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Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos

Conference:

Abstract

Using a method described in another paper presented at this Symposium, the authors measured non-stationary neutron spectra in zirconium hydride and in water at room temperature as a function of slowing-down time, with a resolution of 3.5 {mu}s. The spectra measured in a large ZrH prism (B{sup 2} = 3.8 x 10{sup -2} cm{sup 2}) belong to a slowing-down time range (t > 30 {mu}s) in which the mean neutron energy is less than 0.13 eV and the energy exchange between neutron gas and the medium is caused mainly by the excitation of acoustic lattice vibrations. In this range thermalization proceeds at a comparatively slow rate and the time required to establish an equilibrium neutron spectrum is of the order of 400 {mu}s. In a small ZrH assembly (B{sup 2} Asymptotically-Equal-To 20 x 10{sup -2} cm{sup 2}) a strong diffusion-cooling effect is observed. The spectra measured at long slowing-down times are found to differ considerably from the Maxwellian distribution with the temperature of the medium. The time required to establish an equilibrium energy distribution increases with decreasing system size. The neutron energy spectra in water (B{sup 2} = 2.56 x 10{sup -2}cm{sup 2}) are presented for slowing-down times of over  More>>
Authors:
Ishmaev, S. N.; Mostovoj, V. I.; Sadikov, I. P.; Chernyshov, A. A. [1] 
  1. Gosudarstvennyj Komitet po Ispol'zovaniju Atomnoj Ehnergii SSSR, Institut Atomnoj Ehnergii Im. I.V.Kurchatova, Moskva, SSSR (Russian Federation)
Publication Date:
Aug 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-62/107
Resource Relation:
Conference: Symposium on Pulsed Neutron Research, Karlsruhe (Germany), 10-14 May 1965; Other Information: 11 refs., 7 figs., 2 tabs.; Related Information: In: Pulsed Neutron Research. Vol. I. Proceedings of the Symposium on Pulsed Neutron Research| 713 p.
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BOLTZMANN STATISTICS; DIFFUSION; ENERGY SPECTRA; ENERGY TRANSFER; EXCITATION; EXPERIMENTAL DATA; FAST NEUTRONS; LATTICE VIBRATIONS; MODERATORS; NEUTRON SPECTRA; TEMPERATURE RANGE 0273-0400 K; THERMALIZATION; WATER; ZIRCONIUM HYDRIDES
OSTI ID:
22122993
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
Russian
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2600078795
Submitting Site:
INIS
Size:
page(s) 643-656
Announcement Date:
Aug 30, 2013

Conference:

Citation Formats

Ishmaev, S. N., Mostovoj, V. I., Sadikov, I. P., and Chernyshov, A. A. Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos. IAEA: N. p., 1965. Web.
Ishmaev, S. N., Mostovoj, V. I., Sadikov, I. P., & Chernyshov, A. A. Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos. IAEA.
Ishmaev, S. N., Mostovoj, V. I., Sadikov, I. P., and Chernyshov, A. A. 1965. "Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos." IAEA.
@misc{etde_22122993,
title = {Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos}
author = {Ishmaev, S. N., Mostovoj, V. I., Sadikov, I. P., and Chernyshov, A. A.}
abstractNote = {Using a method described in another paper presented at this Symposium, the authors measured non-stationary neutron spectra in zirconium hydride and in water at room temperature as a function of slowing-down time, with a resolution of 3.5 {mu}s. The spectra measured in a large ZrH prism (B{sup 2} = 3.8 x 10{sup -2} cm{sup 2}) belong to a slowing-down time range (t > 30 {mu}s) in which the mean neutron energy is less than 0.13 eV and the energy exchange between neutron gas and the medium is caused mainly by the excitation of acoustic lattice vibrations. In this range thermalization proceeds at a comparatively slow rate and the time required to establish an equilibrium neutron spectrum is of the order of 400 {mu}s. In a small ZrH assembly (B{sup 2} Asymptotically-Equal-To 20 x 10{sup -2} cm{sup 2}) a strong diffusion-cooling effect is observed. The spectra measured at long slowing-down times are found to differ considerably from the Maxwellian distribution with the temperature of the medium. The time required to establish an equilibrium energy distribution increases with decreasing system size. The neutron energy spectra in water (B{sup 2} = 2.56 x 10{sup -2}cm{sup 2}) are presented for slowing-down times of over 13 {mu}s, where distortions from resolution are insignificant. The shape of the spectrum is only fully consistent with the Maxwellian distribution at room temperature after about 100 {mu}s following a fast neutron burst. The time required to establish an equilibrium neutron spectrum in this experiment is three to four times longer than the values calculated by various other authors. The possible reasons for this discrepancy are discussed. (author) [French] A l'aide de la methode que les auteurs ont decrite dans un autre memoire presente au Colloque, ils ont mesure, en fonction du temps de ralentissement, les spectres non stationnaires des neutrons dans l'hydrure de zirconium et dans l'eau a la temperature ambiante, avec un pouvoir de resolution de 3,5 {mu}s. Les spectres ont ete determines au moyen d'un prisme de ZrH de grande dimension (B{sup 2} = 3,8 * 10{sup -2} cm{sup -2}) pour des temps de ralentissement superieurs a 30 {mu}s; pour ces valeurs du temps, l'energie moyenne des neutrons est inferieure a 0,13 eV et l'echange d'energie entre le gaz neutronique et le milieu s'opere essentiellement du fait de l'apparition d'oscillations acoustiques dans le reseau; en outre, le processus de thermalisation suit un rythme relativement lent et le temps necessaire pour obtenir un spectre de neutrons a l'etat d'equilibre est de l'ordre de 400 {mu}s. Dans un assemblage a ZrH de petite dimension (B{sup 2} Asymptotically-Equal-To 20 * 10{sup -2} cm{sup -2}) on constate un puissant effet de refroidissement par diffusion. Les spectres mesures pour des temps de ralentissement prolonges different sensiblement de la distribution maxwellienne a la temperature ambiante. Le temps requis pour obtenir une distribution equilibree de l'energie augmente avec la reduction des dimensions dy systeme. Les auteurs presentent les spectres energetiques des neutrons dans l'eau (B{sup 2} = 2,56 * 10{sup -2} cm{sup -2}) pour des temps de ralentissement superieurs a 13 {mu}s ou les deformations provoquees aux depens du pouvoir de resolution sont insignifiantes. La forme du spectre ne concorde entierement avec la distribution maxwellienne a la temperature ambiante qu'apres un delai d'environ 100 {mu}s apres la bouffee de neutrons rapides. Dans l'experience, le temps necessaire a la formation d'un spectre de neutrons a l'etat d'equilibre etait de trois a quatre fois superieur a celui qu'indiquent les calculs effectues par differents auteurs. Les causes possibles de ces divergences font l'objet d'un examen critique. (author) [Spanish] Con ayuda del metodo descrito en otra memoria presentada a este Simposio, los autores han medido en funcion del tiempo de moderacion los espectros neutronicos no estacionarios en hidruro de circonio y en agua a temperatura ambiente, con un poder de resolucion de 3,5 {mu}s. Los espectros medidos en un prisma de ZrH de gran tamano (B{sup 2} = 3,8 * 10{sup -2} cm{sup 2}) pertenecen a un intervalo de tiempos de moderacion (t > 30 {mu}s) en el cual la energia media de los neutrones es inferior a 0,13 eV y el intercambio de energia entre el gas neutronico y el medio se debe fundamentalmente a la excitacion de vibraciones acusticas en el reticulado. Dentro de este intervalo, la termaiizacion se desarrolla a un ritmo comparativamente lento y el tiempo necesario para obtener un espectro neutronico de equilibrio es del orden de 400 {mu}s. En montajes de ZrH de pequenas dimensiones (B{sup 2} Asymptotically-Equal-To 20 * 10{sup -2} cm{sup -2}) se observa un marcado efecto de enfriamiento por difusion. Los espectros medidos para tiempos de moderacion prolongados difieren considerablemente de la distribucion maxwelliana correspondiente a la temperatura ambiente. El tiempo necesario para lograr una distribucion energetica de equilibrio aumenta a medida que disminuyen las dimensiones del sistema. Los autores presentan espectros energeticos de neutrones en agua (B{sup 2} = 2,56 * 10{sup -2} cm{sup -2}) para tiempos de moderacion superiores a 13 {mu}s donde las deformaciones debidas a la resolucion son insignificantes. La forma del espectro solo concuerda con la distribucion maxwelliana a temperatura ambiente, al cabo de unos 100 {mu}s despues de emitida una rafaga de neutrones rapidos. El tiempo necesario para que el espectro de neutrones alcance el equilibrio es, en este experimento, tres a cuatro veces mas prolongado que los valores calculados por diversos autores. En la memoria se analizan los posibles motivos de esta discrepancia. (author) [Russian] S pomoshh'ju metodiki, opisannoj v drugom doklade avtorov na dannuju konferenciju, izmereny nestacionarnye spektry nejtronov v gidride cirkonija i vode pri komnatnoj temperature s razresheniem 3,5 mksek po vremeni zamedlenija. Spektry, izmerennye v prizme iz Z gN bol'shogo razmera (V{sup 2} = 3,8 * 10{sup -2} sm{sup 2}), otnosjatsja k oblasti vremen zamedlenija (t > 30 mksek), gde srednjaja energija nejtronov nizhe 0,13 jev i obmen energiej mezhdu nejtronnym gazom i sredoj proishodit, v osnovnom, za schet vozbuzhdenija akusticheskih kolebanij reshetki. V jetoj oblasti process termalizacii idet sravnitel'no medlenno i vremja, neobhodimoe dlja ustanovlenija ravnovesnogo spektra nejtronov, okazyvaetsja porjadka 400 mksek. V sborke iz ZrH malogo razmera (V{sup 2} Asymptotically-Equal-To 20 * 10{sup -2} sm{sup 2}) projavljaetsja sil'nyj jeffekt diffuzionnogo ohlazhdenija. Spektry, izmerennye pri bol'shih vremenah zamedlenija, sil'no otlichajutsja ot maksvellovskogo raspredelenija s temperaturoj sredy. Vremja, neobhodimoe dlja ustanovlenija ravnovesnogo energeticheskogo raspredelenija, vozrastaet s umen'sheniem razmerov sistemy. energeticheskie spektry nejtronov v vode (V{sup 2} = 2,56 * 10{sup -2} sm{sup -2}) predstavleny dlja vremen zamedlenija bol'shih 13 mksek, gde iskazhenija za schet razreshenija neznachitel'ny. Forma spektra polnost'ju sovpadaet s raspredeleniem Maksvella pri komnatnoj temperature lish' spustja Tilde-Operator 100 mksek posle vspyshki bystryh nejtronov. Nabljudaemoe v jeksperimente vremja ustanovlenija ravnovesnogo spektra nejtronov v 3 - 4 raza bol'she, chem dajut raschety, vypolnennye razlichnymi avtorami. Obsuzhdajutsja vozmozhnye prichiny rashozhdenij. (author)}
place = {IAEA}
year = {1965}
month = {Aug}
}