Memorial Tributes: Volume 27
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  • MANSON BENEDICT (1907-2006)



    MANSON BENEDICT, Institute Professor Emeritus at MIT, was a seminal player in the Manhattan Project and then in postwar government service to ensure the safe and secure application of nuclear energy, and he helped establish the academic discipline of nuclear engineering. He died September 18, 2006, in Naples, Florida, at the age of 98.

    In 1942, as a research chemist with the M.W. Kellogg Company, Benedict began a top-secret job in Oak Ridge, Tennessee. For the next two years, he served a pivotal role in the K-25 program, the Manhattan Project code name for producing uranium-235 for the atom bomb. Through a process of gaseous diffusion that Benedict pioneered, K-25 generated the fissile fodder for Little Boy, the bomb dropped on Hiroshima. The uranium enrichment plant he helped design and manage cost $500 million to build and employed 12,000 workers. Benedict called this “the most significant engineering development problem of my entire life."1

    Renowned for his contributions to the Manhattan Project and the nuclear energy industry, he was also celebrated by his students, colleagues, and academic descendants at MIT for his leadership and vision in the field of nuclear science and engineering education. “The career of Manson Benedict is awe inspiring,” said Dennis Whyte, Hitachi America Professor of Engineering and head of the Plasma Science and Fusion Center at MIT at an event honoring Benedict in 2018. After helping develop a weapon that changed the world, Benedict “turned to peaceful uses of nuclear, and luckily for us, primarily did this at MIT,” said Whyte.

    Benedict joined the chemical engineering department of MIT in 1951 as the university’s first professor of nuclear engineering. At the same time, he served as chief of the operational analysis staff of the US Atomic Energy Commission (AEC), an agency charged with developing nuclear energy for civilian and military applications.

    In 1958 Benedict became head of MIT’s Nuclear Engineering Department (the second in the country, after North Carolina State University). He developed a curriculum and recruited a faculty responsive to both the promise and peril of the atom. He became Institute Professor, MIT’s top faculty rank, in 1969, and retired in 1973.

    Manson was born October 9, 1907, in Lake Linden, Michigan, to Lena (née Manson), born in 1872, and C. (for “Centennial”) Harry Benedict, born in 1876. A chemist for the Calumet and Hecla Consolidated Copper Company, the elder Benedict developed an efficient process for extracting copper ore. According to Manson, the company recovered 30 million pounds of copper that would otherwise have gone to waste and it was used in World War I. In his father’s basement lab the boy became “very enamored of chemistry, and had no doubt whatever that I would use chemistry as my professional career.”

    Like his parents, Benedict attended Cornell University, graduating in 1928 with a bachelor’s degree in chemistry. In search of an education in the humanities, he attended the University of Chicago for two years, at the height of the Depression. There he studied philosophy and economics, read the classics with novelist Thornton Wilder, and befriended students who introduced him to the long lines of the unemployed at soup kitchens and to union organizing. He described these as “timid ventures into socialism,” and later worried that this youthful exploration would prove an obstacle to security clearances he needed both for work on the bomb and for his appointment to the MIT faculty and future research projects.

    After a summer working on a fruit farm in Washington state, Benedict had decided on a career path. Following his brother Bill, he enrolled in a graduate program in physical chemistry at MIT, conducting research comparing the platinum resistance thermometer with the gas thermometer. He received his SM in 1932 and PhD in 1935.

    While at MIT, Benedict became friendly with another physical chemistry graduate student who was working directly across the hall from him. Marjorie Oliver Allen was studying the freezing point of aqueous solutions and spent hours each day shaving pounds of ice for her research, using a hand-cranked machine. “I didn’t think that was a job for a girl to do, so I shaved the ice for her,” he said. They married soon after he received his PhD. While Benedict conducted research at Harvard University on a fellowship, Marjorie earned her PhD and went to work at Harvard Medical School.

    The two soon left Cambridge, first for Buffalo, New York, where Benedict worked at the National Aniline and Chemical Company. A year later, he took a position with the M.W. Kellogg Company petroleum research laboratory in Jersey City, New Jersey. His portfolio involved predicting the behavior of hydrocarbon mixtures. He earned a handsome salary of $300 a month.

    In his research at Kellogg, Benedict, with the help of MIT chemical engineering graduate George Webb and lab supervisor Louis C. Rubin, developed a model for describing real gas behavior. What came to be known as the Benedict-Webb-Rubin equation of state proved a major advance in understanding the thermodynamic properties of fluids. He also began working on novel separation processes for refinery gases. His method, which relied on gaseous diffusion, became his calling card to the Manhattan Project’s K-25 program.

    He was named head of process development for Kellex Corporation, the Kellogg subsidiary tasked with extracting uranium isotopes by gaseous diffusion. Under pressure from General Leslie R. Groves, head of the Manhattan Project, Benedict engineered a design for separating uranium-235 from gas that involved a cascade of isotope extraction through hundreds of miles of sealed pipes. The plant was u-shaped, a mile long, and four stories high. At one point, Benedict had to persuade the physicist Edward Teller (NAS 1948) that this process was sound. “He was a know-it-all, you couldn’t tell Edward anything,” Benedict recalled. The plant was designed for one kilogram of U-235 a day—and ultimately produced three.

    “It was so exciting for me to be down there as the first stages of the plant went in operation and to see that it performed not only as well as we had predicted but eventually better,” said Benedict. “It was a marvelous experience for a young chemical engineer.” He was in his mid-30s at the time.

    After the war Benedict decided to stay in Oak Ridge with colleagues who had started a new company, Hydrocarbon Research. He developed a low-temperature process for extracting deuterium from hydrocarbon refinery gases and from ammonia synthesis gas. He filed patents for techniques of mass diffusion and gas absorption.

    Teller, who had become a colleague by war’s end, brought Benedict onto the AEC’s Reactor Safeguard Committee. It was through this assignment that Benedict first learned of the plutonium production side of the Manhattan Project. “We knew there were sites out West to do something, but because of compartmentalization we weren’t even told what they were producing,” he said. During trips to Hanford, Washington, Benedict saw the plutonium production reactors and learned of the dangers posed by plutonium. “I knew the world would never be the same again; it was really an eye-opener.”

    He was also drafted into another AEC project: evaluating the most efficient models for producing fissionable material. As he shouldered new, governmental responsibilities, Benedict decided to leave industry for academia. Karl Compton (NAS 1924), president of MIT, believed that the technological advances ushered in by the Manhattan Project should become part of the MIT engineering curriculum, and that Benedict was the ideal person to tailor nuclear concepts and technologies for an engineering education.

    In 1951, starting with a few core subjects—nuclear reactor theory and engineering, nuclear physics for engineers, reactor dynamics, the nuclear fuel cycle, disposal of radioactive waste—Benedict quickly built a curriculum and a powerful program. The first master’s student in nuclear engineering graduated in 1953, the first PhD was awarded in 1957, and the university’s nuclear research reactor came online in 1958, the same year MIT announced the launch of its Department of Nuclear Engineering.

    The rapid development of this nuclear education program was enabled in part by the declassification of much Manhattan Project technology. This allowed Benedict and MIT colleague Thomas H. Pigford (NAE 1976) to write their foundational text, Nuclear Chemical Engineering (McGraw-Hill, 1957, revised 1981 with Hans Wolfgang Levi), and to bring international students to MIT.

    Benedict earned the loyalty and admiration of students and department colleagues alike. “He was a super teacher, a brilliant man who was very modest,” recalls Kent Hansen (NAE 1982), MIT professor emeritus of nuclear science and engineering who attended one of Benedict’s first nuclear engineering classes and graduated with an ScD in nuclear engineering in 1958. “People wanted to work for and with Manson, because of his enormous achievements but also because he was a charming person who gave a great deal of himself, paying close attention to and deeply interested in others. He had no ego, and wasn’t concerned about his place in history.”

    Benedict recruited Sidney Yip to MIT in 1965. “I looked up to him as the most invaluable and trustworthy mentor, professionally and personally,” says Yip, now a professor emeritus of nuclear science and engineering. “He was caring, honest, and always fair, my career-long inspiration.”

    I joined the MIT nuclear faculty a few years after Yip and found Benedict to be a fatherly figure in the department with a straightforward, sincere demeanor that was effective in instilling confidence in others. Faculty wanted to follow his lead both in doing outstanding science and engineering work and in service to the country.

    While serving as department head, Benedict was a member of both the AEC’s General Advisory Committee and Massachusetts Advisory Council on Radiation Protection. After his MIT retirement in 1973, he joined the Energy Research and Development Advisory Council of the new Federal Energy Administration, charged with addressing the energy crisis of the 1970s.

    Benedict earned a raft of honors for his achievements. He won the 1975 National Medal of Science in Engineering for “inspired and ingenious leadership in the development of gaseous diffusion plants for uranium isotope separation, and for his role in creating the discipline of nuclear engineering,” and in 1976 he won the NAE Founders Award. He was elected a fellow of the American Academy of Arts and Sciences (1952) and a member of the National Academy of Sciences (1956) and National Academy of Engineering (1967). Among his other laurels: the William R. Walker Award from the American Institute of Chemical Engineers (1947); Perkin Medal (1966); Arthur Holly Compton Award from the American Nuclear Society (1969); and AEC Enrico Fermi Award (1972).

    Marjorie died in 1995, after 59 years of marriage. Manson was survived by daughters Marjorie Benedict Cohn, Carl A. Weyerhaeuser Curator of Prints Emerita at the Harvard University Art Museums, and Mary Benedict Sauer of Naples, Florida, who conducted research on radiation chemistry.

    At the end of his 1991 interview, Benedict said, “I would like most to be remembered for the part I played in educating five hundred men and women who studied nuclear engineering at MIT while I was a faculty member there and who are now contributing to the development and use of this important energy source.”

    The MIT Department of Nuclear Science and Engineering paid tribute to his legacy with the creation of its first fellowship, the Manson Benedict Fellowship, established in 1983 at the department’s 25th anniversary celebration.

    The author appreciates input from colleagues in the MIT Department of Nuclear Science and Engineering.​
    1Manson Benedict, interview by James J. Bohning at Naples, Florida, January 24, 1991. Philadelphia: Chemical Heritage Foundation, Oral History Transcript #0088.