STRUCTURAL ANALYSIS OF A LIGHT WATER SMALL MODULAR REACTOR UNDER COOLANT RECIRCULATION CONDITIONS

U.S. Nuclear Regulatory Commission proposes a method for evaluating integrity of reactor vessels (RVs) against pressurized thermal shock (PTS) via the code of federal regulation. Before evaluating the PTS, dominant locations of a postulated crack should be selected considering effects of thermal-hydraulic loads. Recently, with the development of a light water small modular reactor (SMR), substantial changes have made in the emergency core cooling system as a part of passive safety design that releases and condenses steam forming a pool outside the RV and recirculates it. The objectives of this research are to numerically investigate structural behaviors of the RV subjected to supercooling loads and significant pressure generated by external fluid. A typical coolant recirculation scenario was assumed based on the height of recirculation valve, temperature, and flow rate as variables. Firstly, the transient data of the coolant were derived through systematic computational fluid dynamics simulations for eight cases. Subsequently, accompanying structural analyses were performed to quantify stress states, which are used for selecting the crack location. Finally, sensitivity analyses were conducted to assess interaction of parameters and contribution of each parameter. As results, for the developing light water SMR, dominant locations and variables were determined under the coolant recirculation scenario, and relevant features were discussed.