Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 4 — Failure Behavior of Crossover Piping for Seismic Isolation System

Abstract

This paper provides a part of the series titled “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. This part shows the failure behavior of crossover piping installed in a seismic isolated plant. The considered crossover piping is supported on one side by an isolated building and by a non-isolated building on the other side. During an earthquake, the piping structure is deformed due to the large relative displacements between the two buildings and at the same time excited by the different building seismic responses. Therefore, the high-pressure crossover piping structure requires both flexibility and strength. In this study, 1/10 scaled shaking tests and FEM analyses have been performed to investigate the failure behavior of the crossover piping, where both seismic motions and excitations have been taken into account. It was confirmed that the failure occurs at the piping elbow through low cycle fatigue. Moreover, the results of the elastic-plastic response analysis, which simulates an extreme level of excitation corresponding to more than three times the design level, are in good agreement with the test results. The simulation also succeeded in predicting the experimental failure location.

Seismic qualification of crossover piping systems on a sodium-cooled fast reactor with a seismic isolation system

“…With regard to the failure mode of the crossover piping, some studies were conducted to apply seismic isolation systems to LWRs as a part of a national Japanese project (Otani et al, 2014;Otoyo et al, 2014). These studies concluded that the failure mode of the crossover piping under seismic loads was low-cycle fatigue, similar to that of the piping of ordinary non-isolated plants, through a series of dynamic tests using a 1/10 scale model and analyses.…”