Management-retrieval code system of fission barrier parameter sub-library
International Nuclear Information System (INIS)
Zhang Limin; Su Zongdi; Ge Zhigang
1995-01-01
The fission barrier parameter (FBP) library, which is a sub-library of Chinese Evaluated Nuclear Parameter library (CENPL), stores various popular used fission barrier parameters from different historical period, and could retrieve the required fission barrier parameters by using the management retrieval code system of the FBP sub-library. The function, feature and operation instruction of the code system are described briefly
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
Fission barriers of superheavy nuclei
International Nuclear Information System (INIS)
Burvenich, T.
2001-01-01
Full text: Self consistent microscopic mean-field models are powerful tools for the description of nuclear structure phenomena in the region of known elements, where they have reached a good quality. Especially the Skyrme-Hartree-Fock (SHF) method and the Relativistic Mean-Field (RMF) model will be considered in the discussion of the properties of these models. When it comes to extrapolation to the region of superheavy elements, though there is agreement concerning the global trends, these model exhibit significant differences in their predictions concerning fission barrier heights and structures. (Author)
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)
Fusion barrier distributions and fission anisotropies
International Nuclear Information System (INIS)
Hinde, D.J.; Morton, C.R.; Dasgupta, M.; Leigh, J.R.; Lestone, J.P.; Lemmon, R.C.; Mein, J.C.; Newton, J.O.; Timmers, H.; Rowley, N.; Kruppa, A.T.
1995-01-01
Fusion excitation functions for 16,17 O+ 144 Sm have been measured to high precision. The extracted fusion barrier distributions show a double-peaked structure interpreted in terms of coupling to inelastic collective excitations of the target. The effect of the positive Q-value neutron stripping channel is evident in the reaction with 17 O. Fission and evaporation residue cross-sections and excitation functions have been measured for the reaction of 16 O+ 208 Pb and the fusion barrier distribution and fission anisotropies determined. It is found that the moments of the fusion l-distribution determined from the fusion and fission measurements are in good agreement. ((orig.))
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
Fission barriers of two odd-neutron heavy nuclei
International Nuclear Information System (INIS)
Koh, Meng-Hock; Bonneau, L.; Nhan Hao, T. V.; Duc, Dao Duy; Quentin, P.
2015-01-01
The fission barriers of two odd-neutron heavy odd nuclei,namely the 235 U and 239 Pu isotopes have been calculated within a self-consistent Hartree-Fock-plus-BCS approach with blocking. A Skyrme nucleon-nucleon effective interaction has been used together with a seniority force to describe pairing correlations. A full account of the genuine time-reversal symmetry breaking due to the presence of an unpaired nucleon has been incorporated at the mean field level. The SIII and SkM* parametrizations of the Skyrme interaction have been retained as well as for a part a newer parametrization, SLy5*. The seniority force parameters have been fitted to reproduce experimental odd-even mass differences in the actinide region. To assess the relevance of our calculated fission barrier distribution (as a function of the quantum numbers), we have studied the quality of our results with respect to the spectroscopy of band heads (for configurations deemed to be a pure single particle character) in the ground and fission isomeric states. Fission barriers of the considered odd nuclei have been compared with what is obtained for their even-even neighbouring isotopes (namely 234 U and 236 U, 238 Pu and 240 Pu respectively) to determine the so-called specialization energies. Various corrections and associated uncertainties have been discussed in order to compare our results with available data
International Nuclear Information System (INIS)
Su Zongdi
1995-01-01
Description of program or function: CENPL - GDRP (Giant Dipole Resonance Parameters for Gamma-Ray): - Format: special format described in documentation; - Nuclides: V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, I, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Lu, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, Th, U, Np, Pu. - Origin: Experimental values offered by S.S. Dietrich and B.L. Berman. CENPL - FBP (Fission Barrier Parameter Sub-Library): - Format: special format described in documentation; - Nuclides: (1) 51 nuclei region from Th-230 to Cf-255, (2) 46 nuclei region from Th-229 to Cf-253, (3) 24 nuclei region from Pa-232 to Cf-253; - Origin: (1) Lynn, (2) Analysis of experimental data by Back et al., (3) Ohsawa. CENPL - DLS (Discrete level scheme and branch ratio of gamma decay: - Format: Special format described in documentation; - Origin: ENSDF - BNL. CENPL - NLD (Nuclear Level Density): - Format: Special format described in documentation; - Origin: Huang Zhongfu et al. CENPL - OMP (Optical model parameter sub-library): - Format: special format described in documentation ; - Origin: CENDL, ENDF/B-VI, JENDL-3. CENPL - MC (I) and (II) (Atomic masses and characteristic constants for nuclear ground states) : - Format: Brief table format; - Nuclides: 4760 nuclides ranging from Z=0 A=1 to Z=122 A=318. - Origin: Experimental data and systematic results evaluated by Wapstra, theoretical results calculated by Moller, ENSDF - BNL and Nuclear Wallet Cards. CENPL contains the following six sub-libraries: 1. Atomic Masses and Characteristic Constants for nuclear ground states (MCC). This data consists of calculated and in most cases also measured mass excesses, atomic masses, total binding energies, spins, parities, and half-lives of nuclear ground states, abundances, etc. for 4800 nuclides. 2. Discrete Level Schemes and branching ratios of gamma decay (DLS). The data on nuclear discrete levels are based on the Evaluated
Fundamentals of the double-humped fission barrier
International Nuclear Information System (INIS)
Brack, M.
1980-01-01
We review the development of the theory of the fission barrier over the past forty years. Special emphasis is put on the shell-correction method of Strutinsky and its foundation and numerical verification from microscopical Hartree-Fock calculations. The different practical realisations of the method and its applications to the calculation of deformation energy surfaces are reviewed. The influence of the different shape degrees of freedom of the nucleus on the form of the fission barrier is discussed. Finally, we summarize some more recent developments concerning both experimental and theoretical aspects of the double-humped fission barrier. (author)
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...
Optimal systematics of single-humped fission barriers for statistical calculations
International Nuclear Information System (INIS)
Mashnik, S.G.
1993-01-01
A systematic comparison of the existing phenomenological approaches and models for describing single-humped fast-computing fission barriers are given. The experimental data on excitation energy dependence of the fissility of compound nuclei are analyzed in the framework of the statistical approach by using different models for fission barriers, shell and pairing corrections and level-density parameter in order to identify their reliability and region of applicability for Monte Carlo calculations of evaporative cascades. The energy dependence of fission cross-sections for reactions induced by intermediate energy protons has been analyzed in the framework of the cascade-exiton model. 53 refs., 15 figs., 3 tabs
Specific fission J-window and angular momentum dependence of the fission barrier
Energy Technology Data Exchange (ETDEWEB)
Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto; Yokoyama, Akihiko [Osaka Univ., Suita (Japan); Shinohara, Atsushi
1997-04-01
A method to determine a unique J-window in the fission process was devised and the fissioning nuclide associated with thus extracted J-window was identified for each of the heavy-ion reaction systems. Obtained fission barriers at the resulting J-window were compared with the calculated values by the rotating finite range model (RFRM). The deduced barriers for individual nuclides were compared with the RFRM barriers to reproduce more or less the angular momentum dependence the RFRM prediction. The deduced systematic behavior of the fission barrier indicates no even-odd and shell corrections are necessary. The nuclear dissipation effect based on Kramer`s model revealed substantial reduction of the statistically deduced barrier heights and brought a fairly large scattering from the RFRM J-dependence. However, introduction of the temperature-dependent friction coefficient ({gamma} = 2 for T {>=} 1.0 MeV and 0.5 for T < 1.0 MeV) was found to bring about satisfactory agreement with both RFRM fission barriers and the pre-fission neutron multiplicity systematics. (author). 81 refs.
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)
Inclusion of temperature dependence of fission barriers in statistical model calculations
International Nuclear Information System (INIS)
Newton, J.O.; Popescu, D.G.; Leigh, J.R.
1990-08-01
The temperature dependence of fission barriers has been interpolated from the results of recent theoretical calculations and included in the statistical model code PACE2. It is shown that the inclusion of temperature dependence causes significant changes to the values of the statistical model parameters deduced from fits to experimental data. 21 refs., 2 figs
Remarks on the fission barriers of super-heavy nuclei
Energy Technology Data Exchange (ETDEWEB)
Hofmann, S. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Goethe-Universitaet Frankfurt, Institut fuer Physik, Frankfurt (Germany); Heinz, S.; Mann, R.; Maurer, J.; Muenzenberg, G.; Barth, W.; Dahl, L.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Runke, J.; Scheidenberger, C.; Tinschert, K. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Antalic, S. [Comenius University, Department of Nuclear Physics and Biophysics, Bratislava (Slovakia); Eberhardt, K.; Thoerle-Pospiech, P.; Trautmann, N. [Johannes Gutenberg-Universitaet Mainz, Mainz (Germany); Grzywacz, R. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of Tennessee, Knoxville, TN (United States); Hamilton, J.H. [Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States); Henderson, R.A.; Kenneally, J.M.; Moody, K.J.; Shaughnessy, D.A.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Miernik, K. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of Warsaw, Warsaw (Poland); Miller, D. [University of Tennessee, Knoxville, TN (United States); Morita, K. [RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama (Japan); Nishio, K. [Japan Atomic Energy Agency, Tokai, Ibaraki (Japan); Popeko, A.G.; Yeremin, A.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Roberto, J.B.; Rykaczewski, K.P. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Uusitalo, J. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland)
2016-04-15
Shell-correction energies of super-heavy nuclei are approximated by using Q{sub α} values of measured decay chains. Five decay chains were analyzed, which start at the isotopes {sup 285}Fl, {sup 294}118, {sup 291}Lv, {sup 292}Lv and {sup 293}Lv. The data are compared with predictions of macroscopic-microscopic models. Fission barriers are estimated that can be used to eliminate uncertainties in partial fission half-lives and in calculations of evaporation-residue cross-sections. In that calculations, fission probability of the compound nucleus is a major factor contributing to the total cross-section. The data also provide constraints on the cross-sections of capture and quasi-fission in the entrance channel of the fusion reaction. Arguments are presented that fusion reactions for synthesis of isotopes of elements 118 and 120 may have higher cross-sections than assumed so far. (orig.)
An improved JWKB approximation for multiple-humped fission barriers
International Nuclear Information System (INIS)
Martinelli, T.; Menapace, E.; Ventura, A.
1977-01-01
Penetrabilities of two- and three-humped fission barriers are calculated in semiclassical (JWKB) approximation, valid also in the case where classical turning points are close, or coincident (excitation energy near the top of some hump). Numerical results are shown for Th 234 . (author)
Fission barriers in the quasi-molecular shape path
International Nuclear Information System (INIS)
Royer, G.; Bonilla, C.; Zbiri, K.; Gherghescu, R.A.
2003-01-01
New observed phenomena like asymmetric fission of intermediate mass nuclei, nuclear molecules in light nuclei, super and hyperdeformations, cluster radioactivity, fast-fission of heavy systems and fragmentation have renewed interest in investigating the fusion-like fission valley which leads rapidly to two touching spherical fragments and quasi-molecular shapes. Furthermore, rotating super and hyperdeformed nuclear states and superheavy nuclei can be formed only in heavy-ion collisions for which the initial configuration is two close quasi-spherical nuclei. For these shapes the balance between the Coulomb forces and surface tension forces does not allow to link the sheets of the potential energy surface corresponding to one-body shapes and to two separated fragments, respectively. It is necessary to add another term called proximity energy reproducing the finite-range effects of the nuclear force in the neck or the gap between the nascent fission fragments. A generalized liquid drop model has been developed to take into account this nuclear proximity energy, the mass and charge asymmetry, an accurate nuclear radius and the temperature effects. The initial value of the surface energy coefficient has been kept. Microscopic corrections have been determined within the asymmetric two center shell model or simpler algebraic approximations. With this model and deformation valley first studies had led to the following results: (i) good agreement between the potential barrier heights and the experimental fission barrier heights in the whole mass range; (ii) saddle-point corresponding to two separated fragments maintained in unstable equilibrium by the balance between the repulsive Coulomb forces and the attractive proximity forces; (iii) strong enhancement of the maximal angular momentum against fission; (iv) reasonable agreement with experimental data on the double-humped barriers of actinides. Within this same approach we have recently shown that the calculated potential
Fission of heavy nuclei: microscopic study of fission barriers and fragments angular momentum
International Nuclear Information System (INIS)
Bonneau, L.
2003-11-01
A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J 2 in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J 2 operator. (A.C.)
A constrained approximation for nuclear barrier penetration and fission
International Nuclear Information System (INIS)
Tang, H.H.K.; Negele, J.W.; Massachusetts Inst. of Tech., Cambridge; Massachusetts Inst. of Tech., Cambridge
1983-01-01
An approximation to the time-dependent mean-field theory for barrier penetration by a nucleus is obtained in terms of constrained Hartree-Fock wave functions and a coherent velocity field. A discrete approximation to the continuum theory suitable for practical numerical calculations is presented and applied to three illustrative models. Potential application of the theory to the study of nuclear fission is discussed. (orig.)
Masses and fission barriers of nuclei in the LSD model
Energy Technology Data Exchange (ETDEWEB)
Pomorski, Krzysztof
2009-07-01
Recently developed Lublin-Strasbourg Drop (LSD) model together with the microscopic corrections taken r is very successful in describing many features of nuclei. In addition to the classical liquid drop model the LSD contains the curvature term proportional to the A{sup 1/3}. The r.m.s. deviation of the LSD binding energies of 2766 isotopes with Z,N>7 from the experimental ones is 0.698 MeV only. It turns out that the LSD model gives also a satisfactory prediction of the fission barrier heights. In addition, it was found in that taking into account the deformation dependence of the congruence energy proposed by Myers and Swiatecki significantly approaches the LSD-model barrier-heights to the experimental data in the case of light isotopes while the fission barriers for heavy nuclei remain nearly unchanged and agree well with experiment. It was also shown in that the saddle point masses of transactinides from {sup 232}Th to {sup 250}Cf evaluated using the LSD differ by less than 0.67 MeV from the experimental data.
I. Fission Probabilities, Fission Barriers, and Shell Effects. II. Particle Structure Functions
Energy Technology Data Exchange (ETDEWEB)
Jing, Kexing [Univ. of California, Berkeley, CA (United States)
1999-05-01
In Part I, fission excitation functions of osmium isotopes ^{185,186, 187, 189} Os produced in ^{3}He +^{182,183, 184, 186}W reactions, and of polonium isotopes ^{209,210, 211, 212}Po produced in ^{3}He/^{4}He + ^{206, 207, 208}Pb reactions, were measured with high precision. These excitation functions have been analyzed in detail based upon the transition state formalism. The fission barriers, and shell effects for the corresponding nuclei are extracted from the detailed analyses. A novel approach has been developed to determine upper limits of the transient time of the fission process. The upper limits are constrained by the fission probabilities of neighboring isotopes. The upper limits for the transient time set with this new method are 15x 10^{–21} sec and 25x 10^{–21} sec for 0s and Po compound nuclei, respectively. In Part II, we report on a search for evidence of the optical modulations in the energy spectra of alpha particles emitted from hot compound nuclei. The optical modulations are expected to arise from the ~-particle interaction with the rest of the nucleus as the particle prepares to exit. Some evidence for the modulations has been observed in the alpha spectra measured in the 3He-induced reactions, ^{3}He + ^{nat}Ag in particular. The identification of the modulations involves a technique that subtracts the bulk statistical background from the measured alpha spectra, in order for the modulations to become visible in the residuals. Due to insufficient knowledge of the background spectra, however, the presented evidence should only be regarded as preliminary and tentative.
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
Semiclassical shell structure and nuclear double-humped fission barriers
Directory of Open Access Journals (Sweden)
A. G. Magner
2010-09-01
Full Text Available We derived the semiclassical trace formulas for the level density as sums over periodic-orbit families and isolated orbits within the improved stationary phase method. Averaged level-density shell corrections and shell-structure energies are continuous through all symmetry-breaking (bifurcation points with the correct asymptotics of the standard stationary phase approach accounting for continuous symmetries. We found enhancement of the nuclear shell structure near bifurcations in the superdeformed region. Our semiclassical results for the averaged level densities with the gross-shell and more thin-shell structures and the energy shell corrections for critical deformations are in good agreement with the quantum calculations for several single-particle Hamiltonians, in particular for the potentials with a sharp spheroidal shape. Enhancement of the shell structure owing to bifurcations of the shortest 3-dimensional orbits from equatorial orbits is responsible for the second well of fission barrier in a superdeformation region.
Determination of shell energies. Nuclear deformations and fission barriers
International Nuclear Information System (INIS)
Koura, Hiroyuki; Tachibana, Takahiro; Uno, Masahiro; Yamada, Masami.
1996-01-01
We have been studying a method of determining nuclear shell energies and incorporating them into a mass formula. The main feature of this method lies in estimating shell energies of deformed nuclei from spherical shell energies. We adopt three assumptions, from which the shell energy of a deformed nucleus is deduced to be a weighted sum of spherical shell energies of its neighboring nuclei. This shell energy should be called intrinsic shell energy since the average deformation energy also acts as an effective shell energy. The ground-state shell energy of a deformed nucleus and its equilibrium shape can be obtained by minimizing the sum of these two energies with respect to variation of deformation parameters. In addition, we investigate the existence of fission isomers for heavy nuclei with use of the obtained shell energies. (author)
Statistical fission parameters for nuclei at high excitation and angular momenta
International Nuclear Information System (INIS)
Blann, M.; Komoto, T.A.
1982-01-01
Experimental fusion/fission excitation functions are analyzed by the statistical model with modified rotating liquid drop model barriers and with single particle level densities modeled for deformation for ground state (a/sub ν/) and saddle point nuclei (a/sub f/). Values are estimated for the errors in rotating liquid drop model barriers for the different systems analyzed. These results are found to correlate well with the trends predicted by the finite range model of Krappe, Nix, and Sierk, although the discrepancies seem to be approximately 1 MeV greater than the finite range model predictions over the limited range tested. The a priori values calculated for a/sub f/ and a/sub ν/ are within +- 2% of optimum free parameter values. Analyses for barrier decrements explore the importance of collective enhancement on level densities and of nuclear deformation in calculating transmission coefficients. A calculation is performed for the 97 Rh nucleus for which a first order angular momentum scaling is used for the J = 0 finite range corrections. An excellent fit is found for the fission excitation function in this approach. Results are compared in which rotating liquid drop model barriers are decremented by a constant energy, or alternatively multiplied by a constant factor. Either parametrization is shown to be capable of satisfactorily reproducing the data although their J = 0 extrapolated values differ markedly from one another. This underscores the dangers inherent in arbitrary barrier extrapolations
Energy Technology Data Exchange (ETDEWEB)
Bonneau, L
2003-11-01
A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J{sup 2} in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J{sup 2} operator. (A.C.)
Energy Technology Data Exchange (ETDEWEB)
Bonneau, L
2003-11-01
A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J{sup 2} in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J{sup 2} operator. (A.C.)
Concentration of E2 strength near the fission barrier of 232Th
International Nuclear Information System (INIS)
Arruda Neto, J.D.T.; Vannucci, M.F.B.M.; Herdade, S.B.; Vannucci, A.; Nascimento, I.C. do.
1981-08-01
The electrofission angular distribution of 232 Th, in the energy interval 5.5-7 MeV, was measured. The analysis of substantial amount of E2 fission strength is concentrated near the fission barrier, corresponding to (8 +- 2)% of one energy weighted sum rule unity. (Author) [pt
A new set of parameters for 5 Gaussian fission yields systematics
International Nuclear Information System (INIS)
Katakura, Jun-ichi
2003-01-01
A new set of parameters for 5 Gaussian-type fission yields systematics has been proposed for applying to high energy neutron or proton fission and to various kinds of fissioning systems including minor actinides. The mass yields calculated using the systematics were compared with various kinds of measured data including the fission with incident energy higher than 100 MeV and the fission of minor actinide nuclides. The comparisons showed rather good agreement between the calculated values and measured ones for various kinds of fissioning systems. (author)
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)
Directory of Open Access Journals (Sweden)
Sagaidak Roman
2017-01-01
Full Text Available The cross section data for fission and evaporation residue production in fusion reactions leading to nuclei from Po to Ra have been considered in a systematic way in the framework of the conventional barrier-passing (fusion model coupled with the statistical model. The cross section data obtained in very asymmetric projectile-target combinations can be described within these models rather well with the adjusted model parameters. In particular, one can scale and fix the macroscopic (liquid-drop fission barrier heights (FBHs for nuclei involved in the de-excitation of compound nuclei produced in the reactions. The macroscopic FBHs for nuclei from Po to Ra have been derived in the framework of such analysis and compared with the predictions of various theoretical models.
Gamma-ray multiplicities in sub-barrier fission of 226Th
International Nuclear Information System (INIS)
Chubaryan, G.G.; Hurst, B.J.; O'Kelly, D.J.
1998-01-01
The γ rays from the multimodal fission of the 226 Th formed in 18 O + 208 Pb were investigated at the sub-barrier energies. The corresponding excitation energies at the saddle point, E sp * , ranged from 16.4 to 19.2 MeV. The average γ-ray multiplicities and relative γ-ray energies as a function of the mass of the fission fragments exhibit a complex structure and strong variations. Such strong variations have never been previously observed in heavy ion-induced fusion-fission reactions. Obtained results may be explained with the influence of shell effects on the properties of the fission fragments. The present work is one in series of investigations of the multimodal fission phenomena in At-Th region
Chai, Qing-Zhen; Zhao, Wei-Juan; Liu, Min-Liang; Wang, Hua-Lei
2018-05-01
Static fission barriers for 95 even-even transuranium nuclei with charge number Z = 94–118 have been systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the potential energy surface approach in multidimensional (β 2, γ, β 4) deformation space. Taking the heavier 252Cf nucleus (with the available fission barrier from experiment) as an example, the formation of the fission barrier and the influence of macroscopic, shell and pairing correction energies on it are analyzed. The results of the present calculated β 2 values and barrier heights are compared with previous calculations and available experiments. The role of triaxiality in the region of the first saddle is discussed. It is found that the second fission barrier is also considerably affected by the triaxial deformation degree of freedom in some nuclei (e.g., the Z=112–118 isotopes). Based on the potential energy curves, general trends of the evolution of the fission barrier heights and widths as a function of the nucleon numbers are investigated. In addition, the effects of Woods-Saxon potential parameter modifications (e.g., the strength of the spin-orbit coupling and the nuclear surface diffuseness) on the fission barrier are briefly discussed. Supported by National Natural Science Foundation of China (11675148, 11505157), the Project of Youth Backbone Teachers of Colleges and Universities of Henan Province (2017GGJS008), the Foundation and Advanced Technology Research Program of Henan Province (162300410222), the Outstanding Young Talent Research Fund of Zhengzhou University (1521317002) and the Physics Research and Development Program of Zhengzhou University (32410017)
Fission in Empire-II version 2.19 beta1, Lodi
International Nuclear Information System (INIS)
Sin, M.
2003-01-01
This is a description of the fission model implemented presently in EMPIRE-II. This package offers two ways to calculate the fission probability selected by parameters in the optional input. Fission barriers, fission transmission coefficients, fission cross sections and fission files are calculated
International Nuclear Information System (INIS)
Behera, B.R.; Jena, S.; Satapathy, M.; Ison, V.V.; Kailas, S.; Chatterjee, A.; Shrivastava, A.; Mahata, K.; Satpathy, L.; Basu, P.; Roy, S.; Sharan, M.; Chatterjee, M.L; Datta, S.K.
2000-01-01
Fission fragment angular distributions of heavy-ion induced fission in actinide nuclei at near-barrier energies show anomalous fragment anisotropies. At above barrier energies entrance channel dependence is a probable cause and explanation in terms of pre-equilibrium fission and the critical mass asymmetry parameter (Businaro-Gallone) has been tried. Target deformation and ground state spin also seem to influence the measured anisotropy. To understand the extent of importance of some or all of these features, we performed a set of experiments where (i) entrance channel dependence (ii) mass asymmetry on the two sides of Businaro-Gallone and (iii) different ground state spins are present. The channels chosen are 14 N+ 232 Th and 11 B+ 235 U. Experiments were done using the Pelletron accelerators at NSC, New Delhi and BARC-TIFR, Bombay. Compound nucleus populated in both cases is 246 Bk. 232 Th has ground state spin zero and 235 U has spin 7/2. Fragment anisotropies have been measured from 10-15 % above barrier to 10 % below barrier at similar excitation energy (around 40 MeV to 58 MeV). The mean square angular momentum is matched at least at one energy. Results indicate that when both excitation energy and angular momentum are matched, there are differences in the measured values of fission anisotropies. This implies entrance channel dependence consistent with the expectation of pre-equilibrium fission model. (authors)
Stability of trans-fermium elements at high spin: Measuring the fission barrier of 254No
International Nuclear Information System (INIS)
Henning, Greg
2012-01-01
Super heavy nuclei provide opportunities to study nuclear structure near three simultaneous limits: in charge Z, spin I and excitation energy E*. These nuclei exist only because of a fission barrier, created by shell effects. It is therefore important to determine the fission barrier and its spin dependence B f (I), which gives information on the shell energy E(shell)(I). Theoretical calculations predict different fission barrier heights from B f (I = 0) = 6.8 MeV for a macro-microscopic model to 8.7 MeV for Density Functional Theory calculations using the Gogny or Skyrme interactions. Hence, a measurement of B f provides a test for theories.To investigate the fission barrier, an established method is to measure the rise of fission with excitation energy, characterized by the ratio of decay widths Γ(fission)/Γ(total), using transfer reactions. However, for heavy elements such as 254 No, there is no suitable target for a transfer reaction. We therefore rely on the complementary decay widths ratio Γ γ /Γ(fission) and its spin dependence, deduced from the entry distribution (I, E*).Measurements of the gamma-ray multiplicity and total energy for 254 No have been performed with beam energies of 219 and 223 MeV in the reaction 208 Pb( 48 Ca,2n) at ATLAS (Argonne Tandem Linac Accelerator System). The 254 No gamma rays were detected using the Gammasphere array as a calorimeter - as well as the usual high resolution γ-ray detector. Coincidences with evaporation residues at the Fragment Mass Analyzer focal plane separated 254 No gamma rays from those from fission fragments, which are ≥ 10 6 more intense. From this measurement, the entry distribution - i.e. the initial distribution of I and E* - is constructed. Each point (I,E*) of the entry distribution is a point where gamma decay wins over fission and, therefore, gives information on the fission barrier. The measured entry distributions show an increase in the maximum spin and excitation energy from 219 to 223 Me
Challenging fission dynamics around the barrier: The case of {sup 34}S + {sup 186}W
Energy Technology Data Exchange (ETDEWEB)
Kozulin, E.M.; Itkis, I.; Knyazheva, G.; Novikov, K.; Bogachev, A.; Dmitriev, S.; Loktev, T. [Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, Dubna (Russian Federation); Vardaci, E. [Dipartamento di Scienze Fisiche, Napoli (Italy); INFN, Napoli (Italy); Harca, I.M. [Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, Dubna (Russian Federation); Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering (IFIN-HH), Bucharest - Magurele (Romania); Universitatea din Bucuresti, Facultatea de Fizica, Bucharest (Romania); Schmitt, C.; Piot, J. [GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, BP 55027, Caen (France); Azaiez, F.; Matea, I.; Verney, D.; Gottardo, A. [Universite Paris-Saclay, IPN, CNRS/IN2P3, Orsay (France); Dorvaux, O. [Universite de Strasbourg, IPHC, CNRS/IN2P3, Strasbourg (France); Chubarian, G. [Texas A and M University, Cyclotron Institute, College Station, TX (United States); Trzaska, W.H. [Accelerator Laboratory of University of Jyvaskyla (JYFL), Jyvaskyla (Finland); Hanappe, F. [Universite Libre de Bruxelles (ULB), Bruxelles (Belgium); Borcea, C.; Calinescu, S.; Petrone, C. [Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering (IFIN-HH), Bucharest - Magurele (Romania)
2016-09-15
The current status of fission dynamics studies in heavy-ion collisions around the Coulomb barrier is illustrated with the {sup 34}S + {sup 186}W reaction. The fission-fragment mass and total kinetic energy were measured at the ALTO facility at IPN Orsay, France, with a dedicated set-up using the (v, E) approach. The measurement reveals the presence of an asymmetric fission component on top of a predominantly symmetric distribution. The asymmetric structure, pointed out for the first time, is discussed along with results of previous experiments studying the same reaction. While these analyses suggested the contribution from either quasi-fission or pre-equilibrium fission, we offer an alternative interpretation, in terms of shell-driven compound-nucleus fission. The present measurement demonstrates the critical influence of resolution when addressing puzzling cases, situated at the crossroads of the various channels opened in a heavy-ion collision. Current status in the field clearly calls for innovative measurements involving manifold correlations and new observables. The outcome of the attempt done in this work in this direction, based on the coincident measurement of prompt γ-rays is reported, and encouraging perspectives are discussed. (orig.)
Critical angular momentum dependence of the fission barriers and the stability of superheavy nuclei
International Nuclear Information System (INIS)
Magda, M.T.; Sandulescu, A.
1978-10-01
Measured complete fusion and evaporation cross section data are used to determine the critical angular momenta for which the fission barriers are vanishing in the region of nuclei with Z = 102 - 116. It is shown that, in order to fit these data, larger values of the critical angular momenta are obtained for superheavy nuclei (Z = 110 - 112) than for heavy ones (Z = 102 - 107), which indicates a relatively higher stability against fission for superheavy nuclei, in agreement with the theoretically predicted island of stability. (author)
The Effect of Stiffness Parameter on Mass Distribution in Heavy-Ion Induced Fission
Soheyli, Saeed; Khalil Khalili, Morteza; Ashrafi, Ghazaaleh
2018-06-01
The stiffness parameter of the composite system has been studied for several heavy-ion induced fission reactions without the contribution of non-compound nucleus fission events. In this research, determination of the stiffness parameter is based on the comparison between the experimental data on the mass widths of fission fragments and those predicted by the statistical model treatments at the saddle and scission points. Analysis of the results shows that for the induced fission reactions of different targets by the same projectile, the stiffness parameter of the composite system decreases with increasing the fissility parameter, as well as with increasing the mass number of the compound nucleus. This parameter also exhibits a similar behavior for the reactions of a given target induced by different projectiles. As expected, nearly same stiffness values are obtained for different reactions leading to the same compound nucleus.
Fission excitation function for 19F + 194,196,198Pt at near and above barrier energies
Directory of Open Access Journals (Sweden)
Singh Varinderjit
2015-01-01
Full Text Available Fission excitation functions for 19F + 194,196,198Pt reactions populating 213,215,217Fr compound nuclei are reported. Out of these three compound nuclei, 213Fr is a shell closed (N=126 compound nucleus and the other two are away from the shell closure. From a comparison of the experimental fission cross-sections with the statistical model predictions, it is observed that the fission cross-sections are underestimated by the statistical model predictions using shell corrected finite range rotating liquid drop model (FRLDM fission barriers. Further the FRLDM fission barriers are reduced to fit the fission cross-sections over the entire measured energy range.
Fission barrier theory and its application to the calculation of actinide neutron cross-sections
International Nuclear Information System (INIS)
Lynn, J.E.
1980-01-01
The lectures discuss the possibilities and realisations of applying nuclear fission theory to the calculation of unknown nuclear data required for applications, principally in the nuclear power field. A brief description of the fundamentals of fission theory, the nature of the potential energy surface in the deformation plane, and of the inertial tensor, is given, and the accuracy of the theoretical calculations is discussed. It is concluded that it is impracticable to obtain required quantities such as neutron cross-sections from such fundamental calculations at present. On the other hand the fundamental theory reveals a wealth of phenomenological aspects of the fission process which can be incorporated into nuclear reaction theory. It is then shown how reaction theory thus extended to take correct account of the structured (''double-humped'') fission barrier can be used to parametrise the barrier by analysis of experimental data, and subsequently to calculate new data. Descriptions of computer programmes and illustrations of the application of the methods to actual physical examples are included in this account. (author)
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)
Fission barrier heights in the A ∼ 200 mass region
Indian Academy of Sciences (India)
The know- ledge about the shell corrections at the saddle point in A ∼ 200 mass region is ambiguous. ... value of the level density parameter at the saddle-point deformation (˜af ) may be different from that of ˜an due to the ... Hence, fusion cross-sections for α-induced reactions were estimated using the Bass systematics.
Fusability and fissionability in 86Kr induced reactions near and below the fusion barrier
International Nuclear Information System (INIS)
Reisdorf, W.; Hessberger, F.P.; Hildenbrand, K.D.; Hofmann, S.; Muenzenberg, G.; Schmidt, K.H.; Schneider, W.F.W.; Suemmerer, K.; Wirth, G.; Kratz, J.V.; Schlitt, K.; Sahm, C.C.
1985-04-01
Evaporation-residue excitation functions for the reactions 86 Kr + sup(70,76)Ge, sup(92,100)Mo, sup(99,102,104)Ru have been measured using activation methods and the velocity filter SHIP. The data span the region from well below the fusion barrier up to and beyond the energy where limitation by fission competition takes place. The data are shown to be compatible with the concept of complete fusion followed by the statistical decay of the equilibrated compound nucleus. Information on both the fusion probability at and below the fusion threshold and the fissionability of the compound nuclei formed is extracted. The model dependence of the extracted fission barriers is discussed in detail. In analogy to studies involving lighter projectiles, strong correlations between the low-energy nuclear-structure properties of the nuclei and the subbarrier fusion probability are found. A relative shift of the fusion barrier to higher energies, that increases with the number of valence neutrons in the target nuclei, is observed. (orig.)
International Nuclear Information System (INIS)
Moeller, Peter; Sierk, Arnold J.; Bengtsson, Ragnar; Iwamoto, Akira
2003-01-01
We present fission-barrier-height calculations for nuclei throughout the periodic system based on a realistic theoretical model of the multi-dimensional potential-energy surface of a fissioning nucleus. This surface guides the nuclear shape evolution from the ground state, over inner and outer saddle points, to the final configurations of separated fission fragments. We have previously shown that our macroscopic-microscopic nuclear potential-energy model yields calculated 'outer' fission-barrier heights (E B ) for even-even nuclei throughout the periodic system that agree with experimental data to within about 1.0 MeV. We present final results of this work. Just recently we have enhanced our macroscopic-microscopic nuclear potential-energy model to also allow the consideration of axially asymmetric shapes. This shape degree of freedom has a substantial effect on the calculated height (E A ) of the inner peak of some actinide fission barriers. We present examples of fission-barrier calculations by use of this model with its redetermined constants. Finally we discuss what the model now tells us about fission barriers at the end of the r-process nucleosynthesis path. (author)
Energy Technology Data Exchange (ETDEWEB)
Kerr, P. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-02-28
An SNM attribute Information Barrier (IB) system was developed for a 2011 US/UK Exercise. The system was modified and extensively tested in a 2013-2014 US-UK Measurement Campaign. This work demonstrated rapid deployment of an IB system for potential treaty use. The system utilizes an Ortec Fission Meter neutron multiplicity counter and custom computer code. The system demonstrates a proof-of-principle automated Pu-240 mass determination with an information barrier. After a software start command is issued, the system automatically acquires and downloads data, performs an analysis, and displays the results. This system conveys the results of a Pu mass threshold measurements in a way the does not reveal sensitive information. In full IB mode, only red/green ‘lights’ are displayed in the software. In test mode, more detailed information is displayed. The code can also read in, analyze, and display results from previously acquired or simulated data. Because the equipment is commercial-off-the-shelf (COTS), the system demonstrates a low-cost short-lead-time technology for treaty SNM attribute measurements. A deployed system will likely require integration of additional authentication and tamper-indicating technologies. This will be discussed for the project in this and future progress reports.
International Nuclear Information System (INIS)
Capote Noy, Roberto; Simakov, Stanislav; Goriely, Stephane; Hilaire, Stephane; Iwamoto, Osamu; Kawano, Toshihiko; Koning, Arjan
2014-12-01
A Consultants’ Meeting on “Recommended Input Parameters for Fission Cross-Section Calculations” was held at IAEA Headquarters, Vienna, Austria to define the scope, deliverables and appropriate work programme of a possible Coordinated Research Project (CRP) on the subject. Presentations are available online at https://www-nds.iaea.org/indexmeeting-crp/CM-RIPL-fission/. A new CRP was endorsed to recommend a comprehensive set of fission input parameters needed for the modelling of fission cross sections. Special attention will be given to the modelling of photon and nucleon induced reactions on actinides with emphasis on incident energies below 30 MeV. The goals and detailed deliverables of the planned CRP were proposed. A Hauser-Feshbach code intercomparison was recommended. (author)
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)
Fission barriers within the liquid drop model with the surface-curvature term
International Nuclear Information System (INIS)
Pomorski, K.; Dudek, J.
2004-01-01
The recently revised liquid drop model (PRC 67(2003) 044316) containing the curvature term reproduces the masses of 2766 experimentally known isotopes having Z≥8 and N≥8 with the r.m.s. deviation equal to 0.698 MeV when the microscopic corrections of Moeller et al. is used. The influence of the congruence energy as well as the compression term on the barrier heights is discussed within this new macroscopic model. The r.m.s. deviation of the fission barrier heights of 40 isotopes with Z≥34 is 1.73 MeV only when deformation-dependent congruence energy is included. The effect of the compression term in the liquid drop energy has rather weak influence on the barrier heights. (author)
The congruence energy: a contribution to nuclear masses, deformation energies and fission barriers
International Nuclear Information System (INIS)
Myers, W.D.; Swiatecki, W.J.
1997-01-01
The difference between measured binding energies and those calculated using a shell- and pairing-corrected Thomas-Fermi model can be described approximately by C(I)=-10 exp(-4.2 vertical stroke I vertical stroke) MeV, where I=(N-Z)/A. Our interpretation of this extra binding is in terms of the granularity of quantal nucleonic density distributions, which leads to a stronger interaction for a neutron and proton with congruent nodal structures of their wave functions. The predicted doubling of this congruence energy in fission is supported by an analysis of measured fission barriers and by a study of wave functions in a dividing Hill-Wheeler box potential. A semi-empirical formula for the shape-dependent congruence energy is described. (orig.)
International Nuclear Information System (INIS)
Cancio, D.; Menossi, C.A.; Ciallella, N.R.
1978-01-01
The paper presents results of research carried out in Argentina on transfer parameters of fission and activation products which may be present in the effluents of nuclear power reactors. For some nuclides, as Sr-90, Co-137 and I-131, the parameters were obtained by studies of the fallout, from measurements of integrated levels in the environment and in the food chains. Other values are concentration factors derived from laboratory and field experiments. They refer to fish, molluscs, crustaces and fresh water plants, for several fission and activation nuclides. Transfer parameters obtained have been of significant importance for environmental assessments, relating to nuclear installations in Argentina. (author)
International Nuclear Information System (INIS)
Sola, A.
1978-01-01
An analytical sensitivity analysis has been made of the effect of various parameters on the evaluation of fission product concentration. Such parameters include cross sections, decay constants, branching ratios, fission yields, flux and time. The formulae are applied to isotopes of the Tin, Antimony and Tellurium series. The agreement between analytically obtained data and that derived from a computer evaluated model is good, suggesting that the analytical representation includes all the important parameters useful to the evaluation of the fission product concentrations
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
Nuclear data project in Korea and resonance parameter evaluation of fission products
International Nuclear Information System (INIS)
Chang, Jonghwa; Oh, Soo-Youl
2000-01-01
Nuclear data activities in the fields of evaluation, processing, measurement, and service in Korea are presented in this paper. As one of the current activities, the neutron resonance parameters for stable or long-lived nineteen fission products have been evaluated and the results are presented here. (author)
Simulating fission product transients via the history-based local-parameter methodology
International Nuclear Information System (INIS)
Jenkins, D.A.; Rouben, B.; Salvatore, M.
1993-01-01
This paper describes the fission-product-calculation capacity of the history-based local-parameter methodology for evaluating lattice properties for use in core-tracking calculations in CANDU reactors. In addition to taking into account the individual past history of each bundles flux/power level, fuel temperature, and coolant density and temperature that the bundle has seen during its stay in the core, the latest refinement of the history-based method provides the capability of fission-product-drivers. It allows the bundle-specific concentrations of the three basic groups of saturating fission products to be calculated in steady state or following a power transient, including long shutdowns. The new capability is illustrated by simulating the startup period following a typical long-shutdown, starting from a snapshot in the Point Lepreau operating history. 9 refs., 7 tabs
International Nuclear Information System (INIS)
Khouri, M.T.F.C.; Koskinas, M.F.; Andrade, C. de; Vilela, E.C.; Hinostroza, H.; Kaschiny, J.R.A.; Costa, M.S. da; Rizzo, P.; Santos, W.M.S.
1990-01-01
The technique of particle detection by solid track detectors, types of developing and analysis of results are presented. Efficiency measurements of alpha particle detection with Makrofol e and surface barrier detector are made. Detection of Cf-252 fission fragments is shown. (L.C.)
International Nuclear Information System (INIS)
Khouri, M.T.F.C.; Koskinas, M.F.; Andrade, C. de; Vilela, E.C.; Hinostroza, H.; Kaschiny, J.E.A.; Costa, M.S. da; Rizzo, P.; Santos, W.M.S.
1990-01-01
A technique for particle detection by using track solid detector and also types of revealing and result analysis are presented concerned to Cf-252 fission fragments detection. Measurements of alpha particles detection efficiency using Makrofol E and surface barrier detector are performed. (L.C.J.A.)
International Nuclear Information System (INIS)
Lazarev, Yu.A.
1986-01-01
An analytically solvable model is used to study the potential barrier penetrability in the case when the gap parameter Δ is treated as a dynamical variable governed by the least action principle. It is found that, as compared to the standard (BCS) approach, the dynamical treatment of pairing results in a considerably weakened dependence of the fission barrier penetrability on the intensity of pairing correlations in the initial state (Δ 0 ), on the barrier height, and on the energy of the initial state. On this basis, a more adequate explanation is proposed for typical order-of-magnitude values of the empirical hidrance factors for groun-state spontaneous fission of odd nuclei. It is also shown that a large enhancement of superfluidity in tunneling - the inherent effect of the dynamical treatment of pairing - strongly facilitates deeply subbarier fusion of complex nuclei. Finally, an analysis is given for the probability of spontaneous fission from K-isomeric quasiparticle (q-p) states in even-even heavy nuclei. The relative change of the partial spontaneous fission half-life in going from the ground-state to a high-spin q-p isomeric state, T* sf /T sf , is found to be strongly dependent on whether or not there takes place the dynamically induced enhancement of superfluidity in tunneling. Measurements of T* sf /T sf provide thus a unique possibility of verifying theoretical predictions about the strong, inverse-square Δ dependence of the effective inertia associated with large-scale subbarrier rearrangements of nuclei
Pulcini, A.; Vardaci, E.; Kozulin, E.; Ashaduzzaman, M.; Borcea, C.; Bracco, A.; Brambilla, S.; Calinescu, S.; Camera, F.; Ciemala, M.; de Canditiis, B.; Dorvaux, O.; Harca, I. M.; Itkis, I.; Kirakosyan, V. V.; Knyazheva, G.; Kozulina, N.; Kolesov, I. V.; La Rana, G.; Maj, A.; Matea, I.; Novikov, K.; Petrone, C.; Quero, D.; Rath, P.; Saveleva, E.; Schmitt, C.; Sposito, G.; Stezowski, O.; Trzaska, W. H.; Wilson, J.
2018-05-01
Compound nucleus fission and quasi-fission are both binary decay channels whose common properties make the experimental separation between them difficult. A way to achieve this separation could be to probe the angular momentum of the binary fragments. This can be done detecting gamma rays in coincidence with the two fragments. As a case study, the reaction 32S + 197Au near the Coulomb barrier has been performed at the Tandem ALTO facility at IPN ORSAY. ORGAM and PARIS, two different gamma detectors arrays, are coupled with the CORSET detector, a two-arm time-of-flight spectrometer. TOF-TOF data were analyzed to reconstruct the mass-energy distribution of the primary fragments coupled with gamma multiplicity and spectroscopic analysis. Preliminary results of will be shown.
Near-barrier Fusion Evaporation and Fission of 28Si+174Yb and 32S+170Er
Wang, Dongxi; Lin, Chengjian; Jia, Huiming; Ma, Nanru; Sun, Lijie; Xu, Xinxing; Yang, Lei; Yang, Feng; Zhang, Huanqiao; Bao, Pengfei
2017-11-01
Fusion evaporation residues and fission fragments have been measured, respectively, at energies around the Coulomb barrier for the 28Si+174Yb and 32S+170Er systems forming the same compound nucleus 202Po. The excitation function of fusion evaporation, fission as well as capture reactions were deduced. Coupled-channels analyses reveal that couplings to the deformations of targets and the two-phonon states of projectiles contribute much to the enhancement of capture cross sections at sub-barrier energies. The mass and total kinetic energy of fission fragments were deduced by the time-difference method assuming full momentum transfer in a two-body kinematics. The mass-energy and mass-angle distributions were obtained and no obvious quasi-fission components were observed in this bombarding energy range. Further, mass distributions of fission fragments were fitted to extract their widths. Results show that the mass widths decrease monotonically with decreasing energy, but might start to increase when Ec.m./VB < 0.95 for both systems.
International Nuclear Information System (INIS)
Sola, A.
1978-01-01
An analytical sensitivity analysis has been made of the effect of various parameters on the evaluation of fission product concentration. Such parameters include cross-sections, decay constants, branching ratios, fission yields, flux and time. The formulae are applied to isotopes of the iodine, xenon, caesium and barium series. The agreement between analytically obtained data and that derived from a computer-evaluated model is good, suggesting that the analytical representation includes all the important parameters useful to the evaluation of the fission product concentrations
Nuclear irradiation parameters of beryllium under fusion, fission and IFMIF irradiation conditions
International Nuclear Information System (INIS)
Fischer, U.; Chen, Y.; Leichtle, D.; Simakov, S.; Moeslang, A.; Vladimirov, P.
2004-01-01
A computational analysis is presented of the nuclear irradiation parameters for Beryllium under irradiation in typical neutron environments of fission and fusion reactors, and of the presently designed intense fusion neutron source IFMIF. The analysis shows that dpa and Tritium production rates at fusion relevant levels can be achieved with existing high flux fission reactors while the achievable Helium production is too low. The resulting He-Tritium and He/dpa ratios do not meet typical fusion irradiation conditions. Irradiation simulations in the medium flux test modules of the IFMIF neutron source facility were shown to be more suitable to match fusion typical irradiation conditions. To achieve sufficiently high production rates it is suggested to remove the creep-fatigue testing machine together with the W spectra shifter plate and move the tritium release module upstream towards the high flux test module. (author)
International Nuclear Information System (INIS)
Mancusi, D; Charity, R J; Cugnon, J
2013-01-01
The de-excitation of compound nuclei has been successfully described for several decades by means of statistical models. However, accurate predictions require some fine-tuning of the model parameters. This task can be simplified by studying several entrance channels, which populate different regions of the parameter space of the compound nucleus. Fusion reactions play an important role in this strategy because they minimise the uncertainty on the entrance channel by fixing mass, charge and excitation energy of the compound nucleus. If incomplete fusion is negligible, the only uncertainty on the compound nucleus comes from the spin distribution. However, some de-excitation channels, such as fission, are quite sensitive to spin. Other entrance channels can then be used to discriminate between equivalent parameter sets. The focus of this work is on fission and intermediate-mass-fragment emission cross sections of compound nuclei with 70 70 ≲ A ≲ 240. 240. The statistical de-excitation model is GEMINI++. The choice of the observables is natural in the framework of GEMINI++, which describes fragment emission using a fissionlike formalism. Equivalent parameter sets for fusion reactions can be resolved using the spallation entrance channel. This promising strategy can lead to the identification of a minimal set of physical ingredients necessary for a unified quantitative description of nuclear de-excitation.
Natural uranium impurities in fission track detectors and associated geocronological parameters
International Nuclear Information System (INIS)
Ricabarra, G.H.; Bovisio de Ricabarra, M.D.; Waisman, Dina; Faradjie de Turjanski, Rosa
1981-01-01
A technique, based in counting neutron induced fission tracks, has been developed for the measurement of uranium impurities in mica. Uranium concentrations of 10 -10 and 10 -9 (U atom/mica atom) have been measured. As a part of the development of this technique, the mica geological age was also measured, by fossil and induced track detection. The agreement obtained by this method, T = (472+-52) x 10 6 years with that of (450+-15) x 10 6 years obtained by the Ar-K technique is satisfactory and is an indirect test of the fission track technique used. A careful analysis of the neutron field parameters and nuclear data used in the age determination was made. This analysis is useful for applications in geocronology. According to this analysis a value of lambdasub(f)=(7.1+-0.1) x 10 -17 years -1 is recommended for the spontaneous fission of U238. However, in order to compare the results, the quoted age, T=(472+-52) x 10 6 years, was obtained with the generally accepted value of lambdasub(f)=(6.85-0.20) x 10 -17 years -1 (Fleischer and Price 1964). (author) [es
Total and fission cross-sections of 239Pu - statistical study of resonance parameters
International Nuclear Information System (INIS)
Derrien, H.; Blons, J.; Eggermann, C.; Michaudon, A.; Paya, D.; Ribon, P.
1967-01-01
The authors measured the total and fission cross-sections of 239 Pu with the linear accelerator at Saclay as a pulsed source of neutrons. The total cross-section was measured in the range from 4 to 700 eV and the best resolution used was 1.5 ns/m; the fission cross-section was measured between 4 eV and 6 keV, the best resolution having been 6 ns/m. The transmission measurements on five samples were made at the temperature of liquid nitrogen, and comparisons made with supplementary experiments at ambient temperature made it possible to determine the Doppler broadening factor (Δ = η√E). The resonances were identified from 4 to 500 eV in the total cross-section; the average level spacing was of the order of 2.4 eV. It would appear that, in this energy range, nearly all the levels were identified. The resonance parameters were determined by analysis of shape in conjunction with a least-squares programme on an IBM-7094 computer. The existence of a large number of broad resonances corresponding to very large fission widths has been shown to exist. Statistical study of the fission widths actually shows the existence of two families of resonances, one corresponding to a mean Γ f of the order of 45 meV and the other to a mean Γ/f of about 750 meV. The authors were therefore able to postulate a classification of resonances in terms of two spin states, the level population ratio in each family being: (2J 1 +1)/(2J 2 +1) = 1/3; J 1 = 0 corresponds to the broad resonances and J 2 = 1 to the narrow ones. The partial widths for radiative capture fluctuate slightly around a mean value of 40 meV. By using a multilevel programme, the authors were able to investigate the extent to which the existence of large fission widths might give rise to fictitious resonances (quasi-resonances) and perturbations and also to make a statistical study of the resonance parameters. (author) [fr
Energy Technology Data Exchange (ETDEWEB)
Lopez Jimenez, M.J. [CEA/DIF/DPTA/Service de Physique Nucleaire, B.P. 12, F-91680 Bruyeres-le-Chatel (France); Morillon, B. [CEA/DIF/DPTA/Service de Physique Nucleaire, B.P. 12, F-91680 Bruyeres-le-Chatel (France); Romain, P. [CEA/DIF/DPTA/Service de Physique Nucleaire, B.P. 12, F-91680 Bruyeres-le-Chatel (France)]. E-mail: pascal.romain@cea.fr
2005-01-15
A new neutron-induced cross-section evaluation of {sup 238}U from 1 keV up to 200 MeV has been performed using only nuclear reactions models. A new fission penetrability model taking into account a triple humped barrier has been developed. A clear improvement has been observed for K-effective validation tests (up to 30 MeV) with this new evaluation. This improvement is mainly due to a better treatment of the inelastic exit channel.
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)
International Nuclear Information System (INIS)
Tajik, M.; Ghasemizad, A.
2008-01-01
In this research, new physical fission reactor parameters which have very sensitive effects on the qualitative behavior of a reactor, are introduced. Therefore, the two, the nonlinear dynamics of two, three and four dimensional, considering almost the effective parameters are formulated for describing nuclear fission reactor systems. Using both analytical and numerical methods, the stability and instability of the given dynamical equations and the conditions of stability are studied in these systems. We have shown that the two parameters of the mean energy residence time in fuel and coolant and also their ratios have the most qualitative effects on the dynamical behaviour of a typical nuclear fission reactor. Increasing or decreasing of these parameters from a captain limit can lead to stability or un stability in a given system
International Nuclear Information System (INIS)
Sola, A.
1978-01-01
An analytical sensitivity analysis has been made of the effect' of various parameters on the evaluation of fission product concentration. Such parameters include cross sections, decay constants, branching ratios, fission yields, flux and time. The formulae are applied to isotopes of the Antimony, Tellurium, Iodine and Xenon series. The agreement between analytically obtained data and that derived from a computer evaluated model is good, suggesting that the analytical representation includes all the important parameters useful to the evaluation of the fission product concentrations
International Nuclear Information System (INIS)
Chiba, Go; Tsuji, Masashi; Narabayashi, Tadashi
2014-01-01
In order to properly quantify fission reactor neutronics parameter uncertainties, we have to use covariance data and sensitivity profiles consistently. In the present paper, we establish two consistent methodologies for uncertainty quantification: a self-shielded cross section-based consistent methodology and an infinitely-diluted cross section-based consistent methodology. With these methodologies and the covariance data of uranium-238 nuclear data given in JENDL-3.3, we quantify uncertainties of infinite neutron multiplication factors of light water reactor and fast reactor fuel cells. While an inconsistent methodology gives results which depend on the energy group structure of neutron flux and neutron-nuclide reaction cross section representation, both the consistent methodologies give fair results with no such dependences.
Directory of Open Access Journals (Sweden)
GO CHIBA
2014-06-01
Full Text Available In order to properly quantify fission reactor neutronics parameter uncertainties, we have to use covariance data and sensitivity profiles consistently. In the present paper, we establish two consistent methodologies for uncertainty quantification: a self-shielded cross section-based consistent methodology and an infinitely-diluted cross section-based consistent methodology. With these methodologies and the covariance data of uranium-238 nuclear data given in JENDL-3.3, we quantify uncertainties of infinite neutron multiplication factors of light water reactor and fast reactor fuel cells. While an inconsistent methodology gives results which depend on the energy group structure of neutron flux and neutron-nuclide reaction cross section representation, both the consistent methodologies give fair results with no such dependences.
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.)
International Nuclear Information System (INIS)
Kumar, K.
1990-03-01
It is shown that the quasi-classical condition for the validity of the WKB approximation is satisfied although the mass associated with the spontaneous fission of 240 Pu varies by a factor of 12. A general numerical estimate of the allowed variations in such a mass is also given. (author)
International Nuclear Information System (INIS)
Veeck, A.C.; Lawrence Livermore National Lab., CA; Lawrence Berkeley National Lab., CA
1996-08-01
Excitation functions have been measured for complex fragment emission from the compound nucleus 98 Mo, produced by the reaction of 86 Kr with 12 C. Mass asymmetric fission barriers have been obtained by fitting the excitation functions with a transition state formalism. The extracted barriers are ∼ 5.7 MeV higher, on average, than the calculations of the Rotating Finite Range Model (RFRM). These data clearly show an isospin dependence of the conditional barriers when compared with the extracted barriers from 90 Mo and 94 Mo. Eleven different liquid/liquid extractants were synthesized based upon the chelating moieties 3,2-HOPO and 3,4-HOPO; additionally, two liquid/liquid extractants based upon the 1,2-HOPO chelating moiety were obtained for extraction studies. The Pu(IV) extractions, quite surprisingly, yielded results that were very different from the Fe(III) extractions. The first trend remained the same: the 1,2-HOPOs were the best extractants, followed closely by the 3,2-HOPOs, followed by the 3,4-HOPOs; but in these Pu(IV) extractions the 3,4-HOPOs performed much better than in the Fe(III) extractions. 129 refs
Energy Technology Data Exchange (ETDEWEB)
Veeck, A.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Livermore National Lab., CA (United States). Glenn T. Seaborg Inst. for Transactinium Science]|[Lawrence Berkeley National Lab., CA (United States). Nuclear Science Div.
1996-08-01
Excitation functions have been measured for complex fragment emission from the compound nucleus {sup 98}Mo, produced by the reaction of {sup 86}Kr with {sup 12}C. Mass asymmetric fission barriers have been obtained by fitting the excitation functions with a transition state formalism. The extracted barriers are {approximately} 5.7 MeV higher, on average, than the calculations of the Rotating Finite Range Model (RFRM). These data clearly show an isospin dependence of the conditional barriers when compared with the extracted barriers from {sup 90}Mo and {sup 94}Mo. Eleven different liquid/liquid extractants were synthesized based upon the chelating moieties 3,2-HOPO and 3,4-HOPO; additionally, two liquid/liquid extractants based upon the 1,2-HOPO chelating moiety were obtained for extraction studies. The Pu(IV) extractions, quite surprisingly, yielded results that were very different from the Fe(III) extractions. The first trend remained the same: the 1,2-HOPOs were the best extractants, followed closely by the 3,2-HOPOs, followed by the 3,4-HOPOs; but in these Pu(IV) extractions the 3,4-HOPOs performed much better than in the Fe(III) extractions. 129 refs.
Actinide neutron-induced fission up to 20 MeV
International Nuclear Information System (INIS)
Maslov, V.M.
2001-01-01
Fission and total level densities modelling along with double-humped fission barrier parameters allow to describe available actinide neutron-induced fission cross section data in the incident neutron energy range of ∼ 10 keV - 20 MeV. Saddle asymmetries relevant to shell correction model calculations influence fission barriers, extracted by cross section data analysis. The inner barrier was assumed axially symmetric in case of U, Np and Pu neutron-deficient nuclei. It is shown that observed irregularities in neutron-induced fission cross section data in the energy range of 0.5-3 MeV could be attributed to the interplay of few-quasiparticle excitations in the level density of fissioning and residual nuclei. Estimates of first-chance fission cross section and secondary neutron spectrum model were validated by 238 U fission, (n,2n) and (n,3n) data description up to 20 MeV. (author)
Actinide neutron-induced fission up to 20 MeV
Energy Technology Data Exchange (ETDEWEB)
Maslov, V M [Radiation Physics and Chemistry Problems Institute, Minsk-Sosny (Belarus)
2001-12-15
Fission and total level densities modelling along with double-humped fission barrier parameters allow to describe available actinide neutron-induced fission cross section data in the incident neutron energy range of {approx} 10 keV - 20 MeV. Saddle asymmetries relevant to shell correction model calculations influence fission barriers, extracted by cross section data analysis. The inner barrier was assumed axially symmetric in case of U, Np and Pu neutron-deficient nuclei. It is shown that observed irregularities in neutron-induced fission cross section data in the energy range of 0.5-3 MeV could be attributed to the interplay of few-quasiparticle excitations in the level density of fissioning and residual nuclei. Estimates of first-chance fission cross section and secondary neutron spectrum model were validated by {sup 238}U fission, (n,2n) and (n,3n) data description up to 20 MeV. (author)
Monte Carlo code Serpent calculation of the parameters of the stationary nuclear fission wave
Directory of Open Access Journals (Sweden)
V. M. Khotyayintsev
2017-12-01
Full Text Available n this work, propagation of the stationary nuclear fission wave was simulated for series of fixed power values using Monte Carlo code Serpent. The wave moved in the axial direction in 5 m long cylindrical core of fast reactor with pure 238U raw fuel. Stationary wave mode arises some period later after the wave ignition and lasts sufficiently long to determine kef with high enough accuracy. The velocity characteristic of the reactor was determined as the dependence of the wave velocity on the neutron multiplication factor. As we have recently shown within a one-group diffusion description, the velocity characteristic is two-valued due to the effect of concentration mechanisms, while thermal feedback affects it only quantitatively. The shape and parameters of the velocity characteristic critically affect feasibility of the reactor design since stationary wave solutions of the lower branch are unstable and do not correspond to any real waves in self-regulated reactor, like CANDLE. In this work calculations were performed without taking into account thermal feedback. They confirm that theoretical dependence correctly describes the shape of the velocity characteristic calculated using the results of the Serpent modeling.
Asymmetrically deformed third minimum in the 231Th and 233Th fission barriers
International Nuclear Information System (INIS)
Blons, J.; Mazur, C.; Paya, D.; Ribrag, M.; Weigmann, H.
1981-01-01
Neutron induced fission cross-sections of 230 Th and 232 Th have been measured up to 5 MeV. The electron linear accelerator (GELINA) has been used as a neutron time of flight spectrometer with a nominal resolution of 84 psec/m for 230 Th(n,f) and 42 psec/m for 232 Th(n,f) reaction. The fission fragment detector was a 6 cell gas scintillator filled with xenon. The existence of fine structure peaks, a few keV wide, in both the 230 Th(n,f) and 232 Th(n,f) cross sections, is definitively confirmed. The analysis of the two vibrational resonances located respectively at 720 keV for 230 Th(the figure) and 1.6 MeV for 232 Th, shows clearly that these peaks can be interpreted, in terms of two rotational bands with opposite parities. This parity degeneracy is a consequence of the asymmetric, pear-like deformation of the excited nucleus [ru
International Nuclear Information System (INIS)
Ruffenach, J.-C.
1979-09-01
Mass spectrometry and isotopic dilution technique are used in order to carry out, on various samples from the fossil nuclear reactors at Oklo, Gabon, isotopic and chemical analyses of some particular elements involved in the nuclear reactions: uranium, lead, bismuth, thorium, rare gases (krypton, xenon), rare earths (neodymium, samarium, europium, gadolinium, dysprosium), ruthenium and palladium. Interpretations of these analyses lead to the determination of many neutron parameters such as the neutron fluence received by the samples, the spectrum index, the conversion coefficient, and also the percentages of fissions due to uranium-238 and plutonium-239 and the total number of fissions relative to uranium. All these results make it possible to determine the age of the nuclear reactions by measuring the amounts of fission rare earths formed, i.e. 1.97 billion years. This study brings some informations to the general problem of radioactive wastes storage in deep geological formations, the storage of uranium, plutonium and many fission products having been carried out naturally, and for about two billion years [fr
Khurelbaatar, Zagarzusem; Kil, Yeon-Ho; Shim, Kyu-Hwan; Cho, Hyunjin; Kim, Myung-Jong; Lee, Sung-Nam; Jeong, Jae-chan; Hong, Hyobong; Choi, Chel-Jong
2016-03-01
We investigated the electrical properties of chemical vapor deposition-grown monolayer graphene/n-type germanium (Ge) Schottky barrier diodes (SBD) using current-voltage (I-V) characteristics and low frequency noise measurements. The Schottky barrier parameters of graphene/n-type Ge SBDs, such as Schottky barrier height (VB), ideality factor (n), and series resistance (Rs), were extracted using the forward I-V and Cheung's methods. The VB and n extracted from the forward ln(I)-V plot were found to be 0.63 eV and 1.78, respectively. In contrast, from Cheung method, the VB and n were calculated to be 0.53 eV and 1.76, respectively. Such a discrepancy between the values of VB calculated from the forward I-V and Cheung's methods indicated a deviation from the ideal thermionic emission of graphene/n-type Ge SBD associated with the voltage drop across graphene. The low frequency noise measurements performed at the frequencies in the range of 10 Hz-1 kHz showed that the graphene/n-type Ge SBD had 1/f γ frequency dependence, with γ ranging from 1.09 to 1.12, regardless of applied forward biases. Similar to forward-biased SBDs operating in the thermionic emission mode, the current noise power spectral density of graphene/n-type Ge SBD was linearly proportional to the forward current.
International Nuclear Information System (INIS)
Imshennik, V.S.
2006-01-01
Within the conditions of Heavy-Ion Fusion (HIF) arises a possibility to obtain the fission chain reaction for a cylindrical HIF target. The paper contains the solution interpolated with the diffusion approximation in order to receive the general approximation expressions for the bar critical radius as well as for over-critical state. The obtained critical parameters generalized for uranium envelope are used for rough evaluation of the energy release in HIF hybrid targets [ru
Hyperfission - a new mode of nuclear fission
International Nuclear Information System (INIS)
Ion, D.B.; Ivascu, M.; Ion-Mihai, R.
1988-02-01
In this paper the nuclear hyperfission as a new mode of fission, possible for heavy elements with Z > 92, is investigated. The Q-systematics, hyperfissibility parameters, hyperfission barrier as well as the essential hindrance factors are presented. The hyperfission hindrance factor relative to that of fission is found to be in the interval 1.0x10 -17 - 3.4x10 -16 for the parent nuclei with Z = 92-108. (orig.)
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.
Energy Technology Data Exchange (ETDEWEB)
Kerr, P. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Decman, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Prasad, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Castro, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2018-01-03
An SNM attribute Information Barrier (IB) system was developed for a 2011 US/UK Exercise. The system was modified and extensively tested in a 2013-2014 US-UK Measurement Campaign. This work demonstrated rapid deployment of an IB system for potential treaty use. The system utilizes an Ortec Fission Meter neutron multiplicity counter and custom computer code. The system demonstrates a proof-of-principle automated Pu-240 mass determination with an information barrier. After a software start command is issued, the system automatically acquires and downloads data, performs an analysis, and displays the results. This system conveys the results of a Pu mass threshold measurements in a way the does not reveal sensitive information. In full IB mode, only the pass/fail result is displayed as a “Mass <= Threshold Amount” or “Mass >= Threshold Amount” as shown in Figure 4. This can easily be adapted to a red/green “lights” display similar to the Detective IB system for Pu isotopics as shown in Figure 6. In test mode, more detailed information is displayed. The code can also read in, analyze, and display results from previously acquired or simulated data. Because the equipment is commercial-off-the-shelf (COTS), the system demonstrates a low-cost short-lead-time technology for treaty SNM attribute measurements. A deployed system will likely require integration of additional authentication and tamper-indicating technologies. This will be discussed for the project in this and future progress reports.
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
International Nuclear Information System (INIS)
Aydin, A.; Yalim, H.A.; Tel, E.; Sarer, B.; Unal, R.; Sarpuen, I.H.; Kaplan, A.; Dag, M.
2009-01-01
This study aims to show the dependence on the choice of the ratio of the level density parameters a f and a n corresponding to the saddle point of fission and equilibrium deformation of nucleus, respectively, of the proton induced fission cross sections of some subactinide targets. The method was employed using different level density parameter ratios for each fission cross section calculation in ALICE/ASH computer code. The ALICE/ASH code calculations were compared both with the available experimental data and with the Prokofiev systematics data. It is found that the fission cross sections dependent heavily on the choice of level density parameter ratio in the fission and neutron emission channels, a f /a n , for some subactinide nuclei. To get a good description of the measured fission cross sections for subactinide nuclei, we used a ratio of the level density parameters in the fission and neutron emission channels, a f /a n , depending both on the target-nucleus and on the energy of the projectile, in agreement with results published in literature.
Calculation of fission product behavior in a multiple reactor barriers in case of an accident
International Nuclear Information System (INIS)
Ezzedin, A. A.; Dakhil, A. S.; Elbaden, S. E.
2012-12-01
Radiation protection of the population in case of a reactor accident utilizes reference levels which are based on doses values. Therefore, adequate provisions for effective and timely dose assessment for population in case of accidents at nuclear power plant (NPP) are important. Developing the background for such provisions is the objective of this study. In particular, an exponential model has been developed and utilized to calculate the release rate of the most volatile gaseous materials from different reactor barriers. Calculation has been performed for noble gases (1 33X e, 1 35X e, 1 38X e, 8 5K r, 8 7K r, 8 8K r) and the halogens(1'3 1I , 1 32I , 1 33I , 1'3 4I , 1 35I ). The effective dose rate equivalent is calculations in the nearly stage of a reactor accident. Calculations are performed using the MCNP-4C code. The results are comparable with the final analysis report which utilizes different codes. Results of our calculation shows no excessive dose in populated regions and it is recommended to use secondary containment barrier for highly reduction of the release rate to the environment. (Author)
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.
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
Experimental survey of the potential energy surfaces associated with fission
International Nuclear Information System (INIS)
Britt, H.C.
1980-01-01
Progress in the experimental determination of the properties of the potential energy surface associated with fission is reviewed. The importance of nuclear symmetry effects on the calculation of fission widths is demonstrated. Evidence is presented for the fragmentation of the mass-asymmetric second barrier in the thorium region and the axial asymmetric first barrier in the californium region. Detailed analyses of experimental data suggest the presence of two parallel second barriers; the normal mass-asymmetric, axial-symmetric barrier and a slightly higher mass-symmetric, axial-asymmetric barrier. Experimental barrier parameters are determined systematically and compared with calculations from various theoretical models. Techniques for expanding fission probability measurements to higher energies are discussed. (author)
The effect of outflowing water coolant with supercritical parameters on a barrier
Directory of Open Access Journals (Sweden)
Alekseev Maksim
2017-01-01
Full Text Available The outflow of supercritical coolant with different initial parameters and its impact on the barrier have been numerically simulated. Spatial and axial distributions of pressure and steam quality are presented. The force acting on the barrier at different parameters of the outflow has been calculated.
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
Processus of fission at medium energy
International Nuclear Information System (INIS)
Delagrange, H.
1977-01-01
Excitation functions for the reactions 233 U, 234 U, 235 U( 4 He,xn)Pu have been measured radiochimically between 20 and 45 MeV. Neutron emission probabilities have been deduced from these measurements, for 239 Pu, 238 Pu. These results have been analysed in the framework of a statistical model; the double humped fission barrier has been taken into account explicitly and the parameters of the barrier extracted. In the case of heavy ion reactions, fission probabilities have been calculated with the help of the Bohr-Wheeler formula and compared to experimental data from other authors. Deduced fission parameters (asub(f)/asub(n), Bsub(f)) are compared to different theoretical models [fr
Energy Technology Data Exchange (ETDEWEB)
Reichert, Sebastian [TU Munich (Germany); Collaboration: NP1306-SAMURAI14-Collaboration
2015-07-01
Violent stellar processes are currently assumed to be a major origin of the elements beyond iron and their abundances. The conditions during stellar explosions lead to the so called r-process in which the rapid capture of neutrons and subsequent β decays form heavier elements. This extension of the nuclei stops at the point when the repulsive Coulomb energy induces fission. Its recycling is one key aspect to describe the macroscopic structure of the r-process and the well known elemental abundance pattern. The RIBF at RIKEN is able to provide such neutron rich heavy element beams and a first test with the primary beam {sup 238}U was performed to understand the response of the SAMURAI spectrometer and detectors for heavy beams. The final goal is the definition of the fission barrier height with a resolution of 1 MeV (in σ) using the missing mass method using (p,2p) reactions in inverse kinematics.
International Nuclear Information System (INIS)
Kikuchi, Yasuyuki; Togawa, Orihiko; Nakagawa, Tsuneo
1986-03-01
The resonance parameters of 39 fission product nuclides have been evaluated. The present work is a part of the evaluation of 100 fission product nuclei for JENDL-2 by Japanese Nuclear Data Committee. All the available experimental data were collected, stored in REPSTOR system and compared with one another. The evaluation was made on the basis of the experimental data. The precise description of the evaluation is given in this report. The presently evaluated resonance parameters are tabulated in Appendix with the experimental data. (author)
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)
Investigation of anodizing parameter effect on barrier layer of anodic zirconium oxide
International Nuclear Information System (INIS)
Kharchenko, Eh.P.
1979-01-01
Effect of fluoride concentration and forming direction upon kinetics of barrier layer transformations in the process of preparation of phase anodic zirconium oxide in acid fluorine-containing solutions is considered. Suppositions are made on the mechanism of barrier layer transformation under the effect of the parameters mentioned. The thickness of the barrier layer is determined by two methods and it is shown that coefficient of the layer thickess growth at the voltage increase by 1 V is much lower than during formation of the barrier films in non-agressive electrolytes
Smith, Charles W.; Reinertson, Randal C.; Dolan, P. J., Jr.
1993-05-01
The theoretical description by Blonder, Tinkham, and Klapwijk [Phys. Rev. B 25, 4515 (1982)] of the I-V curves of normal: superconductor point contacts encompasses a broad range of experimental behavior, from the tunnel junction case, on the one hand, to the clean metallic microconstriction limit on the other. The theory characterizes point contacts in terms of a single parameter, the barrier strength. The differential conductance of a point contact, at zero bias, as a function of temperature, offers a direct experimental method by which the barrier strength parameter can be evaluated. In view of the full range of phenomena incorporated by this theory, we suggest several different strategies for the evaluation of the barrier strength parameter from data in the low and intermediate barrier strength regimes and for measurements in the low temperature (near T=0 K) and high temperature (near T=Tc) limits.
The fusion-fission process in the reaction {sup 34}S+{sup 186}W near the interaction barrier
Energy Technology Data Exchange (ETDEWEB)
Harca, I. M. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna, Russia and Faculty of Physics, University of Bucharest - P.O. Box MG 11, RO 77125, Bucharest-Magurele (Romania); Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna (Russian Federation); Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D. [IPN, CNRS/IN2P3, Univ. Paris-Sud, 91405 Orsay (France); Chubarian, G. [Cyclotron Institute, Texas A and M University, College Station, TX 77843-3366 (United States); Hanappe, F. [Universite Libre de Bruxelles (ULB), Bruxelles (Belgium); Piot, J.; Schmitt, C. [GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, BP 55027, F-14076 Caen Cedex 5 (France); Trzaska, W. H. [Accelerator Laboratory of University of Jyväskylä (JYFL), Jyväskylä (Finland); Vardaci, E. [Dipartamento di Scienze Fisiche and INFN (INFN-Na), Napoli (Italy)
2015-02-24
The reaction {sup 34}S+{sup 186}W at E{sub lab}=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF–γ coincidence method is of better use then the γ – γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.
Assessment of retention parameters of the fission products in the soil
International Nuclear Information System (INIS)
Endo, Laura Sakiko
1978-01-01
In many countries the discharge of radioactive liquid wastes into the ground is a common practice. The retention capacity presented by soils allows the discharge of bulky amounts of wastes in low and intermediate concentrations, within safety conditions. In addition, operations of ground disposal have advantages in economy and simplicity. However, the possibility of contamination of water resources is important in the site selection for such purpose. In this work, the I.E.A. soil behavior related to the retention capacity of cesium and strontium was studied. Distribution coefficients (Kd) were determined for both elements in function of its concentrations, p H and the presence of K + and Na + in the waste solutions. Soil analysis by X-ray diffraction showed the predominance Kaolinite argyle in this region. Soil parameters were also determined in laboratory conditions, such as permeability, porosity and density. The observed retention capacity for both elements was between 0,7 and 2,0 meg/100 of soil. Evaluation of ground water velocity and ions migration rates were carried out through the results obtained in laboratory measurements. It was also evaluated the amounts of 137 Cs and 90 Sr that if discharged into the ground would produce in the critical group a dose equal to the dose limit fixed by the norms. It was concluded that the maximum discharge amounts is limited by heat dissipation capacity of ground water table, and through a very conservative evaluation the total beta-gamma activity for long-lives radioisotopes presented a value of 3,6 X 10 6 Ci/y. (author)
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
Dynamic treatment of fission and fusion in two dimensions
International Nuclear Information System (INIS)
Nazareth, R.A.M.S.
1977-01-01
The barrier penetrability in two dimensions for nuclear fusion and fission phenomena is studied. The equations of fission static trajectories (minimum potential) in Hofmann formalism are derived and the influence of inertia parameters on the penetrability is verified. For fusion case, a realistic potential for exactly penetrability calculation is proposed. The transverse momentum to the fusion and the unidimensional calculation in classical approximation by choose the trajectory which turn into maximum the penetrability are considered. The exact penetrability is compared with calculation in the classical approximation which takes in account the possibility of appearing discontinuity in the barrier along of fusion pathway. (M.C.K.) [pt
Baumgarten, Lorenz; Kierfeld, Jan
2018-05-01
We study the influence of thermal fluctuations on the buckling behavior of thin elastic capsules with spherical rest shape. Above a critical uniform pressure, an elastic capsule becomes mechanically unstable and spontaneously buckles into a shape with an axisymmetric dimple. Thermal fluctuations affect the buckling instability by two mechanisms. On the one hand, thermal fluctuations can renormalize the capsule's elastic properties and its pressure because of anharmonic couplings between normal displacement modes of different wavelengths. This effectively lowers its critical buckling pressure [Košmrlj and Nelson, Phys. Rev. X 7, 011002 (2017), 10.1103/PhysRevX.7.011002]. On the other hand, buckled shapes are energetically favorable already at pressures below the classical buckling pressure. At these pressures, however, buckling requires to overcome an energy barrier, which only vanishes at the critical buckling pressure. In the presence of thermal fluctuations, the capsule can spontaneously overcome an energy barrier of the order of the thermal energy by thermal activation already at pressures below the critical buckling pressure. We revisit parameter renormalization by thermal fluctuations and formulate a buckling criterion based on scale-dependent renormalized parameters to obtain a temperature-dependent critical buckling pressure. Then we quantify the pressure-dependent energy barrier for buckling below the critical buckling pressure using numerical energy minimization and analytical arguments. This allows us to obtain the temperature-dependent critical pressure for buckling by thermal activation over this energy barrier. Remarkably, both parameter renormalization and thermal activation lead to the same parameter dependence of the critical buckling pressure on temperature, capsule radius and thickness, and Young's modulus. Finally, we study the combined effect of parameter renormalization and thermal activation by using renormalized parameters for the energy
International Nuclear Information System (INIS)
Wei Suxia
1992-01-01
A method concerning selection of design parameters of diffusion barrier in a passive 222 Rn sampler based on activated charcoal adsorption. The proper parameter value of diffusion barrier is obtained by means of linearization of 222 Rn adsorption versus the exposure time. Thus, the influence of temperature on measured results may be greatly decreased, and higher sensitivity of the detector may be maintained
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
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
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.
International Nuclear Information System (INIS)
Frosio, Thomas; Bonaccorsi, Thomas; Blaise, Patrick
2016-01-01
Highlights: • Nuclear data uncertainty propagation for neutronic quantities in coupled problems. • Uncertainties are detailed for local isotopic concentrations and local power maps. • Correlations are built between space areas of the core and for different burnups. - Abstract: In a previous paper, a method was investigated to calculate sensitivity coefficients in coupled Boltzmann/Bateman problem for nuclear data (ND) uncertainties propagation on the reactivity. Different methodologies were discussed and applied on an actual example of multigroup cross section uncertainty problem for a 2D Material Testing Reactor (MTR) benchmark. It was shown that differences between methods arose from correlations between input parameters, as far as the method enables to take them into account. Those methods, unlike Monte Carlo (MC) sampling for uncertainty propagation and quantification (UQ), allow obtaining sensitivity coefficients, as well as correlations values between nuclear data, during the depletion calculation for the parameters of interest. This work is here extended to local parameters such as power factors and isotopic concentrations. It also includes fission yield (FY) uncertainty propagation, on both reactivity and power factors. Furthermore, it introduces a new methodology enabling to decorrelate direct and transmutation terms for local quantities: a Monte-Carlo method using built samples from a multidimensional Gaussian law is used to extend the previous studies, and propagate fission yield uncertainties from the CEA’s COMAC covariance file. It is shown that, for power factors, the most impacting ND are the scattering reactions, principally coming from 27 Al and (bounded hydrogen in) H 2 O. The overall effect is a reduction of the propagated uncertainties throughout the cycle thanks to negatively correlated terms. For fission yield (FY), the results show that neither reactivity nor local power factors are strongly affected by uncertainties. However, they
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 ...
Hamouda, Ajmi B. H.; Blel, Sonia; Einstein, T. L.
2012-02-01
Growing one-dimensional metal structures is an important task in the investigation of the electronic and magnetic properties of new devices. We used kinetic Monte-Carlo (kMC) method to simulate the formation of nanowires of several metallic and non-metallic adatoms on Cu and Pt vicinal surfaces. We found that mono-atomic chains form on step-edges due to energetic barriers (the so-called Ehrlich-shwoebel and exchange barriers) on step-edge. Creation of perfect wires is found to depend on growth parameters and binding energies. We measure the filling ratio of nanowires for different chemical species in a wide range of temperature and flux. Perfect wires were obtained at lower deposition rate for all tested adatoms, however we notice different temperature ranges. Our results were compared with experimental ones [Gambardella et al., Surf. Sci.449, 93-103 (2000), PRB 61, 2254-2262, (2000)]. We review the role of impurities in nanostructuring of surfaces [Hamouda et al., Phys. Rev. B 83, 035423, (2011)] and discuss the effect of their energetic barriers on the obtained quality of nanowires. Our work provides experimentalists with optimum growth parameters for the creation of a uniform distribution of wires on surfaces.
International Nuclear Information System (INIS)
Difilippo, F.C.; Perez, R.B.; de Saussure, G.; Olsen, D.K.; Ingle, R.W.
1977-01-01
The neutron-induced 238 U subthreshold fission cross section has been measured in the neutron energy range between 0.6 and 100 keV. A total of 28 fission clusters were identified. The well-known clusters at 721 and 1210 eV appeared resolved into their Class I components. Average 238 U subthreshold fission cross sections were determined and compared with available results in the literature. The measurement is interpreted in terms of fission doorway (Class II levels) arising from the assumption of the existence of a double-humped fission barrier for the ( 238 U + n) compound nucleus at large deformations. On the basis of this model, several fission barrier parameters were determined
Sub-barrier photofission of 238U
International Nuclear Information System (INIS)
Bhandari, B.S.
Photofission cross section of 238 U below threshold have been calculated using a double humped potential barrier parameterized by smoothly joining four parabolas, and a coulomb potential at and beyond the scission point. Relative strength in the fission channel has been calculated and an attempt has been made to interpret the apparent resonance structures observed recently in photofission experiments of 238 U as excited states of the fission isomer. A set of parameters for a double humped barrier are found which are consistent with known spontaneous fission and isomeric fission half lives. In addition to reproducing satisfactorily the observed resonance structure near threshold, the calculation also predicts several low energy resonances in the cross sections [pt
International Nuclear Information System (INIS)
Nishina, Kojiro; Oyamatsu, Kazuhiro; Kondo, Shunsuke; Sekimoto, Hiroshi; Ishitani, Kazuki; Yamane, Yoshihiro; Miyoshi, Yoshinori
2000-01-01
This accident occurred when workers were pouring a uranium solution into a precipitation tank with handy operation against the established procedure and both the cylindrical diameter and the total mass exceeded the limited values. As a result, nuclear fission chain reactor in the solution reached not only a 'criticality' state continuing it independently but also an instantly forming criticality state exceed the criticality and increasing further nuclear fission number. The place occurring the accident at this time was not reactor but a place having not to form 'criticality' called by a processing process of uranium fuel. In such place, as because of relating to mechanism of chain reaction, it is required naturally for knowledge on the reactor physics, it is also necessary to understand chemical reaction in chemical process, and functions of tanks, valves and pumps mounted at the processes. For this purpose, some information on uranium concentration ratio, atomic density of nuclides largely affecting to chain reaction such as uranium, hydrogen, and so forth in the solution, shape, inner structure and size of container for the solution, and its temperature and total volume, were necessary for determining criticality volume of the accident uranium solution by using nuclear physics procedures. Here were described on estimation of energy emission in the JCO accident, estimation from analytical results on neutron and solution, calculation of various nuclear physics property estimation on the JCO precipitation tank at JAERI. (G.K.)
International Nuclear Information System (INIS)
Fischer, U.; Herring, S.; Hogenbirk, A.; Leichtle, D.; Nagao, Y.; Pijlgroms, B.J.; Ying, A.
2000-01-01
Nuclear irradiation parameters relevant to displacement damage and burn-up of the breeder materials Li 2 O, Li 4 SiO 4 and Li 2 TiO 3 have been evaluated and compared for a fusion power demonstration reactor and the high flux fission test reactor (HFR), Petten, the advanced test reactor (ATR, INEL) and the Japanese material test reactor (JMTR, JAERI). Based on detailed nuclear reactor calculations with the MCNP Monte Carlo code and binary collision approximation (BCA) computer simulations of the displacement damage in the polyatomic lattices with MARLOWE, it has been investigated how well the considered HFRs can meet the requirements for a fusion power reactor relevant irradiation. It is shown that a breeder material irradiation in these fission test reactors is well suited in this regard when the neutron spectrum is well tailored and the 6 Li-enrichment is properly chosen. Requirements for the relevant nuclear irradiation parameters such as the displacement damage accumulation, the lithium burn-up and the damage production function W(T) can be met when taking into account these prerequisites. Irradiation times in the order of 2-3 full power years are necessary for the HFR to achieve the peak values of the considered fusion power Demo reactor blanket with regard to the burn-up and, at the same time, the dpa accumulation
(d,p)-transfer induced fission of heavy radioactive beams
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.
International Nuclear Information System (INIS)
Berg, M.S. van den.
1995-01-01
Thermodynamic parameters and transport coefficients have been calculated for a multicomponent reacting U-C-F gas mixture in the steady flow gaseous core fission reactor. Element abundances are consistent with thermodynamic equilibrium between the gas mixture and a cooled solid graphite wall at 2500 K. Results are presented for various pressures, a fluorine potential of 5.6 and temperatures between 2500 and 7000 K. As a result of dissociation processes of uranium and carbon fluoride compounds, ''effective'' values of thermodynamic parameters and transport coefficients show anomalous behaviour with respect to so-called ''frozen'' values. The chemical reaction energy of the U-C-F gas mixture has been calculated as the driving-force behind the process of fuel redistribution to attain criticality conditions inside a functioning reactor. (author)
Directory of Open Access Journals (Sweden)
Nicholas Curry
2015-07-01
Full Text Available Suspension plasma spraying has become an emerging technology for the production of thermal barrier coatings for the gas turbine industry. Presently, though commercial systems for coating production are available, coatings remain in the development stage. Suitable suspension parameters for coating production remain an outstanding question and the influence of suspension properties on the final coatings is not well known. For this study, a number of suspensions were produced with varied solid loadings, powder size distributions and solvents. Suspensions were sprayed onto superalloy substrates coated with high velocity air fuel (HVAF -sprayed bond coats. Plasma spray parameters were selected to generate columnar structures based on previous experiments and were maintained at constant to discover the influence of the suspension behavior on coating microstructures. Testing of the produced thermal barrier coating (TBC systems has included thermal cyclic fatigue testing and thermal conductivity analysis. Pore size distribution has been characterized by mercury infiltration porosimetry. Results show a strong influence of suspension viscosity and surface tension on the microstructure of the produced coatings.
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.
The Use of Feature Parameters to Asses Barrier Properties of ALD coatings for Flexible PV Substrates
International Nuclear Information System (INIS)
Blunt, Liam; Fleming, Leigh; Elrawemi, Mohamed; Robbins, David
2014-01-01
This paper reports on the recent work carried out as part of the EU funded NanoMend project. The project seeks to develop integrated process inspection, cleaning, repair and control systems for nano-scale thin films on large area substrates. In the present study flexible photovoltaic films have been the substrate of interest. Flexible PV films are the subject of significant development at present and the latest films have efficiencies at or beyond the level of Si based rigid PV modules. These flexible devices are fabricated on polymer film by the repeated deposition, and patterning, of thin layer materials using roll-to-roll processes, where the whole film is approximately 3um thick prior to encapsulation. Whilst flexible films offer significant advantages in terms of mass and the possibility of building integration (BIPV) they are at present susceptible to long term environmental degradation as a result of water vapor transmission through the barrier layers to the CIGS (Copper Indium Gallium Selenide CuIn x Ga (1-x) Se 2 ) PV cells thus causing electrical shorts and efficiency drops. Environmental protection of the GIGS cell is provided by a thin (40nm) barrier coating of Al 2 O 3 . The highly conformal aluminium oxide barrier layer is produced by atomic layer deposition (ALD) where, the ultra-thin Al 2 O 3 layer is deposited onto polymer thin films before these films encapsulate the PV cell. The surface of the starting polymer film must be of very high quality in order to avoid creating defects in the device layers. Since these defects reduce manufacturing yield, in order to prevent them, a further thin polymer coating (planarization layer) is generally applied to the polymer film prior to deposition. The presence of surface irregularities on the uncoated film can create defects within the nanometre-scale, aluminium oxide, barrier layer and these are measured and characterised. This paper begins by reporting the results of early stage measurements conducted to
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
Directory of Open Access Journals (Sweden)
Murugan K
2015-03-01
Full Text Available Karmani Murugan, Yahya E Choonara, Pradeep Kumar, Divya Bijukumar, Lisa C du Toit, Viness Pillay Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Abstract: Cellular internalization and trans-barrier transport of nanoparticles can be manipulated on the basis of the physicochemical and mechanical characteristics of nanoparticles. Research has shown that these factors significantly influence the uptake of nanoparticles. Dictating these characteristics allows for the control of the rate and extent of cellular uptake, as well as delivering the drug-loaded nanosystem intra-cellularly, which is imperative for drugs that require a specific cellular level to exert their effects. Additionally, physicochemical characteristics of the nanoparticles should be optimal for the nanosystem to bypass the natural restricting phenomena of the body and act therapeutically at the targeted site. The factors at the focal point of emerging smart nanomedicines include nanoparticle size, surface charge, shape, hydrophobicity, surface chemistry, and even protein and ligand conjugates. Hence, this review discusses the mechanism of internalization of nanoparticles and ideal nanoparticle characteristics that allow them to evade the biological barriers in order to achieve optimal cellular uptake in different organ systems. Identifying these parameters assists with the progression of nanomedicine as an outstanding vector of pharmaceuticals. Keywords: nanoparticles, transport mechanisms, cellular uptake, size, shape, charge
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
Barrier heights of plutonium isotopes from (n,n'f)-thresholds
International Nuclear Information System (INIS)
Knitter, H.-H.; Budtz-Joergensen, C.
1983-01-01
The neutron induced second chance fission cross section for the isotopes 238 Pu, 239 Pu, 240 Pu, 241 Pu, 242 Pu and 244 Pu are studied in the region of the threshold using a simple model. Numerical values are obtained for the inner fission barrier heights of the mentioned isotopes and of the nuclear temperatures governing the neutron evaporation process at incident neutron energies around the second chance fission threshold. The comparisons of the present parameters with those obtained by other methods give hints to possible insufficiencies of experimental cross section data in the region of the second chance fission threshold. (Auth.)
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 ...
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
Directory of Open Access Journals (Sweden)
Shiqi Zhou
2013-10-01
Full Text Available Monte Carlo simulations in the canonical ensemble are performed for fluid with potential consisting of a square-well plus a square-barrier to obtain thermodynamic properties such as pressure, excess energy, constant volume excess heat capacity, and excess chemical potential, and structural property such as radial distribution function. The simulations cover a wide density range for the fluid phase, several temperatures, and different combinations of the parameters defining the potential. These simulation data have been used to test performances of a coupling parameter series expansion (CPSE recently proposed by one of the authors [S. Zhou, Phys. Rev. E 74, 031119 (2006], and a traditional 2nd-order high temperature series expansion (HTSE based on a macroscopic compressibility approximation (MAC used with confidence since its introduction in 1967. It is found that (i the MCA-based 2nd-order HTSE unexpectedly and depressingly fails for most situations investigated, and the present simulation results can serve well as strict criteria for testing liquid state theories. (ii The CPSE perturbation scheme is shown to be capable of predicting very accurately most of the thermodynamic properties simulated, but the most appropriate level of truncating the CPSE differs and depends on the range of the potential to be calculated; in particular, the shorter the potential range is, the higher the most appropriate truncating level can be, and along with rising of the potential range the performance of the CPSE perturbation scheme will decrease at higher truncating level. (iii The CPSE perturbation scheme can calculate satisfactorily bulk fluid rdf, and such calculations can be done for all fluid states of the whole phase diagram. (iv The CPSE is a convergent series at higher temperatures, but show attribute of asymptotic series at lower temperatures, and as a result, the surest asymptotic value occurs at lower-order truncation.
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.)
International Nuclear Information System (INIS)
Rahmani, Faezeh; Khosravinia, Hossein
2016-01-01
Theoretical studies on the optimization of Silicon (Si) parameters as the base of betavoltaic battery have been presented using Monte Carlo simulations and the state equations in semiconductor to obtain maximum power. Si with active area of 1 cm 2 has been considered in p-n junction and Schottky barrier structure to collect the radiation induced-charge from 10 mCi cm −2 of Nickle-63 ( 63 Ni) Source. The results show that the betavoltaic conversion efficiency in the Si p-n structure is about 2.7 times higher than that in the Ni/Si Schottky barrier structure. - Highlights: • Silicon parameters were studied in betavoltaic batteries. • Studied betavoltaic batteries include p-n and Schottky barrier structures. • The p-n structure has higher conversion efficiency.
Dynamical chaos and induced nuclear fission
Energy Technology Data Exchange (ETDEWEB)
Bolotin, Yu L; Krivoshej, I V
1985-01-01
It is shown that the exponential instability of trajectories, which arises at negative curvature of the potential energy surface, leads to diffusion of the image point through the barrier and determines real time delays in induced nuclear 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 ...
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
Theoretical Description of the Fission Process
International Nuclear Information System (INIS)
Witold Nazarewicz
2003-01-01
The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process
Cold valleys in fusion and fission
International Nuclear Information System (INIS)
Misicu, S.
2003-01-01
The cold fission configuration after the preformation of the fragments resembles a short-lived dinuclear or quasi-molecular system. The most conceivable scission configuration is given by two fission fragments in touching with the symmetry axes aligned (pole-pole orientation). This conclusion was based on the simple argument that this configuration offers the optimal tunneling time, i.e. the difference between the Coulomb barrier and the decay energy Q is minimal. Other orientations are apparently precluded in cold spontaneous fission and should be regarded as quasi-fission doorways in the synthesis of superheavy elements by cold fusion. (orig.)
Theoretical Description of the Fission Process
Energy Technology Data Exchange (ETDEWEB)
Witold Nazarewicz
2003-07-01
The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.
Progress on Chinese evaluated nuclear parameter library (CENPL) (II)
International Nuclear Information System (INIS)
Su Zhongdi; Ge Zhigang; Zhou Chunmei
1993-01-01
CENPL collected, evaluated and compiled nuclear basic constants and model parameters. CENPL-1 contain six sub-libraries, they are: (1) Atomic masses and characteristic constants for nuclear ground states; (2) discrete level schemes and branch ratios of γ decay; (3) level density parameters; (4) giant dipole resonance parameters for γ-ray strength function (5) fission barrier parameter; (6) optical model parameters. Their progresses are introduced
Physics parameter calculations for a Tandem Mirror Reactor with thermal barriers
International Nuclear Information System (INIS)
Boghosian, B.M.; Lappa, D.A.; Logan, B.G.
1979-01-01
Thermal barriers are localized reductions in potential between the plugs and the central cell, which effectively insulate trapped plug electrons from the central cell electrons. By then applying electron heating in the plug, it is possible to obtain trapped electron temperatures that are much greater than those of the central cell electrons. This, in turn, effects an increase in the plug potential and central cell confinement with a concomitant decrease in plug density and injection power. Ions trapped in the barrier by collisions are removed by the injection of neutral beams directed inside the barrier cell loss cone; these beam neutrals convert trapped barrier ions to neutrals by charge exchange permitting their escape. We describe a zero-dimensional physics model for this type of reactor, and present some preliminary results for Q
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
Gamma Radiation from Fission Fragments
International Nuclear Information System (INIS)
Higbie, Jack
1969-10-01
The gamma radiation from the fragments of the thermal neutron fission of 235 U has been investigated, and the preliminary data are presented here with suggestions for further lines of research and some possible interpretations of the data. The data have direct bearing on the fission process and the mode of fragment de-excitation. The parameters measured are the radiation decay curve for the time interval (1 - 7) x 10 -10 sec after fission, the photon yield, the total gamma ray energy yield, and the average photon energy. The last three quantities are measured as a function of the fragment mass
Gamma Radiation from Fission Fragments
Energy Technology Data Exchange (ETDEWEB)
Higbie, Jack
1969-10-15
The gamma radiation from the fragments of the thermal neutron fission of {sup 235}U has been investigated, and the preliminary data are presented here with suggestions for further lines of research and some possible interpretations of the data. The data have direct bearing on the fission process and the mode of fragment de-excitation. The parameters measured are the radiation decay curve for the time interval (1 - 7) x 10{sup -10} sec after fission, the photon yield, the total gamma ray energy yield, and the average photon energy. The last three quantities are measured as a function of the fragment mass.
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.
A search for parameters of universal sub-barrier fusion excitation function
Energy Technology Data Exchange (ETDEWEB)
Qu, W.W. [Medical College of Soochow University, School of Radiation Medicine and Protection, Soochow (China); Zhang, G.L. [Beihang University, School of Physics and Nuclear Energy Engineering, Beijing (China); Wolski, R. [Henryk Niewodniczanski Institute of Nuclear Physics PAS, Cracow (Poland)
2016-11-15
Many fusion experimental data have been analyzed in terms of a simple universal function which could be used for predictions of fusion cross section below the barrier for arbitrary systems. Sub-barrier fusions based on the concept of Q -fusion value dependence were studied. It is attempted to parameterize the energy-reduced fusion excitation functions around the Coulomb barriers by an analytical phenomenological function. It was found that the speed of driving nuclei towards fusion is faster with the increase of mass asymmetry of colliding systems and those systems with a large difference of the ratio of neutrons to protons. However, a general trend with respect to total mass has not been observed. An exposition of more qualitative conclusions is hindered by apparent inconsistencies of measured fusion cross sections. (orig.)
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.)
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
Recent progress in the study of fission reaction
International Nuclear Information System (INIS)
Blons, J.; Paya, D.; Signarbieux, C.
1977-01-01
The different steps of the fission phenomenon are briefly recalled before a more detailed study of the static aspect of the fission barrier crossing. The experiments performed at Saclay during the last few years seem to confirm the calculations according to which a triple humped fission barrier is expected for the thorium isotopes. The last part deals with some dynamical aspects of the process. Recent results are presented which tend to prove that the nuclear viscosity decreases when the excitation energy increases [fr
Spontaneous-fission half-lives for even nuclei with Z> or =92
International Nuclear Information System (INIS)
Randrup, J.; Larsson, S.E.; Moller, P.; Nilsson, S.G.; Pomorski, K.; Sobiczewski, A.
1976-01-01
The spontaneous-fission process for doubly even nuclei with Z> or =92 is studied in a semiempirical WKB framework. One-dimensional fission barrier potentials are established from theoretical deformation-energy surfaces based on the droplet model and the modified-oscillator model. The effects of axial asymmetry as well as reflection asymmetry have been taken into account. Macroscopic (irrotational flow) inertial-mass functions and, alternatively, microscopic (cranking model) inertial mass parameters have been employed for the calculation of the fission half-lives. With one over-all normalization parameter it is possible to fit the experimental half-lives to within a factor of 20 on the average. The resulting effective inertial-mass functions are used to estimate the stability of the transactinide elements. Only minor differences with previous estimates for the r process and superheavy nuclei are encountered
Modelling of migration from multi-layers and functional barriers: Estimation of parameters
Dole, P.; Voulzatis, Y.; Vitrac, O.; Reynier, A.; Hankemeier, T.; Aucejo, S.; Feigenbaum, A.
2006-01-01
Functional barriers form parts of multi-layer packaging materials, which are deemed to protect the food from migration of a broad range of contaminants, e.g. those associated with reused packaging. Often, neither the presence nor the identity of the contaminants is known, so that safety assessment
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...
Amjad, M.; Salam, Z.; Ishaque, K.
2014-04-01
In order to design an efficient resonant power supply for ozone gas generator, it is necessary to accurately determine the parameters of the ozone chamber. In the conventional method, the information from Lissajous plot is used to estimate the values of these parameters. However, the experimental setup for this purpose can only predict the parameters at one operating frequency and there is no guarantee that it results in the highest ozone gas yield. This paper proposes a new approach to determine the parameters using a search and optimization technique known as Differential Evolution (DE). The desired objective function of DE is set at the resonance condition and the chamber parameter values can be searched regardless of experimental constraints. The chamber parameters obtained from the DE technique are validated by experiment.
Energy Technology Data Exchange (ETDEWEB)
Seetharam, Suresh C; Perko, Janez; Jacques, Diederik [Belgian Nuclear Research Centre SCK-CEN, Mol (Belgium); Mallants, Dirk [CSIRO Land and Water, Urrbrae (Australia)
2013-07-01
This paper presents a consistent approach for the development of a comprehensive data base of time-dependent hydraulic and transport parameters for concrete engineered barriers of the future Dessel near surface repository for low level waste. The parameter derivation is based on integration of selected data obtained through an extensive literature review, data from experimental studies on cementitious materials specific for the Dessel repository and numerical modelling using physically-based models of water and mass transport. Best estimate parameter values for assessment calculations are derived, together with source and expert range and their probability density function wherever the data was sufficient. We further discuss a numerical method for up-scaling laboratory derived parameter values to the repository scale; the resulting large-scale effective parameters are commensurate with numerical grids used in models for radionuclide migration. To accommodate different levels of conservatism in the various assessment calculations defined by ONDRAF/NIRAS, several sets of parameter values have been derived based on assumptions that introduce different degrees of conservatism. For pertinent parameters, the time evolution of such properties due to the long-term concrete degradation is also addressed. The implementation of the consistent approach is demonstrated by considering the pore water diffusion coefficient as an example. (authors)
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
Bimodal nature in low-energy fission of light actinides
International Nuclear Information System (INIS)
Nagame, Yuichiro; Nishinaka, Ichiro; Tsukada, Kazuaki; Ikezoe, Hiroshi; Otsuki, Tsutomu; Sueki, Keisuke; Nakahara, Hiromichi; Kudo, Hisaaki.
1995-01-01
To solve various problems in the mass division process of light actinoids, some experiments on the basis of bimodal fission were carried. Mass and kinetic energy distribution of Th-232 and U-238 were determined. Pa-225 (N= 134) and Pa-227 (N=136), fission nuclei, were produced by Bi-209 + 0-16 and Bi-209 + 0-18 heavy ion nucleus reactions, and the mass yield distribution were determined by the time-of-flight method and the radiochemical procedure. From the results, two independent deforming processes were proved in the fission process of light actinoid nuclei. On the deforming process through the low fission barrier, nucleus fissioned after small deformation under the influence of stabilization of the shell structure of fission product. In the case of process through the high barrier, however, the nucleus fissioned after large deformation. The unsymmetrical mass division was derived from the former and the symmetrical one from the latter. (S.Y.)
Fission-product retention in HTGR fuels
International Nuclear Information System (INIS)
Homan, F.J.; Kania, M.J.; Tiegs, T.N.
1982-01-01
Retention data for gaseous and metallic fission products are presented for both Triso-coated and Biso-coated HTGR fuel particles. Performance trends are established that relate fission product retention to operating parameters, such as temperature, burnup, and neutron exposure. It is concluded that Biso-coated particles are not adequately retentive of fission gas or metallic cesium, and Triso-coated particles which retain cesium still lose silver. Design implications related to these performance trends are identified and discussed
Directory of Open Access Journals (Sweden)
Katarzyna Porzych
2017-01-01
Full Text Available Background. The goal of this study is to assess the natural antioxidant barrier of the organism and selected psychological aspects of the aging process in patients above 60 years old. Methods. The study included a total of 52 patients aged above 60 (mean age 67 ± 3.4 and 32 healthy subjects (mean age 22 ± 3.4 as a control group. All patients underwent psychological assessment using Test of Attentional Performance version 2.3 (TAP 2.3, four subtests: alertness, cross-modal integration, neglect with central task, and working memory and biochemical analysis of venous blood concerning values of the selected parameters of oxidative stress (HT, GSH, GPXOS, GPXRBC, GRRBC1, SODRBC1, MDARBC1, NO2−/NO3−, and CP. Results. Disorders of attention were observed mainly in elderly people, but an assumption that elderly people have developed more efficient ways of working memory use than younger people may be true. Results showed the reduced effectiveness of the body’s natural antioxidant barrier in elderly people. Moderate positive and negative correlations among parameters of oxidative stress and psychological parameters were observed in the control group. Discussion. Intensification of the attention deficits and oxidative stress may be observed as one of the pathogenic factors of age-dependent diseases.
Directory of Open Access Journals (Sweden)
Mike Collier
2011-11-01
Full Text Available A dielectric barrier discharge excited neutral argon (Ar I excimer lamp has been developed and characterised. The aim of this study was to develop an excimer lamp operating at atmospheric pressure that can replace mercury lamps and vacuum equipment used in the sterilisation of medical equipment and in the food industry. The effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV emission at 126 nm and near infrared (NIR lines at 750.4 nm and 811.5 nm have been investigated. These three lines were chosen as they represent emissions resulting from de-excitation of excimer states that emit energetic photons with an energy of 9.8 eV. We observed that the intensity of the VUV Ar_{2}* excimer emission at 126 nm increased with increasing gas pressure, but decreased with increasing excitation pulse frequency and pulse width. In contrast, the intensities of the NIR lines decreased with increasing gas pressure and increased with increasing pulse frequency and pulse width. We have demonstrated that energetic VUV photons of 9.8 eV can be efficiently generated in a dielectric barrier discharge in Ar.
Theoretical study of fission dynamics with muons
International Nuclear Information System (INIS)
Oberacker, V.E.; Umar, A.S.; Bottcher, C.; Strayer, M.R.; Maruhn, J.A.; Frankfurt Univ.
1992-01-01
Following muon capture by actinide atoms, some of the inner shell muonic transitions proceed by inverse internal conversion, i.e. the excitation energy of the muonic atom is transferred to the nucleus. In particular, the muonic E2:(3d→1s) transition energy is close to the peak of the isoscalar giant quadrupole resonance in actinide nuclei which exhibits a large fission width. Prompt fission in the presence of a bound muon allows us to study the dynamics of large-amplitude collective motion. We solve the time-dependent Dirac equation for the muonic spinor wave function in the Coulomb field of the fissioning nucleus on a 3-dimensional lattice and demonstrate that the muon attachment probability to the light fission fragment is a measure of the nuclear energy dissipation between the outer fission barrier and the scission point
Fission decay properties of nuclear giant multipole resonances
International Nuclear Information System (INIS)
Dias, H.; Arruda Neto, J.D.T.; Hussein, M.S.; Carlson, B.V.
1986-05-01
The statistical fission decay properties of the giant dipole, quadrupole and monopole resonances in 236 U are investigated with the aid of the Hauser-Feshbach model. It is found, contrary to several recent claims, that the GQR fission decay probability is as large as that of the GDR, at energies higher than the fission barrier. At energies close to the f.b., the GQR fission probability is found to be appreciably larger than that of the GDR. The GMR fission probability follows closely that of the GQR. (Author) [pt
Neutronics of Laser Fission-Fusion Systems
International Nuclear Information System (INIS)
Velarde, G.
1976-01-01
Neutronics of Fission-Fusion microsystems inertially confined by Lasers are analysed by transport calculation, both stationary (DTF, TIHOC) and time dependent (TDA, TIHEX), discussing the results obtained for the basic parameters of the fission process (multiplication factor, neutron generation time and Rossi-∞). (Author) 14 refs
Neutronics of Laser Fission-Fusion Systems
Energy Technology Data Exchange (ETDEWEB)
Velarde, G
1976-07-01
Neutronics of Fission-Fusion microsystems inertially confined by Lasers are analysed by transport calculation, both stationary (DTF, TIHOC) and time dependent (TDA, TIHEX), discussing the results obtained for the basic parameters of the fission process (multiplication factor, neutron generation time and Rossi-{infinity}). (Author) 14 refs.
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...
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.)
A Numerical Procedure to Obtain the Creep Parameters of the Thermal Barrier Coating
Directory of Open Access Journals (Sweden)
Shifeng Wen
2014-05-01
Full Text Available Three-point bending creep test was used to understand the creep behavior of typical thin film/substrate systems—thermal barrier coating (TBC systems. Firstly, a simplified model, which does not consider the local effect, has been set up to get an analytical relationship. The important result is that creep stress exponent of materials is equal to the creep load exponent of the steady-state deflection rate of BC specimens. Secondly, in order to consider the local effect of bending, the finite element method (FEM has been carried out. FEM calculation shows that there is a steady stage of the creep deflection under a constant applied load. And the exponent of the steady-state creep deflection rate to the applied load is found to be equal to the creep stress exponent of materials. The creep constant of the materials can be obtained by a set of trials with assumed creep constants of materials and can be finally determined by the best fit method. Finally, the finite element results show that the influences of the friction, the thickness of TBCs, and the modulus ratio of TBC to the substrate on stress distribution are important.
Theoretical Description of the Fission Process
International Nuclear Information System (INIS)
Nazarewicz, Witold
2009-01-01
Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation's nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic
Measurements of fission yields
International Nuclear Information System (INIS)
Denschlag, H.O.
2000-01-01
After some historical introductory remarks on the discovery of nuclear fission and early fission yield determinations, the present status of knowledge on fission yields is briefly reviewed. Practical and fundamental reasons motivating the pursuit of fission yield measurements in the coming century are pointed out. Recent results and novel techniques are described that promise to provide new interesting insights into the fission process during the next century. (author)
Radiochemical studies on fission
Energy Technology Data Exchange (ETDEWEB)
None
1973-07-01
Research progress is reported on nuclear chemistry; topics considered include: recoil range and kinetic energy distribution in the thermal neutron ftssion of /sup 245/Cm; mass distribution and recoil range measurements in the reactor neutron-induced fission of /sup 232/U; fission yields in the thermal neutron fission of /sup 241/PU highly asymmetric binary fission of uranium induced by reactor neutrons; and nuclear charge distribution in low energy fission. ( DHM)
Directory of Open Access Journals (Sweden)
Hassan Maktuff Jaber Al-Ta'ii
2015-02-01
Full Text Available Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al/DNA/silicon (Si rectifying junctions using their current-voltage (I-V characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0 was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min. These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors.
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.)
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)
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
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
Fifty years of nuclear fission: Nuclear data and measurements series
International Nuclear Information System (INIS)
Lynn, J.E.
1989-06-01
This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs
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.)
Calculated apparent yields of rare gas fission products
International Nuclear Information System (INIS)
Delucchi, A.A.
1975-01-01
The apparent fission yield of the rare gas fission products from four mass chains is calculated as a function of separation time for six different fissioning systems. A plot of the calculated fission yield along with a one standard deviation error band is given for each rare gas fission product and for each fissioning system. Those parameters in the calculation that were major contributors to the calculated standard deviation at each separation time were identified and the results presented on a separate plot. To extend the usefulness of these calculations as new and better values for the input parameters become available, a third plot was generated for each system which shows how sensitive the derived fission yield is to a change in any given parameter used in the calculation. (U.S.)
Thermodynamic analysis of volatile organometallic fission products
International Nuclear Information System (INIS)
Auxier II, J.D.; Hall, H.L.; Cressy, Derek
2016-01-01
The ability to perform rapid separations in a post nuclear weapon detonation scenario is an important aspect of national security. In the past, separations of fission products have been performed using solvent extraction, precipitation, etc. The focus of this work is to explore the feasibility of using thermochromatography, a technique largely employed in superheavy element chemistry, to expedite the separation of fission products from fuel components. A series of fission product complexes were synthesized and the thermodynamic parameters were measured using TGA/DSC methods. Once measured, these parameters were used to predict their retention times using thermochromatography. (author)
Energy Technology Data Exchange (ETDEWEB)
Zamrun, Muhammad; Usman, Ida; Variani, Viska Inda [Department of Physics, Haluoleo University, Kendari, Sulawesi Tengagra, 93232 (Indonesia); Kassim, Hasan Abu [Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2014-03-05
We study the heavy-ion collision at sub-barrier energies of {sub 16}O+{sub 144}Sm system using full order coupled-channels formalism. We especially investigate the sensitivity of fusion and quasi-elastic barrier distributions for this system on the coupling radius parameter. We found that the coupled-channels calculations of the fusion and the quasi-elastic barrier distributions are sensitive to the coupling radius for this reaction in contrast to the fusion and quasi-elastic cross section. Our study indicates that the larger coupling radius, i.e., r{sub coup}=1.20, is required by the experimental quasi-elastic barrier distribution. However, the experimental fusion barrier distribution compulsory the small value, i.e., r{sub coup}=1.06.
Modelisation of the fission cross section
International Nuclear Information System (INIS)
Morariu, Claudia
2013-03-01
The neutron cross sections of four nuclear systems (n+ 235 U, n+ 233 U, n+ 241 Am and n+ 237 Np) are studied in the present document. The target nuclei of the first case, like 235 U and 239 Pu, have a large fission cross section after the absorption of thermal neutrons. These nuclei are called 'fissile' nuclei. The other type of nuclei, like 237 Np and 241 Am, fission mostly with fast neutrons, which exceed the fission threshold energy. These types of nuclei are called 'fertile'. The compound nuclei of the fertile nuclei have a binding energy higher than the fission barrier, while for the fissile nuclei the binding energy is lower than the fission barrier. In this work, the neutron induced cross sections for both types of nuclei are evaluated in the fast energy range. The total, reaction and shape-elastic cross sections are calculated by the coupled channel method of the optical model code ECIS, while the compound nucleus mechanism are treated by the statistical models implemented in the codes STATIS, GNASH and TALYS. The STATIS code includes a refined model of the fission process. Results from the theoretical calculations are compared with data retrieved from the experimental data base EXFOR. (author) [fr
Application of pulse shape discrimination in Si detector for fission ...
Indian Academy of Sciences (India)
Pulse shape discrimination (PSD) with totally depleted transmission type Si surface barrier detector in reverse mount has been investigated to identify fission fragments in the presence of elastic background in heavy ion-induced fission reactions by both numerical simulation and experimental studies. The PSD method is ...
Bimodality in macroscopic dynamics of nuclear fission
International Nuclear Information System (INIS)
Bastrukov, S.I.; Salamatin, V.S.; Strteltsova, O.I.; Molodtsova, I.V.; Podgainy, D.V.; )
2000-01-01
The elastodynamic collective model of nuclear fission is outlined whose underlying idea is that the stiff structure of nuclear shells imparts to nucleus properties typical of a small piece of an elastic solid. Emphasis is placed on the macroscopic dynamics of nuclear deformations resulting in fission by two energetically different modes. The low-energy S-mode is the fission due to disruption of elongated quadrupole spheroidal shape. The characteristic features of the high-energy T-mode of division by means of torsional shear deformations is the compact scission configuration. Analytic and numerical estimates for the macroscopic fission-barrier heights are presented, followed by discussion of fingerprints of the above dynamical bimodality in the available data [ru
Upgrading DRACULA setup to be used for light products - fission fragments coincidence measurements
International Nuclear Information System (INIS)
Simion, V.; Petrovici, M.; Pop, A.; Berceanu, I.; Duma, M.; Moisa, D.; Pagano, A.; Geraci, E.
1999-01-01
At low bombarding energy (E/A 238 U give rise to a number of fission processes, all leading to very similar fission products. Therefore, in order to understand the fission processes in this energy domain it is of interest to determine the amount of fission occurring after a peripheral interaction relative to that originating from compound nucleus formation. Although the detection of a projectile residue (PLF) in coincidence with the fission fragments is a very promising probe for the macroscopic features of the mechanism of induced fission, at incident energies in the vicinity of the Coulomb barrier (E/A 2 cross section area uses the phoswich technique by coupling a thin fast NE102A plastic scintillator to a 10 cm long BaF 2 crystal of hexagonal section. The BaF 2 crystal detectors have been successfully used in modular multielement detector ARGOS in the context of GANCT and HOTCT researches at LNS. The light response of the phoswich configuration as a function of the plastic thickness and of the energy and charge of the incident ion has been studied at Tandem energies. Both arrays will be placed in separate vacuum chambers attached to the remaining large angular opening windows of the reaction chamber. By rotating the whole device the fission fragment detection arrays will cover a range of 96 angle in the horizontal plane. The main advantage of this setup is that it allows to perform continuous measurements in energy and angle of the reaction products. The geometry of the whole device has been tested by Monte Carlo calculations using the code ELPHIC. The coincidence condition is completely fulfilled for the first two positions of the setup and partially for the third one. Measurements are intended to be performed at the SMP Tandem from LNS-Catania using light beams ( 16 O, 19 F, 20 Ne, 32 S) at ∼ 6 MeV/A on high fissility parameter targets. (authors)
Systematics of Fission-Product Yields
International Nuclear Information System (INIS)
Wahl, A.C.
2002-01-01
Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z F = 90 thru 98, mass number A F = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru ∼200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from ∼ 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron (∼ fission spectrum) induced fission reactions
Systematics of Fission-Product Yields
Energy Technology Data Exchange (ETDEWEB)
A.C. Wahl
2002-05-01
Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z{sub F} = 90 thru 98, mass number A{sub F} = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru {approx}200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from {approx} 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron ({approx} fission spectrum) induced fission reactions.
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.
Rajagopal Reddy, V.; Asha, B.; Choi, Chel-Jong
2017-06-01
The Schottky barrier junction parameters and structural properties of Zr/p-GaN Schottky diode are explored at various annealing temperatures. Experimental analysis showed that the barrier height (BH) of the Zr/p-GaN Schottky diode increases with annealing at 400 °C (0.92 eV (I-V)/1.09 eV (C-V)) compared to the as-deposited one (0.83 eV (I-V)/0.93 eV (C-V)). However, the BH decreases after annealing at 500 °C. Also, at different annealing temperatures, the series resistance and BH are assessed by Cheung's functions and their values compared. Further, the interface state density (N SS) of the diode decreases after annealing at 400 °C and then somewhat rises upon annealing at 500 °C. Analysis reveals that the maximum BH is obtained at 400 °C, and thus the optimum annealing temperature is 400 °C for the diode. The XPS and XRD analysis revealed that the increase in BH may be attributed to the creation of Zr-N phases with increasing annealing up to 400 °C. The BH reduces for the diode annealed at 500 °C, which may be due to the formation of Ga-Zr phases at the junction. The AFM measurements reveal that the overall surface roughness of the Zr film is quite smooth during rapid annealing process. Project supported by the R&D Program for Industrial Core Technology (No. 10045216) and the Transfer Machine Specialized Lighting Core Technology Development Professional Manpower Training Project (No. N0001363) Funded by the Ministry of Trade, Industry and Energy (MOTIE), Republic of Korea.
Shin, Jaewoo; Kong, Chanho; Cho, Jae Sung; Lee, Jihyeon; Koh, Chin Su; Yoon, Min-Sik; Na, Young Cheol; Chang, Won Seok; Chang, Jin Woo
2018-02-01
OBJECTIVE The application of pharmacological therapeutics in neurological disorders is limited by the ability of these agents to penetrate the blood-brain barrier (BBB). Focused ultrasound (FUS) has recently gained attention for its potential application as a method for locally opening the BBB and thereby facilitating drug delivery into the brain parenchyma. However, this method still requires optimization to maximize its safety and efficacy for clinical use. In the present study, the authors examined several sonication parameters of FUS influencing BBB opening in small animals. METHODS Changes in BBB permeability were observed during transcranial sonication using low-intensity FUS in 20 adult male Sprague-Dawley rats. The authors examined the effects of FUS sonication with different sonication parameters, varying acoustic pressure, center frequency, burst duration, microbubble (MB) type, MB dose, pulse repetition frequency (PRF), and total exposure time. The focal region of BBB opening was identified by Evans blue dye. Additionally, H & E staining was used to identify blood vessel damage. RESULTS Acoustic pressure amplitude and burst duration were closely associated with enhancement of BBB opening efficiency, but these parameters were also highly correlated with tissue damage in the sonicated region. In contrast, MB types, MB dose, total exposure time, and PRF had an influence on BBB opening without conspicuous tissue damage after FUS sonication. CONCLUSIONS The study aimed to identify these influential conditions and provide safety and efficacy values for further studies. Future work based on the current results is anticipated to facilitate the implementation of FUS sonication for drug delivery in various CNS disease states in the near future.
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
The behavior of fission products during nuclear rocket reactor tests
International Nuclear Information System (INIS)
Bokor, P.C.; Kirk, W.L.; Bohl, R.J.
1991-01-01
Fission product release from nuclear rocket propulsion reactor fuel is an important consideration for nuclear rocket development and application. Fission product data from the last six reactors of the Rover program are collected in this paper to provide as basis for addressing development and testing issues. Fission product loss from the fuel will depend on fuel composition and reactor design and operating parameters. During ground testing, fission products can be contained downstream of the reactor. The last Rover reactor tested, the Nuclear Furnance, was mated to an effluent clean-up system that was effective in preventing the discharge of fission products into the atmosphere
About total kinetic energy distribution between fragments of binary fission
International Nuclear Information System (INIS)
Khugaev, A.V.; Koblik, Yu.N.; Pikul, V.P.; Ioannou, P.; Dimovasili, E.
2002-01-01
At the investigation of binary fission reactions one of the main characteristic of process is total kinetic energy (TKE) of fission fragments and it distribution between them. From the values of these characteristics it is possible to extract the information about structure of fission fragments in the break up point of initial fissionable nuclear system. In our work TKE dependence from the deformation parameters of shape and density distribution of charge in the fission fragments are investigated. In the end of paper some generalizations of obtaining results are carried out and presented in the form of tables and figures
Role of ternary fission in synthesis of bypassed nuclei
International Nuclear Information System (INIS)
Kramarovskij, Ya.M.; Chechev, V.P.
1983-01-01
A possible influence of ternary fission with escape of neutron-enriched light charged particles on the synthesis of bypassed nuclides is considered. It is shown that this concept cannot give explanation of bypassed isotope concentrations, but it can make some contribution, if the probability of ternary fission for superheavy nuclei grows sharply with Z 2 /A parameter. The account of β-delayed fission contributes to the shift of ternary fission fragments into the region of neutron-deficient isotopes. Consistent consideration of the ternary fission role in the nucleosynthesis is possible only with an important accumulation of experimental and theoretical data on this process, particularly for the nuclei with Z > 100
Fission times of excited nuclei: An experimental overview
International Nuclear Information System (INIS)
Morjean, M.; Morjean, M.; Jacquet, D.
2009-01-01
An overview of selected recent experimental results on fission times is presented. Evidences for over-damped motion up to saddle point during the fission process of highly excited nuclei have been obtained independently through fission probability, pre-scission multiplicity and direct time measurements. In addition, strong clues have been found for a temperature dependency of friction. Experiments probing transient effects through fission probabilities are presented and the counterbalanced effects of friction and level density parameters are discussed. Promising perspectives for super-heavy stability studies, based on fission time measurements, are presented. (authors)
Fission dynamics in the proton induced fission of heavy nuclei
Energy Technology Data Exchange (ETDEWEB)
Rubchenya, V.A. E-mail: rubchen@phys.jyu.fi; Trzaska, W.H.; Itkis, I.M.; Itkis, M.G.; Kliman, J.; Kniajeva, G.N.; Kondratiev, N.A.; Kozulin, E.M.; Krupa, L.; Pokrovski, I.V.; Voskressenski, V.M.; Hanappe, F.; Materna, T.; Dorvaux, O.; Stuttge, L.; Chubarian, G.; Khlebnikov, S.V.; Vakhtin, D.N.; Lyapin, V.G
2004-04-05
Multi-parameter correlation study of the reaction {sup 242}Pu(p, f) at E{sub p} 13, 20 and 55 MeV has been carried out. Fission fragment mass and kinetic energy distributions and the double differential neutron spectra have been measured. It was observed that the two-humped shape of mass distributions prevailed up to highest proton energy. Manifestation of the nuclear shell Z 28 near fragment mass A{sub fr} = 70 has been detected. The experimental results were analyzed in the framework of a time-dependent statistical model with inclusion of nuclear friction effects in the fission process. The multi-parameter correlation study of the reaction.
Mass distributions in nucleon-induced fission at intermediate energies
Duijvestijn, M C; Hambsch, F J
2001-01-01
Temperature-dependent fission barriers and fission-fragment mass distributions are calculated in the framework of the multimodal random neck-rupture model (MM-RNRM). It is shown how the distinction between the different fission modes disappears at higher excitation energies, due to the melting of shell effects. The fission-fragment mass yield calculations are coupled to the nuclear reaction code ALICE-91, which takes into account the competition between the other reaction channels and fission. With the combination of the temperature-dependent MM-RNRM and ALICE-91 nucleon-induced fission is investigated at energies between 10 and 200 MeV for nuclei varying from Au to Am. (72 refs).
Neutron-induced fission of uranium isotopes up to 100 MeV
International Nuclear Information System (INIS)
Lestone, J.P.; Gavron, A.
1994-01-01
The statistical-model description of the neutron-induced fission of U isotopes has been developed using densities of intrinsic states and spin cutoff parameters obtained directly from appropriate Nilsson model single-particle levels. The first-chance fission cross sections are reproduced well when the rotational contributions to the nuclear level densities are taken into account. In order to fit the U(n,f) cross sections above the threshold of second-chance fission, we must: (1) assume that the triaxial level-density enhancement is washed out at an excitation energy of approximately 7 MeV above the triaxial barriers with a width of approximately 1 MeV, implying a γ deformation for the first barriers where 10<γ<20 degree, and (2) include preequilibrium particle emission in the calculations. Above an incoming-neutron kinetic energy of approximately 17 MeV, our statistical model U(n,f) of cross sections increasingly overestimates the experimental data. This is not surprising since, at these high energies, little data exist on the scattering of neutrons to help guide the choice of optical-model parameters. A satisfactory reproduction of all of the available U(n,f) cross sections above 17 MeV is obtained by scaling our calculated compound-nucleus formation cross sections. This scaling factor falls from 1.0 at 17 MeV to 0.82 at 100 MeV
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.)
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
Influence of spin on fission fragments anisotropy
Directory of Open Access Journals (Sweden)
Ghodsi Omid N.
2005-01-01
Full Text Available An analysis of selected fission fragment angular distribution when at least one of the spins of the projectile or target is appreciable in induced fission was made by using the statistical scission model. The results of this model predicate that the spins of the projectile or target are affected on the nuclear level density of the compound nucleus. The experimental data was analyzed by means of the couple channel spin effect formalism. This formalism suggests that the projectile spin is more effective on angular anisotropies within the limits of energy near the fusion barrier.
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
On the mechanism of fission neutron emission
International Nuclear Information System (INIS)
Maerten, H.; Richter, D.; Seeliger, D.
1986-01-01
This review represents the present knowledge of the mechanism of prompt fission neutron emission. Starting with a brief fission process characterization related with neutron emission, possible emission mechanisms are discussed. It is emphasized that the experimental study of special mechanisms, i.e. scission neutron emission processes, requires a sufficiently correct description of emission probabilities on the base of the main mechanism, i.e. the evaporation from fully accelerated fragments. Adequate statistical-model approaches have to account for the complexity of nuclear fission reflected by an intricate fragment distribution. The present picture of scission neutron emission is not clarified neither experimentally nor theoretically. Deduced data are contradictory and depend on the used analysis procedures often involving rough discriptions of evaporated-neutron distributions. The contribution of two secondary mechanisms of fission neutron emission, i.e. the neutron evaporation during fragment acceleration and neutron emission due to the decay of 5 He after ternary fission, is estimated. We summarize the recent progress of the theoretical description of fission neutron spectra in the framework of statistical models considering the standard spectrum of 252 Cf(sf) neutrons especially. The main experimental basis for the study of fission neutron emission is the accurate measurement of emission probabilities as a function of emission energy and angle (at least) as well as fragment parameters (mass number ratio and kinetic energy). The present status is evaluated. (author)
Smirnov, D. I.; Giniyatyllin, R. M.; Zyul'kov, I. Yu.; Medetov, N. A.; Gerasimenko, N. N.
2013-07-01
Results of a comprehensive analysis of process variables of TiN/Ti diffuse barrier structures used in modern microelectronics are presented. To provide reliable spectral ellipsometry results, which is a common technique for postprocess control of these structures during the testing stage of the manufacturing process, a comprehensive approach is suggested that consists in consistent processing of transmission electron microscopy and X-ray reflectometry data. The resulting data were used to calculate the variances of optical coefficients of spectral ellipsometry, which depend on features of the manufacturing process and are required for analysis of the parameters of manufactured diffuse barrier structures.
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)
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
Tunneling process in heavy-ion fusion and fission
Energy Technology Data Exchange (ETDEWEB)
Iwamoto, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kondratyev, V.; Bonasera, A.
1998-10-01
We present a model towards the many-body description of sub-barrier fusion and spontaneous fission based on the semiclassical Vlasov equation and the Feynman path integral method. We define suitable collective variables from the Vlasov solution and use the imaginary time technique for the dynamics below the Coulomb barrier. (author)
Migration of fission products in UO2. Final report
International Nuclear Information System (INIS)
Prussin, S.G.; Olander, D.R.
1995-01-01
Results of an experimental and calculational effort to examine the fundamental mechanisms of fission product migration in and release from polycrystalline uranium dioxide are reported. The experiments were designed to provide diffusion parameters for the representative fission products tellurium, iodine, xenon, molybdenum and ruthenium under both reducing and oxidizing conditions. The calculational effort applied a new model of fission product release from reactor fuel that incorporates grain growth as well as grain boundary and lattice diffusion
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
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)
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)
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.
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
Anisotropy in the ternary cold fission
Delion, D S; Greiner, W
2003-01-01
We describe the spontaneous ternary cold fission of sup 2 sup 5 sup 2 Cf, accompanied by sup 4 He, sup 1 sup 0 Be and sup 1 sup 4 C within a stationary scattering formalism. We show that the light cluster should be born in the neck region. It decays from the first resonant eigenstate in the Coulomb plus harmonic oscillator potential, centred in this region and eccentric with respect to the symmetry axis. This description gives a simple answer to the question why the averaged values in the energy spectra of emitted clusters are close to each other, in spite of different Coulomb barriers. We have shown that the angular distribution of the emitted light particle is strongly connected with its deformation and the equatorial distance. Experimental angular distributions can be explained by the spherical shapes of emitted clusters, except for a deformed sup 1 sup 0 Be. We also predicted some dependences of half-lives for such tri-nuclear systems upon potential parameters.
Fission and r-process nucleosynthesis in neutron star mergers
International Nuclear Information System (INIS)
Giuliani, Samuel Andrea
2018-01-01
rates are used in r-process calculations for matter dynamically ejected in neutron star mergers and we compare our results with those obtained from a more conventional set of reaction rates. We find that all the models predict the onset of fission above the shell closure N=184 and Z=100 due to the sudden decrease in fission barriers. However, the amount of material accumulated at N=184 turns out to be very sensitive to the height of the fission barriers and the shell gap. Finally, we have also explored the impact of recent advances in fission calculations on the theoretical estimation of spontaneous fission lifetimes. We find that performing dynamical approaches based on the minimization of the integral action with nontraditional collective degrees of freedom has a strong impact in the fission barriers and the spontaneous fission lifetimes. The possible consequences of this new approach for the calculation of neutron induced fission rates has to be addressed.
International Nuclear Information System (INIS)
Benedict, U.
1977-01-01
The Relative Lattice Parameter Difference (RLPD) is defined for a solute element with respect to cubic carbides and nitrides of uranium and plutonium as solvents. Rules are given for the relationship between the solubility and the RLPD. NaCl type monocarbides with RLPD's from -10.2% to +7.8% are completely miscible with UC and PuC. NaCl type mononitrides with RLPD's from -7.5% to +8.5% are completely miscible with UN and PuN. The solubility in the sesquicarbides increases with decreasing RPLD and becomes complete in Pu 2 C 3 at RLPD = +4%, and in U 2 C 3 at RLPD approximately +1.5%. Solubilities are predicted on the basis of these rules for the cases where no experimental results are available
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
Fission dynamics of superheavy nuclei formed in uranium induced reactions
International Nuclear Information System (INIS)
Gurjit Kaur; Sandhu, Kirandeep; Sharma, Manoj K.
2017-01-01
The compound nuclear system follows symmetric fission if the competing processes such as quasi-elastic, deep inelastic, quasi-fission etc are absent. The contribution of quasi fission events towards the fusion-fission mechanism depends on the entrance channel asymmetry of reaction partners, deformations and orientations of colliding nuclei beside the dependence on energy and angular momentum. Usually the 209 Bi and 208 Pb targets are opted for the production of superheavy nuclei with Z CN =104-113. The nuclei in same mass/charge range can also be synthesized using actinide targets + light projectiles (i.e. asymmetric reaction partners) via hot fusion interactions. These actinide targets are prolate deformed which prefer the compact configurations at above barrier energies, indicating the occurrence of symmetric fission events. Here an attempt is made to address the dynamics of light superheavy system (Z CN =104-106), formed via hot fusion interactions involving actinide targets
Fusion-fission of superheavy nuclei at low excitation energies
International Nuclear Information System (INIS)
Itkis, M.G.; Oganesyan, Yu.Ts.; Kozulin, E.M.
2000-01-01
The process of fusion-fission of superheavy nuclei with Z = 102 -122 formed in the reactions with 22 Ne, 26 Mg, 48 Ca, 58 Fe and 86 Kr ions at energies near and below the Coulomb barrier has been studied. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR) using a time-of-flight spectrometer of fission fragments CORSET and a neutron multi-detector DEMON. As a result of the experiments, mass and energy distributions of fission fragments, fission and quasi-fission cross sections, multiplicities of neutrons and gamma-rays and their dependence on the mechanism of formation and decay of compound superheavy systems have been studied
Correlated prompt fission data in transport simulations
Talou, P.; Vogt, R.; Randrup, J.; Rising, M. E.; Pozzi, S. A.; Verbeke, J.; Andrews, M. T.; Clarke, S. D.; Jaffke, P.; Jandel, M.; Kawano, T.; Marcath, M. J.; Meierbachtol, K.; Nakae, L.; Rusev, G.; Sood, A.; Stetcu, I.; Walker, C.
2018-01-01
Detailed information on the fission process can be inferred from the observation, modeling and theoretical understanding of prompt fission neutron and γ-ray observables. Beyond simple average quantities, the study of distributions and correlations in prompt data, e.g., multiplicity-dependent neutron and γ-ray spectra, angular distributions of the emitted particles, n - n, n - γ, and γ - γ correlations, can place stringent constraints on fission models and parameters that would otherwise be free to be tuned separately to represent individual fission observables. The FREYA and CGMF codes have been developed to follow the sequential emissions of prompt neutrons and γ rays from the initial excited fission fragments produced right after scission. Both codes implement Monte Carlo techniques to sample initial fission fragment configurations in mass, charge and kinetic energy and sample probabilities of neutron and γ emission at each stage of the decay. This approach naturally leads to using simple but powerful statistical techniques to infer distributions and correlations among many observables and model parameters. The comparison of model calculations with experimental data provides a rich arena for testing various nuclear physics models such as those related to the nuclear structure and level densities of neutron-rich nuclei, the γ-ray strength functions of dipole and quadrupole transitions, the mechanism for dividing the excitation energy between the two nascent fragments near scission, and the mechanisms behind the production of angular momentum in the fragments, etc. Beyond the obvious interest from a fundamental physics point of view, such studies are also important for addressing data needs in various nuclear applications. The inclusion of the FREYA and CGMF codes into the MCNP6.2 and MCNPX - PoliMi transport codes, for instance, provides a new and powerful tool to simulate correlated fission events in neutron transport calculations important in
Correlated prompt fission data in transport simulations
Energy Technology Data Exchange (ETDEWEB)
Talou, P.; Jaffke, P.; Kawano, T.; Stetcu, I. [Los Alamos National Laboratory, Nuclear Physics Group, Theoretical Division, Los Alamos, NM (United States); Vogt, R. [Lawrence Livermore National Laboratory, Nuclear and Chemical Sciences Division, Livermore, CA (United States); University of California, Physics Department, Davis, CA (United States); Randrup, J. [Lawrence Berkeley National Laboratory, Nuclear Science Division, Berkeley, CA (United States); Rising, M.E.; Andrews, M.T.; Sood, A. [Los Alamos National Laboratory, Monte Carlo Methods, Codes, and Applications Group, Los Alamos, NM (United States); Pozzi, S.A.; Clarke, S.D.; Marcath, M.J. [University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Ann Arbor, MI (United States); Verbeke, J.; Nakae, L. [Lawrence Livermore National Laboratory, Nuclear and Chemical Sciences Division, Livermore, CA (United States); Jandel, M. [Los Alamos National Laboratory, Nuclear and Radiochemistry Group, Los Alamos, NM (United States); University of Massachusetts, Department of Physics and Applied Physics, Lowell, MA (United States); Meierbachtol, K. [Los Alamos National Laboratory, Nuclear Engineering and Nonproliferation, Los Alamos, NM (United States); Rusev, G.; Walker, C. [Los Alamos National Laboratory, Nuclear and Radiochemistry Group, Los Alamos, NM (United States)
2018-01-15
Detailed information on the fission process can be inferred from the observation, modeling and theoretical understanding of prompt fission neutron and γ-ray observables. Beyond simple average quantities, the study of distributions and correlations in prompt data, e.g., multiplicity-dependent neutron and γ-ray spectra, angular distributions of the emitted particles, n-n, n-γ, and γ-γ correlations, can place stringent constraints on fission models and parameters that would otherwise be free to be tuned separately to represent individual fission observables. The FREYA and CGMF codes have been developed to follow the sequential emissions of prompt neutrons and γ rays from the initial excited fission fragments produced right after scission. Both codes implement Monte Carlo techniques to sample initial fission fragment configurations in mass, charge and kinetic energy and sample probabilities of neutron and γ emission at each stage of the decay. This approach naturally leads to using simple but powerful statistical techniques to infer distributions and correlations among many observables and model parameters. The comparison of model calculations with experimental data provides a rich arena for testing various nuclear physics models such as those related to the nuclear structure and level densities of neutron-rich nuclei, the γ-ray strength functions of dipole and quadrupole transitions, the mechanism for dividing the excitation energy between the two nascent fragments near scission, and the mechanisms behind the production of angular momentum in the fragments, etc. Beyond the obvious interest from a fundamental physics point of view, such studies are also important for addressing data needs in various nuclear applications. The inclusion of the FREYA and CGMF codes into the MCNP6.2 and MCNPX-PoliMi transport codes, for instance, provides a new and powerful tool to simulate correlated fission events in neutron transport calculations important in nonproliferation
Energy Technology Data Exchange (ETDEWEB)
Zaika, N I; Kibkalo, Yu V; Parlag, O A; Sikora, D I; Tokarev, V P; Shityuk, V A [AN Ukrainskoj SSR, Kiev (Ukrainian SSR). Inst. Yadernykh Issledovanij
1989-04-01
Two-parameter measurements of the mass and energy distributions of fission products in the fission of {sup 232}Th by 21.0-26.4 MeV {alpha}-particles (h=1 MeV) are conducted using the correlation method. The obtained results show that in the region under investigation the average total kinetic energies of the fission products E-bar{sub k} have no noticeable variations within the experimental error of {plus minus} 1.5 MeV and the dispersion {sigma}{sup 2}E{sub k} slowly increases. For the E-bar{sub k} mass dependence of heavy fraction the maximum is observed at A=132, that confirms a hypothesis on the influence of the closed-shell effects at the magic numbers of Z=50 and N=82. Assuming the existence of different barrier values for two models of the fission the ratio of symmetric and asymmetric fission yields are analyzed in the statistical model. It is shown that the barrier difference for two modes of fission is 1.3-1.4 MeV, which is in good agreement with the model of two fission modes.
Fission fragment angular distributions in proton-induced fission of 209Bi (p,f) and 197Au (p,f)
International Nuclear Information System (INIS)
Soheily, S.; Noshad, H.; Lamehi-Rashti, M.
2002-01-01
The fission fragment angular distributions have been measured for proton-induced fission of 209 B i and 197 A u nuclei using surface barrier detectors at several energies between 25 MeV and 30 MeV. The experimental anisotropies are found to be in agreement with the predictions of the Standard Saddle-Point Statistical Model. The fission cross sections of 209 B i and 197 A u nuclei were also measured and compared with the previous works
Polarization and alignment of nucleus fission fragments
International Nuclear Information System (INIS)
Barabanov, A.L.; Grechukhin, D.P.
1987-01-01
Correlation of fragment orientation with orientation axis of fissile nucleus and with n-vector f vector of fragment divergence is considered. Estimations of polarization and alignment of fission fragments of preliminarily oriented nuclei in correlation (with n-vector f recording) and integral (with n-vector f averaging) experiments were conducted. It is shown that high sensitivity of polarization and fragment alignment to the character of nucleus movement at the stage of descent from barrier to rupture point exists
Directory of Open Access Journals (Sweden)
Rita B. Figueira
2015-04-01
Full Text Available Previous studies have shown that the barrier effect and the performance of organic-inorganic hybrid (OIH sol-gel coatings are highly dependent on the coating deposition method as well as on the processing conditions. However, studies on how the coating deposition method influences the barrier properties in alkaline environments are scarce. The aim of this experimental research was to study the influence of experimental parameters using the dip-coating method on the barrier performance of an OIH sol-gel coating in contact with simulated concrete pore solutions (SCPS. The influence of residence time (Rt, a curing step between each dip step and the number of layers of sol-gel OIH films deposited on hot-dip galvanized steel to prevent corrosion in highly alkaline environments was studied. The barrier performance of these OIH sol-gel coatings, named U(400, was assessed in the first instants of contact with SCPS, using electrochemical impedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings in SCPS was monitored during eight days by macrocell current density. The morphological characterization of the surface was performed by Scanning Electronic Microscopy before and after exposure to SCPS. Glow Discharge Optical Emission Spectroscopy was used to investigate the thickness of the U(400 sol-gel coatings as a function of the number of layers deposited with and without Rt in the coatings thickness.
Recent progress in fission at saddle point and scission point
International Nuclear Information System (INIS)
Blons, J.; Paya, D.; Signarbieux, C.
High resolution measurements of 230 Th and 232 Th fission cross sections for neutrons exhibit a fine structure. Such a structure is interpreted as a superposition of two rotational bands in the third, asymmetric, well of the fission barrier. The fragment mass distribution in the thermal fission of 235 U and 233 U does not show any even-odd effect, even at the highest kinetic energies. This is the mark of a strong viscosity in the descent from saddle point to scission point [fr
A method for prediction of prompt fission neutron spectra
International Nuclear Information System (INIS)
Grashin, A.F.; Lepeshkin, M.V.
1988-01-01
Three-parameter formula for the prompt-fission-neutron integral spectrum is derived from a thermodynamical model. Two parameters, scission-neutron weight p = 11 % and anisotropy factor for accelerated fragments b = 10 %, are determined from experimental data, the same values being assumed for any type of fission. The thermodynamical theory provides the value of the third parameter, temperature τ, thus prognozing neutron spectrum and average energy with an error about 1 %. (author)
International Nuclear Information System (INIS)
Mikheev, V.L.; Tret'yakova, S.P.; Golovchenko, A.N.; Timofeeva, O.V.; Hussonnois, M.; Le Naour, C.
1998-01-01
The low limit of the 226 Ra spontaneous fission half-life corresponding to T 1/2 ≥ 4 · 10 18 years is measured. The 226 Ra spontaneous fission probability proved to be about 50 times less than the value expected from the known systematics, connecting the ratios of theα-decay and spontaneous fission probabilities with the fissility parameter Z 2 /A. It is shown that the probabilities of spontaneous fission, α-decay and cluster decay can be systematized in the same way according to the difference between the decay products Coulomb energy near the scission point and decay energy Q
The effects of fission gas release on PWR fuel rod design and performance
International Nuclear Information System (INIS)
Leech, W.J.; Kaiser, R.S.
1980-01-01
The purpose of this investigation was to determine the effects of fission gas release on PWR fuel rod design and performance. Empirical models were developed from fission gas release data. Fission gas release during normal operation is a function of burnup. There is little additional fission gas release during anticipated transients. The empirical models were used to evaluate Westinghouse fuel rod designs. It was determined that fission gas release is not a limiting parameter for obtaining rod average burnups in the range of 50,000 to 60,000 MWD/MTU. Fission gas release during anticipated transients has a negligible effect on the margins to rod design limits. (author)
Fineman, Stanley; Dowling, Paul; O'Rourke, Dianne
2013-12-01
Anaphylaxis is life-threatening and requires rapid medical intervention. Knowledge of treatment guidelines and addressing barriers to care are essential for appropriate management. To investigate allergists' self-reported practices in managing patients at risk for anaphylaxis, specifically in following practice parameters for diagnosis, treatment, and appropriate use of epinephrine, and to identify perceived barriers to care. Online questionnaires were distributed to members of the American College of Allergy, Asthma, and Immunology. The US physicians who self-identified as "allergist/immunologist" were eligible to participate. The first 500 completed questionnaires were analyzed. Nearly all (≥95%) reported adherence to practice parameters in prescribing an epinephrine auto-injector and instructing patients on its use, taking a detailed allergy history, counseling patients on avoidance measures, and educating patients on the signs and symptoms of anaphylaxis. More than 90% stated they determined the best diagnostic procedures to identify triggers and coordinated laboratory and allergy testing. Adherence to practice parameters was less robust for providing patients with written action plans and in-office anaphylaxis preparedness. Perceived barriers to care included a significant proportion of patients who were uncomfortable using epinephrine auto-injectors and inadequate knowledge of anaphylaxis among referral physicians. Allergists overwhelmingly adhere to practice parameter recommendations for the treatment and management of anaphylaxis, including appropriate use of epinephrine as first-line treatment, educating patients, and testing to diagnose anaphylaxis and identify its triggers. Opportunities for improvement include preparing staff and patients for anaphylactic events, providing written action plans, and improving knowledge of referring physicians. Copyright © 2013 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights
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.
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
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.)
International Nuclear Information System (INIS)
Ramamurthy, V.S.; Prakash, M.; Kapoor, S.
1976-01-01
It is found that for level schemes obtained from a folded Yukawa potential, the Strutinsky smearing procedure for the evaluation of the shell correction to the total potential energy of nuclei does not lead to a unique value for nuclear shapes near and beyond the outer fission barrier deformations and consequently introduces uncertainties in the relative fission barrier heights. (author)
Analytic description of the fusion and fission processes through compact quasi-molecular shapes
International Nuclear Information System (INIS)
Royer, G.; Normand, C.; Druet, E.
1997-01-01
Recent studies have shown that the characteristics of the entrance and exit channels through compact quasi-molecular shapes are compatible with the experimental data on fusion, fission and cluster radioactivity when the deformation energy is determined within a generalized liquid drop model. Analytic expressions allowing to calculate rapidly the main characteristics of this deformation path through necked shapes with quasi-spherical ends are presented now; namely formulas for the fusion and fission barrier heights, the fusion barrier radius, the symmetric fission barriers and the proximity energy. (author)
Methods to Collect, Compile, and Analyze Observed Short-lived Fission Product Gamma Data
Energy Technology Data Exchange (ETDEWEB)
Finn, Erin C.; Metz, Lori A.; Payne, Rosara F.; Friese, Judah I.; Greenwood, Lawrence R.; Kephart, Jeremy D.; Pierson, Bruce D.; Ellis, Tere A.
2011-09-29
A unique set of fission product gamma spectra was collected at short times (4 minutes to 1 week) on various fissionable materials. Gamma spectra were collected from the neutron-induced fission of uranium, neptunium, and plutonium isotopes at thermal, epithermal, fission spectrum, and 14-MeV neutron energies. This report describes the experimental methods used to produce and collect the gamma data, defines the experimental parameters for each method, and demonstrates the consistency of the measurements.
Electronic parameters of high barrier Au/Rhodamine-101/n-Inp Schottky diode with organic ınterlayer
International Nuclear Information System (INIS)
Güllü, Ö.; Aydoğan, S.; Türüt, A.
2012-01-01
In this work, we present that Rhodamine-101 (Rh-101) organic molecules can control the electrical characteristics of conventional Au/n-InP metal–semiconductor contacts. An Au/n-InP Schottky junction with Rh-101 interlayer has been formed by using a simple cast process. A potential barrier height as high as 0.88 eV has been achieved for Au/Rh-101/n-InP Schottky diodes, which have good current–voltage (I–V) characteristics. This good performance is attributed to the effect of formation of interfacial organic thin layer between Au and n-InP. By using capacitance-voltage measurement of the Au/Rh-101/n-InP Schottky diode the diffusion potential and the barrier height have been calculated as 0.78 V and 0.88 eV, respectively. From the I–V measurement of the diode under illumination, short circuit current and open circuit voltage have been extracted as 1.70 μA and 240 mV, respectively.
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
Rieprich, J.; Winterfeldt, M.; Kernke, R.; Tomm, J. W.; Crump, P.
2018-03-01
High power broad area diode lasers with high optical power density in a small focus spot are in strong commercial demand. For this purpose, the beam quality, quantified via the beam parameter product (BPP), has to be improved. Previous studies have shown that the BPP is strongly affected by current-induced heating and the associated thermal lens formed within the laser stripe. However, the chip structure and module-assembly related factors that regulate the size and the shape of the thermal lens are not well known. An experimental infrared thermographic technique is used to quantify the thermal lens profile in diode lasers operating at an emission wavelength of 910 nm, and the results are compared with finite element method simulations. The analysis indicates that the measured thermal profiles can best be explained when a thermal barrier is introduced between the chip and the carrier, which is shown to have a substantial impact on the BPP and the thermal resistance. Comparable results are observed in further measurements of samples from multiple vendors, and the barrier is only observed for junction-down (p-down) mounting, consistent with the barrier being associated with the GaAs-metal transition.
A possible mechanism in heavy ion induced reactions: 'fast fission process'
International Nuclear Information System (INIS)
Borderie, B.; Gardes, D.; Berlanger, M.
1980-01-01
The influence of the orbital angular momentum l on the mass distribution of fission fragments is studied, both on previously available data on heavy ion induced fission and in new specifically planned experiments: systems 40 Ar + 165 Ho and 24 Mg + 181 Ta at bombarding energies ranging from 180 up to 391 MeV and leading to the same fissionning nucleus 205 At wigh different l distributions. When l values corresponding to a vanished fission barrier are reached, the mass distribution broadens. This suggest the existence of a specific process, 'fast fission', at l-values leading to compound nucleus formation and deep inelastic collisions, respectively. This process and its conditions of occurrence are discussed; of special interest are the correlated differences between the limitations to the fission cross-section and the fission mass distributions broadenings, respectively, for the Ar + Ho and Mg + Ta systems
Korponyai, Csilla; Szél, Edit; Behány, Zoltán; Varga, Erika; Mohos, Gábor; Dura, Ágnes; Dikstein, Shabtay; Kemény, Lajos; Erős, Gábor
2017-02-08
Glycerol and xylitol hydrate the skin and improve its barrier function over a short period. We studied the effects of glycerol and xylitol on the physiological properties and morphology of the skin after longer-term application. Twelve volunteers with dry skin were examined. Three areas on the arms were determined. Area 1 served as untreated control. The vehicle was applied to area 2, while area 3 was treated twice daily with a formulation containing glycerol (5%) and xylitol (5%) for 14 days. Transepidermal water loss (TEWL), hydration and biomechanical properties of the skin were monitored. Biopsies were taken for routine histology and immunohistochemistry for filaggrin and matrix metalloproteinase-1 (MMP-1). The polyols increased the skin hydration and protein quantity of filaggrin, elevated the interdigitation index, decreased the TEWL and improved the biomechanical properties of the skin, but did not change the protein expression of MMP-1. A combination of glycerol and xylitol can be useful additional therapy for dry skin.
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)
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.
Laser solenoid fusion--fission design
International Nuclear Information System (INIS)
Steinhauer, L.C.; Taussig, R.T.
1976-01-01
The dependence of breeding performance on system engineering parameters is examined for laser solenoid fusion-fission reactors. Reactor performance is found to be relatively insensitive to most of the engineering parameters, and compact designs can be built based on reasonable technologies. Point designs are described for the prototype series of reactors (mid-term technologies) and for second generation systems (advanced technologies). It is concluded that the laser solenoid has a good probability of timely application to fuel breeding needs
International Nuclear Information System (INIS)
Bernard, Remi
2012-01-01
Fission is a complex process which highlights many nuclear properties. A major challenge in theoretical nuclear physics nowadays is the development of a consistent approach able to describe on the same footing the whole fission process, i.e. properties of the fissioning system, fission dynamics and fission fragment distributions. As a first step, a microscopic time-dependent and quantum mechanical formalism has been developed based on the Gaussian Overlap Approximation of the Generator Coordinate Method with the adiabatic approximation. Pioneering results obtained for the low-energy fission of 238 U encouraged us to perform new studies of fission along these lines with some additional improvements. For instance, at higher energies, a few MeV above the barrier, the adiabatic approximation doesn't seem valid anymore, and intrinsic excitations have to be taken into account. For that purpose, a new theoretical framework called the Schroedinger Collective Intrinsic Model (SCIM) has been developed, which allows in a microscopic way a simultaneous coupling of single particle and collective degrees of freedom. Such an approach is based on a generalized Generator Coordinate Method (GCM), where the general GCM ansatz of the nuclear wave function is extended by a few excited configurations. Indeed, one considers as generating wave functions not only Hartree Fock Bogolyubov ground-state configurations with different values for the collective generator coordinate but also two quasi particle excited states. Such an approach has the advantage of describing in a completely quantum-mechanical fashion and without phenomenological parameters the coupling of quasi-particle degrees of freedom to the collective motion of the nucleons. In this talk, I will focus on the derivation of the newly developed SCIM formalism. I will first discuss the generalized Hill and Wheeler equation and its transformation into a non local Schroedinger equation by inverting the expansion of the overlap
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
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
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
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)
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
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.
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
Fission-product SiC reaction in HTGR fuel
International Nuclear Information System (INIS)
Montgomery, F.
1981-01-01
The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels
Recent advances in heavy-ion-induced fission
International Nuclear Information System (INIS)
Plasil, F.
1984-01-01
Three topics are discussed. The first deals with results that have been published recently on angular-momentum-dependent fission barriers. They are discussed because of the significance that we attach to them. We feel that, after a decade of study and controversy, we have arrived at a quantitative understanding of the competition between heavy-ion-induced fission and particle emission from compound nuclei at relatively low bombarding energies. The second topic concerns the extension of our heavy-ion-induced fission studies to higher energies. It is clear that in this regime the effects, both of fission following incomplete fusion and of extra-push requirements, need to be considered. Finally, discussed are our recent conclusions concerning the fissionlike decay of products from reactions between two 58 Ni nuclei at an incident energy, E/A, of 15.3 MeV, as well as the impact of our findings on the conclusions drawn from previous, similar measurements. 39 references
Malinina, A. A.; Starikovskaya, S. M.; Malinin, A. N.
2015-01-01
Spectral and electrical characteristics of atmospheric-pressure nanosecond barrier discharge plasma in a HgBr2/Kr/He mixture have been investigated. The discharge was initiated by positive 10-kV voltage pulses with a rise time of 4 ns and a half-amplitude duration of 28 ns. Emission from exciplex HgBr ( B 2Σ{1/2/+} - X 2Σ{1/2/+}) and KrBr ( B 2Σ{1/2/+} - X 2Σ{1/2/+}, C3/2-AΠ1/2, D1/2-AΠ1/2) molecules have been studied. From the time evolution of the B-X transition spectra of the HgBr molecule (502 nm) and KrBr molecule (207 nm), a mechanism of the formation of the exciplex molecules in the nanosecond discharge has been deduced. The distributions of the energies and rates of the processes responsible for emission from HgBr and KrBr molecules have been analyzed by numerically solving the Boltzmann equation for the electron distribution function. Experiments have confirmed the possibility of optimizing the voltage supply pulse for maximizing the efficiency of simultaneous emission in the UV and visible (green) spectral ranges from atmospheric-pressure discharge in the HgBr2/Kr/He mixture.
A new mechanistic and engineering fission gas release model for a uranium dioxide fuel
International Nuclear Information System (INIS)
Lee, Chan Bock; Yang, Yong Sik; Kim, Dae Ho; Kim, Sun Ki; Bang, Je Geun
2008-01-01
A mechanistic and engineering fission gas release model (MEGA) for uranium dioxide (UO 2 ) fuel was developed. It was based upon the diffusional release of fission gases from inside the grain to the grain boundary and the release of fission gases from the grain boundary to the external surface by the interconnection of the fission gas bubbles in the grain boundary. The capability of the MEGA model was validated by a comparison with the fission gas release data base and the sensitivity analyses of the parameters. It was found that the MEGA model correctly predicts the fission gas release in the broad range of fuel burnups up to 98 MWd/kgU. Especially, the enhancement of fission gas release in a high-burnup fuel, and the reduction of fission gas release at a high burnup by increasing the UO 2 grain size were found to be correctly predicted by the MEGA model without using any artificial factor. (author)
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.
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 ...
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
Study of nuclear photoexcitation mechanisms in the Δ region (3,3) through the fission
International Nuclear Information System (INIS)
Arruda Neto, J.D.T.
1986-01-01
Experimental results and conclusions obtained for the Bi sup(209) electro and photofission in an energy range between the fission barrier (∼ Mev) and the neighbourhood of the delta peak are presented. (E.G.)
Neutron induced fission of U isotopes up to 100 MeV
International Nuclear Information System (INIS)
Lestone, J.P.; Gavron, A.
1993-01-01
We have developed a statistical model description of the neutron induced fission of U isotopes using densities of intrinsic states and spin cut off parameters obtained directly from appropriate Nilsson model single particle levels. The first chance fission cross sections are well reproduced when the rotational contributions to the nuclear level densities are taken into account. In order to fit the U(n,f) cross sections above the threshold of second chance fission, we need to: (1) assume that the triaxial level density enhancement is washed out at an excitation energy of ∼7 MeV above the triaxial barriers with a width of ∼1 MeV, implying a γ deformation for the first barriers of 10 degree < γ < 20 degree; and (2) include pre-equilibrium particle emission in the calculations. Above an incoming neutron kinetic energy of ∼17 MeV our statistical model U(n,f) cross sections increasingly overestimate the experimental data when so called ''good'' optical model potentials are used to calculate the compound nucleus formation cross sections. This is not surprising since at these high energies little data exists on the scattering of neutrons to help guide the choice of optical model parameters. A satisfactory reproduction of all the available U(n,f) cross sections above 17 MeV is obtained by a simple scaling of our calculated compound nucleus formation cross sections. This scaling factor falls from 1.0 at 17 MeV to 0.82 at 100 MeV
On the safety of conceptual fusion-fission hybrid reactors
International Nuclear Information System (INIS)
Kastenberg, W.E.; Okrent, D.; Badham, V.; Caspi, S.; Chan, C.K.; Ferrell, W.J.; Frederking, T.H.K.; Grzesik, J.; Lee, J.Y.; McKone, T.E.; Pomraning, G.C.; Ullman, A.Z.; Ting, T.D.; Kim, Y.I.
1979-01-01
A preliminary examination of some potential safety questions for conceptual fusion-fission hybrid reactors is presented in this paper. The study and subsequent analysis was largely based upon one design, a conceptual mirror fusion-fission reactor, operating on the deuterium-tritium plasma fusion fuel cycle and the uranium-plutonium fission fuel cycle. The major potential hazards were found to be: (a) fission products, (b) actinide elements, (c) induced radioactivity, and (d) tritium. As a result of these studies, it appears that highly reliable and even redundent decay heat removal must be provided. Loss of the ability to remove decay heat results in melting of fuel, with ultimate release of fission products and actinides to the containment. In addition, the studies indicate that blankets can be designed which will remain subcritical under extensive changes in both composition and geometry. Magnet safety and the effects of magnetic fields on thermal parameters were also considered. (Auth.)
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
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
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
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)
Lamprecht, Manfred; Bogner, Simon; Steinbauer, Kurt; Schuetz, Burkhard; Greilberger, Joachim F; Leber, Bettina; Wagner, Bernhard; Zinser, Erwin; Petek, Thomas; Wallner-Liebmann, Sandra; Oberwinkler, Tanja; Bachl, Norbert; Schippinger, Gert
2015-01-01
Zeolites are crystalline compounds with microporous structures of Si-tetrahedrons. In the gut, these silicates could act as adsorbents, ion-exchangers, catalysts, detergents or anti-diarrheic agents. This study evaluated whether zeolite supplementation affects biomarkers of intestinal wall permeability and parameters of oxidation and inflammation in aerobically trained individuals, and whether it could improve their performance. In a randomized, double-blinded, placebo controlled trial, 52 endurance trained men and women, similar in body fat, non-smokers, 20-50 years, received 1.85 g of zeolite per day for 12 weeks. Stool samples for determination of intestinal wall integrity biomarkers were collected. From blood, markers of redox biology, inflammation, and DNA damage were determined at the beginning and the end of the study. In addition, VO2max and maximum performance were evaluated at baseline and after 12 weeks of treatment. For statistical analyses a 2-factor ANOVA was used. At baseline both groups showed slightly increased stool zonulin concentrations above normal. After 12 weeks with zeolite zonulin was significantly (p zeolite group. There were no significant changes observed in the other measured parameters. Twelve weeks of zeolite supplementation exerted beneficial effects on intestinal wall integrity as indicated via decreased concentrations of the tight junction modulator zonulin. This was accompanied by mild anti-inflammatory effects in this cohort of aerobically trained subjects. Further research is needed to explore mechanistic explanations for the observations in this study.
Fission decay properties of ultra neutron-rich uranium isotopes
Indian Academy of Sciences (India)
in the chain of neutron-rich uranium isotopes is examined here. The neutron ... mean field theory, this nucleus is shown to undergo exotic decay mode of thermal neu- .... For 250U with a fission barrier of 4.3 MeV [5], we obtain the value of.
Prompt muon-induced fission: A probe for nuclear friction in large-amplitude collective motion
International Nuclear Information System (INIS)
Oberacker, V.E.; Umar, A.S.; Wells, J.C.; Strayer, M.R.; Maruhn, J.A.; Reinhard, P.G.
1998-01-01
Excited muonic atoms in the actinide region may induce prompt fission by inverse internal conversion, i.e. the excitation energy of the muonic atom is transferred to the nucleus. The authors solve the time dependent Dirac equation for the muonic spinor wave function in the Coulomb field of the fissioning nucleus on a 3-dimensional lattice and demonstrate that the muon attachment probability to the light fission fragment is a measure of the nuclear energy dissipation between the outer fission barrier and the scission point
Verbeke, Jérôme M.; Petit, Odile; Chebboubi, Abdelhazize; Litaize, Olivier
2018-01-01
Fission modeling in general-purpose Monte Carlo transport codes often relies on average nuclear data provided by international evaluation libraries. As such, only average fission multiplicities are available and correlations between fission neutrons and photons are missing. Whereas uncorrelated fission physics is usually sufficient for standard reactor core and radiation shielding calculations, correlated fission secondaries are required for specialized nuclear instrumentation and detector modeling. For coincidence counting detector optimization for instance, precise simulation of fission neutrons and photons that remain correlated in time from birth to detection is essential. New developments were recently integrated into the Monte Carlo transport code TRIPOLI-4 to model fission physics more precisely, the purpose being to access event-by-event fission events from two different fission models: FREYA and FIFRELIN. TRIPOLI-4 simulations can now be performed, either by connecting via an API to the LLNL fission library including FREYA, or by reading external fission event data files produced by FIFRELIN beforehand. These new capabilities enable us to easily compare results from Monte Carlo transport calculations using the two fission models in a nuclear instrumentation application. In the first part of this paper, broad underlying principles of the two fission models are recalled. We then present experimental measurements of neutron angular correlations for 252Cf(sf) and 240Pu(sf). The correlations were measured for several neutron kinetic energy thresholds. In the latter part of the paper, simulation results are compared to experimental data. Spontaneous fissions in 252Cf and 240Pu are modeled by FREYA or FIFRELIN. Emitted neutrons and photons are subsequently transported to an array of scintillators by TRIPOLI-4 in analog mode to preserve their correlations. Angular correlations between fission neutrons obtained independently from these TRIPOLI-4 simulations, using
Elastocapillary Instability in Mitochondrial Fission
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.
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)
Laser driven fusion fission hybrids
International Nuclear Information System (INIS)
Hansen, L.F.; Maniscalco, J.A.
1977-11-01
The role of the fusion-fission hybrid reactor (FFHR) as a fissile fuel and/or power producer is discussed. As long range options to supply the world energy needs, hybrid-fueled thermal-burner reactors are compared to liquid metal fast breeder reactors (LMFBR). A discussion of different fuel cycles (thorium, depleted uranium, and spent fuel) is presented in order to compare the energy multiplication, the production of fissile fuel, the laser efficiency and pellet gain requirements of the hybrid reactor. Lawrence Livermore Laboratory (LLL) has collaborated with Bechtel Corporation and with Westinghouse in two engineering design studies of laser fusion driven hybrid power plants. The hybrid designs which have resulted from these two studies are briefly described and analyzed by considering operational parameters, such as energy multiplication, power density, burn-up and plutonium production as a function time
Evidence of pair correlations in actinide neutron-induced fission cross sections
International Nuclear Information System (INIS)
Maslov, V.M.
2000-01-01
It is shown that irregularities in fission cross sections in MeV incident neutron energy region could be attributed to the interplay of few-quasiparticle excitations in the level density of the fissioning and residual nuclei. It is suggested the intrinsic quasiparticle state density modelling approach both at stable and saddle-point deformations. The experimental manifestation of few-quasiparticle irregularities in the level density depends on the fission barrier structure and internal excitation energy at the saddle point, corresponding to the higher barrier hump. The explicit evidence is observed in case of fissile and non-fissile target nuclides [ru
International Nuclear Information System (INIS)
Voronov, G S; Voronova, E V; Akulina, D K; Gladkov, G A
2006-01-01
Boronization of the vacuum chamber of the L-2M stellarator has resulted in modification of the electron temperature profile. In particular, a well-defined jump in the electron temperature to T e ∼ 100 eV in a narrow region Δr/r ∼ 0.05 is observed in the temperature profile at the plasma edge. In the present paper, the value and shape of the jump in T e are studied at different values of plasma parameters and ECR heating power. A jump in T e is absent at a power of P ∼ 100 kW, whereas at P ∼ 200 kW the electron temperature drops from 150 eV to zero within Δr ∼ 0.5 cm. The value of threshold power for the formation of a jump in T e at n e ∼ 1.7 x 10 19 m -3 lies within the range P ∼ 100-160 kW. In terms of power per particle this power threshold is P/V/N e ∼ 0.2-0.3 Mw/m 3 /10 19 m -3 , the value of which coincides with threshold power for ETB formation found recently in the CHS stellarator. When the helical-field strength is 25% or 50% below its standard value, a jump in T e at the plasma edge in L-2M is absent
Correlation properties of delayed neutrons from fast neutron induced fission
International Nuclear Information System (INIS)
Piksaikin, V.M.; Isaev, S.G.
1998-01-01
The experimental studies of the energy dependence of the delayed neutron parameters for various fissioning systems has shown that the behavior of a some combination of delayed neutron parameters (group relative abundances a i and half lives T i ) has a similar features. On the basis of this findings the systematics of delayed neutron experimental data for thorium, uranium, plutonium and americium isotopes have been investigated with the purpose to find a correlation of DN parameters with characteristics of fissioning system as well as a correlation between the delayed neutron parameters themselves. Below we will present the preliminary results which were obtained during this study omitting the physics interpretation of the results. (author)
Fission product behavior in the Molten Salt Reactor Experiment
International Nuclear Information System (INIS)
Compere, E.L.; Kirslis, S.S.; Bohlmann, E.G.; Blankenship, F.F.; Grimes, W.R.
1975-10-01
Essentially all the fission product data for numerous and varied samples taken during operation of the Molten Salt Reactor Experiment or as part of the examination of specimens removed after particular phases of operation are reported, together with the appropriate inventory or other basis of comparison, and relevant reactor parameters and conditions. Fission product behavior fell into distinct chemical groups. Evidence for fission product behavior during operation over a period of 26 months with 235 U fuel (more than 9000 effective full-power hours) was consistent with behavior during operation using 233 U fuel over a period of about 15 months (more than 5100 effective full-power hours)
Description of light charged particle emission in ternary fission
International Nuclear Information System (INIS)
Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kuklin, S. N.; Scheid, W.
2010-01-01
We consider the motion of three fragments starting from the scission point of ternary system. In the alpha-accompanied ternary fission the initial conditions are not the free parameters and determined by minimization of potential energy at scission point. In the trajectory calculations the angular distribution and mean value of the kinetic energy of the alpha-particles are well described in the spontaneous ternary fission of 252 Cf. In the Be- and C-accompanied ternary fission we found that the emission of the third particle occurs from one of the heavy fragments after their separation. (authors)
Matching of dense plasma focus devices with fission reactors
International Nuclear Information System (INIS)
Harms, A.A.; Heindler, M.
1978-01-01
The potential role of dense plasma focus devices as compact neutron sources for fissile fuel breeding in conjunction with existing fission reactors is considered. It is found that advanced plasma focus devices can be used effectively in conjunction with neutronically efficient fission reactors to constitute ''self-sufficient'' breeders. Correlations among the various parameters such as the power output and conversion ratio of the fission reactor with the neutron yield and capacitor bank energy of the dense plasma focus device are presented and discussed
Double-energy double-velocity measurement system for fission fragments and its application
International Nuclear Information System (INIS)
Kanno, Ikuo
1987-10-01
A new system of double-energy double-velocity (DEDV) measurement for fission fragments has been developed. In this system, the energies of fission fragments are measured by silicon surface barrier detectors (SSB) and the velocities by the time-of-flight (TOF) method utilizing thin film detectors (TFD) as start detectors and SSBs as stop detectors of TOF. Theoretical and experimental studies on TFDs and SSBs have been performed before the construction of the DEDV measurement system. The TFD consists of a thin plastic scintillator film and light guide. The author proposes a new model of the luminescence production in a scintillator film. This model takes into account the thickness of the scintillator film and uses only one parameter. The calculated TFD response to charged particles shows good agreement with other experiments. The dependence of the TFD response to the thickness of the scintillator film has been studied experimentally and analyzed by the luminescence production model. The results of this analysis shows the validity of the luminescence production model. The time resolution of the DEDV measurement system using TFDs and SSBs was 133 ps. As an application of this system, the DEDV measurement for the thermal neutron-induced fission of 233 U has been carried out at the super mirror neutron guide tube facility of Kyoto University Reactor (KUR). The energy and velocity of each fission fragment have been stored on magnetic disk event by event in a list mode. The analyzed results of masses, energies and velocities of light and heavy fragments agree well with other authors' works. The value of the total neutron emission number is 2.53 and shows good agreement within experimental error, with the JENDL-2 value, 2.49. The light fragment shows a slightly greater number of neutrons emitted than the other works. This suggests the possibility of larger deformation of light fragments at the scission point. (author)
Energy Technology Data Exchange (ETDEWEB)
Weissfloch, R
1973-07-15
The fuel elements of high-temperature reactors, coated with pyrolitic carbon and covered with graphite, release fission products like all other fuel elements. Because of safety reasons, the rate of this release has to be kept low and has also to be predictable. Measured values from irradiation tests and from post-irradiation tests about the actual release of different fission products are presented. The physical and chemical mechanism, which determines the release, is extraordinarily complex and in particular not clearly defined. Because of the mentioned reasons, a simplified calculation model was developed, which only considers the release-mechanisms phenomenologically. This calculation model coincides very well in its results with values received in experiments until now. It can be held as an interim state on the way to a complete theory.
International Nuclear Information System (INIS)
Weissfloch, R.
The fuel elements of High-Temperature Reactors, coated with pyrolitic carbon and covered with graphite, release fission products like all other fuel elements. Because of safety reasons the rate of this release has to be kept low and has also to be predictable. Measured values from irradiation tests and from post-irradiation tests about the actual release of different fission products are present. The physical and chemical mechanism, which determines the release, is extraordinarily complex and in particular not clearly defined. Because of the mentioned reasons a simplified calculation model was developed, which only considers the release-mechanisms phenomenologically. This calculation model coincides very well in its results with values received in experiments until now. It can serve as an interim state on the way to a complete theory. (U.S.)
Low-energy nuclear fission and our understanding of the nucleus
International Nuclear Information System (INIS)
Hall, H.L.; Hoffman, D.C.
1990-01-01
The interactions between experimental discoveries in low-energy nuclear fission and the theoretical understanding of the structure of the nucleus are reviewed. The history of this synergistic relationship begins with the discovery of fission, the development of the liquid-drop model and the experimental evidence for magic numbers, continues through the development of the shell model, the experimental discovery of shape isomerism, the double-humped fission barrier the spontaneous fission half-life disaster, the discovery of symmetric mass division in spontaneous fission and theoretical treatments based on different paths to scission. It concludes with a brief review of current experimental and theoretical understanding of low-energy fission and the prospects for future developments. (author) 150 refs.; 5 figs.; 1 tab
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)
Fusion-fission dynamics and perspectives of future experiments
International Nuclear Information System (INIS)
Zagrebaev, V.I.; Itkis, M.G.; Oganessian, Yu.Ts.
2003-01-01
The paper is focused on reaction dynamics of superheavy-nucleus formation and decay at beam energies near the Coulomb barrier. The aim is to review the things we have learned from recent experiments on fusion-fission reactions leading to the formation of compound nuclei with Z ≥ 102 and from their extensive theoretical analysis. Major attention is paid to the dynamics of formation of very heavy compound nuclei taking place in strong competition with the process of fast fission (quasifission). The choice of collective degrees of freedom playing a fundamental role and finding the multidimensional driving potential and the corresponding dynamic equation regulating the whole process are discussed. A possibility of deriving the fission barriers of superheavy nuclei directly from performed experiments is of particular interest here. In conclusion, the results of a detailed theoretical analysis of available experimental data on the 'cold' and 'hot' fusion-fission reactions are presented. Perspectives of future experiments are discussed along with additional theoretical studies in this field needed for deeper understanding of the fusion-fission processes of very heavy nuclear systems
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.
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)
[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
Study of electron-capture delayed fission in Am-232
International Nuclear Information System (INIS)
Kreek, S.A.; Hall, H.L.; Hoffman, D.C.; Strellis, D.; Gregorich, K.E.
1996-01-01
An automated x-ray-fission coincidence system was designed and constructed by LLNL and Lawrence Berkeley National Laboratory (LBNL) for use inside the Gammasphere high efficiency gamma-ray detector array at LBNL. The x-ray-fission coincidence apparatus detection station consists of two surface barrier detectors (for detection of fission fragments) and two high-purity Ge (HPGe) planar x-ray detectors (for measurement of x-rays and low-energy gamma rays). The detection station is placed inside Gammasphere at the 88-Inch Cyclotron at LBNL and used in conjunction with Gammasphere to measure the x-rays, low-energy gamma-rays and fission fragments resulting from the ECDF process. A series of collaborative experiment between LLNL, LBNL, and LANL utilizing various components of the x-ray-fission coincidence apparatus to measure x-rays and gamma-rays in the decay of a stationary 252 Cf source were performed to test the various components of the x-ray-fission coincidence apparatus. The test experiments have been completed and the data is currently being analyzed by LBNL. Preliminary test results indicate that the system performed better than expected (e.g., the x-ray detectors performed better than expected with no evidence of microphonic noise that would reduce the photon energy resolution)
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
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
Backtracing neutron analysis in the fusion-fission dynamics study
International Nuclear Information System (INIS)
Brennand, E. de Goes; Hanappe, F.; Stuttge, L.
2001-01-01
A new method for the analysis of multi parametric experimental data is used in the study of the dynamics of the fission process for the compound system 126 Ba. We apply this method to obtain the correlation between thermal energy related to the neutron total multiplicity and the correlation between pre-scission neutron and pos-scission neutron multiplicities. The results obtained are interpreted into the framework of a dynamical model. From this interpretation we have access to the following information: the friction intensity which drives the dynamical evolution of the system; the initial deformation of the compound system; the barrier evolution with temperature and angular momentum, and fission times. (author)
Modelling animal group fission using social network dynamics.
Directory of Open Access Journals (Sweden)
Cédric Sueur
Full Text Available Group life involves both advantages and disadvantages, meaning that individuals have to compromise between their nutritional needs and their social links. When a compromise is impossible, the group splits in order to reduce conflict of interests and favour positive social interactions between its members. In this study we built a dynamic model of social networks to represent a succession of temporary fissions involving a change in social relations that could potentially lead to irreversible group fission (i.e. no more group fusion. This is the first study that assesses how a social network changes according to group fission-fusion dynamics. We built a model that was based on different parameters: the group size, the influence of nutritional needs compared to social needs, and the changes in the social network after a temporary fission. The results obtained from this theoretical data indicate how the percentage of social relation transfer, the number of individuals and the relative importance of nutritional requirements and social links influence the average number of days before irreversible fission occurs. The greater the nutritional needs and the higher the transfer of social relations during temporary fission, the fewer days will be observed before an irreversible fission. It is crucial to bridge the gap between the individual and the population level if we hope to understand how simple, local interactions may drive ecological systems.
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
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.
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)
Fission yield measurements at IGISOL
Lantz, M.; Al-Adili, A.; Gorelov, D.; Jokinen, A.; Kolhinen, V. S.; Mattera, A.; Moore, I.; Penttilä, H.; Pomp, S.; Prokofiev, A. V.; Rakopoulos, V.; Rinta-Antila, S.; Simutkin, V.; Solders, A.
2016-06-01
The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.
Fission yield measurements at IGISOL
Directory of Open Access Journals (Sweden)
Lantz M.
2016-01-01
Full Text Available The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f and Th(p,f have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.
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.)
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
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.
Fission yield calculation using toy model based on Monte Carlo simulation
International Nuclear Information System (INIS)
Jubaidah; Kurniadi, Rizal
2015-01-01
Toy model is a new approximation in predicting fission yield distribution. Toy model assumes nucleus as an elastic toy consist of marbles. The number of marbles represents the number of nucleons, A. This toy nucleus is able to imitate the real nucleus properties. In this research, the toy nucleons are only influenced by central force. A heavy toy nucleus induced by a toy nucleon will be split into two fragments. These two fission fragments are called fission yield. In this research, energy entanglement is neglected. Fission process in toy model is illustrated by two Gaussian curves intersecting each other. There are five Gaussian parameters used in this research. They are scission point of the two curves (R c ), mean of left curve (μ L ) and mean of right curve (μ R ), deviation of left curve (σ L ) and deviation of right curve (σ R ). The fission yields distribution is analyses based on Monte Carlo simulation. The result shows that variation in σ or µ can significanly move the average frequency of asymmetry fission yields. This also varies the range of fission yields distribution probability. In addition, variation in iteration coefficient only change the frequency of fission yields. Monte Carlo simulation for fission yield calculation using toy model successfully indicates the same tendency with experiment results, where average of light fission yield is in the range of 90fission yield is in about 135
Fission yield calculation using toy model based on Monte Carlo simulation
Energy Technology Data Exchange (ETDEWEB)
Jubaidah, E-mail: jubaidah@student.itb.ac.id [Nuclear Physics and Biophysics Division, Department of Physics, Bandung Institute of Technology. Jl. Ganesa No. 10 Bandung – West Java, Indonesia 40132 (Indonesia); Physics Department, Faculty of Mathematics and Natural Science – State University of Medan. Jl. Willem Iskandar Pasar V Medan Estate – North Sumatera, Indonesia 20221 (Indonesia); Kurniadi, Rizal, E-mail: rijalk@fi.itb.ac.id [Nuclear Physics and Biophysics Division, Department of Physics, Bandung Institute of Technology. Jl. Ganesa No. 10 Bandung – West Java, Indonesia 40132 (Indonesia)
2015-09-30
Toy model is a new approximation in predicting fission yield distribution. Toy model assumes nucleus as an elastic toy consist of marbles. The number of marbles represents the number of nucleons, A. This toy nucleus is able to imitate the real nucleus properties. In this research, the toy nucleons are only influenced by central force. A heavy toy nucleus induced by a toy nucleon will be split into two fragments. These two fission fragments are called fission yield. In this research, energy entanglement is neglected. Fission process in toy model is illustrated by two Gaussian curves intersecting each other. There are five Gaussian parameters used in this research. They are scission point of the two curves (R{sub c}), mean of left curve (μ{sub L}) and mean of right curve (μ{sub R}), deviation of left curve (σ{sub L}) and deviation of right curve (σ{sub R}). The fission yields distribution is analyses based on Monte Carlo simulation. The result shows that variation in σ or µ can significanly move the average frequency of asymmetry fission yields. This also varies the range of fission yields distribution probability. In addition, variation in iteration coefficient only change the frequency of fission yields. Monte Carlo simulation for fission yield calculation using toy model successfully indicates the same tendency with experiment results, where average of light fission yield is in the range of 90fission yield is in about 135
Measurement of Fission Product Yields from Fast-Neutron Fission
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.
The LOFA analysis of fusion-fission hybrid reactor
International Nuclear Information System (INIS)
Yu, Z.-C.; Xie, H.
2014-01-01
The fusion-fission hybrid energy reactor can produce energy, breed nuclear fuel, and handle the nuclear waste, etc, with the fusion neutron source striking the subcritical blanket. The passive safety system, consisting of passive residual heat removal system, passive safety injection system and automatic depressurization system, was adopted into the fusion-fission hybrid energy reactor in this paper. Modeling and nodalization of primary loop, passive core cooling system and partial secondary loop of the fusion-fission hybrid energy reactor using RELAP5 were conducted and LOFA (Loss of Flow Accident) was analyzed. The results of key transient parameters indicated that the PRHRs could mitigate the accidental consequence of LOFA effectively. It is also concluded that it is feasible to apply the passive safety system concept to fusion-fission hybrid energy reactor. (author)
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
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
International Nuclear Information System (INIS)
Perez, R.B.; Difilippo, F.C.
1992-01-01
In the late 1960s, Strutinsky's theoretical work on the structure of the fission barrier, together with some new neutron cross-section measurements performed at Saclay and Gel, was called to Gerard de Saussure's attention, and he immediately recognized the importance of those developments. Indeed, de Saussure was quick to note that for neutron energies in the range of the fission barrier potential energy, fission cross-section measurements would yield direct information about the physical properties of the fission barrier. Under his leadership, a set of extensive and precise measurements was performed at the Oak Ridge Electron Linear Accelerator (ORELA) by an international group of researchers, lasting over two decades. Those measurements were unique in many respects: Fission widths were determined for many previously unreported resonances in the subthreshold region, and a detailed study was performed on the physical properties of the fission barrier at high nuclear deformations. In this paper, we report a specific part of the de Saussure's extensive involvement in the area of subthreshold fission physics: the 1979 measurement of the 238 U(n,f) cross ection in the subthreshold and near-subthreshold regions. This cross section was measured in the energy region between 5 eV and 3.5 MeV using a large fission chamber loaded with high-purity 238 U, which had 235 U
Malinina, A. A.; Guivan, N. N.; Shimon, L. L.; Shuaibov, A. K.
2010-09-01
Results are presented from experimental and theoretical studies of the optical characteristics and parameters of the plasma of an atmospheric-pressure barrier discharge excited in a HgBr2: N2: He mixture, which was used as the working medium of a small-size (with a radiation area of 8 cm2) exciplex gas-discharge radiation source. The mean radiation power of 87 mW was achieved at the radiation wavelength λmax = 502 nm. The electron energy distribution function, the transport characteristics, the specific energy lost in the processes involving electrons, the electron temperature and density, and the rate constants of elastic and inelastic electron scattering by the components of the working mixture were calculated as functions of the reduced field E/ N. The plasma of a discharge excited in a HgBr2: N2: He mixture can be used as the working medium of a small-size blue-green radiation source. Such a source can find application in biotechnology, photonics, and medicine and can also be used to manufacture gas-discharge display panels.
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
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...
Cold fission description with constant and varying mass asymmetries
International Nuclear Information System (INIS)
Duarte, S.B.; Rodriguez, O.; Tavares, O.A.P.; Goncalves, M.; Garcia, F.; Guzman, F.
1998-01-01
Different description for varying the mass asymmetry in the fragmentation process are used to calculate the cold fission barrier penetrability. The relevance of the appropriate choice for both the description of the pre-scission phase and inertia coefficient to unify alpha decay, cluster radioactivity, and spontaneous cold fission processes in the same theoretical framework is explicitly shown. We calculate the half-life of all possible partition modes of nuclei of A > 200 following the most recent Mass Table by Audi and Wapstra. It is shown that if one uses the description in which the mass asymmetry is maintained constant during the fragmentation process, the experimental half-life-values and mass yield of 234 U cold fission are satisfactorily reproduced. (author)
International Nuclear Information System (INIS)
Moosavi, K.; Setayeshi, S.; Maragheh, M.Gh.; Ahmadi, S.J.; Kardan, M.R.; Banaem, L.M.
2009-01-01
In this study, an experimental design using artificial neural networks for an optimization on the strontium separation model for fission products (inactive trace elements) is investigated. The goal is to optimize the separation parameters to achieve maximum amount of strontium that is separated from the fission products. The result of the optimization method causes a proper purity of Strontium-89 that was separated from the fission products. It is also shown that ANN may be establish a method to optimize the separation model.
Fission fragment driven neutron source
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.
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.
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
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
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.
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
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
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
Energy Technology Data Exchange (ETDEWEB)
Nishio, Katsuhisa; Yamamoto, Hideki; Kimura, Itsuro; Nakagome, Yoshihiro [Kyoto Univ. (Japan)
1997-03-01
Simultaneous measurement of fission fragments and prompt neutrons following the thermal neutron induced fission of U-235 has been performed in order to obtain the neutron multiplicity (v) and its emission energy ({eta}) against the specified mass (m{sup *}) and the total kinetic energy (TKE). The obtained value of -dv/dTKE(m{sup *}) showed a saw-tooth distribution. The average neutron energy <{eta}>(m{sup *}) had a distribution with a reflection symmetry around the half mass division. The measurement also gave the level density parameters of the specified fragment, a(m{sup *}), and this parameters showed a saw-tooth trend too. The analysis by a phenomenological description of this parameters including the shell and collective effects suggested the existence of a collective motion of the fission fragments. (author)
Fusion-fission in Ar-heavy nuclei collisions
International Nuclear Information System (INIS)
Zaric, Alexandre
1984-01-01
Fusion-fission products have been studied for three reactions: Ar + Au, Ar + Bi and Ar + U (5.25-7.5 MeV/u). By measuring symmetric fragmentation components (fission-like events), cross sections for fusion were deduced and compared with the prediction of static and dynamic models. With increasing projectile energy, the width of the mass distributions strongly increases for the two lighter systems. By contrast, for Ar + U it remains essentially constant at a very large value. These results clearly demonstrate that the large increase of the width of the mass distribution cannot be attributed simply to large values of the angular momentum. However, they can be explained by the occurrence of a different dissipative process, fast fission, which can be expected if there is no barrier to fission. For the reaction Ar + Au, the total kinetic-energy distributions were also studied in detail. In this case fast fission occurs only at high incident energy. The average total kinetic energy (TKE) was found to be constant with increasing energy. (author) [fr
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
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
What can we learn about heavy ion fusion by studying fission angular distributions
International Nuclear Information System (INIS)
Back, B.B.
1984-01-01
Determinations of complete fusion reactions leading to fissionable systems are associated with problems of separating fragments from quasi-fission reactions from those arising from fission of the completely fused system. Inferring complete fusion cross sections from the minute cross sections for the evaporation residue channel is hampered by the insufficient knowledge of the branching ratio for neutron emission and fission in the decay sequence of the completely fused system. From a quantitative analysis of the fragment angular distributions it is, however, possible under certain assumptions to deduce the relative contribution of complete fusion and quasi-fission. It is found that the complete fusion process is hindered for heavy projectiles. The excess radial energy over the interaction barrier needed to induce fusion with heavy projectiles is determined in several cases and systematic trends are presented
The impact of intermediate structure on the average fission cross sections
International Nuclear Information System (INIS)
Bouland, O.; Lynn, J.E.; Talou, P.
2014-01-01
This paper discusses two common approximations used to calculate average fission cross sections over the compound energy range: the disregard of the W II factor and the Porter-Thomas hypothesis made on the double barrier fission width distribution. By reference to a Monte Carlo-type calculation of formal R-matrix fission widths, this work estimates an overall error ranging from 12% to 20% on the fission cross section in the case of the 239 Pu fissile isotope in the energy domain from 1 to 100 keV with very significant impact on the competing capture cross section. This work is part of a recent and very comprehensive formal R-matrix study over the Pu isotope series and is able to give some hints for significant accuracy improvements in the treatment of the fission channel. (authors)
Directory of Open Access Journals (Sweden)
Kaplan Abdullah
2015-01-01
Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.
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
Energy dissipation in the process of ternary fission in heavy nuclear reaction
International Nuclear Information System (INIS)
Li Xian; Wang Chengqian; Yan Shiwei
2015-01-01
We studied the evolution of the collective motion, interaction potential, the total kinetic and excitation energies in ternary fissions of 197 Au + 197 Au system at 15 MeV/u, and discussed energy dissipation of this reaction. Through the comparison with energy-angle correlation data in binary fissions, we preliminarily concluded that the rst fission of ternary fission was an extreme deep-inelastic process. We further analyzed the correlation of the total kinetic energy with impact parameters in both binary and ternary reactions, and found that the total energy of binary reactions systems was lost about 150 MeV more than ternary fission with small impact parameters, and with larger impact parameters the total energy of ternary reactions were lost 300 MeV more than binary reactions. (authors)
Bellot-Gurlet, L; Dorighel, O; Oddone, M; Poupeau, G; Yegingil, Z
1999-01-01
Comparison of fission-track parameters - age and track densities - is an alternative tool for correlating obsidian artefacts with their potential natural sources. This method was applied by different fission-track groups in various regions and results were compared with those obtained using the more popular provenance identification techniques based on chemical composition studies. Hundreds of analyses prove that fission-track dating is a complementary technique which turns out to be very useful, specially when the chemical composition does not fully discriminate different sources. Archaeologically significant results were obtained applying the fission-track analysis in various regions of earth.
International Nuclear Information System (INIS)
Bellot-Gurlet, L.; Bigazzi, G.; Dorighel, O.; Oddone, M.; Poupeau, G.; Yegingil, Z.
1999-01-01
Comparison of fission-track parameters - age and track densities - is an alternative tool for correlating obsidian artefacts with their potential natural sources. This method was applied by different fission-track groups in various regions and results were compared with those obtained using the more popular provenance identification techniques based on chemical composition studies. Hundreds of analyses prove that fission-track dating is a complementary technique which turns out to be very useful, specially when the chemical composition does not fully discriminate different sources. Archaeologically significant results were obtained applying the fission-track analysis in various regions of earth
Comparative energetics of three fusion-fission symbiotic nuclear reactor systems
International Nuclear Information System (INIS)
Gordon, C.W.; Harms, A.A.
1975-01-01
The energetics of three symbiotic fusion-fission nuclear reactor concepts are investigated. The fuel and power balances are considered for various values of systems parameters. The results from this analysis suggest that symbiotic fusion-fission systems are advantageous from the standpoint of economy and resource utilization. (Auth.)
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
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.
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)
What can we learn from the fission time of the super-heavy elements?
Boilley, D.; Marchix, A.; Wilgenbus, D.; Lallouet, Y.; Gimbert, F.; Abe, Y.
2007-01-01
International audience; Recent experiments performed at GANIL with a crystal blocking technique have shown direct evidences of long fission times in the Super-Heavy Elements (SHE) region. Aimed to localize the SHE island of stability, can these experiments give access to the fission barrier and then to the shell-correction energy? In this paper, we calculate the fission time of heavy elements by using a new code, KEWPIE2, devoted to the study of the SHE.We also investigate the effect of poten...
Static aspects of the fission and fusion of liquid 3He drops
International Nuclear Information System (INIS)
Guilleumas, M.; Barranco, M.; Pi, M.
1992-01-01
Using an effective 3 He- 3 He interaction, the fission and fusion of 3 He drops have been investigated from a static point of view. The calculations show that a fission barrier develops for these neutral systems, and that their saddle configurations are rather elongate. The transition from oblate to prolate shapes as a function of the angular momentum L, as well as critical values for fission and fusion are discussed for some selected cases. A kind of proximity potential can be extracted from the drop-drop interaction potentials. (author) 33 refs.; 9 figs
Yields of fission products produced by thermal-neutron fission of 245Cm
International Nuclear Information System (INIS)
Dickens, J.K.; McConnell, J.W.
1981-01-01
Absolute yields have been determined for 105 gamma rays emitted in the decay of 95 fission products representing 54 mass chains created during thermal-neutron fission of 245 Cm. These results include 17 mass chains for which no prior yield data exist. Using a Ge(Li) detector, spectra were obtained of gamma rays between 30 sec and 0.3 yr after very short irradiations of thermal neutrons on a 1 μg sample of 245 Cm. On the basis of measured gamma-ray yields and known nuclear data, total chain mass yields and relative uncertainties were obtained for 51 masses between 84 and 156. The absolute overall normalization uncertainty is 239 Pu and for 252 Cf(s.f.); the influences of the closed shells Z=50, N=82 are not as marked as for thermal-neutron fission of 239 Pu but much more apparent than for 252 Cf(s.f.). Information on the charge distribution along several isobaric mass chains was obtained by determining fractional yields for 12 fission products. The charge distribution width parameter, based upon data for the heavy masses, A=128 to 140, is independent of mass to within the uncertainties of the measurements. Gamma-ray assignments were made for decay of short-lived fission products for which absolute gamma-ray transition probabilities are either not known or in doubt. Absolute gamma-ray transition probabilities were determined as (51 +- 8)% for the 374-keV gamma ray from decay of 110 Rh, (35 +- 7)% for the 1096-keV gamma ray from decay of 133 Sb, and (21.2 +- 1.2)% for the 255-keV gamma ray from decay of 142 Ba
Singlet Fission in Rubrene Derivatives: Impact of Molecular Packing
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.
Directory of Open Access Journals (Sweden)
Guardasoni C.
2018-03-01
Full Text Available A Semi-Analytical method for pricing of Barrier Options (SABO is presented. The method is based on the foundations of Boundary Integral Methods which is recast here for the application to barrier option pricing in the Black-Scholes model with time-dependent interest rate, volatility and dividend yield. The validity of the numerical method is illustrated by several numerical examples and comparisons.
Mirror hybrid (fusion--fission) reactor
International Nuclear Information System (INIS)
Bender, D.J.; Lee, J.D.; Neef, W.S.; Devoto, R.S.; Galloway, T.R.; Fink, J.H.; Schultz, K.R.; Culver, D.; Rao, S.
1977-10-01
The reference mirror hybrid reactor design performed by LLL and General Atomic is summarized. The reactor parameters have been chosen to minimize the cost of producing fissile fuel for consumption in fission power reactors. As in the past, we have emphasized the use of existing technology where possible and a minimum extrapolation of technology otherwise. The resulting reactor may thus be viewed as a comparatively near-term goal of the fusion program, and we project improved performance for the hybrid in the future as more advanced technology becomes available
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
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)
Extraction chromatography of fission products
International Nuclear Information System (INIS)
Bonnevie-Svendsen, M.; Goon, K.
1978-01-01
Various cases of using extraction chromatography during analysis of fission products are reviewed. The use of the extraction chromatography method is considered while analysing reprocessed products of nuclear fuel for quantitative radiochemical analysis and control of fission product and actinoide separation during extraction and their chemical state in production solutions. The method is used to obtain pure fractions of typical burnup monitors (neodymium, molybdenum, cerium, cesium, europium, lanthanides) during determination of nuclear fuel burnup degree. While studying the nature of nuclear reactions the method is used to separate quickly short-life isotopes, to purify β-radiator fractions before measuring their half-life periods, to enrich isotopes forming with low output during fission. Examples of using extraction chromatography are given to separate long half-life or stable fission products from spent solutions, to control environment object contamination
Chemical 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
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
A Covariance Generation Methodology for Fission Product Yields
Directory of Open Access Journals (Sweden)
Terranova N.
2016-01-01
Full Text Available Recent safety and economical concerns for modern nuclear reactor applications have fed an outstanding interest in basic nuclear data evaluation improvement and completion. It has been immediately clear that the accuracy of our predictive simulation models was strongly affected by our knowledge on input data. Therefore strong efforts have been made to improve nuclear data and to generate complete and reliable uncertainty information able to yield proper uncertainty propagation on integral reactor parameters. Since in modern nuclear data banks (such as JEFF-3.1.1 and ENDF/BVII.1 no correlations for fission yields are given, in the present work we propose a covariance generation methodology for fission product yields. The main goal is to reproduce the existing European library and to add covariance information to allow proper uncertainty propagation in depletion and decay heat calculations. To do so, we adopted the Generalized Least Square Method (GLSM implemented in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation, developed at CEA-Cadarache. Theoretical values employed in the Bayesian parameter adjustment are delivered thanks to a convolution of different models, representing several quantities in fission yield calculations: the Brosa fission modes for pre-neutron mass distribution, a simplified Gaussian model for prompt neutron emission probability, theWahl systematics for charge distribution and the Madland-England model for the isomeric ratio. Some results will be presented for the thermal fission of U-235, Pu-239 and Pu-241.
Preparation of Total RNA from Fission Yeast.
Bähler, Jürg; Wise, Jo Ann
2017-04-03
Treatment with hot phenol breaks open fission yeast cells and begins to strip away bound proteins from RNA. Deproteinization is completed by multiple extractions with chloroform/isoamyl alcohol and separation of the aqueous and organic phases using MaXtract gel, an inert material that acts as a physical barrier between the phases. The final step is concentration of the RNA by ethanol precipitation. The protocol can be used to prepare RNA from several cultures grown in parallel, but it is important not to process too many samples at once because delays can be detrimental to RNA quality. A reasonable number of samples to process at once would be three to four for microarray or RNA sequencing analyses and six for preliminary investigations of mutants implicated in RNA metabolism. © 2017 Cold Spring Harbor Laboratory Press.
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.)
Resolution of the nature of the coupling in subthreshold fission in 238U+n
International Nuclear Information System (INIS)
Auchampaugh, G.F.; de Saussure, G.; Olsen, D.K.; Ingle, R.W.; Perez, R.B.; Macklin, R.L.
1986-01-01
The analysis of a recent high-resolution neutron capture measurement at 152 m has provided the first evidence that the strong fission resonance at 721 eV is a class-II resonance. This conclusion is based on the measured capture width of 4.7 +- 0.6 MeV, which is considerably smaller than the average capture width of 23.5 MeV for the neighboring resonances. Furthermore, after analyzing the fission widths for the 721- and 1211-eV clusters, we conclude for the J/sup π/ = 1/2 + fission barrier in 239 U that the inner barrier is lower than the outer barrier by approx.1.5 MeV
Study of α-particle multiplicity in 16O+196Pt fusion-fission reaction
International Nuclear Information System (INIS)
Kapoor, K.; Kumar, A.; Bansal, N.
2016-01-01
Study of dynamics of fusion-fission reaction is one of the interesting parts of heavy-ion-induced nuclear reaction. Extraction of fission time scales using different probes is of central importance for understanding the dynamics of fusion-fission process. In the past, extensive theoretical and experimental efforts have been made to understand the various aspects of the heavy ion induced fusion-fission reactions. Compelling evidences have been obtained from the earlier studies that the fission decay of hot nuclei is protracted process i.e. slowed down relative to the expectations of the standard statistical model, and large dynamical delays are required due to this hindrance. Nuclear dissipation is assumed to be responsible for this delay and more light particles are expected to be emitted during the fission process. One of neutron multiplicity measurements have been performed for the 16,18 O+ 194,198 Pt populating the CN 210,212,214,216 Rn and observed fission delay due to nuclear viscosity. In order to have complete understanding for the dynamics of 212 Rn nucleus, we measured the charged particle multiplicity for 16 O+ 196 Pt system. Study of charged particles will give us more information about the emitter in comparison to neutrons as charged particles faces Coulomb barrier and are more sensitive probe for understanding the dynamics of fusion-fission reactions. In the present work, we are reporting some of the preliminary results of charged particle multiplicity
International Nuclear Information System (INIS)
Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Landrum, J.H.; Dougan, R.J.; Mustafa, M.; Ghiorso, A.; Nitschke, J.M.
1979-01-01
The mass and kinetic energy distributions of fission fragments from the spontaneous fission of th newly discovered nuclide 259 Md were obtained. 259 Md was identified as the E. C. daughter of 259 No, and was found to decay entirely (> 95%) by spontaneous fission with a 95-min half-life. From the kinetic energies measured for 397 pairs of coincident fragments, a mass distribution was derived that is symmetric with sigma = 13 amu. 259 Md, together with 258 Fm and 259 Fm, form a select group of three nuclides whose mass division in spontaneous fission is highly symmetric. Unlike the total-kinetic-energy (TKE) distributions of 258 Fm and 259 Fm, which peak at approx. = to 240 MeV, this distribution for 259 Md is broad and is 50 MeV lower in energy. Analysis of the mass and energy distributions shows that events near mass symmetry also exhibit a broad TKE distribution, with one-third of the symmetric events having TKEs less than 200 MeV. The associated of low TKEs with symmetric mass division in the fission of very heavy actinides is anomalous and inconsistent with theories based upon the emergence of fragment shells near the scission point. Either three-body fragmentation or peculiar fragment shapes are assumed as the cause for the large consumption of Coulomb energy observed for a significant fraction of symmetric fissions in 259 Md. 6 figures
Modelling isothermal fission gas release
International Nuclear Information System (INIS)
Uffelen, P. van
2002-01-01
The present paper presents a new fission gas release model consisting of two coupled modules. The first module treats the behaviour of the fission gas atoms in spherical grains with a distribution of grain sizes. This module considers single atom diffusion, trapping and fission induced re-solution of gas atoms associated with intragranular bubbles, and re-solution from the grain boundary into a few layers adjacent to the grain face. The second module considers the transport of the fission gas atoms along the grain boundaries. Four mechanisms are incorporated: diffusion controlled precipitation of gas atoms into bubbles, grain boundary bubble sweeping, re-solution of gas atoms into the adjacent grains and gas flow through open porosity when grain boundary bubbles are interconnected. The interconnection of the intergranular bubbles is affected both by the fraction of the grain face occupied by the cavities and by the balance between the bubble internal pressure and the hydrostatic pressure surrounding the bubbles. The model is under validation. In a first step, some numerical routines have been tested by means of analytic solutions. In a second step, the fission gas release model has been coupled with the FTEMP2 code of the Halden Reactor Project for the temperature distribution in the pellets. A parametric study of some steady-state irradiations and one power ramp have been simulated successfully. In particular, the Halden threshold for fission gas release and two simplified FUMEX cases have been computed and are summarised. (author)
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
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
Radiochemistry and the Study of Fission
Energy Technology Data Exchange (ETDEWEB)
Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-11-14
These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since its discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since its discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.
Radiochemistry and the Study of Fission
International Nuclear Information System (INIS)
Rundberg, Robert S.
2016-01-01
These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since its discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since its discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.
Stablité des Eléments Trans-ferminums à Haut Spin : Mesure de la barrière de fission de 254No
Henning , Gregoire
2012-01-01
Super heavy nuclei provide opportunities to study nuclear structure near three simultaneous limits: in charge Z, spin I and excitation energy E∗. These nuclei exist only because of a fission barrier, created by shell effects. It is therefore important to determine the fission barrier and its spin dependence Bf(I), which gives information on the shell energy Eshell(I). Theoretical calculations predict different fission barrier heights from Bf(I = 0) = 6.8 MeV for a macro-microscopic model to 8...
Calculation of the nuclear fission data based on the framework of the QMD + SDM
International Nuclear Information System (INIS)
Rong Jian; Iwamoto, O.; Fukahori, T.
2002-01-01
The quantum molecular dynamics (QMD), statistical decay model (SDM) and the statistical fission theory were used to analyze the mass distribution of the fission products, the prompt fission neutron spectrum (x(E)) and the prompt fission neutron multiplicities (ν-bar pf (E)) caused by the intermediate energy nucleon-induced fission. The semi-empirical formula of energy level density parameter used in the statistical process was also studied. Very few adjustable parameters were included in the present method. By some physical analysis, it can be thought that the present results are reasonable. The x(E) and ν-bar pf (E) can be obtained in the intermediate energy region by the present method
Possible Mechanisms of Ternary Fission in the 197Au+197 Au System at 15 AMeV
International Nuclear Information System (INIS)
Jun-Long, Tian; Xian, Li; Shi-Wei, Yan; Xi-Zhen, Wu; Zhu-Xia, Li
2009-01-01
Ternary fission in 197 Au+ 197 Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are reproduced for the first time without any freely adjusting parameters. The mechanisms of ternary fission in central and semi-central collisions are dynamically studied. In direct prolate ternary fission, two necks are found to be formed almost simultaneously and rupture sequentially in a very short time interval. Direct oblate ternary fission is a very rare fission event, in which three necks are formed and rupture simultaneously, forming three equally sized fragments along space-symmetric directions in the reaction plane. In sequential ternary fission a binary division is followed by another binary fission event after hundreds of fm/c. (nuclear physics)
International Nuclear Information System (INIS)
Jacquet, P.; Pailloux, A.; Doizi, D.; Aoust, G.; Jeannot, J.-P.
2013-06-01
Safety and availability are key issues of the generation IV reactors. Hence, the three radionuclide confinement barriers, including fuel cladding, must stay tight during the reactor operation. During the primary gaseous failure, fission products xenon and krypton are released. Their fast and sensitive detection guarantees the first confinement barrier tightness. In the frame of the French ASTRID project, an optical spectroscopy technique - Cavity Ring Down Spectroscopy (CRDS) - is investigated for the gaseous fission products measurement. A dedicated CRDS set-up is needed to detect the rare gases with a commercial laser. Indeed, the CRDS is coupled to a glow discharge plasma, which generates a population of metastable atoms. The xenon plasma conditions are optimized to 110 Pa and 1.3 W (3 mA). The production efficiency of metastable Xe is then 0.8 %, stable within 0.5% during hours. The metastable number density is proportional to the xenon over argon molar fraction. The spectroscopic parameters of the strong 823.16 nm xenon transition are calculated and/or measured in order to optimize the fit of the experimental spectra and make a quantitative measurement of the metastable xenon. The CRDS is coupled to the discharge cell. The laser intensity inside the cavity is limited by the optical saturation process, resulting from the strong optical pumping of the metastable state. The resulting weak CRDS signal requires a fast and very sensitive photodetector. A 600 ppt xenon molar fraction was measured by CRDS. With the present set-up, the detection limits are estimated from the baseline noise to approximately 20 ppt for each even isotope, 60 ppt for the 131 Xe and 55 ppt for the 129 Xe. This sensitivity matches the specifications required for gaseous leak measurement; approximately 100 ppt for 133 Xe (4 GBq/m 3 ) and 10 ppb for stable isotopes. The odd isotopes are selectively measured, whereas the even isotopes overlap, a spectroscopic feature that applies for stable or
Sequential Detection of Fission Processes for Harbor Defense
Energy Technology Data Exchange (ETDEWEB)
Candy, J V; Walston, S E; Chambers, D H
2015-02-12
With the large increase in terrorist activities throughout the world, the timely and accurate detection of special nuclear material (SNM) has become an extremely high priority for many countries concerned with national security. The detection of radionuclide contraband based on their γ-ray emissions has been attacked vigorously with some interesting and feasible results; however, the fission process of SNM has not received as much attention due to its inherent complexity and required predictive nature. In this paper, on-line, sequential Bayesian detection and estimation (parameter) techniques to rapidly and reliably detect unknown fissioning sources with high statistical confidence are developed.
Lambda attachment in fission: a probe of the necking dynamics
International Nuclear Information System (INIS)
Nifenecker, H.; Malek, F.
1991-02-01
A schematic scission model is applied to the lambda attachment function recently obtained by the LEAR PS177 collaboration, in their measurement of the prompt fission of hypernuclei. The relationship between the slope parameter and the fission dynamics was examined in a more quantitative way. It is shown that the attachment function is sensitive to the scission configuration, necking dynamics and nuclear temperature at scission. It provides a new and powerful way to study the nuclear scission process. (R.P.) 19 refs., 9 figs
Energy Technology Data Exchange (ETDEWEB)
Albinsson, H [Chalmers Univ. of Technology, Goeteborg (SE)
1971-07-01
Fission gamma radiation yields as functions of the total fragment kinetic energy were obtained for 235U thermal-neutron induced fission. The fragments were detected with silicon surface-barrier detectors and the gamma radiation with a Nal(Tl) scintillator. In some of the measurements mass selection was used so that the gamma radiation could also 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. Fission-neutron and gamma-ray data of previous experiments were used for comparisons of the yields, and estimates were made of the variation of the prompt gamma-ray energy with the total fragment kinetic energy
Fission product and actinide data evaluations for ENDF/B--V
International Nuclear Information System (INIS)
Schenter, R.E.
1978-05-01
The planned content and performance of fission product and actinide nuclide evaluations for the ENDF/B-V collection of data are reviewed. Representative values of parameters for a few nuclides are shown. 10 figures, 5 tables
Fusion barrier distributions - What have we learned?
International Nuclear Information System (INIS)
Hinde, D. J.; Dasgupta, M.
1998-01-01
The study of nuclear fusion received a strong impetus from the realisation that an experimental fusion barrier distribution could be determined from precisely measured fusion cross-sections. Experimental data for different reactions have shown in the fusion barrier distributions clear signatures of a range of nuclear excitations, for example the effects of static quadrupole and hexadecapole deformations, single- and double-phonon states, transfer of nucleons, and high-lying excited states. The improved understanding of fusion barrier distributions allows more reliable prediction of fusion angular momentum distributions, which aids interpretation of fission probabilities and fission anisotropies, and understanding of the population of super-deformed bands for nuclear structure studies. Studies of the relationship between the fusion barrier distribution and the extra-push energy should improve our understanding of the mechanism of the extra-push effect, and may help to predict new ways of forming very heavy or super-heavy nuclei
Asha, B.; Harsha, Cirandur Sri; Padma, R.; Rajagopal Reddy, V.
2018-05-01
The electrical characteristics of a V/p-GaN Schottky junction have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) characteristics under the assumption of the thermionic emission (TE) theory in the temperature range of 120-280 K with steps of 40 K. The zero-bias barrier height (ΦB0), ideality factor (n), flat-band barrier height (ΦBF) and series resistance (R S) values were evaluated and were found to be strongly temperature dependent. The results revealed that the ΦB0 values increase, whereas n, ΦFB and R S values decrease, with increasing temperature. Using the conventional Richardson plot, the mean barrier height (0.39 eV) and Richardson constant (8.10 × 10-10 Acm-2 K-2) were attained. The barrier height inhomogeneities were demonstrated by assuming a Gaussian distribution function. The interface state density (N SS) values were found to decrease with increasing temperature. The reverse leakage current mechanism of the V/p-GaN Schottky junction was found to be governed by Poole-Frenkel emission at all temperatures.
Systems study of tokamak fusion--fission reactors
International Nuclear Information System (INIS)
Tenney, F.H.; Bathke, C.G.; Price, W.G. Jr.; Bohlke, W.H.; Mills, R.G.; Johnson, E.F.; Todd, A.M.M.; Buchanan, C.H.; Gralnick, S.L.
1978-11-01
This publication reports the results of a two to three year effort at a systematic analysis of a wide variety of tokamak-driven fissioning blanket reactors, i.e., fusion--fission hybrids. It addresses the quantitative problems of determining the economically most desirable mix of the two products: electric power and fissionable fuel and shows how the price of electric power can be minimized when subject to a variety of constraints. An attempt has been made to avoid restricting assumptions, and the result is an optimizing algorithm that operates in a six-dimensional parameter space. Comparisons are made on sets of as many as 100,000 distinct machine models, and the principal results of the study have been derived from the examination of several hundred thousand possible reactor configurations
Effects of nuclear structure on quasi-fission
International Nuclear Information System (INIS)
Simenel, Cedric; Wakhle, Aditya; Hinde, D.J.; Rietz, R. du; Dasgupta, M.; Evers, M.; Lin, C.J.; Luong, D.H.; Avez, B.
2012-01-01
The quasi-fission mechanism hinders fusion of heavy systems because of a mass flow between the reactants, leading to a re-separation of more symmetric fragments in the exit channel. A good understanding of the competition between fusion and quasi-fission mechanisms is expected to be of great help to optimize the formation and study of heavy and superheavy nuclei. Quantum microscopic models, such as the time-dependent Hartree-Fock approach, allow for a treatment of all degrees of freedom associated to the dynamics of each nucleon. This provides a description of the complex reaction mechanisms, such as quasi-fission, with no parameter adjusted on reaction mechanisms. In particular, the role of the deformation and orientation of a heavy target, as well as the entrance channel magicity and isospin are investigated with theoretical and experimental approaches. (authors)
Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling
Energy Technology Data Exchange (ETDEWEB)
Pastore, Giovanni, E-mail: Giovanni.Pastore@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Swiler, L.P., E-mail: LPSwile@sandia.gov [Optimization and Uncertainty Quantification, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1318 (United States); Hales, J.D., E-mail: Jason.Hales@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Novascone, S.R., E-mail: Stephen.Novascone@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Perez, D.M., E-mail: Danielle.Perez@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Spencer, B.W., E-mail: Benjamin.Spencer@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Luzzi, L., E-mail: Lelio.Luzzi@polimi.it [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, via La Masa 34, I-20156 Milano (Italy); Van Uffelen, P., E-mail: Paul.Van-Uffelen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, Hermann-von-Helmholtz-Platz 1, D-76344 Karlsruhe (Germany); Williamson, R.L., E-mail: Richard.Williamson@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)
2015-01-15
The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code with a recently implemented physics-based model for fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO{sub 2} single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information in the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior predictions with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, significantly higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes.
Thorium-uranium fission radiography
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.
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
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)
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
Nuclear fission and neutron-induced fission cross-sections
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
Asymmetry of mass and charge division in spontaneous fission
International Nuclear Information System (INIS)
Chakraborty, P.P.; Iyer, M.R.; Ganguly, A.K.
The order-disorder model (ODM) has been used to explain asymmetry of mass and charge division and related phenomena in fission. According to this model the fission process involves two steps consisting of charge polarisation into two impending fragments with beta stable neutron numbers and subsequent distribution of the balance neutrons between the two. The statistics developed on the principle of equal a priori probability of all charge polarisation is used. The shell effects comes into play only in deciding stable neutron number for the charges. The total isotopic yield distribution for a number of fission reactions are presented. These show asymmetry in the actinide region which reduces with increasing mass/charge of the fissioning nuclide and bunching of the higher z peaks. The mass yields obtained therefrom for a number of fission reactions are compared with experimental results. Though there is general agreement with experimental data, the peaks of the distributions are slightly shifted away from the symmetric point and the distributions are somewhat narrower. Charge distribution parameters obtained from these results are also presented. The model predicts preference of asymmetric division for super heavy nuclides. (author)
Energy Technology Data Exchange (ETDEWEB)
Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto [Osaka Univ., Suita (Japan)] [and others
1997-09-01
Fission product kinetic energies were measured by the double-energy method for thermal-neutron fission of {sup 235,233}U and proton-induced fission of {sup 238}U at the 15.8-MeV excitation. From the obtained energy-mass correlation data, the kinetic-energy distribution was constructed from each mass bin to evaluate the first moment of the kinetic energy for a given fragment mass. The resulting kinetic energy was then converted to the effective distance between the charge centers at the moment of scission. The effective distances deduced for the proton-induced fission was concluded to be classified into two constant values, one for asymmetric and the other for symmetric mode, irrespective of the mass though an additional component was further extracted in the asymmetric mass region. This indicates that the fission takes place via two well-defined saddles, followed by the random neck rupture. On the contrary, the effective distances obtained for thermal-neutron induced fission turned out to lie along the contour line at the same level as the equilibrium deformation in the two-dimensional potential map. This strongly suggests that it is essentially a barrier-penetrating type of fission rather than the over-barrier fission. (author). 73 refs.
International Nuclear Information System (INIS)
Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto
1997-01-01
Fission product kinetic energies were measured by the double-energy method for thermal-neutron fission of 235,233 U and proton-induced fission of 238 U at the 15.8-MeV excitation. From the obtained energy-mass correlation data, the kinetic-energy distribution was constructed from each mass bin to evaluate the first moment of the kinetic energy for a given fragment mass. The resulting kinetic energy was then converted to the effective distance between the charge centers at the moment of scission. The effective distances deduced for the proton-induced fission was concluded to be classified into two constant values, one for asymmetric and the other for symmetric mode, irrespective of the mass though an additional component was further extracted in the asymmetric mass region. This indicates that the fission takes place via two well-defined saddles, followed by the random neck rupture. On the contrary, the effective distances obtained for thermal-neutron induced fission turned out to lie along the contour line at the same level as the equilibrium deformation in the two-dimensional potential map. This strongly suggests that it is essentially a barrier-penetrating type of fission rather than the over-barrier fission. (author). 73 refs
Influence of fusion dynamics on fission observables: A multidimensional analysis
Schmitt, C.; Mazurek, K.; Nadtochy, P. N.
2018-01-01
An attempt to unfold the respective influence of the fusion and fission stages on typical fission observables, and namely the neutron prescission multiplicity, is proposed. A four-dimensional dynamical stochastic Langevin model is used to calculate the decay by fission of excited compound nuclei produced in a wide set of heavy-ion collisions. The comparison of the results from such a calculation and experimental data is discussed, guided by predictions of the dynamical deterministic HICOL code for the compound-nucleus formation time. While the dependence of the latter on the entrance-channel properties can straigthforwardly explain some observations, a complex interplay between the various parameters of the reaction is found to occur in other cases. A multidimensional analysis of the respective role of these parameters, including entrance-channel asymmetry, bombarding energy, compound-nucleus fissility, angular momentum, and excitation energy, is proposed. It is shown that, depending on the size of the system, apparent inconsistencies may be deduced when projecting onto specific ordering parameters. The work suggests the possibility of delicate compensation effects in governing the measured fission observables, thereby highlighting the necessity of a multidimensional discussion.
Fusion-fission dynamics and synthesis of the superheavy elements
International Nuclear Information System (INIS)
Abe, Yasuhisa
2003-01-01
Experiments of fusion-fission reactions clarify that the life time of nuclear fission is much longer than that expected from Bohr-Wheeler formula from the measurements of multiplicities of neutrons, gamma rays etc. emitted prior scission, and thereby appear to require a dynamical treatment of the process. Following the pioneering work by Kramers with the dissipation- fluctuation dynamics, the fissioning degree of freedom is described with the viewpoint of Brownian motion under incessant interactions with the heat bath particles, i.e., with nucleons in thermal equilibrium, in the present case. In the dynamical description the fission width is no more constant in time, but has a transient feature, as well as the reduction factor, the so-called Kramers factor. Both result in a longer life time, consistent with anomalous multiplicities measured. In the fusion process, Coulomb barriers play a crucial role in lighter heavy ion systems, but in very heavy systems it is known that there exists a hindrance in fusion. That is, the Coulomb barrier is not enough for determination of fusion probability, but an extra-energy above the barrier height is required for the system to fuse. This is understood by the properties of the Liquid Drop Model. After overcoming the Coulomb barrier, the ions touch with each other. But the united system, i.e., the pear-shaped configuration is located outside of the conditional saddle point or of the ridgeline. Therefore, in order to form the spherical compound nucleus, the system has to overcome one more barrier. Naturally, in such a situation, the kinetic energy carried in by the incident projectile has been more or less dissipated, i.e., the composite system is heated up. Thus, the shape evolution toward the spherical shape or toward the re-separation can be considered as a Brownian motion with the heat bath inside. The present author et al. have proposed the two-step model for fusion of massive heavy-ion systems where the fusion probability is
Pauwels, D B; Lane, J
2008-01-01
In our recent experiment (March 2007) at the velocity filter SHIP(GSI) we observed the electron-capture delayed fission of the odd-odd isotope $^{194}$At. This is the first unambiguous identification of this phenomenon in the very neutron-deficient nuclei in the vicinity of the proton shell closure at Z=82. In addition, the total kinetic energy (TKE) for the daughter nuclide $^{194}$Po was measured, despite the fact that this isotope does not decay via spontaneous fission. Semi-empirical analysis of the electron-capture Q$_{EC}$ values and fission barriers B$_{f}$ shows that a relatively broad island of ECDF must exist in this region of the Nuclide Chart, with some of the nuclei having unusually high ECDF probabilities. Therefore, this Proposal is intended to initiate the systematic identification and study of $\\beta$-delayed fission at ISOLDE in the very neutron-deficient lead region. Our aim is to provide unique low-energy fission data (e.g. probabilities, TKE release, fission barriers and their isospin dep...
Nuclear energy technology transfer: the security barriers
International Nuclear Information System (INIS)
Rinne, R.L.
1975-08-01
The problems presented by security considerations to the transfer of nuclear energy technology are examined. In the case of fusion, the national security barrier associated with the laser and E-beam approaches is discussed; for fission, the international security requirements, due to the possibility of the theft or diversion of special nuclear materials or sabotage of nuclear facilities, are highlighted. The paper outlines the nuclear fuel cycle and terrorist threat, examples of security barriers, and the current approaches to transferring technology. (auth)
Systematic of delayed neutron parameters
International Nuclear Information System (INIS)
Isaev, S.G.; Piksaikin, V.M.
2000-01-01
The experimental studies of the energy dependence of the delayed neutron (DN) parameters for various fission systems has shown that the behaviour of a some combination of delayed neutron parameters has a similar features. On the basis of this findings the systematics of delayed neutron experimental data for thorium, uranium, plutonium and americium isotopes have been investigated with the purpose to find a correlation of DN parameters with characteristics of fissioning system as well as a correlation between the delayed neutron parameters themselves. It was presented the preliminary results which were obtained during study the physics interpretation of the results [ru
Directory of Open Access Journals (Sweden)
Schmidt K.-H.
2010-10-01
Full Text Available A new model description of fission-fragment yields and prompt neutron emission is developed. The yields of the different fission channels and their properties are attributed to the number of relevant states above the potential-energy landscape on the fission path at the moment of dynamical freeze-out, which is specific to the collective coordinate considered. The model combines well established ideas with novel concepts. The separability principle of macroscopic properties of the compound nucleus and microscopic properties of the fragments strongly reduces the number of model parameters and assures a high predictive power. The recently discovered energy-sorting mechanism in superfluid nuclear dynamics determines the sharing of intrinsic excitation energy at scission and the enhancement of even-odd structure in asymmetric splits.
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.)
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
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.)
Study of transfer induced fission and fusion-fission reactions for 28 Si + 232 Th system at 340 MeV
International Nuclear Information System (INIS)
Prete, G.; Rizzi, V.; Fioretto, E.; Cinausero, M.; Shetty, D.V.; Pesente, S.; Brondi, A.; La Rana, G.; Moro, R.; Vardaci, E.; Boiano, A.; Ordine, A.; Gelli, N.; Lucarelli, F.; Bortignon, P.F.; Saxena, A.; Nayak, B.K.; Biswas, D.C.; Choudhury, R.K.; Kapoor, R.S.
2001-01-01
and fusion-fission reactions. We have extracted the ratio of yield of transfer induced fission events to the singles yield of transfer products observed at grazing angle for different Z of ejectiles (PLF). It is seen that transfer induced fission yield increases with increasing Z transfer up to DZ = 4 and then becomes flat and starts to decrease for higher Z-transfers. This may indicate the onset of other processes which inhibit the fission; projectile break-up may be responsible for lowering the transfer of excitation energy and angular momentum to the fissioning system or the evaporation of charged particles may promptly reduce the excitation energy of the compound system which survive fission. This has been investigated looking at PLF in coincidence with protons, a particles, fission and target-like fragments. We have also analyzed the neutron energy spectra for the fusion-fission reaction obtained after correcting for the neutron detector efficiency. Fourteen laboratory neutron energy spectra for various fission-neutron correlation angles were simultaneously fitted with three moving sources. The results show a post- and pre-scission temperature of about 1.0 MeV and 2.24 MeV respectively, comparable to that observed in others low energy measurements and consistent with the compound nuclear excitation energy of 218 MeV, assuming a level density parameter a =A/8 MeV-1. (Author)
Open problems in sub-barrier fusion
International Nuclear Information System (INIS)
Vandenbosch, R.
1992-01-01
Two aspects of sub-barrier fusion are discussed. A challenge to the use of fission fragment angular distributions to probe the spin distribution in fusion is addressed. Evidence from excitation functions for the importance of neutron transfer and the neck degree of freedom is examined
Energy Technology Data Exchange (ETDEWEB)
Shanglian, Bao; Jinquan, Liu [Beijing Univ., BJ (China); Batenkov, O I; Blinov, M V; Smirnov, S N [V.G. Khlopin Radium Institute, ST. Petersburg (Russian Federation)
1994-09-01
The {sup 252}Cf spontaneous prompt fission neutron spectrum at 0 degree and 180 degree relative to the motion direction of corresponding fission fragments was measured. High angular resolution for fragment measurements and high energy resolution for neutron measurements were obtained using multi-parameter TOF spectrometer. The results showed that there is a symmetric distribution of `forward` and `backward` for low energy in C.M.S. neutrons, which was an evidence of nonequilibrium neutrons existed in fission process.
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)
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.
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)
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.)
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)
Heavy neutron-deficient radioactive beams: fission studies and fragment distributions
Energy Technology Data Exchange (ETDEWEB)
Schmidt, K.H.; Benlliure, J.; Heinz, A.; Voss, B. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Boeckstiegel, C.; Grewe, A.; Steinhaeuser, S.; Clerc, H.G.; Jong, M. de; Junghans, A.R.; Mueller, J. [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Pfuetzner, M. [Warsaw Univ. (Poland). Inst. of Experimental Physics
1998-02-01
The secondary-beam facility of GSI Darmstadt was used to study the fission process of short-lived radioactive nuclei. Relativistic secondary projectiles were produced by fragmentation of a 1 A GeV {sup 238}U primary beam and identified in nuclear charge and mass number. Their production cross sections were determined, and the fission competition in the statistical deexcitation was deduced for long isotopical chains. New results on the enhancement of the nuclear level density in spherical and deformed nuclei due to collective rotational and vibrational excitations were obtained. Using these reaction products as secondary beams, the dipole giant resonance was excited by electromagnetic interactions in a secondary lead target, and fission from excitation energies around 11 MeV was induced. The fission fragments were identified in nuclear charge, and their velocity vectors were determined. Elemental yields and total kinetic energies have been determined for a number of neutron-deficient actinides and preactinides which were not accessible with conventional techniques. The characteristics of multimodal fission of nuclei around {sup 226}Th were systematically investigated and related to the influence of shell effects on the potential energy and on the level density between fission barrier and scission. A systematic view on the large number of elemental yields measured gave rise to a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of pair breaking in large-scale collective motion. (orig.)
Gamma ray transitions in de-excitation of 252Cf spontaneous fission fragments
International Nuclear Information System (INIS)
Khan, N.A.; Rashid, K.; Ahmad, M.; Qureshi, I.E.; Alam, G.D.; Ali, A.; Bhatti, N.; Horsch, F.
1983-11-01
Gamma rays in the range from 60 keV to 730 keV have been observed following the spontaneous fission of 252 Cf, with high resolution Ge(Li) detector, full width at half maximum (FWHM) of 700 eV at 122 keV, in coincidence with the two fission fragments observed with surface barrier detectors. A total number of 18, 636, 549 events were recorded over a run period of about 150 hours stretching over three weeks. The events were sorted to generate gamma ray spectra belonging to 2 amu intervals gamma of the fragment masses and 6 MeV intervals of the total kinetic energy released. Some of the prominent gamma lines belonging to various masses of the fission fragments have been identified. For some gamma lines, the intensities have been evaluated as a function of the total kinetic energy of the fission fragments. (authors)
Interaction of noble-metal fission products with pyrolytic silicon carbide
International Nuclear Information System (INIS)
Lauf, R.J.; Braski, D.N.
1982-01-01
Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain layers of pyrolytic carbon and silicon carbide, which act as a miniature pressure vessel and form the primary fission product barrier. Of the many fission products formed during irradiation, the noble metals are of particular interest because they interact significantly with the SiC layer and their concentrations are somewhat higher in the low-enriched uranium fuels currently under consideration. To study fission product-SiC interactions, particles of UO 2 or UC 2 are doped with fission product elements before coating and are then held in a thermal gradient up to several thousand hours. Examination of the SiC coatings by TEM-AEM after annealing shows that silver behaves differently from the palladium group
The importance of the giant resonances in hadron and muon induced fission
International Nuclear Information System (INIS)
Hartfiel, J.
1985-01-01
In the first part of the thesis the fission probability of 238 U by means of the reaction 238 U(α,α'f) is studied at an incident energy of 480 MeV and a scattering angle of 3.4 0 . In the measured spectrum of the inelastically scattered α particles a strong resonance is found in the excitation energy range from 8 to 13 MeV. The center of mass of the resonance lies at 11 MeV. Its width extends to 4.5 MeV. In the second part of the thesis the muon induced fission of 235 U, 238 U, 237 Np, 242 Pu, and 244 Pu is studied. Thereby both fission fragments are detected in coincidence by two surface barrier detectors. By this it is possible for the first time to measure the mass and kinetic energy distribution of the fission fragments. (orig./HSI) [de
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)
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
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.)
Dynamin's helical geometry does not destabilize membranes during fission.
McDargh, Zachary A; Deserno, Markus
2018-05-01
It is now widely accepted that dynamin-mediated fission is a fundamentally mechanical process: dynamin undergoes a GTP-dependent conformational change, constricting the neck between two compartments, somehow inducing their fission. However, the exact connection between dynamin's conformational change and the scission of the neck is still unclear. In this paper, we re-evaluate the suggestion that a change in the pitch or radius of dynamin's helical geometry drives the lipid bilayer through a mechanical instability, similar to a well-known phenomenon occurring in soap films. We find that, contrary to previous claims, there is no such instability. This lends credence to an alternative model, in which dynamin drives the membrane up an energy barrier, allowing thermal fluctuations to take it into the hemifission state. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Resolved resonance parameters for 236Np
International Nuclear Information System (INIS)
Morogovskij, G.B.; Bakhanovich, L.A.
2002-01-01
Multilevel Breit-Wigner parameters were obtained for fission cross-section representation in the 0.01-33 eV energy region from evaluation of a 236 Np experimental fission cross-section in the resolved resonance region. (author)
Computer program FPIP-REV calculates fission product inventory for U-235 fission
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.
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)
Alkaline glass as induced fission fragment detectors
International Nuclear Information System (INIS)
Amorim, A.M.M.
1986-01-01
The slide glass, registered trade marks INLAB, INVICT and PERFECTA were compared. For the three kinds of glasses the following studies were done: chemical composition; general dissolution rate for hydrofluoric acid solutions of concentrations between 1 and 10M, at 30 0 C and ultrasound shaking; relative efficiency for recording fission fragment tracks from 252 Cf. The INLAB glass was selected due to the better quality of its surface after chemical etching. The HF concentration 2.5M was determined for chemical etching of INLAB glass, and the optimum etching time was chosen between 8 and 10 minutes. The thermal attenuation of latent tracks in the environmental temperature was observed for intervals uo to 31 days between the detector exposure to the fission fragment source and etching of tracks. Several methods were used for determining the detector parameters, such as: critical angle, angle of the cone and efficiency of etching. The effects of gamma irradiation from 60 Co and reactor neutrons in material properties as track detector were studied. Attenuation of latent tracks and saturation of color centers were observed for doses over 100M Rad. Since this kind of material contains uranium as impurity, uniformely distributed, slide glass were calibrated to be applied as a monitor of thermal neutron flux in nuclear reactor. (Author) [pt
Fuel and fission product release from sodium
International Nuclear Information System (INIS)
Sauter, H.
1992-01-01
The NALA program at Kernforschungszentrum Karlsruhe is concerned with the release of fuel and fission products from hot or boiling sodium pools (radiological secondary source term) in a liquid-metal fast breeder reactor accident scenario with tank failure. The main concern is to determine retention factors (RF), to uncover the most essential parameters that influence the RF values, and to describe the way they do it. In the framework of the last NALA series, NALA IIIc, the influence of sodium-concrete interaction was investigated, partly with subsequent sodium burning. In our experiments, ∼3 kg of sodium and added pieces of concrete reaching from 4 to 40 g was used. The composition of the concrete was suitable for shielding and construction as used in the SNR-300 reactor. Fuel was simulated by 20-μm particles of depleted UO 2 , and CeO 2 , NaI, and TeO 2 were used as fission products. Most experiments were performed in an inert argon gas atmosphere with monitored hydrogen development. In some cases, the preheated pool was allowed to come into contact with ambient air, which caused an ordinary sodium fire. For the latter case, we used the 220-m 3 FAUNA vessel as an outer containment and collected the fire aerosols by a trap and subsequent filters for analysis
International Nuclear Information System (INIS)
Ahn, Joon-Hong; Ikeda, Takao; Ohe, Toshiaki
1995-01-01
Performance assessment of each barrier consisting of geologic disposal system for high-level radioactive wastes is carried out quantitatively, and key radionuclides and parameters are pointed out. Chemical compositions and solubilities of radionuclides under repository conditions are determined by PHREEQE code staring from compositions of granitic groundwater observed in Japan. Glass dissolution analysis based on mass transfer theory and precipitation analysis have been done in order to determine the inner boundary condition for radionuclide diffusion through a bentonite-filled buffer region, where multi-member decay chain and isotopic sharing of solubility at the inner boundary are considered. Natural barrier is treated as homogeneous porous rock, or porous rock with infinite planar fractures. Performance of each barrier is evaluated in terms of non-dimensionalized hazard defined as the ratio of annual radioactivity release from each barrier to the annual limit on intake. At the outer edge of the engineered barriers, 239 Pu is the key unclide to the performance, whereas at the exit of the natural barrier, weakly-sorbing fission product nuclides such as 135 Cs, 129 I and 99 Tc dominate the hazard. (author) 50 refs
Neutron gamma competition in fast fission
International Nuclear Information System (INIS)
Frehaut, J.
1989-01-01
In the present paper we analyse the data we have obtained on the distribution of the gamma-ray energy per fission, as well as on the average energy E-barγ released per fission for the neutron induced fission of several isotopes, in the energy range up to 15 MeV. 6 refs, 9 figs
Fission 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
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 ...
Cluster radioactivity and very asymmetric fission through quasi-molecular shapes
International Nuclear Information System (INIS)
Royer, G.
1997-01-01
The decay of radioactive nuclei which emit heavy clusters like C, O, Ne, Mg and Si has been studied in the fission valley which leads one spherical nucleus towards two spherical touching nuclei before crossing the barrier. Assuming volume conservation, the deformation energy has been calculated within a generalized liquid drop model taking into account the proximity effects between the cluster and the daughter nucleus. The theoretical partial half-lives obtained within the WKB barrier penetration probability are in good agreement with the experimental data for the heaviest clusters. The Ne, Mg and Si emission looks like a very-asymmetric spontaneous fission. The 14 C radioactivity is not correctly described within the fission hypothesis. The 14 C and apparently also the 20 O are probably pre-born in the parent nucleus, the emission being similar to the α decay process. (author)
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 ...
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.
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
Nuclear fission with inertial confinement
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
Calculating the mass distribution of heavy nucleus fission product by neutrons
International Nuclear Information System (INIS)
Gudkov, A.N.; Koldobskij, A.B.; Kolobashkin, V.M.; Semenova, E.V.
1981-01-01
The technique of calculating the fission product mass yields by neutrons which are necessary for performing nucleus physical calculations in designing nuclear reactor cores is considered. The technique is based on the approximation of fission product mass distribution over the whole mass range by five Gauss functions. New analytical expressions for determining energy weights of used gaussians are proposed. The results of comparison of experimental data with calculated values for fission product mass obtained for reference processes in the capacity of which the fission reactions are chosen: 233 U, 235 U fission by thermal neutrons, 232 Th, 233 U, 235 U, 238 U by fission spectrum neutrons and 14 MeV neutrons and for 232 Th fission reactions by 11 MeV neutrons and 238 U by 7.7 MeV neutrons. On the basis of the analysis of results obtained the conclusion is drawn on a good agreement of fission product mass yield calculation values obtained using recommended values of mass distribution parameters with experimental data [ru
Pion-induced fission of 209Bi and 119Sn: measurements, calculations, analyses and comparison
International Nuclear Information System (INIS)
Rana, M.A.; Sher, G.; Manzoor, S.; Shehzad, M.I.
2011-01-01
Cross-sections for the π - -induced fission of 209 Bi and 119 Sn have been measured using the most sensitive CR-39 solid-state nuclear track detector. In experiments, target–detector stacks were exposed to negative pions of energy 500, 672, 1068, and 1665 MeV at the Brookhaven National Laboratory, USA. An important aspect of the present paper is the comparison of pion-induced fission fragment spectra of above mentioned nuclei with the spontaneous fission fragment spectra of 252 Cf. This comparison is made in terms of fission fragment track lengths in the CR-39 detectors. Measurement results are compared with calculations of Monte Carlo and statistical weight functions methods using the computer code CEM95. Agreement between measurements and calculations is fairly good for 209 Bi target nuclei whereas it is indigent for the case of 119 Sn. The possibilities of the trustworthy calculations, using the computer code CEM95, comparable with measurements of pion-induced fission in intermediate and heavy nuclei are explored by employing various systematics available in the code. Energy dependence of pion-induced fission in 119 Sn and 209 Bi is analyzed employing a newly defined parameter geometric-size-normalized fission cross-section (χ f g ). It is found that the collective nuclear excitations, which may lead to fission, become more probable for both 209 Bi and 119 Sn nuclei with increasing energy of negative pions from 500 to 1665 MeV. (author)
Nuclear structure in cold rearrangement processes in fission and fusion
Energy Technology Data Exchange (ETDEWEB)
Armbruster, P.
1998-11-01
In fission and fusion of heavy nuclei large numbers of nucleons are rearranged at a scale of excitation energy very small compared to the binding energy of the nuclei. The energies involved are less than 40 MeV at nuclear temperatures below 1.5 MeV. The shapes of the configurations in the rearrangement of a binary system into a monosystem in fusion, or vice versa in fission, change their elongations by as much as 8 fm, the radius of the monosystem. The dynamics of the reactions macroscopically described by a potential energy surface, inertia parameters, dissipation, and a collision energy is strongly modified by the nuclear structure of the participating nuclei. Experiments showing nuclear structure effects in fusion and fission of the heaviest nuclei are reviewed. The reaction kinematics and the multitude of isotopes involved are investigated by detector techniques and by recoil spectrometers. The advancement of the latter allows to find very small reaction branches in the range of 10{sup -5} to 10{sup -10}. The experiments reveal nuclear structure effects in all stages of the rearrangement processes. These are discussed pointing to analogies in fusion and fission on the microscopic scale, notwithstanding that both processes macroscopically are irreversible. Heavy clusters, as 132Sn, 208Pb, nuclei with closed shell configurations N=82,126, Z=50,82 survive in large parts of the nuclear rearrangement. They determine the asymmetry in the mass distribution of low energy fission, and they allow to synthesise superheavy elements, until now up to element 112. Experiments on the cold rearrangement in fission and fusion are presented. Here, in the range of excitation energies below 12 MeV the phenomena are observed most convincingly. (orig.)
Choice of initial conditions in dynamical calculations of distributions of nuclear fission fragments
International Nuclear Information System (INIS)
Kosenko, G.I.
1993-01-01
The distribution function in the coordinates and momenta for a fissioning system traversing a barrier is determined in terms of Langevin fluctuation-dissipation dynamics. It is shown that this distribution is best described by the Kramers distribution. The equilibrium distribution can be used as the initial condition, provided that the system is in the overdamping regime. 28 refs., 5 figs., 3 tabs
International Nuclear Information System (INIS)
Behrens, J.W.
1977-01-01
Recent studies have shown straightforward systematic behavior as a function of constant proton and neutron number for neutron-induced fission cross sections of the actinide elements in the incident-neutron energy range 3 to 5 MeV. In this report, the second in a series, fission cross-section values are studied over the MeV incident-neutron energy range, and at 0.0253 eV. Fission-barrier heights and neutron-binding energies are correlated by constant proton and neutron number; however, these systematic behaviors alone do not explain the trends observed in the fission cross-section values
Formation and distribution of fragments in the spontaneous fission of 240Pu
Sadhukhan, Jhilam; Zhang, Chunli; Nazarewicz, Witold; Schunck, Nicolas
2017-12-01
Background: Fission is a fundamental decay mode of heavy atomic nuclei. The prevalent theoretical approach is based on mean-field theory and its extensions where fission is modeled as a large amplitude motion of a nucleus in a multidimensional collective space. One of the important observables characterizing fission is the charge and mass distribution of fission fragments. Purpose: The goal of this Rapid Communication is to better understand the structure of fission fragment distributions by investigating the competition between the static structure of the collective manifold and the stochastic dynamics. In particular, we study the characteristics of the tails of yield distributions, which correspond to very asymmetric fission into a very heavy and a very light fragment. Methods: We use the stochastic Langevin framework to simulate the nuclear evolution after the system tunnels through the multidimensional potential barrier. For a representative sample of different initial configurations along the outer turning-point line, we define effective fission paths by computing a large number of Langevin trajectories. We extract the relative contribution of each such path to the fragment distribution. We then use nucleon localization functions along effective fission pathways to analyze the characteristics of prefragments at prescission configurations. Results: We find that non-Newtonian Langevin trajectories, strongly impacted by the random force, produce the tails of the fission fragment distribution of 240Pu. The prefragments deduced from nucleon localizations are formed early and change little as the nucleus evolves towards scission. On the other hand, the system contains many nucleons that are not localized in the prefragments even near the scission point. Such nucleons are distributed rapidly at scission to form the final fragments. Fission prefragments extracted from direct integration of the density and from the localization functions typically differ by more than
Studies on the reaction mechanism of the muon induced nuclear fission
International Nuclear Information System (INIS)
Mutius, R. von.
1985-01-01
The mass and energy distribution of the fission fragments after muon induced nuclear fission allows the determination of the mean excitation energy of the fissioning nucleus after muon capture. By the systematic comparison with a mass distribution of a corresponding reaction for the first time for this an accuracy of about 1 MeV could be reached. Theoretical calculations on the excitation probability in the muon capture allow in connection with the fission probability an estimating calculation of this energy. The experimental result represents by this a test criterium for the valuation of the theoretical calculation. The measured probabilities for the occurrence of radiationless transitions in the muonic γ cascade of 237 Np permit an indirect experimental determination of the barrier enhancement which causes the muon present during the fission process. The value found for this extends to 0.75+-0.1 MeV. A change of the mass distribution by the muon cannot be detected in the nuclides 235 U, 237 Np, and 242 Pu studied here. Only the mean total kinetic energy of the fission products is reduced in these three nuclides in the prompt μ - induced fission by 1 to 2 MeV. For this result the incomplete screening of the nuclear charge during the fission process is made responsible. A mass dependence of this reduction has not been stated. Because the muon has appearently no influence on the mass splitting it can be valied as nearly ideal particle in order to study the hitherto little studied dynamics of the fission process. (orig.) [de
Fluctuations in Fission Characteristics in the Resonance Range
International Nuclear Information System (INIS)
Fort, E.; Courcelle, A.
2006-01-01
In the resonance range, experimental data exhibit meaningful fluctuations of the number of prompt neutrons ν p (E) and γ-rays emitted in fission. Fluctuations of delayed-neutrons multiplicity ν d (E) are also expected. Although these fluctuations may have a non-negligible impact on reactor integral parameters (such as k eff , β eff ), they are usually not described in the current nuclear-data libraries Endf, JENDL or Jeff (except for 239 Pu evaluation in Jeff.1). Experiments by Hambsch et al. on 235 U have justified the fluctuations of total kinetic energy of fission fragments [i.e TKE(E)] by the fluctuations in the mass distributions. An interesting channel-mode formalism, described by Furman, provides a methodology to assess the fluctuations of fission characteristics in the resonance range. This approach is based on ideas relating fission channels or transition states as proposed by Bohr and fission modes as parameterized for instance by Brosa et al. This formalism requires the knowledge of physical parameters rarely measured up to now, such as PP JK (E), the energy dependant probability to form a transition state with a spin J and its projection along the deformation axis K, w m JK , the probability to feed the fission mode m from a (J,K) transition state. Nevertheless, in the case of 3 - and 4 - resonances of 235 U, various experiments permit these data to be extracted. The present study proposes a tentative evaluation of ν p of 235 U based on these ideas. The evaluation of νp for 239 Pu, performed in the 80's for the JEF library, was also revisited. At that time, the model was based on the existence of pre-fission gamma (the so called n-γf effect) as well as a spin effect (prescription of different ν p values for each spin state 0 + and 1 + ). This paper emphasizes the need for further measurements to provide more accurate information on the parameters used in this formalism, and improve the present work. (authors)
Progress in fission product nuclear data
International Nuclear Information System (INIS)
Lammer, G.
1976-05-01
The purpose of this series is to inform scientists working on Fission Product Nuclear Data, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. This report consists of reproductions of essentially unaltered original contributions which the authors have sent to IAEA/NDS. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields; neutron cross-section data of fission products; data related to β-, γ-decay of fission products; delayed neutron data; and fission product decay-heat
Fission product behaviour in severe accidents
International Nuclear Information System (INIS)
Jokiniemi, J.; Auvinen, A.; Maekynen, J.; Valmari, T.
1998-01-01
The understanding of fission product (FP) behaviour in severe accidents is important for source term assessment and accident mitigation measures. For example in accident management the operator needs to know the effect of different actions on the behaviour and release of fission products. At VTT fission product behaviour have been studied in different national and international projects. In this presentation the results of projects in EU funded 4th framework programme Nuclear Fission Safety 1994-1998 are reported. The projects are: fission product vapour/aerosol chemistry in the primary circuit (FI4SCT960020), aerosol physics in containment (FI4SCT950016), revaporisation of test samples from Phebus fission products (FI4SCT960019) and assessment of models for fission product revaporisation (FI4SCT960044). Also results from the national project 'aerosol experiments in the Victoria facility' funded by IVO PE and VTT Energy are reported
Material synergism fusion-fission
International Nuclear Information System (INIS)
Sankara Rao, K.B.; Raj, B.; Cook, I.; Kohyama, A.; Dudarev, S.
2007-01-01
In fission and fusion reactors the common features such as operating temperatures and neutron exposures will have the greatest impact on materials performance and component lifetimes. Developing fast neutron irradiation resisting materials is a common issue for both fission and fusion reactors. The high neutron flux levels in both these systems lead to unique materials problems like void swelling, irradiation creep and helium embitterment. Both fission and fusion rely on ferritic-martensitic steels based on 9%Cr compositions for achieving the highest swelling resistance but their creep strength sharply decreases above ∝ 823K. The use of oxide dispersion strengthened (ODS) alloys is envisaged to increase the operating temperature of blanket systems in the fusion reactors and fuel clad tubes in fast breeder reactors. In view of high operating temperatures, cyclic and steady load conditions and the long service life, properties like creep, low cycle fatigue,fracture toughness and creepfatigue interaction are major considerations in the selection of structural materials and design of components for fission and fusion reactors. Currently, materials selection for fusion systems has to be based upon incomplete experimental database on mechanical properties. The usage of fairly well developed databases, in fission programmes on similar materials, is of great help in the initial design of fusion reactor components. Significant opportunities exist for sharing information on technology of irradiation testing, specimen miniaturization, advanced methods of property measurement, safe windows for metal forming, and development of common materials property data base system. Both fusion and fission programs are being directed to development of clean steels with very low trace and tramp elements, characterization of microstructure and phase stability under irradiation, assessment of irradiation creep and swelling behaviour, studies on compatibility with helium and developing
Exclusion of nuclear forces in heavy-ion Coulomb excitation and Coulomb fission experiments
International Nuclear Information System (INIS)
Neese, R.E.; Guidry, M.W.
1982-01-01
A simple prescription for estimating the energy at which nuclear forces begin to play a role in heavy-ion Coulomb excitation and Coulomb fission experiments is presented. The method differs from most commonly used recipes in accounting for projectile and target nucleus deformation effects. Using a single adjustable parameter the formula reproduces the energy for the onset of Coulomb-nuclear interference effects for a broad range of heavy-ion systems. It is suggested that most Coulomb fission experiments which have been done involve both Coulomb and nuclear excitation processes and should more properly be termed Coulomb-nuclear fission experiments
The measurement of prompt neutron spectrum in spontaneous fission of {sup 244}Cm
Energy Technology Data Exchange (ETDEWEB)
Batenkov, O.I.; Boykov, G.S.; Drapchinsky, L.V.; Majorov, M.Ju.; Trenkin, V.A. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)
1997-03-01
Under the Program of Measurements of Prompt Fission Neutron Spectra of Minor Actinides for Transmutation Purposes the integral neutron spectrum in spontaneous fission of {sup 244}Cm has been measured by the time-of-flight method in the energy range of 0.1-15 MeV relative to the standard neutron spectrum in {sup 252}Cf spontaneous fission. Essential attention was paid to revealing of possible systematic errors. It is shown, that the {sup 244}Cm spectrum shape may be well described by using Mannhart evaluation with appropriate parameter of Maxwell temperature T{sub M} = 1.37 MeV. (author)
Characteristics of prompt fission gamma-ray emission - Experimental results and predictions
International Nuclear Information System (INIS)
Oberstedt, Andreas; Billnert, Robert; Oberstedt, Stephan
2014-01-01
Systematics from 2001, describing prompt fission gamma-ray spectra (PFGS) characteristics as function of mass and atomic number of the fissioning system, has been revisited and parameters have been revised based on recent experimental results. Although originally expressed for spontaneous and thermal neutron-induced fission, validity for fast neutrons was assumed and applied to predict PFGS characteristics for the reaction n + 238 U up to incident neutron energies of E n = 20 MeV. The results from this work are in good agreement with corresponding results from both model calculations and experiments. (authors)
International Nuclear Information System (INIS)
Demetriou, P.; Keutgen, Th.; Prieels, R.; El Masri, Y.
2010-01-01
Fission properties of proton-induced fission on 232 Th, 237 Np, 238 U, 239 Pu, and 241 Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code talys. The code couples the multimodal random neck-rupture model with the pre-equilibrium exciton and statistical models to predict fission fragment mass yields, pre- and post-scission neutron multiplicities, and total fission cross sections in a consistent approach. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed in detail.
International Nuclear Information System (INIS)
Koch, M.; Kazimi, M.S.
1991-04-01
Limitations of the fission fuel resources will presumably mandate the replacement of thermal fission reactors by fast fission reactors that operate on a self-sufficient closed fuel cycle. This replacement might take place within the next one hundred years, so the direct competitors of fusion reactors will be fission reactors of the latter rather than the former type. Also, fast fission reactors, in contrast to thermal fission reactors, have the potential for transmuting long-lived actinides into short-lived fission products. The associated reduction of the long-term activation of radioactive waste due to actinides makes the comparison of radioactive waste from fast fission reactors to that from fusion reactors more rewarding than the comparison of radioactive waste from thermal fission reactors to that from fusion reactors. Radioactive waste from an experimental and a commercial fast fission reactor and an experimental and a commercial fusion reactor has been characterized. The fast fission reactors chosen for this study were the Experimental Breeder Reactor 2 and the Integral Fast Reactor. The fusion reactors chosen for this study were the International Thermonuclear Experimental Reactor and a Reduced Activation Ferrite Helium Tokamak. The comparison of radioactive waste parameters shows that radioactive waste from the experimental fast fission reactor may be less hazardous than that from the experimental fusion reactor. Inclusion of the actinides would reverse this conclusion only in the long-term. Radioactive waste from the commercial fusion reactor may always be less hazardous than that from the commercial fast fission reactor, irrespective of the inclusion or exclusion of the actinides. The fusion waste would even be far less hazardous, if advanced structural materials, like silicon carbide or vanadium alloy, were employed
Energy Technology Data Exchange (ETDEWEB)
Koch, M.; Kazimi, M.S.
1991-04-01
Limitations of the fission fuel resources will presumably mandate the replacement of thermal fission reactors by fast fission reactors that operate on a self-sufficient closed fuel cycle. This replacement might take place within the next one hundred years, so the direct competitors of fusion reactors will be fission reactors of the latter rather than the former type. Also, fast fission reactors, in contrast to thermal fission reactors, have the potential for transmuting long-lived actinides into short-lived fission products. The associated reduction of the long-term activation of radioactive waste due to actinides makes the comparison of radioactive waste from fast fission reactors to that from fusion reactors more rewarding than the comparison of radioactive waste from thermal fission reactors to that from fusion reactors. Radioactive waste from an experimental and a commercial fast fission reactor and an experimental and a commercial fusion reactor has been characterized. The fast fission reactors chosen for this study were the Experimental Breeder Reactor 2 and the Integral Fast Reactor. The fusion reactors chosen for this study were the International Thermonuclear Experimental Reactor and a Reduced Activation Ferrite Helium Tokamak. The comparison of radioactive waste parameters shows that radioactive waste from the experimental fast fission reactor may be less hazardous than that from the experimental fusion reactor. Inclusion of the actinides would reverse this conclusion only in the long-term. Radioactive waste from the commercial fusion reactor may always be less hazardous than that from the commercial fast fission reactor, irrespective of the inclusion or exclusion of the actinides. The fusion waste would even be far less hazardous, if advanced structural materials, like silicon carbide or vanadium alloy, were employed.
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
Radiation shielding for fission reactors
Energy Technology Data Exchange (ETDEWEB)
Oka, Yoshiaki [Tokyo Univ., Nuclear Engineering Research Laboratory, Tokyo (Japan)
2000-03-01
Radiation shielding aspects relating fission reactors have been reviewed. Domestic activities in the past five years have been mainly described concerning nuclear data, calculation methods, shielding and skyshine experiments, Advanced Boiling Water Reactor (ABWR), Advanced Pressurized Water Reactor (APWR), High Temperature Engineering Test Reactor (HTTR), Experimental and Prototype Fast Reactors (JOYO, MONJU), Demonstration FBR, core shroud replacement of BWR, and spent fuel transportation cask and vessel. These studies have valuable information in safety and cost reduction issues of fission reactor design for not only existing reactors but also new reactor concepts in the next century. It has been concluded that we should maintain existing shielding technologies and improve these data and methods for coming generations in the next millennium. (author)
Nuclear Dissipation from Fission Time
International Nuclear Information System (INIS)
Gontchar, I.; Morjean, M.; Basnary, S.
2000-01-01
Fission times, pre-scission neutron multiplicities and GDR pre-scission γ-ray multiplicities measured for uranium or thorium nuclei formed with temperatures T ∼ 1.8 MeV have been compared with calculations performed with CDSM2, a two-dimensional dynamical model combined with a statistical one. Among the three experimental approaches considered, fission times give access to the most precise pieces of information on nuclear dissipation at high excitation energy. For the temperature range under consideration, an agreement between the model and data is achieved if one-body dissipation is used with a strength factor k red ∼ 0.45 ± 0.10 applied to the wall term for the mononuclear configuration. (authors)
International Nuclear Information System (INIS)
Teller, E.
1985-01-01
As the history of the development of fusion energy shows, a sustained controlled fusion reaction is much more difficult to produce than rapid uncontrolled release of fusion energy. Currently, the ''magnetic bottle'' technique shows sufficient progress that it might applied for the commercial fuel production of /sup 233/U, suitable for use in fission reactors, by developing a fusion-fission hybrid. Such a device would consist of a fusion chamber core surrounded by a region containing cladded uranium pellets cooled by helium, with lithium salts also present to produce tritium to refuel the fusion process. Successful development of this hybrid might be possible within 10 y, and would provide both experience and funds for further development of controlled fusion energy
Fission product separations testing
Energy Technology Data Exchange (ETDEWEB)
Bostick, D.A.; DePaoli, S.M. [Oak Ridge National Lab., TN (United States)
1997-10-01
The initial goal of this task is to adequately understand the treatment needs of the end user in treating contaminated wastewater. These needs are then incorporated into the evaluation of new treatment technologies for wastewater treatment. Pertinent information is than supplied to the end user so that they can select a preferred process to meet their waste treatment needs. New sorbent materials, ion-exchange materials, or other processes of interest to DOE`s Office of Environmental Restoration (EM-40) will be evaluated initially for the removal of {sup 90}Sr and {sup 137}Cs from groundwater and process wastewater. Laboratory studies will strive to obtain a quantitative understanding of the behavior of these new materials and to evaluate their sorption efficiency in reference to a standard benchmark treatment technique. Testing of the new materials will begin by conducting scoping tests where new treatment materials are compared with standard, commercially available materials in batch shaker tests. Experimental data for the most promising sorbents will then be fit to an equilibrium model so that nuclide sorption can be predicted for variable wastewater composition. Additional testing with actual wastewater will be conducted with two or three of the most effective treatment methods. Once batch testing of a treatment method is completed, dynamic column tests will be performed to validate the equilibrium sorption model and to obtain the defining column operating parameters for scaling up the technology.
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.
First-Principle Characterization for Singlet Fission Couplings.
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.
Neutron detector for detecting rare events of spontaneous fission
International Nuclear Information System (INIS)
Ter-Akop'yan, G.M.; Popeko, A.G.; Sokol, E.A.; Chelnokov, L.P.; Smirnov, V.I.; Gorshkov, V.A.
1981-01-01
The neutron detector for registering rare events of spontaneous fission by detecting multiple neutron emission is described. The detector represents a block of plexiglas of 550 mm diameter and 700 mm height in the centre of which there is a through 160 mm diameter channel for the sample under investigation. The detector comprises 56 3 He filled counters (up to 7 atm pressure) with 1% CO 2 addition. The counters have a 500 mm length and a 32 mm diameter. The sampling of fission events is realized by an electron system which allows determining the number of detected neutrons, numbers of operated counters, signal amplitude and time for fission event detecting. A block diagram of a neutron detector electron system is presented and its operation principle is considered. For protection against cosmic radiation the detector is surronded by a system of plastic scintillators and placed behind the concrete shield of 6 m thickness. The results of measurements of background radiation are given. It has been found that the background radiation of single neutron constitutes about 150 counts per hour, the detecting efficiency of single neutron equals 0.483 +- 0.005, for a 10l detector sensitive volume. By means of the detector described the parameters of multiplicity distribution of prompt neutrons for 256 Fm spontaneous fission are measured. The average multiplicity equals 3.59+-0.06 the dispersion being 2.30+-0.65
Fission product retention during faults involving steam generator tube rupture
International Nuclear Information System (INIS)
Rodliffe, R.S.
1983-08-01
In some PWR fault conditions, such as stuck open safety relief valve in the secondary circuit or main steam line break, the release of fission products to the atmosphere may be increased by the leakage of primary coolant into the secondary circuit following steam generator tube rupture. The release may be reduced by retention either within the primary circuit or within the affected steam generator unit (SGU). The mechanisms leading to retention are reviewed and quantified where possible. The parameters on which any analysis will be most critically dependent are identified. Fission product iodine and caesium may be retained in the secondary side of a SGU either by partition to retained water or by droplet deposition on surfaces and subsequent evaporation to dryness. Two extreme simplifications are considered: SGU 'dry', i.e. the secondary side is steam filled, and SGU 'wet', i.e. the tube bundle is covered with water. Consideration is given to: the distribution of fission products between gaseous and aerosol forms; mechanisms for droplet formation, deposition and resuspension; fission product retention during droplet or film evaporation primary coolant mixing and droplet scrubbing in a wet SGU; and the performance of moisture separators and steam driers. (author)
Monte Carlo based toy model for fission process
International Nuclear Information System (INIS)
Kurniadi, R.; Waris, A.; Viridi, S.
2014-01-01
There are many models and calculation techniques to obtain visible image of fission yield process. In particular, fission yield can be calculated by using two calculations approach, namely macroscopic approach and microscopic approach. This work proposes another calculation approach in which the nucleus is treated as a toy model. Hence, the fission process does not represent real fission process in nature completely. The toy model is formed by Gaussian distribution of random number that randomizes distance like the distance between particle and central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. These three points have different Gaussian distribution parameters such as mean (μ CN , μ L , μ R ), and standard deviation (σ CN , σ L , σ R ). By overlaying of three distributions, the number of particles (N L , N R ) that are trapped by central points can be obtained. This process is iterated until (N L , N R ) become constant numbers. Smashing process is repeated by changing σ L and σ R , randomly
Sexual differentiation in fission yeast
DEFF Research Database (Denmark)
Egel, R; Nielsen, O; Weilguny, D
1990-01-01
The regulation of sexual reproduction in yeast constitutes the highest level of differentiation observed in these unicellular organisms. The various ramifications of this system involve DNA rearrangement, transcriptional control, post-translational modification (such as protein phosphorylation) a......) and receptor/signal processing. A few basic similarities are common to both fission and budding yeasts. The wiring of the regulatory circuitry, however, varies considerably between these divergent yeast groups....
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.
Fission tracks dating for obsidian
International Nuclear Information System (INIS)
Picon, C.
1991-01-01
Obsidian from South America are dated by fission tracks methods. Samples are irradiated in a nuclear reactor with a flux of 10 15 n/cm 2 . Results, corrected by 'Plateau' methods, are the following: obsidian from Bolivia: 4.14 x 10 6 yr., Ecuador: 8.79 x 10 5 yr., Colombia: 3.52 x 10 6 yr., Peru: 6.55 x 10 6 yr., Chile: 1.13 x 10 6 yr. (MMZ). 5 refs., 3 tabs
The VERDI fission fragment spectrometer
Directory of Open Access Journals (Sweden)
Frégeau M.O.
2013-12-01
Full Text Available The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.
Energies and Yields of Prompt Gamma Rays from Fragments in Slow-Neutron Induced Fission of 235U
Energy Technology Data Exchange (ETDEWEB)
Albinsson, H [Chalmers Univ. of Technology, Goeteborg (SE)
1971-04-15
Measurements were made on the gamma radiation emitted from fission fragments in slow-neutron induced fission of 235U. 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 it was possible to select various collimator settings and let gamma radiation of different half-lives be enhanced. Gamma-ray energy spectra from these time components were then recorded as function of mass. The spectrum shape differed greatly depending on the half-life of the radiation and the fragment from which it was emitted. The results of the present measurements were discussed in the light of existing fission models, and comparisons were made with prompt gamma-ray and neutron data from other fission experiments
Energies and Yields of Prompt Gamma Rays from Fragments in Slow-Neutron Induced Fission of 235U
International Nuclear Information System (INIS)
Albinsson, H.
1971-04-01
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 it was possible to select various collimator settings and let gamma radiation of different half-lives be enhanced. Gamma-ray energy spectra from these time components were then recorded as function of mass. The spectrum shape differed greatly depending on the half-life of the radiation and the fragment from which it was emitted. The results of the present measurements were discussed in the light of existing fission models, and comparisons were made with prompt gamma-ray and neutron data from other fission experiments
Stochastic approaches to dynamics of heavy ion collisions, the case of thermal fission
International Nuclear Information System (INIS)
Boilley, D.; Abe, Y.
1994-01-01
In order to study the influence of fluctuations on various phenomena linked to heavy ion collisions, a Langevin equation has been derived from a microscopic model. Parameters entering this equation are completely determined from microscopic quantities characterizing nuclear matter. This equation has been applied to various phenomena at intermediate energies. This paper focuses on large amplitude motions and especially thermal fission. Fission rate is calculated and compared to experimental results
Coupling of mass and charge distributions for low excited nuclear fission
International Nuclear Information System (INIS)
Salamatin, V.S.; )
2000-01-01
The simple model for calculation of charge distributions of fission fragments for low exited nuclear fission from experimental mass distributions is offered. The model contains two parameters, determining amplitude of even-odd effect of charge distributions and its dependence on excitation energy. Results for reactions 233 U(n th ,f), 235 U(n th ,f), 229 Th(n th ,f), 249 Cf(n th ,f) are spent [ru
Correlation studies of neutron multiplicities in the 252Cf spontaneous fission
International Nuclear Information System (INIS)
Alkhazov, I.D.; Dmitriev, V.D.; Kovalenko, S.S.; Kuznetsov, A.V.; Malkin, L.Z.; Petrzhak, K.A.; Petrov, B.F.; Shpakov, V.I.
1988-01-01
Correlations between the numbers of neutrons emitted by the 252 Cf spontaneous fission fragments have been studied as a function of the fragment mass and total kinetic energy. Behaviour of the neutron number dispersions and covariances was studied for the region of symmetric fission. Parameters of the complementary fragment excitation energy distribution (mean values, dispersions, covariances) were determined. Various factors describing correlations between the complementary fragment excitation energies are considered
The discovery of uranium fission
International Nuclear Information System (INIS)
Brix, P.
1990-01-01
Uranium was discovered 200 years ago. Its radioactive character was first demonstrated in 1896 and two years later radium was extracted from uranium minerals. In 1911 studies with alpha rays from radioactive decay led to the unexpected discovery of the atomic nucleus. Exposure of beryllium to alpha rays yielded neutrons, first detected in 1932. Starting in 1934, neutron irradiation of uranium produced radioactive substances erroneously attributed to transuranium elements but with confusing properties. Painstaking experiments by chemists left no doubt on 17 December 1938 that barium was produced by these irradiations: the neutrons had split some uranium nuclei. The physics of the fission process was understood two weeks later; after a few months, neutron multiplication was found to be probable. This review deals with the eminent scientists involved, their successes, errors and disappointments, and the unexpected insights which occurred on the paths and detours of scientific research. It is, therefore, instructive also to discuss how fission was not discovered. The momentous discovery must be considered inevitable; the great tragedy was that Germany started World War II just at the time when the possibility of nuclear chain reactions and bombs became known. The consequences and anxieties that remain after 50 years of nuclear fission demand that mankind act with reason and conscience to maintain peace. (author)
Metallic fission product releases from HTR-spherical fuel elements
International Nuclear Information System (INIS)
Helmbold, M.; Amian, W.; Stoever, D.; Hecker, R.
1978-01-01
Fission product releases from fuel determines to a large extent the feasibility of a special reactor concept. Basic data describing the diffusion behaviour from coated particle fuel are presented concerning isotopes Cs 137 , Sr 90 and Agsup(110m). Taking into account these data for typical 3000MWth plants release calculations are performed. Sensitive release parameters could be defined and the results show low release figures for all the considered reactor concepts. (author)
Target conception for the Munich fission fragment accelerator
Maier, H J; Gross, M L; Grossmann, R; Kester, O; Thirolf, P
1999-01-01
For the new high-flux reactor FRM II, the fission fragment accelerator MAFF is under design. MAFF will supply intense mass-separated radioactive ion beams of very neutron-rich nuclei with energies around the Coulomb barrier. A central part of this accelerator is the ion source with the fission target, which is operated at a neutron flux of 1.5x10 sup 1 sup 4 cm sup - sup 2 s sup - sup 1. The target consists of typically 1 g of sup 2 sup 3 sup 5 U dispersed in a cylindrical graphite matrix, which is encapsulated in a Re container. To enable diffusion and extraction of the fission products, the target has to be maintained at a temperature of up to 2400 deg. C during operation. It has to stand this temperature for at least one reactor cycle of 1250 h. Comprehensive tests are required to study the long-term behaviour of the involved materials at these conditions prior to operation in the reactor. The present paper gives details of the target conception and the projected tests.
Recent results in heavy-ion-induced fission
International Nuclear Information System (INIS)
Plasil, F.; Awes, T.C.; Cheynis, B.
1984-01-01
A systematic investigation of angular-momentum-dependent fission barriers has been completed. Fission excitation functions were measured for the compound nuclei 153 Tb, 158 Er, 181 Re, 186 Os, and 204 206 208 210 Po. In the case of 153 Tb and 181 Re, evaporation residue cross sections were also measured. With the exception of some of the Po systems, two to five different reactions were used to produce the same compound nucleus with projectiles ranging from 9 Be to 64 Ni. 12 C reactions with 174 Yb, 198 Pt, and 238 U at energies from 95 to 291 MeV; 16 O reactions with 142 Nd, 170 Er, 192 Os, and 238 U at energies from 140 to 315 Mev; 32 S reactions with 126 Te, 144 Nd, and 238 U at energies from 350 to 700 MeV; and 58 Ni reactions with 96 Zr, 116 Cd, and 238 U at 352 and 875 MeV have also been studied. Also, fission fragment angular distributions were measured for the above 12 C- and 16 O-induced reactions. The results were analyzed in terms of saddle-point moments of inertia obtained from the RFRM
Beta-delayed fission and neutron emission calculations for the actinide cosmochronometers
International Nuclear Information System (INIS)
Meyer, B.S.; Howard, W.M.; Mathews, G.J.; Takahashi, K.; Moeller, P.; Leander, G.A.
1989-01-01
The Gamow-Teller beta-strength distributions for 19 neutron-rich nuclei, including ten of interest for the production of the actinide cosmochronometers, are computed microscopically with a code that treats nuclear deformation explicitly. The strength distributions are then used to calculate the beta-delayed fission, neutron emission, and gamma deexcitation probabilities for these nuclei. Fission is treated both in the complete damping and WKB approximations for penetrabilities through the nuclear potential-energy surface. The resulting fission probabilities differ by factors of 2 to 3 or more from the results of previous calculations using microscopically computed beta-strength distributions around the region of greatest interest for production of the cosmochronometers. The indications are that a consistent treatment of nuclear deformation, fission barriers, and beta-strength functions is important in the calculation of delayed fission probabilities and the production of the actinide cosmochronometers. Since we show that the results are very sensitive to relatively small changes in model assumptions, large chronometric ages for the Galaxy based upon high beta-delayed fission probabilities derived from an inconsistent set of nuclear data calculations must be considered quite uncertain
Fission mode analysis of the reaction 237Np(n,f) - possibilities and perspectives
International Nuclear Information System (INIS)
Siegler, P.
1996-01-01
Fission fragment properties for the reaction 237 Np(n,f) have been measured at the Van de Graaff Laboratory of the IRMM. Using a double gridded ionization chamber the mass, kinetic energy and the angular distribution for both fission fragments could be determined simultaneously for an incident neutron energy range from E n =0.3 MeV upto E n =5.5 MeV. Complete datasets have been acquired for 13 different neutron energies covering sub barrier fission as well as fission in the plateau region. A detailed analysis of the fragment distributions and the respective momenta has been carried out, checking the coherence against the excitation energy of the compound nucleus. The consideration of multi-modal fission offers an improved possibility for the description of the fragment distributions backed up by theoretical calculations on the basis of the multi-model random-neck rupture model of Brosa, Grossmann and Mueller. The changes of the fission fragment properties under investigation are completely described and an interpretation of the findings is presented. (author)
Sreenu, K.; Venkata Prasad, C.; Rajagopal Reddy, V.
2017-10-01
A Ti/Orange G/ p-InP metal/interlayer/semiconductor (MIS) junction has been prepared with Orange G (OG) organic layer by electron beam evaporation and spin coating processes. The electrical properties of Ti/ p-InP metal/semiconductor (MS) and Ti/OG/ p-InP MIS junctions have been analyzed based on current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics. The MIS junction exhibited higher rectifying behavior than the MS junction. The higher barrier height (BH) of the MIS junction compared with the MS junction indicates effective modification by the OG layer. Also, the BH, ideality factor, shunt resistance, and series resistance were extracted based on the I- V characteristic, Cheung's and Norde's methods, and the ΨS- V plot. The BH evaluated by Cheung's and Norde's methods and the ΨS- V plot was shown to be similar, confirming the reliability and validity of the methods applied. The extracted interface state density ( N SS) of the MIS junction was less than for the MS junction, revealing that the OG organic layer reduced the N SS value. Analysis demonstrated that, in the lower bias region, the reverse current conduction mechanism was dominated by Poole-Frenkel emission for both the MS and MIS junction. Meanwhile, in the higher bias region, Schottky emission governed the reverse current conduction mechanism. The results suggest that such OG layers have potential for use in high-quality electronic devices.
Simulation of neutron rich nuclei production through 239U fission at intermediates energies
International Nuclear Information System (INIS)
Mirea, M.; Clapier, F.; Pauwels, N.; Proust, J.
1997-01-01
The theoretical part and some results obtained from a model realised for fission processes in wide range of mass-asymmetries are presented. The fission barriers are computed in a tridimensional configuration space using the Yukawa - plus - exponential macroscopic energies corrected within the Strutinsky procedure. It is assumed that channel probabilities are proportional with Gamow penetrabilities. The model is applied for the disintegration of the 239 U in order to determine the relative yields for the production of neutron rich nuclei at diverse intermediate energies. (author)
Device for measuring fission product density
International Nuclear Information System (INIS)
Kaneda, Mitsunori.
1980-01-01
Purpose: To determine the fission product density of xenon or the like and enable measurement of real time of fission product density in a reactor by calculating the disintegration and annihilation of the fission product on the basis of neutron detected output. Constitution: The neutron flux in a reactor is detected by a detector, and applied to first and second density calculators. Second fission product density signal of xenon or the like outputted from first device is again inputted to the device to form an annihilation signal due to disintegration to determine the present density of the second fission product of xenon or the like corresponding to the decrease of the neutron due to the poison of xeron or the like. Similarly, second device determines the first fission product density of iodine or the like. (Sekiya, K.)
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
Fission-energy release for 16 fissioning nuclides. Final report
International Nuclear Information System (INIS)
Sher, R.
1981-03-01
Results are presented of a least-squares evaluation of the components of energy release per fission in 232 Th, 233 U, 235 U, 238 U, 239 Pu, and 241 Pu. For completeness, older (1978) results based on systematics are presented for these and ten other isotopes of interest. There have been recent indications that the delayed energy components may be somewhat higher than those used previously, but the LSQ results do not seem to change significantly when modest (approx. 1 MeV) increases in the total delayed energy are included in the inputs. Additional measurements of most of the energy components are still needed to resolve remaining discrepancies
What do we learn on the dynamics of fission from α-accompanied fission data
International Nuclear Information System (INIS)
Guet, C.; Asghar, M.; Nifenecker, H.; Perrin, P.
1978-01-01
Measurements of the angular distribution of α-particles emitted by thermal fission of 236 U are presented. Also the dependence of the angular distribution on the kinetic energy of the fission products is studied. (WL) [de
Clement, J. D.
1973-01-01
Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.
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
Monte carlo sampling of fission multiplicity.
Energy Technology Data Exchange (ETDEWEB)
Hendricks, J. S. (John S.)
2004-01-01
Two new methods have been developed for fission multiplicity modeling in Monte Carlo calculations. The traditional method of sampling neutron multiplicity from fission is to sample the number of neutrons above or below the average. For example, if there are 2.7 neutrons per fission, three would be chosen 70% of the time and two would be chosen 30% of the time. For many applications, particularly {sup 3}He coincidence counting, a better estimate of the true number of neutrons per fission is required. Generally, this number is estimated by sampling a Gaussian distribution about the average. However, because the tail of the Gaussian distribution is negative and negative neutrons cannot be produced, a slight positive bias can be found in the average value. For criticality calculations, the result of rejecting the negative neutrons is an increase in k{sub eff} of 0.1% in some cases. For spontaneous fission, where the average number of neutrons emitted from fission is low, the error also can be unacceptably large. If the Gaussian width approaches the average number of fissions, 10% too many fission neutrons are produced by not treating the negative Gaussian tail adequately. The first method to treat the Gaussian tail is to determine a correction offset, which then is subtracted from all sampled values of the number of neutrons produced. This offset depends on the average value for any given fission at any energy and must be computed efficiently at each fission from the non-integrable error function. The second method is to determine a corrected zero point so that all neutrons sampled between zero and the corrected zero point are killed to compensate for the negative Gaussian tail bias. Again, the zero point must be computed efficiently at each fission. Both methods give excellent results with a negligible computing time penalty. It is now possible to include the full effects of fission multiplicity without the negative Gaussian tail bias.
Measurements of Fission Cross Sections of Actinides
Wiescher, M; Cox, J; Dahlfors, M
2002-01-01
A measurement of the neutron induced fission cross sections of $^{237}$Np, $^{241},{243}$Am and of $^{245}$Cm is proposed for the n_TOF neutron beam. Two sets of fission detectors will be used: one based on PPAC counters and another based on a fast ionization chamber (FIC). A total of 5x10$^{18}$ protons are requested for the entire fission measurement campaign.
Neutron-induced fission cross sections
International Nuclear Information System (INIS)
Weigmann, H.
1991-01-01
In the history of fission research, neutron-induced fission has always played the most important role. The practical importance of neutron-induced fission rests upon the fact that additional neutrons are produced in the fission process, and thus a chain reaction becomes possible. The practical applications of neutron-induced fission will not be discussed in this chapter, but only the physical properties of one of its characteristics, namely (n,f) cross sections. The most important early summaries on the subject are the monograph edited by Michaudon which also deals with the practical applications, the earlier review article on fission by Michaudon, and the review by Bjornholm and Lynn, in which neutron-induced fission receives major attention. This chapter will attempt to go an intermediate way between the very detailed theoretical treatment in the latter review and the cited monograph which emphasizes the applied aspects and the techniques of fission cross-section measurements. The more recent investigations in the field will be included. Section II will survey the properties of cross sections for neutron-induced fission and also address some special aspects of the experimental methods applied in their measurement. Section Ill will deal with the formal theory of neutron-induced nuclear reactions for the resolved resonance region and the region of statistical nuclear reactions. In Section IV, the fission width, or fission transmission coefficient, will be discussed in detail. Section V will deal with the broader structures due to incompletely damped vibrational resonances, and in particular will address the special case of thorium and neighboring isotopes. Finally, Section VI will briefly discuss parity violation effects in neutron-induced fission. 74 refs., 14 figs., 3 tabs
Fission of nuclei far from stability
International Nuclear Information System (INIS)
Schmidt, K.H.; Benlliure, J.; Junghans, A.R.
2000-11-01
The secondary-beam facility of GSI provided the technical equipment for a new kind of fission experiment. Fission properties of short-lived neutron-deficient nuclei have been investigated in inverse kinematics. The measured element distributions reveal new kinds of systematics on shell structure and even-odd effects and lead to an improved understanding of structure effects in nuclear fission. Prospects for further experimental studies are discussed. (orig.)
International conference on fifty years research in nuclear fission
International Nuclear Information System (INIS)
1989-02-01
These proceedings contain extended abstracts of the papers presented at the named conference. They deal with static properties of fission, instrumentation for fission studies, fission in compound-nucleus reactions, fission dynamics, fission-like heavy ion reactions, and fusion reactions. See hints under the relevant topics. (HSI)
Status of fission product yield data
International Nuclear Information System (INIS)
Cuninghame, J.G.
1978-01-01
The topics covered in this paper are: (a) cumulative yields in thermal neutron fission and in fast fission up to 14 MeV incident neutron energy, (b) dependence of the yields on incident neutron energy and spectrum, (c) independent yields, (d) charge dispersion and distribution, and (e) yields of light particles from ternary fission. The paper reviews information on these subjects for fission of actinides from 232 Th upwards with special emphasis on data published since the 1973 Bologna FPND Panel, compares data sets, and discusses the gaps still to be found in them. (author)
True ternary fission in 310126X
International Nuclear Information System (INIS)
Banupriya, B.; Vijayaraghavan, K.R.; Balasubramaniam, M.
2015-01-01
All possible combinations are minimized by the two dimensional minimization process and minimized with respect to neutron numbers and proton numbers of the fragments. Potential energy is low and Q - value is high at true ternary fission region. It shows that true ternary mode is the dominant mode in the ternary fission of superheavy nuclei. Also, the results show that the fragments with neutron magic numbers are the dominant one in the ternary fission of superheavy nuclei whereas the fragments with proton magic numbers are the dominant one in the ternary fission of heavy nuclei
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)
Nuclear fission studies: from LOHENGRIN to FIPPS
International Nuclear Information System (INIS)
Chebboubi, Abdelaziz
2015-01-01
Nuclear fission consists in splitting a nucleus, in general an actinide, into smaller nuclei. Despite nuclear fission was discovered in 1939 by Hahn and Strassman, fission models cannot predict the fission observables with an acceptable accuracy for nuclear fuel cycle studies for instance. Improvement of fission models is an important issue for the knowledge of the process itself and for the applications. To reduce uncertainties of the nuclear data used in a nuclear reactor simulation, a validation of the models hypothesis is mandatory. In this work, two features of the nuclear fission were investigated in order to test the resistance of the theories. One aspect is the study of the symmetric fission fragments through the measurement of their yield and kinetic energy distribution. The other aspect is the study of the fission fragment angular momentum.Two techniques are available to assess the angular momentum of a fission fragment. The first one is to look at the properties of the prompt gamma. The new spectrometer FIPPS (Fission Product Prompt gamma-ray Spectrometer), is currently under development at the ILL and will combine a fission filter with a large array of gamma and neutron detectors in order to respond to these issues. The first part of this work is dedicated to the study of the properties of a Gas Filled Magnet (GFM) which is the type of fission filter considered for the FIPPS project.The second part of this work deals with the measurement of isomeric yields and evaluations of the angular momentum distribution of fission fragments. The study of the spherical nucleus 132 Sn shed the light on the current limits of fission models. Finally, the last part of this work is about the measurement of the yields and kinetic energy distributions of symmetric fission fragments. Since models predict the existence of fission modes, the symmetry region is a suitable choice to investigate this kind of prediction. In parallel with all these studies, an emphasis on the
Process for the extraction of fission products
International Nuclear Information System (INIS)
Anav, M.; Chesne, A.; Leseur, A.; Miquel, P.; Pascard, R.
1979-01-01
A process is described for the extraction of fission products contained in irradiated nuclear fuel elements which have been subject to a temperature of at least 1200 0 C during their irradiation prior to dissolving the fuel by the wet process. After mechanically treating the elements in order to decan and/or cut them they are brought into contact with water in order to pass the fission products into aqueous solution. The treated elements are then separated from the thus obtained aqueous solution. At least one of the fission products is then recovered from the aqueous solution. The fission products are iodine, cesium, rubidium and tritium
A spin exchange model for singlet fission
Yago, Tomoaki; Wakasa, Masanobu
2018-03-01
Singlet fission has been analyzed with the Dexter model in which electron exchange occurs between chromophores, conserving the spin for each electron. In the present study, we propose a spin exchange model for singlet fission. In the spin exchange model, spins are exchanged by the exchange interaction between two electrons. Our analysis with simple spin functions demonstrates that singlet fission is possible by spin exchange. A necessary condition for spin exchange is a variation in exchange interactions. We also adapt the spin exchange model to triplet fusion and triplet energy transfer, which often occur after singlet fission in organic solids.
Mass-yield distributions of fission products from 20, 32, and 45 MeV proton-induced fission of 232Th
Naik, H.; Goswami, A.; Kim, G. N.; Kim, K.; Suryanarayana, S. V.
2013-10-01
The yields of various fission products in the 19.6, 32.2, and 44.8 MeV proton-induced fission of 232Th have been determined by recoil catcher and an off-line γ-ray spectrometric technique using the BARC-TIFR Pelletron in India and MC-50 cyclotron in Korea. The mass-yield distributions were obtained from the fission product yield using the charge distribution corrections. The peak-to-valley (P/V) ratio of the present work and that of literature data for 232Th(p,f) and 238U(p,f) were obtained from the mass yield distribution. The present and the existing literature data for 232Th(p,f), 232Th(n,f), and 232Th( γ,f) at various energies were compared with those for 238U(p,f), 238U(n,f), and 238U( γ,f) to examine the probable nuclear structure effect. The role of Th-anomaly on the peak-to-valley ratio in proton-, neutron-, and photon-induced fission of 232Th was discussed with the similar data in 238U. On the other hand, the fine structure in the mass yield distributions of the fissioning systems at various excitation energies has been explained from the point of standard I and II asymmetric mode of fission besides the probable role of even-odd effect, A/ Z ratio, and fissility parameter.
Fission - track age of the Marjalahti Pallasite
International Nuclear Information System (INIS)
Bondar, Yu.V.; Perelygin, V.P.
2006-01-01
Full text: Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Over geological time, meteorites crystals have accumulated a record of tracks produced by heavily charged energetic particles from both internal (spontaneous fission of 238U and some other extinct isotopes) and external sources (galactic cosmic rays with Z>20). The fortunate fact that meteorite grains can accumulate latent and very long-lived tracks since soon after the end of nucleosynthesis in the solar nebula enables one to decode their radiation history and to detect any thermal events in the meteorite cosmic history by revealing these tracks through suitable etching procedures. Only a few minerals in meteorites (mainly phosphates) contain small amount of uranium; the fact that 238 U undergoes fission with fission-decay constant λ f ∼ 8.2x10 -17 yr -1 allows one to use this isotope as a chronometer. By measuring the U concentration in the crystals (by reactor irradiation) and the density of the spontaneous-fission tracks it is relatively easy to calculate the 'fission-track age' if 238 U is the main source of fission tracks. However the fission-track dating of extraterrestrial samples compared with the terrestrial ones has some peculiar features due to presence of a number of other potential track sources except the spontaneous fission of 238 U, such as the spontaneous fission of presently extinct 244 Pu, heavy nuclei of cosmic rays and induced fission by cosmic ray primaries. Only tracks from the spontaneous fission of U and Pu are suitable for fission-track dating. The competing effects of these fissioning elements, whose half-lives differ by a factor of ∼50, form a basis for a fission-track chronology for samples older than ∼ 4.0 Gyr. Over small intervals in time (∼ few x10 8 yr ) the track density from spontaneous fission of 238 U is nearly constant. However, the
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
Baby fission chambers; Etude de chambres a fission miniatures
Energy Technology Data Exchange (ETDEWEB)
Guery, U; Tachon, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1957-07-01
The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)
Baby fission chambers; Etude de chambres a fission miniatures
Energy Technology Data Exchange (ETDEWEB)
Guery, U.; Tachon, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1957-07-01
The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)
Fission fragment excited laser system
McArthur, David A.; Tollefsrud, Philip B.
1976-01-01
A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.
Fission tracks diameters in glasses
International Nuclear Information System (INIS)
Garzon Ruiperez, L.; Veiguela, J.
1974-01-01
Standard glass microscope slides have been irradiated with fission fragments from the uranium. The etching track conditions have been the same for the series, having changed the etching time only for each specimen. For each glass, a minimum of 250 measurements of the tracks diameters have been made, the distributions of which are the bimodal type. Diameters-etching dependence with time is roughly lineal. Energy determinations have been made with the help of the diameters-energy relations. The calculated values agree very well with the know ones. (author) [es
Convective-diffusive transport of fission products in the gap of a failed fuel element
International Nuclear Information System (INIS)
Lian, Z.W.; Carlucci, L.N.; Arimescu, V.I.
1995-03-01
A model is presented to describe the transport behaviour of gaseous fission products along the axial fuel-to-sheathe gap of a failed fuel element to the coolant system. The model is applicable to an element having failed under normal operating conditions or loss-of coolant-accident conditions. Because of the large differences in operating parameters, the transport characteristics of gaseous fission products in a failed element under these two operating conditions are significantly different. However, in both cases the transport process can be described by convection-diffusion caused by the continuous release of fission products from the fuel to the gap. Under normal operating conditions, the bulk-flow velocity is found to be negligible, due to the low release rate of fission products from fuel. The process can be well approximated by the diffusion of fission products in a stagnant gas-steam mixture. The effect of convection on the fission product transport, however, becomes significant under loss-of-coolant-accident conditions, where the release rates of fission products from fuel can be several orders of magnitude higher that that under normal operating conditions. The convection of the mixture in the gap not only contributes an additional flux to the gas-mixture transport, but also increases the gradient of fission products concentration across the opening, and therefore increases the diffusion flux to the coolant. As a result of the bulk flow, the transport of fission products along the gap is accelerated and the hold-up of short-lived isotopes in the gap is significantly reduced. Steam ingress through the opening into the gap is obstructed by the bulk flow, resulting in low steam concentrations in the gap under loss-of-coolant-accident conditions. (author). 6 refs., 8 figs
Simultaneous analysis of fission and capture cross section with Adler-Adler resonance formula
International Nuclear Information System (INIS)
Cao Hengdao; Qiu Guochun
1989-01-01
The method of simultaneous analysis of fission and capture cross section for fissile nuclide with Adler-Adler resonance formula and the corresponding computer code are presented. A simple and convenient method to correct parameters μ, γ simultaneously is given in order to acquire optimized parameters. The results are satisfactory
Preliminary neutronics calculation of fusion-fission hybrid reactor breeding spent fuel assembly
International Nuclear Information System (INIS)
Ma Xubo; Chen Yixue; Gao Bin
2013-01-01
The possibility of using the fusion-fission hybrid reactor breeding spent fuel in PWR was preliminarily studied in this paper. According to the fusion-fission hybrid reactor breeding spent fuel characteristics, PWR assembly including fusion-fission hybrid reactor breeding spent fuel was designed. The parameters such as fuel temperature coefficient, moderator temperature coefficient and their variation were investigated. Results show that the neutron properties of uranium-based assembly and hybrid reactor breeding spent fuel assembly are similar. The design of this paper has a smaller uniformity coefficient of power at the same fissile isotope mass percentage. The results will provide technical support for the future fusion-fission hybrid reactor and PWR combined with cycle system. (authors)
A reconsideration of fission fragment angular distributions from nuclei of high spin
International Nuclear Information System (INIS)
Vaz, L.C.; Alexander, J.M.
1983-01-01
It has often been stated that fission fragment angular anisotropy, as predicted by equilibrium statistical theory, should disappear with increasing spin of the composite nucleus. However, several recent experimental studies reveal strong anisotropies for fission fragments from high-spin nuclear systems. We discuss this apparent discrepancy and its relationship to the rigid-rotor approximation used in the standard theory. A systematic comparison is given for fission fragment anisotropies from many experiments via the empirical parameters K 0 2 and Ssub(eff). These systematics indicate a strong regularity, provided one allows for the perturbing effects of fission after transfer reactions. Many of the observed anisotropies exceed the predictions of the standard theory, but, as these predictions are based on a rigid rotor model, this does not seem particularly noteworthy. (orig.)
Conceptual design of a fusion-fission hybrid reactor for transmutation of high level nuclear waste
International Nuclear Information System (INIS)
Qiu, L.J.; Wu, Y.C.; Yang, Y.W.; Wu, Y.; Luan, G.S.; Xu, Q.; Guo, Z.J.; Xiao, B.J.
1994-01-01
To assess the feasibility of the transmutation of long-lived radioactive waste using fusion-fission hybrid reactors, we are studying all the possible types of blanket, including a comparison of the thermal and fast neutron spectrum blankets. Conceptual designs of a small tokamak hybrid blanket with small inventory of actinides and fission products are presented. The small inventory of wastes makes the system safer. The small hybrid reactor system based on a fusion core with experimental parameters to be realized in the near future can effectively transmute actinides and fission products at a neutron wall loading of 1MWm -2 . An innovative energy system is also presented, including a fusion driver, fuel breeder, high level waste transmuter, fission reactor and so on. An optimal combination of all types of reactor is proposed in the system. ((orig.))
Uranium borehole logging using delayed or prompt fission neutrons
International Nuclear Information System (INIS)
Schulze, G.; Wuerz, H.
1977-04-01
The measurement of induced fission neutrons using Cf 252 and 14 MeV neutrons is a sensitive method for an in situ determination of Uranium. Applying this methods requires a unique relation between concentration of Uranium and intensity of induced fission neutrons. A discussion of parameters influencing the determination of concentration is given. A simple method is developed allowing an elemination of the geochemistry of the deposit and of the borehole configuration. Borehole probes using the methods described are of considerable help during the phase of detailed exploration of uranium ore deposits. These on-line tools allow an immediate determination of concentration. Thus avoiding the expensive and time consuming step of core drilling and subsequent chemical analysis. (orig./HP) [de
Measurement of fission product release during LWR fuel failure
International Nuclear Information System (INIS)
Osetek, D.J.; King, J.J.
1979-01-01
The PBF is a specialized test reactor consisting of an annular core and a central test space 21 cm in diameter and 91 cm high. A test loop circulates coolant through the central experimental section at typical power reactor conditions. Light-water-reactor-type fuel rods are exposed to power bursts simulating reactivity insertion transients, and to power-cooling-mismatch conditions during which the rods are allowed to operate in film boiling. Fission product concentrations in the test loop coolant are continuously monitored during these transients by a Ge(Li) detector based gamma spectrometer. Automatic batch processing of pulse height spectra results in a list of radionuclide concentrations present in the loop coolant as a function of time during the test. Fission product behavior is then correlated to test parameters and posttest examination of the fuel rods. Data are presented from Test PCM-1
Quantitative analysis of fission products by γ spectrography
International Nuclear Information System (INIS)
Malet, G.
1962-01-01
The activity of the fission products present in treated solutions of irradiated fuels is given as a function of the time of cooling and of the irradiation time. The variation of the ratio ( 144 Ce + 144 Pr activity)/ 137 Cs activity) as a function of these same parameters is also given. From these results a method is deduced giving the 'age' of the solution analyzed. By γ-scintillation spectrography it was possible to estimate the following elements individually: 141 Ce, 144 Ce + 144 Pr, 103 Ru, 106 Ru + 106 Rh, 137 Cs, 95 Zr + 95 Nb. Yield curves are given for the case of a single emitter. Of the various existing methods, that of the least squares was used for the quantitative analysis of the afore-mentioned fission products. The accuracy attained varies from 3 to 10%. (author) [fr
Fission product release from HTGR coated microparticles and fuel elements
International Nuclear Information System (INIS)
Gusev, A.A.; Deryugin, A.I.; Lyutikov, R.A.; Chernikov, A.S.
1991-01-01
The article presents the results of the investigation of fission products release from microparticles with UO 2 core and five-layer HII PyC- and SiC base protection layers of TRICO type as well as from spherical fuel elements based thereon. It is shown that relative release of short-lived xenon and crypton from microparticles does not exceed (2-3) 10 -7 . The release of gaseous fission products from fuel elements containing no damaged coated microparticles, is primarily determined by the contamination of matrix graphite with fuel. An analytical dependence is derived, the dependence described the relation between structural parameters of coated microparticles, irradiation conditions and fuel burnup at which depressurization of coated microparticles starts
Least squares analysis of fission neutron standard fields
International Nuclear Information System (INIS)
Griffin, P.J.; Williams, J.G.
1997-01-01
A least squares analysis of fission neutron standard fields has been performed using the latest dosimetry cross sections. Discrepant nuclear data are identified and adjusted spectra for 252 Cf spontaneous fission and 235 U thermal fission fields are presented
Formation of heavy compound nuclei, their survival and correlation with longtime-scale fission
International Nuclear Information System (INIS)
Karamyan, S.A.; Yakushev, A.B.
2006-01-01
Fusion of two massive nuclei with formation of super-heavy compound nucleus (CN) is driven by the potential energy gradient, as follows from the analysis of nuclear reaction cross-sections. The conservative energy of the system is deduced in simple approximation using regularized nuclear mass and interaction barrier values. Different reactions for the synthesis of Z c 110-118 nuclei are compared and the favourable conditions are found for fusion of the stable (W-Pt) isotopes with radioactive fission fragment projectiles, like 94 Kr or 100 Sr. Thus, the cold fusion method can be extended for a synthesis of elements with Z > 113. Survival of the evaporation residue is defined by the neutron-to-fission probability ratio and by the successful emission of gammas at the final step of the reaction. Numerical estimates are presented. Fixation of evaporation residue products must correlate with longtime-scale fission and available experimental results are discussed
Measurement of mass distribution of U-235 fission products in the intermediate neutron region
International Nuclear Information System (INIS)
Nakagomi, Yoshihiro; Kobayashi, Shohei; Yamamoto, Shuji; Kanno, Ikuo; Wakabayashi, Hiroaki.
1982-01-01
The mass distribution and the momentum distribution of U-235 fission products in the intermediate neutron region were measured by using a combination system of the Yayoi intermediate neutron column and an electron linear accelerator. The double energy measurement method was applied. A fission chamber, which consists of an enriched uranium target and two Si surface barrier detectors, was used for the measurement of the neutrons with energy above 1.3 eV. The linear accelerator was operated at the repetition rate of 100 Hz and the pulse width of 10 ns. The data obtained by the two-dimensional pulse height analysis were analyzed by the Schmitt's method. The preliminary results of the mass distribution and the momentum distribution of fission fragments were obtained. (Kato, T.)
International Nuclear Information System (INIS)
Fischer, E.A.; Vaeth, L.
1989-04-01
The transient fission gas behaviour and the fission gas induced fuel motion were studied in in-pile experiments in different countries, under conditions typical for hypothetical accidents. This report summarizes first the different experiment series and the main results. Then, a comparative evaluation is given, which provides a basis for the choice of the fission gas parameters in the accident code SAS3D
Nuclear Power from Fission Reactors. An Introduction.
Department of Energy, Washington, DC. Technical Information Center.
The purpose of this booklet is to provide a basic understanding of nuclear fission energy and different fission reaction concepts. Topics discussed are: energy use and production, current uses of fuels, oil and gas consumption, alternative energy sources, fossil fuel plants, nuclear plants, boiling water and pressurized water reactors, the light…
Progress in fission product nuclear data
International Nuclear Information System (INIS)
Lammer, M.
1981-06-01
This is the seventh issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields (neutron induced and spontaneous fission); neutron reaction cross sections of fission products; data related to the radioactive decay of fission products; delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The sixth issue of this series has been published in June 1980 as INDC(NDS)-113/G+P. The present issue includes contributions which were received by NDS between 1 August 1980 and 25 May 1981
Options for Affordable Fission Surface Power Systems
International Nuclear Information System (INIS)
Houts, Mike; Gaddis, Steve; Porter, Ron; Van Dyke, Melissa; Martin, Jim; Godfroy, Tom; Bragg-Sitton, Shannon; Garber, Anne; Pearson, Boise
2006-01-01
Fission surface power systems could provide abundant power anywhere on the surface of the moon or Mars. Locations could include permanently shaded regions on the moon and high latitudes on Mars. To be fully utilized, however, fission surface power systems must be safe, have adequate performance, and be affordable. This paper discusses options for the design and development of such systems. (authors)
Progress in fission product nuclear data
International Nuclear Information System (INIS)
Lammer, M.
1982-07-01
This is the eighth issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The main part of this report consists of unaltered original contributions which the authors have sent to IAEA/NDS. Therefore, the IAEA cannot be held responsible for the information contained nor for any consequences resulting from the use of this information. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission); Neutron reaction cross sections of fission products; Data related to the radioactive decay of fission products; Delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The seventh issue of this series has been published in July 1981 as INDC(NDS)-116. The present issue includes contributions which were received by NDS between 1 August 1981 and 15 June 1982
Progress in fission product nuclear data
International Nuclear Information System (INIS)
Lammer, M.
1983-08-01
This is the ninth issue of a report series on Fission Product Nuclear Data (FPND) which is published by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). The purpose of this series is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The main part of this report consists of unaltered original contributions which the authors have sent to IAEA/NDS. The present issue contains also a section with some recent references relative to fission product nuclear data, which were not covered by the contributions submitted. The types of activities being included in this report are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission); Neutron reaction cross sections of fission products; Data related to the radioactive decay of fission products; Delayed neutron data of fission products; and lumped fission product data (decay heat, absorption etc.). The eighth issue of this series has been published in July 1982 as INDC(NDS)-130. The present issue includes contributions which were received by NDS between 1 August 1982 and 25 June 1983
Induced-Fission Imaging of Nuclear Material
International Nuclear Information System (INIS)
Hausladen, Paul; Blackston, Matthew A.; Mullens, James Allen; McConchie, Seth M.; Mihalczo, John T.; Bingham, Philip R.; Ericson, Milton Nance; Fabris, Lorenzo
2010-01-01
This paper presents initial results from development of the induced-fission imaging technique, which can be used for the purpose of measuring or verifying the distribution of fissionable material in an unopened container. The technique is based on stimulating fissions in nuclear material with 14 MeV neutrons from an associated-particle deuterium-tritium (D-T) generator and counting the subsequent induced fast fission neutrons with an array of fast organic scintillation detectors. For each source neutron incident on the container, the neutron creation time and initial trajectory are known from detection of the associated alpha particle of the d + t → α + n reaction. Many induced fissions will lie along (or near) the interrogating neutron path, allowing an image of the spatial distribution of prompt induced fissions, and thereby fissionable material, to be constructed. A variety of induced-fission imaging measurements have been performed at Oak Ridge National Laboratory with a portable, low-dose D-T generator, including single-view radiographic measurements and three-dimensional tomographic measurements. Results from these measurements will be presented along with the neutron transmission images that have been performed simultaneously. This new capability may have applications to a number of areas in which there may be a need to confirm the presence or configuration of nuclear materials, such as nuclear material control and accountability, quality assurance, treaty confirmation, or homeland security applications.
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.)