Study on inelastic analysis method for structural design,1; Estimation method of loadig histry effect

Tanaka, Yoshihiko; Kasahara, Naoto

The advanced loop-type reactor system, one of the promising concepts in the Feasibility study of the FBR Cycle, adopts many innovative ideas to meet the challenging requirements for safety and economy. As a results, it seems that the structures of the reactor system would be subjected to severer loads than the predecessors. 0ne of the countermeasures to them is the design by inelastic analysis. In the past, many studies showed that structural design by inelastic analysis is much more reasonable than one by conservative elastic analysis. However, inelastic analysis has hardly been adopted in nuclear design so far. One of the reasons is that inelastic analysis has loading history effect, that is, the analysis result would differ depending on the order of loads. It seems to be difficult to find the general solution for the loading history effect. Consequently, inelastic analysis output from the four deferent thermal load histories which consists of the thermal load cycle including the severest cold shock ("C")and the one including the severest hot shock ("H") were compared with each other. From this comparison, it was revealed that the thermal load history with evenly distributed "H"s among "C" s tend to give the most conservative damage estimation derived from inelastic analysis output. Therefore, such thermal load history pattern is proposed for the structural design by inelastic analysis.