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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

SRF Cavity Instability Detection with Machine Learning at CEBAF

During the operation of CEBAF, one or more unstable superconducting radio-frequency (SRF) cavities often cause beam loss trips while the unstable cavities themselves do not necessarily trip off. Identifying an unstable cavity out of the hundreds of cavities installed at CEBAF is difficult and time-consuming. The present RF controls for the legacy cavities report at only 1 Hz, which is too slow to detect fast transient instabilities. A fast data acquisition system for the legacy SRF cavities is being developed which samples and reports at 5 kHz to allow for detection of transients. A prototype chassis has been installed and tested in CEBAF. An autoencoder based machine learning model is being developed to identify anomalous SRF cavity behavior. The model is presently being trained on the slow (1 Hz) data that is currently available, and a separate model will be developed and trained using the fast (5 kHz) DAQ data once it becomes available. This paper will discuss the present status of the new fast data acquisition system and results of testing the prototype chassis. This paper will also detail the initial performance metrics of the autoencoder model.

Carpenter, A.↗
DOE OSTI2026

Modeling Framework for Data Center

This chapter highlights the critical need for advanced modeling of data centers due to their rapidly increasing energy consumption and impact on grid reliability. Driven by the demand for AI applications, data centers are projected to consume a significant portion of US energy by 2028, putting stress on an already challenged power grid. The chapter emphasizes the importance of "fast" time-scale models to understand the dynamic interactions between data centers and the grid, especially given the rapid power fluctuations of AI workloads. It outlines a modeling framework that includes both offline and real-time EMT domain simulations, detailing the necessary representations for various components like utility interfaces, transformers, IT loads, UPS, cooling loads, Battery Energy Storage Systems (BESS), generators, protection systems, and higher-level control systems. While standard simulation tools like PSCAD offer basic models, custom development is often required to accurately capture the unique and fast-changing behaviors of modern data centers. The chapter also discusses key metrics and test cases for validating these models, focusing on transient load responses, protection relay coordination, and demand flexibility. Finally, it addresses the challenges of modeling large-scale data centers, such as computational complexity and the trade-off between model fidelity and practicality, suggesting hybrid modeling approaches as a solution. The overarching goal is to create a robust framework that helps assess data center impacts on grid stability, identify vulnerabilities, and inform the development of standards for reliable integration of these large loads into the bulk power system.

25 ENERGY STORAGE↗
DOE OSTI2023

Anomaly Detection in Liquid Sodium Cold Trap Operation with Multisensory Data Fusion Using Long Short-Term Memory Autoencoder

Sodium-cooled fast reactors (SFR), which use high temperature fluid near ambient pressure as coolant, are one of the most promising types of GEN IV reactors. One of the unique challenges of SFR operation is purification of high temperature liquid sodium with a cold trap to prevent corrosion and obstructing small orifices. We have developed a deep learning long short-term memory (LSTM) autoencoder for continuous monitoring of a cold trap and detection of operational anomaly. Transient data were obtained from the Mechanisms Engineering Test Loop (METL) liquid sodium facility at Argonne National Laboratory. The cold trap purification at METL is monitored with 31 variables, which are sensors measuring fluid temperatures, pressures and flow rates, and controller signals. Loss-of-coolant type anomaly in the cold trap operation was generated by temporarily choking one of the blowers, which resulted in temperature and flow rate spikes. The input layer of the autoencoder consisted of all the variables involved in monitoring the cold trap. The LSTM autoencoder was trained on the data corresponding to cold trap startup and normal operation regime, with the loss function calculated as the mean absolute error (MAE). The loss during training was determined to follow log-normal density distribution. During monitoring, we investigated a performance of the LSTM autoencoder for different loss threshold values, set at a progressively increasing number of standard deviations from the mean. The anomaly signal in the data was gradually attenuated, while preserving the noise of the original time series, so that the signal-to-noise ratio (SNR) averaged across all sensors decreased below unity. Results demonstrate detection of anomalies with sensor-averaged SNR < 1.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Test Plan for Cyclic Heating of AGR-3/4 Compact 8-1

Post irradiation examination (PIE) and heating tests of tristructural isotropic (TRISO)-coated fuel particles, fuel compacts, and graphite from Advanced Gas Reactor (AGR) irradiation experiment AGR 3/4 are in progress. The AGR-3/4 test train consisted of twelve separate capsules irradiated in the northeast flux trap of the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) from December 14, 2011, to April 12, 2014 (Collin 2015). The plan for the reirradiation in the Neutron Radiography Reactor (NRAD) and subsequent 1200°C heating test of AGR-3/4 Compact 8-1 in the Fuel Accident Condition Simulator (FACS) furnace was described previously in (Stempien 2019). One of the main goals of that test was to assess the retention of short-lived fission products I-131 (t1/2 = 8.02 d) and Xe-133 (t1/2 = 5.2 d) in fuel kernels. Xe-133 release had ostensibly leveled off after approximately 80 hours. An issue with the condensation plate exchanges forced this test to be stopped after approximately 96 hours. The issue was resolved, and the test was restarted by heating FACS back up to 1200°C. During this reheating phase, an additional release of Xe-133, approximately equal in size to the release during the initial heating to 1200°C, was detected in the fission gas monitoring system (FGMS). To test whether this release is related to temperature transients (i.e. from heating and reheating), this new plan will describe three additional temperature cycles.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

PERLE A ‘STEPPING STONE’ FOR THE NEXT GENERATION ERLS

PERLE (Powerful ERL for Experiments) is a novel Energy Recovery Linac (ERL) test facility, which has been designed to validate choices for a 50 GeV ERL foreseen in the design of the LHeC and the FCC-eh, and to later serve a set of dedicated nuclear and particle physics experiments. Its main thrust is to probe high current, continuous wave (CW), multi-pass operation with superconducting cavities at 802 MHz (and perhaps testing other frequencies of interest). With very high transient beam power (~10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERL design and become a ?stepping stone? between present state-of-art 1 MW ERLs and future 100 MW scale applications. PERLE design features flexible momentum compaction lattice architecture for six vertically stacked return arcs and a high current, 7 MeV, photo-injector. With only one pair of four cavity cryomodules, 500 MeV beam energy can be reached in three re-circulation passes, with beam currents of about 20 mA. The beam is decelerated in three consecutive passes back to the injection energy. Work on the engineering design of PERLE has just begun.

Bogacz, S.↗
DOE OSTI2019

Intercomparison of Commercially Available Active Radon Measurement Devices in a Discovered Radon Chamber

An unventilated 70 m 3 underground space, with 2.1 m high ceilings and an inner set of concrete walls to damp vibrations, was discovered to have relatively stable radon levels of ~1,080 Bq m -3 over a 1-y period. The addition of radium sources was not required to achieve high and somewhat variable radon levels, as these arise naturally in the space. Several active radon monitoring devices designed for homeowners, radon screeners, radon mitigation professionals, and researchers were tested in the space. These devices were variable in both cost and intended user sophistication. Data were collected at specific time intervals that varied for each device. A cellphone was deployed with an available camera application to periodically capture photographs of the displays of devices not enabled for automatic temporal recording. Attempts were made to alter the radon concentration using fans, radium-laden objects, and radon impermeable sheets. Statistical methods were employed to compare the device's performance under the minor radon transients produced by the addition of 226 Ra sources during the test period. The evaluation of the overall accuracy, noise, and response to transients revealed highly affordable devices that may be useful for future research applications.While unsuitable for precise calibrations at stable radon levels, the space was determined to be adequate as a radon chamber for general research purposes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

DMTN-080: Coaddition Artifact Rejection and CompareWarp

LSST images will be contaminated with transient artifacts, such as optical ghosts, satellite trails, and cosmic rays, and with transient astronomical sources, such as asteroid ephemerides. We developed and tested an algorithm to find and reject these artifacts during coaddition, in order to produce clean coadds to be used for deep detection and preliminary object characterization. This algorithm, CompareWarpAssembleCoadd, uses the time-series of PSF-matched warped images to identify transient artifacts. It detects artifact candidates on the image differences between each PSF-matched warp and a static sky model. These artifact candidates include both true transient artifacts and difference-image false positives such as difficult-subtract-sources and variable sources such as stars and quasars. We use the feature that true transients appear at a given position in the difference images in only a small fraction (configurable) of visits, whereas variable sources and difficult-to-subtract sources appear in most difference images. In this report, we present a description of the method and an evaluation using Hyper SuprimeCam PDR1 data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Transient expression in Nicotiana benthamiana for rapid functional analysis of genes involved in non‐photochemical quenching and carotenoid biosynthesis

Summary Plants must switch rapidly between light harvesting and photoprotection in response to environmental fluctuations in light intensity. This switch can lead to losses in absorbed energy usage, as photoprotective energy dissipation mechanisms can take minutes to hours to fully relax. One possible way to improve photosynthesis is to engineer these energy dissipation mechanisms (measured as non‐photochemical quenching of chlorophyll a fluorescence, NPQ ) to induce and relax more quickly, resulting in smaller losses under dynamic light conditions. Previous studies aimed at understanding the enzymes involved in the regulation of NPQ have relied primarily on labor‐intensive and time‐consuming generation of stable transgenic lines and mutant populations – approaches limited to organisms amenable to genetic manipulation and mapping. To enable rapid functional testing of NPQ ‐related genes from diverse organisms, we performed Agrobacterium tumefaciens ‐mediated transient expression assays in Nicotiana benthamiana to test if NPQ kinetics could be modified in fully expanded leaves. By expressing Arabidopsis thaliana genes known to be involved in NPQ , we confirmed the viability of this method for studying dynamic photosynthetic processes. Subsequently, we used naturally occurring variation in photosystem II subunit S, a modulator of NPQ in plants, to explore how differences in amino acid sequence affect NPQ capacity and kinetics. Finally, we functionally characterized four predicted carotenoid biosynthesis genes from the marine algae Nannochloropsis oceanica and Thalassiosira pseudonana and examined the effect of their expression on NPQ in N. benthamiana . This method offers a powerful alternative to traditional gene characterization methods by providing a fast and easy platform for assessing gene function in planta .

Plant Sciences↗
DOE OSTI2018

Gearbox high-speed-stage bearing slip induced by electric excitation in a test facility

The goal of this paper is to investigate the behaviour of the high-speed stage of a wind turbine gearbox during transient grid-loss events triggered at different power levels in a full-scale nacelle dynamometer test. The gear mesh behaviour and the bearing roller slip during these events are characterized by strain measurements placed in the gear teeth roots and embedded in the outer rings of the tapered roller bearing locating pair. From our experiments, we conclude that the high-speed stage experiences a multidimensional loading consisting of bending and torsional deformation during the transient event. This loading propagates throughout the gearbox and results in unfavourable loading conditions at the bearing that have the potential to go beyond the preload during the torque reversals that occur during the grid-loss event. During the torque reversal, roller slip can occur in the bearings. It is observed that the slip behaviour is directly linked to the initial power level of the generator. Electrically induced excitation that typically leads to dynamic torque events can therefore cause mechanical gearbox degradation.

17 WIND ENERGY↗
DOE OSTI2020

Using optical fibers to examine thermal mixing of liquid sodium in a pool-type geometry

Sodium fast reactors (SFR) are poised to be a leading candidate for the next generation of commercial nuclear reactor deployment. Companies are commissioning designs for SFR increasing the need for experimental and computational analysis to improve the economics and safety of these reactors. Analysis of SFR behavior during reactor transients directly informs the understanding of reactor safety. Particularly, investigating the thermal transients associated with the reactor loss of flow transient allows for informed design decisions to be made regarding reactor safety. During loss of flow transients the flow rate of the coolant is significantly reduced, but not necessarily stopped. The reduction in flow rate results in coolant temperatures exiting the reactor core that can be drastically different than the coolant in upper pool. When these different temperature fluids interact, thermally stratified layers can form causing cyclic thermal fatigue on the reactor vessel potentially leading to pre-material failure. Past experimental studies have lacked high resolution temperature measurements. This research focuses on demonstrating the reliability of novel techniques for acquiring high resolution temperature measurements in a scaled liquid sodium facility. Tests are conducted that simulate postulated loss of flow transients and provide unprecedented spatial temperature distribution measurements.

42 ENGINEERING↗
DOE OSTI2019

Thermal Analysis Of Saltstone Disposal Units

SRR requested that SRNL develop a two-dimensional computer simulation model to be capable of predicting grout temperatures attained in Saltstone Disposal Units (SDUs) during the transient addition of saltstone grout and its subsequent storage period. A simulation model was developed to calculate the transient grout temperatures of the SDU facility by taking an axisymmetric and two-dimensional Computational Fluid Dynamics (CFD) approach. The final performance calculations were based on the conduction and radiation model without a convection cooling mechanism for conservative estimate of the grout temperatures and computational efficiency. While convection within the SDU is disabled in the current calculations, the simulation model has the capability of turning convection back on if desired by the user. Hence, the thermal model in its current configuration is best characterized as a finite-volume heat transfer model. However, given that the model can account for convection if desired by the user, it will be referred to as a CFD model. The grout material contains a transient heat source due to the exothermic hydration reactions of the cementitious material mixed with salt solution. The model can predict the transient temperatures at point locations within the poured grout and the overlying vapor space, and at the interior and exterior surfaces of the structure. The thermal model has been developed for two SDUs at the Savannah River Site (SRS); namely, SDU 2A and SDU 6. SDU 2A is a cylindrical unit measuring 150 feet (ft) in diameter, 22 ft tall, and holds approximately three million gallons of grout. SDU 6 is 375 ft in diameter and 43 ft high with a capacity of over thirty million gallons. Prior to performing the thermal calculations for the SDU 6 facility, the benchmarking test for the smaller SDU 2A unit was performed to establish the solution method and to verify the computational results using existing thermocouple data. Based on the Lagrangian discrete method and boundary conditions established by the SDU 2A benchmarking test, the CFD calculations were performed to predict the transient temperatures at local positions of the poured grout and air spaces within the SDU 6 structure.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Development of the Variable Atmosphere Testing Facility for Blow-Down Analysis of the Mars Hopper Prototype

Recent developments at the Center for Space Nuclear Research (CSNR) on a Martian exploration probe have lead to the assembly of a multi-functional variable atmosphere testing facility (VATF). The VATF has been assembled to perform transient blow-down analysis of a radioisotope thermal rocket (RTR) concept that has been proposed for the Mars Hopper; a long-lived, long-ranged mobile platform for the Martian surface. This study discusses the current state of the VATF as well as recent blow-down testing performed on a laboratory-scale prototype of the Mars Hopper. The VATF allows for the simulation of Mars ambient conditions within the pressure vessel as well as to safely perform blow-down tests through the prototype using CO2 gas; the proposed propellant for the Mars Hopper. Empirical data gathered will lead to a better understanding of CO2 behavior and will provide validation of simulation models. Additionally, the potential of the VATF to test varying propulsion system designs has been recognized. In addition to being able to simulate varying atmospheres and blow-down gases for the RTR, it can be fitted to perform high temperature hydrogen testing of fuel elements for nuclear thermal propulsion.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

RELAP5-3D Pre-test Prediction for High Temperature Test Facility Test PG-26

The RELAP5-3D computer code has been used to perform a pre-test prediction for Test PG-26 in the High Temperature Test Facility at Oregon State University. Test PG-26 will simulate a pressurized conduction cooldown transient following a trip of the primary coolant system gas circulator. The facility is initialized with a steady-state power of 700 kW and prototypic core inlet and outlet helium coolant temperatures of 259 and 687°C, respectively. Sensitivity calculations addressed the flow coastdown time, the reactor cavity cooling system flow rate and temperature, and decay power.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Optimizing a magnitude-limited spectroscopic training sample for photometric classification of supernovae

ABSTRACT In preparation for photometric classification of transients from the Legacy Survey of Space and Time (LSST) we run tests with different training data sets. Using estimates of the depth to which the 4-m Multi-Object Spectroscopic Telescope (4MOST) Time Domain Extragalactic Survey (TiDES) can classify transients, we simulate a magnitude-limited sample reaching rAB ≈ 22.5 mag. We run our simulations with the software snmachine, a photometric classification pipeline using machine learning. The machine-learning algorithms struggle to classify supernovae when the training sample is magnitude limited, in contrast to representative training samples. Classification performance noticeably improves when we combine the magnitude-limited training sample with a simulated realistic sample of faint high-redshift supernovae observed from larger spectroscopic facilities; the algorithms’ range of average area under receiver operator characteristic curve (AUC) scores over 10 runs increases from 0.547–0.628 to 0.946–0.969 and purity of the classified sample reaches 95 per cent in all runs for two of the four algorithms. By creating new, artificial light curves using the augmentation software avocado, we achieve a purity in our classified sample of 95 per cent in all 10 runs performed for all machine-learning algorithms considered. We also reach a highest average AUC score of 0.986 with the artificial neural network algorithm. Having ‘true’ faint supernovae to complement our magnitude-limited sample is a crucial requirement in optimization of a 4MOST spectroscopic sample. However, our results are a proof of concept that augmentation is also necessary to achieve the best classification results.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

High Altitude Electromagnetic Pulse Testing of Photovoltaic Modules

This report details the test setup, process, and results for radiated susceptibility testing of multicrystalline silicon photovoltaic (PV) modules as part of the EMP-Resilient Electric Grid Grand Challenge Laboratory Directed Research and Development (LDRD) project at Sandia National Laboratories. Testing was conducted over October 10-17, 2019, where 8 photovoltaic modules were exposed to E1 transient pulses with peak field levels up to 100 kV/m. Modules were terminated in a resistive load representing connected components. State of health testing conducted via I-V curve tracing of the photovoltaic modules showed no observable loss of device function due to large electric field transients. Differential mode currents were measured on the order of 10's of amps for up to a microsecond following the radiated field pulse. Common mode currents took the form of a damped sinusoid with a maximum peak of 10's to 100's of amps with a resonance near 60 MHz.

14 SOLAR ENERGY↗
DOE OSTI2016

Sensitivity Analysis of OECD ATLAS A5.1 Test using MARS-KS code

The ATLAS was designed to model a reduced-height primary system of a typical APR1400 which was developed by the Korean Nuclear Industry. The ATLAS has the 1/2-height, 1/144-area and 1/288-volume scales for the APR 1400 and it is scaled for full pressure and temperature conditions. A benchmark test, test A5.1, was performed to analyze and quantify the extent of scaling distortion in the ATLAS, as a part of a OECD-ATLAS project. The SB-CL-32 test which was conducted using the Large Scale Test Facility (LSTF) of the Rig-of-Safety Assessment-V (ROSA-V) Program was selected as the counterpart test to address the scaling issue. The detailed description of the LSTF test facility and the SB-CL-32 test can be found in the literature. The objective of the A5.1 test is to investigate the thermal hydraulic phenomena during cold leg small break LOCA with steam generator secondary side depressurization as the Accident Management action. In addition to that, the scaling effect analysis of ATLAS was performed in the several viewpoints. In this study, sensitivity analysis of A5.1 test was performed using MARS-KS code. Several experimental conditions of A5.1 test were varied to study effects on the reactor coolant system during the SBLOCA transient. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Benchmarking of Improved DPAC Transient Deflagration Analysis Code

The deflagration pressure analysis code (DPAC) has been upgraded for use in modeling hydrogen deflagration transients. The upgraded code is benchmarked using data from vented hydrogen deflagration tests conducted at the HYDRO-SC Test Facility at the University of Pisa. DPAC originally was written to calculate peak pressures for deflagrations in radioactive waste storage tanks and process facilities at the Savannah River Site. Upgrades include the addition of a laminar flame speed correlation for hydrogen deflagrations and a mechanistic model for turbulent flame propagation, incorporation of inertial effects during venting, and inclusion of the effect of water vapor condensation on vessel walls. In addition, DPAC has been coupled with chemical equilibrium with applications (CEA), a NASA combustion chemistry code. The deflagration tests are modeled as end-to-end deflagrations. As a result, the improved DPAC code successfully predicts both the peak pressures during the deflagration tests and the times at which the pressure peaks.

42 ENGINEERING↗
DOE OSTI2014

The agile alert system for gamma-ray transients

In recent years, a new generation of space missions has offered great opportunities for discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) on board the AGILE space mission. AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many γ-ray transients of both galactic and extragalactic origin. This work presents the AGILE innovative approach to fast γ-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for γ-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, via e-mail, and via push notifications from an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in γ-ray astrophysics.

79 ASTRONOMY AND ASTROPHYSICS↗