Award Date

5-15-2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Committee Member

Alexander Barzilov

Second Committee Member

Brendan O'Toole

Third Committee Member

Charlotta Sanders

Fourth Committee Member

Emma Regentova

Number of Pages

108

Abstract

The U. S. Department of Transportation’s (DOT) 49 CFR 173.453 Fissile Exceptions provide a regulatory classification that helps eliminate burdensome regulatory requirements. The current fissile exceptions are based on past technical basis reviews. These reviews may be overly conservative, and the final ruling potentially applied significant administrative over-conservatism. This thesis reviewed and presents several recommendations to the fissile exception criteria, as well as 49 CFR 173.453 section’s additions.

Using Monte Carlo N-Particle (MCNP) code version 6.3.0, several infinite sea mixtures and array systems were modeled for fissile isotopes 233U and 235U. The research demonstrated that for fissile exception (a) there was significant over-conservatism applied and the max gram loading can be increased from 2 g per container to 4 g per container. The recommendation is that the revised exception should read: (a) An individual package containing 4 grams or less of fissile material.

A new approach by incorporating new material-specific exceptions was also proposed. One material-specific recommendation was to create a new exemption for Portland Concrete that states: An individual or bulk packaging containing a homogenous mixture of 900 grams or less of fissile material provided the package has at least 200 grams of Portland concrete for every gram of fissile material. The H/U ratio must be greater than or equal to 2000. Lead, beryllium, graphite, and hydrogenous material enriched in deuterium may not be present in the packaging.

The implementation of these revisions and recommendations would significantly reduce the work hours, container cost, shipping cost, and radioactive waste disposal costs. They also provide relief to the overall shipping industry by allowing for more specific processes to fall under the fissile exceptions while maintaining the de minimis classification.

Keywords

49 CFR; Avian Blumhorst; Criticality Safety; Fissile Material Exceptions; Mechanical Engineering; UNLV

Disciplines

Engineering | Mechanical Engineering | Nuclear Engineering

File Format

PDF

File Size

1635 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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