Lead extrusion dampers for reducing seismic response of coolant channel assembly

In Indian type pressurized heavy water reactors (PHWRs), two fuelling machines (F/Ms) are located on either side of the reactor. The behavior of the coolant channel and tie rod when fuelling machines are engaged on both the ends of the channel for refueling under earthquake is studied. It is observed that the loads acting on the coolant tube were high. In order to reduce the earthquake load acting on coolant channel the fuelling machines are restrained by energy absorbers called lead extrusion dampers (LED). The design of an LED is performed based on the extrusion principle. The aim of the paper is to study the effectiveness of such a device in reducing the response. It was observed that the stresses in the coolant channel due to earthquake are reduced significantly when LEDs are used. Response spectrum analysis is also carried out for the system with LED. In this analysis the LED is replaced with an equivalent viscous damper and stiffness obtained using Caughy’s linearisation techniques. Response spectrum analysis results and the nonlinear time history analysis results show good agreement.