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Sample records for watt fission spectrum

  1. Fission Spectrum

    Science.gov (United States)

    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

  2. Prompt fission neutron spectrum of actinides

    Energy Technology Data Exchange (ETDEWEB)

    Capote, R. [International Atomic Energy Agency, Vienna (Austria); Chen, Y. -J. [China Institute of Atomic Energy, Beijing (China); Hambsch, F. J. [European Commission, Joint Research Centre - IRRM, Geel (Belgium); Jurado, B. [CENBG, CNRS/IN2P3, Gradignan (France); Kornilov, N. [Ohio Univ., Athens, OH (United States); Lestone, J. P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Litaize, O. [CEA, DEN, DER, SPRC, Saint-Paul-Lez-Durance (France); Morillon, B. [CEA, DAM, DIF, Arpajon (France); Neudecker, D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Oberstedt, S. [European Commission, Joint Research Centre - IRRM, Geel (Belgium); Ohsawa, T. [Kinki Univ., Osaka-fu (Japan); Otuka, N. [International Atomic Energy Agency, Vienna (Austria); Pronyaev, V. G. [Institute of Physics and Power Engineering, Obninsk (Russian Federation); Saxena, A. [Bhabha Atomic Research Centre, Mumbai (India); Schmidt, K. H. [CENBG, CNRS/IN2P3, Gradignan (France); Serot, O. [CEA, DEN, DER, SPRC, Saint-Paul-Lez-Durance (France); Shcherbakov, O. A. [Petersburg Nuclear Physics Institute of NRC " Kurchatov Institute" , Gatchina (Russian Federation); Shu, N. -C. [China Institute of Atomic Energy, Beijing (China); Smith, D. L. [Argonne National Lab. (ANL), Argonne, IL (United States); Talou, P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Trkov, A. [International Atomic Energy Agency, Vienna (Austria); Tudora, A. C. [Univ. of Bucharest, Magurele (Romania); Vogt, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Davis, CA (United States); Vorobyev, A. S. [Petersburg Nuclear Physics Institute of NRC " Kurchatov Institute" , Gatchina (Russian Federation)

    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. Fission Product Yields from Fission Spectrum n+ 239Pu for ENDF/B-VII.1

    Science.gov (United States)

    Chadwick, M. B.; Kawano, T.; Barr, D. W.; Mac Innes, M. R.; Kahler, A. C.; Graves, T.; Selby, H.; Burns, C. J.; Inkret, W. C.; Keksis, A. L.; Lestone, J. P.; Sierk, A. J.; Talou, P.

    2010-12-01

    We describe a new cumulated fission product yield (FPY) evaluation for fission spectrum neutrons on plutonium that updates the ENDF/B-VI evaluation by England and Rider, for the forthcoming ENDF/B-VII.1 database release. We focus on FPs that are needed for high accuracy burnup assessments; that is, for inferring the number of fissions in a neutron environment. Los Alamos conducted an experiment in the 1970s in the Bigten fast critical assembly to determine fission product yields as part of the Interlaboratory Reaction Rate (ILRR) collaboration, and this has defined the Laboratory's fission standard to this day. Our evaluation includes use of the LANL-ILRR measurements (not previously available to evaluators) as well as other Laboratory FPY measurements published in the literature, especially the high-accuracy mass spectrometry data from Maeck and others. Because the measurement database for some of the FPs is small — especially for 99Mo — we use a meta-analysis that incorporates insights from other accurately-measured benchmark FP data, using R-value ratio measurements. The meta-analysis supports the FP measurements from the LANL-ILRR experiment. Differences between our new evaluations and ENDF/B-VI are small for some FPs (less than 1-2%-relative for 95Zr, 140Ba, 144Ce), but are larger for 99Mo (4%-relative) and 147Nd (5%-relative, at 1.5 MeV) respectively. We present evidence for an incident neutron energy dependence to the 147Nd fission product yield that accounts for observed differences in the FPY at a few-hundred keV average energy in fast reactors versus measurements made at higher average neutron energies in Los Alamos' fast critical assemblies. Accounting for such FPY neutron energy dependencies is important if one wants to reach a goal of determining the number of fissions to accuracies of 1-2%. An evaluation of the energy-dependence of fission product yields is given for all A values based on systematical trends in the measured data, with a focus on

  4. Evaluation of fission product yields from fission spectrum n+239Pu using a meta analysis of benchmark data

    Science.gov (United States)

    Chadwick, Mark B.

    2009-10-01

    Los Alamos conducted a dual fission-chamber experiment in the 1970s in the Bigten critical assembly to determine fission product data in a fast (fission neutron spectrum) environment, and this defined the Laboratory's fission basis today. We describe how the data from this experiment are consistent with other benchmark fission product yield measurements for 95,97Zr, 140Ba, 143,144Ce, 137Cs from the NIST-led ILRR fission chamber experiments, and from Maeck's mass-spectrometry data. We perform a new evaluation of the fission product yields that is planned for ENDF/B-VII.1. Because the measurement database for some of the FPs is small—especially for 147Nd and 99Mo—we use a meta-analysis that incorporates insights from other accurately-measured benchmark FP data. The %-relative changes compared to ENDF/B-VI are small for some FPs (less than 1% for 95Zr, 140Ba, 144Ce), but are larger for 99Mo (3%) and 147Nd (5%). We suggest an incident neutron energy dependence to the 147Nd fission product yield that accounts for observed differences in the FPY at a few-hundred keV average energy in fast reactors versus measurements made at higher average energies.

  5. Experimental determination of the antineutrino spectrum of the fission products of {sup 238}U

    Energy Technology Data Exchange (ETDEWEB)

    Haag, Nils-Holger

    2013-10-09

    Fission of {sup 238}U contributes about 10 % to the antineutrino emission of a pressurized water reactor. In the present thesis, the beta spectrum of the fission products of {sup 238}U was determined in an experiment at the neutron source FRM II. This beta spectrum was subsequently converted into an antineutrino spectrum. This first measurement of the antineutrino spectrum supports all current and future reactor antineutrino experiments.

  6. The measurement of prompt neutron spectrum in spontaneous fission of {sup 244}Cm

    Energy Technology Data Exchange (ETDEWEB)

    Batenkov, O.I.; Boykov, G.S.; Drapchinsky, L.V.; Majorov, M.Ju.; Trenkin, V.A. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)

    1997-03-01

    Under the Program of Measurements of Prompt Fission Neutron Spectra of Minor Actinides for Transmutation Purposes the integral neutron spectrum in spontaneous fission of {sup 244}Cm has been measured by the time-of-flight method in the energy range of 0.1-15 MeV relative to the standard neutron spectrum in {sup 252}Cf spontaneous fission. Essential attention was paid to revealing of possible systematic errors. It is shown, that the {sup 244}Cm spectrum shape may be well described by using Mannhart evaluation with appropriate parameter of Maxwell temperature T{sub M} = 1.37 MeV. (author)

  7. The measurement of prompt neutron spectrum in spontaneous fission of {sup 244}Cm

    Energy Technology Data Exchange (ETDEWEB)

    Batenkov, O.I.; Boykov, G.S.; Drapchinsky, L.V.; Majorov, M.Ju.; Trenkin, V.A. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)

    1997-03-01

    Under the Program of Measurements of Prompt Fission Neutron Spectra of Minor Actinides for Transmutation Purposes the integral neutron spectrum in spontaneous fission of {sup 244}Cm has been measured by the time-of-flight method in the energy range of 0.1-15 MeV relative to the standard neutron spectrum in {sup 252}Cf spontaneous fission. Essential attention was paid to revealing of possible systematic errors. It is shown, that the {sup 244}Cm spectrum shape may be well described by using Mannhart evaluation with appropriate parameter of Maxwell temperature T{sub M} = 1.37 MeV. (author)

  8. Refinements in the Los Alamos model of the prompt fission neutron spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Madland, D.G., E-mail: dgm@lanl.gov; Kahler, A.C.

    2017-01-15

    This paper presents a number of refinements to the original Los Alamos model of the prompt fission neutron spectrum and average prompt neutron multiplicity as derived in 1982. The four refinements are due to new measurements of the spectrum and related fission observables many of which were not available in 1982. They are also due to a number of detailed studies and comparisons of the model with previous and present experimental results including not only the differential spectrum, but also integral cross sections measured in the field of the differential spectrum. The four refinements are (a) separate neutron contributions in binary fission, (b) departure from statistical equilibrium at scission, (c) fission-fragment nuclear level-density models, and (d) center-of-mass anisotropy. With these refinements, for the first time, good agreement has been obtained for both differential and integral measurements using the same Los Alamos model spectrum.

  9. Experimental Determination of the Antineutrino Spectrum of the Fission Products of $^{238}$U

    CERN Document Server

    Haag, N; Hofmann, M; Oberauer, L; Potzel, W; Schreckenbach, K; Wagner, F M

    2013-01-01

    An experiment was performed at the scientific neutron source FRM II in Garching to determine the cumulative antineutrino spectrum of the fission products of $^{238}$U. This was achieved by irradiating target foils of natural uranium with a thermal and a fast neutron beam and recording the emitted $\\beta$-spectra with a gamma-suppressing electron-telescope. The obtained $\\beta$-spectrum of the fission products of $^{235}$U was normalized to the data of the magnetic spectrometer BILL of $^{235}$U. This method strongly reduces systematic errors in the $^{238}$U measurement. The $\\beta$-spectrum of $^{238}$U was converted into the corresponding antineutrino spectrum. The final $\\bar\

  10. Prompt neutron fission spectrum mean energies for the fissile nuclides and /sup 252/Cf

    Energy Technology Data Exchange (ETDEWEB)

    Holden, N.E.

    1985-01-01

    The international standard for a neutron spectrum is that produced from the spontaneous fission of /sup 252/Cf, while the thermal neutron induced fission neutron spectra for the four fissile nuclides, /sup 233/U, /sup 235/U, /sup 239/Pu, and /sup 241/Pu are of interest from the standpoint of nuclear reactors. The average neutron energies of these spectra are tabulated. The individual measurements are recorded with the neutron energy range measured, the method of detection as well as the average neutron energy for each author. Also tabulated are the measurements of the ratio of mean energies for pairs of fission neutron spectra. 75 refs., 9 tabs. (LEW)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-09

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

  12. Studies on the properties of hard-spectrum, actinide fissioning reactors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, J.B.; Prichard, A.W.; Schofield, P.E.; Robinson, A.H.; Spinrad, B.I.

    1980-01-01

    It is technically feasible to construct an operable (e.g., safe and stable) reactor to burn waste actinides rapidly. The heart of the concept is a driver core of EBR-II type, with a central radial target zone in which fuel elements, made entirely of waste actinides are exposed. This target fuel undergoes fission, as a result of which actinides are rapidly destroyed. Although the same result could be achieved in more conventionally designed LWR or LMFBR systems, the fast spectrum reactor does a much more efficient job, by virtue of the fact that in both LWR and LMFBR reactors, actinide fission is preceded by several captures before a fissile nuclide is formed. In the fast spectrum reactor that is called ABR (actinide burning reactor), these neutron captures are short-circuited.

  13. The 235U Prompt Fission Neutron Spectrum in the BR1 Reactor at SCK•CEN

    Directory of Open Access Journals (Sweden)

    Wagemans Jan

    2016-01-01

    Full Text Available The BR1 research reactor at SCK•CEN has a spherical cavity in the graphite above the reactor core. In this cavity an accurately characterised Maxwellian thermal neutron field is present. Different converters can be loaded in the cavity in order to obtain other types of neutron (and gamma irradiation fields. Inside the so-called MARK III converter a fast 235U(n,f prompt fission neutron field can be obtained. With the support of MCNP calculations, irradiations in MARK III can be directly related to the pure 235U(n,f prompt fission neutron spectrum. For this purpose MARK III spectrum averaged cross sections for the most relevant fluence dosimetry reactions have been determined. A calibration factor for absolute measurements has been determined applying activation dosimetry following ISO/IEC 17025 standards.

  14. The 235U Prompt Fission Neutron Spectrum in the BR1 Reactor at SCK•CEN

    Science.gov (United States)

    Wagemans, Jan; Malambu, Edouard; Borms, Luc; Fiorito, Luca

    2016-02-01

    The BR1 research reactor at SCK•CEN has a spherical cavity in the graphite above the reactor core. In this cavity an accurately characterised Maxwellian thermal neutron field is present. Different converters can be loaded in the cavity in order to obtain other types of neutron (and gamma) irradiation fields. Inside the so-called MARK III converter a fast 235U(n,f) prompt fission neutron field can be obtained. With the support of MCNP calculations, irradiations in MARK III can be directly related to the pure 235U(n,f) prompt fission neutron spectrum. For this purpose MARK III spectrum averaged cross sections for the most relevant fluence dosimetry reactions have been determined. A calibration factor for absolute measurements has been determined applying activation dosimetry following ISO/IEC 17025 standards.

  15. Measurement of Prompt Fission Neutron Spectrum of 238U at 2.8 MeV

    Institute of Scientific and Technical Information of China (English)

    HUANG; Han-xiong; RUAN; Xi-chao; REN; Jie; LI; Guang-wu; LUAN; Guang-yuan

    2015-01-01

    The prompt fission neutron spectrum(PFNS,Fig.1)of 238U was measured at 2.8MeV incident neutron energy by using the Cockcroft&Walton accelerator in China Institute of Atomic Energy(CIAE).The effect-to-background ratio was improved by increasing the amount of sample mass and adding an appropriate shielding.The final uncertainty of neutron energy spectrum is less than 20%below 10MeV region at an bin size

  16. The Possibilities of Fission Material Reproduction Increase in Thermal Reactor with the Assemblies with a Hard Neutron Spectrum

    Directory of Open Access Journals (Sweden)

    Vladimir M. Kotov

    2011-01-01

    The possibility of additional neutron source development with the use of fast neutrons with an energy distribution close to the fission spectrum in the major part of thermal reactor core is researched in this paper.

  17. Prompt fission γ -ray spectrum characteristics from 240Pu(sf ) and 242Pu(sf )

    Science.gov (United States)

    Oberstedt, S.; Oberstedt, A.; Gatera, A.; Göök, A.; Hambsch, F.-J.; Moens, A.; Sibbens, G.; Vanleeuw, D.; Vidali, M.

    2016-05-01

    In this paper we present first results for prompt fission γ -ray spectra (PFGS) characteristics from the spontaneous fission (sf) of 240Pu and 242Pu. For 242Pu(sf ) we obtained, after proper unfolding of the detector response, an average energy per photon ɛ¯γ=(0.843 ±0.012 ) MeV, an average multiplicity M¯γ=(6.72 ±0.07 ) , and an average total γ -ray energy release per fission E¯γ ,tot = (5.66 ± 0.06) MeV. The 240Pu(sf ) emission spectrum was obtained by applying a so-called detector-response transformation function determined from the 242Pu spectrum measured in exactly the same geometry. The results are an average energy per photon ɛ¯γ=(0.80 ±0.07 ) MeV, the average multiplicity M¯γ = (8.2 ± 0.4), and an average total γ -ray energy release per fission E¯γ ,tot = (6.6 ± 0.5) MeV. The PFGS characteristics for 242Pu(sf ) are in very good agreement with those from thermal-neutron-induced fission on 241Pu and scales well with the corresponding prompt neutron multiplicity. Our results in the case of 240Pu(sf ), although drawn from a limited number of events, show a significantly enhanced average multiplicity and average total energy, but may be understood from a different fragment yield distribution in 240Pu(sf ) compared to that of 242Pu(sf ).

  18. Determination of the Spectral Index in the Fission Spectrum Energy Regime

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Amy Sarah [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-16

    Neutron reaction cross sections play a vital role in tracking the production and destruction of isotopes exposed to neutron fluence. They are central to the process of reconciling the initial and final atom inventories. Measurements of irradiated samples by radiochemical methods in tangent with an algorithm are used to evaluate the fluence a sample is exposed to over the course of the irradiation. This algorithm is the Isotope Production Code (IPC) created and used by the radiochemistry data assessment team at Los Alamos National Laboratory (LANL). An integral result is calculated by varying the total neutron fluence seen by a sample. A sample, irradiated in a critical assembly, will be exposed to a unique neutron flux defined by the neutron source and distance of the sample from the source. Neutron cross sections utilized are a function of the hardness of the neutron spectrum at the location of irradiation. A spectral index is used an indicator of the hardness of the neutron spectrum. Cross sections fit forms applied in IPC are collapsed from a LANL 30-group energy structure. Several decades of research and development have been performed to formalize the current IPC cross section library. Basis of the current fission spectrum neutron reaction cross section library is rooted in critical assembly experiments performed from the 1950’s through the early 1970’s at LANL. The focus of this report is development of the spectral index used an indicator of the hardness of the neutron spectrum in the fission spectrum energy regime.

  19. The Prompt Fission Neutron Spectrum of 235U for Einc 0.7-5.0 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, Jaime A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Devlin, Matthew James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Haight, Robert Cameron [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); O' Donnell, John M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lee, Hye Young [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mosby, Shea Morgan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Taddeucci, Terry Nicholas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kelly, Keegan John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Fotiadis, Nikolaos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Neudecker, Denise [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); White, Morgan Curtis [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Talou, Patrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rising, Michael Evan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Solomon, Clell Jeffrey Jr. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wu, Ching-Yen [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bucher, Brian Michael [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Buckner, Matthew Quinn [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Henderson, Roger Alan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-03-23

    The Chi-Nu experiment aims to accurately measure the prompt fission neutron spectrum (PFNS) for the major actinides. At the Los Alamos Neutron Science Center (LANSCE), fission can be induced using the white neutron source. Using a two arm time of flight (T.O.F) technique; Chi-Nu presents a preliminary result of the low energy component of the 235U PFNS measured using an array of 22-Lithium glass scintillators.

  20. Watt and joule balances

    Science.gov (United States)

    Robinson, Ian A.

    2014-04-01

    The time is fast approaching when the SI unit of mass will cease to be based on a single material artefact and will instead be based upon the defined value of a fundamental constant—the Planck constant—h . This change requires that techniques exist both to determine the appropriate value to be assigned to the constant, and to measure mass in terms of the redefined unit. It is important to ensure that these techniques are accurate and reliable to allow full advantage to be taken of the stability and universality provided by the new definition and to guarantee the continuity of the world's mass measurements, which can affect the measurement of many other quantities such as energy and force. Up to now, efforts to provide the basis for such a redefinition of the kilogram were mainly concerned with resolving the discrepancies between individual implementations of the two principal techniques: the x-ray crystal density (XRCD) method [1] and the watt and joule balance methods which are the subject of this special issue. The first three papers report results from the NRC and NIST watt balance groups and the NIM joule balance group. The result from the NRC (formerly the NPL Mk II) watt balance is the first to be reported with a relative standard uncertainty below 2 × 10-8 and the NIST result has a relative standard uncertainty below 5 × 10-8. Both results are shown in figure 1 along with some previous results; the result from the NIM group is not shown on the plot but has a relative uncertainty of 8.9 × 10-6 and is consistent with all the results shown. The Consultative Committee for Mass and Related Quantities (CCM) in its meeting in 2013 produced a resolution [2] which set out the requirements for the number, type and quality of results intended to support the redefinition of the kilogram and required that there should be agreement between them. These results from NRC, NIST and the IAC may be considered to meet these requirements and are likely to be widely debated

  1. The LANL/LLNL Prompt Fission Neutron Spectrum Program at LANSCE and Approach to Uncertainties

    Energy Technology Data Exchange (ETDEWEB)

    Haight, R.C., E-mail: haight@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545,USA (United States); Wu, C.Y. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Lee, H.Y.; Taddeucci, T.N.; Perdue, B.A.; O' Donnell, J.M.; Fotiades, N.; Devlin, M.; Ullmann, J.L.; Bredeweg, T.A.; Jandel, M.; Nelson, R.O.; Wender, S.A.; Neudecker, D.; Rising, M.E.; Mosby, S.; Sjue, S.; White, M.C. [Los Alamos National Laboratory, Los Alamos, NM 87545,USA (United States); Bucher, B.; Henderson, R. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States)

    2015-01-15

    New data on the prompt fission neutron spectra (PFNS) from neutron-induced fission with higher accuracies are needed to resolve discrepancies in the literature and to address gaps in the experimental data. The Chi-Nu project, conducted jointly by LANL and LLNL, aims to measure the shape of the PFNS for fission of {sup 239}Pu induced by neutrons from 0.5 to 20 MeV with accuracies of 3–5% in the outgoing energy from 0.1 to 9 MeV and 15% from 9 to 12 MeV and to provide detailed experimental uncertainties. Neutrons from the WNR/LANSCE neutron source are being used to induce fission in a Parallel-Plate Avalanche Counter (PPAC). Two arrays of neutron detectors are used to cover the energy range of neutrons emitted promptly in the fission process. Challenges for the present experiment include background reduction, use of {sup 239}Pu in a PPAC, and understanding neutron detector response. Achieving the target accuracies requires the understanding of many systematic uncertainties. The status and plans for the future will be presented.

  2. The Prompt Fission Neutron Spectrum: From Experiment to the Evaluated Data and its Impact on Critical Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Rising, Michael Evan [Los Alamos National Laboratory

    2015-06-10

    After a brief introduction concerning nuclear data, prompt fission neutron spectrum (PFNS) evaluations and the limited PFNS covariance data in the ENDF/B-VII library, and the important fact that cross section uncertainties ~ PFNS uncertainties, the author presents background information on the PFNS (experimental data, theoretical models, data evaluation, uncertainty quantification) and discusses the impact on certain well-known critical assemblies with regard to integral quantities, sensitivity analysis, and uncertainty propagation. He sketches recent and ongoing research and concludes with some final thoughts.

  3. Calculation of Prompt Fission Neutron Spectrum for 233U(n, f) Reaction by Semi-empirical Method

    Institute of Scientific and Technical Information of China (English)

    CHEN; Yong-jing; LIU; Ting-jin; SHU; Neng-chuan

    2013-01-01

    The prompt fission neutron spectra for neutron-induced fission of 233U for low energy neutron(below 6 MeV)are calculated using the nuclear evaporation theory with a semi-empirical method,in which the partition of the total excitation energy between the fission fragments for the nth+233U fission

  4. Estimation of Covariances on Prompt Fission Neutron Spectra and Impact of the PFNS Model on the Vessel Fluence

    Directory of Open Access Journals (Sweden)

    Berge Léonie

    2016-01-01

    Full Text Available As the need for precise handling of nuclear data covariances grows ever stronger, no information about covariances of prompt fission neutron spectra (PFNS are available in the evaluated library JEFF-3.2, although present in ENDF/B-VII.1 and JENDL-4.0 libraries for the main fissile isotopes. The aim of this work is to provide an estimation of covariance matrices related to PFNS, in the frame of some commonly used models for the evaluated files, such as the Maxwellian spectrum, the Watt spectrum, or the Madland-Nix spectrum. The evaluation of PFNS through these models involves an adjustment of model parameters to available experimental data, and the calculation of the spectrum variance-covariance matrix arising from experimental uncertainties. We present the results for thermal neutron induced fission of 235U. The systematic experimental uncertainties are propagated via the marginalization technique available in the CONRAD code. They are of great influence on the final covariance matrix, and therefore, on the spectrum uncertainty band width. In addition to this covariance estimation work, we have also investigated the importance on a reactor calculation of the fission spectrum model choice. A study of the vessel fluence depending on the PFNS model is presented. This is done through the propagation of neutrons emitted from a fission source in a simplified PWR using the TRIPOLI-4® code. This last study includes thermal fission spectra from the FIFRELIN Monte-Carlo code dedicated to the simulation of prompt particles emission during fission.

  5. Estimation of Covariances on Prompt Fission Neutron Spectra and Impact of the PFNS Model on the Vessel Fluence

    Science.gov (United States)

    Berge, Léonie; Litaize, Olivier; Serot, Olivier; Archier, Pascal; De Saint Jean, Cyrille; Pénéliau, Yannick; Regnier, David

    2016-02-01

    As the need for precise handling of nuclear data covariances grows ever stronger, no information about covariances of prompt fission neutron spectra (PFNS) are available in the evaluated library JEFF-3.2, although present in ENDF/B-VII.1 and JENDL-4.0 libraries for the main fissile isotopes. The aim of this work is to provide an estimation of covariance matrices related to PFNS, in the frame of some commonly used models for the evaluated files, such as the Maxwellian spectrum, the Watt spectrum, or the Madland-Nix spectrum. The evaluation of PFNS through these models involves an adjustment of model parameters to available experimental data, and the calculation of the spectrum variance-covariance matrix arising from experimental uncertainties. We present the results for thermal neutron induced fission of 235U. The systematic experimental uncertainties are propagated via the marginalization technique available in the CONRAD code. They are of great influence on the final covariance matrix, and therefore, on the spectrum uncertainty band width. In addition to this covariance estimation work, we have also investigated the importance on a reactor calculation of the fission spectrum model choice. A study of the vessel fluence depending on the PFNS model is presented. This is done through the propagation of neutrons emitted from a fission source in a simplified PWR using the TRIPOLI-4® code. This last study includes thermal fission spectra from the FIFRELIN Monte-Carlo code dedicated to the simulation of prompt particles emission during fission.

  6. Makahiki+WattDepot

    DEFF Research Database (Denmark)

    Johnson, Philip M.; Xu, Yongwen; Brewer, Robert S.;

    2013-01-01

    Satisfying the radically different requirements and operating assumptions of the next generation smart grid requires new kinds of software that enable research and experimentation into the ways that electrical energy production and consumption can be collected, analyzed, visualized, and provided...... to consumers. Since 2009, we have been designing, implementing, and evaluating an open source software "stack" to facilitate this research. This software stack consists of two custom systems called WattDepot and Makahiki, along with the open source components they rely upon (Java, Restlet, Postgres, Python...

  7. Evaluating the 239Pu Prompt Fission Neutron Spectrum Induced by Thermal to 30 MeV Neutrons

    Directory of Open Access Journals (Sweden)

    Neudecker D.

    2016-01-01

    Full Text Available We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. Selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

  8. Evaluating the 239Pu Prompt Fission Neutron Spectrum Induced by Thermal to 30 MeV Neutrons

    Science.gov (United States)

    Neudecker, D.; Talou, P.; Kawano, T.; Kahler, A. C.; Rising, M. E.; White, M. C.

    2016-03-01

    We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. Selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

  9. Measurements of structural material capture to uranium-235 fission rate ratios in an intermediate spectrum assembly

    Energy Technology Data Exchange (ETDEWEB)

    Azzoni, P.; Benzi, V.; Chiodi, P.L.; Giuliani, C.; Guardini, S.; Marrasi, R.; Salomoni, A.; Tassan, S.

    1980-10-01

    Experimental determinations of capture rates of structural materials used in fast breeder reactors, such as iron, chromium, nickel, and stainless steel, normalized to the /sup 235/U fission rate, were performed. The aim of these experiments was to check structural material multigroup cross-section libraries in the 1- to 100-keV range, where substantial discrepancies among various cross-section evaluations are not yet resolved. The experiments were carried out in an ARGONAUTtype RB-2 reactor, using the Null Reactivity Oscillation method, on test media composed of quasi-homogeneous loose particle mixtures. Comparisons were carried out with corresponding calculated values, showing a trend of these values to overestimate the measured quantities. These results are not in disagreement with the indications of recent /sup 235/U cross-section measurements as far as the sigma /SUB c/ /sigma /SUB f/ of /sup 235/U is concerned.

  10. Measurement of the energy spectrum of {sup 252}Cf fission fragments using nuclear track detectors and digital image processing

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa, G.; Golzarri, J. I. [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Castano, V. M. [UNAM, Centro de Fisica Aplicada y Tecnologia Avanzada, Boulevard Juriquilla 3001, Santiago de Queretaro, 76230 Queretaro (Mexico); Gaso, I. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Mena, M.; Segovia, N. [UNAM, Instituto de Geofisica, Circuito de la Investigacion Cientifica, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2010-02-15

    The energy spectrum of {sup 252}Cf fission fragments was measured using nuclear track detectors and digital image analysis system. The detection material was fused silica glass. The detectors were chemically etched in an 8% HF solution. After experimenting with various etching time, it was found that the best resolution of the track diameter distribution was obtained after 30 minutes of etching. Both Gaussian and Lorentzian curves were fit to the track diameter distribution histograms and used to determine the basic parameters of the distribution of the light (N{sub L}) and heavy (N{sub H}) formed peaks and the minimum of the central valley (N{sub V}). Advantages of the method presented here include the fully-automated analysis process, the low cost of the nuclear track detectors and the simplicity of the nuclear track method. The distribution resolution obtained by this method is comparable with the resolution obtained by electronic analysis devices. The descriptive variables calculated were very close to those obtained by other methods based on the use of semiconductor detectors. (Author)

  11. Thermal-neutron-induced alpha-accompanied fission of /sup 235/U investigation of the low energy part of the alpha spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Caitucoli, F. (CEA Centre d' Etudes Nucleaires de Grenoble, 38 (France). Dept. de Recherche Fondamentale); Leroux, B.; Cajan, N.; Benfoughal, T.; Doan, T.P.; El Hage, F.; Sicre, A. (CEA Centre d' Etudes Nucleaires de Bordeaux-Gradignan, 33 - Gradignan (France)); Asghar, M. (Institut Max von Laue - Paul Langevin, 38 - Grenoble (France)); Barreau, G.; Perrin, P. (Institut Max von Laue - Paul Langevin, 38 - Grenoble (France))

    1980-01-01

    The energy spectrum of the ..cap alpha..-particles emitted in the thermal-neutron induced fission of /sup 235/U was measured from 11.5 MeV down to 2 MeV using the parabola mass spectrometer Lohengrin at the I.L.L. high flux reactor. This low energy part of the energy spectrum presents a smooth connection with the energy spectra which have been recently reported above 7 MeV. The overall energy spectrum, which is known to be quasi-gaussian above 12 MeV, is slightly asymmetric at low energy, where the observed particles are 6% more than expected from a gaussian shape. As a consequence, all the values reported for /sup 235/ U for the rate of ..cap alpha..-accompanied fission compared to binary fission have to be multiplied by 1.06. This asymmetry is about 2 times less important than the one reported for /sup 252/Cf. No evidence was seen for any intense low energy component as reported before. The possible reasons for the existence of this asymmetry are discussed.

  12. Comparisons of fission track age-determination and radioactivation analysis among radiation fields. Characteristic values for pneumatic tube, JRR-3M PN2

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Tatsuro [Kagoshima Univ. (Japan). Faculty of Education; Tomura, Kenji

    1996-01-01

    It is necessary for Fission track age determination and radioactivation analysis to define the energy spectrum of a reactor neutron as the basis for calculating the nuclear reaction rate. This study was made aiming to define the spectrum for PN2 pneumatic tube of No. 3 plant of Japan Atomic Energy Research Institute (JAERI). Characteristics such as conventional flux, cross reaction, neutron temperature and integral fast flux were examined for 3 facilities; JRR-2, JRR-4 and JRR-3M. And the neutron spectrum for each facility was estimated based on the assumptions; Maxwell distribution for thermal neutrons, 1/E for intermediate neutrons and Watt`s formula for fast neutrons. The present results showed that the spectrum for JRR-3M, PN2 was discontinuous in the range from the intermediate to the fast neutron, whereas those for other facilities were found considerably improved. (M.N.)

  13. Delayed fission

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-07-01

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

  14. Nuclear Fission

    Science.gov (United States)

    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.

  15. Using MCNP6 to Estimate Fission Neutron Properties of a Reflected Plutonium Sphere

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Alexander Rich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nelson, Mark Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hutchinson, Jesson D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-08-08

    The purpose of this project was to determine the fission multiplicity distribution, p(v), for the Beryllium Reflected Plutonium (BeRP) ball and to determine whether or not it changed appreciably for various High Density Polyethylene (HDPE) reflected configurations. The motivation for this project was to determine whether or not the average number of neutrons emitted per fission, v, changed significantly enough to reduce the discrepancy between MCNP6 and Robba, Dowdy, Atwater (RDA) point kinetic model estimates of multiplication. The energy spectrum of neutrons that induced fissions in the BeRP ball, NIF (E), was also computed in order to determine the average energy of neutrons inducing fissions, NIF . p(v) was computed using the FMULT card, NIF (E) and NIF were computed using an F4 tally with an FM tally modifier (F4/FM) card, and the multiplication factor, keff, was computed using the KCODE card. Although NIF (E) changed significantly between bare and HDPE reflected configurations of the BeRP ball, the change in p(v), and thus the change in v, was insignificant. This is likely due to a difference between the way that NIF is computed using the FMULT and F4/FM cards. The F4/FM card indicated that NIF (E) was essentially Watt-fission distributed for a bare configuration and highly thermalized for all HDPE reflected configurations, while the FMULT card returned an average energy between 1 and 2 MeV for all configurations, which would indicate that the spectrum is Watt-fission distributed, regardless of the amount of HDPE reflector. The spectrum computed with the F4/FM cards is more physically meaningful and so the discrepancy between it and the FMULT card result is being investigated. It is hoped that resolving the discrepancy between the FMULT and F4/FM card estimates of NIF(E) will provide better v estimates that will lead to RDA multiplication estimates that are in better agreement with MCNP6 simulations.

  16. Reflections: Michael Watts interviewed by Murat Arsel

    NARCIS (Netherlands)

    M. Arsel (Murat)

    2009-01-01

    textabstractMichael Watts is ‘Class of 1963’ Chair in Undergraduate Studies and Chancellor’s Professor of Geography at the University of California, Berkeley. Born and raised in rural southwest England, Watts studied at University College London and completed his PhD in 1979 at the University of Mic

  17. Influence of dose rate on the transformation of Syrian hamster embryo cells by fission-spectrum neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Jones, C.A.; Sedita, B.A.; Hill, C.K.; Elkind, M.M.

    1988-01-01

    Several explanations for this neutron dose-rate effect have been proposed, but further investigation is necessary to determine the mechanisms involved. In all cell transformation studies to date the immortalized, aneuploid 10T1/2 cell-line has been used. These cells may be premalignant; thus their response characteristics and, in particular, the nature of the transformation event, might differ from that in a normal, fibroblast cell. One reason for the present study was to determine whether the low-dose-rate effect of fission neutrons could be demonstrated in normal cells. If so, a normal cell system, which would more closely resemble a normal in vivo system, could be used for mechanistic studies. We chose Syrian hamster embryo (SHE) fibroblasts which are normal, diploid cells with a limited life span in culture. Upon exposure to low doses of ionizing radiation, the fraction of the cells that are transformed can be identified in a standard 8--10 day colony assay by examining their clonal morphology. Transformed cells form colonies with a dense, criss-crossed or piled-up structure. A high percentage of the transformed colonies can be further propagated and will acquire additional neoplastic characteristics; i.e., anchorage independence, immortality, altered proteolytic activity, karyotype alterations, and finally, tumorigenicity.

  18. James Watt making the world anew

    CERN Document Server

    Russell, Ben

    2014-01-01

    Scottish inventor and mechanical engineer James Watt (1736-1819) is best known for his pioneering work on the steam engine that became fundamental to the incredible changes and developments wrought by the Industrial Revolution. But in this new biography, Ben Russell tells a much bigger, richer story, peering over Watt's shoulder to more fully explore the processes he used and how his ephemeral ideas were transformed into tangible artifacts. Over the course of the book, Russell reveals as much about the life of James Watt as he does a history of Britain's early industrial transformation and the

  19. Sensitivity studies of beam directionality, beam size, and neutron spectrum for a fission converter-based epithermal neutron beam for boron neutron capture therapy.

    Science.gov (United States)

    Sakamoto, S; Kiger, W S; Harling, O K

    1999-09-01

    Sensitivity studies of epithermal neutron beam performance in boron neutron capture therapy are presented for realistic neutron beams with varying filter/moderator and collimator/delimiter designs to examine the relative importance of neutron beam spectrum, directionality, and size. Figures of merit for in-air and in-phantom beam performance are calculated via the Monte Carlo technique for different well-optimized designs of a fission converter-based epithermal neutron beam with head phantoms as the irradiation target. It is shown that increasing J/phi, a measure of beam directionality, does not always lead to corresponding monotonic improvements in beam performance. Due to the relatively low significance, for most configurations, of its effect on in-phantom performance and the large intensity losses required to produce beams with very high J/phi, beam directionality should not be considered an important figure of merit in epithermal neutron beam design except in terms of its consequences on patient positioning and collateral dose. Hardening the epithermal beam spectrum, while maintaining the specific fast neutron dose well below the inherent hydrogen capture dose, improves beam penetration and advantage depth and, as a desirable by-product, significantly increases beam intensity. Beam figures of merit are shown to be strongly dependent on beam size relative to target size. Beam designs with J/phi approximately 0.65-0.7, specific fast neutron doses of 2-2.6x10(-13) Gy cm2/n and beam sizes equal to or larger than the size of the head target produced the deepest useful penetration, highest therapeutic ratios, and highest intensities.

  20. Watt-Lite; Energy Statistics Made Tangible

    DEFF Research Database (Denmark)

    Jönsson, Li; Broms, Loove; Katzeff, Cecilia

    2011-01-01

    in the physical environments of its employees. The design of Watt-Lite is meant to explore ways of representing, understanding and interacting with electricity in industrial workspaces. We discuss three design inquiries and their implications for the design of Watt-Lite: the use of tangible statistics......Increasing our knowledge of how design affects behaviour in the workplace has a large potential for reducing electricity consumption. This would be beneficial for the environment as well as for industry and society at large. In Western society energy use is hidden and for the great mass...... of consumers its consequences are poorly understood. In order to better understand how we can use design to increase awareness of electricity consumption in everyday life, we will discuss the design of Watt-Lite, a set of three oversized torches projecting real time energy statistics of a factory...

  1. Ternary fission

    Indian Academy of Sciences (India)

    M Balasubramaniam; K R Vijayaraghavan; C Karthikraj

    2015-09-01

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

  2. 10 Watts Double-Cladding Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Considering the wavelength characteristics of the pump high-power laser diode, a modified Fabry-Perot fiber laser resonator is designed. And a fiber laser with more than 10Watts output, near diffraction-limited and operating in the 1110nm region is developed.

  3. Radiochemistry and the Study of Fission

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-14

    These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since 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.

  4. Spectrum

    DEFF Research Database (Denmark)

    Høgfeldt Hansen, Leif

    2016-01-01

    The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum.......The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum....

  5. Energy Partition in n+233U Fission Reaction

    Institute of Scientific and Technical Information of China (English)

    CHEN; Yong-jing; LIU; Ting-jin; SHU; Neng-chuan

    2012-01-01

    <正>The partition of the total excitation energy between the fission fragments for the n+233U fission reactions are analyzed with a semi-empirical model, and it is a key point for calculating the prompt fission neutron spectrum, and it is still a long-standing problem for nuclear fission, and attracts more and more attention. With the available experimental data, such as the average total number of emitted neutrons, the

  6. Los Alamos National Laboratory Fission Basis

    Energy Technology Data Exchange (ETDEWEB)

    Keksis, A.L.; Chadwick, M.B.; Selby, H.D.; Mac Innes, M.R.; Barr, D.W.; Meade, R.A.; Burns, C.J.; Wallstrom, T.C. [Los Alamos National Laboratory, NM 87545 (United States)

    2011-07-01

    This report is an overview of two main publications that provide a comprehensive review of the Los Alamos National Laboratory (LANL) Fission Basis. The first is the experimental paper, {sup F}ission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on {sup 239}Pu, {sup 235}U, {sup 238}U, [Selby, H. D., et al., Nucl. Data Sheets, Vol. 111 2010, pp. 2891-2922] and the second is the theoretical paper, Fission Product Yields from Fission Spectrum n+ {sup 239}Pu for ENDF/B-VII.1, [Chadwick, M. B., et al., Nucl. Data Sheets, Vol. 111, 2010, pp. 2923-2964]. One important note is that none of this work would have been possible without the great documentation of the experimental details and results by G.W. Knobeloch, G. Butler, C.I. Browne, B. Erdal, B. Bayhurst, R. Prestwood, V. Armijo, J. Hasty and many others. (authors)

  7. Toolkits for Automatic Service Generation: WATT and Kill-A-WATT

    Science.gov (United States)

    Qu, Y.; Bollig, E. F.; Erlebacher, G.

    2007-12-01

    As part of the NSF funded VLab consortium [1], we have been involved in the automatic generation of visualization web services using the Web Automation and Translation Toolkit (WATT) compiler. The WATT compiler converts VTK Tcl input scripts into equivalent yet more efficient C++ web services by interpreting code structure, translating and then integrating bindings to the gSOAP library. WATT seeks to completely automate code distribution, integration of transport protocols and interface generation. Ideally, developers should concentrate on writing core applications, and let WATT transform them into web services in the background. Currently, the WATT compiler is limited to converting known Tcl commands and types to C++. For VTK a simple one to one mapping between Tcl and C++ is enforced, but Tcl commands without direct mappings slow the compilation process and require new mappings to be created. Loops and conditional statements are not yet implemented. In an effort to move forward with automation and not get caught up in the details of cross-language compilation, we developed a new application: Kill-A-WATT (KWATT). KWATT is a C++ application that utilizes the C++/Tcl library [2] to evaluate Tcl input scripts using the official Tcl interpreter. During evaluation of the input script, KWATT interprets code structure, integrating communication details via a Tcl-specific SOAP library [3]. Since KWATT drives the Tcl interpreter, the application has access to the full Tcl command base plus the ability to load new commands from other packages. KWATT is not a compiler; instead, it is a stand-alone application that is itself a web service. When KWATT consumes Tcl input, the generated web methods extend the list of previously available commands. This implies that C++ web methods statically defined in KWATT provide a set of standard methods available to every service. Also, since KWATT uses the Tcl interpreter, it has the potential to accept additional Tcl at any time while

  8. Ideological Fission

    DEFF Research Database (Denmark)

    Christiansen, Steen Ledet

    ; it is a materialisation of an ideological fission which attempts to excise certain ideological constructions, yet paradoxically casting them in a form that is recognizable and familiar. The monstrous metonomy which is used shows us glimpses of a horrid being, intended to vilify the attack on New York City. However......, it is a being which is reminiscent of earlier monsters - from Godzilla to The Blob. It is evident that the Cloverfield monster is a paradoxical construction which attempts to articulate fear and loathing about terrorism, but ends up trapped in an ideological dead-end maze, unable to do anything other than...

  9. Recent progress on the BIPM watt balance

    Directory of Open Access Journals (Sweden)

    Fang Hao

    2014-01-01

    Full Text Available We present the recent progress on the BIPM (Bureau International des Poids et Mesures watt balance. The existing apparatus was transferred to the dedicated new laboratory with better thermal and vibrational conditions. The apparatus is fully operational in air. An improvement by a factor of three was achieved on the S/N ratio of both the voltage-to-velocity and force-to-current ratios. The fabrication of the parts of the new magnet is completed and its assembly is finished.

  10. Application of the dinuclear system model to fission process

    Directory of Open Access Journals (Sweden)

    Andreev A. V.

    2016-01-01

    Full Text Available A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the mass, total kinetic energy, and angular distribution of fission fragments for the neutron–induced fission of 239Pu.

  11. Complex fission phenomena

    CERN Document Server

    Poenaru, D N; Greiner, W

    2005-01-01

    Complex fission phenomena can be studied in a unified way. Very general reflection asymmetrical equilibrium (saddle-point) nuclear shapes, may be obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in cold fission phenomena can be explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined. Predictions of two alpha accompanied fission are experimentally confirmed.

  12. To fission or not to fission

    CERN Document Server

    Pomorski, Krzysztof; Ivanyuk, Fedir A

    2016-01-01

    The fission-fragments mass-yield of 236U is obtained by an approximate solution of the eigenvalue problem of the collective Hamiltonian that describes the dynamics of the fission process whose degrees of freedom are: the fission (elongation), the neck and the mass-asymmetry mode. The macroscopic-microscopic method is used to evaluate the potential energy surface. The macroscopic energy part is calculated using the liquid drop model and the microscopic corrections are obtained using the Woods-Saxon single-particle levels. The four dimensional modified Cassini ovals shape parametrization is used to describe the shape of the fissioning nucleus. The mass tensor is taken within the cranking-type approximation. The final fragment mass distribution is obtained by weighting the adiabatic density distribution in the collective space with the neck-dependent fission probability. The neck degree of freedom is found to play a significant role in determining that final fragment mass distribution.

  13. Advanced modeling of prompt fission neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Talou, Patrick [Los Alamos National Laboratory

    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.

  14. Multi-modal calculations of prompt fission neutrons from 238U(n, f) at low induced energy

    Institute of Scientific and Technical Information of China (English)

    ZHENG Na; ZHONG Chun-Lai; FAN Tie-Shuan

    2011-01-01

    Properties of prompt fission neutrons from 238U(n,f) are calculated for incident neutron energies below 6 MeV using the multi-modal model,including the prompt fission neutron spectrum,the average prompt fission neutron multiplicity,and the prompt fission neutron multiplicity as a function of the fission fragment mass v(A) (usually named “sawtooth” data) The three most dominant fission modes are taken into account.The model parameters are determined on the basis of experimental fission fragment data.The predicted results are in good agreement with the experimental data.

  15. SOURCES 4C : a code for calculating ([alpha],n), spontaneous fission, and delayed neutron sources and spectra.

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, W. B. (William B.); Perry, R. T. (Robert T.); Shores, E. F. (Erik F.); Charlton, W. S. (William S.); Parish, Theodore A.; Estes, G. P. (Guy P.); Brown, T. H. (Thomas H.); Arthur, Edward D. (Edward Dana),; Bozoian, Michael; England, T. R.; Madland, D. G.; Stewart, J. E. (James E.)

    2002-01-01

    SOURCES 4C is a computer code that determines neutron production rates and spectra from ({alpha},n) reactions, spontaneous fission, and delayed neutron emission due to radionuclide decay. The code is capable of calculating ({alpha},n) source rates and spectra in four types of problems: homogeneous media (i.e., an intimate mixture of a-emitting source material and low-Z target material), two-region interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material), three-region interface problems (i.e., a thin slab of low-Z target material sandwiched between {alpha}-emitting source material and low-Z target material), and ({alpha},n) reactions induced by a monoenergetic beam of {alpha}-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 44 actinides. The ({alpha},n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 107 nuclide decay {alpha}-particle spectra, 24 sets of measured and/or evaluated ({alpha},n) cross sections and product nuclide level branching fractions, and functional {alpha}-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code provides the magnitude and spectra, if desired, of the resultant neutron source in addition to an analysis of the'contributions by each nuclide in the problem. LASTCALL, a graphical user interface, is included in the code package.

  16. 5 Watt, Solid State, EHF Transmitter.

    Science.gov (United States)

    2014-09-26

    satellite-communication ground terminals. This state-of- the- art transmitter demonstrates efficient and cost-effective RF power generation at EHF for...are relatively little or no spectrum allocation problems, is that the state-of-the- art in RF power generation is far below the required levels for...accomplished using E-H hybrid magic tees of reduced height waveguide with good balance and isolation characteristics. Modulation and other signal

  17. Complex fission phenomena

    Science.gov (United States)

    Poenaru, D. N.; Gherghescu, R. A.; Greiner, W.

    2005-01-01

    Complex fission phenomena are studied in a unified way. Very general reflection asymmetrical equilibrium (saddle point) nuclear shapes are obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in binary cold fission of Th and U isotopes is explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined.

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

    Science.gov (United States)

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

    2011-10-01

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

  19. On the Percolation BCFT and the Crossing Probability of Watts

    CERN Document Server

    Ridout, David

    2008-01-01

    The logarithmic conformal field theory describing critical percolation is further explored using Watts' determination of the probability that there exists a cluster connecting both horizontal and vertical edges. The boundary condition changing operator which governs Watts' computation is identified with a primary field which does not fit naturally within the extended Kac table. Instead a ``shifted'' extended Kac table is shown to be relevant. Augmenting the previously known logarithmic theory based on Cardy's crossing probability by this field, a larger theory is obtained, in which new classes of indecomposable rank-2 modules are present. No rank-3 Jordan cells are yet observed. A highly non-trivial check of the identification of Watts' field is that no Gurarie-Ludwig-type inconsistencies are observed in this augmentation. The article concludes with an extended discussion of various topics related to extending these results including projectivity, boundary sectors and inconsistency loopholes.

  20. Coil motion effects in watt balances: a theoretical check

    Science.gov (United States)

    Li, Shisong; Schlamminger, Stephan; Haddad, Darine; Seifert, Frank; Chao, Leon; Pratt, Jon R.

    2016-04-01

    A watt balance is a precision apparatus for the measurement of the Planck constant that has been proposed as a primary method for realizing the unit of mass in a revised International System of Units. In contrast to an ampere balance, which was historically used to realize the unit of current in terms of the kilogram, the watt balance relates electrical and mechanical units through a virtual power measurement and has far greater precision. However, because the virtual power measurement requires the execution of a prescribed motion of a coil in a fixed magnetic field, systematic errors introduced by horizontal and rotational deviations of the coil from its prescribed path will compromise the accuracy. We model these potential errors using an analysis that accounts for the fringing field in the magnet, creating a framework for assessing the impact of this class of errors on the uncertainty of watt balance results.

  1. Thermal fission rates with temperature dependent fission barriers

    CERN Document Server

    Zhu, Yi

    2016-01-01

    \\item[Background] The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. \\item[Purpose] We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and mass parameters. \\item[Methods] The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures ...

  2. Caracterización y control del regulador de WATT

    OpenAIRE

    Carrillo Salagre, Isabel

    2011-01-01

    El propósito de este proyecto es hacer un análisis detallado del regulador de Watt. Desde un punto de vista didáctico, se plantea fabricar un modelo del regulador de Watt. En la actualidad, los alumnos que realizan prácticas de control manejan los controladores mediante un software determinado, dónde modifican unos parámetros y obtienen unos resultados, de esta forma eléctrica no acaban de comprender su funcionamiento. El objetivo de la construcción del regulador es mostrar físicamente en...

  3. Particle Swarm Optimization with Watts-Strogatz Model

    Science.gov (United States)

    Zhu, Zhuanghua

    Particle swarm optimization (PSO) is a popular swarm intelligent methodology by simulating the animal social behaviors. Recent study shows that this type of social behaviors is a complex system, however, for most variants of PSO, all individuals lie in a fixed topology, and conflict this natural phenomenon. Therefore, in this paper, a new variant of PSO combined with Watts-Strogatz small-world topology model, called WSPSO, is proposed. In WSPSO, the topology is changed according to Watts-Strogatz rules within the whole evolutionary process. Simulation results show the proposed algorithm is effective and efficient.

  4. The nature of singlet exciton fission in carotenoid aggregates.

    Science.gov (United States)

    Musser, Andrew J; Maiuri, Margherita; Brida, Daniele; Cerullo, Giulio; Friend, Richard H; Clark, Jenny

    2015-04-22

    Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region of the solar spectrum to capture the energy generally lost as waste heat. However, many questions remain about the underlying fission mechanism. The relation between intermolecular geometry and singlet fission rate and yield is poorly understood and remains one of the most significant barriers to the design of new singlet fission sensitizers. Here we explore the structure-property relationship and examine the mechanism of singlet fission in aggregates of astaxanthin, a small polyene. We isolate five distinct supramolecular structures of astaxanthin generated through self-assembly in solution. Each is capable of undergoing intermolecular singlet fission, with rates of triplet generation and annihilation that can be correlated with intermolecular coupling strength. In contrast with the conventional model of singlet fission in linear molecules, we demonstrate that no intermediate states are involved in the triplet formation: instead, singlet fission occurs directly from the initial 1B(u) photoexcited state on ultrafast time scales. This result demands a re-evaluation of current theories of polyene photophysics and highlights the robustness of carotenoid singlet fission.

  5. Fission Measurements with Dance

    Science.gov (United States)

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

    2008-08-01

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

  6. Swisswoodhouse -a building for the 2000-Watt Society; Swisswoodhouse - ein Gebaeude fuer die 2000-Watt-Gesellschaft - Synthesebericht

    Energy Technology Data Exchange (ETDEWEB)

    Menz, T.; Wallbaum, H.; Hardziewski, R.; Graf, S.; Trachsel-Gerber, N.; Koschenz, M.; Guentert, P.

    2009-05-15

    This report deals with a building conceived to meet the requirements of the Swiss '2000-Watt Society' concept. The aims of the project are discussed which feature the demonstration of a forward-looking architectural layout, comfortable and healthy living, environmentally compatible and low resource consumption, standardisation and cost reduction. The report contains seven sections: Basics of the '2000-Watt Society' concept, optimisation of the whole building system, investor-orientated rating, use-oriented monitoring system, the development of the building, standardised building technology and, finally, a description of this pilot project.

  7. A Simple Watt Balance for the Absolute Determination of Mass

    Science.gov (United States)

    Quinn, Terry; Quinn, Lucas; Davis, Richard

    2013-01-01

    A watt balance is an electromechanical device that allows a mass to be determined in terms of measurable electrical and mechanical quantities, themselves traceable to the fundamental constants of physics. International plans are well advanced to redefine the unit of mass, the kilogram, in terms of a fixed numerical value for the Planck constant. A…

  8. 300-Watt Power Source Development at the Jet Propulsion Laboratory

    Science.gov (United States)

    Valdez, Thomas I.

    2005-01-01

    This viewgraph presentation reviews the JPL program to develop a 300 Watt direct methanol fuel cell. The immediate use of the fuel cell is to power test instrumentation on armored vehicles. It reviews the challenges, the system design and the system demonstration.

  9. A Simple Watt Balance for the Absolute Determination of Mass

    Science.gov (United States)

    Quinn, Terry; Quinn, Lucas; Davis, Richard

    2013-01-01

    A watt balance is an electromechanical device that allows a mass to be determined in terms of measurable electrical and mechanical quantities, themselves traceable to the fundamental constants of physics. International plans are well advanced to redefine the unit of mass, the kilogram, in terms of a fixed numerical value for the Planck constant. A…

  10. Stray capacitances in the watt balance operation: electrostatic forces

    CERN Document Server

    Quagliotti, Danilo

    2014-01-01

    In a watt balance, stray capacitances exist between the coil and the magnet. Since the electric current flowing in the coil originates a difference between the coil and magnet electric-potentials, their electrostatic interactions must be taken into account. This paper reports the results of a finite element analysis of the forces acting on the coil.

  11. Stray capacitances in the watt balance operation: electrostatic forces

    DEFF Research Database (Denmark)

    Quagliotti, Danilo; Mana, G.

    2014-01-01

    In a watt balance, stray capacitances exist between the coil and the magnet. Since the electric current flowing in the coil creates a difference in electric potentials between the coil and magnet, their electrostatic interactions must be taken into account. This paper reports the results of a fin...

  12. Theology and psychology – the interdisciplinary work of Fraser Watts

    Directory of Open Access Journals (Sweden)

    Willem J. Smith

    2005-10-01

    Full Text Available In the preface to his book, Theology and Psychology, Fraser Watts, a lecturer in Theology and Natural Science at the University of Cambridge, states that he approaches “… the interface between theology and psychology by looking at each discipline from the perspective of the other. This includes a religious perspective on several current hot topics in psychology, such as evolution, neuroscience, and computer intelligence. I also consider theological topics like divine action, salvation history and eschatology, in each case using the psychological perspective in a different way”. By taking an interdisciplinary approach, Watts aims at proposing a psychology of religious experience. He considers theology to be the rational reflection on the Christian tradition. When exponents of this tradition are in dialogue with exponents of psychology, the focus falls on human nature. Watts admits that a certain lack of competence in one of the two disciplines can be a problem when working in an interdisciplinary way. However, he is willing to take the risk. Watts worked in psychology for 25 years and was also involved with a medical research council, before taking up a position at the Faculty of Divinity, University of Cambridge.

  13. Applications of Event-by-Event Fission Modeling with FREYA

    Directory of Open Access Journals (Sweden)

    Vogt R.

    2012-02-01

    Full Text Available The recently developed code FREYA (Fission Reaction Event Yield Algorithm generates large samples of complete fission events, consisting of two receding product nuclei as well as a number of neutrons and photons, all with complete kinematic information. Thus it is possible to calculate arbitrary correlation observables whose behavior may provide unique insight into the fission process. We first discuss the present status of FREYA, which has now been extended to include spontaneous fission. Concentrating on 239Pu(nth,f, 240Pu(sf and 252Cf(sf, we discuss the neutron multiplicity correlations, the dependence of the neutron energy spectrum on the neutron multiplicity, and the relationship between the fragment kinetic energy and the number of neutrons and their energies. We also suggest novel fission observables that could be measured with modern detectors.

  14. Angular Anisotropy of the Fission Fragments in the Dinuclear System Mo del

    Institute of Scientific and Technical Information of China (English)

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

    2015-01-01

    A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system (DNS) model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the angular distribution of fission fragments for the neutron–induced fission of 239Pu.

  15. Comparison of {sup 235}U fission cross sections in JENDL-3.3 and ENDF/B-VI

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, Toshihiko [Kyushu Univ., Fukuoka (Japan); Carlson, Allan D. [National Institute of Standards and Technology (United States); Matsunobu, Hiroyuki [Data Engineering, Inc., Fujisawa, Kanagawa (Japan); Nakagawa, Tsuneo; Shibata, Keiichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Talou, Patrick; Young, Philip G.; Chadwick, Mark B. [Los Alamos National Laboratory, Los Alamos, NM (United States)

    2002-01-01

    Comparisons of evaluated fission cross sections for {sup 235}U in JENDL-3.3 and ENDF/B-VI are carried out. The comparisons are made for both the differential and integral data. The fission cross sections as well as the fission ratios are compared with the experimental data in detail. Spectrum averaged cross sections are calculated and compared with the measurements. The employed spectra are the {sup 235}U prompt fission neutron spectrum, the {sup 252}Cf spontaneous fission neutron spectrum, and the neutron spectrum produced by a {sup 9}Be(d, xn) reaction. For {sup 235}U prompt fission neutron spectrum, the ENDF/B-VI evaluation reproduces experimental averaged cross sections. For {sup 252}Cf and {sup 9}Be(d, xn) neutron spectra, the JENDL-3.3 evaluation gives better results than ENDF/B-VI. (author)

  16. Improved Fission Neutron Data Base for Active Interrogation of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Pozzi, Sara; Czirr, J. Bart; Haight, Robert; Kovash, Michael; Tsvetkov, Pavel

    2013-11-06

    This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).

  17. True ternary fission

    Science.gov (United States)

    Vijayaraghavan, K. R.; Balasubramaniam, M.; von Oertzen, W.

    2015-04-01

    The study of the ternary fission of nuclei has received new interest recently. It is of general interest for nuclear dynamics, although the process is very rare. In the present work, we discuss the possibilities of true ternary fission (fragment masses A >30 ) in 252Cf for different mass splits. These mass splits are strongly favored in a collinear geometry. Based on the three cluster model (TCM), it is shown that the true ternary fission into fragments with almost equal masses is one of the possible fission modes in 252Cf . For general decays it is shown that the formation of the lightest fragment at the center has the highest probability. Further the formation of tin isotopes and/or other closed shell fragments are favored. For the decay products the presence of closed shell nuclei among the three fragments enhances the decay probabilities.

  18. Fission in a Plasma

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-26

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

  19. Alignment of the magnetic circuit of the BIPM watt balance

    Science.gov (United States)

    Bielsa, F.; Lu, Y. F.; Lavergne, T.; Kiss, A.; Fang, H.; Stock, M.

    2015-12-01

    The International Bureau of Weights and Measures (BIPM) is developing a watt balance for the forthcoming redefinition of the kilogram. An improved version of the apparatus, based on a new closed magnetic circuit is now being assembled. The new apparatus will significantly reduce the type B uncertainty due to misalignment of the magnetic circuit as this work demonstrates. We present two techniques recently developed to accurately align the magnetic field of the circuit perpendicular to the direction defined by the local acceleration of gravity. Uncertainty below 30 μrad was achieved for both techniques which fulfils the requirements for the BIPM watt balance to enable a Planck constant determination at the 1  ×  10-8 level.

  20. Prompt γ-ray production in neutron-induced fission of 239Pu

    Science.gov (United States)

    Ullmann, J. L.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Kawano, T.; Lee, H. Y.; O'Donnell, J. M.; Hayes, A. C.; Stetcu, I.; Taddeucci, T. N.; Talou, P.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Chyzh, A.; Gostic, J.; Henderson, R.; Kwan, E.; Wu, C. Y.

    2013-04-01

    Background: The prompt gamma-ray spectrum from fission is important for understanding the physics of nuclear fission, and also in applications involving fission. Relatively few measurements of the prompt gamma spectrum from 239Pu(n,f) have been published.Purpose: This experiment measured the multiplicity, individual gamma energy spectrum, and total gamma energy spectrum of prompt fission gamma rays from 239Pu(n,f) in the neutron energy range from thermal to 30 keV, to test models of fission and to provide information for applications.Method: Gamma rays from neutron-induced fission of 239Pu were measured using the DANCE gamma-ray calorimeter. Fission events were tagged by detecting fission products in a parallel-plate avalanche counter in the center of DANCE. The measurements were corrected for detector response using a geant4 model of DANCE. A detailed analysis for the gamma rays from the 1+ resonance complex at 10.93 eV is presented.Results: A six-parameter analytical parametrization of the fission gamma-ray spectrum was obtained. A Monte Carlo Hauser-Feshbach calculation provided good general agreement with the data, but some differences remain to be resolved.Conclusions: An analytic parametrization can be made of the gamma-ray multiplicity, energy distribution, and total-energy distribution for the prompt gamma rays following neutron-induced fission of 239Pu. This parametrization may be useful for applications. Modern Monte Carlo Hauser-Feshbach calculations can do a good job of calculating the fission gamma-ray emission spectrum, although some details remain to be understood.

  1. Two-watt, 4-Kelvin closed cycle refrigerator performance

    Science.gov (United States)

    Britcliffe, M.

    1987-01-01

    A 2-watt, 4-K helium refrigerator using the Gifford-McMahon/Joule Thomson cycle is described. The unit features a removable displacer cylinder and high-efficiency, low-pressure drop heat exchangers. These improvements result in a 100 percent increase in cooling power over the existing Deep Space Network system. The effects of the heat exchanger efficiency and Gifford-McMahon expander performance on refrigerator capacity are also discussed.

  2. Thermal fission rates with temperature dependent fission barriers

    Science.gov (United States)

    Zhu, Yi; Pei, J. C.

    2016-08-01

    Background: The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. Purpose: We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and collective mass parameters. Methods: The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures has to incorporate the reflection above barriers. Results: Our results of spontaneous fission rates reasonably agree with other studies and experiments. The temperature dependencies of fission barrier heights and curvatures have been discussed. The temperature dependent behaviors of mass parameters have also been discussed. The thermal fission rates from low to high temperatures with a smooth connection have been given by different approaches. Conclusions: Since the temperature dependencies of fission barrier heights and curvatures, and the mass parameters can vary rapidly for different nuclei, the microscopic descriptions of thermal fission rates are very valuable. Our studies without free parameters provide a consistent picture to study various fissions such as that in fast-neutron reactors, astrophysical environments, and fusion reactions for superheavy nuclei.

  3. Calculation of 239Pu fission observables in an event-by-event simulation

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, R; Randrup, J; Pruet, J; Younes, W

    2010-03-31

    The increased interest in more exclusive fission observables has demanded more detailed models. We describe a new computational model, FREYA, that aims to meet this need by producing large samples of complete fission events from which any observable of interest can then be extracted consistently, including any interesting correlations. The various model assumptions are described and the potential utility of the model is illustrated. As a concrete example, we use formal statistical methods, experimental data on neutron production in neutron-induced fission of {sup 239}Pu, along with FREYA, to develop quantitative insights into the relation between reaction observables and detailed microscopic aspects of fission. Current measurements of the mean number of prompt neutrons emitted in fission taken together with less accurate current measurements for the prompt post-fission neutron energy spectrum, up to the threshold for multi-chance fission, place remarkably fine constraints on microscopic theories.

  4. Material recognition using fission gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Viesti, G. [Dipartimento di Fisica dell' Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy)], E-mail: giuseppe.viesti@pd.infn.it; Sajo-Bohus, L. [Universidad Simon-Bolivar, Laboratorio Fisica Nuclear, Apartado 8900, 1080 A. Caracas (Venezuela, Bolivarian Republic of); Fabris, D. [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Lunardon, M.; Moretto, S. [Dipartimento di Fisica dell' Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Nebbia, G.; Pesente, S. [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2009-07-21

    Material recognition is studied by measuring the transmission spectrum of {sup 252}Cf fission gamma rays in the energy range E{sub {gamma}}=0.1-5.5 MeV for 0.1-MeV-wide energy bins through a number of elementary samples. Each transmitted spectrum is compared with a library of reference spectra for different elements providing the possibility of material identification. In case of elemental samples with known thickness, this procedure allows the identification of the sample Z with uncertainty typically lower than 3 Z-units over a wide range of elements. Applications to composite materials are also reported.

  5. Fission waves can oscillate

    CERN Document Server

    Osborne, Andrew G

    2016-01-01

    Under the right conditions, self sustaining fission waves can form in fertile nuclear materials. These waves result from the transport and absorption of neutrons and the resulting production of fissile isotopes. When these fission, additional neutrons are produced and the chain reaction propagates until it is poisoned by the buildup of fission products. It is typically assumed that fission waves are soliton-like and self stabilizing. However, we show that in uranium, coupling of the neutron field to the 239U->239Np->239Pu decay chain can lead to a Hopf bifurcation. The fission reaction then ramps up and down, along with the wave velocity. The critical driver for the instability is a delay, caused by the half-life of 239U, between the time evolution of the neutron field and the production of 239Pu. This allows the 239Pu to accumulate and burn out in a self limiting oscillation that is characteristic of a Hopf bifurcation. Time dependent results are obtained using a numerical implementation of a reduced order r...

  6. Modernizing the Fission Basis

    Science.gov (United States)

    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.

  7. Fission Product Library and Resource

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-29

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

  8. Fission modelling with FIFRELIN

    Energy Technology Data Exchange (ETDEWEB)

    Litaize, Olivier; Serot, Olivier; Berge, Leonie [CEA, DEN, DER, SPRC, Saint Paul Lez Durance (France)

    2015-12-15

    The nuclear fission process gives rise to the formation of fission fragments and emission of particles (n,γ, e{sup -}). 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

  9. Fission modelling with FIFRELIN

    Science.gov (United States)

    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

  10. Angular distribution in the neutron-induced fission of actinides

    Directory of Open Access Journals (Sweden)

    Leong L.S.

    2013-12-01

    Full Text Available Above 1 MeV of incident neutron energy the fission fragment angular distribution (FFAD has generally a strong anisotropic behavior due to the combination of the incident orbital momentum and the intrinsic spin of the fissioning nucleus. This effect has to be taken into account for the efficiency estimation of devices used for fission cross section measurements. In addition it bears information on the spin deposition mechanism and on the structure of transitional states. We designed and constructed a detection device, based on Parallel Plate Avalanche Counters (PPAC, for measuring the fission fragment angular distributions of several isotopes, in particular 232Th. The measurement has been performed at n_TOF at CERN taking advantage of the very broad energy spectrum of the neutron beam. Fission events were recognized by back to back detection in coincidence in two position-sensitive detectors surrounding the targets. The detection efficiency, depending mostly on the stopping of fission fragments in backings and electrodes, has been computed with a Geant4 simulation and validated by the comparison to the measured case of 235U below 3 keV where the emission is isotropic. In the case of 232Th, the result is in good agreement with previous data below 10 MeV, with a good reproduction of the structures associated to vibrational states and the opening of second chance fission. In the 14 MeV region our data are much more accurate than previous ones which are broadly scattered.

  11. Fission Product Yields of 233U, 235U, 238U and 239Pu in Fields of Thermal Neutrons, Fission Neutrons and 14.7-MeV Neutrons

    Science.gov (United States)

    Laurec, J.; Adam, A.; de Bruyne, T.; Bauge, E.; Granier, T.; Aupiais, J.; Bersillon, O.; Le Petit, G.; Authier, N.; Casoli, P.

    2010-12-01

    The yields of more than fifteen fission products have been carefully measured using radiochemical techniques, for 235U(n,f), 239Pu(n,f) in a thermal spectrum, for 233U(n,f), 235U(n,f), and 239Pu(n,f) reactions in a fission neutron spectrum, and for 233U(n,f), 235U(n,f), 238U(n,f), and 239Pu(n,f) for 14.7 MeV monoenergetic neutrons. Irradiations were performed at the EL3 reactor, at the Caliban and Prospero critical assemblies, and at the Lancelot electrostatic accelerator in CEA-Valduc. Fissions were counted in thin deposits using fission ionization chambers. The number of fission products of each species were measured by gamma spectrometry of co-located thick deposits.

  12. Discoveries of isotopes by fission

    Indian Academy of Sciences (India)

    M Thoennessen

    2015-09-01

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

  13. Fission dynamics of hot nuclei

    Indian Academy of Sciences (India)

    Santanu Pal; Jhilam Sadhukhan

    2014-04-01

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

  14. Student Experiments in Spontaneous Fission.

    Science.gov (United States)

    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…

  15. LARGE GAMMA ANISOTROPY OBSERVED IN THE CF-252 SPONTANEOUS-FISSION PROCESS

    NARCIS (Netherlands)

    VANDERPLOEG, H; BACELAR, JC; VANDENBERG, T; IACOB, VE; JONGMAN, [No Value; VANDERWOUDE, A

    1992-01-01

    The energy spectrum and the angular dependence relative to the fission direction of photons in the energy region between 2 and 40 MeV have been measured for the spontaneous fission of Cf-252. A large anisotropy was found in the energy region 8 to 12 MeV implying that photons in this region are emitt

  16. 500 Watt Diesel Fueled TPV Portable Power Supply

    Science.gov (United States)

    Horne, W. E.; Morgan, M. D.; Sundaram, V. S.; Butcher, T.

    2003-01-01

    A test-bed 500 watt diesel fueled thermophotovoltaic (TPV) portable power supply is described. The goal of the design is a compact, rugged field portable unit weighing less than 15 pounds without fuel. The conversion efficiency goal is set at 15% fuel energy to electric energy delivered to an external load at 24 volts. A burner/recuperator system has been developed to meet the objectives of high combustion air preheat temperatures with a compact heat exchanger, low excess air operation, and high convective heat transfer rates to the silicon carbide emitter surface. The burner incorporates a air blast atomizer with 100% of the combustion air passing through the nozzle. Designed firing rate of 2900 watts at 0.07 gallons of oil per hour. This incorporates a single air supply dc motor/fan set and avoids the need for a system air compressor. The recuperator consists of three annular, concentric laminar flow passages. Heat from the combustion of the diesel fuel is both radiantly and convectively coupled to the inside wall of a cylindrical silicon carbide emitter. The outer wall of the emitter then radiates blackbody energy at the design temperature of 1400°C. The cylindrical emitter is enclosed in a quartz envelope that separates it from the photovoltaic (PV) cells. Spectral control is accomplished by a resonant mesh IR band-pass filter placed between the emitter and the PV array. The narrow band of energy transmitted by the filter is intercepted and converted to electricity by an array of GaSb PV cells. The array consists of 216 1-cm × 1-cm GaSb cells arranged into series and parallel arrays. An array of heat pipes couple the PV cell arrays to a heat exchanger which is cooled by forced air convection. A brief status of the key TPV technologies is presented followed by data characterizing the performance of the 500 watt TPV system.

  17. Characterization of flexure hinges for the French watt balance experiment

    Directory of Open Access Journals (Sweden)

    Pinot Patrick

    2014-01-01

    Full Text Available In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1 an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2 a mass comparator to determine the bending stiffness of unloaded pivots; 3 a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.

  18. High Throughput 600 Watt Hall Effect Thruster for Space Exploration

    Science.gov (United States)

    Szabo, James; Pote, Bruce; Tedrake, Rachel; Paintal, Surjeet; Byrne, Lawrence; Hruby, Vlad; Kamhawi, Hani; Smith, Tim

    2016-01-01

    A nominal 600-Watt Hall Effect Thruster was developed to propel unmanned space vehicles. Both xenon and iodine compatible versions were demonstrated. With xenon, peak measured thruster efficiency is 46-48% at 600-W, with specific impulse from 1400 s to 1700 s. Evolution of the thruster channel due to ion erosion was predicted through numerical models and calibrated with experimental measurements. Estimated xenon throughput is greater than 100 kg. The thruster is well sized for satellite station keeping and orbit maneuvering, either by itself or within a cluster.

  19. Characterization of flexure hinges for the French watt balance experiment

    Science.gov (United States)

    Pinot, Patrick; Genevès, Gérard

    2014-08-01

    In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1) an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2) a mass comparator to determine the bending stiffness of unloaded pivots; 3) a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.

  20. Dynamical features of nuclear fission

    Indian Academy of Sciences (India)

    Santanu Pal

    2015-08-01

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

  1. Fission modes of mercury isotopes

    CERN Document Server

    Warda, M; Nazarewicz, W

    2012-01-01

    Recent experiments on beta-delayed fission in the mercury-lead region and the discovery of asymmetric fission in $^{180}$Hg [1] have stimulated renewed interest in the mechanism of fission in heavy nuclei. Here we study fission modes and fusion valleys in $^{180}$Hg and $^{198}$Hg using the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals. We show that the observed transition from asymmetric fission in $^{180}$Hg towards more symmetric distribution of fission fragments in $^{198}$Hg can be explained in terms of competing fission modes of different geometries that are governed by shell effects in pre-scission configurations. The density distributions at scission configurations are studied and related to the experimentally observed mass splits.

  2. Sensitivity studies of spin cut-off models on fission fragment observables

    Directory of Open Access Journals (Sweden)

    Thulliez L.

    2016-01-01

    Full Text Available A fission fragment de-excitation code, FIFRELIN, is being developed at CEA Cadarache. It allows probing the characteristics of the prompt emitted particles, neutrons and gammas, during the de-excitation process of fully accelerated fission fragments. The knowledge of the initial states of the fragments is important to accurately reproduce the fission fragment observables. In this paper a sensitivity study of various spin cut-off models, completely defining the initial fission fragment angular momentum distribution has been performed. This study shows that the choice of the model has a significant impact on gamma observables such as spectrum and multiplicity and almost none on the neutron observables.

  3. Fission Matrix Capability for MCNP Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-05

    In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a

  4. ORNL Trusted Corridors Project: Watts Bar Dam Inland Waterway Project

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Randy M [ORNL; Gross, Ian G [ORNL; Smith, Cyrus M [ORNL; Hill, David E [ORNL

    2011-11-01

    Radiation has existed everywhere in the environment since the Earth's formation - in rocks, soil, water, and plants. The mining and processing of naturally occurring radioactive materials for use in medicine, power generation, consumer products, and industry inevitably generate emissions and waste. Radiological measuring devices have been used by industry for years to measure for radiation in undesired locations or simply identify radioactive materials. Since the terrorist attacks on the United States on 9-11-01 these radiation measuring devices have proliferated in many places in our nation's commerce system. DOE, TVA, the Army Corps and ORNL collaborated to test the usefulness of these devices in our nation's waterway system on this project. The purpose of the Watts Bar Dam ORNL Trusted Corridors project was to investigate the security, safety and enforcement needs of local, state and federal government entities for state-of-the-art sensor monitoring in regards to illegal cargo including utilization of the existing infrastructure. TVA's inland waterways lock system is a recognized and accepted infrastructure by the commercial carrier industry. Safety Monitoring activities included tow boat operators, commercial barges and vessels, recreational watercraft and their cargo, identification of unsafe vessels and carriers, and, monitoring of domestic and foreign commercial vessels and cargo identification. Safety Enforcement activities included cargo safety, tracking, identification of hazardous materials, waterway safety regulations, and hazardous materials regulations. Homeland Security and Law Enforcement Applications included Radiological Dispersive Devices (RDD) identification, identification of unsafe or illicit transport of hazardous materials including chemicals and radiological materials, and screening for shipments of illicit drugs. In the Fall of 2005 the SensorNet funding for the project expired. After several unsuccessful attempts to

  5. Watts Bar Unit 2 Startup Results with VERA

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, Andrew T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Collins, Benjamin S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gentry, Cole A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Stimpson, Shane G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ritchie, John A. [Tennessee Valley Authority (TVA), Knoxville, TN (United States)

    2017-03-01

    CASL members TVA, Westinghouse, and Oak Ridge National Laboratory have successfully completed a detailed simulation of the initial startup of Watts Bar Nuclear Unit 2 (WBN2) using the advanced reactor simulation tools known as VERA. WBN2 is the first commercial power reactor to join the nation’s electrical grid in over two decades, and the modern core design and availability of data make it an excellent benchmark for CASL. Calculations were performed three months prior to the startup, and in the first blind application of VERA to a new reactor, predicted criticality and physics parameters very close to those later measured by TVA. Subsequent calculations with the latest version of VERA and using exact measurement conditions improved the results even further.

  6. Evaluation and compilation of fission product yields 1993

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-12-31

    This document is the latest in a series of compilations of fission yield data. Fission yield measurements reported in the open literature and calculated charge distributions have been used to produce a recommended set of yields for the fission products. The original data with reference sources, and the recommended yields axe presented in tabular form. These include many nuclides which fission by neutrons at several energies. These energies include thermal energies (T), fission spectrum energies (F), 14 meV High Energy (H or HE), and spontaneous fission (S), in six sets of ten each. Set A includes U235T, U235F, U235HE, U238F, U238HE, Pu239T, Pu239F, Pu241T, U233T, Th232F. Set B includes U233F, U233HE, U236F, Pu239H, Pu240F, Pu241F, Pu242F, Th232H, Np237F, Cf252S. Set C includes U234F, U237F, Pu240H, U234HE, U236HE, Pu238F, Am241F, Am243F, Np238F, Cm242F. Set D includes Th227T, Th229T, Pa231F, Am241T, Am241H, Am242MT, Cm245T, Cf249T, Cf251T, Es254T. Set E includes Cf250S, Cm244S, Cm248S, Es253S, Fm254S, Fm255T, Fm256S, Np237H, U232T, U238S. Set F includes Cm243T, Cm246S, Cm243F, Cm244F, Cm246F, Cm248F, Pu242H, Np237T, Pu240T, and Pu242T to complete fission product yield evaluations for 60 fissioning systems in all. This report also serves as the primary documentation for the second evaluation of yields in ENDF/B-VI released in 1993.

  7. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    D N Poenaru; R A Gherghescu

    2015-09-01

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

  8. Hidden systematics of fission channels

    Directory of Open Access Journals (Sweden)

    Schmidt Karl-Heinz

    2013-12-01

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

  9. Fission yield measurements at IGISOL

    Directory of Open Access Journals (Sweden)

    Lantz M.

    2016-01-01

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

  10. 78 FR 53494 - Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams

    Science.gov (United States)

    2013-08-29

    ... Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams AGENCY: Tennessee... preferred alternative in its final environmental impact statement (EIS) for the dam safety modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams. The notice of availability (NOA) of the...

  11. The Frequency-Watt Function: Simulation and Testing for the Hawaiian Electric Companies

    Energy Technology Data Exchange (ETDEWEB)

    Hoke, Anderson F. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nelson, Austin A. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Tan, Jin [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Mahmud, Rasel [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Elkhatib, Mohamed [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Antonio, Chris [Hawaiian Electric Companies, Honolulu, HI (United States); Arakawa, Dean [Hawaiian Electric Companies, Honolulu, HI (United States); Fong, Ken [Hawaiian Electric Companies, Honolulu, HI (United States)

    2017-07-25

    This interim report describes research related to frequency-watt control of solar photovoltaic (PV) inverters conducted under the U.S. Department of Energy's Grid Modernization Laboratory Consortium (GMLC) by a regional partnership for Hawaii. The purpose of this report is to inform an ongoing discussion around frequency-watt control activation in Hawaii.

  12. The SPIDER fission fragment spectrometer for fission product yield measurements

    Energy Technology Data Exchange (ETDEWEB)

    Meierbachtol, K.; Tovesson, F. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shields, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States); Arnold, C. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Blakeley, R. [University of New Mexico, Albuquerque, NM 87131 (United States); Bredeweg, T.; Devlin, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hecht, A.A.; Heffern, L.E. [University of New Mexico, Albuquerque, NM 87131 (United States); Jorgenson, J.; Laptev, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mader, D. [University of New Mexico, Albuquerque, NM 87131 (United States); O' Donnell, J.M.; Sierk, A.; White, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2015-07-11

    The SPectrometer for Ion DEtermination in fission Research (SPIDER) has been developed for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E–2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). The SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using {sup 229}Th and {sup 252}Cf radioactive decay sources. For commissioning, the fully assembled system measured fission products from spontaneous fission of {sup 252}Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Mass yield results measured from {sup 252}Cf spontaneous fission products are reported from an E–v measurement.

  13. Measurement of Fission Product Yields from Fast-Neutron Fission

    Science.gov (United States)

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

    2014-09-01

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

  14. Fission neutrons experiments, evaluation, modeling and open problems

    CERN Document Server

    Kornilov, Nikolay

    2014-01-01

    Although the fission of heavy nuclei was discovered over 75 years ago, many problems and questions still remain to be addressed and answered. The reader will be presented with an old, but persistent problem of this field: The contradiction between Prompt Fission Neutron (PFN) spectra measured with differential (microscopic) experiments and integral (macroscopic and benchmark) experiments (the Micro-Macro problem). The difference in average energy is rather small ~3% but it is stable and we cannot explain the difference due to experimental uncertainties. Can we measure the PFN spectrum with hig

  15. Request for One-Time Shipment of 32 Watt PU-328 Source in 9968 Packaging

    Energy Technology Data Exchange (ETDEWEB)

    Massey, W.M.

    1998-11-25

    The 9968 package is designed for surface shipment of fissile and other radioactive materials where a high degree of double containment is required. The use of the 9968 radioactive material package for a one time shipment of a 32 watt heat source versus the SARP approved maximum 30 watt heat source is addressed in this report. The analyses show that the small increase in heat load from 30 watts to 32 watts does not substantially increase internal temperatures or pressures that would approach limits for the package. Also, the weight of the content is within the current 9968 package limits. It is concluded that the 32-watt heat source can be safely shipped in the 9968 package and therefore a waiver to ship the source is justified.

  16. Energy from nuclear fission(*

    Directory of Open Access Journals (Sweden)

    Ripani M.

    2015-01-01

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

  17. Membrane biology: fission behind BARs.

    Science.gov (United States)

    Haucke, Volker

    2012-06-05

    Membrane bending is accomplished in part by amphipathic helix insertion into the bilayer and the assembly of BAR domain scaffolds preparing the membrane for fission. Two recent studies highlight the roles of amphipathic helices and BAR scaffolds in membrane fission and establish the structural basis of membrane bending by the N-BAR protein endophilin.

  18. Fission throughout the periodic table

    Energy Technology Data Exchange (ETDEWEB)

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

    1989-04-01

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

  19. Investigation of inconsistent ENDF/B-VII.1 independent and cumulative fission product yields with proposed revisions

    Energy Technology Data Exchange (ETDEWEB)

    Pigni, Marco T [ORNL; Francis, Matthew W [ORNL; Gauld, Ian C [ORNL

    2015-01-01

    A recent implementation of ENDF/B-VII. independent fission product yields and nuclear decay data identified inconsistencies in the data caused by the use of updated nuclear scheme in the decay sub-library that is not reflected in legacy fission product yield data. Recent changes in the decay data sub-library, particularly the delayed neutron branching fractions, result in calculated fission product concentrations that are incompatible with the cumulative fission yields in the library, and also with experimental measurements. A comprehensive set of independent fission product yields was generated for thermal and fission spectrum neutron induced fission for 235,238U and 239,241Pu in order to provide a preliminary assessment of the updated fission product yield data consistency. These updated independent fission product yields were utilized in the ORIGEN code to evaluate the calculated fission product inventories with experimentally measured inventories, with particular attention given to the noble gases. An important outcome of this work is the development of fission product yield covariance data necessary for fission product uncertainty quantification. The evaluation methodology combines a sequential Bayesian method to guarantee consistency between independent and cumulative yields along with the physical constraints on the independent yields. This work was motivated to improve the performance of the ENDF/B-VII.1 library in the case of stable and long-lived cumulative yields due to the inconsistency of ENDF/B-VII.1 fission p;roduct yield and decay data sub-libraries. The revised fission product yields and the new covariance data are proposed as a revision to the fission yield data currently in ENDF/B-VII.1.

  20. Ternary fission and cluster radioactivities

    CERN Document Server

    Poenaru, D N; Greiner, W; Gherghescu, R A; Hamilton, J H; Ramayya, A V

    2002-01-01

    Ternary fission yield for different kinds of light particle accompanied fission processes is compared to the Q-values for the corresponding cold phenomena, showing a striking correlation. The experimental evidence for the existence of a quasimolecular state in sup 1 sup 0 Be accompanied fission of sup 2 sup 5 sup 2 Cf may be explained using a three-center phenomenological model which generates a third minimum in the deformation energy at a separation distance very close to the touching point. This model is a natural extension of the unified approach to three groups of binary decay modes (cold fission, cluster radioactivities and alpha decay), illustrated by sup 2 sup 3 sup 4 U decay modes, and the alpha valley on the potential energy surfaces of sup 1 sup 0 sup 6 Te. New measurements of cluster decay modes, confirming earlier predictions within analytical superasymmetric fission model, are included in a comprehensive half-life systematics. (authors)

  1. Decay modes in spontaneous fission

    CERN Document Server

    Gönnenwein, F

    1999-01-01

    Spontaneous fission (SF) is considered to be the choice reaction for studying the influence of shell and pairing effects in fission in general, and in particular their impact on the mass and energy distributions of fission fragments. For the time being some 35 SF reactions have been analysed in detail for elements ranging from Pu up to Rf. Going from the lighter to the heavier actinides both, the distributions of fragment mass (or charge) and of total kinetic energy undergo dramatic changes. It is observed in experiment, however, that these distributions may be well described as a superposition of a few fission modes, each with its own characteristic mass an energy pattern. The experimental modes are traced in theory to fine structures in the potential energy surface of a fissioning nucleus, provided shell and pairing corrections to the basic liquid drop model are accounted for.

  2. Narrow linewidth picosecond UV pulsed laser with mega-watt peak power.

    Science.gov (United States)

    Huang, Chunning; Deibele, Craig; Liu, Yun

    2013-04-08

    We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth picosecond pulse generator, and a fiber based preamplifier. A very high extinction ratio (45 dB) has been achieved by using an adaptive bias control of the EOM. The multi-stage Nd:YAG amplifier system allows a uniformly temporal shaping of the macropulse with a tunable pulse duration. The light output from the amplifier is converted to 355 nm, and over 1 MW peak power is obtained when the laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).

  3. Prompt Fission Neutron Spectra of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Capote, R; Chen, Y J; Hambsch, F J; Kornilov, N V; Lestone, J P; Litaize, O; Morillon, B; Neudecker, D; Oberstedt, S; Ohsawa, T; Smith, D. L.

    2016-01-01

    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. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS data are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data

  4. Comparison of Fission Product Yields and Their Impact

    Energy Technology Data Exchange (ETDEWEB)

    S. Harrison

    2006-02-01

    This memorandum describes the Naval Reactors Prime Contractor Team (NRPCT) Space Nuclear Power Program (SNPP) interest in determining the expected fission product yields from a Prometheus-type reactor and assessing the impact of these species on materials found in the fuel element and balance of plant. Theoretical yield calculations using ORIGEN-S and RACER computer models are included in graphical and tabular form in Attachment, with focus on the desired fast neutron spectrum data. The known fission product interaction concerns are the corrosive attack of iron- and nickel-based alloys by volatile fission products, such as cesium, tellurium, and iodine, and the radiological transmutation of krypton-85 in the coolant to rubidium-85, a potentially corrosive agent to the coolant system metal piping.

  5. Spontaneous fission properties of superheavy elements

    Energy Technology Data Exchange (ETDEWEB)

    Hessberger, F.P. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Helmholtz-Institut Mainz, Mainz (Germany)

    2017-04-15

    Spontaneous fission properties of transuranium isotopes are reviewed. Specific emphasis was laid on brief historical overviews of theoretical descriptions and experimental determination of basic properties as spontaneous fission half-lives, fission barriers, or total kinetic energy release in fission. Experimental spontaneous fission half-lives are compared with the results of recent theoretical predictions. Hindrance factors for spontaneous fission of odd-mass nuclei are discussed in context with the configuration (spin, parity) of the fissioning states and the change in energy of single particle levels at deformation. Kinetic energy release and mass distributions are discussed in the context of different fission modes, as symmetric and asymmetric or fission from elongated or compact shapes of the nascent fission fragments. An overview of recent fission barrier calculations of superheavy elements on the basis of macroscopic-microscopic models or self-consistent calculations is given, and the results are compared for selected examples. (orig.)

  6. Fission modes in charged-particle induced fission

    Energy Technology Data Exchange (ETDEWEB)

    Matthies, A.; Kotte, R.; Seidel, W.; Stary, F.; Wohlfarth, D. (Zentralinstitut fuer Kernforschung, Rossendorf bei Dresden (German Democratic Republic))

    1990-12-01

    The population of the three fission modes predicted by Brosa's multi-channel fission model for the uranium region was studied in different fissioning systems. They were produced bombarding {sup 232}Th and {sup 238}U targets by light charged particles with energies slightly above the Coulomb barrier. Though the maximum excitation energy of the compound nucleus amounted to about 22 MeV, the influences of various spherical and deformed nuclear shells on the mass and total kinetic energy distributions of fission fragments are still pronounced. The larger variances of the total kinetic energy distributions compared to those of thermal neutron induced fission were explained by temperature dependent fluctuations of the amount and velocity of alteration of the scission point elongation of the fissioning system. From the ratio of these variances the portion of the potential energy dissipated among intrinsic degrees of freedom before scission was deduced for the different fission channels. It was found that the excitation remaining after pre-scission neutron emission is mainly transferred into intrinsic heat and less into pre-scission kinetic energy. (orig.).

  7. Multi-Watt Small Radioisotope Thermoelectric Generator Conceptual Design Study

    Science.gov (United States)

    Determan, William R.; Otting, William; Frye, Patrick; Abelson, Robert; Ewell, Richard; Miyake, Bob; Synder, Jeff

    2007-01-01

    A need has been identified for a small, light-weight, reliable power source using a radioisotope heat source, to power the next generation of NASA's small surface rovers and exploration probes. Unit performance, development costs, and technical risk are key criteria to be used to select the best design approach. Because safety can be a major program cost and schedule driver, RTG designs should utilize the DOE radioisotope safety program's data base to the maximum extent possible. Other aspects important to the conceptual design include: 1) a multi-mission capable design for atmospheric and vacuum environments, 2) a module size based on one GPHS Step 2 module, 3) use of flight proven thermoelectric converter technologies, 4) a long service lifetime of up to 14 years, 5) maximize unit specific power consistent with all other requirements, and 6) be ready by 2013. Another critical aspect of the design is the thermal integration of the RTG with the rover or probe's heat rejection subsystem and the descent vehicle's heat rejection subsystem. This paper describes two multi-watt RTG design concepts and their integration with a MER-class rover.

  8. Ternary fission of (_

    Directory of Open Access Journals (Sweden)

    Dariush Naderi

    2017-05-01

    Full Text Available Using three cluster model, the ternary fission of (_"98" ^"252" Cf is studied. We applied collinear and equatorial configurations to study the ternary fission of (_"98" ^"252" Cf when three fragments are Sn, Ni and Ca. The potential energy of collinear and equatorial configurations is calculated. We calculated the potential energy for odd and even values of A3. Also, we compared the potential energy for (_"50" ^(A_"1" Sn+(_"28" ^(A_"2" Ni+(_"20" ^(A_"3" Ca and (_"50" ^(A_"1" -"1" Sn+(_"28" ^(A_"2" +"1" Ni+(_"20" ^(A_"3" Ca to investigate the influence of neutron numbers of three fragments. Obtained results show that for (_"50" ^(A_"1" Sn+(_"28" ^(A_"2" Ni+(_"20" ^(A_"3" Ca reaction with even A3 in collinear and equatorial configurations, the potential energy and penetration probability have ,respectively, minimum and maximum values in A3=48 whereas for odd values of A3 the minimum value for the potential energy and the maximum value of penetration probability take place in A3=49. For (_"50" ^(A_"1" -"1" Sn+(_"28" ^(A_"2" +"1" Ni+(_"20" ^(A_"3" Ca reactions in collinear and equatorial cases, the minimum value of potential energy and maximum value of penetration probability take place in A3=49 and A3=50, respectively, for even and odd values of A3. Also, among all the possible reactions the lowest value of potential energy and highest value of penetration probability happen for (_"50" ^132Sn+(_"28" ^72Ni+(_"20" ^48Ca configuration.

  9. The spectroscopy of fission fragments

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-31

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

  10. Intrinsic energy partition in fission

    Directory of Open Access Journals (Sweden)

    Mirea M.

    2013-03-01

    Full Text Available The intrinsic energy partition between two complementary fission fragments is investigated microscopically. The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234U parent nucleus.

  11. Measurements of fast neutron-induced fission data of Np-237

    Energy Technology Data Exchange (ETDEWEB)

    Win, Than; Saito, Keiichiro; Baba, Mamoru; Iwasaki, Tomohiko; Ibaraki, Masanobu; Miura, Takako; Sanami, Toshiya; Nauchi, Yasushi; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

    1998-03-01

    We have performed the following measurements for {sup 237}Np using the 4.5 MV Dynamitron accelerator of Tohoku University as the pulsed neutron source: (1) Prompt fission neutron spectrum for 0.62 MeV incident neutrons, and (2) Neutron-Induced fission cross-section between 10 and 100 keV. The prompt fission neutron spectrum was measured using TOF method with a heavily shielded NE213 scintillation detector. The Maxwellian temperature T{sub m} derived is 1.28 MeV, which is lower than that of 1.38 MeV in JENDL-3.2. The fission cross sections were measured between 10 - 100 keV. The results are between JENDL-3.2 and ENDF/B-VI. (author)

  12. Curves and tables of neutron cross sections of fission product nuclei in JENDL-3

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, Tsuneo [ed.

    1992-06-15

    Neutron cross sections of 172 nuclei in the fission product region stored in JENDL-3 are shown in graphs and tables. The evaluation work of these nuclei was made by the Fission Product Nuclear Data Working Group of the Japanese Nuclear Data Committee, in the neutron energy region from 10{sup {minus}5} eV to 20 MeV. Almost of the cross section data reproduced in graphs in this report. The cross section averaged over 38 energy intervals are listed in a table. Shown in order tables are thermal cross sections, resonance integrals, Maxwellian neutron flux average cross sections, fission spectrum average cross sections, 14-MeV cross sections, one group average cross sections in neutron flux of typical types of fission reactors and average cross sections in the 30-keV Maxwellian spectrum.

  13. The Watts-Strogatz network model developed by including degree distribution: theory and computer simulation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y W [Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Zhang, L F [Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Huang, J P [Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China)

    2007-07-20

    By using theoretical analysis and computer simulations, we develop the Watts-Strogatz network model by including degree distribution, in an attempt to improve the comparison between characteristic path lengths and clustering coefficients predicted by the original Watts-Strogatz network model and those of the real networks with the small-world property. Good agreement between the predictions of the theoretical analysis and those of the computer simulations has been shown. It is found that the developed Watts-Strogatz network model can fit the real small-world networks more satisfactorily. Some other interesting results are also reported by adjusting the parameters in a model degree-distribution function. The developed Watts-Strogatz network model is expected to help in the future analysis of various social problems as well as financial markets with the small-world property.

  14. A Liquid Hydrogen Cooler with a Cooling Capacity of 20 Watts Project

    Data.gov (United States)

    National Aeronautics and Space Administration — For the future spaceport and long-term storage of liquid hydrogen NASA requires cryocoolers that can provide cooling power in the range of 20 watts at 20 K. The...

  15. First measurements of the flux integral with the NIST-4 watt balance

    CERN Document Server

    Haddad, D; Chao, L S; Cao, A; Sineriz, G; Pratt, J R; Newell, D B; Schlamminger, S

    2015-01-01

    In early 2014, construction of a new watt balance, named NIST-4, has started at the National Institute of Standards and Technology (NIST). In a watt balance, the gravitational force of an unknown mass is compensated by an electromagnetic force produced by a coil in a magnet system. The electromagnetic force depends on the current in the coil and the magnetic flux integral. Most watt balances feature an additional calibration mode, referred to as velocity mode, which allows one to measure the magnetic flux integral to high precision. In this article we describe first measurements of the flux integral in the new watt balance. We introduce measurement and data analysis techniques to assess the quality of the measurements and the adverse effects of vibrations on the instrument.

  16. Parity violation in ternary fission

    Science.gov (United States)

    Gönnenwein, F.; Belozerov, A. V.; Beda, A. G.; Burov, S. I.; Danilyan, G. V.; Martem'yanov, A. N.; Pavlov, V. S.; Shchenev, V. A.; Bondarenko, L. N.; Mostovoĭ, Yu. A.; Geltenbort, P.; Last, J.; Schreckenbach, K.

    1994-01-01

    The parity-violating correlation between incoming neutron spin and fragment momentum has been measured simultaneously for binary and ternary fission of 233U(n, f) and 239Pu(n, f). The experiment has been performed with a polarized cold neutron beam of the Institut Laue-Langevin in Grenoble/France. The ratios of the parity-violating asymmetry coefficients, α ternf and α binnf, for ternary and binary fission, respectively, are found to be {α ternf}/{α binnf = 1.05 ± 0.10 } and 1.12 ± 0.08 for the 233U and 239Pu target nucleus, respectively. Both experiments are compatible with {α ternf}/{α binnf = 1 }. The implications of this result for models of ternary fission are discussed. The conclusion drawn is that ternary particles are emitted at the very last stage of fission.

  17. Measurements of prompt fission gamma-rays and neutrons with lanthanide halide scintillation detectors

    CERN Document Server

    Oberstedt, A; Billnert, R; Borcea, R; Brys, T; Chaves, C; Gamboni, T; Geerts, W; Göök, A; Guerrero, C; Hambsch, F-J; Kis, Z; Martinez, T; Oberstedt, S; Szentmiklosi, L; Takács, K; Vivaldi, M

    2014-01-01

    Photons have been measured with lanthanide halide scintillation detectors in coincidence with fission fragments. Using the time-of-flight information, reactions from γ-rays and neutrons could easily be distinguished. In several experiments on $^{252}$Cf(sf), $^{235}$U(n$_{th}$,f) and $^{241}$Pu(n$_{th}$,f) prompt fission γ-ray spectra characteristics were determined with high precision and the results are presented here. Moreover, a measured prompt fission neutron spectrum for $^{235}$U(n$_{th}$,f) is shown in order to demonstrate a new detection technique.

  18. Advanced Space Fission Propulsion Systems

    Science.gov (United States)

    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

  19. Fission hindrance and nuclear viscosity

    Indian Academy of Sciences (India)

    Indranil Mazumdar

    2015-08-01

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

  20. Construction of a new watt balance with the goal to realize the kilogram in the US

    Science.gov (United States)

    Schlamminger, Stephan; Haddad, Darine; Seifert, Frank; Chao, Leon; Newell, David; Pratt, Jon

    2015-04-01

    A watt balance is a mechanical device that compares mechanical power to electrical power. Since electrical power is measured using quantum physics by employing the Josephson effect and the Quantum Hall effect, electrical power can be measured as a product of a known factor, two frequencies, and the Planck constant h. Mechanical power is given by mgv , where m is the mass of a weight, g the local acceleration, and v the velocity. Hence, the watt balance provides a link between mass and Planck's constant. Currently several watt balances worldwide are employed to measure h. A redefinition of the international system of units (SI) is currently in discussion and may become reality as early as 2018. In the new SI, the numerical value of the Planck constant will be fixed and the watt balance is a means to realize the unit of mass. Researchers at NIST are preparing for a new SI and we have started in 2011 with plans to design a new watt balance capable of realizing the kilogram with relative uncertainties of a few parts in 108. Construction of the new watt balance has started in 2014. In my talk, I will show some of the latest results achieved with this apparatus.

  1. Assessment of fissionable material behaviour in fission chambers

    Energy Technology Data Exchange (ETDEWEB)

    Cabellos, O., E-mail: oscar.cabellos@upm.e [Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Fernandez, P. [Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Rapisarda, D. [Laboratorio Nacional de Fusion, EURATOM-CIEMAT, 28040 Madrid (Spain); Garcia-Herranz, N. [Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain)

    2010-06-21

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

  2. Fission gas in thoria

    Science.gov (United States)

    Kuganathan, Navaratnarajah; Ghosh, Partha S.; Galvin, Conor O. T.; Arya, Ashok K.; Dutta, Bijon K.; Dey, Gautam K.; Grimes, Robin W.

    2017-03-01

    The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO2 we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO2 is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO2 is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO2-x the most favourable solution equilibrium site is the NTV1 while in ThO2 it is the DV.

  3. Thorium-uranium fission radiography

    Science.gov (United States)

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

    1976-01-01

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

  4. Experimental approach to fission process of actinides

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-07-01

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

  5. Nuclear fission and neutron-induced fission cross-sections

    CERN Document Server

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

    2013-01-01

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

  6. Spontaneous Muon Emission during Fission, a New Nuclear Radioactivity

    CERN Document Server

    Ion, D B; Ion-Mihai, Reveica

    2011-01-01

    In this paper the essential theoretical predictions for the nuclear muonic radioactivity are presented by using a special fission-like model similar with that used in description of the pionic emission during fission. Hence, a fission-like model for the muonic radioactivity takes into account the essential degree of freedom of the system: muon-fissility, muon-fission barrier height, etc. Using this model it was shown that most of the SHE-nuclei lie in the region where the muonic fissility parameters attain their limiting value X=1. Hence, the SHE-region is characterized by the absence of a classical barrier toward spontaneous muon and pion emissions. Numerical estimations on the yields for the natural muonic radioactivities of the transuranium elements as well numerical values for barrier heights are given only for even-even parent nuclei. Some experimental results from LCP-identification emission spectrum are reviewed. Also, the experimental results obtained by Khryachkov et al, using new spectrometer for in...

  7. Ternary fission of superheavy elements

    Science.gov (United States)

    Balasubramaniam, M.; Vijayaraghavan, K. R.; Manimaran, K.

    2016-01-01

    Ternary fission of superheavy nuclei is studied within the three-cluster model potential energy surfaces (PESs). Due to shell effects, the stability of superheavy nuclei has been predicted to be associated with Z =114 , 120, and 126 for protons and N =184 for neutrons. Taking some representative nuclei we have extended the ternary fission studies to superheavy nuclei. We adopted two minimization procedures to minimize the potential and considered different arrangements of the fragments. The PES from one-dimensional minimization reveals a strong cluster region favoring various ternary breakups for an arrangement in which the lightest fragment is kept at the center. The PES obtained from two-dimensional minimization reveals strong preference of ternary fragmentation in the true ternary fission region. Though the dominant decay mode of superheavy nuclei is α decay, the α -accompanied ternary breakup is found to be a nonfavorable one. Further, the prominent ternary combinations are found to be associated with the neutron magic number.

  8. Dynamic treatment of ternary fission

    Science.gov (United States)

    Rubchenya, V. A.; Yavshits, S. G.

    1988-06-01

    The new dynamic model of light charged particle (LCP) formation in ternary fission is presented. The model is based on the assumption that light particles are formed as a result of two random neck ruptures during the time interval about one single-particle period. The connection of the final stage of ternary fission and of the saddle point descent stage was obtained in the framework of the density moments method. The analysis of LCP formation has shown that LCP mass and charge distributions are strongly governed by statistical nucleon exchange in the LCP-light fragment double system. New semiclassical expressions for the calculations of LCP yields and relative ternary fission probability are given. The results of calculations are in satisfactory agreement with the experimental data.

  9. Spontaneous fission of superheavy nuclei

    Indian Academy of Sciences (India)

    R A Gherghescu; D N Poenaru

    2015-09-01

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

  10. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-01

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

  11. The '2000-Watt per person'- industrial society - Utopia, vision or necessity?; Die '2000 Watt pro Kopf'-Industriegesellschaft - Utopie, Vision oder Notwendigkeit?

    Energy Technology Data Exchange (ETDEWEB)

    Jochem, E

    2006-07-01

    This short article takes a look at the '2000-Watt per person' concept initially developed at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, in 1998. The author is of the opinion that the concept is not utopian but a vision that can be realised - providing it is accepted socially and that politics can implement it. Further work on the concept done at the ETH over the years is listed and commented on. A diagram provides an overview of energy resources, energy transformation and energy flows to final energy consumption. The question as to if the realisation of such a '2000-Watt'-society is actually necessary is posed.

  12. A discussion of $Bl$ conservation on a two dimensional magnetic field plane in watt balances

    CERN Document Server

    Li, Shisong; Huang, Songling

    2015-01-01

    The watt balance is an experiment being pursued in national metrology institutes for precision determination of the Planck constant $h$. In watt balances, the $1/r$ magnetic field, expected to generate a geometrical factor $Bl$ independent to any coil horizontal displacement, can be created by a strict two dimensional, symmetric (horizontal $r$ and vertical $z$) construction of the magnet system. In this paper, we present an analytical understanding of magnetic field distribution when the $r$ symmetry of the magnet is broken and the establishment of the $Bl$ conservation is shown. By using either Gauss's law on magnetism with monopoles or conformal transformations, we extend the $Bl$ conservation to arbitrary two dimensional magnetic planes where the vertical magnetic field component equals zero. The generalized $Bl$ conservation allows a relaxed physical alignment criteria for watt balance magnet systems.

  13. A LEGO Watt balance: An apparatus to determine a mass based on the new SI

    Science.gov (United States)

    Chao, L. S.; Schlamminger, S.; Newell, D. B.; Pratt, J. R.; Seifert, F.; Zhang, X.; Sineriz, G.; Liu, M.; Haddad, D.

    2015-11-01

    A global effort to redefine our International System of Units (SI) is underway, and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed numerical values of seven reference constants. In particular, the unit of mass (the kilogram) will be realized through a fixed value of the Planck constant h. A so-called watt balance, for example, can then be used to realize the kilogram unit of mass within a few parts in 108. Such a balance has been designed and constructed at the National Institute of Standards and Technology. For educational outreach and to demonstrate the principle, we have constructed a LEGO tabletop watt balance capable of measuring a gram-level masses to 1% relative uncertainty. This article presents the design, construction, and performance of the LEGO watt balance and its ability to determine h.

  14. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for 235U (n ,fission) at Thermal and Fast Neutron Energies

    Science.gov (United States)

    Sonzogni, A. A.; McCutchan, E. A.; Johnson, T. D.; Dimitriou, P.

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 235U 235 fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of 86Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  15. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    Science.gov (United States)

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  16. Random walk in degree space and the time-dependent Watts-Strogatz model

    CERN Document Server

    Grande, H L Casa; Hase, M O

    2016-01-01

    In this work, we propose a scheme that provides an analytical estimate for the time-dependent degree distribution of some networks. This scheme maps the problem into a random walk in degree space, and then we choose the paths that are responsible for the dominant contributions. The method is illustrated on the dynamical versions of the Erd\\"os-R\\'enyi and Watts-Strogatz graphs, which were introduced as static models in the original formulation. We have succeeded in obtaining an analytical form for the dynamics Watts-Strogatz model, which is asymptotically exact for some regimes.

  17. Evolutionary snowdrift game on heterogeneous Newman-Watts small-world network

    Institute of Scientific and Technical Information of China (English)

    Yang Han-Xin; Gao Kun; Han Xiao-Pu; Wang Bing-Hong

    2008-01-01

    We study the evolutionary snowdrift game in a heterogeneous Newman-Watts small-world network. The hetero-geneity of the network is controlled by the number of hubs. It is found that the moderate heterogeneity of the network can promote the cooperation best. Besides, we study how the hubs affect the evolution of cooperative behaviours of the heterogeneous Newman-Watts small-world network. Simulation results show that both the initial states of hubs and the connections between hubs can play an important role. Our work gives a further insight into the effect of hubs on the heterogeneous networks.

  18. Development of Fission Chamber Assembly

    Institute of Scientific and Technical Information of China (English)

    YANGJinwei; ZHANGWei; SONGXianying; LIXu

    2003-01-01

    The fission chambers which are gas counters with fissile material inside chamber,provide essential information for plasma opcharacteristics. In conjunction with the neutron flux monitor system these provide time-resolved measurements of the global neutron source strength and fusion power from thermal nuclear fusion reactor as ITER for all plasma conditions for which neutrons are produced.

  19. Method of fission product beta spectra measurements for predicting reactor anti-neutrino emission

    Energy Technology Data Exchange (ETDEWEB)

    Asner, D.M.; Burns, K.; Campbell, L.W.; Greenfield, B.; Kos, M.S., E-mail: markskos@gmail.com; Orrell, J.L.; Schram, M.; VanDevender, B.; Wood, L.S.; Wootan, D.W.

    2015-03-11

    The nuclear fission process that occurs in the core of nuclear reactors results in unstable, neutron-rich fission products that subsequently beta decay and emit electron antineutrinos. These reactor neutrinos have served neutrino physics research from the initial discovery of the neutrino to today's precision measurements of neutrino mixing angles. The prediction of the absolute flux and energy spectrum of the emitted reactor neutrinos hinges upon a series of seminal papers based on measurements performed in the 1970s and 1980s. The steadily improving reactor neutrino measurement techniques and recent reconsiderations of the agreement between the predicted and observed reactor neutrino flux motivates revisiting the underlying beta spectra measurements. A method is proposed to use an accelerator proton beam delivered to an engineered target to yield a neutron field tailored to reproduce the neutron energy spectrum present in the core of an operating nuclear reactor. Foils of the primary reactor fissionable isotopes placed in this tailored neutron flux will ultimately emit beta particles from the resultant fission products. Measurement of these beta particles in a time projection chamber with a perpendicular magnetic field provides a distinctive set of systematic considerations for comparison to the original seminal beta spectra measurements. Ancillary measurements such as gamma-ray emission and post-irradiation radiochemical analysis will further constrain the absolute normalization of beta emissions per fission. The requirements for unfolding the beta spectra measured with this method into a predicted reactor neutrino spectrum are explored.

  20. Method of fission product beta spectra measurements for predicting reactor anti-neutrino emission

    Energy Technology Data Exchange (ETDEWEB)

    Asner, David M.; Burns, Kimberly A.; Campbell, Luke W.; Greenfield, Bryce A.; Kos, Marek S.; Orrell, John L.; Schram, Malachi; VanDevender, Brent A.; Wood, Lynn S.; Wootan, David W.

    2015-03-01

    The nuclear fission process that occurs in the core of nuclear reactors results in unstable, neutron-rich fission products that subsequently beta decay and emit electron antineutrinos. These reactor neutrinos have served neutrino physics research from the initial discovery of the neutrino to today's precision measurements of neutrino mixing angles. The prediction of the absolute flux and energy spectrum of the emitted reactor neutrinos hinges upon a series of seminal papers based on measurements performed in the 1970s and 1980s. The steadily improving reactor neutrino measurement techniques and recent reconsiderations of the agreement between the predicted and observed reactor neutrino flux motivates revisiting the underlying beta spectra measurements. A method is proposed to use an accelerator proton beam delivered to an engineered target to yield a neutron field tailored to reproduce the neutron energy spectrum present in the core of an operating nuclear reactor. Foils of the primary reactor fissionable isotopes placed in this tailored neutron flux will ultimately emit beta particles from the resultant fission products. Measurement of these beta particles in a time projection chamber with a perpendicular magnetic field provides a distinctive set of systematic considerations for comparison to the original seminal beta spectra measurements. Ancillary measurements such as gamma-ray emission and post-irradiation radiochemical analysis will further constrain the absolute normalization of beta emissions per fission. The requirements for unfolding the beta spectra measured with this method into a predicted reactor neutrino spectrum are explored.

  1. Two neutron correlations in photo-fission

    Science.gov (United States)

    Dale, D. S.; Kosinov, O.; Forest, T.; Burggraf, J.; Stave, S.; Warren, G.; Starovoitova, V.

    2016-09-01

    A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.

  2. Fusion-Fission Hybrid for Fissile Fuel Production without Processing

    Energy Technology Data Exchange (ETDEWEB)

    Fratoni, M; Moir, R W; Kramer, K J; Latkowski, J F; Meier, W R; Powers, J J

    2012-01-02

    Two scenarios are typically envisioned for thorium fuel cycles: 'open' cycles based on irradiation of {sup 232}Th and fission of {sup 233}U in situ without reprocessing or 'closed' cycles based on irradiation of {sup 232}Th followed by reprocessing, and recycling of {sup 233}U either in situ or in critical fission reactors. This study evaluates a third option based on the possibility of breeding fissile material in a fusion-fission hybrid reactor and burning the same fuel in a critical reactor without any reprocessing or reconditioning. This fuel cycle requires the hybrid and the critical reactor to use the same fuel form. TRISO particles embedded in carbon pebbles were selected as the preferred form of fuel and an inertial laser fusion system featuring a subcritical blanket was combined with critical pebble bed reactors, either gas-cooled or liquid-salt-cooled. The hybrid reactor was modeled based on the earlier, hybrid version of the LLNL Laser Inertial Fusion Energy (LIFE1) system, whereas the critical reactors were modeled according to the Pebble Bed Modular Reactor (PBMR) and the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) design. An extensive neutronic analysis was carried out for both the hybrid and the fission reactors in order to track the fuel composition at each stage of the fuel cycle and ultimately determine the plant support ratio, which has been defined as the ratio between the thermal power generated in fission reactors and the fusion power required to breed the fissile fuel burnt in these fission reactors. It was found that the maximum attainable plant support ratio for a thorium fuel cycle that employs neither enrichment nor reprocessing is about 2. This requires tuning the neutron energy towards high energy for breeding and towards thermal energy for burning. A high fuel loading in the pebbles allows a faster spectrum in the hybrid blanket; mixing dummy carbon pebbles with fuel pebbles enables a softer spectrum in

  3. Fission dynamics at low excitation energy

    CERN Document Server

    Aritomo, Y

    2013-01-01

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

  4. Fission yield studies at the IGISOL facility

    Energy Technology Data Exchange (ETDEWEB)

    Penttilae, H.; Elomaa, V.V.; Eronen, T.; Hakala, J.; Jokinen, A.; Kankainen, A.; Moore, I.D.; Rahaman, S.; Rinta-Antila, S.; Rissanen, J.; Saastamoinen, A.; Weber, C.; Aeystoe, J. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); Rubchenya, V. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); V.G. Khlopin Radium Institute, St. Petersburg (Russian Federation)

    2012-04-15

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

  5. Method of Fission Product Beta Spectra Measurements for Predicting Reactor Anti-neutrino Emission

    CERN Document Server

    Asner, D M; Campbell, L W; Greenfield, B; Kos, M S; Orrell, J L; Schram, M; VanDevender, B; Wood, 1 L S; Wootan, D W

    2014-01-01

    The nuclear fission process that occurs in the core of nuclear reactors results in unstable, neutron rich fission products that subsequently beta decay and emit electron anti-neutrinos. These reactor neutrinos have served neutrino physics research from the initial discovery of the neutrino to current precision measurements of neutrino mixing angles. The prediction of the absolute flux and energy spectrum of the emitted reactor neutrinos hinges upon a series of seminal papers based on measurements performed in the 1970s and 1980s. The steadily improving reactor neutrino measurement techniques and recent re-considerations of the agreement between the predicted and observed reactor neutrino flux motivates revisiting the underlying beta spectra measurements. A method is proposed to use an accelerator proton beam delivered to an engineered target to yield a neutron field tailored to reproduce the neutron energy spectrum present in the core of an operating nuclear reactor. Foils of the primary reactor fissionable i...

  6. Cluster fission from the standpoint of nuclear fission

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sangmoo [Tsukuba Univ., Ibaraki (Japan). Inst. of Physics

    1996-03-01

    Atomic nucleus belongs to a quantal finite many body system. Nucleus shows great resemblance to cluster, above all metal cluster, although the strength of interaction is different. The works of Brechignac group, Saunder, Martin and P. Froeblich are explained by the critical size Nc as the central term. The differences between cluster and nucleus are investigated and a future view of cluster fission is explained. (S.Y.)

  7. A fission fragment detector for correlated fission output studies

    Energy Technology Data Exchange (ETDEWEB)

    Mosby, S., E-mail: smosby@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tovesson, F.; Couture, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Duke, D.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States); Kleinrath, V. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Idaho State University, Pocatello, ID 83201 (United States); Meharchand, R.; Meierbachtol, K.; O' Donnell, J.M.; Perdue, B.; Richman, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shields, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States)

    2014-09-01

    A digital data acquisition system has been combined with a double Frisch gridded ionization chamber for use at both moderated and unmoderated neutron sources at the Los Alamos Neutron Science (LANSCE) facility. The high efficiency of the instrument combined with intense LANSCE beams and new acquisition system permits fission output measurements across 11 orders of magnitude incident neutron energy. The acquisition and analysis system is presented along with the first in-beam performance tests of the setup.

  8. Texture and microstructure evolution in nickel electrodeposited from an additive-free Watts electrolyte

    DEFF Research Database (Denmark)

    Alimadadi, Hossein; da Silva Fanta, Alice Bastos; Kasama, Takeshi;

    2016-01-01

    Nickel layers with 〈100〉, 〈210〉, 〈110〉 and 〈211〉 fiber textures were electrodeposited from additive-free Watts type electrolytes by adjusting both the pH and the applied current density. Quantitative crystallographic texture analysis by XRD was supplemented by micro-texture analysis applying EBSD...

  9. A 1-Watt Ku-Band Power Amplifier MMIC Using Cost-Effective Organic SMD Package

    NARCIS (Netherlands)

    Bessemoulin, A.; Parisot, M.; Quentin, P.; Saboureau, C.; Heijningen, M. van; Priday, J.

    2004-01-01

    This paper presents the design and performance of a compact 1-Watt Ku-band power amplifier MMIC implemented in a novel microwave organic power package, compatible with SMD assembly lines. Due to the use of simple materials, like RO4003 substrate and copper, it allows significant cost reduction for

  10. A 1-Watt Ku-Band Power Amplifier MMIC Using Cost-Effective Organic SMD Package

    NARCIS (Netherlands)

    Bessemoulin, A.; Parisot, M.; Quentin, P.; Saboureau, C.; Heijningen, M. van; Priday, J.

    2004-01-01

    This paper presents the design and performance of a compact 1-Watt Ku-band power amplifier MMIC implemented in a novel microwave organic power package, compatible with SMD assembly lines. Due to the use of simple materials, like RO4003 substrate and copper, it allows significant cost reduction for R

  11. Registration error study of digital watt-hour meters under distorted conditions

    Science.gov (United States)

    Reta-Hernandez, Manuel

    The increasing application of non-linear loads based on the use of converters, uninterruptible power supplies, and other solid-state switching devices has increased the harmonic content in voltage and current at metering points. One of many problems caused by the voltage and current distortion is the effect on the watt-hour meter performance. The digital watt-hour meter is replacing the old induction meter for measuring electric energy, obtaining additional flexibility and functionality. However, the digital meter performance can be deeply affected when a dc current component is added to the distorted conditions. This dissertation presents a study of the digital watt-hour meter's performance under different nonsinusoidal conditions, including a dc current component. The work is divided into two sections: experimental and analytical. The experimental section consists of accuracy testing on several models of digital meters, both single-phase and three-phase units, subjected to computer-controlled distortion. The system setup used for the measurements was designed by using 12-bits data acquisition hardware (DAQ) and virtual-instrument software (VI) installed in a personal computer. Additional testing on electromechanical watt-hour meters is included for comparison purposes.

  12. Results of metallographical diagnostic examination of Navy half-watt thermoelectric converters degraded by accelerated tests

    Science.gov (United States)

    Rosell, F. E., Jr.; Rouklove, P. G.

    1977-01-01

    To verify the 15-year reliability of the Navy half-watt radioisotope thermoelectric generator (RTG), bismuth-telluride thermoelectric converters were submitted to testing at high temperatures which accelerated the degradation and caused failure of the converters. Metallographic diagnostic examination of failed units verified failure mechanisms. Results of diagnostic examinations are presented.

  13. Design of multihundred-watt dynamic isotope power system for robotic space missions

    Science.gov (United States)

    Bents, D. J.; Geng, S. M.; Schreiber, J. G.; Withrow, C. A.; Schmitz, P. C.; McComas, T. J.

    The design of a multihundred-watt dynamic isotope power system (DIPS) based on the US Department of Energy (DOE) general-purpose heat source (GPHS) and small (multihundred-watt) free-piston Stirling engine (FPSE) is described as a potential lower cost alternative to radioisotope thermoelectric generators (RTGs). The design is targeted at the power needs of future unmanned deep space and planetary surface exploration missions. Since the competitive potential of FPSE as an isotope convertor was first identified, work has focused on the feasibility of directly integrating GPHS with the Stirling heater head. Thermal modeling of various radiatively coupled heat source/heater head geometries has been performed using data furnished by the developers of FPSE and GPHS. The analysis indicates that, for the 1050 K heater head configurations considered, GPHS fuel clad temperatures remain safe operating limits under all conditions including shutdown of one engine on a twin engine unit. Based on these results, preliminary characterizations of multihundred-watt units have been established. They indicate that, per electrical watt, the GPHS/small Stirling DIPS will be roughly equivalent to MOD RTG in size and mass but will require about a third the amount of isotope fuel.

  14. Rock the Watt: An Energy Conservation Campaign at Pacific Northwest National Lab

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-01-01

    Case study describes Pacific Northwest National Laboratory's (PNNL) three-month Rock the Watt campaign to reduce energy use at its main campus in Richland, Washington. The campaign objectives were to educate PNNL employees about energy conservation opportunities in their workplace and to motivate them to help PNNL save energy and costs and to reduce greenhouse gas emissions.

  15. Method of defining isolation parameters in 1000 Watt symmetric electricity network

    Directory of Open Access Journals (Sweden)

    Samat Amurgaliev

    2009-10-01

    Full Text Available The authors define parameters for isolation three-phase electric network to provide safety conditions for personnel working at open-operated coal deposits. The authors conclude the technique provides satisfactory accuracy of the parameters’ defining, as well as simplicity and safety of coal mining works with electric network having pressure up to 1000 Watt.

  16. 76 FR 34799 - Permanent Dam Safety Modification at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams, TN

    Science.gov (United States)

    2011-06-14

    ... Permanent Dam Safety Modification at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams, TN AGENCY... various alternatives for permanent modifications to the existing dam facilities at Cherokee, Fort Loudoun, Tellico, and Watts Bar dams in Tennessee. The level of review will be determined after the public...

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

    Science.gov (United States)

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

    2009-10-01

    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 252Cf(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 252Cf(SF) reaction with data available from literature.

  18. Delayed Fission Gamma-ray Characteristics of Th-232 U-233 U-235 U-238 and Pu-239

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Taylor [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Parma, Edward J. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-08-01

    Delayed fission gamma-rays play an important role in determining the time dependent ioniz- ing dose for experiments in the central irradiation cavity of the Annular Core Research Reactor (ACRR). Delayed gamma-rays are produced from both fission product decay and from acti- vation of materials in the core, such as cladding and support structures. Knowing both the delayed gamma-ray emission rate and the time-dependent gamma-ray energy spectrum is nec- essary in order to properly determine the dose contributions from delayed fission gamma-rays. This information is especially important when attempting to deconvolute the time-dependent neutron, prompt gamma-ray, and delayed gamma-ray contribution to the response of a diamond photo-conducting diode (PCD) or fission chamber in time frames of milliseconds to seconds following a reactor pulse. This work focused on investigating delayed gamma-ray character- istics produced from fission products from thermal, fast, and high energy fission of Th-232, U-233, U-235, U-238, and Pu-239. This work uses a modified version of CINDER2008, a transmutation code developed at Los Alamos National Laboratory, to model time and energy dependent photon characteristics due to fission. This modified code adds the capability to track photon-induced transmutations, photo-fission, and the subsequent radiation caused by fission products due to photo-fission. The data is compared against previous work done with SNL- modified CINDER2008 [ 1 ] and experimental data [ 2 , 3 ] and other published literature, includ- ing ENDF/B-VII.1 [ 4 ]. The ability to produce a high-fidelity (7,428 group) energy-dependent photon fluence at various times post-fission can improve the delayed photon characterization for radiation effects tests at research reactors, as well as other applications.

  19. Fission Fragment Angular Distribution of 232Th(n,f) at the CERN n_TOF Facility

    CERN Document Server

    Tarrío, D; Audouin, L; Duran, I.; Paradela, C.; Tassan-Got, L; Altstadt, S; Andrzejewski, J; Barbagallo, M; Bécares, V; Bečvář, F; Belloni, F; Berthoumieux, E; Billowes, J; Boccone, V; Bosnar, D; Brugger, M; Calviani, M; Calviño, F; Cano-Ott, D; Carrapiço, C; Cerutti, F; Chiaveri, E; Chin, M; Colonna, N; Cortés, G; Cortés-Giraldo, M A; Diakaki, M; Domingo-Pardo, C; Dzysiuk, N; Eleftheriadis, C; Ferrari, A; Fraval, K; Ganesan, S; García, A R; Giubrone, G; Gómez-Hornillos, M B; Gonçalves, I F; González-Romero, E; Griesmayer, E; Guerrero, C; Gunsing, F; Gurusamy, P; Jenkins, D G; Jericha, E; Kadi, Y; Käppeler, F; Karadimos, D; Koehler, P; Kokkoris, M; Krtička, M; Kroll, J; Langer, C; Lederer, C; Leeb, H; Losito, R; Manousos, A; Marganiec, J; Martínez, T; Massimi, C; Mastinu, P F; Mastromarco, M; Meaze, M; Mendoza, E; Mengoni, A; Milazzo, P M; Mingrone, F; Mirea, M; Mondalaers, W; Pavlik, A; Perkowski, J; Plompen, A; Praena, J; Quesada, J M; Rauscher, T; Reifarth, R; Riego, A; Roman, F; Rubbia, C; Sarmento, R; Schillebeeckx, P; Schmidt, S; Tagliente, G; Tain, J L; Tsinganis, A; Valenta, S; Vannini, G; Variale, V; Vaz, P; Ventura, A; Versaci, R; Vermeulen, M J; Vlachoudis, V; Vlastou, R; Wallner, A; Ware, T; Weigand, M; Weiß, C; Wright, T J; Žugec, P

    2014-01-01

    The angular distribution of fragments emitted in neutron-induced fission of Th-232 was measured in the white spectrum neutron beam at the n\\_TOF facility at CERN. A reaction chamber based on Parallel Plate Avalanche Counters (PPAC) was used, where the detectors and the targets have been tilted 45 degrees with respect to the neutron beam direction in order to cover the full angular range of the fission fragments. A GEANT4 simulation has been developed to study the setup efficiency. The data analysis and the preliminary results obtained for the Th-232(n,f) between fission threshold and 100 MeV are presented here.

  20. Fission properties for r-process nuclei

    CERN Document Server

    Erler, J; Loens, H P; Martínez-Pinedo, G; Reinhard, P -G

    2011-01-01

    We present a systematics of fission barriers and fission lifetimes for the whole landscape of super-heavy elements (SHE), i.e. nuclei with Z>100. The fission lifetimes are also compared with the alpha-decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parameterizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bi-modal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expec...

  1. The Fission of thorium with Alpha Particles

    Energy Technology Data Exchange (ETDEWEB)

    Newton, Amos S.

    1948-10-15

    Soon after the discovery of fission, Meitner, Bretscher and Cook found differences in the decay of various chemical fractions separated from uranium irradiated with slow neutrons and thorium irradiated with fast neutrons respectively and suggested that a difference existed in the distribution of fission products in the two cases. In 1940, Turner suggested that the distribution in various modes of fission should be investigated. The fact that elements such as tin, cadmium, palladium, and silver were found in fast neutron and deuteron fission of uranium and thorium before they were found in slow neutron fission of uranium suggested that the middle region of the distribution was raised as the energy of the incident particle was increased. Since the compound nucleus formed in the fission of thorium with alpha particles is U{sup 236}, the same compound nucleus formed in the fission of U{sup 235} with neutrons, it is of interest to study the fission of thorium with alphas and compare the resulting distribution of fission products with that found with uranium with slow and thorium with fast neutrons. Any difference between the various results where the same compound nucleus is formed must be due to differences in energy content and possible differences in distribution of the nucleons in the compound nucleus at the time of fission.

  2. Fission: statistical nucleon pair breaking

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, M. (Instituto Peruano de Energia Nuclear, Lima (Peru))

    1984-06-01

    In order to explain the odd-even effect observed in low energy fission fragment distributions it has been recently required a double mechanism of nucleon pair breaking: before scission (early pair breaking) and at scission (late pair breaking), respectively. In the present work we show that, using the same formulae but considering only the early pair breaking mechanism, one can reproduce fairly well all the available experimental data on the odd-even effects.

  3. The VERDI fission fragment spectrometer

    Science.gov (United States)

    Frégeau, M. O.; Bryś, T.; Gamboni, Th.; Geerts, W.; Oberstedt, S.; Oberstedt, A.; Borcea, R.

    2013-12-01

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

  4. The VERDI fission fragment spectrometer

    Directory of Open Access Journals (Sweden)

    Frégeau M.O.

    2013-12-01

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

  5. Is the Double Giant Dipole Resonance Process Responsible for Alpha Emission in Ternary Fission?

    Science.gov (United States)

    Han, Hong-Yin; Wand, Yi-Hua; Mouze, G.

    2001-11-01

    The Monte Carlo program built on the double giant dipole resonance model proposed by Mouze et al. [Nuovo Cimento A 110(1997)1097] was employed to calculate the energy spectrum of alpha particles emitted in the spontaneous ternary fission of 252Cf. It has been found that in the case of the zero orbital angular momentum of alpha particles in the alpha decay of the fragments, the measured alpha spectrum can be reproduced approximately by the model without any adjustable parameter.

  6. Is the Double Giant Dipole Resonance Process Responsible for Alpha Emission in Ternary Fission?

    Institute of Scientific and Technical Information of China (English)

    HAN Hong-Yin(韩洪银); WAND Yi-Hua(王屹华); G.Mouze

    2001-01-01

    The Monte Carlo program built on the double giant dipole resonance model proposed by Mouze et al. [Nuovo Cimento A 110(1997)1097] was employed to calculate the energy spectrum of alpha particles emitted in the spontaneous ternary fission of 252Cf. It has been found that in the case of the zero orbital angular momentum of alpha particles in the alpha decay of the fragments, the measured alpha spectrum can be reproduced approximately by the model without any adjustable parameter.

  7. Technical Application of Nuclear Fission

    Science.gov (United States)

    Denschlag, J. O.

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

  8. Influence of thermal and resonance neutron on fast neutron flux measurement by Pu-239 fission chamber

    CERN Document Server

    zeng, Lina; Song, Lingli; Zheng, Chun

    2014-01-01

    The Pu-239 fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the mean time the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of Pu-239 are measured as 1.791*10-16,2.350*10-16 and 1.385*10-15 per second for 15mm thick B cover, 0.5mm thick Cd cover, and no cover respectively. While the fission reaction rate of Pu-239 is rapidly increased to 2.569*10-14 for a 20mm thick polythene covering fission chamber. The average Pu-239 fission cross-section of thermal and resonance neutrons is calculated to be 500b and 24.95b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30*106,2.24*106 and 1.04*108cm-2s-1.

  9. Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    CERN Document Server

    Goddard, P M; Rios, A

    2015-01-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the ...

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

    Science.gov (United States)

    Clement, J. D.

    1973-01-01

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

  11. Radiochemical studies on nuclear fission at Trombay

    Indian Academy of Sciences (India)

    Asok Goswami

    2015-08-01

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

  12. Collective spectra along the fission barrier

    Directory of Open Access Journals (Sweden)

    Pigni M. T.

    2012-12-01

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

  13. Introducing Nuclear Data Evaluations of Prompt Fission Neutron Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Neudecker, Denise [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    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.

  14. Measurements of Fission Cross Sections of Actinides

    CERN Multimedia

    Wiescher, M; Cox, J; Dahlfors, M

    2002-01-01

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

  15. Fission-product retention in HTGR fuels

    Energy Technology Data Exchange (ETDEWEB)

    Homan, F.J.; Kania, M.J.; Tiegs, T.N.

    1982-01-01

    Retention data for gaseous and metallic fission products are presented for both Triso-coated and Biso-coated HTGR fuel particles. Performance trends are established that relate fission product retention to operating parameters, such as temperature, burnup, and neutron exposure. It is concluded that Biso-coated particles are not adequately retentive of fission gas or metallic cesium, and Triso-coated particles which retain cesium still lose silver. Design implications related to these performance trends are identified and discussed.

  16. Rapid Separation of Fission Product 141La

    Institute of Scientific and Technical Information of China (English)

    XIA; Wen; YE; Hong-sheng; LIN; Min; CHEN; Ke-sheng; XU; Li-jun; ZHANG; Wei-dong; CHEN; Yi-zhen

    2013-01-01

    141La was separated and purified from fission products in this work for physical measurements aimed at improving the accuracy of its decay parameters.As the impact of 142La and other fission products,cesium(141Cs,142Cs included)was rapid separated from the fission products,141Cs and 142Ba separation was prepared after a cooling time about 25 s when 142Cs decays to daughter 142Ba,141La purification then

  17. Fission Product Decay Heat Calculations for Neutron Fission of 232Th

    Science.gov (United States)

    Son, P. N.; Hai, N. X.

    2016-06-01

    Precise information on the decay heat from fission products following times after a fission reaction is necessary for safety designs and operations of nuclear-power reactors, fuel storage, transport flasks, and for spent fuel management and processing. In this study, the timing distributions of fission products' concentrations and their integrated decay heat as function of time following a fast neutron fission reaction of 232Th were exactly calculated by the numerical method with using the DHP code.

  18. Theoretical Description of the Fission Process

    Energy Technology Data Exchange (ETDEWEB)

    Witold Nazarewicz

    2003-07-01

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

  19. Some aspects of fission and quasifission processes

    Indian Academy of Sciences (India)

    B B Back

    2015-08-01

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

  20. Effect of nuclear viscosity on fission process

    Energy Technology Data Exchange (ETDEWEB)

    Li Shidong; Kuang Huishun; Zhang Shufa; Xing Jingru; Zhuo Yizhong; Wu Xizhen; Feng Renfa

    1989-02-01

    According to the fission diffusion model, the deformation motion of fission nucleuses is regarded as a diffusion process of quasi-Brownian particles under fission potential. Through simulating such Brownian motion in two dimensional phase space by Monte-Carlo mehtod, the effect of nuclear visocity on Brownian particle diffusion is studied. Dynamical quanties, such as fission rate, kinetic energy distribution on scission, and soon are numerically calculated for various viscosity coefficients. The results are resonable in physics. This method can be easily extended to deal with multi-dimensional diffusion problems.

  1. A hemi-fission intermediate links two mechanistically distinct stages of membrane fission.

    Science.gov (United States)

    Mattila, Juha-Pekka; Shnyrova, Anna V; Sundborger, Anna C; Hortelano, Eva Rodriguez; Fuhrmans, Marc; Neumann, Sylvia; Müller, Marcus; Hinshaw, Jenny E; Schmid, Sandra L; Frolov, Vadim A

    2015-08-06

    Fusion and fission drive all vesicular transport. Although topologically opposite, these reactions pass through the same hemi-fusion/fission intermediate, characterized by a 'stalk' in which only the outer membrane monolayers of the two compartments have merged to form a localized non-bilayer connection. Formation of the hemi-fission intermediate requires energy input from proteins catalysing membrane remodelling; however, the relationship between protein conformational rearrangements and hemi-fusion/fission remains obscure. Here we analysed how the GTPase cycle of human dynamin 1, the prototypical membrane fission catalyst, is directly coupled to membrane remodelling. We used intramolecular chemical crosslinking to stabilize dynamin in its GDP·AlF4(-)-bound transition state. In the absence of GTP this conformer produced stable hemi-fission, but failed to progress to complete fission, even in the presence of GTP. Further analysis revealed that the pleckstrin homology domain (PHD) locked in its membrane-inserted state facilitated hemi-fission. A second mode of dynamin activity, fuelled by GTP hydrolysis, couples dynamin disassembly with cooperative diminishing of the PHD wedging, thus destabilizing the hemi-fission intermediate to complete fission. Molecular simulations corroborate the bimodal character of dynamin action and indicate radial and axial forces as dominant, although not independent, drivers of hemi-fission and fission transformations, respectively. Mirrored in the fusion reaction, the force bimodality might constitute a general paradigm for leakage-free membrane remodelling.

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

    NARCIS (Netherlands)

    Plicht, J. van der

    1980-01-01

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

  3. Evidence for a Novel Reaction Mechanism of a Prompt Shock-Induced Fission Following the Fusion of 78Kr and 40Ca Nuclei at E/A =10 MeV

    CERN Document Server

    Henry, E; Nyibule, S; Quinlan, M; Schroder, W U; Ademard, G; Amorini, F; Auditore, L; Beck, C; Berceanu, I; Bonnet, E; Borderie, B; Cardella, G; Chbihi, A; Colonna, M; De Filippo, E; DOnofrio, A; Frankland, J D; Geraci, E; La Guidara, E; La Commara, M; Lanzalone, G; Lautesse, P; Lebhertz, D; Neindre, N Le; Lombardo, I; Loria, D; Mazurek, K; Pagano, A; Papa, M; Piasecki, E; Pirrone, S; Politi, G; Porto, F; Rizzo, F; Rosato, E; Rusotto, P; Spadaccini, G; Trifiro, A; Trimarchi, M; Verde, G; Vigilante, M; Wieleczko, J P

    2014-01-01

    An analysis of experimental data from the inverse-kinematics ISODEC experiment on 78Kr+40Ca reaction at a bombarding energy of 10 AMeV has revealed signatures of a hitherto unknown reaction mechanism, intermediate between the classical damped binary collisions and fusion-fission, but also substantially different from what is being termed in the literature as fast fission or quasi fission. These signatures point to a scenario where the system fuses transiently while virtually equilibrating mass asymmetry and energy and, yet, keeping part of the energy stored in a collective shock-imparted and, possibly, angular momentum bearing form of excitation. Subsequently the system fissions dynamically along the collision or shock axis with the emerging fragments featuring a broad mass spectrum centered around symmetric fission, relative velocities somewhat higher along the fission axis than in transverse direction, and virtually no intrinsic spin. The class of massasymmetric fission events shows a distinct preference fo...

  4. Isoscaling of the Fission Fragments with Langevin Equation

    Institute of Scientific and Technical Information of China (English)

    WANG Kun; TIAN Wen-Dong; ZHONG Chen; ZHOU Xing-Fei; MA Yu-Gang; WEI Yi-Bin; CAI Xiang-Zhou; CHEN Jin-Gen; FANG De-Qing; GUO Wei; MA Guo-Liang; SHEN Wen-Qing

    2005-01-01

    @@ The Langevin equation is used to simulate the fission process of 112Sn + 112Sn and 116Sn + 116Sn. The mass distribution of the fission fragments are given by assuming the process of symmetric fission or asymmetric fission with the Gaussian probability sampling. The isoscaling behaviour has been observed from the analysis of fission fragments of both the reactions, and the isoscaling parameter α seems to be sensitive to the width of fission probability and the beam energy.

  5. Optimizing performance per watt on GPUs in High Performance Computing: temperature, frequency and voltage effects

    CERN Document Server

    Price, D C; Barsdell, B R; Babich, R; Greenhill, L J

    2014-01-01

    The magnitude of the real-time digital signal processing challenge attached to large radio astronomical antenna arrays motivates use of high performance computing (HPC) systems. The need for high power efficiency (performance per watt) at remote observatory sites parallels that in HPC broadly, where efficiency is an emerging critical metric. We investigate how the performance per watt of graphics processing units (GPUs) is affected by temperature, core clock frequency and voltage. Our results highlight how the underlying physical processes that govern transistor operation affect power efficiency. In particular, we show experimentally that GPU power consumption grows non-linearly with both temperature and supply voltage, as predicted by physical transistor models. We show lowering GPU supply voltage and increasing clock frequency while maintaining a low die temperature increases the power efficiency of an NVIDIA K20 GPU by up to 37-48% over default settings when running xGPU, a compute-bound code used in radio...

  6. Optimization of solar cell contacts by system cost-per-watt minimization

    Science.gov (United States)

    Redfield, D.

    1977-01-01

    New, and considerably altered, optimum dimensions for solar-cell metallization patterns are found using the recently developed procedure whose optimization criterion is the minimum cost-per-watt effect on the entire photovoltaic system. It is also found that the optimum shadow fraction by the fine grid is independent of metal cost and resistivity as well as cell size. The optimum thickness of the fine grid metal depends on all these factors, and in familiar cases it should be appreciably greater than that found by less complete analyses. The optimum bus bar thickness is much greater than those generally used. The cost-per-watt penalty due to the need for increased amounts of metal per unit area on larger cells is determined quantitatively and thereby provides a criterion for the minimum benefits that must be obtained in other process steps to make larger cells cost effective.

  7. Monolithic watt-level millimeter-wave diode-grid frequency tripler array

    Science.gov (United States)

    Hwu, R. J.; Luhmann, N. C., Jr.; Rutledge, D. B.; Hancock, B.; Lieneweg, U.

    1988-01-01

    In order to provide watt-level CW output power throughout the millimeter and submillimeter wave region, thousands of solid-state diodes have been monolithically integrated using a metal grid to produce a highly efficient frequency multiplier. Devices considered include GaAs Schottky diodes, thin MOS diodes, and GaAs Barrier-Intrinsic-N(+)diodes. The performance of the present compact low-cost device has been theoretically and experimentally validated.

  8. Fractional watt Vuillemier cryogenic refrigerator program engineering notebook. Volume 2: Stress analysis

    Science.gov (United States)

    Miller, W. S.

    1974-01-01

    A structural analysis performed on the 1/4-watt cryogenic refrigerator. The analysis covered the complete assembly except for the cooling jacket and mounting brackets. Maximum stresses, margin of safety, and natural frequencies were calculated for structurally loaded refrigerator components shown in assembly drawings. The stress analysis indicates that the design is satisfactory for the specified vibration environment, and the proof, burst, and normal operating loads.

  9. Low-cost high-efficient 10-Watt X-band high-power amplifier

    NARCIS (Netherlands)

    Bent, G. van der; Hek, A.P. de; Bessemoulin, A.; Vliet, F.E. van

    2009-01-01

    A high power X-band amplifier with an output power over 10 Watts and a Power Added Efficiency (PAE) in excess of 40 percent has been developed. The design was fabricated in a 0.25 μm pHEMT GaAs process (WIN Semiconductor PP25-01). The small die area in combination with a 6-inch wafer technology prov

  10. A 20 GHz, 70 watt, 48 percent efficient space communications TWT

    Science.gov (United States)

    McDermott, M. A.; Tamashiro, R. N.

    A space qualifiable helix traveling wave tube capable of producing saturated output power levels above 70 watts at 48 percent total efficiency has been developed for 20 GHz satellite communications systems. The design approach stresses high reliability consistent with high power and efficiency. Advanced construction features incorporated into the design are a five stage collector, an M-type dispenser cathode, and a dynamic velocity tapered (DVT) helix.

  11. The distribution of the electric current in a watt-balance coil

    CERN Document Server

    Sasso, Carlo Paolo; Mana, Giovanni

    2013-01-01

    In the watt balance experiment, separate measurements of the Lorentz and electromotive forces in a coil in a radial magnetic field enable a virtual comparison between mechanical and electric powers to be carried out, which lead to an accurate measurement of the Planck constant. This paper investigates the effect of a spatially inhomogeneous distribution of the electric current in the coil due to the higher or lower resistance of the outer or inner paths.

  12. Spectroscopy of heavy fissionable nuclei

    Indian Academy of Sciences (India)

    S K Tandel

    2015-09-01

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

  13. Towards ten-watt-level 3-5 µm Raman lasers using tellurite fiber.

    Science.gov (United States)

    Zhu, Gongwen; Geng, Lixiang; Zhu, Xiushan; Li, Li; Chen, Qian; Norwood, R A; Manzur, T; Peyghambarian, N

    2015-03-23

    Raman lasers based on mid-infrared fibers operating at 3-5 µm atmospheric transparency window are attractive sources for several applications. Compared to fluoride and chalcogenide fibers, tellurite fibers are more advantageous for high power Raman fiber laser sources at 3-5 µm because of their broader Raman gain bandwidth, much larger Raman shift and better physical and chemical properties. Here we report on our simulations for the development of 10-watt-level 3-5 µm Raman lasers using tellurite fibers as the nonlinear gain medium and readily available continuous-wave (cw) and Q-switched erbium-doped fluoride fiber lasers at 2.8 µm as the pump sources. Our results show that a watt-level or even ten-watt-level fiber laser source in the 3-5 µm atmospheric transparency window can be achieved by utilizing the 1st- and 2nd-order Raman scattering in the tellurite fiber. The presented numerical study provides valuable guidance for future 3-5 um Raman fiber laser development.

  14. An analytical algorithm for 3D magnetic field mapping of a watt balance magnet

    CERN Document Server

    Fu, Zhuang; Li, Zhengkun; Zhao, Wei; Han, Bing; Lu, Yunfeng; Li, Shisong

    2015-01-01

    A yoke-based permanent magnet, which has been employed in many watt balances at national metrology institutes, is supposed to generate strong and uniform magnetic field in an air gap in the radial direction. However, in reality the fringe effect due to the finite height of the air gap will introduce an undesired vertical magnetic component to the air gap, which should either be measured or modeled towards some optimizations of the watt balance. A recent publication, i.e., {\\it Metrologia} 52(4) 445 [1], presented a full field mapping method, which in theory will supply useful information for profile characterization and misalignment analysis. This article is an additional material of [1], which develops a different analytical algorithm to represent the 3D magnetic field of a watt balance magnet based on only one measurement for the radial magnetic flux density along the vertical direction, $B_r(z)$. The new algorithm is based on the electromagnetic nature of the magnet, which has a much better accuracy.

  15. Nuclear Power from Fission Reactors. An Introduction.

    Science.gov (United States)

    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…

  16. Correlation measurements of fission-fragment properties

    Science.gov (United States)

    Oberstedt, S.; Belgya, T.; Billnert, R.; Borcea, R.; Cano-Ott, D.; Göök, A.; Hambsch, F.-J.; Karlsson, J.; Kis, Z.; Martinez, T.; Oberstedt, A.; Szentmiklosi, L.; Takác, K.

    2010-10-01

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

  17. Correlation measurements of fission-fragment properties

    Directory of Open Access Journals (Sweden)

    Oberstedt A.

    2010-10-01

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

  18. Gamma-ray Output Spectra from 239Pu Fission

    Directory of Open Access Journals (Sweden)

    Ullmann John

    2015-01-01

    Full Text Available Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. Theoretical Description of the Fission Process

    Energy Technology Data Exchange (ETDEWEB)

    Witold Nazarewicz

    2009-10-25

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

  1. Airborne measurements of fission product fall-out

    Energy Technology Data Exchange (ETDEWEB)

    Hovgaard, J.; Korsbech, U.

    1992-12-01

    During 1993 the Danish Emergency Management Agency will install an airborne [gamma]-ray detector system for area survey of contamination with radioactive nuclides - primarily fission products that may be released during a heavy accident at a nuclear power plant or from accidents during transport of radioactive material. The equipment is based on 16 liter NaI(TI) crystals and multichannel analysers from Exploranium (Canada). A preliminary investigation of the possibilities for detection of low and high level contamination - and the problems that may be expected during use of the equipment, and during interpretation of the measured data, is described. Several days after reactor shut-down some of the nuclides can be identified directly from the measured spectrum, and contamination levels may be determined within a factor two. After several weeks, most fission products have decayed. Concentrations and exposure rates can be determined with increasing accuracy as time passes. Approximate calibration of the equipment for measurements of surface contamination and natural radioactivity can be performed in the laboratory. Further checks of equipment should include accurate measurements of the spectrum resolution. Detectors should be checked individually, and all together. Further control of dead time and pulse pile-up should be performed. Energy calibration, electronics performance and data equipment should be tested against results from the original calibration. (AB).

  2. Superfluid dynamics of 258Fm fission

    CERN Document Server

    Scamps, Guillaume; Lacroix, Denis

    2015-01-01

    Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. The latter stage is essentially unexplored. However, it is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained with the time-dependent Hartree-Fock theory including BCS dynamical pairing correlations. The fission modes of the 258Fm nucleus are studied. The resulting fission fragment characteristics show a good agreement with experimental data. Quantum shell effects are shown to play a crucial role in the dynamics and formation of the fragments. The importance of quantum fluctuations beyond the independent particle/quasi-particle picture is underlined and qualitatively studied.

  3. Fission dynamics at low excitation energy. 2

    CERN Document Server

    Aritomo, Y; Ivanyuk, F A

    2014-01-01

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

  4. Cold fission as heavy ion emission

    Energy Technology Data Exchange (ETDEWEB)

    Poenaru, D.N.; Maruhn, J.A.; Greiner, W.; Ivascu, M.; Mazilu, D.; Gherghescu, R.

    1987-11-01

    The last version of the analytical superasymmetric fission model is applied to study cold fission processes. Strong shell effects are present either in one or both fission fragments. A smooth behaviour is observed when the proton or the neutron numbers are changed by four units. Increasing Z and N, in the transuranium region, a sharp transition from asymmetry with a large peak-to-valley ratio to symmetry at Z=100 and/or N=164 is obtained. The transition toward asymmetry at higher Z and N is much smoother. The most probable cold fission light fragments from /sup 234/U, /sup 236/U, /sup 239/Np and /sup 240/Pu are /sup 100/Zr, /sup 104/Mo, /sup 106/Mo and /sup 106/Mo, respectively, in good agreement with experimental data. The unified treatment of alpha decay, heavy ion radioactivities and cold fission is illustrated for /sup 234/U - the first nucleus in which all three groups have been already observed.

  5. Fission dynamics with systems of intermediate fissility

    Indian Academy of Sciences (India)

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

    2015-08-01

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

  6. Intermediate steps towards the 2000-Watt society in Switzerland: an energy-economic scenario analysis[Dissertation 17314

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, T. F

    2007-07-01

    In this dissertation by Thorsten Frank Schulz the intermediate steps necessary to realise the 2000-Watt Society in Switzerland are examined. An analysis of an energy-economic scenario shows that the 2000-Watt Society should be seen as a long-term goal. According to the author, the major changes required to allow the implementation of this project concern energy-transformation and energy-demand technologies. Electricity will, according to the author, play an important role in a service-oriented society in the future. In such a transformation even intermediate steps are associated with considerable expense. The aims of the 2000-Watt Society project are listed. Energy and CO{sub 2} balances for the domestic and transport sectors are presented and discussed. Complementary analyses are presented concerning fuel cells and wood-based fuel technologies. Finally, the implications of the 2000-Watt society and the effects of technological change are summarised and an outlook is presented.

  7. Relative fission product yield determination in the USGS TRIGA Mark I reactor

    Science.gov (United States)

    Koehl, Michael A.

    Fission product yield data sets are one of the most important and fundamental compilations of basic information in the nuclear industry. This data has a wide range of applications which include nuclear fuel burnup and nonproliferation safeguards. Relative fission yields constitute a major fraction of the reported yield data and reduce the number of required absolute measurements. Radiochemical separations of fission products reduce interferences, facilitate the measurement of low level radionuclides, and are instrumental in the analysis of low-yielding symmetrical fission products. It is especially useful in the measurement of the valley nuclides and those on the extreme wings of the mass yield curve, including lanthanides, where absolute yields have high errors. This overall project was conducted in three stages: characterization of the neutron flux in irradiation positions within the U.S. Geological Survey TRIGA Mark I Reactor (GSTR), determining the mass attenuation coefficients of precipitates used in radiochemical separations, and measuring the relative fission products in the GSTR. Using the Westcott convention, the Westcott flux, modified spectral index, neutron temperature, and gold-based cadmium ratios were determined for various sampling positions in the USGS TRIGA Mark I reactor. The differential neutron energy spectrum measurement was obtained using the computer iterative code SAND-II-SNL. The mass attenuation coefficients for molecular precipitates were determined through experiment and compared to results using the EGS5 Monte Carlo computer code. Difficulties associated with sufficient production of fission product isotopes in research reactors limits the ability to complete a direct, experimental assessment of mass attenuation coefficients for these isotopes. Experimental attenuation coefficients of radioisotopes produced through neutron activation agree well with the EGS5 calculated results. This suggests mass attenuation coefficients of molecular

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

    CERN Multimedia

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

  9. Investigation of fine-structure dips in fission-fragment mass distribution: An asymmetric two centre shell model approach

    Science.gov (United States)

    Malik, Sham S.

    2017-04-01

    The fission fragment mass distribution followed by neutron emission is studied for the 208Pb (18O , f) reaction using the asymmetric two centre shell model. The measured mass distribution spectrum reveals new kind of systematics on shell structure and leads to an improved understanding of structure effects in nuclear fission. A detailed investigation of shell effects both in potential and cranking mass parameter has been carried out for explaining the observed fine structure dips (i.e., less probable distributions) corresponding to shell closure (Z = 50 and/or N = 82) of fission fragments and their complementary partners. The available energy states for the decay process are obtained by solving the Schrödinger equation and found that first-five eigenstates are sufficient in reproducing the observed mass distribution spectrum. An outcome of the asymmetric two centre shell model also completely favours the observed claim that ;the total number of emitted neutrons between correlated pairs of fission fragments should not exceed 6;. A complete observed spectrum is obtained by adding the mass distribution yields of all 6-neutron emission channels. This suggests a possible importance of extending these calculations to get new insight into an understanding of the dynamical behaviour of fragment formation in the fission process.

  10. The Multi MegaWatt target station of EURISOL facility and its performance (SATIF9)

    CERN Document Server

    Kharoua, C

    This presentation summarises the work carried out for the Multi Megawatt target station of the EURISOL Design Study with a special attention to the coupled neutronics of the liquid converter and fission target (MAFF/PIAFE design like) and the overall performance of the facility, which will sustain fast neutron fluxes of the order of 1014 n/cm2/s. The production of radionuclides in the actinide targets as well as in the liquid metal are also evaluated, showing that the targeted 1015 fissions/s can be achieved.

  11. Neutron-induced fission fragment angular distribution at CERN n TOF: The Th-232 case

    CERN Document Server

    Tarrio, Diego; Paradela, Carlos

    This thesis work was done in the frame of the study of the neutron-induced fission of actinides and subactinides at the CERN n TOF facility using a fast Parallel Plate Avalanche Counters (PPACs) setup. This experimental setup provide us with an intense neutron beam with a white spectrum from thermal to 1 GeV and with an outstanding high resolution provided by its flight path of 185 m. In our experiment, fission events were identified by detection of both fission fragments in time coincidence in the two PPAC detectors flanking the corresponding target. This technique allowed us to discriminate the fission events from the background produced by α disintegration of radioactive samples and by particles produced in spallation reactions. Because PPAC detectors are insensitive to the γ flash, it is possible to reach energies as high as 1 GeV. The stripped cathodes provide the spatial position of the hits in the detectors, so that the emission angle of the fission fragments can be measured. Inside the reaction cham...

  12. Decay characteristics of fission products and summation calculation

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Tadashi [Faculty of Engineering, Musashi Institute of Technology, Tokyo (Japan)

    1999-02-01

    This paper reviews the decay characteristics of fission products on the viewpoint of summation calculation. The fission products (FPs) are accumulated in the operating power reactors. As they are neutron-rich at the time of scission, they undergo successive beta decays toward stable nuclides. To grasp the quantity of an arbitrary nuclide, fission yields, decay constants and blanching ratios of the nuclide in the same decay chain ( a mass chain of the fixed mass is sufficient) must be known. As a neutron capture increases the mass, and release of a delayed neutron decreases the mass, capture cross sections and delayed neutron emitting ratios are also required. If these values of all FP are known, the quantities such as time dependent decay heat and the delayed neutron fraction can be calculated by summation of the contribution of the nuclides. A computer code ORIGEN-2 is a typical example to compute these quantities. The more important than computer code is the data library for summation calculation which includes physical constants such as fission yields, decay constants, blanching ratio, beta and gamma energy emitted at a beta decay, delayed neutron emitting ratios, and neutron capture cross sections for more than 1000 FP nuclides. They are realized in JNDC FP Decay Data Library-Version 2 of Japan, JEF-2 by western European countries, and ENDF/B-VI of USA. The early versions (until early 80's) of these full-scale libraries showed worse agreement with experiment than the old libraries based on approximations and estimates. The application of the gross theory to beta-decay' to short-lived FPs could solve the problem. The above disagreement is explained by having dropped of high excitation levels of short lived daughter nuclides. This is called as Pandemonium Problem. The summation calculation for the gamma ray spectrum succeeded to predict the experimental value by correcting theoretical spectrum. However, there remains still an underestimate for cooling

  13. Binary and Ternary Fission Within the Statistical Model

    Science.gov (United States)

    Adamian, Gurgen G.; Andreev, Alexander V.; Antonenko, Nikolai V.; Scheid, Werner

    The binary and ternary nuclear fission are treated within the statistical model. At the scission point we calculate the potentials as functions of the deformations of the fragments in the dinuclear model. The potentials give the mass and charge distributions of the fission fragments. The ternary fission is assumed to occur during the binary fission.

  14. Recovery and use of fission product noble metals

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, G.A.; Rohmann, C.A.; Perrigo, L.D.

    1980-06-01

    Noble metals in fission products are of strategic value. Market prices for noble metals are rising more rapidly than recovery costs. A promising concept has been developed for recovery of noble metals from fission product waste. Although the assessment was made only for the three noble metal fission products (Rh, Pd, Ru), there are other fission products and actinides which have potential value. (DLC)

  15. Temperature dependent fission fragment distribution in the Langevin equation

    Institute of Scientific and Technical Information of China (English)

    WANG Kun; MA Yu-Gang; ZHENG Qing-Shan; CAI Xiang-Zhou; FANG De-Qing; FU Yao; LU Guang-Cheng; TIAN Wen-Dong; WANG Hong-Wei

    2009-01-01

    The temperature dependent width of the fission fragment distributions was simulated in the Langevin equation by taking two-parameter exponential form of the fission fragment mass variance at scission point for each fission event. The result can reproduce experimental data well, and it permits to make reliable estimate for unmeasured product yields near symmetry fission.

  16. Dynamics of Rotationally Fissioned Asteroids

    Science.gov (United States)

    Jacobson, Seth A.; Scheeres, D. J.

    2010-10-01

    We present a model for near-Earth asteroid (NEA) rotational fission that results in the evolution of all observed types of NEA systems: synchronous binaries, asteroid pairs, doubly synchronous binaries, high-e binaries, ternary systems, and contact binaries. The model consists of "rubble pile” asteroid geophysics, the YORP and binary YORP effects, and mutual gravitational interactions. An NEA can be modeled as a ``rubble pile"--a collection of gravitationally bound boulders with a distribution of size scales and very little tensile strength between them. The YORP effect torques a "rubble pile” asteroid until the asteroid reaches its disruption spin limit, and then two collections of boulders will enter into orbit about each other determined by the largest distance between mass centers. This binary system dynamically evolves under the effects of non-spherical gravitational potentials, solar gravitational perturbations, and mutual body tides. The coupling between the spin states and orbit state chaotically drives the system into the observed asteroid classes with mass ratio, q, distinguishing two evolutionary tracks. High mass ratio systems, q>0.2, evolve tidally into doubly synchronous binaries and then continued to be evolved by BYORP. Low mass ratio systems, qfission, creating a chaotic ternary system. We call this new process secondary fission. The resulting triple system may eject one body or, more often, send one into a slow speed impact with the primary. These processes tend to stabilize the initially chaotic binaries to create synchronous binaries. These results emphasize the importance of the initial component size distribution and configuration within the parent body. This work is supported by NASA's PGG and OPR programs through grants: NNX08AL51G and NNX09AU23G.

  17. Fission cross section measurements for minor actinides

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-03-01

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

  18. Fission induced by nucleons at intermediate energies

    CERN Document Server

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

    2014-01-01

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

  19. Rearrangement of cluster structure during fission processes

    DEFF Research Database (Denmark)

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

    2004-01-01

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

  20. Fission cross section measurements for minor actinides

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-03-01

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

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

    CERN Document Server

    Goddard, P M; Rios, A

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Rossi P C R

    2012-02-01

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

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

    CERN Document Server

    Veselsky, Martin

    2012-01-01

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

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

    Indian Academy of Sciences (India)

    R G Thomas

    2015-08-01

    Synthesis of heavy and superheavy elements is severely hindered by fission and fission-like processes. The probability of these fission-like, non-equilibrium processes strongly depends on the entrance channel parameters. This article attempts to summarize the recent experimental findings and classify the signatures of these non-equilibrium processes based on macroscopic variables. The importance of the sticking time of the dinuclear complex with respect to the equilibration times of various degrees of freedom is emphasized.

  5. Measurement of fast electrons spectra generated by interaction between solid target and peta watt laser

    Energy Technology Data Exchange (ETDEWEB)

    Tanimoto, T; Habara, H; Tanaka, K A; Kodama, R [Graduate School of Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nakatsutsumi, M [Laboratoire pour l' Utilisation des Laser Intenses (LULI), CNRS, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau, Cedex F 91128 (France); Lancaster, K L; Green, J S; Scott, R H H; Sherlock, M; Norreys, P A [STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX (United Kingdom); Evans, R G; Haines, M G [Department of Physics, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2BZ (United Kingdom); Kar, S; Zepf, M [Centre for Plasma Physics, School of Mathematics and Physics, Queens University Belfast, University Road, Belfast BT7 1NN (United Kingdom); King, J; Ma, T; Wei, M S; Yabuuchi, T; Beg, F N [Department of Mechanical and Aerospace Engineering, UC San Diego, 9500 Gillman Drive 0411, La Jolla, California 92093-0411, United States of America (United States); Key, M H, E-mail: tanimoto@ile.osaka-u.ac.j [Lawrence Livermore National Laboratory, PO Box 808, Livermore, California 94550, United States of America (United States)

    2010-08-01

    Fast electron energy spectra have been measured for a range of intensities between 10{sup 18} Wcm{sup -2} and 10{sup 21} Wcm{sup -2} and for different target materials using electron spectrometers. Several experimental campaigns were conducted on peta watt laser facilities at the Rutherford Appleton Laboratory and Osaka University. In these experimental campaigns, the pulse duration was varied from 0.5 ps to 5 ps. The laser incident angle was also changed from normal incidence to 40{sup 0} in p-polarized. The results show a reduction from the ponderomotive scaling on fast electrons over 10{sup 20} Wcm{sup -2}.

  6. Lumen Maintenance Testing of the Philips 60-Watt Replacement Lamp L Prize Entry

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Kelly L.; Hafen, Ryan P.; Hathaway, John E.; McCullough, Jeffrey J.

    2012-09-01

    This paper describes testing conducted to evaluate the Philips' L Prize award winning 60-watt LED replacement product's ability to meet the lifetime/lumen maintenance requirement of the competition, which was: "having 70 percent of the lumen value under subparagraph (A) [producing a luminous flux greater than 900 lumens] exceeding 25,000 hours under typical conditions expected in residential use." A custom test apparatus was designed and constructed for this testing and a statistical approach was developed for use in evaluating the test results. This will be the only publicly available, third-party data set of long-term LED product operation.

  7. Design of New Long-Distance Intelligent Watt-Hour Meter

    Institute of Scientific and Technical Information of China (English)

    Zhao Wenlei; Xue Yanbing

    2005-01-01

    The design scheme for a new kind of long-distance intelligent watt-hour meter is presented. In the system, the control computer communicates with the bank's host computer by the X. 25 network; the built-in embeded secure access module (FSAM) can verify data by commutation with the intelligent nodes that enhance the security of the data. IC TSS721 is adopted to collect data remotely,and the CPU IC card is used to ensure the the bargaining security and reliability. In addition, the software of the system is introduced.

  8. Chaos in complex motor networks induced byNewman-Watts small-world connections

    Institute of Scientific and Technical Information of China (English)

    WeiDu-Qu; Luo Xiao-Shu; Zhang Bo

    2011-01-01

    We investigate how dynamical behaviours of complex motor networks depend on the Newman-Watts small-world (NWSW) connections.Network elements are described by the permanent magnet synchronous motor (PMSM) with the values of parameters at which each individual PMSM is stable.It is found that with the increase of connection probability p,the motor in networks becomes periodic and falls into chaotic motion as p further increases.These phenomena imply that NWSW connections can induce and enhance chaos in motor networks.The possible mechanism behind the action of NWSW connections is addressed based on stability theory.

  9. Acoustic emission monitoring of hot functional testing: Watts Bar Unit 1 Nuclear Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Hutton, P.H.; Dawson, J.F.; Friesel, M.A.; Harris, J.C.; Pappas, R.A.

    1984-06-01

    Acoustic emission (AE) monitoring of selected pressure boundary areas at TVA's Watts Bar, Unit 1 Nuclear Power Plant during hot functional preservice testing is described in this report. The report deals with background, methodology, and results. The work discussed here is a major milestone in a program supported by NRC to develop and demonstrate application of AE monitoring for continuous surveillance of reactor pressure boundaries to detect and evaluate growing flaws. The subject work demonstrated that anticipated problem areas can be overcome. Work is continuing toward AE monitoring during reactor operation.

  10. Dynamics of a periodic Watt-type predator-prey system with impulsive effect

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiaoqin [Faculty of Science, Shaanxi University of Science and Technology, Xianyang, Shaanxi 712081 (China)], E-mail: wangxiaoqin@sust.edu.cn; Wang Weiming [School of Mathematics and Information Science, Wenzhou University, Wenzhou, Zhejiang 325035 (China)], E-mail: weimingwang2003@163.com; Lin Xiaolin [Faculty of Science, Shaanxi University of Science and Technology, Xianyang, Shaanxi 712081 (China)

    2009-02-15

    In this paper, an impulsive periodic predator-prey system with Watt-type functional response is investigated. By using the Floquet theory of linear periodic impulsive equation, the stability conditions for the prey-eradication positive periodic solution are given, and the boundedness of the system is proved. By the method of coincidence degree, the sufficient conditions for the existence of at least one strictly positive periodic solution are obtained. Furthermore, we give numerical analysis to confirm our theoretical results. It will be useful for ecosystem control.

  11. 3-D model of a radial flow sub-watt methanol fuel processor

    Energy Technology Data Exchange (ETDEWEB)

    Holladay, J. D.; Wang, Y.

    2015-10-01

    A 3-D model is presented for a novel sub-watt packed bed reactor. The reactor uses an annular inlet flow combined with a radial flow packed bed reactor. The baseline reactor is compared to a reactor with multiple outlets and a reactor with 3 internal fins. Increasing the outlets from 1 to 4 did improve the flow distribution, but did not increase the performance in the simulation. However, inserting fins allowed a decrease in temperature with same inlet flow of approximately 35K. Or the inlet flow rate could be increased by a factor of 2.8x while maintaining >99% conversion.

  12. Comment on 'Critical materials assessment program' (S. A. Smith and R. Watts, Battelle Memorial Institute)

    Energy Technology Data Exchange (ETDEWEB)

    Zweibel, K.; Jackson, B.; Hermann, A.

    1986-01-15

    In the article ''Critical materials assessment program'' (1984) Smith and Watts examine the availability of indium for use in CuInSe/sub 2//CdS solar cells and conclude that indium's use should be ''decreased or eliminated''. Our response to this article is an update of the status of indium usage in CuInSe/sub 2/ cells. It will be shown that the use of indium is being significantly reduced and that pressures on the world indium supply can be minimal. Our conclusion is that the CdS/CuInSe/sub 2/ solar cell technology is viable, not limited by indium availability or cost.

  13. Synchronization of Coupled Oscillators on Newman-Watts Small-World Networks

    Institute of Scientific and Technical Information of China (English)

    GUAN Jian-Yue; XU Xin-Jian; WU Zhi-Xi; WANG Ying-Hai

    2006-01-01

    We investigate the collection behaviour of coupled phase oscillators on Newman- Watts small-world networks in one and two dimensions. Each component of the network is assumed as an oscillator and each interacts with the others following the Kuramoto model. We then study the onset of global synchronization of phases and frequencies based on dynamic simulations and finite-size scah'ng. Both the phase and frequency synchronization are observed to emerge in the presence of a tiny fraction of shortcuts and enhanced with the increases of nearest neighbours and lattice dimensions.

  14. Angular momenta of fission fragments in the α-accompanied fission of 252Cf

    Science.gov (United States)

    Jandel, M.; Kliman, J.; Krupa, L.; Morháč, M.; Hamilton, J. H.; Kormicki, J.; Ramayya, A. V.; Hwang, J. K.; Luo, Y. X.; Fong, D.; Gore, P.; Ter-Akopian, G. M.; Oganessian, Yu. Ts.; Rodin, A. M.; Fomichev, A. S.; Popeko, G. S.; Daniel, A. V.; Rasmussen, J. O.; Macchiavelli, A. O.; Stoyer, M. A.; Donangelo, R.; Cole, J. D.

    2005-06-01

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

  15. Measurement of 235U Fission Yield Induced by 252Cf Fission Neutron

    Institute of Scientific and Technical Information of China (English)

    YANG; Yi; LIU; Shi-long; JIANG; Wen-gang

    2015-01-01

    We measured fission yields of 235U by 252Cf fission neutrons with the directγray spectrometric method.Square sample foils of 15 mm,abundance of 235U is 90.2%,mass of 0.7gram,covered by pure aluminum foil.After irradiations every sample was measured by HPGe spectrometry for about 2months.Based on 140Ba’s fission yield,we get relative fission yields and the results were shown in Fig.1.

  16. Fission fragment angular distribution in heavy-ion-induced fission with anomalous behavior

    Science.gov (United States)

    Soheyli, S.; Feizi, B.

    2014-08-01

    Fission fragment angular distribution in heavy-ion-induced fission reactions is of particular importance. Transition state theory is provided to determine the angular distribution of fission fragments which includes standard saddle-point statistical and standard scission-point statistical models. The standard saddle-point statistical model was not able to reproduce the experimental fission fragment angular anisotropies for several heavy-ion-induced fission systems. In contrast to the standard saddle-point model, the standard scission-point statistical model was fairly successful in the prediction of angular anisotropy in heavy-ion-induced fission reaction systems with an anomalous behavior in angular anisotropy of fission fragments, but this model is not widely used as the standard saddle-point statistical model. In this research, a generalized model is introduced for the prediction of fission fragments angular anisotropy in the heavy-ion-induced fission reaction systems having an anomalous behavior. For this purpose, we study the N14,O16,F19+Th232;O16,F19+U238;Mg24,Si28,S32+Pb208;S32+Au197; and O16+Cm248 reaction systems. Finally, it is shown that the presented model is much more successful than previous models.

  17. Measurements of the effective cumulative fission yields of 143Nd, 145Nd, 146Nd, 148Nd and 150Nd for 235U in the PHENIX fast reactor

    Directory of Open Access Journals (Sweden)

    Privas Edwin

    2016-01-01

    Full Text Available The effective Neodymium cumulative fission yields for 235U have been measured in the fast reactor PHENIX relatively to the 235U fission cross-section. The data were derived from isotope-ratio measurements obtained in the frame of the PROFIL-1, PROFIL-2A and PROFIL-2B programs. The interpretations of the experimental programs were performed with the ERANOS code in association with the Joint Evaluated Fission and Fusion library JEFF-3.1.1. Final results for 143Nd, 145Nd, 146Nd, 148Nd and 150Nd were 5.61%, 3.70%, 2.83%, 1.64% and 0.66%, respectively. The relative uncertainties attached to each of the cumulative fission yields lie between 2.1% and 2.4%. The main source of uncertainty is due to the fluence scaling procedure (<2%. The uncertainties on the Neodymium capture cross-sections provide a contribution lower than 1%. The energy dependence of the fission yields was studied with the GEF code from the thermal energy to 20 MeV. Neutron spectrum average corrections, deduced from GEF calculations, were applied to our effective fission yields with the aim of estimating fission yields at 400 keV and 500 keV, as given in the International Evaluated Nuclear Data Files (JEFF, ENDF/B and JENDL. The neutron spectrum average correction calculated for the PROFIL results remains lower than 1.5%.

  18. Monte-Carlo Hauser-Feshbach simulations of prompt fission gamma-ray properties

    Science.gov (United States)

    Stetcu, Ionel; Talou, Patrick; Kawano, Toshihiko; Jandel, Marian

    2014-09-01

    Properties of prompt fission neutrons and γ rays, emitted before the weak decays of the fission fragments toward stability, are important for both nuclear technologies and a better understanding of the fission process. In the present work, we use the Hauser-Feshbach model to simulate the de-excitation of the fully accelerated fission fragments treated as compound nuclei. Our Monte-Carlo implementation of the Hauser-Feshbach statistical model, which takes into account the competition between the neutron and γ emissions, allows the description of both average quantities, like in the Los Alamos model, and correlations between the emitted particles. Our simulations will be compared against available experimental data and current evaluations. In particular, we will compare our average γ-ray spectrum with recent measurements at the research reactor KFKI in Budapest for the 235U(nth , f) and 252Cf(sf) reactions, as well as multiplicity-dependent distributions obtained at the DANCE facility at LANSCE. Properties of prompt fission neutrons and γ rays, emitted before the weak decays of the fission fragments toward stability, are important for both nuclear technologies and a better understanding of the fission process. In the present work, we use the Hauser-Feshbach model to simulate the de-excitation of the fully accelerated fission fragments treated as compound nuclei. Our Monte-Carlo implementation of the Hauser-Feshbach statistical model, which takes into account the competition between the neutron and γ emissions, allows the description of both average quantities, like in the Los Alamos model, and correlations between the emitted particles. Our simulations will be compared against available experimental data and current evaluations. In particular, we will compare our average γ-ray spectrum with recent measurements at the research reactor KFKI in Budapest for the 235U(nth , f) and 252Cf(sf) reactions, as well as multiplicity-dependent distributions obtained at the

  19. Ternary fission induced by polarized neutrons

    Science.gov (United States)

    Gönnenwein, Friedrich

    2013-12-01

    Ternary fission of (e,e) U- and Pu- isotopes induced by cold polarized neutrons discloses some new facets of the process. In the so-called ROT effect shifts in the angular distributions of ternary particles relative to the fission fragments show up. In the so-called TRI effect an asymmetry in the emission of ternary particles relative to a plane formed by the fragment momentum and the spin of the neutron appear. The two effects are shown to be linked to the components of angular momentum perpendicular and parallel to the fission axis at the saddle point of fission. Based on theoretical models the spectroscopic properties of the collective transitional states at the saddle point are inferred from experiment.

  20. Fission of Multiply Charged Alkali Clusters

    Science.gov (United States)

    Barnett, Robert N.; Yannouleas, Constantine; Landman, Uzi

    2001-03-01

    We use ab-initio molecular dynamics simulations to investigate the fission of multiply charged pure and mixed alkali clusters. Positive (+2 to +4) clusters of up to 30 atoms are considered. The clusters are initially equilibrated with a charge of +1 or +2 (depending on size) and at temperatures of 150 to 800 K. subsequently the clusters are further ionized and their evolution is followed. For doubly charged clusters binary fission occurs, while higher charged clusters fission through ternary or quaternary channels. The most common occurrence is the emission of a singly charged 3-atom cluster, which may occur repeatedly until the remaining cluster is stable. The dynamics of the fission process is discussed, and the results are compared with experiments and with the predictions of the liquid-drop and shell-corrected jellium models.

  1. "UCx fission targets oxidation test stand"

    CERN Document Server

    Lacroix, Rachel

    2014-01-01

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

  2. Development of fission Mo-99 production technology

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-05-01

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

  3. The Coincident Fission Fragment Detector (CFFD)

    Science.gov (United States)

    Wakhle, A.; Hammerton, K.; Kohley, Z.; Yurkon, J.; Stiefel, K.

    2017-08-01

    A Parallel Plate Avalanche Counter (PPAC) based fission detector system, called the Coincident Fission Fragment Detector (CFFD), has been developed for the ReA3 re-accelerator facility of the National Superconducting Cyclotron Laboratory (NSCL). Binary reaction kinematics are reconstructed based on position and time-of-flight measurements of fission fragments. Large area PPACs provide 1 ns level time resolution and mm level position resolution. The detectors allow measurements of fission product angular and mass distributions of heavy-ion induced fusion reactions. The 30 cm by 40 cm active area of each PPAC provides large solid angle coverage well suited for measurements of low intensity rare-isotope beams (RIBs).

  4. Characteristics of spontaneous fission of 250No

    Science.gov (United States)

    Svirikhin, A. I.; Andreev, A. V.; Yeremin, A. V.; Izosimov, I. N.; Isaev, A. V.; Kuznetsov, A. N.; Kuznetsova, A. A.; Malyshev, O. N.; Popeko, A. G.; Popov, Y. A.; Sokol, E. A.; Chelnokov, M. L.; Chepigin, V. I.; Schneidman, T. M.; Gall, B.; Dorvaux, O.; Brione, P.; Hauschild, K.; Lopez-Martenz, A.; Rezynkina, K.; Mullins, S.; Jones, P.; Mosat, P.

    2017-07-01

    This study describes an experiment on investigating the properties of spontaneous fission of shortlived neutron-deficient nuclei synthesized in the reaction of complete fusion 48Ca + 204Pb = 252No*. The experiment is performed using the SHELS separator and the beam of multicharged ions at U-400 accelerator (LNR, JINR). Two activities undergoing spontaneous fission, which can be related to the ground and isomeric states of 250No nucleus, are registered. The half-lives, total kinetic energies of fission fragments, and neutron multiplicities are measured for the short-lived nuclei. The average number of neutrons per fission for the activity with t 1/2 = 5.1 ± 0.3 μs is = 4.38 ± 0.13 μs, and for nuclei with the half-life t 1/2 = 36 ± 3 μs it is xxxxx.

  5. Energy from nuclear fission an introduction

    CERN Document Server

    De Sanctis, Enzo; Ripani, Marco

    2016-01-01

    This book provides an overview on nuclear physics and energy production from nuclear fission. It serves as a readable and reliable source of information for anyone who wants to have a well-balanced opinion about exploitation of nuclear fission in power plants. The text is divided into two parts; the first covers the basics of nuclear forces and properties of nuclei, nuclear collisions, nuclear stability, radioactivity, and provides a detailed discussion of nuclear fission and relevant topics in its application to energy production. The second part covers the basic technical aspects of nuclear fission reactors, nuclear fuel cycle and resources, safety, safeguards, and radioactive waste management. The book also contains a discussion of the biological effects of nuclear radiation and of radiation protection, and a summary of the ten most relevant nuclear accidents. The book is suitable for undergraduates in physics, nuclear engineering and other science subjects. However, the mathematics is kept at a level that...

  6. Modeling Fission Product Sorption in Graphite Structures

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-04-08

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

  7. Emission of intermediate mass fragments during fission

    Science.gov (United States)

    Chen, S. L.; de Souza, R. T.; Cornell, E.; Davin, B.; Hamilton, T. M.; Hulbert, D.; Kwiatkowski, K.; Lou, Y.; Viola, V. E.; Korteling, R. G.; Wile, J. L.

    1996-11-01

    Ternary fission in the reaction 4He + 232Th at Elab=200 MeV has been observed. Intermediate mass fragments (IMF: 3fission. The widths of the energy spectra are relatively constant for neck fragments with Z>=4, suggesting little variability in the scission configurations. A linear dependence of on Z is observed for the neck IMFs. The observed trend is compared with a Coulomb trajectory model.

  8. MCNP6 Fission Multiplicity with FMULT Card

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-06-18

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

  9. Detector instrumentation for nuclear fission studies

    Indian Academy of Sciences (India)

    Akhil Jhingan

    2015-09-01

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

  10. A revised calculational model for fission

    Energy Technology Data Exchange (ETDEWEB)

    Atchison, F.

    1998-09-01

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

  11. Seventy-five years of nuclear fission

    Indian Academy of Sciences (India)

    S S Kapoor

    2015-08-01

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

  12. Neutron spectrum unfolding: Pt. 2; Experimental

    Energy Technology Data Exchange (ETDEWEB)

    Matiullah (Centre for Nuclear Studies, Nilore, Islamabad (Pakistan)); Wiyaja, D.S. (PPTN - BATAN, Bandung (Indonesia)); Berzonis, M.A.; Bondars, H.; Lapenas, A.A. (Latvijskij Gosudarstvennyj Univ., Riga (USSR)); Kudo, K. (Electrotechnical Lab., Tsukuba, Ibaraki (Japan)); Majeed, A.; Durrani, S.A. (Birimingham Univ. (United Kingdom). School of Physics and Space Research)

    1991-01-01

    In Part I of this paper, we described the use of the computer code SAIPS in neutron spectrum unfolding. Here in Part II, we present our experimental work carried out to study the shape of the neutron spectrum in different experimental channels of a 5 MW light-water cooled and moderated research reactor. The spectral neutron flux was determined using various fission foils (placed in close contact with mica track detectors) and activation detectors. From the measured activities, the neutron spectrum was unfolded by SAIPS. (author).

  13. In-beam investigation of ternary fission

    Science.gov (United States)

    Kotte, R.; Fromm, W. D.; Hentschel, E.; Ortlepp, H. G.; Schilling, K. D.; Seidel, W.; Stary, F.; Zwicker, G.

    1988-06-01

    Nuclear fission accompanied by long-range alpha particles has been investigated. Fission was induced by irradiating a natural uranium target with 13.5 MeV deuterons. The alpha energy and angular distributions are similar to those observed in spontaneous or thermal neutron induced fission. The correlation angle between alpha particles and light fission fragments has a most probable value ofbar \\vartheta _{l f - α } = 82.1^circ ± 0.9^circ and a dispersion (FWHM) of Δϑ=18.4°±1.2°. The mean value and dispersion of the energy distribution arebar E_α = 14.8 ± 1.0 MeV and ΔE=9.1±1.2 MeV (FWHM), respectively. The peak-to-valley ratio of the ternary fission fragment mass distribution is found to increase with increasing alpha energy. For near-symmetric mass division, a strong broadening of the angular distribution is observed. The results are discussed in the frame of a multichannel-fission model.

  14. Spontaneous fission of the heaviest elements

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, D.C.

    1989-04-01

    Although spontaneous fission was discovered in /sup 238/U in 1940, detailed studies of the process were first made possible in the 1960's with the availability of milligram quantities of /sup 252/Cf. The advent of solid-state detectors made it possible to perform measurements of coincident fission fragments from even very short-lived spontaneous fission activities or those available in only very small quantities. Until 1971 it was believed that the main features of the mass and kinetic-energy distributions were essentially the same as those for thermal neutron-induced fission and that all low-energy fission proceeded via asymmetric mass division with total kinetic energies which could be derived by linear extrapolation from those of lighter elements. In 1971, measurements of /sup 257/Fm showed an increase in symmetric mass division with anomalously high TKE's. Subsequent experiments showed that in /sup 258/Fm and /sup 259/Fm, the most probable mass split was symmetric with very high total kinetic energy. Measurements for the heavier elements have shown symmetric mass distributions with both high and low total kinetic energies. Recent results for spontaneous fission properties of the heaviest elements are reviewed and compared with theory. 31 refs., 8 figs., 1 tab.

  15. The watt balance: determination of the Planck constant and redefinition of the kilogram.

    Science.gov (United States)

    Stock, M

    2011-10-28

    Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last material artefact to define a base unit of the SI, and it influences several other base units. This situation is no longer acceptable in a time of ever-increasing measurement precision. It is therefore planned to redefine the unit of mass by fixing the numerical value of the Planck constant. At the same time three other base units, the ampere, the kelvin and the mole, will be redefined. As a first step, the kilogram redefinition requires a highly accurate determination of the Planck constant in the present SI system, with a relative uncertainty of the order of 1 part in 10(8). The most promising experiment for this purpose, and for the future realization of the kilogram, is the watt balance. It compares mechanical and electrical power and makes use of two macroscopic quantum effects, thus creating a relationship between a macroscopic mass and the Planck constant. In this paper, the operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all available experimental determinations of the Planck constant, and it is shown that further investigation is needed before the redefinition of the kilogram can take place. Independent of this requirement, a consensus has been reached on the form that future definitions of the SI base units will take.

  16. Remedial investigation/feasibility study report for Lower Watts Bar Reservoir Operable Unit

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-03-01

    This document is the combined Remedial Investigation and Feasibility Study Report for the lower Watts Bar Reservoir (LWBR) Operable Unit (OU). The LWBR is located in Roane, Rhea, and Meigs counties, Tennessee, and consists of Watts Bar Reservoir downstream of the Clinch river. This area has received hazardous substances released over a period of 50 years from the US Department of Energy`s Oak Ridge Reservation (ORR), a National Priority List site established under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). As required by this law, the ORR and all off-site areas that have received contaminants, including LWBR, must be investigated to determine the risk to human health and the environment resulting from these releases, the need for any remedial action to reduce these risks, and the remedial actions that are most feasible for implementation in this OU. Contaminants from the ORR are primarily transported to the LWBR via the Clinch River. There is little data regarding the quantities of most contaminants potentially released from the ORR to the Clinch River, particularly for the early years of ORR operations. Estimates of the quantities released during this period are available for most radionuclides and some inorganic contaminants, indicating that releases 30 to 50 years ago were much higher than today. Since the early 1970s, the release of potential contaminants has been monitored for compliance with environmental law and reported in the annual environmental monitoring reports for the ORR.

  17. Effects of choline chloride on electrodeposited Ni coating from a Watts-type bath

    Science.gov (United States)

    Wang, Yurong; Yang, Caihong; He, Jiawei; Wang, Wenchang; Mitsuzak, Naotoshi; Chen, Zhidong

    2016-05-01

    Electrodeposition of bright nickel (Ni) was carried out in a Watts-type bath. Choline chloride (ChCl) was applied as a multifunctional additive and substitute for nickel chloride (NiCl2) in a Watts-type bath. The function of ChCl was investigated through conductivity tests, anodic polarization, and cathodic polarization experiments. The studies revealed that ChCl performed well as a conducting salt, anodic activator, and cathodic inhibitor. The effects of ChCl on deposition rate, preferred orientation, grain size, surface morphology, and microhardness of Ni coatings were also studied. The deposition rate reached a maximum value of greater than 27 μm h-1 when 20 g L-1 ChCl was introduced to the bath. Using X-ray diffraction, it was confirmed that progressive addition of ChCl promoted the preferred crystal orientation modification from (2 0 0) and (2 2 0) to (1 1 1), refined grain size, and enhanced microhardness. The presence of ChCl lowered the roughness of the coating.

  18. Microcombustor-thermoelectric power generator for 10-50 watt applications

    Science.gov (United States)

    Marshall, Daniel S.; Cho, Steve T.

    2010-04-01

    Fuel-based portable power systems, including combustion and fuel cell systems, take advantage of the 80x higher energy density of fuel over lithium battery technologies and offer the potential for much higher energy density power sources - especially for long-duration applications, such as unattended sensors. Miniaturization of fuel-based systems poses significant challenges, including processing of fuel in small channels, catalyst poisoning, and coke and soot formation. Recent advances in micro-miniature combustors in the 200Watt thermal range have enabled the development of small power sources that use the chemical energy of heavy fuel to drive thermal-to-electric converters for portable applications. CUBE Technology has developed compact Micro-Furnace combustors that efficiently deliver high-quality heat to optimized thermal-to-electric power converters, such as advanced thermoelectric power modules and Stirling motors, for portable power generation at the 10-50Watt scale. Key innovations include a compact gas-gas recuperator, innovative heavy fuel processing, coke- & soot-free operation, and combustor optimization for low balance-of-plant power use while operating at full throttle. This combustor enables the development of robust, high energy density, miniature power sources for portable applications.

  19. A five-watt G-M/J-T refrigerator for LHe target at BNL

    Science.gov (United States)

    Jia, L. X.; Wang, L.; Addessi, L.; Miglionico, G.; Martin, D.; Leskowicz, J.; McNeill, M.; Yatauro, B.; Tallerico, T.

    2002-05-01

    A five-watts G-M/J-T refrigerator was built and installed for the high-energy physics research at Brookhaven National Laboratory in 2001. A liquid helium target of 8.25 liters was required for an experiment in the proton beam line at the Alternating Gradient Synchrotron (AGS) of BNL. The large radiation heat load towards the target requires a five-watts refrigerator at 4.2 K to support a liquid helium flask of 0.2 meter in diameter and 0.3 meter in length, which is made of Mylar film of 0.35 mm in thickness. The liquid helium flask is thermally exposed to the vacuum windows that are also made of 0.35 mm thickness Mylar film at room temperature. The refrigerator uses a two-stage Gifford-McMahon cryocooler for precooling the Joule-Thomson circuit that consists of five Linde-type heat exchangers. A mass flow rate of 0.8˜1.0 grams per second at 17.7 atm is applied to the refrigerator cold box. The two-phase helium flows between the liquid target and liquid/gas separator by means of a thermosyphon. This paper presents the system design as well as the test results including the control of the thermal oscillation.

  20. Reconciling Planck constant determinations via watt balance and enriched-silicon measurements at NRC Canada

    Science.gov (United States)

    Steele, A. G.; Meija, J.; Sanchez, C. A.; Yang, L.; Wood, B. M.; Sturgeon, R. E.; Mester, Z.; Inglis, A. D.

    2012-02-01

    The next revision to the International System of Units will emphasize the relationship between the base units (kilogram, metre, second, ampere, kelvin, candela and mole) and fundamental constants of nature (the speed of light, c, the Planck constant, h, the elementary charge, e, the Boltzmann constant, kB, the Avogadro constant, NA, etc). The redefinition cannot proceed without consistency between two complementary metrological approaches to measuring h: a 'physics' approach, using watt balances and the equivalence principle between electrical and mechanical force, and a 'chemistry' approach that can be viewed as determining the mass of a single atom of silicon. We report the first high precision physics and chemistry results that agree within 12 parts per billion: h (watt balance) = 6.626 070 63(43) × 10-34 J s and h(silicon) = 6.626 070 55(21) × 10-34 J s. When combined with values determined by other metrology laboratories, this work helps to constrain our knowledge of h to 20 parts per billion, moving us closer to a redefinition of the metric system used around the world.

  1. Field representation of a watt balance magnet by partial profile measurements

    CERN Document Server

    Li, Shisong; Zhao, Wei; Huang, Songling

    2015-01-01

    Permanent magnets with high-permeability yokes have been widely used in watt balances for supplying a robust and strong magnetic field at the coil position. Subjected to the mechanical realization, only several $B_r(z)$ (radial magnetic field along the vertical direction) profiles can be measured by coils for field characterization. In this article, we present an algorithm that can construct the global magnetic field of the air gap based on $N(N\\geq1)$ additional measurements of $B_r(z)$ profiles. The proposed algorithm is realized by polynomially estimating the $B_z(r)$ function with analysis of basic relations between two magnetic components in air gap, i.e., $B_r(r,z)$ and $B_z(r,z)$, following the Maxwell's equations. The algorithm, verified by FEM simulations, can characterize the three-dimensional contribution of the magnetic field for a watt balance magnet with acceptable accuracy, which would supply basic field parameters for alignment and misalignment corrections.

  2. Feasibility study of a 110 watt per kilogram lightweight solar array system

    Science.gov (United States)

    Shepard, N. F.; Stahle, C. V.; Schneider, A.; Hanson, K. L.

    1972-01-01

    An investigation of the feasibility of a solar array panel subsystem which will produce 10,000 watts of electrical output at 1 A.U. with an overall beginning-of-life power-to-weight ratio of at least 110 watt/kg is reported. A description of the current baseline configuration which meets these requirements is presented. A parametric analysis of the single boom, two blanket planar solar array system was performed to arrive at the optimum system aspect ratio. A novel concept for the stiffening of a lightweight solar array by canting the solar cell blankets at a small angle to take advantage of the inherent in-plane stiffness to increase the symmetric out-of-plane frequency is introduced along with a preliminary analysis of the stiffening effect. A comparison of welded and soldered solar cell interconnections leads to the conclusion that welding is required on this ultralightweight solar array. The use of a boron/aluminum composite material in a BI-STEM type deployable boom is investigated as a possible advancement in the state-of-the-art.

  3. Measurement of the energy spectra of fission fragments using nuclear track detectors and digital image processing

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa, Guillermo; Golzarri, Jose I. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, Mexico D.F. 01000 (Mexico); Castano, Victor M., E-mail: castano@fata.unam.m [Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, Boulevard Juriquilla 3001, Santiago de Queretaro, Queretaro 76230 (Mexico)

    2010-08-15

    Energy spectra of fission fragments were determined using a Nuclear Track Methodology (NTM) supported by digital image analysis and numerical data processing using a standard personal computer. The analysis of a californium ({sup 252}Cf) spectrum with this approach shows improvement compared with the values reported previously using the standard procedure, in terms of resolution and accuracy. This new method adds full automation to the technical advantages and cost effectiveness of an NTM.

  4. Fission Fusion Hybrids: a nearer term application of Fusion

    Science.gov (United States)

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

    2011-10-01

    Fission-fusion hybrids enjoy unique advantages for addressing long standing societal acceptability issues of nuclear fission power at a much lower level of technical development than a competitive fusion power plant. For waste incineration, hybrids burn intransigent transuranic residues (with the long lived biohazard) from light water reactors (LWRs). The number of hybrids needed is 5-10 times less than the corresponding number of fast reactors (FRs). The highly sub-critical hybrids, with a thermal/epithermal spectrum, incinerate > 95% of the waste in decades rather than the centuries needed for FRs. For fuel production, hybrids can produce fuel for 3-4 times as many LWRs with no fuel reprocessing. Thorium fuel rods exposed to neutrons in the hybrid reach fissile concentrations that enable efficient burning in LWR without the proliferation risks of reprocessing. The proliferation risks of this method are far less than other fuel breeding approaches, including today's gas centrifuge. With this cycle, US Thorium reserves could supply the entire US electricity supply for centuries. The centerpiece of the fuel cycle is a high power density Compact Fusion Neutron Source (major+minor radius ~ 2.5-3.5 m), which is made feasible by the super-X divertor.

  5. Inclusive spectra of hadrons created by color tube fission; 1, Probability of tube fission

    CERN Document Server

    Gedalin, E V

    1997-01-01

    The probability of color tube fission that includes the tube surface small oscillation corrections is obtained with pre-exponential factor accuracy on the basis of previously constructed color tube model. Using these expressions the probability of the tube fission in $n$ point is obtained that is the basis for calculation of inclusive spectra of produced hadrons.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bhatia, C.; Fallin, B. [Department of Physics, Duke University, Durham, NC 27708 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Gooden, M.E., E-mail: megooden@tunl.duke.edu [Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Department of Physics, North Carolina State University, Raleigh, NC 27605 (United States); Howell, C.R. [Department of Physics, Duke University, Durham, NC 27708 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Kelley, J.H. [Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Department of Physics, North Carolina State University, Raleigh, NC 27605 (United States); Tornow, W. [Department of Physics, Duke University, Durham, NC 27708 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Arnold, C.W.; Bond, E.M.; Bredeweg, T.A.; Fowler, M.M.; Moody, W.A.; Rundberg, R.S.; Rusev, G.; Vieira, D.J.; Wilhelmy, J.B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Becker, J.A.; Macri, R.; Ryan, C.; Sheets, S.A.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); and others

    2014-09-01

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

  7. A LEGO Watt Balance: An apparatus to demonstrate the definition of mass based on the new SI

    CERN Document Server

    Chao, L S; Newell, D B; Pratt, J R; Sineriz, G; Seifert, F; Cao, A; Haddad, D; Zhang, X

    2014-01-01

    A global effort to redefine our International System of Units (SI) is underway and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed numerical values of seven reference constants. More specifically, the unit of mass, the kilogram, will be realized through a fixed value of the Planck constant $h$. For instance, a watt balance can be used to realize the kilogram unit of mass within a few parts in $10^8$. Such a balance has been designed and constructed at the National Institute of Standards and Technology. For educational outreach and to demonstrate the principle, we have constructed a LEGO tabletop watt balance capable of measuring a gram size mass to 1 % relative uncertainty. This article presents the design, construction, and performance of the LEGO watt balance and its ability to determine $h$

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

    CERN Document Server

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

    2012-01-01

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

  9. Derivation of Energy Generated by Nuclear Fission-Fusion Reaction

    OpenAIRE

    Kayano, Hideo; Teshigawara, Makoto; Konashi, Kenji; Yamamoto, Takuya

    1994-01-01

    In the solids which contain fissionable elements and deuterium, it is expected that the energy generated by nuclear fission contributes to the promotion of the D-D nuclear fusion in the solids. When nuclear fission occurs by neutrons in the solid, the fissionable elements divide into two fission product nuclei having the energy of 100MeV, respectively. It is expected that the hige energy fission products promote rapidly nuclear fision reaction by knocking out the D atoms in the solids and by ...

  10. Development Of Multi-users Multi-function Watt-hour Meter Based On ATT7022B

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>According to the feature of city’s apartment building in China,a kind of Multi-users Watt-hour Meter based on ATT7022B has been developed in this paper.The master-slave MCU control model and the principles of Time Sharing Multiplex are adopted in this Watt-hour Meter,its function includes the measurement of current, voltage,power,power factor and the overload protection.It supports remote reading,pre-payment,multi-rate and etc. The practice shows that this meter has high accuracy,runs stable.It has wide prospect in the future market.

  11. Anatomy of neck configuration in fission decay

    CERN Document Server

    Patra, S K; Satpathy, L

    2010-01-01

    The anatomy of neck configuration in the fission decay of Uranium and Thorium isotopes is investigated in a microscopic study using Relativistic mean field theory. The study includes $^{236}U$ and $^{232}Th$ in the valley of stability and exotic neutron rich isotopes $^{250}U$, $^{256}U$, $^{260}U$, $^{240}Th$, $^{250}Th$, $^{256}Th$ likely to play important role in the r-process nucleosynthesis in stellar evolution. Following the static fission path, the neck configurations are generated and their composition in terms of the number of neutrons and protons are obtained showing the progressive rise in the neutron component with the increase of mass number. Strong correlation between the neutron multiplicity in the fission decay and the number of neutrons in the neck is seen. The maximum neutron-proton ratio is about 5 for $^{260}$U and $^{256}$Th suggestive of the break down of liquid-drop picture and inhibition of the fission decay in still heavier isotopes. Neck as precursor of a new mode of fission decay li...

  12. Excitation-energy dependence of the nuclear fission characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Baba, H.; Saito, T.; Takahashi, N. [Osaka City Univ. (Japan). Faculty of Science] [and others

    1996-03-01

    It is known that the width parameter of the fragment mass yield distribution follows a beautiful systematics with respect to the excitation energy. According to this systematics, the fission characteristics following the systematics should disappear when the excitation energy Ex goes down to 14 MeV. The present purpose is to elucidate if, where, how and why a transition takes place in the fission characteristics of the asymmetric fission of light actinide elements. Two types of experiments are performed, one is the double-energy measurement of the kinetic energies of complementary fragments in the thermal-neutron fission of {sup 235,233}U and proton-induced fission of {sup 238}U at 13.3- and 15.7-MeV excitations, and the other is the radiochemical study of proton-induced fission and photofission of {sup 238}U at various excitation energies. In conclusion, it has demonstrated that there are two distinctive fission mechanisms in the low-energy fission of light actinide elements and the transition between them takes place around 14-MeV excitation. The characteristics of proton fission and photofission in the energy range lower than the above transition point are the essentially the same as those of thermal-neutron fission and also spontaneous fission. The results of GDR fission indicates the fission in the high-energy side starts from the nuclear collective states, whereas the lower-energy fission is of non-collective nature. It is likely that thermal-neutron fission is rather of the barrier-penetrating type like spontaneous fission than the threshold fission. (S.Y.)

  13. Fusion-fission study at IUAC: Recent results

    Science.gov (United States)

    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.

  14. How James Watt invented the copier forgotten inventions of our great scientists

    CERN Document Server

    Schils, René

    2012-01-01

    Features 25 different scientists and the ideas which may not have made them famous, but made history… Typically, we remember our greatest scientists from one single invention, one new formula or one incredible breakthrough. This narrow perspective does not give justice to the versatility of many scientists who also earned a reputation in other areas of science. James Watt, for instance, is known for inventing the steam engine, yet most people do not know that he also invented the copier. Alexander Graham Bell of course invented the telephone, but only few know that he invented artificial breathing equipment, a prototype of the ‘iron lung’. Edmond Halley, whose name is associated with the comet that visits Earth every 75 years, produced the first mortality tables, used for life insurances. This entertaining book is aimed at anyone who enjoys reading about inventions and discoveries by the most creative minds. Detailed illustrations of the forgotten designs and ideas enrich the work throughout.

  15. Evolutionary Games on Weighted Newman-Watts Small-World Networks

    Institute of Scientific and Technical Information of China (English)

    DU Wen-Bo; CAO Xian-Bin; ZHAO Lin; ZHOU Hong

    2009-01-01

    We investigate the evolutionary prisoner's dilemma game (PDG) on weighted Newman-Watts (NW) networks. In weighted NW networks, the link weight wij is assigned to the link between the nodes i and j as: wij = (ki · kj)β,where ki(kj) is the degree of node i(j) and β represents the strength of the correlations. Obviously, the link weight can be tuned by only one parameter β. We focus on the cooperative behavior and wealth distribution in the system. Simulation results show that the cooperator frequency is promoted by a large range of β and there is a minimal cooperation frequency around β = - 1. Moreover, we also employ the Gini coefficient to study the wealth distribution in the population. Numerical results show that the Gini coefficient reaches its minimum when β≈ -1. Our work may be helpful in understanding the emergence of cooperation and unequal wealth distribution in society.

  16. Hundred-Watt-Level, All-Fiber-Integrated Supercontinuum Generation from Photonic Crystal Fiber

    Science.gov (United States)

    Chen, Hongwei; Chen, Zilun; Chen, Shengping; Hou, Jing; Lu, Qisheng

    2013-03-01

    A photonic crystal fiber (PCF) based supercontinuum source with hundred-watt-level average power output is presented in this paper. The output delivery fiber of a 120 W picosecond master-oscillator power-amplifier (MOPA) laser with a 15 µm fiber core is directly spliced with a 2.6-m-long PCF to form the all-fiber-integrated SC source. Using the controlled air-hole collapse technique to expand the core diameter of the PCF, a super-low splice loss (˜0.2 dB) between the delivery fiber and the PCF has been demonstrated. A 92.5 W SC spanning from about 700 nm to beyond 1700 nm is obtained.

  17. Design of a 300-Watt Isolated Power Supply for Ultra-Fast Tracking Converters

    DEFF Research Database (Denmark)

    Nguyen-Duy, Khiem; Ouyang, Ziwei; Petersen, Lars Press;

    2015-01-01

    that an overall circuit input-to-output parasitic capacitance of 10 pF in a 300 W prototype can be achieved. The circuit input-to-output capacitance per watt is therefore 30 times lower than that of existing approaches. A mathematical model of the inter-winding capacitance of the proposed transformer, circuit......This paper presents the design of a medium-powerrating isolated power supply for ultra-fast tracking converters and MOS-gate driver circuits in medium and high voltage applications. The key feature of the design is its very low circuit input-to-output parasitic capacitance, which maximizes its...... noise immunity from noise due to fast changes in voltage. The converter is a voltage-controlled current source, utilizing a transformer with extremely low inter-winding parasitic capacitance, which is achieved by separating the windings by a significant distance. Experimental measurements show...

  18. Autaptic self-feedback-induced synchronization transitions in Newman-Watts neuronal network with time delays

    Science.gov (United States)

    Wang, Qi; Gong, Yubing; Wu, Yanan

    2015-04-01

    Autapse is a special synapse that connects a neuron to itself. In this work, we numerically study the effect of chemical autapse on the synchronization of Newman-Watts Hodgkin-Huxley neuron network with time delays. It is found that the neurons exhibit synchronization transitions as autaptic self-feedback delay is varied, and the phenomenon enhances when autaptic self-feedback strength increases. Moreover, this phenomenon becomes strongest when network time delay or coupling strength is optimal. It is also found that the synchronization transitions by network time delay can be enhanced by autaptic activity and become strongest when autaptic delay is optimal. These results show that autaptic delayed self-feedback activity can intermittently enhance and reduce the synchronization of the neuronal network and hence plays an important role in regulating the synchronization of the neurons. These findings could find potential implications for the information processing and transmission in neural systems.

  19. Optimization of Watt's Six-bar Linkage to Generate Straight and Parallel Leg Motion

    Directory of Open Access Journals (Sweden)

    Saeed Akbarnejad

    2008-11-01

    Full Text Available This paper considers optimal synthesis of a special type of four-bar linkages. Combination of this optimal four-bar linkage with on of it's cognates and elimination of two redundant cognates will result in a Watt's six-bar mechanism, which generates straight and parallel motion. This mechanism can be utilized for legged machines. The advantage of this mechanism is that the leg remains straight during it's contact period and because of it's parallel motion, the legs can be as wide as desired to increase contact area and decrease the number of legs required to keep body's stability statically and dynamically. "Genetic algorithm" optimization method is used to find optimal lengths. It is especially useful for problems like the coupler curve equation which are completely nonlinear or extremely difficult to solve.

  20. Autaptic activity-induced synchronization transitions in Newman-Watts network of Hodgkin-Huxley neurons

    Science.gov (United States)

    Wu, Yanan; Gong, Yubing; Wang, Qi

    2015-04-01

    In this paper, we numerically study the effect of autapse on the synchronization of Newman-Watts small-world Hodgkin-Huxley neuron network. It is found that the neurons exhibit synchronization transitions as autaptic self-feedback delay is varied, and the phenomenon becomes strongest when autaptic self-feedback strength is optimal. This phenomenon also changes with the change of coupling strength and network randomness and become strongest when they are optimal. There are similar synchronization transitions for electrical and chemical autapse, but the synchronization transitions for chemical autapse occur more frequently and are stronger than those for electrical synapse. The underlying mechanisms are briefly discussed in quality. These results show that autaptic activity plays a subtle role in the synchronization of the neuronal network. These findings may find potential implications of autapse for the information processing and transmission in neural systems.

  1. First Passage Percolation on the Newman-Watts Small World Model

    Science.gov (United States)

    Komjáthy, Júlia; Vadon, Viktória

    2016-02-01

    The Newman-Watts model is given by taking a cycle graph of n vertices and then adding each possible edge (i,j), |i-j|≠ 1 mod n with probability ρ /n for some ρ >0 constant. In this paper we add i.i.d. exponential edge weights to this graph, and investigate typical distances in the corresponding random metric space given by the least weight paths between vertices. We show that typical distances grow as 1/λ log n for a λ >0 and determine the distribution of smaller order terms in terms of limits of branching process random variables. We prove that the number of edges along the shortest weight path follows a Central Limit Theorem, and show that in a corresponding epidemic spread model the fraction of infected vertices follows a deterministic curve with a random shift.

  2. Singlet fission/silicon solar cell exceeding 100% EQE (Conference Presentation)

    Science.gov (United States)

    Pazos, Luis M.; Lee, Jumin; Kirch, Anton; Tabachnyk, Maxim; Friend, Richard H.; Ehrler, Bruno

    2016-09-01

    Current matching limits the commercialization of tandem solar cells due to their instability over spectral changes, leading to the need of using solar concentrators and trackers to keep the spectrum stable. We demonstrate that voltage-matched systems show far higher performance over spectral changes; caused by clouds, dust and other variations in atmospheric conditions. Singlet fission is a process in organic semiconductors which has shown very efficient, 200%, down-conversion yield and the generated excitations are long-lived, ideal for solar cells. As a result, the number of publications has grown exponentially in the past 5 years. Yet, so far no one has achieved to combine singlet fission with most low bandgap semiconductors, including crystalline silicon, the dominating solar cell material with a 90% share of the PV Market. Here we show that singlet fission can facilitate the fabrication of voltage-matched systems, opening a simple design route for the effective implementation of down-conversion in commercially available photovoltaic technologies, with no modification of the electronic circuitry of such. The implemention of singlet fission is achieved simply by decoupling the fabrication of the individual subcells. For this demonstration we used an ITO/PEDOT/P3HT/Pentacene/C60/Ag wide-bandgap subcell, and a commercial silicon solar cell as the low-bandgap component. We show that the combination of the two leads to the first tandem silicon solar cell which exceeds 100% external quantum efficiency.

  3. Relative motion correction to fission barriers

    CERN Document Server

    Skalski, J

    2007-01-01

    We discuss the effect of kinetic energy of the relative motion becoming spurious for separate fragments on the selfconsistent mean-field fission barriers. The treatment of the relative motion in the cluster model is contrasted with the necessity of a simpler and approximate approach in the mean-field theory. A scheme of the energy correction to the Hartree-Fock is proposed. The results obtained with the effective Skyrme interaction SLy6 show that the correction, previously estimated as $\\sim$ 8 MeV in $A=70-100$ nuclei, amounts to 4 MeV in the medium heavy nucleus $^{198}$Hg and to null in $^{238}$U. However, the corrected barrier implies a shorter fission half-life of the latter nucleus. The same effect is expected to lower barriers for multipartition (i.e. ternary fission, etc) and make hyperdeformed minima less stable.

  4. Relative Motion Correction to Fission Barriers

    Science.gov (United States)

    Skalski, J.

    We discuss the effect of kinetic energy of the relative motion becoming spurious for separate fragments on the selfconsistent mean-field fission barriers. The treatment of the relative motion in the cluster model is contrasted with the necessity of a simpler and approximate approach in the mean-field theory. A scheme of the energy correction to the Hartree-Fock is proposed. The results obtained with the effective Skyrme interaction SLy6 show that the correction, previously estimated as ~ 8 MeV in A = 70 - 100 nuclei, amounts to 4 MeV in the medium heavy nucleus 198Hg and to null in 238U. However, the corrected barrier implies a shorter fission half-life of the latter nucleus. The same effect is expected to lower barriers for multipartition (i.e. ternary fission, etc) and make hyperdeformed minima less stable.

  5. Fission Enhanced diffusion of uranium in zirconia

    CERN Document Server

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

    2005-01-01

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

  6. Dissipative dynamics in quasi-fission

    CERN Document Server

    Oberacker, V E; Simenel, C

    2014-01-01

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

  7. Phase Transition Induced Fission in Lipid Vesicles

    CERN Document Server

    Leirer, C; Myles, V M; Schneider, M F

    2010-01-01

    In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (Tfission of the neck, while the mother vesicle remains intact. Pearling tubes which formed upon heating break-up and decay into multiple individual vesicles which then diffuse freely. Finally we demonstrate that mimicking the intracellular bulk viscosity by increasing the bulk viscosity to 40cP does not affect the overall fission process, but leads to a significant decrease in size of the released vesicles.

  8. Solar vs. Fission Surface Power for Mars

    Science.gov (United States)

    Rucker, Michelle A.; Oleson, Steve; George, Pat; Landis, Geoffrey A.; Fincannon, James; Bogner, Amee; Jones, Robert E.; Turnbull, Elizabeth; Martini, Michael C.; Gyekenyesi, John Z.; Colozza, Anthony J.; Schmitz, Paul C.; Packard, Thomas W.

    2016-01-01

    A multi-discipline team of experts from the National Aeronautics and Space Administration (NASA) developed Mars surface power system point design solutions for two conceptual missions. The primary goal of this study was to compare the relative merits of solar- versus fission-powered versions of each surface mission. First, the team compared three different solar power options against a fission power system concept for a sub-scale, uncrewed demonstration mission. The 4.5 meter (m) diameter pathfinder lander's primary mission would be to demonstrate Mars entry, descent, and landing techniques. Once on the Martian surface, the lander's In Situ Resource Utilization (ISRU) payload would demonstrate liquid oxygen propellant production using atmospheric resources. For the purpose of this exercise, location was assumed to be at the Martian equator. The three solar concepts considered included a system that only operated during daylight hours (at roughly half the daily propellant production rate of a round-the-clock fission design), a battery-augmented system that operated through the night (matching the fission concept's propellant production rate), and a system that operated only during daylight, but at a higher rate (again, matching the fission concept's propellant production rate). Including 30% mass growth allowance, total payload masses for the three solar concepts ranged from 1,116 to 2,396 kg, versus the 2,686 kg fission power scheme. However, solar power masses are expected to approach or exceed the fission payload mass at landing sites further from the equator, making landing site selection a key driver in the final power system decision. The team also noted that detailed reliability analysis should be performed on daytime-only solar power schemes to assess potential issues with frequent ISRU system on/off cycling. Next, the team developed a solar-powered point design solution for a conceptual four-crew, 500-day surface mission consisting of up to four landers per

  9. Prompt fission neutron emission: Problems and challenges

    Directory of Open Access Journals (Sweden)

    Hambsch F.-J.

    2013-12-01

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

  10. Energy partition in low energy fission

    CERN Document Server

    Mirea, M

    2011-01-01

    The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the another separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The fission path is obtained in the frame of the macroscopic-microscopic model. The single particle level schemes are obtained within the two center Woods-Saxon shell model. It is shown that the available intrinsic dissipated energy is not shared proportionally to the masses of the two fission fragments. If the heavy fragment possesses nucleon numbers close to the magic ones, the accumulated intrinsic excitation energy is lower than that of the light fragment.

  11. Nuclear fission problem and Langevin equation

    Directory of Open Access Journals (Sweden)

    M Sakhaee

    2011-12-01

    Full Text Available  A combined dynamical and statistical model for fission was employed in our calculation. There is no doubt that a Langevin description plus a Monte Carlo treatment of the evaporation processes provide the most adequate dynamical description. In this paper, we would consider a strongly shaped dependent friction force and we use the numerical method rather than the analytical one. The objective of this article is to calculate the time dependent fission widths of the 224Th nucleus. The fission widths were calculated with both chaos-weighted wall friction (CWWF and wall friction (WF dissipations. The calculations are repeated for 100000 trajectories. The result was compared to the others' work. We use nuclear elongation coordinate with time and it is necessary to repeat the small steps many times to improve the accuracy.

  12. Antiproton Induced Fission and Fragmentation of Nuclei

    CERN Multimedia

    2002-01-01

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

  13. Neck Emission of Intermediate Mass Fragments During Fission

    Science.gov (United States)

    de Souza, R. T.; Chen, S. L.; Cornell, E. W.; Davin, B.; Hamilton, T. M.; Hulburt, D.; Kwiatkowski, K.; Lou, Y.; Viola, V. E.; Wile, J. L.; Korteling, R.

    1996-05-01

    Ternary fission of heavy nuclei provides a unique opportunity to constrain models of the dissipative forces which occur during fission. We have measured neck emission of Intermediate mass fragments (IMF:3 model are made.

  14. Research on Nuclear Reaction Network Equation for Fission Product Nuclides

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Nuclear Reaction Network Equation calculation system for fission product nuclides was developed. With the system, the number of the fission product nuclides at different time can be calculated in the different neutron field intensity and neutron energy spectra

  15. Fundamental Fission Research with the NIFFTE Time Projection Chamber

    Science.gov (United States)

    Kleinrath, Verena; Niffte Collaboration

    2013-10-01

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

  16. Solar Versus Fission Surface Power for Mars

    Science.gov (United States)

    Rucker, Michelle A.; Oleson, Steve; George, Pat; Landis, Geoffrey A.; Fincannon, James; Bogner, Amee; Jones, Robert E.; Turnbull, Elizabeth; McNatt, Jeremiah; Martini, Michael C.; Gyekenyesi, John Z.; Colozza, Anthony J.; Schmitz, Paul C.; Packard, Thomas W.

    2016-01-01

    A multi-discipline team of experts from the National Aeronautics and Space Administration (NASA) developed Mars surface power system point design solutions for two conceptual missions to Mars using In-situ resource utilization (ISRU). The primary goal of this study was to compare the relative merits of solar- versus fission-powered versions of each surface mission. First, the team compared three different solar-power options against a fission power system concept for a sub-scale, uncrewed demonstration mission. This “pathfinder” design utilized a 4.5 meter diameter lander. Its primary mission would be to demonstrate Mars entry, descent, and landing techniques. Once on the Martian surface, the lander’s ISRU payload would demonstrate liquid oxygen propellant production from atmospheric resources. For the purpose of this exercise, location was assumed to be at the Martian equator. The three solar concepts considered included a system that only operated during daylight hours (at roughly half the daily propellant production rate of a round-the-clock fission design), a battery-augmented system that operated through the night (matching the fission concept’s propellant production rate), and a system that operated only during daylight, but at a higher rate (again, matching the fission concept’s propellant production rate). Including 30% mass growth allowance, total payload masses for the three solar concepts ranged from 1,128 to 2,425 kg, versus the 2,751 kg fission power scheme. However, solar power masses increase as landing sites are selected further from the equator, making landing site selection a key driver in the final power system decision. The team also noted that detailed reliability analysis should be performed on daytime-only solar power schemes to assess potential issues with frequent ISRU system on/off cycling.

  17. A fission-fragment-sensitive target for X-ray spectroscopy in neutron-induced fission

    CERN Document Server

    Ethvignot, T; Giot, L; Casoli, P; Nelson, R O

    2002-01-01

    A fission-fragment-sensitive detector built for low-energy photon spectroscopy applications at the WNR 'white' neutron source at Los Alamos is described. The detector consists of eight layers of thin photovoltaic cells, onto which 1 mg/cm sup 2 of pure sup 2 sup 3 sup 8 U is deposited. The detector serves as an active target to select fission events from background and other reaction channels. The fairly small thickness of the detector with respect to transmission of 20-50 keV photons permits the measurement of prompt fission-fragment X-rays. Results with the GEANIE photon spectrometer are presented.

  18. Optimally moderated nuclear fission reactor and fuel source therefor

    Science.gov (United States)

    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.

  19. Ionization Chamber for Prompt Fission Neutron Investigations

    OpenAIRE

    ZEYNALOV Sh.; ZEYNALOVA O. V.; Hambsch, Franz-Josef; Sedyshev, P.; SHVETSOV V.

    2014-01-01

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electro...

  20. Analysis of RNA metabolism in fission yeast

    DEFF Research Database (Denmark)

    Wise, Jo Ann; Nielsen, Olaf

    2017-01-01

    Here we focus on the biogenesis and function of messenger RNA (mRNA) in fission yeast cells. Following a general introduction that also briefly touches on other classes of RNA, we provide an overview of methods used to analyze mRNAs throughout their life cycles.......Here we focus on the biogenesis and function of messenger RNA (mRNA) in fission yeast cells. Following a general introduction that also briefly touches on other classes of RNA, we provide an overview of methods used to analyze mRNAs throughout their life cycles....

  1. Fission Yeast Cell Cycle Synchronization Methods.

    Science.gov (United States)

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

    2016-01-01

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

  2. Uranium arc fission reactor for space propulsion

    Science.gov (United States)

    Watanabe, Yoichi; Maya, Isaac; Vitali, Juan; Appelbaum, Jacob; Schneider, Richard T.

    1991-01-01

    Combining the proven technology of solid core reactors with uranium arc confinement and non-equilibrium ionization by fission fragments can lead to an attractive propulsion system which has a higher specific impulse than a solid core propulsion system and higher thrust than an electric propulsion systems. A preliminary study indicates that a system with 300 MW of fission power can achieve a gas exhaust velocity of 18,000 m/sec and a thrust of 10,000 Newtons utilizing a magnetohydrodynamic generator and accelerator. An experimental program is underway to examine the major mass and energy transfer issues.

  3. Alpha decay from fission isomeric states

    Energy Technology Data Exchange (ETDEWEB)

    Poenaru, D.N.; Ivascu, M. (Institutul de Fizica si Inginerie Nucleara, Bucharest (Romania))

    1981-07-01

    Alpha-decay half-lives from shape isomeric states of some even-even isotopes of U, Pu and Cm nuclei are calculated by using fission theory in the parametrisation of a spheroid intersected with a sphere. The potential barrier was calculated in the framework of the liquid-drop model of Myers and Swiatecki (Art. Fys.; 36: 343 (1967)) extended for systems with different charge densities; a phenomenological shell correction was introduced. The WKB computed lifetimes are many orders of magnitude longer than that of the spontaneous fission process, in agreement with experimental results.

  4. Actinide and fission product separation and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-07-01

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

  5. Watt loss in three-phase transformers with circular and hexagonal forming contours of twisted spatial magnetic core rods

    Directory of Open Access Journals (Sweden)

    E.A. Avdieieva

    2014-04-01

    Full Text Available For spatial three-phase axial electromagnetic systems with circular and hexagonal cross-section configurations of twisted butt-end magnetic core rods, analytical dependences for optimal geometrical relations determination over the transformer minimum watt loss criterion are obtained, comparative analysis of the systems energy efficiency made.

  6. 75 FR 80731 - Request for Exclusion of 120 Volt, 100 Watt R20 Short Incandescent Reflector Lamps

    Science.gov (United States)

    2010-12-23

    ... of energy conservation standards for incandescent reflector lamps a 120 volt, 100 watt R20 short lamp....gov . SUPPLEMENTARY INFORMATION: The Administrative Procedure Act (APA), 5 U.S.C. 551 et seq... APA, NEMA petitioned the Department of Energy for the issuance of a new rule, as set forth below....

  7. Design of a 300-Watt Isolated Power Supply with Minimized Circuit Input-to-Output Parasitic Capacitance

    DEFF Research Database (Denmark)

    Nguyen-Duy, Khiem; Petersen, Lars Press; Knott, Arnold;

    2014-01-01

    This paper presents the design of a 300-Watt isolated power supply for MOS gate driver circuit in medium and high voltage applications. The key feature of the developed power supply is having a very low circuit input-to-output parasitic capacitance, thus maximizing its noise immunity. This makes ...

  8. 76 FR 70169 - Draft Supplement 2 to Final Environmental Statement Related to the Operation of Watts Bar Nuclear...

    Science.gov (United States)

    2011-11-10

    ...The U.S. Nuclear Regulatory Commission (NRC) is requesting comments on NUREG-0498, ``Final Environmental Statement, Supplement 2, Related to the Operation of Watts Bar Nuclear Plant [WBN], Unit 2-- Draft Report for Comment'' (draft SFES). The NRC will hold a public meeting on the draft SFES on December 8,...

  9. A compact broadband high efficient X-band 9-watt PHEMT MMIC high-power amplifier for phased array radar applications

    NARCIS (Netherlands)

    Hek, A.P. de; Hunneman, P.A.H.; Demmler, M.; Hulsmann, A.

    1999-01-01

    ln this paper the development and measurement results of a compact broadband 9-Watt high efficient X-band high-power amplifier are discussed. The described amplifier has the following state-of-the art performance: an average ouput power of 9 Watt, a gain of 20 dB and an average Power Added

  10. A compact broadband high efficient X-band 9-watt PHEMT MMIC high-power amplifier for phased array radar applications

    NARCIS (Netherlands)

    Hek, A.P. de; Hunneman, P.A.H.; Demmler, M.; Hulsmann, A.

    1999-01-01

    ln this paper the development and measurement results of a compact broadband 9-Watt high efficient X-band high-power amplifier are discussed. The described amplifier has the following state-of-the art performance: an average ouput power of 9 Watt, a gain of 20 dB and an average Power Added Efficienc

  11. Developing an "atomic clock" for fission lifetime measurements

    NARCIS (Netherlands)

    Wilschut, H.W.E.M.; Kravchuk, V.

    2004-01-01

    The relevance of measuring fission lifetimes of hot nuclei is briefly discussed. It is shown that K X-ray emission prior to fission can be used to measure fission lifetimes. The preparation of the K-shell hole, the simultaneous nuclear excitation, and the analysis of the X-ray spectra is described.

  12. SYMMETRICAL AND ASYMMETRIC TERNARY FISSION OF HOT NUCLEI

    NARCIS (Netherlands)

    SIWEKWILCZYNSKA, K; WILCZYNSKI, J; LEEGTE, HKW; SIEMSSEN, RH; WILSCHUT, HW; GROTOWSKI, K; PANASIEWICZ, A; SOSIN, Z; WIELOCH, A

    1993-01-01

    Emission of a particles accompanying fusion-fission processes in the Ar-40 + Th-232 reaction at E(Ar-40) = 365 MeV was studied in a wide range of in-fission-plane and out-of-plane angles. The exact determination of the emission angles of both fission fragments combined with the time-of-flight measur

  13. SPIDER Progress Towards High Resolution Correlated Fission Product Data

    Science.gov (United States)

    Shields, Dan; Meierbachtol, Krista; Tovesson, Fredrik; Arnold, Charles; Blackeley, Rick; Bredeweg, Todd; Devlin, Matt; Hecht, Adam; Jandel, Marian; Jorgenson, Justin; Nelson, Ron; White, Morgan; Spider Team

    2014-09-01

    The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. This work is in part supported by LANL Laboratory Directed Research and Development Projects 20110037DR and 20120077DR.

  14. Fission barrier heights in the A ∼ 200 mass region

    Indian Academy of Sciences (India)

    K Mahata

    2015-08-01

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

  15. SYMMETRICAL AND ASYMMETRIC TERNARY FISSION OF HOT NUCLEI

    NARCIS (Netherlands)

    SIWEKWILCZYNSKA, K; WILCZYNSKI, J; LEEGTE, HKW; SIEMSSEN, RH; WILSCHUT, HW; GROTOWSKI, K; PANASIEWICZ, A; SOSIN, Z; WIELOCH, A

    1993-01-01

    Emission of a particles accompanying fusion-fission processes in the Ar-40 + Th-232 reaction at E(Ar-40) = 365 MeV was studied in a wide range of in-fission-plane and out-of-plane angles. The exact determination of the emission angles of both fission fragments combined with the time-of-flight measur

  16. Mass Distribution Measurement of 252Cf Spontaneous Fission

    Institute of Scientific and Technical Information of China (English)

    LIU; Shi-long; YANG; Yi; ZHANG; Chun-li; HAN; Hong-yin

    2015-01-01

    The E-v method of measuring the kinetic energy(E)and velocity(v)of outgoing fission products has been utilized,with the goal of measuring the mass resolution better than 1atomic mass units(amu),and could identify every mass for light fission products of unsymmetrical fission.This work measured mass yield distribution

  17. Design and Simulation of High Radioactivity Fission Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    WANG; Qi

    2012-01-01

    <正>It is great effect that the fission neutron release in 239Pu(n, 2n) cross section measurement by using multi-unit gadolinium loaded liquid scintillation detector system, for the 239Pu fission cross section is larger than (n, 2n) cross section one order of magnitude. In order to deduct the effect of fission neutrons,

  18. Overview of research by the fission group in Trombay

    Indian Academy of Sciences (India)

    R K Chourdhury

    2015-08-01

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

  19. Viscosity, fission time scale and deformation of Dy-156

    NARCIS (Netherlands)

    van't Hof, G; Bacelar, JCS; Dioszegi, [No Value; Harakeh, MN; Hesselink, WHA; Kalantar-Nayestanaki, N; Kugler, A; van der Ploeg, H; Plompen, AJM; van Schagen, JPS

    1998-01-01

    In the fusion-fission reaction Ar-40 + Cd-116 --> Dy-156*, fission, at E-b = 216 MeV and 238 MeV, gamma-rays were measured in coincidence with fission fragments. The interpretation of the gamma-ray spectra is done with the help of a modified version of the statistical-model code CASCADE. The spectra

  20. Developing an "atomic clock" for fission lifetime measurements

    NARCIS (Netherlands)

    Wilschut, H.W.E.M.; Kravchuk, V.

    2004-01-01

    The relevance of measuring fission lifetimes of hot nuclei is briefly discussed. It is shown that K X-ray emission prior to fission can be used to measure fission lifetimes. The preparation of the K-shell hole, the simultaneous nuclear excitation, and the analysis of the X-ray spectra is described.

  1. Modeling of the saturation current of a fission chamber taking into account the distorsion of electric field due to space charge effects

    CERN Document Server

    Poujade, O; Poujade, Olivier; Lebrun, Alain

    1999-01-01

    Fission chambers were first made fifty years ago for neutron detection. At the moment, the French Atomic Energy Commission \\textsf{(CEA-Cadarache)} is developing a sub-miniature fission chamber technology with a diameter of 1.5 mm working in the current mode (Bign). To be able to measure intense fluxes, it is necessary to adjust the chamber geometry and the gas pressure before testing it under real neutron flux. In the present paper, we describe a theoretical method to foresee the current-voltage characteristics (sensitivity and saturation plateau) of a fission chamber whose geometrical features are given, taking into account the neutron flux to be measured (spectrum and intensity). The proposed theoretical model describes electric field distortion resulting from charge collection effect. A computer code has been developed on this model basis. Its application to 3 kinds of fission chambers indicates excellent agreement between theoretical model and measured characteristics.

  2. Fission-fragment energy correlation measurements for the spontaneous fission of /sup 244/Cm

    Energy Technology Data Exchange (ETDEWEB)

    Caitucoli, F.; Leroux, B.; Barreau, G.; Sicre, A.; Doan, T.P. (Bordeaux-1 Univ., 33 - Gradignan (France). Centre d' Etudes Nucleaires); Asghar, M.; Hamadache, K.; Allab, M. (Centre des Sciences et de la Technologie Nucleaires, Algiers (Algeria))

    1983-02-28

    Fission-fragment mass and kinetic energy distributions and their correlations have been measured for the spontaneous fission of /sup 244/Cm. About 3.54 x 10/sup 5/ fission events were collected. The global mass distribution shows shoulders at ..mu..sub(H) approx.= 134 and ..mu..sub(H) approx.= 143-144. The peak/valley ratio is 86. The dip ..delta..Esub(K) value at symmetry is 13.4 +- 1.5 MeV. In the yields for high-kinetic-energy selected events, the masses 139 and 144 dominate. The results of /sup 244/Cm are compared with the other isotopes of Cm and discussed in terms of the structures present in the potential energy surface of the fissioning system caused by the structures in the nascent fragments.

  3. Fission yeast meets a legend in Kobe: report of the Eighth International Fission Yeast Meeting.

    Science.gov (United States)

    Asakawa, Haruhiko; Yamamoto, Takaharu G; Hiraoka, Yasushi

    2015-12-01

    The Eighth International Fission Yeast Meeting, which was held at Ikuta Shrine Hall in Kobe, Japan, from 21 to 26 June 2015, was attended by 327 fission yeast researchers from 25 countries (190 overseas and 137 domestic participants). At this meeting, 124 talks were held and 145 posters were presented. In addition, newly developed database tools were introduced to the community during a workshop. Researchers shared cutting-edge knowledge across broad fields of study, ranging from molecules to evolution, derived from the superior model organism commonly used within the fission yeast community. Intensive discussions and constructive suggestions generated in this meeting will surely advance the understanding of complex biological systems in fission yeast, extending to general eukaryotes.

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

    CERN Document Server

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

    2015-01-01

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

  5. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few μm in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one

  6. Unification of binary and LCP fission processes

    Science.gov (United States)

    Asghar, M.; Bouzid, B.; Medkour, G.; Djebara, M.

    1996-11-01

    This paper discusses the ambiguities of the parameters of the models used to calculate the yields of binary and light-charged-particle-accompanied (LCP) ternary fission processes. A model based on the adiabatic perturbation theory is set up. It removes these ambiguities and helps to treat the two processes in a unified way.

  7. Energy-loss distributions of fission fragments

    Energy Technology Data Exchange (ETDEWEB)

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

    1976-03-05

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

  8. Development of fission Mo-99 production technology

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-05-01

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

  9. Liquid uranium alloy-helium fission reactor

    Science.gov (United States)

    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.

  10. Fission neutron output measurements at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Ronald Owen [Los Alamos National Laboratory; Haight, Robert C [Los Alamos National Laboratory; Devlin, Matthew J [Los Alamos National Laboratory; Fotiadis, Nikolaos [Los Alamos National Laboratory; Laptev, Alexander [Los Alamos National Laboratory; O' Donnell, John M [Los Alamos National Laboratory; Taddeucci, Terry N [Los Alamos National Laboratory; Tovesson, Fredrik [Los Alamos National Laboratory; Ullmann, J L [Los Alamos National Laboratory; Wender, Stephen A [Los Alamos National Laboratory; Bredeweg, T A [Los Alamos National Laboratory; Jandel, M [Los Alamos National Laboratory; Vieira, D J [Los Alamos National Laboratory; Wu, Ching - Yen [LLNL; Becker, J A [LLNL; Stoyer, M A [LLNL; Henderson, R [LLNL; Sutton, M [LLNL; Belier, Gilbert [BRUYERES-LE-CHATEL, FRANCE; Chatillon, A [BRUYERES-LE-CHATEL, FRANCE; Granier, Thierry [CEA, BRUYERES-LE-CHATEL, FRANCE; Laurent, Benoit [CEA, BRUYERES-LE-CHATEL, FRANCE; Taieb, Julien [CEA, BRUYERES-LE-CHATEL, FRANCE

    2010-01-01

    Accurate data for both physical properties and fission properties of materials are necessary to properly model dynamic fissioning systems. To address the need for accurate data on fission neutron energy spectra, especially at outgoing neutron energies below about 200 keV and at energies above 8 MeV, ongoing work at LANSCE involving collaborators from LANL, LLNL and CEA Bruyeres-le-Chatel is extending the energy range, efficiency and accuracy beyond previous measurements. Initial work in the outgoing neutron energy range from 1 to 7 MeV is consistent with current evaluations and provides a foundation for extended measurements. As part of these efforts, a new fission fragment detector that reduces backgrounds and improves timing has been designed fabricated and tested, and new neutron detectors are being assessed for optimal characteristics. Simulations of experimental designs are in progress to ensure that accuracy goals are met. Results of these measurements will be incorporated into evaluations and data libraries as they become available.

  11. After Apollo: Fission Origin of the Moon

    Science.gov (United States)

    O'Keefe, John A.

    1973-01-01

    Presents current ideas about the fission process of the Moon, including loss of mass. Saturnian rings, center of the Moon, binary stars, and uniformitarianism. Indicates that planetary formation may be best explained as a destructive, rather than a constructive process. (CC)

  12. Angular-momentum-bearing modes in fission

    Energy Technology Data Exchange (ETDEWEB)

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

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs.

  13. Fission in intermediate energy heavy ion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wilhelmy, J.B.; Begemann-Blaich, M.; Blaich, T.; Boissevain, J.; Fowler, M.M.; Gavron, A.; Jacak, B.V.; Lysaght, P.S. (Los Alamos National Lab., NM (USA)); Britt, H.C.; Fields, D.J.; Hansen, L.F.; Lanier, R.G.; Massoletti, D.J.; Namboodiri, M.M.; Remington, B.A.; Sangster, T.C.; Struble, G.L.; Webb, M.L. (Lawrence Livermore National Lab., CA (USA)); Chan, Y.D.; Dacai, A.; Harmon, A.; Leyba, J.; Pouliot, J.; Stokstad, R.G. (Lawrence Berkeley Lab., CA (USA)); Hansen, O.; Levine, M.J.; Thorn, C.E.; Trautmann, W. (Brookhaven National Lab., Upton, NY (USA)); Dichter, B.; Kaufman, S.; Videbaek, F. (Argonne National Lab. (USA)); Fraenkel, Z.; Mamane, G. (Weizmann Inst. of Science, Rehovoth (Israel)); Cebra, D.; Westfall, G.D. (Michigan State Univ., East Lansing (USA))

    1989-10-09

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

  14. Otto Hahn (1944). Discovery of nuclear fission

    CERN Document Server

    Hahn, Otto

    2003-01-01

    Otto Hahn (Frankfurt-on-Main, 1879-Gotinga, 1968) is the discoverer of nuclear fission, which awarded him the Nobel Prize for Chemistry in 1944. After leaving Germany during the Second World War to settle in the United Kingdom, he returned to this country as a renown figure.

  15. Formation of asteroid pairs by rotational fission.

    Science.gov (United States)

    Pravec, P; Vokrouhlický, D; Polishook, D; Scheeres, D J; Harris, A W; Galád, A; Vaduvescu, O; Pozo, F; Barr, A; Longa, P; Vachier, F; Colas, F; Pray, D P; Pollock, J; Reichart, D; Ivarsen, K; Haislip, J; Lacluyze, A; Kusnirák, P; Henych, T; Marchis, F; Macomber, B; Jacobson, S A; Krugly, Yu N; Sergeev, A V; Leroy, A

    2010-08-26

    Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.

  16. Actinide and fission product partitioning and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-07-01

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

  17. Propagation of a constant velocity fission wave

    Science.gov (United States)

    Deinert, Mark

    2011-10-01

    The ideal nuclear fuel cycle would require no enrichment, minimize the need fresh uranium, and produce few, if any, transuranic elements. Importantly, the latter goal would be met without the reprocessing. For purely physical reasons, no reactor system or fuel cycle can meet all of these objectives. However, a traveling-wave reactor, if feasible, could come remarkably close. The concept is simple: a large cylinder of natural (or depleted) uranium is subjected to a fast neutron source at one end, the neutrons would transmute the uranium downstream and produce plutonium. If the conditions were right, a self-sustaining fission wave would form, producing yet more neutrons which would breed more plutonium and leave behind little more than short-lived fission products. Numerical studies have shown that fission waves of this type are also possible. We have derived an exact solution for the propagation velocity of a fission wave through fertile material. The results show that these waves fall into a class of traveling wave phenomena that have been encountered in other systems. The solution places a strict conditions on the shapes of the flux, diffusive, and reactive profiles that would be required for such a phenomenon to persist. The results are confirmed numerically.

  18. Brownian shape motion: Fission fragment mass distributions

    Directory of Open Access Journals (Sweden)

    Sierk Arnold J.

    2012-02-01

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

  19. Neutron induced fission of 234U

    Directory of Open Access Journals (Sweden)

    Pomp S.

    2012-02-01

    Full Text Available The fission fragment properties of 234U(n,f were investigated as a function of incident neutron energy from 0.2 MeV up to 5 MeV. The fission fragment mass, angular distribution and kinetic energy were measured with a double Frisch-grid ionization chamber using both analogue and digital data acquisition techniques. The reaction 234U(n,f is relevant, since it involves the same compound nucleus as formed after neutron evaporation from highly excited 236U*, the so-called second-chance fission of 235U. Experimental data on fission fragment properties like fission fragment mass and total kinetic energy (TKE as a function of incident neutron energy are rather scarce for this reaction. For the theoretical modelling of the reaction cross sections for Uranium isotopes this information is a crucial input parameter. In addition, 234U is also an important isotope in the Thorium-based fuel cycle. The strong anisotropy of the angular distribution around the vibrational resonance at En = 0.77 MeV could be confirmed using the full angular range. Fluctuations in the fragment TKE have been observed in the threshold region around the strong vibrational resonance at En = 0.77 MeV. The present results are in contradiction with corresponding literature values. Changes in the mass yield around the vibrational resonance and at En = 5 MeV relative to En = 2 MeV show a different signature. The drop in mean TKE around 2.5 to 3 MeV points to pair breaking as also observed in 235,238U(n,f. The measured two-dimensional mass yield and TKE distribution have been described in terms of fission modes. The yield of the standard 1 (S1 mode shows fluctuations in the threshold of the fission cross section due to the influence of the resonance and levels off at about 20% yield for higher incident neutron energies. The S2 mode shows the respective opposite behaviour. The mean TKE of both modes decreases with En. The decrease in mean TKE overrules the increase in S1 yield, so the mean

  20. The partial fission of fast spinning asteroids

    Science.gov (United States)

    Tardivel, Simon; Sanchez, Paul; Scheeres, Daniel J.

    2016-10-01

    The spin rates of asteroids systematically change over time due the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. Above a certain spin rate that depends on the body's density, regions of an asteroid can enter in tension, with components held to the body by cohesive forces. When the body fails, deformation or fission can occur. Catastrophic fission leading to complete disruption has been directly observed in active asteroid P/2013 R3. Partial fission, the loss of only part of the body, has been proposed as a mechanism for the formation of binaries and is explored here.The equatorial cavities of (341843) 2008 EV5 and of (185851) 2000 DP107 (a binary system) are consistent with a localized partial fission of the body (LPSC 2016 #1036). The examination of the gravity field of these bodies reveals that a mass placed within these cavities could be shed. In this mechanism, the outward pull of inertial forces creates an average stress at the cavity interface of ≈1 Pa for 2008 EV5 and ≈3 Pa for 2000 DP107 at spin periods of ≈3.15 h for the assumed densities of 1.3 g/cm3.This work continues the study of this partial, localized fission. Specifically, it addresses the issue of the low cohesion necessary to the mechanism. These cohesion values are typically lower than global strength values inferred on other asteroids (10 - 200 Pa), meaning that partial fission may occur prior to larger-scale deformations. Yet, several processes can explain the discrepancy, as they can naturally segregate particles by size. For instance, landslides or granular convection (Brazil nut effect) could bring larger boulders to the equator of the body, while finer particles are left at higher latitudes or sink to the center. Conversely, failure of the interior could bring boulders to the surface. The peculiar profile shape of these asteroids, shared by many binaries (e.g. 1999 KW4, 1996 FG3) may also be a clue of this heterogeneity, as this "spin top" shape is obtained in simulations with

  1. Innovative Fission Measurements with a Time Projection Chamber

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-11-16

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

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

    Directory of Open Access Journals (Sweden)

    Bazin D.

    2012-07-01

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

  3. The Oklo natural reactor: Cumulative fission yields and retentivity of the symmetric mass region fission products

    Science.gov (United States)

    De Laeter, J. R.; Rosman, K. J. R.; Smith, C. L.

    1980-10-01

    Solid source mass spectrometry has been used to determine the relative cumulative fission yields of five elements in three samples of uranium ore from reactor zones in the Oklo mine site. Eighteen fission chains covering the mass range from 105 ≤ A ≤ 130 have been measured for Pd, Ag, Cd, Sn and Te. These measurements have enabled a number of nuclear parameters to be calculated including the relative proportions of 235U, 238U and 239Pu involved in the fission process. The concentration of the five elements in the Oklo samples have also been measured using the stable isotope dilution technique. These values have then been compared to the estimates of the amount of these elements produced by fission under the conditions that are appropriate to the three samples. This procedure enables the retentivity of the elements in the reactor zones to be evaluated. Our work confirms the fact that Pd and Te are retained almost in their entirety in the samples, whereas the other three elements have been partially lost from the reactor site. Almost all the Cd fission products have been lost, and more than 50% of the Ag and Sn fission-produced material has been removed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

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

  5. Microscopic theory of nuclear fission: a review

    Science.gov (United States)

    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

  6. Burning high-level TRU waste in fusion fission reactors

    Science.gov (United States)

    Shen, Yaosong

    2016-09-01

    Recently, the concept of actinide burning instead of a once-through fuel cycle for disposing spent nuclear fuel seems to get much more attention. A new method of burning high-level transuranic (TRU) waste combined with Thorium-Uranium (Th-U) fuel in the subcritical reactors driven by external fusion neutron sources is proposed in this paper. The thorium-based TRU fuel burns all of the long-lived actinides via a hard neutron spectrum while outputting power. A one-dimensional model of the reactor concept was built by means of the ONESN_BURN code with new data libraries. The numerical results included actinide radioactivity, biological hazard potential, and much higher burnup rate of high-level transuranic waste. The comparison of the fusion-fission reactor with the thermal reactor shows that the harder neutron spectrum is more efficient than the soft. The Th-U cycle produces less TRU, less radiotoxicity and fewer long-lived actinides. The Th-U cycle provides breeding of 233U with a long operation time (>20 years), hence significantly reducing the reactivity swing while improving safety and burnup.

  7. Optimization of Recoil-Proton Detection System Used in Fission Neutron Field%裂变中子辐射场反冲质子探测系统的优化设计

    Institute of Scientific and Technical Information of China (English)

    张显鹏; 张忠兵; 陈亮; 张建福

    2014-01-01

    The key problem in measurement of high energy neutron fluence in intense pulsed fission neutron-gamma mixed field using recoil-proton detection system is to improve its sig-nal-to-noise ratioSNR.In this paperwe use MCNPX code and the watt spectrum as input spectrum to investigate the possibility of improving the SNR of a recoil-proton detection sys-tem by changing the structure of the detection system.The study includes the influence of the dimension of the target and the PIN detectorthe angle of the wings of the target cham-berthe thickness of the Ni window of the chamberas well as the shield structure of the de-tection system.The results show that SNR can be obviously improved by decreasing the thickness of the detector or the angle of the wings of the chamberand decreasing the thick-ness of the Ni window or using the bell-mouthed shield are also helpful.%在强脉冲裂变中子伽马混合辐射场中,通常利用反冲质子探测系统对高能中子进行测量,如何提高探测系统的信噪比是设计的关键。采用MCNPX程序,模拟输入watt谱,对系统的结构进行了优化设计,其中包括:靶和 PIN探测器的直径、厚度、放置角度,靶腿角度,靶室镍窗厚度以及辐射屏蔽结构等。结果表明,减小PIN探测器厚度以及靶腿角度可显著改善系统的信噪比;减小镍窗厚度以及采用阶梯状喇叭口屏蔽也可有效提高系统信噪比。

  8. Fission Surface Power Technology Demonstration Unit Test Results

    Science.gov (United States)

    Briggs, Maxwell H.; Gibson, Marc A.; Geng, Steven M.; Sanzi, James L.

    2016-01-01

    The Fission Surface Power (FSP) Technology Demonstration Unit (TDU) is a system-level demonstration of fission power technology intended for use on manned missions to Mars. The Baseline FSP systems consists of a 190 kWt UO2 fast-spectrum reactor cooled by a primary pumped liquid metal loop. This liquid metal loop transfers heat to two intermediate liquid metal loops designed to isolate fission products in the primary loop from the balance of plant. The intermediate liquid metal loops transfer heat to four Stirling Power Conversion Units (PCU), each of which produce 12 kWe (48 kW total) and reject waste heat to two pumped water loops, which transfer the waste heat to titanium-water heat pipe radiators. The FSP TDU simulates a single leg of the baseline FSP system using an electrically heater core simulator, a single liquid metal loop, a single PCU, and a pumped water loop which rejects the waste heat to a Facility Cooling System (FCS). When operated at the nominal operating conditions (modified for low liquid metal flow) during TDU testing the PCU produced 8.9 kW of power at an efficiency of 21.7 percent resulting in a net system power of 8.1 kW and a system level efficiency of 17.2 percent. The reduction in PCU power from levels seen during electrically heated testing is the result of insufficient heat transfer from the NaK heater head to the Stirling acceptor, which could not be tested at Sunpower prior to delivery to the NASA Glenn Research Center (GRC). The maximum PCU power of 10.4 kW was achieved at the maximum liquid metal temperature of 875 K, minimum water temperature of 350 K, 1.1 kg/s liquid metal flow, 0.39 kg/s water flow, and 15.0 mm amplitude at an efficiency of 23.3 percent. This resulted in a system net power of 9.7 kW and a system efficiency of 18.7 percent.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. ND:GLASS LASER DESIGN FOR LASER ICF FISSION ENERGY (LIFE)

    Energy Technology Data Exchange (ETDEWEB)

    Caird, J A; Agrawal, V; Bayramian, A; Beach, R; Britten, J; Chen, D; Cross, R; Ebbers, C; Erlandson, A; Feit, M; Freitas, B; Ghosh, C; Haefner, C; Homoelle, D; Ladran, T; Latkowski, J; Molander, W; Murray, J; Rubenchik, S; Schaffers, K; Siders, C W; Stappaerts, E; Sutton, S; Telford, S; Trenholme, J; Barty, C J

    2008-10-28

    We have developed preliminary conceptual laser system designs for the Laser ICF (Inertial Confinement Fusion) Fission Energy (LIFE) application. Our approach leverages experience in high-energy Nd:glass laser technology developed for the National Ignition Facility (NIF), along with high-energy-class diode-pumped solid-state laser (HEC-DPSSL) technology developed for the DOE's High Average Power Laser (HAPL) Program and embodied in LLNL's Mercury laser system. We present laser system designs suitable for both indirect-drive, hot spot ignition and indirect-drive, fast ignition targets. Main amplifiers for both systems use laser-diode-pumped Nd:glass slabs oriented at Brewster's angle, as in NIF, but the slabs are much thinner to allow for cooling by high-velocity helium gas as in the Mercury laser system. We also describe a plan to mass-produce pump-diode lasers to bring diode costs down to the order of $0.01 per Watt of peak output power, as needed to make the LIFE application economically attractive.

  11. Conceptual Design of 500 watt portable thermophotovoltaic power supply using JP-8 fuel

    Science.gov (United States)

    DeBellis, Crispin L.; Scotto, Mark V.; Scoles, Stephen W.; Fraas, Lewis

    1997-03-01

    Babcock & Wilcox (B&W) and JX Crystals (JXC) have developed an innovative design for a compact, 500 watt net electric (We), 24-VDC thermophotovoltaic (TPV) power supply using JP-8 fuel. As currently envisioned, the TPV generator will be approximately 20 cm (8 inches) in diameter and 50 cm (20 inches) high, not including a fuel tank and controls. The total system may weigh as little as 7.5 kg (16.5 lb) without fuel. This system will achieve high efficiency and high power density relative to its size through the use of low bandgap gallium antimonide (GaSb) PV cells and a matched emitter. A thermally integrated fuel vaporizer and recuperator will boost system efficiency by transferring the unused energy in the exhaust stream to the incoming fuel and combustion air. At rated conditions and 500 We output, the system is expected to have an overall efficiency of 8% to 10%. This paper examines the trade-offs between system efficiency, power density, and weight required in the selection and configuration of the major system components.

  12. Component development for 500 watt diesel fueled portable thermophotovoltaic (TPV) power supply

    Science.gov (United States)

    DeBellis, Crispin L.; Scotto, Mark V.; Fraas, Lewis; Samaras, John; Watson, Ron C.; Scoles, Stephen W.

    1999-03-01

    McDermott Technology, Inc. (MTI) and JX Crystals have developed an innovative design for a compact, 500-watt, thermophotovoltaic (TPV) power supply using diesel fuel. Under a contract with the Defense Advanced Research Projects Agency (DARPA) and managed by the U.S. Army Communications-Electronics Command (CECOM), this design is being reduced to hardware. Prototypes of the two main subsystems, the power converter assembly (PCA) and the burner/emitter/recuperator (BER), have been designed, fabricated, and tested. The PCA uses low-band-gap gallium antimonide (GaSb) photovoltaic (PV) cells for high efficiency and power density. The prototype PCA will be air cooled for system simplicity and portability. However, initial testing was performed on a water-cooled PCA. The BER uses a thermal vaporizer to produce a stable, high-intensity, low-emissions combustion zone inside an impervious emitter. A thermally integrated recuperator is utilized to boost system efficiency by transferring the unused energy in the exhaust stream to the incoming fuel and combustion air. This paper describes the design, testing and performance of the first-generation PCA and BER along with model predictions used for design and evaluation.

  13. Quantum transport with long-range steps on Watts-Strogatz networks

    Science.gov (United States)

    Wang, Yan; Xu, Xin-Jian

    2016-07-01

    We study transport dynamics of quantum systems with long-range steps on the Watts-Strogatz network (WSN) which is generated by rewiring links of the regular ring. First, we probe physical systems modeled by the discrete nonlinear schrödinger (DNLS) equation. Using the localized initial condition, we compute the time-averaged occupation probability of the initial site, which is related to the nonlinearity, the long-range steps and rewiring links. Self-trapping transitions occur at large (small) nonlinear parameters for coupling ɛ=-1 (1), as long-range interactions are intensified. The structure disorder induced by random rewiring, however, has dual effects for ɛ=-1 and inhibits the self-trapping behavior for ɛ=1. Second, we investigate continuous-time quantum walks (CTQW) on the regular ring ruled by the discrete linear schrödinger (DLS) equation. It is found that only the presence of the long-range steps does not affect the efficiency of the coherent exciton transport, while only the allowance of random rewiring enhances the partial localization. If both factors are considered simultaneously, localization is greatly strengthened, and the transport becomes worse.

  14. Quantification of degeneracy in Hodgkin-Huxley neurons on Newman-Watts small world network.

    Science.gov (United States)

    Man, Menghua; Zhang, Ya; Ma, Guilei; Friston, Karl; Liu, Shanghe

    2016-08-07

    Degeneracy is a fundamental source of biological robustness, complexity and evolvability in many biological systems. However, degeneracy is often confused with redundancy. Furthermore, the quantification of degeneracy has not been addressed for realistic neuronal networks. The objective of this paper is to characterize degeneracy in neuronal network models via quantitative mathematic measures. Firstly, we establish Hodgkin-Huxley neuronal networks with Newman-Watts small world network architectures. Secondly, in order to calculate the degeneracy, redundancy and complexity in the ensuing networks, we use information entropy to quantify the information a neuronal response carries about the stimulus - and mutual information to measure the contribution of each subset of the neuronal network. Finally, we analyze the interdependency of degeneracy, redundancy and complexity - and how these three measures depend upon network architectures. Our results suggest that degeneracy can be applied to any neuronal network as a formal measure, and degeneracy is distinct from redundancy. Qualitatively degeneracy and complexity are more highly correlated over different network architectures, in comparison to redundancy. Quantitatively, the relationship between both degeneracy and redundancy depends on network coupling strength: both degeneracy and redundancy increase with complexity for small coupling strengths; however, as coupling strength increases, redundancy decreases with complexity (in contrast to degeneracy, which is relatively invariant). These results suggest that the degeneracy is a general topologic characteristic of neuronal networks, which could be applied quantitatively in neuroscience and connectomics.

  15. Stochastic resonance on Newman-Watts networks of Hodgkin-Huxley neurons with local periodic driving

    Energy Technology Data Exchange (ETDEWEB)

    Ozer, Mahmut [Zonguldak Karaelmas University, Engineering Faculty, Department of Electrical and Electronics Engineering, 67100 Zonguldak (Turkey)], E-mail: mahmutozer2002@yahoo.com; Perc, Matjaz [University of Maribor, Faculty of Natural Sciences and Mathematics, Department of Physics, Koroska cesta 160, SI-2000 Maribor (Slovenia); Uzuntarla, Muhammet [Zonguldak Karaelmas University, Engineering Faculty, Department of Electrical and Electronics Engineering, 67100 Zonguldak (Turkey)

    2009-03-02

    We study the phenomenon of stochastic resonance on Newman-Watts small-world networks consisting of biophysically realistic Hodgkin-Huxley neurons with a tunable intensity of intrinsic noise via voltage-gated ion channels embedded in neuronal membranes. Importantly thereby, the subthreshold periodic driving is introduced to a single neuron of the network, thus acting as a pacemaker trying to impose its rhythm on the whole ensemble. We show that there exists an optimal intensity of intrinsic ion channel noise by which the outreach of the pacemaker extends optimally across the whole network. This stochastic resonance phenomenon can be further amplified via fine-tuning of the small-world network structure, and depends significantly also on the coupling strength among neurons and the driving frequency of the pacemaker. In particular, we demonstrate that the noise-induced transmission of weak localized rhythmic activity peaks when the pacemaker frequency matches the intrinsic frequency of subthreshold oscillations. The implications of our findings for weak signal detection and information propagation across neural networks are discussed.

  16. Simulation of Watts Bar Unit 1 Initial Startup Tests with Continuous Energy Monte Carlo Methods

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, Andrew T [ORNL; Gehin, Jess C [ORNL; Bekar, Kursat B [ORNL; Celik, Cihangir [ORNL

    2014-01-01

    The Consortium for Advanced Simulation of Light Water Reactors* is developing a collection of methods and software products known as VERA, the Virtual Environment for Reactor Applications. One component of the testing and validation plan for VERA is comparison of neutronics results to a set of continuous energy Monte Carlo solutions for a range of pressurized water reactor geometries using the SCALE component KENO-VI developed by Oak Ridge National Laboratory. Recent improvements in data, methods, and parallelism have enabled KENO, previously utilized predominately as a criticality safety code, to demonstrate excellent capability and performance for reactor physics applications. The highly detailed and rigorous KENO solutions provide a reliable nu-meric reference for VERAneutronics and also demonstrate the most accurate predictions achievable by modeling and simulations tools for comparison to operating plant data. This paper demonstrates the performance of KENO-VI for the Watts Bar Unit 1 Cycle 1 zero power physics tests, including reactor criticality, control rod worths, and isothermal temperature coefficients.

  17. A nonlinearity in permanent-magnet systems used in watt balances

    CERN Document Server

    Li, Shisong; Pratt, Jon

    2014-01-01

    Watt balances are used to measure the Planck constant and will be used in the future to realize mass at the kilogram level. They increasingly rely on permanent magnet systems to generate the magnetic flux. It has been known that the weighing current might effect the magnetization state of the permanent magnetic system used in these systems causing a systematic bias that can lead to an error in the result if not accounted for. In this article a simple model explaining the effect of the weighing current on the yoke of the magnet is developed. This model leads to a nonlinear dependence of the magnetic flux density in the gap that is proportional to the squared value of the coil current. The effect arises from changing the reluctance of the yoke by the additional field produced by the coil. Our analysis shows that the effect depends on the width of the air gap, the magnetic flux density in the air gap, and the $BH$ curve of the yoke material. Suggestions to reduce the nonlinear effect are discussed.

  18. Sub-library of Updated Fission Barrier Parameters(CENPL-FBP2)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The fission barrier parameters are important to determine the fission character of a nucleus. The fission barrier parameters and fission level densities are key ingredients in calculations of not only fission cross section but also various cross sections, and spectra for the fissile nuclides, even heavy nuclides at higher incident energies. It is necessaries that the accuracy of fission barrier parameters requires even higher, and nuclides with fission barrier parameters can cover even wider nuclear range.

  19. Axisymmetric Magnetic Mirror Fusion-Fission Hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Moir, R. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Martovetsky, N. N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Molvik, A. W. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ryutov, D. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simonen, T. C. [Univ. of California, Berkeley, CA (United States)

    2011-05-13

    The achieved performance of the gas dynamic trap version of magnetic mirrors and today’s technology we believe are sufficient with modest further efforts for a neutron source for material testing (Q=Pfusion/Pinput~0.1). The performance needed for commercial power production requires considerable further advances to achieve the necessary high Q>>10. An early application of the mirror, requiring intermediate performance and intermediate values of Q~1 are the hybrid applications. The Axisymmetric Mirror has a number of attractive features as a driver for a fusion-fission hybrid system: geometrical simplicity, inherently steady-state operation, and the presence of the natural divertors in the form of end tanks. This level of physics performance has the virtue of low risk and only modest R&D needed and its simplicity promises economy advantages. Operation at Q~1 allows for relatively low electron temperatures, in the range of 4 keV, for the DT injection energy ~ 80 keV. A simple mirror with the plasma diameter of 1 m and mirror-to-mirror length of 35 m is discussed. Simple circular superconducting coils are based on today’s technology. The positive ion neutral beams are similar to existing units but designed for steady state. A brief qualitative discussion of three groups of physics issues is presented: axial heat loss, MHD stability in the axisymmetric geometry, microstability of sloshing ions. Burning fission reactor wastes by fissioning actinides (transuranics: Pu, Np, Am, Cm, .. or just minor actinides: Np, Am, Cm, …) in the hybrid will multiply fusion’s energy by a factor of ~10 or more and diminish the Q needed to less than 1 to overcome the cost of recirculating power for good economics. The economic value of destroying actinides by fissioning is rather low based on either the cost of long-term storage or even deep geologic disposal so most of the revenues of hybrids will come from electrical power. Hybrids that obtain revenues from

  20. The Fission-fragment Spectrometer VERDI

    Science.gov (United States)

    Frégeau, M. O.; Oberstedt, S.

    VERDI (VElocity foR Direct particle Identification) is a fission-fragment spectrometer presently under construction at the Joint Research Centre IRMM. It will allow measuring the kinetic energy and the velocity of both fission fragments simultaneously. The velocity information provide information about the pre-neutron mass of each fission fragment when isotropic prompt-neutron emission from the fragments is assumed. The kinetic energy, in complement of the velocity, will provide us with the post-neutron mass. From the difference between pre- and post-neutron masses the number of neutrons emitted by each fragment may be deter- mined. Knowledge of this quantity as a function of the total kinetic energy will contribute to the understanding of how the available excitation energy is shared between both fission fragments at scission. The contemplated pre-neutron mass resolving power, A/ΔA, of at least 126 requires a time-of-flight (TOF) resolution better than 200 ps (FWHM) and an energy resolution, ΔE/E of 0.3% for a post-neutron mass. The VERDI spectrometer provides the best compromise between geometrical efficiency and time of flight. It consists of an electron detector located very close to the fissionable target and a double array of silicon detectors located 50 cm away on both sides of the target. Each silicon detector has an area of 450 mm2 and is made from neutron transmutation-doped (NTD) silicon to reduce rise-time variation, to minimize pulse height defect and to reduce the plasma delay time. The intrinsic timing resolution of the electron detector was determined, using a 241Am alpha source (Eα = 5.49 MeV), against a previously characterized single-crystal diamond to σ = 140 ps. The timing resolution of the NTD silicon detectors was determined using the spontaneous fission of 252Cf in conjunction with Monte-Carlo simulations to σNTD = 150 ps. With the present timing resolution, σTOF VERDI is already close to the set goals. The excellent timing properties

  1. WattJournals: Towards an Economic and Lightweight Search Tool Alternative for Libraries To Help Their Students and Researchers Keep Up-To-Date

    Directory of Open Access Journals (Sweden)

    Santiago Chumbe

    2010-12-01

    Full Text Available Learn how Heriot-Watt University Library's WattJournals could be just the search tool your patrons need to efficiently find the content that your library subscribes to. Built on top of a RESTful search API created by the JISC-sponsored JournalTOCs Project, WattJournals is a toolkit for connecting fulltext articles to the people who need them. This article provides a technical overview of the system, showing how it uses citation data pulled from the JournalTOCs table of contents awareness service to provide access to just your library's subscriptions.

  2. Recent studies in heavy ion induced fission reactions

    Science.gov (United States)

    Choudhury, R. K.

    2001-08-01

    Nuclear fission process involves large scale shape changes of the nucleus, while it evolves from a nearly spherical configuration to two separated fission fragments. The dynamics of these shape changes in the nuclear many body system is governed by a strong interplay of the collective and single particle degrees of freedom. With the availability of heavy ion accelerators, there has been an impetus to study the nuclear dynamics through the investigations of nucleus--nucleus collisions involving fusion and fission process. From the various investigations carried out in the past years, it is now well recognized that there is large scale damping of collective modes in heavy ion induced fission reactions, which in other words implies that nuclear motion is highly viscous. In recent years, there have been many experimental observations in heavy ion induced fission reactions at medium bombarding energies, which suggest possible occurrence of various non-equilibrium modes of fission such as quasi-fission, fast fission and pre-equilibrium fission, where some of the internal degrees of freedom of the nucleus is not fully equilibrated. We have carried out extensive investigations on the fission fragment angular distributions at near barrier bombarding energies using heavy fissile targets. The measured fragment anisotropies when compared with the standard saddle point model (SSPM) calculations show that for projectile-target systems having zero or low ground state spins, the angular anisotropy exhibits a peak-like behaviour at the sub barrier energies, which cannot be explained by the SSPM calculations. For projectiles or targets with large ground state spins, the anomalous peaking gets washed out due to smearing of the K-distribution by the intrinsic entrance channel spins. Recently studies have been carried out on the spin distributions of fission fragments through the gamma ray multiplicity measurements. The fission fragments acquire spin mainly from two sources: (i) due to

  3. A new role for myosin II in vesicle fission.

    Science.gov (United States)

    Flores, Juan A; Balseiro-Gomez, Santiago; Cabeza, Jose M; Acosta, Jorge; Ramirez-Ponce, Pilar; Ales, Eva

    2014-01-01

    An endocytic vesicle is formed from a flat plasma membrane patch by a sequential process of invagination, bud formation and fission. The scission step requires the formation of a tubular membrane neck (the fission pore) that connects the endocytic vesicle with the plasma membrane. Progress in vesicle fission can be measured by the formation and closure of the fission pore. Live-cell imaging and sensitive biophysical measurements have provided various glimpses into the structure and behaviour of the fission pore. In the present study, the role of non-muscle myosin II (NM-2) in vesicle fission was tested by analyzing the kinetics of the fission pore with perforated-patch clamp capacitance measurements to detect single vesicle endocytosis with millisecond time resolution in peritoneal mast cells. Blebbistatin, a specific inhibitor of NM-2, dramatically increased the duration of the fission pore and also prevented closure during large endocytic events. Using the fluorescent markers FM1-43 and pHrodo Green dextran, we found that NM-2 inhibition greatly arrested vesicle fission in a late phase of the scission event when the pore reached a final diameter of ∼ 5 nm. Our results indicate that loss of the ATPase activity of myosin II drastically reduces the efficiency of membrane scission by making vesicle closure incomplete and suggest that NM-2 might be especially relevant in vesicle fission during compound endocytosis.

  4. A new approach to prompt fission neutron TOF data treatment

    Science.gov (United States)

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

    The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. A new mathematical approach, applicable to single events, was developed for prompt fission neutron (PFN) time-offlight distribution unfolding. The main goal was to understand the reasons of the long existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of the fission fragments (FF). Since the 252Cf (sf) reaction is one of the main references for nuclear data the understanding of the PFN emission mechanism is very important both for nuclear fission theory and nuclear data. The experimental data were taken with a twin Frisch-grid ionization chamber and a NE213-equivalent neutron detector in an experimental setup similar to the well known work of C. Budtz-Jorgensen and H.-H. Knitter. About 2.5 × 105 coincidences between fission fragment (FF) and neutron detector response to prompt fission neutron detection have been registered (∼ 1.6 × 107 of total recorded fission events). 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. The main goal of this work was a detailed description of the prompt fission neutron treatment.

  5. Pulsed Laser Centre (CLPU). The Salamanca peta watt laser; Centro de Laseres Pulsados (CLPU). El laser de Petavatio de Salamanca

    Energy Technology Data Exchange (ETDEWEB)

    Franco, L. R.

    2016-08-01

    With pulses lasting 30 photo seconds, the CLPU VEGA laser is capable of generating a peak power level of one peta watt, this making it one of the worlds most powerful lasers. When focussed it can reach extreme intensities. The way in which a pulse of this nature interacts with an atom or what its applications might be are among the questions answered by this article. (Author)

  6. Evaluation of the spectrometric and dose characteristics of neutron fields inside the Russian segment of the ISS by fission detectors

    Science.gov (United States)

    Shurshakov, V. A.; Vorob'ev, I. B.; Nikolaev, V. A.; Lyagushin, V. I.; Akatov, Yu. A.; Kushin, V. V.

    2016-03-01

    The results of measuring the dose and the energy spectrum of neutrons inside the Russian segment of the International Space Station (ISS) from March 21 until November 10, 2002 are presented. Statistically reliable results of measurement are obtained by using thorium- and uranium-based fission detectors with cadmium and boron filters. The kits of the detectors with filters have been arranged in three compartments within assembled passive detectors in the BRADOS space experiment. The ambient dose rate H* = 139 μSv day and an energy spectrum of neutrons in the range of 10-2-104 MeV is obtained as average for the ISS compartments and is compared with the measurements carried out inside the compartments of the MIR space station. Recommendations on how to improve the procedure for using the fission detectors to measure the characteristics of neutron fields inside the compartments of space stations are formulated.

  7. Axial symmetry around the recoil axis for the 238U(α, α'f) reaction and the fission probability in the giant resonance region

    NARCIS (Netherlands)

    Leo, R. de; Harakeh, M.N.; Micheletti, S.; Plicht, J. van der; van der Woude, Adriaan; David, P.; Janszen, H.

    1982-01-01

    A measurement of the α-spectrum in the region of the isoscalar giant resonances from 238U at Eα = 120 MeV in coincidence with out-of-plane fission fragments shows the validity of the hypothesis of axial symmetry with respect to the recoil axis. Similar to what was observed in previous in-plane

  8. Detection of fission fragments by secondary emission; Detection des fragments de fission par emission secondaire

    Energy Technology Data Exchange (ETDEWEB)

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

    1965-07-01

    This fission fragment detecting apparatus is based on the principle that fragments traversing a thin foil will cause emission of secondary electrons. These electrons are then accelerated (10 kV) and directly detected by means of a plastic scintillator and associated photomultiplier. Some of the advantages of such a detector are, its rapidity, its discriminating power between alpha particles and fission fragments, its small energy loss in detecting the fragments and the relatively great amount of fissionable material which it can contain. This paper is subdivided as follows: a) theoretical considerations b) constructional details of apparatus and some experimental details and c) a study of the secondary emission effect itself. (author) [French] Le detecteur de fragments de fission que nous avons realise est base sur le principe de l'emission secondaire produite par les fragments de fission traversant une feuille mince: les electrons secondaires emis sont acceleres a des tensions telles (de l'ordre de 10 kV), qu'ils soient directement detectables par un scintillateur plastique associe a un photomultiplicateur. L'interet d'un tel detecteur reside: dans sa rapidite, sa tres bonne discrimination alpha, fission, la possibilite de detecter les fragments de fission avec une perte d'energie pouvant rester relativement faible, et la possibilite d'introduire des quantites de matiere fissile plus importantes que dans les autres types de detecteurs. Ce travail comporte: -) un apercu bibliographique de la theorie du phenomene, -) realisation et mise au point du detecteur avec etude experimentale de quelques parametres intervenant dans l'emission secondaire, -) etude de l'emission secondaire (sur la face d'emergence des fragments de fission) en fonction de l'energie du fragment et en fonction de l'epaisseur de matiere traversee avant emission secondaire, et -) une etude comparative de l'emission secondaire sur la

  9. Nuclear Fission Investigation with Twin Ionization Chamber

    Science.gov (United States)

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

    2011-11-01

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

  10. Fusion-fission energy systems evaluation

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-01-01

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

  11. Microscopic Calculations of 240Pu Fission

    Energy Technology Data Exchange (ETDEWEB)

    Younes, W; Gogny, D

    2007-09-11

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

  12. FYPO: the fission yeast phenotype ontology.

    Science.gov (United States)

    Harris, Midori A; Lock, Antonia; Bähler, Jürg; Oliver, Stephen G; Wood, Valerie

    2013-07-01

    To provide consistent computable descriptions of phenotype data, PomBase is developing a formal ontology of phenotypes observed in fission yeast. The fission yeast phenotype ontology (FYPO) is a modular ontology that uses several existing ontologies from the open biological and biomedical ontologies (OBO) collection as building blocks, including the phenotypic quality ontology PATO, the Gene Ontology and Chemical Entities of Biological Interest. Modular ontology development facilitates partially automated effective organization of detailed phenotype descriptions with complex relationships to each other and to underlying biological phenomena. As a result, FYPO supports sophisticated querying, computational analysis and comparison between different experiments and even between species. FYPO releases are available from the Subversion repository at the PomBase SourceForge project page (https://sourceforge.net/p/pombase/code/HEAD/tree/phenotype_ontology/). The current version of FYPO is also available on the OBO Foundry Web site (http://obofoundry.org/).

  13. Fission Fragment characterization with FALSTAFF at NFS

    Directory of Open Access Journals (Sweden)

    Pancin J.

    2013-03-01

    Full Text Available The Neutrons for Science (NFS facility will be one of the first installations of the SPIRAL2 facility. NFS will be composed of a time-of-flight baseline and irradiation stations and will allow studying neutron-induced reactions for energies going from some hundreds of keV up to 40 MeV. Continuous and quasi-monoenergetic energy neutron beams will be available. Taking advantage of this new installation, the development of an experimental setup for a full characterization of actinide fission fragments in this energy domain has been undertaken. To achieve this goal a new detection system called FALSTAFF (Four Arm cLover for the STudy of Actinide Fission Fragments in under development. In this paper, the characteristics of the NFS facility will be exposed and the motivations for the FALSTAFF experiment will be presented. The experimental setup will be described and the expected resolutions based on realistic GEANT4 simulations will be discussed.

  14. FALSTAFF: A new tool for fission studies

    Directory of Open Access Journals (Sweden)

    Dore D.

    2013-12-01

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

  15. SABR Fusion-Fission Hybrid Studies

    Science.gov (United States)

    Stewart, Chris

    2012-03-01

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

  16. Doppler-free intermodulated fluorescence spectroscopy of $^4He$ $2^3P-3^{1,3}D$ transitions at 588 nm with a one-watt compact laser system

    CERN Document Server

    Luo, Pei-Ling; Feng, Yan; Wang, Li-Bang; Shy, Jow-Tsong

    2015-01-01

    We have demonstrated Doppler-free intermodulated fluorescence spectroscopy of helium $2^3P-3^{1,3}D$ transitions in an rf discharged sealed-off cell using a compact laser system at 588 nm. An external cavity diode laser at 1176 nm was constructed to seed a Raman fiber amplifier. Laser power of more than one watt at 588 nm was produced by frequency doubling of the fiber amplifier output using a MgO:PPLN crystal. A doubling efficiency of 23 % was achieved. The power-dependent spectra of the $2^3P-3^3D$ transitions were investigated. Furthermore, the Doppler-free spectrum of the spin-forbidden $2^3P-3^1D$ transitions was observed for the first time. Our results are crucial towards precision test of QED atomic calculations, especially for improving the determination of the helium $3^1D-3^3D$ separation.

  17. Comparison of the Danish step test and the watt-max test for estimation of maximal oxygen uptake

    DEFF Research Database (Denmark)

    Aadahl, Mette; Zacho, Morten; Linneberg, Allan René

    2013-01-01

    test may be a feasible alternative for estimation of VO(2max.)Aim: To compare a simple fitness test, the Danish step test, to an indirect maximal test, the watt-max test, for estimation of VO(2max.)Methods: In the population-based Health2008 study, 2218 men and women aged 30-60 years were invited....... Altogether, 795 eligible participants (response rate 35.8%) performed the watt max and the Danish step test. Correlation and agreement between the two VO(2max) test results was explored by Pearson's rho, Bland-Altman plots, Kappa(w), and gamma coefficients.Results: The correlation between VO(2max) (ml....../kg/min) estimated by the two tests was moderate to high (men: r = 0.69, p test slightly overestimated VO(2max )compared to the watt-max test, more so in women than in men. Agreement between the two tests when VO(2max) was classified in five levels was gamma = 0...

  18. A new Cu(TiBN x ) alloy film for boosting the per-watt illuminance of high power LEDs

    Science.gov (United States)

    Lin, Chon-Hsin

    2017-01-01

    In this study, a new Cu(TiBN x ) alloy film has been explored and utilized as a flexible heat dissipation layer for the substrate of high power LEDs to boost their per-watt illuminance by reducing the thermal resistance and increasing the thermal conductivity of the substrate. The new film is a Cu-alloy seed layer fabricated by co-sputtering Cu and TiB in an N2 atmosphere on a Ta/polyimide (Ta/PI) substrate. The film was then annealed at 340 °C for 1 h without noticeable Cu oxide formation around the film-substrate interface. The new film exhibits low resistivity, high thermal conductivity and low thermal resistance, rendering a substantially higher per-watt illuminance for LEDs that utilize the film as their additional heat dissipation layer. The experimental results gained in the study appear to confirm the new Cu(TiBN x ) film as a good candidate material, at least, for boosting the per-watt illuminance of high power LEDs.

  19. Time Delay and Long-Range Connection Induced Synchronization Transitions in Newman-Watts Small-World Neuronal Networks

    Science.gov (United States)

    Qian, Yu

    2014-01-01

    The synchronization transitions in Newman-Watts small-world neuronal networks (SWNNs) induced by time delay and long-range connection (LRC) probability have been investigated by synchronization parameter and space-time plots. Four distinct parameter regions, that is, asynchronous region, transition region, synchronous region, and oscillatory region have been discovered at certain LRC probability as time delay is increased. Interestingly, desynchronization is observed in oscillatory region. More importantly, we consider the spatiotemporal patterns obtained in delayed Newman-Watts SWNNs are the competition results between long-range drivings (LRDs) and neighboring interactions. In addition, for moderate time delay, the synchronization of neuronal network can be enhanced remarkably by increasing LRC probability. Furthermore, lag synchronization has been found between weak synchronization and complete synchronization as LRC probability is a little less than 1.0. Finally, the two necessary conditions, moderate time delay and large numbers of LRCs, are exposed explicitly for synchronization in delayed Newman-Watts SWNNs. PMID:24810595

  20. Time delay and long-range connection induced synchronization transitions in Newman-Watts small-world neuronal networks.

    Science.gov (United States)

    Qian, Yu

    2014-01-01

    The synchronization transitions in Newman-Watts small-world neuronal networks (SWNNs) induced by time delay τ and long-range connection (LRC) probability P have been investigated by synchronization parameter and space-time plots. Four distinct parameter regions, that is, asynchronous region, transition region, synchronous region, and oscillatory region have been discovered at certain LRC probability P = 1.0 as time delay is increased. Interestingly, desynchronization is observed in oscillatory region. More importantly, we consider the spatiotemporal patterns obtained in delayed Newman-Watts SWNNs are the competition results between long-range drivings (LRDs) and neighboring interactions. In addition, for moderate time delay, the synchronization of neuronal network can be enhanced remarkably by increasing LRC probability. Furthermore, lag synchronization has been found between weak synchronization and complete synchronization as LRC probability P is a little less than 1.0. Finally, the two necessary conditions, moderate time delay and large numbers of LRCs, are exposed explicitly for synchronization in delayed Newman-Watts SWNNs.

  1. Decay spectroscopy of exotic fission products

    Science.gov (United States)

    Rykaczewski, Krzysztof

    2014-09-01

    The beta decay studies of exotic fission products have been performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The scientific program was focused on the beta-strength function measurements and resulting new half-lives and beta-delayed neutron properties. These observables are important for nuclear structure analysis and modeling of the nucleosynthesis within rapid neutron capture process. The highlights include ten new beta half-lives and several Pn branching ratios including an observation of beta-delayed two-neutron emitter 86Ga. In addition, the measurements of the beta-strength within beta-gamma emission window were performed using a Modular Total Absorption Spectrometer for 22 fission products. These MTAS results are also important for the analysis of reactor anti-neutrino anomaly. The beta decay studies of exotic fission products have been performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The scientific program was focused on the beta-strength function measurements and resulting new half-lives and beta-delayed neutron properties. These observables are important for nuclear structure analysis and modeling of the nucleosynthesis within rapid neutron capture process. The highlights include ten new beta half-lives and several Pn branching ratios including an observation of beta-delayed two-neutron emitter 86Ga. In addition, the measurements of the beta-strength within beta-gamma emission window were performed using a Modular Total Absorption Spectrometer for 22 fission products. These MTAS results are also important for the analysis of reactor anti-neutrino anomaly. Supported by the U.S. DOE Office of Nuclear Physics under Contracts DE-AC05-00R22725 (ORNL), DE-FG02-96ER40983 (UTK).

  2. Taxonomy Icon Data: fission yeast [Taxonomy Icon

    Lifescience Database Archive (English)

    Full Text Available fission yeast Schizosaccharomyces pombe Schizosaccharomyces_pombe_L.png Schizosaccharomy...ces_pombe_NL.png Schizosaccharomyces_pombe_S.png Schizosaccharomyces_pombe_NS.png http://biosciencedbc.jp/taxonomy..._icon/icon.cgi?i=Schizosaccharomyces+pombe&t=L http://biosciencedbc.jp/taxonomy_icon/icon.cgi?i=Schizosaccharomy...ces+pombe&t=NL http://biosciencedbc.jp/taxonomy_icon/icon.cgi?i=Schizosaccharomy...ces+pombe&t=S http://biosciencedbc.jp/taxonomy_icon/icon.cgi?i=Schizosaccharomyces+pombe&t=NS

  3. Singlet fission: Towards efficient solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Zdeněk; Wen, Jin [Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6 (Czech Republic); Michl, Josef [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6 (Czech Republic)

    2015-12-31

    Singlet fission (SF) offers an opportunity to improve solar cell efficiency, but its practical use is hindered by the limited number of known efficient materials, limited knowledge of SF mechanism, mainly the relation between the dimer structure and SF efficiency and diffusion of the triplet states allowing injection of electrons into the solar cell semiconductor band. Here we report on our attempt to design new classes of chromophores and to study the relation between the structure and SF efficiency.

  4. REMOVAL OF FISSION PRODUCTS FROM WATER

    Science.gov (United States)

    Rosinski, J.

    1961-12-19

    A process is given for precipitating fission products from a body of water having a pH of above 6.5. Calcium permanganate and ferrous sulfate are added in a molar ratio of l: 3, whereby a mixed precipitate of manganese dioxide, ferric hydroxide and calcium sulfate is formed; the precipitate carries the fisston products and settles to the bottom of the body of water. (AEC)

  5. Actinide and fission product partitioning and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-07-01

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

  6. Search for ternary fission of chromium-48

    Science.gov (United States)

    Dummer, Andrew K.

    1999-07-01

    Both alpha cluster model calculations and macroscopic energy calculations that allow for a double-neck shape of the compound nucleus suggest the possibility of a novel three 16O, chain-like configuration in 48 Cr. Such a configuration might lead to an enhanced cross section for three-16O breakup. To explore this possibility, the three-body exit channels for the 36Ar + 12C reaction at a beam energy of 210 MeV have been studied. The cross section for 16O + 16O + 16O breakup has been deduced and has been found to be in excess of what would be expected to result from a sequential binary fission process. However, the observation of a similarly enhanced 12C + 16O + 20Ne breakup cross section suggests that the observed 16O + 16O + 16O yields might still be associated with a statistical fission process. The results are discussed in the context of the fission of light nuclear systems and a simple cluster model calculation. This latter, ``Harvey model'' calculation suggests a possible inhibition of the formation of a three- 16O chain configuration from the 36Ar + 12C entrance channel. A further measurement using the 20Ne + 28Si-entrance channel is suggested.

  7. Simulating an Exploding Fission-Bomb Core

    Science.gov (United States)

    Reed, Cameron

    2016-03-01

    A time-dependent desktop-computer simulation of the core of an exploding fission bomb (nuclear weapon) has been developed. The simulation models a core comprising a mixture of two isotopes: a fissile one (such as U-235) and an inert one (such as U-238) that captures neutrons and removes them from circulation. The user sets the enrichment percentage and scattering and fission cross-sections of the fissile isotope, the capture cross-section of the inert isotope, the number of neutrons liberated per fission, the number of ``initiator'' neutrons, the radius of the core, and the neutron-reflection efficiency of a surrounding tamper. The simulation, which is predicated on ordinary kinematics, follows the three-dimensional motions and fates of neutrons as they travel through the core. Limitations of time and computer memory render it impossible to model a real-life core, but results of numerous runs clearly demonstrate the existence of a critical mass for a given set of parameters and the dramatic effects of enrichment and tamper efficiency on the growth (or decay) of the neutron population. The logic of the simulation will be described and results of typical runs will be presented and discussed.

  8. Spontaneous fission of superheavy nucleus $^{286}$Fl

    CERN Document Server

    Poenaru, Dorin N

    2016-01-01

    The decimal logarithm of spontaneous fission half-life of the superheavy nucleus $^{286}$Fl experimentally determined is $\\log_{10} T_f^{exp} (s) = -0.632$. We present a method to calculate the half-life based on the cranking inertia and the deformation energy, functions of two independent surface coordinates, using the best asymmetric two center shell model. In the first stage we study the statics. At a given mass asymmetry up to about $\\eta=0.5$ the potential barrier has a two hump shape, but for larger $\\eta$ it has only one hump. The touching point deformation energy versus mass asymmetry shows the three minima, produced by shell effects, corresponding to three decay modes: spontaneous fission, cluster decay and $\\alpha$~decay. The least action trajectory is determined in the plane $(R,\\eta)$ where $R$ is the separation distance of the fission fragments and $\\eta$ is the mass asymmetry. We may find a sequence of several trajectories one of which gives the least action. The parametrization with two deforma...

  9. Capture and fission with DANCE and NEUANCE

    Energy Technology Data Exchange (ETDEWEB)

    Jandel, M.; Baramsai, B.; Bond, E.; Rusev, G.; Walker, C.; Bredeweg, T.A.; Chadwick, M.B.; Couture, A.; Fowler, M.M.; Hayes, A.; Kawano, T.; Mosby, S.; Stetcu, I.; Taddeucci, T.N.; Talou, P.; Ullmann, J.L.; Vieira, D.J.; Wilhelmy, J.B. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

    2015-12-15

    A summary of the current and future experimental program at DANCE is presented. Measurements of neutron capture cross sections are planned for many actinide isotopes with the goal to reduce the present uncertainties in nuclear data libraries. Detailed studies of capture gamma rays in the neutron resonance region will be performed in order to derive correlated data on the de-excitation of the compound nucleus. New approaches on how to remove the DANCE detector response from experimental data and retain the correlations between the cascade gamma rays are presented. Studies on {sup 235}U are focused on quantifying the population of short-lived isomeric states in {sup 236}U after neutron capture. For this purpose, a new neutron detector array NEUANCE is under construction. It will be installed in the central cavity of the DANCE array and enable the highly efficient tagging of fission and capture events. In addition, developments of fission fragment detectors are also underway to expand DANCE capabilities to measurements of fully correlated data on fission observables. (orig.)

  10. Mitochondrial fusion, fission, and mitochondrial toxicity.

    Science.gov (United States)

    Meyer, Joel N; Leuthner, Tess C; Luz, Anthony L

    2017-08-05

    Mitochondrial dynamics are regulated by two sets of opposed processes: mitochondrial fusion and fission, and mitochondrial biogenesis and degradation (including mitophagy), as well as processes such as intracellular transport. These processes maintain mitochondrial homeostasis, regulate mitochondrial form, volume and function, and are increasingly understood to be critical components of the cellular stress response. Mitochondrial dynamics vary based on developmental stage and age, cell type, environmental factors, and genetic background. Indeed, many mitochondrial homeostasis genes are human disease genes. Emerging evidence indicates that deficiencies in these genes often sensitize to environmental exposures, yet can also be protective under certain circumstances. Inhibition of mitochondrial dynamics also affects elimination of irreparable mitochondrial DNA (mtDNA) damage and transmission of mtDNA mutations. We briefly review the basic biology of mitodynamic processes with a focus on mitochondrial fusion and fission, discuss what is known and unknown regarding how these processes respond to chemical and other stressors, and review the literature on interactions between mitochondrial toxicity and genetic variation in mitochondrial fusion and fission genes. Finally, we suggest areas for future research, including elucidating the full range of mitodynamic responses from low to high-level exposures, and from acute to chronic exposures; detailed examination of the physiological consequences of mitodynamic alterations in different cell types; mechanism-based testing of mitotoxicant interactions with interindividual variability in mitodynamics processes; and incorporating other environmental variables that affect mitochondria, such as diet and exercise. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Capture and fission with DANCE and NEUANCE

    Science.gov (United States)

    Jandel, M.; Baramsai, B.; Bond, E.; Rusev, G.; Walker, C.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M. M.; Hayes, A.; Kawano, T.; Mosby, S.; Stetcu, I.; Taddeucci, T. N.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.

    2015-12-01

    A summary of the current and future experimental program at DANCE is presented. Measurements of neutron capture cross sections are planned for many actinide isotopes with the goal to reduce the present uncertainties in nuclear data libraries. Detailed studies of capture gamma rays in the neutron resonance region will be performed in order to derive correlated data on the de-excitation of the compound nucleus. New approaches on how to remove the DANCE detector response from experimental data and retain the correlations between the cascade gamma rays are presented. Studies on 235U are focused on quantifying the population of short-lived isomeric states in 236U after neutron capture. For this purpose, a new neutron detector array NEUANCE is under construction. It will be installed in the central cavity of the DANCE array and enable the highly efficient tagging of fission and capture events. In addition, developments of fission fragment detectors are also underway to expand DANCE capabilities to measurements of fully correlated data on fission observables.

  12. Undergraduate Measurements For Fission Reactor Applications

    Science.gov (United States)

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

    2011-06-01

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

  13. Accurate fission data for nuclear safety

    CERN Document Server

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

    2013-01-01

    The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it 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 (10^12 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...

  14. Life test result of Ricor K529N 1watt linear cryocooler

    Science.gov (United States)

    Nachman, Ilan; Veprik, Alexander; Pundak, Nachman

    2007-04-01

    The authors summarize the results of the accelerated life testing of the Ricor type K529N 1 Watt linear split Stirling cooler. The test was conducted in the period 2003-2006, during which the cooler accumulated in excess of 27,500 working hours at an elevated ambient temperature, which is equivalent to 45,000 hours at normal ambient conditions, and performed about 7,500 operational cycles including cooldown and steady-state phases. The cryocooler performances were assessed through the cooldown time and power consumption; no visible degradation in performances was observed. After the cooler failure and the compressor disassembling, an electrical short was discovered in the driving coil. The analysis has shown that the wire insulating varnish was not suitable for such elevated temperatures. It is important to note that the cooler under test was taken from the earliest engineering series; in the later manufacturing line military grade wire with high temperature insulation was used, no customer complaints have been recorded in this instance Special attention was paid to the thorough examination of the technical condition of the critical components of the cooler interior. In particular, dynamic piston-cylinder seal, flying leads, internal O-rings and driving coil were examined in the compressor. As to the cold head, we focused on studying the conditions of the dynamic bushing-plunger seal, O-rings and displacer-regenerator. In addition, a leak test was performed to assess the condition of the metallic crushed seals. From the analysis, the authors draw the conclusion that the cooler design is adequate for long life performance (in excess of 20,000 working hours) applications.

  15. Standalone BISON Fuel Performance Results for Watts Bar Unit 1, Cycles 1-3

    Energy Technology Data Exchange (ETDEWEB)

    Clarno, Kevin T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pawlowski, Roger [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stimpson, Shane [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Powers, Jeffrey [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-07

    The Consortium for Advanced Simulation of Light Water Reactors (CASL) is moving forward with more complex multiphysics simulations and increased focus on incorporating fuel performance analysis methods. The coupled neutronics/thermal-hydraulics capabilities within the Virtual Environment for Reactor Applications Core Simulator (VERA-CS) have become relatively stable, and major advances have been made in analysis efforts, including the simulation of twelve cycles of Watts Bar Nuclear Unit 1 (WBN1) operation. While this is a major achievement, the VERA-CS approaches for treating fuel pin heat transfer have well-known limitations that could be eliminated through better integration with the BISON fuel performance code. Several approaches are being implemented to consider fuel performance, including a more direct multiway coupling with Tiamat, as well as a more loosely coupled one-way approach with standalone BISON cases. Fuel performance typically undergoes an independent analysis using a standalone fuel performance code with manually specified input defined from an independent core simulator solution or set of assumptions. This report summarizes the improvements made since the initial milestone to execute BISON from VERA-CS output. Many of these improvements were prompted through tighter collaboration with the BISON development team at Idaho National Laboratory (INL). A brief description of WBN1 and some of the VERA-CS data used to simulate it are presented. Data from a small mesh sensitivity study are shown, which helps justify the mesh parameters used in this work. The multi-cycle results are presented, followed by the results for the first three cycles of WBN1 operation, particularly the parameters of interest to pellet-clad interaction (PCI) screening (fuel-clad gap closure, maximum centerline fuel temperature, maximum/minimum clad hoop stress, and cumulative damage index). Once the mechanics of this capability are functioning, future work will target cycles with

  16. Assessment of Pellet-Clad Interaction Indicators in Watts Bar Unit 1 using the VERA Framework

    Energy Technology Data Exchange (ETDEWEB)

    Stimpson, Shane G [ORNL; Powers, Jeffrey J [ORNL; Clarno, Kevin T [ORNL; Pawlowski, Roger [Sandia National Laboratory (SNL); Bratton, Ryan [Pennsylvania State University

    2015-01-01

    The Consortium for Advanced Simulation of Light Water Reactors (CASL) aims to provide high-fidelity, multiphysics simulations of light water reactors (LWRs) by coupling a variety of codes within the Virtual Environment for Reactor Analysis (VERA). One of the primary goals of CASL is to predict local cladding failure through pellet-clad interaction (PCI). This capability is currently being pursued through several different approaches, such as with Tiamat, which is a simulation tool within VERA that more tightly couples the MPACT neutron transport solver, the CTF thermal hydraulics solver, and the MOOSE-based Bison-CASL fuel performance code. However, the process in this paper focuses on running fuel performance calculations with Bison-CASL to predict PCI using the multicycle output data from coupled neutron transport/thermal hydraulics simulations. In recent work within CASL, Watts Bar Unit 1 has been simulated over 12 cycles using the VERA core simulator capability based on MPACT and CTF. Using the output from these simulations, Bison-CASL results can be obtained without rerunning all 12 cycles, while providing some insight into PCI indicators. Multi-cycle Bison-CASL results are presented and compared against results from the FRAPCON fuel performance code. There are several quantities of interest in considering PCI and subsequent fuel rod failures, such as the clad hoop stress and maximum centerline fuel temperature, particularly as a function of time. Bison-CASL performs single-rod simulations using representative power and temperature distributions, providing high-resolution results for these and a number of other quantities. This will assist in identifying fuels rods as potential failure locations for use in further analyses.

  17. De Novo Transcriptome Sequencing of Oryza officinalis Wall ex Watt to Identify Disease-Resistance Genes

    Directory of Open Access Journals (Sweden)

    Bin He

    2015-12-01

    Full Text Available Oryza officinalis Wall ex Watt is one of the most important wild relatives of cultivated rice and exhibits high resistance to many diseases. It has been used as a source of genes for introgression into cultivated rice. However, there are limited genomic resources and little genetic information publicly reported for this species. To better understand the pathways and factors involved in disease resistance and accelerating the process of rice breeding, we carried out a de novo transcriptome sequencing of O. officinalis. In this research, 137,229 contigs were obtained ranging from 200 to 19,214 bp with an N50 of 2331 bp through de novo assembly of leaves, stems and roots in O. officinalis using an Illumina HiSeq 2000 platform. Based on sequence similarity searches against a non-redundant protein database, a total of 88,249 contigs were annotated with gene descriptions and 75,589 transcripts were further assigned to GO terms. Candidate genes for plant–pathogen interaction and plant hormones regulation pathways involved in disease-resistance were identified. Further analyses of gene expression profiles showed that the majority of genes related to disease resistance were all expressed in the three tissues. In addition, there are two kinds of rice bacterial blight-resistant genes in O. officinalis, including two Xa1 genes and three Xa26 genes. All 2 Xa1 genes showed the highest expression level in stem, whereas one of Xa26 was expressed dominantly in leaf and other 2 Xa26 genes displayed low expression level in all three tissues. This transcriptomic database provides an opportunity for identifying the genes involved in disease-resistance and will provide a basis for studying functional genomics of O. officinalis and genetic improvement of cultivated rice in the future.

  18. Effects of coal fly ash on tree swallow reproduction in Watts Bar Reservoir, Tennessee.

    Science.gov (United States)

    Walls, Suzanne J; Meyer, Carolyn B; Iannuzzi, Jacqueline; Schlekat, Tamar H

    2015-01-01

    Coal-fly ash was released in unprecedented amounts (4.1 × 10(6) m(3) ) into the Emory River from the Tennessee Valley Authority Kingston Fossil Plant on Watts Bar Reservoir in Tennessee. Tree swallows were exposed to ash-related constituents at the ash release via their diet of emergent aquatic insects, whose larval forms can accumulate constituents from submerged river sediments. Reproduction of tree swallow colonies was assessed over a 2-year period by evaluating whether 1) ash constituent concentrations were elevated in egg, eggshell, and nestling tissues at colonies near ash-impacted river reaches compared to reference colonies, 2) production of fledglings per nesting female was significantly lower in ash-impacted colonies versus reference colonies, and 3) ash constituent concentrations or diet concentrations were correlated with nest productivity measures (clutch size, hatching success, and nestling survival, and fledglings produced per nest). Of the 26 ash constituents evaluated, 4 (Se, Sr, Cu, and Hg) were significantly elevated in tissues potentially from the ash, and 3 (Se, Sr, and Cu) in tissues or in swallow diet items were weakly correlated to at least one nest-productivity measure or egg weight. Tree swallow hatching success was significantly reduced by 12%, but fledgling production per nest was unaffected due to larger clutch sizes in the impacted than reference colonies. Bioconcentration from the ash to insects in the diet to tree swallow eggs appears to be low. Overall, adverse impacts of the ash on tree swallow reproduction were not observed, but monitoring is continuing to further ensure Se from the residual ash does not adversely affect tree swallow reproduction over time. Integr Environ Assess Manag 2015;11:56-66. © 2014 SETAC.

  19. Results of Performance Tests Performed on the John Watts Casing Connection on 7" Pipe

    Energy Technology Data Exchange (ETDEWEB)

    John D. Watts

    1999-08-01

    Stress Engineering Services (SES) was contracted by Mr. John Watts to test his threaded connection developed for oilfield oil and gas service. This particular test required the application of a variety of loads including axial tension and compression, internal pressure (gas), external pressure (water), bending and both low and elevated temperature. These loads were used to determine the sealing and structural limits of the connection. The connection design tested had tapered threads with 10 threads per inch. A square thread form and a round thread form were tested. The square thread form had a 2{sup o} load flank and 15{sup o} stab flank. The round thread had a 0{sup o} load flank and 20{sup o} stab flank. Most of the testing was performed on the round thread form. Both a coupled connection design and an integral connection design were tested. The coupling was a pin by pin (male) thread, with the pipe having a box (female) thread. Both designs have outside and inside diameters that are flush with the pipe body. Both designs also contain a small external shoulder. The test procedure selected for this evaluation was the newly written ISO 13679 procedure for full scale testing of casing and tubing connections. The ISO procedure requires a variety of tests that includes makeup/breakout testing, internal gas sealability/external water sealability testing with axial tension, axial compression, bending, internal gas thermal cycle tests and limit load (failure) tests. This test was performed with four coupled samples and included most of these loads. Two integral samples were also included for limit load testing ISO makeup/breakout tests are divided into three types--initial makeup, IML1, repeated makeup within the same sample, MBL, and repeated makeup using several samples called round robin, RR. IMU and MBL were performed in this project. The ISO sealing and structural procedure is divided into four primary tests and identified as Series A, B, C and Limit Load (failure

  20. Results of Performance Tests Performed on the John Watts Casing Connection on 7" Pipe

    Energy Technology Data Exchange (ETDEWEB)

    John D. Watts

    1999-08-01

    Stress Engineering Services (SES) was contracted by Mr. John Watts to test his threaded connection developed for oilfield oil and gas service. This particular test required the application of a variety of loads including axial tension and compression, internal pressure (gas), external pressure (water), bending and both low and elevated temperature. These loads were used to determine the sealing and structural limits of the connection. The connection design tested had tapered threads with 10 threads per inch. A square thread form and a round thread form were tested. The square thread form had a 2{sup o} load flank and 15{sup o} stab flank. The round thread had a 0{sup o} load flank and 20{sup o} stab flank. Most of the testing was performed on the round thread form. Both a coupled connection design and an integral connection design were tested. The coupling was a pin by pin (male) thread, with the pipe having a box (female) thread. Both designs have outside and inside diameters that are flush with the pipe body. Both designs also contain a small external shoulder. The test procedure selected for this evaluation was the newly written ISO 13679 procedure for full scale testing of casing and tubing connections. The ISO procedure requires a variety of tests that includes makeup/breakout testing, internal gas sealability/external water sealability testing with axial tension, axial compression, bending, internal gas thermal cycle tests and limit load (failure) tests. This test was performed with four coupled samples and included most of these loads. Two integral samples were also included for limit load testing ISO makeup/breakout tests are divided into three types--initial makeup, IML1, repeated makeup within the same sample, MBL, and repeated makeup using several samples called round robin, RR. IMU and MBL were performed in this project. The ISO sealing and structural procedure is divided into four primary tests and identified as Series A, B, C and Limit Load (failure

  1. Mass and energy dependence of pion-induced fission

    Science.gov (United States)

    Peterson, R. J.; Debarros, S.; Desouza, I. O.; Gaspar, M. B.; Khan, Hameed Ahmed; Manzoor, Shahid

    1995-06-01

    Data for fission induced by pi meson beams from 80 to 500 MeV are presented for nuclei from Fe through Pu as measured by solid state track detectors. The general trends for binary fission with π + are reproduced fairly well by a calculation in the ‘high excitation’ limit with standard level density and fission barrier parameters, but π - data are underpredicted. A universal dependence of the binary fission probabilities with the fissility ( Z±1)2/A is found to be valid for both pion beam charges for all beam energies below the delta resonance. Probabilities for observing three fragments with π + are not reproduced by a ternary fission application of the model found to work for binary fission.

  2. Negative Pion Induced Fission with Heavy Target Nuclei

    Institute of Scientific and Technical Information of China (English)

    G. Sher; Mukhtar A. Rana; S. Manzoor; M. I. Shahzad

    2011-01-01

    We investigate fission induced by negative pions in copper and bismuth targets using CR-39 dielectric track detectors. The target-detector assemblies in Air-geometric configuration were exposed at the AGS facility of Brookhaven National Laboratory, USA. The exposed detectors were chemically etched under appropriate etching conditions and scanned to collect data in the form of fission fragments tracks produced as a result of interaction of pions with the target nuclei. Using the track counts, the experimental fission cross sections for copper and bismuth have been measured at energies of 500, 672, 1068 and 1665 MeV and compared with the calculation using the Cascade-Exciton Model code (CEM95). The values of fission probability based on experimental fission cross-sections have been compared with the theoretically calculated values of fission probabilities obtained using the CEM95 code. Good agreement is observed between the measured and computed results.

  3. Prompt Fission Gamma-ray Studies at DANCE

    Science.gov (United States)

    Jandel, M.; Rusev, G.; Bond, E. M.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M. M.; Haight, R. C.; Kawano, T.; Keksis, A. L.; Mosby, S. M.; O'Donnell, J. M.; Rundberg, R. S.; Stetcu, I.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Stoyer, M. A.; Haslett, R. J.; Henderson, R. A.; Becker, J. A.; Wu, C. Y.

    Measurements of correlated data on prompt-fission γ-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of γ-ray multiplicity and energy. New results on two- dimensional prompt-fission γ-ray multiplicity versus energy distributions from spontaneous fission on 252Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and 239Pu. Correlated PFG data from 252Cf are also compared to results of the detailed theoretical model developed at LANL, for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and γ-rays at DANCE are presented.

  4. Total kinetic energy release in the fast neutron-induced fission of $^{235}$U

    CERN Document Server

    Yanez, R; King, J; Barrett, J S; Fotiades, N; Lee, H Y

    2016-01-01

    We have measured the total kinetic energy (TKE) release for the $^{235}$U(n,f) reaction for $E_{n}$=2-100 MeV using the 2E method with an array of Si PIN diode detectors. The neutron energies were determined by time of flight measurements using the white spectrum neutron beam at the LANSCE facility. To benchmark the TKE measurement, the TKE release for $^{235}$U(n$_{th}$,f) was also measured using a thermal neutron beam from the Oregon State University TRIGA reactor, giving pre-neutron emission $E^*_{TKE}=170.7\\pm0.4$ MeV in good agreement with known values. Our measurements are thus absolute measurements. The TKE in $^{235}$U(n,f) decreases non-linearly from 169.0 MeV to 161.4 MeV for $E_{n}$=2-90 MeV. Comparison of the data with the multi-modal fission model of Brosa indicates the TKE decrease is a consequence of the growth of symmetric fission and the corresponding decrease of asymmetric fission with increasing neutron energy. The average TKE associated with the Brosa superlong, standard I and standard II ...

  5. Radioactive Ion Beam Production by Fast-Neutron-Induced Fission in Actinide Targets at EURISOL

    CERN Document Server

    Herrera-Martínez, Adonai

    The European Isotope Separation On-Line Radioactive Ion Beam Facility (EURISOL) is set to be the 'next-generation' European Isotope Separation On-Line (ISOL) Radioactive Ion Beam (RIB) facility. It will extend and amplify current research on nuclear physics, nuclear astrophysics and fundamental interactions beyond the year 2010. In EURISOL, the production of high-intensity RIBs of specific neutron-rich isotopes is obtained by inducing fission in large-mass actinide targets. In our contribution, the use of uranium targets is shown to be advantageous to other materials, such as thorium. Therefore, in order to produce fissions in U-238 and reduce the plutonium inventory, a fast neutron energy spectrum is necessary. The large beam power required to achieve these RIB levels requires the use of a liquid proton-to-neutron converter. This article details the design parameters of the converter, with special attention to the coupled neutronics of the liquid converter and fission target. Calculations performed with the ...

  6. Total kinetic energy release in the fast neutron-induced fission of $^{235}$U

    CERN Document Server

    Yanez, R; King, J; Barrett, J S; Fotiades, N; Lee, H Y

    2015-01-01

    We have measured the total kinetic energy (TKE) release for the $^{235}$U(n,f) reaction for $E_{n}$=2-100 MeV using the 2E method with an array of Si PIN diode detectors. The neutron energies were determined by time of flight measurements using the white spectrum neutron beam at the LANSCE facility. (To calibrate the apparatus, the TKE release for $^{235}$U(n$_{th}$,f) was also measured using a thermal neutron beam from the OSU TRIGA reactor). The TKE decreases non-linearly from 169.0 MeV to 161.4 MeV for $E_{n}$=2-90 MeV. The standard deviation of the TKE distribution is constant from $E_{n}$=20-90 MeV. Comparison of the data with the multi-modal fission model of Brosa indicates the TKE decrease is a consequence of the growth of symmetric fission and the corresponding decrease of asymmetric fission with increasing neutron energy. The average TKE associated with the Brosa superlong, standard I and standard II modes for a given mass is independent of neutron energy.

  7. Isomer production ratios and the angular momentum distribution of fission fragments

    Science.gov (United States)

    Stetcu, I.; Talou, P.; Kawano, T.; Jandel, M.

    2013-10-01

    Latest generation fission experiments provide an excellent testing ground for theoretical models. In this contribution we compare the measurements for 235U(nth,f), obtained with the Detector for Advanced Neutron Capture Experiments (DANCE) calorimeter at Los Alamos Neutron Science Center (LANSCE), with our full-scale simulation of the primary fragment de-excitation, using the recently developed cgmf code, based on a Monte Carlo implementation of the Hauser-Feshbach theoretical model. We compute the isomer ratios as a function of the initial angular momentum of the fission fragments, for which no direct information exists. Comparison with the available experimental data allows us to determine the initial spin distribution. We also study the dependence of the isomer ratio on the knowledge of the low-lying discrete spectrum input for nuclear fission reactions, finding a high degree of sensitivity. Finally, in the same Hauser-Feshbach approach, we calculate the isomer production ratio for thermal neutron capture on stable isotopes, where the initial conditions (spin, excitation energy, etc.) are well understood. We find that with the current parameters involved in Hauser-Feshbach calculations, we obtain up to a factor of 2 deviation from the measured isomer ratios.

  8. Transient coupled calculations of the Molten Salt Fast Reactor using the Transient Fission Matrix approach

    Energy Technology Data Exchange (ETDEWEB)

    Laureau, A., E-mail: laureau.axel@gmail.com; Heuer, D.; Merle-Lucotte, E.; Rubiolo, P.R.; Allibert, M.; Aufiero, M.

    2017-05-15

    Highlights: • Neutronic ‘Transient Fission Matrix’ approach coupled to the CFD OpenFOAM code. • Fission Matrix interpolation model for fast spectrum homogeneous reactors. • Application for coupled calculations of the Molten Salt Fast Reactor. • Load following, over-cooling and reactivity insertion transient studies. • Validation of the reactor intrinsic stability for normal and accidental transients. - Abstract: In this paper we present transient studies of the Molten Salt Fast Reactor (MSFR). This generation IV reactor is characterized by a liquid fuel circulating in the core cavity, requiring specific simulation tools. An innovative neutronic approach called “Transient Fission Matrix” is used to perform spatial kinetic calculations with a reduced computational cost through a pre-calculation of the Monte Carlo spatial and temporal response of the system. Coupled to this neutronic approach, the Computational Fluid Dynamics code OpenFOAM is used to model the complex flow pattern in the core. An accurate interpolation model developed to take into account the thermal hydraulics feedback on the neutronics including reactivity and neutron flux variation is presented. Finally different transient studies of the reactor in normal and accidental operating conditions are detailed such as reactivity insertion and load following capacities. The results of these studies illustrate the excellent behavior of the MSFR during such transients.

  9. Revision of the JENDL FP Fission Yield Data

    Directory of Open Access Journals (Sweden)

    Katakura Jun-ichi

    2016-01-01

    Full Text Available Some fission yields data of JENDL FP Fission Yields Data File 2011 (JENDL/FPY-2011 revealed inadequacies when applied to delayed neutron related subjects. The sensitivity analyses of decay heat summation calculations also showed some problems. From these results the fission yields of JENDL/FPY-2011 have been revised. The present report describes the revision of the yield data by emphasizing the sensitivity analyses.

  10. Fission fragment mass distributions in reactions populating 200Pb

    CERN Document Server

    Chaudhuri, A; Ghosh, T K; Banerjee, K; Sadhukhan, Jhilam; Bhattacharya, S; Roy, P; Roy, T; Bhattacharya, C; Asgar, Md A; Dey, A; Kundu, S; Manna, S; Meena, J K; Mukherjee, G; Pandey, R; Rana, T K; Srivastava, V; Dubey, R; Kaur, Gurpreet; Saneesh, N; Sugathan, P; Bhattacharya, P

    2016-01-01

    The fission fragment mass distributions have been measured in the reactions 16O + 184W and 19F+ 181Ta populating the same compound nucleus 200Pb? at similar excitation energies. It is found that the widths of the mass distribution increases monotonically with excitation energy, indicating the absence of quasi-fission for both reactions. This is contrary to two recent claims of the presence of quasi-fission in the above mentioned reactions.

  11. Proton induced fission of 181-Ta at relativistic energies

    CERN Document Server

    Ayyad, Y; Casarejos, E; Álvarez-Pol, H; Bacquias, A; Boudard, A; Caamaño, M; Enqvist, T; Föhr, V; Kelić-Heil, A; Kezzar, K; Leray, S; Paradela, C; Pérez-Loureiro, D; Pleskač, R; Tarrío, D

    2012-01-01

    Total fission cross sections of 181-Ta induced by protons at different relativistic energies have been measured at GSI, Darmstadt. The inverse kinematics technique used together with a dedicated set-up, made it possible to determine these cross sections with high accuracy. The new data obtained in this experiment will contribute to the understanding of the fission process at high excitation energies. The results are compared with data from previous experiments and systematics for proton-induced fission cross sections.

  12. The wastes of nuclear fission; Les dechets de la fission nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Doubre, H. [Paris-11 Univ., Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, IN2P3/CNRS, 91 - Orsay (France)

    2005-07-01

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

  13. Ternary fission yields of 241Pu(nth,f)

    Science.gov (United States)

    Köster, Ulli; Faust, Herbert; Fioni, Gabriele; Friedrichs, Thomas; Groß, Martin; Oberstedt, Stephan

    1998-10-01

    Ternary events in the thermal neutron induced fission of 241Pu were studied with the recoil separator LOHENGRIN at the Institut Laue Langevin in Grenoble. Yields and energy distributions could be determined for most isotopes of the elements hydrogen to oxygen. Also several heavier nuclei up to 30Mg could be observed. Yields were measured for 42 isotopes, for further 17 isotopes upper limits could be deduced. For the first time the halo nuclei 11Li and 14Be were found in neutron induced fission with yields of some 10-10 per fission. This is orders of magnitude lower than predicted by most of the ternary fission models.

  14. Increased Exploration Capacity Promotes Group Fission in Gregarious Foraging Herbivores

    Science.gov (United States)

    Lardy, Sophie; Fortin, Daniel; Pays, Olivier

    2016-01-01

    Many gregarious species display rapid fission-fusion dynamics with individuals frequently leaving their groups to reunite or to form new ones soon after. The adaptive value of such ephemeral associations might reflect a frequent tilt in the balance between the costs and benefits of maintaining group cohesion. The lack of information on the short-term advantages of group fission, however, hampers our understanding of group dynamics. We investigated the effect of group fission on area-restricted search, a search tactic that is commonly used when food distribution is spatially autocorrelated. Specifically, we determine if roe deer (Capreolus capreolus) improve key aspects of their extensive search mode immediately after fission. We found that groups indeed moved faster and farther over time immediately after than before fission. This gain was highest for the smallest group that resulted from fission, which was more likely to include the fission’s initiator. Sex of group members further mediated the immediate gain in search capacity, as post-fission groups moved away at farthest rate when they were only comprised of males. Our study suggests that social conflicts during the extensive search mode can promote group fission and, as such, can be a key determinant of group fission-fusion dynamics that are commonly observed in gregarious herbivores. PMID:27907143

  15. Dissipative effects in fission investigated in complete kinematics measurements

    Science.gov (United States)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Taïeb, J.; Ramos, D.; 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.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Vargas, J.; Voss, B.

    2017-09-01

    The study of dissipative effects in fission has been carried out with fusion-fission reactions by using a limited number of observables, such as the fission probabilities, the mass distribution of the fission fragments, or the neutron multiplicities. However, the large angular momenta gained by the compound nucleus in this kind of reaction could affect the conclusions drawn from such experiments. In this work, we propose to investigate the fission dynamics by the use of spallation reactions on 208Pb because the fissioning systems are produced with low angular momentum, small deformations, and high excitation energies, enhancing the dissipative effects. The complete kinematics measurements of the fission fragments and light-charged particles were performed by the use of the SOFIA setup combined with the inverse kinematics technique, allowing us for the first time a full indentification in atomic and mass number of the two fission fragments. These measurements permit us to define new fission observables for the investigation of the temperature and deformation dependencies of the dissipation parameter.

  16. Fission source sampling in coupled Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, Boerge; Dufek, Jan [KTH Royal Inst. of Technology, Stockholm (Sweden). Div. of Nuclear Research Technology

    2017-05-15

    We study fission source sampling methods suitable for the iterative way of solving coupled Monte Carlo neutronics problems. Specifically, we address the question as to how the initial Monte Carlo fission source should be optimally sampled at the beginning of each iteration step. We compare numerically two approaches of sampling the initial fission source; the tested techniques are derived from well-known methods for iterating the neutron flux in coupled simulations. The first technique samples the initial fission source using the source from the previous iteration step, while the other technique uses a combination of all previous steps for this purpose. We observe that the previous-step approach performs the best.

  17. Generalized Energy-Dependent Q Values for Fission

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, R

    2010-03-31

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

  18. A high-resolution time-of-flight spectrometer for fission fragments and ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Kosev, Krasimir Milchev

    2007-07-01

    For the purpose of fission-fragment detection a double time-of-flight (TOF) spectrometer has been developed. The key component of the TOF spectrometer is a TOF detector consisting of multichannel-plate (MCP) detectors with a position-sensitive readout, a foil for secondary electron (SE) production and an electrostatic mirror. The fission fragments are detected by measuring the SEs impinging on the position-sensitive anode after emission from the foil, acceleration and deflection by the electrostatic mirror. The functionality of the different detector components is proven in detail. Optimised schemes for the high-voltage supplies of the MCP detectors have been implemented successfully. In order to process the multichannel-plate detector signals optimally, a new state-of-the-art constant-fraction discriminator based on the amplitude and rise time compensated technique with very low threshold capabilities and optimised walk properties has been developed and incorporated into the setup. In a setup consisting of two mirror MCP detectors, we could successfully observe the TOF spectrum of a mixed ({sup 226}Ra,{sup 222}Rn,{sup 210}Po,{sup 218}Po,{sup 214}Po) {alpha}-source. Testing photo-fission experiments were performed at the bremsstrahlung facility at the ELBE accelerator. The setup consisted of two mirror detectors (first arm) and a 80 mm diameter MCP detector (second arm) with a {sup 238}U target positioned in between. TOF measurements with two bremsstrahlung end-point energies of 12.9 and 16.0 MeV were carried out. A clear cut separation of the TOF peaks for the medium-mass and heavy fission fragments was observed. (orig.)

  19. Mechanism of Ternary Fission in System 197Au+197Au at 15 AMeV

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>For very heavy nuclear systems there is very clear evidence for fission into three comparable mass fragments. The responsible mechanisms for this type of fission are the direct ternary fission and

  20. Fission barrier, damping of shell correction and neutron emission in the fission of A$\\sim$200

    CERN Document Server

    Mahata, K; Kapoor, S S

    2015-01-01

    Decay of $^{210}$Po compound nucleus formed in light and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good description of all the excitation functions have been achieved with a fission barrier of 21.9 $\\pm$ 0.2 MeV. For this barrier height, the predicted statistical pre-fission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies ($\\sim$ 50~MeV) in the mass region A $\\sim$ 200. When only heavy-ion induced fission excitation functions and the pre-fission neutron multiplicities are included in the fits, the deduced best fit fission barrier depends on the assumed fission delay time during which dynamical neutrons can be emitted. A fission delay of (0.8 $\\pm$ 0.1 )$\\times 10^{-19}$ s has been estimated correspondin...

  1. Rupturing the hemi-fission intermediate in membrane fission under tension: Reaction coordinates, kinetic pathways, and free-energy barriers.

    Science.gov (United States)

    Zhang, Guojie; Müller, Marcus

    2017-08-14

    Membrane fission is a fundamental process in cells, involved inter alia in endocytosis, intracellular trafficking, and virus infection. Its underlying molecular mechanism, however, is only incompletely understood. Recently, experiments and computer simulation studies have revealed that dynamin-mediated membrane fission is a two-step process that proceeds via a metastable hemi-fission intermediate (or wormlike micelle) formed by dynamin's constriction. Importantly, this hemi-fission intermediate is remarkably metastable, i.e., its subsequent rupture that completes the fission process does not occur spontaneously but requires additional, external effects, e.g., dynamin's (unknown) conformational changes or membrane tension. Using simulations of a coarse-grained, implicit-solvent model of lipid membranes, we investigate the molecular mechanism of rupturing the hemi-fission intermediate, such as its pathway, the concomitant transition states, and barriers, as well as the role of membrane tension. The membrane tension is controlled by the chemical potential of the lipids, and the free-energy landscape as a function of two reaction coordinates is obtained by grand canonical Wang-Landau sampling. Our results show that, in the course of rupturing, the hemi-fission intermediate undergoes a "thinning → local pinching → rupture/fission" pathway, with a bottle-neck-shaped cylindrical micelle as a transition state. Although an increase of membrane tension facilitates the fission process by reducing the corresponding free-energy barrier, for biologically relevant tensions, the free-energy barriers still significantly exceed the thermal energy scale kBT.

  2. Molecular distinction between true centric fission and pericentric duplication-fission

    NARCIS (Netherlands)

    Perry, J; Nouri, S; La, P; Daniel, A; Wu, ZH; Purvis-Smith, S; Northrop, E; Choo, KHA; Slater, HR

    2005-01-01

    Centromere (centric) fission, also known as transverse or lateral centric misdivision, has been defined as the splitting of one functional centromere of a metacentric or submetacentric chromosome to produce two derivative centric chromosomes. It has been observed in a range of organisms and has been

  3. Fission neutron spectra measurements at LANSCE - status and plans

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Robert C [Los Alamos National Laboratory; Noda, Shusaku [Los Alamos National Laboratory; Nelson, Ronald O [Los Alamos National Laboratory; O' Donnell, John M [Los Alamos National Laboratory; Devlin, Matt [Los Alamos National Laboratory; Chatillon, Audrey [CEA-FRANCE; Granier, Thierry [CEA-FRANCE; Taieb, Julien [CEA-FRANCE; Laurent, Benoit [CEA-FRANCE; Belier, Gilbert [CEA-FRANCE; Becker, John A [LLNL; Wu, Ching - Yen [LLNL

    2009-01-01

    A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.

  4. Uranium and Plutonium Average Prompt-fission Neutron Energy Spectra (PFNS) from the Analysis of NTS NUEX Data

    Science.gov (United States)

    Lestone, J. P.; Shores, E. F.

    2014-05-01

    In neutron experiments (NUEX) conducted at the Nevada Test Site (NTS) by Los Alamos National Laboratory, the time-of-flight of fission-neutrons emitted from nuclear tests were observed by measuring the current generated by the collection of protons scattered from a thin CH2 foil many meters from the nuclear device into a Faraday cup. The time dependence of the Faraday cup current is a measure of the energy spectrum of the neutrons that leak from the device. With good device models and accurate neutron-transport codes, the leakage spectra can be converted into prompt fast-neutron-induced fission-neutron energy spectra. This has been done for two events containing plutonium, and for an earlier event containing uranium. The prompt-fission neutron spectra have been inferred for 1.5-MeV 239Pu(n,f) and 235U(n,f) reactions for outgoing neutron energies from 1.5 to ∼10.5 MeV, in 1-MeV steps. These spectra are in good agreement with the Los Alamos fission model.

  5. Some aspects of the nuclear fission process; Quelques aspects du processus de fission nucleaire

    Energy Technology Data Exchange (ETDEWEB)

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

    1961-07-01

    In the following report one can find first a short general view on the present situation of our knowledge concerning the nuclear fission process, namely on the nucleus going through the saddle-point. Then there are some aspects connected with the excitation energy of the fissioning nucleus. The measurements made at Saclay on the fast neutron fission cross-section of U{sup 233}, U{sup 235}, Pu{sup 239}, U{sup 238} are described at the beginning of this work. It appears that for U{sup 233} there is some characteristic shape modulation of the cross-section curve, in relation with the collective excited state of the deformed nucleus at the saddle-point. Good evidence of this is also given by the study of the relative fission rate with emission of long-range particles; it appears also that this ternary fission rate does not change substantially for neutron between thermal energy and 2 MeV, but that is very lower for the compound nucleus U{sup 239} than for even-even compound nuclei. At the end there are some experiments on the strong 4,5 MeV gamma-ray originated by slow neutron absorption in U{sup 235}. Time-of-flight device is used to establish that this 4,5 MeV gamma-ray seems mostly connected with radiative capture. (author) [French] Le present travail debute par un apercu de l'etat actuel de nos connaissances sur le processus de fission nucleaire, notamment sur le passage par le point-seuil. Puis sont evoques des aspects lies au niveau d'energie d'excitation auquel est porte le noyau qui subit la fission. Les mesures de sections efficaces de fission induite dans {sup 233}U, {sup 235}U, {sup 239}Pu et {sup 238}U par des neutrons rapides effectuees a Saclay sont decrites en premier lieu; elles font apparaitre pour {sup 233}U une ondulation caracteristique du role des etats collectifs d'excitation du noyau deforme au point-seuil. Des experiences sur la fission avec emission de particules de long parcours confirment cet aspect tout en demontrant que

  6. Nuclear multifragmentation and fission: similarity and differences

    CERN Document Server

    Karnaukhov, V; Avdeyev, S; Rodionov, V; Kirakosyan, V; Simonenko, A; Rukoyatkin, P; Budzanowski, A; Karcz, W; Skwirczynska, I; Czech, B; Chulkov, L; Kuzmin, E; Norbeck, E; Botvina, A

    2006-01-01

    Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid--fog phase transition deep inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed. It is concluded that the decay process of hot nuclei is characterized by two size parameters: transition state and freeze-out volumes. The similarity between dynamics of fragmentation and ordinary fission is discussed. The IMF emission time is related to the mean rupture time at the multi-scission point, which corresponds to the kinetic freeze-out configuration.

  7. Ceramics in fission and fusion technology

    Energy Technology Data Exchange (ETDEWEB)

    Olander, D.R.

    1986-04-01

    The role of ceramic components in fission and fusion reactors is described. Almost all of the functions normally performed by ceramics, except mechanical, are required of nuclear ceramics. The oxides of uranium and plutonium are of predominant importance in nuclear applications, but a number of other ceramics play peripheral roles. The unique service conditions under which nuclear ceramics must operate include intense radiation fields, high temperatures and large temperature gradients, and aggressive chemical environments. Examples of laboratory research designed to broaden understanding of the behavior of uranium dioxide in such conditions are given. The programs described include high temperature vaporization, diffusional processes, and interaction with hydrogen.

  8. Weld Development for Aluminum Fission Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Cross, Carl Edward [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez, Jesse Norris [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-16

    The Sigma welding team was approached to help fabricate a small fission chamber (roughly ½ inch dia. x ½ inch tall cylinder). These chambers are used as radiation sensors that contain small traces of radionuclides (Cf 252, U 235, and U 238) that serve to ionize gas atoms in addition to external radiation. When a voltage is applied within the chamber, the resulting ion flow can be calibrated and monitored. Aluminum has the advantage of not forming radioactive compounds when exposed to high external radiation (except from minor Na alloy content). Since aluminum has not been used before in this application, this presented an unexplored challenge.

  9. Results of Performance Tests Performed on the John Watts WW Casing Connection on 7" Pipe

    Energy Technology Data Exchange (ETDEWEB)

    John D. Watts

    2000-02-01

    Stress Engineering Services (SES) was contracted by Mr. John Watts to test his ''WW'' threaded connection developed for oilfield oil and gas service. This work was a continuation of testing performed by SES as reported in August of 1999. The connection design tested was identified as ''WW''. The samples were all integral (no coupled connections) and contained a wedge thread form with 90{sup o} flank angles relative to the pipe centerline. The wedge thread form is a variable width thread that primarily engages on the flanks. This thread form provides very high torque capacity and good stabbing ability and makeup. The test procedure selected for one of the samples was the newly written ISO 13679 procedure for full scale testing of casing and tubing connections, which is currently going through the ISO acceptance process. The ISO procedure requires a variety of tests that includes makeup/breakout testing, internal gas sealability/external water sealability testing with axial tension, axial compression, bending, internal gas thermal cycle tests and limit load (failure) tests. This test procedure was performed with one sample. Four samples were tested to failure. Table 1 contains a summary of the tasks performed by SES. The project started with the delivery of test samples by Mr. Watts. Pipe from the previous round of tests was used for the new samples. Figure 1 shows the structural and sealing results relative to the pipe body. Sample 1 was used to determine the torque capacity of the connection. Torque was applied to the capacity of SES's equipment which was 28,424 ft-lbs. From this, an initial recommended torque range of 7,200 to 8,800 ft-lbs. was selected. The sample was disassembled and while there was no galling observed in the threads, the end of the pin had collapsed inward. Sample 2 received three makeups. Breakouts 1 and 2 also had collapsing of the pin end, with no thread galling. From these make/breaks, it was

  10. Results of Performance Tests Performed on the John Watts WW Casing Connection on 7" Pipe

    Energy Technology Data Exchange (ETDEWEB)

    John D. Watts

    2000-02-01

    Stress Engineering Services (SES) was contracted by Mr. John Watts to test his ''WW'' threaded connection developed for oilfield oil and gas service. This work was a continuation of testing performed by SES as reported in August of 1999. The connection design tested was identified as ''WW''. The samples were all integral (no coupled connections) and contained a wedge thread form with 90{sup o} flank angles relative to the pipe centerline. The wedge thread form is a variable width thread that primarily engages on the flanks. This thread form provides very high torque capacity and good stabbing ability and makeup. The test procedure selected for one of the samples was the newly written ISO 13679 procedure for full scale testing of casing and tubing connections, which is currently going through the ISO acceptance process. The ISO procedure requires a variety of tests that includes makeup/breakout testing, internal gas sealability/external water sealability testing with axial tension, axial compression, bending, internal gas thermal cycle tests and limit load (failure) tests. This test procedure was performed with one sample. Four samples were tested to failure. Table 1 contains a summary of the tasks performed by SES. The project started with the delivery of test samples by Mr. Watts. Pipe from the previous round of tests was used for the new samples. Figure 1 shows the structural and sealing results relative to the pipe body. Sample 1 was used to determine the torque capacity of the connection. Torque was applied to the capacity of SES's equipment which was 28,424 ft-lbs. From this, an initial recommended torque range of 7,200 to 8,800 ft-lbs. was selected. The sample was disassembled and while there was no galling observed in the threads, the end of the pin had collapsed inward. Sample 2 received three makeups. Breakouts 1 and 2 also had collapsing of the pin end, with no thread galling. From these make/breaks, it was

  11. Fission energy program of the US Department of Energy, FY 1981

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Transuranics Transmutation Using Neutrons Spectrum from Spallation Reactions

    Directory of Open Access Journals (Sweden)

    Maurício Gilberti

    2015-01-01

    Full Text Available The aim is to analyse the neutron spectrum influence in a hybrid system ADS-fission inducing transuranics (TRUs transmutation. A simple model consisting of an Accelerator-Driven Subcritical (ADS system containing spallation target, moderator or coolant, and spheres of actinides, “fuel,” at different locations in the system was modelled. The simulation was performed using the MCNPX 2.6.0 particles transport code evaluating capture (n,γ and fission (n,f reactions, as well as the burnup of actinides. The goal is to examine the behaviour and influences of the hard neutron spectrum from spallation reactions in the transmutation, without the contribution or interference of multiplier subcritical medium, and compare the results with those obtained from the neutron fission spectrum. The results show that the transmutation efficiency is independent of the spallation target material used, and the neutrons spectrum from spallation does not contribute to increased rates of actinides transmutation even in the vicinity of the target.

  13. Immobilization of fission products in phosphate ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-10-01

    The goal of this project is to develop and demonstrate the feasibility of a novel low-temperature solidification/stabilization (S/S) technology for immobilizing waste streams containing fission products such as cesium, strontium, and technetium in a chemically bonded phosphate ceramic. This technology can immobilize partitioned tank wastes and decontaminate waste streams containing volatile fission products.

  14. Neutron angular distribution in plutonium-240 spontaneous fission

    Energy Technology Data Exchange (ETDEWEB)

    Marcath, Matthew J., E-mail: mmarcath@umich.edu [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Shin, Tony H.; Clarke, Shaun D. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Peerani, Paolo [European Commission at the Joint Research Centre, Ispra (Italy); Pozzi, Sara A. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States)

    2016-09-11

    Nuclear safeguards applications require accurate fission models that exhibit prompt neutron anisotropy. In the laboratory reference frame, an anisotropic neutron angular distribution is observed because prompt fission neutrons carry momentum from fully accelerated fission fragments. A liquid organic scintillation detector array was used with pulse shape discrimination techniques to produce neutron-neutron cross-correlation time distributions and angular distributions from spontaneous fission in a {sup 252}Cf, a 0.84 g {sup 240}Pu{sub eff} metal, and a 1.63 g {sup 240}Pu{sub eff} metal sample. The effect of cross-talk, estimated with MCNPX-PoliMi simulations, is removed from neutron-neutron coincidences as a function of the angle between detector pairs. Fewer coincidences were observed at detector angles near 90°, relative to higher and lower detector angles. As light output threshold increases, the observed anisotropy increases due to spectral effects arising from fission fragment momentum transfer to emitted neutrons. Stronger anisotropy was observed in Cf-252 spontaneous fission prompt neutrons than in Pu-240 neutrons. - Highlights: • Pu-240 prompt fission fast-neutron anisotropy was quantified for the first time. • MCNPX-PoliMi and MPPost codes were used to remove cross-talk neutron detections from experiment results. • Cf-252 spontaneous fission neutrons were found to be more anisotropic than Pu-240 neutrons.

  15. Metal cluster fission: jellium model and Molecular dynamics simulations

    DEFF Research Database (Denmark)

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

    2004-01-01

    Fission of doubly charged sodium clusters is studied using the open-shell two-center deformed jellium model approximation and it ab initio molecular dynamic approach accounting for all electrons in the system. Results of calculations of fission reactions Na_10^2+ --> Na_7^+ + Na_3^+ and Na_18^2+ ...

  16. Fission Product Neutron Cross Section Library and Its Reliability Assessment

    Institute of Scientific and Technical Information of China (English)

    QIAN; Jing; SUN; Zheng-jun; LIU; Ting-jin; SHU; Neng-chuan

    2013-01-01

    A complete library of neutron cross section data has been developed for fission product nuclides.It contains data for 1 121 fission product nuclides of mass number A from 66 to 172 and atomic numbers Z from 22 to 72,where involves a lot of very short-lived radioactive ones.The data were taken from better

  17. EMISSION OF PHOTONS IN SPONTANEOUS FISSION OF CF-252

    NARCIS (Netherlands)

    VANDERPLOEG, H; BACELAR, JCS; BUDA, A; LAURENS, CR; VANDERWOUDE, A; GAARDHOJE, JJ; ZELAZNY, Z; VANTHOF, G; KALANTARNAYESTANAKI, N

    1995-01-01

    High energy photon emission accompanying the spontaneous fission of Cf-252 is measured for different mass splits. The photon yields up to an energy of 20 MeV are obtained at several angles relative to the fission direction. Statistical model calculations are used to interpret the data. The photon yi

  18. Monte Carlo simulation based toy model for fission process

    Science.gov (United States)

    Kurniadi, Rizal; Waris, Abdul; Viridi, Sparisoma

    2016-09-01

    Nuclear fission has been modeled notoriously using two approaches method, macroscopic and microscopic. This work will propose another approach, where the nucleus is treated as a toy model. The aim is to see the usefulness of particle distribution in fission yield calculation. Inasmuch nucleus is a toy, then the Fission Toy Model (FTM) does not represent real process in nature completely. The fission event in FTM is represented by one random number. The number is assumed as width of distribution probability of nucleon position in compound nuclei when fission process is started. By adopting the nucleon density approximation, the Gaussian distribution is chosen as particle distribution. This distribution function generates random number that randomizes distance between particles and a central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. The yield is determined from portion of nuclei distribution which is proportional with portion of mass numbers. By using modified FTM, characteristic of particle distribution in each fission event could be formed before fission process. These characteristics could be used to make prediction about real nucleons interaction in fission process. The results of FTM calculation give information that the γ value seems as energy.

  19. Late Time Emission of Prompt Fission Gamma Rays

    CERN Document Server

    Talou, P; Stetcu, I; Lestone, J P; McKigney, E; Chadwick, M B

    2016-01-01

    The emission of prompt fission $\\gamma$ rays within a few nanoseconds to a few microseconds following the scission point is studied in the Hauser-Feshbach formalism applied to the deexcitation of primary excited fission fragments. Neutron and $\\gamma$-ray evaporations from fully accelerated fission fragments are calculated in competition at each stage of the decay, and the role of isomers in the fission products, before $\\beta$-decay, is analyzed. The time evolution of the average total $\\gamma$-ray energy, average total $\\gamma$-ray multiplicity, and fragment-specific $\\gamma$-ray spectra, is presented in the case of neutron-induced fission reactions of $^{235}$U and $^{239}$Pu, as well as spontaneous fission of $^{252}$Cf. The production of specific isomeric states is calculated and compared to available experimental data. About 7% of all prompt fission $\\gamma$ rays are predicted to be emitted between 10 nsec and 5 $\\mu$sec following fission, in the case of $^{235}$U and $^{239}$Pu $(n_{\\rm th},f)$ reactio...

  20. Fission-track ages from the Precambrian of Shropshire.

    Science.gov (United States)

    Naeser, C.W.; Toghill, P.; Ross, R.J.

    1982-01-01

    Four samples of Longmyndian and Uriconian strata from S of Shrewsbury, England have been processed for apatite and/or zircon fission-track ages. The resultant ages illustrate how depth of burial may affect fission-track ages. The analytical procedures followed were as described in Naeser (1979).-from Authors

  1. Fast neutron spectrum unfolding of a TRIGA Mark II reactor and measurement of spectrum-averaged cross sections. Integral tests of differential cross sections of neutron threshold reactions

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S.; Hossain, S.M.; Khan, R. [Atomic Energy Research Establishment, Dhaka (Bangladesh). Inst. of Nuclear Science and Technology (INST); Sudar, S. [Debrecen Univ. (Hungary). Inst. of Experimental Physics; Zulquarnain, M.A. [Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Qaim, S.M. [Forschungszentrum Juelich (Germany). Inst. fuer Neurowissenschaften und Medizin (INM-5)

    2013-07-01

    The spectrum of fast neutrons having energies from 0.5 to 20 MeV in the core of the 3MW TRIGA Mark II reactor at Savar, Dhaka, Bangladesh, was unfolded by activating several metal foils to induce threshold nuclear reactions covering the whole spectrum, and then doing necessary iterative calculations utilizing the activation results and the code SULSA. The analysed shape of the spectrum in the TRIGA core was found to be similar to that of the pure {sup 235}U-fission spectrum, except for the energies between 0.5 and 1.5 MeV, where it was slightly higher than the fission spectrum. Spectrum-averaged cross sections were determined by integral measurements. The integral values measured in this work were compared with the recommended values for a pure fission spectrum as well as with the integrated data deduced from measured and evaluated excitation functions of a few reactions given in some data files. The good agreement between integral measurements and integrated data in case of well-investigated reactions shows that the fast neutron field at the TRIGA Mark II reactor can be used for validation of evaluated data of neutron threshold reactions. (orig.)

  2. Airborne measurements of fission product fall-out. An investigation of possibilities and problems

    Energy Technology Data Exchange (ETDEWEB)

    Hovgaard, J.; Korsbech, U.

    1992-12-01

    During 1993 the Danish Emergency Management Agency will install an airborne {gamma}-ray detector system for area survey of contamination with radioactive nuclides - primarily fission products that may be released during a heavy accident at a nuclear power plant or from accidents during transport of radioactive material. The equipment is based on 16 liter NaI(TI) crystals and multichannel analysers from Exploranium (Canada). A preliminary investigation of the possibilities for detection of low and high level contamination - and the problems that may be expected during use of the equipment, and during interpretation of the measured data, is described. Several days after reactor shut-down some of the nuclides can be identified directly from the measured spectrum, and contamination levels may be determined within a factor two. After several weeks, most fission products have decayed. Concentrations and exposure rates can be determined with increasing accuracy as time passes. Approximate calibration of the equipment for measurements of surface contamination and natural radioactivity can be performed in the laboratory. Further checks of equipment should include accurate measurements of the spectrum resolution. Detectors should be checked individually, and all together. Further control of dead time and pulse pile-up should be performed. Energy calibration, electronics performance and data equipment should be tested against results from the original calibration. (AB).

  3. Zellweger Spectrum

    Science.gov (United States)

    ... severe defect, resulting in essentially nonfunctional peroxisomes. This phenomenon produces the range of severity of the disorders. How is the Zellweger Spectrum Diagnosed? The distinctive shape of the head and face of a child born with one of the diseases of the ...

  4. Modelling the widths of fission observables in GEF

    Directory of Open Access Journals (Sweden)

    Schmidt K.-H.

    2013-03-01

    Full Text Available The widths of the mass distributions of the different fission channels are traced back to the probability distributions of the corresponding quantum oscillators that are coupled to the heat bath, which is formed by the intrinsic degrees of freedom of the fissioning system under the influence of pairing correlations and shell effects. Following conclusion from stochastic calculations of Adeev and Pashkevich, an early freezing due to dynamical effects is assumed. It is shown that the mass width of the fission channels in low-energy fission is strongly influenced by the zero-point motion of the corresponding quantum oscillator. The observed variation of the mass widths of the asymmetric fission channels with excitation energy is attributed to the energy-dependent properties of the heat bath and not to the population of excited states of the corresponding quantum oscillator.

  5. Activated singlet exciton fission in a semiconducting polymer.

    Science.gov (United States)

    Musser, Andrew J; Al-Hashimi, Mohammed; Maiuri, Margherita; Brida, Daniele; Heeney, Martin; Cerullo, Giulio; Friend, Richard H; Clark, Jenny

    2013-08-28

    Singlet exciton fission is a spin-allowed process to generate two triplet excitons from a single absorbed photon. This phenomenon offers great potential in organic photovoltaics, but the mechanism remains poorly understood. Most reports to date have addressed intermolecular fission within small-molecular crystals. However, through appropriate chemical design chromophores capable of intramolecular fission can also be produced. Here we directly observe sub-100 fs activated singlet fission in a semiconducting poly(thienylenevinylene). We demonstrate that fission proceeds directly from the initial 1Bu exciton, contrary to current models that involve the lower-lying 2Ag exciton. In solution, the generated triplet pairs rapidly recombine and decay through the 2Ag state. In films, exciton diffusion breaks this symmetry and we observe long-lived triplets which form charge-transfer states in photovoltaic blends.

  6. Fission fragment mass distributions via prompt -ray spectroscopy

    Indian Academy of Sciences (India)

    L S Danu; D C Biswas; B K Nayak; R K Choudhury

    2015-09-01

    The distribution of fragment masses formed in nuclear fission is one of the most striking features of the process. Such measurements are very important to understand the shape evolution of the nucleus from ground state to scission through intermediate saddle points. The fission fragment mass distributions, generally obtained via conventional methods (i.e., by measuring the energy and/or the velocity of the correlated fission fragments) are limited to a mass resolution of 4–5 units. On the other hand, by employing the -ray spectroscopy, it is possible to estimate the yield of individual fission fragments. In this work, determination of the fission fragment mass distribution by employing prompt -ray spectroscopy is described along with the recent results on 238U(18O, f) and 238U(32S, f) systems.

  7. ISOLDE experiment explores new territory in nuclear fission

    CERN Multimedia

    CERN Bulletin

    2011-01-01

    An international collaboration led by the University of Leuven, Belgium, exploiting ISOLDE’s radioactive beams, has recently discovered an unexpected new type of asymmetric nuclear fission, which challenges current theories. The surprising result opens the way for new nuclear structure models and further theories to elucidate the question.   Resonance Ionization Laser Ion Source (RILIS) in action at ISOLDE. RILIS was instrumental in providing the pure beam necessary for the successful nuclear fission experiment. In nuclear fission, the nucleus splits into two fragments (daughter nuclei), releasing a huge amount of energy. Nuclear fission is exploited in power plants to produce energy. From the fundamental research point of view, fission is not yet fully understood decades after its discovery and its properties can still surprise nuclear physicists. The way the process occurs can tell us a lot about the internal structure of the nucleus and the interactions taking place inside the com...

  8. Fission of highly excited nuclei investigated in complete kinematic measurements

    Directory of Open Access Journals (Sweden)

    Rodríguez-Sánchez J.L.

    2013-12-01

    Full Text Available Fission is an extremely complex mechanism that requires a dynamical approach to describe the evolution of the process in terms of intrinsic and collective excitations of the nuclear constituents. In order to determine these effects a complex experimental setup was mounted at GSI, which allowed us for the first time the full identification in charge and mass of all fission fragments thanks to a magnetic separation and the use of the inverse kinematic technique. Moreover, we also measured the neutron multiplicities and the light-charged particles emitted in coincidence with fission. These complete kinematic measurements will be used to define sensitive observables to dissipative and transient effects in fission. In this manuscript we present the first results for the total fission cross sections.

  9. Simple estimate of fission rate during JCO criticality accident

    Energy Technology Data Exchange (ETDEWEB)

    Oyamatsu, Kazuhiro [Faculty of Studies on Contemporary Society, Aichi Shukutoku Univ., Nagakute, Aichi (Japan)

    2000-03-01

    The fission rate during JCO criticality accident is estimated from fission-product (FP) radioactivities in a uranium solution sample taken from the preparation basin 20 days after the accident. The FP radioactivity data are taken from a report by JAERI released in the Accident Investigation Committee. The total fission number is found quite dependent on the FP radioactivities and estimated to be about 4x10{sup 16} per liter, or 2x10{sup 18} per 16 kgU (assuming uranium concentration 278.9 g/liter). On the contrary, the time dependence of the fission rate is rather insensitive to the FP radioactivities. Hence, it is difficult to determine the fission number in the initial burst from the radioactivity data. (author)

  10. Characterization of the scission point from fission-fragment velocities

    CERN Document Server

    Caamaño, M; Delaune, O; Schmidt, K -H; Schmitt, C; Audouin, L; Bacri, C -O; Benlliure, J; Casarejos, E; Derkx, X; Fernández-Domínguez, B; Gaudefroy, L; Golabek, C; Jurado, B; Lemasson, A; Ramos, D; Rodríguez-Tajes, C; Roger, T; Shrivastava, A

    2015-01-01

    The isotopic-yield distributions and kinematic properties of fragments produced in transfer-induced fission of 240Pu and fusion-induced fission of 250Cf, with 9 MeV and 45 MeV of excitation energy respectively, were measured in inverse kinematics with the spectrometer VAMOS. The kinematic properties of identified fission fragments allow to derive properties of the scission configuration such as the distance between fragments, the total kinetic energy, the neutron multiplicity, the total excitation energy, and, for the first time, the proton- and neutron-number sharing during the emergence of the fragments. These properties of the scission point are studied as functions of the fragment atomic number. The correlation between these observables, gathered in one single experiment and for two different fissioning systems at different excitation energies, give valuable information for the understanding and modeling of the fission process.

  11. Determining isotopic distributions of fission products with a penning trap

    Energy Technology Data Exchange (ETDEWEB)

    Penttilae, H.; Karvonen, P.; Eronen, T.; Elomaa, V.V.; Hager, U.; Hakala, J.; Jokinen, A.; Kankainen, A.; Moore, I.D.; Peraejaervi, K.; Rahaman, S.; Rinta-Antila, S.; Saastamoinen, A.; Sonoda, T.; Aeystoe, J. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); Rubchenya, V. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); V.G. Khlopin Radium Institute, St. Petersburg (Russian Federation)

    2010-04-15

    A novel method to determine independent yields in particle-induced fission employing the ion guide technique and ion counting after a Penning trap has been developed. The method takes advantage of the fact that a Penning trap can be used as a precision mass filter, which allows an unambiguous identification of the fission fragments. The method was tested with 25MeV and 50MeV proton-induced fission of {sup 238}U. The data is internally reproducible with an accuracy of a few per cent. A satisfactory agreement was obtained with older ion guide yield measurements in 25MeV proton-induced fission. The results for Rb and Cs yields in 50MeV proton-induced fission agree with previous measurements performed at an isotope separator equipped with a chemically selective ion source. (orig.)

  12. Exciton Correlations in Intramolecular Singlet Fission.

    Science.gov (United States)

    Sanders, Samuel N; Kumarasamy, Elango; Pun, Andrew B; Appavoo, Kannatassen; Steigerwald, Michael L; Campos, Luis M; Sfeir, Matthew Y

    2016-06-15

    We have synthesized a series of asymmetric pentacene-tetracene heterodimers with a variable-length conjugated bridge that undergo fast and efficient intramolecular singlet fission (iSF). These compounds have distinct singlet and triplet energies, which allow us to study the spatial dynamics of excitons during the iSF process, including the significant role of exciton correlations in promoting triplet pair generation and recombination. We demonstrate that the primary photoexcitations in conjugated dimers are delocalized singlets that enable fast and efficient iSF. However, in these asymmetric dimers, the singlet becomes more localized on the lower energy unit as the length of the bridge is increased, slowing down iSF relative to analogous symmetric dimers. We resolve the recombination kinetics of the inequivalent triplets produced via iSF, and find that they primarily decay via concerted processes. By identifying different decay channels, including delayed fluorescence via triplet-triplet annihilation, we can separate transient species corresponding to both correlated triplet pairs and uncorrelated triplets. Recombination of the triplet pair proceeds rapidly despite our experimental and theoretical demonstration that individual triplets are highly localized and unable to be transported across the conjugated linker. In this class of compounds, the rate of formation and yield of uncorrelated triplets increases with bridge length. Overall, these constrained, asymmetric systems provide a unique platform to isolate and study transient species essential for singlet fission, which are otherwise difficult to observe in symmetric dimers or condensed phases.

  13. Ceramic Hosts for Fission Products Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Peter C Kong

    2010-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-25

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

  15. Application of U10Mo Fuel for Space Fission Power Applications - White Paper

    Energy Technology Data Exchange (ETDEWEB)

    James Werner

    2014-07-01

    A novel reactor design has been proposed for space applications to provide hundreds of watts to one or two kilowatts of electrical power. The reactor concept proposed uses the alloy U10Mo (uranium with 10 weight percent molybdenum) as the fuel. This fuel was selected for its high uranium density, high thermal conductivity, and excellent neutronic characteristics for this application. The core is surrounded by a BeO reflector. Heat is carried from the reactor by liquid metal heat pipes. A shadow shield of LiH tungsten is also utilized to reduce the neutron and gamma radiation dose to the rest of the spacecraft. This design represents a best effort at minimizing the complexity of the fission system and reducing the mass of the system. The compact nature of the block UMo core and BeO radial reflector allows the reactor diameter to be as small as practical while still meeting the neutronic and thermal power demands. This directly results in a reduced shield mass since the reactor diameter dictates the footprint of the radiation shield. The use of heat pipes offers a straightforward primary heat transport approach using proven liquid-metal heat pipe technology. Further, the elimination of a liquid core coolant system heat transport components, both at the reactor side and radiator side, contributes to reducing the total part-count and lowering system mass. The proposed reactor is using a fuel that is being developed by DOE, but there are significant differences in the fuels enrichment, operating conditions and the physical shape of the fuel itself. This paper attempts to highlight some of the basic consideration and needs that would be expected to be met in developing this fuel and qualifying it for use.

  16. Application of U10Mo Fuel for Space Fission Power Applications - White Paper

    Energy Technology Data Exchange (ETDEWEB)

    James Werner

    2014-07-01

    A novel reactor design has been proposed for space applications to provide hundreds of watts to one or two kilowatts of electrical power. The reactor concept proposed uses the alloy U10Mo (uranium with 10 weight percent molybdenum) as the fuel. This fuel was selected for its high uranium density, high thermal conductivity, and excellent neutronic characteristics for this application. The core is surrounded by a BeO reflector. Heat is carried from the reactor by liquid metal heat pipes. A shadow shield of LiH tungsten is also utilized to reduce the neutron and gamma radiation dose to the rest of the spacecraft. This design represents a best effort at minimizing the complexity of the fission system and reducing the mass of the system. The compact nature of the block UMo core and BeO radial reflector allows the reactor diameter to be as small as practical while still meeting the neutronic and thermal power demands. This directly results in a reduced shield mass since the reactor diameter dictates the footprint of the radiation shield. The use of heat pipes offers a straightforward primary heat transport approach using proven liquid-metal heat pipe technology. Further, the elimination of a liquid core coolant system heat transport components, both at the reactor side and radiator side, contributes to reducing the total part-count and lowering system mass. The proposed reactor is using a fuel that is being developed by DOE, but there are significant differences in the fuels enrichment, operating conditions and the physical shape of the fuel itself. This paper attempts to highlight some of the basic consideration and needs that would be expected to be met in developing this fuel and qualifying it for use.

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

    Science.gov (United States)

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

    2014-05-01

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

  18. Report on simulation of fission gas and fission product diffusion in UO2

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Perriot, Romain Thibault [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Pastore, Giovanni [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Tonks, Michael R. [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Cooper, Michael William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Goyal, Anuj [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Uberuaga, Blas P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division

    2016-07-22

    In UO2 nuclear fuel, the retention and release of fission gas atoms such as xenon (Xe) are important for nuclear fuel performance by, for example, reducing the fuel thermal conductivity, causing fuel swelling that leads to mechanical interaction with the clad, increasing the plenum pressure and reducing the fuel–clad gap thermal conductivity. We use multi-­scale simulations to determine fission gas diffusion mechanisms as well as the corresponding rates in UO2 under both intrinsic and irradiation conditions. In addition to Xe and Kr, the fission products Zr, Ru, Ce, Y, La, Sr and Ba have been investigated. Density functional theory (DFT) calculations are used to study formation, binding and migration energies of small clusters of Xe atoms and vacancies. Empirical potential calculations enable us to determine the corresponding entropies and attempt frequencies for migration as well as investigate the properties of large clusters or small fission gas bubbles. A continuum reaction-­diffusion model is developed for Xe and point defects based on the mechanisms and rates obtained from atomistic simulations. Effective fission gas diffusivities are then obtained by solving this set of equations for different chemical and irradiation conditions using the MARMOT phase field code. The predictions are compared to available experimental data. The importance of the large XeU3O cluster (a Xe atom in a uranium + oxygen vacancy trap site with two bound uranium vacancies) is emphasized, which is a consequence of its high mobility and high binding energy. We find that the XeU3O cluster gives Xe diffusion coefficients that are higher for intrinsic conditions than under irradiation over a wide range of temperatures. Under irradiation the fast-­moving XeU3O cluster recombines quickly with irradiation induced interstitial U ions, while this mechanism is less important for intrinsic conditions. The net result is higher

  19. Report on simulation of fission gas and fission product diffusion in UO2

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Perriot, Romain Thibault [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Pastore, Giovanni [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Tonks, Michael R. [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Cooper, Michael William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Goyal, Anuj [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Uberuaga, Blas P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division

    2016-07-22

    In UO2 nuclear fuel, the retention and release of fission gas atoms such as xenon (Xe) are important for nuclear fuel performance by, for example, reducing the fuel thermal conductivity, causing fuel swelling that leads to mechanical interaction with the clad, increasing the plenum pressure and reducing the fuel–clad gap thermal conductivity. We use multi-­scale simulations to determine fission gas diffusion mechanisms as well as the corresponding rates in UO2 under both intrinsic and irradiation conditions. In addition to Xe and Kr, the fission products Zr, Ru, Ce, Y, La, Sr and Ba have been investigated. Density functional theory (DFT) calculations are used to study formation, binding and migration energies of small clusters of Xe atoms and vacancies. Empirical potential calculations enable us to determine the corresponding entropies and attempt frequencies for migration as well as investigate the properties of large clusters or small fission gas bubbles. A continuum reaction-­diffusion model is developed for Xe and point defects based on the mechanisms and rates obtained from atomistic simulations. Effective fission gas diffusivities are then obtained by solving this set of equations for different chemical and irradiation conditions using the MARMOT phase field code. The predictions are compared to available experimental data. The importance of the large XeU3O cluster (a Xe atom in a uranium + oxygen vacancy trap site with two bound uranium vacancies) is emphasized, which is a consequence of its high mobility and high binding energy. We find that the XeU3O cluster gives Xe diffusion coefficients that are higher for intrinsic conditions than under irradiation over a wide range of temperatures. Under irradiation the fast-­moving XeU3O cluster recombines quickly with irradiation-induced interstitial U ions, while this mechanism is less important for intrinsic conditions. The net result is higher

  20. I. Fission Probabilities, Fission Barriers, and Shell Effects. II. Particle Structure Functions

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Kexing [Univ. of California, Berkeley, CA (United States)

    1999-05-01

    In Part I, fission excitation functions of osmium isotopes 185,186, 187, 189 Os produced in 3He +182,183, 184, 186W reactions, and of polonium isotopes 209,210, 211, 212Po produced in 3He/4He + 206, 207, 208Pb reactions, were measured with high precision. These excitation functions have been analyzed in detail based upon the transition state formalism. The fission barriers, and shell effects for the corresponding nuclei are extracted from the detailed analyses. A novel approach has been developed to determine upper limits of the transient time of the fission process. The upper limits are constrained by the fission probabilities of neighboring isotopes. The upper limits for the transient time set with this new method are 15x 10–21 sec and 25x 10–21 sec for 0s and Po compound nuclei, respectively. In Part II, we report on a search for evidence of the optical modulations in the energy spectra of alpha particles emitted from hot compound nuclei. The optical modulations are expected to arise from the ~-particle interaction with the rest of the nucleus as the particle prepares to exit. Some evidence for the modulations has been observed in the alpha spectra measured in the 3He-induced reactions, 3He + natAg in particular. The identification of the modulations involves a technique that subtracts the bulk statistical background from the measured alpha spectra, in order for the modulations to become visible in the residuals. Due to insufficient knowledge of the background spectra, however, the presented evidence should only be regarded as preliminary and tentative.

  1. General Description of Fission Observables: GEF Model Code

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, K.-H. [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Jurado, B., E-mail: jurado@cenbg.in2p3.fr [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Amouroux, C. [CEA, DSM-Saclay (France); Schmitt, C., E-mail: schmitt@ganil.fr [GANIL, Bd. Henri Becquerel, B.P. 55027, F-14076 Caen Cedex 05 (France)

    2016-01-15

    The GEF (“GEneral description of Fission observables”) model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass- and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and energy spectra from neutron-induced and spontaneous fission. Derived properties of delayed neutrons and decay heat are also considered. The GEF model is based on a general approach to nuclear fission that explains a great part of the complex appearance of fission observables on the basis of fundamental laws of physics and general properties of microscopic systems and mathematical objects. The topographic theorem is used to estimate the fission-barrier heights from theoretical macroscopic saddle-point and ground-state masses and experimental ground-state masses. Motivated by the theoretically predicted early localisation of nucleonic wave functions in a necked-in shape, the properties of the relevant fragment shells are extracted. These are used to determine the depths and the widths of the fission valleys corresponding to the different fission channels and to describe the fission-fragment distributions and deformations at scission by a statistical approach. A modified composite nuclear-level-density formula is proposed. It respects some features in the superfluid regime that are in accordance with new experimental findings and with theoretical expectations. These are a constant-temperature behaviour that is consistent with a considerably increased heat capacity and an increased pairing condensation energy that is

  2. Modelling animal group fission using social network dynamics.

    Science.gov (United States)

    Sueur, Cédric; Maire, Anaïs

    2014-01-01

    Group life involves both advantages and disadvantages, meaning that individuals have to compromise between their nutritional needs and their social links. When a compromise is impossible, the group splits in order to reduce conflict of interests and favour positive social interactions between its members. In this study we built a dynamic model of social networks to represent a succession of temporary fissions involving a change in social relations that could potentially lead to irreversible group fission (i.e. no more group fusion). This is the first study that assesses how a social network changes according to group fission-fusion dynamics. We built a model that was based on different parameters: the group size, the influence of nutritional needs compared to social needs, and the changes in the social network after a temporary fission. The results obtained from this theoretical data indicate how the percentage of social relation transfer, the number of individuals and the relative importance of nutritional requirements and social links influence the average number of days before irreversible fission occurs. The greater the nutritional needs and the higher the transfer of social relations during temporary fission, the fewer days will be observed before an irreversible fission. It is crucial to bridge the gap between the individual and the population level if we hope to understand how simple, local interactions may drive ecological systems.

  3. Symmetric and asymmetric ternary fission of hot nuclei

    Science.gov (United States)

    Siwek-Wilczynska, K.; Wilczynski, J.; Leegte, H. K. W.; Siemssen, R. H.; Wilschut, H. W.; Grotowski, K.; Panasiewicz, A.; Sosin, Z.; Wieloch, A.

    1993-07-01

    Emission of α particles accompanying fusion-fission processes in the 40Ar +232Th reaction at E(40Ar) = 365 MeV was studied in a wide range of in-fission-plane and out-of-plane angles. The exact determination of the emission angles of both fission fragments combined with the time-of-flight measurements allowed us to reconstruct the complete kinematics of each ternary event. The coincident energy spectra of α particles were analyzed by using predictions of the energy spectra of the statistical code cascade . The analysis clearly demonstrates emission from the composite system prior to fission, emission from fully accelerated fragments after fission, and also emission during scission. The analysis is presented for both symmetric and asymmetric fission. The results have been analyzed using a time-dependent statistical decay code and confronted with dynamical calculations based on a classical one-body dissipation model. The observed near-scission emission is consistent with evaporation from a dinuclear system just before scission and evaporation from separated fragments just after scission. The analysis suggests that the time scale of fission of the hot composite systems is long (about 7×10-20 s) and the motion during the descent to scission almost completely damped.

  4. Single particle fluorescence burst analysis of epsin induced membrane fission.

    Science.gov (United States)

    Brooks, Arielle; Shoup, Daniel; Kustigian, Lauren; Puchalla, Jason; Carr, Chavela M; Rye, Hays S

    2015-01-01

    Vital cellular processes, from cell growth to synaptic transmission, rely on membrane-bounded carriers and vesicles to transport molecular cargo to and from specific intracellular compartments throughout the cell. Compartment-specific proteins are required for the final step, membrane fission, which releases the transport carrier from the intracellular compartment. The role of fission proteins, especially at intracellular locations and in non-neuronal cells, while informed by the dynamin-1 paradigm, remains to be resolved. In this study, we introduce a highly sensitive approach for the identification and analysis of membrane fission machinery, called burst analysis spectroscopy (BAS). BAS is a single particle, free-solution approach, well suited for quantitative measurements of membrane dynamics. Here, we use BAS to analyze membrane fission induced by the potent, fission-active ENTH domain of epsin. Using this method, we obtained temperature-dependent, time-resolved measurements of liposome size and concentration changes, even at sub-micromolar concentration of the epsin ENTH domain. We also uncovered, at 37°C, fission activity for the full-length epsin protein, supporting the argument that the membrane-fission activity observed with the ENTH domain represents a native function of the full-length epsin protein.

  5. Fission-product SiC reaction in HTGR fuel

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, F.

    1981-07-13

    The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels.

  6. Modification of apparent fission yields by Chemical Fractionation following Fission (CFF)

    Science.gov (United States)

    Hohenberg, Charles; Meshik, Alex

    2008-04-01

    Grain-by-grain studies of the 2 billion year old Oklo natural reactor, using laser micro-extraction^1,2, yield detailed information about Oklo, a water-moderated pulsed reactor, cycle times, total neutron fluence and duration, but it also demonstrates Chemical Fractionation following Fission. In the CFF process, members of an isobaric yield chain with long half-lives are subject to migration before decay can occur. Of particular interest is the 129 isobar where 17 million ^129I can migrate out of the host grain before decay, and iodine compounds are water soluble. This is amply demonstated by the variation of Xe spectra between micron-sized uranium-bearing minerals and adjacent uranium-free minerals. Fission 129 yields for the spontaneous fission of ^238U generally come from measured ^129Xe in pitchblend^2, ores emplaced by aqueous activity, and are incorrect due to the CFF process. ^238U yields for the 131 and 129 chains, reported in Hyde^3, as 0.455 +- .02 and < 0.012, respectively, the latter being anomalously low. ^1A Meshik, C Hohenberg and O Pravdivtesva, PRL 93, 182302 (2004); A Meshik Sci. Am. Nov (2005), 55; ^2E K Hyde, Nucl Prop of Heavy Elements III (1964).

  7. Absolute fission yields in the fast neutron induced fission of sup 2 sup 3 sup 3 U by track etch combined with gamma-ray spectrometry

    CERN Document Server

    Ramaswami, A; Kalsi, P C; Dange, S P

    2003-01-01

    The absolute fission yields of twenty seven fission products were determined in the fast neutron induced fission of sup 2 '3 sup 3 U, employing track etch in combination with gamma-ray spectrometry. The total number of fissions was measured by registering the fission tracks on a small strip of lexan, a solid state track detector. The fission products were analysed by gamma-ray spectrometry. The measured yield values were compared to the ENDF/B-VI compilation and show a good agreement. (author)

  8. (Fuel, fission product, and graphite technology)

    Energy Technology Data Exchange (ETDEWEB)

    Stansfield, O.M.

    1990-07-25

    Travel to the Forschungszentrum (KFA) -- Juelich described in this report was for the purpose of participating in the annual meeting of subprogram managers for the US/DOE Umbrella Agreement for Fuel, Fission Product, and Graphite Technology. At this meeting the highlights of the cooperative exchange were reviewed for the time period June 1989 through June 1990. The program continues to contribute technology in an effective way for both countries. Revision 15 of the Subprogram Plan will be issued as a result of the meeting. There was interest expressed by KFA management in the level of support received from the NPR program and in potential participation in the COMEDIE loop experiment being conducted at the CEA.

  9. Lasers from fission. [nuclear pumping feasibility experiments

    Science.gov (United States)

    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.

  10. Reflections on the discovery of fission

    Energy Technology Data Exchange (ETDEWEB)

    Peieris, Rudolf (Oxford Univ. (UK). Dept. of Theoretical Physics)

    1989-12-28

    In this article an eminent scientist looks back on the fifty years since the discovery of nuclear fission. Starting with Enrico Fermi's work with neutrons in the 1930s, the author then introduces Neils Bohr's ideas about atomic structure. The puzzle of what happens when uranium was bombarded by neutrons was gradually unravelled. Finally by 1939 it was becoming realised that the uranium nucleus had split in two. Gradually physicists began to speculate on the possibility of harnessing some of the energy stored in the nucleus and on the idea of a chain reaction. As the end of the decade approached, workers in the field combined with military forces to develop a weapon based on this reaction, the Manhatton Project. The author notes how fast an obscure, esoteric piece of physics research, can be taken up into the military and political area. (UK).

  11. Nuclear fission and the transuranium elements

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Detecting fission from special nuclear material sources

    Science.gov (United States)

    Rowland, Mark S.; Snyderman, Neal J.

    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.

  13. Asteroid spin-up fission systems

    Science.gov (United States)

    Pravec, P.

    2014-07-01

    Among asteroids smaller than about 15 km in diameter, there is a population of binary and multiple asteroid systems that show characteristics strongly suggesting their formation by spin-up fission. I will review the current observational data we have on the systems and compare them with predictions from theories of formation of asteroid systems. I will show that the best explanation of their observed properties is provided by the theory of fission of cohesionless (rubble-pile) asteroids spun up to the critical spin frequency by the YORP effect. Observed asteroid systems are of two kinds: bound and unbound. Bound asteroid systems typically consist of a larger primary and one or two smaller satellites. Unbound systems consist of two asteroids orbiting the Sun on highly similar orbits, again with one being typically larger (primary) and the other being smaller (secondary). These two groups are not exclusive; there exist systems with one or two bound and an unbound secondary. Our current sample consists of 133 bound asteroid systems (binaries or triples) with primary sizes between 0.12 and 13 km and of 178 asteroid pairs with similar primary sizes. Bound systems have been observed in heliocentric orbits from near the Earth to the outer main belt, while asteroid pairs are recognizable only in the main belt where their orbits are only slowly dispersed so the pairs can be identified for up to 2 Myr after formation. The leading observational techniques for discovery and characterization of asteroid systems are radar imagery (for near-Earth asteroid systems) and lightcurve photometry (for main-belt ones). The observed characteristics of asteroid systems suggesting their formation by rotational fission of parent rubble-pile asteroids after being spun up by the YORP effect are as follows. The angular momentum content of binary asteroids is close to critical. The orientations of satellite orbits are non-random; the orbital poles concentrate near the obliquities of 0 and 180

  14. Structural materials for fission & fusion energy

    Directory of Open Access Journals (Sweden)

    Steven J. Zinkle

    2009-11-01

    Full Text Available Structural materials represent the key for containment of nuclear fuel and fission products as well as reliable and thermodynamically efficient production of electrical energy from nuclear reactors. Similarly, high-performance structural materials will be critical for the future success of proposed fusion energy reactors, which will subject the structures to unprecedented fluxes of high-energy neutrons along with intense thermomechanical stresses. Advanced materials can enable improved reactor performance via increased safety margins and design flexibility, in particular by providing increased strength, thermal creep resistance and superior corrosion and neutron radiation damage resistance. In many cases, a key strategy for designing high-performance radiation-resistant materials is based on the introduction of a high, uniform density of nanoscale particles that simultaneously provide good high temperature strength and neutron radiation damage resistance.

  15. Actinide and fission product separation and transmutation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1991-07-01

    The first international information exchange meeting on actinide and fission product separation and transmutation, took place in Mito in Japan, on 6-8 November 1990. It starts with a number of general overview papers to give us some broad perspectives. Following that it takes a look at some basic facts about physics and about the quantities of materials it is talking about. Then it proceeds to some specific aspects of partitioning, starting with evolution from today commercially applied processes and going on to other possibilities. At the end of the third session it takes a look at the significance of partitioning and transmutation of actinides before it embarks on two sessions on transmutation, first in reactors and second in accelerators. The last session is designed to throw back into the discussion the main points which need to be looked at when considering future work in this area. (A.L.B.)

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

    Indian Academy of Sciences (India)

    L Satpathy; S K Patra; R K Choudhury

    2008-01-01

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

  17. Hardening neutron spectrum for advanced actinide transmutation experiments in the ATR.

    Science.gov (United States)

    Chang, G S; Ambrosek, R G

    2005-01-01

    The most effective method for transmuting long-lived isotopes contained in spent nuclear fuel into shorter-lived fission products is in a fast neutron spectrum reactor. In the absence of a fast test reactor in the United States, initial irradiation testing of candidate fuels can be performed in a thermal test reactor that has been modified to produce a test region with a hardened neutron spectrum. Such a test facility, with a spectrum similar but somewhat softer than that of the liquid-metal fast breeder reactor (LMFBR), has been constructed in the INEEL's Advanced Test Reactor (ATR). The radial fission power distribution of the actinide fuel pin, which is an important parameter in fission gas release modelling, needs to be accurately predicted and the hardened neutron spectrum in the ATR and the LMFBR fast neutron spectrum is compared. The comparison analyses in this study are performed using MCWO, a well-developed tool that couples the Monte Carlo transport code MCNP with the isotope depletion and build-up code ORIGEN-2. MCWO analysis yields time-dependent and neutron-spectrum-dependent minor actinide and Pu concentrations and detailed radial fission power profile calculations for a typical fast reactor (LMFBR) neutron spectrum and the hardened neutron spectrum test region in the ATR. The MCWO-calculated results indicate that the cadmium basket used in the advanced fuel test assembly in the ATR can effectively depress the linear heat generation rate in the experimental fuels and harden the neutron spectrum in the test region.

  18. Fission Surface Power System Initial Concept Definition

    Science.gov (United States)

    2010-01-01

    Under the NASA Exploration Technology Development Program (ETDP) and in partnership with the Department of Energy (DOE), NASA has embarked on a project to develop Fission Surface Power (FSP) technology. The primary goals of the project are to 1) develop FSP concepts that meet expected surface power requirements at reasonable cost with added benefits over other options, 2) establish a hardwarebased technical foundation for FSP design concepts and reduce overall development risk, 3) reduce the cost uncertainties for FSP and establish greater credibility for flight system cost estimates, and 4) generate the key products to allow NASA decision-makers to consider FSP as a preferred option for flight development. The FSP project was initiated in 2006 as the Prometheus Program and the Jupiter Icy Moons Orbiter (JIMO) mission were phased-out. As a first step, NASA Headquarters commissioned the Affordable Fission Surface Power System Study to evaluate the potential for an affordable FSP development approach. With a cost-effective FSP strategy identified, the FSP team evaluated design options and selected a Preliminary Reference Concept to guide technology development. Since then, the FSP Preliminary Reference Concept has served as a point-of-departure for several NASA mission architecture studies examining the use of nuclear power and has provided the foundation for a series of "Pathfinder" hardware tests. The long-term technology goal is a Technology Demonstration Unit (TDU) integrated system test using full-scale components and a non-nuclear reactor simulator. The FSP team consists of Glenn Research Center (GRC), Marshall Space Flight Center (MSFC) and the DOE National Laboratories at Los Alamos (LANL), Idaho (INL), Oak Ridge (ORNL), and Sandia (SNL). The project is organized into two main elements: Concept Definition and Risk Reduction. Under Concept Definition, the team performs trade studies, develops analytical tools, and formulates system concepts. Under Risk

  19. Long Range Alpha the Ternary Cold Fission of $^{252}$Cf

    CERN Document Server

    Misicu, S; Cãrstoiu, F; Rizea, M; Greiner, W; Misicu, Serban

    1998-01-01

    We compute the final kinetic energies of the fragments emitted in the light charged particle accompanied cold fission of $^{252}$Cf taking into account the ground state quadrupole deformation and the finite-size effects of the fragments and integrating the equations of motion for a three-body system subjected only to Coulomb forces. The initial conditions for the trajectory calculations were derived in the frame of a deformed cluster model which includes also the effect due to the absorbative nuclear part. Although the distributions of initial kinetic energies is rather broad we show that in cold fission the initial conditions can be better determined than in the usual spontaneous fission.

  20. Thermodynamic treatment of noble metal fission products in nuclear fuel

    Science.gov (United States)

    Kaye, M. H.; Lewis, B. J.; Thompson, W. T.

    2007-06-01

    Based on a critical evaluation of the literature, a comprehensive thermodynamic model has been developed for the complete quinary system involving the noble metal fission products in nuclear fuel: Mo-Pd-Rh-Ru-Tc. This treatment was based on the foundation of ten binary systems and an interpolation scheme. The thermodynamic model has been demonstrated to fit the available experimental data for the ternary sub-systems. This work can be used with other models for potentially non-stoichiometric UO 2+ x containing fission products, as well as data for other phases, to assess the chemical form of fission products in irradiated fuel material.