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Sample records for state fission rates

  1. Solid State Track Recorder fission rate measurements at high neutron fluence and high temperature

    International Nuclear Information System (INIS)

    Ruddy, F.H.; Roberts, J.H.; Gold, R.

    1985-01-01

    Solid State Track Recorder (SSTR) techniques have been used to measure 239-Pu, 235-U, and 237-Np fission rates for total neutron fluences approaching 5 x 10 17 n/cm 2 at temperatures in the range 680 to 830 0 F. Natural quartz crystal SSTRs were used to withstand the high temperature environment and ultra low-mass fissionable deposits of the three isotopes were required to yield scannable track densities at the high neutron fluences. The results of these high temperature, high neutron fluence measurements are reported

  2. Solid State Track Recorder fission rate measurements in low power light water reactor pressure vessel mockups

    International Nuclear Information System (INIS)

    Ruddy, F.H.; Roberts, J.H.; Kellogg, L.S.

    1985-01-01

    The results of extensive SSTR measurements made at the Pool Critical Assembly (PCA) facility at Oak Ridge National Laboratory have been reported previously. Measurements were made at key locations in PCA which is an idealized mockup of the water gap, thermal shield, pressure vessel geometry of a light water reactor. Recently, additional SSTR fission rate measurements have been carried out for 237-Np, 238-U, and 235-U in key locations in the NESTOR Shielding and Dosimetry Improvement Program (NESDIP) mockup facility located at Winfrith, England. NESDIP is a replica of the PCA facility, and comparisons will be made between PCA and NESDIP measurements. The results of measurements made at the engineering mockup at the VENUS critical assembly at CEN/SCK, Mol, Belgium will also be reported. Measurements were made at selected radial and azimuthal locations in VENUS, which models the in-core and near-core regions of a pressurized water reactor. Comparisons of absolute SSTR fission rates with absolute fission rates made with the Mol miniature fission chamber will be reported. Absolute fission rate comparisons have also been made between the NBS fission chamber, radiometric fission foils, and SSTRs, and these results will be summarized

  3. A method for the measurement of fission rates in fast neutron fields using solid state track detectors

    International Nuclear Information System (INIS)

    Hansen, W.; Vogel, W.

    1984-04-01

    Solid state track detectors (SSTDs) are increasingly used for the registration of radiation in different fields of nuclear physics. Because of their small sizes and masses and the absence of any electronics during exposure SSTDs do not cause distortions in the system to be investigated and are useful for measurements at such places being difficult of access. The elaboration of a method is described for fission rate measurements in fast neutron fields applying SSTDs and different fissionable isotopes which were electrodeposited on stainless steel backings. Experiences of the electrodeposition and results of quality checks are presented. The evaluation of the etched tracks is performed with spark counter technique. The dependence of the counting result on essential influence parameters is discussed. (author)

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  5. Dosimetric measurement of the disintegration rate of fission products

    International Nuclear Information System (INIS)

    Solymosi, J.; Nagy, L.G.; Zagyvai, P.

    1992-01-01

    Investigations on the disintegration rate of fission products of 238 U and 239 Pu are presented. The intensity of the β-and γ-radiation of fission products were measured continously in an interval of 1-1300 hours following the fission, offering the possibility for determining the general and specific characteristics of the individual fission products. A universal measuring procedure was elaborated for the rapid in situ determination of the dosimetric features of fission products, which is suitable for the accurate evaluation and prediction of external absorbed dose even in case of fission products of various origin and unknown composition. (author) 6 refs.; 7 figs.; 1 tab

  6. Fission rate measurements in fuel plate type assembly reactor cores

    International Nuclear Information System (INIS)

    Rogers, J.W.

    1988-01-01

    The methods, materials and equipment have been developed to allow extensive and precise measurement of fission rate distributions in water moderated, U-Al fuel plate assembly type reactor cores. Fission rate monitors are accurately positioned in the reactor core, the reactor is operated at a low power for a short time, the fission rate monitors are counted with detectors incorporating automated sample changers and the measurements are converted to fission rate distributions. These measured fission rate distributions have been successfully used as baseline information related to the operation of test and experimental reactors with respect to fission power and distribution, fuel loading and fission experiments for approximately twenty years at the Idaho National Engineering Laboratory (INEL). 7 refs., 8 figs

  7. BIG-10 fission product generation and reaction rates

    International Nuclear Information System (INIS)

    Rogers, J.W.

    1976-01-01

    Fission product generation rates for high quality fission foils and reaction rates of nonfission foils have been measured by gamma ray activation analyses. These foils were irradiated in the BIG-10 facility and the activities were measured by NaI counting techniques

  8. 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)

  9. Simple estimate of fission rate during JCO criticality accident

    International Nuclear Information System (INIS)

    Oyamatsu, Kazuhiro

    2000-01-01

    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 16 per liter, or 2x10 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. Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

    KAUST Repository

    Pace, Natalie A.

    2017-11-30

    The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. In this paper, we investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically, and is strongly dependent on side-chain identity. These results show that it may be necessary to carefully engineer the solid-state microstructure of these “singlet fission polymers” in order to produce the long-lived triplets needed to realize efficient photovoltaic devices.

  11. Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

    KAUST Repository

    Pace, Natalie A.; Zhang, Weimin; Arias, Dylan H.; McCulloch, Iain; Rumbles, Garry; Johnson, Justin C.

    2017-01-01

    The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. In this paper, we investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically, and is strongly dependent on side-chain identity. These results show that it may be necessary to carefully engineer the solid-state microstructure of these “singlet fission polymers” in order to produce the long-lived triplets needed to realize efficient photovoltaic devices.

  12. A rigorous nonorthogonal configuration interaction approach for the calculation of electronic couplings between diabatic states applied to singlet fission

    NARCIS (Netherlands)

    Wibowo, Meilani; Broer, Ria; Havenith, Remco W. A.

    2017-01-01

    For the design of efficient singlet fission chromophores, knowledge of the factors that govern the singlet fission rate is important. This rate is approximately proportional to the electronic coupling between the lowest (diabatic) spin singlet state that is populated following photoexcitation state

  13. Fission gas behaviour in UO2 under steady state and transient conditions

    International Nuclear Information System (INIS)

    Zimmermann, H.

    1980-01-01

    Fission gas behaviour in UO 2 is determined by the limited capacity of the fuel to retain fission gas. This capacity depends primarily on temperature, but also on fission rate, pressure loading, and fuel microstructure. Under steady state irradiation conditions fission gas behaviour can be described qualitatively as follows: At the beginning of the irradiation most of the fission gas remains in the grains in irradiation-induced solution. With increasing gas content in the grains the gas transport to the grain boundaries increases, too. The fission gas release from the grain boundaries occurs primarily by interlinkage of inter-granular bubbles. The fission gas release without noticeable fuel swelling during the short-term heating in the LOCA tests and the powdering of the high burnup UO 2 in the annealing tests can only be accounted for by formation of inter-granular separations, which are caused by the fission gas accumulated in the grain boundaries. Besides this short-term effect there are diffusion-controlled long-term effects, such as growth and coalescence of bubbles and formation of inter-connected porosity, which result in time-dependent fission gas release and fuel swelling

  14. Fission distribution measurements of Atucha's fuel pellets with solid state track detectors

    International Nuclear Information System (INIS)

    Ricabarra, M.D. Bovisio de; Waisman, Dina.

    1979-08-01

    Distribution of fissions in a UO 2 rod has been measured by means of solid state detectors. Mica muscovite and Makrofol-N detectors were used in the experiment. The merits of mica muscovite relative to the Makrofol-N for the detection of fission fragments have been verified. However both fission track detectors closely agree (0,5%) in the final fission distribution of the UO 2 rod. Sensitivity of the detectors shows to be linear in the range between 50.000and 360.000 fission tracks per square centimeter. Due to the high spatial resolution this method is better than any other technique. Determination were made in UO 2 pellets similar to the fuel element of the Atucha reactor. The average fission rate in the rod has been measured within 0,8% error, and provides an accurate determination for the distribution of fissions in the rod wich is needed for the determination of energy liberated per fission in the natural uranium rod.(author) [es

  15. Fission neutron damage rates and efficiencies in several metals

    International Nuclear Information System (INIS)

    Klabunde, C.E.; Coltman, R.R. Jr.

    1981-11-01

    Initial rates of resistivity-measured low-temperature damage production by fission-spectrum fast neutrons have been determined for 14 metals in the same very well characterized irradiation facility. Six of these metals were fcc, 5 bcc, and 3 hcp. Most were of quite high purity. Observed damage rates, after correction for all known extraneous resistivity-producing effects, were compared with rates predicted by the damage calculation code RECOIL, using parameters chosen from the literature. These parameters, effective displacement threshold energy, E/sub d/, and Frenkel-pair resistivity, rho/sub F/, were in many cases only best estimates, the further refinement of which may be aided by the present results. Damage efficiencies (measured/predicted rates) follow the same trends by crystal classes as seen in other fast-neutron studies

  16. Measurement of 237Np fission rate ratio relative to 235U fission rate in cores with various thermal neutron spectrum at the Kyoto University Critical Assembly

    International Nuclear Information System (INIS)

    Unesaki, Hironobu; Shiroya, Seiji; Iwasaki, Tomohiko; Fujiwara, Daisuke; Kitada, Takanori; Kuroda, Mitsuo; Kohashi, Akio; Kato, Takeshi; Ikeuchi, Yoshitaka

    2000-01-01

    Integral measurements of 237 Np fission rate ratio relative to 235 U fission rate have been performed at Kyoto University Citrical Assembly. The fission rates have been measured using the back-to back type double fission chamber at five thermal cores with different H/ 235 U ratio so that the neutron spectra of the cores were systematically varied. The measured fission rate ratio per atom was 0.00439 to 0.0298, with a typical uncertainty of 2 to 3%. The measured data were compared with the calculated results using SRAC/TWOTRAN and MVP based on JENDL-3.2, which gave the averaged C/E values of 0.93 and 0.95, respectively. Obtained results of C/E using 237 Np cross sections from JENDL-3/2, ENDF/B-VI.5 and JEF2.2 show that the latter two gave smaller results than JENDL-3.2 by about 4%, which clearly reflects the discrepancy in the evaluated cross section among the libraries. This difference arises from both fast fission and resonance region. Although further improvement is recommended, 237 Np fission cross section in JENDL-3.2 is considered to be superior to those in the other libraries and can be adopted for use in design calculations for minor actinide transmutation system using thermal reactors with prediction precision of 237 Np fission rate with in 10%. (author)

  17. Decay rate in a multi-dimensional fission problem

    Energy Technology Data Exchange (ETDEWEB)

    Brink, D M; Canto, L F

    1986-06-01

    The multi-dimensional diffusion approach of Zhang Jing Shang and Weidenmueller (1983 Phys. Rev. C28, 2190) is used to study a simplified model for induced fission. In this model it is shown that the coupling of the fission coordinate to the intrinsic degrees of freedom is equivalent to an extra friction and a mass correction in the corresponding one-dimensional problem.

  18. 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)

  19. Optical efficiency for fission fragment track counting in Muscovite solid state track recorders

    International Nuclear Information System (INIS)

    Roberts, J.H.; Ruddy, F.H.; Gold, R.

    1984-01-01

    In order to determine absolute fission rates from thin actinide deposits placed in direct contact with Muscovite Solid State Track Recorders, it is necessary to know the efficiency with which fission fragment tracks are recorded. In this paper, a redetermination of the 'optical efficiency', i.e. the fraction of fission events recorded and observed in the Muscovite is reported. The value obtained from a well-calibrated thin deposit of 252 Cf and Muscovite etched about 90 min. in 49% HF at room temperature, is 0.9875 +- 0.0085. Manual counting was used. Preliminary results from a deposit of 242 Pu are also reported, along with preliminary comparisons of track counting with an automated system. Reasons for the discrepancy of the optical efficiency reported here with an earlier measurement are also reported. (author)

  20. Optical efficiency for fission-fragment track counting in Muscovite Solid-State Track Recorders

    International Nuclear Information System (INIS)

    Roberts, J.H.; Ruddy, F.H.; Gold, R.

    1983-07-01

    In order to determine absolute fission rates from thin actinide deposits placed in direct contact with Muscovite Solid-State Track Recorders, it is necessary to know the efficiency with which fission-fragment tracks are recorded. In this paper, a redetermination of the optical efficiency, i.e., the fraction of fission events recorded and observed in the Muscovite, is reported. The value obtained from a well-calibrated thin deposit of 252 Cf and Muscovite etched about 90 min. in 49% HF at room temperature, is 0.9875 +- 0.0085. Manual counting was used. Preliminary results from a deposit of 242 Pu are also reported, along with preliminary comparisons of track counting with an automated system. Reasons for the discrepancy of the optical efficiency reported here with an earlier measurement are also reported. 5 references, 1 figure, 3 tables

  1. Reaction Rate Benchmark Experiments with Miniature Fission Chambers at the Slovenian TRIGA Mark II Reactor

    Science.gov (United States)

    Štancar, Žiga; Kaiba, Tanja; Snoj, Luka; Barbot, Loïc; Destouches, Christophe; Fourmentel, Damien; Villard, Jean-François AD(; )

    2018-01-01

    A series of fission rate profile measurements with miniature fission chambers, developed by the Commisariat á l'énergie atomique et auxénergies alternatives, were performed at the Jožef Stefan Institute's TRIGA research reactor. Two types of fission chambers with different fissionable coating (235U and 238U) were used to perform axial fission rate profile measurements at various radial positions and several control rod configurations. The experimental campaign was supported by an extensive set of computations, based on a validated Monte Carlo computational model of the TRIGA reactor. The computing effort included neutron transport calculations to support the planning and design of the experiments as well as calculations to aid the evaluation of experimental and computational uncertainties and major biases. The evaluation of uncertainties was performed by employing various types of sensitivity analyses such as experimental parameter perturbation and core reaction rate gradient calculations. It has been found that the experimental uncertainty of the measurements is sufficiently low, i.e. the total relative fission rate uncertainty being approximately 5 %, in order for the experiments to serve as benchmark experiments for validation of fission rate profiles. The effect of the neutron flux redistribution due to the control rod movement was studied by performing measurements and calculations of fission rates and fission chamber responses in different axial and radial positions at different control rod configurations. It was confirmed that the control rod movement affects the position of the maximum in the axial fission rate distribution, as well as the height of the local maxima. The optimal detector position, in which the redistributions would have minimum effect on its signal, was determined.

  2. EURISOL-DS Multi-MWatt Hg Target: Neutron flux and fission rate calculations for the MAFF configuration

    CERN Document Server

    Romanets, Y; Vaz, P; Herrera-Martinez, A; Kadi, Y; Kharoua, C; Lettry, J; Lindroos, M

    The EURISOL (The EURopean Isotope Separation On-Line Radioactive Ion Beam) project aims at producing high intensity radioactive ion beams produced by neutron induced fission on a fissile target (235U) surrounding a liquid mercury converter. A proton beam of 1 GeV and 4 MW impinges on the Hg converter generating by spallation reactions high neutron fluxes. In this work the state-of-the-art Monte Carlo codes MCNPX and FLUKA were used to assess the neutronics performance of the system which geometry, inspired from the MAFF concept, allows a versatile manipulation of the fission targets. The objective of the study was to optimize the geometry of the system and the materials used in the fuel and reflector elements of the system, in order to achieve the highest possible fission rate.

  3. HLW disposal by fission reactors; calculation of trans-mutation rate and recycle

    International Nuclear Information System (INIS)

    Mulyanto

    1997-01-01

    Transmutation of MA (Minor actinide) and LLFPS (long-lived fission products) into stable nuclide or short-lived isotopes by fission reactors seem to become an alternative technology for HLW disposal. in this study, transmutation rate and recycle calculation were developed in order to evaluate transmutation characteristics of MA and LLFPs in the fission reactors. inventory of MA and LLFPs in the transmutation reactors were determined by solving of criticality equation with 1-D cylindrical geometry of multigroup diffusion equations at the beginning of cycle (BOC). transmutation rate and burn-up was determined by solving of depletion equation. inventory of MA and LLFPs was calculated for 40 years recycle. From this study, it was concluded that characteristics of MA and LLFPs in the transmutation reactors can be evaluated by recycle calculation. by calculation of transmutation rate, performance of fission reactor for transmutation of MA or LLFPs can be discussed

  4. Steady state behaviour of gaseous fission products in UO2 nuclear fuel at low temperature

    International Nuclear Information System (INIS)

    Rao, C.B.; Raj, Baldev

    1980-01-01

    Theoretical modelling studies have been performed on steady state fission gas behaviour in UO 2 fuels at temperatures in the range 1073deg K to 1473deg K. The concentrations of gas atoms in the matrix and in the bubbles are determined. Fraction of total generated gas atoms migrating to and forming bubbles at grain boundaries is calculated. Contributions of intragranular and intergranular bubbles to the swelling are also computed. The various assumptions made to simplify computer calculations and their validity are discussed at length. Effects of changes in the fission rate, the resolution parameter, bubble concentration, gas atom diffusivity and grain radius on swelling and gas release are studied. The results of this model are compared to other theoretical models and experimental results available in literature. Possibility of extending the present model to advanced carbide and nitride fuels is discussed. (auth.)

  5. Steady-state and transient fission gas release and swelling model for LIFE-4

    International Nuclear Information System (INIS)

    Villalobos, A.; Liu, Y.Y.; Rest, J.

    1984-06-01

    The fuel-pin modeling code LIFE-4 and the mechanistic fission gas behavior model FASTGRASS have been coupled and verified against gas release data from mixed-oxide fuels which were transient tested in the TREAT reactor. Design of the interface between LIFE-4 and FASTGRASS is based on an earlier coupling between an LWR version of LIFE and the GRASS-SST code. Fission gas behavior can significantly affect steady-state and transient fuel performance. FASTGRASS treats fission gas release and swelling in an internally consistent manner and simultaneously includes all major mechanisms thought to influence fission gas behavior. The FASTGRASS steady-state and transient analysis has evolved through comparisons of code predictions with fission-gas release and swelling data from both in- and ex-reactor experiments. FASTGRASS was chosen over other fission-gas behavior models because of its availability, its compatibility with the LIFE-4 calculational framework, and its predictive capability

  6. Rate theory scenarios study on fission gas behavior of U 3 Si 2 under LOCA conditions in LWRs

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin; Gamble, Kyle A.; Andersson, David; Mei, Zhi-Gang; Yacout, Abdellatif M.

    2018-01-01

    Fission gas behavior of U3Si2 under various loss-of-coolant accident (LOCA) conditions in light water reactors (LWRs) was simulated using rate theory. A rate theory model for U3Si2 that covers both steady-state operation and power transients was developed for the GRASS-SST code based on existing research reactor/ion irradiation experimental data and theoretical predictions of density functional theory (DFT) calculations. The steady-state and LOCA condition parameters were either directly provided or inspired by BISON simulations. Due to the absence of in-pile experiment data for U3Si2's fuel performance under LWR conditions at this stage of accident tolerant fuel (ATF) development, a variety of LOCA scenarios were taken into consideration to comprehensively and conservatively evaluate the fission gas behavior of U3Si2 during a LOCA.

  7. Critical angles for fission fragment registrations in some solid state track detectors

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, A D; Bahromi, I I; Beresina, N V [AN Uzbekskoj SSR, Tashkent. Inst. Yadernoj Fiziki; and others

    1980-03-01

    In studies of the registration efficiency of various solid state track detectors (polycarbonate, polyethyleneterephthalate, cellulose nitrate and muscovite) the detectors were irradiated with spontaneous fission fragments from /sup 252/Cf and with fission fragments from /sup 235/U separated according to mass and energy. Experimental details are given. Critical angles for the registration of fission fragments in the various detectors are given for specified energies and masses.

  8. Measurement of fission track of uranium particle by solid state nuclear track detector

    International Nuclear Information System (INIS)

    Son, S. C.; Pyo, H. W.; Ji, K. Y.; Kim, W. H.

    2002-01-01

    In this study, we discussed results of the measurement of fission tracks for the uranium containing particles by solid state nuclear track detector. Uranium containing silica and uranium oxide particles were prepared by uranium sorption onto silica powder in weak acidic medium and laser ablation on uranium pellet, respectively. Fission tracks for the uranium containing silica and uranium oxide particles were detected on Lexan plastic detector. It was found that the fission track size and shapes depend on the particle size uranium content in particles. Correlation of uranium particle diameter with fission track radius was also discussed

  9. Influence of mass-asymmetry and ground state spin on fission fragment angular distributions

    International Nuclear Information System (INIS)

    Thomas, R.G.; Biswas, D.C.; Saxena, A.; Pant, L.M.; Nayak, B.K.; Vind, R.P.; Sahu, P.K.; Sinha, Shrabani; Choudhury, R.K.

    2001-01-01

    The strong influence of the target or/and projectile ground state spin on the anomalously large anisotropies of fission fragments produced in the heavy-ion induced fission of actinide targets were reported earlier. Interestingly, all those systems studied were having a mass asymmetry greater than the Businaro-Gallone critical asymmetry and hence the presence of pre-equilibrium fission was unambiguously ruled out. The observed anisotropies were successfully explained using the ECD-K-States model. It is of interest to know the influence of the target/projectile ground state spin on systems having an entrance channel mass asymmetry less than the critical value where pre-equilibrium fission cannot be ignored. With this motivation we performed measurements of fission fragment angular distributions of the 16 O+ 235 U (spin=7/2) system

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  11. A delayed neutron technique for measuring induced fission rates in fresh and burnt LWR fuel

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, K.A., E-mail: kajordan@gmail.co [Paul Scherrer Institut, Laboratory for Reactor Physics and System Behaviour, 5232 Villigen (Switzerland); Perret, G. [Paul Scherrer Institut, Laboratory for Reactor Physics and System Behaviour, 5232 Villigen (Switzerland)

    2011-04-01

    The LIFE-PROTEUS program at the Paul Scherrer Institut is being undertaken to characterize the interfaces between burnt and fresh fuel assemblies in modern LWRs. Techniques are being developed to measure fission rates in burnt fuel following re-irradiation in the zero-power PROTEUS research reactor. One such technique utilizes the measurement of delayed neutrons. To demonstrate the feasibility of the delayed neutron technique, fresh and burnt UO{sub 2} fuel samples were irradiated in different positions in the PROTEUS reactor, and their neutron outputs were recorded shortly after irradiation. Fission rate ratios of the same sample irradiated in two different positions (inter-positional) and of two different samples irradiated in the same position (inter-sample) were derived from the measurements and compared with Monte Carlo predictions. Derivation of fission rate ratios from the delayed neutron measured signal requires correcting the signal for the delayed neutron source properties, the efficiency of the measurement setup, and the time dependency of the signal. In particular, delayed neutron source properties strongly depend on the fissile and fertile isotopes present in the irradiated sample and must be accounted for when deriving inter-sample fission rate ratios. Measured inter-positional fission rate ratios generally agree within 1{sigma} uncertainty (on the order of 1.0%) with the calculation predictions. For a particular irradiation position, however, a bias of about 2% is observed and is currently under investigation. Calculated and measured inter-sample fission rate ratios have C/E values deviating from unity by less than 1% and within 2{sigma} of the statistical uncertainties. Uncertainty arising from delayed neutron data is also assessed, and is found to give an additional 3% uncertainty factor. The measurement data indicate that uncertainty is overestimated.

  12. Benchmark experiments at ASTRA facility on definition of space distribution of 235U fission reaction rate

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  13. Fusion-fission hybrid studies in the United States

    International Nuclear Information System (INIS)

    Moir, R.W.; Lee, J.D.; Berwald, D.H.; Cheng, E.T.; Delene, J.G.; Jassby, D.L.

    1986-01-01

    Systems and conceptual design studies have been carried out on the following three hybrid types: (1) The fission-suppressed hybrid, which maximizes fissile material produced (Pu or 233 U) per unit of total nuclear power by suppressing the fission process and multiplying neutrons by (n,2n) reactions in materials like beryllium. (2) The fast-fission hybrid, which maximizes fissile material produced per unit of fusion power by maximizing fission of 238 U (Pu is produced) in which twice the fissile atoms per unit of fusion power (but only a third per unit of nuclear power) are made. (3) The power hybrid, which amplifies power in the blanket for power production but does not produce fuel to sell. All three types must sell electrical power to be economical

  14. New isomeric states in 152,154,156Nd produced by spontaneous fission of 252Cf

    International Nuclear Information System (INIS)

    Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C.; Belier, G.; Girod, M.; Meot, V.; Peru, S.; Astier, A.; Ducroux, L.; Meyer, M.; Redon, N.

    1998-01-01

    Isomeric states have been observed in fission-fragments produced by spontaneous fission of 252 Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between γ-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2μs have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the 152,154,156 Nd show evidence for K-isomers. (orig.)

  15. Standard Test Method for Measuring Reaction Rates by Analysis of Barium-140 From Fission Dosimeters

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method describes two procedures for the measurement of reaction rates by determining the amount of the fission product 140Ba produced by the non-threshold reactions 235U(n,f), 241Am(n,f), and 239Pu(n,f), and by the threshold reactions 238U(n,f), 237Np(n,f), and 232Th(n,f). 1.2 These reactions produce many fission products, among which is 140Ba, having a half-life of 12.752 days. 140Ba emits gamma rays of several energies; however, these are not easily detected in the presence of other fission products. Competing activity from other fission products requires that a chemical separation be employed or that the 140Ba activity be determined indirectly by counting its daughter product 140La. This test method describes both procedure (a), the nondestructive determination of 140Ba by the direct counting of 140La several days after irradiation, and procedure (b), the chemical separation of 140Ba and the subsequent counting of 140Ba or its daughter 140La. 1.3 With suitable techniques, fission neutron fl...

  16. Analysis for In-situ Fission Rate Measurements using 4He Gas Scintillation Detectors

    International Nuclear Information System (INIS)

    Lewis, Jason M.; Raetz, Dominik; Jordan, Kelly A.; Murer, David

    2013-06-01

    Active neutron interrogation is a powerful NDA technique that relies on detecting and analyzing fission neutrons produced in a fuel sample by an interrogating high neutron flux. 4 He scintillation gas fast neutron detectors are investigated in this paper for use in a novel fission rate measurement technique The He-4 detectors have excellent gamma rejection, a fast response time, and give significant information on incident neutron energy allowing for energy cuts to be applied to the detected signal. These features are shown in this work to allow for the detection of prompt fission neutrons in-situ during active neutron interrogation of a 238 U sample. The energy spectrum from three different neutrons sources ( 252 Cf, AmBe, AmLi) is measured using the 4 He detection system and analyzed. An initial response matrix for the detector is determined using these measurements and the kinematic interaction properties of the elastic scattering with the 4 He. (authors)

  17. Asymmetrically deformed states of thorium isotopes during fission process

    International Nuclear Information System (INIS)

    Blons, J.

    1982-05-01

    Some theoretical considerations are recalled on fission barriers calculated from macroscopic, microscopic or macroscopic-microscopic and ''thorium anomaly'' problem is set. Experimental techniques used to measure fission cross sections in (n,f) reactions near the threshold are described. Fission dectector is described; stray resonance problems and retrodiffused neutrons are discussed. Results obtained in experimental study of 230 Th(n,f) and 232 Th(n,f) reactions are presented. They are compared with results obtained in other laboratories. The analysis model which allows to describe a (n,f) reaction is exposed. The compound nucleus formation cross section and transmission coefficients in neutron and gamma output channel are presented according to neutron energy for each value of angular moment and parity. Cross-section analysis and angular distribution obtained respectively in 230 Th(n,f) and 232 Th(n,f) reactions is exposed. Result interpretation show new aspects of nuclei rotational spectra and new nuclear forms [fr

  18. Characterization of a facility for the measurement of fission fragment transport effects: experimental determination of the fission rates for fissile and fissionable isotopes

    International Nuclear Information System (INIS)

    Benetti, P.; Raselli, G.L.; Tigliole, A. Borio di; Cagnazzo, M.; Cesana, A.; Mongelli, S.; Terrani, M.

    2002-01-01

    The transfer facility of the LENA laboratory allows the direct neutron irradiation of fissionable material in the D channel of the TRIGA reactor. A test measurement carried out with a ionization chamber and a 239 Pu sample shows the possibility to use this tool for the study of the transport effects of the fission fragment emerging from thin layers of fissile materials. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1958-07-01

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

  20. Fission rates measured using high-energy gamma-rays from short half-life fission products in fresh and spent nuclear fuel

    International Nuclear Information System (INIS)

    Kroehnert, H.

    2011-02-01

    In recent years, higher discharge burn-ups and initial fuel enrichments have led to more and more heterogeneous core configurations in light water reactors (LWRs), especially at the beginning of cycle when fresh fuel assemblies are loaded next to highly burnt ones. As this trend is expected to continue in the future, the Paul Scherrer Institute has, in collaboration with the Swiss Association of Nuclear Utilities, swissnuclear, launched the experimental programme LIFE(at)PROTEUS. The LIFE(at)PROTEUS programme aims to better characterise interfaces between burnt and fresh UO 2 fuel assemblies in modern LWRs. Thereby, a novel experimental database is to be made available for enabling the validation of neutronics calculations of strongly heterogeneous LWR core configurations. During the programme, mixed fresh and highly burnt UO 2 fuel lattices will be investigated in the zero-power research reactor PROTEUS. One of the main types of investigations will be to irradiate the fuel in PROTEUS and measure the resulting fission rate distributions across the interface between fresh and burnt fuel zones. The measurement of fission rates in burnt fuel re-irradiated in a zero-power reactor requires, however, the development of new experimental techniques which are able to discriminate against the high intrinsic activity of the fuel. The principal goal of the present research work has been to develop such a new measurement technique. The selected approach is based on the detection of high-energy gamma-ray lines above the intrinsic background (i.e. above 2200 keV), which are emitted by short-lived fission products freshly created in the fuel. The fission products 88 Kr, 142 La, 138 Cs, 84 Br, 89 Rb, 95 Y, 90m Rb and 90 Rb, with half-lives between 2.6 min and 2.8 h, have been identified as potential candidates. During the present research work, the gamma-ray activity of short-lived fission products has, for the first time, been measured and quantitatively evaluated for re

  1. Fission rates measured using high-energy gamma-rays from short half-life fission products in fresh and spent nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kroehnert, H.

    2011-02-15

    In recent years, higher discharge burn-ups and initial fuel enrichments have led to more and more heterogeneous core configurations in light water reactors (LWRs), especially at the beginning of cycle when fresh fuel assemblies are loaded next to highly burnt ones. As this trend is expected to continue in the future, the Paul Scherrer Institute has, in collaboration with the Swiss Association of Nuclear Utilities, swissnuclear, launched the experimental programme LIFE(at)PROTEUS. The LIFE(at)PROTEUS programme aims to better characterise interfaces between burnt and fresh UO{sub 2} fuel assemblies in modern LWRs. Thereby, a novel experimental database is to be made available for enabling the validation of neutronics calculations of strongly heterogeneous LWR core configurations. During the programme, mixed fresh and highly burnt UO{sub 2} fuel lattices will be investigated in the zero-power research reactor PROTEUS. One of the main types of investigations will be to irradiate the fuel in PROTEUS and measure the resulting fission rate distributions across the interface between fresh and burnt fuel zones. The measurement of fission rates in burnt fuel re-irradiated in a zero-power reactor requires, however, the development of new experimental techniques which are able to discriminate against the high intrinsic activity of the fuel. The principal goal of the present research work has been to develop such a new measurement technique. The selected approach is based on the detection of high-energy gamma-ray lines above the intrinsic background (i.e. above 2200 keV), which are emitted by short-lived fission products freshly created in the fuel. The fission products {sup 88}Kr, {sup 142}La, {sup 138}Cs, {sup 84}Br, {sup 89}Rb, {sup 95}Y, {sup 90m}Rb and {sup 90}Rb, with half-lives between 2.6 min and 2.8 h, have been identified as potential candidates. During the present research work, the gamma-ray activity of short-lived fission products has, for the first time, been

  2. GRASS-SST, Fission Products Gas Release and Fuel Swelling in Steady-State and Transients

    International Nuclear Information System (INIS)

    Zawadzki, S.

    2001-01-01

    1 - Description of program or function: GRASS-SST is a comprehensive, mechanistic model for the prediction of fission-gas behaviour in UO 2 -base fuels during steady-state and transient conditions. GRASS-SST treats fission-gas release and fuel swelling on an equal basis and simultaneously treats all major mechanisms that influence fission-gas behaviour. Models are included for intra- and inter-granular fission-gas bubble behaviour as well as a mechanistic description of the role of grain-edge inter-linked porosity on fission-gas release and swelling. GRASS-SST calculations include the effects of gas production from fissioning uranium atoms, bubble nucleation, a realistic equation of state for xenon, lattice bubble diffusivities based on experimental observations, bubble migration, bubble coalescence, re-solution, temperature and temperature gradients, inter-linked porosity, and fission-gas interaction with structural defects (dislocations and grain boundaries) on both the distribution of fission-gas within the fuel and on the amount of fission-gas released from the fuel. GRASS-SST includes the effects of the degree of nonequilibrium in the UO 2 lattice on fission-gas bubble mobility and bubble coalescence and also accounts for the observed formation of grain-surface channels. GRASS-SST also includes mechanistic models for grain-growth/grain boundary sweeping and for the behaviour of fission gas during liquefaction/dissolution and fuel melting conditions. 2 - Method of solution: A system of coupled equations for the evolution of the fission-gas bubble-size distributions in the lattice, on dislocations, on grain faces, and grain edges is derived based on the GRASS-SST models. Given a set of operating conditions, GRASS-SST calculates the bubble radii for the size classes of bubbles under consideration using a realistic equation of state for xenon as well as a generalised capillary relation. 3 - Restrictions on the complexity of the problem: Maxima of : 1 axial section

  3. Detection of fission fragments using thick samples in contact with solid state nuclear track detectors

    International Nuclear Information System (INIS)

    Lima, D.A. de; Martins, J.B.; Tavares, O.A.P.

    1987-01-01

    Whenever use is made of thick samples in contact with solid state nuclear track detectors for determining fission yields, one of the fundamental problems is the evaluation of the effective number of target nuclei which contributes to the fraction of the number of fission events that will be recorded. The evaluation of the effective number of target nuclei which contributes to recorded events is based on the effective thickness of the sample. A method for evaluating effective thickness of thick samples for binary fission modes, is presented. A cross section equation which takes into account all the necessary corrections due to fragment attenuation effects by a thick target for calculation induced fission yields, was obtained. (Author) [pt

  4. Measurement of tritium production rate distribution for a fusion-fission hybrid conceptual reactor

    International Nuclear Information System (INIS)

    Wang Xinhua; Guo Haiping; Mou Yunfeng; Zheng Pu; Liu Rong; Yang Xiaofei; Yang Jian

    2013-01-01

    A fusion-fission hybrid conceptual reactor is established. It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium. The tritium production rate (TPR) distribution in the conceptual reactor was measured by DT neutrons using two sets of lithium glass detectors with different thicknesses in the hole in the vertical direction with respect to the D + beam of the Cockcroft-Walton neutron generator in direct current mode. The measured TPR distribution is compared with the calculated results obtained by the three-dimensional Monte Carlo code MCNP5 and the ENDF/B-Ⅵ data file. The discrepancy between the measured and calculated values can be attributed to the neutron data library of the hydrogen lithium lack S(α, β) thermal scattering model, so we show that a special database of low-energy and thermal neutrons should be established in the physics design of fusion-fission hybrid reactors. (authors)

  5. Mica fission detectors

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  6. Fission barriers and asymmetric ground states in the relativistic mean-field theory

    International Nuclear Information System (INIS)

    Rutz, K.; Reinhard, P.G.; Greiner, W.

    1995-01-01

    The symmetric and asymmetric fission path for 240 Pu, 232 Th and 226 Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations. (orig.)

  7. Breast Cancer Rates by State

    Science.gov (United States)

    ... Associated Lung Ovarian Prostate Skin Uterine Cancer Home Breast Cancer Rates by State Language: English (US) Español (Spanish) ... from breast cancer each year. Rates of Getting Breast Cancer by State The number of people who get ...

  8. Fission track dating and uranium estimation in pegmatitic minerals of Rajasthan state (India)

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S; Virk, H S [Punjabi Univ., Patiala (India). Dept. of Physics

    1978-12-01

    Fission track geochronology of muscovite samples collected from some pegmatitic mines of Bhilwara and Ajmer districts of Rajasthan state (India) has been discussed. The ages obtained suggest the occurrence of Delhi Orogenic Cycle as the last major metamorphic activity in the region. The atomic fraction of uranium in muscovite samples is less than 1 p.p.b.

  9. Modeling steady state and transient fission gas behaviour with the Karlsruhe code LAKU

    International Nuclear Information System (INIS)

    Vaeth, L.

    1984-08-01

    The programme LAKU models the behaviour of gaseous fission products in reactor fuel under steady state and transient conditions, including molten fuel. A presentation of the full model is given, starting with gas behaviour in the grains and on grain faces and including the treatment of release from porosity. The results of some recent calculations are presented. (orig.) [de

  10. Unveiling Singlet Fission Mediating States in TIPS-pentacene and its Aza Derivatives.

    Science.gov (United States)

    Herz, Julia; Buckup, Tiago; Paulus, Fabian; Engelhart, Jens U; Bunz, Uwe H F; Motzkus, Marcus

    2015-06-25

    Femtosecond pump-depletion-probe experiments were carried out in order to shed light on the ultrafast excited-state dynamics of triisopropylsilylethynyl (TIPS)-pentacene and two nitrogen-containing derivatives, namely, diaza-TIPS-pentacene and tetraaza-TIPS-pentacene. Measurements performed in the visible and near-infrared spectral range in combination with rate model simulations reveal that singlet fission proceeds via the extremely short-lived intermediate (1)TT state, which absorbs in the near-infrared spectral region only. The T1 → T3 transition probed in the visible region shows a rise time that comprises two components according to a consecutive reaction (S1 → (1)TT → T1). The incorporation of nitrogen atoms into the acene structure leads to shorter dynamics, but the overall triplet formation follows the same kinetic model. This is of particular importance, since experiments on tetraaza-TIPS-pentacene allow for investigation of the triplet state in the visible range without an overlapping singlet contribution. In addition, the pump-depletion-probe experiments show that the triplet absorption in the visible (T1 → T3) and near-infrared (T1 → T2) regions occurs from the same initial state, which was questioned in previous studies. Furthermore, an additional ultrafast transfer between the excited triplet states (T3 → T2) is identified, which is also in agreement with the rate model simulation. By applying depletion pulses, which are resonant with higher vibrational levels, we gain insight into internal vibrational energy redistribution processes within the triplet manifold. This additional information is of great relevance regarding the study of loss channels within these materials.

  11. Acute myeloid leukemia induction in CBA/H mice by irradiation with fission neutrons as a function of exposure rate

    International Nuclear Information System (INIS)

    Huiskamp, R.

    1991-01-01

    Radiation-induced acute myeloid leukemia (AML) in male CBA/H mice was used as a model for investigation of the effect of reduced fast fission neutron exposure rates on radiation-induced carcinogenesis. Groups of about 90 male CBA/H mice were irradiated or sham-irradiated at the age of 15-20 weeks. The animals were exposed to 400 mGy fast fission neutrons at exposure rates of 2, 10 or 100 mGy/min. The investigation clearly showed that reducing the exposure rate of high-LET fast fission neutrons had no influence on the incidence of AML or on the survival of the irradiated mice. In contrast, a higher incidence of lymphosarcomas was observed in mice irradiated with higher exposure rates. (orig./MG)

  12. Acute myeloid leukemia induction in CBA/H mice by irradiation with fission neutrons as a function of exposure rate

    Energy Technology Data Exchange (ETDEWEB)

    Huiskamp, R [Stichting Energieonderzoek Centrum Nederland, Petten (Netherlands). Radiobiology and Radio-Ecology Unit

    1991-06-01

    Radiation-induced acute myeloid leukemia (AML) in male CBA/H mice was used as a model for investigation of the effect of reduced fast fission neutron exposure rates on radiation-induced carcinogenesis. Groups of about 90 male CBA/H mice were irradiated or sham-irradiated at the age of 15-20 weeks. The animals were exposed to 400 mGy fast fission neutrons at exposure rates of 2, 10 or 100 mGy/min. The investigation clearly showed that reducing the exposure rate of high-LET fast fission neutrons had no influence on the incidence of AML or on the survival of the irradiated mice. In contrast, a higher incidence of lymphosarcomas was observed in mice irradiated with higher exposure rates. (orig./MG).

  13. From ground state to fission fragments: A complex, multi-dimensional multi-path problem

    International Nuclear Information System (INIS)

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

    1992-01-01

    Experimental results on the fission properties of nuclei close to 264 Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus 258 Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic-energy distribution peaked at about 235 MeV whereas 256 Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic-energy distribution peaked at about 200 MeV. Qualitatively, these sudden changes have been postulated to be due to the emergence of fragment shells in symmetric-fission products close to 132 Sn. Here we present a quantitative calculation that shows where high-kinetic-energy symmetric fusion occurs and why it is associated with a sudden and large decrease in fission half-lives. We base our study on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. We use the three-quadratic-surface parameterization to generate the shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. Since these shapes are thought to correspond to the scission shapes for the high-kinetic-energy events it is of crucial importance that a continuous sequence of shapes leading from the nuclear ground state to these configurations can be studied within the framework of the model. We present the results of the calculations in terms of potential-energy surfaces and fission half-lives for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. They clearly show the appearance of a second fission valley, which leads to scission configurations close to tow touching spheres, for fissioning systems in the vicinity of 264 Fm

  14. The low-lying electronic states of pentacene and their roles in singlet fission.

    Science.gov (United States)

    Zeng, Tao; Hoffmann, Roald; Ananth, Nandini

    2014-04-16

    We present a detailed study of pentacene monomer and dimer that serves to reconcile extant views of its singlet fission. We obtain the correct ordering of singlet excited-state energy levels in a pentacene molecule (E (S1) pentacene, we use a well-developed diabatization scheme to characterize the six low-lying singlet states of a pentacene dimer that approximates the unit cell structure of crystalline pentacene. The local, single-excitonic diabats are not directly coupled with the important multiexcitonic state but rather mix through their mutual couplings with one of the charge-transfer configurations. We analyze the mixing of diabats as a function of monomer separation and pentacene rotation. By defining an oscillator strength measure of the coherent population of the multiexcitonic diabat, essential to singlet fission, we find this population can, in principle, be increased by small compression along a specific crystal direction.

  15. Lung Cancer Rates by State

    Science.gov (United States)

    ... the Biggest Cancer Killer in Both Men and Women” Stay Informed Rates by State for Other Kinds of Cancer All Cancers Combined Breast Cervical Colorectal (Colon) HPV-Associated Ovarian Prostate Skin Uterine Cancer Home Lung Cancer Rates by State Language: English (US) ...

  16. Measurement and analysis of thorium fission rate in a polyethylene shell with a D-T neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Lei [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Yang, Yiwei, E-mail: winfield1920@126.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Liu, Zhujun [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Department of Nuclear Engineering and Technology, Sichuan University, Chengdu 610065,China (China); Liu, Rong, E-mail: liurongzy@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Jiang, Li; Wang, Mei [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2016-12-15

    Highlights: • Associated angular dependencies of the source neutron energy and intensity was given. • Two sets of fission yields from evaluated libraries were considered and applied. • Calculated results employing ENDF/B-VII.0 agreed with the experimental ones best. • Small discrepancies exist between thorium fission cross section evaluated libraries. - Abstract: In order to validate the {sup 232}Th fission cross section, an integral experiment was carried out using the activation method in a polyethylene shell with a D-T neutron source. Thorium samples were arranged in the 0° direction to the incident D{sup +} beam. The {sup 232}Th fission rate was determined by measuring the 151.195 keV characteristic γ ray emitted from the fission fragment {sup 85m}Kr, and the experimental uncertainties were about 5.3%. MCNP calculation results employing ENDF/B-VII.0, JENDL-3.3, JENDL-4.0 libraries are in good agreement with that of experiments within uncertainties except that employing ENDF/B-VII.1 (∼6.5%). The experiment results can be used to re-evaluate the {sup 232}Th fission cross section.

  17. A model of fission gas behavior during steady-state operation

    International Nuclear Information System (INIS)

    Villalobos, A.

    1981-01-01

    A model of fission gas behavior during the steady-state operation of a nuclear reactor that uses uranium dioxide as fuel is developed. The basic physical phenomena encountered in analyzing the disposition of fission gas have been retained, but in a simplified form for ease of calculation. The analysis code, includes treatment of intragranular, grain face, and grain edge gas and release to the open spaces. The code is utilized to obtain comparisons with experimental data and to perform fuel behavior sensitivity studies. The results obtained in the sensitivity studies indicate the importance of including grain face and grain edge bubbles treatments in modeling fission gas. It is found that representation of release in different sections of the fuel pin is possible in a simple way by assuming evenly spaced bubbles on the edge, and that grain edge bubble interlinkage is a necessary condition for release to the open spaces. It is also indicated by the sensitivity studies that fission gas swelling is mainly due to grain edge bubbles. Grain face bubbles, although large in size, are few in number and contribute little to swelling. Intragranular swelling is intermediate between these two values. The resulting code can be used in predicting fuel element performance, that is necessary in nuclear fuel design, safety analysis, and interpretation of experimental data on fuel element behavior

  18. Effect of fission rate on the microstructure of coated UMo dispersion fuel

    Energy Technology Data Exchange (ETDEWEB)

    Leenaers, A.; Parthoens, Y.; Cornelis, G.; Kuzminov, V.; Koonen, E.; Van den Berghe, S.; Ye, B.; Hofman, G. L.; Schulthess, Jason

    2017-10-01

    Compared to previous irradiation experiments containing UMo/Al dispersion fuel plates, the SELENIUM irradiation experiment performed at the SCK.CEN BR2 reactor in 2012 showed an improved plate swelling behavior. However, in the high burn-up area of the plates a significant increase in meat thickness was still measured. The origin of this increase is currently not firmly established, but it is clear from the observed microstructure that the swelling rate still is too high for practical purposes and needs to be reduced. It was stipulated that the swelling occurred at the high burnup areas which are also the high power zones at beginning of life. For that reason, an experiment was proposed to investigate the influence of fission rate (i.e. power) on some of the observed phenomena. For this purpose, a sibling plate to a high power (BOL>470 W/cm(2)) SELENIUM plate was irradiated during four BR2 cycles. The SELENIUM 1a fuel plate was submitted to a local maximum heat flux below 350 W/cm(2), throughout the full irradiation. At the end of the last cycle, the SELENIUM 1a fuel plate reached a maximum local burnup value of close to 75%U-235 compared to 70%U-235 for the SELENIUM high power plates. When comparing to the results on the SELENIUM plates, the non-destructive tests clearly show a continued linear swelling behavior of the low power irradiated fuel plate SELENIUM 1a in the high burn-up region. The influence of the fission rate is also evidenced in the microstructural examination of the fuel showing that there is no formation of interaction layer at the high burn-up region.

  19. Effect of fission rate on the microstructure of coated UMo dispersion fuel

    Science.gov (United States)

    Leenaers, A.; Parthoens, Y.; Cornelis, G.; Kuzminov, V.; Koonen, E.; Van den Berghe, S.; Ye, B.; Hofman, G. L.; Schulthess, Jason

    2017-10-01

    Compared to previous irradiation experiments containing UMo/Al dispersion fuel plates, the SELENIUM irradiation experiment performed at the SCK·CEN BR2 reactor in 2012 showed an improved plate swelling behavior. However, in the high burn-up area of the plates a significant increase in meat thickness was still measured. The origin of this increase is currently not firmly established, but it is clear from the observed microstructure that the swelling rate still is too high for practical purposes and needs to be reduced. It was stipulated that the swelling occurred at the high burnup areas which are also the high power zones at beginning of life. For that reason, an experiment was proposed to investigate the influence of fission rate (i.e. power) on some of the observed phenomena. For this purpose, a sibling plate to a high power (BOL>470 W/cm2) SELENIUM plate was irradiated during four BR2 cycles. The SELENIUM 1a fuel plate was submitted to a local maximum heat flux below 350 W/cm2, throughout the full irradiation. At the end of the last cycle, the SELENIUM 1a fuel plate reached a maximum local burnup value of close to 75%235U compared to 70%235U for the SELENIUM high power plates. When comparing to the results on the SELENIUM plates, the non-destructive tests clearly show a continued linear swelling behavior of the low power irradiated fuel plate SELENIUM 1a in the high burn-up region. The influence of the fission rate is also evidenced in the microstructural examination of the fuel showing that there is no formation of interaction layer at the high burn-up region.

  20. Study of advanced fission power reactor development for the United States. Volume I

    International Nuclear Information System (INIS)

    1976-01-01

    This volume summarizes the results and conclusions of an assessment of five advanced fission power reactor concepts in the context of potential nuclear power economies developed over the time period 1975 to 2020. The study was based on the premise that the LMFBR program has been determined to be the highest priority fission reactor program and it will proceed essentially as planned. Accepting this fact, the overall objective of the study was to provide evaluations of advanced fission reactor systems for input to evaluating the levels of research and development funding for fission power. Evaluation of the reactor systems included the following categories: (1) power plant performance, (2) fuel resource utilization; (3) fuel-cycle requirements; (4) economics; (5) environmental impact; (6) risk to the public; and (7) R and D requirements to achieve commercial status. The specific major objectives of the study were twofold: (1) to parametrically assess the impact of various reactor types for various levels of power demand through the year 2020 on fissile fuel utilization, economics, and the environment, based on varying but reasonable assumptions on the rates of installation; and (2) to qualitatively assess the practicality of the advanced reactor concepts, and their research and development. The reactor concepts examined were limited to the following: advanced high-temperature, gas-cooled reactor (HTGR) systems including the thorium/U-233 fuel cycle, gas turbine, and binary cycle (BIHTGR); gas-cooled fast breeder reactor (GCFR); molten salt breeder reactor (MSBR); light water breeder reactor (LWBR); and CANDU heavy water reactor

  1. Variational RRKM calculation of thermal rate constant for C–H bond fission reaction of nitro methane

    Directory of Open Access Journals (Sweden)

    Afshin Taghva Manesh

    2017-02-01

    Full Text Available The present work provides quantitative results for the rate constants of unimolecular C–H bond fission reactions in the nitro methane at elevated temperatures up to 2000 K. In fact, there are three different hydrogen atoms in the nitro methane. The potential energy surface for each C–H bond fission reaction of nitro methane was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C–H bond fission channel is a barrierless reaction, we have used variational RRKM theory to predict rate coefficients. By means of calculated rate coefficients at different temperatures, the Arrhenius expression of the channel over the temperature range of 100–2000 K is k(T = 5.9E19∗exp(−56274.6/T.

  2. Fission rate distribution at the 84-pin radial section of a SVEA-96 Optima2 BWR assembly

    Energy Technology Data Exchange (ETDEWEB)

    Perret, Gregory; Murphy, Michael F.; Jatuff, Fabian [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Chawla, Rakesh [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2008-07-01

    Westinghouse boiling water reactor SVEA-96 Optima2 assemblies were studied during the LWRPROTEUS program at the PROTEUS facility in the Paul Scherrer Institute. Measured radial fission rate distributions at the 84-pin elevation are compared with MCNPX predictions using both ENDF/B-VI (Release 2) and JEFF-3.1 data libraries. Predicted fission rates agree within +-4.5% using both libraries. Fission rates were over-predicted in UO{sub 2} pins close to the missing 1/3 pins and under-predicted in UO{sub 2} pins close to the missing 2/3 pins. Recurrent under-estimations were observed in the UO{sub 2}-Gd{sub 2}O{sub 3} pins, for both libraries, which might be explained by over-estimated thermal cross-sections of {sup 157}Gd, as suggested in a recent work of G. Leinweber et al. (2006). (authors)

  3. New isomeric states in {sup 152,154,156}Nd produced by spontaneous fission of {sup 252}Cf

    Energy Technology Data Exchange (ETDEWEB)

    Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C. [Commissariat l`Energie Atomique de Saclay, Gif sur Yvette (France). DSM/DAPINA/SPhN; Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires de Bordeaux-Gradignan, Domaine du Haut Vigneau, F-33175 Gradignan (France); Belier, G.; Girod, M.; Meot, V.; Peru, S. [Commissariat a l`Energie Atomique de Bruyeres-le-Chatel, DAM/SPN, BP12, F-91680 Bruyeres-le-Chatel (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Institut de Physique Nucleaire de Lyon, F-69622 Villeurbanne Cedex (France)

    1998-04-01

    Isomeric states have been observed in fission-fragments produced by spontaneous fission of {sup 252}Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between {gamma}-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2{mu}s have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the {sup 152,154,156}Nd show evidence for K-isomers. (orig.) With 8 figs., 27 refs.

  4. Absence of Intramolecular Singlet Fission in Pentacene-Perylenediimide Heterodimers: The Role of Charge Transfer State.

    Science.gov (United States)

    Wang, Long; Wu, Yishi; Chen, Jianwei; Wang, Lanfen; Liu, Yanping; Yu, Zhenyi; Yao, Jiannian; Fu, Hongbing

    2017-11-16

    A new class of donor-acceptor heterodimers based on two singlet fission (SF)-active chromophores, i.e., pentacene (Pc) and perylenediimide (PDI), was developed to investigate the role of charge transfer (CT) state on the excitonic dynamics. The CT state is efficiently generated upon photoexcitation. However, the resulting CT state decays to different energy states depending on the energy levels of the CT state. It undergoes extremely rapid deactivation to the ground state in polar CH 2 Cl 2 , whereas it undergoes transformation to a Pc triplet in nonpolar toluene. The efficient triplet generation in toluene is not due to SF but CT-mediated intersystem crossing. In light of the energy landscape, it is suggested that the deep energy level of the CT state relative to that of the triplet pair state makes the CT state actually serve as a trap state that cannot undergoes an intramolecular singlet fission process. These results provide guidance for the design of SF materials and highlight the requisite for more widely applicable design principles.

  5. Steady-state fission gas behavior in uranium-plutonium-zirconium metal fuel elements

    International Nuclear Information System (INIS)

    Steele, W.G.; Wazzan, A.R.; Okrent, D.

    1989-01-01

    An analysis of fission gas release and induced swelling in steady state irradiated U-Pu-Zr metal fuels is developed and computer coded. The code is used to simulate, with fair success, some gas release and induced swelling data obtained under the IFR program. It is determined that fuel microstructural changes resulting from zirconium migration, anisotropic swelling, and thermal variations are major factors affecting swelling and gas release behavior. (orig.)

  6. Measurements of fission cross-sections and of neutron production rates

    International Nuclear Information System (INIS)

    Billaud, P.; Clair, C.; Gaudin, M.; Genin, R.; Joly, R.; Leroy, J.L.; Michaudon, A.; Ouvry, J.; Signarbieux, C.; Vendryes, G.

    1958-01-01

    a) Measurements of neutron induced fission cross-sections in the low energy region. The variation of the fission cross sections of several fissile isotopes has been measured and analysed, for neutron energies below 0,025 eV. The monochromator was a crystal spectrometer used in conjunction with a mechanical velocity selector removing higher order Bragg reflections. The fissile material was laid down on the plates of a fission chamber by painting technic. An ionization chamber, having its plates coated with thin 10 B layers, was used as the neutron flux monitor. b) Measurement of the fission cross section of 235 U. We intend to measure the variation of the neutron induced fission cross section of 235 U over the neutron energy range from 1 keV by the time of flight method. The neutron source is the uranium target of a pulsed 28 MeV electron linear accelerator. The detector is a large fission chamber, with parallel plates, containing about 10 g of 235 U (20 deposits of 25 cm diameter). The relative fission data were corrected for the neutron spectrum measured with a set of BF 3 proportional counters. c) Mean number ν of neutrons emitted in neutron induced fission. We measured the value of ν for several fissile isotopes in the case of fission induced by 14 MeV neutrons. The 14 MeV neutrons were produced by D (t, n) α reaction by means of a 300 kV Cockcroft Walton generator. (author) [fr

  7. On the combination of delayed neutron and delayed gamma techniques for fission rate measurement in nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Perret, G.; Jordan, K. A. [Paul Scherrer Institut, Villigen, 5232 (Switzerland)

    2011-07-01

    Novel techniques to measure newly induced fissions in spent fuel after re-irradiation at low power have been developed and tested at the Proteus zero-power research reactor. The two techniques are based on the detection of high energy gamma-rays emitted by short-lived fission products and delayed neutrons. The two techniques relate the measured signals to the total fission rate, the isotopic composition of the fuel, and nuclear data. They can be combined to derive better estimates on each of these parameters. This has potential for improvement in many areas. Spent fuel characterisation and safeguard applications can benefit from these techniques for non-destructive assay of plutonium content. Another application of choice is the reduction of uncertainties on nuclear data. As a first application of the combination of the delayed neutron and gamma measurement techniques, this paper shows how to reduce the uncertainties on the relative abundances of the longest delayed neutron group for thermal fissions in {sup 235}U, {sup 239}Pu and fast fissions in {sup 238}U. The proposed experiments are easily achievable in zero-power research reactors using fresh UO{sub 2} and MOX fuel and do not require fast extraction systems. The relative uncertainties (1{sigma}) on the relative abundances are expected to be reduced from 13% to 4%, 16% to 5%, and 38% to 12% for {sup 235}U, {sup 238}U and {sup 239}Pu, respectively. (authors)

  8. Block-free optical quantum Banyan network based on quantum state fusion and fission

    International Nuclear Information System (INIS)

    Zhu Chang-Hua; Meng Yan-Hong; Quan Dong-Xiao; Zhao Nan; Pei Chang-Xing

    2014-01-01

    Optical switch fabric plays an important role in building multiple-user optical quantum communication networks. Owing to its self-routing property and low complexity, a banyan network is widely used for building switch fabric. While, there is no efficient way to remove internal blocking in a banyan network in a classical way, quantum state fusion, by which the two-dimensional internal quantum states of two photons could be combined into a four-dimensional internal state of a single photon, makes it possible to solve this problem. In this paper, we convert the output mode of quantum state fusion from spatial-polarization mode into time-polarization mode. By combining modified quantum state fusion and quantum state fission with quantum Fredkin gate, we propose a practical scheme to build an optical quantum switch unit which is block free. The scheme can be extended to building more complex units, four of which are shown in this paper. (general)

  9. Comparison of reconstructed radial pin total fission rates with experimental results in full scale BWR fuel elements

    Energy Technology Data Exchange (ETDEWEB)

    Giust, Flavio [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Nordostschweizerische Kraftwerke AG, Parkstrasse 23, CH-5401 Baden (Switzerland); Grimm, Peter; Jatuff, Fabian [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Chawla, Rakesh [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    2008-07-01

    Total fission rate measurements have been performed on full size BWR fuel assemblies of type SVEA-96+ in the zero power reactor PROTEUS at the Paul Scherrer Institute. This work presents comparisons of reconstructed 2D pin fission rates in two configurations, I-1A and I-2A. Both configurations contain, in the central test zone, an array of 3x3 SVEA-96+ fuel elements moderated with light water at 20 deg. C. In configuration I-2A, an L-shaped hafnium control blade (half of a real cruciform blade) is inserted adjacent to the NW corner of the central fuel element. To minimize the impact of the surroundings, all measurements were done in fuel pins belonging to the central assembly. The 3x3 experimental configuration was modeled using the core monitoring and design tools that are applied at the Leibstadt Nuclear Power Plant (KKL). These are the 2D transport code HELIOS, used for the cross-section generation, and the 3D, 2-group nodal diffusion code PRESTO-2. The exterior is represented, in the axial and radial directions, by 2-group albedos calculated at the test zone boundary using a full-core 3D MCNPX model. The calculated-to-experimental (C/E) ratios of the total fission rates have a standard deviation of 1.3% in configuration I-1A (uncontrolled) and 3.2% in configuration I-2A (controlled). Sensitivity cases are analyzed to show the impact of certain parameters on the calculated fission rate distribution and reactivity. It is shown that the relative pin fission rate is only weakly dependent on these parameters. In cases without a control blade, the pin power reconstruction methodology delivers the same level of accuracy as 2D transport calculations. On the other hand, significant deviations, that are inherent to the use of reflected geometry in the lattice calculations, are observed in cases when the control blade is inserted. (authors)

  10. Nonequilibrium behavior of fission gas bubbles with emphasis on the effects of the equation of state

    International Nuclear Information System (INIS)

    Steele, W.G.

    1976-12-01

    The paper presents a computer code designed to estimate fission gas behavior during transient fuel conditions, allowing for nonequilibrium bubble states, with emphasis on equation of state sensitivity. The computer code is a modification of the original code by R. G. Esteves, A. R. Wazzan, and D. Okrent, which in its present form includes the following: resolution, coalescence, leakage to the grain boundary, bubble volume adjustment from a nonequilibrium state by vacancy diffusion, a choice of equation of state between the Van der Waals and the perfect gas equation, the incorporation of hydrostatic pressure values, if known, and conservation of gas atoms. Also, there is a version of the code that allows the existence of single gas atoms in solution in the lattice. The original code is discussed to provide a model of the physical processes and to show a general numerical approach to the estimation of the fission gas behavior. The incorporation of various new features into the original work, such as the option of the Van der Waals gas equation, is described. The various physical models are examined for sensitivity to equation of state for both the equilibrium and nonequilibrium bubble descriptions. Selected computer results of a transient simulation are also presented and general conclusions are drawn upon these results

  11. Experiments to determine the rate of beta energy release following fission of Pu239 andU235 in a fast reactor

    International Nuclear Information System (INIS)

    Murphy, M.F.; Taylor, W.H.; Sweet, D.W.; March, M.R.

    1979-02-01

    Measurements have been made of the rate of beta energy release from Pu239 and U235 fission fragments over a period of 107 seconds following a 105 second irradiation in the zero-power fast reactor Zebra. Results are compared with predictions using the UKFPDD-1 decay data file and two different sets of fission product yield data. (author)

  12. Assessment of pin-by-pin fission rate distribution within MOX/UO{sub 2} fuel assembly using MCNPX code

    Energy Technology Data Exchange (ETDEWEB)

    Louis, Heba Kareem; Amin, Esmat [Nuclear and Radiological Regulation Authority (NRRA), Cairo (Egypt). Safety Engineering Dept.

    2016-03-15

    The aim of the present paper is to assess the calculations of pin-by-pin group integrated fission rates within MOX/UO{sub 2} Fuel assemblies using the Monte Carlo code MCNP2.7c with two sets of the available latest nuclear data libraries used for calculating MOX-fueled systems. The data that are used in this paper are based on the benchmark by the NEA Nuclear Science Committee (NSC). The k{sub ∞} and absorption/fission reaction rates per isotope, k{sub eff} and pin-by-pin group integrated fission rates on 1/8 fraction of the geometry are determined. To assess the overall pin-by-pin fission rate distribution, the collective per cent error measures were investigated. The results of AVG, MRE and RMS error measures were less than 1 % error. The present results are compared with other participants using other Monte Carlo codes and with CEA results that were taken in the benchmark as reference. The results with ENDF/B-VI.6 are close to the results received by MVP (JENDL3.2) and SCALE 4.2 (JEF2.2). The results with ENDF/BVII.1 give higher values of k{sub ∞} reflecting the changes in the newer evaluations. In almost all results presented here, the MCNP calculated results with ENDF/B VII.1 should be considered more than those obtained by using other Monte Carlo codes and nuclear data libraries. The present calculations may be consider a reference for evaluating the numerical schemes in production code systems, as well as the global performance including cross-section data reduction methods as the calculations used continuous energy and no geometrical approximations.

  13. Electron Transfer from Triplet State of TIPS-Pentacene Generated by Singlet Fission Processes to CH3NH3PbI3 Perovskite.

    Science.gov (United States)

    Lee, Sangsu; Hwang, Daesub; Jung, Seok Il; Kim, Dongho

    2017-02-16

    To reveal the applicability of singlet fission processes in perovskite solar cell, we investigated electron transfer from TIPS-pentacene to CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite in film phase. Through the observation of the shorter fluorescence lifetime in TIPS-pentacene/MAPbI 3 perovskite bilayer film (5 ns) compared with pristine MAPbI 3 perovskite film (20 ns), we verified electron-transfer processes between TIPS-pentacene and MAPbI 3 perovskite. Furthermore, the observation of singlet fission processes, a faster decay rate, TIPS-pentacene cations, and the analysis of kinetic profiles of the intensity ratio between 500 and 525 nm in the TA spectra of the TIPS-pentacene/MAPbI 3 perovskite bilayer film indicate that electron transfer occurs from triplet state of TIPS-pentacene generated by singlet fission processes to MAPbI 3 perovskite conduction band. We believe that our results can provide useful information on the design of solar cells sensitized by singlet fission processes and pave the way for new types of perovskite solar cells.

  14. Chemical states of fission products in irradiated uranium-plutonium mixed oxide fuel

    International Nuclear Information System (INIS)

    Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke

    1999-01-01

    The chemical states of fission products (FPs) in irradiated uranium-plutonium mixed oxide (MOX) fuel for the light water reactor (LWR) were estimated by thermodynamic equilibrium calculations on system of fuel and FPs by using ChemSage program. A stoichiometric MOX containing 6.1 wt. percent PuO 2 was taken as a loading fuel. The variation of chemical states of FPs was calculated as a function of oxygen potential. Some pieces of information obtained by the calculation were compared with the results of the post-irradiation examination (PIE) of UO 2 fuel. It was confirmed that the multicomponent and multiphase thermodynamic equilibrium calculation between fuel and FPs system was an effective tool for understanding the behavior of FPs in fuel. (author)

  15. Thermal decay rate of a metastable state with two degrees of ...

    Indian Academy of Sciences (India)

    I I Gontchar

    2017-06-01

    Jun 1, 2017 ... expected to agree with the long time limit of the escape rate obtained using ..... distribution with zero averages and variances equal to 2. Although in the fission ... Here (t) is the probability that the metastable state has ..... the (kt)−1/2 dependence and has been adjusted to εR at some intermediate points.

  16. Effects of low dose rate fission neutron irradiation on the lymphocyte subpopulations of peripheral blood in rats

    International Nuclear Information System (INIS)

    Jiang Dingwen; Lei Chengxiang; Shen Xianrong; Ma Li; Yang Yifang; Peng Wulin; Dai Shourong

    2008-01-01

    Objective: To evaluate the effects of long-term, low dose rate fission neutron irradiation on lymphocyte subpopulations in peripheral blood of rats. Methods: Ninety-six rats were randomly divided into control group and irradiated group exposed to low dose rate fission neutron ( 252 Cf,0.35 mGy/h) for 20.5 h every day. At days 14,28,42,56 and 70 d after irradiation and 35 d after stopping irradiation, After 8 rats of each group were killed, WBC and lymphocyte subpopulations of CD4 + CD3 + , CD8 + CD3 + and CD45RA + /CD161α + in peripheral blood were estimated respectively. Results: Compared with the control group, WBC was reduced significantly at dose of 0.3, 0.4 and 0.5 Gy (P + CD3 - was evidently higher compared with control group at doses of 0.1,0.3, 0.4 and 0.5 Gy and 35 d after stopping irradiation (P + CD3 - was obviously higher compared with control group at dose of 0.2 and 0.3 Gy (P + CD3 + at dose of 0.1 Gy (P + CD3 + at doses of 0.1 and 0.2 Gy (P + CD45RA - ) was increased significantly at doses of 0.2-0.3 Gy, and peripheral blood B cells(CD161α - CD45RA + ) was reduced remarkably at doses of 0.1-0.5 Gy and 35 d after stopping irradiation compared with the control group. Conclusions: Long-term irradiation with low dose rate fission neutron could make TCR (T-cell-receptor) mutant, therefore, WBC, B cells in peripheral blood significantly reduced and NK cells increased. These changes may could not recover at 35 d after Stopping irradiation. (authors)

  17. Effects of long-term, low dose rate fission neutron irradiation on the peripheral hematological cells in rats

    International Nuclear Information System (INIS)

    Jiang Dingwen; Lei Chengxiang; Shen Xianrong; Ma Li; Yang Xufang; Peng Wulin; Dai Shourong

    2008-01-01

    Objective: To evaluate the effects of long-term, low dose rate fission neutron irradiation on the peripheral hematological cells in rats. Methods: 96 rats were randomly divided into the control group and the irradiation group with low dose rate fission neutron ( 252 Cf, 0.35 mGy/h) irradiation 20.5 h every day. 8 rats of each group were killed at 14 d, 28 d, 42d, 56d, 70d after irradiation and 35d after the irradiation, and their peripheral hematological cells were tested respectively. Results: Compared with the control group, peripheral blood WBC was reduced significantly at the dose of 0.3Gy and 0.4Gy (P < 0.05), and was reduced remarkably at dose of 0.5Gy (P<0.01) and 35d after stopping irradiation(P<0.01). At dose of 0.2Gy, Peripheral blood RBC was abnormally higher comparing with the control group (P<0.01), accompanying with higher HCT and HGB, which suggests condensed blood. At the other point, RBC tend to become lower, but only at dose 0.5Gy, and the difference is significant comparing with control group(P <0.05). At dose of 0.3Gy, 0.4Gy and 0.5Gy, HCT were significantly lower comparing with control group. Comparing with control group, MCV was higher at 35d after stopping irradiation, and PLT was significantly lower in dose of 0.2Gy. Conclusion: Long-term irradiation with low dose rate fission neutron could significantly reduce peripheral blood WBC, with less effects on RBC and PLT. The reduced WBC could not recover at 35d after stopping irradiation. (authors)

  18. Fission meter

    Science.gov (United States)

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

    2012-04-10

    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.

  19. Reassessment of fission fragment angular distributions from continuum states in the context of transition-state theory

    International Nuclear Information System (INIS)

    Vaz, L.C.; Alexander, J.M.

    1983-01-01

    Fission angular distributions have been studied for years and have been treated as classic examples of transition-state theory. Early work involving composite nuclei of relatively low excitation energy Esup(*) ( 2 0 (K 2 0 = Psub(eff)T/(h/2π) 2 ) are presented along with comparissons of Psub(eff) to moments of inertia for saddle-point nuclei from the rotating liquid drop model. This model gives an excellent guide for the intermediate spin zone (30 < or approx. I < or approx. 65), while strong shell and/or pairing effects are evident for excitations less than < or approx. 35 MeV. Observations of strong anisotropies for very high-spin systems signal the demise of certain approximations commonly made in the theory, and suggestions are made toward this end. (orig.)

  20. Long-Lived Triplet Excited States of Bent-Shaped Pentacene Dimers by Intramolecular Singlet Fission.

    Science.gov (United States)

    Sakuma, Takao; Sakai, Hayato; Araki, Yasuyuki; Mori, Tadashi; Wada, Takehiko; Tkachenko, Nikolai V; Hasobe, Taku

    2016-03-24

    Intramolecular singlet fission (ISF) is a promising photophysical process to construct more efficient light energy conversion systems as one excited singlet state converts into two excited triplet states. Herein we synthesized and evaluated bent-shaped pentacene dimers as a prototype of ISF to reveal intrinsic characters of triplet states (e.g., lifetimes of triplet excited states). In this study, meta-phenylene-bridged TIPS-pentacene dimer (PcD-3Ph) and 2,2'-bipheynyl bridged TIPS-pentacene dimer (PcD-Biph) were newly synthesized as bent-shaped dimers. In the steady-state spectroscopy, absorption and emission bands of these dimers were fully characterized, suggesting the appropriate degree of electronic coupling between pentacene moieties in these dimers. In addition, the electrochemical measurements were also performed to check the electronic interaction between two pentacene moieties. Whereas the successive two oxidation peaks owing to the delocalization were observed in a directly linked-pentacene dimer (PcD) by a single bond, the cyclic voltammograms in PcD-Biph and PcD-3Ph implied the weaker interaction compared to that of p-phenylene-bridged TIPS-pentacene dimer (PcD-4Ph) and PcD. The femtosecond and nanosecond transient absorption spectra clearly revealed the slower ISF process in bent-shaped pentacene dimers (PcD-Biph and PcD-3Ph), more notably, the slower relaxation of the excited triplet states in PcD-Biph and PcD-3Ph. Namely, the quantum yields of triplet states (ΦT) by ISF approximately remain constant (ca. 180-200%) in all dimer systems, whereas the lifetimes of the triplet excited states became much longer (up to 360 ns) in PcD-Biph as compared to PcD-4Ph (15 ns). Additionally, the lifetimes of the corresponding triplet states in PcD-Biph and PcD-3Ph were sufficiently affected by solvent viscosity. In particular, the lifetimes of PcD-Biph triplet state in THF/paraffin (1.0 μs) increased up to approximately three times as compared to that in THF

  1. Study of the stability of the ground states and K-isomeric states of 250Fm and 254102 against spontaneous fission

    International Nuclear Information System (INIS)

    Lazarev, Yu.A.; Lobanov, Yu.V.; Sagajdak, R.N.; Utenkov, V.K.; Kharitonov, Yu.P.; Shirokovskij, I.V.; Tret'yakova, S.P.; Oganessyan, Yu.Ts.

    1988-01-01

    By employing the 249 Cf( 4 He, 3n) and 208 Pb( 48 Ca,2n) reactions, experiments to study the stability against spontaneous fission of the nuclides 250 Fm and 254 102 as well as of the two-quasi-particle (2 q-p) K isomers 250 Fm (T 1/2 =1,8±0,1 s) and 254 102 (T 1/2 =0,28±0,04 s) have been performed. The groundstate spontaneous fission of the two nuclides has been discovered and the corresponding branching ratios b sf and partial half-lives T sf , respectively, have been determined to be: (6,9±1,0)x10 -5 , 0,83±0,15 yr for 250 Fm; (1,7±0,5)x10 -3 , (3,2±0,9)x10 4 s for 254 102. As a by-product of these studies, new data about cross sections of the 206,208 Pb( 48 Ca,xn) reactions have been obtained. Experiments designed to search for the spontaneous fission of the 2 q-p K-isometric states in 250 Fm and 254 102 have not revealed the effect in question. The lower limits of the ratios of the partial spontaneous fission half-lives for the 2 q-p K-isomeric states to those for the respective ground states, T * sf /T sf , have been established to be≥10 -1 for 250m Fm/ 250 Fm and ≥5x10 -3 for 254m 102/ 254 102. This means that the stability of the 2 q-p K-isomeric states in 250 Fm and 254 102 against spontaneous fission is practically not inferior to that of the ground states of these nuclei. In accord with the experimental findings, the theoretical estimates of T * sf /T sf made in the present paper show that, due to the influence of the specialization and blocking effects on the potential energy and the effective mass associated with fission, spontaneous fission from 2 q-p K-isomeric states cannot be facilitated but, on the contrary, should be essentially hindered compared with ground-state spontaneous fission

  2. Thermal history, thermal state, and related tectonism of a moon of fission origin

    International Nuclear Information System (INIS)

    Binder, A.B.; Lange, M.A.

    1980-01-01

    Thermal history of an initially totally molten moon of fission origin properly accounts for (1) the mare basalt epoch, in terms of its duration, the depth of the source region, and degrees of partial melting which produced the magmas; (2) the present-day heat flow of 17--18 ergs cm -2 s -1 ; and (3) the current high temperatures of the lower mantle as deduced from magnetic and seismic data. The model moon has a radius decrease of 5.4 km (3.1 x 10 -3 R) during lunar history. This value is within the rather poorly defined limits for the maximum change of the lunar radius of 10 -3 -10 -2 R. The majority of the thermoelastic stresses produced by the cooling of the moon have been dissipated via aseismic creep in the upper parts of the lunar mantle, not via faulting activity. A lower limit of 10 24 P for the viscosity of the mantle of the moon (at subsolidus temperatures) is suggested, based on the apparent absence of solid state convection in the moon at any time during its history. This is 10 3 times larger than that for the terrestrial mantle. The energy derived from the thermoelastic stresses in the type A moonquake zone is orders of magnitude smaller than the available tidal energy. Hence the thermoelastic stresses are not an important energy source for the tidal moon-quakes. The thermoelastic stresses can easily supply the energy for the high-frequency tele-seismic moonquakes. The relative rarity of HFT's is explained by the long times (10 8 -10 9 years) needed to accumulate the energy required to initiate faulting in the predicted source regions. These regions are in the uppermost mantle (depths between 80 and 200 km), where tensional quakes can occur, and at 10-km depths in the crust, where compressional quakes can occur. The consistency between our thermal history model results and the corresponding characteristics now known for the moon add further support for the fission model for the origin of the moon

  3. The present state of research on the vitrification of concentrated solutions of fission products (1962)

    International Nuclear Information System (INIS)

    Bonniaud, R.; Sombret, C.

    1961-01-01

    The present report gives the actual point of studies on vitrification of concentrated solutions of fission products. An active cell, giving glasses in crucibles, permitted to study various glass compositions. The leaching rate from the glass raises 1 to 2 10 -7 g of glass/cm 2 /day. Activity loss by volatility during vitrification remains weak and often below 0.1 per cent of total activity. Off gas cleaning is made easier by presence of filter which is compound of granules including iron oxide. After saturation the content of this filter can be melt. Moreover different processes are in experimentation for a more important production. Daily 72 liters of solution containing tracer activity are treated in a continuous calcination and vitrification plant. The loss in 106 Ru is still important and a modification of installation has been necessary. A pot vitrification plant is in study. In order to reduce cost of processing the possibility to pour glass after melting is actuality in study. A production set of very active glass is also in project. (authors) [fr

  4. Gamma-ray spectrometric measurements of fission rate ratios between fresh and burnt fuel following irradiation in a zero-power reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kröhnert, H., E-mail: hanna.kroehnert@ensi.ch [Paul Scherrer Institut (PSI), CH-5232 Villigen (Switzerland); École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Perret, G.; Murphy, M.F. [Paul Scherrer Institut (PSI), CH-5232 Villigen (Switzerland); Chawla, R. [Paul Scherrer Institut (PSI), CH-5232 Villigen (Switzerland); École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2013-01-11

    The gamma-ray activity from short-lived fission products has been measured in fresh and burnt UO{sub 2} fuel samples after irradiation in a zero-power reactor. For the first time, short-lived gamma-ray activity from fresh and burnt fuel has been compared and fresh-to-burnt fuel fission rate ratios have been derived. For the measurements, well characterized fresh and burnt fuel samples, with burn-ups up to 46 GWd/t, were irradiated in the zero-power research reactor PROTEUS. Fission rate ratios were derived based on the counting of high-energy gamma-rays above 2200 keV, in order to discriminate against the high intrinsic activity of the burnt fuel. This paper presents the measured fresh-to-burnt fuel fission rate ratios based on the {sup 142}La (2542 keV), {sup 89}Rb (2570 keV), {sup 138}Cs (2640 keV) and {sup 95}Y (3576 keV) high-energy gamma-ray lines. Comparisons are made with the results of Monte Carlo modeling of the experimental configuration, carried out using the MCNPX code. The measured fission rate ratios have 1σ uncertainties of 1.7–3.4%. The comparisons with calculated predictions show an agreement within 1–3σ, although there appears to be a slight bias (∼3%).

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

    International Nuclear Information System (INIS)

    Wright, A.L.

    1994-06-01

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

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

    International Nuclear Information System (INIS)

    Wright, A.L.

    1994-06-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Wright, A.L. [Oak Ridge National Lab., TN (United States)

    1994-06-01

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

  8. Characterization of aerosols containing fissionable elements using solid-state track recorders

    International Nuclear Information System (INIS)

    Roberts, J.H.; Kafalenos, V.P.; Yule, T.J.

    1976-01-01

    An aerosol of U 3 O 3 highly enriched in 235 U was generated with a nebulizer from a suspension of U 3 O 8 powder in distilled water. The aerosol was collected on a membrane filter. Polycarbonate plastic, placed in good contact with the filter, was used to record fission tracks when the package was exposed to known fluences of slow neutrons. Fission-track stars associated with individual particles of U 3 O 8 were observed in the plastic. The fission-track distributions were converted to a particle size distribution for the aerosol. For a log normal distribution the geometric mean and standard deviation can be determined with better than 5% accuracy. This method can be applied to plutonium and other transuranic aerosols. (orig.) [de

  9. The nuclear fission

    International Nuclear Information System (INIS)

    Fiorentino, J.

    1983-01-01

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

  10. Fission fragment angular distributions and fission cross section validation

    International Nuclear Information System (INIS)

    Leong, Lou Sai

    2013-01-01

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

  11. Analysis of C/E results of fission rate ratio measurements in several fast lead VENUS-F cores

    Science.gov (United States)

    Kochetkov, Anatoly; Krása, Antonín; Baeten, Peter; Vittiglio, Guido; Wagemans, Jan; Bécares, Vicente; Bianchini, Giancarlo; Fabrizio, Valentina; Carta, Mario; Firpo, Gabriele; Fridman, Emil; Sarotto, Massimo

    2017-09-01

    During the GUINEVERE FP6 European project (2006-2011), the zero-power VENUS water-moderated reactor was modified into VENUS-F, a mock-up of a lead cooled fast spectrum system with solid components that can be operated in both critical and subcritical mode. The Fast Reactor Experiments for hybrid Applications (FREYA) FP7 project was launched in 2011 to support the designs of the MYRRHA Accelerator Driven System (ADS) and the ALFRED Lead Fast Reactor (LFR). Three VENUS-F critical core configurations, simulating the complex MYRRHA core design and one configuration devoted to the LFR ALFRED core conditions were investigated in 2015. The MYRRHA related cores simulated step by step design peculiarities like the BeO reflector and in pile sections. For all of these cores the fuel assemblies were of a simple design consisting of 30% enriched metallic uranium, lead rodlets to simulate the coolant and Al2O3 rodlets to simulate the oxide fuel. Fission rate ratios of minor actinides such as Np-237, Am-241 as well as Pu-239, Pu-240, Pu-242 and U-238 to U-235 were measured in these VENUS-F critical assemblies with small fission chambers in specially designed locations, to determine the spectral indices in the different neutron spectrum conditions. The measurements have been analyzed using advanced computational tools including deterministic and stochastic codes and different nuclear data sets like JEFF-3.1, JEFF-3.2, ENDF/B7.1 and JENDL-4.0. The analysis of the C/E discrepancies will help to improve the nuclear data in the specific energy region of fast neutron reactor spectra.

  12. Nuclear fission

    International Nuclear Information System (INIS)

    Kodama, T.

    1981-01-01

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

  13. Diamond as a solid state micro-fission chamber for thermal neutron detection at the VR-1 research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Pomorski, Michal; Mer-Calfati, Christine [CEA-LIST, Diamond Sensors Laboratory, 91191, Gif-sur-Yvette (France); Foulon, Francois [CEA, National Institute for Nuclear Science and Technology, 91191, Gif-sur-Yvette (France); Sklenka, Lubomir; Rataj, Jan; Bily, Tomas [Department of Nuclear Reactors,Faculty of Nuclear Science and Physical Engineering, Czech Technical University, V. Holesovickach 2, 180 00 PRAHA 8 (Czech Republic)

    2015-07-01

    Diamond exhibits a combination of properties which makes it attractive for neutron detection in hostile conditions. In the particular case of detection in a nuclear reactor, it is resilient to radiation, exhibits a natural low sensitivity to gamma rays, and its small size (as compared with that of gas ionisation chambers) enables fluency monitoring with a high position resolution. We report here on the use of synthetic CVD diamond as a solid state micro-fission chamber with U-235 converting material for in-core thermal neutron monitoring. Two types of thin diamond detectors were developed for this application. The first type of detector is fabricated using thin diamond membrane obtained by etching low-cost commercially available single crystal CVD intrinsic diamond, so called 'optical grade' material. Starting from a few hundred of micrometre thick samples, the sample is sliced with a laser and then plasma etched down to a few tenths of micrometre. Here we report the result obtained with a 17 μm thick device. The detection surface of this detector is equal to 1 mm{sup 2}. Detectors with surfaces up to 1 cm{sup 2} can be fabricated with this technique. The second type of detector is fabricated by growing successively two thin films of diamond, by the microwave enhanced chemical vapour deposition technique, on HPHT single crystal diamond. A first, a film of boron doped (p+) single crystal diamond, a few microns thick, is deposited. Then a second film of intrinsic diamond with a thickness of a few tens of microns is deposited. This results in a P doped, Intrinsic, Metal structure (PIM) structure in which the intrinsic volume id the active part of the detector. Here we report the results obtained with a 20 μm thick intrinsic whose detection surface is equal to 0.5 mm{sup 2}, with the possibility to enlarge the surface of the detector up to 1 cm{sup 2}. These two types of detector were tested at the VR-1 research reactor at the Czech Technical University in

  14. Diamond as a solid state micro-fission chamber for thermal neutron detection at the VR-1 research reactor

    International Nuclear Information System (INIS)

    Pomorski, Michal; Mer-Calfati, Christine; Foulon, Francois; Sklenka, Lubomir; Rataj, Jan; Bily, Tomas

    2015-01-01

    Diamond exhibits a combination of properties which makes it attractive for neutron detection in hostile conditions. In the particular case of detection in a nuclear reactor, it is resilient to radiation, exhibits a natural low sensitivity to gamma rays, and its small size (as compared with that of gas ionisation chambers) enables fluency monitoring with a high position resolution. We report here on the use of synthetic CVD diamond as a solid state micro-fission chamber with U-235 converting material for in-core thermal neutron monitoring. Two types of thin diamond detectors were developed for this application. The first type of detector is fabricated using thin diamond membrane obtained by etching low-cost commercially available single crystal CVD intrinsic diamond, so called 'optical grade' material. Starting from a few hundred of micrometre thick samples, the sample is sliced with a laser and then plasma etched down to a few tenths of micrometre. Here we report the result obtained with a 17 μm thick device. The detection surface of this detector is equal to 1 mm 2 . Detectors with surfaces up to 1 cm 2 can be fabricated with this technique. The second type of detector is fabricated by growing successively two thin films of diamond, by the microwave enhanced chemical vapour deposition technique, on HPHT single crystal diamond. A first, a film of boron doped (p+) single crystal diamond, a few microns thick, is deposited. Then a second film of intrinsic diamond with a thickness of a few tens of microns is deposited. This results in a P doped, Intrinsic, Metal structure (PIM) structure in which the intrinsic volume id the active part of the detector. Here we report the results obtained with a 20 μm thick intrinsic whose detection surface is equal to 0.5 mm 2 , with the possibility to enlarge the surface of the detector up to 1 cm 2 . These two types of detector were tested at the VR-1 research reactor at the Czech Technical University in Prague. The

  15. Determination of gamma-ray exposure rate from short-lived fission products under criticality accident conditions

    International Nuclear Information System (INIS)

    Yanagisawa, Hiroshi; Ohno, Akio; Aizawa, Eijyu

    2002-01-01

    For the assessment of γ-ray doses from short-lived fission products (FPs) under criticality accident conditions, γ-ray exposure rates varying with time were experimentally determined in the Transient Experiment Critical Facility (TRACY). The data were obtained by reactivity insertion in the range of 1.50 to 2.93$. It was clarified from the experiments that the contribution of γ-ray from short-lived FPs to total exposure during the experiments was evaluated to be 15 to 17%. Hence, the contribution cannot be neglected for the assessment of γ-ray doses under criticality accident conditions. Computational analyses also indicated that γ-ray exposure rates from short-lived FPs calculated with the Monte Carlo code, MCNP4B, and photon sources based on the latest FP decay data, the JENDL FP Decay Data File 2000, well agreed with the experimental results. The exposure rates were, however, extremely underestimated when the photon sources were obtained by the ORIGEN2 code. The underestimation is due to lack of energy-dependent photon emission data for major short-lived FP nuclides in the photon database attached to the ORIGEN2 code. It was also confirmed that the underestimation arose in 1,000 or less of time lapse after an initial power burst. (author)

  16. Investigation of (n, 2n) reaction and fission rates in iron-shielded uranium samples bombarded by 14.9 MeV neutrons

    International Nuclear Information System (INIS)

    Shani, G.

    1976-01-01

    The effect of the thickness of iron shielding on the (n, 2n) reaction rate in a fusion reactor (hybrid) blanket is investigated. The results are compared with the fission rate-dependence. Samples of natural uranium are irradiated with 14 MeV neutrons, with iron slabs of various thickness between the neutron generator target and the samples. Both reactions are threshold reactions but the fact that the 238 U (n, 2n) reaction threshold is at 6 MeV and that of fission is at 2 MeV makes the ratio between the two very much geometry-dependent. Two geometrical effects take place, the 1/r 2 and the build-up. While the build-up affects the (n, 2n) reaction rate, the fission rate is affected more by the 1/r 2 effect. The reason is that both elastic and inelastic scattering end up with neutrons with energy above fission threshold, while only elastic scattering brings high energy neutrons to the sample and causes (n, 2n) reaction. A comparison is made with calculated results where the geometrical effects do not exist. (author)

  17. Monte Carlo analysis of the long-lived fission product neutron capture rates at the Transmutation by Adiabatic Resonance Crossing (TARC) experiment

    International Nuclear Information System (INIS)

    Abánades, A.; Álvarez-Velarde, F.; González-Romero, E.M.; Ismailov, K.; Lafuente, A.; Nishihara, K.; Saito, M.; Stanculescu, A.; Sugawara, T.

    2013-01-01

    Highlights: ► TARC experiment benchmark capture rates results. ► Utilization of updated databases, included ADSLib. ► Self-shielding effect in reactor design for transmutation. ► Effect of Lead nuclear data. - Abstract: The design of Accelerator Driven Systems (ADS) requires the development of simulation tools that are able to describe in a realistic way their nuclear performance and transmutation rate capability. In this publication, we present an evaluation of state of the art Monte Carlo design tools to assess their performance concerning transmutation of long-lived fission products. This work, performed under the umbrella of the International Atomic Energy Agency, analyses two important aspects for transmutation systems: moderation on Lead and neutron captures of 99 Tc, 127 I and 129 I. The analysis of the results shows how shielding effects due to the resonances at epithermal energies of these nuclides affects strongly their transmutation rate. The results suggest that some research effort should be undertaken to improve the quality of Iodine nuclear data at epithermal and fast neutron energy to obtain a reliable transmutation estimation.

  18. Monte Carlo analysis of the long-lived fission product neutron capture rates at the Transmutation by Adiabatic Resonance Crossing (TARC) experiment

    Energy Technology Data Exchange (ETDEWEB)

    Abanades, A., E-mail: abanades@etsii.upm.es [Grupo de Modelizacion de Sistemas Termoenergeticos, ETSII, Universidad Politecnica de Madrid, c/Ramiro de Maeztu, 7, 28040 Madrid (Spain); Alvarez-Velarde, F.; Gonzalez-Romero, E.M. [Centro de Investigaciones Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense, 40, Ed. 17, 28040 Madrid (Spain); Ismailov, K. [Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Lafuente, A. [Grupo de Modelizacion de Sistemas Termoenergeticos, ETSII, Universidad Politecnica de Madrid, c/Ramiro de Maeztu, 7, 28040 Madrid (Spain); Nishihara, K. [Transmutation Section, J-PARC Center, JAEA, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Saito, M. [Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Stanculescu, A. [International Atomic Energy Agency (IAEA), Vienna (Austria); Sugawara, T. [Transmutation Section, J-PARC Center, JAEA, Tokai-mura, Ibaraki-ken 319-1195 (Japan)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer TARC experiment benchmark capture rates results. Black-Right-Pointing-Pointer Utilization of updated databases, included ADSLib. Black-Right-Pointing-Pointer Self-shielding effect in reactor design for transmutation. Black-Right-Pointing-Pointer Effect of Lead nuclear data. - Abstract: The design of Accelerator Driven Systems (ADS) requires the development of simulation tools that are able to describe in a realistic way their nuclear performance and transmutation rate capability. In this publication, we present an evaluation of state of the art Monte Carlo design tools to assess their performance concerning transmutation of long-lived fission products. This work, performed under the umbrella of the International Atomic Energy Agency, analyses two important aspects for transmutation systems: moderation on Lead and neutron captures of {sup 99}Tc, {sup 127}I and {sup 129}I. The analysis of the results shows how shielding effects due to the resonances at epithermal energies of these nuclides affects strongly their transmutation rate. The results suggest that some research effort should be undertaken to improve the quality of Iodine nuclear data at epithermal and fast neutron energy to obtain a reliable transmutation estimation.

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

    International Nuclear Information System (INIS)

    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

  20. 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.

  1. Freshly induced short-lived gamma-ray activity as a measure of fission rates in lightly re-irradiated spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kroehnert, H., E-mail: hanna.kroehnert@psi.c [Paul Scherrer Institut (PSI), OPRA-E07, CH-5232 Villigen (Switzerland); Perret, G., E-mail: gregory.perret@psi.c [Paul Scherrer Institut (PSI), OPRA-E07, CH-5232 Villigen (Switzerland); Murphy, M.F., E-mail: mike.murphy@psi.c [Paul Scherrer Institut (PSI), OPRA-E07, CH-5232 Villigen (Switzerland); Chawla, R., E-mail: rakesh.chawla@epfl.c [Paul Scherrer Institut (PSI), OPRA-E07, CH-5232 Villigen (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2010-12-01

    A new measurement technique has been developed to determine fission rates in burnt fuel, following re-irradiation in a zero-power research reactor. The development has been made in the frame of the LIFE-PROTEUS program at the Paul Scherrer Institute, which aims at characterizing the interfaces between fresh and highly burnt fuel assemblies in modern LWRs. To discriminate against the high intrinsic gamma-ray activity of the burnt fuel, the proposed measurement technique uses high-energy gamma-rays, above 2000 keV, emitted by short-lived fission products freshly produced in the fuel. To demonstrate the feasibility of this technique, a fresh UO{sub 2} sample and a 36 GWd/t burnt UO{sub 2} sample were irradiated in the PROTEUS reactor and their gamma-ray activities were recorded directly after irradiation. For both fresh and the burnt fuel samples, relative fission rates were derived for different core positions, based on the short-lived {sup 142}La (2542 keV), {sup 89}Rb (2570 keV), {sup 138}Cs (2640 keV) and {sup 95}Y (3576 keV) gamma-ray lines. Uncertainties on the inter-position fission rate ratios were mainly due to the uncertainties on the net-area of the gamma-ray peaks and were about 1-3% for the fresh sample, and 3-6% for the burnt one. Thus, for the first time, it has been shown that the short-lived gamma-ray activity, induced in burnt fuel by irradiation in a zero-power reactor, can be used as a quantitative measure of the fission rate. For both fresh and burnt fuel, the measured results agreed, within the uncertainties, with Monte Carlo (MCNPX) predictions.

  2. Utilization of freshly induced high-energy gamma-ray activity as a measure of fission rates in re-irradiated burnt UO{sub 2} fuel

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M. F.; Perret, G. [Paul Scherrer Institut (PSI), CH-5232 Villigen (Switzerland); Krohnert, H.; Chawla, R. [Paul Scherrer Institut (PSI), CH-5232 Villigen (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2009-07-01

    In the frame of the LIFE-PROTEUS (Large-scale Irradiation Fuel Experiments at PROTEUS) program, a measurement technique is being developed to measure fission rates in burnt fuel, following re-irradiation in a zero-power research reactor. In the presented approach, the fission rates are estimated by measuring high energy gamma-rays (above 2000 keV) emitted by short-lived fission products freshly produced in the fuel. Due to their high energies, these gamma-rays can be discriminated against the high intrinsic gamma-ray activity of the burnt fuel, which reaches energies up to 2000 keV. To demonstrate the feasibility of this approach, fresh and burnt fuel samples (with burn-ups varying from 36 to 64 MWd/kg) were irradiated in the PROTEUS reactor at the Paul Scherrer Institut, and their emitted gamma-ray spectra were recorded shortly after irradiation. It was possible, for the first time, to detect the short-lived gamma-ray activity in the high-energy region, even in the presence of the intrinsic gamma-ray background of the burnt fuel samples. Using the short-lived gamma-ray lines {sup 142}La (2542 keV), {sup 89}Rb (2570 keV), 95Y (2632 keV), {sup 138}Cs (2640 keV) and {sup 95}Y (3576 keV), relative fission rates between different core positions were derived for a fresh sample as well as for a burnt sample with a burn-up of 36 MWd/kg. It was shown that, for both the fresh and burnt fuel samples, the measured fission rate ratios agreed well, i.e. within the statistical uncertainties, with calculation results obtained by Monte Carlo simulations. (authors)

  3. Fission via compound states and JπK A. Bohr's channels: what we can learn from recent studies with slow neutrons

    Directory of Open Access Journals (Sweden)

    Furman W.I.

    2012-02-01

    Full Text Available Last data on angular correlations of fission fragments from slow (s-wave neutron induced binary fission of spin-aligned nuclei 235U are discussed in the context of JπK A. Bohrs channels. Special attention is paid to K = 0 channel. Reasons for its suppression are specified for compound nucleus states of negative parity. A brief overview of recent data on T-odd angular correlations in ternary and binary (with emission of a third particle, a neutron or γ-quantum fission induced by slow polarized neutrons is presented. On the basis of the developed theoretical approach it is shown that a valuable information on JπK fission channels at scission point can be inferred from these T-odd angular correlations.

  4. High-Yield Excited Triplet States in Pentacene Self-Assembled Monolayers on Gold Nanoparticles through Singlet Exciton Fission.

    Science.gov (United States)

    Kato, Daiki; Sakai, Hayato; Tkachenko, Nikolai V; Hasobe, Taku

    2016-04-18

    One of the major drawbacks of organic-dye-modified self-assembled monolayers on metal nanoparticles when employed for efficient use of light energy is the fact that singlet excited states on dye molecules can be easily deactivated by means of energy transfer to the metal surface. In this study, a series of 6,13-bis(triisopropylsilylethynyl)pentacene-alkanethiolate monolayer protected gold nanoparticles with different particle sizes and alkane chain lengths were successfully synthesized and were employed for the efficient generation of excited triplet states of the pentacene derivatives by singlet fission. Time-resolved transient absorption measurements revealed the formation of excited triplet states in high yield (172±26 %) by suppressing energy transfer to the gold surface. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Influence of fission gases on the mechanical state of irradiated oxide fuels

    International Nuclear Information System (INIS)

    Cagna, Celine

    2016-01-01

    The irradiation generates in the fuel, fission gases, mainly xenon and krypton, present in dissolved form and in the form of bubbles. This research objective is to contribute to the fission gas bubbles methodology of characterization and thus to bring elements of reference for the models validation. Two approaches are studied. Based on an existing method of bubbles average pressure evaluation by the coupling of three techniques: EPMA, SEM and SIMS, a new complementary method has been developed on an isolated bubble under the surface. The methodology consists in identifying a closed and filled bubble with xenon by microprobe mapping and SEM images and to measure the amount of present gas by SIMS. 3D observation by FIB abrasion provides an estimation of the bubble volume and thus allows to calculate the bubble pressure. At 300 K, an estimation of the pressure levels is obtained on intragranular micrometric bubbles from the fuel pellets center area. Meanwhile, a method of elastic field strain measurement, produced by the presence of pressurized bubbles, is developed by HR-EBSD. A finite element model evaluates the levels of strain around the fission gas bubbles and shows that only nano-metric bubbles generate measurable elastic strain by this technique. First, the method was calibrated from four points bending tests on monocrystalline silicon and ceramics implanted with xenon, allowing to take into account free strains. This step defines the parameters of acquisition and optimum treatment for its application on irradiated fuels. Measurement of elastic strain with HR-EBSD on irradiated fuel is a relative measure that will require further consideration in the choice of the reference. (author) [fr

  6. Behavior of fission products released from severely damaged fuel during the PBF severe fuel damage tests

    International Nuclear Information System (INIS)

    Osetek, D.J.; Cronenberg, A.W.; Hagrman, D.L.; Broughton, J.M.; Rest, J.

    1984-01-01

    The results of fission product release behavior during the first two Power Burst Facility Severe Fuel Damage tests are presented. Measured fission product release is compared with calculated release using temperature dependent release rate correlations and FASTGRASS analysis. The test results indicate that release from fuel of the high volatility fission products (Xe, Kr, I, Cs, and Te) is strongly influenced by parameters other than fuel temperature; namely fuel/fission product morphology, fuel and cladding oxidation state, extent of fuel liquefaction, and quench induced fuel shattering. Fission product transport from the test fuel through the sample system was strongly influenced by chemical effects. Holdup of I and Cs was affected by fission product chemistry, and transport time while Te release was primarily influenced by the extent of zircaloy oxidation. Analysis demonstrates that such integral test data can be used to confirm physical, chemical, and mechanistic models of fission product behavior for severe accident conditions

  7. Experimental validation of CASMO-4E and CASMO-5M for radial fission rate distributions in a westinghouse SVEA-96 Optima2 BWR fuel assembly

    Energy Technology Data Exchange (ETDEWEB)

    Grimm, P.; Perret, G. [Paul Scherrer Inst., CH-5232 Villigen PSI (Switzerland)

    2012-07-01

    Measured and calculated radial total fission rate distributions are compared for the three axial sections of a Westinghouse SVEA-96 Optima2 BWR fuel assembly, comprising 96, 92 and 84 fuel rods, respectively. The measurements were performed on a full-size fuel assembly in the PROTEUS zero-power experimental facility. The measured fission rates are compared to the results of the CASMO-4E and CASMO-5M fuel assembly codes. Detailed measured geometrical data were used in the models, and effects of the surrounding zones of the reactor were taken into account by correction factors derived from MCNPX calculations. The results of the calculations agree well with those of the experiments, with root-mean-square deviations between 1.2% and 1.5% and maximum deviations of 3-4%. The quality of the predictions by CASMO-4E and CASMO-5M is comparable. (authors)

  8. Simulated production rates of exotic nuclei from the ion guide for neutron-induced fission at IGISOL

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Kaj; Al-Adili, Ali; Nilsson, Nicklas; Norlin, Martin; Solders, Andreas [Uppsala University, Department of Physics and Astronomy, Uppsala (Sweden)

    2017-12-15

    An investigation of the stopping efficiency of fission products, in the new ion guide designed for ion production through neutron-induced fission at IGISOL in Jyvaeskylae, Finland, has been conducted. Our simulations take into account the new neutron converter, enabling measurements of neutron-induced fission yields, and thereby provide estimates of the obtained yields as a function of primary proton beam current. Different geometries, targets, and pressures, as well as models for the effective charge of the stopped ions were tested, and optimisations to the setup for higher yields are suggested. The predicted number of ions stopped in the gas lets us estimate the survival probability of the ions reaching the downstream measurements stations. (orig.)

  9. Funneled potential and flux landscapes dictate the stabilities of both the states and the flow: Fission yeast cell cycle.

    Directory of Open Access Journals (Sweden)

    Xiaosheng Luo

    2017-09-01

    Full Text Available Using fission yeast cell cycle as an example, we uncovered that the non-equilibrium network dynamics and global properties are determined by two essential features: the potential landscape and the flux landscape. These two landscapes can be quantified through the decomposition of the dynamics into the detailed balance preserving part and detailed balance breaking non-equilibrium part. While the funneled potential landscape is often crucial for the stability of the single attractor networks, we have uncovered that the funneled flux landscape is crucial for the emergence and maintenance of the stable limit cycle oscillation flow. This provides a new interpretation of the origin for the limit cycle oscillations: There are many cycles and loops existed flowing through the state space and forming the flux landscapes, each cycle with a probability flux going through the loop. The limit cycle emerges when a loop stands out and carries significantly more probability flux than other loops. We explore how robustness ratio (RR as the gap or steepness versus averaged variations or roughness of the landscape, quantifying the degrees of the funneling of the underlying potential and flux landscapes. We state that these two landscapes complement each other with one crucial for stabilities of states on the cycle and the other crucial for the stability of the flow along the cycle. The flux is directly related to the speed of the cell cycle. This allows us to identify the key factors and structure elements of the networks in determining the stability, speed and robustness of the fission yeast cell cycle oscillations. We see that the non-equilibriumness characterized by the degree of detailed balance breaking from the energy pump quantified by the flux is the cause of the energy dissipation for initiating and sustaining the replications essential for the origin and evolution of life. Regulating the cell cycle speed is crucial for designing the prevention and curing

  10. Microscopic theory of singlet exciton fission. III. Crystalline pentacene

    International Nuclear Information System (INIS)

    Berkelbach, Timothy C.; Reichman, David R.; Hybertsen, Mark S.

    2014-01-01

    We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems

  11. Microscopic theory of singlet exciton fission. III. Crystalline pentacene

    Energy Technology Data Exchange (ETDEWEB)

    Berkelbach, Timothy C., E-mail: tcb2112@columbia.edu; Reichman, David R., E-mail: drr2103@columbia.edu [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Hybertsen, Mark S., E-mail: mhyberts@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

    2014-08-21

    We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.

  12. Shell correction approach to nuclear state densities and the competition between fission and neutron emission of 210Po

    International Nuclear Information System (INIS)

    Gottschalk, P.A.; Ledergerber, T.

    Starting from the Hartree-Fock approximation to the grand-canonical partition function we formulate a consistent renormalization of the ground state energy and the intrinsic state density as a function of deformation. The relationship to recent selfconsistent temperature dependent calculations is discussed. The competition between fission and neutron emission, GAMMA sub(f)/GAMMA sub(n)(E), of 210 Po is studied within the framework of the statistical theory as an example. Calculations using renormalized state densities are compared with usual shell model calculations and experimental data. It is found that the usual calculations reflect the incorrect uniform deformation dependence of the shell model spectral function. Important changes due to renormalization are found: a rapid change of the shape of the transition state at approximately 45 MeV excitation energy, GAMMA sub(f)/GAMMA sub(n)(E) remains smaller than unity for all excitation energies and the deformation of the transition state increases after the 'shape transition' at 45 MeV monotonically towards the liquid drop saddle point deformation with a tendency towards slightly larger deformations. (author)

  13. Ternary fission

    International Nuclear Information System (INIS)

    Wagemans, C.

    1991-01-01

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

  14. Some aspects of the nuclear fission process

    International Nuclear Information System (INIS)

    Netter, F.

    1961-01-01

    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 233 , U 235 , Pu 239 , U 238 are described at the beginning of this work. It appears that for U 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 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 235 . Time-of-flight device is used to establish that this 4,5 MeV gamma-ray seems mostly connected with radiative capture. (author) [fr

  15. Study of advanced fission power reactor development for the United States. Volume II

    International Nuclear Information System (INIS)

    1976-01-01

    This report presents the results of a multi-phase research study which had as its objective the comparative study of various advanced fission reactors and evaluation of alternate strategies for their development in the USA through the year 2020. By direction from NSF, ''advanced'' reactors were defined as those which met the dual requirements of (1) offering a significant improvement in fissile fuel utilization as compared to light-water reactors and (2) currently receiving U.S. Government funding. (A detailed study of the LMFBR was specifically excluded, but cursory baseline data were obtained from ERDA sources.) Included initially were the High-Temperature Gas-Cooled Reactor (HTGR), Gas-Cooled Fast Reactor (GCFR), Molten Salt Reactor (MSR), and Light-Water Breeder Reactor (LWBR). Subsequently, the CANDU Heavy Water Reactor (HWR) was included for comparison due to increased interest in its potential. This volume presents the reasoning process and analytical methods utilized to arrive at the conclusions for the overall study

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

    International Nuclear Information System (INIS)

    Rider, B.F.

    1995-01-01

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

  17. Radiochemistry and the Study of Fission

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-14

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

  18. Radiochemistry and the Study of Fission

    International Nuclear Information System (INIS)

    Rundberg, Robert S.

    2016-01-01

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

  19. Fission properties of superheavy nuclei for r -process calculations

    Science.gov (United States)

    Giuliani, Samuel A.; Martínez-Pinedo, Gabriel; Robledo, Luis M.

    2018-03-01

    We computed a new set of static fission properties suited for r -process calculations. The potential energy surfaces and collective inertias of 3640 nuclei in the superheavy region are obtained from self-consistent mean-field calculations using the Barcelona-Catania-Paris-Madrid energy density functional. The fission path is computed as a function of the quadrupole moment by minimizing the potential energy and exploring octupole and hexadecapole deformations. The spontaneous fission lifetimes are evaluated employing different schemes for the collective inertias and vibrational energy corrections. This allows us to explore the sensitivity of the lifetimes to those quantities together with the collective ground-state energy along the superheavy landscape. We computed neutron-induced stellar reaction rates relevant for r -process nucleosynthesis using the Hauser-Feshbach statistical approach and study the impact of collective inertias. The competition between different reaction channels including neutron-induced rates, spontaneous fission, and α decay is discussed for typical r -process conditions.

  20. Nuclear fission as a macroscopic quantum tunneling

    International Nuclear Information System (INIS)

    Takigawa, N.

    1995-01-01

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

  1. Micro plate fission chamber development

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  2. Fission yield measurements at IGISOL

    Science.gov (United States)

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

    2016-06-01

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

  3. 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.

  4. Microscopic description of the competition between spontaneous fission and α -decay in neutron-rich Ra, U and Pu nuclei

    International Nuclear Information System (INIS)

    Rodríguez-Guzmán, R; Robledo, L M

    2017-01-01

    Constrained mean-field calculations, based on the Gogny-D1M energy density functional, have been carried out to describe fission in Ra, U and Pu nuclei with neutron number 144 ≤ N ≤ 176. Fission paths, collective masses and zero-point quantum vibrational and rotational corrections are used to compute the spontaneous fission half-lives. We also pay attention to isomeric states along the considered fission paths. Alpha decay half-lives have also been computed using a parametrization of the Viola-Seaborg formula. Though there exists a strong variance of the predicted fission rates with respect to the details involved in their computation a robust trend is obtained indicating, that with increasing neutron number fission dominates over α -decay. Our results also suggest that a dynamical treatment of pairing correlations is required within the microscopic studies of the fission process in heavy nuclear systems. (paper)

  5. Potentials of fissioning plasmas

    International Nuclear Information System (INIS)

    Karlheinz, Thom.

    1979-01-01

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

  6. Study of electrochemical corrosion parameters in the detection of fission fragments in solid state trace detectors (SSTD)

    International Nuclear Information System (INIS)

    Silva Oliveira, S. da; Rogers, J.D.

    1980-01-01

    The basic properties of the electrochemical corrosion method, for the Makrofol E plastic, irradiated with fission fragments from a 252 Cf source were studied and discussed in this paper. (A.C.A.S.) [pt

  7. Tip model of cold fission

    International Nuclear Information System (INIS)

    Goennenwein, F.; Boersig, B.

    1991-01-01

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

  8. Thermochronology of the South American platform in the state of Sao Paulo, Brazil, through apatite fission tracks

    International Nuclear Information System (INIS)

    Tello Saenz, C.A.; Hadler Neto, J.C.; Iunes, P.J.; Guedes, S.; Hackspacher, P.C.; Ribeiro, L.F.B.; Paulo, S.R.; Osorio A, A.M.

    2005-01-01

    The fission-track method (FTM) in apatite was applied to 45 samples collected in the Serra da Mantiqueira (Mantiqueira mountain range), the Serra do Mar (Mar mountain range), regions next to these mountain ranges and the coastal region between Ubatuba and Santos in the State of Sao Paulo, Brazil, to study the thermochronology of the South American Platform in southeast Brazil and its influence on Santos and Campos basins. The data presented in this work complement the previously presented data on the same region (Tello Saenz et al., 2003. J. S. Am. Earth Sci. 15, 765-774) with 31 new samples analyzed. The weighted mean of the corrected ages from high Mantiqueira (around 1000m), (121+/-6)Ma, coincides with the South Atlantic opening. The fact that its thermal history starts at a relatively low temperature (∼80 deg. C) suggests that the age of ∼120Ma would be the formation age of Serra da Mantiqueira due to a rapid pulse, in which tracks had no time to be retained at the closure temperature, that is ∼120 deg. C. The Serra do Mar presents a more complicated thermal history, with several reactivations indicated by the changes in the slope of its cooling curve. The thermal histories obtained in the regions next to these mountain ranges are compatible with the results mentioned above. The Santos Basin has unconformities that agree with changes in the slope thermal histories of the studied region

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

    International Nuclear Information System (INIS)

    Pandey, A.K.; Sharma, R.C.; Padalkar, S.K.; Kalsi, P.C.; Iyer, R.H.

    1992-01-01

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

  10. Calculations of fission rate distribution in the core of WWER-1000 mock-up on the LR-0 reactor using alternative methods and comparison with results of measurements

    International Nuclear Information System (INIS)

    Zaritskiy, S.; Kovalishin, A.; Tsvetkov, T.; Rypar, V.; Svadlenkova, M.

    2011-01-01

    General review of experimental and calculation researches on WWER-440 and WWER-1000 mock-ups on the reactor LR-0 was introduced on the twentieth Symposium AER. The experimental core fission rate distribution was obtained by means of gamma-scanning of the fuel pins - 140La single peak (1596 keV) measurements and wide energy range (approximately 600-900 keV) measurements. Altogether from 260 to 500 fuel pins were scanned in different experiments. The measurements were arranged in the middle of the fuel (the active part of pin). Pin-to-pin calculations of the WWER-1000 mock-up core fission rate distribution were performed with several codes: Monte Carlo codes MCU-REA/2 and MCNPX with different nuclear data libraries, diffusion code RADAR (63 energy groups library) and code SVL based on Surface Harmonics Method (69 energy groups). Calculated data are compared with experimental ones. The obtained results allow developing the benchmark for core calculations methodologies, evaluating and validating source reliability for the out-of-core (inside and outside pressure vessel) neutron transport calculations. (Authors)

  11. Ternary fission

    Indian Academy of Sciences (India)

    the energy minimization of all possible ternary breakups of a heavy radioactive nucleus. Further, within the TCM we have analysed the competition between different geometries as well as different positioning of the fragments. Also, an attempt was made to calculate the mass distribution of ternary fission process within the ...

  12. Fifty years with nuclear fission

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  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. Capture and Fission rate of 232-Th, 238-U, 237-Np and 239-Pu from spallation neutrons in a huge block of lead.

    CERN Document Server

    Vlachoudis, Vasilis

    2000-01-01

    The study is centered on the research of the incineration possibility of nuclear waste, by the association of a particle accelerator with a multiplying medium of neutrons, in the project "Energy Amplifier" of C. Rubbia. It consists of the experimental determination of the rates of capture and fission of certain elements (232-Th, 238-U, 237-Np and 239-Pu) subjected to a fluence of fast spallation neutrons. These neutrons are produced by the interaction of high kinetic energy protons (several GeV) provided by the CERN-PS accelerator, on a large lead solid volume. The measurement techniques used in this work, are based on the activation of elements in the lead volume and the subsequent gamma spectroscopy of the activated elements, and also by the detection of fission fragment traces. The development, of a Monte Carlo code makes it possible, on one hand, to better understand the relevant processes, and on the other hand, to validate the code, by comparison with measurements, for the design and the construction of...

  15. Fission fragment angular momentum

    International Nuclear Information System (INIS)

    Frenne, D. De

    1991-01-01

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

  16. Fifty years with nuclear fission

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  17. Decay Curves and Half-Lives of Gamma-Emitting States from a Study of Prompt Fission Gamma Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Albinsson, H [Chalmers Univ. of Technology, Goeteborg (SE)

    1971-04-15

    Measurements were made on the time distributions of the prompt gamma radiation emitted from fragments in the thermal-neutron induced fission of 235U. The gamma radiation emitted during different time intervals after the fission event was studied with the help of a collimator, the position of which was changed along the path of the fragments. In this way decay curves were obtained from which half-lives could be estimated. Time components with half-lives of 7.5, 18 and 60 ps were found and their relative intensities were calculated. Half-lives and associated intensities are in good agreement with earlier data from uranium and californium fission. Problems involved in this type of study are discussed. The collimator technique has proved to be effective for determination of half lives down to less than 10 ps

  18. The effects of the physical states of a simulated fission product on the linear thermal expansion of (U0.924Ce0.076)O2

    International Nuclear Information System (INIS)

    Kim, Dong-Joo; Kim, Yong-Soo; Yang, Jae-Ho; Kim, Si-Hyung; Lee, Young-Woo; Kim, Han-Soo

    2006-01-01

    The linear thermal expansions of an (U 0.924 Ce 0.076 )O 2 pellet, doped a simulated fission product (Nd 2 O 3 or Ru), were measured from room temperature to 1673 K in a flowing argon atmosphere using TMA. Nd 2 O 3 and Ru represent the physical states of a fission product, a dissolved oxide and a metallic precipitate, respectively. Using the measured data, the mean coefficients of a linear thermal expansion was obtained as a function of the temperature, and the effects of the physical states of a simulated fission product on the thermal expansion were investigated. In the case of the Nd 2 O 3 forming a dissolved oxide, the thermal expansion of the sample increased and the increment was proportional to the Nd contents, because the melting point of the Nd 2 O 3 was lower than that of UO 2 and although the metallic precipitate hardly affected the crystal structure, the linear thermal expansion also increased with an increasing Ru contents

  19. Fission modelling with FIFRELIN

    International Nuclear Information System (INIS)

    Litaize, Olivier; Serot, Olivier; Berge, Leonie

    2015-01-01

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

  20. NCHS - Births and General Fertility Rates: United States

    Data.gov (United States)

    U.S. Department of Health & Human Services — This dataset includes crude birth rates and general fertility rates in the United States since 1909. The number of states in the reporting area differ historically....

  1. Measurement of fission gas release, internal pressure and cladding creep rate in the fuel pins of PHWR bundle of normal discharge burnup

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, U.K. [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sah, D.N., E-mail: dnsah@barc.gov.i [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Rath, B.N.; Anantharaman, S. [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2009-08-01

    Fuel pins of a Pressurised Heavy Water Reactor (PHWR) fuel bundle discharged from Narora Atomic Power Station unit no. 1 after attaining a fuel burnup of 7528 MWd/tU have been subjected to two types of studies, namely (i) puncture test to estimate extent of fission gas release and internal pressure in the fuel pin and (ii) localized heating of the irradiated fuel pin to measure the creep rate of the cladding in temperature range 800 deg. C - 900 deg. C. The fission gas release in the fuel pins from the outer ring of the bundle was found to be about 8%. However, only marginal release was found in fuel pins from the middle ring and the central fuel pin. The internal gas pressure in the outer fuel pin was measured to be 0.55 +- 0.05 MPa at room temperature. In-cell isothermal heating of a small portion of the outer fuel pins was carried out at 800 deg. C, 850 deg. C and 900 deg. C for 10 min and the increase in diameter of the fuel pin was measured after heat treatment. Creep rates of the cladding obtained from the measurement of the diameter change of the cladding due to heating at 800 deg. C, 850 deg. C and 900 deg. C were found respectively to be 2.4 x 10{sup -5} s{sup -1}, 24.6 x 10{sup -5} s{sup -1} and 45.6 x 10{sup -5} s{sup -1}.

  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. 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...

  4. Analytical measurements of fission products during a severe nuclear accident

    Science.gov (United States)

    Doizi, D.; Reymond la Ruinaz, S.; Haykal, I.; Manceron, L.; Perrin, A.; Boudon, V.; Vander Auwera, J.; tchana, F. Kwabia; Faye, M.

    2018-01-01

    The Fukushima accident emphasized the fact that ways to monitor in real time the evolution of a nuclear reactor during a severe accident remain to be developed. No fission products were monitored during twelve days; only dose rates were measured, which is not sufficient to carry out an online diagnosis of the event. The first measurements were announced with little reliability for low volatile fission products. In order to improve the safety of nuclear plants and minimize the industrial, ecological and health consequences of a severe accident, it is necessary to develop new reliable measurement systems, operating at the earliest and closest to the emission source of fission products. Through the French program ANR « Projet d'Investissement d'Avenir », the aim of the DECA-PF project (diagnosis of core degradation from fission products measurements) is to monitor in real time the release of the major fission products (krypton, xenon, gaseous forms of iodine and ruthenium) outside the nuclear reactor containment. These products are released at different times during a nuclear accident and at different states of the nuclear core degradation. Thus, monitoring these fission products gives information on the situation inside the containment and helps to apply the Severe Accident Management procedures. Analytical techniques have been proposed and evaluated. The results are discussed here.

  5. Analytical measurements of fission products during a severe nuclear accident

    Directory of Open Access Journals (Sweden)

    Doizi D.

    2018-01-01

    Full Text Available The Fukushima accident emphasized the fact that ways to monitor in real time the evolution of a nuclear reactor during a severe accident remain to be developed. No fission products were monitored during twelve days; only dose rates were measured, which is not sufficient to carry out an online diagnosis of the event. The first measurements were announced with little reliability for low volatile fission products. In order to improve the safety of nuclear plants and minimize the industrial, ecological and health consequences of a severe accident, it is necessary to develop new reliable measurement systems, operating at the earliest and closest to the emission source of fission products. Through the French program ANR « Projet d’Investissement d’Avenir », the aim of the DECA-PF project (diagnosis of core degradation from fission products measurements is to monitor in real time the release of the major fission products (krypton, xenon, gaseous forms of iodine and ruthenium outside the nuclear reactor containment. These products are released at different times during a nuclear accident and at different states of the nuclear core degradation. Thus, monitoring these fission products gives information on the situation inside the containment and helps to apply the Severe Accident Management procedures. Analytical techniques have been proposed and evaluated. The results are discussed here.

  6. Germanium-gated γ–γ fast timing of excited states in fission fragments using the EXILL and FATIMA spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Régis, J.-M., E-mail: regis@ikp.uni-koeln.de [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Simpson, G.S., E-mail: Gary.Simpson@uws.ac.uk [Laboratoire de Physique Subatomique et de Cosmologie Grenoble, 53, rue des Martyrs, 38026 Grenoble Cedex (France); School of Engineering, University of the West of Scotland, Paisley PA1 2BE, Scotland (United Kingdom); Blanc, A. [Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9 (France); France, G. de [Grand Accélérateur National d' Ions Lourds, Bd Henri Becquerel, BP 55027, 14076 Caen Cedex 05 (France); Jentschel, M.; Köster, U.; Mutti, P. [Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9 (France); Paziy, V. [Grupo de Física Nuclear, FAMN, Universidad Complutense, CEI Moncloa, 28040 Madrid (Spain); Saed-Samii, N. [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Soldner, T. [Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9 (France); Ur, C.A. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Urban, W. [Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9 (France); Faculty of Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw (Poland); Bruce, A.M. [School of Computing, Engineering and Mathematics, University of Brighton, Lewes Road, Brighton BN2 4GJ (United Kingdom); Drouet, F. [Laboratoire de Physique Subatomique et de Cosmologie Grenoble, 53, rue des Martyrs, 38026 Grenoble Cedex (France); and others

    2014-11-01

    A high-granularity mixed spectrometer consisting of high-resolution Ge and very fast LaBr{sub 3}(Ce)-scintillator detectors has been installed around a fission target at the cold-neutron guide PF1B of the high-flux reactor of the Institut Laue–Langevin. Lifetimes of excited states in the range of 10 ps to 10 ns can be measured in around 100 exotic neutron-rich fission fragments using Ge-gated LaBr{sub 3}(Ce)–LaBr{sub 3}(Ce) or Ge–Ge–LaBr{sub 3}(Ce)–LaBr{sub 3}(Ce) coincidences. We report on various characteristics of the EXILL and FATIMA spectrometer for the energy range of 40 keV up to 6.8 MeV and present results of ps-lifetime test measurements in a fission fragment. The results are discussed with respect to possible systematic errors induced by background contributions.

  7. 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...

  8. A stochastic approach to fission

    International Nuclear Information System (INIS)

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

    1992-01-01

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

  9. STATE CREDIT RATING MARK: PRESENT DOMESTIC REALITIES

    OpenAIRE

    Kovalko, N. M.

    2017-01-01

    The article discusses the problematic aspects of credit ratings and ranking. The economic and legal aspects of ranking relations are addressed. It is concluded that a low credit standing of Ukraine is a sign of our country’s low debt sustainability.It is proved that both for Ukraine and for economically developed countries, the issue of credit ratings is quite important, and at times problematic. The issue is related to the development of the national and international financial credit resour...

  10. Nuclear fission with a Langevin equation

    International Nuclear Information System (INIS)

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

    1992-01-01

    A microscopically derived Langevin equation is applied to thermally induced nuclear fission. An important memory effect is pointed out and discussed. A strong friction coefficient, estimated from microscopic quantities, tends to decrease the stationary limit of the fission rate and to increase the transient time. The calculations are performed with a collective mass depending on the collective variable and with a constant mass. Fission rates calculated at different temperatures are shown and compared with previous available results. (author) 23 refs.; 7 figs

  11. Craving Ravens: Individual ‘haa’ Call Rates at Feeding Sites as Cues to Personality and Levels of Fission-Fusion Dynamics?

    Directory of Open Access Journals (Sweden)

    Georgine Szipl

    2014-08-01

    Full Text Available Common ravens aggregate in large non-breeder flocks for roosting and foraging until they achieve the status of territorial breeders. When discovering food, they produce far-reaching yells or ‘haa’ calls, which attract conspecifics. Due to the high levels of fission-fusion dynamics in non-breeders’ flocks, assemblies of feeding ravens were long thought to represent anonymous aggregations. Yet, non-breeders vary in their degree of vagrancy, and ‘haa’ calls convey individually distinct acoustic features, which are perceived by conspecifics. These findings give rise to the assumption that raven societies are based on differential social relationships on an individual level. We investigated the occurrence of ‘haa’ calling and individual call rates in a group of individually marked free-ranging ravens. Calling mainly occurred in subadult and adult females, which showed low levels of vagrancy. Call rates differed significantly between individuals and with residency status, and were correlated with calling frequency and landing frequency. Local ravens called more often and at higher rates, and were less likely to land at the feeding site than vagrant birds. The results are discussed with respect to individual degrees of vagrancy, which may have an impact on social knowledge and communication in this species.

  12. Equation of state for L.M.F.B.R. fuel (measurement of fission gas release during transients)

    International Nuclear Information System (INIS)

    Combette, P.; Barthelemy, P.

    1979-01-01

    A sample of fuel (UO 2 or UPuO 2 ) can be heated by fission in a heating transient up to energy deposition 4000 j/g, in the Silene reactor. The Kistler type capsule, the calorimeter device and the radiochemical analysis of fission products enable the pressure pulse and the fuel energy deposition to be measured. So, the relationship between the fuel vapour pressure and the fuel specific energy can be deduced. Peaks pressure (about 1 MPa) coming from fresh UO 2 vaporization, have been measured on a 7 milliseconds time scale. There is a good agreement with the E.O.S. for fresh UO 2 , which is well known for low pressure (1 MPa). Numerous tests have been done with 93% enriched UO 2 and a first test with highly active fuel containing plutonium (15 at %) has been performed. The capsule allows the released gas coming from the irradiated fuel to be retained for measurements and analysis. To investigate the mode of fuel disruption, in-pile fission-heated fuel pellets has been recorded by high speed cinematography

  13. United States Nuclear Regulatory Commission research program on core debris/concrete interactions and ex-vessel fission-product release

    International Nuclear Information System (INIS)

    Burson, S.B.

    1987-01-01

    The study of core debris/concrete interaction phenomena has been a significant element of the NRC's Severe Accident Research Program for a number of years. The CORCON and VANESA codes used to predict the consequences of high-temperature debris attack on concrete and fission-product aerosol release are state-of-the-art computational tools. The major thrust of current NRC sponsored research focuses on the refinement, verification, and validation of these codes. An overview of the analytical and experimental aspects of the NRC research program is presented

  14. Extraction chromatography of fission products

    International Nuclear Information System (INIS)

    Bonnevie-Svendsen, M.; Goon, K.

    1978-01-01

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

  15. (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.

  16. Evaluation of axial fission gas transport in power ramping experiments

    International Nuclear Information System (INIS)

    Kinoshita, Motoyasu

    1986-01-01

    The LINUS code calculates advective and diffusional transport of fission gas towards an upper plenum through the pellet-cladding gap. The basic equations were modified for analyzing a multi-component gas mixture in the gap and also for dealing with opening and/or closing of the gap, which induces additional axial gas flow. Analysis of the Petten ramp experiment shows that helium pressurization is effective in suppressing an ascending rate of fission gas concentration. After the maximum concentration is achieved through power ramping, the gas concentration could be described by a steady state analytical solution which does not depend on the filling gas pressure. (author)

  17. Fission theory and actinide fission data

    Energy Technology Data Exchange (ETDEWEB)

    Michaudon, A.

    1975-06-01

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

  18. Nuclear fission and reactions

    International Nuclear Information System (INIS)

    Anon.

    1975-01-01

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

  19. Calibration of a special neutron dosemeter based on solid-state track detectors and fission radiators in various neutron fields

    International Nuclear Information System (INIS)

    Doerschel, B.; Krusche, M.; Schuricht, V.

    1980-01-01

    The calibration of a personnel neutron dosemeter in different neutron fields is described. The badge-like dosemeter contains 5 detectors: polycarbonate foil (10 μm, Makrofol KG), 232 Th, natural uranium, natural uranium with boron, and natural uranium with cadmium. Detector sensitivity and calibration factors have been calculated and measured in radiation fields of 252 Cf fission neutrons, WWR-S reactor neutrons with and without Cd and Fe shielding, 3-MeV (d,t) generator neutrons, and 238 PuBe neutrons. Measurement range and achievable accuracy are discussed from the point of view of applying the dosemeter in routine and emergency uses

  20. Advanced burnup calculation code system in a subcritical state with continuous-energy Monte Carlo code for fusion-fission hybrid reactor

    International Nuclear Information System (INIS)

    Matsunaka, Masayuki; Ohta, Masayuki; Miyamaru, Hiroyuki; Murata, Isao

    2009-01-01

    The fusion-fission (FF) hybrid reactor is a promising energy source that is thought to act as a bridge between the existing fission reactor and the genuine fusion reactor in the future. The burnup calculation system that aims at precise burnup calculations of a subcritical system was developed for the detailed design of the FF hybrid reactor, and the system consists of MCNP, ORIGEN, and postprocess codes. In the present study, the calculation system was substantially modified to improve the calculation accuracy and at the same time the calculation speed as well. The reaction rate estimation can be carried out accurately with the present system that uses track-length (TL) data in the continuous-energy treatment. As for the speed-up of the reaction rate calculation, a new TL data bunching scheme was developed so that only necessary TL data are used as long as the accuracy of the point-wise nuclear data is conserved. With the present system, an example analysis result for our proposed FF hybrid reactor is described, showing that the computation time could really be saved with the same accuracy as before. (author)

  1. Modelling isothermal fission gas release

    International Nuclear Information System (INIS)

    Uffelen, P. van

    2002-01-01

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

  2. Investigation of spatial distribution of fission-rate of natural uranium nuclei in the blanket of electronuclear setup 'Energy plus Transmutation' at Dubna Nuclotron proton beam at energy 1.5 GeV

    International Nuclear Information System (INIS)

    Hashemi-Nezhad, S.R.; Zhuk, I.V.; Kievets, M.; Krivopustov, M.I.; Sosnin, A.N.; Westmeier, W.; Brandt, R.

    2008-01-01

    The 'Energy plus Transmutation' experimental setup of the Veksler and Baldin Laboratory of High Energy Physics within the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, is a lead target (with a diameter of 8.4 cm and length of 45.6 cm) surrounded by a uranium blanket (weight 206.4 kg of natural uranium). A polyethylene plus cadmium shield is placed around the target-blanket assembly to modify the spallation and fission neutron spectra in the system. The setup was irradiated by a proton beam of energy 1.5 GeV using the Nuclotron accelerator. The spatial distribution of natural uranium fission-rate in the assembly and fission-rate in the blanket was determined experimentally and compared with Monte Carlo predictions using the MCNPX 2.6C code. Besides neutron-induced fission the calculations include the Nat U(p,f), Nat U(π,f) as well as Nat U(γ,f) reactions. Good agreement between the experimental and calculation results was obtained. The possible sources of errors in the experiment and calculations are discussed in detail

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1961-07-01

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

  4. Measurements of fission yields

    International Nuclear Information System (INIS)

    Denschlag, H.O.

    2000-01-01

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

  5. Radiochemical studies on fission

    Energy Technology Data Exchange (ETDEWEB)

    None

    1973-07-01

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

  6. Higher USA State Resident Neuroticism Is Associated With Lower State Volunteering Rates.

    Science.gov (United States)

    McCann, Stewart J H

    2017-12-01

    Highly neurotic persons have dispositional characteristics that tend to precipitate social anxiety that discourages formal volunteering. With the 50 American states as analytical units, Study 1 found that state resident neuroticism correlated highly ( r = -.55) with state volunteering rates and accounted for another 26.8% of the volunteering rate variance with selected state demographics controlled. Study 2 replicated Study 1 during another period and extended the association to college student, senior, secular, and religious volunteering rates. Study 3 showed state resident percentages engaged in other social behaviors involving more familiarity and fewer demands than formal volunteering related to state volunteering rates but not to neuroticism. In Study 4, state resident neuroticism largely accounted statistically for relations between state volunteering rates and state population density, collectivism, social capital, Republican preference, and well-being. This research is the first to show that state resident neuroticism is a potent predictor of state volunteering rates.

  7. On the rate determining step in fission gas release from high burn-up water reactor fuel during power transients

    International Nuclear Information System (INIS)

    Walker, C.T.; Mogensen, M.

    1987-01-01

    The radial distribution of grain boundary gas in a PWR and a BWR fuel is reported. The measurements were made using a new approach involving X-ray fluorescence analysis and electron probe microanalysis. In both fuels the concentration of grain boundary gas was much higher than hitherto suspected. The gas was mainly contained in the bubble/pore structure. The factors that determined the fraction of gas released from the grains and the level of gas retention on the grain boundaries are identified and discussed. The variables involved are the local fuel stoichiometry, the amount of open porosity, the magnitude of the local compressive hydrostatic stress and the interaction of metallic precipitates with gas bubbles on the grain faces. It is concluded that under transient conditions the interlinkage of gas bubbles on the grain faces and the subsequent formation of grain edge tunnels is the rate determining step for gas release; at least when high burn-up fuel is involved. (orig.)

  8. The resonance neutron fission on heavy nuclei

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  9. Effect of excited states on thermonuclear reaction rates

    International Nuclear Information System (INIS)

    Sargood, D.G.

    1983-01-01

    Values of the ratio of the thermonuclear reaction rate of a reaction, with target nuclei in a thermal distribution of energy states, to the reaction rate with all target nuclei in their ground states are tabulated for neutron, proton and α-particle induced reactions on the naturally occurring nuclei from 20 Ne to 70 Zn, at temperatures of 1, 2, 3.5 and 5x10 9 K. The ratios are determined from reaction rates based on statistical model cross sections

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

    International Nuclear Information System (INIS)

    Hasan, A.A.

    1984-12-01

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

  12. Fission products collecting devices

    International Nuclear Information System (INIS)

    Matsumoto, Hiroshi

    1979-01-01

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

  13. Energy released in fission

    International Nuclear Information System (INIS)

    James, M.F.

    1969-05-01

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

  14. Do State-Based Policies Have an Impact on Teen Birth Rates and Teen Abortion Rates in the United States?

    Science.gov (United States)

    Chevrette, Marianne; Abenhaim, Haim Arie

    2015-10-01

    The United States has one of the highest teen birth rates among developed countries. Interstate birth rates and abortion rates vary widely, as do policies on abortion and sex education. The objective of our study is to assess whether US state-level policies regarding abortion and sexual education are associated with different teen birth and teen abortion rates. We carried out a state-level (N = 51 [50 states plus the District of Columbia]) retrospective observational cross-sectional study, using data imported from the National Vital Statistics System. State policies were obtained from the Guttmacher Institute. We used descriptive statistics and regression analysis to study the association of different state policies with teen birth and teen abortion rates. The state-level mean birth rates, when stratifying between policies protective and nonprotective of teen births, were not statistically different-for sex education policies, 39.8 of 1000 vs 45.1 of 1000 (P = .2187); for mandatory parents' consent to abortion 45 of 1000, vs 38 of 1000 when the minor could consent (P = .0721); and for deterrents to abortion, 45.4 of 1000 vs 37.4 of 1000 (P = .0448). Political affiliation (35.1 of 1000 vs 49.6 of 1000, P births. Lower teen abortion rates were, however, associated with restrictive abortion policies, specifically lower in states with financial barriers, deterrents to abortion, and requirement for parental consent. While teen birth rates do not appear to be influenced by state-level sex education policies, state-level policies that restrict abortion appear to be associated with lower state teen abortion rates. Copyright © 2015 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

  15. Exchange rate predictability and state-of-the-art models

    OpenAIRE

    Yeșin, Pınar

    2016-01-01

    This paper empirically evaluates the predictive performance of the International Monetary Fund's (IMF) exchange rate assessments with respect to future exchange rate movements. The assessments of real trade-weighted exchange rates were conducted from 2006 to 2011, and were based on three state-of-the-art exchange rate models with a medium-term focus which were developed by the IMF. The empirical analysis using 26 advanced and emerging market economy currencies reveals that the "diagnosis" of ...

  16. 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.

  17. HAC and fission reactors

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  18. 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 la frequence

  19. First-Principle Characterization for Singlet Fission Couplings.

    Science.gov (United States)

    Yang, Chou-Hsun; Hsu, Chao-Ping

    2015-05-21

    The electronic coupling for singlet fission, an important parameter for determining the rate, has been found to be too small unless charge-transfer (CT) components were introduced in the diabatic states, mostly through perturbation or a model Hamiltonian. In the present work, the fragment spin difference (FSD) scheme was generalized to calculate the singlet fission coupling. The largest coupling strength obtained was 14.8 meV for two pentacenes in a crystal structure, or 33.7 meV for a transition-state structure, which yielded a singlet fission lifetime of 239 or 37 fs, generally consistent with experimental results (80 fs). Test results with other polyacene molecules are similar. We found that the charge on one fragment in the S1 diabatic state correlates well with FSD coupling, indicating the importance of the CT component. The FSD approach is a useful first-principle method for singlet fission coupling, without the need to include the CT component explicitly.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  1. Premature death rates diverge in the United States

    Science.gov (United States)

    An NCI press release on a study that shows premature death rates have declined in the United States among Hispanics, blacks, and Asian/Pacific Islanders but increased among whites and American Indian/Alaska Natives.

  2. Attachment of gaseous fission products to aerosols

    International Nuclear Information System (INIS)

    Skyrme, G.

    1985-01-01

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

  3. State estimation for networked control systems using fixed data rates

    Science.gov (United States)

    Liu, Qing-Quan; Jin, Fang

    2017-07-01

    This paper investigates state estimation for linear time-invariant systems where sensors and controllers are geographically separated and connected via a bandwidth-limited and errorless communication channel with the fixed data rate. All plant states are quantised, coded and converted together into a codeword in our quantisation and coding scheme. We present necessary and sufficient conditions on the fixed data rate for observability of such systems, and further develop the data-rate theorem. It is shown in our results that there exists a quantisation and coding scheme to ensure observability of the system if the fixed data rate is larger than the lower bound given, which is less conservative than the one in the literature. Furthermore, we also examine the role that the disturbances have on the state estimation problem in the case with data-rate limitations. Illustrative examples are given to demonstrate the effectiveness of the proposed method.

  4. Thermochromatographic investigations of fission product transport and chemistry

    International Nuclear Information System (INIS)

    Growcock, F.B.; Aronson, S.; Friedlander, M.; Skalyo, J. Jr.; Hosseini, A.; Taylor, R.D.

    1978-01-01

    A thermochromatographic technique has been developed to investigate the chemical states of fission products from irradiated fuel as well as in fission product simulation studies. Some recent work on iodine transport and on release of fission products from irradiated fuel kernels will be discussed

  5. Mass dependence of positive pion-induced fission

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  6. Fission Research at IRMM

    Directory of Open Access Journals (Sweden)

    Al-Adili A.

    2010-03-01

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

  7. On rate-state and Coulomb failure models

    Science.gov (United States)

    Gomberg, J.; Beeler, N.; Blanpied, M.

    2000-01-01

    We examine the predictions of Coulomb failure stress and rate-state frictional models. We study the change in failure time (clock advance) Δt due to stress step perturbations (i.e., coseismic static stress increases) added to "background" stressing at a constant rate (i.e., tectonic loading) at time t0. The predictability of Δt implies a predictable change in seismicity rate r(t)/r0, testable using earthquake catalogs, where r0 is the constant rate resulting from tectonic stressing. Models of r(t)/r0, consistent with general properties of aftershock sequences, must predict an Omori law seismicity decay rate, a sequence duration that is less than a few percent of the mainshock cycle time and a return directly to the background rate. A Coulomb model requires that a fault remains locked during loading, that failure occur instantaneously, and that Δt is independent of t0. These characteristics imply an instantaneous infinite seismicity rate increase of zero duration. Numerical calculations of r(t)/r0 for different state evolution laws show that aftershocks occur on faults extremely close to failure at the mainshock origin time, that these faults must be "Coulomb-like," and that the slip evolution law can be precluded. Real aftershock population characteristics also may constrain rate-state constitutive parameters; a may be lower than laboratory values, the stiffness may be high, and/or normal stress may be lower than lithostatic. We also compare Coulomb and rate-state models theoretically. Rate-state model fault behavior becomes more Coulomb-like as constitutive parameter a decreases relative to parameter b. This is because the slip initially decelerates, representing an initial healing of fault contacts. The deceleration is more pronounced for smaller a, more closely simulating a locked fault. Even when the rate-state Δt has Coulomb characteristics, its magnitude may differ by some constant dependent on b. In this case, a rate-state model behaves like a modified

  8. Quality Rating and Improvement System State Evaluations and Research

    Science.gov (United States)

    Ferguson, Daniel

    2016-01-01

    A quality rating and improvement system (QRIS) is a method used by states and local jurisdictions to assess the level of quality of child care and early education programs, improve quality, and convey quality ratings to parents and other consumers. A typical QRIS incorporates the following components: quality standards for participating providers;…

  9. Finite fission chain length and symmetry around prompt-criticality

    International Nuclear Information System (INIS)

    Xie Qilin; Yin Yanpeng; Gao Hui; Huang Po; Fang Xiaoqiang

    2012-01-01

    Probability distribution of finite fission chain length was derived by assuming that all neutrons behave identically. Finite fission chain length was also calculated using a zero-dimension Monte-Carlo method based on point kinetics. Then symmetry of finite fission chain length probability distribution around prompt-criticality was deduced, which helps understanding the emission rate of delayed neutrons and initiation of fission chain in super-prompt-critical system. (authors)

  10. Equilibrium fission model calculations

    International Nuclear Information System (INIS)

    Beckerman, M.; Blann, M.

    1976-01-01

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

  11. Introduction to State Estimation of High-Rate System Dynamics.

    Science.gov (United States)

    Hong, Jonathan; Laflamme, Simon; Dodson, Jacob; Joyce, Bryan

    2018-01-13

    Engineering systems experiencing high-rate dynamic events, including airbags, debris detection, and active blast protection systems, could benefit from real-time observability for enhanced performance. However, the task of high-rate state estimation is challenging, in particular for real-time applications where the rate of the observer's convergence needs to be in the microsecond range. This paper identifies the challenges of state estimation of high-rate systems and discusses the fundamental characteristics of high-rate systems. A survey of applications and methods for estimators that have the potential to produce accurate estimations for a complex system experiencing highly dynamic events is presented. It is argued that adaptive observers are important to this research. In particular, adaptive data-driven observers are advantageous due to their adaptability and lack of dependence on the system model.

  12. Fission product behaviour in the primary circuit of an HTR

    International Nuclear Information System (INIS)

    Decken, C.B. von der; Iniotakis, N.

    1981-01-01

    The knowledge of fission product behaviour in the primary circuit of a High Temperature Reactor (HTR) is an essential requirement for the estimations of the availability of the reactor plant in normal operation, of the hazards to personnel during inspection and repair and of the potential danger to the environment from severe accidents. On the basis of the theoretical and experimental results obtained at the ''Institute for Reactor Components'' of the KFA Juelich /1/,/2/ the transport- and deposition behaviour of the fission- and activation products in the primary circuit of the PNP-500 reference plant has been investigated thoroughly. Special work had been done to quantify the uncertainties of the investigations and to calculate or estimate the dose rate level at different components of the primary cooling circuit. The contamination and the dose rate level in the inspection gap in the reactor pressure vessel is discussed in detail. For these investigations in particular the surface structure and the composition of the material, the chemical state of the fission products in the cooling gas, the composition of the cooling gas and the influence of dust on the transport- and deposition behaviour of the fission products have been taken into account. The investigations have been limited to the nuclides Ag-110m; Cs-134 and Cs-137

  13. Fission mass yields of excited medium heavy nuclei

    International Nuclear Information System (INIS)

    Sandulescu, A.; Depta, K.; Herrmann, R.; Greiner, W.; Scheid, W.

    1985-01-01

    The mass distributions resulting from the fission of excited medium mass nuclei are discussed on the basis of the fragmentation theory. It is shown that very asymmetric fission events can be expected with rates which are only a few orders of magnitude smaller than the rates for symmetric fission. As an example a calculation of the fission mass distribution of the excited 172 Yb compound nucleus is presented. This mass distribution reveals observable structures over the entire range of the mass asymmetry due to valleys in the potential energy surface for fission fragments with closed proton and neutron shells

  14. Fission gas behaviour in water reactor fuels

    International Nuclear Information System (INIS)

    2002-01-01

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

  15. States with low non-fatal injury rates have high fatality rates and vice-versa.

    Science.gov (United States)

    Mendeloff, John; Burns, Rachel

    2013-05-01

    State-level injury rates or fatality rates are sometimes used in studies of the impact of various safety programs or other state policies. How much does the metric used affect the view of relative occupational risks among U.S. states? This paper uses a measure of severe injuries (fatalities) and of less severe injuries (non-fatal injuries with days away from work, restricted work, or job transfer-DART) to examine that issue. We looked at the correlation between the average DART injury rate (from the BLS Survey of Occupational Injuries and Illnesses) and an adjusted average fatality rate (from the BLS Census of Fatal Occupational Injuries) in the construction sector for states for 2003-2005 and for 2006-2008. The RAND Human Subjects Protection Committee determined that this study was exempt from review. The correlations between the fatal and non-fatal injury rates were between -0.30 and -0.70 for all construction and for the subsector of special trade contractors. The negative correlation was much smaller between the rate of fatal falls from heights and the rate of non-fatal falls from heights. Adjusting for differences in the industry composition of the construction sector across states had minor effects on these results. Although some have suggested that fatal and non-fatal injury rates should not necessarily be positively correlated, no one has suggested that the correlation is negative, which is what we find. We know that reported non-fatal rates are influenced by workers' compensation benefits and other factors. Fatality rates appear to be a more valid measure of risk. Efforts to explain the variations that we find should be undertaken. Copyright © 2012 Wiley Periodicals, Inc.

  16. Terrestrial gamma dose rate in Pahang state Malaysia

    International Nuclear Information System (INIS)

    Gabdo, H.T.; Federal College of Education, Yola; Ramli, A.T.; Sanusi, M.S.; Saleh, M.A.; Garba, N.N.; Ahmadu Bello University, Zaria

    2014-01-01

    Environmental terrestrial gamma radiations (TGR) were measured in Pahang state Malaysia between January and April 2013. The TGR dose rates ranged from 26 to 750 nGy h -1 . The measurements were done based on geology and soil types of the area. The mean TGR dose rate was found to be 176 ± 5 nGy h -1 . Few areas of relatively enhanced activity were located in Raub, Temerloh, Bentong and Rompin districts. These areas have external gamma dose rates of between 500 and 750 nGy h -1 . An Isodose map of the state was produced using ArcGIS9 software version 9.3. To evaluate the radiological hazard due to terrestrial gamma dose, the annual effective dose equivalent and the mean population weighted dose rate were calculated and found to be 0.22 mSv year -1 and 168 nGy h -1 respectively. (author)

  17. Overview of tritium fast-fission yields

    International Nuclear Information System (INIS)

    Tanner, J.E.

    1981-03-01

    Tritium production rates are very important to the development of fast reactors because tritium may be produced at a greater rate in fast reactors than in light water reactors. This report focuses on tritium production and does not evaluate the transport and eventual release of the tritium in a fast reactor system. However, if an order-of-magnitude increase in fast fission yields for tritium is confirmed, fission will become the dominant production source of tritium in fast reactors

  18. Fission level densities

    International Nuclear Information System (INIS)

    Maslov, V.M.

    1998-01-01

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

  19. Separation of short-lived fission products

    International Nuclear Information System (INIS)

    Tamai, Tadaharu; Ohyoshi, Emiko; Ohyoshi, Akira; Kiso, Yoshiyuki; Shinagawa, Mutsuaki.

    1976-01-01

    A rbief review is presented on the various methods of separation available for both gaseous and liquid states, for the separation of short-lived fission products formed by binary fission of neutron irradiated uranium. The means available for gaseous state are the hot atom reaction, the hydride method and on-line mass separation. For liquid state, use can be made of precipitation, ionic or atomic exchange, solvent extraction and paper electrophoresis. Particular reference is made to electrophoretic separation of ions produced by fission in aqueous solution of uranium. The principle of electrophoretic separation and the procedures for separating the element of interest from the other fission products are outlined, with reference made to the results obtained with the method by the present authors. The elements in question are alkalines, alkaline earths, rare earths, halogens, selenium and

  20. Investigation of exotic fission modes

    International Nuclear Information System (INIS)

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

    2002-01-01

    Fission approach to the cluster radioactivities and α-decay has been systematically developed during the last two decades. A more complex process, the ternary fission, was observed since 1946 both in neutron-induced and spontaneous fission. We obtained interesting results concerning the binary fission saddle-point reflection asymmetric nuclear shapes, and we can explain how a possible nuclear quasimolecular state is formed during the 10 Be accompanied cold fission of 252 Cf. The equilibrium nuclear shapes in fission theory are usually determined by minimizing the deformation energy for a given surface equation. We developed a method allowing to obtain a very general saddle-point shape as a solution of a differential equation without an a priori introduction of a shape parametrization. In the approach based on a liquid drop model (LDM), saddle-point shapes are always reflection symmetric: the deformation energy increases with the mass-asymmetry parameter η = (A 1 - A 2 )/(A 1 + A 2 ). By adding the shell corrections to the LDM deformation energy, we obtained minima at a finite mass asymmetry for parent nuclei 238 U, 232,228 Th in agreement with experiments. This correction was calculated phenomenologically. A technique based on the fragment identification by using triple γ coincidences in the large arrays of Ge-detectors, like GAMMASPHERE, was employed at Vanderbilt University to discover new characteristics of the fission process, and new decay modes. The possibility of a whole family of new decay modes, the multicluster accompanied fission, was envisaged. Besides the fission into two or three fragments, a heavy or superheavy nucleus spontaneously breaks into four, five or six nuclei of which two are asymmetric or symmetric heavy fragments and the others are light clusters, e.g. α-particles, 10 Be, 14 C, or combinations of them. Examples were presented for the two-, three- and four cluster accompanied cold fission of 252 Cf and 262 Rf, in which the emitted

  1. K-State Problem Identification Rating Scales for College Students

    Science.gov (United States)

    Robertson, John M.; Benton, Stephen L.; Newton, Fred B.; Downey, Ronald G.; Marsh, Patricia A.; Benton, Sheryl A.; Tseng, Wen-Chih; Shin, Kang-Hyun

    2006-01-01

    The K-State Problem Identification Rating Scales, a new screening instrument for college counseling centers, gathers information about clients' presenting symptoms, functioning levels, and readiness to change. Three studies revealed 7 scales: Mood Difficulties, Learning Problems, Food Concerns, Interpersonal Conflicts, Career Uncertainties,…

  2. Measurement of Am-242 fission yields at the Lohengrin spectrometer; improvement and Benchmarking of the semi-empirical code GEF

    International Nuclear Information System (INIS)

    Amouroux, Charlotte

    2014-01-01

    The study of fission yields has a major impact on the characterization and understanding of the fission process and is mandatory for reactor applications. While the yields are known for the major actinides (U-235, Pu-239) in the thermal neutron-induced fission, only few measurements were performed on Am-242. Moreover, the two main data libraries do not agree among each other on the light peak. Am-241 and Am-242 are nuclei of interest for the MOX-fuel reactors and for the reduction of nuclear waste radiotoxicity using transmutation reactions. Thus, a campaign of precise measurement of the fission mass yields from the reaction Am-241(2n,f) was performed at the Lohengrin mass spectrometer (ILL, France) for both the light and the heavy peak. Forty-one masses were measured. Moreover, the measurement of the isotopic fission yields on the heavy peak by gamma-ray spectrometry led to the extraction of 20 independent isotopic yields. Our measurement was also meant to determine whether there is a difference in fission yields between the Am-242 isomeric state and its ground state as it exists in fission cross sections. The experimental method used to answer this question is based on the measurement a set of fission mass yields as a function of the ratio of Am-242gs to Am-242m fission rate. Results show that the mass yields are independent of the fission rate ratio. A future experimental campaign is proposed to observe a possible influence on the isomeric yields. The theoretical models are nowadays unable to predict the fission yields with enough accuracy and therefore we have to rely on experimental data and phenomenological models. The accuracy of the predictions of the semi empirical GEF fission model predictions makes it a useful tool for evaluation. This thesis also presents the physical content and part of the development of this model. Validation of the kinetic energy distributions, isomeric yields and fission yields predictions was performed. The extension of the GEF

  3. Fast fission phenomena

    International Nuclear Information System (INIS)

    Gregoire, Christian.

    1982-03-01

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

  4. Solid state track recorder measurements in the poolside critical assembly

    International Nuclear Information System (INIS)

    Ruddy, F.H.; Gold, R.; Roberts, J.H.

    1979-01-01

    Fission rate measurements using solid state track recorders (SSTR) have been performed at the PCA. A schematic representation of a cross-section of the PCA is shown. Fission rates were measured in the pressure vessel simulator at the T/4, T/2 and 3T/4 positions and in the void box (VB). SSTR measurements were carried out with 232 Th, 235 U (bare and cadmium covered), 238 U and 237 Np fissionable deposits. Midplane only measurements were carried out for 235 U and 237 Np, while 5 axial locations at 1/4T and 1/2T and 3 axial locations at 3/4T and in the VB were sampled for 232 Th and 238 U. The HEDL SSTR fission rate measurements reported herein for both configurations together with NBS and CEN/SCK fission chamber measurements will be used to establish absolute and relative fission reaction rates, and ratios for the PCA pressure vessel Benchmark Facility

  5. 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...

  6. Fission product yields

    International Nuclear Information System (INIS)

    Valenta, V.; Hep, J.

    1978-01-01

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

  7. Fission neutron multiplicity calculations

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  8. Intermediate energy nuclear fission

    International Nuclear Information System (INIS)

    Hylten, G.

    1982-01-01

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

  9. 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)

  10. Ternary fission of spontaneously fissile uranium isomers excited by neutrons

    International Nuclear Information System (INIS)

    Makarenko, V.E.; Molchanov, Y.D.; Otroshchenko, G.A.; Yan'kov, G.B.

    1989-01-01

    Spontaneously fissile isomers (SFI) of uranium were excited in the reactions 236,238 U(n,n') at an average neutron energy 4.5 MeV. A pulsed electrostatic accelerator and time analysis of the fission events were used. Fission fragments were detected by the scintillation method, and long-range particles from fission were detected by an ionization method. The relative probability of fission of nuclei through a spontaneously fissile isomeric state was measured: (1.30±0.01)·10 -4 ( 236 U) and (1.48±0.02)·10 -4 ( 238 U). Half-lives of the isomers were determined: 121±2 nsec (the SFI 236 U) and 267±13 nsec (the SFI 238 U). In study of the ternary fission of spontaneously fissile isotopes of uranium it was established that the probability of the process amounts to one ternary fission per 163±44 binary fissions of the SFI 236 U and one ternary fission per 49±14 binary fissions of the SFI 238 U. The substantial increase of the probability of ternary fission of SFI of uranium in comparison with the case of ternary fission of nuclei which are not in an isomeric state may be related to a special nucleon configuration of the fissile isomers of uranium

  11. Late Paleozoic-Middle Mesozoic uplift rate, cooling rate and geothermal gradient for south-central New York state

    International Nuclear Information System (INIS)

    Johnsson, M.J.

    1985-01-01

    Apatite and zircon crystals were recovered from the Tioga metabentonite (Middle Devonian) at Cherry Valley, New York and from a metabentonite at the top of the Black River Group (Middle Ordovician) at Middleville, New York. Fission-track ages obtained from these minerals are younger than the stratigraphic ages of the units, indicating total or partial resetting of the mineral ages due to thermal annealing of fission-tracks. The age data allow for calculation of a mean uplift rate of 0.019 +- 0.009 mm/yr for the interval 193 to 155 Myr, and a mean cooling rate of 0.38 +- 0.11 0 C/Myr for the interval 354 to 155 Myr. An average geothermal gradient for the interval 354 to 155 Myr is 20 +- 11 C/km. The partially reset zircon age from the Black River metabentonite indicates that the Middle Ordovician rocks of south-central New York have been exposed to temperatures approaching approx. 175 C. This temperature, in conjunction with the calculated geothermal gradient, implies burial of these units to depths approaching 8 km. Such burial suggests that extensive Carboniferous sediments once covered southern New York, and that the Alleghenian Orogeny had a stronger sedimentalogical influence in the northern portion of the Appalachian Basin than has been previously recognized. (author)

  12. Parent Ratings of Impulsivity and Inhibition Predict State Testing Scores

    Directory of Open Access Journals (Sweden)

    Rebecca A. Lundwall

    2018-03-01

    Full Text Available One principle of cognitive development is that earlier intervention for educational difficulties tends to improve outcomes such as future educational and career success. One possible way to help students who struggle is to determine if they process information differently. Such determination might lead to clues for interventions. For example, early information processing requires attention before the information can be identified, encoded, and stored. The aim of the present study was to investigate whether parent ratings of inattention, inhibition, and impulsivity, and whether error rate on a reflexive attention task could be used to predict child scores on state standardized tests. Finding such an association could provide assistance to educators in identifying academically struggling children who might require targeted educational interventions. Children (N = 203 were invited to complete a peripheral cueing task (which measures the automatic reorienting of the brain’s attentional resources from one location to another. While the children completed the task, their parents completed a questionnaire. The questionnaire gathered information on broad indicators of child functioning, including observable behaviors of impulsivity, inattention, and inhibition, as well as state academic scores (which the parent retrieved online from their school. We used sequential regression to analyze contributions of error rate and parent-rated behaviors in predicting six academic scores. In one of the six analyses (for science, we found that the improvement was significant from the simplified model (with only family income, child age, and sex as predictors to the full model (adding error rate and three parent-rated behaviors. Two additional analyses (reading and social studies showed near significant improvement from simplified to full models. Parent-rated behaviors were significant predictors in all three of these analyses. In the reading score analysis

  13. Use of code DTF-4 for determining the coefficient of back-reflection of the neutron within the thermonuclear plasma of a thermonuclear reactor controlled by the rate of the fission reactions. Pt. 1

    International Nuclear Information System (INIS)

    Cristea, G.

    1975-01-01

    The neutron problems are discussed of the thermonuclear reactor controlled by the rate of the fission reactions. The results obtained by rolling the DTF-4 program in a spherical geometry in the case of an ''external source'' problem permit to draw conclusions concerning the problems of the neutronics system of this thermonuclear reactor type. A relation is deduced for estimating the coefficient of back-reflection of the neutrons within the thermonuclear plasma and the focussion system is discussed of the neutronics of this reactor type

  14. The Correlation of Sovereign Rating and Bonds’ Interest Rate in EU Member States

    Directory of Open Access Journals (Sweden)

    Emilian-Constantin MIRICESCU

    2015-06-01

    Full Text Available The importance of borrowing is fundamental for central public administration and it consists in sources of f nancing budget def cit and ref nanc-ing government debt. In the last years, a lot of countries had diff culties regarding the payment of public loans at their maturity due to the burden of government debt to GDP ratio. In this situa-tion, investors lose their conf dence not only in the country that is facing problems, but also in other states that pay their debt at maturity. For this reason, they are careful at any change that affects sovereign rating. From our investigation we found that sover-eign rating has a negative inf uence on bonds’ interest rate. As such, decision makers from central public administration should focus on improving sovereign ratings in order to decrease interest rates.

  15. Progress toward Increasing National and State Graduation Rates. Raising Graduation Rates: A Series of Data Briefs

    Science.gov (United States)

    Balfanz, Robert; West, Thomas C.

    2006-01-01

    This is the first in a series of briefs examining the progress in raising high school graduation rates over the past decade. During this period, the prevailing belief has been that all students who wanted to or needed to graduate did so. However, it is now recognized that in every state there are too many communities and schools where high school…

  16. Birth to death analysis of the energy payback ratio and CO2 gas emission rates from coal, fission, wind, and DT-fusion electrical power plants

    International Nuclear Information System (INIS)

    White, Scott W.; Kulcinski, Gerald L.

    2000-01-01

    The amount of electrical energy produced over the lifetime of coal, LWR fission, UP fusion, and wind power plants is compared to the total amount of energy required to procure the fuel, build, operate, and decommission the power plants. The energy payback ratio varies from a low of 11 for coal plants to a high of 27 for DT-fusion plants. The magnitude of the energy investment and the source of the various energy inputs determine the CO 2 emission factor. This number varies from a low of 9 to a high of 974 tonnes of CO 2 per GW e h for DT-fusion and coal plants, respectively

  17. 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)

  18. Theories of fission gas behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Dias, J W.C. [Companhia Brasileira de Tecnologia Nuclear, Rio de Janeiro (Brazil). Diretoria de Tecnologia e Desenvolvimento; Merckx, K R

    1976-01-01

    A review is presented of the theoretical developments and experimental evidence that have helped to evolve current models used to describe the behavior of inert fission gases created during the irradiation of reactor fuel materials. The phenomena which are stressed relate primarily to steady state behavior of fuel elements but are also relevant to an understanding of transient behavior. The processes considered include gas atom solubility; gas atom diffusivity; bubble nucleation; and bubble growth by bubble coalescence.

  19. Above-threshold structure in {sup 244}Cm neutron-induced fission cross section

    Energy Technology Data Exchange (ETDEWEB)

    Maslov, V.M. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)

    1997-03-01

    The quasi-resonance structure appearing above the fission threshold in neutron-induced fission cross section of {sup 244}Cm(n,f) is interpreted. It is shown to be due to excitation of few-quasiparticle states in fissioning {sup 245}Cm and residual {sup 244}Cm nuclides. The estimate of quasiparticle excitation thresholds in fissioning nuclide {sup 245}Cm is consistent with pairing gap and fission barrier parameters. (author)

  20. On Estimating Marginal Tax Rates for U.S. States

    OpenAIRE

    Reed, W. Robert; Rogers, Cynthia L; Skidmore, Mark

    2011-01-01

    This paper presents a procedure for generating state-specific time-varying estimates of marginal tax rates (MTRs). Most estimates of MTRs follow a procedure developed by Koester and Kormendi (1989) (K&K). Unfortunately, the time-invariant nature of the K&K estimates precludes their use as explanatory variables in panel data studies with fixed effects. Furthermore, the associated MTR estimates are not explicitly linked to statutory tax parameters. Our approach addresses both shortcomings. Usin...

  1. Microscopic description of fission in odd-mass uranium and plutonium nuclei with the Gogny energy density functional

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Guzman, R. [Kuwait University, Physics Department, Kuwait (Kuwait); Robledo, L.M. [Universidad Autonoma de Madrid, Departamento de Fisica Teorica, Madrid (Spain); Universidad Politecnica de Madrid, Center for Computational Simulation, Boadilla del Monte (Spain)

    2017-12-15

    The parametrization D1M of the Gogny energy density functional is used to study fission in the odd-mass Uranium and Plutonium isotopes with A = 233,.., 249 within the framework of the Hartree-Fock-Bogoliubov (HFB) Equal Filling Approximation (EFA). Ground state quantum numbers and deformations, pairing energies, one-neutron separation energies, barrier heights and fission isomer excitation energies are given. Fission paths, collective masses and zero point rotational and vibrational quantum corrections are used to compute the systematic of the spontaneous fission half-lives t{sub SF}, the masses and charges of the fission fragments as well as their intrinsic shapes. Although there exits a strong variance of the predicted fission rates with respect to the details involved in their computation, it is shown that both the specialization energy and the pairing quenching effects, taken into account fully variationally within the HFB-EFA blocking scheme, lead to larger spontaneous fission half-lives in odd-mass U and Pu nuclei as compared with the corresponding even-even neighbors. It is shown that modifications of a few percent in the strengths of the neutron and proton pairing fields can have a significant impact on the collective masses leading to uncertainties of several orders of magnitude in the predicted t{sub SF} values. Alpha-decay lifetimes have also been computed using a parametrization of the Viola-Seaborg formula. (orig.)

  2. Dynamics in heavy ion fusion and fission

    International Nuclear Information System (INIS)

    Bjoernholm, S.

    1972-01-01

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

  3. Fission gas detection system

    International Nuclear Information System (INIS)

    Colburn, R.P.

    1984-01-01

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

  4. Muon-induced fission

    International Nuclear Information System (INIS)

    Polikanov, S.

    1980-01-01

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

  5. Relativistic Coulomb Fission

    Science.gov (United States)

    Norbury, John W.

    1992-01-01

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

  6. Effects of Intermolecular Coupling on Excimer Formation and Singlet Fission

    Science.gov (United States)

    Mauck, Catherine McKay

    compelling strategy for improving organic photovoltaic device efficiencies. The formation of triplet states through singlet fission can be characterized using femtosecond visible transient absorption spectroscopy (fsTA). However, in PDI, the triplet-triplet absorption spectrum is strongly overlapped with the ground state bleach absorption. Here, a dyad molecule where PDI is covalently attached to an apocarotene triplet acceptor is synthesized, and studied in solution aggregates and thin films with fsTA, to demonstrate that apocarotene can be used as a sensitive spectral tag for triplet formation in PDI due to triplet-triplet energy transfer from PDI to the carotenoid. The efficiency of singlet fission in DPP can be tuned by modulating the crystal packing in the solid state. By synthesizing 3,6-bis(thiophene) derivatives of DPP with a series of different sidechains, thin film DPP singlet fission is related to the crystal structure intermolecular geometries, to more precisely determine the relationship between interchromophore coupling and singlet fission rate, which will inform the design of more robust chromophores for singlet fission. Finally, the role of the dielectric environment and stabilization of charge transfer configurations and charge transfer states is explored in DPP singlet fission, through aqueous nanoparticles of 3,6-bis(phenylthiophene) with different surface area-to-volume ratios, and a covalently linked dimer of DPP in solvents of varying polarity which can undergo symmetry-breaking charge separation.

  7. Fabrication and testing of a 4-node micro-pocket fission detector array for the Kansas State University TRIGA Mk. II research nuclear reactor

    Science.gov (United States)

    Reichenberger, Michael A.; Nichols, Daniel M.; Stevenson, Sarah R.; Swope, Tanner M.; Hilger, Caden W.; Unruh, Troy C.; McGregor, Douglas S.; Roberts, Jeremy A.

    2017-08-01

    Advancements in nuclear reactor core modeling and computational capability have encouraged further development of in-core neutron sensors. Micro-Pocket Fission Detectors (MPFDs) have been fabricated and tested previously, but successful testing of these prior detectors was limited to single-node operation with specialized designs. Described in this work is a modular, four-node MPFD array fabricated and tested at Kansas State University (KSU). The four sensor nodes were equally spaced to span the length of the fuel-region of the KSU TRIGA Mk. II research nuclear reactor core. The encapsulated array was filled with argon gas, serving as an ionization medium in the small cavities of the MPFDs. The unified design improved device ruggedness and simplified construction over previous designs. A 0.315-in. (8-mm) penetration in the upper grid plate of the KSU TRIGA Mk. II research nuclear reactor was used to deploy the array between fuel elements in the core. The MPFD array was coupled to an electronic support system which has been developed to support pulse-mode operation. Neutron-induced pulses were observed on all four sensor channels. Stable device operation was confirmed by testing under steady-state reactor conditions. Each of the four sensors in the array responded to changes in reactor power between 10 kWth and full power (750 kWth). Reactor power transients were observed in real-time including positive transients with periods of 5, 15, and 30 s. Finally, manual reactor power oscillations were observed in real-time.

  8. Study of hypernuclei fission

    International Nuclear Information System (INIS)

    Malek, F.

    1990-01-01

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

  9. The nuclear fission process

    International Nuclear Information System (INIS)

    Wagemans, C.

    1991-01-01

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

  10. Distribution of nuclear charge and angular momentum in chains 132-137, 99, and 102 of thermal neutron fission of 235U at various kinetic energies and charge states of the fragments

    International Nuclear Information System (INIS)

    Denschlag, H.O.; Braun, H.; Wolfsberg, K.

    1979-01-01

    The fission product yields of the members of the decay chains 132 to 137, 99, and 102 in 235 U(n/sub th/,f) were measured at various kinetic energies and ionic charge states of the fragments using the mass separator for unslowed fission products LOHENGRIN. The results are discussed with respect to four aspects: A preferential formation of neutron rich chain members found at high kinetic energy of the fragments is predominantly due to decreasing prompt neutron evaporation. A particularly large effect in chain 132 is attributed to the double shell closure in Sn-132. The persistence of an even-odd pairing effect in the yields throughout the range of kinetic energies studied leads to the conclusion that the high internal excitation energy of the fragments is tied up mainly in the form of collective energy (e.g., deformation energy) rather than single particle excitation. Generally, the yield distribution at constant kinetic energy is invariant with respect to the ionic charge state of the isotopes separated. Deviations from this behavior found in chains 99, 102, 133, and 136 are interpreted as being due to Auger events following a converted transition in the decay of ns-isomers taking place in the vacuum of the separator. A pronounced variation of the independent formation ratio of single isomeric states with the kinetic energy of the fragments is providing direct information on the controversial topic of the change of angular momentum of fission fragments as a function of deformation (scission distance). 34 references

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

    International Nuclear Information System (INIS)

    2009-01-01

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

  12. Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission

    KAUST Repository

    Dean, Jacob C.

    2017-08-18

    Quantitative singlet fission has been observed for a variety of acene derivatives such as tetracene and pentacene, and efforts to extend the library of singlet fission compounds is of current interest. Preliminary calculations suggest anthradithiophenes exhibit significant exothermicity between the first optically-allowed singlet state, S1, and 2 × T1 with an energy difference of >5000 cm−1. Given the fulfillment of this ingredient for singlet fission, here we investigate the singlet fission capability of a difluorinated anthradithiophene dimer (2ADT) covalently linked by a (dimethylsilyl)ethane bridge and derivatized by triisobutylsilylethynyl (TIBS) groups. Photophysical characterization of 2ADT and the single functionalized ADT monomer were carried out in toluene and acetone solution via absorption and fluorescence spectroscopy, and their photo-initiated dynamics were investigated with time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopy. In accordance with computational predictions, two conformers of 2ADT were observed via fluorescence spectroscopy and were assigned to structures with the ADT cores trans or cis to one another about the covalent bridge. The two conformers exhibited markedly different excited state deactivation mechanisms, with the minor trans population being representative of the ADT monomer showing primarily radiative decay, while the dominant cis population underwent relaxation into an excimer geometry before internally converting to the ground state. The excimer formation kinetics were found to be solvent dependent, yielding time constants of ∼1.75 ns in toluene, and ∼600 ps in acetone. While the difference in rates elicits a role for the solvent in stabilizing the excimer structure, the rate is still decidedly long compared to most singlet fission rates of analogous dimers, suggesting that the excimer is neither a kinetic nor a thermodynamic trap, yet singlet fission was still not observed. The result

  13. Ternary fission induced by polarized neutrons

    Directory of Open Access Journals (Sweden)

    Gönnenwein Friedrich

    2013-12-01

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

  14. Fission fragment spins and spectroscopy

    International Nuclear Information System (INIS)

    Durell, J.L.

    1988-01-01

    Prompt γ-ray coincidence experiments have been carried out on γ-rays emitted from post-neutron emission fission fragments produced by the aup 19F + 197 Au and 18 O + 232 Th reactions. Decay schemes have been established for even-even nuclei ranging from 78 Se to 148 Nd. Many new states with spin up to ∼ 12h have been observed. Apart from providing a wealth of new information on the spectroscopy of neutron-rich nuclei, the data have been analyzed to determine the average spin of primary fission fragments as a function of fragment mass. The results suggest that the fragment spins are determined by the temperature and shape of the primary fragments at or near to scission

  15. Formation probabilities and relaxation rates of muon states in germanium

    International Nuclear Information System (INIS)

    Clawson, C.W.; Haller, E.E.; Crowe, K.M.; Rosenblum, S.S.; Brewer, J.H.; British Columbia Univ., Vancouver

    1981-01-01

    We report the first results of a study of the muonium states in ultra-pure germanium crystals grown under a variety of conditions at Lawrence Berkeley Laboratory. Among the variations studied are: 1) Hydrogen, deuterium, or nitrogen atmosphere during growth; 2) Dislocation-free vs. dislocated crystals; 3) Grown from quartz, graphite, and pyrolytic graphite coated quartz crucibles; 4) n-type vs. p-type. We report a significant difference in the muonium relaxation rate between the dislocated and non-dislocated crystals. (orig.)

  16. Vital Signs: Trends in State Suicide Rates - United States, 1999-2016 and Circumstances Contributing to Suicide - 27 States, 2015.

    Science.gov (United States)

    Stone, Deborah M; Simon, Thomas R; Fowler, Katherine A; Kegler, Scott R; Yuan, Keming; Holland, Kristin M; Ivey-Stephenson, Asha Z; Crosby, Alex E

    2018-06-08

    Suicide rates in the United States have risen nearly 30% since 1999, and mental health conditions are one of several factors contributing to suicide. Examining state-level trends in suicide and the multiple circumstances contributing to it can inform comprehensive state suicide prevention planning. Trends in age-adjusted suicide rates among persons aged ≥10 years, by state and sex, across six consecutive 3-year periods (1999-2016), were assessed using data from the National Vital Statistics System for 50 states and the District of Columbia. Data from the National Violent Death Reporting System, covering 27 states in 2015, were used to examine contributing circumstances among decedents with and without known mental health conditions. During 1999-2016, suicide rates increased significantly in 44 states, with 25 states experiencing increases >30%. Rates increased significantly among males and females in 34 and 43 states, respectively. Fifty-four percent of decedents in 27 states in 2015 did not have a known mental health condition. Among decedents with available information, several circumstances were significantly more likely among those without known mental health conditions than among those with mental health conditions, including relationship problems/loss (45.1% versus 39.6%), life stressors (50.5% versus 47.2%), and recent/impending crises (32.9% versus 26.0%), but these circumstances were common across groups. Suicide rates increased significantly across most states during 1999-2016. Various circumstances contributed to suicides among persons with and without known mental health conditions. States can use a comprehensive evidence-based public health approach to prevent suicide risk before it occurs, identify and support persons at risk, prevent reattempts, and help friends and family members in the aftermath of a suicide.

  17. History of the discovery of uranium fission by neutrons

    International Nuclear Information System (INIS)

    Simane, C.

    1989-01-01

    The history is briefly described of the discovery of uranium fission by neutrons, based on the texts of original scientific studies, memories or biographies of those who participated in the discovery and of their contemporaries. Obstacles that stood in the way of the discovery are discussed. It is stated that only a few scientists contributed to the discovery of uranium fission. The fission process itself still remains subject of physical research which studies its detailed laws. (Z.M.). 2 tabs., 16 refs

  18. The Concept of State Capacity: Comparative International Ratings against State Legitimacy

    Directory of Open Access Journals (Sweden)

    Vladimir Gennadievich Ivanov

    2015-12-01

    Full Text Available In the given article, the author analyzes the concept of state capacity, widely popular among political scientists and international relations specialists. The author proves that the evaluations of the level of state capacity of the developing and postcommunist countries based on popular comparative ratings are generally biased because of methodological defects and discrepancy of the whole theory as well as politicization and indoctrination of the given ratings. The negative evaluations of the quality of the government and state capacity of a country could be used to discredit and delegitimize the political regime as well as substantiation of mass protests and color revolutions and a tool of information war. The author concludes that numerous comparative international ratings are often used as a tool of political influence.

  19. A microscopic model of rate and state friction evolution

    Science.gov (United States)

    Li, Tianyi; Rubin, Allan M.

    2017-08-01

    Whether rate- and state-dependent friction evolution is primarily slip dependent or time dependent is not well resolved. Although slide-hold-slide experiments are traditionally interpreted as supporting the aging law, implying time-dependent evolution, recent studies show that this evidence is equivocal. In contrast, the slip law yields extremely good fits to velocity step experiments, although a clear physical picture for slip-dependent friction evolution is lacking. We propose a new microscopic model for rate and state friction evolution in which each asperity has a heterogeneous strength, with individual portions recording the velocity at which they became part of the contact. Assuming an exponential distribution of asperity sizes on the surface, the model produces results essentially similar to the slip law, yielding very good fits to velocity step experiments but not improving much the fits to slide-hold-slide experiments. A numerical kernel for the model is developed, and an analytical expression is obtained for perfect velocity steps, which differs from the slip law expression by a slow-decaying factor. By changing the quantity that determines the intrinsic strength, we use the same model structure to investigate aging-law-like time-dependent evolution. Assuming strength to increase logarithmically with contact age, for two different definitions of age we obtain results for velocity step increases significantly different from the aging law. Interestingly, a solution very close to the aging law is obtained if we apply a third definition of age that we consider to be nonphysical. This suggests that under the current aging law, the state variable is not synonymous with contact age.

  20. Cardiopulmonary Resuscitation Training Rates in the United States

    Science.gov (United States)

    Anderson, Monique L.; Cox, Margueritte; Al-Khatib, Sana M.; Nichol, Graham; Thomas, Kevin L.; Chan, Paul S.; Saha-Chaudhuri, Paramita; Fosbol, Emil L.; Eigel, Brian; Clendenen, Bill; Peterson, Eric D.

    2014-01-01

    Context Bystander cardiopulmonary resuscitation (CPR) improves the likelihood of surviving out-of-hospital cardiac arrest (OHCA), yet treatment rates differ by a community’s racial and income composition. Objective To determine if CPR training differs by the race and income of communities across the United States (U.S.). Design, Setting, and Participants We analyzed county-level CPR training rates from 2010–2011 using CPR training data from the American Heart Association, the American Red Cross, and the Health and Safety Institute. We utilized multivariable logistic regression models to examine the association of annual adult CPR training rates with a county’s proportion of black residents and median household income (categorized as tertiles), as well as other demographic, geographic, and healthcare characteristics. Main Outcome Measure CPR training rate. Results From 07/01/2010–06/30/2011, 13.1 million persons in 3143 U.S. counties received CPR training. The median county training rate ranged from 0.00%–1.29% (median=0.51%) in the lower tertile, 1.29%–4.07% (median=2.39%) in the middle tertile, and >4.07% (median=6.81%) in the upper tertile. Counties that were most likely to have CPR training rates in the lower tertile included those with a higher proportion of rural (odds ratio [OR] 1.12, 95% confidence interval [CI] 1.10, 1.15 per 5 percentage point [PP] change), black (OR 1.09, 95% CI 1.06, 1.13 per 5 PP change), and Hispanic residents (OR 1.06, 95% CI 1.02, 1.11 per 5 PP change); those with a lower median household income (OR 1.18, 95% CI 1.04, 1.34 per $10,000 decrease); those with a higher median age (OR 1.28, 95% CI 1.04, 1.53 per 10 year change); and those located in the South. Conclusions Counties with a higher proportion of rural, black, Hispanic, and lower income residents had lower CPR training rates. Differences in CPR training by race and income may contribute to recognized disparities in bystander CPR treatment and OHCA survival, and

  1. 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.

  2. Fission gas in thoria

    Energy Technology Data Exchange (ETDEWEB)

    Kuganathan, Navaratnarajah, E-mail: n.kuganathan@imperial.ac.uk [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom); Ghosh, Partha S. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Galvin, Conor O.T. [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom); Arya, Ashok K. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Dutta, Bijon K. [Homi Bhabha National Institute, Trombay, Mumbai 400 094 (India); Dey, Gautam K. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Grimes, Robin W. [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom)

    2017-03-15

    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 ThO{sub 2} 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 ThO{sub 2} is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO{sub 2} 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 ThO{sub 2−x} the most favourable solution equilibrium site is the NTV1 while in ThO{sub 2} it is the DV. - Highlights: • We have considered Xe and Kr in point defects and defect clusters (neutral and charged) using Density Functional Theory (DFT) with a dispersion correction. • The most favourable charge state for a point defect (vacancy or interstitial) is that with full ionic charge and we have found that in all cases gas atoms occupy the fully charged vacancy sites. • The number of fission gas atoms accommodated in ThO{sub 2} is

  3. Status of fission power

    International Nuclear Information System (INIS)

    Levenson, M.

    1977-01-01

    Fission energy is reviewed from the viewpoints of technology, economics, politics, manufacturers, consumers, and foreign countries. Technically, the reactor program is operating and the light water reactor industry shows signs of maturing, although recent business has been disappointing. Marketing of gas-cooled reactors depends, not on technical, but economic and political issues. Liquid metal fast breeder reactors have been demonstrated worldwide, while the gas-cooled fast breeder remains an undemonstrated option. Nuclear plants, currently costing the same as coal plants with scrubbers, are the cheapest option for utilities because most of the cost is imbedded. The defeat of nuclear initiatives in seven states indicates that public feeling is not as anti-nuclear as opponents to nuclear power claim. The harshness of last winter demonstrated the advantages of a power source that is not so sensitive to the weather for reliable operation and transport, as well as low cost energy. Other nations are proceeding to build a nuclear capability, which the U.S. may jeopardize because of concerns about the fuel cycle, nuclear waste disposal, uranium reserves, and nuclear proliferation

  4. Microscopic Theory of Fission

    International Nuclear Information System (INIS)

    Younes, W; Gogny, D

    2008-01-01

    In recent years, the microscopic method has been applied to the notoriously difficult problem of nuclear fission with unprecedented success. In this paper, we discuss some of the achievements and promise of the microscopic method, as embodied in the Hartree-Fock method using the Gogny finite-range effective interaction, and beyond-mean-field extensions to the theory. The nascent program to describe induced fission observables using this approach at the Lawrence Livermore National Laboratory is presented

  5. Fusion-fission dynamics

    International Nuclear Information System (INIS)

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

    1992-01-01

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

  6. Preconceptual design and analysis of a solid-breeder blanket test in an existing fission reactor

    International Nuclear Information System (INIS)

    Deis, G.A.; Hsu, P.Y.; Watts, K.D.

    1983-01-01

    Preconceptual design and analysis have been performed to examine the capabilities of a proposed fission-based test of a water-cooled Li 2 O blanket concept. The mechanical configuration of the test piece is designed to simulate a unit cell of a breeder-outside-tube concept. This test piece will be placed in a fission test reactor, which provides an environment similar to that in a fusion reactor. The neutron/gamma flux from the reactor produces prototypical power density, tritium production rates, and operating temperatures and stresses. Steady-state tritium recovery from the test piece can be attained in short-duration (5-to-6-day) tests. The capabilities of this test indicate that fission-based testing can provide important near-term engineering information to support the development of fusion technology

  7. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

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

  8. Rates of cardiopulmonary resuscitation training in the United States.

    Science.gov (United States)

    Anderson, Monique L; Cox, Margueritte; Al-Khatib, Sana M; Nichol, Graham; Thomas, Kevin L; Chan, Paul S; Saha-Chaudhuri, Paramita; Fosbol, Emil L; Eigel, Brian; Clendenen, Bill; Peterson, Eric D

    2014-02-01

    Prompt bystander cardiopulmonary resuscitation (CPR) improves the likelihood of surviving an out-of-hospital cardiac arrest. Large regional variations in survival after an out-of-hospital cardiac arrest have been noted. To determine whether regional variations in county-level rates of CPR training exist across the United States and the factors associated with low rates in US counties. We used a cross-sectional ecologic study design to analyze county-level rates of CPR training in all US counties from July 1, 2010, through June 30, 2011. We used CPR training data from the American Heart Association, the American Red Cross, and the Health & Safety Institute. Using multivariable logistic regression models, we examined the association of annual rates of adult CPR training of citizens by these 3 organizations (categorized as tertiles) with a county's geographic, population, and health care characteristics. Completion of CPR training. Rate of CPR training measured as CPR course completion cards distributed and CPR training products sold by the American Heart Association, persons trained in CPR by the American Red Cross, and product sales data from the Health & Safety Institute. RESULTS During the study period, 13.1 million persons in 3143 US counties received CPR training. Rates of county training ranged from 0.00% to less than 1.29% (median, 0.51%) in the lower tertile, 1.29% to 4.07% (median, 2.39%) in the middle tertile, and greater than 4.07% or greater (median, 6.81%) in the upper tertile. Counties with rates of CPR training in the lower tertile were more likely to have a higher proportion of rural areas (adjusted odds ratio, 1.12 [95% CI, 1.10-1.15] per 5-percentage point [PP] change), higher proportions of black (1.09 [1.06-1.13] per 5-PP change) and Hispanic (1.06 [1.02-1.11] per 5-PP change) residents, a lower median household income (1.18 [1.04-1.34] per $10 000 decrease), and a higher median age (1.28 [1.04-1.58] per 10-year change). Counties in the South

  9. The role of fission products in whole core accidents

    Energy Technology Data Exchange (ETDEWEB)

    Baker, A R [FRSD, UKAEA, RNPDE, Risley, Warrington (United Kingdom); Teague, H J [SRD, UKAEA, Culcheth, Warrington (United Kingdom)

    1977-07-01

    The review of the role of fission products in whole-core accidents falls into two parts. Firstly, there is a discussion of the hypothetical accidents usually considered in the UK and how they are dealt with. Secondly, there is a discussion of individual topics where fission products are known to be important or might be so. There is a brief discussion of the UK work on the establishment of an equation of state for unirradiated fuel and how this might be extended to incorporate fission product effects. The main issue is the contribution of fission products to the effective vapour pressure and the experimental programme on the pulsed reactor VIPER investigates this. Fission products may influence the probability of occurrence and the severity of MFCIs. Finally, the fission product effects in the pre-disassembly, disassembly and recriticality stages of an accident are discussed. (author)

  10. Decay rates of resonance states at high level density

    International Nuclear Information System (INIS)

    Persson, E.; Technische Univ. Dresden; Gorin, T.; Technische Univ. Dresden; Rotter, I.; Technische Univ. Dresden

    1996-05-01

    The time dependent Schroedinger equation of an open quantum mechanical system is solved by using the stationary bi-orthogonal eigenfunctions of the non-Hermitean time independent Hamilton operator. We calculate the decay rates at low and high level density in two different formalism. The rates are, generally, time dependent and oscillate around an average value due to the non-orthogonality of the wavefunctions. The decay law is studied disregarding the oscillations. In the one-channel case, it is proportional to t -b with b∼3/2 in all cases considered, including the critical region of overlapping where the non-orthogonality of the wavefunctions is large. Starting from the shell model, we get b∼2 for 2 and 4 open decay channels and all coupling strengths to the continuum. When the closed system is described by a random matrix, b∼1+K/2 for K=2 and 4 channels. This law holds in a limited time interval. The distribution of the widths is different in the two models when more than one channel are open. This leads to the different exponents b in the power law. Our calculations are performed with 190 and 130 states, respectively, most of them in the critical region. The theoretical results should be proven experimentally by measuring the time behaviour of de-excitation of a realistic quantum system. (orig.)

  11. Regulatory simplification of fission product chemistry

    International Nuclear Information System (INIS)

    Read, J.B.J.; Soffer, L.

    1986-01-01

    The requirements for design provisions intended to limit fission product escape during reactor accidents have been based since 1962 upon a small number of simply-stated assumptions. These assumptions permeate current reactor regulation, but are too simple to deal with the complex processes that can reasonably be expected to occur during real accidents. Potential chemical processes of fission products in severe accidents are compared with existing plant safety features designed to minimize off-site consequences, and the possibility of a new set of simply-stated assumptions to replace the 1982 set is discussed

  12. Assessing positive emotional states in dogs using heart rate and heart rate variability.

    Science.gov (United States)

    Zupan, Manja; Buskas, Julia; Altimiras, Jordi; Keeling, Linda J

    2016-03-01

    Since most animal species have been recognized as sentient beings, emotional state may be a good indicator of welfare in animals. The goal of this study was to manipulate the environment of nine beagle research dogs to highlight physiological responses indicative of different emotional experiences. Stimuli were selected to be a more or a less positive food (meatball or food pellet) or social reward (familiar person or less familiar person). That all the stimuli were positive and of different reward value was confirmed in a runway motivation test. Dogs were tested individually while standing facing a display theatre where the different stimuli could be shown by lifting a shutter. The dogs approached and remained voluntarily in the test system. They were tested in four sessions (of 20s each) for each of the four stimuli. A test session consisted of four presentation phases (1st exposure to stimulus, post exposure, 2nd exposure, and access to reward). Heart rate (HR) and heart rate variability (HRV) responses were recorded during testing in the experimental room and also when lying resting in a quiet familiar room. A new method of 'stitching' short periods of HRV data together was used in the analysis. When testing different stimuli, no significant differences were observed in HR and LF:HF ratio (relative power in low frequency (LF) and the high-frequency (HF) range), implying that the sympathetic tone was activated similarly for all the stimuli and may suggest that dogs were in a state of positive arousal. A decrease of HF was associated with the meatball stimulus compared to the food pellet and the reward phase (interacting with the person or eating the food) was associated with a decrease in HF and RMSSD (root mean square of successive differences of inter-beat intervals) compared to the preceding phase (looking at the person or food). This suggests that parasympathetic deactivation is associated with a more positive emotional state in the dog. A similar reduction

  13. Constitutive law for seismicity rate based on rate and state friction: Dieterich 1994 revisited.

    Science.gov (United States)

    Heimisson, E. R.; Segall, P.

    2017-12-01

    Dieterich [1994] derived a constitutive law for seismicity rate based on rate and state friction, which has been applied widely to aftershocks, earthquake triggering, and induced seismicity in various geological settings. Here, this influential work is revisited, and re-derived in a more straightforward manner. By virtue of this new derivation the model is generalized to include changes in effective normal stress associated with background seismicity. Furthermore, the general case when seismicity rate is not constant under constant stressing rate is formulated. The new derivation provides directly practical integral expressions for the cumulative number of events and rate of seismicity for arbitrary stressing history. Arguably, the most prominent limitation of Dieterich's 1994 theory is the assumption that seismic sources do not interact. Here we derive a constitutive relationship that considers source interactions between sub-volumes of the crust, where the stress in each sub-volume is assumed constant. Interactions are considered both under constant stressing rate conditions and for arbitrary stressing history. This theory can be used to model seismicity rate due to stress changes or to estimate stress changes using observed seismicity from triggered earthquake swarms where earthquake interactions and magnitudes are take into account. We identify special conditions under which influence of interactions cancel and the predictions reduces to those of Dieterich 1994. This remarkable result may explain the apparent success of the model when applied to observations of triggered seismicity. This approach has application to understanding and modeling induced and triggered seismicity, and the quantitative interpretation of geodetic and seismic data. It enables simultaneous modeling of geodetic and seismic data in a self-consistent framework. To date physics-based modeling of seismicity with or without geodetic data has been found to give insight into various processes

  14. Birth and fertility rates for states by Hispanic origin subgroups: United States, 1990 and 2000.

    Science.gov (United States)

    Sutton, Paul D; Mathews, T J

    2006-05-01

    This report presents U.S. and State-level data on births, birth rates, and fertility rates for Hispanic origin subgroups for 1990 and 2000. Data for non-Hispanic whites and non-Hispanic blacks are provided for comparison. Data are presented in detailed tables, graphs, and maps. Between 1990 and 2000, the total U.S. Hispanic population increased 58 percent, from 22,353,999 to 35,305,818. Over the same period of time, births to Hispanic mothers increased 37 percent, from 595,073 to 815,868. The smaller increases in births compared with the population resulted in a falling birth rate among Hispanic mothers (26.7 in 1990 to 23.1 births per 1,000 total population in 2000). Birth and fertility rates for Mexican, Puerto Rican, and Cuban mothers all fell between 1990 and 2000. Among the Hispanic subgroups, fertility rates in 2000 ranged from 105.1 births per 1,000 women aged 15-44 years for Mexican women to 49.3 for Cuban women. Differences in fertility exist not only between Hispanic subgroups but also within groups among States. For example, total fertility rates for Puerto Rican mothers, which estimates the number of children a group of 1,000 women will have in their lifetime, ranged in 2000 from 1,616.5 in New York to 2,403.0 in Pennsylvania.

  15. Hefei experimental hybrid fusion-fission reactor conceptual design

    International Nuclear Information System (INIS)

    Qiu Lijian; Luan Guishi; Xu Qiang

    1992-03-01

    A new concept of hybrid reactor is introduced. It uses JET-like(Joint European Tokamak) device worked at sub-breakeven conditions, as a source of high energy neutrons to induce a blanket fission of depleted uranium. The solid breeding material and helium cooling technique are also used. It can produce 100 kg of 239 Pu per year by partial fission suppressed. The energy self-sustained of the fusion core is not necessary. Plasma temperature is maintained by external 20 MW ICRF (ion cyclotron resonance frequency) and 10 MW ECRF (electron cyclotron resonance frequency) heating. A steady state plasma current at 1.5 Ma is driven by 10 MW LHCD (lower hybrid current driven). Plasma density will be kept by pellet injection. ICRF can produce a high energy tail in ion distribution function and lead to significant enhancement of D-T reaction rate by 2 ∼ 5 times so that the neutron source strength reaches to the level of 1 x 10 19 n/s. This system is a passive system. It's power density is 10 W/cm 3 and the wall loading is 0.6 W/cm 2 that is the lower limitation of fusion and fission technology. From the calculation of neutrons it could always be in sub-critical and has intrinsic safety. The radiation damage and neutron flux distribution on the first wall are also analyzed. According to the conceptual design the application of this type hybrid reactor earlier is feasible

  16. Fission-gas-bubble mobility in oxide fuel: a critical analysis

    International Nuclear Information System (INIS)

    Tam, S.W.; Johnson, C.E.

    1983-08-01

    The available volatile fission product release data has confirmed the general viability of the scaling model of volatile fission product release in which the fractional release rates of the volatile fission products scale as that of the fission gas. The question of whether fission gas bubbles can move sufficiently fast to be a significant mechanism responsible for fission gas release from the fuel is considered. The mean jump distance per jump of the hopping process in gas bubble motion is analyzed. Surface roughness is also considered

  17. Investigation of delayed fission gas release

    International Nuclear Information System (INIS)

    Cayet, Nicolas

    1996-05-01

    The study of the fission gas release process in the high burnup rig IFA-562 has revealed a particular fuel behaviour: a delay in the fission gas release process. It appeared that an important release of gas was measured by the pressure transducers once the power had decreased, whereas, during steady-state operation, the pressure did not increase very much. After examinations, the gap size has been concluded to be the main parameter involving this delay. However the burnup could have been a potential factor, its role is mainly to close the gap by swelling. The observations of low burnup rods have shown the same delayed fission gas release, the gap being small by design and closed essentially by thermal expansion. The study of the kinetics has demonstrated the time-independency of the phenomenon. Thus the proposed mechanism driving this delayed fission gas release would involve three consecutives stages. During steady-state, the gas is released into the interlinkage network of grain boundary bubbles and cracks. Due to the closed gap, the gas is trapped in some void volumes, unable to escape the pellet. During power reduction, the gap and some old/new cracks open, immediately providing a path for the gas to the pressure transducers and explaining this delay in the fission gas release. (author)

  18. Verification of dosimetry cross sections above 10 MeV based on measurement of activation reaction rates in fission neutron field

    International Nuclear Information System (INIS)

    Odano, Naoteru; Miura, Toshimasa; Yamaji, Akio.

    1996-01-01

    To validate the dosimetry cross sections in fast neutron energy range, activation reaction rates were measured for 5 types of dosimetry cross sections which have sensitivity in the energy rage above 10 MeV utilizing JRR-4 reactor of JAERI. The measured reaction rates were compared with the calculations reaction rates by a continuous energy monte carlo code MVP. The calculated reaction rates were based on two dosimetry files, JENDL Dosimetry File and IRDF-90.2. (author)

  19. NSF Funding Rate History By State and Organization

    Data.gov (United States)

    National Science Foundation — Contains FY 2006-FY 2015 National Science Foundation (NSF) funding rates for competitive research proposals by organizational unit. The funding rate is calculated by...

  20. Determination of the quadrupole moment of the fission-isomeric state in 238U by a modified charge-plunger method

    International Nuclear Information System (INIS)

    Pedersen, J.; Goerlach, U.; Habs, D.; Just, M.; Metag, V.; Mosler, E.; Schukraft, J.; Singer, P.; Specht, H.J.; Ulfert, G.

    1978-01-01

    A modified version of the charge plunger method has been developed which, by utilizing electrostatic fields, renders possible the separation of low- and high-charge recoil ions over short flight distances. With this technique the quadrupole moment of the 200 ns fission isomer in 238 U has been determined to be (29 +- 3) b. The corresponding deformation of c/a = (1.8 +- 0.1) provides another quantitative proof for shape isomerism in the actinide region. (orig.) [de

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-01-01

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

  2. Fission and r-process nucleosynthesis in neutron star mergers

    International Nuclear Information System (INIS)

    Giuliani, Samuel Andrea

    2018-01-01

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

  3. The evaluation for reference fission yield of 238U fission

    International Nuclear Information System (INIS)

    Liang Qichang; Liu Tingjin

    1998-01-01

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

  4. Fission product release from nuclear fuel I. Physical modelling in the ASTEC code

    International Nuclear Information System (INIS)

    Brillant, G.; Marchetto, C.; Plumecocq, W.

    2013-01-01

    Highlights: • Physical modeling of FP and SM release in ASTEC is presented. • The release is described as solid state diffusion within fuel for high volatile FP. • The release is described as FP vaporisation for semi volatile FP. • The release is described as fuel vaporisation for low volatile FP. • ASTEC validation is presented in the second paper. - Abstract: This article is the first of a series of two articles dedicated to the mechanisms of fission product release from a degraded core as they are modelled in the ASTEC code. The ASTEC code aims at simulating severe accidents in nuclear reactors from the initiating event up to the radiological consequences on the environment. This code is used for several applications such as nuclear plant safety evaluation including probabilistic studies and emergency preparedness. To cope with the requirements of robustness and low calculation time, the code is based on a semi-empirical approach and only the main limiting phenomena that govern the release from intact rods and from debris beds are considered. For solid fuel, fission products are classified into three groups, depending on their degree of volatility. The kinetics of volatile fission products release depend on the rate-limiting process of solid-state diffusion through fuel grains. For semi-volatile fission products, the release from the open fuel porosities is assumed to be governed by vaporisation and mass transfer processes. The key phenomenon for the release of low volatile fission products is supposed to be fuel volatilisation. A similar approach is used for the release of fission products from a rubble bed. An in-depth validation of the code including both analytical and integral experiments is the subject of the second article

  5. Current status of the FASTGRASS/PARAGRASS models for fission product release from LWR fuel during normal and accident conditions

    International Nuclear Information System (INIS)

    Rest, J.; Zawadski, S.A.; Piasecka, M.

    1983-10-01

    The theoretical FASTGRASS model for the prediction of the behavior of the gaseous and volatile fission products in nuclear fuels under normal and transient conditions has undergone substantial improvements. The major improvements have been in the atomistic and bubble diffusive flow models, in the models for the behavior of gas bubbles on grain surfaces, and in the models for the behavior of the volatile fission products iodine and cesium. The thoery has received extensive verification over a wide range of fuel operating conditions, and can be regarded as a state-of-the-art model based on our current level of understanding of fission product behavior. PARAGRASS is an extremely efficient, mechanistic computer code with the capability of modeling steady-state and transient fission-product behavior. The models in PARAGRASS are based on the more detailed ones in FASTGRASS. PARAGRASS updates for the FRAPCON (PNL), FRAP-T (INEL), and SCDAP (INEL) codes have recently been completed and implemented. Results from an extensive FASTGRASS verification are presented and discussed for steady-state and transient conditions. In addition, FASTGRASS predictions for fission product release rate constants are compared with those in NUREG-0772. 21 references, 13 figures

  6. Fission product detection

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  7. Low energy nuclear fission

    International Nuclear Information System (INIS)

    Nifenecker, H.

    1982-02-01

    In these lectures we present the liquid drop model of fission and compare some of its prediction with experiment. The liquid drop analogy allows to define in a rather simple and intuitive way a number of useful concepts and possible observables. We then discuss, using the example of the oscillator model, the generality of shell effects. We show how a synthesis of the liquid drop model and of the shell model can be made using the Strutinsky shell averaging procedure. Some experimental data related to the existence of shape isomers are presented and discussed. We conclude by discussing some aspects, both experimental and theoretical, of fission dynamics

  8. Fission of heavy hypernuclei

    International Nuclear Information System (INIS)

    Nifenecker, H.

    1993-01-01

    The results on delayed and prompt fission of heavy hypernuclei obtained by the LEAR PS177 collaboration are recalled and discussed. It is shown that the hypernuclei life-times can be explained in term of a weak strangeness violating lambda-nucleon interaction with a cross section close to 6.0 10 -15 barns. The lambda attachment function is shown to be sensitive to the scission configuration, just before fission, and to the neck dynamics. This function provides a new way to study the nuclear scission process. (author)

  9. Fission gas measuring technology

    International Nuclear Information System (INIS)

    Lee, Hyung Kwon; Kim, Eun Ka; Hwang, Yong Hwa; Lee, Eun Pyo; Chun, Yong Bum; Seo, Ki Seog; Park, Dea Gyu; Chu, Yong Sun; Ahn, Sang Bok.

    1998-02-01

    Safety and economy of nuclear plant are greatly affected by the integrity of nuclear fuels during irradiation reactor core. A series of post-irradiation examination (PIE) including non-destructive and destructive test is to be conducted to evaluate and characterize the nuclear performance. In this report, a principle of the examination equipment to measure and analyse fission gases existing nuclear fuels were described and features of the component and device consisting the fission gas measuring equipment are investigated. (author). 4 refs., 2 tabs., 6 figs

  10. Fission gas measuring technology

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyung Kwon; Kim, Eun Ka; Hwang, Yong Hwa; Lee, Eun Pyo; Chun, Yong Bum; Seo, Ki Seog; Park, Dea Gyu; Chu, Yong Sun; Ahn, Sang Bok

    1998-02-01

    Safety and economy of nuclear plant are greatly affected by the integrity of nuclear fuels during irradiation reactor core. A series of post-irradiation examination (PIE) including non-destructive and destructive test is to be conducted to evaluate and characterize the nuclear performance. In this report, a principle of the examination equipment to measure and analyse fission gases existing nuclear fuels were described and features of the component and device consisting the fission gas measuring equipment are investigated. (author). 4 refs., 2 tabs., 6 figs.

  11. Low energy nuclear fission

    International Nuclear Information System (INIS)

    Nifenecker, H.

    1980-08-01

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

  12. 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.

  13. Spontaneous fission of superheavy nuclei

    Indian Academy of Sciences (India)

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

  14. Mirror fusion--fission hybrids

    International Nuclear Information System (INIS)

    Lee, J.D.

    1978-01-01

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

  15. Chemistry of fission products for accident analysis

    International Nuclear Information System (INIS)

    Potter, P.E.

    1985-01-01

    Current knowledge concerning the chemical state of the fission product elements during the development of accidents in water reactor systems is reviewed in this paper. The fission product elements which have been considered are Cs, I, Te, Sr and Ba but aspects of the behavior of Mo, Ru and the lanthanides are also discussed. Some features of the reactions of the various species of these elements with other components of the reactor systems are described. The importance of having an adequate knowledge of thermodynamic data and phase equilibria of relatively simple systems in order to interpret experimental observations on complex multi-component systems is stressed

  16. 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.)

  17. Alpha and fission autoradiography of uranium rods

    International Nuclear Information System (INIS)

    Copic, M.; Ilicj, R.; Najzher, M.; Rant, J.

    1977-01-01

    Macro and micro-distribution of uranium minerals in ore bodies are investigated by alpha autoradiography and by neutron induced fission autoradiography using LR 115 solid state track detector. Optimal conditions are determined experimentally for both methods and examples presented. For field applications the alpha autoradiography (author)

  18. Nuclear fission induced by heavy ions

    International Nuclear Information System (INIS)

    Newton, J.O.

    1988-09-01

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

  19. Process for treating fission waste

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  20. 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...

  1. Measurements of Short-Lived Fission Isomers

    Science.gov (United States)

    Finch, Sean; Bhike, Megha; Howell, Calvin; Krishichayan, Fnu; Tornow, Werner

    2016-09-01

    Fission yields of the short lived isomers 134mTe (T1 / 2 = 162 ns) and 136mXe (T1 / 2 = 2 . 95 μs) were measured for 235U and 238U. The isomers were detected by the γ rays associated with the decay of the isomeric states using high-purity germanium detectors. Fission was induced using both monoenergetic γ rays and neutrons. At TUNL's High-Intensity Gamma-ray Source (HI γS), γ rays of 9 and 11 MeV were produced . Monoenergetic 8 MeV neutrons were produced at TUNL's tandem accelerator laboratory. Both beams were pulsed to allow for precise time-gated spectroscopy of both prompt and delayed γ rays following fission. This technique offers a non-destructive probe of special nuclear materials that is sensitive to the isotopic identity of the fissile material.

  2. The Influence of the Student Mobility Rate on the Graduation Rate in the State of New Jersey

    Science.gov (United States)

    Ross, Lavetta S.

    2016-01-01

    This study examined the influence of the student mobility rate on the high school graduation rate of schools in the state of New Jersey. Variables found to have an influence on the graduation rate in the extant literature were evaluated and reported. The analysis included multiple and hierarchical regression models for school variables (i.e.,…

  3. 50 years of nuclear fission

    International Nuclear Information System (INIS)

    Hilscher, D.

    1989-01-01

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

  4. Fission dynamics of hot nuclei

    Indian Academy of Sciences (India)

    2014-04-05

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

  5. Status of fission yield measurements

    International Nuclear Information System (INIS)

    Maeck, W.J.

    1979-01-01

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

  6. Fuel morphology effects on fission product release

    International Nuclear Information System (INIS)

    Osetek, D.J.; Hartwell, J.K.; Cronenberg, A.W.

    1986-01-01

    Results are presented of fission product release behavior observed during four severe fuel damage tests on bundles of UO 2 fuel rods. Transient temperatures up to fuel melting were obtained in the tests that included both rapid and slow cooldown, low and high (36 GWd/t) burnup fuel and the addition of Ag-In-Cd control rods. Release fractions of major fission product species and release rates of noble gas species are reported. Significant differences in release behavior are discussed between heatup and cooldown periods, low and high burnup fuel and long- and short-lived fission products. Explanations for the observed differences are offered that relate fuel morphology changes to the releases

  7. The discovery of fission

    International Nuclear Information System (INIS)

    McKay, H.A.C.

    1978-01-01

    In this article by the retired head of the Separation Processes Group of the Chemistry Division, Atomic Energy Research Establishment, Harwell, U.K., the author recalls what he terms 'an exciting drama, the unravelling of the nature of the atomic nucleus' in the years before the Second World War, including the discovery of fission. 12 references. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-12-31

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

  9. State variation in rates of cesarean and VBAC delivery: 1989 and 1993.

    Science.gov (United States)

    Clarke, S C; Taffel, S M

    1996-01-01

    There is wide variation among states in rates of cesarean and vaginal births after cesarean (VBAC) deliveries. In general, states in the South have the highest cesarean rates, states in the West have the lowest, and states in the Northeast and Midwest are intermediate. Louisiana had the highest overall rate in 1993 (27.7 per 100 births) while Alaska had the lowest rate (15.2). The majority of states had declines in their cesarean rate between 1989 and 1993. Patterns in primary cesarean rates are similar to those of the overall rate-states in the South generally have the highest rates while states in the West have the lowest rates. Primary cesarean rates ranged between a high of 19.6 in Louisiana to a low of 10.6 in Wisconsin. In general, states with low cesarean rates have among the highest rates of VBAC delivery. Alaska had the highest VBAC rate (40.0), which was almost quadruple the rate of Louisiana (11.2), the state with the lowest rate. Most states had substantial increases in VBAC rates between 1989 and 1993. When examining cesarean rates by maternal age and birth order, states with the highest overall rates also have among the highest age/birth order-specific rates. Cesarean rates were lowest for mothers under 25 years of age having a second or higher order birth in Alaska, 10.4, and highest for mothers 35 years of age or over having a first birth in Mississippi, 51.3. Standardized cesarean rates which were adjusted for differences between states in maternal age and birth order distributions did not diminish the variation among areas.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  11. Fast fission ratio and relative conversion ratio measurements in gadolinium poisoned water moderated UO2 lattices

    International Nuclear Information System (INIS)

    Murphy, M.F.

    1984-01-01

    A programme of criticality experiments has been carried out for BNFL by the Battelle reactor facility at Pacific Northwest Laboratories in Washington State, USA. A series of water moderated lattices of 4.3% enriched, 12.7 mm diameter, UO 2 fuel rods was studied, the fuel pitch was varied and the effects of gadolinium poison were measured. This report deals with the measurement of Fast Fission Ratios and Relative Conversion Ratios at the centre of five of the critical lattices. The Fast Fission Ratio (FFR) is defined here as the ratio of the fission rate per atom of U238, to the fission rate per atom of U235. The Relative Conversion Ratio (RCR) is defined as the ratio of the capture rate per ,atom of U238, to the fission rate per atom of U235, in the reactor fuel, relative to the corresponding ratio in a well thermalised neutron spectrum. A major aspect of these measurements was that the packs of foils were prepared at AEEW Winfrith, despatched to the USA for irradiation and returned to Winfrith for counting. This resulted in a considerable logistics problem but by good planning and the co-operation and diligence of all concerned this problem was overcome. However, the long distance involved inevitably meant that samples were not available for measurement until about 28 hours after the irradiation. It was therefore necessary to modify the techniques that are normally used in the Reactor Physics Division Counting Laboratory, where samples are normally available about two hours after shut-down. The techniques used and the results obtained are given below

  12. Photocurrent enhanced by singlet fission in a dye-sensitized solar cell.

    Science.gov (United States)

    Schrauben, Joel N; Zhao, Yixin; Mercado, Candy; Dron, Paul I; Ryerson, Joseph L; Michl, Josef; Zhu, Kai; Johnson, Justin C

    2015-02-04

    Investigations of singlet fission have accelerated recently because of its potential utility in solar photoconversion, although only a few reports definitively identify the role of singlet fission in a complete solar cell. Evidence of the influence of singlet fission in a dye-sensitized solar cell using 1,3-diphenylisobenzofuran (DPIBF, 1) as the sensitizer is reported here. Self-assembly of the blue-absorbing 1 with co-adsorbed oxidation products on mesoporous TiO2 yields a cell with a peak internal quantum efficiency of ∼70% and a power conversion efficiency of ∼1.1%. Introducing a ZrO2 spacer layer of thickness varying from 2 to 20 Å modulates the short-circuit photocurrent such that it is initially reduced as thickness increases but 1 with 10-15 Å of added ZrO2. This rise can be explained as being due to a reduced rate of injection of electrons from the S1 state of 1 such that singlet fission, known to occur with a 30 ps time constant in polycrystalline films, has the opportunity to proceed efficiently and produce two T1 states per absorbed photon that can subsequently inject electrons into TiO2. Transient spectroscopy and kinetic simulations confirm this novel mode of dye-sensitized solar cell operation and its potential utility for enhanced solar photoconversion.

  13. Elastocapillary Instability in Mitochondrial Fission

    Science.gov (United States)

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

    2015-08-01

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

  14. A threshold for dissipative fission

    International Nuclear Information System (INIS)

    Thoennessen, M.; Bertsch, G.F.

    1993-01-01

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

  15. The relationship between dose rate and transformation induction in C3H/10T1/2 cells by TRIGA reactor fission neutrons at 0.3 Gy

    International Nuclear Information System (INIS)

    Balcer-Kubiczek, E.K.; Harrison, G.H.

    1989-01-01

    The authors present their own and other data showing dose-effect relations for cell survival and the induction of transformations in C3H/IOT 1/2 cells in exponential or stationary cultures after a range of high dose-rate irradiations with X-rays or AFRRI neutrons. (UK)

  16. Conductor and Ensemble Performance Expressivity and State Festival Ratings

    Science.gov (United States)

    Price, Harry E.; Chang, E. Christina

    2005-01-01

    This study is the second in a series examining the relationship between conducting and ensemble performance. The purpose was to further examine the associations among conductor, ensemble performance expressivity, and festival ratings. Participants were asked to rate the expressivity of video-only conducting and parallel audio-only excerpts from a…

  17. Transient fission gas release from UO2 fuel for high temperature and high burnup

    International Nuclear Information System (INIS)

    Szuta, M.

    2001-01-01

    In the present paper it is assumed that the fission gas release kinetics from an irradiated UO 2 fuel for high temperature is determined by the kinetics of grain growth. A well founded assumption that Vitanza curve describes the change of uranium dioxide re-crystallization temperature and the experimental results referring to the limiting grain size presented in the literature are used to modify the grain growth model. Algorithms of fission gas release due to re-crystallization of uranium dioxide grains are worked out. The defect trap model of fission gas behaviour described in the earlier papers is supplemented with the algorithms. Calculations of fission gas release in function of time, temperature, burn-up and initial grain sizes are obtained. Computation of transient fission gas release in the paper is limited to the case where steady state of irradiation to accumulate a desired burn-up is performed below the temperature of re-crystallization then the subsequent step temperature increase follows. There are considered two kinds of step temperature increase for different burn-up: the final temperature of the step increase is below and above the re-crystallization temperature. Calculations show that bursts of fission gas are predicted in both kinds. The release rate of gas liberated for the final temperature above the re-crystallization temperature is much higher than for final temperature below the re-crystallization temperature. The time required for the burst to subside is longer due to grain growth than due to diffusion of bubbles and knock-out release. The theoretical results explain qualitatively the experimental data but some of them need to be verified since this sort of experimental data are not found in the available literature. (author)

  18. Barium 139 as Fission Indicator

    Energy Technology Data Exchange (ETDEWEB)

    Broda, E.

    1943-07-01

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

  19. 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.

  20. Volatilization and reaction of fission products in flowing steam

    International Nuclear Information System (INIS)

    Johnson, I.; Steidl, D.V.; Johnson, C.E.

    1985-01-01

    The principal risk to the public from nuclear power plants derives from the highly radioactive atoms (fission products) generated as energy is produced in the nuclear fuel. The revolatilization of fission products from reactor system surfaces due to self-heating by radioactive decay has become a complicating factor in the source-term redefinition effort. It has had a major impact on calculations of fission product distributions in accident safety analyses. The focus of this research effort was to investigate the volatilization and transport of fission products and control rod materials in a flowing gaseous steam-hydrogen mixture. Fission product and control rod materials in various combinations were studied including CsI, CsOH, TeO 2 , SrO, Ag, In, Cd and Mn. The vaporization behavior of the deposits were characterized with respect to vaporization rates, chemical species and downstream transport behavior

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

    Science.gov (United States)

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

    1991-08-01

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

  2. Behavior of solid fission products in irradiated fuel

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  3. Fusion-fission dynamics

    International Nuclear Information System (INIS)

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

    1991-04-01

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

  4. Explaining Cross-State Differences in Elderly Suicide Rates and Identifying State-Level Public Policy Responses that Reduce Rates

    Science.gov (United States)

    Giles-Sims, Jean; Lockhart, Charles

    2006-01-01

    Elderly Americans commit suicide at higher rates than other age groups. We contend that macro- and micro-social variables contribute distinct aspects to explanations of this tragic loss: the former focus on circumstances that affect overall rates, the latter reveal why certain individuals succumb to suicide. Our analysis focuses on the…

  5. Spray removal of fission products in PWR containments

    International Nuclear Information System (INIS)

    Grist, D.R.

    1982-11-01

    Models and parameters for assessing the rate and extent of removal of various fission product species are described. A range of droplet sizes and of spray additive options is considered and removal of vapour phase inorganic iodine species, of organic iodides and of aerosols containing fission products is discussed. Aerosol removal is assessed in terms of contributing removal mechanisms and the removal rate modelled as a function of the radius of the aerosol particulate species. (author)

  6. The fission track method

    International Nuclear Information System (INIS)

    Hansen, K.

    1990-01-01

    During the last decade fission track (FT) analysis has evolved as an important tool in exploration for hydrocarbon resources. Most important is this method's ability to yield information about temperatures at different times (history), and thus relate oil generation and time independently of other maturity parameters. The purpose of this paper is to introduce the basics of the method and give an example from the author's studies. (AB) (14 refs.)

  7. Dielectronic recombination rate coefficients to the excited states of CI from CII

    International Nuclear Information System (INIS)

    Dubau, J.; Kato, T.; Safronova, U.I.

    1998-01-01

    The dielectronic recombination rate coefficients to the excited states for n=2-6 are calculated including 1s 2 2l 1 2l 2 2l 3 nl (n=2-6, l≤(n-1)) states. The values for the excited states higher than n=6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The rate coefficients to the excited states are fitted to an analytical formula and the fit parameters are given. (author)

  8. Effect of irradiation temperature and strain rate on the mechanical properties of V-4Cr-4Ti irradiated to low doses in fission reactors

    International Nuclear Information System (INIS)

    Zinkle, S.J.; Snead, L.L.; Rowcliffe, A.F.; Alexander, D.J.; Gibson, L.T.

    1998-01-01

    Tensile tests performed on irradiated V-(3-6%)Cr-(3-6%)Ti alloys indicate that pronounced hardening and loss of strain hardening capacity occurs for doses of 0.1--20 dpa at irradiation temperatures below ∼330 C. The amount of radiation hardening decreases rapidly for irradiation temperatures above 400 C, with a concomitant increase in strain hardening capacity. Low-dose (0.1--0.5 dpa) irradiation shifts the dynamic strain aging regime to higher temperatures and lower strain rates compared to unirradiated specimens. Very low fracture toughness values were observed in miniature disk compact specimens irradiated at 200--320 C to ∼1.5--15 dpa and tested at 200 C

  9. The Impact of State Abortion Policies on Teen Pregnancy Rates

    Science.gov (United States)

    Medoff, Marshall

    2010-01-01

    The availability of abortion provides insurance against unwanted pregnancies since abortion is the only birth control method which allows women to avoid an unwanted birth once they are pregnant. Restrictive state abortion policies, which increase the cost of obtaining an abortion, may increase women's incentive to alter their pregnancy avoidance…

  10. Corn nitrogen fertilization rate tools compared over eight Midwest states

    Science.gov (United States)

    Publicly-available nitrogen (N) rate recommendation tools are utilized to help maximize yield in corn production. These tools often fail when N is over-applied and results in excess N being lost to the environment, or when N is under-applied and results in decreased yield and economic returns. Perfo...

  11. The High Cost of South Carolina's Low Graduation Rate. School Choice Issues in the State

    Science.gov (United States)

    Gottlob, Brian J.

    2007-01-01

    Research has documented a crisis in South Carolina's high school graduation rate. While state officials report a graduation rate above 70 percent, researchers from South Carolina and elsewhere place the rate just above 50 percent, with rates among minority students lower than 50 percent. South Carolina's graduation rate is the worst of all 50…

  12. Robust singlet fission in pentacene thin films with tuned charge transfer interactions.

    Science.gov (United States)

    Broch, K; Dieterle, J; Branchi, F; Hestand, N J; Olivier, Y; Tamura, H; Cruz, C; Nichols, V M; Hinderhofer, A; Beljonne, D; Spano, F C; Cerullo, G; Bardeen, C J; Schreiber, F

    2018-03-05

    Singlet fission, the spin-allowed photophysical process converting an excited singlet state into two triplet states, has attracted significant attention for device applications. Research so far has focused mainly on the understanding of singlet fission in pure materials, yet blends offer the promise of a controlled tuning of intermolecular interactions, impacting singlet fission efficiencies. Here we report a study of singlet fission in mixtures of pentacene with weakly interacting spacer molecules. Comparison of experimentally determined stationary optical properties and theoretical calculations indicates a reduction of charge-transfer interactions between pentacene molecules with increasing spacer molecule fraction. Theory predicts that the reduced interactions slow down singlet fission in these blends, but surprisingly we find that singlet fission occurs on a timescale comparable to that in pure crystalline pentacene. We explain the observed robustness of singlet fission in such mixed films by a mechanism of exciton diffusion to hot spots with closer intermolecular spacings.

  13. A model for the release of low-volatility fission products in oxidizing conditions

    International Nuclear Information System (INIS)

    Cox, D.S.; Hunt, C.E.L.; Liu, Z.; Keller, N.A.; Barrand, R.D.; O'Connor, R.F.

    1991-07-01

    A thermodynamic and kinetic model has been developed for calculating low-volatility fission-product releases from UO 2 at high temperatures in oxidizing conditions. Volatilization of the UO 2 matrix is assumed to be the rate controlling process. Oxidation kinetics of the UO 2 are modelled by either interfacial rate control, gas phase oxidant transport control, or solid-state diffusion of oxygen. The vapour pressure of UO 3 in equilibrium with the oxidizing fuel is calculated from thermodynamic data, and volatilization rates are determined using a model for forced convective mass transport. Low-volatility fission-product releases are calculated from the volume of vapourized fuel. Model calculations are conservative compared to experimental data for Zr, La, Ce and Nb fission-product releases from irradiated UO 2 exposed to air at 1973-2350 K. The implications of this conservatism are discussed in terms of possible rate control by processes other than convective mass transport of UO 3 . Coefficients for effective surface area (based on experimental data) and for heterogeneous rate controlling reaction kinetics are introduced to facilitate agreement between calculations and the experimental data.

  14. Coulomb fission and transfer fission at heavy ion collisions

    International Nuclear Information System (INIS)

    Himmele, G.

    1981-01-01

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

  15. Singlet fission in pentacene dimers

    Science.gov (United States)

    Zirzlmeier, Johannes; Lehnherr, Dan; Coto, Pedro B.; Chernick, Erin T.; Casillas, Rubén; Basel, Bettina S.; Thoss, Michael; Tykwinski, Rik R.; Guldi, Dirk M.

    2015-01-01

    Singlet fission (SF) has the potential to supersede the traditional solar energy conversion scheme by means of boosting the photon-to-current conversion efficiencies beyond the 30% Shockley–Queisser limit. Here, we show unambiguous and compelling evidence for unprecedented intramolecular SF within regioisomeric pentacene dimers in room-temperature solutions, with observed triplet quantum yields reaching as high as 156 ± 5%. Whereas previous studies have shown that the collision of a photoexcited chromophore with a ground-state chromophore can give rise to SF, here we demonstrate that the proximity and sufficient coupling through bond or space in pentacene dimers is enough to induce intramolecular SF where two triplets are generated on one molecule. PMID:25858954

  16. 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.

  17. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, Travis Shane [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mincher, Bruce Jay [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schmitt, Nicholas C [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  18. Fission in intermediate energy heavy ion reactions

    International Nuclear Information System (INIS)

    Wilhelmy, J.B.; Begemann-Blaich, M.; Blaich, T.; Boissevain, J.; Fowler, M.M.; Gavron, A.; Jacak, B.V.; Lysaght, P.S.; Britt, H.C.; Fields, D.J.; Hansen, L.F.; Lanier, R.G.; Massoletti, D.J.; Namboodiri, M.M.; Remington, B.A.; Sangster, T.C.; Struble, G.L.; Webb, M.L.; Chan, Y.D.; Dacai, A.; Harmon, A.; Leyba, J.; Pouliot, J.; Stokstad, R.G.; Hansen, O.; Levine, M.J.; Thorn, C.E.; Trautmann, W.; Dichter, B.; Kaufman, S.; Videbaek, F.; Fraenkel, Z.; Mamane, G.; Cebra, D.; Westfall, G.D.

    1989-01-01

    A systematic study of reaction mechanisms at intermediate energies (50-100 MeV/A) has been performed at the Lawrence Berkeley Laboratory's BeValac using medium weight projectiles on medium and heavy element targets. A gas and plastic phoswich detector system was employed which gave large geometric coverage and a wide dynamic response. The particles identified with the gas detectors could be characterized into three components - intermediate mass fragments (IMF), fission fragments (FF) and heavy residues (HR). Major observed features are: The reaction yields are similar in the 50 to 100 MeV/A range, central collisions have high 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.)

  19. Fission in intermediate energy heavy ion reactions

    International Nuclear Information System (INIS)

    Wilhelmy, J.B.; Begemann-Blaich, M.; Blaich, T.

    1989-01-01

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

  20. A small flat fission chamber

    International Nuclear Information System (INIS)

    Li Yijun; Wang Dalun; Chen Suhe

    1999-01-01

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

  1. Fission barriers of light nuclei

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  2. Fission blanket benchmark experiment on spherical assembly of uranium and PE with PE reflector

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Tonghua; Lu, Xinxin; Wang, Mei; Han, Zijie, E-mail: neutron_integral@aliyun.com; Jiang, Li; Wen, Zhongwei; Liu, Rong

    2016-04-15

    Highlights: • The fission rate distribution on two depleted uranium assemblies was measured with plate fission chambers. • We do calculations using MCNP code and ENDF/B-V.0 library. • The overestimation of calculations to the measured fission rates was found. • The observed discrepancy are discussed. - Abstract: New concept of fusion-fission hybrid for energy generation has been proposed. To validate the nuclear performance of fission blanket of hybrid, as part of series of validation experiment, two types of fission blanket assemblies were setup in this work and measurements were made of the reaction rate distribution for uranium fission in the spherical assembly of depleted uranium and polyethylene by Plate Fission Chamber (PFC). There are two PFCs in experiment, one is depleted uranium chamber and the other is enriched uranium chamber. The Monte-Carlo transport code MCNP5 and continuous energy cross sections library ENDF/BV.0 were used for the analysis of fission rate distribution in the two types of assemblies. The calculated results were compared with the experimental ones. The overestimation of fission rate for depleted uranium and enriched uranium were found in the inner boundary of the two assemblies. However, the C/E ratio tends to decrease for the distance from the core slightly and the results for enriched uranium are better than that for depleted uranium.

  3. Fission Detection Using the Associated Particle Technique

    International Nuclear Information System (INIS)

    R.P. Keegan; J.P. Hurley; J.R. Tinsley; R. Trainham; S.C. Wilde

    2008-01-01

    A beam of tagged 14 MeV neutrons from the deuterium-tritium (DT) reaction is used to induce fission in a target composed of depleted uranium. The generator yield is 10 7 neutrons/second radiated into a 4 x 4 in. NaI detectors are used for gamma-ray detection. The fission process is known to produce multiple gamma-rays and neutrons. Triple coincidences (α-γ-γ) are measured as a function of neutron flight time up to 90 ns after fission, where the α-particle arises from the DT reaction. A sudden increase in the triple coincidence rate at the location of the material is used to localize and detect fission in the interrogated target. Comparisons are made with experiment runs where lead, tungsten, and iron were used as target materials. The triple coincidence response profile from depleted uranium is noted to be different to those observed from the other target materials. The response from interrogation targets composed of fissile material is anticipated to be even more unique than that observed from depleted uranium

  4. Fission gas release of MOX with heterogeneous structure

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  5. Nuclear Forensics and Radiochemistry: Fission

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-11-07

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

  6. Fusion-fission type collisions

    International Nuclear Information System (INIS)

    Oeschler, H.

    1980-01-01

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

  7. Fission fragment mass and total kinetic energy distributions of spontaneously fissioning plutonium isotopes

    Science.gov (United States)

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

    2018-03-01

    The fission-fragment mass and total kinetic energy (TKE) distributions are evaluated in a quantum mechanical framework using elongation, mass asymmetry, neck degree of freedom as the relevant collective parameters in the Fourier shape parametrization recently developed by us. The potential energy surfaces (PES) are calculated within the macroscopic-microscopic model based on the Lublin-Strasbourg Drop (LSD), the Yukawa-folded (YF) single-particle potential and a monopole pairing force. The PES are presented and analysed in detail for even-even Plutonium isotopes with A = 236-246. They reveal deep asymmetric valleys. The fission-fragment mass and TKE distributions are obtained from the ground state of a collective Hamiltonian computed within the Born-Oppenheimer approximation, in the WKB approach by introducing a neck-dependent fission probability. The calculated mass and total kinetic energy distributions are found in good agreement with the data.

  8. 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.

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

    International Nuclear Information System (INIS)

    Damm, G.; Thiel, K.

    1977-01-01

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

  10. Teen Birth Rates for Age Group 15-19 in the United States by County

    Data.gov (United States)

    U.S. Department of Health & Human Services — This data set contains mean teen birth rates by year for each county and state in the United States. Hierarchical Bayesian space-time models were used to generate...

  11. Energy from nuclear fission()

    Science.gov (United States)

    Ripani, M.

    2015-08-01

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

  12. Ternary fission in an effective liquid drop model

    International Nuclear Information System (INIS)

    Duarte, Sergio B.; Tavares, Odilon A.P.; Dimarco, A.; Goncalves, Marcello; Guzman, Fernando; Trallero-Herrera, Carlos; Rodriguez, Oscar; Garcia, Fermin

    2001-01-01

    Full text follows: The nuclear partition in three fragments has been observed in recent experiments for fission process of 252 Cf and 24 '0 Pu. We apply the Effective Liquid Drop Model (ELDM), successfully used for discussing binary cold fission and cluster emissions for a three center geometric shape parametrization, describing the quasi-molecular deformation which can lead to ternary fragmentation. A preliminary calculation for rates of these processes are performed and the results are compared to the rate of the dominant binary fission process. A large range of parent nuclei (spherical and deformed) is covered in the calculation. The purpose is to point out others possible ternary fission process experimentally measurable. (author)

  13. Economic Conditions and the Divorce Rate: A Time-Series Analysis of the Postwar United States.

    Science.gov (United States)

    South, Scott J.

    1985-01-01

    Challenges the belief that the divorce rate rises during prosperity and falls during economic recessions. Time-series regression analysis of postwar United States reveals small but positive effects of unemployment on divorce rate. Stronger influences on divorce rates are changes in age structure and labor-force participation rate of women.…

  14. An Application of Durkheim's Theory of Suicide to Prison Suicide Rates in the United States

    Science.gov (United States)

    Tartaro, Christine; Lester, David

    2005-01-01

    E. Durkheim (1897) suggested that the societal rate of suicide might be explained by societal factors, such as marriage, divorce, and birth rates. The current study examined male prison suicide rates and suicide rates for men in the total population in the United States and found that variables based on Durkheim's theory of suicide explained…

  15. The fission products palladium and rhodium: Their state in solutions, their behavior in the regeneration of fuel of atomic power stations, and the search for selective extraction techniques

    International Nuclear Information System (INIS)

    Arseenkov, L.V.; Zakharkin, B.S.; Lunichkina, K.P.; Renard, E.V.; Rogozhkin, V.Yu.; Shorokhov, N.A.

    1992-01-01

    At the present time many research centers are working on the extraction of noble metals in the form of fission fragments. Consistent data has been obtained on the mass accumulation of noble metals in various forms of processed nuclear fuel. Requirements are noted that must be met for obtaining industrial and economic efficiency in the extraction of noble metals by the Purex process. Presently there is a lack of information on the extraction of noble metals from spent fuel, particularly as far as the nitric acid media of the Purex process are concerned. The authors will discuss individual test observations on simulating systems and real systems with noble metals. The investigations focused on the noble metals of lowest radioactivity, namely palladium and rhodium. The complexity of the chemistry of ruthenium, on the one hand, and the possible selective, clearing distillation of ruthenium tetroxide from nitric acid solutions, on the other hand, make it necessary to focus the attention on the unresolved problems of the extraction of palladium and rhodium. The article further includes discussion on the following topics: noble metals in solutions of purex process, electrochemical operations involving noble metals, extraction systems for rhodium and palladium, separation of palladium from real solutions

  16. General Theory of Decoy-State Quantum Cryptography with Dark Count Rate Fluctuation

    International Nuclear Information System (INIS)

    Xiang, Gao; Shi-Hai, Sun; Lin-Mei, Liang

    2009-01-01

    The existing theory of decoy-state quantum cryptography assumes that the dark count rate is a constant, but in practice there exists fluctuation. We develop a new scheme of the decoy state, achieve a more practical key generation rate in the presence of fluctuation of the dark count rate, and compare the result with the result of the decoy-state without fluctuation. It is found that the key generation rate and maximal secure distance will be decreased under the influence of the fluctuation of the dark count rate

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

    International Nuclear Information System (INIS)

    Madland, D.G.

    1997-01-01

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

  18. Photofission observations in reactor environments using selected fission-product yields

    International Nuclear Information System (INIS)

    Gold, R.; Ruddy, F.H.; Roberts, J.H.

    1982-01-01

    A new method for the observation of photofission in reactor environments is advanced. It is based on the in-situ observation of fission product yield. In fact, at a given in-situ reactor location, the fission product yield is simply a weighted linear combination of the photofission product yield, Y/sub gamma/, and the neutron induced fission product yield, Y/sub n. The weight factors arising in this linear combination are the photofission fraction and neutron induced fission fraction, respectively. This method can be readily implemented with established techniques for measuring in-situ reactor fission product yield. For example, one can use the method based on simultaneous irradiation of radiometric (RM) and solid state track recorder (SSTR) fission monitors. The sensitivity and accuracy and current knowledge of fission product yields. Unique advantages of this method for reactor applications are emphasized

  19. Generalization of Kramer's formula: Fission over a multidimensional potential barrier

    International Nuclear Information System (INIS)

    Jing-Shang, Z.; Weidenmueller, H.A.

    1983-01-01

    We generalize Kramers's rate expression for diffusion over a potential barrier to the case of a diffusion problem for n degrees of freedom. These can be thought of as the shape degrees of freedom of a fissioning nucleus. We present our formula for the fission width and discuss its dependence on the parameters: the mass tensor, the friction tensor, and the shape of the potential landscape

  20. The temperature dependence of the friction in the fission

    International Nuclear Information System (INIS)

    Yamaji, Shuhei

    1996-01-01

    We study the slow collective motion at finite excitation on the basis of the linear response theory. The transport coefficients such as friction γ, inertia M and local stiffness C formulated within a locally harmonic approximation are computed along the fission path of 224 Th. It is found that the effective damping rate η = γ/=2√(M|C|)= increases with the temperature T in accord with the fission experiment with the emission of γ-rays. (author)

  1. A new technique to measure fission-product diffusion coefficients in UO2 fuel

    International Nuclear Information System (INIS)

    Hocking, W.H.; Verrall, R.A.; Bushby, S.J.

    1999-01-01

    This paper describes a new out-reactor technique for the measurement of fission-product diffusion rates in UO 2 . The technique accurately simulates in-reactor fission-fragment effects: a thermal diffusion that is due to localized mixing in the fission track, radiation-enhanced diffusion that is due to point-defect creation by fission fragments, and bubble resolution. The technique utilizes heavy-ion accelerators - low energy (40 keV to 1 MeV) for fission-product implantation, high energy (72 MeV) to create fission-fragment damage effects, and secondary ion mass spectrometry (SIMS) for measuring the depth profile of the implanted species. Preliminary results are presented from annealing tests (not in the 72 MeV ion flux) at 1465 deg. C and 1650 deg. C at low and high concentrations of fission products. (author)

  2. Transient core characteristics of small molten salt reactor coupling problem between heat transfer/flow and nuclear fission reaction

    International Nuclear Information System (INIS)

    Yamamoto, Takahisa; Mitachi, Koshi

    2004-01-01

    This paper performed the transient core analysis of a small Molten Salt Reactor (MSR). The emphasis is that the numerical model employed in this paper takes into account the interaction among fuel salt flow, nuclear reaction and heat transfer. The model consists of two group diffusion equations for fast and thermal neutron fluexs, balance equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and graphite moderator. The results of transient analysis are that (1) fission reaction (heat generation) rate significantly increases soon after step reactivity insertion, e.g., the peak of fission reaction rate achieves about 2.7 times larger than the rated power 350 MW when the reactivity of 0.15% Δk/k 0 is inserted to the rated state, and (2) the self-control performance of the small MSR effectively works under the step reactivity insertion of 0.56% Δk/k 0 , putting the fission reaction rate back on the rated state. (author)

  3. Fission fragment driven neutron source

    Science.gov (United States)

    Miller, Lowell G.; Young, Robert C.; Brugger, Robert M.

    1976-01-01

    Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.

  4. Neutron multiplicity of fission fragments

    Energy Technology Data Exchange (ETDEWEB)

    Abdelrahman, Y S [Physics department, mu` rah university Al-Karak, (Jordan)

    1995-10-01

    The total average neutron multiplicity of the fission fragments produced by the spontaneous fission of {sup 248} Cm has been measured. This measurement has been done by using a new experimental technique. This technique mainly depends on {gamma}-{gamma} coincidence using a very high resolution high purity germanium (HPGe) detector. 2 figs.

  5. Fission throughout the periodic table

    International Nuclear Information System (INIS)

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

    1989-04-01

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

  6. The Association between State Policy Environments and Self-Rated Health Disparities for Sexual Minorities in the United States

    Directory of Open Access Journals (Sweden)

    Gilbert Gonzales

    2018-06-01

    Full Text Available A large body of research has documented disparities in health and access to care for lesbian, gay, and bisexual (LGB people in the United States. Less research has examined how the level of legal protection afforded to LGB people (the state policy environment affects health disparities for sexual minorities. This study used data on 14,687 sexual minority adults and 490,071 heterosexual adults from the 2014–2016 Behavioral Risk Factor Surveillance System to document differences in health. Unadjusted state-specific prevalence estimates and multivariable logistic regression models were used to compare poor/fair self-rated health by gender, sexual minority status, and state policy environments (comprehensive versus limited protections for LGB people. We found disparities in self-rated health between sexual minority adults and heterosexual adults in most states. On average, sexual minority men in states with limited protections and sexual minority women in states with either comprehensive or limited protections were more likely to report poor/fair self-rated health compared to their heterosexual counterparts. This study adds new findings on the association between state policy environments and self-rated health for sexual minorities and suggests differences in this relationship by gender. The associations and impacts of state-specific policies affecting LGB populations may vary by gender, as well as other intersectional identities.

  7. Progress in fission product nuclear data

    International Nuclear Information System (INIS)

    Lammer, M.

    1984-09-01

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

  8. Mechanisms of fission neutron emission

    International Nuclear Information System (INIS)

    Maerten, H.

    1991-01-01

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

  9. Origins of Singlet Fission in Solid Pentacene from an ab initio Green's Function Approach

    Science.gov (United States)

    Refaely-Abramson, Sivan; da Jornada, Felipe H.; Louie, Steven G.; Neaton, Jeffrey B.

    2017-12-01

    We develop a new first-principles approach to predict and understand rates of singlet fission with an ab initio Green's-function formalism based on many-body perturbation theory. Starting with singlet and triplet excitons computed from a G W plus Bethe-Salpeter equation approach, we calculate the exciton-biexciton coupling to lowest order in the Coulomb interaction, assuming a final state consisting of two noninteracting spin-correlated triplets with finite center-of-mass momentum. For crystalline pentacene, symmetries dictate that the only purely Coulombic fission decay process from a bright singlet state requires a final state consisting of two inequivalent nearly degenerate triplets of nonzero, equal and opposite, center-of-mass momenta. For such a process, we predict a singlet lifetime of 30-70 fs, in very good agreement with experimental data, indicating that this process can dominate singlet fission in crystalline pentacene. Our approach is general and provides a framework for predicting and understanding multiexciton interactions in solids.

  10. NCLB Implementation Report: State Approaches for Calculating High School Graduation Rates.

    Science.gov (United States)

    Swanson, Christopher B.

    This review investigated the state accountability Workbooks provisionally approved and publicly reported by the U.S. Department of Education (DOE) as of June 2003. These documents were obtained from the DOE Web site. This report examines state definitions of high school graduation rates and strategies for constructing graduation rate indicators. A…

  11. Fission gas release in LWR fuel measured during nuclear operation

    International Nuclear Information System (INIS)

    Appelhans, A.D.; Skattum, E.; Osetek, D.J.

    1980-01-01

    A series of fuel behavior experiments are being conducted in the Heavy Boiling Water Reactor in Halden, Norway, to measure the release of Xe, Kr, and I fission products from typical light water reactor design fuel pellets. Helium gas is used to sweep the Xe and Kr fission gases out of two of the Instrumented Fuel Assembly 430 fuel rods and to a gamma spectrometer. The measurements of Xe and Kr are made during nuclear operation at steady state power, and for 135 I following reactor scram. The first experiments were conducted at a burnup of 3000 MWd/t UO 2 , at bulk average fuel temperatures of approx. 850 K and approx. 23 kW/m rod power. The measured release-to-birth ratios (R/B) of Xe and Kr are of the same magnitude as those observed in small UO 2 specimen experiments, when normalized to the estimated fuel surface-to-volume ratio. Preliminary analysis indicates that the release-to-birth ratios can be calculated, using diffusion coefficients determined from small specimen data, to within a factor of approx. 2 for the IFA-430 fuel. The release rate of 135 I is shown to be approximately equal to that of 135 Xe

  12. Dielectronic recombination rate coefficients to the excited states of CI from CII

    Energy Technology Data Exchange (ETDEWEB)

    Dubau, J. [Observatoire of Paris, 92 MEUDON (France); Kato, T.; Safronova, U.I.

    1998-01-01

    The dielectronic recombination rate coefficients to the excited states for n=2-6 are calculated including 1s{sup 2}2l{sub 1}2l{sub 2}2l{sub 3}nl (n=2-6, l{<=}(n-1)) states. The values for the excited states higher than n=6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The rate coefficients to the excited states are fitted to an analytical formula and the fit parameters are given. (author)

  13. 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

  14. Measurement of mass and isotopic fission yields for heavy fission products with the LOHENGRIN mass spectrometer

    International Nuclear Information System (INIS)

    Bail, A.

    2009-05-01

    In spite of the huge amount of fission yield data available in different libraries, more accurate values are still needed for nuclear energy applications and to improve our understanding of the fission process. Thus measurements of fission yields were performed at the mass spectrometer Lohengrin at the Institut Laue-Langevin in Grenoble, France. The mass separator Lohengrin is situated at the research reactor of the institute and permits the placement of an actinide layer in a high thermal neutron flux. It separates fragments according to their atomic mass, kinetic energy and ionic charge state by the action of magnetic and electric fields. Coupled to a high resolution ionization chamber the experiment was used to investigate the mass and isotopic yields of the light mass region. Almost all fission yields of isotopes from Th to Cf have been measured at Lohengrin with this method. To complete and improve the nuclear data libraries, these measurements have been extended in this work to the heavy mass region for the reactions 235 U(n th ,f), 239 Pu(n th ,f) and 241 Pu(n th ,f). For these higher masses an isotopic separation is no longer possible. So, a new method was undertaken with the reaction 239 Pu(n th ,f) to determine the isotopic yields by spectrometry. These experiments have allowed to reduce considerably the uncertainties. Moreover the ionic charge state and kinetic energy distributions were specifically studied and have shown, among others, nanosecond isomers for some masses. (author)

  15. RSAC, Gamma Doses, Inhalation and Ingestion Doses, Fission Products Inventory after Fission Products Release

    International Nuclear Information System (INIS)

    Richardson, L.C.

    1967-01-01

    1 - Description of problem or function: RSAC generates a fission product inventory from a given set of reactor operating conditions and then computes the external gamma dose, the deposition gamma dose, and the inhalation-ingestion dose to critical body organs as a result of exposure to these fission products. Program output includes reactor operating history, fission product inventory, dosages, and ingestion parameters. 2 - Method of solution: The fission product inventory generated by the reactor operating conditions and the inventory remaining at various times after release are computed using the equations of W. Rubinson in Journal of Chemical Physics, Vol. 17, pages 542-547, June 1949. The external gamma dose and the deposition gamma dose are calculated by determining disintegration rates as a function of space and time, then integrating using Hermite's numerical techniques for the spatial dependence. The inhalation-ingestion dose is determined by the type and quantity of activity inhaled and the biological rate of decay following inhalation. These quantities are integrated with respect to time to obtain the dosage. The ingestion dose is related to the inhalation dose by an input constant

  16. The Association of State Rate Review Authority with Health Insurance Premiums.

    Science.gov (United States)

    Ticse, Caroline

    2015-10-01

    Key findings. (1) Adjusted premiums in the individual market in states with prior approval authority combined with loss ratio requirements were lower in 2010-2013 than premiums in states with no rate review authority or file-and-use regulations only. (2) Adjusted premiums declined modestly in prior approval states while premiums increased in states with no rate review authority or with file-and-use regulations only. (3) The findings suggest that states with prior approval authority and loss ratio requirements constrained increases in health insurance premiums.

  17. How fission was discovered

    International Nuclear Information System (INIS)

    Fluegge, S.

    1989-01-01

    After the great survey of neutron induced radioactivity by Fermi and co-workers, the laboratories in Paris and Berlin-Dahlen tried to disentangle the complex results found in uranium. At that time neutron sources were small, activities low, and equipment very simple. Chemistry beyond uranium still was unknown. Hahn and Meitner believed to have observed three transuranic isomeric chains, a doubtful result even then. Early in 1938, Curie and Savic in Paris found an activity interpreted to be actinium, and Hahn and Meitner another to be radium. Both interpretations seemed impossible from energy considerations. Hahn and Strassmann, therefore, continued this work and succeeded to separate the new activity from radium. There remained no doubt that a barium isotope had been produced, the uranium nucleus splitting in the yet-unknown process we now call fission

  18. Variations in teenage birth rates, 1991-98: national and state trends.

    Science.gov (United States)

    Ventura, S J; Curtin, S C; Mathews, T J

    2000-04-24

    This report presents national birth rates for teenagers for 1991-98 and the percent change, 1991-98. State-specific teenage birth rates by age, race, and Hispanic origin for 1991 and 1998 and the percent change, 1991 to 1998, are also presented. Tabular and graphical descriptions of the trends in teenage birth rates for the Nation and each State, by age group, race, and Hispanic origin of the mother, are discussed. Birth rates for teenagers 15-19 years declined nationally between 1991 and 1998 for all age and race and Hispanic origin populations, with the steepest declines recorded for black teenagers. State-specific rates fell significantly in all States for ages 15-19 years; declines ranged from 10 to 38 percent. In general, rates by State fell more for younger than for older teenagers, ranging by State from 10 to 46 percent for ages 15-17 years. Statistically significant reductions for older teenagers ranged from 3 to 39 percent. Reductions by State were largest for black teenagers 15-19 years, with rates falling 30 percent or more in 15 States. Among the factors accounting for these declines are decreased sexual activity, increases in condom use, and the adoption of the implant and injectable contraceptives.

  19. Preparative electrophoresis of industrial fission product solutions

    International Nuclear Information System (INIS)

    Tret, Joel

    1971-07-01

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

  20. Fission gas retention in irradiated metallic fuel

    International Nuclear Information System (INIS)

    Fenske, G.R.; Gruber, E.; Kramer, J.M.

    1987-01-01

    Theoretical calculations and experimental measurements of the quantity of retained fission gas in irradiated metallic fuel (U-5 wt. % Fs) are presented. (The symbol 'Fs' designates fissium, a 'pseudo-element' which, in reality, is an alloy whose composition is representative of fission products that remain in reprocessed fuel). The calculations utilize the Booth method to model the steady-state release of gases from fuel grains and a simplified grain-boundary gas model to predict the gas release from intergranular regions. The quantity of gas retained in as-irradiated fuel was determined by collecting the gases released from short segments of EBR-II driver fuel that were melted in a gas-tight furnace. Comparison of the calculations with the measurements shows quantitative agreement in both the magnitude and the axial variation of the retained gas content. (orig.)

  1. Transport of fission products in matrix and graphite

    International Nuclear Information System (INIS)

    Hoinkis, E.

    1983-06-01

    In the past years new experimental methods were applied to or developed for the investigation of fission product transport in graphitic materials and to characterization of the materials. Models for fission product transport and computer codes for the calculation of core release rates were improved. Many data became available from analysis of concentration profiles in HTR-fuel elements. New work on the effect on diffusion of graphite corrosion, fast neutron flux and fluence, heat treatment, chemical interactions and helium pressure was reported on recently or was in progress in several laboratories. It seemed to be the right time to discuss the status of transport of metallic fission products in general, and in particular the relationship between structural and transport properties. Following a suggestion a Colloquium was organized at the HMI Berlin. Interdisciplinary discussions were stimulated by only inviting a limited number of participants who work in different fields of graphite and fission product transport research. (orig./RW)

  2. Fission product release from fuel of water-cooled reactors

    International Nuclear Information System (INIS)

    Strupczewski, A.; Marks, P.; Klisinska, M.

    1997-01-01

    The report contains a review of theoretical models and experimental works of gaseous and volatile fission products from uranium dioxide fuel. The experimental results of activity release at low burnup and the model of fission gas behaviour at initial stage of fuel operational cycle are presented. Empirical models as well as measured results of transient fission products release rate in the temperature up to UO 2 melting point, with consideration of their chemical reactions with fuel and cladding, are collected. The theoretical and experimental data were used for calculations of gaseous and volatile fission products release, especially iodine and caesium, to the gas volume of WWER-1000 and WWER-440 type fuel rods at low and high burnup and their further release from defected rods at the assumed loss-of-coolant accident. (author)

  3. Identification of Fissionable Materials Using the Tagged Neutron Technique

    International Nuclear Information System (INIS)

    Keegan, R.P.; Hurley, J.P.; Tinsley, J.R.; Trainham, R.

    2009-01-01

    This summary describes experiments to detect and identify fissionable materials using the tagged neutron technique. The objective of this work is to enhance homeland security capability to find fissionable material that may be smuggled inside shipping boxes, containers, or vehicles. The technique distinguishes depleted uranium from lead, steel, and tungsten. Future work involves optimizing the technique to increase the count rate by many orders of magnitude and to build in the additional capability to image hidden fissionable materials. The tagged neutron approach is very different to other techniques based on neutron die-away or photo-fission. This work builds on the development of the Associated Particle Imaging (API) technique at the Special Technologies Laboratory (STL). Similar investigations have been performed by teams at the Oak Ridge National Laboratory (ORNL), the Khlopin Radium Institute in Russia, and by the EURITRACK collaboration in the European Union

  4. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices.

    Science.gov (United States)

    Wilson, Mark W B; Rao, Akshay; Ehrler, Bruno; Friend, Richard H

    2013-06-18

    Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons

  5. Adjustment of the 235U Fission Spectrum

    International Nuclear Information System (INIS)

    GRIFFIN, PATRICK J.; WILLIAMS, J.G.

    1999-01-01

    The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the 235 U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the 235 U spectrum. An improved 235 U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses

  6. Ancestral state reconstruction, rate heterogeneity, and the evolution of reptile viviparity.

    Science.gov (United States)

    King, Benedict; Lee, Michael S Y

    2015-05-01

    Virtually all models for reconstructing ancestral states for discrete characters make the crucial assumption that the trait of interest evolves at a uniform rate across the entire tree. However, this assumption is unlikely to hold in many situations, particularly as ancestral state reconstructions are being performed on increasingly large phylogenies. Here, we show how failure to account for such variable evolutionary rates can cause highly anomalous (and likely incorrect) results, while three methods that accommodate rate variability yield the opposite, more plausible, and more robust reconstructions. The random local clock method, implemented in BEAST, estimates the position and magnitude of rate changes on the tree; split BiSSE estimates separate rate parameters for pre-specified clades; and the hidden rates model partitions each character state into a number of rate categories. Simulations show the inadequacy of traditional models when characters evolve with both asymmetry (different rates of change between states within a character) and heterotachy (different rates of character evolution across different clades). The importance of accounting for rate heterogeneity in ancestral state reconstruction is highlighted empirically with a new analysis of the evolution of viviparity in squamate reptiles, which reveal a predominance of forward (oviparous-viviparous) transitions and very few reversals. © The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Microprobe study of fission product behavior in high-burnup HTR fuels

    International Nuclear Information System (INIS)

    Kleykamp, H.

    Electron microprobe analysis of irradiated coated particles with high burnup (greater than 50 percent fima) gives detailed information on the chemical state and the transport behavior of the fission products in UO 2 and UC 2 kernels and in the coatings. In oxide fuel kernels, metallic inclusions and ceramic precipitations are observed. The solubility behavior of the fission products in the fuel matrix has been investigated. Fission product inclusions could not be detected in carbide fuel kernels; post irradiation annealed UC 2 kernels, however, give information on the element combinations of some fission product phases. Corresponding to the chemical state in the kernel, Cs, Sr, Ba, Pd, Te and the rare earths are released easily and diffuse through the entire pyrocarbon coating. These fission products can be retained by a silicon carbide layer. The initial stage of a corrosive attack of the SiC coating by the fission products is evidenced

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  9. Pump--probe measurements of state-to-state rotational energy transfer rates in N2 (v=1)

    International Nuclear Information System (INIS)

    Sitz, G.O.; Farrow, R.L.

    1990-01-01

    We report direct measurements of the state-to-state rotational energy transfer rates for N 2 (υ=1) at 298 K. Stimulated Raman pumping of Q-branch (υ=1 left-arrow 0) transitions is used to prepare a selected rotational state of N 2 in the υ=1 state. After allowing an appropriate time interval for collisions to occur, 2+2 resonance-enhanced multiphoton ionization is used (through the a 1 Π g left-arrow X 1 Σ + g transition) to detect the relative population of the pumped level and other levels to which rotational energy transfer has occurred. We have performed a series of measurements in which a single even rotational level (J i =0--14) is excited and the time-dependent level populations are recorded at three or more delay times. This data set is then globally fit to determine the best set of state-to-state rate constants. The fitting procedure does not place any constraints (such as an exponential gap law) on the J or energy dependence of the rates. We compare our measurements and best-fit rates with results predicted from phenomenological rate models and from a semiclassical scattering calculation of Koszykowski et al. [J. Phys. Chem. 91, 41 (1987)]. Excellent agreement is obtained with two of the models and with the scattering calculation. We also test the validity of the energy-corrected sudden (ECS) scaling theory for N 2 by using our experimental transfer rates as basis rates (J=L→0), finding that the ECS scaling expressions accurately predict the remaining rates

  10. State infant mortality: an ecologic study to determine modifiable risks and adjusted infant mortality rates.

    Science.gov (United States)

    Paul, David A; Mackley, Amy; Locke, Robert G; Stefano, John L; Kroelinger, Charlan

    2009-05-01

    To determine factors contributing to state infant mortality rates (IMR) and develop an adjusted IMR in the United States for 2001 and 2002. Ecologic study of factors contributing to state IMR. State IMR for 2001 and 2002 were obtained from the United States linked death and birth certificate data from the National Center for Health Statistics. Factors investigated using multivariable linear regression included state racial demographics, ethnicity, state population, median income, education, teen birth rate, proportion of obesity, smoking during pregnancy, diabetes, hypertension, cesarean delivery, prenatal care, health insurance, self-report of mental illness, and number of in-vitro fertilization procedures. Final risk adjusted IMR's were standardized and states were compared with the United States adjusted rates. Models for IMR in individual states in 2001 (r2 = 0.66, P < 0.01) and 2002 (r2 = 0.81, P < 0.01) were tested. African-American race, teen birth rate, and smoking during pregnancy remained independently associated with state infant mortality rates for 2001 and 2002. Ninety five percent confidence intervals (CI) were calculated around the regression lines to model the expected IMR. After adjustment, some states maintained a consistent IMR; for instance, Vermont and New Hampshire remained low, while Delaware and Louisiana remained high. However, other states such as Mississippi, which have traditionally high infant mortality rates, remained within the expected 95% CI for IMR after adjustment indicating confounding affected the initial unadjusted rates. Non-modifiable demographic variables, including the percentage of non-Hispanic African-American and Hispanic populations of the state are major factors contributing to individual variation in state IMR. Race and ethnicity may confound or modify the IMR in states that shifted inside or outside the 95% CI following adjustment. Other factors including smoking during pregnancy and teen birth rate, which are

  11. Gamma Radiation from Fission Fragments

    International Nuclear Information System (INIS)

    Higbie, Jack

    1969-10-01

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

  12. Energy partition in nuclear fission

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  13. Gamma Radiation from Fission Fragments

    Energy Technology Data Exchange (ETDEWEB)

    Higbie, Jack

    1969-10-15

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

  14. Fission-product source terms

    International Nuclear Information System (INIS)

    Lorenz, R.A.

    1981-01-01

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

  15. 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.

  16. The spectroscopy of fission fragments

    International Nuclear Information System (INIS)

    Phillips, W.R.

    1998-01-01

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

  17. Measurement of 235U fission spectrum-averaged cross sections and neutron spectrum adjusted with the activation data

    International Nuclear Information System (INIS)

    Kobayashi, Katsuhei; Kobayashi, Tooru

    1992-01-01

    The 235 U fission spectrum-averaged cross sections for 13 threshold reactions were measured with the fission plate (27 cm in diameter and 1.1 cm thick) at the heavy water thermal neutron facility of the Kyoto University Reactor. The Monte Carlo code MCNP was applied to check the deviation from the 235 U fission neutron spectrum due to the room-scattered neutrons, and it was found that the resultant spectrum was close to that of 235 U fission neutrons. Supplementally, the relations to derive the absorbed dose rates with the fission plate were also given using the calculated neutron spectra and the neutron Kerma factors. Finally, the present values of the fission spectrum-averaged cross sections were employed to adjust the 235 U fission neutron spectrum with the NEUPAC code. The adjusted spectrum showed a good agreement with the Watt-type fission neutron spectrum. (author)

  18. A study of the effect of intermediate structure in the fission cross section of 239Pu on self-shielding factors

    International Nuclear Information System (INIS)

    Ganesan, S.

    1978-01-01

    A set of energy dependent fission widths of 1 + spin state corresponding to the recommended fission cross sections of Sowerby et al is evaluated by adjustment in the energy region 600 ev to 25 Kev. Corresponding to these mean fission widths of 1 + spin state, the intermediate resonance parameters based on Weigmann's formulation of Struitinsky's double humped fission barrier model are then obtained. Pseudorandom resonances are generated with and without the intermediate structure in the mean fission but leading to the same value of infinite dilution fission cross section. The effect of the intermediate structure on the self shielding factors was then investigated. (author)

  19. Singlet Fission in Rubrene Derivatives: Impact of Molecular Packing

    KAUST Repository

    Sutton, Christopher

    2017-03-13

    We examine the properties of six recently synthesized rubrene derivatives (with substitutions on the side phenyl rings) that show vastly different crystal structures. In order to understand how packing in the solid state affects the excited states and couplings relevant for singlet fission, the lowest excited singlet (S), triplet (T), multiexciton (TT), and charge-transfer (CT) states of the rubrene derivatives are compared to known singlet fission materials [tetracene, pentacene, 5,12-diphenyltetracene (DPT), and rubrene itself]. While a small difference of less than 0.2 eV is calculated for the S and TT energies, a range of 0.50 to 1.2 eV in the CT energies and nearly 3 orders of magnitude in the electronic couplings are computed for the rubrene derivatives in their crystalline packings, which strongly affects the role of the CT state in facilitating SF. To rationalize experimental observations of singlet fission occurring in amorphous phases of rubrene, DPT, and tetracene, we use molecular dynamics (MD) simulations to assess the impact of molecular packing and orientations and to gain a better understanding of the parameters that control singlet fission in amorphous films compared to crystalline packings. The MD simulations point to a crystalline-like packing for thin films of tetracene; on the other hand, DPT, rubrene, and the rubrene derivatives all show various degrees of disorder with a number of sites that have larger electronic couplings than in the crystal, which can facilitate singlet fission in such thin films. Our analysis underlines the potential of these materials as promising candidates for singlet fission and helps understand how various structural motifs affect the critical parameters that control the ability of a system to undergo singlet fission.

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

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  1. A uniform semi-classical approach to the Coulomb fission problem

    International Nuclear Information System (INIS)

    Levit, S.; Smilansky, U.

    1978-01-01

    A semi-classical theory based on the path integral formalism is applied to the description of Coulomb fission. Complex classical trajectories are used to compute the classically forbidden transitions from the target's ground state to fission. In a simple model the energy spectrum and angular distributions of the fragments are calculated for the Coulomb fission in the Xe + U collision. Theoretical predictions are made which may be checked experimentally. (author)

  2. Identifying transition rates of ionic channels via observations at a single state

    CERN Document Server

    Deng Ying Chun; Qian Min Ping; Feng Jian Feng

    2003-01-01

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included.

  3. Identifying transition rates of ionic channels via observations at a single state

    International Nuclear Information System (INIS)

    Deng Yingchun; Peng Shenglun; Qian Minping; Feng Jianfeng

    2003-01-01

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included

  4. Identifying transition rates of ionic channels via observations at a single state

    Energy Technology Data Exchange (ETDEWEB)

    Deng Yingchun [School of Mathematics, Peking University, Beijing (China); Peng Shenglun [School of Mathematics, Peking University, Beijing (China); Qian Minping [School of Mathematics, Peking University, Beijing (China); Feng Jianfeng [COGS, Sussex University, Brighton (United Kingdom)

    2003-02-07

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included.

  5. Fission dynamics with systems of intermediate fissility

    Indian Academy of Sciences (India)

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

  6. Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

    International Nuclear Information System (INIS)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-01-01

    Highlights: • State-to-state approach for coupled vibrational relaxation and chemical reactions. • Self-consistent model for rates of non-equilibrium reactions and energy transitions. • In viscous flows mass action law is violated. • Cross coupling between reaction rates and non-equilibrium pressure in viscous flow. • Results allow implementing the state-to-state approach for viscous flow simulations. - Abstract: Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman–Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N 2 flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure

  7. Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

    Energy Technology Data Exchange (ETDEWEB)

    Kustova, Elena V., E-mail: e.kustova@spbu.ru [Department of Mathematics and Mechanics, Saint Petersburg State University, 198504 Universitetskiy pr. 28, Saint Petersburg (Russian Federation); Kremer, Gilberto M., E-mail: kremer@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba (Brazil)

    2014-12-05

    Highlights: • State-to-state approach for coupled vibrational relaxation and chemical reactions. • Self-consistent model for rates of non-equilibrium reactions and energy transitions. • In viscous flows mass action law is violated. • Cross coupling between reaction rates and non-equilibrium pressure in viscous flow. • Results allow implementing the state-to-state approach for viscous flow simulations. - Abstract: Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman–Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N{sub 2} flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure.

  8. ''In situ'' investigations of the radioactive fissionable element infiltration and retention in different soils

    International Nuclear Information System (INIS)

    Oncescu, M.; Danis, A.; Sahagia, M.; Negrescu, C.; Bobe, M.; Balanescu, P.; Burcescu, M.; Tautu, N.

    1980-01-01

    ''In situ'' investigations of the natural and forced infiltration and retention of the fissionable elements from a liquid residue in several natural compacted soils and compacted clays are presented. The velocities and flow rates for different stages of the residue infiltration are determined. The retention of the fissionable elements by variation of the fissionable element concentration with the distance from the place of the residue depot is investigated. (author)

  9. Statistical model calculations with a double-humped fission barrier GIVAB computer code

    International Nuclear Information System (INIS)

    Delagrange, H.; Gilat, J.

    1979-01-01

    Neutron and gamma emission probabilities and fission probabilities are computed, taking into account the special feature of the actinide fission barriers with two maxima. Spectra and cross sections are directly deduced from these probabilities. Populations of both wells are followed step by step. For each initial E and J, decay rates are computed and normalized in order to obtain the de-excitation probabilities imposed by the two-humped fission barrier

  10. Spin measurement for symmetric fission states of sup 24 Mg. A new angle on the sup 12 C+ sup 12 C interaction

    Energy Technology Data Exchange (ETDEWEB)

    Fulton, B.R.; Bennett, S.J.; Freer, M.; Murgatroyd, J.T. (School of Physics and Space Research, Birmingham Univ. (United Kingdom)); Gyapong, G.J.; Jarvis, N.S.; Jones, C.D.; Watson, D.L. (Dept. of Physics, York Univ. (United Kingdom)); Brown, J.D.; Rae, W.D.M.; Smith, A.E. (Dept. of Nuclear Physics, Oxford Univ. (United Kingdom)); Lilley, J.S. (Daresbury Lab., Warrington (United Kingdom))

    1991-09-19

    A new high resolution measurement of the {sup 12}C({sup 24}Mg, {sup 12}C{sup 12}C){sup 12}C breakup reaction has been performed. Sequential breakup is observed from specific states in {sup 24}Mg at excitation energies ranging from 20 to 26 MeV. Angular correlation measurements indicate that states with spins ranging from J=4 to 8 are populated. These states are consistent with superdeformed shape isomeric bands predicted by cranked cluster model and Nilsson-Strutinsky calculations. (orig.).

  11. Estimation of track registration efficiency in solution medium and study of gamma irradiation effects on the bulk-etch rate and the activation energy for bulk etching of CR-39 (DOP) Solid State Nuclear Track Detector

    International Nuclear Information System (INIS)

    Kalsi, P.C.

    2010-01-01

    The fission track registration efficiency of diethylene glycol bis allyl carbonate (dioctyl phthalate doped) (CR-39 (DOP)) solid state nuclear track detector (SSNTD) in solution medium (K wet ) has been experimentally determined and is found to be (9.7 ± 0.5).10 -4 cm. This is in good agreement with the values of other SSNTDs. The gamma irradiation effects in the dose range of 50.0-220.0 kGy on the bulk etch rate, V b and the activation energy for bulk etching, E of this solid state nuclear track detector (SSNTD) have also been studied. It is observed that the bulk etch rates increase and the activation energies for bulk etching decrease with the increase in gamma dose. These results have been explained on the basis of scission of the detector due to gamma irradiation

  12. Chemical effects of fission recoils

    International Nuclear Information System (INIS)

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

    1978-01-01

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

  13. Chemical Production using Fission Fragments

    International Nuclear Information System (INIS)

    Dawson, J. K.; Moseley, F.

    1960-01-01

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

  14. Physics and chemistry of fission

    International Nuclear Information System (INIS)

    1979-01-01

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

  15. Angular distributions in quasi-fission reactions

    International Nuclear Information System (INIS)

    Luetzenkirchen, K.; Kratz, J.V.; Lucas, R.; Poitou, J.; Gregoire, C.; Wirth, G.; Bruechle, W.; Suemmerer, K.

    1985-10-01

    Angular distributions for fission-like fragments were measured in the systems 50 Ti, 56 Fe + 208 Pb by applying an off-line KX-ray activation technique. The distributions d 2 sigma/dTHETAdZ exhibit forward-backward asymmetries that are strongly Z-dependent. They result from a process (quasi-fission) which yields nearly symmetric masses in times comparable to the rotational period of the composite system. A method for obtaining the variance of the tilting angular momentum, K 0 2 , from these skewed, differential angular distributions is described. The results indicate that the tilting mode is not fully excited in quasi-fission reactions. The results are compared to the sum of the variances of all statistical spin components, measured via γ-multiplicities. Integration of the angular distributions d 2 sigma/dTHETAdZ over all values of Z yields integral angular distributions dsigma/dTHETA and dsigma/dΩ symmetric around 90 0 . The associated unusually large anisotropies do not at all provide an adequate basis for tests or modifications of the transition state theory. A deconvolution of d 2 sigma/dTHETAdZ is performed with gaussian distributions depending on rotational angles ΔTHETA extending over a range of up to 540 0 . From the mean values a time scale for the evolution of K 0 is calculated. (orig.)

  16. 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.)

  17. Mass and Inertia Parameters for Nuclear Fission

    International Nuclear Information System (INIS)

    Damgaard, J.; Pauli, H.C.; Strutinsky, V.M.; Wong, C.Y.; Brack, M.; Stenholm-Jensen, A.

    1969-01-01

    The effective mass parameter and the moments of inertia for a deformed nucleus are evaluated using the cranking-model formalism. Special attention is paid to the dependence of these quantities on the intrinsic structure, which may arise due to shells in deformed nuclei. It is found that these inertial parameters are very much influenced by the shells present. The effective-mass parameter, which appears in an important way in the theory of spontaneous fission, fluctuates in the same manner as the shell-energy corrections. Its values at the fission barrier are up to two or three times larger than those at the equilibrium minima. This correlation comes about because for the effective mass the change in the local density of single-particle states is very important, much more so than the change in the pairing correlation. The moments of inertia which enter in the theory of angular anisotropy of fission fragments, also fluctuate as a function of the deformation. At low temperatures, the fluctuation is large and shows a distinct but more complicated correlation with the shells. At high temperatures, the moments of inertia fluctuate with a smaller amplitude about the rigid-body value in correlation with the energy-shell corrections. For the first-and second barriers, the rigid-body values are essentially reached at a nuclear temperature of 0.8 to 1.0 MeV. (author)

  18. Gas-phase transport of fission products

    International Nuclear Information System (INIS)

    Tang, I.N.; Munkelwitz, H.R.

    1982-01-01

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

  19. International handling of fissionable material

    International Nuclear Information System (INIS)

    1975-01-01

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

  20. Managed care market share and cesarean section rates in the United States: is there a link?

    Science.gov (United States)

    Hueston, W J; Sutton, A

    2000-11-01

    After peaking during the early 1980s, cesarean section rates in the United States have been falling for the last decade. At the same time, managed care enrollment has increased dramatically. This study examines whether managed care penetration in local markets is associated with lower cesarean section rates in those geographic area. A cross-sectional comparison of cesarean section rates and health maintenance organization (HMO) market penetration in 61 selected metropolitan areas in the United States was conducted. National birth certificate data for 1996 were used to calculate crude and race-adjusted cesarean section rates for residents in each area. No relationship between overall cesarean section rates in the metropolitan areas and managed care penetration was observed. Subanalyses of racial groups demonstrated the existence of a weak association between managed care penetration and cesarean section rates for white women (21.2% for the highest quartile of HMO penetration, compared with 19.1% for the lowest quartile; P = .03), but not for African-Americans or other minorities. Managed care penetration in a market may have an association with cesarean section rates for white women, but the strength of this relationship is small. Even if managed care delivery systems reduce cesarean section rates in their own populations, this change is likely to have only a small impact on overall cesarean rates. HMO penetration is unlikely to influence national cesarean section rates, nor does it appear to explain state variations in these rates.

  1. Theory of nuclear fission: a review

    International Nuclear Information System (INIS)

    Mosel, U.

    1976-01-01

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

  2. NCHS - Birth Rates for Unmarried Women by Age, Race, and Hispanic Origin: United States

    Data.gov (United States)

    U.S. Department of Health & Human Services — This dataset includes birth rates for unmarried women by age group, race, and Hispanic origin in the United States since 1970. National data on births by Hispanics...

  3. NCHS - Teen Birth Rates for Females by Age Group, Race, and Hispanic Origin: United States

    Data.gov (United States)

    U.S. Department of Health & Human Services — This dataset includes teen birth rates for females by age group, race, and Hispanic origin in the United States since 1960. National data on births by Hispanic...

  4. Average Rate of Heat-Related Hospitalizations in 23 States, 2001-2010

    Data.gov (United States)

    U.S. Environmental Protection Agency — This map shows the 2001–2010 average rate of hospitalizations classified as “heat-related” by medical professionals in 23 states that participate in CDC’s...

  5. Success rate and entanglement measure in Grover's search algorithm for certain kinds of four qubit states

    International Nuclear Information System (INIS)

    Chamoli, Arti; Bhandari, C.M.

    2005-01-01

    Entanglement plays a crucial role in the efficacy of quantum algorithms. Whereas the role of entanglement is quite obvious and conspicuous in teleportation and superdense coding, it is not so distinct in other situations such as in search algorithm. The starting state in Grover's search algorithm is supposedly a uniform superposition state (not entangled) with a success probability around unity. An operational entanglement measure has been defined and investigated analytically for two qubit states [O. Biham, M.A. Neilsen, T. Osborne, Phys. Rev. A 65 (2002) 062312, Y. Shimoni, D. Shapira, O. Biham, Phys. Rev. A 69 (2004) 062303] seeking a relationship with the success rate of search algorithm. This Letter examines the success rate of search algorithm for various four-qubit states. Analytic expressions for the same have been worked out which can provide the success rate and entanglement measure for certain kinds of four qubit input states

  6. Evaluation of Cross-Section Sensitivities in Computing Burnup Credit Fission Product Concentrations

    International Nuclear Information System (INIS)

    Gauld, I.C.

    2005-01-01

    U.S. Nuclear Regulatory Commission Interim Staff Guidance 8 (ISG-8) for burnup credit covers actinides only, a position based primarily on the lack of definitive critical experiments and adequate radiochemical assay data that can be used to quantify the uncertainty associated with fission product credit. The accuracy of fission product neutron cross sections is paramount to the accuracy of criticality analyses that credit fission products in two respects: (1) the microscopic cross sections determine the reactivity worth of the fission products in spent fuel and (2) the cross sections determine the reaction rates during irradiation and thus influence the accuracy of predicted final concentrations of the fission products in the spent fuel. This report evaluates and quantifies the importance of the fission product cross sections in predicting concentrations of fission products proposed for use in burnup credit. The study includes an assessment of the major fission products in burnup credit and their production precursors. Finally, the cross-section importances, or sensitivities, are combined with the importance of each major fission product to the system eigenvalue (k eff ) to determine the net importance of cross sections to k eff . The importances established the following fission products, listed in descending order of priority, that are most likely to benefit burnup credit when their cross-section uncertainties are reduced: 151 Sm, 103 Rh, 155 Eu, 150 Sm, 152 Sm, 153 Eu, 154 Eu, and 143 Nd

  7. Spontaneous fission of 259Md

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  8. Dielectronic recombination rate coefficients to the excited states of CII from CIII

    International Nuclear Information System (INIS)

    Kato, Takako; Safronova, U.; Ohira, Mituhiko.

    1996-02-01

    Energy levels, radiative transition probabilities and autoionization rates for CII including 1s 2 2l2l'nl'' (n=2-6, l'≤(n-1)) states were calculated by using multi-configurational Hartree-Fock (Cowan code) method. Autoionizing levels above three thresholds: 1s 2 2s 2 ( 1 S), 1s 2 2s2p( 3 P), 1s 2 2s2p( 1 P) were considered. Branching ratios related to the first threshold and the intensity factor were calculated for satellite lines of CII ion. The dielectronic recombination rate coefficients to the excited states for n=2-6 are calculated with these atomic data. The rate coefficients are fitted to an analytical formula and the fit parameters are given. The values for higher excited states than n=6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The effective recombination rate coefficient for different electron densities are also derived. (author)

  9. Dielectronic recombination rate coefficients to excited states of Be-like oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Izumi; Safronova, Ulyana I.; Kato, Takako

    2001-05-01

    We have calculated energy levels, radiative transition probabilities, and autoionization rates for Be-like oxygen (O{sup 4+}) including ls{sup 2}2lnl' (n=2 - 8, l {<=} n - 1) and 1s{sup 2}3l'nl (n=3 - 6, l {<=} n - l) states by multi-configurational Hartree-Fock method (Cowan code) and perturbation theory Z-expansion method (MZ code). The state selective dielectronic recombination rate coefficients to excited states of Be-like O ions are obtained. Configuration mixing plays an important role for the principal quantum number n distribution of the dielectronic recombination rate coefficients for 2snl (n {<=} 5) levels at low electron temperature. The orbital angular momentum quantum number l distribution of the rate coefficients shows a peak at l = 4. The total dielectronic recombination rate coefficient is derived as a function of electron temperature. (author)

  10. An Approach to Dynamic Line Rating State Estimation at Steady State Using Direct and Indirect Measurements

    DEFF Research Database (Denmark)

    Alvarez, David; Silva, Filipe Miguel Faria da; Mombello, Enrique E.

    2018-01-01

    Dynamic line rating has emerged as a solution for reducing congestion in overhead lines, allowing the optimization of power systems assets. This technique is based on direct and/or indirect monitoring of conductor temperature. Different devices and methods have been developed to sense conductor...

  11. Fission gas release and pellet microstructure change of high burnup BWR fuel

    International Nuclear Information System (INIS)

    Itagaki, N.; Ohira, K.; Tsuda, K.; Fischer, G.; Ota, T.

    1998-01-01

    UO 2 fuel, with and without Gadolinium, irradiated for three, five, and six irradiation cycles up to about 60 GWd/t pellet burnup in a commercial BWR were studied. The fission gas release and the rim effect were investigated by the puncture test and gas analysis method, OM (optical microscope), SEM (scanning electron microscope), and EPMA (electron probe microanalyzer). The fission gas release rate of the fuel rods irradiated up to six cycles was below a few percent; there was no tendency for the fission gas release to increase abruptly with burnup. On the other hand, microstructure changes were revealed by OM and SEM examination at the rim position with burnup increase. Fission gas was found depleted at both the rim position and the pellet center region using EPMA. There was no correlation between the fission gas release measured by the puncture test and the fission gas depletion at the rim position using EPMA. However, the depletion of fission gas in the center region had good correlation with the fission gas release rate determined by the puncture test. In addition, because the burnup is very large at the rim position of high burnup fuel and also due to the fission rate of the produced Pu, the Xe/Kr ratio at the rim position of high burnup fuel is close to the value of the fission yield of Pu. The Xe/Kr ratio determined by the gas analysis after the puncture test was equivalent to the fuel average but not to the pellet rim position. From the results, it was concluded that fission gas at the rim position was released from the UO 2 matrix in high burnup, however, most of this released fission gas was held in the porous structure and not released from the pellet to the free volume. (author)

  12. Contribution to research on the metabolism of fission product. Studies on the physico-chemical state and the metabolic fate of radio-cerium solution

    International Nuclear Information System (INIS)

    Aeberhardt, A.

    1961-01-01

    This paper describes a study of the physico-chemical state of radio-cerium in dilute solutions on the tracer scale, as a function of the pH of the solution. The way in which this radioelement is transported in the blood is studied in vitro and in vivo, with reference to the ionic or colloidal state of the radio-cerium used. The distribution of cerium amongst the various components of the blood is studied by a new method of blood fractionation and by paper electrophoresis. Evidence of a cerium globulin connection is shown in the case of ionic cerium. A study of the initial distribution of radio-cerium in rats, after intravenous administration of ionic or colloidal solutions, shows considerable differences according to the physico-chemical state of the cerium injected. (author) [fr

  13. Comparison of heart rate variability between resting state and external-cuff-inflation-and-deflation state: a pilot study.

    Science.gov (United States)

    Ji, Lizhen; Liu, Chengyu; Li, Peng; Wang, Xinpei; Yan, Chang; Liu, Changchun

    2015-10-01

    Heart rate variability (HRV) has been widely used in clinical research to provide an insight into the autonomic control of the cardiovascular system. Measurement of HRV is generally performed under a relaxed resting state. The effects of other conditions on HRV measurement, such as running, mountaineering, head-up tilt, etc, have also been investigated. This study aimed to explore whether an inflation-and-deflation process applied to a unilateral upper arm cuff would influence the HRV measurement. Fifty healthy young volunteers aged between 21 and 30 were enrolled in this study. Electrocardiogram (ECG) signals were recorded for each subject over a five minute resting state followed by a five minute external-cuff-inflation-and-deflation state (ECID state). A one minute gap was scheduled between the two measurements. Consecutive RR intervals in the ECG were extracted automatically to form the HRV data for each of the two states. Time domain (SDNN, RMSSD and PNN50), frequency domain (LFn, HFn and LF/HF) and nonlinear (VLI, VAI and SampEn) HRV indices were analyzed and compared between the two states. In addition, the effects of mean artery pressure (MAP) and heart rate (HR) on the aforementioned HRV indices were assessed for the two states, respectively, by Pearson correlation analysis. The results showed no significant difference in all aforementioned HRV indices between the resting and the ECID states (all p  >  0.05). The corresponding HRV indices had significant positive correlation (all p    0.05) for either state. Besides, none of the indices showed HR-related change (all p  >  0.05) for either state except the index of VLI in the resting state. To conclude, this pilot study suggested that the applied ECID process hardly influenced those commonly used HRV indices. It would thus be applicable to simultaneously measure both blood pressure and HRV indices in clinical practice.

  14. The Relationship Between Gun Ownership and Firearm Homicide Rates in the United States, 1981–2010

    Science.gov (United States)

    Ross, Craig S.

    2013-01-01

    Objectives. We examined the relationship between levels of household firearm ownership, as measured directly and by a proxy—the percentage of suicides committed with a firearm—and age-adjusted firearm homicide rates at the state level. Methods. We conducted a negative binomial regression analysis of panel data from the Centers for Disease Control and Prevention’s Web-Based Injury Statistics Query and Reporting Systems database on gun ownership and firearm homicide rates across all 50 states during 1981 to 2010. We determined fixed effects for year, accounted for clustering within states with generalized estimating equations, and controlled for potential state-level confounders. Results. Gun ownership was a significant predictor of firearm homicide rates (incidence rate ratio = 1.009; 95% confidence interval = 1.004, 1.014). This model indicated that for each percentage point increase in gun ownership, the firearm homicide rate increased by 0.9%. Conclusions. We observed a robust correlation between higher levels of gun ownership and higher firearm homicide rates. Although we could not determine causation, we found that states with higher rates of gun ownership had disproportionately large numbers of deaths from firearm-related homicides. PMID:24028252

  15. Isotopic resolution of fission fragments from 238U + 12C transfer and fusion reactions

    International Nuclear Information System (INIS)

    Caamano, M.; Rejmund, F.; Derkx, X.; Schmidt, K. H.; Andouin, L.; Bacri, C. O.; Barreau, G.; Benlliure, J.; Casarejos, E.; Fernandez-Dominguez, B.; Gaudefroy, L.; Golabek, C.; Jurado, B.; Lemasson, A.; Navin, A.; Rejmund, M.; Roger, T.; Shrivastava, A.; Schmitt, C.; Taieb, J.

    2010-01-01

    Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238 U beam and a 12 C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments. (authors)

  16. Fission fragment simulation of fusion neutron radiation effects on bulk mechanical properties

    International Nuclear Information System (INIS)

    Van Konynenburg, R.A.; Mitchell, J.B.; Guinan, M.W.; Stuart, R.N.; Borg, R.J.

    1976-01-01

    This research demonstrates the feasibility of using homogeneously-generated fission fragments to simulate high-fluence fusion neutron damage in niobium tensile specimens. This technique makes it possible to measure radiation effects on bulk mechanical properties at high damage states, using conveniently short irradiation times. The primary knock-on spectrum for a fusion reactor is very similar to that produced by fission fragments, and nearly the same ratio of gas atoms to displaced atoms is produced in niobium. The damage from fission fragments is compared to that from fusion neutrons and fission reactor neutrons in terms of experimentally measured yield strength increase, transmission electron microscopy (TEM) observations, and calculated damage energies

  17. Relaxation of the 5s22D3/2 state of the Cd II ion during collision with He atoms in a He-Cd medium excited by fission fragments

    International Nuclear Information System (INIS)

    Barysheva, N.M.; Bochkov, A.V.; Bochkova, N.V.; Grebenkin, K.F.; Kryzhanovskii, V.A.; Magda, E.P.; Neznakhina, A.E.

    1992-01-01

    Based on measurements of the luminescence intensities of the 5s 2 2 D 5/2 →5p 2 P 3/2 (λ=0.4416 μm) and 5s 2 2 D 3/2 →5p 2 P 1/2 (λ=0.325 μm) lines in a dense He-Cd medium excited by fission fragments, the reaction constant is determined for Cd + (5s 2 2 D 3/2 )+He→Cd + (5s 2 2 D 5/2 )+He. The assumption that the 5s 2 2 D 3/2 state of the Cd II ion is strongly deexcited by collisions with atoms of the buffer gas was not confirmed. The question of quasicontinuous lasing at the 5s 2 2 D 3/2 → 5p 2 P 1/2 (λ=0.325 μm) transition requires further study. 6 refs., 1 fig

  18. STEADY STATE FLAMMABLE GAS RELEASE RATE CALCULATION AND LOWER FLAMMABILITY LEVEL EVALUATION FOR HANFORD TANK WASTE

    Energy Technology Data Exchange (ETDEWEB)

    HU TA

    2009-10-26

    Assess the steady-state flammability level at normal and off-normal ventilation conditions. The hydrogen generation rate was calculated for 177 tanks using the rate equation model. Flammability calculations based on hydrogen, ammonia, and methane were performed for 177 tanks for various scenarios.

  19. Widespread increase of tree mortality rates in the western United States

    Science.gov (United States)

    Phillip J. van Mantgem; Nathan L. Stephenson; John C. Byrne; Lori D. Daniels; Jerry F. Franklin; Peter Z. Fule; Mark E. Harmon; Andrew J. Larson; Jeremy M. Smith; Alan H. Taylor; Thomas T. Veblen

    2009-01-01

    Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29...

  20. Water and Wastewater Annual Price Escalation Rates for Selected Cities across the United States

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2017-10-27

    Pacific Northwest National Laboratory conducted this study for the Federal Energy Management Program to identify trends in annual water and wastewater price escalation rates across the United States. This study can be used to inform the selection of an appropriate escalation rates for inclusion in LCCA.

  1. RATING OF SOCIAL MEDIA MARKETING COMPETENCIES POSSESSED BY ENTREPRENEURS IN DELTA STATE, NIGERIA

    OpenAIRE

    Ezenwafor, J. I.; Onokpaunu, Michel O.; Nna-Emmanuel, Sarah W.

    2017-01-01

    The need for wide utilization of social media marketing for entrepreneurial development in Delta State necessitated this study which sought to determine how competent practicing entrepreneurs are for their use in Delta State. One research question guided the study. A survey research design was adopted. The population consisted of 200 entrepreneurs in Delta North Senatorial District of Delta State. A validated 22 item on a 5-point rating scale questionnaire was used for data collection. Mean a...

  2. Time-frequency feature analysis and recognition of fission neutrons signal based on support vector machine

    International Nuclear Information System (INIS)

    Jin Jing; Wei Biao; Feng Peng; Tang Yuelin; Zhou Mi

    2010-01-01

    Based on the interdependent relationship between fission neutrons ( 252 Cf) and fission chain ( 235 U system), the paper presents the time-frequency feature analysis and recognition in fission neutron signal based on support vector machine (SVM) through the analysis on signal characteristics and the measuring principle of the 252 Cf fission neutron signal. The time-frequency characteristics and energy features of the fission neutron signal are extracted by using wavelet decomposition and de-noising wavelet packet decomposition, and then applied to training and classification by means of support vector machine based on statistical learning theory. The results show that, it is effective to obtain features of nuclear signal via wavelet decomposition and de-noising wavelet packet decomposition, and the latter can reflect the internal characteristics of the fission neutron system better. With the training accomplished, the SVM classifier achieves an accuracy rate above 70%, overcoming the lack of training samples, and verifying the effectiveness of the algorithm. (authors)

  3. Fission time-scale in experiments and in multiple initiation model

    Energy Technology Data Exchange (ETDEWEB)

    Karamian, S. A., E-mail: karamian@nrmail.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)

    2011-12-15

    Rate of fission for highly-excited nuclei is affected by the viscose character of the systemmotion in deformation coordinates as was reported for very heavy nuclei with Z{sub C} > 90. The long time-scale of fission can be described in a model of 'fission by diffusion' that includes an assumption of the overdamped diabatic motion. The fission-to-spallation ratio at intermediate proton energy could be influenced by the viscosity, as well. Within a novel approach of the present work, the cross examination of the fission probability, time-scales, and pre-fission neutron multiplicities is resulted in the consistent interpretation of a whole set of the observables. Earlier, different aspects could be reproduced in partial simulations without careful coordination.

  4. Prompt Gamma Radiation from Fragments in the Thermal Fission of 235U

    International Nuclear Information System (INIS)

    Albinsson, H.; Lindow, L.

    1970-06-01

    Measurements were made on the gamma radiation emitted from fission fragments in slow neutron induced fission of 235 U. The fragments were detected with solid state detectors of the surface barrier type and the gamma radiation with a Nal(Tl) scintillator. Mass selection was used so that the gamma radiation could be measured as a function of fragment mass. Time discrimination between the fission gammas and the prompt neutrons released in the fission process was employed to reduce the background. The gamma radiation emitted during different time intervals after the fission event was studied with the help of a collimator, the position of which was changed along the path of the fission fragments. In this way a decay curve was obtained from which the life-time of one of the gamma-emitting states could be estimated. The relative yield of the gamma-rays was determined as a function of mass for different gamma-ray energy portions and two specific time intervals after the fission events. Comparisons were made with data obtained from 252 Cf-fission. Attention is drawn to some features which seem to be the same in 235 U and 252 Cf-fission

  5. Prompt Gamma Radiation from Fragments in the Thermal Fission of {sup 235}U

    Energy Technology Data Exchange (ETDEWEB)

    Albinsson, H [Chalmers Univ. of Technology, Goteborg (Sweden); Lindow, L [AB Atomenergi, Nykoeping (Sweden)

    1970-06-15

    Measurements were made on the gamma radiation emitted from fission fragments in slow neutron induced fission of {sup 235}U. The fragments were detected with solid state detectors of the surface barrier type and the gamma radiation with a Nal(Tl) scintillator. Mass selection was used so that the gamma radiation could be measured as a function of fragment mass. Time discrimination between the fission gammas and the prompt neutrons released in the fission process was employed to reduce the background. The gamma radiation emitted during different time intervals after the fission event was studied with the help of a collimator, the position of which was changed along the path of the fission fragments. In this way a decay curve was obtained from which the life-time of one of the gamma-emitting states could be estimated. The relative yield of the gamma-rays was determined as a function of mass for different gamma-ray energy portions and two specific time intervals after the fission events. Comparisons were made with data obtained from {sup 252} Cf-fission. Attention is drawn to some features which seem to be the same in {sup 235}U and {sup 252} Cf-fission.

  6. State ownership, agency conflict and effective tax rates: Evidence from China

    Directory of Open Access Journals (Sweden)

    Sun Jianfu

    2016-02-01

    Full Text Available Agency conflict between minority and controlling shareholders in state owned firms has to be considered in order to examine the variability on effective tax rates. In China, state ownership helps the government to achieve its social objectives by optimizing corporate income tax. We provide a significant result to prove that state owned firms paid higher corporate income taxes than private firms. Our results also indicate that corporate effective tax rates are positively associated with firm sized and inventory intensity. However, we have no strong evidence to support the association with leverage, return on assets and capital intensity.

  7. Terrestrial gamma radiation dose rates and radiological mapping of Terengganu state, Malaysia

    International Nuclear Information System (INIS)

    Garba, N.N.

    2015-01-01

    Measurement of terrestrial gamma radiation dose (TGRD) rates in Terengganu state, Malaysia was carried out from 145 different locations using NaI[Tl] micro roentgen survey meter. The measured TGRD rates ranged from 35 to 340 nGy h -1 with mean value of 150 nGy h -1 . The annual effective dose to population was found to be 0.92 mSv y -1 . The data obtained were used in constructing the gamma isodose map using ArcGis 9.3 which shows the distribution of TGRD rates across the state. (author)

  8. Structure/property relations of aluminum under varying rates and stress states

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, Matthew T [Los Alamos National Laboratory; Horstemeyer, Mark F [MISSISSIPPI STATE UNIV; Whittington, Wilburn R [MISSISSIPPI STATE UNIV; Solanki, Kiran N [MISSISSIPPI STATE UNIV.

    2010-11-19

    In this work we analyze the plasticity, damage, and fracture characteristics of three different processed aluminum alloys (rolled 5083-H13, cast A356-T6, and extruded 6061-T6) under varying stress states (tension, compression, and torsion) and strain rates (0.001/, 1/s., and 1000/s). The stress state difference had more of a flow stress effect than the applied strain rates for those given in this study (0.001/sec up to 1000/sec). The stress state and strain rate also had a profound effect on the damage evolution of each aluminum alloy. Tension and torsional straining gave much greater damage nucleation rates than compression. Although the damage of all three alloys was found to be void nucleation dominated, the A356-T6 and 5083-H131 aluminum alloys incurred void damage via micron scale particles where the 6061-T6 aluminum alloy incurred void damage from two scales, micron-scale particles and nanoscale precipitates. Having two length scales of particles that participated in the damage evolution made the 6061-T6 incur a strain rate sensitive damage rate that was different than the other two aluminum alloys. Under tension, as the strain rate increased, the 6061-T6 aluminum alloy's void nucleation rate decreased, but the A356-T6 and 5083-H131 aluminum alloys void nucleation rate increased.

  9. Chemical etching of fission tracks in ethylene-tetrafluoroethylene copolymer

    International Nuclear Information System (INIS)

    Komaki, Y.; Tsujimura, S.; Seguchi, T.

    1979-01-01

    The chemical etching of fission tracks in ethylene-tetrafluoroethylene copolymer was studied. Etched holes 3000 to 4000 A in diameter were recognized by electron microscopy for a film bombarded by fission fragments in oxygen and etched in a 12N sodium hydroxide solution at 125 0 C. The radial etching rate at 125 0 C was 6 to 8 A/hr, which is less than 17 A/hr for polyvinylidene fluoride in the same sodium hydroxide concentration at 85 0 C. The smaller rate is a reflection of the larger chemical resistivity of ethylene-tetrafluoroethylene copolymer than polyvinylidene fluoride. (author)

  10. Advances on fission chamber modelling

    International Nuclear Information System (INIS)

    Filliatre, Philippe; Jammes, Christian; Geslot, Benoit; Veenhof, Rob

    2013-06-01

    In-vessel, online neutron flux measurements are routinely performed in mock-up and material testing reactors by fission chambers. Those measurements have a wide range of applications, including characterization of experimental conditions, reactor monitoring and safety. Depending on the application, detectors may experience a wide range of constraints, of several magnitudes, in term of neutron flux, gamma-ray flux, temperature. Hence, designing a specific fission chamber and measuring chain for a given application is a demanding task. It can be achieved by a combination of experimental feedback and simulating tools, the latter being based on a comprehensive understanding of the underlying physics. A computation route that simulates fission chambers, named CHESTER, is presented. The retrieved quantities of interest are the neutron-induced charge spectrum, the electronic and ionic pulses, the mean current and variance, the power spectrum. It relies on the GARFIELD suite, originally developed for drift chambers, and makes use of the MAGBOLTZ code to assess the drift parameters of electrons within the filling gas, and the SRIM code to evaluate the stopping range of fission products. The effect of the gamma flux is also estimated. Computations made with several fission chambers exemplify the possibilities of the route. A good qualitative agreement is obtained when comparing the results with the experimental data available to date. In a near future, a comprehensive experimental programme will be undertaken to qualify the route using the known neutron sources, mock-up reactors and wide choice of fission chambers, with a stress on the predictiveness of the Campbelling mode. Depending on the results, a refinement of the modelling and an effort on the accuracy of input data are also to be considered. CHESTER will then make it possible to predict the overall sensitivity of a chamber, and to optimize the design for a given application. Another benefit will be to increase the

  11. Toward an implicit measure of emotions: ratings of abstract images reveal distinct emotional states.

    Science.gov (United States)

    Bartoszek, Gregory; Cervone, Daniel

    2017-11-01

    Although implicit tests of positive and negative affect exist, implicit measures of distinct emotional states are scarce. Three experiments examined whether a novel implicit emotion-assessment task, the rating of emotion expressed in abstract images, would reveal distinct emotional states. In Experiment 1, participants exposed to a sadness-inducing story inferred more sadness, and less happiness, in abstract images. In Experiment 2, an anger-provoking interaction increased anger ratings. In Experiment 3, compared to neutral images, spider images increased fear ratings in spider-fearful participants but not in controls. In each experiment, the implicit task indicated elevated levels of the target emotion and did not indicate elevated levels of non-target negative emotions; the task thus differentiated among emotional states of the same valence. Correlations also supported the convergent and discriminant validity of the implicit task. Supporting the possibility that heuristic processes underlie the ratings, group differences were stronger among those who responded relatively quickly.

  12. Are chargemaster rates for imaging studies lower in States that cap noneconomic damages (tort reform)?

    Science.gov (United States)

    Stein, Seth I; Barry, Jeffrey R; Jha, Saurabh

    2014-08-01

    To determine whether chargemaster (a list of prices for common services and procedures set by individual hospitals) rates for diagnostic imaging were lower in states that cap awards for noneconomic damages (NED) than states with unlimited awards for medical negligence. We analyzed 2011 chargemaster data from the Centers for Medicare & Medicaid, pertaining to 6 ambulatory patient classifications specific to imaging. The dataset includes outpatient imaging facilities and hospitals in 49 states and the District of Columbia. The association between caps on NED and chargemaster rates for imaging in a sample of 15,218 data points was analyzed using linear regression and two-sample t tests assuming unequal variances. In states that cap NED, the chargemaster rates were higher for the following modalities: Level II Echocardiogram without Contrast (mean charges: $2,015.60 versus $1,884.81, P = .0018); Level II Cardiac Imaging ($4,670.25 versus $4,398.58, P = .002); MRI & Magnetic Resonance Angiography without Contrast ($2,654.31 versus $2,526.74, P = .002); and Level III Diagnostic and Screening Ultrasound ($1,073.31 versus $1,027.32, P = .037). High charge-to-payment ratios were associated with states with the highest charges. There was a positive correlation between number of outpatient centers in the state and the average chargemaster rates for the state (mean chargemaster rate = 1727 + 0.79*Number of Outpatient Centers; R-squared = 0.23, P = .0004). Chargemaster rates for select imaging services are not lower in states that have capped NED. Copyright © 2014 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  13. Study of fission mechanism with the reactions 230Th, 231Pa, 235U, 237Np(n,f) and 252Cf(fs)

    International Nuclear Information System (INIS)

    Benfoughal, T.

    1983-01-01

    In this work, the different stages of the nuclear fission process have been investigated. The analysis of fission cross-section and fission fragment angular distribution measurements are made using the hypothesis of asymmetrically deformed states. From the correlation between fissioning nucleus excitation energy and fragment total kinetic energy measurement for several fissioning systems, it is shown that the nuclear viscosity is relatively strong during the saddle-point to scission-point transition. The study of the spontaneous fission of 252 Cf shows that the fragment mass and kinetic energy distributions are mainly determinated by the nucleon shell effects and pairing correlations [fr

  14. Teen Birth Rates for Urban and Rural Areas in the United States, 2007-2015.

    Science.gov (United States)

    Hamilton, Brady E; Rossen, Lauren M; Branum, Amy M

    2016-11-01

    Data from the National Vital Statistics System •Birth rates for teenagers aged 15-19 declined in urban and rural counties from 2007 through 2015, with the largest declines in large urban counties and the smallest declines in rural counties. •From 2007 through 2015, the teen birth rate was lowest in large urban counties and highest in rural counties. •Declines in teen birth rates in all urban counties between 2007 and 2015 were largest in Arizona, Massachusetts, Connecticut, Minnesota, and Colorado, with 17 states experiencing a decline of 50% or more. •Declines in teen birth rates in all rural counties between 2007 and 2015 were largest (50% or more) in Colorado and Connecticut. •In 2015, teen birth rates were highest in rural counties and lowest in large urban counties for non-Hispanic white, non-Hispanic black, and Hispanic females. Teen birth rates have demonstrated an unprecedented decline in the United States since 2007 (1). Declines occurred in all states and among all major racial and Hispanic-origin groups, yet disparities by both geography and demographic characteristics persist (2,3). Although teen birth rates and related declines have been described by state, patterns by urban-rural location have not yet been examined. This report describes trends in teen birth rates in urban (metropolitan) and rural (nonmetropolitan) areas in the United States overall and by state from 2007 through 2015 and by race and Hispanic origin for 2015. All material appearing in this report is in the public domain and may be reproduced or copied without permission; citation as to source, however, is appreciated.

  15. Energy distribution of antineutrinos originating from the decay of fission products in a nuclear reactor

    International Nuclear Information System (INIS)

    Rudstam, G.; Aleklett, K.

    1979-01-01

    The energy spectrum of antineutrinos around a nuclear reactor has been derived by summing contributions from individual fission products. The resulting spectrum is weaker at energies above approx. 8 MeV than earlier published antineutrino spectra. The reason may be connected to the strong feeding of high-lying daughter states in the beta decay of fission products with high disintegration energies

  16. Role of fission product in whole core accidents: research in the USA

    International Nuclear Information System (INIS)

    Jackson, J.F.; Deitrich, L.W.

    1977-01-01

    The techniques being developed in the United States for analyzing postulated whole-core accidents in LMFBRs are briefly reviewed. The key mechanistic analysis methods are discussed in detail. Important research projects in the area of fission product effects are examined. Some typical results on the role of fission products in whole-core accidents are presented

  17. Fission gas behavior in mixed-oxide fuel during transient overpower

    International Nuclear Information System (INIS)

    Randklev, E.H.; Treibs, H.A.; Mastel, B.; Baldwin, D.L.

    1979-01-01

    Fission gas behavior can be important in determining fuel pin and core performance during a reactor transient. The results are presented of examinations characterizing the changes in microstructural distribution and retention of fission gas in fuel for a series of transient overpower (50 cents/s) tested mixed-oxide fuel pins and their steady state siblings

  18. Calculation of burnup and power dependence on fission gas released from PWR type reactor fuel element

    International Nuclear Information System (INIS)

    Edy-Sulistyono

    1996-01-01

    Burn up dependence of fission gas released and variation power analysis have been conducted using FEMXI-IV computer code program for Pressure Water Reactor Fuel During steady-state condition. The analysis result shows that the fission gas release is sensitive to the fuel temperature, the increasing of burn up and power in the fuel element under irradiation experiment

  19. Fission gas release from oxide fuels at high burnups (AWBA development program)

    International Nuclear Information System (INIS)

    Dollins, C.C.

    1981-02-01

    The steady state gas release, swelling and densification model previously developed for oxide fuels has been modified to accommodate the slow transients in temperature, temperature gradient, fission rate and pressure that are encountered in normal reactor operation. The gas release predictions made by the model were then compared to gas release data on LMFBR-EBRII fuels obtained by Dutt and Baker and reported by Meyer, Beyer, and Voglewede. Good agreement between the model and the data was found. A comparison between the model and three other sets of gas release data is also shown, again with good agreement

  20. Fission gas retention in irradiated metallic fuel

    International Nuclear Information System (INIS)

    Fenske, G.R.; Gruber, E.E.; Kramer, J.M.

    1987-01-01

    Theoretical calculations and experimental measurements of the quantity of retained fission gas in irradiated metallic fuel (U-5Fs) are presented. The calculations utilize the Booth method to model the steady-state release of gases from fuel grains and a simplified grain-boundary gas model to predict the gas release from intergranular regions. The quantity of gas retained in as-irradiated fuel was determined by collecting the gases released from short segments of EBR-II driver fuel that were melted in a gas-tight furnace. Comparison of the calculations to the measurements shows quantitative agreement with both the magnitude and the axial variation of the retained gas content

  1. Nuclear wastes: fission

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    Progress is reported on investigations of transuranics in soils and plants that have demonstrated the importance of valence state, complexation, competing elements, migration down the soil profile, and weathering cycles in governing transuranic, 129 I and 99 Tc availability to plants and, in the case of Pu, to the consuming animals. In the latter case, it was demonstrated, for the first time, that ingestion of plant tissues containing Pu may result in greater transfer across the gut compared to gavaging animals with inorganic Pu solutions, underscoring the importance of detailed studies of the soil, plant, and animal factors influencing uptake by the ingestion pathway. Further evidence of the importance of the ingestion pathway was provided in studies of foliar interception of airborne transuranic elements in which it was shown that Pu in particles in the respiratory size range were effectively intercepted and retained by plants, and significant quantities of intercepted Pu were transported to roots and seeds. Similar studies on the terrestrial ingestion pathway have been initiated with other actinides including, U, Am, Cm, and Np. Radioecological field studies were directed toward establishment of pertinent ingestion pathways and exposure levels through description of habitat types, population densities, and, in several instances, dosimetry, for major insects, reptiles, birds, and mammalian species. These studies were extended to agricultural ecosystems through definition of the uptake of long-lived nuclides and digestibility in cattle of several forage species. In studies on a pond ecosystem at the nuclear fuel reprocessing plant, Pu and Am uptake rates were studied for major biotic components including organic floc, algae, fish, and ducks. The results indicated that assimilation of transuranics by the biota and export from the pond system were low compared to the total inventory

  2. Suicide Rates and State Laws Regulating Access and Exposure to Handguns.

    Science.gov (United States)

    Anestis, Michael D; Anestis, Joye C

    2015-10-01

    Using previous research, we examined the impact of 4 handgun laws (waiting periods, universal background checks, gun locks, and open carrying regulations) on suicide rates. We used publicly available databases to collect information on statewide laws, suicide rates, and demographic characteristics for 2013. Each law was associated with significantly lower firearm suicide rates and the proportion of suicides resulting from firearms. In addition, each law, except for that which required a waiting period, was associated with a lower overall suicide rate. Follow-up analyses showed a significant indirect effect on overall suicide rates through the proportion of suicides by firearms, indicating that the reduced overall suicide rate was attributable to fewer suicide attempts, fewer handguns in the home, suicide attempts using less lethal means, or a combination of these factors. States that implemented any of these laws saw a decreased suicide rate in subsequent years, whereas the only state that repealed 1 of these laws saw an increased suicide rate. Our results were supportive of a potentially vital role in suicide prevention for state legislation that limits access and exposure to handguns.

  3. United States private schools have higher rates of exemptions to school immunization requirements than public schools.

    Science.gov (United States)

    Shaw, Jana; Tserenpuntsag, Boldtsetseg; McNutt, Louise-Anne; Halsey, Neal

    2014-07-01

    To compare medical, religious, and personal belief immunization exemption rates between private and public schools in US. Exemption rates were calculated using the Centers for Disease Control and Prevention School Immunization Assessment Surveys for the 2009-2010 school year excluding states with incomplete survey data. Standardized exemption rates weighted on enrollments in public and private schools were calculated. Differences in exemption rates between public and private schools were tested using Wilcoxon signed rank test. The overall state exemption rate was higher in US private than public schools, 4.25% (SD 4.27) vs 1.91% (1.67), P = .0001 and private schools had higher exemption rates for all types of exemptions; medical 0.58% (0.71) vs 0.34% (0.34) respectively (P = .0004), religious 2.09% (3.14) vs 0.83% (1.05) respectively (P = .0001), and personal belief 6.10% (4.12) vs 2.79% (1.57), respectively (P = .006). Overall exemption rates were significantly higher in states that allowed personal belief exemptions. Exemption rates were significantly higher in US private than in public schools. Children attending private schools may be at higher risk of vaccine-preventable diseases than public school children. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Studies of Fission-Induced Surface Damage in Actinides Using Ultracold Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Broussard, Leah J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-03-05

    This report describes the results of the fission-induced actinide studies at LANL. Previously, there was no fission data at these energies though there were initial characterizations of UCN energy dependence and material thickness. The proof of principle was demonstrated and the initial characterizations of sputtered rates, angular and size distribution are underway.

  5. Energy production using fission fragment rockets

    International Nuclear Information System (INIS)

    Chapline, G.; Matsuda, Y.

    1991-08-01

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

  6. Contribution to the study of nuclear fission

    International Nuclear Information System (INIS)

    Serot, O.

    2009-09-01

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

  7. Muon induced fission and fission track dating of minerals

    International Nuclear Information System (INIS)

    Marques, A.

    1988-01-01

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

  8. 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

  9. State Performance-Based Regulation Using Multiyear Rate Plans for U.S. Electric Utilities

    Energy Technology Data Exchange (ETDEWEB)

    Lowry, Mark Newton [Pacific Economics Group Research LLC (United States); Makos, Matt [Pacific Economics Group Research LLC (United States); Deason, Jeff [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Schwartz, Lisa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-07-31

    Electric utilities today must contain costs at a time when many need to modernize aging systems and all face major changes in technologies, customer preferences and competitive pressures.Most U.S. electric utility facilities are investor-owned, subject to rate and service regulation by state public utility commissions. Regulatory systems under which these utilities operate affect their performance and ability to meet these challenges. In this business environment, multiyear rate plans have some advantages over traditional rate regulation.The report focuses on key design issues and provides case studies of the multiyear rate plan approach, applicable to both vertically integrated and restructured states. Mark Newton Lowry and Matt Makos of Pacific Energy Group Research and Jeff Deason of Berkeley Lab authored the report; Lisa Schwartz, Berkeley Lab, was project manager and technical editor.The report is aimed primarily at state utility regulators and stakeholders in the state regulatory process. The multiyear rate approach also provides ideas on how to streamline oversight of public power utilities and rural electric cooperatives for their governing boards.Two key provisions of multiyear rate plans strengthen cost containment incentives and streamline regulation: 1. Reducing frequency of rate cases, typically to every four or five years 2. Using an attrition relief mechanism to escalate rates or revenue between rate cases to address cost pressures such as inflation and growth in number of customers, independently of the utility’s own cost Better utility performance can be achieved under well-designed multiyear rate plans while achieving lower regulatory costs. Benefits can be shared between utilities and their customers. But plans can be complex and involve significant changes in the regulatory system. Designing plans that stimulate utility performance without undue risk and share benefits fairly can be challenging.This report discusses the rationale for multiyear

  10. Report of fission study meeting

    International Nuclear Information System (INIS)

    1986-03-01

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

  11. Status of fission yield data

    International Nuclear Information System (INIS)

    England, T.R.; Blachot, J.

    1988-01-01

    In this paper we summarize the current status of the recent US evaluation for 34 fissioning nuclides at one or more neutron incident energies and for spontaneous fission. Currently there are 50 yields sets, and for each we have independent and cumulative yields and uncertainties for approximately 1100 fission products. When finalized the recommended data will become part of Version VI of the US ENDF/B. Other major evaluations in progress that are included in a recently formed IAEA Coordinated Research Program are also summarized. In a second part we review two empirical models in use to estimate independent yields. Comparison of model estimates with measured data is presented, including a comparison with some recent data obtained from Lohengrin (Cf-249 T). 18 refs., 13 figs., 3 tabs

  12. 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.)

  13. FREVAP-6, Metal Fission Products Release from HTGR Fuel Elements

    International Nuclear Information System (INIS)

    Pierce, V.H.

    2005-01-01

    1 - Description of problem or function: The FREVAP type of code for estimating the release of longer-lived metallic fission products from HTGR fuel elements has been developed to take into account the combined effects of the retention of metallic fission products by fuel particles and the rather strong absorption of these fission products by the graphite of the fuel elements. Release calculations are made on the basis that the loss of fission product nuclides such as strontium, cesium, and barium is determined by their evaporation from the graphite surfaces and their transpiration induced by the flowing helium coolant. The code is devised so that changes of fission rate (fuel element power), fuel temperature, and graphite temperature may be incorporated into the calculation. Temperature is quite important in determining release because, in general, both release from fuel particles and loss by evaporation (transpiration) vary exponentially with the reciprocal of the absolute temperature. NESC0301/02: This version differs from the previous one in the following points: The source and output files were converted from BCD to ASCII coding. 2 - Method of solution: A problem is defined as having a one-dimensional segment made up of three parts - (1) the fission product source (fuel particles) in series with, (2) a non-source and absorption part (element graphite) and (3) a surface for evaporation to the coolant (graphite-helium interface). More than one segment may be connected (possibly segments stacked axially) by way of the coolant. At any given segment, a continuity equation is solved assuming equilibrium between the source term, absorption term, evaporation at coolant interface and the partial pressure of the fission product isotope in the coolant. 3 - Restrictions on the complexity of the problem - Maxima of: 5 isotopes; 10 time intervals for time-dependent variable; 49 segments (times number of isotopes); 5 different output print time-steps

  14. Experiments to investigate the effects of small changes in fuel stoichiometry on fission gas release

    Energy Technology Data Exchange (ETDEWEB)

    Copeland, P S; Smith, R C [Windscale Lab., AEA Technology, Seascale, Cumbria (United Kingdom)

    1997-08-01

    Fuel pin failure in-reactor leads to fission product and in the case of a PWR fuel debris release to the coolant. For economic reasons immediate shutdown and discharge of failed fuel needs to be avoided but this needs to be counter-balanced against the increasing dose to operators. PWR practice is to continue running wit failed rods, monitoring coolant activity, and only shutting down the reactor and discharging the fuel when circuit activity levels become unacceptable. The rate of fission product release under failed fuel conditions is of key importance and considerable effort has been directed towards establishing the dependency of release on temperature, heating rate, burn-up, and also the extent of fuel oxidation. As a precursor to a possible wider investigation of this area, a small programme was mounted during 1992/1993 to confirm whether small changes in the oxidation state of the fuel, for example those caused by minor cladding defects, would significantly effect fuel behaviour during postulated design basis faults. The objective of the programme was to determine the effects of small departures from stoichiometric fuel composition on fission gas release, and to compare the results with the current methodology for calculating releases under fault conditions. A total of eight experiments was performed. Two were intended as baseline tests to provide a reference with which to compare the effect of oxidation state influenced behaviour with that of thermal effects. It was found that small changes in stoichiometry of {sup {approx}}1 x 10{sup -6} had little or no effect on release but that changes of {sup {approx}} 1 x 10{sup -4} were observed to increase the diffusion coefficient, for {sup 85}Kr, by up to an order of magnitude and hence greatly increase the release rate. The stoichiometry of the sample used in these tests was, for convenience, adjusted using He/H{sub 2}/H{sub 2}O atmospheres. (Abstract Truncated)

  15. Analysis of physical properties controlling steady-state infiltration rates on tropical savannah soils

    International Nuclear Information System (INIS)

    Mbagwu, J.S.C.

    1993-10-01

    A knowledge of physical properties influencing the steady-state infiltration rates (ic) of soils is needed for the hydrologic modelling of the infiltration process. In this study evidence is provided to show that effective porosity (Pe) (i.e. the proportion of macro pore spaces with equivalent radius of > 15 μm) and dry bulk density are the most important soil physical properties controlling the steady-state infiltration rates on a tropical savannah with varying land use histories. At a macro porosity value of ≤ 5.0% the steady-state infiltration rate is zero. Total porosity and the proportion of water-retaining pores explained only a small fraction of the variation in this property. Steady-state infiltration rates can also be estimated from either the saturated hydraulic conductivity (Ks) by the equation, i c = 31.1 + 1.06 (Ks), (R 2 = 0.8104, p ≤ 0.001) or the soil water transmissivity (A) by the equation, i c = 30.0 + 29.9(A), (R 2 = 0.8228, ρ ≤ 0.001). The Philip two-parameter model under predicted steady-state infiltration rates generally. Considering the ease of determination and reliability it is suggested that effective porosity be used to estimate the steady-state infiltration rates of these other soils with similar characteristics. The model is, i c 388.7(Pe) - 10.8(R 2 = 0.7265, p ≤ 0.001) where i c is in (cm/hr) and Pe in (cm 3 /cm 3 ). (author). 20 refs, 3 figs, 4 tabs

  16. Comparisons of theoretical and experimental neutron spectra, 115In(n,n') and fission rates, in the centre of three spherical natural uranium and iron shell configurations, located at BR1

    International Nuclear Information System (INIS)

    De Leeuw-Gierts, G.; De Leeuw, S.; Gilliam, D.M.

    1984-01-01

    Three spherical configurations of iron and uranium shells have been studied. The configurations were a 1-cm thick natural uranium shell, a 1-cm thick natural uranium shell with an inner 7-cm thick iron shell and a 1-cm thick natural uranium shell with an inner iron shell of 14-cm thickness. For the measurements, the shells were located at the centre of a hollow cavity, 100-cm in diameter, in the vertical graphite thermal column of the BR1 reactor. The central neutron spectra were calculated by means of the DTF-IV code, using the 208-group KEDAK-3 library, and by means of the ANISN code, using the 171-group VITAMIN-C library. Central neutron spectra, measured by the proton-recoil and 6 Li(n,α)t spectrometry techniques, are compared to the theory between ∼ 100 keV and 5 MeV. Mean fission cross-sections of 240 Pu, 237 Np, 234 U, 235 U, 236 U and 238 U were deduced from the calculations. Their ratios with respect to 238 U are compared to measurements made with NBS dual fission chambers. (Auth.)

  17. THE IMPACT OF FISCAL AND BUDGETARY POLICIES ON THE UNEMPLOYMENT RATE IN THE EU MEMBER STATES

    Directory of Open Access Journals (Sweden)

    ALEXANDRU DRONCA

    2015-03-01

    Full Text Available The tax system is one of the main tools by which a State exercises sovereignty through the collection, allocation and redistribution of revenues in a given territory. This paper aims to highlight how the characteristics of tax systems, in the Member States of the European Union, affect the unemployment rate. To achieve this goal, indicators for the 28 Member States of the European Union for the period 2004-2012 where used in the study. Starting with an analysis of panel data models, developed using a range of indicators specific for tax systems (budget revenues, budget expenditures, public investment, direct taxes, indirect taxes and social contributions,as exogenous variables and the unemployment rate, as an endogenous variable. The results show that the fiscal and budgetary policies of EU Member States can play a positive role in reducing unemployment, provided that their application and use will meet certain standards and performance criteria and do not harm business.

  18. NEACRP thermal fission product benchmark

    International Nuclear Information System (INIS)

    Halsall, M.J.; Taubman, C.J.

    1989-09-01

    The objective of the thermal fission product benchmark was to compare the range of fission product data in use at the present time. A simple homogeneous problem was set with 200 atoms H/1 atom U235, to be burnt up to 1000 days and then decay for 1000 days. The problem was repeated with 200 atoms H/1 atom Pu239, 20 atoms H/1 atom U235 and 20 atoms H/1 atom Pu239. There were ten participants and the submissions received are detailed in this report. (author)

  19. Fission 99Mo production technology

    International Nuclear Information System (INIS)

    Miao Zengxing; Luo Zhifu; Ma Huimin; Liang Yufu; Yu Ningwen

    2003-01-01

    This paper describes a production technology of fission 99 Mo in the Department Isotope, CIAE. The irradiation target is tubular U-Al alloy containing highly enriched uranium. The target is irradiated in the swimming pool reactor core. The neutron flux is about 4x10 13 /cm 2 .sec. The production scale is 3.7-7.4 TBq (100-200Ci) of fission 99 Mo per batch. Total recovery of 99 Mo is more than 70%. The production practice proves that the process and equipment are safe and reliable. (author)

  20. The wastes of nuclear fission

    International Nuclear Information System (INIS)

    Doubre, H.

    2005-01-01

    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.)

  1. 40 years of nuclear fission

    International Nuclear Information System (INIS)

    Koch, H.

    1979-01-01

    On the occasion of both the 100th birthday of the discoverer of nuclear fission, Otto Hahn, and the 40th anniversary of this outstanding scientific discovery the historical development is described, which led to nuclear fission. Aspects of scientific life in Berlin and in the whole world at that time are presented, and relations between scientists are characterized by quotations. In particular, stress is laid on the life and activities of Otto Hahn as a human being and as a scientist, and his outstanding scientific achievements are appreciated. (author)

  2. Nickel-hydrogen battery state of charge during low rate trickle charging

    Science.gov (United States)

    Lurie, C.; Foroozan, S.; Brewer, J.; Jackson, L.

    1996-01-01

    The NASA AXAF-I program requires high battery state of charge at launch. Traditional approaches to providing high state of charge, during prelaunch operations, require significant battery cooling. The use of active cooling, in the AXAF-I prelaunch environment, was considered and proved to be difficult to implement and very expensive. Accordingly alternate approaches were considered. An approach utilizing adiabatic charging and low rate trickle charge, was investigated and proved successful.

  3. Nickel-hydrogen battery state of charge during low rate trickle charging

    Energy Technology Data Exchange (ETDEWEB)

    Lurie, C.; Foroozan, S.; Brewer, J.; Jackson, L. [TRW Space and Electronics Group, Redondo Beach, CA (United States)

    1996-02-01

    The NASA AXAF-I program requires high battery state of charge at launch. Traditional approaches to providing high state of charge, during prelaunch operations, require significant battery cooling. The use of active cooling, in the AXAF-I prelaunch environment, was considered and proved to be difficult to implement and very expensive. Accordingly alternate approaches were considered. An approach utilizing adiabatic charging and low rate trickle charge, was investigated and proved successful.

  4. Dielectronic recombination rate coefficients to the excited states of CIII from CIV

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, U.; Kato, Takako; Ohira, Mituhiko

    1996-07-01

    Energy levels, radiative transition probabilities and autoionization rates for CIII including 1s{sup 2}2pnl` (n=2/6, l`{<=}(n-1)) and 1s{sup 2}3lnl` (n=3/6, l`{<=}(n-1)) states were calculated by using multi-configurational Hartree-Fock (Cowan code) method. Autoionizing levels above the 1s{sup 2}2s and 1s{sup 2}2p thresholds were considered and their contributions were computed. Branching ratios on the autoionization rate to the first threshold and intensity factor were calculated for satellite lines of CIII ion. The dielectronic recombination rate coefficients to the excited states for n=2-6 were calculated. The values for the excited states higher than n=6 were extrapolated and the total dielectronic recombination rate coefficients were also derived. The rate coefficients to the excited states were fitted to an analytical formula and the fitting parameters are given. (author)

  5. Epidemiologic Surveillance of Teenage Birth Rates in the United States, 2006-2012.

    Science.gov (United States)

    Amin, Raid; Decesare, Julie Zemaitis; Hans, Jennifer; Roussos-Ross, Kay

    2017-06-01

    To investigate the geographic variation in the average teenage birth rates by county in the contiguous United States. Data from the National Center for Health Statistics were used in this retrospective cohort to count the total number of live births to females aged 15-19 years by county between 2006 and 2012. Software for disease surveillance and spatial cluster analysis was used to identify clusters of high or low teenage births in counties or areas of greater than 100,000 teenage females. The analysis was then adjusted for percentage of poverty and high school diploma achievement. The unadjusted analysis identified the top 10 clusters of teenage births. The cluster with the highest rate was a city and the surrounding 40 counties, demonstrating an average teen birth rate of 67 per 1,000 females in the age range, 87% higher than the rate in the contiguous United States. Adjustments for poverty rates and high school diploma achievement shifted the top clusters to other areas. Despite an overall national decline in the teenage birth rate, clusters of elevated teenage birth rates remain. These clusters are not random and remain higher than expected when adjusted for poverty and education. This data set provides a framework to focus targeted interventions to reduce teenage birth rates in this high-risk population.

  6. Direct determination of bulk etching rate for LR-115-II solid state ...

    Indian Academy of Sciences (India)

    The thickness of the removed layer of the LR-115-II solid state nuclear track detector during etching is measured directly with a rather precise instrument. Dependence of bulk etching rate on temperature of the etching solution is investigated. It has been found that the bulk etching rate is 3.2 m/h at 60°C in 2.5 N NaOH of ...

  7. State-Space Dynamic Model for Estimation of Radon Entry Rate, based on Kalman Filtering

    Czech Academy of Sciences Publication Activity Database

    Brabec, Marek; Jílek, K.

    2007-01-01

    Roč. 98, - (2007), s. 285-297 ISSN 0265-931X Grant - others:GA SÚJB JC_11/2006 Institutional research plan: CEZ:AV0Z10300504 Keywords : air ventilation rate * radon entry rate * state-space modeling * extended Kalman filter * maximum likelihood estimation * prediction error decomposition Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.963, year: 2007

  8. Sommerfeld-Watson transformation for nuclear fission

    International Nuclear Information System (INIS)

    Alexandru, G.

    1978-01-01

    It is proved that the fission matrix element can be written like a Sommerfeld-Watson relation. This leads to a dispersion relation for the fission process in which the substraction term is uniquely determined. (author)

  9. Fission properties of the heaviest elements

    International Nuclear Information System (INIS)

    Moller, P.; Nix, R.

    1995-01-01

    The authors discuss fission properties of the heaviest elements. In particular they focus on stability with respect to spontaneous fission and on the prospects of extending the region of known nuclei beyond the peninsula of currently known nuclides

  10. Fission fragment distributions within dynamical approach

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-04-15

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

  11. Absolute calibration technique for spontaneous fission sources

    International Nuclear Information System (INIS)

    Zucker, M.S.; Karpf, E.

    1984-01-01

    An absolute calibration technique for a spontaneously fissioning nuclide (which involves no arbitrary parameters) allows unique determination of the detector efficiency for that nuclide, hence of the fission source strength

  12. Red states, blue states, and divorce: understanding the impact of conservative Protestantism on regional variation in divorce rates.

    Science.gov (United States)

    Glass, Jennifer; Levchak, Philip

    2014-01-01

    Why do states with larger proportions of religious conservatives have higher divorce rates than states with lower proportions of religious conservatives? This project examines whether earlier transitions to marriage and parenthood among conservative Protestants (known risk factors for divorce) contribute to this paradox while attending to other plausible explanations. County-level demographic information from all 50 states is combined from a variety of public data sources and merged with individual records from the National Surveys of Family Growth to estimate both aggregated county and multilevel individual models of divorce. Results show that individual religious conservatism is positively related to individual divorce risk, solely through the earlier transitions to adulthood and lower incomes of conservative Protestants. However, the proportion of conservative Protestants in a county is also independently and positively associated with both the divorce rate in that county and an individual's likelihood of divorcing. The earlier family formation and lower levels of educational attainment and income in counties with a higher proportion of conservative Protestants can explain a substantial portion of this association. Little support is found for alternative explanations of the association between religious conservatism and divorce rates, including the relative popularity of marriage versus cohabitation across counties.

  13. Reimbursement rates and policies for primary molar pit-and-fissure sealants across state Medicaid programs.

    Science.gov (United States)

    Chi, Donald L; Singh, Jennifer

    2013-11-01

    Little is known about Medicaid policies regarding reimbursement for placement of sealants on primary molars. The authors identified Medicaid programs that reimbursed dentists for placing primary molar sealants and hypothesized that these programs had higher reimbursement rates than did state programs that did not reimburse for primary molar sealants. The authors obtained Medicaid reimbursement data from online fee schedules and determined whether each state Medicaid program reimbursed for primary molar sealants (no or yes). The outcome measure was the reimbursement rate for permanent tooth sealants (calculated in 2012 U.S. dollars). The authors compared mean reimbursement rates by using the t test (α = .05). Seventeen Medicaid programs reimbursed dentists for placing primary molar sealants (34 percent), and the mean reimbursement rate was $27.57 (range, $16.00 [Maine] to $49.68 [Alaska]). All 50 programs reimbursed dentists for placement of sealants on permanent teeth. The mean reimbursement for permanent tooth sealants was significantly higher in programs that reimbursed for primary molar sealants than in programs that did not ($28.51 and $23.67, respectively; P = .03). Most state Medicaid programs do not reimburse dentists for placing sealants on primary molars, but programs that do so have significantly higher reimbursement rates. Medicaid reimbursement rates are related to dentists' participation in Medicaid and children's dental care use. Reimbursement for placement of sealants on primary molars is a proxy for Medicaid program generosity.

  14. Further microscopic studies of the fission barriers of heavy nuclei

    International Nuclear Information System (INIS)

    Nhan Hao, T.V.; Le Bloas, J.; Bonneau, L.; Quentin, P.; Koh, Meng-Hock

    2012-01-01

    Two systematic sources of error in most current microscopic evaluations of fission-barrier heights are studied. They are concerned with an approximate treatment of the Coulomb exchange terms (known as the Slater approximation) in the self-consistent mean-fields and the projection on good parity states (e.g., of positive parity for the spontaneous fission of an even–even nucleus) of left–right reflection asymmetric intrinsic solutions (e.g., around the second barrier). Approximate or unprojected solutions are shown to lead each to an underestimation of the barrier heights by a few hundred keV. (author)

  15. The chemistry of fission products for accident analysis

    International Nuclear Information System (INIS)

    Potter, P.E.

    1985-01-01

    Current knowledge concerning the chemical state of the fission product elements during the development of accidents in water reactor systems is reviewed in this paper. The fission products elements which have been considered are Cs, I, Te, Sr and Ba but aspects of the behaviour of Mo, Ru and the lanthanides are also discussed. Some features of the reactions of the various species of these elements with other components of the reactor systems are described. The importance of having an adequate knowledge of thermodynamic data and phase equilibria of relatively simple systems in order to interpret experimental observations on complex multi-component systems is stressed

  16. Applications for fission product data to problems in stellar nucleosynthesis

    International Nuclear Information System (INIS)

    Mathews, G.J.

    1983-10-01

    A general overview of the nucleosynthesis mechanisms for heavy (A greater than or equal to 70) nuclei is presented with particular emphasis on critical data needs. The current state of the art in nucleosynthesis models is described and areas in which fission product data may provide useful insight are proposed. 33 references, 10 figures

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

    Science.gov (United States)

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

    1967-01-01

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

  18. Rate Reduction for State-labelled Markov Chains with Upper Time-bounded CSL Requirements

    Directory of Open Access Journals (Sweden)

    Bharath Siva Kumar Tati

    2016-07-01

    Full Text Available This paper presents algorithms for identifying and reducing a dedicated set of controllable transition rates of a state-labelled continuous-time Markov chain model. The purpose of the reduction is to make states to satisfy a given requirement, specified as a CSL upper time-bounded Until formula. We distinguish two different cases, depending on the type of probability bound. A natural partitioning of the state space allows us to develop possible solutions, leading to simple algorithms for both cases.

  19. Stabilization effect of fission source in coupled Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, Borge; Dufek, Jan [Div. of Nuclear Reactor Technology, KTH Royal Institute of Technology, AlbaNova University Center, Stockholm (Sweden)

    2017-08-15

    A fission source can act as a stabilization element in coupled Monte Carlo simulations. We have observed this while studying numerical instabilities in nonlinear steady-state simulations performed by a Monte Carlo criticality solver that is coupled to a xenon feedback solver via fixed-point iteration. While fixed-point iteration is known to be numerically unstable for some problems, resulting in large spatial oscillations of the neutron flux distribution, we show that it is possible to stabilize it by reducing the number of Monte Carlo criticality cycles simulated within each iteration step. While global convergence is ensured, development of any possible numerical instability is prevented by not allowing the fission source to converge fully within a single iteration step, which is achieved by setting a small number of criticality cycles per iteration step. Moreover, under these conditions, the fission source may converge even faster than in criticality calculations with no feedback, as we demonstrate in our numerical test simulations.

  20. Molecular dynamics simulations of cluster fission and fusion processes

    DEFF Research Database (Denmark)

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

    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 analyzed. It is demonstrated that the energy necessary for removing homothetic...... separation of the daughter fragments begins and/or forming a "neck" between the separating fragments. A novel algorithm for modeling the cluster growth process is described. This approach is based on dynamic search for the most stable cluster isomers and allows one to find the optimized cluster geometries...... 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...

  1. State residence restrictions and forcible rape rates: a multistate quasi-experimental analysis of UCR data.

    Science.gov (United States)

    Socia, Kelly M

    2015-04-01

    This study examines whether the presence of state residence restrictions resulted in changes in statewide rates of forcible rape. It builds on the limited geographic coverage of prior studies by including state-level Uniform Crime Report (UCR) data across 19 years for 49 states and the District of Columbia. It uses a quasi-experimental research method based on a longitudinal fixed-effects panel model design, which can help control for relatively static differences between states. Results indicate that when a state residence restriction was present, regardless of how it was measured, rates of UCR forcible rape were higher in the state than when the policy was not present. This suggests that residence restrictions, at least at the state level, are not useful as an overall crime prevention measure, but may be useful for increasing detection or reporting levels of such crimes. However, results also suggest that the size of the increase varied by whether the policy only applied to offenders with child victims or also included those with adult victims. Implications for research and policy are discussed. © The Author(s) 2013.

  2. Investigation of component failure rates for pulsed versus steady state tokamak operation

    International Nuclear Information System (INIS)

    Cadwallader, L.C.

    1992-07-01

    This report presents component failure rate data sources applicable to magnetic fusion systems, and defines multiplicative factors to adjust these data for specific use on magnetic fusion experiment designs. The multipliers address both long pulse and steady state tokamak operation. Thermal fatigue and radiation damage are among the leading reasons for large multiplier values in pulsed operation applications. Field failure rate values for graphite protective tiles are presented, and beryllium tile failure rates in laboratory testing are also given. All of these data can be used for reliability studies, safety analyses, design tradeoff studies, and risk assessments

  3. Characteristics of the samples in the FNG fission deposit collection

    Energy Technology Data Exchange (ETDEWEB)

    Meadows, J.W.

    1990-12-01

    Information concerning the samples in the Fast Neutron Generator (FNG) Group's fission deposit collection has been assembled. This includes the physical dimensions, isotopic analyses, half-lives, alpha emission rates specific activities and deposit weights. 10 refs., 9 figs., 5 tabs.

  4. 45 CFR 284.20 - What information will we use to determine the child poverty rate in each State?

    Science.gov (United States)

    2010-10-01

    ... child poverty rate in each State? 284.20 Section 284.20 Public Welfare Regulations Relating to Public... TERRITORY'S CHILD POVERTY RATE IS THE RESULT OF THE TANF PROGRAM § 284.20 What information will we use to determine the child poverty rate in each State? (a) General. We will determine the child poverty rate in...

  5. Neutron gamma competition in fast fission

    International Nuclear Information System (INIS)

    Frehaut, J.

    1989-01-01

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

  6. Fission yield data evaluation system FYDES

    International Nuclear Information System (INIS)

    Liu Tingjin

    1998-01-01

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

  7. Fission fragment mass and angular distributions

    Indian Academy of Sciences (India)

    2015-07-22

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

  8. Some aspects of fission and quasifission processes

    Indian Academy of Sciences (India)

    2015-07-22

    Jul 22, 2015 ... 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 ...

  9. Charged particle-induced nuclear fission reactions

    Indian Academy of Sciences (India)

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

  10. Fission product removal from molten salt using zeolite

    International Nuclear Information System (INIS)

    Pereira, C.; Babcock, B.D.

    1996-01-01

    Spent nuclear fuel (SNF) can be treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission product cations from the molten salt. Breakthrough of cesium and the alkaline earths occurred more rapidly than was observed for the rare earths. The effluent composition as a function of time is presented, as well as results for the distribution of fission products along the length of the column. Effects of temperature and salt flow rate are also discussed

  11. Solid state nuclear track detectors

    International Nuclear Information System (INIS)

    Medeiros, J.A.; Carvalho, M.L.C.P. de

    1992-12-01

    Solid state nuclear track detectors (SSNTD) are dielectric materials, crystalline or vitreous, which registers tracks of charged nuclear particles, like alpha particles or fission fragments. Chemical etching of the detectors origin tracks that are visible at the optical microscope: track etching rate is higher along the latent track, where damage due to the charged particle increase the chemical potential, and etching rate giving rise to holes, the etched tracks. Fundamental principles are presented as well as some ideas of main applications. (author)

  12. Fission approach to cluster radioactivity

    Indian Academy of Sciences (India)

    2015-08-04

    Aug 4, 2015 ... Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster ... those of the staff, the journals, various programmes, and Current Science, has changed from 'ias.ernet.in' (or 'academy.ias.ernet.in') to 'ias.ac.in'. Thus ...

  13. Spectroscopy of heavy fissionable nuclei

    Indian Academy of Sciences (India)

    2015-08-05

    Aug 5, 2015 ... Nuclei in the actinide chain and beyond are prone to fission owing to ... mass nuclei are typically more difficult, because the intensity is .... j15/2 neutron alignments in a region where shell stablization effects are crucial.

  14. Space Fission System Test Effectiveness

    International Nuclear Information System (INIS)

    Houts, Mike; Schmidt, Glen L.; Van Dyke, Melissa; Godfroy, Tom; Martin, James; Bragg-Sitton, Shannon; Dickens, Ricky; Salvail, Pat; Harper, Roger

    2004-01-01

    Space fission technology has the potential to enable rapid access to any point in the solar system. If fission propulsion systems are to be developed to their full potential, however, near-term customers need to be identified and initial fission systems successfully developed, launched, and utilized. One key to successful utilization is to develop reactor designs that are highly testable. Testable reactor designs have a much higher probability of being successfully converted from paper concepts to working space hardware than do designs which are difficult or impossible to realistically test. ''Test Effectiveness'' is one measure of the ability to realistically test a space reactor system. The objective of this paper is to discuss test effectiveness as applied to the design, development, flight qualification, and acceptance testing of space fission systems. The ability to perform highly effective testing would be particularly important to the success of any near-term mission, such as NASA's Jupiter Icy Moons Orbiter, the first mission under study within NASA's Project Prometheus, the Nuclear Systems Program

  15. Nuclear fission with inertial confinement

    CERN Document Server

    Koshkarev, D G

    2002-01-01

    The possibility of initiating the explosive fission reaction in a small quantity of fissile material through the heavy ions beam from the powerful accelerator-driver, developed for realization of the thermonuclear synthesis in the deuterium-tritium cylindrical targets with the direct ignition, is considered. The consequences of applying this method in the nuclear engineering are discussed

  16. Dynamical features of nuclear fission

    Indian Academy of Sciences (India)

    Wheeler underestimates several observables in heavy-ion-induced ... excitation energies, there may not be sufficient nuclei near the fission barrier after the .... Dissipation in nuclear dynamics in the mean-field regime accounts for the coupling of the .... barrier for different isotopes of Fr. The lines are drawn to guide the eye.

  17. Femtosecond stimulated Raman evidence for charge-transfer character in pentacene singlet fission.

    Science.gov (United States)

    Hart, Stephanie M; Silva, W Ruchira; Frontiera, Renee R

    2018-02-07

    Singlet fission is a spin-allowed process in which an excited singlet state evolves into two triplet states. We use femtosecond stimulated Raman spectroscopy, an ultrafast vibrational technique, to follow the molecular structural evolution during singlet fission in order to determine the mechanism of this process. In crystalline pentacene, we observe the formation of an intermediate characterized by pairs of excited state peaks that are red- and blue-shifted relative to the ground state features. We hypothesize that these features arise from the formation of cationic and anionic species due to partial transfer of electron density from one pentacene molecule to a neighboring molecule. These observations provide experimental evidence for the role of states with significant charge-transfer character which facilitate the singlet fission process in pentacene. Our work both provides new insight into the singlet fission mechanism in pentacene and demonstrates the utility of structurally-sensitive time-resolved spectroscopic techniques in monitoring ultrafast processes.

  18. Efficient Computation of Transition State Resonances and Reaction Rates from a Quantum Normal Form

    NARCIS (Netherlands)

    Schubert, Roman; Waalkens, Holger; Wiggins, Stephen

    2006-01-01

    A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for

  19. National- and State-Level High School Graduation Rates for English Learners. Fast Facts

    Science.gov (United States)

    Office of English Language Acquisition, US Department of Education, 2016

    2016-01-01

    The Office of English Language Acquisition (OELA) has synthesized key data on English learners (ELs) into two-page PDF sheets, by topic, with graphics, plus key contacts. The topic for this report on English Learners (ELs) are national- and state-level high school graduation rates for English Learners. The following data are presented: (1)…

  20. State-related differences in heart rate variability in bipolar disorder

    DEFF Research Database (Denmark)

    Faurholt-Jepsen, Maria; Brage, Søren; Kessing, Lars Vedel

    2017-01-01

    Heart rate variability (HRV) is a validated measure of sympato-vagal balance in the autonomic nervous system. HRV appears decreased in patients with bipolar disorder (BD) compared with healthy individuals, but the extent of state-related alterations has been sparingly investigated. The present...... bipolar disorder and could...