New Developments in Materials for Molten-Salt Reactors

Operating experience with the Molten-Salt Reactor Experiment (MSRE) has demonstrated the excellent compatibility of the graphite-Hastelloy-N-fluoride salt system at 650°C. Several improvements in materials are needed for a molten-salt breeder reactor with a basic plant life of 30 years; specifically: Hastelloy-N with improved resistance to embrittlement by thermal neutrons; graphite with better dimensional stability in a fast neutron flux; graphite that is sealed to obtain a surface permeability of <10^-8 cm²/sec; and a secondary coolant that is inexpensive and has a melting point of ∼400°C. A brief description is given of the materials work in progress to satisfy each of these requirements.