Very High Temperature Gas Cooled Reactors - VHTGRs are studied by several research groups for the development of advanced reactors that can meet the world's growing energy demand. The analysis of the flow of helium coolant around the various geometries at the core of these reactors through computational fluid dynamics techniques is an essential tool in the development of conceptual designs of nuclear power plants that provide added security. This analysis suggests a close analogy with aeronautical cases widely studied using computational numerical techniques to solve systems of governing equations for the flow involved. The present work consists in using the DISSIPA2D_EULER code, to solve the Euler equations in a conservative form, in two-dimensional space employing a finite difference formulation for spatial discretization using the Euler method for explicit marching in time. The physical problem of supersonic flow of helium gas along a ramp and diffusor configurations is considered. For this, the Jameson and Mavriplis algorithm and the linear artificial dissipation model of Pulliam was implemented. A spatially variable time step is employed aiming to accelerate the convergence to the steady state solution. The main purpose of this work is obtain computational tools for flow analysis through the study the cited dissipation model and describe their characteristics in relation to the overall quality of the solution, as well as obtain preliminary results for the development of computational tools of dynamic analysis of helium gas flow in gas-cooled reactors.

A energia nuclear é uma das principais alternativas para futuras fontes de energia sem emissões de gases contribuintes ao efeito estufa. Neste contexto os reatores nucleares modulares de pequeno porte têm grande potencial de desenvolvimento. Nesta categoria, por suas características de segurança e semelhanças com os reatores atuais em operação, destacam-se os reatores integrais de água pressurizada (iPWR). Neste trabalho, é apresentado um modelo computacional neutrônico baseado no código Monte Carlo Serpent para o projeto e análise de um ciclo de combustível estendido de quatro anos em um reator de tipo iPWR. Os principais parâmetros do comportamento neutrônico do núcleo são calculados e comparados com as recomendações para retores refrigerados a água.

Wax deposition along the extensive oilfield pipelines is a problem that affects the flow assurance. To solve it, one must monitor the wax formation in its initial stage. In this light, nuclear techniques are an effective alternative solution, as they can detect characteristics of materials or substances in an indirect and non-invasive manner. The present work shows a computational model using the MCNP6 (Monte Carlo N-Particle 6) code and the gamma radiation transmission profiling technique to detect different wax thickness. This fact is directly related to the attenuation of the gamma radiation beam when crossing the wax thicknesses.

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