Actinide Neutron-induced Fission Cross Section Measurements at LANSCE.
Actinide Neutron-induced Fission Cross Section Measurements at LANSCE.

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Published: 2010

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Fission cross sections of a range of actinides have been measured at the Los Alamos Neutron Science Center (LANSCE) in support of nuclear energy applications in a wide energy range from sub-thermal energies up to 200 MeV. A parallel-plate ionization chamber are used to measure fission cross sections ratios relative to the 235U standard while incident neutron energies are determined using the time-of-flight method. Recent measurements include the {sup 233,238}U, 239−242Pu and 243Am neutron-induced fission cross sections. Obtained data are presented in comparison with ex isting evaluations and previous data.

Neutron-Induced Fission Cross Section Measurements for Uranium Isotopes and Other Actinides at LANSCE.
Neutron-Induced Fission Cross Section Measurements for Uranium Isotopes and Other Actinides at LANSCE.

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Published: 2012

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A well established program of neutron-induced fission cross section measurement at Los Alamos Neutron Science Center (LANSCE) is supporting the Fuel Cycle Research program (FC R & D). The incident neutron energy range spans from sub-thermal up to 200 MeV by combining two LANSCE facilities, the Lujan Center and the Weapons Neutron Research center (WNR). The time-of-flight method is implemented to measure the incident neutron energy. A parallel-plate fission ionization chamber was used as a fission fragment detector. The event rate ratio between the investigated foil and a standard 235U foil is translated into a fission cross section ratio. Thin actinide targets with deposits of

Fission Cross Section Measurements of Actinides at LANSCE.
Fission Cross Section Measurements of Actinides at LANSCE.

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Published: 2010

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Fission cross sections of a range of actinides have been measured at the Los Alamos Neutron Science Center (LANSCE) in support of nuclear energy applications. By combining measurement at two LANSCE facilities, Lujan Center and the Weapons Neutron Research center (WNR), differential cross sections can be measured from sub-thermal energies up to 200 MeV. Incident neutron energies are determined using the time-of-flight method, and parallel-plate ionization chambers are used to measure fission cross sections relative to the 235U standard. Recent measurements include the {sup 233,238}U, {sup 239,242}Pu and 243Am neutron-induced fission cross sections. In this paper preliminary results for cross section data of 243Am and 233U will be presented.

Nuclear Fission and Neutron-induced Fission Cross-sections
Nuclear Fission and Neutron-induced Fission Cross-sections

Author: Gordon Douglas James

Publisher: Pergamon

Published: 1981

Total Pages: 304

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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.

Actinide Cross Section Evaluations
Actinide Cross Section Evaluations

Author: D. A. Brown

Publisher:

Published: 2004

Total Pages: 7

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The Livermore Computational Nuclear Physics group is charged with producing updated neutron incident cross section evaluations for all the actinides in the coming year, concentrating on neutron induced fission, neutron capture and (n,2n) cross sections. We attack this daunting task either by adopting other recent evaluations or by performing our own. Owing to the large number of nuclei involved, we seek to automate this process as much as possible. For this purpose, we have developed a series of computer codes: x41, an interface to the EXFOR database, fete, a code that translates ENDF/B formatted evaluations into a computationally convenient form, and da{_}fit, a fitting code that takes all relevant EXFOR data for a reaction or set of reactions and performs a generalized least square fit to them, subject to various constraints and other prior information.

Measurements of Neutron-induced Fission Cross-section Ratios Involving Isotopes of Uranium and Plutonium. [0. 001 to 30 MeV, Cross Sections].
Measurements of Neutron-induced Fission Cross-section Ratios Involving Isotopes of Uranium and Plutonium. [0. 001 to 30 MeV, Cross Sections].

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Published: 1976

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A procedure, called the threshold cross section method was applied to our experimental data involving four uranium (233U 234U, 236U, and 238U) and five plutonium (239Pu, 24°Pu, 241Pu, 242Pu, and 244Pu) isotopes to determine ratios of fission cross sections relative to 235U. The data were gathered using ionization fission chambers and the time-of-flight technique at the LLL 100-MeV electron linear accelerator: measurements span the neutron energy range of 0.001 to 30 MeV. Experimental uncertainties common to past measurements were either eliminated or significantly reduced in this study by use of the threshold method, thereby making higher accuracies possible. The cross section ratios are absolute in the sense that they do not depend on the work of others. Results from our ratios involving 233U, 235U, 238U, and 239Pu are used to illustrate this method.

Neutron-induced Fission-cross-section Measurements and Calculations of Selected Transplutonic Isotopes
Neutron-induced Fission-cross-section Measurements and Calculations of Selected Transplutonic Isotopes

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Published: 1982

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The neutron-induced fission cross sections of /sup 242m/Am and 245Cm have been measured over an energy range of 10−4 eV to approx. 20 MeV in a series of experiments at three facilities during the past several years. The combined results of these measurements, in which only sub-milligram quantities of enriched isotopes were used, yield cross sections with uncertainties of approximately 5% below 10 MeV relative to the 235U standard cross section used to normalize the data. We summarize the resonance analysis of the /sup 242m/Am(n, f) cross section in the eV region. Hauser-Feshbach statistical calculations of the detailed fission cross sections of 235U and 245Cm have been carried out over the energy region from 0.1 to 5 MeV and these results are compared with our experimental data.

Neutron-Induced Partial Gamma-Ray Cross-Section Measurements with GEANIE at LANSCE
Neutron-Induced Partial Gamma-Ray Cross-Section Measurements with GEANIE at LANSCE

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Published: 2000

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GEANIE is the first large-scale Ge detector array used in conjunction with a high-energy neutron spallation source. GEANIE consists of eleven Compton-suppressed planar detectors, nine suppressed and six unsuppressed co-axial detectors. Spallation neutrons are provided by the LANSCE/WNR facility, and reaction neutron energies are determined via time-of-flight. neutron flux is monitored in-beam with a fission chamber. GEANIE at LANSCE/WNR currently emphasizes the measurement of partial gamma-ray cross sections as a function of neutron energy. Absolute cross section measurements require a complete understanding of array performance. Important effects include intrinsic detector efficiency, beam and detector geometry corrections, target attenuation, and deadtime. Measurements and calculations of these effects will be presented for the specific cases of iron and actinide targets. The use of radioactive targets incurs a large deadtime penalty. In order to increase data throughput they are making plans to move to a triggerless data acquisition system. These modifications and other improvements to the electronics for better timing will be discussed.