Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Physics and Astronomy

First Advisor

Mark L. Williams


The purpose of this study is to develop a new method to compute a continuous-energy representation of the neutron flux spectrum using the one-dimensional discrete ordinates method. The technique provides a rigorous calculational tool for applications that require a detailed description of the fine-structure variation in the space-dependent neutron energy spectrum over some energy ranges. This technique uses the combination of multigroup (MG) and rigorous pointwise (PW) solutions to the steady state Boltzmann transport equation in the calculations. Also utilized in this methodology are two new methods called "sub-moment" expansion and "cumulative integral" operator to accurately evaluate the Legendre moments of the elastic scatter and the integral terms associated with the down scatter source at each point in the PW range. A comprehensive computer program called CENTRM has been developed based on this technique to provide problem specific angular fluxes and flux moments. One primary use of these detailed fluxes is in processing problem-dependent MG cross sections. The obtained MG cross sections are used in other MG calculations for reactor physics and criticality safety applications. This computer program is to function as one of the primary components in a comprehensive nuclear reactor analysis code system being developed by Oak Ridge National Laboratory for U.S. Nuclear Regulatory Commission.