Contribution to the study of low-energy (d,p) reactions on light nuclei; Contribution a l'etude des reactions (d,p) a basse energie sur noyaux legers

Energy Technology Data Exchange (ETDEWEB)

Nguyen Van, S. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1967-05-15

This work is carried out with a view to analysing low energy (d,p) reactions on light nuclei measured at Grenoble or Algiers and suggesting a direct mechanism. The distorted wave approximation has been applied; this requires the development of programmes for the IBM 7044 computer at the 'Institut des Mathematiques Appliquees' in Grenoble. The (d,p) reactions on {sup 14}N, {sup 9}Be, {sup 22}Ne and {sup 16}O are dealt with. A calculation of the interference of the direct interaction and of resonating effects has been applied to {sup 16}O. (author) [French] Ce travail a pour but d'analyser les reactions (d,p) a basse energie sur noyaux legers, mesurees a Grenoble ou a Alger et qui suggerent un mecanisme direct. L'approximation des ondes distordues a ete appliquee, necessitant la mise au point de programmes sur l'ordinateur IBM 7044 de l'Institut des Mathematiques Appliquees de Grenoble. Des reactions (d,p) sur {sup 14}N, {sup 9}Be, {sup 22}Ne et {sup 16}O sont traitees. Un calcul de l'interference de l'interaction directe et des effets resonnants a ete applique a {sup 16}O. (auteur)

Study of some continuous spectra produced by nuclear reactions with light nuclei; Etude de quelques spectres continus produits par reactions nucleaires avec des noyaux legers

Energy Technology Data Exchange (ETDEWEB)

Marquez, L

1966-07-01

The continuous spectra coming from several nuclear reactions with light nuclei were measured. The spectra can be explained by a two-step reaction mechanism; however, the reactions produced by {sup 6}Li are different. A mechanism was proposed to explain their spectra based on the following assumptions: {sup 6}Li makes a nuclear molecule with the target which subsequently breaks up in such a way that an {alpha} particle comes out with the kinetic energy that it has in the molecule. The calculated spectra and those measured are in good agreement. (author) [French] Nous avons mesure les spectres continus produits dans plusieurs reactions nucleaires avec des noyaux legers. A l'exception des spectres produits par {sup 6}Li, on a trouve qu'on pouvait expliquer ces spectres par le mecanisme des reactions en deux etapes. Nous avons propose un mecanisme pour expliquer les spectres produits par {sup 6}Li. On suppose que {sup 6}Li forme une molecule nucleaire avec la cible qui eclate ensuite de facon telle qu'une particule alpha de la molecule sort avec l'energie cinetique de son mouvement propre dans la molecule. Les spectres calcules avec ces hypotheses et les spectres mesures sont en bon accord. (auteur)

Some considerations of the energy spectrum of odd-odd deformed nuclei; Quelqes considerations sur le spectre d'energie des noyaux impair-impair deformes

Energy Technology Data Exchange (ETDEWEB)

Alceanu-G, Pinho de; Picard, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The odd-odd deformed nuclei are described as a rotator plus two odd nucleons moving in orbitals {omega}{sub p} and {omega}{sub n} of the deformed potential. We investigate the energies and wave functions of the various states of the ({omega}{sub p}, {omega}{sub n}) configurations by calculating and numerically diagonalizing the Hamiltonian matrix (with R.P.C. and residual interactions). The Gallagher-Mosskowski coupling rules ana the abnormal K equals 0 rotational bands are discussed. (authors) [French] Les noyaux impair-impairs deformes sont decrits comme un rotateur plus deux nucleons non apparies dans les orbites {omega}{sub p} et {omega}{sub n} du potentiel deforme. Nous etudions le spectre d'energie et les fonctions d'onde des configurations ({omega}{sub p}, {omega}{sub n}) en tenant compte de l'interaction particule-rotation et de la force residuelle entre les deux nucleons celibataires.

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

Energy Technology Data Exchange (ETDEWEB)

Rae, E. R. [Atomic Energy Research Establishment, Harwell, Didcot, Berks. (United Kingdom)

1965-07-15

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

Some considerations of the energy spectrum of odd-odd deformed nuclei; Quelqes considerations sur le spectre d'energie des noyaux impair-impair deformes

Energy Technology Data Exchange (ETDEWEB)

Alceanu-G, Pinho de; Picard, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The odd-odd deformed nuclei are described as a rotator plus two odd nucleons moving in orbitals {omega}{sub p} and {omega}{sub n} of the deformed potential. We investigate the energies and wave functions of the various states of the ({omega}{sub p}, {omega}{sub n}) configurations by calculating and numerically diagonalizing the Hamiltonian matrix (with R.P.C. and residual interactions). The Gallagher-Mosskowski coupling rules ana the abnormal K equals 0 rotational bands are discussed. (authors) [French] Les noyaux impair-impairs deformes sont decrits comme un rotateur plus deux nucleons non apparies dans les orbites {omega}{sub p} et {omega}{sub n} du potentiel deforme. Nous etudions le spectre d'energie et les fonctions d'onde des configurations ({omega}{sub p}, {omega}{sub n}) en tenant compte de l'interaction particule-rotation et de la force residuelle entre les deux nucleons celibataires.

L'analyse par activation de neutrons de réacteur

Science.gov (United States)

Meyer, G.

2003-02-01

Quand les neutrons traversent la matière, certains sont transmis sans interaction, les autres interagissent avec le milieu traversé par diffusion et par absorption. Ce phénomène d'absorption est utilisé pour se protéger des neutrons, mais aussi pour les détecter; il peut également être utilisé pour identifier les noyaux “absorbants" et ainsi analyser le milieu traversé. En effet par différentes réactions nucléaires (n,γ), (n,p), (n,α), (n,fission), on obtient des noyaux résiduels qui sont souvent radioactifs; on dit que l'échantillon est “activé". Si l'on connaît le rendement d'activation et donc le pourcentage de noyaux ainsi “transmutés", les mesures de radioactivité induite vont permettre de déterminer la composition de l'échantillon irradié. Cette méthode dite d'analyse par activation neutronique est pratiquée depuis la découverte du neutron. Elle a permis grâce à sa sélectivité et à sa sensibilité d'avoir accès au domaine des traces et des ultra-traces dans des champs d'application très divers comme la métallurgie, l'archéologie, la biologie, la géochimie etc...

Contribution to the study of the fission-gas release in metallic nuclear fuels; Contribution a l'etude du degagement des gaz de fission dans les combustibles nucleaires metalliques

Energy Technology Data Exchange (ETDEWEB)

Kryger, B [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-10-01

In order to study the effect of an external pressure on the limitation of swelling due to fission-gas precipitation, some irradiations have been carried out at burn-ups of about 35.000 MWd/ton, and at average sample temperatures of 575 Celsius degrees, of non-alloyed uranium and uranium 8 per cent molybdenum gained in a thick stainless steel can. A cylindrical central hole allows a fuel swelling from 20 to 33 per cent according to the experiment. After irradiation, the uranium samples showed two types of can rupture: one is due to the fuel swelling, and the other, to the pressure of the fission gases, released through a network of microcracks. The cans of the uranium-molybdenum samples are all undamaged and it is shown that the gas release occurs by interconnection of the bubbles for swelling values higher than those obtained in the case of uranium. For each type of fuel, a swelling-fission gas release relationship is established. The results suggest that good performances with a metallic fuel intended for use in fast reactor conditions can be obtained. (author) [French] Afin d'etudier l'effet d'une pression exterieure sur la limitation du gonflement due a la precipitation des gaz de fission, on a irradie a des taux de combustion d'environ 35.000 MWj/t et a des temperatures moyennes de 575 degres des echantillons d'uranium non allie et d'uranium-molybdene 8 pour cent contenus dans une gaine en acier inoxydable epaisse. Un trou cylindrique central permet au combustible de gonfler librement de 20 a 33 pour cent suivant les cas. Apres irradiation les echantillons d'uranium presentent deux types de ruptures de gaine: l'une due au gonflement du combustible, l'autre a la pression des gaz degages, ce degagement des gaz etant provoque par un reseau de micro-fissures. Les gaines des echantillons d'alliage uranium-molybdene sont toutes intactes et l'on montre que le relachement des gaz opere par interconnexion des bulles pour des valeurs de gonflement plus elevees que dans

A new detector for the measurement of neutron flux in nuclear reactors; Nouvelle methode de mesure des flux de neutrons dans les reacteurs atomiques

Energy Technology Data Exchange (ETDEWEB)

Koch, L; Labeyrie, J; Tarassenko, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The detector described is designed for the instantaneous measurement of thermal neutron fluxes, in the presence of high {gamma} ray activity; this detector can withstand temperatures as high as 500 deg. C. It is based on the following principle: radioactive atoms resulting from heavy-nucleus fission are carried by a gas flow to a detector recording their {beta} and {gamma} disintegration. Thermal neutron fluxes as low as few neutrons per cm{sup 2} per second can be measured. This detector may be used to control a nuclear reactor, to plot the thermal flux distribution with an excellent definition (1 mm{sup 2}) for fluxes higher than 10{sup 8} n/cm{sup 2}/s. The time response of the system to a sharp variation of flux is limited, in case of large fluxes, to the transit time of the gas flow between the fission product emitter and the detector; of the order of one tenth of a sec per meter of piping. The detector may also be applied for spectroscopy of fission products eider than 0,1 s. (author)Fren. [French] On decrit un appareil permettant la mesure instantanee des flux de neutrons thermiques accompagnes de flux intenses de rayons {gamma} et situes dans des enceintes pouvant etre portees a des temperatures superieures a 500 deg. C. On utilise la radioactivite des atomes resultant de la fission des noyaux lourds; ces atomes sont entraines par un courant gazeux vers un detecteur de radioactivite qui enregistre leurs desintegrations {beta} et {gamma}. On peut mesurer des flux partir de quelques neutrons thermiques par cm{sup 2} et par seconde. L'appareil permet de suivre la puissance d'un reacteur atomique, de tracer des cartes de densite de neutrons avec une tres bonne definition (1 mm{sup 2}) dans le cas de flux superieurs a 10{sup 8} cm{sup 2}/s. Le temps de reponse du systeme a une variation du flux de neutrons est limite, poes flux importants, par le temps de transit du gaz entre l'emetteur de produits de fission et le detecteur: soit quelques dizaines de

Caractérisation physico-chimique des sables usés de la fonderie

African Journals Online (AJOL)

SEI Joseph

Liés avec des argiles ou des résines, les sables de fonderie sont utilisés pour confectionner des moules et des noyaux dans lesquels sont coulés les métaux en fusion. Après l'opération de démoulage des pièces métalliques, une grande partie des sables est réutilisée sur place par régénération, tandis que les sables usés ...

Comparison of fission probabilities with emission of long range particles under the action of slow and fast neutrons on various materials; Probabilites comparees de fission avec emission de particules de long parcours pour divers materiaux sous l'action des neutrons lents et rapides

Energy Technology Data Exchange (ETDEWEB)

Netter, F; Faraggi, H; Garin-Bonnet, A; Julien, J; Corge, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Turkiewicz, J [Institut de Recherches Nucleaire de Varsovie (Poland)

1958-07-01

The authors describe relative cross-section measurements of fission of the isotopes of uranium and plutonium (more particularly {sup 235}U, {sup 238}U, {sup 239}Pu), with emission of long range particles, under the action of neutrons of various energies: thermal neutrons, pile neutrons, neutrons produced with the Van de Graaff accelerator by reaction of protons on tritium. The measurements are carried out: 1) with the aid of photographic plates, by submitting to the action of the neutrons a layer of fissile material coupled with an Ilford nuclear emulsion of 200 microns; a tin sheet laying between the plate and the layer stops the {alpha} particles and the fission fragments. By an appropriate development the tracks of the long range particles can be distinguished in the emulsion, from the tracks of the recoil protons resulting of fission neutrons, or of the last primary neutrons. For neutrons of energy under 1 MeV, the compared frequency of the tracks of long range particles and of the recoils caused by the fission neutrons gives a measurement of the fission cross-section with emission of long range particles relative to the product of the fission cross-section by the mean number of neutrons emitted by fission. For neutrons of higher energy, one measures only the frequency of the tracks of long range particles, comparatively with the flux of primary neutrons. Some precautions are taken to eliminate the action of thermal neutrons in the measurements with fast neutrons. 2) with the aid of a system of ionization chamber and proportional counter, the rate of coincidence between the impulsions caused by the long range particles and the impulsions provided by one of the fission fragments is measured comparatively with the counting rate of fission fragme (author) [French] Les auteurs decrivent des mesures relatives a la section efficace de fission des isotopes de l'uranium et du plutonium (notamment {sup 235}U, {sup 238}U, {sup 239}Pu) avec emission de particules de long

The inelastic scattering of medium energy {alpha} particles; Sur la diffusion inelastique des particules {alpha} a moyenne energie

Energy Technology Data Exchange (ETDEWEB)

Crut, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1960-07-01

The aim of this work is to find out what are the properties of the so-called 'anomalous states' in medium weight nuclei. These states preferentially excited in the inelastic scattering of medium energy charged particles have an excitation energy at about 4 MeV for nuclei with Z {<=} 29 and in the range 2-3 MeV for high Z nuclei. From a combination of angular distribution data in the elastic and inelastic scattering of 30 MeV {alpha} particles, and correlation data between inelastic {alpha} particles and deexcitation {gamma} rays, we show that for even-even nuclei, we can attribute spin 3 and parity minus to these 'anomalous states'. This is quite in agreement with the interpretation of these levels suggested by Lane as due to collective octupole oscillations. We give a resume of the theories used in the analysis of the data and a description of the experimental set-up. (author) [French] Le but de cette etude est de determiner les proprietes des niveaux dits 'anormalement excites' lors de la diffusion inelastique des particules chargees de moyenne energie sur des noyaux de masse moyenne et lourde. L'energie de ces niveaux est de l'ordre de 4 MeV pour les noyaux avec Z {<=} 29 et de 2 a 3 MeV pour les noyaux de Z plus eleve. De l'examen des courbes de distribution angulaire des particules {alpha} de 30 MeV diffusees elastiquement et inelastiquement, et de la correlation angulaire entre {alpha} excitant ces niveaux 'anormaux' et {gamma} de desexcitation, on deduit que, dans le cas des pair-pair, on peut attribuer a ces niveaux spin 3 et parite moins. Ceci renforce l'hypothese emise par Lane qui attribue ces niveaux a des oscillations octupolaires de la surface du noyau. On donne un apercu des theories utilisees dans l'analyse des resultats et une description des dispositifs experimentaux. (auteur)

New results concerning the behaviour of fission gases in in-pile UO{sub 2} at high temperatures; Resultats nouveaux sur le comportement des gaz de fission a haute temperature dans l'UO{sub 2} en pile

Energy Technology Data Exchange (ETDEWEB)

Soulhier, R; Schurenkamper, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

The authors consider in the first part the various phenomena giving rise to the production of fission gases towards the exterior of nuclear fuels. The following aspects are dealt with: diffusion, for which is considered the influence of the predecessors of the radioactive gases, the fission recoil, atom expulsion along the fission paths and the evaporation. In the second part the authors present the results obtained on UO{sub 2} samples subjected to irradiation at temperatures of between 150 and 2000 deg C: - At low temperatures the variation of the amount produced as a function of the half-life of the isotopes studied shows that recoil is hot the only cause of gas production. - Above 1800 deg C, a weight loss by evaporation has been observed and the influence of this phenomenon on gas liberation has been studied; thus the fraction of {sup 135}Xe liberated at 2000 deg C by processes other than evaporation is of the order of 10 per cent. - The influence of the various mechanism on the overall effect as a function of temperature is discussed. (authors) [French] Dans une premiere partie, les auteurs etudient les differents phenomenes pouvant donner lieu au degagement des gaz de fission hors d'un combustible. Sont traites successivement: la diffusion, pour laquelle on discute l'influence des predecesseurs des gaz radioactifs, le recul de fission, l'expulsion des atomes le long des trajets de fission et l'evaporation. Dans une deuxieme partie ils exposent les resultats obtenus sur des echantillons d'UO{sub 2} portes sous irradiation a des temperatures comprises entre 150 deg C et 2000 deg C: - A basse temperature la variation de la quantite degagee suivant la periode des isotopes etudies montre que le recul n'est pas la seule cause du degagement des gaz. - Au-dessus de 1800 deg C on a note une perte de poids par evaporation et on a evalue l'influence de ce phenomene sur la liberation des gaz: ainsi la fraction du {sup 135}Xe liberee a 2000 deg C par d'autres processus

Study and industrial applications of the external slowing-down {beta}{sup -} radiation of the yttrium - 90; Etude et applications industrielles du rayonnement de freinage externe des {beta}{sup -} de l'yttrium - 90

Energy Technology Data Exchange (ETDEWEB)

Leveque, P; Martinelli, P; Chauvin, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

Inelastic scattering of the {beta}{sup -} particles on the nucleus gives place to the emission of a X-ray Bremsstrahlung radiation. In view of possible industrial applications, we studied the slowing-down radiation of {sup 90}(Sr + Y) sources in various materials. This pure {beta}{sup -} emitter of long period is in the fission products of uranium. Among of the industrial applications, these sources of weak X-rays energy can be used for the radiography of thin pieces, for measuring the thickness, or for the analysis by fluorescence. (M.B.) [French] La diffusion inelastique des particules {beta}{sup -} sur les noyaux donne lieu a l'emission d'un rayonnement X de freinage. En vue de possibles applications industrielles, nous avons etudie le rayonnement de freinage des sources {sup 90}(Sr + Y) dans divers materiaux. Cet emetteur {beta}{sup -} pur a longue periode se trouve dans les produits de fission de l'uranium. Parmi les applications industrielles a l'etude, ces sources de rayons X de faible energie peuvent etre utilisees pour la radiographie de pieces minces, la mesure d'epaisseurs, ou encore pour l'analyse par fluorescence. (M.B.)

On some uses of the recording op fission fragments occurring in insulators; Sur quelques utilisations de l'enregistrement des fragments de fission dans les isolants

Energy Technology Data Exchange (ETDEWEB)

Mory, J [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1965-07-01

The passage of fission fragments is manifested in insulators by the formation of damage lines which can easily be observed by transparence using the electron microscope after a suitable chemical attack. Since the recording efficiency is 100 per cent for mica and plastics this phenomenon has a certain number of applications. After briefly recalling the interaction processes between charged particles and matter, and giving a quantitative study of the relationships connecting the various parameters, the author considers here some of these applications: - thermal neutron dosimetry: it is possible to measure integrated fluxes of between lO{sup 3} and 10{sup 21} n/cm{sup 2}, according to the method used; - fast neutron dosimetry: by using fission fragment threshold sources it is easy to measure biological type doses of about 1 rem: - dosage of very low fissile impurity concentrations: atomic concentrations of about 10{sup -9}; can be measured; this limit has never been attained by conventional methods; - study of fissile elements occurring in atmospheric dusts. Results are then briefly given of an automated counting test for traces effected by measuring the electrical resistivity, of the irradiated membrane. Finally are given the advantages and disadvantages of these solid detectors, especially with respect to nuclear emulsions whose uses are approximately identical. (author) [French] Le passage des fragments de fission se materialise dans les isolants par des lignes de dommages que l'on peut facilement observer par transparence au microscope optique apres une attaque chimique appropriee. L'efficacite d'enregistrement etant de 100 pour cent dans le mica et les plastiques, ce phenomene peut avoir un certain nombre d'applications. Apres un bref rappel des processus d'interaction entre particules chargees et matiere, et une etude quantitative des relations unissant les differents parametres, on etudie ici quelques-unes de ces applications: - dosimetrie de neutrons

Evaluation des conditions de germination des noyaux de Grewia ...

African Journals Online (AJOL)

personnel

31 janv. 2014 ... 1Laboratoire de Physiologie et Production Végétales, Université Marien NGOUABI,. Faculté des Sciences et Techniques, BP.69. Brazzaville, Republique du Congo. 2Ecole Nationale Supérieure d'Agronomie et Forestérie, Université Marien NGOUABI,. BP. 69. Brazzaville, Republique du Congo.

Some methods for the detection of fissionable matter; Quelques methodes de detection des corps fissiles

Energy Technology Data Exchange (ETDEWEB)

Guery, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-03-01

A number of equipments or processes allowing to detect uranium or plutonium in industrial plants, and in particular to measure solution concentrations, are studied here. Each method has its own field of applications and has its own performances, which we have tried to define by calculations and by experiments. The following topics have been treated: {gamma} absorptiometer with an Am source, detection test by neutron multiplication, apparatus for the measurement of the {alpha} activity of a solution, fissionable matter detection by {gamma} emission, fissionable matter detection by neutron emission. (author) [French] On examine ici plusieurs appareils ou procedes qui permettent de detecter l'uranium ou le plutonium dans les installations industrielles, et en particulier de mesurer les concentrations de solutions. Chacune des methodes a son domaine d'application et ses performances, qu'on a tente de definir par le calcul et par des experiences. Les sujets traites sont les suivants: absorptiometre {gamma} a source d'americium, essais de detection par multiplication neutronique, appareil de mesure de l'activite {alpha} d'une solution, detection des matieres fissiles par leur emission {gamma}, detection des matieres fissiles par leur emission neutronique. (auteur)

Prompt neutron emission; Emission des neutrons prompts de fission

Energy Technology Data Exchange (ETDEWEB)

Sher, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

It is shown that Ramanna and Rao's tentative conclusion that prompt fission neutrons are emitted (in the fragment system) preferentially in the direction of fragment motion is not necessitated by their angular distribution measurements, which are well explained by the usual assumptions of isotropic emission with a Maxwell (or Maxwell-like) emission spectrum. The energy distribution (Watt spectrum) and the angular distribution, both including the effects of anisotropic emission, are given. (author) [French] On montre que la conclusion experimentale de Ramanna et Rao selon laquelle les neutrons prompts de fission sont emis (dans le systeme de reference des fragments) preferentiellement dans la direction du mouvement du fragment, ne decoule pas necessairement de leurs mesures de distribution angulaire. Celles-ci sont bien expliquees par l'hypothese classique de l'emission isotrope et d'un spectre d'emission maxwellien (ou quasi-maxwellien). On donne la distribution en energie (ou spectre de Watt) et la distribution angulaire, comprenant toutes les deux les effets d'emission anisotrope. (auteur)

Dosage of fission products in irradiated fuel treatment effluents (radio-chemical method); Dosage des produits de fission dans les effluents du traitement des combustibles irradies (methode radiochimique)

Energy Technology Data Exchange (ETDEWEB)

Auchapt, J [Commissariat a l' Energie Atomique, Marcoule (France). Centre d' Etudes Nucleaires

1966-07-01

The dosage methods presented here are applicable to relatively long-lived fission products present in the effluents resulting from irradiated fuel treatment processes (Sr - Cs - Ce - Zr - Nb - Ru - I). The methods are based on the same principle: - addition of a carrying-over agent - chemical separation over several purification stages, - determination of the chemical yield by calorimetry - counting of an aliquot liquid portion. (author) [French] Les methodes de dosage presentees concernent les produits de fission a vie relativement longue presents dans les effluents de traitement des combustibles irradies (Sr - Cs - Ce - Zr - Nb - Ru - I). Elles sont toutes basees sur le meme principe: - addition d'entraineur, - separation chimique en plusieurs stades de purification, - determination du rendement chimique par calorimetrie, - comptage d'une aliquote liquide. (auteur)

Experimental study of the thermal fission of uranium 235 in the region of symmetrical masses; Contribution a l'etude experimentale de la fission thermique de l'uranium 235 dans la region des masses symetriques

Energy Technology Data Exchange (ETDEWEB)

Ribrag, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-03-15

Energy correlation experiments with fission fragments are strongly perturbed, in the symmetric region, by the detection of spurious events caused by the apparatus. We show that the measurement of an additional parameter, namely the difference in time-of-flight between the fragments, enables us to eliminate these difficulties. In this work we show also an original method of calibration of the time-of-flight set-up. For thermal fission of {sup 235}U, values of mass yields in the symmetric region are found to agree quantitatively with radiochemical values. Moreover, the average total kinetic energy distribution as a function of the pre-neutron emission masses of the fragments has been calculated. This curve presents in the symmetric region a large dip, the value of which takes on the value 21.2 {+-} 0.8 MeV. This value is smaller than previously published results. (author) [French] Les mesures correlees des energies cinetiques des fragments de fission sont fortement perturbees, dans la region symetrique, par la detection d'evenements aberrants d'origine instrumentale. Nous montrons que la mesure d'un parametre supplementaire, a savoir, la difference des temps de vol des deux fragments, nous permet d'eliminer ces difficultes. Dans ce travail, nous indiquons egalement une methode originale de calibration du dispositif de mesure des temps de vol. Dans le cas de la fission thermique de {sup 235}U, nous avons trouve, dans la region symetrique, une courbe de rendement des masses, en accord quantitatif avec les donnees radiochimiques. De plus, nous avons calcule la distribution de l'energie cinetique totale moyenne en fonction de la masse des fragments, avant emission neutronique. Cette courbe presente, dans la region symetrique, un creux important, dont la valeur atteint 21,2 {+-} 0,8 MeV. Cette valeur est inferieure aux resultats precedemment publies. (auteur)

Fission product determination in irradiated fuel processing waste (electrophoresis); Dosage des produits de fission dans les effluents de traitement des combustibles irradies (electrophorese)

Energy Technology Data Exchange (ETDEWEB)

Auchapt, J M; Tret, J [Commissariat a l' Energie Atomique, Centre de Marcoule, 30 - Bagnols-sur-Ceze (France). Centre de Production de Plutonium de Marcoule. Services d' Extraction du Plutonium

1966-07-01

This dosage method concerns fission products present in the waste produced from the processing of cooled irradiated fuels. - Sr, Cs, Ce, Y, Ru by quantitative analysis; - Zr, Nb by qualitative analysis. It includes electrophoresis on paper strips one meter long which is then analysed between two window-less Geiger counters. For an activity of 10{sup -2} {mu}Ci of any cation in a 10 {mu}l spot, the standard error {sigma} if 3 to 4 per cent. complete analysis lasts about 5 hours. (authors) [French] Cette methode de dosage concerne les produits de fission presents dans les effluents de traitement des combustibles irradies refroidis: - Sr, Cs, Ce, Y, Ru en analyse quantitative; - Zr, Nb en analyse qualitative. Elle comporte une electrophorese sur bande de papier de un metre de longueur suivie d'un depouillement entre deux compteurs Geiger sans fenetre. Pour une activite de 10{sup -2} {mu}Ci d'un cation quelconque dans une tache de 10 {mu}l l'erreur standard {sigma} est de 3 a 4 pour cent. L'analyse complete demande environ 5 heures. (auteurs)

Solidification of residual fission-product solutions; laboratory studies; Solidification de solutions residuaires concentrees de produits de fission: etudes de laboratoire

Energy Technology Data Exchange (ETDEWEB)

Boniaud, R; Cohen, P; Sombret, C [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1961-07-01

This paper describes the results obtained, at laboratory scale, during the study of the incorporation of fission products into glasses and synthetic micas. The rate of leaching of fission products from the glass and their volatility during firing were measured. A hot cell was built to complete these results. (author) [French] Ce rapport resume le resultat des etudes faites en laboratoire (activite de l'ordre du millicurie) sur l'incorporation des produits de fission dans des verres et micas synthetiques. On a mesure le taux de lixiviation des produits de fission et leur volatilisation au cours de la cuisson. Une cellule chaude a ete installee pour completer ces resultats au moyen d'essais realises avec une activite superieure. (auteur)

Reactor AQUILON. The hardening of neutron spectrum in natural uranium rods, with a computation of epithermal fissions (1961); Pile AQUILON. Durcissement du spectre des neutrons dans les barreaux d'uranium et calcul des fissions epithermiques (1961)

Energy Technology Data Exchange (ETDEWEB)

Durand -Smet, R; Lourme, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

- Microscopic flux measurements in reactor Aquilon have allowed to investigate the thermal and epithermal flux distribution in natural uranium rods, then to obtain the neutron spectrum variations in uranium, Wescott '{beta}' term of the average spectrum in the rod, and the ratio of epithermal to therma fissions. A new definition for the infinite multiplication factor is proposed in annex, which takes into account epithermal parameters. (authors) [French] - Un certain nombre de mesures effectuees dans la pile Aquilon ont permis d'etablir la distribution fine des flux thermique et epithermique dans les barreaux d'uranium, et d'en deduire les variations du spectre des neutrons dans l'uranium, le terme {beta} du spectre de Wescott moyen dans le barreau et le nombre de fissions epithermiques. En annexe, il est propose une definition nouvelle du coefficient de multiplication infini, qui fait intervenir les parametres epithermiques. (auteurs)

Experiments on the incorporation of concentrated solutions of fission products in glasses and micas; Essais d'incorporation de solutions concentrees de produits de fission dans des verres et des micas

Energy Technology Data Exchange (ETDEWEB)

Bonniaud, R; Cohen, P; Sombret, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

1) The plants designed for extracting the plutonium of the G1, G2, G3 reactors fuel rods will produce extremely concentrated tions of fission products. 2) Let us consider a synthetic solution of the 'G2' type: (2N NO{sub 3}H - 2,25 meq/cm{sup 3} AI{sup +++} - 5.10{sup -3} {sup 134}Cs - {sup 137}Cs tracer). We made various glasses and micas by adding and mixing the necessary adjuvants and baking (900 to 1400 deg. C) in a graphite crucible. 3) The products obtained had either the shape of a cylindrical pellet or were reduced into a fine powder. They were mixed with 300 cm{sup 3} of synthetic sea water during variable periods of time in order to study leaching of the activity. 4) Experiments were first carried on caesium because of its solubility. 5) Fabrication of micas on a large scale sets many technological problems more difficult to solve (1400 deg. C) than in the case of glasses (1000 deg. C). A comparative study on both micas and glasses showed that leaching of activity was more important in the micas. (author)Fren. [French] 1) La mise en service de l'Usine d'Extraction du Plutonium destinee en particulier au traitement des barres de combustibles de G1, G2, G3 fournira des solutions residuaires concentrees de produits de fission. 2) Partant d'une solution synthetique 'G2': (2N NO{sub 3}H - 2,25meq/cm{sup 3} AI{sup +++} - 5.10{sup -3} {sup 134}Cs - {sup 137}Cs traceur) nous avens realise differents verres et micas apres adduction et melange des adjuvants necessaires suivis de cuisson (900 a 1400 deg. C) dans un creuset de graphite. 3) Les produits obtenus ont ete, soit sous forme d'eprouvette cylindrique, soit sous forme de poudre finement broyee, mis en contact et agites avec 300 cm{sup 3} d'eau de mer synthetique, durant des temps varies pour etudier la retention de l'activite. 4) Le cesium a ete choisi pour ces essais a cause de sa solubilite. 5) La fabrication de micas a grande echelle pose des problemes technologiques plus difficiles (1400 deg. C) a

Measurement of the fission cross-section of {sup 235}U and {sup 239}Pu for thermal neutrons; Mesures des sections de fission de {sup 235}U et de {sup 239}Pu en neutrons thermiques

Energy Technology Data Exchange (ETDEWEB)

Fraysse, G; Prosdocimi, A; Netter, F; Samour, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

Improved techniques of fast detection have been applied for determining the fission cross-sections of {sup 235}U and {sup 239}Pu with reference to the absorption cross-section of Boron. Monochromatic neutron beams of 0.0322 eV, 0.0626 eV and 0.275 eV have been employed. Use has been made of a Xe-filled gaseous scintillator and of a low-geometry solid state ion chamber. Both measured alpha and fission rates. The results at the reference energy of 0.0253 eV are: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (authors) [French] Des techniques avancees de comptage rapide ont ete mise en oeuvre pour determiner la section efficace de fission de {sup 235}U et de {sup 239}Pu par rapport a celle d'absorption du bore. Des faisceaux de neutrons monochromatiques de 0,0322 eV, 0,0626 eV et 0,275 eV ont ete employes. Les detecteurs utilises sont un scintillateur gazeux rempli de xenon et une chambre d'ionisation a etat solide a basse geometrie. Les deux ont mesure les taux des desintegrations alpha et des fissions. Les resultats a l'energie de reference de 0,0253 eV sont: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (auteurs)

Study of the isomer nuclei produced in the spontaneous fission of {sup 252}Cf; Etude des noyaux isomeriques produits dans la fission spontanee de {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Thiesen, Ch. [Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires, Bordeaux-1 Univ., 33 Gradignan (France); Belier, G.; Girod, M.; Meot, M.V. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Astier, G.; Meot, V.; Peru, S. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Inst.de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

1997-06-01

Isomeric states have been studied in fission fragments produced by spontaneous fission of {sup 252}Cf. 34 isomeric nuclei have been identified by using coincidences between {gamma}-rays detected in EUROGAM II and fission fragments detected in photovoltaic cells. Lifetimes from 20 ns up to 2 {mu}s have been measured. Microscopic interpretation of the isomeric levels discovered has been tried by means of the Hartree-Fock-Bogolyubov procedure using Gogny force. It was found that the {sup 152,154,156}Nd nuclei have prolate deformation in their ground state; the rotational band built on this ground state is well reproduced by the calculation. For these nuclei the 2 quasi-particle excited states energies are above 1 MeV in agreement with the experiment. The computation confirms the similitude of the {sup 156}Nd and {sup 158}Sm isomeric states associated to neutron 2 quasi-particles of J{sup {pi}} K{sup {pi}} = 5{sup -} ({nu} 5/2 (642) x {nu} 5/2 (523)) while such similitude does not occur for the isotone nuclei {sup 154}Nd and {sup 156}Sm. The computation predicts a proton 2 quasi-particle excited states of J{sup {pi}} = 5{sup -}, near the isomeric level measured in {sup 156}Sm but not for that of {sup 154}Nd. Concerning the {sup 152}Nd the calculated level density is very near that of the states measured in the 1.6 to 2.3 MeV interval. However, the lack of precise information on spins and parities of the measured levels does make not possible a confrontation with the calculations. An up-graded equipment implying 32 photovoltaic cells instead of 2 cells is to be developed and installed by the EUROGAM 3 refs.

Release of Fission Products from UC-ZrC Fuel Inserts; Degagement des produits de fission liberes dans des noyaux combustibles UC-ZrC; Vydelenie produktov deleniya iz topliv UC - ZrC; Liberacion de productos de fision por pastillas de combustible de UC-ZrC

Energy Technology Data Exchange (ETDEWEB)

Barth, F.; Von der Decken, C. B.; Schifferstein, K. [Brown Boveri/Krupp Reaktorbau G.M.B.H., Duesseldorf (Germany); Clauss, A.; Reichel, H.; Rygaert, J.; Ruston, W. R. [Societe d' Etudes de Recherches et d' Applications pour l' Industrie (S.E.R.A.I.), Brussels (Belgium)

1963-11-15

energies obtained from different types of pellets, although the values of D/r{sub 0}{sup 2} sometimes differed by four orders of magnitude at the same sample temperatures. After irradiation, the activities of the isotopes I{sup 131}, Sr{sup 85}, Ba{sup 140} and Ce{sup 141} were determined in the graphite of the capsules. Except for I{sup 131}, the activities were higher than those expected for a release by recoil only. The values for Sr{sup 89}, Ba{sup 140} and Ce{sup 141} are too high to be a result of a diffusion of their corresponding rare gas precursors. It is assumed that the measured isotopes or their non-rare gas precursors were released by diffusion. (author) [French] Les auteurs ont etudie sous irradiation, dans une boucle, le degagement des produits de fission liberes par des pastilles dont la composition approximative etait UC + 20 ZrC. Il s'agissait de verifier la possibilite d'utiliser ces pastilles comme noyaux d'elements combustibles spheriques pour le reacteur a haute temperature actuellement construit a Juliers par la societe Brown-Boveri/Krupp Reaktorbau GmbH. Les essais ont ete faits sur des pastilles encapsulees dans du graphite et sur des pastilles non encapsulees. La surface de certaines pastilles etait constituee par une couche de carbure de zirconium pur d'une epaisseur de 1 a 2 mm. Les echantillons ent ete places dans des fours electriques a resistance pouvant atteindre une temperature de 1600{sup o}C. Pendant l'irradiation, les flux de neutrons etaient de 3 a 4 x 10{sup 10}n/cm{sup 2}s. La boucle permettait de mesurer, pendant l'irradiation, le degagement de {sup 85m}Kr, {sup 87}Kr, {sup 88}Kr, {sup 133}Xe et {sup 135}Xe et de determiner indirectement les quantites de {sup 133}I et {sup 135}I, apres l'arret du reacteur. Le degagement minimum de {sup 131}I, {sup 89}Sr, {sup 140}Ba et {sup 141}Ce a ete determine radiochimiquement apres retrait des echantillons. Il a ete egalement possible de mesurer la fraction de recul {epsilon}{sub R} seule, le

The present state of research on the vitrification of concentrated solutions of fission products (1962); Etat des etudes sur la vitrification des solutions concentrees de produits de fission (1962)

Energy Technology Data Exchange (ETDEWEB)

Bonniaud, R; Sombret, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

The present report gives the actual point of studies on vitrification of concentrated solutions of fission products. An active cell, giving glasses in crucibles, permitted to study various glass compositions. The leaching rate from the glass raises 1 to 2 10{sup -7} g of glass/cm{sup 2}/day. Activity loss by volatility during vitrification remains weak and often below 0.1 per cent of total activity. Off gas cleaning is made easier by presence of filter which is compound of granules including iron oxide. After saturation the content of this filter can be melt. Moreover different processes are in experimentation for a more important production. Daily 72 liters of solution containing tracer activity are treated in a continuous calcination and vitrification plant. The loss in {sup 106}Ru is still important and a modification of installation has been necessary. A pot vitrification plant is in study. In order to reduce cost of processing the possibility to pour glass after melting is actuality in study. A production set of very active glass is also in project. (authors) [French] Le present rapport fait le point des etudes menees sur la vitrification des solutions concentrees de produits de fission. Une installation active, produisant des verres en creusets, a permis d'etudier plusieurs compositions de verres. Le taux de perte d'activite par lixiviation a l'eau atteint 1 a 2 10{sup -7} gramme de verre/cm{sup 2}/jour. Les pertes d'activite par volatilite au cours de la cuisson restent faibles et souvent inferieures a 0,1 pour cent de l'activite totale. L'epuration des gaz de cuisson est facilitee par la presence d'un filtre a granules riches en oxyde de fer, dont le contenu peut etre fondu apres saturation. Differentes techniques sont, en outre, en experimentation pour une production plus importante: Une installation de calcination et vitrification continue traite 72 litres par jour de solution contenant une activite traceur. La perte en Ru{sup 106} est encore importante

Fission ionisation chamber for the measurement of low fluxes of slow neutrons; Chambre d'ionisation a fission pour la mesure des faibles flux de neutrons lents

Energy Technology Data Exchange (ETDEWEB)

Weill, J; Duchene, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The ionisation chamber described is designed for the measurement of slow neutron fluxes of average or low intensity, in the presence, eventually, of very high gamma fluxes. The capture of a slow neutron by a fissile material, in this case {sup 235}U, gives rise to fission fragments, high-energy particles which ionise the gas contained in the chamber. The neutrons are detected by virtue of the potential pulses, on the collecting electrode of the chamber, deriving from the collection of the ions produced by the fission fragments. The pulses are counted by means of a measuring system consisting of a preamplifier, a 2 Mc amplifier, a discriminator and an electronic scale with numerator or integrator. The general characteristics are as follows: sensitivity to neutrons: 0.07 kicks/n/cm{sup 2}.s, sensitivity to {gamma} rays: zero up to 3.10{sup 4} R/H, a background noise at the normal discrimination voltage: 0.01 kicks/s, working H.T.: -500 V, capacity: 40 {mu}{mu}F, average height of pulse: 8 mV, limits of use: from several neutrons to 10{sup 6} n/cm{sup 2}.s. This chamber may be used in all cases where low fluxes of slow neutrons must be measured, especially in the presence of high gamma fluxes, for example in the checking of Pu concentrations in an extraction plant or for the starting up of reactors. (author) [French] La chambre d'ionisation decrite est destinee a la mesure des flux de neutrons lents d'intensite moyenne ou faible, en presence eventuelle de flux gamma tres importants. La capture d'un neutron lent par un materiau fissile, en l'occurrence {sup 235}U, donne naissance a des fragments de fission, particules de grande energie qui ionisent le gaz contenu dans la chambre. Les neutrons sont detectes grace aux impulsions de potentiel, sur l'electrode collectrice de la chambre, provenant de la collection des ions produits par les fragments de fission. Une chaine de mesure comprenant un preamplificateur, un amplificateur 2 Mc, un discriminateur, une echelle

Experimental measurement of fission fragments paths in uranium gold, molybdenum, zirconium and silicon; Mesure experimentale des parcours des fragments de fission dans l'uranium, l'or, le molybdene, le zirconium et le silicium

Energy Technology Data Exchange (ETDEWEB)

Faraggi, H; Garin-Bonnet, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The measurement of total number of fissiongments emerging from an homogeneous, thick alloy composed of uranium plus another element (the concentration of uranium being known) allows to obtain the range of the fragments in this alloy. By varying the concentration, the range of the fragments in uranium and in the other element can be deduced. (author)Fren. [French] La mesure du nombre total de fragments de fission sortant d'un alliage homogene epais d'uranium et d'un autre element, pour lequel la concentration en uranium est donnee, permet la mesure du parcours des fragments dans cet alliage. En faisant varier la concentration, on peut deduire de ces mesures le parcours des fragments dans l'uranium et dans l'autre element. (auteur)

Recent progress in fission product separation; Progres recents de la separation des produits de fission

Energy Technology Data Exchange (ETDEWEB)

Raggenbass, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

saturated with magnesium in order to avoid as far as possible the extraction of strontium, extraction of strontium at pH 4. (author) [French] La methode decrite a Geneve en 1958 a ete experimentee avec succes. Des ameliorations importantes ont ete apportees a ce procede: 1 - Initialement, la precipitation phosphotungstique du cesium etait suivie d'une reprise a la baryte en centrifugeuse et d'une distillation de l'ammoniac dans un concentrateur. Ensuite, l'hydroxyde de baryum etait elimine par precipitation carbonique et centrifugation. 1 - Il a ete prouve que la distillation de l'ammoniac pouvait etre remplacee par une evaporation au cours de la centrifugation, ce qui supprime le concentrateur. Il a ensuite ete possible d'effectuer la carbonatation sur le melange solide-liquide provenant de l'attaque a la baryte. 2 - Pour appliquer le precedent procede au traitement des solutions provenant des combustibles uranium-molybdene, nous avons recommande une concentration qui maintient en solution le molybdene par complexation par l'acide phosphorique. Cette complexation fournit une suspension de phosphate de zirconium et de phosphotungstate d'ammonium. Ils sont separes en repassant en milieu basique qui fait precipiter la zircone, puis en revenant en milieu acide, la suite du traitement restant le meme. 3 - Les etudes sur les proprietes d'echange des sels d'hetero-polyacides poursuivies dans plusieurs pays ont toujours rencontre l'ecueil des mauvaises qualites mecaniques de ces produits. Cette difficulte a ete surmontee en emprisonnant le phosphotungstate d'ammonium dans une matrice en phosphate de zirconium. L'echangeur obtenu possede: - des proprietes mecaniques satisfaisantes - une capacite de 0,1 milliequivalent par gramme en milieu acide nitrique concentre. II est eluable et regenerable par une solution d'un sel d'ammonium. Le schema de recuperation de ces differents produits de fission est succinctement le suivant: - extraction des terres rares par l'acide di-2-ethyl hexyl

Chrono-thermométrie par traces de fission : une perspective nouvelle pour la prospection pétrolière Chronothermometry by Fission-Track Dating: New Means for Petroleum Prospection

Directory of Open Access Journals (Sweden)

Storzer D.

2006-11-01

Full Text Available La propriété caractéristique des traces de fission d'enregistrer les paléotempératures offre la possibilité unique de caler des événements thermiques dans leur contexte géologique et donc de modéliser quantitativement les histoires thermiques des roches. Le thermomètre traces de fission-apatite enregistre les paléo-températures dans un intervalle compris entre 30 et 170°C, domaine qui inclut les températures généralement retenues pour la genèse optimale des hydrocarbures liquides. La formation, la maturation et la destruction des hydrocarbures, de la même façon que la guérison des traces latentes, sont fonction des deux paramètres temps et températures; en conséquence, l'étude détaillée de l'effacement progressif des traces latentes fossiles dans les apatites en fonction de leur profondeur dans un puits, conduit à des indications précises sur les variations de la température en fonction du temps à l'intérieur de la fenêtre à huile. Ces deux informations sont obtenues en combinant la datation traces de fission-isochrone et les analyses de longueurs des traces de fission. Le potentiel de la méthode des traces de fission dans son application à la reconstitution de l'histoire thermique des bassins sédimentaires est illustré à partir de l'analyse d'apatites détritiques provenant des bassins intérieur et côtier du Gabon d'une part et du bassin d'Otway en Australie du Sud d'autre part. The characteristic property of fission tracks to record paleotemperatures provides a unique possibility of setting thermal events in their geological context and hence of quantitatively modeling the thermal histories of rocks. The fission track apatite-thermometer records paleotemperatures in the interval between 30 and 170°C, a range that includes the temperatures generally considered to be required for the optimum formation of liquid hydrocarbons. The formation, maturation and destruction of hydrocarbons, as well as the

Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Samour, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Samour, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

Study of fission product {gamma} spectra in the band 2-500 keV; Etude du spectre {gamma} des produits de fission dans la bande 0-500 keV

Energy Technology Data Exchange (ETDEWEB)

Rousseau, A. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the study of the {gamma} spectrum of uranium fission products, particular attention has been given in this note to the part of the spectrum ranging between 0 and 500 keV after a given pile operating programme and the evolution of this spectrum with time after a pile shutdown has been followed. The study be related to the fission products which appear in the pile as a whole or on those produced in a uranium sample assumed to have been placed in the pile. The latter case has been envisaged here. The spectrum determination is based partly on theory and partly on experiment. The pile operating conditions are different in the two cases, which widens the range of validity of the spectra traced here. (author) [French] Dans l'etude du spectre {gamma} des produits de fission de l'uranium, on s'est plus particulierement interesse dans la presente note a determiner la partie du spectre qui s'etend entre 0 et 500 keV, au bout d'un fonctionnement donne de pile, et a suivre l'evolution de ce spectre dans le temps apres un arret de pile. L'etude peut porter sur les produits de fission apparus dans toute la pile ou sur ceux apparus dans un echantillon d'uranium suppose place en pile. C'est ce dernier cas que nous avons envisage. La determination du spectre s'appuie sur une partie theorique et sur une partie experimentale. Les fonctionnements de pile choisis sont differents dans les deux cas, ce qui permet d'etendre la gamme de validite des spectres traces ici. (auteur)

Study of fission product {gamma} spectra in the band 2-500 keV; Etude du spectre {gamma} des produits de fission dans la bande 0-500 keV

Energy Technology Data Exchange (ETDEWEB)

Rousseau, A [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the study of the {gamma} spectrum of uranium fission products, particular attention has been given in this note to the part of the spectrum ranging between 0 and 500 keV after a given pile operating programme and the evolution of this spectrum with time after a pile shutdown has been followed. The study be related to the fission products which appear in the pile as a whole or on those produced in a uranium sample assumed to have been placed in the pile. The latter case has been envisaged here. The spectrum determination is based partly on theory and partly on experiment. The pile operating conditions are different in the two cases, which widens the range of validity of the spectra traced here. (author) [French] Dans l'etude du spectre {gamma} des produits de fission de l'uranium, on s'est plus particulierement interesse dans la presente note a determiner la partie du spectre qui s'etend entre 0 et 500 keV, au bout d'un fonctionnement donne de pile, et a suivre l'evolution de ce spectre dans le temps apres un arret de pile. L'etude peut porter sur les produits de fission apparus dans toute la pile ou sur ceux apparus dans un echantillon d'uranium suppose place en pile. C'est ce dernier cas que nous avons envisage. La determination du spectre s'appuie sur une partie theorique et sur une partie experimentale. Les fonctionnements de pile choisis sont differents dans les deux cas, ce qui permet d'etendre la gamme de validite des spectres traces ici. (auteur)

Burn up physics; Physique des combustibles irradies

Energy Technology Data Exchange (ETDEWEB)

Tretiakoff, O [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

requires samples of the order of several kilograms only. The relationships between these measurements and the investigations of lattices are discussed, and an outline is given of the way of carrying out the systematic study of fuels of various compositions. The method has been successfully applied to the systematic study of irradiated fuels (analysed independently by the methods mentioned above) thus giving the possibility of measuring in situ the absorption of fission products. (author) [French] Cette communication expose un ensemble d'etudes theoriques et d'experiences, effectuees au CEA et destinees a faire progresser la connaissance de l'evolution de la reactivite (au cours de l'irradiation du combustible) dans les reacteurs a uranium naturel ou faiblement enrichi.,. On rappelle les difficultes de l'experimentation directe sur des masses importantes de combustible irradie - en particulier dans les reacteurs de puissance en fonctionnement - et on souligne la necessite d'experiences a caractere fondamental distinguant: d'une part l'evolution de la composition des combustibles (chaines de noyaux lourds, produits de fission), d'autre part l'effet des modifications de composition sur le bilan de neutrons. Avant de presenter trois categories d'experiences que l'on est conduit a entreprendre, on rappelle l'importance des problemes lies aux spectres de neutrons et on decrit rapidement les methodes pratiques de calcul utilisees. L'irradiation systematique de quelques types de combustibles, suivie de leur analyse chimique et isotopique est en cours depuis plusieurs annees. On donne un apercu de l'ensemble du programme experimental et on decrit les moyens et les methodes mis en oeuvre: chaine {alpha}, {beta}, {gamma} pour la preparation des echantillons, dosage du Plutonium par coulommetrie et double dilution isotopique, separation du Bore utilise dans certains cas pour la mesure des densites de neutrons integrees. On discute sur quelques exemples l'interpretation des mesures

Study of a device for the direct measurement of the fission gas pressure inside an in-pile fuel element; Etude d'un dispositif pour la mesure directe de la pression des gaz de fission a l'interieur d'un element combustible en pile

Energy Technology Data Exchange (ETDEWEB)

Lavaud, B; Uschanoff, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

The fission gas pressure inside a fuel element made of a refractory fuel constitutes an important limiting factor for the burn-up. Although it is possible to calculate approximately the volume of gas produced outside the fuel during its life-time; it is nevertheless very difficult to evaluate the pressure since the volume allowed to the fission gases, as well as their temperature are known only very approximately. This physical value, which is essential for the technologist, can only be known by direct in-pile measurement of the pressure. The report describes the equipment which has been developed for this test. (authors) [French] La pression des gaz de fission a l'interieur d'un element combustible a combustible refractaire constitue une des limitations importantes du taux de combustion. Si on peut approcher par calcul la determination du volume, des gaz degages hors du combustible au cours de sa vie, il est par contre tres difficile d'evaluer la pression car le volume alloue aux gaz de fission et leur temperature sont tres mal connus. Cette donnee essentielle pour le technologue ne peut etre atteinte que par une mesure directe en pile de la pression. Le rapport decrit l'appareillage qui a ete mis au point pour cet essai. (auteurs)

Structures and properties of (U,Pu)O{sub 2} containing non-active fission products. A simulation of irradiated nuclear fuel; Structure et proprietes de (U, Pu)O{sub 2} contenant des produits de fission sous forme inactive. Une simulation de combustible nucleaire irradie

Energy Technology Data Exchange (ETDEWEB)

Schmitz, F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-07-01

We have made oxides with the same uranium and plutonium content, the same stoichiometry and the same fission product content as an oxide fuel (U{sub 0,8}PuO{sub 2})O{sub 1,96} after 2 per cent burn up. We have calculated the stoichiometry changes due to irradiation and checked the calculation by X rays parameters measurements. We have calculated and measured the contraction of the oxide lattice due to fission products in solid solution. Microprobe analysis of precipitates have been made and have lead to the identification of non metallic barium containing compounds and have shown the particular behaviour of molybdenum. Some physical properties have been measured especially the electrical resistivity, the thermal diffusivity and the vapour pressure of zirconium in solid solution. (author) [French] Nous avons fabrique des oxydes dont la composition en uranium et plutonium, la stoechiometrie et la teneur en produit de fission, sont identiques a celles d'un oxyde (U{sub 0,8}PuO{sub 2})O{sub 1,96} ayant subi 2 pour cent de combustion. Nous avons calcule les changements de stoechiometrie entraines par l'irradiation et controle ces calculs par des mesures de parametre. Nous avons calcule et mesure la contraction du reseau due aux produits de fissions solubles dans la matrice. Des analyses a la microsonde des precipites de produits de fission insolubles ont ete faites et ont conduit a l'identification de composes non metalliques contenant du baryum et a la mise en evidence du role particulier du molybdene. Certaines proprietes physiques ont ete mesurees sur ces composes, en particulier la resistivite electrique, la diffusivite thermique et la tension de vapeur du zirconium dissout dans la matrice. (auteur)

Chemical Production using Fission Fragments; Emploi des fragments de fission dans la production de substances chimiques; Ispol'zovanie produkto v raspada v khimicheskom proizvodstve; Empleo de los fragmentos de fision en la industria quimica

Energy Technology Data Exchange (ETDEWEB)

Dawson, J K; Moseley, F [AERE, Harwell (United Kingdom)

1960-07-15

Some reactor design considerations of the use of fission recoil fragment energy for the production of chemicals of industrial importance have been discussed previously in a paper given at the Second United Nations International Conference on the Peaceful Uses of Atomic Energy [A/Conf. 15/P.76]. The present paper summarizes more recent progress made on this topic at AERE, Harwell. The range-energy relationship for fission fragments is discussed in the context of the choice of fuel system for a chemical production reactor, and the experimental observation of a variation of chemical effect along the length of a fission fragment track is described for the irradiation of nitrogen-oxygen mixtures. Recent results are given on the effect of fission fragments on carbon monoxide-hydrogen gas mixtures and on water vapour. No system investigated to date shows any outstanding promise for large-scale chemical production. (author) [French] En ce qui concerne la construction de reacteurs, certaines considerations relatives a l'emploi de l'energie des fragments de fission de recul pour la production de certaines substances chimiques d'importance industrielle ont deja ete examinees dans un memoire soumis a la deuxieme Conference internationale sur l'utilisation de l'energie atomique a des fins pacifiques [A/Conf. 15/PP. 76]. Le present memoire donne un apercu des progres accomplis depuis lors dans ce domaine par 1'Atomic Energy Research Establishment a Harwell. Les auteurs etudient la relation entre le parcours et l'energie pour des fragments de fission a propos du choix du combustible pour un reacteur destine a la production de substances chimiques; ils decrivent aussi une variation d'effet chimique observee le long de la trajectoire d'un fragment de fission pendant l'irradiation de melanges azote-oxygene. Les auteurs fournissent les resultats de recherches recentes relatives a l'effet des fragments de fission sur des melanges oxyde de carbone-hydrogen e et sur la vapeur d

Measurements of fission cross-sections and of neutron production rates; Mesures de sections efficaces de fission et du nombre de neutrons prompts emis par fission

Energy Technology Data Exchange (ETDEWEB)

Billaud, P; Clair, C; Gaudin, M; Genin, R; Joly, R; Leroy, J L; Michaudon, A; Ouvry, J; Signarbieux, C; Vendryes, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

a) Measurements of neutron induced fission cross-sections in the low energy region. The variation of the fission cross sections of several fissile isotopes has been measured and analysed, for neutron energies below 0,025 eV. The monochromator was a crystal spectrometer used in conjunction with a mechanical velocity selector removing higher order Bragg reflections. The fissile material was laid down on the plates of a fission chamber by painting technic. An ionization chamber, having its plates coated with thin {sup 10}B layers, was used as the neutron flux monitor. b) Measurement of the fission cross section of {sup 235}U. We intend to measure the variation of the neutron induced fission cross section of {sup 235}U over the neutron energy range from 1 keV by the time of flight method. The neutron source is the uranium target of a pulsed 28 MeV electron linear accelerator. The detector is a large fission chamber, with parallel plates, containing about 10 g of {sup 235}U (20 deposits of 25 cm diameter). The relative fission data were corrected for the neutron spectrum measured with a set of BF{sub 3} proportional counters. c) Mean number {nu} of neutrons emitted in neutron induced fission. We measured the value of {nu} for several fissile isotopes in the case of fission induced by 14 MeV neutrons. The 14 MeV neutrons were produced by D (t, n) {alpha} reaction by means of a 300 kV Cockcroft Walton generator. (author)Fren. [French] a) Mesures de sectionficaces de fission a basse energie. Nous avons mesure et analyse la variation de la section efficace de fission de divers isotopes fissiles pour des neutrons d'energie inferieure a 0,025 eV. Le monochromateur est constitue par un spectrometre a cristal auquel est associe un selecteur mecanique destine a eliminer les diffractions de Bragg d'ordre superieur au premier. Le materiau fissile est contenu dans une chambre a fission sous forme de depots realises par peinture; une chambre d'ionisation a depots minces de B{sub 10

Fission Data and Nuclear Technology; Constantes de Fission et Technologie NucleAire; 0414 0410 041d 041d 042b 0415 . 041e 0414 0415 041b 0415 041d 0418 0418 0418 042f 0414 0415 0420 041d 0410 042f 0422 0415 0425 041d 041e 041b 041e 0413 0418 042f ; Datos Sobre la Fision y Tecnologia Nuclear

Energy Technology Data Exchange (ETDEWEB)

Hanna, G. C. [Chalk River Nuclear Laboratories, Chalk River, ON (Canada)

1965-07-15

Accurate nuclear data for fissile nuclei are required not only by reactor designers, but also by reactor physicists for the interpretation of integral experiments, e.g. studies of the change of reactivity with irradiation. Some of the requests that have been made for such fission data, and the reasons behind them, are discussed, along with the progress that has been made towards their fulfilment. An attempt is made to outline those areas where better data are required. (author) [French] On a besoin de valeurs exactes des constantes nucleaires concernant les noyaux fissiles, non seulement pour les etudes de reacteurs, mais egalement pour la physique des reacteurs lorsqu'on veut interpreter les experiences integrales, c'est-a-dire dans les etudes sur les modifications de la reactivite avec l'irradiation. L'auteur discute certaines des demandes de renseignements sur les constantes de fission, les raisons pour lesquelles elles ont ete faites et la mesure dans laquelle elles ont pu etre satisfaites. Il s'efforce egalement de delimiter les domaines dans lesquels on aurait besoin de valeurs plus precises. (author) [Spanish] No solo quienes trabajan.en el proyecto de reactores requieren datos nucleares exactos sobre los nucleos fisionables, sino que tambien los fisicos de reactores los necesitan para interpretar los resultados de experimentos integrales, como por ejemplo, en los estudios sobre la variacion de la reactividad en funcion de la irradiacion. El autor describe algunas de las peticiories de datos de esa clase que se han formulado, asi como los adelantos realizados con objeto de satisfacerlas. Tambien indica, en lineas generales, aiquellas esferas en las que se necesitan datos mas amplios y exactos. (author) [Russian] Tochnye jadernye dannye o rasshhepljajushhihsja jadrah neobhodimy ne tol'ko konstruktoram reaktorov, no takzhe i fizikam-reak- torshhikam dlja interpretacii integral'nyh jeksperimentov, to est' dlja izuchenija izmenenija reaktivnosti po mere

Contribution to the study of the action of electromagnetic fields on the angular correlations of nuclear radiation (1960); Contribution a l'etude de l'action des champs electromagnetiques sur les correlations angulaires des rayonnements nucleaires (1960)

Energy Technology Data Exchange (ETDEWEB)

Lehmann, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-01-15

This work deals with the study of interaction of E.M. fields with nuclear moments of nuclei emitting gamma rays. We describe first experiments on delayed angular correlation showing the role played by statistic quadrupole interaction. We have measured the magnetic moment of the second excited state of {sup 19}F using an external magnetic field. In the case of {sup 19}O, experiments of angular distributions and angular correlations of gamma -rays taking into account the possibility of perturbations, allow us to determine the spin and parities of the three first levels. (author) [French] Le present travail concerne l'etude de l'interaction des champs electromagnetiques et des moments nucleaires de noyaux emettant des rayonnements gamma. Nous decrivons des experiences de correlation angulaire differee dont l'interpretation met en coincidence le role joue par les interactions quadrupolaires statiques. Nous avons mesure le moment magnetique de {sup 19}F dans un etat excite en utilisant un champ magnetique exterieur a la source radioactive. Enfin, dans le cas de {sup 19}O, nous montrons l'utilite d'un examen des possibilites de perturbations dans l'interpretation des resultats fournis par des correlations ou des distributions angulaires. (auteur)

Radio-chemical applications of columns of precipitated insoluble sulphates - contribution to the study of fission product solutions (1962); Applications en radiochimie de colonnes de precipites de sulfates insolubles - contribution a l'etude des solutions vieillies de produits de fission (1962)

Energy Technology Data Exchange (ETDEWEB)

Sauvagnac, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Barrachina, M [Junta de la Energia Nuclear, Madrid (Spain)

1962-07-01

After describing the preparation of SrSO{sub 4} and BaS0{sub 4} columns, the authors study the following variables affecting fixation of Sr{sup 90}: - influence of pH, of the SO{sub 4}{sup --} concentration in the solution studied, of the column density, of the flow rate, of the use of the EDTA complex. A mechanism is proposed for the exchange and fixation. Once the column characteristics had been chosen, the fixation of rare-earths in the absence or presence of EDTA was studied. - it was observed that for nitrate or chloride concentrations of over 2 mg/ml, or in the presence of stronger than 1 N HNO{sub 3} or HCl, barium was fixed selectively. - these results were applied to radiochemical separations in fission product solutions: Ba{sup 140} and Sr{sup 90} separation, and that of the ceric earth group and the yttric earth group. - In order to establish a complete scheme for the radio-chemical separation in fission product solution, after at least one year ageing, the techniques of column separation and of solvent extraction using thenoyltrifluoroacetone and bis di-ethylhexylphosphoric acid are combined. (authors) [French] Apres avoir decrit la preparation des colonnes de SrS0{sub 4} et BaS0{sub 4}, on etudie les variables suivantes pour la fixation de {sup 90}Sr: - influence du pH, de la concentration en SO{sub 4}{sup --} dans la solution etudiee, de la densite de la colonne, de la vitesse de passage, de l'emploi du complexant EDTA. On propose une explication du mode d'echange et de fixation. Les caracteristiques de la colonne etant choisies, on a etudie la fixation des terres rares en presence ou non de EDTA. - on a d'autre part constate qu'en milieu chlorure ou nitrate, de concentration superieure a 2 mg/ml, ou en presence de HNO{sub 3} ou HCl superieur a 1 N, on fixait selectivement le baryum. - on a applique ces resultats a des separations radiochimiques dans des solutions de produits de fission: separation de {sup 140}Ba, {sup 90}Sr, separation du groupe des

The influence of the (n, 2n) and (n, {alpha}) reactions of beryllium on the neutron balance in a BeO or Be moderated reactor and its consequences on the long term reactivity changes; Influence des reactions (n, 2n) et (n, {alpha}) du beryllium sur le bilan neutronique d'un reacteur modere a l'oxyde de beryllium ou au beryllium. Consequences sur l'evolution a long terme de la reactivite

Energy Technology Data Exchange (ETDEWEB)

Sahai, K; Benoist, P; Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The reaction probabilities in an infinite and homogeneous medium of BeO or Be have been calculated from neutron cross-section curves, for a neutron produced with an energy distribution similar to a fission spectrum; the calculation shows that, after several elastic collisions, the neutron has yet an appreciable probability to undergo a reaction, in spite of the energy degradation in the spectrum due to each collision. This degradation has been calculated, taking into account of anisotropy of the collisions. The gain of the reactivity in a reactor has been obtained after correcting these probabilities for the attenuation of the flux of fission neutrons due to the inelastic scattering in the uranium. Finally, the calculation shows that in a power reactor, this gain of reactivity is in practice destroyed in a few years by the accumulation of poisonous nuclei such as Li{sup 6} and He{sup 3} following (n, {alpha}) reaction. (author) [French] Les probabilites de reaction en milieu infini et homogene de glucine (BeO) ou de beryllium ont ete calculees a partir des courbes de section efficace pour un neutron naissant suivant un spectre de fission; le calcul montre qu'apres plusieurs diffusions elastiques le neutron a encore une probabilite appreciable de subir une reaction, malgre la degradation du spectre a chaque diffusion; cette degradation a ete calculee en tenant compte de l'anisotropie du choc. Le gain de reactivite dans un reacteur a ensuite ete obtenu en corrigeant les probabilites en milieu homogene de l'effet l'attenuation du flux des neutrons de fission par les chocs inelastiques dans les barres d'uranium. Enfin, le calcul montre que, dans un reacteur de puissance, ce gain de reactivite est pratiquement detruit en peu d'annees par l'accumulation de noyaux poisons Li{sup 6} et He{sup 3} consecutive a la reaction (n, {alpha}). (auteur)

Modélisation macroscopique des milieux stratifiés conducteurs

Science.gov (United States)

Matagne, E.; Conard, J. Ph.

1997-11-01

Many laminated structures are recognised in Electrotechnics : magnetic cores, flat conductors windings, slotted surfaces... These structures exhibit macroscopic properties, as magnetic than electric ones. This paper shows how these characteristics can be obtained by homogenisation. It deals with linear materials but taking into account the effect of eddy currents, as well on the macroscopic magnetic permeability as on the macroscopic electric conductivity, which become then complex numbers. An example of use of the macroscopic properties is provided. On peut identifier en électrotechnique de nombreuses structures stratifiées: noyaux magnétiques, bobinages formés de conducteurs plats, surfaces encochées... Ces structures présentent des propriétés macroscopiques tant magnétiques qu'électriques. Cet article montre comment ces caractéristiques peuvent être obtenues par homogénéisation. Il se limite au cas de matériaux linéaires mais en prenant en compte l'effet des courants de Foucault aussi bien sur la perméabilité magnétique macroscopique que sur la conductivité électrique macroscopique, grandeurs qui deviennent alors des nombres complexes. Un exemple d'utilisation des caractéristiques macroscopiques est fourni.

Contribution to the study of the action of electromagnetic fields on the angular correlations of nuclear radiation (1960); Contribution a l'etude de l'action des champs electromagnetiques sur les correlations angulaires des rayonnements nucleaires (1960)

Energy Technology Data Exchange (ETDEWEB)

Lehmann, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-01-15

This work deals with the study of interaction of E.M. fields with nuclear moments of nuclei emitting gamma rays. We describe first experiments on delayed angular correlation showing the role played by statistic quadrupole interaction. We have measured the magnetic moment of the second excited state of {sup 19}F using an external magnetic field. In the case of {sup 19}O, experiments of angular distributions and angular correlations of gamma -rays taking into account the possibility of perturbations, allow us to determine the spin and parities of the three first levels. (author) [French] Le present travail concerne l'etude de l'interaction des champs electromagnetiques et des moments nucleaires de noyaux emettant des rayonnements gamma. Nous decrivons des experiences de correlation angulaire differee dont l'interpretation met en coincidence le role joue par les interactions quadrupolaires statiques. Nous avons mesure le moment magnetique de {sup 19}F dans un etat excite en utilisant un champ magnetique exterieur a la source radioactive. Enfin, dans le cas de {sup 19}O, nous montrons l'utilite d'un examen des possibilites de perturbations dans l'interpretation des resultats fournis par des correlations ou des distributions angulaires. (auteur)

Contribution to the study of the desorption of fission gases formed in irradiated uranium oxide; Contribution a l'etude de la desorption des gaz de fission formes dans l'oxyde d'uranium irradie

Energy Technology Data Exchange (ETDEWEB)

Berry, J -L; Darras, R; Roger, B [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

1966-09-01

The release of {sup 133}Xe from irradiated UO{sub 2} has been studied in the temperature range 1300 to 1900 deg C, using various monocrystalline or sintered samples. Up to 1600 deg C, this release is proportional to the square root of the time and thus occurs essentially by diffusion. The apparent diffusion constant D' decreases and the activation energy of the corresponding process increases as the integrated neutron flux received by the fuel increases. As the density of the sintered samples decreases however, the activation energy of the release also decreases, so that the difference between D' values for sintered samples of different densities decreases as the temperature rises. Finally, above 1600 deg C, the fission gas release phenomenon is governed by UO{sub 2} evaporation, and all the different types of oxide studied have similar behaviors, characterized by poor retention of these gases. (authors) [French] La desorption du xenon 133 forme dans le bioxyde d'uranium irradie a ete etudiee dans l'intervalle de 1300 a 1900 C, a l'aide de differents echantillons monocristallins ou frittes. Jusqu'a 1600 C, elle s'effectue proportionnellement a la racine carree du temps, donc essentiellement par diffusion. La pseudo-constante de desorption D' decroit et l'energie d'activation du processus correspondant croit lorsque le flux de neutrons integre recu par le combustible augmente. Cependant, lorsque la densite des frittes diminue, l'energie d'activation de desorption diminue egalement, de sorte que l'ecart entre les valeurs de D' relatives a des frittes de densites differentes se restreint lorsque, la temperature s'eleve. Finalement, au-dessus de 1600 C, l'evaporation de l'UO{sub 2} regit le phenomene de liberation des gaz de fission, et toutes les qualites d'oxyde etudiees presentent alors des comportements voisins a cet egard, caracterises par une mediocre retention de ces gaz. (auteurs)

Mass and Charge Distribution in Low-Energy Fission; Repartition des Masses et des Charges dans la Fission a Basse energie; 0420 0410 0421 041f 0420 0415 0414 0415 041b 0415 041d 0418 0415 041c 0410 0421 0421 042b 0418 0417 0410 0420 042f 0414 0410 041f 0420 0418 0414 0415 041b 0415 041d 0418 0418 , 0412 042b 0417 0412 0410 041d 041d 041e 041c 0427 0410 0421 0422 0418 0426 0410 041c 0418 041c 0410 041b 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Distribucion de Masas y de Cargas en la Fision a Bajas Energias

Energy Technology Data Exchange (ETDEWEB)

Wahl, A. C. [Washington University, St. Louis, MO (United States)

1965-07-15

repartition des masses et des charges dans la fission de {sup 235}U par neutrons thermiques et la compare ensuite a la repartition correspondante dans les autres processus de fission a basse energie. Les questions a examiner en ce qui concerne la repartition des masses dans la fission comprennent les positions des sommets et de la vallee et la structure fine de la distribution des produits de fission Selon la masse pour des couches fermees, ainsi que les changements de position qui se produisent lorsque le noyau subissant la fission et l'energie d'excitation ne sont pas les memes. L'auteur examine egalement la repartition des masses dans le cas de la fission ternaire. Au sujet de la fission binaire et de la fission ternaire, il fait des observations touchant la repartition des masses entre les fragments primaires (avant 'evaporation' des neutrons) et les produits de fission (apres 'evaporation' des neutrons). L'auteur etudie la repartition des charges d'apres la dispersion des charges entre les produits de fission ayant le meme nombre de masse, et la variation de Zp Selon la masse, la 'charge la plus probable' (non entiere) pour une.masse donnee. Bien que des renseignements directs sur la repartition des charges soient limites aux produits de fission, l'auteur presente des estimations de la repartition des charges pour les fragments de fission primaires. D'apres des donnees et des estimations relatives a la repartition des masses et des charges pour un procede de fission, on peut determiner les rendements primaires en tous produits ou fragments de fission. Bien que l'estimation de nombreux rendements primaires soit tout a fait approximative en raison surtout de l'absence de donnees sur la repartition des charges, notamment pour les produits de fission dont le rendement est faible, l'auteur presente des estimations des rendements primaires pour illustrer la necessite d'une nouvelle experimentation et ses possibilites pratiques de realisation. Les processus de fission - autres

Fission gas pressure build-up and fast-breeder economy; Accumulation de la pression des gaz de fission et economie des reacteurs surgenerateurs a neutrons rapides; Nakoplenie davleniya gazov produktov deleniya i ehkonomika reaktorov-razmnozhitelej na bystrykh nejtronakh; Aumento de la presion de los gases de fision y economia de los reactores reproductores rapidos

Energy Technology Data Exchange (ETDEWEB)

Engelmann, P [Kernforschungszentrum, Karlsruhe (Germany)

1962-03-15

Fuel-cycle costs and doubling time of fast-breeder reactors are strongly affected by the fuel-burn-up obtainable. Use of oxide or carbide fuel offers the possibility of reaching a burn-up of 100 000 MWd/t. In fuel-clad elements, a limiting factor is the fission-gas-pressure build-up. At the high burn-up considered, an appreciable fraction of the fission gases gets into the pores and thus contributes to the pressure on the can. Starting from the known fission-product yields and decay chains, gas production and pressure build-up have been calculated. Three physical models have been employed in calculating the pressure acting upon the can : the gas is contained either in interconnected pores, in separate pores, or in a central hole. The pressure-dependence upon free volume (fuel density) and temperature will be discussed. Cans made of high-strength materials as Ineonel-X and molybdenum could stand the fission-gas pressure at operating temperatures. Unfortunately, these materials have higher absorption cross-sections than stainless steel. Results of a multi-group calculation are given, showing the effect of using these can materials and of decreasing the fuel density on critical mass and breeding ratio in small and medium-size breeders. (author) [French] Le cout du cycle de combustible et la periode de doublement des reacteurs surgenerateurs a neutrons rapides dependent etroitement du taux de combustion. En utilisant pour combustible un oxyde ou un carbure, on peut atteindre un taux de combustion de 100 000 MW j/t. Avec des combustibles gaines, l'accumulation de la pression des gaz de fission est un facteur limitatif. Pour le fort taux de combustion envisage, une fraction non negligeable des gaz de fission penetre dans les interstices et contribue ainsi a la pression sur la gaine. A partir des rendements en produits de fission et des chaines de desintegration connus, l'auteur a calcule la production de gaz et l'accumulation de pression. Pour calculer la pression

Baby fission chambers; Etude de chambres a fission miniatures

Energy Technology Data Exchange (ETDEWEB)

Guery, U; Tachon, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)

Amount and activity of fission products which will be obtainable in France in the immediate future taking into account the development of atomic energy; Quantite et activite des produits de fission abtenus en France dans les annees a venir compte tenu du developpement de l'energie atomique

Energy Technology Data Exchange (ETDEWEB)

Guirlet, J; Lavie, J M [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

By using the Wigner and Way formula, the activity of the complex mixture of fission products produced in a pile may be estimated theoretically in advance. This study was carried out on the basis of forecasts, in the case of France for the production of electricity of atomic origin up to the year 1975. The uranium was assumed to be in the pile during periods of three months and six months. It is also possible to find the activity of a particular fission product and to give its decay rate. The element chosen is strontium for a three months' activation period. Each set of curves gives at any moment the total activity accumulated, and the characteristic activity of the fission products corresponding to a given half-life. (author) [French] En utilisant la formule de Wigner et Way, il est possible de prevoir theoriquement l'activite du melange complexe de produits de fission provenant d'une pile. L'etude a ete faite en tenant compte de previsions, en ce qui concerne la France, de la production d'electricite d'origine atomique jusqu'en 1975. On a suppose des temps de sejour en pile de l'uranium de trois mois et de six mois. Il est possible egalement de trouver l'activite d'un produit de fission particulier, et de donner sa decroissance. Le corps choisi est le strontium pour un temps d'activation de trois mois. Chaque ensemble de courbes donne a tout instant l'activite totale accumulee, et l'activite propre des produits de fission correspondant a une periode donnee. (auteur)

Recovery of trans-plutonium elements; Recuperation des elements transplutoniens

Energy Technology Data Exchange (ETDEWEB)

Espie, J Y; Poncet, B; Simon, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1970-07-01

The object of this work is to study the recovery of americium and curium from the fission-product solution obtained from the processing of irradiated fuel elements made of natural metallic uranium alloyed with aluminium, iron and silicon; these elements have been subjected to an average irradiation of 4000 MW days/ton in a gas-graphite type reactor having a thermal power of 3.7 MW/ton of uranium. The process used consists of 3 extraction cycles and one americium-curium separation: - 1) extraction cycle in 40 per cent TBP: extraction of actinides and lanthanides; elimination of fission products; - 2) extraction cycle in 8 per cent D2EHPA: decontamination from the fission products, decontamination of actinides from lanthanides; - 3) extraction cycle in 40 per cent TBP: separation of the complexing agent and concentration of the actinides; - 4) americium-curium separation by precipitation. (authors) [French] Cette etude a pour objet, la recuperation de l'americium et du curium de la solution de produits de fission provenant du traitement de combustibles irradies a base d'uranium naturel metallique allie a l'aluminium, le fer, et le silicium, et ayant subi une irradiation moyenne de 4000 MWj/t dans une pile du type graphite-gaz, dont la puissance thermique est de 3.7 MW/t d'uranium. Le procede utilise comprend 3 cycles d'extraction et une separation americium-curium: - 1. cycle d'extraction dans le TBP a 40 pour cent: extraction des actinides et des lanthanides, elimination des produits de fission; - 2. cycle d'extraction dans le D2EHPA a 8 pour cent: decontamination en produits de fission, decontamination des actinides en lanthanides; - 3. cycle d'extraction dans le TBP a 40 pour cent: separation du complexant et concentration des actinides; - 4. separation americium-curium par precipitation. (auteurs)

Systematic study of the use of electrical fields for improving heat exchange in boiling liquids; Etude systematique de l'utilisation de champs electriques pour l'amelioration des echanges thermiques dans des liquides bouillants

Energy Technology Data Exchange (ETDEWEB)

Bochirol, L; Bonjour, E; Lagnier, R; Verdier, J; Weil, L [Commissariat a l' Energie Atomique, Grenoble (France).Centre d' Etudes Nucleaires

1961-07-01

We have studied, at the boiling point, for liquids with various electrical properties (hexane, benzene, trichloroethylene, demineralized water, acetone, methyl-ethyl-ketone, etc...) the effect of the application of electric fields on the exchange coefficients and on the maximum dissipative powers before calefaction. We have given the mechanism of the significant improvements obtained (multiplication by a factor of 2 to 10): - in the natural convection zone by showing the role played by the dielectric properties of the liquids under study; - in the zone of nuclear boiling by analysis of the forces acting on the boiling nuclei. Finally we give some experimental results concerning measurements made under pressure until local boiling occurred: they show the possibility of some interesting applications of the method. (author) [French] On a etudie, a l'ebullition, sur des liquides de caracteristiques electriques diverses (hexane, benzene, trichlorethylene, eau demineralisee, acetone, methylethylcetone, etc...) les effets de l'application de champs electriques sur les coefficients d'echanges et les puissances maximales dissipables avant calefaction. On a precise le mecanisme des ameliorations importantes obtenues (multiplication par un facteur 2 a 10): - dans la zone de convection naturelle en mettant en evidence le role des caracteristiques dielectriques des liquides etudies; - dans la zone d'ebullition nucleaire par analyse des forces mises en jeu sur les noyaux d'ebullition. On donne enfin des resultats experimentaux sur des mesures effectuees sous pression jusqu'a l'ebullition locale: ils illustrent des possibilites d'applications interessantes du procede. (auteur)

Baby fission chambers; Etude de chambres a fission miniatures

Energy Technology Data Exchange (ETDEWEB)

Guery, U.; Tachon, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)

Noyaux et radioactivité une introduction à la physique des particules et à la physique nucléaire

CERN Document Server

Debu, Pascal

2017-01-01

Nées au début du XXe siècle, la physique nucléaire et la physique des particules ont bouleversé notre vision du monde et révolutionné la société par leurs innombrables applications : l'énergie nucléaire et l'utilisation des rayonnements pour la médecine et les sciences des matériaux en sont des exemples emblématiques. L'objectif de cet ouvrage est de permettre au lecteur d'appréhender les phénomènes nucléaires et la physique des hautes énergies, d'illustrer les retombées de la physique fondamentale dans la société, et d'éveiller ainsi la curiosité et l'intérêt pour ces disciplines. Le premier chapitre rappelle les notions indispensables de mécanique quantique et de relativité restreinte. Il se termine par une introduction sur l'antimatière et ses applications. Le deuxième chapitre aborde la physique des particules par la description des constituants de la matière et des lois qui gouvernent leurs interactions. L'interaction faible est l'occasion de développements sur les notions...

Decontamination of Surfaces by Ultrasonics; La decontamination des surfaces par l'emploi des ultra-sons

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Cerre, P; Mestre, E; Kerdelleau, J de [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

1962-07-01

A study was made of factors such as frequency, intensity, and time in the case of steel and of cotton cloth contaminated by fission products. Results show that the method is only of value in the case of steel and that it is necessary to operate at an optimum frequency of 80 khz and with an intensity of at least 4 W/cm{sup 2}. The difficulty of proposing a valid explanation for the decontamination mechanism is discussed. (authors) [French] Apres un examen des donnees theoriques du probleme, les auteurs font une etude systematique des facteurs frequence, intensite et temps dans le cas de l'acier et des tissus de coton contamines par des produits de fission. Ils montrent que la methode n'est interessante que pour l'acier qu'il faut operer a la frequence optimale de 80 kHz avec une intensite d'au moins 4 W/cm{sup 2}. Ils concluent en insistant sur la difficulte de proposer une explication valable pour le mecanisme de decontamination. (auteurs)

Use of electron beams for the production of radioactive nuclei through photo-fission; Utilisation de faisceaux d'electrons pour la production des noyaux radioactifs par photo-fission

Energy Technology Data Exchange (ETDEWEB)

M' garrech, Slah

2004-09-01

The IPN (institute of nuclear physics) of Orsay decided to build a linear accelerator in order to produce an electron beam of 50 MeV energy and of 10 {mu}A average intensity. It is the ALTO project (Linear Accelerator near the Tandem of Orsay). This project will be dedicated to the production of the radioactive ions using the photo-fission process. The central topic of this thesis is the study of the beam dynamics of the ALTO facility. The first part presents studies concerning the injector. The simulations made with the simulation code PARMELA allowed the optimization of the characteristics of pre-buncher (dephasing HF, accelerating field peak...) to obtain a good bunching factor at the entrance of the buncher and at the entrance of the accelerating section according to the distance separating the two systems. The second part of this thesis is related to measurements of transverse emittance of the beam at the buncher exit. The three gradients method has been selected and the optical system used is a solenoid. The results obtained are in good agreement with former measurements. Finally a calculation of the beam line was carried out to optimize the transport of the beam to the PARRNe target without degrading its characteristics. The calculation codes that have been used are BETA and TRACE-WIN. (author)

Half-life distribution table of radioactive nuclei; Table de distribution des periodes des noyaux radioactifs

Energy Technology Data Exchange (ETDEWEB)

Gugenberger, P [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

1954-07-01

This table allows to identify an element if its period is known. Data for this table were taken from the half-life values adopted by Hollander, PERLMAN and SEABORG (Rev. mod. Phys., 1953, 22 number 2). Moreover for each nucleus, the mass number, the charge number and the type of decay are given in the table. (author) [French] Cette table permet l'identification d'un element dont la periode est connue. Elle a ete etablie en utilisant les valeurs des periodes donnees par HOLLANDER, PERLMAN et SEABORG dans Rev. mod. Phys., 1953, 25 numero 2. On y trouve en outre, pour chaque nuclide, les caracteristiques suivantes: Z, A, modes de desintegration. (auteur)

Half-life distribution table of radioactive nuclei; Table de distribution des periodes des noyaux radioactifs

Energy Technology Data Exchange (ETDEWEB)

Gugenberger, P. [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

1954-07-01

This table allows to identify an element if its period is known. Data for this table were taken from the half-life values adopted by Hollander, PERLMAN and SEABORG (Rev. mod. Phys., 1953, 22 number 2). Moreover for each nucleus, the mass number, the charge number and the type of decay are given in the table. (author) [French] Cette table permet l'identification d'un element dont la periode est connue. Elle a ete etablie en utilisant les valeurs des periodes donnees par HOLLANDER, PERLMAN et SEABORG dans Rev. mod. Phys., 1953, 25 numero 2. On y trouve en outre, pour chaque nuclide, les caracteristiques suivantes: Z, A, modes de desintegration. (auteur)

Dislocations and radiation damage in {alpha}-uranium; Dislocations et effets des radiations dans l'uranium {alpha}

Energy Technology Data Exchange (ETDEWEB)

Leteurtre, J [Commissariat a l' Energie Atomique, 92 - Fontenay-Aux-Roses (France). Centre d' Etudes Nucleaires

1968-07-01

Dislocations in {alpha}-uranium were studied by electron microscopy. Electropolishing of thin foils was performed at low temperature (-110 deg. C) to prevent oxidation. Burgers vectors of twins dislocations are defined. Interactions between slip and twinning are studied from both experimental and theoretical point of view. Samples irradiated at several burn-up were examined. In order to explain our micrographic results, and also all information gathered in literature about radiation damage in {alpha}-uranium, a coherent model is propound for the fission particles effects. We analyse the influences of parameters: temperature, dislocation density, impurity content. The number of point defects created by one initial fission is determined for pure and annealed metal. The importance of the self-anneal which occurs immediately in each displacement spike, and the anneal due to a new fission on the damage resulting from a previous fission, are estimated. The focussing distance in [100] direction is found to be about 1000 Angstrom, at 4 deg. K. (author) [French] Ce travail est une etude par microscopie electronique des dislocations induites dans l'uranium {alpha}, soit par deformation plastique, soit par irradiation. Une methode de preparation des lames minces a basse temperature (-110 deg. C) a ete mise au point. Les vecteurs de Burgers des diverses dislocations de macles de ce metal ont ete definis. Les interactions glissements- maclages sont etudiees experimentalement et theoriquement. Des echantillons irradies a divers taux de combustion ont ete examines. Pour expliquer nos resultats micrographiques, et aussi l'ensemble des informations recueillies dans la litterature concernant l'endommagement par irradiation de l'uranium-{alpha}, nous proposons un modele coherent de l'effet des fragments de fission dans ce metal. L'influence des parametres: temperature, densite de dislocations, impuretes est analysee. Le nombre de defauts ponctuels crees par une fission dans du metal

Some studies on the fission of uranium with the help of a self-controlled wilson chamber; Quelques etudes sur la fission de l'uranium a l'aide d'une chambre de wilson autocommandee

Energy Technology Data Exchange (ETDEWEB)

Laboulaye, H de; Tzara, C; Olkowsky, J [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

1953-07-01

The authors applied the method of Wilson's chamber self intern control to the survey of the uranium fission with neutrons of the core. This method allowed them: 1) - to establish a distribution of the courses of the fission fragments in argon on a big number of events. 2) - to search for the probability of production of tri-partitions to third fragment of short course. The authors succeed to the conclusion that in relation to ordinary fission, this, probability is lower to (1 {+-} 3)/1000, what permits to doubt the existence of the phenomenon. (author) [French] Les auteurs ont applique la methode de la chambre de Wilson a autocommande interne a l'etude de la fission de l'uranium par neutrons de pile. Cette methode leur a permis: 1) - d'etablir une distribution des parcours des fragments de fission dans l'argon portant sur un grand nombre d'evenements. 2) - de rechercher la probabilite de production de tripartitions a troisieme fragment de court parcours. Les auteurs aboutissent a la conclusion que par rapport a la fission ordinaire, cette probabilite est inferieure a (1 {+-} 3)/1000, ce qui permet de douter de l'existence du phenomene. (auteur)

Fission-Fragment Angular, Energy, and Mass Division Correlations for the U{sup 234} (d, Pf) Reaction; Correlation des Angles, des energies et des Masses pour les Fragments de Fission Produits par la Reaction {sup 234}U(d, pf); K 041e 0420 0420 0415 041b 042f 0426 0418 042f 041c 0415 0416 0414 0423 0420 0410 0421 041f 0420 0415 0414 0415 041b 0415 041d 0418 0415 041c 041e 0421 K 041e 041b K 041e 0412 0414 0415 041b 0415 041d 0418 042f 041f 041e 0423 0413 041b 0423 , 041f 041e 042d 041d 0415 0420 0413 0418 0418 0418 041f 041e 041c 0410 0421 0421 0415 0412 0420 0415 0417 0423 041b 042c 0422 0410 0422 0415 0420 0415 0410 K 0426 0418 0419 (d, pf) 0423 0420 0410 041d 0410 -234; Correlaciones Entre la Distribucion Angular, la Energia y la Division Masica de los Fragmentos en la Reaccion {sup 234}U (d, pf)

Energy Technology Data Exchange (ETDEWEB)

Vandenbosch, R. [University of Washington, Seattle, WA (United States); Unik, J. P.; Huizenga, J. R. [Argonne National Laboratory, Argonne, IL (United States)

1965-07-15

'un analyseur a trois parametres ils ont enregistre simultanement les energies cinetiques des deux fragments de fission et l'energie du proton pour chaque coincidence. L'energie d'excitation pour laquelle la fission se produit est definie par l'energie cinetique du proton libere. Les variations de l'anisotropie angulaire Selon l'energie d'excitation ont une structure beaucoup plus nette que celle que Lamphere a obtenue pour le meme moyau, en bombardant {sup 234}U par des neutrons rapides. Les auteurs ont observe au moins huit voies de fission au point d'etranglement dans la region des energies comprises entre le seuil et 2 MeV au-dessus du seuil. Ils ont calcule (calculs de type Nilsson) des energies de particules isolees pour des noyaux deformes dans le cas de deformations plus grandes qui dorment une description pius precise de la configuration au point d'etranglement. Les etats d'une particule isolee identifies par Lamphere sont en accord avec ceux dont on a trouve par le calcul qu'ils sont voisins de la surface de Fermi pour des deformations raisonnables au point d'etranglement. Ces experiences avaient primitivement pour but de rechercher s'il n'y avait pas une correlation entre l'asymetrie de masse et l'anisotropie angulaire. Les rendements Selon la masse obtenus a partir des energies de fragments en correlation ne font apparaitre aucune variation de l'anisotropie Selon le rapport des masses, contrairement a ce que se passe dans les experiences ou l'on ne fixe pas l'energie d'excitation a laquelle la fission a lieu (experiences ou l'on observe effectivement une variation de l'anisotropie Selon le rapport des masses). On ne saurait donc affirmer, d'apres les mesures de l'anisotropie, que les proprietes du point d'etranglement influencent la repartition finale des masses. La moyenne de l'energie cinetique totale liberee au cours de la fission varie dans une proportion inferieure a 0,5% pour les differentes voies a l'etranglement observees. Les auteurs ont aussi etudie la

Dislocations and radiation damage in {alpha}-uranium; Dislocations et effets des radiations dans l'uranium {alpha}

Energy Technology Data Exchange (ETDEWEB)

Leteurtre, J. [Commissariat a l' Energie Atomique, 92 - Fontenay-Aux-Roses (France). Centre d' Etudes Nucleaires

1968-07-01

Dislocations in {alpha}-uranium were studied by electron microscopy. Electropolishing of thin foils was performed at low temperature (-110 deg. C) to prevent oxidation. Burgers vectors of twins dislocations are defined. Interactions between slip and twinning are studied from both experimental and theoretical point of view. Samples irradiated at several burn-up were examined. In order to explain our micrographic results, and also all information gathered in literature about radiation damage in {alpha}-uranium, a coherent model is propound for the fission particles effects. We analyse the influences of parameters: temperature, dislocation density, impurity content. The number of point defects created by one initial fission is determined for pure and annealed metal. The importance of the self-anneal which occurs immediately in each displacement spike, and the anneal due to a new fission on the damage resulting from a previous fission, are estimated. The focussing distance in [100] direction is found to be about 1000 Angstrom, at 4 deg. K. (author) [French] Ce travail est une etude par microscopie electronique des dislocations induites dans l'uranium {alpha}, soit par deformation plastique, soit par irradiation. Une methode de preparation des lames minces a basse temperature (-110 deg. C) a ete mise au point. Les vecteurs de Burgers des diverses dislocations de macles de ce metal ont ete definis. Les interactions glissements- maclages sont etudiees experimentalement et theoriquement. Des echantillons irradies a divers taux de combustion ont ete examines. Pour expliquer nos resultats micrographiques, et aussi l'ensemble des informations recueillies dans la litterature concernant l'endommagement par irradiation de l'uranium-{alpha}, nous proposons un modele coherent de l'effet des fragments de fission dans ce metal. L'influence des parametres: temperature, densite de dislocations, impuretes est analysee. Le nombre de defauts ponctuels crees

Apparatus for studying the diffusion of rare gases in stainless steel; Appareil pour etude de la diffusion des gaz rares dans l'acier inoxydable

Energy Technology Data Exchange (ETDEWEB)

Stohr, J A; Alfille, L [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

This apparatus enables measurements to be carried out on the diffusion of gaseous fission products and of gases in general across thin metallic walls at high temperatures. This work was initially intended to solve the problems involved in systems for detecting the rupture of a fuel element can (D.R.G.) by the diffusion of fission products through the cans at high temperatures. The extension of the work to other fields is envisaged. (author) [French] Cet appareil permet d'effectuer des mesures sur la diffusion des produits de fission gazeux, et des gaz en general, au travers de parois metalliques minces a haute temperature. Au depart, ce procede devait contribuer a resoudre les problemes poses aux systemes detecteurs de rupture de gaine (D.R.G.), par la diffusion des produits de fission au travers des gaines de cartouches a haute temperature. Son extension a d'autres etudes est envisagee. (auteur)

Détermination du rapport d’embranchement de la transition super-permise du carbone 10 et développement et intégration de la ligne de faisceau PIPERADE au CENBG

CERN Document Server

AUTHOR|(CDS)2091894; Giovinazzo, Jérôme

Les études de la radioactivité bêta dans les milieux nucléaires permettent en partie de participer à la détermination d’un des paramètres qui décrit l'interaction faible (la constante de couplage vectoriel). Pour cela, de nombreuses mesures permettent déjà d’atteindre de grandes précisions sur ce paramètre pour un grand nombre de noyaux des transitions bêta super-permise. Cependant, pour le carbone 10, l'incertitude relative du rapport d'embranchement reste encore élevée par rapport aux autres noyaux pères avec une valeur de l’ordre de 0,13 %. Ceci est dû à l’énergie du photon émis par l’état 0+ du noyau fils qui est de 1021,6 keV, c’est-à-dire proche de l’énergie d’empilement de deux signaux de photons de 511 keV. En mai 2015, notre groupe a réalisé, à ISOLDE au CERN, une expérience afin de mesurer très précisément cette transition. Pour produire le carbone 10,nous avons réalisé des réactions nucléaires qui produisaient en grandes parties les noyaux d’inté...

Study of some properties of bound levels and virtual levels excited with resonance neutrons; Etude de quelques proprietes de niveaux lies et de niveaux virtuels excites a l'aide de neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Alves, R N [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

Many neutron resonance parameters of some nuclei with a spin value I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) are determined to find the strength function S{sub 0} with accuracy. For those nuclei, the S{sub 0} value seems not to depend on the spin value J=1 or 2 but could be depend on neutron energy for {sup 197}Au. Total radiative width variation against mass number A and spacing distributions between resonances (for {sup 197}Au) are studied and discussed. Analysis methods of neutron capture experiments are described in detail and level schemes of Cl, Mn, Fe, Co, Cu, Tm, Hg are presented sometimes with the spin value. Intensities of E{sub 1} and M{sub 1} transitions with direct capture and interference effects are discussed in view of experimental results. (author) [French] On determine les parametres des resonances de quelques noyaux de spin I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) en nombre suffisant pour obtenir la fonction densite S{sub 0} avec precision. Cette valeur S{sub 0} apparat pour ces noyaux etre independante de la valeur du spin J=1 ou 2 mais para?t, dans le cas de {sup 197}Au, dependre de l'energie. On etudie et on essaie d'interpreter la variation de la largeur radiative totale {gamma}{sub {gamma}} en fonction du nombre de masse A et les distributions des espacements entre resonances pour {sup 197}Au. On expose en detail les methodes d'analyse des experiences de capture et on presente les schemas des niveaux des noyaux: Cl, Mn, Fe, Co, Cu, Tm, Hg. Les intensites des transitions de type E{sub 1} et M{sub 1} ainsi que les effets d'interference et de capture directe sont discutes. (auteur)

Contribution to the study of samarium-151 excited levels; Contribution a l'etude des niveaux excites du samarium-151

Energy Technology Data Exchange (ETDEWEB)

Locard, P [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Grenoble, 38 (France)

1967-07-01

The nucleus of {sup 151}Sm, which has 89 neutrons, happens to be on the lower edge of the deformed nuclei of region II. Therefore, the study of its levels is very interesting for the verification of the goodness of the collective models for deformed nuclei when the deformation is small (we introduce these models in the first chapter). {sup 151}Sm has often been studied, but the direct gamma spectrum measured with a lithium drift-germanium detector (chapter 3) shows many high energy transitions which did not appear in the previous level schemes. In order to settle these transitions, we have undertaken gamma-gamma coincidence spectra (as well as sum-coincidence spectra) experiments with a scintillation spectrometer designed in our laboratory (chapter 2). The investigation of the intensities of these coincidences leads us to modify the last proposed level schemes: we suppress the levels at 405,5 and 650 keV, we add levels at 245,6 - 306,6 - 522 - 952 and 962 keV. We have also verified the multipolarities of the main transitions and measured the half-lives of a few levels (chapter 3) (we find a half-life of 1.1 {+-} 0.5 nanosecond for the level at 167,7 keV). In chapter 4, we compare our results to the predictions of the models described in chapter 1. (author) [French] Le noyau de {sup 151}Sm, qui possede 89 neutrons, se trouve a la limite inferieure des noyaux deformes de la region II. L'etude de ses niveaux excites est donc d'un interet tout particulier pour la verification de la validite des differents modeles collectifs pour les noyaux deformes, lorsque la deformation est petite (nous introduisons ces modeles dans un premier chapitre). Le {sup 151}Sm a deja fait l'objet de nombreuses etudes, mais le spectre gamma direct fait avec une jonction de germanium compense au lithium (chapitre 3), nous a montre l'existence d'un grand nombre de transitions de hautes energies qui ne sont pas placees dans les schemas proposes jusqu'a ce jour. Pour preciser la place de ces

Pathogenesis of Intrapulmonary Haemorrhage in Dogs Exposed to Pulsed Fission-Spectrum Neutrons; Pathogenese de l'Hemorragie Intrapulmonaire chez des Chiens Exposes a des Neutrons de Fission Pulses; Patogenez vnutrilegochnykh krovoizliyanij u sobak pri obluchenii impul'snymi nejtronami spektra deleniya; Patogenesis de la Hemorragia Intrapulmonar en Perros Expuestos a Neutrones de Fision Pulsados

Energy Technology Data Exchange (ETDEWEB)

Jones, R. K.; Engel, R. E.; Godden, W. R. [Kirtland AFB, New Mexico (United States)

1964-05-15

marrow megakaryocytes was found to be inversely proportional to the severity of intrapulmonary haemorrhage. (author) [French] Des comparaisons precedemment effectuees dans le laboratoire des auteurs entre les modifications tissulaires observees chez des chiens exposes a des rayons X de 250 kV-crete et a des neutrons de fission puises ont montre que, dans les deux cas, les reactions etaient en general semblables. Cependant, les poumons des animaux exposes aux neutrons de fission ont ete beaucoup plus souvent le siege d'hemorragies peribronchiales et peri vasculaires. On a essaye de determiner la pathogenese de cette lesion en exposant cinq bigles a une dose de 400 rad (DMA) de neutronsrapides emanant d'un reacteur du type GODIVA et en sacrifiant successivement les animaux a intervalles reguliers. Cinq jours apres l 'exposition, on a pu discerner un ensemble d'alterations pathologiques constituees par de petites hemorragies pulmonaires sporadiques a la peripherie. Leur nombre a augmente progressivement vers le neuvieme jour. Les modifications les plus frappantes sont survenues au bout de 13 j sous forme de grandes hemorragies perivasculaires autour des ramuscules des arteres pulmonaires, depuis le hile jusqu' a la suriace de la plevre. Les premieres modifications histologiques observees dans les poumons sont survenues le cinquieme jour, sour forme de foyers nettement demarques de congestion alveolaire,- de gonflement des cellules capillaires endotheliales et d'extravasion alveolaire legere des globules rouges. Ces alterations se sont generalisees au bout de neuf jours et on.a pu observer en outre des foyers d'extravasion peribronchiale du sang autour des deux bronches primaires. On a constate, chez les animaux autopsies le treizieme jour apres l ' exposition, une grosse hemorragie-peri vasculaire autour des grandes et des petites arteres pulmonaires. Le sang se trouvait dans le tissu conjonctif externe et dans les vaisseaux lymphatiques periarteriels. Les vaisseaux

Construction of an apparatus for nuclear orientation measurements at low temperatures. Application to neodymium-cobalt alloy; Realisation d'un appareil pour des mesures d'orientation nucleaire a basse temperature. Application a l'alliage neodyme-cobalt

Energy Technology Data Exchange (ETDEWEB)

Mayer, E [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1965-10-01

We describe experiments along which has been studied the anisotropy of {gamma} radiations emitted by oriented nuclei. We have used the great hyperfine fields acting on nuclei in ferromagnetic metals so as to produce alignment at low temperature. By irradiation we obtained a few cobalt 60 nuclei in our samples which were then cooled down to 0,01 K. The anisotropic rate of the 1,33 MeV {gamma} radiation was measured in function of the sample temperature, using as thermometer the anisotropy of {gamma} radiation emitted by cobalt 60 nuclei in a cobalt single crystal. Cobalt 60 was lined up in a cobalt nickel alloy (40% Ni). The hyperfine field at the cobalt was measured compared to the effective field in metallic cobalt: Heff(Co Ni)/Heff(Co metal) = 0.71 {+-} 0.12. These results are in good agreement with specific heat measurements made previously. Cobalt 60 has been polarised in a neodymium-cobalt alloy (NdCo{sub 5}). The field at the cobalt in NdCo{sub 5} has been measured compared to the field in metallic cobalt and taking the non-saturation into account we found 165000 oersteds < Heff(NdCo{sub 5}) < 220000 oersteds. (author) [French] Nous decrivons des experiences au cours desquelles nous avons etudie l'anisotropie de rayonnements {gamma} emis par des noyaux orientes. Nous avons utilise les grands champs hyperfins agissant sur las noyaux dans les metaux ferromagnetiques pour produire l'alignement a basse temperature. Par irradiation nous avons obtenu quelques noyaux de cobalt 60 dans nos echantillons qui furent ensuite refroidis a 0,01 K. Le degre d'anisotropie du rayonnement {gamma} de 1,33 MeV fut mesure en fonction de la temperature de l'echantillon en utilisant l'anisotropie du rayonnement {gamma} de noyaux de cobalt 60 dans un monocristal de cobalt metallique utilise comme thermometre. Le cobalt 60 a ete aligne dans un alliage de cobalt-nickel (40% Ni). Le champ hyperfin au niveau du cobalt a ete mesure par rapport au champ effectif dans le cobalt metallique

Radiation hazards in the neighbourhood of uranium reactors; Dangers des rayonnements aupres des piles a uranium

Energy Technology Data Exchange (ETDEWEB)

Joffre, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1956-07-01

Radiation hazards near uranium reactors may be divided in two groups. Hazards when the reactor is normally operating: {gamma} radiation from hot uranium or air contamination by fission gases, {gamma} radiation or contamination by the coolant (air, nitrogen, heavy-water), {gamma} radiation from radioisotopes. Hazards in the case of an accident: presence of hot uranium in the atmosphere, soil contamination. (author) [French] Les dangers d'irradiation aupres des piles a uranium sont a classer essentiellement en deux groupes. Les dangers existant aupres d'une pile exploitee normalement: irradiation {gamma} par l'uranium irradie ou contamination de l'air par des gaz de fission, irradiation {gamma} ou contamination par les fluides de refroidissement (air, azote, eau lourde), irradiation {gamma} par les radioelements fabriques. Les dangers en cas d'accident survenant a un reacteur en fonctionnement, ayant pour consequence : la presence dans l'air d'uranium irradie, la contamination du sol. (auteur)

Spectroscopic study of near closed-shell nuclei Z = 50, by means of the ({sup 3}He,d) and (d, {sup 3}He) reactions on all even tin isotopes, and the ({sup 3}He, d) reaction on the A = 113 and A = 115 indium isotopes; Etude spectroscopique des noyaux au voisinage de la couche fermee Z = 50, au moyen des reactions ({sup 3}He, d) et (d, {sup 3}He) sur tous les isotopes pairs de l'etain, et de la reaction ({sup 3}He, d) sur les isotopes 113, 115 de l'indium

Energy Technology Data Exchange (ETDEWEB)

Harar, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-06-01

A systematic study of ({sup 3}He, d) reactions at 18 MeV incident energy and (d, {sup 3}He) reactions at 22 MeV incident energy on {sup 112,114,116,118,120,122,124}Sn is presented. The distorted wave Born approximation (DWBA) is used to extract informations on (a) the transferred angular momentum l{sub p}, (b) the change of parity and (c) the spectroscopic factor. We have investigated the influence of the proton-neutron residual interaction on the spread of the pure proton configuration (particle or hole), and on the observed level sequence. Experimental results and predictions of the Kisslinger and Sorensen model are in reasonable agreement. A study of {sup 113,115}In ({sup 3}He, d) {sup 114,116}Sn reactions shows strong experimental evidence that the proton particle hole components are weak in the first excited states of tin nuclei. Furthermore, highly excited states ({approx} 4 to 6 MeV) having a simple structure with one predominant particle-hole configuration have been located. (authors) [French] Nous presentons une etude systematique des reactions ({sup 3}He, d) a 18 MeV et (d, {sup 3}He) a 22 MeV sur {sup 112,114,116,118,120,122,124}Sn. L'approximation des ondes deformees (DWBA) est utilisee pour obtenir des informations sur le moment angulaire transfere l{sub p}, sur le changement de parite et le facteur spectroscopique. Nous avons etudie l'influence de l'interaction residuelle proton-neutron sur la repartition de l'intensite a une seule particule ou trou de proton, et sur les sequences des niveaux observes. Les resultats experimentaux et les previsions theoriques du modele de Kisslinger et Sorensen sont en assez bon accord. L'etude des reactions {sup 113,115}In ({sup 3}He, d) {sup 114,116}Sn apporte la preuve experimentale que les composantes particule - trou de protons des premiers etats excites des noyaux residuels sont faibles. Elle permet aussi de localiser des niveaux a une energie d'excitation elevee ({approx} 4 a 6 MeV), ayant une structure simple a

Spectroscopic study of near closed-shell nuclei Z = 50, by means of the ({sup 3}He,d) and (d, {sup 3}He) reactions on all even tin isotopes, and the ({sup 3}He, d) reaction on the A = 113 and A = 115 indium isotopes; Etude spectroscopique des noyaux au voisinage de la couche fermee Z = 50, au moyen des reactions ({sup 3}He, d) et (d, {sup 3}He) sur tous les isotopes pairs de l'etain, et de la reaction ({sup 3}He, d) sur les isotopes 113, 115 de l'indium

Energy Technology Data Exchange (ETDEWEB)

Harar, S. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-06-01

A systematic study of ({sup 3}He, d) reactions at 18 MeV incident energy and (d, {sup 3}He) reactions at 22 MeV incident energy on {sup 112,114,116,118,120,122,124}Sn is presented. The distorted wave Born approximation (DWBA) is used to extract informations on (a) the transferred angular momentum l{sub p}, (b) the change of parity and (c) the spectroscopic factor. We have investigated the influence of the proton-neutron residual interaction on the spread of the pure proton configuration (particle or hole), and on the observed level sequence. Experimental results and predictions of the Kisslinger and Sorensen model are in reasonable agreement. A study of {sup 113,115}In ({sup 3}He, d) {sup 114,116}Sn reactions shows strong experimental evidence that the proton particle hole components are weak in the first excited states of tin nuclei. Furthermore, highly excited states ({approx} 4 to 6 MeV) having a simple structure with one predominant particle-hole configuration have been located. (authors) [French] Nous presentons une etude systematique des reactions ({sup 3}He, d) a 18 MeV et (d, {sup 3}He) a 22 MeV sur {sup 112,114,116,118,120,122,124}Sn. L'approximation des ondes deformees (DWBA) est utilisee pour obtenir des informations sur le moment angulaire transfere l{sub p}, sur le changement de parite et le facteur spectroscopique. Nous avons etudie l'influence de l'interaction residuelle proton-neutron sur la repartition de l'intensite a une seule particule ou trou de proton, et sur les sequences des niveaux observes. Les resultats experimentaux et les previsions theoriques du modele de Kisslinger et Sorensen sont en assez bon accord. L'etude des reactions {sup 113,115}In ({sup 3}He, d) {sup 114,116}Sn apporte la preuve experimentale que les composantes particule - trou de protons des premiers etats excites des noyaux residuels sont faibles. Elle permet aussi de localiser des niveaux a une energie d'excitation elevee ({approx} 4 a 6 Me

Study of transfer reactions ({alpha},t), ({alpha},{sup 3}He) in the f-p shell: mechanism and spectroscopic use; Etude des reactions de transfert ({alpha},t), ({alpha},{sup 3}He) dans la couche f-p mecanisme et utilisation spectroscopique

Energy Technology Data Exchange (ETDEWEB)

Roussel, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

We describe an experimental study of ({alpha},t), ({alpha},{sup 3}He) reactions at 44 MeV using a solid-state identifier, on the target-nuclei {sup 54}Fe and {sup 58,60,62,64}Ni. A critical study of optical model and of disturbed wave analysis has been performed. We show the complementarity of different transfer-reactions, the ambiguity of spectroscopic factors, the importance of the problem of the reaction mechanism. (author) [French] On decrit une etude experimentale des reactions ({alpha},t), ({alpha},{sup 3}He) a 44 MeV utilisant un systeme identificateur de particules sur les noyaux-cibles {sup 54}Fe et {sup 58,60,62,64}Ni. Une etude critique de modele optique et d'analyse en ondes deformees (D.W.B.A.) a ete entreprise. On montre la complementarite des differentes reactions de transfert, l'ambiguite des facteurs spectroscopiques, l'importance du probleme du mecanisme. (auteur)

The Technology and Applications of Large Fission Product Beta Sources; Technologie et applications des grandes sources beta de fission; Tekhnologiya i primenenie krupnykh istochnikov beta-izluchenij, ispuskaemykh produktami deleniya; Tecnologia y utilizacion de los productos de fision como fuentes de irradiacion beta de elevada intensidad

Energy Technology Data Exchange (ETDEWEB)

Silverman, Joseph [Radiation Applications Incorporated (United States)

1960-07-15

test the validity of the calculations. 4. An engineering cost analysis indicates that fission product beta power can be competitive with alternative sources of radiation. (author) [French] Si les emetteurs beta ne sont pas entres en ligne de compte en tant que sources de rayonnement de grandes dimensions, c'est que dans le passe les procedes sous irradiation presentant un interet pour l'industrie etaient bases sur l'utilisation de particules a grand pouvoir de penetration; de la l'importance considerable que l'on accordait aux rayons gamma et aux electrons artificiellement acceleres. Il y a environ quatre ans, il devint evident que de vastes perspectives s'ouvraient aux applications pratiques des rayonnements beta dans le domaine du traitement par irradiation superficielle, par exemple, la modification par copolymerisation greffee de la surface des moulages en matiere plastique et la pasteurisation superficielle des aliments. En effet, l'irradiation en profondeur occasionne dans ces cas des pertes et peut meme presenter des dangers. D'autre part, il y a deux autres domaines dans lesquels l'utilisation des electrons artificiellement acceleres ne semble pas indiquee; ce sont les syntheses chimiques amorcees par irradiation dans des cuves sous pression et certaines categories de reactions en chaine provoquees par des radicaux libres pour lesquels le taux de production par kilowatt decroit en fonction de la racine carree de l'intensite d'irradiation. Dans tous ces domaines, les sources beta de grandes dimensions presentent des avantages potentiels evidents; puisque la fission nucleaire permet d'en obtenir en quantites importantes, elles meritent que leurs- possibilites d'utilisation fassent l'objet d'un examen approfondi. Compte tenu de ces considerations, on a procede - sous l'egide de la Commission de l'energie atomique - a une etude des applications'et de la technologie des sources beta de fission. Cette etude a permis d'aboutir aux conclusions suivantes: 1. Des

Burnup determination of power reactor fuel elements by gamma spectrometry; Determination par spectrometrie {gamma} du taux d'irradiation des elements combustibles des reacteurs de puissance

Energy Technology Data Exchange (ETDEWEB)

Robin, M; Jastrzeb, M; Boisliveau, S; Boyer, R; Vidal, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-07-01

This report describes a method for determining by {gamma} spectrometry the burn up and the specific power of fuel elements irradiated in power reactors. The energy spectrum of {gamma} rays emitted by fission products is measured by means of a simple equipment using a sodium iodide detector and a multichannel analyzer. In order to extract from the spectrum a quantity proportional to the burn up, it is necessary to: - isolate an activity specific of one emitter,- give the same importance to fissions in uranium and plutonium - take into account the radioactive decay during and after irradiation. One hundred fuel elements were studied and burn up values obtained by {gamma} spectrometry are compared to results given by chemical analyses. Preliminary measurements show that the accuracy of the results is greatly increased by the use of a germanium detector, due to its good resolution. (authors) [French] Ce rapport expose une methode de determination par spectrometrie {gamma} du taux d'irradiation et de la puissance specifique des elements combustibles irradies dans les reacteurs de puissance. Une installation simple utilisant un detecteur d'iodure de sodium et un selecteur multicanaux mesure le spectre en energie du rayonnement {gamma} emis par les produits de fission. Afin d'extraire du spectre une quantite proportionnelle au taux de combustion, il faut: - isoler une activite specifique a un emetteur, - donner la meme importance aux fissions survenues dans l'uranium et le plutonium, - prendre en compte la decroissance radioactive pendant et apres l'irradiation. Les mesures ont porte sur une centaine d'elements combustibles et les taux de combustion obtenus par spectrometrie {gamma} sont compares aux resultats des analyses chimiques. Des mesures preliminaires montrent que l'utilisation d'un detecteur de germanium augmente considerablement la precision des resultats, en raison de son excellente resolution. (auteurs)

Contribution to the study of light nuclei with polarized deuterons; Contribution a l'etude des noyaux legers au moyen de deutons polarises

Energy Technology Data Exchange (ETDEWEB)

Arvieux, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-04-15

We describe roughly the vector and tensor-polarized deuteron source associated with the Saclay fixed energy (22 MeV) cyclotron. This has been used to measure the deuteron asymmetry in d-{alpha} scattering (between 17.7 and 21.4 MeV) and in d-p scattering at 21.7 MeV. Then we develop the formalism of irreducible tensor operators used to describe the polarization of a particle of given spin and we study the helicity formalism used to describe the scattering amplitudes for scattering of deuterons by {alpha} (spin 0) and protons (spin 1/2). We apply the preceding results to the phase shift analysis of scattering cross-sections and: 1) deuteron polarization in d-{alpha} scattering from 10 to 27 MeV from which we obtain indications about the excited states of {sup 6}Li; 2) proton and deuteron polarizations in p-d (or d-p) scattering from 1.5 to 12 MeV so as to get the splitting (due to spin interactions) of P and D waves. (author) [French] On decrit sommairement la source de deutons polarises vectoriellement et tensoriellement associee au cyclotron a energie fixe de Saclay avec laquelle on a mesure l'asymetrie des deutons dans la diffusion d-{alpha} de 17,7 a 21,4 MeV et d-p a 21,7 MeV. Puis or developpe le formalisme des operateurs tensoriels irreductibles utilise pour decrire la polarisation d'une particule de spin quelconque. On etudie ensuite le formalisme de l'helicite dans lequel on etudie la diffusion elastique des deutons diffuses par des particules {alpha} (spin 0) et des protons (spin 1/2). On applique les resultats precedents a l'analyse en dephasages de la section efficace et des polarisations: 1 )des deutons dont la diffusion d-{alpha} de 10 a 27 MeV destinee a donner des indications sur les niveaux excites de {sup 6}Li; 2) des protons et des deutons dans la diffusion p-d de 1,5 a 12 MeV en vue de l'etude de la separation suivant les differentes valeurs du moment total J, des ondes P et D (separation due aux interactions de spin). (auteur)

Contribution to the study and use of ionisation chambers for nuclear reactor control (1965); Contribution a l'etude et a l'utilisation des chambres d'ionisation pour le controle des reacteurs nucleaires (1965)

Energy Technology Data Exchange (ETDEWEB)

Duchene, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-02-15

high-power reactors. (author) [French] Les chambres d'ionisation sont actuellement les detecteurs les mieux adaptes au controle des reacteurs nucleaires par des mesures neutroniques. Nous avons cru bon de rappeler quelques generalites concernant la dynamique des reacteurs, les differents procedes de detection des neutrons, le fonctionnement des chambres d'ionisation et les methodes de mesure utilisees. Notre contribution aux techniques de controle des reacteurs consiste d'une part en une tentative de synthese des facteurs intervenant dans le fonctionnement des chambres d'ionisation, l'etude de ces facteurs, et d'autre part l'elaboration de chambres d'ionisation a fission et a bore permettant de suivre la marche d'un reacteur du demarrage jusqu'a la puissance maximale. Dans le domaine des chambres a fission, nous avons en particulier ameliore les techniques de depot d'oxyde d'uranium sur l'aluminium et realise la mise au point de depots par electrolyse sur d'autres metaux: acier inoxydable, cuivre, molybdene, nickel, tantale, titane, kovar, tungstene et beryllium. Nous avons elabore plusieurs types de chambres a fission servant au demarrage des reacteurs: un type de performances moyennes actuellement utilise dans les piles francaises un type a haute sensibilite un type a haute temperature qui a fonctionne jusqu'a 600 deg. C. En ce qui concerne les chambres a bore, nous avons etudie les perturbations apportees dans les mesures par l'exposition des chambres a d'importants flux de neutrons et a un rayonnement {gamma} intense. Cette exposition produit une modification des proprietes des materiaux constitutifs et la production dans les chambres d'un bruit de fond qui peut gener considerablement les mesures neutroniques. Nous avons montre que la technique de compensation permettait de limiter l'importance de ce bruit de fond et d'augmenter ainsi la plage de fonctionnement des chambres d'ionisation classiques destinees aux mesures de puissance. Enfin, nous avons realise deux

Study of some properties of 's' neutron resonance parameters for target nuclei I = 1/2 and I = 3/2 in function of spin value J = I + 1/2 in the energy range 1 {yields} 5000 eV; Etude de quelques proprietes des parametres de resonances des neutrons ''s'' pour des noyaux cibles I = 1/2 et I = 3/2 en fonction de la valeur du spin J = I + 1/2 dans le domaine d'energie 1 eV {yields} 5000 eV

Energy Technology Data Exchange (ETDEWEB)

Julien, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-05-15

Different kinds of experiments and analysis methods allowing to achieve neutron resonances parameters in the low energy range (1 eV {yields} 5000 eV) are described. A great deal of effort to improve experimental conditions and data processing in order to know the spin value J = I {+-} 1/2 has been spent. The time of flight method was used. A few target nuclei I = 3/2 and 1 = 1/2 have been studied. For I = 3/2 (Ga, As, 3r, Au) we find S{sub o} J = 2 {approx_equal} 2 S{sub o} J = 1 and S{sub o} J = 1 {approx_equal} S{sub o} J = 0 for I = 1/2 (Tm, Pt) but {sup 77}Se. Fluctuations of the total radiative width {gamma}{sub {gamma}} depend on the spin value I = I {+-} 1/2 when E1 transition, are enhanced for one of the both spin states. The magnitude of these fluctuations can be explained of the strength of E1 transitions (E{sub {gamma}} {approx} 7 MeV) is supposed to be proportional to E{sup 5}{sub {gamma}} instead of E{sup 3}{sub {gamma}}. The distribution of levels spacings against spin value J are considered and are compared to theoretical predictions. (author) [French] On decrit les differentes methodes d'analyse permettant d'obtenir les parametres des resonances de neutron dans le domaine d'energie 1 eV {yields} 5000 eV. Un effort particulier a ete fait pour connaitre la valeur du spin J = I {+-} 1/2. Les types d'experience et les analyses des donnees, developpes et ameliores pour determiner J sont decrits. Les resultats obtenus ont permis l'etude de differentes proprietes en fonction du spin J. On trouve: S{sub o} J 2 {approx_equal} 2 S{sub o} J = 1 pour les noyaux I = 3/2 etudies (Ga, As, Br, Au) et S{sub o} J = 1 {approx_equal} S{sub o} J = 0 Pour le Tm et {sup 195}Pt de spin I = 1/2. On constate que les largeurs radiatives totales {gamma}{sub {gamma}} fluctuent si des transitions E1 aux premiers etats excites sont favorisees. Ces fluctuations peuvent etre expliquees si on suppose que les intensites de ces transitions sont proportionnelles a E{sup 5}{sub {gamma

Study of some properties of bound levels and virtual levels excited with resonance neutrons; Etude de quelques proprietes de niveaux lies et de niveaux virtuels excites a l'aide de neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Alves, R.N. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

Many neutron resonance parameters of some nuclei with a spin value I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) are determined to find the strength function S{sub 0} with accuracy. For those nuclei, the S{sub 0} value seems not to depend on the spin value J=1 or 2 but could be depend on neutron energy for {sup 197}Au. Total radiative width variation against mass number A and spacing distributions between resonances (for {sup 197}Au) are studied and discussed. Analysis methods of neutron capture experiments are described in detail and level schemes of Cl, Mn, Fe, Co, Cu, Tm, Hg are presented sometimes with the spin value. Intensities of E{sub 1} and M{sub 1} transitions with direct capture and interference effects are discussed in view of experimental results. (author) [French] On determine les parametres des resonances de quelques noyaux de spin I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) en nombre suffisant pour obtenir la fonction densite S{sub 0} avec precision. Cette valeur S{sub 0} apparat pour ces noyaux etre independante de la valeur du spin J=1 ou 2 mais para?t, dans le cas de {sup 197}Au, dependre de l'energie. On etudie et on essaie d'interpreter la variation de la largeur radiative totale {gamma}{sub {gamma}} en fonction du nombre de masse A et les distributions des espacements entre resonances pour {sup 197}Au. On expose en detail les methodes d'analyse des experiences de capture et on presente les schemas des niveaux des noyaux: Cl, Mn, Fe, Co, Cu, Tm, Hg. Les intensites des transitions de type E{sub 1} et M{sub 1} ainsi que les effets d'interference et de capture directe sont discutes. (auteur)

Le Phénomène Wolf-Rayet au Sein des Etoiles chaudes de Populations I et II: Histoire des Vents stellaires et Impact sur la Structure nébulaire circumstellaire

Science.gov (United States)

Grosdidier, Yves

2000-12-01

Les spectres des étoiles Wolf-Rayet pop. I (WR) présentent de larges raies en émission dues à des vents stellaires chauds en expansion rapide (vitesse terminale de l'ordre de 1000 km/s). Le modèle standard des étoiles WR reproduit qualitativement le profil général et l'intensité des raies observées. Mais la spectroscopie intensive à moyenne résolution de ces étoiles révèle l'existence de variations stochastiques dans les raies (sous-pics mobiles en accélération échelles de temps: environ 10-100 min.). Ces variations ne sont pas comprises dans le cadre du modèle standard et suggèrent une fragmentation intrinsèque des vents. Cette thèse de doctorat présente une étude de la variabilité des raies spectrales en émission des étoiles WR pop. II; la question de l'impact d'un vent WR fragmenté sur le milieu circumstellaire est aussi étudiée: 1) à partir du suivi spectroscopique intensif des raies CIIIl5696 et CIVl5801/12, nous analysons quantitativement (via le calcul des Spectres de Variance Temporelle) les vents issus de 5 étoiles centrales de nébuleuses planétaires (NP) galactiques présentant le phénomène WR; 2) nous étudions l'impact de la fragmentation des vents issus de deux étoiles WR pop. I sur le milieu circumstellaire via: i) l'imagerie IR (NICMOS2/HST) de WR 137, et ii) l'imagerie H-alpha (WFPC2/HST) et l'interférométrie Fabry-Perot H-alpha (SIS-CFHT) de la nébuleuse M 1-67 (étoile centrale: WR 124). Les principaux résultats sont les suivants: VENTS WR POP. II: (1) Nous démontrons la variabilité spectroscopique intrinsèque des vents issus des noyaux de NP HD 826 ([WC 8]), BD +30 3639 ([WC 9]) et LSS 3169 ([WC 9]), observés durant respectivement 22, 15 et 1 nuits, et rapportons des indications de variabilité pour les noyaux [WC 9] HD 167362 et He 2-142. Les variabilités de HD 826 et BD +30 3639 apparaissent parfois plus soutenues (``bursts'' qui se maintiennent durant plusieurs nuits); (2) La cinématique des sous

Measurement of the fission cross section induced by fast neutrons of the {sup 232}Th/{sup 233}U nuclei within the innovating fuel cycles framework; Mesure de la section efficace de fission induite par neutrons rapides des noyaux {sup 232}Th/{sup 233}U dans le cadre des cycles de combustible innovants

Energy Technology Data Exchange (ETDEWEB)

Grosjean, C

2005-03-15

The thorium-U{sup 233} fuel cycle might provided safer and cleaner nuclear energy than the present Uranium/Pu fuelled reactors. Over the last 10 years, a vast campaign of measurements has been initiated to bring the precision of neutron data for the key nuclei (Th{sup 232}, Pa{sup 233} and U{sup 233}) at the level of those for the U-Pu cycle. This is the framework of these measurements, the energy dependent neutron induced fission cross section of Th{sup 232} and U{sup 233} has been measured from 1 to 7 MeV with a target accuracy lesser than 5 per cent. These measurements imply the accurate determination of the fission rate, the number of the target nuclei as well as the incident neutron flux impinging on the target, the latter has been obtained using the elastic scattering (n,p). The cross section of which is very well known in a large neutron energy domain ({approx} 0,5 % from 1 eV to 50 MeV) compared to the U{sup 235}(n,f) reaction. This technique has been applied for the first time to the Th{sup 232}(n,f) and U{sup 233}(n,f) cases. A Hauser-Feshbach statistical model has been developed. It consists of describing the different decay channels of the compound nucleus U{sup 234} from 0,01 to 10 MeV neutron energy. The parameters of this model were adjusted in order to reproduce the measured fission cross section of U{sup 233}. From these parameters, the cross sections from the following reactions could be extracted: inelastic scattering U{sup 233}(n,n'), radiative capture U{sup 233}(n,{gamma}) and U{sup 233}(n,2n). These cross sections are still difficult to measure by direct neutron reactions. The calculated values have allowed us to fill the lack of experimental data for the major fissile nucleus of the thorium cycle. (author)

Some magnetic resonance properties of solutions of sodium in liquid ammonia; Contribution a l'etude des solutions de sodium dans l'ammoniac liquide par resonance magnetique

Energy Technology Data Exchange (ETDEWEB)

Lambert, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-02-01

Dilute solutions of sodium in liquid ammonia are studied by the mean of dynamic polarization techniques, and with the aid of Becker Lindquist and Alder model. Paramagnetic shifts are computed as a function of the 'average spin density', for each of the nuclear spin system. The nuclear contributions to the Overhauser shift are computed in the same way. A theoretical study of the main relaxation processes is carried out for each of the nuclear spin system and for the electronic spin system. The dynamic polarization experiments consist in classical measurement of the Overhauser enhancement for nitrogen, and in direct measurements of nitrogen Knight shift and nuclear contributions to the Overhauser shift by the mean of double irradiation techniques. The results show that, in dilute solutions, the relaxation of nitrogen arises from quadrupole interaction and from hyperfine interaction with unpaired electrons. Both interactions are of the same order of magnitude. Overhauser shift measurements show that the spin density is negative at the proton site, in agreement with Hughes results. (author) [French] Les solutions diluees de sodium dans l'ammoniac sont etudiees au moyen des techniques de la polarisation dynamique, sur la base du modele de Becker Lindquist et Aider. Les deplacements paramagnetiques des raies de resonance nucleaire des differents noyaux sont analyses en faisant appel a la notion de ''densite moyenne de spin'' introduite par l'auteur; et les differentes contributions nucleaires au deplacement d'Overhauser sont calculees en fonction de cette meme grandeur. Une etude theorique de la relaxation de chaque systeme de spin permet d'evaluer l'importance relative des differents mecanismes mis en jeu. Les experiences de polarisation dynamique effectuees au cours de ce travail consistent en mesures classiques de l'effet Overhauser sur l'azote, d'une part, et en la mise en oeuvre de techniques originales pour mesurer le deplacement de Knight de l'azote et les

Saddle-Point Rotational States from Resonance Fission of Oriented Nuclei; Etats Rotationnels a l'Etranglement Resultant de la Fission, par Neutrons de Resonance, de Noyaux Orientes; 0412 0420 0410 0429 0410 0422 0415 041b 042c 041d 042b 0415 0421 041e 0421 0422 041e 042f 041d 0418 042f 0421 0415 0414 041b 041e 0412 041e 0419 0422 041e 0427 K 0418 0412 0420 0415 0417 0423 041b 042c 0422 0410 0422 0415 0420 0415 0417 041e 041d 0410 041d 0421 041d 041e 0413 041e 0414 0415 041b 0415 041d 0418 042f 041e 0420 0418 0415 041d 0422 0418 0420 041e 0412 0410 041d 041d 042b 0425 042f 0414 0415 0420 ; Estados Rotacionales en el Punto de Estrangulacion Debidos a la Fision por Resonancia de Nucleos Orientados

Energy Technology Data Exchange (ETDEWEB)

Dabbs, J. W.T.; Walter, F. J.; Parker, G. W. [Oak Ridge National Laboratory, Oak Ridge, TN (United States)

1965-07-15

consistent with other data such as the variation of peak-to-valley ratio of Faler and Tromp; thus the rather strong indication that J(0.3 eV) {ne} J(1.14 eV) should not yet be accepted as conclusive. Further measurements are in progress. (author) [French] Il est possible d'aligner des noyaux des actinides U, Np et Pu dans les composes XO{sub 2}Rb(NO{sub 3}){sub 3} par interaction du moment quadrupolaire du noyau avec le gradient du champ electrique du cristal, en refroidissant tout simplement le monocristal interessant. Un alignement de ce genre correspond a une distribution angulaire non uniforme, dans l'espace, de l'axe de symetrie du noyau compose, qui reflete en premier lieu la valeur de K. Si l'on suppose que les fragments presentent cette meme distribution, on arrive a une methode qui permet d'etablir le nombre quantique-K a l'etranglement. Des experiences faites a Oak Ridge sur des noyaux alignes de {sup 233}U et de {sup 235}U a 1,2 Degree-Sign K et avec des neutrons thermiques ont deja fait l'objet d'articles dans des revues. Depuis, ces experiences ont ete etendues aux energies des neutrons de resonance et a des temperatures de l'ordre de 0,5 Degree-Sign K. Faite conjointement avec des determinations directes (a l'aide de neutrons polarises et de noyaux polarises) des valeurs de J associees a chaque resonance, la nouvelle serie d'experiences permet de se faire une idee beaucoup plus exacte du nombre et de la nature des voies de fission disponibles; il s'agit la de questions qui se posent depuis longtemps en matiere dcfission. Dans {sup 235}U, une anisotropie des fragments de fission approchant le maximum possible a ete relevee pour les resonances de 1,14 et 8,8 eV, avec le signe contraire de celui qui avait ete trouve anterieurement pour les particules alpha. En outre, une diminution considerable de l'anisotropie a ete observee pour les energies neutroniques dans le voisinage de la resonance bien connue de 0,3 eV. En l'absence de renseignements directs sur les

Industrial treatment of solutions of fission products. Separation of caesium-137; Traitement industriel de solutions de produits de fission. Separation du cesium-137

Energy Technology Data Exchange (ETDEWEB)

Fisher, C; Raggenbass, A [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Two types of chemical treatment can be considered for the manufacture of solid sources for industrial uses from fission product solutions remaining after plutonium extraction: a) concentration of the solution and preparation of solid sources from the bulk material, without separation, b) separation of one or several fission products from which the sources are made. Examination of the radio-chemical composition of the mixture of fission products that will be available from the Marcoule reactors (G1, G2 and G3) shows that caesium-137 accounts for 30 per cent of the {gamma} energy available immediately after the plutonium separation, 70 per cent two years after and 100 per cent after five years. There is practically no advantage in making sources from bulk fission products, since the separation of caesium-137 is no more complicated and yet it results in a material with more potential uses. The separation of caesium-137 by a method based on the standard phospho-tungstate precipitation method has been considered. Previously, the precipitated caesium phospho-tungstate was dissolved and caesium was recovered from the solution by cation-exchange or by removal of phosphate and tungstate ions by anion-exchange. A study has now been made, of the metathesis of caesium phospho-tungstate to barium phosphate and tungstate by the action of barium hydroxide, the caesium being obtained in solution as the hydroxide. The advantages of this new procedure are: - greater decontamination of caesium-137 without further purification, - possibility of direct transformation to caesium sulphate, - general simplification of the procedure and, consequently, of the equipment. (author) [French] Deux types de traitement chimique peuvent etre envisages pour amener a l'etat de sources solides utilisables industriellement les produits de fission contenus dans les solutions residuaires de l'extraction du plutonium. Ces traitements sont les suivants: a) concentration des solutions et confection de

Industrial treatment of solutions of fission products. Separation of caesium-137; Traitement industriel de solutions de produits de fission. Separation du cesium-137

Energy Technology Data Exchange (ETDEWEB)

Fisher, C.; Raggenbass, A. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Two types of chemical treatment can be considered for the manufacture of solid sources for industrial uses from fission product solutions remaining after plutonium extraction: a) concentration of the solution and preparation of solid sources from the bulk material, without separation, b) separation of one or several fission products from which the sources are made. Examination of the radio-chemical composition of the mixture of fission products that will be available from the Marcoule reactors (G1, G2 and G3) shows that caesium-137 accounts for 30 per cent of the {gamma} energy available immediately after the plutonium separation, 70 per cent two years after and 100 per cent after five years. There is practically no advantage in making sources from bulk fission products, since the separation of caesium-137 is no more complicated and yet it results in a material with more potential uses. The separation of caesium-137 by a method based on the standard phospho-tungstate precipitation method has been considered. Previously, the precipitated caesium phospho-tungstate was dissolved and caesium was recovered from the solution by cation-exchange or by removal of phosphate and tungstate ions by anion-exchange. A study has now been made, of the metathesis of caesium phospho-tungstate to barium phosphate and tungstate by the action of barium hydroxide, the caesium being obtained in solution as the hydroxide. The advantages of this new procedure are: - greater decontamination of caesium-137 without further purification, - possibility of direct transformation to caesium sulphate, - general simplification of the procedure and, consequently, of the equipment. (author) [French] Deux types de traitement chimique peuvent etre envisages pour amener a l'etat de sources solides utilisables industriellement les produits de fission contenus dans les solutions residuaires de l'extraction du plutonium. Ces traitements sont les suivants: a) concentration des solutions et

A project for storing the radioactive sludges from Marcoule in the soil (1960); Une solution de stockage dans le sol des boues radioactives de Marcoule (1960)

Energy Technology Data Exchange (ETDEWEB)

Cohen, P; Gailledreau, C [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

A study of the feasibility of storing radioactive sludges in the soil. Special attention is paid to the case of the Marcoule plant, producing three kinds of sludges. The movement of the different fission products is given. (author) [French] Etude de la possibilite de stocker dans le sol des boues radioactives. Le cas de la station de traitement des effluents de Marcoule, produisant trois types de boues, est etudie plus specialement. Le mouvement des divers produits de fission est precise. (auteur)

Comparison of the Economic Aspects of the Treatment and Storage of Fission Products from Installations Processing Irradiated Natural Uranium; Aspects Economiques Compares du Traitement et du Stockage des Produits de Fission Issus des Usines de Traitement de l'Uranium Naturel Irradie; Sravnitel'nye ehkonomicheskie aspekty obrabotki i khraneniya produktov deleniya, poluchaemykh na zavodakh po pererabotke obluchennogo prirodnogo urana; Aspectos Economicos Comparados del Tratamiento y del Almacenamiento de los Productos de Fision que Salen de las Plantas de Tratamiento de Uranio Natural Irradiado

Energy Technology Data Exchange (ETDEWEB)

Thiriet, L.; Lesur, P.; Giraud, R. [Commissariat a l' Energie Atomique, Paris (France); Wanlin, J. [Societe Saint-Gobain Techniques Nouvelles, Paris (France)

1966-02-15

The paper summarizes the main policies adopted for the management of fission product effluents and briefly describes the essential technical features of the stainless steel storage installations (in acid medium) used in France, giving a breakdown of the costs involved. The dependence of these costs on the activity of the solutions stored and on their heat release is shown. The second part of the paper discusses the cost of storage in terms of feasible tank size. The optimum size for such tanks and the rate at which they are placed in service are determined in relation to the characteristics of the fission products to be stored and to the respective capacities of the installations for processing irradiated natural uranium. It is shown that although storage costs depend on the assumptions made regarding the useful life of installations, rates of interest and operating costs, optimum policy decisions (as to size and rate of entry into service) are independent of these assumptions, being determined solely by the variation in the cost of tanks, according to size. These are the factors which enter into the optimized cost of storing these effluents indefinitely. In the third part, this method of indefinite storage is compared with other possibilities of fission product management, e.g. vitrification and separation of Cs and Sr. The paper discusses the economics of the various methods and summarizes some possible long-term solutions. (author) [French] Apres avoir rappele les principales politiques de gestion le plus souvent envisagees pour les produits de fission, le memoire decrit sommairement les caracteristiques techniques essentielles des installations de stockage en acier inoxydable (en milieu acide) utilisees en France et la structure des couts de ces installations. U montre la sensibilite de ces couts a l'activite des solutions stockees et a leur degagement de chaleur. Dans une deuxieme partie, les auteurs examinent leur cout de stockage, selon la taille des

Fission theory and actinide fission data

Energy Technology Data Exchange (ETDEWEB)

Michaudon, A.

1975-06-01

The understanding of the fission process has made great progress recently, as a result of the calculation of fission barriers, using the Strutinsky prescription. Double-humped shapes were obtained for nuclei in the actinide region. Such shapes could explain, in a coherent manner, many different phenomena: fission isomers, structure in near-threshold fission cross sections, intermediate structure in subthreshold fission cross sections and anisotropy in the emission of the fission fragments. A brief review of fission barrier calculations and relevant experimental data is presented. Calculations of fission cross sections, using double-humped barrier shapes and fission channel properties, as obtained from the data discussed previously, are given for some U and Pu isotopes. The fission channel theory of A. Bohr has greatly influenced the study of low-energy fission. However, recent investigation of the yields of prompt neutrons and γ rays emitted in the resonances of {sup 235}U and {sup 239}Pu, together with the spin determination for many resonances of these two nuclei cannot be explained purely in terms of the Bohr theory. Variation in the prompt neutron and γ-ray yields from resonance to resonance does not seem to be due to such fission channels, as was thought previously, but to the effect of the (n,γf) reaction. The number of prompt fission neutrons and the kinetic energy of the fission fragments are affected by the energy balance and damping or viscosity effects in the last stage of the fission process, from saddle point to scission. These effects are discussed for some nuclei, especially for {sup 240}Pu.

Study of the retention of fission products by a few common minerals. Application to the treatment of medium activity effluents (1962); Etude de la retention des produits de fission par quelques mineraux usuels. Application aux traitements d'effluents de moyenne activite specifique (1962)

Energy Technology Data Exchange (ETDEWEB)

Auchapt, J M [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

1962-07-01

The conditions in which strontium is fixed on calcite (the object of the Geneva report P/395 - USA - 1958) are more closely studied and the work is extended to five fission products present in the effluents, and to 17 common rocks and minerals. Although as it turns out this fixation is not suitable as a method of treating the S.T.E. effluents (i.e. those from the Effluent Treatment plant at Marcoule), the study shows that all the crystals considered are strongly contaminated by simple contact with the effluents. (author) [French] Les conditions de fixation du strontium sur la calcite (objet du rapport de Geneve P/395 - USA - 1958) sont approfondies et l'etude est etendue aux cinq produits de fission presents dans les effluents et a 17 roches et minerais courants. Bien qu'en definitive cette fixation se revele inutilisable comme procede de traitement d'effluents S.T.E. (Station de Traitement des Effluents, Marcoule), l'etude montre que tous les cristaux consideres se contaminent fortement par simple contact avec les effluents. (auteur)

Can-rupture detection in gas-cooled nuclear reactors; La detection des ruptures de gaine dans les piles nucleaires refroidies par gaz

Energy Technology Data Exchange (ETDEWEB)

Roguin, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

Can-rupture detection (DRG) is one important aspect of pile safety, more particularly so in the case of gas-cooled reactors. A rapid and sure detection constitutes also an improvement as far as the efficiency of electricity-producing nuclear power stations are concerned. Among the numerous can-rupture detection methods, that based on the measurement of the concentration of short-lived fission gases in the heat-carrying fluid has proved to be the most sensitive and the most rapid. A systematic study of detectors based on the electrostatic collection of the daughter products of fission gases has been undertaken with a view to equip the reactors EL 2, G 3, EDF 1, EDF 2 and EDF 3, the gas loops of PEGASE and EL 4. The different parameters are studied in detail in order to obtain a maximum sensitivity and to make it possible to construct detection devices having the maximum operational reliability and requiring the minimum maintenance. The primary applications of these devices are examined in the case of the above-mentioned reactors. (author) [French] La Detection des Ruptures de Gaines (D. R. G.) est un aspect important de la securite des piles et plus particulierement des piles refroidies par un gaz. Une detection rapide et sure constitue aussi un element d'amelioration du rendement des centrales nucleaires productrices d'energie electrique. Parmi les nombreuses methodes de detection des ruptures de gaines, la mesure de la concentration dans le fluide caloporteur des gaz de fission a vie courte s'est revelee comme la plus sensible et la plus rapide. Une etude systematique des detecteurs a collection electrostatique des descendants des gaz de fission a ete entreprise en vue d'equiper les piles EL 2, G 3, EDF 1, EDF 2 et EDF 3, les boucles a gaz de la pile Pegase et la pile EL 4. Les divers parametres sont etudies en detail pour obtenir une sensibilite maximum et permettre la realisation de dispositifs de detection ayant le maximum de securite de fonctionnement et le

Can-rupture detection in gas-cooled nuclear reactors; La detection des ruptures de gaine dans les piles nucleaires refroidies par gaz

Energy Technology Data Exchange (ETDEWEB)

Roguin, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

Can-rupture detection (DRG) is one important aspect of pile safety, more particularly so in the case of gas-cooled reactors. A rapid and sure detection constitutes also an improvement as far as the efficiency of electricity-producing nuclear power stations are concerned. Among the numerous can-rupture detection methods, that based on the measurement of the concentration of short-lived fission gases in the heat-carrying fluid has proved to be the most sensitive and the most rapid. A systematic study of detectors based on the electrostatic collection of the daughter products of fission gases has been undertaken with a view to equip the reactors EL 2, G 3, EDF 1, EDF 2 and EDF 3, the gas loops of PEGASE and EL 4. The different parameters are studied in detail in order to obtain a maximum sensitivity and to make it possible to construct detection devices having the maximum operational reliability and requiring the minimum maintenance. The primary applications of these devices are examined in the case of the above-mentioned reactors. (author) [French] La Detection des Ruptures de Gaines (D. R. G.) est un aspect important de la securite des piles et plus particulierement des piles refroidies par un gaz. Une detection rapide et sure constitue aussi un element d'amelioration du rendement des centrales nucleaires productrices d'energie electrique. Parmi les nombreuses methodes de detection des ruptures de gaines, la mesure de la concentration dans le fluide caloporteur des gaz de fission a vie courte s'est revelee comme la plus sensible et la plus rapide. Une etude systematique des detecteurs a collection electrostatique des descendants des gaz de fission a ete entreprise en vue d'equiper les piles EL 2, G 3, EDF 1, EDF 2 et EDF 3, les boucles a gaz de la pile Pegase et la pile EL 4. Les divers parametres sont etudies en detail pour obtenir une sensibilite maximum et permettre la realisation de dispositifs de detection ayant le maximum de securite de

Volatility of ruthenium during vitrification operations on fission products. part 1. nitric solutions distillation concentrates calcination. part 2. fixation on a steel tube. decomposition of the peroxide; Volatilite du ruthenium au cours des operations de vitrification des produits de fission. 1. partie distillation des solutions nitriques calcination des concentrats 2. partie fixation sur un tube d'acier decomposition du peroxyde

Energy Technology Data Exchange (ETDEWEB)

Ortins de Bettencourt, A.; Jouan, A. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-07-01

During vitrification of fission product solutions, a high percentage of the ruthenium initially present in these solutions in the form of nitrosyl-ruthenium nitrates is volatilized with the production of the peroxide which itself is decomposed to ruthenium dioxide. The aim of this work has been to study the volatility of the ruthenium during the vitrification processes. During the distillation of the nitric solutions, we have studied in particular the influence on the volatility of the temperature , of the chemical form in which the ruthenium is introduced, of the bubbling of a gas through the solution, of the nitric concentration and of the nitrate concentration. During the calcination, we have observed the influence of the temperature, of the time, of the flow rate and of the nature of the carrier gas, as well as of the action of the ruthenium bi-oxide and the iron oxide on the volatility of the ruthenium. Part 2. This report deals with the study of the thermal decomposition of ruthenium peroxide, RuO{sub 4}, and its deposition on steel tubing. After a brief bibliographic review of the various properties of this substance, a study is made, in the first part, of its deposition on a steel tube. In order to do this, we pass a gas current containing RuO{sub 4} marked with {sup 106}Ru through a stainless steel tube subjected to a temperature gradient which decreases in the direction of the gas flow. The temperature at which RuO{sub 4} is deposited or is fixed on the tube is determined and the influence of the flow rate on this deposit is studied. In the second part, an attempt has been made to study by a static method the kinetics of the decomposition reaction of ruthenium peroxide to give the dioxide: RuO{sub 4} {yields} RuO{sub 2} + O{sub 2}. To do this, we have tried to introduce gaseous RuO{sub 4} into a container placed in an electric oven, and to follow the reaction by {gamma} counting. (author) [French] Au cours de la vitrification des solutions de produits de

Volatility of ruthenium during vitrification operations on fission products. part 1. nitric solutions distillation concentrates calcination. part 2. fixation on a steel tube. decomposition of the peroxide; Volatilite du ruthenium au cours des operations de vitrification des produits de fission. 1. partie distillation des solutions nitriques calcination des concentrats 2. partie fixation sur un tube d'acier decomposition du peroxyde

Energy Technology Data Exchange (ETDEWEB)

Ortins de Bettencourt, A; Jouan, A [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-07-01

During vitrification of fission product solutions, a high percentage of the ruthenium initially present in these solutions in the form of nitrosyl-ruthenium nitrates is volatilized with the production of the peroxide which itself is decomposed to ruthenium dioxide. The aim of this work has been to study the volatility of the ruthenium during the vitrification processes. During the distillation of the nitric solutions, we have studied in particular the influence on the volatility of the temperature , of the chemical form in which the ruthenium is introduced, of the bubbling of a gas through the solution, of the nitric concentration and of the nitrate concentration. During the calcination, we have observed the influence of the temperature, of the time, of the flow rate and of the nature of the carrier gas, as well as of the action of the ruthenium bi-oxide and the iron oxide on the volatility of the ruthenium. Part 2. This report deals with the study of the thermal decomposition of ruthenium peroxide, RuO{sub 4}, and its deposition on steel tubing. After a brief bibliographic review of the various properties of this substance, a study is made, in the first part, of its deposition on a steel tube. In order to do this, we pass a gas current containing RuO{sub 4} marked with {sup 106}Ru through a stainless steel tube subjected to a temperature gradient which decreases in the direction of the gas flow. The temperature at which RuO{sub 4} is deposited or is fixed on the tube is determined and the influence of the flow rate on this deposit is studied. In the second part, an attempt has been made to study by a static method the kinetics of the decomposition reaction of ruthenium peroxide to give the dioxide: RuO{sub 4} {yields} RuO{sub 2} + O{sub 2}. To do this, we have tried to introduce gaseous RuO{sub 4} into a container placed in an electric oven, and to follow the reaction by {gamma} counting. (author) [French] Au cours de la vitrification des solutions de produits de

Measurement of the production of K{sup +} mesons by protons in nuclei (1960); Mesure de la production des mesons K{sup +} par des protons dans les noyaux (1960)

Energy Technology Data Exchange (ETDEWEB)

Teiger, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1960-07-01

K{sup +} mesons produced by the internal proton beam of Saturne have been identified by means of scintillation and Cerenkov counters. The production cross sections are given per target nucleus measured at a laboratory angle of 35 deg. as well as the cross section relative to {pi}{sup +} mesons of the same momentum for: - incident protons of kinetic energy between 1.3 and 2.8 GeV, - targets of C, Cu and Pb, - K{sup +} produced with kinetic energies between 0.45 and 0.65 GeV. From these results we have tried to deduce the importance of indirect production by intermediate {pi} mesons with respect to direct production by proton-nucleon collisions. (author) [French] Au moyen de detecteurs a scintillations et a rayonnement Cerenkov, on a identifie les mesons lourds K{sup +} produits par les protons du faisceau interne de 'Saturne'. On donne les sections efficaces de production, par noyau cible, mesurees a 35 deg. dans le laboratoire, ainsi que les sections efficaces relatives par rapport aux mesons {pi}{sup +} de meme impulsion pour: - des protons incidents d'energie cinetique entre 1,3 GeV et 2,8 GeV, - des cibles de C, de Cu et de Pb, - des K{sup +} produits avec des energies cinetiques entre 0,45 et 0,65 GeV. De ces resultats, on a essaye de deduire l'importance de la production indirecte, par mesons {pi} intermediaires, par rapport a la production directe dans un choc proton-nucleon. (auteur)

Study of radio-active ions in the atmosphere; Etude des ions radioactifs de l'atmosphere

Energy Technology Data Exchange (ETDEWEB)

Renoux, A [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1965-01-01

A comparative study is made of active, deposits of radon and thoron in suspension in the atmosphere by means of {alpha} radiation counting, using ZELENY tubes, scattering equipment, filter papers or membranes. It has been possible to show the existence of small and large ions which are negative and positive, as well as of neutral radio-active nuclei; their properties are studied. A theoretical interpretation of the results is presented. The average content of radon (using the Ra A concentration) and of Th B in the air has been determined. The radioactive equilibrium between radon and its daughter products in atmospheric air are examined. The techniques developed for active radon and thoron deposits are applied to the study of artificial radio-activity, the analyses being carried out by means of {gamma} spectrometry. (author) [French] On effectue une etude comparative entre les depots actifs du radon et du thoron en suspension dont l'atmosphere a l'aide de comptages de rayonnement {alpha}, en utilisant des tubes de ZELENY, une batterie de diffusion, des papiers filtres ou des membranes. On met ainsi en evidence la presence de petits et gros ions negatifs et positifs, ainsi que celle de noyaux neutres radioactifs, et on etudie leurs proprietes. Une Interpretation theorique des resultats obtenus est developpee. On determine la teneur moyenne de l'air en radon (a partir de la concentration en Ra A) et en Th B. L'equilibre radioactif entre le radon et ses descendants, dans l'air atmospherique, est examine. Les Techniques mises au point pour les depots actifs du radon et du thoron sont appliquees a l'etude de la radioactivite artificielle, les depouillements s'effectuant par spectrometrie {gamma}. (auteur)

Burst slug detection system in french power reactors (1961); La detection des ruptures de gaines dans les reacteurs de puissance francais (1961)

Energy Technology Data Exchange (ETDEWEB)

Megy, J; Roguin, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

Gas samples are taken from the channels of the reactor and the short lived fission products are electrostatically collected to be analysed by a phosphor and photomultiplier system. The electrostatic collection and rotating electrode detector is described and its main uses exposed. Experience has shown the interest of measuring the evolution of fission products activities and not their absolute value only. In this way, data processing equipment have been designed and adapted to the detection apparatus. The system developed and realized for the G-l - G-2 - G-3 - EDF-1 - EDF-2 reactors are compared. (authors) [French] Un prelevement de gaz est effectue dans les canaux du reacteur et les produits de fission a vie courte sont collectes electrostatiquement pour etre analyses par un ensemble scintillateur-photomultiplicateur. Le detecteur a collection electrostatique et electrode tournante est decrit et ses applications principales sont exposees. L'experience a montre l'interet de mesurer l'evolution des activites en produits de fission et non seulement leur valeur absolue. D'ou le developpement d'ensembles de traitement des informations associes aux chaines de detection. Comparaison des realisations sur les reacteurs G-l - G-2 - G-3 - EDF-1 et EDF-2. (auteurs)

Radiobiological researches on Dianthus caryophyllus L. carnation chimeras; Recherches radiobiologiques sur des chimeres d'oeillet Dianthus caryophyllus L.

Energy Technology Data Exchange (ETDEWEB)

Pereau-Leroy, Pierre

1975-04-12

du corpus. Cependant, a la suite de l'irradiation de la chimere triple, on observe, sans pouvoir encore l'expliquer, une transmission de la radiosensibilite de la T{sub 2} au corpus mais pas a la T{sub 1}. Par contre, la difference de radiosensibilite entre les cellules des zones axiales (siege des necroses) et laterales (anneau initial) dans le meristeme caulinaire, pourrait s'expliquer par la difference de volume nucleaire, les gros noyaux des cellules de la zone axiale subissant davantage de degats du fait de la plus gra nde quantite d'energie absorbee. La phase du cycle mitotique dans laquelle se trouvent les noyaux ne semble pas determiner la radiosensibilite des cellules des differentes zones. Les autotetraploides d'oeillet obtenus par traitement a la colchicine sont plus radiosensibles que les formes diploides correspondantes, alors que la polyploidie est reputee conferer une certaine radioresistance chez d'autres especes. Une explication partielle de cette divergence est basee sur la difference de volume chromosomique moyen. Chez les polyploides naturels, le volume chromosomique diminue avec l'augmentation du nombre de genomes; le volume chromosomique moyen etant plus petit, les radiolesions sont moindres chez les polyploides que chez les diploides en raison de la plus faible quantite d'energie absorbee. Chez nos autotetraploides d'oeillet, le volume chromosomique moyen est le meme que celui des diploides, la radiosensibilite des deux types de plantes devrait donc, dans cette hypothese, etre la meme. Il reste a rechercher les causes de la plus grande radiosensibilite des tetraploides que l'on retrouve egalement chez les levures. (auteur)

Validity of the electrical model representation of the effects of nuclear magnetic resonance (1961); Validite de la representation par modele electrique des effets de resonance magnetique nucleaire (1961)

Energy Technology Data Exchange (ETDEWEB)

Bonnet, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1961-07-01

When studying the behaviour of a magnetic resonance transducer formed by the association of an electrical network and of a set of nuclear spins, it is possible to bring about a representation that is analytically equivalent by means of an entirely electrical model, available for transients as well as steady-state. A detailed study of the validity conditions justifies its use in most cases. Also proposed is a linearity criterion of Bloch's equations in transient state that is simply the prolongation of the well-known condition of non-saturation in the steady-state. (author) [French] L'etude du comportement d'un transducteur a resonance magnetique forme de l'association d'un reseau electrique et d'un ensemble de noyaux dotes de spin, montre qu'il est possible d'en deduire une representation analytiquement equivalente au moyen d'un modele entierement electrique utilisable pour un regime transitoire aussi bien que pour un regime permanent. Une etude detaillee des conditions de validite permet d'en justifier l'emploi dans la majorite des cas. On propose enfin un critere de linearite des equations de Bloch en regime transitoire, qui constitue un prolongement de la condition connue de non-saturation en regime stationnaire. (auteur)

Detection of burst cans in the reactors cooled by gaseous phase; Detection des ruptures de gaine dans les reacteurs refroidis par phase gazeuse

Energy Technology Data Exchange (ETDEWEB)

Labeyrie, J; Roguin, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

In a nuclear reactor including the bars or plates cooled by a gaseous fluid, burst risks to occur in the sheath assuring the tightness separation between the cooling gas and the fissile materials. It is necessary to be able to detect the formation of these cracks as possible in order to avoid all risk of fission products release or any reaction of uranium to the contact of the refrigerating gas. It is however the increase of the radioactivity in the cooling gas due to the scattering of the fission products that permits to signal the apparition of a crack or to follow its evolution. It is possible to detect cracks of the order of the square millimeter. In this report, we will detail the principle and the realization of a device used for the surveillance of a natural uranium reactor cooled by air circulation. (M.B.) [French] Dans un reacteur nucleaire comportant des barres ou des plaques refroidies par un fluide gazeux des fissures risquent de se produire dans les gaines assurant la separation etanche entre le gaz de refroidissement et les materiaux fissiles. II est necessaire de pouvoir detecter la formation de ces fissures des que possible afin d'eviter tout risque de liberation de produits de fission ou de reaction de l'uranium au contact du gaz refrigerant. C'est cependant l'augmentation de la radioactivite du gaz de refroidissement due a la dispersion des produits de fission qui permet de signaler l'apparition d'une fissure ou de suivre son evolution. On peut ainsi detecter des fissures de l'ordre du millimetre carre. Dans ce rapport, nous detaillerons le principe et la realisation d'un appareil utilise pour la surveillance d'un reacteur a uranium naturel refroidi par circulation d'air. (M.B.)

Photofission of Even-Even Nuclei Near the Threshold; Photofission des Noyaux Pair-Pair au Voisinage du Seuil; 0424 041e 0422 041e 0414 0415 041b 0415 041d 0418 0415 0427 0415 0422 041d 041e - 0427 0415 0422 041d 042b 0425 042f 0414 0415 0420 0412 0411 041b 0418 0417 0418 041f 041e 0420 041e 0413 0410 ; Fotofision de los Nucleos Par-Par Cerca del Umbral

Energy Technology Data Exchange (ETDEWEB)

Rabotnov, N. S.; Smirenkin, G. N.; Soldatov, A. C.; Usachev, L. N. [Fiziko-Energeticheskij Institut, Obninsk, SSSR (Russian Federation); Kapica, S. P.; Cipenjuk, I. Ju.M. [Institut Fizicheskih Problem, Moskva, SSSR (Russian Federation)

1965-07-15

-Than-Or-Equal-To 6 MeV, les fissions liees a l'absorption quadripolaire des photons contribuent faiblement a la section efficace totale de fission. On montre pour la premiere fois que conformement aux previsions theoriques fondees sur le modele des voies de fission elabore par A. Bohr, le poids relatif de la composante quadripolaire ne joue un role important que lorsque les energies d'excitation sont inferieures au seuil de fission 'bipolaire' correspondant a la voie lv(K = 0). Ainsi, dans la distribution angulaire des fragments de photofission de {sup 238}U, lorsque le spectre du rayonnement de freinage presente une energie maximum E{sub max} = 5,4 MeV et 5,2 MeV, la contribution de la composante quadripdlaire a la section efficace totale de photofission s'eleve respectivement a 10 et 43%, alors-que pour E{sub max} > 6 MeV, elle ne depasse pas 3 a 3,5%. Parmi les noyaux fissiles Selon le mode pair-pair, l'effet de fission 'quadripolaire' apparaft le plus nettement pour {sup 240}Pu et moins nettement pour {sup 232}Th. Grace aux resultats de ces mesures on peut evaluer le rapport entre les sections efficaces partielles de photoabsorption dans les noyaux lourds. Les auteurs examinent la question de la parite de l'etat fondamental de {sup 239}Pu en tenant compte des resultats obtenus par les mesures de la distribution angulaire des fragments de photofission de {sup 239}Pu, qui revele une modification du signe de l'anisotropie conformement aux previsions theoriques relatives aux voies K = 1/2 et 3/2. (author) [Spanish] En la memoria se presentan los resultados de la medicion de las distribuciones angulares de los fragmentos formados en la fotofision del {sup 238}U, {sup 232}Th, {sup 240}Pu y {sup 239}Pu, en un haz de rayos gamma de frenado. Como fuente se utilizo el microtron de 12 MeV del Instituto de Problemas Fisicos de la Academia de Ciencias de la Union Sovietica. El empleo de esta fuente permitio medir la distribucion angular en el intervalo de energias gamma, importante pero aun

Instruments used to measure or check {alpha}, {beta}, {gamma} activity and neutron emission in the course of processing ore or irradiated fuel; Appareils de mesure ou de controle {alpha}, {beta}, {gamma}, n, des circuits des usines de traitement du minerai ou du combustible irradie

Energy Technology Data Exchange (ETDEWEB)

Blanc, A; Brunet, M; Kermagoret, M; Labeyrie, J; Roux, G; Vasseur, J; Weil, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-07-01

One of the methods checking ores in the course of treatment is the rapid quantitative determination of thorium. This measurement is carried out by means of a scintillation instrument which shows the {beta} and {alpha} coincidences of ThC and ThC'. The treatment of irradiated fuel is accompanied by a large number of radioactive checks relative to the performance of the fixation and elution operations of uranium in the ion exchangers, to the concentration of radioactivity of effluent sent from the plant into watercourses. The operations of fixation and elution of the uranium are checked automatically by an instrument which takes a sample of 5 cm{sup 3} of solution, evaporates it and measures its activity every 10 or 20 minutes. Plutonium concentrations are measured: - in the presence of strong {beta} {gamma} activities, by means of rotating cylinder detectors; - in the presence of weak {beta} {gamma} activities, by means of {alpha} detectors scanning a constant level liquid surface; - by means of fission chambers relatively insensitive to {gamma}. Fission product concentrations are measured by chambers, counters or scintillators, according to the amount of {gamma} activity present. Finally, the activity of effluent to be emptied into watercourses is checked by means of a scintillation instrument, which measures the {alpha} activity on the one hand, and on the other hand the {beta} {gamma} activity of residue from a 100 cm{sup 3} sample taken and evaporated in 20 minutes. (author) [French] Parmi les controles relatifs au minerai en cours de traitement, figure le dosage rapide de thorium. Cette mesure est realisee au moyen d'un appareillage a scintillation qui met en evidence la coincidence des emissions {beta} et {alpha} du ThC et du ThC'. Le traitement des combustibles irradies s'accompagne d'un grand nombre de controles radioactifs portant sur le fonctionnement des operations de fixation et d'elution de l'uranium dans les echangeurs d'ions, sur la concentration du

Determination by neutron activation of the uranium-235 concentration in uranium oxides; Determination par activation neutronique de la concentration d'uranium-235 dans des oxydes d'urane

Energy Technology Data Exchange (ETDEWEB)

May, S; Leveque, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Classical methods of measuring isotopic abundance have the disadvantage of being long and of requiring chemical separation. A non-destructive method of measuring the uranium-235 content is described. It is based on an overall measurement of the short lived fission product activity formed during a 15 s neutron irradiation. The precision is of the order {+-} 1.5 per cent for 20 per cent enriched samples. The error due to the contribution from fast fission is discussed in detail. (author) [French] Les methodes classiques de mesure de l'abondance isotopique presentent le gros inconvenient d'etre longues et de necessiter des separations chimiques. Nous exposons une methode non destructive de mesure de la concentration d'uranium-235. Elle est basee sur la mesure globale de l'activite des produits de fission de courte periode formes par une irradiation neutronique de 15 s de l'echantillon. La precision est de l'ordre de {+-} 1,5 pour cent pour des echantillons enrichis jusqu'a 20 pour cent. L'erreur a la contribution de la fission rapide est discutee en detail. (auteur)

Study of neutron resonances of barium and copper isotopes by the time-of-flight method at low energies (0 to 15 keV); Etude des resonances de neutrons pour les isotopes du baryum et du cuivre par la methode de temps-de-vol a basse energie (0-15 kev)

Energy Technology Data Exchange (ETDEWEB)

Chevillon-Pitollat, P L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-01-01

Resonance parameters of Cu (0-15 keV) and Ba (0-1000 eV) have been determined, using the time-of-flight method. Spin assignment (J = I{+-}1/2) being not possible with usual capture methods, the 'sum coincident' method was used in Ba study. A careful analysis of transmission curves including interference effects between levels of the same spin afforded to assign the J value to the most of Cu resonances. Strength function values (S{sub 0}) for those nuclei I = 3/2 confirm previous results obtained for other nuclei having the same value of spin I = 3/2, i.e. S{sub 0} (J = 2) {approx_equal} 2 S{sub 0} (J = 1). Another result has to be mentioned: total radiative width exhibits large fluctuation for different isotopes of Cu and Ba. Experimental methods, specially the 'sum coincidence' one are described in detail and results are discussed in view of theoretical predictions. (author) [French] Les parametres des resonances de {sup 63}Cu et {sup 65}Cu ont ete determines dans le domaine d'energie de zero a 15 keV et ceux du baryum dans le domaine de zero a 1000 eV. Les methodes habituelles de capture n'etant pas applicables pour trouver la valeur du spin S = I{+-}1/2, la methode 'somme coincidence' fut appliquee pour l'attribution de J aux resonances du baryum tandis qu'une analyse soigneuse des courbes de transmission, tenant compte en particulier des effets d'interference entre niveaux de meme spin permettait de determiner J pour la plupart des resonances du cuivre. Les resultats trouves pour ces differents noyaux de spin I = 3/2 confirment ceux deja trouves pour d'autres noyaux I = 3/2 c'est-a-dire que la valeur de la fonction densite S{sub 0} pour J 2 est deux fois celle pour J = 1. Un autre resultat interessant est la variation de la largeur radiative totale pour les isotopes du cuivre et du baryum. Les methodes experimentales surtout la methode 'somme coincidence' sont decrites en detail et les resultats compares aux predictions theoriques. (auteur)

Study of the propagation of fast neutrons in water, by Monte-Carlo methods; Etude de la propagation des neutrons rapides dans l'eau par des methodes de Monte-Carlo

Energy Technology Data Exchange (ETDEWEB)

Lafore, P; Lattes, R; Millot, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

We have studied the propagation in water of neutrons from mono-directional plane sources with energies ranging from 300 keV to 19,66 MeV, placed in an infinite water medium. The exact paths of a number of neutrons are determined, taking into account the microscopic sections, assuming that inelastic collisions of the neutrons on oxygen are absorptions, and neglecting the loss of energy by elastic collisions on oxygen. The neutron lifetimes have been made use of to study the propagation of neutrons from fission sources, Po-Be, Po-B and Ra-Be, as well as the reflection of fast neutrons on a semi-infinite water medium. We have taken complete account of the first collision in order to improve the precision of the results. The calculations were carried out by Mrs J. VASSEUR and Mr A. GUILLOU. (author)Fren. [French] Nous etudions la propagation dans l'eau des neutrons a partir de sources planes monodirectionnelles dont les energies sont repartis de 300 keV a 19,66 MeV, placees dans un milieu infini d'eau. Nous determinons les trajectoires exactes d'un certain nombre de neutrons en tenant compte des sections microscopiques, en supposant que les chocs inelastiques des neutrons sur l'oxygene sont des absorptions, et en negligeant la perte d'energie par chocs elastiques sur l'oxygene. Les vies de neutrons ont ete exploitees pour etudier la propagation des neutrons a partir de sources de fission, Po-Be, Po-B et Ra-Be, ainsi que la reflexion des neutrons rapides sur un milieu semi-infini d'eau. On a tenu compte integralement du premier choc pour ameliorer la precision des resultats. Les calculs ont ete effectues par Mme J. VASSEUR et M.A. GUILLOU. (auteur)

Delayed Neutrons and Photoneutrons from Fission Products; Neutrons Retardes et Photoneutrons Emis par des Produits de Fission; 0417 0410 041f 0410 0417 0414 042b 0412 0410 042e 0429 0418 0415 041d 0415 0419 0422 0420 041e 041d 042b 0418 0424 041e 0422 041e 041d 0415 0419 0422 0420 041e 041d 042b 041f 0420 041e 0414 0423 041a 0422 041e 0412 0414 0415 041b 0415 041d 0418 042f ; Neutrones Retardados y Fotoneutrones de los Productos de Fision

Energy Technology Data Exchange (ETDEWEB)

Amiel, S. [Soreq Nuclear Research Centre, Atomic Energy Commission, Yavne (Israel)

1965-07-15

photoneutron emission after fission represents the composite decay of the corresponding gamma- ray-emifting nuclides in the mixture of fission product chains. The gross photoneutron decay curves from both D{sub 2}O and beryllium have been resolved into nine groups with half-lives ranging from a few seconds to {approx}13 d. Each of these groups represents a complex composite of nuclides. Derailed information on the constituents of these groups is important for reactors in which fission products fractionation may take place and affect relative group abundances. Such information exists only for the longer-lived fission products whose properties and yields are well known, and where experimental results are in agreement with calculated values based on fission mass and charge distributions and decay schemes. The characterization of individual nuclides in the more complex short-lived groups is indeed a formidable task, but this information is of considerable practical and theoretical importance, and warrants further extensive study. (author) [French] Neutrons retardes: La plupart des etudes sur les neutrons retardes emis par des produits de fission impliquent l'analyse du comportement cinetique des systemes qui subissent une reaction de fission en chaine, l'analyse de la desintegration totale des neutrons (se resolvant en six groupes avec des periodes d'environ 0,2, 0,5, 2, 6, 22 et 55 s) et cettaines mesures des spectres de neutrons - ayant une energie comprise entre 0,1 et 1.2 MeV, avec des pics dans la gamme de 0,2 a 0,5 MeV. Des separations rapides des halogenes produits par fission ont mis en evidence la presence de sept isotopes ({sup 87,88,89,90}Br et {sup 137,138,139}I) et le dosage des gaz rares a permis d'identifier Kr (1,5 s) et Rb (6 s), comme precurseurs de neutrons retardes. Environ 80% des rendements totaux en neutrons retardes doivent etre attribues aux precurseurs ainsi identifies. A la suite de recherches theoriques, quelques dizaines de ces nucleides ont ete

The industrial production of fuel elements; La fabrication en france des elements combustibles

Energy Technology Data Exchange (ETDEWEB)

Boussard, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires; Nadal, J [Societe Industrielle de Combustible Nucleaire (SICN), 75 - Paris (France); Pellen, A [Compagnie pour l' Etude et la Realisation de Combustibles Atomiques (CERCA), 75 - Paris (France)

1964-07-01

indiquent pourquoi et comment l'on est passe de la gaine filee a la gaine usinee et mentionnent quelques caracteristiques de l'appareillage utilise ainsi que les controles effectues. Ils donnent egalement quelques indications sur la fabrication et l'usinage des chemises. Apres avoir rappele comment se presente en France a la mi-1964 l'industrie des combustibles nucleaires, les auteurs insistent sur les aspects economiques de la fabrication des elements combustibles. Ils montrent l'importance relative des investissements sur le prix de revient du combustible proprement dit, dont ils examinent ensuite les differentes pertes. Ils font une analyse du prix de revient de l'element combustible complet en tirant les enseignements actuels. Pour conclure les auteurs indiquent les points particuliers sur lesquels doit porter l'action a venir pour diminuer le cout d'une fabrication assez delicate, mais maintenant bien au point, et supputent le developpement de cette branche industrielle nouvelle. 2eme Partie - FABRICATION INDUSTRIELLE DES ELEMENTS COMBUSTIBLES POUR REACTEURS DU TYPE PISCINE: Les auteurs indiquent comment a ete elude en France le probleme de la fabrication industrielle des elements combustibles obtenue par laminage et les trois phases par lesquelles on est passe: 1 - Assemblage des plaques fabriquees aux U.S.A., 2 - Laminage des noyaux fabriques aux U.S.A. pour obtenir les plaques, 3 - Elaboration de l'alliage U.Al et fabrication des noyaux. Ils rappellent ensuite brievement les caracteristiques des differents elements combustibles actuellement fabriques. Ils decrivent ensuite les differents stades de l'elaboration en donnant des indications sur l'appareillage et en insistant sur l'importance des controles effectues a chaque stade. Pour finir ils examinent le developpement futur de ce type de fabrication, compte tenu des ameliorations prevues ou envisageables. (auteurs)

Neutron Dosimetry and Irradiation of Solids; Dosimetrie des neutrons et irradiation des solides

Energy Technology Data Exchange (ETDEWEB)

Perriot, G; Schmitt, A P [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

1962-07-01

Results of work at C.E.A. from 1958 to 1960 are reviewed. The possibilities offered by classical dosimetry methods are discussed. The tests which led to the utilization, for fast neutron dosimetry, of resistivity variations induced in solid W by such neutrons are described. Experimental W irradiation results led to a definition of neutron efficiency which describes the relations between neutron energy and their effects on materials. Possibilities offered by detectors which make use of radiation damage and are sensitive to neutrons at keV energies were explored. In other work, the principal French reactors were classified according to their ability to produce damage in materials such as W. (authors) [French] Dans ce rapport on a presente les resultats essentiels de travaux qui ont ete effectues de 1958 a 1980 par des chercheurs du CEA issus de differents services. En meme temps qu'une revue des possibilites offertes a l'epoque par les methodes classiques de dosimetrie (utilisation des detecteurs par activation), on a decrit les essais qui devaient permettre d'utiliser, a la dosimetrie les neutrons rapides, les variations de resistivite qu'ils creent dans un corps solide (tungstene). L'irradiation du tungstene a montre l'importance qu'il y avait a definir 'l'efficacite' des neutrons, c'est-a-dire leur aptitude plus ou moins grande, selon leur energie, a creer des defauts dans les materiaux. L'efficacite d'un emplacement d'irradiation se trouvant liee au spectre neutronique, on a vu les difficultes qu'il y avait a utiliser les detecteurs par activation des qu'on n'avait plus affaire a un spectre en 1/E ou de fission et on a pu entrevoir les possibilites offertes par les detecteurs utilisant la creation des defauts qui repondent a tous les neutrons d'energies, superieures a quelques keV. Enfin, on a classe les principaux types de Piles Francaises selon leur aptitude a creer plus ou moins rapidement des dommages dans des materiaux comme le tungstene. (auteur)

Measurement of the absolute values of cross-sections in neutron photoproduction (1962); Mesure de sections efficaces de photoproduction de neutrons en valeur absolue (1962)

Energy Technology Data Exchange (ETDEWEB)

Schuhl, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

The absolute values of photoneutrons production cross-sections for the case of intermediate and heavy nuclei (lanthanium, cerium, tantalum, gold, lead and bismuth) are determined with an error of 15 per cent. The results obtained agree with theories in which the giant resonance is explained by the collective motion of the protons against the neutrons. The effect of the nuclear deformation on the shape of the giant resonance is seen in the case of Ta{sup 181}, it will be possible to determine the quadrupole momenta of deformed nuclei with a good accuracy when we shall increase the statistics of measurements. (author) [French] Les sections efficaces de production de photoneutrons par divers noyaux moyens et lourds (lanthane, cerium, tantale, or, plomb et bismuth) sont determinees en valeur absolue avec une erreur relative de 15 pour cent. Les resultats obtenus s'accordent avec les theories qui interpretent la resonance geante par un mouvement collectif des protons par rapport aux neutrons. L'influence de la deformation du noyau sur la forme de la resonance geante est soulignee dans le cas de {sup 181}Ta pour lequel elle se decompose en deux pics. Une amelioration de la statistique des mesures permettra de determiner les moments quadrupolaires des noyaux deformes avec une meilleure precision. (auteur)

Treatment of solutions of fission products - Separation of caesium-137; Traitement des solutions de produits de fission - Separation du cesium-137; Obrabotka rastvorov produktov deleniya - Razdelenie tseziya-137; Tratamiento de soluciones de productos de fision - Separacion del cesio-137

Energy Technology Data Exchange (ETDEWEB)

Stiennon-Bovy, R [Centre d' Etude de l' Energie Nucleaire, Mol (Belgium); Gvion, R [Commission Israelienne de l' Energie Atomique, Tel-Aviv (Israel)

1962-01-15

For the industrial recovery of caesium-137 from solutions of fission products, the authors utilized the analytical method for determination of caesium by dipicrylamine, adapting it to use on an industrial scale and to the high level of the activities encountered. The process recommended makes it possible both to isolate caesium as a chloride and to recover the precipitation reagent, in one and the same operation. A basic method is suggested. The authors studied the effect of radiation on dipicrylamine and its compounds, this effect proving to be practically nil for solid compounds and negligible for their solutions. The entrainment of caesium by ammonia ion was also studied. The advantages of the proposed process are : high decontamination of the caesium, simple operation and free recycling fo the reagent, high yield for caesium recovery and for dipicrylamine, considerable concentration of caesium activity, operation at room temperature and possibility of continuous operation. By this process caesium can be recovered before certain fission products are eliminated. (author) [French] Pour la recuperation industrielle du cesium-137 des solutions de produits de fission, les auteurs ont adapte le procede analytique de dosage du cesium par la dipicrylamine a l'echelle industrielle et au niveau eleve des activites traitees. Le procede preconise permet en une seule operation d'isoler le cesium sous forme de chlorure et de recuperer aisement le reactif de precipitation; un schema de principe est propose. Les auteurs ont etudie l'effet des radiations sur la dipicrylamine et ses composes; cet effet s'avere pratiquement nul pour les composes solides et negligeable pour leurs solutions. L'entrainement du cesium par l'ion ammoniaque est etudie. Les avantages du procede propose sont la decontamination elevee du cesium, la simplicite du mode operatoire avec recyclage aise du reactif, le rendement eleve pour la recuperation du cesium et pour la dipicrylamine, une concentration

Contribution to the study of the thermal fission process for uranium 235 (1964); Contribution a l'etude du processus de la fission thermique de l'uranium 235 (1964)

Energy Technology Data Exchange (ETDEWEB)

Chahrtache, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-12-15

This report deals with the study of the distribution of the masses of the fragments produced by the disintegration of the U-236 nucleus, formed when a U-235 nucleus captures a thermal neutron. The experimental method chosen consists in the simultaneous measurement using p-n silicon junction detectors of the energies of the two fragments emitted in coincidence. This measurement is first made by a conditioned analysis of the energy of one of the fragments and then by a two dimensional analysis of the energies of the two fragments. Systematic results, are obtained concerning the distribution of the masses for different values of the total kinetic energy. The five structures appearing both for the mass distributions and for the energies of the fragments are studied and discussed. Generally speaking, our results are in agreement with those obtained by the time-of-flight method. (author) [French] Le present rapport a pour objet t'etude de la distribution des masses des fragments emis lors de la fission du noyau U-236, forme par capture d'un neutron thermique par un noyau d'U-235. La methode experimentale choisie consiste en la mesure simultanee - a l'aide de detecteurs a jonction p-n au silicium des energies des deux fragments emis en coincidence. Cette mesure est d'abord effectuee par analyse conditionnee de l'energie de l'un des fragments puis par analyse bidimensionnelle des energies des deux fragments. Des resultats systematiques sont obtenus sur les distributions des masses pour differentes valeurs de l'energie cinetique totale. Les 'structures fines' apparaissant tant sur les distributions des masses que sur celles des energies des fragments sont egalement etudiees et discutees. D'une facon generale, nos resultats sont en accord avec ceux obtenus par la methode du temps de vol. (auteur)

Fission 2009 4. International Workshop on Nuclear Fission and Fission Product Spectroscopy - Compilation of slides

International Nuclear Information System (INIS)

2009-01-01

This conference is dedicated to the last achievements in experimental and theoretical aspects of the nuclear fission process. The topics include: mass, charge and energy distribution, dynamical aspect of the fission process, nuclear data evaluation, quasi-fission and fission lifetime in super heavy elements, fission fragment spectroscopy, cross-section and fission barrier, and neutron and gamma emission. This document gathers the program of the conference and the slides of the presentations

Nuclear fission and neutron-induced fission cross-sections

Energy Technology Data Exchange (ETDEWEB)

James, G.D.; Lynn, J.E.; Michaudon, A.; Rowlands, J.; de Saussure, G.

1981-01-01

A general presentation of current knowledge of the fission process is given with emphasis on the low energy fission of actinide nuclei and neutron induced fission. The need for and the required accuracy of fission cross section data in nuclear energy programs are discussed. A summary is given of the steps involved in fission cross section measurement and the range of available techniques. Methods of fission detection are described with emphasis on energy dependent changed and detector efficiency. Examples of cross section measurements are given and data reduction is discussed. The calculation of fission cross sections is discussed and relevant nuclear theory including the formation and decay of compound nuclei and energy level density is introduced. A description of a practical computation of fission cross sections is given.

Nuclear fission and fission-product spectroscopy: 3. International workshop on nuclear fission and fission-product spectroscopy

International Nuclear Information System (INIS)

Goutte, Heloise; Fioni, Gabriele; Faust, Herbert; Goutte, Dominique

2005-01-01

The present book contains the proceedings of the third workshop in a series of workshops previously held in Seyssins in 1994 and 1998. The meeting was jointly organized by different divisions of CEA and two major international laboratories. In the opening address, Prof. B. Bigot, the French High Commissioner for Atomic Energy, outlined France's energy policy for the next few decades. He emphasized the continuing progress of nuclear fission in both technical and economic terms, allowing it to contribute to the energy needs of the planet even more in the future than it does today. Such progress implies a very strong link between fundamental and applied research based on experimental and theoretical approaches. The workshop gathered the different nuclear communities studying the fission process, including topics as the following: - nuclear fission experiments, - spectroscopy of neutron rich nuclei, - fission data evaluation, - theoretical aspects of nuclear fission, - and innovative nuclear systems and new facilities. The scientific program was suggested by an International Advisory Committee. About 100 scientists from 13 different countries attended the conference in the friendly working atmosphere of the Castle of Cadarache in the heart of the Provence. The proceedings of the workshop were divided into 11 sections addressing the following subject matters: 1. Cross sections and resonances (5 papers); 2. Fission at higher energies - I (5 papers); 3. Fission: mass and charge yields (4 papers); 4. Light particles and cluster emission (4 papers); 5. Spectroscopy of neutron rich nuclei (5 papers); 6. Resonances, barriers, and fission times (5 papers); 7. Fragment excitation and neutron emission (4 papers); 8. Mass and energy distributions (4 papers); 9. Needs for nuclear data and new facilities - I (4 papers); 10. Angular momenta and fission at higher Energies - II (3 papers); 11. New facilities - II (2 papers). A poster session of 8 presentations completed the workshop

Delayed fission

Energy Technology Data Exchange (ETDEWEB)

Hatsukawa, Yuichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1997-07-01

Delayed fission is a nuclear decay process that couples {beta} decay and fission. In the delayed fission process, a parent nucleus undergoes {beta} decay and thereby populates excited states in the daughter. If these states are of energies comparable to or greater than the fission barrier of the daughter, then fission may compete with other decay modes of the excited states in the daughter. In this paper, mechanism and some experiments of the delayed fission will be discussed. (author)

Delayed neutron detection in canning burst detection studies (1961); Etude sur la detection des neutrons differes en vue de la detection des ruptures de gaines (1961)

Energy Technology Data Exchange (ETDEWEB)

Perlini, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

This paper describes a theoretical and experimental study on the detection of neutrons present in the primary cooling circuit of a reactor cooled by heavy or light water, with a view to the installation of a canning burst detection unit. The concentration of background neutrons is first calculated, taking into account the neutrons from nitrogen 17 decay, and the photoneutrons produced by the decay of nitrogen 16 and sodium 24. The emission of delayed fission neutrons, originating at a given crack in the canning, has been estimated. Using the D{sub 2}O circuit of the pile EL-3, three units have been developed by means of which the following three types of detector may be compared: 1) BF{sub 3} proportional counter 2) Boron scintillator 3) Fission chamber Under the present experimental conditions the BF{sub 3} counter gave the best results. The influence on these detectors of the {gamma} flux, which in certain cases reaches 200 R/h, is analysed. Finally a calibration is carried out with an experimental crack of 30 mm{sup 2} of uranium exposed to a flux of 5.8 x 10{sup 13} n.cm{sup -2}.s{sup -1}. The sensitivity obtained with the BF{sub 3} counter during this test is 2 counts/s per mm{sup 2} of exposed uranium. (author) [French] Le present rapport est une etude theorique et experimentale sur la detection des neutrons presents dans le circuit primaire de refroidissement d'un reacteur refrigere par l'eau lourde ou l'eau legere, en vue d'une installation de detection de ruptures de gaines. On fait d'abord un calcul sur la concentration des neutrons de bruit de fond en tenant compte: des neutrons de decroissance de l'azote 17 et des photoneutrons produits par les decroissances de l'azote 16 et du sodium 24. L'emission des neutrons differes de fission, qui ont pour origine une fissure de gaine donnee, a ete evaluee. Utilisant le circuit D{sub 2}O de la pile EL3, trois installations ont ete mises au point permettant de comparer les trois types de detecteurs suivants: 1

Evaluation des conditions de germination des noyaux de Grewia ...

African Journals Online (AJOL)

personnel

31 janv. 2014 ... graines de G.coriacea afin de parvenir à un meilleur taux de germination naturellement médiocre. ... fourchettes) et comme matériau de ...... contre, les chocs thermiques par l'eau .... stockage et de la durée de chauffage.

Detection of radioactive gases in the CO{sub 2} cooling the reactors G 2 - G 3; Detection des gaz radioactifs dans le CO{sub 2} de refroidissement des piles G2 - G3

Energy Technology Data Exchange (ETDEWEB)

Pouthier, J; Rossi, J [Commissariat a l' Energie Atomique, Chusclan (France). Centre de Production de Plutonium de Marcoule

1968-07-01

The carbon dioxide cooling the reactors G2 - G3 contains activation gases and fission gases. It is of interest to know their concentration, for example to be able to deduce rapidly the norms which would have to be applied in the case of an incident in the circuit. Gas-phase chromatography is applied daily for carrying out analyses. The chromatogram has separate peaks due to tritium, argon 41, krypton 85 and the 133 and 135 isotopes of xenon. By integrating each peak it is possible to calculate the specific activity of each product. The construction of an apparatus for carrying out continuous measurements is under consideration. (authors) [French] Le gaz carbonique, refroidissant les reacteurs G2 - G3, contient des gaz d'activation et des gaz de fission. Il est interessant de connaitre leur teneur par exemple pour etre en mesure de deduire rapidement les normes qu'il y aurait lieu d'appliquer en cas d'incidents sur le circuit. La methode de chromatographie en phase gazeuse est employee quotidiennement pour faire des analyses. Le chromatogramme se presente sous forme de pics distincts dus au tritium, a l'argon 41, au krypton 85 et aux isotopes 133 et 135 du xenon. L'integration de chaque pic permet de calculer l'activite specifique de chaque compose. Il est envisage de construire un appareil pour des mesures en continu. (auteurs)

Coulomb fission and transfer fission at heavy ion collisions

International Nuclear Information System (INIS)

Himmele, G.

1981-01-01

In the present thesis the first direct evidence of nuclear fission after inelastic scattering of heavy ions (sup(183,184)W, 152 Sm → 238 U; 184 W → 232 Th; 184 W, 232 Th → 248 Cm) is reported. Experiments which were performed at the UNILAC of the Gesellschaft fuer Schwerionenforschung in Darmstadt show the observed heavy ion induced fission possesses significant properties of the Coulomb fission. The observed dependence of the fission probability for inelastic scattering on the projectile charge proves that the nuclear fission is mediated by the electromagnetic interaction between heavy ions. This result suggests moreover a multiple Coulomb-excitation preceding the fission. Model calculations give a first indication, that the Coulomb fission proceeds mainly from the higher β phonons. In the irradiation with 184 W the fission probability of 232 Th is for all incident energies about 40% smaller that at 238 U. The target dependence of the Coulomb fission however doesn't allow, to give quantitative statements about the position and B(E2)-values of higher lying β phonons. (orig./HSI) [de

Development of an experimental device based on the digitalization of the signal and dedicated to the characterization of fission fragments and prompt neutrons; Developpement d'un dispositif experimental base sur la digitalisation des signaux et dedie a la caracterisation des fragments de fission et des neutrons prompts emis

Energy Technology Data Exchange (ETDEWEB)

Varapai, N

2006-12-15

The present work demonstrates the application of the digital technique for nuclear measurements. This new technique is based on the digitalization of the signals from the detectors and has several advantages. This technique allows us to extract the maximum amount of information contained in the signal shape. In the case of an ionization chamber this signal contains the necessary information on the particle kinetic energy, emission angle and mass. This method has been implemented for measurements of promptly emitted fission neutrons in coincidence with fission fragments from {sup 252}Cf(sf). A double Frisch-grid ionization chamber is used as fission fragment detector. The promptly emitted neutrons are detected by a NE213 liquid scintillation detector. This work displays how delicate analysis of the digitalized signals permitted us to infer the mass and kinetic energy distributions of the fission fragments as well as the neutron energy spectrum and multiplicity. The outline of this thesis is as follows: Chapter 2 gives an overview of the experimental tools used in this work. Chapter 3 explains the analysis procedure of the digitalized anode signal from an ionization chamber. Chapter 4 gives a detailed explanation of the analysis procedure of the digitalized signal from a neutron detector. In Chapter 5 the analysis procedure of the fission fragment events in coincidence with neutrons is given.

Metabolism of fission products in man: Marshallese experience; Metabolisme des produits de fission radioactifs chez l'homme: donnees recueillies aux iles Marshall; Metabolizm radioaktivnykh produktov deleniya v organizme cheloveka. (dannye obsledovaniya zhite- lej marshal'skikh ostrovov); Metabolismo de productos de fision radiactivos en el hombre: datos obtenidos en los habitantes de las islas Marshall

Energy Technology Data Exchange (ETDEWEB)

Cohn, S. H. [Brookhaven National Laboratory, Upton, Long Island, NY (United States)

1963-02-15

The medical study of the Marshallese accidentally exposed to local fall-out in 1954 is unique in that; along with he Japanese fishermen study, it provides the only data existing on the metabolism of mixed fission products in a human population. Early diagnosis of the internal radioactive contamination was made by radiochemical analysis of the excreta of the exposed people and by radiochemical analysis of the tissues of animals simultaneously exposed. Initially, Sr{sup 89}, Ba{sup 140}, I{sup 131} and its shorter-lived daughters and a number of rare-earth elements contributed the major portion of the internal radiation dose. After a year, the principal radioisotopes were Sr{sup 90}, Cs{sup 137} and Zn{sup 65}. Subsequently these radionuclides and more recently, Co{sup 60}, have been measured periodically. Since 1958, the {gamma}-spectra of a number of Marshallese have been obtained with a portable whole-body counter. The report discusses the findings of these studies for the past eight years. The results of an early attempt o alter the rate of removal of the mixed fission products in the Marshallese with calcium disodium EDTA are presented. The metabolism of die radionuclides and their relationship to levels present in the environment is also discussed. (author) [French] L'enquete medicale a laquelle ont ete soumis les habitants des iles Marshall qui, en 1954, ont ete exposes accidentellement a des retombees locales presente un caractere unique en ce sens que, tout comme l'enquete sur les pecheurs japonais, elle fournit les seules donnees que l'on possede sur le metabolisme d'un melange de produits de fission chez l'homme. Un premier diagnostic de la contamination radioactive interne a ete fait par analyse radiochimique des excreta des sujets exposes et par analyse radiochimique des tissus des animaux exposes simultanement. Au debut, {sup 89}Sr, {sup 140}Ba, {sup 131}I et leurs produits de filiation de courte periode,ainsi qu'un certain nombre de terres rares

Physico-Chimie des Atomcules d'Hélium antiprotonique: Modélisation de Processus réactifs en présence d'Antimatière

Science.gov (United States)

Sauge, Sébastien

2000-07-01

Environ 3%des antiprotons (p) stoppés dans l'hélium survivent plusieurs microsecondes, contre quelques picosecondes dans tout autre matériau. Cette métastabilité inhabituelle résulte d'une capture sur des états liés de l'atome exotique pHe+, dénommé atomcule car il s'apparente à la fois à un atome de Rydberg quasi-circulaire quasi-classique de grand moment angulaire l n-1 37et à une molécule diatomique composée d'un noyau chargé négativement et caractérisée par une forte excitation rotationnelle J=l. En dehors de cette structure duale originale accessible par spectroscopie laser, la physico-chimie de leur interaction avec d'autres atomes ou molécules a fait l'objet d'études microscopiques. Alors que les atomcules résistent à des millions de collisions dans l'hélium pur, des contaminants moléculaires comme H2 les détruisent immédiatement, y compris à basse température. Dans le cadre Born-Oppenheimer, nous interprétons l'interaction moléculaire, calculée par des techniques de chimie quantique {ab initio}, en termes de chemins réactifs classiques, qui présentent des barrières d'activation compatibles avec celles mesurées dans He et H2.Nous montrons par une approche Monte Carlo de trajectoires classiques que la thermalisation détruit fortement les populations initiales, portant la fraction estimée des états de capture à 3%. Nous étudions aussi la recombinaison dissociative pHe+ + e+ e -dans une approche de trajectoires classiques pour les noyaux: nous prédisons la synthèse d'antihydrogène avec un rapport de branchement de 10%, ainsi qu'une nouvelle classe d'atomcules métastables ?={p}, e+, 2e-, qui pourrait être confirmée par spectroscopie. Ce travail illustre la transférabilité des concepts de chimie physique à l'étude de processus exotiques en présence d'antimatière, et apporte un éclairage nouveau sur la physico-chimie des radicaux interstellaires froids.

Behaviour of rare gases in solids at high temperature; Comportement des gaz rares dans les solides a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Blin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

In this article a number of simple results regarding the solubility and displacement of rare gases in solids have been assembled. These results were obtained from elementary considerations on highly compressed gases and on dislocations. They provide a better understanding of the now fairly numerous experiments dealing with the swelling of irradiated fuels, this swelling being due to the presence of a high proportion of gases in the fission products. Finally, the chances of success of the various methods which may be devised to diminish the swelling are examined. (author) [French] Nous avons rassemble dans ce texte un certain nombre de resultats simples relatifs a la solubilite et au deplacement des gaz rares dans les solides. Ces resultats ont ete obtenus par des considerations elementaires sur les gaz tres comprimes et sur les dislocations. Ils permettent de mieux comprendre les experiences, maintenant assez nombreuses, qui ont trait au gonflement des combustibles irradies; gonflement qui est du a la presence d'une forte proportion de gaz dans les produits de fission. On examine finalement les chances de succes des differents moyens que l'on peut imaginer pour attenuer le gonflement. (auteur)

Investigation of the fission yields of the fast neutron-induced fission of {sup 233}U; Mesure de la distribution en masse et en charge des produits de la fission rapide de l'{sup 233}U

Energy Technology Data Exchange (ETDEWEB)

Galy, J

1999-09-01

As a stars, a survey of the different methods of investigations of the fission product yields and the experimental data status have been studied, showing advantages and shortcomings for the different approaches. An overview of the existing models for the fission product distributions has been as well intended. The main part of this thesis was the measurement of the independent yields of the fast neutron-induced fission of{sup 233}U, never investigated before this work. The experiment has been carried out using the mass separator OSIRIS (Isotope Separator On-Line). Its integrated ion-source and its specific properties required an analysis of the delay-parameter and ionisation efficiency for each chemical species. On the other hand, this technique allows measurement of independent yields and cumulative yields for elements from Cu to Ba, covering most of the fission yield distribution. Thus, we measured about 180 independent yields from Zn (Z=30) to Sr (Z=38) in the mass range A=74-99 and from Pd (Z=46) to Ba (Z=56) in the mass range A=113-147, including many isomeric states. An additional experiment using direct {gamma}-spectroscopy of aggregates of fission products was used to determine more than 50 cumulative yields of element with half-life from 15 min to a several days. All experimental data have been compared to estimates from a semi-empirical model, to calculated values and to evaluated values from the European library JEF 2.2. Furthermore, a study of both thermal and fast neutron-induced fission of {sup 233}U measured at Studsvik, the comparison of the OSIRIS and LOHENGRIN facilities and the trends in new data for the Reactors Physics have been discussed. (author)

Measurement of Fission Product Yields from Fast-Neutron Fission

Science.gov (United States)

Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Henderson, R.; Kenneally, J.; Macri, R.; McNabb, D.; Ryan, C.; Sheets, S.; Stoyer, M. A.; Tonchev, A. P.; Bhatia, C.; Bhike, M.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.

2014-09-01

One of the aims of the Stockpile Stewardship Program is a reduction of the uncertainties on fission data used for analyzing nuclear test data [1,2]. Fission products such as 147Nd are convenient for determining fission yields because of their relatively high yield per fission (about 2%) and long half-life (10.98 days). A scientific program for measuring fission product yields from 235U,238U and 239Pu targets as a function of bombarding neutron energy (0.1 to 15 MeV) is currently underway using monoenergetic neutron beams produced at the 10 MV Tandem Accelerator at TUNL. Dual-fission chambers are used to determine the rate of fission in targets during activation. Activated targets are counted in highly shielded HPGe detectors over a period of several weeks to identify decaying fission products. To date, data have been collected at neutron bombarding energies 4.6, 9.0, 14.5 and 14.8 MeV. Experimental methods and data reduction techniques are discussed, and some preliminary results are presented.

Measurement of the fission cross section of uranium-235 between 4 eV and 20 keV; Mesure de la section efficace de fission de l'uranium-235 entre 4 eV et 20 keV

Energy Technology Data Exchange (ETDEWEB)

Michaudon, A; Genin, R; Joly, R; Vendryes, G

1959-01-01

The neutron fission cross section of uranium-235 has been measured between 4 ev and 20 kev by the time of flight method with the Saclay electron linear accelerator as a pulsed neutron source. After a brief description of the experimental apparatus and the conditions of work during the experiment, the curve {sigma}{sub F} {radical}E in the energy range studied is shown. This curve is then analyzed by the ''area'' method and a set of {sigma}{sub 0} {gamma}{sub F} values is obtained. With {sigma}{sub 0} {gamma} values measured in other laboratories, it is possible to compute fission widths for several resonances and to study their distribution. This distribution is then compared to Porter-Thomas distributions with different values of the number of exit channels. (authors) [French] La section efficace de fission de l'uranium--235 a ete mesuree entre 4 eV et 20 KeV par la methode du temps de vol en utilisant l'accelerateur lineaire a electrons de Saclay comme source pulses de neutrons. Apres une rapide description de l'appareillage experimental et des conditions de fonctionnement au cours de l'experience, on presente la courbe {sigma}{sub F} {radical}E obtenue dans la game d'energie etudiee. Cette courbe est ensuite analysee par la methode de surface des resonances et un lot de valeurs de {sigma}{sub 0} {gamma}{sub F} est obtenue. Conjuguee avec les valeurs de {sigma}{sub 0} {gamma} obtenues dans d'autres laboratoires, cette analyse permet de calculer les largeurs de fission pour plusieurs resonances et d'etudier leur distribution. Cette distribution est ensuite comparee aux distributions de Porter et Thomas correspondant a differentes valeurs du nombre de voies de sortie. (auteurs)

The ultrasonic copper and brass decontamination study; Etude de la decontamination du cuivre et des laitons en presence d'ultra-sons

Energy Technology Data Exchange (ETDEWEB)

Courtault, J; Kerdelleau, J de; Mestre, E [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The use of ultra-sounds as a decontamination technic does not bring an absolute solution. As a function of the materials it seemed necessary to find what was the optimum conditions for using the ultra-sounds and to define not only the ultra-sonic factors but also the chemical solutions which bring some appreciable decontamination factors without bringing any too important corrosion processus. This report gives the results of this study applied to copper and brass. This study allowed to select some effective treatment baths on the two types of contamination: plutonium and fission products. (authors) [French] L'emploi des ultra-sons comme technique de decontamination n'amene pas une solution absolue. Il est apparu necessaire de rechercher en fonction de la nature du materiau a decontaminer quelles etaient les conditions optimales d'utilisation des ultra-sons et de definir alors non seulement les facteurs ultrasoniques mais encore les solutions chimiques qui apportent des facteurs de decontamination appreciables sans amener des phenomenes de corrosion trop importants. Ce rapport donne les resultats de cette etude appliquee au cuivre et aux laitons. Cette etude a permis de selectionner des bains de traitement efficaces dans les deux cas de contamination: plutonium et produits de fission. (auteurs)

[Fission product yields of 60 fissioning reactions]. Final report

International Nuclear Information System (INIS)

Rider, B.F.

1995-01-01

In keeping with the statement of work, I have examined the fission product yields of 60 fissioning reactions. In co-authorship with the UTR (University Technical Representative) Talmadge R. England ''Evaluation and Compilation of Fission Product Yields 1993,'' LA-UR-94-3106(ENDF-349) October, (1994) was published. This is an evaluated set of fission product Yields for use in calculation of decay heat curves with improved accuracy has been prepared. These evaluated yields are based on all known experimental data through 1992. Unmeasured fission product yields are calculated from charge distribution, pairing effects, and isomeric state models developed at Los Alamos National Laboratory. The current evaluation has been distributed as the ENDF/B-VI fission product yield data set

Irradiation and development of the nuclear emulsions exposed to intense fluxes of thermal neutrons with {gamma} rays; Irradiation et developpement des emulsions nucleaires exposees a des flux intenses de neutrons thermiques, accompagnes de rayons {gamma}

Energy Technology Data Exchange (ETDEWEB)

Faraggi, H; Bonnet, A; Cohen, J [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1952-07-01

The thermal neutron fluxes provided by nuclear reactors permit the survey of relatively rare phenomenons, and dosage of very weak quantities of some elements. One of the most favorable detection technique are constituted by the use of the nuclear emulsions. one can mention: - the dosage of uranium by counting in the emulsion the number of traces due to fission fragments after irradiation. - The dosage of the lithium and the boron as trace amounts with the help of nuclear reactions (n, {alpha}) and thermal neutrons. - The research of reactions (n, {alpha}) or (n, p) of very weak cross section for middle or heavy elements. These different applications require however important neutrons fluxes. It had therefore obliged us to search for the most favorable irradiation and development of the emulsions conditions, to get the best visibility of the trajectories and decrease the phenomena of fog on the emulsion, which prevents any observation. (M.B.) [French] Les flux de neutrons thermiques fournis par les reacteurs nucleaires permettent l'etude de phenomenes relativement rares, et le dosage de tres faibles quantites de certains elements. Un des moyens de detection les plus favorables est constitue par l'utilisation des emulsions nucleaires. on peut citer: - le dosage de l'uranium par comptage dans l'emulsion du nombre de traces dues aux fragments de fission apres irradiation. - Le dosage du lithium et du bore a l'etat de traces a l'aide des reactions (n, {alpha}) sous l'action des neutrons thermiques. - La recherche de reactions (n,{alpha}) ou (n,p) de tres faible section efficace pour des elements moyens ou lourds. Ces differentes applications necessite cependant des flux de neutrons important. On a donc ete amene a rechercher les conditions les plus favorables d'irradiation et de developpement des emulsions, de maniere a obtenir la meilleure visibilite des trajectoires et diminuer les phenomenes de voile de l'emulsion, qui empeche toute observation. (M.B.)

Irradiation and development of the nuclear emulsions exposed to intense fluxes of thermal neutrons with {gamma} rays; Irradiation et developpement des emulsions nucleaires exposees a des flux intenses de neutrons thermiques, accompagnes de rayons {gamma}

Energy Technology Data Exchange (ETDEWEB)

Faraggi, H.; Bonnet, A.; Cohen, J. [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1952-07-01

The thermal neutron fluxes provided by nuclear reactors permit the survey of relatively rare phenomenons, and dosage of very weak quantities of some elements. One of the most favorable detection technique are constituted by the use of the nuclear emulsions. one can mention: - the dosage of uranium by counting in the emulsion the number of traces due to fission fragments after irradiation. - The dosage of the lithium and the boron as trace amounts with the help of nuclear reactions (n, {alpha}) and thermal neutrons. - The research of reactions (n, {alpha}) or (n, p) of very weak cross section for middle or heavy elements. These different applications require however important neutrons fluxes. It had therefore obliged us to search for the most favorable irradiation and development of the emulsions conditions, to get the best visibility of the trajectories and decrease the phenomena of fog on the emulsion, which prevents any observation. (M.B.) [French] Les flux de neutrons thermiques fournis par les reacteurs nucleaires permettent l'etude de phenomenes relativement rares, et le dosage de tres faibles quantites de certains elements. Un des moyens de detection les plus favorables est constitue par l'utilisation des emulsions nucleaires. on peut citer: - le dosage de l'uranium par comptage dans l'emulsion du nombre de traces dues aux fragments de fission apres irradiation. - Le dosage du lithium et du bore a l'etat de traces a l'aide des reactions (n, {alpha}) sous l'action des neutrons thermiques. - La recherche de reactions (n,{alpha}) ou (n,p) de tres faible section efficace pour des elements moyens ou lourds. Ces differentes applications necessite cependant des flux de neutrons important. On a donc ete amene a rechercher les conditions les plus favorables d'irradiation et de developpement des emulsions, de maniere a obtenir la meilleure visibilite des trajectoires et diminuer les phenomenes de voile de l'emulsion, qui

Ternary fission

International Nuclear Information System (INIS)

Wagemans, C.

1991-01-01

Since its discovery in 1946, light (charged) particle accompanied fission (ternary fission) has been extensively studied, for spontaneous as well as for induced fission reactions. The reason for this interest was twofold: the ternary particles being emitted in space and time close to the scission point were expected to supply information on the scission point configuration and the ternary fission process was an important source of helium, tritium, and hydrogen production in nuclear reactors, for which data were requested by the nuclear industry. Significant experimental progress has been realized with the advent of high-resolution detectors, powerful multiparameter data acquisition systems, and intense neutron and photon beams. As far as theory is concerned, the trajectory calculations (in which scission point parameters are deduced from the experimental observations) have been very much improved. An attempt was made to explain ternary particle emission in terms of a Plateau-Rayleigh hydrodynamical instability of a relatively long cylindrical neck or cylindrical nucleus. New results have also been obtained on the so-called open-quotes trueclose quotes ternary fission (fission in three about-equal fragments). The spontaneous emission of charged particles has also clearly been demonstrated in recent years. This chapter discusses the main characteristics of ternary fission, theoretical models, light particle emission probabilities, the dependence of the emission probabilities on experimental variables, light particle energy distributions, light particle angular distributions, correlations between light particle accompanied fission observables, open-quotes trueclose quotes ternary fission, and spontaneous emission of heavy ions. 143 refs., 18 figs., 8 tabs

Fission level densities

International Nuclear Information System (INIS)

Maslov, V.M.

1998-01-01

Fission level densities (or fissioning nucleus level densities at fission saddle deformations) are required for statistical model calculations of actinide fission cross sections. Back-shifted Fermi-Gas Model, Constant Temperature Model and Generalized Superfluid Model (GSM) are widely used for the description of level densities at stable deformations. These models provide approximately identical level density description at excitations close to the neutron binding energy. It is at low excitation energies that they are discrepant, while this energy region is crucial for fission cross section calculations. A drawback of back-shifted Fermi gas model and traditional constant temperature model approaches is that it is difficult to include in a consistent way pair correlations, collective effects and shell effects. Pair, shell and collective properties of nucleus do not reduce just to the renormalization of level density parameter a, but influence the energy dependence of level densities. These effects turn out to be important because they seem to depend upon deformation of either equilibrium or saddle-point. These effects are easily introduced within GSM approach. Fission barriers are another key ingredients involved in the fission cross section calculations. Fission level density and barrier parameters are strongly interdependent. This is the reason for including fission barrier parameters along with the fission level densities in the Starter File. The recommended file is maslov.dat - fission barrier parameters. Recent version of actinide fission barrier data obtained in Obninsk (obninsk.dat) should only be considered as a guide for selection of initial parameters. These data are included in the Starter File, together with the fission barrier parameters recommended by CNDC (beijing.dat), for completeness. (author)

Irradiation effects and behaviour of fission products in zirconia and spinel; Effets d'irradiation et comportement des produits de fission dans la zircone et le spinelle

Energy Technology Data Exchange (ETDEWEB)

Gentils, A

2003-10-01

Crystalline oxides, such as zirconia (ZrO{sub 2}) and spinel (MgAl{sub 2}O{sub 4}), are promising inert matrices for the transmutation of plutonium and minor actinides. This work deals with the study of the physico-chemical properties of these matrices, more specifically their behaviour under irradiation and their capacity to retain fission products. Irradiations at low energy and incorporation of stable analogs of fission products (Cs, I, Xe) into yttria-stabilized zirconia and magnesium-aluminate spinel single crystals were performed by using the ion implanter IRMA (CSNSM-Orsay). Irradiations at high energy were made on several heavy ion accelerators (GANIL-Caen, ISL-Berlin, HIL-Warsaw). The damage induced by irradiation and the release of fission products were monitored by in situ Rutherford Backscattering Spectrometry experiments. Transmission electron microscopy was also used in order to determine the nature of the damage induced by irradiation. The results show that irradiation of ZrO{sub 2} and MgAl{sub 2}O{sub 4} with heavy ions (about hundred keV and about hundred MeV) induces a huge structural damage in crystalline matrices. Total disorder (amorphization) is however never reached in zirconia, contrary to what is observed in the case of spinel. The results also emphasize the essential role played by the concentration of implanted species on their retention capacity. A dramatic release of fission products was observed when the concentration exceeds a threshold of a few atomic percent. Irradiation of implanted samples with medium-energy noble-gas ions leads to an enhancement of the fission product release. The exfoliation of spinel crystals implanted at high concentration of Cs ions is observed after a thermal treatment at high temperature. (author)

Some aspects of in-pile swelling of fissile materials, 1. part: non-alloyed {alpha} uranium; Quelques aspects du gonflement en pile des materiaux fissiles. 1. partie: uranium {alpha} non allie

Energy Technology Data Exchange (ETDEWEB)

Mikailoff, H [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-07-01

An examination has been carried out of non-alloyed uranium samples, having various structural states, cold-worked and recrystallized, as-cast and {beta}-treated, and irradiated at temperatures of between 450 and 600 C and with burn-ups from 1300 to 5500 MW days/metric ton. These samples swelled because of precipitation of the fission gases the porosity thus produced has a morphology depending mainly on the type of deformation to which the metal has been subjected and which is due to in-pile growth. The most homogeneous distribution of pores, and thus that leading to the minimum swelling, is only observed in the material having a marked [010] texture in which the growth and perhaps the thermal cycling introduce little or no strain. For other materials the deformation /swelling association causes a more rapid destruction of the samples either by cracking when the deformation is due to twinning, or by pronounced swelling localized in the bands when deformation is due to slipping. Finally the fission-gas precipitation considerably facilitates, above 500 C, the germination and growth of the intergranular cracks which can then develop at low stresses. (author) [French] On a examine des echantillons d'uranium non allie, de divers etats structuraux, marteles et recristallises, bruts de coulee et traites {beta}, irradies a des temperatures comprises entre 450 et 600 C, et a des taux de combustion allant de 1300 a 5500 MWj/t. Ces echantillons ont gonfle par suite de la precipitation de gaz de fission: la porosite ainsi fournie a une morphologie qui depend principalement des modes de deformation subie par le metal et due a la croissance en pile. La repartition la plus homogene des pores, donc celle qui donnera le gonflement minimum, est observee seulement dans le materiau a forte texture [010] dans lequel la croissance et eventuellement le cyclage thermique introduisent peu ou pas de contraintes. Dans les autres materiaux l'association deformation/gonflement rend plus rapide

Nuclear explosion and internal contamination; Explosion nucleaire et contamination interne

Energy Technology Data Exchange (ETDEWEB)

Aeberhardt, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1956-07-01

By the study of the conditions of internal contamination due to the radioactive mixture produced by a nuclear explosion, the parts played by the relative weights of the different elements and the mode of expression of the doses are considered. Only the knowledge of the weight composition of the contamination mixture and of its evolution as a function of time can provide the required basis for the study of its metabolism in the organism. The curves which give the composition of the fission product mixture - in number of nuclei - - as a function of time - have been established. These curves are applied to some practical examples, particularly relative to the nature of contamination, radiotoxicity of some elements and assessment of hazards. (author) [French] Etudiant les modalites de la contamination interne par les elements radioactifs apparus lors d'une explosion nucleaire, le role de la 'masse' et le mode d'expression des doses sont envisages. La connaissance de la composition en 'masse' du melange contaminant et de son evolution en fonction du temps peut seule apporter les bases necessaires a l'etude de son comportement dans l'organisme. Les courbes donnant la composition du melange de produits de fission - en nombre de noyaux - - en fonction du temps - ont ete etablies. Quelques applications pratiques, relatives en particulier a la nature de la contamination, a la radiotoxicite de certains elements et a l'evaluation de risque, sont envisagees a titre d'exemple. (auteur)

The study of neutron propagation in natural uranium; Etude de la propagation des neutrons dans l'uranium naturel

Energy Technology Data Exchange (ETDEWEB)

Campan, J L; Clauzon, P P; Kirchner, B; Ribon, P; Zaleski, C P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

Fast exponential experiment. Experimental facilities are described; the experimental results obtained with the block of natural uranium are then presented. Detectors used were fission chambers, activation detectors and nuclear emulsions. One tries to explain the results, which are, then compared with theoretical values obtained by calculations based on diffusion theory. Measured spectrum (pseudo equilibrium) may be characterised by the following values: diffusion length: 95,25 {+-} 0,5; {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 238} : 230 {+-} 10, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Np{sub 237} : 14 {+-} 0.5, {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 233} : 0.67 {+-} 0.03, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Pu{sub 239} : 0.90 {+-} 0.05, {sigma}{sub f}U{sub 235}/{sigma}(ny) In : 230 {+-}10. (author) [French] Experience exponentielle rapide. Apres une description du dispositif experimental, on presente des resultats de mesures effectuees dans un massif d'uranium naturel. Les detecteurs utilises sont des chambres a fission, des detecteurs d'activation et des emulsions nucleaires. Une interpretation des resultats est donnee; ceux-ci sont compares a des valeurs theoriques obtenues par des calculs utilisant la theorie de la diffusion. Le spectre mesure (pseudo equilibre) peut etre caracterise par les valeurs suivantes: Longueur de diffusion: 95,25 {+-} 0,5; {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 238} : 230 {+-} 10, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Np{sub 237} : 14 {+-} 0.5, {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 233} : 0.67 {+-} 0.03, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Pu{sub 239} : 0.90 {+-} 0.05, {sigma}{sub f}U{sub 235}/{sigma}(ny) In : 230 {+-}10. (auteur)

Fission-Product Separation as a Final Solution to the Problem of Storing Highly Radioactive Waste; La Separation des Produits de Fission Comme Solution Definitive du Stockage des Dechets Fortement Radioactifs; 0412 042b 0414 ; La Separacion de los Productos de Fision Como Solucion Definitiva del Problema del Almacenamiento de los Desechos de Elevada Radiactividad

Energy Technology Data Exchange (ETDEWEB)

Raggenbass, A.; Lefevre, J. [Centre d' Etudes Nucleaires, Saclay (France)

1963-02-15

'isolement du cesium-137 et du strontium-90 avec un facteur de decontamination d'au moins 10{sup 4}, ce qui permettrait d'envisager le rejet, apres un traitement d'effluents classique, au bout d'une periode de 10 a 20 ans. Le but du memoire est de faire le point de cette question en l'annee 1962. Les progres realises dans les methodes de separation du cesium et du strontium permettent d'envisager l'obtention de ce facteur 10{sup 4} dans des conditions exploitables industriellement. Des methodes pleines de promesses sont: a) Pour le cesium-137, la precipitation par l'acide phosphotungstique, l'echange sur un sel d'ammonium d'un heteropolyacide, la fixation par un phosphate de zirconium. b) Pour le strontium-90, la precipitation d'oxalate, l'extraction par l'acide di-2-ethyl-hexylphosphorique, l'echange sur des sels varies, sulfate de strontium, etc. Ces progres chimiques sont renforces par les progres realises dans le traitement industriel des effluents et permettent de considerer comme techniquement possible la solution preconisee par Glueckauf. Parallelement, le developpement de l'utilisation de grandes quantites de produits de fission, particulierement dans les programmes SNAP, justifie des investissements qui seront au moins pairtiellement recuperes par la vente des produits fabriques. Il est certain que des sources refractaires, a resistance tres elevee a tous les agents d'agression exterieurs, constituent le mode de stockage le plus satisfaisant pour des produits aussi dangereux et d'aussi longue periode. L'auteur considere done, techniquement et psychologiquement, Inverted-Exclamation-Mark /utilisation de sources concentrees a gainage riche comme le moyen de stockage presentant le plus de garanties. Une discussion comparative de cette methode avec la methode d'incorporation dans les verres meriterait un examen complet et approfondi. (author) [Spanish] En la Conferencia de Ginebra de 1955, Glueckauf formplo la hipotesis de que los problemas planteados por las soluciones de

Bitumen coating of the radio-active sludges from the effluent treatment plant at the Marcoule centre. Review of the progress reports 1, 2, 3 and 4 (1963); Enrobage par le bitume des boues radioactives de la station de traitement des effluents du centre de Marcoule. Mise au point des etats d'avancement 1, 2, 3 et 4. (1963)

Energy Technology Data Exchange (ETDEWEB)

Rodier, J.; Lefillatre, G.; Scheidhauer, J. [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

1963-07-01

Besides the very high activity liquids containing fission products, the chemical treatment of irradiated fuels produces a large volume of aqueous effluents and solid waste of relatively low radioactivity. These weakly active products can be eliminated in the ground, in a hydrographic land system or in the sea. Techniques of evaporation, of resin concentration, and of coprecipitation give rise to inorganic sludges with a high water content. All these residues occupy a large volume and represent a far from negligible weight. In the case of the sludge, their relative fluidity necessitates a conditioning guaranteeing safe storage. The solution to the problem will consist in passing directly from a liquid or a suspension, to a solid whose structure is homogeneous and whose matter is inert with respect to the storage medium (soil, sea, etc. ). We have proposed to coat the radioactive products with bitumen. This article is designed to give a review of the studies undertaken on this method. It consists of a progress report rather than a final assessment. (authors) [French] En dehors des liquides de tres haute activite contenant des produits de fission, le traitement chimique des combustibles irradies produit un volume important d'effluents aqueux et de residus solides de radioactivite relativement faible. Ces produits, faiblement actifs, peuvent etre elimines dans le sol, dans un systeme hydrographique terrestre ou dans la mer. Les techniques d'evaporation, de concentration sur resine, de coprecipitation, permettent la decontamination prealable des liquides. La coprecipitation donne naissance a des boues minerales dont la teneur en eau est elevee. Tous ces residus occupent un volume important et representent un poids non negligeable. Dans le cas des boues, leur fluidite relative exige un conditionnement donnant toutes garanties de securite au stockage. La solution du probleme consistera a passer directement d'un liquide ou d'une suspension a un solide

Bitumen coating of the radio-active sludges from the effluent treatment plant at the Marcoule centre. Review of the progress reports 1, 2, 3 and 4 (1963); Enrobage par le bitume des boues radioactives de la station de traitement des effluents du centre de Marcoule. Mise au point des etats d'avancement 1, 2, 3 et 4. (1963)

Energy Technology Data Exchange (ETDEWEB)

Rodier, J; Lefillatre, G; Scheidhauer, J [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

1963-07-01

Besides the very high activity liquids containing fission products, the chemical treatment of irradiated fuels produces a large volume of aqueous effluents and solid waste of relatively low radioactivity. These weakly active products can be eliminated in the ground, in a hydrographic land system or in the sea. Techniques of evaporation, of resin concentration, and of coprecipitation give rise to inorganic sludges with a high water content. All these residues occupy a large volume and represent a far from negligible weight. In the case of the sludge, their relative fluidity necessitates a conditioning guaranteeing safe storage. The solution to the problem will consist in passing directly from a liquid or a suspension, to a solid whose structure is homogeneous and whose matter is inert with respect to the storage medium (soil, sea, etc. ). We have proposed to coat the radioactive products with bitumen. This article is designed to give a review of the studies undertaken on this method. It consists of a progress report rather than a final assessment. (authors) [French] En dehors des liquides de tres haute activite contenant des produits de fission, le traitement chimique des combustibles irradies produit un volume important d'effluents aqueux et de residus solides de radioactivite relativement faible. Ces produits, faiblement actifs, peuvent etre elimines dans le sol, dans un systeme hydrographique terrestre ou dans la mer. Les techniques d'evaporation, de concentration sur resine, de coprecipitation, permettent la decontamination prealable des liquides. La coprecipitation donne naissance a des boues minerales dont la teneur en eau est elevee. Tous ces residus occupent un volume important et representent un poids non negligeable. Dans le cas des boues, leur fluidite relative exige un conditionnement donnant toutes garanties de securite au stockage. La solution du probleme consistera a passer directement d'un liquide ou d'une suspension a un solide dont la structure

Post-scission fission theory: Neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1997-01-01

A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N (E) and the average prompt neutron multiplicity bar ν p . Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N (E) and bar ν p upon the fissioning nucleus and its excitation energy are treated. Recent work in the calculation of the prompt fission neutron spectrum matrix N (E, E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of our ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches

Fission products collecting devices

International Nuclear Information System (INIS)

Matsumoto, Hiroshi

1979-01-01

Purpose: To enable fission products trap with no contamination to coolants and cover gas by the provision of a fission products trap above the upper part of a nuclear power plant. Constitution: Upon fuel failures in a reactor core, nuclear fission products leak into coolants and move along the flow of the coolants to the coolants above the reactor core. The fission products are collected in a trap container and guided along a pipeline into fission products detector. The fission products detector monitors the concentration of the fission products and opens the downstream valve of the detector when a predetermined concentration of the fission products is detected to introduce the fission products into a waste gas processing device and release them through the exhaust pipe. (Seki, T.)

Improvements of the sensitivity of burst cartridge detection; Amelioration du seuil de detection des ruptures de gaine

Energy Technology Data Exchange (ETDEWEB)

Vasnier, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

I - Special tests for improving the sensitivity of burst cartridge detection equipment in power reactors II - Scintillator purge-flow tests using aged gas in the B.C.D. /E.D.F. 2 Summary. - The first part of this report describes the tests carried out on fission product detectors by a process in which gas is continuously injected in front of the scintillator. Using this system, the background is reduced and perturbations caused by pneumatic switches on the prospecting circuits are eliminated. The quality of the signals thus obtained permits better processing of the data and thus leads to a possible improvement in the sensitivity of burst cartridge detection. The second part gives results of tests carried out with both fresh and aged gases, the economic advantage of the latter being that it permits recycling through the reactor. Reduction of the background is less pronounced but the advantage of the stable signals is conserved. (author) [French] I - Essais speciaux pour ameliorer le seuil de detection des installations de D.R.G. des reacteurs de puissance II- Essais de balayage sous scintillateur avec gaz vieilli a la D.R.G. /E.D.F. 2 Sommaire. - La premiere partie de ce rapport decrit les essais effectues sur les detecteurs de produits de fission par un procede d'injection continue de gaz sous le scintillateur. Grace a ce systeme on obtient une reduction du bruit de fond et l'elimination des perturbations causees par les commutations pneumatiques des circuits de prospection. La qualite des signaux obtenus ainsi permet un meilleur traitement des informations d'ou une amelioration possible du seuil de detection des ruptures de gaines. La seconde partie donne les resultats d'essais effectues avec du gaz propre et vieilli, l'utilisation de ce dernier presentant l'avantage economique d'etre recycle du reacteur. La reduction du bruit de fond est moins importante mais on conserve l'avantage de la stabilisation des signaux. (auteur)

Nuclear fission and reactions

International Nuclear Information System (INIS)

Anon.

1975-01-01

The nuclear fission research programs are designed to elucidate basic features of the fission process. Specifically, (1) factors determining how nucleons of a fissioning nucleus are distributed between two fission fragments, (2) factors determining kinetic energy and excitation energies of fragments, and (3) factors controlling fission lifetimes. To these ends, fission studies are reported for several heavy elements and include investigations of spontaneous and neutron-induced fission, heavy ion reactions, and high energy proton reactions. The status of theoretical research is also discussed. (U.S.)

Use of the helium-3 proportional counter for neutron spectrometry; Utilisation du compteur proportionnel a helium 3 pour la spectrometrie des neutrons

Energy Technology Data Exchange (ETDEWEB)

Vialettes, H; Le Thanh, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

compteur proportionnel a helijum 3 a e,te envisagee. Ce rapport presente les principes d'utilisation du spectrometre a helium 3, et les methodes de calcul qui permettent de tenir compte des deux effets principaux qui tendent a deformer le spectre obtenus: - l'absorption d'energie par les parois du compteur - la perte d'energie des neutrons incidents par chocs elastiques sur les noyaux d'helium 3. A titre d'application on a trace le spectre des neutrons emis par une source de polonium-lithium; les resultats obtenus sont en excellent accord avec les predictions theoriques. (auteurs)

New features of nuclear excitation by {alpha} particles scattering; Nouveaux aspects de l'excitation nucleaire par diffusion de particules {alpha}

Energy Technology Data Exchange (ETDEWEB)

Saudinos, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

Inelastic scattering of medium energy a particles by nuclei is known to excite preferentially levels of collective character. We have studied the scattering of isotopically enriched targets of Ca, Fe, Ni, Cu, Zn. In part I, we discuss the theoretical features of the interaction. In part II, we describe the experimental procedure. Results are presented and analysed in part III. {alpha} particles scattering by Ca{sup 40} is showed to excite preferentially odd parity levels. In odd nuclei we have observed multiplets due to the coupling of the odd nucleon with the even-even core vibrations. For even-even nuclei, a few levels are excited with lower cross-sections between the well-known first 2{sup +} and 3{sup -} states. Some could be members of the two phonon quadrupole excitation and involve a double nuclear excitation process. (author) [French] On sait que la diffusion inelastique des particules alpha de moyenne energie excite preferentiellement des niveaux de caractere collectif. Nous avons etudie la diffusion des particules alpha de 44 MeV du cyclotron de Saclay par des isotopes separes de Ca, Fe, Ni, Cu, Zn. Dans la premiere partie nous exposons les theories de cette interaction. Dans la seconde nous decrivons le systeme experimental. Les resultats sont donnes dans la troisieme partie. Nous montrons que les niveaux excites preferentiellement pour {sup 40}Ca par diffusion ({alpha},{alpha}') sont de parite negative. Dans les noyaux pair-impair nous avons observe des multiplets dus au couplage du nucleon celibataire avec les vibrations du coeur pair-pair. Pour les noyaux pair-pair nous avons pu etudier entre le premier niveau 2{sup +} et le niveau 3{sup -} deja bien connus certains etats plus faiblement excites. Il semble qu'ils sont dus a une excitation quadrupolaire a deux phonons et impliquent un processus de double excitation nucleaire. (auteur)

Determination of the neutron-induced fission cross section of {sup 242}Pu; Bestimmung des neutroneninduzierten Spaltquerschnitts von {sup 242}Pu

Energy Technology Data Exchange (ETDEWEB)

Koegler, Toni Joerg

2016-04-26

Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For {sup 242}Pu, current uncertainties are of around 21%. Sensitivity studies show that the total uncertainty has to be reduced to below 5% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of {sup 235}U and {sup 242}Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of {sup 242}Pu relative to {sup 235}U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of {sup 242}Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using results of different neutron transport simulations (Geant 4, MCNP 6 and FLUKA).

Fission-product yields for thermal-neutron fission of curium-243

International Nuclear Information System (INIS)

Breederland, D.G.

1982-01-01

Cumulative fission yields for 25 gamma rays emitted during the decay of 23 fission products produced by thermal-neutron fission of 243 Cm have been determined. Using Ge(Li) spectroscopy, 33 successive pulse-height spectra of gamma rays emitted from a 77-ng sample of 243 Cm over a period of approximately two and one-half months were analyzed. Reduction of these spectra resulted in the identification and matching of gamma-ray energies and half-lives to specific radionuclides. Using these results, 23 cumulative fission-product yields were calculated. Only those radionuclides having half-lives between 6 hours and 65 days were observed. Prior to this experiment, no fission-product yields had been recorded for 243 Cm

Neutron emission as a probe of fusion-fission and quasi-fission dynamics

International Nuclear Information System (INIS)

Hinde, D.J.

1991-01-01

Pre- and post scission neutron yeilds have been measured as a function of projectile mass, compound nucleus fissility, and fission mass-split and total kinetic energy (TKE) for 27 fusion-fission and quasi-fission reactions induced by beams of 16,18 O, 40 Ar and 64 Ni. A new method of interpretation of experimental pre-scission neutron multiplicities ν-pre and mean kinetic energies ε ν allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35±15) x 10 -21 s for symmetric fission. All reactions show that ν-pre falls quite rapidly with increasing mass-asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass-asymmetry. For quasi-fission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass-asymmetry, but that the time scale is virtually independent of mass-asymmetry. It is concluded that for fusion-fission there is no dependence of ν-pre on TKE, whilst for 64 Ni-induced quasi-fission reactions, a strong increase of ν-pre with decreasing TKE is observed, probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data. 54 refs., 17 tabs., 25 figs

Energy released in fission

International Nuclear Information System (INIS)

James, M.F.

1969-05-01

The effective energy released in and following the fission of U-235, Pu-239 and Pu-241 by thermal neutrons, and of U-238 by fission spectrum neutrons, is discussed. The recommended values are: U-235 ... 192.9 ± 0.5 MeV/fission; U-238 ... 193.9 ± 0.8 MeV/fission; Pu-239 ... 198.5 ± 0.8 MeV/fission; Pu-241 ... 200.3 ± 0.8 MeV/fission. These values include all contributions except from antineutrinos and very long-lived fission products. The detailed contributions are discussed, and inconsistencies in the experimental data are pointed out. In Appendix A, the contribution to the total useful energy release in a reactor from reactions other than fission are discussed briefly, and in Appendix B there is a discussion of the variations in effective energy from fission with incident neutron energy. (author)

The evaluation for reference fission yield of 238U fission

International Nuclear Information System (INIS)

Liang Qichang; Liu Tingjin

1998-01-01

In the fission yield data evaluation and measurement, the reference yield is very important, good or poor recommended or measurement values depend upon the reference data to a great extent. According to the CRP's requirement, the evaluation of reference fission yields have been and will be carried out in CNDC, as a part of the whole work (contract No.9504/R 0 /Regular Budget Fund), the evaluation for 29 reference fission yields of 15 product nuclides from 238 U fission have been completed

Fission yield covariance generation and uncertainty propagation through fission pulse decay heat calculation

International Nuclear Information System (INIS)

Fiorito, L.; Diez, C.J.; Cabellos, O.; Stankovskiy, A.; Van den Eynde, G.; Labeau, P.E.

2014-01-01

Highlights: • Fission yield data and uncertainty comparison between major nuclear data libraries. • Fission yield covariance generation through Bayesian technique. • Study of the effect of fission yield correlations on decay heat calculations. • Covariance information contribute to reduce fission pulse decay heat uncertainty. - Abstract: Fission product yields are fundamental parameters in burnup/activation calculations and the impact of their uncertainties was widely studied in the past. Evaluations of these uncertainties were released, still without covariance data. Therefore, the nuclear community expressed the need of full fission yield covariance matrices to be able to produce inventory calculation results that take into account the complete uncertainty data. State-of-the-art fission yield data and methodologies for fission yield covariance generation were researched in this work. Covariance matrices were generated and compared to the original data stored in the library. Then, we focused on the effect of fission yield covariance information on fission pulse decay heat results for thermal fission of 235 U. Calculations were carried out using different libraries and codes (ACAB and ALEPH-2) after introducing the new covariance values. Results were compared with those obtained with the uncertainty data currently provided by the libraries. The uncertainty quantification was performed first with Monte Carlo sampling and then compared with linear perturbation. Indeed, correlations between fission yields strongly affect the uncertainty of decay heat. Eventually, a sensitivity analysis of fission product yields to fission pulse decay heat was performed in order to provide a full set of the most sensitive nuclides for such a calculation

Computer program FPIP-REV calculates fission product inventory for U-235 fission

Science.gov (United States)

Brown, W. S.; Call, D. W.

1967-01-01

Computer program calculates fission product inventories and source strengths associated with the operation of U-235 fueled nuclear power reactor. It utilizes a fission-product nuclide library of 254 nuclides, and calculates the time dependent behavior of the fission product nuclides formed by fissioning of U-235.

Mica fission detectors

International Nuclear Information System (INIS)

Wong, C.; Anderson, J.D.; Hansen, L.; Lehn, A.V.; Williamson, M.A.

1977-01-01

The present development status of the mica fission detectors is summarized. It is concluded that the techniques have been refined and developed to a state such that the mica fission counters are a reliable and reproducible detector for fission events

Fission fragment angular distributions and fission cross section validation

International Nuclear Information System (INIS)

Leong, Lou Sai

2013-01-01

The present knowledge of angular distributions of neutron-induced fission is limited to a maximal energy of 15 MeV, with large discrepancies around 14 MeV. Only 238 U and 232 Th have been investigated up to 100 MeV in a single experiment. The n-TOF Collaboration performed the fission cross section measurement of several actinides ( 232 Th, 235 U, 238 U, 234 U, 237 Np) at the n-TOF facility using an experimental set-up made of Parallel Plate Avalanche Counters (PPAC), extending the energy domain of the incident neutron above hundreds of MeV. The method based on the detection of the 2 fragments in coincidence allowed to clearly disentangle the fission reactions among other types of reactions occurring in the spallation domain. I will show the methods we used to reconstruct the full angular resolution by the tracking of fission fragments. Below 10 MeV our results are consistent with existing data. For example in the case of 232 Th, below 10 MeV the results show clearly the variation occurring at the first (1 MeV) and second (7 MeV) chance fission, corresponding to transition states of given J and K (total spin and its projection on the fission axis), and a much more accurate energy dependence at the 3. chance threshold (14 MeV) has been obtained. In the spallation domain, above 30 MeV we confirm the high anisotropy revealed in 232 Th by the single existing data set. I'll discuss the implications of this finding, related to the low anisotropy exhibited in proton-induced fission. I also explore the critical experiments which is valuable checks of nuclear data. The 237 Np neutron-induced fission cross section has recently been measured in a large energy range (from eV to GeV) at the n-TOF facility at CERN. When compared to previous measurements, the n-TOF fission cross section appears to be higher by 5-7 % beyond the fission threshold. To check the relevance of n-TOF data, we simulate a criticality experiment performed at Los Alamos with a 6 kg sphere of 237 Np. This

Measurements of fission yields

International Nuclear Information System (INIS)

Denschlag, H.O.

2000-01-01

After some historical introductory remarks on the discovery of nuclear fission and early fission yield determinations, the present status of knowledge on fission yields is briefly reviewed. Practical and fundamental reasons motivating the pursuit of fission yield measurements in the coming century are pointed out. Recent results and novel techniques are described that promise to provide new interesting insights into the fission process during the next century. (author)

Radiochemical studies on fission

Energy Technology Data Exchange (ETDEWEB)

None

1973-07-01

Research progress is reported on nuclear chemistry; topics considered include: recoil range and kinetic energy distribution in the thermal neutron ftssion of /sup 245/Cm; mass distribution and recoil range measurements in the reactor neutron-induced fission of /sup 232/U; fission yields in the thermal neutron fission of /sup 241/PU highly asymmetric binary fission of uranium induced by reactor neutrons; and nuclear charge distribution in low energy fission. ( DHM)

Measurement of prompt fission gamma-ray spectra in fast neutron-induced fission

International Nuclear Information System (INIS)

Laborie, J.M.; Belier, G.; Taieb, J.

2012-01-01

Knowledge of prompt fission gamma-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission gamma-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the gamma-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other gamma-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the Al-27(p, gamma) reaction. First prompt fission gamma-ray spectrum measurements performed for the spontaneous fission of Cf-252 and for 1.7 and 15.6 MeV neutron-induced fission of U-238 at the CEA, DAM, DIF Van de Graaff accelerator, will be presented. (authors)

Fast fission phenomena

International Nuclear Information System (INIS)

Gregoire, Christian.

1982-03-01

Experimental studies of fast fission phenomena are presented. The paper is divided into three parts. In the first part, problems associated with fast fission processes are examined in terms of interaction potentials and a dynamic model is presented in which highly elastic collisions, the formation of compound nuclei and fast fission appear naturally. In the second part, a description is given of the experimental methods employed, the observations made and the preliminary interpretation of measurements suggesting the occurence of fast fission processes. In the third part, our dynamic model is incorporated in a general theory of the dissipative processes studied. This theory enables fluctuations associated with collective variables to be calculated. It is applied to highly inelastic collisions, to fast fission and to the fission dynamics of compound nuclei (for which a schematic representation is given). It is with these calculations that the main results of the second part can be interpreted [fr

Nuclear fission

International Nuclear Information System (INIS)

Kodama, T.

1981-01-01

The nuclear fission process is pedagogically reviewed from a macroscopic-microscopic point of view. The Droplet model is considered. The fission dynamics is discussed utilizing path integrals and semiclassical methods. (L.C.) [pt

Experiments on neutron-attenuation by water-lead mixtures; Etude experimentale de l'attenuation des neutrons dans les melanges plomb-eau

Energy Technology Data Exchange (ETDEWEB)

Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

The penetration of fission neutrons in water-lead mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 65 per cent. For smaller water contents, the measurements show the evidence of streaming presumably due to slowing-down neutrons of energy smaller than 300 keV. (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges plomb-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 65 pour cent en volume. Pour des proportions inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. (auteur)

Recent progress in the detection of bursts in the canning in French reactors; Progres recents de la detection des ruptures de gaines dans les reacteurs francais G1, EL2, G3, EL3

Energy Technology Data Exchange (ETDEWEB)

Goupil, J; Grenon, M; Raffailhac, J; Roguin, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-07-01

method. A scintillator and an electronic system provide a specific signal of the fission products which is then marked on a recorder. In a case where the activity threshold is exceeded, the cell involved is isolated from the prospection system and taker, over by a 'follow-up' detector which follows the evolution of the crack. A year of working on the pile G{sub 1}, which is cooled by air at atmospheric pressure, has made it possible to obtain results on the operation of the canning-burst detection appliance, which has led us to perfect the original device by installing an 'evolution-meter' of the type described above for G{sub 3}. The reactor EL{sub 3}, cooled by heavy water, uses a detection system based on the measurement by GM counters of the activity of the fission gases carried by diluted helium into the heavy water, then extracted by hydro-cyclones. The selectivity of the system gives it a low sensitivity to parasite activities, and an excellent performance. (author) [French] Dans les piles refroidies par gaz carbonique sous pression, du type G{sub 3}, la radioactivite principale du gaz est celle de l'azote 16 creee par reaction {sup 16}O(n, p) {sup 16}N des neutrons rapides sur l'oxygene. Cette activite, de vie courte et de forte energie {beta}, masque l'activite des gaz de fission s'echappant par une fissure de gaine dans le gaz carbonique et oblige a utiliser une methode de separation materielle des produits de fission solides avant la detection proprement dite. Cette detection est faite par une chaine electronique speciale dont l'entree est un scintillateur associe a un photomultiplicateur. Un systeme de mesure d'evolution de fissure avec compensation des variations de puissance permet de suivre la vitesse d'evolution d'une fissure. Cet appareil, baptise evolumetre, est destine a ramener a une methode de zero la mesure de l'activite du gaz de refroidissement des canaux, il permet de s'affranchir: 1) de l'activite propre du gaz restant apres la discrimination

Prompt fission neutron spectra of n + 235U above the (n, nf) fission threshold

International Nuclear Information System (INIS)

Shu Nengchuan; Chen Yongjing; Liu Tingjin; Jia Min

2015-01-01

Calculations of prompt fission neutron spectra (PFNS) from the 235 U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n, xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n, xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n, nf) or (n, 2nf) reactions influences the PFNS shape, and the neutron spectra of the (n, xnf) fission-channel are soft compared with the neutron spectra of the (n, f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. (authors)

Fission product yields

International Nuclear Information System (INIS)

Valenta, V.; Hep, J.

1978-01-01

Data are summed up necessary for determining the yields of individual fission products from different fissionable nuclides. Fractional independent yields, cumulative and isobaric yields are presented here for the thermal fission of 235 U, 239 Pu, 241 Pu and for fast fission (approximately 1 MeV) of 235 U, 238 U, 239 Pu, 241 Pu; these values are included into the 5th version of the YIELDS library, supplementing the BIBFP library. A comparison is made of experimental data and possible improvements of calculational methods are suggested. (author)

Cumulative fission yield of Ce-148 produced by thermal-neutron fission of U-235

International Nuclear Information System (INIS)

Hasan, A.A.

1984-12-01

Cumulative fission yield of 148 cesium isotopes and some other fission products produced by thermal-neutron fission of 235 uranium is determined by Germanium/Lithium spectroscopic methods. The measuremets were done at Tsing-Hua open pool reactor using 3 to 4 mg of 93.15% enriched 235 uranium samples. Gamma rays are assigned to the responsible fission products by matching gamma rays energies and half lives. Fission rate is calculated by fission track method. Cumulative fission yields of 148 cesium, 90 krypton, 130 iodine, 144 lanthanum, 89 krypton, 136 xenon, 137 xenon and 140 cesium are calculated. This values are compared with previously predicted values and showed good agreement. 21 Ref

HAC and fission reactors

International Nuclear Information System (INIS)

Fujiwara, I.; Moriyama, H.; Tachikawa, E.

1984-01-01

In the fission process, newly formed fission products undergo hot atom reactions due to their energetic recoil and abnormal positive charge. The hot atom reactions of the fission products are usually accompanied by secondary effects such as radiation damage, especially in condensed phase. For reactor safety it is valuable to know the chemical behaviour and the release behaviour of these radioactive fission products. Here, the authors study the chemical behaviour and the release behaviour of the fission products from the viewpoint of hot atom chemistry (HAC). They analyze the experimental results concerning fission product behaviour with the help of the theories in HAC and other neighboring fields such as radiation chemistry. (Auth.)

Measure of the slowing down area of thermal state 1,45 eV neutrons in the graphite; Mesure de l'aire de ralentissement des neutrons dans le graphite de 1,45 eV a l'etat thermique

Energy Technology Data Exchange (ETDEWEB)

Robert, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1956-12-15

The life of a neutron emitted as a fast one within a moderating medium may be divided into two parts; at first it is slowed down colliding with the nuclei of the medium; later on, as soon as its energy is of the order of the thermal agitation energy, it diffuses until captured by some nucleus. As a matter of fact, dividing the evolution of a neutron into two phases, a slowing down phase and a diffusing phase is arbitrary, since the thermal equilibrium is attained stepwise. This report is intended to examine the means of inferring the distribution of thermal neutrons from the distribution of fast neutrons on the basis of the distribution of nascent thermal neutrons and of the law of scattering. (author) [French] La vie d'un neutron emis a l'etat rapide dans un milieu moderateur comprend 2 parties: au debut il se ralentit par chocs sur les noyaux du milieu; ensuite, lorsque son energie est de l'ordre de l'energie d'agitation thermique, il diffuse jusqu'a sa capture par un noyau. La separation de l'evolution d'un neutron en deux phases, phase de ralentissement, puis phase de diffusion, est, en realite, arbitraire; un neutron doit atteindre l'equilibre thermique progressivement. L'objet de ce rapport est de voir comment on peut deduire la repartition des thermiques de la repartition des rapides connaissant la repartition des thermiques naissants et la loi de diffusion. (au0010te.

Measuring fission lifetimes with the crystal-blocking technique in mono-crystal, access to nuclear dissipation

International Nuclear Information System (INIS)

Basnary, St.

2002-10-01

Energy dissipation in nuclear matter may play an important role in the determination of the way through which heavy nuclei des-excite: fission or particle evaporation. An important dissipation should imply longer interval of time during which the nucleus is deformed. In that way the measurement of fission lifetimes may shed light on energy dissipation, but these measurements are very delicate to perform. Most available data on deformation times come from indirect measurements combined with the use of more or less valid models. The crystal-blocking lifetime technique in mono-crystals allows the direct measurement of long fission lifetimes. This technique has been applied to different nuclei situated in the proximity of lead. We have obtained relatively high values: τ > 3.10 -19 s for both lead and uranium which implies a strong dissipation of energy. The computation of dissipation coefficients has led to the following values: β ≅ 2.10 21 /s for lead and β ≥ 6.10 21 /s for uranium (E * > 120 MeV). These results show that dissipation effects have to be taken into account in the determination of the deexcitation way. (A.C.)

Measuring fission lifetimes with the crystal-blocking technique in mono-crystal, access to nuclear dissipation; Mesures de temps de fission par la technique d'ombre dans les monocristaux: un acces a la dissipation nucleaire

Energy Technology Data Exchange (ETDEWEB)

Basnary, St

2002-10-01

Energy dissipation in nuclear matter may play an important role in the determination of the way through which heavy nuclei des-excite: fission or particle evaporation. An important dissipation should imply longer interval of time during which the nucleus is deformed. In that way the measurement of fission lifetimes may shed light on energy dissipation, but these measurements are very delicate to perform. Most available data on deformation times come from indirect measurements combined with the use of more or less valid models. The crystal-blocking lifetime technique in mono-crystals allows the direct measurement of long fission lifetimes. This technique has been applied to different nuclei situated in the proximity of lead. We have obtained relatively high values: {tau} > 3.10{sup -19} s for both lead and uranium which implies a strong dissipation of energy. The computation of dissipation coefficients has led to the following values: {beta} {approx_equal} 2.10{sup 21} /s for lead and {beta} {>=} 6.10{sup 21} /s for uranium (E{sup *} > 120 MeV). These results show that dissipation effects have to be taken into account in the determination of the deexcitation way. (A.C.)

Fission cross-section calculations and the multi-modal fission model

International Nuclear Information System (INIS)

Hambsch, F.J.

2004-01-01

New, self consistent, neutron-induced reaction cross section calculations for 235,238 U, 237 Np have been performed. The statistical model code STATIS was improved to take into account the multimodality of the fission process. The three most dominant fission modes, the two asymmetric standards I (S1) and standard II (S2) modes and the symmetric superlong (SL) mode have been taken into account. De-convoluted fission cross sections for those modes for 235,238 U(n,f) and 237 Np(n,f) based on experimental branching ratios, were calculated for the first time up to the second chance fission threshold. For 235 U(n,f), the calculations being made up to 28 MeV incident neutron energy, higher fission chances have been considered. This implied the need for additional calculations for the neighbouring isotopes. As a side product also mass yield distributions could be calculated at energies hitherto not accessible by experiment. Experimental validation of the predictions is being envisaged

Interpretation of criticality experiments on homogeneous solutions of plutonium and uranium; Interpretation des experiences de criticite sur des solutions homogenes de plutonium et d'uranium

Energy Technology Data Exchange (ETDEWEB)

Ithurralde, M F; Kremser, J; Leclerc, J; Lombard, Ch; Moreau, J; Robin, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

Criticality experiments on solutions of fissionable materials have been carried out in tanks of various geometries (cylinder, isolated annular cylinder, interacting annular cylinders); the reflexion conditions have also been varied (without reflection, semi-reflection and total reflexion by water). The range of the studied concentrations is rather large (18,8 to 104 gms/liter). The interpretation of these experiments has been undertaken in order to resolve the problems of the industrial use of homogeneous plutonium and uranium solutions. Several methods the fields of application of which are different have been used: diffusion method, transport method and Monte-Carlo method. (authors) [French] Des experiences critiques sur des solutions de matieres fissiles ont ete faites dans des cuves de diverses geometries (cylindre, cylindre annulaire isole, cylindre annulaire en interaction), les conditions de reflexion ont ete egalement variees (sans reflexion, semi reflexion et reflexion totale par l'eau). La gamme des concentrations etudiees est assez etendue (18,8 a 104 g/l ). L'interpretation de ces experiences a ete entreprise dans le but de pouvoir resoudre les problemes poses par l'emploi industriel de solutions homogenes de plutonium et d'uranium, plusieurs methodes dont les domaines d'application sont differents ont ete employees: methode de diffusion, methode de transport, methode de Monte-Carlo. (auteurs)

Fission Research at IRMM

Directory of Open Access Journals (Sweden)

Al-Adili A.

2010-03-01

Full Text Available Fission Research at JRC-IRMM has a longstanding tradition. The present paper is discussing recent investigations of fission fragment properties of 238 U(n,f, 234 U(n,f, prompt neutron emission in fission of 252 Cf(SF as well as the prompt fission neutron spectrum of 235 U(n,f and is presenting the most important results.

Use of an oscillation technique to measure effective cross-sections of fissionable samples in critical assemblies; Mesure des sections efficaces effectives d'echantillons fissiles par une methode d'oscillation dans les-assemblages critiques

Energy Technology Data Exchange (ETDEWEB)

Tretiakoff, O; Vidal, R; Carre, J C; Robin, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

The authors describe the technique used to measure the effective absorption and neutron-yield cross-sections of a fissionable sample. These two values are determined by analysing the signals due to the variation in reactivity (over-all signal) and the local perturbation in the flux (local signal) produced by the oscillating sample. These signals are standardized by means of a set of samples containing quantities of fissionable material ({sup 235}U) and an absorber, boron, which are well known. The measurements are made for different neutron spectra characterized by lattice parameters which constitute the central zone within which the sample moves. This technique is used to study the effective cross-sections of uranium-plutonium alloys for different heavy-water and graphite lattices in the MINERVE and MARIUS critical assemblies. The same experiments are carried out on fuel samples of different irradiations in order to determine the evolution of effective cross-sections as a function of the spectrum and the irradiations. (authors) [French] On decrit la methode utilisee pour mesurer les sections efficaces effectives d'absorption et de production de neutrons d'un echantillon fissile. Ces deux grandeurs sont determinees en analysant les signaux dus a la variation de reactivite (signal global) et a la perturbation locale de flux (signal local) produits par l'echantillon oscillant. Ces signaux sont etalonnes a l'aide d'un jeu d'echantillons dont les teneurs en materiau fissile ({sup 235}U) et en absorbeur (bore) sont bien connues. Les mesures sont realisees pour differents spectres de neutrons caracterises par les parametres du reseau constituant la zone centrale a l'interieur de laquelle se deplace l'echantillon. A l'aide de cette methode on etudie les sections efficaces effectives d'alliage uranium-plutonium pour differents reseaux a eau lourde et a graphite dans les assemblages crtiques MINERVE et MARIUS. Les memes experiences sont effectuees sur des echantillons de

Stablité des Eléments Trans-ferminums à Haut Spin : Mesure de la barrière de fission de 254No

OpenAIRE

Henning , Gregoire

2012-01-01

Super heavy nuclei provide opportunities to study nuclear structure near three simultaneous limits: in charge Z, spin I and excitation energy E∗. These nuclei exist only because of a fission barrier, created by shell effects. It is therefore important to determine the fission barrier and its spin dependence Bf(I), which gives information on the shell energy Eshell(I). Theoretical calculations predict different fission barrier heights from Bf(I = 0) = 6.8 MeV for a macro-microscopic model to 8...

Etude structurale et propriétés des verres peralumineux de conditionnement des produits de fission et actinides mineurs"

OpenAIRE

Gasnier , Estelle

2013-01-01

In this work, peraluminous glasses (lack of alkaline and alkaline earth ions regarding aluminum) are under study to assess the potentiality of these matrices to confine fission products and minor actinides (FPA) at higher rate than current R7T7 glass (18,5 wt % FPA). The first part of this work aims at studying the physical and chemical properties of complex peraluminous glasses containing increasing FPA rate (18.5 to 32 wt %) to compare them with the specifications. The very low crystallizat...

Study on the effect factor of the absolute fission rates measured by depleted uranium fission chamber

International Nuclear Information System (INIS)

Jiang Li; Liu Rong; Wang Dalun; Wang Mei; Lin Jufang; Wen Zhongwei

2003-01-01

The absolute fission rates was measured by the depleted uranium fission chamber. The efficiency of the fission fragments recorded in the fission chamber was analyzed. The factor influencing absolute fission rates was studied in the experiment, including the disturbing effect between detectors and the effect of the structural of the fission chamber, etc

Investigation of short-living fission products from the spontaneous fission of Cf-252

International Nuclear Information System (INIS)

Klonk, H.

1976-01-01

In this paper, a method of separating and measuring fission products of Cf-252 is presented. The measurement was achieved by means of γ-spectrometry and thus provides a quantitative analysis with a good separation of the fission products with respect to both atomic number Z and mass number A. The separation of the fission products from the fission source was achieved by means of solid traps. An automatic changing apparatus made it possible to keep irradiation and measuring times short, so even very short-lived fission products could be registered. The quantitative evaluation of primary fission products was made possible by correction according to Bateman equations. With that, the yields of single nuclides and the dispersion of charge can be determined. (orig./WL) [de

Accounting Systems for Heavy Water and Fissionable Materials; Comptabilite de l'Eau Lourde et des Matieres Fissiles; Sistema ucheta tyazheloj vody i delyashchikhsya materialov; Sistemas de Contabilidad para el Agua Pesada y los Materiales Fisionables

Energy Technology Data Exchange (ETDEWEB)

Fletcher, G. W.; Reid, H. B.; Jenkinson, W. G. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

1966-02-15

Detailed accounting and reporting procedures used by Atomic Energy of Canada Limited (AECL) for maintaining adequate records and control of heavy water supplies and stocks of fissionable materials are described, along with the duties and responsibilities of those administering the system. An appraisal is made of these procedures with respect to their adaptability for use in rapidly expanding research and power programmes. In particular the use of electronic data processing equipment is evaluated. A senior management committee is responsible for ensuring that there is a proper system for recording, reporting and controlling fissionable materials. The Production Planning and Control Branch (Pp and C B) of the Operations Division at the Chalk River Nuclear Laboratories (CRNL) is responsible to the committee for keeping the over-all records and for the general administration of the system. The duties involved are detailed in the report. The system for fissionable materials is segregated into several accountability units 15 of which are allocated to AECL departments and the others to Canadian industries and research organizations. A control ledger is kept by PP and CB for each of the units; however, the units are responsible for preparing detailed accounts of all material under their jurisdiction. The basic recording procedures covering the movement Of materials between units, the changing of forms within units, the handling of gains and losses, and disposals, are outlined in the report. The transfer of this data to IBM cards, the ultimate processing through an IBM 1401 computer and the preparation of reports for management approval are described. The heavy-water accounting system based on the same principles as used for the fissionable materials is explained. In this case the control ledger lists the pounds of D{sub 2}O allocated to each of the 15 accountability units. Again the basic recording methods and the use of a computer system are outlined. (author) [French

The nuclear fission process

International Nuclear Information System (INIS)

Wagemans, C.

1991-01-01

Fifty years after its discovery, the nuclear fission phenomenon is of recurring interest. When its fundamental physics aspects are considered, fission is viewed in a very positive way, which is reflected in the great interest generated by the meetings and large conferences organized for the 50th anniversary of its discovery. From a purely scientific and practical point of view, a new book devoted to the (low energy) nuclear fission phenomenon was highly desirable considering the tremendous amount of new results obtained since the publication of the book Nuclear Fission by Vandenbosch and Huizenga in 1973 (Academic Press). These new results could be obtained thanks to the growth of technology, which enabled the construction of powerful new neutron sources, particle and heavy ion accelerators, and very performant data-acquisition and computer systems. The re-invention of the ionization chamber, the development of large fission fragment spectrometers and sophisticated multiparameter devices, and the production of exotic isotopes also contributed significantly to an improved understanding of nuclear fission. This book is written at a level to introduce graduate students to the exciting subject of nuclear fission. The very complete list of references following each chapter also makes the book very useful for scientists, especially nuclear physicists. The book has 12 chapters covering the fission barrier and the various processes leading to fission as well as the characteristics of the various fission reaction products. In order to guarantee adequate treatment of the very specialized research fields covered, several distinguished scientists actively involved in some of these fields were invited to contribute their expertise as authors or co-authors of the different chapters

Intermediate energy nuclear fission

International Nuclear Information System (INIS)

Hylten, G.

1982-01-01

Nuclear fission has been investigated with the double-kinetic-energy method using silicon surface barrier detectors. Fragment energy correlation measurements have been made for U, Th and Bi with bremsstrahlung of 600 MeV maximum energy. Distributions of kinetic energy as a function of fragment mass are presented. The results are compared with earlier photofission data and in the case of bismuth, with calculations based on the liquid drop model. The binary fission process in U, Yb, Tb, Ce, La, Sb, Ag and Y induced by 600 MeV protons has been investigated yielding fission cross sections, fragment kinetic energies, angular correlations and mass distributions. Fission-spallation competition calculations are used to deduce values of macroscopic fission barrier heights and nuclear level density parameter values at deformations corresponding to the saddle point shapes. We find macroscopic fission barriers lower than those predicted by macroscopic theories. No indication is found of the Businaro Gallone limit expected to occur somewhere in the mass range A = 100 to A = 140. For Ce and La asymmetric mass distributions similar to those in the actinide region are found. A method is described for the analysis of angular correlations between complementary fission products. The description is mainly concerned with fission induced by medium-energy protons but is applicable also to other projectiles and energies. It is shown that the momentum and excitation energy distributions of cascade residuals leading to fission can be extracted. (Author)

The Cyrano program. 1 - description and operation of an irradiation device 'Cyrano'. 2 - results of the experiments Cyrano 1 and 2 (study of the EL 4 first-bach pencil); measurement of the thermal conductivity integral for UO{sub 2} sintered up to 2300 deg C; evolution of fission gases at constant power; Programme Cyrano. 1 - description et exploitation d'un dispositif d'irradiation ''cyrano''. 2 - resultats des experiences cyrano 1 et 2 (etude du crayon EL4 1. jeu). Mesure de l'integrale de conductibilite thermique d'UO{sub 2} fritte jusqu'a 2300 deg C. Evolution des gaz de fission a puissance constante

Energy Technology Data Exchange (ETDEWEB)

Stora, J P; Chenebault, P [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

Two rods of the type 'EL 4 first score' have been irradiated in 'Cyrano' capsules which are suited for continuous measurement of the nuclear power evolved and equipped with thermocouples. The variations of the integral of conductivity of sintered 96 per cent theoretical dense UO{sub 2} has been established until 2300 deg. C; these variations are coherent with those previously measured out-of-pile. The released fission gases have been recovered at different times during the irradiation: the kinetics of release of stable gases is such that, in the experimental conditions (T{sub surface} = 610 deg. C, {integral}{sub T{sub s}}{sup T{sub c}} kdT = 34.7 W cm{sup -1}) the fraction of released gases is still widely increasing after 12 days of irradiation. Numerous observations have been made on concentrations of rare gases locally present in the irradiated fuel. (authors) [French] L'irradiation de deux crayons combustibles type EL 4, 1er jeu, a ete menee a bien dans des capsules 'Cyrano' equipees de dispositifs de mesure continue de la puissance nucleaire et de plusieurs reperes de temperatures; la variation de l'integrale de conductibilite thermique de l'oxyde d'uranium fritte (96 pour cent d. th.) a ete tracee jusqu'a 2300 deg. C; la courbe representative de ces variations est coherente avec celle obtenue precedemment hors pile. Les gaz de fission apparus hors du combustible ont ete extraits du crayon a plusieurs reprises pendant l'experience: la cinetique d'accumulation des gaz stables est telle que dans les conditions etudiees (T{sub surface} = 610 deg. C, {integral}{sub T{sub s}}{sup T{sub c}} kdT = 34.7 W cm{sup -1}) la fraction des gaz degages est encore largement croissante apres 12 jours d'irradiation. De nombreuses observations ont ete recueillies sur la nature et la concentration des gaz rares presents en differents points du combustible irradie. (auteurs)

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, M.

1984-09-01

This is the tenth issue of a report series on Fission Product Data, which informs us about all the activities in this field, which are planned, ongoing, or have recently been completed. The types of activities included are measurements, compilations and evaluations of: fission product yields (neutron induced and spontaneous fission), neutron reaction cross sections of fission products, data related to the radioactive decay of fission products, delayed neutron data of fission products, lumped fission product data (decay heat, absorption, etc.). There is also a section with recent references relative to fission product nuclear data

Effects of fissioning nuclei distributions on fragment mass distributions for high energy fission

Directory of Open Access Journals (Sweden)

Rossi P C R

2012-02-01

Full Text Available We study the effects of fissioning nuclei mass- and energy-distributions on the formation of fragments for fission induced by high energy probes. A Monte Carlo code called CRISP was used for obtaining mass distributions and spectra of the fissioning nuclei for reactions induced by 660 MeV protons on 241Am and on 239Np, by 500 MeV protons on 208Pb, and by Bremsstrahlung photons with end-point energies at 50 MeV and 3500 MeV on 238U. The results show that even at high excitation energies, asymmetric fission may still contribute significantly to the fission cross section of actinide nuclei, while it is the dominante mode in the case of lead. However, more precise data for high energy fission on actinide are necessary in order to allow definite conclusions.

Forecasting the Quantity and Activity of Fission Products in France in Future Years in the Light of Atomic Energy Development; Quantite et Activite des Produits de Fission Obtenus en France dans les Annees a Venir Compte Tenu du Developpement de l'Energie Atomique; 041a 041e 041b 0414 ; Cantidad y Actividad de los Productos de Fision que se Obtendran en Francia en los Anos Venideros, Habida Cuenta del Desarrollo de la Energia Atomica

Energy Technology Data Exchange (ETDEWEB)

Guirlet, J.; Lavie, J. M. [Commissariat a l' Energie Atomique, Saclay (France)

1960-07-01

With the aid of Wigner and Way's formula it is possible to predict theoretically the activity of the complex mixture of fission products originating in a reactor. Account is taken in the study of prospective nuclear power production in France up to 1975. It is assumed that the uranium stays in the reactor for periods of three and of six months. It is also possible to determine the activity of a given fission product and to calculate its decay time. The substance selected was strontium for an activation period of three months. Each group of curves shows total activity at any moment and the activity of particular fission products over a given period. (author) [French] En utilisant la formule de Wigner et Way, il est possible de prevoir theoriquement l'activite du melange complexe de produits de fission provenant d'une pile. L'etude a ete faite en tenant compte de previsions en ce qui concerne en France la production d'electricite d'origine atomique jusqu'en 1975. On a suppose des temps de sejour en pile de l'uranium de trois mois et de six mois. Il est possible egalement de trouver l'activite d'un produit de fission particulier, et de donner sa decroissance. Le corps choisi est le strontium pour un temps d'activation de trois mois. Chaque ensemble de courbes donne a tout instant l'activite totale, et l'activite propre des produits de fission correspondant a une periode donnee. (author) [Spanish] Empleando la formula de Wigner y Way se puede calcular teoricamente la actividad de la mezcla compleja de productos de fision procedentes de una pila. Para esta memoria se han tenido en cuenta las previsiones de produccion de electricidad nucleoelectrica en Francia hasta 1975. Los autores suponen que el uranio permanece tres o seis meses en la pila y han conseguido determinar la actividad de un producto de fision determinado, asi como su periodo de desintegracion. Han escogido el estroncio, con un tiempo de activacion de 3 meses. Cada conjunto de curvas da la actividad total

Angular momenta of fission fragments in the {alpha}-accompanied fission of {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Jandel, M.; Kliman, J.; Krupa, L.; Morhac, M. [Slovak Academy of Sciences, Department of Nuclear Physics, Bratislava (Slovakia); Joint Institute for Nuclear Research, Flerov Laboratory for Nuclear Reactions, Dubna (Russian Federation); Hamilton, J.H.; Kormicki, J.; Ramayya, A.V.; Hwang, J.K.; Luo, Y.X.; Fong, D.; Gore, P. [Vanderbilt University, Department of Physics, Nashville, TN (United States); Ter-Akopian, G.M.; Oganessian, Yu.Ts.; Rodin, A.M.; Fomichev, A.S.; Popeko, G.S. [Joint Institute for Nuclear Research, Flerov Laboratory for Nuclear Reactions, Dubna (Russian Federation); Daniel, A.V. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Rasmussen, J.O.; Macchiavelli, A.O.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Donangelo, R.; Cole, J.D.

2005-06-01

For the first time, average angular momenta of the ternary fission fragments {sup 100,102}Zr, {sup 106}Mo, {sup 144,146}Ba and {sup 138,140,142}Xe from the {alpha}-accompanied fission of {sup 252}Cf were obtained from relative intensities of prompt {gamma}-ray transitions with the use of the statistical model calculation. Average values of the angular momenta were compared with the corresponding values for the same fission fragments from the binary fission of {sup 252}Cf. Results indicate the presence of a decreasing trend in the average values of angular momenta induced in ternary fission fragments compared to the same binary fission fragments. On the average, the total angular momentum extracted for ternary fission fragments is {proportional_to}1.4{Dirac_h} lower than in binary fission. Consequently, results indicate that the mechanism of the ternary {alpha}-particles emission may directly effect an induction of angular momenta of fission fragments, and possible scenarios of such mechanisms are discussed. Further, the dependence of the angular momenta of {sup 106}Mo and {sup 140}Xe on the number of emitted neutrons from correlated pairs of primary fragments was obtained also showing a decreasing dependence of average angular momenta with increasing number of emitted neutrons. Consequences are briefly discussed. (orig.)

Specific fission J-window and angular momentum dependence of the fission barrier

Energy Technology Data Exchange (ETDEWEB)

Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto; Yokoyama, Akihiko [Osaka Univ., Suita (Japan); Shinohara, Atsushi

1997-04-01

A method to determine a unique J-window in the fission process was devised and the fissioning nuclide associated with thus extracted J-window was identified for each of the heavy-ion reaction systems. Obtained fission barriers at the resulting J-window were compared with the calculated values by the rotating finite range model (RFRM). The deduced barriers for individual nuclides were compared with the RFRM barriers to reproduce more or less the angular momentum dependence the RFRM prediction. The deduced systematic behavior of the fission barrier indicates no even-odd and shell corrections are necessary. The nuclear dissipation effect based on Kramer`s model revealed substantial reduction of the statistically deduced barrier heights and brought a fairly large scattering from the RFRM J-dependence. However, introduction of the temperature-dependent friction coefficient ({gamma} = 2 for T {>=} 1.0 MeV and 0.5 for T < 1.0 MeV) was found to bring about satisfactory agreement with both RFRM fission barriers and the pre-fission neutron multiplicity systematics. (author). 81 refs.

Dispersions of Oxides in Oxide Matrices as High-Temperature Reactor Fuels; Dispersions d'oxyde dans des matrices d'oxyde, utilisees comme combustibles dans des reacteurs a haute temperature; Dispersiya okisej v okislovykh matritsakh v kachestve topliva dlya vysokotemperaturnogo reaktora; Empleo de dispersiones de oxidos en matrices de oxidos, como combustibles para reactores de elevada temperatura

Energy Technology Data Exchange (ETDEWEB)

Williams, J. [Atomic Energy Research Establishment, Harwell (United Kingdom)

1963-11-15

The potential usefulness of dispersions of PuO{sub 2}, UO{sub 2} and ThO{sub 2} in matrices of BeO, Al{sub 2}O{sub 3}, MgO and SiO{sub 2} is reviewed in terms of fuel integrity and fabrication. Dimensional stability and fission-product retentivity are the two features most important to fuel integrity. Compatibility of the constituents of the fuels with one another and with the coolant will influence dimensional stability, but oxide fuels are well favoured in these respects. Dimensional changes under irradiation will contain contributions from neutron and fission fragment damage to the matrix, from radiation damage to the fissile-fertile phase and from agglomerated fission-product gases. Thermal stresses are also capable of effecting changes in shape. However, information on mechanisms for stress relaxation is too limited to enable any reasonable theoretical assessment of behaviour to be made. Both light irradiation and high burn-up studies of fission-product release from the fissile-fertile oxides have concerned themselves mainly with the gaseous products, chiefly xenon. Data on the release of other fission products is very limited as is also information on the movement of fission products in general through the potential matrix materials. Studies of the permeability of sintered pure oxides indicate that densities of at least 95% theoretical density (maybe even 98%) will be needed to eliminate open porosity in such matrices. A variety of techniques are available for the preparation of fissile-fertile particles, for their coating and for their incorporation into high-density matrices. Work on laboratory-scale fabrication processes is well advanced. (author) [French] L'auteur examine la possibilite d'utiliser des combustibles disperses - PuO{sub 2}, UO{sub 2} et ThO{sub 2} et matrices de BeO, Al{sub 2}O{sub 3}, MgO et SiO{sub 2} - dans des reacteurs a haute temperature, au point de vue de l'integrite du combustible et de sa transformation. La stabilite dimensionnelle

The structure of nuclear matter; La structure de la matiere nucleaire

Energy Technology Data Exchange (ETDEWEB)

Bloch, [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Brueckner indique les derniers resultats concernant l'application de sa theorie aux noyaux finis. Le professeur Migdal resume les resultats qu'il a obtenu a l'aide de la methode des fonctions de Green sur les proprietes de superconductivite des noyaux finis. Le professeur Weisskopf donne une explication qualitative du succes de la theorie de Brueckner. (auteur)

Neutron-induced fission cross sections

International Nuclear Information System (INIS)

Weigmann, H.

1991-01-01

In the history of fission research, neutron-induced fission has always played the most important role. The practical importance of neutron-induced fission rests upon the fact that additional neutrons are produced in the fission process, and thus a chain reaction becomes possible. The practical applications of neutron-induced fission will not be discussed in this chapter, but only the physical properties of one of its characteristics, namely (n,f) cross sections. The most important early summaries on the subject are the monograph edited by Michaudon which also deals with the practical applications, the earlier review article on fission by Michaudon, and the review by Bjornholm and Lynn, in which neutron-induced fission receives major attention. This chapter will attempt to go an intermediate way between the very detailed theoretical treatment in the latter review and the cited monograph which emphasizes the applied aspects and the techniques of fission cross-section measurements. The more recent investigations in the field will be included. Section II will survey the properties of cross sections for neutron-induced fission and also address some special aspects of the experimental methods applied in their measurement. Section Ill will deal with the formal theory of neutron-induced nuclear reactions for the resolved resonance region and the region of statistical nuclear reactions. In Section IV, the fission width, or fission transmission coefficient, will be discussed in detail. Section V will deal with the broader structures due to incompletely damped vibrational resonances, and in particular will address the special case of thorium and neighboring isotopes. Finally, Section VI will briefly discuss parity violation effects in neutron-induced fission. 74 refs., 14 figs., 3 tabs

Study of niobium isotopes having excess neutrons and a short half-life; Etude des isotopes du niobium excedentaires en neutrons et de courte periode

Energy Technology Data Exchange (ETDEWEB)

Huebenthal, K [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1968-02-01

By irradiating Mo with 14 MeV neutrons isomers have been found for {sup 98}Nb (2.8 s half-life) {sup 99}Nb (9 s) and {sup 100}Nb (2.4 s). No isomer of this type seems to exist for {sup 96}Nb. Rapid separation methods are developed for isolating {sup 98}Zr from fission products, and for separating Zr and Nb. The half-life of {sup 98}Zr is measured (31 s) and the formation of {sup 98}Nb (2.8 s) from {sup 98}Zr (31 s) is shown by milking. Rough {beta} and {gamma} measurements of these nuclei are described. The {gamma} spectrum of {sup 98}Nb (51 mn) is studied with a high-resolution Ge/Li - detector. (authors) [French] Des irradiations des isotopes de molybdene avec des neutrons de 14 MeV ont mis en evidence l'existence des isomeres de {sup 98}Nb (periode 2.8 s) {sup 99}Nb (9 s) et {sup 100}Nb (2.4 s). Pour le {sup 96}Nb un isomere de ce type ne semble pas exister. Des methodes rapides de separation sont mises au point pour isoler le zirconium 98 des produits de fission, et pour separer ensuite le niobium du zirconium. La periode du {sup 98}Zr est de 3l s, et on demontre la formation du {sup 98}Nb (2.8 s) a partir du Zr (31 s). Ces corps sont etudies sommairement en spectroscopie {beta} et {gamma}. Le spectre gamma de {sup 98}Nb (periode 51 mn) est etudie avec un detecteur Ge/Li de haute resolution. (auteurs)

Study of the variation with the energy of the fission cross-sections of {sup 233}U, {sup 235}U, {sup 239}Pu for the fast neutrons; Etude de la variation avec l'energie des sections efficaces de fission de {sup 233}U, {sup 235}U, {sup 239}Pu pour les neutrons rapides

Energy Technology Data Exchange (ETDEWEB)

Szteinsznaider, D; Naggiar, V; Netter, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

This measurements have been done while taking the value of the fission cross-sections of {sup 238}U as reference. The neutrons are produced by the reaction {sup 7}Li(p,n) in the Van de Graaff generator of Saclay. The explored domain spreads from some tenths to 2000 keV. We find: for {sup 239}Pu: {sigma}{sub f} = 2,04 {+-} 0,12 barns, cross-section constant between 150 and 2000 keV, for {sup 235}U: {sigma}{sub f} = 1,15 {+-} 0,15 barns, cross-section constant between 700 and 1000 keV, for {sup 233}U: {sigma}{sub f} = 1,92 {+-} 0,25 barns, for neutrons of 850 keV. (authors) [French] Ces mesures ont ete effectuees en prenant la valeur de la section efficace de fission de {sup 238}U comme reference. Les neutrons sont produits par la reaction {sup 7}Li(p,n) au generateur Van de Graaff de Saclay. Le domaine explore s'etend de quelques dizaines de kev a 2000 kev. Nous trouvons: pour {sup 239}Pu: {sigma}{sub f} = 2,04 {+-} 0,12 barns, section efficace constante entre 150 et 2000 kev. pour {sup 235}U: {sigma}{sub f} = 1,15 {+-} 0,15 barns, section efficace constante entre 700 et 1000 kev. pour {sup 233}U: {sigma}{sub f} = 1,92 {+-} 0,25 barns, pour des neutrons de 850 kev. (auteurs)

Correlation of errors in the Monte Carlo fission source and the fission matrix fundamental-mode eigenvector

International Nuclear Information System (INIS)

Dufek, Jan; Holst, Gustaf

2016-01-01

Highlights: • Errors in the fission matrix eigenvector and fission source are correlated. • The error correlations depend on coarseness of the spatial mesh. • The error correlations are negligible when the mesh is very fine. - Abstract: Previous studies raised a question about the level of a possible correlation of errors in the cumulative Monte Carlo fission source and the fundamental-mode eigenvector of the fission matrix. A number of new methods tally the fission matrix during the actual Monte Carlo criticality calculation, and use its fundamental-mode eigenvector for various tasks. The methods assume the fission matrix eigenvector is a better representation of the fission source distribution than the actual Monte Carlo fission source, although the fission matrix and its eigenvectors do contain statistical and other errors. A recent study showed that the eigenvector could be used for an unbiased estimation of errors in the cumulative fission source if the errors in the eigenvector and the cumulative fission source were not correlated. Here we present new numerical study results that answer the question about the level of the possible error correlation. The results may be of importance to all methods that use the fission matrix. New numerical tests show that the error correlation is present at a level which strongly depends on properties of the spatial mesh used for tallying the fission matrix. The error correlation is relatively strong when the mesh is coarse, while the correlation weakens as the mesh gets finer. We suggest that the coarseness of the mesh is measured in terms of the value of the largest element in the tallied fission matrix as that way accounts for the mesh as well as system properties. In our test simulations, we observe only negligible error correlations when the value of the largest element in the fission matrix is about 0.1. Relatively strong error correlations appear when the value of the largest element in the fission matrix raises

Radiochemistry and the Study of Fission

Energy Technology Data Exchange (ETDEWEB)

Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-11-14

These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since its discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since its discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.

Radiochemistry and the Study of Fission

International Nuclear Information System (INIS)

Rundberg, Robert S.

2016-01-01

These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since its discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since its discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.

Radioprotection rayonnements, dosimétrie, protection

CERN Document Server

Marey, Gérard

2014-01-01

Pour tous les travailleurs du nucléaire comme pour les étudiants des licences professionnelles et des BTS Environnement nucléaire et BTS radioprotection, l'ouvrage rassemble de façon progressive, claire et précise toutes les informations scientifiques et pratiques qui leur sont indispensables. Une première partie résume les données de base relatives à la structure de la matière, la stabilité des noyaux, les différents rayonnements, leur énergie et la décroissance radioactive. La deuxième partie constitue une approche progressive de la radioprotection s'appuyant sur l'influence des rayonnement sur la matière pour définir les notions de dose et aborder le dimensionnement des protections biologiques et des éléments de ventilation. Enfin, la dernière partie traite de la mise en oeuvre pratique de la radioprotection sur le terrain et de la gestion des déchets nucléaires en application de la technologie actuelle, de la réglementation et des directives imposées par l'exploitant qu'est EDF. De...

The Growth of Sea cucumber Stichopus herrmanni After Transverse Induced Fission in Two and Three Fission Plane

Directory of Open Access Journals (Sweden)

Retno Hartati

2016-06-01

Full Text Available Transverse induced fission proven could be done in Teripang Tril, Stichopus herrmanni. This present works aimed to analyze wound recovery, regeneration period and growth of Teripang Trill  after asexual reproduction by fission using two and three fission plane. Observations were made every day until the sea cucumber body separated into two or more (depending on treatment and reared for 16 weeks.  The results showed that there are differences in wound recovery, regeneration period and growth of S. herrmanni depend on their different fission plane. The wound recovery and regeneration period (days of anterior, middle and posterior individu S. herrmanni resulted from two and three fission plane were varied but the two fission plane the anterior individu recover for longer period than posterior part and  the wound recover process in both end for thee fission plane was same. Average growth of anterior and posterior fragment were longer for two fission plane than three fission plane.  The middle fragment (M1 and M2 both fission plane was able to grow but very low.  It showed that three fission plane gave very slow growth in every fragment of the body. Keywords: growth, post-fission, fission plane, Stichopus herrmanni

Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons

International Nuclear Information System (INIS)

Nix, J.R.; Madland, D.G.; Sierk, A.J.

1985-01-01

With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, we discuss recent advances in a unified macroscopic-microscopic description of large-amplitude collective nuclear dynamics. The conversion of collective energy into single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving the Hamilton equations of motion for initial conditions appropriate to fission, we obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of our calculations with experimental data are shown

Equilibrium fission model calculations

International Nuclear Information System (INIS)

Beckerman, M.; Blann, M.

1976-01-01

In order to aid in understanding the systematics of heavy ion fission and fission-like reactions in terms of the target-projectile system, bombarding energy and angular momentum, fission widths are calculated using an angular momentum dependent extension of the Bohr-Wheeler theory and particle emission widths using angular momentum coupling

Measurements of the charge exchange and dissociation cross-sections of the H{sub 2}+ ion in a wide energy range; Mesures des sections efficaces d'echange de charge et de dissociation des ions H{sub 2}{sup +} dans une large gamme d'energie (25 - 250 keV)

Energy Technology Data Exchange (ETDEWEB)

Guidini, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

celles qui arrivent en coincidence sur deux detecteurs differents. Les resultats montrent une forte variation de la section efficace d'echange de charge en fonction de l'energie des ions H{sub 2}{sup +}. Les variations des sections efficaces de dissociation et d'ionisation sont moins prononcees. Pour une energie donnee, les valeurs des sections efficaces sont d'autant plus grandes que la masse atomique des particules cibles est plus grande. Ces mesures ont ete etendues au cas d'ions H{sub 2}{sup +} traversant une cible constituee par des particules chargees. Des resultats preliminaires montrent une augmentation de la valeur des sections efficaces par rapport au cas precedent. Enfin la diffusion des produits de reactions a ete etudiee, elle a permis de voir que l'angle de diffusion provient de ce que les molecules formees au cours d'une reaction se trouvent dans un etat instable et les noyaux ou atomes s'ecartent l'un de l'autre. (auteur)

Study of {gamma} radiation from uranium rods during deactivation; Etude du rayonnement {gamma} des barres d'uranium en court de desactivation

Energy Technology Data Exchange (ETDEWEB)

Balestic, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

The classical formulae giving the {gamma} activities of the fission products contained in a uranium rod after unloading from the pile are reviewed without being proved. The knowledge of these activities makes it possible, by means of the method proposed here, to determine the intensities of ionisation at a point outside the rod, and thus to establish {gamma} radiation diagrams. The different parameters introduced in the calculation are geometric (dimensions of the bars and coordinates of the point considered), energetic (power at which the bar has been irradiated) and temporal (duration of the irradiation and deactivation). A numerical example follows the demonstration of the general formulae, {gamma} flux measurements carried out in the deactivation well of P2 (Saclay pile) define the accuracy of the method. In conclusion, it is suggested that radiation diagrams be used in (planning the use of) industrial irradiators for radiochemical polymerisation or the preservation of food products. (author) [French] On rappelle sans demonstration les formules classiques donnant les activites {gamma} des produits de fission contenus dans une barre d'uranium apres defournement. La connaissance de ces activites permet par la methode proposee de passer aux intensites d'ionisation en un point exterieur a la barre et d'etablir ainsi des diagrammes de rayonnement {gamma}. Les differents parametres introduits dans le calcul sont d'ordre geometrique (dimensions des barres et coordonnees du point considere), d'ordre energetique (puissance a laquelle la barre a ete irradiee) et fonction du temps (duree d'irradiation et de desactivation). Un exemple numerique fait suite a la demonstration des formules generales. Des mesures de flux {gamma} effectuees au puits de desactivation de P2 (pile de Saclay) fixent le degre d'approximation de la methode. En conclusion, on suggere l'utilisation des diagrammes de rayonnement dans l'etablissement de projets d'irradiateurs industriels pour les

Fusion-fission type collisions

International Nuclear Information System (INIS)

Oeschler, H.

1980-01-01

Three examples of fusion-fission type collisions on medium-mass nuclei are investigated whether the fragment properties are consistent with fission from equilibrated compound nuclei. Only in a very narrow band of angular momenta the data fulfill the necessary criteria for this process. Continuous evolutions of this mechnism into fusion fission and into a deep-inelastic process and particle emission prior to fusion have been observed. Based on the widths of the fragment-mass distributions of a great variety of data, a further criterion for the compound-nucleus-fission process is tentatively proposed. (orig.)

Fission neutron multiplicity calculations

International Nuclear Information System (INIS)

Maerten, H.; Ruben, A.; Seeliger, D.

1991-01-01

A model for calculating neutron multiplicities in nuclear fission is presented. It is based on the solution of the energy partition problem as function of mass asymmetry within a phenomenological approach including temperature-dependent microscopic energies. Nuclear structure effects on fragment de-excitation, which influence neutron multiplicities, are discussed. Temperature effects on microscopic energy play an important role in induced fission reactions. Calculated results are presented for various fission reactions induced by neutrons. Data cover the incident energy range 0-20 MeV, i.e. multiple chance fission is considered. (author). 28 refs, 13 figs

Contribution to the study of the diffusion {alpha}-proton for {alpha} particles of 3,1 and 5,3 MeV; Contribution a l'etude de la diffusion {alpha}-proton pour des particules {alpha} d'energie comprise entre 3,1 et 5,3 MeV

Energy Technology Data Exchange (ETDEWEB)

Ruhla, C [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

1953-07-01

The diffusion of the particles has by the light cores that present a weak gate of potential, must permit the survey of the nuclear strengths. Some authors, studying the distribution in energy of the protons given out by a hydrogenated target submitted to a bombardment has variable energy, signal that this distribution has a structure of groups. We tried to reproduce experiences of diffusion {alpha}-proton, in order to verify the existence of the groups of signaled protons in the previous works. However in spite of finer experimental conditions, we had recovered any group structures in the distribution of the protons. This work permits to conclude that there is not a resonance in the {alpha}-proton diffusion for included energies between 3,1 and 5,3 MeV. The absence of resonances confirms the existence of the fundamental level of {sup 5}Li above in the neighborhood of 1,8 MeV {sup 4}He + {sup 1}H. (M.B.) [French] La diffusion des particules a par les noyaux legers qui presentent une faible barriere de potentiel, doit permettre l'etude des forces nucleaires. certains auteurs, etudiant la distribution en energie des protons emis par une cible hydrogenee soumise a un bombardement a d'energie variable, signalent que cette distribution a une structure de groupes. Nous avons essaye de reproduire les experiences du type diffusion {alpha}-proton, afin de verifier l'existence des groupes de protons signales dans les travaux anterieurs. Cependant malgre des conditions experimentales plus fines, nous n'avons retrouve aucunce structure de groupe dans la distribution des protons. Ce travail permet de conclure qu'il n'y a pas de resonance dans la diffusion {alpha}-proton pour des energies comprises entre 3,1 et 5,3 MeV. L'absence de resonances confirme l'existence du niveau fondamental de {sup 5}Li au voisinage de 1,8 MeV au-dessus de {sup 4}He + {sup 1}H. (M.B.)

Fission yield measurements at IGISOL

Science.gov (United States)

Lantz, M.; Al-Adili, A.; Gorelov, D.; Jokinen, A.; Kolhinen, V. S.; Mattera, A.; Moore, I.; Penttilä, H.; Pomp, S.; Prokofiev, A. V.; Rakopoulos, V.; Rinta-Antila, S.; Simutkin, V.; Solders, A.

2016-06-01

The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

Fission yield measurements at IGISOL

Directory of Open Access Journals (Sweden)

Lantz M.

2016-01-01

Full Text Available The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f and Th(p,f have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

Measurement of the {sup 240}Pu concentration of a plutonium sample by the spontaneous fission method (1960); Mesure de la teneur d'un plutonium en {sup 240}Pu par la methode des fissions spontanees (1960)

Energy Technology Data Exchange (ETDEWEB)

Caizergues, R; Clouet d' Orval, C [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

It is very important to know the plutonium-240 content of the plutonium formed in piles. The method of measurement described here consists in counting the number of spontaneous fissions produced in a known quantity of plutonium. This measurement is carried out in a multiple-plate ionisation chamber, the plutonium being deposited on the plates. The disintegration constant of plutonium-240 by spontaneous fission being known the plutonium-240 content in the sample can be calculated. (author) [French] La connaissance de la teneur en plutonium-240 du plutonium forme dans les piles est une question importante. La methode de mesure presentee ici consiste a compter le nombre de fissions spontanees issues d'une quantite connue de plutonium. Cette mesure est effectuee dans une chambre d'ionisation a plateaux multiples sur lesquels est depose le plutonium. La connaissance de la constante de desintegration du plutonium-240 par fissions spontanees permet de calculer la teneur en plutonium-240. (auteur)

Contribution to the study of the diffusion of fission products in uranium; Contribution a l'etude de la diffusion des produits de fission dans l'uranium

Energy Technology Data Exchange (ETDEWEB)

Tournier, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-10-15

In this work we have developed a simple method for determining the diffusion constants and the solid-state solubilities of a metal which is volatile and only slightly soluble in second metal. This method has been applied to the behaviour of certain fission products in {gamma} uranium: strontium, barium, lanthanum, samarium and cerium. This work has made it possible to show the effect of the atomic radius of the solute on the diffusion constants. (author) [French] Dans ce travail nous avons mis au point une methode simple permettant de determiner les constantes de diffusion ainsi que les solubilites a l'etat solide d'un metal volatil et peu soluble dans un autre. Cette methode a ete appliquee au comportement de certains produits de fission dans l'uranium {gamma}: strontium, baryum, lanthane, samarium et cerium. Cette etude a permis de mettre en evidence le role du rayon atomique du solute sur les constantes de diffusion. (auteur)

Study of hypernuclei fission

International Nuclear Information System (INIS)

Malek, F.

1990-01-01

This work is about PS177 experience made on LEAR machine at CERN in 1988. The annihilation reaction of anti protons on a target of Bismuth or Uranium is studied. Lambda particles are produced by this reaction, in the nucleus in 2% of cases 7.1 10 -3 hypernuclei by stopped antiproton in the target are produced. The prompt hypernucleus fission probability of uranium is 75% and that of Bismuth 10%. The mass distribution of fission fragments is symmetrical ((≡ the excitation energy of the nucleus is very high). If the nucleus hasn't fissioned, the non-mesonic lambda decay, gives it an energy of 100 MeV, what allows to fission later. This fission is delayed because the hypernucleus lifetime is 1.3 +0.25 -0.21 10 -10 sec for Bismuth [fr

Elastocapillary Instability in Mitochondrial Fission

Science.gov (United States)

Gonzalez-Rodriguez, David; Sart, Sébastien; Babataheri, Avin; Tareste, David; Barakat, Abdul I.; Clanet, Christophe; Husson, Julien

2015-08-01

Mitochondria are dynamic cell organelles that constantly undergo fission and fusion events. These dynamical processes, which tightly regulate mitochondrial morphology, are essential for cell physiology. Here we propose an elastocapillary mechanical instability as a mechanism for mitochondrial fission. We experimentally induce mitochondrial fission by rupturing the cell's plasma membrane. We present a stability analysis that successfully explains the observed fission wavelength and the role of mitochondrial morphology in the occurrence of fission events. Our results show that the laws of fluid mechanics can describe mitochondrial morphology and dynamics.

Experiments on neutron-attenuation by ordinary concrete; Etude experimentale de l'attenuation des neutrons dans le beton ordinaire

Energy Technology Data Exchange (ETDEWEB)

Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

The penetration of fission-neutrons in water and glass mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 15 per cent. For smaller water-contents the measurements show the evidence of streaming, presumably due to slowing-down neutrons of energy smaller than 300 keV. Since a volume proportion of about 15 per cent of water in glass corresponds to the composition of ordinary concrete, the present work enables to predict the effects of a desiccation of concrete. Moreover, it is seen that there is no interest in increasing the proportion of water in ordinary concrete beyond the usual values (15-20 per cent). (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges verre-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 15 pour cent en volume. Pour des proportions d'eau inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. La composition des melanges verre-eau aux environs de 15 pour cent d'eau en volume correspondant au beton ordinaire, la presente etude permet de prevoir les effets d'une dessication du beton, et montre, en outre, qu'il n'y a pas interet a essayer d'augmenter la proportion d'eau dans le beton ordinaire au dela des valeurs usuelles (15 a 20 pour cent). (auteur)

Determination of the fission products yields, lanthanide and yttrium, in the fission of 238U with neutrons of fission spectra

International Nuclear Information System (INIS)

Nicoli, I.G.

1981-06-01

A radiochemical investigation is performed to measure the cumulative fission product yields of several lantanides and yttrium nuclides in the 238 U by fission neutron spectra. Natural and depleted uranium are irradiated under the same experimental conditions in order to find a way to subtract the contribution of the 235 U fission. 235 U percentage in the natural uranium was 3.5 times higher than in the depleted uranium. Uranium oxides samples are irradiated inside the core of the Argonaut Reactor, at the Instituto de Engenharia Nuclear, and the lantanides and yttrium are chemically separated. The fission products gamma activities were detected, counted and analysed in a system constituted by a high resolution Ge(Li) detector, 4096 multichannel analyser and a PDP-11 computer. Cumulative yields for fission products with half-lives between 1 to 33 hours are measured: 93 Y, 141 La, 142 La, 143 Ce and 149 Nd. The chain total yields are calculated. The cumulative fission yields measured for 93 Y, 141 La, 142 La, 143 Ce and 149 Nd are 4,49%, 4,54%, 4,95%, 4,16% and 1,37% respectively and they are in good agreement with the values found in the literature. (Author) [pt

Barium 139 as Fission Indicator

Energy Technology Data Exchange (ETDEWEB)

Broda, E.

1943-07-01

This report is based on a measurement performed at the Cavendish Laboratory (Cambridge) by E. Broda in December 1943 where a technique has been worked out for measuring the fission density in a uranium containing medium in relative units by determining the amount of a suitable fission product formed. Generally a given fission product will be formed in natural uranium by slow neutron fission of U235 or by fast neutron fission of either U235 or U238. It is intended to translate the relative units into absolute units by comparison of the Ba yield with the indication of UF6 fission chamber in the same medium. This has to be done separately for fast and slow neutron fission as the yields may be different. Another application of the technique developed is the measurement of thermal neutron density in an uraniferous medium without using a detector subject to variations of sensitivity according to the properties of the medium. (nowak)

Contribution to the experimental study of excited levels of some light nuclei by using the method of angular correlation of internal conversion pairs and monopolar pairs; Contribution a l'etude experimentale de niveaux excites de quelques noyaux legers par la methode des Correlations angulaires des paires de conversion interne Et des paires monopolaires

Energy Technology Data Exchange (ETDEWEB)

Armbruster, Raymond

1950-07-01

In a first part, the author presents a brief theory of angular correlations of internal conversion pairs and monopolar pairs, and indicates the complete formulations which are used to compute all the angular correlations corresponding to the performed experiments. In a second part, he describes a beta spectrometer, outlines factors which govern the energy resolving power, and the peculiarity of summation of two pulses proportional to the energy of the electron and positron which build up an internal pair. In a third part, the author reports experiments of angular correlations, indicates the shapes of monopolar spectra for different angles between electron and positron emission directions, determines the multipolarity of gamma radiations from the first excited levels of {sup 13}C and {sup 12}C, and gives the angular moments, parity and isobaric spin of two excited levels of the {sup 12}C [French] Dans la premiere partie de notre travail, nous exposons une theorie sommaire des correlations angulaires des paires de conversion interne et des paires monopolaires. A la fin de cette premiere partie sont indiquees les formules completes, qui nous ont servi a calculer pratiquement toutes les correlations angulaires correspondant a nos experiences. Dans la deuxieme partie, nous decrivons un spectrometre beta a scintillation. Nous insistons surtout sur les elements qui determinent le pouvoir de resolution en energie et sur la particularite de sommation de deux impulsions proportionnelles a l'energie de l'electron et du positron formant une paire interne. Dans la troisieme partie, nous exposons nos experiences de correlations angulaires. Nous avons repris une mesure precise de la correlation angulaire des paires monopolaires provenant du niveau 6,05 Mev de l'Oxygene 16. Il nous a ete egalement possible de donner l'allure des spectres monopolaires pour differents angles formes par les directions d'emission de l'electron et du positron. Nous avons determine par la methode des

Detection of {alpha} particles using semiconductors. Application to the control of plutonium extraction; Detection des particules {alpha} par semiconducteurs application au controle de l'extraction du plutonium

Energy Technology Data Exchange (ETDEWEB)

Tanguy, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-03-01

A study is made of a particles produced by thick sources, using either diffused junction or surface barrier semiconductor detectors for controlling continuously the plutonium extraction process. For this, a presenting apparatus is described in which the solutions to be analyzed flow in contact with the detector protected by a thin mica membrane. A method is described which gives a precise recording of the spectra and which thus allows the separation of two or more {alpha} emitters present in the same solution. This method has been applied to the measurement of {sup 239}Pu in the the presence of {sup 241}Am with an accuracy of {+-}5 per cent. In the second part of the report is considered the detection of plutonium in solutions of {beta} - {gamma} emitting fission products. Pile-up is reduced by using a fast amplification chain associated to totally depleted thin detectors. Under these conditions a few mg of {sup 239}Pu can be detected in solutions of fission products having an activity of 100 curies/liter. A method is given for discriminating {alpha} and {beta} particles, it is based on the difference in the collection times for the charges liberated by these particles in the detector. (author) [French] On etudie la detection de particules {alpha} issues de sources epaisses par detecteurs semiconducteurs a jonction diffusee ou a barriere de surface pour le controle continu du procede d'extraction du plutonium. A cet effet on decrit un appareil presentateur dans lequel les solutions a analyser circulent au contact du detecteur protege par une membrane mince de mica. On decrit une methode qui permet par le trace precis des spectres de separer deux ou plusieurs emetteurs {alpha} presents dans une meme solution. Cette methode a ete appliquee a la mesure du {sup 239}Pu en presence de {sup 241}Am avec une precision de {+-} 5 pour cent. Dans la deuxieme partie on traite de la detection du plutonium dans des solutions de produits de fission emetteurs {beta} and {gamma}. On

Automation of nonlinear calculations in the theory of fusion reactor; Automatisation des calculs non lineaires dans la theorie des reacteurs a fusion

Energy Technology Data Exchange (ETDEWEB)

Braffort, P; Chaigne, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

1) Introduction: The difficulties of the formulation of the equations of phenomena occurring during the operation of a fusion reactor are underlined. 2) The possibilities presented by analog computation of the solution of nonlinear differential equations are enumerated. The accuracy and limitations of this method are discussed. 3) The analog solution in the stationary problem of the measurement of the discharge confinement is given and comparison with experimental results. 4) The analog solution of the dynamic problem of the evolution of the discharge current in a simple case is given and it is compared with experimental data. 5) The analog solution of the motion of an isolated ion in the electromagnetic field is given. A spatial field simulator used for this problem (bidimensional problem) is described. 6) The analog solution of the preceding problem for a tridimensional case for particular geometrical configurations using simultaneously 2 field simulators is given. 7) A method of computation derived from Monte Carlo method for the study of dynamic of plasma is described. 8) Conclusion: the essential differences between the analog computation of fission reactors and fusion reactors are analysed. In particular the theory of control of a fusion reactor as described by SCHULTZ is discussed and the results of linearized formulations are compared with those of nonlinear simulation. (author)Fren. [French] 1) Introduction. On souligne les difficultes que presente la mise en equation des phenomenes mis en jeu lors du fonctionnement d'un reacteur a fusion. On selectionne un certain nombre d'equations generalement utilisees et on montre les impossibilites analytiques auxquelles on se heurte alors. 2) On rappelle les possibilites du calcul analogique pour la resolution des systemes differentiels non lineaires et on indique la precision de la methode ainsi que ses limitations. 3) On decrit esolution analogique du probleme statique de la mesure du confinement de la decharge

Determination of the fission barrier height in fission of heavy radioactive beams induced by the (d,p)-transfer

CERN Multimedia

A theoretical framework is described, allowing to determine the fission barrier height using the observed cross sections of fission induced by the (d,p)-transfer with accuracy, which is not achievable in another type of low-energy fission of neutron-deficient nuclei, the $\\beta$-delayed fission. The primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission of...

Fission fragment distributions within dynamical approach

Energy Technology Data Exchange (ETDEWEB)

Mazurek, K. [Institute of Nuclear, Physics Polish Academy of Sciences, Krakow (Poland); Nadtochy, P.N. [Omsk State Technical University, Omsk (Russian Federation); Ryabov, E.G.; Adeev, G.D. [Omsk State University, Physics Department, Omsk (Russian Federation)

2017-04-15

The review covers recent developments and achievements in the dynamical description of fission process at high excitation energy. It is shown that the dynamical approach based on multidimensional Langevin equations combined with the statistical description of nuclear decay by particles evaporation is capable of fairly well describing the formation of fission fragment mass-energy, charge, and angular distributions of fission fragments in coincidence with the pre- and post-scission particle emission. The final yields of fission and evaporation residues channels products could be obtained. The detailed description of fission dynamics allows studying different stages of fission process, indicating the most important ingredients governing fission process and studying in detail such fundamental nuclear properties as nuclear viscosity and fission timescale. The tasks and perspectives of multidimensional dynamical approach are also discussed. (orig.)

Tip model of cold fission

International Nuclear Information System (INIS)

Goennenwein, F.; Boersig, B.

1991-01-01

Cold fission is defined to be the limiting case of nuclear fission where virtually all of the available energy is converted into the total kinetic energy of the fragments. The fragments have, therefore, to be born in or at least close to their respective ground states. Starting from the viewpoint that cold fission corresponds to most compact scission configurations, energy constraints have been exploited to calculate minimum tip distances between the two nascent fragments in binary fission. Crucial input parameters to this tip model of cold fission are the ground-state deformations of fragment nuclei. It is shown that the minimum tip distances being compatible with energy conservation vary strongly with both the mass and charge fragmentation of the fission prone nucleus. The tip distances refer to nuclei with equivalent sharp surfaces. In keeping with the size of the surface width of leptodermous nuclei, only configurations where the tip distances are smaller than a few fm may be considered as valid scission configurations. From a comparison with experimental data on cold fission this critical tip distance appears to be 3.0 fm for the model parameters chosen. Whenever the model calculation yields tip distances being smaller than the critical value, a necessary condition for attaining cold fission is considered to be fulfilled. It is shown that this criterion allows to understand in fair agreement with experiment which mass fragmentations are susceptible to lead to cold fission and which fragment-charge divisions are the most favored in each isobaric mass chain. Being based merely on energy arguments, the model cannot aim at predicting fragment yields in cold fission. However, the tip model proposed appears well suited to delineate the phase space where cold fission phenomena may come into sight. (orig.)

A threshold for dissipative fission

International Nuclear Information System (INIS)

Thoennessen, M.; Bertsch, G.F.

1993-01-01

The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and γ-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T thresh to the (temperature-dependent) fission barrier height E Bar (T). The statistical model reproduces the data for T thresh /E Bar (T) thresh /E Bar (T) independent of mass and fissility of the systems

Measurement of isotopic cross sections of the fission fragments produced in 500 AMeV {sup 208}Pb + p reaction; Etude de la production des fragments de fission issus de la reaction {sup 208}Pb + p a 500 AMeV

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Dominguez, B

2003-03-01

The aim of this work is the study of the fission fragments produced in the spallation reaction {sup 208}Pb + p at 500 AMeV. The fission fragments from Z=23 up to Z=59 have been detected and identified by using the inverse kinematics technique with the high-resolution spectrometer FRS. The production cross sections and the recoil velocities of 430 nuclei have been measured. The measured data have been compared with previous data. The isotopic distributions show a high precision. However, the absolute value of the fission cross section is higher than expected. From the experimental data the characteristics of the average fissioning system have been reconstructed (Z{sub fis}, A{sub fis}, E*{sub fis}). In addition, the number of post-fission neutrons emitted from the fission fragments, v{sub post}, has been determined by using a new method. The experimental data have been compared to the two-steps models describing the spallation reaction. The impact of the model parameters on the observables has been analysed and the reasons Leading to the observed differences between the codes are also presented. This analyse shows a good agreement with the INCL4+ABLA code. (author)

Insights into nuclear structure and the fission process from spontaneous fission

Energy Technology Data Exchange (ETDEWEB)

Hamilton, J.H.; Butler-Moore, K.; Ramayya, A.V. [Vanderbilt Univ., Nashville, TN (United States)] [and others

1993-12-31

The {gamma}-rays emitted following spontaneous and induced fission are rich sources of information about the structure of neutron-rich nuclei and about the fission process itself. The study of spontaneous fissioning isotopes with large Ge detector arrays are providing a wealth of such information as seen, for example, in recent reports. In this paper we present some of our most recent results on nuclear structure studies and conclusions on the fission process itself. In our work, we have employed in spontaneous fission, a triple gamma coincidence study for the first time and a high resolution, X-ray detector-{gamma}-coincidence study. These data provide powerful ways of separating the gamma rays which belong to a particular nucleus. The triple coincidence technique was used to uniquely identify the levels in {sup 136}Te and higher spin states in its N=84 isotones, {sup 138}Xe and {sup 140}Ba{sup 171}. Some other examples of the level structures observed in the low and high mass partners are presented, including a detailed analysis of the backbending of the moment of inertia in {sup 112,114,116}Pd. Finally, we present the first examples of how our analysis allows one to extract a detailed picture of the dependence of the angular momentum on the mass and atomic numbers of the fission fragments and of the long-sought neutron multiplicity distribution from zero-n to ten-n as a function of the charge and mass asymmetry.

Dual-fission chamber and neutron beam characterization for fission product yield measurements using monoenergetic neutrons

Science.gov (United States)

Bhatia, C.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.; Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rundberg, R. S.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Macri, R.; Ryan, C.; Sheets, S. A.; Stoyer, M. A.; Tonchev, A. P.

2014-09-01

A program has been initiated to measure the energy dependence of selected high-yield fission products used in the analysis of nuclear test data. We present out initial work of neutron activation using a dual-fission chamber with quasi-monoenergetic neutrons and gamma-counting method. Quasi-monoenergetic neutrons of energies from 0.5 to 15 MeV using the TUNL 10 MV FM tandem to provide high-precision and self-consistent measurements of fission product yields (FPY). The final FPY results will be coupled with theoretical analysis to provide a more fundamental understanding of the fission process. To accomplish this goal, we have developed and tested a set of dual-fission ionization chambers to provide an accurate determination of the number of fissions occurring in a thick target located in the middle plane of the chamber assembly. Details of the fission chamber and its performance are presented along with neutron beam production and characterization. Also presented are studies on the background issues associated with room-return and off-energy neutron production. We show that the off-energy neutron contribution can be significant, but correctable, while room-return neutron background levels contribute less than <1% to the fission signal.

Reexamination of fission fragment angular distributions and the fission process: Formalism

International Nuclear Information System (INIS)

Bond, P.D.

1985-01-01

The theory of fission fragment angular distributions is examined and the universally used expression is found to be valid only under restrictive assumptions. A more general angular distribution formula is derived and applied to recent data of high spin systems. At the same time it is shown that the strong anisotropies observed from such systems can be understood without changing the essential basis of standard fission theory. The effects of reaction mechanisms other than complete fusion on fission fragment angular distributions are discussed and possible angular distribution signatures of noncompound nucleus formation are mentioned

Process for treating fission waste

International Nuclear Information System (INIS)

Rohrmann, C.A.; Wick, O.J.

1983-01-01

A method is described for the treatment of fission waste. A glass forming agent, a metal oxide, and a reducing agent are mixed with the fission waste and the mixture is heated. After melting, the mixture separates into a glass phase and a metal phase. The glass phase may be used to safely store the fission waste, while the metal phase contains noble metals recovered from the fission waste

Investigation of the heavy nuclei fission with anomalously high values of the fission fragments total kinetic energy

Science.gov (United States)

Khryachkov, Vitaly; Goverdovskii, Andrei; Ketlerov, Vladimir; Mitrofanov, Vecheslav; Sergachev, Alexei

2018-03-01

Binary fission of 232Th and 238U induced by fast neutrons were under intent investigation in the IPPE during recent years. These measurements were performed with a twin ionization chamber with Frisch grids. Signals from the detector were digitized for further processing with a specially developed software. It results in information of kinetic energies, masses, directions and Bragg curves of registered fission fragments. Total statistics of a few million fission events were collected during each experiment. It was discovered that for several combinations of fission fragment masses their total kinetic energy was very close to total free energy of the fissioning system. The probability of such fission events for the fast neutron induced fission was found to be much higher than for spontaneous fission of 252Cf and thermal neutron induced fission of 235U. For experiments with 238U target the energy of incident neutrons were 5 MeV and 6.5 MeV. Close analysis of dependence of fission fragment distribution on compound nucleus excitation energy gave us some explanation of the phenomenon. It could be a process in highly excited compound nucleus which leads the fissioning system from the scission point into the fusion valley with high probability.

Fifty years with nuclear fission

International Nuclear Information System (INIS)

Behrens, J.W.; Carlson, A.D.

1989-01-01

The news of the discovery of nuclear fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fifieth anniversary of its discovery by holding a topical meeting entitled, ''Fifty Years with Nuclear Fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent development in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicated a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two fully days of sessions (April 27 and 28) at the main site of the NIST in Gaithersburg, Maryland. The wide range of topics covered in this Volume 1 by this topical meeting included plenary invited, and contributed sessions entitled: Preclude to the First Chain Reaction -- 1932 to 1942; Early Fission Research -- Nuclear Structure and Spontaneous Fission; 50 Years of Fission, Science, and Technology; Nuclear Reactors, Secure Energy for the Future; Reactors 1; Fission Science 1; Safeguards and Space Applications; Fission Data; Nuclear Fission -- Its Various Aspects; Theory and Experiments in Support of Theory; Reactors and Safeguards; and General Research, Instrumentation, and By-Product. The individual papers have been cataloged separately

Muon-induced fission

International Nuclear Information System (INIS)

Polikanov, S.

1980-01-01

A review of recent experimental results on negative-muon-induced fission, both of 238 U and 232 Th, is given. Some conclusions drawn by the author are concerned with muonic atoms of fission fragments and muonic atoms of the shape isomer of 238 U. (author)

Energy production using fission fragment rockets

International Nuclear Information System (INIS)

Chapline, G.; Matsuda, Y.

1991-08-01

Fission fragment rockets are nuclear reactors with a core consisting of thin fibers in a vacuum, and which use magnetic fields to extract the fission fragments from the reactor core. As an alternative to ordinary nuclear reactors, fission fragment rockets would have the following advantages: Approximately twice as efficient if one can directly convert the fission fragment energy into electricity; by reducing the buildup of a fission fragment inventory in the reactor one could avoid a Chernobyl type disaster; and collecting the fission fragments outside the reactor could simplify the waste disposal problem. 6 refs., 4 figs., 2 tabs

Fission dynamics of hot nuclei

Indian Academy of Sciences (India)

2014-04-05

Apr 5, 2014 ... across the fission barrier is very small or in other words, the fission barrier is much ... of this shape evolution, the gross features of the fissioning nucleus can be described ..... [7] Y Abe, C Gregoire and H Delagrange, J. Phys.

Study on fission blanket fuel cycling of a fusion-fission hybrid energy generation system

International Nuclear Information System (INIS)

Zhou, Z.; Yang, Y.; Xu, H.

2011-01-01

This paper presents a preliminary study on neutron physics characteristics of a light water cooled fission blanket for a new type subcritical fusion-fission hybrid reactor aiming at electric power generation with low technical limits of fission fuel. The major objective is to study the fission fuel cycling performance in the blanket, which may possess significant impacts on the feasibility of the new concept of fusion-fission hybrid reactor with a high energy gain (M) and tritium breeding ratio (TBR). The COUPLE2 code developed by the Institute of Nuclear and New Energy Technology of Tsinghua University is employed to simulate the neutronic behaviour in the blanket. COUPLE2 combines the particle transport code MCNPX with the fuel depletion code ORIGEN2. The code calculation results show that soft neutron spectrum can yield M > 20 while maintaining TBR >1.15 and the conversion ratio of fissile materials CR > 1 in a reasonably long refuelling cycle (>five years). The preliminary results also indicate that it is rather promising to design a high-performance light water cooled fission blanket of fusion-fission hybrid reactor for electric power generation by directly loading natural or depleted uranium if an ITER-scale tokamak fusion neutron source is achievable.

Physics and chemistry of fission

International Nuclear Information System (INIS)

1979-01-01

Full text: In the pleasant and hospitable atmosphere of the Kernforschungsanlage Juelich in the Federal Republic of Germany, the IAEA symposium on the Physics and Chemistry of Fission took place. Almost 200 scientists attended, 154 abstracts were submitted, and 57 papers presented, but more important than the numbers was the quality of the contributions and the progress reported at the symposium. The neutron was discovered almost 50 years ago; 40 years ago the idea of nuclear fission was born. Since then, a number of laboratories have worked hard to explain the phenomenon of fission One would expect that by now scientists would know exactly what happens in a nucleus before and during the process of fission, particularly as there are hundreds of power and research reactors in operation, and fission of uranium isotopes is the basis of their functioning. At first glance, fission seems a simple process: a neutron hits and penetrates the uranium nucleus which becomes excited, i.e. has a surplus of energy. One way to get rid of this energy is for the nucleus to split into two parts; additional products of this process are energy and more neutrons. Nature, however, seems to dislike such straightforward explanations. In the case of fission, scientists have observed a number of phenomena which disagree with a simple model. Sometimes, a nucleus will split into two parts without being 'attacked' by a neutron; this spontaneous fission opens up a new line of fission research and several contributions at the symposium reported on sophisticated experiments designed to unravel some of its specific details. Sometimes, a fissioning nucleus will emit another particle: ternary fission has become a powerful tool for studying the properties of nuclei during the fission process. For the scientist, it is fascinating to observe how the nucleus behaves during fission. They invent models which are supposed to reproduce the most probable course of events leading to fission. In one of these

Theoretical Description of the Fission Process

International Nuclear Information System (INIS)

Nazarewicz, Witold

2009-01-01

Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation's nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic

Experimental approach to fission process of actinides

Energy Technology Data Exchange (ETDEWEB)

Baba, Hiroshi [Osaka Univ., Toyonaka (Japan). Faculty of Science

1997-07-01

From experimental views, it seems likely that the mechanism of nuclear fission process remains unsolved even after the Bohr and Weeler`s study in 1939. Especially, it is marked in respect of mass distribution in unsymmetric nuclear fission. The energy dependency of mass distribution can be explained with an assumption of 2-mode nuclear fission. Further, it was demonstrated that the symmetrical fission components and the unsymmetrical ones have different saddle and fission points. Thus, the presence of the 2-mode fission mechanism was confirmed. Here, transition in the nuclear fission mechanism and its cause were investigated here. As the cause of such transition, plausible four causes; a contribution of multiple-chance fission, disappearance of shell effects, beginning of fission following collective excitation due to GDR and nuclear phase transition were examined in the condition of excitation energy of 14.0 MeV. And it was suggested that the transition in the nuclear fission concerned might be related to phase transition. In addition, the mechanism of nuclear fission at a low energy and multi-mode hypothesis were examined by determination of the energy for thermal neutron fission ({sup 233,235}U and {sup 239}Pu) and spontaneous nuclear fission ({sup 252}Cf). (M.N.)

Dynamic of fission and quasi-fission revealed by pre-scission neutron evaporation

International Nuclear Information System (INIS)

Hinde, D.J.

1991-06-01

The dependence of pre-scission neutron multiplicities (ν-pre) on the mass-split and total kinetic energy (TKE) in fusion-fission and quasi-fission has been measured for a wide range of projectile-target combinations. the data indicate that the fusion-fission time scale is shorter for asymmetric splits than for symmetric splits, whilst there is no dependence on TKE. For quasi-fission reactions induced using 64 Ni projectiles, ν-pre falls rapidly with increasing TKE, indicating that these neutrons are emitted near to or after scission. A new interpretation of both neutron multiplicities and mean energies (the neutron clock-thermometer) allows the extraction of time scales with much less uncertainty than previously, and also gives information about the deformation from which the neutrons are emitted. 15 refs., 13 figs

Theory of nuclear fission: a review

International Nuclear Information System (INIS)

Mosel, U.

1976-01-01

General properties of nuclear fission are reviewed and related to our present knowledge of fission theory. For this purpose the basic reasons for the shape of the fission barriers are discussed and their consequences compared with experimental results on barrier shapes and structures. Special emphasis is put on the asymmetry of the fission barriers and mass-distributions and its relation to the shells of the nascent fragment shells. Finally the problem of calculating fission cross sections is discussed

Experimental Determination of the Neutron Characteristics of UO{sub 2}-PuO{sub 2}-H{sub 2}O Lattices; Determination Experimentale Des Caracteristiques Neutroniques De Reseaux UO{sub 2}-PuO{sub 2}-H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Debrue, J.; Fabry, A.; Leenders, L.; Motte, F.; Van Den Broeck, H. [Centre d' Etude de l' Energie Nucleaire, Mol (Belgium)

1967-09-15

plutonium: fission density measurements by direct counting of the fission products formed in the mixed fuel as a result of irradiation, and measurements of spectral indices by means of fission detectors and detectors having resonances close to those of the isotopes of plutonium. The optimum conditions for applying these techniques are described and the effect on the fuel cycle of uncertainties in the values for the spectral indices (ratios of cross-sections) is discussed. A brief reference is finally made to a programme of sub-critical experiments conducted hitherto with two batches of UO{sub 2} fuel enriched to 5% and 7% {sup 235}U, and having the purpose of studying possible methods of exciting a sub-critical lattice by means of an external neutron source in pulsed and modulated operation. The aim of this programme is to ascertain to what extent these methods, which employ a quantity of fuel considerably less than the critical mass, can help in determining the characteristics of a lattice. The advantages of such methods are particularly obvious in the case of plutonium fuels. (author) [French] Au cours de l'etude dans l'installation critique VENUS du coeur a moderation variable du reacteur BR3/VULCAIN, un assemblage combustible constitue de 37 crayons UO{sub 2}-PuO{sub 2} (94% UO{sub 2} naturel, PuO{sub 2}) a ete substitue a un des assemblages combustibles UO{sub 2} enrichi a 7% {sup 235}U constituant le coeur de ce reacteur. Des experiences ont ete effectuees dans le but de permettre l'ajustement des modeles du calcul des performances de cet assemblage special: on a notamment mesure la distribution de la densite de fission ainsi que l'evolution du rapport des sections efficaces effectives de fission dans {sup 239}Pu et {sup 235}U. Une experience critique directement orientee sur les problemes de recyclage du plutonium dans les reacteurs thermiques a eau legere pressurisee est en cours d'execution dans la meme installation critique. A cette fin, on dispose de deux

Micro plate fission chamber development

International Nuclear Information System (INIS)

Wang Mei; Wen Zhongwei; Lin Jufang; Jiang Li; Liu Rong; Wang Dalun

2014-01-01

To conduct the measurement of neutron flux and the fission rate distribution at several position in assemblies, the micro plate fission chamber was designed and fabricated. Since the requirement of smaller volume and less structure material was taken into consideration, it is convinient, commercial and practical to use fission chamber to measure neutron flux in specific condition. In this paper, the structure of fission chamber and process of fabrication were introduced and performance test result was presented. The detection efficiency is 91.7%. (authors)

Nuclear Forensics and Radiochemistry: Fission

Energy Technology Data Exchange (ETDEWEB)

Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-11-07

Radiochemistry has been used to study fission since it’ discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution.

Mechanisms of fission neutron emission

International Nuclear Information System (INIS)

Maerten, H.

1991-01-01

The time evolution in fission is the starting point for discussing not only the main mechanism of fission neutron emission, the evaporation from fully accelerated fragments, but also possible secondary ones connected with dynamical features of nuclear fission. ''Asymptotic'' conditions as relevant for describing the particle release from highly excited, rapidly moving fragments are defined. Corresponding statistical model approaches to fission neutron emission, based on the adequate consideration of the intricate fragment occurrence probability, reproduce most of the experimental data. The remarkable influence of fission modes on neutron observables is analyzed in the framework of a macroscopic-microscopic scission point model consistent with energy conservation. Finally, chances and deficiencies for solving the mechanism puzzle are summarized. (author). 87 refs, 21 figs

Fission in a Plasma

Energy Technology Data Exchange (ETDEWEB)

Younes, W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-10-26

A three-year theory project was undertaken to study the fission process in extreme astrophysical environments, such as the crust of neutron stars. In the first part of the project, the effect of electron screening on the fission process was explored using a microscopic approach. For the first time, these calculations were carried out to the breaking point of the nucleus. In the second part of the project, the population of the fissioning nucleus was calculated within the same microscopic framework. These types of calculations are extremely computer-intensive and have seldom been applied to heavy deformed nuclei, such as fissioning actinides. The results, tools and methodologies produced in this work will be of interest to both the basic-science and nuclear-data communities.

Development of a “Fission-proxy” Method for the Measurement of 14-MeV Neutron Fission Yields at CAMS

Energy Technology Data Exchange (ETDEWEB)

Gharibyan, Narek [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-10-25

Relative fission yield measurements were made for 50 fission products from 25.6±0.5 MeV alpha-induced fission of Th-232. Quantitative comparison of these experimentally measured fission yields with the evaluated fission yields from 14-MeV neutron-induced fission of U-235 demonstrates the feasibility of the proposed fission-proxy method. This new technique, based on the Bohr-independence hypothesis, permits the measurement of fission yields from an alternate reaction pathway (Th-232 + 25.6 MeV α → U-236* vs. U-235 + 14-MeV n → U-236*) given that the fission process associated with the same compound nucleus is independent of its formation. Other suitable systems that can potentially be investigated in this manner include (but are not limited to) Pu-239 and U-237.

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, M.

1981-06-01

This is the seventh issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields (neutron induced and spontaneous fission); neutron reaction cross sections of fission products; data related to the radioactive decay of fission products; delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The sixth issue of this series has been published in June 1980 as INDC(NDS)-113/G+P. The present issue includes contributions which were received by NDS between 1 August 1980 and 25 May 1981

Nuclear fission and neutron-induced fission cross-sections

CERN Document Server

James, G D; Michaudon, A; Michaudon, A; Cierjacks, S W; Chrien, R E

2013-01-01

Nuclear Fission and Neutron-Induced Fission Cross-Sections is the first volume in a series on Neutron Physics and Nuclear Data in Science and Technology. This volume serves the purpose of providing a thorough description of the many facets of neutron physics in different fields of nuclear applications. This book also attempts to bridge the communication gap between experts involved in the experimental and theoretical studies of nuclear properties and those involved in the technological applications of nuclear data. This publication will be invaluable to those interested in studying nuclear fis

Ternary Fission of U{sup 235} by Resonance Neutrons; Fission Ternaire de {sup 235}U par des Neutrons de Resonance; 0422 0420 041e 0419 041d 041e 0415 0414 0415 041b 0415 041d 0418 0415 0423 0420 0410 041d 0410 -235 041d 0410 0420 0415 0417 041e 041d 0410 041d 0421 041d 042b 0425 041d 0415 0419 0422 0420 041e 041d 0410 0425 ; Fision Ternaria del {sup 235}U por Neutrones de Resonancia

Energy Technology Data Exchange (ETDEWEB)

Kvitek, I.; Popov, Ju. P.; Rjabov, Ju. V. [Ob' edinennyj Institut Jadernyh Issledovanij, Dubna, SSSR (Russian Federation)

1965-07-15

range 0.1 to 0.2 eV. The paper discusses the possible effect of the (n, {alpha}) reaction on the results obtained in experiments not using the coincidence of a long-range particle with a fission fragment. (author) [French] On a publie recemment des etudes dans lesquelles on signale que, lors du passage d'une resonance a une aune, le rapport entre les sections efficaces de fission ternaire et binaire de {sup 235}U subit des variations considerables. Or, les auteurs n'ont constate aucune variation de ce genre ni pour {sup 233}U ni pour {sup 2}'3{sup 9}Pu. Le memoire fait etat de recherches sur la fission ternaire de {sup 285}U par neutrons de 0,1 a 30 eV. Contrairement a d'autres travaux consacres a la fission ternaire de chaque fission ternaire a ete identifiee par coincidence entre l'un des fragments de fission et une particule legere a long parcours. Grace a ce procede, les fissions ternaires ont pu Etre separees de la contribution qui pourrait etre due a la reaction (n, {alpha}). Les mesures ont ete faites dans le reacteur a neutrons rapides de l'Institut unifie de recheiches nucleaires par la methode du temps de vol. Les auteucs ont utilise a cet effet une base de vol de 100 m, ce qui a permis d'obtenir un pouvoir de resolution de 0,6 {mu}s/m. Pour enregistrer les fragments de fission et la particule legere a long parcours, ils se sont servis de compteurs a scintillateur gazeux remplis de xenon sous une pression de 2 atm. Une couche de {sup 235}U enrichi d'environ 300 cm{sup 2} et de 2 mg/cm{sup 2} d'epaisseur a ete appliquee sur une feuille d'aluminium de 20 {mu}m. Dans le volume de gaz on a enregistre d'un cote de la feuille les scintillations dues aux fragments de fission et, de l'autre cote, celles qui pro venaient des particules legeres a long parcours. En vue d'evaluer le bruit de fond (par exemple les coincidences entre l'Impulsion provoquee par un fragment et l'impulsion due a un photon de fission gamma ou un proton provenant de la reaction (n, p) dans la

Dynamique identitaire, implication et representations sociales du travail: dinâmica identitária e implicação

Directory of Open Access Journals (Sweden)

Eduardo Marquez

2012-08-01

Full Text Available Dans cette recherche, on étudie l'impact des modalités d'ancrage de la représentation sociale du travail en fonction du statut professionnel (cadres / employés pour une population de salariés de la fonction publique française. La représentation du travail que le groupe « cadres » mobilise renvoie aux pratiques professionnelles, celle du groupe « employés » renvoie à une dimension économique et sociale qui s'exprime par l'importance accordée au salaire et aux relations de travail. L'examen des résultats montre que les éléments de la dimension normative d'un groupe correspondent aux éléments fonctionnels de l'autre groupe, mettant ainsi en évidence la nature de l'asymétrie des groupes étudiés.Cette différence représentationnelle est fondée sur la compositionqualitative des noyaux centraux des représentations du travail des deux groupes étudiés (objectivation différente. La discussion portenotamment sur le lien entre les résultats obtenus et l'implication au travail.

Fission product behaviour in severe accidents

International Nuclear Information System (INIS)

Jokiniemi, J.; Auvinen, A.; Maekynen, J.; Valmari, T.

1998-01-01

The understanding of fission product (FP) behaviour in severe accidents is important for source term assessment and accident mitigation measures. For example in accident management the operator needs to know the effect of different actions on the behaviour and release of fission products. At VTT fission product behaviour have been studied in different national and international projects. In this presentation the results of projects in EU funded 4th framework programme Nuclear Fission Safety 1994-1998 are reported. The projects are: fission product vapour/aerosol chemistry in the primary circuit (FI4SCT960020), aerosol physics in containment (FI4SCT950016), revaporisation of test samples from Phebus fission products (FI4SCT960019) and assessment of models for fission product revaporisation (FI4SCT960044). Also results from the national project 'aerosol experiments in the Victoria facility' funded by IVO PE and VTT Energy are reported

The nuclear fission

International Nuclear Information System (INIS)

Fiorentino, J.

1983-01-01

The nuclear fission process considering initially the formation of compound nucleus and finishing with radioactive decay of fission products is studied. The process is divided in three parts which consist of the events associated to the nucleus of intermediate transitional state, the scission configuration, and the phenomenum of post scission. (M.C.K.) [pt

Detection and location of can rupture in reactors cooled by a flow of water; Detection et localisation des ruptures de gaines sur les reacteurs refroidis par circulation d'eau

Energy Technology Data Exchange (ETDEWEB)

Le Meur, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

This report brings together the principal methods of fission-product detection used for water reactors. The position, type and method of adjustment is given for each detector. The methods for localizing the defective elements are explained, in particular those using water sampling or decreases in the flux. A few installations are briefly described. They correspond to particular types of reactors using boiling, pressurized or cold water. Amongst the many methods used, it can be noted that when the fuel is resistant, the installations are fairly compact. In nuclear super-heated reactors on the other hand, the study of fuel behaviour calls for larger installations. An identification of defective elements exists when the reactor structure allows it. If this is not possible, a localization in a group of elements is obtained by a flux depression. (author) [French] Ce rapport rassemble les principales methodes de detection de produits de fission utilisees pour des reacteurs a eau. On indique pour les detecteurs leurs emplacements, leurs types, leurs reglages. On explique quelles sont les methodes de localisation des elements defectueux, en particulier celles utilisant des prelevements d'eau ou des depressions de flux. Quelques installations sont decrites sommairement. Elles correspondent a des types particuliers de reacteurs a eau bouillante, pressurisee ou froide. Parmi les nombreuses methodes utilisees, on constate que les installations sont peu importantes, lorsque le combustible est resistant. Par contre dans les reacteurs a surchauffe nucleaire l'etude du comportement du combustible necessite des installations plus importantes. Une identification d'elements defectueux existe lorsque la structure du reacteur le permet. A defaut une localisation dans un groupe d'elements est obtenue par depression de flux. (auteur)

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, G.

1976-05-01

The purpose of this series is to inform scientists working on Fission Product Nuclear Data, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. This report consists of reproductions of essentially unaltered original contributions which the authors have sent to IAEA/NDS. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields; neutron cross-section data of fission products; data related to β-, γ-decay of fission products; delayed neutron data; and fission product decay-heat

Monte-Carlo method for studying the slowing down of neutrons in a thin plate of hydrogenated matter; Methode de Monte-Carlo pour l'etude du ralentissement des neutrons dans une plaque mince de matiere hydrogenee

Energy Technology Data Exchange (ETDEWEB)

Ribon, P; Michaudon, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The studies of interaction of slow neutrons with atomic nuclei by means of the time of flight methods are made with a pulsed neutron source with a broad energy spectrum. The measurement accuracy needs a high intensity and an output time as short as possible and well defined. If the neutrons source is a target bombarded by the beam of a pulsed accelerator, it is usually required to slow down the neutrons to obtain a sufficient intensity at low energies. The purpose of the Monte-Carlo method which is described in this paper is to study the slowing down properties, mainly the intensity and the output time distribution of the slowed-down neutrons. The choice of the method and parameters studied is explained as well as the principles, some calculations and the program organization. A few results given as examples were obtained in the line of this program, the limits of which are principally due to simplifying physical hypotheses. (author) [French] l'etude de l'interaction des neutrons lents avec les noyaux atomiques par la methode du temps de vol s'effectue avec une source pulsee de neutrons dont le spectre en energie est assez etendu. La precision des mesures demande que la source soit intense et que la duree d'emission des neutrons soit breve et bien definie. Si la source est une cible bombardee par le faisceau de particules d'un accelerateur pulse, il est generalement indispensable de ralentir les neutrons pour avoir une intensite suffisante a basse energie. Nous presentons ici une methode de Monte-Carlo pour l'etude detaillee de ce ralentissement, notamment l'intensite et la distribution des temps de sortie des neutrons ralentis. Cette presentation comprend: la justification du choix de la methode de Monte-Carlo, les principes generaux, les differentes etapes du calcul et du programme ecrit pour le calculateur electronique IBM 7090. Nous indiquons aussi les restrictions qui sont apportees au domaine d'application de ce programme et qui proviennent surtout des

Status of fission yield measurements

International Nuclear Information System (INIS)

Maeck, W.J.

1979-01-01

Fission yield measurement and yield compilation activities in the major laboratories of the world are reviewed. In addition to a general review of the effort of each laboratory, a brief summary of yield measurement activities by fissioning nuclide is presented. A new fast reactor fission yield measurement program being conducted in the US is described

A stochastic approach to fission

International Nuclear Information System (INIS)

Boilley, D.; Suraud, E.; Abe, Yasuhisa

1992-01-01

A microscopically derived Langevin equation is applied to thermally induced nuclear fission. An important memory effect is pointed out. A strong friction coefficient, calculated from microscopic quantities, tends to decrease the stationary limit of the fission rate and to increase the transient time. Fission was described as a diffusion over a barrier of a collective variable, and a Langevin Equation (LE) was used to study the phenomenon. A study of the stationary flow over the saddle point with a Fokker-Planck Equation (FPE), equivalent to the LE was used to give formula for the stationary fission rate (or reaction rate for the chemistry applications). More recently, a complete study of the fission process was performed numerically with both FPE and LE. A long transient time, that could allow more pre-scission neutrons to evaporate, was pointed out. The derivation of this new LE is recalled, followed by the description of the memory dependence and by the effect of a large friction coefficient on the fission rate. (author) 6 refs., 3 figs

Influence of the cosmic-ray induced fission tracks on the fission track of extraterrestric minerals via the 238U spontaneous fission

International Nuclear Information System (INIS)

Damm, G.; Thiel, K.

1977-01-01

The age determined by counting fission tracks of lunar and meteorite materials is obviously falsified by additional fission track parts not to be accounted for by the spontaneous fission of uranium 238. For this p and n induced fissions of U, Th and other hreavy elements through the cosmic radiation come into consideration. In order to determine the possible part of such interference factors, a simulation experiment at the proton synchrocycloton (CERN, Geneva) has been carried out and independently of this, the production rates for the p and n induced U, Th, Bi, Pb and Au in the surface-near regolith layers of the moon were calculated. It could be seen that the irradiation age as well as the spacial distribution of the heavy metals in the samples to be dated must be considered. (RB) [de

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, M.

1983-08-01

This is the ninth issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The main part of this report consists of unaltered original contributions which the authors have sent to IAEA/NDS. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission); Neutron reaction cross sections of fission products; Data related to the radioactive decay of fission products; Delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The eighth issue of this series has been published in July 1982 as INDC(NDS)-130. The present issue includes contributions which were received by NDS between 1 August 1982 and 25 June 1983

Properties of Fission-Product decay heat from Minor-Actinide fissioning systems

International Nuclear Information System (INIS)

Oyamatsu, Kazuhiro; Mori, Hideki

2000-01-01

The aggregate Fission-Product (FP) decay heat after a pulse fission is examined for Minor Actinide (MA) fissiles 237 Np, 241 Am, 243 Am, 242 Cm and 244 Cm. We find that the MA decay heat is comparable but smaller than that of 235 U except for cooling times at about 10 8 s (approx. = 3 y). At these cooling times, either the β or γ component of the FP decay heat for these MA's is substantially larger than the one for 235 U. This difference is found to originate from the cumulative fission yield of 106 Ru (T 1/2 = 3.2x10 7 s). This nuclide is the parent of 106 Rh (T 1/2 = 29.8 s) which is the dominant source of the decay heat at 10 8 s (approx. = 3 y). The fission yield is nearly an increasing function of the fissile mass number so that the FP decay heat is the largest for 244 Cm among the MA's at the cooling time. (author)

Mirror fusion--fission hybrids

International Nuclear Information System (INIS)

Lee, J.D.

1978-01-01

The fusion-fission concept and the mirror fusion-fission hybrid program are outlined. Magnetic mirror fusion drivers and blankets for hybrid reactors are discussed. Results of system analyses are presented and a reference design is described

Monte carlo sampling of fission multiplicity.

Energy Technology Data Exchange (ETDEWEB)

Hendricks, J. S. (John S.)

2004-01-01

Two new methods have been developed for fission multiplicity modeling in Monte Carlo calculations. The traditional method of sampling neutron multiplicity from fission is to sample the number of neutrons above or below the average. For example, if there are 2.7 neutrons per fission, three would be chosen 70% of the time and two would be chosen 30% of the time. For many applications, particularly {sup 3}He coincidence counting, a better estimate of the true number of neutrons per fission is required. Generally, this number is estimated by sampling a Gaussian distribution about the average. However, because the tail of the Gaussian distribution is negative and negative neutrons cannot be produced, a slight positive bias can be found in the average value. For criticality calculations, the result of rejecting the negative neutrons is an increase in k{sub eff} of 0.1% in some cases. For spontaneous fission, where the average number of neutrons emitted from fission is low, the error also can be unacceptably large. If the Gaussian width approaches the average number of fissions, 10% too many fission neutrons are produced by not treating the negative Gaussian tail adequately. The first method to treat the Gaussian tail is to determine a correction offset, which then is subtracted from all sampled values of the number of neutrons produced. This offset depends on the average value for any given fission at any energy and must be computed efficiently at each fission from the non-integrable error function. The second method is to determine a corrected zero point so that all neutrons sampled between zero and the corrected zero point are killed to compensate for the negative Gaussian tail bias. Again, the zero point must be computed efficiently at each fission. Both methods give excellent results with a negligible computing time penalty. It is now possible to include the full effects of fission multiplicity without the negative Gaussian tail bias.

Yields of fission products produced by thermal-neutron fission of 229Th

International Nuclear Information System (INIS)

Dickens, J.K.; McConnell, J.W.

1983-01-01

Absolute yields have been determined for 47 gamma rays emitted in the decay of 37 fission products representing 25 mass chains created during thermal-neutron fission of 229 Th. Using a Ge(Li) detector, spectra were obtained of gamma rays emitted between 15 min and 0.4 yr after very short irradiations by thermal neutrons of a 15-μg sample of 229 Th. On the basis of measured gamma-ray yields and known nuclear data, yields for cumulative production of 37 fission products were deduced. The absolute overall normalization uncertainty is 235 U, we postulate a simple functional dependence sigma = sigma(Z/sub p/), and using this dependence obtain values of Z/sub p/(A) for 15 mass chains created during fission of 229 Th. Values of Z/sub p/(A) were estimated for other mass chains based upon results of a recent study of Z/sub p/(A). Charge distributions determined using the deduced mass distribution and the deduced sets of Z/sub p/(A) and sigma(Z/sub p/) are in very good agreement with recent measurements, exhibiting a pronounced even-odd effect in elemental yields. These results may be used to predict unmeasured yields for 229 Th fission

Systematics of Fission-Product Yields

International Nuclear Information System (INIS)

Wahl, A.C.

2002-01-01

Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z F = 90 thru 98, mass number A F = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru ∼200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from ∼ 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron (∼ fission spectrum) induced fission reactions

Systematics of Fission-Product Yields

Energy Technology Data Exchange (ETDEWEB)

A.C. Wahl

2002-05-01

Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z{sub F} = 90 thru 98, mass number A{sub F} = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru {approx}200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from {approx} 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron ({approx} fission spectrum) induced fission reactions.

Asymmetry in ternary fission induced by polarized neutrons and fission mechanism

International Nuclear Information System (INIS)

Bunakov, V.E.; Gennenvajn, F.; Dzhessinger, P.; Mutterer, M.; Petrov, G.A.

2003-01-01

The results of measuring the P-odd, P-even (right-left) and T-odd asymmetries of the charged particles emission in the double and ternary fission, induced by the polarized neutrons, are considered. It is shown, what kind of information on the mechanism of the ternary nuclear fission may be obtained from the theoretical analysis of these data [ru

Neutron penetrabilities using an optical model potential (1963); Penetrabilites des neutrons selon le modele du potentiel optique (1963)

Energy Technology Data Exchange (ETDEWEB)

Mani, G S; Melkanoff, M A; Iori, I [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

The neutron penetrabilities and reaction cross-sections are presented in these tables for the case of an optical model potential for the nucleus, for nuclei up to mass 230. (authors) [French] Les penetrabilites et les sections efficaces de reaction pour les neutrons sont donnees dans ces tables en utilisant le modele du potentiel optique, pour les noyaux cibles jusqu'a la masse 230. (auteurs)

Neutron penetrabilities using an optical model potential (1963); Penetrabilites des neutrons selon le modele du potentiel optique (1963)

Energy Technology Data Exchange (ETDEWEB)

Mani, G.S.; Melkanoff, M.A.; Iori, I. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

The neutron penetrabilities and reaction cross-sections are presented in these tables for the case of an optical model potential for the nucleus, for nuclei up to mass 230. (authors) [French] Les penetrabilites et les sections efficaces de reaction pour les neutrons sont donnees dans ces tables en utilisant le modele du potentiel optique, pour les noyaux cibles jusqu'a la masse 230. (auteurs)

Potentials of fissioning plasmas

International Nuclear Information System (INIS)

Karlheinz, Thom.

1979-01-01

Successful experiments with the nuclear pumping of lasers have demonstrated that in gaseous medium the kinetic energy of fission fragments can be converted directly into non-equilibrium optical radiation. This confirms the concept that the fissioning medium in a gas-phase nuclear reactor shows an internal structure such as a plasma in nearly thermal equilibrium varying up to a state of extreme-non-equilibrium. The accompanying variations of temperatures, pressure and radiative spectrum suggest wide ranges of applications. For example, in the gas-phase fission reactor concept enriched uranium hexafluoride or an uranium plasma replaces conventional fuel elements and permits operation above the melting point of solid materials. This potential has been motivation for the US National Aeronautics and Space Administration (NASA) to conduct relevant research for high specific impulse propulsion in space. The need to separate the high temperature gaseous fuel from the surfaces of a containing vessel and to protect them against thermal radiation has led to the concept of an externally moderated reactor in which the fissioning gaseous material is suspended by fluid dynamic means and the flow of opaque buffer gas removes the power. The gaseous nuclear fuel can slowly be circulated through the reactor for continuous on-site reprocessing including the annihilation of transuranium actinides at fission when being fed back into the reactor. An equilibrium of the generation and destruction of such actinides at fission when being fed back into the reactor. An equilibrium of the generation and destruction of such actinides can thus be achieved. These characteristics and the unique radiative properties led to the expectation that the gas-phase fission reactor could feature improved safety, safeguarding and economy, in addition to new technologies such as processing, photochemistry and the transmission of power over large distances in space

Thorium-uranium fission radiography

Science.gov (United States)

Haines, E. L.; Weiss, J. R.; Burnett, D. S.; Woolum, D. S.

1976-01-01

Results are described for studies designed to develop routine methods for in-situ measurement of the abundance of Th and U on a microscale in heterogeneous samples, especially rocks, using the secondary high-energy neutron flux developed when the 650 MeV proton beam of an accelerator is stopped in a 42 x 42 cm diam Cu cylinder. Irradiations were performed at three different locations in a rabbit tube in the beam stop area, and thick metal foils of Bi, Th, and natural U as well as polished silicate glasses of known U and Th contents were used as targets and were placed in contact with mica which served as a fission track detector. In many cases both bare and Cd-covered detectors were exposed. The exposed mica samples were etched in 48% HF and the fission tracks counted by conventional transmitted light microscopy. Relative fission cross sections are examined, along with absolute Th track production rates, interaction tracks, and a comparison of measured and calculated fission rates. The practicality of fast neutron radiography revealed by experiments to data is discussed primarily for Th/U measurements, and mixtures of other fissionable nuclei are briefly considered.

Relativistic Coulomb Fission

Science.gov (United States)

Norbury, John W.

1992-01-01

Nuclear fission reactions induced by the electromagnetic field of relativistic nuclei are studied for energies relevant to present and future relativistic heavy ion accelerators. Cross sections are calculated for U-238 and Pu-239 fission induced by C-12, Si-28, Au-197, and U-238 projectiles. It is found that some of the cross sections can exceed 10 b.

Fission-product source terms

International Nuclear Information System (INIS)

Lorenz, R.A.

1981-01-01

This presentation consists of a review of fission-product source terms for light water reactor (LWR) fuel. A source term is the quantity of fission products released under specified conditions that can be used to calculate the consequences of the release. The source term usually defines release from breached fuel-rod cladding but could also describe release from the primary coolant system, the reactor containment shell, or the site boundary. The source term would be different for each locality, and the chemical and physical forms of the fission products could also differ

Part 1: The detection of criticality accidents in the Commissariat a l'Energie Atomique. Part 2: The Burst Slug Detection; 1. partie: la detection des accidents de criticite au Commissariat a l'Energie Atomique. 2. partie.: la detection des ruptures de gaines

Energy Technology Data Exchange (ETDEWEB)

Debrie, G; Lavie, J; Planque, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

In all installations where fissionable materials are handled in quantities virtually greater than the critical mass, there exists permanent risk of accidental nuclear excursion entailing a serious irradiation hazard to the personnel, in spite of all the precautions that might be taken. Immediate detection followed by rapid evacuation greatly limits the risks of irradiation due to the fission products or to the sustained nuclear reaction. The necessity for a suitable equipment for the detection of accidents of criticality is imposed by the fact that the physical phenomena accompanying a nuclear, excursion are insufficient to follow the alarm, and may lead to confusion. Taking into account the accidents which have occurred and the role expected from a detector, we choose a dose integration device for the detecting probe proper, and a system based on the coincidence of several information to trigger the alarm. At the demand of the Commission des Masses Critiques, the minimal physical and electronic features required to obtain a very reliable system with minimal risk of false alarm has been established. These features are described in some detail. The equipment constructed at the Commissariat a l'Energie Atomique on the basis of these recommendations has been tested systematically under actual conditions of nuclear excursions at the Health Physics Research Reactor of the National Laboratory at Oak Ridge. These tests have served to determine two types of detection probes which will be described: a photomultiplier and a semiconductor probe. Finally the authors present an example of a complete unit for the detection of criticality accidents in an installation for the processing of fissile material. B - The evolution of the installations for burst slug detection (BSD) in french reactors. The main part of the effort in the field of the Burst Slug Detection has been orientated on the large gas-cooled reactors where the problem of bursts slugs is associated with the economics

Nuclear fission studies: from LOHENGRIN to FIPPS

International Nuclear Information System (INIS)

Chebboubi, Abdelaziz

2015-01-01

Nuclear fission consists in splitting a nucleus, in general an actinide, into smaller nuclei. Despite nuclear fission was discovered in 1939 by Hahn and Strassman, fission models cannot predict the fission observables with an acceptable accuracy for nuclear fuel cycle studies for instance. Improvement of fission models is an important issue for the knowledge of the process itself and for the applications. To reduce uncertainties of the nuclear data used in a nuclear reactor simulation, a validation of the models hypothesis is mandatory. In this work, two features of the nuclear fission were investigated in order to test the resistance of the theories. One aspect is the study of the symmetric fission fragments through the measurement of their yield and kinetic energy distribution. The other aspect is the study of the fission fragment angular momentum.Two techniques are available to assess the angular momentum of a fission fragment. The first one is to look at the properties of the prompt gamma. The new spectrometer FIPPS (Fission Product Prompt gamma-ray Spectrometer), is currently under development at the ILL and will combine a fission filter with a large array of gamma and neutron detectors in order to respond to these issues. The first part of this work is dedicated to the study of the properties of a Gas Filled Magnet (GFM) which is the type of fission filter considered for the FIPPS project.The second part of this work deals with the measurement of isomeric yields and evaluations of the angular momentum distribution of fission fragments. The study of the spherical nucleus 132 Sn shed the light on the current limits of fission models. Finally, the last part of this work is about the measurement of the yields and kinetic energy distributions of symmetric fission fragments. Since models predict the existence of fission modes, the symmetry region is a suitable choice to investigate this kind of prediction. In parallel with all these studies, an emphasis on the

Generalized Energy-Dependent Q Values for Fission

Energy Technology Data Exchange (ETDEWEB)

Vogt, R

2010-03-31

We extend Madland's parameterization of the energy release in fission to obtain the dependence of the fission Q value for major and minor actinides on the incident neutron energies in the range 0 {le} E{sub n} {le} 20 MeV. Our parameterization is based on the actinide evaluations recommended for the ENDF/B-VII.1 release. This paper describes the calculation of energydependent fission Q values based on the calculation of the prompt energy release in fission by Madland. This calculation was adopted for use in the LLNL ENDL database and then generalized to obtain the prompt fission energy release for all actinides. Here the calculation is further generalized to the total energy release in fission. There are several stages in a fission event, depending on the time scale. Neutrons and gammas may be emitted at any time during the fission event.While our discussion here is focussed on compound nucleus creation by an incident neutron, similar parameterizations could be obtained for incident gammas or spontaneous fission.

New fission-neutron-spectrum representation for ENDF

International Nuclear Information System (INIS)

Madland, D.G.

1982-04-01

A new representation of the prompt fission neutron spectrum is proposed for use in the Evaluated Nuclear Data File (ENDF). The proposal is made because a new theory exists by which the spectrum can be accurately predicted as a function of the fissioning nucleus and its excitation energy. Thus, prompt fission neutron spectra can be calculated for cases where no measurements exist or where measurements are not possible. The mathematical formalism necessary for application of the new theory within ENDF is presented and discussed for neutron-induced fission and spontaneous fission. In the case of neutron-induced fission, expressions are given for the first-chance, second-chance, third-chance, and fourth-chance fission components of the spectrum together with that for the total spectrum. An ENDF format is proposed for the new fission spectrum representation, and an example of the use of the format is given

Device for measuring fission product density

International Nuclear Information System (INIS)

Kaneda, Mitsunori.

1980-01-01

Purpose: To determine the fission product density of xenon or the like and enable measurement of real time of fission product density in a reactor by calculating the disintegration and annihilation of the fission product on the basis of neutron detected output. Constitution: The neutron flux in a reactor is detected by a detector, and applied to first and second density calculators. Second fission product density signal of xenon or the like outputted from first device is again inputted to the device to form an annihilation signal due to disintegration to determine the present density of the second fission product of xenon or the like corresponding to the decrease of the neutron due to the poison of xeron or the like. Similarly, second device determines the first fission product density of iodine or the like. (Sekiya, K.)

Detection of {alpha} particles using semiconductors. Application to the control of plutonium extraction; Detection des particules {alpha} par semiconducteurs application au controle de l'extraction du plutonium

Energy Technology Data Exchange (ETDEWEB)

Tanguy, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-03-01

A study is made of a particles produced by thick sources, using either diffused junction or surface barrier semiconductor detectors for controlling continuously the plutonium extraction process. For this, a presenting apparatus is described in which the solutions to be analyzed flow in contact with the detector protected by a thin mica membrane. A method is described which gives a precise recording of the spectra and which thus allows the separation of two or more {alpha} emitters present in the same solution. This method has been applied to the measurement of {sup 239}Pu in the the presence of {sup 241}Am with an accuracy of {+-}5 per cent. In the second part of the report is considered the detection of plutonium in solutions of {beta} - {gamma} emitting fission products. Pile-up is reduced by using a fast amplification chain associated to totally depleted thin detectors. Under these conditions a few mg of {sup 239}Pu can be detected in solutions of fission products having an activity of 100 curies/liter. A method is given for discriminating {alpha} and {beta} particles, it is based on the difference in the collection times for the charges liberated by these particles in the detector. (author) [French] On etudie la detection de particules {alpha} issues de sources epaisses par detecteurs semiconducteurs a jonction diffusee ou a barriere de surface pour le controle continu du procede d'extraction du plutonium. A cet effet on decrit un appareil presentateur dans lequel les solutions a analyser circulent au contact du detecteur protege par une membrane mince de mica. On decrit une methode qui permet par le trace precis des spectres de separer deux ou plusieurs emetteurs {alpha} presents dans une meme solution. Cette methode a ete appliquee a la mesure du {sup 239}Pu en presence de {sup 241}Am avec une precision de {+-} 5 pour cent. Dans la deuxieme partie on traite de la detection du plutonium dans des solutions de produits de fission emetteurs {beta} and {gamma

Fission cross section and fission fragment angular distribution for oriented nucleus fission by intermediate energy neutrons (epsilon < or approximately 1 Mev)

International Nuclear Information System (INIS)

Barabanov, A.L.; Grechukhin, D.P.

1985-01-01

General analysis is conducted, and formulae for fission cross section and angular distribution of fission fragments of oriented nuclei by fast neutrons are presented. Geometrical coefficients making up the formulae permitting to carry out calculations for target nuclei with spins I=3/2, 5/2, 7/2 at interaction energies epsilon < or approximately 1 MeV are tabulated. Results of demonstrative calculation of fission fragment angular distribution of oriented sup(235)U nuclei by 0.1 <= epsilon <= 1.0 MeV neutrons reveal that angular distribution weakly depends on the set of permeability factors of neutron waves applied in the calculations

Contribution to the study of nuclear fission

International Nuclear Information System (INIS)

Serot, O.

2009-09-01

The author proposes an overview of his research activity during the past fifteen years and more particularly that dealing with nuclear fission. The first part reports works on nucleus physics at the scission via the investigation of ternary fission (experimental procedure, influence of fission modes, influence of resonance spin, influence of excitation energy of the fissioning nucleus, emission probabilities, energy spectra of ternary alphas and tritons, emission mechanism). The second part reports measurements and assessments of neutron-induced fission cross sections. The third part reports the investigation of some properties of fission products (efficiencies, branching ratios of the main delayed neutron precursors)

Fission - track age of the Marjalahti Pallasite

International Nuclear Information System (INIS)

Bondar, Yu.V.; Perelygin, V.P.

2006-01-01

Full text: Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Over geological time, meteorites crystals have accumulated a record of tracks produced by heavily charged energetic particles from both internal (spontaneous fission of 238U and some other extinct isotopes) and external sources (galactic cosmic rays with Z>20). The fortunate fact that meteorite grains can accumulate latent and very long-lived tracks since soon after the end of nucleosynthesis in the solar nebula enables one to decode their radiation history and to detect any thermal events in the meteorite cosmic history by revealing these tracks through suitable etching procedures. Only a few minerals in meteorites (mainly phosphates) contain small amount of uranium; the fact that 238 U undergoes fission with fission-decay constant λ f ∼ 8.2x10 -17 yr -1 allows one to use this isotope as a chronometer. By measuring the U concentration in the crystals (by reactor irradiation) and the density of the spontaneous-fission tracks it is relatively easy to calculate the 'fission-track age' if 238 U is the main source of fission tracks. However the fission-track dating of extraterrestrial samples compared with the terrestrial ones has some peculiar features due to presence of a number of other potential track sources except the spontaneous fission of 238 U, such as the spontaneous fission of presently extinct 244 Pu, heavy nuclei of cosmic rays and induced fission by cosmic ray primaries. Only tracks from the spontaneous fission of U and Pu are suitable for fission-track dating. The competing effects of these fissioning elements, whose half-lives differ by a factor of ∼50, form a basis for a fission-track chronology for samples older than ∼ 4.0 Gyr. Over small intervals in time (∼ few x10 8 yr ) the track density from spontaneous fission of 238 U is nearly constant. However, the

A small flat fission chamber

International Nuclear Information System (INIS)

Li Yijun; Wang Dalun; Chen Suhe

1999-01-01

With fission materials of depleted uranium, natural uranium, enriched uranium, 239 Pu, and 237 Np, the authors have designed and made a series of small flat fission chamber. The authors narrated the construction of the fission chamber and its technological process of manufacture, and furthermore, the authors have measured and discussed the follow correct factor, self-absorption, boundary effect, threshold loss factor, bottom scatter and or so

50 years of nuclear fission

International Nuclear Information System (INIS)

Hilscher, D.

1989-01-01

The article tells the story of the discovery of nuclear fission in Berlin 50 years ago by Otto Hahn and Fritz Strassmann in cooperation with Lise Meitner. 50 years later nuclear fission is still a subject of research. Some question remain unanswered. Selected new research results are used to discuss the dynamics of the collective movement of the elementary nuclear fission process. (orig.) [de

Fission modelling with FIFRELIN

International Nuclear Information System (INIS)

Litaize, Olivier; Serot, Olivier; Berge, Leonie

2015-01-01

The nuclear fission process gives rise to the formation of fission fragments and emission of particles (n,γ, e - ). The particle emission from fragments can be prompt and delayed. We present here the methods used in the FIFRELIN code, which simulates the prompt component of the de-excitation process. The methods are based on phenomenological models associated with macroscopic and/or microscopic ingredients. Input data can be provided by experiment as well as by theory. The fission fragment de-excitation can be performed within Weisskopf (uncoupled neutron and gamma emission) or a Hauser-Feshbach (coupled neutron/gamma emission) statistical theory. We usually consider five free parameters that cannot be provided by theory or experiments in order to describe the initial distributions required by the code. In a first step this set of parameters is chosen to reproduce a very limited set of target observables. In a second step we can increase the statistics to predict all other fission observables such as prompt neutron, gamma and conversion electron spectra but also their distributions as a function of any kind of parameters such as, for instance, the neutron, gamma and electron number distributions, the average prompt neutron multiplicity as a function of fission fragment mass, charge or kinetic energy, and so on. Several results related to different fissioning systems are presented in this work. The goal in the next decade will be i) to replace some macroscopic ingredients or phenomenological models by microscopic calculations when available and reliable, ii) to be a support for experimentalists in the design of detection systems or in the prediction of necessary beam time or count rates with associated statistics when measuring fragments and emitted particle in coincidence iii) extend the model to be able to run a calculation when no experimental input data are available, iv) account for multiple chance fission and gamma emission before fission, v) account for the

Fission gas detection system

International Nuclear Information System (INIS)

Colburn, R.P.

1984-01-01

A device for collecting fission gas released by failed fuel rods which device uses a filter adapted to pass coolant but to block passage of fission gas bubbles due to the surface tension of the bubbles. The coolant may be liquid metal. (author)

Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers

Science.gov (United States)

Bhatia, C.; Fallin, B.; Howell, C.; Tornow, W.; Gooden, M.; Kelley, J.; Arnold, C.; Bond, E.; Bredeweg, T.; Fowler, M.; Moody, W.; Rundberg, R.; Rusev, G.; Vieira, D.; Wilhelmy, J.; Becker, J.; Macri, R.; Ryan, C.; Sheets, S.; Stoyer, M.; Tonchev, A.

2014-05-01

To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced γ-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.

Fifty years with nuclear fission

International Nuclear Information System (INIS)

Behrens, J.W.; Carlson, A.D.

1989-01-01

The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a topical meeting entitled, ''Fifty years with nuclear fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent developments in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicating a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two full days of sessions (April 27 and 28) at the main sites of the NIST in Gaithersburg, Maryland. The wide range of topics covered by Volume 2 of this topical meeting included plenary invited, and contributed sessions entitled, Nuclear fission -- a prospective; reactors II; fission science II; medical and industrial applications by by-products; reactors and safeguards; general research, instrumentation, and by-products; and fission data, astrophysics, and space applications. The individual papers have been cataloged separately

Shell effects in fission and quasi-fission of heavy and superheavy nuclei

Energy Technology Data Exchange (ETDEWEB)

Itkis, M.G. E-mail: itkis@flnr.jinr.ru; Aeystoe, J.; Beghini, S.; Bogachev, A.A.; Corradi, L.; Dorvaux, O.; Gadea, A.; Giardina, G.; Hanappe, F.; Itkis, I.M.; Jandel, M.; Kliman, J.; Khlebnikov, S.V.; Kniajeva, G.N.; Kondratiev, N.A.; Kozulin, E.M.; Krupa, L.; Latina, A.; Materna, T.; Montagnoli, G.; Oganessian, Yu.Ts.; Pokrovsky, I.V.; Prokhorova, E.V.; Rowley, N.; Rubchenya, V.A.; Rusanov, A.Ya.; Sagaidak, R.N.; Scarlassara, F.; Stefanini, A.M.; Stuttge, L.; Szilner, S.; Trotta, M.; Trzaska, W.H.; Vakhtin, D.N.; Vinodkumar, A.M.; Voskressenski, V.M.; Zagrebaev, V.I

2004-04-05

Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions {sup 12}C+{sup 204}Pb, {sup 48}Ca+{sup 144,154}Sm, {sup 168}Er, {sup 208}Pb, {sup 244}Pu, {sup 248}Cm; {sup 58}Fe+{sup 208}Pb, {sup 244}Pu, {sup 248}Cm, and {sup 64}Ni+{sup 186}W, {sup 242}Pu are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes {sup 283}112, {sup 289}114 and {sup 283}116 at Dubna [1],[2] using the same reactions. The {sup 58}Fe and {sup 64}Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET[3] and the neutron multi-detector DEMON[4],[5]. The role of shell effects and the influence of the entrance channel on the mechanism of the compound nucleus fusion-fission and the competitive process of quasi-fission are discussed.

Independent fission yields of Rb and Cs from thermal-neutron-induced fission of 239Pu

International Nuclear Information System (INIS)

Balestrini, S.J.; Forman, L.

1975-01-01

The relative independent fission yields of Rb and Cs from thermal-neutron-induced fission of 239 Pu have been measured on line using a mass spectrograph and thermalized neutrons from a burst reactor. Independent yields were derived by normalizing the measurements to products of chain yields and fractional independent yields, estimating the latter from measured cumulative yields of Kr and Xe. Comparing the independent yields with those from 238 U fission, the 239 Pu results show shifts in isotopic yield distribution toward lower mass for both Rb and Cs and also toward the production of more Cs and less Rb when 239 Pu is fissioned

A position sensitive parallel plate avalanche fission detector for use in particle induced fission coincidence measurements

NARCIS (Netherlands)

Plicht, J. van der

1980-01-01

A parallel plate avalanche detector developed for the detection of fission fragments in particle induced fission reactions is described. The active area is 6 × 10 cm2; it is position sensitive in one dimension with a resolution of 2.5 mm. The detector can withstand a count rate of 25000 fission

Physics of neutron emission in fission

International Nuclear Information System (INIS)

Lemmel, H.D.

1989-06-01

The document contains the proceedings of the IAEA Consultants' Meeting on the Physics of Neutron Emission in Fission, Mito City (Japan), 24-27 May 1988. Included are the conclusions and recommendations reached at the meeting and the papers presented by the meeting participants. These papers cover the following topics: Energy dependence of the number of fission neutrons ν-bar (3 papers), multiplicity distribution of fission neutrons (3 papers), competition between neutron and γ-ray emission (4 papers), the fission neutron yield in resonances (2 papers) and the energy spectrum of fission neutrons in experiment (9 papers), theory (4 papers) and evaluation (1 paper). A separate abstract was prepared for each of these papers. Refs, figs and tabs

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, G.

1975-01-01

This is the first issue of a report series on Fission Product Nuclear Data (FPND), published every six months by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). Its purpose is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields; neutron cross-section data of fission products; data related to β-, γ-decay of fission products; delayed neutron data; and fission product decay-heat. The present issue includes contributions which were received by NDS before 1 November 1975

Fission dynamics with systems of intermediate fissility

Indian Academy of Sciences (India)

results concerning nuclear dissipation and fission time-scale obtained from several of these studies. In particular ... alent to the assumption that fission is delayed, namely, that the fission probability is not .... parameters to be adjusted on the experimental data. ..... (b) Time distribution of all fission events for the 132Ce nucleus.

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, M.

1982-07-01

This is the eighth issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The main part of this report consists of unaltered original contributions which the authors have sent to IAEA/NDS. Therefore, the IAEA cannot be held responsible for the information contained nor for any consequences resulting from the use of this information. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission); Neutron reaction cross sections of fission products; Data related to the radioactive decay of fission products; Delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The seventh issue of this series has been published in July 1981 as INDC(NDS)-116. The present issue includes contributions which were received by NDS between 1 August 1981 and 15 June 1982

Induced-Fission Imaging of Nuclear Material

International Nuclear Information System (INIS)

Hausladen, Paul; Blackston, Matthew A.; Mullens, James Allen; McConchie, Seth M.; Mihalczo, John T.; Bingham, Philip R.; Ericson, Milton Nance; Fabris, Lorenzo

2010-01-01

This paper presents initial results from development of the induced-fission imaging technique, which can be used for the purpose of measuring or verifying the distribution of fissionable material in an unopened container. The technique is based on stimulating fissions in nuclear material with 14 MeV neutrons from an associated-particle deuterium-tritium (D-T) generator and counting the subsequent induced fast fission neutrons with an array of fast organic scintillation detectors. For each source neutron incident on the container, the neutron creation time and initial trajectory are known from detection of the associated alpha particle of the d + t → α + n reaction. Many induced fissions will lie along (or near) the interrogating neutron path, allowing an image of the spatial distribution of prompt induced fissions, and thereby fissionable material, to be constructed. A variety of induced-fission imaging measurements have been performed at Oak Ridge National Laboratory with a portable, low-dose D-T generator, including single-view radiographic measurements and three-dimensional tomographic measurements. Results from these measurements will be presented along with the neutron transmission images that have been performed simultaneously. This new capability may have applications to a number of areas in which there may be a need to confirm the presence or configuration of nuclear materials, such as nuclear material control and accountability, quality assurance, treaty confirmation, or homeland security applications.

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le ...

African Journals Online (AJOL)

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le foreur des tiges du cacaoyer ( Eulophonotus myrmeleon Felder : Lepidoptera, Cossidae). Implications dans la stratégie de protection de la cacaoculture en Côte d'Ivoire.

Fission fragment mass and angular distributions

Indian Academy of Sciences (India)

2015-07-22

Jul 22, 2015 ... Synthesis of heavy and superheavy elements is severely hindered by fission and fission-like processes. The probability of these fission-like, non-equilibrium processes strongly depends on the entrance channel parameters. This article attempts to summarize the recent experimental findings and classify the ...

The resonance neutron fission on heavy nuclei

International Nuclear Information System (INIS)

Kopach, Yu.N.; Popov, A.B.; Furman, V.I.; Alfimenkov, V.P.; Lason', L.; Pikel'ner, L.B.; ); Gonin, N.N.; Kozlovskij, L.K.; Tambovtsev, D.I.; Gagarskij, A.M.; Petrov, G.A.; Sokolov, V.E.

2001-01-01

A new approach to the description of the fission, similar to the well-known reaction theory and based on the helicity representation for the exit fission channels, is briefly summarized. This approach allows one to connect the multimodal fission representation with A. Bohr's concept of the fission transition states and to obtain formulae for the partial and differential fission cross sections. The formulae are used for analysis of the angular anisotropy of fragments in the neutron resonance induced fission of aligned 235 U nuclei and of the P-even angular forward-backward and right-left correlations of fragments oe the P-odd correlations caused by the interference of s- and p-wave neutron resonances [ru

Charged particle-induced nuclear fission reactions

Indian Academy of Sciences (India)

The nuclear fission phenomenon continues to be an enigma, even after nearly 75 years of its discovery. Considerable progress has been made towards understanding the fission process. Both light projectiles and heavy ions have been employed to investigate nuclear fission. An extensive database of the properties of ...

What do we learn on the dynamics of fission from α-accompanied fission data

International Nuclear Information System (INIS)

Guet, C.; Asghar, M.; Nifenecker, H.; Perrin, P.

1978-01-01

Measurements of the angular distribution of α-particles emitted by thermal fission of 236 U are presented. Also the dependence of the angular distribution on the kinetic energy of the fission products is studied. (WL) [de

Santé des adolescents et des jeunes au Burkina Faso : état des ...

African Journals Online (AJOL)

Il s'est agi d'une étude évaluative ayant utilisé une revue documentaire associée à une interview des acteurs clés et un atelier de validation et d'identification des interventions pertinentes pour un plan stratégique national. La situation de la santé des adolescents et des jeunes est caractérisée par des grossesses précoces ...

Study of transfer induced fission and fusion-fission reactions for 28 Si + 232 Th system at 340 MeV

International Nuclear Information System (INIS)

Prete, G.; Rizzi, V.; Fioretto, E.; Cinausero, M.; Shetty, D.V.; Pesente, S.; Brondi, A.; La Rana, G.; Moro, R.; Vardaci, E.; Boiano, A.; Ordine, A.; Gelli, N.; Lucarelli, F.; Bortignon, P.F.; Saxena, A.; Nayak, B.K.; Biswas, D.C.; Choudhury, R.K.; Kapoor, R.S.

2001-01-01

Full text: Fission induced by nucleons transfer has been investigated in the reaction 28 Si + 232 Th at 340 MeV. Looking at the projectile-like-fragments (PLF), the fission yield increases as the transfer increases, but a decreases is observed for transfers with DZ . Light charged particles in coincidence with PLF and Fission have been detected with large solid angle and show an increasing multiplicity as the Z of PLF is reduced and a constant value when fission is requested. The present results indicate inhibition of transfer induced fission reaction for higher Z transfer and increasing probability for decay through charged particle evaporation. Fission is the dominant decay process in heavy reactions involving fissile systems but the dynamical evolution of the composite system is largely governed by the formation and decay mechanisms. Important insight into the formation and the survival probability of the heavy composite nuclei formed in heavy ion collisions can be gained by simultaneously investigate the fission process and light particle emission over a continuous range of excitation energy, angular momentum and fissility. This can be achieved by studying fission induced by transfer of nucleons between the interacting projectile and the target nucleus. In the present work, we have carried out measurements on multinucleon transfer induced fission reactions in 28 Si + 232 Th system at Elab = 340 MeV. The experiment has been performed at the Laboratori Nazionale di Legnaro (LNL) using the 8pLP detector in its final configuration with 257 DE-E telescopes. The backward detectors were used to measure both light charged particles and fission fragments. The projectile-like fragments were detected using separate DE-E telescopes around the grazing angle. Two neutron detectors were placed at a distance of 115.5 cm from the target to measure neutrons emitted in coincidence with fission fragments. Here we present the results of the data analysis of transfer induced fission

Measurements of fission cross-sections. Chapter 4

International Nuclear Information System (INIS)

James, G.D.

1981-01-01

The steps involved in the measurement of fission cross sections are summarized and the range of techniques available are considered. Methods of fission detection are described with particular emphasis on the neutron energy dependent properties of the fission process and the details of fragment energy loss which can lead to energy-dependent changes in detector efficiency. Selected examples of fission cross-section measurements are presented and methods of data reduction, storage, analysis and evaluation, are examined. Finally requested accuracies for fission cross section data are compared to estimated available accuracies. (U.K.)

Primary Distributions of Nuclear Charge for Fission-Fragment Masses 132, 134, 136 and 137 from Thermal Fission of U{sup 235}; Repartition Primaire de la Charge Nucleaire pour les Fragments de Masse 132, 134, 136 et 137, Provenant de la Fission de {sup 235}U par Neutrons Thermiques; 041f 0415 0420 0414 ; Distribuciones Primarias de las Cargas Nucleares de los Fragmentos de Masa 132, 134, 136 y 137, Resultantes de la Fision del {sup 235}U por Neutrones Termicos

Energy Technology Data Exchange (ETDEWEB)

Konecny, E.; Opower, H.; Guenther, H.; Goebel, H. [Physik-Department der Technischen Hochschule Muenchen, Munich and II. Physikalisches Institut der Justus Liebig-Universitaet Giessen, Federal Republic of Germany (Germany)

1965-07-15

the statistical error arising from the transformation from 2{pi}- to 4{pi}-distribution, and for various kinetic energies as parameters, are in preparation. (author) [French] A l'aide d'un spectrometre de masse, on separe avec precision les fragments de la fission thermique de {sup 235}U d'apres leur masse et leur energie cinetique dans la microseconde qui suit la fission. Les fragments separes sont retenus dans une emulsion Ilford G 5 sensible aux particules {beta}, qui est placee dans le plan focal du spectrometre. Les emulsions irradiees sont developpees, dans la mesure du possible, apres un delai relativement long par rapport a la periode la plus longue de la serie radioactive consideree. Les periodes de l'ordre de plusieurs jours ou plus longues encoxe ne sont pas prises en consideration, mais il est facile d'appliquer un facteur de correction approprie. Apres avoir developpe les emulsions, on peut observer au microscope toutes les traces {beta} qui prolongent chacune des traces de fragments de fission. La possibilite d'etablir une correlation entre une trace {beta} et une trace de fragment de fission permet d'evaluer le nombre n(x) de fragments de fission possedant un nombre x de traces {beta}, ce qui indique non seulement la longueur moyenne de la serie mais aussi la distribution des particules {beta}. Le nucleide stable de chaque serie etant connu, la distribution des particules {beta} constitue une image exacte de la repartition primaire des charges nucleaires. Au cours des mesures effectuees jusqu'a present, on n'a en-' registre que les particules {beta} emises dans le demi-angle solide forme par la plaque d'emulsion, mais un calcul statistique simple permet d'evaluer la distribution. 4{pi} voulue. Grace a cette methode, on obtient la distribution des particules 0 a des energies cinetiques determinees proches de l'energie cinetique moyenne de chaque fragment pour les masses 132, 134, 136 et 137. Pour les masses 132 et 134, c'est a la couche de neutrons N

Muon induced fission and fission track dating of minerals

International Nuclear Information System (INIS)

Marques, A.

1988-01-01

The effects of muon induced fission on geological dating of samples by the fission track method are evaluated for the case of muscovite minerals. It is found a small but significant effect, greater for the longer ages. Since calculations are developped under the hypothesis of constant atmosphere and primary cosmic ray flux it is suggested that any discrepancy found in ages of very old material that cannot be accounted for by well known environmental influences, be taken as an indication of variation on either the atmospheric stopping power or the intensity of cosmic radiation along the ages. (author) [pt

La fabrique des sciences des institutions aux pratiques

CERN Document Server

Benninghoff, Martin; Crettaz von Roten, Fabienne; Merz, Martina

2006-01-01

Aujourd'hui, les façons de produire, d'organiser, d'évaluer et d'utiliser les savoirs sont en profond débat. De plus en plus, l'Etat, la société civile et l'économie tentent d'influencer les activités des universités et des laboratoires de recherche. Ces développements mettent à l'épreuve tout à la fois les fondements des systèmes d'enseignement supérieur et de recherche, l'autonomie des institutions scientifiques, la définition des frontières des savoirs et l'acceptation des sciences. Dans des contextes suisses et européens, cet ouvrage s'intéresse aux manières dont les sciences et les technologies sont fabriquées, en analysant leurs institutions et les pratiques. A partir d'une approche relationnelle, les sciences et les technologies sont conçues comme des phénomènes profondément sociaux, culturels et politiques. Une telle démarche déstabilise les visions parfois idéalisées et stéréotypées de la construction des savoirs. Des études de cas détaillées décrivent des phénomè...

Fission barriers of light nuclei

International Nuclear Information System (INIS)

Grotowski, K.; Planeta, R.; Blann, M.; Komoto, T.

1989-01-01

Experimental fission excitation functions for compound nuclei /sup 52/Fe, /sup 49/Cr, /sup 46/V, and /sup 44/Ti formed in heavy-ion reactions are analyzed in the Hauser-Feshbach/Bohr-Wheeler formalism using fission barriers based on the rotating liquid drop model of Cohen et al. and on the rotating finite range model of Sierk. We conclude that the rotating finite range approach gives better reproduction of experimental fission yields, consistent with results found for heavier systems

True ternary fission in 310126X

International Nuclear Information System (INIS)

Banupriya, B.; Vijayaraghavan, K.R.; Balasubramaniam, M.

2015-01-01

All possible combinations are minimized by the two dimensional minimization process and minimized with respect to neutron numbers and proton numbers of the fragments. Potential energy is low and Q - value is high at true ternary fission region. It shows that true ternary mode is the dominant mode in the ternary fission of superheavy nuclei. Also, the results show that the fragments with neutron magic numbers are the dominant one in the ternary fission of superheavy nuclei whereas the fragments with proton magic numbers are the dominant one in the ternary fission of heavy nuclei

Status of fission product yield data

International Nuclear Information System (INIS)

Cuninghame, J.G.

1978-01-01

The topics covered in this paper are: (a) cumulative yields in thermal neutron fission and in fast fission up to 14 MeV incident neutron energy, (b) dependence of the yields on incident neutron energy and spectrum, (c) independent yields, (d) charge dispersion and distribution, and (e) yields of light particles from ternary fission. The paper reviews information on these subjects for fission of actinides from 232 Th upwards with special emphasis on data published since the 1973 Bologna FPND Panel, compares data sets, and discusses the gaps still to be found in them. (author)

Monte-Carlo method - codes for the study of criticality problems (on IBM 7094); Methode de Monte- Carlo - codes pour l'etude des problemes de criticite (IBM 7094)

Energy Technology Data Exchange (ETDEWEB)

Moreau, J; Rabot, H; Robin, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The two codes presented here allow to determine the multiplication constant of media containing fissionable materials under numerous and divided forms; they are based on the Monte-Carlo method. The first code apply to x, y, z, geometries. The volume to be studied ought to be divisible in parallelepipeds, the media within each parallelepiped being limited by non-secant surfaces. The second code is intended for r, 0, z geometries. The results include an analysis of collisions in each medium. Applications and examples with informations on time and accuracy are given. (authors) [French] Les deux codes presentes dans ce rapport permettent la determination des coefficients de multiplication de milieux contenant des matieres fissiles sous des formes tres variees et divisees, ils reposent sur la methode de Monte-Carlo. Le premier code s'applique aux geometries x, y, z, le volume a etudier doit pouvoir etre decompose en parallelepipedes, les milieux a l'interieur de chaque parallelepipede etant limites par des surfaces non secantes. Le deuxieme code s'applique aux geometries r, 0, z. Les resultats comportent une analyse des collisions dans chaque milieu. Des applications et des exemples avec les indications de temps et de precision sont fournis. (auteurs)

Neutron gamma competition in fast fission

International Nuclear Information System (INIS)

Frehaut, J.

1989-01-01

In the present paper we analyse the data we have obtained on the distribution of the gamma-ray energy per fission, as well as on the average energy E-barγ released per fission for the neutron induced fission of several isotopes, in the energy range up to 15 MeV. 6 refs, 9 figs

Fission energy of uranium isotopes and transuranium elements

International Nuclear Information System (INIS)

Nemirovskij, P.Eh.; Manevich, L.G.

1981-01-01

A comparison is made between the prompt fission energy, Esub(pr), calculated from the mass and binding energy spectrum and the Esub(pr) value obtained from the experimental data on the kinetic energy of fragments, the energy of prompt neutrons and prompt γ-quanta. Basing on the data on β-decay chains of fission fragments, the energies of neutrinos, γ-quanta and β-electrons are obtained, which permits to calculate the actual energy released during fission. The calculations are performed for thermal neutron-induced fission, fast-neutron induced fission and for fission after bombardment with 14 MeV neutrons. The available experimental data on the fission fragment kinetic energy, prompt γ-quanta energy and fission neutron energy are presented. The comparison of the Esub(pr) values obtained experimentally for the thermal-neutron-induced fission with the calculated Esub(pr) value shows that for 233 U, 239 Pu, 241 Pu the agreement is rather favourable. For 235 U the agreement is within the error limits. As to the Esub(pr) values for the fast-neutron-induced fission, the agreement between the calculated and experimental data for all nuclides is quite good

Fission product induced swelling of U–Mo alloy fuel

International Nuclear Information System (INIS)

Kim, Yeon Soo; Hofman, G.L.

2011-01-01

Highlights: ► We measured fuel swelling of U–Mo alloy by fission products at temperatures below 250 °C. ► We quantified the swelling portion of U–Mo by fission gas bubbles. ► We developed an empirical model as a function of fission density. - Abstract: Fuel swelling of U–Mo alloy was modeled using the measured data from samples irradiated up to a fission density of ∼7 × 10 27 fissions/m 3 at temperatures below ∼250 °C. The overall fuel swelling was measured from U–Mo foils with as-fabricated thickness of 250 μm. Volume fractions occupied by fission gas bubbles were measured and fuel swelling caused by the fission gas bubbles was quantified. The portion of fuel swelling by solid fission products including solid and liquid fission products as well as fission gas atoms not enclosed in the fission gas bubbles is estimated by subtracting the portion of fuel swelling by gas bubbles from the overall fuel swelling. Empirical correlations for overall fuel swelling, swelling by gas bubbles, and swelling by solid fission products were obtained in terms of fission density.

Fusion-fission dynamics

International Nuclear Information System (INIS)

Blocki, J.; Planeta, R.; Brzychczyk, J.; Grotowski, K.

1992-01-01

Classical dynamical calculations of the heavy ion induced fission processes have been performed for the reactions 40 Ar+ 141 Pr, 20 Ne+ 165 Ho and 12 C+ 175 Lu leading to the iridium like nucleus. As a result prescission lifetimes were obtained and compared with the experimental values. The comparison between the calculated and experimental lifetimes indicates that the one-body dissipation picture is much more relevant in describing the fusion-fission dynamics than the two-body one. (orig.)

The spectroscopy of fission fragments

International Nuclear Information System (INIS)

Phillips, W.R.

1998-01-01

High-resolution measurements on γ rays from fission fragments have provided a rich source of information, unobtainable at the moment in any other way, on the spectroscopy of neutron-rich nuclei. In recent years important data have been obtained on the yrast- and near yrast-structure of neutron-rich fission fragments. We discuss the scope of measurements which can be made on prompt gamma rays from secondary fission fragments, the techniques used in the experiments and some results recently obtained. (author)

Fission fragment angular momentum

International Nuclear Information System (INIS)

Frenne, D. De

1991-01-01

Most of the energy released in fission is converted into translational kinetic energy of the fragments. The remaining excitation energy will be distributed among neutrons and gammas. An important parameter characterizing the scission configuration is the primary angular momentum of the nascent fragments. Neutron emission is not expected to decrease the spin of the fragments by more than one unit of angular momentum and is as such of less importance in the determination of the initial fragment spins. Gamma emission is a suitable tool in studying initial fragment spins because the emission time, number, energy, and multipolarity of the gammas strongly depend on the value of the primary angular momentum. The main conclusions of experiments on gamma emission were that the initial angular momentum of the fragments is large compared to the ground state spin and oriented perpendicular to the fission axis. Most of the recent information concerning initial fragment spin distributions comes from the measurement of isomeric ratios for isomeric pairs produced in fission. Although in nearly every mass chain isomers are known, only a small number are suitable for initial fission fragment spin studies. Yield and half-life considerations strongly limit the number of candidates. This has the advantage that the behavior of a specific isomeric pair can be investigated for a number of fissioning systems at different excitation energies of the fragments and fissioning nuclei. Because most of the recent information on primary angular momenta comes from measurements of isomeric ratios, the global deexcitation process of the fragments and the calculation of the initial fragment spin distribution from measured isomeric ratios are discussed here. The most important results on primary angular momentum determinations are reviewed and some theoretical approaches are given. 45 refs., 7 figs., 2 tabs

Fission yield data evaluation system FYDES

International Nuclear Information System (INIS)

Liu Tingjin

1998-01-01

Taking account of some features of fission yield data, to do the fission yield data evaluation conveniently, a fission yield data evaluation system FYDES has been developed for last two years. Outline of the system, data retrieval and data table standardization, data correction codes, data averaging code, simultaneous evaluation code and data fit programs were introduced

Fission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on 239Pu, 235U, 238U

International Nuclear Information System (INIS)

Selby, H.D.; Mac Innes, M.R.; Barr, D.W.; Keksis, A.L.; Meade, R.A.; Burns, C.J.; Chadwick, M.B.; Wallstrom, T.C.

2010-01-01

We describe measurements of fission product data at Los Alamos that are important for determining the number of fissions that have occurred when neutrons are incident on plutonium and uranium isotopes. The fission-spectrum measurements were made using a fission chamber designed by the National Institute for Standards and Technology (NIST) in the BIG TEN critical assembly, as part of the Inter-laboratory Liquid Metal Fast Breeder Reactor (LMFBR) Reaction Rate (ILRR) collaboration. The thermal measurements were made at Los Alamos' Omega West Reactor. A related set of measurements were made of fission-product ratios (so-called R-values) in neutron environments provided by a number of Los Alamos critical assemblies that range from having average energies causing fission of 400-600 keV (BIG TEN and the outer regions of the Flattop-25 assembly) to higher energies (1.4-1.9 MeV) in the Jezebel, and in the central regions of the Flattop-25 and Flattop-Pu, critical assemblies. From these data we determine ratios of fission product yields in different fuel and neutron environments (Q-values) and fission product yields in fission spectrum neutron environments for 99 Mo, 95 Zr, 137 Cs, 140 Ba, 141,143 Ce, and 147 Nd. Modest incident-energy dependence exists for the 147 Nd fission product yield; this is discussed in the context of models for fission that include thermal and dynamical effects. The fission product data agree with measurements by Maeck and other authors using mass-spectrometry methods, and with the ILRR collaboration results that used gamma spectroscopy for quantifying fission products. We note that the measurements also contradict earlier 1950s historical Los Alamos estimates by ∼5-7%, most likely owing to self-shielding corrections not made in the early thermal measurements. Our experimental results provide a confirmation of the England-Rider ENDF/B-VI evaluated fission-spectrum fission product yields that were carried over to the ENDF/B-VII.0 library, except

Measurements of actinide-fission product yields in Caliban and Prospero metallic core reactor fission neutron fields

Energy Technology Data Exchange (ETDEWEB)

Casoli, P.; Authier, N. [CEA, Centre de Valduc, 21120 Is-sur-Tille (France); Laurec, J.; Bauge, E.; Granier, T. [CEA, Centre DIF, 91297 Arpajon (France)

2011-07-01

In the 1970's and early 1980's, an experimental program was performed on the facilities of the CEA Valduc Research Center to measure several actinide-fission product yields. Experiments were, in particular, completed on the Caliban and Prospero metallic core reactors to study fission-neutron-induced reactions on {sup 233}U, {sup 235}U, and {sup 239}Pu. Thick actinide samples were irradiated and the number of nuclei of each fission product was determined by gamma spectrometry. Fission chambers were irradiated simultaneously to measure the numbers of fissions in thin deposits of the same actinides. The masses of the thick samples and the thin deposits were determined by mass spectrometry and alpha spectrometry. The results of these experiments will be fully presented in this paper for the first time. A description of the Caliban and Prospero reactors, their characteristics and performances, and explanations about the experimental approach will also be given in the article. A recent work has been completed to analyze and reinterpret these measurements and particularly to evaluate the associated uncertainties. In this context, calculations have also been carried out with the Monte Carlo transport code Tripoli-4, using the published benchmarked Caliban description and a three-dimensional model of Prospero, to determine the average neutron energy causing fission. Simulation results will be discussed in this paper. Finally, new fission yield measurements will be proposed on Caliban and Prospero reactors to strengthen the results of the first experiments. (authors)

Cold valleys in fusion and fission

International Nuclear Information System (INIS)

Misicu, S.

2003-01-01

The cold fission configuration after the preformation of the fragments resembles a short-lived dinuclear or quasi-molecular system. The most conceivable scission configuration is given by two fission fragments in touching with the symmetry axes aligned (pole-pole orientation). This conclusion was based on the simple argument that this configuration offers the optimal tunneling time, i.e. the difference between the Coulomb barrier and the decay energy Q is minimal. Other orientations are apparently precluded in cold spontaneous fission and should be regarded as quasi-fission doorways in the synthesis of superheavy elements by cold fusion. (orig.)

(d,p)-transfer induced fission of heavy radioactive beams

CERN Document Server

Veselsky, Martin

2012-01-01

(d,p)-transfer induced fission is proposed as a tool to study low energy fission of exotic heavy nuclei. Primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission offers a possibility for systematic study the low energy fission of heavy exotic nuclei at the ISOLDE.

Fusion-fission of heavy systems

International Nuclear Information System (INIS)

Rivet, M.F.; Alami, R.; Borderie, B.; Fuchs, H.; Gardes, D.; Gauvin, H.

1988-01-01

The influence of the entrance channel on fission processes was studied by forming the same composite system by two different target-projectile combinations ( 40 Ar + 209 Bi and 56 Fe + 187 Re, respectively). Compound nucleus fission and quasi fission were observed and the analysis was performed in the framework of the extra-extra-push model, which provides a qualitative interpretation of the results; limits for the extra-extra-push threshold are given, but problems with quantitative predictions for the extra-push are noted. (orig.)

The spectroscopy of fission fragments

Energy Technology Data Exchange (ETDEWEB)

Phillips, W.R. [Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)

1998-12-31

High-resolution measurements on {gamma} rays from fission fragments have provided a rich source of information, unobtainable at the moment in any other way, on the spectroscopy of neutron-rich nuclei. In recent years important data have been obtained on the yrast- and near yrast-structure of neutron-rich fission fragments. We discuss the scope of measurements which can be made on prompt gamma rays from secondary fission fragments, the techniques used in the experiments and some results recently obtained. (author) 24 refs., 8 figs., 1 tab.

Progress in fission product nuclear data. No. 14

International Nuclear Information System (INIS)

Lammer, M.

1994-06-01

This is the 14th issue of a report series on Fission Product Nuclear Data published by the Nuclear Data Section of the IAEA. The types of activities included are measurements, compilations and evaluations of fission product yields, neutron reaction cross sections of fission products, data related to the radioactive decay of fission products, delayed neutron data from neutron induced and spontaneous fission, lumped fission product data. The first part of the report consists of unaltered original contributions which the authors have sent to IAEA/NDS. The second part contains some recent references relative to fission product nuclear data, which were not covered by the contributions submitted, and selected papers from conferences. The third part contains requirements for further measurements

Progress in fission product nuclear data. No. 13

International Nuclear Information System (INIS)

Lammer, M.

1990-11-01

This is the 13th issue of a report series published by the Nuclear Data Section of the IAEA. The types of activities included are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission), neutron reaction cross-sections of fission products, data related to the radioactive decay of fission products, delayed neutron data of fission products and bumped fission product data (decay heat, absorption, etc.). The first part of the report consists of unaltered original data which the authors have sent to IAEA/NDS. The second part contains some recent references relative to fission product nuclear data, which were not covered by the contributions submitted, and selected papers from conferences. Part 3 contains requirements for further measurements

The role of the dinuclear system in the processes of nuclear fusion, quasi-fission, fission and cluster formation

International Nuclear Information System (INIS)

Volkov, V.V.

1999-01-01

The nuclear fusion, quasi-fission, fission and cluster formation in an excited nucleus are considered as the processes of the formation and evolution of the dinuclear system. This approach allows one to reveal new aspects of nuclear fusion, to show that quasi-fission plays an important role in nuclear reactions used to synthesise superheavy elements. A qualitative picture is given of the fission process of an excited nucleus and an important role of cluster formation in this process is shown

Fission product detection

International Nuclear Information System (INIS)

Liatard, E.; Akrouf, S.; Bruandet, J.F

1987-01-01

The response of photovoltaic cells to heavy ions and fission products have been tested on beam. Their main advantages are their extremely low price, their low sensitivity to energetic light ions with respect to fission products, and the possibility to cut and fit them together to any shape without dead zone. The time output signals of a charge sensitive preamplifier connected to these cells allows fast coincidences. A resolution of 12ns (F.W.H.M.) have been measured between two cells [fr

Utilization of fission reactors for fusion engineering testing

International Nuclear Information System (INIS)

Deis, G.A.; Miller, L.G.

1985-01-01

Fission reactors can be used to conduct some of the fusion nuclear engineering tests identified in the FINESSE study. To further define the advantages and disadvantages of fission testing, the technical and programmatic constraints on this type of testing are discussed here. This paper presents and discusses eight key issues affecting fission utilization. Quantitative comparisons with projected fusion operation are made to determine the technical assets and limitations of fission testing. Capabilities of existing fission reactors are summarized and compared with technical needs. Conclusions are then presented on the areas where fission testing can be most useful

Options for development of space fission propulsion systems

International Nuclear Information System (INIS)

Houts, Mike; Van Dyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbud, Ivana

2001-01-01

Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission systems have only been used in Earth orbit. The first step towards utilizing advanced fission propulsion systems is development of a safe, near-term, affordable fission system that can enhance or enable near-term missions of interest. An evolutionary approach for developing space fission propulsion systems is proposed

Attachment of gaseous fission products to aerosols

International Nuclear Information System (INIS)

Skyrme, G.

1985-01-01

Accidents may occur in which the integrity of fuel cladding is breached and volatile fission products are released to the containment atmosphere. In order to assess the magnitude of the subsequent radiological hazard it is necessary to know the transport behaviour of such fission products. It is frequently assumed that the fission products remain in the gaseous phase. There is a possibility, however, that they may attach themselves to particles and hence substantially modify their transport properties. This paper provides a theoretical assessment of the conditions under which gaseous fission products may be attached to aerosol particles. Specific topics discussed are: the mass transfer of a gaseous fission product to an isolated aerosol particle in an infinite medium; the rate at which the concentration of fission products in the gas phase diminishes within a container as a result of deposition on a population of particles; and the distribution of deposited fission product between different particle sizes in a log-normal distribution. It is shown that, for a given mass, small particles are more efficient for fission product attachment, and that only small concentrations of such particles may be necessary to achieve rapid attachment. Conditions under which gaseous fission products are not attached to particles are also considered, viz, the competing processes of deposition onto the containment walls and onto aerosol particles, and the possibility of the removal of aerosols from the containment by various deposition processes, or agglomeration, before attachment takes place. (author)

Use of proportional counter in X-Ray spectrometry between 5 and 100 keV. Application to the detection of fission products and to the determination of absolute X-Ray disintegration rates; Utilisation d'un compteur proportionnel en spectrometrie de rayons X entre 5 et 100 keV. Application a la detection des produits de fission et a la determination des taux d'emission X absolus

Energy Technology Data Exchange (ETDEWEB)

Cerf, J [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

1969-07-01

The measurement of electromagnetic radiations is difficult in the energy range 20-100 keV. We made suitable for this purpose a regular proportional counter, modifying both the nature and pressure of the gaseous mixture filling the detector volume. We selected the CPEN-SAIP counter, which is able to withstand such modifications. In the energy range considered, the counter is to be standardized with radioactive sources. Such standards were selected according to their disintegration schemes. We thus defined the conditions of use (resolution, yield) of the CPN counter, filled with an argon-methane mixture under a pressure of about 3 bars, in the energy range 5-100 keV. With such an equipment, we were able to measure the absolute disintegration rate for the X-rays of 133 Ba and 75 Se, then to perform the study of a mixed fission products sample. In the same way, we used xenon-based gaseous mixtures, in order to improve the detector yield; in the later case, we carefully examined the limitations introduced by the presence of many parasite rays emitted by the gas. We thus displayed in addition to the leakage peak, the fluorescence ray of the gas, whose origin is difficult to explain. (author) [French] La mesure des rayonnements electromagnetiques est difficile dans une bande d'energie comprise entre 20 et 100 keV environ. Nous avons rendu utilisable, a cet effet, un compteur proportionnel existant en modifiant la nature et la pression du melange gazeux constituant le volume detecteur. De par sa construction, le compteur CPXN, fabrique par les Etablissements S.A.I.P., rend ces experiences possibles. C'est pourquoi nous l'avons choisi. Dans le domaine d'energie consideree l'etalonnage du compteur necessite l'emploi de sources radioactives. Pour les preparer, nous sommes amenes a choisir les radio-nucleides utilisables par l'etude de leur schema de desintegration. Ainsi, nous avons defini les conditions d'utilisation (resolution, efficacite) du compteur CPNX rempli d

Spontaneous fission of 259Md

International Nuclear Information System (INIS)

Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Landrum, J.H.; Dougan, R.J.; Mustafa, M.; Ghiorso, A.; Nitschke, J.M.

1979-01-01

The mass and kinetic energy distributions of fission fragments from the spontaneous fission of th newly discovered nuclide 259 Md were obtained. 259 Md was identified as the E. C. daughter of 259 No, and was found to decay entirely (> 95%) by spontaneous fission with a 95-min half-life. From the kinetic energies measured for 397 pairs of coincident fragments, a mass distribution was derived that is symmetric with sigma = 13 amu. 259 Md, together with 258 Fm and 259 Fm, form a select group of three nuclides whose mass division in spontaneous fission is highly symmetric. Unlike the total-kinetic-energy (TKE) distributions of 258 Fm and 259 Fm, which peak at approx. = to 240 MeV, this distribution for 259 Md is broad and is 50 MeV lower in energy. Analysis of the mass and energy distributions shows that events near mass symmetry also exhibit a broad TKE distribution, with one-third of the symmetric events having TKEs less than 200 MeV. The associated of low TKEs with symmetric mass division in the fission of very heavy actinides is anomalous and inconsistent with theories based upon the emergence of fragment shells near the scission point. Either three-body fragmentation or peculiar fragment shapes are assumed as the cause for the large consumption of Coulomb energy observed for a significant fraction of symmetric fissions in 259 Md. 6 figures

Modelling isothermal fission gas release

International Nuclear Information System (INIS)

Uffelen, P. van

2002-01-01

The present paper presents a new fission gas release model consisting of two coupled modules. The first module treats the behaviour of the fission gas atoms in spherical grains with a distribution of grain sizes. This module considers single atom diffusion, trapping and fission induced re-solution of gas atoms associated with intragranular bubbles, and re-solution from the grain boundary into a few layers adjacent to the grain face. The second module considers the transport of the fission gas atoms along the grain boundaries. Four mechanisms are incorporated: diffusion controlled precipitation of gas atoms into bubbles, grain boundary bubble sweeping, re-solution of gas atoms into the adjacent grains and gas flow through open porosity when grain boundary bubbles are interconnected. The interconnection of the intergranular bubbles is affected both by the fraction of the grain face occupied by the cavities and by the balance between the bubble internal pressure and the hydrostatic pressure surrounding the bubbles. The model is under validation. In a first step, some numerical routines have been tested by means of analytic solutions. In a second step, the fission gas release model has been coupled with the FTEMP2 code of the Halden Reactor Project for the temperature distribution in the pellets. A parametric study of some steady-state irradiations and one power ramp have been simulated successfully. In particular, the Halden threshold for fission gas release and two simplified FUMEX cases have been computed and are summarised. (author)

Spontaneous fission of superheavy nuclei

Indian Academy of Sciences (India)

The fission-like configurations are used for the total deformation energy calculations. A ... oscillator potential for the two fission fragment regions reads as ... Beyond this limit, the contribution of more remote levels is negligible. Once the density ...

Extraction chromatography of fission products

International Nuclear Information System (INIS)

Bonnevie-Svendsen, M.; Goon, K.

1978-01-01

Various cases of using extraction chromatography during analysis of fission products are reviewed. The use of the extraction chromatography method is considered while analysing reprocessed products of nuclear fuel for quantitative radiochemical analysis and control of fission product and actinoide separation during extraction and their chemical state in production solutions. The method is used to obtain pure fractions of typical burnup monitors (neodymium, molybdenum, cerium, cesium, europium, lanthanides) during determination of nuclear fuel burnup degree. While studying the nature of nuclear reactions the method is used to separate quickly short-life isotopes, to purify β-radiator fractions before measuring their half-life periods, to enrich isotopes forming with low output during fission. Examples of using extraction chromatography are given to separate long half-life or stable fission products from spent solutions, to control environment object contamination

Chemical effects of fission recoils

International Nuclear Information System (INIS)

Meisels, G.G.; Freeman, J.P.; Gregory, J.P.; Richardson, W.C.; Sroka, G.J.

1978-01-01

The production of nitrogen from nitrous oxide at high density was employed to investigate the energy deposition efficiency of fission recoils produced from fission of U 235 in uranium-palladium foils clad with platinum. Nitrogen production varied linearly with fission recoil dose from 1.1 x 10 20 to 9.0 x 10 20 eV, and was independent of density between 12.5 and 127.5 g l -1 N 2 O. 16.2 +- 0.8% of the fission recoil energy was deposited external to the foil. Electron microprobe analysis showed some unevenness of new foil and polymer buildup on the surface after irradiation of ethylene-oxygen mixtures. Subsequent irradiation in the presence of nitrous oxide restored some of the original efficiency. This is ascribed to chemical oxidation of the polymer induced by reactive intermediates produced from nitrous oxide. (author)

Nuclear fission: a review of experimental advances and phenomenology

Science.gov (United States)

Andreyev, A. N.; Nishio, K.; Schmidt, K.-H.

2018-01-01

In the last two decades, through technological, experimental and theoretical advances, the situation in experimental fission studies has changed dramatically. With the use of advanced production and detection techniques both much more detailed and precise information can now be obtained for the traditional regions of fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies. This work first of all reviews the recent developments in experimental fission techniques, in particular the resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams. The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of the other fission observables, such as prompt neutron and γ-ray emission will also be reviewed. A particular attention will be given to the low-energy fission in the so far scarcely explored nuclei in the very neutron-deficient lead region. They recently became the focus for several complementary experimental studies, such as β-delayed fission with radioactive beams at ISOLDE(CERN), Coulex-induced fission of relativistic secondary beams at FRS(GSI), and several prompt fusion–fission studies. The synergy of these approaches allows a unique insight in the new region of asymmetric fission around {\\hspace{0pt}}180 Hg, recently discovered at ISOLDE. Recent extensive theoretical efforts in this region will also be outlined. The unprecedented high-quality data for fission fragments, completely identified in Z and A, by means of reactions in inverse kinematics at FRS(GSI) and VAMOS(GANIL) will be also reviewed. These experiments explored an extended range of mercury-to-californium elements, spanning from the neutron-deficient to neutron-rich nuclides, and covering both asymmetric, symmetric and transitional fission regions

Fission Product Library and Resource

Energy Technology Data Exchange (ETDEWEB)

Burke, J. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Padgett, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-09-29

Fission product yields can be extracted from an irradiated sample by performing gamma ray spectroscopy on the whole sample post irradiation. There are several pitfalls to avoid when trying to determine a specific isotope's fission product yield.

Tombes et cimetières éthiopiens : des rois, des saints, des anonymes1

OpenAIRE

Derat, Marie-Laure

2009-01-01

L’histoire des tombes et cimetières éthiopiens, dans la longue durée, en est encore à ses balbutiements. Si les tombes des saints et des rois nous sont un peu mieux connus grâce à des textes témoignant à la fois des enjeux entourant les sépultures de ces personnages hors du commun et des soins apportés à leur inhumation, en revanche, les cimetières ordinaires échappent encore largement à l’enquête, en grande partie parce que le commun des mortels est inhumé dans l’anonymat et dans un grand dé...

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1989-01-01

Following a summary of the observables in neutron emission in fission, a brief history is given of theoretical representations of the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity /bar /nu///sub p/. This is followed by descriptions, together with examples, of modern approaches to the calculation of these quantities including recent advancements. Emphasis will be placed upon the predictability and accuracy of the modern approaches. In particular, the dependence of N(E) and /bar /nu///sub p/ on the fissioning nucleus and its excitation energy will be discussed, as will the effects of and competition between first-, second- and third-chance fission in circumstances of high excitation energy. Finally, properties of neutron-rich (fission-fragment) nuclei are discussed that must be better known to calculate N(E) and /bar /nu///sub p/ with higher accuracy than is currently possible. 17 refs., 11 figs

Calculated apparent yields of rare gas fission products

International Nuclear Information System (INIS)

Delucchi, A.A.

1975-01-01

The apparent fission yield of the rare gas fission products from four mass chains is calculated as a function of separation time for six different fissioning systems. A plot of the calculated fission yield along with a one standard deviation error band is given for each rare gas fission product and for each fissioning system. Those parameters in the calculation that were major contributors to the calculated standard deviation at each separation time were identified and the results presented on a separate plot. To extend the usefulness of these calculations as new and better values for the input parameters become available, a third plot was generated for each system which shows how sensitive the derived fission yield is to a change in any given parameter used in the calculation. (U.S.)

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

Face à ce constat, le défi de la recherche serait la détermination du niveau actuel de contamination des légumes feuilles et des eaux du barrage et celui de l'État serait l'initiation de programmes de sensibilisation des producteurs par rapport à une gestion plus rigoureuse des pesticides. Mots-clés : pratiques paysannes, ...

International conference on fifty years research in nuclear fission

International Nuclear Information System (INIS)

1989-02-01

These proceedings contain extended abstracts of the papers presented at the named conference. They deal with static properties of fission, instrumentation for fission studies, fission in compound-nucleus reactions, fission dynamics, fission-like heavy ion reactions, and fusion reactions. See hints under the relevant topics. (HSI)

Theoretical Description of the Fission Process

International Nuclear Information System (INIS)

Witold Nazarewicz

2003-01-01

The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process

Theoretical Description of the Fission Process

Energy Technology Data Exchange (ETDEWEB)

Witold Nazarewicz

2003-07-01

The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.

E=mc$^{2}$ l'équation de tous les possibles

CERN Document Server

Galfard, Christophe

2017-01-01

"E=mc² est une espèce de signal, un panneau marquant l'entrée dans une nouvelle réalité, différente de celle que nous connaissons tous. Et cela a des implications profondes dans le monde de l'infiniment petit comme dans celui de l'infiniment grand..." E=mc², la plus célèbre de toutes les équations... Elle a bouleversé à jamais la façon dont nous comprenons le monde, en libérant pour commencer la colossale énergie enfermée dans les noyaux des atomes. Mais que signifie vraiment cette formule ? Pour le savoir, laissez Christophe Galfard vous raconter l'équation de tous les possibles. Plongez dans un univers d'énergie pure où tous vos repères seront définitivement abolis...

La convergence des rôles respectifs des relationnistes et des journalistes influence-t-elle la perception qu'ils ont les uns des autres?

DEFF Research Database (Denmark)

Valentini, Chiara

2017-01-01

la convergence des rôles respectifs des praticiens des relations publiques et des journalistes a un effet favorable sur la perception qu’ils ont les uns des autres. L’effet est plus marqué chez les praticiens des relations publiques, car leur vision de la profession en journalisme correspond à celle...

Mécanique des sols et des roches

CERN Document Server

Vullier, Laurent; Zhao, Jian

2016-01-01

La mécanique des sols et la mécanique des roches sont des disciplines généralement traitées séparément dans la littérature. Pour la première fois, un traité réunit ces deux spécialités, en intégrant également les connaissances en lien avec les écoulements souterrains et les transferts thermiques. A la fois théorique et pratique, cet ouvrage propose tout d'abord une description détaillée de la nature et de la composition des sols et des roches, puis s'attache à la modélisation de problèmes aux conditions limites et présente les essais permettant de caractériser les sols et les roches, tant d'un point de vue mécanique qu'hydraulique et thermique. La problématique des sols non saturés et des écoulements multiphasiques est également abordée. Une attention particulière est portée aux lois de comportement mécanique et à la détermination de leurs paramètres par des essais in situ et en laboratoire, et l'ouvrage offre également une présentation détaillée des systèmes de classi...

Fission of nuclei far from stability

International Nuclear Information System (INIS)

Schmidt, K.H.; Benlliure, J.; Junghans, A.R.

2000-11-01

The secondary-beam facility of GSI provided the technical equipment for a new kind of fission experiment. Fission properties of short-lived neutron-deficient nuclei have been investigated in inverse kinematics. The measured element distributions reveal new kinds of systematics on shell structure and even-odd effects and lead to an improved understanding of structure effects in nuclear fission. Prospects for further experimental studies are discussed. (orig.)

Analysis and composition of the first U-Pu charge (0,043 per cent of Pu); Analyse et constitution du 1. jeu U-Pu (0,043 pour cent de Pu)

Energy Technology Data Exchange (ETDEWEB)

Brunet, J P; Lapparent, D de; Lourme, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

Checking the homogeneity in the content of plutonium of 0,043 per cent Pu-natural uranium alloy slugs has been made by Pu 240 and U 238 spontaneous fissions neutrons counting. The purpose of the test was to select groups of slugs to be correctly associated into fuel rods for critical experiments. General technic for spontaneous fissions counting, then elaboration of data in view of ranking the slugs are described. Results are given for this particular case. (authors) [French] On a effectue un controle d'homogeneite de teneur en plutonium sur des billettes d'alliage 0,043 pour cent Pu-uranium naturel, par comptage des fissions spontanees du plutonium 240 et de l'uranium 238. Le but du controle etait de permettre une association correcte de ces billettes a l'interieur des elements combustibles destines a servir dans des experiences critiques. On indique la methode generale de comptage des fissions spontanees, puis le depouillement des donnees en vue du classement des barreaux. Les resultats pour ce cas particulier sont donnes dans le rapport. (auteurs)

Mass dependence of positive pion-induced fission

International Nuclear Information System (INIS)

Khan, H.A.; Khan, N.A.; Peterson, R.J.

1991-01-01

Fission cross sections for a range of targets have been measured by solid-state track detectors following 80 and 100 MeV π + bombardment. Fission probabilities have been inferred by comparison to computed reaction cross sections. Fission probabilities for heavy targets agree with those for other probes of comparable energy and with statistical calculations. Probabilities for lighter targets are much above those previously observed or computed. Ternary fission cross sections and multiplicities of light fragments have also been determined

Towards a microscopic description of the fission process

CERN Document Server

Goutte, H; Berger, J F

2010-01-01

One major issue in nuclear physics is to develop a consistent model able to describe on the same footing the different aspects of the fission process, i.e. properties of the fissioning system, fission dynamics and fragment distributions. Microscopic fission studies based on the mean-field approximation are here presented.

Yields of fission products produced by thermal-neutron fission of 245Cm

International Nuclear Information System (INIS)

Dickens, J.K.; McConnell, J.W.

1981-01-01

Absolute yields have been determined for 105 gamma rays emitted in the decay of 95 fission products representing 54 mass chains created during thermal-neutron fission of 245 Cm. These results include 17 mass chains for which no prior yield data exist. Using a Ge(Li) detector, spectra were obtained of gamma rays between 30 sec and 0.3 yr after very short irradiations of thermal neutrons on a 1 μg sample of 245 Cm. On the basis of measured gamma-ray yields and known nuclear data, total chain mass yields and relative uncertainties were obtained for 51 masses between 84 and 156. The absolute overall normalization uncertainty is 239 Pu and for 252 Cf(s.f.); the influences of the closed shells Z=50, N=82 are not as marked as for thermal-neutron fission of 239 Pu but much more apparent than for 252 Cf(s.f.). Information on the charge distribution along several isobaric mass chains was obtained by determining fractional yields for 12 fission products. The charge distribution width parameter, based upon data for the heavy masses, A=128 to 140, is independent of mass to within the uncertainties of the measurements. Gamma-ray assignments were made for decay of short-lived fission products for which absolute gamma-ray transition probabilities are either not known or in doubt. Absolute gamma-ray transition probabilities were determined as (51 +- 8)% for the 374-keV gamma ray from decay of 110 Rh, (35 +- 7)% for the 1096-keV gamma ray from decay of 133 Sb, and (21.2 +- 1.2)% for the 255-keV gamma ray from decay of 142 Ba

Fission in Empire-II version 2.19 beta1, Lodi

International Nuclear Information System (INIS)

Sin, M.

2003-01-01

This is a description of the fission model implemented presently in EMPIRE-II. This package offers two ways to calculate the fission probability selected by parameters in the optional input. Fission barriers, fission transmission coefficients, fission cross sections and fission files are calculated

The study of prompt and delayed muon induced fission III. The ratios of prompt to delayed fission yields

NARCIS (Netherlands)

Rösel, Ch.; Hänscheid, H.; Hartfiel, J.; Mutius, von R.; Achard van Enschut, d' J.F.M.; David, P; Janszen, H.; Johansson, T.; Konijn, J.; Krogulski, T.; Laat, de C.T.A.M.; Paganetti, H.; Petitjean, C.; Polikanov, S.M.; Reist, H.W.; Risse, F.; Schaller, L.A.; Schrieder, W.; Sinha, A.K.; Taal, A.; Theobald, J.P.; Tibell, G.; Trautmann, N.

1993-01-01

The ratios of prompt to delayed fission yields for the isotopes U-233, U-234, U-235, U-236, U-238, Np-237, Pu-242, and Pu-244 and the fission probabilities relative to each other have been investigated experimentally. Using the value of the total fission probability for Np-237 the absolute

Fission throughout the periodic table

International Nuclear Information System (INIS)

Moretto, L.G.; Wozniak, G.J.

1989-04-01

The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission, and light particle evaporation are seen as different aspects of a single process. 47 refs., 22 figs

What happens to the fission process above the 2nd- and 3rd-chance fission thresholds

International Nuclear Information System (INIS)

Stewart, L.; Howerton, R.J.

1976-01-01

Although the multiple fission process is important at high neutron energies, most of the evaluations available today do not include these individual fission cross sections or their associated fission spectra. The representations used in the Los Alamos and Livermore libraries are described and calculations compared with 14-MeV integral experiments available on 235 U, 238 U, and 239 Pu. Further work is needed to clearly delineate the specific problems in order to propose unique solutions

Chemical Production using Fission Fragments

International Nuclear Information System (INIS)

Dawson, J. K.; Moseley, F.

1960-01-01

Some reactor design considerations of the use of fission recoil fragment energy for the production of chemicals of industrial importance have been discussed previously in a paper given at the Second United Nations International Conference on the Peaceful Uses of Atomic Energy [A/Conf. 15/P.76]. The present paper summarizes more recent progress made on this topic at AERE, Harwell. The range-energy relationship for fission fragments is discussed in the context of the choice of fuel system for a chemical production reactor, and the experimental observation of a variation of chemical effect along the length of a fission fragment track is described for the irradiation of nitrogen-oxygen mixtures. Recent results are given on the effect of fission fragments on carbon monoxide-hydrogen gas mixtures and on water vapour. No system investigated to date shows any outstanding promise for large-scale chemical production. (author) [fr

50 years with nuclear fission, April 25-28, 1989. A prelude to fission: France

International Nuclear Information System (INIS)

Savic, P.

1989-01-01

A personal account of the events leading to the 1938 discovery, by Irene Joliot-Curie and the author, of the unidentified element R 3.5h will be presented, as well as the experimental methods proving the R 3.5h had chemical properties similar to lanthanum which in turn led Hahn and Strassmann to the discovery of fission in 1939. The author points out that Irene Curie's intuition indicated the path towards the solution of the problem of uranium irradiated by neutrons, which made possible the discovery of fission by Hahn and Strassmann. Further applications of fission became possible by tremendous efforts and excellent contributions of scientists in the USA

Apparatus for measuring the release of fission gases and other fission products by degassing

Energy Technology Data Exchange (ETDEWEB)

Stradal, Karl Alfred

1970-10-15

In gas-cooled high-temperature reactors, the fuel is, in general, inserted in the fuel elements in the form of small particles, which are, for example, coated with pyrolytic carbon. The purpose of this coating is to keep the fission products separate from the coolant gas. The further development of these coated particles makes it necessary to check the retention capacity. One possible method of doing this is the degassing test after irradiation in the reactor. An apparatus is described below, which was developed and installed in order to measure to a higher degree of sensitivity and in serial measurements the release of fission gases and sparingly volatile fission products.

The fast fission effect in a cylindrical fuel element

Energy Technology Data Exchange (ETDEWEB)

Carlvik, I; Pershagen, B

1959-06-15

A new formula for the fast fission factor is derived, which takes proper account to fast capture. The fission neutron spectrum is divided into two groups with constant fission cross section in one group and zero fission cross section in the other. The average total, elastic, inelastic and capture cross sections in the two groups are calculated. Different assumptions regarding anisotropic and inelastic scattering are investigated. The effects of backscattering from the moderator and fast fission in neighbouring fuel elements are pointed out. Formulas for the fast fission ratio and for the fast conversion ratio are derived. The calculated fast fission ratios are compared with experimental values. Curves are given for the fast fission factor in uranium metal and uranium oxide.

Nuclear fission as a macroscopic quantum tunneling

International Nuclear Information System (INIS)

Takigawa, N.

1995-01-01

We discuss nuclear fission from the point of view of a macroscopic quantum tunneling, one of whose major interests is to study the effects of environments on the tunneling rate of a macroscopic variable. We show that a vibrational excitation of the fissioning nucleus significantly enhances the fission rate. We show this effect by two different methods. The one is to treat the vibrational excitation as an environmental degree of freedom, the other treats the fission as a two dimensional quantum tunneling. (author)

Behavior of solid fission products in irradiated fuel

International Nuclear Information System (INIS)

Song, Ung Sup; Jung, Yang Hong; Kim, Hee Moon; Yoo, Byun Gok; Kim, Do Sik; Choo, Yong Sun; Hong, Kwon Pyo

2004-01-01

Many fission products are generated by fission events in UO 2 fuel under irradiation in nuclear reactor. Concentration of each fission product is changed by conditions of neutron energy spectrum, fissile material, critical thermal power, irradiation period and cooling time. Volatile materials such as Cs and I, the fission products, degrade nuclear fuel rod by the decrease of thermal conductivity in pellet and the stress corrosion cracking in cladding. Metal fission products (white inclusion) make pellet be swelled and decrease volume of pellet by densification. It seems that metal fission products are filled in the pore in pellet and placed between UO 2 lattices as interstitial. In addition, metal oxide state may change structural lattice volume. Considering behavior of fission products mentioned above, concentration of them is important. Fission products could be classified as bellows; solid solution in matrix : Sr, Zr, Nb, Y, La, Ce, Pr, Nd, Pm, Sm - metal precipitates : Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sb, Te - oxide precipitates : Ba, Zr, Nb, Mo, (Rb, Cs, Te) - volatile and gases : Kr, Xe, Br, I, (Rb, Cs, Te)

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

SARAH

30 sept. 2017 ... ... de Biochimie et Immunologie Appliquée, Centre de Recherche en Sciences Biologiques, Alimentaires et .... l'intoxication des agriculteurs et des consommateurs, ... source d'alimentation en eau et au pouvoir d'achat des.

Fission and r-process nucleosynthesis in neutron star mergers

International Nuclear Information System (INIS)

Giuliani, Samuel Andrea

2018-01-01

Fission plays a crucial role for the r-process nucleosynthesis in neutron star mergers. Due to the high neutron densities achieved in this astrophysical scenario the sequence of neutron captures and beta decays that constitutes the r process produces superheavy neutron rich nuclei that become unstable against fission. Fission determines thus the heaviest nuclei that can be produced by the r process and the fission yields shape the abundances of lighter nuclei. But despite the key role of fission the sensitivity of the r-process nucleosynthesis to uncertainties in fission predictions has not been explored. Nowadays there are only few set of fission rates suited for r-process calculations and most of them rely on a simplified treatment of the fission process. In this thesis we go beyond these approximations and compute the fission properties of r-process nuclei using the energy density functional approach. Fission is described as a tunneling process where the nucleus ''moves'' in a collective space characterized by coordinates describing the nuclear shape. Thus fission depends on the evolution of the energy with the deformation but also on the inertia due to the motion in the collective space. This is analogous to the quantum mechanical tunneling of a particle inside a potential well. In our study the relevant quantities for the description of the fission process are consistently computed for 3642 nuclei following the Hartree-Fock-Bogolyubov theory with constraining operators. We perform an extensive benchmark against the available experimental data and explore the variations of the fission properties along the superheavy landscape. We find that while collective inertias have a strong impact in the fission probabilities of light nuclei their role becomes less relevant in r -process nuclei. Within the statistical model we compute the neutron induced stellar reaction rates relevant for the r-process nucleosynthesis. These sets of stellar reaction

New experimental approaches to investigate the fission dynamics

Energy Technology Data Exchange (ETDEWEB)

Benlliure, J., E-mail: j.benlliure@usc.es; Rodríguez-Sánchez, J. L.; Alvarez-Pol, H.; Ayyad, Y.; Cortina-Gil, D.; Paradela, C.; Pietras, B.; Ramos, D.; Vargas, J. [Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain); Audouin, L.; Boutoux, G. [Institut de Physique Nucléaire d’Orsay, F-91406 Orsay (France); Bélier, G.; Chatillon, A.; Gorbinet, T.; Laurent, B.; Martin, J.-F.; Pellereau, E.; Taïeb, J. [CEA, DAM, DIF, F-91297 Arpajon (France); Casarejos, E. [Universidad de Vigo, E-36200 Vigo (Spain); Heinz, A. [Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); and others

2016-07-07

The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of {sup 208}Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point.

Fission gas release of MOX with heterogeneous structure

International Nuclear Information System (INIS)

Nakae, N.; Akiyama, H.; Kamimura, K; Delville, R.; Jutier, F.; Verwerft, M.; Miura, H.; Baba, T.

2015-01-01

It is very useful for fuel integrity evaluation to accumulate knowledge base on fuel behavior of uranium and plutonium mixed oxide (MOX) fuel used in light water reactors (LWRs). Fission gas release is one of fuel behaviors which have an impact on fuel integrity evaluation. Fission gas release behavior of MOX fuels having heterogeneous structure is focused in this study. MOX fuel rods with a heterogeneous fuel microstructure were irradiated in Halden reactor (IFA-702) and the BR-3/BR-2 CALLISTO Loop (CHIPS program). The 85 Kr gamma spectrometry measurements were carried out in specific cycles in order to examine the concerned LHR (Linear Heat Rate) for fission gas release in the CHIPS program. The concerned LHR is defined in this paper to be the LHR at which a certain additional fission gas release thermally occurs. Post-irradiation examination was performed to understand the fission gas release behavior in connection with the pellet microstructure. The followings conclusions can be made from this study. First, the concerned LHR for fission gas release is estimated to be in the range of 20-23 kW/m with burnup over 37 GWd/tM. It is moreover guessed that the concerned LHR for fission gas release tends to decrease with increasing burnup. Secondly It is observed that FGR (fission gas release rate) is positively correlated with LHR when the LHR exceeds the concerned value. Thirdly, when burnup dependence of fission gas release is discussed, effective burnup should be taken into account. The effective burnup is defined as the burnup at which the LHR should be exceed the concerned value at the last time during all the irradiation period. And fourthly, it appears that FGR inside Pu spots is higher than outside and that retained (not released) fission gases mainly exist in the fission gas bubbles. Since fission gases in bubbles are considered to be easily released during fuel temperature increase, this information is very important to estimate fission gas release behavior

Gamma Radiation from Fission Fragments

International Nuclear Information System (INIS)

Higbie, Jack

1969-10-01

The gamma radiation from the fragments of the thermal neutron fission of 235 U has been investigated, and the preliminary data are presented here with suggestions for further lines of research and some possible interpretations of the data. The data have direct bearing on the fission process and the mode of fragment de-excitation. The parameters measured are the radiation decay curve for the time interval (1 - 7) x 10 -10 sec after fission, the photon yield, the total gamma ray energy yield, and the average photon energy. The last three quantities are measured as a function of the fragment mass

Gamma Radiation from Fission Fragments

Energy Technology Data Exchange (ETDEWEB)

Higbie, Jack

1969-10-15

The gamma radiation from the fragments of the thermal neutron fission of {sup 235}U has been investigated, and the preliminary data are presented here with suggestions for further lines of research and some possible interpretations of the data. The data have direct bearing on the fission process and the mode of fragment de-excitation. The parameters measured are the radiation decay curve for the time interval (1 - 7) x 10{sup -10} sec after fission, the photon yield, the total gamma ray energy yield, and the average photon energy. The last three quantities are measured as a function of the fragment mass.

Energy partition in nuclear fission

International Nuclear Information System (INIS)

Ruben, A.; Maerten, H.; Seeliger, D.

1990-01-01

A scission point model (two spheroid model TSM) including semi-empirical temperature-dependent shell correction energies for deformed fragments at scission is presented. It has been used to describe the mass-asymmetry-dependent partition of the total energy release on both fragments from spontaneous and induced fission. Characteristic trends of experimental fragment energy and neutron multiplicity data as function of incidence energy in the Th-Cf region of fissioning nuclei are well reproduced. Based on model applications, information on the energy dissipated during the descent from second saddle of fission barrier to scission point have been deduced. (author). 39 refs, 13 figs

Modelisation of the fission cross section

International Nuclear Information System (INIS)

Morariu, Claudia

2013-03-01

The neutron cross sections of four nuclear systems (n+ 235 U, n+ 233 U, n+ 241 Am and n+ 237 Np) are studied in the present document. The target nuclei of the first case, like 235 U and 239 Pu, have a large fission cross section after the absorption of thermal neutrons. These nuclei are called 'fissile' nuclei. The other type of nuclei, like 237 Np and 241 Am, fission mostly with fast neutrons, which exceed the fission threshold energy. These types of nuclei are called 'fertile'. The compound nuclei of the fertile nuclei have a binding energy higher than the fission barrier, while for the fissile nuclei the binding energy is lower than the fission barrier. In this work, the neutron induced cross sections for both types of nuclei are evaluated in the fast energy range. The total, reaction and shape-elastic cross sections are calculated by the coupled channel method of the optical model code ECIS, while the compound nucleus mechanism are treated by the statistical models implemented in the codes STATIS, GNASH and TALYS. The STATIS code includes a refined model of the fission process. Results from the theoretical calculations are compared with data retrieved from the experimental data base EXFOR. (author) [fr

Modelisation des effets physico-techniques pour la conception des ...

African Journals Online (AJOL)

automatisation dans les installations industrielles a besoin d'une régulation automatique des commandes des processus technologiques pour lesquelles certaines contraintes sont à relever compte tenu des exigences des innovations scientifiques de ...

Fission gas behaviour in water reactor fuels

International Nuclear Information System (INIS)

2002-01-01

During irradiation, nuclear fuel changes volume, primarily through swelling. This swelling is caused by the fission products and in particular by the volatile ones such as krypton and xenon, called fission gas. Fission gas behaviour needs to be reliably predicted in order to make better use of nuclear fuel, a factor which can help to achieve the economic competitiveness required by today's markets. These proceedings communicate the results of an international seminar which reviewed recent progress in the field of fission gas behaviour in light water reactor fuel and sought to improve the models used in computer codes predicting fission gas release. State-of-the-art knowledge is presented for both uranium-oxide and mixed-oxide fuels loaded in water reactors. (author)

Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 2: Power from nuclear fission

Science.gov (United States)

Clement, J. D.

1973-01-01

Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.

Measurement of the fission yields of selected prompt and decay fission product gamma-rays of spontaneously fissioning 252Cf and 244Cm

International Nuclear Information System (INIS)

Reber, E.L.; Gehrke, R.J.; Aryaeinejad, R.; Hartwell, J.K.

2005-01-01

Gamma-ray spectrometry measurements have been made of the fission yields of selected γ -rays emitted by the spontaneously fissioning isotopes 252 Cf and 244 Cm. The measured γ-rays were selected based on their relative abundance in the spectrum and their freedom from interference or, in a few instances, ease of interference correction. From these data and the cumulative and independent yield data of England and Rider, those γ-rays that are primarily produced by radioactive decay, as opposed to direct yield, were converted into the decays per spontaneous fission expressed in percent and compared to cumulative yield values of England and Rider. For those γ-rays whose production is dominated by direct (independent) yield, the ratio of γ-rays per spontaneous fission is reported. The γ-ray yield can be compared to the independent yield values of England and Rider when 100% of the direct feeding passes through the γ-ray. In those cases where both cumulative and independent yields contribute to the observed γ-ray emission rate, a direct comparison is not possible but a method to quantify the contribution from each is proposed. (author)

Fission decay properties of nuclear giant multipole resonances

International Nuclear Information System (INIS)

Dias, H.; Arruda Neto, J.D.T.; Hussein, M.S.; Carlson, B.V.

1986-05-01

The statistical fission decay properties of the giant dipole, quadrupole and monopole resonances in 236 U are investigated with the aid of the Hauser-Feshbach model. It is found, contrary to several recent claims, that the GQR fission decay probability is as large as that of the GDR, at energies higher than the fission barrier. At energies close to the f.b., the GQR fission probability is found to be appreciably larger than that of the GDR. The GMR fission probability follows closely that of the GQR. (Author) [pt

Fission times of excited nuclei: An experimental overview

International Nuclear Information System (INIS)

Morjean, M.; Morjean, M.; Jacquet, D.

2009-01-01

An overview of selected recent experimental results on fission times is presented. Evidences for over-damped motion up to saddle point during the fission process of highly excited nuclei have been obtained independently through fission probability, pre-scission multiplicity and direct time measurements. In addition, strong clues have been found for a temperature dependency of friction. Experiments probing transient effects through fission probabilities are presented and the counterbalanced effects of friction and level density parameters are discussed. Promising perspectives for super-heavy stability studies, based on fission time measurements, are presented. (authors)

Angular momentum distribution of primary fission fragments by measurement of the relative yield of isomeric fission products

International Nuclear Information System (INIS)

Dornhoefer, H.

1980-01-01

The fission products 132 I and 136 I produced in the fission reactions 238 U(α,f) and 238 U(d,f) were spectroscoped using a gas transport system. Thereby was taken advantage of the fact that at the transport with pure helium without aerosols only iodine activities were collected in a membrane filter. The relative independent yields of the isomeric fission products of 132 I and 136 I were determined for different excitation energies. Thereby was taken advantage of the fact that the transport yield of the gas transport system for 136 I directly produced from the fission was greater than for iodine indirectly produced by β-decay. (orig./HSI) [de

Fission-product release during accidents

International Nuclear Information System (INIS)

Hunt, C.E.L.; Cox, D.S.

1991-09-01

One of the aims when managing a reactor accident is to minimize the release of radioactive fission products. Release is dependent not only on the temperature, but also on the partial pressure of oxygen. Strongly oxidizing atmospheres, such as those that occurred during the Chernobyl accident, released semi-volatile elements like ruthenium, which has volatile oxides. At low temperatures, UO 2 oxidization to U 3 O 8 can result in extensive breakup of the fuel, resulting in the release of non-volatile fission products as aerosols. Under less oxidizing conditions, when hydrogen accumulates from the zirconium-water reaction, the resulting low oxygen partial pressure can significantly reduce these reactions. At TMI-2, only the noble gases and volatile fission products were released in significant quantities. A knowledge of the effect of atmosphere as well as temperature on the release of fission products from damaged reactor cores is therefore a useful, if not necessary, component of information required for accident management

Recovery and use of fission product noble metals

International Nuclear Information System (INIS)

Jensen, G.A.; Rohmann, C.A.; Perrigo, L.D.

1980-06-01

Noble metals in fission products are of strategic value. Market prices for noble metals are rising more rapidly than recovery costs. A promising concept has been developed for recovery of noble metals from fission product waste. Although the assessment was made only for the three noble metal fission products (Rh, Pd, Ru), there are other fission products and actinides which have potential value

Vecteurs Singuliers des Theories des Champs Conformes Minimales

Science.gov (United States)

Benoit, Louis

En 1984 Belavin, Polyakov et Zamolodchikov revolutionnent la theorie des champs en explicitant une nouvelle gamme de theories, les theories quantiques des champs bidimensionnelles invariantes sous les transformations conformes. L'algebre des transformations conformes de l'espace-temps presente une caracteristique remarquable: en deux dimensions elle possede un nombre infini de generateurs. Cette propriete impose de telles conditions aux fonctions de correlations qu'il est possible de les evaluer sans aucune approximation. Les champs des theories conformes appartiennent a des representations de plus haut poids de l'algebre de Virasoro, une extension centrale de l'algebre conforme du plan. Ces representations sont etiquetees par h, le poids conforme de leur vecteur de plus haut poids, et par la charge centrale c, le facteur de l'extension centrale, commune a toutes les representations d'une meme theorie. Les theories conformes minimales sont constituees d'un nombre fini de representations. Parmi celles-ci se trouvent des theories unitaires dont les representation forment la serie discrete de l'algebre de Virasoro; leur poids h a la forme h_{p,q}(m)=[ (p(m+1) -qm)^2-1] (4m(m+1)), ou p,q et m sont des entiers positifs et p+q= 2. Ces representations possedent un sous-espace invariant engendre par deux sous-representations avec h_1=h_{p,q} + pq et h_2=h_{p,q} + (m-p)(m+1-q) dont chacun des vecteurs de plus haut poids portent le nom de vecteur singulier et sont notes respectivement |Psi _{p,q}> et |Psi_{m-p,m+1-q}>. . Les theories super-conformes sont une version super-symetrique des theories conformes. Leurs champs appartiennent a des representation de plus haut poids de l'algebre de Neveu-Schwarz, une des deux extensions super -symetriques de l'algebre de Virasoro. Les theories super -conformes minimales possedent la meme structure que les theories conformes minimales. Les representations sont elements de la serie h_{p,q}= [ (p(m+2)-qm)^2-4] /(8m(m+2)) ou p,q et m sont

Advances on fission chamber modelling

International Nuclear Information System (INIS)

Filliatre, Philippe; Jammes, Christian; Geslot, Benoit; Veenhof, Rob

2013-06-01

In-vessel, online neutron flux measurements are routinely performed in mock-up and material testing reactors by fission chambers. Those measurements have a wide range of applications, including characterization of experimental conditions, reactor monitoring and safety. Depending on the application, detectors may experience a wide range of constraints, of several magnitudes, in term of neutron flux, gamma-ray flux, temperature. Hence, designing a specific fission chamber and measuring chain for a given application is a demanding task. It can be achieved by a combination of experimental feedback and simulating tools, the latter being based on a comprehensive understanding of the underlying physics. A computation route that simulates fission chambers, named CHESTER, is presented. The retrieved quantities of interest are the neutron-induced charge spectrum, the electronic and ionic pulses, the mean current and variance, the power spectrum. It relies on the GARFIELD suite, originally developed for drift chambers, and makes use of the MAGBOLTZ code to assess the drift parameters of electrons within the filling gas, and the SRIM code to evaluate the stopping range of fission products. The effect of the gamma flux is also estimated. Computations made with several fission chambers exemplify the possibilities of the route. A good qualitative agreement is obtained when comparing the results with the experimental data available to date. In a near future, a comprehensive experimental programme will be undertaken to qualify the route using the known neutron sources, mock-up reactors and wide choice of fission chambers, with a stress on the predictiveness of the Campbelling mode. Depending on the results, a refinement of the modelling and an effort on the accuracy of input data are also to be considered. CHESTER will then make it possible to predict the overall sensitivity of a chamber, and to optimize the design for a given application. Another benefit will be to increase the

Experimental studies of some of the physical features of beryllium-moderated intermediate reactors; Etude experimentale de quelques particularites physiques des reacteurs a neutrons intermediaires, ralentis au beryllium; Ehksperimental'ny e issledovaniya nekotorykh fizicheskikh osobennostej promezhutochnykh reaktorov s berillievym zamedlitelem; Estudios experimentales de algunas caracteristicas fisicas de los reactores intermedios moderados con berilio

Energy Technology Data Exchange (ETDEWEB)

Lejpunskij, A I; Kuznetsov, V A; Artyukhov, G Ya; Mogil' ner, A I; Prokhorov, Yu A; Steklovski, V M; Chernov, L A [Akademiya Nauk, Moskva, Union of Soviet Socialist Republics (Russian Federation)

1962-03-15

of neutrons absorbed by the uranium. The paper provides data, derived from the same assembly, on the efficiency of rods made of various absorbing materials. It gives the experimentally measured distribution of neutron density for neutrons of various energies in the neighbourhood of a boron-carbide rod, and the density of neutron captures by a 1/v detector within the rod. The paper also discusses methods used and the results obtained from experiments designed to assess the efficiency of recompensation, cylinders placed on the boundary between core and reflector. (author) [French] Le memoire analyse les resultats de plusieurs experiences effectuees sur l'ensemble critique PF-4, qui est destine a l'etude detaillee des particularites physiques des reacteurs a neutrons intermediaires. Les coeurs et les reflecteurs des differents esembles critiques etaient constitues par un assemblage compact de tubes en acier ou en aluminium dans lesquels etaient inseres des diques de diverses matieres. En combinant selon differentes proportions les disques d'uranium enrichi a 90% et les matieres de ralentissement et en introduisant dans le reflecteur des couches de ralentisseur de diverses epaisseurs, on a pu obtenir de grandes modifications du spectre des neutrons provoquant la fission. Le memoire decrit l'ensemble critique PF-4 et les differents assemblages qui le composent. Les auteurs analysent l'efficacite relative du ralentissement interieur et exterieur pour des reacteurs dans lesquels le rapport noyaux du ralentisseur noyaux d'uranium dans le coeur est tres peu eleve. Il ressort des experiences que, meme lorsqu'on emploie des reflecteurs tres epais, la faible dilution de l'uranium par le ralentisseur (le rap- port entre les noyaux du beryllium et de l'uranium-235 etant: {partial_derivative}Be/{partial_derivative}{sup 235}U{approx_equal}1) entraine un accroissement de la masse critique. Une partie importante du memoire est consacree a une analyse des effets hetero- genes produits

Ternary fission induced by polarized neutrons

Directory of Open Access Journals (Sweden)

Gönnenwein Friedrich

2013-12-01

Full Text Available Ternary fission of (e,e U- and Pu- isotopes induced by cold polarized neutrons discloses some new facets of the process. In the so-called ROT effect shifts in the angular distributions of ternary particles relative to the fission fragments show up. In the so-called TRI effect an asymmetry in the emission of ternary particles relative to a plane formed by the fragment momentum and the spin of the neutron appear. The two effects are shown to be linked to the components of angular momentum perpendicular and parallel to the fission axis at the saddle point of fission. Based on theoretical models the spectroscopic properties of the collective transitional states at the saddle point are inferred from experiment.

Fission dynamics in the proton induced fission of heavy nuclei

Energy Technology Data Exchange (ETDEWEB)

Rubchenya, V.A. E-mail: rubchen@phys.jyu.fi; Trzaska, W.H.; Itkis, I.M.; Itkis, M.G.; Kliman, J.; Kniajeva, G.N.; Kondratiev, N.A.; Kozulin, E.M.; Krupa, L.; Pokrovski, I.V.; Voskressenski, V.M.; Hanappe, F.; Materna, T.; Dorvaux, O.; Stuttge, L.; Chubarian, G.; Khlebnikov, S.V.; Vakhtin, D.N.; Lyapin, V.G

2004-04-05

Multi-parameter correlation study of the reaction {sup 242}Pu(p, f) at E{sub p} 13, 20 and 55 MeV has been carried out. Fission fragment mass and kinetic energy distributions and the double differential neutron spectra have been measured. It was observed that the two-humped shape of mass distributions prevailed up to highest proton energy. Manifestation of the nuclear shell Z 28 near fragment mass A{sub fr} = 70 has been detected. The experimental results were analyzed in the framework of a time-dependent statistical model with inclusion of nuclear friction effects in the fission process. The multi-parameter correlation study of the reaction.

Fission-product retention in HTGR fuels

International Nuclear Information System (INIS)

Homan, F.J.; Kania, M.J.; Tiegs, T.N.

1982-01-01

Retention data for gaseous and metallic fission products are presented for both Triso-coated and Biso-coated HTGR fuel particles. Performance trends are established that relate fission product retention to operating parameters, such as temperature, burnup, and neutron exposure. It is concluded that Biso-coated particles are not adequately retentive of fission gas or metallic cesium, and Triso-coated particles which retain cesium still lose silver. Design implications related to these performance trends are identified and discussed

Investigation of exotic fission modes

International Nuclear Information System (INIS)

Poenaru, D. N.; Gherghescu, R. A.; Greiner, W.; Nagame, Y.; Hamilton, J. H.; Ramayya, A. V.

2002-01-01

Fission approach to the cluster radioactivities and α-decay has been systematically developed during the last two decades. A more complex process, the ternary fission, was observed since 1946 both in neutron-induced and spontaneous fission. We obtained interesting results concerning the binary fission saddle-point reflection asymmetric nuclear shapes, and we can explain how a possible nuclear quasimolecular state is formed during the 10 Be accompanied cold fission of 252 Cf. The equilibrium nuclear shapes in fission theory are usually determined by minimizing the deformation energy for a given surface equation. We developed a method allowing to obtain a very general saddle-point shape as a solution of a differential equation without an a priori introduction of a shape parametrization. In the approach based on a liquid drop model (LDM), saddle-point shapes are always reflection symmetric: the deformation energy increases with the mass-asymmetry parameter η = (A 1 - A 2 )/(A 1 + A 2 ). By adding the shell corrections to the LDM deformation energy, we obtained minima at a finite mass asymmetry for parent nuclei 238 U, 232,228 Th in agreement with experiments. This correction was calculated phenomenologically. A technique based on the fragment identification by using triple γ coincidences in the large arrays of Ge-detectors, like GAMMASPHERE, was employed at Vanderbilt University to discover new characteristics of the fission process, and new decay modes. The possibility of a whole family of new decay modes, the multicluster accompanied fission, was envisaged. Besides the fission into two or three fragments, a heavy or superheavy nucleus spontaneously breaks into four, five or six nuclei of which two are asymmetric or symmetric heavy fragments and the others are light clusters, e.g. α-particles, 10 Be, 14 C, or combinations of them. Examples were presented for the two-, three- and four cluster accompanied cold fission of 252 Cf and 262 Rf, in which the emitted

Basic physics of the fission process. Chapter 2

International Nuclear Information System (INIS)

Michaudon, A.

1981-01-01

A general description of the fission process is given with special emphasis on those aspects which are necessary for the understanding of the measurements and calculations of neutron-induced fission cross-sections. Having considered the various phases of the process, some typical properties of the low-energy fission of actinide nuclei are presented and the more specific features of neutron induced fission are examined. (U.K.)

Utilisation sans risque des eaux usées, des excréta et des eaux ...

International Development Research Centre (IDRC) Digital Library (Canada)

Les responsables de ce projet piloteront l'application et l'adaptation des principes directeurs relatifs à l'utilisation sans risque des eaux usées, des excreta et des eaux grises en agriculture et en aquaculture (Guidelines for the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture), que ...

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1998-01-01

A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity bar ν p . Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and some examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N(E) and bar ν p upon the fissioning nucleus and its excitation energy are treated in detail for the Los Alamos model. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of the ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches. This paper is an extension of a similar paper presented at the International Centre for Theoretical Physics in 1996

Fission fragment yields and total kinetic energy release in neutron-induced fission of235,238U,and239Pu

Science.gov (United States)

Tovesson, F.; Duke, D.; Geppert-Kleinrath, V.; Manning, B.; Mayorov, D.; Mosby, S.; Schmitt, K.

2018-03-01

Different aspects of the nuclear fission process have been studied at Los Alamos Neutron Science Center (LANSCE) using various instruments and experimental techniques. Properties of the fragments emitted in fission have been investigated using Frisch-grid ionization chambers, a Time Projection Chamber (TPC), and the SPIDER instrument which employs the 2v-2E method. These instruments and experimental techniques have been used to determine fission product mass yields, the energy dependent total kinetic energy (TKE) release, and anisotropy in neutron-induced fission of U-235, U-238 and Pu-239.

Fission mass yields of excited medium heavy nuclei

International Nuclear Information System (INIS)

Sandulescu, A.; Depta, K.; Herrmann, R.; Greiner, W.; Scheid, W.

1985-01-01

The mass distributions resulting from the fission of excited medium mass nuclei are discussed on the basis of the fragmentation theory. It is shown that very asymmetric fission events can be expected with rates which are only a few orders of magnitude smaller than the rates for symmetric fission. As an example a calculation of the fission mass distribution of the excited 172 Yb compound nucleus is presented. This mass distribution reveals observable structures over the entire range of the mass asymmetry due to valleys in the potential energy surface for fission fragments with closed proton and neutron shells

Theoretical descriptions of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1991-01-01

Brief descriptions are given of the observables in neutron emission in fission together with early theoretical representations of two of these observables, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity ν-bar p . This is followed by summaries, together with examples, of modern approaches to the calculation of these two quantities. Here, emphasis is placed upon the predictability and accuracy of the new approaches. In particular, the dependencies of N(E) and ν-bar p upon the fissioning nucleus and its excitation energy are discussed. Then, recent work in multiple-chance fission and other recent work involving new measurements are presented and discussed. Following this, some properties of fission fragments are mentioned that must be better known and better understood in order to calculate N(E) and ν-bar p with higher accuracy than is currently possible. In conclusion, some measurements are recommended for the purpose of benchmarking simultaneous calculations of neutron emission and gamma emission in fission. (author). 32 refs, 26 figs

Les enjeux du modèle standard

CERN Document Server

CERN. Geneva

2008-01-01

Toute la matière visible dans l'Univers est décrite par le « Modèle Standard ». Selon cette théorie, la matière est constituée d'atomes, qui contiennent des électrons orbitant autour de noyaux, dont les composants fondamentaux sont les quarks. Quatre forces fondamentales agissent entre ces particules élémentaires : les forces électromagnétique est gravitationnelle, et les interactions nucléaires forte et faible. La description fournie par le Modèle Standard de ces particules et de leurs interactions est en parfait accord avec les expériences. Néanmoins, des questions fondamentales restent sans réponse jusqu'à maintenant : d'où vient la masse des particules ? Pourquoi y a-t-il tant de types de particules ? Existe-t-il une théorie unifiée de toutes les interactions ? Quelle est la nature de la matière cachée prédite par les astrophysiciens ? Le LHC au CERN donnera des éléments de réponse à ces questions au-delà du Modèle Standard.

Characterization of a facility for the measurement of fission fragment transport effects: experimental determination of the fission rates for fissile and fissionable isotopes