TY - CONF TI - Tensile behavior of inconel X750 Sheets: Effect of heat treatment AU - Marsh, C. AU - Kaoumi, D. C2 - 2016/// C3 - Transactions of the American Nuclear Society DA - 2016/// VL - 115 SP - 469-472 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85029410263&partnerID=MN8TOARS ER - TY - CONF TI - In-situ ion irradiation of ZIRLO® alloy AU - Kaoumi, D. AU - Garde, A. AU - Pan, G. C2 - 2016/// C3 - Top Fuel 2016: LWR Fuels with Enhanced Safety and Performance DA - 2016/// SP - 417-424 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85019028888&partnerID=MN8TOARS ER - TY - JOUR TI - Spline-based finite-element method for the stationary quasi-geostrophic equations on arbitrary shaped coastal boundaries AU - Jiang, W. AU - Kim, T.-Y. T2 - Computer Methods in Applied Mechanics and Engineering AB - This work concerns a B-spline based finite-element algorithm for the stationary quasi-geostrophic equations to treat the large scale wind-driven ocean circulation on arbitrary shaped domains. The algorithm models arbitrary shaped coastal boundaries on intra-element, or embedded boundaries. Dirichlet boundary conditions on the embedded boundaries are weakly imposed and stabilization is achieved via Nitsche’s method. We employ a hierarchical local refinement approach to improve the geometrical representation of curved boundaries. Results from several benchmark problems on rectangular and curved domains are provided to demonstrate the accuracy and robustness of the method. We also provide the Mediterranean sea example that illustrates the effectiveness of the approach in the wind-driven ocean circulation simulation. DA - 2016/// PY - 2016/// DO - 10.1016/j.cma.2015.11.003 VL - 299 SP - 144-160 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84947924685&partnerID=MN8TOARS ER - TY - RPRT TI - Quarterly Management Document – FY16, 4th Quarter, Physics-based Creep Simulations of Thick Section Welds in High Temperature and Pressure Applications AU - Lillo, Thomas M. AU - Jiang, Wen A3 - Office of Scientific and Technical Information (OSTI) AB - During the 4th quarter of FY16 welds in Alloy 740H were made and charactrerized. Also, cross weld creep specimens were made and creep tests were initiated in support of the creep modeling and simulation effort. Also, aging of weld material for future characterization was initiated. The creep model was evolved to describe the vacancy concentration that enables the climb of dislocations during power law creep. DA - 2016/10/1/ PY - 2016/10/1/ DO - 10.2172/1504929 PB - Office of Scientific and Technical Information (OSTI) UR - https://doi.org/10.2172/1504929 ER - TY - RPRT TI - MARMOT update for oxide fuel modeling AU - Zhang, Yongfeng AU - Schwen, Daniel AU - Chakraborty, Pritam AU - Jiang, Chao AU - Aagesen, Larry AU - Ahmed, Karim AU - Jiang, Wen AU - Biner, Bulent AU - Bai, Xianming AU - Tonks, Michael AU - Millett, Paul A3 - Office of Scientific and Technical Information (OSTI) AB - This report summarizes the lower-length-scale research and development progresses in FY16 at Idaho National Laboratory in developing mechanistic materials models for oxide fuels, in parallel to the development of the MARMOT code which will be summarized in a separate report. This effort is a critical component of the microstructure based fuel performance modeling approach, supported by the Fuels Product Line in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. The progresses can be classified into three categories: 1) development of materials models to be used in engineering scale fuel performance modeling regarding the effect of lattice defects on thermal conductivity, 2) development of modeling capabilities for mesoscale fuel behaviors including stage-3 gas release, grain growth, high burn-up structure, fracture and creep, and 3) improved understanding in material science by calculating the anisotropic grain boundary energies in UO$_2$ and obtaining thermodynamic data for solid fission products. Many of these topics are still under active development. They are updated in the report with proper amount of details. For some topics, separate reports are generated in parallel and so stated in the text. The accomplishments have led to better understanding of fuel behaviors and enhance capability of the MOOSE-BISON-MARMOT toolkit. DA - 2016/9/1/ PY - 2016/9/1/ DO - 10.2172/1364504 PB - Office of Scientific and Technical Information (OSTI) ER - TY - RPRT TI - Grizzly Usage and Theory Manual AU - Spencer, B. W. AU - Backman, M. AU - Chakraborty, P. AU - Schwen, D. AU - Zhang, Y. AU - Huang, H. AU - Bai, X. AU - Jiang, W. A3 - Office of Scientific and Technical Information (OSTI) AB - Grizzly is a multiphysics simulation code for characterizing the behavior of nuclear power plant (NPP) structures, systems and components (SSCs) subjected to a variety of age-related aging mechanisms. Grizzly simulates both the progression of aging processes, as well as the capacity of aged components to safely perform. This initial beta release of Grizzly includes capabilities for engineering-scale thermo-mechanical analysis of reactor pressure vessels (RPVs). Grizzly will ultimately include capabilities for a wide range of components and materials. Grizzly is in a state of constant development, and future releases will broaden the capabilities of this code for RPV analysis, as well as expand it to address degradation in other critical NPP components. DA - 2016/3/1/ PY - 2016/3/1/ DO - 10.2172/1261013 PB - Office of Scientific and Technical Information (OSTI) ER - TY - JOUR TI - Error Analysis of a B-Spline Based Finite-Element Method for Modeling Wind-Driven Ocean Circulation AU - Rotundo, N. AU - Kim, T.-Y. AU - Jiang, W. AU - Heltai, L. AU - Fried, E. T2 - Journal of Scientific Computing DA - 2016/// PY - 2016/// DO - 10.1007/s10915-016-0201-1 VL - 69 IS - 1 SP - 430-459 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963997998&partnerID=MN8TOARS ER - TY - CONF TI - Ablation of Tungsten-Alternative Plasma-Facing Components due to Edge Localized Modes (ELMs) and Hard Disruptions” AU - Coburn, Jonathan AU - Bourham, Mohamed T2 - ANS 22nd Topical Meeting on the Technology of Fusion Energy (TOFE) C2 - 2016/// C3 - Proceedings of the ANS 22nd Topical Meeting on the Technology of Fusion Energy (TOFE) CY - Philadelphia, PA DA - 2016/// PY - 2016/8/22/ ER - TY - JOUR TI - Microstructure Evolution in Ion-Irradiated UO2 AU - He, L. AU - Gan, J. AU - Allen, T.R. T2 - Transactions of the American Nuclear Society DA - 2016/// PY - 2016/// VL - 114 SP - 1130–1131 ER - TY - JOUR TI - MAX Phases for the Nuclear Industry: Possibilities and Pitfalls AU - Barsoum, M.W. AU - Tallman, D.J. AU - He, L. AU - Gan, J. T2 - Transactions of the American Nuclear Society DA - 2016/// PY - 2016/// VL - 114 SP - 1242–1243 ER - TY - JOUR TI - Air plasma treatment of liquid covered tissue: long timescale chemistry AU - Lietz, Amanda M AU - Kushner, Mark J T2 - Journal of Physics D: Applied Physics AB - Atmospheric pressure plasmas have shown great promise for the treatment of wounds and cancerous tumors. In these applications, the sample is usually covered by a thin layer of a biological liquid. The reactive oxygen and nitrogen species (RONS) generated by the plasma activate and are processed by the liquid before the plasma produced activation reaches the tissue. The synergy between the plasma and the liquid, including evaporation and the solvation of ions and neutrals, is critical to understanding the outcome of plasma treatment. The atmospheric pressure plasma sources used in these procedures are typically repetitively pulsed. The processes activated by the plasma sources have multiple timescales—from a few ns during the discharge pulse to many minutes for reactions in the liquid. In this paper we discuss results from a computational investigation of plasma–liquid interactions and liquid phase chemistry using a global model with the goal of addressing this large dynamic range in timescales. In modeling air plasmas produced by a dielectric barrier discharge over liquid covered tissue, 5000 voltage pulses were simulated, followed by 5 min of afterglow. Due to the accumulation of long-lived species such as ozone and N x O y , the gas phase dynamics of the 5000th discharge pulse are different from those of the first pulse, particularly with regards to the negative ions. The consequences of applied voltage, gas flow, pulse repetition frequency, and the presence of organic molecules in the liquid on the gas and liquid reactive species are discussed. DA - 2016/10/26/ PY - 2016/10/26/ DO - 10.1088/0022-3727/49/42/425204 VL - 49 IS - 42 SP - 425204 UR - http://dx.doi.org/10.1088/0022-3727/49/42/425204 ER - TY - JOUR TI - Image driven machine learning methods for microstructure recognition AU - Chowdhury, Aritra AU - Kautz, Elizabeth AU - Yener, Bülent AU - Lewis, Daniel T2 - Computational Materials Science AB - Computer vision and machine learning methods were applied to the challenge of automatic microstructure recognition. Here, a case study on dendritic morphologies was performed. Two classification tasks were completed, and involved distinguishing between micrographs that depict dendritic morphologies from those that do not contain this particular microstructural feature (Task 1), and from those micrographs identified as depicting dendrites, different cross-sectional views (longitudinal or transverse) were identified (Task 2). Data sets were comprised of images taken over a range of magnifications, from materials with different compositions and varying orientations of microstructural features. Feature extraction and dimensionality reduction were performed prior to training machine learning algorithms to classify microstructural image data. Visual bag of words, texture and shape statistics, and pre-trained convolutional neural networks (deep learning algorithms) were used for feature extraction. Classification was then performed using support vector machine, voting, nearest neighbors, and random forest models. For each model, classification was completed using full (original size) and reduced feature vectors for each feature extraction method tested. Performance comparisons were done to evaluate all possible combinations of feature extraction, selection, and classifiers for the task of micrograph classification. Results demonstrate that pre-trained neural networks represent microstructure image data well, and when used for feature extraction yield the highest classification accuracies for the majority of classifier and feature selection methods tested. Thus, deep learning algorithms can successfully be applied to micrograph recognition tasks. Maximum classification accuracies of 91.85 ± 4.25% and 97.37 ± 3.33% for Tasks 1 and 2 respectively, were achieved. This work is a broad investigation of computer vision and machine learning methods that acts as a step towards applying these established methods to more sophisticated materials recognition or characterization tasks. The approach presented here could offer improvements over established stereological measurements by removing the requirement of expert knowledge (bias) for interpretation of image data prior to characterization. DA - 2016/10// PY - 2016/10// DO - 10.1016/j.commatsci.2016.05.034 VL - 123 SP - 176-187 J2 - Computational Materials Science LA - en OP - SN - 0927-0256 UR - http://dx.doi.org/10.1016/j.commatsci.2016.05.034 DB - Crossref KW - Microstructure KW - Computer vision KW - Machine learning KW - Classification KW - Convolutional neural networks KW - Micrograph ER - TY - JOUR TI - Subsurface imaging of grain microstructure using picosecond ultrasonics AU - Khafizov, M. AU - Pakarinen, J. AU - He, L. AU - Henderson, H.B. AU - Manuel, M.V. AU - Nelson, A.T. AU - Jaques, B.J. AU - Butt, D.P. AU - Hurley, D.H. T2 - Acta Materialia AB - We report on imaging subsurface grain microstructure using picosecond ultrasonics. This approach relies on elastic anisotropy of crystalline materials where ultrasonic velocity depends on propagation direction relative to the crystal axes. Picosecond duration ultrasonic pulses are generated and detected using ultrashort light pulses. In materials that are transparent or semitransparent to the probe wavelength, the probe monitors gigahertz frequency Brillouin oscillations. The frequency of these oscillations is related to the ultrasonic velocity and the optical index of refraction. Ultrasonic waves propagating across a grain boundary experience a change in velocity due to a change in crystallographic orientation relative to the ultrasonic propagation direction. This change in velocity is manifested as a change in the Brillouin oscillation frequency. Using the ultrasonic propagation velocity, the depth of the interface can be determined from the location in time of the transition in oscillation frequency. A subsurface image of the grain boundary is obtained by scanning the beam along the surface. We demonstrate this subsurface imaging capability using a polycrystalline UO2 sample. Cross section liftout analysis of the grain boundary using electron microscopy was used to verify our imaging results. DA - 2016/// PY - 2016/// DO - 10.1016/j.actamat.2016.04.003 VL - 112 SP - 209-215 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964328395&partnerID=MN8TOARS KW - Picosecond ultrasonics KW - Grain orientation KW - Boundary characterization ER - TY - CHAP TI - Irradiation Effects in Generation IV Nuclear Reactor Materials AB - Generation IV reactor structural materials will be exposed to high doses and temperatures during reactor operation that may lead to irradiation-induced degradation. This degradation will differ from that seen in light water reactors and therefore understanding mechanisms controlling material performance during irradiation is critical for evaluating the viability of Generation IV nuclear reactor concepts. This chapter discusses irradiation effects and microstructural changes that affect mechanical properties and dimensional stability of Generation IV reactor materials. PY - 2016/9/16/ DO - http://dx.doi.org/10.1016/B978-0-08-100906-2.00007-0 UR - http://www.sciencedirect.com/science/article/pii/B9780081009062000070 ER - TY - JOUR TI - Effect of neutron irradiation on defect evolution in Ti3SiC2 and Ti2AlC AU - Tallman, D.J. AU - He, L. AU - Garcia-Diaz, B.L. AU - Hoffman, E.N. AU - Kohse, G. AU - Sindelar, R.L. AU - Barsoum, M.W. T2 - Journal of Nuclear Materials AB - Herein we report on the characterization of defects formed in polycrystalline Ti3SiC2 and Ti2AlC samples exposed to neutron irradiation – up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti3SiC2 and Ti2AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ± 5 nm, the loop diameters in the Ti3SiC2 and Ti2AlC samples, respectively, were comparable. At 1 × 1023 loops/m3, the dislocation loop density in Ti2AlC was ≈1.5 orders of magnitude greater than in Ti3SiC2, at 3 × 1021 loops/m3. After irradiation at 350 °C, extensive microcracking was observed in Ti2AlC, but not in Ti3SiC2. The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti3SiC2. The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al2O3. Based on these results, Ti3SiC2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti2AlC. DA - 2016/// PY - 2016/// DO - 10.1016/j.jnucmat.2015.10.030 VL - 468 SP - 194-206 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84948445492&partnerID=MN8TOARS KW - Ti3SiC2 KW - Ti2AlC KW - MAX phases KW - Neutron irradiation KW - Dislocation loops ER - TY - JOUR TI - Corrosion-induced microstructural developments in 316 stainless steel during exposure to molten Li2BeF4 (FLiBe) salt AU - Zheng, G. AU - He, L. AU - Carpenter, D. AU - Sridharan, K. T2 - Journal of Nuclear Materials AB - The microstructural developments in the near-surface regions of AISI 316 stainless steel during exposure to molten Li2BeF4 (FLiBe) salt have been investigated with the goal of using this material for the construction of the fluoride salt-cooled high-temperature reactor (FHR), a leading nuclear reactor concept for the next generation nuclear plants (NGNP). Tests were conducted in molten FLiBe salt (melting point: 459 °C) at 700 °C in graphite crucibles and 316 stainless steel crucibles for exposure duration of up to 3000 h. Corrosion-induced microstructural changes in the near-surface regions of the samples were characterized using scanning electron microscopy (SEM) in conjunction with energy dispersive x-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (STEM) with EDS capabilities. Intergranular corrosion attack in the near-surface regions was observed with associated Cr depletion along the grain boundaries. High-angle grain boundaries (15–180°) were particularly prone to intergranular attack and Cr depletion. The depth of attack extended to the depths of 22 μm after 3000-h exposure for the samples tested in graphite crucible, while similar exposure in 316 stainless steel crucible led to the attack depths of only about 11 μm. Testing in graphite crucibles led to the formation of nanometer-scale Mo2C, Cr7C3 and Al4C3 particle phases in the near-surface regions of the material. The copious depletion of Cr in the near-surface regions induced a γ-martensite to α-ferrite phase (FeNix) transformation. Based on the microstructural analysis, a thermal diffusion controlled corrosion model was developed and experimentally validated for predicting long-term corrosion attack depth. DA - 2016/// PY - 2016/// DO - 10.1016/j.jnucmat.2016.10.023 VL - 482 SP - 147-155 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84992143288&partnerID=MN8TOARS KW - Nuclear reactor KW - 316 stainless steel KW - Molten salt KW - Microstructure KW - Corrosion ER - TY - JOUR TI - Toroidal mode number determination of ELM associated phenomena on ASDEX Upgrade T2 - Plasma Physics and Controlled Fusion AB - In highly confined tokamak plasmas periodically appearing edge localized modes (ELMs) are accompanied by mode-like magnetohydrodynamic (MHD) activities with defined toroidal mode numbers. DA - 2016/// PY - 2016/// DO - 10.1088/0741-3335/58/12/125013 VL - 58 IS - 12 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84997610947&partnerID=MN8TOARS KW - edge localized mode KW - magnetic pick-up coils KW - mode numbers KW - pedestal ER - TY - JOUR TI - Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium AU - Willensdorfer, M. AU - Denk, S.S. AU - Strumberger, E. AU - Suttrop, W. AU - Vanovac, B. AU - Brida, D. AU - Cavedon, M. AU - Classen, I. AU - Dunne, M. AU - Fietz, S. AU - Fischer, R. AU - Kirk, A. AU - Laggner, F.M. AU - Liu, Y.Q. AU - Odstr?il, T. AU - Ryan, D.A. AU - Viezzer, E. AU - Zohm, H. AU - Luhmann, I.C. T2 - Plasma Physics and Controlled Fusion AB - The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the low field side midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the prediction from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m| > |nq|, whereas the poloidal mode structure of its displacement is almost resonant |m| ~ |nq|. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response. DA - 2016/// PY - 2016/// DO - 10.1088/0741-3335/58/11/114004 VL - 58 IS - 11 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84993965398&partnerID=MN8TOARS KW - magnetic perturbations KW - plasma response KW - ideal MHD KW - ECE KW - ECE imaging ER - TY - JOUR TI - Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions AU - Birkenmeier, G. AU - Cavedon, M. AU - Conway, G.D. AU - Manz, P. AU - Stroth, U. AU - Fischer, R. AU - Fuchert, G. AU - Happel, T. AU - Laggner, F.M. AU - Maraschek, M. AU - Medvedeva, A. AU - Nikolaeva, V. AU - Prisiazhniuk, D. AU - Pütterich, T. AU - Ryter, F. AU - Shao, L.M. AU - Willensdorfer, M. AU - Wolfrum, E. AU - Zohm, H. T2 - Nuclear Fusion AB - Abstract Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field B θ with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f ( B t 1 / 2 I p 3 / 2 ) / ( n T ) . DA - 2016/// PY - 2016/// DO - 10.1088/0029-5515/56/8/086009 VL - 56 IS - 8 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84979747838&partnerID=MN8TOARS KW - magnetic confinement KW - pedestal KW - high confinement mode KW - L-H transition KW - limit-cycle oscillations KW - edge localized modes ER - TY - JOUR TI - The role of carbon and nitrogen on the H-mode confinement in ASDEX Upgrade with a metal wall AU - Beurskens, M. N. A. AU - Dunne, M. G. AU - Frassinetti, L. AU - Bernert, M. AU - Cavedon, M. AU - Fischer, R. AU - Jarvinen, A. AU - Kallenbach, A. AU - Laggner, F. M. AU - McDermott, R. M. AU - Potzel, S. AU - Schweinzer, J. AU - Tardini, G. AU - Viezzer, E. AU - Wolfrum, E. AU - Team, ASDEX Upgrade AU - Team, EUROfusion MST1 T2 - Nuclear Fusion AB - Abstract Carbon (CD 4 ) and nitrogen (N 2 ) have been seeded in ASDEX Upgrade (AUG) with a tungsten wall and have both led to a 20–30% confinement improvement. The reference plasma is a standard target plasma with I p / B T = 1 MA/2.5 T, total input power P tot ~ 12 MW and normalized pressure of β N ~ 1.8. Carbon and nitrogen are almost perfectly exchangeable for the core, pedestal and divertor plasma in this experiment where impurity concentrations of C and N of 2% are achieved and Z eff only mildly increases from ~1.3 to ~1.7. As the radiation potentials of C and N are similar and peak well below 100 eV, both impurities act as divertor radiators and radiate well outside the pedestal region. The outer divertor is purposely kept in an attached state when C and N are seeded to avoid confinement degradation by detachment. As reported in earlier publications for nitrogen, carbon is also seen to reduce the high field side high density (the so-called HFSHD) in the scrape off layer above the inner divertor strike point by about 50%. This is accompanied by a confinement improvement for both low ( δ ~ 0.25) and high ( δ ~ 0.4) triangularity configurations for both seeding gases, due to an increase of pedestal temperature and stiff core temperature profiles. The electron density profiles show no apparent change due to the seeding. As an orthogonal effect, increasing the triangularity leads to an additionally increased pedestal density, independent of the impurity seeding. This experiment further closes the gap in understanding the confinement differences observed in carbon and metal wall devices; the absence of carbon can be substituted by nitrogen which leads to a similar confinement benefit. So far, no definite physics explanation for the confinement enhancement has been obtained, but the experimental observations in this paper provide input for further model development. DA - 2016/// PY - 2016/// DO - 10.1088/0029-5515/56/5/056014 VL - 56 IS - 5 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000375229300017&KeyUID=WOS:000375229300017 KW - confinement KW - metal wall KW - impurity seeding KW - carbon KW - nitrogen KW - tungsten KW - radiation ER - TY - JOUR TI - On the role of the edge density profile for the L-H transition power threshold in ASDEX Upgrade AU - Shao, L. M. AU - Wolfrum, E. AU - Ryter, F. AU - Birkenmeier, G. AU - Laggner, F. M. AU - Viezzer, E. AU - Fischer, R. AU - Willensdorfer, M. AU - Kurzan, B. AU - Lunt, T. AU - Team, ASDEX Upgrade T2 - Plasma Physics and Controlled Fusion AB - The L–H transition power threshold () in full tungsten (W) wall discharges is lower by 25% compared to those with graphite (C) mix tungsten walls in ASDEX Upgrade (Ryter et al 2013 Nucl. Fusion 53 113003). The lower power threshold in the full tungsten wall discharges has been found to correlate with higher edge density as well as steeper edge density gradient. An estimate of the minimum in the neoclassical radial electric field well inside the separatrix yields a constant value for all analyzed L–H transitions at fixed toroidal magnetic field (). The decrease of the threshold power is explained by the steeper edge density gradient in the discharges with full tungsten wall. DA - 2016/// PY - 2016/// DO - 10.1088/0741-3335/58/2/025004 VL - 58 IS - 2 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000371570900005&KeyUID=WOS:000371570900005 KW - L-H transition KW - power threshold KW - edge density profile ER - TY - JOUR TI - High frequency magnetic fluctuations correlated with the inter-ELM pedestal evolution in ASDEX Upgrade AU - Laggner, F. M. AU - Wolfrum, E. AU - Cavedon, M. AU - Mink, F. AU - Viezzer, E. AU - Dunne, M. G. AU - Manz, P. AU - Doerk, H. AU - Birkenmeier, G. AU - Fischer, R. AU - Fietz, S. AU - Maraschek, M. AU - Willensdorfer, M. AU - Aumayr, F. AU - Team, Eurofusion MST1 AU - Team, ASDEX Upgrade T2 - Plasma Physics and Controlled Fusion AB - In order to understand the mechanisms that determine the structure of the high confinement mode (H-mode) pedestal, the evolution of the plasma edge electron density and temperature profiles between edge localised modes (ELMs) is investigated. The onset of radial magnetic fluctuations with frequencies above 200 kHz is found to correlate with the stagnation of the electron temperature pedestal gradient. During the presence of these magnetic fluctuations the gradients of the edge electron density and temperature are clamped and stable against the ELM onset. The detected magnetic fluctuation frequency is analysed for a variety of plasma discharges with different electron pressure pedestals. It is shown that the magnetic fluctuation frequency scales with the neoclassically estimated velocity at the plasma edge. This points to a location of the underlying instability in the gradient region. Furthermore, the magnetic signature of these fluctuations indicates a global mode structure with toroidal mode numbers of approximately 10. The fluctuations are also observed on the high field side with significant amplitude, indicating a mode structure that is symmetric on the low field side and high field side. The associated fluctuations in the current on the high field side might be attributed to either a strong peeling part or the presence of non-adiabatic electron response. DA - 2016/// PY - 2016/// DO - 10.1088/0741-3335/58/6/065005 VL - 58 IS - 6 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000376275600010&KeyUID=WOS:000376275600010 KW - plasma KW - tokamak KW - H-mode KW - edge localised modes KW - profile ER - TY - JOUR TI - A compact lithium pellet injector for tokamak pedestal studies in ASDEX Upgrade AU - Parra, R. Arredondo AU - Quicios, R. Moreno AU - Ploeckl, B. AU - Birkenmeier, G. AU - Herrmann, A. AU - Kocsis, G. AU - Laggner, F. M. AU - Lang, P. T. AU - Lunt, T. AU - Macian-Juan, R. AU - Rohde, V. AU - Sellmair, G. AU - Szepesi, T. AU - Wolfrum, E. AU - Zeidner, W. AU - Neu, R. AU - Team, ASDEX Upgrade T2 - Review of Scientific Instruments AB - Experiments have been performed at ASDEX Upgrade, aiming to investigate the impact of lithium in an all-metal-wall tokamak and attempting to enhance the pedestal operational space. For this purpose, a lithium pellet injector has been developed, capable of injecting pellets carrying a particle content ranging from 1.82 × 1019 atoms (0.21 mg) to 1.64 × 1020 atoms (1.89 mg). The maximum repetition rate is about 2 Hz. Free flight launch from the torus outboard side without a guiding tube was realized. In such a configuration, angular dispersion and speed scatter are low, and a transfer efficiency exceeding 90% was achieved in the test bed. Pellets are accelerated in a gas gun; hence special care was taken to avoid deleterious effects by the propellant gas pulse. Therefore, the main plasma gas species was applied as propellant gas, leading to speeds ranging from 420 m/s to 700 m/s. In order to minimize the residual amount of gas to be introduced into the plasma vessel, a large expansion volume equipped with a cryopump was added into the flight path. In view of the experiments, an optimal propellant gas pressure of 50 bars was chosen for operation, since at this pressure maximum efficiency and low propellant gas flux coincide. This led to pellet speeds of 585 m/s ± 32 m/s. Lithium injection has been achieved at ASDEX Upgrade, showing deep pellet penetration into the plasma, though pedestal broadening has not been observed yet. DA - 2016/// PY - 2016/// DO - 10.1063/1.4942122 VL - 87 IS - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85013956452&partnerID=MN8TOARS ER - TY - JOUR TI - Photocurrent response of B12As2 crystals to blue light, and its temperature- dependent electrical characterizations AU - Gul, R. AU - Cui, Y. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Egarievwe, S. U. AU - Hossain, A. AU - Roy, U. N. AU - Yang, G. AU - Edgar, J. H. AU - Nwagwu, U. AU - James, R. B. T2 - AIP Advances AB - With the global shortage of 3He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B12As2) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B12As2 bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W−1 and 2.47 mA ⋅ cm−2, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B12As2 bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm−2 and 7.6x105-7.7x103 Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors. DA - 2016/2// PY - 2016/2// DO - 10.1063/1.4941937 VL - 6 IS - 2 SP - 025206 J2 - AIP Advances LA - en OP - SN - 2158-3226 UR - http://dx.doi.org/10.1063/1.4941937 DB - Crossref ER - TY - JOUR TI - Point defects: Their influence on electron trapping, resistivity, and electron mobility-lifetime product in CdTexSe1−x detectors AU - Gul, R. AU - Roy, U. N. AU - Egarievwe, S. U. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Cui, Y. AU - Hossain, A. AU - Yang, G. AU - James, R. B. T2 - Journal of Applied Physics AB - In this research, we assessed the abundance of point defects and their influence on the resistivity, the electron mobility-lifetime (μτe) product, and the electron trapping time in CdTeSe crystals grown under different conditions using the traveling heater method. We used current-deep level transient spectroscopy to determine the traps' energy, their capture cross-section, and their concentration. Further, we used these data to determine the trapping and de-trapping times for the charge carriers. The data show that detectors with a lower concentration of In-dopant have a higher density of A-centers and Cd double vacancies (VCd- -). The high concentrations of VCd- - and A-centers, along with the deep trap at 0.86 eV and low density of 1.1 eV energy traps, are the major cause of the detectors' low resistivity, and most probably, a major contributor to the low μτe product. Our results indicate that the energy levels of point defects in the bandgap, their concentrations, capture cross-sections, and their trapping and de-trapping times play an important role in the detector's performance, especially for devices that rely solely on electron transport. DA - 2016/1/14/ PY - 2016/1/14/ DO - 10.1063/1.4939647 VL - 119 IS - 2 SP - 025702 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4939647 DB - Crossref ER - TY - RPRT TI - Indoor Health Monitoring System AU - Naeim, A. AU - Ramezani, R. AU - Arjun AU - Moatamed, B. AU - Sarrafzadeh, M. DA - 2016/5/2/ PY - 2016/5/2/ M1 - 62/330,730 M3 - U.S. Provisional Patent Application SN - 62/330,730 ER - TY - CONF TI - Low-cost indoor health monitoring system AU - Moatamed, Babak AU - Arjun AU - Shahmohammadi, Farhad AU - Ramezani, Ramin AU - Naeim, Arash AU - Sarrafzadeh, Majid T2 - 2016 IEEE 13th International Conference on Wearable and Implantable Body Sensor Networks (BSN) AB - The advent of smart infrastructure or Internet of Things (IoT) has enabled scenarios in which objects with unique identifiers can communicate and transfer data over a network without human to human/computer interactions. Incorporating hardware in such networks is so cheap that it has opened the possibility of connecting just about anything from simple nodes to complex, remotely-monitored sensor networks. In the paper, we describe a low-cost scalable and potentially ubiquitous system for indoor remote health monitoring using low energy bluetooth beacons and a smartwatch. Our system was implemented in a rehabilitation facility in Los Angeles and the overall assessments revealed promising results. C2 - 2016/6// C3 - 2016 IEEE 13th International Conference on Wearable and Implantable Body Sensor Networks (BSN) DA - 2016/6// DO - 10.1109/bsn.2016.7516252 PB - IEEE SN - 9781509030873 UR - http://dx.doi.org/10.1109/bsn.2016.7516252 DB - Crossref ER - TY - CONF TI - Evaluation of Bluetooth beacons behavior AU - Bouchard, Kevin AU - Ramezani, Ramin AU - Arjun AU - Naeim, Arash T2 - 2016 IEEE 7th Annual Ubiquitous Computing, Electronics & Mobile Communication Conference (UEMCON) AB - Bluetooth low energy beacons have gained traction among ambient intelligence researchers. Their low cost and robustness make them a fit choice for ambient assisted living or other healthcare applications. Nevertheless, similar to many other radio-frequency based technologies, beacons pose serious challenges when it comes to developing applications that require predictability. Moreover, the multipath propagation characteristics of Bluetooth beacons prevent ambient intelligent researchers to solely rely on using theoretical models to describe their behaviors. In this paper, we present an empirical evaluation of Bluetooth beacons behaviors. We describe the observed pattern of the signal through a series of experiments totalizing more than 3 million samples. C2 - 2016/10// C3 - 2016 IEEE 7th Annual Ubiquitous Computing, Electronics & Mobile Communication Conference (UEMCON) DA - 2016/10// DO - 10.1109/uemcon.2016.7777846 PB - IEEE SN - 9781509014965 UR - http://dx.doi.org/10.1109/uemcon.2016.7777846 DB - Crossref ER - TY - JOUR TI - {112̅1}-{101̅2} double twinning in a Zircaloy-4 alloy during rolling at ambient temperature AU - Zhang, M. AU - Luan, B.F. AU - Song, Z.L. AU - Xin, R.L. AU - Murty, K.L. AU - Liu, Q. T2 - Scripta Materialia AB - In this paper, we report the formation of an atypical double twinning sequence in Zircaloy-4 during rolling at room temperature. The grain orientation analysis based on electron backscattering diffraction (EBSD) data reveals that this double twinning mode is of the 112̅1-101̅2 type, namely, the secondary 101̅2 twin generated within the primary 112̅1 twin. Based on the combinative analysis of Schmid factor and local strain accommodation, the formation and variant selection mechanism of this double twinning are discussed. DA - 2016/9// PY - 2016/9// DO - 10.1016/J.SCRIPTAMAT.2016.05.003 VL - 122 SP - 77–81 SN - 1359-6462 UR - http://dx.doi.org/10.1016/J.SCRIPTAMAT.2016.05.003 KW - Zircaloy-4 KW - Double twinning KW - Electron backscattering diffraction (EBSD) KW - Schmid factor KW - Local strain accommodation ER - TY - JOUR TI - Code improvement and model validation for Ascó-II Nuclear Power Plant model using a coupled 3D neutron kinetics/thermal–hydraulic code AU - Pericas, R. AU - Ivanov, K. AU - Reventós, F. AU - Batet, L. T2 - Annals of Nuclear Energy AB - This paper provides a Best Estimate validation calculation with a coupled thermal–hydraulic and 3D neutron kinetic model for Ascó-II Nuclear Power Plant. Common NRC codes have been used for its purpose. TRACE is the code used for the thermal–hydraulic system calculations; PARCS is the code used for the 3D neutron kinetics calculations. Cross section calculations were performed with the HELIOS lattice physics code, finally GenPMAXS was used to convert the cross section into the PARCS format. A simplified three dimensional 3D neutronics model of the Ascó II NPP is used as a core kinetics model. A 3D cylindrical thermal–hydraulic vessel plus 1D representation of the remainder of the full plant model is used as the thermal–hydraulic model. The transient selected to ensure the model validation is an actual 50% Loss of Load. This transient is characterized by space–time effects and was used to validate different thermal–hydraulic system models for the GET university group in the past. The scenario is also good to ensure the validation of a coupled 3D neutron kinetics code since it provides a transient situation between two stable regions at 100% and 50%. From the current code versions used, some source code modifications have been carried out in order to ensure the correct feedback between thermal–hydraulic and neutron kinetics code. In that sense, a dynamic control rod movement between TRACE and PARCS has been implemented. This is a complete control rod position feedback during transient scenarios. After all the work was performed, the important TH and NK time trend parameters were compared to the plant data and the comparison was reasonable with some discrepancy, thus the developed system models and the code modifications are robust enough to be used for future safety analysis. New coupled code capability has been tested and found as a required capability, when validating 3D NK–TH coupled calculations. DA - 2016/1// PY - 2016/1// DO - 10.1016/J.ANUCENE.2015.09.024 VL - 87 SP - 366-374 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2015.09.024 DB - Crossref KW - Nuclear safety KW - 3D neutron kinetics KW - Reactor physics modeling KW - Best Estimate calculation KW - 3D NK-TH KW - Dynamic control rod movement ER - TY - RPRT TI - VERA Benchmarking Results for Watts Bar Nuclear Plant Unit 1 Cycles 1-12 AU - Godfrey, Andrew T ; AU - Collins, Benjamin S ; AU - Kim, Kang Seog ; AU - Montgomery, Rosemary ; AU - Powers, Jeffrey J ; AU - Salko, Robert K ; AU - Stimpson, Shane G ; AU - Wieselquist, William A ; AU - Clarno, Kevin T ; AU - Gehin, Jess C ; AU - Palmtag, Scott ; AU - Montgomery, Robert ; AU - Jabaay, Dan ; AU - Kochunas, Brendan ; AU - Downar, Thomas ; AU - Capps, Nathan A ; AU - Secker, Jeffrey DA - 2016/1// PY - 2016/1// UR - https://www.osti.gov/scitech/biblio/1260079-vera-benchmarking-results-watts-bar-nuclear-plant-unit-cycles ER - TY - RPRT TI - Simulation of CRUD Induced Power Shift using the VERA Core Simulator and MAMBA AU - Clarno, Kevin T ; AU - Palmtag, Scott ; AU - Secker, Jeffrey ; AU - Kendrick, Brian ; AU - Montgomery, Rosemary DA - 2016/1// PY - 2016/1// UR - https://www.osti.gov/scitech/biblio/1325433-simulation-crud-induced-power-shift-using-vera-core-simulator-mamba ER - TY - RPRT TI - MPACT VERA Input User s Manual, Version 2.2.0 AU - Collins, Benjamin S. ; AU - Downar, Thomas ; AU - Fitzgerald, Andrew ; AU - Gehin, Jess C. ; AU - Godfrey, Andrew T. ; AU - Graham, Aaron ; AU - Jabaay, Daniel ; AU - Kelley, Blake W. ; AU - Kim, Kang ; AU - Kochunas, Brendan ; AU - Kulesza, Joel A. ; AU - Larsen, Edward W. ; AU - Liu, Yuxuan ; AU - Liu, Zhouyu ; AU - Martin, William R. ; AU - Nelson, Adam G. ; AU - Palmtag, Scott ; AU - Rose, Michael ; AU - Saller, Thomas ; AU - Stimpson, Shane G. ; AU - Trahan, Travis ; AU - Wang, J. W. ; AU - Wieselquist, William A. ; AU - Young, Mitchell ; AU - Zhu, Ang AB - The MPACT (Michigan PArallel Charactistics based Transport) code is designed to perform high-fidelity light water reactor (LWR) analysis using whole-core pin-resolved neutron transport calculations on modern parallel-computing hardware. The code consists of several libraries which provide the functionality necessary to solve steady-state eigenvalue problems. Several transport capabilities are available within MPACT including both 2-D and 3-D Method of Characteristics (MOC). A three-dimensional whole core solution based on the 2D-1D solution method provides the capability for full core depletion calculations. DA - 2016/6// PY - 2016/6// DO - 10.2172/1342675 UR - https://www.osti.gov/scitech/biblio/1342675-mpact-vera-input-user-manual-version ER - TY - RPRT TI - MPACT Theory Manual, Version 2.2.0 AU - Downar, Thomas ; AU - Collins, Benjamin S. ; AU - Gehin, Jess C. ; AU - Godfrey, Andrew T. ; AU - Jabaay, Daniel ; AU - Kelley, Blake W. ; AU - Clarno, Kevin T. ; AU - Kim, Kang ; AU - Kochunas, Brendan ; AU - Larsen, Edward W. ; AU - Liu, Yuxuan ; AU - Liu, Zhouyu ; AU - Martin, William R. ; AU - Palmtag, Scott ; AU - Rose, Michael ; AU - Saller, Thomas ; AU - Stimpson, Shane ; AU - Trahan, Travis ; AU - Wang, J. W. ; AU - Wieselquist, William A. ; AU - Young, Mitchell ; AU - Zhu, Ang AB - This theory manual describes the three-dimensional (3-D) whole-core, pin-resolved transport calculation methodology employed in the MPACT code. To provide sub-pin level power distributions with sufficient accuracy, MPACT employs the method of characteristics (MOC) solutions in the framework of a 3-D coarse mesh finite difference (CMFD) formulation. MPACT provides a 3D MOC solution, but also a 2D/1D solution in which the 2D planar solution is provided by MOC and the axial coupling is resolved by one-dimensional (1-D) lower order (diffusion or P3) solutions. In Chapter 2 of the manual, the MOC methodology is described for calculating the regional angular and scalar fluxes from the Boltzmann transport equation. In Chapter 3, the 2D/1D methodology is described, together with the description of the CMFD iteration process involving dynamic homogenization and solution of the multigroup CMFD linear system. A description of the MPACT depletion algorithm is given in Chapter 4, followed by a discussion of the subgroup and ESSM resonance processing methods in Chapter 5. The final Chapter 6 describes a simplified thermal hydraulics model in MPACT. DA - 2016/6// PY - 2016/6// DO - 10.2172/1340449 UR - https://www.osti.gov/scitech/biblio/1340449-mpact-theory-manual-version ER - TY - RPRT TI - MPACT Standard Input User s Manual, Version 2.2.0 AU - Collins, Benjamin S. ; AU - Downar, Thomas ; AU - Fitzgerald, Andrew ; AU - Gehin, Jess C. ; AU - Godfrey, Andrew T. ; AU - Graham, Aaron ; AU - Jabaay, Daniel ; AU - Kelley, Blake W. ; AU - Kim, Kang ; AU - Kochunas, Brendan ; AU - Kulesza, Joel A. ; AU - Larsen, Edward W. ; AU - Liu, Yuxuan ; AU - Liu, Zhouyu ; AU - Martin, William R. ; AU - Nelson, Adam G. ; AU - Palmtag, Scott ; AU - Rose, Michael ; AU - Saller, Thomas ; AU - Stimpson, Shane G. ; AU - Trahan, Travis ; AU - Wang, J. W. ; AU - Wieselquist, William A. ; AU - Young, Mitchell ; AU - Zhu, Ang AB - The MPACT (Michigan PArallel Charactistics based Transport) code is designed to perform high-fidelity light water reactor (LWR) analysis using whole-core pin-resolved neutron transport calculations on modern parallel-computing hardware. The code consists of several libraries which provide the functionality necessary to solve steady-state eigenvalue problems. Several transport capabilities are available within MPACT including both 2-D and 3-D Method of Characteristics (MOC). A three-dimensional whole core solution based on the 2D-1D solution method provides the capability for full core depletion calculations. DA - 2016/8// PY - 2016/8// DO - 10.2172/1342674 UR - https://www.osti.gov/scitech/biblio/1342674-mpact-standard-input-user-manual-version ER - TY - RPRT TI - Demonstrate VERA Core Simulator Performance Improvements L2:PHI.P13.03 AU - Collins, Benjamin S. ; AU - Hamilton, Steven P. ; AU - Jarrett, Michael G. ; AU - Kim, Kang Seog ; AU - Kochunas, Brendan ; AU - Liu, Yuxuan ; AU - Palmtag, Scott ; AU - Salko, Robert K. ; AU - Stimpson, Shane G. ; AU - Toth, Alex ; AU - Yee, Ben AB - This report describes the performance improvements made to the VERA Core Simulator (VERA-CS) during FY2016. The development of the VERA Core Simulator has focused on the capability needed to deplete physical reactors and help solve various problems; this capability required the accurate simulation of many operating cycles of a nuclear power plant. The first section of this report introduces two test problems used to assess the run-time performance of VERA-CS using a source dated February 2016. The next section provides a brief overview of the major modifications made to decrease the computational cost. Following the descriptions of the major improvements, the run-time for each improvement is shown. Conclusions on the work are presented, and further follow-on performance improvements are suggested. DA - 2016/8// PY - 2016/8// DO - 10.2172/1338536 UR - https://www.osti.gov/scitech/biblio/1338536-demonstrate-vera-core-simulator-performance-improvements-l2-phi-p13 ER - TY - RPRT TI - CTF Validation and Verification Manual AU - Salko, Robert K. ; AU - Blyth, Taylor S. ; AU - Dances, Christopher A. ; AU - Magedanz, Jeffrey W. ; AU - Jernigan, Caleb ; AU - Kelly, Joeseph ; AU - Toptan, Aysenur ; AU - Gergar, Marcus ; AU - Gosdin, Chris ; AU - Avramova, Maria ; AU - Palmtag, Scott ; AU - Gehin, Jess C. AB - Coolant-Boiling in Rod Arrays- Two Fluids (COBRA-TF) is a Thermal/Hydraulic (T/H) simulation code designed for Light Water Reactor (LWR) analysis. It uses a two-fluid, three-field (i.e. fluid film, fluid drops, and vapor) modeling approach. Both sub-channel and 3D Cartesian forms of nine conservation equations are available for LWR modeling. The code was originally developed by Pacific Northwest Laboratory in 1980 and has been used and modified by several institutions over the last several decades. COBRA-TF is also used at the Pennsylvania State University (PSU) by the Reactor Dynamics and Fuel Management Group (RDFMG), and has been improved, updated, and subsequently became the PSU RDFMG version of COBRA-TF (CTF). One part of the improvement process includes validating the methods in CTF. This document seeks to provide a certain level of certainty and confidence in the predictive capabilities of the code for the scenarios it was designed to model--rod bundle geometries with operating conditions that are representative of prototypical Pressurized Water Reactor (PWR)s and Boiling Water Reactor (BWR)s in both normal and accident conditions. This is done by modeling a variety of experiments that simulate these scenarios and then presenting a qualitative and quantitative analysis of the results that demonstrates the accuracy to which CTF is capable of capturing specific quantities of interest. DA - 2016/5// PY - 2016/5// DO - 10.2172/1342678 UR - https://www.osti.gov/scitech/biblio/1342678-ctf-validation-verification-manual ER - TY - RPRT TI - Assessment of Thermal Hydraulic Feedback Models AU - Graham, Aaron ; AU - Downar, Thomas ; AU - Palmtag, Scott DA - 2016/1// PY - 2016/1// UR - https://www.osti.gov/scitech/biblio/1325432-assessment-thermal-hydraulic-feedback-models ER - TY - JOUR TI - Analysis of heat transfer under high heat flux nucleate boiling conditions AU - Liu, Y. AU - Dinh, N. T2 - Kerntechnik AB - Abstract Analysis was performed for a heater infrared thermometric imaging temperature data obtained from high heat flux pool boiling and liquid film boiling experiments BETA. With the OpenFOAM solver, heat flux distribution towards the coolant was obtained by solving transient heat conduction of heater substrate given the heater surface temperature data as boundary condition. The so-obtained heat flux data was used to validate them against the state-of-art wall boiling model developed by Shaver [1] with the assumption of micro-layer hydrodynamics. Good agreement was found between the model prediction and data for conditions away from the critical heat flux (CHF). However, the data indicate a different heat transfer pattern under CHF, which is not captured by the current model. Experimental data strengthen the notion of burnout caused by the irreversible hot spot due to failure of rewetting. The observation forms a basis for a detailed modeling of micro-layer hydrodynamics under high heat flux. DA - 2016/// PY - 2016/// DO - 10.3139/124.110750 VL - 81 IS - 3 SP - 308-314 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85017625515&partnerID=MN8TOARS ER - TY - CONF TI - A study of bwr mark i station blackout accident with GOTHIC modeling AU - Bao, H. AU - Dinh, N. AU - Omotowa, O. AU - Zhao, H. AU - Zhang, H. AU - Zou, L. AU - Szilard, R.H. C2 - 2016/// C3 - International Congress on Advances in Nuclear Power Plants, ICAPP 2016 DA - 2016/// VL - 1 SP - 184-193 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84986182404&partnerID=MN8TOARS ER - TY - CONF TI - A computational study of thin film dynamics on micro-structured surfaces AU - Lin, L. AU - Sampath, R. AU - Dinh, N.T. AU - Akinci, N. AB - The present study is motivated by interest in understanding of physical mechanisms that govern the effect of material and micro-structural characteristics of heat surface on boiling heat transfer and burnout at high heat fluxes. The effect was reported and investigated experimentally and analytically over several past decades. Only recently, with the advent of nanotechnology including microscale manufacturing, it becomes possible to perform high heat-flux boiling experiments with control of surface conditions. Of particular importance for practice is the potential for significant enhancement of boiling heat transfer (BHT) and critical heat flux (CHF) in pool and flow boiling on heaters with specially manufactured and controlled micro-structured surfaces. This enhancement is very important to a very wide range of engineering applications, like heat exchanger and cooling system, where maximum flux is needed. Currently, there are many controlled experiments that investigate such effect and they lend themselves a subject for detailed computational analysis. The focus of this study is micro-hydrodynamics of the evaporating thin liquid film at the receding triple contact line, corresponding to formation of dry spot in the footprint of a growing bubble. Parametric investigations are performed to assess the hypotheses that micro-structured surfaces enhance resilience to burnout due to residual liquid in the dry patch after contact line receding. Towards the study objective, a particle-based (mesh-less) method of computational fluid dynamics called Smoothed Particle Hydrodynamics (SPH) is adopted. The SPH method is selected for its capability to handle fluid dynamics in complex geometries and free surface problems without mass loss (characteristic of alternative interface capturing schemes used in mesh-based methods). Both surface tension and surface adhesion (hydrophilicity) are implemented and tested. The solid (heater) surface and manufactured micro-structures are represented by solid-type particles. Heat transfer, phase change (evaporation) and vapor dynamics are not included in the present simulation. The bouncing drop case measures the contact time of water droplet with solid surface. This case is used for “mesh” sensitivity (particle size) study and calibration of boundary conditions and surface tension coefficient. Subsequently, case studies are formulated and performed for contact line dynamics on heater surfaces with the fabricated Micro Pillar Arrays surfaces (MPA) and smooth surface. Variable characteristics include surface tension and pillar density on structured surface (modified by changing distance between pillars). First of all, residual fluid are found in all simulations with structured surface, while fluid are drained for smooth cases. For structured surface, it’s found that after the contact line recedes, fluid with higher surface tension resides in the dry patch more than fluid with lower coefficient, and the relation tends to be non-linear. While for smooth surface, all fluid will be drained after certain time and the relations are non-monotonic; it’s also found that the amount of residual fluid increase as the distance between pillars decreases until a limit. The fluid then starts to decrease with pillars being set further apart. The increase starts from 30 μm and the limit is around 10 μm. C2 - 2016/// C3 - ASME 2016 Heat Transfer Summer Conference, HT 2016, collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels DA - 2016/// DO - 10.1115/HT2016-7382 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85002986155&partnerID=MN8TOARS ER - TY - CONF TI - Investigation of similarity metrics for simulation based scaling analysis AU - Athe, P. AU - Dinh, N. AU - Abdel-Khalik, H. C2 - 2016/// C3 - International Topical Meeting on Advances in Thermal Hydraulics 2016, ATH 2016 DA - 2016/// SP - 409-425 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84992126794&partnerID=MN8TOARS ER - TY - CONF TI - High-fidelity simulation-driven model development for coarse-grained computational fluid dynamics AU - Hanna, B.N. AU - Dinh, N.T. AU - Bolotnov, I.A. C2 - 2016/// C3 - International Topical Meeting on Advances in Thermal Hydraulics 2016, ATH 2016 DA - 2016/// SP - 121-131 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84992089403&partnerID=MN8TOARS ER - TY - CONF TI - Development of a severe accident analysis engine using approximate reasoning AU - Lee, J. AU - Dinh, N. AU - Son, T.C. C2 - 2016/// C3 - Transactions of the American Nuclear Society DA - 2016/// VL - 115 SP - 830-833 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85032884451&partnerID=MN8TOARS ER - TY - CONF TI - A study of physics-informed deep learning for system fluid dynamics closures AU - Chang, C.-W. AU - Dinh, N. C2 - 2016/// C3 - Transactions of the American Nuclear Society DA - 2016/// VL - 115 SP - 1785-1788 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85033222005&partnerID=MN8TOARS ER - TY - CONF TI - Assessment of a smoothed particle hydrodynamics method for thin film on textured surfaces AU - Lin, L. AU - Dinh, N. C2 - 2016/// C3 - Transactions of the American Nuclear Society DA - 2016/// VL - 115 SP - 1453-1456 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85033230091&partnerID=MN8TOARS ER - TY - JOUR TI - Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors AU - Roy, U. N. AU - Mundle, R. M. AU - Camarda, G. S. AU - Cui, Y. AU - Gul, R. AU - Hossain, A. AU - Yang, G. AU - Pradhan, A. K. AU - James, R. B. T2 - Scientific Reports AB - CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability. DA - 2016/5/24/ PY - 2016/5/24/ DO - 10.1038/SREP26384 VL - 6 IS - 1 J2 - Sci Rep LA - en OP - SN - 2045-2322 UR - http://dx.doi.org/10.1038/SREP26384 DB - Crossref ER - TY - JOUR TI - Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals AU - Bolotnikov, A.E. AU - Camarda, G.S. AU - Cui, Y. AU - De Geronimo, G. AU - Eger, J. AU - Emerick, A. AU - Fried, J. AU - Hossain, A. AU - Roy, U. AU - Salwen, C. AU - Soldner, S. AU - Vernon, E. AU - Yang, G. AU - James, R.B. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices. DA - 2016/1// PY - 2016/1// DO - 10.1016/J.NIMA.2015.08.051 VL - 805 SP - 41-54 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/J.NIMA.2015.08.051 DB - Crossref KW - CdZnTe KW - High-granularity detectors KW - 3D pixelated detectors KW - Crystal defects KW - Charge sharing KW - Charge-loss correction ER - TY - JOUR TI - Growth and characterization of CdMnTe by the vertical Bridgman technique AU - Roy, U.N. AU - Camarda, G.S. AU - Cui, Y. AU - Gu, G. AU - Gul, R. AU - Hossain, A. AU - Yang, G. AU - Egarievwe, S.U. AU - James, R.B. T2 - Journal of Crystal Growth AB - We grew Cd1−xMnx Te crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The structural quality of the crystal was evaluated by white beam X-ray topography in the National Synchrotron Light Source (NSLS) facility at Brookhaven National Laboratory (BNL). We observed that the crystal was free from a sub-grain boundary network, as revealed by X-ray topography and verified by our etching study. The concentration of the secondary phases, averaged over the entire ingot, was 2–3 times lower than in conventional Bridgman grown cadmium zinc telluride (CZT) crystals. DA - 2016/3// PY - 2016/3// DO - 10.1016/J.JCRYSGRO.2015.12.017 VL - 437 SP - 53-58 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/J.JCRYSGRO.2015.12.017 DB - Crossref KW - Characterization KW - Extended defects KW - Sub-grain boundary network KW - Bridgman KW - CdMnTe KW - Semiconducting II-VI materials ER - TY - JOUR TI - A high temperature mechanical study on PH 13-8 Mo maraging steel AU - Huang, Z. AU - Abad, M.D. AU - Ramsey, J.K. AU - de Figueiredo, M. Rebelo AU - Kaoumi, D. AU - Li, N. AU - Asta, M. AU - Gronbech-Jensen, N. AU - Hosemann, P. T2 - Materials Science and Engineering: A AB - High temperature mechanical measurements were conducted to study the effect of the dynamic precipitation process of PH 13-8 Mo maraging steel. Yield stress, ultimate tensile strength, total elongation, hardness, strain rate sensitivity and activation volume were evaluated as a function of the temperature. The dynamic changes in the mechanical properties at different temperatures were evaluated and a balance between precipitation hardening and annealed softening is discussed. A comparison between hardness and yield stress and ultimate tensile strength over a temperature range from 300 to 600 °C is made. The behavior of the strain rate sensitivity was correlated with the intermetallic precipitates formed during the experiments. DA - 2016/1// PY - 2016/1// DO - 10.1016/J.MSEA.2015.10.077 VL - 651 SP - 574-582 J2 - Materials Science and Engineering: A LA - en OP - SN - 0921-5093 UR - http://dx.doi.org/10.1016/J.MSEA.2015.10.077 DB - Crossref KW - Mechanical characterization KW - Nanoindentation KW - Martensite KW - Aging KW - Hardening KW - Precipitation ER - TY - JOUR TI - Effects of Microstructure and Processing Methods on Creep Behavior of AZ91 Magnesium Alloy AU - Shahbeigi Roodposhti, Peiman AU - Sarkar, Apu AU - Murty, Korukonda L. AU - Scattergood, Ronald O. T2 - Journal of Materials Engineering and Performance DA - 2016/7/13/ PY - 2016/7/13/ DO - 10.1007/S11665-016-2222-1 VL - 25 IS - 9 SP - 3697-3709 J2 - J. of Materi Eng and Perform LA - en OP - SN - 1059-9495 1544-1024 UR - http://dx.doi.org/10.1007/S11665-016-2222-1 DB - Crossref KW - AZ91 KW - creep KW - die cast KW - intermetallic phases KW - mild steel cast KW - thixoform ER - TY - JOUR TI - Effect of strain and temperature on the threshold displacement energy in body-centered cubic iron AU - Beeler, B. AU - Asta, M. AU - Hosemann, P. AU - Gr?nbech-Jensen, N. T2 - Journal of Nuclear Materials AB - The threshold displacement energy (TDE) is the minimum amount of kinetic energy required to displace an atom from its lattice site. The magnitude of the TDE displays significant variance as a function of the crystallographic direction, system temperature and applied strain, among a variety of other factors. It is critically important to determine an accurate value of the TDE in order to calculate the total number of displacements due to a given irradiation condition, and thus to understand the materials response to irradiation. In this study, molecular dynamics simulations have been performed to calculate the threshold displacement energy in body-centered cubic iron as a function of strain and temperature. With applied strain, a decrease of the TDE of up to approximately 14 eV was observed. A temperature increase from 300 K to 500 K can result in an increase of the TDE of up to approximately 9 eV. DA - 2016/// PY - 2016/// DO - 10.1016/j.jnucmat.2016.03.017 VL - 474 SP - 113-119 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963585213&partnerID=MN8TOARS KW - Threshold displacement energy KW - Radiation damage KW - Iron KW - Molecular dynamics ER - TY - RPRT TI - Novel Engineered Refractory Materials for Advanced Reactor Applications AU - Shannon, Steven AU - Eapen, Jacob AU - Maria, Jon-Paul AU - Weber, William A3 - Office of Scientific and Technical Information (OSTI) AB - This report summarizes the results of DOE-NEUP grant 10-853. The project spanned 48 months (36 months under the original grant plus a 12 month no cost extension). The overarching goal of this work was to fabricate and characterize refractory materials engineered at the atomic scale with emphasis on their tolerance to accumulated radiation damage. With an emphasis on nano-scale structure, this work included atomic scale simulation to study the underlying mechanisms for modified radiation tolerance at these atomic scales. DA - 2016/3/14/ PY - 2016/3/14/ DO - 10.2172/1246903 PB - Office of Scientific and Technical Information (OSTI) UR - http://dx.doi.org/10.2172/1246903 DB - Crossref ER - TY - RPRT TI - Energy Flow in Dense Off-Equilibrium Plasma AU - Putterman, Seth AU - Bataller, Alex AU - Koulakis, John AU - Pree, Seth AU - Latshaw, Alexandra A3 - University of California, Los Angeles Los Angeles United States DA - 2016/// PY - 2016/// PB - University of California, Los Angeles Los Angeles United States ER - TY - JOUR TI - Comment on “Early stage time evolution of a dense nanosecond microdischarge used in fast optical switching applications”[Phys. Plasmas 22, 123518 (2015)] AU - Bataller, A AU - Koulakis, J AU - Pree, S AU - Putterman, S T2 - Physics of Plasmas DA - 2016/// PY - 2016/// VL - 23 IS - 3 SP - 034705 ER - TY - JOUR TI - Observation of Shell Structure, Electronic Screening, and Energetic Limiting in Sparks AU - Bataller, A. AU - Putterman, S. AU - Pree, S. AU - Koulakis, J. T2 - Physical Review Letters AB - We study the formation of micron-sized spark discharges in high-pressure xenon on the nanosecond time scale. The spark's energy per length is measured through the expansion dynamics of the generated shock wave, and is observed to scale linearly with the spark radius. At the same time, the surface temperature of the spark channel remains constant. Together, these observations allow us to conclude that the spark channel, up to 40 μm in overall radius, is actually an energetically hollow shell about 20 μm thick. Further, the energy per nucleus in the shell is about 15 eV, independent of size and density. To reconcile these findings with the opacity to visible light, we appeal to collective screening processes that dramatically lower the effective ionization potential, allowing a much higher electron density than is otherwise expected. Thus, nanosecond measurements of sparks provide access to the thermodynamics and kinetics of strongly correlated plasmas. DA - 2016/8/19/ PY - 2016/8/19/ DO - 10.1103/PhysRevLett.117.085001 VL - 117 IS - 8 SP - 085001 J2 - Phys. Rev. Lett. LA - en OP - SN - 0031-9007 1079-7114 UR - http://dx.doi.org/10.1103/PhysRevLett.117.085001 DB - Crossref ER - TY - JOUR TI - Efficient Charge Transfer and Fine-Tuned Energy Level Alignment in a THF-Processed Fullerene-Free Organic Solar Cell with 11.3% Efficiency AU - Zheng, Zhong AU - Awartani, Omar M. AU - Gautam, Bhoj AU - Liu, Delong AU - Qin, Yunpeng AU - Li, Wanning AU - Bataller, Alexander AU - Gundogdu, Kenan AU - Ade, Harald AU - Hou, Jianhui AU - al., T2 - Advanced Materials AB - Fullerene-free organic solar cells show over 11% power conversion efficiency, processed by low toxic solvents. The applied donor and acceptor in the bulk heterojunction exhibit almost the same highest occupied molecular orbital level, yet exhibit very efficient charge creation. DA - 2016/11/28/ PY - 2016/11/28/ DO - 10.1002/adma.201604241 VL - 29 IS - 5 SP - 1604241 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/adma.201604241 DB - Crossref ER - TY - CONF TI - Zero dimensional model of atmospheric SMD discharge and afterglow in humid air AU - Smith, Ryan T. AU - Kemaneci, Efe AU - Offerhaus, Bjorn AU - Stapelmann, Katharina AU - Brinkmann, Ralf-Peter AB - Summary form only given. Multiple time-scaled zero-dimensional models are used to simulate the time resolved number densities of multiple reactive oxygen and nitrogen species(RONs), including O 3 , NO 2 , NO 3 , N 2 O, N 2 O 5 , H 2 O 2 , HNO 2 and HNO 3 , in a humid air plasma process at atmospheric pressure. Simulated is a total of 26 ionic species, electrons and 26 neutral species including multiple excited states. From the local Electron Energy Distribution Function (EEDF) the mean electron energy is determined and used in various reaction rate coefficients. A total of 624 reactions between the 53 species are simulated in two interdependent zero-dimensional models that differ in nine orders magnitude in temporal resolution, thereby reducing the computational load that is traditionally required in a complex system. A single homogenous volumetric discharge generated by a Surface Micro Discharge(SMD) setup is simulated. Through control variables, parameters such as: ignition frequency, deposited power density, duty cycle, discharge size, and humidity level will be varied in order to predict ideal operating conditions for appropriate SMD devices. The described model has been verified by matching simulation parameters and comparing results to that of previous works1 as well as matching current operating conditions and comparing to the measurements of an experimental mesh-like SMD. C2 - 2016/6// C3 - 2016 IEEE International Conference on Plasma Science (ICOPS) DA - 2016/6// DO - 10.1109/plasma.2016.7534332 SP - 395 PB - Institute of Electrical and Electronics Engineers (IEEE) UR - https://publons.com/wos-op/publon/10782980/ ER - TY - CONF TI - Zero dimensional model of atmospheric SMD discharge and afterglow in humid air AU - Stapelmann, Katharina AU - Kogelheide, Friederike AU - Baldus, Sabrina AU - Lackmann, Jan-Wilm AU - Awakowicz, Peter AU - Kartaschew, Konstantin AU - Havenith, Martina AU - Schröder, Daniel AU - Gathen, Volker Schulz-von AU - Suschek, Christoph V. AU - Opländer, Christian C2 - 2016/// C3 - 69th Annual Gaseous Electronics Conference DA - 2016/// DO - UR - https://meetings.aps.org/Meeting/GEC16/Session/NW3.2 ER - TY - JOUR TI - VUV absorption spectroscopy of bacterial spores and DNA components AU - Fiebrandt, Marcel AU - Lackmann, Jan-Wilm AU - Raguse, Marina AU - Moeller, Ralf AU - Awakowicz, Peter AU - Stapelmann, Katharina T2 - Plasma Physics and Controlled Fusion AB - Low-pressure plasmas can be used to inactivate bacterial spores and sterilize goods for medical and pharmaceutical applications. A crucial factor are damages induced by UV and VUV radiation emitted by the plasma. To analyze inactivation processes and protection strategies of spores, absorption spectra of two B. subtilis strains are measured. The results indicate, that the inner and outer coat of the spore significantly contribute to the absorption of UV-C and also of the VUV, protecting the spore against radiation based damages. As the sample preparation can significantly influence the absorption spectra due to salt residues, the cleaning procedure and sample deposition is tested for its reproducibility by measuring DNA oligomers and pUC18 plasmid DNA. The measurements are compared and discussed with results from the literature, showing a strong decrease of the salt content enabling the detection of absorption structures in the samples. DA - 2016/10// PY - 2016/10// DO - 10.1088/0741-3335/59/1/014010 VL - 59 IS - 1 SP - 014010 KW - VUV spectroscopy KW - absorption KW - bacterial spores KW - DNA KW - Bacillus subtilis ER - TY - JOUR TI - Micro-plasmoids in self organized filamentary dielectric barrier discharges AU - Engelhardt, Max AU - Kogelheide, Friederike AU - Stapelmann, Katharina AU - Bibinov, Nikita AU - Awakowicz, Peter T2 - Plasma Processes and Polymers AB - A filamentary dielectric barrier discharge (DBD) is ignited on a silicon wafer under atmospheric pressure conditions in a mixture of argon and air (0.5/0.5) in two different modes, namely a stochastically ignited filamentary discharge and a self‐organized filamentary discharge by the application of high voltage (HV) pulses at two repetition frequencies, 0.5 and 5 kHz. The discharge conditions are characterized by optical emission spectroscopy and current–voltage measurements. The silicon wafer surface treated with the DBD is studied with an electron microscope. The formation of a homogeneous silicon oxide layer is observed after treatment under a stochastically filamentary DBD. Whereas, in the self‐organized filamentary DBD, etching tracks (thin channels) and blisters are produced on the silicon wafer surface, which are interpreted as tracks of plasmoids, namely plasma objects without any direct contact to a power supply. The transition between the different filamentary modes of the DBD plasma occurs in the presented study through an increase of the repetition frequency of HV pulses, but it can also be caused by small silicon splinters on the wafer surface. The splinters cause ignitions in stable positions, and therefore induce a combination of discharge modes, namely stochastically and self‐organized DBD mode. In close proximity to the splinters, tracks of plasmoids are observed, even in the DBD at low frequency. DA - 2016/10// PY - 2016/10// DO - 10.1002/ppap.201600095 VL - 10 IS - 7 SP - 1 - 10 KW - DBD KW - etching tracks KW - plasmoids KW - silicon wafer KW - surface modifications ER - TY - JOUR TI - A combined low-pressure hydrogen peroxide evaporation plus hydrogen plasma treatment method for sterilization − Part 2: An intercomparison study of different biological systems AU - Lackmann, Jan-Wilm AU - Fiebrandt, Marcel AU - Raguse, Marina AU - Kartaschew, Konstantin AU - Havenith, Martina AU - Bandow, Julia E. AU - Moeller, Ralf AU - Awakowicz, Peter AU - Stapelmann, Katharina T2 - Plasma Processes and Polymers AB - Low‐pressure plasmas are a promising alternative to modern sterilization processes. As plasma is a surface process, multilayered stacks of spores are a crucial challenge to overcome. Here, a combined process of condensed hydrogen peroxide and hydrogen plasma is analyzed for its efficacy against various spore concentrations showing a clear increase in efficacy using a combined process compared to the two steps used separately. Besides spores, protein contaminations are a major issue in clinics and the combined process is investigated for protein removal efficiency using the well‐established BSA model. Furthermore, RNase A serves as a difficult‐to‐inactivate protein model to investigate protein inactivation efficiency. Finally, inactivation mechanisms of RNase A with a special focus on sulfur‐based modifications are investigated using Raman spectroscopy. DA - 2016/// PY - 2016/// DO - 10.1002/ppap.201600199 VL - 12 IS - 8 SP - 201600199 KW - bacterial spores KW - capacitively coupled KW - low-pressure discharges KW - proteins KW - sterilization ER - TY - JOUR TI - An investigation of the secondary electron emission coefficient of aluminum and graphite disc electrodes AU - Radwan, S. AU - Bourham, M. T2 - Arab Journal of Nuclear Sciences and Applications DA - 2016/// PY - 2016/// VL - 49 IS - 4 SP - 121-128 ER - TY - CONF TI - Bayesian metropolis methods applied to sensor networks for radiation source localization AU - Hite, J. M. AU - Mattingly, J. K. AU - Schmidt, K. L. AU - Stelanescu, R. AU - Smith, R. AB - We present an application of statistical techniques to the localization of an unknown gamma source in an urban environment. By formulating the problem as a task of Bayesian parameter estimation, we are able to apply Markov Chain Monte Carlo (MCMC) to generate a full posterior probability density estimating the source location and intensity based on counts reported from a distributed detector network. To facilitate the calibration procedure, we employ a simplified photon transport model with low computational cost and test the proposed methodology in a simulated urban environment, with calibration data generated using the radiation transport code MCNP. The Bayesian methodology is able to identify the source location and intensity along with providing a full posterior density. C2 - 2016/// C3 - 2016 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI) DA - 2016/// DO - 10.1109/mfi.2016.7849519 SP - 389-393 ER - TY - JOUR TI - Understanding of the importance of the spore coat structure and pigmentation in the Bacillus subtilis spore resistance to low-pressure plasma sterilization AU - Raguse, Marina AU - Fiebrandt, Marcel AU - Denis, Benjamin AU - Stapelmann, Katharina AU - Eichenberger, Patrick AU - Driks, Adam AU - Eaton, Peter AU - Awakowicz, Peter AU - Moeller, Ralf T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - Low-pressure plasmas have been evaluated for their potential in biomedical and defense purposes. The sterilizing effect of plasma can be attributed to several active agents, including (V)UV radiation, charged particles, radical species, neutral and excited atoms and molecules, and the electric field. Spores of Bacillus subtilis were used as a bioindicator and a genetic model system to study the sporicidal effects of low-pressure plasma decontamination. Wild-type spores, spores lacking the major protective coat layers (inner, outer, and crust), pigmentation-deficient spores or spore impaired in encasement (a late step in coat assembly) were systematically tested for their resistance to low-pressure argon, hydrogen, and oxygen plasmas with and without admixtures. We demonstrate that low-pressure plasma discharges of argon and oxygen discharges cause significant physical damage to spore surface structures as visualized by atomic force microscopy. Spore resistance to low-pressure plasma was primarily dependent on the presence of the inner, and outer spore coat layers as well as spore encasement, with minor or less importance of the crust and spore pigmentation, whereas spore inactivation itself was strongly influenced by the gas composition and operational settings. DA - 2016/7/20/ PY - 2016/7/20/ DO - 10.1088/0022-3727/49/28/285401 VL - 49 IS - 28 SP - SN - 1361-6463 UR - https://publons.com/wos-op/publon/627173/ KW - bioindicator KW - plasma sterilization KW - decontamination KW - spores KW - Bacillus subtilis KW - spore coat KW - spore resistance ER - TY - JOUR TI - Improvement of Biological Indicators by Uniformly Distributing Bacillus subtilis Spores in Monolayers To Evaluate Enhanced Spore Decontamination Technologies AU - Raguse, Marina AU - Fiebrandt, Marcel AU - Stapelmann, Katharina AU - Madela, Kazimierz AU - Laue, Michael AU - Lackmann, Jan-Wilm AU - Thwaite, Joanne E. AU - Setlow, Peter AU - Awakowicz, Peter AU - Moeller, Ralf AU - Schaffner, D. W. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - Novel decontamination technologies, including cold low-pressure plasma and blue light (400 nm), are promising alternatives to conventional surface decontamination methods. However, the standardization of the assessment of such sterilization processes remains to be accomplished. Bacterial endospores of the genera Bacillus and Geobacillus are frequently used as biological indicators (BIs) of sterility. Ensuring standardized and reproducible BIs for reliable testing procedures is a significant problem in industrial settings. In this study, an electrically driven spray deposition device was developed, allowing fast, reproducible, and homogeneous preparation of Bacillus subtilis 168 spore monolayers on glass surfaces. A detailed description of the structural design as well as the operating principle of the spraying device is given. The reproducible formation of spore monolayers of up to 5 × 10(7) spores per sample was verified by scanning electron microscopy. Surface inactivation studies revealed that monolayered spores were inactivated by UV-C (254 nm), low-pressure argon plasma (500 W, 10 Pa, 100 standard cubic cm per min), and blue light (400 nm) significantly faster than multilayered spores were. We have thus succeeded in the uniform preparation of reproducible, highly concentrated spore monolayers with the potential to generate BIs for a variety of nonpenetrating surface decontamination techniques. DA - 2016/4// PY - 2016/4// DO - 10.1128/aem.03934-15 VL - 82 IS - 7 SP - 2031-2038 SN - 1098-5336 UR - https://publons.com/wos-op/publon/627177/ ER - TY - JOUR TI - FTIR spectroscopy of cysteine as a ready-to-use method for the investigation of plasma-induced chemical modifications of macromolecules AU - Kogelheide, Friederike AU - Kartaschew, Konstantin AU - Strack, Martin AU - Baldus, Sabrina AU - Metzler-Nolte, Nils AU - Havenith, Martina AU - Awakowicz, Peter AU - Stapelmann, Katharina AU - Lackmann, Jan-Wilm T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - A rapid screening method for the investigation of plasma-induced chemical modifications was developed by analyzing cysteine using Fourier Transform Infrared (FTIR) spectroscopy. Cysteine is a key amino acid in proteins due to the presence of a thiol group which provides unique structural features by offering the possibility to form disulfide bonds. Its chemical composition makes cysteine a well-suited model for the investigation of plasma-induced modifications at three functional groups—the amino, the carboxyl and the thiol group—all highly abundant in proteins. FTIR spectroscopy is present in most physical laboratories and offers a fast way to assess changes in the chemical composition of cysteine substrates due to plasma treatment and to compare different treatment conditions or plasma sources with each other. Significant changes in the fingerprint spectra of cysteine samples treated with a dielectric barrier discharge (DBD) compared to untreated controls were observed using a FTIR spectrometer. The loss of the thiol signal and the simultaneous increase of bands originating from oxidized sulfur and nitrogen species indicate that the thiol group of cysteine is modified by reactive oxygen and nitrogen species during DBD treatment. Furthermore, other plasma-induced modifications, such as changes of the amino and carbonyl groups, could be observed. Complementary mass spectrometry measurements confirmed these results. DA - 2016/3/2/ PY - 2016/3/2/ DO - 10.1088/0022-3727/49/8/084004 VL - 49 IS - 8 SP - SN - 1361-6463 UR - https://publons.com/wos-op/publon/627180/ KW - cysteine KW - FTIR spectroscopy KW - dielectric barrier discharge KW - chemical modifications ER - TY - JOUR TI - Effects of Low-Temperature Plasma-Sterilization on Mars Analog Soil Samples Mixed with Deinococcus radiodurans AU - Schirmack, Janosch AU - Fiebrandt, Marcel AU - Stapelmann, Katharina AU - Schulze-Makuch, Dirk T2 - Life AB - We used Ar plasma-sterilization at a temperature below 80 °C to examine its effects on the viability of microorganisms when intermixed with tested soil. Due to a relatively low temperature, this method is not thought to affect the properties of a soil, particularly its organic component, to a significant degree. The method has previously been shown to work well on spacecraft parts. The selected microorganism for this test was Deinococcus radiodurans R1, which is known for its remarkable resistance to radiation effects. Our results showed a reduction in microbial counts after applying a low temperature plasma, but not to a degree suitable for a sterilization of the soil. Even an increase of the treatment duration from 1.5 to 45 min did not achieve satisfying results, but only resulted in in a mean cell reduction rate of 75% compared to the untreated control samples. DA - 2016/5// PY - 2016/5// DO - 10.3390/life6020022 VL - 6 IS - 2 SP - 22 UR - https://publons.com/wos-op/publon/627172/ ER - TY - JOUR TI - Mechanical Properties of High Entropy Alloy Al0.1CoCrFeNi for Peripheral Vascular Stent Application AU - Alagarsamy, Karthik AU - Fortier, Aleksandra AU - Komarasamy, Mageshwari AU - Kumar, Nilesh AU - Mohammad, Atif AU - Banerjee, Subhash AU - Han, Hai-Chao AU - Mishra, Rajiv S. T2 - CARDIOVASCULAR ENGINEERING AND TECHNOLOGY DA - 2016/12// PY - 2016/12// DO - 10.1007/s13239-016-0286-6 VL - 7 IS - 4 SP - 448-454 SN - 1869-4098 KW - High entropy alloys KW - Stent implants KW - Peripheral stenting KW - Fatigue analysis KW - Finite element analysis KW - Superficial femoral artery ER - TY - JOUR TI - All The Catalytic Active Sites of MoS2 for Hydrogen Evolution AU - Li, Guoqing AU - Zhang, Du AU - Qiao, Qiao AU - Yu, Yifei AU - Peterson, David AU - Zafar, Abdullah AU - Kumar, Raj AU - Curtarolo, Stefano AU - Hunte, Frank AU - Shannon, Steve AU - Zhu, Yimei AU - Yang, Weitao AU - Cao, Linyou T2 - Journal of the American Chemical Society AB - MoS2 presents a promising low-cost catalyst for the hydrogen evolution reaction (HER), but the understanding about its active sites has remained limited. Here we present an unambiguous study of the catalytic activities of all possible reaction sites of MoS2, including edge sites, sulfur vacancies, and grain boundaries. We demonstrate that, in addition to the well-known catalytically active edge sites, sulfur vacancies provide another major active site for the HER, while the catalytic activity of grain boundaries is much weaker. The intrinsic turnover frequencies (Tafel slopes) of the edge sites, sulfur vacancies, and grain boundaries are estimated to be 7.5 s-1 (65-75 mV/dec), 3.2 s-1 (65-85 mV/dec), and 0.1 s-1 (120-160 mV/dec), respectively. We also demonstrate that the catalytic activity of sulfur vacancies strongly depends on the density of the vacancies and the local crystalline structure in proximity to the vacancies. Unlike edge sites, whose catalytic activity linearly depends on the length, sulfur vacancies show optimal catalytic activities when the vacancy density is in the range of 7-10%, and the number of sulfur vacancies in high crystalline quality MoS2 is higher than that in low crystalline quality MoS2, which may be related with the proximity of different local crystalline structures to the vacancies. DA - 2016/12/15/ PY - 2016/12/15/ DO - 10.1021/jacs.6b05940 VL - 138 IS - 51 SP - 16632-16638 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/jacs.6b05940 DB - Crossref ER - TY - JOUR TI - Spectral Analysis of Single- and Two-Phase Bubbly DNS in Different Geometries AU - Brown, C. S. AU - Bolotnov, I. A. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - The spectral analysis of turbulent single- and two-phase direct numerical simulation (DNS) data in flat plane channel, circular pipe, and reactor subchannel geometries is performed using the recorded DNS velocity fluctuations as a function of time and applying the fast Fourier transform. This results in an energy spectrum of the liquid turbulence in a frequency domain. The complexity of multiphase flow results in a mixed velocity time history coming from either the liquid or the gas phase. A modified single-phase signal that mimics the presence of bubbles (“pseudo-void”) is developed to quantify the effect of the liquid signal intermittency as the bubble passes through a virtual probe.Comparisons of single-phase, pseudo-void, and two-phase results quantify the changes to the expected #x2013;5/3 slope of the energy spectrum for single-phase flows due to turbulent interactions caused by the wakes behind a bubble. The two-phase energy spectra show a slope close to #x2013;3 and similar shape in the different geometries while single-phase energy spectra exhibit the expected #x2013;5/3 slope. Pseudo-void results indicate that the change to the energy spectrum in bubbly two-phase flows is due entirely from liquid turbulence interactions with the bubble wakes.A comprehensive spectral analysis for different geometries and different Reynolds number flows at varying distances from the wall is an essential step in developing physically sound closure models for bubble-liquid interactions. The comparison between different geometries demonstrates the direct applicability of various models to reactor-relevant geometries. DA - 2016/11// PY - 2016/11// DO - 10.13182/nse15-126 VL - 184 IS - 3 SP - 363-376 SN - 1943-748X KW - Multiphase DNS KW - energy spectrum KW - spectral analysis ER - TY - JOUR TI - Nonlinear Diffusion Acceleration Method with Multigrid in Energy for k-Eigenvalue Neutron Transport Problems AU - Cornejo, Luke R. AU - Anistratov, Dmitriy Y. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - We present a multilevel method for solving multigroup neutron transport k-eigenvalue problems in two-dimensional Cartesian geometry. It is based on the nonlinear diffusion acceleration (NDA) method. The multigroup low-order NDA (LONDA) equations are formulated on a sequence of energy grids. Various multigrid cycles are applied to solve the hierarchy of multigrid LONDA equations. The algorithms developed accelerate transport iterations and are effective in solving the multigroup NDA low-order equations. We present numerical results for model reactor-physics problems with a large number of groups to demonstrate the performance of different iterative schemes. DA - 2016/12// PY - 2016/12// DO - 10.13182/nse16-78 VL - 184 IS - 4 SP - 514-526 SN - 1943-748X KW - Neutron transport KW - eigenvalue problems KW - iteration methods ER - TY - JOUR TI - Foreword special issue on the 16th international topical meeting on nuclear reactor thermal hydraulics AU - Corradini, M. AU - Dinh, N. T. AU - Leon, S. B. Y. T2 - Nuclear Science and Engineering DA - 2016/// PY - 2016/// VL - 184 IS - 3 SP - III- ER - TY - JOUR TI - Comment on "Fluid modeling of a high-voltage nanosecond pulsed xenon microdischarge" [Phys. Plasmas 23, 073513 (2016)] AU - Koulakis, J. AU - Bataller, A. AU - Pree, S. AU - Putterman, S. T2 - PHYSICS OF PLASMAS AB - Simulations of sparks in 10 atmosphere Xenon gas by Levko and Raja [Phys. Plasmas 23, 073513 (2016)] are unable to reproduce the experimental fact of their opacity to visible light [Bataller et al., Appl. Phys. Lett. 105, 223501 (2014)]. Levko and Raja have argued the discrepancy is due to enhanced ionization from the probing laser radiation and/or cathode field emission. Having observed comparable opacity in similar systems without probing lasers and without electrodes, we instead argue that the enhanced ionization is a thermodynamic result of dense plasma screening effects that lower the effective ionization potential. Levko and Raja do not adequately address these density effects in their spark discharge simulations. DA - 2016/11// PY - 2016/11// DO - 10.1063/1.4967851 VL - 23 IS - 11 SP - SN - 1089-7674 ER - TY - JOUR TI - Applications of Doppler-free saturation spectroscopy for edge physics studies AU - Martin, E. H. AU - Zafar, A. AU - Caughman, J. B. O. AU - Isler, R. C. AU - Bell, G. L. T2 - REVIEW OF SCIENTIFIC INSTRUMENTS AB - Doppler-free saturation spectroscopy provides a very powerful method to obtain detailed information about the electronic structure of the atom through measurement of the spectral line profile. This is achieved through a significant decrease in the Doppler broadening and essentially an elimination of the instrument broadening inherent to passive spectroscopic techniques. In this paper we present the technique and associated physics of Doppler-free saturation spectroscopy in addition to how one selects the appropriate transition. Simulations of Hδ spectra are presented to illustrate the increased sensitivity to both electric field and electron density measurements. DA - 2016/11// PY - 2016/11// DO - 10.1063/1.4961287 VL - 87 IS - 11 SP - SN - 1089-7623 ER - TY - JOUR TI - A temporally and spatially resolved electron density diagnostic method for the edge plasma based on Stark broadening AU - Zafar, A. AU - Martin, E. H. AU - Shannon, S. C. AU - Isler, R. C. AU - Caughman, J. B. O. T2 - Review of Scientific Instruments AB - An electron density diagnostic (≥1010 cm−3) capable of high temporal (ms) and spatial (mm) resolution is currently under development at Oak Ridge National Laboratory. The diagnostic is based on measuring the Stark broadened, Doppler-free spectral line profile of the n = 6–2 hydrogen Balmer series transition. The profile is then fit to a fully quantum mechanical model including the appropriate electric and magnetic field operators. The quasi-static approach used to calculate the Doppler-free spectral line profile is outlined here and the results from the model are presented for H-δ spectra for electron densities of 1010–1013 cm−3. The profile shows complex behavior due to the interaction between the magnetic substates of the atom. DA - 2016/7/18/ PY - 2016/7/18/ DO - 10.1063/1.4955484 VL - 87 IS - 11 SP - 11E505 J2 - Rev. Sci. Instrum. LA - en OP - SN - 0034-6748 1089-7623 UR - http://dx.doi.org/10.1063/1.4955484 DB - Crossref ER - TY - CONF TI - Synthesizing route travel time distributions considering spatial dependencies AU - Isukapati, I. K. AU - List, G. F. C2 - 2016/// C3 - 2016 IEEE 19th International Conference on Intelligent Transportation Systems (ITSC) DA - 2016/// SP - 2143-2149 ER - TY - JOUR TI - Synthesis of Antifungal Agents from Xanthene and Thiazine Dyes and Analysis of Their Effects AU - Kim, Joo Ran AU - Michielsen, Stephen T2 - NANOMATERIALS AB - Indoor fungi growth is an increasing home health problem as our homes are more tightly sealed. One thing that limits durability of the antifungal agents is the scarcity of reactive sites on many surfaces to attach these agents. In order to increase graft yield of photosensitizers to the fabrics, poly(acrylic acid-co-styrene sulfonic acid-co-vinyl benzyl rose bengal or phloxine B) were polymerized and then grafted to electrospun fabrics. In an alternative process, azure A or toluidine blue O were grafted to poly(acrylic acid), which was subsequently grafted to nanofiber-based and microfiber-based fabrics. The fabrics grafted with photosensitizers induced antifungal effects on all seven types of fungi in the order of rose bengal > phloxine B > toluidine blue O > azure A, which follows the quantum yield production of singlet oxygen for these photoactive dyes. Their inhibition rates for inactivating fungal spores decreased in the order of P. cinnamomi, T. viride, A. niger, A. fumigatus, C. globosum, P. funiculosum, and M. grisea, which is associated with lipid composition in membrane and the morphology of fungal spores. The antifungal activity was also correlated with the surface area of fabric types which grafted the photosensitizer covalently on the surface as determined by the bound color strength. DA - 2016/12// PY - 2016/12// DO - 10.3390/nano6120243 VL - 6 IS - 12 SP - SN - 2079-4991 KW - antifungal photosensitizer KW - nanofiber KW - Aspergillus KW - Chaetomium KW - Magnaporthe ER - TY - JOUR TI - Radial Profile of Plasma Flow Parameters Following Evolution of Electrothermal Polycarbonate Plasma into a Large Chamber Simulating Impurity Expansion in Fusion Reactor Vacuum Vessel AU - Majumdar, Rudrodip AU - Bourham, Mohamed A. T2 - Journal of Fusion Energy DA - 2016/7/5/ PY - 2016/7/5/ DO - 10.1007/s10894-016-0107-9 VL - 35 IS - 6 SP - 795-806 J2 - J Fusion Energ LA - en OP - SN - 0164-0313 1572-9591 UR - http://dx.doi.org/10.1007/s10894-016-0107-9 DB - Crossref KW - Plasma flow KW - Fusion particle expansion KW - Impurity following disruption KW - Electrothermal simulation ER - TY - JOUR TI - Laminar/turbulent airflow and microsphere deposition in a patient-specific airway geometry using an open-source solver AU - Vaish, Mayank AU - Kleinstreuer, Clement AU - Kolanjiyil, Arun V. AU - Saini, Nadish AU - Pillalamarri, Narasimha R. T2 - INTERNATIONAL JOURNAL OF BIOMEDICAL ENGINEERING AND TECHNOLOGY AB - Using the open-source software OpenFOAM as the solver, airflow and microsphere transport have been simulated in a patient-specific lung-airway model. A suitable transitional turbulence model was validated and implemented to accurately simulate airflow fields, as the laryngeal jet occurring in the throat region may induce turbulence immediately downstream. Furthermore, a modified eddy interaction model with a generalised near-wall correction factor is presented that more accurately simulates the particle trajectories and subsequent deposition phenomena which are especially affected by near-wall velocity fluctuations. Particle depositions in the realistic lung-airway configuration are compared with those in an idealised upper airway model. The results indicate that for microsphere deposition in turbulent airflow regions, selection of an appropriate near-wall correction factor can reduce the problem of subject variability for different lung-airway configurations. Open-source solvers for lung-aerosol dynamics simulations, such as OpenFOAM, are predictive tools which are basically cost-free, flexible, largely user-friendly, and portable. DA - 2016/// PY - 2016/// DO - 10.1504/ijbet.2016.079145 VL - 22 IS - 2 SP - 145-161 SN - 1752-6426 KW - OpenFOAM solver KW - patient-specific geometry and idealised configuration KW - modified eddy interaction model KW - microsphere transport and deposition KW - practical Stokes number range ER - TY - CONF TI - Interface tracking simulation of phase-change phenomena: boiling and condensation verification AU - Li, M. N. AU - Bolotnov, Igor AB - Interface tracking simulation (ITS) is one of the promising approaches to describe heat transfer of boiling phenomena and their underlying mechanisms. Better understanding and modeling of this process will benefit various engineering systems. In modern nuclear reactors, study on nucleate boiling phenomena is very important for the prediction of the Critical Heat Flux (CHF) phenomena. The presented research will implement and verify the capability of evaporation process modeling by the massively parallel research code, PHASTA. The comparison of the numerical results and the analytical results demonstrates that the overall behavior of the simulation compares well with the analytical solution. A second simulation of the single bubble growth with non-uniform temperature distribution demonstrates both condensation and evaporation modeling. In the third simulation flow boiling capabilities were preliminary tested with laminar flow demonstration case. These results will be applied to a larger scale, multi-bubble simulations and help modeling of nucleate boiling phenomena. C2 - 2016/// C3 - Proceedings of the asme fluids engineering division summer meeting, 2016, vol 1a DA - 2016/// DO - 10.1115/fedsm2016-7701 ER - TY - JOUR TI - Coupling between magnetic exchange and charge activation in Cu-Doped LaFeO3 AU - Dogdibegovic, E. AU - Cai, Q. S. AU - James, W. J. AU - Yelon, W. B. AU - Anderson, H. U. AU - Yang, J. B. AU - Zhou, X. D. T2 - Journal of the American Ceramic Society AB - Material research on perovskite‐type oxides (ABO 3 ) has been driven by the recognition of their unique properties primarily attributed to the presence of oxygen octahedron (BO 6 ). Since 2003, the discovery of strong coupling in TbMnO 3 and BiFeO 3 has stimulated new interests in understanding the relationship between magnetic and electric properties in perovskites. In this article, we report our recent work on the magnetic superexchange interaction and charge formation in copper‐doped LaFeO 3 using high‐temperature neutron diffraction and thermoelectric measurements. In situ neutron diffraction measurements show a loss of antiferromagnetic ordering above 450°C. With an increase in Cu content, the (Fe, Cu)‐O bond length decreases and the (Fe, Cu)–O–(Fe, Cu) bond angle increases, which leads to an enhancement of the Fe–O–Fe superexchange interaction. Thermoelectric and electrical measurements show that the formation of electron holes in Cu‐doped LaFeO 3 is a thermally activated process with two distinct regions with a transition temperature near 450°C, in congruence with the magnetic measurements. Our work show that Cu is in 3+ state in La(Fe,Cu)O 3 at room temperature, resulting in the maximum superexchange interaction between Fe 3+ ions. DA - 2016/// PY - 2016/// DO - 10.1111/jace.14061 VL - 99 IS - 6 SP - 2035-2039 ER - TY - JOUR TI - Surface Ablation and Melting of Fusion Materials Simulated by Transient High Heat Flux Generated in an Electothermal Plasma Source AU - Almousa, Nouf M. AU - Gilligan, John G. AU - Bourham, Mohamed T2 - IEEE Transactions on Plasma Science AB - An electrothermal (ET) plasma source has been used to produce intense transient high heat flux to evaluate surface erosion and melting of plasma-facing materials. The source produces high heat flux relevant to expected conditions during disruption event in future large fusion devices. Surface vaporization has been evaluated for selected fusion-relevant materials under radiant energy deposition. Additional simulation included the effect of melting and splattering. Vapor and droplet formation and their associated shielding effect have been investigated in this paper to assess the difference between a developed boundary layer from only vapor or melt layer or the mixed vapor-melt layer with possible ejection of molten droplets away from the surface. Fully self-consistent erosion models are developed and implemented in the ET ETFLOW code in a new version ETFLOW-boundary layer to model the response of plasma-facing materials and their erosive behavior under transient ET plasma high heat fluxes closely similar to expected ones in future fusion large tokamaks. DA - 2016/9// PY - 2016/9// DO - 10.1109/tps.2016.2566445 VL - 44 IS - 9 SP - 1642-1648 J2 - IEEE Trans. Plasma Sci. OP - SN - 0093-3813 1939-9375 UR - http://dx.doi.org/10.1109/TPS.2016.2566445 DB - Crossref KW - Plasma-facing components (PFCs) KW - surface erosion KW - tokamak disruption KW - vapor and melt layer shielding ER - TY - JOUR TI - Effect of heat treatment on the temperature dependence of the fracture behavior of X-750 alloy AU - Marsh, C. AU - Depinoy, S. AU - Kaoumi, D. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - X-750 is a nickel-chromium based super alloy of usefulness in a wide variety of applications such as gas turbines, rocket engines, nuclear reactors, pressure vessels, tooling, and aircraft structures. Its good mechanical properties are due to the strengthening from precipitation of γ′ particles upon prior ageing heat treatment. In this work, the effect of such heat treatment on the fracture mechanisms of X-750 was studied at various temperatures by comparing it with a non-aged, solution annealed X-750. Tensile tests were conducted from room temperatures up to 900 °C; fracture surfaces were analyzed by means of SEM observations. In addition, the microstructure of both aged and solution annealed materials were studied using SEM and TEM, both on as received and on tested specimens. In terms of mechanical properties, as expected, the yield strength and the ultimate tensile strength of the aged material were better than for the solution-annealed one, and only slightly decreased with increasing temperature when tested between room temperatures and 650 °C. In this range of temperature, the fracture surface of aged material evolves from purely intergranular to purely transgranular due to the thermal activation of dislocation mobility that relieves the stress at the grain boundaries, while the rupture of the solution annealed material is due to the coalescence of voids induced by decohesion at the MC carbides/matrix interface. At higher temperatures, precipitation of γ’ particles upon testing of the solution-annealed material leads to a temperature-dependent increase in both yield strength and ultimate tensile strength, which nevertheless remain below the aged material ones with the exception of the higher temperatures. At the same time, an overall decrease of the aged material mechanical properties is observed. Minimum ductility was observed at 750 °C for both solution annealed and aged specimen, due to the oxidation of grain boundaries leading to an environmentally-induced fracture mechanism. At higher temperatures, dynamic recovery and dynamic recrystallization occur which prevents such a rupture mechanism, but finally leads to rupture by grain boundary slipping at 900 °C. DA - 2016/11/20/ PY - 2016/11/20/ DO - 10.1016/j.msea.2016.09.081 VL - 677 SP - 474-484 SN - 1873-4936 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84988689036&partnerID=MN8TOARS KW - Nickel super-alloy KW - X-750 KW - Fracture mechanisms KW - Tensile tests KW - Heat treatment ER - TY - JOUR TI - Contributions of Various Radiological Sources to Background in a Suburban Environment AU - Milvenan, Richard D. AU - Hayes, Robert B. T2 - HEALTH PHYSICS AB - This work is a brief overview and comparison of dose rates stemming from both indoor and outdoor natural background radiation and household objects within a suburban environment in North Carolina. Combined gamma and beta dose rates were taken from indoor objects that ranged from the potassium in fruit to the americium in smoke detectors. For outdoor measurements, various height and time data samples were collected to show fluctuations in dose rate due to temperature inversion and geometric attenuation. Although each sample tested proved to have a statistically significant increase over background using Students t-test, no sample proved to be more than a minor increase in natural radiation dose. The relative contributions from natural radioactivity such as potassium in foods and common household items are shown to be easily distinguished from background using standard handheld instrumentation when applied in a systematic, methodological manner. DA - 2016/11// PY - 2016/11// DO - 10.1097/hp.0000000000000564 VL - 111 IS - 5 SP - S193-S199 SN - 1538-5159 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84991228575&partnerID=MN8TOARS KW - operational topics KW - dose assessment KW - environmental assessment KW - radiation KW - background ER - TY - JOUR TI - The IAEA coordinated research programme on HTGR uncertainty analysis: Phase I status and Ex. I-1 prismatic reference results AU - Bostelmann, Friederike AU - Strydom, Gerhard AU - Reitsma, Frederik AU - Ivanov, Kostadin T2 - NUCLEAR ENGINEERING AND DESIGN AB - The quantification of uncertainties in design and safety analysis of reactors is today not only broadly accepted, but in many cases became the preferred way to replace traditional conservative analysis for safety and licensing analysis. The use of a more fundamental methodology is also consistent with the reliable high fidelity physics models and robust, efficient, and accurate codes available today. To facilitate uncertainty analysis applications a comprehensive approach and methodology must be developed and applied, in contrast to the historical approach where sensitivity analysis were performed and uncertainties then determined by a simplified statistical combination of a few important input parameters. New methodologies are currently under development in the OECD/NEA Light Water Reactor (LWR) Uncertainty Analysis in Best-Estimate Modelling (UAM) benchmark activity. High Temperature Gas-cooled Reactor (HTGR) designs require specific treatment of the double heterogeneous fuel design and large graphite quantities at high temperatures. The IAEA has therefore launched a Coordinated Research Project (CRP) on HTGR Uncertainty Analysis in Modelling (UAM) in 2013 to study uncertainty propagation specifically in the HTGR analysis chain. Two benchmark problems are defined, with the prismatic design represented by the General Atomics (GA) MHTGR-350 and a 250 MW modular pebble bed design similar to the Chinese HTR-PM. Work has started on the first phase and the current CRP status is reported in the paper. A comparison of the Serpent and SCALE/KENO-VI reference Monte Carlo results for Ex. I-1 of the MHTGR-350 design is also included. It was observed that the SCALE/KENO-VI Continuous Energy (CE) k∞ values were 395 pcm (Ex. I-1a) to 803 pcm (Ex. I-1b) higher than the respective Serpent lattice calculations, and that within the set of the SCALE results, the KENO-VI 238 Multi-Group (MG) k∞ values were up to 800 pcm lower than the KENO-VI CE values. The use of the latest ENDF-B-VII.1 cross section library in Serpent lead to ∼180 pcm lower k∞ values compared to the older ENDF-B-VII.0 dataset, caused by the modified graphite neutron capture cross section. The fourth beta release of SCALE 6.2 likewise produced lower CE k∞ values when compared to SCALE 6.1, and the improved performance of the new 252-group library available in SCALE 6.2 is especially noteworthy. A SCALE/TSUNAMI uncertainty analysis of the Hot Full Power variant for Ex. I-1a furthermore concluded that the 238U(n,γ) (capture) and 235U(v¯) cross-section covariance matrices contributed the most to the total k∞ uncertainty of 0.58%. DA - 2016/9// PY - 2016/9// DO - 10.1016/j.nucengdes.2015.12.009 VL - 306 SP - 77-88 SN - 1872-759X ER - TY - JOUR TI - Recent Studies on the Asymptotic Convergence of the Spatial Discretization for Two-Dimensional Discrete Ordinates Solutions AU - Barichello, L. B. AU - Tres, A. AU - Picoloto, C. B. AU - Azmy, Y. Y. T2 - JOURNAL OF COMPUTATIONAL AND THEORETICAL TRANSPORT AB - In this work, four types of quadrature schemes are used to define discrete directions in the solution of a two-dimensional fixed-source discrete ordinates problem in Cartesian geometry. Such schemes enable generating numerical results for averaged scalar fluxes over specified regions of the domain with high number (up to 105) of directions per octant. Two different nodal approaches, the ADO and AHOT-N0 methods, are utilized to obtain the numerical results of interest. The AHOT-N0 solutions on a sequence of refined meshes are then used to develop an asymptotic analysis of the spatial discretization error in order to derive a reference solution. It was more clearly observed that the spatial discretization error converges asymptotically with second order for the source region with all four quadratures employed, while for the other regions refined meshes along with tighter convergence criterion must be applied to evidence the same behavior. However, in that case, some differences among the four quadrature schemes results were found. DA - 2016/// PY - 2016/// DO - 10.1080/23324309.2016.1171242 VL - 45 IS - 4 SP - 299-313 SN - 2332-4325 KW - Discrete ordinates KW - Two-dimensional geometry KW - Asymptotic Spatial Convergence ER - TY - JOUR TI - Microstructural, textural and hardness evolution of commercially pure Zr surface-treated by high current pulsed electron beam AU - Chai, Linjiang AU - Chen, Baofeng AU - Wang, Shuyan AU - Zhang, Zhuo AU - Murty, Korukonda L. T2 - APPLIED SURFACE SCIENCE AB - High current pulsed electron beam (HCPEB) treatments were performed for a commercially pure Zr sheet, with remarkable surface modifications demonstrated. After the HCPEB treatments, the prior equiaxed grains with a bimodal basal texture are replaced by ultra fine plates with dense nanotwins and an unusual fiber texture of <112¯0> normal to the sheet surface. Increased number of pulses leads to further refined microstructures and intensified textures, jointly resulting in continuous increase of hardness. Reasons for such modifications could mainly be attributed to ultra fast heating/cooling and strong variant selection due to presence of complex thermal and stress fields. DA - 2016/12/30/ PY - 2016/12/30/ DO - 10.1016/j.apsusc.2016.08.128 VL - 390 SP - 430-434 SN - 1873-5584 KW - Zr KW - Microstructure KW - Texture KW - Hardness KW - Electron beam methods ER - TY - CONF TI - Investigation of thermo-mechanical processing and mechanical properties of CoCrFeNiMn high entropy alloy for peripheral vascular stent application AU - Alagarsamy, K. AU - Fortier, A. AU - Mishra, R. AU - Kumar, N. AB - High entropy alloys (HEAs) are a new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community however, their application is yet to be explored. This paper discusses the mechanical and microstructural behavior of CoCrFeNiMn HEA subjected to thermo-mechanical processing, and its potential application in peripheral vascular stent implants that are prone to high failure rate. Results show that CoCrFeNiMn has characteristics that can potentially find use in peripheral vascular stent implants and extend their life-cycle. C2 - 2016/// C3 - Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 1 DA - 2016/// DO - 10.1115/msec2016-8770 ER - TY - JOUR TI - Impact of fuel thermal conductivity degradation on Doppler feedback during rod ejection accident AU - Yilmaz, Mine O. AU - Avramova, Maria N. AU - Andersen, Jens G. M. T2 - NUCLEAR ENGINEERING AND DESIGN AB - This paper discusses the importance of the fuel thermal conductivity degradation modeling for accurate predictions of the Doppler feedback during reactivity insertion transients. The impact of the fuel thermal conductivity degradation model, recently implemented in the coupled sub-channel thermal-hydraulic/time-dependent neutron transport code system CTF/TORT-TD, on Doppler feedback predictions during a control rod ejection accident was investigated. The rod ejection was simulated for a 4 × 4 pressurized water reactor pin array, extracted from the Purdue University MOX (mixed oxide) benchmark, starting at both hot zero power and hot full power conditions with the control rod being half-inserted before the ejection. The two scenarios were simulated with CTF/TORT-TD and the effect of the fuel thermal conductivity degradation on the Doppler feedback was analyzed. The results were compared with existing reference calculations performed with the coupled sub-channel thermal-hydraulic/time-dependent neutron transport/fuel performance code system CTF/TORT-TD/FRAPCON-FRAPTRAN. The power pulse, the time evolution of average fuel temperature, and the peak enthalpy rise during the transient were examined. It was confirmed that the impact of the fuel thermal conductivity degradation is more significant when the control rod is ejected at hot full power conditions. If the fuel conductivity degradation was not taken into account, less conservative CTF/TORT-TD predictions for the transient power response were obtained. For the selected 4 × 4 pin array, the coupled code calculated 13 MW higher power pulse when modeling degradation effects on fuel conductivity. The difference in the power response is due to the less negative prompt fuel temperature (Doppler) coefficient at elevated temperatures. Lower thermal conductivity will lead to higher fuel pellet temperatures, and subsequently to a less negative Doppler coefficient, which will result in a stronger power pulse. The maximum fuel enthalpy rise during the hot full power rod ejection accident was found to be 60 cal/g (251,208 J/kg). DA - 2016/10// PY - 2016/10// DO - 10.1016/j.nucengdes.2016.07.021 VL - 307 SP - 339-353 SN - 1872-759X ER - TY - CONF TI - Benchmarking the NEM real-time core model for VVER-1000 simulator application - asymmetric core AU - Georgieva, E. AU - Dinkov, Y. AU - Ivanov, Kostadin AU - Stieglitz, R. AB - A real-time version of the Nodal Expansion Method (NEM) code is developed and implemented into Kozloduy 6 full-scope replica control room simulator. Combined with an enhanced thermal-hydraulics and I&C models the whole package is a high-fidelity simulation tool for operator training and various other applications. The fidelity and accuracy of simulation with emphasis on reactor core model is illustrated through comparison with plant-specific data. The transient of ‘Switching-off of One of the Four Operating Main Circulation Pumps at Nominal Reactor Power’ as described in OECD/NEA Kalinin 3 Coolant Transient Benchmark is an example of an asymmetric core scenario with a range of parameter changes. Simulation results concerning fuel assembly power and axial power distribution during the transient are compared with records from Kalinin 3 in-core monitoring system. Main operating parameters of nuclear steam supply system of a VVER-1000/V320 series units vary to a considerable degree. While Kalinin 3 benchmark specification contains very good description of the transient, as well as record of many parameters of the unit, the document provides only superfluous description of the reference unit. In such a case, an approach based on a ‘generic’ V320 model by default introduces deviations which are difficult to quantify. There are several examples which warrant discussion. One example is core coolant flow and pressure loss during the transient. Pump head and pressure loss across reactor vessel are measured and recorded and in-core monitoring system provides estimation of core coolant flow, which is quite high in comparison with some other V320 units (e.g. by about 5 % larger). Without more detailed pressure loss data across the main circulation loop and specific pump characteristics, however, one can only guess how much simulation is off the mark. Another detail of the same problem is coolant flow through a specific fuel assembly. The presence of a fuel assembly of different design (TVS-M type) surrounded by TVSA type fuel assemblies shall be thoroughly considered, because secondary sources indicate significant differences in fuel assembly pressure loss coefficients between the two types. Coolant flow affects coolant (and fuel) temperature profile and thus neutron cross-sections. Yet another example, even more strongly affecting our ability to interpret simulation results is core power reconstruction provided by the in-core monitoring system of the unit. The SPND (Self-Powered Neutron Detector) current readings are subject of conversion by an algorithm based upon simulated spatial neutron flux distribution across the reactor core. While error estimation of the parameters in stationary conditions is available from secondary sources, there is no reliable estimation of error magnitude during the transient. C2 - 2016/// C3 - Proceedings of the 24th International Conference on Nuclear Engineering, 2016, vol 5 DA - 2016/// DO - 10.1115/icone24-60135 ER - TY - JOUR TI - A method to improve the sensitivity of neutron porosity measurement based on D-T source AU - Liu, Juntao AU - Zhang, Feng AU - Gardner, Robin P. AU - Hou, Guojing AU - Zhang, Quanying AU - Zhang, Yan AU - Li, Xianghui AU - Li, Hu AU - Hu, Cong T2 - JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING AB - Compensated porosity logging tool utilizing deuterium-tritium (D-T) source shows a lower sensitivity to the variation of formation porosity compared with that adopting Am-Be source. In order to improve the sensitivity, the factors of an infinite homogeneous formation influencing slowing-down length and the near to far counts ratio are analyzed. Then Monte Carlo simulation method is used to build well logging models to study the responses of a neutron porosity logging tool to hydrogen index and formation density. It shows that in addition to hydrogen index, the variation of the density also has a great impact on slowing-down length and the ratio which reduces the response sensitivity to porosity. A new model depicts the relationship between the count ratio and porosity is proposed. When the model is used to process the measured ratio, the ratio shows improved dynamic range and sensitivity to porosity compared with the values without processing. DA - 2016/7// PY - 2016/7// DO - 10.1016/j.jngse.2016.06.028 VL - 33 SP - 879-884 SN - 2212-3865 KW - D-T source KW - Neutron porosity KW - Measurement sensitivity ER - TY - JOUR TI - A Phonon-Based Covariance Methodology for ENDF S(alpha, beta) and Thermal Neutron Inelastic Scattering Cross Sections AU - Holmes, Jesse C. AU - Hawari, Ayman I. AU - Zerkle, Michael L. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - The S(α, β) double-differential thermal neutron scattering law tabulated in Evaluated Nuclear Data File (ENDF) File 7 is, by convention, produced theoretically through fundamental scattering physics models. Currently, no published ENDF evaluations contain covariance data for S(α, β) or associated scattering cross sections. Furthermore, no accepted methodology exists for quantifying or representing these covariances. Thermal scattering cross sections depend on the interatomic structure and dynamics of the material. For many solids, the influence of these properties on inelastic scattering cross sections can be adequately described through the phonon energy spectrum. The phonon spectrum can be viewed as a probability density function and is commonly the fundamental input for calculating S(α, β). Probable variation in the shape of the phonon spectrum may be established that characterizes uncertainties in the physics models and methodology employed in its production. Through Monte Carlo sampling of perturbations from the reference phonon spectrum, an S(α, β) covariance matrix may be generated. With appropriate sensitivity information, the S(α, β) covariance matrix can be propagated to generate covariance data for differential and integral cross sections. In this work, hexagonal graphite is used as an example material for demonstrating the proposed procedures for analyzing, calculating, and processing uncertainty information for theoretically generated thermal neutron inelastic scattering data. DA - 2016/9// PY - 2016/9// DO - 10.13182/nse15-89 VL - 184 IS - 1 SP - 84-113 SN - 1943-748X KW - Thermal neutron KW - thermal scattering KW - covariance ER - TY - JOUR TI - 3D in-core fuel management optimization for breed-and-burn reactors AU - Hou, Jason AU - Qvist, Staffan AU - Kellogg, Roger AU - Greenspan, Ehud T2 - PROGRESS IN NUCLEAR ENERGY AB - Breed-and-burn (B&B) reactors are a special class of fast reactors that are designed to utilize low grade fuel such as depleted uranium without fuel reprocessing. One of the most challenging practical design feasibility issues faced by B&B reactors is the high level of radiation damage their fuel cladding has to withstand in order to sustain the B&B mode of operation – more than twice the maximum radiation damage cladding materials were exposed to so far in fast reactors. This study explores the possibility of reducing the minimum required peak radiation damage by employment of 3-dimensional (3D) fuel shuffling that enables a significant reduction in the peak-to-average axial burnup, that is, more uniform fuel utilization. A new conceptual design of a B&B core made of axially segmented fuel assemblies was adopted to facilitate the 3D shuffling. Also developed is a Simulated Annealing (SA) algorithm to automate the search for the optimal 3D shuffling pattern (SP). The primary objective of the SA optimization is to minimize the peak radiation damage while its secondary objective is to minimize the burnup reactivity swing, radial power peaking factor and maximum change of fuel assembly power over the cycle. Also studied is the sensitivity of the 3D shuffled core performance to the number of axially stacked sub-assemblies, core height and power level. It was found that compared with the optimal 2-dimensional (2D) shuffled core, the optimal 3D shuffled B&B core made of four 70 cm long axially stacked sub-assemblies and 12 radial shuffling batches offers a 1/3 reduction of the peak radiation damage level – from 534 down to 351 displacements per atom (dpa), along with a 45% increase in the average fuel discharge burnup, and hence, the depleted uranium utilization, while satisfying all major neutronics and thermal-hydraulics design constraints. For the same peak dpa level, the 3D shuffling offers more than double the uranium utilization and the cycle length relative to 2D shuffling. The minimum peak radiation damage is increased to 360 or to 403 dpa if the core is made of, respectively, three – 70 cm or two – 140 cm long axially stacked subassemblies. Reducing the length of the subassemblies of B&B cores made of three-segment assemblies from 70 cm to 60 or 50 cm results in an increase in the peak radiation damage from 360 dpa to, respectively, 368 and 397 dpa. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.pnucene.2015.12.002 VL - 88 SP - 58-74 SN - 0149-1970 UR - https://doi.org/10.1016/j.pnucene.2015.12.002 KW - Breed-and-burn reactor KW - Peak radiation damage KW - 3D fuel shuffling optimization KW - Simulated annealing KW - Optimal core design ER - TY - JOUR TI - Vapor Shield Models for Fusion Reactors Plasma-Facing Components AU - AlMousa, Nouf AU - Bourham, Mohamed A. T2 - Journal of Fusion Energy DA - 2016/6/30/ PY - 2016/6/30/ DO - 10.1007/s10894-016-0106-x VL - 35 IS - 5 SP - 786-794 J2 - J Fusion Energ LA - en OP - SN - 0164-0313 1572-9591 UR - http://dx.doi.org/10.1007/s10894-016-0106-x DB - Crossref KW - Vapor shield plasma KW - Plasma-surface interface KW - Electrothermal plasma KW - Capillary discharges KW - Disruption high heat flux ER - TY - JOUR TI - The role of interfacial reactions in determining plasma-liquid chemistry AU - Anderson, C. E. AU - Cha, N. R. AU - Lindsay, A. D. AU - Clark, D. S. AU - Graves, D. B. T2 - Plasma Chemistry and Plasma Processing DA - 2016/// PY - 2016/// VL - 36 IS - 6 SP - 1393-1415 ER - TY - JOUR TI - Properties of cellulose–soy protein blend biofibers regenerated from an amine/salt solvent system AU - Boy, Ramiz AU - Bourham, Mohamed AU - Kotek, Richard T2 - Cellulose DA - 2016/9/24/ PY - 2016/9/24/ DO - 10.1007/s10570-016-1072-1 VL - 23 IS - 6 SP - 3747-3759 J2 - Cellulose LA - en OP - SN - 0969-0239 1572-882X UR - http://dx.doi.org/10.1007/s10570-016-1072-1 DB - Crossref KW - Cellulose KW - Soy protein isolate KW - Blend KW - Biofiber KW - Biodegradation ER - TY - JOUR TI - Evaluation of plastic zone development in WE43 magnesium alloy upon friction stir processing using finite element modeling AU - Lipscomb, Celena A. AU - Fortier, Aleksandra AU - Kong, Fanrong AU - Das, Shamiparna AU - Kumar, Nilesh AU - Mishra, Rajiv S. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The evolution of the plastic zone in two different cases of WE43 magnesium alloy has been evaluated using finite element model (FEM) with a pressure load as the only loading condition. The FEM model for each of the two cases consists of WE43 material as follows: case 1: as-received (AR) condition and case 2: friction stir processed (FSP) condition. The simulations account for the stress behavior in the tear test specimen with and without the friction stir processing. A simple analytical model is developed to estimate the resulting stress gradient in each material which is considered as one of the main causes for fracture. The modeled stress in the specimens is presented and compared to experimental measurements generated with digital image correlation technology (DIC) for the two cases. DA - 2016/9/15/ PY - 2016/9/15/ DO - 10.1016/j.msea.2016.07.051 VL - 673 SP - 178-184 SN - 1873-4936 KW - Friction stir processing KW - Mg-alloy KW - FEM KW - Kahn-tear test KW - DIC imaging KW - Plastic deformation ER - TY - JOUR TI - Effect of friction stir processing on microstructure and mechanical properties of laser-processed Mg-4Y-3Nd alloy AU - Kumar, N. AU - Mishra, R. S. AU - Dahotre, N. B. AU - Brennan, R. E. AU - Doherty, K. J. AU - Cho, K. C. T2 - Materials & Design AB - The development of advanced structural materials is dependent, among many factors, on the choice of manufacturing processes. Laser processing and friction stir processing (FSP) are two such advanced manufacturing processes. Individually, they have been studied quite extensively to understand their potential for developing high efficiency structures. However, there is no study describing the sequential integration of laser processing and FSP on microstructure and mechanical properties. The present study deals with FSP of the laser processed Mg4Y3Nd (WE43) alloy. The laser surface melting was carried out in air at 1800 W laser power, 30 mm/s laser speed, and 0.6 mm spot size on the surface using continuous wave Nd:YAG fiber laser followed by FSP of laser processed region at 500 rpm and 4 ipm. Scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy were carried out to understand microstructural evolution within the laser melted and friction stir processed regions. Mechanical properties were evaluated using uniaxial tensile testing at a strain-rate of 10− 3 s− 1. FSP led to significant improvement in strength and ductility of the laser processed material. An analysis of the strengthening mechanisms revealed that the dominant strengthening mechanism(s) in the WE43 alloy was dependent on the processing step. DA - 2016/// PY - 2016/// DO - 10.1016/j.matdes.2016.08.039 VL - 110 SP - 663-675 ER - TY - JOUR TI - Development, verification, and validation of a fuel thermal conductivity degradation model in CTF AU - Yilmaz, Mine O. AU - Avramova, Maria N. AU - Andersen, Jens G. M. T2 - ANNALS OF NUCLEAR ENERGY AB - This paper discusses the implementation of a burnup dependent fuel thermal conductivity model within the Reactor Dynamics and Fuel Modeling Group (RDFMG) version of the subchannel thermal-hydraulics code COBRA-TF (CTF). The model takes into account the degradation of fuel thermal conductivity at high burnups and its dependence on the Gadolinium content for both UO2 (uranium dioxide) and MOX (mixed oxide) nuclear fuel rods. The modified Nuclear Fuel Industries (NFI) model for UO2 rods and the Duriez/Modified NFI model for MOX rods were incorporated in CTF. To validate the models, the fuel centerline temperatures predicted with CTF were compared to Halden reactor experimental data and to high fidelity FRAPCON-3.4 calculations. Halden test cases for UO2 fuel rods at the beginning of life (BOL), through lifetime with and without Gd2O3; and for MOX fuel rods were simulated with CTF. It was demonstrated that CTF with the new burnup dependent fuel thermal conductivity model predicts the fuel centerline temperature with less than a 5% error as compared to the Halden measurements. CTF calculations were performed for fifty-eight (58) data points. Statistical analyses of the dimensionless predicted-to-measured fuel centerline temperature ratios had confirmed the advantage of the new model – the mean value of the predicted-to-measured temperature ratios was increased from 0.8920 to 1.0082 and the standard deviation was decreased from 0.0693 to 0.0382. DA - 2016/11// PY - 2016/11// DO - 10.1016/j.anucene.2016.07.020 VL - 97 SP - 246-261 SN - 0306-4549 KW - Fuel thermal conductivity KW - Fuel centerline temperature KW - CTF KW - FRAPCON-3.4 ER - TY - JOUR TI - Best estimate plus uncertainty analysis of departure from nucleate boiling limiting case with CASL core simulator VERA-CS in response to PWR main steam line break event AU - Brown, C. S. AU - Zhang, H. AU - Kucukboyaci, V. AU - Sung, Y. T2 - Nuclear Engineering and Design DA - 2016/// PY - 2016/// VL - 309 SP - 8-22 ER - TY - JOUR TI - Grain boundary sliding mechanism during high temperature deformation of AZ31 Magnesium alloy AU - Roodposhti, Peiman Shahbeigi AU - Sarkar, Apu AU - Murty, Korukonda Linga AU - Brody, Harold AU - Scattergood, Ronald T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - High temperature tensile creep tests were conducted on AZ31 Magnesium alloy at low stress range of 1–13 MPa to clarify the existence of grain boundary sliding (GBS) mechanism during creep deformation. Experimental data within the GBS regime shows the stress exponent is ~2 and the activation energy value is close to that for grain boundary diffusion. Analyses of the fracture surface of the sample revealed that the GBS provides many stress concentrated sites for diffusional cavities formation and leads to premature failure. Scanning electron microscopy images show the appearances of both ductile and brittle type fracture mechanism. X-ray diffraction line profile analysis (based on Williamson-Hall technique) shows a reduction in dislocation density due to dynamic recovery (DRV). A correlation between experimental data and Langdon's model for GBS was also demonstrated. DA - 2016/7/4/ PY - 2016/7/4/ DO - 10.1016/j.msea.2016.05.076 VL - 669 SP - 171-177 SN - 1873-4936 KW - AZ31 KW - Creep KW - Grain boundary sliding KW - Cavity formation ER - TY - JOUR TI - Amorphization resistance of nano-engineered SiC under heavy ion irradiation AU - Imada, Kenta AU - Ishimaru, Manabu AU - Xue, Haizhou AU - Zhang, Yanwen AU - Shannon, Steven C. AU - Weber, William J. T2 - Journal of Nuclear Materials AB - Silicon carbide (SiC) with a high-density of planar defects (hereafter, ‘nano-engineered SiC’) and epitaxially-grown single-crystalline 3C-SiC were simultaneously irradiated with Au ions at room temperature, in order to compare their relative resistance to radiation-induced amorphization. It was found that the local threshold dose for amorphization is comparable for both samples under 2 MeV Au ion irradiation; whereas, nano-engineered SiC exhibits slightly greater radiation tolerance than single crystalline SiC under 10 MeV Au irradiation. Under 10 MeV Au ion irradiation, the dose for amorphization increased by about a factor of two in both nano-engineered and single crystal SiC due to the local increase in electronic energy loss that enhanced dynamic recovery. DA - 2016/9// PY - 2016/9// DO - 10.1016/j.jnucmat.2016.06.031 VL - 478 SP - 310-314 J2 - Journal of Nuclear Materials LA - en OP - SN - 0022-3115 UR - http://dx.doi.org/10.1016/j.jnucmat.2016.06.031 DB - Crossref KW - Nanostructured materials KW - Carbides KW - Amorphization KW - Scanning/transmission electron microscopy (STEM) ER - TY - JOUR TI - Addition of Monovalent Electrolytes to Improve Storage Stability of Freeze-Dried Protein Formulations AU - Goshima, Hiroshika AU - Forney-Stevens, Kelly M. AU - Liu, Ming AU - Qian, Ken K. AU - Tyagi, Madhusudan AU - Cicerone, Marcus T. AU - Pikal, Michael J. T2 - JOURNAL OF PHARMACEUTICAL SCIENCES AB - This study investigates the effect of low levels of electrolytes on storage stability in freeze-dried sucrose-based protein formulations. Both bovine serum albumin and recombinant human serum albumin were freeze dried with sucrose and alkali halides (LiCl, NaCl, KCl, RbCl, and CsCl) at selected low levels. All formulations were stored at 50°C and 65°C up to 2 months and then assayed for protein aggregation. The data demonstrate that low levels of LiCl and NaCl enhance stability. No obvious correlations with either protein secondary structure or global dynamics (structural relaxation time) were found. However, good correlations were found between stability and both free-volume hole size via positron annihilation lifetime spectroscopy (PALS) and fast dynamics by neutron scattering. Volume changes on mixing and the partial molal volume of salt were also studied in an effort to detect decreases in free volume. These data did not support the hypothesis that reduction in free volume was the primary mechanism for salt-induced stabilization. Finally, a positive effect of postlyophilization annealing on stability was demonstrated. In summary, we find that small amounts of LiCl and NaCl significantly stabilize these proteins, which is a result at variance with conventional formulation wisdom. DA - 2016/2// PY - 2016/2// DO - 10.1016/j.xphs.2015.10.004 VL - 105 IS - 2 SP - 530-541 SN - 1520-6017 KW - protein formulation KW - stability KW - freeze drying KW - lyophilization KW - glass dynamics KW - mobility KW - free volume KW - PALS KW - mean square displacement KW - neutron scattering ER - TY - JOUR TI - Investigation of the d(gamma,n)p reaction for gamma beam monitoring at ELI-NP AU - Matei, C. AU - Mueller, J. M. AU - Sikora, M. H. AU - Suliman, G. AU - Ur, C. A. AU - Weller, H. R. T2 - Journal of Instrumentation DA - 2016/// PY - 2016/// VL - 11 ER - TY - JOUR TI - Gamma-ray mass attenuation coefficient and half value layer factor of some oxide glass shielding materials AU - Waly, El-Sayed A. AU - Fusco, Michael A. AU - Bourham, Mohamed A. T2 - ANNALS OF NUCLEAR ENERGY AB - The variation in dosimetric parameters such as mass attenuation coefficient, half value layer factor, exposure buildup factor, and the photon mean free path for different oxide glasses for the incident gamma energy range 0.015–15 MeV has been studied using MicroShield code. It has been inferred that the addition of PbO and Bi2O3 improves the gamma ray shielding properties. Thus, the effect of chemical composition on these parameters is investigated in the form of six different glass compositions, which are compared with specialty concrete for nuclear radiation shielding. The composition termed ‘Glass 6’ in this paper has the highest mass attenuation and the smallest half value layer and may have potential applications in radiation shielding. An example dry storage cask utilizing an additional layer of Glass 6 as an intermediate shielding layer, simulated in MicroShield, is capable of reducing the exposure rate at the cask surface by over 20 orders of magnitude compared to the case without a glass layer. Based on this study, Glass 6 shows promise as a gamma-ray shielding material, particularly for dry cask storage. DA - 2016/10// PY - 2016/10// DO - 10.1016/j.anucene.2016.05.028 VL - 96 SP - 26-30 SN - 0306-4549 KW - Mass attenuation coefficient KW - Half value layer factor KW - Glasses KW - Concrete KW - Shielding materials ER - TY - JOUR TI - Coupled MCNP6/CTF code: Development, testing, and application AU - Bennett, A. AU - Avramova, M. AU - Ivanov, K. T2 - ANNALS OF NUCLEAR ENERGY AB - This paper presents the development and testing of a high fidelity Monte Carlo based multi-physics code. The coupling was done between the Monte Carlo neutronics code MCNP6 and the thermal-hydraulic sub-channel code CTF. The coupling for the MCNP6/CTF code was done internally at the pin level. On-The-Fly cross sections were used to decrease the complexity of the coupled code as well as to decrease the memory requirement. The relaxation acceleration technique was applied to the coupled code and was shown that it could satisfy much stricter convergence criterions. The technique can also guarantee convergence and be used as a tool to decrease the computational time. The coupled code was tested against two other coupled Monte Carlo/thermal-hydraulic sub-channel codes and the results were similar. The coupled code was also tested on a full assembly problem. DA - 2016/10// PY - 2016/10// DO - 10.1016/j.anucene.2016.05.008 VL - 96 SP - 1-11 SN - 0306-4549 KW - MCNP6 KW - CTF KW - Internal coupling KW - Relaxation acceleration ER - TY - JOUR TI - IMPLEMENTATION OF A PORTABLE HPGE FOR FIELD CONTAMINATION ASSAY AU - Hayes, Robert Bruce T2 - HEALTH PHYSICS AB - Using MCNP to construct a detector model based initially on x-ray images of a portable high purity germanium (HPGe) detector followed by normalizing covering material values to also agree with check source responses, a validation of the model was attained. By calibrating the detector parameters using large count spectra, rigorous reproducibility is attained for high activity measurements but does not prevent deviations from normality in error distributions at the very low count events where spectral peaks are not always identifiable. The resulting model was created to allow operational assay of contamination over large areal distributions that could not otherwise be measured, such as the exhaust shaft at the Waste Isolation Pilot Plant (WIPP). Results indicate that contamination levels of activity in the exhaust shaft can be assayed to within a factor of 2. Detection limits are evaluated to be well below the contamination levels, which would constitute a legal environmental release if unfiltered ventilation of the underground facility were used. DA - 2016/6// PY - 2016/6// DO - 10.1097/hp.0000000000000501 VL - 110 IS - 6 SP - 571-579 SN - 1538-5159 KW - Am-241 KW - accidents KW - nuclear KW - contamination KW - waste disposal ER - TY - JOUR TI - Corrosion of single layer thin film protective coatings on steel substrates for high level waste containers AU - Fusco, Michael A. AU - Ay, Yasar AU - Casey, Abigail H. M. AU - Bourham, Mohamed A. AU - Winfrey, A. Leigh T2 - PROGRESS IN NUCLEAR ENERGY AB - Single-layer thin film coatings have been deposited on steel substrates and tested for their corrosion resistance. These coatings include TiN, ZrO2, TiO2, Al2O3, and MoS2, and it is proposed that they will act as barriers to provide protection to the steel canisters that are part of the dry cask storage system for high level nuclear waste. Corrosion testing was completed using electrochemical potentiodynamic polarization techniques in aerated 1 M NaCl solution. Results show an exponential increase in corrosion rate with increasing temperature and an exponential decrease in the passive breakdown overpotential, which is directly related to the ability of a material to form and sustain a corrosion-inhibiting passive film in a given environment. Additionally, kinetic activation parameters have been experimentally determined for each material, leading to predictive equations for corrosion rates. The bare and coated samples corrode analogously, indicative of pores allowing the coating and substrate to corrode simultaneously. The samples were also placed in circulating salt brines of varying pH as a supplementary corrosion testing mechanism to explore their corrosivity over extended time. Negligible weight change was experienced by the bare and coated steel samples over a period of 5 months. Increasing the coating thickness and the number of layers may provide higher resistance to uniform and localized corrosion. DA - 2016/5// PY - 2016/5// DO - 10.1016/j.pnucene.2016.02.016 VL - 89 SP - 159-169 SN - 0149-1970 KW - Spent nuclear fuel KW - Nuclear waste canister KW - Dry cask storage KW - Electrochemical corrosion KW - Corrosion KW - Thin film coatings KW - Passivity KW - Activation ER - TY - JOUR TI - Using anisotropies in prompt fission neutron coincidences to assess the neutron multiplication of highly multiplying subcritical plutonium assemblies AU - Mueller, J. M. AU - Mattingly, J. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Abstract There is a significant and well-known anisotropy between the prompt neutrons emitted from a single fission event; these neutrons are most likely to be observed at angles near 0° or 180° relative to each other. However, the propagation of this anisotropy through different generations of a fission chain reaction has not been previously studied. We have measured this anisotropy in neutron–neutron coincidences from a subcritical highly-multiplying assembly of plutonium metal. The assembly was a 4.5 kg α-phase plutonium metal sphere composed of 94% 239Pu and 6% 240Pu by mass. Data were collected using two EJ-309 liquid scintillators and two EJ-299 plastic scintillators. The angular distribution of neutron–neutron coincidences was measured at 90° and 180° and found to be largely isotropic. Simulations were performed using MCNPX-PoliMi of similar plutonium metal spheres of varying sizes and a correlation between the neutron multiplication of the assembly and the anisotropy of neutron–neutron coincidences was observed. In principle, this correlation could be used to assess the neutron multiplication of an unknown assembly. DA - 2016/7/21/ PY - 2016/7/21/ DO - 10.1016/j.nima.2016.04.027 VL - 825 SP - 87-92 SN - 1872-9576 KW - Passive interrogation KW - Plutonium KW - Nonproliferation KW - Special nuclear material KW - Neutron angular anisotropy KW - Neutron detectors ER - TY - JOUR TI - Uncertainty quantification and sensitivity analysis with CASL Core Simulator VERA-CS AU - Brown, C. S. AU - Zhang, H. B. T2 - Annals of Nuclear Energy DA - 2016/// PY - 2016/// VL - 95 SP - 188-201 ER - TY - JOUR TI - The Role of Grain Size on Neutron Irradiation Response of Nanocrystalline Copper AU - Mohamed, Walid AU - Miller, Brandon AU - Porter, Douglas AU - Murty, Korukonda T2 - MATERIALS AB - The role of grain size on the developed microstructure and mechanical properties of neutron irradiated nanocrystalline copper was investigated by comparing the radiation response of material to the conventional micrograined counterpart. Nanocrystalline (nc) and micrograined (MG) copper samples were subjected to a range of neutron exposure levels from 0.0034 to 2 dpa. At all damage levels, the response of MG-copper was governed by radiation hardening manifested by an increase in strength with accompanying ductility loss. Conversely, the response of nc-copper to neutron irradiation exhibited a dependence on the damage level. At low damage levels, grain growth was the primary response, with radiation hardening and embrittlement becoming the dominant responses with increasing damage levels. Annealing experiments revealed that grain growth in nc-copper is composed of both thermally-activated and irradiation-induced components. Tensile tests revealed minimal change in the source hardening component of the yield stress in MG-copper, while the source hardening component was found to decrease with increasing radiation exposure in nc-copper. DA - 2016/3// PY - 2016/3// DO - 10.3390/ma9030144 VL - 9 IS - 3 SP - SN - 1996-1944 KW - copper KW - nanocrystalline KW - neutron irradiation KW - grain growth KW - radiation hardening KW - thermal stability ER - TY - JOUR TI - Fully coupled simulation of the plasma liquid interface and interfacial coefficient effects AU - Lindsay, Alexander D AU - Graves, David B AU - Shannon, Steven C T2 - Journal of Physics D: Applied Physics AB - There is a growing interest in the study of coupled plasma-liquid systems because of their applications to biomedicine, biological and chemical disinfection, agriculture, and other areas. Optimizing these applications requires a fundamental understanding of the coupling between phases. Though much progress has been made in this regard, there is still more to be done. One area that requires more research is the transport of electrons across the plasma-liquid interface. Some pioneering works (Rumbach et al 2015 Nat. Commun. 6, Rumbach et al 2015 J. Phys. D: Appl. Phys. 48 424001) have begun revealing the near-surface liquid characteristics of electrons. However, there has been little work to determine the near-surface gas phase electron characteristics. Without an understanding of the near-surface gas dynamics, modellers are left to make assumptions about the interfacial conditions. For instance it is commonly assumed that the surface loss or sticking coefficient of gas-phase electrons at the interface is equal to 1. In this work we explore the consequences of this assumption and introduce a couple of ways to think about the electron interfacial condition. In one set of simulations we impose a kinetic condition with varying surface loss coefficient on the gas phase interfacial electrons. In a second set of simulations we introduce a Henry's law like condition at the interface in which the gas-phase electron concentration is assumed to be in thermodynamic equilibrium with the liquid-phase electron concentration. It is shown that for a range of electron Henry coefficients spanning a range of known hydrophilic specie Henry coefficients, the gas phase electron density in the anode can vary by orders of magnitude. Varying reflection of electrons by the interface also has consequences for the electron energy profile; increasing reflection may lead to increasing thermalization of electrons depending on choices about the electron energy boundary condition. This variation in anode electron density and energy as a function of the interface characteristics could also lead to significant variation in near-surface gas chemistries when such reactions are included in the model; this could very well in turn affect the reactive species impinging on the liquid surface. We draw the conclusion that in order to make more confident model predictions about plasma-liquid systems, finer scale simulations and/or new experimental techniques must be used to elucidate the near-surface gas phase electron dynamics. DA - 2016/5/6/ PY - 2016/5/6/ DO - 10.1088/0022-3727/49/23/235204 VL - 49 IS - 23 SP - 235204 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/49/23/235204 DB - Crossref KW - plasma-liquid interface KW - DC discharge with water anode KW - multiphysics simulation ER - TY - JOUR TI - Advances in the Pennsylvania State University NEM code AU - Thompson, S. A. AU - Ivanov, K. N. T2 - ANNALS OF NUCLEAR ENERGY AB - The Pennsylvania State University NEM code has been updated in an attempt to enable the code to model more neutronically complex reactor cores, such as those containing mixed-oxide fuel, low leakage cores, and cores that contain multiple burnable poison types. Current nodal methods, which are primarily focused on solving the diffusion equation using a nodal expansion method with the transverse leakage term solved using the quadratic leakage approximation, are known to be inaccurate in such environments. The NEM code is updated with a transport capability based upon the SP3 approximation, a semi-analytical solution, and an advanced transverse leakage method based upon the use of analytic basis functions. Each of these new features is described followed by the results of benchmarks to test their effectiveness. DA - 2016/8// PY - 2016/8// DO - 10.1016/j.anucene.2016.03.014 VL - 94 SP - 251-262 SN - 0306-4549 KW - SP3 KW - MOX KW - Nodal expansion method KW - Neutron diffusion KW - Transverse leakage ER - TY - JOUR TI - Temperature-Dependent Hypersonic Flow Patterns of Expanding High-Density Metal Vapor Plasma from Capillary Source Simulating Plasma Flow Following a Fusion Disruption AU - Majumdar, Rudrodip AU - Bourham, Mohamed T2 - JOURNAL OF FUSION ENERGY DA - 2016/4// PY - 2016/4// DO - 10.1007/s10894-015-0027-0 VL - 35 IS - 2 SP - 312-326 SN - 1572-9591 KW - Electrothermal plasma expansion KW - Metal vapor plasma KW - Adiabatic compressibility index KW - Fusion disruption KW - PFC disruption KW - Particulate expansion ER - TY - JOUR TI - Neutron-antineutron oscillations: Theoretical status and experimental prospects AU - Phillips, D. G., II AU - Snow, W. M. AU - Babul, K. AU - Banerjee, S. AU - Baxter, D. V. AU - Berezhiani, Z. AU - Bergevin, M. AU - Bhattacharya, S. AU - Brooijmans, G. AU - Castellanos, L. AU - Chen, M. -C. AU - Coppola, C. E. AU - Cowsik, R. AU - Crabtree, J. A. AU - Das, P. AU - Dees, E. B. AU - Dolgov, A. AU - Ferguson, P. D. AU - Frost, M. AU - Gabrie, T. AU - Gal, A. AU - Gallmeier, F. AU - Ganezer, K. AU - Golubeva, E. AU - Greene, G. AU - Hartfiel, B. AU - Hawari, A. AU - Heilbronn, L. AU - Johnson, C. AU - Kamyshkov, Y. AU - Kerbikov, B. AU - Kitaguchi, M. AU - Kopeliovich, B. Z. AU - Kopeliovich, V. B. AU - Kuzmin, V. A. AU - Liu, C. -Y. AU - McGaughey, P. AU - Mocko, M. AU - Mohapatra, R. AU - Mokhov, N. AU - Muhrer, G. AU - Mumm, H. P. AU - Okun, L. AU - Pattie, R. W., Jr. AU - Quigg, C. AU - Ramberg, E. AU - Ray, A. AU - Roy, A. AU - Ruggles, A. AU - Sarkar, U. AU - Saunders, A. AU - Serebrov, A. P. AU - Shimizu, H. M. AU - Shrock, R. AU - Sikdar, A. K. AU - Sjue, S. AU - Striganov, S. AU - Townsend, L. W. AU - Tschirhart, R. AU - Vainshtein, A. AU - Van Kooten, R. AU - Wang, Z. AU - Young, A. R. T2 - PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS AB - The observation of neutrons turning into antineutrons would constitute a discovery of fundamental importance for particle physics and cosmology. Observing the n–n̄ transition would show that baryon number (B) is violated by two units and that matter containing neutrons is unstable. It would provide a clue to how the matter in our universe might have evolved from the B=0 early universe. If seen at rates observable in foreseeable next-generation experiments, it might well help us understand the observed baryon asymmetry of the universe. A demonstration of the violation of B–L by 2 units would have a profound impact on our understanding of phenomena beyond the Standard Model of particle physics. Slow neutrons have kinetic energies of a few meV. By exploiting new slow neutron sources and optics technology developed for materials research, an optimized search for oscillations using free neutrons from a slow neutron moderator could improve existing limits on the free oscillation probability by at least three orders of magnitude. Such an experiment would deliver a slow neutron beam through a magnetically-shielded vacuum chamber to a thin annihilation target surrounded by a low-background antineutron annihilation detector. Antineutron annihilation in a target downstream of a free neutron beam is such a spectacular experimental signature that an essentially background-free search is possible. An authentic positive signal can be extinguished by a very small change in the ambient magnetic field in such an experiment. It is also possible to improve the sensitivity of neutron oscillation searches in nuclei using large underground detectors built mainly to search for proton decay and detect neutrinos. This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron oscillations, and suggests avenues both for theoretical investigation and for future improvement in the experimental sensitivity. DA - 2016/2/11/ PY - 2016/2/11/ DO - 10.1016/j.physrep.2015.11.001 VL - 612 SP - 1-45 SN - 1873-6270 KW - Neutron-antineutron oscillation KW - Baryon number violation KW - Spallation KW - Cold neutron source KW - Quasi-free condition ER - TY - JOUR TI - Modeling irradiation creep of graphite using rate theory AU - Sarkar, Apu AU - Eapen, Jacob AU - Raj, Anant AU - Murty, K. L. AU - Burchell, T. D. T2 - JOURNAL OF NUCLEAR MATERIALS AB - We have examined irradiation induced creep of graphite in the framework of transition state rate theory. Experimental data for two grades of nuclear graphite (H-337 and AGOT) have been analyzed to determine the stress exponent (n) and activation energy (Q) for plastic flow under irradiation. We show that the mean activation energy lies between 0.14 and 0.32 eV with a mean stress-exponent of 1.0 ± 0.2. A stress exponent of unity and the unusually low activation energies strongly indicate a diffusive defect transport mechanism for neutron doses in the range of 3–4 × 1022 n/cm2. DA - 2016/5// PY - 2016/5// DO - 10.1016/j.jnucmat.2016.01.036 VL - 473 SP - 197-205 SN - 1873-4820 KW - Graphite KW - Creep KW - Irradiation KW - Activation energy ER - TY - JOUR TI - Modeling and simulation challenges pursued by the Consortium for Advanced Simulation of Light Water Reactors (CASL) AU - Turinsky, Paul J. AU - Kothe, Douglas B. T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - The Consortium for the Advanced Simulation of Light Water Reactors (CASL), the first Energy Innovation Hub of the Department of Energy, was established in 2010 with the goal of providing modeling and simulation (M&S) capabilities that support and accelerate the improvement of nuclear energy's economic competitiveness and the reduction of spent nuclear fuel volume per unit energy, and all while assuring nuclear safety. To accomplish this requires advances in M&S capabilities in radiation transport, thermal-hydraulics, fuel performance and corrosion chemistry. To focus CASL's R&D, industry challenge problems have been defined, which equate with long standing issues of the nuclear power industry that M&S can assist in addressing. To date CASL has developed a multi-physics “core simulator” based upon pin-resolved radiation transport and subchannel (within fuel assembly) thermal-hydraulics, capitalizing on the capabilities of high performance computing. CASL's fuel performance M&S capability can also be optionally integrated into the core simulator, yielding a coupled multi-physics capability with untapped predictive potential. Material models have been developed to enhance predictive capabilities of fuel clad creep and growth, along with deeper understanding of zirconium alloy clad oxidation and hydrogen pickup. Understanding of corrosion chemistry (e.g., CRUD formation) has evolved at all scales: micro, meso and macro. CFD R&D has focused on improvement in closure models for subcooled boiling and bubbly flow, and the formulation of robust numerical solution algorithms. For multiphysics integration, several iterative acceleration methods have been assessed, illuminating areas where further research is needed. Finally, uncertainty quantification and data assimilation techniques, based upon sampling approaches, have been made more feasible for practicing nuclear engineers via R&D on dimensional reduction and biased sampling. Industry adoption of CASL's evolving M&S capabilities, which is in progress, will assist in addressing long-standing and future operational and safety challenges of the nuclear industry. DA - 2016/5/15/ PY - 2016/5/15/ DO - 10.1016/j.jcp.2016.02.043 VL - 313 SP - 367-376 SN - 1090-2716 KW - Modeling KW - Simulation KW - Core simulator KW - Multiphysics KW - Nuclear energy ER - TY - JOUR TI - MHD Simulation for Neutron Yield, Radiations and Beam-Ion Properties in the Spherical Plasma Focus AU - Ay, Yasar AU - Abd Al-Halim, Mohamed A. AU - Bourham, Mohamed A. T2 - JOURNAL OF FUSION ENERGY DA - 2016/4// PY - 2016/4// DO - 10.1007/s10894-015-0046-x VL - 35 IS - 2 SP - 407-414 SN - 1572-9591 KW - Spherical plasma focus KW - Neutron yield KW - Ion beam KW - Radiation KW - MHD KW - Simulation ER - TY - JOUR TI - Dose dependence of helium bubble formation in nano-engineered SiC at 700 °C AU - Chen, C.-H. AU - Zhang, Y. AU - Wang, Y. AU - Crespillo, M.L. AU - Fontana, C.L. AU - Graham, J.T. AU - Duscher, G. AU - Shannon, S.C. AU - Weber, W.J. T2 - Journal of Nuclear Materials AB - Knowledge of radiation-induced helium bubble nucleation and growth in SiC is essential for applications in fusion and fission environments. Here we report the evolution of microstructure in nano-engineered (NE) 3C SiC, pre-implanted with helium, under heavy ion irradiation at 700 °C up to doses of 30 displacements per atom (dpa). Elastic recoil detection analysis confirms that the as-implanted helium depth profile does not change under irradiation to 30 dpa at 700 °C. While the helium bubble size distribution becomes narrower with increasing dose, the average size of bubbles remains unchanged and the density of bubbles increases somewhat with dose. These results are consistent with a long helium bubble incubation process under continued irradiation at 700 °C up to 30 dpa, similar to that reported under dual and triple beam irradiation at much higher temperatures. The formation of bubbles at this low temperature is enhanced by the nano-layered stacking fault structure in the NE SiC, which enhances point defect mobility parallel to the stacking faults. This stacking fault structure is stable at 700 °C up to 30 dpa and suppresses the formation of dislocation loops normally observed under these irradiation conditions. DA - 2016/4// PY - 2016/4// DO - 10.1016/j.jnucmat.2016.01.029 VL - 472 SP - 153-160 J2 - Journal of Nuclear Materials LA - en OP - SN - 0022-3115 UR - http://dx.doi.org/10.1016/j.jnucmat.2016.01.029 DB - Crossref KW - SiC KW - Helium KW - High temperature KW - Irradiation effects KW - TEM KW - ERDA ER - TY - JOUR TI - Shielding properties of protective thin film coatings and blended concrete compositions for high level waste storage packages AU - Fusco, Michael A. AU - Winfrey, Leigh AU - Bourham, Mohamed A. T2 - ANNALS OF NUCLEAR ENERGY AB - Various thin film coatings have been proposed to protect stainless steel high level waste (HLW) containers from premature failure due to localized corrosion, hydrogen embrittlement, and mechanical wear. These coatings include TiN, ZrO2, MoS2, TiO2, and Al2O3, to be deposited either in multiple layers or as a thicker, single-layer composite. Linear attenuation coefficients of these materials have been simulated using MicroShield and measured experimentally for various photon energies. Additionally, spent fuel casks with overpacks made of two different types of concrete were simulated to compare exposure rate at the cask surface. In the energy range that is significant for high level waste storage all coating materials possess very similar attenuation behavior. A specialty concrete, containing magnetite (Fe3O4) and lead oxide (PbO), reduces the exposure rate at the outer surface of the overpack by several orders of magnitude. The higher-Z elements not present in ordinary concrete greatly increase attenuation of intermediate-energy gammas (0.4–1.0 MeV). The thin film coatings do not affect the shielding capabilities of the HLW packaging, as their total proposed thickness is nearly three orders of magnitude less than the mean free path (MFP) of the primary photons of interest. DA - 2016/3// PY - 2016/3// DO - 10.1016/j.anucene.2015.11.026 VL - 89 SP - 63-69 SN - 0306-4549 KW - Shielding KW - Protective coatings KW - High-level waste storage KW - Dry cask overpack composition KW - Concrete blending KW - Gamma ray shielding ER - TY - JOUR TI - CONSEQUENCE ASSESSMENT OF THE WIPP RADIOLOGICAL RELEASE FROM FEBRUARY 2014 AU - Hayes, Robert Bruce T2 - HEALTH PHYSICS AB - On 14 February 2014, a continuous air monitor (CAM) alarm at the exit of panel 7 in the Waste Isolation Pilot Plant (WIPP) underground facility caused the mine ventilation to shift from unfiltered air over to HEPA filtration for its effluent. Subsequent measurements of the effluent at both pre- and post-HEPA filtration using representative sampling demonstrated that a release had occurred. Using modeling based on measured effluent activity, onsite dose estimates were calculated and later measured via bioassay to be less than 0,1 mSv from intakes of radioactivity. The maximum offsite dose potential to nearby dwellings was modeled to be 1 µSv or less, which was consistent with air samples being taken at those dwellings during the release, demonstrating impressive accuracy and precision. No worker or public dose limits have been exceeded, and the release was substantially below the annual release limits for the WIPP site. DA - 2016/4// PY - 2016/4// DO - 10.1097/hp.0000000000000477 VL - 110 IS - 4 SP - 342-360 SN - 1538-5159 KW - accident analysis KW - accidents KW - nuclear KW - air sampling KW - dose assessment ER - TY - JOUR TI - Modeling, Calibration, and Verification of a Fission Chamber for ACRR Experimenters AU - Coburn, Jonathan AU - Luker, S. Michael AU - Parma, Edward J. AU - DePriest, K. Russell T2 - ISRD 15 - INTERNATIONAL SYMPOSIUM ON REACTOR DOSIMETRY AB - When performing research at a reactor facility, experimenters often need to determine the neutron fluence achieved during an operation. Facilities typically provide guidance in the form of neutron fluence per megajoule (MJ) or through passive dosimetry results. After experiment completion, there is sometimes a delay of several days (or weeks) before the passive dosimetry results are available. In the interim, an experimenter does not have confirmation that the desired irradiation levels were reached. Active dosimetry may provide an estimate of neutron fluxes, but few active detectors are available that have been calibrated to measure neutron fluxes obtained inside the Annular Core Research Reactor (ACRR) central cavity environment. For past experiments at the ACRR, the neutron fluence was calculated by integrating the response of a fission chamber rate detection signal and then normalizing this integral to fluence determined from passive dosimetry. An alternative method of directly measuring neutron flux is desired; the new methodology described provides a complete neutron flux profile after a reactor pulse, utilizing fission chamber physics in combination with a compensating ion chamber to extract and convert a current signal to neutron flux as a function of time. DA - 2016/// PY - 2016/// DO - 10.1051/epjconf/201610605001 VL - 106 SP - SN - 2100-014X ER - TY - JOUR TI - Assessment of a hybrid finite element and finite volume code for turbulent incompressible flows AU - Xia, Yidong AU - Wang, Chuanjin AU - Luo, Hong AU - Christon, Mark AU - Bakosi, Jozsef T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - Hydra-TH is a hybrid finite-element/finite-volume incompressible/low-Mach flow simulation code based on the Hydra multiphysics toolkit being developed and used for thermal-hydraulics applications. In the present work, a suite of verification and validation (V&V) test problems for Hydra-TH was defined to meet the design requirements of the Consortium for Advanced Simulation of Light Water Reactors (CASL). The intent for this test problem suite is to provide baseline comparison data that demonstrates the performance of the Hydra-TH solution methods. The simulation problems vary in complexity from laminar to turbulent flows. A set of RANS and LES turbulence models were used in the simulation of four classical test problems. Numerical results obtained by Hydra-TH agreed well with either the available analytical solution or experimental data, indicating the verified and validated implementation of these turbulence models in Hydra-TH. Where possible, some form of solution verification has been attempted to identify sensitivities in the solution methods, and suggest best practices when using the Hydra-TH code. DA - 2016/2/15/ PY - 2016/2/15/ DO - 10.1016/j.jcp.2015.12.022 VL - 307 SP - 653-669 SN - 1090-2716 KW - Incompressible flow KW - Turbulence model KW - RANS KW - LES ER -