O trabalho teve como objetivo a investigação de Metodologias de Cálculo dos Reatores Subcríticos acionados por fonte externa de nêutrons, tais como, \"Accelerator Driven Subcritical Reactor\" (ADSR) e \"Fusion Driven Subcritical Reator\" (FDSR) , que são reatores nucleares subcríticos com uma fonte externa de nêutrons. Tais nêutrons são produzidos, no caso do ADSR, através da interação de partículas aceleradas (prótons, deutério) com um alvo (Pb, Bi, etc) ou através das reações de fusão, no caso do FDSR. Este conceito de reator vem sendo objeto de intensa pesquisa, sobretudo pela possibilidade de ser utilizado para transmutar o enorme inventario de rejeitos nucleares, principalmente os transurânicos (TRU) e os produtos de fissão de meia-vida longa (LLFP). Neste trabalho enfatiza os seguintes aspectos: (i) complementar e aprimorar a metodologia de cálculos neutrônicos com queima e transmutação e implementá-la computacionalmente; (ii) e utilizando esta metodologia, participar dos Projetos Coordenados de Pesquisa (CRP) da Agência Internacional de energia Atômica \"Analytical and Experimental Benchmark Analysis of ADS\" e \"Collaborative work on use of LEU in ADS\", principalmente na reprodução dos resultados experimentais da instalação subcrítica Yalina Booster e também no cálculo de um núcleo subcrítico do reator IPEN/MB-01, (iii) analisar comparativamente diferentes bibliotecas de dados nucleares, no cálculo de parâmetros integrais (keff), diferenciais (espectro, fluxo) e de queima e transmutação (inventário ao final do ciclo) e (iv) aplicar a metodologia desenvolvida em um estudo que possa ajudar na escolha futura de um sistema transmutador dedicado. Foram utilizados para tanto os seguintes códigos: MCNP (Transporte de partículas por Monte Carlo), MCB (acoplamento do MCNP com código de transmutação) e o sistema NJOY para o processamento dos arquivos de dados nucleares avaliados. / This works had as goal to investigate calculational methodologies on subcritical source driven reactor, such as Accelerator Driven Subcritical Reactor (ADSR) and Fusion Driven Subcritical Reactor (FDSR). Intense R&D has been done about these subcritical concepts, mainly due to Minor Actinides(MA) and Long Lived Fission Products(LLFP) transmutation possibilities. In this work, particular emphasis has been given to: (i ) complement and improve calculation methodology with neutronic transmutation and decay capabilities and implement it computationally, (ii ) utilization of this methodology in the Coordinated Research Project (CRP) of the International Atomic Energy Agency Analytical and Experimental Benchmark Analysis of ADS and in the Collaborative Work on Use of Low Enriched Uranium in ADS, especially in the reproduction of the experimental results of the Yalina Booster subcritical assembly and study of a subcritical core of IPEN/MB-01 reactor, (iii ) to compare dierent nuclear data libraries calculation of integral parameters,such as keff and ksrc, and dierential distributions, such as spectrum and ux, and nuclides inventories and (iv ) apply the developed methodology in a study that may help future choices about dedicated transmutation system. The following tools have been used in this work: MCNP (Monte Carlo N particle transport code), MCB (enhanced version of MCNP that allows burnup calculation) and NJOY to process nuclear data from evaluated nuclear data files.

O trabalho teve como objetivo a investigação de Metodologias de Cálculo dos Reatores Subcríticos acionados por fonte externa de nêutrons, tais como, \"Accelerator Driven Subcritical Reactor\" (ADSR) e \"Fusion Driven Subcritical Reator\" (FDSR) , que são reatores nucleares subcríticos com uma fonte externa de nêutrons. Tais nêutrons são produzidos, no caso do ADSR, através da interação de partículas aceleradas (prótons, deutério) com um alvo (Pb, Bi, etc) ou através das reações de fusão, no caso do FDSR. Este conceito de reator vem sendo objeto de intensa pesquisa, sobretudo pela possibilidade de ser utilizado para transmutar o enorme inventario de rejeitos nucleares, principalmente os transurânicos (TRU) e os produtos de fissão de meia-vida longa (LLFP). Neste trabalho enfatiza os seguintes aspectos: (i) complementar e aprimorar a metodologia de cálculos neutrônicos com queima e transmutação e implementá-la computacionalmente; (ii) e utilizando esta metodologia, participar dos Projetos Coordenados de Pesquisa (CRP) da Agência Internacional de energia Atômica \"Analytical and Experimental Benchmark Analysis of ADS\" e \"Collaborative work on use of LEU in ADS\", principalmente na reprodução dos resultados experimentais da instalação subcrítica Yalina Booster e também no cálculo de um núcleo subcrítico do reator IPEN/MB-01, (iii) analisar comparativamente diferentes bibliotecas de dados nucleares, no cálculo de parâmetros integrais (keff), diferenciais (espectro, fluxo) e de queima e transmutação (inventário ao final do ciclo) e (iv) aplicar a metodologia desenvolvida em um estudo que possa ajudar na escolha futura de um sistema transmutador dedicado. Foram utilizados para tanto os seguintes códigos: MCNP (Transporte de partículas por Monte Carlo), MCB (acoplamento do MCNP com código de transmutação) e o sistema NJOY para o processamento dos arquivos de dados nucleares avaliados. / This works had as goal to investigate calculational methodologies on subcritical source driven reactor, such as Accelerator Driven Subcritical Reactor (ADSR) and Fusion Driven Subcritical Reactor (FDSR). Intense R&D has been done about these subcritical concepts, mainly due to Minor Actinides(MA) and Long Lived Fission Products(LLFP) transmutation possibilities. In this work, particular emphasis has been given to: (i ) complement and improve calculation methodology with neutronic transmutation and decay capabilities and implement it computationally, (ii ) utilization of this methodology in the Coordinated Research Project (CRP) of the International Atomic Energy Agency Analytical and Experimental Benchmark Analysis of ADS and in the Collaborative Work on Use of Low Enriched Uranium in ADS, especially in the reproduction of the experimental results of the Yalina Booster subcritical assembly and study of a subcritical core of IPEN/MB-01 reactor, (iii ) to compare dierent nuclear data libraries calculation of integral parameters,such as keff and ksrc, and dierential distributions, such as spectrum and ux, and nuclides inventories and (iv ) apply the developed methodology in a study that may help future choices about dedicated transmutation system. The following tools have been used in this work: MCNP (Monte Carlo N particle transport code), MCB (enhanced version of MCNP that allows burnup calculation) and NJOY to process nuclear data from evaluated nuclear data files.

<p dir="ltr">In the last few decades, the US Department of Energy established the Generation-IV Initiative to advance the design of nuclear energy systems with a focus on fast nuclear reactors. Special interest has been placed on Sodium-cooled Fast Reactors (SFRs) along with metallic fuels. SFRs are attractive because of their ability to utilize fast neutrons effectively, allowing for efficient transmutation of long-lived radioactive isotopes and a more complete use of fissile material. This capability significantly reduces nuclear waste and improves fuel sustainability compared to other Generation IV reactors. The metallic fuels, such as U-Zr and U-Pu-Zr, are attractive because of their higher thermal conductivity and higher density of fissile material, leading to improved breeding ratios and higher burnup rates. Through years of testing, SFRs, such as the EBR-II, could achieve a very high burnup (up to 750 GWD/tU) while traditional generation I to III+ reactors achieve around 30 GWD/tU. Since fast reactors, particularly SFRs, operate on a hard neutron spectrum, they utilize different geometries and cooling materials. This requires the use of different mechanistic models in nuclear codes to accurately capture the underlying physics. The NRC has recently shown interest in upgrading its diffusion codes to support the integration of SFRs. They have shown additional interest in improving the simulation capability of SFR metallic fuel, specifically U-10wt%Zr, even for high fuel burnups in excess of 10 at.%. </p><p dir="ltr">The purpose of this thesis is multifaceted. It serves to develop new mechanistic modelsto support the modeling and analysis of SFRs in existing nodal codes; it also serves to advance the current understanding of the principal effects of U-Zr fuel behavior during steady-state conditions. From the neutronics perspective, a new nodal method will be developed within the PARCS nodal code, along with generalized concepts such as reactivity feedback coefficients and thermal expansion, which will then be validated against the EBRII steady-state benchmark. From the fuel behavior perspective, mechanistic models that describe fuel redistribution, temperature distribution, fission gas, mechanical stresses, and point defect generation will be developed into the Purdue Fuel Performance (PFP) code for U-Zr fuel. The code will then be validated against the radial fuel concentration profile of two EBR-II U-Zr fuel pins.</p>