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Analyse et développement d’un schéma de discrétisation numérique de l’équation du transport des neutrons en géométrie tridimensionnelle

Laurent Naymeh 1 
1 LTSD - Laboratoire de Transport Stochastique et Déterministe
SERMA - Service des Réacteurs et de Mathématiques Appliquées : DEN/DM2S/SERMA
Abstract : The method of characteristics is a flexible and efficient method solving the transport equation. It has been largely used in two dimension calculations because it enables to study complex geometries and it has a good time/precision ratio. However, despite agreat improvement in storage capacities and computing power, a direct three dimension calculation is still unreachable.In the following work, we introduce and analyze several modifications of the methodof characteristics (MOC) in order to reduce the memory usage as well as calculation burden. This document aims at studying a higher order spatial approximation for theflux. It steps away from the classical method (constant MOC) by introducing an increaseof details of the representation of the flux, which may enable to reduce the size of thegrid while keeping a good precision. Numerical results tested on benchmarks show animprovement of time/precision ratio.Regarding the memory storage, the number of trajectories has an influence on the amount of data to be stored. Hence, we study a tracking method based on local tracks defined for all subdomains having the same geometry. Redundancies happening in a reactor core suggest an important reduction of required memory. Two tracking methods have been studied, the first one being a non-uniform tracking method including subdomain discontinuities and the other being a method based on periodic and continuous trajectories for a subdomain to another.
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Laurent Naymeh. Analyse et développement d’un schéma de discrétisation numérique de l’équation du transport des neutrons en géométrie tridimensionnelle. Autre [cond-mat.other]. Université Paris Sud - Paris XI, 2013. Français. ⟨NNT : 2013PA112282⟩. ⟨tel-00952314⟩

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