The Molten Salt Reactor Experiment (MSRE) achieved criticality on June 1, 1965, having taken about two years and a total of $80 million to build. In 1968, it became the first reactor to run on Uranium-233 and proved both that U-233 could act as a fuel source and also that the molten salt liquid fuel could act both as a carrier/energy container and as a coolant. During an event to introduce the MSRE, Alvin Weinberg pointed to barrels near an assembled crowd containing the salts and fuel that had no radiologocial protection—as none was needed.
The MSRE logged more than 13,000 hours at full power and many more at partial power levels—although it is not clear that the power was ever connected to an electric grid—but was eventually shut down in 1969 and the molten salt program itself in 1973, when the political decision was made by the Atomic Energy Commission to “focus on other designs.”
Today, governments and industry are once again reviewing the achievements of the MRSE and re-evaluating whether molten salt technology provides some of the answers to the global energy challenge that we face. There are numerous next-generation groups working on variations on the MSRE design for deployment in the coming decade.
Read more in the ORNL Review: “Time Warp: Molten Salt Reactor Experiment—Alvin Weinberg’s magnum opus” and at Energy from Thorium: MSRE 50th Anniversary“ by Kirk Sorenson.