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Master's Dissertation
DOI
10.11606/D.85.2010.tde-12082011-134814
Document
Author
Full name
Luís Felipe Liambos Mura
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2010
Supervisor
Committee
Bitelli, Ulysses D'Utra (President)
Santos, Adimir dos
Vieira, Wilson Jose
Title in Portuguese
Medidas de taxas de reação nuclear e de índices espectrais ao longo do raio das pastilhas combustíveis do reator IPEN/MB-01
Keywords in Portuguese
auto-blindagem
combustível nuclear
índices espectrais
taxas de reação nuclear
Abstract in Portuguese
Este trabalho apresenta as medidas das taxas de reação nuclear ao longo da direção radial da pastilha combustível por irradiação e posterior espectrometria gama de um fino disco de UO2 com enriquecimento de 4,3% no reator IPEN/MB- 01. A partir de sua irradiação, a taxa de captura radioativa e de fissão foram medidas em função do raio do disco utilizando um detector HPGe. Colimadores de chumbo foram utilizados para esse fim. O disco de UO2 é inserido no interior de uma vareta combustível desmontável e esta é então colocada na posição central do núcleo do reator IPEN/MB-01 e irradiada durante uma hora sob um fluxo de nêutrons de aproximadamente 9 x 108 n/cm2s. Na espectrometria gama, 10 colimadores com diâmetros diferentes foram utilizados, consequentemente, as reações nucleares de captura radioativa que ocorrem nos átomos de 238U e as fissões que ocorrem em ambos 235U e 238U são mensuradas em função de 10 regiões distintas do disco combustível. Correções de eficiência geométrica devido à introdução dos colimadores no sistema de detecção HPGe foram estimados usando o código MCNP-4C. Alguns valores calculados da taxa de reação nuclear de captura radioativa e fissão obtidos pela metodologia de Monte Carlo, utilizando o código MCNP-4C, são apresentados e comparados aos dados experimentais apresentando boa concordância. Além de taxas de reação nuclear, os índices espectrais 28ρ e 25δ foram obtidos para cada raio do disco combustível.
Title in English
Measurements of nuclear reaction rates and spectral indices along of the radius of fuel pellets at IPEN/MB-01 reactor
Keywords in English
nuclear fuel
nuclear reaction rates
spectral indices
Abstract in English
This work presents the measurements of the nuclear reaction rates along the radial direction of the fuel pellet by irradiation and posterior gamma spectrometry of a thin slice of fuel pellet of UO2 with 4,3% enrichment. From its irradiation the rate of radioactive capture and fission have been measured as a function of the radius of the pellet disk using a HPGe detector. Lead collimators has been used for this purpose. Simulating the fuel pellet in the pin fuel of the IPEN/MB-01 reactor, a thin UO2 disk is used. This disk is inserted in the interior of a dismountable fuel rod. This fuel rod is then placed in the central position of the IPEN/MB-01 reactor core and irradiated during 1 hour under a neutron flux of around 9 x 108 n/cm2s. For gamma spectrometry 10 collimators with different diameters have been used, consequently, the nuclear reactions of radioactive capture that occurs in atoms of 238U ans fissions that occur on both 235U and 238U are measured in function of 10 different region (diameter of collimator) of the fuel pellet disk. Corrections in the geometric efficiency due to introduction of collimators on HPGe detection system were estimated using photon transport of MCNP-4C code. Some calculated values of nuclear reaction rate of radioactive capture and fission along of the radial direction of the fuel pellet obtained by Monte Carlo methodology, using the MCNP-4C code, are presented and compared to the experimental data showing very good agreement. Besides nuclear reaction rates, the spectral indices 28ρ and 25δ have been obtained at each different radius of the fuel pellet disk.
 
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2010MuraMedidas.pdf (2.46 Mbytes)
Publishing Date
2011-08-18
 
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