# Evaluation of Structural and Functional Behavior of Battery
## 1 Introduction  
Nuclear power plants (NPPs) in South Korea have been designed according to the U.S. NRC Regulatory Guide 1.60 (RG 1.60) design spectrum or low-frequency motion with a similar spectrum based on a modified spectrum where the peak frequency range is 2-10 Hz [1]. RG 1.60 could be modified depending on the adapted peak ground acceleration (PGA) at the seismic zone of the NPP. However, the characteristics at the Korea NPP sites are different from those in the western United States on which the RG 1.60 is based. The recent Gyeongju earthquakes in South Korea had a lower amplification at a low-frequency range and a higher amplification at a high-frequency range [2]. The structural members of NPPs were designed to withstand earthquake motions; however, the equipment attached to the structural members is generally sensitive to earthquakes, including low- and high-frequency motions. The importance of equipment safety when operating NPPs and the type of failure modes have been reported for sensitive equipment or components, such as contact chatter, change in the output signal, and electrical connection discontinuity [3]. The qualification of sensitive equipment or components was conducted for in-structure or in-cabinet motions consistent with the safe shutdown earthquake (SSE) defined for each plant. In addition, the qualification of the electrical systemmust be evaluated to consider low- and high-frequency motions because of the design spectrum and high-frequency effects. The electrical equipment in NPPs is generally installed in a cabinet, and the seismic performance of the cabinet is evaluated by numerical analysis and a shaking-table test [4; 5; 6; 7; 8]. [PERSON] et al. [4] suggested to evaluate not only the validity of finite element analysis results but also the premise for developing the Ritz vector approach based on the shake table test results of two different cabinets. [PERSON] et al. [5], [PERSON] et al. [6] and [PERSON] et al. [7] compared seismic behavior prediction for a safety-related electrical cabinet and finite element analysis. [PERSON] et al. [8] evaluated seismic demands of the electrical cabinet under high-frequency earthquakes and also seismic qualification of the electrical cabinet using the identification of experimental tests and numerical models. [PERSON] et al. [9] proposed an approach for collapse risk assessment depending on the evaluated vulnerability of electric cabinets in nuclear power plants. However, it is difficult to evaluate the dynamic characteristics of an electrical cabinet because of the various sizes and shapes of the NPPs. [PERSON] et al. [6], [PERSON] et al. [10] and [PERSON] et al. [11] performed seismic qualifications of electrical equipment under low- and high-frequency motions by seismic tests according to the cabinet type. However, it has not been evaluated for contact chatter under a seismic qualification that can be used to evaluate the contact chatter of sensitive components in NPPs. [PERSON] et al. [12] summarizes the types of components evaluated in the test program, the test methods investigated within the program, and the results of seismic testing performed on a diverse group of 153 components using high-frequency input motions. [PERSON] et al. [13] monitored the functionality of test items with normally open contacts during seismic tests depending on virous input levels. The critical characteristics of a relay, such as configuration, pick-up/drop-out voltage, voltage rating, current rating, chatter and response time, were monitored. In the equipment fragility test, a nonconformance report was generated when the function failure of the equipment did not occur because of the contact chatter of the relay component. However, the contact chatter of the relay under the fragility test of a component was a significant indicator of the performance requirements for electric components. A battery charger (BC) was installed to supply a charging current to the inverter and the battery that supplies safety and non-safety loads at the NPP.