In 1951, the liquid fuel effort at Oak Ridge began by attempting to solve the impossibly difficult problem of powering an airplane with a nuclear reactor. The engineers knew that they had to have both high temperature and low pressure. They tried many ideas before coming up with molten salt. This culminated in the Aircraft Reactor Experiment (ARE), a 2.5 MWt reactor which ran successfully for 1000 hours in 1954. The ARE operated at an outlet temperature of 860C. This required a large R and D effort which produced 100’s of high quality reports on salt properties, corrosion, radiation response, etc.
The ARE was a remarkable achievement. But just about everybody involved knew the real target was civilian power. In 1956, Oak Ridge obtained modest funding for a civilian liquid fuel reactor. In 1959, 4 million dollars was allocated for a 8 MWt pilot plant, dubbed the Molten Salt Reactor Experiment (MSRE). Oak Ridge moved at a leisurely pace. It was not until 1962 that construction started. On June 1, 1965, the MSRE achieved first criticality. On May 23, 1966, the reactor was taken to full power. In December, 1966 they began extended runs at full power on U-235. In January, 1969, the fuel was switched to U-233. By end of 1969, Oak Ridge felt they had learned all they could from the extensively instrumented MSRE. This knowledge was carefully documented in scores of reports. In December, 1969, the MSRE was shut down after a total of 13,172 full power hours. In its last 15 months, the reactor had an 87% availability, an unprecedented number for a first of a kind pilot plant.
Overall, the MSRE was an extremely successful experiment answering many questions, and raising almost no new ones. It produced the knowledge base that ThorCon is built on. Without the MSRE, ThorCon’s schedule would be unthinkable.