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Title: NEUTRON CROSS SECTION EVALUATIONS OF FISSION PRODUCTS BELOW THE FAST ENERGY REGION

Neutron cross section evaluations of the fission-product isotopes, {sup 95}Mo, {sup 99}Tc, {sup 101}Ru, {sup 103}Rh, {sup 105}Pd, {sup 109}Ag, {sup 131}Xe, {sup 133}Cs, {sup 141}Pr, {sup 141}Nd, {sup 147}Sm, {sup 149}Sm, {sup 150}Sm, {sup 151}Sm, {sup 152}Sm, {sup 153}Eu, {sup 155}Gd, and {sup 157}Gd were carried out below the fast neutron energy region within the framework of the BNL-KAERI international collaboration. In the thermal energy region, the energy dependence of the various cross-sections was calculated by applying the multi-level Breit-Wigner formalism. In particular, the strong energy dependence of the coherent scattering lengths of {sup 155}Gd and {sup 157}Gd were determined and were compared with recent calculations of Lynn and Seeger. In the resonance region, the recommended resonance parameters, reported in the BNL compilation, were updated by considering resonance parameter information published in the literature since 1981. The s-wave and, if available, p-wave reduced neutron widths were analyzed in terms of the Porter-Thomas distribution to determine the average level spacings and the neutron strength functions. Average radiative widths were also calculated from measured values of resolved energy resonances. The average resonance parameters determined in this study were compared with those in the BNL and other compilations, as well as the more » ENDF/B-VI, JEF-2.2, and JENDL-3.2 data libraries. The unresolved capture cross sections of these isotopes, computed with the determined average resonance parameters, were compared with measurements, as well as the ENDF/B-VI evaluations. To achieve agreement with the measurements, in a few cases minor adjustments in the average resonance parameters were made. Because of astrophysical interest, the Maxwellian capture cross sections of these nuclides at a neutron temperature of 30 keV were computed and were compared with other compilations and evaluations. « less
Authors:
; ;
Publication Date:
OSTI Identifier:
759039
Report Number(s):
BNL--NCS-67469; KB0401040
R&D Project: NE003; KB0401040; TRN: US0005223
DOE Contract Number:
AC02-98CH10886
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 11 May 2000
Research Org:
Brookhaven National Lab., Upton, NY (US)
Sponsoring Org:
DOE/SC (US)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CAPTURE; COHERENT SCATTERING; CROSS SECTIONS; FAST NEUTRONS; FISSION PRODUCTS; NEUTRON TEMPERATURE; PORTER-THOMAS DISTRIBUTION; STRENGTH FUNCTIONS; MOLYBDENUM 95; TECHNETIUM 99; RUTHENIUM 101; RHODIUM 103; PALLADIUM 105; SILVER 109; XENON 131; CESIUM 133; PRASEODYMIUM 141; NEODYMIUM 141; SAMARIUM 147; SAMARIUM 149; SAMARIUM 150; SAMARIUM 151; SAMARIUM 152; EUROPIUM 153; GADOLINIUM 155; GADOLINIUM 157