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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Materials processing in space program tasks-supplement

An overview of the program scope for managers and scientists in industry, university, and government communities is provided. An introductory description of the program, its history, strategy, and overall goals; identification of the organizational structures and people involved; and a description of each research task, together with a list of recent publications are included. The tasks are grouped into six categories: crystal growth; solidification of metals, alloys, and composites; fluids, transports, and chemical processes; and ultrahigh vacuum and containerless processing technologies; combustion experiments; and experimental technology.

Pentecost, E.↗
NASA NTRS1989

Land altimetry using satellite data from the GEOSAT sea altimeter

Several techniques are proposed or assessed from the GEOSAT sea altimeter, and changes are recommended in future RADAR altimeters. The first technique tried was to cross-correlate each waveform with the preceding one. Then the position giving the maximum correlation was taken as the correct placement of the new waveform in its data window. The resulting altitude profile was slightly more variable than that of the on-board tracker over flat rock (Salar de Uyuni), so apparently successive waveforms are too dissimilar to correlate. When cross-correlation failed, compensation was made for averaging. Raw waveforms are averaged in groups of 100 and it is these average waveforms which are available for ground processing. But while the 100 are being received, the window position is moved in time, at different constant rates for the first 50 and last 50. Assuming an unchanging waveform and a single window rate for the 100, first and last waveforms were obtained. Averaging their half-height arrival times gave an altitude profile similar to the median and centroid methods. The variability of this altitude profile suggests that even raw waveforms in a group of 100 may be too dissimilar to correlate. In other techniques, the pulse was judged to have arrived when one of these criteria was met: the wave amplitude meets a certain absolute threshold; wave amplitude meets a certain relative threshold; certain fraction of the area of the waveform has passed; and centroid of the waveform has passed. All methods gave altitude profiles at least as variable as the on-board tracker, and all were biased at least 0.5 meter to low altitudes, except the threshold detector. The threshold detector can be filtered spatially to resemble the on-board tracker, and perhaps it could be implemented without feedback. For operating over land, these changes are recommended in future altimeters: The window should not move while raw waveforms are being averaged; some of the raw waveforms should be telemetered to earth for study, placing the waveform in the window should allow for shape variety; and some form of threshold detector might be used to find the signal and place it.

Luft, Philip E.↗
NASA NTRS2013

A Framework for Robust Multivariable Optimization of Integrated Circuits in Space Applications

Application Specific Integrated Circuit (ASIC) design for space applications involves multiple challenges of maximizing performance, minimizing power and ensuring reliable operation in extreme environments. This is a complex multidimensional optimization problem which must be solved early in the development cycle of a system due to the time required for testing and qualification severely limiting opportunities to modify and iterate. Manual design techniques which generally involve simulation at one or a small number of corners with a very limited set of simultaneously variable parameters in order to make the problem tractable are inefficient and not guaranteed to achieve the best possible results within the performance envelope defined by the process and environmental requirements. What is required is a means to automate design parameter variation, allow the designer to specify operational constraints and performance goals, and to analyze the results in a way which facilitates identifying the tradeoffs defining the performance envelope over the full set of process and environmental corner cases. The system developed by the Mixed Signal ASIC Group (MSAG) at the Goddard Space Flight Center is implemented as framework of software modules, templates and function libraries. It integrates CAD tools and a mathematical computing environment, and can be customized for new circuit designs with only a modest amount of effort as most common tasks are already encapsulated. Customization is required for simulation test benches to determine performance metrics and for cost function computation. Templates provide a starting point for both while toolbox functions minimize the code required. Once a test bench has been coded to optimize a particular circuit, it is also used to verify the final design. The combination of test bench and cost function can then serve as a template for similar circuits or be re-used to migrate the design to different processes by re-running it with the new process specific device models. The system has been used in the design of time to digital converters for laser ranging and time-of-flight mass spectrometry to optimize analog, mixed signal and digital circuits such as charge sensitive amplifiers, comparators, delay elements, radiation tolerant dual interlocked (DICE) flip-flops and two of three voter gates.

DuMonthier, Jeffrey↗
DOE OSTI2020

Sequence-selective dynamic covalent assembly of information-bearing oligomers

Relatively robust dynamic covalent interactions have been employed extensively to mediate molecular self-assembly reactions; however, these assembly processes often do not converge to a thermodynamic equilibrium, instead yielding mixtures of kinetically-trapped species. Here, we report a dynamic covalent self-assembly process that mitigates kinetic trapping such that multiple unique oligomers bearing covalently coreactive pendant groups are able to undergo simultaneous, sequence-selective hybridization with their complementary strands to afford biomimetic, in-registry molecular ladders with covalent rungs. Analogous to the thermal cycling commonly employed for nucleic acid melting and annealing, this is achieved by raising and lowering the concentration of a multi-role reagent to effect quantitative dissociation and subsequently catalyze covalent bond rearrangement, affording selective assembly of the oligomeric sequences. The hybridization specificity afforded by this process further enabled information encoded in oligomers to be retrieved through selective hybridization with complementary, mass-labeled sequences.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Kinetics of the functionalization of mesoporous silica nanoparticles: Implications on surface group distributions, adsorption and catalysis

The post-synthesis functionalization (grafting) kinetics of mesoporous silica nanoparticles (MSN) with organotrimethoxysilanes (R-TMS) is studied via solution 1 H NMR spectroscopy. The process involves a rapid adsorption/ desorption pre-equilibrium followed by reaction of R-TMS with surface silanols. Grafting rates are affected by the functional group in R-TMS. For example, the grafting rate of aminopropyl-trimethoxysilane (AP-TMS) is one order of magnitude higher than other R-TMS. High concentrations of AP-TMS result in substrate-inhibition kinetics, likely due to steric and mobility constraints for reactant alignment at high coverage. The higher rates of AP-TMS grafting indicate a catalytic effect of amine groups. This effect depends on the amine’s basicity and can be used to control the grafting rates and degree of condensation of other R-TMS. Adjusting the rate of mercaptopropyl-trimethoxysilane (MP-TMS) grafting using amines gives MP-MSN materials of varying adsorptive and catalytic activities, illustrated by Pd scavenging experiments and use of Pd@MP-MSN as catalysts for a Suzuki-Miyaura cross-coupling reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Solid phase characterization and transformation of illite mineral with gas-phase ammonia treatment

In situ remediation applications of ammonia (NH 3 ) gas have potential for sequestration of subsurface contamination. Ammonia gas injections initially increase the pore water pH leading to mineral dissolution followed by formation of secondary precipitates as the pH is neutralized. However, there is a lack of understanding of fundamental alteration processes due to NH 3 treatment. In these batch studies, phyllosilicate minerals (illite and montmorillonite) were exposed to NH 3 gas with subsequent aeration to simulate in situ remediation. Following treatments, solids were characterized using a variety of techniques, including X-ray diffraction, N 2 adsorption-desorption analysis for surface area, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and microscopy methods to investigate physicochemical transformations. The results of this study indicate that, at high pH, the clays are altered as observed by differences in morphology and particle size via microscopy. However, the two clays interact differently with NH 3 . While montmorillonite interlayers collapsed due to intercalation, illite layers were unaffected as confirmed by FTIR analysis. Further, structural changes in silicate ([SiO 4 ] n- ) and aluminol (Al-OH) groups were identified by NMR and FTIR. This research showed that mineral alteration processes occur during and after NH 3 gas treatment which may be used to remove radionuclides from the aqueous phase through sorption, co-precipitation, and coating with secondary phyllosilicate alteration products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

Overview of SatCORPS Satellite-Derived Cloud and Radiation Retrieval Coverage of ARM Domains

The ARM Climate Research Facility program maintains a number of climatically representative sites, which provide long-term cloud- and climate-monitoring records via ground-based instrumentation. These measurements provide a valuable data record over a localized region, but can be greatly enhanced by use of satellite monitoring. Satellite analyses over larger domains can provide parameters helpful for monitoring climate and evaluating models. The NASA/Langley Cloud group routinely derives such cloud and radiative parameters, from various geostationary and polar-orbiting satellite coverage over ARM sites; the group provides near-realtime analyses covering the 3 ARM fixed sites, as well as the GO-Amazon AMF site. This is accomplished by employing a suite of algorithms including VISST (Visible Infrared Solar Split-Window Technique), SIST (Solar Infrared Split-Window Technique), and SINT (Solar-infrared Infrared Near-Infrared Technique), now collectively called SatCORPS (Satellite Cloud Observations and Radiative Property retrieval System). An overview and catalog of SatCORPS-derived datasets processed for ASR, and available from both the ARM archive and the NASA/Langley Cloud group website, is provided. Specific improvements included in recently added datasets such as GO-Amazon and Azores are highlighted, including an improved cloud-detection mask, as well as improvements in derived Top-of-Atmosphere (TOA) SW albedoes and LW fluxes. New narrowband-to-broadband (NB-BB) fits and corrections for improved TOA fluxes are illustrated, including MTSAT-1/CERES Aqua NB-BB fits for the TWPICE field campaign, as well as new fits covering the Azores region which incorporate GERB TOA fluxes (Geostationery Earth Radiation Budget). Finally, validation of the reprocessed SatCORPS datasets is shown.

M M Khader↗
DOE OSTI2022

Skeletal Ni electrode-catalyzed C-O cleavage of diaryl ethers entails direct elimination via benzyne intermediates

Diaryl ethers undergo electrocatalytic hydrogenolysis (ECH) over skeletal Ni cathodes in a mild, aqueous process that achieves direct C-O cleavage without initial benzene ring saturation. Mechanistic studies find that aryl phenyl ethers with a single para or meta functional group (methyl, methoxy, or hydroxy) are selectively cleaved to the substituted benzene and phenol, in contrast to recently reported homogeneous catalytic cleavage processes. Ortho positioning of substituents reverses this C-O bond selectivity, except for the 2-phenoxyphenol case. Together with isotope labeling and co-solvent studies, these results point to two distinct cleavage mechanisms: (a) dual-ring coordination and C-H activation, leading to vicinal elimination to form phenol and a surface-bound aryne intermediate which is then hydrogenated and released as the arene; and (b) surface binding in keto form by the phenolic ring of the hydroxy-substituted substrates, followed by direct displacement of the departing phenol. Notably, acetone inhibits the well-known reduction of phenol to cyclohexanol, affording control of product ring saturation. A byproduct of this work is the discovery that the ECH treatment completely defluorinates substrates bearing aromatic C-F and C-CF 3 groupings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Forced torsional properties of PMR composites with varying nadic ester concentrations and processing histories

PMR polyimide resin was prepared from 4,4'-methylenedianiline, the dimethyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid and the monomethyl ester of 5-norbornene-2,3-dicarboxylic acid (NE). The NE group serves as a chain terminator and crosslinking site. PMR/Celion 6000 composites were fabricated from resins having varying NE concentrations using two molding processes, and the laminates characterized in forced torsion. Glass transition temperatures (T(g)) of 360-390 C were observed in the crosslinked resins, as compared with the literature value of 284 C reported for the uncrosslinked system. T(g) did not decrease with decreasing NE concentrations over the range from 2.0 to 1.25 moles. Stoichiometry, within the range studied, showed little influence on shear properties; however, a 25% variation in matrix shear modulus with processing was observed. The G(12) values determined in forced torsion were in excellent agreement with those reported from tensile tests of + or - 45 deg laminates. A branching and possible secondary crosslink mechanism is proposed based on dynamic mechanical behavior and infrared spectra of the composites.

Hurwitz, F. I.↗
DOE OSTI2021

Data Processing Package for Cyclic Integrated Reversible Bending Fatigue Testing

A data processing software package has been introduced. The package was developed using MATLAB with the aid of the Curve Fitting Toolbox. The package is made up of four modules: pre-processing, data processing for static testing, data processing for monitoring, and data processing for measurements. CIRFT data are structured with multiple levels of architecture involving group, specimen, session, and scan/block. The degree of complexity of the data structure depends on whether a test is static or cyclic.The test results are presented in figures, scatter plots, and tables. For static testing, the output in tables provides bending mechanical properties and characteristic points of moment–curvature relation: flexural rigidities in linear segments of loading and unloading stages, intersection points between characteristic segments of the curve, and equivalent stress and strain quantities. For cyclic testing, the table output lists control and fatigue life and responsive/dependent quantities including moment, curvature, flexural rigidity, flexural hysteresis, rigidity phase angle, and equivalent stresses and strains. In addition, derivatives such as half-gage length and sensor spacing correction are included. The output also provides standard deviations of the reported quantities when they are applicable or available. The data processing package can serve as a fundamental characterization tool in mechanical study of materials. The package is intended primarily for data processing for the CIRFT process and can also be used in applications for which similar testing requirements exist.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Role of Gd{sup 3+} ion on downshifting and upconversion emission properties of Pr{sup 3+}, Yb{sup 3+} co-doped YNbO{sub 4} phosphor and sensitization effect of Bi{sup 3+} ion

Dual-mode luminescence (downshifting-DS and upconversion-UC) properties of Pr{sup 3+}/Yb{sup 3+} co-doped Y{sub 1−x}Gd{sub x}NbO{sub 4} (x = 0.0, 0.5, and 1.0) phosphors synthesized by solid state reaction technique have been explored with and without Gd{sup 3+} ion. The structural characterizations (XRD, SEM, and FTIR) confirm the pure phase of YNbO{sub 4} phosphor. Further, with the Gd{sup 3+} ion co-doping, the YNbO{sub 4} phosphors having a random shape and the large particle size are found to be transformed into nearly spherical shape particles with the reduced particle size. The optical band gaps (E{sub g}) of Y{sub 1−x}Gd{sub x}NbO{sub 4} (x = 0.00, 0.25, 0.50, and 1.00) calculated from UV-Vis-NIR measurements are ∼3.69, 4.00, 4.38, and 4.44 eV, respectively. Moreover, YNbO{sub 4} phosphor is a promising blue emitting material, whereas Y{sub 1−x−y−z}Pr{sub y}Yb{sub z}Gd{sub x}NbO{sub 4} phosphor gives intense green, blue, and red emissions via dual-mode optical processes. The broad blue emission arises due to (NbO{sub 4}){sup 3−} group of the host with λ{sub ex} = 264 nm, whereas Pr{sup 3+} doped YNbO{sub 4} phosphor gives dominant red and blue emissions along with comparatively weak green emission on excitation with λ{sub ex} = 300 nm and 491 nm. The concentration dependent variation in emission intensity at 491 nm ({sup 3}P{sub 0}→{sup 3}H{sub 4} transition) and 612 nm ({sup 1}D{sub 2}→{sup 3}H{sub 4} transition); at 612 nm ({sup 1}D{sub 2}→{sup 3}H{sub 4} transition) and 658 nm ({sup 3}P{sub 0}→{sup 3}F{sub 2} transition) of Pr{sup 3+} ion in YNbO{sub 4} phosphor with λ{sub ex} = 300 nm and 491 nm excitations, respectively, has been thoroughly explored and explained by the cross-relaxation process through different channels. The sensitization effect of Bi{sup 3+} ion co-doping on DS properties of the phosphor has also been studied. The observed DS results have been optimized by varying the concentration of Pr{sup 3+} and Bi{sup 3+} ions, and the results are explained by the well-known simple band structure model. The study of Gd{sup 3+} co-doping reveals noticeable differences in DS characteristics of Y{sub 1−x}Pr{sub x}NbO{sub 4} phosphors: the overall decrement and increment (except for 612 nm emission) in intensity of DS emission on excitation with λ{sub ex} = 264 nm and 491 nm, respectively. These observations have been thoroughly explained, and the {sup 1}D{sub 2}→{sup 3}H{sub 4} transition (612 nm) of Pr{sup 3+} ion is found to be strongly dependent on surrounding environment of the host matrix. The UC properties of Y{sub 0.95−x}Pr{sub x}Yb{sub 0.05}NbO{sub 4} phosphors have been explored using Near Infra-Red (NIR) excitation. The material gives intense green and relatively weak blue and red UC emissions with λ{sub ex} = 980 nm. Interestingly, the UC emission intensity is further enhanced in the case of Y{sub 0.949−x}Pr{sub 0.001}Yb{sub 0.05}Gd{sub x}NbO{sub 4} phosphors. In addition, the less explored laser induced heating effect with the pump power as well as the irradiation time on the UC emission has been explored in Y{sub 0.949−x}Pr{sub 0.001}Yb{sub 0.05}Gd{sub x}NbO{sub 4} (x = 0, 0.5, and 0.949) phosphor samples, and subsequently, this feature has been found to be superior for Gd{sub 0.949}Pr{sub 0.001}Yb{sub 0.05}NbO{sub 4} phosphor. The comparative study between the two hosts, viz., YNbO{sub 4} and GdNbO{sub 4} shows that GdNbO{sub 4} is better than YNbO{sub 4} for UC emission behavior; however, a reverse is observed as for as DS behavior is concerned only for the particular excitation wavelength (λ{sub ex} = 264 nm).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength “trabecular Nitinol” scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1–1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

36 MATERIALS SCIENCE↗
NASA NTRS2008

Final Report on NASA Portable Laser Coating Removal Systems Field Demonstrations and Testing

Processes currently used throughout the National Aeronautics and Space Administration (NASA) to remove corrosion and coatings from structures, ground service equipment, small parts and flight components result in waste streams consisting of toxic chemicals, spent media blast materials, and waste water. When chemicals are used in these processes they are typically high in volatile organic compounds (VOC) and are considered hazardous air pollutants (HAP). When blast media is used, the volume of hazardous waste generated is increased significantly. Many of the coatings historically used within NASA contain toxic metals such as hexavalent chromium, and lead. These materials are highly regulated and restrictions on worker exposure continue to increase. Most recently the Occupational Safety and Health Administration (OSHA) reduced the permissible exposure limit (PEL) for hexavalent chromium (CrVI) from 52 to 5 micrograms per cubic meter of air as an 8-hour time-weighted average. Hexavalent chromium is found in numerous pretreatment and primer coatings used within the Space Shuttle Program. In response to the need to continue to protect assets within the agency and the growing concern over these new regulations, NASA is researching different ways to continue the required maintenance of both facility and flight equipment in a safe, efficient, and environmentally preferable manner. The use of laser energy to prepare surfaces for a variety of processes, such as corrosion and coating removal, weld preparation, and non destructive evaluation (NDE) is a relatively new application of the technology that has been proven to be environmentally preferable and in many cases less labor intensive than currently used removal methods. The novel process eliminates VOCs and blast media and captures the removed coatings with an integrated vacuum system. This means that the only waste generated are the coatings that are removed, resulting in an overall cleaner process. The development of a Portable Laser Coating Removal System (PLCRS) started as the goal of a Joint Group on Pollution Prevention (JG-PP) project, led by the Air Force, where several types of lasers in several configurations were thoroughly evaluated. Following this project, NASA decided to evaluate the best performers on processes and coatings specific to the agency. Laser systems used during this project were all of a similar design, between 40 and 500 Watts, most of which had integrated vacuum systems in order to collect materials removed from substrate surfaces during operation.

Rothgeb, Matthew J↗
NASA NTRS2002

Application of LES (Large Eddy Simulation) to Understanding and Parameterizing the Arctic Cloudy Boundary Layer

The GEWEX (Global Energy and Water Cycle Experiment) Cloud Systems Studies Working Group 5 Polar Clouds was formed largely to exploit the enormous potential of the FIRE.ACE (FIRE Arctic Cloud Experiment) and SHEBA (Surface Heat Budget of the Arctic Ocean) data sets to improve parameterizations of clouds, radiation, and atmospheric boundary layer processes in the polar regions. The web page for this project is a clearinghouse of information for polar clouds in general and specifically for FIRE.ACE and SHEBA modelling activities. Note that the GCSS Working Group and Polar Clouds leverages heavily the FIRE.ACE investment, since it involves a large group of international scientists and has adopted the modelling goals and other issues related to cloud and radiation processes that are articulated by the FIRE.ACE Science Plan. The supplemental funds in this proposal are targeted at providing the continued coordination for the GCSS Working Group on Polar Clouds, which will insure that final FIRE.ACE project objectives regarding modelling and cloud and radiative processes are achieved.

Curry, Judith↗
NASA NTRS2019

Role of CEOS Working Group on Calibration and Validation in Analysis Ready Data Products

The Committee on Earth Observation Satellites (CEOS) is leading the CEOS Analysis Ready Data for Land (CARD4L) initiative. A goal of analysis ready data products is to limit the effort needed by users to pre-process the data allowing them to concentrate on the end products. CARD4L provides a set of specifications that data providers need to meet to be considered to satisfy CARD4L. One of the working groups within CEOS, the Working Group on Calibration and Validation (WGCV) is providing a peer review process to evaluate the documentation of the data providers validation and data product accuracy assessment. The approach makes use of the expertise within WGCV to collaborate with both the CEOS Land Surface Imaging Virtual Constellation and the data providers to work towards acceptance of the...

Thome, K.↗
NASA NTRS1983

Space station needs, attributes and architectural options study commercialization working group briefing

The benefits for each of the following commercial areas was investigated: communications, remote sensing, materials processing in space, low Earth orbit (LEO) satellite assembly, testing, and servicing, and space tourism. In each case, where economic benefits are derived, the costs for accomplishing tasks with the Space Station are compared with the cost with the Space Transportation System only.

Source record↗
DOE OSTI2019

Directed Hydrogen Bond Placement: Low Viscosity Amine Solvents for CO2 Capture

Capture of CO2 from power generation is required for its conversion or sequestration. Toward this goal, numerous CO2 capture processes have been developed, with the most widely deployed technology utilizing aqueous solutions of amines. Our group has focused on the design of several classes of water-lean solvents in order to identify molecular-level descriptors to control materials properties such as viscosity and regeneration energy. Large scale molecular simulations have shown that strategic placement of hydrogen bonding and tuning of the acid/base equilibria are critical for controlling viscosity at CO2-rich loadings. Here, we extend these principles to a new class of pyridine-based molecules with a secondary amine functionality for binding CO2. The result is a class of water-lean amines that retain high gravimetric capacity (20%) while exhibiting the lowest CO2-rich viscosities (<150 cP, 40 °C) of any 100% concentrated amine currently known. Additionally, these newly identified solvents exhibit regeneration temperatures as low as 60 °C when applying a polarity swing assisted regeneration, resulting in a solvent that can conceptually absorb and desorb CO2 with only a 20 °C temperature swing.

Malhotra, Deepika↗
DOE OSTI2014

Anisotropic Elastic Resonance Scattering model for the Neutron Transport equation

The resonance scattering transfer cross-section has been reformulated to account for anisotropic scattering in the center-of-mass of the neutron-nucleus system. The main innovation over previous implementations is the relaxation of the ubiquitous assumption of isotropic scattering in the center-of-mass and the actual effective use of scattering angle distributions from evaluated nuclear data files in the computation of the angular moments of the resonant scattering kernels. The formulas for the high order anisotropic moments in the laboratory system are also derived. A multi-group numerical formulation is derived and implemented into a module incorporated within the NJOY nuclear data processing code. An ultra-fine energy mesh cross section library was generated using these new theoretical models and then was used for fuel assembly calculations with the PARAGON lattice physics code. The results obtained indicate a strong effect of this new model on reactivity, multi-group fluxes and isotopic inventory during depletion.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗