Patrick Talou

Monte Carlo Simulation for Particle and γ-Ray Emissions in Statistical Hauser-Feshbach Model

Monte Carlo simulations for particle and γ-ray emissions from a compound nucleus based on the Hauser-Feshbach statistical theory with pre-equilibrium emission are performed. The simulation yields reliable nuclear-reaction-wise energy spectra, or so-called exclusive spectra, for emitted neutrons and γ-rays, which are required in particle transport calculations for nuclear applications. The Monte Carlo method is applied to neutron-induced nuclear reactions on 56Fe, and the results are compared with a traditional deterministic method. The neutron and γ-ray emission correlation is examined by gating on an 847 keV γ-ray that is produced by an inelastic scattering process. The partial γ-ray energy spectra for different γ-ray multiplicities are inferred using this Monte Carlo method. In addition, we investigate a correlation between two neutrons in the (n,2n) reaction.

Evaluation and propagation of the 239Pu fission cross-section uncertainties using a monte carlo technique

Abstract We present an approach to uncertainty quantification for nuclear applications that combines the covariance evaluation of differential cross-section data and the error propagation from matching a criticality experiment using a neutron-transport calculation. We have studied the reduction in uncertainty of 239Pu fission cross sections by using a one-dimensional neutron-transport calculation with the PARTISN code. The evaluation of 239Pu differential cross-section data is combined with a criticality measurement (Jezebel) using a Bayesian method. To quantify the uncertainty in such calculations, we generate a set of random samples of the cross sections, which represents the covariance matrix, and estimate the distribution of calculated quantities, such as criticality. We show that inclusion of the Jezebel data reduces uncertainties in estimating neutron multiplicity.

Uncertainty Quantification of Prompt Fission Neutron Spectrum for n(0.5 MeV) + 239Pu

Abstract Uncertainties associated with the prompt fission neutron spectrum (PFNS) of n(0.5 MeV) + 239Pu evaluated for the ENDF/B-VII.0 library are estimated using known experimental information and model parameter uncertainties in the framework of the Madland-Nix model. The model parameters used for the ENDF/B-VII.0 evaluation are also used in the present work. A covariance matrix is obtained, and its eigenvalues are estimated. Sampled spectra are then used in PARTISN transport simulations to infer the impact of PFNS uncertainties on the calculation of the multiplication factor keff in the Jezebel critical assembly. The present evaluated PFNS uncertainties lead to ˜0.24% uncertainty in the Jezebel keff. Finally, multigroup covariance matrices are produced in 33- and 590-group structures.

Evaluation and Uncertainty Quantification of Prompt Fission Neutron Spectra of Uranium and Plutonium Isotopes

Abstract The prompt fission neutron spectra (PFNS) of the low-incident-energy neutron-induced fission reactions n + 229-238U and n + 235-242Pu have been systematically evaluated using differential experimental data and the Los Alamos model (LA model). Using the first-order, linear Kalman filter, the LA model parameters are constrained using the experimental data and an evaluation of the PFNS and its uncertainties across a suite of isotopes’ results. Correlations between isotopes of each actinide are presented through the model parameter correlations, and the resulting evaluations can be used to fill in inconsistencies within the ENDF/B-VII.1 library where PFNS data are scarce or in need of an update.

Improved Evaluations of Neutron-Induced Reactions on Americium Isotopes

Abstract The suite of neutron-induced reactions on 241Am, 242gAm, 242mAm, and 243Am has been evaluated for incident neutron energies above the unresolved resonance region and up to 20 MeV. Modern theoretical models and computational techniques were extensively used because of the rather limited experimental information. However, when available, experimental data were used to guide and benchmark the present evaluation work. All evaluation results were formatted and distributed as ENDF data files for possible inclusion in the ENDF/B-VII library.

Late-time emission of prompt fission γ rays

The emission of prompt fission

Benchmarking nuclear fission theory

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Impact of the Normalization Condition and Model Information on Evaluated Prompt Fission Neutron Spectra and Associated Uncertainties

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

Correlated Prompt Fission Data in Transport Simulations

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Uncertainties in nuclear fission data

-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