**1. Introduction**

In this book we are focusing on a broad range of nuclear technologies. In particular, we would like to give special attention to energy systems. The feasible way to utilize nuclear energy today is via deployment of fission reactors. While fusion reactors are technically possible and their physics has been demonstrated, it will take a much longer time to bring fusion systems into the feasible and competitive energy engineering domain of commercially viable systems. However, material developments targeting performance under extreme conditions is relevant to both pathways enabling options for fission and fusion technologies. As such, this book discusses developments broadly relevant to nuclear energy systems, fission and fusion.

Materials play the key role in the nuclear energy system feasibility. So much so, they are among the key classification factors and metrics for nuclear systems:

Nuclear system type (fission or fusion)


Focusing on nuclear fission systems as the near term and already available commercial option, there are a few well-explored directions as well as emerging new technologies. Materials play the enabling role for contemporary nuclear reactors creating possibilities for extending their lifetimes. Materials are also the key factor making emerging new technologies viable. As notable examples, there are developments of paramount significance offering accident tolerant fuels and

robust structural materials performing under extreme conditions due to high temperatures and high energy radiation effects.
