DOI
https://doi.org/10.25772/9A4Z-P717
Author ORCID Identifier
0000-0001-5643-3591
Defense Date
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Mechanical and Nuclear Engineering
First Advisor
Zeyun Wu
Second Advisor
Daren Chen
Third Advisor
Gennady Miloshevsky
Abstract
Molten salt reactors (MSRs) are a promising class of advanced nuclear reactors selected as
one of the generation IV reactors. This class of reactors employs a unique design, where fissile
material is dissolved in a molten salt mixture, serving as fuel and coolant of the reactor. The design
features high-temperature low-pressure operation and efficient heat transfer capability, which
leads to significant improvements in reactor thermal efficiency, safety, and waste management.
However, MSRs also have complex phenomena not observed in conventional reactors, such as
fission product transport in the circulating fuel loop. These phenomena impact neutron distribution
and reactivity feedback mechanisms in reactor operations, especially during reactor transient
scenarios. To address these complexities, reliable benchmark data from experimental MSR
operations are essential for developing and validating accurate computational models that are
crucial for the safe design and operation of future MSRs.
The dissertation focuses on developing and evaluating reactor transient benchmarks for
MSRs, using measured data from the Molten Salt Reactor Experiment (MSRE). The MSRE
represents a unique data source for MSRs as it remains the only MSR operated in America. For
the purpose of the reactor benchmark development and evaluation, a series of computational models with varying levels of fidelity are developed and implemented in COMSOL Multiphysics platform. The developed models are used in simulating various operational scenarios in MSRE, covering stationary fuel, steady-state circulating fuel, and transient scenarios. The results produced by the models showed good agreement with the experimental data which sufficiently validate the underlying assumptions made in the models. The models are further used to investigate the effect of various modeling choices such as the few-group structure used in the multigroup neutron diffusion model and the diffusion coefficient of the delayed neutron precursors. Using the developed benchmark models, the dissertation evaluates three MSRE transients: pump transient test, reactivity insertion test, and low-power natural circulation test. For pump transients, two distinctive flow models are developed to assess the effects of the flow filed on reactivity changes. A detailed uncertainty quantification analysis is performed to understand the uncertainty in the experimental data during the transients. The reactivity insertion test is a set of transients aiming to investigate the reactor’s response to external reactivity insertion. A consistent point reactor kinetics (PRK) model-based method is developed to simulate the test, providing sufficient validation of the PRK model for circulating fuel systems. A sensitivity analysis of the model outputs on various input parameters is performed through Sobol’s method. Finally, the natural circulation test, which is a lower-power experimental test conducted to establish the load following characteristics, is simulated. This transient further validates the model's capabilities in simulating fluid flow driven by density variations. The MSRE transient benchmark developed by this dissertation will be tailored and incorporated as part of the International Reactor Physics Experiment Evaluation Project (IRPhE) handbook. This benchmarking effort will significantly aid in validating computational tools for MSRs and provide an essential foundation for future reactor safety analysis, design optimization, and
performance assessment for MSRs.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
4-1-2025