Correlation studies of neutron multiplicities in the 252Cf spontaneous fission

International Nuclear Information System (INIS)

Alkhazov, I.D.; Dmitriev, V.D.; Kovalenko, S.S.; Kuznetsov, A.V.; Malkin, L.Z.; Petrzhak, K.A.; Petrov, B.F.; Shpakov, V.I.

1988-01-01

Correlations between the numbers of neutrons emitted by the 252 Cf spontaneous fission fragments have been studied as a function of the fragment mass and total kinetic energy. Behaviour of the neutron number dispersions and covariances was studied for the region of symmetric fission. Parameters of the complementary fragment excitation energy distribution (mean values, dispersions, covariances) were determined. Various factors describing correlations between the complementary fragment excitation energies are considered

A search for back-to-back e+e- pairs in the spontaneous-fission disintegration of 252Cf

International Nuclear Information System (INIS)

Tsunoda, T.; Nakamura, S.; Orito, S.; Minowa, M.

1995-01-01

A back-to-back electron-positron pair is searched for in spontaneous-fission disintegration of 252 Cf. The emission of such a pair, if observed, might be a manifestation of production and prompt decay of a heretofore unknown neutral particle. The emission rate of such a pair is found to be less than (2.5-5.5) . 10 -10 per fission at the 95% confidence level depending on the mass of the hypothetical particle which is between 40 and 200 MeV/c 2 . (orig.)

Correlated spins of complementary fragment pairs in the spontaneous fission of 252Cf

International Nuclear Information System (INIS)

Smith, A. G.; Simpson, G. S.; Billowes, J.; Dagnall, P. J.; Durell, J. L.; Freeman, S. J.; Leddy, M.; Phillips, W. R.; Roach, A. A.; Smith, J. F.

1999-01-01

A study of the γ-ray decay of low-lying excited states in fragments produced in the spontaneous fission of 252 Cf has revealed a significant correlation between the angles of emission of the 2 1 + →0 1 + transitions of complementary fragment pairs. Calculations of the amount of dealignment that is needed to reproduce the measured a 2 values, and a comparison with the results of previous fragment-γ angular distribution measurements, suggests that at scission there may be significant population of m≠0 substates associated with the projection of the fragment spin vector on the fission axis. Fragments from the spontaneous fission of 248 Cm emit 2 1 + →0 1 + γ rays that show markedly reduced interfragment correlations, suggesting that either a larger role is played by the relative angular momentum of the fragments, or that the dealignment introduced by the neutron emission and statistical γ decay to the 2 1 + state is larger in 248 Cm than 252 Cf fission. (c) 1999 The American Physical Society

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

International Nuclear Information System (INIS)

Rodríguez-Guzmán, R; Robledo, L M

2017-01-01

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

Kr and Xe isotopes from spontaneous fission of 248Cm and 250Cf

International Nuclear Information System (INIS)

Srinivasan, B.

1980-01-01

Relative yields of Kr and Xe isotopes from the spontaneous fission of 248 Cm and 250 Cf have been determined mass spectrometrically. The yields are as follows: 83 Kr/ 84 Kr/ 85 Kr/ 86 Kr = 0.223/0.458/0.596/ identical 1.00 and 0.306/0.582/0.793/ identical 1.00; 131 Xe/ 134 Xe/ 136 Xe = 0.486/0.819/1.075 identical 1.00 and 0.343/0.506/0.851/ identical 1.00 from 248 Cm and 250 Cf, respectively. The Xe yields from 248 Cm agree with an earlier determination by Leich et al. Neither of these yield patterns matches that of fissiogenic Kr and Xe in carbonaceous chondrites and hence 248 Cm and 250 Cf are ruled out as progenitors of the meteoritic Kr and Xe. In general, none of the spontaneously fissioning nuclides of actinide elements can be identified as a possible progenitor. Even the mixtures of actinides, including a combination of 248 Cm and 250 Cm, are unsuitable. The origin of anomalous Kr and Xe in carbonaceous chondrites must then be traced either to the spontaneous fission of a superheavy element or to peculiarities in specific nucleosynthetic reactions. (orig.)

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)

Study of the shielding for spontaneous fission sources of Californium-252

International Nuclear Information System (INIS)

Davila R, I.

1991-06-01

A shielding study is made to attenuate, until maximum permissible levels, the neutrons radiation and photons emitted by spontaneous fission coming from a source of Californium-252. The compound package by a database (Library DLC-23) and the ANISNW code is used, in it version for personal computer. (Author)

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

International Nuclear Information System (INIS)

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

1988-01-01

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

Prompt neutron energy spectrum for the spontaneous fission of Cf-252

International Nuclear Information System (INIS)

Blinov, M.V.; Boykov, G.S.; Vitenko, V.A.

1985-06-01

The prompt neutron spectrum for the spontaneous fission of Cf-252 has been measured in 0.01-10 MeV region by the time-of-flight technique using a fast ionization chamber with U-235 layers as the neutron detector. Numerical data for the spectrum are presented, with an error file. (author)

Spontaneous-fission half-lives for even nuclei with Z> or =92

International Nuclear Information System (INIS)

Randrup, J.; Larsson, S.E.; Moller, P.; Nilsson, S.G.; Pomorski, K.; Sobiczewski, A.

1976-01-01

The spontaneous-fission process for doubly even nuclei with Z> or =92 is studied in a semiempirical WKB framework. One-dimensional fission barrier potentials are established from theoretical deformation-energy surfaces based on the droplet model and the modified-oscillator model. The effects of axial asymmetry as well as reflection asymmetry have been taken into account. Macroscopic (irrotational flow) inertial-mass functions and, alternatively, microscopic (cranking model) inertial mass parameters have been employed for the calculation of the fission half-lives. With one over-all normalization parameter it is possible to fit the experimental half-lives to within a factor of 20 on the average. The resulting effective inertial-mass functions are used to estimate the stability of the transactinide elements. Only minor differences with previous estimates for the r process and superheavy nuclei are encountered

Gamma ray transitions in de-excitation of 252Cf spontaneous fission fragments

International Nuclear Information System (INIS)

Khan, N.A.; Rashid, K.; Ahmad, M.; Qureshi, I.E.; Alam, G.D.; Ali, A.; Bhatti, N.; Horsch, F.

1983-11-01

Gamma rays in the range from 60 keV to 730 keV have been observed following the spontaneous fission of 252 Cf, with high resolution Ge(Li) detector, full width at half maximum (FWHM) of 700 eV at 122 keV, in coincidence with the two fission fragments observed with surface barrier detectors. A total number of 18, 636, 549 events were recorded over a run period of about 150 hours stretching over three weeks. The events were sorted to generate gamma ray spectra belonging to 2 amu intervals gamma of the fragment masses and 6 MeV intervals of the total kinetic energy released. Some of the prominent gamma lines belonging to various masses of the fission fragments have been identified. For some gamma lines, the intensities have been evaluated as a function of the total kinetic energy of the fission fragments. (authors)

Yields of correlated fragment pairs and neutron multiplicity in spontaneous fission of {sup 242}Pu

Energy Technology Data Exchange (ETDEWEB)

Veselsky, M.; Kliman, J.; Morhaccaron, M. [Institute of Physics of Slovak Academy of Sciences, Dubravska 9, 84228 Bratislava (Slovakia); Ramayya, A.V.; Kormicki, J.; Daniel, A.V. [Physics Department, Vanderbilt University, Nashville (United States)] Rasmussen, J.O. [Lawrence Berkeley National Laboratory, Berkeley (United States)] Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore (United States); Daniel, A.V.; Popeko, G.S.; Oganessian, Yu. Ts. [Joint Institute for Nuclear Research, Dubna (Russia)] Greiner, W. [Institut fur Theoretische Physik, J. W. Goethe Universitaet, Frankfurt a. M. (Germany); Aryaeinejad, R. [Idaho National Engineering Laboratory, Idaho Falls (United States)

1998-10-01

Yields of correlated fragment pairs were obtained in spontaneous fission of {sup 242}Pu. Charge, mass and neutron multiplicity distributions of fragment pairs were determined and compared to available data. The yield of cold fission without neutron emission was determined to about 10{percent} for the set of observed correlated fragment pairs. {copyright} {ital 1998 American Institute of Physics.}

Prompt neutron spectrum of the spontaneous fission of californium-252

International Nuclear Information System (INIS)

Zamyatnin, Yu.S.; Kroshkin, N.I.; Korostylev, V.A.; Nefedov, V.N.; Ryazanov, D.K.; Starostov, B.I.; Semenov, A.F.

1976-01-01

The californium-252 spontaneous fission neutron spectrum was measured in the energy range of 0.01 to 10 MeV by the time-of-flight technique using various neutron detectors. The measurements of 252 Cf neutron spectrum at energies of 0.01 to 5 MeV were performed as a function of fission fragment kinetic energy. The mean neutron spectrum energy in the range of 0.7 to 10 MeV was found from the results of measurements. The irregularity in the 252 Cf neutron spectrum in the neutron energy range of less than 0.7 MeV compared to theoretical values is discussed. The mechanism of 252 Cf neutron emission is also discussed on the basis of neutron yield angle measurements. 12 references

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

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

International Nuclear Information System (INIS)

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

1998-01-01

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

Energy and angular distributions of neutrons from 252Cf spontaneous fission

International Nuclear Information System (INIS)

Vasil'ev, Yu.A.; Sidorov, L.V.; Vasil'eva, N.K.

1982-01-01

Some results from a first series of measurements of energy and angular distributions of neutrons from 252 Cf spontaneous fission using a spectrometer with high neutron detection efficiency, i.e. a 4π neutron time-of-flight spectrometer, were already presented. Subsequently, a second series of measurements was performed using a more sophisticated technique. For this second series, we used a more intense 252 Cf layer (25,000 spontaneous fissions per second). The angular resolution was improved by a factor of 2-3 by combining the hexahedral counter modules, placed at the same angle with respect to the direction of motion of the fragments, in new panoramic counters. The neutron counters were calibrated against the average 252 Cf neutron spectrum at several positions of the axis of the fragment detector with respect to the neutron counters. In the spectrum measurements and calibration work, the scattered neutron background was not determined theoretically, as in the first series of measurements, but experimentally using four extra scintillation counters with scatter cones; the counters were set up at 60 deg., 80 deg., 100 deg., and 120 deg. to the direction of separation of the fragments

Search for spontaneous fission activity in Salton Sea and Atlantis II hot brines

International Nuclear Information System (INIS)

Ter-Akopian, G.M.; Sokol, E.A.; Fam Ngoc Chuong; Ivanov, M.P.; Popeko, G.S.; Molzahn, D.; Lund, T.; Feige, G.; Brandt, R.

1984-01-01

A search for an unknown spontaneously fissioning activity, possibly due to SHE, was carried out with the Dubna 3 He-counter system. In the investigation of Salton Sea samples and Atlantis II samples no such activity could be detected with limits -12 g/g. (orig.)

An evaluation of the spontaneous fission prompt neutron spectrum of 252Cf

International Nuclear Information System (INIS)

Bojkov, G.S.; Yurevich, V.I.

1987-01-01

An evaluation of the spontaneous fission prompt neutron spectrum of 252 Cf from 1 keV to 20 MeV is described. Variance-covariance matrices for a number of recent experimental data sets were constructed and used to evaluate the neutron spectrum following a Bayesian procedure. The evaluated spectrum is compared with various experimental and theoretical representations. (author)

Dispersions and correlations of the distributions of products of 252Cf spontaneous fission

International Nuclear Information System (INIS)

Vidyakin, G.S.; Vyrodov, V.N.; Gurevich, I.I.; Kirillov, B.F.; Kozlov, Y.V.; Martem'yanov, V.P.; Sukhotin, S.V.; Tarasenkov, V.G.; Khakimov, S.K.

1982-01-01

We report the results of two experiments on study of the dispersions and correlations of the distributions of products of the spontaneous fission of 252 Cf. In each experiment about 10 8 fissions were recorded with simultaneous measurement of the number of neutrons produced and in one case the fragment kinetic energy and in the other case the energy of the prompt #betta# rays. The quantities obtained were the probabilities of production of a given number of neutrons per fission, the dispersions of the distributions of the number of neutrons produced and of the fragment kinetic energy, and the dependence of the average #betta#-ray energy and the average fragment kinetic energy on the number of neutrons produced. A calculation is made of the spectrum of the total energy carried away by fragments and neutrons, and its dispersion is determined. An estimate of the total energy release in the 252 Cf fission process is made

Observed mass distribution of spontaneous fission fragments from samples of lime - an SSNTD study

CERN Document Server

Paul, D; Ghose, D; Sastri, R C

1999-01-01

SSNTD is one of the most commonly used detectors in the studies involving nuclear phenomena. The ease of registration of the presence of alpha particles and fission fragments has made it particularly suitable in studies where stable long exposures are needed to extract reliable information. Studies on the presence of alpha emitting nuclides in the environment assume importance since they are found to be carcinogenic. Lime samples from Silchar in Assam of Eastern India have shown the presence of spontaneous fission fragments besides alphas. In the present study we look at the ratio of the average mass distribution of these fission fragments, that gives us an indication of the presence of the traces of transuranic elements.

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

Spontaneous mutation rates and the rate-doubling dose

International Nuclear Information System (INIS)

Von Borstel, R.C.; Moustaccki, E.; Latarjet, R.

1978-01-01

The amount of radiation required to double the frequency of mutations or tumours over the rate of those that occur spontaneously is called the rate-doubling dose. An equivalent concept has been proposed for exposure to other environmental mutagens. The doubling dose concept is predicated on the assumption that all human populations have the same spontaneous mutation rate, and that this spontaneous mutation rate is known. It is now established for prokaryotes and lower eukaryotes that numerous genes control the spontaneous mutation rate, and it is likely that the same is true for human cells as well. Given that the accepted mode of evolution of human populatons is from small, isolated groups of individuals, it seems likely that each population would have a different spontaneous mutation rate. Given that a minimum of twenty genes control or affect the spontaneous mutation rate, and that each of these in turn is susceptible to spontaneously arising or environmentally induced mutations, it seems likely that every individual within a population (except for siblings from identical multiple births) will have a unique spontaneous mutation rate. If each individual in a population does have a different spontaneous mutation rate, the doubling dose concept, in rigorous terms, is fallacious. Therefore, as with other concepts of risk evaluation, the doubling dose concept is subject to criticism. Nevertheless, until we know individual spontaneous mutation rates with precision, and can evaluate risks based on this information, the doubling dose concept has a heuristic value and is needed for practical assessment of risks for defined populations. (author)

Total and spontaneous fission half-lives of the americium and curium nuclides

International Nuclear Information System (INIS)

Holden, N.E.

1984-01-01

The total half-life and the half-life for spontaneous fission are evaluated for the various long-lived nuclides of interest. Recommended values are presented for 241 Am, /sup 242m/Am, 243 Am, 242 Cm, 243 Cm, 244 Cm, 245 Cm, 246 Cm, 247 Cm, 248 Cm, and 250 Cm. The uncertainties are provided at the 95% confidence limit for each of the recommended values

Fresnel zone plate imaging of a 252Cf spontaneous fission source

International Nuclear Information System (INIS)

Stalker, K.T.; Hessel, K.R.

1976-11-01

The feasibility of coded aperture imaging for nuclear fuel motion monitoring is shown using Cf 252 spontaneous fission source. The theory of coded aperture imaging for Fresnel zone plate apertures is presented and design considerations for zone plate construction are discussed. Actual images are obtained which demonstrate a transverse resolution of 1.7 mm and a tomographic resolution of 1.5 millimeters. The capability of obtaining images through 12.7 mm of stainless steel is also shown

Spectroscopy of neutron-rich nuclei populated in the spontaneous fission of 252Cf and 248Cm

International Nuclear Information System (INIS)

Smith, A. G.; Simpson, G. S.; Billowes, J.; Durell, J. L.; Phillips, W. R.; Dagnall, P. J.; Freeman, S. J.; Leddy, M.; Roach, A. A.; Smith, J. F.

1999-01-01

In this paper we present research that has been carried out using the Euroball and Eurogam arrays to detect γ rays emitted from spontaneously fissioning 248 Cm and 252 Cf. The paper focuses on three sub-areas of current activity, namely, the measurement of yields of secondary fragment pairs, the measurement of state lifetimes at around spin 10, and recent measurements of g-factors of excited states in fission fragments. (c) 1999 American Institute of Physics

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

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 ...

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1998-04-01

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

Study of ternary and quaternary spontaneous fission of 252Cf with the NESSI detector

International Nuclear Information System (INIS)

Tishchenko, V.G.; Jahnke, U.; Herbach, C.M.; Hilscher, D.

2002-11-01

Ternary and quaternary spontaneous decay of 252 Cf was studied with the NESSI detector, a combination of two 4π detectors for charged particles, neutrons and γ-rays. The applied method of particle identification by measuring the energies and relative time-of-flights of the decay products is shown to be very effective for the study of rare decay modes. The energy and angular distributions of the decay products, the associated neutron multiplicities, the total energy of the prompt γ-radiation as well as correlations between the various observables were measured for the first time in a single full-scale experiment. The characteristics of ternary fission known from previous investigations are confirmed in the frame of a methodically independent experiment. Preliminary estimates of the quaternary fission yield are presented. An attempt is made to determine the mechanism of quaternary fission. (orig.)

Fission properties of superheavy nuclei for r -process calculations

Science.gov (United States)

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

2018-03-01

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

Extensions to COGEND for ENDF/B-V output of spontaneous fission decay data

International Nuclear Information System (INIS)

Tobias, A.

1978-06-01

The computer code COGEND, used to produce ENDF/B-IV or -V format nuclear decay scheme data, has been modified in order to extend its range of application. Details are given of the additional facilities which permit the handling of spontaneous fission decay data including any associated continuous spectra. In order to accommodate these additional features it is necessary to increase the core region by 4 kilobytes. (author)

{sup 252}Cf spontaneous prompt fission neutron spectrum measured at 0 degree and 180 degree relative to the fragment motion

Energy Technology Data Exchange (ETDEWEB)

Shanglian, Bao; Jinquan, Liu [Beijing Univ., BJ (China); Batenkov, O I; Blinov, M V; Smirnov, S N [V.G. Khlopin Radium Institute, ST. Petersburg (Russian Federation)

1994-09-01

The {sup 252}Cf spontaneous prompt fission neutron spectrum at 0 degree and 180 degree relative to the motion direction of corresponding fission fragments was measured. High angular resolution for fragment measurements and high energy resolution for neutron measurements were obtained using multi-parameter TOF spectrometer. The results showed that there is a symmetric distribution of `forward` and `backward` for low energy in C.M.S. neutrons, which was an evidence of nonequilibrium neutrons existed in fission process.

Nuclear isomerism in fission fragments produced by the spontaneous fission of {sup 252}Cf; Isomerisme nucleaire dans les fragments de fission produits dans la fission spontanee du {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Gautherin, C

1997-09-01

This thesis is devoted to the study of the nuclear structure of neutron-rich nuclei, via the search of isomeric nuclear states. Neutron-rich nuclei were produced in the spontaneous fission of {sup 252}Cf. The experimental study of isomeric states in these nuclei was performed with the {gamma}-array EUROGAM II, coupled to an additional and original fission fragment detector composed by photovoltaic cells, SAPhIR. The photovoltaic cells are well adapted to detect low energy heavy ions and have good energy and time resolutions to obtain a good fission fragment detection. This experiment led to the discovery of new isomeric states in {sup 135}Xe, {sup 104}Mo, {sup 146,147,148}Ce and {sup 152,154,156}Nd, with lifetimes between 60 ns and 2 {mu}s. Level schemes of these nuclei have been completed. An interpretation of the isomeric states in the nuclei {sup 154,156}Nd and {sup 156,158}Sm was performed by Hartree-Fock-Bogolyubov calculations using the DIS Gogny force with two quasi-particles excitations. The confrontation with the experimental results led to an interpretation of these isomeric states as K-isomers. (author)

BIG-10 fission product generation and reaction rates

International Nuclear Information System (INIS)

Rogers, J.W.

1976-01-01

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

Multiplicity and correlated energy of gamma rays emitted in the spontaneous fission of Californium-252

International Nuclear Information System (INIS)

Brunson, G.S. Jr.

1982-06-01

An array of eight high-speed plastic scintillation detectors has been used to infer a mathematical model for the emission multipliciy of prompt gammas in the spontaneous fission of 252 Cf. Exceptional time resolution and coincidence capability permitted the separation of gammas from fast neutrons over a flight path of approximately 10 cm. About 20 different distribution models were tested. The average energy of the prompt gammas is inversely related to the number emitted; however, this inverse relationship is not strong and the total gamma energy does increase with increasing gamma number. An extension of the experiment incorporated a lithium-drifted germanium gamma spectrometer that resolved nearly 100 discrete gammas associated with fission. Of these gammas, some were preferentially associated with fission in which few gammas were emitted. Certain others were more frequent when many gammas were emitted. Results are presented

Maximum permissible concentration (MPC) values for spontaneously fissioning radionuclides

International Nuclear Information System (INIS)

Ford, M.R.; Snyder, W.S.; Dillman, L.T.; Watson, S.B.

1976-01-01

The radiation hazards involved in handling certain of the transuranic nuclides that exhibit spontaneous fission as a mode of decay were reaccessed using recent advances in dosimetry and metabolic modeling. Maximum permissible concentration (MPC) values in air and water for occupational exposure (168 hr/week) were calculated for 244 Pu, 246 Cm, 248 Cm, 250 Cf, 252 Cf, 254 Cf, /sup 254m/Es, 255 Es, 254 Fm, and 256 Fm. The half-lives, branching ratios, and principal modes of decay of the parent-daughter members down to a member that makes a negligible contribution to the dose are given, and all daughters that make a significant contribution to the dose to body organs following inhalation or ingestion are included in the calculations. Dose commitments for body organs are also given

Measurement of the {sup 240}Pu concentration of a plutonium sample by the spontaneous fission method (1960); Mesure de la teneur d'un plutonium en {sup 240}Pu par la methode des fissions spontanees (1960)

Energy Technology Data Exchange (ETDEWEB)

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

1960-07-01

It is very important to know the plutonium-240 content of the plutonium formed in piles. The method of measurement described here consists in counting the number of spontaneous fissions produced in a known quantity of plutonium. This measurement is carried out in a multiple-plate ionisation chamber, the plutonium being deposited on the plates. The disintegration constant of plutonium-240 by spontaneous fission being known the plutonium-240 content in the sample can be calculated. (author) [French] La connaissance de la teneur en plutonium-240 du plutonium forme dans les piles est une question importante. La methode de mesure presentee ici consiste a compter le nombre de fissions spontanees issues d'une quantite connue de plutonium. Cette mesure est effectuee dans une chambre d'ionisation a plateaux multiples sur lesquels est depose le plutonium. La connaissance de la constante de desintegration du plutonium-240 par fissions spontanees permet de calculer la teneur en plutonium-240. (auteur)

Determination of 114Pd cumulative yield and investigation of the fine-structure at light peak in mass distribution of 252Cf spontaneous fission

International Nuclear Information System (INIS)

Yu Runlan; Li Xueliang; Cui Anzhi; Guo Jingru; Yan Shuhen; Tang Peijia; Liu Daming

1991-07-01

A rapid radiochemical procedure for Pd separation was developed. It was the first time to use radiochemical techniques to determine 114 Pd cumulative yield (2.50 ± 0.14)% in 252 Cf spontaneous fission. The cumulative yields of (3.50 ± 0.13)% and (3.70 ± 0.11)% for 112 Pd and 113g Ag were also obtained. These are in agreement with Skovorodkin's results. The cumulative yields determined show that there is a fine-structure at light peak of mass number A = 113 in the mass distribution of 252 Cf spontaneous fission

Simple estimate of fission rate during JCO criticality accident

Energy Technology Data Exchange (ETDEWEB)

Oyamatsu, Kazuhiro [Faculty of Studies on Contemporary Society, Aichi Shukutoku Univ., Nagakute, Aichi (Japan)

2000-03-01

The fission rate during JCO criticality accident is estimated from fission-product (FP) radioactivities in a uranium solution sample taken from the preparation basin 20 days after the accident. The FP radioactivity data are taken from a report by JAERI released in the Accident Investigation Committee. The total fission number is found quite dependent on the FP radioactivities and estimated to be about 4x10{sup 16} per liter, or 2x10{sup 18} per 16 kgU (assuming uranium concentration 278.9 g/liter). On the contrary, the time dependence of the fission rate is rather insensitive to the FP radioactivities. Hence, it is difficult to determine the fission number in the initial burst from the radioactivity data. (author)

Simple estimate of fission rate during JCO criticality accident

International Nuclear Information System (INIS)

Oyamatsu, Kazuhiro

2000-01-01

The fission rate during JCO criticality accident is estimated from fission-product (FP) radioactivities in a uranium solution sample taken from the preparation basin 20 days after the accident. The FP radioactivity data are taken from a report by JAERI released in the Accident Investigation Committee. The total fission number is found quite dependent on the FP radioactivities and estimated to be about 4x10 16 per liter, or 2x10 18 per 16 kgU (assuming uranium concentration 278.9 g/liter). On the contrary, the time dependence of the fission rate is rather insensitive to the FP radioactivities. Hence, it is difficult to determine the fission number in the initial burst from the radioactivity data. (author)

Fission - track age of the Marjalahti Pallasite

International Nuclear Information System (INIS)

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

2006-01-01

Full text: Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Over geological time, meteorites crystals have accumulated a record of tracks produced by heavily charged energetic particles from both internal (spontaneous fission of 238U and some other extinct isotopes) and external sources (galactic cosmic rays with Z>20). The fortunate fact that meteorite grains can accumulate latent and very long-lived tracks since soon after the end of nucleosynthesis in the solar nebula enables one to decode their radiation history and to detect any thermal events in the meteorite cosmic history by revealing these tracks through suitable etching procedures. Only a few minerals in meteorites (mainly phosphates) contain small amount of uranium; the fact that 238 U undergoes fission with fission-decay constant λ f ∼ 8.2x10 -17 yr -1 allows one to use this isotope as a chronometer. By measuring the U concentration in the crystals (by reactor irradiation) and the density of the spontaneous-fission tracks it is relatively easy to calculate the 'fission-track age' if 238 U is the main source of fission tracks. However the fission-track dating of extraterrestrial samples compared with the terrestrial ones has some peculiar features due to presence of a number of other potential track sources except the spontaneous fission of 238 U, such as the spontaneous fission of presently extinct 244 Pu, heavy nuclei of cosmic rays and induced fission by cosmic ray primaries. Only tracks from the spontaneous fission of U and Pu are suitable for fission-track dating. The competing effects of these fissioning elements, whose half-lives differ by a factor of ∼50, form a basis for a fission-track chronology for samples older than ∼ 4.0 Gyr. Over small intervals in time (∼ few x10 8 yr ) the track density from spontaneous fission of 238 U is nearly constant. However, the

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

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 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.)

Fission and r-process nucleosynthesis in neutron star mergers

International Nuclear Information System (INIS)

Giuliani, Samuel Andrea

2018-01-01

rates are used in r-process calculations for matter dynamically ejected in neutron star mergers and we compare our results with those obtained from a more conventional set of reaction rates. We find that all the models predict the onset of fission above the shell closure N=184 and Z=100 due to the sudden decrease in fission barriers. However, the amount of material accumulated at N=184 turns out to be very sensitive to the height of the fission barriers and the shell gap. Finally, we have also explored the impact of recent advances in fission calculations on the theoretical estimation of spontaneous fission lifetimes. We find that performing dynamical approaches based on the minimization of the integral action with nontraditional collective degrees of freedom has a strong impact in the fission barriers and the spontaneous fission lifetimes. The possible consequences of this new approach for the calculation of neutron induced fission rates has to be addressed.

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

Neutron-neutron angular correlations in spontaneous fission of 252Cf and 240Pu

Science.gov (United States)

Verbeke, J. M.; Nakae, L. F.; Vogt, R.

2018-04-01

Background: Angular anisotropy has been observed between prompt neutrons emitted during the fission process. Such an anisotropy arises because the emitted neutrons are boosted along the direction of the parent fragment. Purpose: To measure the neutron-neutron angular correlations from the spontaneous fission of 252Cf and 240Pu oxide samples using a liquid scintillator array capable of pulse-shape discrimination. To compare these correlations to simulations combining the Monte Carlo radiation transport code MCNPX with the fission event generator FREYA. Method: Two different analysis methods were used to study the neutron-neutron correlations with varying energy thresholds. The first is based on setting a light output threshold while the second imposes a time-of-flight cutoff. The second method has the advantage of being truly detector independent. Results: The neutron-neutron correlation modeled by FREYA depends strongly on the sharing of the excitation energy between the two fragments. The measured asymmetry enabled us to adjust the FREYA parameter x in 240Pu, which controls the energy partition between the fragments and is so far inaccessible in other measurements. The 240Pu data in this analysis was the first available to quantify the energy partition for this isotope. The agreement between data and simulation is overall very good for 252Cf(sf ) and 240Pu(sf ) . Conclusions: The asymmetry in the measured neutron-neutron angular distributions can be predicted by FREYA. The shape of the correlation function depends on how the excitation energy is partitioned between the two fission fragments. Experimental data suggest that the lighter fragment is disproportionately excited.

High energy {gamma} emission in the spontaneous fission of {sup 252}Cf; Emission {gamma} de grande energie dans la fission spontanee de {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires, Bordeaux-1 Univ., 33 Gradignan (France); Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Thiesen, Ch. [Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Belier, G.; Meot, M.V. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Inst.de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

1997-06-01

The prompt {gamma} emission in the spontaneous fission of {sup 252}Cf is characterized by an energy spectrum which extends up to 20 MeV. It was established that the spectrum presents in the neighbourhood of symmetric fission an intensity bump in the 3-8 MeV {gamma} energy interval. The origin of this phenomenon is still not well understood, so that it was found interesting to carry out new measurements. The spectrum of the {gamma} rays emitted in spontaneous fission of {sup 252}Cf has been measurement in the EUROGAM II multidetector using photovoltaic cells to detect fragments. The aim of the experiment was to investigate the {gamma} yield enhancement which appears for mass fragment ratio near 132/120. This enhancement was found to be composed of two peaks located at 4 MeV and 5.5 MeV respectively. The results obtained confirm the intensity bound in the 3-8 MeV region but this augmentation reaches the maximum when the heavy fragment is near the mass 132. Beyond mass 140 the phenomenon diminish and the {gamma} spectrum regains the behaviour expected for a statistic emission. The additional structure at 5.5 MeV does not vary with excitation energy while the excitation function of the 4 MeV structure is more structured and presents a maximum when the excitation energy is near 8 MeV. It is likely that all or part of this observed phenomenon is due to a particular excitation mode of this isotope associated for instance with a low energy dipole resonance. A theoretical study of this collective effect is under way 3 refs.

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

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

Identification of new neutron-rich rare-earth nuclei produced in /sup 252/Cf spontaneous fission

CERN Document Server

Greenwood, R C; Gehrke, R J; Meikrantz, D H

1981-01-01

A program of systematic study of the decay properties of neutron-rich rare-earth nuclei with 30 sspontaneous fission, is currently underway using the Idaho ESOL (Elemental Separation On Line) Facility. The chemistry system used for the rare-earth elemental separations consists of two high-performance chromatography columns connected in series and coupled to the /sup 252 /Cf fission source via a helium gas-jet transport arrangement. The time delay for separation and initiation of gamma -ray counting with results which have been obtained to date with this system include the identification of a number of new neutron-rich rare-earth isotopes including /sup 155/Pm (t/sub 1/2/=48+or-4 s) and /sup 163/Gd (t/sub 1 /2/=68+or-3 s), in addition to 5.51 min /sup 158/Sm which was identified in an earlier series of experiments. (11 refs).

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

International Nuclear Information System (INIS)

Kroehnert, H.

2011-02-01

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

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

Tapping Into Rate Flexibility: Musical Training Facilitates Synchronization Around Spontaneous Production Rates

Science.gov (United States)

Scheurich, Rebecca; Zamm, Anna; Palmer, Caroline

2018-01-01

The ability to flexibly adapt one’s behavior is critical for social tasks such as speech and music performance, in which individuals must coordinate the timing of their actions with others. Natural movement frequencies, also called spontaneous rates, constrain synchronization accuracy between partners during duet music performance, whereas musical training enhances synchronization accuracy. We investigated the combined influences of these factors on the flexibility with which individuals can synchronize their actions with sequences at different rates. First, we developed a novel musical task capable of measuring spontaneous rates in both musicians and non-musicians in which participants tapped the rhythm of a familiar melody while hearing the corresponding melody tones. The novel task was validated by similar measures of spontaneous rates generated by piano performance and by the tapping task from the same pianists. We then implemented the novel task with musicians and non-musicians as they synchronized tapping of a familiar melody with a metronome at their spontaneous rates, and at rates proportionally slower and faster than their spontaneous rates. Musicians synchronized more flexibly across rates than non-musicians, indicated by greater synchronization accuracy. Additionally, musicians showed greater engagement of error correction mechanisms than non-musicians. Finally, differences in flexibility were characterized by more recurrent (repetitive) and patterned synchronization in non-musicians, indicative of greater temporal rigidity. PMID:29681872

Tapping Into Rate Flexibility: Musical Training Facilitates Synchronization Around Spontaneous Production Rates

Directory of Open Access Journals (Sweden)

Rebecca Scheurich

2018-04-01

Full Text Available The ability to flexibly adapt one’s behavior is critical for social tasks such as speech and music performance, in which individuals must coordinate the timing of their actions with others. Natural movement frequencies, also called spontaneous rates, constrain synchronization accuracy between partners during duet music performance, whereas musical training enhances synchronization accuracy. We investigated the combined influences of these factors on the flexibility with which individuals can synchronize their actions with sequences at different rates. First, we developed a novel musical task capable of measuring spontaneous rates in both musicians and non-musicians in which participants tapped the rhythm of a familiar melody while hearing the corresponding melody tones. The novel task was validated by similar measures of spontaneous rates generated by piano performance and by the tapping task from the same pianists. We then implemented the novel task with musicians and non-musicians as they synchronized tapping of a familiar melody with a metronome at their spontaneous rates, and at rates proportionally slower and faster than their spontaneous rates. Musicians synchronized more flexibly across rates than non-musicians, indicated by greater synchronization accuracy. Additionally, musicians showed greater engagement of error correction mechanisms than non-musicians. Finally, differences in flexibility were characterized by more recurrent (repetitive and patterned synchronization in non-musicians, indicative of greater temporal rigidity.

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

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

Science.gov (United States)

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

2018-01-01

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

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.

Study of the shielding for spontaneous fission sources of Californium-252; Estudio de blindaje para fuentes de fision espontanea de Californio-252

Energy Technology Data Exchange (ETDEWEB)

Davila R, I

1991-06-15

A shielding study is made to attenuate, until maximum permissible levels, the neutrons radiation and photons emitted by spontaneous fission coming from a source of Californium-252. The compound package by a database (Library DLC-23) and the ANISNW code is used, in it version for personal computer. (Author)

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.

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

International Nuclear Information System (INIS)

Mulyanto

1997-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Kroehnert, H.

2011-02-15

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

Asymmetry of mass and charge division in spontaneous fission

International Nuclear Information System (INIS)

Chakraborty, P.P.; Iyer, M.R.; Ganguly, A.K.

The order-disorder model (ODM) has been used to explain asymmetry of mass and charge division and related phenomena in fission. According to this model the fission process involves two steps consisting of charge polarisation into two impending fragments with beta stable neutron numbers and subsequent distribution of the balance neutrons between the two. The statistics developed on the principle of equal a priori probability of all charge polarisation is used. The shell effects comes into play only in deciding stable neutron number for the charges. The total isotopic yield distribution for a number of fission reactions are presented. These show asymmetry in the actinide region which reduces with increasing mass/charge of the fissioning nuclide and bunching of the higher z peaks. The mass yields obtained therefrom for a number of fission reactions are compared with experimental results. Though there is general agreement with experimental data, the peaks of the distributions are slightly shifted away from the symmetric point and the distributions are somewhat narrower. Charge distribution parameters obtained from these results are also presented. The model predicts preference of asymmetric division for super heavy nuclides. (author)

Fast-neutron-induced fission of 242Pu at nELBE

Directory of Open Access Journals (Sweden)

Kögler Toni

2017-01-01

Full Text Available The fast neutron-induced fission cross section of 242Pu was determined in the range of 0.5 MeV to 10 MeV relative to 235U(n,f at the neutron time-of-flight facility nELBE. The number of target nuclei was calculated by means of measuring the spontaneous fission rate of 242Pu. Neutron transport simulations with Geant4 and MCNP6 are used to correct the relative cross section for neutron scattering. The determined results are in good agreement with current experimental and evaluated data sets.

Measurements of the prompt neutron spectra in 233U, 235U, 239Pu thermal neutron fission in the energy range of 0.01-5 MeV and in 252Cf spontaneous fission in the energy range of 0.01-10 MeV

International Nuclear Information System (INIS)

Starostov, B.I.; Semenov, A.F.; Nefedov, V.N.

1978-01-01

The measurement results on the prompt neutron spectra in 233 U, 235 U, 239 Pu thermal neutron fission in the energy range of 0.01-5 MeV and in 252 Cf spontaneous fission in the energy range of 0.01-10 MeV are presented. The time-of-flight method was used. The exceeding of the spectra over the Maxwell distributions is observed at E 252 Cf neutron fission spectra. The spectra analysis was performed after normalization of the spectra and corresponding Maxwell distributions for one and the same area. In the range of 0.05-0.22 MeV the yield of 235 U + nsub(t) fission neutrons is approximately 8 and approximately 15 % greater than the yield of 252 Cf and 239 Pu + nsub(t) fission neutrons, respectively. In the range of 0.3-1.2 MeV the yield of 235 U + nsub(t) fission neutrons is 8 % greater than the fission neutron yield in case of 239 Pu + nsub(t) fission. The 235 U + nsub(t) and 233 U + nsub(t) fission neutron spectra do not differ from one another in the 0.05-0.6 MeV range

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)

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.)

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

International Nuclear Information System (INIS)

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

1985-01-01

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

Determination of the fast-neutron-induced fission cross-section of 242Pu at nELBE

Science.gov (United States)

Kögler, Toni; Beyer, Roland; Junghans, Arnd R.; Schwengner, Ronald; Wagner, Andreas

2018-03-01

The fast-neutron-induced fission cross section of 242Pu was determined in the energy range of 0.5 MeV to 10MeV at the neutron time-of-flight facility nELBE. Using a parallel-plate fission ionization chamber this quantity was measured relative to 235U(n,f). The number of target nuclei was thereby calculated by means of measuring the spontaneous fission rate of 242Pu. An MCNP 6 neutron transport simulation was used to correct the relative cross section for neutron scattering. The determined results are in good agreement with current experimental and evaluated data sets.

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

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 properties of odd-A nuclei in a mean field framework

International Nuclear Information System (INIS)

Perez-Martin, S.; Robledo, L.M.

2009-01-01

Theoretical tools at the level of the mean field approximation are used to explore the spontaneous fission properties of odd-A nuclei. The tools rely on the equal (or uniform) filling approximation to deal with the unpaired nucleon in a time-reversal preserving manner. Realistic calculations have been carried out with the finite range Gogny force D1S, which was tailored to reasonably reproduce fission properties in the actinides. The preliminary results obtained for the nucleus 235 U are analyzed and the physical origin for the hindrance factor for the spontaneous fission half life is discussed. (author)

Neutron emission during acceleration of 252Cf fission fragments

International Nuclear Information System (INIS)

Batenkov, O.I.; Blinov, M.V.; Blinov, A.B.; Smirnov, S.N.

1991-01-01

We investigate neutron emission during acceleration of fission fragments in the process of spontaneous fission of 252 Cf. Experimental angular and energy distributions of neutrons are compared with the results of calculations of neutron evaporation during fragment acceleration. (author). 8 refs, 3 figs

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-12-15

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

The statistical model calculation of prompt neutron spectra from spontaneous fission of {sup 244}Cm and {sup 246}Cm

Energy Technology Data Exchange (ETDEWEB)

Gerasimenko, B.F. [V.G. Khlopin Radium Inst., Saint Peterburg (Russian Federation)

1997-03-01

The calculations of integral spectra of prompt neutrons of spontaneous fission of {sup 244}Cm and {sup 246}Cm were carried out. The calculations were done by the Statistical Computer Code Complex SCOFIN applying the Hauser-Feschbach method as applied to the description of the de-excitation of excited fission fragments by means of neutron emission. The emission of dipole gamma-quanta from these fragments was considered as a competing process. The average excitation energy of a fragment was calculated by two-spheroidal model of tangent fragments. The density of levels in an excited fragment was calculated by the Fermi-gas model. The quite satisfactory agreement was reached between theoretical and experimental results obtained in frames of Project measurements. The calculated values of average multiplicities of neutron number were 2,746 for {sup 244}Cm and 2,927 for {sup 246}Cm that was in a good accordance with published experimental figures. (author)

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

Formation and distribution of fragments in the spontaneous fission of 240Pu

Science.gov (United States)

Sadhukhan, Jhilam; Zhang, Chunli; Nazarewicz, Witold; Schunck, Nicolas

2017-12-01

Background: Fission is a fundamental decay mode of heavy atomic nuclei. The prevalent theoretical approach is based on mean-field theory and its extensions where fission is modeled as a large amplitude motion of a nucleus in a multidimensional collective space. One of the important observables characterizing fission is the charge and mass distribution of fission fragments. Purpose: The goal of this Rapid Communication is to better understand the structure of fission fragment distributions by investigating the competition between the static structure of the collective manifold and the stochastic dynamics. In particular, we study the characteristics of the tails of yield distributions, which correspond to very asymmetric fission into a very heavy and a very light fragment. Methods: We use the stochastic Langevin framework to simulate the nuclear evolution after the system tunnels through the multidimensional potential barrier. For a representative sample of different initial configurations along the outer turning-point line, we define effective fission paths by computing a large number of Langevin trajectories. We extract the relative contribution of each such path to the fragment distribution. We then use nucleon localization functions along effective fission pathways to analyze the characteristics of prefragments at prescission configurations. Results: We find that non-Newtonian Langevin trajectories, strongly impacted by the random force, produce the tails of the fission fragment distribution of 240Pu. The prefragments deduced from nucleon localizations are formed early and change little as the nucleus evolves towards scission. On the other hand, the system contains many nucleons that are not localized in the prefragments even near the scission point. Such nucleons are distributed rapidly at scission to form the final fragments. Fission prefragments extracted from direct integration of the density and from the localization functions typically differ by more than

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

Energy dependence of the neutron multiplicity P/sub nu/ in fast neutron induced fission of /sup 235,238/U and 239Pu

International Nuclear Information System (INIS)

Zucker, M.S.; Holden, N.E.

1986-01-01

Certain applications require knowledge of the higher moments of the neutron multiplicity probability. It can be shown that the second factorial moment is proportional to the fission rate in the sample, and that the third factorial moment can be of use in disentangling spontaneous fission from induced fission. Using a source of unpublished work in which neutron multiplicities were derived for the fast neutron induced fission of U-235, U-238, and Pu-239, the multiplicity probability has been calculated as a function of neutron energy for the energy range 0 to 10 MeV

Determination of the fast-neutron-induced fission cross-section of 242Pu at nELBE

Directory of Open Access Journals (Sweden)

Kögler Toni

2018-01-01

Full Text Available The fast-neutron-induced fission cross section of 242Pu was determined in the energy range of 0.5 MeV to 10MeV at the neutron time-of-flight facility nELBE. Using a parallel-plate fission ionization chamber this quantity was measured relative to 235U(n,f. The number of target nuclei was thereby calculated by means of measuring the spontaneous fission rate of 242Pu. An MCNP 6 neutron transport simulation was used to correct the relative cross section for neutron scattering. The determined results are in good agreement with current experimental and evaluated data sets.

Fission track dating of volcanic glass: experimental evidence for the validity of the Size-Correction Method

International Nuclear Information System (INIS)

Bernardes, C.; Hadler Neto, J.C.; Lattes, C.M.G.; Araya, A.M.O.; Bigazzi, G.; Cesar, M.F.

1986-01-01

Two techniques may be employed for correcting thermally lowered fission track ages on glass material: the so called 'size-correcting method' and 'Plateau method'. Several results from fission track dating on obsidian were analysed in order to compare the model rising size-correction method with experimental evidences. The results from this work can be summarized as follows: 1) The assumption that mean size of spontaneous and induced etched tracks are equal on samples unaffected by partial fading is supported by experimental results. If reactor effects such as an enhancing of the etching rate in the irradiated fraction due to the radiation damage and/or to the fact that induced fission releases a quantity of energy slightly greater than spontaneous one exist, their influence on size-correction method is very small. 2) The above two correction techniques produce concordant results. 3) Several samples from the same obsidian, affected by 'instantaneous' as well as 'continuous' natural fading to different degrees were analysed: the curve showing decreasing of spontaneous track mean-size vs. fraction of spontaneous tracks lost by fading is in close agreement with the correction curve constructed for the same obsidian by imparting artificial thermal treatements on induced tracks. By the above points one can conclude that the assumptions on which size-correction method is based are well supported, at least in first approximation. (Author) [pt

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.)

Determination of the neutron-induced fission cross section of 242Pu

International Nuclear Information System (INIS)

Koegler, Toni Joerg

2016-01-01

Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For 242 Pu, current uncertainties are of around 21%. Sensitivity studies show that the total uncertainty has to be reduced to below 5% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of 235 U and 242 Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of 242 Pu relative to 235 U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of 242 Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using results of different neutron transport simulations (Geant 4, MCNP 6 and FLUKA).

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

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

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-track ages and their geological interpretation

International Nuclear Information System (INIS)

Wagner, G.A.

1981-01-01

In fission-track dating, experimental procedures such as etching and thermal pre-treatment may strongly affect the age values determined and their geological interpretation. This peculiarity is due to the common phenomenon of partial fading of fossil (spontaneous-) fission tracks during a sample's geological history. The proper geological interpretation of the age data must take into account the specific experimental conditions, the stability characteristics and size distribution of fission tracks in the sample, the ages of co-existing minerals, and the independent information about the thermal history of the geological region. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-04-01

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

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.

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.

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

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.)

Seventy-five years of nuclear fission

Indian Academy of Sciences (India)

technology can play such a vital role in a nation's development subsequently motivated ... fragments with a broad mass distribution is a unique nuclear phenomenon ... low energy and spontaneous fission of actinide nuclei and how these ...

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

Self-Organized Fission Control for Flocking System

Directory of Open Access Journals (Sweden)

Mingyong Liu

2015-01-01

Full Text Available This paper studies the self-organized fission control problem for flocking system. Motivated by the fission behavior of biological flocks, information coupling degree (ICD is firstly designed to represent the interaction intensity between individuals. Then, from the information transfer perspective, a “maximum-ICD” based pairwise interaction rule is proposed to realize the directional information propagation within the flock. Together with the “separation/alignment/cohesion” rules, a self-organized fission control algorithm is established that achieves the spontaneous splitting of flocking system under conflict external stimuli. Finally, numerical simulations are provided to demonstrate the effectiveness of the proposed algorithm.

Contribution to the study of the influences of the excitation energy on the characteristics of the fission process

International Nuclear Information System (INIS)

Wagemans, C.

1979-01-01

Neutron induced and spontaneous fission with neutron energies from 10 -2 to 2.10 5 eV have been studied. Thermal neutron induced fission measurements in Pa 231 , Th 232 , Np 237 , U 233 , U 235 , Pu 239 and Pu 241 are reported. Energy and mass distributions of heavy fission fragments due to the spontaneous fission of Pu 240 are compared to the results obtained by thermal neutron fission of Pu 239 ; the events observed with U 236 , Pu 240 , Pa 232 and Np 238 are explained by the Bohr theory of fission channels. Ternary fission phenomena of U 233 , U 235 , Pu 239 , Pa 231 and Np 237 induced by thermal neutrons are explained and compared to models of Carjan and Feather. (MDC)

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.)

Observation of new spontaneous fission activities from elements 100 to 105

International Nuclear Information System (INIS)

Somerville, L.P.

1982-03-01

Several new Spontaneous Fission (SF) activities have been found. No definite identification could be made for any of the new SF activities; however, half-lives and possible assignments to element-104 isotopes consistent with several cross bombardments include 257 Rf(3.8 s, 14% SF), 258 Rf(13 ms), 259 Rf(approx. 3 s, 8% SF), 260 Rf(approx. 20 ms), and 262 Rf(approx. 50 ms). The 80-ms SF activity claimed by the Dubna group for the discovery of element 104 ( 260 104) was not observed. A difficulty exists in the interpretation that 260 Rf is a approx. 20-ms SF activity: in order to be correct, for example, the SF activities with half-lives between 14 and 24 ms produced in the reactions 109- to 119-MeV 18 O + 248 Cm, 88- to 100-MeV 15 N + 249 Bk, and 96-MeV 18 O + 249 Cf must be other nuclides due to their large production cross sections, or the cross sections for production of 260 Rf must be enhanced by unknown mechanisms. Based on calculated total production cross sections a possible approx. 1% electron-capture branch in 258 Lr(4.5 s) to the SF emitter 258 No(1.2 ms) and an upper limit of 0.05% for SF branching in 254 No(55 s) were determined. Other measured half-lives from unknown nuclides produced in respective reactions include approx. 1.6 s ( 18 O + 248 CM), indications of a approx. 47-s SF activity (75-MeV 12 C + 249 Cf), and two or more SF activities with 3 s less than or equal to T/sub 1/2/ less than or equal to 60 s ( 18 O + 249 Bk). The most exciting conclusion of this work is that if the tentative assignments to even-even element 104 isotopes are correct, there would be a sudden change in the SF half-life systematics at element 104 which has been predicted theoretically and attributed to the disappearance of the second hump of the double-humped fission barrier

An improved technique for fission track dating

International Nuclear Information System (INIS)

Zhao Yunlong; Wu Zhaohui; Xia Yuliang

1996-01-01

The necessity of improving the fission track dating (FTD) technique both at home and abroad is illustrated. The ways of making such improvement are also proposed. It is suggested to calibrate the constant b value of the uranium standard glass by using the method of fission products activity. The 3 kinds of uranium standard glass which have been calibrated are NBS SRM962a, UB 1 and UB 2 . An established new method σ·Φ ρ d /b, to measure neutron fluence, avoids the influence of the varying neutron spectrum on measuring neutron fluence. The improved etching technique for fission tracks in zircon adopted a two-step method which includes the molten alkali system etching using NaOH + KOH and the mixed acid system etching using HNO 3 + HF; this technique results in adequate track etching, increased track clarity and less interference. In this way the intensity of tracks is authentically reflected. Dividing angular zone in accordance with the angular distribution of spontaneous fission track on the crystal surface of minerals to count the tracks and using the improved etching technique to remove the non-uniform angular distribution of spontaneous fission tracks in zircon, ensure the accuracy of tracks count. The improved FTD techniques were used to finish Laboratory Standardized Calibration. The tests using international FTD age standards samples have proved that above mentioned techniques are reliable and practical in obtaining the accurate FTD data. (8 tabs.; 3 figs.)

Evidence for bimodal fission in the heaviest elements

International Nuclear Information System (INIS)

Hulet, E.K.; Wild, J.F.; Lougheed, R.W.

1987-08-01

We have measured the mass and kinetic-energy partitioning in the spontaneous fission of five heavy nuclides: 258 Fm, 259 Md, 260 Md 258 No, and 260 [104]. Each was produced by heavy-ion reactions with either 248 Cm, 249 Bk, or 254 Es targets. Energies of correlated fragments from the isotopes with millisecond half lives, 258 No and 260 [104], were measured on-line by a special rotating-wheel instrument, while the others were determined off-line after mass separation. All fissioned with mass distributions that were symmetric. Total-kinetic-energy distributions peaked near either 200 or 235 MeV. Surprisingly, because only a single Gaussian energy distribution had been observed previously in actinide fission, these energy distributions were skewed upward or downward from the peak in each case, except for 260 [104], indicating a composite of two energy distributions. We were able to fit accurately two Gaussian curves to the gross energy distributions from the four remaining nuclides. From the multiple TKE distributions and the shapes of the mass distributions, we conclude that there is a low-energy fission component with liquid-drop characteristics which is admixed with a much higher-energy component due to closed fragment shells. We now have further evidence for this conclusion from measurements of the neutron multiplicity in the spontaneous fission of 260 Md. 25 refs., 9 figs

Recurrence rate after thoracoscopic surgery for primary spontaneous pneumothorax.

Science.gov (United States)

Dagnegård, Hanna H; Rosén, Alice; Sartipy, Ulrik; Bergman, Per

2017-08-01

There is an on-going discussion regarding the recurrence rate after surgery for primary spontaneous pneumothorax by video assisted thoracic surgery (VATS) or by thoracotomy access. This study aimed to describe the recurrence rate, and to identify a possible learning curve, following surgery for primary spontaneous pneumothorax by VATS. All patients who underwent surgery for primary spontaneous pneumothorax by VATS at Karolinska University Hospital 2004-2013 were reviewed. Preoperative and operative characteristics were obtained from medical records. Patients were followed-up through telephone interviews or questionnaires and by review of medical records. The primary outcome of interest was time to recurrence of pneumothorax requiring intervention. Outcomes were compared between patients operated during 2004-June 2010 and July 2010-2013. 219 patients who underwent 234 consecutive procedures were included. The mean follow-up times were 6.3 and 2.9 years in the early and late period, respectively. The postoperative recurrence rate in the early period was 16% (11%-25%), 18% (12%-27%), and 18% (12%-27%), at 1, 3 and 5 years, compared to 1.7% (0.4%-6.8%), 7.6% (3.7%-15%), and 9.8% (4.8%-19%) at 1, 3 and 5 years, in the late period (p = 0.016). We found that the recurrence rate after thoracoscopic surgery for primary spontaneous pneumothorax decreased significantly during the study period. Our results strongly suggest that thoracoscopic surgery for pneumothorax involve a substantial learning curve.

Releases of radioiodine from the Karlsruhe nuclear fuel reprocessing plant as a result of spontaneous fission of actinides

International Nuclear Information System (INIS)

Schuettelkopf, H.

1977-02-01

Fro, 23,7,1976 to 28.7.76 and from 8.3.76 to 9.16.76 50 pCi 131 I/m 3 , 116 pCi 133 I/m 3 und 195 pCi 135 I/m 3 were measured on an average in 11 samples of waste air from the Karlsruhe Nuclear Fuel Reprocessing Plant (WAK). During these time intervals no dissolution of fuel material was performed. From 16.9.76 to 27.10.76 18 charges of nuclear fuel were dissolved. During this period 3.3 pCi 131 I/m 3 and 7.9 pCi 133 I/m 3 were obtained as mean waste air concentrations which were higher than the lower detection limit of the method of measurement used. 244 Cm, 242 Cm, 242 Pu, 240 Pu and 238 Pu are responsible for the production of radioiodine in nuclear fuel by spontaneous fission. 244 Cm is the most important nuclide in highly active waste solutions (HAL). The cumulative fission yield is well approximated by 3% for 13 I and by 6% for 133 I. The radioiodine is set free during fuel dissolution by venting of tanks and HAL pipes and during the vritification of such solutions. The radioiodine produced by spontaneous fission is released from WAK only by venting of tanks and HAL pipes. Corresponding to the conditions of venting, air concentrations as high as 4.4 pCi 131 I/m 3 and 8.2 pCi 133 I/m 3 are expected. These concentrations agree well with air concentrations measured during the period of fuel dissolution. Based on plausible assumptions the 131 I and 133 I waste air concentrations for the period of outage are calculated from an evaporated volume of HAL in the pipes corresponding to about 10 g of 244 Cm and with 40% equilibrium between I 2 in evaporated HAL and in waste air. In the worst case 131 I-concentrations in the waste air of WAK result in an annual release of 0.2 mCi 131 I. This value is less than 1% of the authorized annual releases of 1976. For a reprocessing plant of 1,400 t/a capacity the annual expected release of 131 I lies in the mCi range. (orig.) [de

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1980-03-01

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

Study of the isomer nuclei produced in the spontaneous fission of {sup 252}Cf; Etude des noyaux isomeriques produits dans la fission spontanee de {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Thiesen, Ch. [Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires, Bordeaux-1 Univ., 33 Gradignan (France); Belier, G.; Girod, M.; Meot, M.V. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Astier, G.; Meot, V.; Peru, S. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Inst.de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

1997-06-01

Isomeric states have been studied in fission fragments produced by spontaneous fission of {sup 252}Cf. 34 isomeric nuclei have been identified by using coincidences between {gamma}-rays detected in EUROGAM II and fission fragments detected in photovoltaic cells. Lifetimes from 20 ns up to 2 {mu}s have been measured. Microscopic interpretation of the isomeric levels discovered has been tried by means of the Hartree-Fock-Bogolyubov procedure using Gogny force. It was found that the {sup 152,154,156}Nd nuclei have prolate deformation in their ground state; the rotational band built on this ground state is well reproduced by the calculation. For these nuclei the 2 quasi-particle excited states energies are above 1 MeV in agreement with the experiment. The computation confirms the similitude of the {sup 156}Nd and {sup 158}Sm isomeric states associated to neutron 2 quasi-particles of J{sup {pi}} K{sup {pi}} = 5{sup -} ({nu} 5/2 (642) x {nu} 5/2 (523)) while such similitude does not occur for the isotone nuclei {sup 154}Nd and {sup 156}Sm. The computation predicts a proton 2 quasi-particle excited states of J{sup {pi}} = 5{sup -}, near the isomeric level measured in {sup 156}Sm but not for that of {sup 154}Nd. Concerning the {sup 152}Nd the calculated level density is very near that of the states measured in the 1.6 to 2.3 MeV interval. However, the lack of precise information on spins and parities of the measured levels does make not possible a confrontation with the calculations. An up-graded equipment implying 32 photovoltaic cells instead of 2 cells is to be developed and installed by the EUROGAM 3 refs.

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

Spontaneous Emission and Energy Transfer Rates Near a Coated Metallic Cylinder

OpenAIRE

BRADLEY, LOUISE

2014-01-01

PUBLISHED The spontaneous emission and energy transfer rates of quantum systems in proximity to a dielectrically coated metallic cylinder are investigated using a Green's tensor formalism. The excitation of surface plasmon modes can significantly modify these rates. The spontaneous emission and energy transfer rates are investigated as a function of the material and dimensions of the core and coating, as well as the emission wavelength of the donor. For the material of the core we consider...

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

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

Fission neutron damage rates and efficiencies in several metals

International Nuclear Information System (INIS)

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

1981-11-01

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

Description of light charged particle emission in ternary fission

International Nuclear Information System (INIS)

Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kuklin, S. N.; Scheid, W.

2010-01-01

We consider the motion of three fragments starting from the scission point of ternary system. In the alpha-accompanied ternary fission the initial conditions are not the free parameters and determined by minimization of potential energy at scission point. In the trajectory calculations the angular distribution and mean value of the kinetic energy of the alpha-particles are well described in the spontaneous ternary fission of 252 Cf. In the Be- and C-accompanied ternary fission we found that the emission of the third particle occurs from one of the heavy fragments after their separation. (authors)

Recent improvements in the calculation of prompt fission neutron spectra: Preliminary results

International Nuclear Information System (INIS)

Madland, D.G.; LaBauve, R.J.; Nix, J.R.

1989-01-01

We consider three topics in the refinement and improvement of our original calculations of prompt fission neutron spectra. These are an improved calculation of the prompt fission neutron spectrum N(E) from the spontaneous fission of 252 Cf, a complete calculation of the prompt fission neutron spectrum matrix N(E,E n ) from the neutron-induced fission of 235 U, at incident neutron energies ranging from 0 to 15 MeV, and an assessment of the scission neutron component of the prompt fission neutron spectrum. Preliminary results will be presented and compared with experimental measurements and an evaluation. A suggestion is made for new integral cross section measurements. (author). 45 refs, 12 figs, 1 tab

Two methodologies for computing neutron sources from (α,n) and spontaneous fission reactions in vitrified waste

International Nuclear Information System (INIS)

Goldberg, H.J.; Morford, R.J.

1993-06-01

The disposal of high-level defense waste in a geologic repository necessitates conversion of the waste to a stable form. For this purpose, the Hanford Waste Vitrification Plant (HWVP) will be constructed. In this facility the waste will be converted into 6.3 x 10 5 cm 3 glassified cylinders, 59 cm in diameter and 230 cm in height, which will be placed in steel containers and buried. The waste packages must be adequately shielded to ensure the safety of personnel handling them. To calculate the shielding necessary, the radiation source term must be determined. Although the γ-ray source term does not present a problem, the neutron source term is a concern. Because the glass matrix is composed of light elements, the presence of any α-particle emitting radionuclides in the waste will contribute to the neutron flux. This paper attempts to ascertain the neutron flux and spectrum from (α,n) reactions and add it to the flux resulting from spontaneous fission

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

Directory of Open Access Journals (Sweden)

Afshin Taghva Manesh

2017-02-01

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

Decay and fission of the oriented nuclei

CERN Document Server

Kadmenskij, S G

2002-01-01

The fragment angular distributions for binary decay of oriented spherical and deformed nuclei with taking into account the correct transformational properties of wave functions under time inversion have been investigated. It has been shown that for description of fragment angular distributions the adiabatic approximation for collective rotational nuclear degrees of freedom is not correct. It has been demonstrated that this approximation is valid for description of spontaneous and induced low-energy nuclear fission. The dependence of partial fission widths on the orientation of the internal axes spins, projections of spins, and relative angular moments of fission fragments has been analyzed. It has been shown that the adiabatic approximation results in coherent interference of wave functions of fragments relative movement. This interference forms fragments the universal angular distributions of fission fragments for oriented nuclei. For these distributions the deviations from A. Bohr's formula have been invest...

Measurements of fission cross-sections and of neutron production rates

International Nuclear Information System (INIS)

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

1958-01-01

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

Nuclear data for neutron emission in the fission process

International Nuclear Information System (INIS)

Ganesan, S.

1991-11-01

This document contains the proceedings of the IAEA Consultants' Meeting on Nuclear Data for Neutron Emission in the Fission Process, Vienna, 22 - 24 October 1990. Included are the conclusions and recommendations reached at the meeting and the papers presented by the meeting participants. These papers provide a review of the status of experimental and theoretical data on neutron emission in spontaneous and neutron induced fission with reference to the data needs for reactor applications oriented towards actinide burner studies. The specific topics covered are the following: experimental measurements and theoretical predictions and evaluations of fission neutron energy spectra, average prompt fission neutron multiplicity, correlation in neutron emission from complementary fragments, neutron emission during acceleration of fission fragments, statistical properties of neutron rich nuclei by study of emission spectra of neutrons from the excited fission fragments, integral qualification of nu-bar for the major fissile isotopes, nu-bar total of 239 Pu and 235 U, and related problems. Refs figs and tabs

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-07-01

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

Alpha and gamma spectroscopy of fission isomers

International Nuclear Information System (INIS)

Makarenko, V.E.

1988-01-01

The attempts to discover in the experiment decay of fission isomers of heavy nuclei in the U-Am range by emitting α particles or γ quanta are considered. Some facilities for searching αdecay of spontaneously fissile isomers are given in brief. The first experimental results are discussed

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

International Nuclear Information System (INIS)

Huiskamp, R.

1991-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1991-06-01

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

Characteristics of prompt fission gamma-ray emission - Experimental results and predictions

International Nuclear Information System (INIS)

Oberstedt, Andreas; Billnert, Robert; Oberstedt, Stephan

2014-01-01

Systematics from 2001, describing prompt fission gamma-ray spectra (PFGS) characteristics as function of mass and atomic number of the fissioning system, has been revisited and parameters have been revised based on recent experimental results. Although originally expressed for spontaneous and thermal neutron-induced fission, validity for fast neutrons was assumed and applied to predict PFGS characteristics for the reaction n + 238 U up to incident neutron energies of E n = 20 MeV. The results from this work are in good agreement with corresponding results from both model calculations and experiments. (authors)

Decay rate in a multi-dimensional fission problem

Energy Technology Data Exchange (ETDEWEB)

Brink, D M; Canto, L F

1986-06-01

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

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

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...

SSNTD study of the probable influence of alpha activity on the mass distribution of sup 2 sup 5 sup 2 Cf fission fragments

CERN Document Server

Paul, D; Sastri, R C; Ghose, D

1999-01-01

The SSNTD has come a long way in its application for the study of nuclear phenomena. Spontaneous fission of transuranic elements is one such phenomena wherein use of SSNTD offers easy registration of the signature of the fission fragments. The object of the present study is to explore whether any one of the track parameters such as the diameter can be used to estimate the atomic mass ratios of the spontaneous fission fragments. The spontaneous fission data from sup 2 sup 5 sup 2 Cf recorded almost at the end of one and four half-life periods for alpha decay are analysed, taking a plot of the number of tracks versus the track diameter. From these plots it is seen that initially, when significant alpha activity of sup 2 sup 5 sup 2 Cf persists, the fission fragments appear to cluster into two predominant groups as indicated by two peaks. The ratio of the diameters at these peak positions appear to be related to the ratio of average mass numbers of the light and heavy groups of fission fragments. However, absenc...

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Microscopic theory of nuclear fission: a review

Science.gov (United States)

Schunck, N.; Robledo, L. M.

2016-11-01

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

Development of glass ceramics for the incorporation of fission products

International Nuclear Information System (INIS)

De, A.K.; Luckscheiter, B.; Lutze, W.; Malow, G.; Schiewer, E.

1976-01-01

Spontaneous devitrification of fission-product-containing borosilicate glasses can be avoided by controlled crystallization after melting. Glass ceramics have been developed from a vitrified simulated waste and further improvement of product properties was achieved. In particular perovskite, h-celsian, diopside and eucryptite glass ceramics were prepared. These contained leach resistant host phases which exhibited considerable enrichment of long-lived fission products. All products showed increased impact resistance, but the thermal expansion was only slightly improved

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

Attachment behavior of fission products to solution aerosol

Energy Technology Data Exchange (ETDEWEB)

Takamiya, Koichi; Tanaka, Toru; Nitta, Shinnosuke; Itosu, Satoshi; Sekimoto, Shun; Oki, Yuichi; Ohtsuki, Tsutomu [Research Reactor Institute, Kyoto University, Osaka (Japan)

2016-12-15

Various characteristics such as size distribution, chemical component and radioactivity have been analyzed for radioactive aerosols released from Fukushima Daiichi Nuclear Power Plant. Measured results for radioactive aerosols suggest that the potential transport medium for radioactive cesium was non-sea-salt sulfate. This result indicates that cesium isotopes would preferentially attach with sulfate compounds. In the present work the attachment behavior of fission products to aqueous solution aerosols of sodium salts has been studied using a generation system of solution aerosols and spontaneous fission source of {sup 248}Cm. Attachment ratios of fission products to the solution aerosols were compared among the aerosols generated by different solutions of sodium salt. A significant difference according as a solute of solution aerosols was found in the attachment behavior. The present results suggest the existence of chemical effects in the attachment behavior of fission products to solution aerosols.

Dating by fission track method: study of neutron dosimetry with natural uranium thin films

International Nuclear Information System (INIS)

Iunes, P.J.

1990-06-01

Fission track dating is described, focalizing the problem of the decay constant for spontaneous fission of 238 U and the use of neutron dosimetry in fission track analysis. Experimental procedures using thin films of natural uranium as neutron dosimeters and its results are presented. The author shows a intercomparison between different thin films and between the dosimetry with thin film and other dosimetries. (M.V.M.). 52 refs, 12 figs, 9 tabs

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.

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

International Nuclear Information System (INIS)

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

2013-06-01

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

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

International Nuclear Information System (INIS)

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

1985-01-01

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

Status of the general description of fission observables by the GEF code

CERN Document Server

Jurado, B

2014-01-01

The GEneral Fission (GEF) model treats spontaneous fission and fission up to an excitation energy of about 100 MeV of a wide range of heavy nuclei. GEF makes use of general laws of statistical and quantum mechanics, assuring a high predictive power. It is unique in providing a general description of essentially all fission observables in a consistent way while preserving the correlations between all of them. In this contribution we present some of the physical aspects on which the model is based, give an overview on the results that can be obtained with the code and show an example that illustrates how the GEF code can serve as a framework for revealing the sensitivity of the fission observables to some basic nuclear properties.

Prompt fission neutron spectra and average prompt neutron multiplicities

International Nuclear Information System (INIS)

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

1983-01-01

We present a new method for calculating the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity anti nu/sub p/ as functions of the fissioning nucleus and its excitation energy. The method is based on standard nuclear evaporation theory and takes into account (1) the motion of the fission fragments, (2) the distribution of fission-fragment residual nuclear temperature, (3) the energy dependence of the cross section sigma/sub c/ for the inverse process of compound-nucleus formation, and (4) the possibility of multiple-chance fission. We use a triangular distribution in residual nuclear temperature based on the Fermi-gas model. This leads to closed expressions for N(E) and anti nu/sub p/ when sigma/sub c/ is assumed constant and readily computed quadratures when the energy dependence of sigma/sub c/ is determined from an optical model. Neutron spectra and average multiplicities calculated with an energy-dependent cross section agree well with experimental data for the neutron-induced fission of 235 U and the spontaneous fission of 252 Cf. For the latter case, there are some significant inconsistencies between the experimental spectra that need to be resolved. 29 references

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

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

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

Angular distribution in ternary cold fission

International Nuclear Information System (INIS)

Delion, D.S.; J.W. Goethe Univ., Frankfurt; Sandulescu, A.; J.W. Goethe Univ., Frankfurt; Greiner, W.

2003-01-01

We describe the spontaneous ternary cold fission of 252 Cf, accompanied by 4 He, 10 Be and 14 C. The light cluster decays from the first resonant eigenstate in the Coulomb potential plus a harmonic oscillator potential. We have shown that the angular distribution of the emitted light particle is strongly connected with its deformation and the equatorial distance. (author)

Trajectory calculations for the ternary cold fission of 252Cf

International Nuclear Information System (INIS)

Misicu, S.

1998-01-01

We compute the final kinetic energies of the fragments emitted in the light charged particle accompanied by cold fission of 252 Cf taking into account the deformation and the finite-size effects of the fragments and integrating the equations of motion for a three-body system subjected only to Coulomb forces. The initial conditions for the trajectory calculations were derived in the framework of a deformed cluster model which includes also the effect due to the absorbative nuclear part. Although the distributions of initial kinetic energies are rather broad we show that in cold fission the initial conditions can be better determined than in the usual spontaneous fission

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

ESOL facility for the generation and radiochemical separation of short half-life fission products

International Nuclear Information System (INIS)

Gehrke, R.J.; Meikrantz, D.H.; Baker, J.D.; Anderl, R.A.; Novick, V.J.; Greenwood, R.C.

1988-01-01

A facility has been developed at the Idaho National Engineering Laboratory (INEL) for the generation and rapid radiochemical separation of short half-life mixed fission products. This facility, referred to as the Idaho Elemental Separation On Line (ESOL), consists of electro-plated sources of spontaneously fissioning 252 Cf with a helium jet transport arrangement to continuously deliver short half-life, mixed fission products to the radiochemistry laboratory for rapid, computer controlled, radiochemical separations. 18 refs., 13 figs

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

Low Base-Substitution Mutation Rate in the Germline Genome of the Ciliate Tetrahymena thermophila

Science.gov (United States)

2016-09-15

Tetrahymena thermophila, a model eukaryote. PLoS Biol. 4:e286. Farlow A, et al. 2015. The spontaneous mutation rate in the fission yeast Schizosaccharomyces...spontane- ous mutations in yeast . Proc Natl Acad Sci U S A. 105:9272–9277. Lynn DH, Doerder FP. 2012. The life and times of Tetrahymena. Methods Cell...Low Base-Substitution Mutation Rate in the Germline Genome of the Ciliate Tetrahymena thermophila Hongan Long1,2,y, David J. Winter3,*,y, Allan Y.-C

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-07-01

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

Tunneling process in heavy-ion fusion and fission

Energy Technology Data Exchange (ETDEWEB)

Iwamoto, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kondratyev, V.; Bonasera, A.

1998-10-01

We present a model towards the many-body description of sub-barrier fusion and spontaneous fission based on the semiclassical Vlasov equation and the Feynman path integral method. We define suitable collective variables from the Vlasov solution and use the imaginary time technique for the dynamics below the Coulomb barrier. (author)

Cold fission description with constant and varying mass asymmetries

International Nuclear Information System (INIS)

Duarte, S.B.; Rodriguez, O.; Tavares, O.A.P.; Goncalves, M.; Garcia, F.; Guzman, F.

1998-01-01

Different description for varying the mass asymmetry in the fragmentation process are used to calculate the cold fission barrier penetrability. The relevance of the appropriate choice for both the description of the pre-scission phase and inertia coefficient to unify alpha decay, cluster radioactivity, and spontaneous cold fission processes in the same theoretical framework is explicitly shown. We calculate the half-life of all possible partition modes of nuclei of A > 200 following the most recent Mass Table by Audi and Wapstra. It is shown that if one uses the description in which the mass asymmetry is maintained constant during the fragmentation process, the experimental half-life-values and mass yield of 234 U cold fission are satisfactorily reproduced. (author)

Differential and integral comparisons of three representations of the prompt neutron spectrum for the spontaneous fission of 252Cf

International Nuclear Information System (INIS)

Madland, D.G.; LaBauve, R.J.; Nix, J.R.

1984-01-01

Because of their importance as neutron standards, we present comparisons of measured and calculated prompt fission neutron spectra N(E) and average prompt neutron multiplicities anti nu/sub p/ for the spontaneous fission of 252 Cf. In particular, we test three representations of N(E) against recent experimental measurements of the differential spectrum and threshold integral cross sections. These representations are the Maxwellian spectrum, the NBS spectrum, and the Los Alamos spectrum of Madland and Nix. For the Maxwellian spectrum, we obtain the value of the Maxwellian temperature T/sub M/ by a least-squares adjustment to the experimental differential spectrum of Poenitz and Tamura. For the Los Alamos spectrum, a similar least-squares adjustment determines the nuclear level-density parameter a, which is the single unknown parameter that appears. The NBS spectrum has been previously constructed by adjustments to eight differential spectra measured during the period 1965 to 1974. Among these three representations, we find that the Los Alamos spectrum best reproduces both the differential and integral measurements, assuming ENDF/B-V cross sections in the calculation of the latter. Although the NBS spectrum reproduces the integral measurements fairly well, it fails to satisfactorily reproduce the new differential measurement, and the Maxwellian spectrum fails to satisfactorily reproduce the integral measurements. Additionally, we calculate a value of anti nu/sub p/ from the Los Alamos theory that is within approximately 1% of experiment. 25 references

Contribution to the study of prompt gamma-rays from fission

International Nuclear Information System (INIS)

Regnier, D.

2013-01-01

This PhD thesis has essentially been motivated by the nuclear heating problematic in reactors. The main goal of this work was the production of methods capable of simulating the prompt gamma emission from fission. First of all, several algorithms for the treatment of the nucleus deexcitation were implemented. They have been successfully tested through various calculations (isomeric branching ratio, total radiative width, etc). These methods were then incorporated in the frame of the fission code FIFRELIN. The tool which results from this work, enables the determination of numerous fission observables in the frame of a single consistent model. A sensitivity study of the results to several numerical and nuclear models has been realized. At last, calculation have been lead for the 252 Cf spontaneous fission and the thermal neutron induced fission of 235 U and 239 Pu. The prompt gamma spectra obtained for those three fissioning systems have been determined. The results are in good agreement with available experimental data, including recent measurements published in 2012 and 2013. (author) [fr

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-01-11

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

Fission-track ages of Neogene and Quaternary volcanic ashes in south of Osaka, Japan

International Nuclear Information System (INIS)

Yokoyama, Takuo; Nakagawa, Yonosuke; Danhara, Tohru.

1984-01-01

A calculation method is proposed for the fission-track ages of zircon crystals in volcanic material. In this method, it is checked whether the spontaneous fission-track number of respective zircon crystals follows the Poisson distribution. If it does, the age is calculated by population method with all crystals, and if not, only with those crystals following the Poisson distribution, eliminating abnormal crystals. Extraneous zircon crystals are thus excluded and crystals with spontaneous fission-track number zero are not ignored. The following ages were obtained: Tamateyama volcanic ash in the Nijo group, 14.0 +- 0.6 Ma; pink volcanic ash in the Osaka group, 1.0 +- 0.2 Ma; Matsuo volcanic ash in the Ko-Osaka group, 1.5 +- 0.4 Ma; pumice volcanic ash in the Ko-Osaka group, 2.3 +- 0.4 Ma; Asashiro volcanic ash in the Ko-Osaka group, 2.9 +- 0.6 Ma. (Mori, K.)

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-12-15

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

Cavity-enhanced spontaneous emission rates for rhodamine 6-G in levitated microdroplets

International Nuclear Information System (INIS)

Barnes, M.D.; Whitten, W.B.; Ramsey, J.M.; Arnold, S.

1992-01-01

Fluorescence decay kinetics of Rhodamine 6-G molecules in levitated glycerol microdroplets (4--20 microns in diameter) have been investigated to determine the effects of spherical cavity resonances on spontaneous emission rates. For droplet diameters greater than 10 microns, the fluorescence lifetime is essentially the same as in bulk glycerol. As the droplet diameter is decreased below 10 microns, bi-exponential decay behavior is observed with a slow component whose rate is similar to bulk glycerol, and a fast component whose rate is as much as a factor of 10 larger than the bulk decay rate. This fast component is attributed to cavity enhancement of the spontaneous emission rate and, within the weak coupling approximation, a value for the homogeneous linewidth at room temperature can be estimated from the fluorescence lifetime data

Nuclear structure via isomer tagging of fission fragments

Science.gov (United States)

Wu, C. Y.; Cline, D.; Simon, M. W.; Stoyer, M. A.

1997-10-01

The high efficiency for detecting high-fold γ rays by large Ge arrays makes it possible to study the detailed spectroscopy of many neutron-rich nuclei produced by fission. Major progress has been made using sealed spontaneous fission sources. Considerable improvement in selectivity is provided, with an open source, both by gating on isomers and by detection of both fission fragments in coincidence with the deexcitation γ rays (see the preceding contribution). The reconstructed kinematics allows a measure of fragment mass and the Doppler shift correction of γ rays. In a recent experiment, fission fragments were detected using half of the CHICO array and an annular PPAC in coincidence with deexcitation γ rays detected by the Rochester array of eight Compton-suppressed Ge detectors. The annular PPAC was located only 1.0" from a 3.7 μCi ^252Cf source for efficient isomer tagging. The correlation was studied between delayed, within a time window between 150 ns and 10 μs after a fission occurring, and prompt γ rays. Several prominent feeding patterns to isomers in the mass region around 100 and 130 are identified by such correlation study. Experimental details and results will be presented.

Prompt neutron emission from fragments in spontaneous fission of {sup 244,248}Cm and {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Vorobyev, A. S.; Shcherbakov, O. A. [Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, 188300 (Russian Federation); Dushin, V. N.; Jakovlev, V. A.; Kalinin, V. A.; Petrov, B. F. [V.G. Khlopin Radium Institute, St. Petersburg, 194021 (Russian Federation); Hambsch, F.J [EC-JRC-Institute for Reference Materials and Measurements Retieseweg 111, B-2440 Geel (Belgium); Laptev, A. B. [Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, 188300 (Russian Federation); Japan Nuclear Cycle Development Institute, Tokai-mura, Naka-gun, Ibaraki 319-1194 (Japan)

2005-07-01

Neutrons emitted in fission were measured separately for each complementary fragment in correlation with fission fragment energies. Two high efficiency Gd-loaded liquid scintillator tanks were used for neutron registration. Fission fragment energies were measured using a twin Frisch gridded ionization chamber with a pin-hole collimator. The neutron multiplicity distributions were obtained for each value of the fission fragment mass and energy and corrected for neutron registration efficiency, background and pile-up. The dependencies of these distributions on fragment mass and energy for different energy and mass bins, as well as the mass and energy distribution of the fission fragments are presented and discussed. (authors)

Measurement of the neutron-induced fission cross-section of 240,242Pu

International Nuclear Information System (INIS)

Salvador-Castineira, P.; Hambsch, F.J.; Brys, T.; Oberstedt, S.; Vidali, M.; Pretel, C.

2014-01-01

Fast spectrum neutron-induced fission cross-section data for transuranic isotopes are in high demand in the nuclear data community. In particular, highly accurate data are needed for the new Generation-IV nuclear applications. The aim is to obtain precise neutron-induced fission cross-sections for 240 Pu and 242 Pu. In this context accurate data on spontaneous fission half-lives have also been measured. To minimise the total uncertainty on the fission cross-sections the detector efficiency has been studied in detail. Both isotopes have been measured using a twin Frisch-grid ionisation chamber (TFGIC) due to its superiority compared to other detector systems in view of radiation hardness, 2 x 2π solid angle coverage and very good energy resolution. (authors)

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-12-01

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

Prompt neutron fission spectrum mean energies for the fissile nuclides and 252Cf

International Nuclear Information System (INIS)

Holden, N.E.

1985-01-01

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

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

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

CERN Document Server

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

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

Comparison of 235U fission cross sections in JENDL-3.3 and ENDF/B-VI

International Nuclear Information System (INIS)

Kawano, Toshihiko; Carlson, Allan D.; Matsunobu, Hiroyuki; Nakagawa, Tsuneo; Shibata, Keiichi

2002-01-01

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

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)

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

International Nuclear Information System (INIS)

Shani, G.

1976-01-01

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

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)

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

Thermal flow in detectors of CNA-II with spontaneous fissions source of 238U

International Nuclear Information System (INIS)

Mascitti, J. A

2012-01-01

The thermal flux in the position of ex-core and in-core CNA-II Nuclear Power Plant (CNA-II) detectors is estimated considering neutron from the 238 U spontaneous fissions as the source, for the reactor cold state (isothermal state with both coolant and moderator at a temperature of 60 o C, a pressure of 35 ata and 15.46 ppm of natural Boron), and 24% inserted control rods (slightly sub-critical). Results are obtained for two different situations: with and without photo-neutrons due to the (γ,n) reaction in D 2 O. It is concluded that the thermal flux is under the detection limit of the boron trifluoride 104-SR or 282-IB detectors (≅10 -1 cm-2.s -1 ). These detectors are located in opposite positions in the inner concrete shielding, having the lowest detection limit among all ex-core detectors. A significant difference is verified in neutron fluxes between both cases, which suggest that photo-neutrons in large heavy water reactors such as CNA-II should not be ignored. The total neutron flux attenuation factor between the inner and outer region of the reactor pressure vessel was estimated to be 7.0 x 10 -7 . It should be mentioned that none of the results here presented has been affected by any correction factor. Each value has a percentage relative error representing the statistical uncertainty due to the probabilistic Monte Carlo method used to obtain it (author)

Spontaneous mutation rate in Chinese hamster cell clones differing in UV-sensitivity

International Nuclear Information System (INIS)

Manuilova, E.S.; Bagrova, A.M.; Moskovskij Gosudarstvennyj Univ.

1983-01-01

The spontaneous rate of appearance of mutations to 6-mercaptopurine (6 MP) resistence in the cells of CHR2 and CHs2 clones dofferent in sensitivity to lethal and matagenous effect of UV-rays, is investigated. Increased UV-sensitivity of CHs2 clone is caused by the violation of postreplicative DNA reparation. It is established that the purity of spontaneously occuring mutations in both clones turns out to be similar, i.e. (1.5-1.8)x10 -5 for the cell pergeneration. It is shown that the effect of postreplicative DNA reparation in the cells of chinese hamster is not connected with the increase of spontaneous mutation ability. The problem on the possible role of reparation in the mechanism of appearance of spontaneous and induced mutations in the cells of Chinese hamster with increased UV-sensitivity is discussed

Determination of the neutron-induced fission cross section of {sup 242}Pu; Bestimmung des neutroneninduzierten Spaltquerschnitts von {sup 242}Pu

Energy Technology Data Exchange (ETDEWEB)

Koegler, Toni Joerg

2016-04-26

Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For {sup 242}Pu, current uncertainties are of around 21%. Sensitivity studies show that the total uncertainty has to be reduced to below 5% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of {sup 235}U and {sup 242}Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of {sup 242}Pu relative to {sup 235}U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of {sup 242}Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using results of different neutron transport simulations (Geant 4, MCNP 6 and FLUKA).

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.

Mathematical processing of experimental data on neutron yield from separate fission fragments

International Nuclear Information System (INIS)

Basova, B.G.; Rabinovich, A.D.; Ryazanov, D.K.

1975-01-01

The algorithm is described for processing the multi-dimensional experiments on measurements of prompt emission of neutrons from separate fission fragments. While processing the data the effect of a number of experimental corrections is correctly taken into account; random coincidence background, neutron spectrum, neutron detector efficiency, instrument angular resolution. On the basis of the described algorithm a program for BESM-4 computer is realized and the treatment of experimental data is performed according to the spontaneous fission of 252 Cf

Fission-neutrons source with fast neutron-emission timing

Energy Technology Data Exchange (ETDEWEB)

Rusev, G., E-mail: rusev@lanl.gov; Baramsai, B.; Bond, E.M.; Jandel, M.

2016-05-01

A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of {sup 252}Cf. The time is provided by registering the fission fragments in a layer of a thin scintillation film with a signal rise time of 1 ns. The scintillation light output is measured by two silicon photomultipliers with rise time of 0.5 ns. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements using it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.

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

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)

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.

Status of measurements of fission neutron spectra of Minor Actinides

Energy Technology Data Exchange (ETDEWEB)

Drapchinsky, L.; Shiryaev, B. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)

1997-03-01

The report considers experimental and theoretical works on studying the energy spectra of prompt neutrons emitted in spontaneous fission and neutron induced fission of Minor Actinides. It is noted that neutron spectra investigations were done for only a small number of such nuclei, most measurements, except those of Cf-252, having been carried out long ago by obsolete methods and imperfectapparatus. The works have no detailed description of experiments, analysis of errors, detailed numerical information about results of experiments. A conclusion is made that the available data do not come up to modern requirements. It is necessary to make new measurements of fission prompt neutron spectra of transuranium nuclides important for the objectives of working out a conception of minor actinides transmutation by means of special reactors. (author)

Simultaneous investigation of fission fragments and neutrons in 252Cf(s,f)

International Nuclear Information System (INIS)

Budtz-Joergensen, C.; Knitter, H.H.

1986-01-01

The gridded twin ion chamber developed at CBNM is used to measure the kinetic energy-, mass- and angular distributions of the fission fragments of 252 Cf in an advantageous 4π-geometry. Together with a neutron time-of-flight detector this experimental arrangement permits to measure the correlation between neutron emission, fragment angle, mass and energy in the spontaneous fission of 252 Cf. With the present experimental set-up a mass resolution for fission fragments of 0.5 a.m.u., an angular resolution of Δcosθ = 0.05 and a timing resolution of 0.7 ns FWHM were observed. Preliminary evaluations of the raw experimental data are presented for the fission fragment mass distribution, the average total kinetic energy and their variance as function of mass, the angular distribution between fragments and neutrons, the number of neutrons emitted per fragment as function of fragment mass, the average neutron emission energies as function of mass, and the prompt fission neutron spectrum averaged over all fragments. (author)

Further microscopic studies of the fission barriers of heavy nuclei

International Nuclear Information System (INIS)

Nhan Hao, T.V.; Le Bloas, J.; Bonneau, L.; Quentin, P.; Koh, Meng-Hock

2012-01-01

Two systematic sources of error in most current microscopic evaluations of fission-barrier heights are studied. They are concerned with an approximate treatment of the Coulomb exchange terms (known as the Slater approximation) in the self-consistent mean-fields and the projection on good parity states (e.g., of positive parity for the spontaneous fission of an even–even nucleus) of left–right reflection asymmetric intrinsic solutions (e.g., around the second barrier). Approximate or unprojected solutions are shown to lead each to an underestimation of the barrier heights by a few hundred keV. (author)

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

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).

Prompt fissionγ-ray characteristics from neutron-induced fission on 239Pu and the time-dependence of prompt-γray emission

Science.gov (United States)

Gatera, Angélique; Göök, Alf; Hambsch, Franz-Josef; Moens, André; Oberstedt, Andreas; Oberstedt, Stephan; Sibbens, Goedele; Vanleeuw, David; Vidali, Marzio

2018-03-01

Recent years have seen an increased interest in prompt fission γ-ray (PFG) measurements motivated by a high priority request of the OECD/NEA for high precision data, mainly for the nuclear fuel isotopes 235U and 239Pu. Our group has conducted a PFG measurement campaign using state-of-the-art lanthanum halide detectors for all the main actinides to a precision better than 3%. The experiments were performed in a coincidence setup between a fission trigger and γ-ray detectors. The time-of-flight technique was used to discriminate photons, traveling at the speed of light, and prompt fission neutrons. For a full rejection of all neutrons below 20 MeV, the PFG time window should not be wider than a few nanoseconds. This window includes most PFG, provided that no isomeric states were populated during the de-excitation process. When isomeric states are populated, PFGs can still be emitted up to 1 yus after the instant of fission or later. To study these γ-rays, the detector response to neutrons had to be determined and a correction had to be applied to the γ-ray spectra. The latest results for PFG characteristics from the reaction 239Pu(nth,f) will be presented, together with an analysis of PFGs emitted up to 200 ns after fission in the spontaneous fission of 252Cf as well as for thermal-neutron induced fission on 235U and 239Pu. The results are compared with calculations in the framework of the Hauser-Feshbach Monte Carlo code CGMF and FIFRELIN.

Time-zero fission-fragment detector based on low-pressure multiwire proportional chambers

International Nuclear Information System (INIS)

Assamagan, K.; Baker, K.; Bayatyan, G.; Carlini, R.; Danagoulian, S.; Eden, T.; Egiyan, K.; Ent, R.; Fenker, H.; Gan, L.; Gasparian, A.; Grigoryan, N.; Greenwood, Z.; Gueye, P.; Hashimoto, O.; Johnston, K.; Keppel, C.; Knyazyan, S.; Majewski, S.; Margaryan, A.; Margaryan, Yu.; Marikyan, G.; Martoff, J.; Mkrtchyan, H.; Parlakyan, L.; Sato, Y.; Sawafta, R.; Simicevic, N.; Tadevosyan, V.; Takahashi, T.; Tang, L.; Vartanyan, G.; Vulcan, W.; Wells, S.; Wood, S.

1999-01-01

A time-zero fission fragment (FF) detector, based on the technique of low-pressure multiwire proportional chambers (LPMWPC), has been designed and constructed for the heavy hypernuclear lifetime experiment (E95-002) at Thomas Jefferson National Accelerator Facility. Its characteristics and the method of time-zero reconstruction were investigated using fission fragments from a 252 Cf spontaneous fission source. The influence of the ionization energy loss was also studied. It is shown that Heptane, Hexane, and Isobutane gases at a pressure of 1-2 Torr are all suitable for such a FF detector. As desired by experiment, a timing resolution of about 200 ps (FWHM) for a chamber size of 21x21 cm 2 was achieved

Study of fission mechanism with the reactions 230Th, 231Pa, 235U, 237Np(n,f) and 252Cf(fs)

International Nuclear Information System (INIS)

Benfoughal, T.

1983-01-01

In this work, the different stages of the nuclear fission process have been investigated. The analysis of fission cross-section and fission fragment angular distribution measurements are made using the hypothesis of asymmetrically deformed states. From the correlation between fissioning nucleus excitation energy and fragment total kinetic energy measurement for several fissioning systems, it is shown that the nuclear viscosity is relatively strong during the saddle-point to scission-point transition. The study of the spontaneous fission of 252 Cf shows that the fragment mass and kinetic energy distributions are mainly determinated by the nucleon shell effects and pairing correlations [fr

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-03-15

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

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

Fission theory and actinide fission data

Energy Technology Data Exchange (ETDEWEB)

Michaudon, A.

1975-06-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2002-01-01

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

Cluster radioactivity and very asymmetric fission through quasi-molecular shapes

International Nuclear Information System (INIS)

Royer, G.

1997-01-01

The decay of radioactive nuclei which emit heavy clusters like C, O, Ne, Mg and Si has been studied in the fission valley which leads one spherical nucleus towards two spherical touching nuclei before crossing the barrier. Assuming volume conservation, the deformation energy has been calculated within a generalized liquid drop model taking into account the proximity effects between the cluster and the daughter nucleus. The theoretical partial half-lives obtained within the WKB barrier penetration probability are in good agreement with the experimental data for the heaviest clusters. The Ne, Mg and Si emission looks like a very-asymmetric spontaneous fission. The 14 C radioactivity is not correctly described within the fission hypothesis. The 14 C and apparently also the 20 O are probably pre-born in the parent nucleus, the emission being similar to the α decay process. (author)

Isotopic composition of primary xenon and the fission of Pu-244

Energy Technology Data Exchange (ETDEWEB)

Levskii, L K

1983-05-01

The hypothesis that the origin of xenon on earth is due to the fission of uranium and/or transuranium elements is examined. The isotopic composition of primary xenon on earth is calculated using a model (Levskii, 1980) of the isotopic composition of rare gases which is based on the hypothesis of the heterogeneity of the isotopic composition of the elements of the solar system. The isotopic composition of fission-produced xenon in the atmosphere and solid earth is determined to correspond to the abundance of xenon isotopes as a result of the spontaneous fission of Pu-244 (half-life of 8.2 x 10 to the 7th years). The amount of fission-produced xenon in the atmosphere is shown to amount to about 30 percent (Xe-136). Under certain conditions, the degree of the degassing of the solid earth for xenon is 25 percent, which corresponds to a ratio of Kr-84/Xe-130 45 for the earth as a whole.

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...

Endo- and exocytic rate constants for spontaneous and protein kinase C-activated T cell receptor cycling

DEFF Research Database (Denmark)

Menné, Charlotte; Møller Sørensen, Tine; Siersma, Volkert

2002-01-01

To determine the rate constants of spontaneous and activated TCR cycling, we examined TCR endo- and exocytosis in the human T cell line Jurkat by three different methods. Using a simple kinetic model for TCR cycling and non-linear regression analyses, we found that the spontaneous endocytic rate...... constant of the TCR was low (approximately 0.012 min(-1)) whereas the spontaneous exocytic rate constant was similar to that of other cycling receptors (approximately 0.055 min(-1)). Following protein kinase C activation (PKC) the endocytic rate constant was increased tenfold (to approximately 0.128 min(-1......)) whereas the exocytic rate constant was unaffected. Thus, the TCR becomes a rapidly cycling receptor with kinetics similar to classical cycling receptors subsequent to PKC activation. This results in a reduction of the half-life of cell surface expressed TCR from approximately 58 to 6 min and allows rapid...

Time-zero fission-fragment detector based on low-pressure multiwire proportional chambers

CERN Document Server

Assamagan, Ketevi A; Bayatyan, G L; Carlini, R; Danagulyan, S; Eden, T; Egiyan, K; Ent, R; Fenker, H; Gan, L; Gasparian, A; Grigoryan, N K; Greenwood, Z; Gueye, P; Hashimoto, O; Johnston, K; Keppel, C; Knyazyan, S; Majewski, S; Margaryan, A; Margaryan, Yu L; Marikian, G G; Martoff, J; Mkrtchyan, H G; Parlakyan, L; Sato, Y; Sawafta, R; Simicevic, N; Tadevosyan, V; Takahashi, T; Tang, L; Vartanian, G S; Vulcan, W; Wells, S; Wood, S

1999-01-01

A time-zero fission fragment (FF) detector, based on the technique of low-pressure multiwire proportional chambers (LPMWPC), has been designed and constructed for the heavy hypernuclear lifetime experiment (E95-002) at Thomas Jefferson National Accelerator Facility. Its characteristics and the method of time-zero reconstruction were investigated using fission fragments from a sup 2 sup 5 sup 2 Cf spontaneous fission source. The influence of the ionization energy loss was also studied. It is shown that Heptane, Hexane, and Isobutane gases at a pressure of 1-2 Torr are all suitable for such a FF detector. As desired by experiment, a timing resolution of about 200 ps (FWHM) for a chamber size of 21x21 cm sup 2 was achieved.

Ddb1 controls genome stability and meiosis in fission yeast

DEFF Research Database (Denmark)

Holmberg, Christian Henrik; Fleck, Oliver; Hansen, H. A.

2005-01-01

The human UV-damaged DNA-binding protein Ddb1 associates with cullin 4 ubiquitin ligases implicated in nucleotide excision repair (NER). These complexes also contain the signalosome (CSN), but NER-relevant ubiquitination targets have not yet been identified. We report that fission yeast Ddb1......, Cullin 4 (Pcu4), and CSN subunits Csn1 and Csn2 are required for degradation of the ribonucleotide reductase (RNR) inhibitor protein Spd1. Ddb1-deficient cells have >20-fold increased spontaneous mutation rate. This is partly dependent on the error-prone translesion DNA polymerases. Spd1 deletion...... substantially reduced the mutation rate, suggesting that insufficient RNR activity accounts for ~50% of observed mutations. Epistasis analysis indicated that Ddb1 contributed to mutation avoidance and tolerance to DNA damage in a pathway distinct from NER. Finally, we show that Ddb1/Csn1/Cullin 4-mediated Spd1...

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Identification and systematical studies of the electron-capture delayed fission (ECDF) in the lead region

CERN Multimedia

Pauwels, D B; Lane, J

2008-01-01

In our recent experiment (March 2007) at the velocity filter SHIP(GSI) we observed the electron-capture delayed fission of the odd-odd isotope $^{194}$At. This is the first unambiguous identification of this phenomenon in the very neutron-deficient nuclei in the vicinity of the proton shell closure at Z=82. In addition, the total kinetic energy (TKE) for the daughter nuclide $^{194}$Po was measured, despite the fact that this isotope does not decay via spontaneous fission. Semi-empirical analysis of the electron-capture Q$_{EC}$ values and fission barriers B$_{f}$ shows that a relatively broad island of ECDF must exist in this region of the Nuclide Chart, with some of the nuclei having unusually high ECDF probabilities. Therefore, this Proposal is intended to initiate the systematic identification and study of $\\beta$-delayed fission at ISOLDE in the very neutron-deficient lead region. Our aim is to provide unique low-energy fission data (e.g. probabilities, TKE release, fission barriers and their isospin dep...

Studies on fission tracks and distributions of uranium and rare earths in granite materials

International Nuclear Information System (INIS)

Matsuda, Hiroshi; Sakanoue, Masanobu

1987-01-01

Many materials contain fossil records of the slow spontaneous fission of uranium they contain as an impurity. Fission fragments, heavy charged particles released in each fission event, produce microscopic trails of radiation damage that may persist over geological times and may be developed to a size observable under an optical microscope by a suitable etching treatment. Such tracks are also produced by fissions induced by thermal neutron irradiation of the uranium. When the material is heated sufficiently, it anneals and the the microscopic trails become shorter and narrower. The track density decreases, because the chemical etchant will not reach some of the shortened tracks. Measurements of track densities before and after annealing can be used, along with laboratory studies of annealing rates, to determine the annealing temperature. Also, the track density of induced fissions is related to the concentration of uranium and the fluence of neutrons to which it was exposed. If the track density due to induced fissions can be distinguished from that due to fossil tracks, estimates of either the concentration or the fluence can be made if the other is known. Two such materials (one a fragment of a granite paving stone, the other a piece of stained glass from a cathedral window) that had been exposed to the atomic bomb at Nagasaki were used in the present work. The fossil record in zircons in the granite was used to estimate the temperature to which it had been exposed in the bombing. Induced fissions were used to estimate the concentration of uranium in the zircons. Nonuniform heating and cooling and nearly uniform exposure to the neutrons make the granite sample unsuitable for determining the neutron fluence from the bomb. Induced fissions in the stained glass were used to estimate the concentration of uranium and the thermal neutron fluence from the A-bomb. Annealing of tracks in glass was also studied

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

International Nuclear Information System (INIS)

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

1979-02-01

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

Transfer of spontaneously hatching or hatched blastocyst yields better pregnancy rates than expanded blastocyst transfer

Directory of Open Access Journals (Sweden)

Natachandra M Chimote

2013-01-01

Full Text Available Context: Blastocyst stage embryo transfer (ET has become routine practice in recent years. However, probably due to limitations of assisted hatching techniques, expanded blastocyst transfer (EBT is still the preferred mode. Inexplicably, not much consideration has been given to spontaneously hatching/hatched blastocyst transfer (SHBT. Aim: This study aimed to investigate developmental potential of spontaneously hatching/hatched blastocyst against EBT in in vitro fertilization (IVF cycles. Settings and Design: Prospective study of 146 women undergoing their first IVF- ET cycle. SUBJECTS AND Methods: On the basis of blastocyst status, women were classified into SHBT and EBT groups. Intracytoplasmic sperm injection cycles were excluded to remove male factor bias. Implantation rate (IR, clinical pregnancy rate, and live birth rate were the main outcome measures. Statistical Analysis: Graph-pad Prism 5 statistical package. Results: SHBT group showed significantly higher blastocyst formation rate (53.3 ± 17.5 vs. 43.1 ± 14.5%, P = 0.0098, top-quality blastocysts (71.8 vs. 53.7%, P = 0.0436, IR (43.6 vs. 27.9%, P = 0.0408, pregnancy rate (59.4 vs. 45.1%, P = 0.0173, and live birth rate (36.8 vs. 22.8%, P = 0.003 compared to EBT group. Multiple pregnancy rates remained comparable between the two groups. Implantation correlated strongly with top-quality blastocysts (Pearson, r = 0.4441 in SHBT group, while the correlation was nonsignificant in EBT group. Conclusion: Extending culture of expanded blastocysts by a few hours to allow transfer of spontaneously hatching/hatched blastocysts gives higher implantation and pregnancy rates with no added risk of multiple gestations. Spontaneously hatching/hatched blastocysts have a better potential to implant and develop into a positive pregnancy.

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-07-01

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

Evaluation and compilation of fission product yields 1993

International Nuclear Information System (INIS)

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

1995-01-01

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

Evaluation and compilation of fission product yields 1993

Energy Technology Data Exchange (ETDEWEB)

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

1995-12-31

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-10-01

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

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

Science.gov (United States)

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

2017-10-01

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

Estimating spontaneous mutation rates at enzyme loci in Drosophila melanogaster

International Nuclear Information System (INIS)

Mukai, Terumi; Yamazaki, Tsuneyuki; Harada, Ko; Kusakabe, Shin-ichi

1990-04-01

Spontaneous mutations were accumulated for 1,620,826 allele-generations on chromosomes that originated from six stem second chromosomes of Drosophila melanogaster. Only null-electromorph mutations were detected. Band-electromorph mutations were not found. The average rate of null-electromorph mutations was 2.71 x 10 -5 per locus per generation. The 95% confidence interval (μ n ) was 1.97 x 10 -5 n -5 per locus per generation. The upper 95% confidence limit of the band-electromorph mutation rate (μ B ) was 2.28 x 10 -6 per locus per generation. It appeared that null mutations were induced by movable genetic elements and that the mutation rates were different from chromosome to chromosome. (author)

The relationship between fission track length and track density in apatite

International Nuclear Information System (INIS)

Laslett, G.M.; Gleadow, A.J.W.; Duddy, I.R.

1984-01-01

Fission track dating is based upon an age equation derived from a random line segment model for fission tracks. This equation contains the implicit assumption of a proportional relationship between the true mean length of fission tracks and their track density in an isotropic medium. Previous experimental investigation of this relationship for both spontaneous and induced tracks in apatite during progressive annealment model in an obvious fashion. Corrected equations relating track length and density for apatite, an anisotropic mineral, show that the proportionality in this case is between track density and a length factor which is a generalization of the mean track length combining the actual length and crystallographic orientation of the track. This relationship has been experimentally confirmed for induced tracks in Durango apatite, taking into account bias in sampling of the track lengths, and the effect of the bulk etching velocity. (author)

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

A Constant Rate of Spontaneous Mutation in DNA-Based Microbes

Science.gov (United States)

Drake, John W.

1991-08-01

In terms of evolution and fitness, the most significant spontaneous mutation rate is likely to be that for the entire genome (or its nonfrivolous fraction). Information is now available to calculate this rate for several DNA-based haploid microbes, including bacteriophages with single- or double-stranded DNA, a bacterium, a yeast, and a filamentous fungus. Their genome sizes vary by ≈6500-fold. Their average mutation rates per base pair vary by ≈16,000-fold, whereas their mutation rates per genome vary by only ≈2.5-fold, apparently randomly, around a mean value of 0.0033 per DNA replication. The average mutation rate per base pair is inversely proportional to genome size. Therefore, a nearly invariant microbial mutation rate appears to have evolved. Because this rate is uniform in such diverse organisms, it is likely to be determined by deep general forces, perhaps by a balance between the usually deleterious effects of mutation and the physiological costs of further reducing mutation rates.

Fission fragment angular distributions and fission cross section validation

International Nuclear Information System (INIS)

Leong, Lou Sai

2013-01-01

sphere was surrounded by enriched uranium 235 U so as to approach criticality with fast neutrons. The simulation predicts a multiplication factor k eff in better agreement with the experiment (the deviation of 750 pcm is reduced to 250 pcm) when we replace the ENDF/B- VII.0 evaluation of the 237 Np fission cross section by the n-TOF data. We also explore the hypothesis of deficiencies of the inelastic cross section in 235 U which has been invoked by some authors to explain the deviation of 750 pcm. The large distortion that should be applied to the inelastic cross sections in order to reconcile the critical experiment with its simulation is incompatible with existing measurements. Also we show that the ν-bar of 237 Np can hardly be incriminated because of the high accuracy of the existing data. Fission rate ratios or averaged fission cross sections measured in several fast neutron fields seem to give contradictory results on the validation of the 237 Np cross section but at least one of the benchmark experiments, where the active deposits have been well calibrated for the number of atoms, favors the n-TOF data set. These outcomes support the hypothesis of a higher fission cross section of 237 Np. (author)

Apatite fission track dating and thermal history of Qing-He region in Altay Mountains

International Nuclear Information System (INIS)

Bao Zengkuan; Chinese Academy of Sciences, Beijing; Yuan Wanming; Dong Jinquan; Gao Shaokai

2005-01-01

Fission track ages (FTA) and track lengths of apatite from Qing-He diorite intrusion in Altay Mountains are measured. Apatite fission track ages of three diorite samples is range from (78±5) Ma to (95 ± 5) Ma, and the lengths of horizontal confined spontaneous fission tracks are (13.2 ± 1.2)-(13.5 ±1.3) μm. The distribution of the track length is narrow and symmetrical with a mean length of approximately 13.3 μm and a standard deviation of around 0.1 μm. The inverse modeling results show that thermal history of this region has four stages, two rapid uplift of this region still existed magmatic intrusion and tectonic movements in Yanshanian. (authors)

Spontaneous mutation by mutagenic repair of spontaneous lesions in DNA

International Nuclear Information System (INIS)

Hastings, P.J.; Quah, S.-K.; Borstel, R.C. von

1976-01-01

It is stated that strains of yeast carrying mutations in many of the steps in pathways repairing radiation-induced damage to DNA have enhanced spontaneous mutation rates. Most strains isolated because they have enhanced spontaneous mutation carry mutations in DNA repair systems. This suggests that much spontaneous mutation arises by mutagenic repair of spontaneous lesions. (author)

Ternary fission in an effective liquid drop model

International Nuclear Information System (INIS)

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

2001-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

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

Non-destructive assay of fissile materials by detection and multiplicity analysis of spontaneous neutrons

International Nuclear Information System (INIS)

Prosdocimi, A.

1979-01-01

A method for determining the absolute reaction rate of nuclear events giving rise to neutron emission, according to their neutron multiplicity, is proposed. A typical application is the measurement of the (α, n) and spontaneous fission rates in a fissile material sample, particularly of Pu oxide composition. An analysis of random and correlated neutron pulses is carried out on the basis of sequential order without requiring any time interval analysis, then the primary nuclear events are sorted versus their neutron multiplicity. Suitable theoretical relationships enable to derive the absolute (α, n) and SF reaction rates when the physical parameters of the neutron detector and the multiplicity spectrumm of pulses are known. A typical device is described and the results of experiments leading to Pu-239 and Pu-240 assay are given

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2018-01-01

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

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.

Influence of pairing correlations on the probability and dynamics of tunneling through the barrier in fission and fusion of complex nuclei

International Nuclear Information System (INIS)

Lazarev, Yu.A.

1986-01-01

An analytically solvable model is used to study the potential barrier penetrability in the case when the gap parameter Δ is treated as a dynamical variable governed by the least action principle. It is found that, as compared to the standard (BCS) approach, the dynamical treatment of pairing results in a considerably weakened dependence of the fission barrier penetrability on the intensity of pairing correlations in the initial state (Δ 0 ), on the barrier height, and on the energy of the initial state. On this basis, a more adequate explanation is proposed for typical order-of-magnitude values of the empirical hidrance factors for groun-state spontaneous fission of odd nuclei. It is also shown that a large enhancement of superfluidity in tunneling - the inherent effect of the dynamical treatment of pairing - strongly facilitates deeply subbarier fusion of complex nuclei. Finally, an analysis is given for the probability of spontaneous fission from K-isomeric quasiparticle (q-p) states in even-even heavy nuclei. The relative change of the partial spontaneous fission half-life in going from the ground-state to a high-spin q-p isomeric state, T* sf /T sf , is found to be strongly dependent on whether or not there takes place the dynamically induced enhancement of superfluidity in tunneling. Measurements of T* sf /T sf provide thus a unique possibility of verifying theoretical predictions about the strong, inverse-square Δ dependence of the effective inertia associated with large-scale subbarrier rearrangements of nuclei

Overview of tritium fast-fission yields

International Nuclear Information System (INIS)

Tanner, J.E.

1981-03-01

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

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

Science.gov (United States)

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

2015-12-01

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

A twin Frisch-grid ionization chamber as a selective detector for the delayed gamma-spectroscopy of fission fragments

Energy Technology Data Exchange (ETDEWEB)

Gaudefroy, L., E-mail: laurent.gaudefroy@cea.fr [CEA, DAM, DIF, F-91297 Arpajon (France); Roger, T., E-mail: roger@ganil.fr [GANIL, CEA/DSM-CNRS/IN2P3, BP 55027, F-14076 Caen (France); Pancin, J., E-mail: pancin@ganil.fr [GANIL, CEA/DSM-CNRS/IN2P3, BP 55027, F-14076 Caen (France); Spitaels, C. [GANIL, CEA/DSM-CNRS/IN2P3, BP 55027, F-14076 Caen (France); Aupiais, J. [CEA, DAM, DIF, F-91297 Arpajon (France); Mottier, J. [Institut de Physique Nucléaire, Université Paris-Sud-11-CNRS-IN2P3, F-91406 Orsay (France)

2017-05-21

We present a twin Frisch-grid ionization chamber. The detector is meant to provide high selective power for the study of delayed gamma-ray spectroscopy of fission fragments produced via {sup 252}Cf spontaneous fission. A mean energy resolution on the kinetic energy of fission fragments of 675 keV (FWHM) is achieved and allows us to resolve masses of fragments for fission events where neutron emission is not energetically possible. The mean mass resolution measured for these particular events amounts to 0.54 mass units (FWHM). For fission events with neutron emission a resolution of 4 mass units (FWHM) is reported. Information on fragment emission angle is measured with a resolution of 0.1 on the difference of the cosines determined for both halves of the detector. A charge resolution of 4.5 charge units (FWHM) is also demonstrated.

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

Assessment of baroreflex sensitivity from spontaneous oscillations of blood pressure and heart rate: proven clinical value?

International Nuclear Information System (INIS)

Pinna, Gian Domenico; Maestri, Roberto; La Rovere, Maria Teresa

2015-01-01

The baroreceptor-heart rate reflex (baroreflex sensitivity, BRS) is a key mechanism contributing to the neural regulation of the cardiovascular system. Several methods have been proposed so far to assess BRS by analyzing the spontaneous beat-to-beat fluctuations of arterial blood pressure and heart rate. These methods are inherently simple, non-invasive and low-cost. This study is an attempt to address the question of whether spontaneous baroreflex methods have proven to be of value in the clinical setting. In the first part of this article, we critically review most representative clinical studies using spontaneous BRS techniques either for risk stratification or treatment evaluation, these being major issues in the clinical management of the patients. In the second part, we address two important aspects of spontaneous BRS measurements: measurability and reliability. Estimation of BRS in the studies selected for the review was performed according to the sequence, transfer function, alpha-index and phase-rectified signal averaging method. Arterial blood pressure was recorded non-invasively during supine, short-term (<30 min) laboratory recordings. The conclusion from this review is that spontaneous BRS techniques have been shown to be of great value in clinical practice but further work is needed to confirm the validity of previous findings and to widen the field of clinical applications. Measurability and reliability can be a major issue in the measurement of spontaneous BRS, particularly in some patient populations like post-myocardial infarction and heart failure patents. Main causes of poor measurability are: non-sinus rhythm, a high rate of ectopic beats and the need for recorded time series of RR interval and arterial blood pressure to satisfy the constraints of the different BRS estimation algorithms. As for reliability, within-subject variability is rather high in the measurements of spontaneous BRS and, therefore, should be carefully taken into account

(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.

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

International Nuclear Information System (INIS)

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

2008-01-01

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

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)

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

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)

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

International Nuclear Information System (INIS)

Hansen, W.; Vogel, W.

1984-04-01

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

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

The rate of spontaneous mutations in human myeloid cells

International Nuclear Information System (INIS)

Araten, David J.; Krejci, Ondrej; DiTata, Kimberly; Wunderlich, Mark; Sanders, Katie J.; Zamechek, Leah; Mulloy, James C.

2013-01-01

Highlights: • We provide the first measurement of the mutation rate (μ) in human myeloid cells. • μ is measured to be 3.6–23 × 10 −7 per cell division. • The AML-ETO and MLL-AF9 fusions do not seem to increase μ. • Cooperating mutations in NRAS, FLT3 and p53 not seem to increase μ. • Hypermutability may be required to explain leukemogenesis. - Abstract: The mutation rate (μ) is likely to be a key parameter in leukemogenesis, but historically, it has been difficult to measure in humans. The PIG-A gene has some advantages for the detection of spontaneous mutations because it is X-linked, and therefore only one mutation is required to disrupt its function. Furthermore, the PIG-A-null phenotype is readily detected by flow cytometry. Using PIG-A, we have now provided the first in vitro measurement of μ in myeloid cells, using cultures of CD34+ cells that are transduced with either the AML-ETO or the MLL-AF9 fusion genes and expanded with cytokines. For the AML-ETO cultures, the median μ value was ∼9.4 × 10 −7 (range ∼3.6–23 × 10 −7 ) per cell division. In contrast, few spontaneous mutations were observed in the MLL-AF9 cultures. Knockdown of p53 or introduction of mutant NRAS or FLT3 alleles did not have much of an effect on μ. Based on these data, we provide a model to predict whether hypermutability must occur in the process of leukemogenesis

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

Pion-induced fission of 209Bi and 119Sn: measurements, calculations, analyses and comparison

International Nuclear Information System (INIS)

Rana, M.A.; Sher, G.; Manzoor, S.; Shehzad, M.I.

2011-01-01

Cross-sections for the π - -induced fission of 209 Bi and 119 Sn have been measured using the most sensitive CR-39 solid-state nuclear track detector. In experiments, target–detector stacks were exposed to negative pions of energy 500, 672, 1068, and 1665 MeV at the Brookhaven National Laboratory, USA. An important aspect of the present paper is the comparison of pion-induced fission fragment spectra of above mentioned nuclei with the spontaneous fission fragment spectra of 252 Cf. This comparison is made in terms of fission fragment track lengths in the CR-39 detectors. Measurement results are compared with calculations of Monte Carlo and statistical weight functions methods using the computer code CEM95. Agreement between measurements and calculations is fairly good for 209 Bi target nuclei whereas it is indigent for the case of 119 Sn. The possibilities of the trustworthy calculations, using the computer code CEM95, comparable with measurements of pion-induced fission in intermediate and heavy nuclei are explored by employing various systematics available in the code. Energy dependence of pion-induced fission in 119 Sn and 209 Bi is analyzed employing a newly defined parameter geometric-size-normalized fission cross-section (χ f g ). It is found that the collective nuclear excitations, which may lead to fission, become more probable for both 209 Bi and 119 Sn nuclei with increasing energy of negative pions from 500 to 1665 MeV. (author)

Fission in R-processes Elements (FIRE) - Annual Report: Fiscal Year 2017

Energy Technology Data Exchange (ETDEWEB)

Schunck, Nicolas [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-10-18

The goal of the FIRE topical collaboration in nuclear theory is to determine the astrophysical conditions of the rapid neutron capture process (r-process), which is responsible for the formation of heavy elements. This will be achieved by including in r-process simulations the most advanced models of fission (spontaneous, neutron-induced, beta-delayed) that have been developed at LLNL and LANL. The collaboration is composed of LLNL (lead) and LANL for work on nuclear data (ground-state properties, fission, beta-decay), BNL for nuclear data management, and the university of Notre Dame and North Carolina State University for r-process simulations. Under DOE/NNSA agreement, both universities receive funds from the DOE Office of Science, while national laboratories receive funds directly from NA221.

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

Energy Technology Data Exchange (ETDEWEB)

Oberstedt, S.; Hambsch, F.J. [Joint Research Centre IRMM, European Commission, Geel (Belgium); Billnert, R. [Joint Research Centre IRMM, European Commission, Geel (Belgium); Chalmers Tekniska Hoegskola, Fundamental Fysik, Goeteborg (Sweden); Lebois, M.; Wilson, J.N. [Institut de Physique Nucleaire Orsay, Orsay (France); Oberstedt, A. [Chalmers Tekniska Hoegskola, Fundamental Fysik, Goeteborg (Sweden); Ossolution Consulting, Oerebro (Sweden)

2015-12-15

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

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Spontaneous emission of heavy-ions from uranium

International Nuclear Information System (INIS)

Carvalho, H.G. de; Martins, J.B.; Souza, I.O. de; Tavares, O.A.P.

1974-09-01

The experimental evidences that 238 U, and perhaps other heavy nuclei, besides undergoing spontaneous fission, are also emitters of ions in the mass-range from 20 to 70. Estimates obtained by means of the WKB method indicate half-lifes of 10 15 to 10 18 years for some of these processes, which agree with our findings. Our results are supported by a systematic observation of neon and argon with abnormal isotopic abundance in both radioactive minerals and helium-bearing natural gases

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-15

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

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)

Mass and Inertia Parameters for Nuclear Fission

International Nuclear Information System (INIS)

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

1969-01-01

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

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

Experimental characterization of true spontaneous emission rate of optically-pumped InGaAs/GaAs quantum-well laser structure

Directory of Open Access Journals (Sweden)

Q.-N. Yu

2017-08-01

Full Text Available In this paper, an experimental approach to acquiring true spontaneous emission rate of optically-pumped InGaAs/GaAs quantum-well laser structure is described. This method is based on a single edge-emitting laser chip with simple sample processing. The photoluminescence spectra are measured at both facets of the edge-emitting device and transformed to the spontaneous emission rate following the theory described here. The unusual double peaks appearing in the spontaneous emission rate spectra are observed for the InGaAs/GaAs quantum-well structure. The result is analyzed in terms of Indium-rich island and Model-Solid theories. The proposed method is suitable for electrically-pumped quantum-well laser structures, as well.

Analysis of linear energy transfers and quality factors of charged particles produced by spontaneous fission neutrons from 252Cf and 244Pu in the human body

International Nuclear Information System (INIS)

Endo, A.; Sato, T.

2013-01-01

Absorbed doses, linear energy transfers (LETs) and quality factors of secondary charged particles in organs and tissues, generated via the interactions of the spontaneous fission neutrons from. 252 Cf and. 244 Pu within the human body, were studied using the Particle and Heavy Ion Transport Code System (PHITS) coupled with the ICRP Reference Phantom. Both the absorbed doses and the quality factors in target organs generally decrease with increasing distance from the source organ. The analysis of LET distributions of secondary charged particles led to the identification of the relationship between LET spectra and target-source organ locations. A comparison between human body-averaged mean quality factors and fluence-averaged radiation weighting factors showed that the current numerical conventions for the radiation weighting factors of neutrons, updated in ICRP103, and the quality factors for internal exposure are valid. (authors)

Improved fission neutron energy discrimination with {sup 4}He detectors through pulse filtering

Energy Technology Data Exchange (ETDEWEB)

Zhu, Ting, E-mail: ting.zhu@ufl.edu [University of Florida, Gainesville, FL (United States); Liang, Yinong; Rolison, Lucas; Barker, Cathleen; Lewis, Jason; Gokhale, Sasmit [University of Florida, Gainesville, FL (United States); Chandra, Rico [Arktis Radiation Detectors Ltd., Räffelstrasse 11, Zürich (Switzerland); Kiff, Scott [Sandia National Laboratories, CA (United States); Chung, Heejun [Korean Institute for Nuclear Nonproliferation and Control, 1534 Yuseong-daero, Yuseong-gu, Daejeon (Korea, Republic of); Ray, Heather; Baciak, James E.; Enqvist, Andreas; Jordan, Kelly A. [University of Florida, Gainesville, FL (United States)

2017-03-11

This paper presents experimental and computational techniques implemented for {sup 4}He gas scintillation detectors for induced fission neutron detection. Fission neutrons are produced when natural uranium samples are actively interrogated by 2.45 MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greater than 2.45 MeV can be distinguished by their different scintillation pulse height spectra since {sup 4}He detectors retain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to 10 MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and trigger threshold is increased. Pile-up and other unreliable events due to the interrogating neutron flux and background radiation are filtered out prior to the evaluation of pulse height spectra. With these problem-specific calibrations and data processing, the {sup 4}He detector's accuracy at discriminating fission neutrons up to 10 MeV is improved and verified with {sup 252}Cf spontaneous fission neutrons. Given the {sup 4}He detector's ability to differentiate fast neutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of special nuclear materials detection using a {sup 4}He fast neutron detection system.

Coordinate-dependent mass and the validity of the WKB approximation in fission barrier penetration calculations

International Nuclear Information System (INIS)

Kumar, K.

1990-03-01

It is shown that the quasi-classical condition for the validity of the WKB approximation is satisfied although the mass associated with the spontaneous fission of 240 Pu varies by a factor of 12. A general numerical estimate of the allowed variations in such a mass is also given. (author)

4π-spectrometer technique for measurements of secondary neutron average number in nuclear fission by 252Cf neutrons

International Nuclear Information System (INIS)

Vasil'ev, Yu.A.; Barashkov, Yu.A.; Golovanov, O.A.; Sidorov, L.V.

1977-01-01

A method for determining the average number of secondary neutrons anti ν produced in nuclear fission by the neutrons of the 252 Cf fission spectra by means of a 4π time-of-flight spectrometer is described. Layers of 252 Cf and an isotope studied are placed close to each other; if the isotope layer density is 1 mg/cm 2 probability of its fission is about 10 -5 per one spontaneous fission of californium. Fission fragments of 252 Cf and the isotope investigated have been detected by two surface-barrier counters with an efficiency close to 100%. The layers and the counters are situated in a measuring chamber placed in the center of the 4π time-of-flight spectrometer. The latter is utilized as a neutron counter because of its fast response. The method has been verified by carrying out measurements for 235 U and 239 Pu. A comparison of the experimental and calculated results shows that the method suggested can apply to determine the number of secondary neutrons in fission of isotopes that have not been investigated yet

A new look at statistics in fission-track dating

International Nuclear Information System (INIS)

Green, P.F.

1981-01-01

Poissonian errors, as routinely applied in fission-track dating, represent a limiting case, which may not always be attainable in practice. Other experimental factors may introduce additional non-Poissonian errors, which must be taken into account. In the population method, sampling of non-homogeneous uranium distributions introduces experimental error. In the external detector method (EDM), many factors exist to introduce such error. Simply quoting total numbers of spontaneous and induced fission tracks obtained by the EDM may disguise the possible influence of experimental variation. The present work concentrates on the EDM, and describes a test which has recently been proposed to detect the presence of experimental error in EDM analyses. The question of an alternative analysis for cases where such error is present is also considered. A method of presenting EDM data is suggested, which allows assessment of the importance of experimental errors. (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.

Contribution of the fission-track method to the study of the Alpine chains: relationship between tectonics and metamorphism

International Nuclear Information System (INIS)

Carpena, J.

1984-01-01

The fission-track method allows geologists to date rocks and to get information on the thermal history of rocks. Fission tracks in minerals are essentially due to the spontaneous fission of uranium 238. The knowledge of the density of tracks and the concentration of uranium 238 lead to the determination of the age of the rock. The irradiation in a neutron flux of a sample of the rock allows the determination of the concentration of uranium. The age obtained is in fact an apparent age that does not take into account possible geological annealing process that may erase fission tracks, some corrections are then necessary. The first part of this work details the fission-track method, its scope and limitations. It is shown that fission-track method on apatites can reveal the thermal evolution of the rock and that the same method used on zircons can give information of the setting of volcanic rocks. The second part is dedicated to the contribution of the fission-track method to a both dating and thermal evolution study of a french-italian part of the Alpine chain

Some aspects of the nuclear fission process

International Nuclear Information System (INIS)

Netter, F.

1961-01-01

In the following report one can find first a short general view on the present situation of our knowledge concerning the nuclear fission process, namely on the nucleus going through the saddle-point. Then there are some aspects connected with the excitation energy of the fissioning nucleus. The measurements made at Saclay on the fast neutron fission cross-section of U 233 , U 235 , Pu 239 , U 238 are described at the beginning of this work. It appears that for U 233 there is some characteristic shape modulation of the cross-section curve, in relation with the collective excited state of the deformed nucleus at the saddle-point. Good evidence of this is also given by the study of the relative fission rate with emission of long-range particles; it appears also that this ternary fission rate does not change substantially for neutron between thermal energy and 2 MeV, but that is very lower for the compound nucleus U 239 than for even-even compound nuclei. At the end there are some experiments on the strong 4,5 MeV gamma-ray originated by slow neutron absorption in U 235 . Time-of-flight device is used to establish that this 4,5 MeV gamma-ray seems mostly connected with radiative capture. (author) [fr

The fissioning universe: Topological inflation and Kaluza-Klein cosmologies

International Nuclear Information System (INIS)

Kaku, Michio; Lykken, J.

1986-01-01

We propose a Kaluza-Klein cosmology by reversing the usual scenario: instead of starting with a flat 4+N dimensional universe in which N of the dimensions curl up into a compact manifold, we start with a compact 3+N dimensional manifold in which 3 of the dimensions are allowed to peel off and expand into the known universe. We reverse the usual ''spontaneous compactification'' scenario begin with a closed manifold Msup(3+N) which undergoes ''spontaneous fissioning'' into a product manifold M 3 xMsup(N). Remarkably, the 3-dimensional universe M 3 can undergo a rapid de Sitter expansion large enough to solve the horizon and flatness problem. We call this ''topological inflation'', which we propose as an alternative to the usual GUT inflation. The inflationary phase automatically terminates into a big bang phase. (orig.)

[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

Spontaneous actin dynamics in contractile rings

Science.gov (United States)

Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

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)

Solidification of residual fission-product solutions; laboratory studies; Solidification de solutions residuaires concentrees de produits de fission: etudes de laboratoire

Energy Technology Data Exchange (ETDEWEB)

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

1961-07-01

This paper describes the results obtained, at laboratory scale, during the study of the incorporation of fission products into glasses and synthetic micas. The rate of leaching of fission products from the glass and their volatility during firing were measured. A hot cell was built to complete these results. (author) [French] Ce rapport resume le resultat des etudes faites en laboratoire (activite de l'ordre du millicurie) sur l'incorporation des produits de fission dans des verres et micas synthetiques. On a mesure le taux de lixiviation des produits de fission et leur volatilisation au cours de la cuisson. Une cellule chaude a ete installee pour completer ces resultats au moyen d'essais realises avec une activite superieure. (auteur)

Comparison Of ²⁵²Cf Time Correlated Induced Fisssion With AmLi Induced Fission On Fresh MTR Research Reactor Fuel

Energy Technology Data Exchange (ETDEWEB)

Joshi, Jay Prakash [Los Alamos National Laboratory

2017-03-30

The effective application of international safeguards to research reactors requires verification of spent fuel as well as fresh fuel. To accomplish this goal various nondestructive and destructive assay techniques have been developed in the US and around the world. The Advanced Experimental Fuel Counter (AEFC) is a nondestructive assay (NDA) system developed at Los Alamos National Laboratory (LANL) combining both neutron and gamma measurement capabilities. Since spent fuel assemblies are stored in water, the system was designed to be watertight to facilitate underwater measurements by inspectors. The AEFC is comprised of six ³He detectors as well as a shielded and collimated ion chamber. The ³He detectors are used for active and passive neutron coincidence counting while the ion chamber is used for gross gamma counting. Active coincidence measurement data is used to measure residual fissile mass, whereas the passive coincidence measurement data along with passive gamma measurement can provide information about burnup, cooling time, and initial enrichment. In the past, most of the active interrogation systems along with the AEFC used an AmLi neutron interrogation source. Owing to the difficulty in obtaining an AmLi source, a ²⁵²Cf spontaneous fission (SF) source was used during a 2014 field trail in Uzbekistan as an alternative. In this study, experiments were performed to calibrate the AEFC instrument and compare use of the ²⁵²Cf spontaneous fission source and the AmLi (α,n) neutron emission source. The ²⁵²Cf source spontaneously emits bursts of time-correlated prompt fission neutrons that thermalize in the water and induce fission in the fuel assembly. The induced fission (IF) neutrons are also time correlated resulting in more correlated neutron detections inside the ³He detector, which helps reduce the statistical errors in doubles when using the ²⁵²Cf interrogation source instead of

Fission gas release and pellet microstructure change of high burnup BWR fuel

International Nuclear Information System (INIS)

Itagaki, N.; Ohira, K.; Tsuda, K.; Fischer, G.; Ota, T.

1998-01-01

UO 2 fuel, with and without Gadolinium, irradiated for three, five, and six irradiation cycles up to about 60 GWd/t pellet burnup in a commercial BWR were studied. The fission gas release and the rim effect were investigated by the puncture test and gas analysis method, OM (optical microscope), SEM (scanning electron microscope), and EPMA (electron probe microanalyzer). The fission gas release rate of the fuel rods irradiated up to six cycles was below a few percent; there was no tendency for the fission gas release to increase abruptly with burnup. On the other hand, microstructure changes were revealed by OM and SEM examination at the rim position with burnup increase. Fission gas was found depleted at both the rim position and the pellet center region using EPMA. There was no correlation between the fission gas release measured by the puncture test and the fission gas depletion at the rim position using EPMA. However, the depletion of fission gas in the center region had good correlation with the fission gas release rate determined by the puncture test. In addition, because the burnup is very large at the rim position of high burnup fuel and also due to the fission rate of the produced Pu, the Xe/Kr ratio at the rim position of high burnup fuel is close to the value of the fission yield of Pu. The Xe/Kr ratio determined by the gas analysis after the puncture test was equivalent to the fuel average but not to the pellet rim position. From the results, it was concluded that fission gas at the rim position was released from the UO 2 matrix in high burnup, however, most of this released fission gas was held in the porous structure and not released from the pellet to the free volume. (author)

Fission meter

Science.gov (United States)

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

2012-04-10

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source.

Studies of new modes of radioactive decay by spontaneous emission of complex nuclei

International Nuclear Information System (INIS)

Barwick, S.W.; Hulet, E.K.; Moody, K.; Price, P.B.; Ravn, H.L.

1990-01-01

Impressive progress has been made in the two years since Rose and Jones first reported the novel spontaneous decay mode 223 Ra → 14 C + 209 Pb. Since then, the isotopes 222 Ra, 224 Ra, and 226 Ra have been observed to emit 14 C, and stringent upper limits have been set on branching ratios B( 14 C/α) for 221 Ra and 225 Ac. The discoveries of emission of 24 Ne from 232 U, and 231 Pa, and 233 U show that the phenomenon of heavy ion emission is a general one. A goal of recent experiments by the authors collaboration is to test models that differ by as much as 10 5 in predicted half-lives for the emission of complex nuclei with Z ≥ 12. Due to small branching ratios B approx-lt 10 -14 , and large fission background, they are developing new techniques to insure reliable identification of such rare decay modes. Experimental support for the unified models of alpha decay, complex nuclei emission, and spontaneous fission are addressed

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

Spray removal of fission products in PWR containments

International Nuclear Information System (INIS)

Grist, D.R.

1982-11-01

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

Fission 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)

Neutron multiplicity for neutron induced fission of 235U, 238U, and 239Pu as a function of neutron energy

International Nuclear Information System (INIS)

Zucker, M.S.; Holden, N.E.

1986-01-01

Recent development in the theory and practice of neutron correlation (''coincidence'') counting require knowledge of the higher factorial moments of the P/sub ν/ distribution (the probability that (ν) neutrons are emitted in a fission) for the case where the fission is induced by bombarding neutrons of more than thermal energies. In contrast to the situation with spontaneous and thermal neutron induced fission, where with a few exceptions the P/sub ν/ is reasonably well known, in the fast neutron energy region, almost no information is available concerning the multiplicity beyond the average value, [ν], even for the most important nuclides. The reason for this is the difficulty of such experiments, with consequent statistically poor and physically inconsistent results

Fission time-scale in experiments and in multiple initiation model

Energy Technology Data Exchange (ETDEWEB)

Karamian, S. A., E-mail: karamian@nrmail.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)

2011-12-15

Rate of fission for highly-excited nuclei is affected by the viscose character of the systemmotion in deformation coordinates as was reported for very heavy nuclei with Z{sub C} > 90. The long time-scale of fission can be described in a model of 'fission by diffusion' that includes an assumption of the overdamped diabatic motion. The fission-to-spallation ratio at intermediate proton energy could be influenced by the viscosity, as well. Within a novel approach of the present work, the cross examination of the fission probability, time-scales, and pre-fission neutron multiplicities is resulted in the consistent interpretation of a whole set of the observables. Earlier, different aspects could be reproduced in partial simulations without careful coordination.

An absolute measurement of 252Cf prompt fission neutron spectrum at low energy range

International Nuclear Information System (INIS)

Lajtai, A.; Dyachenko, P.P.; Kutzaeva, L.S.; Kononov, V.N.; Androsenko, P.A.; Androsenko, A.A.

1983-01-01

Prompt neutron energy spectrum at low energies (25 keV 252 Cf spontaneous fission has been measured with a time-of-flight technique on a 30 cm flight-path. Ionization chamber and lithium-glass were used as fission fragment and neutron detectors, respectively. Lithium glasses of NE-912 (containing 6 Li) and of NE-913 (containing 7 Li) 45 mm in diameter and 9.5 mm in thickness have been employed alternatively, for the registration of fission neutrons and gammas. For the correct determination of the multiscattering effects - the main difficulty of the low energy neutron spectrum measurements - a special geometry for the neutron detector was used. Special attention was paid also to the determination of the absolute efficiency of the neutron detector. The real response function of the spectrometer was determined by a Monte-Carlo calculation. The scattering material content of the ionization chamber containing a 252 Cf source was minimized. As a result of this measurement a prompt fission neutron spectrum of Maxwell type with a T=1.42 MeV parameter was obtained at this low energy range. We did not find any neutron excess or irregularities over the Maxwellian. (author)

Natural uranium impurities in fission track detectors and associated geocronological parameters

International Nuclear Information System (INIS)

Ricabarra, G.H.; Bovisio de Ricabarra, M.D.; Waisman, Dina; Faradjie de Turjanski, Rosa

1981-01-01

A technique, based in counting neutron induced fission tracks, has been developed for the measurement of uranium impurities in mica. Uranium concentrations of 10 -10 and 10 -9 (U atom/mica atom) have been measured. As a part of the development of this technique, the mica geological age was also measured, by fossil and induced track detection. The agreement obtained by this method, T = (472+-52) x 10 6 years with that of (450+-15) x 10 6 years obtained by the Ar-K technique is satisfactory and is an indirect test of the fission track technique used. A careful analysis of the neutron field parameters and nuclear data used in the age determination was made. This analysis is useful for applications in geocronology. According to this analysis a value of lambdasub(f)=(7.1+-0.1) x 10 -17 years -1 is recommended for the spontaneous fission of U238. However, in order to compare the results, the quoted age, T=(472+-52) x 10 6 years, was obtained with the generally accepted value of lambdasub(f)=(6.85-0.20) x 10 -17 years -1 (Fleischer and Price 1964). (author) [es

Spontaneous first trimester miscarriage rates per woman among parous women with 1 or more pregnancies of 24 weeks or more.

Science.gov (United States)

Cohain, Judy Slome; Buxbaum, Rina E; Mankuta, David

2017-12-22

The purpose of this study was to quantify spontaneous first trimester miscarriage rates per woman among parous women. A vast amount of data has accumulated regarding miscarriage rates per recognized pregnancy as well as about recurrent miscarriage. This is the second study of miscarriage rates per woman in a parous population and the first study of recurrent and non-recurrent, spontaneous first trimester miscarriage rates per woman in a large parous population. Extraction of the following variables from all delivery room admissions from both Hadassah Medical Centers in Jerusalem Israel, 2004-2014: # of first trimester spontaneous miscarriages, # live births; # living children; age on admission, pre-pregnancy height and weight, any smoking this pregnancy, any alcohol or drug abuse this pregnancy, blood type, history of ectopic pregnancy, history of cesarean surgery (CS) and use of any fertility treatment(s). Among 53,479 different women admitted to labor and delivery ward, 43% of women reported having had 1 or more first trimester spontaneous miscarriages; 27% reported having had one, 10% two, 4% three, 1.3% four, 0.6% five and 0.05% reported having 6-16 spontaneous first trimester miscarriages. 18.5% had one or more first trimester miscarriages before their first live birth. Eighty-one percent of women with 11 or more living children experienced one or more first trimester miscarriages. First trimester miscarriage rates rose with increasing age, increasing parity, after previous ectopic pregnancy, after previous cesarean surgery, with any smoking during pregnancy and pre-pregnancy BMI ≥30. Miscarriages are common among parous women; 43% of parous women report having experienced one or more first trimester spontaneous miscarriages, rising to 81% among women with 11 or more living children. One in every 17 parous women have three or more miscarriages. Depending on her health, nutrition and lifestyle choices, even a 39 year old parous woman with a history of 3 or

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.)

Nuclear inertia for fission in a generalized cranking model

International Nuclear Information System (INIS)

Kunz, J.; Nix, J.R.

1984-01-01

The Inglis cranking model has been widely used to calculate the nuclear inertia associated with collective degrees of freedom. After the inclusion of pairing correlations, theoretical results obtained with the cranking model for nuclear rotations and γ-vibrations were in relatively good agreement with experimental data. Calculations of β-vibrational inertias were also performed in the cranking model for fission deformations. Theoretical results were several times the irrotational values and gave reasonable agreement with experimental spontaneous-fission lifetimes, although in one study a renormalization factor of 0.8 was required. However, as pointed out by many authors, the Inglis cranking model possesses two serious deficiencies. First, problems arise when the single-particle potential contains momentum-dependence terms. Second, in the limit of large pairing strength the inertia approaches zero instead of a finite (irrotational) limit. Alternative approaches to the cranking model which did not lead to such unacceptable results were developed by Migdal, Belyaev and Thouless and Valatin. They showed that these deficiencies of the cranking model are due to a lack of self-consistency, since the reaction of the mean field to the collective motion is neglected in the Inglis model. Previously we used their arguments and developed a generalized cranking model for stationary collective motion. Here it is shown how to develop a time-dependent formalism appropriate to β-vibrations and fission. 10 references

Obsidian ages from Ecuador by the fission track dating

International Nuclear Information System (INIS)

Osorio, A.M.; Hadler, J.C.; Bigazzi, G.; Norelli, P.; Coltelli, M.; Salazar, E.

1991-01-01

Fission track dating was applied in order to study obsidian samples originated from Mullumica and Callejones flows, Oyacachi, Ecuador. Preliminary data show that the ratio between the mean diameter os spontaneous and induced tracks is about 0.9, an indication that the analysed samples were submitted to small fading during their geological histories. Ages were obtained around 0.2 x 10 6 a, in agreement with Miller and Wagners's results. Ages ranging from 0.17 x 10 6 a up to 0.23 x 10 6 a were obtained correcting the apparent ages by means of the plateau method. (author)

Spontaneous-fission decay properties and production cross-sections for the neutron-deficient nobelium isotopes formed in the sup 4 sup 4 sup , sup 4 sup 8 Ca+ sup 2 sup 0 sup 4 sup , sup 2 sup 0 sup 6 sup , sup 2 sup 0 sup 8 Pb reactions

CERN Document Server

Belozerov, A V; Chepigin, V I; Drobina, T P; Gorshkov, V A; Kabachenko, A P; Malyshev, O N; Merkin, I M; Oganessian, Yu T; Popeko, A G; Sagaidak, R N; Svirikhin, A I; Yeremin, A V; Berek, G; Brida, I; Sáro, S

2003-01-01

Heavy-ion fusion reactions sup 4 sup 8 Ca+ sup 2 sup 0 sup 4 Pb and sup 4 sup 4 Ca+ sup 2 sup 0 sup 8 Pb leading to the same compound nucleus sup 2 sup 5 sup 2 No sup * were run in attempts to produce new neutron-deficient spontaneous-fission isotopes of sup 2 sup 4 sup 9 sup , sup 2 sup 5 sup 0 No using the electrostatic separator VASSILISSA. Production cross-sections for the spontaneous-fission activities with the half-lives 5.6 and 54 mu s observed in these reactions are compared with the measured ones for the well-known isotopes of sup 2 sup 5 sup 1 sup - sup 2 sup 5 sup 5 No formed in the heavy-ion fusion reactions sup 4 sup 8 Ca+ sup 2 sup 0 sup 6 Pb and sup 4 sup 8 Ca+ sup 2 sup 0 sup 8 Pb. The obtained excitation functions for the reaction products formed after the evaporation of 1-4 neutrons from the corresponding compound No nuclei have been compared with similar data obtained earlier and results of statistical model calculations. (orig.)

Dating by fission track method: study of neutron dosimetry with natural uranium thin films; Datacao com o metodo dos tracos de fissao: estudo da dosimetria de neutrons com filmes finos de uranio natural

Energy Technology Data Exchange (ETDEWEB)

Iunes, P J

1990-06-01

Fission track dating is described, focalizing the problem of the decay constant for spontaneous fission of {sup 238} U and the use of neutron dosimetry in fission track analysis. Experimental procedures using thin films of natural uranium as neutron dosimeters and its results are presented. The author shows a intercomparison between different thin films and between the dosimetry with thin film and other dosimetries. (M.V.M.). 52 refs, 12 figs, 9 tabs.

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

Fuel morphology effects on fission product release

International Nuclear Information System (INIS)

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

1986-01-01

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

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

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

Volatilization and reaction of fission products in flowing steam

International Nuclear Information System (INIS)

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

1985-01-01

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

Estimates of the rate and distribution of fitness effects of spontaneous mutation in Saccharomyces cerevisiae

NARCIS (Netherlands)

Zeyl, C.; Visser, de J.A.G.M.

2001-01-01

The per-genome, per-generation rate of spontaneous mutation affecting fitness (U) and the mean fitness cost per mutation (s) are important parameters in evolutionary genetics, but have been estimated for few species. We estimated U and sh (the heterozygous effect of mutations) for two diploid yeast

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.

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

KAUST Repository

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

2017-01-01

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

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

KAUST Repository

Pace, Natalie A.

2017-11-30

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

First-Principle Characterization for Singlet Fission Couplings.

Science.gov (United States)

Yang, Chou-Hsun; Hsu, Chao-Ping

2015-05-21

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

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

First wall material damage induced by fusion-fission neutron environment

Energy Technology Data Exchange (ETDEWEB)

Khripunov, Vladimir, E-mail: Khripunov_VI@nrcki.ru

2016-11-01

Highlights: • The highest damage and gas production rates are experienced within the first wall materials of a hybrid fusion-fission system. • About ∼2 times higher dpa and 4–5 higher He appm are expected compared to the values distinctive for a pure fusion system at the same DT-neutron wall loading. • The specific nuclear heating may be increased by a factor of ∼8–9 due to fusion and fission neutrons radiation capture in metal components of the first wall. - Abstract: Neutronic performance and inventory analyses were conducted to quantify the damage and gas production rates in candidate materials when used in a fusion-fission hybrid system first wall (FW). The structural materials considered are austenitic SS, Cu-alloy and V- alloys. Plasma facing materials included Be, and CFC composite and W. It is shown that the highest damage rates and gas particles production in materials are experienced within the FW region of a hybrid similar to a pure fusion system. They are greatly influenced by a combined neutron energy spectrum formed by the two-component fusion-fission neutron source in front of the FW and in a subcritical fission blanket behind. These characteristics are non-linear functions of the fission neutron source intensity. Atomic displacement damage production rate in the FW materials of a subcritical system (at the safe subcriticality limit of ∼0.95 and the neutron multiplication factor of ∼20) is almost ∼2 times higher compared to the values distinctive for a pure fusion system at the same 14 MeV neutron FW loading. Both hydrogen (H) and helium (He) gas production rates are practically on the same level except of about ∼4–5 times higher He-production in austenitic and reduced activation ferritic martensitic steels. A proper simulation of the damage environment in hybrid systems is required to evaluate the expected material performance and the structural component residence times.

Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in ^{254}Rf.

Science.gov (United States)

David, H M; Chen, J; Seweryniak, D; Kondev, F G; Gates, J M; Gregorich, K E; Ahmad, I; Albers, M; Alcorta, M; Back, B B; Baartman, B; Bertone, P F; Bernstein, L A; Campbell, C M; Carpenter, M P; Chiara, C J; Clark, R M; Cromaz, M; Doherty, D T; Dracoulis, G D; Esker, N E; Fallon, P; Gothe, O R; Greene, J P; Greenlees, P T; Hartley, D J; Hauschild, K; Hoffman, C R; Hota, S S; Janssens, R V F; Khoo, T L; Konki, J; Kwarsick, J T; Lauritsen, T; Macchiavelli, A O; Mudder, P R; Nair, C; Qiu, Y; Rissanen, J; Rogers, A M; Ruotsalainen, P; Savard, G; Stolze, S; Wiens, A; Zhu, S

2015-09-25

Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) μs have been discovered in the heavy ^{254}Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K^{π}=8^{-}, ν^{2}(7/2^{+}[624],9/2^{-}[734]) two-quasineutron and the K^{π}=16^{+}, 8^{-}ν^{2}(7/2^{+}[624],9/2^{-}[734])⊗8^{-}π^{2}(7/2^{-}[514],9/2^{+}[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the ^{254}Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.

A new type of active actinide target for studying fission and (n,xn) reactions

International Nuclear Information System (INIS)

Belier, G.; Aupiais, J.; Varignon, C.; Vayre, S.

2011-01-01

A new type of active target for the detection of fission of actinides has been developed, it is based on α spectrometry through liquid scintillation. The target uses the liquid-liquid extraction in order to mix the actinide with the liquid organic scintillator. The actinide to be detected is inside the detector itself which maximises the efficiency of the detector. The use of an organic scintillator allows the identification of the particles emitted. Indeed, the time delay for the transfer of the energy deposited in the solvent towards the scintillating molecules depends on the type of the energy deposits: instantaneous fluorescence is obtained for direct excitation while delayed fluorescence is obtained for energy deposits through ionization. By discriminating the different slow and quick components of the photomultiplier signal it is then possible to identify the particle: beta, alpha or fission products. This target has been tested with Cf 252 irradiated with 18 MeV neutrons, the experimental data show different peaks corresponding to alpha decay (97%), spontaneous fission (3%), beta decay and recoil protons due to neutron emissions. (A.C.)

Study on the technical feasibility of Fission-Track dating at two irradiation positions of the RA-6 research reactor

International Nuclear Information System (INIS)

Dorval, Eric

2005-01-01

The method of Fission-Track dating is based upon the detection of the damage caused by fission fragments from the Uranium contained in geological samples.In order to determine the age of a sample, both the amount of spontaneous fissions occurred and the Uranium concentration must be known.The latter requires the irradiation of the samples inside a reactor with a well-thermalized flux, so that fissions are induced over 235 U targets only. Therefore, the Uranium concentration may be determined.The main inconvenient presented by the irradiation sites at the RA-6 MTR-type reactor is that neutron flux is not completely thermal there, which means that fissions due to epithermal and fast neutrons will not be negligible.In the same way, tracks due to fissions of 238 U and 232 Th will be detected. In order to know the corrections that must be applied to those measurements performed in this reactor, it is necessary to characterize fast flux.Because of it, this laboratory's gamma spectrometry equipment had to be calibrated. After that, several activation detectors were irradiated and results were analyzed. Finally, it was determined that it is feasible to Fission-Track date at the I6 position. However, limitations associated to this method were analyzed for the values of flux measured in the different sites

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)

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

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

Reactivity effects of fission product decay in PWRs

International Nuclear Information System (INIS)

Aragones, J.M.; Ahnert, C.

1988-01-01

The purpose of the work reported in this paper is to analyze the effects of fission product chains with radioactive decay on the reactivity in pressurized water reactor (PWR) cores, calculating their accumulation and absorption rates along fuel burnup at continuous operation and after shutdown periods extending from 1 day to a few months. The authors PWR version of the WIMS-D4 code is first used to obtain the individual number densities, absorption rates, and averaged cross sections for every nuclide of the fission product chains with significant decay rates, as a function of fuel burnup at continuous irradiation. Next, by an auxiliary ad hoc code, these data, have been processed together with the required one for fissile nuclides and boron, also taken from WIMS at each burnup step, to calculate the average or effective values relevant for the analysis and the decay and change in overall absorption after several shutdown times. (1) The reactivity effect of fission product decay changes significantly with the shutdown time. The maximum absorption increase by decay is reached in ∼ 10 days' shutdown. (2) The dependence with fuel type, enrichment, and burnup is slight, but the change with previous power density is nearly linear, which might be significant after coast-down in previous cycles. (3) For long shutdown periods, the overall reactivity effect of decay in the three fission product chains considered is much less than if only the samarium peak due to 149 Nd is considered

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

Heat and fission product transport in molten core material pool with crust

International Nuclear Information System (INIS)

Yun, J.I.; Suh, K.Y.; Kang, C.S.

2005-01-01

Heat transfer and fluid flow in a molten pool are influenced by internal volumetric heat generated from the radioactive decay of fission product species retained in the reactor vessel during a severe accident. The pool superheat is determined based on the overall energy balance that equates the heat production rate to the heat loss rate. Decay heat of fission products in the pool is estimated by product of the mass concentration and energy conversion factor of each fission product. Twenty-nine elements are chosen and classified by their chemical properties to calculate heat generation rate in the pool. The mass concentration of a fission product is obtained from released fraction and the tabular output of the ORIGEN 2 code. The initial core and pool inventories at each time can also be estimated using ORIGEN 2. The released fraction of each fission product is calculated based on the bubble dynamics and mass transport. Numerical analysis is performed for heat and fission product transport in a molten core material pool during the Three Mile Island Unit 2 (TMI-2) accident. The pool is assumed to be a partially filled hemisphere, whose change in geometry is neglected during the numerical calculation. Calculated results indicate that the peak temperature in the molten pool is significantly lowered, since a substantial amount of the volatile fission products is released from the molten pool during progression of the accident. The results may directly be applied to the existing severe accident analysis codes to more mechanistically determine the thermal load to the reactor vessel lower head during the in-vessel retention

How much do we know about spontaneous human mutation rates

Energy Technology Data Exchange (ETDEWEB)

Crow, J.F. (Univ. of Wisconsin, Madison, WI (United States))

1993-01-01

The much larger number of cell divisions between zygote and sperm than between zygote and egg, the increased age of fathers of children with new dominant mutations, and the greater evolution rate of pseudogenes on the Y chromosome than of those on autosomes all point to a much higher mutation rate in human males than in females, as first pointed out by Haldane in his classical study of X-linked hemophilia. The age of the father is the main factor determining the human spontaneous mutation rate, and probably the total mutation rate. The total mutation rate in Drosophila males of genes causing minor reduction in viability is at least 0.4 per sperm and may be considerably higher. The great mutation load implied by a rate of [approx] 1 per zygote can be greatly ameliorated by quasi-transition selection. Corresponding data are not available for the human population. The evolution rate of pseudogenes in primates suggests some 10[sup 2] new mutations per zygote. Presumably the overwhelming majority of these are neutral, but even the approximate fraction is not known. Statistical evidence in Drosophilia shows that mutations with minor effects cause about the same heterozygous impairment of fitness as those that are lethal when homozygous. The magnitude of heterozygous effect is such that almost all mutant genes are eliminated as heterozygotes before ever becoming homozygous. Although quantitative data in the human species are lacking, anecdotal information supports the conclusion that partial dominance is the rule here as well. This suggests that if the human mutation rate were increased or decreased, the effects would be spread over a period of 50-100 generations. 31 refs., 3 figs., 2 tabs.

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)

Accuracy of rate coding: When shorter time window and higher spontaneous activity help

Czech Academy of Sciences Publication Activity Database

Leváková, Marie; Tamborrino, M.; Košťál, Lubomír; Lánský, Petr

2017-01-01

Roč. 95, č. 2 (2017), č. článku 022310. ISSN 2470-0045 R&D Projects: GA ČR(CZ) GA15-08066S; GA MŠk(CZ) 7AMB17AT048 Institutional support: RVO:67985823 Keywords : rate coding * observation window * spontaneous activity * Fisher information * perfect integrate- and -fire model * Wiener process Subject RIV: BB - Applied Statistics, Operational Research OBOR OECD: Biology (theoretical, mathematical, thermal, cryobiology, biological rhythm), Evolutionary biology Impact factor: 2.366, year: 2016

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

International Nuclear Information System (INIS)

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

1979-08-01

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

Microscopic theory of singlet exciton fission. III. Crystalline pentacene

International Nuclear Information System (INIS)

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

2014-01-01

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

Fission product release from fuel of water-cooled reactors

International Nuclear Information System (INIS)

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

1997-01-01

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

Microscopic theory of singlet exciton fission. III. Crystalline pentacene

Energy Technology Data Exchange (ETDEWEB)

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

2014-08-21

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

Fission product yield data for the transmutation of minor actinide nuclear waste

International Nuclear Information System (INIS)

2008-04-01

A report issued by an international study group for the transmutation of nuclear waste using accelerator driven systems has highlighted the need for specific sets of nuclear data. These authoritative requirements include fission product yields at an intermediate incident neutron energy of up to 150 MeV. Before the start of the present CRP on fission product yield data for the transmutation of nuclear waste, only four types of evaluated fission yield data sets existed, namely for spontaneous fission, and for fission induced by thermal, fast (or fission) spectrum, and by 'high energy' (14-15 MeV) neutrons. A new type of evaluation for energy dependent neutron induced fission yields was required for this project. In view of the scarcity of experimental data, such an evaluation has to be based on systematics and theoretical model calculations. Unlike fission cross-sections, where nuclear models are being used successfully for the calculation of unmeasured cross-section ranges, such models or theories existed only for low energy fission yields. Hence the CRP participants entered a completely new field of research for which the progress and outcome were unpredictable. Clearly the ultimate goal of such an effort, namely an evaluation of energy dependent fission yields, could not be realized within the perceived lifetime of a CRP. The main emphasis of the CRP was on the development of adequate systematics and models for the calculation of energy dependent fission yields up to 150 MeV incident neutron energy. Several problems had to be solved, such as the correct choice of model parameters and multiplicity distributions of emitted neutrons, and the effect of multi-chance fission. Models and systematics have been tested for lower energy yields, but they failed to reproduce recent experimental data, particularly at higher energies, and the parameters had to be modified. Other models have been developed from the analysis of experimental data in order to derive systematic

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.)

JEFF 3.1.2 - Joint evaluated nuclear data library for fission and fusion applications - February 2012 (DVD)

International Nuclear Information System (INIS)

2012-02-01

The Joint Evaluated Fission and Fusion File (JEFF) project is a collaboration between NEA Data Bank member countries. The JEFF library combines the efforts of the JEFF and EFF/EAF Working Groups to produce a common sets of evaluated nuclear data, mainly for fission and fusion applications. The JEFF-3.1.2 version, released in February 2012, contains a number of different data types, including neutron and proton interaction data, radioactive decay data, fission yields, and thermal scattering law data. Currently, JEFF-3.1.2 data are available in ENDF-6 format (neutron library) from the Web. This new release is an update from JEFF-3.1.1 which concerns 115 material files from the general purpose incident neutron library which have been modified since JEFF-3.1.1. Modifications include: Hf isotopes: 6 new Hf evaluations have replaced previous ones; Gamma production data from neutron capture (MF=6 MT=102) has been added to 89 fission products (FP) evaluations; 47 of these FP have been replaced by ENDF-B/VII.0 evaluations, with gamma data added in this release. Corrections from JEFF-Beta feedback have been incorporated for 15 materials. Corrections that solve NJOY covariance processing problems and JANIS warnings have been made to 6 files. This DVD contains: - General purpose incident neutron data in ENDF-6 and ACE formats; - Activation data; - Thermal scattering data; - Incident proton data; - Radioactive decay data; - Neutron-induced fission yields data; - Spontaneous fission yields data

Fission Detection Using the Associated Particle Technique

International Nuclear Information System (INIS)

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

2008-01-01

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

Simple and effective method of determining multiplicity distribution law of neutrons emitted by fissionable material with significant self -multiplication effect

International Nuclear Information System (INIS)

Yanjushkin, V.A.

1991-01-01

At developing new methods of non-destructive determination of plutonium full mass in nuclear materials and products being involved in uranium -plutonium fuel cycle by its intrinsic neutron radiation, it may be useful to know not only separate moments but the multiplicity distribution law itself of neutron leaving this material surface using the following as parameters - firstly, unconditional multiplicity distribution laws of neutrons formed in spontaneous and induced fission acts of the given fissionable material corresponding nuclei and unconditional multiplicity distribution law of neutrons caused by (α,n) reactions at light nuclei of some elements which compose this material chemical structure; -secondly, probability of induced fission of this material nuclei by an incident neutron of any nature formed during the previous fissions or(α,n) reactions. An attempt to develop similar theory has been undertaken. Here the author proposes his approach to this problem. The main advantage of this approach, to our mind, consists in its mathematical simplicity and easy realization at the computer. In principle, the given model guarantees any good accuracy at any real value of induced fission probability without limitations dealing with physico-chemical composition of nuclear material

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-12-15

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

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.

Measurements of isomeric yield ratios of fission products from proton-induced fission on natU and 232Th via direct ion counting

Directory of Open Access Journals (Sweden)

Rakopoulos Vasileios

2017-01-01

Full Text Available Independent isomeric yield ratios (IYR of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL facility at the University of Jyväskylä. A direct ion counting measurement of the isomeric fission yield ratios was accomplished for the first time, registering the fission products in less than a second after their production. In addition, the IYRs of natU were measured by means of γ-spectroscopy in order to verify the consistency of the recently upgraded experimental setup. From the obtained results, indications of a dependence of the production rate on the fissioning system can be noticed. These data were compared with data available in the literature, whenever possible. Using the TALYS code and the experimentally obtained IYRs, we also deduced the average angular momentum of the fission fragments after scission.

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

International Nuclear Information System (INIS)

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

1999-01-01

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

Transport of fission products in matrix and graphite

International Nuclear Information System (INIS)

Hoinkis, E.

1983-06-01

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

Gas-phase transport of fission products

International Nuclear Information System (INIS)

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

1982-01-01

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

Measurements of integral cross sections in the californium-252 fission neutron spectrum

International Nuclear Information System (INIS)

Alberts, W.G.; Guenther, E.; Matzke, M.; Rassl, G.

1977-01-01

In a low-scattering arrangement cross sections averaged over the californium-252 spontaneous fission neutron spectrum were measured. The reactions 27 Al(n,α) 46 Ti, 47 Ti, 48 Ti(n,p), 54 Fe, 56 Fe(n,p), 58 Ni(n,p), 64 Zn(n,p), 115 In(n,n') were studied in order to obtain a consistent set of threshold detectors used in fast neutron flux density measurements. Overall uncertainties between 2 and 2.5% could be achieved; corrections due to neutron scattering in source and samples are discussed

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

Video-assisted thoracoscopy treatment of spontaneous pneumothorax

International Nuclear Information System (INIS)

Chen Haitao; Ren Jian; Che Jiaming; Hang Junbiao; Qiu Weicheng; Chen Zhongyuan

2002-01-01

Objective: To propose a treatment protocol by video thoracoscopy in spontaneous pneumothorax. Methods: One hundred and three patients underwent Video-assisted thoracoscopy (VATS) treatment of spontaneous pneumothorax and hemothorax. Indications included recurrent pneumothorax, persistent air leakage following conservative therapy, complicated hemothorax and CT scan identified bullae formation. Results: No operative deaths occurred, conversion rate was 2.91%, recurrence rate was 0.97%, complication rate was 3.81% and mean postoperative hospital stay was 5.6 days. Conclusions: VATS treatment of spontaneous pneumothorax is better than open chest surgery and also superior than conservative therapy

Chemical etching of fission tracks in ethylene-tetrafluoroethylene copolymer

International Nuclear Information System (INIS)

Komaki, Y.; Tsujimura, S.; Seguchi, T.

1979-01-01

The chemical etching of fission tracks in ethylene-tetrafluoroethylene copolymer was studied. Etched holes 3000 to 4000 A in diameter were recognized by electron microscopy for a film bombarded by fission fragments in oxygen and etched in a 12N sodium hydroxide solution at 125 0 C. The radial etching rate at 125 0 C was 6 to 8 A/hr, which is less than 17 A/hr for polyvinylidene fluoride in the same sodium hydroxide concentration at 85 0 C. The smaller rate is a reflection of the larger chemical resistivity of ethylene-tetrafluoroethylene copolymer than polyvinylidene fluoride. (author)

Heat and Fission Product Transport in a Molten U-Zr-O Pool With Crust

International Nuclear Information System (INIS)

Yun, J.I.; Suh, K.Y.; Kang, C.S.

2002-01-01

Heat transfer and fluid flow in a molten pool are influenced by internal volumetric heat generated from the radioactive decay of fission product species retained in the pool. The pool superheat is determined based on the overall energy balance that equates the heat production rate to the heat loss rate. Decay heat of fission products in the pool was estimated by product of the mass concentration and energy conversion factor of each fission product. For the calculation of heat generation rate in the pool, twenty-nine elements were chosen and classified by their chemical properties. The mass concentration of a fission product is obtained from released fraction and the tabular output of the ORIGEN 2 code. The initial core and pool inventories at each time can also be estimated using ORIGEN 2. The released fraction of each fission product is calculated based on the bubble dynamics and mass transport. Numerical analysis was performed for the TMI-2 accident. The pool is assumed to be a partially filled hemispherical geometry and the change of pool geometry during the numerical calculation was neglected. Results of the numerical calculation revealed that the peak temperature of the molten pool significantly decreased and most of the volatile fission products were released from the molten pool during the accident. (authors)

Fission product removal from molten salt using zeolite

International Nuclear Information System (INIS)

Pereira, C.; Babcock, B.D.

1996-01-01

Spent nuclear fuel (SNF) can be treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission product cations from the molten salt. Breakthrough of cesium and the alkaline earths occurred more rapidly than was observed for the rare earths. The effluent composition as a function of time is presented, as well as results for the distribution of fission products along the length of the column. Effects of temperature and salt flow rate are also discussed

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Fission gas behaviour in UO2 under steady state and transient conditions

International Nuclear Information System (INIS)

Zimmermann, H.

1980-01-01

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

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

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)

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

{sup 235}U(n,F) prompt fission neutron spectra

Energy Technology Data Exchange (ETDEWEB)

Maslov, M.V.; Tetereva, N.A. [Joint Institute of Nuclear and Energy Research, Minsk-Sosny (Belarus); Pronyaev, V.P.; Kagalenko, A.B. [Institute of Physics and Power Engineering, Obninsk (Russian Federation); Capote, R. [International Atomic Energy Agency, Vienna (Austria); Granier, T.; Morillon, B. [CEA, Centre DAM-IIe de France, 91 - Arpajon (France); Hambsch, F.J. [EC-JRC Institute for Reference Materials and Measurements, Geel (Belgium); Sublet, J.C. [CEA Cadarache, 13 - Saint Paul lez Durance (France)

2009-07-01

The longstanding problem of inconsistency of integral thermal data testing and differential prompt fission neutron spectra data (PFNS) is mostly due to rather poor fits of differential PFNS data in major data libraries. The measured database is updated by using modern standards including Manhart's evaluation of the spontaneous fission neutron spectra of {sup 252}Cf(sf). That largely removes the inconsistency of older thermal neutron-induced PFNS measurements with newest data of JRC IRMM by Hambsch et al. (2009). A phenomenological approach, developed by Kornilov et al. (1999), for the first-chance fission and extended for the emissive fission domain by Maslov et al. (2005) is calibrated at E{sub th} to predict both the PFNS average energy and PFNS shape up to 20 MeV. The latter is extremely important, since rather close values in fact correspond to quite discrepant spectra shapes, which influences reactor neutronics strongly. The proposed phenomenological representation of the PFNS reproduces both soft and hard energy tails of {sup 235}U(n{sub th},F) PFNS at thermal incident neutron energy E{sub th}. In the first-chance and emissive fission domain evaluated PFNS are consistent with the data by Ethvignot et al. (2005). A compiled MF=5 Endf/B-formatted file of the {sup 235}U(n,F) PFNS largely removes the inconsistencies of the evaluated differential PFNS with integral data benchmarks. Almost perfect fits are attained for available differential PFNS data from E{sub th} up to E{sub n}=14.7 MeV, with few exceptions at E{sub n}=2.9 and E{sub n}=5 MeV. Fast integral critical experiment like GODIVA or Flattop benchmarks might be reproduced almost with the same accuracy as with the PFNS of the major data libraries. That reveals a rather delicate compensation effect, since present and previous PFNS shapes are drastically different from each other. Thermal assemblies benchmarking reveals positive biases in k(eff), which might be attributed to the influence of

Fission product inventory calculation by a CASMO/ORIGEN coupling program

Energy Technology Data Exchange (ETDEWEB)

Kim, Do Heon; Kim, Jong Kyung [Hanyang University, Seoul (Korea, Republic of); Choi, Hang Bok; Roh, Gyu Hong; Jung, In Ha [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

A CASMO/ORIGEN coupling utility program was developed to predict the composition of all the fission products in spent PWR fuels. The coupling program reads the CASMO output file, modifies the ORIGEN cross section library and reconstructs the ORIGEN input file at each depletion step. In ORIGEN, the burnup equation is solved for actinides and fission products based on the fission reaction rates and depletion flux of CASMO. A sample calculation has been performed using a 14 x 14 PWR fuel assembly and the results are given in this paper. 3 refs., 1 fig., 1 tab. (Author)

Fission product inventory calculation by a CASMO/ORIGEN coupling program

Energy Technology Data Exchange (ETDEWEB)

Kim, Do Heon; Kim, Jong Kyung [Hanyang University, Seoul (Korea, Republic of); Choi, Hang Bok; Roh, Gyu Hong; Jung, In Ha [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1997-12-31

A CASMO/ORIGEN coupling utility program was developed to predict the composition of all the fission products in spent PWR fuels. The coupling program reads the CASMO output file, modifies the ORIGEN cross section library and reconstructs the ORIGEN input file at each depletion step. In ORIGEN, the burnup equation is solved for actinides and fission products based on the fission reaction rates and depletion flux of CASMO. A sample calculation has been performed using a 14 x 14 PWR fuel assembly and the results are given in this paper. 3 refs., 1 fig., 1 tab. (Author)

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.

Mitochondrial Mutation Rate, Spectrum and Heteroplasmy in Caenorhabditis elegans Spontaneous Mutation Accumulation Lines of Differing Population Size.

Science.gov (United States)

Konrad, Anke; Thompson, Owen; Waterston, Robert H; Moerman, Donald G; Keightley, Peter D; Bergthorsson, Ulfar; Katju, Vaishali

2017-06-01

Mitochondrial genomes of metazoans, given their elevated rates of evolution, have served as pivotal markers for phylogeographic studies and recent phylogenetic events. In order to determine the dynamics of spontaneous mitochondrial mutations in small populations in the absence and presence of selection, we evolved mutation accumulation (MA) lines of Caenorhabditis elegans in parallel over 409 consecutive generations at three varying population sizes of N = 1, 10, and 100 hermaphrodites. The N =1 populations should have a minimal influence of natural selection to provide the spontaneous mutation rate and the expected rate of neutral evolution, whereas larger population sizes should experience increasing intensity of selection. New mutations were identified by Illumina paired-end sequencing of 86 mtDNA genomes across 35 experimental lines and compared with published genomes of natural isolates. The spontaneous mitochondrial mutation rate was estimated at 1.05 × 10-7/site/generation. A strong G/C→A/T mutational bias was observed in both the MA lines and the natural isolates. This suggests that the low G + C content at synonymous sites is the product of mutation bias rather than selection as previously proposed. The mitochondrial effective population size per worm generation was estimated to be 62. Although it was previously concluded that heteroplasmy was rare in C. elegans, the vast majority of mutations in this study were heteroplasmic despite an experimental regime exceeding 400 generations. The frequencies of frameshift and nonsynonymous mutations were negatively correlated with population size, which suggests their deleterious effects on fitness and a potent role for selection in their eradication. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Studies of Fission-Induced Surface Damage in Actinides Using Ultracold Neutrons

Energy Technology Data Exchange (ETDEWEB)

Broussard, Leah J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-03-05

This report describes the results of the fission-induced actinide studies at LANL. Previously, there was no fission data at these energies though there were initial characterizations of UCN energy dependence and material thickness. The proof of principle was demonstrated and the initial characterizations of sputtered rates, angular and size distribution are underway.

Identification of Fissionable Materials Using the Tagged Neutron Technique

International Nuclear Information System (INIS)

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

2009-01-01

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

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.

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

Science.gov (United States)

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

1991-08-01

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

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

Observations of fission-tracks in zircons by atomic force microscope

International Nuclear Information System (INIS)

Ohishi, Shinnosuke; Hasebe, Noriko

2012-01-01

The fission-track (FT) method is a dating technique based on the observation of damage (tracks) by spontaneous fission of 238 U left in a mineral. The date is calculated from the track density and the uranium concentration in the mineral. This is possible because the number of tracks is a function of uranium concentration and time since the start of track accumulation. Usually, the number of tracks is counted under an optical microscope after etching (chemical expansion of a track). However, as FT density per unit area rises, it becomes difficult to count the number of tracks. This is due to the fact that FTs overlap one another and are unable to be readily distinguished. This research examines the potential of atomic force microscope (AFM) for FT dating using zircons, which are likely to show higher FT density than other minerals due to their high U concentrations. To obtain an AFM image for a sample prepared for FT dating, removing the static electricity of the sample is essential to avoid an unexpected movement of the cantilever. A grain should be wider than about 30 μm to bring the cantilever on the mineral surface. Polishing with a fine grained compound is very important. There is not much difference in sharpness between images by AC mode (scanning with vibrating cantilever at a constant cycle) and Contact mode (scanning with the cantilever always in close contact with the surface). To confirm how tracks can be identified with the AFM, an AFM image was compared with an image obtained with the optical microscope. When change in the number of tracks and their shapes were observed through stepwise etching, the track expanded as the etching time increased. In addition, the etching rate was slower for large tracks than those for small tracks. This implied that the AFM can be used to observe etching of zircons with different degrees of nuclear fission damage. A track that could not be seen with the optical microscope due to insufficient etching could be observed by

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

International Nuclear Information System (INIS)

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

1983-01-01

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

Fission induced swelling and creep of U–Mo alloy fuel

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Hofman, G.L. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Cheon, J.S. [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Robinson, A.B.; Wachs, D.M. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States)

2013-06-15

Tapering of U–Mo alloy fuel at the end of plates is attributed to lateral mass transfer by fission induced creep, by which fuel mass is relocated away from the fuel end region where fission product induced fuel swelling is in fact the highest. This mechanism permits U–Mo fuel to achieve high burnup by effectively relieving stresses at the fuel end region, where peak stresses are otherwise expected because peak fission product induced fuel swelling occurs there. ABAQUS FEA was employed to examine whether the observed phenomenon can be simulated using physical–mechanical data available in the literature. The simulation results obtained for several plates with different fuel fabrication and loading scheme showed that the measured data were able to be simulated with a reasonable creep rate coefficient. The obtained creep rate constant lies between values for pure uranium and MOX, and is greater than all other ceramic uranium fuels.

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.

Utilization of fast reactor excess neutrons for burning long-lived fission products

International Nuclear Information System (INIS)

Kawashima, K.; Kobayashi, K.; Kaneto, K.

1995-01-01

An evaluation is made on a large MOX fuel fast reactor's capability of burning long lived fission product Tc-99, which dominates the long term radiotoxicity of the high level radioactive waste. The excess neutrons generated in the fast reactor core are utilized to transmute Tc-99 to stable isotopes due to neutron capture reaction. The fission product target assemblies which consist of Tc-99 are charged to the reactor core periphery. The fission product target neutrons are moderated to a great deal to pursue the possibility of enhancing the transmutation rate. Any impacts of loading the fission product target assemblies on the core nuclear performances are assessed. A long term Tc-99 accumulation scenario is considered in the mix of fission product burner fast reactor and non-burner LWRs. (author)

Fission-product energy release for times following thermal-neutron fission of 235U between 2 and 14000 seconds

International Nuclear Information System (INIS)

Dickens, J.K.; Emery, J.F.; Love, T.A.; McConnell, J.W.; Northcutt, K.J.; Peelle, R.W.; Weaver, H.

1977-10-01

Fission-product decay energy-releases rates were measured for thermal-neutron fission of 235 U. Samples of mass 1 to 10 μg were irradiated for 1 to 100 sec by use of the fast pneumatic-tube facility at the Oak Ridge Research Reactor. The resulting beta- and gamma-ray emissions were counted for times-after-fission between 2 and 14,000 seconds. The data were obtained for beta and gamma rays separately as spectral distributions, N(E/sub γ/) vs E/sub γ/ and N(E/sub beta/) vs E/sub β/. For the gamma-ray data the spectra were obtained by using a NaI detector, while for the beta-ray data the spectra were obtained by using an NE-110 detector with an anticoincidence mantle. The raw data were unfolded to provide spectral distributions of modest resolution. These were integrated over E/sub γ/ and E/sub β/ to provide total yield and energy integrals as a function of time after fission. Results are low compared to the present 1973 ANS Decay-heat standard. A complete description of the experimental apparatus and data-reduction techniques is presented. The final integral data are given in tabular and graphical form and are compared with published data. 41 figures, 13 tables

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

Recent results from SHIP on shape coexistence and electron capture delayed fission in the Pb-Rn region

Energy Technology Data Exchange (ETDEWEB)

Andreyev, Andrei [Insituut voor Kern- en Stralingfysica, Univesity of Leuven (Belgium)

2008-07-01

The contribution reviews the results of our recent experiments at SHIP (GSI, Darmstadt) aimed at the study of very neutron-deficient Pb-Rn nuclides in the vicinity of N=104. The first part presents the unambiguous identification of the EC-delayed fission (ECDF) in the odd-odd isotopes {sup 192,194}At. The ECDF data allow us to study the fission properties of the nuclei which do not decay via spontaneous fission at all. The preliminary analysis indicate unusually high ECDF probabilities for these nuclides. The second part discusses the new data on the shape coexistence in the Pb region. Identification of the new isotopes {sup 193,194}Rn and first experimental evidence for the long-sought ground state deformation in lightest Rn isotopes will be presented. The strong retardation (by a factor of {proportional_to}10) of the half-life of the new isotope {sup 186}Po relative to the classical Geiger-Nuttall rule for alpha decay will be also discussed. This indicates that the Geiger-Nuttall rule is broken in the lightest Po isotopes.

Effect of spontaneous saliva swallowing on short-term heart rate variability (HRV) and reliability of HRV analysis.

Science.gov (United States)

Yildiz, Metin; Doma, Serian

2017-09-26

The effects of effortful swallowing and solid meal ingestions on heart rate variability (HRV) have been examined previously. The effects of spontaneous saliva swallowing on short-term HRV and reliability of HRV analysis have not been studied before. The effect of saliva swallowing on HRV analyses parameters [meanRRI, SDNN (standard deviation of normal-to-normal), LF (low frequency), HF (high frequency) powers, LH/HF] and the reliability of LF and HF powers were investigated by frequency, time-frequency and intraclass correlation coefficient (ICC) analyses. Electrocardiogram and swallowing signal that obtained from an electronic stethoscope placed on the necks of subjects were recorded simultaneously from 30 healthy and young volunteers in sitting position during 15 min. Spontaneous swallowing has been shown to significantly alter some HRV parameters (SDNN, LF power and LF/HF ratio). Time-frequency analysis results showed that the contribution of saliva swallowing to LF (1-58%) and HF (2-42%) powers could change significantly depending on the number of swallowing. The ICC of the LF and HF powers for the successive 5-min signal segments were found 0·89, 0·92, respectively. These values decreased to 0·73 and 0·90 in the subjects with more swallowing rate. When the analyses were made for 2-min signal periods, these values decreased to 0·63 and 0·67. We concluded that spontaneous saliva swallowing can change HRV parameters. We have also seen that changes in swallowing rate and use of short signal segments may reduce the reliability of HRV analyses. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

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

The temperature dependence of the friction in the fission

International Nuclear Information System (INIS)

Yamaji, Shuhei

1996-01-01

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

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.

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.

Nuclear energy: fusion and fission - From the atomic nucleus to energy

International Nuclear Information System (INIS)

2002-09-01

Matter is made up of atoms. In 1912, the English physicist Ernest Rutherford (who had shown that the atom had a nucleus), and the Danish physicist Niels Bohr developed a model in which the atom was made up of a positively charged nucleus surrounded by a cloud of electrons. In 1913, Rutherford discovered the proton, and in 1932, the English physicist Chadwick discovered the neutron. In 1938, Hahn and Strassmann discovered spontaneous fission and the French physicist Frederic Joliot-Curie, assisted by Lew Kowarski and Hans Von Halban, showed in 1939 that splitting uranium nuclei caused an intense release of heat. The discovery of the chain reaction would enable the exploitation of nuclear energy. 'It was the Second World War leaders who, by encouraging research for military purposes, contributed to the development of nuclear energy'. During the Second World War, from 1939 to 1945, studies of fission continued in the United States, with the participation of emigre physicists. The Manhattan project was launched, the aim of which was to provide the country with a nuclear weapon (used at Hiroshima and Nagasaki in 1945). After the war ended, research into energy production by the nuclear fission reaction continued for civil purposes. CEA (the French Atomic Energy Commission) was set up in France in 1945 under the impetus of General de Gaulle. This public research body is responsible for giving France mastery of the atom in the research, health, energy, industrial, safety and defense sectors. (authors)

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-07-01

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

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

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)

Anisotropy in the ternary cold fission

CERN Document Server

Delion, D S; Greiner, W

2003-01-01

We describe the spontaneous ternary cold fission of sup 2 sup 5 sup 2 Cf, accompanied by sup 4 He, sup 1 sup 0 Be and sup 1 sup 4 C within a stationary scattering formalism. We show that the light cluster should be born in the neck region. It decays from the first resonant eigenstate in the Coulomb plus harmonic oscillator potential, centred in this region and eccentric with respect to the symmetry axis. This description gives a simple answer to the question why the averaged values in the energy spectra of emitted clusters are close to each other, in spite of different Coulomb barriers. We have shown that the angular distribution of the emitted light particle is strongly connected with its deformation and the equatorial distance. Experimental angular distributions can be explained by the spherical shapes of emitted clusters, except for a deformed sup 1 sup 0 Be. We also predicted some dependences of half-lives for such tri-nuclear systems upon potential parameters.

Fission 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.)

Evaluation of Cross-Section Sensitivities in Computing Burnup Credit Fission Product Concentrations

International Nuclear Information System (INIS)

Gauld, I.C.

2005-01-01

U.S. Nuclear Regulatory Commission Interim Staff Guidance 8 (ISG-8) for burnup credit covers actinides only, a position based primarily on the lack of definitive critical experiments and adequate radiochemical assay data that can be used to quantify the uncertainty associated with fission product credit. The accuracy of fission product neutron cross sections is paramount to the accuracy of criticality analyses that credit fission products in two respects: (1) the microscopic cross sections determine the reactivity worth of the fission products in spent fuel and (2) the cross sections determine the reaction rates during irradiation and thus influence the accuracy of predicted final concentrations of the fission products in the spent fuel. This report evaluates and quantifies the importance of the fission product cross sections in predicting concentrations of fission products proposed for use in burnup credit. The study includes an assessment of the major fission products in burnup credit and their production precursors. Finally, the cross-section importances, or sensitivities, are combined with the importance of each major fission product to the system eigenvalue (k eff ) to determine the net importance of cross sections to k eff . The importances established the following fission products, listed in descending order of priority, that are most likely to benefit burnup credit when their cross-section uncertainties are reduced: 151 Sm, 103 Rh, 155 Eu, 150 Sm, 152 Sm, 153 Eu, 154 Eu, and 143 Nd

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.)

FIFRELIN - TRIPOLI-4® coupling for Monte Carlo simulations with a fission model. Application to shielding calculations

Science.gov (United States)

Petit, Odile; Jouanne, Cédric; Litaize, Olivier; Serot, Olivier; Chebboubi, Abdelhazize; Pénéliau, Yannick

2017-09-01

TRIPOLI-4® Monte Carlo transport code and FIFRELIN fission model have been coupled by means of external files so that neutron transport can take into account fission distributions (multiplicities and spectra) that are not averaged, as is the case when using evaluated nuclear data libraries. Spectral effects on responses in shielding configurations with fission sampling are then expected. In the present paper, the principle of this coupling is detailed and a comparison between TRIPOLI-4® fission distributions at the emission of fission neutrons is presented when using JEFF-3.1.1 evaluated data or FIFRELIN data generated either through a n/g-uncoupled mode or through a n/g-coupled mode. Finally, an application to a modified version of the ASPIS benchmark is performed and the impact of using FIFRELIN data on neutron transport is analyzed. Differences noticed on average reaction rates on the surfaces closest to the fission source are mainly due to the average prompt fission spectrum. Moreover, when working with the same average spectrum, a complementary analysis based on non-average reaction rates still shows significant differences that point out the real impact of using a fission model in neutron transport simulations.

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

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.

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

International Nuclear Information System (INIS)

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

1980-01-01

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

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

On-chip plasmonic cavity-enhanced spontaneous emission rate at the zero-phonon line

DEFF Research Database (Denmark)

Siampour, Hamidreza; Kumar, Shailesh; Bozhevolnyi, Sergey I.

Highly confined surface plasmon polariton (SPP) modes can be utilized to enhance light-matter interaction at the single emitter level of quantum optical systems [1-4]. Dielectric-loaded SPP waveguides (DLSPPWs) confine SPPs laterally with relatively low propagation loss, enabling to benefit both ...... and an up to 42-fold spontaneous emission rate enhancement at the zero-phonon line (a ∼7-fold resonance enhancement in addition to a ∼6-fold broadband enhancement) is achieved, revealing the potential of our approach for on-chip realization of quantum-optical networks....... from a large Purcell factor and from a large radiative efficiency (low quenching rates) [1, 2]. In this work, we present a DLSPPW-based Bragg cavity resonator to direct emission from a single diamond nitrogen vacancy (NV) center into the zero-phonon line (Fig. 1). A quality factor of ∼70 for the cavity...

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

International Nuclear Information System (INIS)

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

1991-07-01

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

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)

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

International Nuclear Information System (INIS)

Yanagisawa, Hiroshi; Ohno, Akio; Aizawa, Eijyu

2002-01-01

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

Quasi-static method and finite element method for obtaining the modifications of the spontaneous emission rate and energy level shift near a plasmonic nanostructure.

Science.gov (United States)

Zhao, Yun-Jin; Tian, Meng; Wang, Xiao-Yun; Yang, Hong; Zhao, Heping; Huang, Yong-Gang

2018-01-22

We provide numerical demonstrations of the applicability and accuracy of the quasi-static method and the finite-element method in the investigation of the modifications of the spontaneous emission rate and the energy level shift of an emitter placed near a silver-air interface or a silver nano-sphere. The analytical results are presented as a reference. Our calculations show that the finite element method is an accurate and general method. For frequency away from the radiative mode, the quasi-static method can be applied more effectively for calculating the energy level shift than the spontaneous emission rate. But for frequency around, there is a blue shift for both and this shift increases with the increasing of emitter-silver distance. Applying the theory to the nanosphere dimmer, we see similar phenomenon and find extremely large modifications of the spontaneous emission rate and energy level shift. These findings are instructive in the fields of quantum light-matter interactions.

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

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.

Radioactive ion beams produced by neutron-induced fission at ISOLDE

CERN Document Server

Catherall, R; Gilardoni, S S; Köster, U

2003-01-01

The production rates of neutron-rich fission products for the next-generation radioactive beam facility EURISOL are mainly limited by the maximum amount of power deposited by protons in the target. An alternative approach is to use neutron beams to induce fission in actinide targets. This has the advantage of reducing: the energy deposited by the proton beam in the target; contamination from neutron-deficient isobars that would be produced by spallation; and mechanical stress on the target. At ISOLDE CERN, tests have been made on standard ISOLDE actinide targets using fast neutron bunches produced by bombarding thick, high-Z metal converters with 1 and 1.4 GeV proton pulses. This paper reviews the first applications of converters used at ISOLDE. It highlights the different geometries and the techniques used to compare fission yields produced by the proton beam directly on the target with neutron-induced fission. Results from the six targets already tested, namely UC2/graphite and ThO2 targets with tungsten an...

Finite element simulation of fission gas release and swelling in UO2 fuel pellets

International Nuclear Information System (INIS)

Denis, Alicia C.

1999-01-01

A fission gas release model is presented, which solves the atomic diffusion problem with xenon and krypton elements tramps produced by uranium fission during UO 2 nuclear fuel irradiation. The model considers intra and intergranular precipitation bubbles, its re dissolution owing to highly energetic fission products impact, interconnection of intergranular bubbles and gas sweeping by grain border in movement because of grain growth. In the model, the existence of a thermal gradient in the fuel pellet is considered, as well as temporal variations of fission rate owing to changes in the operation lineal power. The diffusion equation is solved by the finite element method and results of gas release and swelling calculation owing to gas fission are compared with experimental data. (author)

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

Convective-diffusive transport of fission products in the gap of a failed fuel element

International Nuclear Information System (INIS)

Lian, Z.W.; Carlucci, L.N.; Arimescu, V.I.

1995-03-01

A model is presented to describe the transport behaviour of gaseous fission products along the axial fuel-to-sheathe gap of a failed fuel element to the coolant system. The model is applicable to an element having failed under normal operating conditions or loss-of coolant-accident conditions. Because of the large differences in operating parameters, the transport characteristics of gaseous fission products in a failed element under these two operating conditions are significantly different. However, in both cases the transport process can be described by convection-diffusion caused by the continuous release of fission products from the fuel to the gap. Under normal operating conditions, the bulk-flow velocity is found to be negligible, due to the low release rate of fission products from fuel. The process can be well approximated by the diffusion of fission products in a stagnant gas-steam mixture. The effect of convection on the fission product transport, however, becomes significant under loss-of-coolant-accident conditions, where the release rates of fission products from fuel can be several orders of magnitude higher that that under normal operating conditions. The convection of the mixture in the gap not only contributes an additional flux to the gas-mixture transport, but also increases the gradient of fission products concentration across the opening, and therefore increases the diffusion flux to the coolant. As a result of the bulk flow, the transport of fission products along the gap is accelerated and the hold-up of short-lived isotopes in the gap is significantly reduced. Steam ingress through the opening into the gap is obstructed by the bulk flow, resulting in low steam concentrations in the gap under loss-of-coolant-accident conditions. (author). 6 refs., 8 figs

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

5He, 7He, and 8Li (E*=2.26 MeV) intermediate ternary particles in the spontaneous fission of 252Cf

International Nuclear Information System (INIS)

Kopatch, Yu.N.; Mutterer, M.; Schwalm, D.; Thirolf, P.; Goennenwein, F.

2002-01-01

The neutron-unstable odd-N isotopes 5 He, 7 He, and 8 Li (in its excited state of E*=2.26 MeV) were measured to show up as short-lived (τ≅10 -21 -10 -20 s) intermediate light charged particles (LCPs) in ternary fission of 252 Cf. For the study a high-efficiency angular correlation measurement between neutrons, LCPs, and main fission fragments has been performed. The evidence for the ternary 5 He and 7 He particles (lifetimes: 1x10 -21 s, and 4x10 -21 s, respectively) was disclosed from the measured angular distributions of their decay neutrons focused by the emission in flight towards the direction of motion of 4 He and 6 He ternary particles. Similarly, neutrons observed to be peaked around Li-particle motion could be attributed to the decay of the second excited state at E*=2.26 MeV (lifetime: 2x10 -20 s) of 8 Li. The fractional yields of the intermediate 5 He and 7 He ternary fission modes relative to the 'true' ternary 4 He and 6 He modes, respectively, were determined to be 0.21(5) for both cases. The mean energy of the 4 He residues resulting from the 5 He decay was determined to be 12.4(3) MeV, compared to 15.7(2) MeV for all ternary α particles registered, and to 16.4(3) MeV for the true ternary α particles. The mean energy of the 6 He residues from the 7 He decay is 11.0(15) MeV, compared to 12.3(5) MeV for all ternary 6 He particles. The population of 8 Li* was deduced to be 0.06(2) relative to Li ternary fission, and 0.33(20) relative to the yield of particle stable 8 Li. The perspective of using the observed intermediate LCPs for probing the ternary scission configuration in 252 Cf fission with the aid of trajectory calculations is briefly discussed

5He, 7He and 8Li (E=2.26 MeV) intermediate ternary particles in the spontaneous fission of 252Cf

International Nuclear Information System (INIS)

Kopatch, Yu. N.; Goennenwein, F.

2002-02-01

The neutron-unstable odd-N isotopes 5 He, 7 He and 8 Li (in its excited state of E * = 2.26 MeV) were measured to show up as short-lived intermediate light-charged-particles (LCP) in ternary fission of 252 Cf. For the study a high-efficiency angular correlation measurement between neutrons, LCPs and main fission fragments has been performed. The evidence for the ternary 5 He and 7 He particles (lifetimes: 1 x 10 -21 s, and 4 x 10 -21 s, respectively) was disclosed from the measured angular distributions of their decay neutrons focused by the emission in flight towards the direction of motion of 4 He and 6 He ternary particles. Similarly, neutrons observed to be peaked around Li-particle motion could be attributed to the decay of the second excited state at E * = 2.26 MeV (lifetime: 2 x 10 -20 s) of 8 Li. The fractional yields of the intermediate 5 He and 7 He ternary fission modes relative to the ''true'' ternary 4 He and 6 He modes, respectively, were determined to be 0.21(5) for both cases. The mean energy of the 4 He residues resulting from the 5 He decay was determined to be 12.4(3) MeV, compared to 15.7(2) MeV for all ternary α-particles registered, and to 16.4(3) MeV for the true ternary α-particles. The mean energy of the 6 He residues from the 7 He decay is 11.0(15) MeV, compared to 12.3(5) MeV for all ternary 6 He particles. The population of 8 Li * was deduced to be 0.06(2) relative to Li ternary fission, and 0.33(20) relative to the yield of particle stable 8 Li. The perspective of using the observed intermediate LCPs for probing the ternary scission configuration in 252 Cf fission with the aid of trajectory calculations is briefly discussed. (orig.)

Analytical measurements of fission products during a severe nuclear accident

Science.gov (United States)

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

2018-01-01

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

Analytical measurements of fission products during a severe nuclear accident

Directory of Open Access Journals (Sweden)

Doizi D.

2018-01-01

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

The (B)link Between Creativity and Dopamine: Spontaneous Eye Blink Rates Predict and Dissociate Divergent and Convergent Thinking

Science.gov (United States)

Chermahini, Soghra Akbari; Hommel, Bernhard

2010-01-01

Human creativity has been claimed to rely on the neurotransmitter dopamine, but evidence is still sparse. We studied whether individual performance (N=117) in divergent thinking (alternative uses task) and convergent thinking (remote association task) can be predicted by the individual spontaneous eye blink rate (EBR), a clinical marker of…

Fission product behaviour in the primary circuit of an HTR

International Nuclear Information System (INIS)

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

1981-01-01

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

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.

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

SFINX: Soviet-French integral experiment on measuring the capture and fission at Masurca and BFS

International Nuclear Information System (INIS)

Doulin, V.A.; Mikhailov, J.M.; Mozhaev, V.K.

1990-01-01

The SFINX experiment was aimed at the comparison of experimental procedures used at the MASURCA and the BFS critical assemblies for measuring the ratio of the 238 U and 239 Pu average fission cross-sections to the 235 U average cross-section (F8/F5, F9/F5) and of the 238 U average capture cross-section to the 239 Pu average fission cross section (C8/F9). As part of the calibration of the measurements F8/F5 and F9/F5 were also measured in a thermal column. To obtain C8/F9, absolute measurements of capture rates in 238 U and fission rates in 239 Pu and 235 U were carried out. The measurements were made in September 1987 at the MASURCA facility (FRANCE) in the BALZAC 1 critical assembly and in the thermal column of the HARMONIE facility. In April 1989 these measurements were complemented by joint measurements of the 239 Pu absolute fission rate at the BFS 55-1 critical assembly (USSR)