Wasn't to be: A drawing of the proposed Advanced Neutron Source, the proposed state-of-the-art research reactor at ORNL.
The ANS was ORNL's signature expansion project in the early 1990s.
ORNL has operated 13 nuclear reactors since the Graphite Reactor started up in November 1943. At one time the expectations were the tally would reach 14.
That 14th reactor, the Advanced Neutron Source, was ORNL's signature expansion project in the early 1990s. The ANS would be the new anchor facility for a national lab with a . Its preferred location would have been in Melton Valley, near the High Flux Isotope Reactor. With a construction start targeted for 1994 and completion in 1999, the ANS would succeed HFIR as the hallmark facility for reactor-produced neutron research, isotope production and materials irradiation studies.
With the ANS the United States would also regain its lost lead in neutron scattering research, which was pioneered at ORNL in the early post-Manhattan Project years. ANS proponents emphasized neutron scattering had become an important tool for materials research. Materials were key to new products, and regaining preeminence in neutron science represented an economic advantage for the nation.
“T sine qua non of the new facility is a reactor which can provide a flux at least five times higher than any existing neutron beam reactor, while meeting extremely stringent safety requirements,” wrote John Hayter, an ORNL solid state physicist and advocate of the project, in 1990.
The project managers and researchers, many of them housed in the Lab’s Solid State Division, also worked to educate the public on the exotic science of neutron scattering, using easy-to-fathom analogies to explain how neutrons bouncing off atomic structures revealed the complex molecular makeup behind a new, advanced material’s desirable properties.
But the ANS was dogged by political concerns associated with nuclear technology in the wake of the Three Mile Island and Chernobyl accidents and the specter of nuclear arms proliferation, owing to its highly enriched uranium fuel. The project was particularly, and probably fatally, challenged by rising projected costs. The ANS cost estimate had reached $3 billion when it was dropped from the president's FY 1996 budget request in a political environment of cost cutting. The ANS designers and engineers shut the project down, archiving what they had designed and learned to that point, and found new pursuits.
Cost and lack of political support were also cited in the 1993 cancellation of the “big science” Superconducting Supercollider Project in Texas, which had reached a $10 billion price tag. The theorized Higgs boson would ultimately be discovered at Europe's Large Hadron Collider.
While the cancellation of the ANS was devastating, the argument for regaining U.S. leadership in neutron science must have resonated. Then-ORNL Director Alvin Trivelpiece announced to Lab staff in 1995, soon after the ANS project was declared dead, that ORNL would instead be the home of a less costly linear accelerator facility that produced neutrons from a pulsed proton beam.
In early 1995 no hard decisions had been made about the design of ORNL's linac-based neutron source or how would it be used, except that it would be a “spallation” neutron source. Five national laboratories (ultimately six) would collaborate on the project — the ANS and Supercollider cancellations taught valuable lessons in gathering broad support for “Big Science” projects.
But what about the research reactor? An article in Science magazine speculated the new facility could produce tritium for nuclear weapons. Bill Appleton, an ORNL associate director who was put in charge of starting up the new project, nixed that idea. Appleton noted a tritium production requires a continuous (reactor) beam of neutrons rather than a pulsed beam, and that a "dual use" facility would require security that wasn't consistent with the operation of an R&D facility.
Nevertheless, he said, the nation needed a reactor-based neutron source. And ORNL already had a good one.
"Spallation can't do a lot of the important things a reactor can do, such as medical isotope production, irradiation of materials for research, and activation analysis for environmental samples," Appleton said in the March 1995 Lab Notes, ORNL's employee newsletter at the time. "HFIR will have to continue to run to complement the accelerator facility," he said.
And so ORNL stayed in the research reactor business as it embarked on the linear accelerator approach. Had the ANS come to fruition it would have represented the world’s most powerful reactor for neutron scattering research, operating at about 330 megawatts — HFIR operates at 85 MW — and would have boosted ORNL’s capabilities for isotope production and materials irradiation studies. Nearly three decades after the cancellation, a research reactor project the scale of the ANS has long since slipped below the horizon.
The story has a positive ending: A modernization campaign that began in 2000 resulted in state- of-the-art facilities at ORNL for nanoscience, bioscience and scientific computing. The combination of the SNS, which went on-line in 2006, and a refurbished and upgraded HFIR established ORNL as a leading center for neutron scattering research and isotope production and has bolstered U.S. capabilities in materials research.
“It ultimately turned out to be a good outcome,” says Jim Roberto, former ORNL deputy for science and technology who was leading the Solid State Division at the time of the ANS project. “T SNS and HFIR complement each other in providing a unique combination of capabilities for neutron science.”
It could be argued the ANS’s ultimate contribution was increasing the public’s and policymakers’ awareness of how neutron science is used to develop technologies that improve lives and drive economies. And if you want to do that kind of research, ORNL is your top destination, just as planned in the ‘90s. — Bill Cabage