| A novel micro-tensile sample fabrication technique for determining the tensile strength of the buffer, IPyC, and buffer-IPyC interlayer regions of surrogate fueled (ZrO2), unirradiated fueled (UCO), and irradiated fueled (UCO) TRISO fuel particle layers was refined and implemented. Copper micro-tensile samples served as baseline materials to verify the methods used. Data from tensile tests performed in this dissertation, while limited in number, were analyzed using standard and Weibull statistics. While the buffer layer was weakest and the IPyC layer was strongest for the surrogate and unirradiated TRISO particles, the buffer-IPyC interlayer region was weakest and the IPyC layer was strongest for the irradiated TRISO particles. These results are desirable because IPyC layer fractures are strongly associated with buffer layer adhesion. All buffer-IPyC interface samples fractured either in the buffer layer region or at the buffer-IPyC interface, yet some of the buffer-IPyC interlayer samples displayed stress-strain and fracture behavior more comparable to the IPyC layer than the buffer layer. These results suggest the buffer-IPyC interlayer region has unique properties, perhaps associated with pyrocarbon infiltration into the buffer layer during particle coating. The clear increase of porosity, major reduction of the ultimate tensile strength, and major reduction of the Weibull modulus/shape parameter in the irradiated TRISO particles buffer-IPyC interlayer region suggests that irradiation induced porosity is the primary cause of delamination between the TRISO particles buffer and IPyC layers. |