From the time he was 4 years old, Ryan Culler wanted to be an astronomer.
It wasn't until after he'd graduated with a master's degree in astrophysics and taught astronomy for a few years that he realized it just wasn't in the stars.
"When I actually started working in astronomy, it wasn't what I thought it was going to be," said Culler, production medical isotope program manager for the Isotope Science and Engineering Directorate's (ISED) Isotope Processing and Manufacturing Division (IPMD) at the Department of Energy's Oak Ridge National Laboratory.
Searching for a job with a purpose, he landed in nuclear medicine - a field that, it turned out, was a perfect fit.
Culler spent three years as a lead chemist and quality control supervisor for a regional nuclear pharmaceutical company in Birmingham, Alabama, that was purchased by Cardinal Health. He spent three more years after the change as facility manager, site supervisor and radiation safety officer.
"I loved that way more than astronomy," Culler said.
He wouldn't have left Cardinal if not for a different kind of love: Culler moved to East Tennessee after marrying his then-wife and gaining a young son who had already established a life in that area. He took a senior chemist position at Colgate Palmolive in Morristown, Tennessee. There he worked his way up to senior quality manager, responsible for overseeing all quality control and compliance operations.
After 16 years at Colgate Palmolive, Culler had his career mapped out. When his son - now in his junior year of high school - leaves for college in two years, Culler planned to move to the company's corporate office in New York. From there, he could go anywhere the company wanted, until retirement.
"It was a solid progression plan," Culler said.
Then, in the summer of 2024, the stars aligned.
IPMD Director Jim Placke was searching for a job candidate who had experience in Good Manufacturing Practices, FDA compliance and medical isotopes production. Culler had all three.
Culler had worked at ORNL before, as a college intern in the 1990s.
"I always dreamed about working here again, but I just never saw the right role," he said - until this position was posted.
"It was my dream job," Culler said. "It was the only thing that could have pulled me away from Colgate Palmolive."
Part of that is personal. Culler's passion for medical isotopes - and for cancer treatments, in particular - grew after his own brother died nearly a decade ago after battling pancreatic cancer. Culler's brother never wavered in his belief that Culler would find a treatment to help him, and his brother's faith in him drives Culler to this day.
"Anything I can do to fight cancer, that's what I want to do," Culler said.
Right now, he believes the isotope actinium-225, used to target cancer inside the body with minimal damage to surrounding cells, is the best shot.
"It's probably the most promising thing I've ever seen for cancer treatment," Culler said - the biggest advance, he thinks, since proton beam therapy, which uses narrow beams of particles to irradiate diseased tissue. "If we can get actinium-225 across the finish line, get it FDA-approved and covered by Medicare and insurance, it could have an incredible impact on the cancer world."
The division Culler joined in ISED was founded in 2022 with the goal of establishing routine production of in-demand isotopes. On Sept. 25, Ac-225 became the first .
Under IPMD, the entire production line of Ac-225 is being standardized, with new processes, staff and equipment to optimize it. The goal is for other isotopes to follow, once the lab has established routine Ac-225 production on a larger scale.
"We're designing the program to accommodate all future medical isotopes," Culler said.
But first, Culler has work to do, including a performance plan with 13 action items related to quality and efficiency. On the list is solving a processing issue with a specific column in the system, an issue that currently presents IPMD's biggest challenge fulfilling customer orders on time with enough product.
"Our customers need all the actinium we can give them, not only to treat patients, but in the bigger picture, to support clinical trials," Culler said.
In the long term, IPMD's goal is to try to get out of the Ac-225 business by improving its production so much that private industry can take it over. However, even if that happens, Culler thinks there will still be demand for the ultra-pure Ac-225 ORNL produces from thorium-229, which will be more difficult for industry to replicate.
When he's not working, Culler most enjoys spending time with his son. They go to concerts and go four-wheeling and hunting, among other things.
"He's brilliant," Culler said, "super, super smart."
And, at the moment, he's the only thing more important than Ac-225, Culler said: "He's my priority."
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. DOE's Office of Science is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science.
