Refractory metal alloys for fusion reactor applications

The properties and general characteristics of alloys of the refractory metals V, Nb, and Mo are reviewed in terms of the materials requirements for fusion reactor first wall and blanket structures. Emphasis in this review is placed upon mechanical properties, radiation response, compatibility with coolants, physical and thermal properties, and fabricability. Where possible, properties are compared to those of the austenitic stainless steels. Refractory metal alloys appear to offer advantages in the areas of: Mechanical properties at temperatures above about 6000C, improved radiation resistance (particularly for V alloys), easier thermal-hydraulic design due to superior physical and thermal properties, and a potential for higher temperature operation in liquid lithium systems. Disadvantages are associated with their higher costs, more difficult fabrication and joining, and poor gas-metal interaction characteristics. V alloys are preferable to Nb alloys on the basis of greater resource availability and apparently better radiation damage resistance but are limited to temperatures below about 6500C. Nb alloys appear to offer the potential for operation up to about 8000C. Mo alloys are limited primarily by poor neutron radiation response at temperatures below about 6000C, and by their poorer fabrication-joining characteristics. V and Nb alloys do not appear to offer operation at temperatures above 4000-5000C in helium cooled environments. (orig.)