The Tower Shielding Facility was built for a nuclear airplane project that never flew. But science soared.
The Tower Shielding Facility is located on the perimeter of the Oak Ridge Reservation on a road blocked by a locked gate. It's still one of ORNL's more conspicuous landmarks because the two towers, from which a small nuclear reactor was at times suspended, can be glimpsed from nearby Interstate 40.
The reactor last operated in 1992 at the end of a joint U.S.-Japanese program. In 1995 the American Nuclear Society named the TSF a Nuclear Historical Landmark. The local chapter of the ANS marked the designation with an outdoor April ceremony and a barbeque dinner inside the facility's underground building.
Among the speakers was Leo Holland, whose ORNL career was practically synonymous with nuclear reactors. It's Holland who is pictured at the famous 1955 Geneva, Switzerland, Atoms for Peace Conference, briefing President Eisenhower on a small, 100-kilowatt reactor ORNL built to demonstrate the peaceful uses of atomic energy.
Holland is associated with the TSF most of all, and he explained some of its history to the 1995 crowd. The purpose of the two towers was to hoist the water-cooled reactor high in the air to eliminate radiation backscattering from the ground. The backscattering interfered with instruments used in experiments to gather data on shielding.
The shielding data was necessary because researchers were exploring the feasibility of a nuclear-powered aircraft, which was being considered when the TSF was built in 1954. Such an aircraft with a nuclear payload could remain aloft almost continuously, it was theorized. The TSF would provide data for and test the concept.
Holland recalled the TSF was built for less than $2 million and incorporated innovative engineering, including a way to assemble fuel elements mechanically instead of by welding, which eliminated corrosion. The shielding research was led by Everitt Blizard, a shielding pioneer who helped design the shielding for the first nuclear submarine, Nautilus.
Holland also remembered the renowned physicist Edward Teller suggesting, as a safety feature, the addition of a glass bubble on the reactor vessel "which the guards could shoot out" if the reactor ran away. (The reactor never experienced any leakage of fission products from its fuel, another attendee noted.)
The nuclear airplane project presented numerous technical challenges including developing lightweight shielding materials to protect the crew from the reactor's radiation. The project was also challenged just to be taken seriously by those knowledgeable in nuclear technology's early days.
Alvin Weinberg, who had just turned 80 years old four days before the ceremony, also addressed the group. In the early 1950s, he said, ORNL lost out as the site for the Materials Test Reactor, a devastating blow to its reactor program. Then along came a "silly" idea to put a nuclear reactor on an aircraft. Weinberg described a "nuclear airplane" as a "contradiction in terms."
But ... the Air Force was putting up $1 billion for research -- "real money in those days," Weinberg said, to laughter. Weinberg saw it as a pathway back into the reactor business. Seizing on the opportunity, ORNL applied its considerable nuclear engineering expertise, and its aircraft nuclear propulsion program thrived.
Ultimately, however, the nuclear airplane project was abandoned, deemed obsolete with the advent of intercontinental ballistic missiles. But "wonderful things came from the nuclear airplane project," Weinberg said. The dubious enterprise that was the raison d'etre for the TSF paid many dividends, including Lab legacies in advanced lightweight materials and health physics research and ORNL's subsequent technical success with molten salts, which has in recent years received renewed attention.
The towers themselves were sometimes used to drop test shipping casks for radioactive cargos. In the 1950s an armored M-51 tank retriever was delivered to the TSF site for experiments on crew exposure. The huge vehicle remained on the site into the 1990s, and was once used to remove snow from local roads. It also pulled up chunks of pavement.
The TSF itself remained a popular research tool to investigate radiation exposure and shielding for projects such as the Liquid Metal Fast Breeder Reactor, the Clinch River Breeder Reactor and High Temperature Gas-Cooled Reactor programs until its shutdown in 1992. By then the TSF had established a scientific legacy that brought it the Nuclear Historic Landmark designation in 1995.