High performance materials are critical for success in both terrestrial and space nuclear applications. Nuclear power currently accounts for about 20% of US electricity and ~24% of worldwide electricity. In the future, advanced fission (“Generation IV”) and fusion reactor systems are proposed to meet growing worldwide energy demand and reduce reliance on fossil fuel energy sources. NASA recently initiated an advanced technology program that will enable several nuclear space reactor missions including orbiter exploration of the moons of Jupiter. This paper will compare and contrast performance requirements and summarize candidate structural materials in existing fission reactors, proposed fusion and Generation IV fission reactors, and proposed space reactors. Structural materials requirements for existing fission reactors include good strength for long times (>40 years) at moderate temperatures, adequate resistance to mechanical property degradation (fracture toughness, etc.) by irradiation, and chemical compatibility with coolants (water, Na). Thermal creep and neutron radiation resistance will be of high importance for structural materials in proposed Generation IV reactors, due to the significantly higher operating temperatures and neutron exposure levels compared to existing fission reactors. Structural materials in proposed fusion reactors will experience similar high temperature and neutron dose demands as Generation IV reactors, but the higher neutron energies associated with fusion will cause additional radiation damage challenges. The use of alloying elements that do not lead to long-lived radioactivity is considered essential for the development of fusion. Due to the requirement to minimize launch mass for space power and propulsion systems (typical launch costs are 10 to 40 k$/pound), high thermal efficiency is essential in space reactor systems. This leads to high operating temperatures for structural materials, with most attention focused on refractory alloys.

Research sponsored by Office of Fusion Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with U.T.-Battelle, LLC.