Application of a seismic isolation system to a sodium-cooled fast reactor (SFR) is currently planned. The crossover piping system between the isolated building (Reactor building) and the non-isolated building (Turbine building) that transports high-temperature steam, is subject to a large relative displacement (Fig. 1). Consequently, a methodology to evaluate structural integrity of the crossover piping is needed.

In this study, we investigated the mechanism of stress occurrence in the crossover piping for an SFR by analysis in consideration of its design features: operation in elevated temperature environments and the adoption of high-chromium steel with superior heat resistance as the piping material. We then systematically organized key findings in order to evaluate the structural integrity of the crossover piping under seismic loading. We found that stress concentration was particularly likely to occur at an elbow in the piping (Fig. 2), and that the seismic response wave of the crossover piping consisted of the combination of a major wave with a long natural period and a minor wave with a relatively short period (Fig. 3). This result means that the number of displacement cycles is low even if piping is subject to a large displacement. It is important to evaluate structural integrity to consider the feature.

Based on these findings, we plan to develop a method to properly evaluate the structural integrity of the crossover piping of an SFR under seismic loading, and continue to contribute to the enhancement of the safety of an SFR.

This study includes part of the results of the “Technical Development Program on a Commercialized FBR Plant in FY2007” entrusted to JAEA by Ministry of Economy, Trade and Industry of Japan (METI).

CommentIf you have any comments or feedback about this page, please click the button to share your thoughts with us.