Scram and nonlinear reactor system seismic analysis for a liquid metal fast reactor

Seismic analyses employing response spectra techniques are usually performed on structural systems which can be adequately modeled with linear elastic behavior. However, when the system is composed of components which may impact each other due to the clearances among them, a nonlinear time history analysis is required. This type of analysis allows the actual system to be better represented in the model with the proper definition of boundary conditions, and will calculate the various impact forces on the components. A nonlinear seismic time history and a scram analysis which were performed on a liquid metal fast reactor are described in this paper. The description includes the derivation of the mathematical model from the actual system, the calculation of the various imput parameters, the scram analysis technique, and typical results. The time history analysis was performed to obtain various seismic responses (such as impact forces and bending moments) for use in other analyses to determine the total effects on the components. The scram analysis was done to calculate the scram times as a function of rod travel distance. (Auth.)