Made available in DSpace on 2014-10-09T12:49:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:56Z (GMT). No. of bitstreams: 1 10276.pdf: 7799693 bytes, checksum: 33b179c5ecbae276e3b4235673393d72 (MD5) / Tese (Doutoramento) / IPEN/T / Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / Includes bibliographical references. / M.S.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / Microfiche copy available in Archives and Science. / Includes bibliographical references. / M.S.

No description available.

Este trabalho apresenta uma nova abordagem experimental para determinar a reatividade de sistemas subcríticos. O método a ser apresentado utiliza o modelo da cinética subcrítica desenvolvido por Gandini e Salvatores e baseia-se apenas em grandezas medidas, tais como a taxa de contagem no detector, e nos parâmetros que surgem do ajuste dos mínimos quadrados APSD (Auto Power Spectral Density) e CPSD (Cross Power Spectral Density), não sendo necessário lidar com as quantidades de maior complexidade como a eficiência de detector. A única hipótese feita neste método foi que a fração efetiva de nêutrons atrasados e o tempo de geração de nêutrons prontos fossem independentes do nível de subcriticalidade do sistema. O método proposto foi aplicado nas medidas de reatividade de várias configurações subcríticas do reator IPEN/MB-01. Foram realizadas medidas da APSD e CPSD em diversos graus de subcriticalidade (até em torno de -7000 pcm). Nos dados das densidades espectrais foram feitos ajustes por meio do método de mínimos quadrados para obter a constante de decaimento pronto (α) e outras grandezas. Com a finalide de melhorar as estatísticas de contagem de nêutrons, fonte externa de nêutrons de Am-Be foi instalada próximo ao núcleo, além da fonte de partida. O método experimental proposto mostra claramente que, a teoria da cinética pontual clássica não descreve a reatividade medida. Em vez disso, a reatividade inferida a partir do modelo da cinética pontual clássica é próxima, em seus valores absolutos, ao índice de subcriticalidade (ζ) para um determinado arranjo das fontes do experimeno. A concordância dos resultados obtidos por MCNP5 e GPT-TORT, ambos utilizando os dados nucleares da biblioteca ENDF/B-VII.0, com os resultados experimentais correspondentes são de boa qualidade. / This work presents a new experimental approach to determine the reactivity levels of subcritical systems. The method employs the subcritical kinetic model developed by Gandini and Salvatores and it is based only on measured quantities such as counting rates of the detectors employed in the experiments and the parameters arising from the least squares fitting of the APSD (Auto Power Spectral Density) and CPSD (Cross Power Spectral Density). Detector efficiencies, quantity required in other procedures such as Neutron Source Multiplication (NSM) method, are not needed in the proposed method. The only hypothesis made in the method was the independence of the effective delayed neutron fraction and the prompt neutron generation time to the subcriticality level of the system. The proposed method was applied to measure the reactivity of several subcritical configurations of the IPEN/MB-01 reactor. Measurements of APSD and CPSD were performed in several degrees of subcriticality (up to around -7000 pcm). The spectral densities data were least squares fitted to get the prompt decay mode (α) and other quantities. Beside the startup source of the facility, an external neutron source of Am-Be was installed near the core in order to improve neutron counting statistics. The final experimental results are of good quality. The proposed experimental method shows clearly that the classical point kinetic theory cannot describe the measured reactivity. Instead, the reactivity inferred from this model follows closely the subcriticality index (ζ) for the source arrangements in the experiment. The agreement of the MCNP5 and GPT-TORT results, both with ENDF/B-VII.0 as the basic nuclear data library, when compared to the corresponding experimental ones was also good.

Este trabalho apresenta uma nova abordagem experimental para determinar a reatividade de sistemas subcríticos. O método a ser apresentado utiliza o modelo da cinética subcrítica desenvolvido por Gandini e Salvatores e baseia-se apenas em grandezas medidas, tais como a taxa de contagem no detector, e nos parâmetros que surgem do ajuste dos mínimos quadrados APSD (Auto Power Spectral Density) e CPSD (Cross Power Spectral Density), não sendo necessário lidar com as quantidades de maior complexidade como a eficiência de detector. A única hipótese feita neste método foi que a fração efetiva de nêutrons atrasados e o tempo de geração de nêutrons prontos fossem independentes do nível de subcriticalidade do sistema. O método proposto foi aplicado nas medidas de reatividade de várias configurações subcríticas do reator IPEN/MB-01. Foram realizadas medidas da APSD e CPSD em diversos graus de subcriticalidade (até em torno de -7000 pcm). Nos dados das densidades espectrais foram feitos ajustes por meio do método de mínimos quadrados para obter a constante de decaimento pronto (α) e outras grandezas. Com a finalide de melhorar as estatísticas de contagem de nêutrons, fonte externa de nêutrons de Am-Be foi instalada próximo ao núcleo, além da fonte de partida. O método experimental proposto mostra claramente que, a teoria da cinética pontual clássica não descreve a reatividade medida. Em vez disso, a reatividade inferida a partir do modelo da cinética pontual clássica é próxima, em seus valores absolutos, ao índice de subcriticalidade (ζ) para um determinado arranjo das fontes do experimeno. A concordância dos resultados obtidos por MCNP5 e GPT-TORT, ambos utilizando os dados nucleares da biblioteca ENDF/B-VII.0, com os resultados experimentais correspondentes são de boa qualidade. / This work presents a new experimental approach to determine the reactivity levels of subcritical systems. The method employs the subcritical kinetic model developed by Gandini and Salvatores and it is based only on measured quantities such as counting rates of the detectors employed in the experiments and the parameters arising from the least squares fitting of the APSD (Auto Power Spectral Density) and CPSD (Cross Power Spectral Density). Detector efficiencies, quantity required in other procedures such as Neutron Source Multiplication (NSM) method, are not needed in the proposed method. The only hypothesis made in the method was the independence of the effective delayed neutron fraction and the prompt neutron generation time to the subcriticality level of the system. The proposed method was applied to measure the reactivity of several subcritical configurations of the IPEN/MB-01 reactor. Measurements of APSD and CPSD were performed in several degrees of subcriticality (up to around -7000 pcm). The spectral densities data were least squares fitted to get the prompt decay mode (α) and other quantities. Beside the startup source of the facility, an external neutron source of Am-Be was installed near the core in order to improve neutron counting statistics. The final experimental results are of good quality. The proposed experimental method shows clearly that the classical point kinetic theory cannot describe the measured reactivity. Instead, the reactivity inferred from this model follows closely the subcriticality index (ζ) for the source arrangements in the experiment. The agreement of the MCNP5 and GPT-TORT results, both with ENDF/B-VII.0 as the basic nuclear data library, when compared to the corresponding experimental ones was also good.

No description available.

Steam property evaluations may represent a significant portion of the computing time necessary for power system simulations. The iterative nature of the solutions for heat transfer and kinetic equations often requires thousands of steam property evaluations during the execution of a single program. Considerable savings may be realized by simplification of property evaluations. Empirical equations have been obtained for the thermodynamic properties of water in the region of interest. To maintain thermodynamic consistency, the compressibility factor Z, in terms of pressure and temperature, was obtained by curve fitting, and the enthalpy, entropy, and internal energy were derived by standard relationships. Formulations for heat capacity, saturation temperature as a function of saturation pressure, the specific volume of saturated water as a function of saturation pressure, and specific volume of saturated water as a function of the saturation temperature were determined by curve fitting of independent equations. Derivatives were obtained by differentiation of the appropriate formulations. Evaporator and superheater components of a liquid metal fast breeder reactor power plant simulator were chosen as test cases for the empirical representations. Results obtained using the empirical equations were comparable to those obtained using tabular values, but significant savings in computational costs were realized. Execution time for the evaporator program with the empirical forms was approximately 27 percent less than for the program with tables. Execution time for the super-heater program was approximately 23 percent less.

Made available in DSpace on 2014-10-09T12:53:07Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:04Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:03/01261-0

Made available in DSpace on 2014-10-09T12:26:15Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:38Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP