TY - JOUR TI - Grain growth in nanocrystalline metal thin films under in situ ion-beam irradiation AU - Kaoumi, D. AU - Motta, A.T. AU - Birtcher, R.C. T2 - Journal of ASTM International AB - In-situ observations in a transmission electron microscope (TEM) were used to study the microstructure evolution in metal Zr, Pt, Cu, and Au nanocrystalline thin films under ion-beam irradiation. Free-standing films were prepared by sputter deposition. Samples were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Ar and Kr ions to fluences in excess of 1016 ion/cm2. As a result of irradiation, grain growth was observed in all samples using Bright Field (BF) imaging in the TEM. The average grain size increased monotonically with ion fluence until it reached a saturation value. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn-D0n=KΦ. The irradiations were done at temperatures ranging from 20 to 773 K. The results suggest the existence of three regimes with respect to irradiating temperature: (i) a purely thermal regime, which appears to start above the bulk coarse-grained recrystallization temperature, (ii) a thermally assisted regime where thermal diffusion and irradiation effects combine to increase the rate of grain growth relative to that resulting from either of these mechanisms alone, and (iii) an athermal regime (low-temperature regime) where irradiation can by itself cause grain growth. The transition temperature between the athermal regime and the thermally assisted regime depends on the material, but is in the range 0.14–0.22 times the melting point. The influence of the ion type was also investigated on Zr-Fe irradiated with 600 keV Kr ions versus 600 keV Ar ions. DA - 2007/// PY - 2007/// DO - 10.1520/JAI100743 VL - 4 IS - 8 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34948911544&partnerID=MN8TOARS ER - TY - RPRT TI - Stain Repellent-Antimicrobial Textiles via Atmospheric Plasma Finishes AU - McCord, M. AU - Bourham, M. A3 - Institute of Textile Technology (ITT) DA - 2007/7// PY - 2007/7// M3 - Technical Report PB - Institute of Textile Technology (ITT) ER - TY - JOUR TI - Synthesis and oxidation of Zr3Al3C5 powders AU - He, L.F. AU - Zhou, Y.C. AU - Bao, Y.W. AU - Wang, J.Y. AU - Li, M.S. T2 - International Journal of Materials Research DA - 2007/// PY - 2007/// VL - 98 IS - 1 SP - 3-9 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33847074954&partnerID=MN8TOARS ER - TY - JOUR TI - Synthesis, physical, and mechanical properties of bulk Zr 3Al3C5 ceramic AU - He, L. AU - Zhou, Y. AU - Bao, Y. AU - Lin, Z. AU - Wang, J. T2 - Journal of the American Ceramic Society AB - An in situ reactive hot‐pressing process using zirconium (zirconium hydride), aluminum, and graphite as staring materials and Si and Y 2 O 3 as additives was used to synthesize bulk Zr 3 Al 3 C 5 ceramics. This method demonstrates the advantages of easy synthesis, lower sintering temperature, high purity and density, and improved mechanical properties of synthesized Zr 3 Al 3 C 5 . Its electrical and thermal properties were measured. Compared with ZrC, Zr 3 Al 3 C 5 has a relatively low hardness (Vickers hardness of 12.5 GPa), comparable stiffness (Young's modulus of 374 GPa), but superior strength (flexural strength of 488 GPa) and toughness (fracture toughness of 4.68 MPa·m 1/2 ). In addition, the stiffness decreases slowly with increasing temperature and at 1600°C remains 78% of that at ambient temperature, indicating that Zr 3 Al 3 C 5 is a potential high‐temperature structural ceramic. DA - 2007/// PY - 2007/// DO - 10.1111/j.1551-2916.2007.01518.x VL - 90 IS - 4 SP - 1164-1170 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34247168553&partnerID=MN8TOARS ER - TY - JOUR TI - Synthesis and characterization of bulk Zr2Al3C 4 ceramic AU - He, L. AU - Lin, Z. AU - Wang, J. AU - Bao, Y. AU - Li, M. AU - Zhou, Y. T2 - Journal of the American Ceramic Society AB - Polycrystalline Zr 2 Al 3 C 4 was fabricated by an in situ reactive hot‐pressing process using zirconium (zirconium hydrides), aluminum, and graphite as starting materials. The investigation on reaction path revealed that the liquid Al played an important role in triggering the formation of ternary zirconium aluminum carbides. The mechanical properties of Zr 2 Al 3 C 4 at room temperature were measured (Vickers hardness of 10.1 GPa, Young's modulus of 362 GPa, flexural strength of 405 MPa, and fracture toughness of 4.2 MPa·m 1/2 ). The electrical resistivity and thermal expansion coefficient were determined as 1.10 μΩ·m and 8.1 × 10 −6 K −1 , respectively. DA - 2007/// PY - 2007/// DO - 10.1111/j.1551-2916.2007.01964.x VL - 90 IS - 11 SP - 3687-3689 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-35948961626&partnerID=MN8TOARS ER - TY - JOUR TI - Physical and mechanical properties of bulk Ta4AlC3 ceramic prepared by an in situ reaction synthesis/hot-pressing method AU - Hu, C. AU - Lin, Z. AU - He, L. AU - Bao, Y. AU - Wang, J. AU - Li, M. AU - Zhou, Y. T2 - Journal of the American Ceramic Society AB - Bulk Ta 4 AlC 3 ceramic was prepared by an in situ reaction synthesis/hot‐pressing method using Ta, Al, and C powders as the starting materials. The lattice parameter and a new set of X‐ray diffraction data were obtained. The physical and mechanical properties of Ta 4 AlC 3 ceramic were investigated. Ta 4 AlC 3 is a good electrical and thermal conductor. The flexural strength and fracture toughness are 372 MPa and 7.7 MPa·m 1/2 , respectively. Typically, plate‐like layered grains contribute to the damage tolerance of Ta 4 AlC 3 . After indentation up to a 200 N load, no obvious degradation of the residual flexural strength of Ta 4 AlC 3 was observed, demonstrating the damage tolerance of this ceramic. Even at above 1200°C in air, Ta 4 AlC 3 still retains a high strength and shows excellent thermal shock resistance, which renders it a promising high‐temperature structural material. DA - 2007/// PY - 2007/// DO - 10.1111/j.1551-2916.2007.01804.x VL - 90 IS - 8 SP - 2542-2548 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34547670744&partnerID=MN8TOARS ER - TY - JOUR TI - Layered stacking characteristics of ternary zirconium aluminum carbides AU - Lin, Z.J. AU - He, L.F. AU - Li, M.S. AU - Wang, J.Y. AU - Zhou, Y.C. T2 - Journal of Materials Research DA - 2007/// PY - 2007/// DO - 10.1557/jmr.2007.0409 VL - 22 IS - 11 SP - 3058-3066 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-36549089117&partnerID=MN8TOARS ER - TY - JOUR TI - In situ synthesis and properties of Ti 3AlC 2/TiB 2 composites AU - Li, C. AU - Li, M. AU - Zhou, Y. AU - Zhang, J. AU - He, L. T2 - Journal of the American Ceramic Society AB - In order to improve the mechanical properties of Ti 3 AlC 2 , near‐fully dense Ti 3 AlC 2 /TiB 2 composites were synthesized using Ti, Al, graphite, and B 4 C powders as the initial materials. Compared with monolithic Ti 3 AlC 2 , the composites exhibit a much higher strength (for the compressive strength, from initial 723 MPa to maximal 2205 MPa; for flexural strength, from initial 340 MPa to maximal 861 MPa), and the strengthening effect can be held at least up to 1100°C. Moreover, besides the enhancement of the elastic modulus and hardness of Ti 3 AlC 2 , the introduction of a TiB 2 phase makes a positive contribution to its electrical conductivity. DA - 2007/// PY - 2007/// DO - 10.1111/j.1551-2916.2007.01954.x VL - 90 IS - 11 SP - 3615-3620 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-35948964516&partnerID=MN8TOARS ER - TY - JOUR TI - Elastic and thermal properties of Zr2 Al3 C4: Experimental investigations and ab initio calculations AU - He, L.F. AU - Wang, J.Y. AU - Bao, Y.W. AU - Zhou, Y.C. T2 - Journal of Applied Physics AB - This article presents the results of combined experimental and theoretical studies of elastic and thermal properties of Zr2Al3C4 carbide. The full set of second order elastic constants, bulk modulus, shear modulus, and Young’s modulus of Zr2Al3C4 were calculated and compared with those of Zr3Al3C5 and ZrC. The experimentally measured Young’s modulus and shear modulus are in good agreement with theoretical ones. The calculated Debye temperature from elastic constants of Zr2Al3C4 is 830 K, which is slightly higher than that of Zr3Al3C5, and exhibits pronounced enhancement in comparison with that of ZrC. The highest Debye temperature of Zr2Al3C4 is related with its highest specific stiffness, i.e., the stiffness-to-weight ratio. The heat capacity and thermal conductivity of Zr2Al3C4 were measured by means of the flash method. The thermal conductivity of Zr2Al3C4 decreases with increasing temperature, for instance the values at room temperature and 1600 K are 15.5 and 10.1 W/m K, respectively. The investigations provide information on elastic and thermal properties of Zr2Al3C4 with promising high temperature applications. DA - 2007/// PY - 2007/// DO - 10.1063/1.2773679 VL - 102 IS - 4 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34548424959&partnerID=MN8TOARS ER - TY - JOUR TI - Synthesis and oxidation of Zr3Al3C5 powders AU - He, L.F. AU - Zhou, Y.C. AU - Bao, Y.W. AU - Wang, J.Y. AU - Li, M.S. T2 - International Journal of Materials Research DA - 2007/// PY - 2007/// VL - 98 IS - 1 SP - 3-9 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33847074954&partnerID=MN8TOARS ER - TY - JOUR TI - Burn-up characteristics of a light-water-cooled nuclear reactor of natural uranium and beryllium AU - Hayes, RB T2 - Journal of Physical & Natural Science DA - 2007/// PY - 2007/// VL - 1 IS - 2 SP - 1–11 ER - TY - JOUR TI - Correlation between Ingot Diameter and Crystal Properties of CdZnTe:In Grown by the Modified Bridgman Method AU - Yang, Ge AU - Jie, Wanqi AU - Wang, Tao AU - Li, Guoqiang AU - Li, Wenwei AU - Hua, Hui T2 - Crystal Growth & Design AB - The compound semiconductor CdZnTe:In is the most promising material for room temperature nuclear radiation detectors. Enlarging the diameter of CdZnTe:In ingot can improve the yield and reduce the production cost, which, however, affects the properties of CdZnTe:In to some extent. Recently, CdZnTe:In ingots of 30 mm and 60 mm diameter were grown by the modified vertical Bridgman method in our laboratory. The crystal properties of both ingots were compared according to etch pit density (EPD) of dislocation, X-ray rocking curve, IR transmission spectra, and photoluminescence (PL) spectra. For the CdZnTe:In ingot of 30 mm diameter, the EPD of dislocation was 2.1 × 104 cm-2, and was up to 1.9 × 105 cm-2 when the CdZnTe:In ingot diameter was enlarged to 60 mm. The full width at half-maximum (FWHM) of X-ray rocking also increased from 0.02014° to 0.02864° at the same time. The two phenomena imply that the crystalline quality of CdZnTe:In deteriorated with the enlarging of the ingot diameter. In addition, when the CdZnTe:In ingot diameter was varied from 30 to 60 mm, the average IR transmittance increased from 27 to 33%. The augmentation of dislocation was responsible for the change, which was confirmed by the improvement of the intensity of the dislocation-related D peak in the PL spectra. DA - 2007/2// PY - 2007/2// DO - 10.1021/cg060464u VL - 7 IS - 2 SP - 435-438 J2 - Crystal Growth & Design LA - en OP - SN - 1528-7483 1528-7505 UR - http://dx.doi.org/10.1021/cg060464u DB - Crossref ER - TY - JOUR TI - Effect of annealing on the residual stress and strain distribution in CdZnTe wafers AU - Zeng, Dongmei AU - Jie, Wanqi AU - Zha, Gangqiang AU - Wang, Tao AU - Yang, Ge T2 - Journal of Crystal Growth AB - The effect of annealing on residual stress and strain distribution in CdZnTe wafers was studied based using an X-ray diffraction (XRD) method. The results proved the effectiveness of annealing on the reduction of the residual stress and strain. By the means of transmission electron microscopy (TEM) and infrared (IR) transmission analyses, it was found that dislocation gliding, decreases in the size of the Te precipitates, dispersing of Te precipitates, composition homogenization, and point defects recombination contributed to a reduction of the residual stress and strain during annealing of the wafer. Additionally, the larger residual stress in CdZnTe wafers introduced bigger lattice misfits. Thus, for more the residual stress and strain in the CdZnTe wafer, the IR transmission will be lowered. DA - 2007/7// PY - 2007/7// DO - 10.1016/j.jcrysgro.2007.04.021 VL - 305 IS - 1 SP - 50-54 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2007.04.021 DB - Crossref KW - annealed KW - lattice misfit KW - precipitate KW - residual stress and strain KW - X-ray diffraction KW - CdZnTe KW - semiconducting II-VT materials ER - TY - JOUR TI - Study on the behaviors of impurities in cadmium zinc telluride AU - Wang, Tao AU - Jie, Wanqi AU - Zhang, Jijun AU - Yang, Ge AU - Zeng, Dongmei AU - Xu, Yadong AU - Ma, Shuying AU - Hua, Hui AU - He, Ke T2 - Journal of Crystal Growth AB - Abstract Impurities in three cadmium zinc telluride (Cd 1− x Zn x Te or CZT) ingots grown by the modified vertical Bridgman (MVB) method were examined by using inductively coupled plasma mass spectrometry (ICP-MS). The distribution and segregation of impurities along the CZT ingots were found to vary with the concentration and the growth conditions. Photoluminescence (PL) and voltage–current measurements were performed to evaluate the effects of the impurities on the optical and electrical properties. The red shift of the ( D 0 , X ) and DAP positions and the broadening of the DAP band in PL spectrum were observed in the high-impurity CZT ingot. The voltage–current measurement shows a higher resistivity when the impurity concentration was increased. The above results imply that the high-impurity CZT ingot was highly compensated. DA - 2007/6// PY - 2007/6// DO - 10.1016/j.jcrysgro.2007.03.013 VL - 304 IS - 2 SP - 313-316 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2007.03.013 DB - Crossref KW - impurities KW - segregation KW - Bridgman technique KW - semiconducting II-VI materials ER - TY - JOUR TI - Utilization of two-dimensional deterministic transport methods for analysis of pebble-bed reactors AU - Tyobeka, Bismark AU - Ivanov, Kostadin AU - Pautz, Andreas T2 - Annals of Nuclear Energy AB - Abstract This paper presents an overview of the investigations on the need for deterministic transport methods for the analysis of pebble-bed reactors. To account for the transport effects present in the PBMR design that cannot be modeled accurately with the diffusion theory, a two-dimensional neutronics solver based on transport theory is implemented in the Penn State NEM-THERMIX code system. The necessity of equipping neutronics analysis codes with neutron transport theory capability is investigated along with the challenge to accomplish this in an efficient and versatile manner. For this purpose a time-dependent two-dimensional neutron transport code DORT is utilized as a first step. The developed benchmark test cases, based on the PBMR 268 MW design, are used for this work and results from the comparative analyzes of these test cases are presented. The results show clearly that even in steady-state calculations, the differences between diffusion and transport-based methods in analyzing the PBMR are observed and need to be addressed. DA - 2007/5// PY - 2007/5// DO - 10.1016/j.anucene.2007.01.014 VL - 34 IS - 5 SP - 396-405 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2007.01.014 DB - Crossref ER - TY - JOUR TI - Challenges in coupled thermal–hydraulics and neutronics simulations for LWR safety analysis AU - Ivanov, Kostadin AU - Avramova, Maria T2 - Annals of Nuclear Energy AB - The simulation of nuclear power plant accident conditions requires three-dimensional (3D) modeling of the reactor core to ensure a realistic description of physical phenomena. The operational flexibility of Light Water Reactor (LWR) plants can be improved by utilizing accurate 3D coupled neutronics/thermal–hydraulics calculations for safety margins evaluations. There are certain requirements to the coupling of thermal–hydraulic system codes and neutron-kinetics codes that ought to be considered. The objective of these requirements is to provide accurate solutions in a reasonable amount of CPU time in coupled simulations of detailed operational transient and accident scenarios. These requirements are met by the development and implementation of six basic components of the coupling methodologies: ways of coupling (internal or external coupling); coupling approach (integration algorithm or parallel processing); spatial mesh overlays; coupled time-step algorithms; coupling numerics (explicit, semi-implicit and implicit schemes); and coupled convergence schemes. These principles of the coupled simulations are discussed in details along with the scientific issues associated with the development of appropriate neutron cross-section libraries for coupled code transient modeling. The current trends in LWR nuclear power generation and regulation as well as the design of next generation LWR reactor concepts along with the continuing computer technology progress stimulate further development of these coupled code systems. These efforts have been focused towards extending the analysis capabilities as well as refining the scale and level of detail of the coupling. This article analyses the coupled phenomena and modeling challenges on both global (assembly-wise) and local (pin-wise) levels. The issues related to the consistent qualification of coupled code systems as well as their application to different types of LWR transients are presented. Finally, the advances in numerical and computation techniques for coupled code simulations are summarized with outlining remaining challenges. DA - 2007/6// PY - 2007/6// DO - 10.1016/j.anucene.2007.02.016 VL - 34 IS - 6 SP - 501-513 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2007.02.016 DB - Crossref ER - TY - JOUR TI - Comparison via parallel performance models of angular and spatial domain decompositions for solving neutral particle transport problems AU - Fischer, James W. AU - Azmy, Y.Y. T2 - Progress in Nuclear Energy AB - A previously reported parallel performance model for angular domain decomposition (ADD) of the discrete ordinates approximation for solving multidimensional neutral particle transport problems is revisited for stronger validation. Three communication schemes, native MPI, the bucket algorithm, and the distributed bucket algorithm, are included in the validation exercise that is successfully conducted on a Beowulf cluster. The parallel component of the parallel performance model is largely independent of the communication scheme, in contrast with the communication component that is strongly dependent on the global reduce algorithm. Correct trends for each component and each communication scheme are measured for the Arbitrarily High Order Transport (AHOT) code, thus validating the performance models. Furthermore, extensive experiments illustrate the superiority of the bucket algorithm, in the sense that it incurs a smaller communication penalty compared to the native MPI and distributed bucket algorithms. The primary question addressed in this work is for a given problem size, which domain decomposition scheme, angular or spatial, is best suited to parallelize discrete ordinates methods on a specific computational platform? We address this question for three-dimensional applications via parallel performance models for the abovementioned ADD, and a previously constructed and validated spatial domain decomposition (SDD) model. The constructed parallel performance models include parameters specifying the problem size and system performance. We conclude that for large problems the parallel component dwarfs the communication component even on moderately large numbers of processors. The main advantages of SDD are (a) scalability to higher numbers of processors of the order of the number of computational cells; (b) smaller memory requirement; (c) better performance than ADD on high-end platforms and large number of processors. On the other hand, the main advantages of ADD are (a) perfect load balance; (b) simple implementation, even on unstructured grids; (c) better performance than SDD on medium- and low-end platforms and large number of discrete ordinates. It follows that programmers and users of discrete ordinates codes must carefully select the appropriate domain decomposition method for the class of problems and multiprocessor platforms they wish to target. DA - 2007/1// PY - 2007/1// DO - 10.1016/j.pnucene.2006.08.003 VL - 49 IS - 1 SP - 37-60 J2 - Progress in Nuclear Energy LA - en OP - SN - 0149-1970 UR - http://dx.doi.org/10.1016/j.pnucene.2006.08.003 DB - Crossref KW - neutral particle transport KW - discrete ordinates KW - parallel mesh sweep KW - multiprocessing KW - spatial domain decomposition KW - angular domain decomposition ER - TY - JOUR TI - Mechanical behavior of nanocrystalline copper AU - Guduru, Ramesh K. AU - Murty, K. Linga AU - Youssef, Khaled M. AU - Scattergood, Ronald O. AU - Koch, Carl C. T2 - Materials Science and Engineering: A AB - The mechanical behavior of nanocrystalline materials has been studied extensively for the past few years. Recent studies on artifact-free materials with nanosize grains less than 100 nm have been very fruitful. These nanograined metals have exhibited very high strengths with reasonably good ductility. While there have been a large number of studies on hardness and strength characteristics, studies on strain rate sensitivity (SRS) are very limited. We describe here some of our recent work in characterizing SRS as well as activation volumes of nanograined copper using different testing procedures. These tests have been carried out under iso-strain rate and iso-structural conditions. DA - 2007/8// PY - 2007/8// DO - 10.1016/j.msea.2006.07.165 VL - 463 IS - 1-2 SP - 14-21 J2 - Materials Science and Engineering: A LA - en OP - SN - 0921-5093 UR - http://dx.doi.org/10.1016/j.msea.2006.07.165 DB - Crossref KW - nanocrystalline materials KW - copper KW - mechanical behavior KW - strain rate sensitivity KW - ductility KW - activation volume ER - TY - JOUR TI - WITHDRAWN: Structural materials for Gen-IV nuclear reactors: Challenges and opportunities AU - Murty, K.L. AU - Charit, I. T2 - Journal of Nuclear Materials AB - This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.jnucmat.2007.09.029 J2 - Journal of Nuclear Materials LA - en OP - SN - 0022-3115 UR - http://dx.doi.org/10.1016/j.jnucmat.2007.09.029 DB - Crossref ER - TY - CONF TI - Steady-state nuclear analysis methods at global nuclear fuel, invited AU - Palmtag, S. AU - Mertyurek, U. AU - Moore, B.R. AU - Sugawara, M. AU - Toishigawa, A. C2 - 2007/// C3 - Transactions of the American Nuclear Society DA - 2007/// VL - 97 SP - 557-558 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-55349115707&partnerID=MN8TOARS ER - TY - CONF TI - Material property effect in steam explosion energetics: Revisited AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-42249093642&partnerID=MN8TOARS ER - TY - CONF TI - Thermal-hydraulic performance of lead-bismuth eutectic in a straight-tube and a U-tube heat exchangers AU - Weimin, M. AU - Karbojian, A. AU - Sehgal, B.R. AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349134568&partnerID=MN8TOARS ER - TY - CONF TI - Simulation of core melt pool formation in a reactor pressure vessel lower head using an effective convectivity model AU - Tran, C.-T. AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44449162101&partnerID=MN8TOARS ER - TY - CONF TI - RELAP5 and TRACE codes comparison and validation under steady-state and transient conditions on the basis of NUPEC data AU - Suchoszek, J. AU - Cadinu, F. AU - Kozlowski, T. AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349127315&partnerID=MN8TOARS ER - TY - CONF TI - Evaluation of coupled codes RELAP5/PARCS capability for BWR global stability prediction AU - Kozlowski, T. AU - Roshan, S. AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349116232&partnerID=MN8TOARS ER - TY - JOUR TI - Aerobreakup in disturbed subsonic and supersonic flow fields AU - Theofanous, T. G. AU - Li, G. J. AU - Dinh, T. N. AU - Chang, C. H. T2 - Journal of Fluid Mechanics AB - This work concerns the breakup of millimetre-scale liquid droplets in gaseous flow fields that are disturbed from free-stream conditions by the presence of solid obstacles or other drops. A broad range of flow conditions is considered – from subsonic to supersonic, from highly rarefied to ambient pressures, and from fixed cylindrical obstacles to free liquid droplets (as obstacles). The liquid is water or tributyl phosphate, a water-like low-viscosity fluid of very low vapour pressure. We present data on deformation and breakup regimes, and, aided by numerical simulations, we discuss governing mechanisms and the time scaling of these events. Thereby a methodology is demonstrated for conveniently forecasting first-order behaviours in disturbed flow fields more generally. The highly resolved images lend themselves to testing/benchmarking numerical simulations of interfacial flows. These results, along with the experimental capability developed, constitute one of the key building blocks for our overall long-term aim towards predicting ultimate particle-size distributions from such intense aerodynamic interactions involving very large quantities of Newtonian and viscoelastic liquids. DA - 2007/11/23/ PY - 2007/11/23/ DO - 10.1017/S0022112007008853 VL - 593 SP - 131-170 J2 - J. Fluid Mech. LA - en OP - SN - 0022-1120 1469-7645 UR - http://dx.doi.org/10.1017/S0022112007008853 DB - Crossref ER - TY - CONF TI - A study on effects of debris bed prototypicality on coolability AU - Weimin, M. AU - Dinh, T.-N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349091618&partnerID=MN8TOARS ER - TY - CONF TI - Dynamics and preconditioning in a single drop vapor explosion AU - Hansson, R.C. AU - Park, H.S. AU - Dinh, T.N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349165747&partnerID=MN8TOARS ER - TY - CONF TI - An analytical study of mechanisms that govern debris packing in a LWR severe accident AU - Kudinov, P. AU - Dinh, N. C2 - 2007/// C3 - Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12 DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44349098203&partnerID=MN8TOARS ER - TY - PAT TI - Plasma Generation And Control Using A Dual Frequency Rf Source AU - C, Shannon Steven AU - Alex, Paterson AU - Theodoros, Panagopoulos AU - P, Holland John AU - Dennis, Grimard AU - Yashushi, Takakura C2 - 2007/1/11/ DA - 2007/1/11/ PY - 2007/1/11/ UR - https://www.lens.org/001-723-961-714-703 ER - TY - PAT TI - Plasma Control Using Dual Cathode Frequency Mixing AU - C, Shannon Steven AU - S, Grimard Dennis AU - Theodoros, Panagopoulos AU - J, Hoffman Daniel AU - G, Chafin Michael AU - S, Detrick Troy AU - Alexander, Paterson AU - Jingbao, Liu AU - Taeho, Shin AU - Y, Pu Bryan C2 - 2007/1/4/ DA - 2007/1/4/ PY - 2007/1/4/ UR - https://www.lens.org/198-151-282-809-229 ER - TY - JOUR TI - BiodosEPR-2006 Meeting: Acute dosimetry consensus committee recommendations on biodosimetry applications in events involving uses of radiation by terrorists and radiation accidents AU - Alexander, George A. AU - Swartz, Harold M. AU - Amundson, Sally A. AU - Blakely, William F. AU - Buddemeier, Brooke AU - Gallez, Bernard AU - Dainiak, Nicholas AU - Goans, Ronald E. AU - Hayes, Robert B. AU - Lowry, Patrick C. AU - Noska, Michael A. AU - Okunieff, Paul AU - Salner, Andrew L. AU - Schauer, David A. AU - Trompier, Francois AU - Turteltaub, Kenneth W. AU - Voisin, Phillipe AU - Wiley, Albert L., Jr. AU - Wilkins, Ruth T2 - Radiation Measurements AB - In the aftermath of a radiological terrorism incident or mass-casualty radiation accident, first responders and receivers require prior guidance and pre-positioned resources for assessment, triage and medical management of affected individuals [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA]. Several recent articles [Dainiak, N., Waselenko, J.K., Armitage, J.O., MacVittie, T.J., Farese, A.M., 2003. The hematologist and radiation casualties. Hematology (Am. Soc. Hematol. Educ. Program) 473–496; Waselenko, J.K., MacVittie, T.J., Blakely, W.F., Pesik, N., Wiley, A.L., Dickerson, W.E., Tsu, H., Confer, D.L., Coleman, C.N., Seed, T., Lowry, P., Armitage, J.O., Dainiak, N., Strategic National Stockpile Radiation Working Group, 2004. Medical management of the acute radiation syndrome: recommendations of the Strategic National Stockpile Radiation Working Group. Ann. Intern. Med. 140(12), 1037–1051; Blakely, W.F., Salter, C.A., Prasanna, P.G., 2005. Early-response biological dosimetry—recommended countermeasure enhancements for mass-casualty radiological incidents and terrorism. Health Phys. 89(5), 494–504; Goans, R.E., Waselenko, J.K., 2005. Medical management of radiation casualties. Health Phys. 89(5), 505–512; Swartz, H.M., Iwasaki, A., Walczak, T., Demidenko, E., Salikhov, I., Lesniewski, P., Starewicz, P., Schauer, D., Romanyukha, A., 2005. Measurements of clinically significant doses of ionizing radiation using non-invasive in vivo EPR spectroscopy of teeth in situ. Appl. Radiat. Isot. 62, 293–299; Weisdorf, D., Chao, N., Waselenko, J.K., Dainiak, N., Armitage, J.O., McNiece, I., Confer, D., 2006. Acute radiation injury: contingency planning for triage, supportive care, and transplantation. Biol. Blood Marrow Transplant. 12(6), 672–682], national [National Council of Radiation Protection and Measurements (NCRP), 1994. Management of persons accidentally contaminated with radionuclides. NCRP Report No. 65, Bethesda, Maryland, USA; NCRP, 2001. Management of terrorist events involving radioactive material. NCRP Report No. 138, Bethesda, Maryland, USA; NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA] and international [IAEA, 2005. Generic procedures for medical response during a nuclear or radiological emergency. EPR-Medical 2005, IAEA, Vienna, Austria] agencies have reviewed strategies for acute-phase biodosimetry. Consensus biodosimetric guidelines include: (a) clinical signs and symptoms, including peripheral blood counts, time to onset of nausea and vomiting and presence of impaired cognition and neurological deficits, (b) radioactivity assessment, (c) personal and area dosimetry, (d) cytogenetics, (e) in vivo electron paramagnetic resonance (EPR) and (f) other dosimetry approaches (i.e. blood protein assays, etc.). Emerging biodosimetric technologies may further refine triage and dose assessment strategies. However, guidance is needed regarding which biodosimetry techniques are most useful for different radiological scenarios and consensus protocols must be developed. The Local Organizing Committee for the Second International Conference on Biodosimetry and Seventh International Symposium on EPR Dosimetry and Applications (BiodosEPR-2006 Meeting) convened an Acute Dosimetry Consensus Committee composed of national and international experts to: (a) review the current literature for biodosimetry applications for acute-phase applications in radiological emergencies, (b) describe the strengths and weaknesses of each technique, (c) provide recommendations for the use of biodosimetry assays for selected defined radiation scenarios, and (d) develop protocols to apply these recommended biological dosimetry techniques with currently available supplies and equipment for first responders. The Acute Dosimetry Consensus Committee developed recommendations for use of a prioritized multiple-assay biodosimetric-based strategy, concluding that no single assay is sufficiently robust to address all of the potential radiation scenarios including management of mass casualties and diagnosis for early medical treatment. These recommendations may be used by first responders/first receivers that span time-windows of (i.e. 0–5 days) after the radiological incident for three radiological scenarios including: (a) radiation exposure device (RED), (b) radiological dispersal device (RDD), and (c) an improvised (or otherwise acquired) nuclear device (IND). Consensus protocols for various bioassays (i.e. signs and symptoms recording, bioassay sampling for radioactivity analysis, nail-clipping sampling for EPR analysis and blood collection for hematology, cytogenetics, and blood chemistry analyses) are presented as Appendix materials. As stated in NCRP Commentary No. 19 [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA], multi-parameter triage (i.e. time to vomiting, lymphocyte kinetics, and other biodosimetry indicators) offers the current best strategy for early assessment of absorbed dose. DA - 2007/7// PY - 2007/7// DO - 10.1016/j.radmeas.2007.05.035 VL - 42 IS - 6-7 SP - 972-996 J2 - Radiation Measurements LA - en OP - SN - 1350-4487 UR - http://dx.doi.org/10.1016/j.radmeas.2007.05.035 DB - Crossref KW - acute dosimetry KW - radiological triage KW - dose assessment KW - electron paramagnetic resonance KW - cytogenetic biodosimetry KW - medical management of radiation casualties ER - TY - JOUR TI - Electron spin relaxation of radicals in irradiated tooth enamel and synthetic hydroxyapatite AU - Sato, Hideo AU - Filas, Benjamen A. AU - Eaton, Sandra S. AU - Eaton, Gareth R. AU - Romanyukha, Alex A. AU - Hayes, Robert AU - Rossi, Alexandre M. T2 - Radiation Measurements AB - Abstract Spin–lattice relaxation times, T 1 , for EPR signals created by irradiation of tooth enamel or carbonate-doped hydroxyapatite were studied by three-pulse inversion recovery and long-pulse saturation recovery. The recovery curves were modeled as the sum of two log-normal distributions of relaxation times. The dominant component in the EPR signal for tooth samples is assigned to CO 2 - replacing phosphate (B-sites) in the hydroxyapatite matrix. For this component the center of the T 1 distribution was 1.4 – 1.6 μ s at 294 K, and did not vary significantly with radiation dose or the source of the sample. The smaller, slower relaxing, component of the signals from the tooth samples had a T 1 distribution centered at 30 – 60 μ s and is assigned to an organic radical ( g ∼ 2.0045 ) . At 294 K the spin–spin relaxation time T 2 measured by two-pulse echo decay was dominated by motion of the CO 2 - and was independent of dose. The dose independence of T 1 and T 2 at ambient temperature provides the basis for using dose-independent microwave powers to record dosimetric tooth signals at microwave powers above the linear response regime. DA - 2007/7// PY - 2007/7// DO - 10.1016/j.radmeas.2007.05.048 VL - 42 IS - 6-7 SP - 997-1004 J2 - Radiation Measurements LA - en OP - SN - 1350-4487 UR - http://dx.doi.org/10.1016/j.radmeas.2007.05.048 DB - Crossref ER - TY - JOUR TI - Global Modeling of Magnetized Capacitive Discharges AU - Carter, Mark D. AU - Hoffman, Dan AU - Shannon, Steve AU - Ryan, Philip M. AU - Buchberger, D. T2 - IEEE Transactions on Plasma Science AB - Capacitive reactors for semiconductor processing must simultaneously balance many physical phenomena with engineering constraints to achieve the desired processing properties. Important phenomena include electromagnetic RF propagation, gas ionization, plasma heating, plasma transport, and nonlinear sheath effects. Constraints are driven by process uniformity, radical production, thermal control, and reactor-component lifetime. These phenomena and constraints are often modeled in isolation; however, in a real system, they can interact in ways that are not easily foreseen. It is highly desirable to have global models that can provide relatively quick feedback for the proposed modifications to these systems. While an approach based on fundamental physics models is highly desirable whenever possible, the system can quickly become too complicated for quick design evaluations. In this paper, we explore the interaction between several processes by combining fundamental physics models when reasonable, with simplified, heuristic, or even empirical models for processes that are difficult to model from first principles. The goal is to understand the interaction between these processes in a global system without becoming overly encumbered by details in the individual components of the model. We study the effects of static magnetic field on plasma transport and electromagnetic effects arising at high RF frequency. We also change the RF-coupled power and ionization efficiency in a simplified 2-D model geometry to contrast the various effects. We find that discharges with very high frequency and high plasma density can exhibit localized nulls in the RF fields caused by electromagnetic-propagation effects in the sheath region. We find that relatively low static magnetic fields can modify the radial-plasma density profiles. Good agreement is found between the radial-plasma profiles given by the model and those measured in an experiment where the currents in two concentric coils near the plasma are the only variables. DA - 2007/10// PY - 2007/10// DO - 10.1109/TPS.2007.906124 VL - 35 IS - 5 SP - 1413-1419 J2 - IEEE Trans. Plasma Sci. OP - SN - 0093-3813 UR - http://dx.doi.org/10.1109/TPS.2007.906124 DB - Crossref KW - capacitance KW - electromagnetic analysis KW - electromagnetic KW - coupling KW - electromagnetic fields KW - electromagnetic heating KW - electromagnetic measurements KW - electromagnetic propagation KW - in absorbing media KW - electromagnetic propagation in anisotropic media KW - electromagnetic propagation in dispersive media KW - electromagnetic propagation in nonhomogeneous media KW - electromagnetic propagation in nonlinear media KW - electromagnetic propagation in plasma media KW - electromagnetic surface waves KW - magnetic confinement KW - magnetic field effects KW - magnetic fields KW - perpendicular KW - magnetic anisotropy KW - plasma applications KW - plasma confinement KW - plasma control KW - plasma devices KW - plasma generation KW - plasma heating KW - plasma materials-processing applications KW - plasma measurements KW - plasma properties KW - plasmas KW - plasma sheaths KW - plasma waves ER - TY - CONF TI - Development of a Modern Pressurized Water Reactor Simulator: Instrumentation, Design and Data Acquisition AU - Osborne, Dustin R. AU - Hou, Jia AU - Graves, Gary AU - Miller, Laurence F. AB - A method is proposed for redesigning an existing pressurized water reactor simulator with modern control and data acquisition electronics along with a custom designed GUI. This system will be used in providing instruction to undergraduate and graduate Nuclear Engineers on the operation of a Pressurized Water Reactor and for simulation of nuclear criticality events. This system will allow users from across the world to access the simulator in order to run modeling and optimization experiments for assisting in the future development of reactor technology and the development of this simulator project. C2 - 2007/10// C3 - 2007 IEEE Nuclear Science Symposium Conference Record DA - 2007/10// DO - 10.1109/nssmic.2007.4436393 PB - Institute of Electrical & Electronics Engineers (IEEE) ER - TY - PAT TI - Gamma ray detectors having improved signal-to-noise ratio and related systems and methods for analyzing materials in an oil well AU - Garnder, R. P. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - JOUR TI - Design and preliminary Monte Carlo calculations of an active Compton-suppressed LaBr3(Ce) detector system for TRU assay in remote-handled wastes AU - Kulisek, J. A. AU - Hartwell, J. K. AU - McIlwain, M. E. AU - Gardner, R. P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Recent studies indicate LaBr3(Ce) scintillating detectors have desirable attributes, such as room temperature operability and excellent energy resolution, which may make them viable alternatives as primary detectors (PD) in a Compton suppression spectrometer (CSS) used for remote-handled transuranic (RH-TRU) waste assay. A CSS with a LaBr3(Ce) PD has been designed and its expected performance evaluated using Monte Carlo analysis. These results indicate that this detector will have a relatively high Compton-suppression capability, with greater suppression ability for large angle-scattered photons in the PD. DA - 2007/9/21/ PY - 2007/9/21/ DO - 10.1016/j.nima.2007.05.060 VL - 580 IS - 1 SP - 226-229 SN - 1872-9576 KW - gamma-ray spectrometry KW - compton suppression KW - scintillation detectors KW - MCNP ER - TY - JOUR TI - Using gamma-gamma coincidence measurements to validate Monte Carlo generated detector response functions AU - Metwally, W. A. AU - Gardner, R. P. AU - Sood, A. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS AB - Monte Carlo simulation of gamma-ray transport for the purpose of performing elemental analysis of bulk samples requires the tracking of gamma rays in the sample and also in the detector(s) used. Detector response functions (DRF’s) are an efficient and accurate variance reduction technique that greatly decreases the simulation time by substituting the tracking of gamma rays inside the detector by predefined single energy gamma-ray spectra. These spectra correspond to the average response of the detector for incident gamma rays. DRF’s are generated by Monte Carlo methods and are benchmarked with experimental data. In this work, prompt gamma–gamma coincidence measurements are presented as a way to validate DRF’s for high-energy gamma rays. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.nimb.2007.04.137 VL - 263 IS - 1 SP - 50-53 SN - 0168-583X KW - PGNAA KW - gamma-gamma coincidence KW - detector response functions (DRF's) ER - TY - JOUR TI - The Monte Carlo code CEARCPG for coincidence prompt gamma-ray neutron activation analysis AU - Han, Xiaogang AU - Gardner, Robin P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS AB - Prompt gamma-ray neutron activation analysis (PGNAA) is widely used to determine the elemental composition of bulk samples. The detection sensitivities of PGNAA are often restricted by the inherent poor signal-to-noise ratio (SNR). There are many sources of noise (background) including the natural background, neutron activation of the detector, gamma-rays associated with the neutron source and prompt gamma-rays from the structural materials of the analyzer. Results of the prompt gamma-ray coincidence technique show that it could greatly improve the SNR by removing almost all of the background interferences. The first specific Monte Carlo code (CEARCPG) for coincidence PGNAA has been developed at the Center for Engineering Application of Radioisotopes (CEAR) to explore the capabilities of this technique. Benchmark bulk sample experiments have been performed with coal, sulfur, and mercury samples and indicate that the code is accurate and will be very useful in the design of coincidence PGNAA devices. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.nimb.2007.04.238 VL - 263 IS - 1 SP - 320-325 SN - 0168-583X KW - coincidence KW - PGNAA KW - Monte Carlo KW - CEARCPG ER - TY - JOUR TI - Non-poisson counting statistics of a hybrid G-M counter dead time model AU - Lee, Sang Hoon AU - Jae, Moosung AU - Gardner, Robin P. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS AB - The counting statistics of a G–M counter with a considerable dead time event rate deviates from Poisson statistics. Important characteristics such as observed counting rates as a function true counting rates, variances and interval distributions were analyzed for three dead time models, non-paralyzable, paralyzable and hybrid, with the help of GMSIM, a Monte Carlo dead time effect simulator. The simulation results showed good agreements with the models in observed counting rates and variances. It was found through GMSIM simulations that the interval distribution for the hybrid model showed three distinctive regions, a complete cutoff region for the duration of the total dead time, a degraded exponential and an enhanced exponential regions. By measuring the cutoff and the duration of degraded exponential from the pulse interval distribution, it is possible to evaluate the two dead times in the hybrid model. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.nimb.2007.04.041 VL - 263 IS - 1 SP - 46-49 SN - 0168-583X KW - G-M counter KW - dead time KW - hybrid model ER - TY - JOUR TI - Simulation of gamma-ray spectrometry of failed TRISO fuel AU - Harp, J. M. AU - Hawari, A. I. AU - Bourham, M. A. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Very High Temperature Reactors (VHTR) utilize the TRISO microsphere as the fundamental fuel unit in the core. To understand better its behavior under in-core conditions, the fuel is irradiated in a controlled environment that resembles anticipated operating conditions. In this work, simulated γ-ray spectra are developed for the fission product gases that are released upon fuel failure. The simulations are based on Monte Carlo calculations of spectra assuming the use of high-purity germaniun (HPGe) and high-pressure xenon (HPXe) detectors. The γ-ray source terms for the simulations are derived from ORIGEN 2.2 fuel depletion calculations. In addition, measured detector resolution information are included in the Monte Carlo simulations to produce realistically broadened spectra. The effect of fission product release processes are incorporated in the simulation by reconstructing the Monte Carlo photon source terms using a specific gas-release model. Consequently, birth and release γ-ray spectra are constructed for the Kr and Xe gaseous fission products. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.04.065 VL - 579 IS - 1 SP - 301-304 SN - 1872-9576 KW - very high temperature reactor KW - TRISO KW - fuel failure KW - fission product release KW - Monte Carlo KW - gamma-ray spectrometry ER - TY - JOUR TI - Performance analysis of the intense slow-positron beam at the NC State University PULSTAR reactor AU - Moxom, J. AU - Hathaway, A. G. AU - Bodnaruk, E. W. AU - Hawari, A. I. AU - Xu, J. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - An intense positron beam, for application in nanophase characterization, is now under construction at the 1 MW PULSTAR nuclear reactor at North Carolina State University (NCSU). A tungsten converter/moderator is used, allowing positrons to be emitted from the surface with energies of a few electron volts. These slow positrons will be extracted from the moderator and formed into a beam by electrostatic lenses and then injected into a solenoidal magnetic field for transport to one of three experimental stations, via a beam switch. To optimize the performance of the beam and to predict the slow-positron intensity, a series of simulations were performed. A specialized Monte-Carlo routine was integrated into the charged-particle transport calculations to allow accounting for the probabilities of positron re-emission and backscattering from multiple-bank moderator/converter configurations. The results indicate that either a two-bank or a four-bank tungsten moderator/converter system is preferred for the final beam design. The predicted slow-positron beam intensities range from nearly 7×108 to 9×108e+/s for the two-bank and the four-bank systems, respectively. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.04.117 VL - 579 IS - 1 SP - 534-537 SN - 0168-9002 KW - slow positron KW - beam KW - nuclear reactor KW - tungsten KW - moderator ER - TY - JOUR TI - Nonlinear weighted flux methods for particle transport problems AU - Roberts, L. AU - Anistratov, D. Y. T2 - TRANSPORT THEORY AND STATISTICAL PHYSICS AB - A new parameterized family of iterative methods for the 1‐D slab geometry transport equation is proposed. The new methods are derived by integrating the transport equation over −1≤μ≤0 and 0≤μ≤1 with weight 1+β|μ|α, where α≥0. The asymptotic diffusion analysis enables us to determine a particular method of this family the solution of which satisfies a good approximation of both the diffusion equation and asymptotic boundary condition in the diffusive regions. Note that none of the α‐weighted nonlinear methods possesses this combination of properties. The convergence properties of the proposed method are similar to the properties of the diffusion‐synthetic acceleration (DSA), quasi‐diffusion, and DSA‐like α‐weighted nonlinear methods. Numerical results are presented to demonstrate the performance of the derived method. DA - 2007/// PY - 2007/// DO - 10.1080/00411450701703647 VL - 36 IS - 7 SP - 589-608 SN - 1532-2424 KW - particle transport equation KW - radiative transfer KW - neutron transport KW - iteration methods ER - TY - JOUR TI - Molecular dynamics simulations of graphite at high temperatures AU - Hehr, Brian D. AU - Hawari, Ayman I. AU - Gillette, Victor H. T2 - NUCLEAR TECHNOLOGY AB - Graphite, a key structural and moderator material in the proposed Generation IV roadmap, is expected to experience irradiation at temperatures up to 1800 K. In this study, a molecular dynamics (MD) code is developed for the purpose of performing atomistic simulations of high-temperature graphite. The MD computations are benchmarked against thermal expansion and mean-squared displacement data, and modifications to the potential energy function are devised as needed to fit experimental measurements. Graphite-specific alterations include a plane-by-plane center-of-mass velocity correction, anisotropy in the potential energy cutoff function, and temperature-dependent parameterization of the interatomic potential. The refined MD model is then employed to investigate the threshold displacement energy at temperatures of 300 and 1800 K. It was found that the threshold displacement energy depends strongly on the knock-on direction, yet the angle-averaged threshold energy exhibits relatively little variation with temperature. DA - 2007/11// PY - 2007/11// DO - 10.13182/NT07-A3897 VL - 160 IS - 2 SP - 251-256 SN - 1943-7471 KW - VHTR KW - graphite KW - molecular dynamics ER - TY - JOUR TI - Implementation of a prototype slow positron beam at the NC State University PULSTAR reactor AU - Hathaway, A. G. AU - Skalsey, M. AU - Frieze, W. E. AU - Vallery, R. S. AU - Gidley, D. W. AU - Hawari, A. I. AU - Xu, J. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Abstract A prototype beam system was designed and tested to verify the potential of utilizing the North Carolina State University PULSTAR reactor in generating slow positrons. An annealed tungsten converter/moderator was placed at the end of beam tube ♯6 near the PULSTAR core and surrounded by 0.5-mm-thick cadmium cover. Fission and cadmium capture γ-rays were used to drive pair production reactions in the tungsten. The positrons emitted from tungsten were electrostatically focused and guided using a magnetic solenoid until they reached the exit of the biological shield. An aluminum plate that was placed near the exit served as an annihilation target for the positrons. A coincidence counting system was set up to measure the true coincidence rate of the 511 keV annihilation photons that are produced once the slow positrons strike the aluminum target. The data demonstrated the production and control of slow positrons at a rate greater than 10 7 e + /s. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.03.036 VL - 579 IS - 1 SP - 538-541 SN - 0168-9002 KW - slow positrons KW - intense positron beam KW - annihilation KW - nuclear reactor ER - TY - JOUR TI - Analysis of the impact of random summing on passive assay of pebble bed reactor fuel using gamma-ray spectrometry AU - Chen, J. AU - Hawari, A. I. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Pebble bed reactors (PBR) are characterized by multi-pass fuel systems in which spherical fuel pebbles are circulated through the core until they reach a proposed burnup limit. The fuel is assayed on-line to ensure that the burnup limit is not breached. However, random summing effects can impact the response of the burnup measurement system and result in distortions that degrade the accuracy of the assay results. Monte Carlo analysis was performed to estimate the magnitude and effect of random summing on the absolute and relative indicators that have been identified as usable in on-line assay. For a throughput rate of 105 counts/s and trapezoidal pulse shaping of the signals, the results show that absolute indicators suffer from severe distortions due to this effect. Relative indicators are found to be resistant to random summing with the deviation in the ratio of peak areas remaining less than 5–15% depending on pulse width. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.04.064 VL - 579 IS - 1 SP - 297-300 SN - 0168-9002 KW - pebble bed reactor KW - burnup KW - nuclear fuel KW - gamma-ray KW - spectrometry KW - Monte Carlo KW - germanium detector KW - random summing ER - TY - JOUR TI - An ultracold neutron source at the NC state university PULSTAR reactor AU - Korobkna, E. AU - Wehring, B. W. AU - Hawari, A. I. AU - Young, A. R. AU - Huffman, P. R. AU - Golub, R. AU - Xu, Y. AU - Palmquist, G. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Research and development is being completed for an ultracold neutron (UCN) source to be installed at the PULSTAR reactor on the campus of North Carolina State University (NCSU). The objective is to establish a university-based UCN facility with sufficient UCN intensity to allow world-class fundamental and applied research with UCN. To maximize the UCN yield, a solid ortho-D2 converter will be implemented coupled to two moderators, D2O at room temperature, to thermalize reactor neutrons, and solid CH4, to moderate the thermal neutrons to cold-neutron energies. The source assembly will be located in a tank of D2O in the space previously occupied by the thermal column of the PULSTAR reactor. Neutrons leaving a bare face of the reactor core enter the D2O tank through a 45×45 cm cross-sectional area void between the reactor core and the D2O tank. Liquid He will cool the disk-shaped UCN converter to below 5 K. Independently, He gas will cool the cup-shaped CH4 cold-neutron moderator to an optimum temperature between 20 and 40 K. The UCN will be transported from the converter to experiments by a guide with an inside diameter of 16 cm. Research areas being considered for the PULSTAR UCN source include time-reversal violation in neutron beta decay, neutron lifetime determination, support measurements for a neutron electric-dipole-moment search, and nanoscience applications. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.04.116 VL - 579 IS - 1 SP - 530–533 SN - 0168-9002 KW - ultracold neutrons KW - cold neutrons KW - neutron source KW - nuclear reactor ER - TY - JOUR TI - A Gd-based gaseous electron multiplier detector for neutron scattering applications AU - DiJulio, D. D. AU - Hawari, A. I. AU - Berliner, R. T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - The optimum configuration of a Gaseous Electron Multiplier (GEM) neutron detector using a CsI–Gd–Kapton–Gd–CsI neutron converter is investigated using Monte-Carlo simulations. Neutrons absorbed in the converter produce secondary electrons that are emitted from the CsI layers. The detector can be assembled from multiple modules where each module consists of the neutron converter, several cascaded GEMs and anode pickup plates on both sides. Position sensitive anodes and localization electronics are then used to detect, timestamp and record the resulting signal. For a single GEM module, the performance can be assessed by estimating the secondary electron (SE) leakage from the converter sandwich. The simulations show that the optimum for a single module, double-sided detector would have a neutron converter composed of 0.1 μm CsI on top of 3 μm Gd plated on each side of a 7.5 μm thick Kapton foil. This detector would have a SE yield of approximately 0.6 SE/neutron and neutron absorption of 60%. Significant enhancements of the SE yield can be obtained for detectors composed of multiple modules with thinner Gd converters. The multi-module design allows for enhanced SE leakage from each converter while maintaining the high neutron absorption efficiency of thicker converters and dividing the detector count rate among multiple sets of decoding electronics. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1016/j.nima.2007.04.015 VL - 579 IS - 1 SP - 71-74 SN - 0168-9002 KW - GEM detector KW - neutron scattering KW - neutron detector KW - Gd ER - TY - PAT TI - Gamma ray detectors having improved signal-to-noise ratio and related systems and methods for analyzing bulk materials AU - Gardner, R. P. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - JOUR TI - Determination of activation volume in nanocrystalline Cu using the shear punch test AU - Guduru, R. K. AU - Wong, P. Z. AU - Darling, K. A. AU - Koch, C. C. AU - Murty, K. L. AU - Scattergood, R. O. T2 - ADVANCED ENGINEERING MATERIALS AB - Stress relaxation test (SRT) is very useful to study the dislocation dynamics and thus the deformation behavior. It becomes quite difficult to use conventional testing methods when the material availability is limited. In such instances, miniaturized specimen testing procedures such as shear punch test (SPT) becomes significantly useful for studying the mechanical behavior of materials. Current research deals with a novel SRT method employed on nanocrystalline Cu using SPT to study the deformation mechanism. DA - 2007/10// PY - 2007/10// DO - 10.1002/adem.200700181 VL - 9 IS - 10 SP - 855-859 SN - 1527-2648 ER - TY - JOUR TI - Proceedings of the Symposium on Radiation Effects, Deformation and Phase Transformations in Metals and Ceramics, Organized in Honor of Prof. Monroe S. Wechsler - TMS Annual Meeting, San Antonio, Texas, USA 12-16 March 2006 - Foreword AU - Wechsler, M. S. T2 - Journal of Nuclear Materials DA - 2007/// PY - 2007/// VL - 361 IS - 2-3 SP - XI- ER - TY - JOUR TI - New functionalities of PA6,6 fabric modified by atmospheric pressure plasma and grafted glycidyl methacrylate derivatives AU - Gawish, S. M. AU - Ramadan, A. M. AU - Cornelius, C. E. AU - Bourham, M. A. AU - Matthews, S. R. AU - McCord, M. G. AU - Wafa, D. M. AU - Breidt, F. T2 - TEXTILE RESEARCH JOURNAL AB - Oxidative atmospheric pressure plasma was utilized to activate surface of PA 6,6 fabrics followed by graft copolymerization of glycidyl methacrylate (GMA) and further reacted with triethylene tetramine (TETA), quaternary ammonium chitosan (HTCC) or β-cyclodextrin (β-CD). The inner CD cavity was complexed with some insecticidal perfumes. Modified PA6,6 fabrics were analyzed by differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Antimicrobial activity and insect repelling assay were conducted and showed efficient antimicrobial and insect repelling properties. DA - 2007/2// PY - 2007/2// DO - 10.1177/0040517507076747 VL - 77 IS - 2 SP - 92-104 SN - 1746-7748 KW - PA6,6 fabrics KW - atmospheric plasma KW - inclusion compounds ER - TY - JOUR TI - Characterization of stress rupture behavior of cornmercial-purity-Ti via burst testing AU - Srikant, G. AU - Marple, B. AU - Charit, I. AU - Murty, K. L. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Abstract An understanding of the stress rupture behavior of Ti alloy tubing is of primary importance for structural applications in energy technology. The stress rupture properties were evaluated using burst testing of closed-end, thin-walled tubing at varied test temperatures and internal pressures. The rupture data are correlated using the Larson–Miller parameter. The uniform hoop strains were also measured along with rupture times from which the strain-rates were calculated. These results were fitted to Monkman–Grant relation with the aim of extrapolating to in-service stress levels. The activation energy for creep deformation was calculated from the Arrhenius equation, and the experimental data were analyzed using Dorn parameters. The analysis indicated a transition from a power-law controlled creep regime to power-law breakdown at high stresses. Transmission electron microscopy studies corroborated the transition in mechanism from power-law region to a power-law breakdown region. DA - 2007/8/15/ PY - 2007/8/15/ DO - 10.1016/j.msea.2006.06.145 VL - 463 IS - 1-2 SP - 203-207 SN - 0921-5093 KW - cp-titanium KW - burst testing KW - power-law creep KW - power-law breakdown ER - TY - JOUR TI - The radiation damage database: Section on helium cross section AU - Lu, W. AU - Wechsler, M. S. T2 - JOURNAL OF NUCLEAR MATERIALS AB - Abstract A radiation damage database with emphasis on spallation interactions is described. Currently, the database contains damage energy, displacement, helium, and hydrogen cross sections for 23 elemental targets irradiated by proton and neutron projectiles up to 3.2 GeV. In this paper, the focus is on proton-induced helium cross sections, but it is shown that for high energies (above about 500 MeV) proton- and neutron-induced helium cross sections are almost equal. The cross section calculations were run on the Cascade–Exciton Model code (no options) and also on the Bertini code with three nuclear level-density models and multistage pre-equilibrium model on and off. Calculation and experimental results are compared. For various targets, we tried to determine which code and options give best agreement with experiment. In some cases, such determinations are uncertain, partly because of limited and conflicting experimental information and partly perhaps because of the need for modifications in the codes. DA - 2007/4/15/ PY - 2007/4/15/ DO - 10.1016/j.jnucmat.2006.12.005 VL - 361 IS - 2-3 SP - 282-288 SN - 1873-4820 ER - TY - JOUR TI - The mechanical behavior of multiphase nanocrystalline materials AU - Koch, Carl C. AU - Scattergood, Ronald O. AU - Murty, K. L. T2 - JOM DA - 2007/3// PY - 2007/3// DO - 10.1007/s11837-007-0042-3 VL - 59 IS - 3 SP - 66-70 SN - 1047-4838 ER - TY - JOUR TI - Synergistic effects of interstitial impurities and radiation defects on mechanical characteristics of ferritic steels AU - Charit, I. AU - Seok, C. S. AU - Murty, K. L. T2 - JOURNAL OF NUCLEAR MATERIALS AB - Ferritic steels are generally used in pressure vessels and various reactor support structures in light water reactors. They are known to exhibit radiation embrittlement in terms of decreased toughness and increased ductile–brittle transition temperature as a result of exposure to neutron radiation. The superimposed effects of strain aging due to interstitial impurity atoms on radiation embrittlement were considered first by Wechsler, Hall and others. Here we summarize some of our efforts on the investigation of synergistic effects between interstitial impurity atoms (IIAs) and radiation-induced point defects, which result in interesting effects at appropriate temperature and strain rate conditions. Two materials, a mild steel and a pressure vessel steel (A516 Gr.70), are evaluated using tensile and three-point bend tests. DA - 2007/4/15/ PY - 2007/4/15/ DO - 10.1016/j.jnucmat.2006.12.003 VL - 361 IS - 2-3 SP - 262-273 SN - 0022-3115 ER - TY - JOUR TI - Proceedings of the Symposium on Radiation Effects, Deformation and Phase Transformations in Metals and Ceramics, Organized in Honor of Prof. Monroe S. Wechsler - TMS Annual Meeting, San Antonio, Texas, USA 12-16 March 2006 - Preface AU - Murty, Korukonda L. AU - Mansur, Louis K. AU - Simonen, Edward P. AU - Bajaj, Ram T2 - JOURNAL OF NUCLEAR MATERIALS AB - Microstructures developed in commercial 15-5 PH precipitation-hardened stainless steel after different heat treatments have been studied. In the as received condition, two types of carbides, NbC and M7C3, were present. Age hardening involves initial formation of fine precipitates rich in copper. Conventional transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) studies have revealed the formation of a 9R structure copper precipitates (4 nm) in the samples aged at temperatures below 500 °C. However, at higher temperatures, in addition to the formation of these precipitates, the austenite phase was formed. After ageing at 500 °C for 128 h, M23C6 carbides were observed. The majority of the M23C6 carbides were in the interface of martensitic matrix and retained austenite. A second type of copper precipitate being, spherical in shape, were observed on ageing at 650 °C. TEM and X-ray microanalysis on thin foils and on carbon extraction replicas used for analysing the structure and metallic compounds of these precipitates. The mechanical properties following strain deformation has been carried out using scanning electron microscope (SEM), TEM and HREM. At peak aged, the 15-5 PH alloy exhibit brittle failure, the major fracture mode was cleavage and/or quasicleavage. DA - 2007/4/15/ PY - 2007/4/15/ DO - 10.1016/j.jnucmat.2006.12.002 VL - 361 IS - 2-3 SP - VII-IX SN - 0022-3115 ER - TY - JOUR TI - Thickness and clearance effects in shear punch testing AU - Guduru, Ramesh K. AU - Nagasekhar, Anumalasetty V. AU - Scattergood, Ronald O. AU - Koch, Carl C. AU - Murty, Korukonda L. T2 - ADVANCED ENGINEERING MATERIALS AB - Shear punch testing (SPT) is a miniaturized specimen testing technique and is often used to predict the tensile properties of metals and alloys by testing a small amount of material. In order to rationalize the testing methodology it is necessary to understand the effect of different testing procedure parameters such as specimen thickness and die-punch clearance on the evaluated mechanical properties. We present our understanding of the above parameters on the SPT yield strength using finite element modeling studies in conjunction with our previous experimental results. DA - 2007/3// PY - 2007/3// DO - 10.1002/adem.200600255 VL - 9 IS - 3 SP - 157-160 SN - 1438-1656 ER - TY - JOUR TI - Mechanical properties of electrodeposited nanocrystalline copper using tensile and shear punch tests AU - Guduru, Ramesh Kumar AU - Darling, Kristopher A. AU - Scattergood, Ronald O. AU - Koch, Carl C. AU - Murty, K. L. T2 - JOURNAL OF MATERIALS SCIENCE DA - 2007/7// PY - 2007/7// DO - 10.1007/s10853-006-1095-3 VL - 42 IS - 14 SP - 5581-5588 SN - 0022-2461 ER - TY - JOUR TI - Atmospheric plasma-aided biocidal finishes for nonwoven polypropylene fabrics. II. Functionality of synthesized fabrics AU - Wafa, D. M. AU - Breidt, F. AU - Gawish, S. M. AU - Matthews, S. R. AU - Donohue, K. V. AU - Roe, R. M. AU - Bourham, M. A. T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Atmospheric plasma‐aided graft copolymerization of textile materials provides single or multiple functionality polypropylene (PP) modified fabrics. Biocidal PP's are modified ones to kill or inhibit the growth of microorganisms such as bacteria, molds, and fungi, and insect and tick repelling action. Novel PP biocidal fabrics synthesized by graft copolymerization using plasma‐aided technique (see part I of this study) using antibacterial and insect repellent agents have been tested and evaluated and proved to be antimicrobial, tick repellent, and antistatic. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1911–1917, 2007 DA - 2007/2/5/ PY - 2007/2/5/ DO - 10.1002/app.24042 VL - 103 IS - 3 SP - 1911-1917 SN - 1097-4628 KW - nonwoven PP KW - atmospheric oxygenated helium plasma KW - GMA KW - beta-CD KW - MCT beta-CD KW - HTCC KW - antistatic KW - antimicrobial KW - insect repellent fabrics ER - TY - JOUR TI - Atmospheric plasma-aided biocidal finishes for nonwoven polypropylene fabrics. I. Synthesis and characterization AU - Gawish, S. M. AU - Matthews, S. R. AU - Wafa, D. M. AU - Breidt, F. AU - Bourham, M. A. T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Novel biocidal fabrics were synthesized by the graft copolymerization of glycidyl methacrylate (GMA) onto plasma‐treated nonwoven polypropylene (PP) to produce PP/GMA grafts. Atmospheric oxygenated helium plasma was used to enhance the PP fabrics' initiation before GMA grafting. The grafted PP/GMA epoxide group was reacted with β‐cyclodextrin, monochlorotrizynyl‐β‐cyclodextrins, or a quaternary ammonium chitosan derivative [ N ‐(2 hydroxy propyl) 3‐trimethylammonium chitosan chloride]. Some interesting biocidal agents were complexed into the cyclodextrin (CD) cavity of PP/GMA/CD grafted fabrics. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and optical and scanning electron microscopies were used to characterize the grafted complexed fabrics. These synthesized biocidal fabrics proved to be antistatic, antimicrobial, and insect‐repelling (see part II of this study). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1900–1910, 2007 DA - 2007/2/5/ PY - 2007/2/5/ DO - 10.1002/app.24021 VL - 103 IS - 3 SP - 1900-1910 SN - 1097-4628 KW - cold plasma KW - graft copolymers KW - polypropylene KW - chitosan KW - inclusion chemistry ER - TY - JOUR TI - Investigation of the impact of simple carbon interstitial formations on thermal neutron scattering in graphite AU - Hawari, Ayman I. AU - Al-Qasir, Iyad I. AU - Ougouag, Abderrafi M. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - In both the prismatic and pebble bed designs of very high temperature reactors, the graphite moderator is expected to reach exposure levels of 1021 to 1022 n/cm2 over the lifetime of the reactor. This exposure results in damage to the graphite structure. Studies of the thermal properties of irradiated graphite show changes in the thermal conductivity and (to a lesser extent) the heat capacity at fluences <1021 n/cm2. In graphite, these properties depend on the behavior of atomic vibrations (phonons) in the solid. Therefore, it can be expected that alterations in the phonon behavior that would produce changes in these properties would have an impact on the thermal neutron scattering behavior of that material. In this work, an atomistic ab initio investigation is performed to explore the potential impact of simple carbon interstitial formations on the inelastic thermal neutron scattering behavior of graphite. Using the VASP/PHONON code system, graphite supercells were modeled with and without either a single carbon interstitial or a di-interstitial (C2) molecule between the graphite planes. This resulted in the production of the phonon frequency spectra for these structures. From the phonon data, the inelastic thermal neutron scattering cross sections were generated, using the NJOY code system, at temperatures of 300 and 1200 K. A comparison of the generated cross sections shows that accounting for the interstitials in the calculations affects the cross sections mainly in the energy range from 0.01 to 0.1 eV. DA - 2007/3// PY - 2007/3// DO - 10.13182/NSE07-A2676 VL - 155 IS - 3 SP - 449-462 SN - 1943-748X ER - TY - JOUR TI - Coupled bundle-core design using fuel rod optimization for boiling water reactors AU - Jessee, Matthew A. AU - Kropaczek, David J. T2 - NUCLEAR SCIENCE AND ENGINEERING AB - An optimization method has been developed to determine the optimal fresh fuel rod configurations, fresh streams, and fresh bundle design placements given a known exposed fuel loading pattern and operational strategy for boiling water reactors. The optimization method is based on a first-order approximation of various core parameters, such as hot excess reactivity and critical power ratio, using fuel rod perturbations to the reference fresh bundle designs. A simulated annealing optimization algorithm is shown to produce fresh bundle designs, consisting of rods selected from a user-defined set of rod types that optimize the core design with respect to its design constraints.The method utilizes a linear superposition method based upon sensitivity coefficients to approximate core parameters. A parallel computing system was implemented to decrease wall clock time for the numerous lattice physics and core simulator calculations. A periodic update of the reference bundle design, without the computational burden of updating the sensitivity coefficients, was introduced and is shown to significantly improve the accuracy of the approximation model. Application of the method demonstrates that improved core designs are achieved when a many-fresh bundle design (i.e., stream) solution is considered as part of the design space. Six-stream (and higher) core designs that increase fuel utilization while simultaneously reducing manufacturing costs through reduction of fuel rod types fabricated, previously unattainable with existing methodologies, are now possible. DA - 2007/3// PY - 2007/3// DO - 10.13182/NSE07-A2670 VL - 155 IS - 3 SP - 378-385 SN - 1943-748X ER -