Issues of Non-Conservatism in the Design of Pressure Vessels Subjected to Long-Time Service at Creep Regime According to ASME B & PV Code Section VIII

In this study, sensitivity analyses were conducted to investigate risks quantitatively associated with high-temperature pressure vessel design subjected to long-time service at high temperatures, as ASME Section VIII Division 2 ('ASME VIII(2)') does not explicitly consider creep effects for high-temperature pressure vessel design. Comparative studies were conducted of design evaluation results from ASME Section III Division 5 and RCC-MRx that explicitly consider hold time with the results from ASME VIII(2). The analytical target was a heat exchanger of IHX in a sodium test facility. STELLA-2 and design evaluations for the sensitivity analyses based on the aforementioned three design codes were conducted. Analytical results showed that the design limits of ASME and RCC-MRx were exceeded if the hold time exceeded certain limits, whereas the results for ASME VIII(2) were always satisfied regardless of the hold time. Therefore, this study showed that ASME VIII(2) might provide non-conservative results for long-time service at high temperatures in the creep range.