Dissertations / Theses on the topic 'Neutrons Prompts de Fission'
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Sardet, Alix. "Spectres en énergie des neutrons prompts de fission : optimisation du dispositif expérimental et application à l'²³⁸U." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS002/document.
Full textThe nuclear fission is a complex phenomenon whose mechanisms are not fully understood. Within the framework of an international cooperation, the CEA/DAM/DIF is taking part in the study of prompt fission neutron energy spectra from fast neutron induced fission, focusing on the low energy domain of these spectra (<1 MeV). This PhD was dedicated to the optimization of the experimental setup. New fission detectors were developed. We report on their conception and their performances in terms of alpha-fission discrimination, timing resolution and distortion on the measured spectrum. In a second step, several neutron detectors were studied (neutron-gamma discrimination, detection efficiency), so as to optimize the detection of low energy neutrons (<1 MeV). In the present document, we report on the results of this comparative study. Finally, the optimized experimental setup was used to measure prompt fission neutron energy spectra for the fast-neutron induced fission of ²³⁸U. After detailing the data analysis method, the results are interpreted in terms of models and evaluations
Berge, Léonie. "Contribution à la modélisation des spectres de neutrons prompts de fission .Propagation d'incertitudes sur un calul de fluence cuve." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI039/document.
Full textThe prompt fission neutron spectrum (PFNS) is very important for various nuclear physics applications. Yet, except for the 252Cf spontaneous fission spectrum which is an international standard and is used for metrology purposes, the PFNS is still poorly known for most of the fissionning nuclides. In particular, few measurements exist for the fast fission spectrum (induced by a neutron whose energy exceeds about 100 keV), and the international evaluations show strong discrepancies. There are also very few data about covariances associated to the various PFNS evaluations. In this work we present three aspects of the PFNS evaluation. The first aspect is about the spectrum modeling with the FIFRELIN code, developed at CEA Cadarache, which simulates the fission fragment de-excitation by successive emissions of prompt neutrons and gammas, via the Monte-Carlo method. This code aims at calculating all fission observables in a single consistent calculation, starting from fission fragment distributions (mass, kinetic energy and spin). FIFRELIN is therefore more predictive than the analytical models used to describe the spectrum. A study of model parameters which impact the spectrum, like the fragment level density parameter, is presented in order to better reproduce the spectrum. The second aspect of this work is about the evaluation of the PFNS and its covariance matrix. We present a methodology to produce this evaluation in a rigorous way, with the CONRAD code, developed at CEA Cadarache. This implies modeling the spectrum through simple models, like the Madland-Nix model which is the most commonly used in the evaluations, by adjusting the model parameters to reproduce experimental data. The covariance matrix arises from the rigorous propagation of the sources of uncertainty involved in the calculation. In particular, the systematic uncertainties arising from the experimental set-up are propagated via a marginalization technique. The marginalization allows propagating these uncertainties on the calculated spectrum, and obtaining realistic uncertainties without having to artificially raise them, as it is sometimes necessary in Bayesian adjustments. The experimental uncertainty propagation also impacts the spectrum correlation matrix. We present the result for thermal neutron-induced fission of 235U and 239Pu. For the Madland-Nix model with constant inverse cross-section, the prompt neutron mean energy is 1.979 MeV for 235U and 2.087 MeV for 239Pu. The last aspect of this work is the calculation of the impact of the PFNS and its covariance matrix on a reactor vessel flux. This calculation is of major importance, since the vessel fluence estimation determines the vessel integrity, and therefore determines the reactor lifetime. We observe the importance of the PFNS correlation terms, to compute in particular the vessel flux uncertainty above 1 MeV, which is of the order of 6% (uncertainty only due to PFNS)
Qi, Liqiang. "Measurements of Prompt Gamma Rays Emitted in Fission of ²³⁸U and ²³⁹ Pu Induced by Fast Neutrons from the LICORNE Neutron Source." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS320/document.
Full textPrompt fission γ-ray spectra are important nuclear data for reactor physics, as an input for gamma heating calculations, since the gamma heating effect can be under-estimated by up to ~28% with present nuclear data. Furthermore the new prompt fission γ-ray information will be useful from a fundamental physics point of view, where results can be compared with many competing theoretical predictions to refine models of fission process. Prompt fission γ-ray spectra have been measured for the fast-neutron-induced fission of ²³⁸U and ²³⁹PuPu, using fast neutrons generated from the LICORNE source. The experimental setup consisted of an ionization chamber and different types of scintillation detectors, including LaBr₃ and PARIS phoswich detectors. An analysis procedure, including unfolding and recovering the γ-ray response in the scintillation detectors, is developed to extract the prompt fission γ-ray spectrum and corresponding spectral characteristics. The experimental results are compared to the fission modeling codes GEF and FREYA. This comparison reveals that the spectral characteristics are related to the energetic conditions, isotopic yields and angular momentum of the fission fragments. The energy dependence of the spectral characteristics shows that the prompt γ-rays emission is quite insensitive to the incident neutron energy. However, a strong dependence on the particular fissioning system is observed
Varapai, Natallia. "Développement d'un dispositif expérimental basé sur la digitalisation des signaux et dédié à la caractérisation des fragments de fission et des neutrons prompt[s] émis." Bordeaux 1, 2006. http://www.theses.fr/2006BOR13274.
Full textRąpała, Michał. "Etude de la fission nucléaire par spectrométrie des rayons gamma prompts." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS390/document.
Full textThe desire to improve the fuel efficiency of nuclear reactors has motivated new solutions in their design. One of them is the heavy reflector used in the generation III+ and in the future generation IV reactors. γ-rays passing through matter cause its excitation and temperature rise. It is a process called γ-heating, and it is responsible for more than 90% of the heat production in the non-fuel region of the nuclear reactor. This is also the case of the heavy reflector. To simulate the γ-heating effect in every state of the nuclear reactor it is necessary to have precise data on the prompt γ-rays emitted by different fission fragments produced in the course of the nuclear chain reaction. In 2012, at the research reactor of the ILL, an innovative experiment, called EXILL, was conducted. It produced a large amount of useful data on the de-excitation of the fission fragments. A large number of HPGe detectors were used to study the neutron induced fission process by measuring the emitted γ-rays. Fissile targets were irradiated by an intense cold neutron beam. In this work we analyzed the ²³⁵U targets. We studied several fission fragments and more generally the fission process by using high-resolution γ-ray spectroscopy. At the beginning, we used the standard γ-γ-γ coincidence analysis method. We were able to filter experimental data, identify the well produced γ-rays, and calculate their relative intensities. The problems we have encountered are related to the background. The results obtained with this method were background dependent and thus presented some problems with reproducibility. We therefore developed and tested a new analysis methodology. Its crucial feature is a coincidence gates scanning in three directions which helps to find the most suitable background. The idea was to move from a “spectroscopic” method, which main purpose is finding new transitions and excited states in a nucleus, to a “spectrometric” method, which allows us to obtain more precise γ-ray intensities. We developed a semi-automatic analysis software which facilitates fitting of the chosen γ-ray peak, the contamination and the background. Various γ-ray intensity calculation schemes were derived to take into account different contamination strengths and placements. The results of the analysis with the new technique are reproducible and more reliable. The standard and the new analysis method were compared in the ¹⁴²Ba analysis. In this work, we also compared our experimental results on some nuclei, such as ¹⁰⁰Zr, with the simulation results performed with the FIFRELIN code. It is a Monte-Carlo code which simulates the fission process and the de-excitation of the fission fragments. It uses various models to describe these processes. We were able to test the behavior of different models implemented in FIFRELIN to find the optimal simulation parameter values and to test how well these setups reproduce the experimental results. FIFRELIN was unable to simultaneously reproduce the γ-ray intensities of ¹⁰⁰Zr and the prompt-neutron multiplicity averaged over all fission fragments. However, with modified simulation parameters, FIFRELIN locally provided correct prompt-neutron multiplicity for the fission fragment with the atomic mass A=100 and well reproduced γ-ray intensities of ¹⁰⁰Zr. We also compared our experimental results on ¹⁰⁰Zr coming from the ²³⁵U(n,f) process with the other available experimental data coming from the experiments on ²⁴⁸Cm(sf) and ²⁵²Cf(sf), and another experiment on ²³⁵U(n,f)
Tovar, Jesus Felipe. "Studies of prompt gamma and neutron yield due to 2.5 MeV neutrons using GEANT4." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Full textMartin, Julie-Fiona. "Coulex fission of ²³⁴U, ²³⁵U, ²³⁷Np and ²³⁸Np studied within the SOFIA experimental program." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112315/document.
Full textSOFIA (Studies On FIssion with Aladin) is an experimental project which aims at systematically measuring the fission fragments' isotopic yields as well as their total kinetic energy, for a wide variety of fissioning nuclei. The PhD work presented in this dissertation takes part in the SOFIA project, and covers the fission of nuclei in the region of the actinides : ²³⁴U, ²³⁵U, ²³⁷Np and ²³⁸Np.The experiment is led at the heavy-ion accelerator GSI in Darmstadt, Germany. This facility provides intense relativistic primary beam of 238U. A fragmentation reaction of the primary beam permits to create a secondary beam of radioactive ions, some of which the fission is studied. The ions of the secondary beam are sorted and identified through the FR-S (FRagment Separator), a high resolution recoil spectrometer which is tuned to select the ions of interest.The selected - fissile - ions then fly further to Cave-C, an experimental area where the fission experiment itself takes place. At the entrance of the cave, the secondary beam is excited by Coulomb interaction when flying through an target; the de-excitation process involves low-energy fission. Both fission fragments fly forward in the laboratory frame, due to the relativistic boost inferred from the fissioning nucleus.A complete recoil spectrometer has been designed and built by the SOFIA collaboration in the path of the fission fragments, around the existing ALADIN magnet. The identification of the fragments is performed by means of energy loss, time of flight and deviation in the magnet measurements. Both fission fragments are fully (in mass and charge) and simultaneously identified.This document reports on the analysis performed for (1) the identification of the fissioning system, (2) the identification of both fission fragments, on an event-by-event basis, and (3) the extraction of fission observables: yields, TKE, total prompt neutron multiplicity. These results, concerning the actinides, are discussed, and the set of data extracted is provided
Varapai, Nathallia. "Développement d'un dispositif expérimental basé sur ladigitalisation des signaux et dédié à la caractérisation desfragments de fission et des neutrons prompte émis." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2006. http://tel.archives-ouvertes.fr/tel-00404495.
Full textAbdelrahman, Y. S. "Prompt gamma-rays from fission fragments." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234192.
Full textMcGinnis, Jason M. "PROMPT FISSION NEUTRON ENERGY SPECTRUM OF n+235U." UKnowledge, 2019. https://uknowledge.uky.edu/physastron_etds/63.
Full textRégnier, David. "Contribution à l'étude des gammas prompts de fission." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI065.
Full textThis PhD thesis has essentially been motivated by the nuclear heating problematic in reactors. The main goal of this work was the production of methods capable of simulating the prompt gamma emission from fission. First of all, several algorithms for the treatment of the nucleus deexcitation were implemented. They have been succesfully tested through various calculations (isomeric branching ratio, total radiative width, etc). These methods were then incorporated in the frame of the fission code FIFRELIN. The tool which results from this work, enables the determination of numerous fission observables in the frame of a single consistent model. A sensitivity study of the results to several numerical and nuclear models has been realized. At last, calculation have been lead for the 252Cf spontaneous fission and the thermal neutron induced fission of 235U and 239Pu. The prompt gamma spectra obtained for those three fissionning systems have been determined. The results are in good agreement with available experimental data, including recent measurements published in 2012 and 2013
Miller, Zachariah W. "A MEASUREMENT OF THE PROMPT FISSION NEUTRON ENERGY SPECTRUM FOR 235U(n,f) AND THE NEUTRON-INDUCED FISSION CROSS SECTION FOR 238U(n,f)." UKnowledge, 2015. http://uknowledge.uky.edu/physastron_etds/29.
Full textGaly, Jean. "Investigation of the fission yields of the fast neutron-induced fission off 233U." Aix-Marseille 1, 1999. https://tel.archives-ouvertes.fr/tel-00620088.
Full textLAU, CHRISTOPHE. "Etude de la production de faisceaux riches en neutrons par fission induite par neutrons rapides." Paris 7, 2000. http://www.theses.fr/2000PA077127.
Full textLacoste, Véronique. "Transmutation de produits de fission à vie longue dans un grand massif de plomb." Bordeaux 1, 1998. http://www.theses.fr/1998BOR10658.
Full textSchilling, Klaus-Dieter, and Horst Märten. "High-resolution spectroscopy of fission fragments, neutrons and gamma-rays." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-32739.
Full textSchilling, Klaus-Dieter, and Horst Märten. "High-resolution spectroscopy of fission fragments, neutrons and gamma-rays." Forschungszentrum Rossendorf, 1993. https://hzdr.qucosa.de/id/qucosa%3A22100.
Full textRyan, James. "Measuring the energies and multiplicities of prompt gamma-ray emissions from neutron-induced fission of 235 U using the STEFF spectrometer." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/measuring-the-energies-and-multiplicities-of-prompt-gammaray-emissions-from-neutroninduced-fission-of-235-u-using-the-steff-spectrometer(5fca332e-58ef-463f-96ba-99d87f0ecf44).html.
Full textMacary, Véra. "Etude expérimentale de l’émission de neutrons retardés issus de la photofission des actinides." Paris 6, 2008. http://www.theses.fr/2008PA066066.
Full textChietera, Andreina. "Angular correlations between fragments and neutrons in the spontaneous fissions of 252 Cf." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE048/document.
Full textThe subject of this thesis is to explore the neutron emission mechanisms in the fission process. In particular a long standing open question, the existence of a dynamical anisotropy in the centre of mass of the fission fragments and/or a possible scission neutron emission is explored. The thesis starts with an overview of the theoretical concepts on the fission process and on the neutron emission mechanisms. Also the necessity to conceive an appropriate analysis method is stressed when a very subtle mechanism is studied as various approximations and/or experimental biases not completely handled can hide the physical phenomena. In the presented work a huge effort was required to write a Monte Carlo procedure based on a coherent model for the spontaneous fission of 252Cf and to couple it with the devices exploited in the CORA3 experiment
Edwards, Ellen. "Measurement of Krypton Fission Product Yields from 14 MeV Neutrons on 238U." Thesis, University of California, Berkeley, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10930784.
Full textPrecisely-known fission yield distributions are used to determine a fissioning isotope and the incident neutron energies in nuclear security applications. 14 MeV neutrons from DT fusion at the National Ignition Facility (NIF) induced fission in depleted uranium (DU) contained in the target assembly hohlraum. The fission yields of Kr isotopes (85m, 87, 88, 89, and 90) were measured relative to the cumulative yield of 88Kr. The fission gas was pumped from the target chamber, collected, and analyzed in the Radiochemical Analysis of Gaseous Samples (RAGS) diagnostic. Isotopes with half-lives ranging 8 s-9 hr can be measured. Kr fission yields have been measured both from the fission of DU in the hohlraum and DU doped into the capsule ablator. Since the mass of U was not known, the relative amounts of Kr isotopes were calculated and compared to existing fission product distribution tables. It was found that measurements can be performed with high precision for isotopes with half lives longer than 4 minutes. A more precise quantification of gas transport needs to be achieved to quantify isotopes with shorter half lives to a precision of the published tables.
Mauborgne, Marie-Laure. "Création d'une bibliothèque d'activation photonucléaire et mesures de spectres d'émission de neutrons retardés." Caen, 2005. http://www.theses.fr/2005CAEN2033.
Full textPetit, Michaël. "Mesure de la section efficace de fission du ²³³Pa." Bordeaux 1, 2002. http://www.theses.fr/2002BOR12554.
Full textCasoli, Pierre. "Etude de la production de fragments dans la fission induite par neutrons sur l'uranium 238." Bordeaux 1, 2003. http://www.theses.fr/2003BOR12710.
Full textMass and charge distributions of fission fragments from the fission induced on uranium 238 by neutrons from 1 to 150 MeV were studied by experimental data and theoretical calculations. Measurements in prompt gamma and x-ray spectroscopy, completed at the LANSCE laboratory of Los Alamos allowed us to determine the secondary fission fragment production yiels. Phtovotaic cells were used as a fission trigger. About one hundred fragments were identified and about thirty excitation functions were extracted. Mass and charge distributions at different incident energies were obtained. The comparison with evaluated sata (Wahl systematics) shows that the calculations are consistent with the measurements below 20 MeV but not predictive enough above. A potential energy surface was drawn from microscopic constrained self-consistent HFB calculations. We obtained a gragment mass distribution by solving the dynamic Schrödinger equation on this surface
KELIC, ALEKSANDRA. "Etude experimentale et theorique de l'emission dynamique de neutrons associee a la fission bi-modale." Université Louis Pasteur (Strasbourg) (1971-2008), 2000. http://www.theses.fr/2000STR13082.
Full textAfarideh, Hossein. "A study of fission in [superior] 238 U induced by Monoenergetic neutrons and heavy ions and of light particle emission in [superior] 252 Cf spontaneous fission." Thesis, University of Birmingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.617021.
Full textCarrel, Frédérick. "Etude et développement d’une technique de dosage des actinides dans les colis de déchets radioactifs par interrogation photonique ou neutronique active et spectrométrie des gamma retardés." Caen, 2007. http://www.theses.fr/2007CAEN2022.
Full textAn accurate estimation of the alpha-activity of a nuclear waste package is necessary to select the best mode of storage. The main purpose of this work is to develop a non-destructive active method, based on the fission process and allowing the identification of actinides (235U, 238U, 239Pu). These three elements are the main alpha emitters contained inside a package. Our technique is based on the detection of delayed gammas emitted by fission products. These latter are created by irradiation with the help of a neutron or photon beam. Performances of this method have been investigated after an Active Photon or Neutron Interrogation (INA or IPA). Three main objectives were fixed in the framework of this thesis. First, we measured many yields of photofission products to compensate the lack of data in the literature. Then, we studied experimental performances of this method to identify a given actinide (239Pu in fission, 235U in photofission) present in an irradiated mixture. Finally, we assessed the application of this technique on different mock-up packages for both types of interrogation (118 l mock-up package containing EVA in fission, 220 l mock-up package with a wall of concrete in photofission)
MAIDANA, NORA L. "Medidas de seccoes de choque medias no espectro de fissao do U-235 para algumas reacoes de limiar." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10314.
Full textMade available in DSpace on 2014-10-09T14:09:04Z (GMT). No. of bitstreams: 1 04784.pdf: 1414862 bytes, checksum: dd92e9abc5bb1044dcef6e7b745b4846 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Schmitt, Christelle. "Fission des Noyaux Lourds et Superlourds." Phd thesis, Université Louis Pasteur - Strasbourg I, 2002. http://tel.archives-ouvertes.fr/tel-00001529.
Full textFerrant, Laure. "Mesures de sections efficaces de fission induite par neutrons sur des actinides du cycle du thorium à n_TOF." Phd thesis, Université Paris Sud - Paris XI, 2005. http://tel.archives-ouvertes.fr/tel-00011454.
Full textFernández-Domínguez, Beatriz. "Etude de la production des fragments de fission issus de la réaction 208Pb+p à 500 AMeV." Caen, 2003. http://www.theses.fr/2003CAEN2021.
Full textVlachoudis, Vassilis. "Taux de capture et de fission du ²³²Th, ²³⁸U, ²³⁷Np et ²³⁹Pu par des neutrons de spallation dans un grand massif de plomb." Bordeaux 1, 2000. http://www.theses.fr/2000BOR10505.
Full textThe study is centered on the research of the incineration possibility of nuclear waste, by the association of a particle accelerator with a multiplying medium of neutrons, in the project “Energy Amplifier” of C. RUBBIA. It consists of the experimental determination of the rates of capture and fission of certain elements (²³²Th, ²³⁸U, ²³⁷Np and ²³⁹Pu) subjected to a fluence of fast spallation neutrons. These neutrons are produced by the interaction of high kinetic energy protons (several GeV) provided by the CERN-PS accelerator, on a large lead solid volume. The measurement techniques used in this work, are based on the activation of elements in the lead volume and the subsequent gamma spectroscopy of the activated elements, and also by the detection of fission fragment traces. The development, of a Monte Carlo code makes it possible, on one hand, to better understand the relevant processes, and on the other hand, to validate the code, by comparison with measurements, for the design and the construction of an incineration system
Chen, Yonghao. "Characterization of the New Neutron Line at CERN-n_TOF and Study of the Neutron-induced Fission of 237Np." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS204/document.
Full textThe neutron time-of-flight (n_TOF)facility at CERN is a unique worldwide pulsedneutron source to measure the nuclear data over thewidest energy range with two beam lines currentlyexploited. One is horizontal with a ~185 metersflight path, sending neutrons to experimental area-1(EAR-1). The second one is a new line sendingneutrons vertically to experimental area-2 (EAR-2)with a ~20 meters flight path.The first part of this PhD work is dedicated to thecharacterization of the beam (flux, geometricalprofile, energy spectrum) of the new EAR-2 neutronbeam, of the utmost importance for the experimentalproposals and analyses. An experiment was carriedout at EAR-2, based on PPAC detectors looking atfission of 235U, and the beam profile and neutronflux have been obtained for the entire availableenergy range (from thermal to 200 MeV).The second part of the thesis aims to study theneutron-induced fission of 237Np. 237Np isabundantly produced in present nuclear reactor andis one of the major long-lived components ofnuclear waste which can be considered as apotential target of incineration in fast neutronreactors. Consequently its neutron-induced fissioncross section has been measured at differentfacilities. However, significant discrepancies existbetween different experiments. Especially, therecent one performed at n_TOF in 2010 is about 6%higher by comparison to the evaluation data basedon previous experiments. Therefore an experimenthas been performed at n_TOF EAR-1 to measure itsfission cross section, in a configuration allowing anaccurate control of the detection efficiency, aimingto give a definite answer to the puzzle. In this work,we found that the efficiencies for different targetelements are different, even though they havesimilar thickness, reflecting the conditions ofelectrodeposition. After application of thisefficiency correction in the energy range from 1 to 5MeV, the newly extracted fission cross section is 2-3% lower compared with our previous measurementin 2010, however they are 3-4% higher than the
Nicol, Tangi. "Caractérisation des colis de déchets radioactifs par activation neutronique." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY021/document.
Full textNuclear activities produce radioactive wastes classified following their radioactive level and decay time. An accurate characterization is necessary for efficient classification and management. Medium and high level wastes containing long lived radioactive isotopes will be stored in deep geological storage for hundreds of thousands years. At the end of this period, it is essential to ensure that the wastes do not represent any risk for humans and environment, not only from radioactive point of view, but also from stable toxic chemicals. This PhD thesis concerns the characterization of toxic chemicals and nuclear material in radioactive waste, by using neutron activation analysis, in the frame of collaboration between the Nuclear Measurement Laboratory of CEA Cadarache, France, and the Institute of Nuclear Waste Management and Reactor Safety of the research center, FZJ (Forschungszentrum Jülich GmbH), Germany. The first study is about the validation of the numerical model of the neutron activation cell MEDINA (FZJ), using MCNP Monte Carlo transport code. Simulations and measurements of prompt capture gamma rays from small samples measured in MEDINA have been compared for a number of elements of interest (beryllium, aluminum, chlorine, copper, selenium, strontium, and tantalum). The comparison was performed using different nuclear databases, resulting in satisfactory agreement and validating simulation in view of following studies. Then, the feasibility of fission delayed gamma-ray measurements of 239Pu and 235U in 225 L waste drums has been studied, considering bituminized or concrete matrixes representative of wastes produced in France and Germany. The delayed gamma emission yields were first determined from uranium and plutonium metallic samples measurements in REGAIN, the neutron activation cell of LMN, showing satisfactory consistency with published data. The useful delayed gamma signals of 239Pu and 235U, homogeneously distributed in the 225 L matrixes, were then determined by MCNP simulations using MEDINA numerical model. Weak signals of about one hundred counts per gram of 239Pu or 235U after 7200 s irradiation were obtained. Because of the high gamma emission in the bituminized waste produced in France (about 1 TBq of 137Cs per drum), the use of collimator and/or shielding is mandatory to avoid electronic saturation, making fission delayed gamma rays undetectable. However, German concrete drums being of lower activity, their corresponding active background was measured in MEDINA with a concrete mock-up, leading to detection limits between 10 and 290 g of 235U or239Pu, depending on the delayed gamma line. In order to improve these performances, the shielding of MEDINA germanium detector was optimized using MCNP calculations, resulting in gamma and neutron background reduction factors of 4 and 5, respectively. The experimental validation of the shielding efficiency was performed by implementing easy-to-build configurations in MEDINA, which confirmed the expected background reduction factors predicted by MCNP. Thanks to an optimized detector shielding, it will also be possible to use a higher neutron emission source, like a high flux neutron generator or an electron LINAC with appropriate conversion targets, in view to further reduce detection limits
HOURY, MICHAEL. "Spectroscopie gamma des noyaux riches en neutrons produits par fission induite 12c + 238u -structure nucleaire des isotopes de palladium." Paris 11, 2000. http://www.theses.fr/2000PA112002.
Full textGrosjean, Cédric. "Mesure de la section efficace de fission induite par neutrons rapides des noyaux ²³²Th / ²³³U dans le cadre des cycles de combustible innovants." Bordeaux 1, 2005. http://www.theses.fr/2005BOR12967.
Full textThe thorium ²³²Th- ²³³U fuel cycle might provided safer and cleaner nuclear energy than the present Uranium/ Pu fuelled reactors. Over the last 10 years, a vast campaign of measurements has been initiated to bring the precision of neutron data for the key nuclei (²³²Th, ²³³Pa and ²³³U) at the level of those of the U- Pu cycle. This is the framework of these measurements, the energy dependent neutron induced fission cross section of ²³²Th and ²³³U has been measured from 1 to 7 MeV with a target accuracy lesser than 5 %. These measurements imply the accurate determination of the fission rate, the number of the target nuclei as well as the incident neutron flux impinging on the target, the latter has been obtained using the elastic scattering (n, p). The cross section of which is the very well known in a large neutron energy domain (~ 0,5 % from 1 eV to 50 MeV) compared to the 235U(n, f) reaction. This technique has been applied for the first time to the 232Th(n, f) and ²³³U(n, f) cases. A Hauser- Feshbach statistical model has been developed. It consists of describing the different decay channels of the compound nucleus 234U from 0,01 to 10 MeV neutron energy. The parameters of this model were adjusted in order to reproduce the measured fission cross section of ²³³U. From these parameters, the cross sections from the following reactions could be extracted: inelastic scattering ²³³U(n, n'), radiative capture ²³³U(n, ) and ²³³U(n, 2n). These cross sections are still difficult to measure by direct neutron reactions. The calculated values allow to fill the lack of experimental data for the major fissile nucleus of the thorium cycle
Riahi, Azzeddine. "Etude des corrélations masse-énergie cinétique-charge nucléaire des fragments produits dans la fission induite par neutrons thermiques de ²³⁹Pu." Bordeaux 1, 1987. http://www.theses.fr/1987BOR10596.
Full textRiahi, Azzeddine. "Etude des corrélations masse-énergie cinétique-charge nucléaire des fragments produits dans la fission induite par neutrons thermiques de ²³⁹Pu." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376093320.
Full textBlanc, de Lanaute Nicolas. "Développement et optimisation de méthodes de mesures neutroniques par chambre à fission auprès de réacteurs expérimentaux. Maîtrise , traitement et réduction des incertitudes." Thesis, Clermont-Ferrand 2, 2012. http://www.theses.fr/2012CLF22217.
Full textNuclear measurement, and in particular neutronic measurement, plays a key role in nuclearresearch and industry. Neutrons, when detected, are able to provide capital pieces ofinformation on the behavior of, for example, a nuclear reactor core. This allows, amongothers things, a safe operating of the reactor, qualifying calculation tools used for theconception of future reactors (such as the JHR or the 4th generation reactors) and makingprogress in fundamental research by improving nuclear data libraries. The result of eachmeasurement is affected by an uncertainty which depends on many factors. Its estimation isa necessity and its reduction is one of the major challenges taken up to by the CEA.Neutrons are not charged particles and are therefore unable to directly ionize the gas of agas filled detector; therefore their detection using this kind of measurement tool requires aconversion reaction, which is, in the case of the fission chamber detector, the induced fissionreaction. The reduction and mastery of the uncertainties affecting the fission chambersmeasurements are the core of the thesis subject. This work was achieved within theExperimental Program Laboratory (LPE) of the Experimental Physics Section (SPEx) at CEACadarache. It is divided into four parts:· the first one consists in a state of the art of fission chambers measurements within theframework of the zero-power experimental reactors. It compiles knowledge aboutmeasurement techniques, technologies and physics used for neutron detection.· the second part study the optimization of two of the key parameters defining thedesign of a fission chamber:o the fissile deposit thickness. The results, obtained thanks to simulation,allowed a better understanding of this parameter’s impact on measurementswhich lead to an improvement of the future detectors design.o the filling gas type and pressure. A deep experimental parametric study wascarried out in the MINERVE facility which enables understanding the impact ofboth filling gas characteristics on results. New filling standards have beendiscovered and are now taken into account when designing new detectors.Those standards allow dividing by two the measurement uncertainties due topressure variations and enable using fission chambers in more variousexperimental setups.· the third part of this works is focused on the improvement of the electronic equipmentand post-treatments used for fission chambers measurements. Three innovativeacquisition devices were chosen for testing in MINERVE. The results obtained enablegiving a set of short term and long term recommendations considering the update ofthe instrumentation used in the SPEx zero power reactors. In addition, a new deadtime correction method was developed during the thesis and is presented in this part.Its positive impact on rod-drop measurement is given for illustration as the gapbetween experimental results and expected values is divided by four thanks to thisinnovative correction method.· the last part is about the optimization of spectral indices measurement. The mostimportant parameters regarding spectral indices assessment are studied, their impacton spectral index is quantified and their respective acquisition methods are optimized.The study was mainly concentrated on the calibration data acquisition. This work ledto significant improvement, most notably concerning the « 238U fission / 235U fission»spectral index measured in the MINERVE core. The gap between calculation andexperimental results has been greatly reduced (from 35.70% to 0.17%) and theassociated uncertainty has also been diminished (from 15.7% to 5.6%). Those resultsalso allowed explaining abnormal gaps between calculation and experimentationobserved in measurement performed in the MINERVE facility in 2004. (...)
Braid, Ryan A. "The Calibration of a Fission Chamber at 14 MeV: Accelerator based Neutron Beam Detection." Ohio University Art and Sciences Honors Theses / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276710315.
Full textVayre, Sylvain. "Développement et caractérisation d’une cible active scintillante pour l’étude de la fission et étude des possibilités de calorimétrie de la fission avec le détecteur CARMEN." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112037/document.
Full textStill, the nuclear fission process and the de-excitation of the fission fragments is not fully understood. Current theoretical models can not predict and explain correctly every experimentally observed correlations, and new correlated data upon neutron emission, gamma-ray emission and kinetic energy of the fission fragments are needed. In this context, coincident use of a fission fragment detector and the CARMEN detector would provide compelling data for these models by measuring both neutron multiplicity, total gamma-ray energy, total kinetic energy and possibly total neutron energy. The work presented here consists in developing a fission fragment detector and using it together with CARMEN in order to perform fission calorimetry measurements. Initially, we developed a new detector for fission studies whose principle is dissolving the actinide of choice into an organic liquid scintillator. Monte Carlo simulations and neutron induced experiments were used to fully characterize its performances and shown it can be used as a fission trigger for various measurements, such as fission cross section or spontaneous fission rate measurements, and used as a fission veto. The second part of this work was dedicated to the study of CARMEN’s ability to measure the total gamma-ray energy and total neutron energy released in fission. For this purpose, lab characterization of the detector’s performances and Monte Carlo simulation and analysis of its “prompt” response to neutrons and gamma-rays were performed
Thiry, Jean-Claude. "Measurement of (n,xng) reaction cross sections of interest for the Generation IV reactors." Strasbourg, 2010. http://www.theses.fr/2010STRA6144.
Full textThe presented work consists of studying 232Th(n,xnγ) and 235U(n,xnγ) reactions in the fast neutron energy domain (up to 20 MeV) with the best precision possible. The experiments are performed at GELINA which delivers a pulsed, white neutron beam at IRMM, Belgium. The time characteristics of the beam enable us to measure neutron energies with the time-of-flight (TOF) technique. The neutron induced reactions (in this case inelastic scattering, (n,2n) and (n,3n) reactions) are identified by online prompt γ spectroscopy with an experimental setup including four HPGe detectors. A double layered fission chamber is used to monitor the incident neutron flux. The obtained results are presented and a comparison between the measured cross sections and the TALYS code predictions will be discussed. In order to achieve a very high precision on the reaction cross sections, an extensive work has been realised on the detection efficiencies of the counters used in the experiment. These quantities were in fact the largest sources of uncertainty in foregoing campaigns. After important efforts including high precision measurements together with Geant4 simulations, the efficiency of the fission chambers as well as of the HPGe detectors could be determined with accuracies below 3 %, accomplishing the final goal of a cross section determination with a precision of 5 %. This work is a further step in the preparation of the measurement of 233U(n,xnγ) reactions, which are completely unknown at this stage although of very high importance in the 232Th regeneration process. For this reason, a new, segmented HPGe detector was conceived, which will complete the current experimental setup
Grosjean, Cédric. "Mesure de la section efficace de fission induite par neutrons rapides des noyaux 232Th / 233U dans le cadre des cycles de combustiblesinnovants." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2005. http://tel.archives-ouvertes.fr/tel-00404551.
Full textPérez, sánchez Ricardo. "La méthode de substitution appliquée au 240Pu." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0136/document.
Full textThis PhD thesis revolves around the study the gamma-decay and fission probabilities of the compound nucleus (CN) 240Pu. These probabilities are obtained by using the surrogate reaction method, which, through charged particle reactions, aims to produce the same compound nucleus as the one that would be formed through a neutron induced reaction, or desired reaction. The objective is to cover the shortage of nuclear data, in cases in which the targets are too radioactive to be measured directly, for astrophysics and applications. As a matter of fact, if the measurement of the desired reaction is not possible, the reaction models reliance is compromised as their parameters cannot be adjusted. In this cases the gamma-decay and fission probabilities of the CN formed through the surrogate reaction, can help to improve the models. To this end, it is crucial to understand the difference between the formation and decay processes in the compound nuclei formed through a surrogate reaction and a neutron induced one.A collaboration between the nuclear physics laboratories, CENBG and CEA/DAM/DIF, is making the state of the art of surrogate reactions advance. In particular giving some insight about the spin distribution of the CN formed with these reactions, which they proved different to that of the nuclei formed through neutron induced reactions and that this played an important role in the competition between gamma-decay and neutron emission. Nevertheless, this does not seem to be the case for fission, whose data are in agreement with neutron induced ones. To better understand this, we have studied 240Pu, an even-even nucleus, using an experimental setup developed by this collaboration to simultaneously measure gamma-decay and fission.With this set-up, we performed an experiment in 2017 at the tandem accelerator at the IPN of Orsay (France). There a 30 MeV alpha particles beam interacted with the 240Pu target. The inelastically scattered alpha particles, ejectiles, were detected by two telescopes, which allow to identify the decaying nucleus and determine its excitation energy. The decay paths of the formed CN were identified, in coincidence with the telescopes, by detecting the gamma-rays and the fission fragments. With this information, the gamma-decay and fission probabilities were obtained by doing the ratio between the number of detected ejectiles and the number of measured coincidences correct by the detection efficiency.To interpret these unique data, we proceeded in three steps. Firstly, we adjusted the reaction model parameters (nuclear level densities, fission barriers, etc.) of the compound nucleus 240Pu with the existing data of the n+239Pu reactions. Then we calculated the branching ratios G of the decaying nucleus, which represent the probability of the nucleus to decay through a certain channel, for a certain excitation energy, spin and parity. Finally, with M. Dupuis (CEA/DAM/DIF), a calculation to predict the spin distribution of the 240Pu formed through the inelastic scattering of alpha particles was done for the first time. The calculation combined a JLM optical potential with the states of the nucleus generated with a QRPA approach.The spin distribution obtained with this calculation was combined with the calculated branching ratios G to calculate the decay probabilities. The comparison of this calculation to our measured probabilities shows a good agreement, which indicates a good a understanding of the reaction mechanism alpha,alpha'. Using this type of inelastic reaction in the future, could provide additional information about the radiative capture and fission cross sections of more exotic nuclei
Dobrowolski, Artur. "Influence de la différence entre les distributions de protons et de neutrons dans le noyau sur les processus de fusion et de fission." Phd thesis, Université Louis Pasteur - Strasbourg I, 2006. http://tel.archives-ouvertes.fr/tel-00391715.
Full textVivès, Florence. "Mesure des propriétés des fragments de fission de la réaction ²³⁸U(n,f) à des énergies de neutrons incidents jusqu'à 5. 8 MeV." Bordeaux 1, 1998. http://www.theses.fr/1998BOR10589.
Full textChauvin, Jean-Pierre. "Réacteurs à eau sous-modérés : contribution aux études et à la qualification des outils de calcul neutronique." Paris 11, 1987. http://www.theses.fr/1987PA112470.
Full textMIRANDA, ANSELMO F. "Mapeamento do fluxo de neutrons no reator IPEN/MB-01 com camara de fissao miniatura." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10643.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Foligno, Daniela. "New evaluation of delayed-neutron data and associated covariances." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0295.
Full textIn the context of nuclear reactor physics, one of the main issues is the control of the chain reaction. After a fission event has occurred, around three prompt neutrons are immediately emitted. Luckily, a small fraction of neutrons - less than 1% - appears with a certain delay with respect to the fission event. Delayed neutrons (DN) are an easy way out from the uncontrollable prompt-neutron driven chain reaction because they slow down the response of the reactor to a change in reactivity. Quantifying the fraction of such neutrons as well as their kinetic behavior is essential to design a safe reactor. The main consequence of a lack of accurate DN data is the conservatism in the design of a reactor. Nowadays, the discrepancy between the reactivity simulated using different international databases, rises up to 16% for LWRs, and the uncertainties associated with the recommended parameters are still too large for the needs of the industry. The DN parameters are generally estimated through a calculation or an integral measurement. This Ph.D. aims at producing a new set of DN parameters by performing both calculations and measurements, and by exploiting the two through the Bayesian inference, with the aim of reducing the uncertainties and creating the associated covariance matrices.The results for 235U, together with the calculated values for 238U, have been tested in three benchmarks, giving satisfying solutions with respect to the effective delayed neutron fraction. The main achievement of this work is the great improvement in the predicted reactivity, especially for negative periods, which is accompanied by an extremely good precision, never exceeding 2.2%
Ridikas, D. "Optimisation de combinaisons de faisceau et de cible pour les systèmes de réacteurs hybrides et pour la production de faisceaux radioactifs par fission." Phd thesis, Université de Caen, 1999. http://tel.archives-ouvertes.fr/tel-00719971.
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