Chi-Nu measurements of the prompt fission neutron spectrum of {sup 235}U and {sup 239}Pu - 25581

Conference · Wed Aug 15 04:00:00 EDT 2018

OSTI ID:23055117

Kelly, K. J.; Gomez, J. A.; O'Donnell, J. M.; Devlin, M.; Haight, R. C.; Taddeucci, T. N.; Mosby, S. M.; Lee, H. Y.; Neudecker, D.; White, M. C.; Talou, P.; Fotiades, N.; Rising, M. E.; Solomon, C. J. ^[1]; Wu, C. Y.; Henderson, R.; Henderson, J.; Buckner, M. Q. ^[2]

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1. Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2. Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)

Knowledge of the prompt fission neutron spectrum is crucial for understanding the behavior of energetic nuclear systems. Although this energy spectrum has been measured for the major actinides {sup 235}U and {sup 239}Pu for decades, the majority of the available literature data lack the coverage of both incident and outgoing neutron energies and the precision required to accurately guide evaluations and fission models. The Chi-Nu experiment is designed to measure the prompt fission neutron spectrum for a wide range of incident and outgoing neutron energies with attention to uncertainty estimation and assessment of systematic errors in order to provide reliable guidance for evaluations and models of nuclear fission. Preliminary results of the prompt fission neutron spectrum from the neutron-induced fission of {sup 235}U and {sup 239}Pu are presented here, with a focus on the presence of spectral features near multi-chance fission thresholds, pre-equilibrium neutrons in the deduced spectrum, and also on trends of the mean fission neutron energy as a function of the incident neutron energy. While the mean energies of from ENDF/B-VIII.0 are in good agreement with those reported for {sup 235}U spectra, significant disagreements exist above an incident neutron energy of approximately 13 MeV for {sup 239}Pu. Furthermore, in general, the physics features regarding multi-chance fission and pre-equilibrium neutron emission newly-introduced into ENDF/B-VIII.0 appear provide an improved description of the data as compared to ENDF/B-VII.1. (authors)

• Research Organization: American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 23055117
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACCURACY
ACTINIDES
DESIGN
ENERGY SPECTRA
ERRORS
FISSION
FISSION NEUTRONS
MEV RANGE
NEUTRON EMISSION
NEUTRON SPECTRA
NUCLEAR DATA COLLECTIONS
PLUTONIUM 239
URANIUM 235