alph Moon of ORNL's Solid State Division has long believed that what this country needs is a new research reactor. Since the mid-1970s, he has urged the Laboratory to design a new reactor to better meet the scientific community's research needs and to win funding for it as a major new government facility. His persistence may pay off in the form of the Advanced Neutron Source proposed for ORNL.
Interest in building a major new source of neutrons for neutron scattering experiments in the United States was strongly expressed at a 1974 workshop at Brookhaven National Laboratory (BNL). American scientists were concerned that the best neutron research was being done at the Institut Laue-Langevin (ILL) reactor in France because it offered a variety of superior neutron scattering instruments, and they wanted a facility as good or better.
Among the speakers at this Workshop on Intense Neutron Sources was Dick Cheverton of ORNL, who had been responsible for the design of the Laboratory's High Flux Isotope Reactor (HFIR). He proposed a 200-megawatt (MW) reactor with a HFIR-like core and heavy water (deuterium oxide, or D2O) as the core coolant and neutron reflector. He estimated that this reactor would produce a thermal flux in the reflector about four times that of the ILL reactor.
As an outgrowth of this workshop, a smaller group of scientists formed an ad hoc panel to formulate recommendations on future neutron sources. In this group were ORNL scientists Mike Wilkinson, Wally Koehler, and Jack Harvey. In a 1974 letter to John Teem, head of the Atomic Energy Commission's (AEC's) Division of Physical Sciences, the ad hoc panel urged the commission "to start engineering design studies" for a high-performance, steady-state neutron source similar to but better than ILL. The scientists' goal was a reactor built by 1984 that would have a neutron flux the same as that proposed for the Advanced Neutron Source today. Also proposed for this reactor was a "cold source" to supply low-energy neutrons because of their suitability for studies leading to practical applications. [The ILL was the first large reactor to have a cold source; in the United States, smaller cold sources are available at BNL's High Flux Beam Reactor (HFBR) and at the National Institute of Standards and Technology reactor.] The AEC made no response to these recommendations.
In May 1976, Alex Zucker, ORNL associate director for the Physical Sciences, formed the Neutron Source Committee to make recommendations on future neutron sources at ORNL, including an upgrade of the Oak Ridge Electron Linear Accelerator (ORELA) so it could be used for neutron scattering experiments. At the time, Argonne National Laboratory had proposed an accelerator-based pulsed neutron source for neutron scattering experiments (which was later built and called the Intense Pulsed Neutron Source).
The ORNL committee, chaired by Moon, recommended against the ORELA upgrade and proposed supporting the Argonne pulsed neutron source--a spallation source in which neutrons are produced by accelerating protons against a target. Most important, the committee also endorsed the Cheverton proposal to design and build a 200-MW reactor using heavy water as the moderator, coolant, and reflector. "It had been known since the 1950s that heavy water was the best coolant and reflector to use in reactors designed specifically for neutron scattering experiments," Moon says. "The ILL and HFBR both use heavy water for their reflectors."
Because of the proposals being made to build neutron sources, the U.S. Department of Energy (DOE) asked the National Academy of Sciences in 1977 to study the scientific opportunities offered by neutron research. A National Research Council committee made the assessment in its report Neutron Research on Condensed Matter. It recommended that a pulsed source be constructed (with a peak flux of 1016 neutrons per square centimeter per second) and that design efforts start for a steady-state source to replace the HFBR and HFIR.
On February 9, 1983, Zucker set up an internal competition as he challenged the staff to come up with ideas for a major new facility for ORNL. Moon proposed a 200-MW reactor with heavy water as coolant and moderator to replace the HFIR. At first, the proposal was dubbed the HFIR-II reactor.
In July 1983, the Laboratory Executive Committee announced it had decided to modify the HFIR to make it more useful as a neutron-scattering facility. Moon was asked to head the HFIR upgrade project. "My response was to argue against this decision because the HFIR building was designed for isotope production, not neutron research. I recommended that a team of ORNL researchers start design on a new 200-MW heavy- water reactor and associated research facility for three purposes--neutron scattering research, materials irradiation studies, and radioisotope production." In August 1983, Dave Bartine was placed in charge of the reactor design team, and Moon agreed to head the project provided that both a HFIR upgrade and a new facility be considered. Startup money of $650,000 was requested for fiscal year 1984 from the Laboratory Director's Research and Development (LDRD) Fund.
In November 1983, the President's Office of Science and Technology Policy asked the National Research Council to assist in establishing priorities for major facilities for materials research and related disciplines. A committee of 22 distinguished scientists and administrators, headed by Frederick Seitz of Rockefeller University and Dean Eastman of IBM, was appointed by the council; the committee began its work in January 1984. A subpanel on neutron scattering was headed by Bob Birgeneau of the Massachusetts Institute of Technology.
On January 24, 1984, a letter from Seitz to ORNL Director Herman Postma arrived on Moon's desk inviting ORNL to make a presentation to Birgeneau's subpanel February 26 at the National Academy of Sciences. On the same day, Moon learned that funds from LDRD were available to begin work on the new reactor facility.
"These events marked the real beginning of what was to become the ANS Project," Moon says. "A fast start was absolutely essential because the Seitz-Eastman committee wanted both an oral and a written report. We had only one month to develop a detailed description of the facility, a cost estimate, and an assessment of the most important recent accomplishments in neutron scattering."
Moon and Herb Mook of ORNL's Solid State Division made presentations to the neutron scattering subpanel in February, and Moon made another presentation to the full Seitz-Eastman committee in March.
In July 1984, the Seitz-Eastman committee made recommendations for new facilities and for upgrades of existing facilities. The highest-priority new facility was an intense X-ray source, now under construction at Argonne National Laboratory and called the Advanced Photon Source. A close second, by only one vote, was an "advanced steady-state neutron source facility" designed to have a neutron flux 5 to 10 times that of ILL. Much to Moon's delight, the document stated, "Instead of upgrading an existing facility, a new reactor should be built."
Moon and representatives from three other national laboratories and the then National Bureau of Standards organized an international meeting held in October 1984 at Shelter Island, New York, on Scientific Opportunities with Advanced Facilities for Neutron Scattering. The chief issue discussed was whether a steady-state neutron source (reactor) or pulsed neutron source (spallation source) would better serve the research community. The attendees supported the conclusion of the Seitz-Eastman committee that an appropriately designed reactor should be constructed first.
Meanwhile, on July 1, 1985, at ORNL, Colin West of the Engineering Technology Division was placed in charge of the newly named Center for Neutron Research (CNR) Project. The CNR Project, like the ORNL reactor design study initiated in 1984, was supported by the LDRD Fund.
On December 16, 1985, Moon helped organize an important workshop on the Advanced Steady-State Neutron Facility, held at the National Institute of Standards and Technology in Gaithersburg, Maryland. There, a national steering committee was formed to promote and guide development of a new steady-state neutron source. In addition, various reactor design concepts and technical alternatives were presented by the speakers (including West), recommendations were made, and critiques were performed. The critique group gave the best grades to the ORNL and Idaho National Engineering Laboratory concepts. Thus, the basic reactor concept continued to gather support as the preferred neutron source for meeting the needs of the U.S. scientific community.
The fiscal year 1987 congressional appropriations bill was passed, providing DOE funds for the first time for an "advanced neutron source." The money was earmarked for ORNL's Center for Neutron Research Project, which changed its name to the Advanced Neutron Source (ANS) Project to reflect the language of the appropriations bill. The ANS Project has been receiving DOE funding ever since.
In 1991, the Basic Energy Sciences Advisory Committee (BESAC) of DOE's Office of Energy Research (OER) was asked by OER Director Will Happer to form a panel to revisit the question of whether a reactor or spallation source would make the best neutron source. The panel was headed by Walter Kohn of the University of California at Santa Barbara, who had been a member of the Seitz-Eastman committee.
In June 1992, the Kohn committee issued its report. According to the report, the BESAC panel concluded that "the nation has a critical need for a complementary pair of sources: a new reactor, the Advanced Neutron Source (ANS), which will be the world's leading neutron source, and a pulsed spallation source. . . .The ANS is the Panel's highest priority for rapid construction. In the Panel's view, any plan that does not include a new, full-performance high-flux reactor is unsatisfactory because of a number of essential functions that can be best or only performed by such a reactor."
President Clinton agrees that the country needs a new reactor. In his 1993 report A Vision of Change for America, the president urged the U.S. Congress to build the ANS. As in fiscal year 1994, the proposed 330-MW ANS is a line item in the president's budget for fiscal 1995, suggesting that initial construction money may be available soon. "I hope it happens," Ralph Moon says with a smile.--Carolyn Krause
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Neutron Scattering at the High Flux Isotope Reactor