## 8 Conclusions  
The assessment of the integrity of engineering structures is a complex task, which needs a deeper look into the materials degradation processes before a crack in the material or structure appears. For this purpose, the use of different NDT techniques presents a great advantage, being able to monitor the materials' response and collect materials data when exposed to a mechanical or electromagnetic wave, without causing any extra degradation on the material or structure. In nuclear power plants, structures are subjected to high temperature transients and harsh environmental conditions and the consequences of structural failure are known to be dramatic. High safety factors have therefore been imposed on those structures, to get failure avoided. On the other hand, those structures would have a residual life potential left when modern technology, not having been available at the time of those structures' design, would have been included. This inclusion could be seen as an invaluable benefit, in case a structure's life extension could be considered. Advanced inspection technology, a better understanding of materials' microstructure as well as behavior, and the option of numerically mimicking the observed phenomena in a prognostic way is far beyond what has been the basis of assumptions having been made in design in the past. This also includes strategies for the replacement of certain parts after an established period of time and may impact design codes and standards. A further economic impact is to be seen by better taking advantage of an infrastructure's potential in general, and in the specific case here the extension of the operational life of nuclear power plants. Assessments of aged materials and structures with respect to their residual fatigue life is a task to be performed relatively quickly and at minimum cost. Furthermore, the availability of adequate material is often highly limited in that case. Generation of S-N curves based on twenty to thirty fatigue tests to be performed--and this even under different environmental conditions--is a close to impossible scenario. As such it becomes clear, that a method to evaluate the S-N curves in a short period is in need. The STEPs for the enhanced evaluation of fatigue data play here an important role, making it possible to generate an S-N curve with three specimens only. The provision of adequate materials information is a prerequisite for an adequate numerical simulation. Enhanced computation power and an increasing number of sophisticated numerical models allow conditions to be simulated today, which were impossible to simulate at the time when most of our current infrastructure has been designed and realized. This also applies to nuclear power plants. These numerical simulation tools are merged in the meantime with increasingly growing databases, that result in what is defined as digital twins. These can be principally established for any type of structure, would it be aged or new. MibaLeb does not claim to provide digital twins for nuclear engineering applications. However, what it claims is to provide appropriate materials information, that can be fed into such digital twins in the longer term. Getting such digital twins established is a tremendous task, possibly living as long as the respective infrastructure's life and possibly beyond. In MibaLeb this digital twin's related activity has been limited to the provision of materials data and information related to AISI 347 (X6 CrNiNb18-10) exposed to a series of hot and cold water flow conditions, and validated as an example on a pressurized hot water pipe segment. MibaLeb has laid a foundation on how such a digital twin could be built up and how it could be fed with data. Since this digital twin development is a living job with a most likely open end, there are still further questions that emerge and that need to be answered in the future, such as:  
* STEPs for the evaluation of fatigue data: Can reliable scatter bands be generated using STEPs?