Dynamic analysis of the coolant channel assembly under seismic excitation

This paper presents the seismic response analysis of the coolant channel assembly of the Narora Atomic Power Plant (NAPP). The major function of the coolant channel is to house the nuclear fuel and to pass the primary coolant over the fuel bundles. In the NAPP, there are 306 identical horizontal coolant channel assemblies. Each assembly mainly consists of two zircaloy-2 tubes passing one inside the other. The outer is the calandria tube of 5.08 m length. The inner tube is the coolant tube and is pre-tensioned at the ends to a level of 7265 kg. The outer tube is also mainly pre-tensioned, but this being small, is here neglected. The tubes with the end fittings are shown in figure 1 . Both the tubes are fixed at their ends. The two tubes are separated in the no loading condition by a distance of 22.4 mm. To maintain a suitable clearance between the tubes, two coiled garter springs are used as spacers. Once the inner tube is loaded with the fuel and the coolant, it bends under the weight and sits on the spacers at the bottom (6 0 clock position). In the lateral direction, there will be a gap of = 1.231 mm between the coolant tube and the spacer ring. Thus, during the SSE event it will be necessary to investigate the response of the tubes in the lateral direction under the horizontal components of the earthquake.