The Effect of Porosity Change in Bentonite Caused by Decay Heat on Radionuclide Transport through Buffer Material

Round 1

Reviewer 1 Report

The manuscript ,,The effect of porosity change in bentonite caused by decay heat on radionuclide transport through buffer material,, offers an interesting topic with interesting conclusions. Before considered publication, the manuscript needs to be improved into a publishable form.

Line 12, Abstract: This section should be shortened and improved. The abstract should concisely contain the objectives of the work, the results and the resulting conclusions. In order for the reader to be able to orient himself, a well-written abstract is a very important part of the manuscript.

Please be sure that your manuscript thoroughly establishes how this work is fundamentally novel. Specific comparisons should be made to previously published materials that have a similar purpose. Please present a strong case for how this work is a major advance. This needs to be done in the manuscript itself, not just in the response to review comments. This is a very important point in terms of which I will further consider the manuscript.

Please be sure that your abstract and your Conclusions section not only summarize the key findings of your work but also explain the specific ways in which this work fundamentally advances the field relative to prior literature.

The significance of this study should be more emphasize in the introduction.

Take a look at these two papers, it may be very helpful. 

https://www.sciencedirect.com/science/article/pii/S0149197021001268

https://www.sciencedirect.com/science/article/pii/S0169131716304252

Line 63, smectite that is caused by higher temperatures of waste decay heat: This important paper has dealt with this in detail and should therefore be added here as a reference. https://www.sciencedirect.com/science/article/pii/S0169433219329411

Any abbreviation that is first mentioned in the manuscript should be clarified for the first time and further only the abbreviation can be used. Please check the entire manuscript to see if this is the case.

Line 70: In the figure there should be only A and B and in the title below the picture there is an explanation of what A and B mean. Please correct it.

Line 78: This board should be named differently. I mean, more generally.

Line 102: Table 2:  What were the measurement deviations? 

Line 106, montmorillonite: This very important document addressed this in detail. Therefore, it would be useful to add it here as a reference.

Line 120: It is possible to add the content of the corresponding oxides to the structural formula of Na-smectite. Did you perform a chemical composition analysis?

Line 164: Name the individual parts of the structure such as the interlayer space, the individual sheets, etc.

Some equations with explanations should be written better.

Line 268: The results and discussion section should be the largest and most important part of the manuscript. In this case, I don't think so. It should be expanded. The experimental part is much larger compared to the results. Please improve it.

Line 347: Indicate the possible risks of such research. Add your recommendations for future research.

Line 374: Make sure the references are added correctly according to the journal's instructions 

Line 421: Acknowledgments should be in front of references.

Author Response

Reviewer #1:

Comments,

1. The manuscript ,,The effect of porosity change in bentonite caused by decay heat on radionuclide transport through buffer material,, offers an interesting topic with interesting conclusions. Before considered publication, the manuscript needs to be improved into a publishable form.

Yes, this study has highlighted the importance of multiple methodology application in waste disposal in subsurface environment. We also used a conceptual model to represent the subsurface system and supported by measurement inputs. We proposed such kind of multifaceted modeling works can support the challenging hidden subsurface aqueous geochemical questions. Our revised manuscript can achieve the key point of the reviewers' comments.

 

2. Line 12, Abstract: This section should be shortened and improved. The abstract should concisely contain the objectives of the work, the results and the resulting conclusions. In order for the reader to be able to orient himself, a well-written abstract is a very important part of the manuscript.

We have revised the abstract and concisely described the objectives of the work, the results and the resulting conclusions. For details, see P1-2 line 12-60 in revised manuscript.

 

3. Please be sure that your manuscript thoroughly establishes how this work is fundamentally novel. Specific comparisons should be made to previously published materials that have a similar purpose. Please present a strong case for how this work is a major advance. This needs to be done in the manuscript itself, not just in the response to review comments. This is a very important point in terms of which I will further consider the manuscript.

We have revised the introduction and added a description of the literature related to this study, as well as a key comparison of the literature. Put forward what was not implemented in the past research and add four discussion subsections, including: 6.1 Mineral types of buffer materials in engineering barrier systems; 6.2 Effects of Porosity change on radionuclides transport; 6.3 Smectite dehydration and rehydration within bentonite; 6.4 Transformation of smectite into illite in bentonite. And revised the manuscript to present a strong case for how this work is a major advance. And make a specific comparison with previously published materials that have similar purposes. Case study examples were provided to illustrate how this work has made significant progress.

P2-3 line 76-148, P3-4 line 153-159, P12 line 317-327 and line 332-345, P16 line 419-437, P21 line 467, P21 line 469-471, P23-28 line 486-line726 in revised manuscript.

 

4. Please be sure that your abstract and your Conclusions section not only summarize the key findings of your work but also explain the specific ways in which this work fundamentally advances the field relative to prior literature.

Yes, the revised abstract and conclusions section in the revised manuscript can summarize the key findings of our work and explain the specific ways in which this work fundamentally advances the field relative to prior literature.

P1-2 line 12-60; P28 line 730-732, line 734-744, line 746-748, and line 757-759 in revised manuscript.

 

5. The significance of this study should be more emphasize in the introduction.

Take a look at these two papers, it may be very helpful.

https://www.sciencedirect.com/science/article/pii/S0149197021001268

https://www.sciencedirect.com/science/article/pii/S0169131716304252

We have added these two references to the introduction. In addition to these two references, we also added several references. Rearrange and add explanations in this revised manuscript, including introduction and discussion.

P2-3 line 76-148, P3-4 line 153-159, P12 line 317-327 and line 332-345, P6 line 419-437, P21 line 467, P21 line 469-471, P23-28 line 486-line726, P29 line 783-784 and line 801-802 in revised manuscript.

 

6. Line 63, smectite that is caused by higher temperatures of waste decay heat: This important paper has dealt with this in detail and should therefore be added here as a reference. https://www.sciencedirect.com/science/article/pii/S0169433219329411

We added several references to explain the effect of temperature on the function of bentonite buffer materials (See P3 line 116-123 and line 130-142). The characteristics of alkylammonium-modified montmorillonite in this reference should belong to organic montmorillonite. Since relevant references suggest that natural clay materials should be used as buffer materials, the relevant explanations of these arguments are in the discussion (See P23 line 495-499). However, we added this reference to the discussion and put forward a description about those of other montmorillonite materials as the buffer (such as the alkylammonium-modified montmorillonite [66]) (See P25 line 624-626).

 

7. Any abbreviation that is first mentioned in the manuscript should be clarified for the first time and further only the abbreviation can be used. Please check the entire manuscript to see if this is the case.

Yes, we have checked that any abbreviations first mentioned in this manuscript have been clarified for the first time and further only the abbreviation. (See P2 line 66 and line 95)

 

8. Line 70: In the figure there should be only A and B and in the title below the picture there is an explanation of what A and B mean. Please correct it.

Yes, we have revised that only A and B are in the figure and in the title below the picture there is an explanation of what A and B are. (See P4 line 161)

 

9. Line 78: This board should be named differently. I mean, more generally.

Yes, we have revised the title of Table 1 to be more generally. (See P5 line 173-174)

 

10. Line 102: Table 2: What were the measurement deviations?

The parameters in Table 2 are from references. These parameters and measurement deviations were not measured in this study. Reference sources for these parameters have been added in this manuscript. (See P6 line 198-199)

 

11. Line 106, montmorillonite: This very important document addressed this in detail. Therefore, it would be useful to add it here as a reference.

We added two references to addressed this in detail. (See P7 line 205)

 

12. Line 120: It is possible to add the content of the corresponding oxides to the structural formula of Na-smectite. Did you perform a chemical composition analysis?

We have added a description of the oxide types and composition of smectite, which are mainly the results obtained from the laboratory analysis of ransom and Helgeson [38,39]. These explanations have been added to this study. The experiment of chemical composition analysis wasn't carried out in this study. (See P7 line 216-221)

 

13. Line 164: Name the individual parts of the structure such as the interlayer space, the individual sheets, etc.

Yes, we have added the name of the individual parts for the structure, such as the interlayer space, the individual sheets and basal spacing. (See P10 line 268-272)

 

14. Some equations with explanations should be written better.

Line 268: The results and discussion section should be the largest and most important part of the manuscript. In this case, I don't think so. It should be expanded. The experimental part is much larger compared to the results. Please improve it.

We separate the original results and discussion into the results section and discussion section. We also added more explanation in the discussion section, the same as the explanation in No. 3. (See P16 line 419-437, P 21 line 467, P 21 line 469-471, P 23-28 line 486-line726)

 

15. Line 347: Indicate the possible risks of such research. Add your recommendations for future research.

We have explained the results of this study in the discussion section and compared this study results with the past literature (See P23-28 line 486-line726). It also puts forward possible deficiencies in the relevant contents of this research results, and puts forward relevant suggestions and recommended research directions in the future study in this revised manuscript.

P24 line 553-560, P25 line 623-627, P26 line 679-681, P27 line 718-722 in revised manuscript.

 

16. Line 374: Make sure the references are added correctly according to the journal's instructions

We have modified that the references are added correctly according to the journal's instructions. (See P28-31 line 766-913)

 

17. Line 421: Acknowledgments should be in front of references.

We modified the acknowledgments to be in front of references. (See P28 line 761-763)

Author Response File: Author Response.docx

Reviewer 2 Report

This paper describes the effect of porosity change in bentonite caused by decay heat on the radionuclide transport through the buffer material. Authors have adopted the chemical kinetic model of smectite dehydration to calculate the amount of water expelled from smectite clay minerals caused by higher temperatures of waste decay heat. The methodological approach seems solid and appropriate. According to their simulation results of near-field radionuclides transport, they found that the modified effective porosity can obtain a more conservative concentration which can be used for the safety assessment of the repository. That is, the porosity correction model proposed in this study proves to be a method approach to the real situation of radionuclide release concentration.

The paper was well organized and the results are important for radiochemistry and applied physics. There is no problem regarding English. Therefore, I feel this paper should be acceptable after minor revision in view of the following specific comments.

 

Among many kinds of radionuclides, why do the authors select I-129 and Ni-59? Is it related to their decay constant? I think Cs-137 or Sr-90 etc. to be also important as target nuclide from the viewpoint of radioactive waste.

 

Based on author’s research results, I also think that smectite (i.e., main mineral in bentonite) would be suitable as a buffer material. It would be better if the data are compared with other previous studies in literatures such as other minerals, if possible.

Author Response

Reviewer #2:

 

Comments,
This paper describes the effect of porosity change in bentonite caused by decay heat on the radionuclide transport through the buffer material. Authors have adopted the chemical kinetic model of smectite dehydration to calculate the amount of water expelled from smectite clay minerals caused by higher temperatures of waste decay heat. The methodological approach seems solid and appropriate. According to their simulation results of near-field radionuclides transport, they found that the modified effective porosity can obtain a more conservative concentration which can be used for the safety assessment of the repository. That is, the porosity correction model proposed in this study proves to be a method approach to the real situation of radionuclide release concentration.

The paper was well organized and the results are important for radiochemistry and applied physics. There is no problem regarding English. Therefore, I feel this paper should be acceptable after minor revision in view of the following specific comments.

We would like to thank the reviewer for valuable and constructive comments and suggestions. We addressed each of them in the revised manuscript. New and/or modified sections in the revised manuscript used track model of MS Word to highlight as suggested. Here we provide a detailed point-by-point reply.

 

Among many kinds of radionuclides, why do the authors select I-129 and Ni-59? Is it related to their decay constant? I think Cs-137 or Sr-90 etc. to be also important as target nuclide from the viewpoint of radioactive waste.

We originally selected I-129 and Ni-59 due to their long half-life. We have added the two radionuclides of Cs-137 and Sr-90. The simulation analysis of four radionuclides of I-129, Ni-59, Cs-137 and Sr-90 were carried out in this revised manuscript. (See P15 line 383, P21 line 467 and 479, P24 line 562-596)

 

Based on author’s research results, I also think that smectite (i.e., main mineral in bentonite) would be suitable as a buffer material. It would be better if the data are compared with other previous studies in literatures such as other minerals, if possible.

We also add some discussion in the subsection “6.1. Mineral types of buffer material in engineering barrier system” in the revised manuscript. We also have added some explanation about the reviewed literature on the sealing capacity of other clay materials. The porosity correction method and data in this study are applicable to bentonite. Other minerals that may be suitable as buffer materials are described in detail in the discussion. (See P23-24 line 487-560)

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has been improved and can be accept.