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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Comparison of Calculated and Experimental Flows and Pressures in the Orifice Flow Test Facility

A new experimental facility for materials irradiation and testing at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) is being developed. Details of this facility have been presented in previous work. A prototype of this facility, the Thermosyphon Test Loop (TSTL), has been built and experimental data have been obtained and analyzed. Comparison of TSTL experimental data and calculations has been presented previously. The TSTL did not measure any flows (water or vapor) inside the test section because flowmeters could not be installed inside. Instead, two pressure sensors (P1 and P2) were installed at the bottom of the test section to measure the pressure differential ({Delta}P = P1-P2) across the orifices between the bottom of the downcomer and the bottom of the boiler. This {Delta}P is proportional to the water flow, but actual flows were not measured. Thus, another facility, the Orifice Flow Test Facility (OFTF), was built to measure water flow vs {Delta}P. The OFTF duplicates the bottom of the test section of the TSTL. The OFTF models the downcomer and the boiler including three dummy heaters (without power) inside the boiler. This paper presents the experimental data obtained and comparison to computer calculations. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Crystal Plasticity Model of Reactor Pressure Vessel Embrittlement in GRIZZLY

The integrity of reactor pressure vessels (RPVs) is of utmost importance to ensure safe operation of nuclear reactors under extended lifetime. Microstructure-scale models at various length and time scales, coupled concurrently or through homogenization methods, can play a crucial role in understanding and quantifying irradiation-induced defect production, growth and their influence on mechanical behavior of RPV steels. A multi-scale approach, involving atomistic, meso- and engineering-scale models, is currently being pursued within the GRIZZLY project to understand and quantify irradiation-induced embrittlement of RPV steels. Within this framework, a dislocation-density based crystal plasticity model has been developed in GRIZZLY that captures the effect of irradiation-induced defects on the flow stress behavior and is presented in this report. The present formulation accounts for the interaction between self-interstitial loops and matrix dislocations. The model predictions have been validated with experiments and dislocation dynamics simulation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1974

An investigation of the open-loop amplification of a Reynolds number dependent process by wave distortion

The response of a constant-temperature hot-wire anemometer to sinusoidal and distorted sinusoidal acoustic oscillations is examined. The output of the anemometer is dependent upon the Reynolds number of the flow over the wire. The response is a measure of the interaction between the anemometer output and the acoustic pressure in the neighborhood of the wire. It is an open-loop prediction of the characteristics of actual closed-loop operation of a system. If the open-loop response is large enough, unstable closed-loop operation is predicted. The study was motivated by a need to investigate the stability limits of liquid-propellant rockets when perturbed by pressure oscillations. The sinusoidal and distorted sinusoidal acoustic oscillations used for this study are the same as those characteristic of unstable rocket combustion. Qualitatively, the results are similar--the response of the system to pure sinusoidal acoustic vibration of the fluid surrounding the wire is small, even when the magnitude of the acoustic pressure is quite large; but the response can be increased by as much as an order of magnitude with respect to the sinusoidal case by the addition of distortion. The amplitude and phase of the distortion component, relative to the fundamental component, are the dominant factors in the increase in the response.

Ventrice, M. B.↗
NASA NTRS1991

Human life support during interplanetary travel and domicile. II - Generic Modular Flow Schematic modeling

This paper describes the Generic Modular Flow Schematic (GMFS) architecture capable of encompassing all functional elements of a physical/chemical life support system (LSS). The GMFS can be implemented to synthesize, model, analyze, and quantitatively compare many configurations of LSSs, from a simple, completely open-loop to a very complex closed-loop. The GMFS model is coded in ASPEN, a state-of-the-art chemical process simulation program, to accurately compute the material, heat, and power flow quantities for every stream in each of the subsystem functional elements (SFEs) in the chosen configuration of a life support system. The GMFS approach integrates the various SFEs and subsystems in a hierarchical and modular fashion facilitating rapid substitutions and reconfiguration of a life support system. The comprehensive ASPEN material and energy balance output is transferred to a systems and technology assessment spreadsheet for rigorous system analysis and trade studies.

Farral, Joseph F.↗
DOE OSTI2018

Final Technical Report for DE-SC0013619

The Facility for Rare Isotope Beams (FRIB) is a new national user facility currently under construction on the campus of Michigan State University (MSU) in the United States. This facility will produce beams of radionuclides that have previously only existed in supernovae explosions and the crusts of neutron stars. As it creates and delivers beams of some of the most exotic nuclei in the universe, FRIB will simultaneously generate thousands of other radionuclides that could be synergistically harvested without impact to the primary experiment. Many of these co-produced isotopes are of significant interest for research in biomedicine, energy, environmental studies, plant sciences, and materials science. The primary beam dump, a spinning titanium container filled with cooling water, will contain the vast majority of co-produced isotopes at FRIB. There are several challenges associated with isotope harvesting from the primary beam dump loop. While a long-lived isotopes like 148Gd (70.9 y) can be harvested from the spent resin beds, methods will need to be developed to efficiently recover trace amounts of the isotope from the large volume resin. Conversely, while short-lived isotopes can be recovered in situ, the neutral pH environment, high flow rates, and large volume introduce unique challenges for efficiently harvesting ultra-trace amounts of an isotope from the circulating water loop. We have demonstrated in this work a way to harvest long-lived isotopes like 148Gd from the spent resin beds in way that minimizes the waste generated from processing nearly 200 L of the resin. We have also demonstrated that hollow fiber supported liquid membranes (HFSLM) can recover 70% of ultra-trace levels (less than 10 parts-per-trillion) of vanadium from a circulating water loop at pH 7. The work also demonstrated recovery from a solution containing the competing species at the concentrations anticipated for a one week run at FRIB with the primary ion beam 58Ni. To the best of our knowledge, this is the first demonstration of HFSLM for such ultra-trace concentrations.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1983

Modeling of transient disturbances in coronal-streamer configurations

Numerical simulations of the formation and propagation of mass ejection, loop transients in coronal streamers are discussed. The simulations are accomplished with numerical solutions of the single fluid, ideal MHD equations of motion in the meridional plane. The streamer is produced by simulating the relaxation of an initially radial hydrodynamic flow coupled with a dipole magnetic field. The simulated transient then results from an energy release at the base of the streamer. The legs of the loop transient produced remain essentially stationary while the loop expands mainly in the radial direction with velocities of 400 to 750 km s-1. Once the leading edge of the transient has passed out of the lower corona, the initial streamer configuration is restored after 15 to 24 hours. A second energy release 2 hours later than, and with an energy release identical to, the first does not produce a significant coronal disturbance.

Steinolfson, R. S.↗
DOE OSTI2017

Vortex and Sink Flows in Eruptive Flares as a Model for Coronal Implosions

Eruptive flares are sudden releases of magnetic energy that involve many phenomena, several of which can be explained by the standard 2D flare model and its realizations in 3D. We analyze a 3D magnetohydrodynamics simulation, in the framework of this model, that naturally explains the contraction of coronal loops in the proximity of the flare sites, as well as the inflow toward the region above the cusp-shaped loops. We find that two vorticity arcs located along the flanks of the erupting magnetic flux rope are generated as soon as the eruption begins. The magnetic arcades above the flux rope legs are then subjected to expansion, rotation, or contraction depending on which part of the vortex flow advects them. In addition to the vortices, an inward-directed magnetic pressure gradient exists in the current sheet below the magnetic flux rope. It results in the formation of a sink that is maintained by reconnection. We conclude that coronal loop apparent implosions observed during eruptive flares are the result of hydromagnetic effects related to the generation of vortex and sink flows when a flux rope moves in a magnetized environment.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Compatibility of SiC with ODS FeCrAl in flowing Pb-Li at 600° - 700°C

To establish the maximum operating temperature for the dual coolant lead lithium (DCLL) blanket concept, thermal convection loop (TCL) experiments were conducted for 1000 h with a peak temperature of 700 °C to determine compatibility with commercial eutectic Pb~17at.%Li. Two TCLs were fabricated from alloy APMT (FeCrAlMo) and the baseline TCL experiment contained only APMT specimens. The second TCL experiment exposed more fusion relevant CVD SiC and ODS Fe-10Cr-6Al specimens in the hot and cold legs. In the second experiment, the mass losses were much larger for the ODS FeCrAl specimens and most of the CVD SiC specimens experienced a mass gain as SiC reacted to form an Fe- and Cr-rich carbide reaction product. Dissolved Fe and Cr reacted with the SiC and removing Fe and Cr from the liquid appeared to increase ODS FeCrAl dissolution. Such a dissimilar material interaction appears consistent with thermodynamic calculations. Significant attack at the top of the hot leg in both experiments suggests that the Pb-Li compatibility of FeCrAl alloys is inadequate at 700 °C in a flowing environment and the maximum PbLi temperature is < 675 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Flow Sensor Test Article (F-STAr) (Design and Fabrication Status Report)

The Flow Sensor Test Article (F-STAr) is a test article currently under construction for the Mechanisms Engineering Test Loop (METL). F-STAr was designed to provide high sodium flowrate capabilities for sensor calibration, component testing, and fluid studies. Figure 1 shows two solid model views of the new test article. F-STAr includes a high-capacity pump that can provide a nominal flowrate of 120 GPM; a test section support structure that can accommodate a wide array of sub-test articles and their instrumentation; and finally, a heating and cooling system to aid in controlling the testing environment. Initially, F-STAr will be configured to test liquid metal flow sensors, specifically field shift sensors like the Eddy Current Flow Sensors (ECFS) based on the RDT C4-7T standard. To test these sensors, two test sections were designed that attempt to model Sodium Fast Reactor (SFR) outlet conditions. Figure 2 shows models of the “Full-Scaled Test Section” (FSTS) that represents a generic SFR fuel handling socket and a “Pseudo-Scaled Test Section” (PSTS) that represents a generic array of scaled fuel handling sockets. While F-STAr will be configured to test ECFS’s, it can also be outfitted to meet other experimental needs. For example, F-STAr could be setup with a test section that includes a fluidic diode or a component test investigating the performance of hydrodynamic bearings. Other test sections include studies of sodium thermal hydraulics like thermal striping. Overall, F-STAr is a flexible test article designed to accommodate many needs. This report will provide a status update on the design and construction of F-STAr. Manufacturing of all components has commenced, and several components have already been completed. These components include the pump and test section assembly stand. Other components, such as the heater, have been completed but were rejected due to the vendor not meeting the requirements of the purchase order. Lastly, the submersible flowmeter and main flange components are under construction, and their status will be reviewed in this report. Overall, most of the F-STAr components and parts will be completed by the end of September 2022.

42 ENGINEERING↗
DOE OSTI2018

Fate of superconductivity in three-dimensional disordered Luttinger semimetals

Superconducting instability can occur in three-dimensional quadratic band crossing semimetals only at a finite coupling strength due to the vanishing of density of states at the quadratic band touching point. Since realistic materials are always disordered to some extent, we study the effect of short-ranged-correlated disorder on this superconducting quantum critical point using a controlled loop-expansion applying dimensional regularization. The renormalization group (RG) scheme allows us to determine the RG flows of the various interaction strengths and shows that disorder destroys the superconducting quantum critical point. In fact, the system exhibits a runaway flow to strong disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Electrostatically driven helical plasma state

A novel plasma state has been found in the presence of a uniformly applied axial magnetic field in periodic cylindrical geometry. This state is driven electrostatically by helical electrodes, providing a driving field that depends on the radius and mθ−nζ, where θ is the poloidal angle and ζ=z/R is the toroidal angle. We focus on m=n=1. The radial magnetic field at the wall is taken to be zero. With weak driving, the resulting distortion is very small, but for stronger driving, the mean field of the state has field line safety factor q0(r) just above the pitch of the electrodes m∕n = 1 except near the edge, where q0 increases monotonically. This state is characterized as a single helicity Ohmic equilibrium with the helical symmetry of the applied field. The plasma appears to be close to force-free in the interior, but current density crosses the magnetic flux surfaces near the edge, where current must enter and exit through the helical electrodes. This perpendicular current density drives large helical plasma flows. The sensitivity of this state to flow boundary conditions, plasma resistivity profile, the strength of electrostatic driving, and parameters such as the loop voltage and the Lundquist number is explored. The magnetic helicity is calculated for both the transient period and time-asymptotic state. Possible applications to current drive in toroidal confinement devices and to electrical transformers are discussed.

Akçay, Cihan↗
DOE OSTI2021

Potential vorticity transport in weakly and strongly magnetized plasmas

Tangled magnetic fields, often coexisting with an ordered mean field, have a major impact on turbulence and momentum transport in many plasmas, including those found in the solar tachocline and magnetic confinement devices. We present a novel mean field theory of potential vorticity mixing in β-plane magnetohydrodynamic (MHD) and drift wave turbulence. Our results show that mean square stochastic fields strongly reduce Reynolds stress coherence. This decoherence of potential vorticity flux due to stochastic field scattering leads to suppression of momentum transport and zonal flow formation. A simple calculation suggests that the breaking of the shear-eddy tilting feedback loop by stochastic fields is the key underlying physics mechanism. Furthermore, a dimensionless parameter that quantifies the increment in power threshold is identified and used to assess the impact of stochastic field on the L-H transition. We discuss a model of stochastic fields as a resisto-elastic network.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Holography beyond conformal invariance and AdS isometry?

We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a special relation between functional determinants of the operators acting in the bulk and on its boundary, provided that the boundary operator represents the inverse propagators of the theory induced on the boundary by the Dirichlet boundary value problem in the bulk spacetime. This relation holds for operators of a general spin-tensor structure on generic manifolds with boundaries irrespective of their background geometry and conformal invariance, and it apparently underlies numerous O(N{sup 0}) tests of the AdS/CFT correspondence, based on direct calculation of the bulk and boundary partition functions, Casimir energies, and conformal anomalies. The generalized holographic duality is discussed within the concept of the “double-trace” deformation of the boundary theory, which is responsible in the case of large-N CFT coupled to the tower of higher-spin gauge fields for the renormalization group flow between infrared and ultraviolet fixed points. Potential extension of this method beyond the one-loop order is also briefly discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Comparison of the PLTEMP code flow instability predictions with measurements made with electrically heated channels for the advanced test reactor.

When the University of Missouri Research Reactor (MURR) was designed in the 1960s the potential for fuel element burnout by a phenomenon referred to at that time as 'autocatalytic vapor binding' was of serious concern. This type of burnout was observed to occur at power levels considerably lower than those that were known to cause critical heat flux. The conversion of the MURR from HEU fuel to LEU fuel will probably require significant design changes, such as changes in coolant channel thicknesses, that could affect the thermal-hydraulic behavior of the reactor core. Therefore, the redesign of the MURR to accommodate an LEU core must address the same issues of fuel element burnout that were of concern in the 1960s. The Advanced Test Reactor (ATR) was designed at about the same time as the MURR and had similar concerns with regard to fuel element burnout. These concerns were addressed in the ATR by two groups of thermal-hydraulic tests that employed electrically heated simulated fuel channels. The Croft (1964), Reference 1, tests were performed at ANL. The Waters (1966), Reference 2, tests were performed at Hanford Laboratories in Richland Washington. Since fuel element surface temperatures rise rapidly as burnout conditions are approached, channel surface temperatures were carefully monitored in these experiments. For self-protection, the experimental facilities were designed to cut off the electric power when rapidly increasing surface temperatures were detected. In both the ATR reactor and in the tests with electrically heated channels, the heated length of the fuel plate was 48 inches, which is about twice that of the MURR. Whittle and Forgan (1967) independently conducted tests with electrically heated rectangular channels that were similar to the tests by Croft and by Walters. In the Whittle and Forgan tests the heated length of the channel varied among the tests and was between 16 and 24 inches. Both Waters and Whittle and Forgan show that the cause of the fuel element burnout is due to a form of flow instability. Whittle and Forgan provide a formula that predicts when this flow instability will occur. This formula is included in the PLTEMP/ANL code.Error! Reference source not found. Olson has shown that the PLTEMP/ANL code accurately predicts the powers at which flow instability occurs in the Whittle and Forgan experiments. He also considered the electrically heated tests performed in the ANS Thermal-Hydraulic Test Loop at ORNL and report by M. Siman-Tov et al. The purpose of this memorandum is to demonstrate that the PLTEMP/ANL code accurately predicts the Croft and the Waters tests. This demonstration should provide sufficient confidence that the PLTEMP/ANL code can adequately predict the onset of flow instability for the converted MURR. The MURR core uses light water as a coolant, has a 24-inch active fuel length, downward flow in the core, and an average core velocity of about 7 m/s. The inlet temperature is about 50 C and the peak outlet is about 20 C higher than the inlet for reactor operation at 10 MW. The core pressures range from about 4 to about 5 bar. The peak heat flux is about 110 W/cm{sup 2}. Section 2 describes the mechanism that causes flow instability. Section 3 describes the Whittle and Forgan formula for flow instability. Section 4 briefly describes both the Croft and the Waters experiments. Section 5 describes the PLTEMP/ANL models. Section 6 compares the PLTEMP/ANL predictions based on the Whittle and Forgan formula with the Croft measurements. Section 7 does the same for the Waters measurements. Section 8 provides the range of parameters for the Whittle and Forgan tests. Section 9 discusses the results and provides conclusions. In conclusion, although there is no single test that by itself closely matches the limiting conditions in the MURR, the preponderance of measured data and the ability of the Whittle and Forgan correlation, as implemented in PLTEMP/ANL, to predict the onset of flow instability for these tests leads one to the conclusion that the same method should be able to predict the onset of flow instability in the MURR reasonably well.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Preliminary Two-Phase Terry Turbine Nozzle Models for RCIC Off-Design Operation Conditions

This report presents the effort to extend the single-phase analytical Terry turbine model to cover two-phase off-design conditions. The work includes: (1) adding well-established two-phase choking models – the Isentropic Homogenous Equilibrium Model (IHEM) and Moody’s model, and (2) theoretical development and implementation of a two-phase nozzle expansion model. The two choking models provide bounding cases for the two-phase choking mass flow rate. The new two-phase Terry turbine model uses the choking models to calculate the mass flow rate, the critical pressure at the nozzle throat, and steam quality. In the divergent stage, we only consider the vapor phase with a similar model for the single-phase case by assuming that the liquid phase would slip along the wall with a much slower speed and will not contribute the impulse on the rotor. We also modify the stagnation conditions according to two-phase choking conditions at the throat and the cross-section areas for steam flow at the nozzle throat and at the nozzle exit. The new two-phase Terry turbine model was benchmarked with the same steam nozzle test as for the single-phase model. Better agreement with the experimental data is observed than from the single-phase model. We also repeated the Terry turbine nozzle benchmark work against the Sandia CFD simulation results with the two-phase model for the pure steam inlet nozzle case. The RCIC start-up tests were simulated and compared with the single-phase model. Similar results are obtained. Finally, we designed a new RCIC system test case to simulate the self-regulated Terry turbine behavior observed in Fukushima accidents. In this test, a period inlet condition for the steam quality varying from 1 to 0 is applied. For the high quality inlet period, the RCIC system behaves just like the normal operation condition with a high pump injection flow rate and a nominal steam release rate through the turbine, with the net addition of water to the primary system; for the low quality inlet period, the RCIC turbine shaft work dramatically decreases and results in a much reduced pump injection flow rate, and the mixture flow rate through the turbine increases due to the high liquid phase flow rate. The net effect for this period is net removal of coolant from the primary loop. With the periodic addition and removal of coolant to the primary loop, the self-regulation mode of the RCIC system can be maintained for a quite long time. Both the IHEM and Moody’s models generate similar phenomena; however noticeable differences can be observed.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Relativistic Shear Boundary Layer and the Gamma-Ray Emission of GW170817

We present an analysis of the radiation characteristics of kinetic shear boundary layers created by relativistic plasma jets. Using a model of electromagnetic field data based on particle-in-cell simulations of an electron–ion plasma, we solve the motion of individual test electrons and compute their instantaneous radiated power and peak frequency. By analyzing a large number of test electrons in this manner, we find two distinct electron populations present around the shear boundary layer. The most highly radiative electrons execute looping motion due to crossed electric and magnetic fields as they are accelerated along the bulk flow of the jet, and eventually cross the shear boundary interface at steep angles. Electrons that never cross the shear boundary interface radiate much less energy as a group. Summing over all of the highly radiative electrons, we compute the distribution of the total radiated energy as a function of the angle relative to the bulk flow. Furthermore, this result has important potential implications for the observed radiation output of short gamma-ray bursts viewed at large angles from the jet axis, such as the neutron star merger event GW170817/GRB 170817A.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Bosch CO2 reduction unit research and development.

Development of Bosch CO2 reduction units for manned spacecraft application has been in progress for a decade. The Bosch process catalytically reacts CO2 with H2 to produce water and carbon. The water may then be electrolyzed to close the biological oxygen and process hydrogen loops. A critical problem has been to confine the reaction so that carbon does not block flow and stop the process. Reaction isolation within a replaceable catalyst cartridge has been successfully demonstrated. Objectives of the current development program are a 25% reduction in operating power, an 80% reduction in expendable weight, and minimized resupply volume.

Holmes, R. F.↗
NASA NTRS1976

Distribution of E/N and N sub e in a cross-flow electric discharge laser

The spatial distribution of the ratio of electric field to neutral gas density on a flowing gas, multiple pin-to-plane discharge was measured in a high-power, closed loop laser. The laser was operated at a pressure of 140 torr (1:7:20, CO2, N2, He) with typically a 100 meter/second velocity in the 5 x 8 x 135 centimeter discharge volume. E/N ratios ranged from 2.7 x 10 to the minus 16th power to 1.4 x 10 to the minus 16th power volts/cu cm along the discharge while the electron density ranged from 2.8 x 10 to the 10th power to 1.2 x 10 to the 10th power cm/3.

Dunning, J. W., Jr.↗