Assessment Of The Thermal Normalization Technique For Measurement Of Neutron Cross Sections Vs Energy Above 20 Kev Resonance Fission Integrals Error Minimization

Refined knowledge of the thermal neutron cross sections of the fissile nuclides and of the (n, .cap alpha.) reaction standards, together with the reasonably well known energy dependence of the latter, have permitted resonance-region and low-keV fissile nuclide cross sections to be based on these standards together with count-rate ratios observed as a function of energy using a pulsed ''white'' source. As one evaluates cross sections for energies above 20 keV, optimum results require combination of cross section shape measurements with all available absolute measurements. The assumptions of the ''thermal normalization method'' are reviewed, and an opinion is given of the status of some of the standards required for its use. The complications which may limit the accuracy of results using the method are listed and examples are given. For the 235U(n, f) cross section, the option is discussed of defining resonance-region fission integrals as standards. The area of the approximately 9 eV resonances in this nuclide may be known to one percent accuracy, but at present the fission integral from 0.1 to 1.0 keV is known to no better than about two percent. This uncertainty is based on the scatter among independent results, and has not been reduced by the most recent measurements. This uncertainty now limits the accuracy attainable for the 235U(n, f) cross section below about 50 keV. Suggestions are given to indicate how future detailed work might overcome past sources of error.

Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.

This is an authoritative compilation of information regarding methods and data used in all phases of nuclear engineering. Addressing nuclear engineers and scientists at all levels, this book provides a condensed reference on nuclear engineering since 1958.

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).