date: 9/30/19

Abstract

This proposed scope of work seeks to advance EMP design efforts for liquid metal reactors by 1.) improving MHD modelling capability, particularly by incorporating turbulence modeling and investigating the MHD stability criteria, 2.) advancing multi-physics simulation of these systems leveraging the open source MOOSE platform that is already used in many nuclear reactor and reactor system efforts, and 3.) constructing a low barrier EMP test loop for model validation and instruction that can be easily replicated at low cost at other facilities.

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Microstructure Experiments-Enabled MARMOT Simulations of SiC/SiC-based Accident Tolerant Nuclear Fuel System

US Dept. of Energy (DOE)(10/01/16 - 9/30/19)

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Microstructure Experiments-Enabled MARMOT Simulations of SiC/SiC-based Accident Tolerant Nuclear Fuel System

Sponsor: US Dept. of Energy (DOE)

Start Date: 10/01/16

End Date: 9/30/19

Abstract

Following the nuclear accident at Fukushima, replacing the current Zr alloy-based cladding with silicon carbide composites has gained traction in the DOE as well as in the industry. The most recent generation of SiC/SiC composites (III), defined by near-stoichiometric chemical composition with reduced oxygen content, have been extensively tested for nuclear applications at ORNL and other places. Relatively new to the manufacturing landscape, the fabrication of SiC/SiC composites-based cladding system poses several challenges; recent evaluations have identified several important technological gaps such joining technology and steam oxidation. In the current work, an experimentally-validated simulation framework is proposed that is specifically addressing the key technology gap associated with steam oxidation attack and irradiation for the Triplex design with two types of composites – Tyranno SA3 and Hi-Nicalon Type S. The framework includes (i) Steam exposure tests-ORNL, (ii) Ion irradiation experiments-UTK/ORNL, (iii) 3D mapping of the microstructure using x-ray microscopy and mechanical tests-USC, and (iv) Microstructure evolution and chemical kinetics in MARMOT, phase field computer code developed at INL, under normal/accident conditions, and under different irradiated conditions, followed by validation against experimental results-NCSU/INL.

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Mechanistic and Validated Creep/Fatigue Predictions for Alloy 709 from Accelerated Experiments and Simulations

US Dept. of Energy (DOE)(10/01/15 - 9/30/18)

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Mechanistic and Validated Creep/Fatigue Predictions for Alloy 709 from Accelerated Experiments and Simulations

Sponsor: US Dept. of Energy (DOE)

Start Date: 10/01/15

End Date: 9/30/18

Abstract

As a promising candidate for fast reactor program, Alloy 709 possesses excellent high temperature thermo-mechanical properties. To support its qualification in the ASME code for Class 1 Components in Elevated Temperature Service (Section 3, Division 1, Subsection NH), we propose mechanistic methods for predicting creep and creep-fatigue deformation rates/strains based on accelerated in-situ and ex-situ tests, and mesoscale dislocation dynamics simulations. There are four research tasks in the proposed program. In Task 1, ex-situ creep and creep-fatigue experiments will be conducted by PD/PI (Murty, NCSU) at high temperatures and stresses followed by microstructure evaluations using high resolution transmission electron microscopy (HR-TEM), and Atom Probe Tomography (APT). To evaluate the time evolution of the microstructure, in Task 2, in-situ X-ray synchrotron (XRD) experiments will be conducted by PI-3 (Almer, ANL) and PI-2 (Kaoumi, USC) at the Advanced Photon Source (APS), along with in-situ TEM experiments by PI-2. Using the microstructure information from Tasks 1 and 2, mesoscale dislocation dynamics (DD) will be conducted by PI-4 (Eapen, NCSU) in Task 3 to follow the microstructure evolution at accelerated and reactor operating conditions. In Task 4, realistic continuum creep damage mechanics (CDM), informed by in-situ experiments and simulations on microstructure evolution, will be employed to predict the accumulated strains during creep and creep-fatigue at reactor operating conditions.

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Aging of Used Nuclear Fuel in Storage: Accelerated Characterization and Modeling of Performance

US Dept. of Energy (DOE)(12/15/11 - 12/15/15)

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Aging of Used Nuclear Fuel in Storage: Accelerated Characterization and Modeling of Performance

Sponsor: US Dept. of Energy (DOE)

Start Date: 12/15/11

End Date: 12/15/15

Abstract

This is a subcontract to TAMU (Dr. Sean McDevitt) with NCSU PIs to work on creep of spent fuel as a part of the proposal on aging of used nuclear fuel in storage being submitted to DOE/NEUP under solicitation: CALL FOR PROPOSALS (CFP) NO. NEUP-002-11 under Integrated Research Projects.

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One-Dimensional Nanostructures for Neutron Detection

US Dept. of Energy (DOE)(9/28/11 - 9/30/14)

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One-Dimensional Nanostructures for Neutron Detection

Sponsor: US Dept. of Energy (DOE)

Start Date: 9/28/11

End Date: 9/30/14

Abstract

Compact size, low operating voltage, fast charge-collection speed and high sensitivity are important measures of neutron detectors. Other measures include low radiation damage and compatibility with different substrates. Recent advances in materials processing show that low dimensional structures such as nanotubes and nanowires have superior electrical sensitivity relative to bulk materials. This proposal aims to develop high efficiency, pixel array neutron detectors using boron carbon nitride nanotubes.

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Consortium for Advanced Simulations for Light Water Reactors (CASL) - Oak Ridge National laboratory

US Dept. of Energy (DOE)(11/30/-1 - 9/30/19)

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Consortium for Advanced Simulations for Light Water Reactors (CASL) - Oak Ridge National laboratory

Sponsor: US Dept. of Energy (DOE)

Start Date: 11/30/-1

End Date: 9/30/19

Abstract

The Consortium for Advanced Simulation of Light Water Reactors, CASL, supports the broad national missions of enabling energy independence; supporting economic growth through the offering of superior technology ; and being good stewards of the environment, buy enabling predictive simulation of nuclear power plants. Such capability will make possible power uprates, lifetime extension and higher fuel burnups for currently operating and new Generation III+ nuclear power plants.

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Fickian and Thermal Diffusion in Nuclear Materials from Linear Response Theory and Multiscale Simulations

US Dept. of Energy (DOE)(7/01/10 - 6/30/13)

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Fickian and Thermal Diffusion in Nuclear Materials from Linear Response Theory and Multiscale Simulations

Sponsor: US Dept. of Energy (DOE)

Start Date: 7/01/10

End Date: 6/30/13

Abstract

The central objective of this proposal is to develop new statistical-mechanical models and long-time atomistic simulation methods to determine complex diffusive properties in nuclear materials. These properties are critical for imparting a predictive capability to the phase-field modeling and simulation effort. Specifically, the proposal will develop new methodologies to compute Fickian and thermal diffusivities in uranium-molybdenum alloy systems (U-Mo) and uranium dioxide (UO2) under different irradiation and ambient conditions. Taken together, molecular and phase field simulations will constitute a hierarchical multiscale methodology.

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Advancing the Underlying Science of Nano-Structured Refractory Materials for Nuclear Energy Systems

US Dept. of Energy (DOE)(7/14/10 - 5/30/15)

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Advancing the Underlying Science of Nano-Structured Refractory Materials for Nuclear Energy Systems

Sponsor: US Dept. of Energy (DOE)

Start Date: 7/14/10

End Date: 5/30/15

Abstract

This program will improve the radiation tolerance and diffusion characteristics of materials for next generation reactor systems through micron-scale and nano-scale design of materials and interfaces. By combining the extensive experience of the investigators in 1) the controlled synthesis of nanostructured materials, 2) computational analysis and prediction, and 3) model irradiation experiments, our team will explore the effects of oriented and random structures fabricated on refractory materials and their benefit with respect to radiation tolerance and fission byproduct diffusion. Thin film synthesis, top-down device fabrication technology, and in-situ irradiation measurements will enable a new focus on the interaction of radiation with nano-scale inhomogeneities and provide design rules their incorporation into next generation reactors.

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Modeling Solute Thermokinetics in LiCL-KCL Molten Salt for Nuclear Waste Separation

Battelle Energy Alliance, LLC(7/20/10 - 7/31/13)

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Modeling Solute Thermokinetics in LiCL-KCL Molten Salt for Nuclear Waste Separation

Sponsor: Battelle Energy Alliance, LLC

Start Date: 7/20/10

End Date: 7/31/13

Abstract

This project will develop first-principles based molecular modeling and simulation approaches to predict fundamental thermokinetic properties of dissolved actinides and fission products in molten salts. Present nuclear waste separation methods are controlled by solute and salt properties that are often difficult to measure experimentally. The simulation results, which are derived from first principles, will therefore be of utmost value for interpreting experimental results, validating analytical models, and for optimizing waste separation by potentially developing new salt configurations and operating conditions. The specific focus of the work will be on property changes with higher concentrations of dissolved fuel components, which is particularly challenging to characterize experimentally. The properties of interest will be density, which is used to assess the amount of dissolved material in the salt, diffusion, which can control rates of material transport during separation, and solute activity, which determines total solubility and reduction potentials used during electrorefining. The work will focus on La, Sr, and U (defined as solutes in this proposal), which are chosen to include the important distinct categories of lanthanides, alkali earths, and actininides, respectively. Studies will be performed for LiCl ? KCl salt at the eutectic composition, which is used for treating spent EBR-II fuel. The same process being used for EBR-II fuel is currently being studied for widespread international implementation. The methods will focus on first-principles and first-principles derived interatomic potential based simulations, primarily with molecular dynamics. Results will be validated against existing literature and a parallel ongoing experimental effort at the lead-PIs institution.

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Understanding Creep Mechanisms in Graphite with Experiments, Multiscale Simulations and Modeling (G4A-1 Technical Work Scope)

US Dept. of Energy (DOE)(10/01/09 - 9/30/13)

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Understanding Creep Mechanisms in Graphite with Experiments, Multiscale Simulations and Modeling (G4A-1 Technical Work Scope)

Sponsor: US Dept. of Energy (DOE)

Start Date: 10/01/09

End Date: 9/30/13

Abstract

This proposal will develop a mechanistic understanding of irradiation and thermal creep mechanisms in graphite through experiments, multiscale simulations and theoretical modeling.Graphite has been used for neutron moderation and structural support from the beginning of nuclear reactor era in 1943. The first sustained operation of a nuclear reactor was that of a graphite reactor at Oak Ridge National Laboratory. For about 30 years after that substantial efforts were devoted to the radiation materials science of graphite. This work abated over the years, until recently when there has been a renewed interest in the science of radiation effects in graphite motivated by its use in advanced reactor cores. Consequently, many of the most important efforts were published several years ago. The final deliverable will include (1) experimental creep data on irradiated reactor grade graphite, (2) XRD and high definition TEM data, (3) mechanical and thermal properties, (4) multiscale simulation results, and direct comparisons to XRD and TEM data, and finally (5) mechanistic models that can underpin the fundamental behavior of irradiation and thermal creep in graphite.

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