Download or read book Neutron Cross Section Covariances in the Resolved Resonance Region written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a detailed analysis of the impact of resonance parameter uncertainties on covariances for neutron capture and fission cross sections in the resolved resonance region. Our analysis uses the uncertainties available in the recently published Atlas of Neutron Resonances employing the Multi-Level Breit-Wigner formalism. We consider uncertainties on resonance energies along with those on neutron-, radiative-, and fission-widths and examine their impact on cross section uncertainties and correlations. We also study the effect of the resonance parameter correlations deduced from capture and fission kernels and illustrate our approach on several practical examples. We show that uncertainties of neutron-, radiative- and fission-widths are important, while the uncertainties of resonance energies can be effectively neglected. We conclude that the correlations between neutron and radiative (fission) widths should be taken into account. The multi-group cross section uncertainties can be properly generated from both the resonance parameter covariance format MF32 and the cross section covariance format MF33, though the use of MF32 is more straightforward and hence preferable.
Download or read book Neutron Cross Section Covariances in the Resonance Region written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, 52Cr, 56Fe and 58Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for 52Cr, 7-8% for 56Fe and 5-6% for 58Ni.
Download or read book Neutron Cross Section Covariances in the Resonance Region written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We evaluated covariances in the neutron resonance region for capture and elastic scattering cross sections on minor structural materials, {sup 50,53}Cr, {sup 54,57}Fe and 6°Ni. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. Our results of most interest for advanced fuel cycle applications, elastic scattering cross section uncertainties at energies around 100 keV, are on the level of about 7-10%.
Download or read book Formalism for Neutron Cross Section Covariances in the Resonance Region Using Kernel Approximation written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We describe analytical formalism for estimating neutron radiative capture and elastic scattering cross section covariances in the resolved resonance region. We use capture and scattering kernels as the starting point and show how to get average cross sections in broader energy bins, derive analytical expressions for cross section sensitivities, and deduce cross section covariances from the resonance parameter uncertainties in the recently published Atlas of Neutron Resonances. The formalism elucidates the role of resonance parameter correlations which become important if several strong resonances are located in one energy group. Importance of potential scattering uncertainty as well as correlation between potential scattering and resonance scattering is also examined. Practical application of the formalism is illustrated on 55Mn(n, [gamma]) and 55Mn(n, el).
Download or read book PRACTICAL METHOD FOR ESTIMATING NEUTRON CROSS SECTION COVARIANCES IN THE RESONANCE REGION written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent evaluations of neutron cross section covariances in the resolved resonance region reveal the need for further research in this area. Major issues include declining uncertainties in multigroup representations and proper treatment of scattering radius uncertainty. To address these issues, the present work introduces a practical method based on kernel approximation using resonance parameter uncertainties from the Atlas of Neutron Resonances. Analytical expressions derived for average cross sections in broader energy bins along with their sensitivities provide transparent tool for determining cross section uncertainties. The role of resonance-resonance and bin-bin correlations is specifically studied. As an example we apply this approach to estimate (n,?) and (n, el) covariances for the structural material 55Mn.
Download or read book Atlas of Neutron Resonances written by Said F. Mughabghab and published by Elsevier. This book was released on 2018-02-09 with total page 698 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atlas of Neutron Resonances: Resonance Properties and Thermal Cross Sections Z=61-102, Sixth Edition, contains an extensive list of detailed individual neutron resonance parameters for Z=61-102, thermal cross sections, capture and fission resonance integrals, average resonance parameters, and a short survey of the physics of thermal and resonance neutrons. The long introduction contains: nuclear physics formulas aimed at neutron physicists; topics of special interest such as valence neutron capture, nuclear level density parameters, and s-, p-, and d-wave neutron strength functions; and various comparisons of measured quantities with the predictions of nuclear models, such as the optical model neutron-induced fission. As in the last edition, additional features have been added to appeal to a wider spectrum of users. These include: spin-dependent scattering lengths that are of interest to solid-state physicists, nuclear physicists and neutron evaluators; calculated and measured Maxwellian average 5-keV and 30-keV capture cross sections of importance to astrophysicists involved in nucleosynthesis modeling; s-, p-, and d- wave average radiative widths; nuclear level density parameters; and average fission widths derived from average fission cross sections. Provides a comparison of average resonance parameters with optical model calculations and with the generalized Landau-Fermi model Presents scattering radii for various partial waves from the analysis of total neutron cross sections in the keV to MeV energy region Includes a brief review of sub-threshold fission Features consistent treatment of average neutron parameters with values from the resolved resonance region
Download or read book Evaluated 182 183 184 186W Neutron Cross Sections and Covariances in the Resolved Resonance Region written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oak Ridge National Laboratory (ORNL) has recently completed the resonance parameter evaluation of four tungsten isotopes, i.e., 182,183,184,186W, in the neutron energy range of thermal up to several keV. This nuclear data work was performed with support from the US Nuclear Criticality Safety Program (NCSP) in an effort to provide improved tungsten cross section and covariance data for criticality safety analyses. The evaluation methodology uses the Reich-Moore approximation of the R-matrix formalism of the code SAMMY to fit high-resolution measurements performed in 2010 and 2012 at the Geel linear accelerator facility (GELINA), as well as other experimental data sets on natural tungsten available in the EXFOR library. In the analyzed energy range, this work nearly doubles the resolved resonance region (RRR) present in the latest US nuclear data library ENDF/B-VII. 1. In view of the interest in tungsten for distinct types of nuclear applications and the relatively homogeneous distribution of the isotopic tungsten--namely, 182W(26.5%), 183W(14.31%), 184W(30.64%), and 186W(28.43%) - the completion of these four evaluations represents a significant contribution to the improvement of the ENDF library. This paper presents an overview of the evaluated resonance parameters and related covariances for total and capture cross sections on the four tungsten isotopes.
Download or read book NEUTRON CROSS SECTION COVARIANCES FROM THERMAL ENERGY TO 20 MeV written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We describe new method for energy-energy covariance calculation from the thermal energy up to 20 MeV. It is based on three powerful basic components: (i) Atlas of Neutron Resonances in the resonance region; (ii) the nuclear reaction model code EMPIRE in the unresolved resonance and fast neutron regions, and (iii) the Bayesian code KALMAN for correlations and error propagation. Examples for cross section uncertainties and correlations on 9°Zr and 193Ir illustrate this approach in the resonance and fast neutron regions.
Download or read book Atlas of Neutron Resonances written by Said F. Mughabghab and published by Elsevier. This book was released on 2018-02-09 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atlas of Neutron Resonances: Resonance Properties and Thermal Cross Sections Z= 1-60, Sixth Edition, contains an extensive list of detailed individual neutron resonance parameters for Z=1-60, as well as thermal cross sections, capture resonance integrals, average resonance parameters and a short survey of the physics of thermal and resonance neutrons. The long introduction contains: nuclear physics formulas aimed at neutron physicists; topics of special interest such as valence neutron capture, nuclear level density parameters, and s-, p-, and d-wave neutron strength functions; and various comparisons of measured quantities with the predictions of nuclear models, such as the optical model. As in the last edition, additional features have been added to appeal to a wider spectrum of users. These include: spin-dependent scattering lengths that are of interest to solid-state physicists, nuclear physicists and neutron evaluators; calculated and measured Maxwellian average 5-keV and 30-keV capture cross sections of importance to astrophysicists involved in nucleosynthesis modeling; s-, p-, and d-wave average radiative widths; and, nuclear level density parameters. Provides a comparison of average resonance parameters with optical model calculations and with the generalized Landau-Fermi model Presents scattering radii for various partial waves from the analysis of total neutron cross sections in the keV to MeV energy region Includes a brief review of sub-threshold fission Examines consistent treatment of average neutron parameters with values from the resolved resonance region
Download or read book The Measurement of Neutron Total Cross Sections in the Resonance Energy Region and written by and published by . This book was released on 1965 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Covariance Evaluation Methodology for Neutron Cross Sections written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the NNDC-BNL methodology for estimating neutron cross section covariances in thermal, resolved resonance, unresolved resonance and fast neutron regions. The three key elements of the methodology are Atlas of Neutron Resonances, nuclear reaction code EMPIRE, and the Bayesian code implementing Kalman filter concept. The covariance data processing, visualization and distribution capabilities are integral components of the NNDC methodology. We illustrate its application on examples including relatively detailed evaluation of covariances for two individual nuclei and massive production of simple covariance estimates for 307 materials. Certain peculiarities regarding evaluation of covariances for resolved resonances and the consistency between resonance parameter uncertainties and thermal cross section uncertainties are also discussed.
Download or read book Atlas of Neutron Resonances written by Said F. Mughabghab and published by Elsevier. This book was released on 2006-04-04 with total page 1373 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Atlas of Neutron Resonances provides detailed information on neutron resonances, thermal neutron cross sections, and average resonance properties which are important to neutron physicist, astrophysicists, solid state physicists, reactor engineers, scientists involved in activation analysis, and evaluators of neutron cross sections. · Compilation and evaluation of the world's thermal neutron cross-sections and resonance parameters for neutron physicists, reactor engineers, and neutron evaluators.· Compilation and evaluation of coherent scattering lengths for solid state physicists and evaluators· Compilation and evaluation of average 30-keV capture cross sections for astrophysicists.· Nuclear level density parameters derived from average spacings of neutron resonances following a new approach (new feature for this edition).· Brief review of sub-threshold fission.· Comparisons of optical model predictions with neutron strength function data and scattering lengths.· Estimation of average E1 radiative widths on the basis of the generalized Landau-Fermi liquid model (a new feature for this edition).
Download or read book Neutron Cross Sections written by S Mughabghab and published by Elsevier. This book was released on 2012-12-02 with total page 847 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron Cross Sections, Volume 1: Neutron Resonance Parameters and Thermal Cross Sections, Part A represents the fourth edition of what was previously known as BNL-325, Neutron Cross Sections, Volume 1. This three-chapter book provides the extensive list of detailed individual resonance parameters for each isotope. The first chapter deals with the thermal cross sections and average resonance parameters, as well as the physics of thermal and resonance neutrons, with particular emphasis on evaluation methods. This chapter also includes tables of standards of capture cross sections and scattering lengths, and commonly used nuclear physics formulas. The second chapter covers the direct or valence capture and the Brink-Axel treatment of electric dipole radiation. These topics are followed by a discussion on spin-dependent scattering lengths that are of interest to solid state. The third chapter describes the Maxwellian 30-keV capture cross sections that are of importance to studies of nucleosynthesis and age of the universe. This chapter also examines the s- and p-wave average radiative widths and gamma-ray strength functions that are required in capture cross section measurements. This book will appeal to nuclear and astrophysicists.
Download or read book Introduction to Theory and Analysis of Resolved and Unresolved Neutron Resonances Via SAMMY written by and published by . This book was released on 1998 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron cross-section data are important for two distinct purposes: first, they provide insight into the nature of matter, thus assisting in the understanding of fundamental physics; second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, and for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this paper, important features of the analysis process are discussed, with emphasis on the particular technique used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.
Download or read book Issues in Neutron Cross Section Covariances written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We review neutron cross section covariances in both the resonance and fast neutron regions with the goal to identify existing issues in evaluation methods and their impact on covariances. We also outline ideas for suitable covariance quality assurance procedures. We show that the topic of covariance data remains controversial, the evaluation methodologies are not fully established and covariances produced by different approaches have unacceptable spread. The main controversy is in very low uncertainties generated by rigorous evaluation methods and much larger uncertainties based on simple estimates from experimental data. Since the evaluators tend to trust the former, while the users tend to trust the latter, this controversy has considerable practical implications. Dedicated effort is needed to arrive at covariance evaluation methods that would resolve this issue and produce results accepted internationally both by evaluators and users.
Download or read book Introduction to the Theory and Analysis of Resolved and Unresolved Neutron Resonances Via SAMMY written by and published by . This book was released on 1998 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron cross-section data are important for two distinct purposes: First, they provide insight into the nature of matter, thus assisting in the understanding of fundamental physics. Second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, and for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this paper, important features of the analysis process are discussed, with emphasis on the particular techniques used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher energy regions.
Download or read book Neutron Cross Sections and Technology written by David T. Goldman and published by . This book was released on 1968 with total page 680 pages. Available in PDF, EPUB and Kindle. Book excerpt:
