Post Neutron Irradiation Recovery and Recrystallization of ITER Grade Forged Tungsten Bar
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have studied the microstructural evolution of neutron irradiated tungsten (W) after annealing, along with its correlation to the corresponding mechanical properties, offers valuable insight into defect interactions and annihilation processes. The topic is certainly relevant to Metals (the journal and the field). The paper is well-written and it can be accepted in present form.
Author Response
Thank you very much for your positive feedback and for taking the time to review our manuscript. We are pleased to hear that you found the manuscript suitable for publication in its present form.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis is really high quality research and presentation: sound methodology, well readable and interesting. From my point of view, almost no modifications are required, just one minor mistake appears on page 1 in the Introduction: Tungsten suffers from high (not "low") ductile-to-brittle transition temperature.
The main question addressed by the research is the Post Neutron Irradiation Recovery and Recrystallization of ITER Grade Forged Tungsten Bar. I consider the topic both original and relevant to the field. It does not address a specific gap in the field, but it extends previous research by adding significant new details. This is the case due to both the specific combination of methods (X-ray diffraction, resistivity measurements, PAS lifetime spectroscopy and Vickers hardness) and the physically sound concept of analysis of recovery and recrystallization. The submission adds a comprehensive picture of the recovery and recrystallization behaviour of one specific neutron-irradiated material of industrial relevance, namely ITER grade tungsten produced via powder metallurgy. In terms of microstructure and properties, the submission provides information on the dislocation density, void size and density, and critical resolved shear stress, each of them as function of annealing temperature. Moreover, the results are analyzed in terms of recovery stages and underlying mechanisms. The conclusions are consistent with the provided evidence. This is simply because of the sound methodology of the submission avoiding misconceptions that sometimes appear in the published literature. Tables and figures are appropriate in the present form.
Author Response
We sincerely thank you for your time, effort, and valuable assessment of our work. The minor mistake you have pointed out regarding DBTT has been corrected.
Reviewer 3 Report
Comments and Suggestions for Authorsplease see the attached pdf.
Comments for author File: 
Comments.pdf
Author Response
Comment 1: Page 1. It should be noted that according to the recent ITER re-baseline, ITER will now operate as a full-W device (both divertor and first wall) [Nucl. Mater. Energy 42, 101854 (2025)].
Reply: Added a phrase addressing the comment (page 1).
Comment 2: Page 2. It should be noted that during disruptions and even during edge-localized modes, even in the presence of strong mitigation, it is rather unavoidable that deep recrystallization will occur [Nucl. Fusion 64, 126002 (2024)].
Reply: A comment has been added addressing this point (page 2).
Comment 3: Page 3. How do the neutron irradiation conditions of this investigation relate to neutron irradiation conditions in ITER/DEMO or a future fusion reactor? Few sentences would be a welcome addition.
Reply: A comment was added on page 3, addressing the similarity between the BR2 reactor fission neutron spectrum and the expected neutron spectrum in the DEMO divertor, as well as the relevance of the specific irradiation conditions.
Comment 4: Page 3 The impurity contents of the W bar are provided in Table 1. Can the authors also provide the % at W purity or even better the residual resistivity ratio (RRR)? This would allow for a rapid understanding of the purity level of the sample by the readers.
Reply: The purity of the W bar sample as provided by Plansee® has been provided (page 3). The RRR is not provided since it is not addressed anywhere in the paper and it requires measurement at a very low temperature (often at 4.2 K).
Comment 5: Page 3 Given the level of detail provided in the experimental methods, some additional details or at least references would be appreciated concerning the simulation tools (MCNPX, FISPACT-II and thermo-hydraulic calculations).
Reply: As the main scope of the present paper is the microstructural evolution after annealing, the authors believe that the information provided regarding the supporting simulation tools are adequate. References for the MCNPX code and FISPACT-II nuclide inventory code have been added (pages 3,4).
Comment 6: Page 4 Below Eq.(1), it should read as “convoluted with the resolution function and superimposed on the background”. Moreover, does the resolution function need to be assumed to be Gaussian? It can be characterized with calibrated spectra, correct?
Reply: The phrasing has been corrected (page 4). The resolution is necessarily assumed Gaussian in the LT10 programme. It is however measured using a 60Co sample, as mentioned in reference [82] where more details on the experimental setup can be found.
Comment 7: Pages 6-7. The mean subgrain size and its standard deviation are inferred from fitting to the lognormal distribution. However, the quality of the fits is rather poor as discerned from Fig.2. The referee would recommend that the authors determine the mean subgrain size and its standard deviation directly from their collected data without first fitting them to the log-normal.
Reply: The analysis of the subgrain size and the fitting of the lognormal distribution allow for the accurate determination of the mean subgrain size along with its standard deviation. This approach also enables the characterization of abnormal grain growth observed in the irradiated material. Evaluating the mean subgrain size and its standard deviation directly from the collected data will assume a normal distribution of the grains which is undeniably not correct. Therefore, the authors believe that its removal would eliminate an important and interesting aspect of the study.
Comment 8: Page 11. The reduction of the thermal conductivity is an important consequence of transmutation. The referee recommends that the authors translate the resistivity data to thermal conductivity data by utilizing the Wiedemann-Franz law with the nominal Lorenz number. This recipe has been shown to be rather accurate for W due to the weak phonon contribution to heat transfer [Nucl. Mater. Energy 13, 42 (2017); Phys. Rev. Lett. 132, 146303 (2024)].
Reply: The authors wholeheartedly agree with this suggestion, and believe that it is important to mention that any recovery of resistivity from annealing in the current study is directly proportional to the recovery of thermal conductivity in the paper. A paragraph has been added on pages 13-14.
Comment 9: Page 19 The reviewer was aware of a much smaller value of the Hall-Petch coefficient for W. Some additional elaboration or extra references would be appreciated. What about the temperature dependence?
Reply: The authors agree that determining the value of the Hall-Petch coefficient is challenging. Reference [122] highlights that and includes the temperature dependence. The value chosen in the present study was selected because the material studied in reference [122] is identical to the material analyzed in this work. A phrase elaborating this has been added.
Comment 10: Page 24 A paragraph focusing on future work / outlook would be appreciated. This could concern potential utilization of additional experimental methods, investigation of different tungsten grades or study of different neutron irradiation conditions.
Reply: A paragraph has been added addressing these points on page 25.
