Nuclear Engineering ETDs

Publication Date

Fall 11-12-2021


This thesis assesses sources of uncertainty in the neutron energy spectrum of the Annular Core Research Reactor (ACRR) Monte Carlo N-Particle Transport Code (MCNP) model. Uncertainty evaluations have been performed on the ACRR core but were computationally intensive and could not isolate the uncertainties associated with discrete sources. Monte Carlo Perturbation Theory (MCPT) is used in MCNP to calculate 640-group neutron energy fluences and their associated uncertainties [1]. To understand the uncertainties associated with only the UO2-BeO fuel, perturbations in densities and dimensions were evaluated. A 640 by 640 covariance and correlation matrices were produced and compared to the previously calculated a priori covariance [2]. The produced covariance matrix only shows covariance along the major variance axis. These results indicate that fuel density and dimension variations are not a significant contributor to energy spectrum covariance and efforts to reduce the uncertainty should place greater attention on other sources.


ACRR, uncertainties, covariance, correlation


Sandia National Laboritories

Document Type




Degree Name

Nuclear Engineering

Level of Degree


Department Name

Nuclear Engineering

First Committee Member (Chair)

Christopher Perfetti, PhD

Second Committee Member

Danielle Redhouse, MS

Third Committee Member

Cassiano Endres de Oliveira, PhD