Integrity Improvement of High-Temperature Pressure Boundary Components in the Creep Range by Applying Alternative Design Rules

In this study, the methodologies for design and integrity evaluations for a heat exchanger made of type 316L stainless steel subjected to high temperatures in the creep range are suggested. Structural design and integrity evaluations are conducted for a sodium-to-air heat exchanger UHX in the STELLA-2 test facility at the Korea Atomic Energy Research Institute (KAERI) for large-scale sodium thermal fluid characteristics integral effect tests and is currently under operation. The helical-type heat exchanger of the UHX has a temperature difference of 530 degrees C with the primary coolant of 550 degrees C sodium and secondary coolant of 20 degrees C air and is made of austenitic stainless steel of type 316L. Methodologies for the structural designs, stress analyses, and integrity evaluations based on 3D finite element analysis are suggested. In the integrity evaluations on the UHX, the technical issues to applying the ASME BPVC Section VIII Division 2 that is generally used for design of the pressure vessel is analyzed and design methodologies for alternative design rules of the RCC-MRx are provided.