A Numerical Solution of Low-Energy Neutron Boltzmann Equation

<p>A multigroup method using a straight ahead approximation is created to calculate low energy neutron fluence due to the elastic scattering of evaporation neutrons produced in interactions of high energy particles with target nuclei. This multigroup method is added to NASA Langley Research Center's HZETRN particle transport code. This new code is used to calculate the energy spectra of the neutron fluence in several different materials. The multigroup method is found to be an efficient way of calculating low energy neutron fluence in multiple atom materials as well as single atom materials. Comparisons to results produced by Monte Carlo methods show that the straight ahead multigroup method is accurate for larger depths but less accurate for small depths due to leakage at the boundary. For this reason, an improved multigroup method is created which propagates neutrons in two directions, forward and backward approximately accounting for the isotropic distribution of the evaporation source. This new multigroup method compares well with the Monte Carlo method at all depths. For this reason, the multigroup method is considered an accurate method which is highly computationally efficient for calculating low energy neutron fluence.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mathematics & Statistics

Year dc:date.available

1999

Author dc:creator

• Clowdsley, Martha Sue

Contributors dc:contributor

• John H. Heinbockel
• John W. Wilson
• John Adam
• Fang Hu

• Boltzmann equation
• Low-energy neutron
• Multigroup
• Neutron fluence
• Mathematics

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9780599285262

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:mathstat_etds-1011