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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Coupling Thermal-Hydraulics with Reactor Pressure Vessel Fracture Models

Because of the importance of maintaining the integrity of the reactor pressure vessel (RPV) in light-water reactors, significant effort has been devoted over the last several decades to understand the potential failure mechanisms, characterize how material properties evolve due to environmental conditions, and develop tools to assess the probability of fracture in aged RPVs during potential transient events. One important aspect of this problem that has not yet been fully addressed is the effects of nonuniform cooling on the RPV inner wall due to the way low-temperature water injected into the primary coolant system is distributed within the RPV during potential loss-of-coolant accident transients. Colder temperatures are expected in the regions near the inlets, causing a “cold-plume” effect. Rapid cooling of the RPV wall increases the likelihood of fracture initiation, and localized cooling due to cold-plume effects could potentially exacerbate this problem. The Grizzly code can perform a three-dimensional simulation of the RPV thermomechanical response as well as the probabilistic assessment of fracture for a population of pre-existing flaws, which is necessary to account for spatial variations in coolant temperature. This report documents a first effort to couple Grizzly RPV fracture models with computational fluid dynamics models performed using the Cardinal code, which allows for a realistic representation of the temperature distribution. This report demonstrates this coupling approach on two test cases: a simplified proof-of-concept scenario and a realistic small-break loss-of-coolant accident scenario. In both cases, the effects of the spatially varying temperature are evident; although, because the small-break loss-of-coolant accident scenario was far from challenging the RPV’s margins, it is still inconclusive how important cold-plume effects are in realistic accident scenarios. However, this effort represents an important step toward performing realistic analyses to determine to what extent spatially nonuniform cooling might affect RPV integrity under more aggressive accident scenarios.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

A machine-learning framework for the simulation of nuclear deflection of Planet-Killer-Asteroids

Here, as detection capabilities in astronomy have dramatically improved over the last two decades, concerns over Planet-Killer-Asteroids (PKAs) have become widespread, with nuclear weapons being proposed to destroy or deflect asteroids that are on a short-term projected collision course with Earth. Two main mitigation strategies have been proposed: • Case 1: Break up an incoming asteroid into smaller pieces that will disperse widely, resulting in smaller-scale, less detrimental, Earth-impacts or • Case 2: Deflect an incoming asteroid trajectory to avoid collision altogether. While the two strategies are not mutually exclusive, deflection is a safer strategy, ideally by harnessing all of the released energy from a nuclear device to move the asteroid as a rigid body. However, this case may not be always possible, since the strength of the energy release may break up the asteroid. In this work, the dynamical response of a PKA to a series of ultra-high energy impulses, such as those generated by nuclear devices, is formulated. A rapid iterative Discrete Element Method (DEM) method is developed to describe the deflection and potential breakup of the PKA as a function of a material bonding strength parameter within the asteroid and the magnitude of the applied impulse. The use of DEM allows for fragmentation of the PKA and the ability to compute the trajectories and distribution of the resulting debris field. Finally, a machine-learning algorithm is then developed and combined with the DEM approach to optimize the pulsation strategy for maximum possible safety and success.

42 ENGINEERING↗
DOE OSTI2023

Stability of perpendicular magnetohydrodynamic shocks in materials with ideal and nonideal equations of state

Magnetized target fusion approach to inertial confinement fusion involves the formation of strong shocks that travel along a magnetized plasma. Shocks, which play a dominant role in thermalizing the upstream kinetic energy generated in the implosion stage, are seldom free from perturbations, and they wrinkle in response to upstream or downstream disturbances. In Z-pinch experiments, significant plasma instability mitigation was observed with pre-embedded axial magnetic fields. To isolate effects, in this work we theoretically study the impact of perpendicular magnetic fields on the planar shock dynamics for different equations of state. For fast magnetosonic shocks in ideal gases, it was found that the magnetic field amplifies the intensity of the perturbations when $\gamma$ > 2 or it weakens them when $\gamma$ < 2. Weak shocks have been found to be stable regardless of the magnetic plasma intensity and gas compressibility; however, for sufficiently strong shocks the magnetic fields can promote a neutral stability/SAE at the shock if the adiabatic index is higher than 1 + $\sqrt{2}$. Finally, results have been validated with numerical simulations performed with the FLASH code.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Finite element analyses of single particle crushing tests incorporating computed tomography imaging and damage mechanics

Fracture of individual grains within a granular assembly affect the strength and deformation behavior of granular materials under large stress states. Interparticle forces, leading to contact stresses and ultimately fracture initiation, are influenced by particle morphology. A numerical method that incorporates both particle fracture and morphology can provide a more accurate model of a granular material’s macro-scale response. This research investigates an approach to modeling fracture initiation and propagation within individual grains, utilizing high resolution X-ray computed tomography (CT) imaging to consider grain morphology and an explicit finite element code optimized for high performance computing which incorporates damage mechanics. Using precisely measured force-displacement curves from single particle crushing tests of manufactured quartz spheres, the method is validated, and the effects of fracture properties on grain fragmentation are determined. This approach is then used to simulate single particle crushing of Ottawa sand, with grain morphology incorporated through discretized CT images. Here the effect of grain orientation on the force and applied displacement at catastrophic splitting is also explored. The proposed discrete particle based finite element framework can be applied to modeling granular assemblies, considering the effect of individual particle shape and fracture on the assembly’s deformation response through well calibrated numerical simulations.

42 ENGINEERING↗
DOE OSTI2021

On the effect of elemental partitioning to secondary phases after solution and aging heat treatments in a Co-Ni-based superalloy

Here, this paper presents the phase stability and elemental partitioning in a Co-40Ni-10Al-7.5W-10Cr-3Nb-0.06B-0.6C (at.%) superalloy (referred to as 3Nb) after a two-step heat treatment. The resulting microstructure consisted of γ, γ', MC carbides and µ-Co 7 W 6 phase decorating the regions near and at the grain boundaries. Nb preferentially partitioned to the γ'-phase and other elements such as Ni, Cr and W were responsible for the μ-phase formation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Subsurface Characteristics of Metal-Halide Perovskites Polished by an Argon Ion Beam

Focused ion beam (FIB) techniques have been frequently used to section metal-halide perovskites for microstructural investigations. However, the ion beams directly irradiating the sample surface may alter its properties far different from those of pristine, potentially leading to modified deterioration mechanisms under aging stressors. Here, we combine complementary approaches to measure the subsurface characteristics of polished perovskites and identify the chemical species responsible for the measured properties. Analysis of the experimental results in conjunction with Monte Carlo simulations indicates that atomic displacements and local heating occur in the first ≈15 nm of the subsurface of methylammonium lead iodide (MAPbI 3 ) by glancing-angle Ar + beam irradiation (4 kV at 3°). The lead-rich, iodine-deficient surface promotes rapid phase segregation under thermal aging conditions. On the other hand, despite the subsurface modification, our experiments confirm that the rest of the MAPbI 3 bulk retains the material integrity. Our observation supports that polished perovskites could serve in studying the properties of bulk or buried junctions far away from the altered subsurface with care.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

We provide theoretical and simulation analysis of the small signal response of SiO{sub 2}/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO{sub 2} interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, C{sub p}, and conductance, G{sub p}. C{sub p} -voltage and G{sub p} -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance R{sub br} and the effective channel resistance. In particular, in the spill-over region, the drop of C{sub p} with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of R{sub br} with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, D{sub it}, from the G{sub p}/ω vs. angular frequency ω curves. A peak in G{sub p}/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the G{sub p}/ω vs. ω peak saturates at high D{sub it}, which can lead to underestimation of D{sub it}. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Shock compression response of highly reactive Ni + Al multilayered thin foils

The shock-compression response of Ni + Al multilayered thin foils is investigated using laser-accelerated thin-foil plate-impact experiments over the pressure range of 2 to 11 GPa. The foils contain alternating Ni and Al layers (parallel but not flat) of nominally 50 nm bilayer spacing. The goal is to determine the equation of state and shock-induced reactivity of these highly reactive fully dense thin-foil materials. The laser-accelerated thin-foil impact set-up involved combined use of photon-doppler-velocimetry to monitor the acceleration and impact velocity of an aluminum flyer, and VISAR interferometry was used to monitor the back free-surface velocity of the impacted Ni + Al multilayered target. The shock-compression response of the Ni + Al target foils was determined using experimentally measured parameters and impedance matching approach, with error bars identified considering systematic and experimental errors. Meso-scale CTH shock simulations were performed using real imported microstructures of the cross-sections of the multilayered Ni + Al foils to compute the Hugoniot response (assuming no reaction) for correlation with their experimentally determined equation of state. It was observed that at particle velocities below ∼150 m/s, the experimentally determined equation of state trend matches the CTH-predicted inert response and is consistent with the observed unreacted state of the recovered Ni + Al target foils from this velocity regime. At higher particle velocities, the experimentally determined equation of state deviates from the CTH-predicted inert response. A complete and self-sustained reaction is also seen in targets recovered from experiments performed at these higher particle velocities. The deviation in the measured equation of state, to higher shock speeds and expanded volumes, combined with the observation of complete reaction in the recovered multilayered foils, confirmed via microstructure characterization, is indicative of the occurrence of shock-induced chemical reaction occurring in the time-scale of the high-pressure state. TEM characterization of recovered shock-compressed (unreacted) Ni + Al multilayered foils exhibits distinct features of constituent mixing revealing jetted layers and inter-mixed regions. These features were primarily observed in the proximity of the undulations present in the alternating layers of the Ni + Al starting foils, suggesting the important role of such instabilities in promoting shock-induced intermetallic-forming reactions in the fully dense highly exothermic multilayered thin foils.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Design of a Single Layer Metamaterial for Pressure Offloading of Transtibial Amputees

While using a prosthesis, transtibial amputees may experience pain and discomfort brought on by large pressure gradients at the interface between the residual limb and prosthetic socket. Current prosthetic interface solutions attempt to alleviate these pressure gradients by using soft homogenous liners to reduce and distribute pressures. This research investigates an additively manufactured metamaterial inlay with a tailored mechanical response to reduce peak pressure gradients around the limb. The inlay uses a hyperelastic behaving metamaterial (US10244818) comprised of triangular pattern unit cells which can be 3D printed with walls of various thicknesses controlled by draft angles. The hyperelastic material properties are modeled using a Yeoh 3rd order model. The 3rd order coefficients can be adjusted and optimized, which corresponds to a change in the unit cell wall thickness to create an inlay that can meet the unique offloading needs of an amputee. Finite element analysis simulations evaluated the pressure gradient reduction from: 1) a common homogenous silicone liner, 2) a prosthetist's inlay prescription that utilizes three variations of the metamaterial, and 3) a metamaterial solution with optimized Yeoh 3rd order coefficients. When compared to a traditional homogenous silicone liner for two unique limb loading scenarios, the prosthetist prescribed inlay and the optimized material inlay can achieve equal or greater pressure gradient reduction capabilities. These results show the potential feasibility of implementing this metamaterial as a method of personalized medicine for transtibial amputees by creating a customizable interface solution to meet the unique performance needs of an individual patient.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Phase Transformation of Thermally Aged and Neutron Irradiated Duplex Stainless Steel Used in LWRs. Final report

The lifetime of reactor components made of duplex stainless steels can be limited by the embrittlement from thermal aging, neutron irradiation or a synergistic effect between thermal aging and neutron irradiation. There is still a large scientific knowledge gap in understanding the phase evolution in duplex stainless steels upon thermal aging with or without neutron irradiation, the synergistic effect between thermal aging and neutron irradiation, and the impacts of structural evolution on material mechanical responses. In this project, totally, five major tasks were completed through this project: a) the in-situ WAXS tensile tests of thermally aged cast duplex stainless steels, b) the EXAFS investigation of thermally aged cast austenitic stainless steel and welds of austenite sainless steel, c) the characterization of irradiation effect on neutron irradiated CASS using APT, d) characterize the ferrite hardening of neutron irradiated CASS using nanoindentation, and e) the FEM modelling to validate the in-situ WAXS tensile tests and to simulate the stress/strain distribution during deformation for thermally aged duplex stainless steel. In summary, the thermal aging without neutron irradiation can significantly increase the strength of ferrite phase through the spinodal decomposition and G-phase precipitations. The in-situ X-ray experiments show that the hardening effect in ferrite phase can significantly alter the load partition between the ferrite and austenite phases. Atom probe tomography characterizations on samples irradiated to 0.08, 3, 5, 10, 20, and 40 dpa shows that neutron irradiation has dominated the microstructural evolution after 3 dpa, and the spinodal decomposition has saturated yet even at 40 dpa based on the quantified wavelength and amplitude.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1975

Read-write holographic memory with iron-doped lithium niobate

The response of iron doped lithium niobate under conditions corresponding to hologram storage and retrieval is described, and the material's characteristics are discussed. The optical sensitivity can be improved by heavy chemical reduction of lightly doped crystals such that most of the iron is in the divalent state, the remaining part being trivalent. The best reduction process found to be reproducible so far is the anneal of the doped crystal in the presence of a salt such as lithium carbonate. It is shown by analysis and simulation that a page-oriented read-write holographic memory with 1,000 bits per page would have a cycle time of about 60 ms and a signal-to-noise ratio of 27 db. This cycle time, although still too long for a practical system, represents an improvement of two orders of magnitude over that of previous laboratory prototypes using different storage media.

Alphonse, G. A.↗
NASA NTRS1976

Iron-doped lithium niobate as a read-write holographic storage medium

The response of iron-doped lithium niobate under conditions corresponding to hologram storage and retrieval is described, and the material characteristics are discussed. The optical sensitivity can be improved by heavy chemical reduction of lightly doped crystals such that most of the iron is in the divalent state, the remaining part being trivalent. The best reduction process found to be reproducible so far is the anneal of the doped crystal in the presence of a salt such as lithium carbonate. It is shown by analysis and simulation that a page-oriented read-write holographic memory with 1000 bits per page would have a cycle time of about 60 msec and a signal-to-noise ratio of 27 dB. This cycle time, although still too long for a practical memory, represents an improvement of two orders of magnitude over that of previous laboratory prototypes using a thermoplastic storage medium

Alphonse, G. A.↗
NASA NTRS1990

Review of acousto-ultrasonic NDE for composites

Acousto-ultrasonics utilizes simulated stress waves to detect and quantify defect states, damage conditions, and variations of mechanical properties in fiber reinforced composites. The term acousto-ultrasonics denotes a combination of aspects of acoustic emission methodology with ultrasonic materials characterization. The acousto-ultrasonic approach was developed to deal primarily with evaluation of the integrated effect of minor flaws and diffuse flaw populations of subcritical flaws in composite and bonded structures. These factors singly and collectively also influence acousto-ultrasonic measurements that, in turn, correlate with dynamic response and mechanical property variations. Since it was first introduced, the acousto-ultrasonic approach was successfully applied to a variety of materials, including polymeric, metallic, and ceramic matrix composites; adhesively bonded materials; paper and wood products; cable and rope; and also human bone. Examples of applications and limitations of the approach are reviewed. Basic methods and guidelines are discussed. The underlying hypothesis and theory development needs are indicated.

Vary, Alex↗
DOE OSTI2012

Modeling Rdamage-6 through -9

The RDamage series of ten experiments is part of a long-term collaboration with RFNC/VNIIEF in pulsed power technology. These experiments use a cylindrical configuration to study spallation damage, which allows for a natural recollection of the damaged material under proper driving conditions and post-shot collection of the damaged target material for subsequent metallographic analysis. Dynamic in-situ experimental velocimetry diagnostics are also employed. LANL is responsible for the design of the experimental load and velocimetry system. VNIIEF is responsible for the design and construction of the driving explosive magnetic generator. In the RDamage-0, -1 and -2 experiments, data was collected about failure initiation of a well-characterized material (aluminum) in a cylindrical geometry. The RDamage-3, -4 and -5 experiments produced data on the behavior of material recollected after damage from pressures in the damage initiation regime. Data on the behavior of material recollected after complete failure was collected in the RDamage-6, -7, -8 and -9 experiments. This presentation shows the recent LANL simulation results for RD-6 through -9.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Deep neural network for the dielectric response of insulators

In this work, we introduce a deep neural network to model in a symmetry preserving way the environmental dependence of the centers of the electronic charge. The model learns from ab initio density functional theory, wherein the electronic centers are uniquely assigned by the maximally localized Wannier functions. When combined with the deep potential model of the atomic potential energy surface, the scheme predicts the dielectric response of insulators for trajectories inaccessible to direct ab initio simulation. The scheme is nonperturbative and can capture the response of a mutating chemical environment. We demonstrate the approach by calculating the infrared spectra of liquid water at standard conditions, and of ice under extreme pressure, when it transforms from a molecular to an ionic crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Reactivity-initiated accident simulation to inform transient testing of candidate advanced cladding

This paper leverages three-dimensional reactor-core-simulation capabilities to provide information on appropriate experimental test conditions for candidate advanced cladding materials in a control-rod-ejection event. These test conditions use three-dimensional nodal kinetics simulations of a reactivity-initiated accident (RIA) in a representative state-of-the-art pressurized water reactor with both nuclear-grade iron-chromium-aluminum (FeCrAl) and silicon-carbide (SiC-SiC)-based cladding materials. The effort yields boundary conditions for experimental mechanical tests, specifically peak cladding strain during the power pulse following the rod ejection. The impact of candidate cladding materials on the reactor kinetics behavior of RIA progression versus that of reference Zr cladding is predominantly due to differences in -1) fuel mass/volume/specific power density, -2) spectral effects due to parasitic neutron absorption, -3) control rod worth due to hardened (or softened) spectrum, and -4) initial conditions due to power peaking and neutron transport cross sections in the equilibrium cycle cores resulting from hardened (or softened) spectrum. This study shows minimal impact of SiC-SiC-based cladding configurations on the transient response versus reference Zircaloy cladding. However, the FeCrAl cladding response indicates similar energy deposition, but with significantly shorter pulses of higher magnitude. Therefore, the FeCrAl-based cases have a more rapid fuel thermal expansion rate, and the resultant pellet-cladding interaction occurs more rapidly. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS2023

Tribological and Radiation Shielding Response of Novel Titanium-Boron Nitride Coatings for Lunar Structural Components

Aluminum (Al) and titanium (Ti) lightweight alloys play a crucial role in space systems due to their exceptional strength-to-weight ratio. However, their premature failure in the presence of lunar regolith and their lack of neutron shielding ability are significant challenges. To address these issues, we have developed air and vacuum plasma-sprayed hBN (hexagonal Boron Nitride) -reinforced titanium coatings with 2 and 10 vol% of hBN. Tribological studies conducted with JSC-1 A lunar regolith simulant revealed a 90 % reduction in wear volume for the Ti/2 vol% hBN coatings compared to conventional materials due to the synergistic action of harder secondary phases and solid lubrication effect of hBN. Additionally, a 27 % enhancement in radiation shielding is obtained based on the mass absorption coefficient (radiation absorbed per sample density and thickness) for VPS Ti/2 vol% hBN coatings.

Wear↗
DOE OSTI2022

In situ study on heavy ion irradiation induced microstructure evolution in single crystal Cu with nanovoids at elevated temperature

Understanding the response of nanovoids to irradiation damage advances our capability to design radiation tolerant materials. Recent in situ studies reveal the shrinkage of hexagon-shaped nanovoids in (110) textured Cu. However, the evolution of voids with irregular geometries under irradiation is less well understood. Here, in situ Kr ion irradiation was performed at 100 °C on single-crystal Cu (112) that possesses nanovoids with high aspect ratio. In situ studies show these elongated voids fragment into smaller voids and shrink gradually with increasing dose. Phase field simulations confirm that fragmentation of the void is governed by the competing kinetics between atoms diffusing toward and away from the elongated nanovoid. In conclusion, cost irradiation analysis reveals the formation of high-density defect clusters.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗