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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Initial Engineering Framework for Species Tracking in MSRs Involving Fuel Salt and Structures

This report implements a high-fidelity multiphysics modeling framework using the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program tools to track leaching and plating of materials between the fuel salt and structures in Molten Salt Reactors (MSRs). Specifically, this framework is demonstrated in modeling various processes within MSRs including hot and cold leg corrosion, redox potential driven corrosion, colloid precipitation and deposition, and noble metal plating and decay heat modeling. The model integrates neutronics, thermal-hydraulics, depletion, and thermochemistry to simulate the evolving chemical behavior of the fuel salt in interactions with structural materials. Initial findings suggest that hot-cold leg corrosion in MSR systems may become significant if the redox potential of the fuel salt is not sufficiently controlled. Additionally, the impact of noble metal decay heat deposition in large power reactors is explored. The resulting engineering framework for species tracking will be applied in the future toward specific validation work with ongoing experimental efforts focusing on both chloride and fluoride salt loop experiments with in-situ corrosion and redox control instrumentation.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Exploring Cr and molten salt interfacial interactions for molten salt applications

Molten salts play an important role in various energy-related applications such as high-temperature heat transfer fluids and reaction media. However, the extreme molten salt environment causes the degradation of materials, raising safety and sustainability challenges. A fundamental understanding of material–molten salt interfacial evolution is needed. This work studies the transformation of metallic Cr in molten 50/50 mol% KCl–MgCl 2 via multi-modal in situ synchrotron X-ray nano-tomography, diffraction and spectroscopy combined with density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Notably, in addition to the dissolution of Cr in the molten salt to form porous structures, a δ-A15 Cr phase was found to gradually form as a result of the metal–salt interaction. This phase change of Cr is associated with a change in the coordination environment of Cr at the interface. DFT and AIMD simulations provide a basis for understanding the enhanced stability of δ-A15 Cr vs. bcc Cr, by revealing their competitive phase thermodynamics at elevated temperatures and probing the interfacial behavior of the molten salt at relevant facets. This study provides critical insights into the morphological and chemical evolution of metal–molten salt interfaces. Finally, the combination of multimodal synchrotron analysis and atomic simulation also offers an opportunity to explore a broader range of systems critical to energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Preconceptual Design of Irradiated Fuel Salt Management System

The National Reactor Innovation Center was established by the U.S. Department of Energy to accelerate the demonstration and deployment of advanced nuclear reactors. To meet this mission, the National Reactor Innovation Center has developed the Laboratory for Operations and Testing in the U.S. (LOTUS) to support the first fast-spectrum molten salt reactor demonstration. The goal of this research is to understand the system requirements that may be applied to a molten salt reactor experiment in the LOTUS test bed and to perform systems analyses and preconceptual development of a storage container for the management of the irradiated molten salt fuel. This study proposes a set of irradiated fuel salt management processes for the molten salt reactor, from defueling to storage or disposal. For that, the historic Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory has served as a crucial source of data for a mock application. This paper proposes a potential geometry for storing irradiated fuel salt based on MSRE data and the Monte Carlo N-Particle radiation transport code. The geometry was analyzed for criticality safety under abnormal situations, such as water ingress and interaction between containers. Based on the determined configuration of the storage system, the decay heat produced from the irradiated fuel salts was calculated to provide a reasonable time scale of the dormancy period. Using the same geometry assumed above, the neutron and gamma dose rates from the irradiated fuel salt at the end of the dormancy period were estimated, which will be useful for understanding the handling and radiation protection requirements for handling the irradiated fuel salt. Lastly, a reactor in the LOTUS test bed could use chloride-based fuel as opposed to the fluoride-based fuel used in MSRE. Thus, a literature study provided data to understand the similarities and differences between the characteristics of fluoride- and chloride-based salts in terms of salt chemistry, material characteristics, postirradiation behavior, neutronics, thermal hydraulics, and heat removal. This study, together with the proposed irradiated fuel salt management processes, preliminary criticality calculations, decay heat, and dose rate estimates, provides a strong basis for future investigation into the management of irradiated fuel salts generated during molten salt reactor technology demonstrations.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1993

Modeling void growth and movement with phase change in thermal energy storage canisters

A scheme was developed to model the thermal hydrodynamic behavior of thermal energy storage salts. The model included buoyancy, surface tension, viscosity, phases change with density difference, and void growth and movement. The energy, momentum, and continuity equations were solved using a finite volume formulation. The momentum equation was divided into two pieces. The void growth and void movement are modeled between the two pieces of the momentum equations. Results showed this scheme was able to predict the behavior of thermal energy storage salts.

Darling, Douglas↗
NASA NTRS1993

Modeling void growth and movement with phase change in thermal energy storage canisters

A scheme was developed to model the thermal hydrodynamic behavior of thermal energy storage salts. The model included buoyancy, surface tension, viscosity, phases change with density difference, and void growth and movement. The energy, momentum, and continuity equations were solved using a finite volume formulation. The momentum equation was divided into two pieces. The void growth and void movement are modeled between the two pieces of the momentum equations. Results showed this scheme was able to predict the behavior of thermal energy storage salts.

Darling, Douglas↗
DOE OSTI2026

Structural coherence model for predicting molten salt thermal conductivity informed by the pair distribution function

To enable thermal behavior prediction and design optimization of molten salt reactors, thermal conductivity of molten salts must be characterized in terms of salt composition and temperature. Current theoretical models fail to provide consistent approximations for all halide mixtures, particularly actinide-bearing melts. This study aims to link the short-range order structure of molten salts to the mean free path of energy carriers through a simple structural coherence model informed by the partial pair distribution function. The proposed method is used to predict the thermal conductivity of 33 alkali and alkaline earth halide salts. Predictions approximate experimental measurements with a mean absolute error of 15.7% for dissociating, complexing, and actinide salts, including unary LiCl, NaCl, and MgCl 2 as well as mixtures LiF–NaF–KF (FLiNaK), LiF–BeF 2 (FLiBe), and NaCl–UCl 3 . The work provides evidence for the validity of energy carrier descriptions of molecular-level heat transfer in molten salts, with implications for improved theories of liquid energy transport in general.

Actinide mixtures↗
DOE OSTI2021

Effect of mono- and multi-valent ionic environments on the in-lattice nanoparticle-grafted single-stranded DNA

The polyelectrolyte (PE) chains respond in a complex manner to the multivalent salt environments, and this behavior depends on pH, temperature, and the presence of specific counter ions. Although much work was done to understand the behaviour of free PE chains, it is important to reveal their behaviour on nanoparticle's surface, where surface constraints, particle geometry, and multi-chain environment can affect their behaviour and contribute to particles assembly states. Our work investigates, using in-situ small-angle x-ray scattering (SAXS), the morphology of PEs (single-stranded DNA) chains grafted onto a surface of spherical gold nanoparticles assembled in a lattice in the presence of monovalent, divalent and trivalent salts. For divalent salts, the DNA brush length was found to decrease at a faster rate with salt concentration than in the monovalent salt environment, while trivalent salt lead to a chain collapse. Using a power law analysis and modified Daoud-Cotton model, we have obtained insight into the mechanism of nanoparticle-grafted chain's response to ionic environments. Our analysis suggests that the decrease in a brush length is due to the conventional electrostatic screening for monovalent systems, whereas for divalent systems both, electrostatic screening and divalent ion bridging must be considered.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Testing to Evaluate Processes Expected to Occur during MSR Salt Spill Accidents

Obtaining a license for a new nuclear reactor requires the identification and assessment of the potential consequences of specified accident scenarios, which are achieved using accident progression models. Those models need to be parameterized and validated using experimental data, but existing experimental data addressing processes relevant to molten salt reactor accidents are sparse. Specifically, experimental data that quantify the sensitives of important processes to the initial conditions of the spill, the ambient environment, and the containment features are needed to parameterize individual process models. Integrated experiments that simulate accident scenarios are also needed to provide data for model validation, but these experiments will require the use of proven methods to quantify the processes under evaluation. The overarching objectives of this work are to develop the methods for simulating the targeted processes, to determine the effectiveness of the methods in producing the data required for model development, to generate data that can be used to parameterize individual process models, and to provide key insights into the behavior of spilled molten salt that should be considered in models. Experimental methods were designed to quantify aspects of individual processes expected to occur during or after a molten salt spill accident that will affect the fate of spilled molten salt and the radionuclides within. These processes include 1) molten salt spreading and heat transfer, 2) molten salt flowing and freezing in tubing, 3) stainless steel corrosion kinetics in molten salt, and 4) molten salt splashing and aerosol generation. The initial tests described in this report were conducted using eutectic FLiNaK to demonstrate the test methods, the data that are generated, and the analyses of the data to derive values needed for modeling. The primary variables that were tested include initial salt temperature and the presence of volatile surrogate fission products (e.g., cesium and iodine). The developed methods are shown to be effective in quantifying the desired processes and can be applied to study more complex salt compositions of interest to molten salt reactor developers, a wide range of environmental conditions of interest to modelers, and additional variables relevant to salt spill accidents. The developed methods and insights gained from laboratory tests can also be incorporated in future large-scale integrated tests used to simulate molten salt spill accidents.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1976

Environmental effects on aluminum fracture

The sustained load stress corrosion cracking (SCC) threshold for aluminum alloy 214 was determined using smooth (sigma sub TH) and precracked (K sub ISCC) specimens, and cyclic load growth behavior in 3.5% NaCl salt solution was studied. The relationship between K sub ISCC and sigma sub TH was also studied. The work showed that 2124-T851 aluminum alloy in plate gage has a moderately high resistance to stress corrosion attack. Experimental results showed that no SCC occurred in the longitudinal and long transverse directions in any of the tests. Some SCC was found by smooth tests in the short transverse direction, and the data were confirmed by two test methods-sigma sub TH = 275 MN/sq m (40 ksi). No SCC was found from compact specimen tests in any direction: surface flaw and center notch specimens evaluated in the short transverse direction exhibited SCC. The data indicate that stress corrosion behavior is defect, size, and stress dependent, but not entirely in accordance with a stress intensity controlled mechanism.

Schwartzberg, F. R.↗
DOE OSTI2023

Effect of metal fluorides on the corrosion of structural materials in molten LiF-NaF-KF

The corrosion of structural materials in molten fluoride salts is predominantly caused by the presence of impurities in the salt. Here, this study focuses on understanding the corrosion behavior of selected alloys in molten FLiNaK salt with addition of similar quantities of metal fluoride impurities such as CrF 2 , CrF 3 , FeF 2 , FeF 3 , and NiF 2 . The results show that the presence of selected metal fluoride impurities increases the extent of corrosion of the selected alloys in molten FLiNaK salt, with the exact effect depending on the thermodynamic stability of the fluoride impurity added as well as the composition of the structural alloy studied.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of different manufacturing methods on polyamide reverse-osmosis membranes for desalination: Insights from molecular dynamics simulations

Membranes are a key technology platform for a broad application of energy-efficient separations. To best serve the separation demands of industry, the manufacturing processes for these membranes are garnering increasing attention. In particular, for water desalination, the industry leading polyamide (PA) reverse osmosis (RO) membranes can be manufactured via molecular layer-by-layer (mLBL) deposition, interfacial polymerization (IP), and 3D-printing technique. However, the influence of different manufacturing methods on PA membrane’s properties is far from understood. Here, in this study, we present the high-pressure transport behavior of water and salt ions for PA membranes formed with IP, mLBL, and 3D-printing through non-equilibrium molecular dynamics simulations. Studies show that membranes fabricated with 3D-printing have similar performances to those manufactured using mLBL, quantified by water permeability, rejection of salt ions, structural integrity, and porosity features. However, the membranes formed with IP exhibit faster water transport, lower rejection, worse structural integrity, and more inhomogeneous network pores than those constructed using mLBL and 3D-printing. The unconnected water-accessible space governs water transport for PA membranes formed with mLBL and 3D-printing, which offers the impermanent open-closed pores that enable water to jump through PA membranes. In contrast, the permeated water-enterable space plays a prominent role in water movement across the PA membrane formed with IP, providing a continuous transport channel at high pressure. Importantly, we observe the more significant compaction features at high pressure for PA membranes formed with IP than mLBL and 3D printing. In short, these findings provide a comprehensive understanding of existing membrane preparation technologies. It also provides a guide for developing the new membrane preparation process at the molecular level.

3D-printing↗
DOE OSTI2024

Cascade CO 2 Insertion in Carbanion Ionic Liquids Driven by Structure Rearrangement

The CO 2 chemisorption in state-of-the-art sorbents based on oxide/hydroxide/amine moieties is driven by strong chemical bonding formation in the carbonate/bicarbonate/carbamate products, which in turn leads to high energy input in sorbent regeneration. In addition, the CO 2 uptake capacity was limited by the active sites’ utilization efficiency, with each active site incorporating one CO 2 molecule or less. In this work, a new concept and generation of sorbent was developed to achieve cascade insertion of multiple CO 2 molecules by leveraging structure rearrangement as the driving force, leading to in situ generation of extra CO 2 -binding sites and significantly reduced energy input for CO 2 release. The designed ionic liquids (ILs) containing carbanions with conjugated and asymmetric structure, deprotonated (methylsulfonyl)acetonitrile ([MSA]) anion, allowed the cascade insertion of two CO 2 molecules via consecutive C–C and O–C bond formations. The proton transfer and structure rearrangement of the carboxylic acid intermediates played critical roles in stabilizing the first integrated CO 2 and generating extra electron-rich oxygen sites for the insertion of the second CO 2 . The structure variation and reaction pathway were confirmed by operando spectroscopy, magnetic resonance spectroscopy (NMR), mass spectroscopy, and computational chemistry. The energy input in sorbent regeneration could be further reduced by harnessing the phase-changing behavior of the carbanion salts in ether solutions upon reacting with CO 2 , avoiding the energy consumption in heating the solvent. In conclusion, the fundamental insights obtained herein provide a promising approach to greatly improve the CO 2 sorption performance via sophisticated molecular-scale structural engineering of the sorbents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

The Electrochemical Behavior of Tellurium Tetrachloride in LiCl-KCl Eutectic Molten Salt at 450 ºC

Cyclic voltammetry CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy measurements were carried out in 1 and 5 wt% TeCl 4 containing LiCl-KCl eutectic molten salt at 450 °C using tungsten and glassy carbon as working electrodes. Reduction of Te(IV) to Te(0) occurred in three steps at potentials more negative than -0.4 V Ag/AgCl . The Te(0) was further reduced to Te 2- at more negative potentials. Formation of Te 2- was observed at potentials more negative than -2.2 V Ag/AgCl . Diffusivities of Te 4+ , Te 2+ , and Te 2- and their formal potentials were estimated from the CV data. The diffusion coefficients of Te 4+ , Te 2+ and Te 2- were 0.9 × 10 -5 , 3.8 × 10 -5 , and 1.5 × 10 -5 cm 2 s -1 , respectively in the 1 wt% TeCl 4 containing LiCl-KCl molten salt. The diffusivity of Te species generally decreased with increase in the concentration of TeCl 4 .

Electrochemistry↗
DOE OSTI2021

Lowering the Impedance of Lanthanum Strontium Manganite-Based Electrodes with Lanthanum Oxychloride and Lanthanum Scavenging Chloride Salts

The impact of infiltrating chloride salts on the electrochemical behavior of lanthanum strontium manganite-yttria stabilized zirconia (LSM-YSZ) cathodes was investigated under solid oxide fuel cell operation. Infiltrating a lanthanum chloride solution resulted in the formation of a lanthanum oxychloride (LaOCl) phase. A LaOCl phase also formed by infiltrating an ammonium chloride solution; however, lanthanum was scavenged from the LSM phase to form LaOCl. The third infiltrating solution, a combination of zirconium chloride and yttrium nitrate, formed LaOCl by scavenging lanthanum from LSM and produced YSZ nanoparticles. Electrochemical impedance spectroscopy results suggest that LaOCl improves oxygen adsorption kinetics compared to a baseline LSM-YSZ cathode, reducing the low frequency impedance by 30%. In addition, scavenging lanthanum from LSM improved oxygen ion diffusion polarization as indicated by the observed 40% reduction in high frequency impedance and improved serial ohmic resistance by 19%. Finally, YSZ nanoparticles further reduced the high frequency impedance and ohmic resistance by 45% and 23%, respectively. The findings reveal new strategies for lowering the impedance of LSM-YSZ cathodes.

Taylor, Thomas H.↗
NASA NTRS1980

Sandia Laboratories in-house activities in support of solar thermal large power applications

The development of thermal energy storage subsystems for solar thermal large power applications is described. The emphasis is on characterizing the behavior of molten nitrate salts with regard to thermal decomposition, environmental interactions, and corrosion. Electrochemical techniques to determine the ionic species in the melt and for use in real time studies of corrosion are also briefly discussed.

Mar, R. W.↗
NASA NTRS2002

Cryogenic Reflectance Spectroscopy in Support of Planetary Missions

Present understanding of planetary composition is based primarily on remotely-sensed data, and in particular upon ultraviolet, visible, and infrared spectroscopy. Spectra acquired by telescopic and spacecraft instruments are compared to laboratory measurements of pure materials in order to identify surface components based on characteristic absorption features. Cryogenic spectral measurements are necessary for the study of worlds beyond the Earth's orbit. While some materials exhibit only small spectral changes as a function of temperature, many others are strongly temperature-dependent. For example, hydrated salts exhibit different spectral behavior under conditions appropriate to Europa than at terrestrial temperatures. The icy satellites of the outer solar system contain significant quantities of volatile ices which do not even exist at standard temperature and pressure (STP). A comprehensive spectral database of ices and minerals covering a wide temperature range will have applications ranging from the study of comets and Kuiper Belt objects to outer planet satellites and the polar regions of Mars. Efforts are presently underway at NASA-Ames to develop capabilities which will contribute to such a database. As spacecraft instruments feature increasing spatial and spectral resolution, appropriate laboratory reference spectra become increasingly critical to accurate interpretation of the spacecraft data.

Dalton, J. B.↗
DOE OSTI2026

Impact of Nd ions on the chemical kinetic behavior of radiolytic transients in molten LiCl-KCl-NdCl3 salt mixtures

Pyrochemical reprocessing technologies can be used to recover valuable materials from used nuclear fuel (UNF), such as uranium. However, other critical materials, such as fission product neodymium, are challenging to recover from molten chloride eutectic mixtures (LiCl-KCl) due to the presence of multivalent states (Nd2+/Nd3+), disproportionation reactions, and re-dissolution in the molten chloride salt. Understanding, predicting, and controlling these processes is further complicated by the presence of ionizing radiation fields, for which little is known on the interaction of neodymium ions with the radiolytic transients (es– and Cl2.–) in molten LiCl-KCl salt mixtures. Here, chemical kinetics, from integrated electron pulse irradiation and transient absorption spectroscopy, are presented for the reaction of Nd3+ ions with es– and Cl2.– as a function of temperature (400–600 ?).

36 - MATERIALS SCIENCE↗