Seismic analysis of helical coil type heat exchanger

The Intermediate Heat Exchanger (IHX) which forms the reactor coolant pressure boundary is one of the most important components of the Multipurpose Experimental Very High Temperature Gas-cooled Reactor (VHTR). This paper presents the result of the finite element modeling and the eigenvalue analysis of the IHX from our investigation of the seismic analyses of it in order to confirm its integrity in earthquakes. For the modeling, the structure of the IHX is separated into a helical tube bundle, inner and outer vessels and a centerpipe, and the eigenvalue analysis was carried out for each structure with the detailed three-dimensional finite element model. Then the simplified model of the whole structure of the IHX was constructed with the result of eigenvalue analysis. The results of the analysis with the simplified model show that the helical tube bundle and the centerpipe have the first natural frequency of 0.4 Hz in the same phase. (author)