Fifty years ago, the era of operating molten-salt reactors came to a prolonged conclusion with the shut down of the Molten-Salt Reactor Experiment. In a personal interview in 2012, Paul Haubenreich had told me the story of the Christmas shutdown of the MSRE. He had described how Milton Shaw, the head of the Atomic Energy Commission’s Division of Reactor Development and Technology (AEC-RDT), wanted the MSRE shut down so more funds could be devoted to his pet project, the Liquid-Metal Fast Breeder Reactor. Others have described to me how it was even more than that: that Shaw wanted molten-salt thoughts driven from Weinberg’s mind, believing that he would then devote his considerable talent to the LMFBR. Shaw was sadly mistaken, but Haubenreich, the director of MSRE operations, was in no position to try to realign Shaw’s thoughts.

In the MSRP semi-annual report that covered these events (ORNL-4548) the sterile conclusion of the adventurous MSRE project is duly reported:

“The system conditions for the interim period between operation and examination were planned, reviewed, and approved before Christmas, and on that day, for the first time in over five years, the reactor was left unattended.”

Haubenreich shared his profound regret with me at the way the MSRE ended. He described advice from other with operating reactors, who said, “when you have an operating reactor, you have a program, but after you shut your reactor down, it’s just a matter of time until you’re cancelled.” Paul reluctantly agreed with them, for that is the way that the MSRE, and later the MSRP, ended.

Floyd Culler, who was ORNL’s assistant lab director, wrote to Shaw on December 3, 1969, and said:

“As you know, we are shutting down the MSRE with great reluctance. Information obtained from the reactor in recent months has indicated that additional experiments on the chemistry of the fuel salt and on the behavior of fission products would be valuable. In addition, because plutonium appears to be an attractive fuel for molten salt converter reactors and for starting up breeders, we believe a complete fueling of the MSRE with plutonium is desirable. Consequently, we have postponed the shutdown as long as we can, but discouraging news about the budget forces us to move rapidly to limit over-expenditures in the molten salt program.”

Culler then informed Shaw of the layoffs in staff that would follow the MSRE shutdown. We have no record of a response from Shaw.