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Talou, Patrick

Publications and source records attributed to Talou, Patrick.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

The Prompt Fission Neutron Spectrum of 235U for Einc 0.7-5.0 MeV

The Chi-Nu experiment aims to accurately measure the prompt fission neutron spectrum (PFNS) for the major actinides. At the Los Alamos Neutron Science Center (LANSCE), fission can be induced using the white neutron source. Using a two arm time of flight (T.O.F) technique; Chi-Nu presents a preliminary result of the low energy component of the 235U PFNS measured using an array of 22-Lithium glass scintillators.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2016

Late-time emission of prompt fission γ rays

The emission of prompt fission γ rays within a few nanoseconds to a few microseconds following the scission point is studied in the Hauser-Feshbach formalism applied to the deexcitation of primary excited fission fragments. Neutron and γ-ray evaporations from fully accelerated fission fragments are calculated in competition at each stage of the decay, and the role of isomers in the fission products, before β decay, is analyzed. The time evolution of the average total γ-ray energy, the average total γ-ray multiplicity, and the fragment-specific γ-ray spectra is presented in the case of neutron-induced fission reactions of 235 U and 239 Pu, as well as spontaneous fission of 252 Cf. The production of specific isomeric states is calculated and compared to available experimental data. About 7% of all prompt fission γ rays are predicted to be emitted between 10 ns and 5 μs following fission, in the case of 235 U and 239 Pu( n th ,f) reactions, and up to 3% in the case of 252 Cf spontaneous fission. The cumulative average total γ-ray energy increases by 2% to 5% in the same time interval. Lastly, those results are shown to be robust against significant changes in the model input parameters.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Neutron-induced fission: properties of prompt neutron and γ rays as a function of incident energy

We have applied the Hauser-Feshbach statistical theory, in a Monte-Carlo implementation, to the de-excitation of fission fragments, obtaining a reasonable description of the characteristics of neutrons and gamma rays emitted before beta decays toward stability. Originally implemented for the spontaneous fission of 252 Cf and the neutroninduced fission of 235 U and 239 Pu at thermal neutron energy, in this contribution we discuss the extension of the formalism to incident neutron energies up to 20 MeV. For the emission of pre-fission neutrons, at incident energies beyond second-chance fission, we take into account both the pre-equilibrium and statistical pre-fission components. Phenomenological parameterizations of mass, charge and TKE yields are used to obtain the initial conditions for the fission fragments that subsequently decay via neutron and emissions. Finally, we illustrate this approach for 239 Pu(n,f).

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Evaluating the 239 Pu prompt fission neutron spectrum induced by thermal to 30 MeV neutrons

We present a new evaluation of the 239 Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. In conclusion, selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Toward a New Evaluation of Neutron Standards

Measurements related to neutron cross section standards and certain prompt neutron fission spectra are being evaluated. In addition to the standard cross sections, investigations of reference data that are not as well known as the standards are being considered. We discuss procedures and codes for performing this work. A number of libraries will use the results of this standards evaluation for new versions of their libraries. Most of these data have applications in neutron dosimetry.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

Impact of new prompt fission neutron spectrum evaluations and the associated cross-correlations on critical assemblies using MCNP6 - 14385

Two recent re-evaluations of the neutron-induced prompt fission neutron spectrum (PFNS) of uranium and plutonium actinides have included some cross-correlated uncertainties that have not been released in a new nuclear data library. The first re-evaluation included cross-isotope correlations of the PFNS within each of the uranium and plutonium suites of actinides below the second-chance fission threshold. The second, more recent re-evaluation includes incident energy-dependent correlations of the {sup 239}Pu(n,f) PFNS. Both of these new evaluations and their cross-correlations, given the importance of these actinide quantities and because the impact of the incident energy-dependent correlations has never been studied previously, could have an impact on a variety of criticality safety applications. For example, the ke uncertainty due to the uranium PFNS uncertainties in the Big Ten critical assembly is underpredicted by ∼10% when the cross-isotope correlations in the uranium PFNS are ignored. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Preface by the CW2014 Organizers-Including Program, Advisory Board, Participants and Photo

This issue of the Nuclear Data Sheets contains the proceedings of the 'International Workshop on Nuclear Data Covariances'. This workshop was the third one in a series that started with the 'Workshop on Neutron Cross Section Covariances' (Port Je erson, USA, 2008) and continued with the 'Second Workshop on Neutron Cross Section Covariances' (Vienna, Austria, 2011). The current workshop returned to the US and took place in the center of the beautiful and historic city of Santa Fe, New Mexico, USA from April 28 to May 1, 2014. The purpose of this workshop was to bring together scientists in the field of nuclear data evaluation, nuclear reaction theory, reactor physics and associated experiments to review recent developments in nuclear data evaluation methodology as well as assess and discuss open questions regarding uncertainty estimates and associated formatting requirements from the point of view of the experimentalist, the theoretician, the evaluator as well as from application side, e.g. in transport calculations. The workshop was open to contributions on a wide variety of nuclear data observables (cross sections, fission yields, energy and angle spectra, etc.), from the resonance range up to the high energy range as well as for light to heavy elements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗