Finite element analyses were performed to investigate the leakage and structural integrity of the bolted flange joint assembly (BFJA) and Grayloc clamp connector (GCC), when each assembly was subjected to bolt preload, internal pressure and thermal loadings. The thermal loadings were divided into spatially-uniform and spatially-nonuniform temperatures. The internal pressure for both assemblies was 27 MPa. The BFJA was found to have satisfactory leakage and structural performance for the thermal loadings expected on the low-temperature (260 °C) side of the Carleton Supercritical Water (CSCW)
loop. The GCC was found to have satisfactory leakage and structural performance for the thermal loadings expected on the high-temperature (600 °C) side of the CSCW loop. The leakage integrity of the GCC was found to fail for temperature gradients as high as 100 °C. The use of the GCC on the exit of the test section employed on the CSCW loop was not recommended.