# Comparative Theoretical Analysis of Halden Reactor Creep Tests on M5 Cladding Material
## 7 Conclusions  
This study evaluated the creep behavior of M5 cladding under in-reactor conditions by comparing experimental data from the HWR-658 and HWR-755 reports with two predictive approaches. While the experimental results provide valuable benchmarks, their reliability is limited by uncertainties related to instrumentation and environmental factors such as oxide growth and crud deposition. This underlines the need for caution when using these data as a sole reference.  
The model developed in this work, based on [PERSON]'s primary creep formulation and expanded to include secondary creep and corrosion effects, demonstrates good agreement with steady-state trends under typical PWR conditions. Its performance suggests that it is a useful tool for interpreting cladding behavior in scenarios where experimental data may lack precision. However, some overestimation of deformation in the early phases highlights the need for further refinements to better account for primary creep transitions and other potential influences, such as anisotropy in material behavior.  
TRANSURANUS, while providing a conservative and widely used approach, tends to underpredict creep deformation in the studied conditions. This is consistent with its current implementation, which does not fully capture complex phenomena such as stress anisotropy or detailed secondary creep mechanics. Future updates to the code could enhance its applicability for advanced materials like M5.  
As a final remark, it would be highly beneficial if post-irradiation examinations (PIEs) were conducted on these rods. Non-destructive PIEs, including dimensional measurements and oxide/crud analysis, would provide a valuable complement to the in-pile data at a practically negligible cost compared to the fabrication and operation of rods and rigs. This is particularly relevant given the diameter gauge setup, which enables precise evaluation of cladding behavior under operational conditions.  
An additional point of consideration includes the higher creep rates observed under tensile stress compared to compressive stress in the Halden experiments. This asymmetry, while not fully explained in the reports, may be influenced by creep and corrosion (C&C) effects, such as accelerated oxidation and hydrogen pickup under tensile loading. Incorporating stress-dependent terms to account for these effects could improve the predictive accuracy of the Romanello model and align it more closely with experimental data. Addressing this phenomenon through targeted experiments and PIEs would further enhance the understanding of MS's performance.  
In conclusion, this work demonstrates the value of integrating robust physics-based modeling approaches with experimental benchmarks to analyze M5 creep behavior. Continued refinement of both models and experimental methodologies, alongside targeted PIEs, will be essential to advancing the understanding and prediction of cladding performance under reactor conditions.  
This research received no external funding.  
Not applicable.  
The data supporting the reported results are partially available. While some of the data used in this study are publicly accessible, the data related to the Halden project experiments, conducted over 20 years ago, may not be readily available. The author do not currently have information on public repositories hosting these data. Interested parties are encouraged to contact the corresponding author for further inquiries.  
The author declares no conflicts of interest.