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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 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

A new set-up for in-situ probing of radiation effects in materials and electronic devices

The micro-probe facility installed at the Van de Graff accelerator at CTN/IST permits simultaneous measurements of Rutherford Backscattering Spectrometry (RBS), Particle Induced X-ray Emission (PIXE) and Iono-Luminescence (IL). Here we present a recent up-grade of the measurement chamber allowing improved optical sensitivity in IL measurements and opening the possibility to perform simultaneously electrical measurements. Combinations of all these characterization techniques make this setup a powerful tool to characterize and modify different materials with spatial resolution. In particular, it can be used to study radiation effects in different materials and electronic devices in-situ. IL is a luminescence technique that uses the ion beam as the excitation source. Compared with other luminescence techniques with spatial resolution like Cathodoluminescence, this technique has the advantage to probe deeper regions of the sample, several microns below the surface. The same ion beam used to produce luminescence, can create a high density of defects, in a controllable way and the new set-up allows monitoring optical and electrical properties in realtime. In this work we combine IL with I-V curve measurements to assess the response of Ga{sub 2}O{sub 3} and GaN to proton irradiation. Ga{sub 2}O{sub 3} and GaN are emerging materials for applications in high power electronics and are considered for radiation resistant electronics. We will present a systematic study of the changes in IL and conductivity in Ga{sub 2}O{sub 3} and GaN samples with the energy of the ion beam and with the time of exposure. In particular, it was observed that during the irradiation some luminescence bands related with intrinsic point defects decrease while other new bands appear. Simulations using the SRIM code were used to determine the depth profiles of ionization and displacement events, helping to correlate the optical and electrical response of the materials with certain radiation effects. These studies show the potentialities of measuring simultaneously IL and electrical conductivity and how these two characterization techniques can work as a sensitive tool to detect and quantify radiation effects. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Setting an optimal procedure for transferring intermediate radioactive effluents: contribution of laboratory experiments - 15234

The INB35 nuclear facility at the CEA Saclay center is in charge of collecting and treating radioactive effluents generated from site's research activities. The first step of the process consists of an evaporation. The concentrate is an IL radioactive suspension with high salt concentration and suspended matter content. Until the 1990's, the resulting effluents were bitumen coated and since 2012 they have been cemented. During the 1990's, concentrates were stored in 7 tanks, named MA50X with X from 1 to 7. With today's changes to safety regulations, the effluents must now be transferred before tank dismantling. According to the site records, the compositions of the liquid wastes MA501, MA502, MA503, MA504, MA506 and MA507 are similar. From 2013 to 2014, effluents contained in MA502, MA503, MA504 tanks have been transferred. Several difficulties have been encountered: - The tanks were historically different, especially manhole tank access - Since the 1990's, effluent composition has changed due to water evaporation. The salt concentration has increased and insoluble elements have formed a deposit in the bottom of the tanks resulting in high composition heterogeneity - In some tanks, a wall breeze-blade exists dividing the tank into two zones, which complicates the interventions. Major challenges have been met and will be described in the presentation. - To obtain an effluent which is as homogeneous as possible, the duration of mixing has been optimized. - To pump the liquid, it has been necessary to treat the effluent with nitric acid. This step has been optimized thanks to experiments in laboratory and hydrodynamic modelling. - A mobile workshop has been designed in order to perform the effluent transfer. It is set up directly above the tanks and can be moved from one tank to another on rails. Laboratory experiments have been carried out to characterize the suspension and sludge in order to understand its chemical behavior. - The treatment of the effluent has been studied in the laboratory and is now mastered. - The analytical strategy has been optimized. The close collaboration between the analytical laboratory and the dismantling project was a real advantage. Thanks to this, the duration of the last transfer on MA 504 was reduced by half, compared to the first operations. Transfer operations will be described and the differences and similarities between laboratory and in-situ observations will be pointed out. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

DOE Oak Ridge Cleanup History - Setting the Stage for Future Success - 16273

The operation of the three DOE sites in Oak Ridge for 70+ years has produced a complex set of contaminated environmental media (water, soil, air) and facilities. In order to effectively plan for cleanup of the remaining contamination, understanding the causes of the contamination and the techniques that have proven effective in cleanup to date is essential. This paper summarizes the operations and resulting radioactive and chemical releases, the cleanup that has been accomplished to date, and the cleanup remaining to be completed. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Turbomachine blade trailing edge cooling circuit with turn passage having set of obstructions

A turbomachine blade, and a coupon for a turbomachine blade, are disclosed. The blade may include an airfoil body having a pressure side and a suction side connected by a leading edge and a trailing edge, a coolant feed passage defined in the airfoil body, and a coolant reuse passage defined in the airfoil body. The blade may also include a first cooling circuit defined in the airfoil body. The first cooling circuit may include a rearward passage extending toward the trailing edge from and fluidly coupled to the coolant feed passage, and a radially spreading return passage extending away from the trailing edge toward and fluidly coupled to the coolant reuse passage. The cooling circuit may also include a radially extending turn passage coupling the rearward passage and the radially spreading return passage. A first set of obstructions may be positioned in the radially extending turn passage.

Dyson, Thomas Earl↗
DOE OSTI2016

Experimental Data Sets for CFD Calculations of Flow and Heat Transfer in Deformed Fuel Assemblies

Liquid-metal fast-breeder reactors (LMFBRs) have traditionally used fuel assemblies consisting of a hexagonal array of pins enclosed in a hexagonally shaped duct. Each fuel pin is surrounded by a wire that is wrapped in a helical configuration, which is used to separate the pins sufficiently to allow sodium coolant to flow through the assembly. The helical wire wrap also promotes mixing of the coolant. Experience with these assemblies has shown that they begin to deform with time during normal operation leading to significant changes in core thermal-hydraulics. For example, deformations of assemblies in the Experimental Breeder Reactor-2 and the Fast Flux Test Facility led to pin overheating resulting from pin-to-duct and pin-to-pin contact. This problem is well known and was investigated extensively in the 1970's and early 1980's. This was a period, however, before the development of modern Computational Fluid Dynamics (CFD) computer codes. Therefore, the experiments performed at the time did not record their results in sufficient detail to be useful for compiling validation datasets for CFD codes. Most of the experiments focused only on bulk measurements, such as the pressure drop across the bundle. When the effects of deformation of the fuel assembly were investigated, the studies performed to quantify these effects considered only bare pins without the wire wrap. With the resurgence of interest in LMFBRs in recent years, particularly in designs that leverage long-life performance of the fuel, the need has arisen for data that are suitable for the validation and benchmarking of CFD codes to predict the thermal-hydraulic behavior of flow in wire-wrapped fuel bundles. Such data must include high-resolution, transient, full-field measurements of the fluid velocity and temperature and an accurate record of the test conditions, including a precise description of the geometry. This paper describes a project to produce a validation-quality set of data that can be used to benchmark CFD codes for modeling flow and thermal performance in wire-wrapped fuel assemblies of the kind used by LMFBR designs. In addition, this effort investigates the changes to the flow and other phenomena that occur in the deformed geometries that can form later in a fuel assembly's life. This work is a joint effort of four organizations. The experimental work is being performed by AREVA and Texas A and M University. The computational work, both to support the experiments and to perform blind benchmark calculations, is being done by TerraPower, LLC, and Argonne National Laboratory (ANL). The experiments use a geometry that consists of a complete assembly of 61 wire-wrapped pins, which is surrounded by a hexagonal duct. This configuration is considered the minimum size necessary to adequately capture the important results of interest, such as the thermal gradients across the assembly and the velocity field effects in the assembly resulting from the surrounding duct. These types of effects cannot be captured by a geometry consisting of only a small group of fuel pins. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Data-Driven Computation of Probabilistic Marching Cubes for Efficient Visualization of Level-Set Uncertainty

Uncertainty visualization is an important emerging research area. Being able to visualize data uncertainty can help scientists improve trust in analysis and decision-making. However, visualizing uncertainty can add computational overhead, which can hinder the efficiency of analysis. In this paper, we propose novel data-driven techniques to reduce the computational requirements of the probabilistic marching cubes (PMC) algorithm. PMC is an uncertainty visualization technique that studies how uncertainty in data affects level-set positions. However, the algorithm relies on expensive Monte Carlo (MC) sampling for the multivariate Gaussian uncertainty model because no closed-form solution exists for the integration of multivariate Gaussian. In this work, we propose the eigenvalue decomposition and adaptive probability model techniques that reduce the amount of MC sampling in the original PMC algorithm and hence speed up the computations. Our proposed methods produce results that show negligible differences compared with the original PMC algorithm demonstrated through metrics, including root mean squared error, maximum error, and difference images. We demonstrate the performance and accuracy evaluations of our data-driven methods through experiments on synthetic and real datasets.

Athawale, Tushar↗
DOE OSTI2024

A Tutorial Set to Prepare for Science with the Vera C. Rubin Observatory

In this poster the Rubin Observatory's Community Science team (CST) presents its current suite of tutorials, which are designed to help people make use of simulated data sets in preparation for the upcoming Legacy Survey of Space and Time (LSST). We will show examples of the tutorial contents, provide custom learning modules for different astronomical fields, and describe the online environment for data analysis (the Rubin Science Platform; RSP). We will also supply a checklist for how to obtain an RSP account and access the tutorials. All are welcome to drop by the poster or the Rubin booth in the exhibit hall with questions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Heterogeneous Point Set Transformers for Segmentation of Multiple View Particle Detectors

NOvA is a long-baseline neutrino oscillation experiment that detects neutrino particles from the NuMI beam at Fermilab. Before data from this experiment can be used in analyses, raw hits in the detector must be matched to their source particles, and the type of each particle must be identified. This task has commonly been done using a mix of traditional clustering approaches and convolutional neural networks (CNNs). Due to the construction of the detector, the data is presented as two sparse 2D images: an XZ and a YZ view of the detector, rather than a 3D representation. We propose a point set neural network that operates on the sparse matrices with an operation that mixes information from both views. Our model uses less than 10% of the memory required using previous methods while achieving a 96.8% AUC score, a higher score than obtained when both views are processed independently (85.4%).

Robles, Edgar E. [UC, Irvine (main)]↗
DOE OSTI2022

Chilled water temperature set-point reset based on outdoor air temperature and its cooling energy performance in an office building

Here, in this study, the cooling energy performance of two strategies for controlling ChWT (chilled water temperature) are compared: the conventional control strategy of constantly fixing ChWT and the OAT (outdoor air temperature) compensation control strategy that adjusts ChWT according to the changes in OAT. OAT compensation control strategy was modeled and realized based on Appendix G of ASHRAE Standard 90.1. It was confirmed that applying OAT compensation control strategy can significantly reduce chiller energy consumption, which accounts for the largest portion of total cooling energy consumption. It was found that the difference in total cooling energy consumption between applying the conventional control of constantly fixing ChWT to 6 °C and applying the OAT compensation control was approximately 8 % and 3 % during spring (March to May) and summer (June to August), respectively. Additionally, during the fall (September–November) period, about 7 % of total cooling energy consumption could be saved.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

An Orbital Basis Set for Double Photoionization of Atoms and Molecules

The ab initio theoretical treatment of one-photon double photoionization processes has been limited to atoms and diatomic molecules by the challenges posed by large grid-based representations of the double ionized continuum wave function. To provide a path for extensions to polyatomics, an energy-adapted orbital basis approach is demonstrated that reduces the dimensions of such representations and simultaneously allows larger time steps in time-dependent computational descriptions of double ionization. Additionally, an algorithm that exploits the diagonal nature of the two-electron integrals in the grid basis and dramatically accelerates the transformation between grid and orbital representations is presented. Excellent agreement between the present results and benchmark theoretical calculations is found for H – and Be atoms, as well as the hydrogen molecule, including for the triply differential cross sections that relate the angular distribution and energy sharing of all of the particles in the molecular frame.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Powers of sets in free groups

We prove that |A{sup n}|{>=}c{sub n}{center_dot}|A|{sup [(n+1)/2]} for any finite subset A of a free group if A contains at least two noncommuting elements, where the c{sub n}>0 are constants not depending on A. Simple examples show that the order of these estimates is best possible for each n>0. Bibliography: 5 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Fall Prevention in Community Settings: Results from Implementing Tai Chi: Moving for Better Balance in Three States

Tai Chi: Moving for Better Balance (TCMBB) is an evidence-based fall prevention exercise program being disseminated in selected communities through state injury prevention programs. This study: (1) describes the personal characteristics of TCMBB participants; (2) quantifies participants’ functional and self-reported health status at enrollment; and (3) measures changes in participants’ functional and self-reported health status post-intervention. There were 421 participants enrolled in 36 TCMBB programs delivered in Colorado, New York, and Oregon. Of the 209 participants who completed both baseline enrollment and post-intervention surveys, the average age of participants was 75.3 (SD ± 8.2) years. Most participants were female (81.3%), non-Hispanic (96.1%), White (94.1%), and described themselves as in excellent or very good health (52.2%). Paired t-test and general estimating equation models assessed changes over the 3-month program period. Pre- and post-assessment self-reported surveys and objective functional data [Timed Up and Go (TUG) test] were collected. On average, TUG test scores decreased (p < 0.001) for all participants; however, the decrease was most noticeable among high-risk participants (mean decreased from 18.5 to 15.7 s). The adjusted odds ratio of reporting feeling confident that a participant could keep themselves from falling was five times greater after completing the program. TCMBB, which addresses gait and balance problems, can be an effective way to reduce falls among the older adult population. By helping older adults maintain their functional abilities, TCMBB can help community-dwelling older adults continue to live independently.

60 APPLIED LIFE SCIENCES↗