DEVELOPMENT OF MARTENSITIC STEELS FOR HIGH NEUTRON DAMAGE APPLICATIONS

Martensitic stainless steels have been developed for both in-core appl ications in advanced liquid metal fast breeder reactors (LMFBR) and fo r first wall and structural materials applications for commercial fusi on reactors. It can now be shown that these steels can be expected to maintain properties to levels as high as 175 or 200 dpa, respectively. The 12Cr-1Mo-0.5W-0.2C alloy HT-9 has been extensively tested for LMF BR applications and shown to resist radiation damage, providing a cree p and swelling resistant alternative to austenitic steels. Degradation of fracture toughness and Charpy impact properties have been observed , but properties are sufficient to provide reliable service. In compar ison, alloys with lower chromium contents are found to decarburize in contact with liquid sodium and are therefore not recommended. Tungsten stabilized martensitic stainless steels have appropriate properties f or fusion applications. Radioactivity levels are benign less than 500 years after service, radiation damage resistance is excellent, includi ng impact properties, and swelling is modest. This report describes th e history of the development effort.