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DOE OSTI2017

Condition monitoring and false alarm reducing of sensors in NPP - 222

With more and more application of digital I and C systems in nuclear power plants (NPP), more and more sensors are also required. Large amount of sensors really can make contribution to the condition monitoring of systems and equipment in NPP, whereas the heavy use also increases the malfunction risk of sensor self. Therefore the reliability and effectiveness of sensors must be guaranteed first. Thus the condition of sensors should be monitored first in a NPP. Since the precise mathematical models of sensors in complex systems are relative difficult to establish, however quantity of operating data can be easily obtained due to the wide application of digital I and C systems, thus this article adopts principal component analysis (PCA) to carry out condition monitoring for sensors. The PCA model developed for sensors is proved to be effective with operating data acquired from a real NPP. It can detect and isolate the fault when an artificial fault is imposed to the normal data. Then the monitoring results are further processed by another control limit (second confidence limit) besides T 2 and Q statistics (first confidence limit) in PCA. The value of second confidence limit is calculated based on the probability statistics of T 2 and Q statistics. And simulation tests show that the application of the second confidence limit can greatly reduce false alarms in the PCA model and the model performance can be greatly improved with the application of false alarms reducing method. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2014

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm{sup −1}, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

NASA NTRSDate not supplied

On Characterization of Flow Disturbances in Arc-Jet Testing

This paper reports computational simulations and analysis of flow characterization tests in high enthalpy arc-jet facilities at NASA Ames Research Center. Flow disturbances and their characterization are presented through case studies, and their implications for testing are discussed. The case studies include free-jet test configurations from three different arc heaters and nozzles: the 60-MW IHF 30-inch conical nozzle, the 10-MW TP3 15-inch conical nozzle, and the 20-MW AHF 12-inch conical nozzle. For all cases, test articles are placed in the jet exiting the conical nozzle, and the existence of a flow disturbance is confirmed through flow survey data using pitot pressure and heat flux probes and accompanying analysis. The paper focuses on cases where the effects of the disturbances on test article surface quantities are important. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzles and test box, including the models tested. Comparisons of computations with the experimental measurements are presented. The computations that reproduce the probe sweep data approximately are essential to interpret the arc-jet test data accurately, while providing insights into several observed calorimeter anomalies caused by flow disturbances.

Arc-jet testing↗

NASA NTRSDate not supplied

On Characterization of Flow Disturbances in Arc-Jet Testing

Arc-jet testing↗

NASA NTRS2015

Evaluating the Utility of Satellite Soil Moisture Retrievals over Irrigated Areas and the Ability of Land Data Assimilation Methods to Correct for Unmodeled Processes

Earth's land surface is characterized by tremendous natural heterogeneity and human-engineered modifications, both of which are challenging to represent in land surface models. Satellite remote sensing is often the most practical and effective method to observe the land surface over large geographical areas. Agricultural irrigation is an important human-induced modification to natural land surface processes, as it is pervasive across the world and because of its significant influence on the regional and global water budgets. In this article, irrigation is used as an example of a human-engineered, often unmodeled land surface process, and the utility of satellite soil moisture retrievals over irrigated areas in the continental US is examined. Such retrievals are based on passive or active microwave observations from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E), the Advanced Microwave Scanning Radiometer 2 (AMSR2), the Soil Moisture Ocean Salinity (SMOS) mission, WindSat and the Advanced Scatterometer (ASCAT). The analysis suggests that the skill of these retrievals for representing irrigation effects is mixed, with ASCAT-based products somewhat more skillful than SMOS and AMSR2 products. The article then examines the suitability of typical bias correction strategies in current land data assimilation systems when unmodeled processes dominate the bias between the model and the observations. Using a suite of synthetic experiments that includes bias correction strategies such as quantile mapping and trained forward modeling, it is demonstrated that the bias correction practices lead to the exclusion of the signals from unmodeled processes, if these processes are the major source of the biases. It is further shown that new methods are needed to preserve the observational information about unmodeled processes during data assimilation.

land data↗

NASA NTRS2003

Bayes Error Rate Estimation Using Classifier Ensembles

The Bayes error rate gives a statistical lower bound on the error achievable for a given classification problem and the associated choice of features. By reliably estimating th is rate, one can assess the usefulness of the feature set that is being used for classification. Moreover, by comparing the accuracy achieved by a given classifier with the Bayes rate, one can quantify how effective that classifier is. Classical approaches for estimating or finding bounds for the Bayes error, in general, yield rather weak results for small sample sizes; unless the problem has some simple characteristics, such as Gaussian class-conditional likelihoods. This article shows how the outputs of a classifier ensemble can be used to provide reliable and easily obtainable estimates of the Bayes error with negligible extra computation. Three methods of varying sophistication are described. First, we present a framework that estimates the Bayes error when multiple classifiers, each providing an estimate of the a posteriori class probabilities, a recombined through averaging. Second, we bolster this approach by adding an information theoretic measure of output correlation to the estimate. Finally, we discuss a more general method that just looks at the class labels indicated by ensem ble members and provides error estimates based on the disagreements among classifiers. The methods are illustrated for artificial data, a difficult four-class problem involving underwater acoustic data, and two problems from the Problem benchmarks. For data sets with known Bayes error, the combiner-based methods introduced in this article outperform existing methods. The estimates obtained by the proposed methods also seem quite reliable for the real-life data sets for which the true Bayes rates are unknown.

Tumer, Kagan↗

DOE OSTI2015

Remote sensing-based estimation of annual soil respiration at two contrasting forest sites

Here, soil respiration (R s ), an important component of the global carbon cycle, can be estimated using remotely sensed data, but the accuracy of this technique has not been thoroughly investigated. In this study, we proposed a methodology for the remote estimation of annual R s at two contrasting FLUXNET forest sites (a deciduous broadleaf forest and an evergreen needleleaf forest). A version of the Akaike's information criterion was used to select the best model from a range of models for annual R s estimation based on the remotely sensed data products from the Moderate Resolution Imaging Spectroradiometer and root-zone soil moisture product derived from assimilation of the NASA Advanced Microwave Scanning Radiometer soil moisture products and a two-layer Palmer water balance model. We found that the Arrhenius-type function based on nighttime land surface temperature (LST-night) was the best model by comprehensively considering the model explanatory power and model complexity at the Missouri Ozark and BC-Campbell River 1949 Douglas-fir sites.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

CyanoCyc cyanobacterial web portal

CyanoCyc is a web portal that integrates an exceptionally rich database collection of information about cyanobacterial genomes with an extensive suite of bioinformatics tools. It was developed to address the needs of the cyanobacterial research and biotechnology communities. The 277 annotated cyanobacterial genomes currently in CyanoCyc are supplemented with computational inferences including predicted metabolic pathways, operons, protein complexes, and orthologs; and with data imported from external databases, such as protein features and Gene Ontology (GO) terms imported from UniProt. Five of the genome databases have undergone manual curation with input from more than a dozen cyanobacteria experts to correct errors and integrate information from more than 1,765 published articles. CyanoCyc has bioinformatics tools that encompass genome, metabolic pathway and regulatory informatics; omics data analysis; and comparative analyses, including visualizations of multiple genomes aligned at orthologous genes, and comparisons of metabolic networks for multiple organisms. CyanoCyc is a high-quality, reliable knowledgebase that accelerates scientists’ work by enabling users to quickly find accurate information using its powerful set of search tools, to understand gene function through expert mini-reviews with citations, to acquire information quickly using its interactive visualization tools, and to inform better decision-making for fundamental and applied research.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1990

A guide to the National Space Science Data Center

This is the second edition of a document that was published to acquaint space and Earth research scientists with an overview of the services offered by the NSSDC. As previously stated, the NSSDC was established by NASA to be the long term archive for data from its space missions. However, the NSSDC has evolved into an organization that provides a multitude of services for scientists throughout the world. Brief articles are presented which discuss these services. At the end of each article is the name, address, and telephone number of the person to contact for additional information. Online Information and Data Systems, Electronic Access, Offline Data Archive, Value Added Services, Mass Storage Activities, and Computer Science Research are all detailed.

Source record↗

NASA NTRS1998

Application of a Planar Doppler Velocimetry System to a High Reynolds Number Compressible Jet

A Planar Doppler Velocimetry (PDV) system has been constructed and used to investigate the instantaneous turbulent velocity structure of a round high-speed compressible air jet with a low-speed co-flow. The exit condition was Mach=0.85 at ambient pressure, yielding a Reynolds number of about 650,000 on diameter. The PDV system was installed at NASA Langley Research Center in the Small Anechoic Jet Facility (SAJF), a chamber in which both the acoustic and aerodynamic properties of jets can be studied. For this test, the goal was to gather data which can be used to relate the turbulence structure of the jet to the levels and character of the acoustic noise produced by the jet. The current PDV system can acquire single-velocity-component, single-shot, planar images (15ns exposures) at 30 Hz. For this paper, the primary data set consists of 240 frames of velocity data acquired with both the jet and the low-speed co-flow seeded with light-scattering articles. Thus, velocities could be measured everywhere in the jet shear layer, both in the jet fluid and in the entrained co-flow. Some data were also taken with only the jet flow seeded. These provided mixing concentration images along with the reduced velocity fields. Other images were taken with only the co-flow seeded. These produced unique quantitative images of high speed entrainment. Optical "laser speckle" noise is the largest source of random noise in pulsed PDV systems. Components for the PDV imaging system were specifically selected to minimize speckle noise. To reduce systematic velocity errors due to laser drift, a frequency monitoring reference leg with a temperature-tuned reference iodine cell, was employed. In the course of this study, a novel flow seeder was developed. It enabled continuously variable seeding of the flow with particles of Sheared Pyrogenic Amorphous Hydrophobic Silica (SPAHS). The seeder comprised a dry fluidized bed hopper and a supersonic nozzle "pickup." Shearing action in the pickup dispersed the seed material in an exceptionally fine cloud (approximately 0.3 micron). These particles followed the flow well, did not clump or cake on screens or model surfaces, and were not susceptible to evaporation. Because of the refractory nature of the particles, SPAHS seeding should also be applicable to anticipated future testing at high temperatures.

Smith, Michael W.↗

DOE OSTI2025

Measurement of the 28 Si ⁢(𝑛,𝑛′⁢𝛾) cross section with 𝑛, 𝛾, and correlated 𝑛−𝛾 angular distributions

Silicon has become an unavoidable element in the circuitry central to everyday life. In turn, the interactions of silicon isotopes with neutrons for nuclear physics applications, among other motivations, have become increasingly important to understand. The dominant isotope of silicon, 28 Si, is thus of primary interest for enhanced understanding for neutron transport calculations and related investigations. Unfortunately, the existing measurement database for neutron scattering reactions on 28 Si is minimal, and nuclear data evaluations on this topic have not been updated for decades. This article details new measurements of the 28 Si ⁢(𝑛,𝑛′⁢𝛾) reaction utilizing multiple analysis methods available within the correlated gamma neutron array for scattering (CoGNAC). Specifically, high-precision near-threshold results and high-incident-energy results were obtained using the 𝛾-only and correlated 𝑛−𝛾 techniques. First-ever measurements of the correlated 𝑛−𝛾 angular distribution for particles emitted following population of the first excited state in 28 Si were obtained as well, which provide unique insight into theoretical descriptions of the inelastic neutron scattering reaction mechanism itself and detailed guidance for nuclear reaction models. The results agree well with literature data where they exist, and substantially expand on the current database for neutron reactions on 28 Si .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS2003

Analysis and Forecast of Two Storms Characterized by Extreme Deepening Rates

Between 25 and 27 December 1999 two very intense cyclones, named Lothar and Martin, swept across northern and western France causing substantial life and property loss. In this work, the finite volume general circulation model and data assimilation system (fvDAS) developed at the Data Assimilation Office of the NASA Goddard Space and Flight Center is being used to investigate these storms. In the first part of this article the dynamics of the storms is analyzed, and some important mechanisms are unveiled. The second part describes a set of eleven data assimilation experiments to study the impact of different data types on the automated analyses. Cloud-track winds provided by EUMETSAT and surface winds from QuikSCAT are being used. These data are assimilated with a range of different parameter settings of the forecast error covariance model. The results show that generally the additional wind data set have positive impacts on the analyses: particularly, the analysis of Lothar can be slightly improved by using the Eumetsat winds, and the analysis of Martin can be strongly improved by using the full-resolution QuikSCAT winds with a more localized influence. The third part of this article is focused on the forecast of Lothar which is very well predicted in the 1-5 day range by the fvDAS system.

Reale, Oreste↗

NASA NTRS2004

Onboard Autonomy on the Earth Observing One Mission

The Earth Observing One Spacecraft is currently flying The Autonomous Sciencecraft Experiment (ASE) - onboard autonomy software to improve science return. The ASE software enables the spacecraft to autonomously detect and respond to science events occurring on the Earth. ASE includes software systems that perform science data analysis, mission planning, and run-time robust execution. In this article we describe the autonomy flight software and how it enables a new paradigm of autonomous science and mission operations.

autonomy↗

DOE OSTI2020

Building fault detection data to aid diagnostic algorithm creation and performance testing

It is estimated that approximately 4-5% of national energy consumption can be saved through corrections to existing commercial building controls infrastructure and resulting improvements to efficiency. Correspondingly, automated fault detection and diagnostics (FDD) algorithms are designed to identify the presence of operational faults and their root causes. A diversity of techniques is used for FDD spanning physical models, black box, and rule-based approaches. A persistent challenge has been the lack of common datasets and test methods to benchmark their performance accuracy. This article presents a first of its kind public dataset with ground-truth data on the presence and absence of building faults. This dataset spans a range of seasons and operational conditions and encompasses multiple building system types. It contains information on fault severity, as well as data points reflective of the measurements in building control systems that FDD algorithms typically have access to. The data were created using simulation models as well as experimental test facilities, and will be expanded over time.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRSDate not supplied

Implementing Geometric Surface Imperfections into Sandwich Composite Cylinder Finite Element Method Models

The buckling responses of certain cylindrical shell structures are extremely sensitive to geometric surface imperfections. The NASA Engineering and Safety Center (NESC) Shell Buckling Knockdown Factor Project (SBKF) is conducting research to develop analysis-based buckling design recommendations. Experiments are used to verify the analysis-based factors, but the sensitivity of the test articles to geometric imperfections requires implementing as-manufactured imperfections into high-fidelity finite element method models. Data collection methods such as structured light scanning are used for all geometric surface data used in this work. Common preprocessing and visualization steps used in SBKF are discussed, and steps on how surface scans are prepared for implementation into a finite element model is described. The Python Tool for Implementing Geometric Imperfections in Reduced Structures (Py_TIGIRS), written specifically for the use with SBKF, is briefly described and uses eight functions to extract, modify, and write geometric imperfections into Abaqus input files. Results of the pre-processing methods and results from Py_TIGIRS are provided and compared for Composite Test Article (CTA) 8.2B. Excellent agreement between the visualized scan data and the FEM-extracted geometry is demonstrated. A brief example of why geometric surface imperfections are significant in nonlinear numerical analyses for thin cylinders in axial compression is provided as motivation to use tools such as Py_TIGIRS. Future development of Py_TIGIRS including expansion to structures of arbitrary geometry is planned.

Sandwich structures↗

NASA NTRS2017

Ecological Study of Lagoons Surrounding the John F. Kennedy Space Center, Brevard County, Florida : Theses and Project Reports - Volume 2

Many of the detailed studies done in connection with Ecological Study of the Lagoons surrounding the John F. Kennedy Space Port were performed as Master's Thesis investigations by various graduate students enrolled at F. I. T. during and subsequent to the report. The scope and purpose of what we came to call "the KSC Baseline Study" caught the imagination and interest of our student body. Many who were not financially or otherwise connected with the project found their inspiration in studies that were directly connected with project, and thus added materially to the totality of the knowledge gained. An example of one such study is the first article included in this Volume, A Master's Thesis study performed by Shen Phillip Chen, who chose the site for his investigation so that his results would correlate with and extend the results of others. In addition to the Master's Theses contained in this Volume, six other graduate studies must be acknowledged here as contributing to this Report, although they have not reached the stage of final publication. Ms. Sandra Fettes has completed a study of the amounts of five trace metals in mangrove leaves from plants at various locations around the Kennedy Space Center. Mr. Bernard Cohenour has isolated and identified a number of oil consuming bacteria endemic in the waters of the Indian Rivers. Mr. Charles Waterhouse has analyzed historic data of tidal gauges in the lagoonal area and correlated it with wind field records. Mr. Renkert Meyer has measured the vertical and horizontal currents of the lagoons and is attempting an interpretation of them in terms of the wind field as a driving force. Mr. Richard Campbell has measured the rate of nitrogen fixation in both the water columns and the sediments under them in the lagoons. Mr. Craig Weiderhold has measured thl3 annual variations in the populations of benthic invertebrates in the lagoons. An integral part of the F. I. T. curriculum is a requirement that each undergraduate student perform an independent study during his Senior year and submit his results in the form and format of a professional scientific report. While none of these senior Project Reports have been included in this Volume because of space limitations, many of them aided significantly in the overall study. Typical of these were: light and dark bottle studies of the blue-green algae respiration; writing and executing computer studies comparing the water chemistry data from various sites; detection and identification of nitrogen fixation bacteria in the Indian River; measurement of dissolved oils and greases in the river, photographically recording the benthic life-forms found in the river bottom; measuring the vertical structure of drift and slope currents in too lagoons; and measurement of water level variations along the long axis of a lagoon as a function of wind stress. These articles are published as a part of this Final Report in an effort to make available for the record as much of the basic data as possible. The few articles published on the Indian River have in general not contained much detailed data, so that comparisons of current status to conditions of the past are difficult or impossible. A major effort of both the Oceanographic and Ecological communities for the past decade has been the retrieval and storage of basic data in order to permit determinations of trends or changes in baseline conditions. It is believed that the information compiled here will be of great value in any future investigations.

Source record↗

NASA NTRS2006

Results from SIM's Thermo-Opto-Mechanical (TOM3) Testbed

Future space-based optical interferometers, such as the Space Interferometer Mission Planet Quest (SIM), require thermal stability of the optical wavefront to the level of picometers in order to produce astrometric data at the micro-arc-second level. In SIM, the internal path of the interferometer will be measured with a small metrology beam whereas the starlight fringe position is estimated from a large concentric annular beam. To achieve the micro-arc-second observation goal for SIM, it is necessary to maintain the optical path difference between the central and the outer annulus portions of the wavefront of the front-end telescope optics to a few tens of picometers. The Thermo-Opto-Mecha nical testbed (TOM3) was developed at the Jet Propulsion Laboratory to measure thermally induced optical deformations of a full-size flight-like beam compressor and siderostat, the two largest optics on SIM, in flight-like thermal environments. A Common Path Heterodyne Interferometer (COPHI) developed at JPL was used for the fine optical path difference measurement as the metrology sensor. The system was integrated inside a large vacuum chamber in order to mitigate the atmospheric and thermal disturbances. The siderostat was installed in a temperature-controlled thermal shroud inside the vacuum chamber, creating a flight-like thermal environment. Detailed thermal and structural models of the test articles (siderostat and compressor) were also developed for model prediction and correlation of the thermal deformations. Experimental data shows SIM required thermal stability of the test articles and good agreement with the model predictions.

interferometry↗

DOE OSTI2018

De-starring Challenging Cygnus Data: A Comparison of Three Methods

This report addresses recent questions concerning the RadPro de-starring process. Ultimately, the issues that gave rise to the questions proved to be unrelated to the de-starring process. However, the nature of the questions exposed some misunderstanding on how to evaluate de-starring results. A fundamental of the de-starring process is that not every data point that is extracted as a star is actually a star. This work applies and compares three different methods to very challenging data to illustrate how to evaluate de-starring results. These three methods include (1) the procedure in RadPro, (2) a version of StarStats8, and (3) a method found in the literature by Abel Diaz (L.A. Cosmic), that was developed for astrophysical applications by Pieter G. van Dokkum. In L.A. Cosmic the radiation stars are generated by cosmic-ray hits and the data of interest are true physical stars and galaxies. Dokkum’s work is heavily referenced and appears in over 1,000 citations; a scholarly article on the topic describes it. The term de-starring will include removing cosmic-ray hits from such data. Another de-starring application, developed by Archambault et al. at the M. D. Anderson Cancer Center at the University of Texas in Houston is reviewed in this work but no comparison is made, as the algorithm is very similar to that of RadPro. This process was not named in their paper, and we will refer to it as MDACC. The focus of this report is on identifying stars. Computing replacement values, a different topic, is not covered in this report.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗