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1
Klein, Dennis William. "Low fluence neutron radiography techniques." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42613.
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Dawson, Martin Nicholas. "Applications of neutron radiography & tomography." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/1641/.
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This thesis represents the investigation and development of neutron imaging techniques as a versatile method that can be used to reveal the presence, position, size, morphology, and chemical composition of structures and materials within a sample. The underlying physics of neutron radiography and tomography mean that it has fundamental similarities to x-ray techniques, although some subtle differences mean that neutrons are often applicable in circumstances where x-rays are not. This complementarity is presented and discussed. Most of the experimental results contained herein were obtained using Neutrograph, the thermal neutron imaging instrument at the Institut Laue-Langevin's high flux research nuclear reactor in Grenoble, France. Neutrograph utilises the world's most intense neutron beam currently in use for this purpose, -3xl09 n·cm-2·s-1 across an area of 220x220 mm2, and is capable of producing high quality images with single-frame exposure times down to the millisecond regime. Meanwhile, the modest beam divergence of 6 mrad (equivalent to a beam length-to-diameter ratio, LID, of -150) can achieve a spatial resolution in the region of 150-300 11m. It is demonstrated how these properties make Neutrograph ideal for obtaining timeresolved measurements of dynamic processes in both two and three dimensions, and for imaging relatively thick samples or highly attenuating materials on a reasonable time-scale. One aspect that is addressed in this research is the potential scope of relevance of neutron imaging methods across a range of scientific disciplines. In this vein, attempts have been made not only to draw examples from a number of different fields (palaeontology, archaeology, and fluid mechanics, for example), but also to improve the performance of the instrumentation and methodology, and to establish novel techniques that will further the applicability of neutron imaging. An illustration of the latter is the use of a polarised neutron beam to investigate the presence and distribution of magnetic components in non-magnetic matrices.
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Abdelrahman, Magdy Shehata. "Scattering correction and image restoration in neutron radiography and computed tomography." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3025066.
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Chen, Kun. "A study of spectroscopic, cold neutron radiography." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3240030.
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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2006."Title from dissertation home page (viewed July 16, 2007)." Source: Dissertation Abstracts International, Volume: 67-10, Section: B, page: 5819. Adviser: Hans-Otto Meyer.
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Jo, Young Gyun. "Development of a thermal neutron imaging facility for real time neutron radiography and computed tomography /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Fink, David Walter. "Detecting corrosion in aircraft components using neutron radiography." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39993.
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Borges, Nicholas P. "Improving Imaging Techniques and Resolution in Neutron Radiography." Digital WPI, 2020. https://digitalcommons.wpi.edu/etd-dissertations/604.
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Hydrogenous samples, such as biological tissues, analyzed in a neutron radiography geometry display reduced image contrast and resolution due to excessive image contributions from scattered neutrons produced from the high neutron-scatter cross section with hydrogen. Because of this, neutrons presently are not used for thick-tissue(>2.5cm) or in-vivo imaging. Two methods of neutron scatter rejection and event centroiding, were employed to enhance the quality of biological neutron imaging by reducing image blurring noise caused by hydrogen and increasing the contrast ratio of the detector. By employing the techniques used herein, event centroiding can increase the natural resolution of the detector by a factor of two without energy dependence and as much as 4 times with energy bins. Scatter rejection can increase the contrast resolution by 7%-10% of an imaging standard and can resolve a 160 μm image through 6mm of acrylic.
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ANDRADE, MARCOS L. G. "Radiografia com elétrons induzida por nêutrons: Neutron induced eletron radiography." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11610.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
9
Woodward, Stephanie. "Development and applications of a pulsed neutron radiography system." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46916.
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Matsubayashi, Masahito. "Study on development of advanced neutron radiography imaging techniques." Kyoto University, 2005. http://hdl.handle.net/2433/144678.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第11690号
エネ博第106号
新制||エネ||17(附属図書館)
23333
UT51-2005-D439
京都大学大学院ｴﾈﾙｷﾞｰ科学研究科ｴﾈﾙｷﾞｰ基礎科学専攻
(主査)教授 三島 嘉一郎, 教授 代谷 誠治, 教授 川端 祐司
学位規則第4条第1項該当
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Chen, Gongyin 1968. "Fast neutron resonance radiography for element imaging : theory and applications." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8681.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2001.Includes bibliographical references (p. 140-143).
Fast Neutron Resonance Radiography (NRR) has been devised as an elemental imaging method, with immediate applications to detecting explosives and drugs in passenger suitcases. In the NRR method, the 2-D elemental mapping of hydrogen, carbon, nitrogen, oxygen and the sum of other elements are obtained from fast neutron radiographic images taken at different neutron energies chosen to cover the resonance cross section features of one or more elements. A radiographic image provides the 2-D mapping of the sum of elemental contents (weighted by the attenuation coefficients) and transmission measurements taken at different neutron energies form a set of linear equations, which can be solved to map individual elemental contents. Explosives and drugs can be identified by their characteristic elemental composition. The object-detector assembly rotates around the neutron source and different energy (2-6 MeV) neutrons can be obtained at different angles from a DD neutron source. A fixed-energy RFQ (2.3 MeV deuteron energy) with a thick target (0.4-0.8 MeV) can be used to generate fast neutrons. The physics of image formation in fast neutron radiography has been studied and a thick (4 cm) plastic scintillator has been recommended as the neutron detector.
(cont.) Variance-checking median filters have been recommended for removing sparkles in the digital image and the direct Householder Transform has been used to solve the ill-conditioned Least-Squares problem. Source shielding for 2x109 neutrons/second has been suggested. Experiments and simulation have proven NRR to be effective. Explosives can be identified with their high nitrogen and oxygen content and drugs with their high C/O ratio. With a 10 [mu]A deuteron current and 6 atmosphere-cm D2 gas target, total imaging time for each piece is expected to be 1-2 minutes. Because multiple objects can be inspected at the same time, it is possible to meet the FAA standard of 8 seconds per piece. Spatial resolution of the image is estimated to be -7.5 mm.
by Gongyin Chen.
Ph.D.
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Puffer, Donald B. "Moderator design for accelerator based neutron radiography and tomography systems." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37528.
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Daniels, Graham Clinton. "Observing flow using fast neutron radiography and positron emission particle tracking." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33606.
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Dynamic flow of material has been studied using fast neutron radiography (FNR) and positron emission particle tracking (PEPT). A new fast neutron imaging system was commissioned at The South African Nuclear Energy Corporation, Pretoria, as part of this study, although FNR measurements were ultimately performed at PhysikalischTechnische Bundesanstalt (PTB), Braunschweig. The PEPT studies were undertaken at the PEPT Cape Town facility located at iThemba LABS, Cape Town. The steady state motion of media, within a laboratory-scale tumbling mill, was studied for a range of speed and media mixes, using both FNR and PEPT. Several operational parameters were derived from the data, which could be related to potential improvements to the milling efficiency. The blending of FNR and PEPT data for the study of steady state flow, was explored for the first time. In addition, the flow of water through porous media was studied using FNR, which enabled the determination of the hydraulic conductivity, and hence intrinsic permeability, of the media within the column. The potential of using FNR, without or without PEPT, for the study of material in motion is discussed.
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Zapp, Andrew M. "Design and Development of an External Fast Neutron Beam Facility at the Ohio State University Research Reactor." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1545075104197272.
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Chuirazzi, William C. "Combinatorial Optimization of Scintillator Screens for Digital Neutron Imaging." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586903047809812.
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Raas, Whitney. "Towards the development of an explosives detection system using Neutron Resonance Radiography." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41290.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references (leaves 183-188).
Detection of conventional explosives remains a challenge to air security, as indicated by recent reports detailing lapses in security screening and new requirements that mandate screening 100% of checked luggage. Neutron Resonance Radiography (NRR) has been under investigation as a supplement to conventional x-ray systems as a non-invasive, non-destructive means of detecting explosive material in checked luggage. Using fast (1-6 MeV) neutrons produced by an accelerator-based D(d,n)3He reaction and a scintillator-coupled CCD camera, NRR provides both an imaging capability and the ability to determine the chemical composition of materials in baggage or cargo. Theoretical studies and simulations have shown the potential of NRR. This thesis takes the first step towards experimental implementation using a deuterium target for multiple-element discrimination. A new neutron source has been developed to provide the high-flux neutron beam required for NRR while simultaneously minimizing gamma ray production. The gas target incorporates a 4 atm D2 gas chamber, separated from the accelerator beamline with thin, 5 [tm tungsten or 7 [im molybdenum foils supported by a honeycomb lattice structure to increase structural integrity and provide a heat removal pathway. An argon gas cooling system is incorporated to cool the target and thus increase the neutron flux. The gas target has been shown to withstand 3.0 MeV deuteron beam currents in excess of 35 ýLA for extended periods without failure, resulting in a neutron flux of 6.6 x 107 neutrons/sr/LA/s. A neutron imaging system was designed to detect the fast neutrons and produce a digital image of objects for analysis.
(cont.) Two neutron detectors, Eljen plastic scintillator EJ-200 and a ZnS(Ag) scintillating screen were tested for their suitability to NRR. Although ZnS(Ag) has a lower detection efficiency, its resolution, minimal light dispersion, and insensitivity to gamma rays made it the more favorable material. An Apogee Instruments, Inc., Alta U9 CCD camera was used to record the light from the scintillator to create radiographs. The gas target and neutron detection system were used to evaluate the results of experimental work to determine the feasibility of NRR. These experiments ultimately indicated that although NRR has promise, significant challenges regarding neutron flux and image processing must be overcome before the technique can be implemented as an explosives detection system. Suggestions are made for improvements.
by Whitney Lyke Raas.
Ph.D.
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Kardjilov, Nikolay. "Further developments and applications of radiography and tomography with thermal and cold neutrons." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969348320.
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Grünauer, Florian. "Design, optimization, and implementation of the new neutron radiography facility at FRM-II." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978958950.
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Bickerton, M. L. "Development of improved techniques for the neutron radiography of CF188 flight control surfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/MQ44833.pdf.
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MENEZES, MARIO O. de. "Radiografia com neutrons em tempo - real." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9284.
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Tese [Doutoramento]
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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MENEZES, MARIO O. de. "Desenvolvimento e aplicacao da tecnica da radiografia de neutrons por conversao direta e indireta." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10366.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Barritt, Andrew Stephen. "Detection of hydrogen embrittlement in steel and steel alloys using methods of neutron radiography." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32597.
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Clark, Michael A. R. "Application of thermal neutron radiography for the mass transport of moisture through freezing soil." Thesis, Aston University, 1989. http://publications.aston.ac.uk/14320/.
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This thesis reports on the development of a technique to evaluate hydraulic conductivities in a soil (Snowcal) subject to freezing conditions. The technique draws on three distinctly different disciplines, Nuclear Physics, Soil Physics and Remote Sensing to provide a non-destructive and reliable evaluation of hydraulic conductivity throughout a freezing test. Thermal neutron radiography is used to provide information on local water/ice contents at anytime throughout the test. The experimental test rig is designed so that the soil matrix can be radiated by a neutron beam, from a nuclear reactor, to obtain radiographs. The radiographs can then be interpreted, following a process of remote sensing image enhancement, to yield information on relative water/ice contents. Interpretation of the radiographs is accommodated using image analysis equipment capable of distinguishing between 256 shades of grey. Remote sensing image enhancing techniques are then employed to develop false colour images which show the movement of water and development of ice lenses in the soil. Instrumentation is incorporated in the soil in the form of psychrometer/thermocouples, to record water potential, electrical resistance probes to enable ice and water to be differentiated on the radiographs and thermocouples to record the temperature gradient. Water content determinations are made from the enhanced images and plotted against potential measurements to provide the moisture characteristic for the soil. With relevant mathematical theory pore water distributions are obtained and combined with water content data to give hydraulic conductivities. The values for hydraulic conductivity in the saturated soil and at the frozen fringe are compared with established values for silts and silty-sands. The values are in general agreement and, with refinement, this non-destructive technique could afford useful information on a whole range of soils. The technique is of value over other methods because ice lenses are actually seen forming in the soil, supporting the accepted theories of frost action. There are economic and experimental restraints to the work which are associated with the use of a nuclear facility, however, the technique is versatile and has been applied to the study of moisture transfer in porous building materials and could be further developed into other research areas.
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Turkoglu, Danyal J. "Design, Construction and Characterization of an External Neutron Beam Facility at The Ohio State University Nuclear Reactor Laboratory." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1325228897.
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ANDRADE, MARCOS L. G. "Caracterizacao de sistemas filme-conversor para radiografia com neutrons." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10986.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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PEREIRA, MARCO A. S. "Emprego dos policarbonatos makrofol-de e CR-30 em radiografia com neutrons." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9293.
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Dissertacao (Mestrado)
IPEN/D
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
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VITUCCI, GIUSEPPE. "Advances in instruments and methods for neutron transmission imaging." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241081.
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Il lavoro presentato in questa tesi si concentra sullo sviluppo e sul miglioramento della strumentazione e dei metodi applicati all'imaging a trasmissione di neutroni. Le attività di ricerca sono state svolte presso il laboratorio di "Imaging and Materials Science and Engineering" (IMAT). Questa struttura fa parte della sorgente di neutroni ISIS presso il Rutherford Appleton Laboratory (UK). I neutroni qui sono prodotti dalla spallazione di un bersaglio di tungsteno colpito da protoni con energia di 800 MeV. I neutroni risultanti vengono moderati e convogliati attraverso le guide dei fasci verso l'area sperimentale IMAT. Lo spettro dei neutroni è caratterizzato dalla presenza di neutroni termici e freddi con una lunghezza d'onda compresa tra 0,68 e 6,8 A. IMAT è stato progettato per acquisire impulsi di neutroni in modalità tempo di volo, registrando il tempo di arrivo dei neutroni, relativo alla loro energia, con una risoluzione temporale massima di 10 ns. Questa analisi viene eseguita con un rilevatore di nuova generazione, che è una combinazione di un convertitore di neutroni “MicroChannel Plate” e un readout elettronico “TIMEPIX”. Mediante questo apparato, radiografie e tomografie con un campo visivo di 28 mm^2 possono essere generate con una risoluzione spaziale di 55 um e a particolari energie dei neutroni incidenti. Una fotocamera CMOS di maggiori dimensioni può essere utilizzata in combinazione con gli scintillatori a 6LiF/ZnS per acquisire immagini fino a 200 * 200 mm^2 in modalità white-beam. Ciò apre diverse possibilità. Da una parte, la tecnica di imaging neutronico risolta in energia può essere utilizzata per studiare composizione e texture dei campioni tramite software di analisi dei Bragg Edge, a costo di un campo visivo ridotto. Dall’altra, i campioni più grandi possono essere studiati con fotocamere standard basate su CMOS o CCD, ma perdendo qualsiasi informazione sull'energia dei neutroni in ingresso. In questo lavoro, la prima parte è dedicata alla descrizione della strumentazione IMAT, incluso il progetto della beamline, l'area sperimentale e i rivelatori. La seconda parte è diretta a casi di studio basati su queste nuove tecniche di strumentazione e di imaging. In particolare, nel campo del patrimonio culturale, tali metodi non distruttivi sono utilizzati, in quanto i campioni sono spesso piccoli e delicati. Per esempio, abbiamo analizzato una perla "soufflè". La loro particolarità risiede nel fatto che sono vuote all'interno. L'ispezione della struttura morfologica della parte interna e l'individuazione dei diversi orientamenti dei cristalliti sono stati condotti con tecniche di imaging risolte in energia. Un secondo esperimento, presentato in questa tesi, riguarda lo studio di una serie di griglie metalliche con una dimensione fino a 200 * 10 mm^2. In questo caso, un modo rapido e non distruttivo per verificare lo spessore dello strato di carburo di boro di 1 um depositato sulle lamelle è stato implementato con successo, considerando un'incertezza di 120 nm. La terza parte è rivolta a mostrare due nuovi metodi sviluppati per migliorare la fotocamera del rivelatore MCP in termini di risoluzione spaziale e affidabilità. Per quanto riguarda la risoluzione spaziale, è stata testata una nuova procedura basata su un algoritmo di centroiding. Questo metodo di acquisizione consente di superare il vincolo fisico dato dalla dimensione dei pixel del readout elettronico e di acquisire immagini con risoluzioni fino a quattro volte superiori. Inoltre, è stato sviluppato un sistema per migliorare le immagini generate dal rivelatore MCP in post-elaborazione. Uno dei punti deboli del readout TIMEPIX installato sul rivelatore MCP è il fatto di essere costituito da quattro matrici di pixel assemblate insieme. Ciò porta a notevoli artefatti che possono causare problemi nell'analisi dei dati. Una procedure con software specifico è stata implementata per risolvere il problema.The work presented in this thesis focuses on the development and improvement of instrumentation and methods applied to neutron transmission imaging. In particular, the research activities have been performed at the "Imaging and Materials Science and Engineering" (IMAT) instrument. This facility is a part of the ISIS neutron source at the Rutherford Appleton Laboratory, in UK. The neutrons here are produced by spallation of a tungsten target hit by protons with energy of 800 MeV. The resulting neutrons are then moderated and convoyed through beam guides towards the IMAT experimental area. The neutrons spectrum in this case is characterized by the presence of thermal and cold neutrons with a wavelength in the range of 0.68 - 6.8 A. IMAT has been designed to acquire neutron pulses in Time-Of-Flight mode, by recording the time of arrival of neutrons, related to their energy, with a maximum of 10 ns timing resolution. This analysis is performed with a new generation detector, that is a combination of a MicroChannel Plate neutron converter with a TIMEPIX electronic readout. By means of this apparatus, radiographies and tomographies with a field of view of 28 mm^2 can be generated with a spatial resolution of 55 \textmu m and with respect to specific neutron energies. Beside this device, a larger CMOS camera can be used in combination with 6LiF/ZnS based neutron screen scintillators to acquire images up to 200 * 200 mm^2 in white-beam imaging. Such configuration opens several possibilities in different case scenarios. In one hand, the energy-resolved neutron imaging technique can be used to investigate the phase fraction composition and texture of the samples via Bragg Edge analysis software tools, at the cost of a reduced field of view. On the other hand, bigger samples can be studied with standard CMOS or CCD based white-beam imaging cameras, but loosing any information about the energy of the incoming neutrons. In this work, the first part is devoted to the description of the IMAT instrumentation, including the beamline design, the experimental area and the detectors. The second part is directed to case studies that made use of these novel instrumentation and imaging techniques. In particular, the cultural heritage takes advantage of such non-destructive methods where small and delicate specimens must be analysed. In this class of examples, a "soufflè" pearl was considered. The peculiarity of these cultured pearls resides in the fact that they are empty inside. The inspection of the morphological structure of the inner part, as well as the individuation of the different orientations of the nacres crystallites was conducted with energy-resolved imaging. A second experiment, presented in this thesis, regards the diagnosis of a series of metallic grids with a size up to 200 * 10 mm^2. For this case, a fast and non destructive way to verify the thickness of 1 um boron carbide layer deposited over the lamellae was successfully implemented, within an uncertainty of 120 nm. The third part is directed to show two new methods developed to improve the MCP detector camera in terms of spatial resolution and reliability. For what concerns the spatial resolution, a new procedure based on a centroiding algorithm has been tested. This acquisition method enables the possibility to go over the physical constraint given by the dimension of the pixels of the electronic readout and to acquire images with a resolutions up to four times higher. Furthermore, an improvement to the resulting images generated by the MCP detector has been developed, based on a post-processing approach. Actually, one of the weak spots of the TIMEPIX readout installed on the MCP detector is that it is constituted by four matrices of pixels assembled together. This brings to noticeable artifacts which, in some cases, may produce issues in the data analysis. A procedure, including a customized software, was implemented to fix such problem.
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Harris, Thomas C. (Thomas Cameron). "High Resolution Quantitative Auto-Radiography to determine microscopic distributions of B-10 in neutron capture therapy." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41271.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references.
The success of Boron Neutron Capture Therapy (BNCT) is heavily dependent on the microscopic distribution of B-10 in tissue. High Resolution Quantitative Auto-Radiography (HRQAR) is a potentially valuable analytical tool due to its ability to simultaneously visualize boron distributions and tissue histology. While powerful, the technique has fallen into disuse, largely due to its complexity. HRQAR was reconstituted, and its accuracy was verified with test samples. Numerous improvements were made to make the process easier and more efficient. Permanent staff members at the Institute were trained in the technique, ensuring the continued vitality of HRQAR. The image acquisition equipment and analysis software were modernized, and made more user-friendly. The microdosimetry analysis software was updated to current versions of programming environments and personal computer operating systems. Verification tests were conducted to ensure the continued accuracy of the underlying algorithms. Several experiments were conducted to demonstrate the applications of HRQAR. One focus of current BNCT research is the development of new boron delivery agents, so a potential new compound was compared with a current-generation boron compound. In order to underscore the broader range of utility of HRQAR, another experiment was conducted using the auto-radiography technique as verification of selective microvasculature irradiation.
by Thomas C. Harris.
S.M.
29
Yoon, Il. "Two-phase flow dynamics by real-time neutron imaging in oscillating heat pipe." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5694.
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Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 19, 2009) Includes bibliographical references.
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Watts, Michael Robert. "The analysis of diffraction measurements of internal strains in metal matrix composites." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313918.
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Cools, Antoine. "Beta and neutron imaging with an optical readout Micromegas detector." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP090.
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Les détecteurs gazeux ont démontré, au cours de ces dernières décennies, leur haute performance pour l'imagerie de particules radioactives, atteignant des résolutions spatiales inférieures à 100 µm. Les propriétés scintillantes de certains mélanges gazeux, combinées au gain important des détecteurs gazeux et à l'usage d'une caméra à bas bruit électronique, ont permis d'utiliser la lumière scintillée pour l'imagerie. Cette approche permet d'obtenir une large surface de détection et une haute résolution spatiale tout en réalisant l'imagerie en temps réel à un coût par pixel réduit, avec une faible complexité d'analyse des données. Les principaux objectifs de cette thèse sont d'optimiser la résolution spatiale ainsi que la sensibilité du détecteur, soit par une méthode d'acquisition "événement par événement" avec des temps d'acquisition d'image courts, soit par "intégration" avec des temps d'acquisition longs.Un détecteur Micromegas en verre innovant pour la lecture optique a été développé, tirant parti de la haute résolution spatiale inhérente au détecteur Micromegas.L'adaptabilité du gain du détecteur Micromegas liée au mécanisme d'amplification par avalanche, lui permet de couvrir une large gamme de flux et d'énergies de particules. Durant cette thèse, des mesures d'imagerie ont été réalisées à l'aide de sources avec des niveaux de radioactivité inférieurs à un Becquerel et des énergies de quelques keV, jusqu'à des flux caractéristiques d'un synchrotron et d'une source de spallation, avec des énergies dépassant le MeV.Le rendement lumineux du détecteur a été étudié pour différents mélanges gazeux et pour diverses valeurs de gain sous irradiation aux rayons-X afin d'optimiser la sensibilité du détecteur. L'homogénéité et la précision de la réponse du détecteur ont été caractérisées par radiographie à rayons-X. La Fonction d'Étalement du Point (PSF) du Micromegas à lecture optique a été mesurée à l'aide d'un faisceau de rayons-X parallèles de quelques microns d'épaisseur, générés par le rayonnement synchrotron. Cette mesure a permis de déterminer la résolution spatiale du détecteur pour différentes configurations et d'identifier et de quantifier les effets qui rentrent en jeux. L'impact de la microgrille et des piliers sur la réponse en scintillation du détecteur a également été observé et quantifié.Deux applications ont été choisies afin d'illustrer le potentiel du Micromegas à lecture optique: l'autoradiographie pour la quantification d'échantillons tritiés de très faible activitié et la radiographie neutronique à haute résolution en environnement hautement radioactif.L'autoradiographie et le comptage radioactif de rayonnements beta faiblement énergétiques ont été réalisés avec des échantillons de glucose tritié. Des activités inférieures à un Becquerel ont été mesurées avec précision et simultanément sur un grand nombre d'échantillons tout en assurant une reconstruction précise de leur position. Ce travail valide la possibilité de quantifier la concentration de médicaments anticancéreux à l'échelle de cellules tumorales uniques.Enfin, l'utilisation du Micromegas à lecture optique pour la neutronographie a été démontrée en utilisant une source de spallation produisant des neutrons thermiques à un flux d'environ 10⁸ n. s⁻¹cm⁻ ² mA⁻¹. L'uniformité de la réponse du détecteur a été étudiée, et les effets de la diffusion et du parcours moyen des particules dans le gaz sur la netteté de l'image ont été mesurés et comparés à une simulation. Une résolution spatiale de l'ordre de 400 µm a été obtenue en utilisant une amplification à double étages au sein du détecteur MicromegasGaseous detectors have demonstrated, over the past decades, their high performance for imaging radioactive particles, achieving spatial resolutions below 100 µm. The scintillating properties of certain gas mixtures, combined with the significant gain of gaseous detectors and the use of a low-noise camera, have enabled the use of scintillation light for imaging. This approach allows for a large detection surface and high spatial resolution while achieving real-time imaging at a low cost per pixel, with low data analysis complexity. The main objectives of this thesis are to optimize the spatial resolution and sensitivity of the detector, either by an "event-by-event" acquisition method with short image acquisition times or by "integration" with long acquisition times.An innovative glass Micromegas detector for optical readout has been developed, taking advantage of the inherently high spatial resolution of the Micromegas detector. The adaptability of the Micromegas detector's gain, due to the avalanche amplification mechanism, allows it to cover a wide range of particle fluxes and energies. During this thesis, imaging measurements were performed using sources with radioactivity levels below one Becquerel and energies of a few keV, up to fluxes characteristic of a synchrotron and a spallation source, with energies exceeding one MeV.The light yield of the detector was studied for different gas mixtures and various gain values under X-ray irradiation to optimize the detector's sensitivity. The homogeneity and precision of the detector's response were characterized by X-ray radiography. The Point Spread Function (PSF) of the optical readout Micromegas was measured using a parallel X-ray beam a few microns thick, generated by synchrotron radiation. This measurement allowed us to determine the detector's spatial resolution for different configurations and to identify and quantify the effects involved. The impact of the micro-mesh and pillars on the detector's scintillation response was also observed and quantified.Two applications were chosen to illustrate the potential of the optical readout Micromegas: autoradiography, for the quantification of very low-activity tritiated samples and high-resolution neutron radiography in highly radioactive environments.Autoradiography and radioactive counting of low-energy beta radiation were performed with tritiated glucose samples. Activities below one Becquerel were measured accurately and simultaneously on a large number of samples, while ensuring precise reconstruction of their position. This work validates the possibility of quantifying the concentration of anticancer drugs at the scale of single tumor cells.Finally, the use of the optical readout Micromegas for neutron imaging was demonstrated using a spallation source which produces thermal neutrons with a flux of approximately 10⁸ n. s⁻¹cm⁻ ² mA⁻¹. The uniformity of the detector's response was studied, and the effects of the diffusion and the mean free path of particles in the gas on image sharpness were measured and compared to a simulation. A spatial resolution on the order of 400 µm was achieved using double-stage amplification within the Micromegas detector
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Owejan, Jon. "Neutron radiography study of water transport in an operating fuel cell : effects of diffusion media and cathode channel properties /." Online version of thesis, 2003. http://hdl.handle.net/1850/5279.
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Shawger, Richard Elwood. "Comparative Analysis of PVT Scintillators for the Development of a Fast Neutron Imager." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460195672.
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PEREIRA, MARCO A. S. "Radiografia com partículas alfa induzida por nêutrons." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11619.
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Made available in DSpace on 2014-10-09T12:53:57Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:29Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Zarebanadkouki, Mohsen [Verfasser], Andrea [Akademischer Betreuer] Carminati, Christoph [Akademischer Betreuer] Leuschner, and Hans-Jörg [Akademischer Betreuer] Vogel. "Quantitative imaging of water flow in soil and roots using neutron radiography and deuterated water / Mohsen Zarebanadkouki. Gutachter: Christoph Leuschner ; Hans-Jörg Vogel. Betreuer: Andrea Carminati." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044770031/34.
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Traore, Issiaka. "Etude et caractérisation des fonctions de réponse des détecteurs solides de traces nucléaires : applications à la dosimétrie radon et neutron." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01067060.
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Cette thèse a été préparée en cotutelle entre l'Université de Strasbourg et l'Université des SciencesTechniques et Technologies de Bamako (Mali). Elle s'articule principalement autour de la caractérisation des Détecteurs Solides de Traces Nucléaires (DSTN) afin de les utiliser pour la métrologie du radon et des neutrons conformément aux nouvelles recommandations de la Commission Internationale de Protection Radiologique (CIPR-103). Les fonctions de réponse de PN3 et Neutrak, associés avec des convertisseurs adaptés, ont été étudiés en les irradiant par des neutrons du calibrateur Am-Be de l'IPHC (Institut Pluridisciplinaire Hubert Curien), aux protons de 1 à 3 MeV de l'accélérateur Van de Graaff de l'INESS (INstitut d'Electronique du Solide et des Systèmes) et par des neutrons de référence thermiques et rapides auprès des installations de l'IRSN (Institut de Radiologie et de Sûreté Nucléaire). En dosimétrie neutronique, nous avons pu reproduire les résultats d'un test d'intercomparaison pour des neutrons rapides organisé par l'IRSN qui a validé nos mesures expérimentales, ce qui a permis de les appliquer aux neutrons thermiques. Un prototype de dosimètre neutrons basé sur la détection des thermiques a été testé avec succès au calibrateur de l'IPHC. Nous avons ainsi pu démontrer la faisabilité d'un dosimètre pouvant discriminer la contribution des neutrons thermiques des neutrons rapides par des convertisseurs chargés en bore BE10 et BN1. Les étalonnages de PN3 par des protons et des particules alpha permettraient de reconstituer le spectre en énergie des neutrons et de déterminer la dose associée.En métrologie radon, l'étalonnage de CR-39 dans une chambre à 222Rn a fourni une valeur de 0,12±0,02tr.cm-2.j-1.Bq-1.m3. Elle a été comparée à la valeur 0,13 tr.cm-2.j-1.Bq-1.m3 obtenue par simulation Monte Carlo à l'aide du code MCNPX. Comme application, la concentration et la dose effective annuelle du radon ont été déterminées pour la première fois dans des habitats de Bamako. Toutes les valeurs obtenues se trouvent dans les limites de sécurité recommandées par la CIPR. Également pour la première fois, des mesures par spectrométrie gamma et par contact radiographie ont été réalisées sur des échantillons de sol malien. Les activités massiques mesurées pour les régions de Ségou, Sikasso, Bamako et Kayes se trouvent dans la gamme de 19,9 à 132 Bq.kg-1.
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Breitwieser, Matthias, Riko Moroni, Jonathan Schock, Michael Schulz, Burkhard Schillinger, Franz Pfeiffer, Roland Zengerle, and Simon Thiele. "Water management in novel direct membrane deposition fuel cells under low humidification." Elsevier, 2016. https://publish.fid-move.qucosa.de/id/qucosa%3A72518.
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Polymer electrolyte membrane fuel cells (PEMFCs) fabricated by direct membrane deposition (DMD) were shown to work even at dry conditions without significant deterioration of the membrane resistance. Here, in situ neutron radiography is used to investigate the water management in those fuel cells to uncover the phenomena that lead to the robust operation under low humidification. A constant level of humidification within the membrane electrode assembly (MEA) of a DMD fuel cell is observed even under dry anode operation and 15% relative humidity on the cathode side. This proves a pronounced back diffusion of generated water from the cathode side to the anode side through the thin deposited membrane layer. Over the entire range of polarization curves a very high similarity of the water evolution in anode and cathode flow fields is found in spite of different humidification levels. It is shown that the power density of directly deposited membranes in contrast to a 50 μm thick N-112 membrane is only marginally affected by dry operation conditions. Water profiles in through-plane direction of the MEA reveal that the water content in the DMD fuel cell remains steady even at high current densities. This is in contrast to the N-112 reference fuel cell which shows a strong increase in membrane resistance and a reduced MEA water content with raising current densities. Thus this new MEA fabrication technique has a promising perspective, since dry operation conditions are highly requested in order to reduce fuel cell system costs.
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Lieboldt, Matthias, and Viktor Mechtcherine. "Einfluss von Rissen auf den Feuchtetransport in textilbewehrtem Beton." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77943.
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In diesem Beitrag wird die Wasserabsorption und die Wasserpermeabilität von axial vorbelasteten Prüfkörpern aus textilbewehrtem Beton (TRC) und biegebelasteten Verbundprüfkörpern (Normalbeton + TRC) im gerissenen Zustand untersucht. Durch in situ Permeabilitätsmessungen wird das dehnungsabhängige Transportverhalten im einaxialen Zugversuch beobachtet und mittels eines analytischen Modells beschrieben. Es besteht eine ausgeprägte Abhängigkeit der Transportraten von Flüssigkeiten zu relevanten Risscharakteristika (Rissanzahl, Rissbreite). Weiterhin wurden Selbstheilungseffekte von feinen Rissen infolge einer zyklischen Wasserbeaufschlagung beobachtet. Die Feuchteverteilung in einer gerissenen Normalbetonprobe und einer Verbundprobe (Normalbeton + TRC) wird mit Hilfe der Neutronenstrahlradiographie zeit- und ortsaufgelöst dargestellt. Das Eindringen von Wasser wird anhand der Messungen qualitativ vorgestellt und diskutiertIn this study water absorption and water permeability were tested on uniaxially preloaded, cracked specimens made of textile reinforced concrete (TRC) and cracked composite specimens (ordinary concrete + TRC) preloaded in bending. The influence of imposed strain on the permeation of water was observed in-situ by using uniaxial tensile tests and described by an analytical model. The transport values for the cracked material correlated with the cracks’ characteristics (number of cracks, crack width). Furthermore, the effect of self-healing phenomena on the transport properties of TRC was considered. The distribution of water in cracked ordinary concrete and cracked composite specimens was studied by means of neutron radiography which provided with a high spatial and temporal resolution. The penetration of water is presented qualitatively and discussed
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Rahon, Jill Marie. "Spectroscopic radiography with monoenergetic neutrons for homeland security applications." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106688.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 68-71).
In this thesis, I discuss the hypothesis, testing, and applications of a radiographic system which uses the spectral analysis of fast neutrons generated in the 11B(d,n[gamma])12C reaction. Neutron radiography in current use systems employs a total count analysis to reconstruct hydrogenous content in scanned cargoes. This research presents a technique which leverages the large differences in the energy dependence of neutron interaction cross sections between hydrogenous materials and those of higher atomic number. These dependencies result in characteristic spectral details of hydrogenous materials which may be analyzed to classify type and areal density of cargo contents. The studies presented here demonstrate that this technique is feasible and suited to the application of national security port monitoring at industry-requisite speeds and cargo dimensions.
by Jill Marie Rahon.
S.M.
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Souza, Erica Silvani. "Caracterização de um sistema digital de aquisição de imagens radiográficas utilizando nêutrons térmicos e raios gama para a inspeção de componentes mecânicos." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7458.
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Ensaio não destrutivo é uma ferramenta essencial quando um equipamento, dispositivo ou componente não pode ser submetido a procedimentos destrutivos ou invasivos devido a razões de segurança, alto custo ou outras restrições físicas ou logísticas. Dentro deste quadro radiografias por transmissão com raios gama e nêutrons térmicos são técnicas singulares para inspecionar um objeto e desvendar sua estrutura interna devido à capacidade de atravessar uma vasta gama de materiais utilizados na indústria. Grosso modo, raios gama são mais atenuados por materiais pesados enquanto nêutrons térmicos são mais atenuados por materiais mais leves, tornando-as ferramentas complementares. Este trabalho apresenta os resultados obtidos na inspeção de vários componentes mecânicos, através da radiografia por transmissão com nêutrons térmicos e raios gama. O fluxo de nêutrons térmicos de 4,46x105 n.cm-2.s-1 disponível no canal principal do reator de pesquisa Argonauta do Instituto de Engenharia Nuclear foi usado como fonte para as imagens radiográficas com nêutrons. Raios dekeV emitidos pelo 198Au, também produzido no reator, foram usados como fonte de radiação para radiografias . Imaging Plates, especificamente produzidos para operar com nêutrons térmicos ou com raios X, foram empregados como detectores e dispositivos de armazenamento e captação de imagens para cada uma dessas radiações. Esses dispositivos exibem varias vantagens quando comparados ao filme radiográfico convencional. Com efeito, além de maior sensibilidade e serem reutilizáveis não são necessários câmaras escuras e processamento químico para a revelação. Em vez disso, ele é lido por um feixe de laser que libera elétrons armadilhados na rede cristalina durante a exposição à radiação, fornecendo uma imagem final digital. O desempenho de ambos os sistemas de aquisição de imagens, assim constituído, foi avaliado com respeito à sensibilidade, resolução espacial, linearidade e range dinâmico, incluído uma comparação com sistemas radiográficos com nêutrons empregando filmes e folhas de gadolínio como conversor de nêutrons em partículas carregadas. Além desta caracterização, diversos equipamentos e componentes foram radiografados com ambos os sistemas visando-se avaliar suas capacidades de desvendar a estrutura interna desses objetos e detectar estruturas e estados anormais. Dentro desta abordagem, uma neutrongrafia detectou a presença de material cerâmico remanescente empregado como molde no processo de fabricação nos canais de refrigeração de uma aleta do estator de uma turbina tipo turbo-fan, que deveria estar livre desse material. O reostato danificado de um sensor de pressão automotivo, foi identificado por neutrongrafia, embora nesse caso a radiografia também conseguiu realizar essa tarefa com melhor resolução, corroborando assim as curvas de resolução espacial obtidas na caracterização dos dois sistemas. A homogeneidade da distribuição do material encapsulado em uma gaxeta explosiva de chumbo utilizada na indústria aeroespacial foi igualmente verificada por neutrongrafia porque esse metal é relativamente transparente para nêutrons, mas suficientemente opaco para o explosivo rico em hidrogênio. Diversos outros instrumentos e componentes tais como variômetro, altímetro, bússola aeronáutica, injetor automotivo de combustível, foto-camera, disco rígido de computador, motor de passo, conectores eletrônicos e projéteis foram radiografados com ambos os sistemas visando avaliar suas habilidades em desvendar diferentes peculiaridades em função do agente interrogador.Non-destructive testing is an essential approach whenever a piece of equipment, device, or component should not be submitted to a destructive or invasive procedure due to safety reasons, high costs or other physical or logistics constraints. Within this frame, transmission radiography with gamma-rays and thermal neutrons are unique techniques to inspect an object and unveil its inner structure thanks to their capability to pass through a wide range of materials employed in the manufacturing industry. Roughly, as a rule of thumb, gamma-rays are more attenuated by heavy materials, while thermal neutrons are attenuated by the light ones, making them complementary tools. This work presents the results obtained in the inspection of several mechanical components through neutron and gamma-ray transmission radiography. The 4.46 x 105 n.cm-2.s-1 thermal neutron flux available at the main port of the Argonauta research reactor in Instituto de Engenharia Nuclear has been used as source for the neutron radiographic imaging. The 412 keV gamma-ray emitted by 198Au, also produced in that reactor, has been used as interrogation agent for the gamma radiography. Imaging Plates - IP specifically designed to operate with thermal neutrons or with X-rays have been employed as detectors and storage devices for each of these radiations. These devices exhibit several advantages with regard to the conventional radiographic film. Indeed, besides a higher sensitivity and reusability, a dark chamber and a cumbersome chemical processing is not required for the development. Instead, it is carried out by a laser beam which interrogates the electric state of the crystal lattices of the IP, yielding a final digital image. Performances of both Image Acquisition Systems so constituted have been evaluated with regard to sensitivity, spatial resolution, linearity and dynamic range, including a comparison with the neutron radiographic system employing films and a Gd foil as neutron-to-charged particle converter. Besides this characterization, several pieces of equipment, have been radiographed with both systems aiming at the evaluation of their capability to unveil the inner features of these components and to detect abnormal structures or states. Within this frame, a neutron radiography detected the presence of remaining ceramic material - employed as a mold during the manufacturing process - in the cooling channels of a turbo-fan stator blade, which should be free of it. Neutron and gamma-ray radiographs have also shown the damaged rheostat of an automotive pressure probe, but the last one exhibited a better spatial resolution corroborating thus the results obtained during the characterization of both systems. The homogeneity of distribution of the stuff encapsulated in an explosive lead-gasket used in the aero-space industry has also been verified by neutron radiography, for this metal is fairly transparent to neutrons but opaque enough to the hydrogen-bearing explosive material. A diversity of other instruments and components such as variometer, altimeter, aeronautical compass, automotive fuel injector, photo-camera, computer hard disk, step-motor, electronic connectors and bullets have been as well radiographed with both systems addressing their ability to unveil different features according to the type of the employed interrogating agente.
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Allen, M. "Ion Acceleration from the Interaction of Ultra-Intense Lasers with Solid Foils." Washington, D.C : Oak Ridge, Tenn. : United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/15011790-SSm9hY/native/.
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Thesis (Ph.D.); Submitted to the Univ. of California, Berkeley, CA (US); 24 Nov 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-208645" Allen, M. 11/24/2004. Report is also available in paper and microfiche from NTIS.
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Laurent-Pettersson, Maria. "Etude de complexes du bore en vue d'une application thérapeutique : utilisation de traceurs isotopiques stables du bore et de l'azote, détectés par « radiographie par capture de neutrons »." Rouen, 1992. http://www.theses.fr/1992ROUES005.
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La boroneutrothérapie consiste à charger les cellules tumorales en bore, grâce à un vecteur approprié, puis à soumettre ce bore à une réaction nucléaire par les neutrons libérant des particules ionisantes qui provoqueront la mort des cellules concernées. Les anticorps monoclonaux sont couramment utilisés comme vecteurs, sur lesquels on peut greffer jusqu'à 2000 atomes de bore par molécule d'anticorps. En utilisant la méthode ELISA et une approche immunohistochimique, le présent travail a montré que les anticorps monoclonaux antiprotéine gliale fibrillaire acide et antihyaluronectine perdaient jusqu'à 90% de leur activité vis-à-vis de l'antigène dès qu'on leur fixait environ 600 atomes de bore par molécule. Il se produisait également des fixations non spécifiques, par l'intermédiaire de la partie borée des complexes. Après injection de borophénylalanine à des souris auxquelles on avait greffé un gliome humain, on a constaté que ce composé s'accumulait rapidement dans les tissus puis qu'il s'éliminait, et qu'il avait pratiquement complètement disparu au bout de la 12ème h; le rapport des concentrations dans la tumeur et dans les tissus sains atteignait une valeur maximale de 2 à 5 vers la 6ème h. Dans ces expériences, la localisation quantitative du bore, et par conséquent l'imagerie des vecteurs de bore in situ, a été faite par radiographie par capture neutronique. La même méthode a permis de faire aussi l'imagerie quantitative de la distribution du bore naturel et de l'azote chez la souris. On a noté une accumulation particulière de bore naturel au niveau de la papille du rein
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Ouznadji-Ramdane, Houria. "Etude de la distribution du lithium chez la souris, dans l'embryon, dans le cerveau des jeunes et le cerveau des mères, par la radiographie par capture de neutrons." Amiens, 1997. http://www.theses.fr/1997AMIE0119.
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Singh, Shifali. "Radioscopie X pour les interactions corium-sodium lors d'un scénario d'accident grave." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS114.
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Dans les réacteurs à neutrons rapides refroidis au sodium (RNR-Na), une défaillance dans le système de refroidissement du coeur ou de protection du réacteur peut conduire à un accident grave. Dans un tel scenario, les matériaux du coeur (combustible et acier) fondent pour former un mélange appelé corium susceptible d'interagir avec le réfrigérant (sodium). Une telle interaction (Fuel Coolant Interaction, FCI) peut générer des évènements énergétiques aptes à mettre en danger les structures du réacteur. La violence de l'explosion dépend essentiellement de l'état du mélange corium-sodium. Connaître les caractéristiques des trois phases en présence dans la zone d'interaction (corium, sodium liquide, vapeur de sodium) est donc crucial. Le manque de connaissances de la phénoménologie de l'interaction conduit à l'étudier au moyen de dispositifs expérimentaux. PLINIUS-2, la future plateforme expérimentale du CEA Cadarache consacrée aux grandes masses, sera dédiée à l'étude de la phénoménologie de l'interaction corium-réfrigérant (eau et sodium). L'objectif du présent travail est de développer, pour cette installation, un système d'imagerie basée sur des radiographies X afin de visualiser et de mieux comprendre l'interaction corium-sodium. Un algorithme de post-traitement de ces images a aussi été écrit afin de les analyser, d'en déduire la répartition des trois phases dans le système et de contribuer ainsi à l'amélioration de la modélisation numérique. Ce travail de thèse a été conduit en trois étapes. La première était consacrée à une étude bibliographique des expériences passées d'interaction corium-sodium et des mécanismes de fragmentation mis en jeu. Cette étude, complétée d'une analyse statistique des distributions de particules obtenue alors, a montré que les particules générées lors de ces expériences sont extrêmement fines avec des diamètres caractéristiques inférieurs au mm. Ces très petites tailles de particules combinées aux limites de détection de notre système d'imagerie nous ont amenés à travailler plutôt sur la détection de nuages de particules que de particules individuelles. Dans une deuxième étape, la simulation du nuage de particules de corium suivie de la conception de fantômes (maquettes 3D) représentant les trois phases du milieu ont été réalisées. Les simulations de nuages de fragments dans le sodium liquide et la vapeur ont été réalisées avec le logiciel CEA MODHERATO. Sur la base des résultats de ces calculs, certains fantômes ont été fabriqués afin de générer des images "réelles" à l'aide d'une chaîne d'imagerie existant au CEA. Ces fantômes représentatifs de la zone d'interaction corium-sodium ont été fabriqués pour faciliter le développement et la calibration du logiciel de traitement d'images. La troisième étape de cette thèse était dédiée à la conduite des expériences avec les fantômes 3D et au développement du logiciel de traitement des images ainsi obtenues. Les radiographies X des fantômes ont été générées à l'aide du système d'imagerie de l'installation KROTOS du CEA Cadarache. Les images ont ensuite été traitées avec le logiciel appelé PICSEL que nous avons développé afin de localiser les trois phases en présence dans la zone d'interaction. PICSEL a ensuite été appliqué à une expérience d'interaction corium-eau réalisée dans l'installation KROTOS dans le cadre du projet ALISA de collaboration Europe-Chine; ceci a permis une première validation du logiciel. Ainsi, lors de cette thèse, un système de radioscopie X a été défini pour visualiser l'interaction corium-sodium dans les expériences de la future installation PLINIUS-2 du CEA Cadarache. Une analyse qualitative des images produites par ce système (expériences menées avec des fantômes) est aussi réalisée avec le logiciel PICSEL développé lors de cette thèse afin de mieux caractériser le mélange, de mieux comprendre les mécanismes de l'interaction et de contribuer ainsi à l'amélioration de la sûreté des réacteurs à neutrons rapidesIn Sodium-cooled Fast Reactors (SFR), hypothetical failure of the core cooling system or the plant protection system may lead to a severe accident scenario. In such a scenario, core materials (fuel and cladding) melt down generating a hot molten mixture called corium. This corium may interact with the coolant (liquid sodium) leading to Fuel Coolant Interaction (FCI) which can generate energetic events and hence jeopardize the reactor structures. The yield of these energetic events strongly depends on the state of the corium-sodium mixture prior to the energetic event. Therefore, the knowledge of the features of the mixture composed of three-phases (i.e., corium, liquid sodium, and sodium vapor) is crucial. The lack of knowledge on the phenomenology of the interaction emphasizes the need to study it with the help of experiments. PLINIUS-2, the future large-mass experimental platform of CEA Cadarache, will be dedicated to experiments aiming at understanding the interaction phenomenology of prototypic corium with coolant (sodium and water). The present research aims to develop a high-energy X-Ray imaging system for this facility, to visualize and better understand the corium-sodium interaction. An image-processing algorithm to analyze the three-phase repartition is also developed to contribute to the improvement of numerical modeling. This Ph.D. research has been executed in three steps. In the first step, a bibliographic study of the past experiments was carried out to better understand the physics of the interaction and the mechanism of fragmentation during corium-sodium interaction. This bibliographic study, along with a statistical analysis of the particle size distribution data of various experiments conducted in the past, revealed that the particles formed in these tests are extremely fine fragments with characteristic diameters smaller than 1 mm. Due to the small particle size and the detection limitations of corium fragments in sodium with our X-Ray system, clouds of particles were detected instead of individual particles. In the second phase, the simulation of clouds of corium particles followed by the designing of phantoms (3D mock-ups) representing the 3-phase medium was carried out. Simulations of clouds of corium fragments in liquid sodium and vapor were performed using the CEA Cadarache in-house tool MODHERATO. Based on the results obtained from the simulations, certain phantoms were designed to conduct some physical experiments. These phantoms representative of the FCI interaction zone were manufactured to experimentally evaluate the performance of the radioscopy system and to facilitate the development and calibration of the image processing software. The third step of this work was dedicated to performing experiments with the phantoms and analyzing the radiographic images by developing an image processing algorithm. Experiments were carried out with phantoms in several configurations with the X-Ray radiography system at the CEA Cadarache KROTOS facility. The radioscopic images obtained were treated by developing a new comprehensive image processing and analysis code called PICSEL to identify the three phases composing the medium. Further verification and validation of the PICSEL software were carried out on a test conducted between corium and water at the KROTOS facility under the Euro-Chinese project “ALISA”. Thus, in this Ph.D. research, an X-Ray imaging system was qualified to visualize the corium-sodium interaction in the future PLINIUS-2-FR facility. A qualitative analysis of the images produced by this system was also performed using the PICSEL software to better characterize the evolution of the three-phase mixture and understand the FCI phenomenon, knowledge of which is deemed essential to improve the safety and designs of future sodium-cooled fast reactors
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Guzek, Jacek. "Elemental radiography using fast neutron beams." Thesis, 2012. http://hdl.handle.net/10539/11454.
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Ramushu, Mokgobi Andrew. "High density shielding concrete for neutron radiography." Thesis, 2015. http://hdl.handle.net/10539/17537.
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In this research report, special High Density-Shielding Concrete (HDSC) was developed. The objective of this research was to investigate, design and test HDSC to be used to construct the newly upgraded South African Neutron Radiography (SANRAD) facility situated at the South African Nuclear Energy Corporation (NECSA).
To understand the concept of radiation shielding in detail, a literature review on several aspects surrounding radiation shielding and interaction of radioactive energies and matter was conducted. This involved aspects such as the types of radiation, theory of radiation shielding, different materials used for radiation shielding and several other topics. Based on the compiled literature and the availability of materials that could be used, concrete was selected as the best shielding material and further undertakings were carried out to develop a specific mixture that would shield the radioactive energies. The main contributing factors in the decision making with regard to the use of concrete were the already existing knowledge and technology, the local availability of most high density concrete aggregates needed, the versatility and composite nature of the material, the economic benefits of using the material, low maintenance and ease of manufacture, and the structural integrity of the material.
The final mixture produced in this research was workable and cohesive with average 28- day compressive cube strength of 29.9 MPa, water to cement ratio of 0.51 and density of 4231 kg/m3. The concrete was made to be of high slump with a height and spread of 230 mm and 510 mm respectively. The final mixture was composed of CEM I 52.5 N, silica fume, water, hematite sand, hematite stone, steel shot, colemanite and chemical admixtures.
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Luo, Xin. "Study on Infrastructure Materials Using Neutron Radiography and Diffraction." 2007. http://trace.tennessee.edu/utk_graddiss/234.
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Advanced nondestructive neutron technology has been utilized to study fundamental issues in the Lost Foam Casting (LFC) process and in the mechanical behavior of infrastructure materials.
Time lapsed neutron radiography combined with digital image processing was used to investigate the real-time LFC process. Behavior and characteristics of the pyrolysis front in the LFC processes were discussed. Evidence shows that neutron radiography offers new insights into the pyrolysis front and the dynamics of the processes involved with the casting. Behavior and characteristics of the pyrolysis front and the molten metal interface in the LFC processes were revealed. The proposed approach will prove to be a powerful tool to characterize the degradation behavior of the expanded polystyrene foam during the LFC process and the interactions of liquid metal.
The stress-strain relationship of particulate materials is complex, and depends on the initial state of packing, past stress history, and the applied stress path. A novel in-situ study methodology has been developed using neutron scattering technique to obtain strains both globally and locally. The significant differences between the global deformation and the local lattice strain for silica sand have been found and discussed. The measured lattice strain was at least one order of magnitude smaller than the measured related global strain. However, the actual stress within the particles could be much higher than the applied global stress. Research results from this study will be useful for developing suitable elasto-plastic constitutive models of frictional granular materials.
Residual stress has a significant impact on the mechanical behavior materials. It is difficult to be measured or predicted using analytical methods, and can lead to premature failure of materials if not appropriately considered in design. Residual strains of identical steel tubular specimens after being subjected to either torsion or tension corresponding to a target equivalent strain invariant were probed using both reactor and spallation neutron sources. The lattice strains based on the hkl reflections that are reported to be both weakly and strongly affected by intergranular strain for tension stress path were investigated. The results indicate the essential difference between tension and torsion from the perspective of yield and failure criteria for materials.
An innovative approach has been developed to study the complete 3-D strain tensor using the 2nd Generation Neutron Residual Stress Facility at Oak Ridge National Laboratory. A procedure was also established to understand the mechanism and to analyze the errors of the calculated strain tensor. This newly developed approach makes it possible to study the strain/stress state in materials under complex conditions.
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Gilbert, Andrew James 1983. "Measuring fluid phase change in capillary tubes using neutron radiography." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1491.
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Neutron radiography is well suited to non-invasive imaging of water within metal containers. The goal of this work is to determine if neutron radiography can be used to image water freezing within a 1.6mm diameter capillary tube with the ultimate goal of observing this phenomena within fuel cells. In this work, radiography was completed at the Thermal Neutron Imaging Facility in the Nuclear Engineering Teaching Lab at The University of Texas at Austin. The source of neutrons was a TRIGA Mark II nuclear research reactor capable of 1.1 MW steady state power, which creates a neutron flux at the neutron imaging plane in beam port 5 of 5×10^6 neutrons/cm^2s. A scintillation screen and CCD camera are utilized to obtain digital radiographs, in which differences in pixel intensity are related to differences in neutron attenuation. An image processing algorithm was developed in Matlab to extract necessary data from each image, analyze water column images, and compare one to another. Also, a neutron flux model was implemented in Matlab in order to understand how a non-unidirectional neutron flux will affect final results. Raw image intensities of the water column in liquid and solid form were found to differ from expectations by at most 12.0% and 13.3%, respectively from the predictions of the Matlab flux model. A difference in pixel intensity comparing liquid water to solid water data is apparent and quantified. A ratio of pixel intensity for the ice image to the water image at full thickness of the water column is expected to be 1.038. Experimental results find a maximum ratio of 1.027, 1.1% off from expectations.text
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Haas, Derek Anderson 1981. "Development of a neutron radiography and computed tomography system at a university research reactor." Thesis, 2006. http://hdl.handle.net/2152/30078.
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Neutron radiography is a non-destructive analysis tool that complements X-ray transmission radiography. The use of neutrons provides the ability to image the interior of an object that has a metal core of steel or lead that would shield the interior from X-ray inspection. Neutron tomography is the use of a set of images of a single sample taken at various angles to produce a three dimensional rendition of the sample that greatly increases the effectiveness of neutron radiography as a non-destructive testing tool. A neutron radiography and tomography system has been built at the 1.1 MW TRIGA Mark II nuclear research reactor at The University of Texas at Austin in the Nuclear Engineering Teaching Lab. The Texas Neutron Imaging Facility is located on beam port five of the reactor and is housed in a shielding cave made of concrete to minimize radiation dose to users. The system itself integrates a sample positioning system and neutron sensitive camera through the use of a control code written in National Instruments Labview software. The code was written to increase the efficiency of the imaging process and to provide flexibility in the system. Precise sample positioning and timing of image acquisition provided by the code allows for the collection of data that can be used in computed tomography. The system has produced results in the form of radiographs and 3-D reconstructions of sample objects.text
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Huang, Chun-Kai, and 黃俊愷. "The Measurement of 2D-Neutron Distribution for Tsing Hua Open-pool Reactor Boron Neutron Capture Therapy Beam Using Indirect Neutron Radiography Method." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/68762658339187971170.
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