Thermal Analysis and Structural Design of the Main Steam Containment Penetration for Multi-Modular High-Temperature Gas-Cooled Reactor Power Plant

Abstract Based on the high-temperature gas-cooled reactor pebble-bed module demonstration plant (HTR-PM), which employed two small modular reactor modules (SMRs) with thermal power of 250 MWth and power generation of approximately 100 MWe per module, several larger versions of the multi-modular high-temperature gas-cooled reactor power plant (MHTGR) with more modules are under design. The newly designed MHTGR contains six to ten modules in a large circular ventilated low-pressure containment (VLPC) for compact design. With this layout, all of the main steam pipes should pass the containment in parallel through a limited area of the containment wall. The multiple main steam pipe containment penetration design for the MHTGR should meet several essential challenges to keep the concrete wall temperature below the temperature limit. Firstly, the main steam temperature for the MHTGR is over 540 °C, one of the highest among all the commercial nuclear plants. Secondly, the wall surface area between pipes is comparatively limited in comparison to HTR-PM and other nuclear plants. The heat rejection by wall surface is restricted. Thirdly, there is no active cooling on the surface or inside the wall. This study first set up a 2-D heat transfer model to discover the influence of the sleeve diameter and insulation thickness on wall temperature. Secondly, 3-D models were established to compute and compare the temperature distribution of potential structural design. Thirdly, the fundamental mechanical parameters were designed considering the temperature distribution and mechanical properties of the materials.