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Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos

Conference:

Abstract

In this work we investigate the time and space dependence of the neutron flux within a highly heterogeneous assembly, in which pulsed or sinusoidally modulated neutrons are injected. We consider, for the sake of simplicity, a device consisting of a cylindrical block of heavy moderator, along the axis of which a line-shaped region of fissionable material is located. The driving neutron source is assumed to be located on one of the end faces of the cylinder. The extent of the fissionable region allows us to deal with it as with an absorbing and multiplying singularity of the neutron field. As our attention is mostly concentrated on space and time variation of the neutron flux, rather crude approximations are assumed as far as the energy dependence of the neutron population is concerned. Within the limits of the age-diffusion theory, the response of the device to any neutron excitation may be found in closed form. For a sinusoidally modulated source of given frequency, it may easily be shown that, if the axial singularity were a purely absorbing one, the neutron waves being propagated along the device would possess a phase shift; a wavelength and an attenuation constant depending on the absorbing properties  More>>
Authors:
Corno, S. E.; [1]  Unversity of Pavia, Pavia (Italy); SNAM, Milan [2] 
  1. Instituto di Fisica ''A. Volta'' (Italy)
  2. Italy
Publication Date:
Oct 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-62/8
Resource Relation:
Conference: Symposium on Pulsed Neutron Research, Karlsruhe (Germany), 10-14 May 1965; Other Information: 10 refs.; Related Information: In: Pulsed Neutron Research. Vol. II. Proceedings of the Symposium on Pulsed Neutron Research| 934 p.
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 22 GENERAL STUDIES OF NUCLEAR REACTORS; CYLINDRICAL CONFIGURATION; ENERGY DEPENDENCE; EQUIPMENT; EXCITATION; FISSIONABLE MATERIALS; FUEL ELEMENTS; HETEROGENEOUS REACTOR CORES; MODERATORS; NEUTRON AGE; NEUTRON DIFFUSION EQUATION; NEUTRON FLUX; NEUTRON SOURCES; NEUTRONS; PHASE SHIFT; PULSED NEUTRON TECHNIQUES; SPACE DEPENDENCE; TIME DEPENDENCE; WAVELENGTHS
OSTI ID:
22123040
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2649078842
Submitting Site:
INIS
Size:
page(s) 863-882
Announcement Date:
Aug 30, 2013

Conference:

Citation Formats

Corno, S. E., Unversity of Pavia, Pavia (Italy), and SNAM, Milan. Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos. IAEA: N. p., 1965. Web.
Corno, S. E., Unversity of Pavia, Pavia (Italy), & SNAM, Milan. Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos. IAEA.
Corno, S. E., Unversity of Pavia, Pavia (Italy), and SNAM, Milan. 1965. "Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos." IAEA.
@misc{etde_22123040,
title = {Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos}
author = {Corno, S. E., Unversity of Pavia, Pavia (Italy), and SNAM, Milan}
abstractNote = {In this work we investigate the time and space dependence of the neutron flux within a highly heterogeneous assembly, in which pulsed or sinusoidally modulated neutrons are injected. We consider, for the sake of simplicity, a device consisting of a cylindrical block of heavy moderator, along the axis of which a line-shaped region of fissionable material is located. The driving neutron source is assumed to be located on one of the end faces of the cylinder. The extent of the fissionable region allows us to deal with it as with an absorbing and multiplying singularity of the neutron field. As our attention is mostly concentrated on space and time variation of the neutron flux, rather crude approximations are assumed as far as the energy dependence of the neutron population is concerned. Within the limits of the age-diffusion theory, the response of the device to any neutron excitation may be found in closed form. For a sinusoidally modulated source of given frequency, it may easily be shown that, if the axial singularity were a purely absorbing one, the neutron waves being propagated along the device would possess a phase shift; a wavelength and an attenuation constant depending on the absorbing properties of the singularity. This picture becomes more and more complicated when neutron multiplication occurs. For this general case the solution derived in our paper obviously turns out to be dependent on both absorption and multiplication properties of the singularity. This circumstance suggests, among others, the idea of using a device of the type described above for testing fuel elements of heterogeneous reactors. (author) [French] L'auteur etudie les variations du flux de neutrons en fonction du temps et du lieu dans un assemblage tres heterogene ou l'on injecte des neutrons puises ou modules sinusoidalement. Il envisage, pour des raisons de simplicite, un dispositif constitue par un ralentisseur lourd en forme de bloc cylindrique sur l'axe duquel est placee une zone de matiere fissile ayant une forme lineaire. La source de neutrons puises est supposee etre placee sur l'unfe des bases du cylindre. L'etendue de la zone de matiere fissile permet a l'auteur de la traiter comme s'il s'agissait d'une zone singuliere d'absorption et de multiplication dans le champ de neutrons. Comme il concentre son attention principalement sur les variations du flux de neutrons en fonction du lieu et du temps, il adopte des approximations assez grossieres pour ce qui est des variations de la population de neutrons en fonction de l'energie. Dans les limites de la theorie diffusion-age, il se peut que la reponse du dispositif a une excitation neutronique quelconque soit obtenue sous forme fermee. Avec une source modulee sinusoidalement de frequence donnee, on peut aisement montrer que, si la zone axiale singuliere est purement absorbante, le dephasage, la longueur d'onde et la constante d'attenuation des ondes neutroniques propagees le long du cylindre dependent des proprietes absoibantes de cette zone. Cet etat de choses se complique de plus en plus lorsqu'une multiplication des neutrons se produit. Dans ce cas general, la solution a laquelle l'auteur aboutit se revele evidemment etre dependante des proprietes d'absorption et de multiplication de la zone singuliere, ce qui peut donner, entre autres, l'idee d'utiliser un dispositif du modele decrit ci-dessus pour soumettre a des essais les elements de combustible des reacteurs heterogenes. (author) [Spanish] El autor ha investigado la variacion del flujo neutronico en funcion del tiempo y del espacio en un conjunto muy heterogeneo en el que se inyectan neutrones pulsados o de modulacion sinusoidal. Para mayor sencillez se opera con una instalacion formada por un bloque cilindrico de moderador pesado, en cuyo eje se encuentra una region lineal de material fisionable. La fuente neutronica se supone situada en una de las caras del cilindro. Gracias a sus dimensiones, la region fisionable puede considerarse como punto singular absorbente y multiplicador del campo neutronico. Como el auto: estudia sobre todo la variacion espacial y temporal del flujo neutronico, utiliza valores relativamente poco precisos por lo que respecta a la variacion de la poblacion neutronica en funcion de la energia. Dentro de los limites de validez de la teorfe de la edad de difusion, la instalacion responde en forma analitica a una excitacion provocada por los neutrones. Cuando se trata de una fuente de modulacion sinusoidal de frecuencia determinada, puede demostrarse facilmente que si el punto singular axial fuese puramente absorbente, las ondas neutronicas que se propagaran a lo largo de la instalacion poseerfan una fase, una longitud de onda y una constante de atenuacion dependiente de las propiedades absorbentes del punto singular. Esto se complica en caso de multiplicacion neutronica. Para este caso general, la solucion presentada en la memoria depende, desde luego, de las propiedades absorbentes y multiplicadoras del punto singular. Esta circunstancia, entre otras, ha inducido a utilizar una instalacion como la que se acaba de describir para ensayar los elementos combustibles de los reactores heterogeneos. (author) [Russian] Issledovalis' vremennaja i prostranstvennaja zavisimosti nejtronnogo potoka na vysoko geterogennoj sborke, kuda inzhektirujutsja impul'snye ili sinusoidno modulirovannye nejtrony. Dlja prostoty rassmatrivaetsja ustrojstvo, sostojashhee iz cilindricheskogo bloka zamedlitelja tjazhelyh nejtronov, po osi kotorogo nahoditsja vytjanutaja oblast' rasshhepljajushhegosja materiala. Predpolagaetsja, chto usiljajushhij istochnik nejtronov razmeshhaetsja na odnoj iz storon cilindra. Razmer rasshhepljajushhejsja oblasti pozvoljaet rassmatrivat' ee kak absorbirujushhuju i razmnozhajushhuju singuljarnuju sostavljajushhuju nejtronnogo polja. Poskol'ku vnimanie koncentriruvalos' glavnym obrazom na prostranstvennom i vremennom izmenenii nejtronnogo potoka, to sdelany dovol'no grubye priblizhenija otnositel'no jenergeticheskoj zavisimosti opredelennoj populjacii nejtronov. V ramkah vozrastno-diffuzionnoj teorii reakcija pribora na ljuboe vozbuzhdenie nejtronov mozhet imet' zakrytuju formu. Dlja sinusoidal'no modulirovannogo istochnika dannoj chastoty mozhno legko pokazat', chto esli osial'naja singuljarnaja sostavljajushhaja javljaetsja chisto absorbirujushhej, to nejtronnye volny, prohodjashhie cherez pribor, budut obladat' fazoj, dlinoj volny i postojannoj oslablenija, kotorye zavisjat ot absorbirujushhih svojstv singuljarnoj sostavljajushhej. Jeta kartina vse bolee uslozhnjaetsja, kogda proishodit razmnozhenie nejtronov. Dlja dannogo obshhego sluchaja reshenie, kotoroe privoditsja v nashem doklade, ochevidno, javljaetsja zavisimym kak ot absorbirujushhih, tak i ot razmnozhajushhih svojstv singuljarnoj sostavljajushhej. Jeto obstojatel'stvo predpolagaet, pomimo prochego, vozmozhnost' ispol'zovanija pribora vysheukazannogo tipa dlja ispytanija toplivnyh jelementov geterogennyh reaktorov. (author)}
place = {IAEA}
year = {1965}
month = {Oct}
}