Physics & Astronomy ETDs

Publication Date

5-19-1969

Abstract

An experimental program has been undertaken at Los Alamos Scientific Laboratory to study delayed neutron effects. As a part of this program, experiments were conducted with thin disks of various fissionable materials to measure the delayed neutron response to a pulse of high-energy neutrons. In support of the experiments, calculations were made with a computer program which solves the Boltzmann transport equation by finite difference methods. Difficulties with the calculations led to an analysis showing that correct treatment of neutrons moving parallel to the faces of the disk was vital to the success of the calculation. As an extension of this analysis, expressions are derived for neutron escape probabilities from thin infinite slabs under various conditions and from a thin disk under special conditions. The original conclusion regarding neutrons moving parallel to the disk faces is confirmed. It was decided to adapt an existing Monte Carlo program which does neutron transport calculations to include delayed neutron effects. The Monte Carlo neutron program treats all scattering directions equally well and simulates a general three-dimensional system. A description is given of the Monte Carlo techniques used in neutron transport problems, and of the calculation which gives the expected number of neutrons reaching a detector. The original Monte Carlo program, which treated prompt neutron effects only in fission calculations, was extended to do delayed neutron calculations. The delayed neutron data used in the new program is tabulated and discussed. The method of including delayed neutrons in the sample population and of obtaining delayed neutron statistics is described. Many delayed neutron calculations were made using the Monte Carlo program, the results agreeing with experiment within estimated errors. An example of one problem investigated using the program is given, and the computer output resulting from four different cases is presented. A discussion of the computer results illustrates the correspondence between the calculation and the actual experiment.

Degree Name

Physics

Level of Degree

Masters

Department Name

Physics & Astronomy

First Committee Member (Chair)

Christopher Pratt Leavitt

Second Committee Member

George I. Bell

Third Committee Member

Derek Bertram Swinson

Fourth Committee Member

James Daniel Finley III

Language

English

Document Type

Thesis

Download

Share

COinS