Advanced Monte Carlo modeling of prompt fission neutrons for thermal and fast neutron-induced fission reactions on {sup 239}Pu

Journal Article · Wed Jun 15 00:00:00 EDT 2011 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.83.064612· OSTI ID:21502796

Talou, P; Kawano, T ^[1]; Becker, B; Danon, Y ^[2]; Chadwick, M B ^[3]

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1. T-2 Nuclear Theory Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, New York 12180 (United States)
3. X-CP, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

Prompt fission neutrons following the thermal and 0.5 MeV neutron-induced fission reaction of {sup 239}Pu are calculated using a Monte Carlo approach to the evaporation of the excited fission fragments. Exclusive data such as the multiplicity distribution P({nu}), the average multiplicity as a function of fragment mass {nu}-bar(A), and many others are inferred in addition to the most used average prompt fission neutron spectrum {chi}(E{sub in},E{sub out}), as well as average neutron multiplicity {nu}-bar. Experimental information on these more exclusive data help constrain the Monte Carlo model parameters. The calculated average total neutron multiplicity is {nu}-bar{sub c}=2.871 in very close agreement with the evaluated value {nu}-bar{sub e}=2.8725 present in the ENDF/B-VII.0 library. The neutron multiplicity distribution P({nu}) is in very good agreement with the evaluation by Holden and Zucker. The calculated average spectrum differs in shape from the ENDF/B-VII.0 spectrum, evaluated with the Madland-Nix model. In particular, we predict more neutrons in the low-energy tail of the spectrum (below about 300 keV) than the Madland-Nix calculations, casting some doubts on how much scission neutrons contribute to the shape of the low-energy tail of the spectrum. The spectrum high-energy tail is very sensitive to the total kinetic energy distribution of the fragments as well as to the total excitation energy sharing at scission. Present experimental uncertainties on measured spectra above 6 MeV are too large to distinguish between various theoretical hypotheses. Finally, comparisons of the Monte Carlo results with experimental data on {nu}-bar(A) indicate that more neutrons are emitted from the light fragments than the heavy ones, in agreement with previous works.

• OSTI ID: 21502796
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 83, Issue 6; Other Information: DOI: 10.1103/PhysRevC.83.064612; (c) 2011 American Institute of Physics; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COMPARATIVE EVALUATIONS
EVAPORATION
EXCITATION
FAST NEUTRONS
FISSION
FISSION FRAGMENTS
FISSION NEUTRONS
HYPOTHESIS
KINETIC ENERGY
MASS
MEV RANGE 01-10
MONTE CARLO METHOD
MULTIPLICITY
NUCLEAR DATA COLLECTIONS
PLUTONIUM 239
SIMULATION
SPECTRA
THERMAL NEUTRONS
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
BARYONS
CALCULATION METHODS
ELEMENTARY PARTICLES
ENERGY
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVALUATION
EVEN-ODD NUCLEI
FERMIONS
HADRONS
HEAVY NUCLEI
ISOTOPES
MEV RANGE
NEUTRONS
NUCLEAR FRAGMENTS
NUCLEAR REACTIONS
NUCLEI
NUCLEONS
PHASE TRANSFORMATIONS
PLUTONIUM ISOTOPES
RADIOISOTOPES
SPONTANEOUS FISSION RADIOISOTOPES
YEARS LIVING RADIOISOTOPES