Experimental Investigation of EU-DEMO Breeding Blanket First Wall Mock-Ups in Support of the Manufacturing and Material Development Programmes

Round 1

Reviewer 1 Report

The paper describes the experimental characterization of two Breeding Blanket First Wall mock-ups under thermal loading. The paper is very interesting, well-written and generally clear. I only have some minor typos, that I listed below divided in sections.

Section 3.3)

There is an unfinished sentence at the end of the paragraph describing the calibration for surface emissivity. “For the present test we use a….”. Please complete it.

Two small typos here: “A well-defined correction formula for such kind of experiments it is difficult to produce….(remove “it”)…we performed a complementary experiment is to deduce a … (remove “is”)”.

A typo here: “Three additional thermocouples have (TC12 - 14) are fixed…(remove “have”)”.

Section 4: Figure 8 was incorrectly labeled as Figure 9 in the text. I would suggest to check also the numbering from that point on, as also the following figures are wrongly referenced in the text (at least up to Figure 17 included).

Section 5.1)

“during the experimental run of from 5th of August 2019”. Please remove “from” and add “the”.

There is a problem in the number of Figure 13. Figure 1 is shown instead of the right number.

Probably it would be better to switch the position of Figure 13 and 14, as Figure 14 is the first one to be quoted in the text.

Section 5.2)

Figure 20 is named figure 2 in the label.

Author Response

Thank you for your positive feedback taking the time to go in such detail through the paper. Your comments were realy helpful.

Section 3.3: the unfinished sentence was removed since missing part was, in fact, moved further up in that paragraph

The typos mentioned have been all corrected.

The figures numbers have been updated.

Reviewer 2 Report

Please see the attached document.

Comments for author File: Comments.pdf

Author Response

First of all I would like to thank you the reviewer for the thorough comments and suggestions. The points raised were of real help to improve the quality of the paper. Now, here are my answers to the specific points:

1. The text has been revisited, in particular the mentioned paragraphs, and we tried to make the text easier to read. More of the other comments made by the reviewer were very helpful in this sense
2. The numbering of the figures was corrected.
3. All formatting of the figures was change according to the reviewer suggestion and MDPI format requirements
4. All dates of the measurements were changed to the longer form
5. the mentioning of the method (vacuum plasma spraying) is added as well as the reference. Additionally, also for ODS the reference is mentioned.
6. The paragraph concerning Figure 1 was rewritten and the reference to the figure is done as suggested
7. the figures were improved and new drawings with dimensions and labelling were added
8. two new tables were added with the helium instrumentation. In this tables we try to avoid also the confusion between the signal/instrumens tags that appear in Figure 5 and sensor types/manufacturer. Concerning the thermocouples we also added some additional information but, from our point of view, mentioning that these thermocouples are of type K and having an accuracy class 1 defines these sensors completely, the corresponding range and uncertainty being prescribed by industrial standards.
   In case of the IR camera we tried to change the text to make it more clear that it was a FLIR Systems, Inc. camera. The camera type,  X6580sc, was also mentioned already in the text but it was probably not explained clearly enough. 
9.   The sentence fragment was removed. 
10. The uncertainties were mentioned in reference [7] so we modified the text to make this more clear.
11. Same as the previous point, the reference is [7] and the text was changed to express this more clearly 
12. Figure 6 was changed as suggested. From the three pictures we kept only one since the others were either repeating information available from the earlier figures or it was deemed not particularly relevant for the paper
13. The sentence was rewritten to avoid the term "fatigue experiments " that could have caused confusion. 
14. Concerning the OriginPro fitting, the text was modified to make it more clear that the method used (Fasano&Vio) is, in fact, part of the Origin package. It is true that the fitting is not the default one (which is the York method) but it is available in the package. The reference cited in the text is the one we found in the Origin Help
15. Limiting the operation to 550C comes from the colleagues that developed the mock-up (reference [4]) that are also people that are active in the material development. The explanation for this limit, from material science perspective, is that above this temperature the EUROFER has a steep decrease in strength. This lead to the fact that, in fusion technology sector, the 550C is often used as an operating limit. However, this approach is debatable from an engineer point of view. In fact, for the ODS mock-up this limit was certainly exceeded but we took care that the stresses that occurred in the mock-up stayed within the limits prescribed by the design code. Nevertheless, since the limit was imposed by the ones that owned the mock-up I would prefer to presented as such without going into more details. 
16. The phrase referring to "deposited power" was changed same as the one concerning the "simplified model" 
17. Added a reference to RCC-MRx design code. Also, we added the fact that 3Sm refers to a ratcheting design criteria from the RCC-MRx code. 
18. The phrase containing the reference to transients has been changed to make it more clear. The term "transients"  is left out.
19. Added a formula used for calculating the power increase in the helium stream
20. Figure 12(b) is now mentioned
21. The part where  the heat flux is estimated has been extended as suggested
22. Concerning Figure 18 we prefer to keep it as it is. We find that, having pictures where you can directly see the dimensions is more worth that having them added by editing. 

Reviewer 3 Report

the paper considers the experimental analysis of Breeding Blanket of mockups the abstract is not clear and needs to be rewritten it is good to start with this sentence this paper presents,....and then continue with other parts.

the introduction is very shorts if there are different ways available describe them and provide the drawbacks and advantages and describe your way and its advantages.

the quality of the figures is good, the conclusion is enough and good the number of references is not enough it needs more references and better introduction.

the uncertainty analysis is not described and needs to add the part about it, and also about how to select the position of thermocouples and how to tune the distance of the thermal camera from distance, moreover have you considered the inlet and outlet temperature of the liquid (coolant from channels and the effect of coolant speed on the performance?

Author Response

I would like to thank you the reviewer for taking the time and read our paper.

Here are our answers concerning the comments and suggestions made by the reviewer: 

• Abstract: we have to admit that we failed to understand what was unclear to the reviewer and what were we supposed to change. In our opinion, the abstract, as it is, expresses the essence of the paper, therefore we politely declined to change it without more precise specifications
• Introduction: it is unclear to us to which ways the reviewer refers too. The paper is about an experimental campaigning, the methods used to gather data or control various parameters of the experimental set-up. The cycling loading conditions are imposed by the owners of the mock-ups and we are simply creating, in our testing facility, the proper conditions to fulfil those requirements. There might be other ways to achieve the required loadings in other facilities but this is not something that we can argue on this paper since testing condition are given by the facility that we have. 
• We have added a reference to the RCC-MRx code but otherwise we are not aware of missing any relevant work that we need to cite in our paper. Also we have added, in the text, reference to the work describing the mock-ups manufacturing as suggested by another reviewer. I would appreciate it if the reviewer could be more specific and point us towards the articles that he thinks we have omitted.
• Uncertainty analysis: the uncertainty analysis of the data is done using the general accepted methodology of the international standards like the ISO Guide to the Expression of uncertainty in measurement. We find that, adding such a part would not bring any additional value to the work presented here
• Information about the position of the thermocouples was added. 
• IR camera is not remotely controlled if this is what the reviewer means. The camera, as well as the mirror system, are set once at the beginning of the testing campaign. When going from one mock-up to the other we just changed the viewing angle of the camera towards the mirror system to better view the mock-up of interest. Such an adjustment is of no real scientific interest so we have not discussed it in the paper.
  If, by tuning you are referring to the calibration of the camera to provide suitable measurements, we have dedicated substantial space for this part in the paper. Since some of the details were presented in an earlier paper (ref. [7]) we decided to not repeat those aspects here and focus on the novel aspects encountered during the present tests
• Regarding the last comment on coolant parameters it is not really clear what the reviewer is referring too, in particular which performance does he mean. It would be helpful if the reviewer could be more specific.

Round 2

Reviewer 3 Report

Dear Authors,

in my opinion, you should use the standard format for the abstract and it needs to change.

the most important thing is to describe, how you calculated the uncertainty analysis, as it depends on several factors and should be added to your paper.

Author Response

The abstract was changed to follow the suggestion from the reviewer.

When introducing the power calculation for FG mock-up and the associated uncertainty, we introduced a more detailed description of the steps we followed and how the uncertainties were calculated.

Round 3

Reviewer 3 Report

Dear Authors

Thank you so much for answering my question.