Spontaneous Fission

Hoffman, Darleane C.; Lane, Michael R.

doi:10.1524/ract.1995.7071.special-issue.135

Cited by 62 publications

(17 citation statements)

References 30 publications

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“…The use of charged-particle or heavy-ion projectiles made a number of additional nuclei available for fission experiments by transfer reactions [238] or fusion (e.g. [239][240][241]). The easy accessibility of higher excitation energies and the inevitable population of larger angular momenta has allowed other aspects of the fission process to be studied.…”

Section: Former Status Of Knowledgementioning

confidence: 99%

“…By 1978, the time-dependent Hartree-Fock method [247] had already been applied to fission. Later, time-dependent calculations based on the generator-coordinate method using Hartree-Fock-Bogoliubov states were performed, and the most probable fission configuration of 240 Pu was analyzed [243]. Wilkins et al [248] performed quantitative calculations of fission quantities, for example fission-fragment mass distributions, charge polarization 2 (which leads to different N/Z ratios of the two complementary fragments), total kinetic energies and promptneutron multiplicities, with a static statistical scission-point model, including the influence of shell effects and pairing correlations 3 .…”

Section: Former Status Of Knowledgementioning

confidence: 99%

“…Dynamical evolution from the ground state to scission obtained with TDGCM-GOA assuming adiabaticity, i.e. no coupling between collective and intrinsic degrees of freedom Fission-fragment mass and charge distributions of few even-even fissioning nuclei, mainly 226 Th, 236,238 U, 240 Pu and 252 Cf at low energies [299,306,77,96,98] Dynamical evolution from a point beyond the fission barrier with TDHF, TDHF-BCS or TDHFB. This implies:…”

Section: Theorymentioning

confidence: 99%

“…Most probable kinetic and excitation energies of the fission fragments for a few even-even fissioning nuclei, mainly 240 Pu at low energy and 258, 264 Fm, spontaneous fission. Only recently have fairly realistic kinetic-energy and fragment-mass distributions been obtained for 258 Fm.…”

Section: Theorymentioning

confidence: 99%

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Review on the progress in nuclear fission—experimental methods and theoretical descriptions

2018

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An overview is given on some of the main advances in the experimental methods, experimental results, theoretical models and ideas of the last few years in the field of nuclear fission. New approaches have considerably extended the availability of fissioning systems for the experimental study of nuclear fission, and have provided a full identification of all fission products in A and Z for the first time. In particular, the transition from symmetric to asymmetric fission around Th, some unexpected structures in the mass distributions in the fission of systems around Z = 80-84, and an extended systematics of the odd-even effect in the fission fragment Z distributions have all been measured (Andreyev et al 2018 Rep. Prog. Phys. 81 016301). Three classes of model descriptions of fission presently appear to be the most promising or the most successful. Self-consistent quantum-mechanical models fully consider the quantum-mechanical features of the fission process. Intense efforts are presently being made to develop suitable theoretical tools (Schunck and Robledo 2016 Rep. Prog. Phys. 79 116301) for modeling the non-equilibrium, large-amplitude collective motion leading to fission. Stochastic models provide a fully developed technical framework. The main features of the fission-fragment mass distribution have been well reproduced from mercury to fermium and beyond (Möller and Randrup 2015 Phys. Rev. C 91 044316). However, limited computer resources still impose restrictions, for example, on the number of collective coordinates and on an elaborate description of the fission dynamics. In an alternative semi-empirical approach (Schmidt et al 2016 Nucl. Data Sheets 131 107), considerable progress in describing the fission observables has been achieved by combining several theoretical ideas, which are essentially well known. This approach exploits (i) the topological properties of a continuous function in multidimensional space, (ii) the separability of the influence of fragment shells and the macroscopic properties of the compound nucleus, (iii) the properties of a quantum oscillator coupled to a heat bath of other nuclear degrees of freedom, (iv) an early freeze-out of collective motion, and (v) the application of statistical mechanics for describing the thermalization of intrinsic excitations in the nascent fragments. This new approach reveals a high degree of regularity and allows the calculation of high-quality data that is relevant to nuclear technology without specifically adjusting the empirical data of individual systems.

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Section: Former Status Of Knowledgementioning

confidence: 99%

Section: Former Status Of Knowledgementioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

See 2 more Smart Citations

Review on the progress in nuclear fission—experimental methods and theoretical descriptions

2018

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“…This is based on the assumptions that the nuclear structure, which may change dramatically from one nucleus to another, plays a minor role. But a difference of only one neutron can change the overall fragment mass distribution from asymmetric to symmetric, as observed for example in the case of 257,258 Fm [33].…”

Section: Cross Section Data and Other Fission Observables For Improvimentioning

confidence: 98%

The fission experimental programme at the CERN n_TOF facility: status and perspectives

et al. 2020

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Neutron-induced fission reactions play a crucial role in a variety of fields of fundamental and applied nuclear science. In basic nuclear physics they provide important information on properties of nuclear matter, while in nuclear technology they are at the basis of present and future reactor designs. Finally, there is a renewed interest in fission reactions in nuclear astrophysics due to the multi-messenger observation of neutron star mergers and the important role played by fission recycling in r -process nucleosynthesis. Although studied for several decades, many fundamental questions still remain on fission reactions, while modern applications and the development of more reliable nuclear models require high-accuracy and consistent experimental data on fission cross sections and other fission observables. To address these needs, an extensive fission research proa gramme has been carried out at the n_TOF neutron timeof-flight facility at CERN during the last 18 years, taking advantage of the high energy resolution, high luminosity and wide energy range of the neutron beam, as well as of the detection and data acquisition systems designed for this purpose. While long-lived isotopes are studied on the 185 m long flight-path, the recent construction of a second experimental area at a distance of about 19 m has opened the way to challenging measurements of short-lived actinides. This article provides an overview of the n_TOF experimental programme on neutron-induced fission reactions along with the main characteristics of the facility, the various detection systems and data analysis techniques used. The most important results on several major and minor actinides obtained so far and the future perspectives of fission measurements at n_TOF are presented and discussed.

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Relativistic Effects of the Superheavy Elements

Schwerdtfeger

Seth

1998

Encyclopedia of Computational Chemistry

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Spontaneous Fission

Cited by 62 publications

References 30 publications

Review on the progress in nuclear fission—experimental methods and theoretical descriptions

Review on the progress in nuclear fission—experimental methods and theoretical descriptions

The fission experimental programme at the CERN n_TOF facility: status and perspectives

Relativistic Effects of the Superheavy Elements

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