Parametric Design Study About Seismic Isolation System for Fast Reactor JSFR

Abstract

Japanese seismic conditions are getting severer and natural frequencies of components are getting lower due to the enlargements of components’ size, therefore response accelerations and buckling margins of reactor vessels were parametrically surveyed with attention to thicknesses, diameters, and isolation frequencies for reviewing necessary isolation specification. For the first, Japanese seismic condition and present specification of JSFR isolation system are introduced in this paper. RV installed floor responses were calculated based on this seismic condition and the relationship of natural frequencies, initiated stresses, and buckling margins against vessel thicknesses and diameters were shown with trend. Expansion characteristic of isolation system was evaluated by parametric acceleration response analyses. Comparing the response of isolation system with 8Hz vertical natural frequency with other natural frequency’s isolation, response ratios against natural frequencies were calculated. Japanese seismic design condition may become severer than present one, and a natural frequency of main component may decrease. However based on the buckling margin with present plant specifications and the expansion characteristic of isolation system, the advanced isolation system with 8Hz vertical natural frequency was selected as the isolation system of JSFR at still present occasion.