Application of Inelastic Method and Its Comparison with Elastic Method for the Assessment of In-Box LOCA Event on EU DEMO HCPB Breeding Blanket Cap Region

Round 1

Reviewer 1 Report

The manuscript deals with the structural verification of DEMO reactor breeding blankets. The work compares the results of elastic and inelastic approaches, reported in the main international standards of the nuclear sector. Significant considerations about the material behavior modeling are reported. The manuscript is clear and well written, with an adequate English level. Results are suitably presented, and conclusions are properly drawn to summarize the main outcomes of the work. The authors also outline further improvements of the analysis methods. Therefore, the paper can be accepted for publication in the present form.

Author Response

Thanks for the review. Updated article is uploaded.

Reviewer 2 Report

Dear Authors,

Great work, The Helium Cooled Pebble Bed (HCPB) breeding blanket for EU DEMO fusion power plant is very original work. A breeding blanket cap region is analyzed by elastic and inelastic methods and results were compared. The study shows that for a given structure, elastic rules are more conservative and could lead to inefficient designs. Although, inelastic analysis shows potential in more efficient designs, some of mentioned assumptions need to be investigated further. 

Author Response

Thanks for the review. Updated article is uploaded.

Reviewer 3 Report

The article is devoted to the study of blanket materials for the reproduction of tritium and use in the field of thermonuclear energy. This direction is of great interest not only from a fundamental point of view, but also of great potential application in the field of nuclear energy and the creation of new types of reactor materials. The main purpose of the work is to assess material damage in the event of an accident. In my opinion, the article can be accepted for publication after the authors answer the following questions that arose after reading it. 1. Abstract requires improvement in terms of reflecting the novelty of the results obtained. 2. In the introduction, the authors should pay attention to the types of materials used for ITER as blankets. 3. Is the decrease in the stress limit as a function of temperature related to the processes of thermal annealing of local stresses arising in the structure? Authors should consider this fact. 4. The appearance of the maxima in Figure 5, the presented dependences of stresses and strains on temperature, requires an explanation. What is the reason for this behavior of materials at temperatures above 400 ° C? 5. The authors should give an explanation of what caused the increase in deformation at the ends of the assemblies shown in Figure 9. Is this related to the processes of irradiation and annealing of defects as a result of heating followed by their migration, or is it a local effect? 6. Authors should expand the Discussion section.

Author Response

Response: Thanks for your review.

1. Updated article as per comments.
2. Updated article as per comments.
3. The decrease in the stress limits corresponds to the typical decrease in yield and ultimate strengths due to the thermal activation of dislocations. However, in order to be conservative, the thermal annealing of local stresses in the operating temperature of BB (300-600) is not accounted in the present study.
4. The decrease in strain limits below 350°C is due to the irradiation hardening, which is less prominent at higher temperatures and becomes insignificant at temperatures above 500°C (Aiello et al., 2011). Consequently, unirradiated strain limits are used at temperatures higher than 500°C and the irradiated saturation value is used temperatures lower than 350°C. The values between these temperatures are linearly interpolated to represent the recovery of irradiation damage.
5. The high stresses observed at the ends of the breeder pins are due to the thermal gradient between the breeder zone and the back supporting structure (Figure 7b). The high stressed locations at the pressure tube ends are attached to the first wall and deformed accordingly. Localized peak stresses at the bonded interfaces between components are discounted for the stress assessment and the results are probed at few elements away were the contour is more stable.
6. Updated article as per comments. Original section-4 (Discussion) was split in to section-4 and section-5 (Conclusions and Outlook) as per the applied sciences template.