In-Pool By-Pass Pipe is a structure which connects the 2 In-Pool Pipes instead of In-Pile Test Section(IPS). It is designed to accommodate the 17.5 MPa and 80 ℃ under the consideration of the FTL pre-operation conditions but the need for high temperature, over 200 ℃, during FTL pre-operation make the additional assessment to be performed. For this study 2 models are used. One is an In-Pool By-Pass Pipe model which affected by HANARO water's elevation, another is an In-Pool By-Pass Pipe Nozzle which has 2 boundary conditions; water and air. After the heat transfer analysis linear stress analysis was performed to achieve Tresca stress. In the region of high stress model's detailed behavior is observed by ASME SectionⅢ NB code. Consequentially it concluded that the model of In-Pool By-Pass Pipe Structure is in reasonable agreement with those code.