Abstract
To ensure the stable operation of safety-related nuclear power plant (NPP) equipment, they are tested by following the seismic qualification procedures. The in-cabinet response spectrum (ICRS) is used to test the mounted components. However, the ICRS varies significantly with the number of uncertainties that include (1) loaded and unloaded condition of the cabinets, (2) the number of connected cabinets (grouping effects), and (3) higher frequency contents in the seismic inputs. This study focuses on the ICRS generation and alteration induced due to the listed uncertainties. A prototype of an electrical cabinet was experimentally examined. Followed by the numerical modeling of the cabinet, the seismic analysis for the group of cabinets was performed using artificial ground motion compatible with the standard design spectrum and the real accelerograms of high and low frequency contents. The seismic response using finite element (FE) analysis manifests (1) natural frequency of loaded cabinets reduced due to the in-cabinet components while for the unloaded cabinets it increased significantly, (2) a consistent reduction in ICRS due to the grouping effect was recorded when excited by the lower-frequency motion, while it was amplified dramatically due to high-frequency pulses. Interconnected cabinets under the low-frequency input motions have a significant reduction of 50% in the ICRS that corresponds to the higher stiffness of the cabinets, while a 100% increase under the high frequency of ground motion was obtained. High frequency of ground motion, usually above 10 Hz, can cause the interconnected cabinets to resonate as the natural frequency of these equipment lies in this range.
Highlights
The seismic evaluation of sensitive equipment is an essential requirement in the nuclear power plant (NPP) industry
The seismic response using finite element (FE) analysis manifests (1) natural frequency of loaded cabinets reduced due to the in-cabinet components while for the unloaded cabinets it increased significantly, (2) a consistent reduction in in-cabinet response spectrum (ICRS) due to the grouping effect was recorded when excited by the lower-frequency motion, while it was amplified dramatically due to high-frequency pulses
Interconnected cabinets under the low-frequency input motions have a significant reduction of 50% in the ICRS that corresponds to the higher stiffness of the cabinets, while a 100% increase under the high frequency of ground motion was obtained
Summary
The seismic evaluation of sensitive equipment is an essential requirement in the nuclear power plant (NPP) industry. Grouping of the cabinets without the internal components reduce the ICRS [5,6], in the case of the loaded cabinets the ICRS manifesting no potential difference for a single cabinet, but a noticeable alteration for the number of cabinets Another aspect is the seismic behavior of the cabinets that are highly influenced by the input ground motion, to evaluate this cause a set of ground motion was selected ranging from low- to highfrequency contents, including the Gyeongju 2016 earthquake and artificial motions compatible to the standard response spectrum of RG 1.60 [16]. Generalizing and extrapolating the seismic response of a single cabinet that may be loaded with or without the internal components have different dynamic characteristics compared to the group of cabinets This different dynamic behavior under the influence of the ground motions with the high- and low-frequency pulses is investigated in this study
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