Glamorous 1959 visitors: ORNL Director Alvin Weinberg points to the Oak Ridge Research Reactor’s pool as then-Sen. John F. Kennedy (to his right) and Sen. Albert Gore Sr. and Jacqueline Kennedy (to Weinberg's left) observe. The S.S.O.R.R. life ring was never deployed.
Oak Ridge Research Reactor, slated for demolition, went online 65 years ago
As ORNL and its historic landmark Graphite Reactor mark their 80th year, another of the Lab's storied nuclear reactors is seeing a milestone birthday: The Oak Ridge Research Reactor, situated in the oldest part of the Lab campus, first went critical 65 years ago, in March 1958.
The reactor served science and radioisotope production until 1987. At one time it was the most powerful research reactor in the world. “Atoms for Peace” were the bywords in the late ’50s, and the ORR, as it was known, drew scientists to the Lab for its unprecedentedly powerful neutron beams.
The ORR was ORNL’s sixth reactor, one of the “swimming pool” reactors with a reactor core located in an 18-foot-tall aluminum vessel, 25-feet below the surface of a pool of demineralized water that provided radiation shielding. It stands in the central campus near the Graphite Reactor, the recently demolished Bulk Shielding Reactor and the Low Intensity Test Reactor. The ORR, inactive for more than three decades, is also slated for demolition.
Its highly enriched uranium fuel emitted the blue glow of Cerenkov radiation that made it an attraction for VIP visitors to the Lab. They included Sen. (and soon-to-be presidential candidate) John F. Kennedy and future First Lady Jacqueline; Sen. and future President Lyndon Johnson in 1959; and Vice President Hubert Humphrey and future President Gerald Ford, both in 1965.
Royal figures stopping by during Oak Ridge visits included Queen Frederika of Greece in 1958, King Leopold of Belgium in 1957 and King Adulyadej of Thailand in 1960. Jordan’s King Hussein visited as a young monarch of 23 in 1959. Other world leaders, either then or later, who visited include Indian ambassador Indira Nehru in 1963, who went on to become Prime Minister Indira Ghandi, and leaders of Afghanistan and Northern Nigeria.
The ORR was born when it became apparent in 1950 that research was progressing beyond what the Graphite Reactor could provide. The original ORR 5-megawatt design was based on the Materials Testing Reactor in Idaho, which involved significant participation by ORNL. Following a review in late 1954, the design power was upped to 20 megawatts. Later improvements to the evaporative air-cooling system increased power, and commensurate neutron production, to 30 megawatts.
The pool design with its shielding water gave easy access to the reactor core, which was a lattice of two-foot long fuel elements each about three inches square. A continuous supply of demineralized water prevented the irradiation of impurities that could result in excess radioactivity and corrosion. The reactor pool, with its much-photographed observation deck, measured 50 feet long, 25 feet deep and 10 feet wide.
In his book The First Nuclear Era, Alvin Weinberg, who was ORNL director when the ORR and nearly all of the Lab’s were built, likened the reactor to a Mississippi River boat, complete with three decks and a life ring labeled S.S.O.R.R.
“Fortunately, no one ever fell into the O.R.R. pool,” Weinberg wrote.
The ORR operated for 10,537 days, producing 5,788,267 megawatt hours of thermal energy and neutrons for radioisotope production, fuels and materials irradiation studies, neutron scattering, neutron activation analysis and basic physics research. It was followed in 1965 by the High Flux Isotope Reactor, located across the ridge in Melton Valley near the Molten Salt Reactor Experiment, another storied ORNL reactor.
The late Corporate Fellow Herb Mook did neutron scattering research in the ORRR for a few years before moving his work to HFIR, which began operation in 1966. The reactors coexisted for more than two decades.
In a 2000 interview Mook said there was little comparison in working with the 20-megawatt ORR and the then 100-megawatt HFIR.
“We did a lot of good science at the ORR, but HFIR was so much better,” Mook said in 2000. “HFIR was the reason I came here.”
Still, working with what the ORR offered, researchers accomplished a lot. ORNL physicists Arthur Snell, Cleland Johnson and Frances Pleasonton confirmed the electron-neutrino theory of nuclear beta decay at the ORR. Harvard’s Norman Ramsey collaborated with ORNL researchers at the ORR to refine his neutron spectrometer, for which, along with other research into the characteristics of protons and neutrons, he received the Nobel Prize for Physics in 1989.
Mike Farrar, who is leading the Radioisotope Processing Facility Project, says the HFIR may have surpassed the ORR in neutron scattering capabilities, but the ORR “was an isotopes and materials-fuels research workhorse for the nation.”
For instance, Mike recalls the ORR did much of the fuel qualification work for TRIGA-LEU (Training, Research, Isotopes, General Atomics low-enriched uranium) fuel. These fuels became the standard at university reactors due to proliferation concerns associated with highly enriched uranium fuels.
After its shutdown the ORR’s pool level was maintained to shield the submerged radioactive materials, which was a considerable expense. The pool has also experienced leaks in more recent years.
ORNL environmental programs coordinator Hurtis Hodges says activities leading up to facility demolition by environmental management contractor UCOR, scheduled for 2027, are under way now, including removing all components (including the reactor), sediment and water from the pool by the end of this year. — Bill Cabage