Engineering Papers⌕ Search

Engineering topics

Yang, Y.

Publications and source records attributed to Yang, Y..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Micro-mechanical evaluation of SiC-SiC composite interphase properties and debond mechanisms

SiC-SiC composites exhibit exceptional high temperature strength and oxidation properties making them an advantageous choice for accident tolerant nuclear fuel cladding. In the present work, small scale mechanical testing along with AFM and TEM analysis were employed to evaluate PyC interphase properties that play a key role in the overall mechanical behavior of the composite. The Mohr-Coulomb formulation allowed for the extraction of the internal friction coefficient and debonding shear strength as a function of the PyC layer thickness, an additional parameter. Here, these results have led to re-evaluation of the Mohr-Coulomb failure criterion and adjustment via a new phenomenological equation.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Future Nuclear Energy Factual Status Document: Resource Document for the Workshop on Basic Research Needs for Future Nuclear Energy, July 2017

Since commercialization in the mid-1950s, nuclear power has been widely deployed and provides an important clean source of energy, primarily through the generation of electricity. There are currently 449 commercial nuclear power reactors operating in 31 countries with over 390 GWe total capacity, with 99 operating units in the United States with a total generating capacity of about 100 GWe. Nuclear power plants provide over 11% of the world’s electricity production and, as of 2016, thirteen countries rely on nuclear energy to supply at least one-quarter of their total electricity. Virtually all of that power is generated with water-cooled reactor systems. A number of advanced nuclear energy system concepts have been developed to provide improved efficiency, greater fissile fuel utilization, reduced high level waste generation, and increased margins of safety over today’s water-cooled systems. However, there are a number of technical challenges that must be addressed to enable the broad deployment of these systems from concept to the electrical grid. This Technical Document is written to provide workshop participants with an overview of the current status of a number of advanced reactor systems: Key issues for advanced nuclear energy, including coolants, materials in extremes (irradiation, coolant, and/or high temperature) and interfaces; Nuclear fuel technologies for key reactor types and limitations in testing and design; State of science and understanding for nuclear systems, including characterization, testing, and modeling and simulation tools. For each of these technical areas, this document describes the technological challenge, current state of the art for the technology, and barriers to advanced nuclear concepts.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Event generator tuning using Bayesian optimization

Monte Carlo event generators contain a large number of parameters that must be determined by comparing the output of the generator with experimental data. Generating enough events with a fixed set of parameter values to enable making such a comparison is extremely CPU intensive, which prohibits performing a simple brute-force grid-based tuning of the parameters. Bayesian optimization is a powerful method designed for such black-box tuning applications. In this article, we show that Monte Carlo event generator parameters can be accurately obtained using Bayesian optimization and minimal expert-level physics knowledge. A tune of the PYTHIA 8 event generator using $e^+e^-$ events, where 20 parameters are optimized, can be run on a modern laptop in just two days. Combining the Bayesian optimization approach with expert knowledge should enable producing better tunes in the future, by making it faster and easier to study discrepancies between Monte Carlo and experimental data.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Thermodynamic and kinetic modeling of grain boundary equilibrium segregation of P in α-Fe

Phosphorus is a primary contributor to interface fracture and embrittlement in steels because of its strong segregation tendency at grain boundaries (GBs). The lack of consistency in literature data imposes great difficulties in performing segregation modeling that is compatible with both the Langmuir-Mclean segregation theory and the thermodynamic description of the Bcc(Fe,P) phase. Our work carefully evaluated experimental data for phosphorus segregation at GBs in -Fe and provided a new formula for converting the auger electron spectroscopy (AES) peak height ratio to GBs. Furthermore, based on newly assessed literature data, this work proposes that the major driving force for phosphorus segregation is the formation of Fe 3 P-type clusters at GBs, which is supported not only by the almost equivalent Gibbs energy of _Fe using the Bcc(Fe,P) substitutional model and the Bcc(Fe,Fe 3 P, P) associate model, but also by the good agreement between thermodynamic/kinetic modeling results and experimental data.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Dynamic phases, clustering, and chain formation for driven disk systems in the presence of quenched disorder

In this paper, we numerically examine the dynamic phases and pattern formation of two-dimensional monodisperse repulsive disks driven over random quenched disorder. We show that there is a series of distinct dynamic regimes as a function of increasing drive, including a clogged or pile-up phase near depinning, a homogeneous disordered flow state, and a dynamically phase separated regime consisting of high-density crystalline regions surrounded by a low density of disordered disks. At the highest drives the disks arrange into one-dimensional moving chains. The phase separated regime has parallels with the phase separation observed in active matter systems, but arises from a distinct mechanism consisting of the combination of nonequilibrium fluctuations with density-dependent mobility. We discuss the pronounced differences between this system and previous studies of driven particles with longer-range repulsive interactions moving over random substrates, such as superconducting vortices or electron crystals, where dynamical phase separation and distinct one-dimensional moving chains are not observed. Finally, our results should be generic to a broad class of systems in which the particle-particle interactions are short ranged, such as sterically interacting colloids or Yukawa particles with strong screening driven over random pinning arrays, superconducting vortices in the limit of small penetration depths, or quasi-two-dimensional granular matter flowing over rough landscapes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

REVISITING A CLASSIC: THE PARKER–MOFFATT PROBLEM

The interaction of two colliding Alfvén wave packets is described here by means of magnetohydrodynamics (MHD) and hybrid kinetic numerical simulations. The MHD evolution revisits the theoretical insights described by Moffatt, Parker, Kraichnan, Chandrasekhar, and Elsässer in which the oppositely propagating large-amplitude wave packets interact for a finite time, initiating turbulence. However, the extension to include compressive and kinetic effects, while maintaining the gross characteristics of the simpler classic formulation, also reveals intriguing features that go beyond the pure MHD treatment.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Muon identification with Muon Telescope Detector at the STAR experiment

The Muon Telescope Detector (MTD) is a newly installed detector in the STAR experiment. It provides an excellent opportunity to study heavy quarkonium physics using the dimuon channel in heavy ion collisions. In this paper, we report the muon identification performance for the MTD using proton-proton collisions at $\sqrt{s}$ = 500 GeV with various methods. Here, the result using the Likelihood Ratio method shows that the muon identification efficiency can reach up to ~ 90% for muons with transverse momenta greater than 3 GeV/c and the significance of the J/ψ signal is improved by a factor of 2 compared to using the basic selection.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Sic-Sic Composite Interphase Evaluation via Small Scale Mechanical Testing

Silicon carbide (SiC) has emerged as a highly capable engineering material for extreme environment applications. It has proven particularly useful for high temperature applications where it exhibits exceptional strength, relative chemical inertness, and low coefficient of thermal expansion. Recent studies have shown that SiC also has excellent neutronic properties including low thermal neutron absorption, low tritium permeability, and high radiation tolerance. As a result, SiC-SiC composites are being considered for application in accident tolerant fuel cladding and other structural components for fission and fusion reactors. The standard crystalline form of SiC is inherently brittle and therefore subject to low damage tolerance. In order to increase the material toughness, SiC-SiC fiber-matrix composites have been developed. These composites are divided into three constituents; a highly crystalline and near stoichiometric SiC fiber (commonly Hi-Nicalon{sup TM} Type-S or Tyranno{sup TM}-SA), a (layered) interphase of graphitized pyrolytic carbon (PyC) around the fiber, and a chemical vapor infiltrated (CVI) SiC matrix that consolidates the material. Increased toughness is achieved through two primary mechanisms: increasing the crack length by introducing more barriers, and fiber pullout via interphase shear within the matrix. As a result, it has become critically important to understand the fundamental properties of SiC-SiC composites. However, comprehensive material properties are difficult to predict unless we have an in depth knowledge of the individual constituents (fiber, matrix, interphase) and how their properties interact with one another at the micro-scale. Of specific interest to this work are the interfacial properties of the fiber-matrix interface. This includes the internal friction coefficient and interfacial debond shear stress. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2016

Uniform corrosion of FeCrAl alloys in LWR coolant environments

The corrosion behavior of commercial and model FeCrAl alloys and type 310 stainless steel was examined by autoclave tests and compared to Zircaloy-4, the reference cladding materials in light water reactors. The corrosion studies were carried out in three distinct water chemistry environments found in pressurized and boiling water reactor primary coolant loop conditions for up to one year. The structure and morphology of the oxides formed on the surface of these alloys was consistent with thermodynamic predictions. Spinel-type oxides were found to be present after hydrogen water chemistry exposures, while the oxygenated water tests resulted in the formation of very thin and protective hematite-type oxides. Unlike the alloys exposed to oxygenated water tests, the alloys tested in hydrogen water chemistry conditions experienced mass loss as a function of time. This mass loss was the result of net sum of mass gain due to parabolic oxidation and mass loss due to dissolution that also exhibits parabolic kinetics. Finally, the maximum thickness loss after one year of LWR water corrosion in the absence of irradiation was ~2 μm, which is inconsequential for a ~300–500 μm thick cladding.

36 MATERIALS SCIENCE↗
DOE OSTI2016

MO-D-BRB-02: SBRT Treatment Planning and Delivery

Increased use of SBRT and hypofractionation in radiation oncology practice has posted a number of challenges to medical physicist, ranging from planning, image-guided patient setup and on-treatment monitoring, to quality assurance (QA) and dose delivery. This symposium is designed to provide current knowledge necessary for the safe and efficient implementation of SBRT in various linac platforms, including the emerging digital linacs equipped with high dose rate FFF beams. Issues related to 4D CT, PET and MRI simulations, 3D/4D CBCT guided patient setup, real-time image guidance during SBRT dose delivery using gated/un-gated VMAT/IMRT, and technical advancements in QA of SBRT (in particular, strategies dealing with high dose rate FFF beams) will be addressed. The symposium will help the attendees to gain a comprehensive understanding of the SBRT workflow and facilitate their clinical implementation of the state-of-art imaging and planning techniques. Learning Objectives: Present background knowledge of SBRT, describe essential requirements for safe implementation of SBRT, and discuss issues specific to SBRT treatment planning and QA. Update on the use of multi-dimensional and multi-modality imaging for reliable guidance of SBRT. Discuss treatment planning and QA issues specific to SBRT. Provide a comprehensive overview of emerging digital linacs and summarize the key geometric and dosimetric features of the new generation of linacs for substantially improved SBRT. NIH/NCI; Varian Medical Systems; F. Yin, Duke University has a research agreement with Varian Medical Systems. In addition to research grant, I had a technology license agreement with Varian Medical Systems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

KLL dielectronic recombination resonant strengths of He-like up to O-like tungsten ions

Dielectronic recombination (DR) is an important process in hot plasma physics as well as in atomic structure and collision theory. This work reports the studies of the KLL DR resonance strengths of He-, Li-, Be-, B-, C-, N-, and O-like tungsten ions, through both experiment and calculation. The experimental resonance strengths were determined within uncertainty below 11% at the Shanghai electron beam ion trap by employing a fast electron beam-energy scanning technique. A fully relativistic configuration interaction method implemented in the flexible atomic code was employed to calculate DR process and also radiative recombination (RR). The consideration of the interference effect between DR and RR was revealed to be necessary to determine the resonance strength.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Robust and compact entanglement generation from diode-laser-pumped four-wave mixing

Four-wave-mixing processes are now routinely used to demonstrate multi-spatial-mode Einstein-Podolsky-Rosen entanglement and intensity difference squeezing. Diode-laser-pumped four-wave mixing processes have recently been shown to provide an affordable, compact, and stable source for intensity difference squeezing, but it was unknown if excess phase noise present in power amplifier pump configurations would be an impediment to achieving quadrature entanglement. Here, we demonstrate the operating regimes under which these systems are capable of producing entanglement and under which excess phase noise produced by the amplifier contaminates the output state. We show that Einstein-Podolsky-Rosen entanglement in two mode squeezed states can be generated by a four-wave-mixing source deriving both the pump field and the local oscillators from a tapered-amplifier diode-laser. This robust continuous variable entanglement source is highly scalable and amenable to miniaturization, making it a critical step toward the development of integrated quantum sensors and scalable quantum information processors, such as spatial comb cluster states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Thermal Aging Phenomena in Cast Duplex Stainless Steels

Cast stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr–rich α'-phase by Spinodal decomposition of δ-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. An approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program and the results are used to describe the precipitation behaviors in duplex stainless steels. These results are also to be used to guide an on-going research aiming to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

Aging↗
DOE OSTI2016

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗