Study Characteristics of a Multipurpose Reactor Building G.A. Siwabessy using Floor Spectral Ratio

¹ BRIN, Directorate of Nuclear Facility Management, Jakarta, Indonesia
² UGM, Faculty of Mathematics and Natural Science, Physics Department, Yogyakarta, Indonesia
³ BRIN, Geological Disaster Research Centre, Bandung, Indonesia

Abstract

The G.A. Siwabessy Reactor is a vital national object of Indonesia’s nuclear infrastructure. These nuclear facilities are vulnerable to earthquake shocks due to regional tectonic activity. This could have a major impact on society and the surrounding environment if a nuclear disaster occurs. To mitigate hazards, we investigate location and building characteristics through Horizontal to Vertical Spectral Ratio (HVSR) and Floor Spectral Ratio (FSR) analysis. We determine the natural or dominant frequency (f₀) and the amplification factor (A₀). We carried out data acquisition on 8 - 19 January 2023 using the Lennartz LE-3D/20s short period seismometer. The data collection time was 31 minutes with 100 Hz sampling. We analyzed the data using Geopsy software. The natural frequency range obtained for wave propagation based on the direction of the NS component is in the range 1,423 – 4,726 Hz. For wave propagation in structures with the EW component direction, the f₀ value is in the range 1,280 Hz to 9,753 Hz and the average f₀ value in this direction is 2,957 Hz. This research will be a reference in the Periodic Safety Assessment regarding the resilience of building structures due to changes in the maximum ground acceleration value as a condition for extending the operational permit for the G.A. Siwabessy reactor.