Monday, September 8, 2008

A Brief History of the Fluid Fuel Reactor: The Molten Salt Reactor Adventure Begins

Eugene Wigner spent a brief period as Research Director of what was then called the Clinton Laboratories. Oak Ride was in 1943 a town that did not exist, so the Laboratory could not be named for it. Instead the assigned name that of Clinton, the old East Tennessee town that was the county seat of Anderson County, where most of the Oak Ridge complex was located. Wigner's stay was not a happy one for him, but is was exceedingly fruitful for the Laboratory. Wigner brought with him a team of brilliant scientists, and attracted more first rate researchers to Oak Ridge. Frederick Seitz, Erich Vogt, and Alvin Weinberg left a brief account of Wigner's stay in Oak Ridge:
"Wigner planned a two-pronged approach. First, he would establish a training program in which some thirty-five young scientists and engineers could learn the principles involved in nuclear reactors. These individuals would become future leaders in reactor development. Second, he would assemble an expert team to design nuclear reactors that could produce useful power efficiently and as safely as possible, placing much emphasis on the so-called "breeder" reactor. A substantial part of his research team in Chicago, including Weinberg and Young, agreed to join him there and spend the next phase of their professional careers promoting the development of nuclear energy for peaceful purposes".
Wigner quickly saw the hand writing on the wall:
"In the meantime, there was a great deal of legislative activity in Washington about the way the national nuclear energy program should be managed in peacetime. The debate was intense and protracted. The final result was the creation of a new civilian agency, the Atomic Energy Commission, which was put in charge of the operation on January 1, 1947. As the year progressed, Wigner eventually decided he was not really suited to serve as manager of a laboratory in such a complex, politicized environment. Many of the most important technical decisions would be made in Washington rather than in the laboratory".
Wigner and Weinberg remained personal friends, and wigner continued to visit the Laboratory on a regular basis. Hence in the Summer of 1971, I was offeed a chance to meet Wigner, along with other ORNL supernumeraries.

Alvin Weinbery was officially the Director oif the Laboratory's Physics Division from 1945 to 1948, when he assumed Eugene Wigner's former position. Weinberg was to become, among other things a custodian of Wigner's legacy, and much of ORNL's work on reactor development overthe next 25 years was to be guided by Weinberg's fidelity to the Wigner vision.

H. G. MacPherson's account of the history of the Molten Salt Reactor states,
"Molten salt reactors were first proposed by Ed Bettis and Ray Briant of ORNL during the post-World War II attempt to design a nuclear-powered aircraft".
Alvin Weinberg stated in 1957,"
At the Oak Ridge National Laboratory we have been investigating another class of fluids which satisfies all three of the requirements for a desirable fluid fuel: large range of uranium and thorium solubility, low pressure, and no radiolytic gas production. These fluids, first suggested by R. C. Briant, are molten mixtures of UF4 and ThF4 with fluorides of the alkali metals, beryllium, or zirconium".
Other sources tell a slightly different story. By M.W. Rosenthal, P.R. Kastin, and R.B. Briggs state "experiments to establish the feasibility of molten- salt fuels were begun in 1947 on
“the initiative of V.P. Calkins, Kermit Anderson, and E.S. Bettis.".
Ray Briant did not come to Clinton Labs until 1948, so it would appear that preliminary MSR research began before his arrival in Oak Ridge.

Rosenthall Kastin, and Briggs add, "At the enthusiastic urging of Bettis and on the recommendation of W.R. Grimes, R.C. Briant adopted molten fluoride salts in 1950 as the main line effort of the Oak Ridge National Laboratory's Aircraft Nuclear Propulsion1 program.”

Here we see a divergence between the collegiate nature of science and the conduits of information. Calkins, Anderson and Bettis appear to have decided on their own to investigate the possibility of a Molten Salt Fuel in 1947, but only Bettis gets credit for their joint invention. Bettis gets credit more for his advocacy than for the uniqueness of his role. Finally Warren Grimes got consulted on the chemistry, because his group was was to be assigned the task of researching MSR chemistry. Now the interesting thing was that in 1950 my father, C.J. Barton, Sr was the expert in Grimes' group on Fluoride Salt Chemistry. That is because my father probably participated in Grimes fluoride salt chemistry literature review that lay behind Grimes recommendation. How much of Grimes' recommendation rested on my father's judgment is probably beyond knowing.

Eugene Wigner was not a politician, not at least a politician in the way that Weinberg was. The giving and taking of credit was an important part of the management system of ORNL in the Weinberg era, and upper level managers were to use the giving and taking of credit to aggrandize themselves, and to reward and punish their subordinates, and not always for the best of reasons.

Bettis, Calkins, and Anderson could not have initiated research without an idea about what they were doing, thus they must jointly be credited with the MSR idea. It would appear that Briant later made the suggestion that thorium could be added to the MSR fuel mix. But note, the idea of converting thorium to U-233 in a fluid fuel reactor goes back to Wigner.

In 1947 a small group of K-25 engineers in Oak Ridge engineers, V.P. Calkins, Kermit Anderson, and Ed Bettis were assigned the task of developing a reactor for the Air Force that could power a bomber. During World War II the Hungarian genius, Eugene Wigner had invented a sodium cooled reactor, an invention which Wigner himself did not like, but in 1947 sodium cooled reactors were all the rage among people who were thinking about advanced nuclear technology. Calkins, Anderson, and Bettis were not working for Eugene Wigner at the X-10 laboratory. Instead they worked for K-25 and someone high up in the management of K-25 had decided that the Air Force needed a sodium cooled reactor to power their bombers. The more the young Oak Ridge engineers looked at the sodium cooled reactor, the less they liked it. It would be, they determined dangerously unstable. The hotter it got, the more power and hence more heat it produced. It could run away in a way similar to the way the Chernobyl reactor did some 39 years later. The young engineers decided that they needed to find a reactor concept that would tend to shut down as soon as it started to over heat. Liquids expand as the become hotter, and the young engineers thought that if the fuel was dissolved in a liquid, the liquid would expand out of the reactor's core as it heated, carrying U-235 out of theu core with it as it expanded, slowing the ongoing nuclear reaction in the core. Wigner was at that time interested in fluid core reactors that used heavy water as a core fluid, but heavy water was not a good candidate for what the K=25 engineers had in mind. K-25 was the world's leading center for fluoride salt chemistry in 1947, and the enginerrs thought that if fluoride salts were heated past their melting point would make an ideal carrier fluid for their reactor. It was a daring and even outrageous concept. In 1950 the project to build a reactor to power the atomic power bomber was turned over to Eugene Wigner's brilliant protoge, Alvin Weinberg, wh had remained in Oak Ridge after Wigner returned to Prinston. Ed Bettis approached scientist who had started thinking about the aircraft reactor project. He quickly convinced a small group of scientists including Ray Briant, Warren Grimes and my father C,J. Barton, Sr., about the liquid salt reactor idea. For the next 25 years, the idea of building a fluid aalt core reactor mesmerized Oak Ridge National Laboratory.

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