Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

James E. Bevins, PhD


The Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization developed the International Monitoring System for monitoring for nuclear explosive testing and compliance with nuclear treaties. Many of the International Monitoring System stations are capable of detecting radionuclides that can be used to determine their origin and creation environment. However, there is not a single unique signature associated with each creation environment. Nuclear reactors, for example, can have a wide range of isotopic concentrations caused by spatial variations in neutron flux intensity and energy. As a single sample only provides a single isotopic measurement, this can make disambiguation difficult for systems that have varying, and potentially overlapping, signatures. To better quantify this phenomena, a 3-D quarter-core CANDU-6 was modeled using Serpent 2 to analyze the spatial flux distribution and develop a spent fuel isotopic database. The model showed an overall relative flux magnitude difference of 45:1 plus or minus 4:5 percent and significant differences in discrete neutron energies ranging from 1 to 30 percent. The developed database provides the full spatial isotopic distribution for 257 isotopes expected from CANDU-6 spent fuel. Actinide and fission product isotopic ratios were analyzed to determine their range and associated confidence intervals. The ratios showed significant bundle-to-bundle variance and significant inter-isotopic distribution variance making it difficult to accurately assess the range of possibilities from analytic methods. The developed CANDU-6 spatial isotopic database provides the increased resolution for future analysis of International Monitoring System signatures thereby enhancing the capabilities of the system to effectively perform their treaty monitoring mission.

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