Dissertations / Theses: 'Fission Reactor Physic'

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ABRATE, NICOLO'. "Methods for safety and stability analysis of nuclear systems." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2971611.

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Kennedy, William B. (William Blake) 1979. "Analysis of the MIT research reactor fission product and actinide radioactivity inventories." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32723.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.
MIT Institute Archives copy: leaves 92-111 bound in reverse order.
Includes bibliographical references (leaf 57).
The current analysis of the MITR core radioactivity inventory eliminates unnecessary assumptions made in previous estimates of the inventory, and revises the list of contributory isotopes to include all actinide and fission product isotopes necessary for a proper accident source term calculation. The result is a power-history-dependent inventory that increases with bum-up, and comprises 41 actinide isotopes and 596 fission product isotopes. The analysis uses the ORIGEN2 depletion code to calculate the activity of actinide and fission product isotopes for eight MITR input models at 32 intervals over a period of 5376MWD. The input models simulate a MITR core loaded with high- enrichment, U-Alx cermet fuel or low-enrichment, monolithic U-Mo fuel, and operated at 6MW with a continuous-burn-up or cyclic-burn-up-and-decay power history. Reorganization of the ORIGEN2 output file, and application of an element reduction criterion creates the condensed matrix file for each MITR input model. This file lists the contribution of each isotope to the core radioactivity inventory at each output interval, and is the basis for all inventory analysis. The inventory analysis yields three important conclusions. First, the assumption of an equilibrium inventory of isotopes in the fuel is accurate to within 3% for all time after 10% fuel bum-up, and conservative over the entire fuel cycle. The equilibrium fuel assumption is invalid for the actinides due to a slow rate of inventory growth. Second, the cyclic-bum-up-and-decay power history yields a lower core inventory than the continuous-burn-up power history for both fuel enrichments. The difference is minimized by increasing the ratio of irradiation time to decay time.
(cont.) Finally, the analysis indicates that conversion to a U-Mo fuel will produce an actinide inventory 18 times greater than that of the current U-Alx fuel, with no significant change in the fission product inventory. However, the actinide inventory is a small fraction of the fission product inventory. The worst-case core inventory available for release is 2.91 E+7Ci for the high-enrichment fuel, and 2.94E+7Ci for the low-enrichment fuel, with a core loading of 24 elements in each case. The best-estimate core inventory available for release is 2.83E+7Ci, and 2.82E+7Ci respectively, and accounts for typical cyclic operation of the MITR.
by William B. Kennedy.
S.B.

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Lapinski, Felicia. "Experimental studies at CERN-nTOF of the 230Th(n,f) reaction." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-417867.

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This work investigates the feasibility to perform an experiment at CERN n_TOF to study the fission cross section and fission fragment angular distribution (FFAD) of the 230Th(n,f) reaction. An analysis of fission fragment energy losses in the experimental target resulted in a choice of target thickness of 0.1 µm (100 µg/cm2 ), which yields good transmission out of the target at up to 45° emission angles from the target normal. A detection setup using ten PPAC detectors with nine thorium targets interleaved in between them was investigated, where the detectors and targets were tilted 45° with respect to the neutron beam. This makes it possible to measure all emission angles needed with respect to the neutron beam in order to determine the FFAD. For the experimental area EAR2 at n_TOF, a prediction of the count rate in the experiment resulted in low statistical uncertainties after a few weeks of beam time, which indicates that an experiment like this is feasible.
Detta projekt undersöker genomförbarheten av ett experiment vid CERN n_TOF för att mäta tvärsnittet och fördelningen av emissionsvinklar av fissionsfragment (FFAD) från 230Th(n,f)-reaktionen. En analys av energiförlusterna av fissionsfragment inuti torium-provet resulterade i en optimal provtjocklek på 0.1 µm (100 µg/cm2 ), vilket medför att fissionsfragment som emitteras i vinklar upp till 45° från provets normal har hög sannolikhet att transmitteras ut ur provet. En detektionsuppställning med tio PPAC-detektorer med nio toriumprov mellan dem undersöktes, där detektorerna och proven antogs vara snedställda med 45° från neutronstrålens riktning. Detta möjliggör detektion av fissionsfragment i alla vinklar som är nödvändiga för att kunna mäta hela FFAD. För experimentanläggningen EAR2 vid n_TOF, resulterade en uppskattning av antalet detekterade fissionsevent per sekund i låga mätosäkerheter efter ett par veckor av mättid, vilket antyder att experimentet är görbart.

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Kern, Kilian [Verfasser]. "Advanced Treatment of Fission Yield Effects and Method Development for Improved Reactor Depletion Calculations / Kilian Kern." Karlsruhe : KIT Scientific Publishing, 2019. http://www.ksp.kit.edu.

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Kern, Kilian [Verfasser], and R. [Akademischer Betreuer] Stieglitz. "Advanced Treatment of Fission Yield Effects and Method Development for Improved Reactor Depletion Calculations / Kilian Kern ; Betreuer: R. Stieglitz." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1174252227/34.

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Todd, Jamie R. D. (James Robert Drysdale). "Angular distributions and kinetic energies of fission products from the 238U(12C,f) reaction." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59911.

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The angular anisotropy, $ omega$, of individual fission products produced from the $ sp{238} rm U( sp{12}$C, f) 119.9 MeV incident heavy-ion induced fission reaction, was modelled in terms of the angular momentum, l, conferred upon the intermediate nucleus. Evidence of incomplete momentum transfer led to a model treating fission products as being the result of two fission inducing processes: complete fusion resulting in compound nucleus formation, and an $ alpha$-transfer incomplete fusion process. The average angular anisotropies for each of the two processes were calculated to be, $ omega sb{ rm CF}$ = 2.57, and $ omega sb alpha$ = 1.71, respectively, which fit well to the experimental data. A new method was developed to estimate the total kinetic energy release of heavy-ion fission events leading to individual fission products from the above reaction. The average total $ langle$E$ sb{ rm k}{ rangle} approx 195$ MeV calculated using the new method is consistent with other experimental data, and with theories regarding heavy-ion induced fission.

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Birgersson, Evert. "Determination of binary fission-fragment yields in the reaction 251Cf(nth, f) and Verification of nuclear reaction theory predictions of fission-fragment distributions in the reaction 238U(n, f)." Doctoral thesis, Örebro : Institutionen för naturvetenskap Department of Natural Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-1474.

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Prokofiev, Alexander. "Nucleon-Induced Fission Cross Sections of Heavy Nuclei in the Intermediate Energy Region." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5009-1/.

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Dufek, Jan. "Development of New Monte Carlo Methods in Reactor Physics : Criticality, Non-Linear Steady-State and Burnup Problems." Doctoral thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10602.

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Skwarcan-Bidakowski, Alexander. "Nuclear reactor core model for the advancednuclear fuel cycle simulator FANCSEE. Advanceduse of Monte Carlo methods in nuclear reactorcalculations." Thesis, Institutionen för Reaktorfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324260.

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A detailed reactor core modeling of the LOVIISA-2 PWR and FORSMARK-3BWR was performed in the Serpent 2 Continuous Energy Monte-Carlocode.Both models of the reactors were completed but the approximations ofthe atomic densities of nuclides present in the core differedsignificantly.In the LOVIISA-2 PWR, the predicted atomic density for the nuclidesapproximated by Chebyshev Rational Approximation method (CRAM)coincided with the corrected atomic density simulated by the Serpent2 program. In the case of FORSMARK-3 BWR, the atomic density fromCRAM poorly approximated the data returned by the simulation inSerpent 2. Due to boiling of the moderator in the core of FORSMARK-3,the model seemed to encounter problems of fission density, whichyielded unusable results.The results based on the models of the reactor cores are significantto the FANCSEE Nuclear fuel cycle simulator, which will be used as adataset for the nuclear fuel cycle burnup in the reactors.
FANCSEE

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Verma, Vasudha. "Development of a Neutron Flux Monitoring System for Sodium-cooled Fast Reactors." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-319945.

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Safety and reliability are one of the key objectives for future Generation IV nuclear energy systems. The neutron flux monitoring system forms an integral part of the safety design of a nuclear reactor and must be able to detect any irregularities during all states of reactor operation. The work in this thesis mainly concerns the detection of in-core perturbations arising from unwanted movements of control rods with in-vessel neutron detectors in a sodium-cooled fast reactor. Feasibility study of self-powered neutron detectors (SPNDs) with platinum emitters as in-core power profile monitors for SFRs at full power is performed. The study shows that an SPND with a platinum emitter generates a prompt current signal induced by neutrons and gammas of the order of 600 nA/m, which is large enough to be measurable. Therefore, it is possible for the SPND to follow local power fluctuations at full power operation. Ex-core and in-core detector locations are investigated with two types of detectors, fission chambers and self-powered neutron detectors (SPNDs) respectively, to study the possibility of detection of the spatial changes in the power profile during two different transient conditions, i.e. inadvertent withdrawal of control rods (IRW) and one stuck rod during reactor shutdown (OSR). It is shown that it is possible to detect the two simulated transients with this set of ex-core and in-core detectors before any melting of the fuel takes place. The detector signal can tolerate a noise level up to 5% during an IRW and up to 1% during an OSR.

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Henning, Gregoire. "Stability of Transfermium Elements at High Spin : Measuring the Fission Barrier of 254No." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00745915.

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Super heavy nuclei provide opportunities to study nuclear structure near three simultaneous limits: in charge Z, spin I and excitation energy E∗. These nuclei exist only because of a fission barrier, created by shell effects. It is therefore important to determine the fission barrier and its spin dependence Bf(I), which gives information on the shell energy Eshell(I). Theoretical calculations predict different fission barrier heights from Bf(I = 0) = 6.8 MeV for a macro-microscopic model to 8.7 MeV for Density Functional Theory calculations using the Gogny or Skyrme interactions. Hence, a measurement of Bf provides a test for theories.To investigate the fission barrier, an established method is to measure the rise of fission with excitation energy, characterized by the ratio of decay widths Γfission/Γtotal, using transfer reactions. However, for heavy elements such as 254No, there is no suitable target for a transfer reaction. We therefore rely on the complementary decay widths ratio Γγ/Γfission and its spin dependence, deduced from the entry distribution (I, E∗).Measurements of the gamma-ray multiplicity and total energy for 254No have been performed with beam energies of 219 and 223 MeV in the reaction 208Pb(48Ca,2n) at ATLAS (Argonne Tandem Linac Accelerator System). The 254No gamma rays were detected using the Gammasphere array as a calorimeter - as well as the usual high resolution γ-ray detector. Coincidences with evaporation residues at the Fragment Mass Analyzer focal plane separated 254No gamma rays from those from fission fragments, which are > 10^6 more intense. From this measurement, the entry distribution - i.e. the initial distribution of I and E∗ - is constructed. Each point (I,E∗) of the entry distribution is a point where gamma decay wins over fission and, therefore, gives information on the fission barrier.The measured entry distributions show an increase in the maximum spin and excitation energy from 219 to 223 MeV of beam energy. The distributions show a saturation of E∗ for high spins. The saturation is attributed to the fact that, as E∗ increases above the saddle, Γfission rapidly dominates. The resulting truncation of the entry distribution at high E∗ allows a determination of the fission barrier height.The experimental entry distributions are also compared with entry distributions calculated with decay cascade codes which take into account the full nucleus formation process, including the capture process and the subsequent survival probability as a function of E∗ and I. We used the KEWPIE2 and NRV codes to simulate the entry distribution.

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Richard, Andrea L. "Measurement of the Breakup Cross Section of the D(d,n) Reaction at 6.94 MeV for the Active Interrogation of Hidden Fissile Materials." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1397479139.

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Dahlfors, Marcus. "Studies of Accelerator-Driven Systems for Transmutation of Nuclear Waste." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6341.

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15

Boutoux, Guillaume. "Sections efficaces neutroniques via la méthode de substitution." Phd thesis, Bordeaux 1, 2011. http://tel.archives-ouvertes.fr/tel-00654677.

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Les sections efficaces neutroniques des noyaux de courte durée de vie sont des données cruciales pour la physique fondamentale et appliquée dans des domaines tels que la physique des réacteurs ou l'astrophysique nucléaire. En général, l'extrême radioactivité de ces noyaux ne nous permet pas de procéder à des mesures induites par neutrons. Cependant, il existe une méthode de substitution (" surrogate " dans la littérature) qui permet de déterminer ces sections efficaces neutroniques par l'intermédiaire de réactions de transfert ou de réactions de diffusion inélastique. Son intérêt principal est de pouvoir utiliser des cibles moins radioactives et ainsi d'accéder à des sections efficaces neutroniques qui ne pourraient pas être mesurées directement. La méthode est basée sur l'hypothèse de formation d'un noyau composé et sur le fait que la désexcitation ne dépend essentiellement que de l'énergie d'excitation et du spin et parité de l'état composé peuplé. Toutefois, les distributions de moments angulaires et parités peuplés dans des réactions de transfert et celles induites par neutrons sont susceptibles d'être différentes. Ce travail fait l'état de l'art sur la méthode substitution et sa validité. En général, la méthode de substitution fonctionne très bien pour extraire des sections efficaces de fission. Par contre, la méthode de substitution dédiée à la capture radiative est mise à mal par la comparaison aux réactions induites par neutrons. Nous avons réalisé une expérience afin de déterminer les probabilités de désexcitation gamma du 176Lu et du 173Yb à partir des réactions de substitution 174Yb(3He,p)176Lu* et 174Yb(3He,alpha)173Yb*, respectivement, et nous les avons comparées avec les probabilités de capture radiative correspondantes aux réactions 175Lu(n,gamma) et 172Yb(n,gamma) qui sont bien connues. Cette expérience a permis de comprendre pourquoi, dans le cas de la désexcitation gamma, la méthode de substitution donne des écarts importants par rapport à la réaction neutronique correspondante. Ce travail dans la région de terres rares a permis d'évaluer dans quelle mesure la méthode de substitution peut s'appliquer pour extraire des probabilités de capture dans la région des actinides. Des expériences précédentes sur la fission ont aussi pu être réinterprétées. Ce travail apporte donc un éclairage nouveau sur la méthode de substitution.

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Nordström, Fredrik. "Benchmark of the fission channels in TALYS." Thesis, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446616.

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In this project, different fission models in the nuclear reaction code TALYS have been compared to GEF version 2020/1.2. The data included in the comparison are mass yield distributions, average prompt neutron energies per fragment mass, and average multiplicities of both neutrons and γ-rays per fragment mass. The reaction studied in the first part of the project is 1 keV neutron-induced fission of 235U. In the second part of the study, a variety of different nuclei and different incident energies were included in comparisons, but a limitation was set to only include neutron-induced fission. The results from the comparison suggested that TALYS fymodel 2 and 3 were less consistent with GEF than fymodel 4. For the comparisons with experimental data, fymodel 4 also performed better overall. TALYS fymodel 2 and 3 make use of implemented partial versions of GEF to produce fission fragment distributions, while fymodel 4 takes fission fragment distribution data from separate yieldfiles. A database of these yieldfiles with 737 different nuclei and 10 energy levels was produced, to be implemented in future versions of TALYS. The energy levels were chosen to get a range of energies that can be accurately interpolated between. This method of using TALYS fymodel 4 with a yieldfile from GEF consistently showed a strong agreement with GEF version 2020/1.2 for the mass yield distributions and the neutron multiplicities. The γ-ray multiplicities and the neutron energies show a slightly weaker agreement, and TALYS gives consistently smaller values than GEF for these quantities.

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Merle-Lucotte, Elsa. "Le cycle Thorium en réacteurs à sels fondus peut-il être une solution au problème énergétique du XXIème siècle ? Le concept de TMSR-NM." Habilitation à diriger des recherches, 2008. http://tel.archives-ouvertes.fr/tel-00354937.

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Un concept innovant de réacteurs nucléaires à sels fondus, le Thorium Molten Salt Reactor (TMSR), a été défini au LPSC Grenoble. Le présent mémoire porte sur les études, optimisations et caractérisations réalisées sur les configurations en spectre rapide de ce concept, appelées ‘TMSR non modérés' ou TMSR-NM, très prometteuses. Le cœur est un simple cylindre dans lequel circule un sel fluore contenant du LiF et le combustible. Nos études portent sur les caractéristiques de ces réacteurs en termes de sûreté, inventaire fissile, retraitement chimique, production de déchets et capacité de régénération et de déploiement. Un tel réacteur présente maints avantages intrinsèques permettant un fonctionnement simple et sûr en cycle du combustible Thorium, ainsi que l'utilisation de divers éléments fissiles au démarrage tels l'233U, 235U ou les transuraniens issus des réacteurs actuels. Ceci permettrait une transition optimisée vers le cycle Thorium tout en fermant le cycle actuel.

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Dissertations / Theses on the topic 'Fission Reactor Physic'

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