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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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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Evaluation of wet tantalum capacitors after exposure to extended periods of ripple current, volume 2

The application of tantalum capacitors in the Viking Lander includes dc voltage and ripple current electrical stress, high temperature during nonoperating times (sterilization), and high vibration and shock loads. The capacitors must survive these severe environments without any degradation if reliable performance is to be achieved. A test program was established to evaluate both wet-slug tantalum and wet-foil capacitors under conditions accurately duplicating actual Viking applications. Test results of the electrical performance characteristics during extended periods of ripple current, the characteristics of the internal silver migration as a function of extended periods of ripple current, and the existence of any memory characteristics are presented.

Ward, C. M.↗
DOE OSTI2018

Processing-induced strain glass states in a Ni 49.5 Ti 50.5 shape memory alloy

Shape memory alloys (SMAs) represent a revolutionary and innovative class of active materials which can provide potential solutions to many of today's engineering problems due to their compact form, high energy densities, and multifunctional capabilities. While many applications in the biomedical, aerospace, and automotive industries have already been investigated and realized for Nickel-Titanium (NiTi) based SMAs, the effects of restricting the ferroelastic transformation to nanosized domains is not well understood and the potential remains untapped. In binary NiTi, the martensitic transformation, which is characterized by long-range strain ordering (LRO), can be replaced with a strain glass transition, which consists of an LRO parent phase and a short-range strain ordered glassy phase. Such alloys have been named strain glass alloys (SGAs) due to the fact that they exhibit a glassy state which results from compositionally- or processing-induced strain. While SGAs do not exhibit a stress-free, temperature-induced macroscopic phase change, they still exhibit the strain recovery and actuation capabilities intrinsic to near equiatomic NiTi and other SMAs. It has been shown in the available literature that certain compositions, for example 51.5 at. % Nickel in binary NiTi, can create a strain glass; however, these compositionally-induced NiTi SGAs generally have transformation temperatures below 173 K and this will restrict their practical applications. In the present study, a new method for producing a strain glass phase in Ti-rich NiTi through sufficient plastic deformation via cold work is reported; the resulting SGA exhibits a temperature-induced ferroelastic recovery above room temperature. Additionally, the macroscopic actuation capabilities are improved when compared to both compositionally-induced SGAs and the base material due to the increased functional stresses of the SGA. To better understand the transition from an SMA to an SGA, Ni49.5Ti50.5 (at. %) rods were processed to several degrees of cold work and characterized via scanning and transmission electron microscopy, differential scanning calorimetry, thermomechanical testing, and synchrotron radiation x-ray diffraction. The experimental results indicate that twin size decreases with additional cold work and, around 45% thickness reduction, stress-free thermal cycling no longer results in a measurable phase transformation; however, mechanically-induced phase transformation is still possible, where fully recoverable strains in these SGAs were observed to be above 4.5% when loaded at room temperature and recovered at 150 °C.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Upgrades of Two Computer Codes for Analysis of Turbomachinery

Major upgrades have been made in two of the programs reported in "ive Computer Codes for Analysis of Turbomachinery". The affected programs are: Swift -- a code for three-dimensional (3D) multiblock analysis; and TCGRID, which generates a 3D grid used with Swift. Originally utilizing only a central-differencing scheme for numerical solution, Swift was augmented by addition of two upwind schemes that give greater accuracy but take more computing time. Other improvements in Swift include addition of a shear-stress-transport turbulence model for better prediction of adverse pressure gradients, addition of an H-grid capability for flexibility in modeling flows in pumps and ducts, and modification to enable simultaneous modeling of hub and tip clearances. Improvements in TCGRID include modifications to enable generation of grids for more complicated flow paths and addition of an option to generate grids compatible with the ADPAC code used at NASA and in industry. For both codes, new test cases were developed and documentation was updated. Both codes were converted to Fortran 90, with dynamic memory allocation. Both codes were also modified for ease of use in both UNIX and Windows operating systems.

Chima, Rodrick V.↗
NASA NTRS2005

Diet as a factor in behavioral radiation protection following exposure to heavy particles

Major risks associated with radiation exposures on deep space missions include carcinogenesis due to heavy-particle exposure of cancer-prone tissues and performance decrements due to neurological damage produced by heavy particles. Because exposure to heavy particles can cause oxidative stress, it is possible that antioxidants can be used to mitigate these risks (and possibly some health risks of microgravity). To assess the capacity of antioxidant diets to mitigate the effects of exposure to heavy particles, rats were maintained on antioxidant diets containing 2% blueberry or strawberry extract or a control diet for 8 weeks prior to exposure to 1.5 or 2.0 Gy of accelerated iron particles at Brookhaven National Laboratory. Following irradiation rats were tested on a series of behavioral tasks: amphetamine-induced taste aversion learning, operant responding and spatial learning and memory. The results indicated that the performance of the irradiated rats maintained on the antioxidant diets was, in general, significantly better than that of the control animals, although the effectiveness of the diets ameliorating the radiation-induced deterioration in performance varied as a function of both the specific diet and the specific endpoint. In addition, animals fed antioxidant diets prior to exposure showed reduced heavy particle-induced tumorigenesis one year after exposure compared to the animals fed the control diet. These results suggest that antioxidant diets have the potential to serve as part of a system designed to provide protection to astronauts against the effects of heavy particles on exploratory missions outside the magnetic field of the earth.

Non-NASA Center↗
DOE OSTI2021

StressNet - Deep learning to predict stress with fracture propagation in brittle materials

Abstract Catastrophic failure in brittle materials is often due to the rapid growth and coalescence of cracks aided by high internal stresses. Hence, accurate prediction of maximum internal stress is critical to predicting time to failure and improving the fracture resistance and reliability of materials. Existing high-fidelity methods, such as the Finite-Discrete Element Model (FDEM), are limited by their high computational cost. Therefore, to reduce computational cost while preserving accuracy, a deep learning model, StressNet, is proposed to predict the entire sequence of maximum internal stress based on fracture propagation and the initial stress data. More specifically, the Temporal Independent Convolutional Neural Network (TI-CNN) is designed to capture the spatial features of fractures like fracture path and spall regions, and the Bidirectional Long Short-term Memory (Bi-LSTM) Network is adapted to capture the temporal features. By fusing these features, the evolution in time of the maximum internal stress can be accurately predicted. Moreover, an adaptive loss function is designed by dynamically integrating the Mean Squared Error (MSE) and the Mean Absolute Percentage Error (MAPE), to reflect the fluctuations in maximum internal stress. After training, the proposed model is able to compute accurate multi-step predictions of maximum internal stress in approximately 20 seconds, as compared to the FDEM run time of 4 h, with an average MAPE of 2% relative to test data.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Effects of high energy radiation on the mechanical properties of epoxy/graphite fiber composites

Studies on the effects of high energy radiation on graphite fiber reinforced composites are summarized. Studies of T300/5208 and C6000/PMR15 composites, T300 fibers and the resin system MY720/DDS (tetraglycidyl-4,4'-diaminodiphenyl methane cured with diaminodiphenyl sulfone) are included. Radiation dose levels up to 8000 Mrads were obtained with no deleterious effects on the breaking stress or modulus. The effects on the structure and morphology were investigated using mechanical tests, electron spin resonance, X-ray diffraction, and electron spectroscopy for chemical analysis (ESCA or X-ray photoelectron spectroscopy). Details of the experiments and results are given. Studies of the fracture surfaces of irradiated samples were studied with scanning electron microscopy; current results indicate no differences in the morphology of irradiated and control samples.

Fornes, R. E.↗
DOE OSTI2016

Challenges of Monte Carlo Transport

These are slides from a presentation for Parallel Summer School at Los Alamos National Laboratory. Solving discretized partial differential equations (PDEs) of interest can require a large number of computations. We can identify concurrency to allow parallel solution of discrete PDEs. Simulated particles histories can be used to solve the Boltzmann transport equation. Particle histories are independent in neutral particle transport, making them amenable to parallel computation. Physical parameters and method type determine the data dependencies of particle histories. Data requirements shape parallel algorithms for Monte Carlo. Then, Parallel Computational Physics and Parallel Monte Carlo are discussed and, finally, the results are given. The mesh passing method greatly simplifies the IMC implementation and allows simple load-balancing. Using MPI windows and passive, one-sided RMA further simplifies the implementation by removing target synchronization. The author is very interested in implementations of PGAS that may allow further optimization for one-sided, read-only memory access (e.g. Open SHMEM). The MPICH_RMA_OVER_DMAPP option and library is required to make one-sided messaging scale on Trinitite - Moonlight scales poorly. Interconnect specific libraries or functions are likely necessary to ensure performance. BRANSON has been used to directly compare the current standard method to a proposed method on idealized problems. The mesh passing algorithm performs well on problems that are designed to show the scalability of the particle passing method. BRANSON can now run load-imbalanced, dynamic problems. Potential avenues of improvement in the mesh passing algorithm will be implemented and explored. A suite of test problems that stress DD methods will elucidate a possible path forward for production codes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Thermodynamic constitutive model for load-biased thermal cycling test of shape memory alloy

Graphical abstract: - Highlights: • Thermodynamic calculation model for martensitic transformation of shape memory alloy was proposed. • Evolution of the self-accommodation was considered independently by a rate-dependent kinetic equation. • Finite element calculation was conducted for B2–B19′ transformation of Ti–44.5Ni–5Cu–0.5 V (at.%). • Three-dimensional numerical results predict the macroscopic strain under bias loading accurately. - Abstract: This paper presents a three-dimensional calculation model for martensitic phase transformation of shape memory alloy. Constitutive model based on thermodynamic theory was provided. The average behavior was accounted for by considering the volume fraction of each martensitic variant in the material. Evolution of the volume fraction of each variant was determined by a rate-dependent kinetic equation. We assumed that nucleation rate is faster for the self-accommodation than for the stress-induced variants. Three-dimensional finite element analysis was conducted and the results were compared with the experimental data of Ti–44.5Ni–5Cu–0.5 V (at.%) alloy under bias loading.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Mechanical and functional behavior of high-temperature Ni-Ti-Pt shape memory alloys

A series of Ti-rich Ni-Ti-Pt ternary alloys with 13 to 18 at. pct Pt were processed by vacuum arc melting and characterized for their transformation behavior to identify shape memory alloys (SMA) that undergo transformation between 448 K and 498 K (175 °C and 225 °C) and achieve recoverable strain exceeding 2 pct. From this broader set of compositions, three alloys containing 15.5 to 16.5 at. pct Pt exhibited transformation temperatures in the vicinity of 473 K (200 °C), thus were targeted for more detailed characterization. Preliminary microstructural evaluation of these three compositions revealed a martensitic microstructure with small amounts of Ti 2 (Ni,Pt) particles. Room temperature mechanical testing gave a response characteristic of martensitic de-twinning followed by a typical work-hardening behavior to failure. Elevated mechanical testing, performed while the materials were in the austenitic state, revealed yield stresses of approximately 500 MPa and 3.5 pct elongation to failure. Thermal strain recovery characteristics were more carefully investigated with unbiased incremental strain-temperature tests across the 1 to 5 pct strain range, as well as cyclic strain-temperature tests at 3 pct strain. As a result, the unbiased shape recovery results indicated a complicated strain recovery path, dependent on prestrain level, but overall acceptable SMA behavior within the targeted temperature and recoverable strain range.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2002

Effects of Thermomechanical History on the Tensile Behavior of Nitinol Ribbon

Shape memory alloys (SMAs) have enormous potential for a wide variety of applications. A large body of work exists on the characterization of the microstructure and stress-strain behavior of these alloys, Nitinol (NiTi) in particular. However, many attributes of these materials are yet to be fully understood. Previous work at NASA Langley Research Center (LaRC) has included fabrication of hybrid composite specimens with embedded Nitinol actuators and modeling of their thermomechanical behavior. An intensive characterization effort has been undertaken to facilitate fundamental understanding of this alloy and to promote implementation of Nitinol in aerospace applications. Previous work revealed attributes of the Nitinol ribbon that were not easily rationalized with existing data in the literature. In particular, tensile behavior at ambient temperature showed significant dependence on the thermomechanical history prior to testing. The present work is focused on characterizing differences in the microstructure of Nitinol ribbons exposed to four different thermomechanical histories and correlation of the microstructure with tensile properties. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) analysis were employed to rationalize the microstructures present after exposure to various thermomechanical histories. Three of the Nitinol ribbon conditions were reversible upon heating (in the DSC) through the reverse transformation temperature (A(sub f) to transform the microstructure to austenite. However, the prior thermomechanical conditioning for the Nitinol ribbon that reflected the entire fabrication procedure (4% thermal cycle condition) was found to have an irreversible effect on the microstructure, as it remained unchanged after repeated complete thermal cycles. Tensile tests were conducted to determine the effect of prior thermomechancal conditioning on both the tensile behavior of the Nitinol ribbons and the stress state of the microstructure. The stress-strain behavior of the Nitinol actuators appears to be governed by the interplay between two major variables: namely, microstructural constituents such as the R-phase and the martensite; and the stress state of these constituents (whether twinned with low residual stresses, or detwinned with high residual stresses). The most significant difference in the stress-strain behavior of the four conditions, the critical stress required to achieve an initial stress plateau, was found to depend on both the amount and stress state (twinned or detwinned) of R-phase present in the initial microstructure. Thus, the effect of prior thermomechanical processing is critical to the resulting tensile behavior of the Nitinol actuator. For numerical modeling inputs one must take into account the entire fabrication process on the Nitinol actuator.

Lach, Cynthia L.↗
DOE OSTI2020

Ferroelastic Hysteresis in Thin Films of Methylammonium Lead Iodide

Mechanical strain can modify the structural and electronic properties of methylammonium lead iodide MAPbI 3 . The consequences of ferroelastic hysteresis, which involves the retention of structural memory upon cycles of deformation, are reported for polycrystalline thin films of MAPbI 3 . Repeatedly bent films were examined using grazing incidence wide-angle X-ray scattering (GIWAXS) to quantitatively characterize the strains and proportions of twin domains. Approximate locations for the coercive stress and saturation on the ferroelastic stress–strain curve are identified, and changes to the stress–strain curve with cyclic strain are characterized. Notably, an external stress source, such as thermal stress from the substrate or a roll-to-roll printing setup, must apply at least |50| MPa to modify the proportions of different twins. The presence of specific twin domains is found to correlate to previously reported strain and defect heterogeneity in MAPbI 3 films. Domains from differently strained twin sets interact with each other. Long-term stability testing reveals that the domain walls are highly immobile over extended periods. Nucleation of new domain walls occurs for specific mechanical strains and correlates closely with degradation. Furthermore, these results help to explain the behavior of ion migration, degradation rate, and photoluminescence in thin films under compressive and tensile strain.

Defects↗
DOE OSTI2021

Performance Characteristics of the BlueField-2 SmartNIC

High-performance computing (HPC) researchers have long envisioned scenarios where application workflows could be improved through the use of programmable processing elements embedded in the network fabric. Recently, vendors have introduced programmable Smart Network Interface Cards (SmartNICs) that enable computations to be offloaded to the edge of the network. There is great interest in both the HPC and high-performance data analytics (HPDA) communities in understanding the roles these devices may play in the data paths of upcoming systems. This paper focuses on characterizing both the networking and computing aspects of NVIDIA’s new BlueField-2 SmartNIC when used in a 100Gb/s Ethernet environment. For the networking evaluation we conducted multiple transfer experiments between processors located at the host, the SmartNIC, and a remote host. These tests illuminate how much effort is required to saturate the network and help estimate the processing headroom available on the SmartNIC during transfers. For the computing evaluation we used the stress-ng benchmark to compare the BlueField-2 to other servers and place realistic bounds on the types of offload operations that are appropriate for the hardware. Our findings from this work indicate that while the BlueField-2 provides a flexible means of processing data at the network’s edge, great care must be taken to not overwhelm the hardware. While the host can easily saturate the network link, the SmartNIC’s embedded processors may not have enough computing resources to sustain more than half the expected bandwidth when using kernel-space packet processing. From a computational perspective, encryption operations, memory operations under contention, and on-card IPC operations on the SmartNIC perform significantly better than the general-purpose servers used for comparisons in our experiments. Therefore, applications that mainly focus on these operations may be good candidates for offloading to the SmartNIC.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Cyclic compression response of micropillars extracted from textured nanocrystalline NiTi thin-walled tubes

Compression-compression cyclic deformation of nanocrystalline NiTi tubes intended for medical stents and with an outer diameter of 1 mm and wall thickness of 70 μm was studied using micropillars produced by FIB with the loading axis orthogonal to the tube axis. These micropillars were cycled in a displacement-controlled mode using a nanoindenter equipped with a flat punch to strain levels of 4, 6 and 8% in each cycle and specimens were subjected to several hundred cycles. Furthermore, the cyclic response of two NiTi tubes, one with Af of 17 °C and the other with an Af of -5 °C is compared. The texture of the tube with the Af of -5 °C was measured at the microscopic level using transmission electron microscopy and at the macroscopic level by X-ray diffraction and good agreement was noted. Characteristics such as i) a reduction in the forward transformation stress, ii) increase in maximum stress for a given displacement amplitude, and iii) a reduction in the hysteresis loop area, all with increasing number of cycles, observed typically during cyclic deformation of conventional macroscopic specimens, were captured in the micropillar cyclic tests. Our observations lead to the conclusion that micropillar compression testing in a cyclic mode can enable characterizing the orientation-dependent response in such small dimension components that see complex loading in service, and additionally provide an opportunity for calibrating constitutive equations in micromechanical models.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Impacts of Substrate Thinning on FPGA Performance and Reliability [Slides]

Substrate thinning is necessary in devices with flip-chip BGA packages to enable both radiation testing and component qualification and high-spatial resolution beam-based failure analysis methods. We investigated three factors affecting device performance: subsurface damage from the thinning process, reduced heat spreading in thin substrates, and changes in device switching speed. We conclude subsurface damage to crystalline Si caused by the thinning process is removable with sufficient SiO 2 slurry polishing. Local temperature differences increase minimally in devices thinned to 3 μm. Compressive stress in the Si increases globally after device thinning and leads to slowing of ring oscillator frequency by about 0.5% compared to full-thickness devices. Future work will include extending the results to submicron Si thickness values, which also has important benefits for failure analysis, debug, and security assessments. We also plan to extend this type of work to other FPGAs and other devices like memory and processors.

36 MATERIALS SCIENCE↗
NASA NTRS2015

A Morphing Radiator for High-Turndown Thermal Control of Crewed Space Exploration Vehicles

Spacecraft designed for missions beyond low earth orbit (LEO) face a difficult thermal control challenge, particularly in the case of crewed vehicles where the thermal control system (TCS) must maintain a relatively constant internal environment temperature despite a vastly varying external thermal environment and despite heat rejection needs that are contrary to the potential of the environment. A thermal control system is in other words required to reject a higher heat load to warm environments and a lower heat load to cold environments, necessitating a quite high turndown ratio. A modern thermal control system is capable of a turndown ratio of on the order of 12:1, but for crew safety and environment compatibility these are massive multi-loop fluid systems. This paper discusses the analysis of a unique radiator design which employs the behavior of shape memory alloys (SMA) to vary the turndown of, and thus enable, a single-loop vehicle thermal control system for space exploration vehicles. This design, a morphing radiator, varies its shape in response to facesheet temperature to control view of space and primary surface emissivity. Because temperature dependence is inherent to SMA behavior, the design requires no accommodation for control, instrumentation, nor power supply in order to operate. Thermal and radiation modeling of the morphing radiator predict a turndown ranging from 11.9:1 to 35:1 independent of TCS configuration. Stress and deformation analyses predict the desired morphing behavior of the concept. A system level mass analysis shows that by enabling a single loop architecture this design could reduce the TCS mass by between 139 kg and 225 kg. The concept is demonstrated in proof-of-concept benchtop tests.

Cognata, Thomas J.↗
NASA NTRS2005

Journal of Gravitational Physiology, Volume 12, Number 1

The following topics were covered: System Specificity in Responsiveness to Intermittent -Gx Gravitation during Simulated Microgravity in Rats; A Brief Overview of Animal Hypergravity Studies; Neurovestibular Adaptation to Short Radius Centrifugation; Effect of Artificial Gravity with Exercise Load by Using Short-Arm Centrifuge with Bicycle Ergometer as a Countermeasure Against Disused Osteoporosis; Perception of Body Vertical in Microgravity during Parabolic Flight; Virtual Environment a Behavioral and Countermeasure Tool for Assisted Gesture in Weightlessness: Experiments during Parabolic Flight; Artificial Gravity: Physiological Perspectives for Long-Term Space Exploration; Comparison of the Effects of DL-threo-Beta-Benzyloxyaspartate on the Glutamate Release from Synaptosomes before and after Exposure of Rats to Artificial Gravity; Do Perception and Postrotatory Vestibulo-Ocular Reflex Share the Same Gravity Reference?; Vestibular Adaptation to Changing Gravity Levels and the Orientation of Listing's Plane; Compound Mechanism Hypothesis on +Gz - Induced Brain Injury and Dysfunction of Learning and Memory; Environmental Challenge Impairs Prefrontal Brain Functions; Effect of 6-Days of Support Withdrawal on Characteristics of Balance Function; Hypergravity-Induced Changes of Neuronal Activities in CA1 Region of Rat Hippocampus; Audiological Findings in Antiorthostatic Position Modelling Microgravitation; Investigating Human Cognitive Performance during Spaceflight; The Relevance of the Minimization of Torque Exchange with the Environment in Weightlessness is Confirmed by Asimulation Study; Characteristics of the Eyes Pursuit Function during Readaptation to Terrestrial Gravity after Prolonged Flights Aboard the International Space Station; Comparison of Cognitive Performance Tests for Promethazine Pharmacodynamics in Human Subjects; Structural Reappraisal of Dendritic Tree of Cerebellar Purkinje Cell for Novel Functional Modeling of Elementary Sensorimotor Adaptive Processes; Orpheus 0 G or Ear in Microgravity to Establish Symptoms Concomittant of Inner and Middle Ear and Osteoporosis in Microgravity; Understanding Visual Perception in the Perspective of Gravity; Cortical Regions Associated with Orthostatic Stress in Conscious Humans; Restoration of Central Blood Volume: Application of a Simple Concept and Simple Device to Counteract Cardiovascular Instability in Syncope and Hemorrhage; WISE-2005: Integrative Cardiovascular Responses with LBNP during 60-Day Bed Rest in Women; Intracranial Pressure Increases during Weightlessness. A Parabolic Flights Study; Lower Limb & Portal Veins Echography for Predicting Risk of Thrombosis during a 90-D Bed Rest; Calf Tissue Liquid Stowage and Muscular and Deep Vein Distension in Orthostatic Tests after a 90-Day Head Down Bed Rest; Morphology of Brain Vessels in the Tail Suspended Rats Exposed to Intermittent 2 G; Alterations in Vasoreactivity of Femoral Artery Induced by Hindlimb Unweighting are Related to the Changes of Contractile Protein in Rats; and Respiratory Sinus Arrhythmia: A Marker of Decreased Parasympathetic Modulation after Short Duration.

Fuller, Charles A.↗
NASA NTRS2014

A Morphing Radiator for High-Turndown Thermal Control of Crewed Space Exploration Vehicles

Spacecraft designed for missions beyond low earth orbit (LEO) face a difficult thermal control challenge, particularly in the case of crewed vehicles where the thermal control system (TCS) must maintain a relatively constant internal environment temperature despite a vastly varying external thermal environment and despite heat rejection needs that are contrary to the potential of the environment. A thermal control system may be required to reject a higher heat load to warm environments and a lower heat load to cold environments, necessitating a relatively high turndown ratio. A modern thermal control system is capable of a turndown ratio of on the order of 12:1, but crew safety and environment compatibility have constrained these solutions to massive multi-loop fluid systems. This paper discusses the analysis of a unique radiator design that employs the behavior of shape memory alloys (SMAs) to vary the turndown of, and thus enable, a single-loop vehicle thermal control system for space exploration vehicles. This design, a morphing radiator, varies its shape in response to facesheet temperature to control view of space and primary surface emissivity. Because temperature dependence is inherent to SMA behavior, the design requires no accommodation for control, instrumentation, or power supply in order to operate. Thermal and radiation modeling of the morphing radiator predict a turndown ranging from 11.9:1 to 35:1 independent of TCS configuration. Coupled thermal-stress analyses predict that the desired morphing behavior of the concept is attainable. A system level mass analysis shows that by enabling a single loop architecture this design could reduce the TCS mass by between 139 kg and 225 kg. The concept has been demonstrated in proof-of-concept benchtop tests.

Cognata, Thomas J.↗
DOE OSTI2023

Implementation of Distributed Memory Computing in MOSAIC to Enable Large 3D Simulations of Irradiated Concrete

The concrete biological shield (CBS) of light-water reactors protects workers and the surrounding environment by absorbing neutron and gamma irradiation emitted from the reactor core. The radiation dose increases with the CBS’s operational time and, in the long term, becomes significant enough to raise the question of irradiation effects on concrete—and particularly on the structural integrity of the CBS. Irradiation-induced damage has been identified as one of the main degradation mechanisms in the CBS. Neutron radiation causes the swelling of aggregate-forming minerals at different rates and amplitudes depending on the mineral’s nature. Silicate-bearing minerals such as quartz are particularly sensitive to neutron radiation and experience up to 17.8% volumetric expansion. Aggregates comprise several minerals with different orientations and are, therefore, subject to cracking as a result of mismatch strains. Additionally, the swelling of aggregates creates significant stresses in the surrounding cement paste matrix, which also results in crack formation. In parallel with the collection of characterization and irradiation test data, development of modeling and simulation tools for irradiated concrete is ongoing with the support of the US Department of Energy Office of Nuclear Energy’s Light Water Reactor Sustainability (LWRS) program. This effort resulted in the development and application of the fast-Fourier transform (FFT)–based code Microstructure-Oriented Scientific Analysis of Irradiated Concrete (MOSAIC) at Oak Ridge National Laboratory.

61 RADIATION PROTECTION AND DOSIMETRY↗