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At least 487 records · Page 27

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DOE OSTI2023

Excited-State Charge Transfer in Push–Pull Platinum(II) π-Extended Porphyrins Fused with Pentacenequinone

Platinum(II) π-extended porphyrins fused with pentacenequinone and dihydropentacene have been successfully synthesized. These porphyrins were investigated using various techniques including absorption, steady-state, and time-resolved phosphorescence spectroscopy and differential pulse voltammetry. UV–vis absorption spectra of pentacenequinone-fused porphyrins (SW-Pt1 and SW-Pt2) showed unusually broad and nontypical absorption patterns. Phosphorescence spectra of SW-Pt1, SW-Pt2, and SW-Pt3 displayed similar emissions in the 704–706 nm region indicating electronic transitions of similar origin; however, the triplet lifetimes were found to be quenched in the case of both SW-Pt1 and SW-Pt2, suggesting the occurrence of excited-state events. Facile reductions were obtained for both the pentacene-quinone-fused monomer (SW-Pt2) and dimer (SW-Pt1) and were identified to be located at the pentacenequinone components. Here, the observed orbital segregations for SW-Pt2 and SW-Pt1 from DFT calculations supported the possibility of charge transfer in these push–pull systems. Interestingly, the established energy level diagram revealed that the charge transfer from the triplet excited Pt porphyrin is thermodynamically an uphill process. Systematic studies involving both femtosecond and nanosecond transient absorption techniques revealed that the singlet excited Pt porphyrins undergo an intermediate charge transfer state prior to populating the triplet state, providing a plausible explanation for phosphorescence quenching. The lifetime of the intermediate charge transfer states was found to be 25.9 and 5.68 ps, respectively, for SW-Pt1 and SW-Pt2.

Charge transfer↗

DOE OSTI2021

Intelliquench: An Adaptive Machine Learning System for Detection of Superconducting Magnet Quenches

In superconducting magnets, the irreversible transition of a portion of the conductor to resistive state is called a “quench.” Having large stored energy, magnets can be damaged by quenches due to localized heating, high voltage, or large force transients. Unfortunately, current quench protection systems can only detect a quench after it happens, and mitigating risks in Low Temperature Superconducting (LTS) accelerator magnets often requires fast response (down to ms). Additionally, protection of High Temperature Superconducting (HTS) magnets is still suffering from prohibitively slow quench detection. In this study, we lay the groundwork for a quench prediction system using an auto-encoder fully-connected deep neural network. After dynamically trained with data features extracted from acoustic sensors around the magnet, the system detects anomalous events seconds before the quench in most of our data. While the exact nature of the events is under investigation, we show that the system can “forecast” a quench before it happens under magnet training conditions through a randomized experiment. This opens up the way of integrated data processing, potentially leading to faster and better diagnostics and detection of magnet quenches

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

A Two-Level Simulation-Assisted Sequential Distribution System Restoration Model With Frequency Dynamics Constraints

Not provided.

Engineering↗

DOE OSTI2020

Electrochemical Characterization of Bromine Reduction to Tribromide in Individual Nitrobenzene-in-Water Emulsion Droplets

We report an electrochemical study of bromine reduction to tribromide in a single nitrobenzene (NB) droplet during a single collision event. The feasibility of this study is based on the favorable distribution of Br 2 in NB rather than in water, which was demonstrated by voltammetry at the NB/water interface. The NB-in-water emulsions containing the ionic liquids trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide (ILPA) as the supporting electrolyte and sodium dodecyl sulfate (SDS) as the surfactant were prepared by a high-power ultrasonication. Its single droplet as an attoliter reactor, colliding on a 25 μm Pt UME, was monitored by chronoamperometry. The spike-type current transients of Br 2 reduction can elucidate the size and size distribution of NB, and measure the diffusion in the droplet as analyzed by a bulk electrolysis model. The frequency of collisions can provide diffusion coefficient of the droplets to the UME. Moreover, the i-t decay behavior can be simulated, which fits well with the experimental one.

25 ENERGY STORAGE↗

DOE OSTI2022

Transient Postclosure Criticality Model Development

A key objective of the United States Department of Energy’s (DOE) Office of Nuclear Energy’s Spent Fuel and Waste Science and Technology (SFWST) Campaign is to better understand the technical basis, risks, and uncertainty associated with the safe and secure disposition of spent nuclear fuel (SNF) and high-level radioactive waste. Commercial nuclear power generation in the United States has resulted in thousands of metric tons of SNF, the disposal of which is the responsibility of the DOE (Nuclear Waste Policy Act of 1982, as amended). Any repository licensed to dispose of SNF must meet requirements regarding the long-term performance of that repository. For an evaluation of the long-term performance of the repository, one of the events that may need to be considered is the SNF achieving a critical configuration during the postclosure period. Of particular interest is the potential behavior of SNF in dualpurpose canisters (DPCs), which are currently licensed and being used to store and transport SNF but were not designed for permanent geologic disposal.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2021

Impact of Surface Recombination on Single-Event Charge Collection in an SOI Technology

Semiconductor–insulator interfaces play an important role in the reliability of integrated devices; however, the impact of these interfaces on the physical mechanisms related to single-event effects has not been previously reported. We present experimental data that demonstrate that single-event charge collection can be impacted by changes in interface quality. The experimental data, combined with simulations, show that single-event response may depend on surface recombination at interface defects. The effect depends on strike location and increases with increasing linear energy transfer (LET). Surface recombination can affect single-event charge collection for interfaces with a surface recombination velocity (SRV) of 1000 cm/s and is a dominant charge collection mechanism with SRV >10 5 cm/s.

42 ENGINEERING↗

DOE OSTI2023

Apparatus and methods of detecting transient discharge modes and/or closed loop control of pulsed systems and method employing same

A system and method for differentiating between different modes of pulsed electrical discharges via of an amplitude to time (ATC) conversion circuit is described. A bipolar ATC circuit is used to add together the positive and negative portions of an attenuated and filtered signal derived either from the voltage or current of a pulse. Alternatively, a unipolar ATC circuit may be employed. The resulting processed signal is compared against a reference voltage to generate an output signal that is active for the amount of time that the processed signal exceeds the reference voltage. Discharge mode is determined based on three factors: did a pulse occur, if a pulse occurred when did the pulse start relative to the original pulse event, and what is the duty cycle of the pulse. Subsequent pulse generated may be controlled accordingly.

Fitzpatrick, Joseph F.↗

DOE OSTI2021

Ir(III)-Naphthoquinone complex as a platform for photocatalytic activity

Inspired by the primary events that take place in Photosystem II (PSII), we designed and synthesized a heteroleptic Ir(III) complex featuring an attached naphthoquinone (NQ) as an electron transfer (ET) auxiliary reminiscent of the plastoquinone electron acceptor in PSII. In this design, NQ is covalently attached to the 2,2'-bipyridyl (bpy) ligand of [Ir(dF(CF 3 )ppy) 2 (bpy)][PF 6 ], (dF(CF 3 )ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine). Following excitation of the photocatalyst ([Ir(dF(CF 3 )ppy) 2 (bpy-NQ)][PF 6 ]), reduced NQ (NQ •– ) was observed in transient absorption spectroscopy. Here, this novel catalyst has potential applications in oxidative and reductive photocatalytic processes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2023

Medium-Voltage Testbed for Comparing Advanced Power Line Sensors vs. Measurement Transformers with Electrical Grid Events

Electrical utilities have relied upon potential transformers (PTs) and current transformers (CTs) for very accurate metering and to provide reliable signals for protective relays. Less expensive alternative sensing technologies offer the possibility of wider deployment, particularly in grids that employ distributed energy resources. In this work, the performance of an advanced medi-um-voltage sensor is compared with a reference PT and CT and experimentally evaluated for different power grid scenarios on an advanced outdoor power line sensor testbed at the US De-partment of Energy’s Oak Ridge National Laboratory. The sensor is based on a capacitive divider for voltage monitoring and a Rogowski coil with integrator for current monitoring. The advanced outdoor power line sensor testbed has a real-time simulator that was used to generate transient scenarios (e.g., electrical faults, capacitor bank operation, service restoration), while the analog signals were recorded by the same high resolution power meter. The behavior of analog signals, harmonic components, total harmonic distortion, and crest factors were assessed for this power line sensor compared with the reference PT/CT, because of the absence for testing standards for advanced outdoor power line sensors.

Piesciorovsky, Emilio↗

DOE OSTI2025

Ion-rich Acceleration during an Eruptive Flux Rope Event in a Multiple Null-point Configuration

We report on the γ-ray emission above 100 MeV from the GOES M3.3 flare SOL2012-06-03. The hard X-ray (HXR) and microwave emissions have typical time profiles with a fast rise to a well-defined peak followed by a slower decay. The >100 MeV emission during the prompt phase displayed a double-peaked temporal structure with the first peak following the HXR and microwaves, and the second one, about 3 times stronger, occurring 17 ± 2 s later. The time profiles seem to indicate two separate acceleration mechanisms at work, where the second γ-ray peak reveals a potentially pure or at least largely dominant ion acceleration. The Atmospheric Imaging Assembly imaging shows a bright elliptical ribbon and a transient brightening in the northwestern (NW) region. Nonlinear force-free extrapolations at the time of the impulsive peaks show closed field lines connecting the NW region to the southeastern part of the ribbon, and the magnetic topology revealed clusters of nulls. These observations suggest a spine-and-fan geometry, and based on these observations, we interpret the second γ-ray peak as being due to the predominant acceleration of ions in a region with multiple null points. The >100 MeV emission from this flare also exhibits a delayed phase with an exponential decay of roughly 350 s. We find that the delayed emission is consistent with ions being trapped in a closed flux tube with gradual escape via their loss cone to the chromosphere.

Pesce-Rollins, Melissa [Istituto Nazionale di Fisi↗

DOE OSTI2021

Adsorption Processes during Electrochemical Atomic Layer Deposition of Gold

Electrochemical atomic layer deposition (e-ALD) technique offers a simple and effective "wet chemistry" approach enabling high-precision monolayer-by-monolayer deposition of metal films. The process of e-ALD of Au involves lead underpotential deposition (PbUPD) followed by its redox replacement by a Au monolayer. The time evolution of the deposit mass during "one-pot" Au e-ALD is known to exhibit a unique three-stage response that is presently not well understood. In this work, we probe this response using voltammetry, electrochemical quartz crystal microgravimetry (e-QCM), and chronoamperometry to unravel the underlying mechanistic events during Au e-ALD. Furthermore, the presence of adsorbed Au +3 -ligand complex(es) (Au-L) on the Au surface is established. In stage I of e-ALD, this Au-L adsorbed layer is reduced to Au while a Pb UPD adlayer is formed. In stage II, the Pb UPD adlayer undergoes spontaneous surface-limited redox replacement by nobler Au under open-circuit conditions. Finally, in stage III, re-adsorption of the Au-L occurs on the newly deposited Au. Quantitative analysis of the deposit mass transients obtained under a variety of conditions provides an estimate of the Au-L mass and its molecular weight.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Status of EM Pump Modeling Capability for VTR

SAS4A/SASSYS-1 is a simulation tool used to perform deterministic analyses of anticipated events as well as design basis and beyond design basis accidents for advanced liquid-metal-cooled nuclear reactors. Most recently, SAS4A/SASSYS-1 has been selected as the safety analysis software for the Versatile Test Reactor (VTR), a new materials testing Sodium Fast Reactor (SFR) to be built by the Department of Energy. In order to support analysis of the VTR, which will utilize ElectroMagnetic (EM) pumps as the primary coolant pumps, the development of new EM pump modeling capabilities has been initiated for SAS4/SASSYS-1. The new physics-based EM pump model captures systems-level transient performance based on equivalent circuit theory and is highly flexible to model a wide range of electromagnetic pumps of the three-phase linear induction type subject to changes in power supply and plant conditions. Within the equivalent circuit framework, two sub-models are developed to provide options for analysts both with and without a detailed geometric characterization of their pump such that minimal information is required to achieve a realistic working model, but specific details of a particular pump design may be captured if sufficient information is provided. In addition, heat generated from pump operation and its transport through the plant system can be modeled to better capture the behavior of certain transients. This paper will outline the model and derive the governing equations of the new EM pump model. An initial comparison between the simple EM pump model and experimental data is made. This comparison shows that the equivalent circuit model can capture pump performance, with greater accuracy near the rated conditions. In order to demonstrate the transient behavior of the new model, a simple transient with an EM pump replacing the centrifugal pumps in the Advanced Burner Test Reactor is included.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2021

Status of EM Pump Modeling Capability for VTR

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2022

Start-up and Emergency Shutdown Modeling for a Coal-fired 10MWe sCO₂ Power Plant

As part of a Phase II Front End Engineering Design (FEED) study for the DOE Fossil Fuel Large Scale Pilots program, investigations of novel start-up and emergency shutdown methods for a stoker-fed, coal-fired, 10MWe sCO₂ power plant proposal were performed. These investigations were performed using 1D transient system models of the plant created within the GT-SUITE system modeling platform. The system model components were created using vendor quotation data (heat exchangers), performance maps (turbomachines), or FMU models (fired heater). Previously, Echogen Power Systems (Echogen) has used a sCO₂ power cycle start-up method that fills the system with liquid CO₂ to facilitate easy use of an electrically-driven start pump to transition the system from initial CO₂ fill to turbo-compressor initialization. The novel start-up method presented attempts this transition with a minimal filling of the system with liquid CO₂, to reduce the total CO₂ inventory required. This method leaves the start pump vulnerable to a two phase inlet condition as system pressure is below the CO₂ saturation pressure for the condenser cooling water temperature (Tcw). System model cases at Tcw of 18°C, 26°C, and 32°C, corresponding to cold, design, and hot ambient days, were analyzed to determine if the SP inlet condition could be kept as a subcooled liquid and estimate the CO₂ inventory reduction amount./p> Stoker-fed, coal-fired heaters continue to emit heat for some time even after emergency shutdown from events such as a power failure. This heat emission would lead to a failure of the fired heater, as the metal overheats, if the CO₂ flow is shut off. The emergency shutdown method presented utilizes CO₂ vented by a controllable vent valve (CRV) to provide CO₂ cooling flow to the fired heater. To determine the effectiveness of this method at keeping the fired heater peak tubing metal temperature below the ASME material temperature limit, for pressures below 5 MPa, of 816 °C, system model cases with CRV diameters ranging from 4” to 10”, and an alternative CO₂ vent routing with CRV size of 6”, were investigated./p>

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2022

Critical heat flux on zircaloy and accident tolerant fuel cladding under prototypical conditions of pressurized and boiling water reactors

First of a kind high spatial and temporal resolution temperature measurements of Pressurized Water Reactor and Boiling Water Reactor simulated fuel pins (high heat flux cosine profile heaters) in annular rod type geometry during nucleate boiling, departure from nucleate boiling and re-wetting has been performed. Distributed fiber optic measurements of the cladding axial temperature with spatial resolutions down to 2.5 mm axially at up to three equally spaced azimuthal locations per rod have demonstrated the similarities and differences of the different accident tolerant fuel cladding materials. These experiments show the performance of accident tolerant cladding with a precise measurement of the location and evolution of dryout followed by the re-wetting phenomena (see supplementary time history of a critical heat flux event). Experimental parameters varied coolant mass fluxes from 1695 to 2712 kg/m 2 s, pressures from 10 to 20 MPa, and inlet subcooling from 10 to 55 °C. It was found that the coatings and different material have little effect on the value of the critical heat flux. Any discrepancies between the local critical heat flux verified among the cladding material are attributed to different departure from nucleate boiling phenomena captured during the experiment with the high-resolution optical fiber temperature data. Substantial differences in the performance of the different cladding material to survive a critical heat flux event were however observed by post-test X-ray and optical inspection. External evident damage and internal cracks to the simulated fuel pin having the bare zircaloy cladding were observed in regions associated with the occurrence of the critical heat flux for longer periods. Such damages were associated with zirconium oxidation, and not noticed on the Cr coated zircaloy or FeCrAl claddings. These results indicate that the use of FeCrAl or a Cr coated zircaloy as cladding in Pressurized Water Reactor and Boiling Water Reactor may increase the survivability of the cladding material for short transients.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2020

Distributed Small-Signal Stability Conditions for Inverter-Based Unbalanced Microgrids

The proliferation of inverter-based generation and advanced sensing, controls, and communication infrastructure have facilitated accelerated deployment of microgrids. A coordinated network of microgrids can maintain reliable power delivery to critical facilities during extreme events. Low-inertia offered by the power-electronics–interfaced energy resources, however, can present significant challenges to ensuring stable operation of the microgrids. In this work, distributed small-signal stability conditions for inverter-based microgrids are developed that involve the droop-controller parameters and the network parameters (e.g. line impedances, loads). The distributed closed-form parametric stability conditions derived in this paper can be verified in a computationally efficient manner, facilitating reliable design and operations of networks of microgrids. Dynamic phasor models have been used to capture the effects of electromagnetic transients. Furthermore, numerical results are presented, along with PSCAD simulations, to validate the analytical stability conditions. Effects of design choices, such as the conductor types, and inverter sizes, on the small-signal stability of inverter-based microgrids are investigated to derive useful engineering insights.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2021

Shallow-to-Deep Convective Transition in the Amazon (Final Report)

The frequent and extensive deep cloud formations over the Amazon Basin provide a vast area of atmospheric heating in the Tropics, forcing large-scale global circulations on daily to secular time scales. Motivated by the importance of these systems to the global climate system and the well-documented seasonal cycle in rainfall over the Amazon Basin, this study focused on improving understanding of the processes governing these systems on seasonal time scales and their impact on the typical growth of convection from early afternoon through evening, termed the shallow-to-deep transition. This study is based on observations from the Department of Energy (DOE) ARM Mobile Facility (AMF) near Manacapuru, Brazil collected during the Observations and Modeling of the Green Ocean Amazon (GOAmazon) field campaign from 1 January 2014 to 30 November 2015, together with total column water vapor (CWV) and surface meteorological observations from a dense Global Navigation Satellite System (GNSS) network within 50 km of the AMF site provided by the CHUVA Program collected in coordination with the GOAmazon campaign. The specific objectives of this study were to address the following questions: 1) What environmental conditions support the shallow-to-deep convective transition over the Central Amazon? 2) How does the relative importance of these conditions compare during the wet and dry seasons? 3) How are these conditions modulated by basin-scale transient forcing? 4) How well are these processes captured by regional model simulations convective resolving scale? Our main hypothesis was that intra-seasonal atmospheric disturbances were a primary driver of rainfall during the wet season in the Central Amazon, while localized surface heating of the land was the primary driver of enhanced rainfall during the dry season. Overall, our findings supported our hypothesis, with the convectively active phase of atmospheric Kelvin waves strongly favoring the development of larger, more organized rain systems during the wet season, while localized isolated deep convection dominated the types of rain events seen during the dry season. These results have implications for the predictability of rainfall over the Central Amazon and for its representation in climate and weather models.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

National Spherical Torus eXperiment - Upgrade NSTX-U: Structural Analysis of Passive Plates Support Brackets

The objective of this analysis is to estimate and assess the stresses in the passive plates caused by a limiting plasma disruption. The objective of this calculation is also to address observed damage to mounting hardware after completion of NSTX operation. These observations initiated diagnostic efforts during the Upgrade project to monitor the severity of the disruptions that were causing the damage, and planned instrumentation to trend the behavior of the mounting hardware. The Recovery Project mission for the passive plate hardware is to appropriately reinforce the passive plates with stainless steel ribs mounted on the back of the plate to reduce their flexure and stress and reinforcements of the “biscuit” components of the bracketry to transfer loads without damage to bolts, biscuits, and bracket plates and welds. Mid-plane disruptions and quenches were manageable with NSTX vintage hardware. The Vertical Displacement Event (VDE) disruptions position the plasma closer to the passive plates and are more severe than the centered plasma. Earlier work pointed to the P1-P5 VDE as limiting. This has been confirmed by A. Brooks work in support of the load generation effort in reference. During vertical displacement large counter currents are generated in the plate as the plasma approaches it. - as would be expected from passive plates. When the plasma disrupts the currents in the plates are reversed, which also reverses the loading on the plates. This report documents the methodology and results of transient structural analysis on the plasma, passive plates support brackets. The loads induced by eddy and halo currents have been considered, and were generated using a separate electromagnetic analysis (NSTXU_1_11_2_1_CALC_051). The structural model also incorporates the effects from preload. Calculation was performed with the assumption that existing biscuits are not participating in the load bearing except the biscuits connected to jumper bolts, which are fully engaged. Results show that with the planned reinforcements, Passive plates and mounting structures satisfy static and fatigue criteria in all areas except welds, where separate analysis was performed. Both symmetric and asymmetric (with locating block) designs were analyzed, and although stresses were higher without locating block they still satisfy NSTX design criteria.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗