SUMMARY

As part of the collaborative effort in the pursuit of realizable fusion energy, the International Thermonuclear Experimental Reactor (ITER) is being developed by a coalition of nations of which the United States is a part of. One critical technological challenge for ITER is the development of adequate plasma facing materials (PFMs) that can withstand the strenuous conditions of operation. To date, high heat flux (HHF) testing has been conducted mainly on non-irradiated specimens due to the difficulty of working with radioactive specimens, such as instrument contamination. In this thesis, the new Irradiated Material Target Station (IMTS) facility for fusion materials at Oak Ridge National Laboratory is considered for neutron-irradiated specimens, especially tungsten. The facility is being used to test irradiated PFMs for magnetic fusion reactors. In order to conduct HHF testing on the PFMs, two sample holder designs were developed to accommodate radioactive specimens during HHF testing.

As part of the effort for designing sample holders that are compatible with the IMTS facility, numerical simulations were performed for each design using the commercial computational fluid dynamics (CFD) software package, ANSYS FLUENT®. The numerical models are validated against experimental temperature measurements obtained from the IMTS facility. These experimentally validated numerical models are used to assess the thermal performance of two sample holder designs and establish safe limits for HHF testing under various operating conditions.

Also, the numerical models are used to parametrically investigate the effect of the operating pressure, mass flow rate, and incident heat flux on the local heat flux distributions and peak surface temperatures. Finally, a comparative analysis is conducted to evaluate the effect of design modifications between the two models in order to provide conclusive recommendations for future sample holder designs.