Armed with a freshly-minted PhD in Chemical Engineering from MIT, Miles Leverett joined Humble Oil (now Exxon-Mobil) in 1938 to do research on mixtures of fluids. He was 28 years old.
Fast forward several years. One day his boss, Thomas V. Moore (T.V.), seemed to have disappeared. Then, just as suddenly, T.V. called Leverett from an undisclosed location to enlist him for a “war project”. And so it was that Miles Leverett joined the Manhattan Project at the University of Chicago. It was May 1942, six months before a group of scientists led by Enrico Fermi demonstrated a sustained nuclear chain reaction at the world’s first nuclear reactor, Chicago Pile-1 (CP-1). Leverett had abruptly changed from oil man to nuke man.
Leverett was subsequently assigned to the Clinton Laboratories in Oak Ridge, Tennessee to form what was ultimately the Technical Division with responsibility for the engineering design of the air-cooled, graphite moderated X-10 reactor. The purpose of this pilot plant was to demonstrate the production of plutonium-239 (Pu239) from uranium-238 (U238) in the reactor and the chemical separation of Pu239 from U238 and fission products. The information gained guided the scale-up to three water-cooled 250-megawatt plutonium production plants in Hanford, Washington. The Technical Division was the precursor to two long-standing divisions of ORNL; namely, the Chemical Technology Division and the Reactor Division. This article outlines the accomplishments of a man who had to translate crude laboratory experiments in the new science of nuclear fission into engineered systems that would yield “mass”-production quantities of fissionable materials for use in atomic weapons to end WWII.
At the University of Chicago, T.V. and Leverett worked in Glenn Seaborg’s group in which they were specifically credited with designing horizontal channels in the Graphite Reactor, that enabled the production of “macro” amounts of plutonium in a “continuous” manner. Slugs of natural uranium could be inserted into the configuration, exposed to a neutron field to produce plutonium, and pushed out of the reactor so that the slugs could be chemically treated to separate Pu239 from the dissolved uranium slugs.. Up until that time, the only way to access the exposed slugs would have been to dismantle Fermi’s radioactive “pile”---the configuration of the CP-1 that demonstrated sustained nuclear fission. This operation that produced only micro quantities of Pu239 in “batch” form would have been quite a risky operation because of the radiation exposure. (For Pu239, “micro” means of the order of micrograms and “macro” means of the order of milligrams or more.)
For this work Enrico Fermi and Miles Leverett received two patents: U. S. Patent 2,813,070 (Method of Sustaining a Neutronic Chain Reacting System), E. Fermi, M. C. Leverett, November 12, 1957; and U. S. Patent 2,837,477 (Chain Reacting System), E. Fermi, M. C. Leverett, June 3, 1958.
Moving to the Clinton Labs, Leverett was assigned to work with DuPont engineers to design, to construct and to operate a scale –up of the Chicago pile that would demonstrate the production of “macro” quantities of plutonium. General Leslie Groves ordered that Leverett and others in the Chicago group to provide nuclear technology guidance to the DuPont chemical process-oriented group on the Oak Ridge Graphite Reactor. This experience enabled the DuPont group to take full responsibility for building and operating the production scale plutonium works at Hanford.
Leverett was also involved in the engineering aspects of remotely separating Pu239 from bulk quantities of irradiated natural uranium. This work involved solving unique problems such as the design, fabrication, and operation of equipment for remotely handling highly radioactive materials and dealing with enormous quantities of radioactive waste on a scale never before attempted. All of this was incorporated into Building 205 (later designated as Building 3019) where “hot cells” were surrounded by five-foot-thick concrete walls to shield workers from intense radioactivity. Remote controls were installed to operate equipment and banks of instruments that monitored the performance of the equipment. Remote observation of operations required the use of television, periscopes, mirrors, etc.
The Oak Ridge Graphite Reactor was built in 10 months, from February 1 to November 4 of 1943, when operation of the pilot plant began. Leverett’s incorporation of horizontal channels in the graphite blocks of the reactor enabled “continuous” production of plutonium for the first time. The design eliminated the need to dismantle the graphite to remove the irradiated natural uranium containing Pu239 as was required in the CP-1 reactor at the University of Chicago.
In Building 205, the plutonium was separated from the irradiated slugs and remaining radioactive waste was treated and stored prior to release. Glenn Seaborg’s chemistry group selected the bismuth phosphate separation process to separate and recover Pu239. By the end of 1943, 1.64 milligrams of plutonium had been extracted from the irradiated slugs and delivered to scientists in Chicago. The pilot plant at Oak Ridge had demonstrated the feasibility of the process and so it was used as the design basis for the large plutonium production plants in Hanford.
Because the Graphite Reactor had fulfilled its mission, it could have been shut down. Fortuitously, however, Leverett’s horizontal channels enabled the Graphite Reactor to become the world’s first facility to make production quantities of radioactive isotopes for nuclear medicine and research that employ radioactive tracers. A broad spectrum of isotopes was produced, purified, packaged and shipped all over the world for 20 years until the Graphite Reactor was shut down in 1963. Alvin Weinberg, director of Oak Ridge National Laboratory from 1955 to 1973, said, “If at some time a heavenly angel should ask what the laboratory in the hills of East Tennessee did to enlarge man’s life and make it better, I daresay the production of radioisotopes for scientific research and medical treatment will surely rate as a candidate for the very first place”.
In early 1945, J. Robert Oppenheimer, director of the Los Alamos laboratory, asked Clinton Labs in Oak Ridge to isolate barium-140 from spent natural uranium removed from the Graphite Reactor and later from the Hanford reactors. The barium was shipped by truck to Los Alamos, where the short-half-life radioactive lanthanum (RaLa) was extracted.
RaLa was needed during and after the Manhattan Project to simulate the behavior of implosion forces necessary to compress the plutonium pit of a nuclear weapon enough to detonate it. This study was considered the single most important experiment for determining the final bomb design.
Within five months of the original request, the Technical Division under Leverett developed the processing technology and converted an existing facility to make the first quantities of barium-140 for Los Alamos. In 1949, increased demand at Los Alamos for quantities of RaLa led to the design and construction of a larger barium-140 separation facility at Oak Ridge.
Starting in 1943, when personnel from the University of Chicago were transferred to Oak Ridge, Eugene Wigner envisioned peaceful uses for atomic energy. Specifically he proposed building a high neutron flux facility for studies of the effects of radiation on candidate reactor materials for nuclear-based production of electric power. Thus, from the beginning, the Technical Division under Miles Leverett expended considerable effort to design a Materials Testing Reactor (MTR) that would have 1000 times the neutron flux of the Graphite Reactor. The long-term effort involved up to 60 people and lasted for more than six years.
The MTR project finally came to fruition in 1954. The demand for RaLa at Los Alamos became so great that increased barium-140 production at Oak Ridge would have exceeded volatile fission product gas release limits for radiation exposure safety. In fact, historically, the RaLa project with its iodine-131 emissions had already been a major contributor to radioactive contamination at ORNL. So, barium-140 separation facilities were incorporated into the MTR program, which also included reactor materials studies. The MTR project that originated at ORNL was moved to the more remote location of what became the Idaho National Laboratory, and it was approved for construction in 1954.
In 1947, the Atomic Energy Commission decided to concentrate all reactor work at Argonne National Laboratory. With no work defined for Leverett in Oak Ridge, he returned to his previous job at Humble Oil in Houston in 1948.
However, it did not take long for Leverett to become involved in the nuclear business again. About that time, the Air Force was pushing for nuclear-powered airplanes. In 1949, Miles Leverett became the technical director of Fairchild Aircraft which was managing the Air Force program. He returned to Oak Ridge where Fairchild had its facilities in the S-50 area, about 10 miles from ORNL. At that point, Leverett actively engaged Alvin Weinberg and ORNL staff in discussions that eventually led to a large AEC-funded program on the Air Force’s nuclear-powered aircraft project at ORNL.
In 1951, the Air Force formally designated the effort as the Aircraft Nuclear Project (ANP). The Air Force replaced Fairchild with a number of contractors including two competing nuclear engine projects, one managed by General Electric and the other managed by Pratt and Whitney. Leverett joined General Electric’s program as the manager of development laboratories and relocated to Cincinnati. During the course of the 10 year program, the number of employees in the G. E. engineering section (laboratory and design) increased to 800 to 900 people. In 1961, President Kennedy cancelled the ANP project. Leverett stayed with General Electric, relocated to San Francisco and eventually retired in 1976.
Leverett was a pioneer in organizing the nuclear engineering profession. He chaired the Nuclear Engineering Committee of the American Institute of Chemical Engineers (AIChE) after World War II and served as the sixth President of the American Nuclear Society, 1960-61.
In 1984, Leverett was admitted into the National Academy of Engineering. His election citation read “For pioneering contributions to nuclear reactor designs and for a broad range of contributions to the enhancement of safety in the nuclear industry”.
Miles Leverett died in 2001 at the age of 91.
In the fall 1976 issue of the ORNL Review, Miles Leverett recalled some of his most memorable experiences in working at the Clinton Labs. One of them involved the Technical Division’s work on the design of the Materials Testing Reactor. A key objective was to satisfy the needs of the technical people who would be performing experiments in the facility. Leverett recalled heated discussions between a design engineer and a group of biologists to determine the correct size of holes needed to study the effects of radiation on various animals, such as mice, rats, and rabbits. Also discussed was the proper size hole for larger animals, such as goats and swine. The discussion went on endlessly. Finally, the exasperated engineer declared, “I have decided. We’ll make the hole big enough for a donkey and call it by its rightful name.”
And so, a pioneer in the history of ORNL, largely unrecognized by most today, emerges as a key individual who helped shape the destiny of ORNL and who enabled our research facility to attain its present stature as a leading world-class research institution.
- Bill Yee, ORNL History Group, 865.576.1946, March 27, 2014