Investigation of Unsteady Pressure Pulsations of Reactor Coolant Pump Passage under Flow Coast-down
Round 1
Reviewer 1 Report (Previous Reviewer 2)
The authors have done a great work to improve the quality of this manuscript, congrats. However, this reviewer would like to make some minor comments:
1. A nuclear power plant has different operational states: normal, failures and emergencies, severe accident, and off-design basis accidents. After the Fukushima accident the industry even talks about extensive damage accidents. Please identify the different scenarios considered in "an extreme accident" and clarify the definition.
2. When I speak of "outline on the research method" I am not referring to the idling condition studied. I am talking about the scientific methodology: (i) mechanical design of the hexahedral structured grids of the CPR flow path; (ii) control points; (iii) pressure pulsation results; (iv) discussion... Please clarify this point.
3. Check references, there are mistakes. They do not adapt to the MDPI format. For example, the correct format of paper is: Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range.
Author Response
- A nuclear power plant has different operational states: normal, failures and emergencies, severe accident, and off-design basis accidents. After the Fukushima accident the industry even talks about extensive damage accidents. Please identify the different scenarios considered in "an extreme accident" and clarify the definition.
Respond: The flow coast-down of the RCP is defined as when the RPC suddenly loses power and stops running, resulting in a sudden decrease of the coolant flow in the core during the process, which threatens the safety of the reactor. The idling of the RPC is defined as the extreme accident because it is located between the reactor and the steam generator, at the main pressure boundary of the primary circuit and under extremely harsh working conditions. When extreme conditions such as power failure, fire or earthquake occur, it plays a key role in the continuous normal and stable work of the reactor.
- When I speak of "outline on the research method" I am not referring to the idling condition studied. I am talking about the scientific methodology: (i) mechanical design of the hexahedral structured grids of the CPR flow path; (ii) control points; (iii) pressure pulsation results; (iv) discussion... Please clarify this point.
Respond: (i)Hexahedral structured grids can reduce the total number of grids and improve the calculation efficiency;(ii)The main purpose is to observe the pressure pulsation in the middle part of the channel, and the pressure pulsation change of the side wall is more complicated by the side wall. Because of the limited conditions, this paper only sets the detection point in the middle part of the channel. ;(iii)Pressure pulsation results: (a)The pressure pulsates violently. At the 1.0TQi of flow coast-down, the pressure coefficients of YL3 and YL4 are similar, and the values of pressure coefficients are similar at each time point. The pressure coefficient of YL1 fluctuates more violently than other monitoring points in impeller, which may be caused by the influence of impeller inflow. Compared with YL1 and YL3, the pressure coefficients of YL2 and YL4 are significantly higher at 1.0TQi and 0.75TQi. The pressure coefficient of YL1 at impeller inlet decreases fastest from 0.75TQi to 0.5TQi, and the average change of pressure coefficient in each stage is 32.72%, 14.9% and 21.16% respectively. The pressure coefficient of YL2 at inlet of impeller blade passage from 0.75TQi to 0.5TQi lowered the fastest, and the average change of pressure coef-ficient in each stage is 19.59%, 44.51%, 29.32%. The average pressure coefficients of YL3 in the middle of impeller blade passage change by 42.2%, 40.66% and 16.96% respectively. The pressure coefficient of YL4 at impeller outlet decreases fastest from 0.75TQi to 0.5TQi, and the average change of pressure coefficient in each stage is 35.29%, 64.52% and 13.23% respectively. The pressure coefficient at each monitoring point of impeller passage de-creases gradually, and the closer to the outlet pressure coefficient of impeller, the faster it decreases. When flow coast-down runs to 0.5TQi , the values of transient pressure coeffi-cients at each monitoring point of impeller gradually close. (b)The pressure coefficient of DY1 at guide vane inlet decreases fastest from 0.75TQi to 0.5TQi, which indicates that the pressure pulsation in this period is strong and the pressure coefficient decreases averagely by 45.75%, 69.06% and 7.94% in each stage. The pressure coefficient of DY2 in the middle of guide vane decreases fastest from 0.5TQi to 0.25TQi, and the pressure coefficient decreases averagely by 50.37%, 16.34% and 68.69% in each period. The pressure coefficient of DY3 at guide vane outlet decreases smoothly, with an average decrease of 48.29%, 44.91% and 41.11% in each period. This may be due to the influence of pressurized water chamber watershed on guide vane outlet area, and which results in strong pressure pulsation during flow coast-down. (c)The pressure coefficient of DY1 at guide vane inlet decreases fastest from 0.75TQi to 0.5TQi, which indicates that the pressure pulsation in this period is strong and the pressure coefficient decreases averagely by 45.75%, 69.06% and 7.94% in each stage. The pressure coefficient of DY2 in the middle of guide vane decreases fastest from 0.5TQi to 0.25TQi, and the pressure coefficient decreases averagely by 50.37%, 16.34% and 68.69% in each period. The pressure coefficient of DY3 at guide vane outlet decreases smoothly, with an average decrease of 48.29%, 44.91% and 41.11% in each period. ; (iv) In the process of idling from 1.0TQi to 0.75TQi, the change rate of the maximum pressure pulsation coefficient of the pump channel appears in the middle of the guide vane DY2 and away from the outlet end V3 of the pressure chamber, and its change rate is more than 50%. In the process of 0.75TQi to 0.5TQi, the change rate of the maximum pressure pulsation coefficient of the pump channel appears in the boundary area YL4-DY1, and its change rate is more than 60%. In the process of 0.5TQi to 0.25TQi, the change rate of the maximum pressure pulsation coefficient of the pump channel appears in DY2 in the middle of the guide vane, and its change rate is as high as 68.69%. Finally, the change of pressure pulsation coefficient tends to be stable.
- Check references, there are mistakes. They do not adapt to the MDPI format. For example, the correct format of paper is: Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range.
Respond: The format of references has been corrected.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (New Reviewer)
Find the attached file for review comments.
Comments for author File: Comments.pdf
Author Response
- It is better to add nomenclature after the abstract.
Respond: There are not many nomenclatures in the text, and all nomenclature are annotated in the text. A more detailed discussion regarding the major contribution of the existing works should be given to highlight the motivation of this work.
- The authors should describe how to organize the paper at the end of the introduction part. I recommend a revision of the introduction.
Respond: It has been revised in the article and some redundant parts have been deleted.
- The authors should add “.”or“,”at the end of each equation an required.
Respond: The "."has been added at the end of the equation.
- There are two figures in the main text having the same caption (Figure 7), on the other hand, Figure 8 is missing. Please check carefully!
Respond: The article has been revised.
- Future research directions should be written in the conclusion section.
Respond: Future writing will pay attention to this point.
- The authors should make sure that all references are well-cited in the main text (e.g., Refs. [11] and [21] are not cited).
Respond: The article has been revised.
- Reference list is not up to date. Authors should add some recent relevant studies to the reference list. Moreover, check and format all the references according to the journal style.
Respond: Cited references, accounting for 60% of the total in the last five years..The format of references has been corrected.
Author Response File: Author Response.pdf
Reviewer 3 Report (New Reviewer)
This is a good paper on an important subject. Unfortunately, for me, it is not clear if the authors performed real tests on real pumps or just simulations.
The papers contains some huge paragraphs that have to be transformed in smaller paragraphs, now they are almost impossible to understand.
In text there are some paragraphs underlined and marked in blue, I guess it is not according to the template.
The authors should add a short paragraph about the predictive maintenance of these pumps.
Not all the references were cited in text.
Some other remarks in the attached file.
Comments for author File: Comments.pdf
Author Response
- The pump is the whole pump, and the internal pressure pulsation is calculated by numerical simulation.
- The middle part of the introduction has been segmented. The second paragraph mainly introduces that there is dynamic and static interference between impeller and guide vane, and the dynamic and static interference will make the pressure fluctuate continuously in the range. The third section is the research on pressure pulsation of RCP by domestic and foreign scholars in recent years. The fourth section introduces the research on the treatment of pressure pulsation of RCP by wavelet transform.
- The formula of Q is to simulate the flow change of RPC during idling, which belongs to transient flow.
- The problem of segmentation format has been modified in this paper.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report (New Reviewer)
The authors have revised the manuscript according to the comments. Therefore, it can be accepted for publication after moderate English language changes.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Major
1.Overall English proofreading of the paper is necessary.
2.What is the originality of the paper in comparison with previous literatures?
3.In Line 134, sensitivity analysis and validation of turbulence models are needed. It would be good to compare the results of other models with the validation results in Fig. 4.
4.Line 80-84, the authors explained that the research results will be used for strong support in safety and stability design. Dose the wavelet phenomenon affect the safety and stability of the pump? In RCP operating conditions, there seems to be no effect by wavelet phenomenon.
5.In section 2.3, it is necessary to add the boundary conditions of inlet and outlet section.
6. Line 83-84, self-plagiarism. "Fluid Energy Conversion Analysis in Hydraulic Channels of reactor coolant pump under flow coastdown transient."
Minor
1.Line 14 : with -> With
2.Line 15 : the ->The
3.Line 27 : Security level? I think it is safety class
4.Line 121-122 : check the unit of Q or change the equation (1)
5.Figure 5, add the information of location (length, height and so on.)
Reviewer 2 Report
Although the article is very interesting and suitable for any reader in this field, some recommendations should be taken into account for publication:
Relevant comments:
1. In the Introduction, include a brief summary of nuclear reactors designs that include RCP in the primary loop. Take like reference the nuclear reactors generations.
2. In the introduction, it is necessary clarify the layout of primary loop and identify the RCP. Could be possible include an infographic.
3. The RCP is one of the most important components in a nuclear reactor. Please, describe with details the functions of this component.
4. Include the operational scenarios where the RCP is operating under flow coast-down.
5. Line 68:describe with more details the explanation about the cavitation effect.
6. Under flow coast-down is a similar situation like LOCA? And in case of startup or shut down?
7. Assess the possibility of include an outline about the research method carried out.
8. Clarify the model of RCP taken in to account. I think that other RCP models, for example, the RCP of KWU reactors, AP1000 or APR1400 have other value to parameters like speed and operation temperature.
9. Modify Figure 1 to speak about intermediate and cold leg.
10. The quantitative study has a high technical leve, but I think one option to improve the quality of the paper is separate section “Results” of the section “Discussion”.
10. Check references, there are mistakes. They do not adapt to the MDPI format. For example, the correct format of paper is: Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range.
11. References are wrong. References must be numbered in order of appearance in the text (including citations in tables and legends) by a numeral or numerals in square brackets—e.g., [1] or [2,3], or [4–6] and listed individually at the end of the manuscript.
12. The conclusions must to be rewritten, not listed.
13. In the references, few papers have been included. Include more references about the topic, for example:
Zhou, L.; Wang, X.; Liu, H.; Xin, J. The Effect of Inflow Distortion on the Rotordynamic Characteristics of a 1400-MW Reactor Coolant Pump Annular Seal. Machines 2022, 10, 65. https://doi.org/10.3390/machines10010065
Wang, J.; Wang, P.; Zhang, X.; Ruan, X.; Xu, Z.; Fu, X. Research of Modal Analysis for Impeller of Reactor Coolant Pump. Appl. Sci. 2019, 9, 4551. https://doi.org/10.3390/app9214551
Fernández-Arias, P.; Vergara, D.; Orosa, J.A. A Global Review of PWR Nuclear Power Plants. Appl. Sci. 2020, 10, 4434. https://doi.org/10.3390/app10134434
Feng, X.; Su, W.; Ma, Y.; Wang, L.; Tan, H. Numerical and Experimental Study on Waviness Mechanical Seal of Reactor Coolant Pump. Processes 2020, 8, 1611. https://doi.org/10.3390/pr8121611
