Abstract
Resolved resonance evaluation of the 239Pu cross section in the energy range up 4 keV has been carried out with the SAMMY computer code. Existing resolved resonance evaluation such as ENDF/B-VIII.0 and JENDL4 data libraries for 239Pu is limited to 2.5 keV whereas above this energy the unresolved resonance methodology is used. High resolution transmission and fission data taken at the Oak Ridge Electron Linear Accelerator (ORELA) permitted extending the resonance region up to 4 keV. The thermal and average fission cross section values calculated with the resonance parameters derived in the evaluation fall close to that indicated in the suggested IAEA fission standards.
Highlights
An R-matrix resonance evaluation of the 239Pu cross section was carried out at the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in support of criticality safety applications
Recent capture data measurement performed at the Los Alamos Neutron Science Center (LANSCE) with the Detector for Advanced Neutron Capture Measurements (DANCE) was included in the evaluation
The resonance evaluation in most of the existing nuclear data library is limited to the energy range from thermal to 2.5 keV with an unresolved resonance range (URR) representation above 2.5 keV
Summary
An R-matrix resonance evaluation of the 239Pu cross section was carried out at the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in support of criticality safety applications. Issues with the unresolved resonance representation of the 239Pu cross sections above 2.5 keV motivated the study of the feasibility of applying a resolved resonance representation from 2.5 keV to 4 keV. A resolved resonance range (RR) evaluation of the 239Pu cross section was carried using the multilevel SAMMY R-matrix code.[1] The resonance evaluation in most of the existing nuclear data library is limited to the energy range from thermal to 2.5 keV with an unresolved resonance range (URR) representation above 2.5 keV. An apparent issue with reproducing the average cross section in the URR exists in the energy range 2.2 keV to 4 keV. While the URR evaluation were carefully done cluster of resonances in the energy range 2.5 keV to 4 keV precluded reproducing the average cross section based solely on the average resonance parameters
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