[en] In order to establish the highly reliable design of heat exchanger and circulator in VHTR and the nuclear steel making system, seismic response calculations were conducted. First, the numerical calculation by the finite element method and the model experiment for the seismic analysis in heat exchanger tubes of helical type and structure of three dimensional frame to support the heat exchanger and other equipments were carried out. A real-sized model was used for the experiment in the heat exchanger and 1 : 9 scale model was used in the supporting structure. It was found that the calculated values agreed well with the experimental values. Next, transient response of the circulator rotor supported in water-lubricated hydrostatic journal bearings to seismic input was investigated numerically by Runge-Kutta-Gill procedure. Numerical results for the rotor which is equivalent to helium circulator for high temperature helium test loop with heat exchanging capacity 1.5 MWt are presented and the effects of operating conditions of the bearing on rotor response are discussed