Condições de contorno albedo para cálculos globais de reatores nucleares térmicos com o modelo de ordenadas discretas a dois grupos de energia

• Autor(a) principal: Nunes, Carlos Eduardo de Araújo
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13756
• topic: Neutral particle transport; Discrete ordinates; Criticality calculus; Albedo boundary conditions; Deterministic methods of neutron transport; Transporte de partículas neutras; Ordenadas discretas; Cálculos de criticalidade; Condições de contorno tipo Albedo; Métodos determinísticos de transporte de nêutrons; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA NUCLEAR

As neutron fission events do not take place in the non-multiplying regions of nuclear reactors, e.g., moderator, reflector, and structural core, these regions do not generate power and the computational efficiency of nuclear reactor global calculations can hence be improved by eliminating the explicit numerical calculations within the non-multiplying regions around the active domain. Discussed here is the computational efficiency of approximate discrete ordinates (SN) albedo boundary conditions for two-energy group eigenvalue problems in X,Y geometry. Albedo, the Latin word for whiteness , was originally defined as the fraction of incident light reflected diffusely by a surface. This Latin word has remained the usual scientific term in astronomy and in this dissertation this concept is extended for the reflection of neutrons. The non-standard SN albedo substitutes approximately the reflector region around the active domain, as we neglect the transverse leakage terms within the nonmultiplying reflector. Should the problem have no transverse leakage terms, i.e., onedimensional slab geometry, then the offered albedo boundary conditions are exact. By computational efficiency we mean analyzing the accuracy of the numerical results versus the CPU execution time of each run for a given model problem. Numerical results to two ¼ symmetric test problems are shown to illustrate this efficiency analysis.