Doctoral Dissertations

Date of Award

12-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

Nicholas R. Brown

Committee Members

Vladimir Sobes, Brian D. Wirth, Jason R. Trelewicz

Abstract

A global initiative on mitigating the use of fossil fuels and transitioning to a more sustainable and cleaner energy source has brought the potential of nuclear energy to the forefront of the conversation. The modular, high temperature, particle fueled reactor platform has become the leading candidate for advanced nuclear reactors because of its robust safety features, enhanced fuel utilization, and the potential of high-quality heat for industrial applications. This particular reactor platform may take on various forms depending on the specific application, but all designs are centered around the use of particle fuel embedded into a solid moderating material and operate at a considerably higher temperature than more conventional nuclear reactors. The particular reactor concepts that are presented in this dissertation are 1) prismatic high temperature gas cooled microreactors, 2) pebble bed fluoride salt cooled high temperature reactors, and 3) pebble bed high temperature gas cooled reactors. The goals and approaches on the various studies for these concepts differ but each study has the underlying theme of evaluating performance and safety to enhance the knowledge of various high temperature reactor technologies/concepts through the use of multiphysics assessment for the enhancement of nuclear power safety, competitiveness, and efficiency.

Results from these studies demonstrate the performance and safety potential of various high temperature reactor concepts as well as highlight some areas for modeling development. A preconceptual high temperature gas cooled microreactor was developed to provide a basis for comparing moderators alternative to graphite for the objective of enhancing reactor performance without compromising safety. The results from the microreactor study demonstrated the higher reactor performance of two-phase composite moderators relative to the industry standard, graphite without compromising intrinsic safety features. A coupled reactor physics and thermal-hydraulics model was used to assess the safety response for a generic pebble bed fluoride salt cooled pebble bed reactor under a set of different transient conditions, demonstrating the resilience of the reactor concept to accidents. Finally, the severe accident and consequence modeling code, MELCOR, was used for verification and validation of steady state and transient conditions for a high temperature gas cooled pebble bed reactor.

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