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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

AMPPED LDRD: Advanced Models of the Physics & Phenomena of Electrical Discharge.

This Laboratory Directed Research and Development (LDRD) project aimed at addressing an unmet need for physics-based models that enable prediction of electrical breakdown in the presence of high voltage gradients and real-world environments. This project focused on understanding coupled plasma-surface feedback phenomena critical to electrical discharge processes and design of breakdown voltages, breakdown times, and breakdown paths. New secondary electron emission and coupled plasma-surface measurement methods and models were developed. Highly reproducible discharge experiments were developed to provide current-voltage data as a function of time, and methods were developed to condition electrodes for predictable discharge. To assess plasma-surface feedback mechanisms, new surface physics capabilities, including measurement systems for local and global photoemission yield and ion-induced secondary electron emission yield were developed. Discharge models were developed to incorporate these yields for predicting discharge behavior to understand influence of surface physics on discharge current and time evolution, and methods to accelerate these simulations were demonstrated. A key finding was that the initiation process of a non-vacuum discharge appears highly dependent on photoemission at the cathode. Advanced diagnostics were developed, including spatial electrical field imaging, spectroscopy of plasmas, and high-speed imaging of discharge event s in metal and dielectric environments. These diagnostics and improved electrical models are a step toward enabling quantitative design margins, assurance of safety architectures, and implementation of novel materials and technologies for wide ranging energy and electronics applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Confronting Dark Matter with the Multiwavelength Sky (Final Technical Report)

The existence of dark matter is a key clue to new fundamental physics, yet its nature and non-gravitational interactions remain mysterious. In the course of this five-year project (spanning July 2015 - July 2020), we have developed novel analysis techniques to separate dark matter signals from astrophysical backgrounds in the inner Galaxy, and measured hitherto-unknown properties of the Fermi Bubbles and the Galactic Center excess in gamma-rays from the inner Milky Way. We have improved predictions for the spatial distribution and energy spectra of photon signals from dark matter, and set new limits from astrophysical and cosmological datasets on dark matter inhabiting complex dark sectors, multi-particle dark matter annihilation, and tiny primordial black holes. We have successfully adapted effective field theory techniques from collider physics to make high-precision predictions for signals from heavy weakly-interacting DM, allowing us to essentially exclude the possibility that DM is a thermal wino, and have discovered novel theoretical and observational implications for dark matter bound states and self-interactions. We have developed a comprehensive public code package for modeling the effects of exotic energy injections, such as from dark matter annihilation and decay, on the ionization and temperature history of the early cosmos, and have used these tools to set robust, powerful and broadly-applicable constraints on models of light dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRSDate not supplied

Enhanced Far Ultra-Violet Optical Properties of Physical Vapor Deposited Aluminum Mirrors Through Fluorination

Astronomical instrumentation for measurements in the Far Ultra-Violet (FUV, 90-200 nm) typically use aluminum (Al) thin films due to their high reflectance over this wavelength range. However, the native aluminum oxide layer that forms on Al upon exposure to the atmosphere is strongly absorbing in this wavelength range, requiring that the films be protected with a dielectric that inhibits oxidation. Typically, magnesium fluoride (MgF 2 ) or lithium fluoride (LiF) coatings are used as protective layers, but each has shortcomings. For example, MgF 2 has an absorption cutoff at 115 nm reducing performance in a critical part of the FUV spectrum of observational interest. A viable option to access these lower wavelengths could be the use of the LiF overcoat as it has a lower absorption cutoff at 102.5 nm, but it is hygroscopic and thus susceptible to degradation in humid conditions. An approach to reduce the hygroscopic nature of LiF would be to implement a passivation process during the deposition of both Al+LiF coatings. Our team at GSFC has developed a new reactive Physical Vapor Deposition (rPVD) process that consists of a fluorination process with XeF 2 gas combined with our traditional PVD process. We have found that this new rPVD coating process offers a protected version of Al+LiF with a more environmentally stable and more transparent LiF layer, along with unprecedent reflectivity. The process starts with a bare optically smooth substrate that is coated with Al in an ultra-high vacuum (UHV) chamber by the conventional PVD process. Then, the bare Al mirror is immediately exposed to a reactive XeF 2 gas before and after the application of the flash PVD evaporated LiF layer. We have also been investigating the use of this rPVD coating process for potential efficiency enhancements of Si-based gratings. Since it is known that the XeF 2 vapor is a strong Si etchant, we are investigating if the native SiO 2 layer on Si is sufficient to protect the groove profile of e-beam-ruled Si gratings from degradation. We will report on the characterization of various Al+LiF witness mirror coatings (both on borosilicate and Si) performed under various deposition conditions using the XeF 2 passivation process. These tests include XPS to determine film stoichiometry and AFM/SEM to measure surface roughness and any etching on the Si substrate. We will also report on FUV reflectance and spectroscopic ellipsometry to characterize optical constants of these passivated films in the UV/Visible/NIR spectral ranges.

Engineering (General)↗
NASA NTRSDate not supplied

Enhanced Far Ultra-Violet Optical Properties of Physical Vapor Deposited Aluminum Mirrors Through Fluorination

Astronomical instrumentation for measurements in the Far Ultra-Violet (FUV, 90-200 nm) typically use aluminum (Al) thin films due to their high reflectance over this wavelength range. However, the native aluminum oxide layer that forms on Al upon exposure to the atmosphere is strongly absorbing in this wavelength range, requiring that the films be protected with a dielectric that inhibits oxidation. Typically, magnesium fluoride (MgF 2 ) or lithium fluoride (LiF) coatings are used as protective layers, but each has shortcomings. For example, MgF 2 has an absorption cutoff at 115 nm reducing performance in a critical part of the FUV spectrum of observational interest. A viable option to access these lower wavelengths could be the use of the LiF overcoat as it has a lower absorption cutoff at 102.5 nm, but it is hygroscopic and thus susceptible to degradation in humid conditions. An approach to reduce the hygroscopic nature of LiF would be to implement a passivation process during the deposition of both Al+LiF coatings. Our team at GSFC has developed a new reactive Physical Vapor Deposition (rPVD) process that consists of a fluorination process with XeF 2 gas combined with our traditional PVD process. We have found that this new rPVD coating process offers a protected version of Al+LiF with a more environmentally stable and more transparent LiF layer, along with unprecedent reflectivity. The process starts with a bare optically smooth substrate that is coated with Al in an ultra-high vacuum (UHV) chamber by the conventional PVD process. Then, the bare Al mirror is immediately exposed to a reactive XeF 2 gas before and after the application of the flash PVD evaporated LiF layer. We have also been investigating the use of this rPVD coating process for potential efficiency enhancements of Si-based gratings. Since it is known that the XeF 2 vapor is a strong Si etchant, we are investigating if the native SiO 2 layer on Si is sufficient to protect the groove profile of e-beam-ruled Si gratings from degradation. We will report on the characterization of various Al+LiF witness mirror coatings (both on borosilicate and Si) performed under various deposition conditions using the XeF 2 passivation process. These tests include XPS to determine film stoichiometry and AFM/SEM to measure surface roughness and any etching on the Si substrate. We will also report on FUV reflectance and spectroscopic ellipsometry to characterize optical constants of these passivated films in the UV/Visible/NIR spectral ranges.

Engineering (General)↗
NASA NTRSDate not supplied

Enhanced Far Ultra-Violet Optical Properties of Physical Vapor Deposited Aluminum Mirrors Through Fluorination

Astronomical instrumentation for measurements in the Far Ultra-Violet (FUV, 90-200 nm) typically use aluminum (Al) thin films due to their high reflectance over this wavelength range. However, the native aluminum oxide layer that forms on Al upon exposure to the atmosphere is strongly absorbing in this wavelength range, requiring that the films be protected with a dielectric that inhibits oxidation. Typically, magnesium fluoride (MgF 2 ) or lithium fluoride (LiF) coatings are used as protective layers, but each has shortcomings. For example, MgF 2 has an absorption cutoff at 115 nm reducing performance in a critical part of the FUV spectrum of observational interest. A viable option to access these lower wavelengths could be the use of the LiF overcoat as it has a lower absorption cutoff at 102.5 nm, but it is hygroscopic and thus susceptible to degradation in humid conditions. An approach to reduce the hygroscopic nature of LiF would be to implement a passivation process during the deposition of both Al+LiF coatings. Our team at GSFC has developed a new reactive Physical Vapor Deposition (rPVD) process that consists of a fluorination process with XeF 2 gas combined with our traditional PVD process. We have found that this new rPVD coating process offers a protected version of Al+LiF with a more environmentally stable and more transparent LiF layer, along with unprecedent reflectivity. The process starts with a bare optically smooth substrate that is coated with Al in an ultra-high vacuum (UHV) chamber by the conventional PVD process. Then, the bare Al mirror is immediately exposed to a reactive XeF 2 gas before and after the application of the flash PVD evaporated LiF layer. We have also been investigating the use of this rPVD coating process for potential efficiency enhancements of Si-based gratings. Since it is known that the XeF 2 vapor is a strong Si etchant, we are investigating if the native SiO 2 layer on Si is sufficient to protect the groove profile of e-beam-ruled Si gratings from degradation. We will report on the characterization of various Al+LiF witness mirror coatings (both on borosilicate and Si) performed under various deposition conditions using the XeF 2 passivation process. These tests include XPS to determine film stoichiometry and AFM/SEM to measure surface roughness and any etching on the Si substrate. We will also report on FUV reflectance and spectroscopic ellipsometry to characterize optical constants of these passivated films in the UV/Visible/NIR spectral ranges.

Engineering (General)↗
DOE OSTI2020

Learning in Modal Space: Solving Time-Dependent Stochastic PDEs Using Physics-Informed Neural Networks

One of the open problems in scientific computing is the long-time integration of nonlinear stochastic partial differential equations (SPDEs), especially with arbitrary initial data. We address this problem by taking advantage of recent advances in scientific machine learning and the spectral dynamically orthogonal (DO) and borthogonal (BO) methods for representing stochastic processes. The recently introduced DO/BO methods reduce the SPDE to solving a system of deterministic PDEs and a system of stochastic ordinary differential equations. Specifically, we propose two new physics-informed neural networks (PINNs) for solving time-dependent SPDEs, namely the neural network (NN)-DO/BO methods. The proposed methods incorporate the DO/BO constraints into the loss function (along with the modal decomposition of the SPDE) with an implicit form instead of generating explicit expressions for the temporal derivatives of the DO/BO modes. Hence, the NN-DO/BO methods can overcome some of the drawbacks of the original DO/BO methods. For example, we do not need the assumption that the covariance matrix of the random coefficients is invertible as in the original DO method, and we can remove the assumption of no eigenvalue crossing as in the original BO method. Moreover, the NN-DO/BO methods can be used to solve time-dependent stochastic inverse problems with the same formulation and same computational complexity as for forward problems. Furthermore, we demonstrate the capability of the proposed methods via several numerical examples, namely: (1) A linear stochastic advection equation with deterministic initial condition: we obtain good results with the proposed methods, while the original DO/BO methods cannot be applied directly in this case. (2) Long-time integration of the stochastic Burgers' equation: we show the good performance of NN-DO/BO methods, especially the effectiveness of the NN-BO approach for such problems with many eigenvalue crossings during the whole time evolution, while the original BO method fails. (3) Nonlinear reaction diffusion equation: we consider both the forward problem and the inverse problems, including very noisy initial point values, to investigate the flexibility of the NN-DO/BO methods in handling inverse and mixed type problems. Taken together, these simulation results demonstrate that the NN-DO/BO methods can be employed to effectively quantify uncertainty propagation in a wide range of physical problems, but future work should address the efficiency issue of PINNs for forward problems.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2008

Intelligent Devices - Sensors and Actuators - A KSC Perspective

The primary objective of this workshop is to identify areas of advancement in sensor measurements and technologies that will help to define standard practices and procedures that will better enable the infusion into flight programs of sensors with improved capabilities but limited or no flight heritage. These standards would be crucial to demonstrating a methodology for validating current models while also creating the possibility of being able to have sufficient data to either update these models (e. g., spatial or temporal resolution, etc.) or develop new models based on the ability to simulate the new measured physical parameters. The workshop is also intended to narrow the gap between sensor measurements (and techniques), data processing techniques and the ability to make use of that data by gathering together experts in the field for a short workshop. This collaboration will unite NASA and other government agencies with contractor capabilities industry-wide to prevent duplication, spawn synergistic growth in sensor technology, help analysts make good engineering decisions and help focus new sensor maturation efforts to better meet future flight program customers' needs. This is the first such workshop designed to specifically address establishing a standardized protocol/methodology for demonstrating the technology readiness of non-flight heritage sensor systems. While other similar workshops are held covering many areas of interest to the sensor development community, no other meeting is specific enough to address this vital but often overlooked topic. By encouraging cross-fertilization of ideas from instrument experts from many different backgrounds, it is hoped that this workshop will initiate innovative new ideas and concepts in sensor development, calibration and validation. It is anticipated this workshop will repeat periodically as needed.

Mata, Carlos T.↗
DOE OSTI2022

Contribution to the IRPHEP handbook since Physor 2018

The Organisation for Economic Co-operation and Development (OECD), the Nuclear Energy Agency (NEA), the International Reactor Physics Experiment Evaluation Project (IRPhEP) continue to preserve and evaluate integral reactor physics experiment data to support nuclear energy and technology needs. International contributions are collated within the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP Handbook). The 2021 edition of the IRPhEP Handbook now contains data for 57 unique nuclear facilities with benchmark specifications for 169 experimental series, of which four are draft evaluations. Distributed with the IRPhEP Handbook and available online is the IRPhEP Database and Analysis Tool (IDAT), allowing users to search and interrogate the data. Since Physor 2018, there have been 11 minor revisions to existing benchmark evaluations, significant revisions to two evaluations, one draft evaluation, and nine new evaluations. The corona virus pandemic has delayed international activities supporting the production of additional content for the IRPhEP Handbook. However, efforts continue for numerous endeavors to complete new reactor physics benchmark evaluations to support current and future validation needs. Those interested in serving as evaluators and/or reviewers are strongly encouraged to participate. This paper provides a summary of IRPhEP content and activities since Physor 2018. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1994

Analysis of the physical state of one Arctic polar stratospheric cloud based on observations

During the Arctic Airborne Stratospheric Expedition (AASE) simultaneous measurements of aerosol size distribution and NO(y)(HN03 + NO + NO2 + 2(N205)) were made along ER-2 flight paths. The flow characteristics of the NO(y) instrument allow us to derive the condensed NO(y) amount (assumed to be HN03) present during polar stratospheric cloud (PSC) events. Analysis of the January 24th flight indicates that this condensed HN03 amount does not agree well with the aerosol volume if the observed PSCs are composed of solid nitric acid trihydrate (NAT), as is generally assumed. However, the composition agrees well with that predicted for liquid H2S04/HN03/H20 solution droplets using a new Aerosol Physical Chemistry Model (APCM). The agreement corresponds in detail to variations in temperature and humidity. The weight percentages of H2SO4, HN03, and H2O derived from the measurements all correspond to those predicted for ternary, liquid solutions.

Drdla, K.↗
DOE OSTI2022

The Muon g-2 Experiment at Fermilab

The muon magnetic anomaly, $a_{\mu}$, is a powerful test of the Standard Model of particle physics. A new experiment at Fermilab has recently measured $a_{\mu}$ with unprecedented precision, confirming the results of the earlier Brookhaven experiment and strengthening the tension with the prediction of the Standard Model as determined by dispersive methods. We here describe the experimental technique, recapitulate the recent result, and discuss some of the improvements made for subsequent analyses.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Variations in the charge radii of indium isotopes between 𝑁=52 and 82

Measurements of the 5⁢𝑝 2 𝑃 3/2 → 9⁢𝑠 2 𝑆 1/2 and 5⁢𝑝 2 𝑃 1/2 → 8⁢𝑠 2 𝑆 1/2 transitions in the indium atom, combined with new atomic physics calculations, were used to extract the changes in mean-square nuclear charge radii, 𝛿⁡⟨𝑟 2 ⟩, of the indium (𝑍 = 49) isotopes 101–111 In , 113–123 In , and 125–131 In . With a proton hole in the closed nuclear shell of 𝑍 = 50, indium provides a detailed study of the effect of unpaired nucleons adjacent to the proton-shell closure, allowing investigation into the charge radii for isotopes between the two major neutron-shell closures at 𝑁 = 50 and 𝑁 = 82. A study of the variations in charge radii between neighboring isotopes with neutron number (the ‘odd-even staggering') is presented and provides further insight and challenges for the theoretical description of the size of proton-hole nuclei. Two nuclear theories, density functional theory and the valence-space in-medium similarity renormalization group method, were employed to interpret the data. The new information obtained in this work provides valuable insights into the successes and shortcomings of the theoretical approaches employed.

ab initio calculations↗
NASA NTRS1999

Mesoscale Eddies, Satellite Altimetry, and New Production in the Sargasso Sea

Satellite altimetry and hydrographic observations are used to characterize the mesoscale eddy field in the Sargasso Sea near Bermuda and to address the role of physical processes on the supply of new nutrients to the euphotic zone. The observed sea level anomaly (SLA) field is dominated by the occurrence of westward propagating features with SLA signatures as large as 25 cm, Eulerian temporal scales of roughly a month, lifetimes of several months, spatial scales of approximately 200 km, and a propagation of approximately 5 cm/s. Hydrographic estimates of dynamic height anomaly (referenced to 4000 dbar) are well correlated with satellite SLA (r(exp 2) = 0.65), and at least 85% of the observed dynamic height variability is associated with the first baroclinic mode of motion. This allows us to apply the satellite observations to remotely sensed estimate isopycnal displacements and the flux of nutrients into the euphotic zone due to eddy pumping. Eddy pumping is the process by which mesoscale eddies induce isopycnal displacements that lift nutrient-replete waters into the euphotic zone, driving new primary production. A kinematic approach to the estimation of the eddy pumping results in a flux of 0.24 +/- 0.1 mol N/sq m (including a scale estimate for the small contribution due to 18 deg water eddies). This flux is more than an order of magnitude larger than the diapycnal diffusive flux as well as scale estimates for the vertical transport due to isopycnal mixing along sloping isopycnal surfaces. Eddy pumping and wintertime convection are the two dominant mechanisms transporting new nutrients into the euphotic zone, and the sum of all physical new nutrient supply fluxes effectively balances previous geochemical estimates of annual new production for this site. However, if biological transports (e.g., nitrogen fixation, etc.) are significant, the new nitrogen supply budget will be in excess of geochemical new production estimates. This suggests that the various physical and biological transport fluxes, as well as geochemical inferences of new production, still need to be reconciled and many outstanding questions remain.

Siegel, David A.↗
NASA NTRS1999

Mesoscale Eddies, Satellite Altimetry, and New Production in the Sargasso Sea

Satellite altimetry and hydrographic observations are used to characterize the mesoscale eddy field in the Sargasso Sea near Bermuda and to address the role of physical processes on the supply of new nutrients to the euphotic zone. The observed sea level anomaly (SLA) field is dominated by the occurrence of westward propagating features with SLA signatures as large as 25 cm, Eulerian temporal scales of roughly a month, lifetimes of several months, spatial scales of approximately 200 km, and a propagation of approximately 5 cm/s . Hydrographic estimates of dynamic height anomaly (referenced to 4000 dbar) are well correlated with satellite SLA (r(sup 2) = 0.65), and at least 85% of the observed dynamic height variability is associated with the first baroclinic mode of motion. This allows us to apply the satellite observations to remotely estimate isopycnal displacements and the flux of nutrients into the euphotic zone due to eddy pumping. Eddy pumping is the process by which mesoscale eddies induce isopycnal displacements that lift nutrient- replete waters into the euphotic zone, driving new primary production. A kinematic approach to the estimation of the eddy pumping results in a flux of 0.24+/-0.1 mol N/sq m/yr (including a scale estimate for the small contribution due to 18 deg water eddies). This flux is more than an order of magnitude larger than the diapycnal diffusive flux as well as scale estimates for the vertical transport due to isopycnal mixing along sloping isopycnal surfaces. Eddy pumping and wintertime convection are the two dominant mechanisms transporting new nutrients into the euphotic zone, and the sum of all physical new nutrient supply fluxes effectively balances previous geochemical estimates of annual new production for this site. However, if biological transports (e.g., nitrogen fixation, etc.) are significant, the new nitrogen supply budget will be in excess of geochemical new production estimates. This suggests that the various physical and biological transport fluxes, as well as geochemical inferences of new production, still need to be reconciled and many outstanding questions remain.

Siegel, David A.↗
DOE OSTI2025

Representing Anthropogenic Dust From Agricultural Sources in E3SMv1: Implementation, Evaluation, and Assessment of the Radiative Forcing

Dust emissions related to anthropogenic activities (i.e., anthropogenic dust) is not represented in most global climate models and its radiative impact remains unassessed. In this study, we develop a new and physically based method to parameterize anthropogenic dust emission from agricultural sources (i.e., agricultural dust, or AD) based on the DOE's Energy Exascale Earth System Model version 1 (E3SMv1). This method relates AD emission to the crop land use fraction in the E3SMv1 land component. Major AD sources simulated by our parameterization include those over Central America, the Sahel, North India, and North China. The annual averaged AD emission with diameter less than 10 μm is 567 Tg yr −1 in present-day (year 2000), which contributes to 13.3% of total dust emission. Model evaluation against satellite and ground-based observations shows that the new parameterization can represent AD emissions and global dust cycle reasonably well. We find that the total dust emission increases by 13.1% (495 Tg yr −1 ) from 1850 to 2000 due to the cropland land use fraction changes without considering the impact from climate changes. This induces a net dust direct effective radiative forcing of −0.041 W m −2 at top of the atmosphere. This dust-induced cooling exceeds 10% of the total anthropogenic aerosol direct effective radiative forcing from 1750 to 2014 estimated by the Intergovernmental Panel on Climate Change Sixth Assessment Report. Our findings indicate an important role of anthropogenic dust in global climate change, which should be included in future climate change assessments.

agricultural dust↗
DOE OSTI2021

Status of EM Pump Modeling Capability for VTR

SAS4A/SASSYS-1 is a simulation tool used to perform deterministic analyses of anticipated events as well as design basis and beyond design basis accidents for advanced liquid-metal-cooled nuclear reactors. Most recently, SAS4A/SASSYS-1 has been selected as the safety analysis software for the Versatile Test Reactor (VTR), a new materials testing Sodium Fast Reactor (SFR) to be built by the Department of Energy. In order to support analysis of the VTR, which will utilize ElectroMagnetic (EM) pumps as the primary coolant pumps, the development of new EM pump modeling capabilities has been initiated for SAS4/SASSYS-1. The new physics-based EM pump model captures systems-level transient performance based on equivalent circuit theory and is highly flexible to model a wide range of electromagnetic pumps of the three-phase linear induction type subject to changes in power supply and plant conditions. Within the equivalent circuit framework, two sub-models are developed to provide options for analysts both with and without a detailed geometric characterization of their pump such that minimal information is required to achieve a realistic working model, but specific details of a particular pump design may be captured if sufficient information is provided. In addition, heat generated from pump operation and its transport through the plant system can be modeled to better capture the behavior of certain transients. This paper will outline the model and derive the governing equations of the new EM pump model. An initial comparison between the simple EM pump model and experimental data is made. This comparison shows that the equivalent circuit model can capture pump performance, with greater accuracy near the rated conditions. In order to demonstrate the transient behavior of the new model, a simple transient with an EM pump replacing the centrifugal pumps in the Advanced Burner Test Reactor is included.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

Status of EM Pump Modeling Capability for VTR

SAS4A/SASSYS-1 is a simulation tool used to perform deterministic analyses of anticipated events as well as design basis and beyond design basis accidents for advanced liquid-metal-cooled nuclear reactors. Most recently, SAS4A/SASSYS-1 has been selected as the safety analysis software for the Versatile Test Reactor (VTR), a new materials testing Sodium Fast Reactor (SFR) to be built by the Department of Energy. In order to support analysis of the VTR, which will utilize ElectroMagnetic (EM) pumps as the primary coolant pumps, the development of new EM pump modeling capabilities has been initiated for SAS4/SASSYS-1. The new physics-based EM pump model captures systems-level transient performance based on equivalent circuit theory and is highly flexible to model a wide range of electromagnetic pumps of the three-phase linear induction type subject to changes in power supply and plant conditions. Within the equivalent circuit framework, two sub-models are developed to provide options for analysts both with and without a detailed geometric characterization of their pump such that minimal information is required to achieve a realistic working model, but specific details of a particular pump design may be captured if sufficient information is provided. In addition, heat generated from pump operation and its transport through the plant system can be modeled to better capture the behavior of certain transients. This paper will outline the model and derive the governing equations of the new EM pump model. An initial comparison between the simple EM pump model and experimental data is made. This comparison shows that the equivalent circuit model can capture pump performance, with greater accuracy near the rated conditions. In order to demonstrate the transient behavior of the new model, a simple transient with an EM pump replacing the centrifugal pumps in the Advanced Burner Test Reactor is included.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Fatty acid foams for nonselective physical removal of microplastics from aqueous solutions

Microplastics (MPs) are pervasive environmental contaminants whose removal from water remains a major challenge due to their small size, chemical diversity, and dynamic surface properties arising from environmental aging/weathering. Here, we present a concept of foam-based separation method that physically traps MPs in the foam phase using microtubular assemblies of 12-hydroxystearic acid. These foams are stabilized by anisotropic fatty acid microtubules formed in the presence of ethanolamine, which jam within the foam channels and suppress fluid drainage thereby enhancing MP retention and foam stability. MPs of different sizes, polymer compositions (including polystyrene, polypropylene, polyethylene terephthalate, and polytetrafluoroethylene), and weathered states were retained in the foam phase without requiring chemical modification or relying on chemical interactions between the fatty acid and MPs. Thermally induced transition of the fatty acid microtubules into nanomicelles above the characteristic phase transition temperature (∼35 °C) enables controlled foam collapse and recovery of trapped MPs. The cumulative removal efficiency can exceed 85% through multiple foaming cycles, matching predictions from a probabilistic retention model. This work shows that foams can provide a simple platform to trap MPs, thus providing a new physical-removal strategy that does not rely on the particles’ chemistry.

Guillot, Kennedy A. [Louisiana State Univ., Baton ↗