Elevated temperature ferritic and martensitic steels and their application to future nuclear reactors

In the 1970s, high chromium (9-12%Cr) ferritic/martensitic steels became candidates for elevated temperature applications in the core of fast reactors. Steels developed for conventional power plants, such as Sandvik HT9, a nominally Fe-12Cr-1Mo-0.5W-0.5Ni-0.25V-0.2C steel (composition in wt-%), were considered in the USA, Europe and Japan. Now, a new generation of fission reactors is in the planning stage, and ferritic, bainitic and martensitic steels are again candidates for in-core and out-of-core applications. Since the 1970s, advances have been made in developing steels with 2-12%Cr for conventional power plants that are significant improvements over steels originally considered. The present study will review the development of the new steels to illustrate the advantages they offer for the new reactor concepts. Elevated temperature mechanical properties will be emphasised. Effects of alloying additions on long-time thermal exposure with and without stress (creep) will be examined. Information on neutron radiation effects will be discussed as it applies to ferritic and martensitic steels.