The Metallurgical Troubles of Hastelloy -N in Molten Salt Reactors

Abstract

Many nuclear energy companies, including two based in Canada (Moltex Energy and Terrestrial Energy), have become interested in reactors that use molten salts in place of water as coolant and as a medium to hold the fuel. They draw technical inspiration from the Molten Salt Reactor Experiment (MSRE), a reactor that operated from 1964 to 1969 at the Oak Ridge National Laboratory, Tennessee (ORNL). One of the challenges with molten salt reactors involves metallurgical materials used to manufacture the various reactor components. These materials would have to work in a highly corrosive environments at elevated temperatures. A new alloy named Hastelloy-N was developed for this purpose.

This literature review examines at a high level the technical problems associated with using Hastelloy -N as a nuclear construction material. After the MSRE was shut down in 1969, Hastelloy-N was found to be inadequate, because it had developed cracks, leading to a decrease in mechanical properties such as creep strength. Such material deficiencies could have catastrophic results inside a nuclear reactor.  These problems have alarming implications for the feasibility of the molten salt reactor designs proposed for Canada.