Modeling of boundary conditions in embedded lattice calculations

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] The coupling of the ne-mesh high-order transport operator with a coarse-mesh low-order approximation, in order to reduce the computational requirements when simulating whole reactor cores, is studied here through the boundary conditions for the ne-mesh solver. A recently developed software, solving the neutron transport equation though a discontinuous Galerkin Finite Element discrete-ordinates method, is used for the ne-mesh high-order solver, and the coarse-mesh low-order solver is simulated by a coarsening process. As a rst step, a veri cation and validation process is necessary to be performed. This is carried out using the softwares DRAGON and MCNP, respectively, as the references in the veri cation and validation processes. A very good agreement is obtained during the veri cation process, while for the validation, results show that di erent quadratures should be considered in order to improve the accuracy. In addition, a parametric study is presented, where the di erent parameters of the spatial and angular discretizations are analyzed, in order to understand the behavior of the solver for di erent con gurations. A second part of the work consists in studying the e ect of coarsening the boundary conditions for a particular problem (C5G7 benchmark). This coarsening is performed to simulate the low-order approximation of the boundary conditions obtained with the coarse-mesh solver. Understanding the loss of accuracy for the ne-mesh calculations is necessary in order to improve the ne-mesh/coarse-mesh coupling for the neutronic solvers.