Science.gov

Sample records for nuclear reactions fission

  1. Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Denschlag, J. O.

    This chapter first gives a survey on the history of the discovery of nuclear fission. It briefly presents the liquid-drop and shell models and their application to the fission process. The most important quantities accessible to experimental determination such as mass yields, nuclear charge distribution, prompt neutron emission, kinetic energy distribution, ternary fragment yields, angular distributions, and properties of fission isomers are presented as well as the instrumentation and techniques used for their measurement. The contribution concentrates on the fundamental aspects of nuclear fission. The practical aspects of nuclear fission are discussed in http://dx.doi.org/10.1007/978-1-4419-0720-2_57 of Vol. 6.

  2. Fission Reaction Event Yield Algorithm

    SciTech Connect

    Hagmann, Christian; Verbeke, Jerome; Vogt, Ramona; Roundrup, Jorgen

    2016-05-31

    FREYA (Fission Reaction Event Yield Algorithm) is a code that simulated the decay of a fissionable nucleus at specified excitation energy. In its present form, FREYA models spontaneous fission and neutron-induced fission up to 20 MeV. It includes the possibility of neutron emission from the nuclear prior to its fussion (nth chance fission).

  3. Interplay between compound and fragments aspects of nuclear fission and heavy-ion reaction

    SciTech Connect

    Moller, Peter; Iwamoto, A; Ichikawa, I

    2010-09-10

    The scission point in nuclear fission plays a special role where one-body system changes to two-body system. Inverse of this situation is realized in heavy-ion fusion reaction where two-body system changes to one body system. Among several peculiar phenomena expected to occur during this change, we focus our attention to the behavior of compound and fragments shell effects. Some aspects of the interplay between compound and fragments shell effect are discussed related to the topics of the fission valleys in the potential energy surface of actinide nuclei and the fusion-like trajectory found in the cold fusion reaction leading to superheavy nuclei.

  4. On fundamental quality of fission chain reaction to oppose rapid runaways of nuclear reactors

    NASA Astrophysics Data System (ADS)

    Kulikov, G. G.; Shmelev, A. N.; Apse, V. A.; Kulikov, E. G.

    2017-01-01

    It has been shown that the in-hour equation characterizes the barriers and resistibility of fission chain reaction (FCR) against rapid runaways in nuclear reactors. Traditionally, nuclear reactors are characterized by the presence of barriers based on delayed and prompt neutrons. A new barrier based on the reflector neutrons that can occur when the fast reactor core is surrounded by a weakly absorbing neutron reflector with heavy atomic weight was proposed. It has been shown that the safety of this fast reactor is substantially improved, and considerable elongation of prompt neutron lifetime "devalues" the role of delayed neutron fraction as the maximum permissible reactivity for the reactor safety.

  5. Fifty years with nuclear fission

    SciTech Connect

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

    1989-01-01

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

  6. Uncertainties in nuclear fission data

    NASA Astrophysics Data System (ADS)

    Talou, Patrick; Kawano, Toshihiko; Chadwick, Mark B.; Neudecker, Denise; Rising, Michael E.

    2015-03-01

    We review the current status of our knowledge of nuclear fission data, and quantify uncertainties related to each fission observable whenever possible. We also discuss the roles that theory and experiment play in reducing those uncertainties, contributing to the improvement of our fundamental understanding of the nuclear fission process as well as of evaluated nuclear data libraries used in nuclear applications.

  7. Dynamical Aspects of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Kliman, J.; Itkis, M. G.; Gmuca, Š.

    2008-11-01

    Fission dynamics. Dependence of scission-neutron yield on light-fragment mass for [symbol]=1/2 [et al.]. Dynamics of capture quasifission and fusion-fission competition / L. Stuttgé ... [et al.] -- Fission-fission. The processes of fusion-fission and quasi-fission of superheavy nuclei / M. G. Itkis ... [et al.]. Fission and quasifission in the reactions [symbol]Ca+[symbol]Pb and [symbol]Ni+[symbol]W / G. N. Knyazheva ... [et al.]. Mass-energy characteristics of reactions [symbol]Fe+[symbol][symbol][symbol]266Hs and [symbol]Mg+[symbol]Cm[symbol][symbol]Hs at Coulomb barrier / L. Krupa ... [et al.]. Fusion of heavy ions at extreme sub-barrier energies / Ş. Mişicu and H. Esbensen. Fusion and fission dynamics of heavy nuclear system / V. Zagrebaev and W. Greiner. Time-dependent potential energy for fusion and fission processes / A. V. Karpov ... [et al.] -- Superheavy elements. Advances in the understanding of structure and production mechanisms for superheavy elements / W. Greiner and V. Zagrebaev. Fission barriers of heaviest nuclei / A. Sobiczewski ... [et al.]. Possibility of synthesizing doubly magic superheavy nuclei / Y Aritomo ... [et al.]. Synthesis of superheavy nuclei in [symbol]Ca-induced reactions / V. K. Utyonkov ... [et al.] -- Fragmentation. Production of neutron-rich nuclei in the nucleus-nucleus collisions around the Fermi energy / M. Veselský. Signals of enlarged core in [symbol]Al / Y. G. Ma ... [et al.] -- Exotic modes. New insight into the fission process from experiments with relativistic heavy-ion beams / K.-H. Schmidt ... [et al.]. New results for the intensity of bimodal fission in binary and ternary spontaneous fission of [symbol]Cf / C. Goodin ... [et al.]. Rare fission modes: study of multi-cluster decays of actinide nuclei / D. V. Kamanin ... [et al.]. Energy distribution of ternary [symbol]-particles in [symbol]Cf(sf) / M. Mutterer ... [et al.]. Preliminary results of experiment aimed at searching for collinear cluster tripartition of

  8. Nuclear Power from Fission Reactors. An Introduction.

    ERIC Educational Resources Information Center

    Department of Energy, Washington, DC. Technical Information Center.

    The purpose of this booklet is to provide a basic understanding of nuclear fission energy and different fission reaction concepts. Topics discussed are: energy use and production, current uses of fuels, oil and gas consumption, alternative energy sources, fossil fuel plants, nuclear plants, boiling water and pressurized water reactors, the light…

  9. Effects of nuclear orientation on fusion and fission process for reactions using actinide target nuclei

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Makii, H.; Nagame, Y.; Watanabe, Y.; Ohtsuki, T.; Hirose, K.; Hofmann, S.

    2010-04-30

    Fission fragment mass distributions in the reaction of {sup 30}Si+{sup 238}U were measured at the energies around the Coulomb barrier. At the above-barrier energies, the mass distribution showed Gaussian shape. At the sub-barrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at A{sub L}/A{sub H}approx =90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections produced by {sup 30}Si+{sup 238}U. The cross-section for {sup 263}Sg at the above-barrier energy agree with the statistical model calculation which assumes that the measured fission cross-sections are equal to the fusion cross-sections, whereas the one for {sup 264}Sg measured at the sub-barrier energy is smaller than the calculation, indicating the presence for quasifission. We also report the results on the fragment mass distributions for {sup 36,34}S+{sup 238}U and {sup 40}Ar+{sup 238}U.

  10. Benchmarking nuclear fission theory

    SciTech Connect

    Bertsch, G. F.; Loveland, W.; Nazarewicz, W.; Talou, P.

    2015-05-14

    We suggest a small set of fission observables to be used as test cases for validation of theoretical calculations. Thus, the purpose is to provide common data to facilitate the comparison of different fission theories and models. The proposed observables are chosen from fission barriers, spontaneous fission lifetimes, fission yield characteristics, and fission isomer excitation energies.

  11. The CCONE Code System and its Application to Nuclear Data Evaluation for Fission and Other Reactions

    SciTech Connect

    Iwamoto, O. Iwamoto, N.; Kunieda, S.; Minato, F.; Shibata, K.

    2016-01-15

    A computer code system, CCONE, was developed for nuclear data evaluation within the JENDL project. The CCONE code system integrates various nuclear reaction models needed to describe nucleon, light charged nuclei up to alpha-particle and photon induced reactions. The code is written in the C++ programming language using an object-oriented technology. At first, it was applied to neutron-induced reaction data on actinides, which were compiled into JENDL Actinide File 2008 and JENDL-4.0. It has been extensively used in various nuclear data evaluations for both actinide and non-actinide nuclei. The CCONE code has been upgraded to nuclear data evaluation at higher incident energies for neutron-, proton-, and photon-induced reactions. It was also used for estimating β-delayed neutron emission. This paper describes the CCONE code system indicating the concept and design of coding and inputs. Details of the formulation for modelings of the direct, pre-equilibrium and compound reactions are presented. Applications to the nuclear data evaluations such as neutron-induced reactions on actinides and medium-heavy nuclei, high-energy nucleon-induced reactions, photonuclear reaction and β-delayed neutron emission are mentioned.

  12. The CCONE Code System and its Application to Nuclear Data Evaluation for Fission and Other Reactions

    NASA Astrophysics Data System (ADS)

    Iwamoto, O.; Iwamoto, N.; Kunieda, S.; Minato, F.; Shibata, K.

    2016-01-01

    A computer code system, CCONE, was developed for nuclear data evaluation within the JENDL project. The CCONE code system integrates various nuclear reaction models needed to describe nucleon, light charged nuclei up to alpha-particle and photon induced reactions. The code is written in the C++ programming language using an object-oriented technology. At first, it was applied to neutron-induced reaction data on actinides, which were compiled into JENDL Actinide File 2008 and JENDL-4.0. It has been extensively used in various nuclear data evaluations for both actinide and non-actinide nuclei. The CCONE code has been upgraded to nuclear data evaluation at higher incident energies for neutron-, proton-, and photon-induced reactions. It was also used for estimating β-delayed neutron emission. This paper describes the CCONE code system indicating the concept and design of coding and inputs. Details of the formulation for modelings of the direct, pre-equilibrium and compound reactions are presented. Applications to the nuclear data evaluations such as neutron-induced reactions on actinides and medium-heavy nuclei, high-energy nucleon-induced reactions, photonuclear reaction and β-delayed neutron emission are mentioned.

  13. Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions

    NASA Astrophysics Data System (ADS)

    Hagen, T. W.; Görgen, A.; Korten, W.; Grente, L.; Salsac, M.-D.; Farget, F.; Ragnarsson, I.; Braunroth, T.; Bruyneel, B.; Celikovic, I.; Clément, E.; de France, G.; Delaune, O.; Dewald, A.; Dijon, A.; Hackstein, M.; Jacquot, B.; Litzinger, J.; Ljungvall, J.; Louchart, C.; Michelagnoli, C.; Napoli, D. R.; Recchia, F.; Rother, W.; Sahin, E.; Siem, S.; Sulignano, B.; Theisen, Ch.; Valiente-Dobon, J. J.

    2017-03-01

    Lifetimes of excited states in 99Y,101Y,101Nb,103Nb, and 105Nb were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a 238U beam and a 9Be target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B (M 1 ) and B (E 2 ) values for the strongly coupled rotational bands built on the [422 ] 5 /2+ ground state in the Y and Nb nuclei with neutron number N ≥60 . The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.

  14. Fifty years with nuclear fission. Volume 1

    SciTech Connect

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

    1989-12-31

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

  15. Nuclear Fission Research at IRMM

    SciTech Connect

    Hambsch, Franz-Josef

    2005-05-24

    The Institute for Reference Materials and Measurements (IRMM) will celebrate its 45th anniversary in 2005. With its 150-MeV Geel Electron Linear Accelerator (GELINA) and 7-MV Van de Graaff accelerator as multi-purpose neutron sources, it served the nuclear physics community for this period.The research in the field of nuclear fission was focused in recent years on both the measurement and calculation of fission cross sections, and the measurement of fission fragment properties.Fission cross sections were determined for 233Pa and 234U; the fission process was studied in the resolved resonance region of 239Pu(n,f) and for 251Cf(nth,f). These measurements derive their interest from accelerator driven systems, the thorium fuel cycle, high temperature reactors, safety issues of current reactors, and basic physics. The measurements are supported by several modeling efforts that aim at improving model codes and nuclear data evaluation.

  16. Spallation-induced fission reactions

    NASA Astrophysics Data System (ADS)

    Benlliure, J.; Rodríguez-Sánchez, J. L.

    2017-03-01

    During the last decade spallation-induced fission reactions have received particular attention because of their impact in the design of spallation-neutron sources or radioactive beam facilities, but also in the understanding of the fission process at high excitation energy. In this paper, we review the main progress brought by modern experimental techniques, in particular those based in the inverse kinematic, as well as the achievements in modelling these reactions. We will also address future possibilities for improving the investigation of fission dynamics.

  17. Fifty years with nuclear fission

    SciTech Connect

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

    1989-01-01

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

  18. Low-energy fission investigated in reactions of 750 AMeV238U-ions with Pb and Be targets. I. Nuclear charge distributions

    NASA Astrophysics Data System (ADS)

    Armbruster, P.; Bernas, M.; Czajkowski, S.; Geissel, H.; Aumann, T.; Dessagne, Ph.; Donzaud, C.; Hanelt, E.; Heinz, A.; Hesse, M.; Kozhuharov, C.; Miehe, Ch.; Münzenberg, G.; Pfützner, M.; Schmidt, K.-H.; Schwab, W.; Stéphan, C.; Sümmerer, K.; Tassan-Got, L.; Voss, B.

    1996-12-01

    Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile238U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the238U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magnetic field for the U/Pb-system, or by peripheral nuclear interactions for the U/Be-system.

  19. Effects of nuclear orientation on fusion and fission process for reactions using {sup 238}U target nucleus

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Makii, H.; Nagame, Y.; Watanabe, Y.; Ohtsuki, T.; Hirose, K.; Hofmann, S.

    2010-06-01

    Fission fragment mass distributions in the reaction of {sup 30}Si+{sup 238}U were measured at the energies around the Coulomb barrier. At the above-barrier energies, the mass distribution showed Gaussian shape. At the sub-barrier energies, asymmetric fission mode peaked at A{sub L}/A{sub H}approx =90/178 was observed. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections produced by {sup 30}Si+{sup 238}U. The cross-section for {sup 263}Sg at the above-barrier energy agree with the statistical model calculation which assumes that the measured fission cross-sections are equal to the fusion cross-sections, whereas the one for {sup 264}Sg measured at the sub-barrier energy is smaller than the calculation, indicating the presence for quasifission. The fragment mass distributions are compared to those for {sup 36}S+{sup 238}U and {sup 40}Ar+{sup 238}U.

  20. Experiments on nuclear fission induced by radioactive beams

    SciTech Connect

    Skobelev, N.K.

    1994-07-01

    The cross sections of {sup 209}Bi nuclear fission induced by secondary beams of {sup 6}He and {sup 4}He are measured under identical conditions. The experimental data are in good agreement with earlier results on the fission cross section of the {sup 4}He + {sup 209}Bi reaction. The measured values of the cross section of {sup 209}Bi fission induced by {sup 6}He ions are much higher than the cross sections of fission induced by {alpha}-particles. It is found that the fission threshold for the {sup 6}He + {sup 209}Bi reaction is shifted as compared to that of the {sup 4}He + {sup 209}Bi reaction. Various factors that can be responsible for the observed peculiarities in the {sup 209}Bi fission induced by the {sup 6}He ions are analyzed. 25 refs., 5 figs.

  1. Role of nuclear dissipation and entrance channel mass asymmetry in pre-scission neutron multiplicity enhancement in fusion-fission reactions

    SciTech Connect

    Singh, Hardev; Sandal, Rohit; Behera, Bivash R.; Singh, Gulzar; Govil, I. M.; Golda, K. S.; Ranjeet,; Jhingan, Akhil; Singh, R. P.; Sugathan, P.; Chatterjee, M. B.; Datta, S. K.; Pal, Santanu; Viesti, G.

    2008-08-15

    Pre-scission neutron multiplicities are measured for {sup 12}C + {sup 204}Pb and {sup 19}F + {sup 197}Au reactions at laboratory energies of 75-95 MeV for the {sup 12}C beam and 98-118 MeV for the {sup 19}F beam. The chosen projectile-target combinations in the present study lie on either side of the Businaro-Gallone mass asymmetry ({alpha}{sub BG}) and populate the {sup 216}Ra compound nucleus. The dissipation strength is deduced after comparing the experimentally measured neutron yield with the statistical model predictions which contains the nuclear viscosity as a free parameter. Present results demonstrate the combined effects of entrance channel mass asymmetry and the dissipative property of nuclear matter on the pre-scission neutron multiplicity in fusion-fission reactions.

  2. Nuclear fission of Fm isotopes

    SciTech Connect

    Asano, T.; Wada, T.; Ohta, M.; Chiba, S.

    2010-06-01

    Multi-modal fission has been systematically investigated for the series of isotopes of Fm and Cf. The multi-dimensional Langevin-type stochastic differential equation is used for the dynamical calculation. The primary fission mode changes from mass-asymmetric fission to mass-symmetric fission with the increase of neutron numbers for both Fm and Cf cases.

  3. Effects of deformations and orientations in the fission of the actinide nuclear system 254Fm* formed in the 11B + 243Am reaction

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Sharma, Manoj K.; Gupta, Raj K.

    2012-12-01

    We have studied the decay of actinide nuclear system 254Fm* formed in 11B + 243Am reaction using the dynamical cluster decay model (DCM), with choices of spherical, quadrupole deformation β2 alone and higher multipole deformations β2-β4. For β2 deformations, the optimum orientations θiopt are used whereas for higher multipole deformations the compact orientations θic of decaying fragments are taken in to account. Besides static-β2 deformations, the effects of dynamical-β2 deformations are also explored. The calculated cross sections find excellent agreement with the available experimental data with spherical as well as deformed choices of fragmentations, enabling us to account for the role of important nuclear deformation effects in the 11B-induced nuclear reaction. Spontaneous decay of 254Fm with cold elongated configuration and optimum orientation is also worked out. The mass distributions of excited fermium isotopes in the neighborhood of 254Fm* are also explored. In addition, the roles of temperature, angular momentum, and fission fragment anisotropies are investigated in the context of the chosen reaction.

  4. Nuclear fission and the transuranium elements

    SciTech Connect

    Seaborg, G.T.

    1989-02-01

    Many of the transuranium elements are produced and isolated in large quantities through the use of neutrons furnished by nuclear fission reactions: plutonium (atomic number 94) in ton quantities; neptunium (93), americium (95), and curium (96) in kilogram quantities; berkelium (97) in 100 milligram quantities; californium (98) in gram quantities; and einsteinium (99) in milligram quantities. Transuranium isotopes have found many practical applications---as nuclear fuel for the large-scale generation of electricity, as compact, long-lived power sources for use in space exploration, as means for diagnosis and treatment in the medical area, and as tools in numerous industrial processes. Of particular interest is the unusual chemistry and impact of these heaviest elements on the periodic table. This account will feature these aspects. 9 refs., 5 figs.

  5. Fifty years with nuclear fission. Volume 2

    SciTech Connect

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

    1989-12-31

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

  6. Nuclear membrane: nuclear envelope PORosity in fission yeast meiosis.

    PubMed

    Sazer, Shelley

    2010-11-09

    The fission yeast Schizosaccharomyces pombe undergoes closed mitosis but 'virtual nuclear envelope breakdown' at anaphase of meiosis II, in which the nuclear envelope is structurally closed but functionally open.

  7. Fission Reaction Event Yield Algorithm, FREYA - For event-by-event simulation of fission

    NASA Astrophysics Data System (ADS)

    Verbeke, J. M.; Randrup, J.; Vogt, R.

    2015-06-01

    From nuclear materials accountability to detection of special nuclear material, SNM, the need for better modeling of fission has grown over the past decades. Current radiation transport codes compute average quantities with great accuracy and performance, but performance and averaging come at the price of limited interaction-by-interaction modeling. For fission applications, these codes often lack the capability of modeling interactions exactly: energy is not conserved, energies of emitted particles are uncorrelated, prompt fission neutron and photon multiplicities are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g. the neutron multiplicity) and correlations between neutrons and photons. The new computational model, FREYA (Fission Reaction Event Yield Algorithm), aims to meet this need by modeling complete fission events. Thus it automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum. FREYA has been integrated into the LLNL Fission Library, and will soon be part of MCNPX2.7.0, MCNP6, TRIPOLI-4.9, and Geant4.10.

  8. Fifty years of nuclear fission: Nuclear data and measurements series

    SciTech Connect

    Lynn, J.E.

    1989-06-01

    This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.

  9. Microscopic description of complex nuclear decay: Multimodal fission

    NASA Astrophysics Data System (ADS)

    Staszczak, A.; Baran, A.; Dobaczewski, J.; Nazarewicz, W.

    2009-07-01

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  10. Microscopic description of complex nuclear decay: Multimodal fission

    SciTech Connect

    Staszczak, A.; Baran, A.; Dobaczewski, J.; Nazarewicz, W.

    2009-07-15

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  11. Accurate Fission Data for Nuclear Safety

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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 Jyväskylä. 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 is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexible design. For studies of exotic nuclei far from stability a high neutron flux (1012 neutrons/s) at energies 1 - 30 MeV is desired while for reactor applications neutron spectra that resembles those of thermal and fast nuclear reactors are preferred. It is also desirable to be able to produce (semi-)monoenergetic neutrons for benchmarking and to study the energy dependence of fission yields. The scientific program is extensive and is planed to start in 2013 with a measurement of isomeric yield ratios of proton induced fission in uranium. This will be followed by studies of independent yields of thermal and fast neutron induced fission of various actinides.

  12. Indirect Methods for Nuclear Reaction Data

    SciTech Connect

    Escher, J E; Dietrich, F S

    2005-11-18

    Several indirect approaches for obtaining reaction cross sections are briefly reviewed. The Surrogate Nuclear Reactions method, which aims at determining cross sections for compound-nuclear reactions, is discussed in some detail. The validity of the Weisskopf-Ewing approximation in the Surrogate approach is studied for the example of neutron-induced fission of an actinide nucleus.

  13. Optimally moderated nuclear fission reactor and fuel source therefor

    DOEpatents

    Ougouag, Abderrafi M.; Terry, William K.; Gougar, Hans D.

    2008-07-22

    An improved nuclear fission reactor of the continuous fueling type involves determining an asymptotic equilibrium state for the nuclear fission reactor and providing the reactor with a moderator-to-fuel ratio that is optimally moderated for the asymptotic equilibrium state of the nuclear fission reactor; the fuel-to-moderator ratio allowing the nuclear fission reactor to be substantially continuously operated in an optimally moderated state.

  14. Complete event simulations of nuclear fission

    NASA Astrophysics Data System (ADS)

    Vogt, Ramona

    2015-10-01

    For many years, the state of the art for treating fission in radiation transport codes has involved sampling from average distributions. In these average fission models energy is not explicitly conserved and everything is uncorrelated because all particles are emitted independently. However, in a true fission event, the energies, momenta and multiplicities of the emitted particles are correlated. Such correlations are interesting for many modern applications. Event-by-event generation of complete fission events makes it possible to retain the kinematic information for all particles emitted: the fission products as well as prompt neutrons and photons. It is therefore possible to extract any desired correlation observables. Complete event simulations can be included in general Monte Carlo transport codes. We describe the general functionality of currently available fission event generators and compare results for several important observables. This work was performed under the auspices of the US DOE by LLNL, Contract DE-AC52-07NA27344. We acknowledge support of the Office of Defense Nuclear Nonproliferation Research and Development in DOE/NNSA.

  15. Nuclear organisation and RNAi in fission yeast.

    PubMed

    Woolcock, Katrina J; Bühler, Marc

    2013-06-01

    Over the last decade, the fission yeast Schizosaccharomyces pombe has been used extensively for investigating RNA interference (RNAi)-mediated heterochromatin assembly. However, only recently have studies begun to shed light on the 3D organisation of chromatin and the RNAi machinery in the fission yeast nucleus. These studies indicate association of repressive and active chromatin with different regions of the nuclear periphery, similar to other model organisms, and clustering of functionally related genomic features. Unexpectedly, RNAi factors were shown to associate with nuclear pores and were implicated in the regulation of genomic features outside of the well-studied heterochromatic regions. Nuclear organisation is likely to contribute to substrate specificity of the RNAi pathway. However, further studies are required to elucidate the exact mechanisms and functional importance of this nuclear organisation.

  16. Nuclear size control in fission yeast.

    PubMed

    Neumann, Frank R; Nurse, Paul

    2007-11-19

    A long-standing biological question is how a eukaryotic cell controls the size of its nucleus. We report here that in fission yeast, nuclear size is proportional to cell size over a 35-fold range, and use mutants to show that a 16-fold change in nuclear DNA content does not influence the relative size of the nucleus. Multi-nucleated cells with unevenly distributed nuclei reveal that nuclei surrounded by a greater volume of cytoplasm grow more rapidly. During interphase of the cell cycle nuclear growth is proportional to cell growth, and during mitosis there is a rapid expansion of the nuclear envelope. When the nuclear/cell (N/C) volume ratio is increased by centrifugation or genetic manipulation, nuclear growth is arrested while the cell continues to grow; in contrast, low N/C ratios are rapidly corrected by nuclear growth. We propose that there is a general cellular control linking nuclear growth to cell size.

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Microscopic theory of nuclear fission: a review

    NASA Astrophysics Data System (ADS)

    Schunck, N.; Robledo, L. M.

    2016-11-01

    This article reviews how nuclear fission is described within nuclear density functional theory. A distinction should be made between spontaneous fission, where half-lives are the main observables and quantum tunnelling the essential concept, and induced fission, where the focus is on fragment properties and explicitly time-dependent approaches are often invoked. Overall, the cornerstone of the density functional theory approach to fission is the energy density functional formalism. The basic tenets of this method, including some well-known tools such as the Hartree-Fock-Bogoliubov (HFB) theory, effective two-body nuclear potentials such as the Skyrme and Gogny force, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The energy density functional 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 Schrödinger equation into a collective Schrödinger-like equation for the nuclear wave-packet. The region of the collective space where the system transitions from one nucleus to two (or more) fragments defines what are called the scission configurations. The inertia tensor that enters the kinetic energy term of the collective Schrödinger-like equation is one of the most essential ingredients of the theory, since it includes the response of the system to small changes in the collective variables. For this reason, the two main approximations used to compute this inertia tensor, the adiabatic time-dependent HFB and the generator coordinate method, are presented in detail, both in their general formulation and in their most common approximations. The collective inertia tensor enters also the Wentzel-Kramers-Brillouin (WKB) formula used to extract

  19. Microscopic Theory of Nuclear Fission: A Review

    DOE PAGES

    Schunck, N.; Robledo, L. M.

    2016-10-11

    This paper reviews how nuclear fission is described within nuclear density functional theory. A distinction should be made between spontaneous fission, where half-lives are the main observables and quantum tunnelling the essential concept, and induced fission, where the focus is on fragment properties and explicitly time-dependent approaches are often invoked. Overall, the cornerstone of the density functional theory approach to fission is the energy density functional formalism. The basic tenets of this method, including some well-known tools such as the Hartree–Fock–Bogoliubov (HFB) theory, effective two-body nuclear potentials such as the Skyrme and Gogny force, finite-temperature extensions and beyond mean-field corrections,more » are presented succinctly. The energy density functional 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 Schrödinger equation into a collective Schrödinger-like equation for the nuclear wave-packet. The region of the collective space where the system transitions from one nucleus to two (or more) fragments defines what are called the scission configurations. The inertia tensor that enters the kinetic energy term of the collective Schrödinger-like equation is one of the most essential ingredients of the theory, since it includes the response of the system to small changes in the collective variables. For this reason, the two main approximations used to compute this inertia tensor, the adiabatic time-dependent HFB and the generator coordinate method, are presented in detail, both in their general formulation and in their most common approximations. The collective inertia tensor enters also the Wentzel–Kramers–Brillouin (WKB) formula

  20. Microscopic Theory of Nuclear Fission: A Review

    SciTech Connect

    Schunck, N.; Robledo, L. M.

    2016-10-11

    This paper reviews how nuclear fission is described within nuclear density functional theory. A distinction should be made between spontaneous fission, where half-lives are the main observables and quantum tunnelling the essential concept, and induced fission, where the focus is on fragment properties and explicitly time-dependent approaches are often invoked. Overall, the cornerstone of the density functional theory approach to fission is the energy density functional formalism. The basic tenets of this method, including some well-known tools such as the Hartree–Fock–Bogoliubov (HFB) theory, effective two-body nuclear potentials such as the Skyrme and Gogny force, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The energy density functional 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 Schrödinger equation into a collective Schrödinger-like equation for the nuclear wave-packet. The region of the collective space where the system transitions from one nucleus to two (or more) fragments defines what are called the scission configurations. The inertia tensor that enters the kinetic energy term of the collective Schrödinger-like equation is one of the most essential ingredients of the theory, since it includes the response of the system to small changes in the collective variables. For this reason, the two main approximations used to compute this inertia tensor, the adiabatic time-dependent HFB and the generator coordinate method, are presented in detail, both in their general formulation and in their most common approximations. The collective inertia tensor enters also the Wentzel–Kramers–Brillouin (WKB) formula used to

  1. Microscopic theory of nuclear fission: a review.

    PubMed

    Schunck, N; Robledo, L M

    2016-11-01

    This article reviews how nuclear fission is described within nuclear density functional theory. A distinction should be made between spontaneous fission, where half-lives are the main observables and quantum tunnelling the essential concept, and induced fission, where the focus is on fragment properties and explicitly time-dependent approaches are often invoked. Overall, the cornerstone of the density functional theory approach to fission is the energy density functional formalism. The basic tenets of this method, including some well-known tools such as the Hartree-Fock-Bogoliubov (HFB) theory, effective two-body nuclear potentials such as the Skyrme and Gogny force, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The energy density functional 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 Schrödinger equation into a collective Schrödinger-like equation for the nuclear wave-packet. The region of the collective space where the system transitions from one nucleus to two (or more) fragments defines what are called the scission configurations. The inertia tensor that enters the kinetic energy term of the collective Schrödinger-like equation is one of the most essential ingredients of the theory, since it includes the response of the system to small changes in the collective variables. For this reason, the two main approximations used to compute this inertia tensor, the adiabatic time-dependent HFB and the generator coordinate method, are presented in detail, both in their general formulation and in their most common approximations. The collective inertia tensor enters also the Wentzel-Kramers-Brillouin (WKB) formula used to extract

  2. Fission fragment mass distributions in reactions forming the {sup 213}Fr compound nucleus

    SciTech Connect

    Appannababu, S.; Mukherjee, S.; Deshmukh, N. N.; Rath, P. K.; Singh, N. L.; Nayak, B. K.; Thomas, R. G.; Choudhury, R. K.; Sugathan, P.; Jhingan, A.; Negi, D.; Prasad, E.

    2011-03-15

    The fission fragment mass angle correlations and mass ratio distributions have been investigated for the two systems {sup 16}O+{sup 197}Au and {sup 27}Al+{sup 186}W, leading to the same compound nucleus {sup 213}Fr around the Coulomb barrier energies. Systematic analysis of the variance of the mass distributions as a function of temperature and angular momentum suggests true compound nuclear fission for both the reactions, indicating the absence of nonequilibrium fission processes.

  3. Mass-asymmetric fission in the 40ca+142Nd reaction

    NASA Astrophysics Data System (ADS)

    Prasad, E.; Hinde, D. J.; Williams, E.; Dasgupta, M.; Carter, I. P.; Cook, K. J.; Jeung, D. Y.; Luong, D. H.; McNeil, S.; Palshetkar, C. S.; Rafferty, D. C.; Simenel, C.; Wakhle, A.; Ramachandran, K.; Khuyagbaatar, J.; Dullmann, Ch. E.; Lommel, B.; Kindler, B.

    2016-09-01

    Shell effects play a major role in fission. Mass-asymmetric fission observed in the spontaneous and low energy fission of actinide nuclei was explained by incorporating the fragment shell properties in liquid drop model. Asymmetric fission has also been observed in the low energy fission of neutron-deficient 180Hg nuclei in recent β-delayed fission experiments. This low-energy β-delayed fission has been explained in terms of strong shell effects in pre-scission configurations associated with the system after capture. Calculations predicted asymmetric fission for heavier Hg isotopes as well, at compound nuclear excitation energy as high as 40 MeV. To explore the evolution of fission fragment mass distribution as a function of neutron and proton numbers and also with excitation energy, fission fragment mass distributions have been measured for the 40Ca+142Nd reaction forming the compound nucleus 182Hg at energies around the capture barrier, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Mass-asymmetric fission is observed in this reaction at an excitation energy of 33.6 MeV. The results are consistent with the β-delayed fission measurements and indicate the presence of shell effects even at higher exciation energies.

  4. Lasers from fission. [nuclear pumping feasibility experiments

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.; Thom, K.; Helmick, H. H.

    1975-01-01

    The feasibility of the nuclear pumping of lasers was demonstrated in three experiments conducted independently at three different laboratories. In this context nuclear pumping of lasers is understood to be the excitation of a laser by the kinetic energy of the fission fragments only. A description is given of research concerned with the use of nuclear energy for the excitation of gas lasers. Experimental work was supplemented by theoretical research. Attention is given to a nuclear pumped He-Xe laser, a nuclear pumped CO laser, and a neon-nitrogen laser pumped by alpha particles. Studies involving uranium hexafluoride admixture to laser media are discussed along with research on uranium hexafluoride-fueled reactors.

  5. The Dispute over Nuclear Fission.

    ERIC Educational Resources Information Center

    Sime, Ruth Lewin

    1996-01-01

    Reveals the stormy relationship and ongoing controversy surrounding the scientific collaboration of Otto Hahn and Lise Meitner. Discusses the controversial 1944 Nobel Prize award to Hahn (ignoring the equal contribution of Meitner), the reaction of the scientific community, and the post-war years of both Meitner and Hahn. (MJP)

  6. Nuclear Fission and Fission{minus}Product Spectroscopy: Second International Workshop. Proceedings

    SciTech Connect

    Fioni, G.; Faust, H.; Oberstedt, S.; Hambsch, F.

    1998-10-01

    These proceedings represent papers presented at the Second International Workshop on Nuclear Fission and Fission{minus}Product Spectroscopy held in Seyssins, France in April, 1998. The objective was to bring together the specialists in the field to overview the situation and to assess our present understanding of the fission process. The topics presented at the conference included nuclear waste management, incineration, neutron driven transmutation, leakage etc., radioactive beams, neutron{minus}rich nuclei, neutron{minus}induced and spontaneous fission, ternary fission phenomena, angular momentum, parity and time{minus}reversal phenomena, and nuclear fission at higher excitation energy. Modern spectroscopic tools for gamma spectroscopy as applied to fission were also discussed. There were 53 papers presented at the conference,out of which 3 have been abstracted for the Energy,Science and Technology database.(AIP)

  7. The Future of Energy from Nuclear Fission

    SciTech Connect

    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

  8. Description of induced nuclear fission with Skyrme energy functionals: Static potential energy surfaces and fission fragment properties

    NASA Astrophysics Data System (ADS)

    Schunck, N.; Duke, D.; Carr, H.; Knoll, A.

    2014-11-01

    Eighty years after its experimental discovery, a description of induced nuclear fission based solely on the interactions between neutrons and protons and quantum many-body methods still poses formidable challenges. The goal of this paper is to contribute to the development of a predictive microscopic framework for the accurate calculation of static properties of fission fragments for hot fission and thermal or slow neutrons. To this end, we focus on the 239Pu(n ,f ) reaction and employ nuclear density functional theory with Skyrme energy densities. Potential energy surfaces are computed at the Hartree-Fock-Bogoliubov approximation with up to five collective variables. We find that the triaxial degree of freedom plays an important role, both near the fission barrier and at scission. The impact of the parametrization of the Skyrme energy density and the role of pairing correlations on deformation properties from the ground state up to scission are also quantified. We introduce a general template for the quantitative description of fission fragment properties. It is based on the careful analysis of scission configurations, using both advanced topological methods and recently proposed quantum many-body techniques. We conclude that an accurate prediction of fission fragment properties at low incident neutron energies, although technologically demanding, should be within the reach of current nuclear density functional theory.

  9. Fission-fragment nuclear lasing of Ar/He/-Xe

    NASA Technical Reports Server (NTRS)

    De Young, R. J.; Shiu, Y. J.; Williams, M. D.

    1980-01-01

    Nuclear-pumped lasing of Ar-Xe and He-Xe has been demonstrated using (U-235)F6 fission-fragment excitation. Fission fragments were created by absorption of thermal neutrons in a combination of gaseous (U-235)F6 and laser-tube wall coatings formed from UF6 chemical reaction products. At a pressure of 600 torr Ar-(3%)Xe, lasing occurred at 2.65 microns in Xe. Up to 3 torr of gaseous (U-235)F6 was added to 600 torr Ar-Xe before serious laser quenching occurred. With 3 torr of (U-235)F6 added, 38% of the energy deposition came from gaseous UF6 and the remainder from the uranium wall coating. The neutron flux at lasing threshold was found to be 4 x 10 to the 15th n/sq cm sec.

  10. Multimodal Fission in Heavy-Ion Induced Reactions

    SciTech Connect

    Pokrovskiy, I. V.; Bogachev, A. A.; Iitkis, M. G.; Iitkis, J. M.; Kondratiev, N. A.; Kozulin, E. M.; Dorvaux, O.; Rowley, N.; Schmitt, Ch.; Stuttge, L.

    2006-08-14

    Mass, energy and folding angle distributions of the fission fragments as well as multiplicities of neutron and gamma-quanta emissions accompanying the fission process were measured for fission of 226Th, 227Pa and 234Pu compound nuclei produced in reactions with 18O and 26Mg projectiles over a wide energy range. Data were analyzed with respect to the presence of fission modes. Asymmetric fission was observed even at very high initial excitation for all the measured systems. The so-called fission mode S1 (caused by the proton shell Z{approx}50 and neutron shell N{approx}82 in heavy fragment) was found to be dominant in asymmetric fission of 234Pu. Reactions with not full linear momentum transfer were observed in the folding spectra for all the measured systems.

  11. Possible Angular Momentum Dependence of Dissipation in Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Toke, Jan; Udo Schroeder, W.

    2008-04-01

    A comparative analysis of the pre-scission neutron multiplicities observed in a new experiment [1] and one reported earlier [2] suggests that, besides known deformation [3] and temperature [4] dependencies, nuclear dissipation in fission may have an angular momentum dependence. The analysis based on a Langevin equation coupled with a statistical decay model [3] considers angular momentum effects on fission dynamics. Pre-saddle reduced dissipation coefficients of β = 2 x10^21s-1 and 3 x10^21s-1 have been extracted for the matched reactions ^16O + ^181Ta and ^19F + ^178Hf [1],respectively. The difference in the extracted β values is attributed to the difference in the angular momenta contributing to the fission process in the two reactions. Work attempting to derive a quantitative expression for an angular momentum dependence of the dissipation strength is in progress. [1] H.Singh et al., Phys. Rev. C76 (2007) 044610 [2] L.G.Moretto et al., Phys. Rev. Lett. 75 (1995) 4186; Phys. Rev. C54 (1996) 3062 [3] P.Frobrich and I.I.Gontchar, Phys. Rep. 292(1998) 131 [4] P.Paul and M.Thoennessen, Ann. Rev. Part. Sci. 44(1994) 65

  12. Biological removal of cationic fission products from nuclear wastewater.

    PubMed

    Ngwenya, N; Chirwa, E M N

    2011-01-01

    Nuclear energy is becoming a preferred energy source amidst rising concerns over the impacts of fossil fuel based energy on global warming and climate change. However, the radioactive waste generated during nuclear power generation contains harmful long-lived fission products such as strontium (Sr). In this study, cationic strontium uptake from solution by microbial cultures obtained from mine wastewater is evaluated. A high strontium removal capacity (q(max)) with maximum loading of 444 mg/g biomass was achieved by a mixed sulphate reducing bacteria (SRB) culture. Sr removal in SRB was facilitated by cell surface based electrostatic interactions with the formation of weak ionic bonds, as 68% of the adsorbed Sr(2+) was easily desorbed from the biomass in an ion exchange reaction with MgCl₂. To a lesser extent, precipitation reactions were also found to account for the removal of Sr from aqueous solution as about 3% of the sorbed Sr was precipitated due to the presence of chemical ligands while the remainder occurred as an immobile fraction. Further analysis of the Sr-loaded SRB biomass by scanning electron microscopy (SEM) coupled to energy dispersive X-ray (EDX) confirmed extracellular Sr(2+) precipitation as a result of chemical interaction. In summary, the obtained results demonstrate the prospects of using biological technologies for the remediation of industrial wastewaters contaminated by fission products.

  13. Mini-fission fusion explosive devices (mini-nukes) for nuclear pulse propulsion

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2005-11-01

    Nuclear pulse propulsion demands low-yield nuclear explosive devices. Because the critical mass of a fission explosive is rather large, this leads to extravagant fission devices with a very low fuel burn-up. For non-fission ignited pure fusion microexplosions the problem is the large ignition apparatus (laser, particle beam, etc.). Fission ignited large fusion explosive devices are for obvious reasons even less desirable. A third category (mini-nukes) are devices where the critical mass of the fission explosive is substantially reduced by its coupling to a DT fusion reaction, with the DT fusion neutrons increasing the fission rate. Whereas in pure fission devices a reduction of the critical mass is achieved by the implosive compression of the fissile core with a chemical high explosive, in the third category the implosion must at the same time heat the DT surrounding the fissile core to a temperature of ⩾107K, at which enough fusion neutrons are generated to increase the fission rate which in turn further increases the temperature and fusion neutron production rate. As has been shown by the author many years ago, such mini-nukes lead to astonishingly small critical masses. In their application to nuclear pulse propulsion the combustion products from the chemical high explosive are further heated by the neutrons and are becoming part of the propellant.

  14. Monitoring system for a liquid-cooled nuclear fission reactor

    DOEpatents

    DeVolpi, Alexander

    1987-01-01

    A monitoring system for detecting changes in the liquid levels in various regions of a water-cooled nuclear power reactor, viz., in the downcomer, in the core, in the inlet and outlet plenums, at the head, and elsewhere; and also for detecting changes in the density of the liquid in these regions. A plurality of gamma radiation detectors are used, arranged vertically along the outside of the reactor vessel, and collimator means for each detector limits the gamma-radiation it receives as emitting from only isolated regions of the vessel. Excess neutrons produced by the fission reaction will be captured by the water coolant, by the steel reactor walls, or by the fuel or control structures in the vessel. Neutron capture by steel generates gamma radiation having an energy level of the order of 5-12 MeV, whereas neutron capture by water provides an energy level of approximately 2.2 MeV, and neutron capture by the fission fuel or its cladding provides an energy level of 1 MeV or less. The intensity of neutron capture thus changes significantly at any water-metal interface. Comparative analysis of adjacent gamma detectors senses changes from the normal condition with liquid coolant present to advise of changes in the presence and/or density of the coolant at these specific regions. The gamma detectors can also sense fission-product gas accumulation at the reactor head to advise of a failure of fuel-pin cladding.

  15. Fission of actinide nuclei using multi-nucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    2014-09-01

    We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

  16. Distribution functions in plasmas generated by a volume source of fission fragments. [in nuclear pumped lasers

    NASA Technical Reports Server (NTRS)

    Deese, J. E.; Hassan, H. A.

    1979-01-01

    The role played by fission fragments and electron distribution functions in nuclear pumped lasers is considered and procedures for their calculations are outlined. The calculations are illustrated for a He-3/Xe mixture where fission is provided by the He-3(n,p)H-3 reaction. Because the dominant ion in the system depends on the Xe fraction, the distribution functions cannot be determined without the simultaneous consideration of a detailed kinetic model. As is the case for wall sources of fission fragments, the resulting plasmas are essentially thermal but the electron distribution functions are non-Maxwellian.

  17. Pairing-induced speedup of nuclear spontaneous fission

    SciTech Connect

    Sadhukhan, Jhilam; Dobaczewski, J.; Nazarewicz, W.; Sheikh, J. A.; Baran, A.

    2014-12-22

    Collective inertia is strongly influenced at the level crossing at which the quantum system changes its microscopic configuration diabatically. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of these configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of 264Fm and 240Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM* and a density-dependent pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of 264Fm, where the effect of triaxiality on the fission barrier is large, the geometry of the fission pathway in the space of the shape degrees of freedom is weakly impacted by pairing. This is not the case for 240Pu, where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. As a result, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.

  18. Pairing-induced speedup of nuclear spontaneous fission

    DOE PAGES

    Sadhukhan, Jhilam; Dobaczewski, J.; Nazarewicz, W.; ...

    2014-12-22

    Collective inertia is strongly influenced at the level crossing at which the quantum system changes its microscopic configuration diabatically. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of these configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of 264Fm and 240Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM* and a density-dependentmore » pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of 264Fm, where the effect of triaxiality on the fission barrier is large, the geometry of the fission pathway in the space of the shape degrees of freedom is weakly impacted by pairing. This is not the case for 240Pu, where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. As a result, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.« less

  19. SOURCE OF PRODUCTS OF NUCLEAR FISSION

    DOEpatents

    Harteck, P.; Dondes, S.

    1960-03-15

    A source of fission product recoil energy suitable for use in radiation chemistry is reported. The source consists of thermal neutron irradiated glass wool having a diameter of 1 to 5 microns and containing an isotope fissionable by thermal neutrons, such as U/sup 235/.

  20. Surrogate Nuclear Reactions using STARS

    SciTech Connect

    Bernstein, L A; Burke, J T; Church, J A; Ahle, L; Cooper, J R; Hoffman, R D; Moody, K; Punyon, J; Schiller, A; Algin, E; Plettner, C; Ai, H; Beausang, C W; Casten, R F; Hughes, R; Ricard-McCutchan, E; Meyer, D; Ressler, J J; Caggiano, J A; Zamfir, N V; Amro, H; Heinz, A; Fallon, P; McMahan, M A; Macchiavelli, A O; Phair, L W

    2004-10-26

    The results from two surrogate reaction experiments using the STARS (Silicon Telescope Array for Reaction Studies) spectrometer are presented. The surrogate method involves measuring the particle and/or {gamma}-ray decay probabilities of excited nuclei populated via a direct reaction. These probabilities can then be used to deduce neutron-induced reaction cross sections that lead to the same compound nuclei. In the first experiment STARS coupled to the GAMMASPHERE {gamma}-ray spectrometer successfully reproduce surrogate (n,{gamma}), (n,n'{gamma}) and (n,2n{gamma}) cross sections on {sup 155,156}Gd using Gd {sup 3}He-induced reactions. In the second series of experiments an energetic deuteron beam from the ESTU tandem at the Wright Nuclear Structure Lab at Yale University was used to obtain the ratio of fission probabilities for {sup 238}U/ {sup 236}U and {sup 237}U/ {sup 239}U populated using the {sup 236,238}U(d,d'f) and {sup 236,238}U(d,pf) reactions. Results from these experiments are presented and the implications for the surrogate reaction technique are discussed.

  1. Description of induced nuclear fission with Skyrme energy functionals. II. Finite temperature effects

    NASA Astrophysics Data System (ADS)

    Schunck, N.; Duke, D.; Carr, H.

    2015-03-01

    Understanding the mechanisms of induced nuclear fission for a broad range of neutron energies could help resolve fundamental science issues, such as the formation of elements in the universe, but could have also a large impact on societal applications in energy production or nuclear waste management. The goal of this paper is to set up the foundations of a microscopic theory to study the static aspects of induced fission as a function of the excitation energy of the incident neutron, from thermal to fast neutrons. To account for the high excitation energy of the compound nucleus, we employ a statistical approach based on finite temperature nuclear density functional theory with Skyrme energy densities, which we benchmark on the 239Pu(n ,f ) reaction. We compute the evolution of the least-energy fission pathway across multidimensional potential energy surfaces with up to five collective variables as a function of the nuclear temperature and predict the evolution of both the inner and the outer fission barriers as a function of the excitation energy of the compound nucleus. We show that the coupling to the continuum induced by the finite temperature is negligible in the range of neutron energies relevant for many applications of neutron-induced fission. We prove that the concept of quantum localization introduced recently can be extended to T >0 , and we apply the method to study the interaction energy and total kinetic energy of fission fragments as a function of the temperature for the most probable fission. While large uncertainties in theoretical modeling remain, we conclude that a finite temperature nuclear density functional may provide a useful framework to obtain accurate predictions of fission fragment properties.

  2. Fission Mode Influence on Prompt Neutrons and γ-rays Emitted in the Reaction 239Pu(nth,f)

    NASA Astrophysics Data System (ADS)

    Serot, O.; Litaize, O.; Regnier, D.

    Recently, a Monte-Carlo code, which simulates the fission fragment de-excitation process, has been developed at CEA- Cadarache. Our aim is to get a tool capable to predict spectra and multiplicities of prompt particles (neutron and gamma) and to investigate possible correlations between fission observables. One of the main challenges is to define properly the share of the available excitation energy at scission between the two nascent fission fragments. Initially, after the full acceleration of the fission fragments, these excitation energies were treated within a Fermi-gas approximation in aT2 (where a and T stand for the level density parameter and the nuclear temperature) and a mass dependent law of the temperature ratio (RT=TL/TH, with TL and TH the temperature of the light and heavy fragment) has been proposed. With this RT-law, the main fission observables of the 252Cf(sf) could be reproduced. Here, in order to take into account the fission modes by which the fissioning nucleus undergoes to fission, we have adopted a specific RT-law for each fission mode. For actinides, the main fission modes are called Standard I, Standard II and Super Long (following Brosa's terminology). This new procedure has been applied in the case of the thermal neutron induced fission of 239Pu, reaction for which fission modes are rather well known.

  3. Generation of Gravitational Waves with Nuclear Reactions

    SciTech Connect

    Fontana, Giorgio; Baker, Robert M. L. Jr.

    2006-01-20

    The problem of efficient generation of High Frequency Gravitational Waves (HFGWs) and pulses of Gravitational Radiation might find a reasonably simple solution by employing nuclear matter, especially isomers. A fissioning isomer not only rotates at extremely high frequency ({approx} 3.03x1024 s-1), but is also highly deformed in the first stages of fission (the nucleus is rotating and made asymmetric 'before' fission). Thus one achieves significant impulsive forces (e.g., 3.67x108 N) acting over extremely short time spans (e.g., 3.3x10-22 s). Alternatively, a pulsed particle beam, which could include antimatter, could trigger nuclear reactions and build up a coherent GW as the particles move through a target mass. The usual difficulty with HFGWs generated by nuclear reactions is the small dimensions of their nuclear-reaction volumes, that is, the small moment of inertia and submicroscopic radii of gyration (e.g., 10-16 m) of the nuclear-mass system. Such a difficulty is overcome by utilizing clusters of nuclear material, whose nuclear reactions are in synchronization (through the use of a computer controlled logic system) and are at a large distance apart, e.g., meters, kilometers, etc. The effective radius of gyration of the overall nuclear mass system is enormous and if the quadrupole formalism holds even approximately, then significant HFGW is generated, for example up to 8.5x1010 W to 1.64x1025 W bursts for the transient asymmetrical spinning nucleus case. In this preliminary analysis, possible conceptual designs of reactors suitable for the generation of HFGWs are discussed as well as applications to space technology. In an optimized dual-beam design, GW amplitudes on the order of A {approx} 0.005 are theoretically achieved in the laboratory, which might have interesting general-relativity and nuclear-physics consequences.

  4. Scaling phenomena of isobaric yields in projectile fragmentation, spallation, and fission reactions

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Huang, Ling; Song, Yi-Dan

    2017-02-01

    Background: The isobaric ratio difference scaling phenomenon, which has been found for the fragments produced in projectile fragmentation reactions, is related to the nuclear density change in reaction systems. Purpose: To verify whether the isobaric ratio difference scaling exists in the fragments produced in the spallation and fission reactions. Methods: The isobaric ratio difference scaling, denoted by SΔ lnR21 , is in theory deduced within the framework of the canonical ensemble theory at the grand-canonical limitation. The fragments measured in a series of projectile fragmentation, spallation, and fission reactions have been analyzed. Results: A good SΔ lnR21 scaling phenomenon is shown for the fragments produced both in the projectile fragmentation reactions and in the spallation reactions, whereas the SΔ lnR21 scaling phenomenon for the fragments in the fission reaction is less obvious. Conclusions: The SΔ lnR21 scaling is used to probe the properties of the equilibrium system at the time of fragment formation. The good scaling of SΔ lnR21 suggests that the equilibrium state can be achieved in the projectile fragmentation and spallation reactions. Whereas in the fission reaction, the result of SΔ lnR21 indicates that the equilibrium of the system is hard to achieve.

  5. Chemistry of fission product iodine under nuclear reactor accident conditions

    SciTech Connect

    Malinauskas, A.P.; Bell, J.T.

    1986-01-01

    The radioisotopes of iodine are generally acknowledged to be the species whose release into the biosphere as a result of a nuclear reactor accident is of the greatest concern. In the course of its release, the fission product is subjected to differing chemical environments; these can alter the physicochemical form of the fission product and thus modify the manner and extent to which release occurs. Both the chemical environments which are characteristic of reactor accidents and their effect in determining physical and chemical form of fission product iodine have been studied extensively, and are reviewed in this report. 76 refs.

  6. Fission Yields and Other Diagnostics for Nuclear Performance

    NASA Astrophysics Data System (ADS)

    Chadwick, M. B.

    2014-06-01

    I summarize advances in our understanding of basic nuclear physics cross sections and decay properties that are needed to characterize the magnitude and energy-dependence of a neutron flux, and to determine the amount of fission burnup in plutonium fuel. The number of fissions that have occurred in a neutron environment can be deduced from measurements of the fission products created, providing that the fission product yields are known accurately. I describe how our understanding of plutonium fission product yields has improved in recent years through a meta-analysis of various measured data, and through identification of fission product yield incident-energy dependencies over the 0.2-2 MeV fast energy region. This led to the resolution of a previous discrepancy between the Los Alamos and Lawrence Livermore National Laboratories in their plutonium yield assessments in the fast energy region, although more experimental work is still needed to resolve discrepancies at 14 MeV. Work is also described that has improved our understanding of (n,2n) cross sections that are used as diagnostics of the high-energy neutron spectrum - both on plutonium and americium, and on the radiochemical detectors yttrium, iridium, and thulium. Finally, some observations are made on the importance of continuing to develop our Evaluated Nuclear Data Files (ENDF) database using physics insights from differential cross section and integral laboratory experiments and from nuclear theory advances.

  7. Fission Yields and Other Diagnostics for Nuclear Performance

    SciTech Connect

    Chadwick, M.B.

    2014-06-15

    I summarize advances in our understanding of basic nuclear physics cross sections and decay properties that are needed to characterize the magnitude and energy-dependence of a neutron flux, and to determine the amount of fission burnup in plutonium fuel. The number of fissions that have occurred in a neutron environment can be deduced from measurements of the fission products created, providing that the fission product yields are known accurately. I describe how our understanding of plutonium fission product yields has improved in recent years through a meta-analysis of various measured data, and through identification of fission product yield incident-energy dependencies over the 0.2-2 MeV fast energy region. This led to the resolution of a previous discrepancy between the Los Alamos and Lawrence Livermore National Laboratories in their plutonium yield assessments in the fast energy region, although more experimental work is still needed to resolve discrepancies at 14 MeV. Work is also described that has improved our understanding of (n,2n) cross sections that are used as diagnostics of the high-energy neutron spectrum – both on plutonium and americium, and on the radiochemical detectors yttrium, iridium, and thulium. Finally, some observations are made on the importance of continuing to develop our Evaluated Nuclear Data Files (ENDF) database using physics insights from differential cross section and integral laboratory experiments and from nuclear theory advances.

  8. Fission of nuclei with Z=102-112 produced in reactions with {sup 22}Ne and {sup 48}Ca ions

    SciTech Connect

    Itkis, M. G.; Oganessian, Yu. Ts.; Kozulin, E. M.; Kondratiev, N. A.; Krupa, L.; Pokrovsky, I. V.; Polyakov, A. N.; Ponomarenko, V. A.; Prokhorova, E. V.; Pustylnik, B. I.; Vakatov, V. I.; Rusanov, A. Ya.

    1998-12-21

    The talk presents new results obtained in the study of fission of superheavy nuclei {sup 256}No, {sup 270}Sg and {sup 286}112 formed in reactions with {sup 22}Ne and {sup 48}Ca ions at energies near or considerably lower than the Coulomb barrier. The experiments have been performed at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (FLNR) with the use of the time-of-flight spectrometer of fission fragments CORSET.

  9. Capture and Fusion-Fission Processes in Heavy Ion Induced Reactions

    NASA Astrophysics Data System (ADS)

    Itkis, M. G.; Beghini, S.; Behera, B. R.; Bogatchev, A. A.; Bouchat, V.; Corradi, L.; Dorvaux, O.; Fioretto, E.; Gadea, A.; Hanappe, F.; Itkis, I. M.; Jandel, M.; Kliman, J.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Krupa, L.; Latina, A.; Lyapin, V. G.; Materna, T.; Montagnoli, G.; Oganessian, Yu. Ts.; Pokrovsky, I. V.; Prokhorova, E. V.; Rowley, N.; Rubchenya, V. A.; Rusanov, A. Ya.; Sagaidak, R. N.; Scarlassara, F.; Schmitt, C.; Stefanini, A. M.; Stuttge, L.; Szilner, S.; Trotta, M.; Trzaska, W. H.; Voskresenski, V. M.

    2005-11-01

    Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions 12C+204Pb, 48Ca+144,154Sm, 168Er, 208Pb, 238U, 244Pu, 248Cm; 58Fe+208Pb, 244Pu, 248Cm, and 64Ni+186W, 242Pu are presented. The choice of the above-mentioned reactions was inspired by the experiments on the production of the isotopes 283112, 289114 and 283116 at Dubna using the same reactions. The 58Fe and 64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET and the neutron multi-detector DEMON. The role of shell effects and the influence of the entrance channel asymmetry and the deformations of colliding nucleus on the mechanism of the fusion-fission and the competitive process of quasi-fission are discussed.

  10. Insights into nuclear structure and the fission process from spontaneous fission

    SciTech Connect

    Hamilton, J.H.; Butler-Moore, K.; Ramayya, A.V.

    1993-12-31

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

  11. A new set-up for the simultaneous measurement of neutron-induced capture and fission reactions

    SciTech Connect

    Guerrero, C.; Berthoumieux, E.; Cano-Ott, D.; Gunsing, F.; Andriamonje, S.

    2011-07-01

    The measurement of the capture cross section of fissile elements, of upmost importance for the design of innovative nuclear reactors and the management of nuclear waste, involves particular difficulties related to the {gamma}-ray background produced in the fission reactions. These difficulties are the reason why five out of the six actinide {sigma}(n,{gamma}) measurements in the NEA High Request Priority List are fissile isotopes. At n-TOF we have combined the Total Absorption Calorimeter capture detector with a set of three {sup 235}U loaded MicroMegas fission detectors for measuring simultaneously the two reactions: capture and fission. In a first test measurement we have succeeded in measuring simultaneously with high efficiency the {sup 235}U capture and fission cross sections, disentangling accurately the two types of reactions. (authors)

  12. Nuclear envelope fission is linked to cytokinesis in budding yeast.

    PubMed

    Lippincott, J; Li, R

    2000-11-01

    We have investigated the relationship between nuclear envelope fission and cytokinesis during mitotic cell division in budding yeast. By carrying out time-lapse and optical sectioning video microscopy analysis of cells that express green fluorescent protein (GFP)-tagged nuclear envelope and actomyosin ring components, we found that nuclear division is temporally coupled to cytokinesis. Light and electron microscopy analysis also showed that nuclear envelope fission and the division of the nucleoplasm are severely delayed in cytokinesis mutants, resulting in discoupling between the nuclear division cycle and the budding cycle. These results suggest that homotypic membrane fusion may be activated by components or the mechanical action of cytokinetic structures and presents a mechanism for the equal partitioning of the nucleus and the temporal coordination of this event with chromosome segregation during mitosis.

  13. Reaction rate calibration techniques at ZPPR for /sup 239/Pu fission, /sup 235/U fission, /sup 238/U fission, and /sup 238/U capture

    SciTech Connect

    Brumbach, S.B.; Maddison, D.W.

    1982-06-10

    Reaction-rate calibration techniques used at ZPPR are described for /sup 239/Pu fission, /sup 235/U fission, /sup 238/U fission and /sup 238/U capture. In addition to these absolute reaction rates, calibration techniques are described for fission-rate ratios and the ratio of /sup 238/U capture to /sup 239/U capture to /sup 239/Pu fission. Uncertainty estimates are presented for all calibrations. Intercomparison measurements are reported which support the validity of the calibration techniques and their estimated uncertainties.

  14. Nuclear fission of neutron-deficient protactinium nuclides

    SciTech Connect

    Nishinaka, I.; Nagame, Y.; Tsukada, K.; Ikezoe, H.; Sueki, K.; Nakahara, H.; Tanikawa, M.; Ohtsuki, T.

    1997-08-01

    Fragment velocity, kinetic energy, mass yield, and element yield distributions in the fission of neutron-deficient Pa isotopes produced in the reactions of {sup 16}O and {sup 18}O on {sup 209}Bi have been measured at incident beam energies near and above the Coulomb barriers by the time-of-flight and radiochemical methods. An asymmetric mass-division component has been observed. Measured fission cross sections were compared with the results of statistical model calculations which take into account two fission barrier heights for symmetric and asymmetric yields. The fission barrier height deduced for the asymmetric fission is found slightly lower than that for the symmetric one. The difference between the two barrier heights in the fission of the present protactinium nuclides (N{approximately}135) is considerably smaller than that in the neutron-rich nuclide of {sup 233}Pa (N{approximately}142), indicating that the difference sensitively depends on the neutron number of the fissioning nuclide. {copyright} {ital 1997} {ital The American Physical Society}

  15. Introducing Nuclear Data Evaluations of Prompt Fission Neutron Spectra

    SciTech Connect

    Neudecker, Denise

    2015-06-17

    Nuclear data evaluations provide recommended data sets for nuclear data applications such as reactor physics, stockpile stewardship or nuclear medicine. The evaluated data are often based on information from multiple experimental data sets and nuclear theory using statistical methods. Therefore, they are collaborative efforts of evaluators, theoreticians, experimentalists, benchmark experts, statisticians and application area scientists. In this talk, an introductions is given to the field of nuclear data evaluation at the specific example of a recent evaluation of the outgoing neutron energy spectrum emitted promptly after fission from 239Pu and induced by neutrons from thermal to 30 MeV.

  16. Fission Cross Sections and Fission-Fragment Mass Yields via the Surrogate Reaction Method

    SciTech Connect

    Jurado, B.; Kessedjian, G.; Aiche, M.; Barreau, G.; Bidaud, A.; Czajkowski, S.; Dassie, D.; Haas, B.; Mathieu, L.; Osmanov, B.; Ahmad, I.

    2008-04-17

    The surrogate reaction method is a powerful tool to infer neutron-induced data of short-lived nuclei. After a short overview of the experimental techniques employed in the present surrogate experiments, we will concentrate on a recent measurement to determine neutron-induced fission cross sections for the actinides {sup 242,243}Cm and {sup 241}Am. The latest direct neutron-induced measurement for the {sup 243}Cm fission cross section is questioned by our results, since there are differences of more than 60% in the 0.7 to 7 MeV neutron energy range. Our experimental set-up has also enabled us to measure for the first time the fission fragment ''pseudo-mass'' distributions of {sup 243,244,245}Cm and {sup 242}Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.

  17. Scaling laws in {sup 3}He induced nuclear fission

    SciTech Connect

    Rubehn, T.; Jing, K.X.; Moretto, L.G.; Phair, L.; Tso, K.; Wozniak, G.J.

    1996-12-01

    Fission excitation functions of compound nuclei in a mass region where shell effects are expected to be very strong are shown to scale exactly according to the transition state prediction once these shell effects are accounted for. Furthermore, the method applied in this paper allows for the model-independent determination of the nuclear shell effects. {copyright} {ital 1996 The American Physical Society.}

  18. Sharp change-over from compound nuclear fission to quasifission

    SciTech Connect

    Ghosh, T. K.; Banerjee, K.; Bhattacharya, C.; Bhattacharya, S.; Kundu, S.; Mali, P.; Meena, J. K.; Mukherjee, G.; Mukhopadhyay, S.; Rana, T. K.; Bhattacharya, P.; Golda, K. S.

    2009-05-15

    Fission fragment mass distributions have been measured from the decay of the compound nucleus {sup 246}Bk that has been populated via two entrance channels. These entrance channels have a slight difference in their mass asymmetries that puts them on either side of the Businaro Gallone mass asymmetry parameter. Both target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies, the width of the fission fragment mass distribution was found to be drastically different for the {sup 14}N+{sup 232}Th reaction compared to the {sup 11}B+{sup 235}U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.

  19. Global Microscopic Models for Nuclear Reaction Calculations

    SciTech Connect

    Goriely, S.

    2005-05-24

    Important effort has been devoted in the last decades to measuring reaction cross sections. Despite such effort, many nuclear applications still require the use of theoretical predictions to estimate experimentally unknown cross sections. Most of the nuclear ingredients in the calculations of reaction cross sections need to be extrapolated in an energy and/or mass domain out of reach of laboratory simulations. In addition, some applications often involve a large number of unstable nuclei, so that only global approaches can be used. For these reasons, when the nuclear ingredients to the reaction models cannot be determined from experimental data, it is highly recommended to consider preferentially microscopic or semi-microscopic global predictions based on sound and reliable nuclear models which, in turn, can compete with more phenomenological highly-parameterized models in the reproduction of experimental data. The latest developments made in deriving such microscopic models for practical applications are reviewed. It mainly concerns nuclear structure properties (masses, deformations, radii, etc.), level densities at the equilibrium deformation, {gamma}-ray strength, as well as fission barriers and level densities at the fission saddle points.

  20. Simultaneous measurement of neutron-induced capture and fission reactions at CERN

    NASA Astrophysics Data System (ADS)

    Guerrero, C.; Berthoumieux, E.; Cano-Ott, D.; Mendoza, E.; Andriamonje, S.; Andrzejewski, J.; Audouin, L.; Barbagallo, M.; Bécares, V.; Bečvář, F.; Belloni, F.; Billowes, J.; Brugger, M.; Calviani, M.; Calviño, F.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Dillmann, I.; Domingo-Pardo, C.; Duran, I.; Eleftheriadis, C.; Fernández-Ordóñez, M.; Ferrari, A.; Ganesan, S.; Giubrone, G.; Gómez-Hornillos, M. B.; Gonçalves, I. F.; González-Romero, E.; Gramegna, F.; Griesmayer, E.; Gunsing, F.; Jenkins, D.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karadimos, D.; Kroll, J.; Krtička, M.; Lebbos, E.; Lederer, C.; Leeb, H.; Losito, R.; Lozano, M.; Manousos, A.; Marganiec, J.; Marrone, S.; Martinez, T.; Massimi, C.; Mastinu, P. F.; Meaze, M.; Mengoni, A.; Milazzo, P. M.; Paradela, C.; Pavlik, A.; Perkowski, J.; Plag, R.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Roman, F.; Rubbia, C.; Sarmento, R.; Tagliente, G.; Tain, J. L.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vermeullen, M.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weiß, C.; Wright, T.

    2012-03-01

    The measurement of the capture cross-section of fissile elements, of utmost importance for the design of innovative nuclear reactors and the management of nuclear waste, faces particular difficulties related to the γ -ray background generated in the competing fission reactions. At the CERN neutron time-of-flight facility n_TOF we have combined the Total Absorption Calorimeter (TAC) capture detector with a set of three 235U loaded MicroMegas (MGAS) fission detectors for measuring simultaneously two reactions: capture and fission. The results presented here include the determination of the three detection efficiencies involved in the process: ensuremath \\varepsilon_{TAC}(n,f) , ensuremath \\varepsilon_{TAC}(n,γ) and ensuremath \\varepsilon_{MGAS}(n,f) . In the test measurement we have succeeded in measuring simultaneously with a high total efficiency the 235U capture and fission cross-sections, disentangling accurately the two types of reactions. The work presented here proves that accurate capture cross-section measurements of fissile isotopes are feasible at n_TOF.

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

    SciTech Connect

    Holden, N.E.

    1989-08-01

    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.

  2. Detecting fission from special nuclear material sources

    DOEpatents

    Rowland, Mark S [Alamo, CA; Snyderman, Neal J [Berkeley, CA

    2012-06-05

    A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

  3. The fusion-fission process in the reaction 34S +186W near the interaction barrier

    NASA Astrophysics Data System (ADS)

    Harca, I. M.; Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K.; Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D.; Chubarian, G.; Hanappe, F.; Piot, J.; Schmitt, C.; Trzaska, W. H.; Vardaci, E.

    2015-02-01

    The reaction 34S +186W at Elab=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF-γ coincidence method is of better use then the γ - γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

  4. Particle γ/fission studies of Uranium nuclei via (p,x) reactions

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Ross, T. J.; Beausang, C. W.; Burke, J. T.; Scielzo, N. D.; Allmond, J. M.; Basunia, M. S.; Campbell, C. M.; Casperson, R. J.; Crawford, H. L.; Munson, J.; Phair, L.; Ressler, J. J.; Stars-Liberace Collaboration

    2011-04-01

    An experiment was conducted at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory to study the structure and measure (n, γ) /(n,fission) cross-sections (via surrogate reactions) of Uranium isotopes. A 28 MeV proton beam incident on236U and 23 8U targets populated states in Uranium isotopes via (p,p'), (p,d) and (p,t) reactions. The STARS array was used for detection of the outgoing light ions for exit channel nucleus tagging (as well as nuclear excitation energy information), and included a detector at backward angles for fission events. Coincident γ rays were detected using the 6 Clover detectors of the LIBERACE array and both p- γ and p-fission events were collected. The data provide a number of results including internal surrogate ratio measurements of (n γ) /(n,fission) cross-sections, and detailed structure information for nuclear levels from the ground state to well above the neutron evaporation thresholds across a range of Uranium isotopes. Preliminary results will be presented. This work is supported in part by the U.S. Department of energy via grant numbers DE-FG02-05 ER41379 & DE-FG52-06 NA26206(University of Richmond), DE-AC52 07NA27344(LLNL) and DE-AC02 05CH11231(LBNL).

  5. Virtual breakdown of the nuclear envelope in fission yeast meiosis.

    PubMed

    Asakawa, Haruhiko; Kojidani, Tomoko; Mori, Chie; Osakada, Hiroko; Sato, Mamiko; Ding, Da-Qiao; Hiraoka, Yasushi; Haraguchi, Tokuko

    2010-11-09

    Asymmetric localization of Ran regulators (RanGAP1 and RanGEF/RCC1) produces a gradient of RanGTP across the nuclear envelope. In higher eukaryotes, the nuclear envelope breaks down as the cell enters mitosis (designated "open" mitosis). This nuclear envelope breakdown (NEBD) leads to collapse of the RanGTP gradient and the diffusion of nuclear and cytoplasmic macromolecules in the cell, resulting in irreversible progression of the cell cycle. On the other hand, in many fungi, chromosome segregation takes place without NEBD (designated "closed" mitosis). Here we report that in the fission yeast Schizosaccharomyces pombe, despite the nuclear envelope and the nuclear pore complex remaining intact throughout both the meiotic and mitotic cell cycles, nuclear proteins diffuse into the cytoplasm transiently for a few minutes at the onset of anaphase of meiosis II. We also found that nuclear protein diffusion into the cytoplasm occurred coincidently with nuclear localization of Rna1, an S. pombe RanGAP1 homolog that is usually localized in the cytoplasm. These results suggest that nuclear localization of RanGAP1 and depression of RanGTP activity in the nucleus may be mechanistically tied to meiosis-specific diffusion of nuclear proteins into the cytoplasm. This nucleocytoplasmic shuffling of RanGAP1 and nuclear proteins represents virtual breakdown of the nuclear envelope.

  6. Fission-Produced (99)Mo Without a Nuclear Reactor.

    PubMed

    Youker, Amanda J; Chemerisov, Sergey D; Tkac, Peter; Kalensky, Michael; Heltemes, Thad A; Rotsch, David A; Vandegrift, George F; Krebs, John F; Makarashvili, Vakho; Stepinski, Dominique C

    2017-03-01

    (99)Mo, the parent of the widely used medical isotope (99m)Tc, is currently produced by irradiation of enriched uranium in nuclear reactors. The supply of this isotope is encumbered by the aging of these reactors and concerns about international transportation and nuclear proliferation. Methods: We report results for the production of (99)Mo from the accelerator-driven subcritical fission of an aqueous solution containing low enriched uranium. The predominately fast neutrons generated by impinging high-energy electrons onto a tantalum convertor are moderated to thermal energies to increase fission processes. The separation, recovery, and purification of (99)Mo were demonstrated using a recycled uranyl sulfate solution. Conclusion: The (99)Mo yield and purity were found to be unaffected by reuse of the previously irradiated and processed uranyl sulfate solution. Results from a 51.8-GBq (99)Mo production run are presented.

  7. Legal and Regulatroy Obstacles to Nuclear Fission Technology in Space

    NASA Astrophysics Data System (ADS)

    Force, Melissa K.

    2013-09-01

    In forecasting the prospective use of small nuclear reactors for spacecraft and space-based power stations, the U.S. Air Force describes space as "the ultimate high ground," providing access to every part of the globe. But is it? A report titled "Energy Horizons: United States Air Force Energy Science &Technology Vision 2011-2026," focuses on core Air Force missions in space energy generation, operations and propulsion and recognizes that investments into small modular nuclear fission reactors can be leveraged for space-based systems. However, the report mentions, as an aside, that "potential catastrophic outcomes" are an element to be weighed and provides no insight into the monumental political and legal will required to overcome the mere stigma of nuclear energy, even when referring only to the most benign nuclear power generation systems - RTGs. On the heels of that report, a joint Department of Energy and NASA team published positive results from the demonstration of a uranium- powered fission reactor. The experiment was perhaps most notable for exemplifying just how effective the powerful anti-nuclear lobby has been in the United States: It was the first such demonstration of its kind in nearly fifty years. Space visionaries must anticipate a difficult war, consisting of multiple battles that must be waged in order to obtain a license to fly any but the feeblest of nuclear power sources in space. This paper aims to guide the reader through the obstacles to be overcome before nuclear fission technology can be put to use in space.

  8. FUEL ELEMENTS FOR THERMAL-FISSION NUCLEAR REACTORS

    DOEpatents

    Flint, O.

    1961-01-10

    Fuel elements for thermal-fission nuclear reactors are described. The fuel element is comprised of a core of alumina, a film of a metal of the class consisting of copper, silver, and nickel on the outer face of the core, and a coating of an oxide of a metal isotope of the class consisting of Un/sup 235/, U/ sup 233/, and Pu/sup 239/ on the metal f ilm.

  9. Fission control system for nuclear reactor

    DOEpatents

    Conley, G.H.; Estes, G.P.

    Control system for nuclear reactor comprises a first set of reactivity modifying rods fixed in a reactor core with their upper ends stepped in height across the core, and a second set of reactivity modifying rods movable vertically within the reactor core and having their lower ends stepped to correspond with the stepped arrangement of the first set of rods, pairs of the rods of the first and second sets being in coaxial alignment.

  10. An Act of Scientific Creativity: Meitner, Frisch, and Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Stuewer, Roger H.

    2002-04-01

    The dominant event that lay in the background to Werner Heisenberg's fateful meeting with Niels Bohr in occupied Copenhagen in September 1941 was the discovery and interpretation of nuclear fission three years earlier. Michael Frayn has explored that meeting in his play "Copenhagen" in an act of extraordinary literary creativity. In this talk I will explore Lise Meitner's and Otto Robert Frisch's interpretation of nuclear fission as an act of extraordinary scientific creativity. My aim is to understand historically how it was possible for Meitner and Frisch, and only Meitner and Frisch, to arrive at their interpretation as they talked and walked in the snow in the small Swedish village of Kungälv over the Christmas holidays in December 1938. This will require us to examine the history of the liquid-drop model of the nucleus over the preceding decade, from George Gamow's conception of that model in 1928, through Heisenberg and Carl Friedrich von Weizsäcker's extension of it between 1933 and 1936, and finally through Bohr's use of it in his theory of the compound nucleus between 1936 and 1938. We will see how Meitner and Frisch combined their different knowledge of these developments creatively to arrive at their momentous interpretation of nuclear fission.

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

    PubMed Central

    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 sequence of codes. The results clearly demonstrate that such a geo-reactor (i) would function as a fast-neutron fuel breeder reactor; (ii) could, under appropriate conditions, operate over the entire period of geologic time; and (iii) would function in such a manner as to yield variable and/or intermittent output power. PMID:11562483

  12. Deep-Earth reactor: nuclear fission, helium, and the geomagnetic field.

    PubMed

    Hollenbach, D F; Herndon, J M

    2001-09-25

    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 (3)He/(4)He 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 sequence of codes. The results clearly demonstrate that such a geo-reactor (i) would function as a fast-neutron fuel breeder reactor; (ii) could, under appropriate conditions, operate over the entire period of geologic time; and (iii) would function in such a manner as to yield variable and/or intermittent output power.

  13. Membrane fission reactions of the mammalian ESCRT pathway.

    PubMed

    McCullough, John; Colf, Leremy A; Sundquist, Wesley I

    2013-01-01

    The endosomal sorting complexes required for transport (ESCRT) pathway was initially defined in yeast genetic screens that identified the factors necessary to sort membrane proteins into intraluminal endosomal vesicles. Subsequent studies have revealed that the mammalian ESCRT pathway also functions in a series of other key cellular processes, including formation of extracellular microvesicles, enveloped virus budding, and the abscission stage of cytokinesis. The core ESCRT machinery comprises Bro1 family proteins and ESCRT-I, ESCRT-II, ESCRT-III, and VPS4 complexes. Site-specific adaptors recruit these soluble factors to assemble on different cellular membranes, where they carry out membrane fission reactions. ESCRT-III proteins form filaments that draw membranes together from the cytoplasmic face, and mechanistic models have been advanced to explain how ESCRT-III filaments and the VPS4 ATPase can work together to catalyze membrane fission.

  14. Membrane Fission Reactions of the Mammalian ESCRT Pathway

    PubMed Central

    McCullough, John; Colf, Leremy A.; Sundquist, Wesley I.

    2014-01-01

    The endosomal sorting complexes required for transport (ESCRT) pathway was initially defined in yeast genetic screens that identified the factors necessary to sort membrane proteins into intraluminal endosomal vesicles. Subsequent studies have revealed that the mammalian ESCRT pathway also functions in a series of other key cellular processes, including formation of extracellular microvesicles, enveloped virus budding, and the abscission stage of cytokinesis. The core ESCRT machinery comprises Bro1 family proteins and ESCRT-I, ESCRT-II, ESCRT-III, and VPS4. Site-specific adaptors recruit these soluble factors to assemble on different cellular membranes, where they carry out membrane fission reactions. ESCRT-III proteins form filaments that draw membranes together from the cytoplasmic face, and mechanistic models have been advanced to explain how ESCRT-III filaments and the VPS4 ATPase can work together to catalyze membrane fission. PMID:23527693

  15. Nuclear Design of the HOMER-15 Mars Surface Fission Reactor

    SciTech Connect

    Poston, David I.

    2002-07-01

    The next generation of robotic missions to Mars will most likely require robust power sources in the range of 3 to 20 kWe. Fission systems are well suited to provide safe, reliable, and economic power within this range. The goal of this study is to design a compact, low-mass fission system that meets Mars surface power requirements, while maintaining a high level of safety and reliability at a relatively low cost. The Heat pipe Power System (HPS) is one possible approach for producing near-term, low-cost, space fission power. The goal of the HPS project is to devise an attractive space fission system that can be developed quickly and affordably. The primary ways of doing this are by using existing technology and by designing the system for inexpensive testing. If the system can be designed to allow highly prototypic testing with electrical heating, then an exhaustive test program can be carried out quickly and inexpensively, and thorough testing of the actual flight unit can be performed - which is a major benefit to reliability. Over the past 4 years, three small HPS proof-of-concept technology demonstrations have been conducted, and each has been highly successful. The Heat pipe-Operated Mars Exploration Reactor (HOMER) is a derivative of the HPS designed especially for producing power on the surface of Mars. The HOMER-15 is a 15-kWt reactor that couples with a 3-kWe Stirling engine power system. The reactor contains stainless-steel (SS)-clad uranium nitride (UN) fuel pins that are structurally and thermally bonded to SS/sodium heat pipes. Fission energy is conducted from the fuel pins to the heat pipes, which then carry the heat to the Stirling engine. This paper describes conceptual design and nuclear performance the HOMER-15 reactor. (author)

  16. Shell effects in fission, quasifission and multinucleon transfer reaction

    NASA Astrophysics Data System (ADS)

    Kozulin, E. M.; Knyazheva, G. N.; Itkis, I. M.; Kozulina, N. I.; Loktev, T. A.; Novikov, K. V.; Harca, I.

    2014-05-01

    Results of the study of mass-energy distributions of binary fragments for a wide range of nuclei with Z= 82-122 produced in reactions of ions located between 22Ne and 136Xe at energies close and below the Coulomb barrier are reported. The role of the shell effects, the influence of the entrance channel asymmetry and the deformations of colliding nuclei on the mechanism of the fusion-fission, quasifission and multinucleon transfer reactions are discussed. The observed peculiarities of the mass and energy distributions of reaction fragments are determined by the shell structure of the formed fragments. Special attention is paid on the symmetric fragment features in order to clarify the origin of these fragments (fission or quasifission). The influence of shell effects on the fragment yield in quasifission and multinucleon transfer reactions is considered. It is noted that the major part of the asymmetric quasifission fragments peaks around the region of the Z=82 and N=126 (double magic lead) and Z=28 and N=50 shells; moreover the maximum of the yield of the quasifission component is a mixing between all these shells. Hence, shell effects are everywhere present and determine the basic characteristics of fragment mass distributions.

  17. Nuclear compartmentalization is abolished during fission yeast meiosis.

    PubMed

    Arai, Kunio; Sato, Masamitsu; Tanaka, Kayoko; Yamamoto, Masayuki

    2010-11-09

    In eukaryotic cells, the nuclear envelope partitions the nucleus from the cytoplasm. The fission yeast Schizosaccharomyces pombe undergoes closed mitosis in which the nuclear envelope persists rather than being broken down, as in higher eukaryotic cells. It is therefore assumed that nucleocytoplasmic transport continues during the cell cycle. Here we show that nuclear transport is, in fact, abolished specifically during anaphase of the second meiotic nuclear division. During that time, both nucleoplasmic and cytoplasmic proteins disperse throughout the cell, reminiscent of the open mitosis of higher eukaryotes, but the architecture of the S. pombe nuclear envelope itself persists. This functional alteration of the nucleocytoplasmic barrier is likely induced by spore wall formation, because ectopic induction of sporulation signaling leads to premature dispersion of nucleoplasmic proteins. A photobleaching assay demonstrated that nuclear envelope permeability increases abruptly at the onset of anaphase of the second meiotic division. The permeability was not altered when sporulation was inhibited by blocking the trafficking of forespore-membrane vesicles from the endoplasmic reticulum to the Golgi. The evidence indicates that yeast gametogenesis produces vesicle transport-mediated forespore membranes by inducing nuclear envelope permeabilization.

  18. Transfer reactions in nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    Bardayan, D. W.

    2016-08-01

    To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star’s fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.

  19. Direct nuclear pumping by a volume source of fission fragments

    NASA Technical Reports Server (NTRS)

    Deese, J. E.; Hassan, H. A.

    1978-01-01

    A detailed kinetic model is presented for the analysis of nuclear pumped lasers when the pumping is a result of a volume source of fission fragments. The results of the model are employed to study a He-3 - Xe laser. For the range of pressures, neutron fluxes and mixtures considered, the gain and power calculations are in good agreement with experiment. Moreover, based on these calculations, it appears that the collisional recombination is the dominant pumping mechanism for 7p-7s transitions while direct excitation is the dominant pumping mechanism for the 5d-6p transitions.

  20. Proceedings of the XVIIIth international symposium on nuclear physics

    SciTech Connect

    Marten, H.; Seeliger, D.

    1992-01-01

    This book contains the proceedings of the XVIII International Symposium on nuclear physics. Topics covered include: fission fragment distributions; fundamental fission problems; theory of nuclear fission; fragment de-excitation; ternary fission; spontaneous-fission and decay; induced fission; heavy-ion reactions; and applications of fission.

  1. Results of a first generation least expensive approach to fission module tests: Non-nuclear testing of a fission system

    NASA Astrophysics Data System (ADS)

    van Dyke, Melissa; Godfroy, Tom; Houts, Mike; Dickens, Ricky; Dobson, Chris; Pederson, Kevin; Reid, Bob; Sena, J. Tom

    2000-01-01

    The use of resistance heaters to simulate heat from fission allows extensive development of fission systems to be performed in non-nuclear test facilities, saving time and money. Resistance heated tests on the Module Unfueled Thermal-hydraulic Test (MUTT) article has been performed at the Marshall Space Flight Center. This paper discusses the results of these experiments to date, and describes the additional testing that will be performed. Recommendations related to the design of testable space fission power and propulsion systems are made. .

  2. Towards a prediction of fission cross sections on the basis of microscopic nuclear inputs

    SciTech Connect

    Goriely, S.; Hilaire, S.; Koning, A. J.; Sin, M.; Capote, R.

    2009-02-15

    Recently, a sound description of some of the basic nuclear ingredients required in the calculation of fission cross sections has been obtained. These concern in particular fission barriers within the Hartree-Fock-Bogoliubov (HFB) method and nuclear level densities at the fission saddle points within the combinatorial model. Both ingredients are determined coherently, the nuclear level densities being estimated on the basis of the single-particle scheme and pairing strength of the same mean field model that was used to determine the fission saddle points. The aim of the present study is to evaluate the quality of such inputs in the calculation of fission cross sections. Although the barrier height can still not be predicted with an accuracy better than about 700 keV, the use of the full HFB fission path and the corresponding WKB calculation of the probability to penetrate the fission barrier clearly provides a better way to estimate fission cross section in comparison with highly parametrized phenomenological models, when no experimental data is available. It is shown that a satisfactory estimate of the fission cross section for nonenergy applications can be achieved with a global renormalization of the barrier height and the microscopic nuclear level densities at the fission saddle points. Good agreement with experimental data can be obtained if both the fission barrier heights and level densities are independently renormalized. The resulting barrier heights required to reproduce experimental cross sections are found to be smaller by a few hundred keV with respect to previous analyses.

  3. Nuclear excitation and precompound nuclear reactions

    SciTech Connect

    De, A.; Ray, S.; Ghosh, S.K.

    1988-06-01

    The angular distribution of nucleons emitted in nucleon-induced precompound nuclear reactions are calculated taking into account the effect of excitation on the kinematics of nucleon-nucleon scattering inside the target-plus-projectile system. The results are compared with quantum mechanical calculations and those of reaction models based on a pure nucleon-nucleon collision picture.

  4. Nuclear fission: the interplay of science and technology.

    PubMed

    Stoneham, A M

    2010-07-28

    When the UK's Calder Hall nuclear power station was connected to the grid in 1956, the programmes that made this possible involved a powerful combination of basic and applied research. Both the science and the engineering were novel, addressing new and challenging problems. That the last Calder Hall reactor was shut down only in 2003 attests to the success of the work. The strengths of bringing basic science to bear on applications continued to be recognized until the 1980s, when government and management fashions changed. This paper identifies a few of the technology challenges, and shows how novel basic science emerged from them and proved essential in their resolution. Today, as the threat of climate change becomes accepted, it has become clear that there is no credible solution without nuclear energy. The design and construction of new fission reactors will need continuing innovation, with the interplay between the science and technology being a crucial component.

  5. Fission cross-sections, prompt fission neutron and γ-ray emission in request for nuclear applications

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; Salvador-Castiñeira, P.; Oberstedt, S.; Göök, A.; Billnert, R.

    2016-06-01

    In recent years JRC-IRMM has been investigating fission cross-sections of 240,242Pu in the fast-neutron energy range relevant for innovative reactor systems and requested in the High Priority Request List (HPRL) of the OECD/Nuclear Energy Agency (NEA). In addition to that, prompt neutron multiplicities are being investigated for the major isotopes 235U, 239Pu in the neutron-resonance region using a newly developed scintillation detector array (SCINTIA) and an innovative modification of the Frisch-grid ionisation chamber for fission-fragment detection. These data are highly relevant for improved neutron data evaluation and requested by the OECD/Working Party on Evaluation Cooperation (WPEC). Thirdly, also prompt fission γ-ray emission is investigated using highly efficient lanthanide-halide detectors with superior timing resolution. Again, those data are requested in the HPRL for major actinides to solve open questions on an under-prediction of decay heat in nuclear reactors. The information on prompt fission neutron and γ-ray emission is crucial for benchmarking nuclear models to study the de-excitation process of neutron-rich fission fragments. Information on γ-ray emission probabilities is also useful in decommissioning exercises on damaged nuclear power plants like Fukushima Daiichi to which JRC-IRMM is contributing. The results on the 240,242Pu fission cross section, 235U prompt neutron multiplicity in the resonance region and correlations with fission fragments and prompt γ-ray emission for several isotopes will be presented and put into perspective.

  6. Table of superdeformed nuclear bands and fission isomers

    SciTech Connect

    Firestone, R.B.; Singh, B.

    1994-06-01

    A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in {sup 152}Dy was predicted for {beta}{sub 2}-0.65. Subsequently, a discrete set of {gamma}-ray transitions in {sup 152}DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of {gamma}-ray detector arrays is already producing a wealth of information about the mechanisms for feeding and deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra.

  7. Fusion and quasi-fission dynamics in nearly-symmetric reactions

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Zhao, Kai; Li, ZhuXia

    2015-11-01

    Some nearly-symmetric fusion reactions are systematically investigated with the improved quantum molecular dynamics (ImQMD) model. By introducing two-body inelastic scattering in the Fermi constraint procedure, the stability of an individual nucleus and the description of fusion cross sections at energies near the Coulomb barrier can be further improved. Simultaneously, the quasifission process in 154Sm+160Gd is also investigated with the microscopic dynamics model for the first time. We find that at energies above the Bass barrier, the fusion probability is smaller than 10-5 for this reaction, and the nuclear contact time is generally smaller than 1500 fm/ c. From the central collisions of Sm+Gd, the neutron-rich fragments such as 164,165Gd, 192W can be produced in the ImQMD simulations, which implies that the quasi-fission reaction could be an alternative way to synthesize new neutron-rich heavy nuclei.

  8. Nuclear reaction studies

    SciTech Connect

    Alexander, J.M.; Lacey, R.A.

    1994-11-01

    Research focused on the statistical and dynamical properties of ``hot`` nuclei formed in symmetric heavy-ion reactions. Theses included ``flow`` measurements and the mechanism for multifragment disassembly. Model calculations are being performed for the reactions C+C, Ne+Al, Ar+Sc, Kr+Nb, and Xe+La. It is planned to study {sup 40}Ar reactions from 27 to 115 MeV/nucleon. 2 figs., 41 refs.

  9. Measurement/Evaluation Techniques and Nuclear Data Associated with Fission of 239Pu by Fission Spectrum Neutrons

    SciTech Connect

    Baisden, P; Bauge, E; Ferguson, J; Gilliam, D; Granier, T; Jeanloz, R; McMillan, C; Robertson, D; Thompson, P; Verdon, C; Wilkerson, C; Young, P

    2010-03-16

    This Panel was chartered to review and assess new evaluations of work on fission product data, as well as the evaluation process used by the two U.S. nuclear weapons physics laboratories. The work focuses on fission product yields resulting from fission spectrum neutrons incident on plutonium, and includes data from measurements that had not been previously published as well as new or revised fission product cumulative yield data, and related quantities such as Q values and R values. This report documents the Panel's assessment of the work presented by Los Alamos National Laboratory (LANL) and Lawrence Livermore National Laboratory (LLNL). Based on the work presented we have seven key observations: (1) Experiments conducted in the 1970s at LANL, some of which were performed in association with a larger, NIST-led, program, have recently been documented. A preliminary assessment of this work, which will be referred to in this document as ILRR-LANL, shows it to be technically sound. (2) LLNL has done a thorough, unbiased review and evaluation of the available literature and is in the process of incorporating the previously unavailable LANL data into its evaluation of key fission product yields. The results of the LLNL effort, which includes a preliminary evaluation of the ILRR-LANL data, have been documented. (3) LANL has also conducted an evaluation of fission product yields for fission spectrum neutrons on plutonium including a meta-analysis of benchmark data as part of a planned upgrade to the ENDF/B compilation. We found that the approach of using meta-analysis provides valuable additional insight for evaluating the sparse data sets involved in this assessment. (4) Both laboratories have provided convincing evidence for energy dependence in the fission product yield of {sup 147}Nd produced from the bombardment of {sup 239}Pu with fission spectrum neutrons over an incident neutron energy range of 0.2 to 1.9 MeV. (5) Consistent, complete, and explicit treatment of

  10. Nuclear Reactions: Studying Peaceful Applications in the Middle and Secondary School.

    ERIC Educational Resources Information Center

    Szymanski Sunal, Cynthia; Sunal, Dennis W.

    1999-01-01

    Asserts that students must learn about nuclear fission and fusion in the social studies curriculum to help them develop a foundation for considering the social issues associated with the everyday use of nuclear reactions. Gives background on the two types of reactions and provides three lessons for middle and secondary classrooms. (CMK)

  11. Recoil-α-fission and recoil-α-α-fission events observed in the reaction 48Ca + 243Am

    NASA Astrophysics Data System (ADS)

    Forsberg, U.; Rudolph, D.; Andersson, L.-L.; Di Nitto, A.; Düllmann, Ch. E.; Fahlander, C.; Gates, J. M.; Golubev, P.; Gregorich, K. E.; Gross, C. J.; Herzberg, R.-D.; Heßberger, F. P.; Khuyagbaatar, J.; Kratz, J. V.; Rykaczewski, K.; Sarmiento, L. G.; Schädel, M.; Yakushev, A.; Åberg, S.; Ackermann, D.; Block, M.; Brand, H.; Carlsson, B. G.; Cox, D.; Derkx, X.; Dobaczewski, J.; Eberhardt, K.; Even, J.; Gerl, J.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nazarewicz, W.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Ragnarsson, I.; Runke, J.; Schaffner, H.; Schausten, B.; Shi, Yue; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Ward, D. E.; Wiehl, N.

    2016-09-01

    Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z = 115, two recoil-α-fission and five recoil- α- α-fission events were observed. The latter five chains are similar to four such events reported from experiments performed at the Dubna gas-filled separator, and three such events reported from an experiment at the Berkeley gas-filled separator. The four chains observed at the Dubna gas-filled separator were assigned to start from the 2n-evaporation channel 289115 due to the fact that these recoil- α- α-fission events were observed only at low excitation energies. Contrary to this interpretation, we suggest that some of these recoil- α- α-fission decay chains, as well as some of the recoil- α- α-fission and recoil-α-fission decay chains reported from Berkeley and in this article, start from the 3n-evaporation channel 288115.

  12. Realistic Development and Testing of Fission System at a Non-Nuclear Testing Facility

    NASA Technical Reports Server (NTRS)

    Godfroy, Tom; VanDyke, Melissa; Dickens, Ricky; Pedersen, Kevin; Lenard, Roger; Houts, Mike

    2000-01-01

    The use of resistance heaters to simulate heat from fission allows extensive development of fission systems to be performed in non-nuclear test facilities, saving time and money. Resistance heated tests on a module has been performed at the Marshall Space Flight Center in the Propellant Energy Source Testbed (PEST). This paper discusses the experimental facilities and equipment used for performing resistance heated tests. Recommendations are made for improving non-nuclear test facilities and equipment for simulated testing of nuclear systems.

  13. Realistic development and testing of fission systems at a non-nuclear testing facility

    NASA Astrophysics Data System (ADS)

    Godfroy, Tom; van Dyke, Melissa; Dickens, Ricky; Pedersen, Kevin; Lenard, Roger; Houts, Mike

    2000-01-01

    The use of resistance heaters to simulate heat from fission allows extensive development of fission systems to be performed in non-nuclear test facilities, saving time and money. Resistance heated tests on a module has been performed at the Marshall Space Flight Center in the Propellant Energy Source Testbed (PEST). This paper discusses the experimental facilities and equipment used for performing resistance heated tests. Recommendations are made for improving non-nuclear test facilities and equipment for simulated testing of nuclear systems. .

  14. Research on fission fragment excitation of gases and nuclear pumping of lasers

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.; Davie, R. N.; Davis, J. F.; Fuller, J. L.; Paternoster, R. R.; Shipman, G. R.; Sterritt, D. E.; Helmick, H. H.

    1974-01-01

    Experimental investigations of fission fragment excited gases are reported along with a theoretical analysis of population inversions in fission fragment excited helium. Other studies reported include: nuclear augmentation of gas lasers, direct nuclear pumping of a helium-xenon laser, measurements of a repetitively pulsed high-power CO2 laser, thermodynamic properties of UF6 and UF6/He mixtures, and nuclear waste disposal utilizing a gaseous core reactor.

  15. Effect of projectile breakup on fission-fragment mass distributions in the Li,76 + 238U reactions

    NASA Astrophysics Data System (ADS)

    Santra, S.; Pal, A.; Rath, P. K.; Nayak, B. K.; Singh, N. L.; Chattopadhyay, D.; Behera, B. R.; Singh, Varinderjit; Jhingan, A.; Sugathan, P.; Golda, K. S.; Sodaye, S.; Appannababu, S.; Prasad, E.; Kailas, S.

    2014-12-01

    Background: Detailed studies on the effect of the breakup of weakly bound projectile on fission are scarce. Distinguishing the events of compound nuclear (CN) fission from the breakup or transfer induced fission to understand the properties of measured fission fragments is difficult but desirable. Purpose: To investigate the effect of projectile breakup and its breakup threshold energy on fission-fragment (FF) mass distributions and folding angle distributions for Li,76 + 238U reactions and find out the differences in the properties of the fission events produced by complete fusion (CF) from the total fusion (TF). Methods: The FF mass and folding angle distributions have been measured at energies around the Coulomb barrier using gas detectors by time-of-flight technique. The results are compared with the ones involving tightly bound projectiles as well as predictions from systematics to bring out the effect of the breakup. Results: A sharp increase in the peak to valley (P:V) ratio of FF mass distribution with the decrease in bombarding energy for Li,76 + 238U reactions is observed when all events are assumed to be CN fission. As the beam energy falls through the fusion barrier, the full width half maximum (FWHM) of the FF folding angle distribution is found to increase at sub-barrier energies, unlike the reactions involving tightly bound projectiles where a linear decrease in FWHM is expected. By selecting pure CN events from the scatter plot of the velocity components of the composite nuclei, the energy dependence of the deduced FWHM is found to be consistent with the ones involving tightly bound projectiles. Similarly, the P:V ratio obtained for the selected CN events is consistent with the theoretical calculations as well as the experimental data for the proton induced reaction forming similar CN. Conclusions: The presence of projectile breakup induced fission and a relatively low breakup threshold for 6Li compared to 7Li explains the observed differences in

  16. The fusion-fission process in the reaction {sup 34}S+{sup 186}W near the interaction barrier

    SciTech Connect

    Harca, I. M.; Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K.; Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D.; Hanappe, F.; Piot, J.; Schmitt, C.; Vardaci, E.

    2015-02-24

    The reaction {sup 34}S+{sup 186}W at E{sub lab}=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF–γ coincidence method is of better use then the γ – γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

  17. Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2007-10-02

    A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  18. Assessment of fission product yields data needs in nuclear reactor applications

    SciTech Connect

    Kern, K.; Becker, M.; Broeders, C.

    2012-07-01

    Studies on the build-up of fission products in fast reactors have been performed, with particular emphasis on the effects related to the physics of the nuclear fission process. Fission product yields, which are required for burn-up calculations, depend on the proton and neutron number of the target nucleus as well as on the incident neutron energy. Evaluated nuclear data on fission product yields are available for all relevant target nuclides in reactor applications. However, the description of their energy dependence in evaluated data is still rather rudimentary, which is due to the lack of experimental fast fission data and reliable physical models. Additionally, physics studies of evaluated JEFF-3.1.1 fission yields data have shown potential improvements, especially for various fast fission data sets of this evaluation. In recent years, important progress in the understanding of the fission process has been made, and advanced model codes are currently being developed. This paper deals with the semi-empirical approach to the description of the fission process, which is used in the GEF code being developed by K.-H. Schmidt and B. Jurado on behalf of the OECD Nuclear Energy Agency, and with results from the corresponding author's diploma thesis. An extended version of the GEF code, supporting the calculation of spectrum weighted fission product yields, has been developed. It has been applied to the calculation of fission product yields in the fission rate spectra of a MOX fuelled sodium-cooled fast reactor. Important results are compared to JEFF-3.1.1 data and discussed in this paper. (authors)

  19. Dynamical simulation of the fission process and anisotropy of the fission fragment angular distributions of excited nuclei produced in fusion reactions

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2016-10-01

    Abstract. A stochastic approach based on four-dimensional Langevin equations was applied to calculate the anisotropy of fission fragment angular distributions, average prescission neutron multiplicity, and the fission probability in a wide range of fissile parameters for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf produced in fusion reactions. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis K were considered in the four-dimensional dynamical model. In the dynamical calculations, nuclear dissipation was generated through the chaos-weighted wall and window friction formula. Furthermore, in the dynamical calculations the dissipation coefficient of K ,γk was considered as a free parameter, and its magnitude inferred by fitting measured data on the anisotropy of fission fragment angular distributions for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf. Comparison of the calculated results for the anisotropy of fission fragment angular distributions with the experimental data showed that the results of the calculations are in good agreement with the experimental data by using values of the dissipation coefficient of K equal to (0.185-0.205), (0.175-0.192), (0.077-0.090), and (0.075-0.085) (MeVzs ) -1 /2 for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf, respectively. It was also shown that the influence of the dissipation coefficient of K on the results of the calculations of the prescission neutron multiplicity and fission probability is small.

  20. Thermal Simulator Development: Non-Nuclear Testing of Space Fission Systems

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Dickens, Ricky E.

    2006-01-01

    Non-nuclear testing can be a valuable tool in the development of a space nuclear power system. At the NASA MSFC Early Flight Fission Test Facility (EFF-TF), highly designed electric heaters are used to simulate the heat from nuclear fuel to test space fission power and propulsion systems. To allow early utilization, nuclear system designs must be relatively simple, easy to fabricate, and easy to test using non-nuclear heaters to closely mimic heat from fission. In this test strategy, highly designed electric heaters are used to simulate the heat from nuclear fuel, allowing one to develop a significant understanding of individual components and integrated system operation without the cost, time and safety concerns associated with nuclear testing.

  1. NUCLEAR REACTION MODELING FOR RIA ISOL TARGET DESIGN

    SciTech Connect

    S. MASHNIK; ET AL

    2001-03-01

    Los Alamos scientists are collaborating with researchers at Argonne and Oak Ridge on the development of improved nuclear reaction physics for modeling radionuclide production in ISOL targets. This is being done in the context of the MCNPX simulation code, which is a merger of MCNP and the LAHET intranuclear cascade code, and simulates both nuclear reaction cross sections and radiation transport in the target. The CINDER code is also used to calculate the time-dependent nuclear decays for estimating induced radioactivities. They give an overview of the reaction physics improvements they are addressing, including intranuclear cascade (INC) physics, where recent high-quality inverse-kinematics residue data from GSI have led to INC spallation and fission model improvements; and preequilibrium reactions important in modeling (p,xn) and (p,xnyp) cross sections for the production of nuclides far from stability.

  2. Dynamics of the tri-nuclear system at spontaneous fission of 252Cf

    NASA Astrophysics Data System (ADS)

    Tashkhodjaev, R. B.; Nasirov, A. K.; Alpomeshev, E. Kh.

    2016-11-01

    To describe the dynamics of ternary fission of 252Cf an equation of motion of the tri-nuclear system was obtained and it was solved numerically. The fission of the 70Ni+50Ca+132Sn channel was chosen as one of the more probable channels of true ternary fission of 252Cf. The collinearity of ternary fission was checked by analyzing the results of the equation of motion. The results show that if initially all nuclei are placed collinearly (potential energy of this position is the smallest) and the component of the middle fragment's initial velocity which is perpendicular to this line is zero, then ternary fission is collinear, otherwise noncollinear ternary fission takes place.

  3. Impact of nuclear fission on r-process nucleosynthesis and origin of solar r-process elements

    SciTech Connect

    Shibagaki, Shota; Kajino, Toshitaka; Mathews, Grant J.; Chiba, Satoshi

    2015-02-24

    Binary neutron star mergers (NSMs) are expected to be main production sites of r-process elements. Their ejecta are extremely neutron-rich (Y{sub e}<0.1), and the r-process path proceeds along the neutron drip line and enters the region of fissile nuclei. In this situation, although superheavy nuclei may be synthesized and the r-process path may reach the island of stability, those are sensitive to theoretical models of nuclear masses and nuclear fission. In this study, we carry out r-process nucleosynthesis simulations in the NSMs. Our new nuclear reaction network code include new theoretical models of nuclear masses and nuclear fission. Our r-process simulation of a binary NSM shows that the final r-process elemental abundances exhibit flat pattern for A∼110-160, and several fission cycling operate in extremely neutron-rich conditions of the NSM. We find that the combination of the NSMs and the magnetorotational supernovae can reproduce the solar r-process elements. We discuss the validity of this interpretation.

  4. Impact of nuclear fission on r-process nucleosynthesis and origin of solar r-process elements

    NASA Astrophysics Data System (ADS)

    Shibagaki, Shota; Kajino, Toshitaka; Mathews, Grant J.; Chiba, Satoshi

    2015-02-01

    Binary neutron star mergers (NSMs) are expected to be main production sites of r-process elements. Their ejecta are extremely neutron-rich (Ye<0.1), and the r-process path proceeds along the neutron drip line and enters the region of fissile nuclei. In this situation, although superheavy nuclei may be synthesized and the r-process path may reach the island of stability, those are sensitive to theoretical models of nuclear masses and nuclear fission. In this study, we carry out r-process nucleosynthesis simulations in the NSMs. Our new nuclear reaction network code include new theoretical models of nuclear masses and nuclear fission. Our r-process simulation of a binary NSM shows that the final r-process elemental abundances exhibit flat pattern for A˜110-160, and several fission cycling operate in extremely neutron-rich conditions of the NSM. We find that the combination of the NSMs and the magnetorotational supernovae can reproduce the solar r-process elements. We discuss the validity of this interpretation.

  5. Nuclear reactions from lattice QCD

    NASA Astrophysics Data System (ADS)

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-02-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, quantum chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three-nucleon (and higher) interactions in a consistent manner. Currently, lattice quantum chromodynamics (LQCD) provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between LQCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from LQCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  6. Nuclear reactions from lattice QCD

    DOE PAGES

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-01-13

    In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculationsmore » of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less

  7. Nuclear reactions from lattice QCD

    SciTech Connect

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-01-13

    In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  8. Mini Fission-Fusion-Fission Explosions (Mini-Nukes). A Third Way Towards the Controlled Release of Nuclear Energy by Fission and Fusion

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2004-06-01

    Chemically ignited nuclear microexplosions with a fissile core, a DT reflector and U238 (Th232) pusher, offer a promising alternative to magnetic and inertial confinement fusion, not only burning DT, but in addition U238 (or Th232), and not depending on a large expensive laser of electric pulse power supply. The prize to be paid is a gram size amount of fissile material for each microexplosion, but which can be recovered by breeding in U238. In such a "mini-nuke" the chemical high explosive implodes a spherical metallic shell onto a smaller shell, with the smaller shell upon impact becoming the source of intense black body radiation which vaporizes the ablator of a spherical U238 (Th232) pusher, with the pusher accelerated to a velocity of ˜200 km/s, sufficient to ignite the DT gas placed in between the pusher and fissile core, resulting in a fast fusion neutron supported fission reaction in the core and pusher. Estimates indicate that a few kg of high explosives are sufficient to ignite such a "mini-nuke", with a gain of ˜103, releasing an energy equivalent to a few tons of TNT, still manageable for the microexplosion to be confined in a reactor vessel. A further reduction in the critical mass is possible by replacing the high explosive with fast moving solid projectiles. For light gas gun driven projectiles with a velocity of ˜ 10 km/s, the critical mass is estimated to be 0.25 g, and for magnetically accelerated 25 km/s projectiles it is as small as ˜ 0.05 g. With the much larger implosion velocities, reached by laser- or particle beam bombardment of the outer shell, the critical mass can still be much smaller with the fissile core serving as a fast ignitor. Increasing the implosion velocity decreases the overall radius of the fission-fusion assembly in inverse proportion to this velocity, for the 10 km/s light gas gun driven projectiles from 10 cm to 5 cm, for the 25 km/s magnetically projectiles down to 2 cm, and still more for higher implosion velocities.

  9. Discovery of a new mode of nuclear fission

    SciTech Connect

    Hulet, E.K.; Wild, J.F.; Dougan, R.J.; Lougheed, R.W.; Landrum, J.H.; Dougan, A.D.; Schaedel, M.; Hahn, R.L.; Baisden, P.A.; Henderson, C.M.

    1986-01-01

    We measured the mass and kinetic-energy partitioning in the spontaneous fission of /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, and /sup 260/(104). Surprisingly, these energy distributions were skewed upward or downward from the peak in each case, except for /sup 260/(104), indicating a composite of two energy distributions. We interpret this as a new mode of fission in which there is mixture of liquid-drop-like and fragment-shell-directed symmetric fission.

  10. Spontaneous Fission Modes and Lifetimes of Superheavy Elements in the Nuclear Density Functional Theory

    SciTech Connect

    Staszczak, A,

    2013-01-01

    Background: The reactions with the neutron-rich 48Ca beam and actinide targets resulted in the detection of new superheavy (SH) nuclides with Z=104 118. The unambiguous identification of the new isotopes, however, still poses a problem because their -decay chains terminate by spontaneous fission (SF) before reaching the known region of the nuclear chart. The understanding of the competition between -decay and SF channels in SH nuclei is, therefore, of crucial importance for our ability to map the SH region and to assess its extent.

    Purpose: We perform self-consistent calculations of the competing decay modes of even-even SH isotopes with 108 Z 126 and 148 N 188.

    Methods: We use the state-of-the-art computational framework based on self-consistent symmetry-unrestricted nuclear density functional theory capable of describing the competition between nuclear attraction and electrostatic repulsion. We apply the SkM* Skyrme energy density functional. The collective mass tensor of the fissioning superfluid nucleus is computed by means of the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (HFB) approach. This paper constitutes a systematic self-consistent study of spontaneous fission in the SH region, carried out at a full HFB level, that simultaneously takes into account both triaxiality and reflection asymmetry.

    Results: Breaking axial symmetry and parity turns out to be crucial for a realistic estimate of collective action; it results in lowering SF lifetimes by more than 7 orders of magnitude in some cases. We predict two competing SF modes: reflection symmetric modes and reflection asymmetric modes.

    Conclusions: The shortest-lived SH isotopes decay by SF; they are expected to lie in a narrow corridor formed by 280Hs, 284Fl, and 118284Uuo that separates the regions of SH nuclei synthesized in cold-fusion and hot-fusion reactions. The region of long-lived SH nuclei is expected to be centered on 294Ds with a total half-life of

  11. Fission product partitioning in aerosol release from simulated spent nuclear fuel

    NASA Astrophysics Data System (ADS)

    Di Lemma, F. G.; Colle, J. Y.; Rasmussen, G.; Konings, R. J. M.

    2015-10-01

    Aerosols created by the vaporization of simulated spent nuclear fuel (simfuel) were produced by laser heating techniques and characterised by a wide range of post-analyses. In particular attention has been focused on determining the fission product behaviour in the aerosols, in order to improve the evaluation of the source term and consequently the risk associated with release from spent fuel sabotage or accidents. Different simulated spent fuels were tested with burn-up up to 8 at. %. The results from the aerosol characterisation were compared with studies of the vaporization process by Knudsen Effusion Mass Spectrometry and thermochemical equilibrium calculations. These studies permit an understanding of the aerosol gaseous precursors and the gaseous reactions taking place during the aerosol formation process.

  12. Special features of the K = 0 channel in nuclear fission

    SciTech Connect

    Barabanov, A. L.; Furman, W. I.

    2009-08-15

    The opinion that the K = 0 fission channel is completely closed if the spin J and the parity {pi} of the nucleus undergoing fission do not satisfy the condition (-1){sup J} = {pi} is widespread. On the basis of a detailed analysis of quantum numbers characterizing the rotational states of deformed nuclei, it is shown that this opinion is erroneous. In fact, the K = 0 channel may be partly open. Its suppression is caused by special features of fission barriers in the state being considered. It is also shown that factors that suppress the K = 0channel may exist even in states characterized by J and {pi} values such that they satisfy the condition (-1){sup J} = {pi}. More precise information about the contribution of the K = 0 channel may be obtained by measuring the hexadecapole component of the angular distribution of fragments originating from the slow-neutron-induced fission of aligned nuclei.

  13. Cross sections and barriers for nuclear fission induced by high-energy nucleons

    SciTech Connect

    Grudzevich, O. T.; Yavshits, S. G.

    2013-03-15

    The cross sections for the fission of {sup 232}Th, {sup 235,238}U, {sup 237}Np, and {sup 239}Pu target nuclei that was induced by 20- to 1000-MeV neutrons and protons were calculated. The respective calculations were based on the multiconfiguration-fission (MCFx) model, which was used to describe three basic stages of the interaction of high-energy nucleons with nuclei: direct processes (intranuclear cascade), equilibration of the emerging compound system, and the decay of the compound nucleus (statistical model). Fission barriers were calculated within the microscopic approach for isotopic chains formed by 15 to 20 nuclei of the required elements. The calculated fission cross sections were compared with available experimental data. It was shown that the input data set and the theoretical model used made it possible to predict satisfactorily cross section for nuclear fission induced by 20- to 1000-MeV nucleons.

  14. Radiation re-solution of fission gas in non-oxide nuclear fuel

    NASA Astrophysics Data System (ADS)

    Matthews, Christopher; Schwen, Daniel; Klein, Andrew C.

    2015-02-01

    Renewed interest in fast nuclear reactors is creating a need for better understanding of fission gas bubble behavior in non-oxide fuels to support very long fuel lifetimes. Collisions between fission fragments and their subsequent cascades can knock fission gas atoms out of bubbles and back into the fuel lattice. We showed that these collisions can be treated as using the so-called "homogenous" atom-by-atom re-solution theory and calculated using the Binary Collision Approximation code 3DOT. The calculations showed that there is a decrease in the re-solution parameter as bubble radius increases until about 50 nm, at which the re-solution parameter stays nearly constant. Furthermore, our model shows ion cascades created in the fuel result in many more implanted fission gas atoms than collisions directly with fission fragments. This calculated re-solution parameter can be used to find a re-solution rate for future bubble simulations.

  15. Light charged particles emitted in fission reactions induced by protons on 208Pb

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Paradela, C.; Ayyad, Y.; Casarejos, E.; Alvarez-Pol, H.; Audouin, L.; Bélier, G.; Boutoux, G.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.

    2016-09-01

    Light charged particles emitted in proton-induced fission reactions on 208Pb have been measured at different kinetic energies: 370 A ,500 A , and 650 A MeV. The experiment was performed by the SOFIA Collaboration at the GSI facilities in Darmstadt (Germany). The inverse kinematics technique was combined with a setup especially designed to measure light charged particles in coincidence with fission fragments. This measurement allowed us, for the first time, to obtain correlations between the light charged particles emitted during the fission process and the charge distributions of the fission fragments. These correlations were compared with different model calculations to assess the ground-to-saddle dynamics. The results confirm that transient and dissipative effects are required for an accurate description of the fission observables.

  16. Molecular screening in nuclear reactions

    NASA Astrophysics Data System (ADS)

    Cvetinovic, A.; Lipoglavsek, M.; Markelj, S.; Vesic, J.

    2015-12-01

    The dependence of electron screening in nuclear reactions on projectile or target atomic number has been studied by bombarding different hydrogen-containing targets with beams of 7Li , 11B , and 19F . The largest electron screening potentials were obtained in a graphite target containing hydrogen as an impurity. Some measured potentials are almost two orders of magnitude above the theoretical predictions. To explain the measurements, a new concept of electron screening is introduced.

  17. Quasifission and fusion-fission in reactions with massive nuclei: Comparison of reactions leading to the Z=120 element

    SciTech Connect

    Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Manganaro, M.; Hanappe, F.; Heinz, S.; Hofmann, S.; Muminov, A. I.; Scheid, W.

    2009-02-15

    The yields of evaporation residues, fusion-fission, and quasifission fragments in the {sup 48}Ca+{sup 144,154}Sm and {sup 16}O+{sup 186}W reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the {sup 48}Ca+{sup 154}Sm reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in {sup 48}Ca+{sup 154}Sm at the large collision energies and the lack of quasifission fragments in the {sup 48}Ca+{sup 144}Sm reaction are explained by the overlap in mass angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element Z=120 (A=302) show that the {sup 54}Cr+{sup 248}Cm reaction is preferable in comparison with the {sup 58}Fe+{sup 244}Pu and {sup 64}Ni+{sup 238}U reactions because the excitation function of the evaporation residues of the former reaction is some orders of magnitude larger than that for the last two reactions.

  18. Nuclear Reactions for Astrophysics and Other Applications

    SciTech Connect

    Escher, J E; Burke, J T; Dietrich, F S; Scielzo, N D; Ressler, J J

    2011-03-01

    Cross sections for compound-nuclear reactions are required for many applications. The surrogate nuclear reactions method provides an indirect approach for determining cross sections for reactions on unstable isotopes, which are difficult or impossible to measure otherwise. Current implementations of the method provide useful cross sections for (n,f) reactions, but need to be improved upon for applications to capture reactions.

  19. Nucleon localization and fragment formation in nuclear fission

    NASA Astrophysics Data System (ADS)

    Zhang, C. L.; Schuetrumpf, B.; Nazarewicz, W.

    2016-12-01

    Background: An electron localization measure was originally introduced to characterize chemical bond structures in molecules. Recently, a nucleon localization based on Hartree-Fock densities has been introduced to investigate α -cluster structures in light nuclei. Compared to the local nucleonic densities, the nucleon localization function has been shown to be an excellent indicator of shell effects and cluster correlations. Purpose: Using the spatial nucleon localization measure, we investigate the emergence of fragments in fissioning heavy nuclei. Methods: To illustrate basic concepts of nucleon localization, we employ the self-consistent energy density functional method with a quantified energy density functional optimized for fission studies. Results: We study the particle densities and spatial nucleon localization distributions along the fission pathways of 264Fm, 232Th, and 240Pu. We demonstrate that the fission fragments are formed fairly early in the evolution, well before scission. We illustrate the usefulness of the localization measure by showing how the hyperdeformed state of 232Th can be understood in terms of a quasimolecular state made of 132Sn and 100Zr fragments. Conclusions: Compared to nucleonic distributions, the nucleon localization function more effectively quantifies nucleonic clustering: its characteristic oscillating pattern, traced back to shell effects, is a clear fingerprint of cluster/fragment configurations. This is of particular interest for studies of fragment formation and fragment identification in fissioning nuclei.

  20. Estimates of fission yields in nuclear criticality excursions

    SciTech Connect

    Choi, J.S.; Thompson, J.W.; Reed, R.

    1995-06-01

    There is a need for computer simulation of hypothetical criticality excursions involving significant quantities of fissionable materials, especially in fissile aqueous system. The need arises due to the requirements for the emergency planning of facilities where the fissionable materials are handled, processed, or stored; and the regulatory requirements associated with facility operation or conversion. It is proposed here that a data base of fission yeilds for critical experiments and known accidents (both aqueous and solid) should be generated by using existing or new computer codes. The success in compiling this data base would provide useful source-terms for criticality excursions, realistic estimates of emergency-response boundary, as well as a replacement for the ``rule-of-thumb`` or ``bounding`` method. 10 refs.

  1. Mechanical and molecular basis for the symmetrical division of the fission yeast nuclear envelope.

    PubMed

    Castagnetti, Stefania; Božič, Bojan; Svetina, Saša

    2015-06-28

    In fission yeast Schizosaccharomyces pombe, the nuclear envelope remains intact throughout mitosis and undergoes a series of symmetrical morphological changes when the spindle pole bodies (SPBs), embedded in the nuclear envelope, are pushed apart by elongating spindle microtubules. These symmetrical membrane shape transformations do not correspond to the shape behavior of an analogous system based on lipid vesicles. Here we report that the symmetry of the dividing fission yeast nucleus is ensured by SPB-chromosome attachments, as loss of kinetochore clustering in the vicinity of SPBs results in the formation of abnormal asymmetric shapes with long membrane tethers. We integrated these findings in a biophysical model, which explains the symmetry of the nuclear shapes on the basis of forces exerted by chromosomes clustered at SPBs on the extending nuclear envelope. Based on this analysis we conclude that the fission yeast nuclear envelope exhibits the same mechanical properties as simple lipid vesicles, but interactions with other cellular components, such as chromosomes, influence the nuclear shape during mitosis, allowing the formation of otherwise energetically unfavorable symmetrical dumbbell structures upon spindle elongation. The model allows us to explain the appearance of abnormal asymmetric shapes in fission yeast mutants with mis-segregated chromosomes as well as with altered nuclear membrane composition.

  2. ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data

    SciTech Connect

    Chadwick, M.B.; Herman, M.; Author : Chadwick,M.B.; Herman,M.; Oblozinsky,P.; Dunn,M.E.; Danon,Y.; Kahler,A.C.; Smith,D.L.; Pritychenko,B.; Arbanas,G.; Arcilla,R.; Brewer,R.; Brown,D.A.; Capote,R.; Carlson,A.D.; Cho,Y.S.; Derrien,H.; Guber,K.; Hale,G.M.; Hoblit,S.; Holloway,S.: Johnson,T.D.; Kawano,T.; Kiedrowski,B.C.; Kim,H.; Kunieda,S.; Larson,N.M.; Leal,L.; Lestone,J.P.; Little,R.C.; McCutchan,E.A.; MacFarlane,R.E.; MacInnes,M.; Mattoon,C.M.; McKnight,R.D.; Mughabghab,S.F.; Nobre,G.P.A.; Palmiotti,G.; Palumbo,A.; Pigni,M.T.; Pronyaev,V.G.; Sayer,R.O.; Sonzogni,A.A.; Summers,N.C.; Talou,P.; Thompson,I.J.; Trkov,A.; Vogt,R.L.; van der Marck,S.C.; Wallner,A.; White,M.C.; Wiarda,D.; Young,P.G.

    2011-12-01

    The ENDF/B-VII.1 library is our latest recommended evaluated nuclear data file for use in nuclear science and technology applications, and incorporates advances made in the five years since the release of ENDF/B-VII.0. These advances focus on neutron cross sections, covariances, fission product yields and decay data, and represent work by the US Cross Section Evaluation Working Group (CSEWG) in nuclear data evaluation that utilizes developments in nuclear theory, modeling, simulation, and experiment. The principal advances in the new library are: (1) An increase in the breadth of neutron reaction cross section coverage, extending from 393 nuclides to 423 nuclides; (2) Covariance uncertainty data for 190 of the most important nuclides, as documented in companion papers in this edition; (3) R-matrix analyses of neutron reactions on light nuclei, including isotopes of He, Li, and Be; (4) Resonance parameter analyses at lower energies and statistical high energy reactions for isotopes of Cl, K, Ti, V, Mn, Cr, Ni, Zr and W; (5) Modifications to thermal neutron reactions on fission products (isotopes of Mo, Tc, Rh, Ag, Cs, Nd, Sm, Eu) and neutron absorber materials (Cd, Gd); (6) Improved minor actinide evaluations for isotopes of U, Np, Pu, and Am (we are not making changes to the major actinides {sup 235,238}U and {sup 239}Pu at this point, except for delayed neutron data and covariances, and instead we intend to update them after a further period of research in experiment and theory), and our adoption of JENDL-4.0 evaluations for isotopes of Cm, Bk, Cf, Es, Fm, and some other minor actinides; (7) Fission energy release evaluations; (8) Fission product yield advances for fission-spectrum neutrons and 14 MeV neutrons incident on {sup 239}Pu; and (9) A new decay data sublibrary. Integral validation testing of the ENDF/B-VII.1 library is provided for a variety of quantities: For nuclear criticality, the VII.1 library maintains the generally-good performance seen for VII.0

  3. ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data

    NASA Astrophysics Data System (ADS)

    Chadwick, M. B.; Herman, M.; Obložinský, P.; Dunn, M. E.; Danon, Y.; Kahler, A. C.; Smith, D. L.; Pritychenko, B.; Arbanas, G.; Arcilla, R.; Brewer, R.; Brown, D. A.; Capote, R.; Carlson, A. D.; Cho, Y. S.; Derrien, H.; Guber, K.; Hale, G. M.; Hoblit, S.; Holloway, S.; Johnson, T. D.; Kawano, T.; Kiedrowski, B. C.; Kim, H.; Kunieda, S.; Larson, N. M.; Leal, L.; Lestone, J. P.; Little, R. C.; McCutchan, E. A.; MacFarlane, R. E.; MacInnes, M.; Mattoon, C. M.; McKnight, R. D.; Mughabghab, S. F.; Nobre, G. P. A.; Palmiotti, G.; Palumbo, A.; Pigni, M. T.; Pronyaev, V. G.; Sayer, R. O.; Sonzogni, A. A.; Summers, N. C.; Talou, P.; Thompson, I. J.; Trkov, A.; Vogt, R. L.; van der Marck, S. C.; Wallner, A.; White, M. C.; Wiarda, D.; Young, P. G.

    2011-12-01

    The ENDF/B-VII.1 library is our latest recommended evaluated nuclear data file for use in nuclear science and technology applications, and incorporates advances made in the five years since the release of ENDF/B-VII.0. These advances focus on neutron cross sections, covariances, fission product yields and decay data, and represent work by the US Cross Section Evaluation Working Group (CSEWG) in nuclear data evaluation that utilizes developments in nuclear theory, modeling, simulation, and experiment. The principal advances in the new library are: (1) An increase in the breadth of neutron reaction cross section coverage, extending from 393 nuclides to 423 nuclides; (2) Covariance uncertainty data for 190 of the most important nuclides, as documented in companion papers in this edition; (3) R-matrix analyses of neutron reactions on light nuclei, including isotopes of He, Li, and Be; (4) Resonance parameter analyses at lower energies and statistical high energy reactions for isotopes of Cl, K, Ti, V, Mn, Cr, Ni, Zr and W; (5) Modifications to thermal neutron reactions on fission products (isotopes of Mo, Tc, Rh, Ag, Cs, Nd, Sm, Eu) and neutron absorber materials (Cd, Gd); (6) Improved minor actinide evaluations for isotopes of U, Np, Pu, and Am (we are not making changes to the major actinides 235,238U and 239Pu at this point, except for delayed neutron data and covariances, and instead we intend to update them after a further period of research in experiment and theory), and our adoption of JENDL-4.0 evaluations for isotopes of Cm, Bk, Cf, Es, Fm, and some other minor actinides; (7) Fission energy release evaluations; (8) Fission product yield advances for fission-spectrum neutrons and 14 MeV neutrons incident on 239Pu; and (9) A new decay data sublibrary. Integral validation testing of the ENDF/B-VII.1 library is provided for a variety of quantities: For nuclear criticality, the VII.1 library maintains the generally-good performance seen for VII.0 for a wide range

  4. A separate effect study of the influence of metallic fission products on CsI radioactive release from nuclear fuel

    NASA Astrophysics Data System (ADS)

    Di Lemma, F. G.; Colle, J. Y.; Beneš, O.; Konings, R. J. M.

    2015-10-01

    The chemistry of cesium and iodine is of main importance to quantify the radioactive release in case of a nuclear reactor accident, or sabotage involving irradiated nuclear materials. We studied the interaction of CsI with different metallic fission products such as Mo and Ru. These elements can be released from nuclear fuel when exposed to oxidising conditions, as in the case of contact of overheated nuclear fuel with air (e.g. in a spent fuel cask sabotage, uncovering of a spent fuel pond, or air ingress accidents). Experiments were performed by vaporizing mixtures of the compounds in air, and analysing the produced aerosols in view of a possible gas-gas and gas-aerosol reactions between the compounds. These results were compared with the gaseous species predicted by thermochemical equilibrium calculations and experimental equilibrium vaporization tests using Knudsen Effusion Mass Spectrometry.

  5. Curved Waveguide Based Nuclear Fission for Small, Lightweight Reactors

    NASA Technical Reports Server (NTRS)

    Coker, Robert; Putnam, Gabriel

    2012-01-01

    The focus of the presented work is on the creation of a system of grazing incidence, supermirror waveguides for the capture and reuse of fission sourced neutrons. Within research reactors, neutron guides are a well known tool for directing neutrons from the confined and hazardous central core to a more accessible testing or measurement location. Typical neutron guides have rectangular, hollow cross sections, which are crafted as thin, mirrored waveguides plated with metal (commonly nickel). Under glancing angles with incoming neutrons, these waveguides can achieve nearly lossless transport of neutrons to distant instruments. Furthermore, recent developments have created supermirror surfaces which can accommodate neutron grazing angles up to four times as steep as nickel. A completed system will form an enclosing ring or spherical resonator system to a coupled neutron source for the purpose of capturing and reusing free neutrons to sustain and/or accelerate fission. While grazing incidence mirrors are a known method of directing and safely using neutrons, no method has been disclosed for capture and reuse of neutrons or sustainment of fission using a circular waveguide structure. The presented work is in the process of fabricating a functional, highly curved, neutron supermirror using known methods of Ni-Ti layering capable of achieving incident reflection angles up to four times steeper than nickel alone. Parallel work is analytically investigating future geometries, mirror compositions, and sources for enabling sustained fission with applicability to the propulsion and energy goals of NASA and other agencies. Should research into this concept prove feasible, it would lead to development of a high energy density, low mass power source potentially capable of sustaining fission with a fraction of the standard critical mass for a given material and a broadening of feasible materials due to reduced rates of release, absorption, and non-fission for neutrons. This

  6. Extended optical model for fission

    SciTech Connect

    Sin, M.; Capote, R.; Herman, M. W.; Trkov, A.

    2016-03-07

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier is used for 234,235U(n,f), while a double-humped fission barrier is used for 238U(n,f) and 239Pu(n,f) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n,f) reactions. The 239Pu(n,f) reaction can be calculated in the complete damping approximation. Calculated cross sections for 235,238U(n,f) and 239Pu(n,f) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. Lastly, the extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.

  7. Extended optical model for fission

    DOE PAGES

    Sin, M.; Capote, R.; Herman, M. W.; ...

    2016-03-07

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier ismore » used for 234,235U(n,f), while a double-humped fission barrier is used for 238U(n,f) and 239Pu(n,f) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n,f) reactions. The 239Pu(n,f) reaction can be calculated in the complete damping approximation. Calculated cross sections for 235,238U(n,f) and 239Pu(n,f) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. Lastly, the extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.« less

  8. Extended optical model for fission

    NASA Astrophysics Data System (ADS)

    Sin, M.; Capote, R.; Herman, M. W.; Trkov, A.

    2016-03-01

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier is used for U,235234(n ,f ) , while a double-humped fission barrier is used for 238U(n ,f ) and 239Pu(n ,f ) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n ,f ) reactions. The 239Pu(n ,f ) reaction can be calculated in the complete damping approximation. Calculated cross sections for U,238235(n ,f ) and 239Pu(n ,f ) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. The extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.

  9. Power deposition in volumetric /U-235/F6-He fission-pumped nuclear lasers

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Deyoung, R. J.

    1978-01-01

    The power deposition in (U-235)F6-He fission-pumped nuclear lasers is studied. Specifically, means to maximize the energy density in the He gas are assessed. Primary loss mechanisms are identified as the fission-fragment transport to the laser-cell wall and UF6 gas excitation. The losses are thus strongly dependent on UF6 concentration. It is found that maximum power will be deposited in a laser tube when the tube radius is as large as the range of fission fragments. Experimental results indicate that when the tube radius equals the fission-fragment range, the ratio of a UF6 partial pressure to total pressure is 0.15, and the UF6-He mixing ratio is 1:6, maximum power will be deposited.

  10. An Inconvenient History: the Nuclear-Fission Display in the Deutsches Museum

    NASA Astrophysics Data System (ADS)

    Sime, Ruth Lewin

    2010-06-01

    One of the longstanding attractions of the Deutsches Museum in Munich, Germany, has been its display of the apparatus associated with the discovery of nuclear fission. Although the discovery involved three scientists, Otto Hahn, Lise Meitner, and Fritz Strassmann, the fission display was designated for over 30 years as the Arbeitstisch von Otto Hahn (Otto Hahn’s Worktable), with Strassmann mentioned peripherally and Meitner not at all, and it was not until the early 1990s that the display was revised to include all three codiscoverers more equitably. I examine the creation of the fission display in the context of the postwar German culture of silencing the National Socialist past, and trace the eventual transformation of the display into a contemporary exhibit that more accurately represents the scientific history of the fission discovery.

  11. Microscopic Calculation of Fission Fragment Energies for the 239Pu(nth,f) Reaction

    SciTech Connect

    Younes, W; Gogny, D

    2011-10-03

    We calculate the total kinetic and excitation energies of fragments produced in the thermal-induced fission of {sup 239}Pu. This result is a proof-of-principle demonstration for a microscopic approach to the calculation of fission-fragment observables for applied data needs. In addition, the calculations highlight the application of a fully quantum mechanical description of scission, and the importance of exploring scission configurations as a function of the moments of the fragments, rather than through global constraints on the moments of the fissioning nucleus. Using a static microscopic calculation of configurations at and near scission, we have identified fission fragments for the {sup 239}Pu (n{sub th}, f) reaction and extracted their total kinetic and excitation energies. Comparison with data shows very good overall agreement between theory and experiment. Beyond their success as a proof of principle, these calculations also highlight the importance of local constraints on the fragments themselves in microscopic calculations.

  12. Direct Reactions for Nuclear Structure and Nuclear Astrophysics

    SciTech Connect

    Jones, Katherine Louise

    2014-12-18

    Direct reactions are powerful probes for studying the atomic nucleus. Modern direct reaction studies are illuminating both the fundamental nature of the nucleus and its role in nucleosynthetic processes occurring in the cosmos. This report covers experiments using knockout reactions on neutron-deficient fragmentation beams, transfer reactions on fission fragment beams, and theoretical sensitivity studies relating to the astrophysical r-process. Results from experiments on 108,106Sn at the NSCL, and on 131Sn at HRIBF are presented as well as the results from the nucleosynthesis study.

  13. Towards many-body based nuclear reaction modelling

    NASA Astrophysics Data System (ADS)

    Hilaire, Stéphane; Goriely, Stéphane

    2016-06-01

    The increasing need for cross sections far from the valley of stability poses a challenge for nuclear reaction models. So far, predictions of cross sections have relied on more or less phenomenological approaches, depending on parameters adjusted to available experimental data or deduced from systematic expressions. While such predictions are expected to be reliable for nuclei not too far from the experimentally known regions, it is clearly preferable to use more fundamental approaches, based on sound physical principles, when dealing with very exotic nuclei. Thanks to the high computer power available today, all the ingredients required to model a nuclear reaction can now be (and have been) microscopically (or semi-microscopically) determined starting from the information provided by a nucleon-nucleon effective interaction. This concerns nuclear masses, optical model potential, nuclear level densities, photon strength functions, as well as fission barriers. All these nuclear model ingredients, traditionally given by phenomenological expressions, now have a microscopic counterpart implemented in the TALYS nuclear reaction code. We are thus now able to perform fully microscopic cross section calculations. The quality of these ingredients and the impact of using them instead of the usually adopted phenomenological parameters will be discussed. Perspectives for the coming years will be drawn on the improvements one can expect.

  14. Non-Nuclear Testing of Fission Technologies at NASA MSFC

    NASA Technical Reports Server (NTRS)

    Houts, Robert G.; Pearson, J. Boise; Aschenbrenner, Kenneth C.; Bradley, David E.; Dickens, Ricky E.; Emrich, William J.; Garber, Anne E.; Godfroy, Thomas J.; Harper, Roger T.; Martin, Jim J.; Polzin, Kurt A.; Schoenfeld, Michael P.; Webster, Kenneth L.

    2011-01-01

    Highly realistic non-nuclear testing can be used to investigate and resolve potential issues with space nuclear power and propulsion systems. Non-nuclear testing is particularly useful for systems designed with fuels and materials operating within their demonstrated nuclear performance envelope. Non-nuclear testing also provides an excellent way for screening potential advanced fuels and materials prior to nuclear testing, and for investigating innovative geometries and operating regimes. Non-nuclear testing allows thermal hydraulic, heat transfer, structural, integration, safety, operational, performance, and other potential issues to be investigated and resolved with a greater degree of flexibility and at reduced cost and schedule compared to nuclear testing. The primary limit of non-nuclear testing is that nuclear characteristics and potential nuclear issues cannot be directly investigated. However, non-nuclear testing can be used to augment the potential benefit from any nuclear testing that may be required for space nuclear system design and development. This paper describes previous and ongoing non-nuclear testing related to space nuclear systems at NASA s Marshall Space Flight Center (MSFC).

  15. Fission yeast cells undergo nuclear division in the absence of spindle microtubules.

    PubMed

    Castagnetti, Stefania; Oliferenko, Snezhana; Nurse, Paul

    2010-10-12

    Mitosis in eukaryotic cells employs spindle microtubules to drive accurate chromosome segregation at cell division. Cells lacking spindle microtubules arrest in mitosis due to a spindle checkpoint that delays mitotic progression until all chromosomes have achieved stable bipolar attachment to spindle microtubules. In fission yeast, mitosis occurs within an intact nuclear membrane with the mitotic spindle elongating between the spindle pole bodies. We show here that in fission yeast interference with mitotic spindle formation delays mitosis only briefly and cells proceed to an unusual nuclear division process we term nuclear fission, during which cells perform some chromosome segregation and efficiently enter S-phase of the next cell cycle. Nuclear fission is blocked if spindle pole body maturation or sister chromatid separation cannot take place or if actin polymerization is inhibited. We suggest that this process exhibits vestiges of a primitive nuclear division process independent of spindle microtubules, possibly reflecting an evolutionary intermediate state between bacterial and Archeal chromosome segregation where the nucleoid divides without a spindle and a microtubule spindle-based eukaryotic mitosis.

  16. EMPIRE: Nuclear Reaction Model Code System for Data Evaluation

    NASA Astrophysics Data System (ADS)

    Herman, M.; Capote, R.; Carlson, B. V.; Obložinský, P.; Sin, M.; Trkov, A.; Wienke, H.; Zerkin, V.

    2007-12-01

    EMPIRE is a modular system of nuclear reaction codes, comprising various nuclear models, and designed for calculations over a broad range of energies and incident particles. A projectile can be a neutron, proton, any ion (including heavy-ions) or a photon. The energy range extends from the beginning of the unresolved resonance region for neutron-induced reactions (∽ keV) and goes up to several hundred MeV for heavy-ion induced reactions. The code accounts for the major nuclear reaction mechanisms, including direct, pre-equilibrium and compound nucleus ones. Direct reactions are described by a generalized optical model (ECIS03) or by the simplified coupled-channels approach (CCFUS). The pre-equilibrium mechanism can be treated by a deformation dependent multi-step direct (ORION + TRISTAN) model, by a NVWY multi-step compound one or by either a pre-equilibrium exciton model with cluster emission (PCROSS) or by another with full angular momentum coupling (DEGAS). Finally, the compound nucleus decay is described by the full featured Hauser-Feshbach model with γ-cascade and width-fluctuations. Advanced treatment of the fission channel takes into account transmission through a multiple-humped fission barrier with absorption in the wells. The fission probability is derived in the WKB approximation within the optical model of fission. Several options for nuclear level densities include the EMPIRE-specific approach, which accounts for the effects of the dynamic deformation of a fast rotating nucleus, the classical Gilbert-Cameron approach and pre-calculated tables obtained with a microscopic model based on HFB single-particle level schemes with collective enhancement. A comprehensive library of input parameters covers nuclear masses, optical model parameters, ground state deformations, discrete levels and decay schemes, level densities, fission barriers, moments of inertia and γ-ray strength functions. The results can be converted into ENDF-6 formatted files using the

  17. Fission yield measurements at IGISOL

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  18. Vesicle-like biomechanics governs important aspects of nuclear geometry in fission yeast.

    PubMed

    Lim H W, Gerald; Huber, Greg; Torii, Yoshihiro; Hirata, Aiko; Miller, Jonathan; Sazer, Shelley

    2007-09-26

    It has long been known that during the closed mitosis of many unicellular eukaryotes, including the fission yeast (Schizosaccharomyces pombe), the nuclear envelope remains intact while the nucleus undergoes a remarkable sequence of shape transformations driven by elongation of an intranuclear mitotic spindle whose ends are capped by spindle pole bodies embedded in the nuclear envelope. However, the mechanical basis of these normal cell cycle transformations, and abnormal nuclear shapes caused by intranuclear elongation of microtubules lacking spindle pole bodies, remain unknown. Although there are models describing the shapes of lipid vesicles deformed by elongation of microtubule bundles, there are no models describing normal or abnormal shape changes in the nucleus. We describe here a novel biophysical model of interphase nuclear geometry in fission yeast that accounts for critical aspects of the mechanics of the fission yeast nucleus, including the biophysical properties of lipid bilayers, forces exerted on the nuclear envelope by elongating microtubules, and access to a lipid reservoir, essential for the large increase in nuclear surface area during the cell cycle. We present experimental confirmation of the novel and non-trivial geometries predicted by our model, which has no free parameters. We also use the model to provide insight into the mechanical basis of previously described defects in nuclear division, including abnormal nuclear shapes and loss of nuclear envelope integrity. The model predicts that (i) despite differences in structure and composition, fission yeast nuclei and vesicles with fluid lipid bilayers have common mechanical properties; (ii) the S. pombe nucleus is not lined with any structure with shear resistance, comparable to the nuclear lamina of higher eukaryotes. We validate the model and its predictions by analyzing wild type cells in which ned1 gene overexpression causes elongation of an intranuclear microtubule bundle that deforms the

  19. Future research program on prompt γ-ray emission in nuclear fission

    NASA Astrophysics Data System (ADS)

    Oberstedt, S.; Billnert, R.; Hambsch, F.-J.; Lebois, M.; Oberstedt, A.; Wilson, J. N.

    2015-12-01

    In recent years the measurement of prompt fission γ-ray spectra (PFGS) has gained renewed interest, after about forty years since the first comprehensive studies of the reactions 235U(n th , f), 239Pu(n th ,f) and 252Cf(sf). The renaissance was initiated by requests for new values especially for γ-ray multiplicity and average total energy release per fission in neutron-induced fission of 235U and 239Pu. Both isotopes are considered the most important ones with respect to the modeling of innovative cores required for the Generation-IV reactors, the majority working with fast neutrons. During the last 5 years we have conducted a systematic study of spectral data for thermal-neutron-induced fission on 235U and 241Pu as well as for the spontaneous fission of 252Cf with unprecedented accuracy. From the new data we conclude that those reactions do not considerably contribute to the observed heat excess and suspect other reactions playing a significant role. Possible contributions may originate from fast-neutron-induced reactions on 238U, which is largely present in the fuel, or from γ-induced fission from neutron capture in the construction material. A first experiment campaign on prompt γ-ray emission from fast-neutron-induced fission on 235,238U was successfully performed in order to test our assumptions. In the following we attempt to summarize, what has been done in the field to date, and to motivate future measurement campaigns exploiting dedicated neutron and photon beams as well as upcoming highly efficient detector assemblies.

  20. ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data

    SciTech Connect

    Chadwick, M. B.; Herman, Micheal W; Oblozinsky, Pavel; Dunn, Michael E; Danon, Y.; Kahler, A.; Smith, Donald L.; Pritychenko, B; Arbanas, Goran; Arcilla, r; Brewer, R; Brown, D A; Capote, R.; Carlson, A. D.; Cho, Y S; Derrien, Herve; Guber, Klaus H; Hale, G. M.; Hoblit, S; Holloway, Shannon T.; Johnson, T D; Kawano, T.; Kiedrowski, B C; Kim, H; Kunieda, S; Larson, Nancy M; Leal, Luiz C; Lestone, J P; Little, R C; Mccutchan, E A; Macfarlane, R E; MacInnes, M; Matton, C M; Mcknight, R D; Mughabghab, S F; Nobre, G P; Palmiotti, G; Palumbo, A; Pigni, Marco T; Pronyaev, V. G.; Sayer, Royce O; Sonzogni, A A; Summers, N C; Talou, P; Thompson, I J; Trkov, A.; Vogt, R L; Van der Marck, S S; Wallner, A; White, M C; Wiarda, Dorothea; Young, P C

    2011-01-01

    The ENDF/B-VII.1 library is our latest recommended evaluated nuclear data file for use in nuclear science and technology applications, and incorporates advances made in the five years since the release of ENDF/B-VII.0. These advances focus on neutron cross sections, covariances, fission product yields and decay data, and represent work by the US Cross Section Evaluation Working Group (CSEWG) in nuclear data evaluation that utilizes developments in nuclear theory, modeling, simulation, and experiment. The principal advances in the new library are: (1) An increase in the breadth of neutron reaction cross section coverage, extending from 393 nuclides to 423 nuclides; (2) Covariance uncertainty data for 190 of the most important nuclides, as documented in companion papers in this edition; (3) R-matrix analyses of neutron reactions on light nuclei, including isotopes of He; Li, and Be; (4) Resonance parameter analyses at lower energies and statistical high energy reactions for isotopes of Cl; K; Ti, V, Mn, Cr, Ni, Zr and W; (5) Modifications to thermal neutron reactions on fission products (isotopes of Mo, Tc, Rh, Ag, Cs, Nd, Sm, Eu) and neutron absorber materials (Cd, Gd); (6) Improved minor actinide evaluations for isotopes of U, Np, Pu, and Am (we are not making changes to the major actinides (235,238)U and (239)Pu at this point, except for delayed neutron data and covariances, and instead we intend to update them after a further period of research in experiment and theory), and our adoption of JENDL-4.0 evaluations for isotopes of Cm, Bk, Cf, Es; Fm; and some other minor actinides; (7) Fission energy release evaluations; (8) Fission product yield advances for fission-spectrum neutrons and 14 MeV neutrons incident on (239)Pu; and (9) A new decay data sublibrary. Integral validation testing of the ENDF/B-VII.1 library is provided for a variety of quantities: For nuclear criticality, the VII.1 library maintains the generally-good performance seen for VII.0 for a wide

  1. The number of PML nuclear bodies increases in early S phase by a fission mechanism.

    PubMed

    Dellaire, Graham; Ching, Reagan W; Dehghani, Hesam; Ren, Ying; Bazett-Jones, David P

    2006-03-15

    Promyelocytic leukemia (PML) nuclear bodies have been implicated in a variety of cellular processes including apoptosis, tumour suppression, anti-viral response, DNA repair and transcriptional regulation. PML nuclear bodies are both positionally and structurally stable over extended periods of interphase. As demonstrated in this study, the structural stability is lost as cells enter S phase, evidenced both by distortions in shape and by fission and fusion events. At the end of this period of structural instability, the number of PML nuclear bodies has increased by a factor of twofold. Association of the fission products with chromatin implies that the PML nuclear bodies respond to changes in chromatin organisation or topology, and thus could play a role in monitoring genome integrity during DNA synthesis or in the continued maintenance of functional chromosomal domains prior to mitosis.

  2. Nuclear reaction inputs based on effective interactions

    NASA Astrophysics Data System (ADS)

    Hilaire, S.; Goriely, S.; Péru, S.; Dubray, N.; Dupuis, M.; Bauge, E.

    2016-11-01

    Extensive nuclear structure studies have been performed for decades using effective interactions as sole input. They have shown a remarkable ability to describe rather accurately many types of nuclear properties. In the early 2000s, a major effort has been engaged to produce nuclear reaction input data out of the Gogny interaction, in order to challenge its quality also with respect to nuclear reaction observables. The status of this project, well advanced today thanks to the use of modern computers as well as modern nuclear reaction codes, is reviewed and future developments are discussed.

  3. Politics, Chemistry, and the Discovery of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Wiesner, Emilie; Settle, Frank A., Jr.

    2001-07-01

    The discovery of fission is an interesting scientific saga involving the fundamentals of chemistry and physics. It is played out in the late 1930s on a European stage. Lise Meitner and Otto Hahn head a cast of characters that include scientific notables Fritz Strassmann, Otto Frisch, James Chadwick, Enrico Fermi, Ida Noddack, Irene Curie, and Neils Bohr. The plot includes the scientific method, the interdependence of chemistry and physics, the influence of external politics, and human frailty. The events surrounding this discovery did not allow the scientists involved to receive equal recognition. Fortunately, the passage of time and extensive historical research are restoring equality.

  4. Fission yeast Lem2 and Man1 perform fundamental functions of the animal cell nuclear lamina.

    PubMed

    Gonzalez, Yanira; Saito, Akira; Sazer, Shelley

    2012-01-01

    In animal cells the nuclear lamina, which consists of lamins and lamin-associated proteins, serves several functions: it provides a structural scaffold for the nuclear envelope and tethers proteins and heterochromatin to the nuclear periphery. In yeast, proteins and large heterochromatic domains including telomeres are also peripherally localized, but there is no evidence that yeast have lamins or a fibrous nuclear envelope scaffold. Nonetheless, we found that the Lem2 and Man1 proteins of the fission yeast Schizosaccharomyces pombe, evolutionarily distant relatives of the Lap2/Emerin/Man1 (LEM) sub-family of animal cell lamin-associated proteins, perform fundamental functions of the animal cell lamina. These integral inner nuclear membrane localized proteins, with nuclear localized DNA binding Helix-Extension-Helix (HEH) domains, impact nuclear envelope structure and integrity, are essential for the enrichment of telomeres at the nuclear periphery and by means of their HEH domains anchor chromatin, most likely transcriptionally repressed heterochromatin, to the nuclear periphery. These data indicate that the core functions of the nuclear lamina are conserved between fungi and animal cells and can be performed in fission yeast, without lamins or other intermediate filament proteins.

  5. The Fukushima nuclear disaster and its effects on media framing of fission and fusion energy technologies

    SciTech Connect

    Schmidt, Luisa; Horta, Ana; Pereira, Sergio; Delicado, Ana

    2015-07-01

    This paper presents results of a comparison of media coverage of fusion and fission energy technologies in three countries (Germany, Spain and Portugal) and in the English language international print media addressing transnational elite, from 2008 to 2012. The analysis showed that the accident in Fukushima in March 2010 did not have significant impact on media framing of nuclear fusion in the major part of print media under investigation. In fact, fusion is clearly dissociated from traditional nuclear (fission) energy and from nuclear accidents. It tends to be portrayed as a safe, clean and unlimited source of energy, although less credited when confronted with research costs, technological feasibility and the possibility to be achieved in a reasonable period of time. On the contrary, fission is portrayed as a hazardous source of energy, expensive when compared to research costs of renewables, hardly a long-term energy option, susceptible to contribute to the proliferation of nuclear weapons or rogue military use. Fukushima accident was consistently discussed in the context of safety problems of nuclear power plants and in many cases appeared not as an isolated event but rather as a reminder of previous nuclear disasters such as Three Miles Island and Chernobyl. (authors)

  6. Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)

    SciTech Connect

    Karnaukhov, V. A.; Oeschler, H.; Budzanowski, A.; Avdeyev, S. P.; Botvina, A. S.; Cherepanov, E. A.; Karcz, W.; Kirakosyan, V. V.; Rukoyatkin, P. A.; Skwirczynska, I.; Norbeck, E.

    2008-12-15

    Critical temperature T{sub c} for the nuclear liquid-gas phase transition is estimated from both the multifragmentation and fission data. In the first case, the critical temperature is obtained by analysis of the intermediate-mass-fragment yields in p(8.1 GeV) + Au collisions within the statistical model of multifragmentation. In the second case, the experimental fission probability for excited {sup 188}Os is compared with the calculated one with T{sub c} as a free parameter. It is concluded for both cases that the critical temperature is higher than 15 MeV.

  7. Accelerator-driven subcritical fission in molten salt core: Closing the nuclear fuel cycle for green nuclear energy

    SciTech Connect

    McIntyre, Peter; Assadi, Saeed; Badgley, Karie; Baker, William; Comeaux, Justin; Gerity, James; Kellams, Joshua; McInturff, Al; Pogue, Nathaniel; Sattarov, Akhdiyor; Sooby, Elizabeth; Tsvetkov, Pavel; Phongikaroon, Supathorn; Simpson, Michael

    2013-04-19

    A technology for accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a basis for the destruction of the transuranics in used nuclear fuel. The molten salt fuel is a eutectic mixture of NaCl and the chlorides of the transuranics and fission products. The core is driven by proton beams from a strong-focusing cyclotron stack. This approach uniquely provides an intrinsically safe means to drive a core fueled only with transuranics, thereby eliminating competing breeding terms.

  8. Fission barriers for Po nuclei produced in complete fusion reactions with heavy ions

    SciTech Connect

    Sagaidak, R. N.; Andreyev, A. N.

    2009-05-15

    Evaporation residues and fission excitation functions obtained in complete fusion reactions leading to Po compound nuclei have been analyzed in the framework of the standard statistical model. Macroscopic fission barriers deduced from the cross-section data analysis are compared with the predictions of various theoretical models and available data. A drop in the Po barriers with the decrease in a neutron number was found, which is stronger than predicted by any theory. The presence of entrance channel effects and collective excitations in the compound nucleus decay is considered as a possible reason for the barrier reduction.

  9. Prompt and Delayed Inelastic Scattering Reactions from Fission Neutron PGAA - First Results of FaNGaS

    SciTech Connect

    Rossbach, M.; Randriamalala, T.; Revay, Zs.; Kudejova, P.; Soelradel, S.; Wagner, F.

    2015-07-01

    The new instrument Fast Neutron Gamma Spectroscopy (FaNGaS) has been installed at the SR10 beam line of the FRM II Research Reactor in Garching and tested successfully. Complimentary to cold neutron PGAA, with FaNGaS inelastic scattering reactions induced by fission neutrons can be studied. Gamma lines from (n,n'γ) reactions up to now have been rarely studied and no adequate compilation of the emitted gamma energies exist. In developing nondestructive analytical techniques using neutron generator based PGAA such data are badly needed for quantification of heavy metals and actinides in e.g. nuclear waste or safeguards samples. A number of elements and relevant actinides have been irradiated in the fast neutron beam SR10 at the FRM II reactor in Garching, Germany. A heavily shielded 50% eff. HPGe detector perpendicular to the beam is looking at the samples exposed to 2.3 E8 cm{sup -2}s{sup -1} fission neutrons. Prompt gamma spectra have been taken and evaluated using the available data in scattered sources. Additional gamma lines have been detected and are being compiled to create a data base for (n,n') reactions. Particular emphasis is given on actinides including {sup 238}U, {sup 232}Th, {sup 237}Np, {sup 242}Pu and {sup 241}Am. Some examples will be given and first results will be discussed in this contribution. (authors)

  10. Nuclear Reaction Data File for Astrophysics (NRDF/A) in Hokkaido University Nuclear Reaction Data Center

    NASA Astrophysics Data System (ADS)

    Katō, Kiyoshi; Kimura, Masaaki; Furutachi, Naoya; Togashi, Tomoaki; Makinaga, Ayano; Otuka, Naohiko

    2010-06-01

    The activities of the Japan Nuclear Reaction Data Centre is explained. The main task of the centre is data compilation of Japanese nuclear reaction data in collaboration of the International Network of Nuclear Reaction Data Centres. As one of recent activities, preparation of a new database (NRDF/A) and evaluation of astronuclear reaction data are reported. Collaboration in the nuclear data activities among Asian countries is proposed.

  11. The Search for Transuranium Elements and the Discovery of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Sime, Ruth Lewin

    The synthesis of new, artificial elements beyond uranium was at the cutting-edge of physical research in the 1930s, and nearly half a dozen transuranium elements were reported between 1934 and 1938. Nuclear physicists and radiochemists collaborated closely, but each field introduced fundamental assumptions that proved to be false: that nuclear changes would always be small, and that transuranium elements would resemble transition elements chemically. With its surprise ending in the discovery of nuclear fission, the misguided transuranium project can be viewed as an example of the illogical progress of scientific discovery. It is also an example of an interdisciplinary collaboration that was flawed yet crucial, for although chemists and physicists both contributed to the delay in discovering fission, their collaboration was essential in leading them to it in the end.

  12. RIPL - Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations

    NASA Astrophysics Data System (ADS)

    Capote, R.; Herman, M.; Obložinský, P.; Young, P. G.; Goriely, S.; Belgya, T.; Ignatyuk, A. V.; Koning, A. J.; Hilaire, S.; Plujko, V. A.; Avrigeanu, M.; Bersillon, O.; Chadwick, M. B.; Fukahori, T.; Ge, Zhigang; Han, Yinlu; Kailas, S.; Kopecky, J.; Maslov, V. M.; Reffo, G.; Sin, M.; Soukhovitskii, E. Sh.; Talou, P.

    2009-12-01

    We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released in January 2009, and is available on the Web through http://www-nds.iaea.org/RIPL-3/. This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations. The numerical data and computer codes included in RIPL-3 are arranged in seven segments: MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi et al. (2003). DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic and γ-ray decay probabilities available from ENSDF in October 2007. NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab. OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment. LEVEL DENSITIES contains

  13. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

    2009-05-05

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  14. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2009-01-27

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  15. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2009-01-06

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  16. Radiation re-solution of fission gas in non-oxide nuclear fuel

    SciTech Connect

    Matthews, Christopher; Schwen, Daniel; Klein, Andrew C.

    2015-02-01

    Renewed interest in fast nuclear reactors is creating a need for better understanding of fission gas bubble behavior in non-oxide fuels to support very long fuel lifetimes. Collisions between fission fragments and their subsequent cascades can knock fission gas atoms out of bubbles and back into the fuel lattice. We showed that these collisions can be treated as using the so-called ‘‘homogenous’’ atom-by-atom re-solution theory and calculated using the Binary Collision Approximation code 3DOT. The calculations showed that there is a decrease in the re-solution parameter as bubble radius increases until about 50 nm, at which the re-solution parameter stays nearly constant. Furthermore, our model shows ion cascades created in the fuel result in many more implanted fission gas atoms than collisions directly with fission fragments. This calculated re-solution parameter can be used to find a re-solution rate for future bubble simulations.

  17. Overview of beneficial uses of nuclear fission products

    SciTech Connect

    Sivinski, J.S.

    1980-01-01

    Recoverable or reprocessed nuclear wastes as conservable resources with significant potential benefits for use as heat sources, or as radiation sources for industrial, agricultural, and medical applications are reviewed. (LCL)

  18. Nuclear fission fragment excitation of electronic transition laser media

    NASA Technical Reports Server (NTRS)

    Lorents, D. C.; Mccusker, M. V.; Rhodes, C. K.

    1976-01-01

    Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media.

  19. Fission fragment charge and mass distributions in 239Pu(n, f ) in the adiabatic nuclear energy density functional theory

    DOE PAGES

    Regnier, D.; Dubray, N.; Schunck, N.; ...

    2016-05-13

    Here, accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics.

  20. Measurement of neutron multiplicity from fission of {sup 228}U and nuclear dissipation

    SciTech Connect

    Singh, Hardev; Behera, B. R.; Singh, Gulzar; Govil, I. M.; Golda, K. S.; Jhingan, Akhil; Singh, R. P.; Sugathan, P.; Chatterjee, M. B.; Datta, S. K.; Pal, Santanu; Ranjeet; Mandal, S.; Shidling, P. D.; Viesti, G.

    2009-12-15

    Pre- and post-scission neutron multiplicities are measured at different excitation energies of the compound nucleus {sup 228}U populated using the {sup 19}F+{sup 209}Bi reaction. The measured yield of pre-scission and total neutrons are compared with the statistical model calculation for the decay of a compound nucleus. The statistical model calculations are performed using the Bohr-Wheeler transition state fission width as well as the dissipative dynamical fission width due to Kramers. Comparison between the measured and the calculated values shows that, while the Bohr-Wheeler fission width grossly underestimates the pre-scission neutron yield, a large amount of dissipation is required in the Kramers width to fit the experimental pre-scission multiplicities. Various factors contributing to the large excitation energy dependence of the fitted values of the dissipation coefficient are discussed.

  1. An IF-FISH Approach for Covisualization of Gene Loci and Nuclear Architecture in Fission Yeast.

    PubMed

    Kim, K-D; Iwasaki, O; Noma, K

    2016-01-01

    Recent genomic studies have revealed that chromosomal structures are formed by a hierarchy of organizing processes ranging from gene associations, including interactions among enhancers and promoters, to topologically associating domain formations. Gene associations identified by these studies can be characterized by microscopic analyses. Fission yeast is a model organism, in which gene associations have been broadly mapped across the genome, although many of those associations have not been further examined by cell biological approaches. To address the technically challenging process of the visualization of associating gene loci in the fission yeast nuclei, we provide, in detail, an IF-FISH procedure that allows for covisualizing both gene loci and nuclear structural markers such as the nuclear membrane and nucleolus.

  2. Modernizing the Fission Basis

    NASA Astrophysics Data System (ADS)

    Tonchev, Anton; Henderson, Roger; Schunck, Nicolas; Sroyer, Mark; Vogt, Ramona

    2016-09-01

    In 1939, Niels Bohr and John Wheeler formulated a theory of neutron-induced nuclear fission based on the hypothesis of the compound nucleus. Their theory, the so-called ``Bohr hypothesis,'' is still at the heart of every theoretical fission model today and states that the decay of a compound nucleus for a given excitation energy, spin, and parity is independent of its formation. We propose the first experiment to validate to 1-2% absolute uncertainties the practical consequences of the Bohr hypothesis during induced nuclear fission. We will compare the fission product yields (FPYs) of the same 240Pu compound nucleus produced via two different reactions (i) n+239Pu and (ii) γ+240 Pu. These high-precision FPYs measurements will be extremely beneficial for our fundamental understanding of the nuclear fission process and nuclear reactions from first principles. This work was performed under the auspices of US DOE by LLNL under Contract DE-AC52-07NA27344. Funding was provided via the LDRD-ERD-069 project.

  3. Fission fragment mass distributions in 35Cl+Sm,154144 reactions

    NASA Astrophysics Data System (ADS)

    Tripathi, R.; Sodaye, S.; Sudarshan, K.; Nayak, B. K.; Jhingan, A.; Pujari, P. K.; Mahata, K.; Santra, S.; Saxena, A.; Mirgule, E. T.; Thomas, R. G.

    2015-08-01

    Background: A new type of asymmetric fission was observed in β -delayed fission of 180Tl [Phys. Rev. Lett. 105, 252502 (2010), 10.1103/PhysRevLett.105.252502] as symmetric mass distribution would be expected based on conventional shell effects leading to the formation of N =50 fragments. Following this observation, theoretical calculations were carried out which predict asymmetric mass distribution for several mercury isotopes around mass region of ˜180 at low and moderate excitation energies [Moller, Randrup, and Sierk, Phys. Rev. C 85, 024306 (2012), 10.1103/PhysRevC.85.024306; Andreev, Adamian, and Antonenko, Phys. Rev. C 86, 044315 (2012), 10.1103/PhysRevC.86.044315]. Studies on fission fragment mass distribution are required in this mass region to investigate this newly observed phenomenon. Purpose: The fission fragment mass distributions have been measured in 35Cl+Sm,154144 reactions at Elab=152.5 ,156.1 ,and 163.7 MeV populating compound nuclei in the mass region of ˜180 with variable excitation energy and neutron number to investigate the nature of mass distribution. Method: The fission fragment mass distribution has been obtained by measuring the "time of flight (TOF)" of fragments with respect to the beam pulse using two multiwire proportional counters placed at θlab=±65 .5∘ with respect to the beam direction. From the TOF of fragments, their velocities were determined, which were used to obtain mass distribution taking the compound nucleus as the fissioning system. Results: For both systems, mass distributions, although, appear to be symmetric, could not be fitted well by a single Gaussian. The deviation from a single Gaussian fit is more pronounced for the 35Cl+144Sm reaction. A clear flat top mass distribution has been observed for the 35Cl+144Sm reaction at the lowest beam energy. The mass distribution is very similar to that observed in the 40Ca+142Nd reaction, which populated a similar compound nucleus, but for the pronounced dip in the

  4. Supernova shock revival by nuclear reactions

    SciTech Connect

    Nakamrua, Ko; Takiwaki, Tomoya; Kotake, Kei; Nishimura, Nobuya

    2012-11-12

    We performed hydrodynamic simulations of core collapse and bounce for a progenitor model with 15.0 solar mass, using ZEUS-MP code in axi-symmetric coordinate. Our numerical code is equipped with a nuclear reaction network including 13 alpha nuclei form {sup 4}He to {sup 56}Ni to investigate the potential role played by nuclear reactions in reviving a stalled shock wave at the central region of core-collapse supernovae. We found that the energy released by nuclear reactions is significantly helpful in accelerating shock waves and is able to produce energetic explosion even if inputted neutrino luminosity is low.

  5. EXFOR Library of Experimental Nuclear Reaction Data

    DOE Data Explorer

    The EXFOR library contains an extensive compilation of experimental nuclear reaction data up to 1 GeV. Neutron reactions have been compiled systematically since the discovery of the neutron, while charged particle(up to carbon) and photon reactions have been covered less extensively. Files contain nuclear reaction data such as cross sections, spectra, angular distributions, polarizations, etc, along with information on experimental technique, error analysis, and applied standards. Numerous search parameters include: target, beam, product, experimental method, and even author and publication names. The library contains data from more than 20,000 experiments. (Specialized Interface)

  6. Actinide incineration in fusion-fission hybrid-A model nuclear synergy

    NASA Astrophysics Data System (ADS)

    Taczanowski, Stefan

    2012-06-01

    The alliance of fusion with fission is a cause worthy of great efforts, as being able to ease (if not even to solve) serious problems that both these forms of nuclear energy are facing. Very high investment costs caused by tokamak enormous size, material consumption and difficult technology put in doubt whether alone the minute demand for fuel raw material (Li) and lack of danger of uncontrolled supercriticality prove sufficient for making it competitive. Preliminary evaluations demonstrated that a radical shift of energy production i.e. the energy gain from plasma to fission blanket is feasible [1]. A reduction in the fusion component to about 2% at given system power allows for a radical drop in plasma Q down to the values of ˜0.2-0.3 achievable in small systems [2] (e.g. mirrors) of sizes comparable to fission reactors. As a result in a Fusion-Driven Actinide Incinerator (FDI) both radiations from the plasma: corpuscular (i.e. neutrons and ions) and photons are drastically reduced. Thus are too, first of all - the neutron induced radiation damage: DPA and gas production, then plasma-wall interactions. The fundamental safety of the system has been proved by simulation of its collapse that has shown preservation its subcriticality. Summarizing, all the above problems may be solved with synergic union of fusion with fission embodied in the concept of FDI - small and less expensive.

  7. Nuclear phenomena in low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B

    2013-09-01

    This is a comment on Storms E (2010) Status of Cold Fusion, Naturwissenschaften 97:861-881. This comment provides the following remarks to other nuclear phenomena observed in low-energy nuclear reactions aside from helium-4 make significant contributions to the overall energy balance; and normal hydrogen, not just heavy hydrogen, produces excess heat.

  8. Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments

    NASA Technical Reports Server (NTRS)

    Tarditi, A. G.; George, J. A.; Miley, G. H.; Scott, J. H.

    2013-01-01

    Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.

  9. Public reactions to nuclear waste

    SciTech Connect

    Dunlap, R.E.; Kraft, M.E.; Rosa, E.A.

    1993-12-31

    For many scientists, engineers, and regulators, the public controversy over siting a repository for high-level nuclear wastes exemplifies the clash between rational scientific judgment and irrational public attitudes. Even many who are more sympathetic to public concerns about risk and management believe the controversy is exacerbated by incompatibilities between good science and public participation in regulatory decision-making. Understanding the incompatibilities, however, is crucial to managing science and technology in a democratic society and provides an important motivation to study the relationship between public opinion and nuclear waste policy. In this book, Dunlap and his colleagues present a solid base of empirical research on the subject, and the strength of the collection is the careful unraveling of social factors and context to explain the overwhelmingly negative public view of nuclear waste and its management.

  10. Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters

    SciTech Connect

    Fioretto, E.; Stefanini, A. M.; Behera, B. R.; Corradi, L.; Gadea, A.; Latina, A.; Trotta, M.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Chizhov, A. Yu.; Itkis, I. M.; Itkis, M. G.; Kniajeva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Pokrovsky, I. V.; Sagaidak, R. N.; Voskressensky, V. M.; Courtin, S.

    2006-04-26

    Experimental results on the fusion inhibition effect near the Coulomb barrier due to the onset of the quasi-fission mechanism are presented. The investigation was focused on reactions induced by 48Ca projectiles on different heavy targets and comparing them to reactions induced by light ions such as 12C and 16O leading to the same compound nuclei. Cross sections and angular distributions of evaporation residues and fission fragments have been measured.

  11. Nuclear fission technology in Spain: History and social concerns.

    PubMed

    Aliende Urtasun, Ana; Luquin, Asunción; Garrido, Julián J

    2017-04-01

    This research examines the evolution of nuclear technology in Spain from the early years of the Franco dictatorship to the global financial crisis and technology's influence on Spanish culture. To this end, we take a sociological perspective, with science culture and social perceptions of risk in knowledge societies serving as the two elements of focus in this work. In this sense, this article analyses the transformation of social relationships in light of technological changes. We propose technology as a strategic place to observe the institutional and organisational dynamics of technologic-scientific risks, the expert role and Spain's science culture. In addition, more specifically, within the language of co-production, we 'follow the actor' and favour new forms of citizen participation that promote ethics to discuss technological issues.

  12. Incorporation of a tilting coordinate into the multidimensional Langevin dynamics of heavy-ion-induced fission: Analysis of experimental data from fusion-fission reactions

    NASA Astrophysics Data System (ADS)

    Nadtochy, P. N.; Ryabov, E. G.; Gegechkori, A. E.; Anischenko, Yu. A.; Adeev, G. D.

    2014-01-01

    A four-dimensional dynamical model was developed and applied to study fission characteristics in a wide range of a fissility parameter. Three collective shape coordinates and the K coordinate were considered dynamically from the ground-state deformation to the scission into fission fragments. A modified one-body mechanism for nuclear dissipation with a reduction coefficient ks of the contribution from a "wall" formula has been used in the study. The inclusion of the K coordinate in the dynamical consideration and use of the "chaos-weighted wall formula" with a deformation-dependent scaling factor ks(q1) lead to fairly good reproduction of the variances of the fission-fragment mass distribution and the prescission neutron multiplicity for a number of fissioning compound nuclei in a wide fissility range. The four-dimensional dynamical calculations describe better experimental prescission neutron multiplicity and variances of fission-fragment mass distribution for heaviest nuclei with respect to a three-dimensional dynamical model, where the K coordinate is assumed to be equal to zero. The estimate of a dissipation coefficient for the orientation degree of freedom, γK≃0.077 (MeVzs)-1/2, is good for heavy nuclei and a larger value of γK≃0.2 (MeVzs)-1/2 is needed for nuclei with mass ACN ≃ 200.

  13. Design related aspects in advanced nuclear fission plants

    NASA Astrophysics Data System (ADS)

    Hoffelner, Wolfgang

    2011-02-01

    Important issues to be considered for design of future reactors are: extrapolation of stress rupture data, creep-fatigue, negligible creep, damage monitoring. The paper highlights some new developments taking examples from a martensitic steel (mod 9% Cr), oxide dispersion strengthened (ODS) steels and nickel-base superalloys. Traditional approaches to extrapolation of (thermal) stress rupture data like Larson-Miller Parameter or Monkman-Grant rule seem to be valid concepts also for advanced reactors. However, a significant influence of cyclic softening on creep rates and stress rupture data can be expected as shown for grade 91. This is particularly true for creep-fatigue interactions. Based on cyclic stress-strain behaviour it is also possible to get very good life-time predictions under creep-fatigue with a strain range separation (inelastic fatigue and creep ranges) technique which could replace the currently used linear life fraction rule. Results from in-beam irradiation creep reveal no significant influence of dispersoid size. It can be assumed that irradiation creep is a matrix property. Finally it is shown that micro-sample testing of exposed material could be used as an advanced method for damage assessment in future nuclear power plants.

  14. Separation of the rare-earth fission product poisons from spent nuclear fuel

    SciTech Connect

    Christian, Jerry D.; Sterbentz, James W.

    2016-08-30

    A method for the separation of the rare-earth fission product poisons comprising providing a spent nuclear fuel. The spent nuclear fuel comprises UO.sub.2 and rare-earth oxides, preferably Sm, Gd, Nd, Eu oxides, with other elements depending on the fuel composition. Preferably, the provided nuclear fuel is a powder, preferably formed by crushing the nuclear fuel or using one or more oxidation-reduction cycles. A compound comprising Th or Zr, preferably metal, is provided. The provided nuclear fuel is mixed with the Th or Zr, thereby creating a mixture. The mixture is then heated to a temperature sufficient to reduce the UO.sub.2 in the nuclear fuel, preferably to at least to 850.degree. C. for Th and up to 600.degree. C. for Zr. Rare-earth metals are then extracted to form the heated mixture thereby producing a treated nuclear fuel. The treated nuclear fuel comprises the provided nuclear fuel having a significant reduction in rare-earths.

  15. Experimental nuclear reaction data collection EXFOR

    SciTech Connect

    Semkova, V.; Otuka, N.; Simakov, S. P.; Zerkin, V.

    2011-07-01

    The International Network of Nuclear Reaction Data Centres (NRDC) constitutes a worldwide cooperation of 14 nuclear data centres. The main activity of the NRDC Network is collection and compilation of experimental nuclear reaction cross section data and the related bibliographic information in the EXFOR and CINDA databases as well as dissemination of nuclear reaction data and associated documentation to users. The database contains information and numerical data from more than about 19000 experiments consisting of more than 140000 datasets. EXFOR is kept up to date by constantly adding newly published experimental information. Tools developed for data dissemination utilise modern database technologies with fast online capabilities over the Internet. Users are provided with sophisticated search options, a user-friendly retrieval interface for downloading data in different formats, and additional output options such as improved data plotting capabilities. The present status of the EXFOR database will be presented together with the latest development for data access and retrieval. (authors)

  16. High-power proton linac for transmuting the long-lived fission products in nuclear waste

    SciTech Connect

    Lawrence, G.P.

    1991-01-01

    High power proton linacs are being considered at Los Alamos as drivers for high-flux spallation neutron sources that can be used to transmute the troublesome long-lived fission products in defense nuclear waste. The transmutation scheme being studied provides a high flux (> 10{sup 16}/cm{sup 2}{minus}s) of thermal neutrons, which efficiently converts fission products to stable or short-lived isotopes. A medium-energy proton linac with an average beam power of about 110 MW can burn the accumulated Tc99 and I129 inventory at the DOE's Hanford Site within 30 years. Preliminary concepts for this machine are described. 3 refs., 5 figs., 2 tabs.

  17. Nuclear chain reaction: forty years later

    SciTech Connect

    Sachs, R.G.

    1984-01-01

    The proceedings from a 1982 symposium 40 years after the first controlled nuclear chain reaction took place in Chicago covers four sessions and public discussion. The session covered the history of the chain reaction; peaceful uses in technology, medicine, and biological science; peaceful uses in power generation; and nuclear weapons control. Among the speakers were Eugene Wigner, Glenn Seaborg, Alvin Weinberg, and others who participated in the first chain reaction experiments. The proceedings reflect differences of opinion among the scientists as well as the general public. References, slides, and tables used to illustrate the individual talks are included with the papers.

  18. Investigation of Shell Effects in the Fusion-Fission Process in the Reaction 34S + 186W Near the Interaction Barrier

    NASA Astrophysics Data System (ADS)

    Harca, I. M.; Kozulin, E. M.; Bogachev, A.; Dmitriev, S. N.; Itkis, J.; Knyazheva, G.; Loktev, T.; Novikov, K.; Vardaci, E.; Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D.; Chubarian, G.; Hanappe, F.; Piot, J.; Schmitt, C.; Trzaska, W. H.

    2015-06-01

    The reaction 34S + 186W at Elab = 160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays coincident with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. The coupling of the ORGAM and CORSET setups enables the FF-γ coincident measurement which offers the opportunity to extract the isotopic distribution of the fragments of different masses formed in the aforementioned reaction and to find the exact neutron multiplicity, the average spin and average angular momenta. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

  19. Determination of Nuclear Charge Distributions of Fission Fragments from ^{235}U (n_th, f) with Calorimetric Low Temperature Detectors

    NASA Astrophysics Data System (ADS)

    Grabitz, P.; Andrianov, V.; Bishop, S.; Blanc, A.; Dubey, S.; Echler, A.; Egelhof, P.; Faust, H.; Gönnenwein, F.; Gomez-Guzman, J. M.; Köster, U.; Kraft-Bermuth, S.; Mutterer, M.; Scholz, P.; Stolte, S.

    2016-08-01

    Calorimetric low temperature detectors (CLTD's) for heavy-ion detection have been combined with the LOHENGRIN recoil separator at the ILL Grenoble for the determination of nuclear charge distributions of fission fragments produced by thermal neutron-induced fission of ^{235}U. The LOHENGRIN spectrometer separates fission fragments according to their mass-to-ionic-charge ratio and their kinetic energy, but has no selectivity with respect to nuclear charges Z. For the separation of the nuclear charges, one can exploit the nuclear charge-dependent energy loss of the fragments passing through an energy degrader foil (absorber method). This separation requires detector systems with high energy resolution and negligible pulse height defect, as well as degrader foils which are optimized with respect to thickness, homogeneity, and energy loss straggling. In the present, contribution results of test measurements at the Maier Leibnitz tandem accelerator facility in Munich with ^{109}Ag and ^{127}I beams with the aim to determine the most suitable degrader material, as well as measurements at the Institut Laue-Langevin will be presented. These include a systematic study of the quality of Z-separation of fission fragments in the mass range 82le A le 132 and a systematic measurement of ^{92}Rb fission yields, as well as investigations of fission yields toward the symmetry region.

  20. The Sustainable Nuclear Future: Fission and Fusion E.M. Campbell Logos Technologies

    NASA Astrophysics Data System (ADS)

    Campbell, E. Michael

    2010-02-01

    Global industrialization, the concern over rising CO2 levels in the atmosphere and other negative environmental effects due to the burning of hydrocarbon fuels and the need to insulate the cost of energy from fuel price volatility have led to a renewed interest in nuclear power. Many of the plants under construction are similar to the existing light water reactors but incorporate modern engineering and enhanced safety features. These reactors, while mature, safe and reliable sources of electrical power have limited efficiency in converting fission power to useful work, require significant amounts of water, and must deal with the issues of nuclear waste (spent fuel), safety, and weapons proliferation. If nuclear power is to sustain its present share of the world's growing energy needs let alone displace carbon based fuels, more than 1000 reactors will be needed by mid century. For this to occur new reactors that are more efficient, versatile in their energy markets, require minimal or no water, produce less waste and more robust waste forms, are inherently safe and minimize proliferation concerns will be necessary. Graphite moderated, ceramic coated fuel, and He cooled designs are reactors that can satisfy these requirements. Along with other generation IV fast reactors that can further reduce the amounts of spent fuel and extend fuel resources, such a nuclear expansion is possible. Furthermore, facilities either in early operations or under construction should demonstrate the next step in fusion energy development in which energy gain is produced. This demonstration will catalyze fusion energy development and lead to the ultimate development of the next generation of nuclear reactors. In this presentation the role of advanced fission reactors and future fusion reactors in the expansion of nuclear power will be discussed including synergies with the existing worldwide nuclear fleet. )

  1. MEANS FOR TERMINATING NUCLEAR REACTIONS

    DOEpatents

    Cooper, C.M.

    1959-02-17

    An apparatus is presented for use in a reactor of the heterogeneous, fluid cooled type for the purpose of quickly terminating the reaction, the coolant being circulated through coolant tubes extending through the reactor core. Several of the tubes in the critical region are connected through valves to a tank containing a poisoning fluid having a high neutron capture crosssection and to a reservoir. When it is desired to quickly terminate the reaction, the valves are operated to permit the flow of the poisoning fluid through these particular tubes and into the reservoir while normal coolant is being circulated through the remaining tubes. The apparatus is designed to prevent contamination of the primary coolant by the poisoning fluid.

  2. Nuclear excitations and reaction mechanisms

    SciTech Connect

    Fallieros, S.; Levin, F.S.

    1990-08-01

    The main theme of this report is the study and interpretation of the sequence of events that occur during the collisions of nuclear particles. Some of the processes discussed in parts A and B involve short range interactions; others involve interactions of long range. In most of part A one of the particles in the initial or in the final state (or in both) is a photon, which serves as a probe of the second particle, which may be a nucleus, a proton, a pion or any other hadron. The complexity of the processes taking place during the collisions makes it necessary to simplify some aspects of the physical problem. This leads to the introduction of modals which are used to describe a limited number of features in as much detail as possible. The main interest is the understanding of the hadronic excitations which result from the absorption of a photon and the determination of the fundamental structure constants of the target particle. In part B, all the particles are hadrons. The purpose here is to develop and apply optimal quantal methods appropriate for describing the interacting systems. Of particular interest are three-particle collision systems in which the final state consists of three free particles. Part B also considers the process of nuclear fusion as catalyzed by bound muons.

  3. Multilayer Network Analysis of Nuclear Reactions

    PubMed Central

    Zhu, Liang; Ma, Yu-Gang; Chen, Qu; Han, Ding-Ding

    2016-01-01

    The nuclear reaction network is usually studied via precise calculation of differential equation sets, and much research interest has been focused on the characteristics of nuclides, such as half-life and size limit. In this paper, however, we adopt the methods from both multilayer and reaction networks, and obtain a distinctive view by mapping all the nuclear reactions in JINA REACLIB database into a directed network with 4 layers: neutron, proton, 4He and the remainder. The layer names correspond to reaction types decided by the currency particles consumed. This combined approach reveals that, in the remainder layer, the β-stability has high correlation with node degree difference and overlapping coefficient. Moreover, when reaction rates are considered as node strength, we find that, at lower temperatures, nuclide half-life scales reciprocally with its out-strength. The connection between physical properties and topological characteristics may help to explore the boundary of the nuclide chart. PMID:27558995

  4. Brownian shape motion on five-dimensional potential-energy surfaces:nuclear fission-fragment mass distributions.

    PubMed

    Randrup, Jørgen; Möller, Peter

    2011-04-01

    Although nuclear fission can be understood qualitatively as an evolution of the nuclear shape, a quantitative description has proven to be very elusive. In particular, until now, there existed no model with demonstrated predictive power for the fission-fragment mass yields. Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of highly variable experimental mass yields. This novel general approach requires only a single new global parameter, namely, the critical neck size at which the mass split is frozen in, and the results are remarkably insensitive to its specific value.

  5. Nuclear retention of fission yeast dicer is a prerequisite for RNAi-mediated heterochromatin assembly.

    PubMed

    Emmerth, Stephan; Schober, Heiko; Gaidatzis, Dimos; Roloff, Tim; Jacobeit, Kirsten; Bühler, Marc

    2010-01-19

    RNaseIII ribonucleases act at the heart of RNA silencing pathways by processing precursor RNAs into mature microRNAs and siRNAs. In the fission yeast Schizosaccharomyces pombe, siRNAs are generated by the RNaseIII enzyme Dcr1 and are required for heterochromatin formation at centromeres. In this study, we have analyzed the subcellular localization of Dcr1 and found that it accumulates in the nucleus and is enriched at the nuclear periphery. Nuclear accumulation of Dcr1 depends on a short motif that impedes nuclear export promoted by the double-stranded RNA binding domain of Dcr1. Absence of this motif renders Dcr1 mainly cytoplasmic and is accompanied by remarkable changes in gene expression and failure to assemble heterochromatin. Our findings suggest that Dicer proteins are shuttling proteins and that the steady-state subcellular levels can be shifted toward either compartment.

  6. Results of a First Generation Propellant Energy Source Module Testing: Non-Nuclear Testing of Fission System

    NASA Technical Reports Server (NTRS)

    VanDyke, Melissa; Godfroy, Tom; Houts, Mike; Dickens, Ricky; Dobson, Chris; Pederson, Kevin; Reid, Bob

    1999-01-01

    The use of resistance heaters to simulate heat from fission allows extensive development of fission systems to be performed in non-nuclear test facilities, saving time and money. Resistance heated tests on the Module Unfueled Thermal- hydraulic Test (MUTT) article has been performed at the Marshall Space Flight Center. This paper discusses the results of these experiments to date, and describes the additional testing that will be performed. Recommendations related to the design of testable space fission power and propulsion systems are made.

  7. Non-statistical effects in bond fission reactions of 1,2-difluoroethane

    NASA Astrophysics Data System (ADS)

    Schranz, Harold W.; Raff, Lionel M.; Thompson, Donald L.

    1991-08-01

    A microcanonical, classical variational transition-state theory based on the use of the efficient microcanonical sampling (EMS) procedure is applied to simple bond fission in 1,2-difluoroethane. Comparison is made with results of trajectory calculations performed on the same global potential-energy surface. Agreement between the statistical theory and trajectory results for CC CF and CH bond fissions is poor with differences as large as a factor of 125. Most importantly, at the lower energy studied, 6.0 eV, the statistical calculations predict considerably slower rates than those computed from trajectories. We conclude from these results that the statistical assumptions inherent in the transition-state theory method are not valid for 1,2-difluoroethane in spite of the fact that the total intramolecular energy transfer rate out of CH and CC normal and local modes is large relative to the bond fission rates. The IVR rate is not globally rapid and the trajectories do not access all of the energetically available phase space uniformly on the timescale of the reactions.

  8. Measurements of charge distributions of the fragments in the low energy fission reaction

    NASA Astrophysics Data System (ADS)

    Wang, Taofeng; Han, Hongyin; Meng, Qinghua; Wang, Liming; Zhu, Liping; Xia, Haihong

    2013-01-01

    The measurement for charge distributions of fragments in spontaneous fission 252Cf has been performed by using a unique style of detector setup consisting of a typical grid ionization chamber and a ΔΕ-Ε particle telescope, in which a thin grid ionization chamber served as the ΔΕ-section and the E-section was an Au-Si surface barrier detector. The typical physical quantities of fragments, such as mass number and kinetic energies as well as the deposition in the gas ΔΕ detector and E detector were derived from the coincident measurement data. The charge distributions of the light fragments for the fixed mass number A2* and total kinetic energy (TKE) were obtained by the least-squares fits for the response functions of the ΔΕ detector with multi-Gaussian functions representing the different elements. The results of the charge distributions for some typical fragments are shown in this article which indicates that this detection setup has the charge distribution capability of Ζ:ΔΖ>40:1. The experimental method developed in this work for determining the charge distributions of fragments is expected to be employed in the neutron induced fissions of 232Th and 238U or other low energy fission reactions.

  9. Linear free energy correlations for fission product release from the Fukushima-Daiichi nuclear accident.

    PubMed

    Abrecht, David G; Schwantes, Jon M

    2015-03-03

    This paper extends the preliminary linear free energy correlations for radionuclide release performed by Schwantes et al., following the Fukushima-Daiichi Nuclear Power Plant accident. Through evaluations of the molar fractionations of radionuclides deposited in the soil relative to modeled radionuclide inventories, we confirm the initial source of the radionuclides to the environment to be from active reactors rather than the spent fuel pool. Linear correlations of the form In χ = −α ((ΔGrxn°(TC))/(RTC)) + β were obtained between the deposited concentrations, and the reduction potentials of the fission product oxide species using multiple reduction schemes to calculate ΔG°rxn (TC). These models allowed an estimate of the upper bound for the reactor temperatures of TC between 2015 and 2060 K, providing insight into the limiting factors to vaporization and release of fission products during the reactor accident. Estimates of the release of medium-lived fission products 90Sr, 121mSn, 147Pm, 144Ce, 152Eu, 154Eu, 155Eu, and 151Sm through atmospheric venting during the first month following the accident were obtained, indicating that large quantities of 90Sr and radioactive lanthanides were likely to remain in the damaged reactor cores.

  10. The fission yeast meiotic checkpoint kinase Mek1 regulates nuclear localization of Cdc25 by phosphorylation.

    PubMed

    Pérez-Hidalgo, Livia; Moreno, Sergio; San-Segundo, Pedro A

    2008-12-01

    In eukaryotic cells, fidelity in transmission of genetic information during cell division is ensured by the action of cell cycle checkpoints. Checkpoints are surveillance mechanisms that arrest or delay cell cycle progression when critical cellular processes are defective or when the genome is damaged. During meiosis, the so-called meiotic recombination checkpoint blocks entry into meiosis I until recombination has been completed, thus avoiding aberrant chromosome segregation and the formation of aneuploid gametes. One of the key components of the meiotic recombination checkpoint is the meiosis-specific Mek1 kinase, which belongs to the family of Rad53/Cds1/Chk2 checkpoint kinases containing forkhead-associated domains. In fission yeast, several lines of evidence suggest that Mek1 targets the critical cell cycle regulator Cdc25 to delay meiotic cell cycle progression. Here, we investigate in more detail the molecular mechanism of action of the fission yeast Mek1 protein. We demonstrate that Mek1 acts independently of Cds1 to phosphorylate Cdc25, and this phosphorylation is required to trigger cell cycle arrest. Using ectopic overexpression of mek1(+) as a tool to induce in vivo activation of Mek1, we find that Mek1 promotes cytoplasmic accumulation of Cdc25 and results in prolonged phosphorylation of Cdc2 at tyrosine 15. We propose that at least one of the mechanisms contributing to the cell cycle delay when the meiotic recombination checkpoint is activated in fission yeast is the nuclear exclusion of the Cdc25 phosphatase by Mek1-dependent phosphorylation.

  11. Linear Free Energy Correlations for Fission Product Release from the Fukushima-Daiichi Nuclear Accident

    SciTech Connect

    Abrecht, David G.; Schwantes, Jon M.

    2015-03-03

    This paper extends the preliminary linear free energy correlations for radionuclide release performed by Schwantes, et al., following the Fukushima-Daiichi Nuclear Power Plant accident. Through evaluations of the molar fractionations of radionuclides deposited in the soil relative to modeled radionuclide inventories, we confirm the source of the radionuclides to be from active reactors rather than the spent fuel pool. Linear correlations of the form ln χ = -α (ΔGrxn°(TC))/(RTC)+β were obtained between the deposited concentration and the reduction potential of the fission product oxide species using multiple reduction schemes to calculate ΔG°rxn(TC). These models allowed an estimate of the upper bound for the reactor temperatures of TC between 2130 K and 2220 K, providing insight into the limiting factors to vaporization and release of fission products during the reactor accident. Estimates of the release of medium-lived fission products 90Sr, 121mSn, 147Pm, 144Ce, 152Eu, 154Eu, 155Eu, 151Sm through atmospheric venting and releases during the first month following the accident were performed, and indicate large quantities of 90Sr and radioactive lanthanides were likely to remain in the damaged reactor cores.

  12. Quark-lattice Nuclear Model Applications -- Neutron Absorption, Radioactive Decay, and Asymmetric Fission

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Montgomery, Jerry R.

    2010-10-01

    The new quark-lattice model of the nucleus has been extended through heavy nuclei. Three specific issues illustrate the power of the model: (1) large thermal neutron absorption cross sections, (2) radioactive decay of K-40, and (3) asymmetric fission. Large neutron absorption cross sections occur when there are openings in the lattice into which neutrons can naturally fit. Examples are He-3, Li-6, and B-10. B-10 results in neutron-activated fission. The decay of K-40 into either Ar-40 or Ca-40 illustrates the role spin plays in determining nuclear structure. K-40 has net spin 4 whereas Ar-40 and Ca-40 both have spin 0. Zome models are used to show these structures. The fission of heavy nuclei occurs, in the lattice model, as the core of the structure separates from the loosely-packed ends. The ends are repacked into a smaller nucleus, which forms the lighter of the two daughter fragments. This explains why the lighter fragment mass increases with total mass whereas the heavier fragment mass remains relatively constant.

  13. Multiple-path fission-foil nuclear lasing of Ar-Xe

    NASA Technical Reports Server (NTRS)

    De Young, R. J.

    1981-01-01

    Nuclear lasing of Ar 10% Xe at 760 torr with a thermal neutron flux of 3.5 x 10 to the 16th n/sq cm s has produced an output power of 50 W. Lasing occurred at 2.6 microns in Xe-I. The argon buffer gas is shown to efficiently stop fission fragments at reasonable pressures emitted from (U-235)3O8 coatings. A unique folded optical path was used to increase the excited gas volume which in turn increases laser output.

  14. Pre-fission neutron emission in {sup 19}F+{sup 209}Bi reaction

    SciTech Connect

    Singh, Hardev; Sugathan, P.; Shidling, P. D.; Behera, B. R.; Singh, Gulzar; Govil, I. M.; Golda, K. S.; Jhingan, Akhil; Singh, R. P.; Chatterjee, M. B.; Datta, S. K.; Pal, Santanu; Viesti, G.

    2009-03-04

    The pre- and post-scission neutron multiplicities are measured for {sup 19}F+{sup 209}Bi reaction at E{sub lab} = 100, 104, 108, 112 and 116 MeV. The measured value of pre-scission neutron multiplicity was found to be increasing with the excitation energy. The comparison of experimental values with the statistical model calculations shows that the measured values are much larger than the model predictions. This difference in excess yield over the model predictions amounts to the survival time of 80{+-}5x10{sup -21} s for the {sup 228}U compound nucleus before it undergoes fission.

  15. Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the 18O + 232Th reaction

    NASA Astrophysics Data System (ADS)

    Léguillon, R.; Nishio, K.; Hirose, K.; Makii, H.; Nishinaka, I.; Orlandi, R.; Tsukada, K.; Smallcombe, J.; Chiba, S.; Aritomo, Y.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.; Tamura, N.; Goto, S.; Tsekhanovich, I.; Petrache, C. M.; Andreyev, A. N.

    2016-10-01

    It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O + 232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.

  16. Nuclear envelope attachment is not necessary for telomere function in fission yeast.

    PubMed

    Chikashige, Yuji; Haraguchi, Tokuko; Hiraoka, Yasushi

    2010-01-01

    Inner nuclear membrane (INM) proteins can be important for positioning chromosomes within the nucleus. Little is known about INM proteins in the fission yeast Schizossacharomayces pombe. Telomeres are the most obvious chromosomal sites that are anchored to the nuclear envelope in this organism. A group of proteins that tether telomeres to the spindle-pole body (SPB) during meiotic prophase, such as Bqt1, Bqt2 and Sad1, has been identified previously, but proteins for anchoring telomeres to the nuclear envelope in vegetative cells have not been identified until recently. A recent report demonstrates that Bqt3 and Bqt4 are INM proteins that affect nuclear positioning of telomeres in vegetative cells, and consequently affect the telomere clustering in meiotic prophase. Interestingly, in the absence of Bqt4, telomeres are separated from the nuclear envelope but telomere silencing and telomere length are properly regulated. An important implication of these results is that the functional integrity of telomeres is maintained independently of their connection to the nuclear envelope.

  17. MODELING AND FISSION CROSS SECTIONS FOR AMERICIUM.

    SciTech Connect

    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. Measurements of extinct fission products in nuclear bomb debris: Determination of the yield of the Trinity nuclear test 70 y later.

    PubMed

    Hanson, Susan K; Pollington, Anthony D; Waidmann, Christopher R; Kinman, William S; Wende, Allison M; Miller, Jeffrey L; Berger, Jennifer A; Oldham, Warren J; Selby, Hugh D

    2016-07-19

    This paper describes an approach to measuring extinct fission products that would allow for the characterization of a nuclear test at any time. The isotopic composition of molybdenum in five samples of glassy debris from the 1945 Trinity nuclear test has been measured. Nonnatural molybdenum isotopic compositions were observed, reflecting an input from the decay of the short-lived fission products (95)Zr and (97)Zr. By measuring both the perturbation of the (95)Mo/(96)Mo and (97)Mo/(96)Mo isotopic ratios and the total amount of molybdenum in the Trinity nuclear debris samples, it is possible to calculate the original concentrations of the (95)Zr and (97)Zr isotopes formed in the nuclear detonation. Together with a determination of the amount of plutonium in the debris, these measurements of extinct fission products allow for new estimates of the efficiency and yield of the historic Trinity test.

  19. Measurements of extinct fission products in nuclear bomb debris: Determination of the yield of the Trinity nuclear test 70 y later

    PubMed Central

    Hanson, Susan K.; Pollington, Anthony D.; Waidmann, Christopher R.; Kinman, William S.; Wende, Allison M.; Miller, Jeffrey L.; Berger, Jennifer A.; Oldham, Warren J.; Selby, Hugh D.

    2016-01-01

    This paper describes an approach to measuring extinct fission products that would allow for the characterization of a nuclear test at any time. The isotopic composition of molybdenum in five samples of glassy debris from the 1945 Trinity nuclear test has been measured. Nonnatural molybdenum isotopic compositions were observed, reflecting an input from the decay of the short-lived fission products 95Zr and 97Zr. By measuring both the perturbation of the 95Mo/96Mo and 97Mo/96Mo isotopic ratios and the total amount of molybdenum in the Trinity nuclear debris samples, it is possible to calculate the original concentrations of the 95Zr and 97Zr isotopes formed in the nuclear detonation. Together with a determination of the amount of plutonium in the debris, these measurements of extinct fission products allow for new estimates of the efficiency and yield of the historic Trinity test. PMID:27382169

  20. Measurements of extinct fission products in nuclear bomb debris: Determination of the yield of the Trinity nuclear test 70 y later

    DOE PAGES

    Hanson, Susan Kloek; Pollington, Anthony Douglas; Waidmann, Christopher Russell; ...

    2016-07-05

    This study describes an approach to measuring extinct fission products that would allow for the characterization of a nuclear test at any time. The isotopic composition of molybdenum in five samples of glassy debris from the 1945 Trinity nuclear test has been measured. Nonnatural molybdenum isotopic compositions were observed, reflecting an input from the decay of the short-lived fission products 95Zr and 97Zr. By measuring both the perturbation of the 95Mo/96Mo and 97Mo/96Mo isotopic ratios and the total amount of molybdenum in the Trinity nuclear debris samples, it is possible to calculate the original concentrations of the 95Zr and 97Zrmore » isotopes formed in the nuclear detonation. Together with a determination of the amount of plutonium in the debris, these measurements of extinct fission products allow for new estimates of the efficiency and yield of the historic Trinity test.« less

  1. Nuclear reactions for nucleosynthesis beyond Fe

    SciTech Connect

    Rauscher, Thomas

    2015-10-15

    Many more nuclear transitions have to be known in the determination of stellar reactivities for trans-iron nucleosynthesis than for reactions of light nuclei. This requires different theoretical and experimental approaches. Some of the issues specific for trans-iron nucleosynthesis are discussed.

  2. Continuum effects in nuclear transfer reactions

    SciTech Connect

    Marta, H. D.; Donangelo, R.; Fernandez Niello, J. O.; Pacheco, A. J.

    2007-02-12

    We develop a semiclassical calculation for nuclear transfer reactions where the continuum is treated in an exact way, and compare the results with those of a treatment in which the continuum is neglected. We conclude that the influence of the continuum is very important for weakly bound reactants.

  3. A Nuclear Reactions Primer with Computers.

    ERIC Educational Resources Information Center

    Calle, Carlos I.; Roach, Jennifer A.

    1987-01-01

    Described is a microcomputer software program NUCLEAR REACTIONS designed for college level students and in use at Sweet Briar College (Sweet Briar, VA). The program is written in Microsoft Basic Version 2.1 for the Apple Macintosh Microcomputer. It introduces two conservation principles: (1) conservation of charge; and (2) conservation of nucleon…

  4. Laser Intertial Fusion Energy: Neutronic Design Aspects of a Hybrid Fusion-Fission Nuclear Energy System

    SciTech Connect

    Kramer, Kevin James

    2010-04-08

    having a packing fraction of 20% in 2 cm diameter fuel pebbles. The fission blanket is cooled by the same radial flibe flow that travels through perforated ODS walls to the reflector blanket. This reflector blanket is 75 cm thick comprised of 2 cm diameter graphite pebbles cooled by flibe. The flibe extraction plenum surrounds the reflector bed. Detailed neutronics designs studies are performed to arrive at the described design. The LFFH engine thermal power is controlled using a technique of adjusting the 6Li/7Li enrichment in the primary and secondary coolants. The enrichment adjusts system thermal power in the design by increasing tritium production while reducing fission. To perform the simulations and design of the LFFH engine, a new software program named LFFH Nuclear Control (LNC) was developed in C++ to extend the functionality of existing neutron transport and depletion software programs. Neutron transport calculations are performed with MCNP5. Depletion calculations are performed using Monteburns 2.0, which utilizes ORIGEN 2.0 and MCNP5 to perform a burnup calculation. LNC supports many design parameters and is capable of performing a full 3D system simulation from initial startup to full burnup. It is able to iteratively search for coolant 6Li enrichments and resulting material compositions that meet user defined performance criteria. LNC is utilized throughout this study for time dependent simulation of the LFFH engine. Two additional methods were developed to improve the computation efficiency of LNC calculations. These methods, termed adaptive time stepping and adaptive mesh refinement were incorporated into a separate stand alone C++ library name the Adaptive Burnup Library (ABL). The ABL allows for other client codes to call and utilize its functionality. Adaptive time stepping is useful for automatically maximizing the size of the depletion time step while maintaining a desired level of accuracy. Adaptive meshing allows for analysis

  5. On-site gamma-ray spectroscopic measurements of fission gas release in irradiated nuclear fuel.

    PubMed

    Matsson, I; Grapengiesser, B; Andersson, B

    2007-01-01

    An experimental, non-destructive in-pool, method for measuring fission gas release (FGR) in irradiated nuclear fuel has been developed. Using the method, a significant number of experiments have been performed in-pool at several nuclear power plants of the BWR type. The method utilises the 514 keV gamma-radiation from the gaseous fission product (85)Kr captured in the fuel rod plenum volume. A submergible measuring device (LOKET) consisting of an HPGe-detector and a collimator system was utilised allowing for single rod measurements on virtually all types of BWR fuel. A FGR database covering a wide range of burn-ups (up to average rod burn-up well above 60 MWd/kgU), irradiation history, fuel rod position in cross section and fuel designs has been compiled and used for computer code benchmarking, fuel performance analysis and feedback to reactor operators. Measurements clearly indicate the low FGR in more modern fuel designs in comparison to older fuel types.

  6. Nuclear structure and shapes from prompt gamma ray spectroscopy of fission products

    SciTech Connect

    Ahmad, I.; Morss, L.R.; Durell, J.L.

    1996-10-01

    Many nuclear shape phenomena are predicted to occur in neutron-rich nuclei. The best source for the production of these nuclides is the spontaneous fission which produces practically hundreds of nuclides with yields of greater than 0.1 % per decay. Measurements of coincident gamma rays with large Ge arrays have recently been made to obtain information on nuclear structures and shapes of these neutron- rich nuclei. Among the important results that have been obtained from such measurements are octupole correlations in Ba isotopes, triaxial shapes in Ru nuclei, two-phonon vibrations in {sup 106}Mo and level lifetimes and quadrupole moments in Nd isotopes and A=100 nuclei. These data have been used to test theoretical models.

  7. Bid mediates fission, membrane permeabilization and peri-nuclear accumulation of mitochondria as a prerequisite for oxidative neuronal cell death.

    PubMed

    Grohm, Julia; Plesnila, Nikolaus; Culmsee, Carsten

    2010-07-01

    Mitochondria are highly dynamic organelles that undergo permanent fusion and fission, a process that is important for mitochondrial function and cellular survival. Emerging evidence suggests that oxidative stress disturbs mitochondrial morphology dynamics, resulting in detrimental mitochondrial fragmentation. In particular, such fatal mitochondrial fission has been detected in neurons exposed to oxidative stress, suggesting mitochondrial dynamics as a key feature in intrinsic death pathways. However, the regulation of mitochondrial fission in neurons exposed to lethal stress is largely unknown. Here, we used a model of glutamate toxicity in HT-22 cells for investigating mitochondrial fission and fusion in neurons exposed to oxidative stress. In these immortalized hippocampal neurons, glutamate induces glutathione depletion and increased formation of reactive oxygen species (ROS). Glutamate toxicity resulted in mitochondrial fragmentation and peri-nuclear accumulation of the organelles. Further, mitochondrial fission was associated with loss of mitochondrial outer membrane potential (MOMP). The Bid-inhibitor BI-6c9 prevented MOMP and mitochondrial fission, and protected the cells from cell death. In conclusion, oxidative stress induced by glutamate causes mitochondrial translocation of Bid thereby inducing mitochondrial fission and associated mitochondrial cell death pathways. Inhibiting regulators of pathological mitochondrial fragmentation is proposed as an efficient strategy of neuroprotection.

  8. Report to the DOE nuclear data committee. [EV RANGE 10-100; CROSS SECTIONS; PHOTONEUTRONS; NEUTRONS; GAMMA RADIATION; COUPLED CHANNEL THEORY; DIFFERENTIAL CROSS SECTIONS; MEV RANGE 01-10; ; CAPTURE; GAMMA SPECTRA; THERMAL NEUTRONS; COMPUTER CALCULATIONS; DECAY; FISSION PRODUCTS; FISSION YIELD; SHELL MODELS; NUCLEAR DATA COLLECTIONS

    SciTech Connect

    Struble, G.L.; Haight, R.C.

    1981-03-01

    Topics covered include: studies of (n, charged particle) reactions with 14 to 15 MeV neutrons; photoneutron cross sections for /sup 15/N; neutron radiative capture; Lane-model analysis of (p,p) and (n,n) scattering on the even tin isotopes; neutron scattering cross sections for /sup 181/Ta, /sup 197/Au, /sup 209/Bi, /sup 232/Th, and /sup 238/U inferred from proton scattering and charge exchange cross sections; neutron-induced fission cross sections of /sup 245/Cm and /sup 242/Am; fission neutron multiplicities for /sup 245/Cm and /sup 242/Am; the transport of 14 MeV neutrons through heavy materials 150 < A < 208; /sup 249/Cm energy levels from measurement of thermal neutron capture gamma rays; /sup 231/Th energy levels from neutron capture gamma ray and conversion electron spectroscopy; new measurements of conversion electron binding energies in berkelium and californium; nuclear level densities; relative importance of statistical vs. valence neutron capture in the mass-90 region; determination of properties of short-lived fission products; fission yield of /sup 87/Br and /sup 137/I from 15 nuclei ranging from /sup 232/Th to /sup 249/Cf; evaluation of charged particle data for the ECPL library; evaluation of secondary charged-particle energy and angular distributions for ENDL; and evaluated nuclear structure libraries derived from the table of isotopes. (GHT)

  9. Virtual Nuclear Envelope Breakdown and Its Regulators in Fission Yeast Meiosis.

    PubMed

    Asakawa, Haruhiko; Yang, Hui-Ju; Hiraoka, Yasushi; Haraguchi, Tokuko

    2016-01-01

    Ran, a small GTPase, is required for the spindle formation and nuclear envelope (NE) formation. After NE breakdown (NEBD) during mitosis in metazoan cells, the Ran-GTP gradient across the NE is lost and Ran-GTP becomes concentrated around chromatin, thus affecting the stability of microtubules and promoting the assembly of spindle microtubules and segregation of chromosomes. Mitosis in which chromosomes are segregated subsequent to NEBD is called "open mitosis." In contrast, many fungi undergo a process termed "closed mitosis" in which chromosome segregation and spindle formation occur without NEBD. Although the fission yeast Schizosaccharomyces pombe undergoes a closed mitosis, it exhibits a short period during meiosis (anaphase of the second meiosis; called "anaphase II") when nuclear and cytoplasmic proteins are mixed in the presence of intact NE and nuclear pore complexes (NPC). This "virtual" nuclear envelope breakdown (vNEBD) involves changes in the localization of RanGAP1, an activator of Ran-GTP hydrolysis. Recently, Nup132, a component of the structural core Nup107-160 subcomplex of the NPC, has been shown to be involved in the maintenance of the nuclear cytoplasmic barrier in yeast meiosis. In this review, we highlight the possible roles of RanGAP1 and Nup132 in vNEBD and discuss the biological significance of vNEBD in S. pombe meiosis.

  10. Fission and quasifission modes in heavy-ion-induced reactions leading to the formation of Hs{sup *}

    SciTech Connect

    Itkis, I. M.; Kozulin, E. M.; Itkis, M. G.; Knyazheva, G. N.; Bogachev, A. A.; Chernysheva, E. V.; Krupa, L.; Oganessian, Yu. Ts.; Zagrebaev, V. I.; Rusanov, A. Ya.; Goennenwein, F.; Dorvaux, O.; Stuttge, L.; Hanappe, F.; Vardaci, E.; Goes Brennand, E. de

    2011-06-15

    Mass and energy distributions of binary reaction products obtained in the reactions {sup 22}Ne+{sup 249}Cf,{sup 26}Mg+{sup 248}Cm, {sup 36}S+{sup 238}U, and {sup 58}Fe+{sup 208}Pb have been measured. All reactions lead to Hs isotopes. At energies below the Coulomb barrier the bimodal fission of Hs{sup *}, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed. In the reaction {sup 36}S+{sup 238}U, leading to the formation of a similar compound nucleus, the main part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier fusion-fission is the main process leading to the formation of symmetric fragments for both reactions with Mg and S ions. In the case of the {sup 58}Fe+{sup 208}Pb reaction the quasifission process dominates at all measured energies.

  11. Fusion-fission and quasifission in the reactions with heavy ions leading to the formation of Hs

    SciTech Connect

    Itkis, I. M.; Itkis, M. G.; Knyazheva, G. N.; Kozulin, E. M.

    2012-10-20

    Mass and energy distributions of binary reaction products obtained in the reactions {sup 22}Ne+{sup 249}Cf,{sup 26}Mg+{sup 248}Cm,{sup 36}S+{sup 238}U and {sup 58}Fe+{sup 208}Pb leading to Hs isotopes have been measured. At energies below the Coulomb barrier the bimodal fission of Hs*, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed. In the reaction {sup 36}S+{sup 238}U the considerable part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier the symmetric fragments originate mainly from fusion-fission process for both reactions with Mg and S ions. In the case of the {sup 58}Fe+{sup 208}Pb reaction the quasifission process dominates at all measured energies. The pre- and post-scission neutron multiplicities as a function of the fragment mass have been obtained for the reactions studied.

  12. Nuclear Reactions Used For Superheavy Element Research

    SciTech Connect

    Stoyer, Mark A.

    2008-04-17

    Some of the most fascinating questions about the limits of nuclear stability are confronted in the heaviest nuclei. How many more new elements can be synthesized? What are the nuclear and chemical properties of these exotic nuclei? Does the 'Island of Stability' exist and can we ever explore the isotopes inhabiting that nuclear region? This paper will focus on the current experimental research on the synthesis and characterization of superheavy nuclei with Z>112 from the Dubna/Livermore collaboration. Reactions using {sup 48}Ca projectiles from the U400 cyclotron and actinide targets ({sup 233,238}U, {sup 237}Np, {sup 242,244}Pu, {sup 243}Am, {sup 245,248}Cm, {sup 249}Cf) have been investigated using the Dubna Gas Filled Recoil Separator in Dubna over the last 8 years. In addition, several experiments have been performed to investigate the chemical properties of some of the observed longer-lived isotopes produced in these reactions. Some comments will be made on nuclear reactions used for the production of the heaviest elements. A summary of the current status of the upper end of the chart of nuclides will be presented.

  13. Nuclear reactions used for superheavy element research

    SciTech Connect

    Stoyer, M A

    2008-02-26

    Some of the most fascinating questions about the limits of nuclear stability are confronted in the heaviest nuclei. How many more new elements can be synthesized? What are the nuclear and chemical properties of these exotic nuclei? Does the 'Island of Stability' exist and can we ever explore the isotopes inhabiting that nuclear region? This paper will focus on the current experimental research on the synthesis and characterization of superheavy nuclei with Z > 112 from the Dubna/Livermore collaboration. Reactions using 48Ca projectiles from the U400 cyclotron and actinide targets ({sup 233,238}U, {sup 237}Np, {sup 242,244}Pu, {sup 243}Am, {sup 245,248}Cm, {sup 249}Cf) have been investigated using the Dubna Gas Filled Recoil Separator in Dubna over the last 8 years. In addition, several experiments have been performed to investigate the chemical properties of some of the observed longer-lived isotopes produced in these reactions. Some comments will be made on nuclear reactions used for the production of the heaviest elements. A summary of the current status of the upper end of the chart of nuclides will be presented.

  14. Fission fragment charge and mass distributions in 239Pu(n ,f ) in the adiabatic nuclear energy density functional theory

    NASA Astrophysics Data System (ADS)

    Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.

    2016-05-01

    Background: Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. Purpose: In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear density functional theory (DFT). Methods: Our theoretical framework is the nuclear energy density functional (EDF) method, where large-amplitude collective motion is treated adiabatically by using the time-dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). In practice, the TDGCM is implemented in two steps. First, a series of constrained EDF calculations map the configuration and potential-energy landscape of the fissioning system for a small set of collective variables (in this work, the axial quadrupole and octupole moments of the nucleus). Then, nuclear dynamics is modeled by propagating a collective wave packet on the potential-energy surface. Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. Results: We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in two-dimensional collective spaces. Theory and experiment agree typically within two mass units for the position of the asymmetric peak. As expected, calculations are sensitive to the structure of the initial state and the prescription for the collective inertia. We emphasize that results are also sensitive to the continuity of the collective landscape near scission. Conclusions: Our analysis confirms

  15. Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn

    SciTech Connect

    Kmiecik, M.; Maj, A.; Brekiesz, M.; Krolas, W.; Meczynski, W.; Styczen, J.; Zieblinski, M.; Million, B.; Bracco, A.; Camera, F.; Benzoni, G.; Leoni, S.; Wieland, O.; Brambilla, S.; Herskind, B.; Kicinska-Habior, M.; Dubray, N.; Dudek, J.; Schunck, N.

    2004-12-01

    The gamma-ray decay of the giant dipole resonance (GDR) in the compound nucleus {sup 216}Rn formed with the reaction {sup 18}O+{sup 198}Pt at the bombarding energy of 96 MeV was investigated. High-energy gamma-ray spectra in coincidence with both prompt and delayed low-energy transitions were measured. The obtained GDR width at the average temperature {approx_equal}1 MeV was found to be larger than that at T=0 MeV and to be approximately constant as a function of spin. The measured width value of 7 MeV is found to be consistent with the predictions based on calculations of the nuclear shape distribution using the newest approach for the treatment of the fission barrier within the liquid drop model. The present study is the first investigation of the giant dipole resonance width from the fusion-evaporation decay channel in this nuclear mass range.

  16. Benchmark experiments at ASTRA facility on definition of space distribution of {sup 235}U fission reaction rate

    SciTech Connect

    Bobrov, A. A.; Boyarinov, V. F.; Glushkov, A. E.; Glushkov, E. S.; Kompaniets, G. V.; Moroz, N. P.; Nevinitsa, V. A.; Nosov, V. I.; Smirnov, O. N.; Fomichenko, P. A.; Zimin, A. A.

    2012-07-01

    Results of critical experiments performed at five ASTRA facility configurations modeling the high-temperature helium-cooled graphite-moderated reactors are presented. Results of experiments on definition of space distribution of {sup 235}U fission reaction rate performed at four from these five configurations are presented more detail. Analysis of available information showed that all experiments on criticality at these five configurations are acceptable for use them as critical benchmark experiments. All experiments on definition of space distribution of {sup 235}U fission reaction rate are acceptable for use them as physical benchmark experiments. (authors)

  17. The spindle pole bodies facilitate nuclear envelope division during closed mitosis in fission yeast.

    PubMed

    Zheng, Liling; Schwartz, Cindi; Magidson, Valentin; Khodjakov, Alexey; Oliferenko, Snezhana

    2007-07-01

    Many organisms divide chromosomes within the confines of the nuclear envelope (NE) in a process known as closed mitosis. Thus, they must ensure coordination between segregation of the genetic material and division of the NE itself. Although many years of work have led to a reasonably clear understanding of mitotic spindle function in chromosome segregation, the NE division mechanism remains obscure. Here, we show that fission yeast cells overexpressing the transforming acid coiled coil (TACC)-related protein, Mia1p/Alp7p, failed to separate the spindle pole bodies (SPBs) at the onset of mitosis, but could assemble acentrosomal bipolar and antiparallel spindle structures. Most of these cells arrested in anaphase with fully extended spindles and nonsegregated chromosomes. Spindle poles that lacked the SPBs did not lead the division of the NE during spindle elongation, but deformed it, trapping the chromosomes within. When the SPBs were severed by laser microsurgery in wild-type cells, we observed analogous deformations of the NE by elongating spindle remnants, resulting in NE division failure. Analysis of dis1Delta cells that elongate spindles despite unattached kinetochores indicated that the SPBs were required for maintaining nuclear shape at anaphase onset. Strikingly, when the NE was disassembled by utilizing a temperature-sensitive allele of the Ran GEF, Pim1p, the abnormal spindles induced by Mia1p overexpression were capable of segregating sister chromatids to daughter cells, suggesting that the failure to divide the NE prevents chromosome partitioning. Our results imply that the SPBs preclude deformation of the NE during spindle elongation and thus serve as specialized structures enabling nuclear division during closed mitosis in fission yeast.

  18. Space Fission Propulsion System Development Status

    NASA Technical Reports Server (NTRS)

    Houts, M.; Van Dyke, M. K.; Godfroy, T. J.; Pedersen, K. W.; Martin, J. J.; Dickens, R.; Williams, E.; Harper, R.; Salvail, P.; Hrbud, I.

    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 space 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 straight-forward. 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 systems. While space fission systems 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 we are to reap the benefits of advanced space fission systems. NASA's Marshall Space Flight Center, working with Los Alamos National Laboratory (LANL), Sandia National Laboratories, and others, has conducted preliminary research related to a Safe Affordable Fission Engine (SAFE). An unfueled core has been fabricated by LANL, and resistance heaters used to verify predicted core thermal performance by closely mimicking heat from fission. The core is designed to use only established nuclear technology and be highly testable. In FY01 an energy conversion system and thruster will be coupled to the core, resulting in an 'end-to-end' nuclear electric propulsion demonstrator being tested using resistance heaters to closely mimic heat from fission. Results of the SAFE test program will be presented. The applicability

  19. Widespread exon skipping triggers degradation by nuclear RNA surveillance in fission yeast.

    PubMed

    Bitton, Danny A; Atkinson, Sophie R; Rallis, Charalampos; Smith, Graeme C; Ellis, David A; Chen, Yuan Y C; Malecki, Michal; Codlin, Sandra; Lemay, Jean-François; Cotobal, Cristina; Bachand, François; Marguerat, Samuel; Mata, Juan; Bähler, Jürg

    2015-06-01

    Exon skipping is considered a principal mechanism by which eukaryotic cells expand their transcriptome and proteome repertoires, creating different splice variants with distinct cellular functions. Here we analyze RNA-seq data from 116 transcriptomes in fission yeast (Schizosaccharomyces pombe), covering multiple physiological conditions as well as transcriptional and RNA processing mutants. We applied brute-force algorithms to detect all possible exon-skipping events, which were widespread but rare compared to normal splicing events. Exon-skipping events increased in cells deficient for the nuclear exosome or the 5'-3' exonuclease Dhp1, and also at late stages of meiotic differentiation when nuclear-exosome transcripts decreased. The pervasive exon-skipping transcripts were stochastic, did not increase in specific physiological conditions, and were mostly present at less than one copy per cell, even in the absence of nuclear RNA surveillance and during late meiosis. These exon-skipping transcripts are therefore unlikely to be functional and may reflect splicing errors that are actively removed by nuclear RNA surveillance. The average splicing rate by exon skipping was ∼ 0.24% in wild type and ∼ 1.75% in nuclear exonuclease mutants. We also detected approximately 250 circular RNAs derived from single or multiple exons. These circular RNAs were rare and stochastic, although a few became stabilized during quiescence and in splicing mutants. Using an exhaustive search algorithm, we also uncovered thousands of previously unknown splice sites, indicating pervasive splicing; yet most of these splicing variants were cryptic and increased in nuclear degradation mutants. This study highlights widespread but low frequency alternative or aberrant splicing events that are targeted by nuclear RNA surveillance.

  20. The Politics of Forgetting: Otto Hahn and the German Nuclear-Fission Project in World War II

    NASA Astrophysics Data System (ADS)

    Sime, Ruth Lewin

    2012-03-01

    As the co-discoverer of nuclear fission and director of the Kaiser Wilhelm Institute for Chemistry, Otto Hahn (1879-1968) took part in Germany`s nuclear-fission project throughout the Second World War. I outline Hahn's efforts to mobilize his institute for military-related research; his inclusion in high-level scientific structures of the military and the state; and his institute's research programs in neutron physics, isotope separation, transuranium elements, and fission products, all of potential military importance for a bomb or a reactor and almost all of it secret. These activities are contrasted with Hahn's deliberate misrepresentations after the war, when he claimed that his wartime work had been nothing but "purely scientific" fundamental research that was openly published and of no military relevance.

  1. Direct nuclear-pumped lasers using the He-3/n,p/H-3 reaction

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.; Jalufka, N. W.; Hohl, F.

    1978-01-01

    A description is presented of experimental results concerning a specific class of direct nuclear-pumped lasers classified as 'volumetric nuclear lasers'. In the considered laser system a fissioning gas, He-3, is mixed with the lasing gas to form a homogeneous mixture, resulting in uniform volume excitation. In typical volumetric nuclear lasers a fast-burst reactor is used as a source of neutrons which penetrate a polyethylene moderator. Here the fast neutrons are thermalized. After thermalization, neutrons scatter into the laser cell. Nuclear reactions produce a proton of 0.56 MeV and a tritium ion of 0.19. These ions produce secondary electrons which pump the laser medium creating a population inversion. The results reported demonstrate direct nuclear pumping of He-3-Ar, Xe, Kr, and Cl with the considered system.

  2. Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging.

    PubMed

    Rose, P B; Erickson, A S; Mayer, M; Nattress, J; Jovanovic, I

    2016-04-18

    Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as "searching for a needle in a haystack" because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

  3. Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

    PubMed Central

    Rose, P. B.; Erickson, A. S.; Mayer, M.; Nattress, J.; Jovanovic, I.

    2016-01-01

    Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications. PMID:27087555

  4. Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

    DOE PAGES

    Rose, P. B.; Erickson, A. S.; Mayer, M.; ...

    2016-04-18

    Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method frommore » being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.« less

  5. Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

    NASA Astrophysics Data System (ADS)

    Rose, P. B.; Erickson, A. S.; Mayer, M.; Nattress, J.; Jovanovic, I.

    2016-04-01

    Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

  6. Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

    SciTech Connect

    Rose, P. B.; Erickson, A. S.; Mayer, M.; Nattress, J.; Jovanovic, I.

    2016-04-18

    Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

  7. Aerosol simulation including chemical and nuclear reactions

    SciTech Connect

    Marwil, E.S.; Lemmon, E.C.

    1985-01-01

    The numerical simulation of aerosol transport, including the effects of chemical and nuclear reactions presents a challenging dynamic accounting problem. Particles of different sizes agglomerate and settle out due to various mechanisms, such as diffusion, diffusiophoresis, thermophoresis, gravitational settling, turbulent acceleration, and centrifugal acceleration. Particles also change size, due to the condensation and evaporation of materials on the particle. Heterogeneous chemical reactions occur at the interface between a particle and the suspending medium, or a surface and the gas in the aerosol. Homogeneous chemical reactions occur within the aersol suspending medium, within a particle, and on a surface. These reactions may include a phase change. Nuclear reactions occur in all locations. These spontaneous transmutations from one element form to another occur at greatly varying rates and may result in phase or chemical changes which complicate the accounting process. This paper presents an approach for inclusion of these effects on the transport of aerosols. The accounting system is very complex and results in a large set of stiff ordinary differential equations (ODEs). The techniques for numerical solution of these ODEs require special attention to achieve their solution in an efficient and affordable manner. 4 refs.

  8. Hadron Cancer Therapy: Role of Nuclear Reactions

    DOE R&D Accomplishments Database

    Chadwick, M. B.

    2000-06-20

    Recently it has become feasible to calculate energy deposition and particle transport in the body by proton and neutron radiotherapy beams, using Monte Carlo transport methods. A number of advances have made this possible, including dramatic increases in computer speeds, a better understanding of the microscopic nuclear reaction cross sections, and the development of methods to model the characteristics of the radiation emerging from the accelerator treatment unit. This paper describes the nuclear reaction mechanisms involved, and how the cross sections have been evaluated from theory and experiment, for use in computer simulations of radiation therapy. The simulations will allow the dose delivered to a tumor to be optimized, whilst minimizing the dos given to nearby organs at risk.

  9. Deposition of fission and activation products after the Fukushima Dai-ichi nuclear power plant accident.

    PubMed

    Shozugawa, Katsumi; Nogawa, Norio; Matsuo, Motoyuki

    2012-04-01

    The Great Eastern Japan Earthquake on March 11, 2011, damaged reactor cooling systems at Fukushima Dai-ichi nuclear power plant. The subsequent venting operation and hydrogen explosion resulted in a large radioactive nuclide emission from reactor containers into the environment. Here, we collected environmental samples such as soil, plant species, and water on April 10, 2011, in front of the power plant main gate as well as 35 km away in Iitate village, and observed gamma-rays with a Ge(Li) semiconductor detector. We observed activation products ((239)Np and (59)Fe) and fission products ((131)I, (134)Cs ((133)Cs), (137)Cs, (110m)Ag ((109)Ag), (132)Te, (132)I, (140)Ba, (140)La, (91)Sr, (91)Y, (95)Zr, and (95)Nb). (239)Np is the parent nuclide of (239)Pu; (59)Fe are presumably activation products of (58)Fe obtained by corrosion of cooling pipes. The results show that these activation and fission products, diffused within a month of the accident.

  10. Fission and quasifission of composite systems with Z =108 -120 : Transition from heavy-ion reactions involving S and Ca to Ti and Ni ions

    NASA Astrophysics Data System (ADS)

    Kozulin, E. M.; Knyazheva, G. N.; Novikov, K. V.; Itkis, I. M.; Itkis, M. G.; Dmitriev, S. N.; Oganessian, Yu. Ts.; Bogachev, A. A.; Kozulina, N. I.; Harca, I.; Trzaska, W. H.; Ghosh, T. K.

    2016-11-01

    Background: Suppression of compound nucleus formation in the reactions with heavy ions by a quasifission process in dependence on the reaction entrance channel. Purpose: Investigation of fission and quasifission processes in the reactions 36S,48Ca,48Ti , and 64Ni+238U at energies around the Coulomb barrier. Methods: Mass-energy distributions of fissionlike fragments formed in the reaction 48Ti+238U at energies of 247, 258, and 271 MeV have been measured using the double-arm time-of-flight spectrometer CORSET at the U400 cyclotron of the Flerov Laboratory of Nuclear Reactions and compared with mass-energy distributions for the reactions 36S,48Ca,64Ni+238U . Results: The most probable fragment masses as well as total kinetic energies and their dispersions in dependence on the interaction energies have been investigated for asymmetric and symmetric fragments for the studied reactions. The fusion probabilities have been deduced from the analysis of mass-energy distributions. Conclusion: The estimated fusion probability for the reactions S, Ca, Ti, and Ni ions with actinide nuclei shows that it depends exponentially on the mean fissility parameter of the system. For the reactions with actinide nuclei leading to the formation of superheavy elements the fusion probabilities are of several orders of magnitude higher than in the case of cold fusion reactions.

  11. Cross Sections Calculations of ( d, t) Nuclear Reactions up to 50 MeV

    NASA Astrophysics Data System (ADS)

    Tel, E.; Yiğit, M.; Tanır, G.

    2013-04-01

    In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of ( d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, ( d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for ( d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in

  12. Fuel Performance Experiments and Modeling: Fission Gas Bubble Nucleation and Growth in Alloy Nuclear Fuels

    SciTech Connect

    McDeavitt, Sean; Shao, Lin; Tsvetkov, Pavel; Wirth, Brian; Kennedy, Rory

    2014-04-07

    Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. Many mechanistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, research, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development such that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.

  13. From simple to complex reactions: Nuclear collisions near the Coulomb barrier

    SciTech Connect

    Rehm, K.E.

    1992-12-01

    Collisions between two heavy nuclei produce a diverse spectrum of reaction modes which is much wider than that observed in light ion studies. For the latter case, two processes are observed: direct reactions and compound nucleus formation. Heavy ion reaction studies on the other hand have identified additional processes such as deep-inelastic scattering, incomplete fusion and quasi-fission reactions. While the boundaries between the various processes are usually not well defined, it is generally accepted that with increasing overlap of the two nuclei the interaction evolves from distant collisions where only elastic scattering and Coulomb excitation processes occur, through grazing-type collisions associated with quasi-elastic reactions to deep-inelastic and fusion-fission processes requiring a substantial nuclear overlap. Varying the bombarding energy is a convenient way to change the overlap of the two nuclei. Measurements of excitation functions can thus probe the onset and the interplay of the various reaction modes. Experiments at bombarding energies in the vicinity of the Coulomb barrier are particularly suited for comparisons with theoretical predictions since the small number of degrees of freedom involved in the interaction greatly simplifies the calculations. In the first part of this contribution a short overview is given on the status of heavy ion reaction studies at energies in the vicinity of the Coulomb barrier. In the second part two experiments, one involving simple and the other studying complex reactions, are discussed in more detail.

  14. From simple to complex reactions: Nuclear collisions near the Coulomb barrier

    SciTech Connect

    Rehm, K.E.

    1992-01-01

    Collisions between two heavy nuclei produce a diverse spectrum of reaction modes which is much wider than that observed in light ion studies. For the latter case, two processes are observed: direct reactions and compound nucleus formation. Heavy ion reaction studies on the other hand have identified additional processes such as deep-inelastic scattering, incomplete fusion and quasi-fission reactions. While the boundaries between the various processes are usually not well defined, it is generally accepted that with increasing overlap of the two nuclei the interaction evolves from distant collisions where only elastic scattering and Coulomb excitation processes occur, through grazing-type collisions associated with quasi-elastic reactions to deep-inelastic and fusion-fission processes requiring a substantial nuclear overlap. Varying the bombarding energy is a convenient way to change the overlap of the two nuclei. Measurements of excitation functions can thus probe the onset and the interplay of the various reaction modes. Experiments at bombarding energies in the vicinity of the Coulomb barrier are particularly suited for comparisons with theoretical predictions since the small number of degrees of freedom involved in the interaction greatly simplifies the calculations. In the first part of this contribution a short overview is given on the status of heavy ion reaction studies at energies in the vicinity of the Coulomb barrier. In the second part two experiments, one involving simple and the other studying complex reactions, are discussed in more detail.

  15. Biological significance of nuclear localization of mitogen-activated protein kinase Pmk1 in fission yeast.

    PubMed

    Sánchez-Mir, Laura; Franco, Alejandro; Madrid, Marisa; Vicente-Soler, Jero; Villar-Tajadura, M Antonia; Soto, Teresa; Pérez, Pilar; Gacto, Mariano; Cansado, José

    2012-07-27

    Mitogen-activated protein kinase (MAPK) signaling pathways play a fundamental role in the response of eukaryotic cells to environmental changes. Also, much evidence shows that the stimulus-dependent nuclear targeting of this class of regulatory kinases is crucial for adequate regulation of distinct cellular events. In the fission yeast Schizosaccharomyces pombe, the cell integrity MAPK pathway, whose central element is the MAPK Pmk1, regulates multiple processes such as cell wall integrity, vacuole fusion, cytokinesis, and ionic homeostasis. In non-stressed cells Pmk1 is constitutively localized in both cytoplasm and nucleus, and its localization pattern appears unaffected by its activation status or in response to stress, thus questioning the biological significance of the presence of this MAPK into the nucleus. We have addressed this issue by characterizing mutants expressing Pmk1 versions excluded from the cell nucleus and anchored to the plasma membrane in different genetic backgrounds. Although nuclear Pmk1 partially regulates cell wall integrity at a transcriptional level, membrane-tethered Pmk1 performs many of the biological functions assigned to wild type MAPK like regulation of chloride homeostasis, vacuole fusion, and cellular separation. However, we found that down-regulation of nuclear Pmk1 by MAPK phosphatases induced by the stress activated protein kinase pathway is important for the fine modulation of extranuclear Pmk1 activity. These results highlight the importance of the control of MAPK activity at subcellular level.

  16. Biological Significance of Nuclear Localization of Mitogen-activated Protein Kinase Pmk1 in Fission Yeast*

    PubMed Central

    Sánchez-Mir, Laura; Franco, Alejandro; Madrid, Marisa; Vicente-Soler, Jero; Villar-Tajadura, M. Antonia; Soto, Teresa; Pérez, Pilar; Gacto, Mariano; Cansado, José

    2012-01-01

    Mitogen-activated protein kinase (MAPK) signaling pathways play a fundamental role in the response of eukaryotic cells to environmental changes. Also, much evidence shows that the stimulus-dependent nuclear targeting of this class of regulatory kinases is crucial for adequate regulation of distinct cellular events. In the fission yeast Schizosaccharomyces pombe, the cell integrity MAPK pathway, whose central element is the MAPK Pmk1, regulates multiple processes such as cell wall integrity, vacuole fusion, cytokinesis, and ionic homeostasis. In non-stressed cells Pmk1 is constitutively localized in both cytoplasm and nucleus, and its localization pattern appears unaffected by its activation status or in response to stress, thus questioning the biological significance of the presence of this MAPK into the nucleus. We have addressed this issue by characterizing mutants expressing Pmk1 versions excluded from the cell nucleus and anchored to the plasma membrane in different genetic backgrounds. Although nuclear Pmk1 partially regulates cell wall integrity at a transcriptional level, membrane-tethered Pmk1 performs many of the biological functions assigned to wild type MAPK like regulation of chloride homeostasis, vacuole fusion, and cellular separation. However, we found that down-regulation of nuclear Pmk1 by MAPK phosphatases induced by the stress activated protein kinase pathway is important for the fine modulation of extranuclear Pmk1 activity. These results highlight the importance of the control of MAPK activity at subcellular level. PMID:22685296

  17. Forging the link between nuclear reactions and nuclear structure

    NASA Astrophysics Data System (ADS)

    Dickhoff, W. H.

    2016-06-01

    A review of the recent applications of the dispersive optical model (DOM) is presented. Emphasis is on the nonlocal implementation of the DOM that is capable of describing ground-state properties accurately when data like the nuclear charge density are available. The present understanding of the role of short- and long-range physics in determining proton properties near the Fermi energy for stable closed-shell nuclei has relied mostly on data from the (e, e' p) reaction. Hadronic tools to extract such spectroscopic information have been hampered by the lack of a consistent reaction description that provides unambiguous and undisputed results. The DOM, conceived by Claude Mahaux, provides a unified description of both elastic nucleon scattering and structure information related to single-particle properties below the Fermi energy. We have recently introduced a nonlocal dispersive optical potential for both the real and imaginary part. Nonlocal absorptive potentials yield equivalent elastic differential cross sections for 40Ca as compared to local ones but change the l-dependent absorption profile suggesting important consequences for the analysis of nuclear reactions. Below the Fermi energy, nonlocality is essential for an accurate representation of particle number and the nuclear charge density. Spectral properties implied by (e, e' p) and (p, 2p) reactions are correctly described, including the energy distribution of about 10% high-momentum protons obtained at Jefferson Lab. The nonlocal DOM allows a complete description of experimental data both above (up to 200 MeV) and below the Fermi energy in 40Ca. It is further demonstrated that elastic nucleon-nucleus scattering data constrain the spectral strength in the continuum of orbits that are nominally bound in the independent-particle model. Extension of this analysis to 48Ca allows a prediction of the neutron skin of this nucleus that is larger than most predictions made so far.

  18. Determination of fission gas release of spent nuclear fuel in puncturing test and in leaching experiments under anoxic conditions

    NASA Astrophysics Data System (ADS)

    González-Robles, E.; Metz, V.; Wegen, D. H.; Herm, M.; Papaioannou, D.; Bohnert, E.; Gretter, R.; Müller, N.; Nasyrow, R.; de Weerd, W.; Wiss, T.; Kienzler, B.

    2016-10-01

    During reactor operation the fission gases Kr and Xe are formed within the UO2 matrix of nuclear fuel. Their quantification is important to evaluate their impact on critical parameters regarding the fuel behaviour during irradiation and (long-term) interim storage, such as internal pressure of the fuel rod and fuel swelling. Moreover the content of Kr and Xe in the plenum of a fuel rod and their content in the UO2 fuel itself are widely used as indicators for the release properties of 129I, 137Cs, and other safety relevant radionuclides with respect to final disposal of spent nuclear fuel. The present study deals with the fission gas release from spent nuclear fuel exposed to simulated groundwater in comparison with the fission gas previously released to the fuel rod plenum during irradiation in reactor. In a unique approach we determined both the Kr and Xe inventories in the plenum by means of a puncturing test and in leaching experiments with a cladded fuel pellet and fuel fragments in bicarbonate water under 3.2 bar H2 overpressure. The fractional inventory of the fission gases released during irradiation into the plenum was (8.3 ± 0.9) %. The fraction of inventory of fission gases released during the leaching experiments was (17 ± 2) % after 333 days of leaching of the cladded pellet and (25 ± 2) % after 447 days of leaching of the fuel fragments, respectively. The relatively high release of fission gases in the experiment with fuel fragments was caused by the increased accessibility of water to the Kr and Xe occluded in the fuel.

  19. Monte Carlo Models for the Production of beta-delayed Gamma Rays Following Fission of Special Nuclear Materials

    SciTech Connect

    Pruet, J; Prussin, S; Descalle, M; Hall, J

    2004-02-03

    A Monte Carlo method for the estimation of {beta}-delayed {gamma}-ray spectra following fission is described that can accommodate an arbitrary time-dependent fission rate and photon collection history. The method invokes direct sampling of the independent fission yield distributions of the fissioning system, the branching ratios for decay of individual fission products and the spectral distributions for photon emission for each decay mode. Though computationally intensive, the method can provide a detailed estimate of the spectrum that would be recorded by an arbitrary spectrometer, and can prove useful in assessing the quality of evaluated data libraries, for identifying gaps in these libraries, etc. The method is illustrated by a first comparison of calculated and experimental spectra from decay of short-lived fission products following the reactions {sup 235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f). For general purpose transport calculations, where detailed consideration of the large number of individual {gamma}-ray transitions in a spectrum may be unnecessary, it is shown that an accurate and simple parameterization of a {gamma}-ray source function can be obtained. These parametrizations should provide high-quality average spectral distributions that should prove useful in calculations describing photons escaping from thick attenuating media.

  20. Venting of fission products and shielding in thermionic nuclear reactor systems

    NASA Technical Reports Server (NTRS)

    Salmi, E. W.

    1972-01-01

    Most thermionic reactors are designed to allow the fission gases to escape out of the emitter. A scheme to allow the fission gases to escape is proposed. Because of the low activity of the fission products, this method should pose no radiation hazards.

  1. Calculation of nuclear reaction cross sections on excited nuclei with the coupled-channels method

    SciTech Connect

    Kawano, T.; Talou, P.; Lynn, J. E.; Chadwick, M. B.; Madland, D. G.

    2009-08-15

    We calculate nuclear cross sections on excited nuclei in the fast neutron energy range. We partition the whole process into two contributions: the direct reaction part and the compound nuclear reactions. A coupled-channels method is used for calculating the direct transition of the nucleus from the initial excited state, which is a member of the ground-state rotational band, to the final ground and excited low-lying levels. This process is strongly affected by the channel coupling. The compound nuclear reactions on the excited state are calculated with the statistical Hauser-Feshbach model, with the transmission coefficients obtained from the coupled-channels calculation. The calculations are performed for a strongly deformed nucleus {sup 169}Tm, and selected cross sections for the ground and first excited states are compared. The calculation is also made for actinides to investigate possible modification to the fission cross section when the target is excited. It is shown that both the level coupling for the entrance channel, and the different target spin, change the fission cross section.

  2. Non-nuclear Testing of Reactor Systems in the Early Flight Fission Test Facilities (EFF-TF)

    NASA Technical Reports Server (NTRS)

    VanDyke, Melissa; Martin, James

    2004-01-01

    The Early Flight Fission-Test Facility (EFF-TF) can assist in the &sign and development of systems through highly effective non-nuclear testing of nuclear systems when technical issues associated with near-term space fission systems are "non-nuclear" in nature (e.g. system s nuclear operations are understood). For many systems. thermal simulators can he used to closely mimic fission heat deposition. Axial power profile, radial power profile. and fuel pin thermal conductivity can be matched. In addition to component and subsystem testing, operational and lifetime issues associated with the steady state and transient performance of the integrated reactor module can be investigated. Instrumentation at the EFF-TF allows accurate measurement of temperature, pressure, strain, and bulk core deformation (useful for accurately simulating nuclear behavior). Ongoing research at the EFF-TF is geared towards facilitating research, development, system integration, and system utilization via cooperative efforts with DOE laboratories, industry, universities, and other NASA centers. This paper describes the current efforts for the latter portion of 2003 and beginning of 2004.

  3. Design and operation of gamma scan and fission gas sampling systems for characterization of irradiated commercial nuclear fuel

    SciTech Connect

    Knox, C.A.; Thornhill, R.E.; Mellinger, G.B.

    1989-09-01

    One of the primary objectives of the Materials Characterization Center (MCC) is to acquire and characterize spent fuels used in waste form testing related to nuclear waste disposal. The initial steps in the characterization of a fuel rod consist of gamma scanning the rod and sampling the gas contained in the fuel rod (referred to as fission gas sampling). The gamma scan and fission gas sampling systems used by the MCC are adaptable to a wide range of fuel types and have been successfully used to characterize both boiling water reactor (BWR) and pressurized water reactor (PWR) fuel rods. This report describes the design and operation of systems used to gamma scan and fission gas sample full-length PWR and BWR fuel rods. 1 ref., 10 figs., 1 tab.

  4. The limits of the nuclear chart set by fission and alpha decay

    NASA Astrophysics Data System (ADS)

    Möller, Peter

    2016-12-01

    I will review how our picture of heavy-element nuclear structure has evolved through remarkably simple ideas and related models. It is well known that the Bethe-Weizsäcker semi-empirical mass model had an important role in unraveling radioactive decay and element transmutation in the heavy-element region in the 1930s. A remarkable aspect is that this model could immediately after the discovery of fission be generalized to explain this phenomenon through the consideration of deformation of a charged liquid drop. Bethe and Bacher already raised the possibility that shell structure (by them calculated in terms of a single-particle oscillator potential) could give rise to noticeable deviations between results of the macroscopic mass model and experiment but limited data prevented firm conclusions. In the 1950s the single-particle models took a realistic form and also included deformation. The possibility of the existence of a relatively stable "island" of superheavy elements was raised already then. But it was not until the work by Strutinsky in the mid 1960s that a quantitative model for the nuclear potential-energy emerged in the form of the macroscopic-microscopic model. Although new elements have been discovered at an almost steady pace since 1940, theory indicates that we are close to the end of this era: repulsive Coulomb effects will set the limit of observable elements to near Z = 120.

  5. State-of-the-art on instant release of fission products from spent nuclear fuel

    SciTech Connect

    Kienzler, Bernhard; Gonzalez-Robles, Ernesto

    2013-07-01

    Within the EURATOM FP7 Collaborative Project 'Fast / Instant Release of Safety Relevant Radionuclides from Spent Nuclear Fuel (CP FIRST-Nuclides)', a State-of-the-Art Report was prepared. The fast / instant release fraction (IRF) is defined as a fraction of the inventory of radionuclides that may be rapidly released from the fuel and fuel assembly materials at the time of canister breaching. In the context of safety analysis for a repository, the time span for mobilization of this fraction can be considered instantaneously, even if the process takes some time in experiments. Radionuclides contributing to the fast release are fission gases (Kr and Xe), easily soluble elements such as cesium and iodine, and other elements which are hardly incorporated in the UO{sub 2} crystal lattice. The present contribution summarizes the results obtained from published studies focused on rapid release experiments carried out with different spent nuclear fuel (SNF), samples, sizes, techniques (batch and flow-through), and durations. A total of 80 experiments cover the study of UO{sub 2} SNF from pressure water reactors (PWR) of different initial enrichments and burn-up, while 20 experiments were performed with UO{sub 2} SNF from boiling water reactors (BWR) and 8 with MOX fuel. (authors)

  6. MetroFission: New high-temperature references and sensors for the nuclear industry

    NASA Astrophysics Data System (ADS)

    Sadli, M.; del Campo, D.; de Podesta, M.; Deuzé, T.; Failleau, G.; Elliott, C. J.; Fourrez, S.; García, C.; Pearce, J. V.

    2013-09-01

    The European metrology research programme (EMRP) allows funding for metrology-oriented projects in the frame of targeted calls aimed at improving metrology for important contemporary and future needs in different fields such as energy, environment and industry. A joint research project (JRP), called "MetroFission", was selected for funding in the "Energy" call of 2010. This JRP, led by NPL (UK), aims to anticipate and to start addressing the metrological needs of the next generation of nuclear power plants. The need for improving the accuracy and reliability of temperature measurements at temperatures higher than those currently measured in nuclear power plants is dealt with in the first workpackage of the project. This project started in September 2010 and will last for three years. This paper summarizes the activities of the first half of the project and the expected final achievements, which will be essentially oriented towards new temperature references and new devices, adapted to the high temperature range as well as the particularly harsh working conditions.

  7. Design and Test Plans for a Non-Nuclear Fission Power System Technology Demonstration Unit

    NASA Technical Reports Server (NTRS)

    Mason, Lee; Palac, Donald; Gibson, Marc; Houts, Michael; Warren, John; Werner, James; Poston, David; Qualls, Arthur Lou; Radel, Ross; Harlow, Scott

    2012-01-01

    A joint National Aeronautics and Space Administration (NASA) and Department of Energy (DOE) team is developing concepts and technologies for affordable nuclear Fission Power Systems (FPSs) to support future exploration missions. A key deliverable is the Technology Demonstration Unit (TDU). The TDU will assemble the major elements of a notional FPS with a non-nuclear reactor simulator (Rx Sim) and demonstrate system-level performance in thermal vacuum. The Rx Sim includes an electrical resistance heat source and a liquid metal heat transport loop that simulates the reactor thermal interface and expected dynamic response. A power conversion unit (PCU) generates electric power utilizing the liquid metal heat source and rejects waste heat to a heat rejection system (HRS). The HRS includes a pumped water heat removal loop coupled to radiator panels suspended in the thermal-vacuum facility. The basic test plan is to subject the system to realistic operating conditions and gather data to evaluate performance sensitivity, control stability, and response characteristics. Upon completion of the testing, the technology is expected to satisfy the requirements for Technology Readiness Level 6 (System Demonstration in an Operational and Relevant Environment) based on the use of high-fidelity hardware and prototypic software tested under realistic conditions and correlated with analytical predictions.

  8. Design and Test Plans for a Non-Nuclear Fission Power System Technology Demonstration Unit

    NASA Astrophysics Data System (ADS)

    Mason, L.; Palac, D.; Gibson, M.; Houts, M.; Warren, J.; Werner, J.; Poston, D.; Qualls, L.; Radel, R.; Harlow, S.

    A joint National Aeronautics and Space Administration (NASA) and Department of Energy (DOE) team is developing concepts and technologies for affordable nuclear Fission Power Systems (FPSs) to support future exploration missions. A key deliverable is the Technology Demonstration Unit (TDU). The TDU will assemble the major elements of a notional FPS with a non-nuclear reactor simulator (Rx Sim) and demonstrate system-level performance in thermal vacuum. The Rx Sim includes an electrical resistance heat source and a liquid metal heat transport loop that simulates the reactor thermal interface and expected dynamic response. A power conversion unit (PCU) generates electric power utilizing the liquid metal heat source and rejects waste heat to a heat rejection system (HRS). The HRS includes a pumped water heat removal loop coupled to radiator panels suspended in the thermal-vacuum facility. The basic test plan is to subject the system to realistic operating conditions and gather data to evaluate performance sensitivity, control stability, and response characteristics. Upon completion of the testing, the technology is expected to satisfy the requirements for Technology Readiness Level 6 (System Demonstration in an Operational and Relevant Environment) based on the use of high-fidelity hardware and prototypic software tested under realistic conditions and correlated with analytical predictions.

  9. Fusion-fission study at IUAC: Recent results

    NASA Astrophysics Data System (ADS)

    Pullanhiotan, Sugathan

    2016-10-01

    Several properties observed in heavy ion induced fission led to the conclusion that fission is not always originated from fully equilibrated compound nucleus. Soon after the collision of two nuclei, it forms a di-nuclear system than can fission before a compound nucleus is formed. This process termed quasi-fission is a major hurdle to the formation of heavier elements by fusion. Fission originated before complete equilibration showed anomalously large angular anisotropy and mass distribution wider than what is expected from compound nucleus fission. The standard statistical model fails to predict the outcome of quasi-fission and currently no dynamical model is fully developed to predict all the features of quasi-fission. Though much progress has been made in recent times, a full understanding of the fission dynamics is still missing. Experiments identifying the influence of entrance channel parameters on dynamics of fusion-fission showed contrasting results. At IUAC accelerator facility many experiments have been performed to make a systematic study of fission dynamics using mass distribution, angular distribution and neutron multiplicity measurements in mass region around A ∼ 200. Recent measurement on mass distribution of fission fragment from reaction 19 F +206,208 Pb around fusion barrier energy showed the influence of multi-mode fission in enhancing the mass variance at low excitation energy. In this talk I will present some of these results.

  10. Multivariate High Order Statistics of Measurements of the Temporal Evolution of Fission Chain-Reactions

    SciTech Connect

    Mattingly, J.K.

    2001-03-08

    The development of high order statistical analyses applied to measurements of the temporal evolution of fission chain-reactions is described. These statistics are derived via application of Bayes' rule to conditional probabilities describing a sequence of events in a fissile system beginning with the initiation of a chain-reaction by source neutrons and ending with counting events in a collection of neutron-sensitive detectors. Two types of initiating neutron sources are considered: (1) a directly observable source introduced by the experimenter (active initiation), and (2) a source that is intrinsic to the system and is not directly observable (passive initiation). The resulting statistics describe the temporal distribution of the population of prompt neutrons in terms of the time-delays between members of a collection (an n-tuplet) of correlated detector counts, that, in turn, may be collectively correlated with a detected active source neutron emission. These developments are a unification and extension of Rossi-a, pulsed neutron, and neutron noise methods, each of which measure the temporal distribution of pairs of correlated events, to produce a method that measures the temporal distribution of n-tuplets of correlated counts of arbitrary dimension n. In general the technique should expand present capabilities in the analysis of neutron counting measurements.

  11. HETEROGENEOUS NUCLEAR REACTOR EMPLOYING SMALL UNCLAD BODIES OF FISSIONABLE MATERIAL AS FUEL

    DOEpatents

    Hyman, H.H.; Katz, J.J.

    1961-05-01

    A nuclear reactor in which fuel pellets are continuously dissolved in a moderator liquid is described. The fuel pellets are fed into the top of elongated baskets which are submerged in moderator liquid, and a portion of the moderator liquid is continuously withdrawn and processed to recove r reaction products.

  12. Fission fragment charge and mass distributions in 239Pu(n, f ) in the adiabatic nuclear energy density functional theory

    SciTech Connect

    Regnier, D.; Dubray, N.; Schunck, N.; Verriere, M.

    2016-05-13

    Here, accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics.

  13. Investigations of nuclear structure and nuclear reactions induced by complex projectiles

    SciTech Connect

    Sarantites, D.G.

    1990-01-01

    This report discusses research in the following areas: nuclear structure; fusion reactions near and below the barrier; incomplete fusion and fragmentation reactions; and instrumentation and analysis. (LSP).

  14. Fission product yield evaluation for the USA evaluated nuclear data files

    SciTech Connect

    Rider, B.F.; England, T.R.

    1994-10-01

    An evaluated set of fission product yields for use in calculation of decay heat curves with improved accuracy has been prepared. These evaluated yields are based on all known experimental data through 1992. Unmeasured fission product yields are calculated from charge distribution, pairing effects, and isomeric state models developed at Los Alamos National Laboratory. The current evaluation has been distributed as the ENDF/B-VI fission product yield data set.

  15. Basic results of investigations of scission neutrons in nuclear fission at low excitation energies

    SciTech Connect

    Petrov, G. A. Gagarski, A. M.; Guseva, I. S.; Sokolov, V. E.; Val'ski, G. V.; Vorobiev, A. S.; Krinitcin, D. O.; Shcherbakov, O. A.; Nikolaev, D. V.; Pleva, Yu. S.; Petrova, V. I.; Zavarukhina, T. A.

    2008-07-15

    To estimate the main characteristics of neutrons emitted shortly before the scission of a fissioning nucleus, various experiments sensitive to the presence of these scission neutrons in thermal-neutron-induced fission of {sup 235}U and spontaneous fission of {sup 252}Cf were performed. The results of the experiments were analyzed within theoretical calculations allowing for various possible neutron-emission mechanisms, including the possibility of the emergence of neutrons from the scission of a nucleus.

  16. Nuclear Reaction Data on Titanium Isotopes

    SciTech Connect

    Oh, S. Y.; Kawano, T.; Kahler, S.; Cowell, S.; Dashdorj, D.

    2008-04-17

    We evaluated the nuclear data on titanium isotopes, {sup 46-50}Ti. We used GNASH, a Hauser-Feshbach reaction model code, for the threshold reactions and CoH for the total and capture cross sections. While we calculated the transmission coefficients using well-known optical potentials for the GNASH calculation, we adjusted the level density and the pre-equilibrium parameters by taking into account the LANSCE/GEANIE experiment on {sup 48}Ti reaction cross sections as well as other experiments available for (n,p), (n,{alpha}), etc. The direct inelastic scattering was also included by using the coupled-channel calculation and the DWBA method. The coupled-channels potential was assumed to be similar to the spherical potential of Koning and Delaroche with proper deformation parameters. Meanwhile we investigated the resolved resonance parameters in the energy region below several hundred keV. In essence, we adopted the parameters from the Mughabghab's 2006 compilation, making some adjustments to mainly reproduce the reference thermal cross sections. This new evaluation was validated with the MCNP calculations of k-eff's on seven hard-spectrum criticality experiments that involve Ti as a reflector or moderator.

  17. Thermonuclear Reaction Rate Parameterization for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Sharp, Jacob; Kozub, Raymond L.; Smith, Michael S.; Scott, Jason; Lingerfelt, Eric

    2004-10-01

    The knowledge of thermonuclear reaction rates is vital to simulate novae, supernovae, X-ray bursts, and other astrophysical events. To facilitate dissemination of this knowledge, a set of tools has been created for managing reaction rates, located at www.nucastrodata.org. One tool is a rate parameterizer, which provides a parameterization for nuclear reaction rate vs. temperature values in the most widely used functional form. Currently, the parameterizer uses the Levenberg-Marquardt method (LMM), which requires an initial estimate of the best-fit parameters. The initial estimate is currently provided randomly from a preselected pool. To improve the quality of fits, a new, active method of selecting parameters has been developed. The parameters of each set in the pool are altered for a few iterations to replicate the input data as closely as possible. Then, the set which most nearly matches the input data (based on chi squared) is used in the LMM as the initial estimate for the final fitting procedure. A description of the new, active algorithm and its performance will be presented. Supported by the U. S. Department of Energy.

  18. A proline-tyrosine nuclear localization signal (PY-NLS) is required for the nuclear import of fission yeast PAB2, but not of human PABPN1.

    PubMed

    Mallet, Pierre-Luc; Bachand, François

    2013-03-01

    Nuclear poly(A)-binding proteins (PABPs) are evolutionarily conserved proteins that play key roles in eukaryotic gene expression. In the fission yeast Schizosaccharomyces pombe, the major nuclear PABP, Pab2, functions in the maturation of small nucleolar RNAs as well as in nuclear RNA decay. Despite knowledge about its nuclear functions, nothing is known about how Pab2 is imported into the nucleus. Here, we show that Pab2 contains a proline-tyrosine nuclear localization signal (PY-NLS) that is necessary and sufficient for its nuclear localization and function. Consistent with the role of karyopherin β2 (Kapβ2)-type receptors in the import of PY-NLS cargoes, we show that the fission yeast ortholog of human Kapβ2, Kap104, binds to recombinant Pab2 and is required for Pab2 nuclear localization. The absence of arginine methylation in a basic region N-terminal to the PY-core motif of Pab2 did not affect its nuclear localization. However, in the context of a sub-optimal PY-NLS, we found that Pab2 was more efficiently targeted to the nucleus in the absence of arginine methylation, suggesting that this modification can affect the import kinetics of a PY-NLS cargo. Although a sequence resembling a PY-NLS motif can be found in the human Pab2 ortholog, PABPN1, our results indicate that neither a functional PY-NLS nor Kapβ2 activity are required to promote entry of PABPN1 into the nucleus of human cells. Our findings describe the mechanism by which Pab2 is imported into the nucleus, providing the first example of a PY-NLS import system in fission yeast. In addition, this study suggests the existence of alternative or redundant nuclear import pathways for human PABPN1.

  19. Search for instantaneous radiation near the instant of break momentum of various fissioning nuclear systems at low excitation energies

    SciTech Connect

    Vorobyev, A. S. Val'ski, G. V.; Gagarskii, A. M.; Guseva, I. S.; Petrov, G. A.; Petrova, V. I.; Serebrin, A. Yu.; Sokolov, V. E.; Shcherbakov, O. A.

    2011-12-15

    The main results of studying the properties of 'instantaneous' neutrons and {gamma} photons during the fission of {sup 233,235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f) nuclei and spontaneous fission of {sup 252}Cf, which were performed on the WWR-M reactor at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences, are presented. Along with obtaining the main characteristics of the instantaneous radiation from fission fragments, these studies were also aimed at gaining deeper insight into such exotic processes as the emission of break neutrons and {gamma} photons from a fissioning nucleus near the break point. These investigations were performed on different experimental setups using different analytical methods. This approach allowed us not only to find but also to reduce to minimum possible systematic effects. The yields of break neutrons were found to be about (5-7) Multiplication-Sign 10{sup -2} of the total number of neutrons per {sup 233,235}U(n, f) fission event and approximately twice as much for {sup 239}Pu(n, f) and {sup 252}Cf. The coefficient of T-odd asymmetry for {gamma} photons is in agreement with the estimate obtained on the assumption that the observed effect is mainly related to the {gamma} photons emitted by excited fragments with highly oriented angular momenta. This fact gave grounds to conclude that the desired break {gamma} photons cannot be reliably selected (within the obtained experimental accuracy) against the much larger background of {gamma} photons from fission fragments.

  20. On the role of energy separated in fission process, excitation energy and reaction channels effects in the isomeric ratios of fission product 135Xe in photofission of actinide elements

    NASA Astrophysics Data System (ADS)

    Thiep, Tran Duc; An, Truong Thi; Cuong, Phan Viet; Vinh, Nguyen The; Mishinski, G. V.; Zhemenik, V. I.

    2016-07-01

    In this work we present the isomeric ratio of fission product 135Xe in the photo-fission of actinide elements 232Th, 233U and 237Np induced by end-point bremsstrahlung energies of 13.5, 23.5 and 25.0 MeV which were determined by the method of inert gaseous flow. The data were analyzed, discussed and compared with the similar data from literature to examine the role of energy separated in fission process, excitation energy and reaction channels effects.

  1. Towards Nuclear Reactions from Lattice QCD

    NASA Astrophysics Data System (ADS)

    Briceno, Raul

    2012-10-01

    In this talk I will motivate the evaluation of nuclear reactions cross sections from Lattice Quantum Chromodynamics (LQCD) and discuss challenges associated with such calculations. In particular, I will explore the connection between the energy spectrum of a three-body system in a finite volume and infinite volume scattering matrix elements using an effective field theoretical approach. The implication of this formalism for studying systems composed of a particle and a bound-state below the bound-state break- up, as well as a trimer state will be discussed. I will show that one in fact recovers a Luscher-like quantization condition for sufficiently low-energy up to exponential corrections in the volume due to the size of the two-particle bound-state. I will briefly discuss the similarities of the three-body problem and that of two- body coupled-channels systems and will comment on challenges in applying the formalism above the inelastic threshold.

  2. Measurements of extinct fission products in nuclear bomb debris: Determination of the yield of the Trinity nuclear test 70 y later

    SciTech Connect

    Hanson, Susan Kloek; Pollington, Anthony Douglas; Waidmann, Christopher Russell; Kinman, William Scott; Wende, Allison Marie; Miller, Jeffrey L.; Berger, Jennifer A.; Oldham, Warren James; Selby, Hugh D.

    2016-07-05

    This study describes an approach to measuring extinct fission products that would allow for the characterization of a nuclear test at any time. The isotopic composition of molybdenum in five samples of glassy debris from the 1945 Trinity nuclear test has been measured. Nonnatural molybdenum isotopic compositions were observed, reflecting an input from the decay of the short-lived fission products 95Zr and 97Zr. By measuring both the perturbation of the 95Mo/96Mo and 97Mo/96Mo isotopic ratios and the total amount of molybdenum in the Trinity nuclear debris samples, it is possible to calculate the original concentrations of the 95Zr and 97Zr isotopes formed in the nuclear detonation. Together with a determination of the amount of plutonium in the debris, these measurements of extinct fission products allow for new estimates of the efficiency and yield of the historic Trinity test.

  3. Ion transport of Fr nuclear reaction products

    SciTech Connect

    Behr, J.A.; Cahn, S.B.; Dutta, S.B.

    1993-04-01

    Experiments planned for fundamental studies of radioactive atoms in magneto-optic traps require efficient deceleration and transport of nuclear reaction products to energies and locations where they can be trapped. The authors have built a low-energy ion transport system for Francium and other alkalis. A thick Au target is held on a W rod at 45{degrees} to the accelerator beam direction. The heavy-ion fusion reaction 115 MeV {sup 18}O + {sup 197}Au produces {sup 211,210,209}Fr recoil products which are stopped in the target. The target is heated to close to the melting point of Au to allow the Fr to diffuse to the surface, where it is ionized due to Au`s high work function, and is directly extracted by an electrode at 90{degrees} to the accelerator beam direction. The Fr is transported by electrostatic optics {approximately}1 m to a catcher viewed by an {alpha} detector: {ge}15% of the Fr produced in the target reaches the catcher. 2{times}10{sup 5} Fr/sec have been produced at the catcher, yielding at equilibrium a sample of 3x10{sup 7}Fr nuclei. This scheme physically decouples the target diffusion from the surface neutralization process, which can occur at a lower temperature more compatible with the neutral-atom trap.

  4. Reaction Rate Parameterization for Nuclear Astrophysics Research

    NASA Astrophysics Data System (ADS)

    Scott, J. P.; Lingerfelt, E. J.; Smith, M. S.; Hix, W. R.; Bardayan, D. W.; Sharp, J. E.; Kozub, R. L.; Meyer, R. A.

    2004-11-01

    Libraries of thermonuclear reaction rates are used in element synthesis models of a wide variety of astrophysical phenomena, such as exploding stars and the inner workings of our sun. These computationally demanding models are more efficient when libraries, which may contain over 60000 rates and vary by 20 orders of magnitude, have a uniform parameterization for all rates. We have developed an on-line tool, hosted at www.nucastrodata.org, to obtain REACLIB parameters (F.-K. Thielemann et al., Adv. Nucl. Astrophysics 525, 1 (1987)) that represent reaction rates as a function of temperature. This helps to rapidly incorporate the latest nuclear physics results in astrophysics models. The tool uses numerous techniques and algorithms in a modular fashion to improve the quality of the fits to the rates. Features, modules, and additional applications of this tool will be discussed. * Managed by UT-Battelle, LLC, for the U.S. D.O.E. under contract DE-AC05-00OR22725 + Supported by U.S. D.O.E. under Grant No. DE-FG02-96ER40955

  5. Investigation of the 238U(d ,p ) surrogate reaction via the simultaneous measurement of γ -decay and fission probabilities

    NASA Astrophysics Data System (ADS)

    Ducasse, Q.; Jurado, B.; Aïche, M.; Marini, P.; Mathieu, L.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Tornyi, T.; Wilson, J. N.; Barreau, G.; Boutoux, G.; Czajkowski, S.; Giacoppo, F.; Gunsing, F.; Hagen, T. W.; Lebois, M.; Lei, J.; Méot, V.; Morillon, B.; Moro, A. M.; Renstrøm, T.; Roig, O.; Rose, S. J.; Sérot, O.; Siem, S.; Tsekhanovich, I.; Tveten, G. M.; Wiedeking, M.

    2016-08-01

    We investigated the 238U(d ,p ) reaction as a surrogate for the n +238U reaction. For this purpose we measured for the first time the γ -decay and fission probabilities of *239U simultaneously and compared them to the corresponding neutron-induced data. We present the details of the procedure to infer the decay probabilities, as well as a thorough uncertainty analysis, including parameter correlations. Calculations based on the continuum-discretized coupled-channels method and the distorted-wave Born approximation (DWBA) were used to correct our data from detected protons originating from elastic and inelastic deuteron breakup. In the region where fission and γ emission compete, the corrected fission probability is in agreement with neutron-induced data, whereas the γ -decay probability is much higher than the neutron-induced data. We have performed calculations of the decay probabilities with the statistical model and of the average angular momentum populated in the 238U(d ,p ) reaction with the DWBA to interpret these results.

  6. Gas-phase detection of solid-state fission product complexes for post-detonation nuclear forensic analysis.

    PubMed

    Stratz, S Adam; Jones, Steven A; Oldham, Colton J; Mullen, Austin D; Jones, Ashlyn V; Auxier, John D; Hall, Howard L

    2016-01-01

    This study presents the first known detection of fission products commonly found in post-detonation nuclear debris samples using solid sample introduction and a uniquely coupled gas chromatography inductively-coupled plasma time-of-flight mass spectrometer. Rare earth oxides were chemically altered to incorporate a ligand that enhances the volatility of the samples. These samples were injected (as solids) into the aforementioned instrument and detected for the first time. Repeatable results indicate the validity of the methodology, and this capability, when refined, will prove to be a valuable asset for rapid post-detonation nuclear forensic analysis.

  7. Fission fragment angular distributions in the reactions {sup 16}O+{sup 188}Os and {sup 28}Si+{sup 176}Yb

    SciTech Connect

    Tripathi, R.; Sudarshan, K.; Sharma, S. K.; Reddy, A. V. R.; Pujari, P. K.; Goswami, A.; Ramachandran, K.

    2009-06-15

    Fission fragment angular distributions have been measured in the reactions {sup 16}O+{sup 188}Os and {sup 28}Si+{sup 176}Yb to investigate the contribution from noncompound nucleus fission. Parameters for statistical model calculations were fixed using fission cross section data in the {sup 16}O+{sup 188}Os reaction. Experimental anisotropies were in reasonable agreement with those calculated using the statistical saddle point model for both reactions. The present results are also consistent with those of mass distribution studies in the fission of {sup 202}Po, formed in the reactions with varying entrance channel mass asymmetry. However, the present studies do not show a large fusion hindrance as reported in the pre-actinide region based on the measurement of evaporation residue cross section.

  8. Ternary fission of a heavy nuclear system within a three-center shell model

    NASA Astrophysics Data System (ADS)

    Karpov, A. V.

    2016-12-01

    Background: Since more than 40 years of theoretical and experimental studies of true ternary fission, one is still quite far from its understanding. The true ternary fission channel, being strongly suppressed by the macroscopic properties of the potential energy, may, however, be present with a significant probability due to shell effects. Purpose: Development of a model for the multidimensional potential energy suitable for analysis of the nucleus-nucleus collisions with the possibility of ternary exit channel. Study of the potential possibility of fission of actinides into three heavy fragments. Method: The asymmetric three-center shell model of deformed nucleus is developed in this paper. The model can be applied for analysis of ternary as well as binary fission processes. Results: The potential energy surfaces for few ternary combinations in the fission channel are calculated for the 252Cf nucleus. Their properties are discussed. Conclusions: The potential energy structures are compared with the experimental observations. It was found that the potential energy has pronounced valleys favorable for ternary fission with formation of doubly magic tin as one of the fragments and two other lighter fragments. The positions of the found fission valleys are in a good agreement with the experimental data.

  9. Our 50-year odyssey with fission: Summary

    SciTech Connect

    Nix, J.R.

    1989-01-01

    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.

  10. Nuclear pumped gas laser research

    NASA Technical Reports Server (NTRS)

    Thom, K.

    1976-01-01

    Nuclear pumping of lasers by fission-fragments from nuclear chain reactions is discussed. Application of the newly developed lasers to spacecraft propulsion or onboard power, to lunar bases for industrial processing, and to earth for utilization of power without pollution and hazards is envisioned. Emphasis is placed on the process by which the fission-fragement kinetic energy is converted into laser light.

  11. Quantification of Uncertainties due to 235,238U, 239,240,241Pu and Fission Products Nuclear Data Uncertainties for a PWR Fuel Assembly

    NASA Astrophysics Data System (ADS)

    da Cruz, D. F.; Rochman, D.; Koning, A. J.

    2014-04-01

    Uncertainty analysis on reactivity and discharged inventory for a typical PWR fuel element as a result of uncertainties in 235,238U, 239,240,241Pu, and fission products nuclear data was performed. The Total Monte-Carlo (TMC) method was applied using the deterministic transport code DRAGON. The nuclear data used in this study is from the JEFF-3.1 evaluations, with the exception of the nuclear data files for U, Pu and fission products isotopes, which are taken from the nuclear data library TENDL-2012. Results show that the calculated total uncertainty in keff (as result of uncertainties in nuclear data of the considered isotopes) is virtually independent on fuel burnp and amounts to 700 pcm. The uncertainties in inventory of the discharged fuel is dependent on the element considered and lies in the range 1-15% for most fission products, and is below 5% for the most important actinides.

  12. Quasifission and fission rates and their lifetimes in asymmetric reactions forming 216Ra within a dinuclear system approach

    NASA Astrophysics Data System (ADS)

    Khanlari, M. Varasteh; Soheyli, S.

    2017-02-01

    Background: The study of evolution of asymmetric dinuclear systems (DNSs) formed in heavy ion collisions is a topic of intense research. The DNS evolution leads to a variety of reaction channels such as deep inelastic, complete fusion, quasifission, fast fission, fusion-fission, and evaporation of particles. The time evolution of the DNS in the quasifission process and the role of relevant parameters are still not fully understood. Purpose: The influence of the entrance channel mass asymmetry on the time evolution of an excited and rotating DNS, populated via four reactions with different entrance channel mass asymmetry parameters which all lead to the compound nucleus 216Ra, is explored. Method: The driving potential, emission barriers for the binary decay (namely the quasifission and intrinsic fusion barriers), rate of the quasifission channel, and the lifetime of an excited DNS, as well as the fission rate and fission lifetime of the compound nucleus 216Ra formed in the 12C+204Pb,19F+197Au,30Si+186W , and 48Ca+168Er reactions, are calculated by the dinuclear system approach. Results: Our results show that the intrinsic fusion barrier values are equal to zero for the 12C+204Pb and 19F+197Au reactions. Therefore, the quasifission signature is extremely hindered for these reactions, while the 30Si+186W and 48Ca+168Er calculated results contain quasifission contributions. Provided the quasifission rate is nonzero, the quasifission rate increases with increasing orbital angular momentum ℓ of the composite system for a given excitation energy ECN * of the compound nucleus. On the other hand, the quasifission lifetime decreases moderately with increasing ℓ . Furthermore, both quasifission and fission rates increase with increasing excitation energy ECN *, while the quasifission and fission lifetimes decrease with increasing ECN * for a given ℓ . Conclusions: Although these reactions with different entrance channels populate the same compound nucleus 216Ra at

  13. Strengthening the fission reactor nuclear science and engineering program at UCLA. Final technical report

    SciTech Connect

    Okrent, D.

    1997-06-23

    This is the final report on DOE Award No. DE-FG03-92ER75838 A000, a three year matching grant program with Pacific Gas and Electric Company (PG and E) to support strengthening of the fission reactor nuclear science and engineering program at UCLA. The program began on September 30, 1992. The program has enabled UCLA to use its strong existing background to train students in technological problems which simultaneously are of interest to the industry and of specific interest to PG and E. The program included undergraduate scholarships, graduate traineeships and distinguished lecturers. Four topics were selected for research the first year, with the benefit of active collaboration with personnel from PG and E. These topics remained the same during the second year of this program. During the third year, two topics ended with the departure o the students involved (reflux cooling in a PWR during a shutdown and erosion/corrosion of carbon steel piping). Two new topics (long-term risk and fuel relocation within the reactor vessel) were added; hence, the topics during the third year award were the following: reflux condensation and the effect of non-condensable gases; erosion/corrosion of carbon steel piping; use of artificial intelligence in severe accident diagnosis for PWRs (diagnosis of plant status during a PWR station blackout scenario); the influence on risk of organization and management quality; considerations of long term risk from the disposal of hazardous wastes; and a probabilistic treatment of fuel motion and fuel relocation within the reactor vessel during a severe core damage accident.

  14. Identifying Understudied Nuclear Reactions by Text-mining the EXFOR Experimental Nuclear Reaction Library

    NASA Astrophysics Data System (ADS)

    Hirdt, J. A.; Brown, D. A.

    2016-01-01

    The EXFOR library contains the largest collection of experimental nuclear reaction data available as well as the data's bibliographic information and experimental details. We text-mined the REACTION and MONITOR fields of the ENTRYs in the EXFOR library in order to identify understudied reactions and quantities. Using the results of the text-mining, we created an undirected graph from the EXFOR datasets with each graph node representing a single reaction and quantity and graph links representing the various types of connections between these reactions and quantities. This graph is an abstract representation of the connections in EXFOR, similar to graphs of social networks, authorship networks, etc. We use various graph theoretical tools to identify important yet understudied reactions and quantities in EXFOR. Although we identified a few cross sections relevant for shielding applications and isotope production, mostly we identified charged particle fluence monitor cross sections. As a side effect of this work, we learn that our abstract graph is typical of other real-world graphs.

  15. Identifying Understudied Nuclear Reactions by Text-mining the EXFOR Experimental Nuclear Reaction Library

    SciTech Connect

    Hirdt, J.A.; Brown, D.A.

    2016-01-15

    The EXFOR library contains the largest collection of experimental nuclear reaction data available as well as the data's bibliographic information and experimental details. We text-mined the REACTION and MONITOR fields of the ENTRYs in the EXFOR library in order to identify understudied reactions and quantities. Using the results of the text-mining, we created an undirected graph from the EXFOR datasets with each graph node representing a single reaction and quantity and graph links representing the various types of connections between these reactions and quantities. This graph is an abstract representation of the connections in EXFOR, similar to graphs of social networks, authorship networks, etc. We use various graph theoretical tools to identify important yet understudied reactions and quantities in EXFOR. Although we identified a few cross sections relevant for shielding applications and isotope production, mostly we identified charged particle fluence monitor cross sections. As a side effect of this work, we learn that our abstract graph is typical of other real-world graphs.

  16. Neutron Transport and Nuclear Burnup Analysis for the Laser Inertial Confinement Fusion-Fission Energy (LIFE) Engine

    SciTech Connect

    Kramer, K J; Latkowski, J F; Abbott, R P; Boyd, J K; Powers, J J; Seifried, J E

    2008-10-24

    Lawrence Livermore National Laboratory is currently developing a hybrid fusion-fission nuclear energy system, called LIFE, to generate power and burn nuclear waste. We utilize inertial confinement fusion to drive a subcritical fission blanket surrounding the fusion chamber. It is composed of TRISO-based fuel cooled by the molten salt flibe. Low-yield (37.5 MJ) targets and a repetition rate of 13.3 Hz produce a 500 MW fusion source that is coupled to the subcritical blanket, which provides an additional gain of 4-8, depending on the fuel. In the present work, we describe the neutron transport and nuclear burnup analysis. We utilize standard analysis tools including, the Monte Carlo N-Particle (MCNP) transport code, ORIGEN2 and Monteburns to perform the nuclear design. These analyses focus primarily on a fuel composed of depleted uranium not requiring chemical reprocessing or enrichment. However, other fuels such as weapons grade plutonium and highly-enriched uranium are also under consideration. In addition, we have developed a methodology using {sup 6}Li as a burnable poison to replace the tritium burned in the fusion targets and to maintain constant power over the lifetime of the engine. The results from depleted uranium analyses suggest up to 99% burnup of actinides is attainable while maintaining full power at 2GW for more than five decades.

  17. Nuclear waste vitrification efficiency: cold cap reactions

    SciTech Connect

    Hrma, Pavel R.; Kruger, Albert A.; Pokorny, Richard

    2012-12-15

    The cost and schedule of nuclear waste treatment and immobilization are greatly affected by the rate of glass production. Various factors influence the performance of a waste-glass melter. One of the most significant, and also one of the least understood, is the process of batch melting. Studies are being conducted to gain fundamental understanding of the batch reactions, particularly those that influence the rate of melting, and models are being developed to link batch makeup and melter operation to the melting rate. Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. These include water evaporation (slurry feed contains as high as 60% water), gas evolution, the melting of salts, the formation of borate melt, reactions of borate melt with molten salts and with amorphous oxides (Fe2O3 and Al2O3), the formation of intermediate crystalline phases, the formation of a continuous glass-forming melt, the growth and collapse of primary foam, and the dissolution of residual solids. To this list we also need to add the formation of secondary foam that originates from molten glass but accumulates on the bottom of the cold cap. This study presents relevant data obtained for a high-level-waste melter feed and introduces a one-dimensional (1D) mathematical model of the cold cap as a step toward an advanced three-dimensional (3D) version for a complete model of the waste glass melter. The 1D model describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup and melter conditions

  18. NUCLEAR WASTE VITRIFICATION EFFICIENCY COLD CAP REACTIONS

    SciTech Connect

    KRUGER AA; HRMA PR; POKORNY R

    2011-07-29

    The cost and schedule of nuclear waste treatment and immobilization are greatly affected by the rate of glass production. Various factors influence the performance of a waste-glass melter. One of the most significant, and also one of the least understood, is the process of batch melting. Studies are being conducted to gain fundamental understanding of the batch reactions, particularly those that influence the rate of melting, and models are being developed to link batch makeup and melter operation to the melting rate. Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. These include water evaporation (slurry feed contains as high as 60% water), gas evolution, the melting of salts, the formation of borate melt, reactions of borate melt with molten salts and with amorphous oxides (Fe{sub 2}O{sub 3} and Al{sub 2}O{sub 3}), the formation of intermediate crystalline phases, the formation of a continuous glass-forming melt, the growth and collapse of primary foam, and the dissolution of residual solids. To this list we also need to add the formation of secondary foam that originates from molten glass but accumulates on the bottom of the cold cap. This study presents relevant data obtained for a high-level-waste melter feed and introduces a one-dimensional (1D) mathematical model of the cold cap as a step toward an advanced three-dimensional (3D) version for a complete model of the waste glass melter. The 1D model describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup

  19. A model for the influence of microstructure, precipitate pinning and fission gas behavior on irradiation-induced recrystallization of nuclear fuels

    NASA Astrophysics Data System (ADS)

    Rest, J.

    2004-03-01

    Irradiation-induced recrystallization appears to be a general phenomenon in that it is observed to occur in a variety of nuclear fuel types, e.g. U-xMo, UO2, and U3O8. For temperatures below that where significant thermal annealing of defects occurs, an expression is derived for the fission density at which irradiation-induced recrystallization is initiated that is athermal and weakly dependent on fission rate. The initiation of recrystallization is to be distinguished from the subsequent progression and eventual consumption of the original fuel grain. The formulation takes into account the observed microstructural evolution of the fuel, the role of precipitate pinning and fission gas bubbles, and the triggering event for recrystallization. The calculated dislocation density, fission gas bubble-size distribution, and fission density at which recrystallization first appears are compared to measured quantities.

  20. The Legnaro National Laboratories and the SPES facility: nuclear structure and reactions today and tomorrow

    NASA Astrophysics Data System (ADS)

    de Angelis, Giacomo; Fiorentini, Gianni

    2016-11-01

    There is a very long tradition of studying nuclear structure and reactions at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (Italian Institute of Nuclear Physics). The wide expertise acquired in building and running large germanium arrays has made the laboratories one of the most advanced research centers in γ-ray spectroscopy. The ’gamma group’ has been deeply involved in all the national and international developments of the last 20 years and is currently one of the major contributors to the AGATA project, the first (together with its American counterpart GRETINA) γ-detector array based on γ-ray tracking. This line of research is expected to be strongly boosted by the coming into operation of the SPES radioactive ion beam project, currently under construction at LNL. In this report, written on the occasion of the 40th anniversary of the Nobel prize awarded to Aage Bohr, Ben R Mottelson and Leo Rainwater and particularly focused on the physics of nuclear structure, we intend to summarize the different lines of research that have guided nuclear structure and reaction research at LNL in the last decades. The results achieved have paved the way for the present SPES facility, a new laboratories infrastructure producing and accelerating radioactive ion beams of fission fragments and other isotopes.

  1. Precise Nuclear Data Measurements Possible with the NIFFTE fissionTPC for Advanced Reactor Designs

    NASA Astrophysics Data System (ADS)

    Towell, Rusty; Niffte Collaboration

    2015-10-01

    The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) Collaboration has applied the proven technology of Time Projection Chambers (TPC) to the task of precisely measuring fission cross sections. With the NIFFTE fission TPC, precise measurements have been made during the last year at the Los Alamos Neutron Science Center from both U-235 and Pu-239 targets. The exquisite tracking capabilities of this device allow the full reconstruction of charged particles produced by neutron beam induced fissions from a thin central target. The wealth of information gained from this approach will allow systematics to be controlled at the level of 1%. The fissionTPC performance will be presented. These results are critical to the development of advanced uranium-fueled reactors. However, there are clear advantages to developing thorium-fueled reactors such as Liquid Fluoride Thorium Reactors over uranium-fueled reactors. These advantages include improved reactor safety, minimizing radioactive waste, improved reactor efficiency, and enhanced proliferation resistance. The potential for using the fissionTPC to measure needed cross sections important to the development of thorium-fueled reactors will also be discussed.

  2. Accelerator-Driven Thorium-Cycle Fission:. Green Nuclear Power for the New Millennium

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter; Sattarov, Akhdiyor

    2011-03-01

    In thorium-cycle fission, fast neutrons are used to transmute thorium to fissionable 233U and then stimulate fission. In accelerator-driven thorium-cycle fission (ADTC) the fast neutrons are produced by injecting a symmetric pattern of 7 energetic proton beams into a Pb spallation zone in the core. The fast neutrons are adiabatically moderated by the Pb so that they capture efficiently on 232Th, and fission heat is transferred via a convective Pb column above the core. The 7 proton beams are generated by a flux-coupled stack of isochronous cyclotrons. ADTC offers a green solution to the Earth's energy needs: the core operates as a sub-critical pile and cannot melt down; it eats its own long-lived fission products; a GW ADTC core can operate with uniform power density for a 7-year fuel cycle without shuffling fuel pins, and there are sufficient thorium reserves to run man's energy needs for the next 2000 years.

  3. EMPIRE: A Reaction Model Code for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Palumbo, A.; Herman, M.; Capote, R.

    2014-06-01

    The correct modeling of abundances requires knowledge of nuclear cross sections for a variety of neutron, charged particle and γ induced reactions. These involve targets far from stability and are therefore difficult (or currently impossible) to measure. Nuclear reaction theory provides the only way to estimate values of such cross sections. In this paper we present application of the EMPIRE reaction code to nuclear astrophysics. Recent measurements are compared to the calculated cross sections showing consistent agreement for n-, p- and α-induced reactions of strophysical relevance.

  4. Theoretical studies in nuclear reactions and nuclear structure

    SciTech Connect

    Not Available

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon's mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon's mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon's mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e{sup +}e{sup {minus}} problem and heavy ion dynamics.

  5. Theoretical studies in nuclear reactions and nuclear structure. Progress report

    SciTech Connect

    Not Available

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon`s mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon`s mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon`s mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e{sup +}e{sup {minus}} problem and heavy ion dynamics.

  6. The Fun30 chromatin remodeler Fft3 controls nuclear organization and chromatin structure of insulators and subtelomeres in fission yeast.

    PubMed

    Steglich, Babett; Strålfors, Annelie; Khorosjutina, Olga; Persson, Jenna; Smialowska, Agata; Javerzat, Jean-Paul; Ekwall, Karl

    2015-03-01

    In eukaryotic cells, local chromatin structure and chromatin organization in the nucleus both influence transcriptional regulation. At the local level, the Fun30 chromatin remodeler Fft3 is essential for maintaining proper chromatin structure at centromeres and subtelomeres in fission yeast. Using genome-wide mapping and live cell imaging, we show that this role is linked to controlling nuclear organization of its targets. In fft3∆ cells, subtelomeres lose their association with the LEM domain protein Man1 at the nuclear periphery and move to the interior of the nucleus. Furthermore, genes in these domains are upregulated and active chromatin marks increase. Fft3 is also enriched at retrotransposon-derived long terminal repeat (LTR) elements and at tRNA genes. In cells lacking Fft3, these sites lose their peripheral positioning and show reduced nucleosome occupancy. We propose that Fft3 has a global role in mediating association between specific chromatin domains and the nuclear envelope.

  7. Primary system fission product release and transport: A state-of-the-art report to the committee on the safety of nuclear installations

    SciTech Connect

    Wright, A.L.

    1994-06-01

    This report presents a summary of the status of research activities associated with fission product behavior (release and transport) under severe accident conditions within the primary systems of water-moderated and water-cooled nuclear reactors. For each of the areas of fission product release and fission product transport, the report summarizes relevant information on important phenomena, major experiments performed, relevant computer models and codes, comparisons of computer code calculations with experimental results, and general conclusions on the overall state of the art. Finally, the report provides an assessment of the overall importance and knowledge of primary system release and transport phenomena and presents major conclusions on the state of the art.

  8. DSP Algorithms for Fission Fragment and Prompt Fission Neutron Spectroscopy

    SciTech Connect

    Zeynalova, O.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.; Fabry, I.

    2009-10-29

    Digital signal processing (DSP) algorithms are in high demand for modern nuclear fission investigation due to importance of increase the accuracy of fissile nuclear data for new generation of nuclear power stations. DSP algorithms for fission fragment (FF) and prompt fission neutron (PFN) spectroscopy are described in the present work. The twin Frisch-grid ionization chamber (GTIC) is used to measure the kinetic energy-, mass- and angular distributions of the FF in the {sup 252}Cf(SF) reaction. Along with the neutron time-of-flight (TOF) measurement the correlation between neutron emission and FF mass and energy is investigated. The TOF is measured between common cathode of the GTIC and the neutron detector (ND) pulses. Waveform digitizers (WFD) having 12 bit amplitude resolution and 100 MHz sampling frequency are used for the detector pulse sampling. DSP algorithms are developed as recursive procedures to perform the signal processing, similar to those available in various nuclear electronics modules, such as constant fraction discriminator (CFD), pulse shape discriminator (PSD), peak-sensitive analogue-to-digital converter (pADC) and pulse shaping amplifier (PSA). To measure the angle between FF and the cathode plane normal to the GTIC a new algorithm is developed having advantage over the traditional analogue pulse processing schemes. Algorithms are tested by comparing the numerical simulation of the data analysis of the {sup 252}Cf(SF) reaction with data available from literature.

  9. Experimental Observation of Nuclear Reactions in Palladium and Uranium - Possible Explanation by Hydrex Mode

    SciTech Connect

    Dufour, J.; Murat, D.; Dufour, X.; Foos, J

    2001-07-15

    Experiments with uranium are presented that show a highly exothermal reaction, which can only be of nuclear origin. One striking point of these results is that they clearly show that what is being observed is not some kind of fusion reaction of the deuterium present (only exceedingly small amounts of it are present). This is a strong indication that hydrogen can trigger nuclear reactions that seem to involve the nuclei of the lattice (which would yield a fission-like pattern of products). Confronted with a situation where some experiments in the field yield a fusion-like pattern of products (CF experiments) and others a fissionlike one (LENR experiments), one can reasonably wonder whether one is not observing two aspects of the same phenomenon. Thus, it is proposed to describe CF and LENR reactions as essentially the same phenomenon based on the possible existence of a still hypothetical proton/electron resonance, which would catalyze fissionlike reactions with a neutron sink. Finally, a series of experiments is proposed to assess this hypothesis.

  10. Accelerator-Driven Subcritical Fission in a Molten Salt Core: Green Nuclear Power for the New Millennium

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter

    2011-10-01

    Scientists at Texas A&M University, Brookhaven National Lab, and Idaho National Lab are developing a design for accelerator-drive subcritical fission in a molten salt core (ADSMS). Three high-power proton beams are delivered to spallation targets in a molten salt core, where they provide ˜3% of the fast neutrons required to sustain 600 MW of fission. The proton beams are produced by a flux-coupled stack of superconducting strong-focusing cyclotrons. The fuel consists of a eutectic of sodium chloride with either spent nuclear fuel from a conventional U power reactor (ADSMS-U) or thorium (ADSMS-Th). The subcritical core cannot go critical under any failure mode. The core cannot melt down even if all power is suddenly lost to the facility for a prolonged period. The ultra-fast neutronics of the core makes it possible to operate in an isobreeding mode, in which neutron capture breeds the fertile nuclide into a fissile nuclide at the same rate that fission burns the fissile nuclide, and consumes 90% of the fertile inventory instead of the 5% consumed in the original use in a conventional power plant. The ultra-fast neutronics produces a very low equilibrium inventory of the long-lived minor actinides, ˜10^4 less than what is produced in conventional power plants. ADSMS offers a method to safely produce the energy needs for all mankind for the next 3000 years.

  11. Surrogate Nuclear Reactions - An Indirect Method for Determining Reaction Cross Sections

    SciTech Connect

    Escher, J; Ahle, L; Bernstein, L; Burke, J; Church, J A; Dietrich, F; Forssen, C; Hoffman, R; Gueorguiev, V

    2005-03-23

    An indirect method for determining cross sections of reactions proceeding through a compound nucleus is presented. Some applications of the Surrogate nuclear reaction approach are considered and challenges that need to be addressed are outlined.

  12. Fine-Group Cross Section Library Based on JEFF3.1 for Nuclear Fission Applications.

    SciTech Connect

    ROBERTO,; ORSI,

    2009-10-16

    Version 00 The NJOY-99.160 data processing system was used for the MATJEFF31.BOLIB library generation to assure the consistency with the previous generation of the VITJEFF31.BOLIB /6/ twin library, based on the same GENDF cross section data file. In particular it used a revised version of the GROUPR /7/ module, originally developed in ENEA-Bologna before the free release of an analogous GROUPR revised version with NJOY-99.161, in order to correctly deal with the non-Cartesian interpolation schemes, contained in 69 JEFF-3.1 evaluated nuclear data files. The TRANSX-2.15 /8/ code was then used to obtain the total (prompt + delayed) fission spectra for U-235, U-238 and Pu-239. These data, contained in the MATJEFF31.BOLIB package, are available in tabulated form as in the VITJEFF31.BOLIB library package. On the contrary the VITAMIN-B6, VITJEF22.BOLIB /9/ and MATJEF22.BOLIB /10/ similar library packages contain in tabulated form only the prompt components. MATJEFF31.BOLIB is a pseudo-problem-independent library based on the Bondarenko /11/ (f-factor) method for the treatment of neutron resonance self-shielding and temperature effects. The library contains 176 nuclides at 4 temperatures, obtained for the most part with 6 to 8 values for the background cross section. Thermal scattering cross sections were processed at all temperatures available in the JEFF-3.1 thermal scattering law data file for 6 additional bound nuclides (H-1 in light water (H-H2O), H-1 in polyethylene (H-CH2), H-1 in zirconium hydride (H-ZrH) (not contained in VITAMIN-B6, VITJEF22.BOLIB and MATJEF22.BOLIB), H-2 in heavy water (H2-D2O), C in graphite (C-GPH) and Be in beryllium metal (Be-TH)). From MATJEFF31.BOLIB it is easily possible to generate, with the use of the TRANSX code, working libraries of collapsed and self-shielded cross sections in GOXS or FIDO-ANISN format for calculations with the DOORS /12/, DANTSYS /13/ and PARTISN /14/ deterministic transport systems and the MORSE /15/ Monte Carlo

  13. Analysis of plasmas generated by fission fragments. [nuclear pumped lasers and helium plasma

    NASA Technical Reports Server (NTRS)

    Deese, J. E.; Hassan, H. A.

    1977-01-01

    A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.

  14. Spent Nuclear Fuel project estimate of volatile fission products release from multi-canister overpacks

    SciTech Connect

    Cooper, T.D.

    1996-08-01

    Spent N-Reactor fuel will be moved from wet pool storage to dry storage at Hanford Washington. This fuel will be sequentially loaded into a Multiple Container Overpack (MCO), moved to the cold vacuum drying station, drained, cold vacuum dried, shipped to the Canister Storage Building (CSB), staged for up to 2 years,hot vacuum dried at 300 degrees C, hot conditioned at 150 degrees C, and finally, sealed and stored for up to 75 years in the CSB.During each proposed process step, the volatile radioactive fission products released to the atmosphere were estimated.Tritium is the only volatile fission product released insignificant amounts during each process step. For an accident scenario involving interior MCO temperature of 600 degrees C for up to 8 hours, it was estimated that many volatile fission products are released.

  15. Hydrogen generation arising from the {sup 59}Ni(n,p) reaction and its impact on fission-fusion correlations

    SciTech Connect

    Greenwood, L.R.; Garner, A.F.

    1996-04-01

    Whilte the influence of transmutant helium on radiation-induced microstructural evolution has often been studied, there is a tendency to overlook the influence of concurrently-generated hydrogen. There have been some recent speculation and studies, however, that suggest that the influence of hydrogen may be enhanced in the presence of large amounts of helium, especially at lower irradiation temperatures typical of projected ITER operation. The impact of the (n,p) reaction on both hydrogen generation rates and displacement rates are evaluated in this paper for a variety of neutron spectra employed in fission-fusion correlation.

  16. Nuclear reaction modeling, verification experiments, and applications

    SciTech Connect

    Dietrich, F.S.

    1995-10-01

    This presentation summarized the recent accomplishments and future promise of the neutron nuclear physics program at the Manuel Lujan Jr. Neutron Scatter Center (MLNSC) and the Weapons Neutron Research (WNR) facility. The unique capabilities of the spallation sources enable a broad range of experiments in weapons-related physics, basic science, nuclear technology, industrial applications, and medical physics.

  17. Nuclear reactions and synthesis of new transuranium species

    SciTech Connect

    Seaborg, G.T.

    1983-01-01

    In this short review, I shall describe the special aspects of heavy ion nuclear reaction mechanisms operative in the transuranium region, the role of new techniques, possible nuclear reactions for the production of additional transuranium elements and nuclear species and the importance of work in this region for the development of nuclear models and theoretical concepts. This discussion should make it clear that a continuing supply of leements and isotopes, some fo them relatively short-lived, produced by the HFIR-TRU facilities, will be a requirement for future synthesis of new elements and isotopes.

  18. Rhn1, a nuclear protein, is required for suppression of meiotic mRNAs in mitotically dividing fission yeast.

    PubMed

    Sugiyama, Tomoyasu; Sugioka-Sugiyama, Rie; Hada, Kazumasa; Niwa, Ryusuke

    2012-01-01

    In the fission yeast Schizosaccharomyces pombe, many meiotic mRNAs are transcribed during mitosis and meiosis and selectively eliminated in mitotic cells. However, this pathway for mRNA decay, called the determinant of selective removal (DSR)-Mmi1 system, targets only some of the numerous meiotic mRNAs that are transcribed in mitotic cells. Here we describe Rhn1, a nuclear protein involved in meiotic mRNA suppression in vegetative fission yeast. Rhn1 is homologous to budding yeast Rtt103 and localizes to one or a few discrete nuclear dots in growing vegetative cells. Rhn1 colocalizes with a pre-mRNA 3'-end processing factor, Pcf11, and with the 5'-3' exoribonuclease, Dhp1; moreover, Rhn1 coimmunoprecipitates with Pcf11. Loss of rhn1 results in elevated sensitivity to high temperature, to thiabendazole (TBZ), and to UV. Interestingly, meiotic mRNAs--including moa1(+), mcp5(+), and mug96(+)--accumulate in mitotic rhn1Δ cells. Accumulation of meiotic mRNAs also occurs in strains lacking Lsk1, a kinase that phosphorylates serine 2 (Ser-2) in the C-terminal domain (CTD) of RNA polymerase II (Pol II), and in strains lacking Sen1, an ATP-dependent 5'-3' RNA/DNA helicase: notably, both Lsk1 and Sen1 have been implicated in termination of Pol II-dependent transcription. Furthermore, RNAi knockdown of cids-2, a Caenorhabditis elegans ortholog of rhn1(+), leads to elevated expression of a germline-specific gene, pgl-1, in somatic cells. These results indicate that Rhn1 contributes to the suppression of meiotic mRNAs in vegetative fission yeast and that the mechanism by which Rhn1 downregulates germline-specific transcripts may be conserved in unicellular and multicellular organisms.

  19. Split-Doa10: a naturally split polytopic eukaryotic membrane protein generated by fission of a nuclear gene.

    PubMed

    Stuerner, Elisabeth; Kuraku, Shigehiro; Hochstrasser, Mark; Kreft, Stefan G

    2012-01-01

    Large polytopic membrane proteins often derive from duplication and fusion of genes for smaller proteins. The reverse process, splitting of a membrane protein by gene fission, is rare and has been studied mainly with artificially split proteins. Fragments of a split membrane protein may associate and reconstitute the function of the larger protein. Most examples of naturally split membrane proteins are from bacteria or eukaryotic organelles, and their exact history is usually poorly understood. Here, we describe a nuclear-encoded split membrane protein, split-Doa10, in the yeast Kluyveromyces lactis. In most species, Doa10 is encoded as a single polypeptide with 12-16 transmembrane helices (TMs), but split-KlDoa10 is encoded as two fragments, with the split occurring between TM2 and TM3. The two fragments assemble into an active ubiquitin-protein ligase. The K. lactis DOA10 locus has two ORFs separated by a 508-bp intervening sequence (IVS). A promoter within the IVS drives expression of the C-terminal KlDoa10 fragment. At least four additional Kluyveromyces species contain an IVS in the DOA10 locus, in contrast to even closely related genera, allowing dating of the fission event to the base of the genus. The upstream Kluyveromyces Doa10 fragment with its N-terminal RING-CH and two TMs resembles many metazoan MARCH (Membrane-Associated RING-CH) and related viral RING-CH proteins, suggesting that gene splitting may have contributed to MARCH enzyme diversification. Split-Doa10 is the first unequivocal case of a split membrane protein where fission occurred in a nuclear-encoded gene. Such a split may allow divergent functions for the individual protein segments.

  20. Multi-channel probes to understand fission dynamics

    SciTech Connect

    Mosby, Shea Morgan

    2016-04-15

    Explaining the origin of the elements is a major outstanding question in nuclear astrophysics. Observed elemental abundance distribution shows strong nuclear physics effects. In conclusion, neutron-induced reactions are important for nuclear astrophysics and applied fields in nuclear energy and security. LANSCE has a program to address many of these questions directly with neutron beams on (near-)stable nuclei. Increasing demand for correlated data to test details of fission models poses additional challenges. Possibilities exist to extend existing experimental efforts to radioactive beam facilities. Kinematic focusing from using inverse kinematics has potential to circumvent some challenges associated with measuring correlations between fission output channels.

  1. Electromagnetic studies of nuclear structure and reactions

    SciTech Connect

    Hersman, F.W.; Dawson, J.F.; Heisenberg, J.H.; Calarco, J.R.

    1990-06-01

    This report contains papers on the following topics: giant resonance studies; deep inelastic scattering studies; high resolution nuclear structure work; and relativistic RPA; and field theory in the Schroedinger Representation.

  2. Low-Energy Nuclear Reactions Resulting as Picometer Interactions with Similarity to K-Shell Electron Capture

    NASA Astrophysics Data System (ADS)

    Hora, H.; Miley, G. H.; Li, X. Z.; Kelly, J. C.; Osman, F.

    2006-02-01

    Since the appeal by Brian Josephson at the meeting of the Nobel Laureates July 2004, it seems to be indicated to summarize the following serious, reproducible and confirmed observations on reactions of protons or deuterons incorporated in host metals such as palladium. Some reflections to Rutherford's discovery of nuclear physics, the Cockroft-Oliphant discovery of anomalous low-energy fusion reactions and the chemist Hahn's discovery of fission had to be included. Using gaseous atmosphere or discharges between palladium targets, rather significant results were seen e.g. from the "life after death" heat production of such high values per host atom that only nuclear reactions can be involved. This supports the earlier evaluation of neutron generation in fully reversible experiments with gas discharges hinting that a reasonable screening effect - preferably in the swimming electron layer - may lead to reactions at nuclear distances d of picometers with reaction probability times U of about megaseconds similar to the K-shell capture radioactivity. Further electrolytic experiments led to low-energy nuclear reactions (LENR) where the involvement of pollution could be excluded from the appearance of very seldom rare earth elements. A basically new theory for DD cross-sections is used to confirm the picometer-megasecond reactions of cold fusion. Other theoretical aspects are given from measured heavy element distributions similar to the standard abundance distribution, SAD, in the Universe with consequences on endothermic heavy nuclei generation, magic numbers and to quark-gluon plasmas.

  3. Nuclear quantum tunnelling in enzymatic reactions--an enzymologist's perspective.

    PubMed

    Johannissen, Linus O; Hay, Sam; Scrutton, Nigel S

    2015-12-14

    Enzyme-catalysed H-transfer reactions are ubiquitous, yet fundamental details of these reactions remain unresolved. In this perspective, we discuss the roles of nuclear quantum tunnelling and (compressive) dynamics during these reactions. Evidence for the coupling of specific substrate and/or protein vibrations to the chemical coordinate is considered and a case is made for the combination of multiple experimental and computational/theoretical approaches when studying these reactions.

  4. Laser inertial fusion-based energy: Neutronic design aspects of a hybrid fusion-fission nuclear energy system

    NASA Astrophysics Data System (ADS)

    Kramer, Kevin James

    the same radial flibe flow that travels through perforated ODS walls to the reflector blanket. This reflector blanket is 75 cm thick comprised of 2 cm diameter graphite pebbles cooled by flibe. The flibe extraction plenum surrounds the reflector bed. Detailed neutronics designs studies are performed to arrive at the described design. The LFFH engine thermal power is controlled using a technique of adjusting the 6Li/7Li enrichment in the primary and secondary coolants. The enrichment adjusts system thermal power in the design by increasing tritium production while reducing fission. To perform the simulations and design of the LFFH engine, a new software program named LFFH Nuclear Control (LNC) was developed in C++ to extend the functionality of existing neutron transport and depletion software programs. Neutron transport calculations are performed with MCNP5. Depletion calculations are performed using Monteburns 2.0, which utilizes ORIGEN 2.0 and MCNP5 to perform a burnup calculation. LNC supports many design parameters and is capable of performing a full 3D system simulation from initial startup to full burnup. It is able to iteratively search for coolant 6Li enrichments and resulting material compositions that meet user defined performance criteria. LNC is utilized throughout this study for time dependent simulation of the LFFH engine. Two additional methods were developed to improve the computation efficiency of LNC calculations. These methods, termed adaptive time stepping and adaptive mesh refinement were incorporated into a separate stand alone C++ library name the Adaptive Burnup Library (ABL). The ABL allows for other client codes to call and utilize its functionality. Adaptive time stepping is useful for automatically maximizing the size of the depletion time step while maintaining a desired level of accuracy. Adaptive meshing allows for analysis of fixed fuel configurations that would normally require a computationally burdensome number of depletion zones

  5. LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.

    PubMed

    Gu, Mingyu; LaJoie, Dollie; Chen, Opal S; von Appen, Alexander; Ladinsky, Mark S; Redd, Michael J; Nikolova, Linda; Bjorkman, Pamela J; Sundquist, Wesley I; Ullman, Katharine S; Frost, Adam

    2017-03-14

    Endosomal sorting complexes required for transport III (ESCRT-III) proteins have been implicated in sealing the nuclear envelope in mammals, spindle pole body dynamics in fission yeast, and surveillance of defective nuclear pore complexes in budding yeast. Here, we report that Lem2p (LEM2), a member of the LEM (Lap2-Emerin-Man1) family of inner nuclear membrane proteins, and the ESCRT-II/ESCRT-III hybrid protein Cmp7p (CHMP7), work together to recruit additional ESCRT-III proteins to holes in the nuclear membrane. In Schizosaccharomyces pombe, deletion of the ATPase vps4 leads to severe defects in nuclear morphology and integrity. These phenotypes are suppressed by loss-of-function mutations that arise spontaneously in lem2 or cmp7, implying that these proteins may function upstream in the same pathway. Building on these genetic interactions, we explored the role of LEM2 during nuclear envelope reformation in human cells. We found that CHMP7 and LEM2 enrich at the same region of the chromatin disk periphery during this window of cell division and that CHMP7 can bind directly to the C-terminal domain of LEM2 in vitro. We further found that, during nuclear envelope formation, recruitment of the ESCRT factors CHMP7, CHMP2A, and IST1/CHMP8 all depend on LEM2 in human cells. We conclude that Lem2p/LEM2 is a conserved nuclear site-specific adaptor that recruits Cmp7p/CHMP7 and downstream ESCRT factors to the nuclear envelope.

  6. LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells

    PubMed Central

    Gu, Mingyu; LaJoie, Dollie; Chen, Opal S.; von Appen, Alexander; Ladinsky, Mark S.; Redd, Michael J.; Nikolova, Linda; Bjorkman, Pamela J.; Sundquist, Wesley I.; Ullman, Katharine S.; Frost, Adam

    2017-01-01

    Endosomal sorting complexes required for transport III (ESCRT-III) proteins have been implicated in sealing the nuclear envelope in mammals, spindle pole body dynamics in fission yeast, and surveillance of defective nuclear pore complexes in budding yeast. Here, we report that Lem2p (LEM2), a member of the LEM (Lap2-Emerin-Man1) family of inner nuclear membrane proteins, and the ESCRT-II/ESCRT-III hybrid protein Cmp7p (CHMP7), work together to recruit additional ESCRT-III proteins to holes in the nuclear membrane. In Schizosaccharomyces pombe, deletion of the ATPase vps4 leads to severe defects in nuclear morphology and integrity. These phenotypes are suppressed by loss-of-function mutations that arise spontaneously in lem2 or cmp7, implying that these proteins may function upstream in the same pathway. Building on these genetic interactions, we explored the role of LEM2 during nuclear envelope reformation in human cells. We found that CHMP7 and LEM2 enrich at the same region of the chromatin disk periphery during this window of cell division and that CHMP7 can bind directly to the C-terminal domain of LEM2 in vitro. We further found that, during nuclear envelope formation, recruitment of the ESCRT factors CHMP7, CHMP2A, and IST1/CHMP8 all depend on LEM2 in human cells. We conclude that Lem2p/LEM2 is a conserved nuclear site-specific adaptor that recruits Cmp7p/CHMP7 and downstream ESCRT factors to the nuclear envelope. PMID:28242692

  7. Cement As a Waste Form for Nuclear Fission Products: The Case of (90)Sr and Its Daughters.

    PubMed

    Dezerald, Lucile; Kohanoff, Jorge J; Correa, Alfredo A; Caro, Alfredo; Pellenq, Roland J-M; Ulm, Franz J; Saúl, Andrés

    2015-11-17

    One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of (90)Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that (90)Sr is stable when it substitutes the Ca(2+) ions in C-S-H, and so is its daughter nucleus (90)Y after β-decay. Interestingly, (90)Zr, daughter of (90)Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for (90)Sr storage.

  8. Inhibition of splicing and nuclear retention of pre-mRNA by spliceostatin A in fission yeast

    SciTech Connect

    Lo, Chor-Wai; Kaida, Daisuke; Nishimura, Shinichi; Matsuyama, Akihisa; Yashiroda, Yoko; Taoka, Hiroshi; Ishigami, Ken; Watanabe, Hidenori; Nakajima, Hidenori; Tani, Tokio; Horinouchi, Sueharu; Yoshida, Minoru

    2007-12-21

    Nuclear retention of pre-mRNAs is tightly regulated by several security mechanisms that prevent pre-mRNA export into the cytoplasm. Recently, spliceostatin A, a methylated derivative of a potent antitumor microbial metabolite FR901464, was found to cause pre-mRNA accumulation and translation in mammalian cells. Here we report that spliceostatin A also inhibits splicing and nuclear retention of pre-mRNA in a fission yeast strain that lacks the multidrug resistance protein Pmd1. As observed in mammalian cells, spliceostatin A is bound to components of the SF3b complex in the spliceosome. Furthermore, overexpression of nup211, a homolog of Saccharomyces cerevisiae MLP1, suppresses translation of pre-mRNAs accumulated by spliceostatin A. These results suggest that the SF3b complex has a conserved role in pre-mRNA retention, which is independent of the Mlp1 function.

  9. Advanced modeling of prompt fission neutrons

    SciTech Connect

    Talou, Patrick

    2009-01-01

    Theoretical and numerical studies of prompt fission neutrons are presented. The main results of the Los Alamos model often used in nuclear data evaluation work are reviewed briefly, and a preliminary assessment of uncertainties associated with the evaluated prompt fission neutron spectrum for n (0.5 MeV)+{sup 239}Pu is discussed. Advanced modeling of prompt fission neutrons is done by Monte Carlo simulations of the evaporation process of the excited primary fission fragments. The successive emissions of neutrons are followed in the statistical formalism framework, and detailed information, beyond average quantities, can be inferred. This approach is applied to the following reactions: {sup 252}Cf (sf), n{sub th} + {sup 239}Pu, n (0.5 MeV)+{sup 235}U, and {sup 236}Pu (sf). A discussion on the merits and present limitations of this approach concludes this presentation.

  10. Lepton nonconserving (μ-,e+) reaction to individual nuclear states

    NASA Astrophysics Data System (ADS)

    Pittel, S.; Vergados, J. D.

    1981-11-01

    Branching ratios for the lepton-violating 40Ca(μ-,e+)40Ar(g.s.) reaction are calculated using a gauge model in which it is mediated by a Majorana neutrino. The predicted branching ratios to the ground state are fairly insensitive to the relevant nuclear structure information and are much smaller than previously calculated total rates. NUCLEAR REACTIONS 40Ca (μ-,e+)40Ar(g.s.) calculated branching ratio. Lepton conversion.

  11. Number-Theory in Nuclear-Physics in Number-Theory: Non-Primality Factorization As Fission VS. Primality As Fusion; Composites' Islands of INstability: Feshbach-Resonances?

    NASA Astrophysics Data System (ADS)

    Siegel, Edward

    2011-04-01

    Numbers: primality/indivisibility/non-factorization versus compositeness/divisibility /factor-ization, often in tandem but not always, provocatively close analogy to nuclear-physics: (2 + 1)=(fusion)=3; (3+1)=(fission)=4[=2 x 2]; (4+1)=(fusion)=5; (5+1)=(fission)=6[=2 x 3]; (6 + 1)=(fusion)=7; (7+1)=(fission)=8[= 2 x 4 = 2 x 2 x 2]; (8 + 1) =(non: fission nor fusion)= 9[=3 x 3]; then ONLY composites' Islands of fusion-INstability: 8, 9, 10; then 14, 15, 16,... Could inter-digit Feshbach-resonances exist??? Applications to: quantum-information and computing non-Shore factorization, millennium-problem Riemann-hypotheses physics-proof as numbers/digits Goodkin Bose-Einstein Condensation intersection with graph-theory ``short-cut'' method: Rayleigh(1870)-Polya(1922)-``Anderson'' (1958)-localization, Goldbach-conjecture, financial auditing/accounting as quantum-statistical-physics;... abound!!!

  12. Number-Theory in Nuclear-Physics in Number-Theory: Non-Primality Factorization As Fission VS. Primality As Fusion; Composites' Islands of INstability: Feshbach-Resonances?

    NASA Astrophysics Data System (ADS)

    Siegel, Edward

    2011-10-01

    Numbers: primality/indivisibility/non-factorization versus compositeness/divisibility /factor-ization, often in tandem but not always, provocatively close analogy to nuclear-physics: (2 + 1)=(fusion)=3; (3+1)=(fission)=4[=2 × 2]; (4+1)=(fusion)=5; (5 +1)=(fission)=6[=2 × 3]; (6 + 1)=(fusion)=7; (7+1)=(fission)=8[= 2 × 4 = 2 × 2 × 2]; (8 + 1) =(non: fission nor fusion)= 9[=3 × 3]; then ONLY composites' Islands of fusion-INstability: 8, 9, 10; then 14, 15, 16,... Could inter-digit Feshbach-resonances exist??? Applications to: quantum-information/computing non-Shore factorization, millennium-problem Riemann-hypotheses proof as Goodkin BEC intersection with graph-theory ``short-cut'' method: Rayleigh(1870)-Polya(1922)-``Anderson'' (1958)-localization, Goldbach-conjecture, financial auditing/accounting as quantum-statistical-physics;... abound!!!

  13. Fission and Properties of Neutron-Rich Nuclei - Proceedings of the Second International Conference

    NASA Astrophysics Data System (ADS)

    Hamilton, J. H.; Phillips, W. R.; Carter, H. K.

    The Table of Contents for the book is as follows: * Preface * Structure of Elementary Matter: Cold Valleys and Their Importance in Fission, Fusion and for Superheavy Nuclei * Tunnelling Phenomena in Nuclear Physics * Heavy Nuclei Studies Using Transfer Reactions * Isomeric Properties of Nuclei Near 78Ni * Investigation of Light Actinide Nuclei at Yale and Beyond * U-Projectile Fission at Relativistic Energies * Cluster Description of Cold Fission Modes in 252Cf * Neutron-pair Transfer Theory for Pear-shaped Ba Fission Fragments * New RMFA Parameters of Normal and Exotic Nuclei * Study of Fission Fragments from 12C+238U Reactions: Prompt and Delayed Spectroscopy * γ-Ray Angular Correlations in 252Cf and 248Cm Fission Fragments * Fragment Angular Momentum and Descent Dynamics in 252Cf Spontaneous Fission * The Experimental Investigation of Neutron-Rich Nuclei * High-Spin Structure of Some Odd-Z Nuclei with A ≈ 100 From Heavy-Ion Induced Fission * Coexistence of Symmetric and Asymmetric Nuclear Shapes and 10Be Ternary Fission * Octupole Effects in the Lanthanides * High Spin Structure of the 113-1l6Cd Isotopes Produced by Heavy-Ion Induced Fission Reaction * Temperature-Dependent Fission Barriers and Mass Distributions for 239U * Strength Distributions for Gamow Teller Transitions in Very Weakly Bound Systems * High Spin Fragmentation Spectroscopy * Search for a Four-Neutron Transfer From 8He to 4He * Microsecond Isomers in Fission Fragments in the Vicinity of the Doubly Magic 132Sn * Recent On-Line NMR/on Nuclear Magnetic Dipole Moments Near 132Sn: Meson Exchange Current Effects at the Shell Closure and Shell Model Treatment of Variation with Proton and Neutron Number * High-spin K-Isomers Beyond the Fusion Limit * High Energy Neutron Induced Fission: Charge Yield Distributions and Search and Spectroscopy of New Isomers * Hartree-Fock Mean-Field Models Using Separable Interactions * Variation of Fission Characteristics Over the Nuclear Chart * Investigation of

  14. Fission Systems for Mars Exploration

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Kim, T.; Dorney, D. J.; Swint, Marion Shayne

    2012-01-01

    Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars.

  15. Ternary fission of nuclei into comparable fragments

    SciTech Connect

    Karpeshin, F. F.

    2015-07-15

    The problem of nuclear fission into three comparable fragments is considered. A mechanism of true ternary fission is proposed. In contrast to sequential fission, where the three fragments arise upon two sequential events of binary fission, the mechanism in question relies on a scenario that originally involves fission into three fragments. This mechanism is driven by a hexadecapole deformation of the fissioning nucleus, in contrast to binary fission associated with quadrupole vibrations of the nuclear surface. The fragment-mass ratios are estimated. The dynamics of formation of collinear fragments and their subsequent motion in opposite directions is traced. The calculated probability of true ternary fission complies with observed values.

  16. Ternary fission of nuclei into comparable fragments

    NASA Astrophysics Data System (ADS)

    Karpeshin, F. F.

    2015-07-01

    The problem of nuclear fission into three comparable fragments is considered. A mechanism of true ternary fission is proposed. In contrast to sequential fission, where the three fragments arise upon two sequential events of binary fission, the mechanism in question relies on a scenario that originally involves fission into three fragments. This mechanism is driven by a hexadecapole deformation of the fissioning nucleus, in contrast to binary fission associated with quadrupole vibrations of the nuclear surface. The fragment-mass ratios are estimated. The dynamics of formation of collinear fragments and their subsequent motion in opposite directions is traced. The calculated probability of true ternary fission complies with observed values.

  17. Performance of the Fourier shape parametrization for the fission process

    NASA Astrophysics Data System (ADS)

    Schmitt, C.; Pomorski, K.; Nerlo-Pomorska, B.; Bartel, J.

    2017-03-01

    The availability of realistic potential energy landscapes in restricted deformation space is the prerequisite starting point for modeling several nuclear properties and reactions, namely large-amplitude phenomena. The achievement of a macroscopic-microscopic approach, employing an innovative four-dimensional (4D) nuclear shape parametrization based on a Fourier expansion, and a realistic potential-energy prescription, is presented. A systematic analysis of the 4D deformation energy landscapes over an extended region of the nuclear chart from Pt to Pu is performed, searching for fission valleys, as well as exotic ground and metastable states. The significance of the approach for predicting mass partitioning in low-energy fission is demonstrated. The ability of the model to address shape-driven effects, like stable octupole and very elongated isomeric configurations, is discussed, too. The proposed approach constitutes an efficient framework for an extended model of fission dynamics over a wide range of fissioning mass, excitation energy, and angular momentum.

  18. A long term radiological risk model for plutonium-fueled and fission reactor space nuclear system

    SciTech Connect

    Bartram, B.W.; Dougherty, D.K.

    1987-01-01

    This report describes the optimization of the RISK III mathematical model, which provides risk assessment for the use of a plutonium-fueled, fission reactor in space systems. The report discusses possible scenarios leading to radiation releases on the ground; distinctions are made for an intact reactor and a dispersed reactor. Also included are projected dose equivalents for various accident situations. 54 refs., 31 figs., 11 tabs. (TEM)

  19. Stress-induced nuclear-to-cytoplasmic translocation of cyclin C promotes mitochondrial fission in yeast.

    PubMed

    Cooper, Katrina F; Khakhina, Svetlana; Kim, Stephen K; Strich, Randy

    2014-01-27

    Mitochondrial morphology is maintained by the opposing activities of dynamin-based fission and fusion machines. In response to stress, this balance is dramatically shifted toward fission. This study reveals that the yeast transcriptional repressor cyclin C is both necessary and sufficient for stress-induced hyperfission. In response to oxidative stress, cyclin C translocates from the nucleus to the cytoplasm, where it is destroyed. Prior to its destruction, cyclin C both genetically and physically interacts with Mdv1p, an adaptor that links the GTPase Dnm1p to the mitochondrial receptor Fis1p. Cyclin C is required for stress-induced Mdv1p mitochondrial recruitment and the efficient formation of functional Dnm1p filaments. Finally, coimmunoprecipitation studies and fluorescence microscopy revealed an elevated association between Mdv1p and Dnm1p in stressed cells that is dependent on cyclin C. This study provides a mechanism by which stress-induced gene induction and mitochondrial fission are coordinated through translocation of cyclin C.

  20. Feasibility study of nuclear transmutation by negative muon capture reaction using the PHITS code

    NASA Astrophysics Data System (ADS)

    Abe, Shin-ichiro; Sato, Tatsuhiko

    2016-06-01

    Feasibility of nuclear transmutation of fission products in high-level radioactive waste by negative muon capture reaction is investigated using the Particle and Heave Ion Transport code System (PHITS). It is found that about 80 % of stopped negative muons contribute to transmute target nuclide into stable or short-lived nuclide in the case of 135Cs, which is one of the most important nuclide in the transmutation. The simulation result also indicates that the position of transmutation is controllable by changing the energy of incident negative muon. Based on our simulation, it takes approximately 8.5 × 108years to transmute 500 g of 135Cs by negative muon beam with the highest intensity currently available.

  1. Med13p prevents mitochondrial fission and programmed cell death in yeast through nuclear retention of cyclin C.

    PubMed

    Khakhina, Svetlana; Cooper, Katrina F; Strich, Randy

    2014-09-15

    The yeast cyclin C-Cdk8 kinase forms a complex with Med13p to repress the transcription of genes involved in the stress response and meiosis. In response to oxidative stress, cyclin C displays nuclear to cytoplasmic relocalization that triggers mitochondrial fission and promotes programmed cell death. In this report, we demonstrate that Med13p mediates cyclin C nuclear retention in unstressed cells. Deleting MED13 allows aberrant cytoplasmic cyclin C localization and extensive mitochondrial fragmentation. Loss of Med13p function resulted in mitochondrial dysfunction and hypersensitivity to oxidative stress-induced programmed cell death that were dependent on cyclin C. The regulatory system controlling cyclin C-Med13p interaction is complex. First, a previous study found that cyclin C phosphorylation by the stress-activated MAP kinase Slt2p is required for nuclear to cytoplasmic translocation. This study found that cyclin C-Med13p association is impaired when the Slt2p target residue is substituted with a phosphomimetic amino acid. The second step involves Med13p destruction mediated by the 26S proteasome and cyclin C-Cdk8p kinase activity. In conclusion, Med13p maintains mitochondrial structure, function, and normal oxidative stress sensitivity through cyclin C nuclear retention. Releasing cyclin C from the nucleus involves both its phosphorylation by Slt2p coupled with Med13p destruction.

  2. Fission Spectrum

    DOE R&D Accomplishments Database

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  3. A,B,C`s of nuclear science

    SciTech Connect

    Noto, V.A.; Norman, E.B.; Chan, Yuen-Dat; Dairiki, J.; Matis, H.S.; McMahan, M.A.; Otto, R.

    1995-08-07

    This introductory level presentation contains information on nuclear structure, radioactivity, alpha decay, beta decay, gamma decay, half-life, nuclear reactions, fusion, fission, cosmic rays, and radiation protection. Nine experiments with procedures and test questions are included.

  4. Membrane Shape at the Edge of the Dynamin Helix Sets Location and Duration of the Fission Reaction

    PubMed Central

    Morlot, Sandrine; Galli, Valentina; Klein, Marius; Chiaruttini, Nicolas; Manzi, John; Humbert, Frédéric; Dinis, Luis; Lenz, Martin; Cappello, Giovanni; Roux, Aurélien

    2013-01-01

    SUMMARY The GTPase dynamin polymerizes into a helical coat that constricts membrane necks of endocytic pits to promote their fission. However, the dynamin mechanism is still debated because constriction is necessary but not sufficient for fission. Here, we show that fission occurs at the interface between the dynamin coat and the uncoated membrane. At this location, the considerable change in membrane curvature increases the local membrane elastic energy, reducing the energy barrier for fission. Fission kinetics depends on tension, bending rigidity, and the dynamin constriction torque. Indeed, we experimentally find that the fission rate depends on membrane tension in vitro and during endocytosis in vivo. By estimating the energy barrier from the increased elastic energy at the edge of dynamin and measuring the dynamin torque, we show that the mechanical energy spent on dynamin constriction can reduce the energy barrier for fission sufficiently to promote spontaneous fission. PMID:23101629

  5. Membrane shape at the edge of the dynamin helix sets location and duration of the fission reaction.

    PubMed

    Morlot, Sandrine; Galli, Valentina; Klein, Marius; Chiaruttini, Nicolas; Manzi, John; Humbert, Frédéric; Dinis, Luis; Lenz, Martin; Cappello, Giovanni; Roux, Aurélien

    2012-10-26

    The GTPase dynamin polymerizes into a helical coat that constricts membrane necks of endocytic pits to promote their fission. However, the dynamin mechanism is still debated because constriction is necessary but not sufficient for fission. Here, we show that fission occurs at the interface between the dynamin coat and the uncoated membrane. At this location, the considerable change in membrane curvature increases the local membrane elastic energy, reducing the energy barrier for fission. Fission kinetics depends on tension, bending rigidity, and the dynamin constriction torque. Indeed, we experimentally find that the fission rate depends on membrane tension in vitro and during endocytosis in vivo. By estimating the energy barrier from the increased elastic energy at the edge of dynamin and measuring the dynamin torque, we show that the mechanical energy spent on dynamin constriction can reduce the energy barrier for fission sufficiently to promote spontaneous fission. :

  6. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, Vladimir

    1986-01-01

    This invention teaches a nuclear fission reactor having a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200.degree.-1800.degree. C. range, and even higher to 2500.degree. C., limited only by the thermal effectiveness of the structural materials, increasing the efficiency of power generation from the normal 30-35% with 300.degree.-500.degree. C. upper limit temperature to 50-65%. Irradiation of the circulating liquid fuel, as contrasted to only localized irradiation of a solid fuel, provides improved fuel utilization.

  7. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  8. Presaddle and postsaddle dissipative effects in fission using complete kinematics measurements

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Taïeb, J.; Alvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Vargas, J.; Voss, B.

    2016-12-01

    A complete kinematics measurement of the two fission fragments was used for the first time to investigate fission dynamics at small and large deformations. Fissioning systems with high excitation energies, compact shapes, and low angular momenta were produced in inverse kinematics by using spallation reactions of lead projectiles. A new generation experimental setup allowed for the first full and unambiguous identification in mass and atomic number of both fission fragments. This measurement permitted us to accurately determine fission cross sections, the charge distribution, and the neutron excess of the fission fragments as a function of the atomic number of the fissioning system. These data are compared with different model calculations to extract information on the value of the dissipation parameter at small and large deformations. The present results do not show any sizable dependence of the nuclear dissipation parameter on temperature or deformation.

  9. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    DOE PAGES

    Nishio, K.; Andreyev, A. N.; Chapman, R.; ...

    2015-06-30

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190 Hg formed in fusion reactions 36Ar + 144 Smand 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(180Hg) = 33-66 MeV and E*(190Hg) = 48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses more » $$\\overline{A}_L$$/$$\\overline{A}_H$$ = 79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of$$\\overline{A}_L$$/$$\\overline{A}_H$$ = 83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. In conclusion, this behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.« less

  10. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    NASA Astrophysics Data System (ADS)

    Nishio, K.; Andreyev, A. N.; Chapman, R.; Derkx, X.; Düllmann, Ch. E.; Ghys, L.; Heßberger, F. P.; Hirose, K.; Ikezoe, H.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Makii, H.; Nishinaka, I.; Ohtsuki, T.; Pain, S. D.; Sagaidak, R.; Tsekhanovich, I.; Venhart, M.; Wakabayashi, Y.; Yan, S.

    2015-09-01

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E* (180Hg) = 33- 66 MeV and E* (190Hg) = 48- 71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses AbarL /AbarH = 79 / 101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+ / EC -delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of AbarL /AbarH = 83 / 107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  11. Realistic fission model and the r-process in neutron star mergers

    SciTech Connect

    Shibagaki, S.; Kajino, T.; Chiba, S.; Mathews, G. J.

    2014-05-09

    About half of heavy elements are considered to be produced by the rapid neutron-capture process, r-process. The neutron star merger is one of the viable candidates for the astrophysical site of r-process nucleosynthesis. Nuclear fission reactions play an important role in the r-process of neutron star mergers. However theoretical predictions about fission properties of neutron-rich nuclei have some uncertainties. Especially, their fission fragment distributions are totally unknown and the phenomenologically extrapolated distribution was often applied to nucleosynthesis calculations. In this study, we have carried out r-process nucleosynthesis calculations based upon new theoretical estimates of fission fragment distributions. We discuss the effects on the r-process in neutron star mergers from the nuclear fission of heavy neutron-rich actinide elements. We also discuss how variations in the fission fragment distributions affect the abundance pattern.

  12. Fission yeast APC/C activators Slp1 and Fzr1 sequentially trigger two consecutive nuclear divisions during meiosis.

    PubMed

    Chikashige, Yuji; Yamane, Miho; Okamasa, Kasumi; Osakada, Hiroko; Tsutsumi, Chihiro; Nagahama, Yuki; Fukuta, Noriko; Haraguchi, Tokuko; Hiraoka, Yasushi

    2017-02-28

    In meiosis, two rounds of nuclear division occur consecutively without DNA replication between the divisions. We isolated a fission yeast mutant in which the nucleus divides only once to generate two spores, as opposed to four, in meiosis. In this mutant, we found that the initiation codon of the slp1(+) gene is converted to ATA, producing a reduced amount of Slp1. As a member of the Fizzy family of APC/C activators, Slp1 is essential for vegetative growth; however, the mutant allele shows a phenotype only in meiosis. Slp1 insufficiency delays degradation of maturation-promoting factor (MPF) at the first meiotic division, and another APC/C activator, Fzr1, which acts late in meiosis, terminates meiosis immediately after the delayed first division to produce two viable spores. This article is protected by copyright. All rights reserved.

  13. Student Experiments in Spontaneous Fission.

    ERIC Educational Resources Information Center

    Becchetti, F. D.; Ying, J. S.

    1981-01-01

    Advanced undergraduate experiments utilizing a commercially available, thin spontaneous fission source are described, including studies of the energy and mass distribution of the fission fragments and their energy and angular correlation. The experiments provide a useful introduction to fission, nuclear mass equations, heavy-ion physics, and…

  14. Dynamical interpretation of average fission-fragment kinetic energy systematics and nuclear scission

    SciTech Connect

    Nadtochy, P.N.; Adeev, G.D.

    2005-11-01

    A dynamical interpretation of the well-known systematics for average total kinetic energy of fission fragments over a wide range of the Coulomb parameter (600fission theory--at zero neck radius and at finite neck radius--have been applied in dynamical calculations. Both have resulted in a fairly good description of the dependence of on the Coulomb parameter. The results of dynamical calculations of within three-dimensional Langevin dynamics show that the mean distance between the centers of mass of nascent fragments at the scission configuration increases linearly with the parameter Z{sup 2}/A{sup 1/3}. This distance changes approximately from 2.35R{sub 0} for {sup 119}Xe to 2.6R{sub 0} for {sup 256}Fm. In spite of this increase in mean distance between future fragments at scission, the linear dependence of on the parameter Z{sup 2}/A{sup 1/3} remains approximately valid over a wide range of the Coulomb parameter Z{sup 2}/A{sup 1/3}.

  15. In-beam Fission Study at JAEA

    NASA Astrophysics Data System (ADS)

    Nishio, Katsuhisa

    2013-12-01

    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.

  16. EXFOR SYSTEMS MANUAL NUCLEAR REACTION DATA EXCHANGE FORMAT.

    SciTech Connect

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    EXFOR is an exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Centers Network. This document has been written for use by the members of the Network and includes matters of procedure and protocol, as well as detailed rules for the compilation of data. Users may prefer to consult EXFOR Basics' for a brief description of the format.

  17. An experimental investigation of (UF-235)6 fission nuclear-pumped lasers

    NASA Technical Reports Server (NTRS)

    Miley, G. H.

    1979-01-01

    A UF6 handling system was designed for use in conjunction with the existing nuclear-pumped laser vacuum system at a nuclear reactor laboratory to perform the experiments described above. A modification to separate the gas fill system from the vacuum system and thus greatly reduce its volume is described as well as operating procedures for the first controlled nuclear pumping experiments with UF6 vapor contained in the laser cell.

  18. Investigations of nuclear structure and nuclear reactions induced by complex projectiles

    SciTech Connect

    Sarantites, D.G.

    1991-01-01

    The research program of our group touches five areas of nuclear physics: (1) Nuclear structure studies at high spin; (2) Studies at the interface between structure and reactions; (3) Production and study of hot nuclei; (4) Incomplete fusion and fragmentation reactions; and (5) Development and use of novel techniques and instrumentation in the above areas of research. The papers from these areas are discussed in this report.

  19. Coulomb and nuclear effects in breakup and reaction cross sections

    NASA Astrophysics Data System (ADS)

    Descouvemont, P.; Canto, L. F.; Hussein, M. S.

    2017-01-01

    We use a three-body continuum discretized coupled channel (CDCC) model to investigate Coulomb and nuclear effects in breakup and reaction cross sections. The breakup of the projectile is simulated by a finite number of square integrable wave functions. First we show that the scattering matrices can be split in a nuclear term and in a Coulomb term. This decomposition is based on the Lippmann-Schwinger equation and requires the scattering wave functions. We present two different methods to separate both effects. Then, we apply this separation to breakup and reaction cross sections of 7Li+208Pb . For breakup, we investigate various aspects, such as the role of the α +t continuum, the angular-momentum distribution, and the balance between Coulomb and nuclear effects. We show that there is a large ambiguity in defining the Coulomb and nuclear breakup cross sections, since both techniques, although providing the same total breakup cross sections, strongly differ for the individual components. We suggest a third method which could be efficiently used to address convergence problems at large angular momentum. For reaction cross sections, interference effects are smaller, and the nuclear contribution is dominant above the Coulomb barrier. We also draw attention to different definitions of the reaction cross section which exist in the literature and which may induce small, but significant, differences in the numerical values.

  20. Public reactions to nuclear waste: Citizens' views of repository siting

    SciTech Connect

    Rosa, E.A.

    1993-01-01

    This book presents revised and updated papers from a panel of social scientists, at the 1989 AAAS meetings, that examined the public's reactions to nuclear waste disposal and the repository siting process. The papers report the results of original empirical research on citizens' views of nuclear waste repository siting. Topics covered include the following: content analysis of public testimony; sources of public concern about nuclear waste disposal in Texas agricultural communities; local attitudes toward high-level waste repository at Hanford; perceived risk and attitudes toward nuclear wastes; attitudes of Nevada urban residents toward a nuclear waste repository; attitudes of rural community residents toward a nuclear waste respository. An introductory chapter provides background and context, and a concluding chapter summarizes the implications of the reports. Two additional chapters cover important features of high-level waste disposal: long term trends in public attitudes toward nuclear energy and nuclear waste policy and assessment of the effects on the Los Vegas convention business if a high-level nuclear waste depository were sited in Nevada.

  1. Characterization of the ptr5{sup +} gene involved in nuclear mRNA export in fission yeast

    SciTech Connect

    Watanabe, Nobuyoshi; Ikeda, Terumasa; Mizuki, Fumitaka; Tani, Tokio

    2012-02-03

    Highlights: Black-Right-Pointing-Pointer We cloned the ptr5{sup +} gene involved in nuclear mRNA export in fission yeast. Black-Right-Pointing-Pointer The ptr5{sup +} gene was found to encode nucleoporin 85 (Nup85). Black-Right-Pointing-Pointer Seh1p and Mlo3p are multi-copy suppressors for the ptr5 mutation. Black-Right-Pointing-Pointer Ptr5p/Nup85p functions in nuclear mRNA export through the mRNA export factor Rae1p. Black-Right-Pointing-Pointer Ptr5p/Nup85p interacts genetically with pre-mRNA splicing factors. -- Abstract: To analyze the mechanisms of mRNA export from the nucleus to the cytoplasm, we have isolated eleven mutants, ptr [poly(A){sup +} RNA transport] 1 to 11, which accumulate poly(A){sup +} RNA in the nucleus at a nonpermissive temperature in Schizosaccharomyces pombe. Of those, the ptr5-1 mutant shows dots- or a ring-like accumulation of poly(A){sup +} RNA at the nuclear periphery after shifting to the nonpermissive temperature. We cloned the ptr5{sup +} gene and found that it encodes a component of the nuclear pore complex (NPC), nucleoporin 85 (Nup85). The ptr5-1 mutant shows no defects in protein transport, suggesting the specific involvement of Ptr5p/Nup85p in nuclear mRNA export in S. pombe. We identified Seh1p, a nucleoporin interacting with Nup85p, an mRNA-binding protein Mlo3p, and Sac3p, a component of the TREX-2 complex involved in coupling of nuclear mRNA export with transcription, as multi-copy suppressors for the ptr5-1 mutation. In addition, we found that the ptr5-1 mutation is synthetically lethal with a mutation of the mRNA export factor Rae1p, and that the double mutant exaggerates defective nuclear mRNA export, suggesting that Ptr5p/Nup85p is involved in nuclear mRNA export through Rae1p. Interestingly, the ptr5-1 mutation also showed synthetic effects with several prp pre-mRNA splicing mutations, suggesting a functional linkage between the NPCs and the splicing apparatus in the yeast nucleus.

  2. Scaling laws, transient times and shell effects in helium induced nuclear fission

    SciTech Connect

    Rubehn, T.; Jing, Kexing; Moretto, L.G.; Phair, L.; Tso, Kin; Wozniak, G.J.

    1996-02-01

    Fission excitation functions are analyzed and discussed according to a method which allows one to check the validity of the transition state rate predictions over a large range of excitation energies and a regime of compound nuclei masses characterized by strong shell effects. Once these shell effects are accounted for, no deviation from transition state rates can be observed. Furthermore, shell effects can be determined directly from the experiment by using the above described procedure. In contrast to the standard method, there is no need to include liquid drop model calculations. Finally, plotting the quantity R{sub f} allows one to search for evidence of transition times (discussed in a series of papers): our results set an upper limit of 10{sup {minus}20} seconds.

  3. Physics with post-accelerated beams at ISOLDE: nuclear reactions

    NASA Astrophysics Data System (ADS)

    Di Pietro, A.; Riisager, K.; Van Duppen, P.

    2017-04-01

    Nuclear-reaction studies have until now constituted a minor part of the physics program with post-accelerated beams at ISOLDE, mainly due to the maximum energy of REX-ISOLDE of around 3 MeV/u that limits reaction work to the mass region below A = 100. We give an overview of the current experimental status and of the physics results obtained so far. Finally, the improved conditions given by the HIE-ISOLDE upgrade are described.

  4. Nuclear reactions induced by high-energy alpha particles

    NASA Technical Reports Server (NTRS)

    Shen, B. S. P.

    1974-01-01

    Experimental and theoretical studies of nuclear reactions induced by high energy protons and heavier ions are included. Fundamental data needed in the shielding, dosimetry, and radiobiology of high energy particles produced by accelerators were generated, along with data on cosmic ray interaction with matter. The mechanism of high energy nucleon-nucleus reactions is also examined, especially for light target nuclei of mass number comparable to that of biological tissue.

  5. Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)

    SciTech Connect

    Otuka, N.; Dupont, E.; Semkova, V.; Pritychenko, B.; Blokhin, A.I.; Aikawa, M.; Babykina, S.; Bossant, M.; Chen, G.; Dunaeva, S.; Forrest, R.A.; Fukahori, T.; Furutachi, N.; Ganesan, S.; Ge, Z.; Gritzay, O.O.; Herman, M.; Hlavač, S.; and others

    2014-06-15

    The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) successfully collaborates in the maintenance and development of the EXFOR library. As the scope of published data expands (e.g. to higher energy, to heavier projectile) to meet the needs of research and applications, it has become a challenging task to maintain both the completeness and accuracy of the EXFOR library. Evolution of the library highlighting recent developments is described.

  6. Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR). International Collaboration Between Nuclear Reaction Data Centres (NRDC)

    SciTech Connect

    Otuka, N.; Pritychenko, B.; Otuka, N.; Dupont, E.; Semkova, V.; Pritychenko, B.; Blokhin, A. I.; Aikawa, M.; Babykina, S.; Bossant, M.; Chen, G.; Dunaeva, S.; Forrest, R. A.; Fukahori, T.; Furutachi, N.; Ganesan, S.; Ge, Z.; Gritzay, O. O.; Herman, M.; Hlavac, S.; Kato, K.; Lalremruata, B.; Lee, Y. O.; Makinaga, A.; Matsumoto, K.; Mikhaylyukova, M.; Pikulina, G.; Pronyaev, V. G.; Saxena, A.; Schwerer, O.; Simakov, S. P.; Soppera, N.; Suzuki, R.; Takacs, S.; Tao, X.; Taova, S.; Tarkanyi, F.; Varlamov, V. V.; Wang, J.; Yang, S. C.; Zerkin, V.; Zhuang, Y.

    2014-06-01

    The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) successfully collaborates in the maintenance and development of the EXFOR library. Likewise, as the scope of published data expands (e.g. to higher energy, to heavier projectile) to meet the needs of research and applications, it has become a challenging task to maintain both the completeness and accuracy of the EXFOR library. Evolution of the library highlighting recent developments is described.

  7. Fusion-fission hybrid studies in the United States

    SciTech Connect

    Moir, R.W.; Lee, J.D.; Berwald, D.H.; Cheng, E.T.; Delene, J.G.; Jassby, D.L.

    1986-05-20

    Systems and conceptual design studies have been carried out on the following three hybrid types: (1) The fission-suppressed hybrid, which maximizes fissile material produced (Pu or /sup 233/U) per unit of total nuclear power by suppressing the fission process and multiplying neutrons by (n,2n) reactions in materials like beryllium. (2) The fast-fission hybrid, which maximizes fissile material produced per unit of fusion power by maximizing fission of /sup 238/U (Pu is produced) in which twice the fissile atoms per unit of fusion power (but only a third per unit of nuclear power) are made. (3) The power hybrid, which amplifies power in the blanket for power production but does not produce fuel to sell. All three types must sell electrical power to be economical.

  8. Energetics of the fission process

    NASA Astrophysics Data System (ADS)

    Gönnenwein, Friedrich

    1994-09-01

    The mass asymmetry of fragments from nuclear fission of heavy nuclei is reviewed. While mass asymmetry is a common and well-known phenomenon for low-energy fission of the lighter actinides, more recent experiments have demonstrated that, for the heaviest actinides, the mass distribution switches to a symmetric one. On the other hand, it has been discovered that, though for fissioning nuclei with mass numbers A225 the mass distribution is basically symmetric, an asymmetric component is clearly to be identified for nuclei down to the Pb-region. In the absence of a generally accepted dynamical theory of fission, the above experimental findings are discussed in terms of static energy considerations. Triggered from the outset by the structure of the potential energy surface at the saddlepoint, the energy balance at the scission point between the available energy ( Q-value) of the reaction and the Coulomb and deformation energy of the nascent fragments is shown to steer the characteristics of the fragment mass distributions.

  9. Role of the protein kinase Kin1 and nuclear centering in actomyosin ring formation in fission yeast.

    PubMed

    Cadou, Angela; La Carbona, Stéphanie; Couturier, Anne; Le Goff, Cathy; Le Goff, Xavier

    2009-08-01

    Cytokinesis is the last step of the cell cycle, producing two daughter cells inheriting equal genetic information. This process involves the assembly of an actomyosin ring during mitosis. In the fission yeast Schizosaccharomyces pombe, cytokinesis occurs at the geometric cell centre, a position which is defined by the interphase nucleus and the anilin-related Mid1 protein. The pom1Delta, tea1Delta and tea4Delta mutants are defective in restricting Mid1 as a band around the nucleus and misplace the division site. We previously reported that inhibition of the protein kinase Kin1 promoted failure of cytokinesis in pom1Delta and tea1Delta cells but the mechanism involving Kin1 remained elusive. Here we investigated the contribution of Kin1 in cytokinesis. We show that Kin1-GFP has a dynamic cell cycle regulated distribution. Like pom1Delta and tea1Delta, tea4Delta exhibits a strong genetic interaction with kin1Delta. Using a conditional repressible kin1 allele that only alters interphase nuclear centering, we observed that Kin1 downregulation severely compromised actomyosin ring formation and septum synthesis in tea4Delta cells. In addition, nuclear displacement induced either by overexpression of a putative catalytically inactive Kin1 mutant, by chemically mediated microtubule depolymerization or by mutation in the par1Delta gene impaired cytokinesis in tea4Delta but not tea4(+) cells. We propose that nuclear mispositioning exacerbates the tea4Delta, pom1Delta and tea1Delta cell division phenotype. Our work reveal that nuclear centering becomes essential when Pom1/Tea1/Tea4 function is compromised and that Kin1 expression level is a key regulatory element in this situation. Our results suggest the existence of distinct overlapping control mechanisms to ensure efficient cell division.

  10. Nuclear Science.

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Education, Harrisburg. Bureau of Curriculum Services.

    This document is a report on a course in nuclear science for the high school curriculum. The course is designed to provide a basic but comprehensive understanding of the atom in the light of modern knowledge, and to show how people attempt to harness the tremendous energy liberated through fission and fusion reactions. The course crosses what are…

  11. Nuclear translocation of RanGAP1 coincides with virtual nuclear envelope breakdown in fission yeast meiosis.

    PubMed

    Asakawa, Haruhiko; Hiraoka, Yasushi; Haraguchi, Tokuko

    2011-05-01

    In higher eukaryotes, mitosis proceeds with nuclear envelope breakdown (NEBD) and disassembly of the nuclear pore complex (NPC); this is designated "open" mitosis. On the other hand, in many fungi, mitosis and chromosome segregation takes place without NEBD; this is designated "closed" mitosis. In a recent study on Schizosaccharomyces pombe, a closed mitosis organism, we reported a novel phenomenon that is equivalent to NEBD: a mixing of nuclear proteins and cytoplasmic proteins occurred transiently for a few minutes in meiosis without physical breakdown of the nuclear envelope. We designated this event virtual nuclear envelope breakdown (V-NEBD). In S. pombe, nuclear translocation of Rna1, a RanGAP1 homolog in S. pombe, occurs during meiosis, and this translocation of Rna1 leads to collapse of the Ran-GTP gradient across the nuclear envelope and occurs coincidently with V-NEBD. Here, we describe possible roles of RanGAP1 in V-NEBD in S. pombe and provide insights into the roles V-NEBD may play in meiosis.

  12. A Laboratory Experiment on the Statistical Theory of Nuclear Reactions

    ERIC Educational Resources Information Center

    Loveland, Walter

    1971-01-01

    Describes an undergraduate laboratory experiment on the statistical theory of nuclear reactions. The experiment involves measuring the relative cross sections for formation of a nucleus in its meta stable excited state and its ground state by applying gamma-ray spectroscopy to an irradiated sample. Involves 3-4 hours of laboratory time plus…

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

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

    Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions 12C+ 204Pb, 48Ca+ 144,154Sm, 168Er, 208Pb, 244Pu, 248Cm; 58Fe+ 208Pb, 244Pu, 248Cm, and 64Ni+ 186W, 242Pu are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes 283112, 289114 and 283116 at Dubna [1],[2] using the same reactions. The 58Fe and 64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET[3] and the neutron multi-detector DEMON[4],[5]. The role of shell effects and the influence of the entrance channel on the mechanism of the compound nucleus fusion-fission and the competitive process of quasi-fission are discussed.

  14. True ternary fission, the collinear decay into fragments of similar size in the 252Cf(sf) and 235U(nth, f) reactions

    NASA Astrophysics Data System (ADS)

    von Oertzen, W.; Nasirov, A. K.

    2014-06-01

    The collinear cluster decay in 252Cf(sf, fff), with three cluster fragments of different masses (e.g. 132Sn, 52-48Ca, 68-72Ni), which has been observed by the FOBOS group in JINR, has established a new decay mode of heavy nuclei, the collinear cluster tripartition (CCT). The same type of ternary fission decay has been observed in the reaction 235U(nth, fff). This kind of “true ternary fission” of heavy nuclei has been predicted many times in theoretical works during the last decades. In the present note we discuss true ternary fission (TFFF) into three nuclei of almost equal size (e.g. Z=98→Zi=32, 34, 32) in the same systems. The possible fission channels are predicted from potential-energy (PES) calculations. These PES's show pronounced minima for several ternary fragmentation decays, e.g. for 252Cf(sf) and for 235U(nth, f). They suggest the existence of a variety of collinear ternary fission modes. The TFFF-decays chosen in this letter have very similar dynamical features as the previously observed collinear CCT-decays. The data obtained in the above mentioned experiments allow us to extract the yield for these TFFF-decays in both systems by using specific gates on the measured parameters. These yields are a few 1.0ṡ10-6/(binary fission).

  15. Review of ENDF/B-VI Fission-Product Cross Sections[Evaluated Nuclear Data File

    SciTech Connect

    Wright, R.Q.; MacFarlane, R.E.

    2000-04-01

    In response to concerns raised in the Defense Nuclear Facilities Safety Board (DNFSB) Recommendation 93-2, the US Department of Energy (DOE) developed a comprehensive program to help assure that the DOE maintain and enhance its capability to predict the criticality of systems throughout the complex. Tasks developed to implement the response to DNFSB recommendation 93-2 included Critical Experiments, Criticality Benchmarks, Training, Analytical Methods, and Nuclear Data. The Nuclear Data Task consists of a program of differential measurements at the Oak Ridge Electron Linear Accelerator (ORELA), precise fitting of the differential data with the generalized least-squares fitting code SAMMY to represent the data with resonance parameters using the Reich-Moore formalism along with covariance (uncertainty) information, and the development of complete evaluations for selected nuclides for inclusion in the Evaluated Nuclear Data File (ENDFB).

  16. Indirect measurement of nuclear reactions of astrophysical interest

    SciTech Connect

    Liu, W. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.; Guo, B.; Lian, G.; Su, J.; Zeng, S.; Wang, B. X.; Yan, S. Q.; Li, Y. J.; Li, E. T.; Jin, S. J.

    2010-05-12

    Systematic indirect measurements of nuclear astrophysical reactions using the unstable ion beam facility GIRAFFE in CIAE were performed. We have measured the angular distributions of transfer reactions, such as {sup 8}Li(d,p){sup 9}Li, {sup 8}Li(d,n){sup 9}Be and {sup 8}Li(p,d){sup 7}Li in inverse kinematics, and derived the astrophysical S-factors or reaction rates for {sup 8}Li(n,gamma){sup 9}Li and {sup 8}Li(p,gamma){sup 9}Be by using asymptotic normalization coefficient (ANC) or spectroscopic factor methods.

  17. Low Energy Nuclear Reactions: A Millennium Status Report

    NASA Astrophysics Data System (ADS)

    Mallove, Eugene F.

    2000-03-01

    This talk will summarize some of the more convincing recent experiments that show that helium-4, nuclear scale excess energy, tritium, low-level neutron production, and the transmutation of heavy elements can occur near room temperature in relatively simple systems. Despite inappropriate theory-based arguments against it and unethical attacks by people unfamiliar with the supporting experiments, the new field of solid state nuclear reactions is progressing. The physical theory behind the associated phenomena continues to be debated among theorists. The facts of the history of this scientific controversy suggest that it is inadvisable to rush to judgment against allegedly ``impossible" new phenomena when increasingly careful experiments have revealed new vistas in physics. Detailed discussion of evidence for solid state nuclear reactions is available elsewhere (http://www.infinite-energy.com). abstract document

  18. Nuclear fusion reaction rates for strongly coupled ionic mixtures

    SciTech Connect

    Chugunov, A. I.; DeWitt, H. E.

    2009-07-15

    We analyze the effect of plasma screening on nuclear reaction rates in dense matter composed of atomic nuclei of one or two types. We perform semiclassical calculations of the Coulomb barrier penetrability taking into account a radial mean-field potential of plasma ions. The mean-field potential is extracted from the results of extensive Monte Carlo calculations of radial pair distribution functions of ions in binary ionic mixtures. We calculate the reaction rates in a wide range of plasma parameters and approximate these rates by an analytical expression that is expected to be applicable to multicomponent ion mixtures. Also, we analyze Gamow-peak energies of reacting ions in various nuclear burning regimes. For illustration, we study nuclear burning in {sup 12}C-{sup 16}O mixtures.

  19. Marmot-Fission-Gas-Diffusion

    SciTech Connect

    Andersson, Anders; Matthews, Christopher

    2016-10-22

    The MARMOT-FISSION-GAS-DIFFUSION software solves a coupled set of partial differential equations describing fission gas evolution in UO2 nuclear fuel. It is part of the MARMOT code, which builds on the MOOSE framework. Both the MARMOT code and the MOOSE framework are developed and maintained by Idaho National Laboratory. The model in MARMOT-FISSION-GAS-DIFFUSION consists of a set of continuum reaction-diffusion equations capturing formation and annihilation of defects, reactions between defects, diffusion of defects and segregation of defects to grain boundaries. Defects refer to vacancies and interstitials as well fission gas atoms (Xe) occupying various trap sites such as uranium and oxygen vacancies and interstitials sites. The code can treat a large number of defect types. The model is formulated within the phase field framework to be compatible with other MARMOT kernels. The driving forces for all reactions, diffusion and segregation events are consistently formulated as a variational derivatives of the free energy of the system. The rates of the reactions are controlled by the corresponding kinetic coefficients. The free energy and the kinetic coefficients for UO2 have been parameterized by lower length scale simulations. The code can be used to simulate defect evolution in a prescribed UO2 microstructure as well as to solve defect clustering problems that control effective diffusivities under both thermal and irradiation conditions. It I possible to extend the current UO2 model to other fuel types such as accident tolerant fuels based on the U3Si2 compound. This would obviously require a new set of material properties describing the behavior of defects in U3Si2 rather than UO2. The framework is however designed to be generic.

  20. Graphite for the nuclear industry

    SciTech Connect

    Burchell, T.D.; Fuller, E.L.; Romanoski, G.R.; Strizak, J.P.

    1991-01-01

    Graphite finds applications in both fission and fusion reactors. Fission reactors harness the energy liberated when heavy elements, such as uranium or plutonium, fragment or fission''. Reactors of this type have existed for nearly 50 years. The first nuclear fission reactor, Chicago Pile No. 1, was constructed of graphite under a football stand at Stagg Field, University of Chicago. Fusion energy devices will produce power by utilizing the energy produced when isotopes of the element hydrogen are fused together to form helium, the same reaction that powers our sun. The role of graphite is very different in these two reactor systems. Here we summarize the function of the graphite in fission and fusion reactors, detailing the reasons for their selection and discussing some of the challenges associated with their application in nuclear fission and fusion reactors. 10 refs., 15 figs., 1 tab.

  1. Effect of nuclear-reaction mechanisms on the population of excited nuclear states and isomeric ratios

    NASA Astrophysics Data System (ADS)

    Skobelev, N. K.

    2016-07-01

    Experimental data on the cross sections for channels of fusion and transfer reactions induced by beams of radioactive halo nuclei and clustered and stable loosely bound nuclei were analyzed, and the results of this analysis were summarized. The interplay of the excitation of single-particle states in reaction-product nuclei and direct reaction channels was established for transfer reactions. Respective experiments were performed in stable (6Li) and radioactive (6He) beams of the DRIBs accelerator complex at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, and in deuteron and 3He beams of the U-120M cyclotron at the Nuclear Physics Institute, Academy Sciences of Czech Republic (Řež and Prague, Czech Republic). Data on subbarrier and near-barrier fusion reactions involving clustered and loosely bound light nuclei (6Li and 3He) can be described quite reliably within simple evaporation models with allowance for different reaction Q-values and couple channels. In reactions involving halo nuclei, their structure manifests itself most strongly in the region of energies below the Coulomb barrier. Neutron transfer occurs with a high probability in the interactions of all loosely bound nuclei with light and heavy stable nuclei at positive Q-values. The cross sections for such reactions and the respective isomeric ratios differ drastically for nucleon stripping and nucleon pickup mechanisms. This is due to the difference in the population probabilities for excited single-particle states.

  2. Penetration Factor for Nuclear Fusion Reaction in Nonthermal Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Ki, Dai-Han; Jung, Young-Dae

    2011-02-01

    The nonthermal effects on the nuclear fusion reaction process are investigated in Lorentzian astrophysical plasmas. The closed expression of the classical turning point in Lorentzian plasmas is obtained by the Lambert W-function. Using the WKB analysis with the effective screening length, the closed expressions of the fusion penetration factor and the cross section for the nuclear fusion reaction in Lorentzian plasmas are obtained as functions of the spectral index, relative kinetic energy, and plasma parameters. It is shown that the nonthermal character of the Lorentzian plasma enhances the fusion penetration factor. In addition, the nonthermal effect on the penetration factor is found to be more significant in plasmas with higher densities. It would be expected that the fusion reaction rates of the p-p chain and the CNO cycle in nonthermal plasmas are always greater than those in thermal Maxwellian plasmas.

  3. Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides

    NASA Astrophysics Data System (ADS)

    Ramos, D.; Rodríguez-Tajes, C.; Caamaño, M.; Farget, F.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clement, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Domínguez, B.; de France, G.; Heinz, A.; Jacquot, B.; Navin, A.; Paradela, C.; Rejmund, M.; Roger, T.; Salsac, M. D.; Schmitt, C.

    2016-03-01

    Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a 238U beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of 250Cf, 244Cm, 240Pu, 239Np and 238U are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.

  4. Characterization of the ptr5+ gene involved in nuclear mRNA export in fission yeast.

    PubMed

    Watanabe, Nobuyoshi; Ikeda, Terumasa; Mizuki, Fumitaka; Tani, Tokio

    2012-02-03

    To analyze the mechanisms of mRNA export from the nucleus to the cytoplasm, we have isolated eleven mutants, ptr [poly(A)(+) RNA transport] 1 to 11, which accumulate poly(A)(+) RNA in the nucleus at a nonpermissive temperature in Schizosaccharomyces pombe. Of those, the ptr5-1 mutant shows dots- or a ring-like accumulation of poly(A)(+) RNA at the nuclear periphery after shifting to the nonpermissive temperature. We cloned the ptr5(+) gene and found that it encodes a component of the nuclear pore complex (NPC), nucleoporin 85 (Nup85). The ptr5-1 mutant shows no defects in protein transport, suggesting the specific involvement of Ptr5p/Nup85p in nuclear mRNA export in S. pombe. We identified Seh1p, a nucleoporin interacting with Nup85p, an mRNA-binding protein Mlo3p, and Sac3p, a component of the TREX-2 complex involved in coupling of nuclear mRNA export with transcription, as multi-copy suppressors for the ptr5-1 mutation. In addition, we found that the ptr5-1 mutation is synthetically lethal with a mutation of the mRNA export factor Rae1p, and that the double mutant exaggerates defective nuclear mRNA export, suggesting that Ptr5p/Nup85p is involved in nuclear mRNA export through Rae1p. Interestingly, the ptr5-1 mutation also showed synthetic effects with several prp pre-mRNA splicing mutations, suggesting a functional linkage between the NPCs and the splicing apparatus in the yeast nucleus.

  5. Research on fission induced plasmas and nuclear pumped lasers at the Los Alamos Scientific Laboratory

    NASA Technical Reports Server (NTRS)

    Helmick, H. H.

    1979-01-01

    A program of research on gaseous uranium and uranium plasmas is being conducted at The Los Alamos Scientific Laboratory under sponsorship of the National Aeronautics and Space Administration. The objective of this work is twofold: (1) to demonstrate the proof of principle of a gaseous uranium fueled reactor, and (2) pursue fundamental research on nuclear pumped lasers. The relevancy of the two parallel programs is embodied in the possibility of a high-performance uranium plasma reactor being used as the power supply for a nuclear pumped laser system. The accomplishments in the two above fields are summarized

  6. Rapid regulation of nuclear proteins by rapamycin-induced translocation in fission yeast.

    PubMed

    Ding, Lin; Laor, Dana; Weisman, Ronit; Forsburg, Susan L

    2014-07-01

    Genetic analysis of protein function requires a rapid means of inactivating the gene under study. Typically, this exploits temperature-sensitive mutations or promoter shut-off techniques. We report the adaptation to Schizosaccharomyces pombe of the anchor-away technique, originally designed in budding yeast by Laemmli lab. This method relies on a rapamycin-mediated interaction between the FRB- and FKBP12-binding domains to relocalize nuclear proteins of interest to the cytoplasm. We demonstrate a rapid nuclear depletion of abundant proteins as proof of principle.

  7. Unified ab initio approaches to nuclear structure and reactions

    DOE PAGES

    Navratil, Petr; Quaglioni, Sofia; Hupin, Guillaume; ...

    2016-04-13

    The description of nuclei starting from the constituent nucleons and the realistic interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of the nuclear forces, with two-, three- and possibly higher many-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD-employing Hamiltonians constructed within chiral effective field theory. After a brief overview of the field, we focus on ab initio many-body approaches—built upon the no-core shell model—that are capable of simultaneously describing both bound and scattering nuclear states, and present results for resonances in light nuclei, reactions important for astrophysics and fusion research. In particular, we review recent calculations of resonances in the 6He halo nucleus, of five- and six-nucleon scattering, and an investigation of the role of chiral three-nucleon interactions in the structure of 9Be. Further, we discuss applications to the 7Bemore » $${({\\rm{p}},\\gamma )}^{8}{\\rm{B}}$$ radiative capture. Lastly, we highlight our efforts to describe transfer reactions including the 3H$${({\\rm{d}},{\\rm{n}})}^{4}$$He fusion.« less

  8. A New Method of Prompt Fission Neutron Energy Spectrum Unfolding

    SciTech Connect

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

    2010-11-25

    The prompt neutron emission in spontaneous fission of {sup 252}Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the {sup 252}Cf(sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 10{sup 7} fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  9. A complementary approach to estimate the internal pressure of fission gas bubbles by SEM-SIMS-EPMA in irradiated nuclear fuels

    NASA Astrophysics Data System (ADS)

    Cagna, C.; Zacharie-Aubrun, I.; Bienvenu, P.; Barrallier, L.; Michel, B.; Noirot, J.

    2016-02-01

    The behaviour of gases produced by fission is of great importance for nuclear fuel in operation. Within this context, a decade ago, a general method for the characterisation of the fission gas including gas bubbles in an irradiated UO2 nuclear fuel was developed and applied to determine the bubbles internal pressure. The method consists in the determination of the pressure, over a large population of bubbles, using three techniques: SEM, EPMA and SIMS. In this paper, a complementary approach using the information given by the same techniques is performed on an isolated bubble under the surface and is aiming for a better accuracy compared to the more general measurement of gas content. SEM and EPMA enable the detection of a bubble filled with xenon under the surface. SIMS enables the detection of the gas filling the bubble. The quantification is achieved using the EPMA data as reference at positions where no or nearly no bubbles are detected.

  10. Sigma: Web Retrieval Interface for Nuclear Reaction Data

    SciTech Connect

    Pritychenko, B. Sonzogni, A.A.

    2008-12-15

    We present Sigma, a Web-rich application which provides user-friendly access in processing and plotting of the evaluated and experimental nuclear reaction data stored in the ENDF-6 and EXFOR formats. The main interface includes browsing using a periodic table and a directory tree, basic and advanced search capabilities, interactive plots of cross sections, angular distributions and spectra, comparisons between evaluated and experimental data, computations between different cross section sets. Interactive energy-angle, neutron cross section uncertainties plots and visualization of covariance matrices are under development. Sigma is publicly available at the National Nuclear Data Center website at (http://www.nndc.bnl.gov/sigma)

  11. Sigma: Web Retrieval Interface for Nuclear Reaction Data

    SciTech Connect

    Pritychenko,B.; Sonzogni, A.A.

    2008-06-24

    The authors present Sigma, a Web-rich application which provides user-friendly access in processing and plotting of the evaluated and experimental nuclear reaction data stored in the ENDF-6 and EXFOR formats. The main interface includes browsing using a periodic table and a directory tree, basic and advanced search capabilities, interactive plots of cross sections, angular distributions and spectra, comparisons between evaluated and experimental data, computations between different cross section sets. Interactive energy-angle, neutron cross section uncertainties plots and visualization of covariance matrices are under development. Sigma is publicly available at the National Nuclear Data Center website at www.nndc.bnl.gov/sigma.

  12. Biomodal spontaneous fission

    SciTech Connect

    Hulet, E.K. )

    1989-09-26

    Investigations of mass and kinetic-energy distributions from spontaneous fission have been extended in recent years to an isotope of element 104 and, for half-lives, to an isotope of element 108. The results have been surprising in that spontaneous fission half-lives have turned out to be much longer than expected and mass and kinetic- energy distributions were found to abruptly shift away from those of the lighter actinides, showing two modes of fission. These new developments have caused a re-evaluation of our understanding of the fission process, bringing an even deeper appreciation of the role played by nuclear shell effects upon spontaneous fission properties. 16 refs., 10 figs.

  13. Talk About Nuclear Power

    ERIC Educational Resources Information Center

    Tremlett, Lewis

    1976-01-01

    Presents an overview of the relation of nuclear power to human health and the environment, and discusses the advantages and disadvantages of nuclear power as an energy source urging technical educators to inculcate an awareness of the problems associated with the production of energy. Describes the fission reaction process, the hazards of…

  14. Absence of entrance channel effects in fission fragment anisotropies of the {sup 215}Fr compound nucleus

    SciTech Connect

    Appannababu, S.; Mukherjee, S.; Singh, N. L.; Rath, P. K.; Kumar, G. Kiran; Thomas, R. G.; Santra, S.; Nayak, B. K.; Saxena, A.; Choudhury, R. K.; Golda, K. S.; Jhingan, A.; Kumar, R.; Sugathan, P.; Singh, Hardev

    2009-08-15

    Fission fragment angular distributions have been measured for the reactions {sup 11}B+{sup 204}Pb and {sup 18}O+{sup 197}Au, both leading to the same compound nucleus {sup 215}Fr at near barrier energies. The measured fission fragment anisotropies as a function of E{sub c.m.}/V{sub B} are found to be consistent with the predictions of the standard saddle point statistical model (SSPM) for both the systems, suggesting the absence of entrance channel effects on fission fragment anisotropies even though the entrance channel mass asymmetries for both these systems fall on either side of the Bussinaro-Gallone critical mass asymmetry. The consistency of the present results with SSPM predictions can be understood within the framework of the pre-equilibrium fission model where fission before K equilibration is severely inhibited by the high values of ratios of fission barrier height to nuclear temperature.

  15. Direct reactions for nuclear structure required for fundamental symmetry tests

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.; Rand, E. T.; Diaz Varela, A.; Ball, G. C.; Bildstein, V.; Faestermann, T.; Hadinia, B.; Hertenberger, R.; Jamieson, D. S.; Jigmeddorj, B.; Leach, K. G.; Svensson, C. E.; Wirth, H.-F.

    2016-09-01

    A program of nuclear structure studies to support fundamental symmetry tests has been initiated. Motivated by the search for an electric dipole moment in 199Hg, the structure in the vicinity has been explored via direct reaction studies. To date, these have included the 198,200Hg(d, d') inelastic scattering reactions, with the aim to obtain information on the E2 and E3 strength distributions, and the 198Hg(d, p) and 200Hg(d, t) reactions to obtain information on the single-particle states in 199Hg. The studies using the 200Hg targets have been fully analyzed using the FRESCO reaction code yielding the E2 and E3 strength distribution to 4 MeV in excitation energy, and the (d, t) single- particle strength to over 3 MeV in excitation energy.

  16. A Covariance Generation Methodology for Fission Product Yields

    NASA Astrophysics Data System (ADS)

    Terranova, N.; Serot, O.; Archier, P.; Vallet, V.; De Saint Jean, C.; Sumini, M.

    2016-03-01

    Recent safety and economical concerns for modern nuclear reactor applications have fed an outstanding interest in basic nuclear data evaluation improvement and completion. It has been immediately clear that the accuracy of our predictive simulation models was strongly affected by our knowledge on input data. Therefore strong efforts have been made to improve nuclear data and to generate complete and reliable uncertainty information able to yield proper uncertainty propagation on integral reactor parameters. Since in modern nuclear data banks (such as JEFF-3.1.1 and ENDF/BVII.1) no correlations for fission yields are given, in the present work we propose a covariance generation methodology for fission product yields. The main goal is to reproduce the existing European library and to add covariance information to allow proper uncertainty propagation in depletion and decay heat calculations. To do so, we adopted the Generalized Least Square Method (GLSM) implemented in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation), developed at CEA-Cadarache. Theoretical values employed in the Bayesian parameter adjustment are delivered thanks to a convolution of different models, representing several quantities in fission yield calculations: the Brosa fission modes for pre-neutron mass distribution, a simplified Gaussian model for prompt neutron emission probability, theWahl systematics for charge distribution and the Madland-England model for the isomeric ratio. Some results will be presented for the thermal fission of U-235, Pu-239 and Pu-241.

  17. RNAi in fission yeast finds new targets and new ways of targeting at the nuclear periphery.

    PubMed

    Holoch, Daniel; Moazed, Danesh

    2012-04-15

    RNAi in Schizosaccharomyces pombe is critical for centromeric heterochromatin formation. It has remained unclear, however, whether RNAi also regulates the expression of protein-coding loci. In the April 1, 2012, issue of Genes & Development, Woolcock and colleagues (pp. 683-667) reported an elegant mechanism for the conditional RNAi-mediated repression of stress response genes involving association with Dcr1 at the nuclear pore. Unexpectedly, the initial targeting of RNAi components to these genes does not require small RNA guides.

  18. Negative regulation of meiotic gene expression by the nuclear poly(a)-binding protein in fission yeast.

    PubMed

    St-André, Olivier; Lemieux, Caroline; Perreault, Audrey; Lackner, Daniel H; Bähler, Jürg; Bachand, François

    2010-09-03

    Meiosis is a cellular differentiation process in which hundreds of genes are temporally induced. Because the expression of meiotic genes during mitosis is detrimental to proliferation, meiotic genes must be negatively regulated in the mitotic cell cycle. Yet, little is known about mechanisms used by mitotic cells to repress meiosis-specific genes. Here we show that the poly(A)-binding protein Pab2, the fission yeast homolog of mammalian PABPN1, controls the expression of several meiotic transcripts during mitotic division. Our results from chromatin immunoprecipitation and promoter-swapping experiments indicate that Pab2 controls meiotic genes post-transcriptionally. Consistently, we show that the nuclear exosome complex cooperates with Pab2 in the negative regulation of meiotic genes. We also found that Pab2 plays a role in the RNA decay pathway orchestrated by Mmi1, a previously described factor that functions in the post-transcriptional elimination of meiotic transcripts. Our results support a model in which Mmi1 selectively targets meiotic transcripts for degradation via Pab2 and the exosome. Our findings have therefore uncovered a mode of gene regulation whereby a poly(A)-binding protein promotes RNA degradation in the nucleus to prevent untimely expression.

  19. The meiosis-specific nuclear passenger protein is required for proper assembly of forespore membrane in fission yeast.

    PubMed

    Takaine, Masak; Imada, Kazuki; Numata, Osamu; Nakamura, Taro; Nakano, Kentaro

    2014-10-15

    Sporulation, gametogenesis in yeast, consists of meiotic nuclear division and spore morphogenesis. In the fission yeast Schizosaccharomyces pombe, the four haploid nuclei produced after meiosis II are encapsulated by the forespore membrane (FSM), which is newly synthesized from spindle pole bodies (SPBs) in the cytoplasm of the mother cell as spore precursors. Although the coordination between meiosis and FSM assembly is vital for proper sporulation, the underlying mechanism remains unclear. In the present study, we identified a new meiosis-specific protein Npg1, and found that it was involved in the efficient formation of spores and spore viability. The accumulation and organization of the FSM was compromised in npg1-null cells, leading to the error-prone envelopment of nuclei. Npg1 was first seen as internuclear dots and translocated to the SPBs before the FSM assembled. Genetic analysis revealed that Npg1 worked in conjunction with the FSM proteins Spo3 and Meu14. These results suggest a possible signaling link from the nucleus to the meiotic SPBs in order to associate the onset of FSM assembly with meiosis II, which ensures the successful partitioning of gametic nuclei.

  20. Advances in Development of the Fission Product Extraction Process for the Separation of Cesium and Strontium from Spent Nuclear Fuel

    SciTech Connect

    JAck D. Law

    2007-09-01

    The Fission Product Extraction (FPEX) Process is being developed as part of the United States Department of Energy Advanced Fuel Cycle Initiative for the simultaneous separation of cesium (Cs) and strontium (Sr) from spent light water reactor (LWR) fuel. Separation of the Cs and Sr will reduce the short-term heat load in a geological repository, and when combined with the separation of americium (Am) and curium (Cm), could increase the capacity of the geological repository by a factor of approximately 100. The FPEX process is based on two highly specific extractants: 4,4',(5')-Di-(t-butyldicyclo-hexano)-18-crown-6 (DtBuCH18C6) and Calix[4]arene-bis-(tert-octylbenzo-crown-6) (BOBCalixC6). The DtBuCH18C6 extractant is selective for strontium and the BOBCalixC6 extractant is selective for cesium. Results of flowsheet testing of the FPEX process with a simulated feed solution in 3.3-cm centrifugal contactors are detailed. Removal efficiencies, distribution coefficient data, coextraction of metals, and process hydrodynamic performance are discussed along with recommendations for future flowsheet testing with actual spent nuclear fuel.

  1. Nuclear structure and reactions using lattice effective field theory

    NASA Astrophysics Data System (ADS)

    Rupak, Gautam

    2016-09-01

    Effective field theory (EFT) formulated on a space-time lattice provides a model-independent framework for ab initio nuclear structure and reaction calculations. The EFT interactions are rooted in quantum chromodynamics through low energy symmetry constraints. In this talk I present several recent developments in lattice EFT, in particular I present the so called adiabatic projection method that enables elastic and in-elastic reaction calculations. Bound state properties of atomic nuclei such as carbon and oxygen will also be presented. Partial support from US National Science Foundation Grant PHY-1307453 is acknowledged.

  2. A Transport Model for Nuclear Reactions Induced by Radioactive Beams

    SciTech Connect

    Li Baoan; Chen Liewen; Das, Champak B.; Das Gupta, Subal; Gale, Charles; Ko, C.M.; Yong, G.-C.; Zuo Wei

    2005-10-14

    Major ingredients of an isospin and momentum dependent transport model for nuclear reactions induced by radioactive beams are outlined. Within the IBUU04 version of this model we study several experimental probes of the equation of state of neutron-rich matter, especially the density dependence of the nuclear symmetry energy. Comparing with the recent experimental data from NSCL/MSU on isospin diffusion, we found a nuclear symmetry energy of Esym({rho}) {approx_equal} 31.6({rho}/{rho}0)1.05 at subnormal densities. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.

  3. Nucleon Transfer Reactions in Few-Body Nuclear Systems

    NASA Astrophysics Data System (ADS)

    Deltuva, A.

    2017-03-01

    Three- and four-body scattering is described solving Faddeev-Yakubovsky or equivalent Alt-Grassberger-Sandhas integral equations for transition operators in momentum-space. Several realistic nuclear interaction models are used; the Coulomb force between charged particles is taken into account via the screening and renormalization method. Differential cross sections and spin observables for various nucleon transfer reactions are calculated and compared with experimental data.

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

    NASA Technical Reports Server (NTRS)

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

    1967-01-01

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

  5. Monitoring system for a liquid-cooled nuclear fission reactor. [PWR

    DOEpatents

    DeVolpi, A.

    1984-07-20

    The invention provides improved means for detecting the water levels in various regions of a water-cooled nuclear power reactor, viz., in the downcomer, in the core, in the inlet and outlet plenums, at the head, and elsewhere; and also for detecting the density of the water in these regions. The invention utilizes a plurality of exterior gamma radiation detectors and a collimator technique operable to sense separate regions of the reactor vessel to give respectively, unique signals for these regions, whereby comparative analysis of these signals can be used to advise of the presence and density of cooling water in the vessel.

  6. Number-Theory in Nuclear-Physics in Number-Theory: Non-Primality Factorization As Fission VS. Primality As Fusion; Composites' Islands of INstability: Feshbach-Resonances?

    NASA Astrophysics Data System (ADS)

    Smith, A.; Siegel, Edward Carl-Ludwig

    2011-03-01

    Numbers: primality/indivisibility/non-factorization versus compositeness/divisibility/ factorization, often in tandem but not always, provocatively close analogy to nuclear-physics: (2 + 1)=(fusion)=3; (3+1)=(fission)=4[=2 x 2]; (4+1)=(fusion)=5; (5 +1)=(fission)=6[=2 x 3]; (6 + 1)=(fusion)=7; (7+1)=(fission)=8[= 2 x 4 = 2 x 2 x 2]; (8 + 1) =(non: fission nor fusion)= 9[=3 x 3]; then ONLY composites' Islands of fusion-INstability: 8, 9, 10; then 14, 15, 16, ... Could inter-digit Feshbach-resonances exist??? Possible applications to: quantum-information/ computing non-Shore factorization, millennium-problem Riemann-hypotheses proof as Goodkin BEC intersection with graph-theory "short-cut" method: Rayleigh(1870)-Polya(1922)-"Anderson"(1958)-localization, Goldbach-conjecture, financial auditing/accounting as quantum-statistical-physics; ...abound!!! Watkins [www.secamlocal.ex.ac.uk/people/staff/mrwatkin/] "Number-Theory in Physics" many interconnections: "pure"-maths number-theory to physics including Siegel [AMS Joint Mtg.(2002)-Abs.# 973-60-124] inversion of statistics on-average digits' Newcomb(1881)-Weyl(14-16)-Benford(38)-law to reveal both the quantum and BEQS (digits = bosons = digits:"spinEless-boZos"). 1881 1885 1901 1905 1925 < 1927, altering quantum-theory history!!!

  7. Energy production using fission fragment rockets

    SciTech Connect

    Chapline, G.; Matsuda, Y.

    1991-08-01

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

  8. Rydberg phases of Hydrogen and low energy nuclear reactions

    NASA Astrophysics Data System (ADS)

    Olafsson, Sveinn; Holmlid, Leif

    2016-03-01

    For over the last 26 years the science of cold fusion/LENR has been researched around the world with slow pace of progress. Modest quantity of excess heat and signatures of nuclear transmutation and helium production have been confirmed in experiments and theoretical work has only resulted in a large flora of inadequate theoretical scenarios. Here we review current state of research in Rydberg matter of Hydrogen that is showing strong signature of nuclear processes. In the presentation experimental behavior of Rydberg matter of hydrogen is described. An extensive collaboration effort of surface physics, catalysis, atomic physics, solid state physics, nuclear physics and quantum information is need to tackle the surprising experimental results that have so far been obtained. Rydberg matter of Hydrogen is the only known state of matter that is able to bring huge collection of protons to so short distances and for so long time that tunneling becomes a reasonable process for making low energy nuclear reactions. Nuclear quantum entanglement can also become realistic process at theses conditions.

  9. Shell Effects in Fusion-Fission of Heavy and Superheavy Nuclei

    NASA Astrophysics Data System (ADS)

    Itkis, M. G.; Bogatchev, A. A.; Itkis, I. M.; Jandel, M.; Kliman, J.; Kniajeva, G. N.; Kondratiev, N. A.; Korzyukov, I. V.; Kozulin, E. M.; Krupa, L.; Oganessian, Yu. Ts.; Pokrovsky, I. V.; Prokhorova, E. V.; Voskresenski, V. M.; Zagrebaev, V. I.; Rusanov, A. Ya.; Corradi, L.; Gadea, A.; Latina, L.; Stefanini, A. M.; Szilner, S.; Trotta, M.; Vinodkumar, A. M.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Äystö, J.; Khlebnikov, S. V.; Rubchenya, V. A.; Trzaska, W. H.; Vakhtin, D. N.; Goverdovski, A. A.; Hanappe, F.; Materna, T.; Dorvaux, O.; Rowley, N.; Stuttge, L.; Giardina, G.

    2003-07-01

    The process of fusion-fission of heavy and superheavy nuclei with Z=82-122 formed in the reactions with 48Ca, 58Fe and 64Ni ions at energies near and below the Coulomb barrier has been studied. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy ) and the Accelerator of the Laboratory of University of Jyväskylä (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET[1] and the neutron multi-detector DEMON[2,3]. As a result of the experiments, mass and energy distributions (MED) of fission fragments, cross-sections of fission, quasi-fission and evaporation residues, multiplicities of neutrons and γ-quanta and their dependence on the mechanism of formation and decay of compound systems have been studied.

  10. Visualized kinematics code for two-body nuclear reactions

    NASA Astrophysics Data System (ADS)

    Lee, E. J.; Chae, K. Y.

    2016-05-01

    The one or few nucleon transfer reaction has been a great tool for investigating the single-particle properties of a nucleus. Both stable and exotic beams are utilized to study transfer reactions in normal and inverse kinematics, respectively. Because many energy levels of the heavy recoil from the two-body nuclear reaction can be populated by using a single beam energy, identifying each populated state, which is not often trivial owing to high level-density of the nucleus, is essential. For identification of the energy levels, a visualized kinematics code called VISKIN has been developed by utilizing the Java programming language. The development procedure, usage, and application of the VISKIN is reported.

  11. Testing actinide fission yield treatment in CINDER90 for use in MCNP6 burnup calculations

    SciTech Connect

    Fensin, Michael Lorne; Umbel, Marissa

    2015-09-18

    Most of the development of the MCNPX/6 burnup capability focused on features that were applied to the Boltzman transport or used to prepare coefficients for use in CINDER90, with little change to CINDER90 or the CINDER90 data. Though a scheme exists for best solving the coupled Boltzman and Bateman equations, the most significant approximation is that the employed nuclear data are correct and complete. Thus, the CINDER90 library file contains 60 different actinide fission yields encompassing 36 fissionable actinides (thermal, fast, high energy and spontaneous fission). Fission reaction data exists for more than 60 actinides and as a result, fission yield data must be approximated for actinides that do not possess fission yield information. Several types of approximations are used for estimating fission yields for actinides which do not possess explicit fission yield data. The objective of this study is to test whether or not certain approximations of fission yield selection have any impact on predictability of major actinides and fission products. Further we assess which other fission products, available in MCNP6 Tier 3, result in the largest difference in production. Because the CINDER90 library file is in ASCII format and therefore easily amendable, we assess reasons for choosing, as well as compare actinide and major fission product prediction for the H. B. Robinson benchmark for, three separate fission yield selection methods: (1) the current CINDER90 library file method (Base); (2) the element method (Element); and (3) the isobar method (Isobar). Results show that the three methods tested result in similar prediction of major actinides, Tc-99 and Cs-137; however, certain fission products resulted in significantly different production depending on the method of choice.

  12. Nano-Scale Fission Product Phases in an Irradiated U-7Mo Alloy Nuclear Fuel

    SciTech Connect

    Dennis Keiser, Jr.; Brandon Miller; James Madden; Jan-Fong Jue; Jian Gan

    2014-09-01

    Irradiated nuclear fuel is a very difficult material to characterize. Due to the large radiation fields associated with these materials, they are hard to handle and typically have to be contained in large hot cells. Even the equipment used for performing characterization is housed in hot cells or shielded glove boxes. The result is not only a limitation in the techniques that can be employed for characterization, but also a limitation in the size of features that can be resolved The most standard characterization techniques include light optical metallography (WM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). These techniques are applied to samples that are typically prepared using grinding and polishing approaches that will always generate some mechanical damage on the sample surface. As a result, when performing SEM analysis, for example, the analysis is limited by the quality of the sample surface that can be prepared. However, a new approach for characterizing irradiated nuclear fuel has recently been developed at the Idaho National Laboratory (INL) in Idaho Falls, Idaho. It allows for a dramatic improvement in the quality of characterization that can be performed when using an instrument like an SEM. This new approach uses a dual-beam scanning microscope, where one of the beams isa focused ion beam (FIB), which can be used to generate specimens of irradiated fuel (-10µm x 10µm) for microstructural characterization, and the other beam is the electron beam of an SEM. One significant benefit of this approach is that the specimen surface being characterized has received much less damage (and smearing) than is caused by the more traditional approaches, which enables the imaging of nanometer­ sized microstructural features in the SEM. The process details are for an irradiated low-enriched uranium (LEU) U-Mo alloy fuel Another type of irradiated fuel that has been characterized using this technique is a mixed oxide fuel.

  13. Characterization of nuclear pore complex components in fission yeast Schizosaccharomyces pombe.

    PubMed

    Asakawa, Haruhiko; Yang, Hui-Ju; Yamamoto, Takaharu G; Ohtsuki, Chizuru; Chikashige, Yuji; Sakata-Sogawa, Kumiko; Tokunaga, Makio; Iwamoto, Masaaki; Hiraoka, Yasushi; Haraguchi, Tokuko

    2014-01-01

    The nuclear pore complex (NPC) is an enormous proteinaceous complex composed of multiple copies of about 30 different proteins called nucleoporins. In this study, we analyzed the composition of the NPC in the model organism Schizosaccharomyces pombe using strains in which individual nucleoporins were tagged with GFP. We identified 31 proteins as nucleoporins by their localization to the nuclear periphery. Gene disruption analysis in previous studies coupled with gene disruption analysis in the present study indicates that 15 of these nucleoporins are essential for vegetative cell growth and the other 16 nucleoporins are non-essential. Among the 16 non-essential nucleoporins, 11 are required for normal progression through meiosis and their disruption caused abnormal spore formation or poor spore viability. Based on fluorescence measurements of GFP-fused nucleoporins, we estimated the composition of the NPC in S. pombe and found that the organization of the S. pombe NPC is largely similar to that of other organisms; a single NPC was estimated as being 45.8-47.8 MDa in size. We also used fluorescence measurements of single NPCs and quantitative western blotting to analyze the composition of the Nup107-Nup160 subcomplex, which plays an indispensable role in NPC organization and function. Our analysis revealed low amounts of Nup107 and Nup131 and high amounts of Nup132 in the Nup107-Nup160 subcomplex, suggesting that the composition of this complex in S. pombe may differ from that in S. cerevisiae and humans. Comparative analysis of NPCs in various organisms will lead to a comprehensive understanding of the functional architecture of the NPC.

  14. Traces of fission products in southeast Spain after the Fukushima nuclear accident.

    PubMed

    Piñero García, F; Ferro García, M A

    2012-12-01

    Traces of (131)I, (134)Cs and (137)Cs were measured after the Fukushima nuclear accident between 23 March and 13 April 2011 in southeast Spain. The movement of the radioactive cloud toward southeast Spain was reconstructed based on the backward and forward trajectory cluster analyses. Polar maritime air masses which had originated over North America transported the radioactive plume toward the southeast Spain. Aerosols, rainwater, vegetables and cheese were analyzed to determine the radioactive risk. The highest concentrations of (131)I, (134)Cs and (137)Cs in air samples were 2.63 ± 0.12 mBq/m(3); 0.10 ± 0.03 mBq/m(3); 0.09 ± 0.02 mBq/m(3), respectively. After precipitation on April 3rd, the maximum concentrations of (131)I, (134)Cs and (137)Cs were detected in rainwater samples, 1.10 ± 0.16 mBq/L; 0.022 ± 0.003 mBq/L; 0.05 ± 0.03 mBq/L, respectively. As a consequence, (131)I was transferred to the human food chain, and found in chard and goat cheese, 0.97 ± 0.20 Bq/kg and 0.52 ± 0.08 Bq/kg, respectively. The traces of (131)I, (134)Cs and (137)Cs detected in the different samples were so low, that there is no impact on human health or the environment in Spain after the Fukushima nuclear accident.

  15. [Electromagnetic studies of nuclear structure and reactions]. Progress summary

    SciTech Connect

    Not Available

    1992-12-31

    The experimental goals are focused on developing an understanding of strong interactions and the structure of hadronic systems by determination of the electromagnetic response; these goals will be accomplished through coincidence detection of final states. Nuclear modeling objectives are to organize and interpret the data through a consistent description of a broad spectrum of reaction observables; calculations are performed in a nonrelativistic diagrammatic framework as well as a relativistic QHD approach. Work is described according to the following arrangement: direct knockout reactions (completion of {sup 16}O(e,e{prime}p), {sup 12}C(e,e{prime}pp) progress, large acceptance detector physics simulations), giant resonance studies (intermediate-energy experiments with solid-state detectors, the third response function in {sup 12}C(e,e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 0}), comparison of the {sup 12}C(e, e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 3}) reactions, quadrupole strength in the {sup 16}O(e,e{prime}{alpha}{sub 0}) reaction, quadrupole strength in the {sup 12}C(e,e{prime}{alpha}) reaction, analysis of the {sup 12}C(e,e{prime}p{sub 1}) and {sup 16}O(e,e{prime}p{sub 3}) angular distributions, analysis of the {sup 40}Ca(e,e{prime}x) reaction at low q, analysis of the higher-q {sup 12}C(e,e{prime}x) data from Bates), models of nuclear structure (experimental work, Hartree-Fock calculations, phonon excitations in spherical nuclei, shell model calculations, variational methods for relativistic fields), and instrumentation development efforts (developments at CEBAF, CLAS contracts, BLAST developments).

  16. Evaluation of Cross-Section Sensitivities in Computing Burnup Credit Fission Product Concentrations

    SciTech Connect

    Gauld, I.C.

    2005-08-12

    U.S. Nuclear Regulatory Commission Interim Staff Guidance 8 (ISG-8) for burnup credit covers actinides only, a position based primarily on the lack of definitive critical experiments and adequate radiochemical assay data that can be used to quantify the uncertainty associated with fission product credit. The accuracy of fission product neutron cross sections is paramount to the accuracy of criticality analyses that credit fission products in two respects: (1) the microscopic cross sections determine the reactivity worth of the fission products in spent fuel and (2) the cross sections determine the reaction rates during irradiation and thus influence the accuracy of predicted final concentrations of the fission products in the spent fuel. This report evaluates and quantifies the importance of the fission product cross sections in predicting concentrations of fission products proposed for use in burnup credit. The study includes an assessment of the major fission products in burnup credit and their production precursors. Finally, the cross-section importances, or sensitivities, are combined with the importance of each major fission product to the system eigenvalue (k{sub eff}) to determine the net importance of cross sections to k{sub eff}. The importances established the following fission products, listed in descending order of priority, that are most likely to benefit burnup credit when their cross-section uncertainties are reduced: {sup 151}Sm, {sup 103}Rh, {sup 155}Eu, {sup 150}Sm, {sup 152}Sm, {sup 153}Eu, {sup 154}Eu, and {sup 143}Nd.

  17. Airborne fission products in the High Arctic after the Fukushima nuclear accident.

    PubMed

    Paatero, Jussi; Vira, Julius; Siitari-Kauppi, Marja; Hatakka, Juha; Holmén, Kim; Viisanen, Yrjö

    2012-12-01

    High-volume aerosol samples were collected at the Mt. Zeppelin Global Atmosphere Watch station, Ny-Ålesund, Svalbard (78°58'N, 11°53'E). The samples were analysed to find out if the radionuclide emissions from the Fukushima nuclear power plant accident in March 2011 could be detected also in the atmosphere of the High Arctic. Iodine-131 and (134)Cs and (137)Cs were observed from 25 March 2011 onwards. The maximum (131)I, (134)Cs and (137)Cs activity concentrations were 810 ± 20, 659 ± 13, and 675 ± 7 μBq/m(3), respectively. The comparison between the measured (131)I activity concentrations at Mt. Zeppelin and those calculated with the SILAM dispersion model revealed that the timing of plume movements could be rather well predicted with the model. The activity concentration levels between the measurements and the model calculations deviated. This can be due to the inaccuracies in the source term. The (134)Cs:(137)Cs activity ratio recorded in Svalbard was high compared to earlier incidents. The ratio was close to 1 which is in agreement with other studies of the Fukushima releases. This distinctive activity ratio in the Fukushima debris could be used as a tracer in Arctic radioecology studies if the activity concentrations are high enough to be detected.

  18. Chromosome conformation maps in fission yeast reveal cell cycle dependent sub nuclear structure.

    PubMed

    Grand, Ralph S; Pichugina, Tatyana; Gehlen, Lutz R; Jones, M Beatrix; Tsai, Peter; Allison, Jane R; Martienssen, Robert; O'Sullivan, Justin M

    2014-11-10

    Successful progression through the cell cycle requires spatial and temporal regulation of gene transcript levels and the number, positions and condensation levels of chromosomes. Here we present a high resolution survey of genome interactions in Schizosaccharomyces pombe using synchronized cells to investigate cell cycle dependent changes in genome organization and transcription. Cell cycle dependent interactions were captured between and within S. pombe chromosomes. Known features of genome organization (e.g. the clustering of telomeres and retrotransposon long terminal repeats (LTRs)) were observed throughout the cell cycle. There were clear correlations between transcript levels and chromosomal interactions between genes, consistent with a role for interactions in transcriptional regulation at specific stages of the cell cycle. In silico reconstructions of the chromosome organization within the S. pombe nuclei were made by polymer modeling. These models suggest that groups of genes with high and low, or differentially regulated transcript levels have preferred positions within the S. pombe nucleus. We conclude that the S. pombe nucleus is spatially divided into functional sub-nuclear domains that correlate with gene activity. The observation that chromosomal interactions are maintained even when chromosomes are fully condensed in M phase implicates genome organization in epigenetic inheritance and bookmarking.

  19. Involvement of the spliceosomal U4 small nuclear RNA in heterochromatic gene silencing at fission yeast centromeres.

    PubMed

    Chinen, Madoka; Morita, Misato; Fukumura, Kazuhiro; Tani, Tokio

    2010-02-19

    prp13-1 is one of the mutants isolated in a screen for defective pre-mRNA splicing at a nonpermissive temperature in fission yeast Schizosaccharomyces pombe. We cloned the prp13(+) gene and found that it encodes U4 small nuclear RNA (snRNA) involved in the assembly of the spliceosome. The prp13-1 mutant produced elongated cells, a phenotype similar to cell division cycle mutants, and displays a high incidence of lagging chromosomes on anaphase spindles. The mutant is hypersensitive to the microtubule-destabilizing drug thiabendazole, supporting that prp13-1 has a defect in chromosomal segregation. We found that the prp13-1 mutation resulted in expression of the ura4(+) gene inserted in the pericentromeric heterochromatin region and reduced recruitment of the heterochromatin protein Swi6p to that region, indicating defects in the formation of pericentromeric heterochromatin, which is essential for the segregation of chromosomes, in prp13-1. The formation of centromeric heterochromatin is induced by the RNA interference (RNAi) system in S. pombe. In prp13-1, the processing of centromeric noncoding RNAs to siRNAs, which direct the heterochromatin formation, was impaired and unprocessed noncoding RNAs were accumulated. These results suggest that U4 snRNA is required for the RNAi-directed heterochromatic gene silencing at the centromeres. In relation to the linkage between the spliceosomal U4 snRNA and the RNAi-directed formation of heterochromatin, we identified a mRNA-type intron in the centromeric noncoding RNAs. We propose a model in which the assembly of the spliceosome or a sub-spliceosome complex on the intron-containing centromeric noncoding RNAs facilitates the RNAi-directed formation of heterochromatin at centromeres, through interaction with the RNA-directed RNA polymerase complex.

  20. Involvement of the Spliceosomal U4 Small Nuclear RNA in Heterochromatic Gene Silencing at Fission Yeast Centromeres*

    PubMed Central

    Chinen, Madoka; Morita, Misato; Fukumura, Kazuhiro; Tani, Tokio

    2010-01-01

    prp13-1 is one of the mutants isolated in a screen for defective pre-mRNA splicing at a nonpermissive temperature in fission yeast Schizosaccharomyces pombe. We cloned the prp13+ gene and found that it encodes U4 small nuclear RNA (snRNA) involved in the assembly of the spliceosome. The prp13-1 mutant produced elongated cells, a phenotype similar to cell division cycle mutants, and displays a high incidence of lagging chromosomes on anaphase spindles. The mutant is hypersensitive to the microtubule-destabilizing drug thiabendazole, supporting that prp13-1 has a defect in chromosomal segregation. We found that the prp13-1 mutation resulted in expression of the ura4+ gene inserted in the pericentromeric heterochromatin region and reduced recruitment of the heterochromatin protein Swi6p to that region, indicating defects in the formation of pericentromeric heterochromatin, which is essential for the segregation of chromosomes, in prp13-1. The formation of centromeric heterochromatin is induced by the RNA interference (RNAi) system in S. pombe. In prp13-1, the processing of centromeric noncoding RNAs to siRNAs, which direct the heterochromatin formation, was impaired and unprocessed noncoding RNAs were accumulated. These results suggest that U4 snRNA is required for the RNAi-directed heterochromatic gene silencing at the centromeres. In relation to the linkage between the spliceosomal U4 snRNA and the RNAi-directed formation of heterochromatin, we identified a mRNA-type intron in the centromeric noncoding RNAs. We propose a model in which the assembly of the spliceosome or a sub-spliceosome complex on the intron-containing centromeric noncoding RNAs facilitates the RNAi-directed formation of heterochromatin at centromeres, through interaction with the RNA-directed RNA polymerase complex. PMID:20018856

  1. Trojan Horse technique to measure nuclear astrophysics rearrangement reactions

    NASA Astrophysics Data System (ADS)

    Spitaleri, Claudio

    2013-03-01

    The knowledge of nucleosynthesis and of energy production in stars requires an increasingly precise measurement of nuclear fusion reactions at the Gamow energy. Because of the Coulomb barrier reaction cross sections in astrophysics cannot be accessed directly at ultra -low energies, unless very favorable conditions are met. Moreover, the energies characterizing nuclear processes in several astrophysical contexts are so low that the presence of atomic electrons must be taken into account. Theoretical extrapolations of available data are then needed to derive astrophysical S(E)-factors. To overcome these experimental difficulties the Trojan Horse Method (THM) has been introduced. The method provides a valid alternative path to measure unscreened low-energy cross sections of reactions between charged particles, and to retrieve information on the electron screening potential when ultra-low energy direct measurements are available. While the theory has been discussed in detail in some theoretical works, present in the scientific literature, also in relation to different types of excitation functions (e.g. non-resonant and resonant), work on detailed methodology used to extract the events to be considered for the bare nucleus cross section measurements is still on going. In this work we will present some critical points in the application of THM that deserve to be discussed in more detail.

  2. Experimental Observation of Nuclear Reactions in Palladium and Uranium

    SciTech Connect

    J. Dufour; D. Murat; X. Dufour; J. Foos

    2001-11-12

    By submitting various metals (Pd, U) containing hydrogen (from 2000 to 700 000 atoms of hydrogen for 1 000 000 atoms of the host metal) to the combined action of electrical currents and magnetic fields, we have observed a sizeable exothermal effect (from 0.1 to 8 W for 500 mg of metal used). This effect is beyond experimental errors, the energy output being typically 130 to 250{percent} of the energy input and not of chemical origin (exothermal effect in the range of 7000 MJ/mol of metal in the case of palladium and of 60 MJ/mol in the case of uranium). New chemical species also appear in the processes metals. It has been shown by a QED calculation that resonances of long lifetime (s), nuclear dimensions (fm), and low energy of formation (eV) could exist. This concept seems to look like the 'shrunken hydrogen atoms' proposed by various authors. It is indeed very different in two ways (a) being a metastable state, it needs energy to be formed (a few eV) and reverts to normal hydrogen after a few seconds, liberating back its energy of formation (it is thus not the source of the energy observed); (b) its formation can be described as the electron spin/proton nuclear spin interaction becoming first order in the lattice environment (whereas it is third order in a normal hydrogen atom). Moreover, we consider that the hydrex cannot yield a neutron because this reaction is strongly endothermic. To explain our results, we put forward the following working hypothesis: In a metal lattice and under proper conditions, the formation of such resonances (metastable state) could be favored. We propose to call them HYDREX, and we assume that they are actually formed in cold fusion (CF) and low-energy nuclear reaction (LENR) experiments. Once formed, a number of HYDREX could gather around a nucleus of the lattice to form a cluster of nuclear size and of very long life time compared to nuclear time (10{sup -22} s). In this cluster, nuclear rearrangements could take place, yielding

  3. EXFOR systems manual: Nuclear reaction data exchange format

    SciTech Connect

    McLane, V.

    1996-07-01

    This document describes EXFOR, the exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Centers Network. In addition to storing the data and its bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. The exchange format, as outlined, is designed to allow a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine).

  4. Ab Initio Calculations Of Nuclear Reactions And Exotic Nuclei

    SciTech Connect

    Quaglioni, S.

    2014-05-05

    Our ultimate goal is to develop a fundamental theory and efficient computational tools to describe dynamic processes between nuclei and to use such tools toward supporting several DOE milestones by: 1) performing predictive calculations of difficult-to-measure landmark reactions for nuclear astrophysics, such as those driving the neutrino signature of our sun; 2) improving our understanding of the structure of nuclei near the neutron drip line, which will be the focus of the DOE’s Facility for Rare Isotope Beams (FRIB) being constructed at Michigan State University; but also 3) helping to reveal the true nature of the nuclear force. Furthermore, these theoretical developments will support plasma diagnostic efforts at facilities dedicated to the development of terrestrial fusion energy.

  5. Constraining the level density using fission of lead projectiles

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Álvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.

    2015-10-01

    The nuclear level density is one of the main ingredients for the statistical description of the fission process. In this work, we propose to constrain the description of this parameter by using fission reactions induced by protons and light ions on 208Pb at high kinetic energies. The experiment was performed at GSI (Darmstadt), where the combined use of the inverse kinematics technique with an efficient detection setup allowed us to measure the atomic number of the two fission fragments in coincidence. This measurement permitted us to obtain with high precision the partial fission cross sections and the width of the charge distribution as a function of the atomic number of the fissioning system. These data and others previously measured, covering a large range in fissility, are compared to state-of-the-art calculations. The results reveal that total and partial fission cross sections cannot unambiguously constrain the level density at ground-state and saddle-point deformations and additional observables, such as the width of the charge distribution of the final fission fragments, are required.

  6. Feasibility of an antiproton catalyzed fission fragment rocket

    SciTech Connect

    Hdinger, D.S.

    1992-03-01

    The purpose of this project was to investigate the feasibility of an antiproton catalyzed fission fragment rocket (FFR). The FFR is characterized by the extraction of fission fragments from the fissile fuel, and the utilization of their kinetic energy for thrust generation. A significant drawback to previous FFR designs was the requirement to maintain a critical nuclear pile as the fission fragment source. The author examined the possibility of replacing the critical pile with a sub-critical pile driven by antiprotons. Recent experiments have revealed that antiprotons stimulate highly energetic fissions in {sup 238}U, with a neutron multiplicity of 13.7 neutrons per fission. This interaction was used as a throttled neutron source. The pile consisted of layers of fissile coated fibers which are designed to allow fission fragments to escape them, where the fragments collide with a fluid. The heated fluid is then ejected from the rocket to provide thrust. The calculations performed indicate that each antiproton injected into the pile can stimulate 8 or more fissions while maintaining a neutron multiplication of less than 0.4. Based on the results seen, the engine design presented is inadequate. Limitations introduced by the reaction fluid far outweigh the simplicity-of-design gained. Despite this, the basic idea of using the antiproton-U interaction as a source of spacecraft propulsion warrants further study.

  7. The use of the U(n,f) reaction dosimetry in the determination of the λf value through fission-track techniques

    NASA Astrophysics Data System (ADS)

    Guedes, S.; Hadler, J. C.; Iunes, P. J.; Zuñiga, A.; Tello, C. A.; Paulo, S. R.

    2003-01-01

    A new set of determinations of the decay constant for spontaneous fission of 238U, λf, using mica-uranium sandwich and thin films of natural uranium is presented. A value of λf=(8.37±0.17)×10 -17 a -1 has been determined. The use of uranium-based neutron dosimetry for the measurement of λf through fission-track techniques is discussed. Particularly, the λf measurement by Roberts et al. (Phys. Rev. 174 (1968) 4847), is analyzed, showing that the value obtained by these authors (7.03×10 -17 a -1) underestimated λf. It is concluded that the dosimetry based on U(n,f) reaction does not support a λf value around 7×10 -17 a -1 determined by various authors using mica-uranium sandwich.

  8. TANGRA-Setup for the Investigation of Nuclear Fission Induced by 14.1 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Ruskov, I. N.; Kopatch, Yu. N.; Bystritsky, V. M.; Skoy, V. R.; Shvetsov, V. N.; Hambsch, F.-J.; Oberstedt, S.; Noy, R. Capote; Sedyshev, P. V.; Grozdanov, D. N.; Ivanov, I. Zh.; Aleksakhin, V. Yu.; Bogolubov, E. P.; Barmakov, Yu. N.; Khabarov, S. V.; Krasnoperov, A. V.; Krylov, A. R.; Obhođaš, J.; Pikelner, L. B.; Rapatskiy, V. L.; Rogachev, A. V.; Rogov, Yu. N.; Ryzhkov, V. I.; Sadovsky, A. B.; Salmin, R. A.; Sapozhnikov, M. G.; Slepnev, V. M.; Sudac, D.; Tarasov, O. G.; Valković, V.; Yurkov, D. I.; Zamyatin, N. I.; Zeynalov, Sh. S.; Zontikov, A. O.; Zubarev, E. V.

    The new experimental setup TANGRA (Tagged Neutrons & Gamma Rays), for the investigation of neutron induced nuclear reactions, e.g. (n,xn'), (n,xn'γ), (n,γ), (n,f), on a number of important isotopes for nuclear science and engineering (235,238U, 237Np, 239Pu, 244,245,248Cm) is under construction and being tested at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in Dubna. The TANGRA setup consists of: a portable neutron generator ING-27, with a 64-pixel Si charge-particle detector incorporated into its vacuum chamber for registering of α-particles formed in the T(d, n)4He reaction, as a source of 14.1 MeV steady-state neutrons radiation with an intensity of ∼5x107n/s; a combined iron (Fe), borated polyethylene (BPE) and lead (Pb) compact shielding-collimator; a reconfigurable multi-detector (neutron plus gamma ray detecting system); a fast computer with 2 (x16 channels) PCI-E 100 MHz ADC cards for data acquisition and hard disk storage; Linux ROOT data acquisition, visualization and analysis software. The signals from the α-particle detector are used to 'tag' the neutrons with the coincident α-particles. Counting the coincidences between the α-particle and the reaction-product detectors in a 20ns time-interval improves the effect/background-ratio by a factor of ∼200 as well as the accuracy in the neutron flux determination, which decreases noticeably the overall experimental data uncertainty.

  9. Nuclear protein quality is regulated by the ubiquitin-proteasome system through the activity of Ubc4 and San1 in fission yeast.

    PubMed

    Matsuo, Yuzy; Kishimoto, Hayafumi; Tanae, Katsuhiro; Kitamura, Kenji; Katayama, Satoshi; Kawamukai, Makoto

    2011-04-15

    Eukaryotic cells monitor and maintain protein quality through a set of protein quality control (PQC) systems whose role is to minimize the harmful effects of the accumulation of aberrant proteins. Although these PQC systems have been extensively studied in the cytoplasm, nuclear PQC systems are not well understood. The present work shows the existence of a nuclear PQC system mediated by the ubiquitin-proteasome system in the fission yeast Schizosaccharomyces pombe. Asf1-30, a mutant form of the histone chaperone Asf1, was used as a model substrate for the study of the nuclear PQC. A temperature-sensitive Asf1-30 protein localized to the nucleus was selectively degraded by the ubiquitin-proteasome system. The Asf1-30 mutant protein was highly ubiquitinated at higher temperatures, and it remained stable in an mts2-1 mutant, which lacks proteasome activity. The E2 enzyme Ubc4 was identified among 11 candidate proteins as the ubiquitin-conjugating enzyme in this system, and San1 was selected among 100 candidates as the ubiquitin ligase (E3) targeting Asf1-30 for degradation. San1, but not other nuclear E3s, showed specificity for the mutant nuclear Asf1-30, but did not show activity against wild-type Asf1. These data clearly showed that the aberrant nuclear protein was degraded by a defined set of E1-E2-E3 enzymes through the ubiquitin-proteasome system. The data also show, for the first time, the presence of a nuclear PQC system in fission yeast.

  10. Deuteron Induced ( d,p) and ( d,2p) Nuclear Reactions up to 50 MeV

    NASA Astrophysics Data System (ADS)

    Yiğit, M.; Tel, E.; Kara, A.

    2013-06-01

    Many studies have shown that the nuclear reactions of charged particles with nuclei are very important in many fields of nuclear physics. The interactions of deuterons with nuclei have been especially the subject of common research in the history of nuclear physics. Moreover, the knowledge of cross section for deuteron-nucleus interactions are required for various application such as space applications, accelerator driven sub-critical systems, nuclear medicine, nuclear fission reactors and controlled thermonuclear fusion reactors. Particularly, the future of controlled thermonuclear fusion reactors is largely dependent on the nuclear reaction cross section data and the selection of structural fusion materials. Finally, the reaction cross section data of deuteron induced reactions on fusion structural materials are of great importance for development and design of both experimental and commercial fusion devices. In this work, reaction model calculations of the cross sections of deuteron induced reactions on structural fusion materials such as Al ( Aluminium), Ti ( Titanium), Cu ( Copper), Ni ( Nickel), Co ( Cobalt), Fe ( Iron), Zr ( Zirconium), Hf ( Hafnium) and Ta ( Tantalum) have been investigated. The new calculations on the excitation functions of 27 Al( d,2p) 27 Mg, 47 Ti( d,2p) 47 Sc, 65 Cu( d,2p) 65 Ni, 58 Ni( d,2p) 58 Co, 59 Co( d,2p) 59 Fe, 58 Fe( d,p) 59 Fe, 96 Zr( d,p) 97 Zr, 180 Hf ( d,p) 181 Hf and 181 Ta( d,p) 182 Ta have been carried out for incident deuteron energies up to 50 MeV. In these calculations, the equilibrium and pre-equilibrium effects for ( d,p) and ( d,2p) reactions have been investigated. The equilibrium effects are calculated according to the Weisskopf-Ewing ( WE) Model. The pre-equilibrium calculations involve the new evaluated the Geometry Dependent Hybrid Model ( GDH) and Hybrid Model. In the calculations the program code ALICE/ASH was used. The calculated results are discussed and compared with the experimental data taken from the

  11. A Nuclear Reaction Analysis study of fluorine uptake in flint

    SciTech Connect

    Jin, Jian-Yue; Weathers, D. L.; Picton, F.; Hughes, B. F.; Duggan, J. L.; McDaniel, F. D.; Matteson, S.

    1999-06-10

    Nuclear Reaction Analysis (NRA) using the {sup 19}F(p,{alpha}{gamma}){sup 16}O resonance reaction is a powerful method of fluorine depth profiling. We have used this method to study the fluorine uptake phenomenon in mineral flint, which could potentially develop into a method of dating archeological flint artifacts. Flint samples cut with a rock saw were immersed in aqueous fluoride solutions for different times for the uptake study. The results suggest that fluorine uptake is not a simple phenomenon, but rather a combination of several simultaneous processes. Fluorine surface adsorption appears to play an important role in developing the fluorine profiles. The surface adsorption was affected by several parameters such as pH value and fluorine concentration in the solution, among others. The problem of surface charging for the insulator materials during ion bombardment is also reported.

  12. Advanced scheme for high-yield laser driven nuclear reactions

    NASA Astrophysics Data System (ADS)

    Margarone, D.; Picciotto, A.; Velyhan, A.; Krasa, J.; Kucharik, M.; Mangione, A.; Szydlowsky, A.; Malinowska, A.; Bertuccio, G.; Shi, Y.; Crivellari, M.; Ullschmied, J.; Bellutti, P.; Korn, G.

    2015-01-01

    The use of a low contrast nanosecond laser pulse with a relatively low intensity (3  ×  1016 W cm-2) allowed the enhancing of the yield of induced nuclear reactions in advanced solid targets. In particular the ‘ultraclean’ proton-boron fusion reaction, producing energetic alpha particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogen-enriched silicon substrate was used as a target. A combination of the specific target composition and the laser pulse temporal shape allowed the enhancing of the yield of alpha particles up to 109 per steradian. This result can be ascribed to the interaction of the long-laser pre-pulse with the target and to the optimal target geometry and composition.

  13. Indirect measurements of nuclear astrophysics reactions at CIAE

    SciTech Connect

    Liu Weiping; Li Zhihong; Bai Xixiang; Wang Youbao; Lian Gang; Guo Bing; Zeng Sheng; Yan Shengquan; Wang Baoxiang; Su Jun; Shu Nengchuan; Chen Yongshou

    2006-11-02

    This paper described the nuclear astrophysical studies using the unstable ion beam facility GIRAFFE, by indirect measurements. We measured the angular distributions for some single proton or neutron transfer reactions, such as 7Be(d,n)8B, 11C(d,n)12N, 8Li(d,n)9Be, 8Li(d,p)9Li and 13N(d,n)14O in inverse kinematics, and derived the astrophysical S-factors or reaction rates of 7Be(p,{gamma})8B, 11C(p,{gamma})12N, 8Li(n,{gamma})9Li, 13N(p,{gamma})14O by asymptotic normalization coefficient, spectroscopic factor, and R-matrix approach at astrophysically relevant energies.

  14. Meiotic nuclear movements in fission yeast are regulated by the transcription factor Mei4 downstream of a Cds1-dependent replication checkpoint pathway.

    PubMed

    Ruan, Kun; Yamamoto, Takaharu G; Asakawa, Haruhiko; Chikashige, Yuji; Masukata, Hisao; Haraguchi, Tokuko; Hiraoka, Yasushi

    2015-03-01

    In meiosis, the fission yeast nucleus displays an elongated morphology, moving back and forth within the cell; these nuclear movements continue for approximately 2 h before meiotic nuclear divisions. Meiotic DNA replication occurs in an early phase of the nuclear movements and is followed by meiotic prophase. Here we report that in mutants deficient in meiotic DNA replication, the duration of nuclear movements is strikingly prolonged to four to 5 h. We found that this prolongation was caused by the Cds1-dependent replication checkpoint, which represses expression of the mei4(+) gene encoding a meiosis-specific transcription factor. In the absence of Mei4, nuclear movements persisted for more than 8 h. In contrast, overproduction of Mei4 accelerated termination of nuclear movements to approximately 30 min. These results show that Mei4 is involved in the termination of nuclear movements and that Mei4-mediated regulatory pathways link a DNA replication checkpoint to the termination of nuclear movements.

  15. Fission in a Plasma

    SciTech Connect

    Younes, W.

    2016-10-26

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

  16. NEUTRONIC REACTION SYSTEM

    DOEpatents

    Wigner, E.P.

    1963-09-01

    A nuclear reactor system is described for breeding fissionable material, including a heat-exchange tank, a high- and a low-pressure chamber therein, heat- exchange tubes connecting these chambers, a solution of U/sup 233/ in heavy water in a reaction container within the tank, a slurry of thorium dioxide in heavy water in a second container surrounding the first container, an inlet conduit including a pump connecting the low pressure chamber to the reaction container, an outlet conduit connecting the high pressure chamber to the reaction container, and means of removing gaseous fission products released in both chambers. (AEC)

  17. Secondary Nuclear Reactions in Magneto-Inertial Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Knapp, Patrick

    2014-10-01

    The goal of Magneto-Inertial Fusion (MIF) is to relax the extreme pressure requirements of inertial confinement fusion by magnetizing the fuel. Understanding the level of magnetization at stagnation is critical for charting the performance of any MIF concept. We show here that the secondary nuclear reactions in magnetized deuterium plasma can be used to infer the magnetic field-radius product (BR), the critical confinement parameter for MIF. The secondary neutron yields and spectra are examined and shown to be extremely sensitive to BR. In particular, embedded magnetic fields are shown to affect profoundly the isotropy of the secondary neutron spectra. Detailed modeling of these spectra along with the ratio of overall secondary to primary neutron yields is used to form the basis of a diagnostic technique used to infer BR at stagnation. Effects of gradients in density, temperature and magnetic field strength are examined, as well as other possible non-uniform fuel configurations. Computational results employing a fully kinetic treatment of charged reaction product transport and Monte Carlo treatment of secondary reactions are compared to results from recent experiments at Sandia National Laboratories' Z machine testing the MAGnetized Liner Inertial Fusion (MagLIF) concept. The technique reveals that the charged reaction products were highly magnetized in these experiments. Implications for eventual ignition-relevant experiments with deuterium-tritium fuel are discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  18. Nuclear Structure of 97Mo from the (d, p) Reaction

    NASA Astrophysics Data System (ADS)

    Chowdhury, M. S.; Booth, W.

    The reaction 96Mo(d, p)97Mo has been studied at 12 MeV using the tandem Van de Graaff accelerator and a multi-channel magnetic spectrograph at the Atomic Weapon Research Establishment, Aldermaston, England. Angular distributions of protons are measured at 12 different angles from 5° to 87.5° at an interval of 7.5° and the reaction products are detected in nuclear emulsion plates. Thirty levels in the energy range from 0.000 to 2.458 MeV have been observed and absolute differential cross-sections for these levels have been measured. The data are analyzed in terms of the distorted-wave Born approximation (DWBA) theory of the direct reactions, and spins, parities and spectroscopic factors are deduced for various levels. Ambiguity in the spin assignments of d5/2 and d3/2 which is allowed in ln = 2(d, p) transition is removed by using the corresponding L-value of the 95 Mo(t, p)97Mo reaction at Et = 12 MeV. Determined value of the sum of spectroscopic factors for transfers of d5/2 neutrons suggests configuration mixing in the ground state of 96Mo. The properties of the levels in 97Mo are compared with previous experimental results and theoretical predictions.

  19. Nuclear Chemistry: Include It in Your Curriculum.

    ERIC Educational Resources Information Center

    Atwood, Charles H.; Sheline, R. K.

    1989-01-01

    Some of the topics that might be included in a nuclear chemistry section are explored. Offers radioactivity, closed shells in nuclei, energy of nuclear processes, nuclear reactions, and fission and fusion as topics of interest. Provided are ideas and examples for each. (MVL)

  20. Exchange-diffusion reactions in HfSiON during annealing studied by Rutherford backscattering spectrometry, nuclear reaction analysis and narrow resonant nuclear reaction profiling

    NASA Astrophysics Data System (ADS)

    Miotti, L.; Bastos, K. P.; Soares, G. V.; Driemeier, C.; Pezzi, R. P.; Morais, J.; Baumvol, I. J. R.; Rotondaro, A. L. P.; Visokay, M. R.; Chambers, J. J.; Quevedo-Lopez, M.; Colombo, L.

    2004-11-01

    HfSiON films deposited on Si (001) by reactive sputtering were submitted to rapid thermal annealing at 1000°C in vacuum, N2 and O2 atmospheres. The stability of the dielectric was evaluated by measuring the atomic transport and exchange of the chemical species, using Rutherford backscattering spectrometry, nuclear reaction analysis and narrow resonant nuclear reaction profiling. Annealing in O2 ambient reduced the N concentration mainly from near-surface regions where oxygen was incorporated in comparable amounts. Vacuum annealing, on the other hand, induced N loss preferentially from the Si/dielectric interface and O loss preferentially from near-surface regions. The results are explained in terms of exchange-diffusion reactions occurring in the HfSiON.

  1. TREATMENT OF FISSION PRODUCT WASTE

    DOEpatents

    Huff, J.B.

    1959-07-28

    A pyrogenic method of separating nuclear reactor waste solutions containing aluminum and fission products as buring petroleum coke in an underground retort, collecting the easily volatile gases resulting as the first fraction, he uminum chloride as the second fraction, permitting the coke bed to cool and ll contain all the longest lived radioactive fission products in greatly reduced volume.

  2. Testing actinide fission yield treatment in CINDER90 for use in MCNP6 burnup calculations

    DOE PAGES

    Fensin, Michael Lorne; Umbel, Marissa

    2015-09-18

    Most of the development of the MCNPX/6 burnup capability focused on features that were applied to the Boltzman transport or used to prepare coefficients for use in CINDER90, with little change to CINDER90 or the CINDER90 data. Though a scheme exists for best solving the coupled Boltzman and Bateman equations, the most significant approximation is that the employed nuclear data are correct and complete. Thus, the CINDER90 library file contains 60 different actinide fission yields encompassing 36 fissionable actinides (thermal, fast, high energy and spontaneous fission). Fission reaction data exists for more than 60 actinides and as a result, fissionmore » yield data must be approximated for actinides that do not possess fission yield information. Several types of approximations are used for estimating fission yields for actinides which do not possess explicit fission yield data. The objective of this study is to test whether or not certain approximations of fission yield selection have any impact on predictability of major actinides and fission products. Further we assess which other fission products, available in MCNP6 Tier 3, result in the largest difference in production. Because the CINDER90 library file is in ASCII format and therefore easily amendable, we assess reasons for choosing, as well as compare actinide and major fission product prediction for the H. B. Robinson benchmark for, three separate fission yield selection methods: (1) the current CINDER90 library file method (Base); (2) the element method (Element); and (3) the isobar method (Isobar). Results show that the three methods tested result in similar prediction of major actinides, Tc-99 and Cs-137; however, certain fission products resulted in significantly different production depending on the method of choice.« less

  3. Ab Initio Nuclear Structure and Reaction Calculations for Rare Isotopes

    SciTech Connect

    Draayer, Jerry P.

    2014-09-28

    We have developed a novel ab initio symmetry-adapted no-core shell model (SA-NCSM), which has opened the intermediate-mass region for ab initio investigations, thereby providing an opportunity for first-principle symmetry-guided applications to nuclear structure and reactions for nuclear isotopes from the lightest p-shell systems to intermediate-mass nuclei. This includes short-lived proton-rich nuclei on the path of X-ray burst nucleosynthesis and rare neutron-rich isotopes to be produced by the Facility for Rare Isotope Beams (FRIB). We have provided ab initio descriptions of high accuracy for low-lying (including collectivity-driven) states of isotopes of Li, He, Be, C, O, Ne, Mg, Al, and Si, and studied related strong- and weak-interaction driven reactions that are important, in astrophysics, for further understanding stellar evolution, X-ray bursts and triggering of s, p, and rp processes, and in applied physics, for electron and neutrino-nucleus scattering experiments as well as for fusion ignition at the National Ignition Facility (NIF).

  4. Study of the fission isomer 240mAm (S. F. ) using laser-induced nuclear polarization. [Cross section of 238U(7Li,5n) at 48 MeV

    SciTech Connect

    Beene, J. R.; Bemis, Jr., C. E.; Young, J. P.; Kramer, S. D.

    1980-01-01

    The optical isomer shift was measured for the spontaneously fissioning isomer /sup 240m/Am. This shift is approximately 27 times greater than the /sup 241/Am-/sup 243/Am isotope shift, and confirms the conventional identification of fission isomers with large deformation. The measured isomer shift is consistent with a nuclear quadrupole moment of 30.4 b, in agreement with theoretical expectations. 2 figures. (RWR)

  5. Correlation between Asian Dust and Specific Radioactivities of Fission Products Included in Airborne Samples in Tokushima, Shikoku Island, Japan, Due to the Fukushima Nuclear Accident

    SciTech Connect

    Sakama, M.; Nagano, Y.; Kitade, T.; Shikino, O.; Nakayama, S.

    2014-06-15

    Radioactive fission product {sup 131}I released from the Fukushima Daiichi Nuclear Power Plants (FD-NPP) was first detected on March 23, 2011 in an airborne aerosol sample collected at Tokushima, Shikoku Island, located in western Japan. Two other radioactive fission products, {sup 134}Cs and {sup 137}Cs were also observed in a sample collected from April 2 to 4, 2011. The maximum specific radioactivities observed in this work were about 2.5 to 3.5 mBq×m{sup -3} in a airborne aerosol sample collected on April 6. During the course of the continuous monitoring, we also made our first observation of seasonal Asian Dust and those fission products associated with the FDNPP accident concurrently from May 2 to 5, 2011. We found that the specific radioactivities of {sup 134}Cs and {sup 137}Cs decreased drastically only during the period of Asian Dust. And also, it was found that this trend was very similar to the atmospheric elemental concentration (ng×m{sup -3}) variation of stable cesium ({sup 133}Cs) quantified by elemental analyses using our developed ICP-DRC-MS instrument.

  6. Radiochemistry and the Study of Fission

    SciTech Connect

    Rundberg, Robert S.

    2016-11-14

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

  7. ADRIANA project: Identification of research infrastructures for the SFR, within the frame of European industrial initiative for sustainable nuclear fission

    SciTech Connect

    Latge, C.; Gastaldi, O.; Vala, L.; Gerbeth, G.; Homann, C.; Benoit, P.; Papin, J.; Girault, N.; Roelofs, F.; Bucenieks, I.; Paffumi, E.; Ciampichetti, A.

    2012-07-01

    Fast neutron reactors have a large potential as sustainable energy source. In particular, Sodium Fast Reactors (SFR) with a closed fuel cycle and potential for minor actinide burning may allow minimization of volume and heat load of high level waste and provide improved use of natural resources (as compared to only 1% energy recovery in the current once-through fuel cycle, with Thermal Reactors, such as EPR). The coordinating action ADRIANA (Advanced Reactor Initiative And Network Arrangement) has been initiated to set up a network dedicated to the construction and operation of research infrastructures in support of developments for the European Industrial Initiative for sustainable nuclear fission. The Project sets these objectives for the following reactor systems and related technologies: Sodium Fast Reactor (SFR), Lead Fast Reactor (LFR), Gas Fast Reactor (GFR, including very high temperature technologies), Instrumentation, diagnostics and experimental devices, Irradiation facilities and hot laboratories, Zero power reactors. Among the fast reactor systems, the sodium cooled reactor has the most comprehensive technological basis as result of the experience gained from worldwide operation of several experimental, prototype and commercial size reactors, since the forties (see Appendix I). This concept is currently considered as the reference, within the European strategy. Innovations are needed to further enhance safety, reduce capital cost and improve efficiency reliability and operability, making the Generation IV SFR an attractive option for electricity production. Currently, in France, a moderate (500 to 600 MWe) power demonstrator named ASTRID (Advanced Sodium Test Reactor for Industrial Demonstration) has been proposed and endorsed by EU. Presently, the reference configuration is a pool concept. General R and D needs have been identified and experimental facilities required to satisfy these needs have been listed for the following domains: material and

  8. The chemical state of fission products in oxide fuels at different stages of the nuclear fuel cycle

    SciTech Connect

    Kleykamp, H.

    1988-03-01

    A survey of work at the Kernforschungszentrum Karlsruhe is presented on the chemical state of selected fission products that are relevant in the fuel cycle of light water reactor (LWR) and fast breeder reactor fuels. The influence of fuel type and irradiation progress on the composition of the Mo-Tc-Ru-Rh-Pd fission product alloys precipitated in the oxide matrix is examined using the respective multicomponent phase diagrams. The kinetics of dissolution of these phases in nitric acid at the reprocessing stage is discussed. Composition and structure of the residues, and the reprecipitation phenomena from highly active waste (HAW), are elucidated. A second metamorphosis of the fission products is recognized during the vitrification process. The formation of Ru(Rh) oxide and Pd(Rh, U, Te) alloys in simulated vitrified HAW concentrate and in HAW concentrate from the reprocessing of irradiated LWR fuels in interpreted on the basis of heterogeneous equilibria.

  9. Atomistic modeling of intrinsic and radiation-enhanced fission gas (Xe) diffusion in UO2 +/- x: Implications for nuclear fuel performance modeling

    SciTech Connect

    Giovanni Pastore; Michael R. Tonks; Derek R. Gaston; Richard L. Williamson; David Andrs; Richard Martineau

    2014-03-01

    Based on density functional theory (DFT) and empirical potential calculations, the diffusivity of fission gas atoms (Xe) in UO2 nuclear fuel has been calculated for a range of non-stoichiometry (i.e. UO2x), under both out-of-pile (no irradiation) and in-pile (irradiation) conditions. This was achieved by first deriving expressions for the activation energy that account for the type of trap site that the fission gas atoms occupy, which includes the corresponding type of mobile cluster, the charge state of these defects and the chemistry acting as boundary condition. In the next step DFT calculations were used to estimate migration barriers and internal energy contributions to the thermodynamic properties and calculations based on empirical potentials were used to estimate defect formation and migration entropies (i.e. pre-exponentials). The diffusivities calculated for out-of-pile conditions as function of the UO2x nonstoichiometrywere used to validate the accuracy of the diffusion models and the DFT calculations against available experimental data. The Xe diffusivity is predicted to depend strongly on the UO2x non-stoichiometry due to a combination of changes in the preferred Xe trap site and in the concentration of uranium vacancies enabling Xe diffusion, which is consistent with experiments. After establishing the validity of the modeling approach, it was used for studying Xe diffusion under in-pile conditions, for which experimental data is very scarce. The radiation-enhanced Xe diffusivity is compared to existing empirical models. Finally, the predicted fission gas diffusion rates were implemented in the BISON fuel performance code and fission gas release from a Risø fuel rod irradiation experiment was simulated. 2014 Elsevier B.V. All rights

  10. Atomistic modeling of intrinsic and radiation-enhanced fission gas (Xe) diffusion in UO2±x: Implications for nuclear fuel performance modeling

    NASA Astrophysics Data System (ADS)

    Andersson, D. A.; Garcia, P.; Liu, X.-Y.; Pastore, G.; Tonks, M.; Millett, P.; Dorado, B.; Gaston, D. R.; Andrs, D.; Williamson, R. L.; Martineau, R. C.; Uberuaga, B. P.; Stanek, C. R.

    2014-08-01

    Based on density functional theory (DFT) and empirical potential calculations, the diffusivity of fission gas atoms (Xe) in UO2 nuclear fuel has been calculated for a range of non-stoichiometry (i.e. UO2±x), under both out-of-pile (no irradiation) and in-pile (irradiation) conditions. This was achieved by first deriving expressions for the activation energy that account for the type of trap site that the fission gas atoms occupy, which includes the corresponding type of mobile cluster, the charge state of these defects and the chemistry acting as boundary condition. In the next step DFT calculations were used to estimate migration barriers and internal energy contributions to the thermodynamic properties and calculations based on empirical potentials were used to estimate defect formation and migration entropies (i.e. pre-exponentials). The diffusivities calculated for out-of-pile conditions as function of the UO2±x non-stoichiometry were used to validate the accuracy of the diffusion models and the DFT calculations against available experimental data. The Xe diffusivity is predicted to depend strongly on the UO2±x non-stoichiometry due to a combination of changes in the preferred Xe trap site and in the concentration of uranium vacancies enabling Xe diffusion, which is consistent with experiments. After establishing the validity of the modeling approach, it was used for studying Xe diffusion under in-pile conditions, for which experimental data is very scarce. The radiation-enhanced Xe diffusivity is compared to existing empirical models. Finally, the predicted fission gas diffusion rates were implemented in the BISON fuel performance code and fission gas release from a Risø fuel rod irradiation experiment was simulated.

  11. Redox reaction and foaming in nuclear waste glass melting

    SciTech Connect

    Ryan, J.L.

    1995-08-01

    This document was prepared by Pacific Northwest Laboratory (PNL) and is an attempt to analyze and estimate the effects of feed composition variables and reducing agent variables on the expected chemistry of reactions occurring in the cold cap and in the glass melt in the nuclear waste glass Slurry-fed, joule-heated melters as they might affect foaming during the glass-making process. Numerous redox reactions of waste glass components and potential feed additives, and the effects of other feed variables on these reactions are reviewed with regard to their potential effect on glass foaming. A major emphasis of this report is to examine the potential positive or negative aspects of adjusting feed with formic acid as opposed to other feed modification techniques including but not limited to use of other reducing agents. Feed modification techniques other than the use of reductants that should influence foaming behavior include control of glass melter feed pH through use of nitric acid. They also include partial replacement of sodium salts by lithium salts. This latter action (b) apparently lowers glass viscosity and raises surface tension. This replacement should decrease foaming by decreasing foam stability.

  12. Ab initio calculations of nuclear reactions important for astrophysics

    NASA Astrophysics Data System (ADS)

    Navratil, Petr; Dohet-Eraly, Jeremy; Calci, Angelo; Horiuchi, Wataru; Hupin, Guillaume; Quaglioni, Sofia

    2016-09-01

    In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. One of the newly developed approaches is the No-Core Shell Model with Continuum (NCSMC), capable of describing both bound and scattering states in light nuclei simultaneously. We will present NCSMC results for reactions important for astrophysics that are difficult to measure at relevant low energies, such as 3He(α,γ)7Be and 3H(α,γ)7Li and 11C(p,γ)12N radiative capture, as well as the 3H(d,n)4He fusion. We will also address prospects of calculating the 2H(α,γ)6Li capture reaction within the NCSMC formalism. Prepared in part by LLNL under Contract DE-AC52-07NA27344. Supported by the U.S. DOE, OS, NP, under Work Proposal No. SCW1158, and by the NSERC Grant No. SAPIN-2016-00033. TRIUMF receives funding from the NRC Canada.

  13. [Electromagnetic studies of nuclear structure and reactions]. [Nuclear Physics Group, Univ. of New Hampshire

    SciTech Connect

    Not Available

    1992-01-01

    The experimental goals are focused on developing an understanding of strong interactions and the structure of hadronic systems by determination of the electromagnetic response; these goals will be accomplished through coincidence detection of final states. Nuclear modeling objectives are to organize and interpret the data through a consistent description of a broad spectrum of reaction observables; calculations are performed in a nonrelativistic diagrammatic framework as well as a relativistic QHD approach. Work is described according to the following arrangement: direct knockout reactions (completion of [sup 16]O(e,e[prime]p), [sup 12]C(e,e[prime]pp) progress, large acceptance detector physics simulations), giant resonance studies (intermediate-energy experiments with solid-state detectors, the third response function in [sup 12]C(e,e[prime]p[sub 0]) and [sup 16]O(e,e[prime]p[sub 0]), comparison of the [sup 12]C(e, e[prime]p[sub 0]) and [sup 16]O(e,e[prime]p[sub 3]) reactions, quadrupole strength in the [sup 16]O(e,e[prime][alpha][sub 0]) reaction, quadrupole strength in the [sup 12]C(e,e[prime][alpha]) reaction, analysis of the [sup 12]C(e,e[prime]p[sub 1]) and [sup 16]O(e,e[prime]p[sub 3]) angular distributions, analysis of the [sup 40]Ca(e,e[prime]x) reaction at low q, analysis of the higher-q [sup 12]C(e,e[prime]x) data from Bates), models of nuclear structure (experimental work, Hartree-Fock calculations, phonon excitations in spherical nuclei, shell model calculations, variational methods for relativistic fields), and instrumentation development efforts (developments at CEBAF, CLAS contracts, BLAST developments).

  14. In-beam fission study for Heavy Element Synthesis

    NASA Astrophysics Data System (ADS)

    Nishio, Katsuhisa

    2013-12-01

    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 qasifission 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.

  15. Nuclear shape, growth and integrity in the closed mitosis of fission yeast depend on the Ran-GTPase system, the spindle pole body and the endoplasmic reticulum.

    PubMed

    Gonzalez, Yanira; Meerbrey, Kristen; Chong, Jennifer; Torii, Yoshihiro; Padte, Neal N; Sazer, Shelley

    2009-07-15

    The double lipid bilayer of the nuclear envelope (NE) remains intact during closed mitosis. In the fission yeast Schizosaccharomyces pombe, the intranuclear mitotic spindle has envelope-embedded spindle pole bodies (SPB) at its ends. As the spindle elongates and the nucleus divides symmetrically, nuclear volume remains constant but nuclear area rapidly increases by 26%. When Ran-GTPase function is compromised in S. pombe, nuclear division is strikingly asymmetrical and the newly synthesized SPB is preferentially associated with the smaller nucleus, indicative of a Ran-dependent SPB defect that interferes with symmetrical nuclear division. A second defect, which specifically influences the NE, results in breakage of the NE upon spindle elongation. This defect, but not asymmetric nuclear division, is partially rescued by slowing spindle elongation, stimulating endoplasmic reticulum (ER) proliferation or changing conformation of the ER membrane. We propose that redistribution of lipid within the ER-NE network is crucial for mitosis-specific NE changes in both open and closed mitosis.

  16. A study of heavy-heavy nuclear reactions. [nuclear research/nuclear particles

    NASA Technical Reports Server (NTRS)

    Khandelwal, G. S.

    1975-01-01

    Calculations are presented for the reaction products in high energy collisions and of the atmospheric transport of particles such as protons, neutrons and other nucleons. The magnetic moments of charmed baryons are examined. Total cross sections which are required for cosmic heavy ion transport and shielding studies are also examined.

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

    DOEpatents

    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.

  18. Screening in Low Energy Nuclear Reactions of Importance to Astrophysics

    NASA Astrophysics Data System (ADS)

    Miley, George H.; Hora, Heinz; Luo, Nie

    2004-05-01

    Recent experiments in the LUNAR (Laboratory for Underground Nuclear Astrophysics) project have shown anonymously high electron screening may occur during acceleration driven low energy (<400 kV) ion bombardment of solid targets [1]. These effects become particularly important for E/ Ue < 100 (here E= ion energy and Ue = electron-screening potential energy). Thus these effects become significant for the understanding of reactions involved in nucleosynthesis of the elements and the interpretation of astrophysical data [1]. Another example of the behavior is the surprising threshold behavior near 18 keV for deuterons stopping in 3He gas at energies below the Bragg peak [2]. As pointed out in ref [1], the theoretical explanation for these effects is still under debate. Several researchers have proposed variations of the Trojan Horse Method (THM) to explain these effects [3]. In this paper, we propose an alternate mechanism associated with electron charge accumulation around the target atoms arising from the solid-state structure of the host. This concept will be explained in terms of density functional calculations of charge density profiles in a target undergoing ion dynamic effects [4]. REFERENCES [1] F. Strieder, et al., Naturwissenschaften (2000)88:461-467 [2] A. Formicola, et al., (2000) Eur Phys J. A 8:443-446 [3] S. Typel and H H Wolter, (2000) Few-Body System 29:75-93 [4] G. Miley and H. Hora, (2000) Nuclear Reactions in Solids, APS mtg. Lansing, MI [5] G. Miley, A. Lipson, N. Luo, and H. Hora, (2003) IEEE NSS/MIC Conf., Portland, OR

  19. Vision of nuclear physics with photo-nuclear reactions by laser-driven γ beams

    NASA Astrophysics Data System (ADS)

    Habs, D.; Tajima, T.; Schreiber, J.; Barty, C. P. J.; Fujiwara, M.; Thirolf, P. G.

    2009-11-01

    A laser-accelerated dense electron sheet with an energy E=tilde{γ} mc^2 can be used as a relativistic mirror to coherently reflect a second laser with photon energy ħω, thus generating by the Doppler boost [A. Einstein, Annalen der Physik 17, 891 (1905); D. Habs et al., Appl. Phys. B 93, 349 (2008)] brilliant high-energy photon beams with hbarω^'=4tilde{γ}^2hbarω and short duration for many new nuclear physics experiments. While the shortest-lived atomic levels are in the atto-second range, nuclear levels can have lifetimes down to zeptoseconds. We discuss how the modulation of electron energies in phase-locked laser fields used for as-measurements [E. Goulielmakis et al., Science 317, 769 (2007)] can be carried over to the new direct measurement of fs-zs nuclear lifetimes by modulating the energies of accompanying conversion electrons or emitted protons. In the field of nuclear spectroscopy we discuss the new perspective as a function of increasing photon energy. In nuclear systems a much higher sensitivity is predicted to the time variation of fundamental constants compared to atomic systems [V. Flambaum, arXiv:nucl-th/0801.1994v1 (2008)]. For energies up to 50 keV Mössbauer-like recoilless absorption allows to produce nuclear bosonic ensembles with many delocalized coherent polaritons [G.V. Smirnov et al., Phys. Rev. A 71, 023804 (2005)] for the first time. Using the ( γ, n) reaction to produce cold, polarized neutrons with a focusing ellipsoidal device [P. Böni, Nucl. Instrum. Meth. A 586, 1 (2008); Ch. Schanzer et al., Nucl. Instrum. Meth. 529, 63 (2004)], brilliant cold polarized micro-neutron beams become available. The compact and relatively cheap laser-generated γ beams may serve for extended studies at university-based facilities.

  20. Fission fragment driven neutron source

    DOEpatents

    Miller, Lowell G.; Young, Robert C.; Brugger, Robert M.

    1976-01-01

    Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.

  1. Analysis of nucleon-induced fission cross sections of lead and bismuth at energies from 45 to 500 MeV

    SciTech Connect

    Prokofyev, A.V.; Mashnik, S.G.; Sierk, A.J.

    1998-08-01

    In order to investigate the applicability of the Cascade-Exciton model (CEM) of nuclear reactions to fission cross sections and hoping to learn more about intermediate-energy fission, the authors use an extended version of the CEM, as realized in the code CEM95 to perform a detailed analysis of proton- and neutron-induced fission cross sections of {sup 209}Bi and {sup 208}Pb nuclei and of the linear momentum transfer to the fissioning nuclei in the 45--500 meV energy range.

  2. Loss of Msp1p in Schizosaccharomyces pombe induces a ROS-dependent nuclear mutator phenotype that affects mitochondrial fission genes.

    PubMed

    Delerue, Thomas; Khosrobakhsh, Farnoosh; Daloyau, Marlène; Emorine, Laurent Jean; Dedieu, Adrien; Herbert, Christopher J; Bonnefoy, Nathalie; Arnauné-Pelloquin, Laetitia; Belenguer, Pascale

    2016-10-01

    Mitochondria continually fuse and divide to dynamically adapt to changes in metabolism and stress. Mitochondrial dynamics are also required for mitochondrial DNA (mtDNA) integrity; however, the underlying reason is not known. In this study, we examined the link between mitochondrial fusion and mtDNA maintenance in Schizosaccharomyces pombe, which cannot survive without mtDNA, by screening for suppressors of the lethality induced by loss of the dynamin-related large GTPase Msp1p. Our findings reveal that inactivation of Msp1p induces a ROS-dependent nuclear mutator phenotype that affects mitochondrial fission genes involved in suppressing mitochondrial fragmentation and mtDNA depletion. This indicates that mitochondrial fusion is crucial for maintaining the integrity of both mitochondrial and nuclear genetic information. Furthermore, our study suggests that the primary roles of Msp1p are to organize mitochondrial membranes, thus making them competent for fusion, and maintain the integrity of mtDNA.

  3. The phebus fission product project

    NASA Astrophysics Data System (ADS)

    von der Hardt, P.; Tattegrain, A.

    1992-06-01

    A new facility is being built at the Phebus test reactor in Cadarache, France, for investigations into phenomena of fuel damage and fission product (FP) release under severe power reactor accident conditions, as part of a large international research program. Phebus FP simulates core, cooling system and containment of an accidented reactor by appropriate scaled-down experimental components. The test fuel, with 25 to 30 GWd/t burnup, is re-irradiated in situ and then overheated up to UO 2 melting. Fission products and other aerosols are swept through the primary pipework into the containment vessel, by hot steam and hydrogen. Experimental instrumentation and posttest analyses will enable the following main phenomena to be studied: structural material and fuel dislocation, final fuel state; release, chemical form and transport/depletion of fission products in the facility, particularly aerosol physics, including nonfission product material and iodine chemistry in terms of volatile species formation through radiolysis, reactions with organic material, aerosol-vapor reactions, etc. Design and development of equipment and experimental procedures are supported by modeling and code calculations with the scope of predicting the experimental sequence, on one hand, and to prepare code validation through the results, on the other hand. More than 25 organisation from Europe and overseas, collaborate in the scientific and technological development of the Phebus FP program. The first in-pile test is planned for spring 1993, and five subsequent experiments are scheduled to follow in yearly intervals. This paper describes facility and support activities, and highlights a number of nuclear materials aspects involved.

  4. The US nuclear reaction data network. Summary of the first meeting, March 13 & 14 1996

    SciTech Connect

    1996-03-01

    The first meeting of the US Nuclear Reaction Data Network (USNRDN) was held at the Colorado School of Mines, March 13-14, 1996 chaired by F. Edward Cecil. The Agenda of the meeting is attached. The Network, its mission, products and services; related nuclear data and data networks, members, and organization are described in Attachment 1. The following progress reports from the members of the USNRDN were distributed prior to the meeting and are given as Attachment 2. (1) Measurements and Development of Analytic Techniques for Basic Nuclear Physics and Nuclear Applications; (2) Nuclear Reaction Data Activities at the National Nuclear Data Center; (3) Studies of nuclear reactions at very low energies; (4) Nuclear Reaction Data Activities, Nuclear Data Group; (5) Progress in Neutron Physics at Los Alamos - Experiments; (6) Nuclear Reaction Data Activities in Group T2; (7) Progress Report for the US Nuclear Reaction Data Network Meeting; (8) Nuclear Astrophysics Research Group (ORNL); (9) Progress Report from Ohio University; (10) Exciton Model Phenomenology; and (11) Progress Report for Coordination Meeting USNRDN.

  5. Fission energy program of the US Department of Energy, FY 1981

    SciTech Connect

    Ferguson, Robert L.

    1980-03-01

    Information is presented concerning the National Energy Plan and fission energy policy; fission energy program management; converter reactor systems; breeder reactor systems; and special nuclear evaluations and systems.

  6. Spontaneous Fission

    DOE R&D Accomplishments Database

    Segre, Emilio

    1950-11-22

    The first attempt to discover spontaneous fission in uranium was made by [Willard] Libby, who, however, failed to detect it on account of the smallness of effect. In 1940, [K. A.] Petrzhak and [G. N.] Flerov, using more sensitive methods, discovered spontaneous fission in uranium and gave some rough estimates of the spontaneous fission decay constant of this substance. Subsequently, extensive experimental work on the subject has been performed by several investigators and will be quoted in the various sections. [N.] Bohr and [A.] Wheeler have given a theory of the effect based on the usual ideas of penetration of potential barriers. On this project spontaneous fission has been studied for the past several years in an effort to obtain a complete picture of the phenomenon. For this purpose the spontaneous fission decay constants {lambda} have been measured for separated isotopes of the heavy elements wherever possible. Moreover, the number {nu} of neutrons emitted per fission has been measured wherever feasible, and other characteristics of the spontaneous fission process have been studied. This report summarizes the spontaneous fission work done at Los Alamos up to January 1, 1945. A chronological record of the work is contained in the Los Alamos monthly reports.

  7. Computer subroutines for the estimation of nuclear reaction effects in proton-tissue-dose calculations

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Khandelwal, G. S.

    1976-01-01

    Calculational methods for estimation of dose from external proton exposure of arbitrary convex bodies are briefly reviewed. All the necessary information for the estimation of dose in soft tissue is presented. Special emphasis is placed on retaining the effects of nuclear reaction, especially in relation to the dose equivalent. Computer subroutines to evaluate all of the relevant functions are discussed. Nuclear reaction contributions for standard space radiations are in most cases found to be significant. Many of the existing computer programs for estimating dose in which nuclear reaction effects are neglected can be readily converted to include nuclear reaction effects by use of the subroutines described herein.

  8. Dynamic approach to description of entrance channel effects in angular distributions of fission fragments

    NASA Astrophysics Data System (ADS)

    Eremenko, D. O.; Drozdov, V. A.; Fotina, O. V.; Platonov, S. Yu.; Yuminov, O. A.

    2016-07-01

    Background: It is well known that the anomalous behavior of angular anisotropies of fission fragments at sub- and near-barrier energies is associated with a memory of conditions in the entrance channel of the heavy-ion reactions, particularly, deformations and spins of colliding nuclei that determine the initial distributions for the components of the total angular momentum over the symmetry axis of the fissioning system and the beam axis. Purpose: We develop a new dynamic approach, which allows the description of the memory effects in the fission fragment angular distributions and provides new information on fusion and fission dynamics. Methods: The approach is based on the dynamic model of the fission fragment angular distributions which takes into account stochastic aspects of nuclear fission and thermal fluctuations for the tilting mode that is characterized by the projection of the total angular momentum onto the symmetry axis of the fissioning system. Another base of our approach is the quantum mechanical method to calculate the initial distributions over the components of the total angular momentum of the nuclear system immediately following complete fusion. Results: A method is suggested for calculating the initial distributions of the total angular momentum projection onto the symmetry axis for the nuclear systems formed in the reactions of complete fusion of deformed nuclei with spins. The angular distributions of fission fragments for the 16O+232Th,12C+235,236,238, and 13C+235U reactions have been analyzed within the dynamic approach over a range of sub- and above-barrier energies. The analysis allowed us to determine the relaxation time for the tilting mode and the fraction of fission events occurring in times not larger than the relaxation time for the tilting mode. Conclusions: It is shown that the memory effects play an important role in the formation of the angular distributions of fission fragments for the reactions induced by heavy ions. The

  9. Helium diffusion coefficient measurements in R7T7 nuclear glass by 3He(d,α) 1H nuclear reaction analysis

    NASA Astrophysics Data System (ADS)

    Chamssedine, F.; Sauvage, T.; Peuget, S.; Fares, T.; Martin, G.

    2010-05-01

    The immobilization of fission products and minor actinides by vitrification is the reference process for industrial management of high-level radioactive wastes generated by spent fuel reprocessing. Radiation damage and radiogenic helium accumulation must be specifically studied to evaluate the effects of minor actinide alpha decay on the glass long-term behavior under repository conditions. A specific experimental study was conducted for a comprehensive evaluation of the behavior of helium and its diffusion mechanisms in borosilicate nuclear waste glass. Helium production was simulated by external implantation with 3He ions at a concentration (≈1 at.%) 30 times higher than obtained after 10,000 years of storage. Helium diffusion coefficients as a function of temperature were extracted from the depth profiles after annealing. The 3He(d,α) 1H nuclear reaction analysis (NRA) technique was successfully adopted for low-temperature in situ measurements of depth profiles. Its high depth resolution revealed helium mobility at temperatures as low as 253 K and the presence of a trapped helium fraction. The diffusion coefficients of un-trapped helium atoms follow an Arrhenius law between 253 K and 323 K. An activation energy of 0.55 ± 0.03 eV was determined, which is consistent with a process controlled by diffusion in the glass free volume.

  10. Fission fragment angular distributions in pre-actinide nuclei

    NASA Astrophysics Data System (ADS)

    Banerjee, Tathagata; Nath, S.; Jhingan, A.; Kaur, Gurpreet; Dubey, R.; Yadav, Abhishek; Laveen, P. V.; Shamlath, A.; Shareef, M.; Gehlot, J.; Saneesh, N.; Prasad, E.; Sugathan, P.; Pal, Santanu

    2016-10-01

    Background: Complete fusion of two nuclei leading to formation of a heavy compound nucleus (CN) is known to be hindered by various fission-like processes, in which the composite system reseparates after capture of the target and the projectile inside the potential barrier. As a consequence of these non-CN fission (NCNF) processes, fusion probability (PCN) starts deviating from unity. Despite substantial progress in understanding, the onset and the experimental signatures of NCNF and the degree of its influence on fusion have not yet been unambiguously identified. Purpose: This work aims to investigate the presence of NCNF, if any, in pre-actinide nuclei by systematic study of fission angular anisotropies and fission cross sections (σfis) in a number of nuclear reactions carried out at and above the Coulomb barrier (VB) . Method: Fission fragment angular distributions were measured for six 28Si-induced reactions involving isotopically enriched targets of 169Tm,176Yb,175Lu,180Hf,181Ta, and 182W leading to probable formation of CN in the pre-actinide region, at a laboratory energy (Elab) range of 129-146 MeV. Measurements were performed with large angular coverage (θlab=41∘ -170∘) in which fission fragments (FFs) were detected by nine hybrid telescope (E -Δ E ) detectors. Extracted fission angular anisotropies and σfis were compared with statistical model (SM) predictions. Results: Barring two reactions involving targets with large non-zero ground state spin (J ) , viz., 175Lu(7/2+) and 181Ta(7/2+) , experimental fission angular anisotropies were found to be higher in comparison with predictions of the statistical saddle point model (SSPM), at Ec .m . near VB. Comparison of present results with those from neighboring systems revealed that experimental anisotropies increasingly deviated from SSPM predictions as one moved from pre-actinide to actinide nuclei. For reactions involving targets with large nonzero J , this deviation was subdued. Comparison between

  11. Isotopic yield measurement in the heavy mass region for {sup 239}Pu thermal neutron induced fission

    SciTech Connect

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Koester, U.; Faust, H.; Letourneau, A.; Panebianco, S.

    2011-09-15

    Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the {sup 239}Pu(n{sub th},f) reaction. In order to do this, a new experimental method based on {gamma}-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

  12. Recent Results from Lohengrin on Fission Yields and Related Decay Properties

    NASA Astrophysics Data System (ADS)

    Serot, O.; Amouroux, C.; Bidaud, A.; Capellan, N.; Chabod, S.; Ebran, A.; Faust, H.; Kessedjian, G.; Köester, U.; Letourneau, A.; Litaize, O.; Martin, F.; Materna, T.; Mathieu, L.; Panebianco, S.; Regis, J.-M.; Rudigier, M.; Sage, C.; Urban, W.

    2014-05-01

    The Lohengrin mass spectrometer is one of the 40 instruments built around the reactor of the Institute Laue-Langevin (France) which delivers a very intense thermal neutron flux. Usually, Lohengrin was combined with a high-resolution ionization chamber in order to obtain good nuclear charge discrimination within a mass line, yielding an accurate isotopic yield determination. Unfortunately, this experimental procedure can only be applied for fission products with a nuclear charge less than about 42, i.e. in the light fission fragment region. Since 2008, a large collaboration has started with the aim of studying various fission aspects, mainly in the heavy fragment region. For that, a new experimental setup which allows isotopic identification by γ-ray spectrometry has been developed and validated. This technique was applied on the 239Pu(nth,f) reaction where about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared with what was that previously available in nuclear data libraries. The same γ-ray spectrometric technique is currently being applied to the study of the 233U(nth,f) reaction. Our aim is to deduce charge and mass distributions of the fission products and to complete the experimental data that exist mainly for light fission fragments. The measurement of 41 mass yields from the 241Am(2nth,f) reaction has been also performed. In addition to these activities on fission yield measurements, various new nanosecond isomers were discovered. Their presence can be revealed from a strong deformed ionic charge distribution compared to a 'normal' Gaussian shape. Finally, a new neutron long-counter detector designed to have a detection efficiency independent of the detected neutron energy has been built. Combining this neutron device with a Germanium detector and a beta-ray detector array allowed us to measure the beta-delayed neutron emission probability Pn of some important fission products for reactor

  13. ICENES '91:Sixth international conference on emerging nuclear energy systems

    SciTech Connect

    Not Available

    1991-01-01

    This document contains the program and abstracts of the sessions at the Sixth International Conference on Emerging Nuclear Energy Systems held June 16--21, 1991 at Monterey, California. These sessions included: The plenary session, fission session, fission and nonelectric session, poster session 1P; (space propulsion, space nuclear power, electrostatic confined fusion, fusion miscellaneous, inertial confinement fusion, [mu]-catalyzed fusion, and cold fusion); Advanced fusion session, space nuclear session, poster session 2P, (nuclear reactions/data, isotope separation, direct energy conversion and exotic concepts, fusion-fission hybrids, nuclear desalting, accelerator waste-transmutation, and fusion-based chemical recycling); energy policy session, poster session 3P (energy policy, magnetic fusion reactors, fission reactors, magnetically insulated inertial fusion, and nuclear explosives for power generation); exotic energy storage and conversion session; and exotic energy storage and conversion; review and closing session.

  14. Next Generation Nuclear Plant Phenomena Identification and Ranking Tables (PIRTs) Volume 3: Fission-Product Transport and Dose PIRTs

    SciTech Connect

    Morris, Robert Noel

    2008-03-01

    This Fission Product Transport (FPT) Phenomena Identification and Ranking Technique (PIRT) report briefly reviews the high-temperature gas-cooled reactor (HTGR) FPT mechanisms and then documents the step-by-step PIRT process for FPT. The panel examined three FPT modes of operation: (1) Normal operation which, for the purposes of the FPT PIRT, established the fission product circuit loading and distribution for the accident phase. (2) Anticipated transients which were of less importance to the panel because a break in the pressure circuit boundary is generally necessary for the release of fission products. The transients can change the fission product distribution within the circuit, however, because temperature changes, flow perturbations, and mechanical vibrations or shocks can result in fission product movement. (3) Postulated accidents drew the majority of the panel's time because a breach in the pressure boundary is necessary to release fission products to the confinement. The accidents of interest involved a vessel or pipe break, a safety valve opening with or without sticking, or leak of some kind. Two generic scenarios were selected as postulated accidents: (1) the pressurized loss-of-forced circulation (P-LOFC) accident, and (2) the depressurized loss-of-forced circulation (D-LOFC) accidents. FPT is not an accident driver; it is the result of an accident, and the PIRT was broken down into a two-part task. First, normal operation was seen as the initial starting point for the analysis. Fission products will be released by the fuel and distributed throughout the reactor circuit in some fashion. Second, a primary circuit breach can then lead to their release. It is the magnitude of the release into and out of the confinement that is of interest. Depending on the design of a confinement or containment, the impact of a pressure boundary breach can be minimized if a modest, but not excessively large, fission product attenuation factor can be introduced into the

  15. Payload dose rate from direct beam radiation and exhaust gas fission products. [for nuclear engine for rocket vehicles

    NASA Technical Reports Server (NTRS)

    Capo, M. A.; Mickle, R.

    1975-01-01

    A study was made to determine the dose rate at the payload position in the NERVA System (1) due to direct beam radiation and (2) due to the possible effect of fission products contained in the exhaust gases for various amounts of hydrogen propellant in the tank. Results indicate that the gamma radiation is more significant than the neutron flux. Under different assumptions the gamma contribution from the exhaust gases was 10 to 25 percent of total gamma flux.

  16. Current Issues in Nuclear Data Evaluation Methodology: {sup 235}U Prompt Fission Neutron Spectra and Multiplicity for Thermal Neutrons

    SciTech Connect

    Trkov, A.; Capote, R.; Pronyaev, V.G.

    2015-01-15

    Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the {sup 235}U are discussed. The inconsistency between the experimental differential and integral data is addressed. By using differential data as ”shape data” good consistency was achieved between available sets of differential data. Integral dosimetry data have been used to define the PFNS slope at high outgoing neutron energies, where the quality of the differential data is poor. The inclusion into the fit of measured integral (spectrum-averaged) cross sections had a very small impact in the region where differential PFNS data are abundant and accurate, but removed the discrepancy with integral data at higher neutron emission energies. All experimental data are consistently fitted giving a PFNS average energy of 2.008 MeV. The impact on criticality prediction of the newly evaluated PFNS was tested. The highly enriched {sup 235}U solution assemblies with high leakage HEU-SOL-THERM-001 and HEU-SOL-THERM-009 benchmarks are the most sensitive to the PFNS. Criticality calculations for those solutions show a significant increase in reactivity if the average neutron energy of the fission neutrons is reduced from the ENDF/B-VI.5 value of 2.03 MeV. The proposed reduction of the PFNS average energy by 1.1% can be compensated by reducing the average number of neutrons per fission ν{sup ¯} at the thermal energy to the Gwin et al. measured value. The simple least-squares PFNS fit was confirmed by a more sophisticated combined fit of differential PFNS data for {sup 233,235}U, {sup 239}Pu and {sup 252}Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

  17. Current Issues in Nuclear Data Evaluation Methodology: 235U Prompt Fission Neutron Spectra and Multiplicity for Thermal Neutrons

    NASA Astrophysics Data System (ADS)

    Trkov, A.; Capote, R.; Pronyaev, V. G.

    2015-01-01

    Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the 235U are discussed. The inconsistency between the experimental differential and integral data is addressed. By using differential data as "shape data" good consistency was achieved between available sets of differential data. Integral dosimetry data have been used to define the PFNS slope at high outgoing neutron energies, where the quality of the differential data is poor. The inclusion into the fit of measured integral (spectrum-averaged) cross sections had a very small impact in the region where differential PFNS data are abundant and accurate, but removed the discrepancy with integral data at higher neutron emission energies. All experimental data are consistently fitted giving a PFNS average energy of 2.008 MeV. The impact on criticality prediction of the newly evaluated PFNS was tested. The highly enriched 235U solution assemblies with high leakage HEU-SOL-THERM-001 and HEU-SOL-THERM-009 benchmarks are the most sensitive to the PFNS. Criticality calculations for those solutions show a significant increase in reactivity if the average neutron energy of the fission neutrons is reduced from the ENDF/B-VI.5 value of 2.03 MeV. The proposed reduction of the PFNS average energy by 1.1% can be compensated by reducing the average number of neutrons per fission νbar at the thermal energy to the Gwin et al. measured value. The simple least-squares PFNS fit was confirmed by a more sophisticated combined fit of differential PFNS data for 233,235U, 239Pu and 252Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

  18. Experimental Progress Report--Modernizing the Fission Basis

    SciTech Connect

    Macri, R A

    2012-02-17

    In 2010 a proposal (Modernizing the Fission Basis) was prepared to 'resolve long standing differences between LANL and LLNL associated with the correct fission basis for analysis of nuclear test data'. Collaboration between LANL/LLNL/TUNL has been formed to implement this program by performing high precision measurements of neutron induced fission product yields as a function of incident neutron energy. This new program benefits from successful previous efforts utilizing mono-energetic neutrons undertaken by this collaboration. The first preliminary experiment in this new program was performed between July 24-31, 2011 at TUNL and had 2 main objectives: (1) demonstrating the capability to measure characteristic {gamma}-rays from specific fission products; (2) studying background effects from room scattered neutrons. In addition, a new dual fission ionization chamber has been designed and manufactured. The production design of the chamber is shown in the picture below. The first feasibility experiment to test this chamber is scheduled at the TUNL Tandem Laboratory from September 19-25, 2011. The dual fission chamber design will allow simultaneous exposure of absolute fission fragment emission rate detectors and the thick fission activation foils, positioned between the two chambers. This document formalizes the earlier experimental report demonstrating the experimental capability to make accurate (< 2 %) precision gamma-ray spectroscopic measurements of the excitation function of high fission product yields of the 239Pu(n,f) reaction (induced by quasimonoenergetic neutrons). A second experiment (9/2011) introduced an compact double-sided fission chamber into the experimental arrangement, and so the relative number of incident neutrons striking the sample foil at each bombarding energy is limited only by statistics. (The number of incident neutrons often limits the experimental accuracy.) Fission chamber operation was so exceptional that 2 more chambers have been

  19. Nuclear-Pumped Lasers. [efficient conversion of energy liberated in nuclear reactions to coherent radiation

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The state of the art in nuclear pumped lasers is reviewed. Nuclear pumped laser modeling, nuclear volume and foil excitation of laser plasmas, proton beam simulations, nuclear flashlamp excitation, and reactor laser systems studies are covered.

  20. Proton-induced fission of actinides at energies 26.5 and 62.9 MeV—Theoretical interpretation

    NASA Astrophysics Data System (ADS)

    Demetriou, P.; Keutgen, Th.; Prieels, R.; El Masri, Y.

    2011-10-01

    Fission properties of proton-induced fission on 232Th, 237Np, 238U, 239Pu and 241Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code TALYS. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed.

  1. Prompt fission neutron spectra of actinides

    DOE PAGES

    Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; ...

    2016-01-06

    Here, the energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.

  2. Prompt fission neutron spectrum of actinides

    SciTech Connect

    Capote, R.; Chen, Y. -J.; Hambsch, F. J.; Jurado, B.; Lestone, J. P.; Litaize, O.; Morillon, B.; Neudecker, D.; Oberstedt, S.; Ohsawa, T.; Otuka, N.; Pronyaev, V. G.; Saxena, A.; Schmidt, K. H.; Shcherbakov, O. A.; Shu, N. -C.; Smith, D. L.; Talou, P.; Trkov, A.; Tudora, A. C.; Vogt, R.; Vorobyev, A. S.

    2016-01-06

    Here, the energy spectrum of prompt neutron emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.

  3. Laser-initiated primary and secondary nuclear reactions in Boron-Nitride

    NASA Astrophysics Data System (ADS)

    Labaune, C.; Baccou, C.; Yahia, V.; Neuville, C.; Rafelski, J.

    2016-02-01

    Nuclear reactions initiated by laser-accelerated particle beams are a promising new approach to many applications, from medical radioisotopes to aneutronic energy production. We present results demonstrating the occurrence of secondary nuclear reactions, initiated by the primary nuclear reaction products, using multicomponent targets composed of either natural boron (B) or natural boron nitride (BN). The primary proton-boron reaction (p + 11B → 3 α + 8.7 MeV), is one of the most attractive aneutronic fusion reaction. We report radioactive decay signatures in targets irradiated at the Elfie laser facility by laser-accelerated particle beams which we interpret as due to secondary reactions induced by alpha (α) particles produced in the primary reactions. Use of a second nanosecond laser beam, adequately synchronized with the short laser pulse to produce a plasma target, further enhanced the reaction rates. High rates and chains of reactions are essential for most applications.

  4. Laser-initiated primary and secondary nuclear reactions in Boron-Nitride.

    PubMed

    Labaune, C; Baccou, C; Yahia, V; Neuville, C; Rafelski, J

    2016-02-17

    Nuclear reactions initiated by laser-accelerated particle beams are a promising new approach to many applications, from medical radioisotopes to aneutronic energy production. We present results demonstrating the occurrence of secondary nuclear reactions, initiated by the primary nuclear reaction products, using multicomponent targets composed of either natural boron (B) or natural boron nitride (BN). The primary proton-boron reaction (p + (11)B → 3 α + 8.7 MeV), is one of the most attractive aneutronic fusion reaction. We report radioactive decay signatures in targets irradiated at the Elfie laser facility by laser-accelerated particle beams which we interpret as due to secondary reactions induced by alpha (α) particles produced in the primary reactions. Use of a second nanosecond laser beam, adequately synchronized with the short laser pulse to produce a plasma target, further enhanced the reaction rates. High rates and chains of reactions are essential for most applications.

  5. Towards an improved evaluation of neutron-induced fission cross sections on actinides

    NASA Astrophysics Data System (ADS)

    Goriely, S.; Hilaire, S.; Koning, A. J.; Capote, R.

    2011-03-01

    Mean-field calculations can now provide all the nuclear ingredients required to describe the fission path from the equilibrium deformation up to the nuclear scission point. The information obtained from microscopic mean-field models has been included in the TALYS reaction code to improve the predictions of neutron-induced fission cross sections. The nuclear inputs concern not only the details of the energy surface along the fission path, but also the coherent estimate of the nuclear level density derived within the combinatorial approach on the basis of the same single-particle properties, in particular at the fission saddle points. The predictive power of such a microscopic approach is tested on the experimental data available for the uranium isotopic chain. It is also shown that the various inputs can be tuned to reproduce, at best, experimental data in one unique coherent framework, so that in a close future it should become possible to make, on the basis of such models, accurate fission-cross-section calculations and the corresponding estimates for nuclei, energy ranges, or reaction channels for which no data exist. Such model uncertainties are usually not taken into account in data evaluations.

  6. Neutron-neutron angular correlations in spontaneous and neutron-induced fission

    NASA Astrophysics Data System (ADS)

    Vogt, Ramona; Randrup, Jorgen

    2015-04-01

    For many years, the state of the art for treating fission in radiation transport codes has involved sampling from average distributions. However, such average fission models have limited interaction-by-interaction capabilities. Energy is not explicitly conserved and no correlations are available because all particles are emitted isotropically and independently. However, in a true fission event, the energies, momenta and multiplicities of emitted particles are correlated. Such correlations are interesting for many modern applications, including detecting small amounts of material and detector development. Event-by-event generation of complete fission events are particularly useful because it is possible to obtain the fission products as well as the prompt neutrons and photons emitted during the fission process, all with complete kinematic information. It is therefore possible to extract any desired correlation observables. Such codes, when included in broader Monte Carlo transport codes, like MCNP, can be made broadly available. We compare results from our fast event-by-event fission code FREYA (Fission Reaction Event Yield Algorithm) with available neutron-neutron angular correlation data and study the sensitivities of these observables to the model inputs. This work was done under the auspices of the US DOE by (RV) LLNL, Contract DE-AC52-07NA27344, and by (JR) LBNL, Contract DE-AC02-05CH11231. We acknowledge support of the Office of Defense Nuclear Nonproliferation Research and Development in DOE/NNSA.

  7. A new look at low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B; Marwan, Jan

    2009-10-01

    This paper presents a new look at low-energy nuclear reaction research, a field that has developed from one of the most controversial subjects in science, "cold fusion." Early in the history of this controversy, beginning in 1989, a strong polarity existed; many scientists fiercely defended the claim of new physical effects as well as a new process in which like-charged atomic nuclei overcome the Coulomb barrier at normal temperatures and pressures. Many other scientists considered the entire collection of physical observations-along with the hypothesis of a "cold fusion"--entirely a mistake. Twenty years later, some people who had dismissed the field in its entirety are considering the validity of at least some of the reported experimental phenomena. As well, some researchers in the field are wondering whether the underlying phenomena may be not a fusion process but a neutron capture/absorption process. In 2002, a related tabletop form of thermonuclear fusion was discovered in the field of acoustic inertial confinement fusion. We briefly review some of this work, as well.

  8. Nuclear structure and reaction studies at medium energies

    SciTech Connect

    Hoffmann, G.W.; Ray, R.L.

    1990-10-01

    This document constitutes the (1988--1991) technical progress report for the ongoing medium energy physics research program supported by the US Department of Energy through special Research Grant FG05-88ER40444. The experiments discussed are conducted at the Los Alamos National Laboratory's (LANL) Clinton P. Anderson Meson Physics Facility (LAMPF), the Alternating Gradient Synchrotron (AGS) facility of the Brookhaven National Laboratory (BNL), and at the Fermi National Accelerator Laboratory (FNAL). The overall motivation for the work discussed in this document is driven by three main objectives: (1) provide hadron-nucleon and hadron-nucleus scattering data which serve to facilitate the study of effective two-body interactions, test (and possibly determine) nuclear structure, and help study reaction mechanisms and dynamics;(2) provide unique, first-of-a-kind exploratory'' hadron-nucleus scattering data in the hope that such data will lead to discovery of new phenomena and new physics; and (3) perform precision tests of fundamental interactions, such as rare decay searches, whose observation would imply fundamental new physics.

  9. Measurements of yields of fission products in the reaction of {sup 238}U with high-energy p, d and n beams

    SciTech Connect

    Nolen, J.A.; Ahmad, I.; Back, B.B.

    1995-08-01

    An experiment was performed at the Michigan State University cyclotron to determine the yields of neutron-rich fission products in the reaction of {sup 238}U with 100-MeV neutrons, 200-MeV deuterons and 200-MeV protons. Several 1-mm-thick {sup 238}U foils were irradiated for 100-second intervals sequentially for each configuration and the ten spectra were added for higher statistics. The three successive spectra, each for a 40 s period, were accumulated for each sample. Ten foils were irradiated. Successive spectra allowed us to determine approximate half-lives of the gamma peaks. Several arrangements, which were similar to the setup we plan to use in our radioactive beam proposal, were used for the production of fission products. For the high-energy neutron irradiation, U foils were placed after a 5-inch-long, 1-inch-diameter Be cylinder which stopped the 200-MeV deuteron beam generating 100-MeV neutrons. Arrangements for deuteron irradiation included direct irradiation of U foils, placing U foils after different lengths of (0.5 inch, 1.0 inch and 1.5 inch) 2-inch diameter U cylinder. Since the deuteron range in uranium is 17 mm, some of the irradiations were due to the secondary neutrons from the deuteron-induced fission of U. Similar arrangements were also used for the 200-MeV proton irradiation of the {sup 238}U foils. In all cases, several neutron-rich fission products were identified and their yields determined. In particular, we were able to observe Sn in all the runs and determine its yield. The data show that with our proposed radioactive device we will be able to produce more than 10{sup 12} {sup 132}Sn atoms per second in the target. Assuming an overall efficiency of 1 %, we will be able to deliver one particle nanoampere of {sup 132}Sn beam at a target location. Detailed analysis of the {gamma}-ray spectra is in progress.

  10. Measurement of Fission Product Yields from Fast-Neutron Fission

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. Effect of a strong magnetic field on the energy yield of nuclear reactions in dense nuclear matter

    SciTech Connect

    Sekerzhitskii, V.S.

    1995-01-01

    According to modern concepts, the electron-neutron-nuclear (Aen) phase of dense highly degenerate matter can be realized in the shells of neutron stars. This phase has relatively stable and absolutely stable states of thermodynamic equilibrium. Strong magnetic fields can exist in neutron stars. For this reason, analysis of their effect on the characteristics of the Aen phase is of great interest. It is specially important to study the influence of strong magnetic fields on the energy yield of nuclear reactions in dense nuclear matter because the transition to the absolute equilibrium state proceeds through these reactions.

  12. The Fission Programme at the CERN n_TOF Facility

    NASA Astrophysics Data System (ADS)

    Tsinganis, A.; Barbagallo, M.; Berthoumieux, E.; Calviani, M.; Chiaveri, E.; Colonna, N.; Diakaki, M.; Duran, I.; Guerrero, C.; Gunsing, F.; Leal-Cidoncha, E.; Leong, L.-S.; Paradela, C.; Tarrio, D.; Tassan-Got, L.; Vlastou, R.

    Since 2001, the scientific programme of the CERN n_TOF facility has focused mainly on the study of radiative neutron capture reactions, which are of great interest to nuclear astrophysics and on neutron-induced fission reactions, which are of relevance for nuclear technology, as well as essential for the development of theoretical models of fission. In particular, taking advantage of the high instantaneous neutron flux and high energy resolution of the facility, as well as of high-performance detection and acquisition systems, accurate new measurements on several long-lived major and minor actinides, from 232Th to 245Cm, have been performed so far. Data on these isotopes are needed in order to improve the safety and efficiency of conventional reactors, as well as to develop new systems for nuclear energy production and treatment of nuclear waste, such as Generation IV reactors, Accelerator Driven Systems and reactors based on innovative fuel cycles. A review of the most important results on fission cross-sections and fragment properties obtained at n_TOF for a variety of (radioactive) isotopes is presented along with the perspectives arising from the coming on line in the second half of 2014 of a new 19 m flight-path, which will allow n_TOF to expand its measurement capabilities to even more rare or short-lived isotopes, such as 230Th, 232U, 238,240Pu and 244Cm.

  13. Advanced Space Fission Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Borowski, Stanley K.

    2010-01-01

    Fission has been considered for in-space propulsion since the 1940s. Nuclear Thermal Propulsion (NTP) systems underwent extensive development from 1955-1973, completing 20 full power ground tests and achieving specific impulses nearly twice that of the best chemical propulsion systems. Space fission power systems (which may eventually enable Nuclear Electric Propulsion) have been flown in space by both the United States and the Former Soviet Union. Fission is the most developed and understood of the nuclear propulsion options (e.g. fission, fusion, antimatter, etc.), and fission has enjoyed tremendous terrestrial success for nearly 7 decades. Current space nuclear research and technology efforts are focused on devising and developing first generation systems that are safe, reliable and affordable. For propulsion, the focus is on nuclear thermal rockets that build on technologies and systems developed and tested under the Rover/NERVA and related programs from the Apollo era. NTP Affordability is achieved through use of previously developed fuels and materials, modern analytical techniques and test strategies, and development of a small engine for ground and flight technology demonstration. Initial NTP systems will be capable of achieving an Isp of 900 s at a relatively high thrust-to-weight ratio. The development and use of first generation space fission power and propulsion systems will provide new, game changing capabilities for NASA. In addition, development and use of these systems will provide the foundation for developing extremely advanced power and propulsion systems capable of routinely and affordably accessing any point in the solar system. The energy density of fissile fuel (8 x 10(exp 13) Joules/kg) is more than adequate for enabling extensive exploration and utilization of the solar system. For space fission propulsion systems, the key is converting the virtually unlimited energy of fission into thrust at the desired specific impulse and thrust

  14. Neutronic Model of a Mirror Based Fusion-Fission Hybrid for the Incineration of Spent Nuclear Fuel and with Potential for Energy Amplification

    NASA Astrophysics Data System (ADS)

    Noack, Klaus; Moiseenko, V. E.; Agren, O.; Hagnestall, A.

    2010-11-01

    In the last decade the Georgia Institute of Technology (Georgia Tech) published several design concepts of tokamak based fusion-fission hybrids which use solid fuels consisting of transuranic elements of the spent nuclear fuel from Light-Water-Reactors. The objectives of the hybrids are the incineration of the transuranic elements and an additional net energy production under the condition of tritium self-sufficiency. The present paper presents a preliminary scientific design of the blanket of a mirror based hybrid which was derived from the results of Monte Carlo neutron transport calculations. The main operation parameters of two hybrid options were specified. One is the analog to Georgia Techs first version of a ``fusion transmutation of waste reactor'' (FTWR) and the other is a possible near-term option which requires minimal fusion power. The latter version shows considerably better performance parameters.

  15. Fission chambers designer based on Monte Carlo techniques working in current mode and operated in saturation regime

    NASA Astrophysics Data System (ADS)

    Antolínez, Alfonso; Rapisarda, David

    2016-07-01

    Fission chambers have become one of the main devices for the measurement of neutron fluxes in nuclear facilities; including fission reactors, future fusion ones, spallation sources, etc. The main goal of a fission chamber is to estimate the neutron flux inside the facility, as well as instantaneous changes in the irradiation conditions. A Monte Carlo Fission Chamber Designer (MCFCD) has been developed in order to assist engineers in the complete design cycle of the fission chambers. So far MCFCD focuses on the most important neutron reactions taking place in a thermal nuclear reactor. A theoretical model describing the most important outcomes in fission chambers design has been developed, including the expected electrical signals (current intensity and drop in potential) and, current-polarization voltage characteristics (sensitivity and saturation plateau); the saturation plateau is the zone of the saturation curve where the output current is proportional to fission rate; fission chambers work in this region. Data provided by MCFCD are in good agreement with measurements available.

  16. Fission: The first 50 years

    SciTech Connect

    Vandenbosch, R.

    1989-01-01

    The possibility of fission had been largely unanticipated prior to its discovery in 1938. This process, with its dramatically large energy release and its formation of previously unknown nuclides, immediately captured the imagination of the scientific community. Both theoretical and experimental developments occurred at a rapid pace. I will begin my discussion of fission with the far-reaching paper of Bohr and Wheeler, who in little more than half a year laid out a framework for understanding many features of the fission process. I will then turn to our current understanding of a number of aspects of fission. One of these is the pronounced tendency of many nuclear species to fission asymmetrically. In fact, the discovery of fission was based on the identification of barium isotopes produced in asymmetric fission. The dramatic changes in the preferred mass division and kinetic energy release with the addition of only a few neutrons to the spontaneously fissioning Fermium isotopes will be emphasized. The problem of the dynamics of saddle to scission will be discussed---this is one aspect of fission for which we do not have all the answers. Another dynamical effect to be discussed is the apparent failure of transition state theory at high excitation energies. The role of single particle (shell) effects in enriching the structure if the potential energy surface will be explored. Spontaneously fissioning isomers and intermediate structure resonances will be discussed. The recognition that short-lived fission isomers are superdeformed shape isomers has been followed by the recent observation of superdeformed shape isomers in the rare earth region. 18 refs., 3 figs.

  17. Fission modelling with FIFRELIN

    NASA Astrophysics Data System (ADS)

    Litaize, Olivier; Serot, Olivier; Berge, Léonie

    2015-12-01

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

  18. Microtubule-driven nuclear movements and linear elements as meiosis-specific characteristics of the fission yeasts Schizosaccharomyces versatilis and Schizosaccharomyces pombe.

    PubMed

    Svoboda, A; Bähler, J; Kohli, J

    1995-11-01

    Meiotic prophase in Schizosaccharomyces pombe is characterized by striking nuclear movements and the formation of linear elements along chromosomes instead of tripartite synaptonemal complexes. We analysed the organization of nuclei and microtubules in cells of fission yeasts undergoing sexual differentiation. S. japonicus var. versatilis and S. pombe cells were studied in parallel, taking advantage of the better cytology in S. versatilis. During conjugation, microtubules were directed towards the mating projection. These microtubules seem to lead the haploid nuclei together in the zygote by interaction with the spindle pole bodies at the nuclear periphery. After karyogamy, arrays of microtubules emanating from the spindle pole body of the diploid nucleus extended to both cell poles. The same differentiated microtubule configuration was elaborated upon induction of azygotic meiosis in S. pombe. The cyclic movements of the elongated nuclei between the cell poles is reflected by a dynamic and coordinated shortening and lengthening of the two microtubule arrays. When the nucleus was at a cell end, one array was short while the other bridged the whole cell length. Experiments with inhibitors showed that microtubules are required for karyogamy and for the elongated shape and movement of nuclei during meiotic prophase. In both fission yeasts the SPBs and nucleoli are at the leading ends of the moving nuclei. Astral and cytoplasmic microtubules were also prominent during meiotic divisions and sporulation. We further show that in S. versatilis the linear elements formed during meiotic prophase are similar to those in S. pombe. Tripartite synaptonemal complexes were never detected. Taken together, these findings suggest that S. pombe and S. versatilis share basic characteristics in the organization of microtubules and the structure and behaviour of nuclei during their meiotic cell cycle. The prominent differentiations of microtubules and nuclei may be involved in the

  19. Modeled Neutron Induced Nuclear Reaction Cross Sections for Radiochemistry in the region of Iriduim and Gold

    SciTech Connect

    Hoffman, R D; Dietrich, F S; Kelley, K; Escher, J; Bauer, R; Mustafa, M

    2008-02-26

    We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron induced nuclear reaction cross sections for targets ranging from osmium (Z = 76) to gold (Z = 79). Of particular interest are the cross sections on Ir and Au including reactions on isomeric targets.

  20. Fission yeast kinesin-8 Klp5 and Klp6 are interdependent for mitotic nuclear retention and required for proper microtubule dynamics.

    PubMed

    Unsworth, Amy; Masuda, Hirohisa; Dhut, Susheela; Toda, Takashi

    2008-12-01

    Fission yeast has two kinesin-8s, Klp5 and Klp6, which associate to form a heterocomplex. Here, we show that Klp5 and Klp6 are mutually dependent on each other for nuclear mitotic localization. During interphase, they are exported to the cytoplasm. In sharp contrast, during mitosis, Klp5 and Klp6 remain in the nucleus, which requires the existence of each counterpart. Canonical nuclear localization signal (NLS) is identified in the nonkinesin C-terminal regions. Intriguingly individual NLS mutants (NLSmut) exhibit loss-of-function phenotypes, suggesting that Klp5 and Klp6 enter the nucleus separately. Indeed, although neither Klp5-NLSmut nor Klp6-NLSmut enters the nucleus, wild-type Klp6 or Klp5, respectively, does so with different kinetics. In the absence of Klp5/6, microtubule catastrophe/rescue frequency and dynamicity are suppressed, whereas growth and shrinkage rates are least affected. Remarkably, chimera strains containing only the N-terminal Klp5 kinesin domains cannot disassemble interphase microtubules during mitosis, leading to the coexistence of cytoplasmic microtubules and nuclear spindles with massive chromosome missegregation. In this strain, a marked reduction of microtubule dynamism, even higher than in klp5/6 deletions, is evident. We propose that Klp5 and Klp6 play a vital role in promoting microtubule dynamics, which is essential for the spatiotemporal control of microtubule morphogenesis.