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in subjects: "Plutonium 239 Target"

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Beta and gamma decay heat measurements between 0.1s-50,000s for neutron fission of {sup 235}U, {sup 238}U and {sup 239}Pu. Progress report, March 1, 1993--January 31, 1994

Decay heat measurements following the fast fission of {sup 238}U are well underway. The He-jet system and spectrometers were moved to the 1 MW research reactor to gain sufficient fast neutron flux for these measurements. On the Van de Graaff accelerator, the He-jet capillary has been shortened so that beta and gamma measurements following the thermal neutron fission of {sup 235}U could be made down to delay times near 0.1 s. Gamma-ray response functions are now well characterized for gamma ener… more

Date: June 1, 1994

Creator: Schier, W. A. & Couchell, G. P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Ternary particles with extreme N/Z ratios from neutron-induced fission

The existing ternary fission models can well reproduce the yields of the most abundant light charged particles. However, these models tend to significantly overestimate the yields of ternary particles with an extreme N/Z ratio: {sup 3}He, {sup 11}Li, {sup 14}Be, etc. The experimental yields of these isotopes were investigated with the recoil separator LOHENGRIN down to a level of 10{sup {minus}10} per fission. Results from the fissioning systems {sup 233}U (n{sub th}, f), {sup 235}U(n{sub th},f… more

Date: May 16, 2000

Creator: Koster, U.; Faust, H.; Friedrichs, T.; Oberstedt, S.; Fioni, G.; Grob, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The data base of the standards and related cross sections after ENDF/B-VI

A brief description is given of the procedure used in the global evaluation of the standards and other important cross sections for ENDF/B-VI. The standards involved were {sup 6}Li(n,t), {sup 10}B(n,{alpha}{sub 1}), {sup 197}Au(n,{gamma}), and {sup 235}U(n,f). Other standards evaluated independently were H(n,p), {sup 3}He(n,p), C(n,f). The other cross sections involved were {sup 238}U(n,{gamma}), {sup 238}U(n,f), and {sup 239}Pu(n,f). The results of the evaluation are compared with new or revis… more

Date: December 31, 1992

Creator: Poenitz, W.P. & Carlson, A.D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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On the ENDF/B unresolved resonance region formalism representation for sup 239 Pu

The purpose of this work is to compare the performance of several cross-section evaluation files for the calculation of average cross sections in the unresolved resonance region and to test the validity of the ENDF/B methodology for the calculation of self-shielding factors in this region. The {sup 239}Pu neutron cross sections were used for this comparison since a multilevel R-matrix analysis was available, which extended the resolved resonance region from its present ENDF/B limit of 300 eV up… more

Date: January 1, 1990

Creator: Ono, S.; Paviotti-Corcuera, R. (Centro Tecnico Aerospacial, Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados); Perez, R.B. (Tennessee Univ., Knoxville, TN (USA). Dept. of Nuclear Engineering) & de Saussure, G. (Oak Ridge National Lab., TN (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron scattering studies in the actinide region. Progress report, August 1, 1992--July 31, 1993

This report discusses the following topics: Prompt fission neutron energy spectra for {sup 235}U and {sup 239}Pu; Two-parameter measurement of nuclear lifetimes; ``Black`` neutron detector; Data reduction techniques for neutron scattering experiments; Inelastic neutron scattering studies in {sup 197}Au; Elastic and inelastic scattering studies in {sup 239}Pu; and neutron induced defects in silicon dioxide MOS structures.

Date: September 1, 1993

Creator: Kegel, G. H. R. & Egan, J. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Neutron scattering studies in the actinide region. Progress report, August 1, 1991--July 31, 1994

During the period August 1, 1991 to July 31, 1994 the authors report progress on the following: (a) prompt fission neutron energy spectra for {sup 235}U and {sup 239}Pu; (b) two-parameter measurement of nuclear lifetimes; (c) `black` neutron detector; (d) data reduction techniques for neutron scattering experiments; (e) elastic and inelastic neutron scattering studies in {sup 197}Au; (f) elastic and inelastic neutron scattering studies in {sup 239}Pu; (g) neutron induced defects in silicon diox… more

Date: September 1, 1994

Creator: Kegel, G. H. R. & Egan, J. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The simultaneous evaluation of the standards and other cross sections of importance for technology

The simultaneous evaluation of the cross sections of {sup 6}Li(n,{alpha}), {sup 6}Li(n,n), {sup 10}B(n,{alpha}{sub 0}), {sup 10}B(n,{alpha}{sup 1}), {sup 10}B(n,n), {sup 197}Au(n,{gamma}), {sup 238}U(n,{gamma}), {sup 235}U(n,f), {sup 239}Pu(n,f), and {sup 238}U(n,f) and the thermal constants was part of the evaluation of these data for ENDF/B-VI The FORTRAN codes and the data files used for the simultaneous evaluation are documented in the present report. Corrections for some data reported in t… more

Date: September 1, 1997

Creator: Poenitz, W.P. & Aumeier, S.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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SUR, a program to generate error covariance files

Covariance matrices were calculated for the $sup 238$U, $sup 241$Pu, and $sup 239$Pu fission cross sections and for the $sub 23$$sub 8$ $sup 240$Pu, $sup 241$Pu, and $sup 239$Pu capture cross sections. A computer program was written which uses the evaluated ENDF/B data files and the measured or evaluated (from other evaluations) cross sections for the calculation of the uncertainty files. An effort has been made to make the output of the program consistent with the ENDF/B error files format. A … more

Date: March 1, 1976

Creator: Difilippo, F. C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Evaluation and testing of n + sup 239 Pu data for ENDF/B-VI in the keV and MeV energy region

A new analysis of neutron-induced reactions on {sup 239}Pu above E{sub n} = 20 keV was performed as part of the evaluation activity for Version 6 of ENDF/B. This study merges results from a new theoretical analysis of n + {sup 239}Pu reactions with covariance analyses of experimental data for the {sup 239}Pu total and (n,f) cross sections and for the prompt fission neutron multiplicity. The results of this study are combined with a new analysis of the resolved and unresolved resonance regions o… more

Date: January 1, 1991

Creator: Young, P.G. & MacFarlane, R.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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General purpose nuclear data evaluations for ENDF/B-VI: Impact of cross-section standards

Over the past year the Cross Section Evaluation Working Group (CSEWG) has finalized and issued new evaluations for over 70 nuclides in Version 6 of ENDF/B. These data provide the foundation for a new series of reactor benchmark calculations. An integral part of the evaluation effort for ENDF/B-VI has been the most ambitious effort ever undertaken to systematically and simultaneously reevaluate the cross sections used for neutron standards. While a number of the materials and reactions identifie… more

Date: January 1, 1990

Creator: Young, P.G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear data and measurements series: Ratio of the prompt-fission-neutron spectrum of plutonium 239 to that of uranium 235

The prompt-fission-neutron spectrum resulting from /sup 239/Pu fission induced by 0.55 MeV incident neutrons is measured from 1.0 to 10.0 MeV relative to that of /sup 235/U fission induced by the same incident-energy neutrons. The measurements employ the time-of-flight technique. Energy-dependent ratios of the two spectra are deduced from the measured values over the energy range 1.0 to 10.0 MeV. The experimentally-derived ratio results are compared with those calculated from ENDF/B-V, revision… more

Date: September 1, 1986

Creator: Sugimoto, M.; Smith, A. B. & Guenther, P. T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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

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

Date: January 1, 1976

Creator: Stewart, L. & Howerton, R. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron spectroscopy. Progress report, 1 October 1976--30 September 1977. [Summary of research progress in neutron spectroscopy at the Columbia University Department of Mechanical and Nuclear Engineering]

During 1977 a six week run was performed at ORELA using the new data acquisition system based on the PDP-11. Coincident double energy fission fragments were measured as a function of neutron time-of-flight for /sup 229/Th, /sup 235/U and /sup 239/Pu. Data was also obtained in the thermal energy region. Extensive results are reported on the 1976 /sup 229/Th measurements with 2 families of widely differing fission widths determined. Earlier results on the variation of the ratio of symmetric to as… more

Date: January 1, 1977

Creator: Havens, W.W. Jr.; Melkonian, E. & Felvinci, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Theoretical analyses of (n,xn) reactions on sup 235 U, sup 238 U, sup 237 Np, and sup 239 Pu for ENDF/B-VI

Theoretical analyses were performed of neutron-induced reactions on {sup 235}U, {sup 238}U, {sup 237}Np, and {sup 239}Pu between 0.01 and 20 MeV in order to calculate neutron emission cross sections and spectra for ENDF/B-VI evaluations. Coupled-channel optical model potentials were obtained for each target nucleus by fitting total, elastic, and inelastic scattering cross section data, as well as low-energy average resonance data. The resulting deformed optical model potentials were used to cal… more

Date: January 1, 1991

Creator: Young, P. G. & Arthur, E. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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

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 calc… more

Date: January 1, 1986

Creator: Zucker, M. S. & Holden, N. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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R-matrix analysis of the /sup 239/Pu neutron cross sections

/sup 239/Pu neutron cross-section data in the resolved resonance region were analyzed with the R-Matrix Bayesian Program SAMMY. Below 30 eV the cross sections computed with the multilevel parameters are consistent with recent fission and transmission measurements as well as with older capture and alpha measurements. Above 30 eV no suitable transmission data were available and only fission cross-section measurements were analyzed. However, since the analysis conserves the complete covariance mat… more

Date: January 1, 1985

Creator: Desaussure, G.; Perez, R.B. & Macklin, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Status of nuclear data of importance for LMFBR applications prior to the evaluation of ENDF/B-VI

The evaluation of nuclear data of importance to the LMFBR program has shifted to a Nuclear Data Evaluation Task Force. It is anticipated that the results of these evaluations will be incorporated in ENDF/B-VI. However, several cross sections for reactor applications are included in a simultaneous evaluation of the standard cross sections for ENDF/B-VI organized by the Standard Subcommittee of CSEWG. Cross sections included in this simultaneous evaluation are those of /sup 6/Li(n,..cap alpha..),… more

Date: January 1, 1984

Creator: Poenitz, W.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron induced fission cross section ratios for /sup 232/Th, /sup 235,238/U, /sup 237/Np, and /sup 239/Pu from 1 to 400 MeV

Time-of-flight measurements of neutron induced fission cross section ratios for /sup 232/Th, /sup 235,238/U, /sup 237/Np, and /sup 239/Pu, were performed using the WNR high intensity spallation neutron source located at Los Alamos National Laboratory. A multiple-plate gas ionization chamber located at a 20-m flight path was used to simultaneously measure the fission rate for all samples over the energy range from 1 to 400 MeV. Because the measurements were made with nearly identical neutron flu… more

Date: 1988

Creator: Lisowski, P. W.; Ullmann, J. L.; Balestrini, S. J.; Carlson, A. D.; Wasson, O. A. & Hill, N. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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R-matrix analyses of the /sup 235/U and /sup 239/Pu neutron cross sections

The resonance parameter analysis code SAMMY was used to perform consistent resonance analyses of several /sup 235/U and /sup 239/Pu fission and capture cross section and transmission measurements up to 110 eV for /sup 235/U and up to 1 keV for /sup 239/Pu. The method of analysis, the measurement selection and the results are briefly outlined in this paper.

Date: January 1, 1988

Creator: Derrien, H.; de Saussure, G.; Larson, N. M.; Leal, L. C. & Perez, R. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear modeling of the /sup 239/Pu(n,xn) excitation function

Calculated excitation functions for the (n,2n) and (n,3n) reactions on /sup 239/Pu are presented. In these calculations precompound plus compound decay models with experimentally deduced fission probabilities are used. A range of results are presented indicating the uncertainty in the model calculations. Experimental measurements which would constrain the range of modeled result are suggested. 21 references.

Date: January 1, 1984

Creator: Blann, M. & White, R.M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Neutron cross section standards evaluations for ENDF/B-VI

The neutron cross section standards are now being evaluated as the initial phase in the development of the new ENDF/B-VI file. These standards evaluations are following a somewhat different process compared with that used for earlier versions of ENDF. The primary effort is concentrated on a simultaneous evaluation using a generalized least squares program, R-matrix evaluations, and a procedure for combining the results of these evaluations. The ENDF/B-VI standards evaluation procedure is outlin… more

Date: 1985

Creator: Carlson, A. D.; Poenitz, W. P.; Hale, G. M. & Peelle, R. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Measurement of the energy dependence of prompt fission neutron emission from /sup 233/U, /sup 235/U, and /sup 239/Pu for E = 0. 0005 to 10 MeV relative to emission from spontaneous fission of /sup 252/Cf

A series of experiments has been performed to measure the dependence on the incident neutron energy of anti nu/sub p/(E), the average number of prompt neutrons emitted per fission, of /sup 233/U, /sup 235/U, and /sup 239/Pu relative to anti nu/sub p/ (/sup 252/Cf), the average number of prompt neutrons emitted in spontaneous fission of /sup 252/Cf. The incident energy range was 0.0005 to 10 MeV. A white neutron source was generated by the Oak Ridge Electron Linear Accelerator and the energies o… more

Date: January 1, 1985

Creator: Gwin, R.; Spencer, R. R. & Ingle, R. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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

Recent development in the theory and practice of neutron correlation (''coincidence'') counting require knowledge of the higher factorial moments of the P/sub ..nu../ distribution (the probability that (..nu..) 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 ..nu../ is reasonably well known, in… more

Date: January 1, 1986

Creator: Zucker, M. S. & Holden, N. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Status of fast neutron nuclear data for /sup 239/Pu

Recent energy-averaged data (fission, total cross section, scattering and anti nu/sub p/) describing the interaction of fast neutrons with /sup 239/Pu are discussed, with emphasis on neutron energies higher than the inelastic scattering threshold. The linkage between such experimental data and new theoretical calculations is described in context of their influence on a new revision to the ENDF/B-V /sup 239/Pu evaluation. Results from this new revision are compared with other current /sup 239/Pu… more

Date: January 1, 1985

Creator: Arthur, E. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department