Doctoral Dissertations

Date of Award

12-2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

G. Ivan Maldonado

Committee Members

Dr. G. Ivan Maldonado, Dr. Nicholas R. Brown, Dr. Sandra Bogetic, Dr. Felipe Santos Novais

Abstract

This dissertation outlines the development of advanced neutronics evaluation and analysis techniques for fusion reactor facilities, focusing on the Fusion Energy System Studies-Fusion Nuclear Science Facility (FESS-FNSF) conceptual design. This study builds on earlier research conducted in 2017 [6] and 2019 [4], which employed different tools and versions of the FNSF design. The current work utilizes updated modeling approaches and a more recent version of the FNSF, demonstrating consistency with previous findings and enhancing confidence in the evaluated methods.

The methodologies discussed are not limited to the FNSF but are applicable to other fusion reactor designs, both current and future. Initial modeling of complex fusion designs like the FNSF often involves CAD software to define detailed geometries. This research compared the use of the traditional MCNP code with the emerging OpenMC tool for neutronics calculations, such as radiation damage (measured by displacement per atom and hydrogen/helium production), neutron wall loading, and nuclear heating from neutrons and gamma rays. The study highlights the strengths and limitations of both tools, noting that while OpenMC simplifies and streamlines the conversion of CAD models into Monte Carlo simulation inputs, MCNP retains valuable features such as point flux calculations not available in OpenMC.

Once reliable FNSF models were established, they were used to assess advanced materials for fusion reactors. Metal hydrides and borohydrides were evaluated as potential alternatives to tungsten carbide (WC) in in-vessel components. Titanium hydride (TiH2) and zirconium hydride (ZrH2) were found to have lower radiation damage compared to WC and other metals. However, alternative shielding materials did not significantly impact magnet nuclear heating.

Additionally, the study examined the aluminization of Reduced Activation Ferritic Martensitic Steel (RAFM), such as F82H, which is used in blankets. Given the issues of corrosion and tritium permeation due to liquid Pb-Li flow, aluminum or aluminum-based coatings were explored to mitigate these problems. The neutronics analysis assessed tritium breeding ratio, nuclear heating, radiation damage, and activation with varying levels of aluminization. The findings indicated that key neutronics parameters, including TBR, radiation damage, neutron/gamma heating, and activation, remained largely unchanged with different aluminization levels.

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