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Sample records for oklo natural fission

  1. Isotopic studies relative to the Oklo natural fission reactors

    International Nuclear Information System (INIS)

    It has been clearly demonstrated that natural fission reactors operated about 2 109 years ago, in rich uranium one deposits of the Oklo mine in the Republique of Gabon. Six reactions zones have been identified in which approximately six tons of 235U were consumed and the same amount of fission products deposited in the ground. These fission products, their filiation isotopes and nuclei formed from neutron captures are precious tracers, which now can be analysed on well localized samples, to obtain informations on the stability in soil of such elements and data on the nuclear parameters and characteristics of the nuclear reactors. The studies which have been developed at Saclay concern several aspects of this phenomenon: the migrations of fission products, the age of the nuclear reaction, the date of the uranium deposit and the temperature of the reaction zones during the operation of the reactors

  2. The Oklo natural nuclear reactors: neutron parameters, age and duration of the reactions, uranium and fission products migrations

    International Nuclear Information System (INIS)

    Mass spectrometry and isotopic dilution technique are used in order to carry out, on various samples from the fossil nuclear reactors at Oklo, Gabon, isotopic and chemical analyses of some particular elements involved in the nuclear reactions: uranium, lead, bismuth, thorium, rare gases (krypton, xenon), rare earths (neodymium, samarium, europium, gadolinium, dysprosium), ruthenium and palladium. Interpretations of these analyses lead to the determination of many neutron parameters such as the neutron fluence received by the samples, the spectrum index, the conversion coefficient, and also the percentages of fissions due to uranium-238 and plutonium-239 and the total number of fissions relative to uranium. All these results make it possible to determine the age of the nuclear reactions by measuring the amounts of fission rare earths formed, i.e. 1.97 billion years. This study brings some informations to the general problem of radioactive wastes storage in deep geological formations, the storage of uranium, plutonium and many fission products having been carried out naturally, and for about two billion years

  3. Reappraisal of the limit on the variation in ? implied by the Oklo natural fission reactors

    Science.gov (United States)

    Davis, Edward D.; Hamdan, Leila

    2015-07-01

    Background: A signature of many dynamical models of dark energy is that they admit variation in the fine structure constant ? over cosmological time scales. Purpose: We reconsider the analysis of the sensitivity of neutron resonance energies Ei to changes in ? with a view to resolving uncertainties that plague earlier treatments. Methods: We point out that with more appropriate choices of nuclear parameters, the standard estimate (from Damour and Dyson) of the sensitivity for resonances in Sm is increased by a factor of 2.5. We go on to identify and compute excitation, Coulomb, and deformation corrections. To this end, we use deformed Fermi density distributions fitted to the output of Hartree-Fock (HF) + BCS calculations (with both the SLy4 and SkM* Skyrme functionals), the energetics of the surface diffuseness of nuclei, and thermal properties of their deformation. We also invoke the eigenstate thermalization hypothesis, performing the requisite microcanonical averages with two phenomenological level densities which, via the leptodermous expansion of the level density parameter, include the effect of increased surface diffuseness. Theoretical uncertainties are assessed with the inter-model prescription of Dobaczewski et al. [J. Phys. G: Nucl. Part. Phys. 41, 074001 (2014), 10.1088/0954-3899/41/7/074001]. Results: The corrections diminish the revised Sm sensitivity but not by more than 25%. Subject to a weak and testable restriction on the change in mq/? (relative to the change in ? ) since the time when the Oklo reactors were active (mq is the average of the u and d current quark masses, and ? is the mass scale of quantum chromodynamics), we deduce that | ?Oklo-?now|<1.1 × 10-8?now (95% confidence level). The corresponding bound on the present-day time variation of ? is tighter than the best limit to date from atomic clock experiments. Conclusions: The order of magnitude of our Oklo bound on changes in ? is reliable. It is one order of magnitude lower than the Oklo-based bound most commonly adopted in earlier attempts to identify phenomenologically successful models of ? variation.

  4. Oklo natural fission reactor program. Progress report, April 1-August 31, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, D.B. (comp.)

    1980-12-01

    An interim report has been published on the redistribution of uranium, thorium, and lead in samples representing several million cubic meters of sandstone and metamorphosed sediments in the Athabasca Basin which is located in the northwest corner of the Canadian province of Saskatchewan. The region of study includes zones of uranium mineralization at Key Lake. Mineralization occurs at the unconformity between the Athabasca sandstone and the underlying metasediments and in fault zones within the metasediments. Lead isotopes record a radiometric age of 1300 +- 150 m.y. in samples from above and below the unconformity. This age probably reflects the time of deposition of the sandstones and an associated redistribution of uranium and/or lead in the underlying rocks. Many of the samples have been fractionated with respect to radiogenic lead and the actinide parent elements since that time. Sandstones and altered rocks from the region above the unconformity have been a transport path and are a repository for lead. In contrast, mineralized rocks are deficient in radiogenic lead and must be an important source of lead in the local geologic environment. Samples from Oklo reactor zone 9 and nearby host rocks have been prepared for isotopic analyses of ruthenium, molybdenum, uranium and lead.

  5. Oklo reactors: natural analogs to nuclear waste repositories

    International Nuclear Information System (INIS)

    The 2-billion-year-old fossil reactors at Oklo are ancient natural nuclear waste sites. Isotope dilution mass spectrometric analyses of the fission products in the reactor core uraninite and the peripheral pelitic sandstone provide data for calculating the reactor operating parameters, the quantities of fissiogenic isotopes produced, the fraction of these isotopes retained in the cores, and the location in the peripheral rocks of the fissiogenic fraction lost from the cores. For a duration of criticality of 3 x 105 yrs, the thermal plus resonance neutron fluence ranged between 1020 and 1021 neutrons/cm2. The fraction of technetium (60 to 85%), ruthenium (75 to 90%), and neodymium (85 to 100%) retained is negatively correlated with fluence. The lost fission products are contained within a few tens of meters of their source, the reactor cores. The systematics of the decay of 99Tc (t/sub 1/2/ = 2.13 x 105 yr) to 99Ru limits the period of fissiogenic element migration to approximately 1 million yr at a time 2 billion yr ago. Thermodynamic calculations of the temperature-dependent solubilities indicate that the loss of fissiogenic elements is diffusion controlled, whereas retention in the surrounding rocks is a result of temperature-dependent deposition from an aqueous solution. These results concerning the geochemistry of technetium, ruthenium, and neodymium at a natural waste site support the concept of geologic burial of man-made radioactive wastes

  6. Lutetium thermometry for Oklo natural reactors: a new look at old data

    CERN Document Server

    Gould, C R; 10.1103/PhysRevC.85.024610

    2012-01-01

    Lutetium thermometry has been used to analyze Oklo natural nuclear reactor zones but leads to widely varying and puzzling predictions for the temperatures $T_O$ which in turn impacts bounds on time variation of the fine structure constant $\\alpha$. We revisit results for reactor zone RZ10 in light of new measurements of the isomer branching ratio $B^g$ in $^{175}$Lu neutron capture at 5 and 25 keV. We recalculate predictions for $T_O$ as a function of $B^g$ using realistic models of the Oklo neutron flux. We find $T_O = 100 \\pm 30$ C using a new value of $B^g$, in contrast to $350 < T_O < 500 $ C using the evaluated value at thermal energy. Lutetium thermometry can be applicable to analyses of Oklo reactor data, but a better measurement of $B^g$ with thermal neutrons is needed to confirm the reliability of temperature predictions.

  7. The Oklo phenomenon as an analogue of radioactive waste disposal. A review

    International Nuclear Information System (INIS)

    This work demonstrates the utility of the Oklo uranium ore deposit and natural fission reactors as a long time scale analogue for man-made radioactive waste repositories. Oklo has opened a new horizon representing an unrivalled opportunity to apply isotopic geochemistry to the study of migrations of fission products after an extremely long cooling and storage time and to define the processes involved in the transport of these elements through geological materials. This is the topic of the first section of this report. In the second section the information available on retention or migration at Oklo of the most interesting fission products is presented trying to illustrate how relevant the Oklo experience is in formulating predictions on the destiny of high activity waste disposed of in stable geological formations

  8. Oklo. A review and critical evaluation of literature

    Energy Technology Data Exchange (ETDEWEB)

    Zetterstroem, Lena [Swedish Museum of Natural History, Stockholm (Sweden). Lab. for Isotope Geology

    2000-10-01

    The Oklo natural fossil fission reactors in Gabon, Equatorial Africa, have been studied as a natural analogue for spent nuclear fuel in a geological environment. For these studies, it is important to know what has happened to these reactors since they formed. This review is focussed on existing geological and geochronological information concerning the Oklo reactors and the surrounding ore. A sequence of geological and geochemical events in the Oklo area, as described in the literature, is given. The data and the studies behind this established geochronology are discussed and evaluated. Of the regional geology, special attention is given to the dating of the Francevillian sediments, and the intrusion of a dolerite dyke swarm. The processes that led to the mineralisation at Oklo, the subsequent formation of the nuclear reactors and later migration of fission products are described. Further discussion concerns the studies of the dolerite dyke swarm, since this appears to be one of the most important events related to fission product migration. A close look at the data related to this event shows that further study of the age of the dolerite dykes, and their effect on the uraninite in the Oklo reactors, is needed.

  9. Oklo. A review and critical evaluation of literature

    International Nuclear Information System (INIS)

    The Oklo natural fossil fission reactors in Gabon, Equatorial Africa, have been studied as a natural analogue for spent nuclear fuel in a geological environment. For these studies, it is important to know what has happened to these reactors since they formed. This review is focussed on existing geological and geochronological information concerning the Oklo reactors and the surrounding ore. A sequence of geological and geochemical events in the Oklo area, as described in the literature, is given. The data and the studies behind this established geochronology are discussed and evaluated. Of the regional geology, special attention is given to the dating of the Francevillian sediments, and the intrusion of a dolerite dyke swarm. The processes that led to the mineralisation at Oklo, the subsequent formation of the nuclear reactors and later migration of fission products are described. Further discussion concerns the studies of the dolerite dyke swarm, since this appears to be one of the most important events related to fission product migration. A close look at the data related to this event shows that further study of the age of the dolerite dykes, and their effect on the uraninite in the Oklo reactors, is needed

  10. The geochemical behavior of radioactive nuclides at the Oklo natural reactor

    International Nuclear Information System (INIS)

    The Oklo uranium mine in the Republic of Gabon, West Africa, has been known as fossil fission reactor. Such a unique phenomenon brings us to not only geochemical information but also practical knowledge about radioactive waste disposal. In this study, isotopic compositions and abundances of various elements (Rb, Sr, Zr, Mo, Ru, Pd and rare earth elements) deeply associated with nuclear reactions were precisely measured with mass spectrometer. On the basis of these data, the authors could investigate the geochemical behavior of fission product nuclides. Zr, Ru, Pd and rare earth elements (except La and Ce) were difficult to move and have been relatively preserved in the reactor. On the other hand, Rb, Sr have almost perfectly disappeared out of the reactor. It is particularly interesting that La and Ce had behaved differently from other rare earth elements and partly removed in spite of chemical similarity among rare earth elements

  11. The Oklo reactors

    International Nuclear Information System (INIS)

    The Oklo reactors comprise up to nine 235-U depleted zones in an uranium ore in the Republic of Gabon in West Africa. The depletion in fissile U-235 has been proved to have caused by nuclear chain reactions. The study of the Oklo phenomenon indicates that very efficient retardation mechanisms may operate in nature - at least under special conditions. A closer study of these processes ought to be made to establish the limitations to their occurrence. The Oklo sandstone formation today would probably be considered unacceptable as a host rock for a repository. (EG)

  12. Oklo working group meeting

    International Nuclear Information System (INIS)

    Natural analogue studies have been carried out for several years in the framework of the European Community's R and D programme on radioactive waste; and within its recent fourth five-year programme on 'Management and storage of radioactive waste (1990-94)' the Community is participating in the Oklo study, natural analogue for transfer processes in a geological repository. The Oklo project is coordinated by CEA-IPSN (F) and involves laboratories from several CEA directorates (IPSN, DTA and DCC) which collaborate with other institutions from France: CREGU, Nancy; CNRS, Strasbourg and ENSMD, Fontainebleau. Moreover, institutes from non-EC member States are also taking part in the Oklo study. The second joint CEC-CEA progress meeting of the Oklo Working Group was held in April 1992 in Brussels and gave the possibility of reviewing and discussing progress made since its first meeting in February 1991 at CEA in Fontenay-aux-Roses. About 40 participants from 15 laboratories and organizations coming from France, Canada, Gabon, Japan, Sweden and the USA underline the great interest in the ongoing research activities. The meeting focused on the different tasks within the CEC-CEA Oklo project concerning (i) field survey and sampling, (ii) characterization of the source term, (iii) studies of the petrographical and geochemical system, and (iv) studies of the hydrogeological system and hydrodynamic modelling. (author) 17 papers are presented

  13. Oklo 2 Billion Years Before Fermi

    International Nuclear Information System (INIS)

    The author aims to present the little-known story of the Oklo natural reactors. He recalls the historical aspects of the Oklo reactors discovery by the CEA in 1972, he explains the scientific phenomenon and the interest, notably as a ''natural analogue'' for the geological disposal of high level radioactive wastes. (A.L.B.)

  14. Radioactive wastes in Oklo

    International Nuclear Information System (INIS)

    The acceptance of the Nuclear Energy as electric power supply implies to give answer to the population on the two main challenges to conquer in the public opinion: the nuclear accidents and the radioactive wastes. Several of the questions that are made on the radioactive wastes, its are the mobility migration of them, the geologic stability of the place where its are deposited and the possible migration toward the aquifer mantels. Since the half lives of the radioactive waste of a Nuclear Reactor are of several hundred of thousands of years, the technical explanations to the previous questions little convince to the public in general. In this work summary the results of the radioactive waste generated in a natural reactor, denominated Oklo effect that took place in Gabon, Africa, it makes several thousands of millions of years, a lot before the man appeared in the Earth. The identification of at least 17 reactors in Oklo it was carried out thanks to the difference in the concentrations of Uranium 235 and 238 prospective, and to the analysis of the non-mobility of the radioactive waste in the site. It was able by this way to determine that the reactors with sizes of hardly some decimeter and powers of around 100 kilowatts were operating in intermittent and spontaneous form for space of 150,000 years, with operation cycles of around 30 minutes. Recent studies have contributed information valuable on the natural confinement of the radioactive waste of the Oklo reactors in matrixes of minerals of aluminum phosphate that caught and immobilized them for thousands of millions of years. This extracted information from the nature contributes guides and it allows 'to verify' the validity of the current proposals on the immobilization of radioactive wastes of a nuclear reactor. This work presents in clear and accessible form to the public in general on the secure 'design', operation, 'decommissioning' and 'storage' of the radioactive waste of the reactors that the nature put into operation in Oklo before the man appeared in the Earth. (Author)

  15. Investigations of the natural fission reactor program. Progress report, October 1977--September 1978

    International Nuclear Information System (INIS)

    The U.S. study of the Oklo natural reactor began in 1973 with the principal objectives of understanding the processes that produced the reactor and that led to the retention of many of its products. Major facets of the program have been the chemical separation and mass spectrometric analysis of the reactor components and products, the petrological and mineralogical examination of samples taken from the reactor zones, and an interdisciplinary modeling of possible processes consistent with reactor physics, geophysics, and geochemistry. Most of the past work has been on samples taken within the reactor zones. Presently, these studies give greater emphasis to the measurement of mobile products in additional suites of samples collected peripherally and ''downstream'' from the reactor zones. This report summarizes the current status of research and the views of U.S. investigators, with particular reference to the extensive work of the French scientists, concerning the main features of the Oklo natural fission reactor. Also mentioned briefly is the U.S. search for natural fission reactors at other locations

  16. Gas, benefits and question marks. The Oklo reactors: 100 % natural. The Kyoto protocol: use it or lose it?. Small hydro power: a great leap forward. The energy mix of South Korea

    Energy Technology Data Exchange (ETDEWEB)

    Anon

    2005-07-01

    This issue of Alternatives newsletter contains a main press-kit about natural gas economics worldwide and 4 articles dealing with the Oklo natural reactor, the Kyoto protocol, the small hydro-power in China, and the energy mix of South Korea: 1 - 'Gas benefits and question marks': The world's most widely distributed fossil fuel, natural gas is also the fastest-growing energy source of the past thirty years. Its position as the fuel of choice in the global energy mix is due in large part to its many domestic and industrial applications. 2 - 'The Oklo reactors: 100% natural': Another look at this extraordinary 2 billion year-old phenomenon in words and pictures: the nuclear fission reaction that created the natural reactors of Gabon. 3 - 'The Kyoto Protocol: use it or lose it?': Nearly eight years after its signature, the Kyoto Protocol is still hotly debated. Two experts give us their views: Spencer Abraham, former U.S. Secretary for Energy, and Jean-Charles Hourcade of CIRED, the international center for research on the environment and development. 4 - 'Small hydro power: a great leap forward': The Chinese government has responded to the need for rural electrification with an aid program for the country's poorest cantons. Enter the small hydro plant in northern Guangxi province. 5 - 'The energy mix of South Korea': Faced with continuing strong economic growth and energy demand, South Korea has multiplied its projects, from hydropower to tidal power to nuclear and even hydrogen in the longer term.

  17. The Oklo phenomenon

    International Nuclear Information System (INIS)

    Until recently, scientists believed that the chemical elements were synthesized only in stars. The discovery of the Oklo phenomenon in the Republic of Gabon in 1972 has revealed, however, that a nuclear ''fire'' had existed on the earth and large-scale transmutations of the elements were occurring on our planet 1.7x109 years ago. The formation of natural (or Pre-Fermi) reactors is closely related to the appearance of life on our planet earth. The Pre-Fermi reactors were probably never formed until about 2x109 years ago, when oxygen was injected into the earth's atmosphere by a new generation of living organisms carrying out photosynthesis. (orig.)

  18. OKLO: fossil reactors

    International Nuclear Information System (INIS)

    Events leading up to the discovery during the summer of 1972 of the Oklo fossil reactor in Gabon and its subsequent exploration are reviewed. Results of studies are summarized; future investigations are outlined

  19. Far field hydrogeochemistry in the Oklo reactor area (Gabon)

    International Nuclear Information System (INIS)

    In the frame of a general study of the Oklo natural reactor, which takes into account the natural analogue aspect, a complete hydrogeological and hydrogeochemical study is undertaken. The partners of this study are the following: - Section de geochimie, CEA (France): P. Toulhoat, J.P. Gallien, P. L'Henoret, V. Moulin (groundwater chemistry and colloids). - Ecole des Mines de Paris (CIG, Fontainebleau) E. Ledoux, I. Gurban (hydrogeology and modelling) - SKB and Conterra AB (Sweden) J.A.T. Smellie, A. Winberg (hydrogeology, isotope geochemistry). The aim of this study is to try to understand and to characterize the possible mobilization of elements or isotopes when groundwaters come in contact with nuclear reaction zones. The first step of the study is presented here, which comprises a general geochemical and hydrodynamical characterization of the site. In this presentation, the site of Bagombe is also mentioned as it has been confirmed as sector in which nuclear fission reactions occurred as in Oklo. (author). 10 refs., 6 figs., 6 tabs

  20. Oklo reactors and implications for nuclear science

    CERN Document Server

    Davis, E D; Sharapov, E I

    2014-01-01

    We summarize the nuclear physics interests in the Oklo natural nuclear reactors, focusing particularly on developments over the past two decades. Modeling of the reactors has become increasingly sophisticated, employing Monte Carlo simulations with realistic geometries and materials that can generate both the thermal and epithermal fractions. The water content and the temperatures of the reactors have been uncertain parameters. We discuss recent work pointing to lower temperatures than earlier assumed. Nuclear cross sections are input to all Oklo modeling and we discuss a parameter, the $^{175}$Lu ground state cross section for thermal neutron capture leading to the isomer $^{176\\mathrm{m}}$ Lu, that warrants further investigation. Studies of the time dependence of dimensionless fundamental constants have been a driver for much of the recent work on Oklo. We critically review neutron resonance energy shifts and their dependence on the fine structure constant $\\alpha$ and the ratio $X_q=m_q/\\Lambda$ (where $m_...

  1. Radioactive wastes in Oklo; Desechos radiactivos en Oklo

    Energy Technology Data Exchange (ETDEWEB)

    Balcazar, M.; Flores R, J.H.; Pena, P.; Lopez, A. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2006-07-01

    The acceptance of the Nuclear Energy as electric power supply implies to give answer to the population on the two main challenges to conquer in the public opinion: the nuclear accidents and the radioactive wastes. Several of the questions that are made on the radioactive wastes, its are the mobility migration of them, the geologic stability of the place where its are deposited and the possible migration toward the aquifer mantels. Since the half lives of the radioactive waste of a Nuclear Reactor are of several hundred of thousands of years, the technical explanations to the previous questions little convince to the public in general. In this work summary the results of the radioactive waste generated in a natural reactor, denominated Oklo effect that took place in Gabon, Africa, it makes several thousands of millions of years, a lot before the man appeared in the Earth. The identification of at least 17 reactors in Oklo it was carried out thanks to the difference in the concentrations of Uranium 235 and 238 prospective, and to the analysis of the non-mobility of the radioactive waste in the site. It was able by this way to determine that the reactors with sizes of hardly some decimeter and powers of around 100 kilowatts were operating in intermittent and spontaneous form for space of 150,000 years, with operation cycles of around 30 minutes. Recent studies have contributed information valuable on the natural confinement of the radioactive waste of the Oklo reactors in matrixes of minerals of aluminum phosphate that caught and immobilized them for thousands of millions of years. This extracted information from the nature contributes guides and it allows 'to verify' the validity of the current proposals on the immobilization of radioactive wastes of a nuclear reactor. This work presents in clear and accessible form to the public in general on the secure 'design', operation, 'decommissioning' and 'storage' of the radioactive waste of the reactors that the nature put into operation in Oklo before the man appeared in the Earth. (Author)

  2. Oklo 2 Billion Years Before Fermi; Les reacteurs naturels d'Oklo (Gabon): 2 milliards d'annees avant Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Barre, B

    2005-02-15

    The author aims to present the little-known story of the Oklo natural reactors. He recalls the historical aspects of the Oklo reactors discovery by the CEA in 1972, he explains the scientific phenomenon and the interest, notably as a 'natural analogue' for the geological disposal of high level radioactive wastes. (A.L.B.)

  3. Natural fission reactors in the Franceville basin, Gabon: A review of the conditions and results of a "critical event" in a geologic system

    Science.gov (United States)

    Gauthier-Lafaye, F.; Holliger, P.; Blanc, P.-L.

    1996-12-01

    Natural nuclear fission reactors are only known in two uranium deposits in the world, the Oklo and Bangombé deposits of the Franceville basin: Gabon. Since 1982, five new reactor zones have been discovered in these deposits and studied since 1989 in a cooperative European program. New geological, mineralogical, and geochemical studies have been carried out in order to understand the behavior of the actinides and fission products which have been stored in a geological environment for more than 2.0 Ga years. The Franceville basin and the uranium deposits remained geologically stable over a long period of time. Therefore, the sites of Oklo and Bangombé are well preserved. For the reactors, two main periods of actinide and radionuclides migration have been observed: during the criticality, under P-T conditions of 300 bars and 400-500°C, respectively, and during a distention event which affected the Franceville basin 800 to 900 Ma ago and which was responsible for the intrusion of dolerite dikes close to the reactors. New isotopic analyses on uranium dioxides, clays, and phosphates allow us to determine their respective importance for the retention of fission products. The UO 2 matrix appears to be efficient at retaining most actinides and fission products such as REEs, Y, and Zr but not the volatile fission products (Cd, Cs, Xe, and Kr) nor Rb, Sr, and Ba. Some fissiogenic elements such as Mo, Tc, Ru, Rh, Pd, and Te could have formed metallic and oxide inclusion in the UO 2 matrix which are similar to those observed in artificial spent fuel. Clays and phosphate minerals also appear to have played a role in the retention of fissiogenic REEs and also of Pu.

  4. Bound on the variation in the fine structure constant implied by Oklo data

    CERN Document Server

    Hamdan, Leila

    2015-01-01

    Dynamical models of dark energy can imply that the fine structure constant $\\alpha$ varies over cosmological time scales. Data on shifts in resonance energies $E_r$ from the Oklo natural fission reactor have been used to place restrictive bounds on the change in $\\alpha$ over the last 1.8 billion years. We review the uncertainties in these analyses, focussing on corrections to the standard estimate of $k_\\alpha\\!=\\!\\alpha\\,dE_r/d\\alpha$ due to Damour and Dyson. Guided, in part, by the best practice for assessing systematic errors in theoretical estimates spelt out by Dobaczewski et al. [in J. Phys. G: Nucl. Part. Phys. 41, 074001 (2014)], we compute these corrections in a variety of models tuned to reproduce existing nuclear data. Although the net correction is uncertain to within a factor of 2 or 3, it constitutes at most no more than 25% of the Damour-Dyson estimate of $k_\\alpha$. Making similar allowances for the uncertainties in the modeling of the operation of the Oklo reactors, we conclude that the rela...

  5. Characterization of near- to far-field ancient migrations around Oklo reaction zones (Gabon) using minerals as geochemical tracers

    International Nuclear Information System (INIS)

    We developed a method allowing the identification of ancient fluid circulations through trace-element patterns in hydrothermal minerals. Application of this technique to Oklo nuclear reactors as natural analogues involves apatite and lanthanides for early circulations, and sulfides and chalcophile elements for late events. At least four different fluid generations have been found, and are tentatively assigned to episodes of Oklo site history. (1) Zr- and U-rich fluids predate criticality near reaction zone 10. (2) Isotopic anomalies of lanthanides provide evidence for mobility of fission products during criticality. Up to now, anomalies are restricted to the near field (desilicified zone around reaction zones). (3) A first pyrite stage is focused around reaction zones, up to a few tens of meters. (4) The latest event is most probably of regional extent. Besides direct evidence of fission-product migration, the present study is expected to provide the geological background and geochemical constraints for modelling ancient fluid circulation and consequent element migration near reaction zones. (orig.)

  6. Petrographic study of organic matter from Oklo

    International Nuclear Information System (INIS)

    Coal petrography techniques were applied to Oklo samples and various types of organic material were determined around the reactor and throughout the region as a whole: e.g. interstratified autochthonous organic material of the coal type, with maximum reflectance in the oil, reaching 6.90%; secondary-filler organic material of the bitume type, with reflectance varying around 2%, which is the type of organic material that is associated with the reactor; and natural coke organic material with fine-grain anisotropy between crossed nicols. An attempt has been made, with a 600-m series intersected by a borehole, to estimate the intensity of the thermal palaeoflux. The research is still only at the initial stage and should be continued. (author)

  7. Attempt at contributing, on the basis of geochemistry, to an assessment of the extent and frequency of phenomena of the Oklo type

    International Nuclear Information System (INIS)

    The group of natural nuclear reactors discovered at Oklo is the only one known at present. This leads one to wonder whether the phenomenon is a highly exceptional one or whether such nuclear reactions were frequent in the past. Judging by the conditions necessary for them to become established, such reactions could have taken place only in fairly remote times (probably over 1000 million years ago), when the concentration of 235U in natural uranium was a few per cent. If, prior to those times, an appreciable fraction of the natural uranium underwent fission chain reactions and the products were redistributed in the earth's crust, the present isotopic composition of the elements which are abundant in fission might be different from the original composition. It would be characterized by a higher concentration of isotopes resulting from fission. Selenium, ruthenium, palladium and tellurium, which are rare in the earth's crust and abundant in fission, would be the elements most likely to experience changes in isotopic composition as a result of such phenomena. Efforts to estimate the order of magnitude of the concentrations of fission-product elements likely to cause detectable isotopic abundance variations has led to a study, in the first place, of ruthenium as a means of finding an upper limit for the extent of the fissions which occurred. For this purpose, chemical and isotopic determinations of ruthenium in very old ores have been performed

  8. Densities of fission tracks in natural detectors

    International Nuclear Information System (INIS)

    Considering a solid track recorder placed inside a standard uranium mineral, the ratio r = rhosub(I).rhosup(S)-1 between the induced tracks densities produced by the internal flux and those produced by the spontaneous fission of the 238U contained in the detector have been studied as a function of certain parameters. (author)

  9. Time-variability of alpha from realistic models of Oklo reactors

    CERN Document Server

    Gould, C R; Lamoreaux, S K

    2006-01-01

    We reanalyze Oklo $^{149}$Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of $\\alpha$, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the $^{149}$Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient $^{149}$Sm effective cross sections, and use these values to set limits on the time-variation of $\\alpha$. Our study resolves a contradictory situation with previous Oklo $\\alpha$-results. Our suggested $2 \\sigma$ bound on a possible time variation of $\\alpha$ over two billion years is stringent: $ -...

  10. Monte-Carlo based numerical modeling and simulation of criticality conditions occurrence in natural Reactor Zone 9 in Oklo deposit (Gabon)

    International Nuclear Information System (INIS)

    The occurrence of the criticality with analogue modelled configurations of the fossil reactor zone n deg 9 (RZ9) from Oklo uranium deposit in Gabon is studied. The RZ9 and the other reaction zones 7 and 8, of the same deposit sector are characterized by a low thickness compared to other zones 1 to 6 and an important presence of organic matter with a lower U content. This makes the simulations performed in the past unable to explain the occurrence of that phenomenon in such zones. In the present work an extrapolation to 2 billion years ago as an initial state of the reactor is done using the MCNP Monte-Carlo based code. To make it more close to the geological reality experimental conditions and geometry, possible porosity, moderators and minimal Uranium content are considered. The minimal critical configuration is obtained by variation of a set of geometrical and physical parameters around the estimated composition of the reactor area. A set of simulations computing the corresponding effective multiplication factor keff, and reactivity are presented. The effect of organic matter as well as the influence on the criticality is discussed. (author)

  11. The Oklo reactors: five years of exploration of the site

    International Nuclear Information System (INIS)

    The main phases of the exploration of the Oklo site since the discovery of the ''reactor'' phenomenon are outlined briefly. Over 180 sampling holes were drilled during the interruption of the mining activities in the sector concerned. Several new zones have been found. Mining was resumed in the second half of 1975, providing an opportunity for highly fruitful geological follow-up work: more precise knowledge was gained of the morphology of the reactors, and very many additional samples were taken. Plant treatment of the ore and the systematic analysis of batches have made it possible to establish a balance of missing uranium-235. A small portion containing sites of intense reaction has been preserved by being anchored to the quarry wall. Mining in this sector has now finished, but new indications of fission have been found, especially in the Okelobondo sector. (author)

  12. Hydrogeology of the Oklo-Okelobondo site

    International Nuclear Information System (INIS)

    This study gives an account of all the hydrogeological data from the Oklo-Okelobondo site obtained so far. This hydrogeological overview has led to the proposal of a hydrodynamic flow pattern for the system and the choice of a study area as a basis for a preliminary modelling of groundwater flow and solute transport in the far field. (author). 5 refs., 4 figs

  13. Technical Application of Nuclear Fission

    Science.gov (United States)

    Denschlag, J. O.

    The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor ?, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.

  14. Uranium deposits of Gabon and Oklo reactors. Metallogenic model for rich deposits of the lower proterozoic

    International Nuclear Information System (INIS)

    The geology of the Franceville basin (Gabon) is examined: stratigraphy, tectonics and geodynamics. The mobile zone of the Ogooue is specially studied: lithology, metamorphism and tectonics, isotopic geochronologic data are given. The different uranium deposits are described. A whole chapter is devoted to the study of Oklo natural nuclear reactor. A metallogenic model is proposed evidencing conditions required for deposit genesis. Tectonics, microstructures sedimentology, organic matter, diagenesis and uraniferous mineralizations are examined

  15. Investigation of the fundamental constants stability based on the reactor Oklo burn-up analysis

    CERN Document Server

    Onegin, M S

    2014-01-01

    New severe constraints on the variation of the fine structure constant have been obtained from reactor Oklo analysis in our previous work. We investigate here how these constraints confine the parameter of BSBM model of varying $\\alpha$. Integrating the coupled system of equations from the Big Bang up to the present time and taking into account the Oklo limits we have obtained the following margin on the combination of the parameters of BSBM model: $$ |\\zeta_m (\\frac{l}{l_{pl}})^2|<6\\cdot 10^{-7}, $$ where $l_{pl}=(\\frac{G\\hbar}{c^3})^{\\frac{1}{2}} \\approx 1.6 \\cdot 10^{-33}$ cm is a Plank length and $l$ is the characteristic length of the BSBM model. The natural value of the parameter $\\zeta_m$ - the fraction of electromagnetic energy in matter - is about $10^{-4}$. As a result it is followed from our analysis that the characteristic length $l$ of BSBM theory should be considerably smaller than the Plank length to fulfill the Oklo constraints on $\\alpha$ variation.

  16. Magnetic Field Generation in Planets and Satellites by Natural Nuclear Fission Reactors

    CERN Document Server

    Herndon, J Marvin

    2007-01-01

    One of the most fundamental problems in physics has been to understand the nature of the mechanism that generates the geomagnetic field and the magnetic fields of other planets and satellites. For decades, the dynamo mechanism, thought to be responsible for generating the geomagnetic field and other planetary magnetic fields, has been ascribed to convection in each planet's iron-alloy core. Recently, I described the problems inherent in Earth-core convection and proposed instead that the geomagnetic field is produced by convection in the electrically conductive, fluid, fission-product sub-shell of a natural nuclear fission reactor at the center of the Earth, called the georeactor. Here I set forth in detail the commonality in the Solar System of the matter like that of the inside of the Earth, which is my basis for generalizing the concept of planetary magnetic field generation by natural planetocentric nuclear fission reactors.

  17. Analysis of possibility of reactors occurring in nature

    International Nuclear Information System (INIS)

    A historical account is presented of the sequence of events which led to the 1956 prediction by the author that nuclear reactors should have existed in nature approximately 2 billion years ago. Following a brief review of the natural reactor theory, some of the results from recent studies of the Oklo Phenomenon are discussed. The report consists of the following chapters: I. Introduction, II. Natural Reactor Theory, III. The Oklo Phenomenon-Models of Natural Reactors, IV. Possibility of the Graphite-type Natural Reactor, V. The Sudbury Phenomenon, and VI. Conclusion. The Chap. IV deals with the studies on the occurrence of fissiogenic xenon isotopes in the carbon-rich mineral thucholite from the Besner Mine, Parry Sound, Ontario, Canada. The thucholite contained fissiogenic xenon isotopes from 238U spontaneous fission, but not from 235U neutron-induced fission. The Chap. V deals with the studies of the abundance pattern of Ne, Ar, Kr and Xe in several granite samples, including the Red Rock granite from the Sudbury structure, Ontario, Canada, which, according to Dietz (1964), was formed by the impact of an asteroid about 1.7 billion years ago. No unusual concentration of fissiogenic xenon isotopes was detected in the Red Rock granite, but the observed rare gas abundance pattern resembled that in meteorites, rather than the terrestrial rare gas abundances. (auth.)

  18. Delayed neutron measurements with a natural uranium fission product source in Fast Breeder Test Reactor

    International Nuclear Information System (INIS)

    Highlights: • Delayed neutron measurements performed with a Fission Product Source (FPS) FBTR. • FPS provided by natural U–Ni pins with perforated clad. • Measurements have helped in quantification of sensitivity of DND system in FBTR. - Abstract: An assessment of the sensitivity and localization capabilities of clad failure detection by Delayed Neutron Detection (DND) system in Fast Breeder Test Reactor at Kalpakkam has been done, by a series of delayed neutron measurements. Experimental simulation of failed fuel pin is done by considering a natural uranium fission product source in the form of special subassembly containing natural uranium pins, each having a large exposed area in the form of small holes. The measurements and analysis of delayed neutron signals with special subassembly in several selected locations are presented

  19. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  20. Migration of U-series radionuclides around the Bangombe natural fission reactor (Gabon)

    International Nuclear Information System (INIS)

    The Bangombe natural fission reactors has undergone extensive weathering phenomena and continues to be affected by the penetration of meteoric waters. Hence this system provides a model for studying the stability of spent fuel uraninite and the influence of various rock matrices on the mobilization/retardation of various actinides and fission products. The Bangombe uranium deposit has been investigated by drilling on a grid. Radiochemical analysis by alpha- and gamma-spectroscopy of the obtained rocks show significant disequilibria of the 234U/238U, 230Th/234U, and 226Ra/230Th parent-daughter pairs. In this paper, a conceptual model for spatio/temporal evolution of the Bangombe system is proposed. (J.P.N.)

  1. Analysis of waters from the Oklo reactor area: preliminary results on the content of organic substances and colloids

    International Nuclear Information System (INIS)

    The migration of radionuclides, in a nuclear waste disposal in geological formation, depends in part on the physico-chemical forms of the radioelements present in the natural aquifer. In particular, the presence of colloids (entities defined as dispersed particles with size of 1 nm-1 ?m) may alter the speciation of radioelements and hence, change their behaviour. Their mobility may be enhanced or decreased by sorption or complexation reactions. These colloids may be inorganic particles (silicates, silico-aluminates, metallic hydroxides, etc) or organic particles (such as humic substances constituted by humic and fulvic acids). Moreover, these colloids may exist in different natural systems (e.g. surface, marine and groundwaters) often associated with humic substances. The evaluation of the importance of colloids in the dissemination of radioactivity necessitates, in particular, the determination of their concentration in the waters sampled on the site, and their characterization (composition, size). In the framework of a general study of the Oklo natural reactor, a complete hydrogeochemical and hydrogeological study is undertaken. Preliminary studies on the colloid content of different water samples from the Oklo reactor area have been performed to complete the study of the groundwater chemistry presented by Toulhoat et al. (1991, 1992). These complementary studies have, as objectives, to evaluate: - the occurrence of colloids by scanning electron microscopy (after ultrafiltration) and by photon correlation spectroscopy, -the occurrence of organic materials by the analysis of the total organic carbon content. (author). 4 refs., 8 figs

  2. Neutronic study of an innovative natural uranium–thorium based fusion–fission hybrid energy system

    International Nuclear Information System (INIS)

    Highlights: • An innovative fusion-fission hybrid reactor blanket design is presented. • The blanket adopts seed–blanket concept to improve overall neutron economy. • The blanket is designed with two types of modules, i.e. uranium and thorium module. • The reactor could reach multi operating system purpose. - Abstract: An innovative design for a water cooled fusion–fission hybrid reactor (FFHR), aiming at efficiently utilizing natural uranium and thorium resources, is presented. The major objective is to study the feasibility of this concept balanced with multi-purposes, including energy gain, tritium breeding and 233U breeding. In order to improve overall neutron economy of the system, the fission blanket is designed with two types of modules, i.e. the natural uranium modules (U-modules) and thorium modules (Th-modules), which are alternately arranged in the toroidal and poloidal directions of the blanket. This innovative design is based on a simple intuition of neutron distribution: with the alternate geometrical arrangement, energy multiplication by uranium fission, tritium breeding and 233U breeding are performed separately in different sub-zones in the blanket. The uranium modules which has excellent neutron economy under the combined neutron spectrum, plays the dominant role in the energy production, neutron multiplication and tritium breeding. Excess neutrons produced by the uranium modules are then used to drive the thorium modules (which have poor neutron economy) to breed 233U fuel. Therefore, it creates a new free dimension to realize the blanket’s balanced design. The COUPLE code developed by INET of Tsinghua University is used to simulate the neutronic behavior in the blanket. The simulated results show that with the volumetric ratio of thorium modules about 0.4, the balanced design for multi purposes is achievable, with energy multiplication M ? 9, tritium breeding ratio TBR ? 1.05, and at the end of the five years refueling cycle, the 233U enrichment in thorium modules exceeding 1.0%. The neutronic analysis results also show that the preliminary design of this innovative FFHR is of great potential to utilize the bred 233U effectively after the initial fuel load of the first ten-year operation

  3. A fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with natural uranium

    Science.gov (United States)

    Reed, Mark; Parker, Ronald R.; Forget, Benoit

    2012-06-01

    This work develops a conceptual design for a fusion-fission hybrid reactor operating in steady-state L-mode tokamak configuration with a subcritical natural or depleted uranium pebble bed blanket. A liquid lithium-lead alloy breeds enough tritium to replenish that consumed by the D-T fusion reaction. The fission blanket augments the fusion power such that the fusion core itself need not have a high power gain, thus allowing for fully non-inductive (steady-state) low confinement mode (L-mode) operation at relatively small physical dimensions. A neutron transport Monte Carlo code models the natural uranium fission blanket. Maximizing the fission power gain while breeding sufficient tritium allows for the selection of an optimal set of blanket parameters, which yields a maximum prudent fission power gain of approximately 7. A 0-D tokamak model suffices to analyze approximate tokamak operating conditions. This fission blanket would allow the fusion component of a hybrid reactor with the same dimensions as ITER to operate in steady-state L-mode very comfortably with a fusion power gain of 6.7 and a thermal fusion power of 2.1 GW. Taking this further can determine the approximate minimum scale for a steady-state L-mode tokamak hybrid reactor, which is a major radius of 5.2 m and an aspect ratio of 2.8. This minimum scale device operates barely within the steady-state L-mode realm with a thermal fusion power of 1.7 GW. Basic thermal hydraulic analysis demonstrates that pressurized helium could cool the pebble bed fission blanket with a flow rate below 10 m/s. The Brayton cycle thermal efficiency is 41%. This reactor, dubbed the Steady-state L-mode non-Enriched Uranium Tokamak Hybrid (SLEUTH), with its very fast neutron spectrum, could be superior to pure fission reactors in terms of breeding fissile fuel and transmuting deleterious fission products. It would likely function best as a prolific plutonium breeder, and the plutonium it produces could actually be more proliferation-resistant than that bred by conventional fast reactors. Furthermore, it can maintain constant total hybrid power output as burnup proceeds by varying the neutron source strength.

  4. Naturally etched tracks in apatites and the correction of fission track dating

    CERN Document Server

    Tien, J L

    1999-01-01

    Naturally etched tracks have been found in apatites from the rapid cooled, high-level Kunon pluton in the Zhangzhou Igneous Complex, SE China. This is manifested by the fact that the apatite fission track (FT) age derived from conventional counting of spontaneous and induced tracks yields a result of 140.6+-6.5 Ma, which is much older than the ages determined using other methods on different minerals from the same rock. When tracks are observed after etching the polished inner sections of the apatite grains, the naturally etched tracks characterized by having hazy boundaries can be distinguished from the normal tracks with sharp boundaries. The age obtained by omitting these fading-resistant hazy tracks, 76.5+-4.0 Ma, indicates the time of the Kunon pluton cooling down to approx 100 deg. C. The corrected peak age (73.8 Ma) is consistent with the other apatite FT peak ages (79.2 to 70.2 Ma) of the nearly contemporaneous plutons in the same igneous complex.

  5. High-energy Neutron-induced Fission Cross Sections of Natural Lead and Bismuth-209

    CERN Document Server

    Tarrio, D; Carrapico, C; Eleftheriadis, C; Leeb, H; Calvino, F; Herrera-Martinez, A; Savvidis, I; Vlachoudis, V; Haas, B; Koehler, P; Vannini, G; Oshima, M; Le Naour, C; Gramegna, F; Wiescher, M; Pigni, M T; Audouin, L; Mengoni, A; Quesada, J; Becvar, F; Plag, R; Cennini, P; Mosconi, M; Rauscher, T; Couture, A; Capote, R; Sarchiapone, L; Vlastou, R; Domingo-Pardo, C; Dillmann, I; Pavlopoulos, P; Karamanis, D; Krticka, M; Jericha, E; Ferrari, A; Martinez, T; Trubert, D; Oberhummer, H; Karadimos, D; Plompen, A; Isaev, S; Terlizzi, R; Cortes, G; Cox, J; Cano-Ott, D; Pretel, C; Colonna, N; Berthoumieux, E; Vaz, P; Heil, M; Lopes, I; Lampoudis, C; Walter, S; Calviani, M; Gonzalez-Romero, E; Embid-Segura, M; Stephan, C; Igashira, M; Papachristodoulou, C; Aerts, G; Tavora, L; Berthier, B; Rudolf, G; Andrzejewski, J; Villamarin, D; Ferreira-Marques, R; Tain, J L; O'Brien, S; Reifarth, R; Kadi, Y; Neves, F; Poch, A; Kerveno, M; Rubbia, C; Lazano, M; Dahlfors, M; Wisshak, K; Salgado, J; Dridi, W; Ventura, A; Andriamonje, S; Assimakopoulos, P; Santos, C; Voss, F; Ferrant, L; Patronis, N; Chiaveri, E; Guerrero, C; Perrot, L; Vicente, M C; Lindote, A; Praena, J; Baumann, P; Kappeler, F; Rullhusen, P; Furman, W; David, S; Marrone, S; Tassan-Got, L; Gunsig, F; Alvarez-Velarde, F; Massimi, C; Mastinu, P; Pancin, J; Papadopoulos, C; Tagliente, G; Haight, R; Chepel, V; Kossionides, E; Badurek, G; Marganiec, J; Lukic, S; Pavlik, A; Goncalves, I; Duran, I; Alvarez, H; Abbondanno, U; Fujii, K; Milazzo, P M; Moreau, C

    2011-01-01

    The CERN Neutron Time-Of-Flight (n\\_TOF) facility is well suited to measure small neutron-induced fission cross sections, as those of subactinides. The cross section ratios of (nat)Pb and (209)Bi relative to (235)U and (238)U were measured using PPAC detectors. The fragment coincidence method allows to unambiguously identify the fission events. The present experiment provides the first results for neutron-induced fission up to 1 GeV for (nat)Pb and (209)Bi. A good agreement with previous experimental data below 200 MeV is shown. The comparison with proton-induced fission indicates that the limiting regime where neutron-induced and proton-induced fission reach equal cross section is close to 1 GeV.

  6. Parametric study of the criticality of natural reactors

    International Nuclear Information System (INIS)

    Conditions for the criticality of natural reactors are investigated from a general point of view; a parametric study is presented, which expresses the possibility of chain reactions as functions of five parameters: the age of the deposit, the ore's uranium content, the volume of high-grade ore, the neutron capture of the vein of ore and the amount of water associated with the uranium. It is demonstrated that although criticality could theoretically be attained for ages that are not in excess of 1000 to 1200 MA, conditions would have to be exceptionally favorable for it since the deposits are clearly much younger than those at Oklo. The study offers a much better appreciation of the probability for discovery of other natural fissionable reactors

  7. Reactor AQUILON. The hardening of neutron spectrum in natural uranium rods, with a computation of epithermal fissions (1961)

    International Nuclear Information System (INIS)

    - 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 '?' 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)

  8. Oklo: The fossil nuclear reactors. Physics study - Translation of chapters 6, 13 and conclusions

    International Nuclear Information System (INIS)

    Three parts of the 1991 book 'Oklo: reacteurs nucleaires fossiles. Etude physique' have been translated in this report. The chapters bear the titles 'Study of criticality'(45 p.), 'Some problems with the overall functioning of the reactor zones'(45 p.) and 'Conclusions' (15 p.), respectively

  9. Fast fission phenomena

    International Nuclear Information System (INIS)

    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

  10. Statistical nature of neutron activity in the fission of heavy nuclei

    International Nuclear Information System (INIS)

    It is shown that some characteristics of the neutron emission can be explained in the framework of statistical theory, which studies the stability of the ensemble of nuclear fragments and fission neutrons. The theory able to reproduce the known experimental sawtooth-curve of the neutron multiplicity n(A) and allows one to set the total neutron multiplicity as a function of (A, Z) and the excitation energy of the initial nucleus

  11. Separation of actinides from a solution of soil material containing natural elements and fission products

    International Nuclear Information System (INIS)

    A diagram for the separation of actinides is proposed. The task was to separate actinides from a soil sample, contaminated by them and fission products. Separations are performed by extraction chromatography and selective stripping followed by ion-exchange purification on small columns. The obtained actinides are free from foreign elements. It is possible to prepare electrodeposited sources for radiometric measurements, alpha- and gamma-countings or deposits for mass-spectrometric measurements. (author)

  12. Natural uranium impurities in fission track detectors and associated geocronological parameters

    International Nuclear Information System (INIS)

    A technique, based in counting neutron induced fission tracks, has been developed for the measurement of uranium impurities in mica. Uranium concentrations of 10-10 and 10-9 (U atom/mica atom) have been measured. As a part of the development of this technique, the mica geological age was also measured, by fossil and induced track detection. The agreement obtained by this method, T = (472+-52) x 106 years with that of (450+-15) x 106 years obtained by the Ar-K technique is satisfactory and is an indirect test of the fission track technique used. A careful analysis of the neutron field parameters and nuclear data used in the age determination was made. This analysis is useful for applications in geocronology. According to this analysis a value of lambdasub(f)=(7.1+-0.1) x 10-17 years-1 is recommended for the spontaneous fission of U238. However, in order to compare the results, the quoted age, T=(472+-52) x 106 years, was obtained with the generally accepted value of lambdasub(f)=(6.85-0.20) x 10-17 years-1 (Fleischer and Price 1964). (author)

  13. Uranium transport around the reactor zone at Okelobondo (Oklo). Data evaluation with M3 and HYTEC

    International Nuclear Information System (INIS)

    The Swedish Nuclear Fuel and Waste Management Company (SKB) is conducting and participating in Natural Analogue activities as part of various studies regarding the final disposal of high level nuclear waste (HLW). The aim of this study is to use the hydrogeological and hydrochemical data from Okelobondo (Oklo Natural Analogue) to compare the outcome of two independent modelling approaches (HYTEC and M3). The modelling helps to evaluate the processes associated with nuclear natural reactors such as redox, adsorption/desorption and dissolution/precipitation of the uranium and to develop more realistic codes which can be used for site investigations and data evaluation. HYTEC (1D and 2D) represents a deterministic, transport and multi-solutes reactive coupled code developed at Ecole des Mines de Paris. M3 (Multivariate Mixing and Mass balance calculations) is a mathematical-statistical concept code developed for SKB. M3 can relatively easily be used to calculate mixing portions and to identify sinks or sources of element concentrations that may exist in a geochemical system. M3 helped to address the reactions in the coupled code HYTEC. Thus, the major flow-paths and reaction paths were identified and used for transport evaluation. The reactive transport results (one-dimensional and two-dimensional simulations) are in good agreement with the statistical approach using the M3 model. M3 and HYTEC show a dissolution of the uranium layer in contact with upwardly oxidising waters. M3 and HYTEC show a gain of manganese rich minerals downstream the reactor. A comparison of the U and Mn plots for M3 deviation and HYTEC results showed an almost mirror behaviour. The U transport stops when the Mn gain increases. Thus, HYTEC and M3 modelling predict that a possible reason for not having U transport up to the surface in Okelobondo is due to an inorganic trap which may hinder the uranium transport. The two independent modelling approaches can be used to complement each other and to better understand the processes that can take place in nature. This provides the opportunity to assess the necessary tools for site investigations, data evaluation and helps to trace the reactions and to identify the hydro-geo-chemical system. Thus, we can build reliable tools which can be used to assess the performance of possible waste repository sites

  14. Speciation of actinides and fission products at smectite rich natural clay-water interface

    International Nuclear Information System (INIS)

    Speciation of actinides (Am(lll), Pu(lV), Np(V)) and long lived fission products, (Cs(l), Sr(II), Tc(VII)) at the interface between smectite rich clay and water has been studied by batch sorption experiments under different experimental conditions of pH, ionic strength and metal ion concentration. Modeling of the sorption data have been used to delineate the mechanism of the sorption of the metal ions on the clay. The study revealed different mechanisms (surface complexation, ion exchange) operating under different pH conditions and for different metal ions. Studies have been extended to diffusion of these radionuclides in the compacted clay to obtain the diffusion coefficient in saturated clay

  15. Detailed spectroscopy from fission

    International Nuclear Information System (INIS)

    Spectroscopic measurements of prompt radiations from fission fragments prior to beta decay are discussed. Post beta decay deexcitation is examined for observations with high fission yield, short lived, prompt products. A comparison of the types of results obtained from prompt decay and beta decay is made in an attempt to demonstrate their complementary nature in giving nuclear structure information. Nuclear information obtained from spectroscopy of fission fragment products is summarized for various regions of interest. (14 figures, 2 tables, 113 references) (U.S.)

  16. Fission-track dating of South American natural glasses: an overview

    International Nuclear Information System (INIS)

    Although many glass-bearing horizons can be found in South American volcanic complexes or sedimentary series, only a relatively few tephra and obsidian-bearing volcanic fields have been studied using the fission-track (FT) dating method. Among them, the volcanics located in the Sierra de Guamani (east of Quito, Ecuador) were studied by several authors. Based upon their ages, obsidians group into three clusters: (1) very young obsidians, ?0.2Ma old (2) intermediate-age obsidians, ?0.4-?0.8Ma old, and (3) older obsidians, ?1.4-?1.6Ma old. The FT method is also an efficient alternative technique for identification of the sources of prehistoric obsidian artefacts. Provenance studies carried out in South America have shown that the Sierra de Guamani obsidian occurrences were important sources of raw material for tool making during pre-Columbian times. Glasses originated from these sources were identified in sites distributed over relatively wide areas of Ecuador and Colombia. Only a few systematic studies on obsidians in other sectors were carried out. Nevertheless, very singular glasses have been recognised in South America, such as Macusanite (Peru) and obsidian Quiron (Argentina), which are being proposed as additional reference materials for FT dating. Analyses of tephra beds interstratified with sedimentary deposits revealed the performance of FT dating in tephrochronological studies. A remarkable example is the famous deposit outcropping at Farola Monte Hermoso, near Bahia Blanca (Buenos Aires Province), described for the first time by the middle of the 19th century by Charles Darwin. Considering the large number of volcanic glasses that were recognised in volcanic complexes and in sedimentary series, South America is a very promising region for the application of FT dating. The examples given above show that this technique may yield important results in different disciplinary fields

  17. Entrance-channel dependence of fission transients

    CERN Document Server

    Charity, R J

    2004-01-01

    Fission transients describe the fission rate as it evolves towards the quasistationary value given by Kramers' formula. The nature of fission transients is dependent on the assumed initial distribution of the compound nuclei along the fission coordinate. Although the standard initial assumption of a near-spherical object leads to a transient suppression of the fission rate (fission delay), a moderate initial fissionlike deformation can reduce the magnitude of this suppression. For still larger initial deformations, transient fission enhancements are possible. Examples of this behavior are illustrated via a one-dimensional Langevin simulation. It is argued that the initial conditions are determined by the fusion dynamics and thus are entrance-channel dependent. Transient fission may be considered intermediate between statistical fission and quasifission as the rapid time scale of transient fission may not lead to an equilibrium of the angular and mass-asymmetry coordinates. The relationship between the mean fi...

  18. Nuclear Data in Oklo and Time-Variability of Fundamental Coupling Constants

    CERN Document Server

    Fujii, Y; Fukahori, T; Ohnuki, T; Nakagawa, M; Hidaka, H; Oura, Y; Møller, P; Fujii, Yasunori; Iwamoto, Akira; Fukahori, Tokio; Ohnuki, Toshihiko; Nakagawa, Masayuki; Hidaka, Hiroshi; Oura, Yasuji; Moller, Peter

    2001-01-01

    We re-examined Shlyakhter's analysis of the Sm data in Oklo. With a special care of minimizing contamination due to the inflow of the isotope after the end of the reactor activity, we confirmed that his result on the time-variability of the fine-structure constant, $|\\dot{\\alpha}/\\alpha |\\lsim 10^{-17}{\\rm y}^{-1}$, was basically correct. In addition to this upper bound, however, we obtained another result that indicates a different value of $\\alpha$ 2 billion years ago. We add comments on the recent result from QSO's.

  19. Natural genetic variation impacts expression levels of coding, non-coding, and antisense transcripts in fission yeast.

    DEFF Research Database (Denmark)

    Clément-Ziza, Mathieu; Marsellach, Francesc X.

    2014-01-01

    Our current understanding of how natural genetic variation affects gene expression beyond well-annotated coding genes is still limited. The use of deep sequencing technologies for the study of expression quantitative trait loci (eQTLs) has the potential to close this gap. Here, we generated the first recombinant strain library for fission yeast and conducted an RNA-seq-based QTL study of the coding, non-coding, and antisense transcriptomes. We show that the frequency of distal effects (trans-eQTLs) greatly exceeds the number of local effects (cis-eQTLs) and that non-coding RNAs are as likely to be affected by eQTLs as protein-coding RNAs. We identified a genetic variation of swc5 that modifies the levels of 871 RNAs, with effects on both sense and antisense transcription, and show that this effect most likely goes through a compromised deposition of the histone variant H2A.Z. The strains, methods, and datasets generated here provide a rich resource for future studies.

  20. Independent yields of Rb and Cs isotopes from the fission of natural uranium induced by protons of energy 80 and 100 MeV

    International Nuclear Information System (INIS)

    The independent yields or production cross sections of rubidium isotopes from mass 86 to 97, and of cesium isotopes from mass 129 to 144, have been measured for the fission of natural uranium induced by 80 and 100 MeV protons. The results were obtained by means of an on-line mass spectrometer. The rubidium distributions are quite symmetric, whereas the cesium distributions show a definite skewness toward the heavy mass side. Comparison with other results at 40, 50, 60 and 150 MeV proton energies shows that the heavy mass sides of the isotopic distributions are relatively insensitive to proton energy, whereas the light mass sides shift downward with increasing proton energy. The average total number of neutrons emitted has been estimated for each fission reaction. The mechanism of nuclear charge division in 80 and 100 MeV proton fission in the mass split studied here appears to be similar to that operating in thermal-neutron and low-energy proton fission. (author)

  1. Chemistry and migration behaviour of the actinides and fission products in natural aquatic systems

    International Nuclear Information System (INIS)

    The 66th PTB seminar was held on April 24th and 25th, 1986, at the Munich Technical University (TUM) in Garching in cooperation with the Institute for Radiochemistry of the Munich Technical University, the 'Nuclear Chemistry' special group of the Society of German Chemists, and UB/SN responsible for the BMFT project. The seminar was organized by the TUM's Institute for Radiochemistry. The seminar dealt with the following main topics: primary geochemical reactions and colloid formation; sorption mechamisms and migration behaviour in Konrad/Gorleben aquifer systems; sampling and experimental investigations; evaluation and interpretation of the data obtained by experiments. The seminar was to achieve the following objectives: information and exchange of experience with regard to the work carried out up to the present; if necessary, formulation of new issues to be discussed; improvement of the interdisciplinary cooperation (chemistry, geosciences, modelling). The following topics and individual aspects were of particular interest and were given special attention: complementary basic research in order to interpret, support and model the results obtained by experiments (sorption mechanisms and thermodynamic data for natural systems); comparability of batch, column and diffusion tests; transferability of laboratory data to natural systems (e.g. Gorleben, Konrad); redox transitions for Np, Tc at Eh values of the natural systems; dependence of the sorption/desorption data on different influencing factors, importance of the influencing factors and selection of data for model calculations. Subject analyses of the individual contributions have been made for the Energy data base. (orig./RB)

  2. Sorption of 239Np and 235U fission products by zeolite Y, Mexican natural erionite, and bentonite

    International Nuclear Information System (INIS)

    Zeolite Y, erionite, and bentonite have been used in this work to remove 239Np and 235U fission products from aqueous solutions at various pH values. It was found that the sorption of fission products by aluminosilicates takes place by different mechanisms, mainly ion exchange, precipitation, and electrostatic surface interaction. The radionuclides content was determined by ?-spectrometry, and X-ray diffraction was used to learn whether the solids maintained their crystallinity at different pH values

  3. Fission isomers

    International Nuclear Information System (INIS)

    After a short historical account of superdeformed nuclei which are able to de-excite by spontaneous fission (hence their name of fission isomers) the principles of different experimental set-ups are described. These set-ups were used to study various properties: half-life, excitation energy, spin, gyromagnetic factor, moment of inertia and quadrupole moment. The most significant values are given. Finally, the question of the various types of excited states of fission isomers is tackled. (author) 20 refs.; 17 figs

  4. Search for ?-delayed fission of 228Ac

    International Nuclear Information System (INIS)

    Radium was radiochemically separated from natural thorium. Thin 228Ra??-228Ac sources were prepared and exposed to mica fission track detectors, and measured by an HPGe ?-ray detector. The ?-delayed fission events of 228Ac were observed and its ?-delayed fission probability was found to be (5±2)x10-12

  5. Fission barriers

    International Nuclear Information System (INIS)

    Immediately after the discovery of fission in 1939 by Hahn and Strassmann and Meitner and Frisch, the latter authors gave a qualitative explanation of the process using the picture of a charged liquid drop. Still in the same year, Bohr and Wheeler developed this picture into their classical theory, which remained the basis for the description of nuclear fission for many years to come. Today it is known that many of the finer details of the fission process cannot be understood without reference to the shell structure of the nucleus. It is the merit of V. M. Strutinsky to have shown a practical way to combine the knowledge about shell structure with the liquid drop model in his open-quotes macroscopic-microscopicclose quotes method and to point to the important effect of shell structure on what we call the open-quotes fission barrierclose quotes. This chapter will thus describe the fission barrier first within the liquid drop model (Section II) and then discuss shell corrections according to the Strutinsky procedure (Section III). Section IV will deal with the transmission through the fission barrier, including the most immediate effects of its double-humped shape. Some of the more detailed consequences of this structure, namely the existence of different classes of compound nuclear states, will be briefly addressed in Section V; however, more detailed discussion of their effect will be postponed to Chapter 4. Finally, Section VI will describe some basic methods of obtaining experimental information on the shape of the fission barrier. 61 refs., 11 figs., 1 tab

  6. Sorption of {sup 239}Np and {sup 235}U fission products by zeolite Y, Mexican natural erionite, and bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Olguin, M.T.; Solache, M.; Iturbe, J.L. [Instituto Nacional de Investigaciones Nucleares, C.P. (Mexico)]|[Universidad Autonoma Metropolitana, C.P. (Mexico)] [and others

    1996-09-01

    Zeolite Y, erionite, and bentonite have been used in this work to remove {sup 239}Np and {sup 235}U fission products from aqueous solutions at various pH values. It was found that the sorption of fission products by aluminosilicates takes place by different mechanisms, mainly ion exchange, precipitation, and electrostatic surface interaction. The radionuclides content was determined by {gamma}-spectrometry, and X-ray diffraction was used to learn whether the solids maintained their crystallinity at different pH values.

  7. Ternary fission

    Indian Academy of Sciences (India)

    M Balasubramaniam; K R Vijayaraghavan; C Karthikraj

    2015-09-01

    We present the ternary fission of 252Cf and 236U within a three-cluster model as well as in a level density approach. The competition between collinear and equatorial geometry is studied by calculating the ternary fragmentation potential as a function of the angle between the lines joining the stationary middle fragment and the two end fragments. The obtained results for the 16O accompanying ternary fission indicate that collinear configuration is preferred to equatorial configuration. Further, for all the possible third fragments, the potential energy surface (PES) is calculated corresponding to an arrangement in which the heaviest and the lightest fragments are considered at the end in a collinear configuration. The PES reveals several possible ternary modes including true ternary modes where the three fragments are of similar size. The complete mass distributions of Si and Ca which accompanied ternary fission of 236U is studied within a level density picture. The obtained results favour several possible ternary combinations.

  8. Ternary fission

    International Nuclear Information System (INIS)

    Recently a number of experimental detailed studies on the fission of compound nuclei 236U, 252Cf accompained by alphas and other charge particles have been finished. On the base of the obtained results in alpha accompained fission of 236U the new stage in trajectory computations for the definition of scission conditions was performed in but the result seems to be not unequivocal. A quantum mechanical approach to the emission of alpha particles of fissioning nuclei sensitive to the descent time from the saddle to the scission point occurs to be very promising. But it is early to say about a good agreement between theory and experiment. The difference in the value of the prescission kinetic energy of fragments E degree F obtained in trajectory calculations, still remains very large, of the order 20 MeV. In this paper the authors attempt to decrease such uncertainty in E degree F, performing calculations and comparing them with all observable variables from thermal fission of 239Pu accompained by alphas

  9. Singlet Fission.

    Czech Academy of Sciences Publication Activity Database

    Smith, M. B.; Michl, Josef

    2010-01-01

    Ro?. 110, ?. 11 (2010), s. 6891-6936. ISSN 0009-2665 Grant ostatní: Department of Energy(US) DE-FG36-08GO18017 Institutional research plan: CEZ:AV0Z40550506 Keywords : solar energy conversion * photovoltaics * singlet fission Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 33.033, year: 2010

  10. Calculations of fission rates for r-process nucleosynthesis

    International Nuclear Information System (INIS)

    Fission plays an important role in the r-process which is responsible not only for the yields of transuranium isotopes, but may have a strong influence on the formation of the majority of heavy nuclei due to fission recycling. We present calculations of beta-delayed and neutron-induced fission rates, taking into account different fission barriers predictions and mass formulae. It is shown that an increase of fission barriers results naturally in a reduction of fission rates, but that nevertheless fission leads to the termination of the r-process. Furthermore, it is discussed that the probability of triple fission could be high for A>260 and have an effect on the formation of the abundances of heavy nuclei. Fission after beta-delayed neutron emission is discussed as well as different aspects of the influence of fission upon r-process calculations

  11. A study of the effect of natural radiation damage in a zircon crystal using thermoluminescence, fission track etching and X-ray diffraction

    International Nuclear Information System (INIS)

    The natural radiation damage in zircon caused by the decay of uranium and thorium, present as impurities, is studied. The radiation damage is first gauged by etching the fission tracks. It is found that thermoluminescence (TL) sensitivity (defined as light output per unit test-dose) decreases as the radiation damage increases, suggesting a destruction of TL centers. The spacing d of the (112)-plane is also measured. It is also found that the d-value increases with radiation damage, suggesting the displacement of atoms from their normal lattice sites. However, as the track density increases beyond ? 3x106 tracks/cm2, the d-value remains at ? 2.52 A. By annealing the crystal, the displaced atoms are found to return to the original lattice sites, and this is followed by a reduction in d-value as well as the recovery of TL sensitivity. The fission track density also decreases and all the tracks disappear at the annealing temperature of ? 8000C. (orig.)

  12. Bacteria, colloids and organic carbon in groundwater at the Bangombe site in the Oklo area

    International Nuclear Information System (INIS)

    This report describes how microorganisms, colloids and organic matter were sampled from groundwater from six boreholes at the Bangombe site in the Oklo region and subsequently analyzed. For analysis of microorganisms, DNA was extracted from groundwater, amplified and cloned and information available in the ribosomal 16S rRNA gene was used for mapping diversity and distribution of bacteria. Each borehole was dominated by species that did not dominate in any of the other boreholes, a result that probably reflects documented differences in the geochemical environment. Analyses of sampled colloids included SEM and ICP-MS analysis of colloids on membrane and single particle analysis of samples in bottles. The colloid concentration was rather low in these Na-Mg-Ca-HCO3 type waters. Trace element results show that transition metals and some heavy metals are associated with the colloid phase. Distribution coefficients of trace elements between the water and colloid phases were estimated. For example for uranium, an average of 200 pg/ml was detected in the water, and 40 pg/ml was detected in the colloid phase. A Kp value of 2* 106 ml/g was calculated, considering (colloid) = 100 ng/ml. Groundwater samples were collected for analysis of the concentration of organic carbon (TOC), humic substances and metals associated with the humic substances. TOC varied in the range 4-14 mg/l in three boreholes, one borehole had a TOC<1.5 mg/l. The metal speciation study indicated that a large fraction, 8-67% of uranium was bound to the humic matter compared to the fractions of Ca and Fe (<0.4% and 0.02-10%, resp.). 60 refs, 8 figs, 16 tabs

  13. Nuclear fission and reactions

    International Nuclear Information System (INIS)

    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.)

  14. Dissolution studies of natural analogues spent fuel and U(VI)-Silicon phases of and oxidative alteration process

    International Nuclear Information System (INIS)

    In order to understand the long-term behavior of the nuclear spent fuel in geological repository conditions, we have performed dissolution studies with natural analogues to UO2 as well as with solid phases representatives of the oxidative alteration pathway of uranium dioxide, as observed in both natural environment and laboratory studies. In all cases, we have studied the influence of the bicarbonate concentration in the dissolution process, as a first approximation to the groundwater composition of a granitic environment, where carbonate is one of the most important complexing agents. As a natural analogue to the nuclear spent fuel some uraninite samples from the Oklo are deposit in Gabon, where chain fission reactions took place 2000 millions years ago, as well as a pitchblende sample from the mine Fe ore deposit, in Salamanca (spain) have been studied. The studies have been performed at 25 and 60 deg C and 60 deg C, and they have focussed on the determination of both the thermodynamic and the kinetic properties of the different samples studied, using batch and continuous experimental methodologies, respectively. (Author)

  15. Seminar on Fission VI

    Science.gov (United States)

    Wagemans, Cyriel; Wagemans, Jan; D'Hondt, Pierre

    2008-04-01

    Topical reviews. Angular momentum in fission / F. Gönnenwein ... [et al.]. The processes of fusion-fission and quasi-fission of heavy and super-heavy nuclei / M. G. Itkis ... [et al.] -- Fission cross sections and fragment properties. Minor-actinides fission cross sections and fission fragment mass yields via the surrogate reaction technique / B. Jurado ... [et al.]. Proton-induced fission on actinide nuclei at medium energy / S. Isaev ... [et al.]. Fission cross sections of minor actinides and application in transmutation studies / A. Letourneau ... [et al.]. Systematics on even-odd effects in fission fragments yields: comparison between symmetric and asymmetric splits / F. Rejmund, M Caamano. Measurement of kinetic energy distributions, mass and isotopic yields in the heavy fission products region at Lohengrin / A. Bail ... [et al.] -- Ternary fission. On the Ternary [symbol] spectrum in [symbol]Cf(sf) / M. Mutterer ... [et al.]. Energy degrader technique for light-charged particle spectroscopy at LOHENGRIN / A. Oberstedt, S. Oberstedt, D. Rochman. Ternary fission of Cf isotopes / S. Vermote ... [et al.]. Systematics of the triton and alpha particle emission in ternary fission / C. Wagemans, S. Vermote, O. Serot -- Neutron emission in fission. Scission neutron emission in fission / F.-J. Hambsch ... [et al.]. At and beyond the Scission point: what can we learn from Scission and prompt neutrons? / P. Talou. Fission prompt neutron and gamma multiplicity by statistical decay of fragments / S. Perez-Martin, S. Hilaire, E. Bauge -- Fission theory. Structure and fission properties of actinides with the Gogny force / H. Goutte ... [et al.]. Fission fragment properties from a microscopic approach / N. Dubray, H. Goutte, J.-P. Delaroche. Smoker and non-smoker neutron-induced fission rates / I. Korneev ... [et al.] -- Facilities and detectors. A novel 2v2E spectrometer in Manchester: new development in identification of fission fragments / I. Tsekhanovich ... [et al.]. Development of PSD and ToF + PSD techniques for fission experiments / M. Sillanpää ... [et al.]. MYRRHA, a new fast spectrum facility / H. Aït Abderrahim, P. D'hondt, D. De Bruyn. The BR1 reactor: a versatile tool for fission experiments / J. Wagemans -- "Special" fission processes. Shape isomers - a key to fission barriers / S. Oberstedt ... [et al.]. Fission in spallation reactions / J. Cugnon, Th. Aoust, A. Boudard -- Conference photo -- List of participants.

  16. Estimation of errors in the cumulative Monte Carlo fission source

    OpenAIRE

    Tuttelberg, Kaur; Dufek, Jan

    2014-01-01

    We study the feasibility of estimating the error in the cumulative fission source in Monte Carlo criticality calculations by utilising the fundamental-mode eigenvector of the fission matrix. The cumulative fission source, representing the source combined over active cycles, contains errors of both statistical and systematic nature. Knowledge of the error in the cumulative fission source is crucial as it determines the accuracy of computed neutron flux and power distributions. While statistica...

  17. Energy released in fission

    International Nuclear Information System (INIS)

    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)

  18. An evaluation of the dissolution process of natural uranium ore as an analogue of nuclear fuel

    International Nuclear Information System (INIS)

    The assumption of congruent dissolution of uraninite as a mechanism for the dissolution behaviour of spent fuel was critically examined with regard to the fate of toxic radionuclides. The fission and daughter products of uranium are typically present in spent unreprocessed fuel rods in trace abundances. The principles of trace element geochemistry were applied in assessing the behaviour of these radionuclides during fluid/solid interactions. It is shown that the behaviour of radionuclides in trace abundances that reside in the crystal structure can be better predicted from the ionic properties of these nuclides rather than from assuming that they are controlled by the dissolution of uraninite. Geochemical evidence from natural uranium ore deposits (Athabasca Basin, Northern Territories of Australia, Oklo) suggests that in most cases the toxic radionuclides are released from uraninite in amounts that are independent of the solution behaviour of uranium oxide. Only those elements that have ionic and thus chemical properties similar to U4+, such as plutonium, americium, cadmium, neptunium and thorium can be satisfactorily modelled by the solution properties of uranium dioxide and then only if the environment is reducing. (84 refs., 7 tabs.)

  19. Fission of metallic clusters

    International Nuclear Information System (INIS)

    The fission of sodium clusters is discussed using Nuclear Physics method. After presenting the Liquid Drop Model for spherical jelly clusters, we introduce shell corrections and compare the obtained energies with self-consistent quantal results. Fission is studied evaluating Q-values and fission barriers, with the shell correction method and the Two Center Shell Model. The threshold of stability with respect to fission is predicted within the Liquid Drop Model. (author)

  20. 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.

  1. Fast and slow fission

    International Nuclear Information System (INIS)

    Measurements of alpha particle induced fission of actinide nuclei and fission of the composite system 170Yb formed in 12C and 20Ne bombardments both show significantly greater neutron emission prior to fission than is consistant with current statistical models. Implications of these results are discussed in the context of possible extreme models: (1) the enhancement of fission at low excitation energies due to shell effects; (2) the inhibition of fission at high excitations due to a limiting of the fission width; and (3) the possibility of significant neutron emission during the descent from saddle to scission. In addition the apparent incompatability between current models of incomplete fusion processes and the analysis of light heavy ion induced fission which ignore incomplete fusion is discussed

  2. Fission neutron statistical emission

    International Nuclear Information System (INIS)

    The statistical model approach FINESSE (FIssion NEutronS' Statistical Emission) for the description of fission neutron multiplicities, energy spectra and angular distributions is described. Based on an extended Weisskopf ansatz and on a realistic temperature distribution it provides a fragment mass number dependent description of fission neutron data. Model parameters (optical potential, n/? competition) were fixed on the basis of the 252Cf(sf) (nuclear data standard). Combined with a phenomenological fission model for predicting relevant fragment data as function of asymmetry. FINESSE can be applied to any fission reaction of actinides in the Th-Cf region without further parameter adjustment. Results are presented for 252Cf(sf) and neutron induced fission of 235U, 239Pu, 232Th. Effects of multiple-chance fission are discussed for 232Th(n,xnf) reacation. (author). 46 refs, 11 figs

  3. Ideological Fission

    DEFF Research Database (Denmark)

    Christiansen, Steen Ledet

    2008-01-01

    Cloverfield's monster is effective precisely because we never really see it, because it remains in our peripheral vision and seems to be mutating, changing, multiple and yet perhaps still one, all at the same time. To say that the monster is abject, is to miss the point. Being abject is part of a monster's very nature, but the monster in Cloverfield is both frightingly different and hauntingly familiar. We have seen such monsters many times before in earlier movies, so we cannot fully feel that ...

  4. Fission level densities

    International Nuclear Information System (INIS)

    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)

  5. Estimation of errors in the cumulative Monte Carlo fission source

    International Nuclear Information System (INIS)

    Highlights: • Fiss. matrix eigenvector can be used in estimating errors in MC fission source. • The estimated values effectively capture the stochastic and systematic errors. • Estimated values appear to be distributed around real errors. - Abstract: We study the feasibility of estimating the error in the cumulative fission source in Monte Carlo criticality calculations by utilising the fundamental-mode eigenvector of the fission matrix. The cumulative fission source, representing the source combined over active cycles, contains errors of both statistical and systematic nature. Knowledge of the error in the cumulative fission source is crucial as it determines the accuracy of computed neutron flux and power distributions. While statistical errors are present in the eigenvector of the fission matrix, it appears that these are not (or they are only weakly) correlated to the errors in the cumulative fission source. This ensures the suggested methodology gives error estimates that are distributed around the real errors, which is also supported by results of our numerical test calculations

  6. Fissionable mass storage device

    International Nuclear Information System (INIS)

    An apparatus for the safe storage of a plurality of fissionable masses including an array of discrete neutron absorbing shields which utilize the principle of the neutron trap to reduce the multipication factor of the storage array to a subcritical value when immersed in a neutron moderating medium is described. Each discrete neutron absorbing shield is designed to perimetrically encircle each of the stored fissionable masses. Each shield is spaced such that the encircled fissionable mass is spaced from the next adjacent neutron absorbing shield by a distance determined by the enrichment of the fissionable masses and attenuation of the moderating medium

  7. Fissionable mass storage device

    International Nuclear Information System (INIS)

    An apparatus for the safe storage of a plurality of fissionable masses including an array of discrete neutron absorbing shields which utilizes the principle of the neutron trap to reduce the multiplication factor of the storage array to a subcritical value when immersed in a neutron moderating medium is claimed. Each discrete neutron absorbing shield is designed to perimetrically encircle each of the stored fissionable masses. Each shield is spaced such that the encircled fissionable mass is spaced from the next adjacent neutron absorbing shield by a distance determined by the enrichment of the fissionable masses and attenuation of the moderating medium. 6 claims, 3 drawing figures

  8. Dissolution studies of natural analogues spent fuel and U(VI)-Silicon phases of and oxidative alteration process; Estudios de disolucion de analogos naturales de combustible nuclear irradiado y de fases de U(VI)-Silicio representativas de un proceso de alteracion oxidativa

    Energy Technology Data Exchange (ETDEWEB)

    Perez Morales, I.

    2000-07-01

    In order to understand the long-term behavior of the nuclear spent fuel in geological repository conditions, we have performed dissolution studies with natural analogues to UO{sub 2} as well as with solid phases representatives of the oxidative alteration pathway of uranium dioxide, as observed in both natural environment and laboratory studies. In all cases, we have studied the influence of the bicarbonate concentration in the dissolution process, as a first approximation to the groundwater composition of a granitic environment, where carbonate is one of the most important complexing agents. As a natural analogue to the nuclear spent fuel some uraninite samples from the Oklo are deposit in Gabon, where chain fission reactions took place 2000 millions years ago, as well as a pitchblende sample from the mine Fe ore deposit, in Salamanca (spain) have been studied. The studies have been performed at 25 and 60 degree centigree and 60 degree centigree, and they have focussed on the determination of both the thermodynamic and the kinetic properties of the different samples studied, using batch and continuous experimental methodologies, respectively. (Author)

  9. Muon-induced fission

    International Nuclear Information System (INIS)

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

  10. Fission Measurements with Dance

    Science.gov (United States)

    Jandel, M.; Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.; Chadwick, M. B.; Clement, R. R.; Couture, A.; O'Donnell, J. M.; Haight, R. C.; Keksis, A. L.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Agvaanluvsan, U.; Dashdorj, D.; Macri, R. A.; Parker, W. E.; Wilk, P. A.; Wu, C. Y.; Becker, J. A.; Angell, C. T.; Tonchev, A. P.; Baker, J. D.

    2008-08-01

    Neutron capture cross section measurements on actinides are complicated by the presence of neutron-induced fission. An efficient fission tagging detector used in coincidence with the Detector for Advanced Neutron Capture Experiments (DANCE) provides a powerful tool in undertaking simultaneous measurements of (n,?) and (n,f) cross sections. Preliminary results on 235U(n,?) and (n,f) and 242mAm(n,f) cross sections measured with DANCE and a custom fission-tagging parallel plate avalanche counter (PPAC) are presented. Additional measurements of ?-ray cluster multiplicity distributions for neutron-induced fission of 235U and 242mAm and spontaneous fission of 252Cf are shown, as well as ?-ray energy and average ?-ray energy distributions.

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

    International Nuclear Information System (INIS)

    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.

  12. Study on Fission Blanket Fuel Cycling of a Fusion-Fission Hybrid Energy Generation System

    International Nuclear Information System (INIS)

    Full text: Direct application of ITER-scale tokamak as a neutron driver in a subcritical fusion-fission hybrid reactor to generate electric power is of great potential in predictable future. This paper reports a primary study on neutronic and fuel cycle behaviors of a fission blanket for a new type of fusion-driven system (FDS), namely a subcritical fusion-fission hybrid reactor for electric power generation aiming at energy generation fueled with natural or depleted uranium. Using COUPLE2 developed at INET of Tsinghua University by coupling the MCNP code with the ORIGEN code to study the neutronic behavior and the refueling scheme, this paper focuses on refueling scheme of the fissionable fuel while keeping some important parameters such as tritium breeding ratio (TBR) and energy gain. Different fission fuels, coolants and their volumetric ratios arranged in the fission blanket satisfy the requirements for power generation. The results show that soft neutron spectrum with optimized fuel to moderator ratio can yield an energy amplifying factor of M> 20 while maintaining the TBR > 1.1 and the CR > 1 (the conversion ratio of fissile materials) in a reasonably long refueling cycle. Using an in-site fuel recycle plant, it will be an attractive way to realize the goal of burning 238U with such a new type of fusion-fission hybrid reactor system to generate electric power. (author)

  13. Fusion-fission dynamics

    International Nuclear Information System (INIS)

    Classical dynamical calculations of the heavy ion induced fission processes have been performed for the reactions 40Ar+141Pr, 20Ne+165Ho and 12C+175Lu 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.)

  14. Singlet exciton fission photovoltaics.

    Science.gov (United States)

    Lee, Jiye; Jadhav, Priya; Reusswig, Philip D; Yost, Shane R; Thompson, Nicholas J; Congreve, Daniel N; Hontz, Eric; Van Voorhis, Troy; Baldo, Marc A

    2013-06-18

    Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption. PMID:23611026

  15. Fission channels of 304120

    International Nuclear Information System (INIS)

    The main fission modes of the double magic 304120 are investigated from both a static and dynamic point of view. A set of spin-orbit and l2 strength parameters is selected such that a minimum occurs in the shell correction energy at Z = 120 and N = 184. The mass asymmetry is settled around the two double magic fragments: 132Sn and 208Pb. Different fission modes (some isotopes of Cd+Hf, Sn+Yb, Te+Er, Hg+Zr, Pb+Sr and Po+Kr) are analysed both staticly and dynamically. The macroscopic-microscopic method was used to calculate the potential energy in a three-dimensional space of deformation. Fission trajectories are obtained by minimization of the action integral. Penetrabilities and lifetimes are computed within the semiclassical WKB method. The most probable fission modes of 304120 correspond to the split in which 128Cd or the double magic 132Sn is the light fragment. Fission at larger mass asymmetry is less probable. (author)

  16. Fission yields for fast-neutron fission of uranium-238

    International Nuclear Information System (INIS)

    Fission yields determined for fission of 238U with monoenergetic neutrons have been used to calculate the fission yields expected in 238U when exposed to a Watt neutron spectrum for 235U and in the center of the Experimental Breeder Reactor II core. The calculated results are compared with the experimental results for several reactors and with the fast fission yields recommended by two compilers

  17. Mirror fusion--fission hybrids

    International Nuclear Information System (INIS)

    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

  18. Low energy nuclear fission

    International Nuclear Information System (INIS)

    In these lectures the liquid drop model of fission is presented and some of its predictions compared with experiment. The liquid drop analogy allows to define in a rather simple and intuitive way a number of useful concepts and possible observables. It is shown how a synthesis of the liquid drop model and of the shell model can be made using the Strutinsky shell averaging procedure. Some experimental data related to the existence of shape isomers are presented and discussed. We conclude by discussing some aspects, both experimental and theoretical, of fission dynamics

  19. Status of fission yield measurements

    International Nuclear Information System (INIS)

    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

  20. Physics and chemistry of fission

    International Nuclear Information System (INIS)

    This conference report gives a summary of the talks on the international symposium about physics and chemistry of fission held in Juelich in 1979. The main topics dealt with were potential energy surfaces, spectroscopy of highly deformed shapes, saddle-to-scission stage in fission and heavy-ion fission

  1. 50 years of nuclear fission

    International Nuclear Information System (INIS)

    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.)

  2. Discoveries of isotopes by fission

    Indian Academy of Sciences (India)

    M Thoennessen

    2015-09-01

    Of the about 3000 isotopes presently known, about 20% have been discovered in fission. The history of fission as it relates to the discovery of isotopes as well as the various reaction mechanisms leading to isotope discoveries involving fission are presented.

  3. Fission dynamics of hot nuclei

    Indian Academy of Sciences (India)

    Santanu Pal; Jhilam Sadhukhan

    2014-04-01

    Experimental evidence accumulated during the last two decades indicates that the fission of excited heavy nuclei involves a dissipative dynamical process. We shall briefly review the relevant dynamical model, namely the Langevin equations for fission. Statistical model predictions using the Kramers’ fission width will also be discussed.

  4. Fission product data library

    International Nuclear Information System (INIS)

    A library is described of data for 584 isotopes of fission products, including decay constants, branching ratios (both burn-up and decay), the type of emitted radiation, relative and absolute yields, capture cross sections for thermal neutrons, and resonance integrals. When a detailed decay scheme is not known, the mean energies of beta particles and neutrino and gamma radiations are given. In the ZVJE SKODA system the library is named BIBFP and is stored on film No 49 of the NE 803 B computer. It is used in calculating the inventory of fission products in fuel elements (and also determining absorption cross sections for burn-up calculations, gamma ray sources, heat generation) and in solving radioactivity transport problems in the primary circuit. It may also be used in the spectrometric method for burn-up determination of fuel elements. The library comprises the latest literary data available. It serves as the basis for library BIBGRFP storing group constants of fission products with independent yields of isotopes from fission. This, in turn, forms the basis for the BIBDN library collecting data on the precursors of delayed neutron emitters. (author)

  5. Spectroscopy of fission fragments

    International Nuclear Information System (INIS)

    The measurement of kinetic energies, velocities, masses and nuclear charges of fission fragments by physical methods is reviewed. The emphasis is put on recent developments aiming at high resolution and precision. The shortcomings of existing techniques are discussed and some improvements in approach are suggested. (orig.)

  6. Fission fragment kinetic energy

    International Nuclear Information System (INIS)

    Alpha induced fission was studied in the energy range of 20 to 29.4MeV. Significant changes in the mass distribution as well as in the kinetic energy were observed versus the compound nucleus excitation energy. The decrease in the average total kinetic energy with the excitation energy was attributed mainly to the changes in the mass distribution

  7. Feasibility of Producing Molybdenum-99 on a Small Scale Using Fission of Low Enriched Uranium or Neutron Activation of Natural Molybdenum. Companion CD-ROM

    International Nuclear Information System (INIS)

    This publication documents the work performed within the IAEA coordinated research project (CRP) on developing techniques for small scale indigenous molybdenum-99 production using low enriched uranium (LEU) fission or neutron activation. The CRP enabled participating institutions to gain the knowledge necessary for indigenous molybdenum-99 production. The outcome serves to capture the steps participants undertook in examining the feasibility of becoming small scale 99Mo producers. Most participants carried out work related to the entire production process, from target assembly through irradiation, planning for target disassembly in hot cells, chemical processing of targets, quality control practices, and managing waste streams. Some participants focused on one particular area, for example, testing new methods for production of LEU foil for targets and the production of gel generators from 99Mo solution. The publication aggregates all of the work undertaken as part of the CRP in order to present the results as a whole. The accomplishments of participating institutions are detailed in individual country reports on this CD-ROM

  8. 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.

  9. Fission rate sensitivities and fission fragment ranges for uranium and thorium-bearing materials irradiated with 252 Cf neutron source

    International Nuclear Information System (INIS)

    The induced fission reactions of 235 U (n, f), 238 U (n,f) and 232Th (n, f) based on the activation of natural uranium and thorium in samples with 252Cf, neutron source, have been evaluated. The obtained results are the average of three samples from each test material (SRM 2710 Montana soil and Zirconia). The prepared samples have been configured in the so-called compensated - beam geometryin which both gamma spectrometry jointly with solid state nuclear track detector techniques, revealed the fission rate sensitivity of 4.64 x 107 fission per gram per second per neutron (F.h1. S1.n1), for zirconia as obtained by gamma activity arising from 134 I fission product (as a good monitor which is produced only from fissions), and the related value for SRM 2710 soil is 5.22 x 108 (F.g1 S1 .n1). while the obtained values of the mean fission fragment ranges in SRM 2710 and zirconia as estimated from the fission track densities (by CR-39) and fission rates (by gamma spectrometry) are 3.97 x 10 3 g. cm2 respectively which reveal good agreement with experiments and calculations done hitherto

  10. Dynamical features of nuclear fission

    Indian Academy of Sciences (India)

    Santanu Pal

    2015-08-01

    It is now established that the transition-state theory of nuclear fission due to Bohr and Wheeler underestimates several observables in heavy-ion-induced fusion–fission reactions. Dissipative dynamical models employing either the Langevin equation or equivalently the Fokker–Planck equation have been developed for fission of heavy nuclei at high excitations (T ?1 MeV or higher). Here, we first present the physical picture underlying the dissipative fission dynamics. We mainly concentrate upon the Kramers’ prescription for including dissipation in fission dynamics. We discuss, in some detail, the results of a statistical model analysis of the pre-scission neutron multiplicity data from the reactions 19F+194,196,198Pt using Kramers’ fission width. We also discuss the multi-dimensional Langevin equation in the context of kinetic energy and mass distribution of the fission fragments.

  11. Feasibility of Producing Molybdenum-99 on a Small Scale Using Fission of Low Enriched Uranium or Neutron Activation of Natural Molybdenum

    International Nuclear Information System (INIS)

    This publication documents the work performed within the IAEA coordinated research project (CRP) on Developing Techniques for Small Scale Indigenous Molybdenum-99 Production Using LEU Fission or Neutron Activation. The project allowed participating institutions to receive training and information on aspects necessary for starting production of molybdenum-99 (99Mo) on a small scale, that is, to become national level producers of this medical isotope. Stable production of 99Mo is one of the most pressing issues facing the nuclear community at present, because the medical isotope technetium-99m (99mTc), which decays from 99Mo, is one of the most widely used radionuclides in diagnostic imaging and treatment around the world. In the past five years, there have been widespread shortages of 99Mo owing to the limited number of producers, many of which use ageing facilities. To assist in stabilizing the production of 99Mo, and to promote the use of production methods that do not rely on the use of highly enriched uranium (HEU), the IAEA initiated the abovementioned CRP on small scale 99Mo production using low enriched uranium (LEU) fission or neutron activation methods. The intention was to enable participating institutions to gain the knowledge necessary to become national level producers of 99Mo in the event of further global shortages. Some of the institutions that participated in the CRP have continued their work on 99Mo production, and are enlisting the assistance of other CRP members and the IAEA’s technical cooperation programme to set up a small scale production capability. In total, the CRP was active for six years, and concluded in December 2011. During the CRP, fourteen IAEA Member States took part; four research coordination meetings were held, and four workshops were held on operational aspects of 99Mo production, LEU target fabrication and waste management. Most participants carried out work related to the entire production process, from target assembly to irradiation (most only performed the thermal and hydraulic calculations necessary for irradiation), to planning for target disassembly in hot cells, chemical processing of targets, quality control practices and managing waste streams. However, some participants focused on one particular area, for example, testing new methods for production of LEU foil for targets or the production of gel generators from 99Mo solution. This publication aggregates all of the work undertaken as part of the CRP in order to present the results as a whole; the accomplishments of participating institutions are detailed in individual country reports on the attached CD-ROM. In addition to presenting the work performed within the CRP, this publication is intended to serve a wide readership that includes nuclear authorities, regulators and any institution that may have an interest in becoming a small scale producer of 99Mo using non-HEU production methods. The details presented here could serve as a template for a feasibility study to be carried out by an institution or State wishing to produce 99Mo; special care has been taken to note areas that were particularly challenging for participants and therefore may not be feasible for other small scale producers without significant investment in human resources or infrastructure

  12. Computer code development programs at JAERI on fission product behavior

    International Nuclear Information System (INIS)

    As a part of computer code development programs on severe accident analysis, computer programs HORN and REMOVAL, are being developed for analysis of fission product release and transport in primary coolant system and containment vessel. HORN is designed to calculate fission product release and transport in primary coolant system and the code is capable of predicting chemical forms of volatile fission products in a leak path based upon equilibrium assumptions. REMOVAL is to calculate aerosol removal by natural mechanisms as well as engineered safety features in the containment vessel. The model includes steam condensation onto aerosol particles. Results of sensitivity analyses are presented along with description of the models used in each code

  13. Computer code development programs at JAERI on fission product behavior

    International Nuclear Information System (INIS)

    As a part of computer code development programs on severe accident analysis, computer programs HORN and REMOVAL, are being developed for analysis of fission product release and transport in primary coolant system and containment vessel. HORN is designed to calculate fission product release and transport in primary coolant system and the code is capable of predicting chemical forms of volatile fission product in a leak path based upon equilibrium assumptions. REMOVAL is to calculate aerosol removal by natural mechanism as well as engineered safety features in containment vessel. The model includes steam condensation onto aerosol particles. Results of sensitivity analyses are presented along with description of the models used in each code

  14. Fission product revaporization

    International Nuclear Information System (INIS)

    One of the major developmental advances in severe accident analysis since the Reactor Safety Study relates to the accounting for radionuclide retention in the reactor coolant system (RCS). The retention is predicted to occur as materials released during core heatup and degradation are transported through the RCS to the break (broken pipe, relief valve, etc.). For accidents involving relatively long RCS-transit times (e.g., station blackout in PWRs), the fraction of released material predicted to remain in the RCS can be large. For example, calculations for the Surry station blackout sequence showed retention of approximately 80% of the cesium and iodine species. Factors affecting fission product revaporization are post-vessel-failure thermal hydraulics, heat loss through vessel and pipe walls, and revaporization chemistry. The accident conditions relevant to this issue range from those present immediately after vessel failure to those present after containment failure. The factors that affect fission product revaporization are discussed

  15. Fusion-fission dynamics

    International Nuclear Information System (INIS)

    Classical dynamical calculations of the heavy ion induced fission process for the reactions 40Ar+141Pr, 20Ne+165Ho and 12C+175Lu leading to the iridium like nucleus have been performed. As a result prescission lifetimes were obtained and compared with the experimental values. The agreement 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. Somewhat bigger calculated times than the experimental ones in case of the C+Lu reaction at 16 MeV/nucleon may be a signal on the energy range applicability of the one-body dissipation model. (author)

  16. Condensed fission products

    International Nuclear Information System (INIS)

    It is presented a method to calculate cross sections of condensed fission product. The group constants are generated by NJOY code, from ENDF/B-V and JENDL-1 data. Cross section of 28 nuclides were grouped with the RRB fast reactor characteristics. To verify the time, number of PF and influence of fuel composition, the one energy group calculation for a fast reactor of 1000/MWE were done. (M.C.K.)

  17. Long-range fission fragments from radiogenic lead. [Fission of nuclides with Z approx = 114

    Energy Technology Data Exchange (ETDEWEB)

    Maly, J.; Walz, D.R

    1978-06-01

    Fission tracks with a range 19 percent longer than tracks produced by uranium fission fragments were observed on mylar foils after a three-year underground (100 m.w.e.) exposure to 3600 cm/sup 2/ of radiogenic lead. Ordinary lead which was simultaneously exposed to mylar foils under the same conditions yielded a background effect of only 3 percent of the effect from radiogenic lead. The observed long-range tracks are best explained as resulting from the spontaneous fission of natural, superheavy elements in the suggested element-114 stability region which were coprecipitated with the radiogenic lead. Most likely they are created by a decay chain starting in the proposed Z = 124 to 126 region from a superheavy element which chemically follows uranium. 2 figures, 3 tables.

  18. Nuclear waste criticality analysis. Final report, 1 July 1995--30 June 1996

    International Nuclear Information System (INIS)

    The natural reactors that occurred in Gabon, Africa over 2 billion years ago present an interesting analog to the underground repositories proposed around the world for the long-term storage of high-level spent nuclear fuel. Many articles have been written concerning the low migration rates of actinides and fission products from the Oklo reactor sites, but Oklo also presents researchers with an opportunity to discover the conditions that led to nuclear criticality in uranium oxides with low enrichments. A computer model was developed to predict the conditions that were necessary to lead to criticality in the Oklo reactors. Critical core dimensions and infinite multiplication factors are presented as a function of time, the porosity of the host rock, and the water and uranium content of the sandstone deposits at Oklo

  19. Measurement of the Ratio of Fissions in U238 to Fissions in U233 Using 1.60 Mev Gamma Rays of the Fission Product La140

    International Nuclear Information System (INIS)

    This paper describes a method for measuring ?28, the ratios of fissions in U238 to fissions in U235. The method was developed as a part of the D2O lattice programme at the Massachusetts Institute of Technology (MIT) ; however, it can be used for measurements in any thermal reactor of natural or slightly enriched uranium. The fast fission factor in uranium cannot be measured directly. It is, however, related to ?28 which can be measured: ? =1 + C?28 , where C is a constant involving nuclear properties of U238 and U235: Previous methods of measuring ?28 utilize a comparison of fission-product gamma or beta activity in foils of differing U235 concentration irradiated within a fuel rod in the lattice. A double fission chamber is then used to relate the U238 and U235 fission product activity to the ratio of the corresponding fission rates. Most of the experimental uncertainty associated with the measurement of ?28 a is generally attributed to the fission chamber calibration. The method developed at MIT avoids the need for a fission chamber calibration and is accomplished directly with foils irradiated within a fuel rod in the lattice. Two foils of differing U235 concentration are irradiated and allowed to cool for at least a week. The relative activity of the 1.60 MeV gamma ray of the fission product La140 is determined for the two foils. This ratio, the foil weights and atomic densities, and the ratio of fission yields ?25/?28 for La140 are then used to determine ?28. This value of ?28 is used to calibrate simpler measurements in which the relative gamma activity above 0.72 MeV is determined for sets of foils irradiated in fuel rods of the lattices of interest. The energy 0.72 MeV is a convenient discrimination level, as it is the maximum energy of Bremsstrahlung from 2.3-d Np239. This method appears to offer the advantages of direct measurement and increased accuracy (the major uncertainty being the ratio of ?25/?28 La140). In addition, the results can be improved as better fission product yield ratio data become available, and the method facilitates comparison of ?28 values obtained by different laboratories. (author). (author)

  20. Statistics for fission track analysis

    CERN Document Server

    Galbraith, Rex F

    2005-01-01

    Statistical analyses of the numbers, lengths, and orientations of fission tracks etched in minerals yield dating and thermal history information valuable in geological and geoscience applications, particularly in oil exploration. Fission tracks can be represented mathematically by a stochastic process of randomly oriented line segments in three dimensions, and this "line segment" model can describe and explain the essential statistical features of the data, providing a rigorous foundation for quantitative modelling and simulation studies.Statistics for Fission Track Analysis explores the line segment model and its consequences for the analysis and interpretation of data. The author derives the equations for fission track data and the theoretical probability distributions for the number, orientation, and length measurements of the tracks. He sets out the theory of fission track dating and through numerical examples, presents methods for analyzing and interpreting fission track counts. Later chapters address st...

  1. Fission barriers of light nuclei

    International Nuclear Information System (INIS)

    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

  2. A simulation of fission chamber

    International Nuclear Information System (INIS)

    Fission chambers are widely used for online neutron flux measurements in nuclear reactors. These detector can cover up the entire range of reactor power operation by using in the pulse, Campbell and DC modes. The paper describes the simulation of fission chamber carried out with the objective of optimizing the design of High temperature fission chambers for PFBR. The Monte Carlo methods has been utilized to study detector performance characteristics

  3. Fission hindrance in hot nuclei

    International Nuclear Information System (INIS)

    The role of dynamics in fission has attracted much interest since the discovery of this process over fifty years ago. However, the study of the dynamical aspects of fission was for many years hampered by the lack of suitable experimental observables against which theoretical calculations could be tested. For example, it was found that the total kinetic energy release in fission can be described equally well by very different dissipation mechanisms, namely the wall formula, that is based on the collisions of the nucleons with the moving wall of the system, as well as a bulk viscosity of the nuclear matter. Although early theoretical work suggested that the fission process may be described as a diffusion process over the fission barrier, this was largely forgotten because of the success of a purely statistical model which instead of enumerating the ultimate final states of the process argues that the fission rate is determined at the open-quote transition state close-quote as the system traverses the fission saddle point. It was therefore significant when Gavron showed that the transition state model was unable to describe the number of neutrons emitted prior to scission at high excitation energy in reactions of 16O+142Nd. Subsequent experimental work using different methods to measure the fission dissipation/viscosity has confirmed these initial observations. It was therefore very surprising when Moretto in recent publications concluded that their analysis of fission excitation functions obtained with a and ? and 3He induced projectiles was perfectly in accord with the transition state model and left no room for fission viscosity. In this paper we'll show that Moretto's analysis is flawed by assuming first chance fission only (in direct contradiction to the experimental observation of pre-scission neutron emission in heavy-ion induced fission), and reveal why the systematics presented by Moretto looked so convincing despite these flaws

  4. Fission track dating of obsidians

    International Nuclear Information System (INIS)

    Fission track dating is applied to 16 obsidian artifacts from an archaeological excavation in Cayonu Tepesi at southeastern Anatolia. Since obsidian samples are rich in bubbles and inclusions, only the six most compact samples were found to be usable for fission track measurements. Size studies of etched fossil and induced fission tracks showed that no strong thermal effects occurred during the history of these glasses so that no fading correction has been applied to the computed ages. The fission track ages obtained range between 7.51 m.y. and 20.89 m.y. It may be stated that these obsidian samples are from the two different origins. (author)

  5. Hidden systematics of fission channels

    Directory of Open Access Journals (Sweden)

    Schmidt Karl-Heinz

    2013-12-01

    Full Text Available It is a common procedure to describe the fission-fragment mass distributions of fissioning systems in the actinide region by a sum of at least 5 Gaussian curves, one for the symmetric component and a few additional ones, together with their complementary parts, for the asymmetric components. These components have been attributed to the influence of fragment shells, e.g. in the statistical scission-point model of Wilkins, Steinberg and Chasman. They have also been associated with valleys in the potential-energy landscape between the outer saddle and the scission configuration in the multi-channel fission model of Brosa. When the relative yields, the widths and the mean mass-asymmetry values of these components are fitted to experimental data, the mass distributions can be very well reproduced. Moreover, these fission channels are characterised by specific values of charge polarisation, total kinetic energy and prompt-neutron yields. The present contribution investigates the systematic variation of the characteristic fission-channel properties as a function of the composition and the excitation energy of the fissioning system. The mean position of the asymmetric fission channels in the heavy fragment is almost constant in atomic number. The deformation of the nascent fragments at scission, which is the main source of excitation energy of the separated fission fragments ending up in prompt-neutron emission, is found to be a unique function of Z for the light and the heavy fragment of the asymmetric fission channels. A variation of the initial excitation energy of the fissioning system above the fission saddle is only seen in the neutron yield of the heavy fragment. The charge polarisation in the two most important asymmetric fission channels is found to be constant and to appreciably exceed the macroscopic value. The variation of the relative yields and of the positions of the fission channels as a function of the composition and excitation energy of the fissioning system obey a hidden systematics that can be explained by the number of states in the vicinity of the outer fission barrier as a function of mass asymmetry, if the potential is constructed as the sum of the macroscopic contribution of the compound nucleus and empirically determined fragment shells. This hidden systematics also explains the transition from asymmetric to symmetric fission around 226Th and around 258Fm.

  6. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    D N Poenaru; R A Gherghescu

    2015-09-01

    Fission theory is used to explain decay. Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster radioactivity. The macroscopic–microscopic method is illustrated for the superheavy nucleus 286Fl. Then a few results of the theoretical approach of decay (ASAF, UNIV and semFIS models), cluster decay (ASAF and UNIV) and spontaneous fission dynamics are described with Werner–Wheeler and cranking inertia. UNIV denotes universal curve and semFIS the fission-based semiempirical formula.

  7. Fission in Rapidly Rotating Nuclei

    Directory of Open Access Journals (Sweden)

    A. K. Rhine Kumar

    2014-02-01

    Full Text Available We study the effect of rotation in fission of the atomic nucleus 256Fm using an independent-particle shell model with the mean field represented by a deformed Woods-Saxon potential and the shapes defined through the Cassinian oval parametrization. The variations of barrier height with increasing angular momentum, appearance of double hump in fission path are analysed. Our calculations explain the appearance of double hump in fission path of 256Fm nucleus. The second minimum vanishes with increase in angular momentum which hints that the fission barrier disappears at large spin.

  8. Nuclear fission reactors as energy sources for the giant outer planets

    International Nuclear Information System (INIS)

    Of the giant planets, Jupiter, Saturn, and Neptune presently radiate into space approximately twice as much energy as they receive from the Sun; Uranus, however, emits little, if any, energy other than absorbed solar energy. Currently, speculative explanations for the energy sources involved propose gravitational potential energy release. The purpose of the present paper is to suggest the possibility of naturally occurring nuclear fission reactors in the giant outer planets. The discovery of a naturally occurring, terrestrial, nuclear fission, 'breeder' reactor is reviewed. Quantitative estimates are made of the planetary energy release by nuclear fission and of the duration that present planetary power output levels could be sustained by nuclear fission energy. (orig.)

  9. Fission decay properties of ultra neutron-rich uranium isotopes

    Indian Academy of Sciences (India)

    L Satpathy; S K Patra; R K Choudhury

    2008-01-01

    The fission decay of highly neutron-rich uranium isotopes is investigated which shows interesting new features in the barrier properties and neutron emission characteristics in the fission process. 233U and 235U are the nuclei in the actinide region in the beta stability valley which are thermally fissile and have been mainly used in reactors for power generation. The possibility of occurrence of thermally fissile members in the chain of neutron-rich uranium isotopes is examined here. The neutron number $N = 162$ or 164 has been predicted to be magic in numerous theoretical studies carried out over the years. The series of uranium isotopes around it with $N = 154-172$ are identified to be thermally fissile on the basis of the fission barrier and neutron separation energy systematics; a manifestation of the close shell nature of $N = 162$ (or 164). We consider here the thermal neutron fission of a typical representative 249U nucleus in the highly neutron-rich region. Semiempirical study of fission barrier height and width shows that 250U nucleus is stable against spontaneous fission due to increase in barrier width arising out of excess neutrons. On the basis of the calculation of the probability of fragment mass yields and the microscopic study in relativistic mean field theory, this nucleus is shown to undergo exotic decay mode of thermal neutron fission (multi-fragmentation fission) whereby a number of prompt scission neutrons are expected to be simultaneously released along with the two heavy fission fragments. Such properties will have important implications in stellar evolution involving -process nucleosynthesis.

  10. Spontaneous fission yields for 246Cm

    International Nuclear Information System (INIS)

    Cumulative yields for 17 fission products in the spontaneous fission of 246Cm have been determined with ?-ray spectrometry. These yields are compared with those determined in the spontaneous fission of 244Cm and 248Cm. (author)

  11. Techniques of fission chamber efficiency calibration

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, S. (Paris-11 Univ., 91 - Orsay (France). Lab. de l' Accelerateur Lineaire); Kaplan, S.N. (California Univ., Berkeley (USA)); Beer, G.A.; Olin, A. (Victoria Univ., British Columbia (Canada))

    1983-10-01

    Multiplate fission chambers were used in experiments at TRIUMF to measure the absolute muon induced fission yield. To determine the yield, the fission chamber detection efficiencies must be known. In this paper, the methods of efficiency calibration have been discussed.

  12. Energy from nuclear fission()

    Science.gov (United States)

    Ripani, M.

    2015-08-01

    The main features of nuclear fission as physical phenomenon will be revisited, emphasizing its peculiarities with respect to other nuclear reactions. Some basic concepts underlying the operation of nuclear reactors and the main types of reactors will be illustrated, including fast reactors, showing the most important differences among them. The nuclear cycle and radioactive-nuclear-waste production will be also discussed, along with the perspectives offered by next generation nuclear assemblies being proposed. The current situation of nuclear power in the world, its role in reducing carbon emission and the available resources will be briefly illustrated.

  13. Study of fission dynamics in fusion–fission reactions

    International Nuclear Information System (INIS)

    Highlights: ? A modified wall and window dissipation was used in Langevin equations. ? Prefission multiplicities of particles were calculated for 200Pb. ? Fission probabilities were calculated for 200Pb and compared with the experimental data. -- Abstract: One-dimensional Langevin equations were applied to study the fission dynamics of compound nucleus 200Pb formed in heavy ion-induced fusion reactions in an intermediate range of excitation energies. A modified wall and window dissipation with a reduction coefficient, ks, has been used in the Langevin equations. The average pre-fission multiplicities of neutrons, light charged particles and fission probabilities were calculated for 200Pb and results compared with the experimental data. It was shown that the results of the calculations are in good agreement with the experimental data of neutron and charged particles (p and alphas) multiplicities and fission probabilities by using values of ks in the range 0.27 ? ks ? 0.48.

  14. Post-scission fission theory: Neutron emission in fission

    Energy Technology Data Exchange (ETDEWEB)

    Madland, D.G.

    1997-11-01

    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 {nu}}{sub 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 {nu}}{sub 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{sub n}), where E{sub 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.

  15. Calculation of the fast fission factor from basic nuclear data

    International Nuclear Information System (INIS)

    Using a two group model the ratio of U238 fissions to U235 fissions, and hence the fast fission factor, ?, is calculated from basic nuclear data in near natural uranium fuelled lattices. Proper account is taken of reflection of fast neutrons from the moderator and of interaction between rods in separate channels. Both these effects are shown to he significant. The calculated fission ratios are compared with the results of a number of experiments in graphite lattices. Agreement is excellent with some 20 metal rod experiments carried out at Harwell and at Brookhaven, the calculated values being within the experimental error for all except the largest rods. Although agreement is not uniformly good with four oxide cluster experiments carried out at Winfrith, the greatest discrepancy amounts to less than 0.3% in ?. (author)

  16. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    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

  17. Disintegration constant of uranium-238 by spontaneous fission redetermined by glass track method

    International Nuclear Information System (INIS)

    The disintegration constant of U238 by spontaneous fission using glass as fission fragment detector was redetermined. A film of natural uranium (UO3) prepared by chemical methods on the glass lamina was used in a long time experience of exposure (about 16 years). The good conditions of sample preparation and storage allow to observe, after chemical etching, fission fragment tracks. (M.C.K.)

  18. Fission throughout the periodic table

    International Nuclear Information System (INIS)

    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

  19. The Fission Time Projection Chamber

    Science.gov (United States)

    Heffner, Mike

    2009-10-01

    New high-precision fission experiments have become a priority within the nuclear energy community due to a growing, world wide, interest in nuclear reactors. In particular, the designs of next generation reactors require reductions in the uncertainties on a number of energy dependent, neutron induced fission cross sections. The fission Time Projection Chamber (fission TPC) is the instrument that has been selected to carry out these challenging cross section measurements. This 6000 pad TPC with 2mm hex pads has a volume of only 2 liters and is filled with a hydrogen working gas. A unique set of electronics have been designed for the TPC that use all off the shelf components to reduce development costs. In this talk, I will show how the TPC will improve previous measurements, the design specifics of the fission TPC and the progress to date.

  20. Fission fragment angular distribution in heavy ion induced fission

    OpenAIRE

    S Soheyli; I Ziaeian

    2006-01-01

      We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a) without neutron correction and b) with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the averag...

  1. Fission fragment angular distribution in heavy ion induced fission

    Directory of Open Access Journals (Sweden)

    S. Soheyli

    2006-06-01

    Full Text Available   We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a without neutron correction and b with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the average emitted neutron from compound nuclei considering the best fit for each system.

  2. The fundamental role of fission during r-process nucleosynthesis in neutron star mergers

    Science.gov (United States)

    Goriely, S.

    2015-02-01

    The rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Despite important efforts, the astrophysical site of the r-process remains unidentified. Here we study r-process nucleosynthesis in a material that is dynamically ejected by tidal and pressure forces during the merging of binary neutron stars. r-process nucleosynthesis during the decompression is known to be largely insensitive to the detailed astrophysical conditions because of efficient fission recycling, producing a composition that closely follows the solar r-abundance distribution for nuclei with mass numbers A > 140. Due to the important role played by fission in such a scenario, the impact of fission is carefully analyzed. We consider different state-of-the-art global models for the determination of the fission paths, nuclear level densities at the fission saddle points and fission fragment distributions. Based on such models, the sensitivity of the calculated r-process abundance distribution is studied. The fission path is found to strongly affect the region of heavy nuclei responsible for the fission recycling, while the fission fragment distribution of nuclei along the A ? 278 isobars defines the abundance pattern of nuclei produced in the 110 ? A ? 170 region. The late capture of prompt fission neutrons is also shown to affect the abundance distribution, and in particular the shape of the third r-process peak around A ? 195.

  3. The fundamental role of fission during r-process nucleosynthesis in neutron star mergers

    Energy Technology Data Exchange (ETDEWEB)

    Goriely, S. [Universite Libre de Bruxelles, Institut d' Astronomie et d' Astrophysique, CP-226, Brussels (Belgium)

    2015-02-01

    The rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Despite important efforts, the astrophysical site of the r-process remains unidentified. Here we study r-process nucleosynthesis in a material that is dynamically ejected by tidal and pressure forces during the merging of binary neutron stars. r-process nucleosynthesis during the decompression is known to be largely insensitive to the detailed astrophysical conditions because of efficient fission recycling, producing a composition that closely follows the solar r-abundance distribution for nuclei with mass numbers A > 140. Due to the important role played by fission in such a scenario, the impact of fission is carefully analyzed. We consider different state-of-the-art global models for the determination of the fission paths, nuclear level densities at the fission saddle points and fission fragment distributions. Based on such models, the sensitivity of the calculated r-process abundance distribution is studied. The fission path is found to strongly affect the region of heavy nuclei responsible for the fission recycling, while the fission fragment distribution of nuclei along the A ? 278 isobars defines the abundance pattern of nuclei produced in the 110 fission neutrons is also shown to affect the abundance distribution, and in particular the shape of the third r-process peak around A ? 195. (orig.)

  4. On prompt fission neutrons

    International Nuclear Information System (INIS)

    Results of calculations of prompt neutron emission characteristics are presented for the spontaneous fission of 252Cf. The average number ?(A) and the average center of mass kinetic energy ?(A) of the neutrons as well as the total neutron spectra are calculated in terms of the fragment mass. The available excitation energies of the fragment pairs are the input data, divided between the fragments by a thermal equilibrium assumption taking into account the equilibrium statistical fluctuations too. The total angular and energy distributions in the laboratory frame are built up of those of the individual fragments. The evaporation calculations show that the high energy behaviour of the spectra is governed rather by the temperatures than by the details of the individual cascade spectrum forms. The experimental data are reproduced by the calculated ones fairly well, so there is no need for assuming existence of additional scission neutrons. (author) 24 refs.; 4 figs

  5. Monte Carlo Based Toy Model for Fission Process

    CERN Document Server

    Kurniadi, R; Viridi, S

    2014-01-01

    Fission yield has been calculated notoriously by two calculations approach, macroscopic approach and microscopic approach. This work will proposes another calculation approach which the nucleus is treated as a toy model. The toy model of fission yield is a preliminary method that use random number as a backbone of the calculation. Because of nucleus as a toy model hence the fission process does not represent real fission process in nature completely. Fission event is modeled by one random number. The number is assumed as width of distribution probability of nucleon position in compound nuclei when fission process is started. The toy model is formed by Gaussian distribution of random number that randomizes distance like between particle and central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. These three points have different Gaussian distribution parameters such as mean ({\\mu}CN, {\\mu}L, {\\mu}R), and standard d...

  6. Comparison of fission signatures from ?- delayed ?-ray and neutron emissions

    Science.gov (United States)

    Cárdenas, E. S.; Reedy, E. T. E.; Seipel, H. A.; Failor, B. H.; Hunt, A. W.

    2015-08-01

    The delayed ?-ray and neutron fission signals utilized in active inspection techniques were measured simultaneously in order to directly compare their detection sensitivities. Fissionable and non-fissionable targets were irradiated by a 15-Hz pulsed bremsstrahlung beam operating at endpoint energies from 7 to 22 MeV. The fissionable mass detection limits for both these signals decreased approximately three orders of magnitude as the irradiation energy was increased with the delayed ?-ray limits 4.3-8.2 times smaller. The signals from the non-fissionable targets were consistent with the natural passive backgrounds for irradiation energies up to 16 MeV. At higher bremsstrahlung energies, there was a target independent active background in the delayed ?-ray signal that accounted for 35% of the gross yield. In addition, these higher irradiation energies resulted in products from 9Be(?,p)8Li and 18O(?,p)17N reactions interfering with the delayed ?-ray and neutron fission signals, respectively.

  7. Gas heating by fission fragments

    Energy Technology Data Exchange (ETDEWEB)

    Karelin, A.V.; Sereda, O.V.; Kharitonov, V.V.; Chikin, K.R.; Naumkin, F.Yu.

    1987-01-01

    The authors describe the use of fission fragments for the direct heating and ionization of gases. The maximum of the ratio of the amount of energy transferred to the gas by fragments to the nonuniformity coefficient of energy release in the gas is used here as the optimization criterion. Parameters are given of heat release nonuniformity and gas heating efficiency in a flat channel. Specific values of the mean free path of fission fragments in different gases are presented. It is found that the optimum conditions of gas heating by fission fragments are not heavily dependent on the law of fragment moderation or on the differences between their initial energies and ranges.

  8. Gas heating by fission fragments

    International Nuclear Information System (INIS)

    The authors describe the use of fission fragments for the direct heating and ionization of gases. The maximum of the ratio of the amount of energy transferred to the gas by fragments to the nonuniformity coefficient of energy release in the gas is used here as the optimization criterion. Parameters are given of heat release nonuniformity and gas heating efficiency in a flat channel. Specific values of the mean free path of fission fragments in different gases are presented. It is found that the optimum conditions of gas heating by fission fragments are not heavily dependent on the law of fragment moderation or on the differences between their initial energies and ranges

  9. Gamma Radiation from Fission Fragments

    International Nuclear Information System (INIS)

    The gamma radiation from the fragments of the thermal neutron fission of 235U 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

  10. The spectroscopy of fission fragments

    International Nuclear Information System (INIS)

    High-resolution measurements on ? 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)

  11. 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.

  12. Diversity and distribution of subterranean bacteria in groundwater at Oklo in Gabon, Africa, as determined by 16S rRNA gene sequencing.

    Science.gov (United States)

    Pedersen, K; Arlinger, J; Hallbeck, L; Pettersson, C

    1996-06-01

    This paper describes how ground water was sampled, DNA extracted, amplified and cloned and how information available in the ribosomal 16S rRNA gene was used for mapping diversity and distribution of subterranean bacteria in groundwater at the Bangombé site in the Oklo region. The results showed that this site was inhabited by a diversified population of bacteria. Each borehole was dominated by species that did not dominate in any of the other boreholes; a result that probably reflects documented differences in the geochemical environment. Two of the sequences obtained were identified at genus level to represent Acinetobacter and Zoogloea, but most of the 44 sequences found were only distantly related to species in the DNA database. The deepest borehole, BAX01 (105 m), had the highest number of bacteria and also total organic carbon (TOC). This borehole harboured only Proteobacteria beta group sequences while sequences related to Proteobacteria beta, gamma and delta groups and Gram-positive bacteria were found in the other four boreholes. Two of the boreholes, BAX02 (34 m) and BAX04 (10 m) had many 16S rRNA gene sequences in common and also had similar counts of bacteria, content of TOC, pH and equal conductivity, suggesting a hydraulic connection between them. PMID:8688960

  13. Pulsed fission/fusion hybrid engines

    International Nuclear Information System (INIS)

    Research into high-thrust, high-specific impulse rocket engines using energy from nuclear reactions which has been conducted at this organization will be discussed. The engines are all conceptual in nature, yet are within the realization of conventional or near-term technology. The engine concepts under study at Foundation, Inc. are designed to obviate or minimize these negative effects of the ORION scheme. By using non-chemical triggers to initiate a non-breakeven fusion reaction at the core of a target composed of both fission and fusion fuel, it should be possible to employ the fusion neutrons thus produced to begin a fission reaction in U-235 or Pu-239. Since the density of the target can be increased by as much as a factor of 250 through compression of the pellet, the amount of fission material necessary to produce a critical mass can be greatly reduced. (This also means that the amount of fission products produced for a giventhrust level is also reduced from the ORION levels.) Coupling this eeffect to the large number of 14 MeV fusion neutrons produced early in the compression process and subsequently to the heating of some additional fusion fuel surrounding the critical mass leads to the very efficient burnup of the target. This insures both high yield from the target as well as low cost per MJ energy released. Finally, the use of such small pellets allows the scale of the energy released to be tailored to a level usable in rocket engines of a few tens of tons thrust level. (orig.)

  14. Natural occurring radioactive substances. Vol. 1

    International Nuclear Information System (INIS)

    Naturally occurring radioactive substances produced by cosmic rays of those of terrestrial origin are surveyed. The different radioactive decay series are discussed. Special emphasis is given to the element radium as regards its properties and distribution in different environmental samples. The properties of naturally occurring k-40 and its distribution in different natural media are also outlined. Induced radionuclides which are formed as a result of the interaction of cosmic rays with the constituents of the atmosphere are mentioned. In this respect the intensity of natural background radiation and the dose at different locations and levels is surveyed. Some regions of exceptionally high radioactivity which result in high exposure rates are mentioned. Monazite deposits and water springs are mentioned in some detail. The Oklo phenomenon as a natural reactor is also discussed. 8 tabs

  15. Background radiation from fission pulses

    Energy Technology Data Exchange (ETDEWEB)

    England, T.R.; Arthur, E.D.; Brady, M.C.; LaBauve, R.J.

    1988-05-01

    Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: /sup 235/U, /sup 238/U, /sup 232/Th, and /sup 239/Pu; these bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For ..beta../sup -/ and ..gamma.. spectra, only /sup 235/U and /sup 239/Pu results are given; fission-product data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total ..beta../sup -/ and ..gamma.. decay energies are included. 27 refs., 47 figs., 9 tabs.

  16. Background radiation from fission pulses

    International Nuclear Information System (INIS)

    Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: 235U, 238U, 232Th, and 239Pu; these bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For ?- and ? spectra, only 235U and 239Pu results are given; fission-product data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total ?- and ? decay energies are included. 27 refs., 47 figs., 9 tabs

  17. Dynamics of cold fission processes

    International Nuclear Information System (INIS)

    The neutron-rich 264 Fm should be the best cold-fissioning nucleus, owing to the strong shell effect of the doubly magic fragments 132 Sn. The optimum cold-fission path in the plane of the two independent shape coordinates, the separation distance R and of the radius of the light fragment R2, is determined. Werner-Wheeler inertia tensor and Yukawa-plus-exponential deformation energy are used to calculate the action integral. Microscopic shell and pairing correction ar based on the asymmetric two-center single-particle model. Different variation laws R2 = R2 (R), for the fission trajectory were tested: polynomials of 2nd, 3rd and 4th degree and an exponential function. The partial half-life for cold fission is estimated to be several orders of magnitude shorter than that of ?-decay. (authors)

  18. Fission hindrance and nuclear viscosity

    Indian Academy of Sciences (India)

    Indranil Mazumdar

    2015-08-01

    We discuss the role of nuclear viscosity in hindering the fission of heavy nuclei as observed in the experimental measurements of GDR -ray spectra from the fissioning nuclei. We review a set of experiments carried out and reported by us previously [see Dioszegi et al, Phys. Rev. C 61, 024613 (2000); Shaw et al, Phys. Rev. C 61, 044612 (2000)] and argue that the nuclear viscosity parameter has no apparent dependence on temperature. However, it may depend upon the deformation of the nucleus.

  19. Composition of fission product mixtures

    International Nuclear Information System (INIS)

    The report gives a compilation of the isotopic composition and specific activity of fission products produced by thermal neutron fission of U-235 and Pu-239. The composition was computed using an electronic computer ES 1040. The presentation comprises data of 27 elements at the end of a neutron irradiation of 3 years and after a time interval of 1, 4 and 10 years after the end of irradiation. (author)

  20. International handling of fissionable material

    International Nuclear Information System (INIS)

    The opinion of the ministry for foreign affairs on international handling of fissionable materials is given. As an introduction a survey is given of the possibilities to produce nuclear weapons from materials used in or produced by power reactors. Principles for international control of fissionable materials are given. International agreements against proliferation of nuclear weapons are surveyed and methods to improve them are proposed. (K.K.)

  1. Modelling isothermal fission gas release

    International Nuclear Information System (INIS)

    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)

  2. Thirty years of nuclear fission in Yugoslavia

    International Nuclear Information System (INIS)

    Experimental nuclear reactor 'RB' in Boris Kidric Institute in Vinca is the first nuclear facility built in Yugoslavia in which the first Yugoslav controlled nuclear fission was achieved thirty years ago on April 26, 1958. Designed by Yugoslav scientist as a bare, natural uranium-heavy water critical assembly, the 'RB' reactor has survived a series of modifications trying to follow directions of contemporary nuclear research. The actual 'RB' reactor technical characteristics and experimental possibilities are described. The modifications are underlined, the experience gained and plans for future are presented. A brief review of reactor operation and experiments performed is shown. (author)

  3. Fission fragment angular distributions and fission cross section validation

    International Nuclear Information System (INIS)

    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 238U and 232Th have been investigated up to 100 MeV in a single experiment. The n-TOF Collaboration performed the fission cross section measurement of several actinides (232Th, 235U, 238U, 234U, 237Np) 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 232Th, 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 232Th 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 237Np 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 237Np. This sphere was surrounded by enriched uranium 235U so as to approach criticality with fast neutrons. The simulation predicts a multiplication factor keff in better agreement with the experiment (the deviation of 750 pcm is reduced to 250 pcm) when we replace the ENDF/B- VII.0 evaluation of the 237Np fission cross section by the n-TOF data. We also explore the hypothesis of deficiencies of the inelastic cross section in 235U which has been invoked by some authors to explain the deviation of 750 pcm. The large distortion that should be applied to the inelastic cross sections in order to reconcile the critical experiment with its simulation is incompatible with existing measurements. Also we show that the ?-bar of 237Np can hardly be incriminated because of the high accuracy of the existing data. Fission rate ratios or averaged fission cross sections measured in several fast neutron fields seem to give contradictory results on the validation of the 237Np cross section but at least one of the benchmark experiments, where the active deposits have been well calibrated for the number of atoms, favors the n-TOF data set. These outcomes support the hypothesis of a higher fission cross section of 237Np. (author)

  4. Relative quantifying technique to measure mass of fission plate in a fission chamber

    International Nuclear Information System (INIS)

    Under the same neutron radiation conditions, fission counts are proportional to the number of fission nuclei. Based on this concept, a relative quantifying method has been developed to measure the mass of fission plate in fission chamber on a 14 MeV accelerator neutron source at the Neutron Physics Laboratory, INPC, CAEP. The experimental assembly was introduced and mass of the fission material in several fission chambers was measured. The results by this method agree well (within 1%) with the ?-quantifying method. Therefore, it is absolutely feasible to quantify the fission plate mass in fission chambers. The measurement uncertainty is 2%-4%. (authors)

  5. Event-by-event study of neutron observables in spontaneous and thermal fission

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, R; Randrup, J

    2011-09-14

    The event-by-event fission model FREYA is extended to spontaneous fission of actinides and a variety of neutron observables are studied for spontaneous fission and fission induced by thermal neutrons with a view towards possible applications for SNM detection. We have shown that event-by-event models of fission, such as FREYA, provide a powerful tool for studying fission neutron correlations. Our results demonstrate that these correlations are significant and exhibit a dependence on the fissioning nucleus. Since our method is phenomenological in nature, good input data are especially important. Some of the measurements employed in FREYA are rather old and statistics limited. It would be useful to repeat some of these studies with modern detector techniques. In addition, most experiments made to date have not made simultaneous measurements of the fission products and the prompt observables, such as neutron and photons. Such data, while obviously more challenging to obtain, would be valuable for achieving a more complete understanding of the fission process.

  6. Systematics of fusion-fission time scales

    International Nuclear Information System (INIS)

    New pre-scission neutron multiplicity (?/sub pre/) data for 7Li-, 16O-, and 20Ne-induced fission are presented, spanning a fissility range from 0.60 to 0.85. Fission time scales have been deduced for two extreme assumptions regarding the mean excitation energy during fission. It is found for fusion-fission reactions that the fission time scale is independent of fissility, within a factor 1.5. A comparison of time scales deduced from ?/sub pre/ measurements for fast-fission with quasifission time- scales deduced from the rotation angle of the composite system allows a minimum fusion-fission time scale of 30 x 10/sup -21/ s to be determined. For the most fissile system, fast-fission (fission without barrier) is shown to be up to three times faster than fusion-fission. Using a model to interpret the fusion-fission time scales, it is concluded that motion in the fission direction is strongly overdamped. This means that the dynamics of fission are dominated by a slow diffusion towards scission, and not by the potential energy surface. It is shown that such a picture can explain the observed lack of dependence of the fission time scale on fissility

  7. Fission product solvent extraction

    International Nuclear Information System (INIS)

    Two main objectives concerning removal of fission products from high-level tank wastes will be accomplished in this project. The first objective entails the development of an acid-side Cs solvent-extraction (SX) process applicable to remediation of the sodium-bearing waste (SBW) and dissolved calcine waste (DCW) at INEEL. The second objective is to develop alkaline-side SX processes for the combined removal of Tc, Cs, and possibly Sr and for individual separation of Tc (alone or together with Sr) and Cs. These alkaline-side processes apply to tank wastes stored at Hanford, Savannah River, and Oak Ridge. This work exploits the useful properties of crown ethers and calixarenes and has shown that such compounds may be economically adapted to practical processing conditions. Potential benefits for both acid- and alkaline-side processing include order-of-magnitude concentration factors, high rejection of bulk sodium and potassium salts, and stripping with dilute (typically 10 mM) nitric acid. These benefits minimize the subsequent burden on the very expensive vitrification and storage of the high-activity waste. In the case of the SRTALK process for Tc extraction as pertechnetate anion from alkaline waste, such benefits have now been proven at the scale of a 12-stage flowsheet tested in 2-cm centrifugal contactors with a Hanford supernatant waste simulant. SRTALK employs a crown ether in a TBP-modified aliphatic kerosene diluent, is economically competitive with other applicable separation processes being considered, and has been successfully tested in batch extraction of actual Hanford double-shell slurry feed (DSSF)

  8. Sequential Detection of Fission Processes for Harbor Defense

    Energy Technology Data Exchange (ETDEWEB)

    Candy, J V; Walston, S E; Chambers, D H

    2015-02-12

    With the large increase in terrorist activities throughout the world, the timely and accurate detection of special nuclear material (SNM) has become an extremely high priority for many countries concerned with national security. The detection of radionuclide contraband based on their ?-ray emissions has been attacked vigorously with some interesting and feasible results; however, the fission process of SNM has not received as much attention due to its inherent complexity and required predictive nature. In this paper, on-line, sequential Bayesian detection and estimation (parameter) techniques to rapidly and reliably detect unknown fissioning sources with high statistical confidence are developed.

  9. Measurement of fission gas release from irradiated nuclear fuel elements

    International Nuclear Information System (INIS)

    A fission gas measurement system for the analysis of released gases from MOX and PHWR fuels has been designed, fabricated and commissioned in the hot cells of Post Irradiation Examination Division of Bhabha Atomic Research Centre, Mumbai. The system was used for the measurement of fission gases released from natural UO2 fuels and ThO2 fuels from PHWRs. The burnups of these fuels ranged from 2 GWD/TeU to 15 GWD/TeU. Some of the results from PHWR fuel elements from Kakrapar Atomic Power Station are presented in the paper, to highlight the utility of the system. (author)

  10. Assessment of fissionable material behaviour in fission chambers

    Science.gov (United States)

    Cabellos, O.; Fernández, P.; Rapisarda, D.; García-Herranz, N.

    2010-06-01

    A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module. In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation.

  11. Assessment of fissionable material behaviour in fission chambers

    International Nuclear Information System (INIS)

    A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module. In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation.

  12. Neutron emission prior to fission

    International Nuclear Information System (INIS)

    In recent years, many groups have measured neutrons and light charged particles in coincidence with fission fragments in heavy ion reactions. In most cases, particles emitted with an energy spectrum and angular distribution characteristic of that of compound nucleus evaporation have been measured in excess of statistical model predictions. They have chosen to investigate this effect in detail by studying neutron emission in the 158Er composite system. The advantage of this system is that it can be produced by a variety of projectile target combinations. They have chosen four combinations which form 158Er with similar critical angular momenta but varying excitation energy. The rationale is to form the same system with different neutron emission times; if the enhanced neutrons are being emitted during the fission process, the different emission time scales might possibly be used to time the fission process. In addition, they impose an additional constraint - that they have a significant fission barrier for most of the partial waves involved in the fission process. The reactions they have selected are 16O + 142Nd (207 MeV beam energy), 24Mg + 134Ba (180 MeV), 32S + 126Te (180 MeV), 50Ti + 108Pd (216 MeV)

  13. Reference reactor module for NASA's lunar surface fission power system

    International Nuclear Information System (INIS)

    Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. The AFSPS concept is now being further developed within the Fission Surface Power (FSP) Project, which is a near-term technology program to demonstrate system-level TRL-6 by 2013. This paper describes the reference FSP reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on the lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based. UO2-fueled, pumped-NaK fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. The ultimate goal of this work is to provide a 'workhorse' power system that NASA can utilize in near-term and future Lunar and Martian mission architectures, with the eventual capability to evolve to very high power, low mass systems, for either surface, deep space, and/or orbital missions.

  14. Change over from compound nuclear fission to quasi-fission

    Directory of Open Access Journals (Sweden)

    Bhattacharya P.

    2010-03-01

    Full Text Available Fission fragment mass distribution has been measured in two reactions to populate compound nucleus 246Bk. Both the target nuclei were deformed. However, entrance channel mass asymmetry of the two systems was on the either side of the Businaro Gallone mass asymmetry parameter. Near the Coulomb barrier, at similar excitation energies, the width of the fission fragment mass distribution was found to be significantly different for the 14N+232Th reaction compared to the 11B+235U reaction. The entrance channel mass asymmetry was found to play a significant role in deciding the fusion process.

  15. 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

  16. Measurements of the effective range of fission fragments in UO2 and the disintegration constant for spontaneous fission of 238U

    International Nuclear Information System (INIS)

    The results of measuments of the disintegration constant for spontaneous fission in 238U are presented, with a discussion on the method used for the detection of fission tracks in muscovite mica. Samples of muscovite mica sandwiched between two natural uranium dioxide cylinders were irradiated with fragments of spontaneous fission and the etched tracks counted with projetion optical microscope. The effective thickness of the UO2 layer which contributed to the observed tracks was measured through irradiation of mica samples, in contact with the UO2 cylinder with 14,0 MeV neutrons from a (d,t) reaction. (Author)

  17. Report of fission study meeting

    International Nuclear Information System (INIS)

    This book is the report of fission Study Meeting held from September 19 to 21, 1985 in the Research Center for Nuclear Physics, Osaka University. The objective of this study meeting was to stimulate the research on nuclear physics in Japan, which began to show new development accompanying the advance of the research on heavy ion nuclear reaction, and to make this a new starting point. More than 50 participants from physical, chemical and engineering fields, who have interest in the theory and experiment related to nuclear fission, gathered, and the meeting was a success beyond expectation. The contents covered a wide range including nuclear smashing reaction as well as nuclear fission in a narrow sense. In this book, the gists of 28 papers are collected. (Kako, I.)

  18. Terracentric Nuclear Fission Reactor: Background, Basis, Feasibility, Structure, Evidence, and Geophysical Implications

    OpenAIRE

    Herndon, J. Marvin

    2013-01-01

    The background, basis, feasibility, structure, evidence, and geophysical implications of a naturally occurring Terracentric nuclear fission georeactor are reviewed. For a nuclear fission reactor to exist at the center of the Earth, all of the following conditions must be met: (1) There must originally have been a substantial quantity of uranium within Earth's core; (2) There must be a natural mechanism for concentrating the uranium; (3) The isotopic composition of the uraniu...

  19. Characterization of Samples with Spontaneously Fissioning Isotopes

    International Science & Technology Center (ISTC)

    Development of the Method for Characterization of the Samples, Containing Spontaneously Fissioning Radionuclides, by Measuring Fission Products Gamma-Radiation (for the System of NM Control and Accountability of the Federal State Unitarian Enterprise "PA"Mayak")

  20. Fission-gas release from UO2

    International Nuclear Information System (INIS)

    An overview is given of the present state of knowledge of fission-gas release from UO2. Topics covered include fission-gas formation and behaviour, release models, experimental methods and release-affecting parameters. (author)

  1. Gamma and alpha compensated fission chamber

    Energy Technology Data Exchange (ETDEWEB)

    Thurlow, N.C. II

    1978-01-31

    A fission chamber neutron detector is described which is both gamma and alpha compensated. The alpha compensation is provided by inclusion of a low neutron cross section, alpha particle emissive isotope within the gamma compensation portion of the fission chamber.

  2. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    This is the 12th issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the 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 type 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 lumped fission product data (decay heat, absorption etc.). The first part of the report consists of unaltered original contributions which the authors have sent to IAEA/NDS. The second part contains recent references relative to fission product nuclear data, which were not covered by the contributions submitted, and selected papers from conferences

  3. Velocity fluctuations of fission fragments

    CERN Document Server

    Llanes-Estrada, Felipe J; Martinez, Jose L Muñoz

    2015-01-01

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramer-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

  4. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  5. The VERDI fission fragment spectrometer

    OpenAIRE

    Frégeau M.O.; Bry? T.; Gamboni Th.; Geerts W; Oberstedt S.; Oberstedt A.; Borcea R.

    2013-01-01

    The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF) technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This conf...

  6. Spontaneous fission of superheavy nuclei

    Indian Academy of Sciences (India)

    R A Gherghescu; D N Poenaru

    2015-09-01

    The macroscopic–microscopic method is extended to calculate the deformation energy and penetrability for binary nuclear configurations typical for fission processes. The deformed two-centre shell model is used to obtain single-particle energy levels for the transition region of two partially overlapped daughter and emitted fragment nuclei. The macroscopic part is obtained using the Yukawa-plus-exponential potential. The microscopic shell and pairing corrections are obtained using the Strutinsky and BCS approaches and the cranking formulae yield the inertia tensor. Finally, the WKB method is used to calculate penetrabilities and spontaneous fission half-lives. Calculations are performed for the decay of 282,292120 nuclei.

  7. The wastes of nuclear fission

    International Nuclear Information System (INIS)

    In this paper the author presents the problems of the radioactive wastes generated by the nuclear fission. The first part devoted to the fission phenomenon explains the incident neutron energy and the target nuclei role. The second part devoted to the nuclear wastes sources presents the production of wastes upstream of the reactors, in the reactors and why these wastes are dangerous. The third part discusses the radioactive wastes management in France (classification, laws). The last part details the associated research programs: the radionuclides separation, the disposal, the underground storage, the transmutation and the thorium cycle. (A.L.B.)

  8. Atomic collisions and fission technology

    International Nuclear Information System (INIS)

    Atomic physics aspects of fission technology are discussed, in particular, isotope enrichment and the slowing down of fission products, neutrons, etc., which leads to radiation damage and heating (and ultimately to power generation). Selective laser excitation of atoms or molecules promises to be a more efficient means of isotope separation than previous methods. Neutron radiation effects can be simulated in much less time by charged-particle transport. Problems in electronic and nuclear stopping of ions are reviewed. Energy loss spectra and stopping power for I ions are shown. 7 figs

  9. Fission Yields in the Iodine Region

    International Nuclear Information System (INIS)

    Independent yields of all iodine isotopes from l118 to I134 except I122 (short-lived), I127(stable) and I129(long-lived) resulting from irradiating natural uranium with 590-MeV and 19-GeV protons have been measured. In addition, cross-sections (mostly cumulative) of many xenon and tellurium isotopes have been obtained. In the experiments extensive use has been made of an electromagnetic isotope separator, constructed at CERN for nuclear reaction studies, by which the iodine (or tellurium) isotopes were separated from samples chemically isolated from the irradiated targets. In the study of xenon isotopes the uranium target was heated in a small oven connected to the separator via a cold trap to stop unwanted activities. After the separation, the activity of the samples was measured by counting methods. In certain cases (I118, I119, I120,I121, Xe118, Xe119, Xe120, Xe121) spectroscopic investigations were performed to provide information for the conversion of the counting data to absolute counting-rates needed for the determination of the fission yields. The experiments show a significant shift in the isotopic cross-section distribution when the 19-GeV results are compared with those obtained at the lower irradiation energy. The yields far out ai the neutron-deficient wing increase considerably whereas the other part of the distribution is depressed. A comparison with spallation data indicates that the neutron-deficient part of the distribution might result from the spallation of uranium. Spallation gives negligible yields in the iodine regional 590 MeV, but at 19 GeV these cross-sections a re expected to be much larger. The competition with spallation decreases the probability for fission, and consequently the yields of the fission products will decrease. (author)

  10. Nuclear fission in covariant density functional theory

    CERN Document Server

    Afanasjev, A V; Ring, P

    2013-01-01

    The current status of the application of covariant density functional theory to microscopic description of nuclear fission with main emphasis on superheavy nuclei (SHN) is reviewed. The softness of SHN in the triaxial plane leads to an emergence of several competing fission pathes in the region of the inner fission barrier in some of these nuclei. The outer fission barriers of SHN are considerably affected both by triaxiality and octupole deformation.

  11. Collective spectra along the fission barrier

    OpenAIRE

    Pigni M.T.; Andreev A.V.; Shneidman T. M.; Massimi C.; Vannini G.; Ventura A.

    2012-01-01

    Discrete and continuous spectra of fissioning nuclei at the humps of fission barriers (Bohr transition states) and in the intermediate wells (superdeformed and hyperdeformed states) play a key role in the calculation of fission cross sections. A theoretical evaluation of the collective parts of the spectra is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two–cluster co...

  12. Non-equilibrium processes in Heavy-ion induced Fission Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, R K; Thomas, R G, E-mail: rkc@barc.gov.in [Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai - 400085 (India)

    2011-02-01

    Heavy ion induced reactions offer a wide range of possibilities in exploring the collective behavior of nuclei and nuclear processes. Recent years have seen a spurt in the experimental and theoretical studies to understand the mechanism of the fission process in heavy target projectile systems, arising from the interest to produce elements in the superheavy region. A number of new features are observed experimentally with respect to the kinetic energy, mass and angular distributions of fission fragments and their correlations, implying prevalence of non-equilibrium phenomena in the fission process in many target projectile systems. There are many theoretical attempts both in terms of static potential energy considerations and dynamics to understand the important degrees of freedom that govern the evolution of the nuclear system from initial interaction to the final fission stages. Depending on the degree and nature of equilibration, various processes such as fast-fission, quasi-fission and pre-equilibrium fission have been invoked that can compete with the fully equilibrated compound nuclear fission process. In what we call a C-T Fissility plot, we show the remarkable dependence of the onset of these non-equilibrium processes on the entrance channel parameters.

  13. Ceramic Hosts for Fission Products Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Peter C Kong

    2010-07-01

    Natural spinel, perovskite and zirconolite rank among the most leach resistant of mineral forms. They also have a strong affinity for a large number of other elements and including actinides. Specimens of natural perovskite and zirconolite were radioisotope dated and found to have survived at least 2 billion years of natural process while still remain their loading of uranium and thorium . Developers of the Synroc waste form recognized and exploited the capability of these minerals to securely immobilize TRU elements in high-level waste . However, the Synroc process requires a relatively uniform input and hot pressing equipment to produce the waste form. It is desirable to develop alternative approaches to fabricate these durable waste forms to immobilize the radioactive elements. One approach is using a high temperature process to synthesize these mineral host phases to incorporate the fission products in their crystalline structures. These mineral assemblages with immobilized fission products are then isolated in a durable high temperature glass for periods measured on a geologic time scale. This is a long term research concept and will begin with the laboratory synthesis of the pure spinel (MgAl2O4), perovskite (CaTiO3) and zirconolite (CaZrTi2O7) from their constituent oxides. High temperature furnace and/or thermal plasma will be used for the synthesis of these ceramic host phases. Nonradioactive strontium oxide will be doped into these ceramic phases to investigate the development of substitutional phases such as Mg1-xSrxAl2O4, Ca1-xSrxTiO3 and Ca1-xSrxZrTi2O7. X-ray diffraction will be used to establish the crystalline structures of the pure ceramic hosts and the substitution phases. Scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) will be performed for product morphology and fission product surrogates distribution in the crystalline hosts. The range of strontium doping is planned to reach the full substitution of the divalent metal ions, Mg and Ca, in the ceramic host phases. The immobilization of rear earth (lanthanide series) fission products in these ceramic host phases will also be studied this year. Cerium oxide is chosen to represent the rear earth fission product for substitution studies in spinel, perovskite and zirconolite ceramic hosts. Cerium has +3 and +4 oxidation states and it can replace some of the trivalent or tetravalent host ions to produce the substitution ceramics such as MgAl2-xCexO4, CaTi1-xCexO3, CaZr1-xCexTi2O7 and CaZrTi2-xCexO7. X-ray diffraction analysis will be used to compare the crystalline structures of the pure ceramic hosts and the substitution phases. SEM-EDX analysis will be used to study the Ce distribution in the ceramic host phases. The range of cerium doping is planned to reach the full substitution of the trivalent or tetravalent ions, Al, Ti and Zr, in the ceramic host phases.

  14. Search for singlet fission chromophores.

    Czech Academy of Sciences Publication Activity Database

    Havlas, Zden?k; Akdag, Akin; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, Josef

    Philadelphia : American Chemical Society, 2012. 31PHYS. ISSN 0065-7727. [National Fall Meeting of the American Chemical Society /244./. 19.08.2012-23.08.2012, Philadelphia] Institutional support: RVO:61388963 Keywords : singlet fission * chromophores Subject RIV: CF - Physical ; Theoretical Chemistry

  15. How spontaneous fission was discovered

    International Nuclear Information System (INIS)

    The 70th anniversary of the discovery of spontaneous fission by the young Russian physicists Konstantin A. Petrzhak and Georgii N. Flerov is commemorated. The situation in the 1940s is described and the activities of the 2 scientists, including their involvement in the development of the A-bomb, is outlined. (P.A.)

  16. Brownian shape dynamics in fission

    Directory of Open Access Journals (Sweden)

    Randrup Jørgen

    2013-12-01

    Full Text Available It was recently shown that remarkably accurate fission-fragment mass distributions are obtained by treating the nuclear shape evolution as a Brownian walk on previously calculated five-dimensional potentialenergy surfaces; the current status of this novel method is described here.

  17. Intrinsic energy partition in fission

    International Nuclear Information System (INIS)

    The intrinsic energy partition between the 2 complementary fission fragments is investigated microscopically. The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with 2 conditions. One of them fixes the number of particles and the other one separates the pairing active spaces associated with the 2 fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234U parent nucleus. It is not possible to extract directly the energy partition from experimental data. Nevertheless, the main de-excitation process is the neutron evaporation. Therefore, indirect information can be obtained from neutron multiplicities, for which accurate results are available in literature. The excitation energy of each fragment can be computed and it is shown that several experimental features are reproduced by theoretical data. The deeply minimum in the neutron multiplicity occurs close to the mass of the doubly magic nucleus 132Sn. A maximal value of the neutron multiplicity is obtained for the mass 116, that is in the symmetric fission region. In general, the excitation energy of the light fragment is larger than that of the heavy one. As for neutron multiplicities, excepting the strong fluctuations related to the large mass asymmetries, the results agree qualitatively well with the experimental data. It is a first microscopic description of the intrinsic energy partition in a wide range of fission channels that succeed to reproduce the main behavior of the neutron multiplicities

  18. Fission of rapidly rotating fluid systems

    International Nuclear Information System (INIS)

    Progress in understanding of the problem of fissional breakup of an equilibrium fluid system through the growth of dynamical distortional instabilities caused by rapid rotation is reviewed. Classic results on equilibrium states, stability, and routes to fission are reviewed, and the equilibrium states of uniformly rotating incompressible fluids, uniformly rotating polytropes, differentially rotating polytropes, rotating isothermal gas clouds, and nonisentropic fluids are discussed in detail. The Bardeen, Friedman, Schutz, and Sorkin (1977) criterion for linear stability in fission modes is considered along with the generic instability of rotating bodies and linear stability of fission modes in hydrodynamic simulations of fission are described in detail

  19. Space Fission Propulsion System Development Status

    Science.gov (United States)

    Houts, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Williams, Eric; Harper, Roger; Salvail, Pat; Hrbud, Ivana; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    The world's first man-made self-sustaining fission reaction was achieved in 1942. Since then fission has been used to propel submarines, generate tremendous amounts of electricity, produce medical isotopes, and provide numerous other benefits to society. Fission systems operate independently of solar proximity or orientation, and are thus well suited for deep spare or planetary surface missions. In addition, the fuel for fission systems (enriched uranium) is virtually non-radioactive. The primary safety issue with fission systems is avoiding inadvertent system start - addressing this issue through proper system design is straightforward. Despite the relative simplicity and tremendous potential of space fission systems, the development and utilization of these systems has proven elusive. The first use of fission technology in space occurred 3 April 1965 with the US launch of the SNAP-10A reactor. There have been no additional US uses of space fission system. While space fission system were used extensively by the former Soviet Union, their application was limited to earth-orbital missions. Early space fission systems must be safely and affordably utilized if Ae are to reap the benefits of advanced space fission systems.

  20. Fission yield studies at the IGISOL facility

    International Nuclear Information System (INIS)

    Low-energy-particle-induced fission is a cost-effective way to produce neutron-rich nuclei for spectroscopic studies. Fission has been utilized at the IGISOL to produce isotopes for decay and nuclear structure studies, collinear laser spectroscopy and precision mass measurements. The ion guide technique is also very suitable for the fission yield measurements, which can be performed very efficiently by using the Penning trap for fission fragment identification and counting. The proton- and neutron-induced fission yield measurements at the IGISOL are reviewed, and the independent isotopic yields of Zn, Ga, Rb, Sr, Cd and In in 25MeV deuterium-induced fission are presented for the first time. Moving to a new location next to the high intensity MCC30/15 light-ion cyclotron will allow also the use of the neutron-induced fission to produce the neutron rich nuclei at the IGISOL in the future. (orig.)

  1. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    This is the eleventh 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 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 main part of this report consists of unaltered original contributions which the authors have sent to IAEA/NDS

  2. Fission dynamics at low excitation energy

    CERN Document Server

    Aritomo, Y

    2013-01-01

    The origin of mass asymmetry in the fission of uranium at a low excitation energy is clarified by a trajectory analysis of the Langevin equation. The positions of the peaks in the mass distribution of fission fragments are mainly determined by fission saddle points originating from the shell correction energy. The widths of the peaks, on the other hand, result from a shape fluctuation around the scission point caused by the random force in the Langevin equation. We found that a random vibration in the oblate direction of fissioning fragments is essential for the fission process. According to this picture, fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup. This is expected to lead to a new viewpoint of fission dynamics and the splitting mechanism.

  3. Experimental study of three-component structure of mass-energy distribution of fission fragments in the vicinity of Pb

    International Nuclear Information System (INIS)

    Measurements and regression analysis of mass-energy distributions of fragments from 213At, 210Po, and 205Bi fission have been made. The results have proved three-component structure of fragment kinetic energy spectra. The nature of the phenomenon and its similarity to recently observed bimodal spontaneous fission of nuclei in the vicinity of Fm are discussed

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

    International Nuclear Information System (INIS)

    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 235U. 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

  5. Sustainable and safe nuclear fission energy technology and safety of fast and thermal nuclear reactors

    CERN Document Server

    Kessler, Günter

    2012-01-01

    Unlike existing books of nuclear reactor physics, nuclear engineering and nuclear chemical engineering this book covers a complete description and evaluation of nuclear fission power generation. It covers the whole nuclear fuel cycle, from the extraction of natural uranium from ore mines, uranium conversion and enrichment up to the fabrication of fuel elements for the cores of various types of fission reactors. This is followed by the description of the different fuel cycle options and the final storage in nuclear waste repositories. In addition the release of radioactivity under normal and possible accidental conditions is given for all parts of the nuclear fuel cycle and especially for the different fission reactor types.

  6. The decay modes of heavy excited nuclei: from binary fission to multifragmentation

    International Nuclear Information System (INIS)

    The decay modes of heavy excited nuclei formed in dissipative collisions for the systems Ar+Au at 60 MeV/u and Kr+Au at 43 MeV/u are studied. A transition from binary fission towards multi-fragment emission is observed around 3 MeV/u excitation energy, independently of the considered system. The charge distributions of the three target-emitted fragments suggest a smooth change from fission events (as a ''natural'' continuity of binary fission) to ''residue protection'' then to ''symmetric ternary fragmentation'' events when the excitation energy increases from 3 MeV/u to 5 MeV/u. (authors). 2 figs

  7. Assembly for fission product transmutation

    International Nuclear Information System (INIS)

    99Tc rods, as fission products, are loaded into fuel cans at the outermost circumference, and 99rods or zirconium hydride (ZrH1.6) as a compound containing hydrogen atoms are loaded into fuel cans at the central portion. Fast neutrons generated in the core of the FBR type reactor are moderated and transmuted into slow neutrons. 99Tc causes capturing reaction by the slow neutrons and is transmuted into 100Tc. Then, 100Tc is transmuted into 100Ru immediately. 100Ru is a stable element. Then, 99Tc can effectively be annihilated. The similar effect can be obtained by using 93Zr or 129I as fission products. Further, the same effect can be obtained by using yttrium hydride or calcium hydride as the compounds containing hydrogen atoms for moderating neutrons. (I.N.)

  8. A brief history of the ''Delayed'' discovery of nuclear fission

    International Nuclear Information System (INIS)

    This year marks the Fiftieth Anniversary of the discovery of Nuclear Fission. In the early 1930's, the neutron was discovered, followed by the discovery of artificial radioactivity and then the use of the neutron to produce artificial radioactivity. The first experiments resulting in the fission of uranium took place in 1934. A paper which speculated on fission as an explanation was almost immediately published, yet no one took it seriously not even the author herself. Why did it take an additional five years before anyone realized what had occurred? This is an abnormally long time in a period when discoveries, particularly in nuclear physics, seemed to be almost a daily occurrence. The events which led up to the discovery are recounted, with an attempt made to put them into their historical perspective. The role played by Mendeleev's Periodic Table, the role of the natural radioactive decay chain of uranium, the discovery of protactinium, the apparent discovery of masurium (technetium) and a speculation on the reason why Irene Curie may have missed the discovery of nuclear fission will all be discussed. 43 refs

  9. Monte Carlo based toy model for fission process

    International Nuclear Information System (INIS)

    There are many models and calculation techniques to obtain visible image of fission yield process. In particular, fission yield can be calculated by using two calculations approach, namely macroscopic approach and microscopic approach. This work proposes another calculation approach in which the nucleus is treated as a toy model. Hence, the fission process does not represent real fission process in nature completely. The toy model is formed by Gaussian distribution of random number that randomizes distance like the distance between particle and central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. These three points have different Gaussian distribution parameters such as mean (?CN, ?L, ?R), and standard deviation (?CN, ?L, ?R). By overlaying of three distributions, the number of particles (NL, NR) that are trapped by central points can be obtained. This process is iterated until (NL, NR) become constant numbers. Smashing process is repeated by changing ?L and ?R, randomly

  10. Sexual differentiation in fission yeast

    DEFF Research Database (Denmark)

    Egel, R; Nielsen, O; Weilguny, D; Nielsen, Olaf

    1990-01-01

    The regulation of sexual reproduction in yeast constitutes the highest level of differentiation observed in these unicellular organisms. The various ramifications of this system involve DNA rearrangement, transcriptional control, post-translational modification (such as protein phosphorylation) and receptor/signal processing. A few basic similarities are common to both fission and budding yeasts. The wiring of the regulatory circuitry, however, varies considerably between these divergent yeast g...

  11. The VERDI fission fragment spectrometer

    Directory of Open Access Journals (Sweden)

    Frégeau M.O.

    2013-12-01

    Full Text Available The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.

  12. Fission fusion hybrids- recent progress

    Science.gov (United States)

    Kotschenreuther, M.; Valanju, P.; Mahajan, S.; Covele, B.

    2012-03-01

    Fission-fusion hybrids enjoy unique advantages for addressing long standing societal acceptability issues of nuclear fission power, and can do this at a much lower level of technical development than a competitive fusion power plant- so it could be a nearer term application. For waste incineration, hybrids can burn intransigent transuranic residues (with the long lived biohazard) from light water reactors (LWRs) with far fewer hybrid reactors than a comparable system within the realm of fission alone. For fuel production, hybrids can produce fuel for ˜4 times as many LWRs with NO fuel reprocessing. For both waste incineration or fuel production, the most severe kind of nuclear accident- runaway criticality- can be excluded, unlike either fast reactors or typical accelerator based reactors. The proliferation risks for hybrid fuel production are, we strongly believe, far less than any other fuel production method, including today's gas centrifuges. US Thorium reserves could supply the entire US electricity supply for centuries. The centerpiece of the fuel cycle is a high power density Compact Fusion Neutron Source (major+minor radius ˜ 2.5-3.5 m), which is made feasible by the super-X divertor.

  13. Deep-Earth reactor: Nuclear fission, helium, and the geomagnetic field

    OpenAIRE

    Hollenbach, D. F.; Herndon, J M

    2001-01-01

    Geomagnetic field reversals and changes in intensity are understandable from an energy standpoint as natural consequences of intermittent and/or variable nuclear fission chain reactions deep within the Earth. Moreover, deep-Earth production of helium, having 3He/4He ratios within the range observed from deep-mantle sources, is demonstrated to be a consequence of nuclear fission. Numerical simulations of a planetary-scale geo-reactor were made by using the SCALE seq...

  14. Fission, fusion and the energy crisis. 2. ed.

    International Nuclear Information System (INIS)

    The subject is covered in chapters, entitled: living on capital (energy reserves and consumption forecasts); the atom and its nucleus, mass and energy; fission and the bomb; the natural uranium reactor; enriched reactors; control and safety; long-term economics (the breeder reactions and nuclear fuel reserves); short-term economics (cost per kilowatt hour); national nuclear power programmes; nuclear power and the environment (including reprocessing, radioactive waste management, public relations); renewable energy sources; the fusion programme; summary and comment. (U.K.)

  15. International conference on fifty years research in nuclear fission

    International Nuclear Information System (INIS)

    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)

  16. New achievements in nuclear fission physics

    International Nuclear Information System (INIS)

    A few recently observed new effects in nuclear fission are reviewed from the experimental side and theoretical explanations are indicated: 1) The structures in the mass yields and in the maximum fragment kinetic energies in cold fission are due to Coulomb effects; 2) Mass-symmetric fission of even-even nuclei does not proceed by splitting the nucleus into two equal parts and the fragments are differently deformed; 3) The dip in the total fragment kinetic energy at symmetry is due to a different symmetrical fission barrier; 4) In analogy to the cold compact fission events with highest kinetic energy, also those events of lowest kinetic energy but highest deformation are cold at the scission point; 5) Cold fission proceeds close to the saddle point

  17. MODELING AND FISSION CROSS SECTIONS FOR AMERICIUM.

    Energy Technology Data Exchange (ETDEWEB)

    ROCHMAN, D.; HERMAN, M.; OBLOZINSKY, P.

    2005-05-01

    This is the final report of the work performed under the LANL contract on the modeling and fission cross section for americium isotopes (May 2004-June 2005). The purpose of the contract was to provide fission cross sections for americium isotopes with the nuclear reaction model code EMPIRE 2.19. The following work was performed: (1) Fission calculations capability suitable for americium was implemented to the EMPIRE-2.19 code. (2) Calculations of neutron-induced fission cross sections for {sup 239}Am to {sup 244g}Am were performed with EMPIRE-2.19 for energies up to 20 MeV. For the neutron-induced reaction of {sup 240}Am, fission cross sections were predicted and uncertainties were assessed. (3) Set of fission barrier heights for each americium isotopes was chosen so that the new calculations fit the experimental data and follow the systematics found in the literature.

  18. Radiochemical studies on nuclear fission at Trombay

    Indian Academy of Sciences (India)

    Asok Goswami

    2015-08-01

    Since the discovery of nuclear fission in the year 1939, both physical and radiochemical techniques have been adopted for the study of various aspects of the phenomenon. Due to the ability to separate individual elements from a complex reaction mixture with a high degree of sensitivity and selectivity, a chemist plays a significant role in the measurements of mass, charge, kinetic energy, angular momentum and angular distribution of fission products in various fissioning systems. At Trombay, a small group of radiochemists initiated the work on radiochemical studies of mass distribution in the early sixties. Since then, radiochemical investigations on various fission observables have been carried out at Trombay in , , and heavy-ion-induced fissions. An attempt has been made to highlight the important findings of such studies in this paper, with an emphasis on medium energy and heavy-ion-induced fission.

  19. Collective spectra along the fission barrier

    Directory of Open Access Journals (Sweden)

    Pigni M. T.

    2012-12-01

    Full Text Available Discrete and continuous spectra of fissioning nuclei at the humps of fission barriers (Bohr transition states and in the intermediate wells (superdeformed and hyperdeformed states play a key role in the calculation of fission cross sections. A theoretical evaluation of the collective parts of the spectra is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two–cluster configurations in a dynamical way, permitting exchange of upper–shell nucleons between clusters. The impact of theoretical spectra on neutron–induced fission cross sections and, in combination with an improved version of the scission–point model, on angular distribution of fission fragments is evaluated for plutonium isotopes of interest to nuclear energy applications.

  20. 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.

  1. Thermal Performance of Deep-Burn Fusion-Fission Hybrid Waste in a Repository

    Energy Technology Data Exchange (ETDEWEB)

    Blink, J A; Chipman, V; Farmer, J; Shaw, H; Zhao, P

    2008-11-25

    The Laser Inertial Confinement Fusion Fission Energy (LIFE) Engine [1] combines a neutron-rich but energy-poor inertial fusion system with an energy-rich but neutron-poor subcritical fission blanket. Because approximately 80% of the LIFE Engine energy is produced from fission, the requirements for laser efficiency and fusion target performance are relaxed, compared to a pure-fusion system, and hence a LIFE Engine prototype can be based on target performance in the first few years of operation of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Similarly, because of the copious fusion neutrons, the fission blanket can be run in a subcritical, driven, mode, without the need for control rods or other sophisticated reactivity control systems. Further, because the fission blanket is inherently subcritical, fission fuels that can be used in LIFE Engine designs include thorium, depleted uranium, natural uranium, spent light water reactor fuel, highly enriched uranium, and plutonium. Neither enrichment nor reprocessing is required for the LIFE Engine fuel cycle, and burnups to 99% fraction of initial metal atoms (FIMA) being fissioned are envisioned. This paper discusses initial calculations of the thermal behavior of spent LIFE fuel following completion of operation in the LIFE Engine [2]. The three time periods of interest for thermal calculations are during interim storage (probably at the LIFE Engine site), during the preclosure operational period of a geologic repository, and after closure of the repository.

  2. Study of actinides fission induced by multi-nucleon transfer reactions in inverse kinematics

    International Nuclear Information System (INIS)

    The study of actinide fission encounters two major issues. On one hand, measurements of the fission fragment distributions and the fission probabilities allow a better understanding of the fission process itself and the discrimination among the models of nuclear structure and dynamics. On the other hand, new measurements are required to improve nuclear data bases, which are a key component for the design of new generation reactors and radio-toxic waste incinerators. This thesis is in line with different French and American experimental projects using the surrogate method, i.e. transfer reactions leading to the same compound nuclei as in neutron irradiation, allowing the study of fission of actinides which are inaccessible by conventional techniques, whereas they are important for applications. The experiment is based on multi-nucleon transfer reactions between a 238U beam and a 12C target, using the inverse kinematics technique to measure, for each transfer channel, the complete isotopic distributions of the fission fragments with the VAMOS spectrometer. The work presented in this dissertation is focused on the identification of the transfer channels and their properties, as their angular distributions and the distributions of the associated excitation energy, using the SPIDER telescope to identify the target recoil nuclei. This work of an exploratory nature aims to generalize the surrogate method to heavy transfers and to measure, for the first time, the fission probabilities in inverse kinematics. The obtained results are compared with available direct kinematics and neutron irradiation measurements. (author)

  3. Fission of nuclei far from stability

    International Nuclear Information System (INIS)

    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.)

  4. Dynamics of incomplete fusion-fission reactions

    OpenAIRE

    Crouzen, Paulus Caorlus Nicolaas,

    1988-01-01

    Fifty years after its first observation, nuclear fission is still a lively field of research. The contemporary interest in this well established phenomenon is mainly related to heavy-ion physics, where fission provides a valuable means for the study of reaction mechanisms. Until recently, most of the experiments on heavy-ion induced fission reactions were inclusive and often could not distinguish between complete and incomplete fusion. The present thesis work, however, was specifically focuss...

  5. Mechanisms of Mitochondrial Fission and Fusion

    OpenAIRE

    van der Bliek, Alexander M.; Shen, Qinfang; Kawajiri, Sumihiro

    2013-01-01

    Mitochondria continually change shape through the combined actions of fission, fusion, and movement along cytoskeletal tracks. The lengths of mitochondria and the degree to which they form closed networks are determined by the balance between fission and fusion rates. These rates are influenced by metabolic and pathogenic conditions inside mitochondria and by their cellular environment. Fission and fusion are important for growth, for mitochondrial redistribution, and for maintenance of a hea...

  6. Accurate fission data for nuclear safety

    OpenAIRE

    Solders, A.; Gorelov, D.; Jokinen, A; Kolhinen, V.S.; Lantz, M.; Mattera, A.; Penttila, H.; Pomp, S.; Rakopoulos, V.; Rinta-Antila, S.

    2013-01-01

    The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it...

  7. Measurements of Fission Cross Sections of Actinides

    CERN Multimedia

    Wiescher, M; Cox, J; Dahlfors, M

    2002-01-01

    A measurement of the neutron induced fission cross sections of $^{237}$Np, $^{241},{243}$Am and of $^{245}$Cm is proposed for the n_TOF neutron beam. Two sets of fission detectors will be used: one based on PPAC counters and another based on a fast ionization chamber (FIC). A total of 5x10$^{18}$ protons are requested for the entire fission measurement campaign.

  8. Statistical Analysis of Fission Chamber Signal

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yu Sun; Cha, Kyoon Ho; Bae, Seong Man [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)

    2012-05-15

    Fission Chamber (FC) is widely used at power range of commercial power reactors to measure neutron flux due to its longer life time than other detectors. However, detecting neutron counts from fission chamber during fuel loading is normally very low counting number. Fission chamber sensitivity is determined by experimental test to validate sensitivity on design specifications and linearity of neutron counts have been verified at fine range from 0.03 to 0.1 cps

  9. Statistical Analysis of Fission Chamber Signal

    International Nuclear Information System (INIS)

    Fission Chamber (FC) is widely used at power range of commercial power reactors to measure neutron flux due to its longer life time than other detectors. However, detecting neutron counts from fission chamber during fuel loading is normally very low counting number. Fission chamber sensitivity is determined by experimental test to validate sensitivity on design specifications and linearity of neutron counts have been verified at fine range from 0.03 to 0.1 cps

  10. Saturation current of miniaturized fission chambers

    International Nuclear Information System (INIS)

    We present the detailed formulae of the saturation currents for the four main categories of fission chambers operating in current mode. The results obtained are function of simple parameters: number of fission reactions within the chamber deposits, geometric characteristics of the electrodes and filling gas properties. A direct relation between the saturation current values and the ambient neutron flux is thus established. These results should reduce the number, the duration and the cost of the calibration procedures required to operate the fission chambers.

  11. Saturation current of miniaturized fission chambers

    Science.gov (United States)

    Chabod, Sébastien P.

    2009-01-01

    We present the detailed formulae of the saturation currents for the four main categories of fission chambers operating in current mode. The results obtained are function of simple parameters: number of fission reactions within the chamber deposits, geometric characteristics of the electrodes and filling gas properties. A direct relation between the saturation current values and the ambient neutron flux is thus established. These results should reduce the number, the duration and the cost of the calibration procedures required to operate the fission chambers.

  12. Nuclear Fission Products: From Source to Environment

    OpenAIRE

    A.W. Ajlouni; Y.S. Almasa`efah; Abdelsalam, M.

    2010-01-01

    After a peer review of data about nuclear fission products, we can see easily that, no clear chemical species, chemical compounds, or chemical processes were available after actual releases of nuclear Fission Products (FP) during planned releases, accidents, or in nuclear detonations. The models based on these ordinary reactions and species could not interpret the behaviors of the fission products or expect their effects in the environment or on the living creatures. To interpret the chemical...

  13. FY04&05 LDRD Final Report Fission Fragment Sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ebbinghaus, B; Trelenberg, T; Meier, T; Felter, T; Sturgeon, J; Kuboda, A; Wolfer, B

    2006-02-22

    Fission fragments born within the first 7 {micro}m of the surface of U metal can eject a thousand or more atoms per fission event. Existing data in the literature show that the sputtering yield ranges from 10 to 10,000 atoms per fission event near the surface, but nothing definitive is known about the energy of the sputtered clusters. Experimental packages were constructed allowing the neutron irradiation of natural uranium foils to investigate the amount of material removed per fission event and the kinetic energy distribution of the sputtered atoms. Samples were irradiated but were never analyzed after irradiation. Similar experiments were attempted in a non-radioactive environment using accelerator driven ions in place of fission induced fragments. These experiments showed that tracks produced parallel to the surface (and not perpendicular to the surface) are the primary source of the resulting particulate ejecta. Modeling studies were conducted in parallel with the experimental work. Because the reactor irradiation experiments were not analyzed, data on the energy of the resulting particulate ejecta was not obtained. However, some data was found in the literature on self sputtering of {sup 252}Cf that was used to estimate the velocity and hence the energy of the ejected particulates. Modeling of the data in the literature showed that the energy of the ejecta was much lower than had been anticipated. A mechanism to understand the nature of the ejecta was pursued. Initially it was proposed that the fission fragment imparts its momenta on the electrons which then impart their momenta on the nuclei. Once the nuclei are in motion, the particulate ejecta would result. This initial model was wrong. The error was in the assumption that the secondary electrons impart their momenta directly on the nuclei. Modeling and theoretical considerations showed that the secondary electrons scatter many times before imparting all their momenta. As a result, their energy transfer is more isotropic than directional. It was therefore concluded that the nuclei are set in motion not by direct collisions with the secondary electrons, but by repulsive forces cased by the temporary net positive local charge of the nuclei. This is cased by ejected electrons and by the reduced bonding nature of the nuclei cased by many of the local electrons being in excited and in nonbonding states.

  14. The Non-Adiabatic dynamics of Singlet Fission in Polyacenes

    Science.gov (United States)

    Bradforth, Stephen

    2015-03-01

    Singlet fission involves the splitting of a single excitation into two coupled triplet excitations and is manifested in an increasing range of aromatic crystals and amorphous thin films. If the energy of the lowest triplet state is one half (or less) of the first singlet excited state, as it is for tetracene or pentacene and their derivatives, singlet fission may occur between two adjacent chromophores. Since there is no change in the overall spin state of the system, singlet fission can be exceptionally fast, occuring on the fs - ps range. If the triplets can diffuse away from the fission site they are available for harvesting as a dissociated carriers with up to two charge carrier pairs per absorbed photon. The possibility of recovering excess energy above the material band gap (in this case determined by the triplet energy) when a higher energy photon is absorbed has led to great recent interest in exploiting this process for increased efficiency solar energy harvesting. The nature of the electronic couplings between the chromophores, intermediate electronic configurations, and the role of entropy in the spin-allowed primary fission event have all come under great scrutiny. Results from a series of femtosecond spectroscopy experiments on a variety of amorphous thin films, nanoparticles and isolated acene dimer compounds will be presented that shed light on the electronic intermediate states key to the efficiency and speed of this process. Work supported as part of the Center for Energy Nanoscience, an Energy Frontier Research Center funded by the U.S. Department of Energy (DE-SC0001013).

  15. Fission-track dating of obsidians

    International Nuclear Information System (INIS)

    Fission-track dating is applied to 16 obsidian artifacts from an archaeological excavation at Cayonu Tepesi in southeastern Anatolia. Since obsidian samples are rich in bubbles and inclusions, only the six most compact samples were found to be usable for fission-track measurements. Size studies of etched fossil- and induced-fission tracks showed that no strong thermal effects occurred during the history of these glasses so that no fading correction has been applied to the computed ages. The fission-track ages obtained range between 8.95 Myr and 25.14 Myr. It may be stated that these obsidian samples are from two different origins. (author)

  16. Fusion – fission dynamics: fragment mass distribution studies

    Directory of Open Access Journals (Sweden)

    Bhattacharya S.

    2015-01-01

    Full Text Available Using the major accelerator facilities available in India, detailed experimental studies have been made to understand the mechanism of quasi-fission and role of nuclear shell effect in heavy nuclei. Fission fragment mass distribution has been used as the probe to explore the role of entrance channel effects on fusion-fission and quasifission dynamics. Fission fragment mass distribution has also been demonstrated to be useful to identify the phenomenon of ‘washing out’ of nuclear shell effect with excitation energy.

  17. Some aspects of fission and quasifission processes

    Indian Academy of Sciences (India)

    B B Back

    2015-08-01

    The discovery of nuclear fission in 1938–1939 had a profound influence on the field of nuclear physics and it brought this branch of physics into the forefront as it was recognized for having the potential for its seminal influence on modern society. Although many of the basic features of actinide fission were described in a ground-breaking paper by Bohr and Wheeler only six months after the discovery, the fission process is very complex and it has been a challenge for both experimentalists and theorists to achieve a complete and satisfactory understanding of this phenomenon. Many aspects of nuclear physics are involved in fission and it continues to be a subject of intense study even three quarters of a century after its discovery. In this talk, I will review an incomplete subset of the major milestones in fission research, and briefly discuss some of the topics that I have been involved in during my career. These include studies of vibrational resonances and fission isomers that are caused by the second minimum in the fission barrier in actinide nuclei, studies of heavy-ion-induced fission in terms of the angular distributions and the mass–angle correlations of fission fragments. Some of these studies provided evidence for the importance of the quasifission process and the attendant suppression of the complete fusion process. Finally, some of the circumstances around the establishment of large-scale nuclear research in India will be discussed.

  18. Experimental Fission Studies at Intermediate Energies

    OpenAIRE

    Elmgren, Klas

    2002-01-01

    A series of nuclear fission experiments have been performed in the intermediate energy range. The dynamics of the fission process have been studied by means of detection of neutrons emitted from compound nuclei formed by ion beams of protons, ?-particles, and 12C-ions, all at a beam energy of 100 MeV. The neutron emission data have been interpreted using a statistical model analysis, and the fission time scale has been found to vary between 6.4 and 170?10-21 s. Neutron-induced fission cross s...

  19. Theoretical Description of the Fission Process

    International Nuclear Information System (INIS)

    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

  20. Status of fission product yield data

    International Nuclear Information System (INIS)

    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 232Th 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)

  1. Attachment of gaseous fission products to aerosols

    International Nuclear Information System (INIS)

    The circumstances under which gaseous fission products may be attached to aerosols are examined. A simple model is assumed for the interaction between the fission product molecules and the aerosol, in which the probability of attachment of a molecule on any encounter is given by a constant ?, the sticking probability. It is concluded that when gaseous fission products are released in the presence of a population of particles, particularly small particles, there is a strong possibility that they will attach rapidly to those particles. In such circumstances gaseous fission product transport would be governed by the transport properties of the particles. (author)

  2. Double ionization chamber for fission fragment detection

    Energy Technology Data Exchange (ETDEWEB)

    Chepigin, V.I.; Stepantsov, S.V.; Nagy, S.; Ter-Akopian, G.M.; Voronin, A.S. (Joint Inst. for Nuclear Research, Dubna (USSR). Lab. of Nuclear Reactions)

    1984-03-01

    In the present paper some problems associated with studies of the spontaneous fission of transfermium elements are considered, and advantages of ionization chambers over other detectors for fission fragment detection are discussed. A double ionization chamber for detecting fission fragments has been built, and the energy and mass calibrations have been performed using the thermal neutron-induced fission of /sup 235/U. The use of a gas jet, in combination with a double ionization chamber as a detector, in experiments with heavy ions is discussed. Model experiments have been carried out.

  3. Fission fragment detection by thin film capacitors

    International Nuclear Information System (INIS)

    Fission fragments produce measurable current pulses in thin film capacitors at electric fields which are high, but still below the breakdown range for fragments. This paper describes the use of silicon dioxide capacitors for the detection of fission fragments by such current pulses. With capacitor areas of 2 x 10-2 cm2, the pulses were insignificant when the oxide was relatively thin, but with 3800 A thick oxide, fission fragments produce detectable pulses of about 10-15 C. The mechanisms producing the current pulses by fission fragments are discussed. (author)

  4. Calculation of fission neutron spectra for spontaneous fission of 240Pu, 238Pu and 242Pu

    International Nuclear Information System (INIS)

    This paper reports on the fission neutron spectra for spontaneous fission of 240Pu, 238Pu and 242Pu calculated using the spin-dependent Madland-Mix model. Experimental data on fission neutron spectra for these nuclei are scarce. The calculated differences in the three spectra are presented and compared with the available data, and some repercussions for plutonium assay work are discussed

  5. Terracentric Nuclear Fission Reactor: Background, Basis, Feasibility, Structure, Evidence, and Geophysical Implications

    CERN Document Server

    Herndon, J Marvin

    2013-01-01

    The background, basis, feasibility, structure, evidence, and geophysical implications of a naturally occurring Terracentric nuclear fission georeactor are reviewed. For a nuclear fission reactor to exist at the center of the Earth, all of the following conditions must be met: (1) There must originally have been a substantial quantity of uranium within Earth's core; (2) There must be a natural mechanism for concentrating the uranium; (3) The isotopic composition of the uranium at the onset of fission must be appropriate to sustain a nuclear fission chain reaction; (4) The reactor must be able to breed a sufficient quantity of fissile nuclides to permit operation over the lifetime of Earth to the present; (5) There must be a natural mechanism for the removal of fission products; (6) There must be a natural mechanism for removing heat from the reactor; (7) There must be a natural mechanism to regulate reactor power level, and; (8) The location of the reactor or must be such as to provide containment and prevent ...

  6. Least squares analysis of fission neutron standard fields

    International Nuclear Information System (INIS)

    A least squares analysis of fission neutron standard fields has been performed using the latest dosimetry cross sections. Discrepant nuclear data are identified and adjusted spectra for 252Cf spontaneous fission and 235U thermal fission fields are presented

  7. Spectroscopy of heavy fissionable nuclei

    Indian Academy of Sciences (India)

    S K Tandel

    2015-09-01

    Structural studies of heavy nuclei are quite challenging due to increased competition from fission, particularly at high spins. Nuclei in the actinide region exhibit a variety of interesting phenomena. Recent advances in instrumentation and analysis techniques have made feasible sensitive measurements of nuclei populated with quite low cross-sections. These include isomers and rotational band structures in isotopes of Pu ( = 94) to Rf ( = 104), and octupole correlations in the Th ( = 90) region. The obtained experimental data have provided insights on various aspects like moments of inertia and nucleon alignments at high spins, quasiparticle energies and evolution of quadrupole and octupole collectivity, among others. An overview of some of these results is presented.

  8. Spallation - Neutrons Beyond Nuclear Fission

    Science.gov (United States)

    Conrad, Harald

    The classical research neutron sources are fission reactors. They have reached their technical limits as far as neutron flux is concerned. But there is an alternative way with many advantages: spallation. The emphasis in this context is on pulsed operation, which is easily achieved with spallation as being accelerator-driven. The extension of neutron scattering to fields not covered with reactors is discussed as well as the utilization of spallation neutrons for other fields such as nuclear waste transmutation and future power reactors.

  9. Analysis of fission-product effects in a Fast Mixed-Spectrum Reactor concept

    International Nuclear Information System (INIS)

    The Fast Mixed-Spectrum Reactor (FMSR) concept has been proposed by BNL as a means of alleviating certain nonproliferation concerns relating to civilian nuclear power. This breeder reactor concept has been tailored to operate on natural uranium feed (after initial startup), thus eliminating the need for fuel reprocessing. The fissile material required for criticality is produced, in situ, from the fertile feed material. This process requires that large burnup and fluence levels be achievable, which, in turn, necessarily implies that large fission-product inventories will exist in the reactor. It was the purpose of this study to investigate the effects of large fission-product inventories and to analyze the effect of burnup on fission-product nuclide distributions and effective cross sections. In addition, BNL requested that a representative 50-group fission-product library be generated for use in FMSR design calculations

  10. Channel Effects in the Kinetic Energy of Fragments of Fission Induced by Low-Energy Resonance Neutrons

    International Nuclear Information System (INIS)

    Recently, Blyumkina et al. have noted tfte existence ot fission channel ettects in the total kinetic energy of fragments of fission induced by s- and p-wave neutrons. Effects of this nature can also be expected in the variation of the fragment kinetic energies from resonance to resonance in low-energy (s-wave) neutron-induced fission. A fission-fragment detector whose efficiency is dependent on the kinetic energy of the fragments was used in the study of the slow-neutron-induced fission of U235. Comparing the counting-rate of this detector with a conventional fission detector, whose efficiency is independent of the fragment kinetic energy, shows that there exists a variation in the kinetic energy of certain fragments with neutron energy in the neutron energy region from 0.025 to 1 eV. In order to determine the response of the kinetic-energy-sensitive detector, it was necessary to measure the rangè-energy relations of fission fragments in various media, including noble gases and metallic foils. It was estimated from these data that the variation in the fragment kinetic energy release is ?500 keV, for those fission events that give the lightest and most energetic of the heavy fragments. The variation in fragment kinetic energy is strongly asymmetric about the 0.28-eV resonance in U235, and suggests that the fragment kinetic energy sensitively reflects the presence of interference effects among resonances in fission. A multi-level multi-channel analysis of the data has been made, based on the parameters of Vogt and under the assumption that different fission channels lead to different configurations at scission, such that the kinetic energy release is also different. Previously a major objection to multi-level multi-channel analysis in fission has been that the parameters obtained are not unique. However, the possibility of observing partial fission cross-sections (fission occurring by way of one channel only) removes one of the ambiguities inherent in the multi-level approach. Studies of this type can not only be expected to give information on the nature of the constraints that exist during the transition from the saddle point to the scission point in the fission process, but may also be of interest in inferring the existence of small variations from resonance to resonance in v, the average number of neutrons emitted per fission. (author)

  11. Neutron energy response of the fission target chamber system

    International Nuclear Information System (INIS)

    The fission target chamber system is composed of vacuum target chamber and 235U fission target and large area PIN detector. The average deposition energy of 235U fission fragment in fission target and large area PIN detector(?60 mm) is investigated by using reactor neutron source. In this way, the variety of deposition energy vs fission target areal density is obtained. By the experiment and calculation the neutron energy response of fission target chamber system is got. (authors)

  12. Probing fusion-fission dynamics in Bi203

    Science.gov (United States)

    Mukul, Ish; Nath, S.; Golda, K. S.; Jhingan, A.; Gehlot, J.; Prasad, E.; Kalkal, Sunil; Naik, M. B.; Banerjee, Tathagata; Varughese, T.; Sugathan, P.; Madhavan, N.; Pal, Santanu

    2015-11-01

    Background: Complete fusion between two massive nuclei after capture inside the potential barrier is inhibited by competing fission-like processes. The target-projectile composite system may reseparate after capture without proceeding towards formation of the compound nucleus (CN), which is equilibrated in all degrees of freedom. The nature of these non-CN fission (NCNF) processes and factors that affect them are not completely known yet. Purpose: The nuclear mass regions from where NCNF processes begin to manifest themselves are not clearly demarcated. This work aims to study the onset of NCNF, if any, in the mass region ˜200 . Methods: Fission fragment (FF) mass and angular distribution (MAD) and pre-scission and post-scission neutron multiplicities were measured for the reaction +W184F19 at a laboratory energy (Elab) range of 84-125 MeV. The measurements were carried out using two multiwire proportional counters (MWPC) to detect the FFs in coincidence and four neutron detectors to measure neutron time of flight (TOF). Statistical model (SM) calculation was performed. Results: No significant mass-angle correlation was observed in the MAD plots. Extracted mass ratio distributions were single-peaked and of Gaussian shape. Measured pre-scission neutron multiplicity values indicated dissipative nature of CN decay for this reaction. Conclusions: No clear signatures of NCNF were observed in the studied reaction, indicating that the target-projectile composite system predominantly proceeds towards formation of the CN after capture.

  13. Future Scenarios for Fission Based Reactors

    Science.gov (United States)

    David, S.

    2005-04-01

    The coming century will see the exhaustion of standard fossil fuels, coal, gas and oil, which today represent 75% of the world energy production. Moreover, their use will have caused large-scale emission of greenhouse gases (GEG), and induced global climate change. This problem is exacerbated by a growing world energy demand. In this context, nuclear power is the only GEG-free energy source available today capable of responding significantly to this demand. Some scenarios consider a nuclear energy production of around 5 Gtoe in 2050, wich would represent a 20% share of the world energy supply. Present reactors generate energy from the fission of U-235 and require around 200 tons of natural Uranium to produce 1GWe.y of energy, equivalent to the fission of one ton of fissile material. In a scenario of a significant increase in nuclear energy generation, these standard reactors will consume the whole of the world's estimated Uranium reserves in a few decades. However, natural Uranium or Thorium ore, wich are not themselves fissile, can produce a fissile material after a neutron capture ( 239Pu and 233U respectively). In a breeder reactor, the mass of fissile material remains constant, and the fertile ore is the only material to be consumed. In this case, only 1 ton of natural ore is needed to produce 1GWe.y. Thus, the breeding concept allows optimal use of fertile ore and development of sustainable nuclear energy production for several thousand years into the future. Different sustainable nuclear reactor concepts are studied in the international forum "generation IV". Different types of coolant (Na, Pb and He) are studied for fast breeder reactors based on the Uranium cycle. The thermal Thorium cycle requires the use of a liquid fuel, which can be reprocessed online in order to extract the neutron poisons. This paper presents these different sustainable reactors, based on the Uranium or Thorium fuel cycles and will compare the different options in term of fissile inventory, capacity to be deployed, induced radiotoxicities, and R&D efforts.

  14. Options for Affordable Fission Surface Power Systems

    International Nuclear Information System (INIS)

    Fission surface power systems could provide abundant power anywhere on the surface of the moon or Mars. Locations could include permanently shaded regions on the moon and high latitudes on Mars. To be fully utilized, however, fission surface power systems must be safe, have adequate performance, and be affordable. This paper discusses options for the design and development of such systems. (authors)

  15. Spontaneous fission properties and lifetime systematics

    International Nuclear Information System (INIS)

    Half-lives for spontaneous fission of nuclides with even and odd numbers of particles are compared with recent theoretical calculations. A summary of odd particle hindrance factors is given. The most recent measurements of kinetic-energy and mass distributions and neutron emission for spontaneous fission of the heaviest nuclides are summarized and discussed. 51 refs., 9 figs

  16. Correlation measurements of fission-fragment properties

    Directory of Open Access Journals (Sweden)

    Oberstedt A.

    2010-10-01

    Full Text Available For the development of future nuclear fission applications and for a responsible handling of nuclear waste the a-priori assessment of the fission-fragments’ heat production and toxicity is a fundamental necessity. The success of an indispensable modelling of the fission process strongly depends on a good understanding of the particular mechanism of scission, the mass fragmentation and partition of excitation energy. Experimental observables are fission-fragment properties like mass- and energy-distributions, and the prompt neutron as well as ?-ray multiplicities and emission spectra. The latter quantities should preferably be known as a function of fragment mass and excitation energy. Those data are highly demanded as published by the OECD-NEA in its high priority data request list. With the construction of the double (v, E spectrometer VERDI we aim at measuring pre- and post-neutron masses directly and simultaneously to avoid prompt neutron corrections. From the simultaneous measurement of pre- and post-neutron fission-fragment data the prompt neutron multiplicity may then be inferred fully correlated with fragment mass yield and total kinetic energy. Using an ultra-fast fission event trigger spectral prompt fission ?-ray measurements may be performed. For that purpose recently developed lanthanum-halide detectors, with excellent timing characteristics, were coupled to the VERDI spectrometer allowing for a very good discrimination of fission ?-rays and prompt neutrons due to their different time-of-flight.

  17. Methods for determination of fission gases

    International Nuclear Information System (INIS)

    This paper describes procedures for determination of fission gases by measuring the quantity of released and remaining gases in the fuel after irradiation. Experiments are described for determining the quantity of fission gases release from fuel during irradiation in the reactor as well as the pressure of gases in fuel cladding. Principles of gamma scintillation spectroscopy, mass spectrometry and gas chromatography are included

  18. Design of a fission product detection system

    International Nuclear Information System (INIS)

    This article presents the design of a fission product detection system, based on the electrostatic precipitation of the Kr and Xe daughters, for use in failure fuel element detection. A comparative study describes some of the most important fission product detection systems, pointing the advantages and disadvantages of each one. (author)

  19. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    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

  20. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    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

  1. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    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

  2. Adsorption and excess fission xenon

    Science.gov (United States)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  3. Quark bags and their fission

    International Nuclear Information System (INIS)

    The aim of this work is to gain more insight into the physics of hadrons and to develop a theoretical framework for the treatment of hadronic fission. The description of hadronic matter in terms of quantum chromodynamics, which is generally accepted as the fundamental theory of strong interactions, is intimately connected with the concept of colour confinement. Since this phenomenon is a property of the vacuum state, much effort has been invested into trying to understand it in analogy with the occurence of the condensed ground state in the theory of superconductivity. In Chapter II, we therefore go back to non-relativistic physics, discuss the methods used there, and report in Chapter III on various attempts to apply these methods in quantum field theories, in particular in connection with the so-called 'dynamical symmetry breaking'. Although the fundamental problem of the 'true' vacuum state has not yet been solved, its solution has been anticipated in the so-called bag models which are discussed in great detail in Chapter IV. In Chapter V, we finally seek to understand the microscopic process of fission of hadrons. (orig./HSI)

  4. Fission

    International Nuclear Information System (INIS)

    Progress is reported in the areas of radiation physics; radiation dosimetry and radiation biophysics; microdosimetry of internal sources; dosimetry of internal emitters; real-time measurement of Pu in air at below-MPC levels; analytical techniques for measurement of 99Tc in environmental samples; and radiation instrumentation--radiological chemistry

  5. Theoretical Description of the Fission Process

    Energy Technology Data Exchange (ETDEWEB)

    Witold Nazarewicz

    2009-10-25

    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 waste and be proliferation-resistant, is a goal for the advanced nuclear fuel cycles program. While in the past the design, construction, and operation of reactors were supported through empirical trials, this new phase in nuclear energy production is expected to heavily rely on advanced modeling and simulation capabilities.

  6. Theoretical Description of the Fission Process

    International Nuclear Information System (INIS)

    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 waste and be proliferation-resistant, is a goal for the advanced nuclear fuel cycles program. While in the past the design, construction, and operation of reactors were supported through empirical trials, this new phase in nuclear energy production is expected to heavily rely on advanced modeling and simulation capabilities.

  7. Large-scale fission product containment tests

    International Nuclear Information System (INIS)

    The Containment Systems Experiment (CSE) program is reviewed, with emphasis on the inherent processes that remove fission products from containment atmospheres and reduce their leakage to the environment. The CSE containment vessel was sized to represent a 1/5 linear scale model of a typical 1000 MW(e) PWR. Nineteen tests were performed in a steam-air atmosphere simulating post-LOCA conditions. In eight tests containment sprays were operated, in five tests a recirculating filter-adsorber loop was operated, and in six tests only natural, passive processes occurred. Sprays were the most effective in removing airborne iodine and particulate aerosols, followed by the filter loop. Although not as effective as the engineered safety features, natural processes of diffusion to surfaces, reaction with paint, gravity settling, and removal in leak paths are shown to be significant. Together they caused a reduction in leakage of 10-2 and 10-3 for iodine and cesium, respectively, during the initial 2-h period. These attenuation factors increased to 10-3 and 10-4, respectively, for the first 24-h period

  8. Systematics of Fission-Product Yields

    International Nuclear Information System (INIS)

    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 ZF = 90 thru 98, mass number AF = 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

  9. Improved Calculation of Thermal Fission Energy

    CERN Document Server

    Ma, X B; Wang, L Z; Chen, Y X; Cao, J

    2013-01-01

    Thermal fission energy is one of the basic parameters needed in the calculation of antineutrino flux for reactor neutrino experiments. It is useful to improve the precision of the thermal fission energy calculation for current and future reactor neutrino experiments, which are aimed at more precise determination of neutrino oscillation parameters. In this article, we give new values for thermal fission energies of some common thermal reactor fuel iso-topes, with improvements on two aspects. One is more recent input data acquired from updated nuclear databases. The other, which is unprecedented, is a consideration of the production yields of fission fragments from both thermal and fast incident neutrons for each of the four main fuel isotopes. The change in calculated antineutrino flux due to the new values of thermal fission energy is about 0.33%, and the uncertainties of the new values are about 30% smaller.

  10. Microscopic Theory of Nuclear Fission: A Review

    CERN Document Server

    Schunck, N

    2015-01-01

    This article reviews how nuclear fission is described within nuclear density functional theory. In spontaneous fission, half-lives are the main observables and quantum tunnelling the essential concept, while in induced fission the focus is on fragment properties and explicitly time-dependent approaches are needed. The cornerstone of the current microscopic theory of fission is the energy density functional formalism. Its basic tenets, including tools such as the HFB theory, effective two-body effective nuclear potentials, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The EDF approach is often combined with the hypothesis that the time-scale of the large amplitude collective motion driving the system to fission is slow compared to typical time-scales of nucleons inside the nucleus. In practice, this hypothesis of adiabaticity is implemented by introducing (a few) collective variables and mapping out the many-body Schr\\"odinger equation into a collective Schr\\"odinge...

  11. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    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 ?-, ?-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

  12. Spontaneous fission with ? -parameterized quasimolecular shape

    Science.gov (United States)

    Zhang, Haifei; Zhang, Hongfei; Li, Junqing; Bao, Xiaojun; Ma, Nana

    2014-11-01

    In the framework of a generalized liquid drop model (GLDM), a quasimolecular mechanism is introduced to describe the deformation of a nucleus in the procedure of nuclear fission or fusion. In order to more appropriately evaluate the shell correction on the fission or fusion path, the quasimolecular shape is described in terms of deformation parameters ? (i.e., so-called ? parameterized) by a transformation. For symmetric fission it is done analytically, whereas for asymmetric fission it is performed in a pure numerical way. Thereafter, for each quasimolecular shape, the shell correction can be calculated by the Strutinsky method where the single-particle energies are derived from a shell model in an axially deformed Woods-Saxon potential with the ? -parameterized quasimolecular shape. We then use this recipe to predict the half-lives of several spontaneous fission channels for some heavy nuclei, and the results are in agreement with the experimental data.

  13. Fission dynamics with systems of intermediate fissility

    Indian Academy of Sciences (India)

    E Vardaci; A Di Nitto; P N Nadtochy; A Brondi; G La Rana; R Moro; M Cinausero; G Prete; N Gelli; E M Kozulin; G N Knyazheva; I M Itkis

    2015-08-01

    A 4 light charged particle spectrometer, called 8 LP, is in operation at the Laboratori Nazionali di Legnaro, Italy, for studying reaction mechanisms in low-energy heavy-ion reactions. Besides about 300 telescopes to detect light charged particles, the spectrometer is also equipped with an anular PPAC system to detect evaporation residues and a two-arm time-of-flight spectrometer to detect fission fragments. The spectrometer has been used in several fission dynamics studies using as a probe light charged particles in the fission and evaporation residues (ER) channels. This paper proposes a journey within some open questions about the fission dynamics and a review of the main results concerning nuclear dissipation and fission time-scale obtained from several of these studies. In particular, the advantages of using systems of intermediate fissility will be discussed.

  14. Twin ionization chamber for fission fragment detection

    Energy Technology Data Exchange (ETDEWEB)

    Budtz-Joergensen, C.; Knitter, H.H.; Straede, C.; Hambsch, F.J.; Vogt, R.

    1987-08-01

    A twin ionization chamber for fission fragment detection is described. The detector permits measurement of the two fission fragment kinetic energies in an advantageous 2 x 2 ..pi.. geometry with an energy resolution of < 0.5 MeV. The fission fragment emission angle THETA with respect to the symmetry axis of the chamber is measured with a resolution in cos THETA of < 0.05. The fission fragment nuclear charge distributions can be determined and a timing signal can be extracted which allows a determination of the instant of fission with a time jitter of < 0.7 ns. A pulse pileup rejection technique was developed which reduces pulse pileup by more than a factor 30. The electronic treatment of the chamber pulses and the data handling procedures including several of the necessary corrections are described in detail.

  15. Criticality calculations with fission spectrum matrix

    International Nuclear Information System (INIS)

    In the present study, the author implemented a procedure to treat a fission spectrum matrix into neutron transport solvers of a code system CBG, and quantified errors of usual procedures utilizing a fission spectrum vector. Numerical results showed that the errors of the usual procedures are negligible if the fission spectrum vector is generated from the fission spectrum matrix with weight functions obtained by cell calculations. On the other hand, when a library built-in function is used as a weight function for the fission spectrum vector generation, the errors become large if there is a large difference between the library built-in function and the neutron energy spectrum of the target system. (author)

  16. Theory of neutron emission in fission

    International Nuclear Information System (INIS)

    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

  17. Fission dynamics at low excitation energy. 2

    CERN Document Server

    Aritomo, Y; Ivanyuk, F A

    2014-01-01

    The mass asymmetry in the fission of U-236 at low excitation energy is clarified by the analysis of the trajectories obtained by solving the Langevin equations for the shape degrees of freedom. It is demonstrated that the position of the peaks in the mass distribution of fission fragments is determined mainly by the saddle point configuration originating from the shell correction energy. The width of the peaks, on the other hand, results from the shape fluctuations close to the scission point caused by the random force in the Langevin equation. We have found out that the fluctuations between elongated and compact shapes are essential for the fission process. According to our results the fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup, but is accompanied by the fluctuations between elongated and compact shapes. This picture presents a new viewpoint of fission dynamics and the splitting mechanism.

  18. Fission fragment angular distribution measurements for {sup 16}O + {sup 194}Pt reaction at energies near the Coulomb barrier

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, E., E-mail: prasad.e.nair@gmail.com [Department of Physics, School of Mathematical and Physical Sciences, Central University of Kerala, Nileshwar, 671328 (India); Department of Physics, University of Calicut, Calicut, 673635 (India); Varier, K.M. [Department of Physics, University of Calicut, Calicut, 673635 (India); Thomas, R.G. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Vinodkumar, A.M. [Department of Physics, University of Calicut, Calicut, 673635 (India); Mahata, K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Appannababu, S. [Department of Physics, Faculty of Science, The M. S. University of Baroda, Vadodara, 390002 (India); Sugathan, P.; Golda, K.S. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, Post Box 10502, New Delhi, 110067 (India); Babu, B.R.S. [Department of Physics, University of Calicut, Calicut, 673635 (India); Department of Physics, Sultan Qaboos University, Muscat (Oman); Saxena, A.; John, B.V.; Kailas, S. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India)

    2012-05-15

    Fission fragment angular distributions have been measured for {sup 16}O + {sup 194}Pt reaction forming the compound system {sup 210}Rn, in the laboratory energy range from 79 to 90 MeV. The measured fission fragment anisotropies as a function of E{sub c.m.}/V{sub B} are compared with the predictions of standard saddle point statistical model (SSPM). Anisotropies calculated using the average excitation energy and angular momentum values could not reasonably fit the experimental data. Statistical model calculations were performed using the PACE with modified fission barrier and level density parameters. Fission probability, evaporation residue cross section and neutron multiplicity were simultaneously used to fix the statistical parameters. Model calculations incorporating the chance nature of fission decay and scaled values of the rotating finite range model (RFRM) moment of inertia could reasonably fit the fragment angular anisotropies.

  19. Correction of Thick Foil Errors in Prompt Neutron (CALIFORNIUM-252 Nu), Fission Cross Section (sigma(f)) and Other Ionization Chamber Fission Data Standards.

    Science.gov (United States)

    Cohensedgh, Farhad

    This research resolves two problems that have long been of important concern in experimental fission physics: (1) determination of pulse height distribution response of ionization chambers in fission fragment detection measurements, and (2) correction of "thick-foil effect" systematic errors in standard values of the fundamental parameters of fission physics--the average number of prompt neutrons per fission (=nu), absolute fission activity and true fission rate of samples (TFR), and isotopic fission cross sections (sigma _{f}). Results are obtained by a comprehensive digital simulation of the electrostatics and pulse height distribution response of the parallel-plate, ungridded, electron-pulse ionization fission chamber together with prompt neutron -fragment multiplicity and angular distribution correlations, neutron-fragment coincidence detection and related variations in the 4pi^here around the chamber for a wide range of the relevant factors--foil thickness, alpha particle interference bias level, fission detector configuration characteristics, fissile isotopes (^{252}Cf, ^{235}U, etc.) and other experimental parameters. Isotope-specific double-energy (E_1,E_2) natural variations in fragment spectrum, in fragment-specific range-energy (dE/dx) relations and in prompt neutron-fragment multiplicity (nu) and nuclear temperature dependent angular distribution correlations are simulated in detail. Detailed results are obtained for double-energy, fragment-specific count loss fractions resulting from in -foil fragment absorption and from alpha -interference discrimination as well as for chamber detection efficiency, fragment spectrum distortion and prompt neutron -fragment coincidence detection distribution variations. Decay alpha pulse pileup statistics are discussed, and the behavior of and factors affecting the fragment pulse height distribution tail are analyzed in detail. Fragment pairs and prompt neutrons issued from them are tracked in the 4pi^ace around the chamber. Light-to-heavy fragment detection ratio variations in neutron-gated coincidence measurements are also obtained in 4pi space. Effects of these systematics on absolute, relative and ratio measurements of fundamental fission parameters are discussed. Magnitudes and mechanisms of production of thick-foil errors are identified and analyzed in detail, and methods for correcting these errors and for improving measurement setup design are given.

  20. Nuclear fission industry in Japan

    International Nuclear Information System (INIS)

    The status of the nuclear fission industry in Japan is described. Japanese nuclear policy, vision, goals, and supporting organizational structures are reviewed. The facilities of the Japanese Atomic Energy Research Institute (JAERI), Power Reactor and Nuclear Fuel development Corporation (PNC), and the Japan Atomic Power Company (JAPCO) are illustrated and described. Nuclear power statistics and power generation costs by power source are shown for Japan. Photographic details and technical descriptions are presented for Japan's: nuclear fuel cycle (NFC), light water reactor (LWR), advanced thermal reactor (ATR), fast breeder reactor (FBR), gas centrifuge uranium enrichment, LWR spent fuel reprocessing, ATR and FBR spent fuel uranium/plutonium mixed oxide fuel (MOX) co-conversion process, high level nuclear waste management (NWM) policy, reactor operation safety, newly developed decommissioning and dismantling policy for obsolete nuclear facilities, and new future technology

  1. Aerosols and fission product transport

    International Nuclear Information System (INIS)

    A survey is presented of current knowledge of the possible role of aerosols in the consequences of in- and out-of-core LOCAs and of end fitting failures in CANDU reactors. An extensive literature search has been made of research on the behaviour of aerosols in possible accidents in water moderated and cooled reactors and the results of various studies compared. It is recommended that further work should be undertaken on the formation of aerosols during these possible accidents and to study their subsequent behaviour. It is also recommended that the fission products behaviour computer code FISSCON II should be re-examined to determine whether it reflects the advances incorporated in other codes developed for light water reactors which have been extensively compared. 47 refs

  2. Downstream behavior of fission products

    International Nuclear Information System (INIS)

    The downstream behavior of fission products has been investigated by injecting mixtures of CsOH, CsI, and Te into a flowing steam/hydrogen stream and determining the physical and chemical changes that took place as the gaseous mixture flowed down a reaction duct on which a temperature gradient (10000 to 2000C) had been imposed. Deposition on the wall of the duct occurred by vapor condensation in the higher temperature regions and by aerosol deposition in the remainder of the duct. Reactions in the gas stream between CsOH and CsI and between CsOH and Te had an effect on the vapor condensation. The aerosol was characterized by the use of impingement tabs placed in the gas stream

  3. Laser driven fusion fission hybrids

    International Nuclear Information System (INIS)

    The role of the fusion-fission hybrid reactor (FFHR) as a fissile fuel and/or power producer is discussed. As long range options to supply the world energy needs, hybrid-fueled thermal-burner reactors are compared to liquid metal fast breeder reactors (LMFBR). A discussion of different fuel cycles (thorium, depleted uranium, and spent fuel) is presented in order to compare the energy multiplication, the production of fissile fuel, the laser efficiency and pellet gain requirements of the hybrid reactor. LLL has collaborated with Bechtel Corporation and with Westinghouse on the conceptual design of laser fusion power plants. The neutronic studies of these two designs are discussed. The operational parameters, such as energy multiplication, power density, burn-up and plutonium production as a function of time, are also presented

  4. Dynamical features of Coulomb-fission

    International Nuclear Information System (INIS)

    Fission following quasielastic scattering was investigated in the reactions 208Pb -> 238U below the Coulomb Barrier and 7.5 MeV/u 238U -> 238U at scattering angles forward of the grazing angle (870). A kinematically complete analysis of 3-body coincidences was carried out measuring position and time-of-flight of the scattered projectile-like particle and 2 fission fragments in large parallel plate detectors. In the reaction 208Pb -> 238U, measured at backward angles, the slope of the differential cross section at 5.4 MeV/u is in qualitative agreement with the theoretical expectation for Coulomb-fission. The angular distribution of the fission fragments, measured with respect to the semisector axis (apex line towards the projectile), is close to 1/sinTHETA and does not show any of the significant structures predicted by several theories. The anisotropy is smaller in all other coordinate systems investigated. The fission probability in the reaction 238U -> 238U, measured down to 5x10-4 at THETAsub(cm)=540 (corresponding to 75% Esub(cb) at the distance of closest approach) as well as the low excitation energy 0 as expected for Coulomb-fission. The absence of a detectable final state Coulomb interaction yields a lower limit of 1-2x10-20s for the lifetime of the fissioning nucleus. (orig./HSI)

  5. On the mechanism of fission neutron emission

    International Nuclear Information System (INIS)

    This review represents the present knowledge of the mechanism of prompt fission neutron emission. Starting with a brief fission process characterization related with neutron emission, possible emission mechanisms are discussed. It is emphasized that the experimental study of special mechanisms, i.e. scission neutron emission processes, requires a sufficiently correct description of emission probabilities on the base of the main mechanism, i.e. the evaporation from fully accelerated fragments. Adequate statistical-model approaches have to account for the complexity of nuclear fission reflected by an intricate fragment distribution. The present picture of scission neutron emission is not clarified neither experimentally nor theoretically. Deduced data are contradictory and depend on the used analysis procedures often involving rough discriptions of evaporated-neutron distributions. The contribution of two secondary mechanisms of fission neutron emission, i.e. the neutron evaporation during fragment acceleration and neutron emission due to the decay of 5He after ternary fission, is estimated. We summarize the recent progress of the theoretical description of fission neutron spectra in the framework of statistical models considering the standard spectrum of 252Cf(sf) neutrons especially. The main experimental basis for the study of fission neutron emission is the accurate measurement of emission probabilities as a function of emission energy and angle (at least) as well as fragment parameters (mass number ratio and kinetic energy). The present status is evaluated. (author)

  6. Automatic fission track counting using the Quantimet 720

    International Nuclear Information System (INIS)

    Several sets of Makrofol SSTR were irradiated on the natural uranium shell of the NISUS assembly at the University of London Reactor CONSORT. In each set pairs of films were placed one on the outer surface of the shell and the other on the inner surface. The ratio of the fission rates in the two positions were calculated by ANISN transport code and found to be 10.86. The etched films were counted by the Quantimet 720 and by eye using an optical microscope. The results showed that for the six pairs satisfactorily counted by eye the mean fission ratio was 10.31 with standard deviation of 1.4%. The mean fission ratio for the same pairs satisfactorily counted by the Quantimet was 10.53 with standard deviation of 2.3%. The relative efficiency of the Quantimet to eye was found to be 0.975 +- 0.005 (random). This value is subject to a systematic error of +-2% attributable to the calibration of the fields of view. (Auth.)

  7. Radiation Specifications for Fission Power Conversion Component Materials

    Science.gov (United States)

    Bowman, Cheryl L.; Shin, E. Eugene; Mireles, Omar R.; Radel, Ross F.; Qualls, A. Louis

    2011-01-01

    NASA has been supporting design studies and technology development that could provide power to an outpost on the moon, Mars, or an asteroid. One power-generation system that is independent of sunlight or power-storage limitations is a fission-based power plant. There is a wealth of terrestrial system heritage that can be transferred to the design and fabrication of a fission power system for space missions, but there are certain design aspects that require qualification. The radiation tolerance of the power conversion system requires scrutiny because the compact nature of a space power plant restricts the dose reduction methodologies compared to those used in terrestrial systems. An integrated research program has been conducted to establish the radiation tolerance of power conversion system-component materials. The radiation limit specifications proposed for a Fission Power System power convertor is 10 Mrad ionizing dose and 5 x 10(exp 14) neutron per square centimeter fluence for a convertor operating at 150 C. Specific component materials and their radiation tolerances are discussed. This assessment is for the power convertor hardware; electronic components are not covered here.

  8. Fission induced by nucleons at intermediate energies

    Energy Technology Data Exchange (ETDEWEB)

    Lo Meo, S., E-mail: sergio.lomeo@enea.it [ENEA, Centro Ricerche Ezio Clementel, 40129 Bologna (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, 40127 Bologna (Italy); Mancusi, D., E-mail: davide.mancusi@cea.fr [CEA, Centre de Saclay, Irfu/SPhN, F91191 Gif-sur-Yvette Cedex (France); Massimi, C., E-mail: cristian.massimi@bo.infn.it [Dipartimento di Fisica ed Astronomia dell' Università di Bologna (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, 40127 Bologna (Italy); Vannini, G., E-mail: gianni.vannini@bo.infn.it [Dipartimento di Fisica ed Astronomia dell' Università di Bologna (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, 40127 Bologna (Italy); Ventura, A., E-mail: alberto.ventura@bo.infn.it [Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, 40127 Bologna (Italy)

    2015-01-15

    Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Liège Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p,f) cross sections and used to predict (n,f) cross sections for the same isotopes.

  9. Fission induced by nucleons at intermediate energies

    International Nuclear Information System (INIS)

    Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Liège Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p,f) cross sections and used to predict (n,f) cross sections for the same isotopes

  10. The chemistry of the fission products

    International Nuclear Information System (INIS)

    This is a review of chemistry of some chemical elements in fission products. The elements mentioned are krypton, xenon, rubidium, caesium, silver, strontium, barium, cadmium, rare earth elements, zirconium, niobium, antimony, molybdenum, tellurium, technetium, bromine, iodine, ruthenium, rhodium and palladium. The chemistry of elements and their oxides is briefly given together with the chemical species in aqueous solution. The report also contains tables of the physical properties of the elements and their oxides, of fission products nuclides with their half-life and fission yields and of the permissible concentrations. (author)

  11. Rearrangement of cluster structure during fission processes

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Andrey V.; Solov'yov, Ilia; Greiner, Walter

    2004-01-01

    Results of molecular dynamics simulations of fission reactions $Na_10^2+ -->Na_7^++ Na_3^+ and Na_18^2+--> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analysed. It is demonstrated that the energy necessary for removing homothetic groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. The importance of rearrangement of the cluster structure during the fission process is elucidated....

  12. Fission induced by nucleons at intermediate energies

    CERN Document Server

    Meo, Sergio Lo; Massimi, Cristian; Vannini, Gianni; Ventura, Alberto

    2014-01-01

    Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Li\\`ege Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p,f) cross sections and used to predict (n,f) cross sections for the same isotopes.

  13. Fission induced by nucleons at intermediate energies

    OpenAIRE

    Meo, Sergio Lo; Mancusi, Davide; Massimi, Cristian; Vannini, Gianni; Ventura, Alberto

    2014-01-01

    Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Li\\`ege Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p,f) cross sections and used to predict (n,f) cross sect...

  14. Fission cross section measurements for minor actinides

    Energy Technology Data Exchange (ETDEWEB)

    Fursov, B. [IPPE, Obninsk (Russian Federation)

    1997-03-01

    The main task of this work is the measurement of fast neutron induced fission cross section for minor actinides of {sup 238}Pu, {sup 242m}Am, {sup 243,244,245,246,247,248}Cm. The task of the work is to increase the accuracy of data in MeV energy region. Basic experimental method, fissile samples, fission detectors and electronics, track detectors, alpha counting, neutron generation, fission rate measurement, corrections to the data and error analysis are presented in this paper. (author)

  15. Fission dynamics within time-dependent Hartree-Fock: boost-induced fission

    CERN Document Server

    Goddard, P M; Rios, A

    2015-01-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide $^{240}$Pu as an example. Methods: Quadrupole constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickl...

  16. 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.

  17. Fission Matrix Capability for MCNP Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Carney, Sean E. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory

    2012-09-05

    In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N{sup 2} values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6],

  18. Fission Matrix Capability for MCNP Monte Carlo

    International Nuclear Information System (INIS)

    In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, keff). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N2 values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6], 3D Kord Smit

  19. Radiation Effects in Fission and Fusion Reactors

    Science.gov (United States)

    Odette, G. Robert; Wirth, Brian D.

    Since the prediction of "Wigner disease" [1] and the subsequent observation of anisotropic growth of the graphite used in the Chicago Pile, the effects of radiation on materials has been an important technological concern. The broad field of radiation effects impacts many critical advanced technologies, ranging from semiconductor processing to severe materials degradation in nuclear reactor environments. Radiation effects also occur in many natural environments, ranging from deep space to inside the Earth's crust. As selected examples that involve many basic phenomena that cross-cut and illustrate the broader impacts of radiation exposure on materials, this article focuses on modeling microstructural changes in iron-based ferritic alloys under high-energy neutron irradiation relevant to light water fission reactor pressure vessels. We also touch briefly on radiation effects in structural alloys for fusion reactor first wall and blanket structures; in this case the focus is on modeling the evolution of self-interstitial atom clusters and dislocation loops. Note, since even the narrower topic of structural materials for nuclear energy applications encompass a vast literature dating from 1942, the references included in this article are primarily limited to these two narrower subjects. Thus, the references cited here are presented as examples, rather than comprehensive bibliographies. However, the interested reader is referred to proceedings of continuing symposia series that have been sponsored by several organizations, several monographs [2-4] and key journals (e.g., Journal of Nuclear Materials, Radiation Effects and Defects in Solids).

  20. Spontaneous 238U fission half-life measurements based on fission-track techniques

    International Nuclear Information System (INIS)

    In the last recommendation of the International Union of Pure and Applied Chemistry (I.U.P.A.C.) on spontaneous fission half-lives for ground-state nuclides, a number of measurements of 238U based on fission-track techniques were discarded. The arguments given by the authors are not clear. A more detailed discussion of these determinations is given, considering the possible systematical errors inherent in fission-track approaches. (author)

  1. Fission fragment mass and angular distributions: Probes to study non-equilibrium fission

    Indian Academy of Sciences (India)

    R G Thomas

    2015-08-01

    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 signatures of these non-equilibrium processes based on macroscopic variables. The importance of the sticking time of the dinuclear complex with respect to the equilibration times of various degrees of freedom is emphasized.

  2. Fission barrier, damping of shell correction, and neutron emission in the fission of A ˜200

    Science.gov (United States)

    Mahata, K.; Kailas, S.; Kapoor, S. S.

    2015-09-01

    Decay of 210Po compound nucleus formed in light- and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good descriptions of all the excitation functions have been achieved with a fission barrier of 21.9 ±0.2 MeV, indicating no significant shell correction at the saddle point. For this barrier height, the predicted statistical prefission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies (˜50 MeV ) in the mass region A ˜200 . When only heavy-ion induced fission excitation functions and the prefission neutron multiplicities are included in the fits, the deduced best-fit fission barrier depends on the assumed fission delay time, during which dynamical neutrons can be emitted. A fission delay of (0.8 ±0.1 ) ×10-19 s has been estimated corresponding to the above fission barrier height, assuming that the entire excess neutrons over and above the statistical model predictions are due to the dynamics. The present observation has implication on the study of fission time scale and nuclear viscosity using neutron emission as a probe.

  3. Subroutines to Simulate Fission Neutrons for Monte Carlo Transport Codes

    OpenAIRE

    Lestone, J. P.

    2014-01-01

    Fortran subroutines have been written to simulate the production of fission neutrons from the spontaneous fission of 252Cf and 240Pu, and from the thermal neutron induced fission of 239Pu and 235U. The names of these four subroutines are getnv252, getnv240, getnv239, and getnv235, respectively. These subroutines reproduce measured first, second, and third moments of the neutron multiplicity distributions, measured neutron-fission correlation data for the spontaneous fission ...

  4. Fission fragment radiolysis of carbon dioxide

    International Nuclear Information System (INIS)

    The fission fragment radiolysis of CO2 and the CO2-C3H8, CO2-NO2 systems is studied in comparison with ? radiolysis. Two kinds of back reactions (re-oxidation of carbon monoxide to carbon dioxide) are operative in the fission fragment radiolysis. One (a rapid back reaction) is the unidentified ionic chain reaction which proceeds at low CO concentrations, and the other (a slow back reaction) is assigned to a radical reaction (CO + O + CO2?2CO2). This slow back reaction is a characteristic of fission fragment radiolysis. The analysis of results gives an upper limit of the radius of fission fragment in the reaction system, rp-2. (auth)

  5. Muscovite SSNTD: detection efficiency for fission fragments

    International Nuclear Information System (INIS)

    We measured the detection efficiency of muscovite mica for fission fragments originating from asymptotically thin, ?0, and thick, ??, uranium films. The values obtained were ?0 = (1.00 ± 0.02) and ?? ? 0.77. (author)

  6. "UCx fission targets oxidation test stand"

    CERN Document Server

    Lacroix, Rachel

    2014-01-01

    "Set up a rig dedicated to the oxidation of UCx and define a procedure for repeatable, reliable and safe method for converting UC2 fission targets into an acceptable uranium carbide oxide waste for subsequent disposal by the Swiss Authorities."

  7. Feasibility study on fission moly target development

    International Nuclear Information System (INIS)

    A multi-purpose research reactor, HANARO has been operated on the beginning of 1995 and can be utilized for production of various radioisotopes. And a R and D program for fission Mo production was established, and the technical and economical feasibility study has been performed for fission Mo production in Korea. In this study the process for fission Mo production was recommended as follows; 1. Target : UO2 of annulus type. 2. Separation and purification : Nitric acid dissolution ? Alumina adsorption ? Benzoin oxime precipitation ? Alumina adsorption. And more desirable plan for steady supply of fission Mo were suggested in following viewpoints; 1. Technical collaboration with foreign company. 2. Backup supply system. 3. Marketing arrangement. (Author)

  8. Neutron and ?-emission from fission fragments

    International Nuclear Information System (INIS)

    The statistical model of nuclear reactions is applied to describe the fission fragment neutron and gamma emission characteristics for spontaneous fission of 252Cf and fission of 235U by thermal neutrons. Averaged excitation energies of fission fragments were obtained from experimental neutron multiplicities. The observable characteristics of an emission are reproduced in a wide range of complementary fragments' total kinetic energies and fragment masses. Observed averaged spins are also reproduced. The fractional independent isomeric yield calculation method, based on the gamma-cascade model, is used to describe experimental data for the 235U(nth,f) and 238U(?,f) reactions. The influence on the calculated isomeric yields of two opposing assumptions regarding the nuclear population spin distributions - one based on the rotational degrees of freedom and one on the internal degrees of freedom of completely accelerated fragments - is investigated. (author)

  9. Vitrification processes for fission product solutions

    International Nuclear Information System (INIS)

    The different processes for fission product vitrification in the world are reviewed. Continuous or discontinuous processes, induction or arc heating, in can melting or casting, tests with radioactive or simulated wastes and industrial realizations are described

  10. Development of fission Mo-99 production technology

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Ho; Choung, W. M.; Lee, K. I. and others

    2000-05-01

    Fission Mo-99 is the only parent nuclide of Tc-99m, an extremely useful tool for mdeical diagnosis, with an estimated usage of greater than 80% of nuclear medicine applicatons. HEU and LEU targets to optimize in HANARO irradiation condition suggested and designed for domestic production of fission Mo-99. The optimum process conditions are established in each unit process to meet quality requirements of fission Mo-99 products, and the results of performance test in combined process show Mo separation and purification yield of the above 97%. The concept of Tc generator production process is established, and the result of performance test show Tc production yield of 98.4% in Tc generator procuction process. The drafts is prepared for cooperation of technical cooperation and business investment with foreign country. Evaluation on economic feasibility is accompanied for fission Mo-99 and Tc-99m generator production.

  11. Fission-product release during accidents

    International Nuclear Information System (INIS)

    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, UO2 oxidization to U3O8 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

  12. Neutron energy spectra of spontaneous fission sources

    International Nuclear Information System (INIS)

    Some characteristics of energy distributions of neutrons from spontaneous fission sources are presented. The data on neutron energy spectrum of 252Cf are considered in detail. Main properties of neutron source on the basis of 252Cf are discussed. (author)

  13. The Fission Time Projection Chamber Project

    Science.gov (United States)

    Hill, Tony

    2009-10-01

    New high-precision fission experiments have become a priority within the low-energy nuclear community. Modern sensitivity calculations have revealed unacceptable liabilities in some of the underlying fundamental nuclear data and have provided target accuracies for new measurements that are well beyond what can be delivered using current experimental technologies. A potential breakthrough in the precision barrier for these measurements is the deployment of a Time Projection Chamber (TPC). TPC detector systems were originally developed within the particle physics community and have played a central role in that field for nearly 25 years. A group of 6 universities and 3 national laboratories have undertaken the task of building the first TPC designed specifically for the purpose of measuring fission cross sections. In this talk, I will present the motivation for the fission TPC concept, a few details of the device and why we think an improvement on 50 years of fission experiments can be accomplished.

  14. TMI-2 fission product inventory estimates (draft)

    International Nuclear Information System (INIS)

    This report presents the results of analyses performed to estimate the inventory and distribution of selected radioisotopes within the TMI-2 reactor system. The intent of the report is to document the method used in estimating the fission product inventory and associated uncertainties. The values presented should be viewed as preliminary. Selected radioisotopes for which best-estimate inventories and uncertainties are presented include: Krypton (Kr-85), Cesium (Cs-137), Iodine (I-129), Antimony (Sb-125), Ruthenium (Ru-106), Strontium (Sr-90), Cerium (Ce-144), and Europium (Eu-154). The TMI-2 inventory data will provide a basis for relating the fission product behavior during a large-scale severe accident to smaller-scale experimental data and fission product behavior modeling work. This is an important link in addressing the many technical questions that relate to core damage progression and fission product behavior during severe accidents. 11 refs., 7 figs., 15 tabs

  15. Fission cross section measurements at intermediate energies

    International Nuclear Information System (INIS)

    The activity in intermediate energy particle induced fission cross-section measurements of Pu, U isotopes, minor actinides and sub-actinides in PNPI of Russia is reviewed. The neutron-induced fission cross-section measurements are under way in the wide energy range of incident neutrons from 0.5 MeV to 200 MeV at the GNEIS facility. In number of experiments at the GNEIS facility, the neutron-induced fission cross sections were obtained for many nuclei. In another group of experiments the proton-induced fission cross-section have been measured for proton energies ranging from 200 to 1000 MeV at 100 MeV intervals using the proton beam of PNPI synchrocyclotron. (author)

  16. Decay and fission of the oriented nuclei

    CERN Document Server

    Kadmenskij, S G

    2002-01-01

    The fragment angular distributions for binary decay of oriented spherical and deformed nuclei with taking into account the correct transformational properties of wave functions under time inversion have been investigated. It has been shown that for description of fragment angular distributions the adiabatic approximation for collective rotational nuclear degrees of freedom is not correct. It has been demonstrated that this approximation is valid for description of spontaneous and induced low-energy nuclear fission. The dependence of partial fission widths on the orientation of the internal axes spins, projections of spins, and relative angular moments of fission fragments has been analyzed. It has been shown that the adiabatic approximation results in coherent interference of wave functions of fragments relative movement. This interference forms fragments the universal angular distributions of fission fragments for oriented nuclei. For these distributions the deviations from A. Bohr's formula have been invest...

  17. Uranium deposits obtention for fission chambers

    International Nuclear Information System (INIS)

    The obtention of uranium deposits of the required quality for small cylindrical fission chambers presents some difficulties. With the method of electroplating here described the uniformity, reproducibility and adherence of the obtained deposits were satisfactory. (Author) 6 refs

  18. Fission product release during reactor operation

    International Nuclear Information System (INIS)

    Chemically assisted mechanical process as stress corrosion cracking is recognized as the principal mode of fracture of Zircaloy in LWR. Clad failure generally occurs during unsteady reactor operation as power ramps. Fission products as iodine, bromine and cesium and their compounds have been recognized as the most aggressive agents in Zircaloy stress corrosion cracking. Some proposed mechanisms of the release of fission products in LWR modern fuel rods of the 17 x 17 type are analyzed. The results of a parametric study performed with the COMETHE III-J code to investigate the effect of power ramping on fission produce release are displayed. The goal of that parametric study was to investigate the possibility of a fission product release enhancement during a power ramp. Three mechanisms leading to such an enhancement are proposed and discussed

  19. Absolute measurements of the 235U and 238U fission cross-sections in the 252Cf fission neutron spectrum

    International Nuclear Information System (INIS)

    Absolute measurements have been made of the fission cross-sections of 235U and 238U in the 252Cf fission neutron spectrum, using the method of coincidences between fission events in a target made of the isotope studied, and the associated fission fragments of californium. A detailed description of the measurement method is provided, covering the reasons for choosing the geometrical conditions of the experiment, the calculations made for that purpose, the preparation of targets, the detection apparatus and sources of errors. 235U and 238U fission cross-sections in the 252Cf fission neutron spectrum are calculated from differential fission cross-section measurements. (author)

  20. Seventy-five years of nuclear fission

    Indian Academy of Sciences (India)

    S S Kapoor

    2015-08-01

    Nuclear fission process is one of the most important discoveries of the twentieth century. In these 75 years since its discovery, the nuclear fission related research has not only provided new insights in the physics of large scale motion, deformation and subsequent division of a heavy nucleus, but has also opened several new frontiers of research in nuclear physics. This article is a narrative giving an overview of the landmarks of the progress in the field.

  1. A revised calculational model for fission

    International Nuclear Information System (INIS)

    A semi-empirical parametrization has been developed to calculate the fission contribution to evaporative de-excitation of nuclei with a very wide range of charge, mass and excitation-energy and also the nuclear states of the scission products. The calculational model reproduces measured values (cross-sections, mass distributions, etc.) for a wide range of fissioning systems: Nuclei from Ta to Cf, interactions involving nucleons up to medium energy and light ions. (author)

  2. MCNP6 Fission Multiplicity with FMULT Card

    Energy Technology Data Exchange (ETDEWEB)

    Wilcox, Trevor [Los Alamos National Laboratory; Fensin, Michael Lorne [Los Alamos National Laboratory; Hendricks, John S. [Los Alamos National Laboratory; James, Michael R. [Los Alamos National Laboratory; McKinney, Gregg W. [Los Alamos National Laboratory

    2012-06-18

    With the merger of MCNPX and MCNP5 into MCNP6, MCNP6 now provides all the capabilities of both codes allowing the user to access all the fission multiplicity data sets. Detailed in this paper is: (1) the new FMULT card capabilities for accessing these different data sets; (2) benchmark calculations, as compared to experiment, detailing the results of selecting these separate data sets for thermal neutron induced fission on U-235.

  3. A revised calculational model for fission

    Energy Technology Data Exchange (ETDEWEB)

    Atchison, F.

    1998-09-01

    A semi-empirical parametrization has been developed to calculate the fission contribution to evaporative de-excitation of nuclei with a very wide range of charge, mass and excitation-energy and also the nuclear states of the scission products. The calculational model reproduces measured values (cross-sections, mass distributions, etc.) for a wide range of fissioning systems: Nuclei from Ta to Cf, interactions involving nucleons up to medium energy and light ions. (author)

  4. Detector instrumentation for nuclear fission studies

    Indian Academy of Sciences (India)

    Akhil Jhingan

    2015-09-01

    The study of heavy-ion-induced fusion–fission reactions require nuclear instrumentation that include particle detectors such as proportional counters, ionization chambers, silicon detectors, scintillation detectors, etc., and the front-end electronics for these detectors. Using the detectors mentioned above, experimental facilities have been developed for carrying out fusion–fission experiments. This paper reviews the development of detector instrumentation at IUAC.

  5. Influence of spin on fission fragments anisotropy

    OpenAIRE

    Ghodsi Omid N.; Behkami Aziz N.; Rahimi Farhad M.

    2005-01-01

    An analysis of selected fission fragment angular distribution when at least one of the spins of the projectile or target is appreciable in induced fission was made by using the statistical scission model. The results of this model predicate that the spins of the projectile or target are affected on the nuclear level density of the compound nucleus. The experimental data was analyzed by means of the couple channel spin effect formalism. This formalism suggests that the projectile spin is more ...

  6. Modeling Fission Product Sorption in Graphite Structures

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [University of Wisconsin, Madison, WI (United States); Morgan, Dane [University of Wisconsin, Madison, WI (United States); Allen, Todd [University of Wisconsin, Madison, WI (United States)

    2013-04-08

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products on each type of graphite site. The model will include multiple simultaneous adsorbing species, which will allow for competitive adsorption effects between different fission product species and O and OH (for modeling accident conditions).

  7. Our 50-year odyssey with fission: Summary

    International Nuclear Information System (INIS)

    On the occasion of this International Conference on Fifty Years Research in Nuclear Fission, we summarize our present understanding of the fission process and the challenges that lie ahead. The basic properties of fission arise from a delicate competition between disruptive Coulomb forces, cohesive nuclear forces, and fluctuating shell and pairing forces. These static forces are primarily responsible for such experimental phenomena as deformed ground-state nuclear shapes, fission into fragments of unequal size, sawtooth neutron yields, spontaneously fissioning isomers, broad resonances and narrow intermediate structure in fission cross sections, and cluster radioactivity. However, inertial and dissipative forces also play decisive roles in the dynamical evolution of a fissioning nucleus. The energy dissipated between the saddle and scission points is small for low initial excitation energy at the saddle point and increases with increasing excitation energy. At moderate excitation energies, the dissipation of collective energy into internal single-particle excitation energy proceeds largely through the interaction of nucleons with the mean field and with each other in the vicinity of the nuclear surface, as well as through the transfer of nucleons between the two portions of the evolving dumbell-like system. These unique dissipation mechanisms arise from the Pauli exclusion principle for fermions and the details of the nucleon-nucleon interaction, which make the mean free path of a nucleon near the Fermi surface at low excitation energy longer than the nuclear radius. With its inverse process of heavy-ion fusion reactions, fission continues to yield surprises in the study of large-amplitude collective nuclear motion. 87 refs., 12 figs

  8. JNDC nuclear data library of fission products

    International Nuclear Information System (INIS)

    The JNDC (Japanese Nuclear Data Committee) FP (Fission Product) nuclear data library for 1172 fission products is described in this report. The gross theory of beta decay has been used extensively for estimating unknown decay data and also some of known decay data with poor accuracy. The calculated decay powers of fission products using the present library show excellent agreement with the latest measurements at ORNL (Oak Ridge National Laboratory), LANL (Los Alamos National Laboratory) and UTT (University of Tokyo, Tokai) for cooling times shorter than 103 s after irradiation. The calculated decay powers by the existing libraries showed systematic deviations at short cooling times; the calculated beta and gamma decay powers after burst fission were smaller than the experimental results for cooling times shorter than 10 s, and in the cooling time range 10 to 103 s the beta-decay power was larger than the measured values and the gamma decay power smaller than the measured results. The present JNDC FP nuclear data library resolved these discrepancies in the short cooling time ranges. The decay power of fission products has been calculated for ten fission types and the results have been fitted by an analytical function with 31 exponentials. This permits the easy application of the present results of decay power calculations to a LOCA (Loss-of-Coolant Accident) analysis of a light water reactor and so on. (author)

  9. Statistical model investigation of nuclear fission

    International Nuclear Information System (INIS)

    To assist in the improvement of fission product yield data libraries, the statistical theory of fission was investigated. Calculation of the theory employs a recent nuclear mass formula and nuclear density of states expression. Yields computed with a simple statement of the theory do not give satisfactory results. A slowly varying empirical parameter is introduced to improve agreement between measured and calculated yields. The parameter is interpreted as the spacing between the tips of the fragments at the instant of scission or as the length of a neck in the fissioning nucleus immediately prior to scission. With this spacing parameter semi-quantitative agreement is obtained between calculated and measured mass chain yields for six cases investigated, 233U(n/sub th/, f), 235U(n/sub th, f), 239Pu(n/sub th/, f), 235U(n+14, f), 238U(n+14, f), and 252Cf(sf). An indication of the source of mass asymmetry in fission is presented. The model developed predicts a mass and energy dependence of some of the parameters of models currently in use in data generation. A procedure for the estimation of the fission product yields for an arbitrary fissioning system is proposed. 63 references

  10. Ionization Chamber for Prompt Fission Neutron Investigations

    Science.gov (United States)

    Zeynalov, Sh.; Zeynalova, O.; Hambsch, F.-J.; Sedyshev, P.; Shvetsov, V.

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical formulae provided for FF angles measured in respect to the coordinate axes. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event-by-event analysis of individual fission reactions from non- point fissile source. Position sensitive neutron induced fission detector for neutron-imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  11. Dynamics in heavy ion fusion and fission

    International Nuclear Information System (INIS)

    Dynamical aspects of heavy ion fussion and fission, mainly the aspect of damping which is meant as the dissipation of kinetic energy and the aspect of the effective mass of the fission motion, are discussed. Two categories of evidence of damping effects are given. One relates to the damping of the fission motion for the ground state shape and for the isomeric more elongated shape. The other relates to the damping of the fission motion from the last barrier to the scission point. The dependence of the effective mass associated with the fission motion on the deormation of nucleus is shown. As the elongation of the nucleus increases the effective mass of the fission motion varies strongly from being about forty times greater than the reduced mass in the beta-vibrational state of the ground state shape to being equal to the reduced mass in the moment of scission. Damping effects are expected to be propartional to the difference between the effective mass and the reduced mass. It is concluded that the damping in fussion reactions is relatively weak for lighter products and quite strong for superheavy products like 236U or 252Cf. (S.B.)

  12. Nuclear fission reactors from thousand of million years

    International Nuclear Information System (INIS)

    This book is about nuclear reactors, not only of the industrial ones that work to provide electric power, neither of those experimental ones as the first one that worked in Chicago in the first half of the XX Century but, mainly, of those that worked in the Earth thousands of millions of years ago. The book examines what happened in last geologic times, when the natural uranium had a different constitution to the current one. We will give you information on the nuclear fission reactors that worked in Gabon, Africa. A discussion of the radioactive isotopes formed during the operation of those reactors and its behavior until our days is presented. (Author)

  13. Fission neutron source in Rome

    Science.gov (United States)

    Coppola, Mario; Di Majo, V.; Ingrao, G.; Rebessi, S.; Testa, A.

    1997-02-01

    A fission neutron source is operating in Rome at the ENEA Casaccia Research Center since 1971, consisting of a low power fast reactor named RSV-Tapiro. it is employed for a variety of experiments, including dosimetry, material testing, radiation protection and biology. In particular, application to experimental radiobiology includes studies of the biological action of neutrons in the whole-body irradiated animal, or in specialized systems in vivo or in vitro. For his purpose a vertical irradiation facility was originally constructed. Recently, a new horizontal irradiation facility has been designed to allow the exposure of larger samples or larger sample batches at one time. Dosimetry at the sample irradiation positions is routinely carried out by the conventional method of using two ion chambers. This physical dosimetry has recently been compared with the results of biological dosimetry based on the detection of chromosomal aberrations in peripheral blood human lymphocytes irradiated in vitro. A characterization of the radiation quality in the two configurations has been carried out by tissue equivalent proportional counter microdosimetry measurements. Information about the main characteristics of the reactor and the two irradiation facilities is provided and relevant results of the various measurements are summarized. Radiobiological results obtained using this neutron source are also briefly outlined.

  14. Fission track geochrobiology of India

    International Nuclear Information System (INIS)

    Fission track technique has been applied for dating muscovite, biotite, vermiculite, apatite, sphene zircon, hornblended and garnet samples collected from different geological regions of India. Geological annealing of tracks in each of these samples was ascertained and observed ages were corrected wherever necessary. The corrected age data ranging between 5 m.y., to 1,500 m.y., though deficient in older age measurements due to inherent limitations of the method, make a significant contribution towards throwing additional light on various metamorphic and thermal episodes in the sub-continent. Age measurements are peaked at 30 m.y., 500 m.y., and 875 m.y., corresponding to the Himalayan Orogeny, Indian Ocean Orogeny and Satpura Orogeny respectively. The data have been compared wherever possible, with the measurements made by other radiometric methods. From the knowledge of annealing characteristics of the minerals, the age data of cogenetic/coexisting minerals have been utilized to delineate the thermal history of different regions of India. (author)

  15. Fission-track ages of four meteorites

    International Nuclear Information System (INIS)

    A method for selective annealing of cosmic-ray tracks has been developed, permitting determination of fission-track ages in the presence of a large background of cosmic-ray tracks. The mesosiderite Bondoc contains 41 fission tracks/cm2, of which about 75% are due to neutron-induced fission of U235 during cosmic-ray exposure. Its net fission-track age is 140 +- 40 Myr, nearly identical to its cosmic-ray exposure age of 150 Myr. The mesosiderite Mincy has a fission-track age of 1500 +- 400 Myr. Nakhla (nakhlite) contains an excess of apparent fission tracks, which may be either genuine fission tracks from Pu244 or etch pits mimicking fission tracks in length, thermal stability, random orientation, and other characteristics. On the assumption that they are fission tracks, the Pu244/U238 ratio at the onset of track retention in Nakhla was (3.1 +- 1.3) x 10-3, nearly an order of magnitude lower than the initial solar system ratio. This may reflect a chemical fractionation of Pu and U, or a late impact or magmatic event. Different minerals of the Washougal howardite have different Pu244/U238 ratios, from (24 +- 7) x 10-3 to (2.3 +- 0.7) x 10-3. This may imply a succession of impacts over a period of time. Additionally, Pu and U may have been chemically fractionated from each other in this meteorite. Shocked meteorites show no consistent pattern in the retentivity of fission tracks and of fissiogenic or radiogenic noble gases. Some meteorites, e.g. Bondoc, Serra de Mage, and Mincy, retain gases more completely than tracks; others e.g. Nakhla and Allende, retain them less completely. Uranium was determined in feldspar and/or pyroxene from 19 Ca-rich achondrites and mesosiderites. For most, only upper limits of 0.01 to 0.03 ppb were obtained. Apparently the uranium in these meteorites resides almost exclusively in minor phases, as in terrestrial and lunar rocks. (author)

  16. Sub-threshold fission of 241Am

    International Nuclear Information System (INIS)

    The neutron-induced sub-threshold fission cross-section of 241Am is measured in the energy range between 1 eV and 3 keV with nominal time-of- flight resolution of 20 ns/m and 2ns/m using the CBNM linear accelerator as pulsed neutron source and a liquid scintillator for the detection of the fission neutrons. This detector is equipped with pulse shape discriminators and pile up rejectors against the high ?-radiation from the sample. This experiment has been motivated by our sub-threshold fission cross-section data on 240Pu showing the groupwise resonance enhancement due to intermediate states in the fission exit channel and by the fission cross-section display of 241Am (n, f) in the Petrel report of P.A. Seeger et al. where intermediate structures of different types are slightly indicated. With our high resolution experiment we try to investigate further the existence of intermediate levels of the type found in sub-threshold fission of 240Pu. The presence of intermediate states as well as the existence of a spontaneously fissioning shape isomer in 242Am found by Flerov et al. have been interpreted by Bjornholm, Lynn and Weigmann on the basis of the theory of Strutinsky. It has been pointed out by J.R. Nix that a quantitative analysis of the experimental results on the ratio of the half-lives of the ground state and the isomeric spontaneous fission of 242Am is not in agreement with the value for the energy of a secondary potential minimum deduced from the isomer excitation function and from fission cross-section resonance spacings. With our experiment we have tried to investigate carefully the latter point. Our result is that between 1 and 3 keV no narrow cross-section structures greater than 1 barn are observed, while we clearly confirm the resonances at low energy up to 150 eV, which have been already measured by C. Bowman as well as P.A. Seeger et al. This result agrees with the discussion of E. Lynn at the Dubna Conference on Nuclear Structure, in which he mentioned that the general behaviour of the 241Am sub-threshold fission cross-section does not fit with the size of the narrow intermediate structures indicated in the Petrel data between 1 and 3 keV. (author)

  17. Microscopic Description of Nuclear Fission: Fission Barrier Heights of Even-Even Actinides

    CERN Document Server

    McDonnell, J; Nazarewicz, W

    2013-01-01

    We evaluate the performance of modern nuclear energy density functionals for predicting inner and outer fission barrier heights and energies of fission isomers of even-even actinides. For isomer energies and outer barrier heights, we find that the self-consistent theory at the HFB level is capable of providing quantitative agreement with empirical data.

  18. 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.

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

    International Nuclear Information System (INIS)

    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

  20. Fission product inventory, release fractions, and radiation levels from fission products released to the test chamber

    Energy Technology Data Exchange (ETDEWEB)

    Maringas, N.

    1978-05-12

    The fission product inventory, fission product release fractions, and radiation levels following a blowdown into the test chamber are presented. Operating sequences discussed are based on present knowledge and are used for the purpose of calculating radiation levels at different times.

  1. Particle evaporation-fission competition in nuclear fission considered as a diffusion process

    International Nuclear Information System (INIS)

    Nuclear fission is treated as a diffusion process in phase space corresponding to the essential collective variable of fission. The solution of the two-dimensional Fokker-Planck equation is used to obtain an escape rate over the collective potential barrier. This escape rate over the barrier presents a transient regime, the asymptotic value of which is identified to the fission width given by the usual statistical model. This time dependent fission width is included in a schematic formalism for the deexcitation of the compound nucleus to calculate the multiplicities of pre-fission neutrons. A sensitive dependence of the multiplicities on the friction and an enhancement of the multiplicities with respect to the standard statistical model at high energy are obtained

  2. Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics

    CERN Document Server

    Farget, F; Delaune, O; Tarasov, O B; Derkx, X; Schmidt, K -H; Amthor, A M; Audouin, L; Bacri, C -O; Barreau, G; Bastin, B; Bazin, D; Blank, B; Benlliure, J; Caceres, L; Casarejos, E; Chibihi, A; Fernandez-Dominguez, B; Gaudefroy, L; Golabek, C; Grevy, S; Jurado, B; Kamalou, O; Lemasson, A; Lukyanov, S; Mittig, W; Morrissey, D J; Navin, A; Pereira, J; Perrot, L; Rejmund, M; Roger, T; Saint-Laurent, M -G; Savajols, H; Schmitt, C; Sherill, B M; Stodel, C; Taieb, J; Thomas, J -C; Villari, A C

    2012-01-01

    During the fission process, the nucleus deforms and elongates up to the two fragments inception and their final separation at scission deformation. The evolution of the nucleus energy with deformation is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most genuine experimental observation of the potential energy landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at energy close to the Coulomb barrier, produce well-defined conditions of the compound nucleus formation, where processes such as quasi-fission, pre-equilibrium emission and incomplete fusion are negligible. In the same time, the excitation energy is sufficient to reduce significantly structural effects, and mostly the macroscopic part of the potential is responsible for the formation of the fission fragmen...

  3. Nuclear fission energy: breeder reactors

    International Nuclear Information System (INIS)

    The U.S. budget authorizations requested for the Liquid Metal (Cooled)-Fast Breeder Reactor (LMFBR) program during 1977 are about $555 x 106. Most of the funds are being spent on a demonstration plant for electrical power production to be located on the Clinch River near Oak Ridge, Tennessee, the Clinch River Breeder Reactor. Other large portions of the program include a Fast Fuel Testing Facility at Richland, Washington, the development of advanced fuel elements to avoid the thermal limitation of uranium-plutonium oxide fuel elements, and the testing of large heat exchangers, pumps, and other apparatuses for handling molten sodium. A program to develop a (helium-) Gas-Cooled Fast (breeder-) Reactor (GCFR) supplements the LMFBR program. Probably more advanced programs to develop fast breeder reactors are under way in France, Germany, England, Russia, and Japan. Phenix, a demonstration plant in France, has been producing 250 MW(e) of electric power since March 1974. The urgent motivation for these programs is a large increase in total energy production from limited supplies of uranium. The available energy may be increased more than one hundred times above that produced by thermal neutron reactors. Alternative means of extending and conserving fission energy resources receive approximately one tenth of the current effort devoted to the LMFBR. The wisdom of the LMFBR program is being questioned on the grounds that uranium and thorium resources may prove to be much larger than the identified reserves, that fast reactors may be too hazardous to operate, and that the large amounts of plutonium flowing in the fuel cycle require impracticably stringent control measures in order to eliminate toxic effects and diversion for the production of nuclear bombs. Design objectives and measures to assure operational safety are discussed

  4. Measurements of the U-235 fission atomic percentage by thermoionic mass spectroscopy

    International Nuclear Information System (INIS)

    The most widely used methods in precise measurements of uranium isotopic abundance and uranium-235 percent fission for the purpose of burnup determination, are based on thermoionic mass spectrometry. Employing a surface ionization mass spectrometer coupled with a data processing system, uranium ratios have been obtained from irradiated and non-irradiated dilute solutions of natural uranium oxide sinterized pellets. The fission products separation and uranium chemical purification have been carried out by anion exchange. Detailed description of irradiation, dissolution, chemical separation and purification, deposition, data collecting and processing procedures is given. (Author)

  5. Progress on the conceptual design of a mirror hybrid fusion--fission reactor

    International Nuclear Information System (INIS)

    A conceptual design study was made of a fusion-fission reactor for the purpose of producing fissile material and electricity. The fusion component is a D-T plasma confined by a pair of magnetic mirror coils in a Yin-Yang configuration and is sustained by neutral beam injection. The neutrons from the fusion plasma drive the fission assembly which is composed of natural uranium carbide fuel rods clad with stainless steel and helium cooled. It was shown conceptually how the reactor might be built using essentially present-day technology and how the uranium-bearing blanket modules can be routinely changed to allow separation of the bred fissile fuel

  6. Measurement of the ?-decay to Spontaneous fission branching ratio of 252Cf with the NIFFTE Fission Time Projection Chamber

    Science.gov (United States)

    Snyder, Lucas; Niffte Collaboration

    2013-10-01

    Neutron-induced fission cross sections are of particular importance when simulating and modeling nuclear fuel cycles. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration is developing a fission Time Projection Chamber (TPC) to measure neutron-induced fission cross sections with total uncertainty of better than 1 %. To achieve such precision, the systematic uncertainties of the previously used measurement techniques must be addressed. The fission TPC will do this, in part, by providing detailed 3-dimensional images of fission fragments and other charged-particles produced in a neutron beam environment. Throughout the fission TPC's development phase the ?-decay and spontaneous fission of 252Cf has been used to benchmark its performance. Recently the first 252Cf data were collected using the fully instrumented fission TPC, which has nearly 6000 individual channels and provides 4 ? coverage. A preliminary analysis of the ?/SF branching ratio will be presented.

  7. Nuclear fission induced by heavy ions

    International Nuclear Information System (INIS)

    Because the accelerators of the 50's and 60's mostly provided beams of light ions, well suited for studying individual quantum states of low angular momentum or reactions involving the transfer of one or two nucleons, the study of fission, being an example of large-scale collective motion, has until recently been outside of the mainstream of nuclear research. This situation has changed in recent years, due to the new generation of accelerators capable of producing beams of heavy ions with energies high enough to overcome the Coulomb barriers of all stable nuclei. These have made possible the study of new examples of large-scale collective motions, involving major rearrangements of nuclear matter, such as deep-inelastic collisions and heavy-ion fusion. Perhaps the most exciting development in the past few years is the discovery that dissipative effects (nuclear viscosity) play an important role in fission induced by heavy ions, contrary to earlier assumptions that the viscosity involved in fission was very weak and played only a minor role. This review will be mainly concerned with developments in heavy-ion induced fission during the last few years and have an emphasis on the very recent results on dissipative effects. Since heavy-ion bombardment usually results in compound systems with high excitation energies and angular momenta, shell effects might be expected to be small, and the subject of low energy fission, where they are important, will not be addressed. 285 refs., 58 figs

  8. Fission-fragment spikes in uranium dioxide

    Science.gov (United States)

    Ronchi, C.; Wiss, T.

    2002-11-01

    The article deals with some fundamental aspects of the fission energy dispersion in nuclear reactor fuel. The analysis starts from the transmission electron microscope observation of tracks produced by energetic fission fragments in thin foils of UO2 single crystals. On the one hand, these tracks appear on the free surface as explosive material displacements. On the other, the passage of fission fragments in the bulk does not leave visible, continuous traces. Furthermore, irradiated U4O9, which consists of a UO2 lattice hosting a temperature sensitive superstructure of interstitial oxygen, persists after experiencing the near-field action of fission fragment thermal spikes. These seemingly inconsistent phenomena have been explained by showing that a large fraction of the fission fragment electronic losses is converted in strong shock waves whose passage in the solid is too fast for producing atomic displacements, but which can release high energies by unloading on free surfaces. The consequent matter displacements have been shown to have important effects on the structural properties of the nuclear fuel.

  9. Theory of neutron emission in fission

    Energy Technology Data Exchange (ETDEWEB)

    Madland, D.G.

    1998-08-01

    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 {nu}}{sub 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 {nu}}{sub 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{sub n}), where E{sub 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.

  10. Some aspects of the nuclear fission process

    International Nuclear Information System (INIS)

    In the following report one can find first a short general view on the present situation of our knowledge concerning the nuclear fission process, namely on the nucleus going through the saddle-point. Then there are some aspects connected with the excitation energy of the fissioning nucleus. The measurements made at Saclay on the fast neutron fission cross-section of U233, U235, Pu239, U238 are described at the beginning of this work. It appears that for U233 there is some characteristic shape modulation of the cross-section curve, in relation with the collective excited state of the deformed nucleus at the saddle-point. Good evidence of this is also given by the study of the relative fission rate with emission of long-range particles; it appears also that this ternary fission rate does not change substantially for neutron between thermal energy and 2 MeV, but that is very lower for the compound nucleus U239 than for even-even compound nuclei. At the end there are some experiments on the strong 4,5 MeV gamma-ray originated by slow neutron absorption in U235. Time-of-flight device is used to establish that this 4,5 MeV gamma-ray seems mostly connected with radiative capture. (author)

  11. Reference reactor module for NASA's lunar surface fission power system

    Energy Technology Data Exchange (ETDEWEB)

    Poston, David I [Los Alamos National Laboratory; Kapernick, Richard J [Los Alamos National Laboratory; Dixon, David D [Los Alamos National Laboratory; Werner, James [INL; Qualls, Louis [ORNL; Radel, Ross [SNL

    2009-01-01

    Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. The AFSPS concept is now being further developed within the Fission Surface Power (FSP) Project, which is a near-term technology program to demonstrate system-level TRL-6 by 2013. This paper describes the reference FSP reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on the lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based. UO{sub 2}-fueled, pumped-NaK fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. The ultimate goal of this work is to provide a 'workhorse' power system that NASA can utilize in near-term and future Lunar and Martian mission architectures, with the eventual capability to evolve to very high power, low mass systems, for either surface, deep space, and/or orbital missions.

  12. Chemical states of volatile and corrosive fission products in thoria based fuels from thermodynamic studies

    International Nuclear Information System (INIS)

    Advanced Heavy Water Reactor (AHWR) uses thoria-based fuel having Urania content of about 3.5 mol%. The fuel chemistry with thoria is not expected to be the same as that experienced with Urania of the conventional reactors. The difference in chemistry originates from the rigid nature of four valency of Th in its compounds as against the flexible valency of four to six seen in the U case. For the analysis of the fuel-clad integrity during the long irradiation period, the knowledge of chemical states of the fission products, particularly those of volatile and corrosive ones are absolutely essential. This paper details the results of thermodynamic and transport properties presently studied in our laboratory, on such volatile and corrosive fission products which leads to the conclusion on the specific characteristics of fission products chemistry in thoria based fuel. (author)

  13. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals

    Science.gov (United States)

    Wang, Rui; Zhang, Chunfeng; Zhang, Bo; Liu, Yunlong; Wang, Xiaoyong; Xiao, Min

    2015-10-01

    Singlet fission can potentially break the Shockley-Queisser efficiency limit in single-junction solar cells by splitting one photoexcited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multiexciton state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this multiexciton state, especially how the doubly excited triplets interact, remains elusive. Here we report a quantitative study on the magnetic dipolar interaction between singlet-fission-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the multiexciton sublevels at room temperature. The resonances of multiexciton sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ~0.008 GHz. Our work quantifies the magnetic dipolar interaction in certain organic materials and marks an important step towards understanding the underlying physics of the multiexciton state in singlet fission.

  14. Control of a laser inertial confinement fusion-fission power plant

    Energy Technology Data Exchange (ETDEWEB)

    Moses, Edward I.; Latkowski, Jeffery F.; Kramer, Kevin J.

    2015-10-27

    A laser inertial-confinement fusion-fission energy power plant is described. The fusion-fission hybrid system uses inertial confinement fusion to produce neutrons from a fusion reaction of deuterium and tritium. The fusion neutrons drive a sub-critical blanket of fissile or fertile fuel. A coolant circulated through the fuel extracts heat from the fuel that is used to generate electricity. The inertial confinement fusion reaction can be implemented using central hot spot or fast ignition fusion, and direct or indirect drive. The fusion neutrons result in ultra-deep burn-up of the fuel in the fission blanket, thus enabling the burning of nuclear waste. Fuels include depleted uranium, natural uranium, enriched uranium, spent nuclear fuel, thorium, and weapons grade plutonium. LIFE engines can meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the highly undesirable stockpiles of depleted uranium, spent nuclear fuel and excess weapons materials.

  15. Control of a laser inertial confinement fusion-fission power plant

    Energy Technology Data Exchange (ETDEWEB)

    Moses, Edward L; Latkowski, Jeffrey F; Kramer, Kevin J

    2015-11-05

    A laser inertial-confinement fusion-fission energy power plant is described. The fusion-fission hybrid system uses inertial confinement fusion to produce neutrons from a fusion reaction of deuterium and tritium. The fusion neutrons drive a sub-critical blanket of fissile or fertile fuel. A coolant circulated through the fuel extracts heat from the fuel that is used to generate electricity. The inertial confinement fusion reaction can be implemented using central hot spot or fast ignition fusion, and direct or indirect drive. The fusion neutrons result in ultra-deep burn-up of the fuel in the fission blanket, thus enabling the burning of nuclear waste. Fuels include depleted uranium, natural uranium, enriched uranium, spent nuclear fuel, thorium, and weapons grade plutonium. LIFE engines can meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the highly undesirable stockpiles of depleted uranium, spent nuclear fuel and excess weapons materials.

  16. Determination of the fission coefficients in thermal nuclear reactors for antineutrino detection

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Lenilson M. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Cabral, Ronaldo G., E-mail: rgcabral@ime.eb.b [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil); Anjos, Joao C.C. dos, E-mail: janjos@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Dept. GLN - G

    2011-07-01

    The nuclear reactors in operation periodically need to change their fuel. It is during this process that these reactors are more vulnerable to occurring of several situations of fuel diversion, thus the monitoring of the nuclear installations is indispensable to avoid events of this nature. Considering this fact, the most promissory technique to be used for the nuclear safeguard for the nonproliferation of nuclear weapons, it is based on the detection and spectroscopy of antineutrino from fissions that occur in the nuclear reactors. The detection and spectroscopy of antineutrino, they both depend on the single contribution for the total number of fission of each actinide in the core reactor, these contributions receive the name of fission coefficients. The goal of this research is to show the computational and mathematical modeling used to determinate these coefficients for PWR reactors. (author)

  17. Some aspects of the interaction between thermal hydraulics and fission product transport in reactor containments under severe accident conditions

    International Nuclear Information System (INIS)

    In past studies of severe accident consequences, containment thermal-hydraulic calculations have been performed first, and used to provide input for the containment fission product transport calculations. However, not all the input required has been supplied. An example of a simple calculation of one such variable, the turbulent energy density dissipation rate, is given. Furthermore fission product transport can itself affect the thermal hydraulics. The fission products are important heat sources for the containment. In light water reactor containments the behavior of steam is affected by the nature of the aerosol present. Modelling evaporating conditions requires a knowledge of the mass of water airborne. Current thermal-hydraulic codes assume a saturation vapor pressure relevant to a plane surface and to pure water. This number will be altered by the curvature of the aerosol droplets and by the presence of soluble fission product forms

  18. Prompt fission neutron emission: Problems and challenges

    Directory of Open Access Journals (Sweden)

    Hambsch F.-J.

    2013-12-01

    Full Text Available This paper presents some of the challenges ahead of us even after 75 years of the discovery of the fission process and large progress made since then. The focus is on application orientation, which requires improved measurements on fission cross-sections and neutron and ?-ray multiplicities. Experimental possibilities have vastly improved the past decade leading to developments of highly sophisticated detector systems and the use of digital data acquisition and signal processing. The development of innovative fast nuclear reactor technology needs improved respective nuclear data. Advancements in theoretical modelling also require better experimental data. Theory has made progress in calculating fission fragment distributions (i.e. GEF code as well as prompt neutron and ?-ray emission to catch up with the improved experiments.

  19. Fission Enhanced diffusion of uranium in zirconia

    CERN Document Server

    Bérerd, N; Moncoffre, N; Sainsot, P; Faust, H; Catalette, H

    2005-01-01

    This paper deals with the comparison between thermal and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding tubes. The experiments under irradiation are performed at the Institut Laue Langevin (ILL) in Grenoble using the Lohengrin spectrometer. A thin $^{235}UO\\_2$ layer in direct contact with an oxidized zirconium foil is irradiated in the ILL high flux reactor. The fission product flux is about 10$^{11}$ ions cm$^{-2}$ s$^{-1}$ and the target temperature is measured by an IR pyrometer. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia from the energy distribution broadening of two selected fission products. It is found to be equal to 10$^{-15}$ cm$^2$ s$^{-1}$ at 480$\\circ$C and compared to uranium thermal diffusion data in ZrO$\\_2$ in the same pressure and temperature conditions. The FED results are analysed in comparison with literature data.

  20. Dissipative dynamics in quasi-fission

    CERN Document Server

    Oberacker, V E; Simenel, C

    2014-01-01

    Quasi-fission is the primary reaction mechanism that prevents the formation of superheavy elements in heavy-ion fusion experiments. Employing the time-dependent density functional theory approach we study quasi-fission in the systems $^{40,48}$Ca+$^{238}$U. Results show that for $^{48}$Ca projectiles the quasi-fission is substantially reduced in comparison to the $^{40}$Ca case. This partly explains the success of superheavy element formation with $^{48}$Ca beams. For the first time, we also calculate the repartition of excitation energies of the two fragments in a dynamic microscopic theory. The system is found in quasi-thermal equilibrium only for reactions with $^{40}$Ca. The differences between both systems are interpreted in terms of initial neutron to proton asymmetry of the colliding partners.

  1. Prompt fission neutron emission: Problems and challenges

    Science.gov (United States)

    Hambsch, F.-J.; Bry?, T.; Gamboni, T.; Geerts, W.; Göök, A.; Matei, C.; Oberstedt, S.; Vidali, M.

    2013-12-01

    This paper presents some of the challenges ahead of us even after 75 years of the discovery of the fission process and large progress made since then. The focus is on application orientation, which requires improved measurements on fission cross-sections and neutron and ?-ray multiplicities. Experimental possibilities have vastly improved the past decade leading to developments of highly sophisticated detector systems and the use of digital data acquisition and signal processing. The development of innovative fast nuclear reactor technology needs improved respective nuclear data. Advancements in theoretical modelling also require better experimental data. Theory has made progress in calculating fission fragment distributions (i.e. GEF code) as well as prompt neutron and ?-ray emission to catch up with the improved experiments.

  2. Process for fine purification of fission molybdenum

    International Nuclear Information System (INIS)

    The invention deals with a method for the fine purification of fission molybdenum, dissolved in anionic form together with the anions of the fission products of J, Sn, Ce, Ru, and Zr in an aqueous mineral acid solution; in this process the fission molybdenum is a) fixed on a metal oxide in a sorption step and b) released again in a desorption step. By the invention, a method shall be created, which is, under less favourable working conditions, almost insusceptible to failure and can be safely carried out with low expenditure of operation time, working equipment and handling technique and which delivers a highly pure Mo-99 product with a decreased volume of radioactive waste at the same time. (orig./RB)

  3. Fission products in glasses. Pt. 2

    International Nuclear Information System (INIS)

    Glass ceramics of different composition with high leach and impact resistance can be produced for fission product solidification. In contrast to commercial glass products, they consist of a number of crystalline phases and a residual glass phase. The major crystalline phase allows a classification into celsian, diopside, encryptite, and perovskite ceramics. They all are of special importance as host phases for long-lived fission products. The paper reports on relations between product composition and melting properties, viscosity, crystallization properties, and fixation capability for fission products. Further investigations deal with dimensional stability, impact resistance, thermal expansion, and thermal conductivity. The properties of the ceramics are compared with those of the basic products. The problems still to be solved with regard to further improvement and application of these products are discussed. (RB)

  4. Fast multilayer fission chamber with 239Pu

    Science.gov (United States)

    Bogdzel, A. A.; Gundorin, N. A.; Duka-Zolyòmi, À.; Kliman, J.; Grigoriev, Yu. V.

    1994-04-01

    For the investigation of neutron induced fission of heavy nuclei in the resonance energy range the fast multilayer ionization fission chamber with a 239Pu content of 1.6 g was constructed. The chamber is compact and a minimum of material has been used for its construction. The chamber is divided into 19 sections containing no more than 100 mg of 239Pu in a section whose intrinsic capacity is less than 100 pF. By using fast preamplifiers and constant fraction discriminators together with the combined method of amplitude and pulse length discrimination the background due to ?-particles is suppressed and a less perturbed pulse height distribution is obtained. The absolute fission fragments detection efficiency of the chamber is (60±8)%. Its time resolution does not exceed 2.6 ns.

  5. Application of fission chamber to uranium microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Kimio; Izumi, Shigeru; Otsuka, Hisao (Hitachi Ltd., Ibaraki (Japan). Energy Research Lab.); Matsumoto, Tetsuo

    1983-02-01

    The possibility of using a fission chamber for quantitative analysis of uranium impurity in dynamic memory materials was studied. The fission chamber had two pairs of parallel disk electrodes. One electrode of each pair was used as a collector and was made of Teflon with a pure aluminum coating, while the other electrode was the material to be measured. Carbon dioxide was used as the ionization gas. Uranium in the materials was irradiated with neutrons and the number of fissions was counted to give the impurity content. Uranium contents in aluminum (99.8%) and Teflon were calculated, and measured values showed a fairly good reproducibility. The detection limit, determined by background fluctuations, for uranium impurity contained in the aluminum coated Teflon electrode was 4.0 ppb.

  6. Application of Fission Chamber to Uranium Microanalysis

    Science.gov (United States)

    Yamada, Kimio; Izumi, Shigeru; Otsuka, Hisao; Matsumoto, Tetsuo

    1983-02-01

    The possibility of using a fission chamber for quantitative analysis of uranium impurity in dynamic memory materials was studied. The fission chamber had two pairs of parallel disk electrodes. One electrode of each pair was used as a collector and was made of Teflon with a pure aluminum coating, while the other electrode was the material to be measured. Carbon dioxide was used as the ionization gas. Uranium in the materials was irradiated with neutrons and the number of fissions was counted to give the impurity content. Uranium contents in aluminum (99.8%) and Teflon were calculated, and measured values showed a fairly good reproducibility. The detection limit, determined by background fluctuations, for uranium impurity contained in the aluminum coated Teflon electrode was 4.0 ppb.

  7. Fast multilayer fission chamber with 239Pu

    International Nuclear Information System (INIS)

    For the investigation of neutron induced fission of heavy nuclei in the resonance energy range, a fast multilayer ionization fission chamber with a 239Pu content of 1.6 g was constructed. The chamber is compact and a minimum of material has been used for its construction. There is not more than 100 mg of plutonium in every section whose intrinsic capacity is less than 100 pF. By using fast preamplifiers and constant fraction discriminators, together with the combined method of amplitude and pulse length discrimination the background due to ?-particles is suppressed and a less perturbed pulse height distribution is obtained. The absolute fission fragment detection efficiency of the chamber is (60±8)%. Its time resolution does not exceed 2.6 ns

  8. Rearrangement of cluster structure during fission processes

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Obolensky, Oleg I.

    2004-01-01

    Results of molecular dynamics simulations of fission reactions $Na_10^2+ -->Na_7^++ Na_3^+ and Na_18^2+--> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analysed. It is demonstrated that the energy necessary for removing homothetic groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. The importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual separation of the daughter fragments begins and/or forming a 'neck' between the separating fragments.

  9. Antiproton Induced Fission and Fragmentation of Nuclei

    CERN Multimedia

    2002-01-01

    The annihilation of slow antiprotons with nuclei results in a large highly localized energy deposition primarily on the nuclear surface. \\\\ \\\\ The study of antiproton induced fission and fragmentation processes is expected to yield new information on special nuclear matter states, unexplored fission modes, multifragmentation of nuclei, and intranuclear cascades.\\\\ \\\\ In order to investigate the antiproton-nucleus interaction and the processes following the antiproton annihilation at the nucleus, we propose the following experiments: \\item A)~Measurement of several fragments from fission and from multifragmentation in coincidence with particle spectra, especially neutrons and kaons. \\item B)~Precise spectra of $\\pi$, K, n, p, d and t with time-of-flight techniques. \\item C)~Installation of the Berlin 4$\\pi$ neutron detector with a 4$\\pi$ Si detector placed inside for fragments and charged particles. This yields neutron multiplicity distributions and consequently distributions of thermal excitation energies and...

  10. Fission product chemistry for serious reactor accidents

    International Nuclear Information System (INIS)

    The behaviour of the radioactive fission products J and Cs under experimental conditions such as prevailing during a serious reactor accident is described. The chemical reactions turn out to be effective retention mechanisms for the fission iodine since as a result of those reactions the greater part of the fission iodine is available in non-volatile form. In contrast to the chemistry of iodine the reactions of cesium have been subject to few investigations only. It may occur as Cs OH, CsJ or in atomic form. With the given volume conditions of sump water and safety containment volume there is a maximum share of 10-6 to 10-5 of the Cs-inventory in the steam phase. (DG)

  11. Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics

    International Nuclear Information System (INIS)

    During the fission process, the atomic nucleus deforms and elongates up to the two fragments inception and their final separation at the scission deformation. The evolution of the nucleus energy with deformation defines a potential energy landscape in the multidimensional deformation space. It is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus, which modifies the macroscopic energy minima. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most genuine experimental observation of the potential energy landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at energy close to the Coulomb barrier, produce well-defined conditions of the compound nucleus formation, where processes such as quasi-fission, pre-equilibrium emission and incomplete fusion are negligible. In the same time, the excitation energy is sufficient to reduce significantly structural effects, and mostly the macroscopic part of the potential is responsible for the formation of the fission fragments. We use inverse kinematics combined with a spectrometer to select and identify the fission fragments produced in 238U+12C at a bombarding energy close to and well-above the Coulomb barrier. For the first time, the isotopic yields are measured over the complete atomic-number distribution, between Z=30 and Z=63. In the experimental set-up, it is also possible to identify transfer-induced reactions, which lead to low-energy fission.

  12. Ternary fission - a level density approach

    International Nuclear Information System (INIS)

    Within level density picture M. Rajasekaran and V. Devanathan studied, the mass distribution for the binary fission of 236U, 240Pu and 258Fm. For calculating the level density, they used single particle levels (energies) of Nilsson model. The mass distributions for the binary fission thus calculated are shown to have good qualitative comparison with the experimental data. This idea is extended in the present work for the study of ternary fission. In a ternary fission process, a parent nucleus can break into three fragments in many different ways. In order to avoid repetition of fragment combinations, a condition that, always A1 ? A2 ? A3 is imposed. Calculations for all possible three body fragmentation are performed but present here only the results corresponding to Ca accompanied fission (A3 = 48). Here, the third fragment mass and charge number is fixed. For the combinations thus generated the single particle energies are retrieved from the Reference Input Parameter Library (RIPL-3) and are due to finite range droplet model. Further, the ternary fission yield is calculated as the ratio of P(Ai,Zi) and ?P(Ai,Zi). The 48Ca accompanied ternary yields of 252Cf and 236U are presented. The favourable ternary breakup for A3=48 is with A1=132Sn and A2=70Ni for 252Cf and A1=130Sn and A2=58Ti for 236U respectively indicating the presence of closed shell in any one of the associated fragments. The yield results obtained for all possible third fragments and calculations due to HFB single particle levels and level densities, for different parent nuclei will also be presented. The obtained results indicate Ca accompanied breakup as a favourable ternary mode to look for experimentally

  13. Classical dynamical description of heavy ion sequential fission

    International Nuclear Information System (INIS)

    Sequential fission processes are investigated in a classical fragmentation model. Dissipative forces are included. In the fissioning process the recoupling of excitational degrees of freedom to kinetic degrees of freedom is found important. 6 figures

  14. Fundamental Fission Research with the NIFFTE Time Projection Chamber

    Science.gov (United States)

    Kleinrath, Verena; Niffte Collaboration

    2013-10-01

    The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) has developed a novel instrument for fission research - a Time Projection Chamber (TPC), which enables detailed tracking of charged particles emitted in neutron-induced fission. While the primary goal of the project is to measure fission cross sections with unprecedented precision, the TPC can also facilitate more fundamental fission studies. The detector's high efficiency (4-pi acceptance) and precise tracking capabilities (including energy deposition) provide a large amount of valuable information. Recent data collected during engineering runs using a U238/U235 target will be used to generate fission fragment angular distributions and yields as a function of incident neutron energy. These experimental results can lend insight into the evolution of nuclear shapes with respect to energy on the path to scission and therefore immediately drive fission theory development. Preliminary angular distributions and yields using the NIFFTE TPC will be presented. Neutron Induced Fission Fragment Tracking Experiment.

  15. Charged particle-induced nuclear fission reactions – Progress and prospects

    Indian Academy of Sciences (India)

    S Kailas; K Mahata

    2014-12-01

    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 fissionable nuclei has been generated. The theoretical developments to describe the fission phenomenon have kept pace with the progress in the corresponding experimental measurements. As the fission process initiated by the neutrons has been well documented, the present article will be restricted to charged particle-induced fission reactions. The progress made in recent years and the prospects in the area of nuclear fission research will be the focus of this review.

  16. Cyclin C mediates stress-induced mitochondrial fission and apoptosis

    OpenAIRE

    Wang, Kun; Yan, Ruilan; Cooper, Katrina F.; Strich, Randy

    2015-01-01

    Mitochondria are dynamic organelles that undergo constant fission and fusion cycles. In response to cellular damage, this balance is shifted dramatically toward fission and apoptosis. This work describes the role of the transcription factor cyclin C in mediating both responses.

  17. New fission-neutron-spectrum representation for ENDF

    International Nuclear Information System (INIS)

    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

  18. Fission Yeast Cell Cycle Synchronization Methods.

    Science.gov (United States)

    Tormos-Pérez, Marta; Pérez-Hidalgo, Livia; Moreno, Sergio

    2016-01-01

    Fission yeast cells can be synchronized by cell cycle arrest and release or by size selection. Cell cycle arrest synchronization is based on the block and release of temperature-sensitive cell cycle mutants or treatment with drugs. The most widely used approaches are cdc10-129 for G1; hydroxyurea (HU) for early S-phase; cdc25-22 for G2, and nda3-KM311 for mitosis. Cells can also be synchronized by size selection using centrifugal elutriation or a lactose gradient. Here we describe the methods most commonly used to synchronize fission yeast cells. PMID:26519320

  19. Beryllium application for fission and fusion

    International Nuclear Information System (INIS)

    At present beryllium is widely used as neutron reflector and moderator in research nuclear reactors. On the other hand, beryllium is also considered as a plasma-facing material in the vacuum vessel of the ITER and as a neutron multiplier in the breeding blanket of the DEMO. Basic mechanisms of radiation damage in beryllium are common for both fission and fusion environments. Strong radiation embrittlement determines the state of beryllium under irradiation. The main problem both in fission and fusion is the storage of radioactive beryllium waste. As very attractive alternative the recycling of irradiated beryllium was recently proposed. (author)

  20. Systematics of neutron-induced fission yields

    International Nuclear Information System (INIS)

    The main characteristics of the mass and charge distributions for thermal neutron induced fission of actinides are reviewed. We show that these distributions can be reasonably reproduced with only 24 data as input. We use a representation where the element yields together with the most probable mass Ap(Z) play the dominant role. The ability of this model to calculate mass yields for the fission of not yet measured actinides is also shown. The influence of the excitation energy of the fissile system on charge and mass distribution is also discussed

  1. Paper electrophoretic separation of fission products

    International Nuclear Information System (INIS)

    Paper electrophoretic separation of fission products has been carried out by using the specially designed migration apparatus. In general, the isolation of rubidium, strontium, zirconium, ruthenium, cesium, cerium, molybdenum, and some short-lived fission products is more efficient under 0.1 M HCl electrolyte as compared with 0.1 M NaOH electrolyte. In addition to Np-239, I-131-135 were, in particular, observed with different iodine chemical species obtained by the paper-electrophoretic separation of short, neutron-irradiated uranyl nitrate solution. (author)

  2. Actinide and fission product separation and transmutation

    International Nuclear Information System (INIS)

    The second international information exchange meeting on actinide and fission product separation and transmutation, took place in Argonne National Laboratory in Illinois United States, on 11-13 November 1992. The proceedings are presented in four sessions: Current strategic system of actinide and fission product separation and transmutation, progress in R and D on partitioning processes wet and dry, progress in R and D on transmutation and refinements of neutronic and other data, development of the fuel cycle processes fuel types and targets. (A.L.B.)

  3. Influence of spin on fission fragments anisotropy

    Directory of Open Access Journals (Sweden)

    Ghodsi Omid N.

    2005-01-01

    Full Text Available An analysis of selected fission fragment angular distribution when at least one of the spins of the projectile or target is appreciable in induced fission was made by using the statistical scission model. The results of this model predicate that the spins of the projectile or target are affected on the nuclear level density of the compound nucleus. The experimental data was analyzed by means of the couple channel spin effect formalism. This formalism suggests that the projectile spin is more effective on angular anisotropies within the limits of energy near the fusion barrier.

  4. High performance, suppressed-fission ICF hybrid

    International Nuclear Information System (INIS)

    The neutronics aspects of an ICF hybrid concept are discussed. The breeding blanket consists of a beryllium neutron multiplier, metallic thorium fertile fuel and a liquid-lithium coolant. The fertile fuel fraction is 30 vol%, which is much higher than previous one-zone, suppressed-fission hybrid concepts. Fission in the bred 233U is suppressed by competition from tritium breeding reactions in 6Li. The total breeding ratio, T + F, is 2.05, and the total neutron energy deposited is 41.1 MeV per DT neutron. The 800-MW (fusion) hybrid produces approx. 3500 kg of 233U per full-power-year

  5. Obsidian dating by fission track method

    International Nuclear Information System (INIS)

    The fission track method was employed to obtain the age of twelve obsidian sample from Ecuador. By using the plateau-age correction method, we obtained the true age of each sample and were able to identify four groups of ages in the studied area. Thereafter we studied the fading of fission tracks in two obsidian samples with different origins: Yanaurcu, Ecuador and Monte Arci, Italy. We constructed Arrhenius plots and calculated activation energies for both samples. The results from thermal annealing experiments were compared with theoretical curves obtained by integrating an equation proposed by Shukolyukov et al (1965). (author). 43 refs, 20 figs, 10 tabs

  6. Actinide and fission product separation and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-07-01

    The second international information exchange meeting on actinide and fission product separation and transmutation, took place in Argonne National Laboratory in Illinois United States, on 11-13 November 1992. The proceedings are presented in four sessions: Current strategic system of actinide and fission product separation and transmutation, progress in R and D on partitioning processes wet and dry, progress in R and D on transmutation and refinements of neutronic and other data, development of the fuel cycle processes fuel types and targets. (A.L.B.)

  7. Fission decay in intermediate heavy ion reactions

    International Nuclear Information System (INIS)

    Results are presented on cross sections, parallel and perpendicular momentum transfers, charge loss and velocity systematics for fission following reactions of Fe and Nb projectiles at 50--100 MeV/A on targets of Ta, Au, and Th. The results at 100 MeV/A are compared to a detailed multistage deexcitation model. The initial collision is modeled with an intranuclear cascade. The resultant excited target residues then undergo a fast preequilibrium decay stage followed by a statistical decay involving nucleon evaporation and fission. Results from this modeling are in reasonable agreement with experimental data. 14 refs., 11 figs

  8. Fission decay in intermediate heavy ion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Britt, H.C.

    1990-10-03

    Results are presented on cross sections, parallel and perpendicular momentum transfers, charge loss and velocity systematics for fission following reactions of Fe and Nb projectiles at 50--100 MeV/A on targets of Ta, Au, and Th. The results at 100 MeV/A are compared to a detailed multistage deexcitation model. The initial collision is modeled with an intranuclear cascade. The resultant excited target residues then undergo a fast preequilibrium decay stage followed by a statistical decay involving nucleon evaporation and fission. Results from this modeling are in reasonable agreement with experimental data. 14 refs., 11 figs.

  9. Fission product release mechanisms and groupings

    International Nuclear Information System (INIS)

    During CANDU postulated accidents the reactor fuel is estimated to be exposed to a variety of conditions. These conditions are dynamic and, during the course of an accident, the fuel may experience a wide range of temperatures and conditions from highly oxidizing to mildly reducing environments. The exposure of the reactor fuel to these environments and temperatures may affect its stoichiometry and release performance. In this paper a review of the important fission product release mechanisms is presented, the results of three out-of-pile experimental programs are summarized, and fission product release groups, for both oxidizing and reducing conditions are proposed. (author)

  10. Chemistry of actinides and fission products

    International Nuclear Information System (INIS)

    This task is concerned primarily with the fundamental chemistry of the actinide and fission product elements. Special efforts are made to develop research programs in collaboration with researchers at universities and in industry who have need of national laboratory facilities. Specific areas currently under investigation include: (1) spectroscopy and photochemistry of actinides in low-temperature matrices; (2) small-angle scattering studies of hydrous actinide and fission product polymers in aqueous and nonaqueous solvents; (3) kinetic and thermodynamic studies of complexation reactions in aqueous and nonaqueous solutions; and (4) the development of inorganic ion exchange materials for actinide and lanthanide separations. Recent results from work in these areas are summarized here

  11. Dynamic properties of the Coulomb fission

    International Nuclear Information System (INIS)

    The heavy ion induced fission after quasi-elastic scattering was studied in the systems 208Pb -> 238U for central collision at energies below the Coulomb barrier and 238U -> 238U for peripheral collisions at scattering angles smaller than the grazing angle. The dynamical properties and the phase-space distributions of the reactions could be determined by the method of the kinematical coincidences where positions and time-of-flight of two fission fragments and a scattered projectile-like nucleus were measured at the same time in large-area gas-filled parallel plate counters. (orig./HSI)

  12. The Future of Energy from Nuclear Fission

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Son H.; Taiwo, Temitope

    2013-04-13

    Nuclear energy is an important part of our current global energy system, and contributes to supplying the significant demand for electricity for many nations around the world. There are 433 commercial nuclear power reactors operating in 30 countries with an installed capacity of 367 GWe as of October 2011 (IAEA PRIS, 2011). Nuclear electricity generation totaled 2630 TWh in 2010 representing 14% the world’s electricity generation. The top five countries of total installed nuclear capacity are the US, France, Japan, Russia and South Korea at 102, 63, 45, 24, and 21 GWe, respectively (WNA, 2012a). The nuclear capacity of these five countries represents more than half, 68%, of the total global nuclear capacity. The role of nuclear power in the global energy system today has been motivated by several factors including the growing demand for electric power, the regional availability of fossil resources and energy security concerns, and the relative competitiveness of nuclear power as a source of base-load electricity. There is additional motivation for the use of nuclear power because it does not produce greenhouse gas (GHG) emissions or local air pollutants during its operation and contributes to low levels of emissions throughout the lifecycle of the nuclear energy system (Beerten, J. et. al., 2009). Energy from nuclear fission primarily in the form of electric power and potentially as a source of industrial heat could play a greater role for meeting the long-term growing demand for energy worldwide while addressing the concern for climate change from rising GHG emissions. However, the nature of nuclear fission as a tremendously compact and dense form of energy production with associated high concentrations of radioactive materials has particular and unique challenges as well as benefits. These challenges include not only the safety and cost of nuclear reactors, but proliferation concerns, safeguard and storage of nuclear materials associated with nuclear fuel cycles. In March of 2011, an unprecedented earthquake of 9 magnitude and ensuing tsunami off the east coast of Japan caused a severe nuclear accident in Fukushima, Japan (Prime Minister of Japan and His Cabinet, 2011). The severity of the nuclear accident in Japan has brought about a reinvestigation of nuclear energy policy and deployment activities for many nations around the world, most notably in Japan and Germany (BBC, 2011; Reuter, 2011). The response to the accident has been mixed and its full impact may not be realized for many years to come. The nuclear accident in Fukushima, Japan has not directly affected the significant on-going nuclear deployment activities in many countries. China, Russia, India, and South Korea, as well as others, are continuing with their deployment plans. As of October 2011, China had the most reactors under construction at 27, while Russia, India, and South Korea had 11, 6, and 5 reactors under construction, respectively (IAEA PRIS, 2011). Ten other nations have one or two reactors currently under construction. Many more reactors are planned for future deployment in China, Russia, and India, as well as in the US. Based on the World Nuclear Association’s data, the realization of China’s deployment plan implies that China will surpass the US in total nuclear capacity some time in the future.

  13. Calculations related to nuclear fission-product yields

    International Nuclear Information System (INIS)

    This report contains three articles on Calculations related to Nuclear Fission-Product Yields which are translated from Russian language. The first one is dealing with the ASIND-MEPhI Library of Independent Actinide Fission Product Yields. The second one deals with Calculation of Independent Fission Product Yields by the Thermodynamic method and the third one is dealing with Long-Lived Fission Product Yields and the Nuclear Transmutation Problem. Refs, figs, tabs

  14. Development and Utilization of Space Fission Power Systems

    Science.gov (United States)

    Houts, Michael G.; Mason, Lee S.; Palac, Donald T.; Harlow, Scott E.

    2009-01-01

    Space fission power systems could enable advanced civilian space missions. Terrestrially, thousands of fission systems have been operated since 1942. In addition, the US flew a space fission system in 1965, and the former Soviet Union flew 33 such systems prior to the end of the Cold War. Modern design and development practices, coupled with 65 years of experience with terrestrial reactors, could enable the affordable development of space fission power systems for near-term planetary surface applications.

  15. A simple method for detection of fission product fallout

    International Nuclear Information System (INIS)

    An outdoor gamma-ray detector with a 76mm x 76mm NaI(T1) crystal and 1 256 channel analyzor measures the ambient gamma-ray background due to natural radioactivity. The data are transmitted to a computer that continuously updates the background count rates of 10 windows for reference purposes. The influence of washout of atmospheric radon-daughters during precipitation is eliminated by a stripping technique. Automatic investigations of the corrected gamma-ray spectrum each 12 minutes unveil whether fission product fallout or other artificial radioactive nuclides are present. Depending on circumstances the level of detection varies form 0.3 to 0.8 microroentgen per hour. The exposure rate due to natural radioactivity at the locality varies from app. 7 to 9 microroentgen per hour on an annual basis with peaks up to 14 microroentgen per hour caused by radon-daughter washout during heavy rain. (author) 11 refs

  16. Overview of research by the fission group in Trombay

    Indian Academy of Sciences (India)

    R K Chourdhury

    2015-08-01

    Nuclear fission studies in Trombay began nearly six decades ago, with the commissioning of the APSARA research reactor. Early experimental work was based on mass, kinetic energy distributions, neutron and X-ray emission in thermal neutron fission of 235U, which were carried out with indigenously developed detectors and electronics instrumentation. With the commissioning of CIRUS reactor and the availability of higher neutron flux, advanced experiments were carried out on ternary fission, pre-scission neutron emission, fragment charge distributions, quarternary fission, etc. In the late eighties, heavy-ion beams from the pelletron-based medium energy heavy-ion accelerator were available, which provided a rich variety of possibilities in nuclear fission studies. Pioneering work on fragment angular distributions, fission time-scales, transfer-induced fission, -ray multiplicities and mass–energy correlations were carried out, providing important information on the dynamics of the fission process. More recently, work on fission fragment -ray spectroscopy has been initiated, to understand the nuclear structure aspects of the neutron-rich fission fragment nuclei. There have also been parallel efforts to carry out theoretical studies in the areas of shell effects, superheavy nuclei, fusion–fission dynamics, fragment angular distributions, etc. to complement the experimental studies. This paper will provide a glimpse of the work carried out by the fission group at Trombay in the above-mentioned topics.

  17. Cold fission studies using a double-ionization chamber

    International Nuclear Information System (INIS)

    An investigation on spontaneous fission of 252Cf is described. Both fission fragments are detected coincidentally with a double ionization chamber as a 4 ? detector. Special techniques are demonstrated which allow the determination of nuclear masses and charges for cold fission fragments. Detector properties such as systematic errors and their correction are studied with the help of ? particles. (orig.)

  18. Consistent dynamical and statistical description of fission and comparison

    International Nuclear Information System (INIS)

    The research survey of consistent dynamical and statistical description of fission is briefly introduced. The channel theory of fission with diffusive dynamics based on Bohr channel theory of fission and Fokker-Planck equation and Kramers-modified Bohr-Wheeler expression according to Strutinsky method given by P.Frobrich et al. are compared and analyzed. (2 figs.)

  19. Chemical immobilization of fission products reactive with nuclear reactor components

    International Nuclear Information System (INIS)

    This invention teaches a method of immobilizing deleterious fission products produced in nuclear fuel materials during nuclear fission chain reactions through the use of additives. The additives are disposed with the nuclear fuel materials in controlled quantities to form new compositions preventing attack of reactor components, especially nuclear fuel cld, by the deleterious fission products. (Patent Office Record)

  20. Fission gas release from the sintered UO2 fuel

    International Nuclear Information System (INIS)

    This paper shoes the phenomena which control fission gases release from the sintered UO2 dependent of the burnup rate: ejection, release, diffusion, increased fission gas accumulation causing structural changes in the fuel. release of fission gases from the fuel for power reactors was studied as well. The influence of factors as temperature, characteristics of fuel, burnup rate and burnup level was analyzed

  1. Fission barrier heights in the A ? 200 mass region

    Indian Academy of Sciences (India)

    K Mahata

    2015-08-01

    Statistical model analysis is carried out for - and -induced fission reactions using a consistent description for fission barrier and level density in A ? 200 mass region. A continuous damping of shell correction with excitation energy is considered. Extracted fission barriers agree well with the recent microscopic–macroscopic model. The shell corrections at the saddle point were found to be insignificant.

  2. Angular distribution in 19F induced fission on 197Au

    International Nuclear Information System (INIS)

    Recent studies on fusion-fission dynamics in the heavy systems with varying entrance channel mass asymmetry have revealed interesting phenomenon like fusion suppression and quasi-fission and shown that the suppression of fusion is accompanied with the quasi-fission in 19F+197Au and 30Si+186W systems producing the same compound nucleus 216Ra

  3. Fission probability of nucleus of sup(232)Th mesoatom

    International Nuclear Information System (INIS)

    The fission probability of the nucleus of the sup(232)Th muonic atom has been measured. The fission yield was measured simultaneously with the intensity of 5g-4f transition in the muonic atom sup(232)Th. A good agreement with previous result obtained in measurements with the fission chamber and evident disagreement with the photoemulsion data have been obtained

  4. GDR emission and first chance fission probability in 200Pb

    International Nuclear Information System (INIS)

    The multiplicities of ?-rays emitted in the giant dipole resonance decay of 200Pb have been measured in coincidence with both evaporation residues and fission fragments. The experimental data have been compared with results of statistical calculations which take into account dynamical fission hindrance. The fission probability distribution has been determined as a function of excitation energy. ((orig.))

  5. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Tompson, Jr., Robert V. [Univ. of Missouri, Columbia, MO (United States); Loyalka, Sudarshan [Univ. of Missouri, Columbia, MO (United States); Ghosh, Tushar [Univ. of Missouri, Columbia, MO (United States); Viswanath, Dabir [Univ. of Missouri, Columbia, MO (United States); Walton, Kyle [Univ. of Missouri, Columbia, MO (United States); Haffner, Robert [Univ. of Missouri, Columbia, MO (United States)

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few ?m in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one graduate student meant that data acquisition with the packed bed systems ended up competing for the graduate student’s available time with the electrodynamic balance redesign and assembly portions of the project. This competition for available time was eventually mitigated to some extent by the later recruitment of an undergraduate student to help with data collection using the packed bed system. It was only the recruitment of the second student that allowed the single particle balance design and construction efforts to proceed as far as they did during the project period. It should be added that some significant time was also spent by the graduate student cataloging previous work involving graphite. This eventually resulted in a review paper being submitted and accepted (“Adsorption of Iodine on Graphite in High Temperature Gas-Cooled Reactor Systems: A Review,” Kyle L. Walton, Tushar K. Ghosh, Dabir S. Viswanath, Sudarshan K. Loyalka, Robert V. Tompson). Our specific revised objectives in this project were as follows: Experimentally obtain isotherms of Iodine for reactor grade IG-110 samples of graphite particles over a range of temperatures and pressures using an EDB and a temperature controlled EDB; Experimentally obtain isotherms of Iodine for reactor grade IG-110 samples of graphite particles over a range of temperatures and pressures using a packed column bed apparatus; Explore the effect that charge has on the adsorption isotherms of iodine by varying the charges on and the voltages used to suspend the microscopic particles in the EDB; and To interpret these results in terms of the existing models (Langmuir, BET, Freundlich, and others) which we will modify as necessary to include charge related effects.

  6. Effect of fission following incomplete fusion on the interpretation of fission fragment angular distributions in heavy-ion fusion reactions

    International Nuclear Information System (INIS)

    It is shown that with the inclusion of fission following incomplete fusion in addition to the normal equilibrium fission following compound nucleus formation and the recently proposed pre-equilibrium fission, one can understand in a quantitative way the host of apparently anomalous fragment angular distributions measured in a number of heavy ion induced fission reactions involving the highly fissile actinides as one of the collision partners

  7. Fission barriers and probabilities of spontaneous fission for elements with Z$\\geq$100

    CERN Document Server

    Baran, A; Reinhard, P -G; Robledo, L M; Staszczak, A; Warda, M

    2015-01-01

    This is a short review of methods and results of calculations of fission barriers and fission half-lives of even-even superheavy nuclei. An approvable agreement of the following approaches is shown and discussed: The macroscopic-microscopic approach based on the stratagem of the shell correction to the liquid drop model and a vantage point of microscopic energy density functionals of Skyrme and Gogny type selfconsistently calculated within Hartree-Fock-Bogoliubov method. Mass parameters are calculated in the Hartree-Fock-Bogoliubov cranking approximation. A short part of the paper is devoted to the nuclear fission dynamics. We also discuss the predictive power of Skyrme functionals applied to key properties of the fission path of $^{266}$Hs. It applies the standard techniques of error estimates in the framework of a $\\chi^2$ analysis.

  8. Fission chamber measurements of /sup 235/U fission for encapsulated /sup 252/Cf sources

    Energy Technology Data Exchange (ETDEWEB)

    Hamblen, R.A.; West, L.

    1987-01-01

    Measurements with a dual fission chamber have been made of the /sup 235/U fission rate in the neutron field of /sup 252/Cf calibration sources to investigate the effect of scattering from source encapsulation. The fission chamber, provided by the US National Bureau of Standards (NBS), is capable of high-precision absolute measurements. Neutron sources investigated include a Savannah River Lab. (SRL) 100-series source (311Z) and a 3000-series source (3009Z). These sources are doubly encapsulated with thick end plugs, which could lead to additional scattering to perturb the neutron field from that of an isotropic point source. Measurements were in the 90-deg plane from the source cylindrical axes; the fission chamber was covered with cadmium. All experimental work was in the irradiation cell at the SEFOR site of the Univ. of Arkansas.

  9. Measuring method of efficiency of energy carrying-out by fission fragments through fissionable material surface

    International Nuclear Information System (INIS)

    Kinetic energy of uranium-235 fission fragments is mainly used for nuclear pumping of gas lasers. The fission fragments are injected to laser channel using energy releasing elements containing uranium-235. A general mathematical model of the efficiency of the energy carrying out by the fission fragments is considered. Based on the model an efficient method of experimental estimating of the energy releasing element is proposed. The efficiency is assessed by the results of direct measurements of the yield of alpha particles due to alpha decay of the fissionable material through the surface of object under consideration. An example of a simple calculational model for defining the efficiency of energy releasing elements is provided

  10. Fission fragment formation and fission yields in the model of octupole neutron-proton oscillations

    Directory of Open Access Journals (Sweden)

    Yavshits S.

    2010-03-01

    Full Text Available The fission fragment formation is considered as a result of neck instability in the process of octupole oscillations of neutrons and protons near the scission point. To describe such a phenomenon the potential surface of fissionning nucleus with neck radius about 1 fm was calculated with shell correction approach. The new version of smooth liquid drop part of deformation energy is proposed. The liquid drop part is formulated in a double folding model with n-n, p-p, and n-p Yukawa interaction potential. Fission fragment mass and charge distributions correspond approximately to isoscalar and isovector modes of vibrations and are defined by wave functions of oscillations. The preliminary calculation results have shown a rather good description of main integral fission yield observables.

  11. Actinide and fission product partitioning and transmutation

    International Nuclear Information System (INIS)

    The third international information exchange meeting on actinide and fission product partitioning and transmutation, took place in Cadarache France, on 12-14 December 1994. The proceedings are presented in six sessions : an introduction session, the major programmes and international cooperation, the systems studies, the reactors fuels and targets, the chemistry and a last discussions session. (A.L.B.)

  12. Development of fission Mo-99 production technology

    International Nuclear Information System (INIS)

    This R and D project is planed to supply domestic demands of Mo-99 through fission route, and consequently this project will be expected to rise up utilization of HANARO and KAERI's capability for marketing extension into domestic and oversea radiopharmaceutical market. HEU and LEU target types are decided and designed for fission Mo-99 production in domestic. Experimental study of target fabrication technology was performed and developed processing equipments. And conceptual design of target loading/unloading in/from HANARO device are performed. Tracer test of Mo-99 separation and purification process was performed, test results reach to Mo-99 recovery yield above 80% and decontamination factor above 1600. Combined Mo-99 separation and purification process was decided for hot test scheduled from next year, and performance test was performed. Conceptual design for modification of existing hot cell for fission Mo-99 production facility was performed and will be used for detail design. Assumption for the comparison of LEU and HEU target in fission Mo-99 production process were suggested and compared of merits and demerits in view of fabrication technology and economy feasibility

  13. Taxonomy Icon Data: fission yeast [Taxonomy Icon

    Lifescience Database Archive (English)

    Full Text Available fission yeast Schizosaccharomyces pombe Schizosaccharomyces_pombe_L.png Schizosaccharomyces_pomb ... saccharomyces_pombe_NS.png http://biosciencedbc.jp/taxonomy _icon/icon.cgi?i=Schizosaccharomyces+pombe&t=L http ... ://biosciencedbc.jp/taxonomy _icon/icon.cgi?i=Schizosaccharomyces+pombe&t=NL htt ...

  14. Density Functional Theory Approach to Nuclear Fission

    CERN Document Server

    Schunck, N

    2012-01-01

    The Skyrme nuclear energy density functional theory (DFT) is used to model neutron-induced fission in actinides. This paper focuses on the numerical implementation of the theory. In particular, it reports recent advances in DFT code development on leadership class computers, and presents a detailed analysis of the numerical accuracy of DFT solvers for near-scission calculations.

  15. Nuclear Fission Products: From Source to Environment

    Directory of Open Access Journals (Sweden)

    A.W. Ajlouni

    2010-01-01

    Full Text Available After a peer review of data about nuclear fission products, we can see easily that, no clear chemical species, chemical compounds, or chemical processes were available after actual releases of nuclear Fission Products (FP during planned releases, accidents, or in nuclear detonations. The models based on these ordinary reactions and species could not interpret the behaviors of the fission products or expect their effects in the environment or on the living creatures. To interpret the chemical behaviors of the fission products and their effects on the environment and in the living creatures, a new approach is introduced in this study. It is assumed here that the ionization states of the new born atoms and the long term high temperatures were not dealt with in an appropriate way and they are the reasons of the failure of the former models. Deep Atomic Binding (DAB approach based on the following: (1 The new born atoms which are highly ionized, 10-12 electrons associated with each nucleus, having a large probability to create bonds between them to form molecules. These bonds are at the L, or M shells and we call it DAB. (2 The molecules stay in the reactor at high temperatures for long periods, so they undergo many stages of composition and decomposition to form giant molecules. By applying DAB approach, field data from Chernobyl and TMI accidents and nuclear detonations could be interpreted with a wide coincidence resulted.

  16. Brownian shape motion: fission fragment mass distributions

    International Nuclear Information System (INIS)

    A recently developed novel method for calculating fission-fragment mass distributions is discussed. It treats the nuclear shape evolution as Brownian motion and in its simplest form performs random walks on previously calculated five-dimensional potential-energy surfaces. Remarkably good reproduction of experimentally measured data is obtained without introduction of any new parameters.

  17. Benchmarking Translat for fission product generation - 227

    International Nuclear Information System (INIS)

    The TransLAT lattice physics code was investigated to characterize its ability to simulate fission product generation in a nuclear reactor. Pin cell models for fuel from H.B. Robinson Unit 2, Calvert Cliffs No. 1, and Mihama Unit 3 were developed using TransLAT. These models were used to simulate reactor operation corresponding to measured samples with isotopic data reported in available literature for the three reactors. For this study, TransLAT was run using the Method of Characteristics. The results of the TransLAT simulations were then compared to the measured data. The results show that the TransLAT could predict the absolute concentrations of most fission products to within ±20% of the measured values and it could predict the ratios of fission products to within ±10% of the measured values. Thus TransLAT may be expected to produce reasonable estimates of fission product concentrations generated during reactor operation even using simple pin cell models. (authors)

  18. Semimicroscopic treatment of nuclear fission barriers

    International Nuclear Information System (INIS)

    The model is proposed to calculate the fission barriers of heavy nuclei with account of their possible dependence on excitation energy. The model is based on the shell correction method for calculation of potential energy of deformation with nuclear shape parameterization in the lemniscate coordinates. (author)

  19. Model for fission-product calculations

    International Nuclear Information System (INIS)

    Many fission-product cross sections remain unmeasurable thus considerable reliance must be placed upon calculational interpolation and extrapolation from the few available measured cross sections. The vehicle, particularly for the lighter fission products, is the conventional optical-statistical model. The applied goals generally are: capture cross sections to 7 to 10% accuracies and inelastic-scattering cross sections to 25 to 50%. Comparisons of recent evaluations and experimental results indicate that these goals too often are far from being met, particularly in the area of inelastic scattering, and some of the evaluated fission-product cross sections are simply physically unreasonable. It is difficult to avoid the conclusion that the models employed in many of the evaluations are inappropriate and/or inappropriately used. In order to alleviate the above unfortunate situations, a regional optical-statistical (OM) model was sought with the goal of quantitative prediction of the cross sections of the lighter-mass (Z = 30-51) fission products. The first step toward that goal was the establishment of a reliable experimental data base consisting of energy-averaged neutron total and differential-scattering cross sections. The second step was the deduction of a regional model from the experimental data. It was assumed that a spherical OM is appropriate: a reasonable and practical assumption. The resulting OM then was verified against the measured data base. Finally, the physical character of the regional model is examined

  20. Fission in intermediate energy heavy ion reactions

    International Nuclear Information System (INIS)

    A systematic study of reaction mechanisms at intermediate energies (50--100 MeV/A) has been performed at the Lawrence Berkeley Laboratory's BeValac using medium weight projectiles on medium and heavy element targets. A gas and plastic phoswich detector system was employed which gave large geometric coverage and a wide dynamic response. The particles identified with the gas detectors could be characterized into three components--intermediate mass fragments (IMF), fission fragments (FF) and heavy residues (HR). Major observed features are: the reaction yields are similar in the 50 to 100 MeV/A range, central collisions have high multiplicity of IMF's with broad angular correlations consistent with a large participant region, effects of final state Coulomb interactions are observed and give information on the size and temporal behavior of the source, true fission yields are dependent on target fissility and correlated with relatively peripheral collisions. Analysis of fission and evaporation yields implies limiting conditions for which fission decay remains a viable deexcitation channel. 15 refs., 7 figs

  1. Fission in intermediate energy heavy ion reactions

    International Nuclear Information System (INIS)

    A systematic study of reaction mechanisms at intermediate energies (50--100 MeV/A) has been performed at the Lawrence Berkeley Laboratory's BeValac using medium weight projectiles on medium and heavy element targets. A gas and plastic phoswich detector system was employed which gave large geometric coverage and a wide dynamic response. The particles identified with the gas detectors could be characterized into three components - intermediate mass fragments (IMF), fission fragments (FF) and heavy residues (HR). Major observed features are: the reaction yields are similar in the 50 to 100 MeV/A range, central collisions have high multiplicity of IMF's with broad angular correlations consistent with a large participant region, effects of final state Coulomb interactions are observed and give information on the size and temporal behavior of the source, true fission yields are dependent on target fissility and correlated with relatively peripheral collisions. Analysis of fission and evaporation yields implies limiting conditions for which fission decay remains a viable deexcitation channel. 7 figs

  2. Fission in intermediate energy heavy ion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wilhelmy, J.B.; Begemann-Blaich, M.; Blaich, T.; Boissevain, J.; Fowler, M.M.; Gavron, A.; Jacak, B.V.; Lysaght, P.S.; Britt, H.C.; Fields, D.J.

    1989-04-01

    A systematic study of reaction mechanisms at intermediate energies (50--100 MeV/A) has been performed at the Lawrence Berkeley Laboratory's BeValac using medium weight projectiles on medium and heavy element targets. A gas and plastic phoswich detector system was employed which gave large geometric coverage and a wide dynamic response. The particles identified with the gas detectors could be characterized into three components--intermediate mass fragments (IMF), fission fragments (FF) and heavy residues (HR). Major observed features are: the reaction yields are similar in the 50 to 100 MeV/A range, central collisions have high multiplicity of IMF's with broad angular correlations consistent with a large participant region, effects of final state Coulomb interactions are observed and give information on the size and temporal behavior of the source, true fission yields are dependent on target fissility and correlated with relatively peripheral collisions. Analysis of fission and evaporation yields implies limiting conditions for which fission decay remains a viable deexcitation channel. 15 refs., 7 figs.

  3. Fission Energy and Other Sources of Energy

    Science.gov (United States)

    Alfven, Hannes

    1974-01-01

    Discusses different forms of energy sources and basic reasons for the opposition to the use of atomic energy. Suggests that research efforts should also be aimed toward the fission technology to make it acceptable besides major research studies conducted in the development of alternative energy sources. (CC)

  4. Actinide and fission product partitioning and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-07-01

    The third international information exchange meeting on actinide and fission product partitioning and transmutation, took place in Cadarache France, on 12-14 December 1994. The proceedings are presented in six sessions : an introduction session, the major programmes and international cooperation, the systems studies, the reactors fuels and targets, the chemistry and a last discussions session. (A.L.B.)

  5. Brownian shape motion: Fission fragment mass distributions

    Directory of Open Access Journals (Sweden)

    Sierk Arnold J.

    2012-02-01

    Full Text Available It was recently shown that remarkably accurate fission-fragment mass distributions can be obtained by treating the nuclear shape evolution as a Brownian walk on previously calculated five-dimensional potential-energy surfaces; the current status of this novel method is described here.

  6. Fission--fusion systems: classification and critique

    International Nuclear Information System (INIS)

    A useful classification scheme for hybrid systems is described and some common features that the scheme makes apparent are pointed out. The early history of fusion-fission systems is reviewed. Some designs are described along with advantages and disadvantages of each. The extension to low and moderate Q devices is noted. (U.S.)

  7. Energy-loss distributions of fission fragments

    Energy Technology Data Exchange (ETDEWEB)

    Demidovich, N.N.; Nakhutin, I.E.; Shatunov, V.G.

    1976-03-05

    The f-f coincidence method was used to investigate the change in the form of the energy-loss distributions of Cf/sup 252/ fission fragments in air, down to fragment energies approx.0.8 MeV. A theoretical model is considered for the estimate of the mean-squared deviations of the fragment energy-loss distributions. (AIP)

  8. Fission fragment rockets - A new frontier

    International Nuclear Information System (INIS)

    A new reactor concept is described which would enable fission fragments to be continuously extracted from the reactor. Such a reactor has the potential of enabling extremely energetic and ambitious deep space missions. In this talk the basic physics issues involved in the operation of this type of reactor are outlined, and some possible applications to space exploration are described

  9. Probing the time scale of asymmetric fission

    International Nuclear Information System (INIS)

    The author describes the measurement of the mass-energy distributions of fission fragments in the reactions 197Au(14N,X) at 34 A.MeV and 232Th(7Li,X) at 43 A.MeV. He presents results on the mass-asymmetry and excitation energy sharing. (HSI)

  10. Development of fission Mo-99 production technology

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Ho; Choung, W. M.; Lee, K. I. and others

    2001-05-01

    This R and D project is planed to supply domestic demands of Mo-99 through fission route, and consequently this project will be expected to rise up utilization of HANARO and KAERI's capability for marketing extension into domestic and oversea radiopharmaceutical market. HEU and LEU target types are decided and designed for fission Mo-99 production in domestic. Experimental study of target fabrication technology was performed and developed processing equipments. And conceptual design of target loading/unloading in/from HANARO device are performed. Tracer test of Mo-99 separation and purification process was performed, test results reach to Mo-99 recovery yield above 80% and decontamination factor above 1600. Combined Mo-99 separation and purification process was decided for hot test scheduled from next year, and performance test was performed. Conceptual design for modification of existing hot cell for fission Mo-99 production facility was performed and will be used for detail design. Assumption for the comparison of LEU and HEU target in fission Mo-99 production process were suggested and compared of merits and demerits in view of fabrication technology and economy feasibility.

  11. Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics

    OpenAIRE

    Farget, F.; Caamano, M.; Delaune, O.; Tarasov, O. B.; X. Derkx; Schmidt, K.-H; Amthor, A.M.; Audouin, L.; Bacri, C. -O.; Barreau, G.; Bastin, B.; Bazin, D.(National Superconducting Cyclotron Laboratory, Department of Physics and Astronomy, Michigan State University, 164 S. Shaw Lane, East Lansing, MI, 48825-1321, USA); Blank, B.; Benlliure, J.; Caceres, L

    2012-01-01

    During the fission process, the nucleus deforms and elongates up to the two fragments inception and their final separation at scission deformation. The evolution of the nucleus energy with deformation is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most ...

  12. Prompt fission neutron spectra and fragment characteristics for spontaneous fission of even Pu-isotopes

    International Nuclear Information System (INIS)

    A phenomenological scission point model including temperature-dependent shell effects has been used to solve the energy partition problem as function of mass asymmetry for Pu-fission. Relevant fragment data were used as the basis for applying a temperature-distribution model, which yields neutron multiplicity, energy and angular distribution of prompt fission neutrons. Calculated data for 238Pu, 240Pu and 242Pu are presented and discussed in comparison with experimental data. (author). 22 refs, 8 figs, 1 tab

  13. The neutronics studies of fusion fission hybrid power reactor

    International Nuclear Information System (INIS)

    In this paper, a series of neutronics analysis of hybrid power reactor is proposed. The ideas of loading different fuels in a modular-type fission blanket is analyzed, fitting different level of fusion developments, i.e., the current experimental power output, the level can be obtained in the coming future and the high-power fusion reactor like ITER. The energy multiplication of fission blankets and tritium breeding ratio are evaluated as the criterion of design. The analysis is implemented based on the D-type simplified model, aiming to find a feasible 1000MWe hybrid power reactor for 5 years' lifetime. Three patterns are analyzed: 1) for the low fusion power, the reprocessed fuel is chosen. The fuel with high plutonium content is loaded to achieve large energy multiplication. 2) For the middle fusion power, the spent fuel from PWRs can be used to realize about 30 times energy multiplication. 3) For the high fusion power, the natural uranium can be directly used and about 10 times energy multiplication can be achieved.

  14. Immobilization of fission products in phosphate ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.; Wagh, A. [Argonne National Lab., IL (United States)

    1997-10-01

    Chemically bonded phosphate ceramics (CBPCs) have several advantages that make them ideal candidates for containing radioactive and hazardous wastes. In general, phosphates have high solid-solution capacities for incorporating radionuclides, as evidenced by several phosphates (e.g., monazites and apatites) that are natural analogs of radioactive and rare-earth elements. The phosphates have high radiation stability, are refractory, and will not degrade in the presence of internal heating by fission products. Dense and hard CBPCs can be fabricated inexpensively and at low temperature by acid-base reactions between an inorganic oxide/hydroxide powder and either phosphoric acid or an acid-phosphate solution. The resulting phosphates are extremely insoluble in aqueous media and have excellent long-term durability. CBPCs offer the dual stabilization mechanisms of chemical fixation and physical encapsulation, resulting in superior waste forms. The goal of this task is develop and demonstrate the feasibility of CBPCs for S/S of wastes containing fission products. The focus of this work is to develop a low-temperature CBPC immobilization system for eluted {sup 99}Tc wastes from sorption processes.

  15. Fission products control by gamma spectrometry in purex process solutions

    International Nuclear Information System (INIS)

    This paper deals with a radiometric method for fission products analysisby gamma spectrometry. This method will be applied for fission productscontrol at the irradiated material processing facility, under construction inthe Instituto de Pesquisas Energeticas e Nucleares, SP, Brazil. Countinggeometry was defined taking into account the activities of process solutionsto be analysed, the remotely operated aliquotation device of analytical celland the available detection system. Natural and 19,91% enriched uraniumsamples were irradiated at IEAR-1 reactor in order to simulate thecomposition of Purex process solutions. After a short decay time, the sampleswere dissolved with HNO3 and then, conditioned in standard flasks withdefined geometry. The spectra were obtained by a Ge(Li) semiconductordetector and analysed by the GELIGAM software system, losing a floppy-diskconnected to a PDP-11/05 computer. Libraries were prepared and calibrationswere made with standard sources to fit the programs to the analysis offission products in irradiated uranium solutions. It was possible to choosethe best program to be used in routine analysis with the obtained data.(author)

  16. SOFIA, a Next-Generation Facility for Fission Yields Measurements and Fission Study. First Results and Perspectives

    Science.gov (United States)

    Audouin, L.; Pellereau, E.; Taieb, J.; Boutoux, G.; Béliera, G.; Chatillon, A.; Ebran, A.; Gorbinet, T.; Laurent, B.; Martin, J.-F.; Tassan-Got, L.; Jurado, B.; Alvarez-Pol, H.; Ayyad, Y.; Benlliure, J.; Caamano, M.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Paradela, C.; Rodriguez-Sanchez, J.-L.; Vargas, J.; Casarejos, E.; Heinz, A.; Kelic-Heil, A.; Kurz, N.; Nociforo, C.; Pietri, S.; Prochazka, A.; Rossi, D.; Schmidt, K.-H.; Simon, H.; Voss, B.; Weick, H.; Winfield, J. S.

    2015-10-01

    Fission fragments play an important role in nuclear reactors evolution and safety. However, fragments yields are poorly known : data are essentially limited to mass yields from thermal neutron-induced fissions on a very few nuclei. SOFIA (Study On FIssion with Aladin) is an innovative experimental program on nuclear fission carried out at the GSI facility, which aims at providing isotopic yields on a broad range of fissioning systems. Relativistic secondary beams of actinides and pre-actinides are selected by the Fragment Separator (FRS) and their fission is triggered by electromagnetic interaction. The resulting excitation energy is comparable to the result of an interaction with a low-energy neutron, thus leading to useful data for reactor simulations. For the first time ever, both fission fragments are completely identified in charge and mass in a new recoil spectrometer, allowing for precise yields measurements. The yield of prompt neutrons can then be deduced, and the fission mechanism can be ascribed, providing new constraints for fission models. During the first experiment, all the technical challenges were matched : we have thus set new experimental standards in the measurements of relativistic heavy ions (time of flight, position, energy loss).This communication presents a first series of results obtained on the fission of 238U; many other fissioning systems have also been measured and are being analyzed presently. A second SOFIA experiment is planned in September 2014, and will be focused on the measurement of the fission of 236U, the analog of 235U+n.

  17. Statistical Theory of Nuclear Fission: ?-Particle Emission

    International Nuclear Information System (INIS)

    Experimental information on angular correlation of the long-range ?-particle emitted in ternary fission with the main fission fragments has recently become available. The results may be compared with theoretical predictions and, as it turned out, provide a very sensitive test of the theory of the fission mechanism. The moving apart of the two fragments and the ?-particle under the action of the Coulomb forces between them is a classical three-body problem; it can be solved numerically by a high-speed computer if the initial conditions, i.e. the initial positions and velocities of the three particles at the scission point, are given. The initial conditions are so numerous and the dependence of the angular correlation on these conditions is so sensitive that it is impossible to reconstruct the initial conditions from the final experimental results. The statistical theory of nuclear fission dealing with the mechanism of fission leads to a complete specification of the initial conditions of the present problem and the computer calculation of the angular correlation based on them may be compared with the experimental results in a critical test of the theory. The calculated results are in good agreement with the experiments. In asymmetric fission in which the heavy fragment involves the 82-neutron shell, the ?-particle is emitted veering towards the light fragment as expected from shell-effect considerations of nuclear deformability. On the other hand, in far asymmetric fission in which the light fragment involves the 50-neutron shell, the simple shell-effect argument predicts the ?-particle veering towards the heavy fragment initially, but detailed dynamical calculation shows that this initial movement leads the ?-particle into a region of retarding field and the ?-particle is eventually pushed back and emitted veering towards the light fragment as experimentally observed. This reversal occurs only when the inital kinetic energy of the: ?-particle takes a value as small as that predicted by statistical theory (about 0.5 MeV). AH dynamical theories are likely to lead to a higher value of this energy and it is/therefore, more difficult to account for the angular correlation observed. (author)

  18. RMSRo : A vitrinite reflectance model consistent with the temperature-apatite fission track system

    DEFF Research Database (Denmark)

    Nielsen, S.B.; Clausen, O.R.

    2014-01-01

    Geophysical Research Abstracts Vol. 16, EGU2014-12484, 2014 EGU General Assembly 2014 © Author(s) 2014. CC Attribution 3.0 License. RMSRo: A vitrinite reflectance model consistent with the temperature-apatite fission track system Søren B. Nielsen, Ole R. Clausen, and Eoin D. McGregor Department of Geoscience, Høegh-Guldbergsgade 2, 8000 Aarhus C, Denmark Observed temperature, vitrinite reflectance and apatite fission tracks provide different but related information regarding temperature history. Their combined use in borehole heat flow determination as well as thermal and tectonic reconstruction requires a set of predictive models which are internally consistent. While the temperature- fission track system seems well-calibrated, several different vitrinite reflectance models exist. Although variability in vitrinite reflectance values is related to natural variations in the organic material such as; initial composition, depositional environment, degree of oxygenation etc., the most important factor affecting the construction of vitrinite reflectance models is bias in the geological temperature history of the samples used for calibration. Here we add to the vitrinite reflectance calibration data set of Suggate (1998) with more borehole data and construct a kinetic vitrinite reflectance model by minimizing the root mean square (RMS) distance between the calibration data set and model predictions. We validate this kinetic model on wells in the North Sea which have maximum temperature at the present day, and on two wells in the eastern North Sea, which have experience cooling since the early Eocene thermal maximum. The two latter wells have unusually high quality temperature, vitrinite reflectance and fission track data, and it appears that the independently derived RMSRo-model is consistent with the temperature-apatite fission track system. Keywords: vitrinite reflectance, basin analysis, thermal history, hydrocarbon exploration, apatite fission tracks Suggate, R.P., 1998. Relations between depth of burial, vitrinite reflectance and geothermal gradient. Jour- nal of Petroleum Geology, v. 21(1), January 1998, 5-32.

  19. Prompt fission neutron spectra in fast-neutron-induced fission of 238U

    Science.gov (United States)

    Desai, V. V.; Nayak, B. K.; Saxena, A.; Suryanarayana, S. V.; Capote, R.

    2015-07-01

    Prompt fission neutron spectrum (PFNS) measurements for the neutron-induced fission of 238U are carried out at incident neutron energies of 2.0, 2.5, and 3.0 MeV, respectively. The time-of-flight technique is employed to determine the energy of fission neutrons. The prompt fission neutron energy spectra so obtained are analyzed using Watt parametrization to derive the neutron multiplicity and average prompt fission neutron energy. The present experimental PFNS data are compared with the evaluated spectra taken from the ENDF/B-VII.1 library and the predictive calculations carried out using the empire-3.2 (Malta) code with built-in Los Alamos (LA) and Kornilov PFNS models. The sensitivity of the empire-3.2 LA model-calculated PFNS to the nuclear level density parameter of the average fission fragment and to the total kinetic energy is investigated. empire-3.2 LA model PFNS calculations that use Madland 2006-recommended values [D. G. Madland, Nucl. Phys. A 772, 113 (2006), 10.1016/j.nuclphysa.2006.03.013] of the total kinetic energy and the level density parameter a =A /(10 ±0.5 ) compare very well to measured data at all incident neutron incident energies.

  20. Fission Product Inventory in CANDU Fuel

    International Nuclear Information System (INIS)

    When the reactor is operated at power, fuel composition changes continuously. The fission reaction produces a large variety of fission fragments which are radioactive and decay into other isotopic species. For different accident analyses or operational events, detailed calculations of the fuel radioactive inventory (fission products and actinides) are needed. The present paper reviews two types of radioactive inventory calculations performed at Cernavoda NPP: one for determining the whole core inventory and one for determining the evolution of the inventory within fuel bundles stored in the Spent Fuel Bay. Two computer codes are currently used for radioactive inventory calculations: ORIGEN-S and ELESTRES-IST. The whole core inventory calculation was performed with both codes, the comparison showing that ELESTRES-IST gives a more conservative result. One of the challenges met during the analysis was to set a credible, yet conservative “image” of the in core fuel power/burnup distribution. Consequently, a statistical analysis was performed to find the best estimate plus uncertainties map for the power/burnup distribution of all in core fuel elements. For each power/burnup in the map, the fission product inventory was computed using a scaled irradiation history based on the Limiting Overpower Envelope. After the Fukushima accident, the problem of assessing the consequences of a loss of cooling event at the Spent Fuel Bay was raised. In order to estimate its impact, a calculation for determining the fission products inventory and decay heat evolution within the spent fuel bundles stored in the bay was performed. The calculation was done for a bay filled with fuel bundles up to its maximum capacity. The results obtained have provided a conservative estimation of the decay heat released and the expected evolution of the water temperature in the bay. This provided a technical basis for selecting the emergency actions required to cope with such events. (author)

  1. Solid state nuclear track detectors in the measurement of alpha to fission branching ratios of heavy actinides

    International Nuclear Information System (INIS)

    A sequential etching procedure for revelation of alpha and fission tracks in CR-39 was developed and optimized. Using this technique alpha and fission tracks can be differentiated unambiguously because of significant differences in their sizes and etching times. This registration and revelation procedure for alpha and fission tracks may be used for the studies of half lives, alpha to fission branching ratios and identification of radionuclides based on their decay schemes. It has the added advantage that both alpha decay and fission events can be studied using one detector and hence uncertainties related to efficiency, registration geometry, registration times, amount of radionuclides etc can be eliminated or minimized. The effects of neutron, gamma and alpha radiations on the alpha and fission fragment tracks registration and revelation properties of CR-39 detectors [CR-39, CR-39 (DOP)] were also studied. The IR spectra were also studied to find out the nature of chemical changes produced by these radiations on CR-39. (author). 32 refs., 7 figs., 4 tabs

  2. Evolution of isotopic fission-fragment yields with excitation energy

    International Nuclear Information System (INIS)

    Two fission experiments have been performed at GANIL using 238U beams at different energies and light targets. Different fissioning systems were produced with excitation energies from 10 to 230 MeV and their decay by fission was investigated with GANIL spectrometers. Preliminary fission-fragment isotopic distributions have been obtained. The evolution with impinging energy of their properties, the neutron excess and the width of the neutron-number distributions, gives important insights into the dynamics of fusion-fission mechanism. (authors)

  3. 14. International workshop on nuclear fission physics. Proceedings

    International Nuclear Information System (INIS)

    The meetings on nuclear fission took place 12-15 October 1998 and was organized by Institute of Physics and Power Engineering. The aim of the workshop was to present and discuss main new both theoretical and experimental results obtained in the area of nuclear fission, dynamical feature, properties of fission fragments and complementary radiation. As usual the program of the workshop was designed to cover a wide range of physical phenomena - from low energy and spontaneous fission to fission of hot rotating nuclei and multifragmentation at intermediate and high energies. Reaction induced by slow and fast neutron, light and heavy ions were discussed

  4. Innovative Fission Measurements with a Time Projection Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Heffner, M D; Barnes, P D; Klay, J L

    2005-11-16

    This study explores a pioneering idea to utilize a Time Projection Chamber (TPC) to measure fission cross sections and other fission quantities. The TPC is inherently capable of measuring fragments from fission events, decay alphas, and beam-material scatters. This document explores whether the TPC can improve the precision of the {sup 239}Pu(n,f) cross section and measure other new and significant fission quantities simultaneously. This work shows that the TPC can in fact deliver sub-1% cross section measurements and should provide breakthroughs in both the quality and quantity of information available from neutron-induced fission experiments.

  5. Simulation of fission product decay heat in nuclear fuel

    International Nuclear Information System (INIS)

    The decay heat of fission products depends on cooling time and on nuclear fuel composition. The average fission energy is increasing with fuel bum-up but decay heat is decreasing: the first value increases to 4 MeV/fission, and the second one decreases to 0.12 MeV/s per fission during fuel burn-up until 18 MWd/kg in RBMK-1500 reactor. The contribution of fission products related to the maximum's regions in mass distribution curve to decay heat is variant during cooling time. (author)

  6. The behavior of fission products during nuclear rocket reactor tests

    International Nuclear Information System (INIS)

    Fission product release from nuclear rocket propulsion reactor fuel is an important consideration for nuclear rocket development and application. Fission product data from the last six reactors of the Rover program are collected in this paper to provide as basis for addressing development and testing issues. Fission product loss from the fuel will depend on fuel composition and reactor design and operating parameters. During ground testing, fission products can be contained downstream of the reactor. The last Rover reactor tested, the Nuclear Furnance, was mated to an effluent clean-up system that was effective in preventing the discharge of fission products into the atmosphere

  7. Prompt and Delayed Gamma-Rays from Fission

    International Nuclear Information System (INIS)

    The following data about gamma-rays from fission are reported and discussed; Total prompt gamma-ray spectrum, and average number and energy of gamma-rays; X-rays in prompt fission, and excitation of X-rays in matter; gamma-ray spectra as a function of the mass ratio in fission, gamma-lines in those spectra, and Doppler effect-, anisotropy in gamma-emission relative to the direction of fragments; average gamma-energy and gamma-spectra as a function of mass of the fission products; delayed gamma-rays; delayed gamma-rays as a function of fission product mass. (author)

  8. 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)

  9. Radiochemical investigations on the mechanism of nuclear fission

    International Nuclear Information System (INIS)

    The following work investigates fission processes in the thermal fission of U-233 and U-235 which are rather improbable, namely 1) the yielding of relatively neutron-deficient fission products within the single mass chains, i.e. of fission products, which are for from the maximum charge distribution and 2) the true ternary fission, thus the fission into three fragments with comparable mass. In part I, the experimental determination of the absolute independent fission yields of Pm 146, Pm 148m and Pm 148g is described by the thermal fission of U-233. They are of the order of magnitude of 10-6 to 10-8% for the thermal fission of U 233 and 10-8 to 10-10 for U 235. Part II reports on the experimental determination of ternary fission products Be 7 and Si 32 in the thermal fission of U 235. 1.9 x 10-12% Be 7 and 7.5 x 10-11% Si 32 are found as upper limiting values. Following radio chemical processing and purification of the samples, the yields were determined by low-level techniques. The yields determined were compared to those described in the literature as well as those to be theoretically expected. (orig./RB)

  10. Fission dynamics study in 243Am* and 254Fm* nuclei

    International Nuclear Information System (INIS)

    Fission dynamics study in the actinide region has enough importance as it can provide crucial information about the formation of super heavy elements. The main hurdle to approach the super heavy region is the non-compound fission processes, which lead to fission before attaining the full equilibration in the composite system. At near barrier energies the significant non-compound nuclear processes are pre-equilibrium fission and quasi-fission. Pre-equilibrium fission occurs before the composite system attain its shape equilibration, whereas in case of quasi-fission mass and shape equilibration are not attained. Here in this paper we explore the model that suits best for the case of 11B + 232Th and 11B + 243Am systems in particular

  11. A transferable model for singlet-fission kinetics

    Science.gov (United States)

    Yost, Shane R.; Lee, Jiye; Wilson, Mark W. B.; Wu, Tony; McMahon, David P.; Parkhurst, Rebecca R.; Thompson, Nicholas J.; Congreve, Daniel N.; Rao, Akshay; Johnson, Kerr; Sfeir, Matthew Y.; Bawendi, Moungi G.; Swager, Timothy M.; Friend, Richard H.; Baldo, Marc A.; van Voorhis, Troy

    2014-06-01

    Exciton fission is a process that occurs in certain organic materials whereby one singlet exciton splits into two independent triplets. In photovoltaic devices these two triplet excitons can each generate an electron, producing quantum yields per photon of >100% and potentially enabling single-junction power efficiencies above 40%. Here, we measure fission dynamics using ultrafast photoinduced absorption and present a first-principles expression that successfully reproduces the fission rate in materials with vastly different structures. Fission is non-adiabatic and Marcus-like in weakly interacting systems, becoming adiabatic and coupling-independent at larger interaction strengths. In neat films, we demonstrate fission yields near unity even when monomers are separated by >5 Å. For efficient solar cells, however, we show that fission must outcompete charge generation from the singlet exciton. This work lays the foundation for tailoring molecular properties like solubility and energy level alignment while maintaining the high fission yield required for photovoltaic applications.

  12. Prediction of fission gas release at high burn-up

    International Nuclear Information System (INIS)

    Reliable design of LWR fuel rods requires the fission gas release to be predicted as accurately as possible. Indeed that physical phenomenon governs both the fuel temperatures and the inner gas pressure. Fission gas release data have been reviewed by the NRC and it has been concluded that a fission gas release enhancement occurs at burn-up above 20 GWd/tM. To correct deficient fission gas release models which do not include burn-up dependence, the NRC developed an empirical correction method to describe burn-up enhancement effect. BELGONUCLEAIRE has developed its own fission gas release model which is utilized in licensing calculation through the COMETHE code. Fission gas release predictions at high burn-up are confronted to the experimental data as well as to the predictions of the NRC correlation. The physics of the fission gas release phenomenon is discussed

  13. Progress in fission product nuclear data. No. 14

    International Nuclear Information System (INIS)

    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

  14. Subroutines to Simulate Fission Neutrons for Monte Carlo Transport Codes

    CERN Document Server

    Lestone, J P

    2014-01-01

    Fortran subroutines have been written to simulate the production of fission neutrons from the spontaneous fission of 252Cf and 240Pu, and from the thermal neutron induced fission of 239Pu and 235U. The names of these four subroutines are getnv252, getnv240, getnv239, and getnv235, respectively. These subroutines reproduce measured first, second, and third moments of the neutron multiplicity distributions, measured neutron-fission correlation data for the spontaneous fission of 252Cf, and measured neutron-neutron correlation data for both the spontaneous fission of 252Cf and the thermal neutron induced fission of 235U. The codes presented here can be used to study the possible uses of neutron-neutron correlations in the area of transparency measurements and the uses of neutron-neutron correlations in coincidence neutron imaging.

  15. Progress in fission product nuclear data. No. 13

    International Nuclear Information System (INIS)

    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

  16. Diffusion of Fission Product Elements in Compacted Bentonite

    International Nuclear Information System (INIS)

    Study on diffusion of fission product in compacted bentonite has been conducted. The information about mobilities of these elements have been obtained from the studies resulted in many countries. It is presented that the diffusion coefficient was varied by the function of solution phase condition as well as the nature of bentonite. It is also showed that the diffusion coefficient decreased by the increasing of density, as well as the increasing of montmorillonite content in bentonite. The ratio of bentonite/silica-sand used, was related to the increasing of elements mobility. In many case variation of diffusion coefficient was related to the variation of pH, redox condition, and the presence of complex ant in solution phase. The lower diffusion coefficient could give the higher retardation factor, which is a favorable factor to retard the radionuclides release from a disposal facility to geosphere. (author)

  17. Early history of soil contamination with fission products

    International Nuclear Information System (INIS)

    Underneath a balloon and instrument hut demolished today and on the natural pasture next to it, a series of 2 to 4-layer soil samples was carried out to determine the contents in Cs-137 and Sr-90. The results showed a sudded decrease of the Cs concentration behind the walls of the hut, but no further decrease towards the centre of the hut. As expected, the decrease of Sr-90 concentration was slower, both in a horizontal line and in the depth. The results reveal that the soil underneath the hut has not received further fission products since it was built in 1956 from depositions of later nuclear weapon tests. Furthermore, the radionuclides were not transported much further into lower strata so that by taking into consideration of the half-life of the two nuclides their concentration in the soil can be traced back to the year 1956 for comparison with the results measured at the time. (orig./HP)

  18. Diffusion coefficients of volatile fission products in single crystal urania

    International Nuclear Information System (INIS)

    The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimen was made from UO2 single crystal powder with natural enrichment and a grain size of 25 ?m. Gamma scanning was performed before and after the annealing test to obtain total fission gas release fractions. The annealing test was performed for 10 hours with three temperature changes. Gamma ray peaks from the trap system were measured every 20 minutes during the annealing test. Activation energy and the pre-exponential factor of the diffusion coefficient equation were calculated using the release fraction data and a diffusion equation. The values were determined to be 360(±0.5%) kJ/mol and 2.0x10-7(±10%), respectively. (author)

  19. Fusion-fission energy systems evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Teofilo, V.L.; Aase, D.T.; Bickford, W.E.

    1980-01-01

    This report serves as the basis for comparing the fusion-fission (hybrid) energy system concept with other advanced technology fissile fuel breeding concepts evaluated in the Nonproliferation Alternative Systems Assessment Program (NASAP). As such, much of the information and data provided herein is in a form that meets the NASAP data requirements. Since the hybrid concept has not been studied as extensively as many of the other fission concepts being examined in NASAP, the provided data and information are sparse relative to these more developed concepts. Nevertheless, this report is intended to provide a perspective on hybrids and to summarize the findings of the rather limited analyses made to date on this concept.

  20. 60 years controlled nuclear fission: CP-1

    International Nuclear Information System (INIS)

    On December 2, 1942, the Chicago Pile 1 (CP-1) went critical for the first time. In this way, the scientists and engineers involved in the project under the leadership of Enrico Fermi succeeded in demonstrating that a self-sustaining nuclear reaction with nuclear fission processes was technically feasible. Only four years after the discovery and proof of nuclear fission by Otto Hahn, Fritz Strassmann, and Lise Meitner, the experiment consisting of graphite blocks as the moderator and uranium dioxide pellets as the fuel, as well as instrumentation and control devices, had been set up in the former squash court of the field and track stadium of the University of Chicago. Precisely at 3.36 a.m. Chicago time, after control rods had been withdrawn, the instruments showed the chain reaction by the neutron flux they indicated. An important cornerstone in the use of nuclear power had thus been laid. (orig.)

  1. Nuclear Fission Investigation with Twin Ionization Chamber

    International Nuclear Information System (INIS)

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  2. In-beam Fission Study at JAEA

    Directory of Open Access Journals (Sweden)

    Nishio Katsuhisa

    2013-12-01

    Full Text Available Fission fragment mass distributions were measured in heavy-ion induced fissions using 238U target nucleus. The measured mass distributions changed drastically with incident energy. The results are explained by a change of the ratio between fusion and quasifission with nuclear orientation. A calculation based on a fluctuation dissipation model reproduced the mass distributions and their incident energy dependence. Fusion probability was determined in the analysis. Evaporation residue cross sections were calculated with a statistical model in the reactions of 30Si + 238U and 34S + 238U using the obtained fusion probability in the entrance channel. The results agree with the measured cross sections for seaborgium and hassium isotopes.

  3. Preparative electrophoresis of industrial fission product solutions

    International Nuclear Information System (INIS)

    The aim of this work is to contribute to the development of the continuous electrophoresis technique while studying its application in the preparative electrophoresis of industrial fission product solutions. The apparatus described is original. It was built for the purposes of the investigation and proved very reliable in operation. The experimental conditions necessary to maintain and supervise the apparatus in a state of equilibrium are examined in detail; their stability is an important factor, indispensable to the correct performance of an experiment. By subjecting an industrial solution of fission products to preparative electrophoresis it is possible, according to the experimental conditions, to prepare carrier-free radioelements of radiochemical purity (from 5 to 7 radioelements): 137Cs, 90Sr, 141+144Ce, 91Y, 95Nb, 95Zr, 103+106Ru. (author)

  4. Delayed Fission Neutrons. Proceedings of a Panel

    International Nuclear Information System (INIS)

    Proceedings of a panel organized by the IAEA and held in Vienna, 24-27 April 1967. The increasing sophistication in reactor design and, in particular, the advent of fast reactors have shown that delayed fission neutrons play a major role in considerations of operational stability and safety. Fourteen leading scientists from nine Member States made vital new data available and defined areas of investigation for future experimental and theoretical work. The data are summarized in an Annex at the end of the Proceedings. The contents include papers on the importance of delayed neutron data in reactor design, on which fission products should be considered as precursors, and on experimental methods for separating and determining the precursors. Each paper is in its original language (11 English, 1 French, 2 Russian) and is preceded by an abstract in English with a second one in the original language if this is not English. The summarized discussions, summary and Annex are in English. (author)

  5. Hemispherical fission chamber for neutron flux monitoring

    International Nuclear Information System (INIS)

    One designed a fission chamber to monitor flux of neutrons from 7Li(p, n)7Be nuclear reaction in the V de G. The chamber has the hemisphere shape with a neutron producing target in the center. 235U isotope was used as a fissile material. The chamber was filled with 97% Ar and 3% CO2 gas working mix. The experimentally measured efficiency of neutron recording within 1-450 keV range constituted 1.6 ·10-5. When proton beam current is equal to ?3 ?A and neutron energy constitutes 1942 keV the fission chamber within ?20 min measuring time ensures determination of neutron integral yield from a thick target with 1% statistical accuracy

  6. Microscopic Calculations of 240Pu Fission

    Energy Technology Data Exchange (ETDEWEB)

    Younes, W; Gogny, D

    2007-09-11

    Hartree-Fock-Bogoliubov calculations have been performed with the Gogny finite-range effective interaction for {sup 240}Pu out to scission, using a new code developed at LLNL. A first set of calculations was performed with constrained quadrupole moment along the path of most probable fission, assuming axial symmetry but allowing for the spontaneous breaking of reflection symmetry of the nucleus. At a quadrupole moment of 345 b, the nucleus was found to spontaneously scission into two fragments. A second set of calculations, with all nuclear moments up to hexadecapole constrained, was performed to approach the scission configuration in a controlled manner. Calculated energies, moments, and representative plots of the total nuclear density are shown. The present calculations serve as a proof-of-principle, a blueprint, and starting-point solutions for a planned series of more comprehensive calculations to map out a large set of scission configurations, and the associated fission-fragment properties.

  7. Fusion-fission energy systems evaluation

    International Nuclear Information System (INIS)

    This report serves as the basis for comparing the fusion-fission (hybrid) energy system concept with other advanced technology fissile fuel breeding concepts evaluated in the Nonproliferation Alternative Systems Assessment Program (NASAP). As such, much of the information and data provided herein is in a form that meets the NASAP data requirements. Since the hybrid concept has not been studied as extensively as many of the other fission concepts being examined in NASAP, the provided data and information are sparse relative to these more developed concepts. Nevertheless, this report is intended to provide a perspective on hybrids and to summarize the findings of the rather limited analyses made to date on this concept

  8. SABR Fusion-Fission Hybrid Studies

    Science.gov (United States)

    Stewart, Chris

    2012-03-01

    The Subcritical Advanced Burner Reactor (SABR) concept is a fast reactor comprised of a tokamak fusion neutron source based on ITER surrounded by an annular fission core adapted from Integral Fast Reactor designs. Previous work has examined SABR used to help close the nuclear fuel cycle by fissioning the transuranics from spent nuclear fuel. One focus of the present work is a SABR Breeder Reactor to achieve tritium self-sufficieny and a Pu breeding ratio significantly above 1 in order to provide fuel for SABR as well as for MOX-fueled LWR's and other fast reactors. Another focus of this research is the dynamic safety simulation of lloss-of-flow loss-of-heat-sink, loss-of-power, and positive reactivity accidents in the TRU fuel SABR burner reactor. The reactivity effect of thermal-induced bowing of fuel pins has been modeled, which is expected to provide passive safety.

  9. Nuclear Fission Investigation with Twin Ionization Chamber

    Science.gov (United States)

    Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

    2011-11-01

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  10. FALSTAFF: A new tool for fission studies

    International Nuclear Information System (INIS)

    The future NFS installation will produce high intensity neutron beams from hundreds of keV up to 40 MeV. Taking advantage of this facility, data of particular interest for the nuclear community in view of the development of the fast reactor technology will be measured. The development of an experimental setup called FALSTAFF for a full characterization of actinide fission fragments has been undertaken. Fission fragment isotopic yields and associated neutron multiplicities will be measured as a function of the neutron energy. Based on time-of-flight and residual energy technique, the setup will allow the simultaneous measurement of the complementary fragments velocity and energy. The performances of TOF detectors of FALSTAFF will be presented and expected resolutions for fragment masses and neutron multiplicities, based on realistic simulations, will be shown. (authors)

  11. Fission fragment detection by thin film capacitors

    International Nuclear Information System (INIS)

    Heavy-ion detection by solid dielectrics has been so far obtained by chemical etching. In this paper the detection of fission fragments is based on the counting of breakdowns in thin films of solid dielectrics. These films are used as dielectric materials in capacitors with one electrode usually less than 1000 A thick. Breakdowns in such capacitors are non-shorting and can be repeated up to millions of times/cm2 of the capacitor area. The property that makes these capacitors suitable for detection is that fission fragments induce breakdown at electric fields distinctly lower than those due to the application of field alone. The characteristics of these new detecting systems are described and compared with those of the damage-track detectors. (author)

  12. Angular anisotropy of fission fragments in the neutron-induced fission of 235U

    International Nuclear Information System (INIS)

    Recent studies of the angular distribution of fission fragments in the fission of heavy nuclei following direct reactions have indicated some evidence for a rather large pairing energy gap in the transition state spectra of even-even fissioning nuclei. In the present work the transition-state nucleus 236U has been investigated by measuring the angular distributions of fission fragments in the fission of 235U induced by monoenergetic neutrons of 20 different neutron energies ranging from 0.1 to 3.1 MeV. These measurements were made with a set-up consisting of three semiconductor detectors which recorded the energy spectra of fission fragments emitted at the average angles of 0 deg, 45 deg and 90 deg with respect to the incident neutron direction. The relative solid angles of detection for the three detectors were experimentally determined using isotropic fragment distributions in the case of thermal-neutron-induced fission of 235U. For each neutron energy the angular anisotropy was obtained by a least-square fit to the measured angular distributions taking into account the angular-resolution effects due to the finite size of the target and the detectors. The parameter K02 of the assumed Gaussian distribution of the K-states at the transition-state nucleus was then determined for each neutron bombarding energy using the theoretical expression for the angular anisotropy which includes the effects of target spin and nuclear deformation. The average orbital angular momenta of the fissioning nucleus for different bombarding energies were evaluated using optical-model neutron-transmission coefficients. The observed variation of K02 with excitation energy shows a steep increase in the value of K02 at an excitation energy of 2.0 ± 0.1 MeV above the fission threshold. This increase in the value of K02 has been interpreted as the onset of two quasi-particle excitations of the highly deformed transition state nucleus 236U. At excitation energies below the two-quasi-particle excitation low values of K02 are expected whereas fairly high values of K02 were observed in the present work. This suggests that the statistical assumption of a Gaussian distribution of K-states below the two-quasi-particle excitation energy may not be valid because only a restricted number of vibrational K-states are available. (author)

  13. Outlook for nuclear fission energy

    International Nuclear Information System (INIS)

    The electric utility industry has made a substantial commitment to nuclear power. The industrial capability to produce nuclear plants is large and well established. Nevertheless, nuclear energy in the United States is at the crossroad, and the direction it will take is not at all assured. The postponements, cancellations, and lack of orders for new plants over the past three years raise some serious questions about the future. The present problems of nuclear energy are primarily nontechnical in nature. If the nontechnical issues can be resolved, the future for nuclear looks bright indeed. The LWR and other converters could provide strong competition for coal and other electric power options for a half century or more. If development goals are met, the nuclear breeder offers the prospect of a very large supply of energy at stabilized prices over a time span of centuries

  14. General Description of Fission Observables - JEFF Report 24. GEF Model

    International Nuclear Information System (INIS)

    The Joint Evaluated Fission and Fusion (JEFF) Project is a collaborative effort among the member countries of the OECD Nuclear Energy Agency (NEA) Data Bank to develop a reference nuclear data library. The JEFF library contains sets of evaluated nuclear data, mainly for fission and fusion applications; it contains a number of different data types, including neutron and proton interaction data, radioactive decay data, fission yield data and thermal scattering law data. The General fission (GEF) model is based on novel theoretical concepts and ideas developed to model low energy nuclear fission. The GEF code calculates fission-fragment yields and associated quantities (e.g. prompt neutron and gamma) for a large range of nuclei and excitation energy. This opens up the possibility of a qualitative step forward to improve further the JEFF fission yields sub-library. This report describes the GEF model which explains the complex appearance of fission observables by universal principles of theoretical models and considerations on the basis of fundamental laws of physics and mathematics. The approach reveals a high degree of regularity and provides a considerable insight into the physics of the fission process. Fission observables can be calculated with a precision that comply with the needs for applications in nuclear technology. The relevance of the approach for examining the consistency of experimental results and for evaluating nuclear data is demonstrated. (authors)

  15. Spark chamber measurement of neutron fission cross-sections and related parameters

    International Nuclear Information System (INIS)

    As reactor burn-up calculations become more detailed, a knowledge of the nuclear properties of the less common heavy nuclides becomes increasingly important. The fission cross-section of many of these nuclides can be measured with modern electron linear accelerators as pulsed neutron sources and a sample of several milligrams. Samples of this size are now becoming available for many nuclides. However, nearly all of these nuclides are much shorter-lived than the more common fissionable nuclides such as 239Pu. Therefore, a major problem in these measurements is the development of a detector which is capable of distinguishing fission fragments from the intense background radiation arising from the natural radioactivity of such samples. The insensitivity of the corona-spark counter to gamma rays, electrons and alpha particles makes it especially useful for measurements on these isotopes. With the exception of spontaneous fission, natural radioactivity appears to be a serious problem in the use of this detector for only a few of the most alpha-active and least fissionable nuclei. Since the detector is insensitive to the intense gamma flash associated with the electron pulse from a high-power linear electron accelerator, measurements can be made at very short times after the gamma burst; that is, into the MeV region. Measurements are, therefore, possible from thermal energy to several MeV with this detector. The cross-section can then be normalized at thermal energy to the usually well-known thermal fission cross-section so that a knowledge of detector efficiency, absolute neutron flux, and sample size are not required for determining absolute cross-sections. The usefulness and limitations of the technique are illustrated by measurements on 242mAm from 0.02 eV to 6 MeV obtained with a 50-mg Am sample containing about 20% 242mAm and 80% 241Am. Other uses of this detector in measuring ?-bar, alpha, and spontaneous fission half-lives are presented. (author)

  16. Method of separating uranium and fission products from alkyl phosphoric acid containing uranium and fission products

    International Nuclear Information System (INIS)

    Purpose: To increase the decontamination rate of uranium and fission products as compared with the case where no ethanol is added, as well as to significantly shorten the time required for the separation of two phases. Method: For removing uranium and fission products from a wasted uranium-containing solvent that contains uranium, fission products and alkyl phosphoric acid as an organic solvent, a sodium carbonate solution is added and stirred to transform the uranium and the fission products into an aqueous phase through reverse extraction and then separate them by settling. If the concentration of the uranium or the sodium carbonate is excessively high, a third phase may be formed to render the phase separation difficult. In view of the above, ethanol is added, mixed, stirred and then settled. This enables rapid phase separation between the aqueous phase and the organic phase while inhibiting the formation of the third phase. After the complete separation of the aqueous phase and the organic phase, they are separated and the uranium and the fission products are removed from the wasted solvent into the sodium carbonate solution. (Horiuchi, T.)

  17. The analyses of neutron coincidence data to verify both spontaneous-fission and fissionable isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Menlove, H.O.; Abedin-Zadeh, R.; Zhu, R. (Los Alamos National Lab., NM (USA); International Atomic Energy Agency, Vienna (Austria); Academia Sinica, Beijing, BJ (China). Inst. of Atomic Energy)

    1989-08-01

    For neutron coincidence counter applications to the assay of plutonium samples, various calibration methods can be used to evaluate the data. The reals (R) and totals (T) rates can be used to predict the induced-fission rate. When this is done, the results give information related to both the spontaneous-fission isotopes and the fissionable isotopes (induced fission). The combination of both approaches is less sensitive to the plutonium isotopic uncertainties than the normal spontaneous-fission approach. Five calibration methods are evaluated for a wide variety of sample types to emphasize the advantages and disadvantages of the methods. For certain sample categories with well-defined geometries, such as light-water reactor and fast breeder reactor mixed-oxide fuel assemblies, a method is presented that allows the verification of the declared isotopics within given constraints. Recommendations are given on analysis procedures to reduce the assay errors for coincidence counting of any type of sample. 15 refs., 11 figs., 15 tabs.

  18. Wear measurement by implantation of fission fragments

    International Nuclear Information System (INIS)

    The results are reported of an investigation into the practicability of the implantation of fission fragments from a 252Cf source and the use of this introduced radioactivity for wear measurements. Details of a series of such measurements on lathe tools are given. These show that small amounts of wear and abrasion can be determined in this way upto some days after the end of irradiation depending on the method of measurement. (U.K.)

  19. Neutron measurements performed with miniature fission chambers

    International Nuclear Information System (INIS)

    This research aims at proposing solutions regarding instruments to perform neutron flow measurements in nuclear power reactors and to perform measurements of the reaction rates of highly radioactive transuranic fissile elements in experimental reactors. This research is also part of a program aimed at the adjustment of the Cadarache cross section set. The report defines the instrumentation, recalls the operation of fission chambers, discusses the implemented instrumentation, and discusses the obtained measurements

  20. Fissionable material handlers certification training program

    International Nuclear Information System (INIS)

    A formal program for certification of fissionable material handlers is presented that cultivates safe working practices. This certification complies with the training requirements of the Department of Energy Directive 0530 (ERDA Manual Chapter 0530), Nuclear Criticality Safety. The program consists of a series of classroom lectures, on-the-job training, and examinations in criticality safety, radiation protection, industrial safety, emergency procedures, and the employee's specific work operations. The program for recertification is also discussed

  1. Actinide and fission product partitioning and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-07-01

    The fourth international information exchange meeting on actinide and fission product partitioning and transmutation, took place in Mito City in Japan, on 111-13 September 1996. The proceedings are presented in six sessions: the major programmes and international cooperation, the partitioning and transmutation programs, feasibility studies, particular separation processes, the accelerator driven transmutation, and the chemistry of the fuel cycle. (A.L.B.)

  2. Opimization of fusion-driven fissioning systems

    International Nuclear Information System (INIS)

    Potential advantages of hybrid or fusion/fission systems can be exploited in different ways. With selection of the 238U--239Pu fuel cycle, we show that the system has greatest value as a power producer. Numerical examples of relative revenue from power production vs. 239Pu production are discussed, and possible plant characteristics described. The analysis tends to show that the hybrid may be more economically attractive than pure fusion systems

  3. Level schemes for some fission product nuclides

    International Nuclear Information System (INIS)

    Level schemes of 24 fission product nuclides comparable between JAERI's and Petten's are presented. When the assignments of spin and parity are different between, the reasons for JAERI's are described. In typical cases are compared the cross section of inelastic scattering and (n,?) reaction calculated using the JAERI's and Petten's level schemes. The distribution of the low-lying levels of which spins and parities are assigned, is also presented. (auth.)

  4. Actinide and fission product partitioning and transmutation

    International Nuclear Information System (INIS)

    The fourth international information exchange meeting on actinide and fission product partitioning and transmutation, took place in Mito City in Japan, on 111-13 September 1996. The proceedings are presented in six sessions: the major programmes and international cooperation, the partitioning and transmutation programs, feasibility studies, particular separation processes, the accelerator driven transmutation, and the chemistry of the fuel cycle. (A.L.B.)

  5. The evaluated reference fission yield data file

    International Nuclear Information System (INIS)

    The reference fission yield file was established. The data were evaluated based on the experimental data available up to the date evaluated. The data were processed by using codes AVERAG for weighted average and ZOTT for simultaneous evaluation. The evaluated data were compared with existing evaluated data from ENDF/B-6, JEF-2, JENDL-3 and CENDL/FY. The data were updated and improved and the errors are considerably reduced comparing with JEF-2 and CENDL/FY

  6. NUCLEAR FISSION PRODUCTS BEHAVIOR IN THE ENVIRONMENT

    OpenAIRE

    HUSSAM AL-RABAI’AH; MANAL ABDELSALAM; OSAMA ABU-HAIJA; ABDUL-WALI AJLOUNI

    2008-01-01

    The movement of radionuclides from its source, inside reactor containment, and in the environment has been studied with the principal objective of tracing the routes by which they accumulate in the food chain and become available for human consumption. A large number of studies and models were established to explain the fission products behavior within terrestrial and water ecosystems, but a number of behaviors were non understandable, which always attributed to unknown reasons. Deep Atomic B...

  7. Tritium chemistry in fission and fusion reactors

    International Nuclear Information System (INIS)

    We are interested in the behaviour of tritium inside the solids where it is generated both in the case of fission nuclear reactor fuel elements, and in that of blankets of future fusion reactor. In the first case it is desirable to be able to predict whether tritium will be found in the hulls or in the uranium oxide, and under what chemical form, in order to take appropriate steps for it's removal in reprocessing plants. In fusion reactors breeding large amounts of tritium and burning it in the plasma should be accomplished in as short a cycle as possible in order to limit inventories that are associated with huge activities. Mastering the chemistry of every step is therefore essential. Amounts generated are not of the same order of magnitude in the two cases studied. Ternary fissions produce about 66 1013Bq (18 000 Ci) per year of tritium in a 1000 MWe fission generator, i.e., about 1.8 1010Bq (0.5 Ci) per day per ton of fuel

  8. Gas-phase transport of fission products

    International Nuclear Information System (INIS)

    The paper presents the results of an experimental investigation to show the importance of nuclear aerosol formation as a mechanism for semi-volatile fission product transport under certain postulated HTGR accident conditions. Simulated fission product Sr and Ba as oxides are impregnated in H451 graphite and released at elevated temperatures into a dry helium flow. In the presence of graphite, the oxides are quantitatively reduced to metals, which subsequently vaporize at temperatures much lower than required for the oxides alone to vaporize in the absence of graphite. A substantial fraction of the released material is associated with particulate matter, which is collected on filters located downstream at ambient temperatures. Increasing carrier-gas flow rate greatly enhances the extent of particulate transport. The release and transport of simulated fission product Ag as metal are also investigated. Electron microscopic examinations of the collected Sr and Ag aerosols show large agglomerates composed of primary particles roughly 0.06 to 0.08 ?m in diameter

  9. MAFF - The Munich accelerator for fission fragments

    Science.gov (United States)

    Beck, L.; Habs, D.; Reiter, P.; Thirolf, P.; Sieber, T.; Bongers, H.; Emhofer, S.; Maier, H. J.

    2002-12-01

    At the new high flux reactor FRM-II in Munich the accelerator MAFF (Munich accelerator for fission fragments) is under design. In the high neutron flux of 10(14) n/cm(2) s up to 10(14) neutron-rich fission fragments per second are produced in the 1 g U-235 target. Ions with an energy of 30 keV are extracted from the ion source. In the mass seperator two isotopes can be selected. One of the beams is used for low energy experiments, the other one is injected into an ECRIS (or EBIS) for charge breeding to a q/A? 0.16. A gas filled RFQ cooler is used for emittance improvement. The subsequent LINAC delivers beams with an energy ranging from 3.7 MeV/u to 5.9 MeV/u. New IH structures are being developed at the Munich tandem laboratory. A small storage ring is planned in a further stage to recycle the fission fragments. A thin target foil can be placed into this ring, e.g., for synthesis of super-heavy elements. The through-going beam tube has been installed in the heavy water tank of the reactor. Tests of the target ion source in a special oven to test long term stability and safety tests were in progress.

  10. Experimental studies of quasi-fission reactions

    International Nuclear Information System (INIS)

    A large body of experimental data on these fission-like processes have become available in recent years using a number of different target-projectile combinations. None of these experimental studies are specifically addressing the question of entrance channel effects. These effects are expected to play an important role if the dynamics in the approach phase of the reaction is responsible for the occurrence of quasi-fission. An alternate interpretation in terms of the disappearance of the fission barrier at large partial waves, which is entirely a property of the completely fused system independent of the formation process, has also been proposed. In order to address these questions we have studied the system 214Th via three different entrance channels, namely 32S/plus/182W, 48Ti/plus/166Er and 60Ni/plus/154Sm. The analysis of the 48Ti/plus/166Er data is, as yet, incomplete and we shall therefore report only on the results of the 32S/plus/182W and 60Ni/plus/154Sm reactions in this paper. 4 refs., 3 figs

  11. Interstellar rendezvous missions employing fission propulsion systems

    International Nuclear Information System (INIS)

    There has been a conventionally held nostrum that fission system specific power and energy content is insufficient to provide the requisite high accelerations and velocities to enable interstellar rendezvous missions within a reasonable fraction of a human lifetime. As a consequence, all forms of alternative mechanisms that are not yet, and may never be technologically feasible, have been proposed, including laser light sails, fusion and antimatter propulsion systems. In previous efforts, [Lenard and Lipinski, 1999] the authors developed an architecture that employs fission power to propel two different concepts: one, an unmanned probe, the other a crewed vehicle to Alpha Centauri within mission times of 47 to 60 years. The first portion of this paper discusses employing a variant of the ''Forward Resupply Runway'' utilizing fission systems to enable both high accelerations and high final velocities necessary for this type of travel. The authors argue that such an architecture, while expensive, is considerably less expensive and technologically risky than other technologically advanced concepts, and, further, provides the ability to explore near-Earth stellar systems out to distances of 8 light years or so. This enables the ability to establish independent human societies which can later expand the domain of human exploration in roughly eight light-year increments even presuming that no further physics or technology breakthroughs or advances occur. In the second portion of the paper, a technology requirement assessment is performed. The authors argue that reasonable to extensive extensions to known technology could enable this revolutionary capability

  12. Hybrid fission-fusion nuclear reactors

    International Nuclear Information System (INIS)

    A fusion-fission hybrid could contribute to all components of nuclear power - fuel supply, electricity production, and waste management. The idea of the fusion-fission hybrid is many decades old. Several ideas, both new and revisited, have been investigated by hybrid proponents. These ideas appear to have attractive features, but they require various levels of advances in plasma science and fusion and nuclear technology. As a first step towards the development of hybrid reactors, fusion neutron sources can be considered as an option. Compact high-field tokamaks can be a candidate for being the neutron source in a fission-fusion hybrid, essentially due to their design characteristics, such as compact dimensions, high magnetic field, flexibility of operation. This study presents the development of a tokamak neutron source for a material testing facility using an Ignitor-based concept. The computed values show the potential of this neutron-rich device for fusion materials testing. Some full-power months of operation are sufficient to obtain relevant radiation damage values in terms of dpa. (Author)

  13. Calculated fission properties of the heaviest elements

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1986-09-01

    A quantitative calculation is presented that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part a Yukawa-plus-exponential model is used and for the microscopic part a folded-Yukawa single-particle potential is used. The three-quadratic-surface parameterization generates shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. The results of the calculations in terms of potential-energy surfaces and fission half-lives are presented for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. 53 refs., 15 figs., 1 tab.

  14. Calculated fission properties of the heaviest elements

    International Nuclear Information System (INIS)

    A quantitative calculation is presented that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part a Yukawa-plus-exponential model is used and for the microscopic part a folded-Yukawa single-particle potential is used. The three-quadratic-surface parameterization generates shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. The results of the calculations in terms of potential-energy surfaces and fission half-lives are presented for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. 53 refs., 15 figs., 1 tab

  15. Undergraduate Measurements For Fission Reactor Applications

    Science.gov (United States)

    Hicks, S. F.; Kersting, L. J.; Lueck, C. J.; McDonough, P.; Crider, B. P.; McEllistrem, M. T.; Peters, E. E.; Vanhoy, J. R.

    2011-06-01

    Undergraduate students at the University of Dallas (UD) have investigated elastic and inelastic neutron scattering cross sections on structural materials important for criticality considerations in nuclear fission processes. Neutrons scattered off of 23Na and NatFe were detected using neutron time-of-flight techniques at the University of Kentucky Low-Energy Nuclear Accelerator Facility. These measurements are part of an effort to increase the efficiency of power generation from existing fission reactors in the US and in the design of new fission systems. Students have learned the basics of how to operate the Model CN Van de Graaff generator at the laboratory, setup detectors and electronics, use data acquisition systems, and they are currently analyzing the angular dependence of the scattered neutrons for incident neutron energies of 3.57 and 3.80 MeV. Most students participating in the project will use the research experience as the material for their undergraduate research thesis required for all Bachelor of Science students at the University of Dallas. The first student projects on this topic were completed during the summer of 2010; an overview of student participation in this investigation and their preliminary results will be presented.

  16. Fission gas release behaviour in MOX fuels

    International Nuclear Information System (INIS)

    As a part of plutonium recycling programme MOX (U,Pu)O2 fuels will be used in Indian boiling water reactors (BWR) and pressurised heavy water reactors (PHWR). Based on successful test irradiation of MOX fuel in CIRUS reactor, 10 MOX fuel assemblies have been loaded in the BWR of Tarapur Atomic Power Station (TAPS). Some of these MOX fuel assemblies have successfully completed the initial target average burnup of ?16,000 MWD/T. Enhancing the burnup target of the MOX fuels and increasing loading of MOX fuels in TAPS core will depend on the feedback information generated from the measurement of released fission gases. Fission gas release behaviour has been studied in the experimental MOX fuel elements (UO2 - 4% PuO2) irradiated in pressurised water loop (PWL) of CIRUS. Eight (8) MOX fuel elements irradiated to an average burnup of ?16,000 MWD/T have been examined. Some of these fuel elements contained controlled porosity pellets and chamfered pellets. This paper presents the design details of the experimental set up for studying fission gas release behaviour including measurement of gas pressure, void volume and gas composition. The experimental data generated is compared with the prediction of fuel performance modeling codes of PROFESS and GAPCON THERMAL-3. (author)

  17. Unified consideration of deep inelastic, quasi-fission and fusion-fission phenomena

    International Nuclear Information System (INIS)

    A new approach is proposed for a unified description of strongly coupled deep inelastic (DI) scattering, fusion, fission and quasi-fission (QF) processes of heavy-ion collisions. The standard (most important) degrees of freedom of the nuclear system, unified driving potential, and a unified set of dynamic equations of motion are used in this approach. This makes it possible to perform a full (continuous) time analysis of the evolution of heavy nuclear systems, starting from the approaching stage, moving up to the formation of the compound nucleus and eventually emerging into two final fission fragments. The calculated mass, charge, energy and angular distributions of the reaction products agree well with the corresponding experimental data. It gives us hope to obtain rather accurate predictions for the probabilities of superheavy element formation in near-barrier fusion reactions

  18. Prompt fission ?-ray emission from thermal- and fast-neutron induced fission

    International Nuclear Information System (INIS)

    In recent years we conducted a systematic investigation of fission-fragment de-excitation through prompt neutron and ?-ray emission. For the latter we were able to obtain spectral data for thermal-neutron induced fission on 235U and 241Pu with unprecedented accuracy. The recently installed neutron source LICORNE, where neutrons are produced in inverse kinematics, enables us to explore prompt de-excitation also for fast-neutron induced fission. A first experiment campaign on 235,238U and 232Th was performed at LICORNE. From our experimental data we established a systematic trend up to incident neutron energies of 20 MeV that compares well with modern theoretical calculations.

  19. De Novo Biosynthesis of Vanillin in Fission Yeast (Schizosaccharomyces pombe) and Baker's Yeast (Saccharomyces cerevisiae) ?

    OpenAIRE

    Hansen, Esben H; Møller, Birger Lindberg; Kock, Gertrud R.; Bünner, Camilla M.; Kristensen, Charlotte; Jensen, Ole R.; Okkels, Finn T.; Olsen, Carl E; Motawia, Mohammed S.; Hansen, Jørgen

    2009-01-01

    Vanillin is one of the world's most important flavor compounds, with a global market of 180 million dollars. Natural vanillin is derived from the cured seed pods of the vanilla orchid (Vanilla planifolia), but most of the world's vanillin is synthesized from petrochemicals or wood pulp lignins. We have established a true de novo biosynthetic pathway for vanillin production from glucose in Schizosaccharomyces pombe, also known as fission yeast or African beer yeast, as well as in baker's yeast...

  20. Study of 231Th fission barrier by (d,pf) reaction. Observation of a third minimum in the fission barrier associated to the fissioning nucleus configurations

    International Nuclear Information System (INIS)

    Results of fission probability and fission fragment angular distribution measurements are presented for the 230Th(d,pf) reaction in the region of the sub-fission threshold resonance (E*=5,85 MeV). A tandem Van de Graaff accelerator is used. The proton energy is measured by means of a QD3 magnetic spectrometer and two gas counters. The energy resolution obtained is 8 keV(deltaE/E approximately = 9.10-4). The fission fragments emission angles are measured with two parallel-plates detectors, the anodes of which are made of several angular sectors. A fine structure is observed in the resonance at 5.85 MeV, the properties of which (parity splitted rotational bands) permit to conclude that a third minimum exists in the fission barrier of the 231Th nucleus