26 research outputs found
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Review of fast-neutron capture cross sections of the higher plutonium isotopes and Am-241
The fast-neutron capture cross sections of Pu-240, 241, 242 and Am-241 are reviewed. These nuclides are important to core physics of reactors that contain Pu-239. There have been several significant measurements of these cross sections in recent years. These measurements were instigated by the need for these cross sections for reactor calculations involving high burn-up and build-up of the higher actinides. These recent measurements have satisfied the urgent need for these cross sections in the context of the accuracy needed relative to these of the major fissile isotopes. Problems that exist in the experimental measurements and their evaluation are discussed
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Direct comparison of different experimental techniques for measuring neutron capture and fission cross sections for Pu
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Review of microscopic neutron cross section data for the higher plutonium isotopes in the resonance region
The microscopic neutron cross section data for plutonium-240, -241, and -242 in the resonance region are reviewed. In the context of importance to reactors, the data on plutonium-240 are acceptable except for the resonance parameters of the 1-eV resonance. Plutonium-241 has discrepancies in the cross sections from thermal to 3 eV and to a lesser extent in the fission and capture cross section in the unresolved resonance region. The plutonium-242 cross sections appear to be known with sufficient accuracy as compared with the other plutonium isotopes. 12 figures, 1 table
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Evaluation of neutron cross sections for fissile and fertile nuclides in the keV range
Procedures for evaluation of radiative capture, elastic and inelastic processes, and fission in the keV region of neutron energies are described. The use of theoretical tools along with the available ENDF utility codes allows the evaluator to extend and expand upon the experimental data, which are often sparse or discrepant. A few problems with the utility codes are noted, and suggestions, made for improvement and extension. Some ENDF/B-V cross sections for important nuclei are plotted in detail, and show significant need for improvement in the shape of the individual partial cross sections to be consistent with theoretical predictions within the constraints of the experimental data. In particular, uranium and plutonium isotopic evaluations, which are of critical importance to fast reactors, deserve careful attention with improved methodology. 8 figures
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Capture in the 1. 15-keV iron resonance
The 1.15-keV resonance in iron is important to reactors in that a major part of the iron capture integral is due to this one resonance. This resonance is also a good test case for capture gamma-ray detectors, which are meant to have an efficiency independent of gamma-ray energy spectra, because this resonance has an unusually hard spectrum and other iron resonances do not. There have been severe discrepancies among different groups who have measured the capture area and transmission of this resonance. A new measurement, employing C/sub 6/F/sub 6/ liquid scintillators and pulse-height weighting to effect total energy detection, has been made of the ratio of the capture area of the 22.8-keV resonance relative to that of the 1.15-keV resonance. The 22.8-keV resonance has a relatively soft gamma-ray spectrum and there is agreement on the capture area. The results (2.91 +- 0.17) agree well with transmission measurements and confirm the applicability of total energy detectors for use on capture resonances with very hard capture gamma-ray spectra
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Compilation of requests for nuclear data
This compilation represents the current needs for nuclear data measurements and evaluations as expressed by interested fission and fusion reactor designers, medical users of nuclear data, nuclear data evaluators, CSEWG members and other interested parties. The requests and justifications are reviewed by the Data Request and Status Subcommittee of CSEWG as well as most of the general CSEWG membership. The basic format and computer programs for the Request List were produced by the National Nuclear Data Center (NNDC) at Brookhaven National Laboratory. The NNDC produced the Request List for many years. The Request List is compiled from a computerized data file. Each request has a unique isotope, reaction type, requestor and identifying number. The first two digits of the identifying number are the year in which the request was initiated. Every effort has been made to restrict the notations to those used in common nuclear physics textbooks. Most requests are for individual isotopes as are most ENDF evaluations, however, there are some requests for elemental measurements. Each request gives a priority rating which will be discussed in Section 2, the neutron energy range for which the request is made, the accuracy requested in terms of one standard deviation, and the requested energy resolution in terms of one standard deviation. Also given is the requestor with the comments which were furnished with the request. The addresses and telephone numbers of the requestors are given in Appendix 1. ENDF evaluators who may be contacted concerning evaluations are given in Appendix 2. Experimentalists contemplating making one of the requested measurements are encouraged to contact both the requestor and evaluator who may provide valuable information. This is a working document in that it will change with time. New requests or comments may be submitted to the editors or a regular CSEWG member at any time