Next Generation Reactor Core Analysis Using Iterative Transport-diffusion Methodology

Open Access
Beacon, Daniel Richard
Graduate Program:
Nuclear Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 08, 2014
Committee Members:
  • Kostadin Nikolov Ivanov, Thesis Advisor
  • Iterative
  • Transport
  • Diffusion
  • ITDM
  • Reactor Analysis
This thesis details the efforts, changes, and improvements that have been made to the Next Generation Method (NGM) Iterative Transport-Diffusion Methodology (ITDM), a long term joint project between The Pennsylvania State University (PSU) and Westinghouse Electric Company. Significant changes to the calculation models have been made including an update to moderator properties and a completely new MCNP6 reference simulation to use for comparison to the ITDM results. However, the axial tilt seen in the previous ITDM results has remained. The cause of the tilt has been under investigation since. Many studies have been performed covering topics such as NEM mesh sizes, PARAGON radial discretization, the B1 approximation, and inter-layer axial leakage. It was found that the B1 approximation, used to adjust for the critical neutron spectrum, had the most significant effect on the axial reaction rate distribution. However, this effect was not consistent between cases and it was decided that the B1 approximation should not be used. The results of the original axial leakage study suggested that there was an issue with the original implementation of the axial leakage routine in the code. Upon investigation, it was found that the energy treatment in the axial leakage routine needed to be updated. This effort is currently in progress as of the writing of this thesis. Specifically, the fine group energy structure for the axial leakage source is to be reconstructed using the previous iteration energy spectra. It is hoped that this change will lead to improved axial results.