## 5 Conclusions and Outlook  
The nonlinear inelastic and elastic analyses on the cap region of HCPB BB have been conducted. Assessments following the inelastic route and elastic route show that the inelastic assessment could help to reduce the conservatism in the design of Eurofer structures. Specific to the HCPB BB structure that is dominated by the temperature-driven secondary loads, it still needs to be decided whether IPFL damage limits based on the uniaxial uniform strain values are appropriate in comparison to the ILFED damage limits. Nevertheless, there remain many assumptions that need to be addressed in further studies to confidently move forward. Some of these are listed out below:  
* Material hardening behavior after the uniform strain point is not precisely known. Conventional uniaxial tension test data is affected by the necking at the uniform strain point and may not be valid after necking. Since Eurofer material has very low uniform strain even at unirradiated conditions, the hardening behavior at higher strains needed to be understood.
* It is assumed that the failure strain-triaxial relationship for Eurofer is as represented in Figure 6, estimated from the equation for SDC-IC ILFED criteria. However, it is known that this equation may not properly represent the material failure dominated by void nucleation at low triaxiality values as opposed to the failure dominated by void growth at high triaxiality. Even at high triaxiality values, the relationship needs to be verified for Eurofer97 material.
* As described in Section 2.4, the work here is performed using tensile stress-strain data at unirradiated conditions. Since at irradiated conditions, the yield stress and ultimate stress increases due to hardening, it is assumed that the unirradiated stress-strain curve is conservative. However, the plastic flow localization is an instability phenomenon and hence it could be affected by any change in the hardening behavior.
* For the HCPB BB, component level tests under similar operating conditions (high secondary-thermal loads combined with relatively low primary loads) could be performed to validate the applicability of IPFL damage limits against the more relaxed ILFED damage limits.  
Conceptualization, A.R.; methodology, A.R., F.A.H. and G.Z.; software, A.R.; validation, F.A.H. and G.Z.; formal analysis, A.R.; investigation, A.R.; resources, F.A.H. and G.Z.; data curation, A.R.; writing--original draft preparation, A.R.; writing--review and editing, F.A.H. and G.Z.; visualization, A.R.; supervision, F.A.H. and G.Z.; project administration, F.A.H.; funding acquisition, F.A.H. All authors have read and agreed to the published version of the manuscript.  
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014-2018 and 2019-2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.  
Not applicable.  
The data are not publicly available due to ongoing research based on the current data.  
The IT and hardware support from [PERSON] and the reviews and suggestions from [PERSON] and [PERSON] at KIT-INR is gratefully acknowledged.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.