Prompt fission neutron spectra from fission induced by 1 to 8 MeV neutrons on 235U and 239Pu using the double time-of-flight technique

International Nuclear Information System (INIS)

Noda, S.; Haight, R. C.; Nelson, R. O.; Devlin, M.; O'Donnell, J. M.; Chatillon, A.; Granier, T.; Belier, G.; Taieb, J.; Kawano, T.; Talou, P.

2011-01-01

Prompt fission neutron spectra from 235 U and 239 Pu were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg 235 U and 90 mg 239 Pu detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced γ-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.

Role of effective distance in the fission mechanism study by the double-energy measurement for uranium isotopes

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.

Role of effective distance in the fission mechanism study by the double-energy measurement for uranium isotopes

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

Sequential double photodetachment of He- in elliptically polarized laser fields

Science.gov (United States)

Génévriez, Matthieu; Dunseath, Kevin M.; Terao-Dunseath, Mariko; Urbain, Xavier

2018-02-01

Four-photon double detachment of the helium negative ion is investigated experimentally and theoretically for photon energies where the transient helium atom is in the 1 s 2 s 3S or 1 s 2 p P3o states, which subsequently ionize by absorption of three photons. Ionization is enhanced by intermediate resonances, giving rise to series of peaks in the He+ spectrum, which we study in detail. The He+ yield is measured in the wavelength ranges from 530 to 560 nm and from 685 to 730 nm and for various polarizations of the laser light. Double detachment is treated theoretically as a sequential process, within the framework of R -matrix theory for the first step and effective Hamiltonian theory for the second step. Experimental conditions are accurately modeled, and the measured and simulated yields are in good qualitative and, in some cases, quantitative agreement. Resonances in the double detachment spectra can be attributed to well-defined Rydberg states of the transient atom. The double detachment yield exhibits a strong dependence on the laser polarization which can be related to the magnetic quantum number of the intermediate atomic state. We also investigate the possibility of nonsequential double detachment with a two-color experiment but observe no evidence for it.

Sequential fission process observed in the reaction (16.7 MeV/u) 238U + nat.Au using mica as dielectric track detector

International Nuclear Information System (INIS)

Shahzad, Muhammad Ikram; Qureshi, Imtinan Elahi; Manzoor, Shahid; Khan, Hameed Ahmed

1999-01-01

The evidence of sequential fission has been found in the heavy-ion reaction (16.7 MeV/u) 238 U + nat. Au, using muscovite mica as Dielectric Track Detector (DTD) placed in a 2π-geometry configuration. The reaction products originating from the interactions of 238 U ions with the atoms of gold were registered in the detector in the form of tracks and identified for performing a detailed kinematical analysis. For this purpose the spherical polar coordinates of the correlated tracks of the multipronged events have been analyzed on an event-by-event basis. Automatic, semi-automatic and manual measuring methods have been employed to collect and manipulate the track data. The known characteristics of binary and ternary events observed in the reaction have been used for the calibration of the detectors. The computed masses, Q-values and relative velocities of the reaction products determined in this analysis are compared with theoretical predictions based on sequential fission process. Agreement within one standard deviation with respect to the experimental values has been found for the majority of analyzed events. Therefore, it is concluded that three particles in the exit channel of the reaction are produced in two successive steps. In the first step of the reaction, two intermediate nuclei are formed as a result of an inelastic collision between projectile and target atoms while in the second step the fission of one of the intermediate nuclei of the previous step takes place. Furthermore no proximity effects have been observed

Angular anisotropy parameters for sequential two-photon double ionization of helium

International Nuclear Information System (INIS)

Ivanov, I A; Kheifets, A S

2009-01-01

We evaluate photoelectron angular anisotropy /3-parameters for the process of sequential two-photon double electron ionization of helium within the time-independent lowest order perturbation theory (LOPT). Our results indicate that for the photoelectron energies outside the interval (E slow , E fast ), where E slow = ω - IP He + and E fast ω - IP He , there is a considerable deviation from the dipole angular distribution thus indicating the effect of electron correlation.

Asymmetry in ternary fission induced by polarized neutrons and fission mechanism

International Nuclear Information System (INIS)

Bunakov, V.E.; Gennenvajn, F.; Dzhessinger, P.; Mutterer, M.; Petrov, G.A.

2003-01-01

The results of measuring the P-odd, P-even (right-left) and T-odd asymmetries of the charged particles emission in the double and ternary fission, induced by the polarized neutrons, are considered. It is shown, what kind of information on the mechanism of the ternary nuclear fission may be obtained from the theoretical analysis of these data [ru

Three-dimensional classical-ensemble modeling of non-sequential double ionization

International Nuclear Information System (INIS)

Haan, S.L.; Breen, L.; Tannor, D.; Panfili, R.; Ho, Phay J.; Eberly, J.H.

2005-01-01

Full text: We have been using 1d ensembles of classical two-electron atoms to simulate helium atoms that are exposed to pulses of intense laser radiation. In this talk we discuss the challenges in setting up a 3d classical ensemble that can mimic the quantum ground state of helium. We then report studies in which each one of 500,000 two-electron trajectories is followed in 3d through a ten-cycle (25 fs) 780 nm laser pulse. We examine double-ionization yield for various intensities, finding the familiar knee structure. We consider the momentum spread of outcoming electrons in directions both parallel and perpendicular to the direction of laser polarization, and find results that are consistent with experiment. We examine individual trajectories and recollision processes that lead to double ionization, considering the best phases of the laser cycle for recollision events and looking at the possible time delay between recollision and emergence. We consider also the number of recollision events, and find that multiple recollisions are common in the classical ensemble. We investigate which collisional processes lead to various final electron momenta. We conclude with comments regarding the ability of classical mechanics to describe non-sequential double ionization, and a quick summary of similarities and differences between 1d and 3d classical double ionization using energy-trajectory comparisons. Refs. 3 (author)

Sequential fission process observed in the reaction (16.7 MeV/u) {sup 238}U + {sup nat.}Au using mica as dielectric track detector

Energy Technology Data Exchange (ETDEWEB)

Shahzad, Muhammad Ikram; Qureshi, Imtinan Elahi; Manzoor, Shahid; Khan, Hameed Ahmed

1999-01-04

The evidence of sequential fission has been found in the heavy-ion reaction (16.7 MeV/u) {sup 238}U + {sup nat.}Au, using muscovite mica as Dielectric Track Detector (DTD) placed in a 2{pi}-geometry configuration. The reaction products originating from the interactions of {sup 238}U ions with the atoms of gold were registered in the detector in the form of tracks and identified for performing a detailed kinematical analysis. For this purpose the spherical polar coordinates of the correlated tracks of the multipronged events have been analyzed on an event-by-event basis. Automatic, semi-automatic and manual measuring methods have been employed to collect and manipulate the track data. The known characteristics of binary and ternary events observed in the reaction have been used for the calibration of the detectors. The computed masses, Q-values and relative velocities of the reaction products determined in this analysis are compared with theoretical predictions based on sequential fission process. Agreement within one standard deviation with respect to the experimental values has been found for the majority of analyzed events. Therefore, it is concluded that three particles in the exit channel of the reaction are produced in two successive steps. In the first step of the reaction, two intermediate nuclei are formed as a result of an inelastic collision between projectile and target atoms while in the second step the fission of one of the intermediate nuclei of the previous step takes place. Furthermore no proximity effects have been observed.

Double-blind photo lineups using actual eyewitnesses: an experimental test of a sequential versus simultaneous lineup procedure.

Science.gov (United States)

Wells, Gary L; Steblay, Nancy K; Dysart, Jennifer E

2015-02-01

Eyewitnesses (494) to actual crimes in 4 police jurisdictions were randomly assigned to view simultaneous or sequential photo lineups using laptop computers and double-blind administration. The sequential procedure used in the field experiment mimicked how it is conducted in actual practice (e.g., using a continuation rule, witness does not know how many photos are to be viewed, witnesses resolve any multiple identifications), which is not how most lab experiments have tested the sequential lineup. No significant differences emerged in rates of identifying lineup suspects (25% overall) but the sequential procedure produced a significantly lower rate (11%) of identifying known-innocent lineup fillers than did the simultaneous procedure (18%). The simultaneous/sequential pattern did not significantly interact with estimator variables and no lineup-position effects were observed for either the simultaneous or sequential procedures. Rates of nonidentification were not significantly different for simultaneous and sequential but nonidentifiers from the sequential procedure were more likely to use the "not sure" response option than were nonidentifiers from the simultaneous procedure. Among witnesses who made an identification, 36% (41% of simultaneous and 32% of sequential) identified a known-innocent filler rather than a suspect, indicating that eyewitness performance overall was very poor. The results suggest that the sequential procedure that is used in the field reduces the identification of known-innocent fillers, but the differences are relatively small.

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)

Towards non-sequential double ionization of Ne and Ar using a femtosecond laser oscillator.

Science.gov (United States)

Liu, Yunquan; Tschuch, Sebastian; Dürr, Martin; Rudenko, Artem; Moshammer, Robert; Ullrich, Joachim; Siegel, Martin; Morgner, Uwe

2007-12-24

We report on first proof-of-principles results on non-sequential double ionization of argon and neon achieved by using a newly developed long-cavity Ti:sapphire femtosecond oscillator with a pulse duration of 45 fs and a repetition of 6.2 MHz combined with a dedicated reaction microscope. Under optimized experimental conditions, peak intensities larger than 2.310(14) W/cm(2) have been achieved. Ion momentum distributions were recorded for both rare gases and show significantly different features for single as well as for double ionization. For single ionization of neon a spike of zero-momentum electrons is found when decreasing the laser intensity towards the lowest ionization rate we can measure which is attributed to a non-resonant ionization channel. As to double ionization, the longitudinal momentum distribution for Ne(2+) displays a clear double-hump structure whereas this feature is found to be smoothened out with a maximum at zero momentum for Ar(2+).

Sequential lineup laps and eyewitness accuracy.

Science.gov (United States)

Steblay, Nancy K; Dietrich, Hannah L; Ryan, Shannon L; Raczynski, Jeanette L; James, Kali A

2011-08-01

Police practice of double-blind sequential lineups prompts a question about the efficacy of repeated viewings (laps) of the sequential lineup. Two laboratory experiments confirmed the presence of a sequential lap effect: an increase in witness lineup picks from first to second lap, when the culprit was a stranger. The second lap produced more errors than correct identifications. In Experiment 2, lineup diagnosticity was significantly higher for sequential lineup procedures that employed a single versus double laps. Witnesses who elected to view a second lap made significantly more errors than witnesses who chose to stop after one lap or those who were required to view two laps. Witnesses with prior exposure to the culprit did not exhibit a sequential lap effect.

Measurements of prompt fission neutron spectra and double-differential neutron inelastic-scattering cross sections for 238U and 232Th

International Nuclear Information System (INIS)

Baba, Mamoru; Itoh, Nobuo; Maeda, Kazuto; Hirakawa, Naohiro; Wakabayashi, Hidetaka.

1989-10-01

This report presents the summary of experimental studies of prompt fission neutron spectra and double-differential neutron inelastic-scattering cross sections of 238 U and 232 Th. The experiments were performed at Tohoku University Fast Neutron Laboratory employing a time-of-flight technique and Dynamitron accelerator as the pulsed neutron generator. From the experiments, we obtained the following data for both nuclei; 1. prompt fission neutron spectrum for 2 MeV neutrons, 2. double-differential neutron inelastic-scattering cross sections for 1.2, 2.0, 4.2, 6.1 and 14.1 MeV incident neutrons. Both in experiments and data processing, cares were taken to obtain reliable data by avoiding systematic uncertainty. The experimental data were compared with those by other experiments, evaluations and model calculations. Through the data comparison, some fundamental problems were found in the experiments by previous authors and the evaluations. The present data will provide useful data base for refinement of the evaluated data and theoretical models. (author)

Production of N-acetyl-D-neuraminic acid using two sequential enzymes overexpressed as double-tagged fusion proteins

Directory of Open Access Journals (Sweden)

Cheng Chung-Hsien

2009-07-01

Full Text Available Abstract Background Two sequential enzymes in the production of sialic acids, N-acetyl-D-glucosamine 2-epimerase (GlcNAc 2-epimerase and N-acetyl-D-neuraminic acid aldolase (Neu5Ac aldolase, were overexpressed as double-tagged gene fusions. Both were tagged with glutathione S-transferase (GST at the N-terminus, but at the C-terminus, one was tagged with five contiguous aspartate residues (5D, and the other with five contiguous arginine residues (5R. Results Both fusion proteins were overexpressed in Escherichia coli and retained enzymatic activity. The fusions were designed so their surfaces were charged under enzyme reaction conditions, which allowed isolation and immobilization in a single step, through a simple capture with either an anionic or a cationic exchanger (Sepharose Q or Sepharose SP that electrostatically bound the 5D or 5R tag. The introduction of double tags only marginally altered the affinity of the enzymes for their substrates, and the double-tagged proteins were enzymatically active in both soluble and immobilized forms. Combined use of the fusion proteins led to the production of N-acetyl-D-neuraminic acid (Neu5Ac from N-acetyl-D-glucosamine (GlcNAc. Conclusion Double-tagged gene fusions were overexpressed to yield two enzymes that perform sequential steps in sialic acid synthesis. The proteins were easily immobilized via ionic tags onto ionic exchange resins and could thus be purified by direct capture from crude protein extracts. The immobilized, double-tagged proteins were effective for one-pot enzymatic production of sialic acid.

Double-radionuclide autoradiographic method using N-isopropyl-iodoamphetamine for sequential measurements of local cerebral blood flow

International Nuclear Information System (INIS)

Obrenovitch, T.P.; Clayton, C.B.; Strong, A.J.

1987-01-01

A double-radionuclide autoradiographic method has been assessed for sequential determinations of local CBF (LCBF). It is based on two successive intravascular injections of N-isopropyl-p-iodoamphetamine (IMP) labelled with different radionuclides, whose concentrations can later be differentiated in the same tissue section using double-radionuclide autoradiography. Previous studies suggested that the distribution of IMP, up to 30 min after its administration, still represents LCBFs. Our data indicate that, provided the tracer is injected directly into the left ventricle, there is little back diffusion from normal brain to blood under physiological conditions for at least 35 min following the tracer injection and an injection of unlabelled IMP, in a dose larger than that used for blood flow determination, does not displace any labelled IMP previously taken up by the brain, nor does it displace any labelled IMP previously accumulated in the lung that would lead to secondary brain uptake. On the basis of these results, we conclude that sequential autoradiographic determinations of LCBF using IMP labelled with different radionuclides is possible. This is a promising experimental method for the simultaneous investigation of changes in LCBF in several CNS structures

Delayed fission of the 238U muonic atom

International Nuclear Information System (INIS)

Ganzorig, Dz.; Krogulski, T.; Kuznetsov, V.D.; Polikanov, S.M.; Sabirov, B.M.

1975-01-01

The time distributions of fission and muon free decay events with respect to the moment of the muon-stop event have been measured for double and triple coincidences between these three events. The triple-coincidence time distributions give an indication of the o-curence of two new effects: the delayed fission of muonic 238 U atom and conversion of muons from the fission fragments

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 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.

Safety device for nuclear fission reactors

International Nuclear Information System (INIS)

Brownlee, M.L.

1982-01-01

A plurality of radially arranged and neutron absorbing baffles are stacked in vertical sets under the fuel core assemblies, and the whole enclosed in a bottle shaped containment vessel. The radially arranged baffles of each set extend vertically, and each set has double the number of baffles as the set above it in the stack. A melt-down of a fuel core assembly drops the fissioning nuclear fuel into the stacked sets of baffles, there, as it passes through, to be progressively divided, redivided and dispersed in smaller and smaller masses between the doubling number of baffles in safe fuel pellet size. Neutron absorbing containment prevents contamination of the environment and together with cooling means stops fissioning of fuel

Fission dynamics as brought out in cold fragmentation studies

International Nuclear Information System (INIS)

Signarbieux, G.

1986-10-01

Fission dynamics problem has been addressed since the beginning. This paper is specifically concerned by ''even-odd effects '' in fragment distribution. These effects are reinterpreted, some complementary thoughts on double ionization chamber are given together with a study of fission dymanics at low energy [fr

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.))

Measurement and analysis of 14 MeV neutron-induced double-differential neutron emission cross sections needed for fission and fusion reactor technology

International Nuclear Information System (INIS)

Wang Dahai.

1990-10-01

The main objectives of this IAEA Co-ordinated Research Programme are to improve the data on 14 MeV neutron-induced double-differential neutron emission cross sections for materials needed for fission and fusion reactor technology. This report summarizes the conclusions and recommendations which were agreed by all participants during the Second Research Co-ordination Meeting

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

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)

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

Studies of the wavelength dependence of non-sequential double ionization of xenon in strong fields

International Nuclear Information System (INIS)

Kaminski, P.; Wiehle, R.; Kamke, W.; Helm, H.; Witzele, B.

2005-01-01

Full text: The non-sequential double ionization of noble gases in strong fields is still a process which is not completely understood. The most challenging question is: what is the dominant physical process behind the knee structure in the yield of doubly charged ions which are produced in the focus of an ultrashort laser pulse in dependence of the intensity? Numerous studies can be explained with the so-called rescattering model, where an electron is freed by the strong laser field and then driven back to its parent ion due to the oscillation of the field. Through this backscattering process it is possible to kick out a second electron. However in the low intensity or multiphoton (MPI) region this model predicts that the first electron can not gain enough energy in the oscillating electric field to further ionize or excite the ion. We present experimental results for xenon in the MPI region which show a significant contribution of doubly charged ions. A Ti:sapphire laser system (800 nm, 100 fs) is used to ionize the atoms. The coincident detection of the momentum distribution of the photoelectrons with an imaging spectrometer and the time of flight spectrum of the ions allows a detailed view into the ionization process. For the first time we also show a systematic study of the wavelength dependence (780-830 nm and 1180-1550 nm) on the non-sequential double ionization. The ratio Xe 2+ /Xe + shows a surprising oscillatory behavior with varying wavelength. Ref. 1 (author)

Enhanced efficacy of sequential administration of Albendazole for the clearance of Wuchereria bancrofti infection: Double blind RCT.

Science.gov (United States)

De Britto, R L; Vanamail, P; Sankari, T; Vijayalakshmi, G; Das, L K; Pani, S P

2015-06-01

Till today, there is no effective treatment protocol for the complete clearance of Wuchereria bancrofti (W.b) infection that causes secondary lymphoedema. In a double blind randomized control trial (RCT), 146 asymptomatic W. b infected individuals were randomly assigned to one of the four regimens for 12 days, DEC 300 mg + Doxycycline 100 mg coadministration or DEC 300 mg + Albendazole 400 mg co-administration or DEC 300 mg + Albendazole 400 mg sequential administration or control regimen DEC 300 mg and were followed up at 13, 26 and 52 weeks post-treatment for the clearance of infection. At intake, there was no significant variation in mf counts (F(3,137)=0.044; P=0.988) and antigen levels (F(3,137)=1.433; P=0.236) between the regimens. Primary outcome analysis showed that DEC + Albendazole sequential administration has an enhanced efficacy over DEC + Albendazole co-administration (80.6 Vs 64.7%), and this regimen is significantly different when compared to DEC + doxycycline co-administration and control (PAlbendazole sequential administration appears to be a better option for rapid clearance of W. b microfilariae in 13 weeks time. (Clinical trials.gov identifier - NCT02005653).

Sequential separation of transuranic elements and fission products from uranium metal ingots in electrolytic reduction process of spent PWR fuels

International Nuclear Information System (INIS)

Chang Heon Lee; Kih Soo Joe; Won Ho Kim; Euo Chang Jung; Kwang Yong Jee

2009-01-01

A sequential separation procedure has been developed for the determination of transuranic elements and fission products in uranium metal ingot samples from an electrolytic reduction process for a metallization of uranium dioxide to uranium metal in a medium of LiCl-Li 2 O molten salt at 650 deg C. Pu, Np and U were separated using anion-exchange and tri-n-butylphosphate (TBP) extraction chromatography. Cs, Sr, Ba, Ce, Pr, Nd, Sm, Eu, Gd, Zr and Mo were separated in several groups from Am and Cm using TBP and di(2-ethylhexyl)phosphoric acid (HDEHP) extraction chromatography. Effect of Fe, Ni, Cr and Mg, which were corrosion products formed through the process, on the separation of the analytes was investigated in detail. The validity of the separation procedure was evaluated by measuring the recovery of the stable metals and 239 Pu, 237 Np, 241 Am and 244 Cm added to a synthetic uranium metal ingot dissolved solution. (author)

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

Binary scission configurations in fission of light actinides

Energy Technology Data Exchange (ETDEWEB)

Ohtsuki, Tsutomu [Tohoku Univ., Sendai (Japan). Lab. of Nuclear Science; Nagame, Y.; Nishinaka, I.; Tsukada, K.; Ikezoe, H.; Tanikawa, M.; Zhao, Y.L.; Sueki, K.; Nakahara, H.

1997-07-01

Mass and kinetic energy distributions of fission fragments have been accurately measured by a double velocity time-of-flight technique in the 13 MeV proton-induced fissions of {sup 232}Th and {sup 238}U. A binary structure is observed in total kinetic energy distributions in the fragments with mass number around A=130 for both the fissions, indicating that there are at least two kinds of scission configurations. A correlation between the scission configurations and mass yield distributions reveals that elongated scission configurations are associated with the symmetric mass distribution and compact scission configurations with the asymmetric mass distribution. (author)

Nuclear fission: What have we learned in 50 years?

International Nuclear Information System (INIS)

Vandenbosch, R.

1989-01-01

Nuclear fission has captured the imagination of chemists and physicists for half a century now. There are several reasons for this. One of course is that it represents the most drastic rearrangement of nuclear matter known, challenged only recently by collisions induced by very heavy ions. Another is that both statistical and dynamical features come into play. Perhaps one of the most compelling reasons is its never-ending capacity to surprise us: asymmetric mass distributions, the sawtooth dependence of neutron yields in fragment mass, spontaneously fissioning isomers and intermediate structure resonances. Finally, and perhaps most importantly, fission is a rich laboratory within which one can explore the delicate interplay between the macroscopic aspects of bulk nuclear matter and the quantal effects of a finite number of Fermions. It will of course be impossible for me to cover all aspects of fission. I have chosen a limited number of topics to cover, with particular topics being chosen either because the have been associated with persistent puzzles in fission or because they have, or hopefully will, tell us something special about how nuclei behave. After a brief historical note, I organize these topics sequentially according to the various stages of the fission process, starting first with the probability for fission to occur and ending with scission phenomena. 56 refs., 11 figs

First results from the new double velocity-double energy spectrometer VERDI

Science.gov (United States)

Frégeau, M. O.; Oberstedt, S.; Gamboni, Th.; Geerts, W.; Hambsch, F.-J.; Vidali, M.

2016-05-01

The VERDI spectrometer (VElocity foR Direct mass Identification) is a two arm time-of-flight spectrometer built at the European Commission Joint Research Centre IRMM. It determines fragment masses and kinetic energy distributions produced in nuclear fission by means of the double velocity and double energy (2v-2E) method. The simultaneous measurement of pre- and post neutron fragment characteristics allows studying the share of excitation energy between the two fragments. In particular, the evolution of fission modes and neutron multiplicity may be studied as a function of the available excitation energy. Both topics are of great importance for the development of models used in the evaluation of nuclear data, and also have important implications for the fundamental understanding of the fission process. The development of VERDI focus on maximum geometrical efficiency while striving for highest possible mass resolution. An innovative transmission start detector, using electrons ejected from the target itself, was developed. Stop signal and kinetic energy of both fragments are provided by two arrays of silicon detectors. The present design provides about 200 times higher geometrical efficiency than that of the famous COSI FAN TUTTE spectrometer [Nuclear Instruments and Methods in Physics Research 219 (1984) 569]. We report about a commissioning experiment of the VERDI spectrometer, present first results from a 2v-2E measurement of 252Cf spontaneous fission and discuss the potential of this instrument to contribute to the investigation prompt fission neutron characteristics as a function of fission fragment properties.

Fission/milligram of 235U in BIG-10 Tests A, C, E, and B

International Nuclear Information System (INIS)

Gilliam, D.M.; Grundl, J.A.; Hansen, G.E.

1976-01-01

The entire series of dosimetry foil tests at BIG-10 (including the preliminary Test A, five fission foil set irradiations--Tests C, five non-fission foil set irradiations--Tests E, and five track-etch detector irradiations--Tests B) were monitored continuously by the NBS double fission chamber PP5 in the central test cavity. The accuracy of the absolute fission counting data (fissions/milligram of 235 U) is estimated to be 1.4% for Tests A, C, and E and 1.5% for Test B. Deposit mass assay uncertainties remain the dominant error

Pion double charge exchange in the Δ33 resonance region

International Nuclear Information System (INIS)

Wirzba, A.; Toki, H.; Siciliano, E.R.; Johnson, M.B.; Gilman, R.

1989-01-01

We examine the model dependence and nuclear-structure sensitivity of several Δ 33 -dominated processes contributing to pion double charge exchange on nuclei in the region of the Δ 33 resonance. These processes include the Δ 33 -nucleon interaction V NΔ and sequential scattering, in which the pion undergoes single charge exchange on two different nucleons. In all cases, the scattering takes place through the exchange of an intermediate π and ρ meson. Sequential-mediated double charge exchange is found to be only moderately sensitive to short-range correlations, meson-nucleon form factors, and the rho meson, whereas V NΔ -mediated double charge exchange is very sensitive to all these effects. Results are given for double charge exchange on 18 O (double isobaric analog transitions) and 16 O (nonanalog transitions). Sequential double charge exchange is shown to favor non-spin-flip matrix elements of the transition operator whereas V NΔ -mediated double charge exchange favors spin-flip matrix elements. The energy dependence of the zero-degree cross sections for V NΔ and sequential scattering are also different: Sequential tends to increase monotonically from 100 to 300 MeV, whereas V NΔ peaks at about 150 MeV. The delta-nucleon interaction is found likely to dominate over sequential scattering in nonanalog double charge exchange. The V NΔ is also large in analog double charge exchange, but it does not enable us to explain the anomalous behavior of the 18 O differential cross sections

Orbital angular momentum transfer and spin desalignment mechanisms in the deep inelastic collisions Ar+Bi and Ni+Pb using the sequential fission method

International Nuclear Information System (INIS)

Steckmeyer, J.C.

1984-10-01

Angular momentum transfer and spin dealignment mechanisms have been studied in the deep inelastic collisions Ar+Bi and Ni+Pb using the sequential fission method. This experimental technique consists to measure the angular distribution of the fission fragments of a heavy nucleus in coincidence with the reaction partner, and leads to a complete determination of the heavy nucleus spin distribution. High spin values are transferred to the heavy nucleus in the interaction and indicate that the dinuclear system has reached the rigid rotation limit. A theoretical model, taking into account the excitation of surface vibrations of the nuclei and the nucleon transfer between the two partners, is able to reproduce the high spin values measured in our experiments. The spin fluctuations are important, with values of the order of 15 to 20 h units. These fluctuations increase with the charge transfer from the projectile to the target and the total kinetic energy loss. The spin dealignment mechanisms act mainly in a plane approximately perpendicular to the heavy recoil direction in the laboratory system. These results are well described by a dynamical transport model based on the stochastic exchange of individual nucleons between the two nuclei during the interaction. The origin of the dealignment mechanisms in the spin transfer processes is then related to the statistical nature of the nucleon exchange. However other mechanisms can contribute to the spin dealignment as the surface vibrations, the nuclear deformations as well their relative orientations [fr

Compound Nucleus Reactions in LENR, Analogy to Uranium Fission

Science.gov (United States)

Hora, Heinrich; Miley, George; Philberth, Karl

2008-03-01

The discovery of nuclear fission by Hahn and Strassmann was based on a very rare microanalytical result that could not initially indicate the very complicated details of this most important process. A similarity is discussed for the low energy nuclear reactions (LENRs) with analogies to the yield structure found in measurements of uranium fission. The LENR product distribution measured earlier in a reproducible way in experiments with thin film electrodes and a high density deuteron concentration in palladium has several striking similarities with the uranium fission fragment yield curve.ootnotetextG.H. Miley and J.A. Patterson, J. New Energy 1, 11 (1996); G.H. Miley et al, Proc ICCF6, p. 629 (1997).This comparison is specifically focussed to the Maruhn-Greiner local maximum of the distribution within the large-scale minimum when the fission nuclei are excited. Implications for uranium fission are discussed in comparison with LENR relative to the identification of fission a hypothetical compound nuclear reaction via a element ^306X126 with double magic numbers.

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)

Sequential probability ratio controllers for safeguards radiation monitors

International Nuclear Information System (INIS)

Fehlau, P.E.; Coop, K.L.; Nixon, K.V.

1984-01-01

Sequential hypothesis tests applied to nuclear safeguards accounting methods make the methods more sensitive to detecting diversion. The sequential tests also improve transient signal detection in safeguards radiation monitors. This paper describes three microprocessor control units with sequential probability-ratio tests for detecting transient increases in radiation intensity. The control units are designed for three specific applications: low-intensity monitoring with Poisson probability ratios, higher intensity gamma-ray monitoring where fixed counting intervals are shortened by sequential testing, and monitoring moving traffic where the sequential technique responds to variable-duration signals. The fixed-interval controller shortens a customary 50-s monitoring time to an average of 18 s, making the monitoring delay less bothersome. The controller for monitoring moving vehicles benefits from the sequential technique by maintaining more than half its sensitivity when the normal passage speed doubles

Separation of fission products using inorganic exchangers

International Nuclear Information System (INIS)

Murthy, T.S.; Balasubramanian, K.R.; Rao, K.L.N.; Venkatachalam, R.; Varma, R.N.

1981-01-01

This paper describes the separation of long lived fission products like caesium-137, strontium-90 using inorganic exchangers ammonium phosphomolybdate and zirconium antimonate. A revised flow sheet is proposed for the sequential separation of these isotopes using the above two compounds. This is a modification of the earlier scheme developed which involved the use of four inorganic exchangers namely ammonium phosphomolybdate, manganese dioxide, zirconium antimonate and polyantimonic acid. The elution of the adsorbed elements like cerium, strontium, and sodium has been studied and it has been possible to elute these using different eluting agents. (author)

Comparison of 252Cf time correlated induced fission with AmLi induced fission on fresh MTR reserach reactor fuel

Energy Technology Data Exchange (ETDEWEB)

Joshi, Jay Prakash [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-05-01

The objectives of this project are to calibrate the Advanced Experimental Fuel Counter (AEFC), benchmark MCNP simulations using experimental results, investigate the effects of change in fuel assembly geometry, and finally to show the boost in doubles count rates with 252Cf active soruces due to the time correlated induced fission (TCIF) effect.

Fission yeast mating-type switching: programmed damage and repair

DEFF Research Database (Denmark)

Egel, Richard

2005-01-01

Mating-type switching in fission yeast follows similar rules as in budding yeast, but the underlying mechanisms are entirely different. Whilst the initiating double-strand cut in Saccharomyces cerevisiae requires recombinational repair for survival, the initial damage in Schizosaccharomyces pombe...

Feasibility study of applying the passive safety system concept to fusion–fission hybrid reactor

International Nuclear Information System (INIS)

Yu, Zhang-cheng; Xie, Heng

2014-01-01

The fusion–fission hybrid 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 consists of passive residual heat removal system, passive safety injection system and automatic depressurization system was adopted into the fusion–fission hybrid reactor in this paper. Modeling and nodalization of primary loop, partial secondary loop and passive core cooling system for the fusion–fission hybrid reactor using relap5 were conducted and small break LOCA on cold leg was analyzed. The results of key transient parameters indicated that the actuation of passive safety system could mitigate the accidental consequence of the 4-inch cold leg small break LOCA on cold leg in the early time effectively. It is feasible to apply the passive safety system concept to fusion–fission hybrid reactor. The minimum collapsed liquid level had great increase if doubling the volume of CMTs to increase its coolant injection and had no increase if doubling the volume of ACCs

Complex fragment emission in the reaction 197Au → 197Au at an incident energy of 15 MeV/u

International Nuclear Information System (INIS)

Schmoll, R.

1988-07-01

For the study of the dominant decay processes in the reaction 15 MeV/u 197 Au → 197 Au in one-particle inclusive experiments the emission characteristics of all ejectiles in the mass range 24 ≤ A ≤ 197 were studied. The deflection function of the projectile-like fragments is for all energy losses at the grazing angle Θ cm gr =27.5 degrees peaked and in fact even for scattering events in which the whole available kinetic energy was dissipated in the collisions. The systematic analysis of the velocity spectra shows that the lightest fragments are formed in double-sequential fission of the highly excited gold-like fragments from the first deep inelastic reaction stage before reaching of a global equilibrium. On the other side symmetrical fission products, which are part of the narrow branch of the mass distribution, are emitted in simple-sequential non-equilibrium fission. This simple-sequential breakup is very closely limited to excitation energies of 75 ≤ E * ≤ 275 MeV of the primary, gold-like fragments, while the probability for double-sequential fission above E * ≅ 200 MeV increases very strongly. Contrarily to equilibrated compound-nucleus fission these processes are characterized by a in the source system strongly anisotropic angular distribution with distinct foreward/backward asymmetry and by an extremely asymmetric mass split. The study of the mass distribution shows that non-equilibrium fission at 15 MeV/u is both in view of the reaction cross section and regarding the creation of the complex fragments is the dominant decay process. The integral cross section of the broad four-body distribution corresponds to 60% of the total reaction cross section; the integral cross section of the narrow three-body distribution corresponds to 10%. (orig./HSI) [de

Correlated prompt fission data in transport simulations

Science.gov (United States)

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

Electromagnetic fission of 238U at 600 and 1000 MeV per nucleon

International Nuclear Information System (INIS)

Rubehn, T.; Mueller, W.F.J.; Bassini, R.; Begemann-Blaich, M.; Blaich, T.; Gross, C.; Imme, G.; Iori, I.; Kunde, G.J.; Kunze, W.D.; Lindenstruth, V.; Lynen, U.; Moehlemkamp, T.; Moretto, L.G.; Ocker, B.; Pochodzalla, J.; Raciti, G.; Reito, S.; Sann, H.; Schuettauf, A.; Serfling, V.; Trautmann, W.; Trzcinski, A.; Verde, G.; Woerner, A.; Zude, E.; Zwieglinski, B.

1995-05-01

Electromagnetic fission of 238 U projectiles at E/A=600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, Al, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizsaecker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragments' charge distribution gives evidence for the excitation of the double giant-dipole resonance in uranium. (orig.)

Proceedings of the specialists' meeting on physics and engineering of fission and spallation, 1989

International Nuclear Information System (INIS)

Nakagome, Yoshihiro

1990-07-01

The third meeting was held on August 1, and the fourth meeting was held on December 12, 1989. The reports of the international conferences on 50 years research on nuclear fission in Germany and USA, and the reports on the nuclear data of fission-produced nuclei for evaluating reactor decay heat, the atomic mass formula considering proton-neutron interaction and unstable nuclei, research on short life fission fragments by on-line isotope separation process, the reactor physics on waste annihilation disposal and fuel breeding with an accelerator, the double differential cross section of back neutrons in nuclear spallation reaction, measurement of fission cross section and fission neutron spectra with fast neutrons, U-235 fission spectra by unfolding activation foil data and production mechanisms of intermediate mass fragments from hot nuclei-emission of complex and fission fragments for 84 Kr+ 27 Al at 10.6 MeV/u were made. (K.I.)

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

International Nuclear Information System (INIS)

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

1992-01-01

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

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

International Nuclear Information System (INIS)

2009-01-01

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

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.

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

International Nuclear Information System (INIS)

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

2000-01-01

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

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Fission - track age of the Marjalahti Pallasite

International Nuclear Information System (INIS)

Bondar, Yu.V.; Perelygin, V.P.

2006-01-01

contribution from 244 Pu doubles every 82 Myr providing a very sensitive measure of the age of a studied sample. The results of the determination of the fission-track age of the Marjalahti pallasite (stony-iron meteorite) are presented. Thorough examination of fossil tracks in the phosphate (whitlockite) crystals coupled with U content determination in whitlockites allowed us to estimate the contributions of all possible track sources to the total track density and to calculate a value of the model fission-track age. It was found out that whitlockite crystals of the Marjalahti pallasite contain fossil tracks due to galactic cosmic rays (VH, VVH nuclei); induced fission of U and Th by cosmic rays; spontaneous fission of 238 U; spontaneous fission of extinct short-lived 244 Pu nuclei presented in significant quantities in the early solar system. The initial ratio ( 244 Pu/ 238 U) 0 at the time of the pallasite parent body formation (taken as 4.6x10 9 yr) was estimated as 0.015. A great track density attributed to the extinct 244 Pu testified to the high value of the fission-track age. The model fission-track ages of (4.37± 0.02)x10 9 yr for the Marjalahti pallasite was calculated. The comparison of the represented data with petrographic analyses allowed us to interpret a value of the fission-track age as the time of the last intensive shock/thermal event in the cosmic history of the pallasite. (author)

Interpretation of the mechanism of spontaneous fission of heavy nuclei in the framework of dinuclear system conception

International Nuclear Information System (INIS)

Volkov, V.V.; Cherepanov, E.A.; Kalandarov, Sh.A.

2016-01-01

A new approach to the interpretation of the process of spontaneous fission of heavy nuclei is suggested. It is based on nuclear physics data which are obtained in heavy ion collisions. The process of spontaneous fission consists of three sequential stages: clusterization of the valent nucleons of a heavy nucleus into a light nucleus-cluster, which leads to the formation of a dinuclear system; evolution of the dinuclear system which proceeds by nucleon transfer from the heavy to light nucleus; and decay of the dinuclear system from the equilibrium configuration into two fragments. [ru

Delayed fission

Energy Technology Data Exchange (ETDEWEB)

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

1997-07-01

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

Study of the field-sequential modulation of Nd:YVO4/MgO:PPLN based intra-cavity frequency doubling green laser

Science.gov (United States)

Zhang, Bin; Gan, Yi; Xu, Chang-Qing

2018-06-01

The field sequential modulation of a Nd:YVO4/MgO:PPLN intra-cavity, frequency doubling green laser was studied. The modulation frequency was set at 1 kHz and the duty cycle was changed from 20% to CW operation. It was shown that the quasi-phase matched (QPM) temperature decreases with an increase of the modulation duty cycle, and in turn causing the peak efficiency to rise. It was found that the temperature change in MgO:PPLN and the thermal lens effect in Nd:YVO4 crystal were the respective origins of these observed experimental phenomena.

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.

Study of scission shapes in spontaneous ternary fission of 252Cf

International Nuclear Information System (INIS)

Singer, P.; Schwalm, D.; Thirolf, P.; Goennenwein, F.; Hesse, M.

1995-06-01

A new kinematic study on the ternary fission of 252 Cf has been conducted by registering prompt neutrons and fission γ rays coincidence with light charged particles (LCP) and fission fragments. The aim is to investigate changes in fragment deformation energy between the binary and ternary fission modes from measured prompt neutron angular distributions and multiplicities, and to explore the influence of light particle emission on the energy distribution, multiplicity and angular anisotropy of γ rays emitted during fragment de-excitation. The experiment was performed at the MPI Heidelberg using the Darmstadt-Heidelberg crystal ball spectrometer as γ-ray and neutron detector. Fragments were identified by a double-E measurement with an angular sensitive twin ionization chamber (IC). Light charged particles from fission were measured by ΔE-E telescopes composed of ΔE ICs and silicon PIN diodes. The telescopes enable to identify various LCPs which are emitted much more rarely than ternary α particles. The parameters of the experiment and the method of data analysis are described and first results presented. (orig.)

Combining Compact Representation and Incremental Generation in Large Games with Sequential Strategies

DEFF Research Database (Denmark)

Bosansky, Branislav; Xin Jiang, Albert; Tambe, Milind

2015-01-01

representation of sequential strategies and linear programming, or by incremental strategy generation of iterative double-oracle methods. In this paper, we present novel hybrid of these two approaches: compact-strategy double-oracle (CS-DO) algorithm that combines the advantages of the compact representation...

Double nanosecond pulses generation in ytterbium fiber laser

Energy Technology Data Exchange (ETDEWEB)

Veiko, V. P.; Samokhvalov, A. A., E-mail: samokhvalov.itmo@gmail.com; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N. [Saint-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky Pr. 49, Saint Petersburg (Russian Federation); Lednev, V. N. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskyave., 4, Moscow (Russian Federation); Pershin, S. M. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation)

2016-06-15

Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential “opening” radio pulses with a delay of 0.2–1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

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)

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

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

International Nuclear Information System (INIS)

Ganesan, S.

1978-01-01

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

In Vivo Evaluation of Synthetic Aperture Sequential Beamforming

DEFF Research Database (Denmark)

Hemmsen, Martin Christian; Hansen, Peter Møller; Lange, Theis

2012-01-01

Ultrasound in vivo imaging using synthetic aperture sequential beamformation (SASB) is compared with conventional imaging in a double blinded study using side-by-side comparisons. The objective is to evaluate if the image quality in terms of penetration depth, spatial resolution, contrast...

Analysis of fission product release from HTGR core during transient temperature excursion

International Nuclear Information System (INIS)

Saito, Takao; Yamatoya, Naotoshi; Onuma, Mamoru

1978-01-01

The computer program ''FRANC'' was developed to calculate the release activity of fission products from a high-temperature gas cooled reactor (HTGR) core during transient temperature excursions such as a hypothetical loss of forced circulation combined with design basis depressurization. The program utilizes a segmented cylindrical core spatial model with the associated values of the prior fuel irradiation history and temperature conditions. The fission product transport and decay chain behavior is expressed by a set of differential equations. This set of equations describes the entire core inventory of fission products by means of calculated parameters based on the detailed spatial core conditions. The program determines the time-dependent amounts of fission product nuclides escaping from the core into the coolant. Coded in Continuous System Simulation Language (CSSL) with double precision, FRANC showed appropriate results for both short- and long-lived fission product nuclides. The sample calculation conducted by applying the program to a large HTGR indicated that it would take about one hour for noble gases and volatile nuclides to be released to the coolant, and several hours for metalic nuclides. (auth.)

α and p emission before, during, and after fission of the fusion nucleus 169Ta: Nuclear deformation, field emission, and nuclear shadow

International Nuclear Information System (INIS)

Brucker, A.

1986-01-01

In the asymmetric system 318 MeV 28 Si + 141 Pr the angular and energy distributions of α particles and protons were measured in coincidence with fission fragments. Identification and separation of the sources of sequential emission before (CN) and after (F) fission of the compound-nucleus 169 Ta yields following multiplicities: M CN α =0.38±0.04, M CN p =0.6±0.15; M F α =0.16±0.03, M F p =0.54±0.15. Measurement of the cross sections δ ER =(608±81) mb and δ F =(679±159) mb for residual nucleus formation respectively fission fixes the mean angular momentum for fission l F =(94±7)ℎ and the maximal angular momentum l F,max =(110±10)ℎ (sharp cut-off model). From the angular correlation relative to the spin direction of the compound-nucleus an anisotropy parameter of A α =6.7±0.8 and A p =1.3±0.2 for α respectively proton emission from the compound-nucleus is measured, and by means of the semiclassical model of Dossing a quadrupole deformation parameter of the compound-nucleus of vertical strokeδvertical stroke=0.43±0.05 consistent within the uncertainties of the analysis determined. Apart from pre-equilibrium emission under small angles to the beam significant deviations from sequential emission are observed only in the α emission and detailedly studied by means of angular correlation and energy spectra: (I) an strong nuclear shadowing of the fragment emission of 1/7 of its sequential value in a narrow angular range (≅40 0 (FWHM)) in the direction of the detected fission fragment. From this a mean lifetime of the compound nucleus τ CN =(140-240).10 -22 s is obtained. (II) A perpendicularly to the scission axis strongly pronounced surplus M SC α =(1.7±0.4).10 -2 and an observed deficit of equal magnitude in direction of the scission axis. (orig./HSI) [de

Measurement of Fission Product Yields from Fast-Neutron Fission

Science.gov (United States)

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

2014-09-01

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

Measurement of the 238U subthreshold fission cross section for incident neutron energies between 0.6 and 100 keV

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

Maruhn-Greiner Maximum of Uranium Fission for Confirmation of Low Energy Nuclear Reactions LENR via a Compound Nucleus with Double Magic Numbers

Science.gov (United States)

Hora, H.; Miley, G. H.

2007-12-01

One of the most convincing facts about LENR due to deuterons of very high concentration in host metals as palladium is the measurement of the large scale minimum of the reaction probability depending on the nucleon number A of generated elements at A = 153 where a local maximum was measured. This is similar to the fission of uranium at A = 119 where the local maximum follows from the Maruhn-Greiner theory if the splitting nuclei are excited to about MeV energy. The LENR generated elements can be documented any time after the reaction by SIMS or K-shell X-ray excitation to show the very unique distribution with the local maximum. An explanation is based on the strong Debye screening of the Maxwellian deuterons within the degenerate rigid electron background especially within the swimming electron layer at the metal surface or at interfaces. The deuterons behave like neutrals at distances of about 2 picometers. They may form clusters due to soft attraction in the range above thermal energy. Clusters of 10 pm diameter may react over long time probabilities (megaseconds) with Pd nuclei leading to a double magic number compound nucleus which splits like in fission to the A = 153 element distribution.

Systematic features of mass yield curves in low-energy fission of actinides

International Nuclear Information System (INIS)

Nagame, Yuichiro

1999-01-01

Characteristics of mass yield curves in fission of wide range of nuclides from pre-actinides through transactinides are reviewed and the following points are discussed. (1) Systematic trends of the mass yield distributions in low-energy proton-induced fission of actinides and in spontaneous fission of actinides are discussed in terms of weighted mean mass numbers of the light and heavy asymmetric mass yield peaks and widths of the heavy asymmetric mass yields. (2) Gross features of the two kinds of mass yield curves, symmetric and asymmetric ones, as a function of a fissioning nucleus. (3) Competition between the symmetric and asymmetric fission as a function of not only Z (proton number) but also N (neutron number) of a fissioning nucleus. (4) Experimental verification of the existence of two kinds of deformation paths in low energy fission of actinides; the first path is initiated at higher threshold energy and ends with elongated scission configuration, giving a final mass yield distribution centered around the symmetric mass division, 'symmetric fission path'. In the second path, a fissioning nucleus experiences lower threshold energy and results in more compact scission configuration, which gives a double humped mass distribution always centered around A=140 for the heavier fragment, 'asymmetric fission path'. (5) Interpretation of the 'bimodal fission' observed in the spontaneous fission of heavy actinides as the presence of the two fission paths of the ordinary asymmetric one and a strongly shell-affected symmetric path from the systematic analysis of scission configurations. (6) A dynamical fission process deduced from the analysis of the experimental mass yield curves and the correlation data of neutron multiplicity and fragment mass and total kinetic energy. (7) Prediction of the characteristics of gross properties of fission in superheavy nuclei around 280 114. (8) Characteristics of highly asymmetric fission: formation cross section as a function of

[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

The LANL/LLNL Program to Measure Prompt Fission Neutron Spectra at LANSCE

Science.gov (United States)

Haight, Robert; Wu, Ching Yen; Lee, Hye Young; Taddeucci, Terry; Mosby, Shea; O'Donnell, John; Fotiades, Nikolaos; Devlin, Mattew; Ullmann, John; Nelson, Ronald; Wender, Stephen; White, Morgan; Solomon, Clell; Neudecker, Denise; Talou, Patrick; Rising, Michael; Bucher, Brian; Buckner, Matthew; Henderson, Roger

2015-10-01

Accurate data on the spectrum of neutrons emitted in neutron-induced fission are needed for applications and for a better understanding of the fission process. At LANSCE we have made important progress in understanding systematic uncertainties and in obtaining data for 235U on the low-energy part of the prompt fission neutron spectra (PFNS), a particularly difficult region because down-scattered neutrons go in this direction. We use a double time-of-flight technique to determine energies of incoming and outgoing neutrons. With data acquisition via waveform digitizers, accidental coincidences between fission chamber and neutron detector are measured to high statistical accuracy and then subtracted from measured events. Monte Carlo simulations with high performance computers have proven to be essential in the design to minimize neutron scattering and in calculating detector response. Results from one of three approaches to analyzing the data will be presented. This work is funded by the US Department of Energy, National Nuclear Security Administration and Office of Nuclear Physics.

Discrimination between sequential and simultaneous virtual channels with electrical hearing.

Science.gov (United States)

Landsberger, David; Galvin, John J

2011-09-01

In cochlear implants (CIs), simultaneous or sequential stimulation of adjacent electrodes can produce intermediate pitch percepts between those of the component electrodes. However, it is unclear whether simultaneous and sequential virtual channels (VCs) can be discriminated. In this study, CI users were asked to discriminate simultaneous and sequential VCs; discrimination was measured for monopolar (MP) and bipolar + 1 stimulation (BP + 1), i.e., relatively broad and focused stimulation modes. For sequential VCs, the interpulse interval (IPI) varied between 0.0 and 1.8 ms. All stimuli were presented at comfortably loud, loudness-balanced levels at a 250 pulse per second per electrode (ppse) stimulation rate. On average, CI subjects were able to reliably discriminate between sequential and simultaneous VCs. While there was no significant effect of IPI or stimulation mode on VC discrimination, some subjects exhibited better VC discrimination with BP + 1 stimulation. Subjects' discrimination between sequential and simultaneous VCs was correlated with electrode discrimination, suggesting that spatial selectivity may influence perception of sequential VCs. To maintain equal loudness, sequential VC amplitudes were nearly double those of simultaneous VCs, presumably resulting in a broader spread of excitation. These results suggest that perceptual differences between simultaneous and sequential VCs might be explained by differences in the spread of excitation. © 2011 Acoustical Society of America

Nuclear-charge polarization at scission in fission from moderately excited light-actinide nuclei

International Nuclear Information System (INIS)

Nishinaka, Ichiro

2009-01-01

Fragment mass yields and the average neutron multiplicity in the proton-induced fission of 232 Th and 238 U were measured by a double time-of-flight method. The most probable charges of secondary fragments were evaluated from the fragment mass yields measured by the double time-of-flight method and the fractional cumulative and independent yields reported in literature. The nuclear-charge polarization of primary fragments at scission was obtained by correcting the most probable charge of secondary fragments for neutron evaporation. The results show that the nuclear-charge polarization at scission is associated with the liquid-drop properties of nuclei and the proton shell effect with Z = 50 of heavy fragments and that it is practically insensitive to mass and excitation energy of the fissioning nucleus in the region of light-actinide nuclei. (author)

Ternary fission

International Nuclear Information System (INIS)

Wagemans, C.

1991-01-01

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

Fission level densities

International Nuclear Information System (INIS)

Maslov, V.M.

1998-01-01

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

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

Speeded Recognition of Ungrammaticality: Double Violations.

Science.gov (United States)

Moore, Timothy E.; Biederman, Irving

1979-01-01

The speed at which sentences with various kinds of violations could be rejected was studied. Compatible with the sequential model was the finding that noun-verb and adjective-noun double violations did not result in shorter reaction times than noun-verb single violations, although double violations were judged less acceptable. (Author/RD)

Footprints of electron correlation in strong-field double ionization of Kr close to the sequential-ionization regime

Science.gov (United States)

Li, Xiaokai; Wang, Chuncheng; Yuan, Zongqiang; Ye, Difa; Ma, Pan; Hu, Wenhui; Luo, Sizuo; Fu, Libin; Ding, Dajun

2017-09-01

By combining kinematically complete measurements and a semiclassical Monte Carlo simulation we study the correlated-electron dynamics in the strong-field double ionization of Kr. Interestingly, we find that, as we step into the sequential-ionization regime, there are still signatures of correlation in the two-electron joint momentum spectrum and, more intriguingly, the scaling law of the high-energy tail is completely different from early predictions on the low-Z atom (He). These experimental observations are well reproduced by our generalized semiclassical model adapting a Green-Sellin-Zachor potential. It is revealed that the competition between the screening effect of inner-shell electrons and the Coulomb focusing of nuclei leads to a non-inverse-square central force, which twists the returned electron trajectory at the vicinity of the parent core and thus significantly increases the probability of hard recollisions between two electrons. Our results might have promising applications ranging from accurately retrieving atomic structures to simulating celestial phenomena in the laboratory.

He and Be ternary spontaneous fission of sup 2 sup 5 sup 2 Cf

CERN Document Server

Hwang, J K; Ramayya, A V; Hamilton, J H

2002-01-01

Ternary and binary fission studies of sup 2 sup 5 sup 2 Cf have been carried out by using the Gammasphere detector array with light charged particle (LCD) detectors. The relative sup 4 He and sup 5 He ternary fission yields were determined. The kinetic energies of the sup 5 He and sup 4 He ternary particles were found to be approximately 11 and 16 MeV, respectively. The sup 5 He particles contribute 10-20 % to the total observed alpha ternary yield. The data indicate that in nuclei with octupole deformations the population for the negative parity bands might be enhanced in the alpha ternary fission. >From LCP-gamma double gated spectra, neutron multiplicity distributions for alpha ternary fission pairs were measured. The average neutron multiplicity decreases about 0.7 AMU in going from the binary to alpha ternary fission in the approximately same mass splittings (104-146). From the analysis of the gamma-gamma matrix gated on the sup 1 sup 0 Be particles, the two fragment pairs of sup 1 sup 3 sup 8 Xe - sup 1...

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

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.)

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.)

Nuclear fission and reactions

International Nuclear Information System (INIS)

Anon.

1975-01-01

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

MELCOR assessment of sequential severe accident mitigation actions under SGTR accident

International Nuclear Information System (INIS)

Choi, Wonjun; Jeon, Joongoo; Kim, Nam Kyung; Kim, Sung Joong

2017-01-01

The representative example of the severe accident studies using the severe accident code is investigation of effectiveness of developed severe accident management (SAM) strategy considering the positive and adverse effects. In Korea, some numerical studies were performed to investigate the SAM strategy using various severe accident codes. Seo et.al performed validation of RCS depressurization strategy and investigated the effect of severe accident management guidance (SAMG) entry condition under small break loss of coolant accident (SBLOCA) without safety injection (SI), station blackout (SBO), and total loss of feed water (TLOFW) scenarios. The SGTR accident with the sequential mitigation actions according to the flow chart of SAMG was simulated by the MELCOR 1.8.6 code. Three scenariospreventing the RPV failure were investigated in terms of fission product release, hydrogen risk, and the containment pressure. Major conclusions can be summarized as follows: (1) According to the flow chart of SAMG, RPV failure can be prevented depending on the method of RCS depressurization. (2) To reduce the release of fission product during the injecting into SGs, a temporary opening of SDS before the injecting into SGs was suggested. These modified sequences of mitigation actions can reduce the release of fission product and the adverse effect of SDS.

An optimized symbiotic fusion and molten-salt fission reactor system

International Nuclear Information System (INIS)

Blinkin, V.L.; Novikov, V.M.

A symbiotic fusion-fission reactor system which breeds nuclear fuel is discussed. In the blanket of the controlled thermonuclear reactor (CTR) uranium-233 is generated from thorium, which circulates in the form of ThF 4 mixed with molten sodium and beryllium fluorides. The molten-salt fission reactor (MSR) burns up the uranium-233 and generates tritium for the fusion reactor from lithium, which circulates in the form of LiF mixed with BeF 2 and 233 UF 4 through the MSR core. With a CTR-MSR thermal power ratio of 1:11 the system can produce electrical energy and breed fuel with a doubling time of 4-5 years. The system has the following special features: (1) Fuel reprocessing is much simpler and cheaper than for contemporary fission reactors; reprocessing consists simply in continuous removal of 233 U from the salt circulating in the CTR blanket by the fluorination method and removal of xenon from the MSR fuel salt by gas scavenging; the MSR fuel salt is periodically exchanged for fresh salt and the 233 U is then removed from it; (2) Tritium is produced in the fission reactor, which is a much simpler system than the fusion reactor; (3) The CTR blanket is almost ''clean''; no tritium is produced in it and fission fragment activity does not exceed the activity induced in the structural materials; (4) Almost all the thorium introduced into the CTR blanket can be used for producing 233 U

Fission-product yields for thermal-neutron fission of curium-243

International Nuclear Information System (INIS)

Breederland, D.G.

1982-01-01

Cumulative fission yields for 25 gamma rays emitted during the decay of 23 fission products produced by thermal-neutron fission of 243 Cm have been determined. Using Ge(Li) spectroscopy, 33 successive pulse-height spectra of gamma rays emitted from a 77-ng sample of 243 Cm over a period of approximately two and one-half months were analyzed. Reduction of these spectra resulted in the identification and matching of gamma-ray energies and half-lives to specific radionuclides. Using these results, 23 cumulative fission-product yields were calculated. Only those radionuclides having half-lives between 6 hours and 65 days were observed. Prior to this experiment, no fission-product yields had been recorded for 243 Cm

CINDER, Depletion and Decay Chain Calculation for Fission Products in Thermal Reactors

International Nuclear Information System (INIS)

England, T.R.; Gorrell, T.C.; Hightower, J.H.

2001-01-01

1 - Description of problem or function: CINDER is a four-group, one- point depletion and fission product program based on the evaluation of a general analytical solution of nuclides coupled in any linear sequence of radioactive decays and neutron absorptions in a specified neutron flux spectrum. The desired depletion and fission product chains and all physical data are specified by the problem originator. The program computes individual nuclide number densities, activities, nine energy-group disintegration rates, and macroscopic and barns/fission poisons at each time-step as well as selected summaries of these data. 2 - Method of solution: Time-dependent variations in nuclide cross sections and neutron fluxes are approximated by a user-specified sequential set of values which are considered constant during the duration of the user-specified associated time-increments. When a nuclide concentration is independent of the concentration of any of its progeny, it is possible to resolve the couplings so as to obtain nuclides fed by a single parent. These chains are referred to as linear. 3 - Restrictions on the complexity of the problem: The program is limited to 500 total nuclides formed in up to 240 chains of 20 or fewer nuclides each. Up to 10 nuclides may act as fission product sources, contributing to power, and as many as 99 time-steps of arbitrary length are permitted. All stable nuclides must have a cross section if zero power time-increments are anticipated

Preliminary results of total kinetic energy modelling for neutron-induced fission

International Nuclear Information System (INIS)

Visan, I.; Giubega, G.; Tudora, A.

2015-01-01

The total kinetic energy as a function of fission fragments mass TKE(A) is an important quantity entering in prompt emission calculations. The experimentally distributions of TKE(A) are referring to a limited number of fission systems and incident energies. In the present paper, a preliminary model for TKE calculation in neutron induced fission system is presented. The range of fission fragments is chosen as in the Point by Point treatment. The model needs as input only mass excesses and deformation parameters taken from available nuclear databases being based on the following approximations: total excitation energy of fully accelerated fission fragments TXE is calculated from energy balance of neutron-induced fission systems as sum of the total excitation energy at scission E*sciss and deformation energy Edef. The deformation energy at scission is given by minimizing the potential energy at the scission configuration. At the scission point, the fission system is described by two spheroidal fragments nearly touching by a pre-scission distance or neck caused by the nuclear forces between fragments. Therefore, the Columbian repulsion depending on neck and, consequently, on the fragments deformation at scission, is essentially in TKE determination. An approximation is made based on the fission modes. For the very symmetric fission, the dominant super long channel is characterized by long distance between fragments leading to low TKE values. Due to magic and double-magic shells closure, the dominant S1 fission mode for pairs with heavy fragment mass AH around 130-134 is characterized by spherical heavy fragment shape and easily deformed light fragment. The nearly spherical shape of the complementary fragments are characterized by minimum distance, and consequently to maximum TKE values. The results obtained for TKE(A) are in good agreement with existing experimental data for many neutron induced fission systems, e.g. ''2''3''3&apos

Neutron emission as a probe of fusion-fission and quasi-fission dynamics

International Nuclear Information System (INIS)

Hinde, D.J.

1991-01-01

Pre- and post scission neutron yeilds have been measured as a function of projectile mass, compound nucleus fissility, and fission mass-split and total kinetic energy (TKE) for 27 fusion-fission and quasi-fission reactions induced by beams of 16,18 O, 40 Ar and 64 Ni. A new method of interpretation of experimental pre-scission neutron multiplicities ν-pre and mean kinetic energies ε ν allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35±15) x 10 -21 s for symmetric fission. All reactions show that ν-pre falls quite rapidly with increasing mass-asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass-asymmetry. For quasi-fission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass-asymmetry, but that the time scale is virtually independent of mass-asymmetry. It is concluded that for fusion-fission there is no dependence of ν-pre on TKE, whilst for 64 Ni-induced quasi-fission reactions, a strong increase of ν-pre with decreasing TKE is observed, probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data. 54 refs., 17 tabs., 25 figs

Energy released in fission

International Nuclear Information System (INIS)

James, M.F.

1969-05-01

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

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

Reference and standard benchmark field consensus fission yields for U.S. reactor dosimetry programs

International Nuclear Information System (INIS)

Gilliam, D.M.; Helmer, R.G.; Greenwood, R.C.; Rogers, J.W.; Heinrich, R.R.; Popek, R.J.; Kellogg, L.S.; Lippincott, E.P.; Hansen, G.E.; Zimmer, W.H.

1977-01-01

Measured fission product yields are reported for three benchmark neutron fields--the BIG-10 fast critical assembly at Los Alamos, the CFRMF fast neutron cavity at INEL, and the thermal column of the NBS Research Reactor. These measurements were carried out by participants in the Interlaboratory LMFBR Reaction Rates (ILRR) program. Fission product generation rates were determined by post-irradiation analysis of gamma-ray emission from fission activation foils. The gamma counting was performed by Ge(Li) spectrometry at INEL, ANL, and HEDL; the sample sent to INEL was also analyzed by NaI(Tl) spectrometry for Ba-140 content. The fission rates were determined by means of the NBS Double Fission Ionization Chamber using thin deposits of each of the fissionable isotopes. Four fissionable isotopes were included in the fast neutron field measurements; these were U-235, U-238, Pu-239, and Np-237. Only U-235 was included in the thermal neutron yield measurements. For the fast neutron fields, consensus yields were determined for three fission product isotopes--Zr-95, Ru-103, and Ba-140. For these fission product isotopes, a separately activated foil was analyzed by each of the three gamma counting laboratories. The experimental standard deviation of the three independent results was typically +- 1.5%. For the thermal neutron field, a consensus value for the Cs-137 yield was also obtained. Subsidiary fission yields are also reported for other isotopes which were studied less intensively (usually by only one of the participating laboratories). Comparisons with EBR-II fast reactor yields from destructive analysis and with ENDF/B recommended values are given

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Computer program FPIP-REV calculates fission product inventory for U-235 fission

Science.gov (United States)

Brown, W. S.; Call, D. W.

1967-01-01

Computer program calculates fission product inventories and source strengths associated with the operation of U-235 fueled nuclear power reactor. It utilizes a fission-product nuclide library of 254 nuclides, and calculates the time dependent behavior of the fission product nuclides formed by fissioning of U-235.

Mica fission detectors

International Nuclear Information System (INIS)

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

1977-01-01

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

Dynamics of nuclear fission and heavy-ion reactions

International Nuclear Information System (INIS)

Nix, J.R.; Sierk, A.J.

1979-01-01

Large-amplitude collective motion in fission and heavy-ion reactions is studied by solving classical equations of motion for the time evolution of the nuclear shape. In the nuclear potential energy of deformation, the generalized surface energy was calculated by means of a double volume integral of a Yukawa-plus-exponential function, which was obtained by requiring that two semi-infinite slabs of constant-density nuclear matter have minimum energy at zero separation. The collective kinetic energy is calculated for nuclear flow that is a superposition of incompressible, nearly irrotational collective-shape motion and rigid-body rotation. Nuclear dissipation is included by means of the Rayleigh dissipation function, which depends upon the physical mechanism that converts collective energy into internal energy. For both ordinary two-body viscosity and a combined wall and window one-body dissipation, fission-fragment kinetic energies are calculated for the fission of nuclei throughout the periodic table and compare with experimental results. Finally, the one-body dynamics of nucleons inside a cylinder colliding with a moving piston is explicitly studied by solving exactly the collisionless Boltzmann equation for the distribution function. By examining the relative phases of the pressure at the piston and the piston's velocity, a dissipative force and an elastic restoring force can be separately identified. 9 references

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

Differential cross sections for non-sequential double ionization of He by 52 eV photons from the Free Electron Laser in Hamburg, FLASH

International Nuclear Information System (INIS)

Kurka, M; Rudenko, A; Jiang, Y H; Kuehnel, K U; Foucar, L; Feist, J; Pazourek, R; Nagele, S; Horner, D A; Rescigno, T N; McCurdy, C W; Schoeffler, M; Belkacem, A; Schulz, M; Herrwerth, O; Lezius, M; Kling, M F; Duesterer, S; Treusch, R; Schneider, B I

2010-01-01

Two-photon double ionization of He is studied at the Free Electron Laser in Hamburg (FLASH) by inspecting He 2+ momentum (P-vector(He 2+ )) distributions at 52 eV photon energy. We demonstrate that recoil ion momentum distributions can be used to infer information about highly correlated electron dynamics and find the first experimental evidence for 'virtual sequential ionization'. The experimental data are compared with the results of two calculations, both solving the time-dependent Schroedinger equation. We find good overall agreement between experiment and theory, with significant differences for cuts along the polarization direction that cannot be explained by the experimental resolution alone.

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)

Measurement of prompt fission gamma-ray spectra in fast neutron-induced fission

International Nuclear Information System (INIS)

Laborie, J.M.; Belier, G.; Taieb, J.

2012-01-01

Knowledge of prompt fission gamma-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission gamma-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the gamma-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other gamma-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the Al-27(p, gamma) reaction. First prompt fission gamma-ray spectrum measurements performed for the spontaneous fission of Cf-252 and for 1.7 and 15.6 MeV neutron-induced fission of U-238 at the CEA, DAM, DIF Van de Graaff accelerator, will be presented. (authors)

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.

Fast fission phenomena

International Nuclear Information System (INIS)

Gregoire, Christian.

1982-03-01

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

Nuclear fission

International Nuclear Information System (INIS)

Kodama, T.

1981-01-01

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

Prompt fission neutron spectra of n + 235U above the (n, nf) fission threshold

International Nuclear Information System (INIS)

Shu Nengchuan; Chen Yongjing; Liu Tingjin; Jia Min

2015-01-01

Calculations of prompt fission neutron spectra (PFNS) from the 235 U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n, xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n, xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n, nf) or (n, 2nf) reactions influences the PFNS shape, and the neutron spectra of the (n, xnf) fission-channel are soft compared with the neutron spectra of the (n, f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. (authors)

Fission product yields

International Nuclear Information System (INIS)

Valenta, V.; Hep, J.

1978-01-01

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

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

International Nuclear Information System (INIS)

Hasan, A.A.

1984-12-01

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

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)

Physics and potentials of fissioning plasmas for space power and propulsion

Science.gov (United States)

Thom, K.; Schwenk, F. C.; Schneider, R. T.

1976-01-01

Fissioning uranium plasmas are the nuclear fuel in conceptual high-temperature gaseous-core reactors for advanced rocket propulsion in space. A gaseous-core nuclear rocket would be a thermal reactor in which an enriched uranium plasma at about 10,000 K is confined in a reflector-moderator cavity where it is nuclear critical and transfers its fission power to a confining propellant flow for the production of thrust at a specific impulse up to 5000 sec. With a thrust-to-engine weight ratio approaching unity, the gaseous-core nuclear rocket could provide for propulsion capabilities needed for manned missions to the nearby planets and for economical cislunar ferry services. Fueled with enriched uranium hexafluoride and operated at temperatures lower than needed for propulsion, the gaseous-core reactor scheme also offers significant benefits in applications for space and terrestrial power. They include high-efficiency power generation at low specific mass, the burnup of certain fission products and actinides, the breeding of U-233 from thorium with short doubling times, and improved convenience of fuel handling and processing in the gaseous phase.

HAC and fission reactors

International Nuclear Information System (INIS)

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

1984-01-01

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

Fission cross-section calculations and the multi-modal fission model

International Nuclear Information System (INIS)

Hambsch, F.J.

2004-01-01

New, self consistent, neutron-induced reaction cross section calculations for 235,238 U, 237 Np have been performed. The statistical model code STATIS was improved to take into account the multimodality of the fission process. The three most dominant fission modes, the two asymmetric standards I (S1) and standard II (S2) modes and the symmetric superlong (SL) mode have been taken into account. De-convoluted fission cross sections for those modes for 235,238 U(n,f) and 237 Np(n,f) based on experimental branching ratios, were calculated for the first time up to the second chance fission threshold. For 235 U(n,f), the calculations being made up to 28 MeV incident neutron energy, higher fission chances have been considered. This implied the need for additional calculations for the neighbouring isotopes. As a side product also mass yield distributions could be calculated at energies hitherto not accessible by experiment. Experimental validation of the predictions is being envisaged

Fission Research at IRMM

Directory of Open Access Journals (Sweden)

Al-Adili A.

2010-03-01

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

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

International Nuclear Information System (INIS)

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

2003-01-01

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

Investigation of short-living fission products from the spontaneous fission of Cf-252

International Nuclear Information System (INIS)

Klonk, H.

1976-01-01

In this paper, a method of separating and measuring fission products of Cf-252 is presented. The measurement was achieved by means of γ-spectrometry and thus provides a quantitative analysis with a good separation of the fission products with respect to both atomic number Z and mass number A. The separation of the fission products from the fission source was achieved by means of solid traps. An automatic changing apparatus made it possible to keep irradiation and measuring times short, so even very short-lived fission products could be registered. The quantitative evaluation of primary fission products was made possible by correction according to Bateman equations. With that, the yields of single nuclides and the dispersion of charge can be determined. (orig./WL) [de

A spike of 4298Mo in yields of uranium spontaneous fission an extension of shell structure effect

International Nuclear Information System (INIS)

Masuda, Akimasa; Takahashi, Kazuya; Kawashima, Atsumichi.

1993-01-01

The investigations of the isotopic abundance ratios of molybdenum in zircon have shown that the molybdenum isotopic composition obtained reflects two effects: (1) spontaneous fission of 92 238 U contained in the zircon and (2) double beta decay of 40 96 Zr. Interestingly, however, the products due to the spontaneous fission appear to have a strange large excess (spike) of 42 98 Mo. It intrigues us that 92 minus 42 leaves 50, one of the outstanding magic numbers. It is suggested in the present communication that the strange spike of 42 98 Mo in question can result from a special type of spontaneous fission having essential bearings on the magic number 50 of protons and the 'magical' numbers 58 and 92 of neutrons. (author)

The nuclear fission process

International Nuclear Information System (INIS)

Wagemans, C.

1991-01-01

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

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

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

Directory of Open Access Journals (Sweden)

Rossi P C R

2012-02-01

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

Angular momenta of fission fragments in the {alpha}-accompanied fission of {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Jandel, M.; Kliman, J.; Krupa, L.; Morhac, M. [Slovak Academy of Sciences, Department of Nuclear Physics, Bratislava (Slovakia); Joint Institute for Nuclear Research, Flerov Laboratory for Nuclear Reactions, Dubna (Russian Federation); Hamilton, J.H.; Kormicki, J.; Ramayya, A.V.; Hwang, J.K.; Luo, Y.X.; Fong, D.; Gore, P. [Vanderbilt University, Department of Physics, Nashville, TN (United States); Ter-Akopian, G.M.; Oganessian, Yu.Ts.; Rodin, A.M.; Fomichev, A.S.; Popeko, G.S. [Joint Institute for Nuclear Research, Flerov Laboratory for Nuclear Reactions, Dubna (Russian Federation); Daniel, A.V. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Rasmussen, J.O.; Macchiavelli, A.O.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Donangelo, R.; Cole, J.D.

2005-06-01

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

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.

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

Correlation of errors in the Monte Carlo fission source and the fission matrix fundamental-mode eigenvector

International Nuclear Information System (INIS)

Dufek, Jan; Holst, Gustaf

2016-01-01

Highlights: • Errors in the fission matrix eigenvector and fission source are correlated. • The error correlations depend on coarseness of the spatial mesh. • The error correlations are negligible when the mesh is very fine. - Abstract: Previous studies raised a question about the level of a possible correlation of errors in the cumulative Monte Carlo fission source and the fundamental-mode eigenvector of the fission matrix. A number of new methods tally the fission matrix during the actual Monte Carlo criticality calculation, and use its fundamental-mode eigenvector for various tasks. The methods assume the fission matrix eigenvector is a better representation of the fission source distribution than the actual Monte Carlo fission source, although the fission matrix and its eigenvectors do contain statistical and other errors. A recent study showed that the eigenvector could be used for an unbiased estimation of errors in the cumulative fission source if the errors in the eigenvector and the cumulative fission source were not correlated. Here we present new numerical study results that answer the question about the level of the possible error correlation. The results may be of importance to all methods that use the fission matrix. New numerical tests show that the error correlation is present at a level which strongly depends on properties of the spatial mesh used for tallying the fission matrix. The error correlation is relatively strong when the mesh is coarse, while the correlation weakens as the mesh gets finer. We suggest that the coarseness of the mesh is measured in terms of the value of the largest element in the tallied fission matrix as that way accounts for the mesh as well as system properties. In our test simulations, we observe only negligible error correlations when the value of the largest element in the fission matrix is about 0.1. Relatively strong error correlations appear when the value of the largest element in the fission matrix raises

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.

Analysis of Double-encapsulated Fuel Rods

Energy Technology Data Exchange (ETDEWEB)

Hales, Jason Dean [Idaho National Laboratory; Medvedev, Pavel G [Idaho National Laboratory; Novascone, Stephen Rhead [Idaho National Laboratory; Perez, Danielle Marie [Idaho National Laboratory; Williamson, Richard L [Idaho National Laboratory

2014-09-01

In an LWR fuel rod, the cladding encapsulates the fuel, contains fission products, and transfers heat directly to the water coolant. In some situations, it may be advantageous to separate the cladding from the coolant through use of a secondary cladding or capsule. This may be done to increase confidence that the fuel or fission products will not mix with the coolant, to provide a mechanism for controlling the rod temperature, or to place multiple experimental rodlets within a single housing. With an axisymmetric assumption, it is possible to derive closed-form expressions for the temperature profile in a fuel rod using radially-constant thermal conductivity in the fuel. This is true for both a traditional fuel-cladding rod and a double-encapsulated fuel (fuel, cladding, capsule) configuration. Likewise, it is possible to employ a fuel performance code to analyse both a traditional and a double-encapsulated fuel. In the case of the latter, two sets of gap heat transfer conditions must be imposed. In this work, we review the equations associated with radial heat transfer in a cylindrical system, present analytic and computational results for a postulated power and gas mixture history for IFA-744, and describe the analysis of the AFC-2A, 2B metallic fuel alloy experiments at the Advanced Test Reactor, including the effect of a release of fission products into the cladding-capsule gap. The computational results for these two cases were obtained using BISON, a fuel performance code under development at Idaho National Laboratory.

The Growth of Sea cucumber Stichopus herrmanni After Transverse Induced Fission in Two and Three Fission Plane

Directory of Open Access Journals (Sweden)

Retno Hartati

2016-06-01

Full Text Available Transverse induced fission proven could be done in Teripang Tril, Stichopus herrmanni. This present works aimed to analyze wound recovery, regeneration period and growth of Teripang Trill  after asexual reproduction by fission using two and three fission plane. Observations were made every day until the sea cucumber body separated into two or more (depending on treatment and reared for 16 weeks.  The results showed that there are differences in wound recovery, regeneration period and growth of S. herrmanni depend on their different fission plane. The wound recovery and regeneration period (days of anterior, middle and posterior individu S. herrmanni resulted from two and three fission plane were varied but the two fission plane the anterior individu recover for longer period than posterior part and  the wound recover process in both end for thee fission plane was same. Average growth of anterior and posterior fragment were longer for two fission plane than three fission plane.  The middle fragment (M1 and M2 both fission plane was able to grow but very low.  It showed that three fission plane gave very slow growth in every fragment of the body. Keywords: growth, post-fission, fission plane, Stichopus herrmanni

Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons

International Nuclear Information System (INIS)

Nix, J.R.; Madland, D.G.; Sierk, A.J.

1985-01-01

With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, we discuss recent advances in a unified macroscopic-microscopic description of large-amplitude collective nuclear dynamics. The conversion of collective energy into single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving the Hamilton equations of motion for initial conditions appropriate to fission, we obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of our calculations with experimental data are shown

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 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.)

Two-photon double ionization of the helium atom by ultrashort pulses

International Nuclear Information System (INIS)

Palacios, Alicia; Horner, Daniel A.; Rescigno, Thomas N.; McCurdy, C. William

2010-01-01

Two-photon double ionization of the helium atom was the subject of early experiments at FLASH and will be the subject of future benchmark measurements of the associated electron angular and energy distributions. As the photon energy of a single femtosecond pulse is raised from the threshold for two-photon double ionization at 39.5 eV to beyond the sequential ionization threshold at 54.4 eV, the electron ejection dynamics change from the highly correlated motion associated with nonsequential absorption to the much less correlated sequential ionization process. The signatures of both processes have been predicted in accurate ab initio calculations of the joint angular and energy distributions of the electrons, and those predictions contain some surprises. The dominant terms that contribute to sequential ionization make their presence apparent several eV below that threshold. In two-color pump probe experiments with short pulses whose central frequencies require that the sequential ionization process necessarily dominates, a two-electron interference pattern emerges that depends on the pulse delay and the spin state of the atom.

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.)

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

Fission yield measurements at IGISOL

Science.gov (United States)

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

2016-06-01

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

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.

Separation and purification of short lived fission products from irradiated uranium

International Nuclear Information System (INIS)

Balasubramanian, K.R.; Rao, K.L.N.; Mathai, C.; Varma, R.N.; Dhiwar, V.I.; Saxena, S.K.

1991-01-01

Fission produced radioisotopes like 95 Zr, 140 Ba, 103 Ru, 89 Sr and 91 Y whose half lives are less than 1 year find a wide variety of applications in the fields of industry, medicine and research. Isotope Division, BARC has been supplying these isotopes in hudreds of mCi amounts during the past several years. A new method for the sequential separation of these isotopes from irradiated uranium has been developed based on synthetic inorganic exchangers like stannic phosphate, polyphospho antimonic acid, hydrous manganese dioxide, etc. This report describes the new flow sheet worked out and adopted for the regular processing of these isotopes at hundreds of milli curie amounts. (author). 19 refs., 4 tabs. , 1 fig

Study of hypernuclei fission

International Nuclear Information System (INIS)

Malek, F.

1990-01-01

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

Elastocapillary Instability in Mitochondrial Fission

Science.gov (United States)

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

2015-08-01

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

Proceedings of the specialists' meeting on interdisciplinary approach to nuclear fission 1998

International Nuclear Information System (INIS)

Nakagome, Yoshihiro

1999-02-01

One of the prominent features of nuclear fission phenomena distinguished from other reactions consists in its many-facet nature. This includes interesting problems in nuclear physics like stability and properties of transactinide and superheavy nuclei, macroscopic and microscopic effects in large-amplitude deformation process, partition of mass and energy at scission, formation of neutron-rich nuclei, neutron- and gamma-ray emission from highly excited states and so on. These aspects are intriguing not only from scientific point of view but also from technological one, because knowledge and understanding of the essential features of the phenomena forms the basis of application of nuclear energy. Physicists expect to obtain a deeper insight into fundamental problems in subjects such as relation between fission process and fusion of heavy-ions, statistical and dynamical processes in nuclear reactions, level structure and decay modes of highly-excited nuclei. On the other hand, there are still continued requests from scientists in nuclear engineering for more accurate data for transuranium nuclei and fission products, as well as for fundamental constants, like fission cross sections, multiplicity and spectra of prompt and delayed neutrons, and other physical quantities that are important in reactor physics. Studies on properties of neutron-rich nuclei are conducted under double interests: one from nucleosynthesis in the universe, another from nuclear incineration of fission products. We considered that these many-facet nature of the fission phenomena should be the central idea of the Specialists' Meeting itself. This implies that we intended to devise a common place where people from different fields encounter, discuss together, exchange ideas and hopefully find good suggestions for pursuing further studies. We are sure that such a meeting, really rare and unique in academic communities in our country, should serve to vitalize research activities relevant to fission

Determination of the fission products yields, lanthanide and yttrium, in the fission of 238U with neutrons of fission spectra

International Nuclear Information System (INIS)

Nicoli, I.G.

1981-06-01

A radiochemical investigation is performed to measure the cumulative fission product yields of several lantanides and yttrium nuclides in the 238 U by fission neutron spectra. Natural and depleted uranium are irradiated under the same experimental conditions in order to find a way to subtract the contribution of the 235 U fission. 235 U percentage in the natural uranium was 3.5 times higher than in the depleted uranium. Uranium oxides samples are irradiated inside the core of the Argonaut Reactor, at the Instituto de Engenharia Nuclear, and the lantanides and yttrium are chemically separated. The fission products gamma activities were detected, counted and analysed in a system constituted by a high resolution Ge(Li) detector, 4096 multichannel analyser and a PDP-11 computer. Cumulative yields for fission products with half-lives between 1 to 33 hours are measured: 93 Y, 141 La, 142 La, 143 Ce and 149 Nd. The chain total yields are calculated. The cumulative fission yields measured for 93 Y, 141 La, 142 La, 143 Ce and 149 Nd are 4,49%, 4,54%, 4,95%, 4,16% and 1,37% respectively and they are in good agreement with the values found in the literature. (Author) [pt

Liver hemangioma: diagnosis with double 99mTc labelling

International Nuclear Information System (INIS)

Piga, M.; Satta, L.; Loi, G.; Careddu, A.; Corrias, N.; Montaldo, C.; Schiffini, P.; Dore, F.; Madeddu, G.

1990-01-01

The authors report on their experience with liver hemangioma (LH) diagnosis by means of a semplified method- that is, the simultaneous, in vivo, double labelling of liver reticuloendothelial system (RES) and of red blood cells (RBC) by 99m Tc. Twenty-eight patients with US diagnosis of suspected LH and 15 controls were examined after sequential iv injection of SnCl 2 , of 99m Tcμcolloid albumin and, after liver scintigraphy, of 99m Tc-pertechnetate to conclude in vivo RBC labelling. All patients underwent CT and, if necessary, CT-guided biopsy. Focal colloid defects were shown in 6/28 cases (expansive process). 15/15 controls showed unchanged non-filling defects after double labelling. Finally, the authors point out that, in the diagnosis of LH, sequential double labelling of liver RES and RBC appears to be a quicker scintigraphic techique than conventional ones. Moreover, this technique has the same high specificity and sensitivity as more time-consuming ones

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)

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

CERN Multimedia

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

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.)

Tip model of cold fission

International Nuclear Information System (INIS)

Goennenwein, F.; Boersig, B.

1991-01-01

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

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

Insights into nuclear structure and the fission process from spontaneous fission

Energy Technology Data Exchange (ETDEWEB)

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

1993-12-31

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

Anatomy of a defective barrier: sequential glove leak detection in a surgical and dental environment.

Science.gov (United States)

Albin, M S; Bunegin, L; Duke, E S; Ritter, R R; Page, C P

1992-02-01

a) To determine the frequency of perforations in latex surgical gloves before, during, and after surgical and dental procedures; b) to evaluate the topographical distribution of perforations in latex surgical gloves after surgical and dental procedures; and c) to validate methods of testing for latex surgical glove patency. Multitrial tests under in vitro conditions and a prospective sequential patient study using consecutive testing. An outpatient dental clinic at a university dental school, the operating suite in a medical school affiliated with the Veteran's Hospital, and a biomechanics laboratory. Surgeons, scrub nurses, and dental technicians participating in 50 surgical and 50 dental procedures. We collected 679 latex surgical gloves after surgical procedures and tested them for patency by using a water pressure test. We also employed an electronic glove leak detector before donning, after sequential time intervals, and upon termination of 47 surgical (sequential surgical), 50 dental (sequential dental), and in three orthopedic cases where double gloving was used. The electronic glove leak detector was validated by using electronic point-by-point surface probing, fluorescein dye diffusion, as well as detecting glove punctures made with a 27-gauge needle. The random study indicated a leak rate of 33.0% (224 out of 679) in latex surgical gloves; the sequential surgical study demonstrated patency in 203 out of 347 gloves (58.5%); the sequential dental study showed 34 leaks in the 106 gloves used (32.1%); and with double gloving, the leak rate decreased to 25.0% (13 of 52 gloves tested). While the allowable FDA defect rate for unused latex surgical gloves is 1.5%, we noted defect rates in unused gloves of 5.5% in the sequential surgical, 1.9% in the sequential dental, and 4.0% in our electronic glove leak detector validating study. In the sequential surgical study, 52% of the leaks had occurred by 75 mins, and in the sequential dental study, 75% of the leaks

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

Science.gov (United States)

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

2014-09-01

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

The smt-0 mutation which abolishes mating-type switching in fission yeast is a deletion

DEFF Research Database (Denmark)

Styrkársdóttir, U; Egel, R; Nielsen, O

1993-01-01

Mating-type switching in the fission yeast, S. pombe, is initiated by a DNA double-strand break (DSB) between the mat1 cassette and the H1 homology box. The mat1-cis-acting mutant, smt-0, abolishes mating-type switching and is shown here to be a 263-bp deletion. This deletion starts in the middle...

Reexamination of fission fragment angular distributions and the fission process: Formalism

International Nuclear Information System (INIS)

Bond, P.D.

1985-01-01

The theory of fission fragment angular distributions is examined and the universally used expression is found to be valid only under restrictive assumptions. A more general angular distribution formula is derived and applied to recent data of high spin systems. At the same time it is shown that the strong anisotropies observed from such systems can be understood without changing the essential basis of standard fission theory. The effects of reaction mechanisms other than complete fusion on fission fragment angular distributions are discussed and possible angular distribution signatures of noncompound nucleus formation are mentioned

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

Investigation of the heavy nuclei fission with anomalously high values of the fission fragments total kinetic energy

Science.gov (United States)

Khryachkov, Vitaly; Goverdovskii, Andrei; Ketlerov, Vladimir; Mitrofanov, Vecheslav; Sergachev, Alexei

2018-03-01

Binary fission of 232Th and 238U induced by fast neutrons were under intent investigation in the IPPE during recent years. These measurements were performed with a twin ionization chamber with Frisch grids. Signals from the detector were digitized for further processing with a specially developed software. It results in information of kinetic energies, masses, directions and Bragg curves of registered fission fragments. Total statistics of a few million fission events were collected during each experiment. It was discovered that for several combinations of fission fragment masses their total kinetic energy was very close to total free energy of the fissioning system. The probability of such fission events for the fast neutron induced fission was found to be much higher than for spontaneous fission of 252Cf and thermal neutron induced fission of 235U. For experiments with 238U target the energy of incident neutrons were 5 MeV and 6.5 MeV. Close analysis of dependence of fission fragment distribution on compound nucleus excitation energy gave us some explanation of the phenomenon. It could be a process in highly excited compound nucleus which leads the fissioning system from the scission point into the fusion valley with high probability.

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

Muon-induced fission

International Nuclear Information System (INIS)

Polikanov, S.

1980-01-01

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

Double-arm time-of-flight mass-spectrometer of nuclear fragments

International Nuclear Information System (INIS)

Ajvazian, G.M.; Astabatyan, R.A.

1995-01-01

A double-arm time-of-flight spectrometer of nuclear fragments for the investigation of heavy nuclei photofission in the intermediate energy range is described. The calibration results and working characteristics of the spectrometer, obtained using 252 Cf as a source of spontaneous fission, are presented. A mass resolution of σ m ∼2-3 a.m.u. was obtained within the registered fragments mass range of 80-160 a.m.u. The spectrometer was tested in the experiment on the investigation of 238 U nuclei fission by Bremsstahlung photons with Eγ max=1.75 GeV

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

Design safety features of containments used for handling plutonium in Reprocessing Plants

International Nuclear Information System (INIS)

Aherwal, P.; Achuthan, P.V.

2016-01-01

The plutonium present in spent fuel is separated from the associated uranium and fission products using solvent extraction cycles in process cells. Product plutonium nitrate solution containing trace concentrations of uranium and fission products is treated in the reconversion facility through a precipitation-calcination route and converted to sinterable grade plutonium oxide (PuO 2 ). All chemical operations involving materials with high plutonium content, both in solid and solution forms are carried out in glove boxes. Glove box provides an effective isolation from radioactive materials handled and acts as a barrier between the operator and the source of radiation. These glove boxes are interconnected for sequential operations and the interconnected glove box trains are installed within secondary enclosures called double skin which provides double barrier protection to operators

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.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Multiplicity counting from fission detector signals with time delay effects

Science.gov (United States)

Nagy, L.; Pázsit, I.; Pál, L.

2018-03-01

In recent work, we have developed the theory of using the first three auto- and joint central moments of the currents of up to three fission chambers to extract the singles, doubles and triples count rates of traditional multiplicity counting (Pázsit and Pál, 2016; Pázsit et al., 2016). The objective is to elaborate a method for determining the fissile mass, neutron multiplication, and (α, n) neutron emission rate of an unknown assembly of fissile material from the statistics of the fission chamber signals, analogous to the traditional multiplicity counting methods with detectors in the pulse mode. Such a method would be an alternative to He-3 detector systems, which would be free from the dead time problems that would be encountered in high counting rate applications, for example the assay of spent nuclear fuel. A significant restriction of our previous work was that all neutrons born in a source event (spontaneous fission) were assumed to be detected simultaneously, which is not fulfilled in reality. In the present work, this restriction is eliminated, by assuming an independent, identically distributed random time delay for all neutrons arising from one source event. Expressions are derived for the same auto- and joint central moments of the detector current(s) as in the previous case, expressed with the singles, doubles, and triples (S, D and T) count rates. It is shown that if the time-dispersion of neutron detections is of the same order of magnitude as the detector pulse width, as they typically are in measurements of fast neutrons, the multiplicity rates can still be extracted from the moments of the detector current, although with more involved calibration factors. The presented formulae, and hence also the performance of the proposed method, are tested by both analytical models of the time delay as well as with numerical simulations. Methods are suggested also for the modification of the method for large time delay effects (for thermalised neutrons).

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

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

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.)

The tumor suppressor homolog in fission yeast, myh1+, displays a strong interaction with the checkpoint gene rad1+

International Nuclear Information System (INIS)

Jansson, Kristina; Warringer, Jonas; Farewell, Anne; Park, Han-Oh; Hoe, Kwang-Lae; Kim, Dong-Uk; Hayles, Jacqueline; Sunnerhagen, Per

2008-01-01

The DNA glycosylase MutY is strongly conserved in evolution, and homologs are found in most eukaryotes and prokaryotes examined. This protein is implicated in repair of oxidative DNA damage, in particular adenine mispaired opposite 7,8-dihydro-8-oxoguanine. Previous investigations in Escherichia coli, fission yeast, and mammalian cells show an association of mutations in MutY homologs with a mutator phenotype and carcinogenesis. Eukaryotic MutY homologs physically associate with several proteins with a role in replication, DNA repair, and checkpoint signaling, specifically the trimeric 9-1-1 complex. In a genetic investigation of the fission yeast MutY homolog, myh1 + , we show that the myh1 mutation confers a moderately increased UV sensitivity alone and in combination with mutations in several DNA repair genes. The myh1 rad1, and to a lesser degree myh1 rad9, double mutants display a synthetic interaction resulting in enhanced sensitivity to DNA damaging agents and hydroxyurea. UV irradiation of myh1 rad1 double mutants results in severe chromosome segregation defects and visible DNA fragmentation, and a failure to activate the checkpoint. Additionally, myh1 rad1 double mutants exhibit morphological defects in the absence of DNA damaging agents. We also found a moderate suppression of the slow growth and UV sensitivity of rhp51 mutants by the myh1 mutation. Our results implicate fission yeast Myh1 in repair of a wider range of DNA damage than previously thought, and functionally link it to the checkpoint pathway

Dynamic of fission and quasi-fission revealed by pre-scission neutron evaporation

International Nuclear Information System (INIS)

Hinde, D.J.

1991-06-01

The dependence of pre-scission neutron multiplicities (ν-pre) on the mass-split and total kinetic energy (TKE) in fusion-fission and quasi-fission has been measured for a wide range of projectile-target combinations. the data indicate that the fusion-fission time scale is shorter for asymmetric splits than for symmetric splits, whilst there is no dependence on TKE. For quasi-fission reactions induced using 64 Ni projectiles, ν-pre falls rapidly with increasing TKE, indicating that these neutrons are emitted near to or after scission. A new interpretation of both neutron multiplicities and mean energies (the neutron clock-thermometer) allows the extraction of time scales with much less uncertainty than previously, and also gives information about the deformation from which the neutrons are emitted. 15 refs., 13 figs

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

Energy Technology Data Exchange (ETDEWEB)

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

1958-07-01

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

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

Doubling time measurement by method of digital integration of pulses from a CFU7 detector

International Nuclear Information System (INIS)

Gauthier, Guy

1968-01-01

The author reports an experimental study which aimed at measuring the doubling time with a CFU7 fission chamber by using an integration method on the Siloette pile with a new core and with a spent core, and at comparing results with those obtained with a specific instrument which receives information from an ionisation chamber. The interest of this method relies on the fact that the fission chamber is insensitive to gamma radiations

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)

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.

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

Fission in a Plasma

Energy Technology Data Exchange (ETDEWEB)

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

2016-10-26

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

Development of a “Fission-proxy” Method for the Measurement of 14-MeV Neutron Fission Yields at CAMS

Energy Technology Data Exchange (ETDEWEB)

Gharibyan, Narek [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-10-25

Relative fission yield measurements were made for 50 fission products from 25.6±0.5 MeV alpha-induced fission of Th-232. Quantitative comparison of these experimentally measured fission yields with the evaluated fission yields from 14-MeV neutron-induced fission of U-235 demonstrates the feasibility of the proposed fission-proxy method. This new technique, based on the Bohr-independence hypothesis, permits the measurement of fission yields from an alternate reaction pathway (Th-232 + 25.6 MeV α → U-236* vs. U-235 + 14-MeV n → U-236*) given that the fission process associated with the same compound nucleus is independent of its formation. Other suitable systems that can potentially be investigated in this manner include (but are not limited to) Pu-239 and U-237.

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

Nuclear fission and neutron-induced fission cross-sections

CERN Document Server

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

2013-01-01

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

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

The nuclear fission

International Nuclear Information System (INIS)

Fiorentino, J.

1983-01-01

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

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 cross section measurement of Am-242m using lead slowing-down spectrometer

Energy Technology Data Exchange (ETDEWEB)

Kai, Tetsuya; Kobayashi, Katsuhei; Yamamoto, Shuji; Fujita, Yoshiaki [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Kimura, Itsuro; Ohkawachi, Yasushi; Wakabayashi, Toshio

1998-03-01

By making use of double fission chamber and lead slowing-down spectrometer coupled to an electron linear accelerator, fission cross section for the {sup 242m}Am(n,f) reaction has been measured relative to that for the {sup 235}U(n,f) reaction in the energy range from 0.1 eV to 10 keV. The measured result was compared with the evaluated nuclear data appeared in ENDF/B-VI and JENDL-3.2, of which evaluated data were broadened by the energy resolution function of the spectrometer. Although the JENDL-3.2 data seem to be a little smaller than the present measurement, good agreement can be seen in the general shape and the absolute values. The ENDF/B-VI data are larger more than 50 % than the present values above 3 eV. (author)

Parallel theoretical study of the two components of the prompt fission neutrons: Dynamically released at scission and evaporated from fully accelerated fragments

Directory of Open Access Journals (Sweden)

Carjan Nicolae

2017-01-01

Full Text Available Prompt fission neutrons (PFN angular and energy distributions for the reaction 235U(nth,f are calculated as a function of the mass asymmetry of the fission fragments using two extreme assumptions: 1 PFN are released during the neck rupture due to the diabatic coupling between the neutron degree of freedom and the rapidly changing neutron-nucleus potential. These unbound neutrons are faster than the separation of the nascent fragments and most of them leave the fissioning system in few 10−21 sec. i.e., at the begining of the acceleration phase. Surrounding the fissioning nucleus by a sphere one can calculate the radial component of the neutron current density. Its time integral gives the angular distribution with respect to the fission axis. The average energy of each emitted neutron is also calculated using the unbound part of each neutron wave packet. The distribution of these average energies gives the general trends of the PFN spectrum: the slope, the range and the average value. 2 PFN are evaporated from fully accelerated, fully equilibrated fission fragments. To follow the de-excitation of these fragments via neutron and γ-ray sequential emissions, a Monte Carlo sampling of the initial conditions and a Hauser-Feshbach statistical approach is used. Recording at each step the emission probability, the energy and the angle of each evaporated neutron one can construct the PFN energy and the PFN angular distribution in the laboratory system. The predictions of these two methods are finally compared with recent experimental results obtained for a given fragment mass ratio.

State dynamics of a double sandbar system

NARCIS (Netherlands)

Price, T.D.; Ruessink, B.G.

2011-01-01

A 9.3-year dataset of low-tide time-exposure images from Surfers Paradise, Northern Gold Coast, Australia was used to characterise the state dynamics of a double sandbar system. The morphology of the nearshore sandbars was described by means of the sequential bar state classification scheme of

Double ionization of H2 caused by two sequential projectile-electron collisions

International Nuclear Information System (INIS)

Edwards, A.K.; Wood, R.M.; Ezell, R.L.

1985-01-01

The impact-parameter calculations of Hansteen et al. [J. Phys. B 17, 3545 (1984)] for K-shell ionization are used to predict the cross sections for the double ionization of H 2 and He by H + and D + projectiles as a function of projectile velocity. The calculated values in the case of the H 2 target are typically a factor of 12 lower than the measured values, but the calculations and measurements show similar velocity dependencies. The results indicate that for projectile energies less than 1 MeV/amu, the double-ionization process of H 2 occurs mainly by two independent interactions between the electrons and projectile. For the He target, the calculated and measured values for the double-ionization cross section are much closer in magnitude, but the calculations predict a more rapid falloff with projectile velocity than is observed

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

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

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

International Nuclear Information System (INIS)

Damm, G.; Thiel, K.

1977-01-01

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

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

Development of fission micro-chambers for nuclear waste incineration studies

CERN Document Server

Fadil, M; Christophe, S; Deruelle, O; Fioni, G; Marie, F; Mounier, C; Ridikas, D; Trapp, J P

2002-01-01

The Incineration by Accelerator (INCA) project of the Directorate for Science of Matter of the French Atomic Energy Authority (CEA/DSM) aims to outline the ideal physical conditions to transmute minor actinides in a high intensity neutron flux obtained either by hybrid systems or innovative critical reactors. To measure on-line the incineration rates of minor actinides, we are developing an innovative Double Deposit Fission Chamber (DDFC) working in current mode. Our method is based on a comparison between the isotope under study and a reference material whose nuclear parameters are well known, as sup 2 sup 3 sup 5 U and sup 2 sup 3 sup 9 Pu. This new fission chamber will be used in the High Flux Reactor in Grenoble/France in a neutron flux of 1.2x10 sup 1 sup 5 n cm sup - sup 2 s sup - sup 1 for 50 days, the operating cycle of the reactor. These specific experimental conditions require substantial modifications of the existing chambers. The first experiment will be carried out in fall 2000.

Properties of Fission-Product decay heat from Minor-Actinide fissioning systems

International Nuclear Information System (INIS)

Oyamatsu, Kazuhiro; Mori, Hideki

2000-01-01

The aggregate Fission-Product (FP) decay heat after a pulse fission is examined for Minor Actinide (MA) fissiles 237 Np, 241 Am, 243 Am, 242 Cm and 244 Cm. We find that the MA decay heat is comparable but smaller than that of 235 U except for cooling times at about 10 8 s (approx. = 3 y). At these cooling times, either the β or γ component of the FP decay heat for these MA's is substantially larger than the one for 235 U. This difference is found to originate from the cumulative fission yield of 106 Ru (T 1/2 = 3.2x10 7 s). This nuclide is the parent of 106 Rh (T 1/2 = 29.8 s) which is the dominant source of the decay heat at 10 8 s (approx. = 3 y). The fission yield is nearly an increasing function of the fissile mass number so that the FP decay heat is the largest for 244 Cm among the MA's at the cooling time. (author)

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

Lecture 2: Equilibrium statistical treatment of angular momenta associated with collective modes in fission and heavy-ion reactions

International Nuclear Information System (INIS)

Moretto, L.G.

1979-01-01

The angular momentum effects in deep inelastic processes and fission have been studied in the limit of statistical equilibrium. The model consists of two touching liquid drop spheres. Angular momentum fractionation has been found to occur along the mass asymmetry coordinate. If neutron competition is included (i.e., in compound nucleus formation and fission), the fractionation occurs only to a slight degree, while extensive fractionation is predicted if no neutron competition occurs (i.e., in fusion--fission without compound nucleus formation). Thermal fluctuations in the angular momentum are predicted to occur due to degrees of freedom which can bear angular momentum, like wriggling, tilting, bending, and twisting. The coupling of relative motion to one of the wriggling modes, leading to fluctuations between orbital and intrinsic angular momentum, is considered first. Next the effect of the excitation of all the collective modes on the fragment spin is treated. General expressions for the first and second moments of the fragment spins are derived as a function of total angular momentum and the limiting behavior at large and small total angular momentum is examined. Furthermore, the effect of collective mode excitation on the fragment spin alignment is explored and is discussed in light of recent experiments. The relevance of the present study to the measured first and second moments of the γ-ray multiplicities as well as to sequential fission angular distributions is illustrated by applying the results of the theory to a well studied heavy ion reaction

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

Energy Technology Data Exchange (ETDEWEB)

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

1965-07-01

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

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.

Yields of fission products produced by thermal-neutron fission of 229Th

International Nuclear Information System (INIS)

Dickens, J.K.; McConnell, J.W.

1983-01-01

Absolute yields have been determined for 47 gamma rays emitted in the decay of 37 fission products representing 25 mass chains created during thermal-neutron fission of 229 Th. Using a Ge(Li) detector, spectra were obtained of gamma rays emitted between 15 min and 0.4 yr after very short irradiations by thermal neutrons of a 15-μg sample of 229 Th. On the basis of measured gamma-ray yields and known nuclear data, yields for cumulative production of 37 fission products were deduced. The absolute overall normalization uncertainty is 235 U, we postulate a simple functional dependence sigma = sigma(Z/sub p/), and using this dependence obtain values of Z/sub p/(A) for 15 mass chains created during fission of 229 Th. Values of Z/sub p/(A) were estimated for other mass chains based upon results of a recent study of Z/sub p/(A). Charge distributions determined using the deduced mass distribution and the deduced sets of Z/sub p/(A) and sigma(Z/sub p/) are in very good agreement with recent measurements, exhibiting a pronounced even-odd effect in elemental yields. These results may be used to predict unmeasured yields for 229 Th fission

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.

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

Thorium-uranium fission radiography

Science.gov (United States)

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

1976-01-01

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

Relativistic Coulomb Fission

Science.gov (United States)

Norbury, John W.

1992-01-01

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

Fission-product source terms

International Nuclear Information System (INIS)

Lorenz, R.A.

1981-01-01

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

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

Generalized Energy-Dependent Q Values for Fission

Energy Technology Data Exchange (ETDEWEB)

Vogt, R

2010-03-31

We extend Madland's parameterization of the energy release in fission to obtain the dependence of the fission Q value for major and minor actinides on the incident neutron energies in the range 0 {le} E{sub n} {le} 20 MeV. Our parameterization is based on the actinide evaluations recommended for the ENDF/B-VII.1 release. This paper describes the calculation of energydependent fission Q values based on the calculation of the prompt energy release in fission by Madland. This calculation was adopted for use in the LLNL ENDL database and then generalized to obtain the prompt fission energy release for all actinides. Here the calculation is further generalized to the total energy release in fission. There are several stages in a fission event, depending on the time scale. Neutrons and gammas may be emitted at any time during the fission event.While our discussion here is focussed on compound nucleus creation by an incident neutron, similar parameterizations could be obtained for incident gammas or spontaneous fission.

New fission-neutron-spectrum representation for ENDF

International Nuclear Information System (INIS)

Madland, D.G.

1982-04-01

A new representation of the prompt fission neutron spectrum is proposed for use in the Evaluated Nuclear Data File (ENDF). The proposal is made because a new theory exists by which the spectrum can be accurately predicted as a function of the fissioning nucleus and its excitation energy. Thus, prompt fission neutron spectra can be calculated for cases where no measurements exist or where measurements are not possible. The mathematical formalism necessary for application of the new theory within ENDF is presented and discussed for neutron-induced fission and spontaneous fission. In the case of neutron-induced fission, expressions are given for the first-chance, second-chance, third-chance, and fourth-chance fission components of the spectrum together with that for the total spectrum. An ENDF format is proposed for the new fission spectrum representation, and an example of the use of the format is given

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.)

Fission cross section and fission fragment angular distribution for oriented nucleus fission by intermediate energy neutrons (epsilon < or approximately 1 Mev)

International Nuclear Information System (INIS)

Barabanov, A.L.; Grechukhin, D.P.

1985-01-01

General analysis is conducted, and formulae for fission cross section and angular distribution of fission fragments of oriented nuclei by fast neutrons are presented. Geometrical coefficients making up the formulae permitting to carry out calculations for target nuclei with spins I=3/2, 5/2, 7/2 at interaction energies epsilon < or approximately 1 MeV are tabulated. Results of demonstrative calculation of fission fragment angular distribution of oriented sup(235)U nuclei by 0.1 <= epsilon <= 1.0 MeV neutrons reveal that angular distribution weakly depends on the set of permeability factors of neutron waves applied in the calculations

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)

The tumor suppressor homolog in fission yeast, myh1{sup +}, displays a strong interaction with the checkpoint gene rad1{sup +}

Energy Technology Data Exchange (ETDEWEB)

Jansson, Kristina; Warringer, Jonas; Farewell, Anne [Department of Cell and Molecular Biology, Lundberg Laboratory, Goeteborg University, P.O. Box 462, Goeteborg SE-405 30 (Sweden); Park, Han-Oh [Bioneer Corporation, 49-3, Munpyeong-dong, Daedeok-gu, Daejon 306-220 (Korea, Republic of); Hoe, Kwang-Lae; Kim, Dong-Uk [Functional Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Yusong, Daejeon (Korea, Republic of); Hayles, Jacqueline [Cell Cycle Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln' s Inn Fields, London WC2A 3PX (United Kingdom); Sunnerhagen, Per [Department of Cell and Molecular Biology, Lundberg Laboratory, Goeteborg University, P.O. Box 462, Goeteborg SE-405 30 (Sweden)], E-mail: per.sunnerhagen@cmb.gu.se

2008-09-26

The DNA glycosylase MutY is strongly conserved in evolution, and homologs are found in most eukaryotes and prokaryotes examined. This protein is implicated in repair of oxidative DNA damage, in particular adenine mispaired opposite 7,8-dihydro-8-oxoguanine. Previous investigations in Escherichia coli, fission yeast, and mammalian cells show an association of mutations in MutY homologs with a mutator phenotype and carcinogenesis. Eukaryotic MutY homologs physically associate with several proteins with a role in replication, DNA repair, and checkpoint signaling, specifically the trimeric 9-1-1 complex. In a genetic investigation of the fission yeast MutY homolog, myh1{sup +}, we show that the myh1 mutation confers a moderately increased UV sensitivity alone and in combination with mutations in several DNA repair genes. The myh1 rad1, and to a lesser degree myh1 rad9, double mutants display a synthetic interaction resulting in enhanced sensitivity to DNA damaging agents and hydroxyurea. UV irradiation of myh1 rad1 double mutants results in severe chromosome segregation defects and visible DNA fragmentation, and a failure to activate the checkpoint. Additionally, myh1 rad1 double mutants exhibit morphological defects in the absence of DNA damaging agents. We also found a moderate suppression of the slow growth and UV sensitivity of rhp51 mutants by the myh1 mutation. Our results implicate fission yeast Myh1 in repair of a wider range of DNA damage than previously thought, and functionally link it to the checkpoint pathway.

A small flat fission chamber

International Nuclear Information System (INIS)

Li Yijun; Wang Dalun; Chen Suhe

1999-01-01

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

50 years of nuclear fission

International Nuclear Information System (INIS)

Hilscher, D.

1989-01-01

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

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

Fission gas detection system

International Nuclear Information System (INIS)

Colburn, R.P.

1984-01-01

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

Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers

Science.gov (United States)

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

2014-05-01

To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced γ-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.

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

Shell effects in fission and quasi-fission of heavy and superheavy nuclei

Energy Technology Data Exchange (ETDEWEB)

Itkis, M.G. E-mail: itkis@flnr.jinr.ru; Aeystoe, J.; Beghini, S.; Bogachev, A.A.; Corradi, L.; Dorvaux, O.; Gadea, A.; Giardina, G.; Hanappe, F.; Itkis, I.M.; Jandel, M.; Kliman, J.; Khlebnikov, S.V.; Kniajeva, G.N.; Kondratiev, N.A.; Kozulin, E.M.; Krupa, L.; Latina, A.; Materna, T.; Montagnoli, G.; Oganessian, Yu.Ts.; Pokrovsky, I.V.; Prokhorova, E.V.; Rowley, N.; Rubchenya, V.A.; Rusanov, A.Ya.; Sagaidak, R.N.; Scarlassara, F.; Stefanini, A.M.; Stuttge, L.; Szilner, S.; Trotta, M.; Trzaska, W.H.; Vakhtin, D.N.; Vinodkumar, A.M.; Voskressenski, V.M.; Zagrebaev, V.I

2004-04-05

Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions {sup 12}C+{sup 204}Pb, {sup 48}Ca+{sup 144,154}Sm, {sup 168}Er, {sup 208}Pb, {sup 244}Pu, {sup 248}Cm; {sup 58}Fe+{sup 208}Pb, {sup 244}Pu, {sup 248}Cm, and {sup 64}Ni+{sup 186}W, {sup 242}Pu are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes {sup 283}112, {sup 289}114 and {sup 283}116 at Dubna [1],[2] using the same reactions. The {sup 58}Fe and {sup 64}Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET[3] and the neutron multi-detector DEMON[4],[5]. The role of shell effects and the influence of the entrance channel on the mechanism of the compound nucleus fusion-fission and the competitive process of quasi-fission are discussed.

Independent fission yields of Rb and Cs from thermal-neutron-induced fission of 239Pu

International Nuclear Information System (INIS)

Balestrini, S.J.; Forman, L.

1975-01-01

The relative independent fission yields of Rb and Cs from thermal-neutron-induced fission of 239 Pu have been measured on line using a mass spectrograph and thermalized neutrons from a burst reactor. Independent yields were derived by normalizing the measurements to products of chain yields and fractional independent yields, estimating the latter from measured cumulative yields of Kr and Xe. Comparing the independent yields with those from 238 U fission, the 239 Pu results show shifts in isotopic yield distribution toward lower mass for both Rb and Cs and also toward the production of more Cs and less Rb when 239 Pu is fissioned

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

NARCIS (Netherlands)

Plicht, J. van der

1980-01-01

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

Physics of neutron emission in fission

International Nuclear Information System (INIS)

Lemmel, H.D.

1989-06-01

The document contains the proceedings of the IAEA Consultants' Meeting on the Physics of Neutron Emission in Fission, Mito City (Japan), 24-27 May 1988. Included are the conclusions and recommendations reached at the meeting and the papers presented by the meeting participants. These papers cover the following topics: Energy dependence of the number of fission neutrons ν-bar (3 papers), multiplicity distribution of fission neutrons (3 papers), competition between neutron and γ-ray emission (4 papers), the fission neutron yield in resonances (2 papers) and the energy spectrum of fission neutrons in experiment (9 papers), theory (4 papers) and evaluation (1 paper). A separate abstract was prepared for each of these papers. Refs, figs and tabs

Progress in fission product nuclear data

International Nuclear Information System (INIS)

Lammer, G.

1975-01-01

This is the first issue of a report series on Fission Product Nuclear Data (FPND), published every six months by the Nuclear Data Section (NDS) of the International Atomic Energy Agency (IAEA). Its purpose is to inform scientists working on FPND, or using such data, about all activities in this field which are planned, ongoing, or have recently been completed. The types of activities being included in this report are measurements, compilations and evaluations of: fission product yields; neutron cross-section data of fission products; data related to β-, γ-decay of fission products; delayed neutron data; and fission product decay-heat. The present issue includes contributions which were received by NDS before 1 November 1975

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.

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

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.

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 ...

Some aspects of the nuclear fission process; Quelques aspects du processus de fission nucleaire

Energy Technology Data Exchange (ETDEWEB)

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

1961-07-01

In the following report one can find first a short general view on the present situation of our knowledge concerning the nuclear fission process, namely on the nucleus going through the saddle-point. Then there are some aspects connected with the excitation energy of the fissioning nucleus. The measurements made at Saclay on the fast neutron fission cross-section of U{sup 233}, U{sup 235}, Pu{sup 239}, U{sup 238} are described at the beginning of this work. It appears that for U{sup 233} there is some characteristic shape modulation of the cross-section curve, in relation with the collective excited state of the deformed nucleus at the saddle-point. Good evidence of this is also given by the study of the relative fission rate with emission of long-range particles; it appears also that this ternary fission rate does not change substantially for neutron between thermal energy and 2 MeV, but that is very lower for the compound nucleus U{sup 239} than for even-even compound nuclei. At the end there are some experiments on the strong 4,5 MeV gamma-ray originated by slow neutron absorption in U{sup 235}. Time-of-flight device is used to establish that this 4,5 MeV gamma-ray seems mostly connected with radiative capture. (author) [French] Le present travail debute par un apercu de l'etat actuel de nos connaissances sur le processus de fission nucleaire, notamment sur le passage par le point-seuil. Puis sont evoques des aspects lies au niveau d'energie d'excitation auquel est porte le noyau qui subit la fission. Les mesures de sections efficaces de fission induite dans {sup 233}U, {sup 235}U, {sup 239}Pu et {sup 238}U par des neutrons rapides effectuees a Saclay sont decrites en premier lieu; elles font apparaitre pour {sup 233}U une ondulation caracteristique du role des etats collectifs d'excitation du noyau deforme au point-seuil. Des experiences sur la fission avec emission de particules de long parcours confirment cet aspect tout en demontrant que la frequence

A comparison of fusion breeder/fission client and fission breeder/fission client systems for electrical energy production

International Nuclear Information System (INIS)

Land, R.J.; Parish, T.A.

1983-01-01

A parametric study that evaluated the economic performance of breeder/client systems is described. The linkage of the breeders to the clients was modelled using the stockpile approach to determine the system doubling time. Since the actual capital costs of the breeders are uncertain, a precise prediction of the cost of a breeder was not attempted. Instead, the breakeven capital cost of a breeder relative to the capital cost of a client reactor was established by equating the cost of electricity from the breeder/client system to the cost of a system consisting of clients alone. Specific results are presented for two breeder/client systems. The first consisted of an LMFBR with LWR clients. The second consisted of a DT fusion reactor (with a 238 U fission suppressed blanket) with LWR clients. The economics of each system was studied as a function of the cost of fissile fuel from a conventional source. Generally, the LMFBR/LWR system achieved relatively small breakeven capital cost ratios; the maximum ratio computed was 2.2 (achieved at approximately triple current conventional fissile material cost). The DTFR/LWR system attained a maximum breakeven capital cost ratio of 4.5 (achieved at the highest plasma quality (ignited device) and triple conventional fissile cost)

High mass-asymmetry distributions of fissioning nuclei

International Nuclear Information System (INIS)

Sandulescu, A.; Lusting, H.J.; Hahn, J.; Greiner, W.

1978-07-01

It is shown that new mass-asymmetry valleys are appearing in the fragmentation potential V(l,eta) as function of the length l and mass-asymmetry coordinate eta = (A 1 - A 2 )to a correct treatment of the shell effects such that for separated fragments the shell effects equal the sum of the shell effects of the individual fragments and correspond to the double magic fragments 48 Ca, 78 Ni, 132 Sn and 208 Pb or may be 56 Ni. Also is shown that the fission mass-distributions have additional peaks corresponding to the bottom of these new valleys. The calculations are illustrated for 252 No and 238 U. The preliminary results show for 238 U relatively high percent yields in agreement with present available experimental data. (author)

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

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 ...

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

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

Full text: Fission induced by nucleons transfer has been investigated in the reaction 28 Si + 232 Th at 340 MeV. Looking at the projectile-like-fragments (PLF), the fission yield increases as the transfer increases, but a decreases is observed for transfers with DZ . Light charged particles in coincidence with PLF and Fission have been detected with large solid angle and show an increasing multiplicity as the Z of PLF is reduced and a constant value when fission is requested. The present results indicate inhibition of transfer induced fission reaction for higher Z transfer and increasing probability for decay through charged particle evaporation. Fission is the dominant decay process in heavy reactions involving fissile systems but the dynamical evolution of the composite system is largely governed by the formation and decay mechanisms. Important insight into the formation and the survival probability of the heavy composite nuclei formed in heavy ion collisions can be gained by simultaneously investigate the fission process and light particle emission over a continuous range of excitation energy, angular momentum and fissility. This can be achieved by studying fission induced by transfer of nucleons between the interacting projectile and the target nucleus. In the present work, we have carried out measurements on multinucleon transfer induced fission reactions in 28 Si + 232 Th system at Elab = 340 MeV. The experiment has been performed at the Laboratori Nazionale di Legnaro (LNL) using the 8pLP detector in its final configuration with 257 DE-E telescopes. The backward detectors were used to measure both light charged particles and fission fragments. The projectile-like fragments were detected using separate DE-E telescopes around the grazing angle. Two neutron detectors were placed at a distance of 115.5 cm from the target to measure neutrons emitted in coincidence with fission fragments. Here we present the results of the data analysis of transfer induced fission

Measurements of fission cross-sections. Chapter 4

International Nuclear Information System (INIS)

James, G.D.

1981-01-01

The steps involved in the measurement of fission cross sections are summarized and the range of techniques available are considered. Methods of fission detection are described with particular emphasis on the neutron energy dependent properties of the fission process and the details of fragment energy loss which can lead to energy-dependent changes in detector efficiency. Selected examples of fission cross-section measurements are presented and methods of data reduction, storage, analysis and evaluation, are examined. Finally requested accuracies for fission cross section data are compared to estimated available accuracies. (U.K.)

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

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

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

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)

A high-resolution time-of-flight spectrometer for fission fragments and ion beams

International Nuclear Information System (INIS)

Kosev, Krasimir Milchev

2007-01-01

For the purpose of fission-fragment detection a double time-of-flight (TOF) spectrometer has been developed. The key component of the TOF spectrometer is a TOF detector consisting of multichannel-plate (MCP) detectors with a position-sensitive readout, a foil for secondary electron (SE) production and an electrostatic mirror. The fission fragments are detected by measuring the SEs impinging on the position-sensitive anode after emission from the foil, acceleration and deflection by the electrostatic mirror. The functionality of the different detector components is proven in detail. Optimised schemes for the high-voltage supplies of the MCP detectors have been implemented successfully. In order to process the multichannel-plate detector signals optimally, a new state-of-the-art constant-fraction discriminator based on the amplitude and rise time compensated technique with very low threshold capabilities and optimised walk properties has been developed and incorporated into the setup. In a setup consisting of two mirror MCP detectors, we could successfully observe the TOF spectrum of a mixed ( 226 Ra, 222 Rn, 210 Po, 218 Po, 214 Po) α-source. Testing photo-fission experiments were performed at the bremsstrahlung facility at the ELBE accelerator. The setup consisted of two mirror detectors (first arm) and a 80 mm diameter MCP detector (second arm) with a 238 U target positioned in between. TOF measurements with two bremsstrahlung end-point energies of 12.9 and 16.0 MeV were carried out. A clear cut separation of the TOF peaks for the medium-mass and heavy fission fragments was observed. (orig.)

A high-resolution time-of-flight spectrometer for fission fragments and ion beams

Energy Technology Data Exchange (ETDEWEB)

Kosev, Krasimir Milchev

2007-07-01

For the purpose of fission-fragment detection a double time-of-flight (TOF) spectrometer has been developed. The key component of the TOF spectrometer is a TOF detector consisting of multichannel-plate (MCP) detectors with a position-sensitive readout, a foil for secondary electron (SE) production and an electrostatic mirror. The fission fragments are detected by measuring the SEs impinging on the position-sensitive anode after emission from the foil, acceleration and deflection by the electrostatic mirror. The functionality of the different detector components is proven in detail. Optimised schemes for the high-voltage supplies of the MCP detectors have been implemented successfully. In order to process the multichannel-plate detector signals optimally, a new state-of-the-art constant-fraction discriminator based on the amplitude and rise time compensated technique with very low threshold capabilities and optimised walk properties has been developed and incorporated into the setup. In a setup consisting of two mirror MCP detectors, we could successfully observe the TOF spectrum of a mixed ({sup 226}Ra,{sup 222}Rn,{sup 210}Po,{sup 218}Po,{sup 214}Po) {alpha}-source. Testing photo-fission experiments were performed at the bremsstrahlung facility at the ELBE accelerator. The setup consisted of two mirror detectors (first arm) and a 80 mm diameter MCP detector (second arm) with a {sup 238}U target positioned in between. TOF measurements with two bremsstrahlung end-point energies of 12.9 and 16.0 MeV were carried out. A clear cut separation of the TOF peaks for the medium-mass and heavy fission fragments was observed. (orig.)

Two-electron time-delay interference in atomic double ionization by attosecond pulses

Energy Technology Data Exchange (ETDEWEB)

Rescigno, Thomas N

2009-10-04

A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

Two-Electron Time-Delay Interference in Atomic Double Ionization by Attosecond Pulses

International Nuclear Information System (INIS)

Palacios, A.; Rescigno, T. N.; McCurdy, C. W.

2009-01-01

A two-color two-photon atomic double ionization experiment using subfemtosecond uv pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

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 energy of uranium isotopes and transuranium elements

International Nuclear Information System (INIS)

Nemirovskij, P.Eh.; Manevich, L.G.

1981-01-01

A comparison is made between the prompt fission energy, Esub(pr), calculated from the mass and binding energy spectrum and the Esub(pr) value obtained from the experimental data on the kinetic energy of fragments, the energy of prompt neutrons and prompt γ-quanta. Basing on the data on β-decay chains of fission fragments, the energies of neutrinos, γ-quanta and β-electrons are obtained, which permits to calculate the actual energy released during fission. The calculations are performed for thermal neutron-induced fission, fast-neutron induced fission and for fission after bombardment with 14 MeV neutrons. The available experimental data on the fission fragment kinetic energy, prompt γ-quanta energy and fission neutron energy are presented. The comparison of the Esub(pr) values obtained experimentally for the thermal-neutron-induced fission with the calculated Esub(pr) value shows that for 233 U, 239 Pu, 241 Pu the agreement is rather favourable. For 235 U the agreement is within the error limits. As to the Esub(pr) values for the fast-neutron-induced fission, the agreement between the calculated and experimental data for all nuclides is quite good

Fission product induced swelling of U–Mo alloy fuel

International Nuclear Information System (INIS)

Kim, Yeon Soo; Hofman, G.L.

2011-01-01

Highlights: ► We measured fuel swelling of U–Mo alloy by fission products at temperatures below 250 °C. ► We quantified the swelling portion of U–Mo by fission gas bubbles. ► We developed an empirical model as a function of fission density. - Abstract: Fuel swelling of U–Mo alloy was modeled using the measured data from samples irradiated up to a fission density of ∼7 × 10 27 fissions/m 3 at temperatures below ∼250 °C. The overall fuel swelling was measured from U–Mo foils with as-fabricated thickness of 250 μm. Volume fractions occupied by fission gas bubbles were measured and fuel swelling caused by the fission gas bubbles was quantified. The portion of fuel swelling by solid fission products including solid and liquid fission products as well as fission gas atoms not enclosed in the fission gas bubbles is estimated by subtracting the portion of fuel swelling by gas bubbles from the overall fuel swelling. Empirical correlations for overall fuel swelling, swelling by gas bubbles, and swelling by solid fission products were obtained in terms of fission density.

Fusion-fission dynamics

International Nuclear Information System (INIS)

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

1992-01-01

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

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)

Multiplicity counting from fission chamber signals in the current mode

Energy Technology Data Exchange (ETDEWEB)

Pázsit, I. [Chalmers University of Technology, Department of Physics, Division of Subatomic and Plasma Physics, SE-412 96 Göteborg (Sweden); Pál, L. [Centre for Energy Research, Hungarian Academy of Sciences, 114, POB 49, H-1525 Budapest (Hungary); Nagy, L. [Chalmers University of Technology, Department of Physics, Division of Subatomic and Plasma Physics, SE-412 96 Göteborg (Sweden); Budapest University of Technology and Economics, Institute of Nuclear Techniques, H-1111 Budapest (Hungary)

2016-12-11

In nuclear safeguards, estimation of sample parameters using neutron-based non-destructive assay methods is traditionally based on multiplicity counting with thermal neutron detectors in the pulse mode. These methods in general require multi-channel analysers and various dead time correction methods. This paper proposes and elaborates on an alternative method, which is based on fast neutron measurements with fission chambers in the current mode. A theory of “multiplicity counting” with fission chambers is developed by incorporating Böhnel's concept of superfission [1] into a master equation formalism, developed recently by the present authors for the statistical theory of fission chamber signals [2,3]. Explicit expressions are derived for the first three central auto- and cross moments (cumulants) of the signals of up to three detectors. These constitute the generalisation of the traditional Campbell relationships for the case when the incoming events represent a compound Poisson distribution. Because now the expressions contain the factorial moments of the compound source, they contain the same information as the singles, doubles and triples rates of traditional multiplicity counting. The results show that in addition to the detector efficiency, the detector pulse shape also enters the formulas; hence, the method requires a more involved calibration than the traditional method of multiplicity counting. However, the method has some advantages by not needing dead time corrections, as well as having a simpler and more efficient data processing procedure, in particular for cross-correlations between different detectors, than the traditional multiplicity counting methods.

Measurement of fission cross section with pure Am-243 sample using lead slowing-down spectrometer

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Katsuhei; Yamamoto, Shuji; Kai, T.; Fujita, Yoshiaki; Yamamoto, Hideki; Kimura, Itsuro [Kyoto Univ. (Japan); Shinohara, Nobuo

1997-03-01

By making use of back-to-back type double fission chambers and a lead slowing-down spectrometer coupled to an electron linear accelerator, the fission cross section for the {sup 243}Am(n,f) reaction has been measured relative to that for the {sup 235}U(n,f) reaction in the energy range from 0.1 eV to 10 keV. The measured result was compared with the evaluated nuclear data appeared in ENDF/B-VI and JENDL-3.2, whose evaluated data were broadened by the energy resolution function of the spectrometer. General agreement was seen between the evaluated data and the measurement except that the ENDF/B-VI data were lower in the range from 15 to 60 eV and that the JENDL-3.2 data seemed to be lower above 100 eV. (author)

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

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Measurements of actinide-fission product yields in Caliban and Prospero metallic core reactor fission neutron fields

Energy Technology Data Exchange (ETDEWEB)

Casoli, P.; Authier, N. [CEA, Centre de Valduc, 21120 Is-sur-Tille (France); Laurec, J.; Bauge, E.; Granier, T. [CEA, Centre DIF, 91297 Arpajon (France)

2011-07-01

In the 1970's and early 1980's, an experimental program was performed on the facilities of the CEA Valduc Research Center to measure several actinide-fission product yields. Experiments were, in particular, completed on the Caliban and Prospero metallic core reactors to study fission-neutron-induced reactions on {sup 233}U, {sup 235}U, and {sup 239}Pu. Thick actinide samples were irradiated and the number of nuclei of each fission product was determined by gamma spectrometry. Fission chambers were irradiated simultaneously to measure the numbers of fissions in thin deposits of the same actinides. The masses of the thick samples and the thin deposits were determined by mass spectrometry and alpha spectrometry. The results of these experiments will be fully presented in this paper for the first time. A description of the Caliban and Prospero reactors, their characteristics and performances, and explanations about the experimental approach will also be given in the article. A recent work has been completed to analyze and reinterpret these measurements and particularly to evaluate the associated uncertainties. In this context, calculations have also been carried out with the Monte Carlo transport code Tripoli-4, using the published benchmarked Caliban description and a three-dimensional model of Prospero, to determine the average neutron energy causing fission. Simulation results will be discussed in this paper. Finally, new fission yield measurements will be proposed on Caliban and Prospero reactors to strengthen the results of the first experiments. (authors)

Break-induced ATR and Ddb1-Cul4(Cdt)² ubiquitin ligase-dependent nucleotide synthesis promotes homologous recombination repair in fission yeast

DEFF Research Database (Denmark)

Moss, Jennifer; Tinline-Purvis, Helen; Walker, Carol A

2010-01-01

Nucleotide synthesis is a universal response to DNA damage, but how this response facilitates DNA repair and cell survival is unclear. Here we establish a role for DNA damage-induced nucleotide synthesis in homologous recombination (HR) repair in fission yeast. Using a genetic screen, we found...... the Ddb1-Cul4(Cdt)² ubiquitin ligase complex and ribonucleotide reductase (RNR) to be required for HR repair of a DNA double-strand break (DSB). The Ddb1-Cul4(Cdt)² ubiquitin ligase complex is required for degradation of Spd1, an inhibitor of RNR in fission yeast. Accordingly, deleting spd1(+) suppressed...

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.)

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

CERN Document Server

Veselsky, Martin

2012-01-01

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

Fusion-fission of heavy systems

International Nuclear Information System (INIS)

Rivet, M.F.; Alami, R.; Borderie, B.; Fuchs, H.; Gardes, D.; Gauvin, H.

1988-01-01

The influence of the entrance channel on fission processes was studied by forming the same composite system by two different target-projectile combinations ( 40 Ar + 209 Bi and 56 Fe + 187 Re, respectively). Compound nucleus fission and quasi fission were observed and the analysis was performed in the framework of the extra-extra-push model, which provides a qualitative interpretation of the results; limits for the extra-extra-push threshold are given, but problems with quantitative predictions for the extra-push are noted. (orig.)

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.

Progress in fission product nuclear data. No. 14

International Nuclear Information System (INIS)

Lammer, M.

1994-06-01

This is the 14th issue of a report series on Fission Product Nuclear Data published by the Nuclear Data Section of the IAEA. The types of activities included are measurements, compilations and evaluations of fission product yields, neutron reaction cross sections of fission products, data related to the radioactive decay of fission products, delayed neutron data from neutron induced and spontaneous fission, lumped fission product data. The first part of the report consists of unaltered original contributions which the authors have sent to IAEA/NDS. The second part contains some recent references relative to fission product nuclear data, which were not covered by the contributions submitted, and selected papers from conferences. The third part contains requirements for further measurements

Progress in fission product nuclear data. No. 13

International Nuclear Information System (INIS)

Lammer, M.

1990-11-01

This is the 13th issue of a report series published by the Nuclear Data Section of the IAEA. The types of activities included are measurements, compilations and evaluations of: Fission product yields (neutron induced and spontaneous fission), neutron reaction cross-sections of fission products, data related to the radioactive decay of fission products, delayed neutron data of fission products and bumped fission product data (decay heat, absorption, etc.). The first part of the report consists of unaltered original data which the authors have sent to IAEA/NDS. The second part contains some recent references relative to fission product nuclear data, which were not covered by the contributions submitted, and selected papers from conferences. Part 3 contains requirements for further measurements

The role of the dinuclear system in the processes of nuclear fusion, quasi-fission, fission and cluster formation

International Nuclear Information System (INIS)

Volkov, V.V.

1999-01-01

The nuclear fusion, quasi-fission, fission and cluster formation in an excited nucleus are considered as the processes of the formation and evolution of the dinuclear system. This approach allows one to reveal new aspects of nuclear fusion, to show that quasi-fission plays an important role in nuclear reactions used to synthesise superheavy elements. A qualitative picture is given of the fission process of an excited nucleus and an important role of cluster formation in this process is shown

Fission product detection

International Nuclear Information System (INIS)

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

1987-01-01

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

Utilization of fission reactors for fusion engineering testing

International Nuclear Information System (INIS)

Deis, G.A.; Miller, L.G.

1985-01-01

Fission reactors can be used to conduct some of the fusion nuclear engineering tests identified in the FINESSE study. To further define the advantages and disadvantages of fission testing, the technical and programmatic constraints on this type of testing are discussed here. This paper presents and discusses eight key issues affecting fission utilization. Quantitative comparisons with projected fusion operation are made to determine the technical assets and limitations of fission testing. Capabilities of existing fission reactors are summarized and compared with technical needs. Conclusions are then presented on the areas where fission testing can be most useful

Options for development of space fission propulsion systems

International Nuclear Information System (INIS)

Houts, Mike; Van Dyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbud, Ivana

2001-01-01

Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission systems have only been used in Earth orbit. The first step towards utilizing advanced fission propulsion systems is development of a safe, near-term, affordable fission system that can enhance or enable near-term missions of interest. An evolutionary approach for developing space fission propulsion systems is proposed

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)

Spontaneous fission of 259Md

International Nuclear Information System (INIS)

Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Landrum, J.H.; Dougan, R.J.; Mustafa, M.; Ghiorso, A.; Nitschke, J.M.

1979-01-01

The mass and kinetic energy distributions of fission fragments from the spontaneous fission of th newly discovered nuclide 259 Md were obtained. 259 Md was identified as the E. C. daughter of 259 No, and was found to decay entirely (> 95%) by spontaneous fission with a 95-min half-life. From the kinetic energies measured for 397 pairs of coincident fragments, a mass distribution was derived that is symmetric with sigma = 13 amu. 259 Md, together with 258 Fm and 259 Fm, form a select group of three nuclides whose mass division in spontaneous fission is highly symmetric. Unlike the total-kinetic-energy (TKE) distributions of 258 Fm and 259 Fm, which peak at approx. = to 240 MeV, this distribution for 259 Md is broad and is 50 MeV lower in energy. Analysis of the mass and energy distributions shows that events near mass symmetry also exhibit a broad TKE distribution, with one-third of the symmetric events having TKEs less than 200 MeV. The associated of low TKEs with symmetric mass division in the fission of very heavy actinides is anomalous and inconsistent with theories based upon the emergence of fragment shells near the scission point. Either three-body fragmentation or peculiar fragment shapes are assumed as the cause for the large consumption of Coulomb energy observed for a significant fraction of symmetric fissions in 259 Md. 6 figures

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)

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 ...

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 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)

Nuclear fission: a review of experimental advances and phenomenology

Science.gov (United States)

Andreyev, A. N.; Nishio, K.; Schmidt, K.-H.

2018-01-01

In the last two decades, through technological, experimental and theoretical advances, the situation in experimental fission studies has changed dramatically. With the use of advanced production and detection techniques both much more detailed and precise information can now be obtained for the traditional regions of fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies. This work first of all reviews the recent developments in experimental fission techniques, in particular the resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams. The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of the other fission observables, such as prompt neutron and γ-ray emission will also be reviewed. A particular attention will be given to the low-energy fission in the so far scarcely explored nuclei in the very neutron-deficient lead region. They recently became the focus for several complementary experimental studies, such as β-delayed fission with radioactive beams at ISOLDE(CERN), Coulex-induced fission of relativistic secondary beams at FRS(GSI), and several prompt fusion–fission studies. The synergy of these approaches allows a unique insight in the new region of asymmetric fission around {\\hspace{0pt}}180 Hg, recently discovered at ISOLDE. Recent extensive theoretical efforts in this region will also be outlined. The unprecedented high-quality data for fission fragments, completely identified in Z and A, by means of reactions in inverse kinematics at FRS(GSI) and VAMOS(GANIL) will be also reviewed. These experiments explored an extended range of mercury-to-californium elements, spanning from the neutron-deficient to neutron-rich nuclides, and covering both asymmetric, symmetric and transitional fission regions

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.

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1989-01-01

Following a summary of the observables in neutron emission in fission, a brief history is given of theoretical representations of the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity /bar /nu///sub p/. This is followed by descriptions, together with examples, of modern approaches to the calculation of these quantities including recent advancements. Emphasis will be placed upon the predictability and accuracy of the modern approaches. In particular, the dependence of N(E) and /bar /nu///sub p/ on the fissioning nucleus and its excitation energy will be discussed, as will the effects of and competition between first-, second- and third-chance fission in circumstances of high excitation energy. Finally, properties of neutron-rich (fission-fragment) nuclei are discussed that must be better known to calculate N(E) and /bar /nu///sub p/ with higher accuracy than is currently possible. 17 refs., 11 figs

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.)

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)

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

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.

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.)

Sequential Power-Dependence Theory

NARCIS (Netherlands)

Buskens, Vincent; Rijt, Arnout van de

2008-01-01

Existing methods for predicting resource divisions in laboratory exchange networks do not take into account the sequential nature of the experimental setting. We extend network exchange theory by considering sequential exchange. We prove that Sequential Power-Dependence Theory—unlike

Mass dependence of positive pion-induced fission

International Nuclear Information System (INIS)

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

1991-01-01

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

Towards a microscopic description of the fission process

CERN Document Server

Goutte, H; Berger, J F

2010-01-01

One major issue in nuclear physics is to develop a consistent model able to describe on the same footing the different aspects of the fission process, i.e. properties of the fissioning system, fission dynamics and fragment distributions. Microscopic fission studies based on the mean-field approximation are here presented.

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

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

The study of prompt and delayed muon induced fission III. The ratios of prompt to delayed fission yields

NARCIS (Netherlands)

Rösel, Ch.; Hänscheid, H.; Hartfiel, J.; Mutius, von R.; Achard van Enschut, d' J.F.M.; David, P; Janszen, H.; Johansson, T.; Konijn, J.; Krogulski, T.; Laat, de C.T.A.M.; Paganetti, H.; Petitjean, C.; Polikanov, S.M.; Reist, H.W.; Risse, F.; Schaller, L.A.; Schrieder, W.; Sinha, A.K.; Taal, A.; Theobald, J.P.; Tibell, G.; Trautmann, N.

1993-01-01

The ratios of prompt to delayed fission yields for the isotopes U-233, U-234, U-235, U-236, U-238, Np-237, Pu-242, and Pu-244 and the fission probabilities relative to each other have been investigated experimentally. Using the value of the total fission probability for Np-237 the absolute

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

What happens to the fission process above the 2nd- and 3rd-chance fission thresholds

International Nuclear Information System (INIS)

Stewart, L.; Howerton, R.J.

1976-01-01

Although the multiple fission process is important at high neutron energies, most of the evaluations available today do not include these individual fission cross sections or their associated fission spectra. The representations used in the Los Alamos and Livermore libraries are described and calculations compared with 14-MeV integral experiments available on 235 U, 238 U, and 239 Pu. Further work is needed to clearly delineate the specific problems in order to propose unique solutions

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

50 years with nuclear fission, April 25-28, 1989. A prelude to fission: France

International Nuclear Information System (INIS)

Savic, P.

1989-01-01

A personal account of the events leading to the 1938 discovery, by Irene Joliot-Curie and the author, of the unidentified element R 3.5h will be presented, as well as the experimental methods proving the R 3.5h had chemical properties similar to lanthanum which in turn led Hahn and Strassmann to the discovery of fission in 1939. The author points out that Irene Curie's intuition indicated the path towards the solution of the problem of uranium irradiated by neutrons, which made possible the discovery of fission by Hahn and Strassmann. Further applications of fission became possible by tremendous efforts and excellent contributions of scientists in the USA

Apparatus for measuring the release of fission gases and other fission products by degassing

Energy Technology Data Exchange (ETDEWEB)

Stradal, Karl Alfred

1970-10-15

In gas-cooled high-temperature reactors, the fuel is, in general, inserted in the fuel elements in the form of small particles, which are, for example, coated with pyrolytic carbon. The purpose of this coating is to keep the fission products separate from the coolant gas. The further development of these coated particles makes it necessary to check the retention capacity. One possible method of doing this is the degassing test after irradiation in the reactor. An apparatus is described below, which was developed and installed in order to measure to a higher degree of sensitivity and in serial measurements the release of fission gases and sparingly volatile fission products.

Sequential boundaries approach in clinical trials with unequal allocation ratios

Directory of Open Access Journals (Sweden)

Ayatollahi Seyyed

2006-01-01

Full Text Available Abstract Background In clinical trials, both unequal randomization design and sequential analyses have ethical and economic advantages. In the single-stage-design (SSD, however, if the sample size is not adjusted based on unequal randomization, the power of the trial will decrease, whereas with sequential analysis the power will always remain constant. Our aim was to compare sequential boundaries approach with the SSD when the allocation ratio (R was not equal. Methods We evaluated the influence of R, the ratio of the patients in experimental group to the standard group, on the statistical properties of two-sided tests, including the two-sided single triangular test (TT, double triangular test (DTT and SSD by multiple simulations. The average sample size numbers (ASNs and power (1-β were evaluated for all tests. Results Our simulation study showed that choosing R = 2 instead of R = 1 increases the sample size of SSD by 12% and the ASN of the TT and DTT by the same proportion. Moreover, when R = 2, compared to the adjusted SSD, using the TT or DTT allows to retrieve the well known reductions of ASN observed when R = 1, compared to SSD. In addition, when R = 2, compared to SSD, using the TT and DTT allows to obtain smaller reductions of ASN than when R = 1, but maintains the power of the test to its planned value. Conclusion This study indicates that when the allocation ratio is not equal among the treatment groups, sequential analysis could indeed serve as a compromise between ethicists, economists and statisticians.

The fast fission effect in a cylindrical fuel element

Energy Technology Data Exchange (ETDEWEB)

Carlvik, I; Pershagen, B

1959-06-15

A new formula for the fast fission factor is derived, which takes proper account to fast capture. The fission neutron spectrum is divided into two groups with constant fission cross section in one group and zero fission cross section in the other. The average total, elastic, inelastic and capture cross sections in the two groups are calculated. Different assumptions regarding anisotropic and inelastic scattering are investigated. The effects of backscattering from the moderator and fast fission in neighbouring fuel elements are pointed out. Formulas for the fast fission ratio and for the fast conversion ratio are derived. The calculated fast fission ratios are compared with experimental values. Curves are given for the fast fission factor in uranium metal and uranium oxide.

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)

Behavior of solid fission products in irradiated fuel

International Nuclear Information System (INIS)

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

2004-01-01

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

Fission and r-process nucleosynthesis in neutron star mergers

International Nuclear Information System (INIS)

Giuliani, Samuel Andrea

2018-01-01

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

New experimental approaches to investigate the fission dynamics

Energy Technology Data Exchange (ETDEWEB)

Benlliure, J., E-mail: j.benlliure@usc.es; Rodríguez-Sánchez, J. L.; Alvarez-Pol, H.; Ayyad, Y.; Cortina-Gil, D.; Paradela, C.; Pietras, B.; Ramos, D.; Vargas, J. [Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain); Audouin, L.; Boutoux, G. [Institut de Physique Nucléaire d’Orsay, F-91406 Orsay (France); Bélier, G.; Chatillon, A.; Gorbinet, T.; Laurent, B.; Martin, J.-F.; Pellereau, E.; Taïeb, J. [CEA, DAM, DIF, F-91297 Arpajon (France); Casarejos, E. [Universidad de Vigo, E-36200 Vigo (Spain); Heinz, A. [Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); and others

2016-07-07

The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of {sup 208}Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point.

Fission gas release of MOX with heterogeneous structure

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

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

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

Fission gas behaviour in water reactor fuels

International Nuclear Information System (INIS)

2002-01-01

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

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

Science.gov (United States)

Clement, J. D.

1973-01-01

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

Measurement of the fission yields of selected prompt and decay fission product gamma-rays of spontaneously fissioning 252Cf and 244Cm

International Nuclear Information System (INIS)

Reber, E.L.; Gehrke, R.J.; Aryaeinejad, R.; Hartwell, J.K.

2005-01-01

Gamma-ray spectrometry measurements have been made of the fission yields of selected γ -rays emitted by the spontaneously fissioning isotopes 252 Cf and 244 Cm. The measured γ-rays were selected based on their relative abundance in the spectrum and their freedom from interference or, in a few instances, ease of interference correction. From these data and the cumulative and independent yield data of England and Rider, those γ-rays that are primarily produced by radioactive decay, as opposed to direct yield, were converted into the decays per spontaneous fission expressed in percent and compared to cumulative yield values of England and Rider. For those γ-rays whose production is dominated by direct (independent) yield, the ratio of γ-rays per spontaneous fission is reported. The γ-ray yield can be compared to the independent yield values of England and Rider when 100% of the direct feeding passes through the γ-ray. In those cases where both cumulative and independent yields contribute to the observed γ-ray emission rate, a direct comparison is not possible but a method to quantify the contribution from each is proposed. (author)

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

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)

Angular momentum distribution of primary fission fragments by measurement of the relative yield of isomeric fission products

International Nuclear Information System (INIS)

Dornhoefer, H.

1980-01-01

The fission products 132 I and 136 I produced in the fission reactions 238 U(α,f) and 238 U(d,f) were spectroscoped using a gas transport system. Thereby was taken advantage of the fact that at the transport with pure helium without aerosols only iodine activities were collected in a membrane filter. The relative independent yields of the isomeric fission products of 132 I and 136 I were determined for different excitation energies. Thereby was taken advantage of the fact that the transport yield of the gas transport system for 136 I directly produced from the fission was greater than for iodine indirectly produced by β-decay. (orig./HSI) [de

Fission-product release during accidents

International Nuclear Information System (INIS)

Hunt, C.E.L.; Cox, D.S.

1991-09-01

One of the aims when managing a reactor accident is to minimize the release of radioactive fission products. Release is dependent not only on the temperature, but also on the partial pressure of oxygen. Strongly oxidizing atmospheres, such as those that occurred during the Chernobyl accident, released semi-volatile elements like ruthenium, which has volatile oxides. At low temperatures, UO 2 oxidization to U 3 O 8 can result in extensive breakup of the fuel, resulting in the release of non-volatile fission products as aerosols. Under less oxidizing conditions, when hydrogen accumulates from the zirconium-water reaction, the resulting low oxygen partial pressure can significantly reduce these reactions. At TMI-2, only the noble gases and volatile fission products were released in significant quantities. A knowledge of the effect of atmosphere as well as temperature on the release of fission products from damaged reactor cores is therefore a useful, if not necessary, component of information required for accident management

Recovery and use of fission product noble metals

International Nuclear Information System (INIS)

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

1980-06-01

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

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

Ternary fission induced by polarized neutrons

Directory of Open Access Journals (Sweden)

Gönnenwein Friedrich

2013-12-01

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

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

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

Basic physics of the fission process. Chapter 2

International Nuclear Information System (INIS)

Michaudon, A.

1981-01-01

A general description of the fission process is given with special emphasis on those aspects which are necessary for the understanding of the measurements and calculations of neutron-induced fission cross-sections. Having considered the various phases of the process, some typical properties of the low-energy fission of actinide nuclei are presented and the more specific features of neutron induced fission are examined. (U.K.)

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1998-01-01

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 some examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N(E) and bar ν p upon the fissioning nucleus and its excitation energy are treated in detail for the Los Alamos model. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of the ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches. This paper is an extension of a similar paper presented at the International Centre for Theoretical Physics in 1996

Fission fragment yields and total kinetic energy release in neutron-induced fission of235,238U,and239Pu

Science.gov (United States)

Tovesson, F.; Duke, D.; Geppert-Kleinrath, V.; Manning, B.; Mayorov, D.; Mosby, S.; Schmitt, K.

2018-03-01

Different aspects of the nuclear fission process have been studied at Los Alamos Neutron Science Center (LANSCE) using various instruments and experimental techniques. Properties of the fragments emitted in fission have been investigated using Frisch-grid ionization chambers, a Time Projection Chamber (TPC), and the SPIDER instrument which employs the 2v-2E method. These instruments and experimental techniques have been used to determine fission product mass yields, the energy dependent total kinetic energy (TKE) release, and anisotropy in neutron-induced fission of U-235, U-238 and Pu-239.

Fission mass yields of excited medium heavy nuclei

International Nuclear Information System (INIS)

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

1985-01-01

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

Theoretical descriptions of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1991-01-01

Brief descriptions are given of the observables in neutron emission in fission together with early theoretical representations of two of these observables, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity ν-bar p . This is followed by summaries, together with examples, of modern approaches to the calculation of these two quantities. Here, emphasis is placed upon the predictability and accuracy of the new approaches. In particular, the dependencies of N(E) and ν-bar p upon the fissioning nucleus and its excitation energy are discussed. Then, recent work in multiple-chance fission and other recent work involving new measurements are presented and discussed. Following this, some properties of fission fragments are mentioned that must be better known and better understood in order to calculate N(E) and ν-bar p with higher accuracy than is currently possible. In conclusion, some measurements are recommended for the purpose of benchmarking simultaneous calculations of neutron emission and gamma emission in fission. (author). 32 refs, 26 figs

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

International Nuclear Information System (INIS)

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

2002-01-01

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

Fission of heavy nuclei: microscopic study of fission barriers and fragments angular momentum; Fission des noyaux lourds: etude microscopique des barrieres de fission et du moment angulaire des fragments

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.)

Correlated Production and Analog Transport of Fission Neutrons and Photons using Fission Models FREYA, FIFRELIN and the Monte Carlo Code TRIPOLI-4® .

Science.gov (United States)

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

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 ...

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

A spin exchange model for singlet fission

Science.gov (United States)

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.

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.

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

Post-irradiation studies on knock-out and pseudo-recoil releases of fission products from fissioning UO2

International Nuclear Information System (INIS)

Yamagishi, S.; Tanifuji, T.

1976-01-01

By using post-irradiation techniques, in-pile releases of 133 Xe, sup(85m)Kr, 88 Kr, 87 Kr and 138 Xe from UO 2 fissioning at low temperatures below about 200 0 C are studied: these are analyzed into a time-dependent knock-out and time-independent pseudo-recoil releases. For the latter, a 'self knock-out' mechanism is proposed: when a fission fragment loses thoroughly its energy near the UO 2 surface and stops there, it will knock out the surface substances and accordingly the fragment (i.e. the fission product) will be released. The effective thickness of the layer where the self knock-out occurs is found to be approximately 7A. As for the knock-out release, the following is estimated from its dependence on various factors: the knock-out release of fission products occurs from the surface layer with the effective thickness of approximately 20A: the shape of UO 2 matrix knocked out by one fission fragment passing through the surface is equivalent to a cylinder approximately 32A diameter by approximately 27A thick, (i.e. the knock-out coefficient for UO 2 is approximately 660 uranium atoms per knock-out event). On the basis of the above estimations, the conclusions derived from the past in-pile studies of fission gas releases are evaluated. (Auth.)

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

Science.gov (United States)

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

2018-03-01

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

Fission product yield measurements using monoenergetic photon beams

Science.gov (United States)

Krishichayan; Bhike, M.; Tonchev, A. P.; Tornow, W.

2017-09-01

Measurements of fission products yields (FPYs) are an important source of information on the fission process. During the past couple of years, a TUNL-LANL-LLNL collaboration has provided data on the FPYs from quasi monoenergetic neutron-induced fission on 235U, 238U, and 239Pu and has revealed an unexpected energy dependence of both asymmetric fission fragments at energies below 4 MeV. This peculiar FPY energy dependence was more pronounced in neutron-induced fission of 239Pu. In an effort to understand and compare the effect of the incoming probe on the FPY distribution, we have carried out monoenergetic photon-induced fission experiments on the same 235U, 238U, and 239Pu targets. Monoenergetic photon beams of Eγ = 13.0 MeV were provided by the HIγS facility, the world's most intense γ-ray source. In order to determine the total number of fission events, a dual-fission chamber was used during the irradiation. These irradiated samples were counted at the TUNL's low-background γ-ray counting facility using high efficient HPGe detectors over a period of 10 weeks. Here we report on our first ever photofission product yield measurements obtained with monoenegetic photon beams. These results are compared with neutron-induced FPY data.

Fission product yield measurements using monoenergetic photon beams

Directory of Open Access Journals (Sweden)

Krishichayan

2017-01-01

Full Text Available Measurements of fission products yields (FPYs are an important source of information on the fission process. During the past couple of years, a TUNL-LANL-LLNL collaboration has provided data on the FPYs from quasi monoenergetic neutron-induced fission on 235U, 238U, and 239Pu and has revealed an unexpected energy dependence of both asymmetric fission fragments at energies below 4 MeV. This peculiar FPY energy dependence was more pronounced in neutron-induced fission of 239Pu. In an effort to understand and compare the effect of the incoming probe on the FPY distribution, we have carried out monoenergetic photon-induced fission experiments on the same 235U, 238U, and 239Pu targets. Monoenergetic photon beams of Eγ = 13.0 MeV were provided by the HIγS facility, the world's most intense γ-ray source. In order to determine the total number of fission events, a dual-fission chamber was used during the irradiation. These irradiated samples were counted at the TUNL's low-background γ-ray counting facility using high efficient HPGe detectors over a period of 10 weeks. Here we report on our first ever photofission product yield measurements obtained with monoenegetic photon beams. These results are compared with neutron-induced FPY data.

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)

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)

Fission neutron spectra measurements at LANSCE - Status and plans

International Nuclear Information System (INIS)

Haight, R. C.; Noda, S.; Nelson, R. O.; O'Donnell, J. M.; Devlin, M.; Chatillon, A.; Granier, T.; Taiebb, J.; Laurent, B.; Belier, G.; Becker, J. A.; Wu, C. Y.

2010-01-01

A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of 235 U, 238 U, 237 Np and 239 Pu. The range of outgoing energies measured so far is from 0.7 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date are summarized in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including measurements of fission neutrons below 0.7 MeV and improvements in the data above 8 MeV. (authors)

The wastes of nuclear fission; Les dechets de la fission nucleaire

Energy Technology Data Exchange (ETDEWEB)

Doubre, H. [Paris-11 Univ., Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, IN2P3/CNRS, 91 - Orsay (France)

2005-07-01

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

Fission cross section calculations for 209Bi target nucleus based on fission reaction models in high energy regions

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.

14. International workshop on nuclear fission physics. Proceedings

International Nuclear Information System (INIS)

2000-01-01

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

Double beta decay of Uranium-238: Proton reactions of 238U in 5--12 MeV range. Final report, April 15, 1987--March 31, 1992

International Nuclear Information System (INIS)

Turkevich, A.; Economou, T.E.

1993-01-01

This report is in two parts. The first part reports on the experimental work determining the half-life for double beta decay of 238 U to 238 PU to be (2.0 ± 0.6) x 10 21 years. This is the first evidence for a third mode of decay of this heaviest naturally occurring nucleus. This rate is about 10 6 times slower than spontaneous fission, which itself is about 10 6 times slower than alpha decay. The implication of this double beta decay to neutrino masses depends on uncertain theoretical calculations of the rate for such a heavy nucleus. The second part reports on yields of principal fission products from 5.6, 7.3, 9.4, and 11.5 MeV proton interactions with 238 U. The yields at 11.5 MeV are similar to those from 14 MeV neutron fission of 238 U. At the same time, the production cross sections of 238 Np at the same energies are determined. This nuclide is produced as often as fission at the lowest energy but only 3.8% as often at the highest energy

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

Fission fragment driven neutron source

Science.gov (United States)

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

1976-01-01

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

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

Search for spontaneous fission of 226Ra and systematics of the spontaneous fission, α-decay and cluster decay probabilities

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

p- and n-induced U-fission tracks as possible error sources in the fission track dating of extraterrestric samples

International Nuclear Information System (INIS)

Thiel, K.

1975-01-01

Using the fission track dating method by means of uranium fission tracks in meteorites and moon samples (according to the successful Apollo and Luna missions), special problems arise, as the samples frequently have a very great age and were subjected to the inmediate effect of primary cosmic radiation. To determine the share of induced fission tracks, an extended 'cosmic ray' simulation experiment was carried out on the p-synchrocyclotron in CERN, Geneva; the performance and results of the test with the proton flux and U fission track measurements are dealt with in detail. (HK/LH) [de

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

Microscopic Theory of Fission

International Nuclear Information System (INIS)

Younes, W; Gogny, D

2008-01-01

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

Fission track analysis of Pu in small specimens of biological material: Technical progress report, August 1, 1987--July 31, 1988

International Nuclear Information System (INIS)

Wrenn, M.E.

1988-01-01

The objective of this research is to develop a highly specific and ultrasensitive method capable of detecting 100 aCi/liter of 239 Pu in human urine. The method using neutron induced fission track analysis is to be made free of interference from uranium, the only naturally occurring element with an isotope which fissions with thermal neutrons. A simplified flow diagram for the method is shown in Figure 1. Briefly 239 Pu is coprecipitated quantitatively from urine with rhodozonic acid. The precipitate containing the 239 Pu is dissolved in HCl and is sequentially passed through two ion exchange columns and reduced in volume. The element is then deposited in a circular area on a thick polycarbonate detector and a thinner detector is placed over the circular deposit. The plastic detectors are then irradiated to a high thermal neutron fluence in a research reactor. The detectors are etched in a caustic solution for controlled times and temperatures in order to develop the fission tracks. Images of tracks are formed both on the thin and thick plastic detectors. Total tracks in the thinner detector are measured with a locally developed spark counter and in the thick plastic are measured by counting with a microscope. The results will be made quantitative by constructing a calibration curve for 239 Pu. 3 refs., 9 figs., 3 tabs

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

International Nuclear Information System (INIS)

Richardson, L.C.

1967-01-01

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

Mass distributions in nucleon-induced fission at intermediate energies

CERN Document Server

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).

Dosimetric measurement of the disintegration rate of fission products

International Nuclear Information System (INIS)

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

1992-01-01

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

Development of an experimental device based on the digitalization of the signal and dedicated to the characterization of fission fragments and prompt neutrons; Developpement d'un dispositif experimental base sur la digitalisation des signaux et dedie a la caracterisation des fragments de fission et des neutrons prompts emis

Energy Technology Data Exchange (ETDEWEB)

Varapai, N

2006-12-15

The present work demonstrates the application of the digital technique for nuclear measurements. This new technique is based on the digitalization of the signals from the detectors and has several advantages. This technique allows us to extract the maximum amount of information contained in the signal shape. In the case of an ionization chamber this signal contains the necessary information on the particle kinetic energy, emission angle and mass. This method has been implemented for measurements of promptly emitted fission neutrons in coincidence with fission fragments from {sup 252}Cf(sf). A double Frisch-grid ionization chamber is used as fission fragment detector. The promptly emitted neutrons are detected by a NE213 liquid scintillation detector. This work displays how delicate analysis of the digitalized signals permitted us to infer the mass and kinetic energy distributions of the fission fragments as well as the neutron energy spectrum and multiplicity. The outline of this thesis is as follows: Chapter 2 gives an overview of the experimental tools used in this work. Chapter 3 explains the analysis procedure of the digitalized anode signal from an ionization chamber. Chapter 4 gives a detailed explanation of the analysis procedure of the digitalized signal from a neutron detector. In Chapter 5 the analysis procedure of the fission fragment events in coincidence with neutrons is given.

Progress in fission product nuclear data. Information about activities in the field of measurements and compilations/evaluations of fission product nuclear data (FPND)

International Nuclear Information System (INIS)

Lammer, G.

1978-07-01

This is the fourth 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 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.)

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.)

Charge and angular distributions as well as sequential decay and γ-ray emission in heavy ion collisions viewed in the light of the diffusion model

International Nuclear Information System (INIS)

Moretto, L.G.

1977-08-01

The hierarchy of the collective relaxation times in heavy ion reactions is briefly reviewed. An improved diffusion model is introduced and applied to interpret the fragment Z and angular distributions for some typical reactions. The equilibrium in the neutron-to-proton ratio as well as the sharing of the excitation energy between fragments is studied by a coincidence method which leads to the measurement of the charge, mass and mean number of nucleons emitted by each fragment. The final destiny of the dissipative energy is determined by measuring the atomic number of two coincident fragments, thus obtaining the missing charge as a function of bombarding energy and the Q of the reaction. The sequential fission probability of the heavy recoil is established as a function of the Z and kinetic energy of the light partner. The out-of-plane angular distribution of the fission fragments is correlated with the fissionability and interpreted in terms of various sources of angular momentum misalignment. The γ-ray multiplicities and the γ-ray angular distributions associated with deep inelastic event are discussed in terms of the angular momentum transfer and in terms of the diffusion model

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

Separation of fission products by the use of recoil; Separation des produits de fission par utilisation du recul

Energy Technology Data Exchange (ETDEWEB)

Henry, R; Beydon, J; Bardy, A [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

We have studied fission recoil in U{sub 3}O{sub 8} organic solvent mixtures. The organic phase chosen was first naphtalene then terphenyl. Graphite and activated carbon were also tried out as recoil media. We first verified that the fission fragments are ejected from the uranium oxide particles under our experimental conditions. The retention phenomenon observed is due to an adsorption occurring either during irradiation or during the chemical treatment. Using naphthalene or terphenyl, the individual separation of the fission products has made it possible to show the influence of the chemical nature of the recoil medium on the retention of each fission product. We put forward a hypothesis concerning this phenomenon: experiments carried out using 'scavengers', together with kinetic studies make it possible to explain the retention phenomenon and to choose the most favorable conditions for reducing this retention to a low value. The thermal recombination kinetics demonstrate the influence of the fission ion charge on the final value of the retention for a given temperature. The origins of this thermal recombination are discussed. (author) [French] On a etudie le recul de fission dans les melanges U{sub 3}0{sub 8}, phase organique. La phase organique choisie a ete le naphtalene puis le terphenyle. Le graphite et le charbon actif ont egalement ete essayes comme milieux de recul. On a d'abord determine que les fragments de fission sortent des particules d'oxyde d'uranium avec un rendement de 100 pour cent dans nos conditions experimentales. Le phenomene de retention observe est du a une adsorption ayant lieu pendant l'irradiation ou pendant le traitement chimique. Dans le naphtalene et le terphenyle, la separation individuelle des produits de fission a permis de mettre en evidence l'influence de la nature chimique du milieu de recul sur la retention de chaque produit de fission. On avance une hypothese sur ce phenomene: des experiences effectuees avec des 'scavengers

Determination of 233U, 235U, 238U and 239Pu fission yields induced by fission and 14.7 MeV neutrons

International Nuclear Information System (INIS)

Laurec, Jean; Adam, Albert; Bruyne, Thierry de.

1981-12-01

The 233 U, 235 U, 238 U, 239 Pu fission yields have been determined by a radiochemical method. A target and a fission chamber made of same fissible material are irradied together. The total fission number is measured from the fission chamber. The fission product activities are directly measured on the target using calibrated Ge-Li detectors. The fissible material masses are determined by alpha and mass spectrometries. The irradiations were made on the critical assemblies PROSPERO and CALIBAN and on the 14 MeV neutron generator of C.E. VALDUC. 3 to 5% fission yield errors are got for the most measured nuclides: 95 Zr, 97 Zr, 99 Mo, 103 Ru, 131 I, 132 Te, 140 Ba, 141 Ce, 143 Ce, 144 Ce, 147 Nd [fr

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

Separation of short-lived fission products

International Nuclear Information System (INIS)

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

1976-01-01

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

Correlation of Meiotic DSB Formation and Transcription Initiation Around Fission Yeast Recombination Hotspots.

Science.gov (United States)

Yamada, Shintaro; Okamura, Mika; Oda, Arisa; Murakami, Hiroshi; Ohta, Kunihiro; Yamada, Takatomi

2017-06-01

Meiotic homologous recombination, a critical event for ensuring faithful chromosome segregation and creating genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) formed at recombination hotspots. Meiotic DSB formation is likely to be influenced by other DNA-templated processes including transcription, but how DSB formation and transcription interact with each other has not been understood well. In this study, we used fission yeast to investigate a possible interplay of these two events. A group of hotspots in fission yeast are associated with sequences similar to the cyclic AMP response element and activated by the ATF/CREB family transcription factor dimer Atf1-Pcr1. We first focused on one of those hotspots, ade6-3049 , and Atf1. Our results showed that multiple transcripts, shorter than the ade6 full-length messenger RNA, emanate from a region surrounding the ade6-3049 hotspot. Interestingly, we found that the previously known recombination-activation region of Atf1 is also a transactivation domain, whose deletion affected DSB formation and short transcript production at ade6-3049 These results point to a possibility that the two events may be related to each other at ade6-3049 In fact, comparison of published maps of meiotic transcripts and hotspots suggested that hotspots are very often located close to meiotically transcribed regions. These observations therefore propose that meiotic DSB formation in fission yeast may be connected to transcription of surrounding regions. Copyright © 2017 by the Genetics Society of America.

Fission neutron spectra measurements at LANSCE - status and plans

International Nuclear Information System (INIS)

Haight, Robert C.; Noda, Shusaku; Nelson, Ronald O.; O' Donnell, John M.; Devlin, Matt; Chatillon, Audrey; Granier, Thierry; Taieb, Julien; Laurent, Benoit; Belier, Gilbert; Becker, John A.; Wu, Ching-Yen

2009-01-01

A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of 235 U, 238 U, 237 Np and 239 Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.

Measurements of Fission Cross Sections of Actinides

CERN Multimedia

Wiescher, M; Cox, J; Dahlfors, M

2002-01-01

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

Fission track geochronology of Eastern Ghats

Energy Technology Data Exchange (ETDEWEB)

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

1978-12-01

Fission track geochronology of Eastern Ghats has been established by using fission track technique in dating micaceous and accessory minerals occurring in the region. Annealing studies confirm that radiation damage fossil tracks can be erased in minerals under intense metamorphic episodes thus resetting the geological clock. The fission track ages of the minerals range between 450 +- 5 m.y. to 622 +- 148 m.y. It is concluded that f.t. ages of the minerals date the last metamorphic event of the Eastern Ghats, known as the Indian Ocean Cycle.

Preliminary results utilizing high-energy fission product γ-rays to detect fissionable material in cargo

Science.gov (United States)

Slaughter, D. R.; Accatino, M. R.; Bernstein, A.; Church, J. A.; Descalle, M. A.; Gosnell, T. B.; Hall, J. M.; Loshak, A.; Manatt, D. R.; Mauger, G. J.; Moore, T. L.; Norman, E. B.; Pohl, B. A.; Pruet, J. A.; Petersen, D. C.; Walling, R. S.; Weirup, D. L.; Prussin, S. G.; McDowell, M.

2005-12-01

A concept for detecting the presence of special nuclear material (235U or 239Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their β-delayed neutron emission or β-delayed high-energy γ radiation between beam pulses provide the detection signature. Fission product β-delayed γ-rays above 3 MeV are nearly 10 times more abundant than β-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified.

Probing nuclear correlations with pion-nucleus double charge exchange

International Nuclear Information System (INIS)

Ginocchio, J.N.

1988-01-01

In this paper we have calculated the lowest order pion double charge reaction mechanism using shell model wavefunctions of medium weight nuclei. We have the sequential reaction mechanism in which the pion undergoes two single-charge exchange scatterings on the valence neutrons. The distortion of the incoming, intermediate, and outgoing pion are included. The closure approximation is made for the intermediate states with an average excitation energy used in the pion propagator. The double-charge exchange is assumed to take place on the valence nucleons which are assumed to be in one spherical shell model orbital. 34 refs., 5 figs., 3 tabs

Fission of heavy nuclei: microscopic study of fission barriers and fragments angular momentum; Fission des noyaux lourds: etude microscopique des barrieres de fission et du moment angulaire des fragments

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.)

Thermochromatographic investigations of fission product transport and chemistry

International Nuclear Information System (INIS)

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

1978-01-01

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

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.)

Measurement of fission yields far from the center of isotopic distributions in the thermal neutron fission of 235U

International Nuclear Information System (INIS)

Shmid, M.

1979-08-01

The main purpose of this work was to measure independent yields, in the thermal neutron fission of 235 U, of fission products which lie far from the centers of the isotopic and isobaric yield distributions. These measurements were used to test the predictions of semi-empirical systematics of fission yields and theoretical fission models. Delay times were measured as a function of temperature in the range 1200-2000degC. The very low delay times achieved in the present work permitted expanding the measurable region to the isotopes 147 , 148 Cs and 99 Rb which are of special interest in the present work. The delay times of Sr and Ba isotopes achieved were more than two orders of magnitude lower than values reported in the literature and thus short-lived isotopes of these elements could be separated for the first time by mass spectrometry. The half-lives of 147 Ba, 148 Ba, 149 La and 149 Ce were measured for the first time. The isotopic distributions of fission yields were measured for the elements Rb, Sr, Cs and Ba in the thermal neutron fission of 235 U, those of 99 Rb, 147 Cs and 148 Cs having been measured for the first time. A comparison of the experimental yields with the predictions of the currently accepted semi-empirical systematics of fission yields, which is the odd-even effect systematics, shows that the systematics succeeds in accounting for the strong odd-even proton effect and the weaker odd-even neutron effect and also in predicting the shape of the distributions in the central region. It is shown that prompt neutron emission broadens the distribution only slightly in the wing of heavy isotopes and more significantly in the wing of light isotopes. But the effect of prompt neutron emission cannot explain the large discrepancies existing between the predictions of fission models and the experimentally measured fission yield in the wings of the isotopic distributions. (B.G.)

Fusion--fission hybrid concepts for laser-induced fusion

International Nuclear Information System (INIS)

Maniscalco, J.

1976-01-01

Fusion-fission hybrid concepts are viewed as subcritical fission reactors driven and controlled by high-energy neutrons from a laser-induced fusion reactor. Blanket designs encompassing a substantial portion of the spectrum of different fission reactor technologies are analyzed and compared by calculating their fissile-breeding and fusion-energy-multiplying characteristics. With a large number of different fission technologies to choose from, it is essential to identify more promising hybrid concepts that can then be subjected to in-depth studies that treat the engineering safety, and economic requirements as well as the neutronic aspects. In the course of neutronically analyzing and comparing several fission blanket concepts, this work has demonstrated that fusion-fission hybrids can be designed to meet a broad spectrum of fissile-breeding and fusion-energy-multiplying requirements. The neutronic results should prove to be extremely useful in formulating the technical scope of future studies concerned with evaluating the technical and economic feasibility of hybrid concepts for laser-induced fusion

Contributions to the theory of fission neutron emission

International Nuclear Information System (INIS)

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

1990-03-01

This report gives a compilation of recent work performed at Technical University, Dresden by D. Seeliger, H. Maerten and A. Ruben on the topic of fission neutron emission. In the first paper calculated fission neutron spectra are presented using the temperature distribution model FINESSE for fissioning actinide nuclei. In the second paper, starting from a general energy balance, Terrell's approach is generalized to describe average fragment energies as a function of incident energy; trends of fragment energy data in the Th-Pu region are well reproduced. In the third contribution, prompt fission neutron spectra and fragment characteristics for spontaneous fission of even Pu-isotopes are presented and discussed in comparison with experimental data using a phenomenological scission point model including temperature dependent shell effects. In the fourth paper, neutron multiplicities and energy spectra as well as average fragment energies for incident energies from threshold to 20 MeV (including multiple-chance fission) for U-238 are compared with traditional data representations. (author). Refs, figs and tabs

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

Ternary fission of spontaneously fissile uranium isomers excited by neutrons

International Nuclear Information System (INIS)

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

1989-01-01

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

Enantioselective Construction of 3-Hydroxypiperidine Scaffolds by Sequential Action of Light and Rhodium upon N-Allylglyoxylamides.

Science.gov (United States)

Ishida, Naoki; Nečas, David; Masuda, Yusuke; Murakami, Masahiro

2015-06-15

3-Hydroxypiperidine scaffolds were enantioselectively constructed in an atom-economical way by sequential action of light and rhodium upon N-allylglyoxylamides. In a formal sense, the allylic C-H bond was selectively cleaved and enantioselectively added across the ketonic carbonyl group with migration of the double bond (carbonyl-ene-type reaction). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ENDF/B-5. Fission Product Yields File

International Nuclear Information System (INIS)

Schwerer, O.

1985-10-01

The ENDF/B-5 Fission Product Yields File contains a complete set of independent and cumulative fission product yields, representing the final data from ENDF/B-5 as received at the IAEA Nuclear Data Section in June 1985. Yields for 11 fissioning nuclides at one or more neutron incident energies are included. The data are available costfree on magnetic tape from the IAEA Nuclear Data Section. (author). 4 refs

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

International Nuclear Information System (INIS)

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

1983-08-01

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

Study of the number of neutrons produced by fission of {sup 239}Pu; Etude du nombre de neutrons produits par la fission de {sup 239}Pu

Energy Technology Data Exchange (ETDEWEB)

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

1958-07-01

Study of the number of neutrons produced by fission of {sup 239}Pu. The counting by coincidence of fissions and neutrons produced by these fissions allows the study of the variation of the mean number of neutrons emitted by {nu} fission. In the first chapter, it studied the variation of the mean number of neutrons emitted by {sup 239}Pu fission with the energy of the incident neutron. A description of the experiment is given: a spectrometer with a crystal of sodium chloride or beryllium (mounted on a goniometer) is used, a fission chamber containing 10 mg of {sup 239}Pu and the neutron detection system constituted of BF{sub 3} counters which are enriched in {sup 10}B. In the second part, the counting by coincidence of fissions and neutrons produced by the same fission and received by two different groups of counters allow the determination of a relationship between the root mean square and the average of neutron number produced by fission. The variation of the mean number of neutrons emitted by fission of {sup 239}Pu is studied when we change from a thermal spectra of neutrons to a fission spectra of incident neutrons. Finally, when separating in two different part the fission chamber, it is possible to measure the mean number of neutrons emitted from fission of two different sources. It compared the mean number of neutrons emitted by fission of {sup 239}Pu and {sup 233}U. (M.P.)

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

Fission cross section measurements at intermediate energies

International Nuclear Information System (INIS)

Laptev, Alexander

2005-01-01

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

Feasibility study on fission moly target development

International Nuclear Information System (INIS)

Kim, Byung Ku; Kim, Seong Nyun; Shon, Dong Seong; Choi, Chang Beom; Lee, Jae Kuk; Park, Jin Ho; Jeong, Won Myung; Jeon, Kwan Sik; You, Jae Hyung; Kang, Kyung Chul; Ahn, Jong Hwan; Ju, Po Kuk

1996-01-01

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

Fission Reaction Event Yield Algorithm FREYA 2.0.2

Science.gov (United States)

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

2018-01-01

FREYA (Fission Reaction Event Yield Algorithm) is a fission event generator which models complete fission events. As such, it automatically includes fluctuations as well as correlations between observables, resulting from conservation of energy and momentum. The purpose of this paper is to present the main differences between FREYA versions 1.0 and 2.0.2 : additional fissionable isotopes, angular momentum conservation, Giant Dipole Resonance form factor for the statistical emission of photons, improved treatment of fission photon emission using RIPL database, and dependence on the incident neutron direction. FREYA 2.0.2 has been integrated into the LLNL Fission Library 2.0.2, which has itself been integrated into MCNP6.2, TRIPOLI-4.10, and can be called from Geant4.10.

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.

Fission of heavy hypernuclei

International Nuclear Information System (INIS)

Nifenecker, H.

1993-01-01

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

Ternary Fission of U235 by Resonance Neutrons

International Nuclear Information System (INIS)

Kvitek, I.; Popov, Ju.P.; Rjabov, Ju.V.

1965-01-01

Recently a number of papers have appeared indicating considerable variations in the ratio of the ternary-fission cross-section to the binary-fission cross-section of U 235 on transition from one neutron resonance to another. However, such variations have not been discovered in U 233 and Pu 239 . The paper reports investigations of the ternary fission of U 235 by neutrons with an energy of 0.1 to 30 eV. Unlike other investigators of the ternary fission of U 235 , we identified the ternary-fission event by the coincidence of one of the fission fragments with a light long-range particle. This made it passible to separate ternary fissions from the possible contribution of the (n, α)reaction. The measurements were performed at the fast pulsed reactor of the Joint Institute for Nuclear Research by the time-of-flight method. A flight length of 100 m was used, giving a resolution of 0.6 μs/m. Gas scintillation counters filled with xenon at a pressure of 2 atm were used to record the fission fragments and the light long-range particle. A layer of enriched U 235 ∼2 mg/cm 2 thick and ∼300 cm 2 in area was applied to an aluminium foil 20-fim thick. The scintillations from the fission fragments were recorded in the gas volume on one side of the foil and those from the light long-range particles in that on the other. In order to assess the background (e.g . coincidences of the pulse from a fragment with that from a fission gamma quantum or a proton from the (n, p) reaction in the aluminium foil), a measurement was carried out in which the volume recording the long-range particle was shielded with a supplementary aluminium filter 1-mm thick. The results obtained indicate the absence of the considerable variations in the ratio between the ternary-and binary- fission cross-sections for U 235 that have been noted by other authors. Measurements showed no irregularity in the ratio of the cross-sections in the energy range 0.1 to 0.2 eV. The paper discusses the possible effect of

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.)

Studies on fission with ALADIN. Precise and simultaneous measurement of fission yields, total kinetic energy and total prompt neutron multiplicity at GSI

International Nuclear Information System (INIS)

Martin, Julie-Fiona; Taieb, Julien; Chatillon, Audrey; Belier, Gilbert; Boutoux, Guillaume; Ebran, Adeline; Gorbinet, Thomas; Grente, Lucie; Laurent, Benoit; Pellereau, Eric; Alvarez-Pol, Hector; Ayyad, Yassid; Benlliure, Jose; Cortina Gil, Dolores; Caamano, Manuel; Fernandez Dominguez, Beatriz; Paradela, Carlos; Ramos, Diego; Rodriguez-Sanchez, Jose-Luis; Vargas, Jossitt; Audouin, Laurent; Tassan-Got, Laurent; Aumann, Thomas; Casarejos, Enrique; Farget, Fanny; Rodriguez-Tajes, Carme; Heinz, Andreas; Jurado, Beatriz; Kelic-Heil, Aleksandra; Kurz, Nikolaus; Nociforo, Chiara; Pietri, Stephane; Rossi, Dominic; Schmidt, Karl-Heinz; Simon, Haik; Voss, Bernd; Weick, Helmut

2015-01-01

A novel technique for fission studies, based on the inverse kinematics approach, is presented. Following pioneering work in the nineties, the SOFIA Collaboration has designed and built an experimental set-up dedicated to the simultaneous measurement of isotopic yields, total kinetic energies and total prompt neutron multiplicities, by fully identifying both fission fragments in coincidence, for the very first time. This experiment, performed at GSI, permits to study the fission of a wide variety of fissioning systems, ranging from mercury to neptunium, possibly far from the valley of stability. A first experiment, performed in 2012, has provided a large array of unprecedented data regarding the nuclear fission process. An excerpt of the results is presented. With this solid starter, further improvements of the experimental set-up are considered, which are consistent with the expected developments at the GSI facility, in order to measure more fission observables in coincidence. The completeness reached in the SOFIA data, permits to scrutinize the correlations between the interesting features of fission, offering a very detailed insight in this still unraveled mechanism. (orig.)

Studies on fission with ALADIN. Precise and simultaneous measurement of fission yields, total kinetic energy and total prompt neutron multiplicity at GSI

Energy Technology Data Exchange (ETDEWEB)

Martin, Julie-Fiona; Taieb, Julien; Chatillon, Audrey; Belier, Gilbert; Boutoux, Guillaume; Ebran, Adeline; Gorbinet, Thomas; Grente, Lucie; Laurent, Benoit; Pellereau, Eric [CEA DAM Bruyeres-le-Chatel, Arpajon (France); Alvarez-Pol, Hector; Ayyad, Yassid; Benlliure, Jose; Cortina Gil, Dolores; Caamano, Manuel; Fernandez Dominguez, Beatriz; Paradela, Carlos; Ramos, Diego; Rodriguez-Sanchez, Jose-Luis; Vargas, Jossitt [Universidad de Santiago de Compostela, Santiago de Compostela (Spain); Audouin, Laurent; Tassan-Got, Laurent [CNRS/IN2P3, IPNO, Orsay (France); Aumann, Thomas [Technische Universitaet Darmstadt, Darmstadt (Germany); Casarejos, Enrique [Universidad de Vigo, Vigo (Spain); Farget, Fanny; Rodriguez-Tajes, Carme [CNRS/IN2P3, GANIL, Caen (France); Heinz, Andreas [Chalmers University of Technology, Gothenburg (Sweden); Jurado, Beatriz [CNRS/IN2P3, CENBG, Gradignan (France); Kelic-Heil, Aleksandra; Kurz, Nikolaus; Nociforo, Chiara; Pietri, Stephane; Rossi, Dominic; Schmidt, Karl-Heinz; Simon, Haik; Voss, Bernd; Weick, Helmut [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)

2015-12-15

A novel technique for fission studies, based on the inverse kinematics approach, is presented. Following pioneering work in the nineties, the SOFIA Collaboration has designed and built an experimental set-up dedicated to the simultaneous measurement of isotopic yields, total kinetic energies and total prompt neutron multiplicities, by fully identifying both fission fragments in coincidence, for the very first time. This experiment, performed at GSI, permits to study the fission of a wide variety of fissioning systems, ranging from mercury to neptunium, possibly far from the valley of stability. A first experiment, performed in 2012, has provided a large array of unprecedented data regarding the nuclear fission process. An excerpt of the results is presented. With this solid starter, further improvements of the experimental set-up are considered, which are consistent with the expected developments at the GSI facility, in order to measure more fission observables in coincidence. The completeness reached in the SOFIA data, permits to scrutinize the correlations between the interesting features of fission, offering a very detailed insight in this still unraveled mechanism. (orig.)

Fission Surface Power Technology Development Update

Science.gov (United States)

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

2011-01-01

Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and places beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA and the Department of Energy are maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for a fission surface power system. The Fission Surface Power Systems project has focused on subscale component and subsystem demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power conversion, heat rejection, and power management and distribution technologies have validated that the fundamental characteristics and performance of these components and subsystems are consistent with a Fission Surface Power preliminary reference concept. In addition, subscale versions of a non-nuclear reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and operated with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the viability of establishing system-level performance and characteristics of fission surface power technologies without requiring a nuclear reactor. While some component and subsystem testing will continue through 2011 and beyond, the results to date provide sufficient confidence to proceed with system level technology readiness demonstration. To demonstrate the system level readiness of fission surface power in an operationally relevant environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power Technology Demonstration Unit (TDU) is under development. The TDU will consist of a non-nuclear reactor simulator, a sodium-potassium heat transfer loop, a power

Simulation of Fission Product Liftoff Behavior During Depressurization Transients

International Nuclear Information System (INIS)

Tak, Nam-il; Yoon, Churl; Lee, Sung Nam

2016-01-01

As one of crucial technologies for the NHDD project, the development of the GAMMA-FP code is on-going. The GAMMA-FP code is targeted for fission product transport analysis under accident conditions. A well-known experiment named COMEDIE considered two important phenomena, i.e., fission product plateout and liftoff, for fission product transport within the primary circuit of a prismatic high temperature gas cooled reactor. The accumulated fission products on the structural material via the plateout can be liftoff during a blowdown phase after a pipe break accident. Since the fission product liftoff can increase a radioactivity risk, it is important to predict the amount of fission product liftoff during depressurization accidents. In this work, a model for fission product liftoff is implemented into the GAMMA-FP code and the GAMMA-FP code with the implemented model is validated using the COMEDIE blowdown test data. The results of GAMMA-FP show that the GAMMA-FP code can reliably simulate a pressure transient during blowdown phase after a pipe break accident. In addition, a reasonable amount of fission product liftoff was predicted by the GAMMA-FP code. The maximum difference between the measured and predicted liftoff fraction was less than a factor of 10. More in-depth study is required to increase the accuracy of prediction for a fission product liftoff

Fusion-fission dynamics

International Nuclear Information System (INIS)

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

1991-04-01

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

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.)

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

Symmetric and asymmetric ternary fission of hot nuclei

International Nuclear Information System (INIS)

Siwek-Wilczynska, K.; Wilczynski, J.; Leegte, H.K.W.; Siemssen, R.H.; Wilschut, H.W.; Grotowski, K.; Panasiewicz, A.; Sosin, Z.; Wieloch, A.

1993-01-01

Emission of α particles accompanying fusion-fission processes in the 40 Ar + 232 Th reaction at E( 40 Ar) = 365 MeV was studied in a wide range of in-fission-plane and out-of-plane angles. The exact determination of the emission angles of both fission fragments combined with the time-of-flight measurements allowed us to reconstruct the complete kinematics of each ternary event. The coincident energy spectra of α particles were analyzed by using predictions of the energy spectra of the statistical code CASCADE . The analysis clearly demonstrates emission from the composite system prior to fission, emission from fully accelerated fragments after fission, and also emission during scission. The analysis is presented for both symmetric and asymmetric fission. The results have been analyzed using a time-dependent statistical decay code and confronted with dynamical calculations based on a classical one-body dissipation model. The observed near-scission emission is consistent with evaporation from a dinuclear system just before scission and evaporation from separated fragments just after scission. The analysis suggests that the time scale of fission of the hot composite systems is long (about 7x10 -20 s) and the motion during the descent to scission almost completely damped

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.

Development of an experimental device based on the digitalization of the signal and dedicated to the characterization of fission fragments and prompt neutrons

International Nuclear Information System (INIS)

Varapai, N.

2006-12-01

The present work demonstrates the application of the digital technique for nuclear measurements. This new technique is based on the digitalization of the signals from the detectors and has several advantages. This technique allows us to extract the maximum amount of information contained in the signal shape. In the case of an ionization chamber this signal contains the necessary information on the particle kinetic energy, emission angle and mass. This method has been implemented for measurements of promptly emitted fission neutrons in coincidence with fission fragments from 252 Cf(sf). A double Frisch-grid ionization chamber is used as fission fragment detector. The promptly emitted neutrons are detected by a NE213 liquid scintillation detector. This work displays how delicate analysis of the digitalized signals permitted us to infer the mass and kinetic energy distributions of the fission fragments as well as the neutron energy spectrum and multiplicity. The outline of this thesis is as follows: Chapter 2 gives an overview of the experimental tools used in this work. Chapter 3 explains the analysis procedure of the digitalized anode signal from an ionization chamber. Chapter 4 gives a detailed explanation of the analysis procedure of the digitalized signal from a neutron detector. In Chapter 5 the analysis procedure of the fission fragment events in coincidence with neutrons is given

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

Energy from nuclear fission an introduction

CERN Document Server

De Sanctis, Enzo; Ripani, Marco

2016-01-01

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

Fission neutron output measurements at LANSCE

International Nuclear Information System (INIS)

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

2010-01-01

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

Fission rate measurements in fuel plate type assembly reactor cores

International Nuclear Information System (INIS)

Rogers, J.W.

1988-01-01

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

Modelling sequentially scored item responses

NARCIS (Netherlands)

Akkermans, W.

2000-01-01

The sequential model can be used to describe the variable resulting from a sequential scoring process. In this paper two more item response models are investigated with respect to their suitability for sequential scoring: the partial credit model and the graded response model. The investigation is

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.)

Status of fission yield data

International Nuclear Information System (INIS)

England, T.R.; Blachot, J.

1988-01-01

In this paper we summarize the current status of the recent US evaluation for 34 fissioning nuclides at one or more neutron incident energies and for spontaneous fission. Currently there are 50 yields sets, and for each we have independent and cumulative yields and uncertainties for approximately 1100 fission products. When finalized the recommended data will become part of Version VI of the US ENDF/B. Other major evaluations in progress that are included in a recently formed IAEA Coordinated Research Program are also summarized. In a second part we review two empirical models in use to estimate independent yields. Comparison of model estimates with measured data is presented, including a comparison with some recent data obtained from Lohengrin (Cf-249 T). 18 refs., 13 figs., 3 tabs

A new neutron counter for fission research

Energy Technology Data Exchange (ETDEWEB)

Laurent, B., E-mail: benoit.laurent@cea.fr [CEA, DAM, DIF, F-91297 Arpajon (France); Granier, T.; Bélier, G.; Chatillon, A.; Martin, J.-F.; Taieb, J. [CEA, DAM, DIF, F-91297 Arpajon (France); Hambsch, F.-J. [EC-JRC Institute for Reference Materials and Measurements (IRMM), Retieseweg, 2440 Geel (Belgium); Tovesson, F.; Laptev, A.B.; Haight, R.C.; Nelson, R.O.; O' Donnell, J.M. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2014-05-01

A new neutron counter for research experiments on nuclear fission has been developed. This instrument is designed for the detection of prompt fission neutrons within relatively high levels of gamma and neutron background. It is composed of a set of {sup 3}He proportional counters arranged within a block of polyethylene which serves as moderator. The detection properties have been studied by means of Monte Carlo simulations and experiments with radioactive sources. These properties are confirmed by an experiment on neutron-induced fission of {sup 238}U at the WNR facility of the Los Alamos Neutron Science Center during which the mean prompt fission neutron multiplicity, or ν{sup ¯} has been measured from 1 to 20 MeV of incident neutron energy.

Low energy nuclear fission

International Nuclear Information System (INIS)

Nifenecker, H.

1980-08-01

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

Monte-Carlo Generation of Time Evolving Fission Chains

Energy Technology Data Exchange (ETDEWEB)

Verbeke, Jerome M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kim, Kenneth S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Prasad, Manoj K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Snyderman, Neal J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2013-08-01

About a decade ago, a computer code was written to model neutrons from their “birth” to their final “death” in thermal neutron detectors (³He tubes): SrcSim had enough physics to track the neutrons in multiplying systems, appropriately increasing and decreasing the neutron population as they interacted by absorption, fission and leakage. The theory behind the algorithms assumed that all neutrons produced in a fission chain were all produced simultaneously, and then diffused to the neutron detectors. For cases where the diffusion times are long compared to the fission chains, SrcSim is very successful. Indeed, it works extraordinarily well for thermal neutron detectors and bare objects, because it takes tens of microseconds for fission neutrons to slow down to thermal energies, where they can be detected. Microseconds are a very long time compared to the lengths of the fission chains. However, this inherent assumption in the theory prevents its use to cases where either the fission chains are long compared to the neutron diffusion times (water-cooled nuclear reactors, or heavily moderated object, where the theory starts failing), or the fission neutrons can be detected shortly after they were produced (fast neutron detectors). For these cases, a new code needs to be written, where the underlying assumption is not made. The purpose of this report is to develop an algorithm to generate the arrival times of neutrons in fast neutron detectors, starting from a neutron source such as a spontaneous fission source (²⁵²Cf) or a multiplying source (Pu). This code will be an extension of SrcSim to cases where correlations between neutrons in the detectors are on the same or shorter time scales as the fission chains themselves.

SYMMETRICAL AND ASYMMETRIC TERNARY FISSION OF HOT NUCLEI

NARCIS (Netherlands)

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

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

Enabling the Use of Space Fission Propulsion Systems

International Nuclear Information System (INIS)

Mike Houts; Melissa Van Dyke; Tom Godfroy; James Martin; Kevin Pedersen; Ricky Dickens; Ivana Hrbud; Leo Bitteker; Bruce Patton; Suman Chakrabarti; Joe Bonometti

2000-01-01

This paper gives brief descriptions of advantages of fission technology for reaching any point in the solar system and of earlier efforts to develop space fission propulsion systems, and gives a more detailed description of the safe, affordable fission engine (SAFE) concept being pursued at the National Aeronautics and Space Administration's Marshall Space Flight Center

Delayed β ray spectrum of 235U fission fragments

International Nuclear Information System (INIS)

Pascholati, P.R.

1973-01-01

The time-dependent electron spectra of fission fragments from the thermal-neutron-induced fission of 235 U are calculated. The Gross theory of nuclear beta decay is used to obtain the decay constant and individual electron spectra. The mean energy per fission carried by the electrons and the number of electrons per fission are also calculated. Comparison of these calculated spectra to experimental ones shows good agreements. (Author) [pt

Finite fission chain length and symmetry around prompt-criticality

International Nuclear Information System (INIS)

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

2012-01-01

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

Fission properties of actinide nuclei from proton-induced fission at 26.5 and 62.9 MeV incident proton energies

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.

Perspective on the fusion-fission energy concept

International Nuclear Information System (INIS)

Liikala, R.C.; Perry, R.T.; Teofilo, V.L.

1978-01-01

A concept which has potential for near-term application in the electric power sector of our energy economy is combining fusion and fission technology. The fusion-fission system, called a hybrid, is distinguished from its pure fusion counterpart by incorporation of fertile materials (uranium or thorium) in the blanket region of a fusion machine. The neutrons produced by the fusion process can be used to generate energy through fission events in the blanket or produce fuel for fission reactors through capture events in the fertile material. The performance requirements of the fusion component of hybrids is perceived as being less stringent than those for pure fusion electric power plants. The performance requirements for the fission component of hybrids is perceived as having been demonstrated or could be demonstrated with a modest investment of research and development funds. This paper presents our insights and observations of this concept in the context of why and where it might fit into the picture of meeting our future energy needs. A bibliography of hybrid research is given

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

Theoretical models of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1992-01-01

A brief 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 v 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 new models. In particular, the dependencies of N(E) and bar v 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 limititations to current and future calculations. Finally, recommendations are presented as to which model should be used currently and which model should be pursued in future efforts

The temperature of fission fragments from spontaneous fission of 252Cf measured by time-of-flight spectrometer

International Nuclear Information System (INIS)

Popkiewicz, M.; Osuch, S.; Szeflinski, Z.; Sztampke, A.; Wilhelmi, Z.; Wolinska, M.; Zaganczyk, R.

1997-01-01

The detection system MONA (Modular Neutron Array) consisting of eight large BC-501A liquid scintillators, was applied to determine the temperature of fission fragments emitted in spontaneous fission of 252 Cf. The determination of the temperature was based on the measurement of the neutron spectra

Determination of palaeotemperatures of apatite with the fission-track method

International Nuclear Information System (INIS)

Bertagnolli, E.; Maerk, E.; Bertel, E.; Pahl, M.; Maerk, T.D.

1981-01-01

As a consequence of thermal fading of fission tracks in minerals, the fission-track dating method can be used to obtain a sensitive geothermometer for unfolding thermal events in the history of rocks, especially if it is possible to determine the temperature associated with a measured fission-track age, i.e., yielding a temperature age. Based on the concept of a minimum fission-track length the differential annealing equation has been solved for apatite, taking into account the fact that the annealing coefficient depends also on the degree of fission-track reduction. This allows us to calculate an improved age-temperature relationship for apatite, which gives for a measured corrected fission-track age the corresponding temperature, assuming either linear or exponential time-dependence of the temperature. The present results for apatite are compared with previous calculations in apatite and sphene. As expected, a fission-track age of apatite dates a younger (lower temperature) point in the thermal-cooling history than a fission-track age of sphene. (author)

Fission cross sections in the intermediate energy region

International Nuclear Information System (INIS)

Lisowski, P.W.; Gavron, A.; Parker, W.E.; Ullmann, J.L.; Balestrini, S.J.; Carlson, A.D.; Wasson, O.A.; Hill, N.W.

1991-01-01

Until recently there has been very little cross section data for neutron-induced fission in the intermediate energy region, primarily because no suitable neutron source has existed. At Los Alamos, the WNR target-4 facility provides a high-intensity source of neutrons nearly ideal for fission measurements extending from a fraction of a MeV to several hundred MeV. This paper summarizes the status of fission cross section data in the intermediate energy range (En > 30 MeV) and presents our fission cross section data for 235 U and 238 U compared to intranuclear cascade and statistical model predictions

Fission cross sections in the intermediate energy region

Energy Technology Data Exchange (ETDEWEB)

Lisowski, P.W.; Gavron, A.; Parker, W.E.; Ullmann, J.L.; Balestrini, S.J. (Los Alamos National Lab., NM (USA)); Carlson, A.D.; Wasson, O.A. (National Inst. of Standards and Technology, Gaithersburg, MD (USA)); Hill, N.W. (Oak Ridge National Lab., TN (USA))

1991-01-01

Until recently there has been very little cross section data for neutron-induced fission in the intermediate energy region, primarily because no suitable neutron source has existed. At Los Alamos, the WNR target-4 facility provides a high-intensity source of neutrons nearly ideal for fission measurements extending from a fraction of a MeV to several hundred MeV. This paper summarizes the status of fission cross section data in the intermediate energy range (En > 30 MeV) and presents our fission cross section data for {sup 235}U and {sup 238}U compared to intranuclear cascade and statistical model predictions.

Uranium content of petroleum by Fission track technique

International Nuclear Information System (INIS)

Paschaa, A.S.; Mafra, O.Y.; Oliveira, C.A.N.; Pinto, L.R.

1982-01-01

This paper examines the feasibility of the fission track registration technique to investigate the natural uranium concentration in petroleum. The application is briefly described and the results obtained indicate the presence of uranium concentrations in samples of Brazilian petroleum which are over the detection limit of the fission track technique. The irradiations were performed by using fluxes with predominance of thermal neutrons, which have a fission cross-section for U 235 equal to 579 barns. Since the neutron fluxes were not comp sed exclusively of thermal neutrons, fissions from fast neutrons would also be taken into account for U 238 and Th 232

An analysis of the additional fission product release phenomena

International Nuclear Information System (INIS)

Takeda, Tsuneo; Nagai, Hitoshi

1978-09-01

The additional fission product release behavior through a defect hole on the cladding of fuel rods has been studied qualitatively with a computer program CODAC-ARFP. The additional fission product release phenomena are described as qualitative evaluation. The additional fission product release behavior in coolant temperature and pressure fluctuations and in reactor start-up and shut-down depends on coolant water flow behavior into and from the free space of fuel rods through a defect hole. Based on the results of evaluations, the experimental results with an inpile water loop OWL-1 are described in detail. The estimation methods of fission product quantity in the free space and fission product release ratio (quantity released into the coolant/quantity in the free space before beginning of release) are necessary for analysis of the fission product release behavior; the estimation method of water flow through a defect hole is also necessary. In development of the above estimation methods, outpile and capsule experiments supporting the additional fission product release experiments are required. (author)

Nuclear dynamics in heavy ion induced fusion-fission reactions

International Nuclear Information System (INIS)

Kapoor, S.S.

1992-01-01

Heavy ion induced fission and fission-like reactions evolve through a complex nuclear dynamics encountered in the medium energy nucleus-nucleus collisions. In the recent years, measurements of the fragment-neutron and fragment-charged particle angular correlations in heavy ion induced fusion-fission reactions, have provided new information on the dynamical times of nuclear deformations of the initial dinuclear complex to the fission saddle point and the scission point. From the studies of fragment angular distributions in heavy ion induced fission it has been possible to infer the relaxation times of the dinuclear complex in the K-degree of freedom and our recent measurements on the entrance channel dependence of fragment anisotropies have provided an experimental signature of the presence of fissions before K-equilibration. This paper reviews recent experimental and theoretical status of the above studies with particular regard to the questions relating to dynamical times, nuclear dissipation and the effect of nuclear dissipation on the K-distributions at the fission saddle in completely equilibrated compound nucleus. (author). 19 refs., 9 figs

New fission valley for 258Fm and nuclei beyond

International Nuclear Information System (INIS)

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

1986-01-01

Experimental results on the fission properties of nuclei close to 264 Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus 258 Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic energy peaked at about 235 MeV whereas 256 Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic energy peaked at about 200 MeV. Qualitatively, these sudden changes hve been postulated to be due to the emergence of fragment shells in symmetric fission products close to 132 Sn. A quantitative calculation that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. The implications of the new fission valley on the stability of the heaviest elements is discussed. 33 refs., 12 figs

Fission properties of very heavy actinides

International Nuclear Information System (INIS)

Hoffman, D.C.

1979-01-01

The existing data on neutron-emission, kinetic-energy and mass distributions, and half-lives for spontaneous fission of the heavy actinides are reviewed. A comparison of the data for the Fm isotopes with heavier and lighter nuclides suggests that the properties of the heavy Fm isotopes may be unique and can qualitatively be explained on the basis of fragment shell effects, i.e., symmetric fission results in two fragments with configurations close to the doubly magic 132 Sn nucleus. The effect of excitation energy and the use of systematics and theoretical predictions of fission properties and half-lives in the identification of new heavy element isotopes is discussed. 54 references

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

Modelling the widths of fission observables in GEF

Directory of Open Access Journals (Sweden)

Schmidt K.-H.

2013-03-01

Full Text Available The widths of the mass distributions of the different fission channels are traced back to the probability distributions of the corresponding quantum oscillators that are coupled to the heat bath, which is formed by the intrinsic degrees of freedom of the fissioning system under the influence of pairing correlations and shell effects. Following conclusion from stochastic calculations of Adeev and Pashkevich, an early freezing due to dynamical effects is assumed. It is shown that the mass width of the fission channels in low-energy fission is strongly influenced by the zero-point motion of the corresponding quantum oscillator. The observed variation of the mass widths of the asymmetric fission channels with excitation energy is attributed to the energy-dependent properties of the heat bath and not to the population of excited states of the corresponding quantum oscillator.

Fission cross section measurements for minor actinides

Energy Technology Data Exchange (ETDEWEB)

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

1997-03-01

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

Modeling Fission Product Sorption in Graphite Structures

International Nuclear Information System (INIS)

Szlufarska, Izabela; Morgan, Dane; Allen, Todd

2013-01-01

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

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.

Non-compound nucleus fission in actinide and pre-actinide regions

Indian Academy of Sciences (India)

2015-07-22

Jul 22, 2015 ... In this article, some of our recent results on fission fragment/product angular distributions are discussed in the context of non-compound nucleus fission. Measurement of fission fragment angular distribution in 28Si+176Yb reaction did not show a large contribution from the non-compound nucleus fission.

Investigation of delayed fission gas release

International Nuclear Information System (INIS)

Cayet, Nicolas