TY - JOUR TI - Introduction AU - Kaoumi, D. AU - Weber, W.J. AU - Hattar, K. AU - Ribis, J. T2 - Journal of Materials Research DA - 2015/// PY - 2015/// DO - 10.1557/jmr.2015.133 VL - 30 IS - 9 SP - 1157 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84940886237&partnerID=MN8TOARS ER - TY - JOUR TI - Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature AU - Allen, T.R. AU - Kaoumi, D. AU - Wharry, J.P. AU - Jiao, Z. AU - Topbasi, C. AU - Kohnert, A. AU - Barnard, L. AU - Certain, A. AU - Field, K.G. AU - Was, G.S. AU - Morgan, D.L. AU - Motta, A.T. AU - Wirth, B.D. AU - Yang, Y. T2 - Journal of Materials Research AB - Abstract DA - 2015/// PY - 2015/// DO - 10.1557/jmr.2015.99 VL - 30 IS - 9 SP - 1246-1274 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84929692498&partnerID=MN8TOARS ER - TY - CONF TI - Deformation induced martensitic transformation in 304 ss AU - Kaoumi, D. AU - Liu, J. AU - Paul, F.-L. C2 - 2015/// C3 - PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015 DA - 2015/// SP - 629-630 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962758624&partnerID=MN8TOARS ER - TY - RPRT TI - Fracture Capabilities in Grizzly with the extended Finite Element Method (X-FEM) AU - Dolbow, John AU - Zhang, Ziyu AU - Spencer, Benjamin AU - Jiang, Wen A3 - Office of Scientific and Technical Information (OSTI) DA - 2015/9/1/ PY - 2015/9/1/ DO - 10.2172/1244633 PB - Office of Scientific and Technical Information (OSTI) ER - TY - JOUR TI - A robust Nitsche's formulation for interface problems with spline-based finite elements AU - Jiang, W. AU - Annavarapu, C. AU - Dolbow, J.E. AU - Harari, I. T2 - International Journal for Numerical Methods in Engineering AB - Summary The extended finite element method (X‐FEM) has proven to be an accurate, robust method for solving embedded interface problems. With a few exceptions, the X‐FEM has mostly been used in conjunction with piecewise‐linear shape functions and an associated piecewise‐linear geometrical representation of interfaces. In the current work, the use of spline‐based finite elements is examined along with a Nitsche technique for enforcing constraints on an embedded interface. To obtain optimal rates of convergence, we employ a hierarchical local refinement approach to improve the geometrical representation of curved interfaces. We further propose a novel weighting for the interfacial consistency terms arising in the Nitsche variational form with B‐splines. A qualitative dependence between the weights and the stabilization parameters is established with additional element level eigenvalue calculations. An important consequence of this weighting is that the bulk as well as the interfacial fields remain well behaved in the presence of large heterogeneities as well as elements with arbitrarily small volume fractions. We demonstrate the accuracy and robustness of the proposed method through several numerical examples. Copyright © 2015 John Wiley & Sons, Ltd. DA - 2015/// PY - 2015/// DO - 10.1002/nme.4766 VL - 104 IS - 7 SP - 676-696 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84943663720&partnerID=MN8TOARS ER - TY - JOUR TI - Evaluation of Mechanical Properties of Coated Steel for HLW Packages AU - Casey, Abigail H.M. AU - Campbell, Caroline A. AU - Fusco, Michael A. AU - Bourham, Mohamed A. AU - Winfrey, A.Leigh T2 - ANS Transaction DA - 2015/11// PY - 2015/11// VL - 113 SP - 599–602 ER - TY - JOUR TI - Corrosion and Radiation Damage of Single Layer Coatings on Steel for High Level Waste Packages” AU - Fusco, Michael AU - Ay, Yasar AU - Casey, Abigail AU - Bourham, Mohamed AU - Winfrey, Leigh T2 - ANS Transaction DA - 2015/11// PY - 2015/11// VL - 113 SP - 595–598 ER - TY - CONF TI - Models and simulation for divertor erosion following plasma disruption in tokomak reactors AU - Almousa, N. M. AU - Gilligan, J. G. AU - Bourham, M. A. T2 - 2015 IEEE 26th Symposium on Fusion Engineering (SOFE) AB - Erosion of plasma facing materials (PFMs) during a tokamak disruption limits the lifetime and increases the need of plasma facing components (PFCs) replacement in the reactor. During disruption, energetic plasma particles deposit high heat fluxes on the PFCs. It has been shown theoretically and experimentally that the deposited energy by plasma particles vaporizes the surface of the PFMs. Besides vaporization some selected metallic PFMs, such as tungsten and molybdenum, may suffer severe surface erosion due to melting. Melting and vaporization of metallic PFMs develop a boundary layer adjacent to the PFCs which shields such critical components as vapor shield, melt-layer shield or mixed melting/vapor shield. Part of the incoming heat flux is being absorbed by the dense and optically thick boundary layer evolved from the exposed surface, which significantly decreases the erosion of the PFCs. The accurate calculations of the net heat flux that hits the surface of PFCs during disruption are of great importance. In this study, the erosion of metallic PFMs is governed by vapor and droplet formation and their associated shielding effects. Fully selfconsistent erosion models are developed and implemented in the ETFLOW code in a new version (ETFLOW-BL) to model the PFMs response as they experience such disruption conditions. The melt-layer and vaporization losses following a disruption are calculated in this study for different values of incident plasma energies relevant to those expected in ITER. The calculated initial sharp rise in the PFMs erosion is due to the direct energy deposition on the PFCs surfaces. As disruption time goes on, boundary layers will accumulate adjacent to PFC surface and less energy penetrates to the original surface, which results in less boiling, scattering and vaporization. Comparisons between cases where both vaporization and melting process takes place are presented. Corresponding mass losses, and erosion thickness, are estimated for both cases. C2 - 2015/5// C3 - 2015 IEEE 26th Symposium on Fusion Engineering (SOFE) DA - 2015/5// DO - 10.1109/sofe.2015.7482350 PB - IEEE UR - http://dx.doi.org/10.1109/sofe.2015.7482350 ER - TY - JOUR TI - Inert Gas Measurement of Single Bubble in CeO2 AU - He, Lingfeng AU - Pakarinen, Janne AU - Bai, Xianming AU - Gan, Jian AU - Wang, Yongqiang AU - El-Azab, Anter AU - Allen, Todd R. T2 - Microscopy and Microanalysis AB - Journal Article Inert Gas Measurement of Single Bubble in CeO2 Get access Lingfeng He, Lingfeng He Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Janne Pakarinen, Janne Pakarinen University of Wisconsin, Madison, WI, USA Search for other works by this author on: Oxford Academic Google Scholar Xianming Bai, Xianming Bai Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Jian Gan, Jian Gan Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Yongqiang Wang, Yongqiang Wang Los Alamos National Laboratory, Los Alamos, NM, USA Search for other works by this author on: Oxford Academic Google Scholar Anter El-Azab, Anter El-Azab Purdue University, West Lafayette, IN, USA Search for other works by this author on: Oxford Academic Google Scholar Todd R Allen Todd R Allen Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 751–752, https://doi.org/10.1017/S1431927615004559 Published: 23 September 2015 DA - 2015/8// PY - 2015/8// DO - 10.1017/s1431927615004559 VL - 21 IS - S3 SP - 751-752 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/s1431927615004559 DB - Crossref ER - TY - JOUR TI - High-Temperature corrosion of UNS N10003 in Molten Li2BeF4 (FLiBe) Salt AU - Zheng, G. AU - Kelleher, B. AU - He, L. AU - Cao, G. AU - Anderson, M. AU - Allen, T. AU - Sridharan, K. T2 - Corrosion AB - Corrosion testing of UNS N10003 in molten fluoride salt was performed in purified molten 27LiF-BeF2 (66–34 mol%) (FLiBe) salt at 700°C for 1,000 h, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an approximately 200 nm porous structure, an approximately 3.5 μm chromium-depleted region, and MoSi2 precipitates. In the tests performed in graphite capsules, the alloy samples gained weight because of the formation of a variety of Cr3C2, Cr7C3, Mo2C, and Cr23C6 carbide phases on the surface and in the subsurface regions of the alloy. A Cr-depleted region was observed in the near-surface region where Mo thermally diffused toward either the surface or the grain boundary, which induced an approximately 1.4 μm Ni3Fe alloy layer in this region. The carbide-containing layer extended to approximately 7 μm underneath the Ni3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in UNS N10003 in molten FLiBe salt. In terms of the depth of attack, graphite clearly accelerates the corrosion, but the results appear to indicate that the formation of the Cr23C6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt. Moreover, a thermal diffusion controlled corrosion model that was fundamentally derived from Fick's second law was applied to predict the corrosion attack depth of 17.2 μm/y for UNS N10003 in molten FLiBe in the pure nickel capsule at 700°C. DA - 2015/// PY - 2015/// DO - 10.5006/1657 VL - 71 IS - 10 SP - 1257-1266 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84942913529&partnerID=MN8TOARS KW - corrosion KW - FLiBe KW - Hastelloy N KW - molten salt KW - nuclear reactor KW - UNS N10003 ER - TY - JOUR TI - Inert Gas Measurement of Single Bubble in CeO2 T2 - Microsc. Microanal. AB - Journal Article Inert Gas Measurement of Single Bubble in CeO2 Get access Lingfeng He, Lingfeng He Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Janne Pakarinen, Janne Pakarinen University of Wisconsin, Madison, WI, USA Search for other works by this author on: Oxford Academic Google Scholar Xianming Bai, Xianming Bai Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Jian Gan, Jian Gan Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Yongqiang Wang, Yongqiang Wang Los Alamos National Laboratory, Los Alamos, NM, USA Search for other works by this author on: Oxford Academic Google Scholar Anter El-Azab, Anter El-Azab Purdue University, West Lafayette, IN, USA Search for other works by this author on: Oxford Academic Google Scholar Todd R Allen Todd R Allen Idaho National Laboratory, Idaho Falls, ID, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 751–752, https://doi.org/10.1017/S1431927615004559 Published: 23 September 2015 DA - 2015/8// PY - 2015/8// DO - doi:10.1017/S1431927615004559 UR - https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/div-classtitleinert-gas-measurement-of-single-bubble-in-ceospan-classsub2spandiv/0099BC0BDFB9315961DDF4E94E99FC1F ER - TY - JOUR TI - Bubble formation and Kr distribution in Kr-irradiated UO2 AU - He, L.F. AU - Valderrama, B. AU - Hassan, A.-R. AU - Yu, J. AU - Gupta, M. AU - Pakarinen, J. AU - Henderson, H.B. AU - Gan, J. AU - Kirk, M.A. AU - Nelson, A.T. AU - Manuel, M.V. AU - El-Azab, A. AU - Allen, T.R. T2 - Journal of Nuclear Materials AB - In situ and ex situ transmission electron microscopy observation of small Kr bubbles in both single-crystal and polycrystalline UO2 were conducted to understand the inert gas bubble behavior in oxide nuclear fuel. The bubble size and volume swelling are shown as weak functions of ion dose but strongly depend on the temperature. The Kr bubble formation at room temperature was observed for the first time. The depth profiles of implanted Kr determined by atom probe tomography are in good agreement with the calculated profiles by SRIM, but the measured concentration of Kr is about 1/4 of the calculated concentration. This difference is mainly due to low solubility of Kr in UO2 matrix and high release of Kr from sample surface under irradiation. DA - 2015/// PY - 2015/// DO - 10.1016/j.jnucmat.2014.09.026 VL - 456 SP - 125-132 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84908031776&partnerID=MN8TOARS ER - TY - JOUR TI - Annealing-induced lattice recovery in room-temperature xenon irradiated CeO2: X-ray diffraction and electron energy loss spectroscopy experiments AU - Pakarinen, J. AU - He, L. AU - Hassan, A.-R. AU - Wang, Y. AU - Gupta, M. AU - El-Azab, A. AU - Allen, T.R. T2 - Journal of Materials Research DA - 2015/// PY - 2015/// DO - 10.1557/jmr.2015.13 VL - 30 IS - 9 SP - 1555-1562 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84929707243&partnerID=MN8TOARS ER - TY - JOUR TI - Recent ASDEX Upgrade research in support of ITER and DEMO T2 - Nuclear Fusion AB - Recent experiments on the ASDEX Upgrade tokamak aim at improving the physics base for ITER and DEMO to aid the machine design and prepare efficient operation. Type I edge localized mode (ELM) mitigation using resonant magnetic perturbations (RMPs) has been shown at low pedestal collisionality . In contrast to the previous high ν* regime, suppression only occurs in a narrow RMP spectral window, indicating a resonant process, and a concomitant confinement drop is observed due to a reduction of pedestal top density and electron temperature. Strong evidence is found for the ion heat flux to be the decisive element for the L–H power threshold. A physics based scaling of the density at which the minimum PLH occurs indicates that ITER could take advantage of it to initiate H-mode at lower density than that of the final Q = 10 operational point. Core density fluctuation measurements resolved in radius and wave number show that an increase of R/LTe introduced by off-axis electron cyclotron resonance heating (ECRH) mainly increases the large scale fluctuations. The radial variation of the fluctuation level is in agreement with simulations using the GENE code. Fast particles are shown to undergo classical slowing down in the absence of large scale magnetohydrodynamic (MHD) events and for low heating power, but show signs of anomalous radial redistribution at large heating power, consistent with a broadened off-axis neutral beam current drive current profile under these conditions. Neoclassical tearing mode (NTM) suppression experiments using electron cyclotron current drive (ECCD) with feedback controlled deposition have allowed to test several control strategies for ITER, including automated control of (3,2) and (2,1) NTMs during a single discharge. Disruption mitigation studies using massive gas injection (MGI) can show an increased fuelling efficiency with high field side injection, but a saturation of the fuelling efficiency is observed at high injected mass as needed for runaway electron suppression. Large locked modes can significantly decrease the fuelling efficiency and increase the asymmetry of radiated power during MGI mitigation. Concerning power exhaust, the partially detached ITER divertor scenario has been demonstrated at Psep/R = 10 MW m−1 in ASDEX Upgrade, with a peak time averaged target load around 5 MW m−2, well consistent with the component limits for ITER. Developing this towards DEMO, full detachment was achieved at Psep/R = 7 MW m−1 and stationary discharges with core radiation fraction of the order of DEMO requirements (70% instead of the 30% needed for ITER) were demonstrated. Finally, it remains difficult to establish the standard ITER Q = 10 scenario at low q95 = 3 in the all-tungsten (all-W) ASDEX Upgrade due to the observed poor confinement at low βN. This is mainly due to a degraded pedestal performance and hence investigations at shifting the operational point to higher βN by lowering the current have been started. At higher q95, pedestal performance can be recovered by seeding N2 as well as CD4, which is interpreted as improved pedestal stability due to the decrease of bootstrap current with increasing Zeff. Concerning advanced scenarios, the upgrade of ECRH power has allowed experiments with central ctr-ECCD to modify the q-profile in improved H-mode scenarios, showing an increase in confinement at still good MHD stability with flat elevated q-profiles at values between 1.5 and 2. DA - 2015/// PY - 2015/// DO - 10.1088/0029-5515/55/10/104010 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000363762900011&KeyUID=WOS:000363762900011 KW - nuclear fusion KW - tokamak physics KW - ITER KW - DEMO ER - TY - JOUR TI - Filament transport, warm ions and erosion in ASDEX Upgrade L-modes AU - Birkenmeier, G. AU - Manz, P. AU - Carralero, D. AU - Laggner, F. M. AU - Fuchert, G. AU - Krieger, K. AU - Maier, H. AU - Reimold, F. AU - Schmid, K. AU - Dux, R. AU - Puetterich, T. AU - Willensdorfer, M. AU - Wolfrum, E. AU - Team, ASDEX Upgrade T2 - Nuclear Fusion AB - The dynamics of blob filaments are investigated in the scrape-off layer of ASDEX Upgrade by means of lithium beam emission spectroscopy. A comparison of the measurements in L-mode with a recently developed analytical blob model based on a drift-interchange-Alfvén fluid model indicates an influence of a finite ion temperature on the blob dynamics which has typically been neglected in other blob models. The blob dynamics agree well with the sheath-connected regime at lower plasma densities, and inertial effects play only a minor role. At higher densities, a transition into another regime with large blob amplitudes and increased transport is found. This points to a prominent role of blob transport at higher Greenwald fractions. On the basis of the measured blob properties, the erosion on plasma facing components is estimated. For pure deuterium plasmas, the high ion temperatures of blobs lead to a dominant erosion induced by blobs. However, if an impurity concentration of 1% is taken into account, the blob-induced erosion plays a minor role and background plasma parameters determine the total gross erosion. DA - 2015/// PY - 2015/// DO - 10.1088/0029-5515/55/3/033018 VL - 55 IS - 3 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000352020500022&KeyUID=WOS:000352020500022 KW - fusion plasma KW - scrape-off layer KW - plasma turbulence KW - plasma wall interaction KW - wall erosion ER - TY - JOUR TI - Collisionality dependence of edge rotation and in-out impurity asymmetries in ASDEX Upgrade H-mode plasmas AU - Viezzer, E. AU - Fable, E. AU - Puetterich, T. AU - Bergmann, A. AU - Cavedon, M. AU - Dux, R. AU - McDermott, R. M. AU - Angioni, C. AU - Churchill, R. M. AU - Dunne, M. G. AU - Laggner, F. M. AU - Lipschultz, B. AU - Stroth, U. AU - Wolfrum, E. AU - Team, ASDEX Upgrade T2 - Nuclear Fusion AB - The poloidal and toroidal impurity flows in the edge transport barrier of H-mode plasmas have been studied over a wide range of pedestal top ion collisionalities. A comparison of the edge poloidal rotation measurements to neoclassical predictions shows good agreement in all cases. The measured edge impurity toroidal rotation is observed to change sign from co-current to counter-current with decreasing collisionality. The switch occurs at the same collisionality at which neoclassical theory predicts the main ion poloidal rotation to change from the electron to the ion diamagnetic direction. The behaviour of these two species, when used to calculate the main ion toroidal rotation via the radial force balance equation, leads to fairly constant co-current main ion toroidal rotation. Hence, at low collisionality, due to a reduced frictional coupling, the main ion-impurity differential rotation can be quite large. The behaviour of impurity ion flows on a flux surface has also been investigated in detail and it was found that the measurements are consistent with the continuity equation only if the poloidally asymmetric impurity density distribution is taken into account. The asymmetry is found to be the result of the interplay of all forces in the parallel momentum balance, with the friction force providing the dominant drive. Close to the separatrix the poloidal centrifugal force, which is usually neglected, also gives an additional contribution to the impurity density asymmetry. Within the experimental uncertainties the ion temperature and the electrostatic potential are simultaneous flux functions, despite the presence of a poloidally asymmetric impurity density profile. DA - 2015/// PY - 2015/// DO - 10.1088/0029-5515/55/12/123002 VL - 55 IS - 12 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000366534500004&KeyUID=WOS:000366534500004 KW - tokamaks KW - magnetic confinement and equilibrium KW - plasma flows KW - impurities in plasma KW - impurity transport ER - TY - RPRT TI - Optimization of Deep Borehole Systems for HLW Disposal AU - Driscoll, Michael ; AU - Baglietto, Emilio ; AU - Buongiorno, Jacopo ; AU - Lester, Richard ; AU - Brady, Patrick ; AU - Arnold, B. W. AB - This is the final report on a project to update and improve the conceptual design of deep boreholes for high level nuclear waste disposal. The effort was concentrated on application to intact US legacy LWR fuel assemblies, but conducted in a way in which straightforward extension to other waste forms, host rock types and countries was preserved. The reference fuel design version consists of a vertical borehole drilled into granitic bedrock, with the uppermost kilometer serving as a caprock zone containing a diverse and redundant series of plugs. There follows a one to two kilometer waste canister emplacement zone having a hole diameter of approximately 40-50 cm. Individual holes are spaced 200-300 m apart to form a repository field. The choice of verticality and the use of a graphite based mud as filler between the waste canisters and the borehole wall liner was strongly influenced by the expectation that retrievability would continue to be emphasized in US and worldwide repository regulatory criteria. An advanced version was scoped out using zinc alloy cast in place to fill void space inside a disposal canister and its encapsulated fuel assembly. This excludes water and greatly improves both crush resistance and thermal conductivity. However the simpler option of using a sand fill was found adequate and is recommended for near-term use. Thermal-hydraulic modeling of the low permeability and porosity host rock and its small (≤ 1%) saline water content showed that vertical convection induced by the waste’s decay heat should not transport nuclides from the emplacement zone up to the biosphere atop the caprock. First order economic analysis indicated that borehole repositories should be cost-competitive with shallower mined repositories. It is concluded that proceeding with plans to drill a demonstration borehole to confirm expectations, and to carry out priority experiments, such as retention and replenishment of in-hole water is in order. DA - 2015/9// PY - 2015/9// DO - 10.2172/1223390 UR - https://www.osti.gov/biblio/1223390-optimization-deep-borehole-systems-hlw-disposal ER - TY - JOUR TI - Research Update: Point defects in CdTexSe1−x crystals grown from a Te-rich solution for applications in detecting radiation AU - Gul, R. AU - Roy, U. N. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Cui, Y. AU - Hossain, A. AU - Lee, W. AU - Yang, G. AU - Cui, Y. AU - Burger, A. AU - James, R. B. T2 - APL Materials AB - We investigated cadmium telluride selenide (CdTeSe) crystals, newly grown by the Traveling Heater Method (THM), for the presence and abundance of point defects. Current Deep Level Transient spectroscopy (I-DLTS) was used to determine the energies of the traps, their capture cross sections, and densities. The bias across the detectors was varied from 1 to 30 V. Four types of point defects were identified, ranging from 10 meV to 0.35 eV. Two dominant traps at energies of 0.18 eV and 0.14 eV were studied in depth. Cd vacancies are found at lower concentrations than other point defects present in the material. DA - 2015/4// PY - 2015/4// DO - 10.1063/1.4917270 VL - 3 IS - 4 SP - 040702 J2 - APL Materials LA - en OP - SN - 2166-532X UR - http://dx.doi.org/10.1063/1.4917270 DB - Crossref ER - TY - JOUR TI - High compositional homogeneity of CdTexSe1−x crystals grown by the Bridgman method AU - Roy, U. N. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Cui, Y. AU - Hossain, A. AU - Lee, K. AU - Lee, W. AU - Tappero, R. AU - Yang, G. AU - Gul, R. AU - James, R. B. T2 - APL Materials AB - We obtained high-quality CdTexSe1−x (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ∼1.0. This high uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing higher efficiency gamma-ray detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional CdxZn1−xTe (CdZnTe or CZT). DA - 2015/2// PY - 2015/2// DO - 10.1063/1.4907250 VL - 3 IS - 2 SP - 026102 J2 - APL Materials LA - en OP - SN - 2166-532X UR - http://dx.doi.org/10.1063/1.4907250 DB - Crossref ER - TY - JOUR TI - Spectral analysis of shielded gamma ray sources using precalculated library data AU - Holmes, Thomas Wesley AU - Gardner, Robin P. T2 - Radiation Physics and Chemistry AB - In this work, an approach has been developed for determining the intensity of a shielded source by first determining the thicknesses of three different shielding materials from a passively collected gamma-ray spectrum by making comparisons with predetermined shielded spectra. These evaluations are dependent on the accuracy and validity of the predetermined library spectra which were created by changing the thicknesses of the three chosen materials lead, aluminum and wood that are used to simulate any actual shielding. Each of the spectra produced was generated using MCNP5 with a sufficiently large number of histories to ensure a low relative error at each channel. The materials were held in the same respective order from source to detector, where each material consisted of three individual thicknesses and a null condition. This then produced two separate data sets of 27 total shielding material situations and subsequent predetermined libraries that were created for each radionuclide source used. The technique used to calculate the thicknesses of the materials implements a Levenberg–Marquardt nonlinear search that employs a tri-linear interpolation with the respective predetermined libraries within each channel for the supplied input unknown spectrum. Given that the nonlinear parameters require an initial guess for the calculations, the approach demonstrates first that when the correct values are input, the correct thicknesses are found. It then demonstrates that when multiple trials of random values are input for each of the nonlinear parameters, the average of the calculated solutions that successfully converges also produced the correct thicknesses. Under situations with sufficient information known about the detection situation at hand, the method was shown to behave in a manner that produces reasonable results and can serve as a good preliminary solution. This technique has the capability to be used in a variety of full spectrum inverse analysis problems including homeland security issues. DA - 2015/11// PY - 2015/11// DO - 10.1016/J.RADPHYSCHEM.2015.04.017 VL - 116 SP - 355-358 J2 - Radiation Physics and Chemistry LA - en OP - SN - 0969-806X UR - http://dx.doi.org/10.1016/J.RADPHYSCHEM.2015.04.017 DB - Crossref KW - Gamma-ray spectra KW - Radiation detection KW - MCNP5 KW - Tr-linear interpolation KW - Inverse analysis ER - TY - JOUR TI - Material and detector properties of cadmium manganese telluride (Cd1−Mn Te) crystals grown by the modified floating-zone method AU - Hossain, A. AU - Gu, G.D. AU - Bolotnikov, A.E. AU - Camarda, G.S. AU - Cui, Y. AU - Roy, U.N. AU - Yang, G. AU - Liu, T. AU - Zhong, R. AU - Schneeloch, J. AU - James, R.B. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - We demonstrated the material- and radiation-detection properties of cadmium manganese telluride (Cd1−xMnxTe; x=0.06), a wide-band-gap semiconductor crystal grown by the modified floating-zone method. We investigated the presence of various bulk defects, such as Te inclusions, twins, and dislocations of several as-grown indium-doped Cd1−xMnxTe crystals using different techniques, viz., IR transmission microscopy, and chemical etching. We then fabricated four planar detectors from selected CdMnTe crystals, characterized their electrical properties, and tested their performance as room-temperature X- and gamma-ray detectors. Our experimental results show that CMT crystals grown by the modified floating zone method apparently are free from Te inclusions. However, we still need to optimize our growth parameters to attain high-resistivity, large-volume single-crystal CdMnTe. DA - 2015/6// PY - 2015/6// DO - 10.1016/J.NIMA.2014.12.060 VL - 784 SP - 33-36 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.2014.12.060 DB - Crossref KW - CdMnTe KW - Te inclusions KW - Dislocations KW - IR transmission KW - Spectral response KW - Mobility-lifetime product ER - TY - JOUR TI - Compositional homogeneity and X-ray topographic analyses of CdTe Se1− grown by the vertical Bridgman technique AU - Roy, U.N. AU - Bolotnikov, A.E. AU - Camarda, G.S. AU - Cui, Y. AU - Hossain, A. AU - Lee, K. AU - Lee, W. AU - Tappero, R. AU - Yang, Ge AU - Cui, Y. AU - Burger, A. AU - James, R.B. T2 - Journal of Crystal Growth AB - We grew CdTexSe1−x crystals with nominal Se concentrations of 5%, 7%, and 10% by the vertical Bridgman technique, and evaluated their compositional homogeneity and structural quality at the NSLS’ X-ray fluorescence and white beam X-ray topography beam lines. Both X-ray fluorescence and photoluminescence mapping revealed very high compositional homogeneity of the CdTexSe1−x crystals. We noted that those crystals with higher concentrations of Se were more prone to twinning than those with a lower content. The crystals were fairly free from strains and contained low concentrations of sub-grain boundaries and their networks. DA - 2015/2// PY - 2015/2// DO - 10.1016/J.JCRYSGRO.2014.10.057 VL - 411 SP - 34-37 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/J.JCRYSGRO.2014.10.057 DB - Crossref KW - Characterization KW - Defects KW - Te-inclusions KW - Subgrain boundary KW - CdTeSe KW - Semiconducting II-VI materials ER - TY - JOUR TI - Microstructural evolution in NF616 (P92) and Fe–9Cr–0.1C-model alloy under heavy ion irradiation AU - Topbasi, Cem AU - Kaoumi, Djamel AU - Motta, Arthur T. AU - Kirk, Mark A. T2 - Journal of Nuclear Materials AB - In this comparative study, in situ investigations of the microstructure evolution in a Fe–9Cr ferritic–martensitic steel, NF616, and a Fe–9Cr–0.1C-model alloy with a similar ferritic–martensitic microstructure have been performed. NF616 and Fe–9Cr–0.1C-model alloy were irradiated to high doses (up to ∼10 dpa) with 1 MeV Kr ions between 50 and 673 K. Defect cluster density increased with dose and saturated in both alloys. The average size of defect clusters in NF616 was constant between 50 and 573 K, on the other hand average defect size increased with dose in Fe–9Cr–0.1C-model alloy around ∼1 dpa. At low temperatures (50–298 K), alignment of small defect clusters resulted in the formation of extensive defects in Fe–9Cr–0.1C-model alloy around ∼2–3 dpa, while similar large defects in NF616 started to form at a high temperature of 673 K around ∼5 dpa. Interaction of defect clusters with the lath boundaries were found to be much more noticeable in Fe–9Cr–0.1C-model alloy. Differences in the microstructural evolution of NF616 and Fe–9Cr–0.1C-model alloy are explained by means of the defect cluster trapping by solute atoms which depends on the solute atom concentrations in the alloys. DA - 2015/11// PY - 2015/11// DO - 10.1016/J.JNUCMAT.2015.07.003 VL - 466 SP - 179-186 J2 - Journal of Nuclear Materials LA - en OP - SN - 0022-3115 UR - http://dx.doi.org/10.1016/J.JNUCMAT.2015.07.003 DB - Crossref KW - Generation-IV nuclear reactors KW - Sodium-cooled fast reactor KW - Heavy ion irradiation KW - In situ technique KW - Transmission electron microscopy KW - Ferritic-martensitic alloys KW - Model alloys ER - TY - JOUR TI - Optimization and parallelization of the thermal–hydraulic subchannel code CTF for high-fidelity multi-physics applications AU - Salko, Robert K. AU - Schmidt, Rodney C. AU - Avramova, Maria N. T2 - Annals of Nuclear Energy AB - This paper describes major improvements to the computational infrastructure of the CTF subchannel code so that full-core, pincell-resolved (i.e., one computational subchannel per real bundle flow channel) simulations can now be performed in much shorter run-times, either in stand-alone mode or as part of coupled-code multi-physics calculations. These improvements support the goals of the Department Of Energy Consortium for Advanced Simulation of Light Water Reactors (CASL) Energy Innovation Hub to develop high fidelity multi-physics simulation tools for nuclear energy design and analysis. A set of serial code optimizations—including fixing computational inefficiencies, optimizing the numerical approach, and making smarter data storage choices—are first described and shown to reduce both execution time and memory usage by about a factor of ten. Next, a “single program multiple data” parallelization strategy targeting distributed memory “multiple instruction multiple data” platforms utilizing domain decomposition is presented. In this approach, data communication between processors is accomplished by inserting standard Message-Passing Interface (MPI) calls at strategic points in the code. The domain decomposition approach implemented assigns one MPI process to each fuel assembly, with each domain being represented by its own CTF input file. The creation of CTF input files, both for serial and parallel runs, is also fully automated through use of a pressurized water reactor (PWR) pre-processor utility that uses a greatly simplified set of user input compared with the traditional CTF input. To run CTF in parallel, two additional libraries are currently needed: MPI, for inter-processor message passing, and the Parallel Extensible Toolkit for Scientific Computation (PETSc), which is used to solve the global pressure matrix in parallel. Results presented include a set of testing and verification calculations and performance tests assessing parallel scaling characteristics up to a full-core, pincell-resolved model of a PWR core containing 193 17 × 17 assemblies under hot full-power conditions. This model, representative of Watts Bar Unit 1 and containing about 56,000 pins, was modeled with roughly 59,000 subchannels, leading to about 2.8 million thermal–hydraulic control volumes in total. Results demonstrate that CTF can now perform full-core analysis of a PWR (not previously possible owing to excessively long runtimes and memory requirements) on the order of 20 min. This new capability not only is useful to stand-alone CTF users, but also is being leveraged in support of coupled code multi-physics calculations being done in the CASL program. DA - 2015/10// PY - 2015/10// DO - 10.1016/J.ANUCENE.2014.11.005 VL - 84 SP - 122-130 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2014.11.005 DB - Crossref KW - Subchannel KW - COBRA-TF KW - Parallel KW - MPI KW - CTF ER - TY - JOUR TI - Microstructural approach to equal channel angular processing of commercially pure titanium—A review AU - Roodposhti, Peiman Shahbeigi AU - Farahbakhsh, Nasim AU - Sarkar, Apu AU - Murty, Korukonda Linga T2 - Transactions of Nonferrous Metals Society of China AB - A review on severe plastic deformation (SPD) technique of equal channel angular pressing (ECAP) process of commercially pure titanium (CP-Ti) alloys was presented with a major emphasize on the influence of ECAP parameters that include channel and curvature angles, processing route, temperature of operation, pressing speed, internal heating, number of pass through the die and back pressure. Various ECAP characteristics such as microstructure, strain inhomogeneity and mechanical properties are considered to achieve the maximum homogeneity, equilibrium grain refinement and mechanical improvement of CP-Ti. Investigations show that a pressing speed of 1–3 mm/s at 450 °C with route BC along with channel and curvature angles of 90°and 20° respectively with backpressure can lead to the most homogeneous ultrafine microstructure. DA - 2015/5// PY - 2015/5// DO - 10.1016/S1003-6326(15)63734-7 VL - 25 IS - 5 SP - 1353-1366 J2 - Transactions of Nonferrous Metals Society of China LA - en OP - SN - 1003-6326 UR - http://dx.doi.org/10.1016/S1003-6326(15)63734-7 DB - Crossref KW - equal channel angular pressing (ECAP) KW - commercially pure titanium (CP-Ti) KW - backpressure KW - channel angle KW - curvature angle KW - pressing speed ER - TY - RPRT TI - Validation and Application of the 3D Neutron Transport MPACT within CASL VERA-CS AU - Kouchunas, Brendan ; AU - Jabaay, Dan ; AU - Downar, Thomas ; AU - Collins, Benjamin S ; AU - Stimpson, Shane G ; AU - Godfrey, Andrew T ; AU - Kim, Kang Seog ; AU - Gehin, Jess C ; AU - Palmtag, Scott ; AU - Franceschini, Fausto DA - 2015/1// PY - 2015/1// UR - https://www.osti.gov/scitech/biblio/1214019-validation-application-neutron-transport-mpact-within-casl-vera-cs ER - TY - RPRT TI - VERA Core Simulator Methodology for PWR Cycle Depletion AU - Kochunas, Brendan ; AU - Collins, Benjamin S ; AU - Jabaay, Daniel ; AU - Kim, Kang Seog ; AU - Graham, Aaron ; AU - Stimpson, Shane ; AU - Wieselquist, William A ; AU - Clarno, Kevin T ; AU - Palmtag, Scott ; AU - Downar, Thomas ; AU - Gehin, Jess C DA - 2015/1// PY - 2015/1// UR - https://www.osti.gov/scitech/biblio/1215576-vera-core-simulator-methodology-pwr-cycle-depletion ER - TY - RPRT TI - L3.PHI.CTF.P10.02-rev2 Coupling of Subchannel T/H (CTF) and CRUD Chemistry (MAMBA1D) AU - Salko, Robert K. ; AU - Palmtag, Scott ; AU - Collins, Benjamin S. ; AU - Kendrick, Brian ; AU - Seker, Jeffrey AB - The purpose of this milestone is to create a preliminary capability for modeling light water reactor (LWR) thermal-hydraulic (T/H) and CRUD growth using the CTF subchannel code and the subgrid version of the MAMBA CRUD chemistry code, MAMBA1D. In part, this is a follow-on to Milestone L3.PHI.VCS.P9.01, which is documented in Report CASL-U-2014-0188-000, titled "Development of CTF Capability for Modeling Reactor Operating Cycles with Crud Growth". As the title suggests, the previous milestone set up a framework for modeling reactor operation cycles with CTF. The framework also facilitated coupling to a CRUD chemistry capability for modeling CRUD growth throughout the reactor operating cycle. To demonstrate the capability, a simple CRUD \surrogate" tool was developed and coupled to CTF; however, it was noted that CRUD growth predictions by the surrogate were not considered realistic. This milestone builds on L3.PHI.VCS.P9.01 by replacing this simple surrogate tool with the more advanced MAMBA1D CRUD chemistry code. Completing this task involves addressing unresolved tasks from Milestone L3.PHI.VCS.P9.01, setting up an interface to MAMBA1D, and extracting new T/H information from CTF that was not previously required in the simple surrogate tool. Speci c challenges encountered during this milestone include (1) treatment of the CRUD erosion model, which requires local turbulent kinetic energy (TKE) (a value that CTF does not calculate) and (2) treatment of the MAMBA1D CRUD chimney boiling model in the CTF rod heat transfer solution. To demonstrate this new T/H, CRUD modeling capability, two sets of simulations were performed: (1) an 18 month cycle simulation of a quarter symmetry model of Watts Bar and (2) a simulation of Assemblies G69 and G70 from Seabrook Cycle 5. The Watts Bar simulation is merely a demonstration of the capability. The simulation of the Seabrook cycle, which had experienced CRUD-related fuel rod failures, had actual CRUD-scrape data to compare with results. As results show, the initial CTF/MAMBA1D-predicted CRUD thicknesses were about half of their expected values, so further investigation will be required for this simulation. DA - 2015/5// PY - 2015/5// DO - 10.2172/1344982 UR - https://www.osti.gov/scitech/biblio/1344982-l3-phi-ctf-p10-rev2-coupling-subchannel-ctf-crud-chemistry-mamba1d ER - TY - RPRT TI - Development of COBRA-TF for Modeling Full-Core Reactor Operating Cycles AU - Salko, Robert K ; AU - Lange, Travis L ; AU - Kucukboyaci, Vefa ; AU - Sung, Yixing ; AU - Palmtag, Scott ; AU - Gehin, Jess C ; AU - Avramova, Maria DA - 2015/1// PY - 2015/1// UR - https://www.osti.gov/scitech/biblio/1185922-development-cobra-tf-modeling-full-core-reactor-operating-cycles ER - TY - CONF TI - Treatment of nucleation and bubble dynamics in high heat flux film boiling AU - Liu, Y. AU - Dinh, N. C2 - 2015/// C3 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015 DA - 2015/// VL - 5 SP - 4097-4111 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962715457&partnerID=MN8TOARS ER - TY - CONF TI - Foreword AU - Dinh, N. AU - No, H.C. AU - Sun, X. AU - Leon, S.B.Y. AU - Merzari, E. AU - Pointer, W.D. C2 - 2015/// C3 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015 DA - 2015/// VL - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962754306&partnerID=MN8TOARS ER - TY - CONF TI - Simulation of BWR Mark i station black-out accident using GOTHIc: An initial demonstration AU - Bao, H. AU - Zhao, H. AU - Zhang, H. AU - Zou, L. AU - Szilard, R.H. AU - Dinh, N. C2 - 2015/// C3 - Transactions of the American Nuclear Society DA - 2015/// VL - 113 SP - 1377-1380 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85043354152&partnerID=MN8TOARS ER - TY - JOUR TI - An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras AU - Bolotnikov, A. E. AU - Ackley, K. AU - Camarda, G. S. AU - Cherches, C. AU - Cui, Y. AU - De Geronimo, G. AU - Fried, J. AU - Hodges, D. AU - Hossain, A. AU - Lee, W. AU - Mahler, G. AU - Maritato, M. AU - Petryk, M. AU - Roy, U. AU - Salwen, C. AU - Vernon, E. AU - Yang, G. AU - James, R. B. T2 - Review of Scientific Instruments AB - We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm(3) detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays' performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects. DA - 2015/7// PY - 2015/7// DO - 10.1063/1.4927455 VL - 86 IS - 7 SP - 073114 J2 - Rev. Sci. Instrum. LA - en OP - SN - 0034-6748 1089-7623 UR - http://dx.doi.org/10.1063/1.4927455 DB - Crossref ER - TY - JOUR TI - Post-growth annealing of Bridgman-grown CdZnTe and CdMnTe crystals for room-temperature nuclear radiation detectors AU - Egarievwe, Stephen U. AU - Yang, Ge AU - Egarievwe, Alexander A. AU - Okwechime, Ifechukwude O. AU - Gray, Justin AU - Hales, Zaveon M. AU - Hossain, Anwar AU - Camarda, Giuseppe S. AU - Bolotnikov, Aleksey E. AU - James, Ralph B. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Bridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray- and gamma-ray-detectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 °C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 °C in Cd vapor for 26 h, whilst their electrical resistivity fell by an order of 102. During the temperature-gradient annealing of CMT at 730 °C and an 18 °C/cm temperature gradient for 18 h in a vacuum of 10−5 mbar, we observed the diffusion of Te from the sample, so causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 °C in a 10 °C/cm temperature gradient, we observed the migration of Te inclusions from a low-temperature region to a high one at 0.022 μm/s. During the temperature-gradient annealing of CZT in a vacuum of 10−5 mbar at 570 °C and 30 °C/cm for 18 h, some Te inclusions moved toward the high-temperature side of the wafer, while other inclusions of the same size, i.e., 10 µm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT- and CMT-wafers are complex phenomena that depend on the conditions in local regions, such as composition and structure, as well as on the annealing conditions. DA - 2015/6// PY - 2015/6// DO - 10.1016/J.NIMA.2015.02.006 VL - 784 SP - 51-55 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.2015.02.006 DB - Crossref KW - CdZnTe and CdMnTe KW - Nuclear radiation detectors KW - Te inclusions KW - Thermal annealing in Cd vapor KW - Te diffusion and migration KW - Temperature gradient annealing ER - TY - JOUR TI - Structural, electrical, and optical properties of CdMnTe crystals grown by modified floating-zone technique AU - Yang, Ge AU - Gu, Genda AU - Bolotnikov, Aleksey E. AU - Cui, Yonggang AU - Camarda, Giuseppe S. AU - Hossain, Anwar AU - Roy, Utpal N. AU - Kivi, Nicholas AU - Liu, Tiansheng AU - James, Ralph B. T2 - Electronic Materials Letters DA - 2015/5// PY - 2015/5// DO - 10.1007/S13391-015-4261-4 VL - 11 IS - 3 SP - 500-504 J2 - Electron. Mater. Lett. LA - en OP - SN - 1738-8090 2093-6788 UR - http://dx.doi.org/10.1007/S13391-015-4261-4 DB - Crossref KW - CdMnTe KW - floating-zone growth KW - Te inclusions KW - twin boundaries KW - radiation detectors ER - TY - JOUR TI - Analysis of Defects on Chemically-Treated CdZnTe Surfaces AU - Hossain, A. AU - Bolotnikov, A. E. AU - Camarda, G. S. AU - Cui, Y. AU - Gul, R. AU - Kim, K.-H. AU - Roy, U. N. AU - Tong, X. AU - Yang, G. AU - James, R. B. T2 - Journal of Electronic Materials DA - 2015/3/28/ PY - 2015/3/28/ DO - 10.1007/S11664-015-3742-4 VL - 44 IS - 9 SP - 3018-3022 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-015-3742-4 DB - Crossref KW - CdZnTe KW - substrate and radiation detector KW - dislocations KW - chemo-mechanical polishing KW - metal-semiconductor interface ER - TY - JOUR TI - Using In-Situ TEM to Characterize the Microstructure Evolution of Metallic Systems under External Solicitation AU - Kaoumi, D. AU - Gautier, T. AU - Adamson, J. AU - Kirk, M. T2 - Microscopy and Microanalysis AB - Journal Article Using In-Situ TEM to Characterize the Microstructure Evolution of Metallic Systems under External Solicitation Get access D Kaoumi, D Kaoumi University of South Carolina, 300 Main St., SC, 29208, USA, djamelkaoumi@gmail. com Search for other works by this author on: Oxford Academic Google Scholar T Gautier, T Gautier University of South Carolina, 300 Main St., SC, 29208, USA, djamelkaoumi@gmail. com Search for other works by this author on: Oxford Academic Google Scholar J Adamson, J Adamson University of South Carolina, 300 Main St., SC, 29208, USA, djamelkaoumi@gmail. com Search for other works by this author on: Oxford Academic Google Scholar M Kirk M Kirk Argonne National Laboratory, Bldg 212, IL, 60439 USA, kirk@anl.gov Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 111–112, https://doi.org/10.1017/S143192761500135X Published: 23 September 2015 DA - 2015/8// PY - 2015/8// DO - 10.1017/S143192761500135X VL - 21 IS - S3 SP - 111-112 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S143192761500135X DB - Crossref ER - TY - JOUR TI - Small-Scale Mechanical Testing on Proton Beam-Irradiated 304 SS from Room Temperature to Reactor Operation Temperature AU - Vo, H. AU - Reichardt, A. AU - Howard, C. AU - Abad, M. D. AU - Kaoumi, D. AU - Chou, P. AU - Hosemann, P. T2 - JOM DA - 2015/8/28/ PY - 2015/8/28/ DO - 10.1007/S11837-015-1596-0 VL - 67 IS - 12 SP - 2959-2964 J2 - JOM LA - en OP - SN - 1047-4838 1543-1851 UR - http://dx.doi.org/10.1007/S11837-015-1596-0 DB - Crossref ER - TY - JOUR TI - Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation AU - Catalini, David AU - Kaoumi, Djamel AU - Reynolds, Anthony P. AU - Grant, Glenn J. T2 - Metallurgical and Materials Transactions A DA - 2015/7/9/ PY - 2015/7/9/ DO - 10.1007/S11661-015-3059-1 VL - 46 IS - 10 SP - 4730-4739 J2 - Metall and Mat Trans A LA - en OP - SN - 1073-5623 1543-1940 UR - http://dx.doi.org/10.1007/S11661-015-3059-1 DB - Crossref ER - TY - JOUR TI - Examination and refinement of fine energy group structure for high temperature reactor analysis AU - Ngeleka, Tholakele P. AU - Ivanov, Kostadin N. AU - Levine, Samuel T2 - Annals of Nuclear Energy AB - Multi-group energy structure SHEM-281 and -361 were refined using a Contributon and Point-Wise Cross Section Driven method (CPXSD). The Contributon and Point-Wise Cross Section Driven method was derived based on the product of the forward and adjoint angular fluxes, and the point-wise cross section of important isotope/material. It is an iterative method that selects effective fine- and broad-group energy structures for a problem of interest. The two selected criteria for determining fine energy group structure were 10 pcm relative deviation of Δk/k for k-effective and 1% relative deviation for reaction rates. The energy group structure refinement was subdivided into fast, epithermal and thermal regions. Firstly, the refinement was done for fast region and a new library was created and applied in the fuel cell unit until the target criteria’s are met. Similar procedure was repeated for epithermal and thermal regions. The dominant parameters for each region are considered as required, fission reaction rate for fast region, absorption reaction rate for epithermal region and absorption and fission reaction rates for thermal region. DA - 2015/6// PY - 2015/6// DO - 10.1016/J.ANUCENE.2015.01.038 VL - 80 SP - 279-292 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2015.01.038 DB - Crossref KW - CPXSD method KW - HTR KW - Energy group structure ER - TY - JOUR TI - Large-scale Monte Carlo neutron transport calculations with thermal hydraulic feedback AU - Ivanov, A. AU - Sanchez, V. AU - Stieglitz, R. AU - Ivanov, K. T2 - Annals of Nuclear Energy AB - The Monte Carlo method provides the most accurate description of the particle transport problem. The criticality problem is simulated by following the histories of individual particles without approximating the energy, angle or the coordinate dependence. These calculations are usually done using homogeneous thermal hydraulic conditions. This is a very crude approximation in the general case. In this paper, the method of internal coupling between neutron transport and thermal hydraulics is presented. The method is based on dynamic material distribution, where coordinate dependent temperature and density information is supplied on the fly during the transport calculation. This method does not suffer from the deficiencies characteristic of the external coupling via the input files. In latter case, the geometry is split into multiple cells having distinct temperatures and densities to supply the feedback. The possibility to efficiently simulate large scale geometries at pin-by-pin and subchannel level resolution was investigated. The Wielandt shift method for reducing the dominance ratio of the system and accelerating the fission source convergence was implemented. During the coupled iteration a detailed distribution of the fission heat deposition is required by the thermal hydraulics calculation. Providing reasonable statistical uncertainties for tallies having large numbers of bins, is a complicated task. This problem was resolved by applying the Uniform Fission Site method. Previous investigations showed that the convergence of the coupled neutron transport/thermal hydraulics calculation is limited by the statistical uncertainty and exhibits strong nonuniform behavior. The stochastic approximation scheme was used to stabilize the convergence. In combination with the Uniform Fission Site method, uniform convergence was achieved. DA - 2015/10// PY - 2015/10// DO - 10.1016/J.ANUCENE.2014.12.030 VL - 84 SP - 204-219 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2014.12.030 DB - Crossref KW - Multiphysics calculations KW - Monte Carlo transport KW - Wielandt method KW - Variance reduction KW - Stochastic approximation KW - Convergence acceleration ER - TY - JOUR TI - The effect of changing enrichments on core performance AU - Levine, S. AU - Blyth, T. AU - Ivanov, K. T2 - Annals of Nuclear Energy AB - Abstract The information presented in this paper has been developed as a follow on to two previous papers published using the same low leakage core configuration with the addition in this paper of evaluating fuel costs. The two previous publications studied the characteristics of this low leakage core with two different enrichment sets, where each enrichment set represents the three batches in the core. The purpose of the two previous papers proved the effectiveness of using the Haling Power Depletion (HPD) method as a guide. The first purpose of this paper is to extend this study to higher enrichment sets to finally attain a core having close to the highest possible cycle length. Three additional similar enrichment sets are studied increasing the number of enrichment sets to five. The ratio between the enrichment sets was maintained constant except for the highest enrichment set. This was done to increase the cycle length to approximately the longest possible cycle length of 800 days for a 1000 MWe reactor limited to a maximum 5% enrichment. The core reactor physics characteristics of these five cores are presented in this paper together with the evaluating of the fuel costs. These core characteristics include radial power fractions (RPF), Haling Power Depletion, RPF distributions, maximum pin peak powers (PPP MAX ), and other important data. The HPD RPFs of all 5 cores were similar and used to help develop the burnable poison placement designs for each core. The longest two cycles required an improved technique using more information than the HPD results to develop successful BP placement designs. Also, it was very difficult to find the correct soluble boron ppmB in the HPD input to have the Studvik HPD calculation converge. There is an error in this algorithm. The fuel costs for the five cores were calculated and the results prove that the fuel costs are lower with the cores having the longest cycle lengths. The details observed in this study are presented in this paper. DA - 2015/1// PY - 2015/1// DO - 10.1016/J.ANUCENE.2014.07.035 VL - 75 SP - 139-145 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2014.07.035 DB - Crossref KW - Low leakage core KW - Haling Power Depletion KW - Burnable poisons KW - Normalized power KW - Pin peak power KW - Fuel costs ER - TY - JOUR TI - High-fidelity multi-physics system TORT-TD/CTF/FRAPTRAN for light water reactor analysis AU - Magedanz, J. AU - Avramova, M. AU - Perin, Y. AU - Velkov, A.K. T2 - Annals of Nuclear Energy AB - A need exists in the nuclear industry for higher-fidelity tools for light water reactor (LWR) analysis, due to increasing core heterogeneity and higher burnup of fuels. In order to address this need, a high-fidelity multi-physics (HFMP) system has been developed at the Pennsylvania State University (PSU). It consists of three codes – CTF for thermal hydraulics, TORT-TD for neutron kinetics, and FRAPTRAN for fuel performance. FRAPCON, which is applied to long-term steady-state fuel performance, is left separate and not modified, but is relevant to the system because it generates the initial conditions used in FRAPTRAN. These codes have been combined into a system in which they are coupled by means of serial integration. FRAPTRAN is the latest addition to the system while the initial coupling of TORT-TD and CTF was verified in different applications. Recent efforts have been directed at the design of an object-oriented system of interfaces for the coupled codes, by which the main program may control them in terms of high-level functionality. Further modifications to the system include the ability to use coolant-centered rather than fuel-centered channels, and the ability for TORT-TD to use a time step size that differs from that of CTF. The obtained results verify this new coupling, as well as demonstrate the advantages of using a fuel-performance code for modeling fuel rod feedback. DA - 2015/10// PY - 2015/10// DO - 10.1016/J.ANUCENE.2015.01.033 VL - 84 SP - 234-243 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2015.01.033 DB - Crossref KW - Coupled codes KW - COBRA-TF KW - FRAPTRAN KW - High-fidelity KW - Fuel performance ER - TY - JOUR TI - Multi-physics and multi-scale benchmarking and uncertainty quantification within OECD/NEA framework AU - Avramova, M. AU - Ivanov, K. AU - Kozlowski, T. AU - Pasichnyk, I. AU - Zwermann, W. AU - Velkov, K. AU - Royer, E. AU - Yamaji, A. AU - Gulliford, J. T2 - Annals of Nuclear Energy AB - • Presentation of latest multi-physics multi-scale NEA/OECD benchmarks. • Utilization of high-quality experimental data for detailed comparative analysis. • Including uncertainty and sensitivity analysis of modeling predictions. • Uncertainty propagation in LWR multi-physics and multi-scale simulations. The development of multi-physics multi-scale coupled methodologies for Light Water Reactor (LWR) analysis requires comprehensive validation and verification procedures, which include well-established benchmarks developed in international cooperation. The Nuclear Energy Agency (NEA) of the Organization for Economic Co-operation and Development (OECD) has provided such framework, and over the years a number of LWR benchmarks have been developed and successfully conducted. The first set of NEA/OECD benchmarks that permits testing of the neutronics/thermal–hydraulics coupling, and verifying the capability of the coupled codes to analyze complex transients with coupled core/plant interactions have been completed and documented. These benchmarks provided a validation basis for the new generation of coupled “best-estimate” codes. The above mentioned OECD/NEA LWR benchmark activities have also stimulated follow up developments and benchmarks to test these developments. The models utilized have been improved when moving from one benchmark to the next and this created a need to validate them using high-quality experimental data. Second set of the NEA/OECD benchmarks have been initiated by the Expert Group on Uncertainty Analysis in Modelling (EGUAM) at the Nuclear Science Committee (NSC), NEA/OECD to address the current trends in the development of LWR multi-physics and multi-scale modeling and simulation. These benchmarks include the following common features, which address some of the issues identified in the first set of OECD/NEA benchmarks: (a) utilization of high-quality experimental data; (b) refined local scale modeling in addition to global predictions; (c) more detailed comparisons and analysis; (d) including uncertainty and sensitivity analysis of modeling predictions. The paper presents each of these new benchmarks by providing description and discussion of comparative analysis of obtained results. Special attention is devoted to uncertainty propagation in LWR multi-physics and multi-scale simulations for design and safety evaluations. DA - 2015/10// PY - 2015/10// DO - 10.1016/J.ANUCENE.2014.12.014 VL - 84 SP - 178-196 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/J.ANUCENE.2014.12.014 DB - Crossref KW - Benchmark KW - Uncertainty KW - Multi-physics KW - Multi-scale ER - TY - JOUR TI - Dislocation Density Evolution During Creep of AZ31 Mg Alloy: A Study by X-ray Diffraction Line Profile Analysis AU - Roodposhti, Peiman Shahbeigi AU - Sarkar, Apu AU - Murty, Korukonda L. AU - Scattergood, Ronald O. T2 - Metallography, Microstructure, and Analysis DA - 2015/9/3/ PY - 2015/9/3/ DO - 10.1007/S13632-015-0220-6 VL - 4 IS - 5 SP - 337-343 J2 - Metallogr. Microstruct. Anal. LA - en OP - SN - 2192-9262 2192-9270 UR - http://dx.doi.org/10.1007/S13632-015-0220-6 DB - Crossref KW - AZ31 KW - Dislocation density KW - Creep KW - Williamson-Hall plot KW - DRX KW - DRV ER - TY - JOUR TI - Fracture Behavior of AZ31 Magnesium Alloy During Low-Stress High-Temperature Deformation AU - Roodposhti, Peiman Shahbeigi AU - Sarkar, Apu AU - Murty, Korukonda Linga T2 - Metallography, Microstructure, and Analysis DA - 2015/2/18/ PY - 2015/2/18/ DO - 10.1007/S13632-015-0189-1 VL - 4 IS - 2 SP - 91-101 J2 - Metallogr. Microstruct. Anal. LA - en OP - SN - 2192-9262 2192-9270 UR - http://dx.doi.org/10.1007/S13632-015-0189-1 DB - Crossref KW - AZ31 KW - Creep KW - Inter-granular fracture KW - Dislocation density KW - Cavity formation ER - TY - JOUR TI - Operational Check Source Recalibration AU - Hayes, Robert B. T2 - Health Physics AB - A formal protocol whereby a segregated source is used for later quality control trending and recalibration of operational sources is described. The method is of potential use for any quality radioactive assay program where multiple sources may be in use such that long term loss in activity is possible and not readily detected and corrected using common statistical assessment criteria. The method relies upon a rigorous initial characterization effort that can later be credited to minimize error propagation during recalibration to monitor the overall uncertainty budget. A simple example attachment for use in written procedures is also provided. DA - 2015/// PY - 2015/// DO - 10.1097/hp.0000000000000309 VL - 109 SP - S156-S161 ER - TY - JOUR TI - Effects of applied strain on radiation damage generation in body-centered cubic iron AU - Beeler, Benjamin AU - Asta, Mark AU - Hosemann, Peter AU - Grønbech-Jensen, Niels T2 - Journal of Nuclear Materials AB - Radiation damage in body-centered cubic (BCC) Fe has been extensively studied by computer simulations to quantify effects of temperature, impinging particle energy, and the presence of extrinsic particles. However, limited investigation has been conducted into the effects of mechanical stresses and strain. In a reactor environment, structural materials are often mechanically strained, and an expanded understanding of how this strain affects the generation of defects may be important for predicting microstructural evolution and damage accumulation under such conditions. In this study, we have performed molecular dynamics simulations in which various types of homogeneous strains are applied to BCC Fe and the effect on defect generation is examined. It is found that volume-conserving shear strains yield no statistically significant variations in the stable number of defects created via cascades in BCC Fe. However, strains that result in volume changes are found to produce significant effects on defect generation. DA - 2015/4// PY - 2015/4// DO - 10.1016/j.jnucmat.2014.12.111 VL - 459 SP - 159-165 ER - TY - CONF TI - Effect of interfaces on radiation damage accumulation in FeNiAl maraging steels AU - Beeler, B. AU - Asta, M. AU - Hosemann, P. AU - Gr?nbech-Jensen, N. C2 - 2015/// C3 - Transactions of the American Nuclear Society DA - 2015/// VL - 112 SP - 328-329 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84988891995&partnerID=MN8TOARS ER - TY - JOUR TI - Defect structures induced by high-energy displacement cascades in γ uranium AU - Miao, Yinbin AU - Beeler, Benjamin AU - Deo, Chaitanya AU - Baskes, Michael I. AU - Okuniewski, Maria A. AU - Stubbins, James F. T2 - Journal of Nuclear Materials AB - Abstract Displacement cascade simulations were conducted for the γ uranium system based on molecular dynamics. A recently developed modified embedded atom method (MEAM) potential was employed to replicate the atomic interactions while an embedded atom method (EAM) potential was adopted to help characterize the defect structures induced by the displacement cascades. The atomic displacement process was studied by providing primary knock-on atoms (PKAs) with kinetic energies from 1 keV to 50 keV. The influence of the PKA incident direction was examined. The defect structures were analyzed after the systems were fully relaxed. The states of the self-interstitial atoms (SIAs) were categorized into various types of dumbbells, the crowdion, and the octahedral interstitial. The voids were determined to have a polyhedral shape with {1 1 0} facets. The size distribution of the voids was also obtained. The results of this study not only expand the knowledge of the microstructural evolution in irradiated γ uranium, but also provide valuable references for the radiation-induced defects in uranium alloy fuels. DA - 2015/1// PY - 2015/1// DO - 10.1016/j.jnucmat.2014.09.016 VL - 456 SP - 1-6 ER - TY - JOUR TI - Atomistic modeling of high temperature uranium-zirconium alloy structure and thermodynamics AU - Moore, A.P. AU - Beeler, B. AU - Deo, C. AU - Baskes, M.I. AU - Okuniewski, M.A. T2 - Journal of Nuclear Materials AB - A semi-empirical Modified Embedded Atom Method (MEAM) potential is developed for application to the high temperature body-centered-cubic uranium–zirconium alloy (γ-U–Zr) phase and employed with molecular dynamics (MD) simulations to investigate the high temperature thermo-physical properties of U–Zr alloys. Uranium-rich U–Zr alloys (e.g. U–10Zr) have been tested and qualified for use as metallic nuclear fuel in U.S. fast reactors such as the Integral Fast Reactor and the Experimental Breeder Reactors, and are a common sub-system of ternary metallic alloys like U–Pu–Zr and U–Zr–Nb. The potential was constructed to ensure that basic properties (e.g., elastic constants, bulk modulus, and formation energies) were in agreement with first principles calculations and experimental results. After which, slight adjustments were made to the potential to fit the known thermal properties and thermodynamics of the system. The potentials successfully reproduce the experimental melting point, enthalpy of fusion, volume change upon melting, thermal expansion, and the heat capacity of pure U and Zr. Simulations of the U–Zr system are found to be in good agreement with experimental thermal expansion values, Vegard's law for the lattice constants, and the experimental enthalpy of mixing. This is the first simulation to reproduce the experimental thermodynamics of the high temperature γ-U–Zr metallic alloy system. The MEAM potential is then used to explore thermodynamics properties of the high temperature U–Zr system including the constant volume heat capacity, isothermal compressibility, adiabatic index, and the Grüneisen parameters. DA - 2015/// PY - 2015/// DO - 10.1016/j.jnucmat.2015.10.016 VL - 467 SP - 802-819 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946780407&partnerID=MN8TOARS ER - TY - RPRT TI - Noble Gas Plasmas with Metallic Conductivity: A New Light Source from a New State of Matter AU - Bataller, Alex AU - Thornton, Alex AU - Latshaw, Alex AU - Pree, Seth AU - Koulakis, John AU - Putterman, Seth A3 - University of California-Los Angeles Los Angeles United States DA - 2015/// PY - 2015/// PB - University of California-Los Angeles Los Angeles United States ER - TY - JOUR TI - Neutronics and fuel performance evaluation of accident tolerant FeCrAl cladding under normal operation conditions AU - Wu, X. AU - Kozlowski, T. AU - Hales, J.D. T2 - Annals of Nuclear Energy AB - Neutronics and fuel performance analysis is done for enhanced accident tolerance fuel (ATF), with the Monte Carlo reactor physics code Serpent and INL’s fuel performance code BISON. The purpose is to evaluate the most promising ATF candidate material FeCrAl, which has excellent oxidation resistance, as fuel cladding under normal operational conditions. Due to several major disadvantages of FeCrAl coating, such as difficulty in fabrication, diametrical compression from reactor pressurization, coating spallation and inter diffusion with zirconium, a monolithic FeCrAl cladding design is suggested. To overcome the neutron penalty expected when using FeCrAl as cladding for current oxide fuel, an optimized FeCrAl cladding design from a detailed parametric study in literature is adopted, which suggests reducing the cladding thickness and slightly increasing the fuel enrichment. A neutronics analysis is done that implementing this FeCrAl cladding design in a Pressurized Water Reactor (PWR) single assembly. The results show that the PWR cycle length requirements will be matched, with a slight increase in total plutonium production. Fuel performance analysis with BISON code is carried out to investigate the effects with this FeCrAl cladding design. The results demonstrate that the application of FeCrAl cladding could improve performance. For example, the axial temperature profile is flattened. The gap closure is significantly delayed, which means the pellet cladding mechanical interaction is greatly delayed. The disadvantages for monolithic FeCrAl cladding are that: (1) fission gas release is increased; and (2) fuel temperature is increased, but the increase is less than 50 K even at high burnup. The better strength, corrosion, and embrittlement properties of FeCrAl enable the fabrication of FeCrAl cladding with thinner walls. FeCrAl cladding proves to be a good alternate for zircaloy cladding, given the advantages and insignificant disadvantages shown by fuel performance analysis. DA - 2015/// PY - 2015/// DO - 10.1016/j.anucene.2015.06.032 VL - 85 SP - 763-775 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946728980&partnerID=MN8TOARS KW - FeCrAl KW - Accident Tolerant Fuel ER - TY - CONF TI - Evaluation of accident tolerant FeCrAl coating for PWR cladding under normal operating conditions with coupled neutron transport and fuel performance AU - Rose, M. AU - Downar, T.J. AU - Wu, X. AU - Kozlowski, T. C2 - 2015/// C3 - Mathematics and Computations, Supercomputing in Nuclear Applications and Monte Carlo International Conference, M and C+SNA+MC 2015 DA - 2015/// VL - 3 SP - 2334-2344 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84949522107&partnerID=MN8TOARS ER - TY - JOUR TI - Coupling of system thermal-hydraulics and Monte-Carlo code: Convergence criteria and quantification of correlation between statistical uncertainty and coupled error AU - Wu, X. AU - Kozlowski, T. T2 - Annals of Nuclear Energy AB - Coupled multi-physics approach plays an important role in improving computational accuracy. Compared with deterministic neutronics codes, Monte Carlo codes have the advantage of a higher resolution level. In the present paper, a three-dimensional continuous-energy Monte Carlo reactor physics burnup calculation code, Serpent, is coupled with a thermal–hydraulics safety analysis code, RELAP5. The coupled Serpent/RELAP5 code capability is demonstrated by the improved axial power distribution of UO2 and MOX single assembly models, based on the OECD-NEA/NRC PWR MOX/UO2 Core Transient Benchmark. Comparisons of calculation results using the coupled code with those from the deterministic methods, specifically heterogeneous multi-group transport code DeCART, show that the coupling produces more precise results. A new convergence criterion for the coupled simulation is developed based on the statistical uncertainty in power distribution in the Monte Carlo code, rather than ad-hoc criteria used in previous research. The new convergence criterion is shown to be more rigorous, equally convenient to use but requiring a few more coupling steps to converge. Finally, the influence of Monte Carlo statistical uncertainty on the coupled error of power and thermal–hydraulics parameters is quantified. The results are presented such that they can be used to find the statistical uncertainty to use in Monte Carlo in order to achieve a desired precision in coupled simulation. DA - 2015/// PY - 2015/// DO - 10.1016/j.anucene.2014.08.016 VL - 75 SP - 377-387 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84907197788&partnerID=MN8TOARS KW - Monte Carlo KW - System thermal-hydraulics KW - Coupled simulation KW - Uncertainty quantification ER - TY - JOUR TI - Phase resolved analysis of the homogeneity of a diffuse dielectric barrier discharge AU - Baldus, Sabrina AU - Kogelheide, Friederike AU - Bibinov, Nikita AU - Stapelmann, Katharina AU - Awakowicz, Peter T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - Abstract Cold atmospheric pressure plasmas have already proven their ability of supporting the healing process of chronic wounds. Especially simple configurations like a dielectric barrier discharge (DBD), comprising of one driven electrode which is coated with a dielectric layer, are of interest, because they are cost-effective and easy to handle. The homogeneity of such plasmas during treatment is necessary since the whole wound should be treated evenly. In this investigation phase resolved optical emission spectroscopy is used to investigate the homogeneity of a DBD. Electron densities and reduced electric field distributions are determined with temporal and spatial resolution and the differences for applied positive and negative voltage pulses are studied. DA - 2015/9/23/ PY - 2015/9/23/ DO - 10.1088/0022-3727/48/37/375202 VL - 48 IS - 37 SP - SN - 1361-6463 UR - https://publons.com/wos-op/publon/627176/ KW - dielectric barrier discharge KW - PROES KW - space resolved KW - electron density ER - TY - JOUR TI - Implications of electron heating and non-uniformities in a VHF-CCP for sterilization of medical instruments AU - Stapelmann, Katharina AU - Fiebrandt, Marcel AU - Styrnoll, Tim AU - Baldus, Sabrina AU - Bibinov, Nikita AU - Awakowicz, Peter T2 - PLASMA SOURCES SCIENCE & TECHNOLOGY AB - A capacitively coupled plasma driven at a frequency of 81.36 MHz from the VHF-band is investigated by means of optical emission spectroscopy (OES) and multipole resonance probe (MRP). The discharge is operated with hydrogen, yielding an electropositive discharge, as well as oxygen, yielding an electronegative discharge, and mixtures of both. Pressure is varied from Pa to Pa. Homogeneity of the discharge is investigated by CCD camera recordings as well as spatially resolved multipole resonance probe measurements. The results indicate the presence of electromagnetic edge effects as well as standing wave effects. Furthermore, a largely homogeneous discharge can be achieved with hydrogen as process gas at a pressure of –10 Pa. With increasing pressure as well as with increasing oxygen content, the discharge appears less homogeneously. The transition from an electropositive to an electronegative discharge leads to a change in electron heating mechanisms, with pronounced local maxima of electron density at the sheath edges. A comparison of OES and MRP results reveal a significant difference in electron density, which can be explained by a non-Maxwellian distribution function of electrons. DA - 2015/5// PY - 2015/5// DO - 10.1088/0963-0252/24/3/034014 VL - 24 IS - 3 SP - SN - 1361-6595 UR - https://publons.com/wos-op/publon/627179/ KW - capacitively coupled RF discharges KW - plasma diagnostics KW - optical emission spectroscopy KW - multipole resonance probe KW - stochastic heating KW - electronegative discharge ER - TY - JOUR TI - Development of an iterative diffusion-transport method based on MICROX-2 cross section libraries AU - Hou, J. AU - Choi, H. AU - Ivanov, K. N. T2 - ANNALS OF NUCLEAR ENERGY AB - This paper introduces an innovative online cross section generation method, developed based on Iterative Diffusion-Transport (IDT) calculation to minimize the inconsistency and inaccuracy in determining physics parameters by feeding actual reactor core conditions into the cross section generation process. A two-dimensional (2-D) pin-by-pin lattice program, NEMA, was developed to generate assembly lattice parameters using the refined MICROX-2 cross section libraries and Nodal Expansion Method (NEM). The proposed method was verified against a 2-D miniature core (mini-core) benchmark problem. First, the few-group cross sections generated by NEMA were compared with those calculated by a Monte Carlo method code Serpent. Next, the analysis of a 2-D Light Water Reactor (LWR) mini-core benchmark problem was carried out by the nodal transport code DIF3D using few-group cross sections generated by NEMA, and the results were compared with those obtained from the Serpent full core calculation. Finally, the same benchmark problem was solved by the NEMA-DIF3D approach using the IDT coupling method. The computational benchmark calculations have shown that the homogenization technique implemented in NEMA is reliable when producing the few-group cross sections for the reactor core calculation. The IDT method also improves the eigenvalue and power distribution predictions. DA - 2015/3// PY - 2015/3// DO - 10.1016/j.anucene.2014.11.014 VL - 77 SP - 335-342 SN - 0306-4549 KW - 2-D lattice calculation KW - Iterative Diffusion-Transport method KW - Cross section generation KW - Boundary condition ER - TY - JOUR TI - Design and performance of 2D and 3D-shuffled breed-and-burn cores AU - Qvist, Staffan AU - Hou, Jason AU - Greenspan, Ehud T2 - ANNALS OF NUCLEAR ENERGY AB - The primary objective of this work is to find design approaches that will enable 3D fuel shuffling in stationary breed-and-burn (B&B) cores and to quantify the attainable reduction in peak DPA and change in additional performance characteristics going from conventional 2D to 3D fuel shuffling strategies. An additional objective is to establish the tradeoff between the minimum required DPA (displacements per atom) and average required burnup (fuel utilization) for B&B cores spanning a core power range from 1250 to 3500 MWth. It is found possible to design a B&B core fuelled with depleted uranium to have a peak radiation damage at or below 350 DPA when using 3D-shuffling. Relative to conventional 2D-shuffling, 3D-shuffling offers between 30% and 40% reduction in the peak DPA along with up to 30% increase in the average discharge burnup and, hence, in the depleted uranium utilization as well as significant increase in the core average and specific power density. Per DPA, the 3D shuffling option offers up to 60% higher uranium utilization. Even though 350 DPA is above the 200 DPA peak radiation damage HT9 steels were exposed to so far, it is below the 400 DPA advanced structural materials are expected to tolerate. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.anucene.2015.04.007 VL - 85 SP - 93-114 SN - 0306-4549 KW - Breed and burn KW - Traveling Wave KW - Core design KW - Fast reactor KW - Shuffling KW - LMFBR ER - TY - JOUR TI - Mobility propagation and dynamic facilitation in superionic conductors AU - Annamareddy, Ajay AU - Eapen, Jacob T2 - The Journal of Chemical Physics AB - In an earlier work [V. A. Annamareddy et al., Phys. Rev. E 89, 010301(R) (2014)], we showed the manifestation of dynamical heterogeneity (DH)-the presence of clustered mobile and immobile regions-in UO2, a model type II superionic conductor. In the current work, we demonstrate the mechanism of dynamic facilitation (DF) in two superionic conductors (CaF2 and UO2) using atomistic simulations. Using the mobility transfer function, DF is shown to vary non-monotonically with temperature with the intensity of DF peaking at temperatures close to the superionic transition temperature (Tλ). Both the metrics quantifying DH and DF show remarkable correspondence implying that DF, in the framework of kinematically constrained models, underpins the heterogeneous dynamics in type II superionic conductors. DA - 2015/11/16/ PY - 2015/11/16/ DO - 10.1063/1.4933209 VL - 143 IS - 19 SP - 194502 J2 - J. Chem. Phys. LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.4933209 DB - Crossref ER - TY - JOUR TI - Simulation of the plasma sheath dynamics in a spherical plasma focus AU - Ay, Yasar AU - Abd Al-Halim, Mohamed A. AU - Bourham, Mohamed A. T2 - EUROPEAN PHYSICAL JOURNAL D DA - 2015/9/3/ PY - 2015/9/3/ DO - 10.1140/epjd/e2015-60063-2 VL - 69 IS - 9 SP - SN - 1434-6079 ER - TY - JOUR TI - Space-Angle Homogenization of the Step Characteristic Scheme AU - Anistratov, Dmitriy Y. AU - Jones, Jesse P. T2 - JOURNAL OF COMPUTATIONAL AND THEORETICAL TRANSPORT AB - We present a new homogenized discretization scheme for solving k-eigenvalue neutron transport problems on coarse grids in space and angle. The developed scheme for 1D slab geometry is based on the step characteristic (SC) method. It is algebraically consistent with fine-mesh SC equations. We analyze the sensitivity of the homogenized transport scheme to perturbations in homogenized cross-sections and other coefficients of the scheme. The obtained results demonstrate that the proposed scheme is stable to small perturbations in its parameters. DA - 2015/// PY - 2015/// DO - 10.1080/23324309.2015.1076848 VL - 44 IS - 4-5 SP - 215-228 SN - 2332-4325 KW - transport equation KW - homogenization methods KW - multiscale problems KW - reactor physics ER - TY - JOUR TI - Effect of Plasma Temperature and Nonlinearity of the Adiabatic Compressibility Index on Flow Parameters for Hypersonic Aerosol Expansion Following a Plasma Disruption AU - Majumdar, Rudrodip AU - Bourham, Mohamed T2 - JOURNAL OF FUSION ENERGY DA - 2015/12// PY - 2015/12// DO - 10.1007/s10894-015-9960-1 VL - 34 IS - 6 SP - 1269-1277 SN - 1572-9591 KW - Plasma flow KW - Fusion particle expansion KW - Electrothermal plasma KW - Adiabatic compressibility KW - Aerosol expansion KW - Plasma disruption ER - TY - CONF TI - Displacement cascades in twist and tilt grain boundaries in Fe-bicrystal: Molecular dynamics studies AU - Dholakia, M. AU - Nandi, P. K. AU - Valsakumar, M. C. C2 - 2015/// C3 - Proceedings of the 59th dae solid state physics symposium 2014 (solid state physics) DA - 2015/// VL - 1665 ER - TY - JOUR TI - Breakdown of the semiclassical approximation during the early stages of preheating AU - Anderson, Paul R. AU - Molina-Paris, Carmen AU - Sanders, Dillon H. T2 - PHYSICAL REVIEW D AB - The validity of the semiclassical approximation is investigated during the preheating phase in models of chaotic inflation using a modification of a criterion previously proposed for semiclassical gravity. If the modified criterion is violated then fluctuations of the two-point function for the quantum fields are large and the semiclassical approximation is not valid. Evidence is provided that the semiclassical approximation breaks down during the early stages of preheating, well before either scattering effects or backreaction effects are important. DA - 2015/10/21/ PY - 2015/10/21/ DO - 10.1103/physrevd.92.083522 VL - 92 IS - 8 SP - SN - 1550-2368 ER - TY - JOUR TI - Atomistic structures of nano-engineered SiC and radiation-induced amorphization resistance AU - Imada, Kenta AU - Ishimaru, Manabu AU - Sato, Kazuhisa AU - Xue, Haizhou AU - Zhang, Yanwen AU - Shannon, Steven AU - Weber, William J. T2 - Journal of Nuclear Materials AB - Nano-engineered 3C–SiC thin films, which possess columnar structures with high-density stacking faults and twins, were irradiated with 2 MeV Si ions at cryogenic and room temperatures. From cross-sectional transmission electron microscopy observations in combination with Monte Carlo simulations based on the Stopping and Range of Ions in Matter code, it was found that their amorphization resistance is six times greater than bulk crystalline SiC at room temperature. High-angle bright-field images taken by spherical aberration corrected scanning transmission electron microscopy revealed that the distortion of atomic configurations is localized near the stacking faults. The resultant strain field probably contributes to the enhancement of radiation tolerance of this material. DA - 2015/10// PY - 2015/10// DO - 10.1016/j.jnucmat.2015.06.036 VL - 465 SP - 433-437 J2 - Journal of Nuclear Materials LA - en OP - SN - 0022-3115 UR - http://dx.doi.org/10.1016/j.jnucmat.2015.06.036 DB - Crossref KW - Nanostructured materials KW - Carbides KW - Amorphization KW - Scanning/transmission electron microscopy (STEM) ER - TY - JOUR TI - Microstructural and textural evolution of commercially pure Zr sheet rolled at room and liquid nitrogen temperatures AU - Chai, Linjiang AU - Luan, Baifeng AU - Xiao, Dongping AU - Zhang, Min AU - Murty, Korukonda L. AU - Liu, Qing T2 - MATERIALS & DESIGN AB - A commercially pure Zr sheet with a typical bimodal basal texture was rolled up to 70% reductions at room temperature (RT) and liquid nitrogen temperature (LNT) to follow its microstructural and textural evolution. Various features developed during rolling were interpreted largely based on analyses on active deformation modes by the use of electron backscatter diffraction (EBSD) technique. Results show that only dislocation slip is activated during RT rolling while both slip and twinning occur in LNT-rolled specimens. There are always some non-deforming grains after RT rolling because their orientations with the c-axes close to the normal direction (ND) of the Zr sheet are unfavorable for slip. The LNT rolling allows these non-deforming grains to be deformed by 112¯2<11¯23> compressive twinning and thus leads to more homogenous microstructures. The angle between basal pole peaks and the ND slightly decreases during RT rolling, which is attributed to the activity of 101¯1<112¯3> pyramidal slip. Many twins initiated at the early stage of LNT rolling could help retard the centralization of bimodal basal texture. In addition, calculations in light of key structural parameters measured by the EBSD reveal that the contribution from grain refinement induced by twinning makes the LNT-rolled specimens harder than the RT-rolled specimens. DA - 2015/11/15/ PY - 2015/11/15/ DO - 10.1016/j.matdes.2015.06.088 VL - 85 SP - 296-308 SN - 1873-4197 KW - Zr KW - Microstructure KW - Texture KW - Deformation mode KW - Rolling ER - TY - JOUR TI - A method to evaluate hydraulic fracture using proppant detection AU - Liu, Juntao AU - Zhang, Feng AU - Gardner, Robin P. AU - Hou, Guojing AU - Zhang, Quanying AU - Li, Hu T2 - APPLIED RADIATION AND ISOTOPES AB - Accurate determination of the proppant placement and propped fracture height are important for evaluating and optimizing stimulation strategies. A technology using non-radioactive proppant and a pulsed neutron gamma energy spectra logging tool to determine the placement and height of propped fractures is proposed. Gd2O3 was incorporated into ceramic proppant and a Monte Carlo method was utilized to build the logging tools and formation models. Characteristic responses of the recorded information of different logging tools to fracture widths, proppant concentrations and influencing factors were studied. The results show that Gd capture gamma rays can be used to evaluate propped fractures and it has higher sensitivity to the change of fracture width and traceable proppant content compared with the exiting non-radioactive proppant evaluation techniques and only an after-fracture measurement is needed for the new method; The changes in gas saturation and borehole size have a great impact on determining propped fractures when compensated neutron and pulsed neutron capture tool are used. A field example is presented to validate the application of the new technique. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.apradiso.2015.08.003 VL - 105 SP - 139-143 SN - 0969-8043 KW - Proppant detection KW - Hydraulic facture height KW - Gd capture gamma rays ER - TY - JOUR TI - Comparative study of different concrete composition as gamma-ray shielding materials AU - Waly, El-Sayed A. AU - Bourham, Mohamed A. T2 - ANNALS OF NUCLEAR ENERGY AB - The addition of some materials with various fractions in the composition of concrete has provided concrete forms more efficient for gamma ray shielding when compared to ordinary concrete. Selected materials were added and the γ-ray linear and mass attenuation coefficients, the mean free path and half value layer (HVL) were calculated. These parameters of dosimetric interest have been investigated in the energy range 0.015–15 MeV. The photon interactions with the concretes have been discussed. The blended composition with 39.195% magnetite Fe3O4 and 15.678% lead oxide PbO, named Concrete 6 in this study, has shown the best mass attenuation coefficient, exposure buildup factor and HVL values among other mixes thus minimizing the exposure rate to the acceptable levels. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.anucene.2015.05.011 VL - 85 SP - 306-310 SN - 0306-4549 KW - Dry cask overpack composition KW - Concrete blending KW - Gamma-ray shielding KW - High-level waste storage ER - TY - JOUR TI - Coble, Orowan Strengthening, and Dislocation Climb Mechanisms in a Nb-Modified Zircaloy Cladding AU - Kombaiah, Boopathy AU - Murty, Korukonda Linga T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE AB - Biaxial creep tests on HANA-4 tubes, Nb-added Zircaloy-4 were conducted using internal pressurization of closed-end tubes to investigate the rate-controlling mechanisms over a range of hoop stresses, $$ 8.38 \times 10^{ - 5} E - 2.87 \times 10^{ - 3} E $$ , at three different temperatures 673 K, 723 K, and 773 K (400 °C, 450 °C, and 500 °C). The mechanistic creep parameters such as stress exponent (n) and activation energy (Q C) were then determined from steady-state creep rates. Based on the variance in stress exponent with respect to the applied stress, three regimes have been identified: a stress exponent close to 1 at low stresses that increased to 3 at the intermediate stresses, which became 4.5 at high stresses. An activation energy value of 226 kJ/mol was evaluated for the n = 3 and n = 4.5 regimes, which lies close to the activation energy for self-diffusion (Q L) in α-Zr alloys. Further, TEM analyses of crept microstructures and comparison of experimental results with standard models were undertaken to find out the rate-controlling mechanisms. Coble creep, climbing of dislocations to bypass β-Nb precipitates, and dynamic recovery by edge dislocation climb are proposed as the rate-controlling mechanisms in the n = 1, n = 3, and n = 4.5 regimes of HANA-4, respectively. DA - 2015/10// PY - 2015/10// DO - 10.1007/s11661-015-3060-8 VL - 46A IS - 10 SP - 4646-4660 SN - 1543-1940 ER - TY - JOUR TI - Attenuation efficiency of X-ray and comparison to gamma ray and neutrons in composite metal foams AU - Chen, Shuo AU - Bourham, Mohamed AU - Rabiei, Afsaneh T2 - RADIATION PHYSICS AND CHEMISTRY AB - Steel–steel composite metal foams (S–S CMFs) and Aluminum–steel composite metal foams (Al–S CMFs) with various sphere sizes and matrix materials were manufactured and investigated for nuclear and radiation environments applications. 316 L Stainless steel, high-speed T15 steel and aluminum materials were used as the matrix material together with 2, 4 and 5.2 mm steel hollow spheres to manufacture various types of composite metal foams (CMFs). High-speed T15 steel is selected due to its high tungsten and vanadium concentration (both high-Z elements) to further improve the shielding efficiency of CMFs. This new type of S–S CMF is called high-Z steel–steel composite metal foam (HZ S–S CMF). Radiation shielding efficiency of all types of CMFs was explored for the attenuation of X-ray, gamma ray and neutron. The experimental results were compared with pure lead and Aluminum A356, and verified theoretically through XCOM and Monte Carlo Z-particle Transport Code (MCNP). It was observed that the radiation shielding effectiveness of CMFs is relatively independent of sphere sizes as long as the ratio of sphere-wall thickness to its outer-radius stays constant. However, the smaller spheres seem to be more efficient in general due to the fine fluctuation in the gray value profile of their 2D Micro-CT images. S–S CMFs and Al–S CMFs are respectively 275% and 145% more effective for X-ray attenuation than Aluminum A356. Compared to pure lead, CMFs show adequate attenuation with additional advantages of being lightweight and more environmentally friendly. The mechanical performance of HZ S–S CMFs under quasi-static compression was compared to that of other classes of S–S CMF. It is observed that the addition of high-Z elements to the matrix of CMFs improved their shielding against X-rays, low energy gamma rays and neutrons, while maintained their low density, high mechanical properties and high-energy absorption capability. DA - 2015/12// PY - 2015/12// DO - 10.1016/j.radphyschem.2015.07.003 VL - 117 SP - 12-22 SN - 0969-806X KW - Composite metal foams KW - X-ray KW - High-Z elements KW - Gamma ray KW - Neutron KW - Attenuation ER - TY - JOUR TI - Polarization asymmetries in the Be-9(gamma, n(0)) reaction AU - Mueller, J. M. AU - Ahmed, M. W. AU - Davis, B. J. AU - Karwowski, H. J. AU - Markoff, D. M. AU - Myers, L. S. AU - Spraker, M. C. AU - Stave, S. AU - Tompkins, J. R. AU - Weller, H. R. AU - Zimmerman, W. R. T2 - PHYSICAL REVIEW C AB - Measurements of the $^{9}\mathrm{Be}(\ensuremath{\gamma},{n}_{0})$ reaction were performed using nearly 100% linearly polarized, high-intensity, and nearly monoenergetic $\ensuremath{\gamma}$-ray beams having energies between 5.5 and 15.5 MeV at the High Intensity $\ensuremath{\gamma}$-ray Source located at Duke University and Triangle Universities Nuclear Laboratory. Eighteen liquid scintillator detectors were used to measure neutron yields parallel and perpendicular to the plane of beam polarization. Polarization asymmetries, which are the differences between yields observed in detectors located in-plane and out-of-plane divided by their sums, were measured for the neutrons which left the residual nucleus $(^{8}\mathrm{Be})$ in its ground state, termed the ${n}_{0}$ group. Asymmetries between 0.4 to 0.7 were discovered over this energy region in addition to a clear trend of increasing asymmetries with increasing beam energy. A prediction of the polarization asymmetry based on a pure $E1$ direct capture model shows good agreement with the experimental measurements. These data and the prediction could be of interest for methods that rely on neutron measurements following photofission to identify the presence of special nuclear material. DA - 2015/9/10/ PY - 2015/9/10/ DO - 10.1103/physrevc.92.034604 VL - 92 IS - 3 SP - SN - 1089-490X ER - TY - JOUR TI - Personal reflections on the highlights and changes in radiation and radioisotope measurement applications AU - Gardner, Robin P. AU - Lee, Kyoung O. T2 - RADIATION PHYSICS AND CHEMISTRY AB - This paper describes the recent changes that the authors have perceived in the use of radiation and radioisotope measurement applications. The first change is that due to the increased use of Monte Carlo simulation which has occurred from a normal evolutionary process. This is due in large part to the increased accuracy that is being obtained by the use of detector response functions (DRFs) and the simultaneous increased computational efficiency that has become available with these DRFs, the availability of a greatly improved weight windows variance reduction method, and the availability of inexpensive computer clusters. This first change is a happy one. The other change that is occurring is in response to recent terrorist activities. That change is the replacement or major change in the use of long-lived radioisotopes in radioisotope measurement and other radioisotope source applications. In general this can be done by improving the security of these radioisotope sources or by replacing them altogether by using machine sources of radiation. In either case one would like to preclude altogether or at least minimize the possibility of terrorists being able to obtain radioisotopes and use them for clandestine purposes. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.radphyschem.2014.11.019 VL - 116 SP - 28-31 SN - 0969-806X KW - Radioisotope applications highlights KW - Radioisotope measurement application changes KW - Monte Carlo simulation ER - TY - JOUR TI - Momentum, heat, and neutral mass transport in convective atmospheric pressure plasma-liquid systems and implications for aqueous targets AU - Lindsay, Alexander AU - Anderson, Carly AU - Slikboer, Elmar AU - Shannon, Steven AU - Graves, David T2 - Journal of Physics D: Applied Physics AB - There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 $\mu$m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results from this study include the presence of a 10 K temperature drop in the gas boundary layer adjacent to the interface that arises from convective cooling and water evaporation. Accounting for the resulting difference between gas and liquid bulk temperatures has a significant impact on reaction kinetics; factor of two changes in terminal aqueous species concentrations like H$_2$O$_2$, NO$_2^-$, and NO$_3^-$ are observed if the effect of evaporative cooling is not included. DA - 2015/9/24/ PY - 2015/9/24/ DO - 10.1088/0022-3727/48/42/424007 VL - 48 IS - 42 SP - 424007 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/48/42/424007 DB - Crossref KW - convective discharges KW - interfacial concentration gradients KW - interfacial temperature gradients KW - coupled momentum KW - heat KW - mass transport ER - TY - JOUR TI - Generalized Scaling Laws of Plasma Parameters in Electrothermal Plasma Sources for Fusion Disruption Erosion and Hypervelocity Launch Applications AU - Gonzalez, P. P. Vergara AU - Gilligan, John AU - Winfrey, Leigh AU - Bourham, Mohamed A. T2 - IEEE TRANSACTIONS ON PLASMA SCIENCE AB - Generalized operational scaling laws have been developed for the peak plasma parameters at the exit of an electrothermal plasma capillary discharge. These parameters are the total ablated mass, plasma kinetic temperature, pressure, bulk velocity, and the radiant heat flux. The obtained scaling laws have particular coefficients depending on the material of the ablating liner inside the capillary source. The generalized scaling laws include the magnitude of the peak discharge current, material property, and the dimensions of the ablating sleeve. The values given by the scaling laws are compared with the ones calculated by the computational ElectroThermal Flow (ETFLOW) code and against the experimental data. The obtained results of the scaling laws have shown low error, especially the scaling laws of the kinetic temperature and the plasma exit velocity. DA - 2015/10// PY - 2015/10// DO - 10.1109/tps.2015.2474835 VL - 43 IS - 10 SP - 3645-3652 SN - 1939-9375 KW - Capillary discharges KW - electrothermal (ET) plasmas KW - high heat flux KW - high-density plasmas KW - plasma launchers ER - TY - JOUR TI - An analytical approach for treating background in spectral analysis measurements AU - Miller, Ian AU - Holmes, Thomas W. AU - Gardner, Robin P. T2 - RADIATION PHYSICS AND CHEMISTRY AB - A method of determining the spectral shape of background radiation present in experimental spectra via a mathematical approach is presented. Elements of interest will be subtracted from an experimental spectrum using the linear correlation coefficient across a characteristic peak to determine their contribution. Once all elements of interest are removed, the remainder of the experimental spectrum should represent an approximation of the background. This approximation can then be used in conjunction with library least-squares to determine the background and elemental contributions to the unknown spectrum. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.radphyschem.2015.01.018 VL - 116 SP - 87-91 SN - 0969-806X KW - Spectral background KW - Analytical background approach ER - TY - JOUR TI - A new G-M counter hybrid dead-time correction model AU - Hou, Guojing AU - Gardner, Robin P. T2 - RADIATION PHYSICS AND CHEMISTRY AB - Abstract A new G–M counter dead-time model based on the hybrid model is proposed and studied. The new model contains the idealized paralyzable and non-paralyzable dead-time models, but also allows the non-paralyzable dead-time to vary with the true counting rate. To validate this model, the decaying source experiment with a very pure 56 Mn source was used. The calculated true counting rates obtained by fitting the experimental data to the model were compared to the data obtained by table lookup. In general, the fitting was in good agreement (within 4.8% up to 5.35 × 10 6 counts / minute ) for a G–M counter with a paralyzable dead-time component of 85.9 μs and a non-paralyzable dead-time component ranging from 438 μs to 24.3 ms. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.radphyschem.2015.05.014 VL - 116 SP - 125-129 SN - 0969-806X KW - G-M counter KW - Dead-time KW - Paralyze ER - TY - JOUR TI - Radiation Source Mapping with Bayesian Inverse Methods AU - Hykes, Joshua M. AU - Azmy, Yousry Y. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - We present a method to map the spectral and spatial distributions of radioactive sources using a limited number of detectors. Locating and identifying radioactive materials is important for border monitoring, in accounting for special nuclear material in processing facilities, and in cleanup operations following a radioactive material spill. Most methods to analyze these types of problems make restrictive assumptions about the distribution of the source. In contrast, the source mapping method presented here allows an arbitrary three-dimensional distribution in space and a gamma peak distribution in energy. To apply the method, the problem is cast as an inverse problem where the system’s geometry and material composition are known and fixed, while the radiation source distribution is sought. A probabilistic Bayesian approach is used to solve the resulting inverse problem since the system of equations is ill-posed. The posterior is maximized with a Newton optimization method. The probabilistic approach also provides estimates of the confidence in the final source map prediction. A set of adjoint, discrete ordinates flux solutions, obtained in this work by the Denovo code, is required to efficiently compute detector responses from a candidate source distribution. These adjoint fluxes form the linear mapping from the state space to the response space. The test of the method’s success is simultaneously locating a set of 137Cs and 60Co gamma sources in a room. This test problem is solved using experimental measurements that we collected for this purpose. Because of the weak sources available for use in the experiment, some of the expected photopeaks were not distinguishable from the Compton continuum. However, by supplanting 14 flawed measurements (out of a total of 69) with synthetic responses computed by MCNP, the proof-of-principle source mapping was successful. The locations of the sources were predicted within 25 cm for two of the sources and 90 cm for the third, in a room with an ˜4-× 4-m floor plan. The predicted source intensities were within a factor of ten of their true value. DA - 2015/4// PY - 2015/4// DO - 10.13182/nse13-91 VL - 179 IS - 4 SP - 364-380 SN - 1943-748X ER - TY - JOUR TI - Plasma-Assisted Preparation of High-Performance Chitosan Nanofibers/Gauze Composite Bandages AU - Nawalakhe, Rupesh AU - Shi, Quan AU - Vitchuli, Narendiran AU - Bourham, Mohamed A. AU - Zhang, Xiangwu AU - McCord, Marian G. T2 - INTERNATIONAL JOURNAL OF POLYMERIC MATERIALS AND POLYMERIC BIOMATERIALS AB - In this work, novel composite bandages were prepared by electrospinning chitosan nanofibers on 100% cotton substrate fabric. In the composite bandages, chitosan nanofiber web serves as a primary wound dressing whereas cotton substrate as a backing material. Cotton substrate was given plasma pretreatment and composite bandages were given plasma posttreatment to improve the durability of composite bandages and adhesion between nanofiber and cotton substrate layers. The adhesion of the nanofibers to the substrates was assessed by qualitative and quantitative techniques. Plasma pretreatment of the substrate with 100% helium and 99% helium/1% oxygen plasmas showed up to four times increase in force required to peel off the nanofiber layer. Even more increase in adhesion was obtained when composite bandages were given plasma pretreatment to substrate as well as posttreatment to composite bandages. Storage modulus, glass transition temperature, and crystallinity of untreated He and He/O2-plasma treated chitosan nanofiber web were studied to observe the effect of plasma treatment on the chitosan nanofibers using dynamic mechanical analysis, differential scanning calorimetry, and wide angle X-ray diffraction, respectively. To understand the mechanism of improved adhesion, surface elemental analysis of plasma treated chitosan nanofibers and cotton substrate was carried out using X-ray photoelectron spectroscopy. DA - 2015/// PY - 2015/// DO - 10.1080/00914037.2014.1002098 VL - 64 IS - 14 SP - 709-717 SN - 1563-535X KW - Nanofibers KW - chitosan KW - medical textiles KW - wound healing KW - plasma treatment KW - composite ER - TY - JOUR TI - Investigation of Portevin - Le Chatelier effect in HT-9 steel AU - Sarkar, Apu AU - Maloy, Sturat A. AU - Murty, Korukonda L. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Portevin−Le Chatelier (PLC) effect has been observed in HT-9 steel. The present study involves different types of tensile testing to characterize the features of PLC effectin HT-9 steel. Stress serrations observed during tensile tests are analyzed using different statistical analysis techniques to investigate the underlying nature of the effect. Peaked type of stress drop distribution indicated occurrence of type B serrations in the steel. Multiscale entropy analysis of the stress serrations indicated substitutional solute atoms to be responsible for the PLC effect in HT-9 steel. DA - 2015/4/17/ PY - 2015/4/17/ DO - 10.1016/j.msea.2015.02.022 VL - 631 SP - 120-125 SN - 1873-4936 KW - Portevin - Le Chatelier effect KW - Dynamic strain aging KW - HT-9 steel KW - Tensile tests ER - TY - JOUR TI - High temperature creep and deformation microstructures in recrystallized Zircaloy-4 AU - Kombaiah, B. AU - Murty, K. Linga T2 - PHILOSOPHICAL MAGAZINE AB - Uniaxial creep tests were performed on recrystallized Zircaloy-4 tensile specimens with an average grain size of 8.5 μm at the stress range of , where E is the elastic modulus, at three temperatures: 500, 550 and 600 °C with an objective to uncover the rate-controlling mechanism(s). A transition in creep mechanism was observed as the stress exponent increased from a value close to 1 at the low stress range to 4.1 at high stresses with the calculated activation energies (Qc) of 196 kJ/mol and 241 kJ/mol, respectively. Possible creep mechanisms have been shortlisted based upon the values of n and Qc. Transmission electron microscopy analyses of the dislocation structures in the crept specimens as well as validation of the experimental results with the predictions by standard creep models were undertaken to ascertain the underlying rate-controlling mechanisms. While Coble creep was noted to be the dominant mechanism in the n ~ 1 regime at low stresses, dislocation climb was identified to control the creep rate in the n ~ 4.1 regime at high stresses. DA - 2015/5/24/ PY - 2015/5/24/ DO - 10.1080/14786435.2015.1042939 VL - 95 IS - 15 SP - 1656-1679 SN - 1478-6443 KW - deformation mechanisms KW - dislocation climb KW - electron microscopy KW - Coble creep KW - Zircaloy-4 KW - creep ER - TY - JOUR TI - Study of High-Enthalpy Electrothermal Energetic Plasma Source Concept AU - Winfrey, A. Leigh AU - Abd Al-Halim, Mohamed A. AU - Mittal, Shawn AU - Bourham, Mohamed A. T2 - IEEE TRANSACTIONS ON PLASMA SCIENCE AB - The electrothermal (ET) energetic plasma source (ETEPS) is a different concept in which the ablation mechanism is forced inside of the open-ended capillary that has energetic liner, a propellant. The generation of the ET plasma results from Joule heating and radiant heat transport to the liner. The discharge initiates erosive burn of the propellant, and the mixed plasma-propellant gasification produces high-enthalpy energetic flow. In the ablation-dominated source, the eroded materials from the solid propellant liner are mixed inside the source before they flow out as a result of the large pressure gradient. The energetic ET source also has another concept in which no ablation occurs and the plasma is generated from the injection of energetic gasses or liquids into the confined open-ended capillary. The ablation-free source generates the plasma from the dissociation of the gaseous/liquid components, which in turn releases the chemical energy of these propellants and mixes the energy with the electrical energy of the plasma. This concept is different from ET chemical (ETC) sources; it generates the propellant or energetic flow without requiring a combustion chamber. It also provides mixing at the ionic level not available in current configurations of ETC launchers, igniters, or thrusters. The ET plasma code ETFLOW-EN was developed to computationally simulate the plasma generation and flow in energetic ET capillary discharges to predict the behavior of the energetic source with the use of lined solid propellants. Operation with liquid/gaseous energetic forms in a nonablative capillary is also a character of this concept and is part of the ETFLOW code. The results of using different forms of energetic materials in solid, liquid, and gaseous mixtures have shown the applicability of ETEPS to produce high-enthalpy energetic plasma flows with sufficient parameters suitable for ETC launch applications. Plasma and flow parameters at the capillary exit were investigated at different mixing ratios. DA - 2015/7// PY - 2015/7// DO - 10.1109/tps.2015.2417879 VL - 43 IS - 7 SP - 2195-2200 SN - 1939-9375 KW - Electrothermal (ET) plasma KW - energetic ET source KW - ET chemical (ETC) source KW - plasma source modeling ER - TY - JOUR TI - Modeling and Analysis of a Dual-Channel Plasma Torch in Pulsed Mode Operation for Industrial, Space, and Launch Applications AU - Zielinski, Alexander E. AU - Fair, Harry D. AU - Winfrey, A. Leigh AU - Bourham, Mohamed A. T2 - IEEE TRANSACTIONS ON PLASMA SCIENCE AB - Dual-channel thermal plasma torch can operate with air, argon, or combustible gases to produce high-temperature plasma flow. This plasma torch can be used in various important applications such as metal industry recycling, surface coating and hardening, space operations using controlled thrust, and macroparticle acceleration based on the electrothermal nature of thermal torches and electrical-to-thermal energy conversion. Power for this torch is supplied from the electric mains and the voltage is stepped up to 6 kV. However, the torch can also operate on dc or pulsed mode. The electrical operation is characterized by the voltampere relationship to determine the power rating of the torch as well as diagnosing the dynamic behavior of the plasma. Experiments on the torch using air and argon have shown plasma temperatures in the range of 0.4-0.6 eV with plasma number density in the range of 10 24 -10 25 /m 3 , indicating a dense plasma regime with the plasma tends to be weakly nonideal. Plasma kinetic temperature and electron number density were obtained from optical emission spectroscopy using the relative line method as the plasma is near local thermodynamic equilibrium condition. Plasma temperature has its peak for low flow rates and decreases for increased flow rates. The torch modeling was conducted using an electrothermal plasma code to simulate and predict the parameters for pulsed mode operation. Simulation was conducted on a single channel as the dual torch is symmetric. Code results for extended pulselength show a plasma temperature between 0.6 and 0.8 eV for nitrogen, oxygen, and helium; which are in good correlation with plasma temperatures obtained from optical emission spectra and measured plasma resistivity. A set of computational experiments using short pulses at higher discharge currents has shown temperature in the range of 2.0-2.5 eV for nitrogen and helium. DA - 2015/7// PY - 2015/7// DO - 10.1109/tps.2015.2424891 VL - 43 IS - 7 SP - 2201-2206 SN - 1939-9375 KW - Dual-channel plasma torch KW - plasma torch modeling KW - pulsed plasma torches ER - TY - JOUR TI - Examination of the impact of electron-phonon coupling on fission enhanced diffusion in uranium dioxide using classical molecular dynamics AU - Wormald, Jonathan L. AU - Hawari, Ayman I. T2 - JOURNAL OF MATERIALS RESEARCH DA - 2015/5/14/ PY - 2015/5/14/ DO - 10.1557/jmr.2014.405 VL - 30 IS - 9 SP - 1485-1494 SN - 2044-5326 ER - TY - JOUR TI - Electric field determination in the plasma-antenna boundary of a lower-hybrid wave launcher in Tore Supra through dynamic Stark-effect spectroscopy AU - Martin, E H AU - Goniche, M AU - Klepper, C C AU - Hillairet, J AU - Isler, R C AU - Bottereau, C AU - Colas, L AU - Ekedahl, A AU - Panayotis, S AU - Pegourie, B AU - Lotte, Ph AU - Colledani, G AU - Caughman, J B AU - Harris, J H AU - Hillis, D L AU - Shannon, S C AU - Clairet, F AU - Litaudon, X T2 - Plasma Physics and Controlled Fusion AB - Interaction of radio-frequency (RF) waves with the plasma in the near-field of a high-power wave launcher is now seen to be an important topic, both in understanding the channeling of these waves through the plasma boundary and in avoiding power losses in the edge. In a recent Letter, a direct non-intrusive measurement of a near antenna RF electric field in the range of lower hybrid (LH) frequencies (ELH) was announced (2013 Phys. Rev. Lett. 110 215005). This measurement was achieved through the fitting of Balmer series deuterium spectral lines utilizing a time dependent (dynamic) Stark effect model. In this article, the analysis of the spectral data is discussed in detail and applied to a larger range of measurements and the accuracy and limitations of the experimental technique are investigated. It was found through an analysis of numerous Tore Supra discharges that good quantitative agreement exists between the measured and full-wave modeled ELH when the launched power exceeds 0.5 MW. For low power the measurement becomes inaccurate utilizing the implemented passive spectroscopic technique because the spectral noise overwhelms the effect of the RF electric field on the line profile. Additionally, effects of the ponderomotive force are suspected at sufficiently high power. DA - 2015/4/22/ PY - 2015/4/22/ DO - 10.1088/0741-3335/57/6/065011 VL - 57 IS - 6 SP - 065011 J2 - Plasma Phys. Control. Fusion OP - SN - 0741-3335 1361-6587 UR - http://dx.doi.org/10.1088/0741-3335/57/6/065011 DB - Crossref KW - optical emission spectroscopy KW - electric field KW - lower hybrid current drive KW - Tore Supra ER - TY - JOUR TI - Control of ion energy distributions using phase shifting in multi-frequency capacitively coupled plasmas AU - Zhang, Yiting AU - Zafar, Abdullah AU - Coumou, David J. AU - Shannon, Steven C. AU - Kushner, Mark J. T2 - Journal of Applied Physics AB - Control of ion energy distributions (IEDs) onto the surface of wafers is an ongoing challenge in microelectronics fabrication. The use of capacitively coupled plasmas (CCPs) using multiple radio frequency (rf) power sources provides many opportunities to customize IEDs. In dual-frequency CCPs using a fundamental frequency and its second harmonic, varying the relative voltages, powers, and phases between the fundamental and second harmonic biases have demonstrated potential as control mechanisms for the shape of the IEDs. In this paper, we report on computational and experimental investigations of IED control in dual-frequency and triple-frequency CCPs where the phase between the fundamental and second harmonic frequency voltage waveform is used as a control variable. The operating conditions were 5–40 mTorr (0.67–5.33 Pa) in Ar and Ar/CF4/O2 gas mixtures. By changing the phase between the applied rf frequency and its second harmonic, the Electrical Asymmetric Effects was significant and not only shifted the dc self-bias but also affected plasma uniformity. When changing phases of higher harmonics, the energies and widths of the IEDs could be controlled. With the addition of a 3rd high-frequency source, the plasma density increased and uniformity improved. Computed results for IEDs were compared with experimental results using an ion energy analyzer in systems using rf phase locked power supplies. DA - 2015/6/17/ PY - 2015/6/17/ DO - 10.1063/1.4922631 VL - 117 IS - 23 SP - 233302 J2 - J. Appl. Phys. LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4922631 DB - Crossref ER - TY - JOUR TI - Comparison of spatial discretization methods for solving the S-N equations using a three-dimensional method of manufactured solutions benchmark suite with escalating order of nonsmoothness AU - Schunert, S. AU - Azmy, Y. T2 - Nuclear Science and Engineering AB - AbstractA comparison of the accuracy and computational efficiency of spatial discretization methods of the three-dimensional SN equations is conducted, including discontinuous Galerkin finite element methods, the arbitrarily high-order transport method of nodal type (AHOTN), the linear-linear method, the linear-nodal (LN) method, and the higher-order diamond difference method. For this purpose, we have developed a suite of method of manufactured solutions benchmarks that provides an exact solution of the SN equations even in the presence of scattering. Most importantly, our benchmark suite permits the user to set an arbitrary level of smoothness of the exact solution across the singular characteristics. Our study focuses on the computational efficiency of the considered spatial discretization methods.Numerical results indicate that the best-performing method depends on the norm used to measure the discretization error. We employ discrete Lp norms and integral error norms in this work. For configurations with continuous exact angular flux, high-order AHOTNs perform best under Lp error norms, while the LN method performs best when measured by integral error norms. When the angular flux is discontinuous, a new singular-characteristic tracking method for three-dimensional geometries performs best among the considered methods. DA - 2015/// PY - 2015/// DO - 10.13182/nse14-77 VL - 180 IS - 1 SP - 1-29 ER - TY - JOUR TI - Scaling Laws of Bulk Plasma Parameters for a 1-D Flow through a Capillary with Extended Converging-Diverging Nozzle for Simulated Expansion into Fusion Reactor Chamber AU - Majumdar, Rudrodip AU - Gilligan, John G. AU - Winfrey, A. Leigh AU - Bourham, Mohamed A. T2 - JOURNAL OF FUSION ENERGY DA - 2015/8// PY - 2015/8// DO - 10.1007/s10894-015-9899-2 VL - 34 IS - 4 SP - 905-910 SN - 1572-9591 KW - Plasma flow KW - Fusion particle expansion KW - Electrothermal plasma scaling laws ER - TY - JOUR TI - Iterative stability analysis of spatial domain decomposition based on block Jacobi algorithm for the diamond-difference scheme AU - Anistratov, Dmitriy Y. AU - Azmy, Yousry Y. T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - We study convergence of the integral transport matrix method (ITMM) based on a parallel block Jacobi (PBJ) iterative strategy for solving particle transport problems. The ITMM is a spatial domain decomposition method proposed for massively parallel computations. A Fourier analysis of the PBJ-based iterations applied to SN diamond-difference equations in 1D slab and 2D Cartesian geometries is performed. It is carried out for infinite-medium problems with homogeneous material properties. To analyze the performance of the ITMM with the PBJ algorithm and evaluate its potential in scalability we consider a limiting case of one spatial cell per subdomain. The analysis shows that in such limit the spectral radius of the iteration method is one without regard to values of the scattering ratio and optical thickness of the spatial cells. This implies lack of convergence in infinite medium. Numerical results of finite-medium problems are presented. They demonstrate effects of finite size of spatial domain on the performance of the iteration algorithm as well as its asymptotic behavior when the extent of the spatial domain increases. These numerical experiments also show that for finite domains iterative convergence to a finite criterion is achievable in a multiple of the sum of number of cells in each dimension. DA - 2015/9/15/ PY - 2015/9/15/ DO - 10.1016/j.jcp.2015.05.033 VL - 297 SP - 462-479 SN - 1090-2716 KW - Particle transport equation KW - Radiative transfer equation KW - Domain decomposition KW - Iterative methods KW - Fourier analysis ER - TY - JOUR TI - Simulation of particle impact on protective coating of high-level waste storage packages AU - Radwan, Samah AU - Winfrey, Leigh AU - Bourham, Mohamed T2 - PROGRESS IN NUCLEAR ENERGY AB - Integrity and survivability of high-level waste packages are critical for their storage and during their transport. Multi-layer, multi-component coatings composed of TiCN/ZrO2–TiO2–Al2O3/MoS2 on the outer shield material can provide engineered barriers resistant to corrosion; radiation, diffusion, and thermal cycling effect that are also wear tolerant and mechanically robust. While waste packages are designed to survive some structural damage, potential coatings applied to future packages may be affected by the development of micro-cracks. In such a case neutrons and gamma rays might interact with the external coatings. In this research, particle impact with multi-layered, multi-component coatings is studied to assess the damage expected in the coatings if micro cracking would happen and heavy particles (neutrons) leak into the coatings. As a first step to investigate this scenario, the open source code SRIM has been used to perform the study using protons as a simulation of the heavy particle interaction. The simulation provides a tool to determine the optimal coating thickness to be manufactured in order to limit the coating surface damage to within minimum values. DA - 2015/5// PY - 2015/5// DO - 10.1016/j.pnucene.2015.01.013 VL - 81 SP - 196-202 SN - 0149-1970 KW - Multilayer coating KW - High-level waste storage KW - Heavy particle interaction with surfaces ER - TY - JOUR TI - ESTIMATION OF SHEAR-INDUCED LIFT FORCE IN LAMINAR AND TURBULENT FLOWS AU - Thomas, Aaron M. AU - Fang, Jun AU - Feng, Jinyong AU - Bolotnov, Igor A. T2 - NUCLEAR TECHNOLOGY AB - The goal of the present study is to demonstrate that direct numerical simulations (DNS) coupled with interface tracking methods can be used to estimate interfacial forces in two-phase flows. Current computational multiphase fluid dynamics codes model interfacial forces utilizing closure laws that are heavily dependent on limited experimental data and simplified analytical approximations. In the present work, a method for improving the current interfacial force database has been developed by using DNS to quantify the lift and drag forces on a single bubble in laminar and turbulent shear flows. A proportional-integral-derivative–based controller was implemented into the finite element–based, multiphase flow solver [PHASTA (Parallel, Hierarchic, higher-order accurate, Adaptive, Stabilized, finite element method Transient Analysis)] to control the bubble position. This capability allowed for utilization of a steady-state force balance on the bubble to determine lift and drag coefficients in various shear flows. Specifically, for low shear flows (2.0 s−1), the effect of the wall presence is analyzed, and for high shear flows, the effect of turbulence is studied. A number of uniform shear (10.0 to 470.0 s−1) laminar flows were simulated to assess lift and drag force behavior as the kinetic energy of the flow increased. Two high shear (236.0 and 470.0 s−1) turbulent flows were simulated to understand bubble-turbulence interaction influence on the drag and lift phenomena. Two uniform shear rates (20.0 and 100 s−1) were simulated utilizing pressurized water reactor fluid properties. The lift and drag coefficients estimated in this work are in agreement with models developed for low shear laminar flows, whereas for high shear laminar and turbulent flows, bubble-turbulence interaction became a dominating influence in the lift and drag coefficient estimation. The novel results and method presented in this paper offer a path to simulating full-fledged reactor coolant environments where the lift and drag forces on a single bubble can be studied. DA - 2015/6// PY - 2015/6// DO - 10.13182/nt14-72 VL - 190 IS - 3 SP - 274-291 SN - 1943-7471 KW - multiphase turbulence KW - direct numerical simulations KW - lift force ER - TY - JOUR TI - A special twin relationship or a common Burgers misorientation between alpha plates after beta quenching in Zr alloy? AU - Chai, Linjiang AU - Chen, Baofeng AU - Zhou, Zhiming AU - Murty, Korukonda L. AU - Ma, Yanlong AU - Huang, Weijiu T2 - MATERIALS CHARACTERIZATION AB - A 101¯1 twin relationship between α plates was repeatedly reported in β-quenched Zr alloys in literature. In this paper, however, we demonstrate that the special twin relationship between α plates should be correctly identified as one of five common Burgers misorientations. The shared plane between two α plates with such a Burgers misorientation is determined to be 101¯1.06. Such a clarification helps to reach more accurate understanding of boundary characteristics of β-quenched microstructure in Zr alloys. DA - 2015/6// PY - 2015/6// DO - 10.1016/j.matchar.2015.04.008 VL - 104 SP - 61-65 SN - 1873-4189 KW - Zr alloy KW - Quenching KW - Misorientation KW - Electron backscatter diffraction ER - TY - JOUR TI - Dislocation cross-slip controlled creep in Zircaloy-4 at high stresses AU - Kombaiah, B. AU - Murty, K. Linga T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Uniaxial creep tests were performed on Zircaloy-4 sheet in the temperature range of 500–600 °C at high stresses (>10−3E), to uncover the rate-controlling mechanism. A stress exponent of 9.3–11 and a stress-dependent activation energy in the range of 220–242 kJ/mol were obtained from the steady state creep data. TEM analyses revealed an extensive presence of hexagonal screw dislocation network on the basal planes indicating recovery of screw dislocations by cross-slip to be the dominant mechanism. The creep data was therefore analyzed in the light of Friedel׳s cross slip model for HCP metals according to which the stress-dependency of the activation energy determined from the creep data was written in the form,U=(150±4)+(2236±124τ)kJ/mol The constriction energy of screw dislocations of 150 kJ/mol is in agreement with the values reported in the literature for zirconium and other HCP metals. Further analysis of the yield strength and the activation volume data obtained from stress relaxation tests in the temperature range 500–600 °C favors cross-slip of screw dislocations as the rate controlling mechanism over the test conditions. DA - 2015/1/19/ PY - 2015/1/19/ DO - 10.1016/j.msea.2014.11.040 VL - 623 SP - 114-123 SN - 1873-4936 KW - Creep KW - Zircaloy KW - Cross slip KW - Electron microscopy ER - TY - JOUR TI - DNS of turbulent flow with hemispherical wall roughness AU - Mishra, Anand V. AU - Bolotnov, Igor A. T2 - JOURNAL OF TURBULENCE AB - The present study of the effect of roughness density on the mean flow turbulence parameters is motivated by the need for new generation of boundary conditions for multiphase computational multiphase fluid dynamics (CMFD) models applied to boiling flows. Effect of roughness element density on the turbulent flow in a channel is quantified through direct numerical simulations (DNSs). The Navier--Stokes equations are solved using finite element method and bubbles are approximated as rigid near-hemispherical obstacles at the wall. Six different cases were analysed including channel flow with smooth wall and channel flow with rough wall for five different bubble nucleation site densities. Friction factor and the law of the wall was calculated and compared with the previously published results. Existing correlations for nucleating bubble site density dependency on a wall heat flux were used to obtain a relation between the heat flux and the friction factor, leading to the law of the wall dependency on the heat flux. This separate effect study provides new guidelines on how the heat flux in subcooled boiling regime affects the turbulence behaviour near the wall and guides the computational fluid dynamics model development for boiling two-phase flows. DA - 2015/// PY - 2015/// DO - 10.1080/14685248.2014.989231 VL - 16 IS - 3 SP - 225-249 SN - 1468-5248 KW - turbulence KW - roughness KW - DNS ER - TY - JOUR TI - Microstructure-mechanical property correlation of cryo rolled Zircaloy-4 AU - Sarkar, Apu AU - Murty, Korukonda L. T2 - JOURNAL OF NUCLEAR MATERIALS AB - The evolution of microstructure and the mechanical properties of cryo-rolled Zircaloy-4 were both investigated to understand the origin of the alloy’s strength processed at a cryogenic temperature. The correlation of dislocation density, grain size and yield stress of the rolled product indicated that an increase in dislocation density due to the suppression of dynamic recovery is the primary source of strengthening. DA - 2015/1// PY - 2015/1// DO - 10.1016/j.jnucmat.2014.09.071 VL - 456 SP - 287-291 SN - 1873-4820 ER - TY - JOUR TI - Subspace-based Inverse Uncertainty Quantification for Nuclear Data Assessment AU - Khuwaileh, B. A. AU - Abdel-Khalik, H. S. T2 - NUCLEAR DATA SHEETS AB - Safety analysis and design optimization depend on the accurate prediction of various reactor attributes. Predictions can be enhanced by reducing the uncertainty associated with the attributes of interest. An inverse problem can be defined and solved to assess the sources of uncertainty, and experimental effort can be subsequently directed to further improve the uncertainty associated with these sources. In this work a subspace-based algorithm for inverse sensitivity/uncertainty quantification (IS/UQ) has been developed to enable analysts account for all sources of nuclear data uncertainties in support of target accuracy assessment-type analysis. An approximate analytical solution of the optimization problem is used to guide the search for the dominant uncertainty subspace. By limiting the search to a subspace, the degrees of freedom available for the optimization search are significantly reduced. A quarter PWR fuel assembly is modeled and the accuracy of the multiplication factor and the fission reaction rate are used as reactor attributes whose uncertainties are to be reduced. Numerical experiments are used to demonstrate the computational efficiency of the proposed algorithm. Our ongoing work is focusing on extending the proposed algorithm to account for various forms of feedback, e.g., thermal-hydraulics and depletion effects. DA - 2015/1// PY - 2015/1// DO - 10.1016/j.nds.2014.12.010 VL - 123 SP - 57-61 SN - 1095-9904 ER - TY - JOUR TI - Neutrons attenuation on composite metal foams and hybrid open-cell Al foam AU - Chen, Shuo AU - Bourham, Mohamed AU - Rabiei, Afsaneh T2 - RADIATION PHYSICS AND CHEMISTRY AB - A comprehensive investigation of monochromatic neutron attenuation effectiveness for close-cell composite metal foams (CMFs) and open-cell Al foam infiltrated with variety of second phase materials is presented using both experimental and theoretical methods. The experimental results indicated higher neutron flux reduction in open-cell Al foam with fillers compared to the close-cell CMFs due to their large percentage of low Z elements such as hydrogen, boron and carbon, with superior neutron attenuation performance, in their filler materials. The main factor controlling the shielding effectiveness of steel–steel CMFs is found to be the ratio of the thickness of the sphere wall to the sphere radius while the intermetallic phases in the matrix of Al–steel CMFs seem to have a major role on their shielding properties. Successful models that link the observed material properties and microstructure have been developed using Monte Carlo N-Particle Transport Code (MCNP) to verify the accuracy of the experimental results. Close-cell CMFs were proposed through three different sphere arrangements: simple cubic, body center cubic and face center cubic, whereas open-cell Al foam with fillers was represented by creating a three-dimensional structure using periodic unit cell through two approaches. The simulation results were found to be in good agreement with the experimental values. This research indicates the potential of utilizing light-weight close-cell CMFs and open-cell Al foam with fillers as nuclear shields replacing conventional materials to achieve a specified shielding level with additional benefits of excellent energy absorption and thermal isolation. DA - 2015/4// PY - 2015/4// DO - 10.1016/j.radphyschem.2014.11.003 VL - 109 SP - 27-39 SN - 0969-806X KW - Metal foam KW - Neutron attenuation KW - Monte Carlo simulation KW - Areal density KW - Radiation shielding ER - TY - JOUR TI - Microstructural development of high temperature deformed AZ31 magnesium alloys AU - Roodposhti, Peiman Shahbeigi AU - Sarkar, Apu AU - Murty, Korukonda Linga T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Due to their significant role in automobile industries, high temperature deformation of Mg–Al–Zn alloys (AZ31) at constant stress (i.e. creep) were studied at a wide range of stresses and temperatures to characterize underlying deformation mechanism, dynamic recrystallization (DRX) and dislocation density evolution. Various microstructures (e.g. grain growth & DRX) are noted during steady-state creep mechanisms such as grain boundary sliding (GBS), dislocation glide creep (DGC) and dislocation climb creep (DCC). Although a combination of DRX and grain growth is characteristic of low stacking fault energy materials like Mg alloys at elevated temperatures, observation reveals grain growth at low strain-rates (GBS region) along with dynamic recovery (DRV) mechanism. X-Ray Diffraction (XRD) analysis revealed a decrease in dislocation density during GBS region while it increased under dislocation based creep mechanisms which could be related to the possible DRV and DRX respectively. Scanning Electron Microscopic (SEM) characterization of the fracture surface reveals more inter-granular fracture for large grains (i.e. GBS region with DRV process) and more dimple shape fracture for small grains (i.e. DGC & DCC region with DRX). DA - 2015/2/25/ PY - 2015/2/25/ DO - 10.1016/j.msea.2014.12.064 VL - 626 SP - 195-202 SN - 1873-4936 KW - Creep KW - AZ31 Mg alloy KW - Dynamic recrystallization KW - Dynamic recovery KW - Dislocation density ER - TY - JOUR TI - Advancing Inverse Sensitivity/Uncertainty Methods for Nuclear Fuel Cycle Applications AU - Arbanas, G. AU - Williams, M. L. AU - Leal, L. C. AU - Dunn, M. E. AU - Khuwaileh, B. A. AU - Wang, C. AU - Abdel-Khalik, H. T2 - NUCLEAR DATA SHEETS AB - The inverse sensitivity/uncertainty quantification (IS/UQ) method has recently been implemented in the Inverse Sensitivity/UnceRtainty Estimator (INSURE) module of the AMPX cross section processing system [M.E. Dunn and N.M. Greene, “AMPX-2000: A Cross-Section Processing System for Generating Nuclear Data for Criticality Safety Applications,” Trans. Am. Nucl. Soc. 86, 118–119 (2002)]. The IS/UQ method aims to quantify and prioritize the cross section measurements along with uncertainties needed to yield a given nuclear application(s) target response uncertainty, and doing this at a minimum cost. Since in some cases the extant uncertainties of the differential cross section data are already near the limits of the present-day state-of-the-art measurements, requiring significantly smaller uncertainties may be unrealistic. Therefore, we have incorporated integral benchmark experiments (IBEs) data into the IS/UQ method using the generalized linear least-squares method, and have implemented it in the INSURE module. We show how the IS/UQ method could be applied to systematic and statistical uncertainties in a self-consistent way and how it could be used to optimize uncertainties of IBEs and differential cross section data simultaneously. We itemize contributions to the cost of differential data measurements needed to define a realistic cost function. DA - 2015/1// PY - 2015/1// DO - 10.1016/j.nds.2014.12.009 VL - 123 SP - 51-56 SN - 1095-9904 ER -