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Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia

Conference:

Abstract

The cross-sections of the heavy nuclei for neutron-induced fission are of fundamental importance to the technology of nuclear energy production. The manner in which these cross-sections vary with the neutron energy and with the mass and charge of the target nuclei also provides much information on the structure of heavy nuclei. In the case of a thermally fissile target nucleus, as the neutron energy is increased from thermal the cross-section first exhibits an inverse velocity dependence, followed by a region in which sharp resonance peaks appear, and finally a continuum region where the cross-section exhibits relatively smooth steps and breaks. All these phenomena can be explained in principle, but certain features of the data have proved very difficult to explain quantitatively. Recent cross-section measurements, stimulated by the needs of reactor technology, have concentrated on improving the energy resolution and accuracy of the data on fuel materials, and this has led to a more detailed study of the resonance region, which is of considerable interest for reactor Doppler effect calculations. More accurate measurements at rather higher energies have established the existence of appreciable fission cross-sections below the so-called fission threshold in certain cases. Careful measurements of this nature have in turn  More>>
Authors:
Rae, E. R. [1] 
  1. Atomic Energy Research Establishment, Harwell, Didcot, Berks. (United Kingdom)
Publication Date:
Jul 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-60/12
Resource Relation:
Conference: Symposium on Physics and Chemistry of Fission, Salzburg (Austria), 22-26 Mar 1965; Other Information: 22 refs., 10 figs., 1 tab.; Related Information: In: Physics and Chemistry of Fission. Vol. I. Proceedings of the Symposium on Physics and Chemistry of Fission| 654 p.
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ACCURACY; CROSS SECTIONS; DOPPLER EFFECT; ENERGY RESOLUTION; FISSION; HEAVY NUCLEI; NEUTRONS; NUCLEAR MODELS; REACTOR TECHNOLOGY; RESONANCE; VELOCITY
OSTI ID:
22183945
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M3148008480
Submitting Site:
INIS
Size:
page(s) 187-203
Announcement Date:
Jan 30, 2014

Conference:

Citation Formats

Rae, E. R. Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia. IAEA: N. p., 1965. Web.
Rae, E. R. Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia. IAEA.
Rae, E. R. 1965. "Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia." IAEA.
@misc{etde_22183945,
title = {Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia}
author = {Rae, E. R.}
abstractNote = {The cross-sections of the heavy nuclei for neutron-induced fission are of fundamental importance to the technology of nuclear energy production. The manner in which these cross-sections vary with the neutron energy and with the mass and charge of the target nuclei also provides much information on the structure of heavy nuclei. In the case of a thermally fissile target nucleus, as the neutron energy is increased from thermal the cross-section first exhibits an inverse velocity dependence, followed by a region in which sharp resonance peaks appear, and finally a continuum region where the cross-section exhibits relatively smooth steps and breaks. All these phenomena can be explained in principle, but certain features of the data have proved very difficult to explain quantitatively. Recent cross-section measurements, stimulated by the needs of reactor technology, have concentrated on improving the energy resolution and accuracy of the data on fuel materials, and this has led to a more detailed study of the resonance region, which is of considerable interest for reactor Doppler effect calculations. More accurate measurements at rather higher energies have established the existence of appreciable fission cross-sections below the so-called fission threshold in certain cases. Careful measurements of this nature have in turn stimulated interest in the interpretation of the cross-sections in terms of nuclear models on a firm quantitative basis. This paper outlines the main features of neutron-induced-fission cross-sections and their interpretation. Some emphasis is placed on recent improvements in the quality of the measurements and in attempts at quantitative interpretation of certain aspects of the data. (author) [French] Les sections efficaces de fission des noyaux lourds ont une importance essentielle pour la technologie de la production d'energie d'origine nucleaire. La maniere dont ces sections efficaces varient Selon l'energie des neutrons et Selon la masse et la charge des noyaux cibles fournit egalement de nombreux renseignements sur la structure des noyaux lourds. Dans le cas d'un noyau cible susceptible de fission thermique, lorsque l'energie des neutrons augmente, la section efficace presente d'abord des variations inversement proportionnelles a la vitesse, puis une region ou des pics de resonance aigus apparaissent, et en dernier lieu une region de continu caracterisee par des variations relativement regulieres. Tous ces phenomenes peuvent recevoir une explication theorique, mais il semble tres difficile d'expliquer quantitativement certaines caracteristiques des donnees. Lors de mesures recentes de sections efficaces destinees a repondre aux besoins de la technologie des reacteurs, les chercheurs se sont surtout efforces d'ameliorer la resolution en energie ainsi que la precision des donnees relatives aux combustibles; ils ont ete ainsi amenes a etudier plus en detail la region de resonance qui a un grand interet pour les calculs de l'effet Doppler dans les reacteurs. Des mesures plus precises a des niveaux d'energie assez eleves ont fait apparaitre dans certains cas l'existence de sections efficaces de fission assez importantes en dessous du seuil d'energie de fission. Ces mesures ont ensuite appele l'attention des chercheurs sur l'interpretation des sections efficaces en fonction de modeles nucleaires qui reposent sur des donnees quantitatives sures. Le memoire expose les principales caracteristiques des sections efficaces de fission par neutrons et en donne une interpretation. Il met l'accent sur les ameliorations qui ont recemment ete apportees a la qualite des mesures et aux essais d'interpretation quantitative de certains aspects des donnees recueillies. (author) [Spanish] Las secciones eficaces de fision, inducida por neutrones, de los nucleos pesados son de fundamental importancia para la tecnologia de la produccion de energia nuclear. Asimismo, la manera en que estas secciones eficaces varian segun la energia neutronica y la masa y carga de los nucleos tomados como blanco, proporciona abundante informacion sobre la estructura de los nucleos pesados. En el caso de un blanco constituido por un nucleo susceptible de fision por bombardeo con neutrones termicos, a medida que la energia aumenta y pasa de la zona termica a niveles superiores, se observa que la seccion eficaz varia primero en forma inversamente proporcional a la velocidad, abarcando despues una region en la que aparecen picos de resonancia pronunciados, para llegar finalmente a una zona en que se presentan escalones de escasa pendiente y algunas discontinuidades. En principio, es posible explicar todos estos fenomenos, pero ciertos aspectos de los datos resultan sumamente dificiles de interpretar en sus aspectos cuantitativos. En los ultimos tiempos, los trabajos de medicion de secciones eficaces, estimulados por los imperativos de la tecnologia de reactores, tienden sobre todo a mejorar el poder resolutivo en energia y la precision de los datos sobre materiales combustibles, lo que ha tenido como resultado un estudio mas a fondo de la region de resonancia, que es de gran interes para el calculo del efecto Doppler en los reactores. Una serie de mediciones mas precisas, efectuadas a energias bastante elevadas, han puesto de manifiesto la' existencia en ciertos casos, de apreciables secciones eficaces de fision por debajo del denominado umbral de fision. A su vez, las mediciones meticulosas de esta indole han estimulado el interes por la interpretacion de las secciones eficaces en funcion de modelos nucleares sobre una base cuantitativa bien asentada. En la memoria se exponen las principales caracteristicas de las secciones eficaces con cierto detenimiento los recientes perfeccionamientos de las tecnicas de medicion y las tentativas de interpretar cuantitativamente ciertos aspectos de los datos. (author) [Russian] Izuchenie sechenij delenija tjazhelyh jader, vyzvannogo nejtronami, imeet reshajushhee znachenie dlja tehnologii proizvodstva jadernoj jenergii. Harakter izmenenija velichiny sechenij v zavisimosti ot jenergij nejtronov, massy i zarjada jader misheni takzhe daet znachitel'nuju informaciju ot nositel'no struktury tjazhelyh jader. V sluchae termicheski deljashhegosja jadra misheni, po mere uvelichenija jenergii nejtronov, vjolichina sechenija projavljaet vnachale obratnuju zavisimost' ot skorosti, smenjaemuju oblast'ju, v kotoroj pojavljajutsja ostrye piki rezonansov i, nakonec, sploshnoj oblast'ju, v kotoroj velichina sechenij sravnitel'no plavno to uvelichivaetsja, to umen'shaetsja. Vse jeti javlenija mozhno v principe ob{sup j}asnit', odnako,nekotorye harakteristiki dannyh okazalis' ochen' trudnymi dlja kolichestvennoj interpretacii. Vo vremja poslednih izmerenij sechenij, vyzvannyh potrebnostjami reaktornoj tehniki, vnimanie bylo sosredotocheno na uluchshenii razreshenija jenergii i tochnosti poluchaemyh dannyh otnositel'no toplivnyh materialov. Jeto privelo k bolee podrobnomu izucheniju rezonansnoj oblasti, kotoraja predstavljaet znachitel'nyj interes pri raschetah jeffekta Dopplera dlja reaktorov. V rezul'tate bolee tochnyh izmerenij pri dovol'no povyshennyh jenergijah vyjavleno nalichie v nekotoryh sluchajah znachitel'nyh velichin sechenij delenija nizhe tak nazyvaemogo poroga delenija. Tshhatel'nye izmerenija takogo haraktera, v svoju ochered', porodili interes k interpretacii sechenij s tochki zrenija jadernyh modelej na tverdoj kolichestvennoj osnove. Namechajutsja osnovnye cherty sechenij delenija, vyzvannogo nejtronami, i ih interpretacii. Nekotoryj upor delaetsja na poslednie usovershenstvovanija v kachestve izmerenij i na popytki kolichestvennoj interpretacii'nekotoryh aspektov dannyh. (author)}
place = {IAEA}
year = {1965}
month = {Jul}
}