Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

First Committee Member

Alexander Barzilov

Second Committee Member

William Culbreth

Third Committee Member

Yi-Tung Chen

Fourth Committee Member

Monika Neda

Fifth Committee Member

Steen Madsen

Number of Pages



In thermal neutron spectrum Molten Salt Reactors (MSR), a graphite moderator contributes a positive reactivity value to the overall temperature reactivity coefficient of the core. When irradiated in the core, graphite undergoes dimensional changes which depend on the neutron spectrum. The graphite lifespan is a limiting parameter in MSR designs; it correlates strongly with the graphite’s dimensional changes. Multi-physics modeling is necessary to evaluate the graphite thermal and mechanical responses to the MSR core conditions. To assess graphite dimensional changes associated with irradiation, a computational model was developed upon the foundation of the multi-physics solver, GeN-Foam. Irradiated graphite dimensional change strain and creep strain solvers have been incorporated into a branch of GeN-Foam, identified as GeN-Foam-G, to account for the moderator’s response to the core’s neutron kinetics. These capabilities enable modeling of the thermal deformation of graphite moderator structures at the thermo-mechanical mesh cell level.

The GeN-Foam-G graphite moderator model was benchmarked using the experimental and computational data of graphite moderator thermal response in high temperature gas-cooled reactors. After developing and benchmarking Gen-Foam-G, the solver was extended to the industry-standard graphite moderator channel concept for the thermal spectrum MSR. Results are presented of the irradiated graphite displacement calculated for the graphite channel in this thermal spectrum MSR. Finally, irradiated graphite creep strain was calculated for the core of the Molten Salt Breeder Reactor (MSBR). This MSBR core model provides the foundation to extend GeN-Foam-G calculations for ever more complex and higher fidelity computational models of thermal spectrum MSR cores.


GeN-Foam; graphite moderator; irradiated creep strain; irradiated dimensional change strain; molten salt reactor; multiphysics


Nuclear Engineering

File Format


File Size

2.7 MB

Degree Grantor

University of Nevada, Las Vegas




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