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Statistical fluctuations in reactors (1960); Fluctuations statistiques dans les piles (1960)

Abstract

The theory of space dependent fluctuations is developed, taking into account the effect of delayed neutrons. The 'diffusion equation' or Fokker-Planck equation is worked out in the case of age and two group theory, but the first one because of in physical significance is used in this report. The theory is applied to the study of the spectral density of fluctuations and fluctuations of counting rate and current flowing through the charge resistor of an ionisation chamber, the effect of the entrance capacity is discussed. The space dependent theory shows that the fluctuations in the core and reflector of a near critical pile obey to the same law. The spectral densities in the core and reflector are similar, there is no sensible attenuation of high frequency fluctuations in the reflector. Compared to the space independent theory, this theory give better agreement with experience, one can use the simple space independent theory but in checking with experiment it is necessary to introduce numerical factors given by the space dependent theory. (author) [French] La theorie des fluctuations statistiques est developpee dans le cas spatial en tenant compte des neutrons retardes, et dans le cadre de la theorie de l'age vitesse. L'equation d'evolution  More>>
Authors:
Raievski, V [1] 
  1. Commissariat a l'Energie Atomique, Saclay (France).Centre d'Etudes Nucleaires
Publication Date:
Jul 01, 1960
Product Type:
Technical Report
Report Number:
CEA-R-1673
Resource Relation:
Other Information: 12 refs
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; CAPTURE-TO-FISSION RATIO; COUNTING RATES; CRITICALITY; DELAYED NEUTRONS; FERMI AGE THEORY; FLUCTUATIONS; FOKKER-PLANCK EQUATION; MULTIGROUP THEORY; NEUTRON DETECTORS; PILE OSCILLATION TECHNIQUES; POLYNOMIALS; REACTOR CORES; REFLECTOR SAVINGS; SLOWING-DOWN; SPACE DEPENDENCE; SPATIAL DISTRIBUTION; SPECTRAL DENSITY
OSTI ID:
20953762
Research Organizations:
CEA Saclay, 91 - Gif-sur-Yvette (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR07R1673105043
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
61 pages
Announcement Date:
Dec 21, 2007

Citation Formats

Raievski, V. Statistical fluctuations in reactors (1960); Fluctuations statistiques dans les piles (1960). France: N. p., 1960. Web.
Raievski, V. Statistical fluctuations in reactors (1960); Fluctuations statistiques dans les piles (1960). France.
Raievski, V. 1960. "Statistical fluctuations in reactors (1960); Fluctuations statistiques dans les piles (1960)." France.
@misc{etde_20953762,
title = {Statistical fluctuations in reactors (1960); Fluctuations statistiques dans les piles (1960)}
author = {Raievski, V}
abstractNote = {The theory of space dependent fluctuations is developed, taking into account the effect of delayed neutrons. The 'diffusion equation' or Fokker-Planck equation is worked out in the case of age and two group theory, but the first one because of in physical significance is used in this report. The theory is applied to the study of the spectral density of fluctuations and fluctuations of counting rate and current flowing through the charge resistor of an ionisation chamber, the effect of the entrance capacity is discussed. The space dependent theory shows that the fluctuations in the core and reflector of a near critical pile obey to the same law. The spectral densities in the core and reflector are similar, there is no sensible attenuation of high frequency fluctuations in the reflector. Compared to the space independent theory, this theory give better agreement with experience, one can use the simple space independent theory but in checking with experiment it is necessary to introduce numerical factors given by the space dependent theory. (author) [French] La theorie des fluctuations statistiques est developpee dans le cas spatial en tenant compte des neutrons retardes, et dans le cadre de la theorie de l'age vitesse. L'equation d'evolution de la probabilite est egalement etablie dans le cadre de la theorie a deux groupes. Ces considerations sont appliquees a l'etude de la densite spectrale des fluctuations et aux fluctuations des taux de comptage et du courant circulant dans la resistance de charge du detecteur. On etudie en particulier l'effet de la constante de temps introduite par la capacite d'entree. Cette theorie etablit que les fluctuations dans le coeur et le reflecteur suivent la meme loi pour une pile critique, il en est de meme pour la densite spectrale meme a frequence elevee. Par rapport a la theorie d'ensemble, la theorie spatiale donne des coefficients numeriques ou facteurs de forme, qui permettent d'obtenir un bon accord entre la theorie et l'experience. (auteur)}
place = {France}
year = {1960}
month = {Jul}
}