Doctoral Dissertations

Date of Award

5-1990

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

R. B. Perez

Committee Members

H. L. Dodds Jr., B. R. Upadhyaya, D. D. Bruns

Abstract

Neutron cross sections of fissile nuclei are of considerable interest for the under standing of parameters such as resonance absorption, resonance escape probability, resonance self-shielding, and the dependence of the reactivity on temperature. In the present study, new techniques for the evaluation of the 235U neutron cross sections are described. The Reich-Moore formalism of the Bayesian computer code SAMMY was used to perform consistent R-matrix multilevel analyses of the selected neutron cross-section data. The Δ3-statistics of Dyson and Mehta, along with high-resolution data and the spin-separated fission cross-section data, have provided the possibility of developing a new methodology for the analysis and evaluation of neutron-nucleus cross sections. The result of the analysis consists of a set of resonance parameters which describe the 235U neutron cross sections up to 500 eV. The set of resonance parameters obtained through a R-matrix analysis are expected to satisfy statistical properties which lead to information on the nuclear structure. The resonance parameters were tested and showed good agreement with the theory. It is expected that the parametrization of the 235U neutron cross sections obtained in this dissertation represents the current state of art in data as well as in theory and, therefore, can be of direct use in reactor calculations.

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