Date of Award

Spring 1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Committee Director

Govind S. Khandelwal

Committee Member

James L. Cox, Jr.

Committee Member

Anatoly Radyushkin

Committee Member

R. L. Kernell

Committee Member

John W. Wilson

Abstract

The problem of energetic nucleon transport through extended bulk matter is considered in the context of the 'straight ahead' approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes 'coupling' of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks. The benchmarks provide precise estimation of the truncation errors involved in the numerical method. A set of continuous benchmarks are developed for cosmic ray transport applications and a set of mono-energetic benchmarks is developed for accelerator applications. The optimized marching scheme is incorporated into the BRYNTRN transport code along with a sophisticated reaction database for nuclear and atomic scattering. The method is applied to typical space shielding applications and comparisons are made with the HETC Monte Carlo benchmarks. The BRYNTRN results compare well with HETC while requiring significantly less computing power. The transport of elastically scattered neutrons is shown to be poorly converged using the coarse energy grids suited to non-elastic scattering. A grid independent model is developed for neutron elastic scattering which maintains particle conservation to within acceptable limits for deep penetration transport cases. The elastic scattering model is applied to a range of shielding cases.

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DOI

10.25777/xaj8-4936

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