Evaluation of Structural and Functional Behavior of Battery Charger for Low/High-Frequency Motions in NPP

Round 1

Reviewer 1 Report

-Why 5% damping level was adopted in Line 114 of the manuscript?

-Suggest the legend color used for the curves in Fig 4(a) & Fig 4(b) be more contrasted. The existing chosen color for the legend is somehow difficult to be observed.

-Short description/discussion should be included for the Fig 4(a)-4(b) and Fig. 5(a)-5(c).

-Equation (1) somehow is blurred and unclear in the manuscript.

Author Response

Question 1. Why 5% damping level was adopted in Line 114 of the manuscript?

 

- The damping ration of required response spectrum(RRS) at IEEE 344 was suggested 2% and 3% damping values for OBE and SSE based on Reg. Guide 1.61 in US. However, IEC 60980 recommends damping values different from IEEE 344. For example, 7% for Control panel, 2 % for motor and 10% for cable tray are recommended. The damping ratio of 5% at seismic test was conservatively chose to consider the IEEE 344 and IEC 60980.

 

Question 2. Suggest the legend color used for the curves in Fig 4(a) & Fig 4(b) be more contrasted. The existing chosen color for the legend is somehow difficult to be observed.

 

- Figure 4(a) and (b) were modified based on your comment.

 

Question 3. Short description/discussion should be included for the Fig 4(a)-4(b) and Fig. 5(a)-5(c).

 

- The required response spectrum at Fig. 4(a)-(b) was explained in Manuscript as follow.

“To evaluate the seismic performance of the BC, three seismic input motions were used. The first was high-frequency motion based on the South Korean NPP site-specific uniform hazard spectrum (UHS) in Uljin [11]. The second was a low-frequency motion based on the RG 1.60 design spectrum. The UHS and RG 1.60 spectrum were generated to obtain the floor response spectra for an auxiliary building at NPP PAB 100′. This was based on a series of time-domain dynamic analyses of the finite-element models of the building and foundation soil.

To consider the effects of the design response spectrum and uniform hazard spectrum, the CRS spectrum shape was defined based on the average of the response spectra of each floor for an auxiliary building. Its spectrum was obtained from the floor response spectra and used at a normalized ZPA of 1.0 g.”

 

Question 4. Equation (1) somehow is blurred and unclear in the manuscript.

 

- Equation (1) was modified based on your comment.

 

Reviewer 2 Report

As in the report

Comments for author File: Comments.docx

Author Response

Reviewer #2

The seismic performance and dynamic characteristics of BC were evaluated using a shaking-table test to ensure the operation of NPPs in South Korea. Seismic tests of BC were performed to consider low frequency (RG 1.60), high frequency (UHS), and a combination of both (CRS). From the tests, the in-structure and in-cabinet dynamic characteristics were evaluated and compared depending on the input motions.

 

Recommendation. I suggest that authors check the names of all the journals in the list of references including the abbreviated of ones.

 

- The reference was added and checked based on your comment.

 

Reviewer 3 Report

This paper describes the evaluation of the structural and functional behavior of battery chargers for low/high-frequency movements in nuclear power plants. The abstract does not clearly indicate the authors' contributions to the study problem addressed. In this way, the advances, results, conclusions, and importance of the research carried out are not appreciated. It is advisable to rewrite the summary indicating the main contributions, as well as the conclusions obtained.

The introduction section includes a brief state of the art. Authors are advised that this state of the art be much more detailed and include, for example, the main research studies related to the analyzed study, as well as the problems addressed. It may be interesting to make comparisons with other research works associated with this context, indicating different applied technologies. In this case, it has not been very clear which are the main contributions of the authors to the problem analyzed, nor the advantages and disadvantages compared to other investigations already carried out.

The number of bibliographical references incorporated in this paper is not adequate. It is necessary to provide a greater number of references related to the scope of the study carried out. All this will allow us to delve even deeper into the state of the art and make comparisons with other similar research studies.

It would be advisable to rename section 2 of the document because that title is not very clear. An example could be: Test sample and test conditions

On the other hand, the topic of the study analyzed has been presented in an integral way. The different figures, diagrams, schemes, and tables incorporated by the authors make it easier for the reader to understand the paper. Also, the mathematical expressions and results shown throughout the document make it easy to follow.

Ideas and different concepts are presented comprehensively. Regarding the conclusions, it is advisable to compare this study with other research documents related to this topic. 

It is also necessary to highlight the main contributions of the authors to the study addressed, as well as the most relevant results of the research carried out.

As for the bibliographic references provided, their number is not adequate for the study presented. It is necessary to increase the search for research papers and similar studies. On the other hand, most of these mentioned research works are directly related to the topic of the document and have also been published in the last decade.

Author Response

Reviewer #3

Question 1. This paper describes the evaluation of the structural and functional behavior of battery chargers for low/high-frequency movements in nuclear power plants. The abstract does not clearly indicate the authors' contributions to the study problem addressed. In this way, the advances, results, conclusions, and importance of the research carried out are not appreciated. It is advisable to rewrite the summary indicating the main contributions, as well as the conclusions obtained.

 

- The abstract was modified based on your comment as follow.

“From seismic test results, the peak acceleration of CRS at the top location (A6) was 1.31 times larger than that of UHS and 1.51 times than that of RG 1.60 and it increased rapidly with increasing PGA levels. Contact chatter was not observed under peak acceleration of 3.4 g on the in-stalled relay of the panel; however, the relay chatter for more than 2 ms in the dropped below the reference voltage 46 times. The major components of electric cabinet were significantly affected by high-frequency motion.”

 

Question 2. The introduction section includes a brief state of the art. Authors are advised that this state of the art be much more detailed and include, for example, the main research studies related to the analyzed study, as well as the problems addressed. It may be interesting to make comparisons with other research works associated with this context, indicating different applied technologies. In this case, it has not been very clear which are the main contributions of the authors to the problem analyzed, nor the advantages and disadvantages compared to other investigations already carried out.

 

- The other research works in the seismic qualification and limit status evaluation was investigated and added in Introduction as follow.

“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 [4–8]. Rustogi et al. [4] suggested to evaluate not only the validity of finite element analysis results but also the premise for developing Ritz vector approach based on shake table test result of two different cabinets. Ries et al. [5], Jeon et al. [6] and Cho et al. [7] compared at seismic behavior prediction for a safety-related electrical cabinet and finite element analy-sis. Son 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. Tran et al. [9] proposed to approach for col-lapse risk assessment depending on evaluated vulnerability of electric cabinet in nuclear power plants. However, it is difficult to evaluate the dynamic characteristics of an electri-cal cabinet because of the various sizes and shapes of the NPPs. Jeon et al. [6], Kim et al. [10] and Chang 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.

Richards et al. [12] summarize 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. Tseng et al. [13] monitored functionality of test items with normally open contacts during seismic test depending on virous input level.”

 

Question 3. The number of bibliographical references incorporated in this paper is not adequate. It is necessary to provide a greater number of references related to the scope of the study carried out. All this will allow us to delve even deeper into the state of the art and make comparisons with other similar research studies.

 

- The reference was added and checked based on your comment.

 

Question 4. It would be advisable to rename section 2 of the document because that title is not very clear. An example could be: Test sample and test conditions

 

- This study was used in real scaled electric cabinet, it was usually used specimens.

 

Question 5. On the other hand, the topic of the study analyzed has been presented in an integral way. The different figures, diagrams, schemes, and tables incorporated by the authors make it easier for the reader to understand the paper. Also, the mathematical expressions and results shown throughout the document make it easy to follow.

 

- Figure 4 was modified based on your comment. The graph type of acceleration signal and amplification were shown to overlap the other data, it is not easy to show fine figure and diagram. Please, understand this problem.

 

Question 6. Ideas and different concepts are presented comprehensively. Regarding the conclusions, it is advisable to compare this study with other research documents related to this topic. It is also necessary to highlight the main contributions of the authors to the study addressed, as well as the most relevant results of the research carried out.

 

- The topic of this study was compared with previous research, it was explained in Introduction.

“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. 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 output signal, and electrical connection discontinuity

Therefore, in this study, the seismic performance and dynamic characteristics of a BC in the electrical subsystem were examined to identify and investigate quantifiably the operation of NPPs in South Korea, where low frequency (design spectrum, RG 1.60), high frequency (uniform hazard spectrum, UHS), and a combination of both (CRS) were chosen and examined because of their different dynamic characteristics and their effects on the electrical equipment. Thus, seismic tests were conducted for the RG 1.60, UHS, and CRS motions. The in-cabinet (electrical component) and in-structure amplification and peak acceleration were compared depending on the input motions. Functional tests were con-ducted to measure the rated voltage of the relay during seismic testing. The acceptance criteria for relay contact chatter were evaluated in accordance with the IEEE standard.”

 

Question 7. As for the bibliographic references provided, their number is not adequate for the study presented. It is necessary to increase the search for research papers and similar studies. On the other hand, most of these mentioned research works are directly related to the topic of the document and have also been published in the last decade.

 

- The previous study for seismic qualification and limit state test in electrical cabinets such as dummy cabinet and real scaled cabinet was investigated and reference was added based on your comment.

Author Response File: Author Response.docx