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RISS 인기검색어
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- 저자 : Keiser, Dennis D. Jr. (검색결과 6 건)
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Keiser, Dennis D. Jr.,Jue, Jan-Fong,Miller, Brandon D.,Gan, Jian,Robinson, Adam B.,Medvedev, Pavel,Madden, James,Wachs, Dan,Meyer, Mitch Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.2
In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U-7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifially, samples from irradiated U-7Mo dispersion fuel elements with pure Al, Al-2Si and AA4043 (~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U-7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U-7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with Al-Si matrices.
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Symbolic Representation in American Schools: Race, Gender, and Intersectionality
Lael Keiser,Donald Haider-Markel 서울대학교행정대학원 2022 The Korean Journal of Policy Studies Vol.37 No.4
A growing body of research suggests that representation among elected and bureaucratic officials can shape the attitudes and behavior of constituents and clients. We explore the impact of race and gender representation in public schools using a unique survey of students and school personnel from 44 different schools in an Ohio county about school discipline. We use ordered logit models to analyze the survey data. Our analysis suggests race affects attitudes toward institutions and authority even when controlling for individual experiences, that Black student attitudes are influenced by minority teacher representation, student attitudes are different depending on teacher gender representation, and student race and gender condition the influence of representation. Our results have potentially broad implications for understanding attitudes about political institutions, the administration of authority, and the theory of representative bureaucracy.
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Dennis D. Keiser,JAN-FONG JUE,BRANDON D. MILLER,JIAN GAN,ADAM B. ROBINSON,PAVEL MEDVEDEV,JAMES MADDEN,DAN WACHS,MITCH MEYER 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.2
In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, differentU–7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electronmicroscopy (SEM). Specifially, samples from irradiated U–7Mo dispersion fuel elements with pure Al, Al–2Si and AA4043(~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ionbeam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. Forthe Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface andevidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U–7Mo fuel was observed forsamples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in thelocalized regions of the microstructure of the U–7Mo may contribute to changes observed in the macroscopic swelling of fuelplates with Al–Si matrices.
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Irradiation Performance of U-Mo Monolithic Fuel
M.K. Meyer,J.GAN,D.D. KEISER,E. PEREZ,A. ROBINSON,D.M. WACHS,N. WOOLSTENHULME,G.L. Hofman,Y. S. Kim 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.2
High-performance research reactors require fuel that operates at high specific power to high fission density, but atrelatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies ofthin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactorsrequires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases havebeen identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. UMoalloys represent the best known tradeoff in these properties. Testing of aluminum matrix U-Mo aluminum matrixdispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of amolybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, thisissue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scopingirradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuelqualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power
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IRRADIATION PERFORMANCE OF U-Mo MONOLITHIC FUEL
Meyer, M.K.,Gan, J.,Jue, J.F.,Keiser, D.D.,Perez, E.,Robinson, A.,Wachs, D.M.,Woolstenhulme, N.,Hofman, G.L.,Kim, Y.S. Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.2
High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. U-Mo alloys represent the best known tradeoff in these properties. Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.
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