You need JavaScript to view this

Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites

Abstract

In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only.  More>>
Authors:
Benoist, P [1] 
  1. Commissariat a l'Energie Atomique, Saclay (France). Centre d'Etudes Nucleaires
Publication Date:
Jan 15, 1964
Product Type:
Thesis/Dissertation
Report Number:
CEA-R-2278
Resource Relation:
Other Information: TH: These ES sciences physiques; 120 refs
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANGULAR CORRELATION; CAVITIES; DIFFUSION LENGTH; FUEL ELEMENT CLUSTERS; MULTIPLICATION FACTORS; NEUTRON LEAKAGE; NEUTRON TRANSPORT THEORY; NUMERICAL SOLUTION; REACTOR LATTICES; VARIATIONAL METHODS
OSTI ID:
20808532
Research Organizations:
CEA Saclay, 91 - Gif-sur-Yvette (France); Feculte des Sciences de l'Universite de Paris, 75 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR06R2278110037
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
176 pages
Announcement Date:
Dec 23, 2006

Citation Formats

Benoist, P. Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites. France: N. p., 1964. Web.
Benoist, P. Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites. France.
Benoist, P. 1964. "Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites." France.
@misc{etde_20808532,
title = {Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites}
author = {Benoist, P}
abstractNote = {In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only. These formulae are very accurate, as seen from the results of a variational method which was studied as a reference. Various correction effects are reviewed. Expressions which allow the exact treatment of fuel rod clusters are presented. The theory is confronted with various experimental results, and a new method of measuring the radial coefficient is proposed. (author) [French] Dans une publication anterieure, on a etablie une formulation simple et generale du coefficient de diffusion, qui definit le mode de ponderation des libres parcours des differents milieux constituants en faisant apparaitre les probabilites de collision dans chaque milieu. On redemontre ici cette expression d'une maniere plus directe, tout en introduisant la variable vitesse, et on met en evidence de nouveaux termes, dont l'existence entraine que la representation de l'aire de diffusion par le carre moyen de la distance en ligne droite de la source a l'absorption est inexacte dans un reseau. Ces termes sont toutefois d'un ordre de grandeur assez faible pour pouvoir etre traites comme une correction. L'expression generale fait d'autre part apparaitre pour le coefficient radial la serie des termes de correlation angulaire qui s'est revelee tres lentement conrergente pour de grands canaux ; le calcul terme a terme, entrepris dans le premier travail, a alors ete abandonne au profit d'une formulation globale, qui fait apparaitre une ressemblance avec le probleme du facteur d'utilisation thermique. L'emploi d'une methode integrale analogue a celle employee dans le calcul de ce facteur permet d'etablir de nouvelles formules pratiques simples, ne taisant intervenir qu'un petit nombre de fonctions de base. La precision de ces formules est tres bonne, comme le montrent les resultats d'une methode variationnelle etudiee a titre de reference. Divers effets correctifs sont ensuite envisages. On donne etalement des expressions permettant le traitement exact de grappes de barres. Une comparaison de La theorie et de divers resultats experimentaux est presentee, et on propose une nouvelle methode de mesure du coefficient radial. (auteur)}
place = {France}
year = {1964}
month = {Jan}
}