Elevated temperature design and integrity evaluation of a large-scale sodium test facility, STELLA-2

Abstract

The construction of a large-scale sodium thermal-hydraulic test facility known as STELLA-2 for use in integral effect tests of a sodium-cooled fast reactor (SFR) at the Korea Atomic Energy Research Institute (KAERI) is scheduled to be completed by the end of 2019. As part of this, elevated temperature design (ETD) evaluations were conducted according to the ETD code of RCC-MRx for all components operating at high temperature in creep ranges whereas for Grade 91 steel components of the intermediate heat exchanger (IHX) and the decay heat exchanger (DHX), ETD evaluations were additionally conducted according to ASME Section III Division 5 Subsection HB as well. Except IHX and DHX, all other components in STELLA-2 are of 316L stainless steel (SS). Since high-temperature material properties for 316L SS are available only in RCC-MRx, mainly RCC-MRx was applied. Comparisons were made between the two ETD codes in terms of chemical compositions, and material properties for austenitic 316 SS and Grade 91 steel. The structural integrity of the sodium test facilities was confirmed based on the design evaluations according to the ETD codes. In addition, design evaluation results from RCC-MRx and ASME Subsection HB were compared for IHX and conservatisms were quantified. Technical aspects that mechanical designers should note associated with application of elevated temperature design rules to actual high temperature components were highlighted.