Happy birthday, HFIR!

Because of Russia’s full-scale invasion of Ukraine in February 2022, Russia is no longer the main source of radioisotopes for Americans desiring them for their medical, industrial and other uses. The reasons: supply chain interruptions and the United States need to be self-sufficient in critical areas.

The 60-year-old, 85-megawatt, $25 million High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory is now a critical source of radioisotopes for the United States. That was one of the messages of Chris Bryan,leader of the Radioisotope Production Engineering and Analysis Section in the Radioisotope Science and Technology Division at ORNL, in a recent talk to Friends of ORNL.

Bryan began his ORNL career in 2009 by leading a successful effort to increase the use ofHFIR’s reactor core for radioisotope production, as well as testing of materials and fuels. He also became involved in solving the problem of relieving the national shortage ofmolybdenum-99 (which is not produced inHFIR). That’s important because moly-99 decays to the technetium-99m radioisotope, the best, most-used nuclear medicine imaging agent for aiding doctors in identifying disorders in the brain, heart and other human organs.

Bryan began his FORNL talk by stating that theHFIRresearch reactor was proposed in 1957 byGlenn T. Seaborg, a Nobel laureate, chairman of the U.S. Atomic Energy Commission (AEC) and discoverer of elements heavier than uranium such as plutonium and californium. Seaborg persuaded the AEC that a reactor that could produce an extremely high number of neutrons each second (high-flux research reactor) was requiredto meet what he thought the nation needs – production of transuranium isotopes in weighable quantities (milligrams) that Seaborg as a researcher wanted because he couldn’t get that amount from an accelerator.

HFIRwas built using a conceptual design by Richard "Dick" Cheverton and five other engineering students. They created the design using slide rules in the late-1950s for their dissertation for a master’s degree in reactor engineering at the Oak Ridge School of Reactor Technology at ORNL.

Cheverton stayed on at the lab as an employee, solved other problems plaguingHFIRin later years and received from the American Nuclear Society the prestigious Reactor Technology Award in 1995.

Alvin Weinberg, while working at the AEC the year before he became ORNL director in 1955, asked Cheverton to add beam tubes to the design. The beamlines for neutrons emitted from the reactor core he helped design enabled scientists to conduct neutron scattering experiments.

The neutrons are streamed from the core through the tubes to specialized instruments. The experimental results have madeHFIRa world leader in revealing the structure and other properties of physical and biological materials, such as plastics, proteins and plants.

Bryan’s talk onHFIR, which went critical 60 years ago on Aug. 25, was attended by 100 people in person at the UT Resource Center on Oak Ridge Turnpike and on Zoom, and the talk is available on YouTube throughwww.fornl.info/past-talks(click on “Video of talk”).

The title of his talk was “HFIRMissions, Highlights, and Key Upgrades.” He mentioned one of the most interesting upgrades proposed: the planned replacement of the pressure vessel in the mid- to late-2030sto extendHFIR’s life to the end of the century, which will make the reactor more than 135 years old. The new pressure vessel will contain the reactor at full power (100 megawatts) and the tens of thousands of gallons of water cooling it every minute.

Presidential tidbit

It was also noted at the lecture that neutron activation analysis used atHFIRcast doubt on a historian’s theory that President Zachary Taylor in 1850 died of arsenic poisoning instead of food poisoning, as originally surmised.

Bryan gave a brief chronology onHFIR: the AEC decided in 1958 to support the design of the reactor,HFIRwent critical in 1965 and the reactor began operating at full power (100 megawatts) in 1966.

Twenty years later in 1986, detection of potential embrittlement of theHFIRreactor vessel caused by neutron bombardment led to a two-and-a-half-year shutdown to identify options to improve the vessel. In 1989,HFIRwas restarted at a lower power (85 MW), extending the vessel life to the 2060s and still carrying out its missions.

In 2007,HFIRwas restarted after a shutdown for installation of a Cold Source – a device that contains extremely cold liquid hydrogen that slows neutrons enough to avoid destroying certain experimental samples and that makes the neutron wavelengths similar in scale to what is being studied.

Bryan saidHFIRis a pressurized light-water reactor with an annular core. Production of neutrons is increased by allowing free neutrons produced by uranium fission to strike a beryllium reflector surrounding the core. The neutrons are reflected by beryllium back to the core, causing additional fissions that boost the number of neutrons available for neutron scattering experiments.

ReplacingHFIR’s beryllium reflector is one of the planned key upgrades. Another upgrade, Bryan said, will be replacingHFIR’s cold-neutron-source helium compressors and expansion engine system that could enable more than eight reactor operating cycles per year and save $1.2 million in annual maintenance costs.

The heat produced by an increased number of fissions is removed by water that circulates through the reactor as it sits in the reactor pool, which provides shielding.

“The primary coolant water runs through heat exchangers that reduce the water temperature enough that cycling it through theHFIRcore again removes more heat,” Bryan said. The spent fuel, which emits hazardous gamma rays, is transferred to another pool to be cooled.

Bryan showed an old photo of theHFIRcontrol room that had analog measurement instruments. They have been replaced with digital gauges, he said.

Neutron scattering research atHFIRis funded by the U.S. Department of Energy’s Office of Science, Basic Energy Sciences.

“That’s what pays the bills for operating the reactor,” Bryan noted. Neutron scientists all over the world who write proposals that are funded each visitHFIRfor days or weeks to use one ofHFIR’s 16 world-class instruments for research in various fields.

Solving practical problems

He showed examples of recent successful neutron scattering experiments that had results that could lead to practical applications. The experiments known as “operando”analyze the structures and properties of samples of materials or devices while they are being exposed to or actively working under real-world conditions.

Danish scientists measured how the chemistry of titanium-zirconium changes in a battery while its energy is being consumed. The intermediate states formed during discharging might be missed in a study that analyzes the material only after the fact, the scientists argued. They said they believe their results will help them design a more efficient battery.

A neutron scattering experiment atHFIR, Bryan said, helped validate a computer model that can predict more quickly and cheaply than current computer simulations the locations and sizes of residual stresses in tiny samples from engine blocks and railroad track components. Residual stresses are hidden forces within a material that can weaken, warp or break it and even lead to failures of parts made of the material.

These residual stresses can develop during revolutionary additive manufacturing (AM), or 3D printing, of intricate metal parts. Insights into how these stresses form are critical to improving AM processes.

Health research

Bryan said insights from “cold” neutron experiments performed by ORNL researchers atHFIRmark a step toward “designing novel drugs to slow the spread of aggressive cancers.” This work follows up research to understand “how COVID-19 viruses multiply and spread,” he said.

According to Bryan’s slide, “neutron experiments helped reveal the one-carbon enzymatic mechanism that synthesizes vital food sources for cancer cells that depend on vitamin B6. This research represents a renewed interest in studying metabolic pathways as targets for developing anti-cancer drug treatments. Metabolic pathways are a series of chemical reactions inside a cell wherein the product of one reaction becomes the base material, or substrate, for the next reaction.”

Bryan then described medical uses of several radioisotopes produced inHFIR. Actinium-227 is the firstHFIR-produced radioisotope that decays into a product (radium-223) that is used in a drug approved by the Food and Drug Administration – in this case, for relieving bone pain. Called Zofigo, it works effectively as a palliative for late-stage, bone-metastasized prostate cancer. Bryan stated that evidence indicates that Zofigo may also treat cancer and that work is ongoing to get it approved for other medical uses.

Another element with medical value is actinium-225, which is generated by decay of thorium-229, which can be produced inHFIR. Ac-225 and the radioisotopes it decays to can provide high-energy alpha particles that will target and kill cancer cells. He added thatHFIRcan also make lead-212, which like actinium-225 can be used for targeted alpha therapy.

“It has a better affinity to cancer-cell targeting molecules and is easier to carry in the body to different locations,” he said.

Another destroyer of cancer cells fromHFIRis californium-252, which is also useful in starting up nuclear power reactors, identifying oil and gas deposits and analyzing the quality and composition of coal to ensure it does not contain too much sulfur to be used in coal power plants.

AHFIRradioisotope with an important security application is nickel-63, which is used for airport surveillance to determine if any passenger packed an explosive or illegal drug in a bag. After an airport security officer swabs a bag’s surface to collect microscopic residue and inserts the swab into an electron capture detector, the collected residue is heated, and the resultant gas is passed through a chamber containing radioactive nickel-63.

This “beta emitter” releases low-energy electrons as it decays and initially ionizes the gas, creating a constant current. If the residue comes from an explosive or illegal drug, it eventually captures the constantly released nickel-63 electrons, causing a sharp drop in the measurable electric current. This sudden change signals the presence of explosive or drug residues, triggering an alarm.

For scientists seeking new elements for the periodic table, an important radioisotope fromHFIRis berkelium-249, which was bombarded by a calcium-48 beam in Dubna, Russia, to produce the new element 117. It was named Tennessine in 2010 because of the participation in its discovery by staff at ORNL, the University of Tennessee and Vanderbilt University.

Because of the Russia-Ukraine conflict, Bryan said, ORNL is planning to make a californium-249 target for researchers at DOE’s Lawrence Berkeley National Laboratory to bombard with a titanium-50 beam to try to produce element 120. In addition, a laboratory in Japan is planning to strike a curium-248 target fromHFIRwith a vanadium-51 beam in the hope of making element 119.

NASA work

A radioisotope important to space and planetary exploration that is produced byHFIRis plutonium-238, which Bryan said provided the electricity for NASA’s first deep space missions (the Voyagers) using radioisotope thermoelectric generators.

Pu-238 from ORNL now powers Curiosity and Perseverance, the two rovers exploring Mars to help us understand its history and potential for life. The next space probe powered by Pu-238 fuel that originated fromHFIRwill be the planned Dragonfly mission to Saturn’s moon Titan.

Work connected to nuclear power

Bryan said HFIRcan show in 18 months what kind of damage from exposure to neutrons would be detected in 40 years in steel samples from a power reactor. The information is needed by operators of nuclear power plants seeking licenses to extend their reactors’ operations for 10 more years.

“We do a lot of work for Canadian nuclear power plants on this issue,” Bryan said.

Neutron damage studies atHFIRare useful to designers of future small modular reactors and developers of first-wall material for ITER, the international fusion reactor under construction in France.HFIRis employed also to determine whether advanced nuclear power reactor fuel, such as TRISO fuel first developed at ORNL that is being proposed for use in advanced reactors, is accident tolerant.

This article originally appeared on Oakridger: Happy birthday, HFIR! High Flux Isotope Reactor in Oak Ridge turns 60