Floor response spectra analysis of a nuclear reactor considering uncertainties in soil parameters

Abstract

Floor response spectra of the nuclear reactor building are an important part of the seismic analysis and design of the whole reactor system. Uncertainties exist in the calculation of floor response spectra considering soil-structure interaction effect due to uncertainties in soil parameters. Stochastic models of shear wave velocity, shear modulus reduction, and damping ratio were built, and random samples were generated via Monte Carlo simulation, according to the survey data of 2 MW Thorium Molten Salt Reactor-Liquid Fuel 1 by the China Earthquake Administration. Site response analysis carried out using an equivalent linear methodology was performed to study the influence of uncertainties in different soil parameters on surface response spectra. The coefficient of variation (Cv) was calculated via generating and enveloping random samples of low strain shear modulus to count for uncertainties in soil parameters, unlike many studies which take Cv as code’s minimum requirement of 0.5 directly. Floor response spectra considering uncertainties in soil parameters were calculated by the time-domain method using Cv. The results indicate that the uncertainty of shear wave velocity has the most significant influence on the surface response spectra. Floor response spectra have increased significantly after considering uncertainties in soil parameters, and the behavior of taking Cv as 0.5 like other studies is not conservative enough to consider uncertainties in soil parameters. Soil uncertainties have not been considered thoroughly in the calculation of floor response spectra in past studies, and this paper addresses this knowledge gap via Monte Carlo simulation. The findings will be used to perform floor response spectra analysis considering uncertainties in soil parameters.